This document summarizes research on 3D lattices of coupled microspheres with whispering gallery modes (WGMs). Key points:
1) The researchers synthesized 3D lattices of dye-doped fluorescent polystyrene spheres with controlled thickness from one to 43 monolayers using flow-assisted self-assembly.
2) Optical transmission spectra of the lattices showed signatures of coupling between spheres, including WGM peak splitting and anomalously high transmission at peak wavelengths.
3) The observed WGM transport is interpreted using an analogy to percolation theory, where optical "bonds" connect lattice sites depending on size dispersion. Near-perfect lattices could enable resonant sensing and light emission applications
The effects of inter-cavity separation on optical coupling in dielectric bisp...Shashaanka Ashili
The optical coupling between two size-mismatched spheres was studied by using one sphere as a local source of light with whispering gallery modes (WGMs) and detecting the intensity of the light scattered by a second sphere playing the part of a receiver of electromagnetic energy. We developed techniques to control inter-cavity gap sizes between microspheres with ~30nm accuracy. We demonstrate high efficiencies (up to 0.2-0.3) of coupling between two separated cavities with strongly detuned eigenstates. At small separations (<1 μm) between the spheres, the mechanism of coupling is interpreted in terms of the Fano resonance between discrete level (true WGMs excited in a source sphere) and a continuum of “quasi”-WGMs with distorted shape which can be induced in the receiving sphere. At larger separations the spectra detected from the receiving sphere originate from scattering of the radiative modes.
This document presents a technique called K-factor image deshadowing that can improve the localization accuracy of single fluorescent particles in stochastic super-resolution fluorescence microscopy. K-factor decomposes an image into a nonlinear set of contrast-ordered images whose product reassembles the original. Applying K-factor to raw fluorescence data prior to localization can improve localization precision by up to 85% compared to single fitting, enabling the localization of overlapping particles and faster data collection. Implementing this on experimental cellular data yielded a 37% improvement in resolution for the same acquisition time, or a 42% decrease in time needed for the same resolution.
This document summarizes a study on errors in particle tracking microrheology. It separates errors into static errors from position measurements of immobilized particles due to limited spatial resolution, and dynamic errors from particle motion during the finite exposure time required for visualization. The authors develop models to calculate how these errors propagate to measurements of mean-squared displacement. They verify the models using simulations and experiments on viscous fluids, showing static errors can be corrected using static experiments at similar noise levels. This increases accuracy for microrheology studies.
This document discusses a new design of plasmonic nanoantenna with a slant gap that can enhance optical chirality. The slant gap provides an enhanced electric field parallel to an external magnetic field with a phase delay of π/2, resulting in enhanced optical chirality in the near field. Numerical simulations show this nanoantenna design can generate a near field with enhanced optical chirality when excited by linearly polarized light. This enhanced optical chirality could allow for circular dichroism analysis using linearly polarized light and may find applications in analyzing the chirality of surface-bound matter.
This document proposes using a thin layer of chalcogenide phase change material like Ge2Sb2Te5 to optically tune the EIT-like response of an all-dielectric metasurface. The metasurface consists of silicon nanoresonators that support an EIT-like resonant response at 1550nm when the phase change material is amorphous. Switching the material to crystalline shifts the EIT response to higher wavelengths due to increased losses. This provides a reversible tuning mechanism for the metasurface response with nanosecond laser pulses, allowing dynamic control over transmission and dispersion properties.
Wei Li has published extensively in international scientific journals and books as well as international conference proceedings. Some of his notable publications include papers on spectral characterization of monolithic mode-locked lasers, superluminescent diodes at 1.55 μm, characterization of 1550 nm Fabry-Perot laser structures, and invited chapters in books on dilute nitride semiconductors and GaInNAs quantum well lasers. He has also published work on extending the emission wavelength of GaInNAs/GaAs quantum well lasers beyond 1300 nm and high performance 1.32 μm GaInNAs/GaAs single-quantum-well lasers.
This document describes a new technique for wide-field background-free fluorescence imaging in vivo using magnetic modulation of fluorescent nanodiamond emission. Fluorescent nanodiamonds are promising probes for in vivo imaging but are limited by autofluorescence. The technique uses a rotating magnetic field to selectively modulate nanodiamond fluorescence, which is then detected using phase-sensitive lock-in detection to improve signal-to-background ratio up to 100-fold. This overcomes autofluorescence and improves nanodiamond imaging capabilities for in vivo applications.
Handbook of coherent domain optical methodsSpringer
This chapter discusses light scattering spectroscopy techniques, both elastic and inelastic. Elastic light scattering spectroscopy measures the size, shape, and optical properties of particles or cells based on the spectrum of light they scatter. Inelastic light scattering spectroscopy, also known as Raman spectroscopy, measures the spectrum of light scattered by molecular vibrations or phonons in solids. These techniques are emerging as useful tools in materials science, environmental science, and biomedicine for applications such as measuring the size distribution of cell nuclei, early cancer detection, and disease diagnosis.
The effects of inter-cavity separation on optical coupling in dielectric bisp...Shashaanka Ashili
The optical coupling between two size-mismatched spheres was studied by using one sphere as a local source of light with whispering gallery modes (WGMs) and detecting the intensity of the light scattered by a second sphere playing the part of a receiver of electromagnetic energy. We developed techniques to control inter-cavity gap sizes between microspheres with ~30nm accuracy. We demonstrate high efficiencies (up to 0.2-0.3) of coupling between two separated cavities with strongly detuned eigenstates. At small separations (<1 μm) between the spheres, the mechanism of coupling is interpreted in terms of the Fano resonance between discrete level (true WGMs excited in a source sphere) and a continuum of “quasi”-WGMs with distorted shape which can be induced in the receiving sphere. At larger separations the spectra detected from the receiving sphere originate from scattering of the radiative modes.
This document presents a technique called K-factor image deshadowing that can improve the localization accuracy of single fluorescent particles in stochastic super-resolution fluorescence microscopy. K-factor decomposes an image into a nonlinear set of contrast-ordered images whose product reassembles the original. Applying K-factor to raw fluorescence data prior to localization can improve localization precision by up to 85% compared to single fitting, enabling the localization of overlapping particles and faster data collection. Implementing this on experimental cellular data yielded a 37% improvement in resolution for the same acquisition time, or a 42% decrease in time needed for the same resolution.
This document summarizes a study on errors in particle tracking microrheology. It separates errors into static errors from position measurements of immobilized particles due to limited spatial resolution, and dynamic errors from particle motion during the finite exposure time required for visualization. The authors develop models to calculate how these errors propagate to measurements of mean-squared displacement. They verify the models using simulations and experiments on viscous fluids, showing static errors can be corrected using static experiments at similar noise levels. This increases accuracy for microrheology studies.
This document discusses a new design of plasmonic nanoantenna with a slant gap that can enhance optical chirality. The slant gap provides an enhanced electric field parallel to an external magnetic field with a phase delay of π/2, resulting in enhanced optical chirality in the near field. Numerical simulations show this nanoantenna design can generate a near field with enhanced optical chirality when excited by linearly polarized light. This enhanced optical chirality could allow for circular dichroism analysis using linearly polarized light and may find applications in analyzing the chirality of surface-bound matter.
This document proposes using a thin layer of chalcogenide phase change material like Ge2Sb2Te5 to optically tune the EIT-like response of an all-dielectric metasurface. The metasurface consists of silicon nanoresonators that support an EIT-like resonant response at 1550nm when the phase change material is amorphous. Switching the material to crystalline shifts the EIT response to higher wavelengths due to increased losses. This provides a reversible tuning mechanism for the metasurface response with nanosecond laser pulses, allowing dynamic control over transmission and dispersion properties.
Wei Li has published extensively in international scientific journals and books as well as international conference proceedings. Some of his notable publications include papers on spectral characterization of monolithic mode-locked lasers, superluminescent diodes at 1.55 μm, characterization of 1550 nm Fabry-Perot laser structures, and invited chapters in books on dilute nitride semiconductors and GaInNAs quantum well lasers. He has also published work on extending the emission wavelength of GaInNAs/GaAs quantum well lasers beyond 1300 nm and high performance 1.32 μm GaInNAs/GaAs single-quantum-well lasers.
This document describes a new technique for wide-field background-free fluorescence imaging in vivo using magnetic modulation of fluorescent nanodiamond emission. Fluorescent nanodiamonds are promising probes for in vivo imaging but are limited by autofluorescence. The technique uses a rotating magnetic field to selectively modulate nanodiamond fluorescence, which is then detected using phase-sensitive lock-in detection to improve signal-to-background ratio up to 100-fold. This overcomes autofluorescence and improves nanodiamond imaging capabilities for in vivo applications.
Handbook of coherent domain optical methodsSpringer
This chapter discusses light scattering spectroscopy techniques, both elastic and inelastic. Elastic light scattering spectroscopy measures the size, shape, and optical properties of particles or cells based on the spectrum of light they scatter. Inelastic light scattering spectroscopy, also known as Raman spectroscopy, measures the spectrum of light scattered by molecular vibrations or phonons in solids. These techniques are emerging as useful tools in materials science, environmental science, and biomedicine for applications such as measuring the size distribution of cell nuclei, early cancer detection, and disease diagnosis.
This study divided animal bones into segments that were cut using different saws and then burned. Microscopy methods including light stereomicroscopy and scanning electron microscopy (SEM) were used to analyze patterns in the cut marks (kerf patterning) on the burned bone segments. SEM provided higher resolution images than light microscopy and allowed observation of striations and fractures not otherwise visible. Energy-dispersive X-ray spectroscopy (EDS) analysis also found differences between the elemental composition of kerf flooring and bone surface, demonstrating the potential of SEM and EDS to study cut marks and help with reconstruction efforts using cremated remains.
This study divided animal bones into segments, cut them with different saws, and burned them to analyze saw kerf patterns under microscopy. Bones from a cow, horse, and elk were each cut once with a circular, reciprocating, or hand saw, creating 16 samples total. The samples were burned at an average temperature of 476.2°C for 5 minutes then analyzed under a stereomicroscope and scanning electron microscope. Microscopy revealed clearer saw kerf patterns and fractures under the SEM compared to the stereomicroscope. Energy dispersive X-ray analysis also showed differences in elemental composition between kerf flooring and bone surface.
This paper presents a study of the extended X-ray emission in the Seyfert galaxy NGC 4151 using deep Chandra observations. Key findings include:
1) Emission line maps show strong OVII, OVIII, and NeIX line emission extending along the northeast-southwest direction, consistent with an ionization cone.
2) Spectral analysis finds the extended emission is well described by photoionized plasma models, supporting a dominant role for nuclear photoionization.
3) Faint extended emission is also seen perpendicular to the ionization cone, indicating some leakage of nuclear ionizing radiation through warm absorbers rather than being blocked by an obscuring torus.
2005 when x rays modify-protein_structure_radiationd_amage at workOsama Abdulkareem
This document discusses radiation damage that can occur during X-ray crystallography experiments used to determine protein structures. When X-rays interact with protein crystals, they can damage the crystals through ionization and the generation of free radicals. This radiation damage can modify the protein structure being analyzed from its native state. A new technique called "multi-crystal data collection" is described that allows determining the structures of different redox states of proteins by collecting data from multiple crystals exposed to different radiation doses. This helps characterize protein structures before they are altered by radiation damage during data collection.
This document describes magnetic tweezers, which are instruments that use magnetic fields to manipulate biomolecules. Magnetic tweezers typically exert piconewton forces on superparamagnetic beads attached to molecules like DNA or proteins to study their mechanical properties. They consist of magnets above a microscope that tracks bead position. Magnetic tweezers allow studying properties of single molecules and complexes by twisting or stretching molecules between a surface and bead. They have high resolution but low throughput. Recent advances aim to improve fields and resolution for diverse single molecule applications.
X-ray Crystallography & Its Applications in Proteomics Akash Arora
X-ray crystallography is a technique that uses X-rays to determine the atomic structure of crystals. It involves crystallizing molecules and bombarding them with X-rays, which produce a diffraction pattern. This pattern is used to deduce the molecular structure. X-ray crystallography has many applications in proteomics, including determining protein structures, studying protein interactions, and elucidating enzyme catalysis mechanisms. It provides atomic-level insights that advance understanding of protein function.
The clustering of_galaxies_in_the_sdss_iii_bossSérgio Sacani
This document summarizes the key results from a study measuring baryon acoustic oscillations (BAO) in galaxies from the Baryon Oscillation Spectroscopic Survey (BOSS) as part of the Sloan Digital Sky Survey III (SDSS-III). The study uses a sample of nearly 1 million galaxies covering 8,500 square degrees and redshifts between 0.2-0.7. It detects the BAO feature at over 7 sigma significance in both the correlation function and power spectrum. Fittings of the BAO feature measure distances of DV=1264 Mpc at z=0.32 and DV=2056 Mpc at z=0.57, with a 1% precision, the
This document lists 37 publications in refereed journals and 10 presentations at conferences by Richard A. Wilson and his collaborators relating to research on semiconductor materials and devices from 2000 to 1982. The publications cover topics including microring resonators, wavelength conversion, filtering, nonlinear effects, temperature dependence of material properties, etching and surface treatments, quantum wells, transistors, and molecular beam epitaxy.
Super Resolution Microscopy publications 2012Firstscientix
Localization Microscopy: Molecular Galaxies of protein transport in human blood-brain-barrier, tight junctions networks, gene transcription, single molecules, nuclear histones, viruses
51 Disintegration of 12C nuclei by 700–1500 MeV photons - Nuclear Physics A,...Cristian Randieri PhD
Disintegration of 12C nuclei by 700–1500 MeV photons - Elsevier Science, Nuclear Physics A, August 2015, Vol. 940, pp. 264-278, DOI: 10.1016/j.nuclphysa.2015.05.001
di V. Nedorezov, A. D’Angelo, O. Bartalini, V. Bellini, M. Capogni, L.E. Casano, M. Castoldi, F. Curciarello, V. De Leo, J.-P. Didelez, R. Di Salvo, A. Fantini, D. Franco, G. Gervino, F. Ghio, G. Giardina, B. Girolami, A. Giusa, A. Lapik, P. Levi Sandri, F. Mammoliti, G. Mandaglio, M. Manganaro, D. Moricciani, A. Mushkarenkov, I. Pshenichnov, C. Randieri, N. Rudnev, G. Russo, C. Schaerf, M. L. Sperduto, M.-C. Sutera, A. Turinge, V. Vegna, I. Zonta (2015)
Abstract
Disintegration of 12C nuclei by tagged photons of 700–1500 MeV energy at the GRAAL facility has been studied by means of the LAGRANγE detector with a wide angular acceptance. The energy and momentum distributions of produced neutrons and protons as well as their multiplicity distributions were measured and compared with corresponding distributions calculated with the RELDIS model based on the intranuclear cascade and Fermi break-up models. It was found that eight fragments are created on average once per about 100 disintegration events, while a complete fragmentation of 12C into 12 nucleons is observed typically only once per 2000 events. Measured multiplicity distributions of produced fragments are well described by the model. The measured total photoabsorption cross section on 12C in the same energy range is also reported.
Magnetic nanoparticles applications and bioavailability for cancer therapyPravin Chinchole
Magnetic nanoparticles can be used for cancer therapy applications. They can be coated or encapsulated to be bioavailable. When exposed to an external alternating magnetic field, the nanoparticles generate heat through hysteresis, friction, and relaxation effects. This localized hyperthermia can directly kill cancer cells or induce heat shock proteins to stimulate anti-cancer immunity. The nanoparticles can also be used for magnetic drug delivery, where drugs are attached and targeted to tumor sites using an external magnetic field, requiring lower doses than conventional treatment and reducing side effects. Studies have shown magnetic nanoparticle hyperthermia and drug delivery can significantly reduce tumor growth in animal models.
This document discusses the techniques of correlated cryo-light microscopy (CLM) and soft X-ray tomography (SXT) for visualizing cell architecture and molecular location. CLM provides high-resolution fluorescent imaging of cells at cryogenic temperatures to localize molecules, while SXT uses soft X-rays to visualize internal cell structure. The two techniques are performed sequentially on the same sample and the data is merged to provide a composite 3D view of both cell structure and molecular location within cells. Specimen preparation, 3D reconstruction, alignment using fiducial markers, and segmentation based on linear absorption coefficients are discussed.
Michael m. woolfson an introduction to x ray crystallography, second edition ...PaReJaiiZz
This chapter introduces the geometry of crystalline materials. Crystals exhibit flat surfaces and internal symmetry. While individual crystal shapes may vary, the set of directions perpendicular to crystal faces (normals) are identical between crystals of the same material and often show symmetry. This symmetry of normals implies an underlying symmetrical atomic arrangement. The chapter describes how stereographic projections are used to represent three-dimensional symmetry of crystal normals on a two-dimensional plane.
Ke Li has over 12 years of experience in optics, lasers, and atomic physics research. He is currently a research fellow at Nanyang Technological University studying defect inspection in semiconductors using a home-built confocal microscope and isolating single defects for quantum information applications. Previously he has held positions at the National University of Singapore, National Institute of Standards and Technology, and Wuhan Institute of Physics and Mathematics, conducting research on topics including laser cooling and trapping of atoms, Bose-Einstein condensation, and optical lattices.
This document summarizes research conducted by Dr. Shiuan Huei Lin and collaborators on developing photopolymer materials for holographic data storage applications. It lists 16 journal publications, 1 book chapter, and 16 conference presentations from 2003 to 2009 reporting on their work investigating various dopants to improve the holographic recording characteristics of poly(methyl methacrylate) photopolymers. The research involved characterization of materials doped with compounds such as phenanthrenequinone and lanthanide organometallics to optimize their properties for volume holographic recording.
Hamiltonian design in readout from room-temperature Raman atomic memory XequeMateShannon
We present an experimental demonstration of the Hamiltonian manipulation in light-atom interface in Raman-type warm rubidium-87 vapor atomic memory. By adjusting the detuning of the driving beam we varied the relative contributions of the Stokes and anti-Stokes scattering to the process of four-wave mixing which reads out a spatially multimode state of atomic memory. We measured the temporal evolution of the readout fields and the spatial intensity correlations between write-in and readout as a function of detuning with the use of an intensified camera. The correlation maps enabled us to resolve between the anti-Stokes and the Stokes scattering and to quantify their contributions. Our experimental results agree quantitatively with a simple, plane-wave theoretical model we provide. They allow for a simple interpretation of the coaction of the anti-Stokes and the Stokes scattering at the readout stage. The Stokes contribution yields additional, adjustable gain at the readout stage, albeit with inevitable extra noise. Here we provide a simple and useful framework to trace it and the results can be utilized in the existing atomic memories setups. Furthermore, the shown Hamiltonian manipulation offers a broad range of atom-light interfaces readily applicable in current and future quantum protocols with atomic ensembles.
This document summarizes research on using metallic nanostructures to enhance fluorescence. Specifically, it proposes using "stair-gratings" - nanostructures with corrugations that have an excavated rectangular section to create a stair-like profile. Experiments show that stair-gratings provide higher fluorescence enhancement and narrower emission directionality compared to conventional gratings, covering both the excitation and emission bands of fluorophores. Finite-difference time-domain simulations agree with experimental results, demonstrating the potential of stair-gratings for applications requiring enhanced and directional single-molecule fluorescence.
Improved two-photon imaging of living neurons in brain tissue through tempora...julian choy
This document describes a study that optimized two-photon imaging of living neurons in brain tissue by temporally gating the incident laser to reduce photon flux while maximizing fluorescence signal. The study found that gating the laser at the sampling frequency compromised cell viability despite high fluorescence. An optimum gating frequency range was identified that maintained cell viability while preserving fluorescence levels in two-photon images. Cell viability was monitored by measuring changes in membrane input resistance during whole-cell patch recording of neurons.
This document presents a multiwavelength analysis of the merging galaxy cluster MACS J0416.1-2403 using observations from Chandra, JVLA, GMRT, and Hubble Space Telescope. The cluster consists of two main subclusters, NE and SW, separated by about 250 kpc. Chandra observations reveal the NE subcluster has a compact core and X-ray cavity, but is not a cool core. A density discontinuity is detected about 450 kpc southwest of the SW subcluster, likely caused by an interaction with a less massive structure detected in lensing maps. For both subclusters, the dark matter and gas components are well-aligned, suggesting MACS J0416.1-2403
1. The document summarizes Tijmen G. Euser's research activities and publications. As a PhD student, he studied dynamic changes in light propagation in photonic crystals and demonstrated optical switching of photonic band gap crystals.
2. As a postdoc, his research included developing hollow-core photonic crystal fibers for optofluidic microreactors, waveguide-based micromanipulation techniques, and spatial light modulation applications. This work enabled new experiments in fields like photochemistry, microparticle transport, and fiber-based spectroscopy.
3. His publications include over 40 peer-reviewed papers investigating topics like optofluidic reactors, optical trapping and propulsion in fibers, spatial mode control
This study divided animal bones into segments that were cut using different saws and then burned. Microscopy methods including light stereomicroscopy and scanning electron microscopy (SEM) were used to analyze patterns in the cut marks (kerf patterning) on the burned bone segments. SEM provided higher resolution images than light microscopy and allowed observation of striations and fractures not otherwise visible. Energy-dispersive X-ray spectroscopy (EDS) analysis also found differences between the elemental composition of kerf flooring and bone surface, demonstrating the potential of SEM and EDS to study cut marks and help with reconstruction efforts using cremated remains.
This study divided animal bones into segments, cut them with different saws, and burned them to analyze saw kerf patterns under microscopy. Bones from a cow, horse, and elk were each cut once with a circular, reciprocating, or hand saw, creating 16 samples total. The samples were burned at an average temperature of 476.2°C for 5 minutes then analyzed under a stereomicroscope and scanning electron microscope. Microscopy revealed clearer saw kerf patterns and fractures under the SEM compared to the stereomicroscope. Energy dispersive X-ray analysis also showed differences in elemental composition between kerf flooring and bone surface.
This paper presents a study of the extended X-ray emission in the Seyfert galaxy NGC 4151 using deep Chandra observations. Key findings include:
1) Emission line maps show strong OVII, OVIII, and NeIX line emission extending along the northeast-southwest direction, consistent with an ionization cone.
2) Spectral analysis finds the extended emission is well described by photoionized plasma models, supporting a dominant role for nuclear photoionization.
3) Faint extended emission is also seen perpendicular to the ionization cone, indicating some leakage of nuclear ionizing radiation through warm absorbers rather than being blocked by an obscuring torus.
2005 when x rays modify-protein_structure_radiationd_amage at workOsama Abdulkareem
This document discusses radiation damage that can occur during X-ray crystallography experiments used to determine protein structures. When X-rays interact with protein crystals, they can damage the crystals through ionization and the generation of free radicals. This radiation damage can modify the protein structure being analyzed from its native state. A new technique called "multi-crystal data collection" is described that allows determining the structures of different redox states of proteins by collecting data from multiple crystals exposed to different radiation doses. This helps characterize protein structures before they are altered by radiation damage during data collection.
This document describes magnetic tweezers, which are instruments that use magnetic fields to manipulate biomolecules. Magnetic tweezers typically exert piconewton forces on superparamagnetic beads attached to molecules like DNA or proteins to study their mechanical properties. They consist of magnets above a microscope that tracks bead position. Magnetic tweezers allow studying properties of single molecules and complexes by twisting or stretching molecules between a surface and bead. They have high resolution but low throughput. Recent advances aim to improve fields and resolution for diverse single molecule applications.
X-ray Crystallography & Its Applications in Proteomics Akash Arora
X-ray crystallography is a technique that uses X-rays to determine the atomic structure of crystals. It involves crystallizing molecules and bombarding them with X-rays, which produce a diffraction pattern. This pattern is used to deduce the molecular structure. X-ray crystallography has many applications in proteomics, including determining protein structures, studying protein interactions, and elucidating enzyme catalysis mechanisms. It provides atomic-level insights that advance understanding of protein function.
The clustering of_galaxies_in_the_sdss_iii_bossSérgio Sacani
This document summarizes the key results from a study measuring baryon acoustic oscillations (BAO) in galaxies from the Baryon Oscillation Spectroscopic Survey (BOSS) as part of the Sloan Digital Sky Survey III (SDSS-III). The study uses a sample of nearly 1 million galaxies covering 8,500 square degrees and redshifts between 0.2-0.7. It detects the BAO feature at over 7 sigma significance in both the correlation function and power spectrum. Fittings of the BAO feature measure distances of DV=1264 Mpc at z=0.32 and DV=2056 Mpc at z=0.57, with a 1% precision, the
This document lists 37 publications in refereed journals and 10 presentations at conferences by Richard A. Wilson and his collaborators relating to research on semiconductor materials and devices from 2000 to 1982. The publications cover topics including microring resonators, wavelength conversion, filtering, nonlinear effects, temperature dependence of material properties, etching and surface treatments, quantum wells, transistors, and molecular beam epitaxy.
Super Resolution Microscopy publications 2012Firstscientix
Localization Microscopy: Molecular Galaxies of protein transport in human blood-brain-barrier, tight junctions networks, gene transcription, single molecules, nuclear histones, viruses
51 Disintegration of 12C nuclei by 700–1500 MeV photons - Nuclear Physics A,...Cristian Randieri PhD
Disintegration of 12C nuclei by 700–1500 MeV photons - Elsevier Science, Nuclear Physics A, August 2015, Vol. 940, pp. 264-278, DOI: 10.1016/j.nuclphysa.2015.05.001
di V. Nedorezov, A. D’Angelo, O. Bartalini, V. Bellini, M. Capogni, L.E. Casano, M. Castoldi, F. Curciarello, V. De Leo, J.-P. Didelez, R. Di Salvo, A. Fantini, D. Franco, G. Gervino, F. Ghio, G. Giardina, B. Girolami, A. Giusa, A. Lapik, P. Levi Sandri, F. Mammoliti, G. Mandaglio, M. Manganaro, D. Moricciani, A. Mushkarenkov, I. Pshenichnov, C. Randieri, N. Rudnev, G. Russo, C. Schaerf, M. L. Sperduto, M.-C. Sutera, A. Turinge, V. Vegna, I. Zonta (2015)
Abstract
Disintegration of 12C nuclei by tagged photons of 700–1500 MeV energy at the GRAAL facility has been studied by means of the LAGRANγE detector with a wide angular acceptance. The energy and momentum distributions of produced neutrons and protons as well as their multiplicity distributions were measured and compared with corresponding distributions calculated with the RELDIS model based on the intranuclear cascade and Fermi break-up models. It was found that eight fragments are created on average once per about 100 disintegration events, while a complete fragmentation of 12C into 12 nucleons is observed typically only once per 2000 events. Measured multiplicity distributions of produced fragments are well described by the model. The measured total photoabsorption cross section on 12C in the same energy range is also reported.
Magnetic nanoparticles applications and bioavailability for cancer therapyPravin Chinchole
Magnetic nanoparticles can be used for cancer therapy applications. They can be coated or encapsulated to be bioavailable. When exposed to an external alternating magnetic field, the nanoparticles generate heat through hysteresis, friction, and relaxation effects. This localized hyperthermia can directly kill cancer cells or induce heat shock proteins to stimulate anti-cancer immunity. The nanoparticles can also be used for magnetic drug delivery, where drugs are attached and targeted to tumor sites using an external magnetic field, requiring lower doses than conventional treatment and reducing side effects. Studies have shown magnetic nanoparticle hyperthermia and drug delivery can significantly reduce tumor growth in animal models.
This document discusses the techniques of correlated cryo-light microscopy (CLM) and soft X-ray tomography (SXT) for visualizing cell architecture and molecular location. CLM provides high-resolution fluorescent imaging of cells at cryogenic temperatures to localize molecules, while SXT uses soft X-rays to visualize internal cell structure. The two techniques are performed sequentially on the same sample and the data is merged to provide a composite 3D view of both cell structure and molecular location within cells. Specimen preparation, 3D reconstruction, alignment using fiducial markers, and segmentation based on linear absorption coefficients are discussed.
Michael m. woolfson an introduction to x ray crystallography, second edition ...PaReJaiiZz
This chapter introduces the geometry of crystalline materials. Crystals exhibit flat surfaces and internal symmetry. While individual crystal shapes may vary, the set of directions perpendicular to crystal faces (normals) are identical between crystals of the same material and often show symmetry. This symmetry of normals implies an underlying symmetrical atomic arrangement. The chapter describes how stereographic projections are used to represent three-dimensional symmetry of crystal normals on a two-dimensional plane.
Ke Li has over 12 years of experience in optics, lasers, and atomic physics research. He is currently a research fellow at Nanyang Technological University studying defect inspection in semiconductors using a home-built confocal microscope and isolating single defects for quantum information applications. Previously he has held positions at the National University of Singapore, National Institute of Standards and Technology, and Wuhan Institute of Physics and Mathematics, conducting research on topics including laser cooling and trapping of atoms, Bose-Einstein condensation, and optical lattices.
This document summarizes research conducted by Dr. Shiuan Huei Lin and collaborators on developing photopolymer materials for holographic data storage applications. It lists 16 journal publications, 1 book chapter, and 16 conference presentations from 2003 to 2009 reporting on their work investigating various dopants to improve the holographic recording characteristics of poly(methyl methacrylate) photopolymers. The research involved characterization of materials doped with compounds such as phenanthrenequinone and lanthanide organometallics to optimize their properties for volume holographic recording.
Hamiltonian design in readout from room-temperature Raman atomic memory XequeMateShannon
We present an experimental demonstration of the Hamiltonian manipulation in light-atom interface in Raman-type warm rubidium-87 vapor atomic memory. By adjusting the detuning of the driving beam we varied the relative contributions of the Stokes and anti-Stokes scattering to the process of four-wave mixing which reads out a spatially multimode state of atomic memory. We measured the temporal evolution of the readout fields and the spatial intensity correlations between write-in and readout as a function of detuning with the use of an intensified camera. The correlation maps enabled us to resolve between the anti-Stokes and the Stokes scattering and to quantify their contributions. Our experimental results agree quantitatively with a simple, plane-wave theoretical model we provide. They allow for a simple interpretation of the coaction of the anti-Stokes and the Stokes scattering at the readout stage. The Stokes contribution yields additional, adjustable gain at the readout stage, albeit with inevitable extra noise. Here we provide a simple and useful framework to trace it and the results can be utilized in the existing atomic memories setups. Furthermore, the shown Hamiltonian manipulation offers a broad range of atom-light interfaces readily applicable in current and future quantum protocols with atomic ensembles.
This document summarizes research on using metallic nanostructures to enhance fluorescence. Specifically, it proposes using "stair-gratings" - nanostructures with corrugations that have an excavated rectangular section to create a stair-like profile. Experiments show that stair-gratings provide higher fluorescence enhancement and narrower emission directionality compared to conventional gratings, covering both the excitation and emission bands of fluorophores. Finite-difference time-domain simulations agree with experimental results, demonstrating the potential of stair-gratings for applications requiring enhanced and directional single-molecule fluorescence.
Improved two-photon imaging of living neurons in brain tissue through tempora...julian choy
This document describes a study that optimized two-photon imaging of living neurons in brain tissue by temporally gating the incident laser to reduce photon flux while maximizing fluorescence signal. The study found that gating the laser at the sampling frequency compromised cell viability despite high fluorescence. An optimum gating frequency range was identified that maintained cell viability while preserving fluorescence levels in two-photon images. Cell viability was monitored by measuring changes in membrane input resistance during whole-cell patch recording of neurons.
This document presents a multiwavelength analysis of the merging galaxy cluster MACS J0416.1-2403 using observations from Chandra, JVLA, GMRT, and Hubble Space Telescope. The cluster consists of two main subclusters, NE and SW, separated by about 250 kpc. Chandra observations reveal the NE subcluster has a compact core and X-ray cavity, but is not a cool core. A density discontinuity is detected about 450 kpc southwest of the SW subcluster, likely caused by an interaction with a less massive structure detected in lensing maps. For both subclusters, the dark matter and gas components are well-aligned, suggesting MACS J0416.1-2403
1. The document summarizes Tijmen G. Euser's research activities and publications. As a PhD student, he studied dynamic changes in light propagation in photonic crystals and demonstrated optical switching of photonic band gap crystals.
2. As a postdoc, his research included developing hollow-core photonic crystal fibers for optofluidic microreactors, waveguide-based micromanipulation techniques, and spatial light modulation applications. This work enabled new experiments in fields like photochemistry, microparticle transport, and fiber-based spectroscopy.
3. His publications include over 40 peer-reviewed papers investigating topics like optofluidic reactors, optical trapping and propulsion in fibers, spatial mode control
This document summarizes two approaches for ultrafast random bit generation based on the chaotic dynamics of a semiconductor laser. The first approach extracts 4 bits per sample and could achieve generation rates up to 160 Gb/s. The second approach extracts 55 bits per sample and could achieve rates up to 2.2 Tb/s. Both approaches compute high-order finite differences of the chaotic laser intensity time series to obtain more symmetrically distributed time series suitable for random bit generation. The randomness of bit sequences from both approaches was tested against standard tests and by calculating statistical bias and serial correlation coefficients.
The document presents evidence for azimuthal variations in cosmic ray ion acceleration at the blast wave of the supernova remnant SN 1006. Using radio, X-ray, and optical observations, the researchers find that the ratio of radii between the blast wave and contact discontinuity varies azimuthally, being smallest in the brightest synchrotron emission regions, indicating more efficient cosmic ray acceleration. They interpret this as evidence that the injection rate, magnetic field strength, and turbulence level - which influence cosmic ray acceleration - all vary azimuthally and are highest in the brightest regions.
A comparative study of living cell micromechanical properties by oscillatory ...Angela Zaorski
This study used an oscillatory optical tweezer-based technique to measure the frequency-dependent viscoelastic properties of cultured alveolar epithelial cells. Both the storage modulus and complex shear modulus followed a weak power law dependence on frequency. Measurements were taken by oscillating either an intracellular organelle or a bead attached to the cell's exterior through membrane receptors. The exponents of the power law were similar between the two measurement methods, but the modulus magnitudes differed significantly. Comparing intracellular and extracellular probing provided insights into cell mechanical properties.
EXTINCTION AND THE DIMMING OF KIC 8462852Sérgio Sacani
To test alternative hypotheses for the behavior of KIC 8462852, we obtained measurements of the star
over a wide wavelength range from the UV to the mid-infrared from October 2015 through December
2016, using Swift, Spitzer and at AstroLAB IRIS. The star faded in a manner similar to the longterm
fading seen in Kepler data about 1400 days previously. The dimming rate for the entire period
reported is 22.1 ± 9.7 milli-mag yr−1
in the Swift wavebands, with amounts of 21.0 ± 4.5 mmag in
the groundbased B measurements, 14.0 ± 4.5 mmag in V , and 13.0 ± 4.5 in R, and a rate of 5.0 ± 1.2
mmag yr−1 averaged over the two warm Spitzer bands. Although the dimming is small, it is seen at
& 3 σ by three different observatories operating from the UV to the IR. The presence of long-term
secular dimming means that previous SED models of the star based on photometric measurements
taken years apart may not be accurate. We find that stellar models with Tef f = 7000 - 7100 K and
AV ∼ 0.73 best fit the Swift data from UV to optical. These models also show no excess in the
near-simultaneous Spitzer photometry at 3.6 and 4.5 µm, although a longer wavelength excess from
a substantial debris disk is still possible (e.g., as around Fomalhaut). The wavelength dependence of
the fading favors a relatively neutral color (i.e., RV & 5, but not flat across all the bands) compared
with the extinction law for the general ISM (RV = 3.1), suggesting that the dimming arises from
circumstellar material
This document summarizes research on using localized surface plasmons generated by gold nanoparticles to optically switch liquid crystals. When gold nanoparticles are excited by laser light at their surface plasmon resonance, they generate strong localized electric fields. These electric fields are able to reversibly switch the orientation of nearby nematic liquid crystals from homeotropic to planar alignment at room temperature with low excitation intensities under 0.03 W/cm^2. The direction of planar alignment can also be controlled by changing the polarization of the excitation light. This provides a new approach for all-optical switching and control of liquid crystals using plasmonic heating and electric fields from gold nanoparticles.
Ion beam irradiation of polycarbonate_TESTMircea Chipara
Ion beam irradiation was used to study the effects on polycarbonate polymers. Ion beams can excite atoms and molecules, generate phonons and heat samples. This can lead to breaking of chemical bonds, ionizations, and formation of radicals and defects. Radicals generated by ion beams can cause macromolecular chain scission or crosslinking. Spectroscopic analysis using ESR, UV-VIS and luminescence revealed that ion beam irradiation generates free radicals along particle tracks coupled by exchange interactions. The concentration of free radicals and deposited dose depends on penetration depth and linear energy transfer.
1. The document lists over 30 journal publications by AJ Rollason dating back to 1981, focusing on using scattering techniques like Compton scattering and (γ,eγ) spectroscopy to determine electron momentum densities and distributions in materials.
2. It also lists one conference proceeding by Rollason from 1995 on x-ray magnetic scattering, and one official report from 1989 co-authored by Rollason and others on determining electron momentum densities using inelastic gamma ray-electron coincidence measurements.
3. The publications cover a wide range of materials from metals like iron, nickel, copper and vanadium to non-metals like carbon and applications including fundamental solid state physics as well as magnetic scattering.
Magnon crystallization in kagomé antiferromagnetsRyutaro Okuma
This document summarizes research on magnon crystallization in kagomé antiferromagnets. Key points include:
1) Observation of a series of magnetization plateaus up to 160 T in CdK and a 1/3 magnetization plateau over 150 T in herbertsmithite.
2) Theoretical calculation showing hexagonal magnon localization and crystallization phases with different magnetization values as the field is increased.
3) Experimental studies of the S=1/2 kagomé magnets volborthite, herbertsmithite, and Cd-kapellasite using ultra-high magnetic fields up to 200 T to observe magnon crystallization phenomena.
Todo mundo sabe que os raios produzidos pela Estrela da Morte em Guerra nas Estrelas não pode existir na vida real, porém no universo existem fenômenos que as vezes conseguem superar até a mais surpreendente ficção.
A galáxia Pictor A, é um desses objetos que possuem fenômenos tão espetaculares quanto aqueles exibidos no cinema. Essa galáxia localiza-se a cerca de 500 milhões de anos-luz da Terra e possui um buraco negro supermassivo no seu centro. Uma grande quantidade de energia gravitacional é lançada, à medida que o material cai em direção ao horizonte de eventos, o ponto sem volta ao redor do buraco negro. Essa energia produz um enorme jato de partículas que viajam a uma velocidade próxima da velocidade da luz no espaço intergaláctico, chamado de jato relativístico.
Para obter imagens desse jato, os cientistas usaram o Observatório de Raios-X Chandra, da NASA várias vezes durante 15 anos. Os dados do Chandra, apresentados em azul nas imagens, foram combinados com os dados obtidos em ondas de rádio a partir do Australia Telescope Compact Array, e são aparesentados em vermelho nas imagens.
Observations of ejecta_clouds_produced_by_impacts_onto_saturn_ringsSérgio Sacani
Three key points from the document:
1. Cassini observations detected dusty ejecta clouds above Saturn's rings that were produced by impacts onto the rings 1 to 50 hours prior.
2. The largest cloud was observed twice, and its brightness and position evolved consistently with this impact hypothesis.
3. The responsible interplanetary meteoroids were initially between 1 cm and several meters in size, and their influx rate is consistent with prior knowledge of smaller meteoroids in the outer solar system.
Matter ejections behind the highs and lows of the transitional millisecond pu...Sérgio Sacani
Transitional millisecond pulsars are an emerging class of sources linking low-mass X-ray binaries to millisecond radio pulsars in
binary systems. These pulsars alternate between a radio pulsar state and an active low-luminosity X-ray disc state. During the active
state, these sources exhibit two distinct emission modes (high and low) that alternate unpredictably, abruptly, and incessantly. X-ray
to optical pulsations are observed only during the high mode. Knowledge of the root reason for this puzzling behaviour remains
elusive. This paper presents the results of the most extensive multi-wavelength campaign ever conducted on the transitional pulsar
prototype, PSR J1023+0038, covering from radio to X-rays. The campaign was carried out over two nights in June 2021, and involved
12 different telescopes and instruments including XMM-Newton, HST, VLT/FORS2 (in polarimetric mode), ALMA, VLA and FAST.
By modelling the broadband spectral energy distributions in both emission modes, we show that the mode switches are caused by
changes in the innermost region of the accretion disc. These changes trigger the emission of discrete mass ejections, which occur on
top of a compact jet, as testified by the detection of at least one short-duration millimetre flare with A
This document provides an introduction to the thesis which focuses on aspects of symmetry, disorder and the Josephson effect in d-wave superconductors. Some key points:
- The thesis studies d-wave superconductors where the gap function changes sign in certain crystal directions, in contrast to conventional s-wave superconductors where the gap is isotropic.
- For a disordered d-wave superconductor, numerical, perturbative and field theoretical methods are used to calculate the density of states, finding it follows a sublinear power law at low energies.
- The Josephson effect in d-wave superconductors is investigated using a tunneling Hamiltonian approach to understand experiments on bicrystal junctions
Long term modulation of cosmic ray intensity in statistical relation with cor...Alexander Decker
This document summarizes a study that analyzed the statistical correlation between long-term cosmic ray intensity and solar activity parameters like coronal mass ejections (CMEs) and solar flare index numbers between 1997 and 2010. The study found a negative correlation between cosmic ray intensity and both CMEs (correlation coefficient of -0.83) and solar flare index (-0.70), indicating that cosmic ray intensity is inversely related to solar activity levels. Figures 1 and 2 show scatter plots illustrating these negative correlations between cosmic ray intensity and the respective solar parameters.
Db8 Acde4 Bdb9 137 E Cae0 Bb8 E4115 B259 172487guest4f037d
This document proposes and analyzes an Ultra-Long Fiber Laser (UFL) system for secure key distribution using classical optical components. The system establishes laser oscillation between two parties based on their randomly chosen spectrally selective mirrors. Each user can extract the other's mirror choice from analyzing the UFL signal, while an adversary can reconstruct only a small fraction of the key. The document provides an extended security analysis considering transient signals and presents initial experimental support. While not unconditionally secure, the system offers simplicity and scalability compared to quantum key distribution.
Similar to Percolation of light through whispering gallery modes in 3D lattices of coupled microspheres (20)
Optical Properties of Mesoscopic Systems of Coupled MicrospheresShashaanka Ashili
Two mechanisms of optical coupling between spherical cavities, tight-binding between their whispering gallery modes and focusing produced by periodically coupled microlenses, are directly observed using spatially resolved scattering spectroscopy and imaging. The results can be used for developing device concepts of lasers, optical filters, microspectrometers and sensors based on mesoscopic systems of coupled microspheres.
A statistical framework for multiparameter analysis at the single cell levelShashaanka Ashili
Phenotypic characterization of individual cells provides crucial insights into intercellular heterogeneity and enables access to information that is unavailable from ensemble averaged, bulk cell analyses. Single-cell studies have attracted significant interest in recent years and spurred the development of a variety of commercially available and research-grade technologies. To quantify cell-to-cell variability of cell populations, we have developed an experimental platform for real-time measurements of oxygen consumption (OC) kinetics at the single-cell level. Unique challenges inherent to these single-cell measurements arise, and no existing data analysis
methodology is available to address them. Here we present a data processing and analysis method that addresses challenges encountered with this unique type of data in order to extract biologically relevant information. We applied the method to analyze OC profiles obtained with single cells of two different cell lines derived from metaplastic and dysplastic human Barrett’s esophageal epithelium. In terms of method development, three main challenges were considered for this heterogeneous dynamic system: (i) high levels of noise, (ii) the lack of a priori knowledge of single-cell dynamics, and (iii) the role of intercellular variability within and across cell types.
Several strategies and solutions to address each of these three challenges are presented. The features such as slopes, intercepts, breakpoint or change-point were extracted for every OC profile and compared across individual cells and cell types. The results demonstrated that the extracted features facilitated exposition of subtle differences between individual cells and their responses to
cell–cell interactions. With minor modifications, this method can be used to process and analyze
data from other acquisition and experimental modalities at the single-cell level, providing a valuable statistical framework for single-cell analysis.
Method for physiologic phenotype characterization at the single-cell level in...Shashaanka Ashili
Intercellular heterogeneity is a key factor in a variety of core cellular processes including proliferation, stimulus response, carcinogenesis, and drug resistance. However, cell-to-cell variability studies at the single-cell level have been hampered by the lack of enabling experimental techniques. We present a measurement platform that features the capability to quantify oxygen consumption rates of individual, non-interacting and interacting cells
under normoxic and hypoxic conditions. It is based on real-time concentration measurements of metabolites of
interest by means of extracellular optical sensors in cell-isolating microwells of subnanoliter volume. We present the results of a series of measurements of oxygen consumption rates (OCRs) of individual non-interacting and interacting human epithelial cells. We measured the effects of cell-to-cell interactions by using the system’s capability to isolate two and three cells in a single well. The major advantages of the approach are: 1. ratiometric, intensity-based characterization of the metabolic phenotype at the single-cell level, 2. minimal invasiveness due to the distant positioning of sensors, and 3. ability to study the effects of cell-cell interactions on cellular respiration rates.
A physical sciences network characterization of non-tumorigenic and metastati...Shashaanka Ashili
To investigate the transition from non-cancerous to metastatic from a physical sciences perspective, the
Physical Sciences–Oncology Centers (PS-OC) Network performed molecular and biophysical comparative studies of the non-tumorigenic MCF-10A and metastatic DA-MB-231 breast epithelial cell lines, commonly used as models of cancer metastasis. Experiments were performed in 20 laboratories from 12 PS-OCs. Each laboratory was supplied with identical aliquots and common reagents and culture protocols. Analyses of these measurements revealed dramatic differences in their mechanics, migration, adhesion, oxygen response, and proteomic profiles. Model-based multi-omics approaches identified key differences between these cells’ regulatory networks involved in morphology and survival. These results provide a multifaceted description of cellular parameters of two widely used cell lines and demonstrate the value of the PS-OC Network approach for integration of diverse experimental observations to elucidate the phenotypes associated with cancer metastasis.
Optical coupling and transport phenomena in chains of spherical dielectric mi...Shashaanka Ashili
The optical transmission properties of chains or circuits of touching polystyrene microspheres with sizes in the 3–20 mm range and a size dispersion of ,1% are studied. The dye-doped spheres with fluorescent peaks due to whispering gallery modes were attached to one end of the chains. The effects of optical transport were detected using spatially resolved scattering spectroscopy. The
attenuation was shown to be ,3 to 4 dB per sphere for the modes with the best transport properties. A mechanism for the observed transport is suggested based on the formation of strongly coupled photonic modes in the systems of randomly detuned resonators with size disorder. It is shown that such circuits possess broad bandpass waveguiding characteristics essential for applications in integrated all-optical network devices.
Automated platform for multiparameter stimulus response studies of metabolic ...Shashaanka Ashili
This document describes an automated platform for performing multiparameter stimulus-response studies on single cells and small groups of interacting cells. The platform allows for minimally invasive monitoring of cell phenotypes while applying various physiological stimuli through microfluidic systems. It features integrated fluorescent probes to monitor intracellular and extracellular physiological changes with high sensitivity. The platform consists of a confocal microscope, microfluidic cassette for single cell confinement and application of stimuli, and software/hardware for automated control and data collection. Preliminary results characterizing metabolic responses of single esophageal cells are presented.
The ability to recreate computational results with minimal effort and actionable metrics provides a solid foundation for scientific research and software development. When people can replicate an analysis at the touch of a button using open-source software, open data, and methods to assess and compare proposals, it significantly eases verification of results, engagement with a diverse range of contributors, and progress. However, we have yet to fully achieve this; there are still many sociotechnical frictions.
Inspired by David Donoho's vision, this talk aims to revisit the three crucial pillars of frictionless reproducibility (data sharing, code sharing, and competitive challenges) with the perspective of deep software variability.
Our observation is that multiple layers — hardware, operating systems, third-party libraries, software versions, input data, compile-time options, and parameters — are subject to variability that exacerbates frictions but is also essential for achieving robust, generalizable results and fostering innovation. I will first review the literature, providing evidence of how the complex variability interactions across these layers affect qualitative and quantitative software properties, thereby complicating the reproduction and replication of scientific studies in various fields.
I will then present some software engineering and AI techniques that can support the strategic exploration of variability spaces. These include the use of abstractions and models (e.g., feature models), sampling strategies (e.g., uniform, random), cost-effective measurements (e.g., incremental build of software configurations), and dimensionality reduction methods (e.g., transfer learning, feature selection, software debloating).
I will finally argue that deep variability is both the problem and solution of frictionless reproducibility, calling the software science community to develop new methods and tools to manage variability and foster reproducibility in software systems.
Exposé invité Journées Nationales du GDR GPL 2024
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
This presentation explores a brief idea about the structural and functional attributes of nucleotides, the structure and function of genetic materials along with the impact of UV rays and pH upon them.
The use of Nauplii and metanauplii artemia in aquaculture (brine shrimp).pptxMAGOTI ERNEST
Although Artemia has been known to man for centuries, its use as a food for the culture of larval organisms apparently began only in the 1930s, when several investigators found that it made an excellent food for newly hatched fish larvae (Litvinenko et al., 2023). As aquaculture developed in the 1960s and ‘70s, the use of Artemia also became more widespread, due both to its convenience and to its nutritional value for larval organisms (Arenas-Pardo et al., 2024). The fact that Artemia dormant cysts can be stored for long periods in cans, and then used as an off-the-shelf food requiring only 24 h of incubation makes them the most convenient, least labor-intensive, live food available for aquaculture (Sorgeloos & Roubach, 2021). The nutritional value of Artemia, especially for marine organisms, is not constant, but varies both geographically and temporally. During the last decade, however, both the causes of Artemia nutritional variability and methods to improve poorquality Artemia have been identified (Loufi et al., 2024).
Brine shrimp (Artemia spp.) are used in marine aquaculture worldwide. Annually, more than 2,000 metric tons of dry cysts are used for cultivation of fish, crustacean, and shellfish larva. Brine shrimp are important to aquaculture because newly hatched brine shrimp nauplii (larvae) provide a food source for many fish fry (Mozanzadeh et al., 2021). Culture and harvesting of brine shrimp eggs represents another aspect of the aquaculture industry. Nauplii and metanauplii of Artemia, commonly known as brine shrimp, play a crucial role in aquaculture due to their nutritional value and suitability as live feed for many aquatic species, particularly in larval stages (Sorgeloos & Roubach, 2021).
ESPP presentation to EU Waste Water Network, 4th June 2024 “EU policies driving nutrient removal and recycling
and the revised UWWTD (Urban Waste Water Treatment Directive)”
Deep Behavioral Phenotyping in Systems Neuroscience for Functional Atlasing a...Ana Luísa Pinho
Functional Magnetic Resonance Imaging (fMRI) provides means to characterize brain activations in response to behavior. However, cognitive neuroscience has been limited to group-level effects referring to the performance of specific tasks. To obtain the functional profile of elementary cognitive mechanisms, the combination of brain responses to many tasks is required. Yet, to date, both structural atlases and parcellation-based activations do not fully account for cognitive function and still present several limitations. Further, they do not adapt overall to individual characteristics. In this talk, I will give an account of deep-behavioral phenotyping strategies, namely data-driven methods in large task-fMRI datasets, to optimize functional brain-data collection and improve inference of effects-of-interest related to mental processes. Key to this approach is the employment of fast multi-functional paradigms rich on features that can be well parametrized and, consequently, facilitate the creation of psycho-physiological constructs to be modelled with imaging data. Particular emphasis will be given to music stimuli when studying high-order cognitive mechanisms, due to their ecological nature and quality to enable complex behavior compounded by discrete entities. I will also discuss how deep-behavioral phenotyping and individualized models applied to neuroimaging data can better account for the subject-specific organization of domain-general cognitive systems in the human brain. Finally, the accumulation of functional brain signatures brings the possibility to clarify relationships among tasks and create a univocal link between brain systems and mental functions through: (1) the development of ontologies proposing an organization of cognitive processes; and (2) brain-network taxonomies describing functional specialization. To this end, tools to improve commensurability in cognitive science are necessary, such as public repositories, ontology-based platforms and automated meta-analysis tools. I will thus discuss some brain-atlasing resources currently under development, and their applicability in cognitive as well as clinical neuroscience.
Phenomics assisted breeding in crop improvementIshaGoswami9
As the population is increasing and will reach about 9 billion upto 2050. Also due to climate change, it is difficult to meet the food requirement of such a large population. Facing the challenges presented by resource shortages, climate
change, and increasing global population, crop yield and quality need to be improved in a sustainable way over the coming decades. Genetic improvement by breeding is the best way to increase crop productivity. With the rapid progression of functional
genomics, an increasing number of crop genomes have been sequenced and dozens of genes influencing key agronomic traits have been identified. However, current genome sequence information has not been adequately exploited for understanding
the complex characteristics of multiple gene, owing to a lack of crop phenotypic data. Efficient, automatic, and accurate technologies and platforms that can capture phenotypic data that can
be linked to genomics information for crop improvement at all growth stages have become as important as genotyping. Thus,
high-throughput phenotyping has become the major bottleneck restricting crop breeding. Plant phenomics has been defined as the high-throughput, accurate acquisition and analysis of multi-dimensional phenotypes
during crop growing stages at the organism level, including the cell, tissue, organ, individual plant, plot, and field levels. With the rapid development of novel sensors, imaging technology,
and analysis methods, numerous infrastructure platforms have been developed for phenotyping.
Comparing Evolved Extractive Text Summary Scores of Bidirectional Encoder Rep...University of Maribor
Slides from:
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Track: Artificial Intelligence
https://www.etran.rs/2024/en/home-english/
Remote Sensing and Computational, Evolutionary, Supercomputing, and Intellige...University of Maribor
Slides from talk:
Aleš Zamuda: Remote Sensing and Computational, Evolutionary, Supercomputing, and Intelligent Systems.
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Inter-Society Networking Panel GRSS/MTT-S/CIS Panel Session: Promoting Connection and Cooperation
https://www.etran.rs/2024/en/home-english/
Travis Hills' Endeavors in Minnesota: Fostering Environmental and Economic Pr...Travis Hills MN
Travis Hills of Minnesota developed a method to convert waste into high-value dry fertilizer, significantly enriching soil quality. By providing farmers with a valuable resource derived from waste, Travis Hills helps enhance farm profitability while promoting environmental stewardship. Travis Hills' sustainable practices lead to cost savings and increased revenue for farmers by improving resource efficiency and reducing waste.
2. 14. V. N. Astratov, J. P. Franchak, and S. P. Ashili, “Optical coupling and transport phenomena in chains of
spherical dielectric microresonators with size disorder,” Appl. Phys. Lett. 85, 5508-5510 (2004).
15. Y. P. Rakovich, J. F. Donegan, M. Gerlach, A. L. Bradley, T. M. Connolly, J. J. Boland, N. Gaponik, and
A. Rogach, “Fine structure of coupled optical modes in photonic molecules,” Phys. Rev. A 70, 051801(R)
(2004).
16. Y. Hara, T. Mukaiyama, K. Takeda, and M. Kuwata-Gonokami, “Heavy photon states in photonic chains of
resonantly coupled cavities with supermonodispersive microspheres,” Phys. Rev. Lett. 94, 203905 (2005).
17. B. M. Möller, U. Woggon, and M. V. Artemyev, “Coupled-resonator optical waveguides doped with
nanocrystals,” Opt. Lett. 30, 2116-2118 (2005).
18. A. V. Kanaev, V. N. Astratov, and W. Cai, “Optical coupling at a distance between detuned spherical
cavities,” Appl. Phys. Lett. 88, 111111 (2006).
19. S. P. Ashili, V. N. Astratov, and E. C. H. Sykes, “The effects of inter-cavity separation on optical coupling
in dielectric bispheres,” Opt. Express 14, 9460-9466 (2006).
20. B. M. Möller, U. Woggon, and M. V. Artemyev, “Bloch modes and disorder phenomena in coupled
resonator chains,” Phys. Rev. B 75, 245327 (2007).
21. S. Deng, W. Cai, and V. N. Astratov, “Numerical study of light propagation via whispering gallery modes
in microcylinder coupled resonator optical waveguides,” Opt. Express 12, 6468-6480 (2004).
22. S. V. Boriskina, “Theoretical prediction of a dramatic Q-factor enhancement and degeneracy removal of
whispering gallery modes in symmetrical photonic molecules,” Opt. Lett. 31, 338-340 (2006).
23. J.E. Heebner, R. W. Boyd, and Q. H. Park, “SCISSOR solitons and other novel propagation effects in
microresonator-midified waveguides,” J. Opt. Soc. Am. B 19, 722-731 (2002).
24. A. Melloni, F. Morichetti, and M. Martinelli, “Linear and nonlinear pulse propagation in coupled resonator
slow-wave optical structures,” Opt. Quantum Electron. 35, 365-379 (2003).
25. B. E. Little, S. T. Chu, P. P. Absil, J. V. Hryniewicz, F. G. Johnson, F. Seiferth, D. Gill, V. Van, O. King,
and M. Trakalo, “Very high-order microring resonator filters for WDM applications,” IEEE Photon.
Technol. Lett. 16, 2263-2265 (2004).
26. J. K. S. Poon, L. Zhu, G. A. DeRose, and A. Yariv, “Transmission and group delay of microring coupled-
resonator optical waveguides,” Opt. Lett. 31, 456-458 (2006).
27. F. Xia, L. Sekaric, and Yu. A. Vlasov, “Ultra-compact optical buffers on a silicon chip,” Nature Photon. 1,
65-71 (2007).
28. A. B. Matsko and V. S. Ilchenko, “Optical resonators with whispering-gallery modes – part I: basics,“ IEEE
J. Sel. Top. Quantum Electron. 12, 3-14 (2006).
29. V. S. Ilchenko and A. B. Matsko, “Optical resonators with whispering-gallery modes – part II:
applications,” IEEE J. Sel. Top. Quantum Electron. 12, 15-32 (2006).
30. S. Mookherjea and A. Oh, “Effect of disorder on slow light velocity in optical slow-wave structures,” Opt.
Lett. 32, 289-291 (2007).
31. R. Albert and A.-L. Barabasi, “Statistical mechanics of complex networks,” Rev. Mod. Phys. 74, 47-97
(2002).
32. C. D. Lorenz and R. M. Ziff, “Precise determination of the bond percolation thresholds and finite-size
scaling corrections for the sc, fcc, and fcc lattices,” Phys. Rev. E 57, 230-236 (1998).
33. M. F.Sykes and J. W. Essam, “Exact critical percolation probabilities for site and bond problems in two
dimensions,” J. of Math. Phys. (N.Y.) 5, 1117-1127 (1964).
34. B. Gates, D. Qin, and Y. Xia, “Assembly of nanoparticles into opaline structures over large areas,” Adv.
Mater. 11, 466-469 (1999).
35. V. N. Astratov, A. M. Adawi, S. Fricker, M. S. Skolnick, D. M. Whittaker, and P. N. Pusey, “Interplay of
order and disorder in the optical properties of opal photonic crystals,” Phys. Rev. B 66, 165215 (2002).
36. Z. Chen, A. Taflove, and V. Backman, “Photonic nanojet enhancement of backscattering of light by
nanoparticles: a potential novel visible-light ultramicroscopy technique,” Opt. Express 12,1214-1220
(2004).
37. A. M. Kapitonov and V. N. Astratov, “Observation of nanojet-induced modes with small propagation losses
in chains of coupled spherical cavities,” Opt. Lett. 32, 409-411 (2007).
38. V. S. Ilchenko, P. S. Volkov, V. L. Velichansky, F. Treussart, V. Lefèvre-Seguin, J.-M. Raimond, and S.
Haroche, “Strain-tunable high-Q optical microsphere resonator,” Opt. Comm. 145, 86-90 (1998).
39. N. Le Thomas, U. Woggon, W. Langbein, and M. V. Artemyev, “Effect of a dielectric substrate on
whispering-gallery-mode sensors,” J. Opt. Soc. Am. B 23, 2361-2365 (2006).
40. H. C. van de Hulst, Light scattering by small particles (Dover Publications, Inc., New York, 1981).
41. M. Sumetsky and B. J. Eggleton, “Modeling and optimization of complex photonic resonant cavity
circuits,” Opt. Express 11, 381-391 (2003).
42. J. E. Heebner, P. Chak, S. Pereira, J. E. Sipe, and R. W. Boyd, “Distributed and localized feedback in
microresonator sequences for linear and nonlinear optics,” J. Opt. Soc. Am. B 21, 1818-1832 (2004).
43. M. Sumetsky, “Modelling of complicated nanometer resonant tunneling devices with quantum dots,” J.
Phys.: Condens. Matter 3, 2651-2664 (1991).
#88612 - $15.00 USD Received 15 Oct 2007; revised 3 Dec 2007; accepted 4 Dec 2007; published 10 Dec 2007
(C) 2007 OSA 10 December 2007 / Vol. 15, No. 25 / OPTICS EXPRESS 17352
3. 1. Introduction
Traditionally, light localization [1,2] and various interference effects [3,4] have been studied
in structures formed by scatterers, such as powders [5,6] of dielectric or semiconductor
materials, with dimensions comparable to the wavelength of light. Recent proposals of high
order optical filters [7] and coupled resonator optical waveguides (CROW) [8,9] stimulated a
strong interest to the optical transport mechanisms in mesoscopic systems formed by spherical
[10-20], cylindrical [21,22], or ring [23-27] resonators with the typical sizes in the order of
several wavelengths. The light is tightly confined in such cavities due to whispering gallery
modes (WGMs) [28,29] with extremely high quality resonances (Q>103
for 4 μm spheres and
up to ~109
for submillimeter spheres). The light transport from cavity to cavity is due to
evanescent coupling of WGMs to neighboring resonators.
It should be noted that disorder plays a fundamental role in the slow light [30] properties
and in the spectral transmission characteristics of CROW structures. One of the problems is
the scattering losses caused by size and shape variations of the cavities which lead to random
energy detuning of their WGM eigenstates. The commercial suspensions of microspheres
have inevitable ~1% size dispersion. By using numerical modeling it was demonstrated [18]
that the size-mismatched spherical cavities can be coupled due to excitation of the quasi-
WGMs with distorted shape. This mechanism provides a limited efficiency of coupling (~0.1-
0.2) between cavities with strongly detuned WGM eigenstantes. Such WGM-related coupling
and transport phenomena were observed in size-mismatched bispheres [19] and in chains
[14,20] of spheres with the size disorder.
In the case of microspheres, the cavities can be micromanipulated and sorted individually
which opens a possibility to select much more uniform resonators [10,12,15-17] on the basis
of spectroscopic characterization of their WGM peak positions. These techniques allow
selecting spheres with the size uniformity ~0.03%. The band structure effects due to tight-
binding model [16] as well as normal mode splitting effects [10,15,17] have been observed in
supermonodispersive spheres. However the sorting of large numbers of microspheres (Q>104
)
with overlapping positions of WGM peaks still remains a challenging problem.
The optical transport in disordered mesoscopic systems of coupled cavities can be
compared with the case of random waveguides [3,4] formed by wavelength scale scatterers. In
random waveguides the importance of interference phenomena such as strong fluctuations in
the transmitted intensity through a disordered sample is determined by the ratio Nl/d, where N
is the number of transverse propagating channels in the waveguide, d its length and l is the
elastic mean free path. To observe strong fluctuations, it is important to achieve as low values
of Nl/d as possible [4]. In coupled cavities, the light effectively propagates along the lines
connecting close neighbors forming a network. Changing direction or “scattering” effectively
takes place at the touching points between the cavities, so the elastic mean free path l can be
associated with the size of the cavities. In the case of large scale 2D or 3D networks of
coupled resonators, the number of transverse paths N can be extremely high meaning that the
interference phenomena can be averaged.
It is interesting to note that the optical transport in systems of coupled cavities can be
considered by analogy with the “bond percolation” problem [31,32] in percolation theory. The
cavities arranged as a lattice are connected at the WGM wavelengths with optical “bonds”
which are present with probability p depending on the cavities’ size dispersion (assuming p≈1
in the resonant case). At small p only a few bonds are present, thus only small clusters of sites
(spheres) can form, but at a critical probability pc, called the percolation threshold [31,32], a
giant cluster appears spanning the entire network. The bond percolation threshold for 2D
triangular lattice is pc= 0.3472963…[33], whereas for 3D face-centered-cubic (fcc) lattice it is
only pc=0.1201635 [32]. It should be noted that in the case of WGM coupling in 3D case the
multiple spheres can be preferably connected in the “atomic” plans of such fcc lattice that
should result in anisotropic properties and higher than pc=0.1201635 thresholds of such
percolative transport, however still the WGM transport in a 3D lattice of spheres is expected
#88612 - $15.00 USD Received 15 Oct 2007; revised 3 Dec 2007; accepted 4 Dec 2007; published 10 Dec 2007
(C) 2007 OSA 10 December 2007 / Vol. 15, No. 25 / OPTICS EXPRESS 17353
4. to be much more robust to the presence of disorder compared to that in 1D chains or 2D
arrays of cavities.
In this paper we study the WGM transport properties of 3D lattices of closely packed
fluorescent (FL) microspheres with the mean diameter 5 μm and 3% size dispersion. Using a
technique of hydrodynamic flow-assisted self-assembly [34], we fabricated a set of samples
with the thickness varying from one monolayer up to 43 monolayers. Using techniques of
local photoexcitation we observed splitting of WGM-related FL transmission peaks above
certain pumping threshold. We also observed an unusual dependence of the WGM-related
transmitted intensity on the thickness of the structure. We explain these results by the
presence of localized clusters or configurations of nearly uniform spheres inside our 3D
structures well connected at the WGM wavelengths.
2. Structures and experimental setup
The 3D close-packed structures formed by 5 μm dye-doped (Green FL, Duke Scientific Corp.)
polystyrene microspheres with ~3% size dispersion were synthesized by the technique [34] of
hydrodynamic flow-assisted self-assembly. As shown in Fig. 1(a) the suspension of spheres
was injected into a cell fabricated by sandwiching a mylar film with a rectangular hole
between two glass substrates. Submicron scratches fabricated on the surface of the mylar film
allowed the liquid to leak out whereas the spheres were trapped inside the cell. The growth of
the close-packed structure with ~1 cm2
area was accelerated under continuous sonication. The
thickness (d) of this structure was controlled by the mylar films in 5 – 177 μm range.
Although polycrystalline, such samples have fcc domains with typical dimensions greater
than 50 μm, as illustrated in Fig. 1(b). The triangular packing of spheres in Fig. 1(b)
represents [35] domains with (111) planes parallel to the surface. About 90% of the total area
of the sample was shown to contain domains with the (111) planes parallel to its surface.
White light illumination was used for imaging different areas of the samples and for taking
transmission spectra of individual spheres, as illustrated in Figs. 1(c,d). The pronounced dip,
around 467 nm, in Fig. 1(d) is due to the absorption of dye molecules doped throughout the
entire volume of microspheres. It should be noted that the illumination of the microspheres
with plane waves leads to the formation of “photonic nanojets” [36] at the back side of
spheres and to the formation of nanojet-induced modes [37] in cavity chains. However the
plane wave illumination is poorly coupled to WGMs in spheres.
Fig. 1. (a) Sketch of the cell for the hydrodynamic flow-assisted self-assembly of microspheres, (b) SEM
image of the top surface of the sample showing its polycrystalline structure, (c) experimental set up, (d)
single dye-doped sphere transmission spectrum.
Spatial filter
White light
Filter λ>500nm
(c)
(b)(a)
d
400 450 500 550 600
0.6
0.7
0.8
0.9
1.0
Transmission(a.u.)
Wavelength (nm)
OPO (d)OPO
(b)
Spectrum
Spatial filter
White light
Filter λ>500nm
(c)
(b)(a)
dd
400 450 500 550 600
0.6
0.7
0.8
0.9
1.0
Transmission(a.u.)
Wavelength (nm)
OPO (d)
400 450 500 550 600
0.6
0.7
0.8
0.9
1.0
Transmission(a.u.)
Wavelength (nm)
OPO (d)OPOOPO
(b)
Spectrum
#88612 - $15.00 USD Received 15 Oct 2007; revised 3 Dec 2007; accepted 4 Dec 2007; published 10 Dec 2007
(C) 2007 OSA 10 December 2007 / Vol. 15, No. 25 / OPTICS EXPRESS 17354
5. In order to study the transport of WGMs we created a localized FL source at one side of
the sample by illuminating it with the focused beam from an optical parametric oscillator
(OPO) system with 5ns pulses and repetition rate of 20Hz, tuned to the center of the
absorption band of the dye (467 nm). The focused spot had a Gaussian intensity distribution at
the sample with the half width a=30 μm leading to an excitation of about 30 spheres in the
first monolayer. The attenuation length of the pump, due to absorption of the dye, can be
estimated as la ~13 μm. Thus, in thick lattices (d>la) the FL source was confined near the
illuminated surface of the structure. As shown in Fig. 1(c) the optical transport properties
were studied by detecting FL transmission spectra from the opposite side of the sample. We
used a 100× objective (NA=0.5) coupled to the spectrometer through a spatial filter selecting a
~10 μm circular area at the surface of the sample located opposite to the center of the
excitation spot.
3. Experimental results and discussion
3.1. Pumping dependence of emission of a single monolayer
We first present in Fig. 2 the results of characterization of a single monolayer of
microspheres. In this case the spheres are coupled laterally, and the effects of transport
between the layers are not involved.
For comparison purposes Fig. 2(a) shows the low-intensity FL emission spectrum of a
single isolated sphere demonstrating WGM peaks with 11-12 nm separations which is
expected given the free spectral range of a 5 μm sphere. This spectrum was obtained by
selecting the emission from a central area on the sphere equator using a spatial filter.
Generally, the WGM resonances in spherical cavities [28,29] are characterized by their
polarization (TE/TM) and by radial (n), angular (l), and azimuthal (m) numbers. In perfect
spheres the WGM modes are 2l+1 fold degenerate in m. This degeneracy can be removed by
deformations from the spherical shape [38]. The modes with n=1 (one antinode of the
electromagnetic field in the radial direction) are most closely confined to the surface of the
sphere, and they have highest Q-factors of their WGM resonances. The spectral resolution in
Fig. 2 is limited by the spectrometer at ~0.2 nm level. Our measurements with higher spectral
resolution showed that the sharpest peaks in Fig. 2(a) (corresponding to n=1) are characterized
Fig. 2. (a) Single 5μm sphere emission spectrum below the threshold for lasing WGMs and (b-f) emission
spectra of a single monolayer of 5μm spheres collected as a function of average excitation intensity from
0.03 W/cm2
to 100 W/cm2
. Inset illustrates geometry of excitation and collection of FL emission.
510 520 530 540 550 560 570
10
-1
10
0
10
1
10
2
10
3
10
4
(f)
(e)
(d)
(c)
(b)
(a)12.011.611.210.8
Intensity(a.u.)
Wavelength (nm)
a FL
510 520 530 540 550 560 570
10
-1
10
0
10
1
10
2
10
3
10
4
(f)
(e)
(d)
(c)
(b)
(a)12.011.611.210.8
Intensity(a.u.)
Wavelength (nm)
a FLa FL
#88612 - $15.00 USD Received 15 Oct 2007; revised 3 Dec 2007; accepted 4 Dec 2007; published 10 Dec 2007
(C) 2007 OSA 10 December 2007 / Vol. 15, No. 25 / OPTICS EXPRESS 17355
6. with Q = 4×103
. It has been demonstrated [39] that such values of Q-factors are much smaller
than that predicted by the Mie theory as a result of an inhomogeneous broadening due to the
spheres shape deformations and as a consequence of a homogeneous broadening for modes
with small azimuthal numbers m due to the tunneling to the substrate. The latter factor leads to
highest Q factors for modes with |m|~l located in the vicinity of equatorial plane of spheres.
The FL emission spectra of a single monolayer of microspheres are presented in Figs. 2(b-
f) as a function of the average excitation intensity (Iav) from 0.03 W/cm2
to 100 W/cm2
. The
low excitation intensity spectra in Figs. 2(b,c) display a series of nearly equidistant broad and
weakly pronounced maxima. These maxima appear due to the inhomogeneous broadening of
the WGM peaks originating from multiple laterally coupled size-disordered cavities located
within the excitation spot. The orientation of WGM orbits close to the equatorial plane favors
coupling between adjacent cavities once they are assembled as a closed packed monolayer on
the substrate. It should be noted however that due to large random detuning (~15 nm) between
the uncoupled WGM eigenstates (caused by ~3% size disorder) such coupling is provided in
an undercoupled regime with a limited (~0.1-0.2) coupling efficiency, as it was demonstrated
by numerical modeling [18] for touching size-mismatched bispheres. The weak coupling
between ~30 touching spheres located within the excitation spot results in a significant
inhomogeneous broadening of the WGM-related maxima in the emission spectra detected
from the central (10 μm) part of this spot.
These maxima are weak since up to a threshold of ~0.3 W/cm2
corresponding to Fig. 2(d)
only a few percent of the total spontaneous emission intensity is coupled to WGMs [12], and
most of the FL intensity is emitted into radiative modes with a broad (510-570nm) spectrum.
Above this threshold, however, the individual spheres start to operate as WGM microlasers.
Lateral coupling of ~30 size-disordered WGM microlasers located within the excitation spot
gives rise to very strong inhomogeneously broadened peaks in the emission spectrum of single
monolayer, as illustrated in Fig. 2(f).
3.2. Pumping dependence of FL transmission of several monolayers thick structures
The spectra of FL transmission through the six monolayer thick structure with d=25.4 μm are
presented in Fig. 3. Since the structure is strongly absorbing at the pump wavelength (467nm),
and nearly transparent at the emission wavelengths at 510-570 nm, the transport of light from
the illuminated side of the sample to the area of collection plays a key role in formation of FL
transmission spectra.
There are two major mechanisms which can be involved in such transport. One is
connected with nonresonant diffusive propagation of radiative modes emitted by the source
spheres. Using traditional scattering terminology [40] this transport can be referred to as a
scattering by large spherical particles (x=2πa/λ>>1, where a=2.5 μm is the radius of
microsphere) with relatively small (0.59) index contrast. In this limit most of the light is
transmitted through each sphere after two refractions without a significant inner reflection. In
the case of plane wave illumination this leads to formation of photonic nanojets [36,37] due to
the focusing effect produced by individual spheres. The second mechanism is connected with
evanescent coupling [18] of WGMs. High pumping intensities strongly favor the latter
mechanism since at highest powers almost 100% of the emission of the source spheres is
provided into the WGM lasing modes as opposed to the radiative modes.
A series of the FL transmission spectra measured as a function of Iav is presented in Fig. 3.
Up to a threshold of Iav~0.3 W/cm2
corresponding to Fig. 3(c), the spectra display a set of
nearly equidistant broad maxima similar to that in Figs. 2(b-c). However, at higher Iav each
maximum is observed to transform into a double-peak structure with 4.0-5.3 nm splitting, as
indicated by dashed lines in Fig. 3. Similar splitting at Iav>0.3 W/cm2
was observed in all
samples with thicknesses ranging from 9.1 μm (2 monolayers) up to 177 μm (43 monolayers).
It is seen in Fig. 3 that the magnitude of splitting does not depend on the pumping intensity.
An inset of Fig. 3 shows the dependence of the FL transmission on the pump intensity for
the peak at 529.3 nm (red line) and for the FL background at the same wavelength (blue line).
#88612 - $15.00 USD Received 15 Oct 2007; revised 3 Dec 2007; accepted 4 Dec 2007; published 10 Dec 2007
(C) 2007 OSA 10 December 2007 / Vol. 15, No. 25 / OPTICS EXPRESS 17356
7. To obtain the net output related to the WGM contribution, we subtracted the broad FL
background that corresponds to the emission from dye molecules in the central regions of the
cavities, as illustrated in the spectrum of Fig. 3(d). It is seen that the WGM contribution (red
line) increases superlinearly with the pump whereas the FL background emission (blue line)
behaves sublinearly, as illustrated by comparison with a linear fit (black line).
The observed formation of a double peak structure in the FL transmission spectra can be
explained by the WGM coupling phenomena in clusters of touching cavities. Due to the 3%
size disorder of cavities in our samples the probability (p) for two randomly selected cavities
to have overlapping WGM resonances with Q = 4×103
is of the order of 1%. In 3D close-pack
lattices however each sphere has 12 nearest neighbors that significantly increase the
probability of finding resonant WGMs. This probability peaks at wavelengths corresponding
to the WGMs in spheres with the mean sizes, as represented by the FL transmission maxima
in Figs. 3(a,b). The likely explanation of the observed double peak structure is connected with
the well-known property of systems of resonant coupled cavities that form two peaks of the
normalized group delay [41-43] at the edges of the transmission band. These peaks provide a
distributed feedback for lasing thus explaining why this double peak structure is seen above
the lasing threshold.
It should be noted that the regimes of evanescent coupling between the spheres inside
such 3D disordered lattices are not well studied at the present time. On the basis of numerical
modeling performed for size-mismatched bispheres [18] it can be suggested that the WGM-
related transport is undercoupled in the cases with strong detuning between WGM eigenstates.
If, however, the detuning is smaller than the on-resonance normal mode splitting [10,15-18]
Fig. 3. FL transmission spectra of a six layer thick sample (d=25.4 μm) collected as a function of
excitation intensity (Iav) from (a) 0.03 W/cm2
to (h) 100 W/cm2
. (c-h) For Iav>0.3 W/cm2
each maximum
transforms into a double peak. Inset: pump dependence of the peak at 529.3 nm (red line), background
emission (blue line) and a linear fit (black line).
510 520 530 540 550 560 570
10
0
10
1
10
2
10
3
10
4
10
5 4.0
Intensity(a.u.)
Wavelength (nm)
(h)
(g)
(f)
(e)
(d)
(c)
(b)
(a)
12.512.312.211.5
4.3
5.1
5.3
OPO
d
FL transmission
10
-2
10
-1
10
0
10
1
10
2
10
0
10
1
10
2
10
3
104
10
5
Intensity(a.u.)
Iav
(W/cm
2
)
510 520 530 540 550 560 570
10
0
10
1
10
2
10
3
10
4
10
5 4.0
Intensity(a.u.)
Wavelength (nm)
(h)
(g)
(f)
(e)
(d)
(c)
(b)
(a)
12.512.312.211.5
4.3
5.1
5.3
510 520 530 540 550 560 570
10
0
10
1
10
2
10
3
10
4
10
5 4.0
Intensity(a.u.)
Wavelength (nm)
(h)
(g)
(f)
(e)
(d)
(c)
(b)
(a)
12.512.312.211.5
4.3
5.1
5.3
OPO
d
FL transmission
OPOOPO
d
FL transmission
10
-2
10
-1
10
0
10
1
10
2
10
0
10
1
10
2
10
3
104
10
5
Intensity(a.u.)
Iav
(W/cm
2
)
#88612 - $15.00 USD Received 15 Oct 2007; revised 3 Dec 2007; accepted 4 Dec 2007; published 10 Dec 2007
(C) 2007 OSA 10 December 2007 / Vol. 15, No. 25 / OPTICS EXPRESS 17357
8. (~3 nm for 5 μm spheres at the average wavelength 535 nm), one can expect much stronger
coupling. More detailed discussion of how the criticality can be achieved in this system can be
found in the Conclusions section of this work. In the case of multiple coupled cavities the
maximal overlap between their evanescent fields can be achieved if they are located in the
same atomic plane of fcc lattice. Within each plane the configurations of well connected
clusters of cavities can have an arbitrary shape since their location follows only the principle
of minimization of the WGM detuning in a given group of spheres. As an example they can
be arranged as sequences of touching cavities with a single path for photons or as clusters of
several spheres in a contact. It can be suggested that the formation of a double peak structure
in the group delay is generic for different configurations of cavities with nearly resonant
WGMs. The physical origin of this phenomenon is connected with the increased dwelling
time for photons [41,42] due to multiple back and forth reflections occurring between the
cavities at the edges of the CROW pass band. The fact that the amount of splitting between
these two peaks does not strongly depend on the spatial arrangement of cavities has been
theoretically proven for several different configurations [43] of electronic coupled quantum
dots systems. It can be suggested that the optical microcavities should possess similar
properties.
In our structures these configurations of cavities with nearly resonant WGMs occupy only
a small fraction of volume of the disordered 3D lattice. For this reason these configurations
are not visibly contributing to the FL transmission spectra at low pumping intensities. With
increasing pumping however, their lasing emission grows stronger than the emission of
individual disordered microlasers due to their higher spectral density and competition between
the modes. This seems to be the reason why we can observe a spectral signature of coupling
between uniform spheres in such disordered 3D lattices. The fact that such clusters of well
coupled cavities can be located in different atomic planes of fcc lattice seems to be an
important condition for observation of splitting perpendicular to the substrate. As an example
in the case of a single monolayer presented in Fig. 2 such photonic molecular states can be
formed only in its plane. Using an analogy with the previously observed directional emission
of strongly coupled states in resonant bispheres [10] along the axis of bisphere it can be
suggested that the molecular states in a single monolayer should be observable rather in the
plane of monolayer than in a perpendicular direction.
This interpretation is also consistent with the magnitude of the observed splitting. For
multiple cavities it is expected [41] to be higher (by the factor of 2) than the normal mode
(WGM) splitting in two identical touching spheres. In this sense the experimentally observed
splitting, indicated in Fig. 3 (4.0-5.3nm for 5 μm spheres at the average wavelength 535 nm),
is found to be in reasonable agreement with the results of measurements [10,15,17] and
modeling [18] of normal mode splitting in polystyrene bispheres with the comparable sizes.
3.3. Thickness dependence of FL transmission
Finally, we studied the dependence of the FL spectral transmission on d using a series of
samples with the thicknesses from 9.1 μm (2 monolayers) up to 177 μm (43 monolayers). To
enable comparison between the transmission data obtained on different samples we used
identical geometries of FL excitation and collection of light, as illustrated in Fig. 4(a) for a six
monolayers thick sample. For each sample, the focusing of the pump beam was provided to
the area with the same a=30 μm size, whereas the FL transmission was collected from the 10
μm circular area at the back surface of the sample located opposite to the center of the
excitation spot. The measurement of the transmitted intensity was complicated by
uncontrollable variations in the conditions of excitation and collection of light from sample to
sample, leading to ~20% random error in determining the absolute transmitted intensity for
different thicknesses (samples). It should be noted however, that the ratio of the intensity of
WGM-related peaks to the FL background can be determined for each sample more accurately
(few percent error) due to the fact that they are extracted from the same spectrum obtained
under identical conditions of excitation and collection of light. It should also be noted, that
#88612 - $15.00 USD Received 15 Oct 2007; revised 3 Dec 2007; accepted 4 Dec 2007; published 10 Dec 2007
(C) 2007 OSA 10 December 2007 / Vol. 15, No. 25 / OPTICS EXPRESS 17358
9. these measurements do not represent the total transmittance [3,4] of the sample because of the
limited area (10 μm) and finite angle (200
) of light collection, but they rather represent its
transmission coefficient obtained for many incoming modes (since our FL source is
multimode) and for a fixed fraction of transmitted modes.
The results are summarized in Fig. 4(c) for the WGM-related peak at 529.3 nm (red lines)
and for the FL background transmission at the same wavelength (blue lines) for various
excitation intensities. The thickness dependence can be divided into three regions: (i) two to
three layers thick (9.1-13.2 μm) structures where d~la, (ii) intermediate (13.2 μm –50 μm)
where d~a > la and (iii) thick (50 μm-177 μm) structures where d>>a, la. The regions (i) and
(iii) display the dependences which can be qualitatively explained by different factors. The
initial increase of the intensities from two to three layers thick structure is explained by more
complete absorption of the pump. The decay of the intensities in region (iii) can be explained
by the diffusive spread of light generated by the point source.
The results for the intermediate range (ii) of thicknesses in Fig. 4(c) show an anomalous
transmission behavior at Iav>0.3 W/cm2
, namely the fact that the WGM-related peak at
529.3nm is growing (red lines) as the thickness of the sample increases from d=13.2 μm to
d=25.4 μm, whereas the intensity of the FL background is markedly decreased (blue lines) in
the same range of thicknesses. This behavior is much better seen in Fig. 4(b) where the peak-
Fig. 4. (a) Geometry of excitation and collection of the FL transmission illustrated for the six
monolayers thick sample. (b) Thickness dependence of the peak-to-background ratio at 529.3nm in the
FL transmission spectra for two pumping intensities. (c) Thickness dependence of the intensity of the
peak at 528nm (red lines) and of the FL background transmission (blue lines). Different curves
correspond to excitation intensity from 0.3 W/cm2
to 30 W/cm2
.
(i)
(ii)
(iii)
10 100
10
0
10
1
10
2
10
3
10
4
Background
Peak 529.3nm
Intensity(a.u.)
Thickness d (μm)
FLa
25.4μm (a)
10 100
5
10
15
Iav
=10 W/cm
2
Iav
=30 W/cm
2
(Ipeak
)/(Ibackground
)
Thickness d (μm)
(b)
(c)
(i)
(ii)
(iii)
10 100
10
0
10
1
10
2
10
3
10
4
Background
Peak 529.3nm
Intensity(a.u.)
Thickness d (μm)
FLa
25.4μm (a)
FLa
25.4μm
FLa
25.4μm
FLa
25.4μm (a)
10 100
5
10
15
Iav
=10 W/cm
2
Iav
=30 W/cm
2
(Ipeak
)/(Ibackground
)
Thickness d (μm)
(b)
10 100
5
10
15
Iav
=10 W/cm
2
Iav
=30 W/cm
2
(Ipeak
)/(Ibackground
)
Thickness d (μm)
(b)
(c)
#88612 - $15.00 USD Received 15 Oct 2007; revised 3 Dec 2007; accepted 4 Dec 2007; published 10 Dec 2007
(C) 2007 OSA 10 December 2007 / Vol. 15, No. 25 / OPTICS EXPRESS 17359
10. to-background ratio is presented in a linear scale as a function of the thickness of the sample
for the two pumping intensities 10 W/cm2
and 30 W/cm2
. The effect observed at 30 W/cm2
is
quite dramatic with the peak-to-background ratio reaching the maximum for the 25.4 μm
sample where it significantly exceeds this ratio for other samples with different thicknesses.
This result cannot be explained simply by more complete absorption of the pump in the 25.4
μm sample since the FL background transmission (which should depend on the absorption of
the pump in a similar way) is markedly decreased in the 25.4 μm sample compared to the
thinner 13.2 μm sample. By translating the sample in the direction perpendicular to the optical
axis of the set-up, we found that the magnitude of this effect is positional dependent. This can
be related to the polycrystalline structure of our samples. Despite its varying magnitude this
effect was present in most of the areas of the sample. It should also be noted that this effect
takes place not for all, but only for some of the WGM-related peaks.
The interpretation of this effect is related to the mechanism of the WGM-related transport.
Since the FL background propagates diffusively, as it was discussed in Section 3.2, the strong
peak-to-background ratio observed in samples with the thickness 25.4 μm means that the
WGM-related transport tends to be more efficient than classical diffusion of light for such
thicknesses. One of the possible interpretations of this result is connected with the assumption
that the WGM-related lasing occurring in the thin, near-surface layer of the structure is highly
directional along the normal to the surface of the sample. This assumption however, is not
supported by our observations of the spatial distribution of the FL transmission as a function
of pumping which demonstrated a broad (>600
) angular spread of the transmitted modes. A
more likely explanation of this effect is connected with the presence of clusters of nearly
resonant spheres stretching from one side to the opposite side of the structure. These clusters
can play the role of very efficient waveguides for WGM transport. The termination of these
waveguides at the back surface of the structure (or inside the structure) leads to a strong
scattering thus explaining the broad angular distribution of the transmitted modes. The
decreased peak-to-background ratio observed in thicker (d≥50 μm) samples, as illustrated in
Fig. 4(b), can be explained in this model by the fact that the characteristic sizes of the
connected clusters are much smaller than the thicknesses of the samples that should lead to
diffusive mechanism of light transport.
4. Conclusions
In conclusion, using techniques of flow-assisted self-assembly, we synthesized 3D lattices of
microspheres with the well controllable thickness from one monolayer up to 43 monolayers of
closed packed spherical cavities. In the low-intensity (Iav<0.3 W/cm2
) FL transmission spectra
of such 3D lattices, we observed a series of nearly equidistant maxima determined by the
inhomogeneous broadening of WGM resonances in the individual size-disordered spheres.
With increasing pumping intensities (Iav>0.3 W/cm2
), we observed that each maximum splits
into a double-peak structure which can be associated with two peaks of normalized group
delay well-known [41-43] for systems of resonant cavities. This effect was explained by the
presence of clusters of spheres with close positions of their WGM resonances inside our
disordered 3D lattices which can be more efficiently excited at high pumping powers. In the
thickness dependence of the FL transmission spectra it was observed that the ratio of the
intensity of some of the WGM-related peaks to the FL background can be anomalously high
for samples with the thickness around 20-30 μm. This effect was explained by the presence of
clusters of spheres with typical sizes 20-30 μm which are well connected at the WGM
wavelengths providing more efficient transport through the structure.
In this paper we developed an approach to understanding the optical transport properties of
such systems based on the analogy with the bond percolation problem [31-33] in percolation
theory. In this approach, the lattice sites (spheres) are connected with optical “bonds” that are
present with probability p depending on the cavities’ size dispersion (assuming p≈1 in the case
of resonance between WGMs). Due to a 3% size disorder, the structures studied in this work
with Q = 4×103
are characterized with p~0.01, thus only small clusters of sites connected by
#88612 - $15.00 USD Received 15 Oct 2007; revised 3 Dec 2007; accepted 4 Dec 2007; published 10 Dec 2007
(C) 2007 OSA 10 December 2007 / Vol. 15, No. 25 / OPTICS EXPRESS 17360
11. bonds can form. However, by selecting more uniform spheres it should be possible to reach a
percolation threshold (pc = 0.1201635 for an fcc lattice [32]) where a giant cluster spans the
entire network. It should be noted that in the case of WGM coupling in 3D case the multiple
spheres can be preferably connected in the “atomic” plans of such fcc lattice that should result
in anisotropic properties and higher than pc=0.1201635 thresholds of such percolative
transport, however still the WGM transport in a 3D lattice of spheres is expected to be much
more robust to the presence of disorder compared to that in 1D chains or 2D arrays of cavities.
Above the percolation threshold such lattices should become transparent for the WGM
transport irrespective of the sample thickness. In comparison with single chains of cavities,
3D structures operating above the WGM percolation threshold can tolerate an order of
magnitude larger dispersion of spheres sizes.
The level of uniformity of spheres required for achieving such WGM percolation threshold
depends on their mean size since smaller spheres have smaller Q-factors of their WGM
resonances which are easier to overlap. We predict that the WGM percolation threshold
should be achievable in close packed 3D lattices formed by cavities with Q~103
and with ~1%
size dispersion. As an example this situation can be realized using commercially available ~3
μm polystyrene spheres in air. The notion of criticality, however, is lost in this case since the
resonators are overcoupled due to the fact that the normal mode splitting exceeds the
uncoupled WGM linewidths. It is interesting to note that there is an additional parameter for
designing such structures which in principle allows achieving regime of critical coupling
under conditions of percolative transport. This parameter is represented by the index of the
external medium. As an example similar values of Q~103
with ~1% size dispersion can be
realized using enlarged (~10 μm) polystyrene spheres in water. In the same spectral range
WGMs in these spheres are characterized with larger angular (l) numbers compared to 3 μm
spheres. On the other hand, as it was demonstrated [21] by using numerical modeling, the
modes with larger l numbers are characterized with smaller coupling constant (and normal
mode splitting) due to smaller fraction of the evanescent field outside the cavity. This effect
was found to be very dramatic [21] for the cylindrical cavities where the change of l from 10
to 16 reduced the coupling constant by approximately five times. On the basis of these results
it seems feasible to achieve critical coupling of enlarged spheres (~10 μm) in a liquid
environment. The exact parameters of spheres and liquid medium should be identified through
numerical modeling that will be the subject of our future work. Such structures of critically
coupled cavities with percolative WGM transport can be used for multi wavelength detection
of biochemical-binding events at the liquid-sphere interface. Thus, such systems can be used
for developing next generation of resonant sensors and arrayed-resonator light emitting
devices.
Acknowledgments
The authors thank M.S. Skolnick, M. Sumetsky, J.J. Baumberg, M.A. Fiddy and M.E. Raikh
for stimulating discussions. This work was supported by ARO grant W911NF-05-1-0529 and
by NSF grant CCF-0513179 as well as, in part, by funds provided by the University of North
Carolina at Charlotte. S.P. Ashili was supported by DARPA grant W911NF-05-2-0053. The
authors are thankful to Duke Scientific Corporation for donating microspheres for the research
presented in this work.
#88612 - $15.00 USD Received 15 Oct 2007; revised 3 Dec 2007; accepted 4 Dec 2007; published 10 Dec 2007
(C) 2007 OSA 10 December 2007 / Vol. 15, No. 25 / OPTICS EXPRESS 17361