Dark field microscopy is a technique that allows samples to appear brightly lit against a dark background. It works by blocking the transmitted light and only allowing oblique rays to illuminate the specimen. This allows largely transparent and unstained samples to be visible. The document discusses how dark field microscopy works, some inexpensive alternatives to expensive equipment, applications like viewing bacteria and minerals, and advantages like being able to see unstained samples clearly. However, it also has disadvantages like being prone to distortions and requiring careful sample preparation. Evidence is presented for its use in research to image things like functionalized gold nanoparticles targeting cancer cells.
DARK FIELD MICROSCOPY by SIVASANGARI SHANMUGAM
Dark-field microscopy is ideally used to illuminate unstained samples causing them to appear brightly lit against a dark background.
This type of microscope contains a special condenser that scatters light and causes it to reflect off the specimen at an angle
DARK FIELD MICROSCOPY by SIVASANGARI SHANMUGAM
Dark-field microscopy is ideally used to illuminate unstained samples causing them to appear brightly lit against a dark background.
This type of microscope contains a special condenser that scatters light and causes it to reflect off the specimen at an angle
during this ppt of microscopes we will be able to know
INTRODUCTION
DEFINITION
HISTORICAL BACKGROUND
VARIABLES USED IN MICROSCOPY
VARIOUS TYPES OF MICROSCOPES
COMPOUND MICROSCOPE - Structure and Function
USE OF MICROSCOPE
CARE OF MICROSCOPE
defintion
A microscope (Greek: micron = small and scopos = aim)
MICROSCOPE - An instrument for viewing objects that are too small to be seen by the naked or unaided eye
MICROSCOPY - The science of investigating small objects using such an instrument is called microscopy
Slides includes all details about Dark field Microscopy.
useful for MTech, pharmacy student which dealing with microbiology. also for reference to study Dark Field Microscopy. includes principle, instrumentation, working, uses etc.
BRIGHT FIELD MICROSCOPY by SIVASANGARI SHANMUGAM
bRIGHT FIELD MICROSCOPY is also called a compound microscope. The name bright - field is derived from the fact that the specimen is dark and contrasted by the surrounding bright viewing field.
this presentation deals with the introduction of some of the commonly used optical microscopes in forensic labs; compound microscope, stereoscopic microscope, comparison microscope, fluorescence microscope and polarized microscope.
during this ppt of microscopes we will be able to know
INTRODUCTION
DEFINITION
HISTORICAL BACKGROUND
VARIABLES USED IN MICROSCOPY
VARIOUS TYPES OF MICROSCOPES
COMPOUND MICROSCOPE - Structure and Function
USE OF MICROSCOPE
CARE OF MICROSCOPE
defintion
A microscope (Greek: micron = small and scopos = aim)
MICROSCOPE - An instrument for viewing objects that are too small to be seen by the naked or unaided eye
MICROSCOPY - The science of investigating small objects using such an instrument is called microscopy
Slides includes all details about Dark field Microscopy.
useful for MTech, pharmacy student which dealing with microbiology. also for reference to study Dark Field Microscopy. includes principle, instrumentation, working, uses etc.
BRIGHT FIELD MICROSCOPY by SIVASANGARI SHANMUGAM
bRIGHT FIELD MICROSCOPY is also called a compound microscope. The name bright - field is derived from the fact that the specimen is dark and contrasted by the surrounding bright viewing field.
this presentation deals with the introduction of some of the commonly used optical microscopes in forensic labs; compound microscope, stereoscopic microscope, comparison microscope, fluorescence microscope and polarized microscope.
The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into various chemical forms as it circulates among the atmosphere and terrestrial and marine ecosystems. The conversion of nitrogen can be carried out through both biological and physical processes. Important processes in the nitrogen cycle include fixation, ammonification, nitrification, and denitrification. The majority of Earth's atmosphere (78%) is nitrogen, making it the largest pool of nitrogen. However, atmospheric nitrogen has limited availability for biological use, leading to a scarcity of usable nitrogen in many types of ecosystems. The nitrogen cycle is of particular interest to ecologists because nitrogen availability can affect the rate of key ecosystem processes, including primary production and decomposition. Human activities such as fossil fuel combustion, use of artificial nitrogen fertilizers, and release of nitrogen in wastewater have dramatically altered the global nitrogen cycle.
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Principles, structure and apllications of bright field and dark field microsc...selvaraj227
BRIGHT-FIELD MICROSCOPY. STEPS OF BRIGHT FIELD MICROSCOPY. DARK FIELD MICROSCOPY.USE OF DARK FILED MICROSCOPE.DIFFERENT BETWEEN THE BRIGHT AND DARK FIELD MICROSCOPY
Darkfield (dark ground) microscopy is a simple and popular method for making unstained transparent specimens clearly visible. Such objects often have refractive indices very close in value to that of their surroundings and are difficult to image in conventional brightfield microscopy. For example, many small aquatic organisms have a refractive index ranging from 1.2 to 1.4, resulting in a negligible optical difference from the surrounding aqueous medium. These are ideal candidates for darkfield illumination.
Dark-field microscope is a machine or matter that can be used for thisobservation of living, unstained cells and microorganisms. In this microscopy, the specimen is brightly illuminated while the background is dark. It is one type of light microscopes.
Used to examine live microorganisms that are not visible with ordinary light microscope.
chapter 2- Microscopy.pptx Microscopy related with medicineHarikantSingh4
It is about microscope in details about microscope. It includes simple microscope, fluoresence microscope, electron microscope and dark field microscope. These are described in details in this presentation. This presentation has images also.
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
The increased availability of biomedical data, particularly in the public domain, offers the opportunity to better understand human health and to develop effective therapeutics for a wide range of unmet medical needs. However, data scientists remain stymied by the fact that data remain hard to find and to productively reuse because data and their metadata i) are wholly inaccessible, ii) are in non-standard or incompatible representations, iii) do not conform to community standards, and iv) have unclear or highly restricted terms and conditions that preclude legitimate reuse. These limitations require a rethink on data can be made machine and AI-ready - the key motivation behind the FAIR Guiding Principles. Concurrently, while recent efforts have explored the use of deep learning to fuse disparate data into predictive models for a wide range of biomedical applications, these models often fail even when the correct answer is already known, and fail to explain individual predictions in terms that data scientists can appreciate. These limitations suggest that new methods to produce practical artificial intelligence are still needed.
In this talk, I will discuss our work in (1) building an integrative knowledge infrastructure to prepare FAIR and "AI-ready" data and services along with (2) neurosymbolic AI methods to improve the quality of predictions and to generate plausible explanations. Attention is given to standards, platforms, and methods to wrangle knowledge into simple, but effective semantic and latent representations, and to make these available into standards-compliant and discoverable interfaces that can be used in model building, validation, and explanation. Our work, and those of others in the field, creates a baseline for building trustworthy and easy to deploy AI models in biomedicine.
Bio
Dr. Michel Dumontier is the Distinguished Professor of Data Science at Maastricht University, founder and executive director of the Institute of Data Science, and co-founder of the FAIR (Findable, Accessible, Interoperable and Reusable) data principles. His research explores socio-technological approaches for responsible discovery science, which includes collaborative multi-modal knowledge graphs, privacy-preserving distributed data mining, and AI methods for drug discovery and personalized medicine. His work is supported through the Dutch National Research Agenda, the Netherlands Organisation for Scientific Research, Horizon Europe, the European Open Science Cloud, the US National Institutes of Health, and a Marie-Curie Innovative Training Network. He is the editor-in-chief for the journal Data Science and is internationally recognized for his contributions in bioinformatics, biomedical informatics, and semantic technologies including ontologies and linked data.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
1. DARK FIELD MICROSCOPY
PRESENATION BY: GIDWANI MANISH N.
1522964
CHARLIE 1
SOURCE: http://www.photomacrography.net/forum/userpix/1469_DSC_4395_2.jpg
2. CONTENTS.
• WHAT IS DARK FIELD MICROSCOPY?
• HOW STUFF WORKS…?
• TRANSFORMATION.
• TOO EXPENSIVE? HERE’S WHAT YOU CAN DO..
• APPLICATIONS, ADVANTAGES &
DISADVANTAGES.
• EVIDENCE FOR USE IN RESEARCH IMAGING.
• REFERENCES.
CHARLIE 2
3. WHAT IS DARK FIELD MICROSCOPY?
Dark Field Microscopy is a technique used to
observe unstained samples causing them to
appear brightly lit against a dark, almost purely
black, background.
CHARLIE 3
PIC: Highly magnified image of sugar crystals using darkfield
microscopy technique.
7. TOO EXPENSIVE? HERE’S WHAT YOU
CAN DO..
• If you do not have access to “STOP” accessories and cannot
afford a dark field kit, there are alternative ways to adapt
your microscope for dark field illumination.
• The expensive stops are all made of opaque material.
• One option is to use a circular object, such as a coin; adhere
the coin to a larger disk and place below the stage.
• You can also cut out a round piece of thick paper, such as
construction paper, cardboard or poster-board, and attach
to the condenser.
• Whatever you use, the trick is to find the right diameter so
that the makeshift stop will block the light and only allow
the oblique rays to illuminate the specimen.
CHARLIE 7
8. APPLICATIONS.
• Viewing blood cells (biological dark field microscope,
combined with phase contrast)
• Viewing bacteria (biological dark field microscope, often
combined with phase contrast)
• Viewing different types of algae (biological dark field
microscope)
• Viewing hairline metal fractures (metallurgical dark field
microscope)
• Viewing diamonds and other precious stones (gemological
microscope or stereo dark field microscope)
• Viewing shrimp or other invertebrates (stereo dark field
microscope)
CHARLIE 8
9. ADVANTAGES & DISADVANTAGES.
ADVANTAGES.
• A dark field microscope is ideal for viewing objects
that are unstained, transparent and absorb little or
no light.
• These specimens often have similar refractive
indices as their surroundings, making them hard to
distinguish with other illumination techniques.
• You can use dark field to study marine organisms
such as algae and plankton, diatoms, insects, fibers,
hairs, yeast and protozoa as well as some minerals
and crystals, thin polymers and some ceramics.
• You can also use dark field in the research of live
bacterium, as well as mounted cells and tissues.
• It is more useful in examining external details, such
as outlines, edges, grain boundaries and surface
defects than internal structure.
• Dark field microscopy is often dismissed for more
modern observation techniques such as phase
contrast and DIC, which provide more accurate,
higher contrasted images and can be used to
observe a greater number of specimens.
• Recently, dark field has regained some of its
popularity when combined with other illumination
techniques, such as fluorescence, which widens its
possible employment in certain fields.
DISADVANTAGES.
• First, dark field images are prone to degradation,
distortion and inaccuracies.
• A specimen that is not thin enough or its density differs
across the slide, may appear to have artifacts throughout
the image.
• The preparation and quality of the slides can grossly
affect the contrast and accuracy of a dark field image.
• You need to take special care that the slide, stage, nose
and light source are free from small particles such as dust,
as these will appear as part of the image.
• Similarly, if you need to use oil or water on the condenser
and/or slide, it is almost impossible to avoid all air
bubbles.
• These liquid bubbles will cause images degradation, flare
and distortion and even decrease the contrast and details
of the specimen.
• Dark field needs an intense amount of light to work. This,
coupled with the fact that it relies exclusively on
scattered light rays, can cause glare and distortion.
• It is not a reliable tool to obtain accurate measurements
of specimens.
• Finally, numerous problems can arise when adapting and
using a dark field microscope. The amount and intensity
of light, the position, size and placement of the condenserCHARLIE 9
13. REFERENCES.
• http://www.microscopemaster.com/dark-field-microscope.html
• http://public.wsu.edu/~omoto/papers/darkfield.html
• https://www.microscopeworld.com/t-darkfield_microscopy.aspx
• http://www.gonda.ucla.edu/bri_core/mic3.gif
• http://secure.tutorsglobe.com/CMSImages/1006_phase%20contrast%20
microscope.jpg
• http://www.photomacrography.net/forum/userpix/1469_DSC_4395_2.jpg
• Robert M. Macnab (3/5/1976): “Examination of Bacterial Flagellation by
Dark-Field Microscopy.” Journal Of Clinical Microbiology, Sept. 1976, p.
258-265. vol. 4, No. 3.
• Sergiy Patskovsky, Eric Bergeron, David Rioux, and Michel Meunier
(26/6/2014): “Wide-field hyperspectral 3D imaging of functionalized Gold
nanoparticles targeting cancer cells by reflected light microscopy.” J.
Biophotonics 1–7 (2014)/DOI 10.1002/jbio.201400025.
CHARLIE 13
When light hits an object, rays are scattered in all azimuths or directions. The design of the dark field microscope is such that it removes the dispersed light, or zeroth order, so that only the scattered beams hit the sample.The introduction of a condenser and/or stop below the stage ensures that these light rays will hit the specimen at different angles, rather than as a direct light source above/below the object. The result is a “cone of light” where rays are diffracted, reflected and/or refracted off the object, ultimately, allowing you to view a specimen in dark field.
Darkfield microscopy relies on a different illumination system. Rather than illuminating the sample with a filled cone of light, the condenser is designed to form a hollow cone of light. The light at the apex of the cone is focused at the plane of the specimen; as this light moves past the specimen plane it spreads again into a hollow cone. The objective lens sits in the dark hollow of this cone; although the light travels around and past the objective lens, no rays enter it The entire field appears dark when there is no sample on the microscope stage; thus the name darkfield microscopy. When a sample is on the stage, the light at the apex of the cone strikes it. The image is made only by those rays scattered by the sample and captured in the objective lens (note the rays scattered by the specimen in Figure 1). The image appears bright against the dark background. This situation can be compared to the glittery appearance of dust particles in a dark room illuminated by strong shafts of light coming in through a side window. The dust particles are very small, but are easily seen when they scatter the light rays. This is the working principle of darkfield microscopy and explains how the image of low contrast material is created: an object will be seen against a dark background if it scatters light which is captured with the proper device such as an objective lens.
1.Light enters the microscope for illumination of the sample.
2.A specially sized disc, the patch stop (see figure) blocks some light from the light source, leaving an outer ring of illumination. A wide phase annulus can also be reasonably substituted at low magnification.
3.The condenser lens focuses the light towards the sample.
4.The light enters the sample. Most is directly transmitted, while some is scattered from the sample.
5.The scattered light enters the objective lens, while the directly transmitted light simply misses the lens and is not collected due to a direct illumination block (see figure).
6.Only the scattered light goes on to produce the image, while the directly transmitted light is omitted.
If a microscope has built-in elements to easily modify for dark field illumination, the manufacturer usually lists this amongst the observation specifications.You can achieve dark field by using condensers, mirrors and/or a “stop.” Some microscopes come with these accessories or researchers can purchase dark field kits, or even use some common items to adapt a microscope for dark field illumination.In bright field illumination, the object is lit from below the stage, resulting in a larger, contrasted image that can be studied.A dark field microscope blocks this central light with a condenser so that only oblique rays hit the object.An Abbe condenser, for example, contains a concave orb that collects light rays in all azimuths that bounce off a sample to form a cone of illumination.If there is nothing on the stage, the aperture of the condenser is greater than the objective and the view will be completely black.A stop is an opaque object that blocks the central light when placed underneath the stage condenser.This also causes light to scatter in all azimuths, resulting in a cone of light that allows for dark field observation.
The above image, taken by Dr. Arlene Wechezak, won second place. The photographed specimen is the red algae Scagelia, showing reproductive spores and golden diatoms. The technique used to take the shot, dark field microscopy, removes the background by illuminating the sample with light that won’t be collected by the objective lens, creating a very dark background with the sample illuminated in the foreground.
LEFT:(A) S. typhimurium during translational movement. Theperitrichous flagella form apolar bundle
(see cartoon, Fig. 1B) which could be mistaken forpolarflagellation. Classifications should therefore be based
on the appearance offlagella on stationary cells. Dark-fieldphotomicrograph taken with high-intensity pulsed
xenon arc. Bar equals 5 gm.
RIGHT: Polar flagellation in pseudomonads. (A) Stationary cell ofP. stutzeri. (B) Same negative [overex-
posed duringprinting] to show cell outline. (C) Cartoon combining information from (A) and (B). (D-F) As
for (A-C) but with P. aeruginosa (note presence oftwo flagella at pole, although species is predominantly
monotrichous). Bar equals 5 ,um.
LEFT: Microscopy images of fixedCD44+-MDA-MB-231 cells incubatedwith CD44-targetedAuNPs taken at differ-ent planes along the optical z-axis (1 μm distance step) in darkfield illumination mode (A1–4) and in reflected light imagingmode (B1–4). For better clarity an embossing filter is applied for imagesA2,A4, B2, B4.
RIGHT:
