Carbon nanotubes are grown using chemical vapor deposition with a metal catalyst particle. Simulations show the carbon nanotube cap controls the chirality and diameter of the grown nanotube. For a nanotube to lift off and grow, the radius of the catalyst particle must be within a specific range determined by the particle's contact angle. The energetics of cap formation and lift off can be modeled and show good agreement with molecular dynamics simulations. Understanding how the cap detaches from the particle may allow controlling the chirality of the grown carbon nanotube.
Talk given at Cambridge DAMTP on Friday, 20 June 2008. Describes recent work on understanding what is necessary to embed accelerating cosmology in higher-dimensional theory.
Anomalous Behavior Of SSPC In Highly Crystallized Undoped Microcrystalline Si...Sanjay Ram
Microcrystalline silicon is a heterogenous material. We show that different effective DOS distribution can be possible for micro-structurally different μc--Si:H thin films
Dielectronic recombination and stability of warm gas in AGNAstroAtom
Paper presented by Susmita Chakravorty at the 17th International Conference on Atomic Processes in Plasmas, Queen's University Belfast, 19-22 July 2011.
Jay amrit kapitza resistance at niobiumsuperfluid he interfacesthinfilmsworkshop
Heat removal from SRF cavity walls to superfluid (HeII) plays a decisive on the thermo-magnetic stability and therefore on the performance of these cavities. The two main parameters are the thermal conductivity of Niobium and the thermal boundary resistance (Kapitza resistance) at the Niobium/superfluid He interface. Here we shall focus mainly on the Kapitza resistance .Theoretical models shall be present to demonstrate that the Kapitza resistance is anomalous at the Niobium/HeII interface, justifying the empirical experimental approach. Various sets of data shall be presented for polycrystalline and single crystal Niobium having different surface morphologies and bulk purities. The impact of surface impurities and dislocations on the Kapitza resistance shall be discussed. New analysis shall be present showing an intrinsic limit to the Kapitza resistance due to interactions between phonons (heat carriers) in He-II and the nanoscale surface roughness of Niobium surface. Potential future experiments shall be proposed.
Talk given at Cambridge DAMTP on Friday, 20 June 2008. Describes recent work on understanding what is necessary to embed accelerating cosmology in higher-dimensional theory.
Anomalous Behavior Of SSPC In Highly Crystallized Undoped Microcrystalline Si...Sanjay Ram
Microcrystalline silicon is a heterogenous material. We show that different effective DOS distribution can be possible for micro-structurally different μc--Si:H thin films
Dielectronic recombination and stability of warm gas in AGNAstroAtom
Paper presented by Susmita Chakravorty at the 17th International Conference on Atomic Processes in Plasmas, Queen's University Belfast, 19-22 July 2011.
Jay amrit kapitza resistance at niobiumsuperfluid he interfacesthinfilmsworkshop
Heat removal from SRF cavity walls to superfluid (HeII) plays a decisive on the thermo-magnetic stability and therefore on the performance of these cavities. The two main parameters are the thermal conductivity of Niobium and the thermal boundary resistance (Kapitza resistance) at the Niobium/superfluid He interface. Here we shall focus mainly on the Kapitza resistance .Theoretical models shall be present to demonstrate that the Kapitza resistance is anomalous at the Niobium/HeII interface, justifying the empirical experimental approach. Various sets of data shall be presented for polycrystalline and single crystal Niobium having different surface morphologies and bulk purities. The impact of surface impurities and dislocations on the Kapitza resistance shall be discussed. New analysis shall be present showing an intrinsic limit to the Kapitza resistance due to interactions between phonons (heat carriers) in He-II and the nanoscale surface roughness of Niobium surface. Potential future experiments shall be proposed.
Variation of Electrical Transport Parameters with Large Grain Fraction in Hig...Sanjay Ram
The electrical transport and its correlation with the microstructural properties in single phase microcrystalline silicon may be very different from the transport in microcrystalline silicon with a mixed phase of amorphous silicon. We have shown that the transport in single phase microcrystalline silicon may be predicted by the large grain fraction.
An automated and user-friendly optical tweezers for biomolecular investigat...Dr. Pranav Rathi
An automated and user-friendly optical tweezers for biomolecular investigations; a versatile, automated, fast, precise and user friendly optical tweezers capable of doing verity of biomolecular experiments.
Structures of Solids
The components can be arranged in a regular repeating three-dimensional array (a crystal lattice), which results in a crystalline solid, or more or less randomly to produce an amorphous solid. Crystalline solids have well-defined edges and faces, diffract x-rays, and tend to have sharp melting points
What are the different types of solids?
There are four different types of crystalline solids: molecular solids, network solids, ionic solids, and metallic solids. A solid's atomic-level structure and composition determine many of its macroscopic properties, including, for example, electrical and heat conductivity, density, and solubility.
What makes a solid a solid?
Solids can hold their shape because their molecules are tightly packed together. ... Atoms and molecules in liquids and gases are bouncing and floating around, free to move where they want. The molecules in a solid are stuck in a specific structure or arrangement of atoms.
What are the 2 types of solids?
Solids can be classified into two types: crystalline and amorphous. Crystalline solids are the most common type of solid. They are characterized by a regular crystalline organization of atoms that confer a long-range order.
What are the examples of solids?
Examples of Solids
Gold.
Wood.
Sand.
Steel.
Brick.
Rock.
Copper.
Brass.
What are the 3 characteristics of solids?
A solid has definite volume and shape, a liquid has a definite volume but no definite shape and gas has neither a definite volume nor shape.
...
Solids
Definite shape (rigid)
Definite volume.
Particles vibrate around fixed axes.
How do you describe solids?
A solid is a sample of matter that retains its shape and density when not confined. The adjective solid describes the state, or condition, of matter having this property. The atom s or molecule s of matter in the solid-state are generally compressed as tightly as the repulsive forces among them will allow.
What is the structure of a solid?
In a solid, molecules are packed together, and it keeps its shape. The matter is the "stuff" of the universe, the atoms, molecules, and ions that make up all physical substances. In a solid, these particles are packed closely together and are not free to move about within the substance
What are some properties of solids?
Explanation:
A solid has a definite shape and volume.
Solids, in general, have a higher density.
In solids, intermolecular forces are strong.
The diffusion of a solid into another solid is extremely slow.
Solids have high melting points.
What are the 4 types of structures?
There are four types of structures;
Frame: made of separate members (usually thin pieces) put together.
Shell: encloses or contains its contents.
Solid (mass): made almost entirely of matter.
liquid (fluid): braking fluid making the brakes.
Variation of Electrical Transport Parameters with Large Grain Fraction in Hig...Sanjay Ram
The electrical transport and its correlation with the microstructural properties in single phase microcrystalline silicon may be very different from the transport in microcrystalline silicon with a mixed phase of amorphous silicon. We have shown that the transport in single phase microcrystalline silicon may be predicted by the large grain fraction.
An automated and user-friendly optical tweezers for biomolecular investigat...Dr. Pranav Rathi
An automated and user-friendly optical tweezers for biomolecular investigations; a versatile, automated, fast, precise and user friendly optical tweezers capable of doing verity of biomolecular experiments.
Structures of Solids
The components can be arranged in a regular repeating three-dimensional array (a crystal lattice), which results in a crystalline solid, or more or less randomly to produce an amorphous solid. Crystalline solids have well-defined edges and faces, diffract x-rays, and tend to have sharp melting points
What are the different types of solids?
There are four different types of crystalline solids: molecular solids, network solids, ionic solids, and metallic solids. A solid's atomic-level structure and composition determine many of its macroscopic properties, including, for example, electrical and heat conductivity, density, and solubility.
What makes a solid a solid?
Solids can hold their shape because their molecules are tightly packed together. ... Atoms and molecules in liquids and gases are bouncing and floating around, free to move where they want. The molecules in a solid are stuck in a specific structure or arrangement of atoms.
What are the 2 types of solids?
Solids can be classified into two types: crystalline and amorphous. Crystalline solids are the most common type of solid. They are characterized by a regular crystalline organization of atoms that confer a long-range order.
What are the examples of solids?
Examples of Solids
Gold.
Wood.
Sand.
Steel.
Brick.
Rock.
Copper.
Brass.
What are the 3 characteristics of solids?
A solid has definite volume and shape, a liquid has a definite volume but no definite shape and gas has neither a definite volume nor shape.
...
Solids
Definite shape (rigid)
Definite volume.
Particles vibrate around fixed axes.
How do you describe solids?
A solid is a sample of matter that retains its shape and density when not confined. The adjective solid describes the state, or condition, of matter having this property. The atom s or molecule s of matter in the solid-state are generally compressed as tightly as the repulsive forces among them will allow.
What is the structure of a solid?
In a solid, molecules are packed together, and it keeps its shape. The matter is the "stuff" of the universe, the atoms, molecules, and ions that make up all physical substances. In a solid, these particles are packed closely together and are not free to move about within the substance
What are some properties of solids?
Explanation:
A solid has a definite shape and volume.
Solids, in general, have a higher density.
In solids, intermolecular forces are strong.
The diffusion of a solid into another solid is extremely slow.
Solids have high melting points.
What are the 4 types of structures?
There are four types of structures;
Frame: made of separate members (usually thin pieces) put together.
Shell: encloses or contains its contents.
Solid (mass): made almost entirely of matter.
liquid (fluid): braking fluid making the brakes.
Antoine - Enhancement of First Penetration Field in Superconducting Multi-lay...thinfilmsworkshop
Enhancement of First Penetration Field in Superconducting Multi-layers Samples (Claire Antoine - 30')
Speaker: Claire Antoine - CEA | Duration: 30 min.
Abstract
In 2006 Gurevich proposed to use nanoscale layers of superconducting materials with high values of Hc > Hc (Nb) for magnetic shielding of bulk niobium to increase the breakdown field of Nb RF cavities.
We have deposited high quality “model” samples by DC magnetron reactive sputtering on R-plane cut sapphire substrates. A 250 nm layer of niobium figures the bulk material as in rf cavities. Such Nb layers were coated with a single or multiple stacks of NbN layers (25 nm or 12 nm) separated by 15 nm MgO barriers, and characterized by X-rays reflectivity and DC transport measurements.
The first magnetic penetration field HC1 has been measured with dc magnetization curves in a SQUID system and with a local probe method based on 3rd harmonic analysis. The Nb samples coated with NbN multi-layers clearly exhibit a higher first penetration field, and the screening effect of the NbN layer was evidenced.
Possibility of a strongly correlated Dirac metal in kagome latticeRyutaro Okuma
A brief review of Dirac cone are given with such materials as graphene and Ba(FeAs)2. A recently published paper which asserts that symmetry protected Dirac cone in kagome lattice be realized by substituting Ga for Zn in Herbertsmithite are introduced. Although, the proposed compound there would be necessarily regarded as just fantasy, newly synthesized transition metal oxides consisting of perfect kagome network are more appropriate to the search for the novel phase.
Evidence Of Bimodal Crystallite Size Distribution In Microcrystalline Silico...Sanjay Ram
It is known that there is a bimodal size distribution in microcrystalline silicon. How can the deconvolution of the Raman spectra be done with incorporation of a bimodal CSD to obtain more accurate and physical picture of the microstructure in this material?
Mobility Measurements Probe Conformational Changes in Membrane-embedded prote...richardgmorris
The function of membrane-embedded proteins such as ion channels depends crucially on their conformation. We demonstrate how conformational changes in asymmetric membrane proteins may be inferred from measurements of their diffusion. Such proteins cause local deformations in the membrane, which induce an extra hydrodynamic drag on the protein. Using membrane tension to control the magnitude of the deformations and hence the drag, measurements of diffusivity can be used to infer--- via an elastic model of the protein--- how conformation is changed by tension. Motivated by recent experimental results [Quemeneur et al., Proc. Natl. Acad. Sci. USA, 111 5083 (2014)] we focus on KvAP, a voltage-gated potassium channel. The conformation of KvAP is found to change considerably due to tension, with its `walls', where the protein meets the membrane, undergoing significant angular strains. The torsional stiffness is determined to be 26.8 kT at room temperature. This has implications for both the structure and function of such proteins in the environment of a tension-bearing membrane.
How to Get CNIC Information System with Paksim Ga.pptxdanishmna97
Pakdata Cf is a groundbreaking system designed to streamline and facilitate access to CNIC information. This innovative platform leverages advanced technology to provide users with efficient and secure access to their CNIC details.
Essentials of Automations: The Art of Triggers and Actions in FMESafe Software
In this second installment of our Essentials of Automations webinar series, we’ll explore the landscape of triggers and actions, guiding you through the nuances of authoring and adapting workspaces for seamless automations. Gain an understanding of the full spectrum of triggers and actions available in FME, empowering you to enhance your workspaces for efficient automation.
We’ll kick things off by showcasing the most commonly used event-based triggers, introducing you to various automation workflows like manual triggers, schedules, directory watchers, and more. Plus, see how these elements play out in real scenarios.
Whether you’re tweaking your current setup or building from the ground up, this session will arm you with the tools and insights needed to transform your FME usage into a powerhouse of productivity. Join us to discover effective strategies that simplify complex processes, enhancing your productivity and transforming your data management practices with FME. Let’s turn complexity into clarity and make your workspaces work wonders!
Unlocking Productivity: Leveraging the Potential of Copilot in Microsoft 365, a presentation by Christoforos Vlachos, Senior Solutions Manager – Modern Workplace, Uni Systems
Threats to mobile devices are more prevalent and increasing in scope and complexity. Users of mobile devices desire to take full advantage of the features
available on those devices, but many of the features provide convenience and capability but sacrifice security. This best practices guide outlines steps the users can take to better protect personal devices and information.
The Art of the Pitch: WordPress Relationships and SalesLaura Byrne
Clients don’t know what they don’t know. What web solutions are right for them? How does WordPress come into the picture? How do you make sure you understand scope and timeline? What do you do if sometime changes?
All these questions and more will be explored as we talk about matching clients’ needs with what your agency offers without pulling teeth or pulling your hair out. Practical tips, and strategies for successful relationship building that leads to closing the deal.
Observability Concepts EVERY Developer Should Know -- DeveloperWeek Europe.pdfPaige Cruz
Monitoring and observability aren’t traditionally found in software curriculums and many of us cobble this knowledge together from whatever vendor or ecosystem we were first introduced to and whatever is a part of your current company’s observability stack.
While the dev and ops silo continues to crumble….many organizations still relegate monitoring & observability as the purview of ops, infra and SRE teams. This is a mistake - achieving a highly observable system requires collaboration up and down the stack.
I, a former op, would like to extend an invitation to all application developers to join the observability party will share these foundational concepts to build on:
GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using Deplo...James Anderson
Effective Application Security in Software Delivery lifecycle using Deployment Firewall and DBOM
The modern software delivery process (or the CI/CD process) includes many tools, distributed teams, open-source code, and cloud platforms. Constant focus on speed to release software to market, along with the traditional slow and manual security checks has caused gaps in continuous security as an important piece in the software supply chain. Today organizations feel more susceptible to external and internal cyber threats due to the vast attack surface in their applications supply chain and the lack of end-to-end governance and risk management.
The software team must secure its software delivery process to avoid vulnerability and security breaches. This needs to be achieved with existing tool chains and without extensive rework of the delivery processes. This talk will present strategies and techniques for providing visibility into the true risk of the existing vulnerabilities, preventing the introduction of security issues in the software, resolving vulnerabilities in production environments quickly, and capturing the deployment bill of materials (DBOM).
Speakers:
Bob Boule
Robert Boule is a technology enthusiast with PASSION for technology and making things work along with a knack for helping others understand how things work. He comes with around 20 years of solution engineering experience in application security, software continuous delivery, and SaaS platforms. He is known for his dynamic presentations in CI/CD and application security integrated in software delivery lifecycle.
Gopinath Rebala
Gopinath Rebala is the CTO of OpsMx, where he has overall responsibility for the machine learning and data processing architectures for Secure Software Delivery. Gopi also has a strong connection with our customers, leading design and architecture for strategic implementations. Gopi is a frequent speaker and well-known leader in continuous delivery and integrating security into software delivery.
Dr. Sean Tan, Head of Data Science, Changi Airport Group
Discover how Changi Airport Group (CAG) leverages graph technologies and generative AI to revolutionize their search capabilities. This session delves into the unique search needs of CAG’s diverse passengers and customers, showcasing how graph data structures enhance the accuracy and relevance of AI-generated search results, mitigating the risk of “hallucinations” and improving the overall customer journey.
In his public lecture, Christian Timmerer provides insights into the fascinating history of video streaming, starting from its humble beginnings before YouTube to the groundbreaking technologies that now dominate platforms like Netflix and ORF ON. Timmerer also presents provocative contributions of his own that have significantly influenced the industry. He concludes by looking at future challenges and invites the audience to join in a discussion.
Pushing the limits of ePRTC: 100ns holdover for 100 daysAdtran
At WSTS 2024, Alon Stern explored the topic of parametric holdover and explained how recent research findings can be implemented in real-world PNT networks to achieve 100 nanoseconds of accuracy for up to 100 days.
GridMate - End to end testing is a critical piece to ensure quality and avoid...ThomasParaiso2
End to end testing is a critical piece to ensure quality and avoid regressions. In this session, we share our journey building an E2E testing pipeline for GridMate components (LWC and Aura) using Cypress, JSForce, FakerJS…
2. Carbon nanotubes
• Carbon nanotubes are one of the most important
nanomaterials
Source: Intel
• For applications, one would like to be able to grow CNTs
of specific chiralities and diameters (which control the
band gap), in place, in devices.
3. Growth of carbon nanotubes
• Growth by Chemical Vapour Deposition (CVD) uses a
metal particle catalyst (e.g. Fe or Ni).
Amara et al, PRL 100, 056105 (2008)
• In small catalyst particles (<5nm) cap nucleates and then
lifts off, resulting in growth of single wall tube.
• Simulating CNT growth is challenging due to timescales
involved – limited success so far.
4. Catalyst size vs. tube size
Fe catalysts, unsupported growth
r
1 .6
rt
Nasibulin et al, Carbon 43 2251 (2005)
5. Focus on cap
• Geometrically, there is a 1:1 relationship
between the cap structure and the tube
chirality
• Hypothesis: CNT cap controls CNT chirality
(Reich et al., Chem. Phys. Lett. 421, 469 (2006))
• If we can understand formation of cap and transition to
tube growth, we may learn how to control chirality
6. CNT growth outcomes
• Cap lift-off (SWNT?)
• Catalyst withdrawal (MWNT?)
Yoshida et al, Nano Lett., 8, 2082–2086 (2008)
7. Metal particles in CNTs
Tsang et al, Nature 372, 159 (1994)
Hsu et al, Thin Solid Films
471, 140 (2005)
Question: How are metal catalyst particles
being drawn into carbon nanotubes?
Metal c Capillary forces?
Ag 124o
Cu 120o
Ni-C 145o
Co 140o
8. Absorption of droplets
Simulation shows Pd droplet
with c=120o
If the droplets are
sufficiently small:
cos c 1
0
rt r
they are be driven in by the
Laplace pressure associated
with their surface tension.
Schebarchov and SCH, Nano Letters 8 2253 – 2257 (2008)
9. Theory of absorption
Co has θc = 140° rt/rd =
0.45 < 0.77
Edgar, Hendy et al, Small (2011)
Schebarchov and Hendy, Nanoscale 3, 134 (2011)
10. Nanopipettery
• We can continue to fill tube by adding small droplets:
• We can also evacuate a tube by immersing it in a droplet
larger than the critical size threshold
Edgar, Hendy, Schebarchov and Tilley, Small 7, 737–774 (2011)
11. Implications for CNT growth
• Capillary absorption places upper bound on radius of
tube that can be grown from catalyst particle:
rt r cos c
e.g. c = 130o so r 1.6rt
• Just consistent with Nasibulin et al (2005) as Fe3C has
c = 140o i.e. r 1.3rt to avoid absorption
• Surface tension and adhesive forces are close to being
in balance
12. Energetics of graphitic cap
• Construct a simple expression model for CNT-catalyst
energy assuming spheres and spherical caps
R re r h
a
2
1 1
E wA 2 a 2 A
r re
r = radius of curvature of cap, A is area of cap
= line tension due to dangling or metal-carbon bonds
= elastic curvature modulus of cap
w= adhesion energy
Schebarchov, Hendy, Erterkin and Grossman PRL (2011)
13. Is lift-off trivial?
• Ni-C, R = 0.5 nm, re = 0, Lc 0.5 nm 3.1 nm
w w
E (eV)
h
Collapsed cap
stable
R (A)
c=90
o
c=140
o
R Lifted cap stable
R (A)
• Lift-off stable only for range of catalyst sizes
14. Reduced model
• Set =0 and use rigid catalyst approximation
2
1 1
E wA 2 A
r re
15. MD experiments
• Cap is slowly
stretched on uniform
catalyst particle
• Lift-off occurs for
some Rcrit that can
be compared with
the reduced model
Schebarchov, Hendy, Erterkin and Grossman PRL (2011)
16. MD experiments
• Simple model can be adjusted to fit MD simulations
• Simulations reveal importance of cap geometry and edge
termination
Schebarchov, Hendy, Erterkin and Grossman PRL (2011)
17. MD experiments
• Other cap geometries:
(9,0)
Schebarchov, Hendy, Erterkin and Grossman PRL (2011)
18. Conclusions
• Lift-off is a non-trivial process in CNT growth: catalyst-
graphite contact angle is a key parameter
• These ideas are consistent with the experimental
correlation between catalyst size and tube size
• Cap geometry is also important for details of lift-off
process; possible that chirality could be controlled
Schebarchov, Hendy, Erterkin and Grossman PRL (2011)
19. Acknowledgements
• Coworkers:
– Aruna Awasthi, Nicola Gaston,
Dmitri Schebarchov,
Nagesh Longanathan
• Collaborators:
– Theory: Barry Cox (Wollongong),
Elif Erterkin (UC Berkeley),
Jeff Grossman (MIT)
– Experiments:
Richard Tilley & Kirsten Edgar (VUW)