Abstract Revision

These are revisions made on abstracts of invited speakers to produce 80-word abstracts. Guide

Table compares original and revised, sentence by sentence to reveal how cutting done.


 
Original Revision

The structural response of systems at the nanoscales to external solicitations is crucial to establish the mechanical stability of nano-structured materials and devices. Can we predict the mechanical stability of nano-structured materials and devices?
 
Due to the prevalence of surface, many systems in this class show quite exotic properties compared to their bulk counterparts that may be exploited in innovative applications. Their large surface-to-volume ratio leads to exotic properties compared to bulk counterparts -- properties that may be exploited innovatively.
 
In this talk I will introduce our computational approach to study isolated nanoparticles under hydrostatic and uniaxial compression with no need of pressurizing media. In our computational approach, the external force (hydrostatic or uniaxial) directly acts on the electronic structure.
 
I will also show pressure induced structural transformations in group-IV (C, Si and Ge) nanoparticles highliting significant differences in the nucleation events and the transformation kinetics in dependence of material choice, size of the system and structure of the surface. For group-IV (C, Si, Ge) nanoparticles, the composition, size and surface structure all significantly affect pressure-induced nucleation and transformation kinetics.
 

Removing "wasted words."
Electronic-structure approaches offer powerful opportunities to understand, characterize, and engineer materials properties at the nanoscale, as long as great care is taken in validating their accuracy and in capturing in the simulations the complexity of realistic nanostructures. Electronic structure methods provide valuable insight into materials at nanoscale, provided the calculation is based on realistic structures and is accurate.
 
We illustrate this research paradigm with the case of carbon nanostructures, where vibrational spectroscopies provide a direct link with experimental observations. Case studies include dielectric screening in multiwall nanotubes, thermalization bottlenecks in interconnects, and covalent functionalizations as fluxional handles that control conductance. For carbon nanotubes, computed vibrational spectroscopies explain experiments on both dielectric screening in multiwall nanotubes and thermal bottlenecks to interconnect conduction.

Electronic noise due to thermal stripe switching
Electrons inside of a material can have their own phases and phase transitions. Electrons in a material can form phases with phase transitions.
 
In many new materials, interactions between electrons cause a "stripe" phase to occur, in which electrons are free to flow in one direction, but not in the others. For example, interactions between electrons can stabilize a "stripe" phase; electrons flow in any stripe but not between them.
 
While this phase has been observed in several materials, the disorder caused by dopant atoms can induce a domain structure, such that stripes run in different directions in different parts of the sample, making the phase exceedingly difficult to detect using conventional experimental techniques. Dopant-induced disorder can induce a domain structure, orienting the stripes differently in the sample, hindering conventional detection of the phase structure.
 
However, thermal fluctuations cause many stripe domains to switch back and forth, leading to characteristic noise and nonequilibrium effects that should be observable experimentally. However, thermal fluctuations induce switching between stripe domains, leading to characteristic noise [and other non-equilibrium effects.]
 
We discuss the consequences of such noise for experiments on resistivity, superfluid density, and scanning tunneling microscopy. This noise shows up in resistivity measurements and scanning tunneling microscopy observations.

Nonlinear Fano effect in self-assembled quantum dots
The signature of Fano effect is an asymmetric line in an absorption spectrum. The Fano interference effect appears when a discrete state of an atom or quantum dot becomes coupled with a continuum of states. In atoms, the coupling is due to the strong Auger processes. In self-assembled quantum dots, the coupling may also come from both the Auger effect and tunnelling [1,2,3]. This study develops a theory of Fano effect in the nonlinear regime, i.e. under the conditions of strong optical pumping. Our treatment is based on the equation of motion of the density matrix. Unlike the atomic systems, the optically-driven quantum dots coupled with a continuum reach a steady state due to the constant repopulation process. Interestingly, our theory shows that the Fano effect becomes greatly enhanced in the non-linear regime. In the linear regime, if the dot-continuum interaction is very weak, the optical detection of Fano effect is impossible because of the Heisenberg uncertainty principle. In other words, in the linear regime, a finite lifetime of an exciton creates an energy uncertainty and the Fano interference effect becomes invisible. However, in the nonlinear regime, the natural radiative broadening does not play the main role and even a very weak dot-continuum interaction becomes apparent. This nonlinear method can be used to detect very weak interactions between a two-level system and a continuum of states of any nature. The nonlinear Fano effect in self-organized quantum dots has been observed in the recent experiments performed in Munich and Edinburgh [3]. What had to go?
  1. Auger process: one time the process occurs it is described but not named.
  2. Remove naming of techniques and methods: optical pumping, density matrix, nonlinear regime, etc.
  3. Omit references.
     
    In atomic absorption spectra, the Fano effect is an asymmetric line arising from the interference between a discrete state and a continuum of states.
     
    Recently a similar effect has been seen in a InAs quantum dot capped with GaAs.
     
    Here the interference arise from competing absorption paths into conduction band: one from valence electron and other from valence level coupled to 2-dimensional valence band (from GaAs cap).
     
    More intense radiation enhances the second path, producing a clear Fano line shape.

 
 
 
 
 


One of the most fundamental properties of functional biopolymers such as enzymes is their ability to fold to a unique 3-dimensional native state. The functioning of biopolymers requires their folding to unique 3-dimensional structures.
 
Understanding how this foldability is determined for ribozymes is complicated by the role of counterions, in particular Mg2+, which are needed to compensate for the very large negative charge of the phosphate backbone. In, for example, ribozymes how do counterions, such as Mg2+, compensate for large negative charge of the phosphate backbone?
 
We will discuss recent x-ray scattering experiments designed to measure the strength of the effective potential between segments of DNA in a model system and discuss the results in terms of the solution of the Poisson-Boltzmann equation. < Recent Xray scattering experiments measure the strength of the effective potential between DNA segments enabling the development of a more realistic model
Current progress suggests that hydrogen-bond formation dominates RNA folding.
More broadly, extensions of folding studies may allow understanding of the formation of protein aggregates involved in illnesses (such as Parkinson's) connected with misfolding.

Your comments and suggestions are appreciated.
To cite this page:

<http://www.physics.ohio-state.edu/~wilkins/writing/Handouts/vgs/absrev.html>
[Sunday, 17-Dec-2017 20:14:43 EST]
Edited by: wilkins@mps.ohio-state.edu on Wednesday, 06-May-2009 11:22:25 EDT