5,267 research outputs found
Mechanical, Electrical, and Magnetic Properties of Ni Nanocontacts
The dynamic deformation upon stretching of Ni nanowires as those formed with
mechanically controllable break junctions or with a scanning tunneling
microscope is studied both experimentally and theoretically. Molecular dynamics
simulations of the breaking process are performed. In addition, and in order to
compare with experiments, we also compute the transport properties in the last
stages before failure using the first-principles implementation of Landauer's
formalism included in our transport package ALACANT.Comment: 5 pages, 6 figure
Localized basis sets for unbound electrons in nanoelectronics
It is shown how unbound electron wave functions can be expanded in a suitably
chosen localized basis sets for any desired range of energies. In particular,
we focus on the use of gaussian basis sets, commonly used in first-principles
codes. The possible usefulness of these basis sets in a first-principles
description of field emission or scanning tunneling microscopy at large bias is
illustrated by studying a simpler related phenomenon: The lifetime of an
electron in a H atom subjected to a strong electric field.Comment: 6 pages, 5 figures, accepted by J. Chem. Phys. (http://jcp.aip.org/
Chronic Post-Concussion Neurocognitive Deficits. I. Relationship with White Matter Integrity.
We previously identified visual tracking deficits and associated degradation of integrity in specific white matter tracts as characteristics of concussion. We re-explored these characteristics in adult patients with persistent post-concussive symptoms using independent new data acquired during 2009-2012. Thirty-two patients and 126 normal controls underwent cognitive assessments and MR-DTI. After data collection, a subset of control subjects was selected to be individually paired with patients based on gender and age. We identified patients' cognitive deficits through pairwise comparisons between patients and matched control subjects. Within the remaining 94 normal subjects, we identified white matter tracts whose integrity correlated with metrics that indicated performance degradation in patients. We then tested for reduced integrity in these white matter tracts in patients relative to matched controls. Most patients showed no abnormality in MR images unlike the previous study. Patients' visual tracking was generally normal. Patients' response times in an attention task were slowed, but could not be explained as reduced integrity of white matter tracts relating to normal response timing. In the present patient cohort, we did not observe behavioral or anatomical deficits that we previously identified as characteristic of concussion. The recent cohort likely represented those with milder injury compared to the earlier cohort. The discrepancy may be explained by a change in the patient recruitment pool circa 2007 associated with an increase in public awareness of concussion
Strain-Based Analysis for Geometrically Nonlinear Beams: A Modal Approach
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97066/1/AIAA2012-1713.pd
Many-body excitations in tunneling current spectra of a few-electron quantum dot
Inherent asymmetry in the tunneling barriers of few-electron quantum dots
induces intrinsically different tunneling currents for forward and reverse
source-drain biases in the non-linear transport regime. Here we show that in
addition to spin selection rules, overlap matrix elements between many-body
states are crucial for the correct description of tunneling transmission
through quantum dots at large magnetic fields. Signatures of excited
(N-1)-electron states in the transport process through the N-electron system
are clearly identified in the measured transconductances. Our analysis clearly
confirms the validity of single-electron quantum transport theory in quantum
dots.Comment: 5 pages, 2 figure
Capas finas de ZrO2 para mejorar la resistencia química de los vidriados mates de calcio
La resistencia al ataque químico de vidriados cerámicos susceptibles al mismo, concretamente formulados a partir de una
frita mate de calcio, se ha mejorado depositando en la superficie una capa delgada de óxido de circonio. Un sol de circonio
estabilizado es el precursor de la capa, el cual se deposita mediante aerografía sobre el vidriado cocido y con un tratamiento
térmico suave (Tmax ≈ 400 ºC), es transformado en ZrO2 y anclado a la superficie. Los ensayos de resistencia química
demuestran que el vidriado protegido no sufre un ataque apreciable visualmente por parte del ácido clorhídrico concentrado,
condiciones en las que el mismo vidriado sin el recubrimiento resulta gravemente dañado. El precursor utilizado genera una
capa de óxido de circonio que protege el vidriado subyacente, de modo que el ataque químico por parte del ácido clorhídrico
queda confinado al entorno de las grietas y discontinuidades de la capa depositadaPeer reviewe
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