775 research outputs found
The Case of Professor James W. Silver
Article about attempts by the legislature and board of trustees to try and remove James Silver from his job at the University of Mississippi; Source: AAUP Bulletinhttps://egrove.olemiss.edu/jws_clip/1030/thumbnail.jp
A Nonlinear Adiabatic Theorem for Coherent States
We consider the propagation of wave packets for a one-dimensional nonlinear
Schrodinger equation with a matrix-valued potential, in the semi-classical
limit. For an initial coherent state polarized along some eigenvector, we prove
that the nonlinear evolution preserves the separation of modes, in a scaling
such that nonlinear effects are critical (the envelope equation is nonlinear).
The proof relies on a fine geometric analysis of the role of spectral
projectors, which is compatible with the treatment of nonlinearities. We also
prove a nonlinear superposition principle for these adiabatic wave packets.Comment: 21 pages, no figur
Energy landscape - a key concept for the dynamics of glasses and liquids
There is a growing belief that the mode coupling theory is the proper
microscopic theory for the dynamics of the undercooled liquid above a critical
temperature T_c. In addition, there is some evidence that the system leaves the
saddlepoints of the energy landscape to settle in the valleys at this critical
temperature. Finally, there is a microscopic theory for the entropy at the
calorimetric glass transition T_g by Mezard and Parisi, which allows to
calculate the Kauzmann temperature from the atomic pair potentials.
The dynamics of the frozen glass phase is at present limited to
phenomenological models. In the spirit of the energy landscape concept, one
considers an ensemble of independent asymmetric double-well potentials with a
wide distribution of barrier heights and asymmetries (ADWP or Gilroy-Phillips
model). The model gives an excellent description of the relaxation of glasses
up to about T_g/4. Above this temperature, the interaction between different
relaxation centers begins to play a role. One can show that the interaction
reduces the number of relaxation centers needed to bring the shear modulus down
to zero by a factor of three.Comment: Contribution to the III Workshop on Nonequilibrium Phenomena in
Supercooled Fluids, Glasses and Amorphous Materials, 22-27 September 2002,
Pisa; 14 pages, 3 figures; Version 3 takes criticque at Pisa into account;
final version 4 will be published in J.Phys.: Condens.Matte
Equilibration times in numerical simulation of structural glasses: Comparing parallel tempering and conventional molecular dynamics
Generation of equilibrium configurations is the major obstacle for numerical
investigation of the slow dynamics in supercooled liquid states. The parallel
tempering (PT) technique, originally proposed for the numerical equilibration
of discrete spin-glass model configurations, has recently been applied in the
study of supercooled structural glasses. We present an investigation of the
ability of parallel tempering to properly sample the liquid configuration space
at different temperatures, by mapping the PT dynamics into the dynamics of the
closest local potential energy minima (inherent structures). Comparing the PT
equilibration process with the standard molecular dynamics equilibration
process we find that the PT does not increase the speed of equilibration of the
(slow) configurational degrees of freedom.Comment: 5 pages, 3 figure
Association of Circulating Renin and Aldosterone With Osteocalcin and Bone Mineral Density in African Ancestry Families
Hypertension is associated with accelerated bone loss, and the renin-angiotensin-aldosterone system is a key regulator of blood pressure. Although components of this system are expressed in human bone cells, studies in humans are sparse. Thus, we studied the association of circulating renin and aldosterone with osteocalcin and bone mineral density. We recruited 373 African ancestry family members without regard to health status from 6 probands (mean family size: 62 and relative pairs: 1687). Participants underwent a clinical examination, dual-energy x-ray absorptiometry, and quantitative computed tomographic scans. Renin activity, aldosterone concentration, and osteocalcin were measured in fasting blood samples. Aldosterone/renin ratio was calculated as aldosterone concentration/renin activity. All models were analyzed using pedigree-based variance components methods. Full models included adjustment for age, sex, body composition, comorbidities, lifestyle factors, blood pressure, and antihypertensive medication. Higher renin activity was significantly associated with lower total osteocalcin and with higher trabecular bone mineral density (both P<0.01). There were also significant genetic correlations between renin activity and whole-body bone mineral density. There were no associations with aldosterone concentration in any model and results for aldosterone/renin ratio were similar to those for renin activity. This is the first study to report a significant association between renin activity and a marker of bone turnover and bone mineral density in generally healthy individuals. Also, there is evidence for significant genetic pleiotropy and, thus, there may be a shared biological mechanism underlying both the renin-angiotensin-aldosterone system and bone metabolism that is independent of hypertension
Indium phosphide photonic circuits on silicon electronics
The intimate integration of photonics and electronics in transceivers facilitates energy-efficiency, bandwidth acceleration and a route to radical miniaturization. We present and implement a wafer-to-wafer integration method which combines electronic and photonic foundry technologies
Time-temperature superposition in viscous liquids
Dielectric relaxation measurements on supercooled triphenyl phosphite show
that at low temperatures time-temperature superposition (TTS) is accurately
obeyed for the primary (alpha) relaxation process. Measurements on 6 other
molecular liquids close to the calorimetric glass transition indicate that TTS
is linked to an high-frequency decay of the alpha loss, while
the loss peak width is nonuniversal.Comment: 4 page
Adaptation of the Structured Clinical Interview for DSM-IV Disorders for assessing depression in women during pregnancy and post-partum across countries and cultures
BackgroundTo date, no study has used standardised diagnostic assessment procedures to determine whether rates of perinatal depression vary across cultures.AimsTo adapt the Structured Clinical Interview for DSMâIV Disorders (SCID) for assessing depression and other non-psychotic psychiatric illness perinatally and to pilot the instrument in different centres and cultures.MethodAssessments using the adapted SCID and the Edinburgh Postnatal Depression Scale were conducted during the third trimester of pregnancy and at 6 months postpartum with 296 women from ten sites in eight countries. Point prevalence rates during pregnancy and the postnatal period and adjusted 6-month period prevalence rates were computed for caseness, depression and major depression.ResultsThe third trimester and 6-month point prevalence rates for perinatal depression were 6.9% and 8.0%, respectively. Postnatal 6-month period prevalence rates for perinatal depression ranged from 2.1% to 31.6% across centres and there were significant differences in these rates between centres.ConclusionsStudy findings suggest that the SCID was successfully adapted for this context. Further research on determinants of differences inprevalence of depression across cultures isneeded
Application of Terahertz Radiation to the Detection of Corrosion under the Shuttle's Thermal Protection System
There is currently no method for detecting corrosion under Shuttle tiles except for the expensive process of tile removal and replacement; hence NASA is investigating new NDE methods for detecting hidden corrosion. Time domain terahertz radiation has been applied to corrosion detection under tiles in samples ranging from small lab samples to a Shuttle with positive results. Terahertz imaging methods have been able to detect corrosion at thicknesses of 5 mils or greater under 1" thick Shuttle tiles and 7-12 mils or greater under 2" thick Shuttle tiles
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