482 research outputs found
Effect of phase relaxation on quantum superpositions in complex collisions
We study the effect of phase relaxation on coherent superpositions of
rotating clockwise and anticlockwise wave packets in the regime of strongly
overlapping resonances of the intermediate complex. Such highly excited
deformed complexes may be created in binary collisions of heavy ions, molecules
and atomic clusters. It is shown that phase relaxation leads to a reduction of
the interference fringes, thus mimicking the effect of decoherence. This
reduction is crucial for the determination of the phase--relaxation width from
the data on the excitation function oscillations in heavy--ion collisions and
bimolecular chemical reactions. The difference between the effects of phase
relaxation and decoherence is discussed.Comment: Extended revised version; 9 pages and 3 colour ps figure
Review of the k-Body Embedded Ensembles of Gaussian Random Matrices
The embedded ensembles were introduced by Mon and French as physically more
plausible stochastic models of many--body systems governed by one--and
two--body interactions than provided by standard random--matrix theory. We
review several approaches aimed at determining the spectral density, the
spectral fluctuation properties, and the ergodic properties of these ensembles:
moments methods, numerical simulations, the replica trick, the eigenvector
decomposition of the matrix of second moments and supersymmetry, the binary
correlation approximation, and the study of correlations between matrix
elements.Comment: Final version. 29 pages, 4 ps figures, uses iopart.st
Measures Matter: Scales for Adaptation, Cultural Distance, and Acculturation Orientation Revisited
Building upon existing measures, four new brief acculturation scales are presented, measuring sociocultural adaptation, psychological adaptation, perceived cultural distance, and acculturation orientation. Following good scale reliability in initial samples, the English scales were translated into nine different languages (Chinese, French, German, Italian, Japanese, Portuguese, Spanish, Thai, and Turkish). The translated scales were administered to a large sample of sojourners (N = 1,929), demonstrating good reliability and adequate structural equivalence across languages. In line with existing theory, sociocultural adaptation and psychological adaptation were positively correlated, and showed a negative association with perceived cultural distance. General measures of well-being were correlated with adaptation and distance, with better adaptation relating to higher well-being, and more distance relating to lower well-being. Acculturation orientation toward the home and host culture were measured separately and a weak negative correlation was found between the two, supporting their independence. Arguing against dichotomization, these subscales were analyzed as continuous variables. Regression analysis showed sojourners to be better adapted, if they were oriented more toward the host culture and less toward the home culture. These new scales are proposed as alternatives to existing measures
Macroscopic quantum superpositions in highly-excited strongly-interacting many-body systems
We demonstrate a break-down in the macroscopic (classical-like) dynamics of
wave-packets in complex microscopic and mesoscopic collisions. This break-down
manifests itself in coherent superpositions of the rotating clockwise and
anticlockwise wave-packets in the regime of strongly overlapping many-body
resonances of the highly-excited intermediate complex. These superpositions
involve many-body configurations so that their internal interactive
complexity dramatically exceeds all of those previously discussed and
experimentally realized. The interference fringes persist over a time-interval
much longer than the energy relaxation-redistribution time due to the
anomalously slow phase randomization (dephasing). Experimental verification of
the effect is proposed.Comment: Title changed, few changes in the abstract and in the main body of
the paper, and changes in the font size in the figure. Uses revTex4, 4 pages,
1 ps figur
Neurology
Contains reports on eight research projects.U.S. Navy (Office of Naval Research (Nonr-1841(70))U. S. Public Health Service (MH-06175-02)U. S. Air Force (AF49(638)-1313)U. S. Public Health Service (B-3055-4)U. S. Public Health Service (B-3090-4
Periodic Chaotic Billiards: Quantum-Classical Correspondence in Energy Space
We investigate the properties of eigenstates and local density of states
(LDOS) for a periodic 2D rippled billiard, focusing on their quantum-classical
correspondence in energy representation. To construct the classical
counterparts of LDOS and the structure of eigenstates (SES), the effects of the
boundary are first incorporated (via a canonical transformation) into an
effective potential, rendering the one-particle motion in the 2D rippled
billiard equivalent to that of two-interacting particles in 1D geometry. We
show that classical counterparts of SES and LDOS in the case of strong chaotic
motion reveal quite a good correspondence with the quantum quantities. We also
show that the main features of the SES and LDOS can be explained in terms of
the underlying classical dynamics, in particular of certain periodic orbits. On
the other hand, statistical properties of eigenstates and LDOS turn out to be
different from those prescribed by random matrix theory. We discuss the quantum
effects responsible for the non-ergodic character of the eigenstates and
individual LDOS that seem to be generic for this type of billiards with a large
number of transverse channels.Comment: 13 pages, 18 figure
Ground-State Magnetization for Interacting Fermions in a Disordered Potential : Kinetic Energy, Exchange Interaction and Off-Diagonal Fluctuations
We study a model of interacting fermions in a disordered potential, which is
assumed to generate uniformly fluctuating interaction matrix elements. We show
that the ground state magnetization is systematically decreased by off-diagonal
fluctuations of the interaction matrix elements. This effect is neglected in
the Stoner picture of itinerant ferromagnetism in which the ground-state
magnetization is simply determined by the balance between ferromagnetic
exchange and kinetic energy, and increasing the interaction strength always
favors ferromagnetism. The physical origin of the demagnetizing effect of
interaction fluctuations is the larger number of final states available for
interaction-induced scattering in the lower spin sectors of the Hilbert space.
We analyze the energetic role played by these fluctuations in the limits of
small and large interaction . In the small limit we do second-order
perturbation theory and identify explicitly transitions which are allowed for
minimal spin and forbidden for higher spin. These transitions then on average
lower the energy of the minimal spin ground state with respect to higher spin.
For large interactions we amplify on our earlier work [Ph. Jacquod and A.D.
Stone, Phys. Rev. Lett. 84, 3938 (2000)] which showed that minimal spin is
favored due to a larger broadening of the many-body density of states in the
low-spin sectors. Numerical results are presented in both limits.Comment: 35 pages, 24 figures - final, shortened version, to appear in
Physical Review
Foxa1 Reduces Lipid Accumulation in Human Hepatocytes and Is Down-Regulated in Nonalcoholic Fatty Liver
Triglyceride accumulation in nonalcoholic fatty liver (NAFL) results from unbalanced lipid metabolism which, in the liver, is controlled by several transcription factors. The Foxa subfamily of winged helix/forkhead box (Fox) transcription factors comprises three members which play important roles in controlling both metabolism and homeostasis through the regulation of multiple target genes in the liver, pancreas and adipose tissue. In the mouse liver, Foxa2 is repressed by insulin and mediates fasting responses. Unlike Foxa2 however, the role of Foxa1 in the liver has not yet been investigated in detail. In this study, we evaluate the role of Foxa1 in two human liver cell models, primary cultured hepatocytes and HepG2 cells, by adenoviral infection. Moreover, human and rat livers were analyzed to determine Foxa1 regulation in NAFL. Results demonstrate that Foxa1 is a potent inhibitor of hepatic triglyceride synthesis, accumulation and secretion by repressing the expression of multiple target genes of these pathways (e.g., GPAM, DGAT2, MTP, APOB). Moreover, Foxa1 represses the fatty acid transporter protein FATP2 and lowers fatty acid uptake. Foxa1 also increases the breakdown of fatty acids by inducing peroxisomal fatty acid β-oxidation and ketone body synthesis. Finally, Foxa1 is able to largely up-regulate UCP1, thereby dissipating energy and consistently decreasing the mitochondria membrane potential. We also report that human and rat NAFL have a reduced Foxa1 expression, possibly through a protein kinase C-dependent pathway. We conclude that Foxa1 is an antisteatotic factor that coordinately tunes several lipid metabolic pathways to block triglyceride accumulation in hepatocytes. However, Foxa1 is down-regulated in human and rat NAFL and, therefore, increasing Foxa1 levels could protect from steatosis. Altogether, we suggest that Foxa1 could be a novel therapeutic target for NAFL disease and insulin resistance
Random matrix ensembles with random interactions: Results for EGUE(2)-SU(4)
We introduce in this paper embedded Gaussian unitary ensemble of random
matrices, for fermions in number of single particle orbits,
generated by random two-body interactions that are SU(4) scalar, called
EGUE(2)-SU(4). Here the SU(4) algebra corresponds to Wigner's supermultiplet
SU(4) symmetry in nuclei. Formulation based on Wigner-Racah algebra of the
embedding algebra allows for
analytical treatment of this ensemble and using this analytical formulas are
derived for the covariances in energy centroids and spectral variances. It is
found that these covariances increase in magnitude as we go from EGUE(2) to
EGUE(2)-\cs to EGUE(2)-SU(4) implying that symmetries may be responsible for
chaos in finite interacting quantum systems.Comment: 11 pages, 2 figures, some formulas in Table 1 corrected, Table 1
changed to Table 1 and 2, Fig. 2 modifie
Plasma protein binding of furosemide in kidney transplant patients
The present investigation was undertaken in order to determine the in vivo plasma protein binding of furosemide in kidney transplant patients and its possible consequence on furosemide effect. Using an equilibrium dialysis technique, serial plasma samples of furosemide taken after intravenous administration were dialyzed against an equal volume of isotonic Krebs Ringer bicarbonate buffer (pH7.4). Dialysis was performed at 37°C for 5 hr, and furosemide concentrations (total as well as free) were analyzed by HPLC using fluorescence detection. It was observed that kidney transplant patients on concomitant sulfisoxazole treatment (KT+) had a significantly greater value for percent free of furosemide as compared to transplant patients not on sulfisoxazole (KT-) (4.4±0.8 for KT+ vs. 1.7±0.3% for KT- ; p<0.01) as well as to healthy volunteers (4.4±0.8 for KT+ vs. 1.2±0.2% for controls ; p<0.01). In addition, kidney transplant patients not on concomitant sulfisoxazole treatment had a significantly higher value for percent free of furosemide with respect to healthy volunteers (p<0.05). Nonlinear plasma protein binding was also observed for one patient, who had values for percent free of furosemide ranging from 1.3 to 12.9%. However, no significant correlation was found between the fraction of the dose excreted unchanged in the urine and percent free of furosemide .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45028/1/10928_2005_Article_BF01062547.pd
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