160 research outputs found
Crossover from coherent to incoherent dynamics in damped quantum systems
The destruction of quantum coherence by environmental influences is
investigated taking the damped harmonic oscillator and the dissipative
two-state system as prototypical examples. It is shown that the location of the
coherent-incoherent transition depends to a large degree on the dynamical
quantity under consideration.Comment: 4 Pages RevTex, to appear as Rapid Communication Phys. Rev.
Voltage-biased quantum wire with impurities
The bosonization technique to describe correlated electrons in a
one-dimensional quantum wire containing impurities is extended to include an
applied voltage source. The external reservoirs are shown to lead to a boundary
condition for the boson phase fields. We use the formalism to investigate the
channel conductance, electroneutrality, and charging effects.Comment: 4 pages REVTeX, incl one figure, to appear in Phys.Rev.Let
Abnormal directed migration of blood polymorphonuclear leukocytes in rheumatoid arthritis. Potential role in increased susceptibility to bacterial infections.
Rheumatoid arthritis (RA) patients are at higher risks of bacterial infection than healthy subjects. Polymorphonuclear leukocytes (PMN) are the first line of nonspecific cellular defence against these infections. We tested the hypothesis that abnormal directed migration of PMN may be one reason for the increased infection rate of RA patients. PMN migration was investigated in 68 peripheral blood samples of 15 RA patients compared with 64 samples of healthy controls in a novel whole blood in vitro membrane filter assay. The migration of PMNs from RA patients and controls was stimulated using the bacterial chemoattractant N-formyl-methionyl-leucyl-phenylalanine (fMLP). Unstimulated PMN migration of RA patients was increased compared with healthy controls as measured by the following parameters: (a) absolute number of migrant PMNs (1954+/-87 vs. 1238 +/-58 PMN/mm2), (b) percentage of PMNs migrated into the filter (total migration index, TMI) (28.6+/-0.9 vs. 24.0+/-0.8%), (c) the distance half the migrating PMNs had covered (distribution characteristic, DC) (22.6+/-1.1 vs. 16.1+/-0.6 mm) and (d) the product of TMI and DC (neutrophil migratory activity, NMA) (669.0+/-45.0 vs. 389.0+/-18.9). fMLP stimulated PMNs of RA patients showed defective migration compared to unstimulated samples as shown by (a) a reduced number of migrant PMNs (1799+/-93 PMN/mm2), (b) lower TMI (26.1+/-0.9%), (c) unremarkable altered distribution characteristic (22.9+/-0.8 mm) and (d) significant reduced migratory activity (600.0+/-30.0). Our data suggest that the high incidence of infections in RA patients may partly be caused by defective migratory activity of PMNs to bacterial chemoattractants as demonstrated by fMLP
Coulomb Charging at Large Conduction
We discuss the suppression of Coulomb charging effects on a small metallic
island coupled to an electrode by a tunnel junction. At high temperatures the
quantum corrections to the classical charging energy , where is
the island capacitance, are evaluated. At low temperatures the large quantum
fluctuations of the island charge cause a strong reduction of the effective
which is determined explicitly in the limit of a large tunneling
conductance.Comment: 4 page
Mikrokredite für Frauen: Instrument zur Akkumulation von symbolischem Kapital?! Empowermentmaßnahmen als Basis für genderspezifischen sozialen Wandel am Beispiel des Mikrokreditsektors in Mittelägypten
Im vorliegenden Beitrag wird die Möglichkeit
diskutiert, genderspezifischen sozialen Wandel
in Schwellen- und Entwicklungsländern
über Mikrokreditvergabesysteme anzustoßen.
Anhand einer in Mittelägypten durchgeführten
Studie mit mehrfach diskriminierten
Frauen wird gezeigt, wie Mikrokredite die
Akkumulation nicht nur von ökonomischem,
sondern vor allem auch von kulturellem und
sozialem Kapital im Bourdieu'schen Sinne unterstützen
können. Wenn in diesem Kontext
eine Veränderung des symbolischen Kapitals
gelingt, kann dies zu neuen Wahrnehmungs-,
Denk- und Handlungsschemata der
Beteiligten und zu Strukturveränderungen
auf der Makroebene führen. Die theoretische
Modellierung von genderspezifischem
sozialem Wandel erfolgt in diesem Artikel
entlang empirischer Daten, die von den Autorinnen
in Mittelägypten erhoben wurden
Is the direct observation of electronic coherence in electron transfer reactions possible?
The observability of electronic coherence in electron transfer reactions is
discussed. We show that under appropriate circumstances large-amplitude
oscillations can be found in the electronic occupation probabilities. The
initial preparation of the system is of crucial importance for this effect, and
we discuss conditions under which experiments detecting electronic coherence
should be feasible. The Feynman-Vernon influence functional formalism is
extended to examine more general and experimentally relevant initial
preparations. Analytical expressions and path integral quantum dynamics
simulations were developed to study the effects of various initial preparations
on the observability of electronic coherence.Comment: 14 pages, 9 figures, to be published in J. Chem. Phy
Electroneutrality and the Friedel sum rule in a Luttinger liquid
Screening in one-dimensional metals is studied for arbitrary
electron-electron interactions. It is shown that for finite-range interactions
(Luttinger liquid) electroneutrality is violated. This apparent inconsistency
can be traced to the presence of external screening gates responsible for the
effectively short-ranged Coulomb interactions. We also draw attention to the
breakdown of linear screening for wavevectors close to 2 K_f.Comment: 4 pages REVTeX, incl one figure, to appear in Phys.Rev.Let
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