38,627 research outputs found
Dynamical control of quantum state transfer within hybrid open systems
We analyze quantum state-transfer optimization within hybrid open systems,
from a "noisy" (write-in) qubit to its "quiet" counterpart (storage qubit).
Intriguing interplay is revealed between our ability to avoid bath-induced
errors that profoundly depend on the bath-memory time and the limitations
imposed by leakage out of the operational subspace. Counterintuitively, under
no circumstances is the fastest transfer optimal (for a given transfer energy)
Variability of the Vela Pulsar-wind Nebula Observed with Chandra
The observations of the pulsar-wind nebula (PWN) around the Vela pulsar with
the Advanced CCD Imaging Spectrometer aboard the Chandra X-ray Observatory,
taken on 2000 April 30 and November 30, reveal its complex morphology
reminiscent of that of the Crab PWN. Comparison of the two observations shows
changes up to 30% in the surface brightness of the PWN features. Some of the
PWN elements show appreciable shifts, up to a few arcseconds (about 10^{16}
cm), and/or spectral changes. To elucidate the nature of the observed
variations, further monitoring of the Vela PWN is needed.Comment: 7 pages (incl. 3 embedded PS figures), AASTEX, uses emulateapj5.sty.
Submitted to ApJ Lett. For a high-resolution color PS image of Figure 3 (6.3
Mby), see http://www.astro.psu.edu/users/divas/velaneb_fig3.p
Zeno and anti-Zeno effects for quantum Brownian motion
In this paper we investigate the occurrence of the Zeno and anti-Zeno effects
for quantum Brownian motion. We single out the parameters of both the system
and the reservoir governing the crossover between Zeno and anti-Zeno dynamics.
We demonstrate that, for high reservoir temperatures, the short time behaviour
of environment induced decoherence is the ultimate responsible for the
occurrence of either the Zeno or the anti-Zeno effect. Finally we suggest a way
to manipulate the decay rate of the system and to observe a controlled
continuous passage from decay suppression to decay acceleration using
engineered reservoirs in the trapped ion context .Comment: 4 pages, 1 figure. v2: Replaced with the published version. Minor
modifications in the text and titl
Pattern formation during de novo assembly of the Arabidopsis shoot meristem
Most multicellular organisms have a capacity to regenerate tissue after wounding. Few, however, have the ability to regenerate an entire new body from adult tissue. Induction of new shoot meristems from cultured root explants is a widely used, but poorly understood, process in which apical plant tissues are regenerated from adult somatic tissue through the de novo formation of shoot meristems. We characterize early patterning during de novo development of the Arabidopsis shoot meristem using fluorescent reporters of known gene and protein activities required for shoot meristem development and maintenance. We find that a small number of progenitor cells initiate development of new shoot meristems through stereotypical stages of reporter expression and activity of CUP-SHAPED COTYLEDON 2 (CUC2), WUSCHEL (WUS), PIN-FORMED 1 (PIN1), SHOOT-MERISTEMLESS (STM), FILAMENTOUS FLOWER (FIL, also known as AFO), REVOLUTA (REV), ARABIDOPSIS THALIANA MERISTEM L1 LAYER (ATML1) and CLAVATA 3 (CLV3). Furthermore, we demonstrate a functional requirement for WUS activity during de novo shoot meristem initiation. We propose that de novo shoot meristem induction is an easily accessible system for the study of patterning and self-organization in the well-studied model organism Arabidopsis
Spontaneous soliton formation and modulational instability in Bose-Einstein condensates
The dynamics of an elongated attractive Bose-Einstein condensate in an
axisymmetric harmonic trap is studied. It is shown that density fringes caused
by self-interference of the condensate order parameter seed modulational
instability. The latter has novel features in contradistinction to the usual
homogeneous case known from nonlinear fiber optics. Several open questions in
the interpretation of the recent creation of the first matter-wave bright
soliton train [Strecker {\it et al.} Nature {\bf 417} 150 (2002)] are
addressed. It is shown that primary transverse collapse, followed by secondary
collapse induced by soliton--soliton interactions, produce bursts of hot atoms
at different time scales.Comment: 4 pages, 3 figures. Phys. Rev. Lett. in pres
Optimal Dynamical Decoherence Control of a Qubit
A theory of dynamical control by modulation for optimal decoherence reduction
is developed. It is based on the non-Markovian Euler-Lagrange equation for the
energy-constrained field that minimizes the average dephasing rate of a qubit
for any given dephasing spectrum.Comment: 6 pages, including 2 figures and an appendi
A new method of observing weak extended x-ray sources with RHESSI
We present a new method, fan-beam modulation, for observing weak extended
x-ray sources with the Reuven Ramaty High-Energy Solar Spectroscopic Imager
(RHESSI). This space-based solar x-ray and gamma-ray telescope has much greater
sensitivity than previous experiments in the 3-25 keV range, but is normally
not well suited to detecting extended sources since their signal is not
modulated by RHESSI's rotating grids. When the spacecraft is offpointed from
the target source, however, the fan-beam modulation time-modulates the
transmission by shadowing resulting from exploiting the finite thickness of the
grids. In this paper we detail how the technique is implemented and verify its
consistency with sources with clear known signals that have occurred during
RHESSI offpointing: microflares and the Crab Nebula. In both cases the results
are consistent with previous and complementary measurements. Preliminary work
indicates that this new technique allows RHESSI to observe the integrated hard
x-ray spectrum of weak extended sources on the quiet Sun.Comment: Publishe
Metabolism impacts upon Candida immunogenicity and pathogenicity at multiple levels
Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved. Open Access funded by Wellcome TrustNon peer reviewedPublisher PD
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