13,984 research outputs found
Fusion of neurohypophyseal membranes in vitro
Freeze cleaving electron microscopy has shown that fusion of isolated secretory vesicles from bovine neurohypophyses was induced by Ca
2+ in micromolar concentrations. Mg
2+ and Sr
2+ were ineffective. Mg
2+ inhibited Ca
2+-induced fusion.
In suspensions containing secretory vesicles as well as sheets of cell membrane, release of vasopressin parallel to intervesicular fusion of secretory vesicles with sheets of cell membrane was observed after exposure to Ca
2+. Mg
2+ and Sr
2+ were ineffective in replacing Ca
2+ as trigger for fusion or vasopressin release.
Intervesicular fusion and exocytotic profiles were observed when isolated neurohypophyses or neurosecretosome were exposed to cold
Classical Concepts in Quantum Programming
The rapid progress of computer technology has been accompanied by a
corresponding evolution of software development, from hardwired components and
binary machine code to high level programming languages, which allowed to
master the increasing hardware complexity and fully exploit its potential.
This paper investigates, how classical concepts like hardware abstraction,
hierarchical programs, data types, memory management, flow of control and
structured programming can be used in quantum computing. The experimental
language QCL will be introduced as an example, how elements like irreversible
functions, local variables and conditional branching, which have no direct
quantum counterparts, can be implemented, and how non-classical features like
the reversibility of unitary transformation or the non-observability of quantum
states can be accounted for within the framework of a procedural programming
language.Comment: 11 pages, 4 figures, software available from
http://tph.tuwien.ac.at/~oemer/qcl.html, submitted for QS2002 proceeding
Performance and Fundamental Processes at Low Energy in a Two-Phase Liquid Xenon Dark Matter Detector
We extend the study of the performance of a prototype two-phase liquid xenon
WIMP dark matter detector to recoil energies below 20 keV. We demonstrate a new
method for obtaining the best estimate of the energies of events using a
calibrated sum of charge and light signals and introduce the corresponding
discrimination parameter, giving its mean value at 4 kV/cm for electron and
nuclear recoils up to 300 and 100 keV, respectively. We show that fluctuations
in recombination limit discrimination for most energies, and reveal an
improvement in discrimination below 20 keV due to a surprising increase in
ionization yield for low energy electron recoils. This improvement is crucial
for a high-sensitivity dark matter search.Comment: 4 pages, 6 figures, submitted to DM06 conference proceedings in Nucl
Phys
Occurrence and diversity of Xanthomonas campestris pv. campestris in vegetable brassica fields in Nepal
Black rot caused by Xanthomonas campestris pv. campestris was found in 28 sampled cabbage fields in five major cabbage-growing districts in Nepal in 2001 and in four cauliflower fields in two districts and a leaf mustard seed bed in 2003. Pathogenic X. campestris pv. campestris strains were obtained from 39 cabbage plants, 4 cauliflower plants, and 1 leaf mustard plant with typical lesions. Repetitive DNA polymerase chain reaction-based fingerprinting (rep-PCR) using repetitive extragenic palindromic, enterobacterial repetitive intergenic consensus, and BOX primers was used to assess the genetic diversity. Strains were also race typed using a differential series of Brassica spp. Cabbage strains belonged to five races (races 1, 4, 5, 6, and 7), with races 4, 1, and 6 the most common. All cauliflower strains were race 4 and the leaf mustard strain was race 6. A dendrogram derived from the combined rep-PCR profiles showed that the Nepalese X. campestris pv. campestris strains clustered separately from other Xanthomonas spp. and pathovars. Race 1 strains clustered together and strains of races 4, 5, and 6 were each split into at least two clusters. The presence of different races and the genetic variability of the pathogen should be considered when resistant cultivars are bred and introduced into regions in Nepal to control black rot of brassicas
Hydrogen atom in phase space. The Kirkwood-Rihaczek representation
We present a phase-space representation of the hydrogen atom using the
Kirkwood-Rikaczek distribution function. This distribution allows us to obtain
analytical results, which is quite unique because an exact analytical form of
the Wigner functions corresponding to the atom states is not known. We show how
the Kirkwood-Rihaczek distribution reflects properties of the hydrogen atom
wave functions in position and momentum representations.Comment: 5 pages (and 5 figures
Determination of electromagnetic medium from the Fresnel surface
We study Maxwell's equations on a 4-manifold where the electromagnetic medium
is described by an antisymmetric -tensor . In this setting,
the Tamm-Rubilar tensor density determines a polynomial surface of fourth order
in each cotangent space. This surface is called the Fresnel surface and acts as
a generalisation of the light-cone determined by a Lorentz metric; the Fresnel
surface parameterises electromagnetic wave-speed as a function of direction.
Favaro and Bergamin have recently proven that if has only a principal
part and if the Fresnel surface of coincides with the light cone for a
Lorentz metric , then is proportional to the Hodge star operator of
. That is, under additional assumptions, the Fresnel surface of
determines the conformal class of . The purpose of this paper is
twofold. First, we provide a new proof of this result using Gr\"obner bases.
Second, we describe a number of cases where the Fresnel surface does not
determine the conformal class of the original -tensor . For
example, if is invertible we show that and have
the same Fresnel surfaces.Comment: 23 pages, 1 figur
Stabilization and control system power sensitivity study
Stabilization and control system sensitivity to power-off failure rate studied by simulated missions using block power switchin
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