1,547 research outputs found
Design and qualification of the SEU/TD Radiation Monitor chip
This report describes the design, fabrication, and testing of the Single-Event Upset/Total Dose (SEU/TD) Radiation Monitor chip. The Radiation Monitor is scheduled to fly on the Mid-Course Space Experiment Satellite (MSX). The Radiation Monitor chip consists of a custom-designed 4-bit SRAM for heavy ion detection and three MOSFET's for monitoring total dose. In addition the Radiation Monitor chip was tested along with three diagnostic chips: the processor monitor and the reliability and fault chips. These chips revealed the quality of the CMOS fabrication process. The SEU/TD Radiation Monitor chip had an initial functional yield of 94.6 percent. Forty-three (43) SEU SRAM's and 14 Total Dose MOSFET's passed the hermeticity and final electrical tests and were delivered to LL
Cloning and characterization of the rat homologues of the Inhibitor of Apoptosis protein 1, 2, and 3 genes.
BACKGROUND: Inhibitor of Apoptosis (IAP) proteins are key intrinsic regulators of apoptosis induced by a variety of triggers. We isolated the rat Inhibitor of Apoptosis genes 1, 2 and 3 and characterized their tissue distribution and expression. RESULTS: Rat iap-1 encodes a protein of 67.1 kDa with 73 % and 89.2 % homology to human and mouse iap-1 respectively. Rat iap-2 encodes a protein of 66.7 kDa with 81.6 % and 89.3 % homology to human and mouse iap-2 respectively. Rat iap-3 encodes a protein of 56.1 kDa with 89.5 % and 93.1 % homology to human and mouse iap-3 respectively. We have generated rabbit polyclonal antibodies against all three rat IAP genes. Northern and Western blot analysis detected rat IAP transcripts and proteins in majority of the tissues examined. In addition, a shorter, alternatively spliced transcript corresponding to iap-2 was found in testes. CONCLUSIONS: We have identified three rat homologues of the IAP genes. The elevated expression of rat iap-1 and iap2 in testes suggests that these two genes play an important antiapoptotic role in spermatogenesis
Evidence for Nodal Superconductivity in LaFePO from Scanning SQUID Susceptometry
We measure changes in the penetration depth of the
K superconductor LaFePO. In the process scanning SQUID susceptometry is
demonstrated as a technique for accurately measuring {\it local}
temperature-dependent changes in , making it ideal for studying early
or difficult-to-grow materials. of LaFePO is found to vary linearly
with temperature from 0.36 to 2 K, with a slope of 14315 \AA/K,
suggesting line nodes in the superconducting order parameter. The linear
dependence up to is similar to the cuprate superconductors,
indicating well-developed nodes.Comment: 4 pages, 5 figure
Anisotropic Structure of the Order Parameter in FeSe0.45Te0.55 Revealed by Angle Resolved Specific Heat
The symmetry and structure of the superconducting gap in the Fe-based
superconductors are the central issue for understanding these novel materials.
So far the experimental data and theoretical models have been highly
controversial. Some experiments favor two or more constant or nearly-constant
gaps, others indicate strong anisotropy and yet others suggest gap zeros
("nodes"). Theoretical models also vary, suggesting that the absence or
presence of the nodes depends quantitatively on the model parameters. An
opinion that has gained substantial currency is that the gap structure, unlike
all other known superconductors, including cuprates, may be different in
different compounds within the same family. A unique method for addressing this
issue, one of the very few methods that are bulk and angle-resolved, calls for
measuring the electronic specific heat in a rotating magnetic field, as a
function of field orientation with respect to the crystallographic axes. In
this Communication we present the first such measurement for an Fe-based
high-Tc superconductor (FeBSC). We observed a fourfold oscillation of the
specific heat as a function of the in-plane magnetic field direction, which
allowed us to identify the locations of the gap minima (or nodes) on the Fermi
surface. Our results are consistent with the expectations of an extended s-wave
model with a significant gap anisotropy on the electron pockets and the gap
minima along the \Gamma M (or Fe-Fe bond) direction.Comment: 32 pages, 7 figure
The Kaon-Photoproduction Of Nucleons In The Quark Model
In this paper, we develop a general framework to study the
meson-photoproductions of nucleons in the chiral quark model. The S and U
channel resonance contributions are expressed in terms of the
Chew-Goldberger-Low-Nambu (CGLN) amplitudes. The kaon-photoproduction
processes, , , and , are calculated. The initial results show that the quark
model provides a much improved description of the reaction mechanism for the
kaon-photoproductions of the nucleon with less parameters than the traditional
phenomenological approaches.Comment: 25 pages, 9 postscript figures can be obtained from the author
Modelling life cycle related and individual shape variation in biological specimens
The main purpose of this research is to develop methods for automatic
identification of biological specimens in digital photographs and drawings
held in a database. Incorporation of taxonomic drawings into a visual indexing
system has not been attempted to date. Diatoms are a single cell microscopic
algae that provide a particularly suitable case study. Identification of
diatoms is a challenging task due to the huge number of the species, blurred
boundaries between species, and life cycle related shape changes. A novel
model based on principal curves representing the life cycle related shape
variation of a number of diatom species has been developed. Our model
is suitable for reconstruction purposes, allowing us to produce drawings of a
variety of diatom shapes, thus providing a link between the photographs and
drawings. We present the classification results of photographed and drawn
specimens based on the model and compare our results to another recent system
for diatom identification. Finally, given a diatom specimen, we are able
not only to identify the species it belongs to but also to pinpoint the stage in
the life cycle it represents
Interplay between magnetism and superconductivity and appearance of a second superconducting transition in alpha-FeSe at high pressure
We synthesized tetragonal alpha-FeSe by melting a powder mixture of iron and
selenium at high pressure. Subsequent annealing at normal pressure results in
removing traces of hexagonal beta- FeSe, formation of a rather sharp transition
to superconducting state at Tc ~ 7 K, and the appearance of a magnetic
transition near Tm = 120 K. Resistivity and ac-susceptibility were measured on
the annealed sample at hydrostatic pressure up to 4.5 GPa. A magnetic
transition visible in ac-susceptibility shifts down under pressure and the
resistive anomaly typical for a spin density wave (SDW) antiferromagnetic
transition develops near the susceptibility anomaly. Tc determined by the
appearance of a diamagnetic response in susceptibility, increases linearly
under pressure at a rate dTc/dP = 3.5 K/GPa. Below 1.5 GPa, the resistive
superconducting transition is sharp; the width of transition does not change
with pressure; and, Tc determined by a peak in drho/dT increases at a rate ~
3.5 K/GPa. At higher pressure, a giant broadening of the resistive transition
develops. This effect cannot be explained by possible pressure gradients in the
sample and is inherent to alpha-FeSe. The dependences drho(T)/dT show a
signature for a second peak above 3 GPa which is indicative of the appearance
of another superconducting state in alpha-FeSe at high pressure. We argue that
this second superconducting phase coexists with SDW antiferromagnetism in a
partial volume fraction and originates from pairing of charge carriers from
other sheets of the Fermi surface
Building shape and texture models of diatoms for analysis and synthesis of drawings and identification
We describe tools for automatic identification of diatoms by comparing their photographs with
other photographs and drawings, via a model. Identification of diatoms, i.e. assigning a new specimen
to one of the known species, has applications in many disciplines, including ecology, paleoecology
and forensic science. The model we build represents life cycle and natural variation of both
external shape and internal texture over multiple species and is based on principal curves. The model
is also suitable for automatically producing drawings of diatoms at any stage of their life cycle development.
Similar drawings are traditionally used for diatom identification, and encapsulate visually
salient diatom features. In this article we describe the methods used to analyse photographs and
drawings, present our model of diatom shape and texture variation, and illustrate our approach with a
collection of drawings synthesised from our model and derived from example photographs. Finally,
we present the results of identification experiments using photographs and drawings
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