3,683 research outputs found
Status of the isophot detector development
ISOPHOT is one of the four focal plane experiments of the European Space Agency's Infrared Space Observatory (ISO). Scheduled for a 1993 launch, it will operate extrinsic silicon and germanium photoconductors at low temperature and low background during the longer than 18 month mission. These detectors cover the wavelength range from 2.5 to 200 microns and are used as single elements and in arrays. A cryogenic preamplifier was developed to read out a total number of 223 detector pixels
A Geometric Theory of Diblock Copolymer Phases
We analyze the energetics of sphere-like micellar phases in diblock
copolymers in terms of well-studied, geometric quantities for their lattices.
We argue that the A15 lattice with Pm3n symmetry should be favored as the
blocks become more symmetric and corroborate this through a self-consistent
field theory. Because phases with columnar or bicontinuous topologies
intervene, the A15 phase, though metastable, is not an equilibrium phase of
symmetric diblocks. We investigate the phase diagram of branched diblocks and
find thatthe A15 phase is stable.Comment: 4 pages, RevTeX, 3 eps figures include
Nucleotide Sequences within the U5 Region of the Viral RNA Genome Are the Major Determinants for an Human Immunodeficiency Virus Type 1 to Maintain a Primer Binding Site Complementary to tRNAHis
AbstractThe initiation of reverse transcription of the human immunodeficiency virus type 1 (HIV-1) genome requires cellular tRNALys,3as a primer and occurs at a site in the viral RNA genome, designated as the primer binding site (PBS), which is complementary to the 3′-terminal 18 nucleotides of tRNALys,3. We previously described an HIV-1 virus [designated as HXB2(His-AC)], which contained a sequence within the U5 region complementary to the anticodon region of tRNAHisin addition to a PBS complementary to the 3′-terminal 18 nucleotides of the tRNAHis. That virus maintained a PBS complementary to tRNAHisafter extendedin vitroculture (Wakefieldet al., J. Virol.70, 966–975, 1996). In the present study, we report that subcloning a 200-base-pair DNA fragment encompassing the U5 and PBS regions from an integrated provirus of HXB2(His-AC) back into the wild-type genome (pHXB2) resulted in an infectious virus, designated as HXB2(His-AC-gac), which again stably maintained a PBS complementary to tRNAHis. DNA sequence analysis of the 200-base-pair region revealed only three nucleotide changes from HXB2(His-AC): a T-to-G change at nucleotide 174, a G-to-A change at nucleotide 181, and a T-to-C change at nucleotide 200. The new mutant virus replicated in CD4+Sup T1 cells similarly to the wild-type virus. Comparison of the nucleotide sequence of nucleocapsid gene of the wild-type and HXB2 (His-AC-gac) virus revealed no differences. Although we found numerous mutations in the reverse transcriptase gene in proviral clones derived from HXB2 (His-AC-gac), no common mutations were found among the 13 clones examined. Comparison of the virion-associated tRNAs of HXB2(His-AC-gac) with those of the wild type revealed that both viruses incorporated a similar subset of cellular tRNAs, with tRNALys,3being the predominant tRNA found within virions. There was no selective enrichment for tRNAHiswithin virions of HXB2(His-AC-gac) virus which selectively use tRNAHisto initiate reverse transcription. The results of these studies suggest that the U5 and PBS regions in the viral RNA genome are important determinants for HXB2(His-AC) viruses in the selective use of tRNAHisto initiate reverse transcription
Exotic smooth structures and symplectic forms on closed manifolds
We give a short proof of the (known) result that there are no Kaehler
structures on exotic tori. This yields a negative solution to a problem posed
by Benson and Gordon. W discuss the symplectic version of the problem and
analyze results which yield an evidence for the conjecture that there are no
symplectic structures on exotic tori.Comment: AMSLaTeX, 16 pages, a new version. A survey of the symplectic version
of the problem is adde
Relativistic Hamiltonians in many-body theories
We discuss the description of a many-body nuclear system using Hamiltonians
that contain the nucleon relativistic kinetic energy and potentials with
relativistic corrections. Through the Foldy-Wouthuysen transformation, the
field theoretical problem of interacting nucleons and mesons is mapped to an
equivalent one in terms of relativistic potentials, which are then expanded at
some order in 1/m_N. The formalism is applied to the Hartree problem in nuclear
matter, showing how the results of the relativistic mean field theory can be
recovered over a wide range of densities.Comment: 14 pages, uses REVTeX and epsfig, 3 postscript figures; a postscript
version of the paper is available by anonymous ftp at
ftp://carmen.to.infn.it/pub/depace/papers/951
The Real-Time Evolution of Sakurai's Star (V4334 Sgr) and other (V)LTP Objects
We report on the progress of our on-going campaign to monitor the evolution
of the VLTP objects V4334 Sgr and V605 Aql, as well as the suspected (V)LTP
object CK Vul. V4334 Sgr does not show signs of increased ionization compared
to our previous observations in 2004. We obtained the first radio detection of
V605 Aql, indicating a strong increase in radio flux since 1987. We also
present the first radio detection of CK Vul and discuss the expansion of the
material ejected during the 1670 event.Comment: 4 pages, 2 figures in eps format, IAU symp. 234: `Planetary Nebulae
in our Galaxy and Beyond', eds. M. J. Barlow & R. H. Mende
Exact 4He Spectral Function in a Semirealistic NN Potential Model
The spectral function of 4He is calculated with the Lorentz integral
transform method in a large energy and momentum range. The excitation spectrum
of the residual 3N-system is fully taken into account. The obtained spectral
function is used to calculate the quasi elastic longitudinal (e,e') response
R_l of 4He for q=300, 400, and 500 MeV/c. Comparison with the exact R_l shows a
rather sizeable disagreement except in the quasi elastic peak, where the
differences reduce to about 10% at q=500 MeV/c. It is shown as well that very
simple momentum distribution approximations for the spectral function provide
practically the same results for R_l as the exact spectral function.Comment: 7 pages, Latex (Revtex), 4 Postscript figures, to appear in Phys.
Rev.
Cognitive Status, Initiation of Lifestyle Changes and Medication Adherence after Acute Coronary Syndrome: TRACE-CORE (Transitions, Risks, and Actions in Coronary Events- Center for Outcomes Research and Education)
Background: Lifestyle changes and medication adherence are often recommended to patients after acute coronary syndrome (ACS) as secondary prevention strategies. However, the impact of cognitive impairment (CI) on these secondary prevention strategies following ACS has not been examined.
Methods: Cognitive status of 1374 patients with ACS from six hospitals in Massachusetts and Georgia enrolled in the ongoing TRACE-CORE (Transitions, Risks, and Actions in Coronary Events- Center for Outcomes Research and Education) study was assessed during hospitalization using the 41-point Telephone Interview for Cognitive Status (TICS). Information on recommendation and initiation of changes to diet, exercise, tobacco and alcohol use, stress, and cardiac rehabilitation attendance was collected through self-report one month after discharge. Medication adherence was assessed using the 8-item Morisky Scale. Among patients who reported receiving a recommendation for a lifestyle change, we modeled associations between CI and initiation of lifestyle changes and medication adherence, adjusting for demographics via logistic regression.
Results: Mean age of participants was 63.0±11.1 years, 67% were male and 79% white; 526 (38.3%) screened positive for CI (TICS score ≤30) during hospitalization. Screening positive for CI was associated with being older, male, non-white, and less educated. Patients with CI more frequently received a recommendation to reduce alcohol use (25% vs. 16% of drinkers, p=.003) but were referred less often to a cardiac rehabilitation program (45% vs. 61%, p=.01). Among patients referred to cardiac rehabilitation (n=743), those with CI at baseline were less likely to report rehabilitation attendance at 1-month (OR= 0.70, 95%CI 0.50-0.97) compared to patients with normal cognitive function. Initiation of other lifestyle changes and medication adherence did not differ by cognitive status.
Conclusions: CI is common among patients hospitalized for ACS and is associated with recommendation and initiation of certain lifestyle changes, making it an important factor to consider during the peri-discharge period
Light and electron microscopical observations of the effects of high-density lipoprotein on growth of Plasmodium falciparum in vitro
Author Posting. © Cambridge University Press, 2004. This article is posted here by permission of Cambridge University Press for personal use, not for redistribution. The definitive version was published in Parasitology 128 (2004): 577-584, doi:10.1017/S0031182004005025.Human serum high-density lipoprotein (HDL) is necessary and sufficient for the short-term maintenance of Plasmodium falciparum in in vitro culture. However, at high concentrations it is toxic to the parasite. A heat-labile component is apparently responsible for the stage-specific toxicity to parasites within infected erythrocytes 12–42 h after invasion, i.e. during trophozoite maturation. The effects of HDL on parasite metabolism (as determined by nucleic acid synthesis) are evident at about 30 h after invasion. Parasites treated with HDL show gross abnormalities by light and electron microscopy.Professor Hajduk was supported by NIH. Professor Day
was supported by a Research Leave Fellowship from The
Wellcome Trust. Dr Imrie and Ms Carter were supported
by Programme Grant funding awarded to Professor Day
from The Wellcome Trust. Dr Ferguson was supported by
an equipment grant from The Wellcome Trust
Relativistic Corrections to the Triton Binding Energy
The influence of relativity on the triton binding energy is investigated. The
relativistic three-dimensional version of the Bethe-Salpeter equation proposed
by Blankenbecler and Sugar (BbS) is used. Relativistic (non-separable)
one-boson-exchange potentials (constructed in the BbS framework) are employed
for the two-nucleon interaction. In a 34-channel Faddeev calculation, it is
found that relativistic effects increase the triton binding energy by about 0.2
MeV. Including charge-dependence (besides relativity), the final triton binding
energy predictions are 8.33 and 8.16 MeV for the Bonn A and B potential,
respectively.Comment: 25 pages of text (latex), 1 figure (not included, available upon
request
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