634 research outputs found
Low-energy particle radiation environment at synchronous altitude
The degradation of thermal control coatings of satellites due to the effects of low energy charged particles in the space environment is discussed. Data obtained from ATS-5 satellite measurement of proton and electron fluxes are presented. The variations in electron density, proton density, and magnetic activity are presented to show correlations which exist between these space factors
Alpha-decay Rates of Yb and Gd in Solar Neutrino Detectors
The -decay rates for the nuclides Yb
and Gd have been estimated from transmission probabilities
in a systematic -nucleus potential and from an improved fit to
-decay rates in the rare-earth mass region. Whereas -decay of
Gd in natural gadolinium is a severe obstacle for the use of gadolinium
as a low-energy solar-neutrino detector, we show that
-decay does not contribute significantly to the background in a
ytterbium detector. An extremely long -decay lifetime of Yb
is obtained from calculation, which may be close to the sensitivity limit in a
low-background solar neutrino detector.Comment: 12 pages, 1 figure; An author name was correcte
Distribution and abundance of long-finned pilot whales in the North Atlantic, estimated from NASS-87 and NASS-89 data
During the summers of 1987 and 1989, large scale transect surveys were conducted
throughout the North Atlantic by several national agencies in Denmark (off Greenland),
Faroe Islands, Iceland, Norway and Spain (North Atlantic Sightings Surveys, NASS-87 and
NASS-89). This paper analyses the pilot whale (Globicephala melas) survey data collected by
three Icelandic and one Faroese survey vessel in 1987, and four Icelandic, one Faroese and
one Spanish vessel in 1989. Norwegian survey vessels operated north and east of this area in
both years, but only five groups (three primary sightings) were observed in 1989 and none in
1987. Furthermore, no sightings were made in the area north and northeast of Iceland, thus
indicating that the joint surveys covered the northernmost areas of pilot whale distribution
east of 42°W. The area further to the west was not covered in either survey. The coastal
European waters between 42-52°N were covered by the Spanish vessel in 1989. Sightings
made in 1989 by the Icelandic vessels tended to be at the southernmost boundaries of the
survey area.
The present data were examined with respect to several potential stratification factors,
namely geographic block, Beaufort (i.e. wind speed), vessel and school size, but sample size
precluded stratification by all these factors simultaneously. The encounter rate was generally
lower in the 1987 survey than in 1989, but the difference was not statistically significant. The
total estimate for the 1989 survey, covering a wider area and further to the south than in 1987,
was 778,000 (CV=0.295). This is regarded as the best available estimate of the total stock of
long-finned pilot whales in the northeastern North Atlantic Ocean, although small numbers
occur outside the NASS survey areas. The paper discusses potential biases in the abundance
estimates, and the problems of estimating pilot whale abundance from sightings data
Sensitivities of Low Energy Reactor Neutrino Experiments
The low energy part of the reactor neutrino spectra has not been
experimentally measured. Its uncertainties limit the sensitivities in certain
reactor neutrino experiments. The origin of these uncertainties are discussed,
and the effects on measurements of neutrino interactions with electrons and
nuclei are studied. Comparisons are made with existing results. In particular,
the discrepancies between previous measurements with Standard Model
expectations can be explained by an under-estimation of the low energy reactor
neutrino spectra. To optimize the experimental sensitivities, measurements for
\nuebar-e cross-sections should focus on events with large (1.5 MeV)
recoil energy while those for neutrino magnetic moment searches should be based
on events 100 keV. The merits and attainable accuracies for
neutrino-electron scattering experiments using artificial neutrino sources are
discussed.Comment: 25 pages, 9 figure
Analisi scientifiche sulle tempere murali di Villa Pace
International audienceThe morphology, mineralogy, and solid-liquid phase separation of the Cu and Zn precipitates formed with sulfide produced in a sulfate-reducing bioreactor were studied at pH 3, 5, and 7. The precipitates formed at pH 7 display faster settling rates, better dewaterability, and higher concentrations of settleable solids as compared to the precipitates formed at pH 3 and 5. These differences were linked to the agglomeration of the sulfidic precipitates and coprecipitation of the phosphate added to the bioreactor influent. The Cu and Zn quenched the intensity of the dissolved organic matter peaks identified by fluorescence-excitation emission matrix spectroscopy, suggesting a binding mechanism that decreases supersaturation, especially at pH 5. X-ray absorption fine structure spectroscopy analyses confirmed the precipitation of Zn-S as sphalerite and Cu-S as covellite in all samples, but also revealed the presence of Zn sorbed on hydroxyapatite. These analyses further showed that CuS structures remained amorphous regardless of the pH, whereas the ZnS structure was more organized at pH 5 as compared to the ZnS formed at pH 3 and 7, in agreement with the cubic sphalerite-type structures observed through scanning electron microscopy at pH 5
Esperanto for histones : CENP-A, not CenH3, is the centromeric histone H3 variant
The first centromeric protein identified in any species was CENP-A, a divergent member of the histone H3 family that was recognised by autoantibodies from patients with scleroderma-spectrum disease. It has recently been suggested to rename this protein CenH3. Here, we argue that the original name should be maintained both because it is the basis of a long established nomenclature for centromere proteins and because it avoids confusion due to the presence of canonical histone H3 at centromeres
On dynamic network entropy in cancer
The cellular phenotype is described by a complex network of molecular
interactions. Elucidating network properties that distinguish disease from the
healthy cellular state is therefore of critical importance for gaining
systems-level insights into disease mechanisms and ultimately for developing
improved therapies. By integrating gene expression data with a protein
interaction network to induce a stochastic dynamics on the network, we here
demonstrate that cancer cells are characterised by an increase in the dynamic
network entropy, compared to cells of normal physiology. Using a fundamental
relation between the macroscopic resilience of a dynamical system and the
uncertainty (entropy) in the underlying microscopic processes, we argue that
cancer cells will be more robust to random gene perturbations. In addition, we
formally demonstrate that gene expression differences between normal and cancer
tissue are anticorrelated with local dynamic entropy changes, thus providing a
systemic link between gene expression changes at the nodes and their local
network dynamics. In particular, we also find that genes which drive
cell-proliferation in cancer cells and which often encode oncogenes are
associated with reductions in the dynamic network entropy. In summary, our
results support the view that the observed increased robustness of cancer cells
to perturbation and therapy may be due to an increase in the dynamic network
entropy that allows cells to adapt to the new cellular stresses. Conversely,
genes that exhibit local flux entropy decreases in cancer may render cancer
cells more susceptible to targeted intervention and may therefore represent
promising drug targets.Comment: 10 pages, 3 figures, 4 tables. Submitte
Distribution and Abundance of Fin whales and other baleen whales in the European Atlantic
The abundance of fin whales (Balaenoptera physalus) and other baleen whales was generated from data collected during
shipboard sightings surveys as part of the Cetacean Offshore Distribution and Abundance in the European Atlantic project
(CODA). The survey area covered offshore waters beyond the continental shelf of the UK, Ireland, France and Spain. The area
was stratified into four blocks and was surveyed by five ships during July 2007. Double platform methods employing the trialconfiguration
method (BT-method) were used. Fin, sei (B. borealis) and minke whales (B. acutorostrata) were positively
identified, with possible sightings of blue whales (B. musculus). Abundance was estimated for these species and for âlarge baleen
whalesâ which included fin, sei, fin/sei and blue whales. Abundance for the larger species was estimated using the Mark-
Recapture Line Transect design-based method and also model-based methods using density surface modelling. Sample size
limitations dictated that conventional line transect sampling methods were used to estimate the abundance of minke whales.
Estimates from the two methods were comparable but model-based methods improved the precision and were considered best
estimates. The density of large baleen whale species was greatest in the southern end of the survey area and water depth,
temperature and distance to the 2000m contour were important predictors of their distribution. The total abundance estimated for
the entire survey area was 9,019 (CV=0.11) fin whales and 9,619 (CV= 0.11) large baleen whales. The uncertainty around these
estimates due to duplicate classification and species identification were explored. The fin whale estimate is likely to be
underestimated because it excludes unidentified large whales, of which a large proportion was likely to have been fin whales.
Notwithstanding this, these large baleen whale abundance estimates are the first robust estimates (corrected for responsive
movement and g(0)) for this area. The estimated abundance of minke whales was 6,765 (CV=0.99) and sightings were restricted
to the northern blocks of the survey area. The minke whale estimate, although imprecise and likely underestimated, does provide a
baseline figure for this area and, when considered with results from the SCANS-II continental shelf surveys of July 2005, gives a
more comprehensive picture of this species in the European Atlantic. These abundance estimates are important contributions to
the conservation and management of these species in the Northeast Atlantic
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