575 research outputs found
Another note on Kempisty's generalized continuity
Under a fairly mild completeness condition on spaces Y and Z we show that every x-continuous function f:X×Y×Z→M has a substantial set C(f) of points of continuity. Some odds and ends concerning a related earlier result shown by the authors are presented. Further, a generalization of S. Kempisty's ideas of generalized continuity on products of finitely many spaces is offered. As a corollary from the above results, a partial answer to M. Talagrand's problem is provided
Last glacial atmospheric CO2 decline due to widespread Pacific deep-water expansion
Ocean circulation critically affects the global climate and atmospheric carbon dioxide through redistribution of heat and carbon in the Earth system. Despite intensive research, the nature of past ocean circulation changes remains elusive. Here we present deep-water carbonate ion concentration reconstructions for widely distributed locations in the Atlantic Ocean, where low carbonate ion concentrations indicate carbon-rich waters. These data show a low-carbonate-ion water mass that extended northward up to about 20° S in the South Atlantic at 3–4 km depth during the Last Glacial Maximum. In combination with radiocarbon ages, neodymium isotopes and carbon isotopes, we conclude that this low-carbonate-ion signal reflects a widespread expansion of carbon-rich Pacific deep waters into the South Atlantic, revealing a glacial deep Atlantic circulation scheme different than commonly considered. Comparison of high-resolution carbonate ion records from different water depths in the South Atlantic indicates that this Pacific deep-water expansion developed from approximately 38,000 to 28,000 years ago. We infer that its associated carbon sequestration may have contributed critically to the contemporaneous decline in atmospheric carbon dioxide, thereby helping to initiate the glacial maximum
FVM 1.0: a nonhydrostatic finite-volume dynamical core for the IFS
We present a nonhydrostatic finite-volume global atmospheric model
formulation for numerical weather prediction with the Integrated Forecasting
System (IFS) at ECMWF and compare it to the established operational
spectral-transform formulation. The novel Finite-Volume Module of the IFS
(henceforth IFS-FVM) integrates the fully compressible equations using
semi-implicit time stepping and non-oscillatory forward-in-time (NFT)
Eulerian advection, whereas the spectral-transform IFS solves the hydrostatic
primitive equations (optionally the fully compressible equations) using a
semi-implicit semi-Lagrangian scheme. The IFS-FVM complements the
spectral-transform counterpart by means of the finite-volume discretization
with a local low-volume communication footprint, fully conservative and
monotone advective transport, all-scale deep-atmosphere fully compressible
equations in a generalized height-based vertical coordinate, and flexible
horizontal meshes. Nevertheless, both the finite-volume and
spectral-transform formulations can share the same quasi-uniform horizontal
grid with co-located arrangement of variables, geospherical
longitude–latitude coordinates, and physics parameterizations, thereby
facilitating their comparison, coexistence, and combination in the IFS.
We highlight the advanced semi-implicit NFT finite-volume integration of the
fully compressible equations of IFS-FVM considering comprehensive
moist-precipitating dynamics with coupling to the IFS cloud parameterization
by means of a generic interface. These developments – including a new
horizontal–vertical split NFT MPDATA advective transport scheme, variable
time stepping, effective preconditioning of the elliptic Helmholtz solver in
the semi-implicit scheme, and a computationally efficient implementation of
the median-dual finite-volume approach – provide a basis for the efficacy of
IFS-FVM and its application in global numerical weather prediction. Here,
numerical experiments focus on relevant dry and moist-precipitating
baroclinic instability at various resolutions. We show that the presented
semi-implicit NFT finite-volume integration scheme on co-located meshes of
IFS-FVM can provide highly competitive solution quality and computational
performance to the proven semi-implicit semi-Lagrangian integration scheme of
the spectral-transform IFS.</p
GRB 080319B: A Naked-Eye Stellar Blast from the Distant Universe
Long duration gamma-ray bursts (GRBs) release copious amounts of energy
across the entire electromagnetic spectrum, and so provide a window into the
process of black hole formation from the collapse of a massive star. Over the
last forty years, our understanding of the GRB phenomenon has progressed
dramatically; nevertheless, fortuitous circumstances occasionally arise that
provide access to a regime not yet probed. GRB 080319B presented such an
opportunity, with extraordinarily bright prompt optical emission that peaked at
a visual magnitude of 5.3, making it briefly visible with the naked eye. It was
captured in exquisite detail by wide-field telescopes, imaging the burst
location from before the time of the explosion. The combination of these unique
optical data with simultaneous gamma-ray observations provides powerful
diagnostics of the detailed physics of this explosion within seconds of its
formation. Here we show that the prompt optical and gamma-ray emissions from
this event likely arise from different spectral components within the same
physical region located at a large distance from the source, implying an
extremely relativistic outflow. The chromatic behaviour of the broadband
afterglow is consistent with viewing the GRB down the very narrow inner core of
a two-component jet that is expanding into a wind-like environment consistent
with the massive star origin of long GRBs. These circumstances can explain the
extreme properties of this GRB.Comment: 43 pages, 18 figures, 3 tables, submitted to Nature May 11, 200
Reversed flow of Atlantic deep water during the Last Glacial Maximum
The meridional overturning circulation (MOC) of the Atlantic Ocean is considered to be one of the most important components of the climate system. This is because its warm surface currents, such as the Gulf Stream, redistribute huge amounts of energy from tropical to high latitudes and influence regional weather and climate patterns, whereas its lower limb ventilates the deep ocean and affects the storage of carbon in the abyss, away from the atmosphere. Despite its significance for future climate, the operation of the MOC under contrasting climates of the past remains controversial. Nutrient-based proxies1, 2 and recent model simulations3 indicate that during the Last Glacial Maximum the convective activity in the North Atlantic Ocean was much weaker than at present. In contrast, rate-sensitive radiogenic 231Pa/230Th isotope ratios from the North Atlantic have been interpreted to indicate only minor changes in MOC strength4, 5, 6. Here we show that the basin-scale abyssal circulation of the Atlantic Ocean was probably reversed during the Last Glacial Maximum and was dominated by northward water flow from the Southern Ocean. These conclusions are based on new high-resolution data from the South Atlantic Ocean that establish the basin-scale north to south gradient in 231Pa/230Th, and thus the direction of the deep ocean circulation. Our findings are consistent with nutrient-based proxies and argue that further analysis of 231Pa/230Th outside the North Atlantic basin will enhance our understanding of past ocean circulation, provided that spatial gradients are carefully considered. This broader perspective suggests that the modern pattern of the Atlantic MOC—with a prominent southerly flow of deep waters originating in the North Atlantic—arose only during the Holocene epoch
Archival data on wild food plants used in Poland in 1948
<p>Abstract</p> <p>Background</p> <p>In 1948, Professor Józef Gajek initiated a detailed census of the wild edible plants used in Poland. The questionnaires were collected by correspondents of the Polish Folklore Society in 95 localities throughout Poland. A major part of these archival materials, including a substantial collection of herbarium specimens, had not undergone thorough analysis prior to this study, which presents a quantitative analysis of this archival set of data.</p> <p>Methods</p> <p>Herbarium specimens were identified and a database was created.</p> <p>Results</p> <p>Ninety-eight taxa identified to genus or species level, including 71 botanical species, identified using herbarium specimens, were found. On average only 11 edible plant species per locality were listed, the longest list included 39 species. No correlation between latitude and the number of edible species was found, whereas there was small but significant correlation with the longitude. Fruits were the most frequently collected part of plants. Most plants were primarily collected by women and children. Children both helped parents to collect wild fruits and also ate many species raw, which were not consumed by adults, but had often been eaten in the past. Eighteen of the taxa had not been reported in a recent comprehensive review of edible plants of Poland. <it>Stratiotes aloides</it>, used as a famine vegetable in the Łódź region, has never been reported as edible in any ethnobotanical literature.</p> <p>Conclusion</p> <p>The results undermine the conclusions of a recent comprehensive review of edible plants of Poland, which stated that many more wild edible plants have been collected in the Carpathians than in lowland Poland. However such results were shown to be caused by the substantially larger number of ethnographic studies undertaken in the Carpathians. In fact, large numbers of edible plant species were collected in the mid-20<sup>th </sup>century in a few regions, particularly along the eastern border, in the Carpathians and in communities originating from the expanded Soviet Union, which had been resettled to the north-west of Poland in 1945.</p
Human brain harbors single nucleotide somatic variations in functionally relevant genes possibly mediated by oxidative stress
Somatic variation in DNA can cause cells to deviate from the preordained
genomic path in both disease and healthy conditions. Here, using exome
sequencing of paired tissue samples, we show that the normal human brain
harbors somatic single base variations measuring up to 0.48% of the total
variations. Interestingly, about 64% of these somatic variations in the brain are
expected to lead to non-synonymous changes, and as much as 87% of these
represent G:C>T:A transversion events. Further, the transversion events in the
brain were mostly found in the frontal cortex, whereas the corpus callosum from
the same individuals harbors the reference genotype. We found a significantly
higher amount of 8-OHdG (oxidative stress marker) in the frontal cortex
compared to the corpus callosum of the same subjects (p<0.01), correlating
with the higher G:C>T:A transversions in the cortex. We found significant
enrichment for axon guidance and related pathways for genes harbouring
somatic variations. This could represent either a directed selection of genetic
variations in these pathways or increased susceptibility of some loci towards
oxidative stress. This study highlights that oxidative stress possibly influence
single nucleotide somatic variations in normal human brain
The Cyprinodon variegatus genome reveals gene expression changes underlying differences in skull morphology among closely related species
Genes in durophage intersection set at 15 dpf. This is a comma separated table of the genes in the 15 dpf durophage intersection set. Given are edgeR results for each pairwise comparison. Columns indicating whether a gene is included in the intersection set at a threshold of 1.5 or 2 fold are provided. (CSV 13Â kb
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