4,864 research outputs found
On the Role of Global Warming on the Statistics of Record-Breaking Temperatures
We theoretically study long-term trends in the statistics of record-breaking
daily temperatures and validate these predictions using Monte Carlo simulations
and data from the city of Philadelphia, for which 126 years of daily
temperature data is available. Using extreme statistics, we derive the number
and the magnitude of record temperature events, based on the observed Gaussian
daily temperatures distribution in Philadelphia, as a function of the number of
elapsed years from the start of the data. We further consider the case of
global warming, where the mean temperature systematically increases with time.
We argue that the current warming rate is insufficient to measurably influence
the frequency of record temperature events over the time range of the
observations, a conclusion that is supported by numerical simulations and the
Philadelphia temperature data.Comment: 11 pages, 6 figures, 2-column revtex4 format. For submission to
Journal of Climate. Revised version has some new results and some errors
corrected. Reformatted for Journal of Climate. Second revision has an added
reference. In the third revision one sentence that explains the simulations
is reworded for clarity. New revision 10/3/06 has considerable additions and
new results. Revision on 11/8/06 contains a number of minor corrections and
is the version that will appear in Phys. Rev.
Az ingĂĄzĂĄs tĂ©rbeli jellegzetessĂ©geinek vĂĄltozĂĄsa az Ăszak-DunĂĄntĂșlon, kĂŒlönös tekintettel GyĆr munkaĂŒgyi vonzĂĄskörzetĂ©re
A tanulmĂĄnyban megvizsgĂĄljuk a KSH ĂĄltal 2001-ben Ă©s 2011-ben elvĂ©gzett nĂ©pszĂĄmlĂĄlĂĄs ingĂĄzĂĄsra vonatkozĂł fĆbb adatainak Ă©s a kĂ©t felvĂ©tel összehasonlĂtĂĄsa sorĂĄn tapasztalt eltĂ©rĂ©sek terĂŒleti konzekvenciĂĄit. A vizsgĂĄlat cĂ©lja elsĆsorban az volt, hogy GyĆr körĂ© szervezĆdĆ ingĂĄzĂł, munkaĂŒgyi vonzĂĄsterek jellegzetessĂ©geit megismerjĂŒk. EzĂ©rt az orszĂĄgos szintƱ vizsgĂĄlatok mellett rĂ©szletesebben koncentrĂĄltunk az Ă©szak-DunĂĄntĂșlra, melynek központrendszerĂ©t tĂĄrtuk fel, s mĂ©g rĂ©szletesebben vizsgĂĄltuk ezen belĂŒl GyĆr, s a vĂĄroskörnyĂ©ki tĂ©r jellegzetessĂ©geit
Hepatocyte ABCA1 deficiency is associated with reduced HDL sphingolipids
ATP binding cassette transporter A1 (ABCA1) limits the formation of high density lipoproteins (HDL) as genetic loss of ABCA1 function causes virtual HDL deficiency in patients with Tangier disease. Mice with a hepatocyte-specific ABCA1 knockout (Abca1 HSKO) have 20% of wild type (WT) plasma HDL-cholesterol levels, suggesting a major contribution of hepatic ABCA1 to the HDL phenotype. Whether plasma sphingolipids are reduced in Tangier disease and to what extent hepatic ABCA1 contributes to plasma sphingolipid (SL) levels is unknown. Here, we report a drastic reduction of total SL levels in plasma of a Tangier patient with compound heterozygosity for mutations in ABCA1. Compared to mutation-free controls, heterozygous mutations in ABCA1 had no significant effect on total SLs in plasma; however, apoB-depleted plasma showed a reduction in total SL also in het carriers. Similarly, liver specific Abca1 KO mice (Abca1 HSKO) showed reduced total sphingolipids in plasma and liver. In parallel, apoM and sphingosine-1-phosphate (S1P) levels were reduced in plasma of Abca1 HSKO mice. Primary hepatocytes from Abca1 HSKO mice showed a modest, but significant reduction in total SLs concentration compared to WT hepatocytes, although SL de novo synthesis and secretion were slightly increased in Abca1 HSKO hepatocytes. We conclude that hepatic ABCA1 is a signficant contributor to maintaining total plasma pool of HDL sphingolipids, including sphingomyelins and S1P
Arctic air pollution: Challenges and opportunities for the next decade
The Arctic is a sentinel of global change. This region is influenced by multiple physical and socio-economic drivers and feedbacks, impacting both the natural and human environment. Air pollution is one such driver that impacts Arctic climate change, ecosystems and health but significant uncertainties still surround quantification of these effects. Arctic air pollution includes harmful trace gases (e.g. tropospheric ozone) and particles (e.g. black carbon, sulphate) and toxic substances (e.g. polycyclic aromatic hydrocarbons) that can be transported to the Arctic from emission sources located far outside the region, or emitted within the Arctic from activities including shipping, power production, and other industrial activities. This paper qualitatively summarizes the complex science issues motivating the creation of a new international initiative, PACES (air Pollution in the Arctic: Climate, Environment and Societies). Approaches for coordinated, international and interdisciplinary research on this topic are described with the goal to improve predictive capability via new understanding about sources, processes, feedbacks and impacts of Arctic air pollution. Overarching research actions are outlined, in which we describe our recommendations for 1) the development of trans-disciplinary approaches combining social and economic research with investigation of the chemical and physical aspects of Arctic air pollution; 2) increasing the quality and quantity of observations in the Arctic using long-term monitoring and intensive field studies, both at the surface and throughout the troposphere; and 3) developing improved predictive capability across a range of spatial and temporal scales
Transmission of Information in Active Networks
Shannon's Capacity Theorem is the main concept behind the Theory of
Communication. It says that if the amount of information contained in a signal
is smaller than the channel capacity of a physical media of communication, it
can be transmitted with arbitrarily small probability of error. This theorem is
usually applicable to ideal channels of communication in which the information
to be transmitted does not alter the passive characteristics of the channel
that basically tries to reproduce the source of information. For an {\it active
channel}, a network formed by elements that are dynamical systems (such as
neurons, chaotic or periodic oscillators), it is unclear if such theorem is
applicable, once an active channel can adapt to the input of a signal, altering
its capacity. To shed light into this matter, we show, among other results, how
to calculate the information capacity of an active channel of communication.
Then, we show that the {\it channel capacity} depends on whether the active
channel is self-excitable or not and that, contrary to a current belief,
desynchronization can provide an environment in which large amounts of
information can be transmitted in a channel that is self-excitable. An
interesting case of a self-excitable active channel is a network of
electrically connected Hindmarsh-Rose chaotic neurons.Comment: 15 pages, 5 figures. submitted for publication. to appear in Phys.
Rev.
Prognostic impact of Claudin 18.2 in gastric and esophageal adenocarcinomas
INTRODUCTION: The tight junction molecule Claudin 18.2 is selectively expressed in healthy and malignant gastric epithelial tissue and is a promising therapy target for high Claudin 18.2 expressing adenocarcinomas of the esophagogastric junction and stomach (AEG/S). METHODS: This study analyzed the prevalence, characteristics and prognostic impact of Claudin 18.2 expression in primary tumor, lymph node and distant metastasis in a large Caucasian AGE/S cohort with 414 patients. RESULTS: Claudin 18.2 was highly expressed in 17.1% of primary tumors, 26.7% of lymph node metastasis and 16.7% of distant metastasis. High Claudin 18.2 expression in lymph node metastasis and primary tumors correlated significantly (pâ<â0.001). High expression of Claudin 18.2 was neither associated with histomorphogical subtype, or tumor state, nor with overall survival. CONCLUSION: In Caucasian AEG/S patients, 17.1% appeared to be eligible for an anti-Claudin 18.2 therapy. Claudin 18.2 expression itself has no impact on prognosis and is not related to any tumor subtype
The Origin of Degeneracies and Crossings in the 1d Hubbard Model
The paper is devoted to the connection between integrability of a finite
quantum system and degeneracies of its energy levels. In particular, we analyze
in detail the energy spectra of finite Hubbard chains. Heilmann and Lieb
demonstrated that in these systems there are crossings of levels of the same
parameter independent symmetry. We show that this apparent violation of the
Wigner-von Neumann noncrossing rule follows directly from the existence of
nontrivial conservation laws and is a characteristic signature of quantum
integrability. The energy spectra of Hubbard chains display many instances of
permanent (at all values of the coupling) twofold degeneracies that cannot be
explained by parameter independent symmetries. We relate these degeneracies to
the different transformation properties of the conserved currents under spatial
reflections and the particle-hole transformation and estimate the fraction of
doubly degenerate states. We also discuss multiply degenerate eigenstates of
the Hubbard Hamiltonian. The wave functions of many of these states do not
depend on the coupling, which suggests the existence of an additional parameter
independent symmetry.Comment: 25 pages, 12 figure
Mechanism of Deep-focus Earthquakes Anomalous Statistics
Analyzing the NEIC-data we have shown that the spatial deep-focus earthquake
distribution in the Earth interior over the 1993-2006 is characterized by the
clearly defined periodical fine discrete structure with period L=50 km, which
is solely generated by earthquakes with magnitude M 3.9 to 5.3 and only on the
convergent boundary of plates. To describe the formation of this structure we
used the model of complex systems by A. Volynskii and S. Bazhenov. The key
property of this model consists in the presence of a rigid coating on a soft
substratum. It is shown that in subduction processes the role of a rigid
coating plays the slab substance (lithosphere) and the upper mantle acts as a
soft substratum. Within the framework of this model we have obtained the
estimation of average values of stress in the upper mantle and Young's modulus
for the oceanic slab (lithosphere) and upper mantle.Comment: 9 pages, 7 figure
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