6,135 research outputs found
Quasi-chemical Theories of Associated Liquids
It is shown how traditional development of theories of fluids based upon the
concept of physical clustering can be adapted to an alternative local
clustering definition. The alternative definition can preserve a detailed
valence description of the interactions between a solution species and its
near-neighbors, i.e., cooperativity and saturation of coordination for strong
association. These clusters remain finite even for condensed phases. The
simplest theory to which these developments lead is analogous to quasi-chemical
theories of cooperative phenomena. The present quasi-chemical theories require
additional consideration of packing issues because they don't impose lattice
discretizations on the continuous problem. These quasi-chemical theories do not
require pair decomposable interaction potential energy models. Since
calculations may be required only for moderately sized clusters, we suggest
that these quasi-chemical theories could be implemented with computational
tools of current electronic structure theory. This can avoid an intermediate
step of approximate force field generation.Comment: 20 pages, no figures replacement: minor typographical corrections,
four references added, in press Molec. Physics 199
Two-dimensional lattice-fluid model with water-like anomalies
We investigate a lattice-fluid model defined on a two-dimensional triangular
lattice, with the aim of reproducing qualitatively some anomalous properties of
water. Model molecules are of the "Mercedes Benz" type, i.e., they possess a D3
(equilateral triangle) symmetry, with three bonding arms. Bond formation
depends both on orientation and local density. We work out phase diagrams,
response functions, and stability limits for the liquid phase, making use of a
generalized first order approximation on a triangle cluster, whose accuracy is
verified, in some cases, by Monte Carlo simulations. The phase diagram displays
one ordered (solid) phase which is less dense than the liquid one. At fixed
pressure the liquid phase response functions show the typical anomalous
behavior observed in liquid water, while, in the supercooled region, a
reentrant spinodal is observed.Comment: 9 pages, 1 table, 7 figure
Effects of climate extremes on the terrestrial carbon cycle : concepts, processes and potential future impacts
This article is protected by copyright. All rights reserved. Acknowledgements This work emerged from the CARBO-Extreme project, funded by the European Community’s 7th framework programme under grant agreement (FP7-ENV-2008-1-226701). We are grateful to the Reviewers and the Subject Editor for helpful guidance. We thank to Silvana Schott for graphic support. Mirco Miglivacca provided helpful comments on the manuscript. Michael Bahn acknowledges support from the Austrian Science Fund (FWF; P22214-B17). Sara Vicca is a postdoctoral research associate of the Fund for Scientific Research – Flanders. Wolfgang Cramer contributes to the Labex OT-Med (n° ANR-11- LABX-0061) funded by the French government through the A*MIDEX project (n° ANR-11-IDEX-0001-02). Flurin Babst acknowledges support from the Swiss National Science Foundation (P300P2_154543).Peer reviewedPublisher PD
Chandra ACIS Survey of M33 (ChASeM33): The enigmatic X-ray emission from IC131
We present the first X-ray analysis of the diffuse hot ionized gas and the
point sources in IC131, after NGC604 the second most X-ray luminous giant HII
region in M33. The X-ray emission is detected only in the south eastern part of
IC131 (named IC131-se) and is limited to an elliptical region of ~200pc in
extent. This region appears to be confined towards the west by a hemispherical
shell of warm ionized gas and only fills about half that volume. Although the
corresponding X-ray spectrum has 1215 counts, it cannot conclusively be told
whether the extended X-ray emission is thermal, non-thermal, or a combination
of both. A thermal plasma model of kT_e=4.3keV or a single power law of
Gamma=2.1 fit the spectrum equally well. If the spectrum is purely thermal
(non-thermal), the total unabsorbed X-ray luminosity in the 0.35-8keV energy
band amounts to L_X = 6.8(8.7)x10^35erg/s. Among other known HII regions
IC131-se seems to be extreme regarding the combination of its large extent of
the X-ray plasma, the lack of massive O stars, its unusually high electron
temperature (if thermal), and the large fraction of L_X emitted above 2keV
(~40-53%). A thermal plasma of ~4keV poses serious challenges to theoretical
models, as it is not clear how high electron temperatures can be produced in
HII regions in view of mass-proportional and collisionless heating. If the gas
is non-thermal or has non-thermal contributions, synchrotron emission would
clearly dominate over inverse Compton emission. It is not clear if the same
mechanisms which create non-thermal X-rays or accelerate CRs in SNRs can be
applied to much larger scales of 200pc. In both cases the existing theoretical
models for giant HII regions and superbubbles do not explain the hardness and
extent of the X-ray emission in IC131-se.Comment: 28 pages, 7 figures and 2 tables. Accepted for publication in ApJ.
For a high resolution version of the paper see
http://hea-www.harvard.edu/vlp_m33_public/publications.htm
Candida dubliniensis candidemia in patients with chemotherapy-induced neutropenia and bone marrow transplantation.
The recently described species Candida dubliniensis has been recovered primarily from superficial oral candidiasis in HIV-infected patients. No clinically documented invasive infections were reported until now in this patient group or in other immunocompromised patients. We report three cases of candidemia due to this newly emerging Candida species in HIV-negative patients with chemotherapy-induced immunosuppression and bone marrow transplantation
Управление финансовой устойчивостью и рентабельностью предприятия
Целью статьи является изучение значения управления финансовой устойчивостью и рентабельностью предприятия в современных условиях хозяйствования
London Hybrid Exposure Model: Improving Human Exposure Estimates to NO2 and PM2.5 in an Urban Setting.
Here we describe the development of the London Hybrid Exposure Model (LHEM), which calculates exposure of the Greater London population to outdoor air pollution sources, in-buildings, in-vehicles, and outdoors, using survey data of when and where people spend their time. For comparison and to estimate exposure misclassification we compared Londoners LHEM exposure with exposure at the residential address, a commonly used exposure metric in epidemiological research. In 2011, the mean annual LHEM exposure to outdoor sources was estimated to be 37% lower for PM2.5 and 63% lower for NO2 than at the residential address. These decreased estimates reflect the effects of reduced exposure indoors, the amount of time spent indoors (∼95%), and the mode and duration of travel in London. We find that an individual's exposure to PM2.5 and NO2 outside their residential address is highly correlated (Pearson's R of 0.9). In contrast, LHEM exposure estimates for PM2.5 and NO2 suggest that the degree of correlation is influenced by their exposure in different transport modes. Further development of the LHEM has the potential to increase the understanding of exposure error and bias in time-series and cohort studies and thus better distinguish the independent effects of NO2 and PM2.5
Microdomains of the C-type lectin DC-SIGN are portals for virus entry into dendritic cells
The C-type lectin dendritic cell (DC)–specific intercellular adhesion molecule grabbing non-integrin (DC-SIGN; CD209) facilitates binding and internalization of several viruses, including HIV-1, on DCs, but the underlying mechanism for being such an efficient phagocytic pathogen-recognition receptor is poorly understood. By high resolution electron microscopy, we demonstrate a direct relation between DC-SIGN function as viral receptor and its microlocalization on the plasma membrane. During development of human monocyte-derived DCs, DC-SIGN becomes organized in well-defined microdomains, with an average diameter of 200 nm. Biochemical experiments and confocal microscopy indicate that DC-SIGN microdomains reside within lipid rafts. Finally, we show that the organization of DC-SIGN in microdomains on the plasma membrane is important for binding and internalization of virus particles, suggesting that these multimolecular assemblies of DC-SIGN act as a docking site for pathogens like HIV-1 to invade the host
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