13,310 research outputs found
Limits on Hot Intracluster Gas Contributions to the Tenerife Temperature Anisotropy Map
We limit the contribution of the hot intracluster gas, by means of the
Sunyaev-Zel'dovich effect, to the temperature anisotropies measured by the
Tenerife experiment. The data is cross-correlated with maps generated from the
ACO cluster catalogue, the ROSAT PSPC catalogue of clusters of galaxies, a
catalogue of superclusters and the HEAO 1 A-1 map of X-ray sources. There is no
evidence of contamination by such sources at an rms level of K at
99% confidence level at angular resolution. We place an upper limit on
the mean Comptonization parameter of at the same
level of confidence. These limits are slightly more restrictive than those
previously found by a similar analysis on the COBE/DMR data and indicate that
most of the signal measured by Tenerife is cosmological.Comment: To be published in ApJ (main journal
Fourier Mukai Transforms for Gorenstein Schemes
We extend to singular schemes with Gorenstein singularities or fibered in
schemes of that kind Bondal and Orlov's criterion for an integral functor to be
fully faithful. We also contemplate a criterion for equivalence. We offer a
proof that is new even if we restrict to the smooth case. In addition, we prove
that for locally projective Gorenstein morphisms, a relative integral functor
is fully faithful if and only if its restriction to each fibre also is it.
These results imply the invertibility of the usual relative Fourier-Mukai
transform for an elliptic fibration as a direct corollary.Comment: Final version. To appear in Advances in Mathematic
ISO spectroscopy of compact HII regions in the Galaxy. II Ionization and elemental abundances
Based on the ISO spectral catalogue of compact HII regions by Peeters et al.
(2001), we present a first analysis of the hydrogen recombination and atomic
fine-structure lines originated in the ionized gas. The sample consists of 34
HII regions located at galactocentric distances between Rgal = 0 and 15 kpc.
The SWS HI recombination lines between 2 and 8 mum are used to estimate the
extinction law at these wavelengths for 14 HII regions. An extinction in the K
band between 0 and 3 mag. has been derived. The fine-structure lines of
N, O, Ne, S and Ar are detected in most of the sources. Most of these elements
are observed in two different ionization stages probing a range in ionization
potential up to 41 eV. The ISO data, by itself or combined with radio data
taken from the literature, is used to derive the elemental abundances relative
to hydrogen. The present data thus allow us to describe for each source its
elemental abundance, its state of ionization and to constrain the properties of
the ionizing star(s).Comment: Accepted in Astronomy and Astrophysics, 22 pages, 20 figures, 9
table
Dynamic earthquake triggering response tracks evolving unrest at Sierra Negra volcano, GalĂĄpagos Islands
The propensity for dynamic earthquake triggering is thought to depend on the local stress state and amplitude of
the stress perturbation. However, the nature of this dependency has not been confirmed within a single crustal
volume. Here, we show that at Sierra Negra volcano, GalĂĄpagos Islands, the intensity of dynamically triggered
earthquakes increased as inflation of a magma reservoir elevated the stress state. The perturbation of short-term
seismicity within teleseismic surface waves also increased with peak dynamic strain. Following rapid coeruptive
subsidence and reduction in stress and background seismicity rates, equivalent dynamic strains no longer triggered
detectable seismicity. These findings offer direct constraints on the primary controls on dynamic triggering
and suggest that the response to dynamic stresses may help constrain the evolution of volcanic unrest
Walls talk: Microbial biogeography of homes spanning urbanization.
Westernization has propelled changes in urbanization and architecture, altering our exposure to the outdoor environment from that experienced during most of human evolution. These changes might affect the developmental exposure of infants to bacteria, immune development, and human microbiome diversity. Contemporary urban humans spend most of their time indoors, and little is known about the microbes associated with different designs of the built environment and their interaction with the human immune system. This study addresses the associations between architectural design and the microbial biogeography of households across a gradient of urbanization in South America. Urbanization was associated with households' increased isolation from outdoor environments, with additional indoor space isolation by walls. Microbes from house walls and floors segregate by location, and urban indoor walls contain human bacterial markers of space use. Urbanized spaces uniquely increase the content of human-associated microbes-which could increase transmission of potential pathogens-and decrease exposure to the environmental microbes with which humans have coevolved
Comparative proteomic analysis of human milk fat globules and paired membranes and mouse milk fat globules identifies core cellular systems contributing to mammary lipid trafficking and secretion
Introduction: Human milk delivers critical nutritional and immunological support to human infants. Milk fat globules (MFGs) and their associated membranes (MFGMs) contain the majority of milk lipids and many bioactive components that contribute to neonatal development and health, yet their compositions have not been fully defined, and the mechanisms responsible for formation of these structures remain incompletely understood.Methods: In this study, we used untargeted mass spectrometry to quantitatively profile the protein compositions of freshly obtained MFGs and their paired, physically separated MFGM fractions from 13 human milk samples. We also quantitatively profiled the MFG protein compositions of 9 pooled milk samples from 18 lactating mouse dams.Results: We identified 2,453 proteins and 2,795 proteins in the majority of human MFG and MFGM samples, respectively, and 1,577 proteins in mouse MFGs. Using paired analyses of protein abundance in MFGMs compared to MFGs (MFGM-MFG; 1% FDR), we identified 699 proteins that were more highly abundant in MFGMs (MFGM-enriched), and 201 proteins that were less abundant in MFGMs (cytoplasmic). MFGM-enriched proteins comprised membrane systems (apical plasma membrane and multiple vesicular membranes) hypothesized to be responsible for lipid and protein secretion and components of membrane transport and signaling systems. Cytoplasmic proteins included ribosomal and proteasomal systems. Comparing abundance between human and mouse MFGs, we found a positive correlation (R2 = 0.44, p < 0.0001) in the relative abundances of 1,279 proteins that were found in common across species.Discussion: Comparative pathway enrichment analyses between human and mouse samples reveal similarities in membrane trafficking and signaling pathways involved in milk fat secretion and identify potentially novel immunological components of MFGs. Our results advance knowledge of the composition and relative quantities of proteins in human and mouse MFGs in greater detail, provide a quantitative profile of specifically enriched human MFGM proteins, and identify core cellular systems involved in milk lipid secretion
The structure of a polyketide synthase bimodule core
Polyketide synthases (PKSs) are predominantly microbial biosynthetic enzymes. They assemble highly potent bioactive natural products from simple carboxylic acid precursors. The most versatile families of PKSs are organized as assembly lines of functional modules. Each module performs one round of precursor extension and optional modification, followed by directed transfer of the intermediate to the next module. While enzymatic domains and even modules of PKSs are well understood, the higher-order modular architecture of PKS assembly lines remains elusive. Here, we visualize a PKS bimodule core using cryo-electron microscopy and resolve a two-dimensional meshwork of the bimodule core formed by homotypic interactions between modules. The sheet-like organization provides the framework for efficient substrate transfer and for sequestration of trans-acting enzymes required for polyketide production
Probing the Early Evolution of Young High-Mass Stars
Near-infrared imaging surveys of high-mass star-forming regions reveal an
amazingly complex interplay between star formation and the environment
(Churchwell et al. 2006; Alvarez et al. 2004). By means of near-IR spectroscopy
the embedded massive young stars can be characterized and placed in the context
of their birth site. However, so far spectroscopic surveys have been hopelessly
incomplete, hampering any systematic study of these very young massive stars.
New integral field instrumentation available at ESO has opened the possibility
to take a huge step forward by obtaining a full spectral inventory of the
youngest massive stellar populations in star-forming regions currently
accessible. Simultaneously, the analysis of the extended emission allows the
characterization of the environmental conditions. The Formation and Early
Evolution of Massive Stars (FEMS) collaboration aims at setting up a large
observing campaign to obtain a full census of the stellar content, ionized
material, outflows and PDR's over a sample of regions that covers a large
parameter space. Complementary radio, mm and infrared observations will be used
for the characterization of the deeply embedded population. For the first eight
regions we have obtained 40 hours of SINFONI observations. In this
contribution, we present the first results on three regions that illustrate the
potential of this strategy.Comment: To appear in ASP Conf. Proceedings of "Massive Star Formation:
Observations confront Theory", H. Beuther et al. (eds.), held in Heidelberg,
September 200
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