1,427 research outputs found
The galactic magnetic field in the quasar 3C216
Multifrequency polarimetric observations made with the Very Long Baseline
Array of the quasar 3C216 reveal the presence of Faraday rotation measures
(RMs) in excess of 2000 rad/m**2 in the source rest frame, in the arc of
emission located at ~ 140 mas from the core. Rotation measures in the range
-300 - +300 rad/m**2 are detected in the inner 5 mas (~30 parsecs). while the
rotation measures near the core can be explained as due to a magnetic field in
the narrow line region, we favor the interpretation for the high RM in the arc
as due to a ``local'' Faraday screen, produced in a shock where the jet is
deflected by the interstellar medium of the host galaxy. Our results indicate
that a galacit magnetic field of the order of 50 microGauss on a scale greater
than 100 pc must be present in the galactic medium.Comment: 23 pages, 3 tables, 11 figures. To appear on The Astronomical
Journal, November 1999 Issu
The World-Trade Web: Topological Properties, Dynamics, and Evolution
This paper studies the statistical properties of the web of import-export
relationships among world countries using a weighted-network approach. We
analyze how the distributions of the most important network statistics
measuring connectivity, assortativity, clustering and centrality have
co-evolved over time. We show that all node-statistic distributions and their
correlation structure have remained surprisingly stable in the last 20 years --
and are likely to do so in the future. Conversely, the distribution of
(positive) link weights is slowly moving from a log-normal density towards a
power law. We also characterize the autoregressive properties of
network-statistics dynamics. We find that network-statistics growth rates are
well-proxied by fat-tailed densities like the Laplace or the asymmetric
exponential-power. Finally, we find that all our results are reasonably robust
to a few alternative, economically-meaningful, weighting schemes.Comment: 44 pages, 39 eps figure
The determinants of election to the United Nations Security Council
This is the author's accepted manuscript. The final publication is available at Springer via http://dx.doi.org/10.1007/s11127-013-0096-4.The United Nations Security Council (UNSC) is the foremost international body responsible for the maintenance of international peace and security. Members vote on issues of global importance and consequently receive perks—election to the UNSC predicts, for instance, World Bank and IMF loans. But who gets elected to the UNSC? Addressing this question empirically is not straightforward as it requires a model that allows for discrete choices at the regional and international levels; the former nominates candidates while the latter ratifies them. Using an original multiple discrete choice model to analyze a dataset of 180 elections from 1970 to 2005, we find that UNSC election appears to derive from a compromise between the demands of populous countries to win election more frequently and a norm of giving each country its turn. We also find evidence that richer countries from the developing world win election more often, while involvement in warfare lowers election probability. By contrast, development aid does not predict election
Pathway deregulation and expression QTLs in response to Actinobacillus pleuropneumoniae infection in swine
Actinobacillus (A.) pleuropneumoniae is among the most important pathogens in pig. The agent causes severe economic losses due to decreased performance, the occurrence of acute or chronic pleuropneumonia, and an increase in death incidence. Since therapeutics cannot be used in a sustainable manner, and vaccination is not always available, new prophylactic measures are urgently needed. Recent research has provided evidence for a genetic predisposition in susceptibility to A. pleuropneumoniae in a Hampshire × German Landrace F2 family with 170 animals. The aim of the present study is to characterize the expression response in this family in order to unravel resistance and susceptibility mechanisms and to prioritize candidate genes for future fine mapping approaches. F2 pigs differed distinctly in clinical, pathological, and microbiological parameters after challenge with A. pleuropneumoniae. We monitored genome-wide gene expression from the 50 most and 50 least susceptible F2 pigs and identified 171 genes differentially expressed between these extreme phenotypes. We combined expression QTL analyses with network analyses and functional characterization using gene set enrichment analysis and identified a functional hotspot on SSC13, including 55 eQTL. The integration of the different results provides a resource for candidate prioritization for fine mapping strategies, such as TF, TFRC, RUNX1, TCN1, HP, CD14, among others
Kinetic formulation and global existence for the Hall-Magneto-hydrodynamics system
This paper deals with the derivation and analysis of the the Hall
Magneto-Hydrodynamic equations. We first provide a derivation of this system
from a two-fluids Euler-Maxwell system for electrons and ions, through a set of
scaling limits. We also propose a kinetic formulation for the Hall-MHD
equations which contains as fluid closure different variants of the Hall-MHD
model. Then, we prove the existence of global weak solutions for the
incompressible viscous resistive Hall-MHD model. We use the particular
structure of the Hall term which has zero contribution to the energy identity.
Finally, we discuss particular solutions in the form of axisymmetric purely
swirling magnetic fields and propose some regularization of the Hall equation
The role of reactive oxygen and nitrogen species in the response of airway epithelium to particulates.
Epidemiologic and occupational studies indicate adverse health effects due to inhalation of particulate air pollutants, but precise biologic mechanisms responsible have yet to be fully established. The tracheobronchial epithelium forms the body's first physiologic barrier to such airborne pollutants, where ciliary movement functions to remove the offending substances caught in the overlying mucus layer. Resident and infiltrating phagocytic cells also function in this removal process. In this paper, we examine the role of reactive oxygen and nitrogen species (ROS/RNS) in the response of airway epithelium to particulates. Some particulates themselves can generate ROS, as can the epithelial cells, in response to appropriate stimulation. In addition, resident macrophages in the airways and the alveolar spaces can release ROS/RNS after phagocytosis of inhaled particles. These macrophages also release large amounts of tumor necrosis factor alpha (TNF-alpha), a cytokine that can generate responses within the airway epithelium dependent upon intracellular generation of ROS/RNS. As a result, signal transduction pathways are set in motion that may contribute to inflammation and other pathobiology in the airway. Such effects include increased expression of intercellular adhesion molecule 1, interleukin-6, cytosolic and inducible nitric oxide synthase, manganese superoxide dismutase, cytosolic phospholipase A2, and hypersecretion of mucus. Ultimately, ROS/RNS may play a role in the global response of the airway epithelium to particulate pollutants via activation of kinases and transcription factors common to many response genes. Thus, defense mechanisms involved in responding to offending particulates may result in a complex cascade of events that can contribute to airway pathology
Decentralization as a Disincentive for Transnational Terror? An Empirical Test
Using panel data for a maximum of 109 countries over the years 1976-2000, we empirically analyze the impact of decentralization on the occurrence of transnational terror. Taking account of the potential simultaneity between terror and decentralization, our results show that expenditure decentralization robustly reduces the number of terror events in a country, while political decentralization has no impact
The intracluster magnetic field power spectrum in A2199
We investigate the magnetic field power spectrum in the cool core galaxy
cluster A2199 by analyzing the polarized emission of the central radio source
3C338. The polarized radiation from the radio emitting plasma is modified by
the Faraday rotation as it passes through the magneto-ionic intracluster
medium. We use Very Large Array observations between 1665 and 8415 MHz to
produce detailed Faraday rotation measure and fractional polarization images of
the radio galaxy. We simulate Gaussian random three-dimensional magnetic field
models with different power-law power spectra and we assume that the field
strength decreases radially with the thermal gas density as n_e^{\eta}. By
comparing the synthetic and the observed images with a Bayesian approach, we
constrain the strength and structure of the magnetic field associated with the
intracluster medium. We find that the Faraday rotation toward 3C338 in A2199 is
consistent with a magnetic field power law power spectrum characterized by an
index n=(2.8 \pm 1.3) between a maximum and a minimum scale of fluctuation of
\Lambda_{max}=(35 \pm 28) kpc and \Lambda_{min}=(0.7 \pm 0.1) kpc,
respectively. By including in the modeling X-ray cavities coincident with the
radio galaxy lobes, we find a magnetic field strength of =(11.7 \pm 9.0)
\mu G at the cluster center. Further out, the field decreases with the radius
following the gas density to the power of \eta=(0.9 \pm 0.5).Comment: 17 pages, 12 figures, A&A accepte
The MBA as Careerist: An Analysis of Early-Career Job Change
This study examined the job changes of 680 early-career business school graduates. Although a number of anecdotal articles characterize MBAs as overly “careerist” and oriented toward job-hopping, little empirical research has focused on this issue. The research included a direct comparison of job-hopping behavior of MBAs with bachelor S degree graduates, taking into account a number of control variables, including demographic and economic variables. Results indicated that MBAs changed jobs less frequently than bachelor 5 degree graduates, even when a variety of other factors were controlled.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline
Far infrared mapping of three Galactic star forming regions : W3(OH), S 209 & S 187
Three Galactic star forming regions associated with W3(OH), S209 and S187
have been simultaneously mapped in two trans-IRAS far infrared (FIR) bands
centered at ~ 140 and 200 micron using the TIFR 100 cm balloon borne FIR
telescope. These maps show extended FIR emission with structures. The HIRES
processed IRAS maps of these regions at 12, 25, 60 & 100 micron have also been
presented for comparison. Point-like sources have been extracted from the
longest waveband TIFR maps and searched for associations in the other five
bands. The diffuse emission from these regions have been quantified, which
turns out to be a significant fraction of the total emission. The spatial
distribution of cold dust (T < 30 K) for two of these sources (W3(OH) & S209),
has been determined reliably from the maps in TIFR bands. The dust temperature
and optical depth maps show complex morphology. In general the dust around S209
has been found to be warmer than that in W3(OH) region.Comment: Accepted for publication in Journal of Astrophysics and Astronomy (20
pages including 8 figures & 3 tables
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