640 research outputs found
Supernovae, Landau Levels, and Pulsar Kicks
We derive the energy asymmetry given the proto-neutronstar during the time
when the neutrino sphere is near the surface of the proto-neutron star, using
the modified URCA process. The electrons produced with the anti-neutrinos are
in Landau levels due to the strong magnetic field, and this leads to asymmetry
in the neutrino momentum, and a pulsar kick. Our main prediction is that the
large pulsar kicks start at about 10 s and last for about 10 s, with the
corresponding neutrinos correlated in the direction of the magnetic field.Comment: 10 pages, seven figure
Metal enrichment of the intracluster medium: SN-driven galactic winds
We investigate the role of supernova (SN)-driven galactic winds in the
chemical enrichment of the intracluster medium (ICM). Such outflows on galactic
scales have their origin in huge star forming regions and expel metal enriched
material out of the galaxies into their surroundings as observed, for example,
in the nearby starburst galaxy NGC 253. As massive stars in OB-associations
explode sequentially, shock waves are driven into the interstellar medium (ISM)
of a galaxy and merge, forming a superbubble (SB). These SBs expand in a
direction perpendicular to the disk plane following the density gradient of the
ISM. We use the 2D analytical approximation by Kompaneets (1960) to model the
expansion of SBs in an exponentially stratified ISM. This is modified in order
to describe the sequence of SN-explosions as a time-dependent process taking
into account the main-sequence life-time of the SN-progenitors and using an
initial mass function to get the number of massive stars per mass interval. The
evolution of the bubble in space and time is calculated analytically, from
which the onset of Rayleigh-Taylor instabilities in the shell can be
determined. In its further evolution, the shell will break up and
high-metallicity gas will be ejected into the halo of the galaxy and even into
the ICM. We derive the number of stars needed for blow-out depending on the
scale height and density of the ambient medium, as well as the fraction of
alpha- and iron peak elements contained in the hot gas. Finally, the amount of
metals injected by Milky Way-type galaxies to the ICM is calculated confirming
the importance of this enrichment process.Comment: 6 pages, 7 figures, to be published in Astronomische Nachrichten
(proceedings of Symposium 6 of the JENAM 2008, Vienna
XMM-Newton study of the lensing cluster of galaxies CL0024+17
We present a detailed gravitational mass measurement based on the XMM-Newton
imaging spectroscopy analysis of the lensing cluster of galaxies CL0024+17 at
z=0.395. The emission appears approximately symmetric. However, on the scale of
r~3.3' some indication of elongation is visible in the northwest-southeast
(NW-SE) direction from the hardness ratio map (HRM). Within 3', we measure a
global gas temperature of 3.52\pm0.17 keV, metallicity of 0.22\pm0.07, and
bolometric luminosity of 2.9\pm0.1 \times 10^{44} h^{-2}_{70} erg/s. We derive
a temperature distribution with an isothermal temperature of 3.9 keV to a
radius of 1.5' and a temperature gradient in the outskirts (1.3<r<3'). Under
the assumption of hydrostatic equilibrium, we measure gravitational mass and
gas mass fraction to be M_{200}=2.0\pm0.3 \times 10^{14} h_{70}^{-1} M_{\odot}
and f_{\rm gas}=0.20\pm0.03 h^{-3/2}_{70} at r_{200}=1.05 h^{-1}_{70} Mpc using
the observed temperature profile. The complex structure in the core region is
the key to explaining the discrepancy in gravitational mass determined from
XMM-Newton X-ray observations and HST optical lensing measurements.Comment: 16 pages, 12 figures, to appear in A&
A Search for Jet Handedness in Hadronic Decays
We have searched for signatures of polarization in hadronic jets from decays using the ``jet handedness'' method. The polar angle
asymmetry induced by the high SLC electron-beam polarization was used to
separate quark jets from antiquark jets, expected to be left- and
right-polarized, respectively. We find no evidence for jet handedness in our
global sample or in a sample of light quark jets and we set upper limits at the
95% C.L. of 0.063 and 0.099 respectively on the magnitude of the analyzing
power of the method proposed by Efremov {\it et al.}Comment: Revtex, 8 pages, 2 figure
Factors related to psychotherapists' self-assessment when treating anxiety and other disorders.
The aim of the study was to replicate and extend recent findings regarding therapists' self-assessment biases. This study examined clinicians' estimates of their abilities when working with general clinical groups and with anxious patients, and of the recovery/improvement rates of their clients. It also considered what clinician personality traits and clinical practice elements were associated with such estimates. A total of 195 out 801 clinicians completed a survey regarding self-ratings, team ratings, therapy outcomes for their clients, and their own personality traits. The great majority of clinicians rated themselves and their teams as being better clinicians than their peers, though not to as extreme a level as in the previous study. They also reported exceptionally positive therapy outcomes. Due to the large proportion of non-responders, it is possible that these findings do not reflect actual self-assessment bias, but a greater willingness to participate among clinicians who are more skilled and with particular personality styles. However, the data suggest that perceptions of skill and therapy outcome might be associated with clinician personality characteristics, though not with other clinical practice variables. These interpretations should be treated with caution due to the limited response rate. Different possible explanations for these patterns of self-assessment are outlined, including conscious and unconscious processes. Methods for enhancing accurate skill perception are discussed, including self-monitoring and supervision
Measurement of the Charged Multiplicities in b, c and Light Quark Events from Z0 Decays
Average charged multiplicities have been measured separately in , and
light quark () events from decays measured in the SLD experiment.
Impact parameters of charged tracks were used to select enriched samples of
and light quark events, and reconstructed charmed mesons were used to select
quark events. We measured the charged multiplicities:
,
, from
which we derived the differences between the total average charged
multiplicities of or quark events and light quark events: and . We compared
these measurements with those at lower center-of-mass energies and with
perturbative QCD predictions. These combined results are in agreement with the
QCD expectations and disfavor the hypothesis of flavor-independent
fragmentation.Comment: 19 pages LaTex, 4 EPS figures, to appear in Physics Letters
Social Class
Discussion of class structure in fifth-century Athens, historical constitution of theater audiences, and the changes in the comic representation of class antagonism from Aristophanes to Menander
Proinflammatory cytokine levels in fibromyalgia patients are independent of body mass index
<p>Abstract</p> <p>Background</p> <p>Fibromyalgia (FM) is characterized by chronic, widespread muscular pain and tenderness and is generally associated with other somatic and psychological symptoms. Further, circulatory levels of proinflammatory cytokines (IL-1β, TNF-α, and IL-6) may be altered in FM patients, possibly in association with their symptoms. Recently, rises in BMI have been suggested to contribute to increased circulating levels of proinflammatory cytokines in FM patients. Our aim was to measure the circulatory levels of proinflammatory cytokines to determine the influence of BMI on these levels in FM patients and healthy volunteers (HVs). In Spanish FM patients (n = 64) and HVs (n = 25), we measured BMI and serum concentrations of proinflammatory cytokines by capture ELISA.</p> <p>Findings</p> <p>There were significant differences in BMI levels between FM patients (26.40 ± 4.46) and HVs (23.64 ± 3.45) and significant increase in IL-6 in FM patients (16.28 ± 8.13 vs 0.92 ± 0.32 pg/ml) (P < 0.001). IL-1β and TNF-α decreased in FM patients compared with HVs. By ANCOVA, there was no significant association between BMI and TNF-α (F = 0.098, p = 0.75) or IL-6 (F = 0.221, p = 0.63) levels in FM patients.</p> <p>Conclusions</p> <p>Our analysis in FM patients of BMI as a covariate of proinflammatory cytokines levels showed that serum TNF-α and IL-6 levels are independent of BMI. Further studies are necessary to dissect these findings and their implication in future therapeutic approaches for FM patients.</p
Diffractive Dijet Production at sqrt(s)=630 and 1800 GeV at the Fermilab Tevatron
We report a measurement of the diffractive structure function of
the antiproton obtained from a study of dijet events produced in association
with a leading antiproton in collisions at GeV at the
Fermilab Tevatron. The ratio of at GeV to
obtained from a similar measurement at GeV is compared with
expectations from QCD factorization and with theoretical predictions. We also
report a measurement of the (-Pomeron) and ( of parton in
Pomeron) dependence of at GeV. In the region
, GeV and , is
found to be of the form , which obeys
- factorization.Comment: LaTeX, 9 pages, Submitted to Phys. Rev. Letter
A Study of B0 -> J/psi K(*)0 pi+ pi- Decays with the Collider Detector at Fermilab
We report a study of the decays B0 -> J/psi K(*)0 pi+ pi-, which involve the
creation of a u u-bar or d d-bar quark pair in addition to a b-bar -> c-bar(c
s-bar) decay. The data sample consists of 110 1/pb of p p-bar collisions at
sqrt{s} = 1.8 TeV collected by the CDF detector at the Fermilab Tevatron
collider during 1992-1995. We measure the branching ratios to be BR(B0 -> J/psi
K*0 pi+ pi-) = (8.0 +- 2.2 +- 1.5) * 10^{-4} and BR(B0 -> J/psi K0 pi+ pi-) =
(1.1 +- 0.4 +- 0.2) * 10^{-3}. Contributions to these decays are seen from
psi(2S) K(*)0, J/psi K0 rho0, J/psi K*+ pi-, and J/psi K1(1270)
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