12,225 research outputs found
On the Spin History of the X-ray Pulsar in Kes 73: Further Evidence For an Utramagnetized Neutron Star
In previous papers, we presented the discovery of a 12-s X-ray pulsar in the
supernova remnant Kes 73, providing the first direct evidence for an
ultramagnetized neutron star, a magnetar, with an equivalent dipole field of
nearly twenty times the quantum critical magnetic field. Our conclusions were
based on two epochs of measurement of the spin, along with an age estimate of
the host supernova remnant. Herein, we present a spin chronology of the pulsar
using additional GINGA, ASCA, XTE, & SAX datasets spanning over a decade.
Timing and spectral analysis confirms our initial results and severely limit an
accretion origin for the observed flux. Over the 10 year baseline, the pulsar
is found to undergo a rapid, constant spindown, while maintaining a steady flux
and an invariant pulse profile. Within the measurement uncertainties, no
systematic departures from a linear spin-down are found - departures as in the
case of glitches or simply stochastic fluctuations in the pulse
times-of-arrival (e.g. red timing noise). We suggest that this pulsar is akin
to the soft gamma-ray repeaters, however, it is remarkably stable and has yet
to display similar outbursts; future gamma-ray activity from this object is
likely.Comment: 6 pages with 3 embedded figures, LaTex, emulateapj.sty. Submitted to
the ApJ Letter
Effect of Inhomogeneous Heat Flow on the Enhancement of Heat Capacity in Helium-II by Counterflow near Tλ
In 2000 Harter et al. reported the first measurements of the enhancement of the heat capacity ÎCQ[equivalent]C(Q)-C(Q=0) of helium-II transporting a heat flux density Q near Tλ. Surprisingly, their measured ÎCQ was ~7â12 times larger than predicted, depending on which theory was assumed. In this report we present a candidate explanation for this discrepancy: unintended heat flux inhomogeneity. Because C(Q) should diverge at a critical heat flux density Qc, homogeneous heat flow is required for an accurate measurement. We present results from numerical analysis of the heat flow in the Harter et al. cell indicating that substantial inhomogeneity occurred. We determine the effect of the inhomogeneity on ÎCQ and find rough agreement with the observed disparity between prediction and measurement
A Damping of the de Haas-van Alphen Oscillations in the superconducting state
Deploying a recently developed semiclassical theory of quasiparticles in the
superconducting state we study the de Haas-van Alphen effect. We find that the
oscillations have the same frequency as in the normal state but their amplitude
is reduced. We find an analytic formulae for this damping which is due to
tunnelling between semiclassical quasiparticle orbits comprising both
particle-like and hole-like segments. The quantitative predictions of the
theory are consistent with the available data.Comment: 7 pages, 5 figure
Transient receptor potential melastatin 7 cation channel kinase new player in angiotensin IIâinduced hypertension
Transient receptor potential melastatin 7 (TRPM7) is a bifunctional protein comprising a magnesium (Mg2+)/cation channel and a kinase domain. We previously demonstrated that vasoactive agents regulate vascular TRPM7. Whether TRPM7 plays a role in the pathophysiology of hypertension and associated cardiovascular dysfunction is unknown. We studied TRPM7 kinaseâdeficient mice (TRPM7Îkinase; heterozygous for TRPM7 kinase) and wild-type (WT) mice infused with angiotensin II (Ang II; 400 ng/kg per minute, 4 weeks). TRPM7 kinase expression was lower in heart and aorta from TRPM7Îkinase versus WT mice, effects that were further reduced by Ang II infusion. Plasma Mg2+ was lower in TRPM7Îkinase versus WT mice in basal and stimulated conditions. Ang II increased blood pressure in both strains with exaggerated responses in TRPM7Îkinase versus WT groups (P<0.05). Acetylcholine-induced vasorelaxation was reduced in Ang IIâinfused TRPM7Îkinase mice, an effect associated with Akt and endothelial nitric oxide synthase downregulation. Vascular cell adhesion moleculeâ1 expression was increased in Ang IIâinfused TRPM7 kinaseâdeficient mice. TRPM7 kinase targets, calpain, and annexin-1, were activated by Ang II in WT but not in TRPM7Îkinase mice. Echocardiographic and histopathologic analysis demonstrated cardiac hypertrophy and left ventricular dysfunction in Ang IIâtreated groups. In TRPM7 kinaseâdeficient mice, Ang IIâinduced cardiac functional and structural effects were amplified compared with WT counterparts. Our data demonstrate that in TRPM7Îkinase mice, Ang IIâinduced hypertension is exaggerated, cardiac remodeling and left ventricular dysfunction are amplified, and endothelial function is impaired. These processes are associated with hypomagnesemia, blunted TRPM7 kinase expression/signaling, endothelial nitric oxide synthase downregulation, and proinflammatory vascular responses. Our findings identify TRPM7 kinase as a novel player in Ang IIâinduced hypertension and associated vascular and target organ damage
Validation of the inverted adsorption structure for free-base tetraphenyl porphyrin on Cu(111)
Utilising normal incidence X-ray standing waves we rigourously scrutinise the âinverted modelâ as the adsorption structure of free-base tetraphenyl porphyrin on Cu(111). We demonstrate that the iminic N atoms are anchored at near-bridge adsorption sites on the surface displaced laterally by 1.1 ± 0.2 Ă
in excellent agreement with previously published calculations
Transverse momentum dependence in the perturbative calculation of pion form factor
By reanalysing transverse momentum dependence in the perturbative calculation
of pion form factor an improved expression of pion form factor which takes into
account the transverse momentum dependenc in hard scattering amplitude and
intrinsic transverse momentum dependence associated with pion wave functions is
given to leading order, which is available for momentum transfers of the order
of a few GeV as well as for . Our scheme can be extended to
evaluate the contributions to the pion form factor beyond leading order.Comment: 13 pages in LaTeX, plus 3 Postscript figure
Feeds and Forages Intervention Strategies for Improved Livestock Nutrition and Productivity in the Northwest Highlands of Vietnam
Livestock production in Vietnam is critical for livelihoods particularly for ethnic minorities in the Northwest Highlands (NWH). Improved livestock management and productivity can be achieved through better feed management and increased cultivation of improved forages, to meet animal nutrition demand. This study aimed at assessing feed intervention strategies to address context-specific feed-related challenges, mainly winter feed shortage in Mai Son district, Son La province, Vietnam. Feed interventions included promotion of improved forages (grasses and legumes) and capacity building on animal nutrition techniques including feed preservation, feed mix and feeding regimes for cattle and pigs. Willing farmers selected from a list of improved forages, were provided with seeds and planting materials, and guided on forage planting, management, and utilization. Farmers reported increased awareness on feed technologies, increased yield, and availability of high-quality feed for their livestock, as well as challenges encountered in forage utilization. Initial results from this study show the potential of feed and forage technologies in improving livestock productivity and lays a foundation for scaling these interventions in Vietnam
Making Sense of Hip Preservation Procedural Coding--Getting Paid for Your Work!
Hip preservation and peri-trochanteric procedures are becoming more commonplace for the arthroplasty surgeon. Understanding the reimbursement for these procedures remains a challenge for those looking to expand this portion of their practice. In order to financially maximize the surgeonâs efforts, we present recommendations for hip preservation procedural coding
Timelike form factors at high energy
The difference between the timelike and spacelike meson form factors is
analysed in the framework of perturbative QCD with Sudakov effects included. It
is found that integrable singularities appear but that the asymptotic behavior
is the same in the timelike and spacelike regions. The approach to asymptotia
is quite slow and a rather constant enhancement of the timelike value is
expected at measurable large . This is in agreement with the trend
shown by experimental data.Comment: 17 pages, report DAPNIA/SPhN 94 0
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