44,868 research outputs found
A multiwavlength study of PSR B0628-28: The first overluminous rotation-powered pulsar?
The ROSAT source RX J0630.8-2834 was suggested by positional coincidence to
be the X-ray counterpart of the old field pulsar PSR B0628-28. This
association, however, was regarded to be unlikely based on the computed
energetics of the putative X-ray counterpart. In this paper we report on
multiwavelength observations of PSR B0628-28 made with the ESO/NTT observatory
in La Silla, the Jodrell Bank radio observatory and XMM-Newton. Although the
optical observations do not detect any counterpart of RX J0630.8-2834 down to a
limiting magnitude of V=26.1 mag and B=26.3 mag, XMM-Newton observations
finally confirmed it to be the pulsar's X-ray counterpart by detecting X-ray
pulses with the radio pulsar's spin-period. The X-ray pulse profile is
characterized by a single broad peak with a second smaller peak leading the
main pulse component by ~144 degree. The fraction of pulsed photons is (38 +-
7)% with no strong energy dependence in the XMM-Newton bandpass. The pulsar's
X-ray spectrum is well described by a single component power law with photon
index 2.63^{+0.23}_{-0.15}, indicating that the pulsar's X radiation is
dominated by non-thermal emission processes. A low level contribution of
thermal emission from residual cooling or from heated polar caps, cannot be
excluded. The pulsar's spin-down to X-ray energy conversion efficiency is
obtained to be ~16% for the radio dispersion measure inferred pulsar distance.
If confirmed, PSR B0628-28 would be the first X-ray overluminous
rotation-powered pulsar identified among all ~1400 radio pulsars known today.Comment: Accepted for publication in ApJ. Find a paper copy with higher
resolution images at
ftp://ftp.xray.mpe.mpg.de/people/web/astro-ph-0505488_rev2.pd
Human Capital, Fertility, and Economic Growth
Our model of growth departs from both the Malthusian and neoclassical approaches by including investments in human capital. We assume, crucially, that rates of return on human capital investments rise, rather than, decline, as the stock of human capital increases, until the stock becomes large. This arises because the education sector uses human capital note intensively than either the capital producing sector of the goods producing sector. This produces multiple steady scares: an undeveloped steady stare with little human capital, low rates of return on human capital investments and high fertility, and a developed steady stats with higher rates of return a large, and, perhaps, growing stock of human capital and low fertility. Multiple steady states mean that history and luck are critical determinants of a country's growth experience.
A 4-Component Dirac Theory of Ionization of Hydrogen Molecular Ion in a Super-Intense Laser Field
In this paper a 4-component Dirac theory of ionization of hydrogen molecular
ion in a super-intense laser field is developed. Simple analytic expressions
for the spin specific as well as the total ionization currents emitted from the
ground state of the ion are derived. The results are given for all polarization
and finite propagation vectors of the field. They apply for inner-shell
ionization of analogous heavier molecular ions as well. The presence of
molecular two-slit interference effect, first found in the non-relativistic
case, and the spin-flip ionization current, and an asymmetry of the up- and
down-spin currents similar to that predicted in the atomic case, are found also
to hold for the present relativistic molecular ionic case. Finally, the
possibility of controlling the dominant spin currents by selecting the
handedness of a circularly polarized incident laser field is pointed out.Comment: 7 pages, no figure
A Coherent Timing Solution for the Nearby Isolated Neutron Star RX J0720.4-3125
We present the results of a dedicated effort to measure the spin-down rate of
the nearby isolated neutron star RX J0720.4-3125. Comparing arrival times of
the 8.39-sec pulsations for data from Chandra we derive an unambiguous timing
solution for RX J0720.4-3125 that is accurate to 5 years.
Adding data from XMM and ROSAT, the final solution yields
Pdot=(6.98+/-0.02)x10^(-14) s/s; for dipole spin-down, this implies a
characteristic age of 2 Myr and a magnetic field strength of 2.4e13 G. The
phase residuals are somewhat larger than those for purely regular spin-down,
but do not show conclusive evidence for higher-order terms or a glitch. From
our timing solution as well as recent X-ray spectroscopy, we concur with recent
suggestions that RX J0720.4-3125 is most likely an off-beam radio pulsar with a
moderately high magnetic field.Comment: 5 pages, 1 figure. Accepted for publication in ApJ
Governance aspects of cross-border EU competition actions: theoretical and practical challenges
This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.The authors have aimed to produce a theoretical model which considers the choice
of governance design of cross-border EU competition law actions. To this end, they have
analysed the current litigation pattern (and litigants’ strategies). On this basis, the specific
issues which arise in cross-border EU competition law actions have been identified with a view
to proposing an appropriate course for any reform in the area. A mix of research methods have
been used - in addition to employing traditional library based legal research methods, opinions
of legal practitioners from England and Germany and policy-makers from Brussels have been
considered. The article demonstrates that, given the diverse nature of the European Union, a
new mode of governance should be used by the EU legislator in order to close the EU
competition law enforcement gap. The authors suggest that Regulation 1/2003 should
incorporate a specifically designated private international law mechanism which promotes
inter-jurisdictional regulatory competition in the area of EU competition law dispute resolution,
and produces efficient enforcement results in a multi-level system of governance. It has been
submitted that some of the specific problems that arise may be best addressed by appropriately
drafted private international rules which address inter alia the low mobility of consumers and
SMEs
Integral field spectroscopy of QSO host galaxies
We describe a project to study the state of the ISM in ~20 low redshift
(z<0.3) QSO host galaxies observed with the PMAS integral field spectrograph.
We describe method developement to access the stellar and gas component of the
spectrum without the strong nuclear emission to access the host galaxy
properties also in the central region. It shows that integral field
spectroscopy promises to be very efficient to study the gas distribution and
its velocity field, and also spatially resolved stellar population in the host
galaxies also of luminous AGN.Comment: 4 pages, 6 figures, Euro3D Science Workshop, Cambridge, May 2003, AN,
accepte
A technique for automatic real time scoring of several simultaneous sleep electroencephalograms
Automatic real-time scoring of simultaneous sleep electroencephalogram
Axillary bud viability and dry matter production of Poa ligularis in Patagonian grasslands
Poa ligularis Nees is one of the dominant perennial grass species in Patagonian grasslands. This is the first field study which investigated the effects of defoliation frequency on its number of viable axillary buds, and subsequent dry matter production during one growing season. Experiments were arranged in a randomized complete block design. Treatments included one defoliation height (10 cm), from one to five times a year, and undefoliated controls. Bud respiratory activity was examined usingthe tetrazolium test and the vital stain Evan's blue. At the end of the growing season, plants that have been defoliated more than three times showed significatively (p<0.05) lower number of respiratory active buds than unclipped controls. A high defoliation frequency increased bud death in stem bases. Both defoliated and undefoliated plants produced more (p<0.05) axillary buds at the periphery than at their center. Defoliation treatments increased shoot weight by 13.4% on average compared with undefoliated controls, but reduced in by 10% the average number of metabolically active axillary buds. This indicates that this reduction, however, was not high enough to constrain dry matter production.It appears that Poa ligularis could tolerate moderate grazing frequency and intensity without compromising its potential regrowth capacity. Longer-term studies of the effects of defoliation on dry matter production and bud metabolic activity are needed to understand the cumulative effects of grazing of P. ligularis in natural grasslands.Poa ligularis Nees es una de las especies de gramíneas perennes dominantes en los pastizales naturales de la Patagonia. Este es el primer estudio que investigó los efectos de la frequencia de defoliación sobre su número de yemas axilares viables, y subsiguiente producción de materia seca durante una estación de crecimiento. Los estudios se efectuaron utilizando un diseño de bloques completamente al azar. Los tratamientos incluyeron una altura de defoliación (10 cm), de una a cinco veces por año, además de controles no defoliados. La actividad respiratoria de las yemas fue examinada usando el método del tetrazolio y el colorante vital azul de Evans.Hacia el final de la estación de crecimiento, las plantas que habían sido defoliadas más de tres veces mostraron un número significativamente menor (p<0.05) de yemas con actividad respiratoria que los controles no defoliados. Una alta frecuencia de defoliación incrementó la muerte de yemas en las bases de tallos. Todas las plantas- defoliadas o no, produjeron más (p<0.05) yemas axilares en su periferia que en su centro. La defoliación incrementó 13.4% el peso de los tallos en promedio, pero redujo en 10% el número promedio de yemas axilares metabólicamente activas. Esto indica que esta reducción , sin embargo, no fue suficiente como para limitar la producción de materia seca. Parece que P. ligularis toleraría una frecuencia e intensidad moderada de pastoreo sin comprometer su capacidad potencial de rebrote. Se necesitan estudios a más largo plazo de los efectos de la defoliación en la producción de materia seca y actividad metabólica de las yemas para entender los efectos acumulativos del pastoreo de Poa ligularis en los pastizales naturales.Fil: Souto, Cintia Paola. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Becker, G. F.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche; ArgentinaFil: Siffredi, G. L.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche; ArgentinaFil: Busso, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; ArgentinaFil: Sterberg, M.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche; Argentin
Quantum Gravity Corrections for Schwarzschild Black Holes
We consider the Matrix theory proposal describing eleven-dimensional
Schwarzschild black holes. We argue that the Newtonian potential between two
black holes receives a genuine long range quantum gravity correction, which is
finite and can be computed from the supergravity point of view. The result
agrees with Matrix theory up to a numerical factor which we have not computed.Comment: 14 pages, Tex, no figure
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