5,054 research outputs found
Mapping New Zealand and Antarctic snowpack from LANDSAT
Ther are no author-identified significant results in this report
Scout motor performance analysis and prediction study /PAPS/
Scout motor performance analysis and predictio
Spectral Transition and Torque Reversal in X-ray Pulsar 4U 1626-67
The accretion-powered, X-ray pulsar 4U 1626-67 has recently shown an abrupt
torque reversal accompanied by a dramatic spectral transition and a relatively
small luminosity change. The time-averaged X-ray spectrum during spin-down is
considerably harder than during spin-up. The observed torque reversal can be
explained by an accretion flow transition triggered by a gradual change in the
mass accretion rate. The sudden transition to spin-down is caused by a change
in the accretion flow rotation from Keplerian to sub-Keplerian. 4U 1626-67 is
estimated to be near spin equilibrium with a mass accretion rate Mdot~2x10**16
g/s, Mdot decreasing at a rate ~6x10**14 g/s/yr, and a polar surface magnetic
field of ~2b_p**{-1/2} 10^**12G where b_p is the magnetic pitch. During
spin-up, the Keplerian flow remains geometrically thin and cool. During
spin-down, the sub-Keplerian flow becomes geometrically thick and hot. Soft
photons from near the stellar surface are Compton up-scattered by the hot
accretion flow during spin-down while during spin-up such scattering is
unlikely due to the small scale-height and low temperature of the flow. This
mechanism accounts for the observed spectral hardening and small luminosity
change. The scattering occurs in a hot radially falling column of material with
a scattering depth ~0.3 and a temperature ~10^9K. The X-ray luminosity at
energies >5keV could be a poor indicator of the mass accretion rate. We briefly
discuss the possible application of this mechanism to GX 1+4, although there
are indications that this system is significantly different from other
torque-reversal systems.Comment: 10 pages, 1 figure, ApJ
Nuclear corrections in neutrino-nucleus DIS and their compatibility with global NPDF analyses
We perform a global chi^2-analysis of nuclear parton distribution functions
using data from charged current neutrino-nucleus deep-inelastic scattering
(DIS), charged-lepton-nucleus DIS, and the Drell-Yan (DY) process. We show that
the nuclear corrections in nu-A DIS are not compatible with the predictions
derived from l^+A DIS and DY data. We quantify this result using a
hypothesis-testing criterion based on the chi^2 distribution which we apply to
the total chi^2 as well as to the chi^2 of the individual data sets. We find
that it is not possible to accommodate the data from nu-A and l^+A DIS by an
acceptable combined fit. Our result has strong implications for the extraction
of both nuclear and proton parton distribution functions using combined
neutrino and charged-lepton data sets.Comment: 5 page
Pulsed Plasma Accelerator Modeling
This report presents the main results of the modeling task of the PPA project. The objective of this task is to make major progress towards developing a new computational tool with new capabilities for simulating cylindrically symmetric 2.5 dimensional (2.5 D) PPA's. This tool may be used for designing, optimizing, and understanding the operation of PPA s and other pulsed power devices. The foundation for this task is the 2-D, cylindrically symmetric, magnetohydrodynamic (MHD) code PCAPPS (Princeton Code for Advanced Plasma Propulsion Simulation). PCAPPS was originally developed by Sankaran (2001, 2005) to model Lithium Lorentz Force Accelerators (LLFA's), which are electrode based devices, and are typically operated in continuous magnetic field to the model, and implementing a first principles, self-consistent algorithm to couple the plasma and power circuit that drives the plasma dynamics
Isolation of microsatellite loci in the Capricorn silvereye, Zosterops lateralis chlorocephalus (Aves : Zosteropidae)
The Capricorn silvereye (Zosterops lateralis chlorocephalus
) is ideally suited to investigating the genetic basis of body size evolution. We have isolated and characterized a set of microsatellite markers for this species. Seven out of 11 loci were polymorphic. The number of alleles
detected ranged from two to five and observed heterozygosities between 0.12 and 0.67. One locus, ZL49, was found to be sex-linked. This moderate level of diversity is consistent with that expected in an isolated, island population
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