4,244 research outputs found
Right-handed sneutrino as thermal dark matter
We study an extension of the MSSM with a singlet S with coupling SH1H2 in
order to solve the mu problem as in the NMSSM, and right-handed neutrinos N
with couplings SNN in order to generate dynamically electroweak-scale Majorana
masses. We show how in this model a purely right-handed sneutrino can be a
viable candidate for cold dark matter in the Universe. Through the direct
coupling to the singlet, the sneutrino can not only be thermal relic dark
matter but also have a large enough scattering cross section with nuclei to
detect it directly in near future, in contrast with most of other right-handed
sneutrino dark matter models.Comment: 5 pages, 2 figures. References added and minor changes. Final version
to appear in Phys. Rev.
Gravitational signals due to tidal interactions between white dwarfs and black holes
In this paper we compute the gravitational signal emitted when a white dwarf
moves around a black hole on a closed or open orbit using the affine model
approach. We compare the orbital and the tidal contributions to the signal,
assuming that the star moves in a safe region where, although very close to the
black hole, the strength of the tidal interaction is insufficient to provoque
the stellar disruption. We show that for all considered orbits the tidal signal
presents sharp peaks corresponding to the excitation of the star non radial
oscillation modes, the amplitude of which depends on how deep the star
penetrates the black hole tidal radius and on the type of orbit. Further
structure is added to the emitted signal by the coupling between the orbital
and the tidal motion.Comment: 21 pages, 8 figres. Submitted to MNRA
A key role for leukemia inhibitory factor in C26 cancer cachexia
Cachexia is an exacerbating event in many types of cancer that is strongly associated with a poor prognosis. We have identified cytokine, signaling, and transcription factors that are required for cachexia in the mouse C26 colon carcinoma model of cancer. C2C12 myotubes treated with conditioned medium from C26 cancer cells induced atrophy and activated a STAT-dependent reporter gene but not reporter genes dependent on SMAD, FOXO, C/EBP, NF-κB, or AP-1. Of the gp130 family members IL-11, IL-6, oncostatin M (OSM), and leukemia inhibitory factor (LIF), only OSM and LIF were sufficient to activate the STAT reporter in myotubes. LIF was elevated in C26 conditioned medium (CM), but IL-6, OSM, TNFα, and myostatin were not. A LIF-blocking antibody abolished C26 CM-induced STAT reporter activation, STAT3 phosphorylation, and myotube atrophy but blocking antibodies to IL-6 or OSM did not. JAK2 inhibitors also blocked C26 CM-induced STAT reporter activation, STAT3 phosphorylation, and atrophy in myotubes. LIF at levels found in the C26 CM was sufficient for STAT reporter activation and atrophy in myotubes. In vivo, an increase in serum LIF preceded the increase in IL-6 in mice with C26 tumors. Overexpression of a dominant negative Stat3Cβ-EGFP gene in myotubes and in mouse muscle blocked the atrophy caused by C26 CM or C26 tumors, respectively. Taken together, these data support an important role of LIF-JAK2-STAT3 in C26 cachexia and point to a therapeutic approach for at least some types of cancer cachexia.R01 AR060217 - NIAMS NIH HHS; UL1 TR000157 - NCATS NIH HHS; UL1-TR000157 - NCATS NIH HHShttp://www.jbc.org/content/290/32/19976.full.pdf?sid=936d126d-814b-4f54-961d-0e98caa31314Published versio
Numerical Analyses of Weakly Nonlinear Velocity-Density Coupling
We study evolution of various statistical quantities of smoothed cosmic
density and velocity fields using N-body simulations. The parameter
characterizes nonlinear coupling of
these two fields and determines behavior of bulk velocity dispersion as a
function of local density contrast.
It is found that this parameter depends strongly on the smoothing scale even
in quasi-linear regimes where the skewness parameter
is nearly constant and close to the predicted value by the second-order
perturbation theory. We also analyze weakly nonlinear effects caused by an
adaptive smoothing known as the gather approach.Comment: 22 pages, 4 figures, to appear in ApJ (558, Sep 10
A global fingerprint of macro-scale changes in urban structure from 1999 to 2009
Urban population now exceeds rural population globally, and 60–80% of global energy consumption by households, businesses, transportation, and industry occurs in urban areas. There is growing evidence that built-up infrastructure contributes to carbon emissions inertia, and that investments in infrastructure today have delayed climate cost in the future. Although the United Nations statistics include data on urban population by country and select urban agglomerations, there are no empirical data on built-up infrastructure for a large sample of cities. Here we present the first study to examine changes in the structure of the world\u27s largest cities from 1999 to 2009. Combining data from two space-borne sensors—backscatter power (PR) from NASA\u27s SeaWinds microwave scatterometer, and nighttime lights (NL) from NOAA\u27s defense meteorological satellite program/operational linescan system (DMSP/OLS)—we report large increases in built-up infrastructure stock worldwide and show that cities are expanding both outward and upward. Our results reveal previously undocumented recent and rapid changes in urban areas worldwide that reflect pronounced shifts in the form and structure of cities. Increases in built-up infrastructure are highest in East Asian cities, with Chinese cities rapidly expanding their material infrastructure stock in both height and extent. In contrast, Indian cities are primarily building out and not increasing in verticality. This new dataset will help characterize the structure and form of cities, and ultimately improve our understanding of how cities affect regional-to-global energy use and greenhouse gas emissions
Correlation analysis of stochastic gravitational wave background around 0.1-1Hz
We discuss prospects for direct measurement of stochastic gravitational wave
background around 0.1-1Hz with future space missions. It is assumed to use
correlation analysis technique with the optimal TDI variables for two sets of
LISA-type interferometers. The signal to noise for detection of the background
and the estimation errors for its basic parameters (amplitude, spectral index)
are evaluated for proposed missions.Comment: 11 pages, 7 figures, revised version, to appear in PR
Relativistic Resonant Relations between Massive Black Hole Binary and Extreme Mass Ratio Inspiral
One component of a massive black hole binary (MBHB) might capture a small
third body, and then a hierarchical, inclined triple system would be formed.
With the post-Newtonian approximation including radiation reaction, we analyzed
the evolution of the triple initially with small eccentricities. We found that
an essentially new resonant relation could arise in the triple system. Here
relativistic effects are crucial. Relativistic resonances, including the new
one, stably work even for an outer MBHB of comparable masses, and significantly
change the orbit of the inner small body.Comment: 9 pages, 5 figures, to appear in PR
Signature of the Overhauser field on the coherent spin dynamics of donor-bound electron in a single CdTe quantum well
We have studied the coherent spin dynamics in an oblique magnetic field of
electrons localized on donors and placed in the middle of a single CdTe quantum
well, by using a time-resolved optical technique: the photo-induced Faraday
rotation. We showed that this dynamics is affected by a weak Overhauser field
created via the hyperfine interaction of optically spin-polarized donor-bound
electrons with the surrounding nuclear isotopes carrying non-zero spins. We
have measured this nuclear field, which is on the order of a few mT and can
reach a maximum experimental value of 9.4 mT. This value represents 13 % of the
maximal nuclear polarization, and corresponds also to 13 % of maximal
electronic polarization.Comment: 15 pages, 4 figure
Gravitational Wave Astrometry for Rapidly Rotating Neutron Stars and Estimation of Their Distances
We discuss an astrometric timing effect on data analysis of continuous
gravitational waves from rapidly rotating isolated neutron stars. Special
attention is directed to the possibility of determining their distances by
measuring the curvature of the wave fronts. We predict that if continuous
gravitational waves from an unknown neutron star with a stable rotation are
detected around 1kHz within 1/3yr by initial LIGO detectors and the ellipticity
parameter epsilon is smaller than 10^{-6}, the distance r to the source can be
estimated with relative error \Delta r/r of \sim 10% by using the broad band
configuration of advanced LIGO detectors over 3 years. By combining the
observed amplitude of the waves with the estimated distance, information on the
parameter can be obtained purely through gravitational wave
measurements.Comment: 6 pages, 1 figure, to appear in PR
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