1,185 research outputs found
X-ray emission from high-redshift miniquasars: self-regulating the population of massive black holes through global warming
Observations of high-redshift quasars at z>6 imply that supermassive black
holes (SMBHs) with masses over a billion solar masses were in place less than 1
Gyr after the Big Bang. If these SMBHs assembled from "seed" BHs left behind by
the first stars, then they must have accreted gas at close to the Eddington
limit during a large fraction (>50%) of the time. A generic problem with this
scenario, however, is that the mass density in million-solar-mass SMBHs at z=6
already exceeds the locally observed SMBH mass density by several orders of
magnitude; in order to avoid this overproduction, BH seed formation and growth
must become significantly less efficient in less massive protogalaxies, while
proceeding uninterrupted in the most massive galaxies that formed first. Using
Monte-Carlo realizations of the merger and growth history of BHs, we show that
X-rays from the earliest accreting BHs can provide such a feedback mechanism.
Our calculations paint a self-consistent picture of black-hole-made climate
change, in which the first miniquasars---among them the ancestors of the z>6
quasar SMBHs---globally warm the IGM and suppress the formation and growth of
subsequent generations of BHs. We present two specific models with global
miniquasar feedback that provide excellent agreement with recent estimates of
the z=6 SMBH mass function. For each of these models, we estimate the rate of
BH mergers at z>6 that could be detected by the proposed gravitational-wave
observatory eLISA/NGO.Comment: 15 pages, 6 figures, accepted to MNRAS; v2 includes minor changes,
mostly to references, to match version to be publishe
Assessment of Epicardial Fat Volume With Threshold-Based 3-Dimensional Segmentation in CT: Comparison With the 2-Dimensional Short Axis-Based Method
Analysis of government policies, institutions, and inward foreign direct investment: evidence from sub-Saharan Africa
Chern-Simons black holes: scalar perturbations, mass and area spectrum and greybody factors
We study the Chern-Simons black holes in d-dimensions and we calculate
analytically the quasi-normal modes of the scalar perturbations and we show
that they depend on the highest power of curvature present in the Chern-Simons
theory. We obtain the mass and area spectrum of these black holes and we show
that they have a strong dependence on the topology of the transverse space and
they are not evenly spaced. We also calculate analytically the reflection and
transmission coefficients and the absorption cross section and we show that at
low frequency limit there is a range of modes which contributes to the
absorption cross section.Comment: 19 pages, 18 figures, the title has been changed to reflect the
addition of an another section on the reflection, transmission coefficients
and absorption cross sections of the Chern-Simons black holes. Version to be
published in JHE
Measuring Daily Events and Experiences: Decisions for the Researcher
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98999/1/j.1467-6494.1991.tb00260.x.pd
Urodynamic Effects of Propiverine on Detrusor Overactivity and Abdominal Straining during Voiding in Awake Rats with Intravesical Prostaglandin E2 Instillation
Experimental determination of the magnetic interactions of frustrated Cairo pentagon lattice materials
We present inelastic neutron scattering measurements of the Cairo pentagon
lattice magnets BiFeO and BiFeOF, supported by high
field magnetisation measurements of BiFeO. Using linear spin wave
theory and mean field analyses we determine the spin exchange interactions and
single-ion anisotropy in these materials. The Cairo lattice is geometrically
frustrated and consists of two inequivalent magnetic sites, both occupied by
Fe ions and connected by two competing nearest neighbour interactions.
We found that one of these interactions, coupling nearest neighbour spins on
the three-fold symmetric sites, is extremely strong and antiferromagnetic.
These strongly coupled dimers are then weakly coupled to a framework formed
from spins occupying the other inequivalent site. In addition we found that the
Fe spins have a non-negligible single-ion anisotropy, which
manifests as a spin anisotropy gap in the neutron spectrum and a spin-flop
transition in high field magnetisation measurements.Comment: 10 pages, 9 figure
VnD: a structure-centric database of disease-related SNPs and drugs
Numerous genetic variations have been found to be related to human diseases. Significant portion of those affect the drug response as well by changing the protein structure and function. Therefore, it is crucial to understand the trilateral relationship among genomic variations, diseases and drugs. We present the variations and drugs (VnD), a consolidated database containing information on diseases, related genes and genetic variations, protein structures and drug information. VnD was built in three steps. First, we integrated various resources systematically to deduce catalogs of disease-related genes, single nucleotide polymorphisms (SNPs), protein mutations and relevant drugs. VnD contains 137 195 disease-related gene records (13 940 distinct genes) and 16 586 genetic variation records (1790 distinct variations). Next, we carried out structure modeling and docking simulation for wild-type and mutant proteins to examine the structural and functional consequences of non-synonymous SNPs in the drug-related genes. Conformational changes in 590 wild-type and 4437 mutant proteins from drug-related genes were included in our database. Finally, we investigated the structural and biochemical properties relevant to drug binding such as the distribution of SNPs in proximal protein pockets, thermo-chemical stability, interactions with drugs and physico-chemical properties. The VnD database, available at http://vnd.kobic.re.kr:8080/VnD/ or vandd.org, would be a useful platform for researchers studying the underlying mechanism for association among genetic variations, diseases and drugs
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