372 research outputs found
Anisotropy of the space orientation of radio sources. I: The catalog
A catalog of the extended extragalactic radio sources consisting of 10461
objects is compiled based on the list of radio sources of the FIRST survey. A
total of 1801 objects are identified with galaxies and quasars of the SDSS
survey and the Veron-Veron catalog. The distribution of the position angles of
the axes of radio sources from the catalog is determined, and the probability
that this distribution is equiprobable is shown to be less then 10^(-7). This
result implies that at Z equal to or smaller then 0.5, spatial orientation of
the axes of radio sources is anisotropic at a statistically significant level.Comment: 8 pages, 7 figure
Intra-osseous synovial sarcoma.
Intra-osseous synovial sarcoma is very rare and its mode of origin is conjectural. Our patient's tumour was situated within the lower femur. The sited of origin of the few intra-osseous synovial sarcomas so far documented may support the concept of intra-osseous synovial rests
Fine-scale genetic variation and evolution of West Nile virus in a transmission "hot spot" in suburban Chicago, USA.
Migraine attacks the Basal Ganglia
<p>Abstract</p> <p>Background</p> <p>With time, episodes of migraine headache afflict patients with increased frequency, longer duration and more intense pain. While episodic migraine may be defined as 1-14 attacks per month, there are no clear-cut phases defined, and those patients with low frequency may progress to high frequency episodic migraine and the latter may progress into chronic daily headache (> 15 attacks per month). The pathophysiology of this progression is completely unknown. Attempting to unravel this phenomenon, we used high field (human) brain imaging to compare functional responses, functional connectivity and brain morphology in patients whose migraine episodes did not progress (LF) to a matched (gender, age, age of onset and type of medication) group of patients whose migraine episodes progressed (HF).</p> <p>Results</p> <p>In comparison to LF patients, responses to pain in HF patients were significantly lower in the caudate, putamen and pallidum. Paradoxically, associated with these lower responses in HF patients, gray matter volume of the right and left caudate nuclei were significantly larger than in the LF patients. Functional connectivity analysis revealed additional differences between the two groups in regard to response to pain.</p> <p>Conclusions</p> <p>Supported by current understanding of basal ganglia role in pain processing, the findings suggest a significant role of the basal ganglia in the pathophysiology of the episodic migraine.</p
On the Hadronic Beam Model for Gamma-ray Production in Blazars
We consider, herein, a model for gamma-ray production in blazars in which a
relativistic, highly-collimated electron-proton beam interacts with a dense,
compact cloud as the jet propagates through the broad and perhaps narrow line
regions (BLR and NLR) of active galactic nuclei (AGN). During the propagation
of the beam through the cloud, the process of excitation of plasma waves
becomes an important energy loss mechanism, especially for mildly relativistic
proton beams. We compute the expected spectra of gamma-rays from the decay of
neutral pions produced in hadronic collisions of the beam with the cloud,
taking into account collisionless losses of the electron-proton beam. This
model may explain the X-ray and TeV gamma-ray (both low and high emission
states) of Mrk 421 as a result of synchrotron emission of secondary pairs from
the decay of charged pions and gamma-ray emission from the decay of neutral
pions for the plausible cloud parameters. However clouds can not be too hot and
too dense. Otherwise the TeV gamma-rays can be attenuated by the bremsstrahlung
radiation in the cloud and the secondary pairs are not able to efficiently
produce synchrotron flares because of the dominant role of inverse Compton
scattering.
The non-variable -ray emission observed from Mrk 421 in the EGRET
energy range cannot be described by the -rays from decay of neutral
pions provided that the spectrum of protons in the beam is well described by a
simple power law. These -rays might only be produced by secondary pairs
scattering the soft non-variable X-rays which might originate in the inner part
of the accretion disk.Comment: 14 pages,3 figures, latex, submitted to Ap
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