1,350 research outputs found
Magnetic fields generated by r-modes in accreting millisecond pulsars
In millisecond pulsars the existence of the Coriolis force allows the
development of the so-called Rossby oscillations (r-modes) which are know to be
unstable to emission of gravitational waves. These instabilities are mainly
damped by the viscosity of the star or by the existence of a strong magnetic
field. A fraction of the observed millisecond pulsars are known to be inside
Low Mass X-ray Binaries (LMXBs), systems in which a neutron star (or a black
hole) is accreting from a donor whose mass is smaller than 1 . Here we
show that the r-mode instabilities can generate strong toroidal magnetic fields
by inducing differential rotation. In this way we also provide an alternative
scenario for the origin of the magnetars.Comment: 6 pages, 3 figures, Proceedings conference "Theoretical Nuclear
Physics", Cortona October 200
The mtDNA 15497 G/A polymorphism in cytochrome b in severe obese subjects from Southern Italy.
Background and aim: A large number of mitochondrial DNA (mtDNA)
mutations have been implicated in degenerative diseases and aging. The aim of this
study was to evaluate whether the 15497 G/A mtDNA polymorphism (G251S) in the
cytochrome b subunit of respiratory complex III, which has been associated with
obesity-related variables and lipid metabolism in a Japanese population, is
associated with severe obesity also in adult Caucasians from southern Italy.
Methods and results: Unrelated severely obese patients (n Z 317; BMI > 40 kg/m2)
and controls (n Z 217; BMI < 25 kg/m2) from Southern Italy were genotyped by
allelic discrimination TaqMan assay for the 15497 G/A mtDNA polymorphism. In
obese patients fasting serum total cholesterol, triglycerides, HDL-cholesterol and
glucose were measured enzymatically and sitting blood pressure and heart rate
were also collected. Mean levels of total cholesterol, triglycerides and glucose were
below the upper reference limit for healthy subjects. Female obese subjects
showed lower levels of blood pressure and heart rate and higher levels of
HDL cholesterol than male obese patients (P < 0.001). All the control subjects and 315/317 severely obese patients were homozygous for the G allele (wild type),
whereas only 2/317, were females homozygous for the A allele.
Conclusions: The mtDNA 15497 G/A polymorphism in cytochrome b was present in
0.6% obese subjects, two females whose lipid parameters and BMI were similar to
those of the overall group. Therefore, this mutation may appear to contribute in
rare instances to severe obesity but does not explain the majority of cases in our
population. A more extensive genetic haplogroup characterization is required to
identify associations to obesity in Caucasians
‘Candidatus Phytoplasma cynodontis’ (16SrXIV group) affecting Oplismenus burmannii (Retz.) P. Beauv. and Digitaria sanguinalis (L.) Scop. in India.
Absence of anomalous interactions in the quantum theory of constrained charged particles in presence of electrical currents
The experimental progress in synthesizing low-dimensional nanostructures
where carriers are confined to bent surfaces has boosted the interest in the
theory of quantum mechanics on curved two-dimensional manifolds. It was
recently asserted that constrained electrically charged particles couple to a
term linear in A_3 M, where A_3 is the transversal component of the
electromagnetic vector potential and M the surface mean curvature, thereby
making a dimensional reduction procedure impracticable in the presence of
fields. Here we resolve this apparent paradox by providing a consistent general
framework of the thin-wall quantization procedure. We also show that the
separability of the equation of motions is not endangered by the particular
choice of the constraint imposed on the transversal fluctuations of the
wavefunction, which renders the thin-wall quantization procedure well-founded.
It can be applied without restrictions.Comment: 4 page
Towards better models of externalities in sponsored search auctions
Sponsored Search Auctions (SSAs) arguably represent the problem at the intersection of computer science and economics with the deepest applications in real life. Within the realm of SSAs, the study of the effects that showing one ad has on the other ads, a.k.a. externalities in economics, is of utmost importance and has so far attracted the attention of much research. However, even the basic question of modeling the problem has so far escaped a definitive answer. The popular cascade model is arguably too idealized to really describe the phenomenon yet it allows a good comprehension of the problem. Other models, instead, describe the setting more adequately but are too complex to permit a satisfactory theoretical analysis. In this work, we attempt to get the best of both approaches: firstly, we define a number of general mathematical formulations for the problem in the attempt to have a rich description of externalities in SSAs and, secondly, prove a host of results drawing a nearly complete picture about the computational complexity of the problem. We complement these approximability results with some considerations about mechanism design in our context
Particle Movement and Separation Phenomena for a Gravity Separator: I. Development of a Markov Probability Model and Estimation of Model Parameters
The complexity of gravity separator mechanics precludes the use of a deterministic model for particle movement on a gravity separator. Particle movement is examined as a stochastic process; a distance-transition Markov probability model for particle movement is proposed. A linear programming method for estimation of the Markov model parameters is explained
Particle Movement and Separation Phenomena for a Gravity Separator: II. Experimental Data and Performance of Distance-Transition Markov Models
Linear programming procedures are used to fit stationary and nonstationary distance-transition Markov probability models to experimentally obtained particle distribution data from the deck of a gravity separator. Particle movement modeled is that of a light discard fraction. Performance of the models is examined by comparing predicted typical\u27\u27 particle pathways with observed particle pathways. The Markov process is found to be an appropriate model of particle movement
First report of a 'Candidatus Phytoplasma cynodontis'-related strain (group 16SrXIV) associated with white leaf disease of Dichanthium annulatum in India
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