11,524 research outputs found
Regulation of fast-spiking basket cell synapses by the chloride channel ClC-2.
Parvalbumin-expressing, fast-spiking basket cells are important for the generation of synchronous, rhythmic population activities in the hippocampus. We found that GABAA receptor-mediated synaptic inputs from murine parvalbumin-expressing basket cells were selectively modulated by the membrane voltage- and intracellular chloride-dependent chloride channel ClC-2. Our data reveal a previously unknown cell type-specific regulation of intracellular chloride homeostasis in the perisomatic region of hippocampal pyramidal neurons
Chandrasekhar's Dynamical Friction and non-extensive statistics
The motion of a point like object of mass passing through the background
potential of massive collisionless particles () suffers a steady
deceleration named dynamical friction. In his classical work, Chandrasekhar
assumed a Maxwellian velocity distribution in the halo and neglected the self
gravity of the wake induced by the gravitational focusing of the mass . In
this paper, by relaxing the validity of the Maxwellian distribution due to the
presence of long range forces, we derive an analytical formula for the
dynamical friction in the context of the -nonextensive kinetic theory. In
the extensive limiting case (), the classical Gaussian Chandrasekhar
result is recovered. As an application, the dynamical friction timescale for
Globular Clusters spiraling to the galactic center is explicitly obtained. Our
results suggest that the problem concerning the large timescale as derived by
numerical -body simulations or semi-analytical models can be understood as a
departure from the standard extensive Maxwellian regime as measured by the
Tsallis nonextensive -parameter.Comment: 16pp 5 figs, revised and extended version of arXiv:1202.1873 .
Accepted for publication by JCA
Supersymmetry and Localization in the Quantum Hall Effect
We study the localization transition in the integer quantum Hall effect as
described by the network model of quantum percolation. Starting from a path
integral representation of transport Green's functions for the network model,
which employs both complex (bosonic) and Grassman (fermionic) fields, we map
the problem of localization to the problem of diagonalizing a one-dimensional
non-Hermitian Hamiltonian of interacting bosons and fermions. An exact solution
is obtained in a restricted subspace of the Hilbert space which preserves
boson-fermion supersymmetry. The physically relevant regime is investigated
using the density matrix renormalization group (DMRG) method, and critical
behavior is found at the plateau transition.Comment: 14 RevTex pages, 3 eps figures; This revised version contains an
extended disussion of supersymmetry and improved numerical result
Influence of Oxygenated Compounds on Reaction Products in a Microwave Plasma Methane Pyrolysis Assembly for Post-Processing of Sabatier Methane
The state-of-the-art Carbon Dioxide Reduction Assembly (CRA) was delivered to the International Space Station (ISS) in April 2010. The system is designed to accept carbon dioxide from the Carbon Dioxide Removal Assembly and hydrogen from the Oxygen Generation Assembly. The two gases are reacted in the CRA in a Sabatier reactor to produce water and methane. Venting of methane results in an oxygen resupply requirement of about 378 lbs per crew member per year. If the oxygen is supplied as water, the total weight for resupply is about 476 lb per crew member per year. For long-term missions beyond low Earth orbit, during which resupply capabilities will be further limited, recovery of hydrogen from methane is highly desirable. For this purpose, NASA is pursuing development of a Plasma Pyrolysis Assembly (PPA) capable of recovering hydrogen from methane. Under certain conditions, water vapor and carbon dioxide (nominally intended to be separated from the CRA outlet stream) may be present in the PPA feed stream. Thus, testing was conducted in 2010 to determine the effect of these "oxygenated" compounds on PPA performance, particularly the effect of inlet carbon dioxide and water variations on the PPA product stream. This paper discusses the test set-up, analysis, and results of this testin
A Special Homotopy Continuation Method For A Class of Polynomial Systems
A special homotopy continuation method, as a combination of the polyhedral
homotopy and the linear product homotopy, is proposed for computing all the
isolated solutions to a special class of polynomial systems. The root number
bound of this method is between the total degree bound and the mixed volume
bound and can be easily computed. The new algorithm has been implemented as a
program called LPH using C++. Our experiments show its efficiency compared to
the polyhedral or other homotopies on such systems. As an application, the
algorithm can be used to find witness points on each connected component of a
real variety
A validated severity score for haemorrhoids as an essential prerequisite for future haemorrhoid trials.
BACKGROUND: There is a lack of standardised outcomes for haemorrhoidal disease making comparison between trials difficult. A need for a very well validated severity score is essential to facilitate meta-analysis of comparative studies, enabling evidence-based clinical practice. METHODS: The Hubble trial provides a large cohort of patients with haemorrhoidal disease randomised to rubber band ligation (RBL) or haemorrhoidal artery ligation. The haemorrhoid severity score (HSS) was collected on each patient at baseline, 6Â weeks and 1Â year after intervention. This allows for the responsiveness of the HSS instrument to be examined and compared with a more specific instrument, the Vaizey incontinence score (also collected). Responsiveness was tested using four methods (effect size, standardised response means (SRM), significance of change, and responsiveness statistic). RESULTS: The four tests of responsiveness demonstrated that the HSS was more responsive to changes in the patient's health status following both of the interventions compared to the Vaizey questionnaire. For example, between baseline and 6Â weeks, the RBL intervention effect size scores and SRM calculations indicated a non-significant small amount of change (0.20 and 0.16 respectively). However, using the HSS, the effect size and SRM demonstrated a large magnitude of change (1.12 and 1.01, respectively) which was significant. Similar results were observed at 1Â year. Significance of change scores and the index of responsiveness were also higher for the HSS questionnaire than the Vaizey across both treatment modalities. CONCLUSIONS: The HSS is a highly responsive tool for the detection of changes in haemorrhoid symptoms. It should form an essential patient-reported outcome tool for future studies on haemorrhoidal disease
Electric Polarizability of Neutral Hadrons from Lattice QCD
By simulating a uniform electric field on a lattice and measuring the change
in the rest mass, we calculate the electric polarizability of neutral mesons
and baryons using the methods of quenched lattice QCD. Specifically, we measure
the electric polarizability coefficient from the quadratic response to the
electric field for 10 particles: the vector mesons and ; the
octet baryons n, , , , and ;
and the decouplet baryons , , and .
Independent calculations using two fermion actions were done for consistency
and comparison purposes. One calculation uses Wilson fermions with a lattice
spacing of fm. The other uses tadpole improved L\"usher-Weiss gauge
fields and clover quark action with a lattice spacing fm. Our results
for neutron electric polarizability are compared to experiment.Comment: 25 pages, 20 figure
Kinetics of Oxygen Surface Exchange on Epitaxial RuddlesdenâPopper Phases and Correlations to First-Principles Descriptors
Through alignment of theoretical modeling with experimental measurements of oxygen surface exchange kinetics on (001)-oriented La[subscript 2âx]Sr[subscript x]MO[subscript 4+ÎŽ] (M = Co, Ni, Cu) thin films, we demonstrate here the capability of the theoretical bulk O 2p-band centers to correlate with oxygen surface-exchange kinetics of the RuddlesdenâPopper oxide (RP[subscript 214]) (001)-oriented thin films. In addition, we demonstrate that the bulk O 2p-band centers can also correlate with the experimental activation energies for bulk oxygen transport and oxygen surface exchange of both the RP[subscript 214] and the perovskite polycrystalline materials reported in the literature, indicating the effectiveness of the bulk O 2p-band centers in describing the associated energetics and kinetics. We propose that the opposite slopes of the bulk O 2p-band center correlations between the RP[subscript 214] and the perovskite materials are due to the intrinsic mechanistic differences of their oxygen surface exchange kinetics and bulk anionic transport.United States. Department of Energy. Solid State Energy Conversion Allianc (Core Technology Program Funding Opportunity Number DEFE0009435)Skoltech-MIT Center for Electrochemical EnergyOak Ridge National Laboratory. Scientific User Facilities DivisionUnited States. Department of Energy. Office of Basic Energy Science. Division of Materials Sciences and EngineeringNational Energy Research Scientific Computing Center (U.S.) (grant number CNMS2013-292
Sex differences in misperceptions of sexual interest can be explained by sociosexual orientation and men projecting their own interest onto women
Sex differences in misperceptions of sexual interest have been well documented; however, it is unclear whether this cognitive bias could be explained by other factors. In the current study, 1226 participants (578 men, 630 women) participated in a speed-dating study, where participants rated their sexual interest in each other as well as the sexual interest they perceived from their partners. Consistent with previous findings, we found that men tended to overperceive sexual interest from their partners, while women tended to underperceive sexual interest. However, this sex difference becomes negligible when considering potential mediators, such as the ratersâ sociosexual orientation, and raters projecting their own levels of sexual interest onto their partners. These findings challenge the popular notion that sex differences in misperceptions in sexual interest have evolved as a specialised adaptation due to different selection pressures in men and women
Directional detection as a strategy to discover Galactic Dark Matter
Directional detection of Galactic Dark Matter is a promising search strategy
for discriminating genuine WIMP events from background ones. Technical progress
on gaseous detectors and read-outs has permitted the design and construction of
competitive experiments. However, to take full advantage of this powerful
detection method, one need to be able to extract information from an observed
recoil map to identify a WIMP signal. We present a comprehensive formalism,
using a map-based likelihood method allowing to recover the main incoming
direction of the signal and its significance, thus proving its galactic origin.
This is a blind analysis intended to be used on any directional data.
Constraints are deduced in the () plane and systematic
studies are presented in order to show that, using this analysis tool,
unambiguous dark matter detection can be achieved on a large range of exposures
and background levels.Comment: 20 pages, 5 figures Final version to appear in Phys. Lett.
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