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V Matveev

Publications and source records attributed to V Matveev.

15 recordsLinked to original sources
PubMed2006

Improved search for nu(mu) --> nu(e) oscillation in a long-baseline accelerator experiment.

We performed an improved search for nu(mu) --> nu(e) oscillation with the KEK to Kamioka (K2K) long-baseline neutrino oscillation experiment, using the full data sample of 9.2 x 10(19) protons on target. No evidence for a nu(e) appearance signal was found, and we set bounds on the nu(mu) --> nu(e) oscillation parameters. At Deltam(2)=2.8 x 10(-3) eV(2), the best-fit value of the K2Knu(mu) disappearance analysis, we set an upper limit of sin(2)2theta(mue) < 0.13 at a 90% confidence level.

Journal Article↗
PubMed2005

Search for coherent charged pion production in neutrino-carbon interactions.

We report the result from a search for charged-current coherent pion production induced by muon neutrinos with a mean energy of 1.3 GeV. The data are collected with a fully active scintillator detector in the K2K long-baseline neutrino oscillation experiment. No evidence for coherent pion production is observed, and an upper limit of is set on the cross section ratio of coherent pion production to the total charged-current interaction at 90% confidence level. This is the first experimental limit for coherent charged pion production in the energy region of a few GeV.

Journal Article↗
PubMed2005

Evidence for muon neutrino oscillation in an accelerator-based experiment.

We present results for nu(mu) oscillation in the KEK to Kamioka (K2K) long-baseline neutrino oscillation experiment. K2K uses an accelerator-produced nu(mu) beam with a mean energy of 1.3 GeV directed at the Super-Kamiokande detector. We observed the energy-dependent disappearance of nu(mu), which we presume have oscillated to nu(tau). The probability that we would observe these results if there is no neutrino oscillation is 0.0050% (4.0 sigma).

Journal Article↗
PubMed2004

Observation of a narrow charm-strange meson D(+)(sJ)(2632)-->D(+)(s)eta and D(0)K(+).

We report the first observation of a charm-strange meson D(+)(sJ)(2632) at a mass of 2632.5+/-1.7 MeV/c(2) in data from SELEX, the charm hadro-production experiment E781 at Fermilab. This state is seen in two decay modes, D(+)(s)eta and D0K+. In the D(+)(s)eta decay mode we observe a peak with 101 events over a combinatoric background of 54.9 events at a mass of 2635.4+/-3.3 MeV/c(2). There is a corresponding peak of 21 events over a background of 6.9 at 2631.5+/-2.0 MeV/c(2) in the decay mode D0K+. The decay width of this state is <17 MeV/c(2) at 90% confidence level. The relative branching ratio Gamma(D0K+)/Gamma(D(+)(s)eta) is 0.14+/-0.06. The mechanism that keeps this state narrow is unclear. Its decay pattern is also unusual, being dominated by the D(+)(s)eta decay mode.

Journal Article↗
PubMed2002

First observation of the doubly charmed baryon Xi(+)(cc).

We observe a signal for the doubly charmed baryon Xi(+)(cc) in the charged decay mode Xi(+)(cc)-->Lambda(+)(c)K-pi(+) in data from SELEX, the charm hadroproduction experiment at Fermilab. We observe an excess of 15.9 events over an expected background of 6.1+/-0.5 events, a statistical significance of 6.3sigma. The observed mass of this state is 3519+/-1 MeV/c(2). The Gaussian mass width of this state is 3 MeV/c(2), consistent with resolution; its lifetime is less than 33 fs at 90% confidence.

Journal Article↗
PubMed2001

Precision measurements of the lambda(+)(c) and D0 lifetimes.

We report new precision measurements of the lifetimes of the Lambda(+)(c) and D0 from SELEX, the charm hadroproduction experiment at Fermilab. Based upon 1630 Lambda(+)(c) and 10 210 D0 decays we observe lifetimes of tau[Lambda(+)(c)] = 198.1+/-7.0+/-5.6 fs and tau[D0] = 407.9+/-6.0+/-4.3 fs.

Journal Article↗
PubMed2000

Implications of all-or-none synaptic transmission and short-term depression beyond vesicle depletion: a computational study.

The all-or-none character of transmission at central synapses is commonly viewed as evidence that only one vesicle can be released per action potential at a single release site. This interpretation is still a matter of debate; its resolution is important for our understanding of the nature of quantal response. In this work we explore observable consequences of the univesicular release hypothesis by studying a stochastic model of synaptic transmission. We investigated several alternative mechanisms for the all-or-none response: (1) the univesicular release constraint realized through lateral inhibition across presynaptic membrane, (2) the constraint of a single releasable vesicle per active zone, and (3) the postsynaptic receptor saturation. We show that both the univesicular release constraint and the postsynaptic receptor saturation lead to a limited amount of depression by vesicle depletion, so that depletion alone cannot account for the strong paired-pulse depression observed at some cortical synapses. Although depression can be rapid if there is only one releasable vesicle per active zone, this scenario leads to a limit on the transmission probability. We evaluate additional mechanisms beyond vesicle depletion, and our results suggest that the strong paired-pulse depression may be a result of activity-dependent inactivation of the exocytosis machinery. Furthermore, we found that the statistical analysis of release events, in response to a long stimulus train, might allow one to distinguish experimentally between univesicular and multivesicular release scenarios. We show that without the univesicular release constraint, the temporal correlation between release events is always negative, whereas it is typically positive with such a constraint if the vesicle fusion probability is sufficiently large.

Exocytosis↗
PubMed2000

Differential short-term synaptic plasticity and transmission of complex spike trains: to depress or to facilitate?

Experimental studies have revealed conspicuous short-term facilitation and depression that are expressed differentially at distinct classes of cortical synapses. To explore computational implications of synaptic dynamics, we investigated transmission of complex spike trains through a stochastic model of cortical synapse endowed with short-term facilitation and vesicle depletion. Inputs to the synapse model were either real spike train data recorded from the visual and prefrontal cortices of behaving monkeys, or were generated numerically with prescribed temporal statistics. We tested the hypothesis that short-term facilitation could enable synapses to filter out single spikes and favor bursts of action potentials. We found that the ratio between release probabilities for a burst spike and an isolated spike grows monotonically with increasing number of spikes per burst, and with increasing interval between isolated spikes. Burst detection is optimal when the facilitation time constant matches the average burst duration. Using fractal-like spike patterns characterized by long-term power-law temporal correlations and similar to those seen in sensory neurons, we found that facilitation increases correlation at short time scales. In contrast, depression leads to a dramatic reduction in temporal correlations at all time scales, and to a flat ('whitened') power spectrum, thereby decorrelating natural input signals.

Action Potentials↗
PubMed1993

N-(2-hydroxybenzyl)-omega-amino carbonic acids and their derivatives as tools for biochemical and biophysical investigations.

We propose N-(2-hydroxybenzyl)-omega-amino carbonic acids (An) as multifunctional probes for fatty acid metabolism studies. Multifunctionality could be achieved by introduction of different isotopes into An molecule. Deuteration of An results in probes for 2H-NMR membrane studies. Introduction of radioactive iodine and bromine isotopes into An gives diagnosticums for gamma-tomography and PET. AnI and AnBr are fluorescence quenchers usable for membrane studies. This multifunctionality of An derivatives is valuable because they participate in such metabolic pathways of fatty acids as beta-oxidation and inclusion into lipids. They can also inhibit natural FA oxidation.

Animals↗
PubMed1979

[Cholinergic regulation of transcription in the liver].

The rate of the RNA synthesis in the rat liver was enhanced 6 hours after intramuscular administration to rats of acetylcholine, carbamylcholine or chlorosil at doses of 20, 1 and 2 mg/kg, respectively. At a dose of 0.025 mg/kg chlorosil failed to influence the transcription rate, but partially blocked its stimulation by carbamylcholine. Chlorosil and carbamylcholine did not change the RNA synthesis rate in isolated hepatocytic nuclei. It is suggested that the effect is mediated by their interaction with the cholinoreceptor or with the cell plasmatic membrane sites structurally associated with it.

Acetylcholine↗