92 research outputs found
Regge Analysis of Diffractive and Leading Baryon Structure Functions from DIS
In this paper we present a combined analysis of the H1 data on leading baryon
and diffractive structure functions from DIS, which are handled as two
components of the same semi-inclusive process. The available structure function
data are analyzed in a series of fits in which three main exchanges are taking
into account: pomeron, reggeon and pion. For each of these contributions, Regge
factorization of the correspondent structure function is assumed. By this
procedure, we extract information about the interface between the diffractive,
pomeron-dominated, region and the leading proton spectrum, which is mostly
ruled by secondary exchanges. One of the main results is that the relative
reggeon contribution to the semi-inclusive structure function is much smaller
than the one obtained from a analysis of the diffractive structure function
alone.Comment: ps file, 22 pages, 5 figures. Totally revised version with major
changes, to appear in Physical Review
Glutamate reduces glucose utilization while concomitantly enhancing AQP9 and MCT2 expression in cultured rat hippocampal neurons.
The excitatory neurotransmitter glutamate has been reported to have a major impact on brain energy metabolism. Using primary cultures of rat hippocampal neurons, we observed that glutamate reduces glucose utilization in this cell type, suggesting alteration in mitochondrial oxidative metabolism. The aquaglyceroporin AQP9 and the monocarboxylate transporter MCT2, two transporters for oxidative energy substrates, appear to be present in mitochondria of these neurons. Moreover, they not only co-localize but they interact with each other as they were found to co-immunoprecipitate from hippocampal neuron homogenates. Exposure of cultured hippocampal neurons to glutamate 100 μM for 1 h led to enhanced expression of both AQP9 and MCT2 at the protein level without any significant change at the mRNA level. In parallel, a similar increase in the protein expression of LDHA was evidenced without an effect on the mRNA level. These data suggest that glutamate exerts an influence on neuronal energy metabolism likely through a regulation of the expression of some key mitochondrial proteins
A new gamma*-p / pbar-p factorization test in diffraction, valid below Q^2 about 6 GeV^2
One of the key experimental issues in high energy hadron physics is the
extent to which data from the diffractive interaction mechanism may be
described by a factorized formula which is the product of a universal term
describing the probability of finding a Pomeron in a proton (loosely referred
to as the "Pomeron flux-factor") and a term decribing the Pomeron's interaction
with the other incident proton. In the present paper, after demonstrating that
existing data on diffractive gamma*-p and pbar-p interactions show that the
Pomeron flux-factor is not universal, we present the results of a new test of
factorization in these interactions which does not rely on universality of the
flux-factor. The test is satisfied to within ~20% for 1 < Q^2 ~ 6 GeV^2 and
beta < 0.2 in the gamma*-p interactions, suggesting that the resons for
non-universality of the flux-factor have a limited effect on the factorization
itself. However, a clear breakdown of this test is observed at larger Q^2.
Kharzeev and Levin suggest that this can be attributed to the onset of QCD
evolution effects in the Pomeron's structure. The breakdown occurs in a Q^2
region which agrees with their estimates of a small Pomeron size.Comment: 20 pages, 7 Encapsulated Postscript figures, LaTex, submitted to
European Phisical Journal
Diffractive production of dijets by double Pomeron exchange processes
A phenomenological description of diffractive dijet hadroproduction via
double Pomeron exchange is presented. This description is based on a modified
version of the Ingelman-Schlein model which includes the evolution of the
Pomeron structure function and corrections regarding rapidity gap suppression
effects. The same quark-dominant Pomeron structure function employed in a
previous report to describe diffractive dijet and W production via single
Pomeron processes is shown here to yield results consistent with the available
data for double Pomeron processes as well.Comment: 4 pages, REVTEX4.
Cell damage and neurogenesis in the dentate granule cell layer of adult rats after pilocarpine- or kainate-induced status epilepticus
Naa And Naag Variation In Neuronal Activation During Visual Stimulation.
N-acetyl-aspartyl-glutamate (NAAG) and its hydrolysis product N-acetyl-L-aspartate (NAA) are among the most important brain metabolites. NAA is a marker of neuron integrity and viability, while NAAG modulates glutamate release and may have a role in neuroprotection and synaptic plasticity. Investigating on a quantitative basis the role of these metabolites in brain metabolism in vivo by magnetic resonance spectroscopy (MRS) is a major challenge since the main signals of NAA and NAAG largely overlap. This is a preliminary study in which we evaluated NAA and NAAG changes during a visual stimulation experiment using functional MRS. The paradigm used consisted of a rest period (5 min and 20 s), followed by a stimulation period (10 min and 40 s) and another rest period (10 min and 40 s). MRS from 17 healthy subjects were acquired at 3T with TR/TE = 2000/288 ms. Spectra were averaged over subjects and quantified with LCModel. The main outcomes were that NAA concentration decreased by about 20% with the stimulus, while the concentration of NAAG concomitantly increased by about 200%. Such variations fall into models for the energy metabolism underlying neuronal activation that point to NAAG as being responsible for the hyperemic vascular response that causes the BOLD signal. They also agree with the fact that NAAG and NAA are present in the brain at a ratio of about 1:10, and with the fact that the only known metabolic pathway for NAAG synthesis is from NAA and glutamate.451031-
Diffractive Deep-Inelastic Scattering
Diffractive deep inelastic events with a large rapidity gap are analyzed by
using a Regge model for the pomeron flux and a gluonic content for the pomeron.
Contrary to the expectations, the simplest assumption for the pomeron
trajectory gives the best agreement with the data on the ratio of diffractive
to the total number of events. In this case the main properties of the model
are described by an analytic expression.Comment: 18 pages (postcript file
Charged Particle Multiplicity in Diffractive Deep Inelastic Scattering
The recent data from H1 Collaboration on hadron multiplicity in diffractive
DIS has been studied in the framework of perturbative QCD as a function of
invariant diffractive mass. The formulas obtained explain the observed excess
of particle production in diffractive DIS relative to that in DIS and
annihilation. It is shown that the results are sensitive to the quark--gluon
structure of the Pomeron. Namely, the data say in favour of a super-hard gluon
distribution at the initial scale.Comment: 12 pages, 3 figures; to be published in Phys. Rev.
Effects of Sulpiride on True and False Memories of Thematically Related Pictures and Associated Words in Healthy Volunteers
Episodic memory, working memory, emotional memory, and attention are subject to dopaminergic modulation. However, the potential role of dopamine on the generation of false memories is unknown. This study defined the role of the dopamine D-2 receptor on true and false recognition memories. Twenty-four young, healthy volunteers ingested a single dose of placebo or 400 mg oral sulpiride, a dopamine D-2-receptor antagonist, just before starting the recognition memory task in a randomized, double-blind, and placebo-controlled trial. The sulpiride group presented more false recognitions during visual and verbal processing than the placebo group, although both groups had the same indices of true memory. These findings demonstrate that dopamine D-2 receptors blockade in healthy volunteers can specifically increase the rate of false recognitions. The findings fit well the two-process view of causes of false memories, the activation/monitoring failures model.Univ Fed Sao Paulo, Dept Psychobiol, Sao Paulo, BrazilAssociacao Fundo Incent Pesquisa, Sao Paulo, BrazilUniv Fed Sao Paulo, Dept Physiol, Sao Paulo, BrazilUniv Fed Sao Paulo, Dept Psychobiol, Sao Paulo, BrazilWeb of Scienc
Diffractive Contribution to the Elasticity and the Nucleonic Flux in the Atmosphere
We calculate the average elasticity considering non-diffractive and single
diffractive interactions and perform an analysis of the cosmic-ray flux by
means of an analytical solution for the nucleonic diffusion equation. We show
that the diffractive contribution is important for the adequate description of
the nucleonic and hadronic fluxes in the atmosphere.Comment: 10 pages, latex, 2 figures (uuencoded PostScript
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