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G Gavrilov

Publications and source records attributed to G Gavrilov.

15 recordsLinked to original sources
PubMed2006

Double-hadron leptoproduction in the nuclear medium.

The first measurements of double-hadron production in deep-inelastic scattering within the nuclear medium were made with the HERMES spectrometer at DESY HERA using a 27.6 GeV positron beam. By comparing data for deuterium, nitrogen, krypton, and xenon nuclei, the influence of the nuclear medium on the ratio of double-hadron to single-hadron yields was investigated. Nuclear effects on the additional hadron are clearly observed, but with little or no difference among nitrogen, krypton, or xenon, and with smaller magnitude than effects seen on previously measured single-hadron multiplicities. The data are compared with models based on partonic energy loss or prehadronic scattering and with a model based on a purely absorptive treatment of the final-state interactions. Thus, the double-hadron ratio provides an additional tool for studying modifications of hadronization in nuclear matter.

Journal Article↗
PubMed2005

Measurement of the tensor structure function b1 of the deuteron.

The Hermes experiment has investigated the tensor spin structure of the deuteron using the 27.6 GeV/c positron beam of DESY HERA. The use of a tensor-polarized deuteron gas target with only a negligible residual vector polarization enabled the first measurement of the tensor asymmetry A(d)zz and the tensor structure function b(d)1 for average values of the Bjorken variable 0.01< <0.45 and of the negative of the squared four-momentum transfer 0.5 GeV2 < <5 GeV2. The quantities A(d)zz and b(d)1 are found to be nonzero. The rise of b(d)1 for decreasing values of x can be interpreted to originate from the same mechanism that leads to nuclear shadowing in unpolarized scattering.

Journal Article↗
PubMed2005

Single-spin asymmetries in semi-inclusive deep-inelastic scattering on a transversely polarized hydrogen target.

Single-spin asymmetries for semi-inclusive electroproduction of charged pions in deep-inelastic scattering of positrons are measured for the first time with transverse target polarization. The asymmetry depends on the azimuthal angles of both the pion (phi) and the target spin axis (phi(S)) about the virtual-photon direction and relative to the lepton scattering plane. The extracted Fourier component sin((phi+phi(S))(pi)(UT) is a signal of the previously unmeasured quark transversity distribution, in conjunction with the Collins fragmentation function, also unknown. The component sin((phi-phi(S)(pi)(UT) arises from a correlation between the transverse polarization of the target nucleon and the intrinsic transverse momentum of quarks, as represented by the previously unmeasured Sivers distribution function. Evidence for both signals is observed, but the Sivers asymmetry may be affected by exclusive vector meson production.

Journal Article↗
PubMed2004

Flavor decomposition of the sea-quark helicity distributions in the nucleon from semiinclusive deep inelastic scattering.

Double-spin asymmetries of semiinclusive cross sections for the production of identified pions and kaons have been measured in deep inelastic scattering of polarized positrons on a polarized deuterium target. Five helicity distributions including those for three sea quark flavors were extracted from these data together with reanalyzed previous data for identified pions from a hydrogen target. These distributions are consistent with zero for all three sea flavors. A recently predicted flavor asymmetry in the polarization of the light quark sea appears to be disfavored by the data.

Journal Article↗
PubMed2003

Evidence for quark-hadron duality in the proton spin asymmetry A1.

Spin-dependent lepton-nucleon scattering data have been used to investigate the validity of the concept of quark-hadron duality for the spin asymmetry A1. Longitudinally polarized positrons were scattered off a longitudinally polarized hydrogen target for values of Q2 between 1.2 and 12 GeV2 and values of W2 between 1 and 4 GeV2. The average double-spin asymmetry in the nucleon resonance region is found to agree with that measured in deep-inelastic scattering at the same values of the Bjorken scaling variable x. This finding implies that the description of A1 in terms of quark degrees of freedom is valid also in the nucleon resonance region for values of Q2 above 1.6 GeV2.

Journal Article↗
PubMed2003

Q2 dependence of nuclear transparency for exclusive rho0 production.

Exclusive coherent and incoherent electroproduction of the rho(0) meson from 1H and 14N targets has been studied at the HERMES experiment as a function of coherence length (l(c)), corresponding to the lifetime of hadronic fluctuations of the virtual photon, and squared four-momentum of the virtual photon (-Q2). The ratio of 14N to 1H cross sections per nucleon, called nuclear transparency, was found to increase (decrease) with increasing l(c) for coherent (incoherent) rho(0) electroproduction. For fixed l(c), a rise of nuclear transparency with Q2 is observed for both coherent and incoherent rho(0) production, which is in agreement with theoretical calculations of color transparency.

Journal Article↗
PubMed1983

[Clinico-therapeutic and microbiologic studies of the Bulgarian antibiotic cephalothin in patients with active pyelonephritis].

A total of 38 patients with active pyelonephritis and significant bacteriuria were treated with the Bulgarian antibiotic cephalotin, the bacteria isolated from their urine manifesting susceptibility to the Bulgarian broad-spectrum antibiotic cephalotin. Twenty six from the patients were with preserved renal function, and 12 with various stages of renal insufficiency. The subjective complaints, febrility, leukocyturia and bacteriuria were best affected. The highest anti-bacterial effect was observed in the patients with uroinfections caused by E. coli, Proteus mirabilis, Klebsiella and staphylococci. Cephalotin has a good tolerance and has no adverse effects. Painful infiltrations were established in some of the patients in the region of the site of intramuscular application, with a transitory character. Cephalotin was assessed, on the base of the study, to be a good and prospective broad-scpectrum antibiotic, deserving to be widely applied in the therapeutic practice.

Adult↗
PubMed1983

[Cellular and humoral immunological characteristics of chronic pyelonephritis].

The following indices were studied in 21 patients with chronic pyelonephritis: T-lymphocytes - early and late, their TG and TM subpopulations; B-lymphocytes: complement-receptor, antibody (hemolysin) synthesizing, carring surface immunoglobulins (sIg+) and cytoplasmatic immunoglobulins (cIg+); immunoblasts in peripheral blood; serum level of immunoglobulins and of C3 - fraction of complement. The authors established a tendency to increase of early T-lymphocytes and their TG - subpopulations in the patients. TM - subpopulations were considerably lower, as compared with those of the healthy subjects. The complement - receptor and immunoglobulin-containing B cella in the patients with chronic pyelonephritis were increased as compared with the same in healthy subjects. Only IgM level in serum of the patients studied was higher than in the healthy subjects from the humoral factors of immune reactivity. Chronic pyelonephritis, was concluded, by the authors, to participate in the cellular-humoral immune mechanisms with a predominating activation of B-populations and IgM synthesis.

Animals↗
PubMed1983

[Changes in the cellular-humoral immune reactivity of patients with lupus nephritis and chronic glomerulonephritis treated with corticosteroids or corticosteroids and imuran].

The changes in cellular-humoral immune reactivity were followed up in 13 patients with lupus nephritis and 10 patients with chronic glomerulonephritis, treated with corticosteroids or with corticosteroids and imuran. A tendency to correction of lymphocyte and T-lymphocyte deficiency, inhibition of FsG- and FsM-receptor lymphocytes and of T-gamma and T-mu lymphocyte subpopulations was established in the patients with lupus nephritis, treated only with corticosteroids. The treatment with corticosteroids and imuran inhibited more sharply T gamma- and T-mu lymphocytes than with corticosteroids alone. It was established, in the patients with chronic glomerulonephritis, treated with corticosteroids, that GsG- and FsM-receptor lymphocytes were with significantly lower values than the non-treated ones. No significant changes were established in B-cellular reactivity and serum level of immunoglobulins (IgG, IgM, IgA) with the treatment with corticosteroids and corticosteroids and imuran in both nosological entities. C3- fraction of the complement in the lupus patients treated was with lower values than in the non-treated. The authors conclude that the corticosteroids and corticosteroids and imuran, inhibiting the reactivity of T-lymphocytes, regulating the immune-biological balance, should be cautiously used and under the control of the cellular populations, exposed to their effect.

Adrenal Cortex Hormones↗
PubMed1979

[Symptomatic arterial hypertension in lupus nephropathy].

Sixty six patients with lupus nephropathy with hypertonic syndrome are examined. In patients with latent (inactive) lupus glomerulonephritis hypertonic syndrome developed 3--8 months after the initiation of the corticosteroid treatment, advancing with fluctuations, in some of the patients the arterial pressure being normalized after the discontinuation of that treatment. In patients with chronic active lupus glomerulonephritis without nephrotic syndrome, the hypertension develops before the initiation of the corticosteroid treatment, fluctuating at the beginning, and gradually assumes a stable character 3--5 months after the beginning of such treatment, sometimes with a malignant course and rapid development of renal insufficiency. The hypertonic syndrome advances most severely and malignantly in chronic lupus glomerulonephritis with nephrotic syndrome and is resistant to the active antihypertensive treatment. In 18, out of 25, such patients, the hypertonic syndrome is manifested in parallel with nephropathy before the inclusion of the cortocosteroid treatment. The grave and malignant course of the hypertonic syndrome is associated with the peculiarities of the clinical form and histomorphological type of that lupus nephropathy. In the patients with nephrosclerosis, the hypertonic syndrome is with a gradually progressing evolution, in parallel with the progress of the renal insufficiency.

Adolescent↗
PubMed1977

[Nephroptosis in the etiopathogenesis of vasorenal hypertension].

Forty three patients with nephroptosis, complicated by hypertension were examined (4 males and 39 females), aged from 18 to 60. Permanent hypertension was found in nine of them (21%), and renovasographically--organic renal-arterial stenosis at the nephroptosis side was established. After the failure of the conservative treatment, those patients had all the indications for operation. Seven of the patients underwent the operation and only in one woman patient--nephrectomy was performed, and in all the rest six patients--reconstructive revascularization and nephropexy. The follow-up of the operated patients so far reveals a very favourable effect upon the hypertension syndrome after the operation.

Adolescent↗