String Model with Dynamical Geometry and Torsion

A string model with dynamical metric and torsion is proposed. The geometry of the string is described by an effective Lagrangian for the scalar and vector fields. The path integral quantization of the string is considered

Off-diagonal quark distribution functions of the pion within an effective single instanton approximation

We develop a relativistic quark model for pion structure, which incorporates the non-trivial structure of the vacuum of Quantum Chromodynamics as modelled by instantons. Pions are boundstates of quarks and the strong quark-pion vertex is determined from an instanton induced effective lagrangian. The interaction of the constituents of the pion with the external electromagnetic field is introduced in gauge invariant form. The parameters of the model, i.e., effective instanton radius and constituent quark masses, are obtained from the vacuum expectation values of the lowest dimensional quark and gluon operators and the low-energy observables of the pion. We apply the formalism to the calculation of the pion form factor by means of the isovector nonforward parton distributions and find agreement with the experimental data.Comment: LaTeX; altered version; references and figures added. Published: paper has been accepted for publication in Nucl. Phys.

πη\pi\eta pair hard electroproduction and exotic hybrid mesons

We show that hard electroproduction is a promising way to study exotic hybrid mesons, in particular through the hybrid decay channel $H \to \pi\eta$. We discuss the $\pi\eta$ generalized distribution amplitude, calculate the production amplitude and propose a forward-backward asymmetry as a signal for the hybrid meson production.Comment: 4 pages, 1 figure, presented by I.V. Anikin at Xth International Conference "BARYONS'04", Palaiseau, Franc

The dual parametrization for gluon GPDs

We consider the application of the dual parametrization for the case of gluon GPDs in the nucleon. This provides opportunities for the more flexible modeling unpolarized gluon GPDs in a nucleon which in particular contain the invaluable information on the fraction of nucleon spin carried by gluons. We perform the generalization of Abel transform tomography approach for the case of gluons. We also discuss the skewness effect in the framework of the dual parametrization. We strongly suggest to employ the fitting strategies based on the dual parametrization to extract the information on GPDs from the experimental data.Comment: 37 pages, 2 figure

Validation of the numerical model of a spark channel expansion in a low-energy atmospheric pressure discharge

Gas-dynamic expansion of a low-energy atmospheric pressure spark discharge was numerically simulated. The calculated data were compared with experimental results to validate the numerical model. A satisfactory correlation of spark photo images with a simulated spark channel expansion was observed. It was found out that an experimental total light intensity of spark discharge corresponds with spark radiation power. Time histories of a particle number concentration and energy input were calculated. Radial temperature, pressure, density and conductivity profiles at various times were investigatedЧисельно досліджено газодинамічне розширення низькоенергетичного іскрового розряду атмосферного тиску. Перевірка математичної моделі проведена шляхом порівняння чисельних та експериментальних результатів. Отримана задовільна кореляція фотозображень іскрового розряду з розрахунковими даними з розширення іскрового каналу. З’ясовано, що повна інтенсивність випромінювання іскрового розряду, яка отримана експериментально, відповідає потужності випромінювання іскри. Розраховано розподіл концентрації компонентів та динаміка вводу енергії в іскру. Досліджені розподіли температури, тиску, густини та провідності в радіальному розрізі в різні моменти часу.Численно исследовано газодинамическое расширение низкоэнергетического искрового разряда атмосферного давления. Проверка математической модели проведена путем сравнения численных и экспериментальных результатов. Получена удовлетворительная корреляция фотоизображений искрового разряда с расчетными данными по расширению искрового канала. Выявлено, что полная интенсивность излучения искрового разряда, получаемая экспериментально, соответствует мощности излучения искры. Рассчитано распределение концентрации компонентов и динамика ввода энергии в искру. Исследованы распределения температуры, давления, плотности и проводимости в радиальном сечении в разные моменты времени

СРАВНЕНИЕ РАЗЛИЧНЫХ МЕТОДОВ МОЛЕКУЛЯРНО- ГЕНЕТИЧЕСКОГО АНАЛИЗА СОМАТИЧЕСКИХ МУТАЦИЙ В ГЕНЕ K-RAS ПРИ КОЛОРЕКТАЛЬНОМ РАКЕ

Two approaches to somatic point mutations in 12 and 13 codones of K-ras gene were analyzed: PCR/SSCP/AСRS/sequencing and allele-specific PCR in the real-life regimen (Russian set «KRAS-7M»). The comparison was carried out on 62 examples of genomic DNA extracted from frozen colon carcinomas, which underwent manual dissection. The results obtained in two attempts were consistent in 95,2% (N=59). Specificity and sensitivity of K-ras mutations detection using «KRAS-7M» set were 100 and 96,4% respectively, and 94,1 and 100% respectievly using PCR/SSCP/AСRS/ automatic sequencing. False positive results were absent when detecting with «KRAS-7M» and accounted for 2 cases (5,9%) when using PCR/SSCP/ AСRS/automatic sequencing. The only false negative response (3,6%) was obtained analyzing mutations using «KRAS-7M».Проведено сравнение двух подходов для анализа соматических точечных мутаций в кодонах 12 и 13 гена K-ras: методов ПЦР/SSCP/AСRS/секвенирования и аллель-специфической ПЦР в режиме реального времени (отечественный коммерческий набор «KRAS-7M»). Сравнение проводили на 62 образцах геномной ДНК, выделенной из замороженных карцином толстой кишки, подвергшихся ручной микродиссекции. Результаты, полученные с помощью двух подходов, совпали для 59 карцином (95,2% случаев). Специфичность и чувствительность детекции K-ras мутаций с помощью набора «KRAS-7M» составили 100 и 96,4%, соответственно, а с использованием методов ПЦР/AСRS/SSCP/ автоматического секвенирования — 94,1 и 100%, соответственно. Ложноположительные данные отсутствовали при детекции мутаций с помощью набора «KRAS-7M» и составили 2 случая (5,9%) при исследовании методами ПЦР/AСRS/SSCP/автоматического секвенирования. Единственный ложноотрицательный результат (3,6%) был получен при анализе мутаций набором «KRAS-7M»

Exclusive two ρ0\rho ^0-mesons production in γγ∗\gamma\gamma^* collision

We give a theoretical description of the L3 Collaboration data on the cross-section of the exclusive two $\rho$-mesons production in $\gamma\gamma ^*$ collision with large photon virtuality. These data prove the scaling behaviour of the leading twist generalized distribution amplitude of vector mesons. They thus prove the relevance of a partonic description of the exclusive process $\gamma\gamma ^*\to\rho ^0\rho ^0$ at $Q^2\geq 1.2 {\rm GeV^2}$ and $W\leq 3.0 {\rm GeV}.$Comment: 6 pages, 1 eps figur

DVCS on the nucleon : study of the twist-3 effects

We estimate the size of the twist-3 effects on deeply virtual Compton scattering (DVCS) observables, in the Wandzura-Wilczek approximation. We present results in the valence region for the DVCS cross sections, charge asymmetries and single spin asymmetries, to twist-3 accuracy.Comment: 20 pages, 6 figure

The target asymmetry in hard vector-meson electroproduction and parton angular momenta

The target asymmetry for electroproduction of vector mesons is investigated within the handbag approach. While the generalized parton distribution (GPD) H is taken from a previous analysis of the elctroproduction cross section, we here construct the GPD E from double distributions and constrain it by the Pauli form factors of the nucleon, positivity bounds and sum rules. Predictions for the target asymmetry are given for various vector mesons and discussed how experimental data on the asymmetry will further constrain E and what we may learn about the angular momenta the partons carry.Comment: 24 pages, 11 figures, late

Gauge invariance, causality and gluonic poles

We explore the electromagnetic gauge invariance of the hadron tensor of the Drell-Yan process with one transversely polarized hadron. The special role is played by the contour gauge for gluon fields. The prescription for the gluonic pole in the twist 3 correlator is related to causality property and compared with the prescriptions for exclusive hard processes. As a result of we get the extra contributions, which naively do not have an imaginary phase. The single spin asymmetry for the Drell-Yan process is enhanced by the factor of two.Comment: 9 pages, 2 figures; References and acknowledgements added