К ГЕОЛОГИЧЕСКИМ ХАРАКТЕРИСТИКАМ ПРОДУКТИВНЫХ ПЛАСТОВ ЗАПАДНО-ЛЕНИНОГОРСКОЙ ПЛОЩАДИ РОМАШКИНСКОГО МЕСТОРОЖДЕНИЯ

The article presents data on reservoir properties of productive horizons West Leninogorsk area Romashkinskoye field, namely, the net pay thickness, porosity and permeability. The author also presents data on the physical properties and is the chemical composition of the reservoir fluid saturation. The above information may be useful for researchers involved in enhanced oil recovery at this fieldВ статье приводятся данные о коллекторских свойствах продуктивных горизонтов Западно-Лениногорской площади Ромашкинского нефтяного месторождения, а именно об эффективных нефтенасыщенных толщинах, пористости и проницаемости. Также авторы приводят данные о физико-химических свойствах и составе насыщающих пласт флюидов. Приведенная информация может быть полезной для исследователей, занимающихся повышением нефтеотдачи на данном месторождении

Enhancement of the Raman Scattering and the Third-Harmonic Generation in Silicon Nanowires

We studied features of Raman scattering and the third-harmonic generation in silicon nanowire (SiNW) ensembles formed by means of chemical etching of crystalline silicon (c-Si) wafers with preliminary deposited silver nanoparticles in hydrofluoric acid. The c-Si wafers of different crystallographic orientations and doping levels were used, which results in variations of the formed nanostructure size and degree of order. For the excitation at 1064 nm the ratio of Raman scattering signals for SiNWs and those for initial c-Si wafer ranges from 2 to 5, whereas for shorter wavelengths the ratio increases for more ordered arrays of SiNWs of greater diameter and decreases for less ordered SiNW structures. The TH signals in SiNW ensembles demonstrate both fall and one- or two-orders-of-magnitude rise in comparison with c-Si depending on the structure of the SiNW ensemble. The obtained results are explained by the effect of partial light localization in SiNW ensembles

RESPONSE OF VEGETATION TO CLIMATE CHANGES DURING LATE GLACIAL AND HOLOCENE INFERRED FROM POLLEN RECORD OF LAKE ONEGA

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Helicity skewed quark distributions of the nucleon and chiral symmetry

We compute the helicity skewed quark distributions $\widetilde{H}$ and $\widetilde{E}$ in the chiral quark-soliton model of the nucleon. This model emphasizes correctly the role of spontaneously broken chiral symmetry in structure of nucleon. It is based on the large-N_c picture of the nucleon as a soliton of the effective chiral lagrangian and allows to calculate the leading twist quark- and antiquark distributions at a low normalization point. We discuss the role of chiral symmetry in the helicity skewed quark distributions $\widetilde{H}$ and $\widetilde{E}$. We show that generalization of soft pion theorems, based on chiral Ward identities, leads in the region of -\xi < x < \xi to the pion pole contribution to $\widetilde{E}$ which dominates at small momentum transfer.Comment: 22 pages, 5 figure

A next-to-leading order analysis of deeply virtual Compton scattering

We present a complete, next-to-leading-order (NLO), leading-twist QCD analysis of deeply virtual Compton scattering (DVCS) observables, in the ${\bar {MS}}$ scheme, and in the kinematic ranges of the H1, ZEUS and HERMES experiments. We use a modified form of Radyushkin's ansatz for the input model for the generalized parton distributions. We present results for leading order (LO) and NLO for representative observables and find that they compare favourably to the available data.Comment: 5 pages, 2 figures, revtex, published version, we modify Radyushkin's ansatz for the GPDs to correct for finite hadronic mass effects, and, using the latest MRST PDFs, now agree with the H1 data (modified figs). Typo in Eq.(3) correcte

Hard exclusive pseudoscalar meson electroproduction and spin structure of a nucleon

The amplitude for hard exclusive pseudoscalar meson electroproduction off nucleon (nuclear) targets is computed in QCD within the leading $\alpha_s \ln {Q^2/\lambda_{QCD}^{2}}$ approximation. We show that the distribution of recoil nucleons depends strongly on the angle between the momentum of the recoil nucleon and the polarization vector of the target (or outgoing nucleon). This dependence is especially sensitive to the spin flip skewed parton distribution (SPD) $\widetilde E$. We argue also that the scaling for this spin asymmetry sets in at lower Q^2 than that for the absolute cross section. Basing on the chiral quark-soliton model of the nucleon we estimate quantitatively the spin asymmetry. In the case of pi+ production this asymmetry is dominated at small t by the contribution of the pion pole in the isovector SPD $\widetilde E$ as required by PCAC. In the case of K0 production off a proton we find a large enhancement of the cross section as compared to the case of pi0 production. For the forward production of neutral pseudoscalar mesons off a deuteron target we find the cross section should be zero for the zero deuteron helicity (along the $\gamma^*D$ direction). We consider also cross sections of quasielastic processes off nuclei including the feasibility to implant K+,rho-mesons into nuclear volume.Comment: 19 pages, one figur

A next-to-leading order QCD analysis of deeply virtual Compton scattering amplitudes

We present a next-to-leading order (NLO) QCD analysis of unpolarized and polarized deeply virtual Compton scattering (DVCS) amplitudes, for two different input scenarios, in the $\bar{MS}$ scheme. We illustrate and discuss the size of the NLO effects and the behavior of the amplitudes in skewedness, $\zeta$, and photon virtuality, $Q^2$. In the unpolarized case, at fixed $Q^2$, we find a remarkable effective power-law behaviour in $\zeta$, akin to Regge factorization, over several orders of magnitude in $\zeta$. We also quantify the ratio of real to imaginary parts of the DVCS amplitudes and their sensitivity to changes of the factorization scale.Comment: 12 pages, 12 figures, revtex, final version to be published in Phys. Rev. D. Corrected error in MRSA' distribution and modified extraplation behavior of GRSV00 distribution. Corrected error in +i\epsilon treatment. Taking now correct sheaf of log. Errors in subtraction equations corrected. Figures and results for affected imaginary part of NLO amplitude changed accordingl

Isovector unpolarized quark distribution in the nucleon in the large-N_c limit

We calculate the isovector (flavor-nonsinglet) unpolarized quark- and antiquark distributions in the nucleon at a low normalization point in the large-N_c limit. The nucleon is described as a soliton of the effective chiral theory. The isovector distribution appears in the next-to-leading order of the 1/N_c-expansion. Numerical results for the quark- and antiquark distributions compare well with the parametrizations of the data at a low normalization point. This large-N_c approach gives a flavor asymmetry of the antiquark distribution (violation of the Gottfried sum rule) in good agreement with the measurements.Comment: 31 pages, LaTeX, 1 table, 4 figures included using eps

Skewed and double distributions in pion and nucleon

We study the non-forward matrix elements of twist-2 QCD light-ray operators and their representations in terms of skewed and double distributions, considering the pion as well as the nucleon. We point out the importance of explicitly including all twist-2 structures in the double distribution representation, which naturally leads to a ``two-component'' structure of the skewed distribution, with different contributions in the regions |X| > xi/2 and |X| < \xi/2. We compute the skewed and double quark distributions in the pion at a low normalization point in the effective chiral theory based on the instanton vacuum. Also, we derive the crossing relations expressing the skewed quark distribution in the pion through the distribution amplitude for two--pion production. Measurement of the latter in two-pion production in gamma^* gamma and gamma^* N reactions could provide direct information about the skewed as well as the usual quark/antiquark-distribution in the pion.Comment: 37 pages, LaTeX. 5 figures included using eps

Chiral dynamics and the growth of the nucleon's gluonic transverse size at small x

We study the distribution of gluons in transverse space in the nucleon at moderately small x (~10^{-2}). At large transverse distances (impact parameters) the gluon density is generated by the 'pion cloud' of the nucleon, and can be calculated in terms of the gluon density in the pion. We investigate the large-distance behavior in two different approaches to chiral dynamics: i) phenomenological soft-pion exchange, ii) the large-N_c picture of the nucleon as a classical soliton of the pion field, which corresponds to degenerate N and Delta states. The large-distance contributions from the 'pion cloud' cause a \~20% increase in the overall transverse size of the nucleon if x drops significantly below M_pi/M_N. This is in qualitative agreement with the observed increase of the slope of the t-dependence of the J/psi photoproduction cross section at HERA compared to fixed-target energies. We argue that the glue in the pion cloud could be probed directly in hard electroproduction processes accompanied by 'pion knockout', gamma^* + N -> gamma (or rho, J/psi) + pi + N', where the transverse momentum of the emitted pion is large while that of the outgoing nucleon is restricted to values of order M_pi.Comment: 20 pages, revtex4, 10 eps figure