Clinical value of determination HIV viral load in the cerebrospinal fluid of HIV-infected patients

Aim. To analyze the concentration of HIV RNA in the cerebrospinal fluid and to evaluate its significance in the pathology of the central nervous system among HIV infected persons.Materials: We examined 36 patients with HIV infection with signs of pathology of the central nervous system. All patients was done completed a standard investigation of cerebrospinal fluid, cytological examination and detection viral load of HIV in the cerebrospinal fluid and serum.Results. A different of opportunistic and HIV-related disease was diagnosed in 29 patients. The most frequent pathology of the nervous system (12 cases) is a diffuse HIV-associated brain damage occurring in 7 patients in the form of aseptic non purulent meningitis and in 5 patients in the form of encephalitis. The average value of the absolute and relative count of CD4-lymphocytes in patients amounted 147,0 cells/μl (40,0; 408,75) and 10.0% (4,00; 18,50). Pathological changes in cellular composition and protein concentration of cerebrospinal fluid detected in 19 cases. Replication of HIV in the cerebrospinal fluid are detected in 31 of 32 patients not receiving antiretroviral therapy, including 17 patients with normal values of cerebrospinal fluid. The average HIV viral load in the cerebrospinal fluid was 15 133,0 copies/ml (2501,0; 30624,0) or 4,18 (3,35; 4,48) lg HIV RNA, average HIV viral load in serum – 62 784,0 copies/ml (6027,5; 173869,0) or 4,80 4,80 (3,7; 5,2) lg HIV RNA. The concentration of HIV in the cerebrospinal fluid was significantly lower than in serum (4,18 and 4,80 lg HIV RNA, p=0.027). 4 patients with severe, multietiology damage of the central nervous system viral, microbial and fungal etiology, there was an inverse relationship between the concentration of HIV in the cerebrospinal fluid and in serum, the concentrations of HIV was higher in the cerebrospinal fluid.Conclusion: Among the majority of HIV-infected patients with signs of the central nervous system pathology HIV replication in the cerebrospinal fluid was detected. Observed in some patients HIV replication in the cerebrospinal fluid in the absence of morphological and laboratory changes in the composition of cerebrospinal fluid may reflect indirect effects of HIV the brain, manifested in the form of functional disorders of the central nervous system

Probing partonic structure in gamma* gamma -> pi pi near threshold

Hadron pair production gamma* gamma -> h hbar in the region where the c.m. energy is much smaller than the photon virtuality can be described in a factorized form, as the convolution of a partonic handbag diagram and generalized distribution amplitudes which are new non-perturbative functions describing the exclusive fragmentation of a quark-antiquark pair into two hadrons. Scaling behavior and a selection rule on photon helicity are signatures of this mechanism. The case where h is a pion is emphasized.Comment: 8 pages, 1 figure, LaTeX2

Skewed parton distributions and the scale dependence of the transverse size parameter

We discuss the scale dependence of a skewed parton distribution of the pion obtained from a generalized light-cone wave function overlap formula. Using a simple ansatz for the transverse momentum dependence of the light-cone wave function and restricting ourselves to the case of a zero skewedness parameter, the skewed parton distribution can be expressed through an ordinary parton distribution multiplied by an exponential function. Matching the generalized and ordinary DGLAP evolution equations of the skewed and ordinary parton distributions, respectively, we derive a constraint for the scale dependence of the transverse size parameter, which describes the width of the pion wave function in transverse momentum space. This constraint has implications for the Fock state probability and valence distribution. We apply our results to the pion form factor.Comment: 10 pages, 4 figures; version to appear in Phys. Rev. D; Refs. added, new discussion of results for pion form factor in view of new dat

On the NLO Power Correction to Photon-Pion Transition Form Factor

We propose a perturbative evaluation for the next-to-leading-order (NLO) $O(1/Q^4)$ power correction to the photon-pion transition form factor. The effects of the NLO power correction are analyzed.Comment: 4 pages, 3 figures, Revtex, revised versio

Off-forward parton distributions and Shuvaev's transformations

We review Shuvaev's transformations, that relate off-forward parton distributions (OFPDs) to so-called effective forward parton distributions (EFPDs). The latter evolve like conventional forward partons. We express nonforward amplitudes, depending on OFPDs, directly in terms of EFPDs and construct a model for the EFPDs, which allows to consistently express them in terms of the conventional forward parton distributions and nucleon form factors. Our model is self-consistent for arbitrary x, xi, mu, and t.Comment: 13 pages, 7 eps-figures, LaTeX2e, added references, corrected typo

Unbiased analysis of CLEO data at NLO and pion distribution amplitude

We discuss different QCD approaches to calculate the form factor F^{\gamma^*\gamma\pi}(Q^2) of the \gamma^*\gamma\to\pi^{0} transition giving preference to the light-cone QCD sum rules (LCSR) approach as being the most adequate. In this context we revise the previous analysis of the CLEO experimental data on F^{\gamma^*\gamma\pi}(Q^{2}) by Schmedding and Yakovlev. Special attention is paid to the sensitivity of the results to the (strong radiative) \alpha_s-corrections and to the value of the twist-four coupling \delta^2. We present a full analysis of the CLEO data at the NLO level of LCSRs, focusing particular attention to the extraction of the relevant parameters to determine the pion distribution amplitude, i.e., the Gegenbauer coefficients a_2 and a_4. Our analysis confirms our previous results and also the main findings of Schmedding and Yakovlev: both the asymptotic, as well as the Chernyak--Zhitnitsky pion distribution amplitudes are completely excluded by the CLEO data. A novelty of our approach is to use the CLEO data as a means of determining the value of the QCD vacuum non-locality parameter \lambda^2_q = / =0.4 GeV^2, which specifies the average virtuality of the vacuum quarks.Comment: 25 pages, 5 figures, 4 tables; format and margins corrected to fit page size; small changes in the text and correction of misprint

Perturbative QCD factorization of πγ∗→γ(π)\pi \gamma^*\to \gamma(\pi) and B→γ(π)lνˉB\to \gamma(\pi)l\bar \nu

We prove factorization theorem for the processes $\pi\gamma^*\to\gamma$ and $\pi\gamma^*\to\pi$ to leading twist in the covariant gauge by means of the Ward identity. Soft divergences cancel and collinear divergences are grouped into a pion wave function defined by a nonlocal matrix element. The gauge invariance and universality of the pion wave function are confirmed. The proof is then extended to the exclusive $B$ meson decays $B\to\gamma l\bar\nu$ and $B\to\pi l\bar\nu$ in the heavy quark limit. It is shown that a light-cone $B$ meson wave function, though absorbing soft dynamics, can be defined in an appropriate frame. Factorization of the $B\to\pi l\bar\nu$ decay in $k_T$ space, $k_T$ being parton transverse momenta, is briefly discussed. We comment on the extraction of the leading-twist pion wave function from experimental data.Comment: 21 pages in Latex file, version to appear in Phys. Rev.

Scheme dependence of NLO corrections to exclusive processes

We apply the so-called conformal subtraction scheme to predict perturbatively exclusive processes beyond leading order. Taking into account evolution effects, we study the scheme dependence for the photon-to-pion transition form factor and the electromagnetic pion form factor at next-to-leading order for different pion distribution amplitudes. Relying on the conformally covariant operator product expansion and using the known higher order results for polarized deep inelastic scattering, we are able to predict perturbative corrections to the hard-scattering amplitude of the photon-to-pion transition form factor beyond next-to-leading order in the conformal scheme restricted to the conformal limit of the theory.Comment: RevTeX, 25 pages, 2 figures, 5 tables, minor changes, to be published in Phys. Rev.

Hard exclusive processes and higher-order QCD corrections

The short review of the higher order corrections to the hard exclusive processes is given. Different approaches are discussed and the importance of higher-order calculations is stressed.Comment: 17 pages; talk given at the 9th Adriatic Meeting, Dubrovnik 200