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An analysis of all available data (CELLO, CLEO, B A B AR) in the range [1÷ 40] GeV for the pion-photon transition form factor in terms of light-cone sum rules with next-to-leading-order accuracy is discussed, including twist-four contributions and next-to-next-to-leading order and twist-six corrections-the latter two via uncertainties. The antithetic trend between the B A B AR data for the γ*γ π and those for the γ* γ η( η′) transition is pointed out, emphasizing the underlying antagonistic mechanisms: endpoint enhancement for the first and endpoint-suppression for the second-each associated with pseudoscalar meson distribution amplitudes with distinct endpoint characteristics. [ABSTRACT FROM AUTHOR]

We study the phenomenon of duality in hard exclusive reactions to which QCD factorization applies. Considering “two-photon”-like processes in the scalar φ model and also two-hadron (pion) production from the collisions of a real (transversely polarized) and a highly-virtual, longitudinally polarized photon in QCD, we identify two regimes of factorization, each of them associated with a distinct nonperturbative mechanism. One mechanism involves twist-3 Generalized Distribution Amplitudes, whereas the other one employs leading-twist Transition Distribution Amplitudes. In the case of the scalar φ model, we find duality in that kinematical region where the two mechanisms overlap. In the QCD case, the appearance of duality is sensitive to the particular nonperturbative model applied and can, therefore, be used as an additional adjudicator. [ABSTRACT FROM AUTHOR]

Background This article presents a study of the Occupational Abilities and Performance Scale (OAPS), developed for administration to schizophrenic patients. The reliability and validity of the OAPS has been evaluated. Method A total of 174 schizophrenic patients who participated in the Psychosocial and Vocational Rehabilitation Unit (PVRU) of the University Mental Health Research Institute (UMHRI) in Athens were assessed. The OAPS is conducted at entry and after 18 months, when the client has completed training. Results The results of the reliability analysis showed very good internal consistency, with high split-half reliability as well as test-retest reliability and inter-rater agreement. The scale was also found to have good predictive validity, as well as concurrent validity. Finally, factor analysis with principal components extraction method was performed in order to assess the construct validity of the scale. Conclusions The results of factor analysis supported the conclusion of good reliability and validity of the OAPS and revealed the existence of five components, each correlated with a set of the original items. [ABSTRACT FROM AUTHOR]

To investigate the effect of exposure to cannabis early in adolescence on subclinical positive and negative symptoms of psychosis.Cross-sectional survey in the context of an ongoing cohort study.Government-supported general population cohort study.A total of 3500 representative 19-year olds in Greece.Subjects filled in the 40-item Community Assessment of Psychic Experiences, measuring subclinical positive (paranoia, hallucinations, grandiosity, first-rank symptoms) and negative psychosis dimensions and depression. Drug use was also reported on.Use of cannabis was associated positively with both positive and negative dimensions of psychosis, independent of each other, and of depression. An association between cannabis and depression disappeared after adjustment for the negative psychosis dimensions. First use of cannabis below age 16 years was associated with a much stronger effect than first use after age 15 years, independent of life-time frequency of use. The association between cannabis and psychosis was not influenced by the distress associated with the experiences, indicating that self-medication may be an unlikely explanation for the entire association between cannabis and psychosis.These results add credence to the hypothesis that cannabis contributes to the population level of expression of psychosis. In particular, exposure early in adolescence may increase the risk for the subclinical positive and negative dimensions of psychosis, but not for depression. [ABSTRACT FROM AUTHOR]

Rates of psychotic disorder and related attenuated psychotic experiences are higher in urban areas. We examined to what degree differences between urban and rural areas could be attributed to differences in cognitive development. Young men from urban areas had higher scores on the SPQ subscale Odd beliefs/magical thinking (OR=1.99, 95% CI: 1.42, 2.78), but lower scores on Excessive social anxiety (OR=0.63, 95% CI: 0.49, 0.81) and No close friends (OR=0.42, 95% CI: 0.29, 0.62). Adjustment for demographic factors, IQ and specific neuropsychological functions did not change the results. When the lower scores on Excessive social anxiety and No close friends were taken into account, the differences on the Odd beliefs/magical thinking subscale became even more pronounced (OR=2.33, 95% CI: 1.56, 3.49). Young men from urban areas are socially more competent, but display higher levels of positive psychotic experiences, which are not mediated by lower IQ or higher levels of neuropsychological impairment. [ABSTRACT FROM AUTHOR]

A total of 940 young men performed a task in which they actively maintained fixation for 50 s in three conditions: a) on a visual target, b) on a visual target while distracting targets appeared briefly on the periphery and c) with no visual target present. The same individuals completed psychometric evaluation tests measuring IQ, schizotypy and current state-dependent psychopathology. The proportion of fixation time decreased and saccade frequency increased in condition b compared wih condition a, and sequentially in condition c compared with condition b. A trend towards a decrease in proportion of fixation time and increase in saccade frequency was found as the subjects maintained fixation during the task and this time-dependent deterioration of performance was again most pronounced in condition c, less so in condition b and absent in condition a. Psychometric test scores were significantly correlated with fixation performance in the population. Worse performance in all three fixation conditions was observed for individuals with lower IQ scores. A deterioration of fixation performance with time in condition b was correlated with disorganization characteristics of schizotypy, suggesting that these individuals had difficulty maintaining active fixation in the presence of increased inhibitory load. A connection of such a difficulty with the frontal lobes and their role in the control of voluntary inhibitory functions is discussed. [ABSTRACT FROM AUTHOR]

Employing the standard hard-scattering approach (HSA) in conjunction with the running coupling (RC) method, the latter joined with the infrared renormalon calculus, we compute power-suppressed corrections ∼1/Q2n ,n=1, 2,… to the massless η′-meson-virtual-gluon transition form factor (FF) Q 2Fη′g*g8 (Q2, w). Contributions to the form factor from the quark and gluon components of the if meson are taken into account. Analytic expressions for the FFs Fη′99*(Q2>,w =±1) and Fη′g*g*(Q2,w= 0) are also presented, as well as Borel transforms B[Q2Fη′g*g*](u) and resummed expressions. It is shown that except for w =±1, 0, the Borel transform contains an infinite number of infrared renormalon poles. It is demonstrated that in the explored range of the total gluon virtuality 1 GeV2

A sample of 676 healthy young males performed visually guided saccades and antisaccades and completed the Porac-Coren questionnaire measuring lateral preferences. There was no difference in mean latency between rightward versus leftward saccades or for saccades executed in the left versus right hemispace. There was also no right/left asymmetry for individuals with left or right dominance as assessed by the lateral preferences questionnaire. The same results were observed for the latency of antisaccades and for the error rate in the antisaccade task. Finally, we did not confirm any substantial subpopulation of individuals with idiosyncratic left/right latency asymmetries that persisted both in the saccade and antisaccade task. These results suggest that neither latency nor antisaccade error rate are good indicators of lateral preferences in these tasks. Other oculomotor tasks might be more sensitive to hemifield differences, or cerebral hemispheric asymmetry is not present at the level of cortical organization of saccades and antisaccades. [ABSTRACT FROM AUTHOR]

The modern formulation of exclusive reactions within Quantum Chromodynamics is reviewed, the emphasis being placed on the pivotal ideas and methods pertaining to perturbative and non-perturbative topics. Specific problems, related to scale locality, infrared safety, gluonic radiative corrections (Sudakov effects), and the role of hadronic size effects (intrinsic transverse momentum), are studied. These issues are more precisely analyzed in terms of the essential mechanisms of momentum transfer to a hadron while remaining intact. Different factorization schemes are considered and the conceptual lacunas are pointed out. The quite technical subject of renormalization-group evolution is given a detailed account. By combining analytical and numerical algorithms, the one-gluon exchange nucleon evolution equation is diagonalized and next-to-leading eigenfunctions are calculated in terms of Appell polynomials. The corresponding anomalous dimensions of trilinear quark operators are found to form a degenerate system whose envelope shows logarithmic large-order behavior. Selected applications of this framework are presented, focusing on the helicity-conserving elastic form factors of the pion and the nucleon. The theoretical constraints imposed by QCD sum rules on the moments of nucleon distribution amplitudes are used to determine a whole spectrum of optional solutions. They organize themselves along an “orbit” characterized by a striking scaling relation between the form-factor ratio $$R= \vert G_{\rm n}^{\rm M}\vert/G_{\rm M}^{\rm p}$$ and the projection coefficient B4 on to the corresponding eigensolution. The main reasons for the failure of the present theoretical predictions to match the experimental data are discussed and workable explanations are sketched. [ABSTRACT FROM AUTHOR]

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The behavior of the proton magnetic form factor is studied within the modified hard scattering picture, which takes into account gluonic radiative corrections in terms of transverse separations. We parallel the analysis given previously by Li and make apparent a serious objection. The appropriate cut-off needed to render the form-factor calculation finite is both detailed and analyzed by considering different cut-off prescriptions. The use of the maximum interquark separation as a common infrared cut-off in the Sudakov suppression factor is proposed, since it avoids difficulties with the α-singularrities and yields a proton form factor insensitive to the inclusion of the soft region which therefore can be confidently attributed to perturbative QCD. Results are presented for a variety of proton wave functions including also their intrinsic transverse momentum. It turns out that the perturbative contribution, although theoretically self-consistent for Q larger than about 6 GeV to 10 GeV, is too small compared to the data. [ABSTRACT FROM AUTHOR]