1,758 research outputs found

    Microscopic Description of Deeply Virtual Compton Scattering off Spin-0 Nuclei

    Full text link
    We evaluate within a microscopic calculation the contributions of both coherent and incoherent deeply virtual Compton scattering from a spin-0 nucleus. The coherent contribution is obtained when the target nucleus recoils as a whole, whereas for incoherent scattering break-up configurations for the final nucleus into a an outgoing nucleon and an A1A-1 system are considered. The two processes encode different characteristics of generalized parton distributions.Comment: 7 pages, 3 figure

    Nuclear Medium Modifications of Hadrons from Generalized Parton Distributions

    Full text link
    We study the structure of generalized parton distributions in spin 0 nuclei within a microscopic approach for nuclear dynamics. GPDs can be used on one side as tools to unravel the deep inelastic transverse structure of nuclei in terms of both transverse spatial and transverse momentum degrees of freedom. On the other, one can obtain information on GPDs themselves by observing how they become modified in the nuclear environment. We derive the structure of the nuclear deeply virtual Compton scattering tensor and generalized parton distributions at leading order in QQ in a field-theoretical framework. The nuclear generalized parton distributions are calculated using a two step process -- the convolution approach -- where the scattering process happens from a quark inside a nucleon, itself inside a nucleus, disregarding final state interactions with both the nuclear and nucleon debris. We point out that details of the nuclear long range interactions such as two-body currents, can be disregarded compared to the deep inelastic induced modifications of the bound GPDs. We show how the pattern of nuclear modifications predicted, and in particular the deviations of off-shell effects from the longitudinal convolution provide clear signals to be sought in experimental measurements. Finally, we find interesting relationships by studying Mellin moments in nuclei: in particular we predict the AA-dependence for the DD-term of GPDs within a microscopic approach, and the behavior with tt of the total momentum carried by quarks in a nucleus. The latter provides an important element for the evaluation of nuclear hadronization phenomena which are vital for interpreting current and future data at RHIC, HERMES and Jefferson Lab.Comment: 29 pages, 10 figure

    The Present status and the projected programme on niobium-tantalum metallurgy in India

    Get PDF
    Niobium and tantalum which belong to the family of ref-ractory rare metals, have assumed great strategic impo-rtance in present day material development programmes, specially in industries like chemical and nuclear engineering, electronics and aerospace. The use of niob-ium as ferroniobium contributing to carbide stabilisat-ion in stainless steel is well established and accounts for the major demand for niobium in the world today. At the same time, niobium-based alloys have been considered excellent for high temperature service, and in particular two alloys (i) SU-16 (Nb- 11 W- 3Mo -21-If-0 - 08C), and (ii) Nb-752 (Nb-IOW- 25Zr)'--have been developed for application in aerospace structure components. With its relatively low neutron absorption cross-section (Q8= I 1 barns), compatibility both with uranium fuels and liquid metal coolants, and good high temperature strength and fabrication characteristics, niobium is also an attra-ctive candidate for nuclear energy application, parti-cularly in fast reactors. Also, a zirconium-alloy conta-ining 2.5% of niobium is a potential competitor to zircaloy for structural core components in water-cooled thermal reactor systems

    Generalized Parton Distributions from Hadronic Observables: Zero Skewness

    Full text link
    We propose a physically motivated parametrization for the unpolarized generalized parton distributions. At zero value of the skewness variable, ζ\zeta, the parametrization is constrained by simultaneously fitting the experimental data on both the nucleon elastic form factors and the deep inelastic structure functions. A rich phenomenology can be addressed based on this parametrization. In particular, we track the behavior of the average: {\it i)} interparton distances as a function of the momentum fraction, XX, {\it ii)} XX as a function of the four-momentum transfer, tt; and {\it iii)} the intrinsic transverse momentum kk_\perp as a function of XX. We discuss the extension of our parametrization to ζ0\zeta \neq 0 where additional constraints are provided by higher moments of the generalized parton distributions obtained from {\it ab initio} lattice QCD calculations.Comment: 42 pages, 21 figure

    Transport in bacteriophage P22-infected Salmonella typhimurium

    Get PDF
    There was rapid efflux of L-leucine, L-phenylalanine, and α-methyl-D-glucoside after infection of Salmonella typhimurium with the clear plaque mutant C1 of phage P22. The efflux was similar to that observed with cyanide or arsenate treatment except that there was partial recovery in the case of phage infection and almost complete recovery under the condition of lysogeny. There was no efflux after infection with the temperature-sensitive mutant ts16C1 at nonpermissive temperature. Superinfection of superinfection exclusion negative lysogen (sie A - sie B-) with C1 led to efflux, whereas the efflux was much less on superinfection of sie A+ Sie B+ lysogen. These results indicate that an effective injection process is enough to cause depression in the cellular transport processes

    On the A-dependence of nuclear generalized parton distributions

    Full text link
    We perform a microscopic evaluation of nuclear GPDs for spin-0 nuclei in the framework of the Walecka model. We demonstrate that the meson (non-nucleon) degrees of freedom dramatically influence nuclear GPDs, which is revealed in the non-trivial and unexpected A-dependence of DVCS observables. In particular, we find that the first moment of the nuclear D-term, d_A(0) ~ A^2.26, which confirms the earlier prediction of M.Polyakov. We find that in the HERMES kinematics, contrary to the free proton case, the nuclear meson degrees of freedom in large nuclei enhance the nuclear DVCS amplitude which becomes comparable to the Bethe-Heitler amplitude, and, thus, give the non-trivial A-dependence to the DVCS asymmetries: as a function of the atomic number the beam-charge asymmetry increases whereas the beam-spin asymmetry decreases slowly.Comment: Final version published in J. Phys. G. 17 pages, 9 figure

    Against the Odds: Psychomotor Development of Children Under 2 years in a Sudanese Orphanage.

    Get PDF
    Providing abandoned children the necessary medical and psychological care as possible after their institutionalization may minimize developmental delays. We describe psychomotor development in infants admitted to an orphanage in Khartoum, Sudan, assessed at admission and over an 18-month follow-up. Psychological state and psychomotor quotients were determined using a simplified Neonatal Behavior Assessment Scale (NBAS), the Brunet-Lezine and Alarm distress baby (ADBB) scale. From May-September 2005, 151 children were evaluated 2, 4, 9, 12 and 18 months after inclusion. At admission, ∼15% of children ≤1 month had a regulation impairment according to the NBAS, and 33.8% presented a distress state (ADBB score >5). More than 85% (129/151) recovered normal psychomotor development. The results of the program reinforce the importance of early detection of psychological disorders followed by rapid implementation of psychological case management to improve the development of young children in similar institutions and circumstances

    Trio: enabling sustainable and scalable outdoor wireless sensor network deployments

    Get PDF
    corecore