1,222 research outputs found

    The nucleon and the nuclear force in the context of effective theory and path-integral methods

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    The nucleon structure and the nuclear force are investigated in the context of the non-perturbative path-integral method of hadronization. Starting from a microscopic quark-diquark model, the nucleon is generated as a relativistic bound state and an effective chiral meson-nucleon Lagrangian is derived. Many of the nucleon physical properties are studied using a theory of at most two free parameters.Comment: 8 pages, 4 figures. To appear in the proceedings of Pan American Advanced Studies Institute on New States of Matter in Hadronic Interactions (PASI2002), Campos do Jordao, Brazil, 7-18 Jan 200

    Quasifree processes from nuclei: Meson photoproduction and electron scattering

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    We have developed a relativistic formalism for studying quasi-free processes from nuclei. The formalism can be applied with ease to a variety of processes and renders transparent analytical expressions for all observables. We have applied it to kaon photoproduction and to electron scattering. For the case of the kaon, we compute the recoil polarization of the lambda-hyperon and the photon asymmetry. Our results indicate that polarization observables are insensitive to relativistic, nuclear target, and distortion effects. Yet, they are sensitive to the reactive content, making them ideal tools for the study of modifications to the elementary amplitude -- such as in the production, propagation, and decay of nucleon resonances -- in the nuclear medium. For the case of the electron, we have calculated the spectral function of He-4. An observable is identified for the clean and model-independent extraction of the spectral function. Our calculations provide baseline predictions for the recently measured, but not yet fully analyzed, momentum distribution of He-4 by the A1-collaboration from Mainz. Our approach predicts momentum distributions for He-4 that rival some of the best non-relativistic calculations to date.Comment: To appear in the proceedings of International Symposium on Electromagnetic Interactions in Nuclear and Hadron Physics (EMI 2001), Osaka, Ibaraki, Japan, 4-7 Dec 200

    Urban development and expansion trends under the political instability in palestine: jerusalem- ramallah case study

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    Urban development, expansion, and Land use changes in the urban environments are a global phenomenon, by 2050, urban population in the world will increase to be more than 6.6 billion inhabitants and they will live with less than 1% of the world land surfaces. Political instability is one of most important drivers that effecting on the land cover/land use change and urban expansion, especially in the areas that faced the political problems and wars. Urban development in Occupied Palestinian Territories (OPT) impacted strongly by Political Transformations during 20th century and early of 21th century. The political instability factor in OPT leaded to distortion of Palestinian urban form and effecting on future urban expansion and development. Therefore, this study aims to assess of urban development and planning in Palestine during the political transformation stages, as well as it aims to explore urban expansion trends under the geopolitical effects in Jerusalem – Ramallah urban region as a model in the Palestinian urban environment. Descriptive, historical, and cartographic methods conducted based on used Geographic Information System to explore existing and future urban expansion trends in Jerusalem – Ramallah region as a case and model in the Palestinian urban environments. The result showed how the political instability conditions effected strongly on the urban development process and expansion in the Occupied Palestinian Territories. Therefore, this study will improve our Knowledge in the urban development research context about the relationship between the urban development and the political transformations. Palestinian policy makers and planners, as well as Palestinian planning organizations at different levels need to put more efforts to prepare of the regional, sub-regional , and master plans for all Palestinian localities and regions especially in the OPT, in the conflict and sensitive areas such as Jerusalem –Ramallah region. This study recommend to adaption a new planning ideas and strategies to face the Israeli physical planning in the Palestinian urban environments like compact communities and principles of smart urban growth

    How Does Population Viral Load Vary with the Evolution of a Large HIV Epidemic in sub-Saharan Africa?

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    Using mathematical modelling, we described the temporal evolution of population HIV-1 viral load in Tanzania throughout the epidemic. Population log10 viral load was found to be stable and not sensitive to epidemic dynamics. However, even modest increases in antiretroviral therapy (ART) coverage were reflected as appreciable reductions in population log10 viral load. As ART coverage expands in sub-Saharan Africa, population log10 viral load will increasingly become a powerful proxy for monitoring ART implementation and HIV incidence trends. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivitives 3.0 License, where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially. http://creativecommons.org/licenses/by-nc-nd/3.0

    Quasifree kaon-photoproduction from nuclei in a relativistic approach

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    We compute the recoil polarization of the lambda-hyperon and the photon asymmetry for the quasifree photoproduction of kaons in a relativistic impulse-approximation approach. Our motivation for studying polarization observables is threefold. First, polarization observables are more effective discriminators of subtle dynamics than the unpolarized cross section. Second, earlier nonrelativistic calculations suggest an almost complete insensitivity of polarization observables to distortions effects. Finally, this insensitivity entails an enormous simplification in the theoretical treatment. Indeed, by introducing the notion of a ``bound-nucleon propagator'' we exploit Feynman's trace techniques to develop closed-form, analytic expressions for all photoproduction observables. Moreover, our results indicate that polarization observables are also insensitive to relativistic effects and to the nuclear target. Yet, they are sensitive to the model parameters, making them ideal tools for the study of modifications to the elementary amplitude --- such as in the production, propagation, and decay of nucleon resonances --- in the nuclear medium.Comment: 15 pages and 6 figures - submitted to PR
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