40,117 research outputs found

    Nucleon-Meson Coupling Constants and Form Factors in the Quark Model

    Get PDF
    We demonstrate the calculation of the coupling constants and form factors required by effective hadron lagrangians using the quark model. These relations follow from equating expressions for strong transition amplitudes in the two approaches. As examples we derive the NNm nucleon-meson coupling constants and form factors for m = pi, eta, eta', sigma, a_0, omega and rho, using harmonic oscillator quark model meson and baryon wavefunctions and the 3P0 decay model; this is a first step towards deriving a quark-based model of the NN force at all separations. This technique should be useful in the application of effective lagrangians to processes in which the lack of data precludes the direct determination of coupling constants and form factors from experiment.Comment: 7 pages, 4 figures, 1 tabl

    Coherent QED, Giant Resonances and (e+e)(e^{+}e^{-}) Pairs in High Energy Nucleus-Nucleus Collisions

    Get PDF
    We show that the coherent oscillations of the e.m. field induced by the collective quantum fluctuations of the nuclear matter field associated with the giant resonances, with frequencies ωA78A1/3\omega_{A}\simeq 78A^{-{1/3}} MeV, give rise to a significant (e+e)(e^+e^-) pair production in high energy Heavy Ion collisions. The approximate parameterless calculation of such yield is in good agreement with recent experimental observations.Comment: 27 pages, 13 figure

    Computational model for evaluating the state of geomechanical systems during computing experiments

    Get PDF
    Purpose. To create a model allowing integration of the diverse features identified for the rock massif behavior by differentiation of various theories and real phenomena into a single information-analytical flow. Methods. System analysis of computational experiments’ results was based on the use of recursive calculation methodology for assessing accuracy of the obtained results with different methods of geometric and physical description applied to individual elements of simulation in the computational domain. Findings. Sample tables were obtained containing the acceptable values of weight characteristics for the various simulated elements in the generalized computational domain. A recursive algorithm for the analysis of the studied objects description’ efficiency in the solution of geomechanics problems by grid numerical methods was formulated and implemented as a computational module. The authors created a system for the assessment of the results obtained via computational experiment at the time of full-scale investigation, which provides a comprehensive analysis of changes in the rock massif state during the operation of the selected support system. The conditions of combining the design characteristics of the simulated support elements functioning in a single load-carrying system under dynamic redistribution of forces were obtained. Originality. The resulting generalized model of mine working and elements affecting its condition allows to determine most accurately the nature of changes in the stress-strain state of geotechnological system regardless of the originally a priori specified limitations. Practical implications. The unified approach can be used in the search for the optimal parameters of implementing combined working supports in the area of mining operations and beyond.Мета. Створити модель, що дозволяє інтегрувати все різноманіття виявлених особливостей поведінки гірського масиву шляхом диференціації різних теорій і реальних явищ у єдиний інформаційно-аналітичний потік. Методика. Системний аналіз результатів обчислювальних експериментів, що побудований на застосуванні рекурсивної методики оцінки розрахункової точності одержуваних результатів при різних методах геометричного й фізичного опису окремих елементів моделювання у розрахунковій області. Результати. Отримано типові таблиці, що містять припустимі величини вагових характеристик для різних елементів, які моделюються в узагальненій розрахунковій області. Сформульовано й реалізовано у вигляді розрахункового модуля рекурсивний алгоритм аналізу ефективності опису досліджуваних об’єктів при рішенні завдань геомеханіки сітковими чисельними методами. Створено систему оцінки одержуваних результатів обчислювального експерименту при проведенні натурних досліджень, яка забезпечує комплексний аналіз зміни стану породного масиву в ході експлуатації обраної системи кріплення. Отримано умови сполучення розрахункових характеристик елементів кріплення, які моделюються й функціонують у єдиній вантажонесучій системі при динамічному перерозподілі зусиль. Наукова новизна. Одержана узагальнена модель гірничої виробки й елементів, що впливають на її стан, гранично точно дозволяє визначати картину зміни напружено-деформованого стану геотехнологічної системи незалежно від початкових апріорі заданих обмежень. Практична значимість. Забезпечується можливість застосування уніфікованого підходу в пошуку оптимальних показників застосування комбінованих кріплень гірничих виробок, які знаходяться поза зоною й у зоні дії очисних робіт.Цель. Создать модель, позволяющую интегрировать все многообразие выявленных особенностей поведения горного массива путем дифференциации различных теорий и реальных явлений в единый информационно-аналитический поток. Методика. Системный анализ результатов вычислительных экспериментов, построенный на применении рекурсивной методики оценки расчетной точности получаемых результатов при различных методах геометрического и физического описания отдельных элементов моделирования в расчетной области. Результаты. Получены типовые таблицы, содержащие допустимые величины весовых характеристик для различных моделируемых элементов в обобщенной расчетной области. Сформулирован и реализован в виде расчетного модуля рекурсивный алгоритм анализа эффективности описания исследуемых объектов при решении задач геомеханики сеточными численными методами. Создана система оценки получаемых результатов вычислительного эксперимента при проведении натурных исследований обеспечивающая комплексный анализ изменения состояния породного массива в ходе эксплуатации выбранной системы крепления. Получены условия совмещения расчетных характеристик моделируемых элементов крепи функционирующих в единой грузонесущей системе при динамическом перераспределении усилий. Научная новизна. Полученная обобщенная модель горной выработки и элементов, влияющих на ее состояние, предельно точно позволяет определять картину изменения напряженно-деформированного состояния геотехнологической системы независимо от первоначально априори заданных ограничений. Практическая значимость. Обеспечивается возможность применения унифицированного подхода в поиске оптимальных показателей применения комбинированных крепей горных выработок находящихся вне зоны и в зоне действия очистных работ.This work would not have been possible without the support of “DTEK Energo” company. The studies were performed within the framework of the state-maintained scientific research topics. The authors express special gratitude to professors of the National Mining University – Volodymyr Bondarenko and Iryna Kovalevska – for the support in conducting the research

    Worldwide Research Trends on Wheat and Barley: A Bibliometric Comparative Analysis

    Get PDF
    Grain cereals such as wheat, barley, rice, and maize are the nutritional basis of humans and animals worldwide. Thus, these crop plants are essential in terms of global food security. We conducted a bibliometric assessment of scientific documents and patents related to wheat and barley through the Scopus database. The number of documents published per year, their affiliation and corresponding scientific areas, the publishing journals, document types and languages were metricized. The main keywords included in research publications concerning these crops were also analysed globally and clustered in thematic groups. In the case of keywords related to agronomy or genetics and molecular biology, we considered documents dated up to 1999, and from 2000 to 2018, separately. Comparison of the results obtained for wheat and barley revealed some remarkable different trends, for which the underlying reasons are further discussed

    Land, Economic Change, and Agricultural Economics

    Get PDF
    This paper analyzes in three contexts the effects of changing economic conditions and varying economic perspectives on the way land is considered in economic doctrine. The first considers agricultural land use where agriculture is connected to the rest of the economy exclusively through input and commodity markets, and when all other parts of the economy are assumed to remain constant. The second connects agriculture to the remainder of the economy by virtue of a shared natural environment, facilitating a discussion of natural resource and environmental economics in relation to agricultural, institutional, and land economics. The third context permits economic change in the entire economy with particular attention given to population density, space, and distance. Private and public decision making are discussed with attention to federal, state, and local division of powers.Land Economics/Use,

    Biosemiosis and Causation: Defending Biosemiotics Through Rosen's Theoretical Biology, or, Integrating Biosemiotics and Anticipatory Systems Theory

    Get PDF
    The fracture in the emerging discipline of biosemiotics when the code biologist Marcello Barbieri claimed that Peircian biosemiotics is not genuine science raises anew the question: What is science? When it comes to radically new approaches in science, there is no simple answer to this question, because if successful, these new approaches change what is understood to be science. This is what Galileo, Darwin and Einstein did to science, and with quantum theory, opposing interpretations are not merely about what theory is right, but what is real science. Peirce's work, as he acknowledged, is really a continuation of efforts of Schelling to challenge the heritage of Newtonian science for the very good reason that the deep assumptions of Newtonian science had made sentient life, human consciousness and free will unintelligible, the condition for there being science. Pointing out the need for such a revolution in science has not succeeded as a defence of Peircian biosemiotics, however. In this paper, I will defend the scientific credentials of Peircian biosemiotics by relating it to the theoretical biology of the bio-mathematician, Robert Rosen. Rosen's relational biology, focusing on anticipatory systems and giving a place to final causes, should also be seen as a rigorous development of the Schellingian project to conceive nature in such a way that the emergence of sentient life, mind and science are intelligible. Rosen has made a very strong case for the characterization of his ideas as a real advance not only in science, but in how science should be understood, and I will argue that it is possible to provide a strong defence of Peircian biosemiotics as science through Rosen's defence of relational biology. In the process, I will show how biosemiotics can and should become a crucial component of anticipatory systems theory

    Why Respect for the Human Embryo?

    Get PDF

    Strongly Coupled Plasmas via Rydberg-Blockade of Cold Atoms

    Full text link
    We propose and analyze a new scheme to produce ultracold neutral plasmas deep in the strongly coupled regime. The method exploits the interaction blockade between cold atoms excited to high-lying Rydberg states and therefore does not require substantial extensions of current ultracold plasma experiments. Extensive simulations reveal a universal behavior of the resulting Coulomb coupling parameter, providing a direct connection between the physics of strongly correlated Rydberg gases and ultracold plasmas. The approach is shown to reduce currently accessible temperatures by more than an order of magnitude, which opens up a new regime for ultracold plasma research and cold ion-beam applications with readily available experimental techniques.Comment: 5 pages, 5 figure
    corecore