排序方式: 共有37条查询结果,搜索用时 15 毫秒
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A. De Stefanis G. Perez G. Caponecchi 《Journal of Radioanalytical and Nuclear Chemistry》1994,188(2):117-125
The -radiolysis of solutions of benzene and naphthalene in carbon tetrachloride has been studied to obtain information about chlorination reactions. The position of naphthalene showed a reactivity 2.5 higher with respect to benzene, while the absence of 2-chloronaphthalene among the products confirmed the relatively high activation energy required for the attack in position. 相似文献
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Patrizia Cafarelli Adriana De Stefanis Giorgio Perez Anthony A.G. Tomlinson 《Reaction Kinetics and Catalysis Letters》2005,86(1):163-169
Summary Pillared clays have been monitored for catalytic destruction of halocarbons. In comparison with HZSM-5 zeolites, the catalysts tested give higher chlorohydrocarbons destruction with polymers formation. Fluorochlorohydro-carbons are destroyed as well. 相似文献
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We consider a three-dimensional lattice model of a network-forming fluid, which has been recently investigated by Girardi et al. by means of Monte Carlo simulations [J. Chem. Phys. 126, 064503 (2007)], with the aim of describing water anomalies. We develop an approximate semianalytical calculation, based on a cluster-variation technique, which turns out to reproduce almost quantitatively different thermodynamic properties and phase transitions determined by the Monte Carlo method. Nevertheless, our calculation points out the existence of two different phases characterized by long-range orientational order, and of critical transitions between them and to a high-temperature orientationally disordered phase. Also, the existence of such critical lines allows us to explain certain "kinks" in the isotherms and isobars determined by the Monte Carlo analysis. The picture of the phase diagram becomes much more complex and richer, though unfortunately less suitable to describe real water. 相似文献
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Karanikas A.I. Ktorides C.N. Stefanis N.G. 《The European Physical Journal C - Particles and Fields》2003,26(3):445-455
We employ the Polyakov world-line path-integral version of QCD to identify and resum at leading perturbative order enhanced
radiative gluon contributions to the Drell-Yan type ( pair annihilation) cross-sections. We emphasize that this is the first time that world-line techniques are applied to cross-section
calculations.
Received: 10 June 2002 / Published online: 31 October 2002
RID="a"
ID="a" e-mail: akaranik@cc.uoa.gr
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ID="b" e-mail: cktorid@cc.uoa.gr
RID="c"
ID="c" e-mail: stefanis@tp2.ruhr-uni-bochum.de 相似文献
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N. G. Stefanis 《EPJ direct》2000,1(1):1-109
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
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. 相似文献