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排序方式: 共有148条查询结果,搜索用时 15 毫秒
71.
Ahlen S Ambrosio M Antolini R Auriemma G Baldini A Barbarino GC Barish BC Battistoni G Bellotti R Bemporad C Bernardini P Bilokon H Bisi V Bloise C Bussino S Cafagna F Calicchio M Campana D Campana P Carboni M Cecchini S Cei F Chiarella V Chiera C Cobis A Cormack R Corona A Coutu S DeCataldo G Dekhussi H DeMarzo C De Vincenzi M Di Credico A Diehl E Erriquez O Favuzzi C Ficenec D Forti C Foti L Fusco P Giacomelli G Giannini G Giglietto N Giubellino P Grassi M Green P Grillo A Guarino F 《Physical review D: Particles and fields》1992,46(11):4836-4845
72.
G Uccello-Barretta R Bernardini F Balzano P Salvadori 《The Journal of organic chemistry》2001,66(1):123-129
Ionic complexes [PtCl3(C2H4)]-[AmH]+, containing chiral secondary amines, constitute a versatile class of chiral derivatizing agents (CDAs) for the enantiomeric purity determination of chiral unsaturated compounds via 195Pt NMR spectroscopy. The NMR conformational analysis allows us to search for the stereochemical basis of their enhanced versatility. 相似文献
73.
A. E. Bernardini 《International Journal of Theoretical Physics》2008,47(4):971-976
We propose a generalized way to formally obtain the gauge invariance of the kinetic part of a field Lagrangian over which
a gauge transformation ruled by an SU(n)
U
⊗
SU(m)
V
coupling symmetry is applied. As an illustrative example, we employ such a formal construction for reproducing the standard
model Lagrangian. This generalized formulation is supposed to contribute for initiating the study of gauge transformation
applied to generalized SU(n)
U
⊗
SU(m)
V
symmetries as well as for complementing an introductory study of the standard model of elementary particles. 相似文献
74.
75.
76.
G.M. Ingo T. de Caro C. Riccucci E. Angelini S. Grassini S. Balbi P. Bernardini D. Salvi L. Bousselmi A. Çilingiroglu M. Gener V.K. Gouda O. Al Jarrah S. Khosroff Z. Mahdjoub Z. Al Saad W. El-Saddik P. Vassiliou 《Applied Physics A: Materials Science & Processing》2006,83(4):513-520
A large number of Cu-based archaeological artefacts from the Mediterranean basin have been selected for investigation of their chemical composition, metallurgical features and corrosion products (i.e. the patina).The guidelines for the selection of the Cu-based artefacts have taken into account the representativeness of the Mediterranean archaeological context, the manufacturing technique, the degradation state and the expected chemical composition and structure of the objects.The results show wide variation of the chemical composition of the alloys that include all kinds of ancient Cu-based alloys such as low and high tin, and also leaded bronzes, copper and copper-iron alloys.The examination of the alloy matrix shows largely different metallurgical features thus indicating the use of different manufacturing techniques for producing the artefacts. The results of the micro-chemical investigation of the patina show the structures and the chemical composition of the stratified corrosion layers where copper or tin depletion phenomenon are commonly observed with a remarkably surface enrichment of some soil elements such as P, S, Ca, Si, Fe, Al and Cl. This information indicates the strict interaction between soil components and corrosion reactions and products. In particular, the ubiquitous and near constant presence of chlorine in the corrosion layers is observed in the patina of the archaeological Cu-based artefacts found in different contexts in Italy, Turkey, Jordan, Egypt, Spain and Tunisia. This latter occurrence is considered dangerous because it could induce a cyclic corrosion reaction of copper that could disfigure the artefact.The micro-chemical and micro-structural results also show that another source of degradation of the bronze archaeological artefacts, are their intrinsic metallurgical features whose formation is induced during the manufacturing of the objects, carried out in ancient times by repeated cycles of cold or hot mechanical work and thermal treatments. These combined treatments induce crystallisation and segregation phenomena of the impurities along the grain boundaries and could cause mechanical weakness and increase the extent of the inter-granular corrosion phenomena. PACS 68.55.Jk; 68.35.Dv; 68.37.Hk; 68.55.Nq; 81.05.Bx 相似文献
77.
A. E. Bernardini 《General Relativity and Gravitation》2011,43(1):245-260
We report about stability conditions for static, spherically symmetric objects that share the essential features of mass varying
neutrinos in cosmological scenarios. Compact structures of particles with variable mass are held together preponderantly by
an attractive force mediated by a background scalar field. Their corresponding conditions for equilibrium and stability are
given in terms of the ratio between the total mass-energy and the spherical lump radius, M/R. We show that the mass varying mechanism leading to lump formation can modify the cosmological predictions for the cosmological
neutrino mass limits. Our study comprises Tolman–Oppenheimer–Volkoff solutions of relativistic objects with non-uniform energy
densities. The results leave open some questions concerning stable regular solutions that, to an external observer, very closely
reproduce the preliminary conditions to form Schwarzschild black holes. 相似文献
78.
We analyze optimized explicit Runge–Kutta schemes (RK) for computational aeroacoustics, and wave propagation phenomena in general. Exploiting the analysis developed in [S. Pirozzoli, Performance analysis and optimization of finite-difference schemes for wave propagation problems, J. Comput. Phys. 222 (2007) 809–831], we rigorously evaluate the performance of several time integration schemes in terms of appropriate error and cost metrics, and provide a general strategy to design Runge–Kutta methods tailored for specific applications. We present families of optimized second- and third-order Runge–Kutta schemes with up to seven stages, and describe their implementation in the framework of Williamson’s 2N-storage formulation [J.H. Williamson, Low-storage Runge–Kutta schemes, J. Comput. Phys. 35 (1980) 48–56]. Numerical simulations of the 1D linear advection equation and of the 2D linearized Euler equations are performed to demonstrate the validity of the theory and to quantify the improvement provided by optimized schemes. 相似文献
79.
Abraham J Abreu P Aglietta M Aguirre C Allard D Allekotte I Allen J Allison P Alvarez-Muñiz J Ambrosio M Anchordoqui L Andringa S Anzalone A Aramo C Argirò S Arisaka K Armengaud E Arneodo F Arqueros F Asch T Asorey H Assis P Atulugama BS Aublin J Ave M Avila G Bäcker T Badagnani D Barbosa AF Barnhill D Barroso SL Bauleo P Beatty JJ Beau T Becker BR Becker KH Bellido JA BenZvi S Berat C Bergmann T Bernardini P Bertou X Biermann PL Billoir P Blanch-Bigas O Blanco F Blasi P Bleve C Blümer H 《Physical review letters》2008,100(21):211101
The surface detector array of the Pierre Auger Observatory is sensitive to Earth-skimming tau neutrinos that interact in Earth's crust. Tau leptons from nu(tau) charged-current interactions can emerge and decay in the atmosphere to produce a nearly horizontal shower with a significant electromagnetic component. The data collected between 1 January 2004 and 31 August 2007 are used to place an upper limit on the diffuse flux of nu(tau) at EeV energies. Assuming an E(nu)(-2) differential energy spectrum the limit set at 90% C.L. is E(nu)(2)dN(nu)(tau)/dE(nu)<1.3 x 10(-7) GeV cm(-2) s(-1) sr(-1) in the energy range 2 x 10(17) eV< E(nu)< 2 x 10(19) eV. 相似文献
80.
Abraham J Abreu P Aglietta M Aguirre C Allard D Allekotte I Allen J Allison P Alvarez-Muñiz J Ambrosio M Anchordoqui L Andringa S Anzalone A Aramo C Argirò S Arisaka K Armengaud E Arneodo F Arqueros F Asch T Asorey H Assis P Atulugama BS Aublin J Ave M Avila G Bäcker T Badagnani D Barbosa AF Barnhill D Barroso SL Baughman B Bauleo P Beatty JJ Beau T Becker BR Becker KH Bellido JA Benzvi S Berat C Bergmann T Bernardini P Bertou X Biermann PL Billoir P Blanch-Bigas O Blanco F Blasi P Bleve C 《Physical review letters》2008,101(6):061101
The energy spectrum of cosmic rays above 2.5 x 10;{18} eV, derived from 20,000 events recorded at the Pierre Auger Observatory, is described. The spectral index gamma of the particle flux, J proportional, variantE;{-gamma}, at energies between 4 x 10;{18} eV and 4 x 10;{19} eV is 2.69+/-0.02(stat)+/-0.06(syst), steepening to 4.2+/-0.4(stat)+/-0.06(syst) at higher energies. The hypothesis of a single power law is rejected with a significance greater than 6 standard deviations. The data are consistent with the prediction by Greisen and by Zatsepin and Kuz'min. 相似文献