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991.
Arnaldi R Banicz K Castor J Chaurand B Cicalò C Colla A Cortese P Damjanovic S David A de Falco A Devaux A Ducroux L En'yo H Fargeix J Ferretti A Floris M Förster A Force P Guettet N Guichard A Gulkanian H Heuser JM Keil M Kluberg L Lourenço C Lozano J Manso F Martins P Masoni A Neves A Ohnishi H Oppedisano C Parracho P Pillot P Poghosyan T Puddu G Radermacher E Ramalhete P Rosinsky P Scomparin E Seixas J Serci S Shahoyan R Sonderegger P Specht HJ Tieulent R Usai G Veenhof R 《Physical review letters》2008,100(2):022302
The NA60 experiment at the CERN SPS has studied low-mass dimuon production in 158A GeV In-In collisions. An excess of pairs above the known meson decays has been reported before. We now present precision results on the associated transverse momentum spectra. The slope parameter Teff extracted from the spectra rises with dimuon mass up to the rho, followed by a sudden decline above. While the initial rise is consistent with the expectations for radial flow of a hadronic decay source, the decline signals a transition to an emission source with much smaller flow. This may well represent the first direct evidence for thermal radiation of partonic origin in nuclear collisions. 相似文献
992.
Ana Paula de Queiroz Mello Ghadeer Albattarni Daniel Humberto Garcia Espinosa Dennys Reis Antonio Martins Figueiredo Neto 《Brazilian Journal of Physics》2018,48(6):560-570
Modified low-density lipoprotein (LDL) is a well-known risk marker for diabetes and cardiovascular disease. In vitro and in vivo studies have shown that native LDL particles, when modified by oxidation and/or glycation processes, become proatherogenic. Other studies have shown that high LDL concentrations also contribute to atherogenic diseases. In the present in vitro study, we investigate structural characteristics, linear and nonlinear optical properties of LDL particles modified by glycation, compared to modified-control and non-modified LDL (LDLnat). LDL particles were isolated from normolipidemic individuals and aliquots were incubated in PBS (LDLcontrol) and glycated (LDLglyc) with glycolaldehyde (GAD) from 2 to 6 days. The nonlinear optical Z-Scan experiments indicate that GAD modifies the optical properties of the LDL. These results indicate the application of a nonlinear optical technique as a tool to investigate the characteristics of LDL particles, in particular when modifications are induced in the particles by glycation. 相似文献
993.
A. F. da SilvaJr. A. S. Martins M. F. de Campos A. P. Lima 《Brazilian Journal of Physics》2018,48(1):39-45
A study of the physical properties of spin glass systems (SG) is carried out within the Monte Carlo technique. The studied systems are the “classic” CuMn and AuFe metallic alloys, where the RKKY interaction is used as a model for the interaction among the magnetic (Mn, Fe) atoms. A careful discussion about the approach to the equilibrium is addressed. By introducing a cutoff radius in the range on the spin-spin interaction, the results show the influence of this range on the spin-glass behavior of the alloys, where the SG behavior is only observed when the full (long range) RKKY is taken into account, specially for low concentrations x <?0.05. 相似文献
994.
F.M.L. Almeida Jr. Y.A. Coutinho J.A. Martins Simñoes M.A.B. do Vale S. Wulck 《The European Physical Journal C - Particles and Fields》2001,22(2):277-281
The possibility of detecting single heavy Dirac and/or Majorana neutrinos at LEP II is investigated for heavy neutrino masses
in the range . We study the process as a clear signature for heavy neutrinos. Numerical estimates for cross sections and distributions for the signal and the
background are calculated and a Monte Carlo reconstruction of final state particles after hadronization is presented.
Received: 20 September 2001 / Published online: 12 November 2001 相似文献
995.
Jo o B.L. Martins Vicent Moliner Juan Andr s Elson Longo Carlton A. Taft 《Journal of Molecular Structure》1995,330(1-3):347-351
The adsorption of water molecule and hydroxyl ions on the (10-10) and (0001) ZnO surfaces has been studied for (ZnO)4, (ZnO)5 and (ZnO)6 cluster models. Different representations for the atomic basis sets and the effective core potential (ECP) approximations have been employed and the effects of cluster size, conformation and basis sets are analyzed and discussed. 相似文献
996.
Marcos A. P. Martins Rogrio A. Freitag Adriano Da Rosa Alex F. C. Flores Nilo Zanatta Helio G. Bonacorso 《Journal of heterocyclic chemistry》1999,36(1):217-220
A one-pot synthesis of 1-methyl- and 1-phenylpyrazole-3(5)-ethyl esters 2,3a-e by the cyclocondensation of β-alkoxyvinyl trichloromethyl ketones 1a-e with methyl and phenyl hydrazine hydrochloride under mild conditions, is reported. A study using compounds 1a-e with different substituents proved that these are versatile building blocks for the synthesis of pyrazole derivatives, having a 3(5)-ethoxycarbonyl substituent in good yields (60–89%). The hydrazine and β-alkoxyvinyl trichloromethyl ketone substituent effects on the reaction regiochemistry on the formation of the 1,3- and 1,5-isomer were observed. 相似文献
997.
S.L. Martins M.G.C. Resende C.C. Ribeiro P.M. Pardalos 《Journal of Global Optimization》2000,17(1-4):267-283
In this paper, we present a parallel greedy randomized adaptive search procedure (GRASP) for the Steiner problem in graphs. GRASP is a two-phase metaheuristic. In the first phase, solutions are constructed using a greedy randomized procedure. Local search is applied in the second phase, leading to a local minimum with respect to a specified neighborhood. In the Steiner problem in graphs, feasible solutions can be characterized by their non-terminal nodes (Steiner nodes) or by their key-paths. According to this characterization, two GRASP procedures are described using different local search strategies. Both use an identical construction procedure. The first uses a node-based neighborhood for local search, while the second uses a path-based neighborhood. Computational results comparing the two procedures show that while the node-based variant produces better quality solutions, the path-based variant is about twice as fast. A hybrid GRASP procedure combining the two neighborhood search strategies is then proposed. Computational experiments with a parallel implementation of the hybrid procedure are reported, showing that the algorithm found optimal solutions for 45 out of 60 benchmark instances and was never off by more than 4% of the optimal solution value. The average speedup results observed for the test problems show that increasing the number of processors reduces elapsed times with increasing speedups. Moreover, the main contribution of the parallel algorithm concerns the fact that larger speedups of the same order of the number of processors are obtained exactly for the most difficult problems. 相似文献
998.
Cynthia M. C. Prado-Manso Ednalva A. Vidoto Fbio S. Vinhado Hrica C. Sacco Katia J. Ciuffi Patrícia R. Martins Antnio G. Ferreira John R. Lindsay-Smith Otaciro R. Nascimento Yassuko Iamamoto 《Journal of molecular catalysis. A, Chemical》1999,150(1-2):251-266
The synthesis, characterization and catalytic activity of the cationic iron porphyrins Fe[M(4-N-MePy)TDCPP]Cl2 and Fe[M(4-N-MePy)TFPP]Cl2 in the epoxidation of (Z)-cyclooctene by PhIO in homogeneous solution and supported on silica gel (SG), imidazole propyl gel (IPG) or SG modified with 2-(4-sulfonatophenyl)ethyl groups (SiSO3) have been accomplished. When supported on IPG, both cationic FeP bind to the support via Fe–imidazole coordination. Fe[M(4-N-MePy)TDCPP]IPG contains a mixture of low-spin bis-coordinated FeIIIP and high-spin mono-coordinated FeIIIP species, whereas Fe[M(4-N-MePy)TFPP]IPG only contains high-spin mono-coordinated FeIIIP. These FePIPG catalysts also contain FeIIP species, whose presence was confirmed by EPR spectroscopy using NO as a paramagnetic probe. Both cationic FePs coordinate to SG through Fe–O ligation and they are present as high-spin FeIIIP species. The cationic FePs supported on SiSO3− are also high-spin FeIIIP species and they bind to the support via electrostatic interaction between the 4-N-methylpyridyl groups and the SO3− groups present on the matrix. In homogeneous solution, both Fe[M(4-N-MePy)TDCPP]Cl2 and Fe[M(4-N-MePy)TFPP]Cl2 have similar catalytic activity to Fe(TDCPP)Cl and Fe(TFPP)Cl, leading to cis-epoxycyclooctane yields of 92%. When supported on inorganic matrices, both FePs lead to epoxide yields comparable to their homogeneous analogues and their anchoring enables catalyst recovery and re-use. Recycling of Fe[M(4-N-MePy)TDCPP]SiSO3− shows that this FeP maintains its activity in a second reaction. 相似文献
999.
Evaluation of the Effect of Melt Memory on Shear‐Induced Crystallization of Low‐Density Polyethylene
Summary: The effect of melt memory on shear‐induced crystallization of a low‐density polyethylene melt is evaluated with a new shear DTA instrument. A critical strain is identified as the controlling factor for saturating the crystallization. Variation of this strain with the temperature of the sheared melt is established, and the melt state responsible for saturating the crystallization is identified by shear‐stress growth experiments at the steady‐state. Reptation times have been evaluated in both viscoelastic nonlinear and linear regimes, and it is shown that small‐angle oscillatory shear experiments cannot be used to probe effectively the effect of shear flow on the overall crystallization kinetics.
1000.