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991.
992.
Hungerford G Amaro M Martins P Ferreira MI Uttamlal M Holmes-Smith AS 《Journal of fluorescence》2008,18(2):297-303
Mixed silica–calcite matrices were prepared by developing a “low” temperature (sol–gel) method in presence of several biocompatible
polymers, thus providing samples with adequate porosity for the flow of biological fluids and also mechanically robust. In
order to analyse and characterise the sample’s microenvironments, the highly solvatochromic probe Nile red was used, which
enabled the role of polymer addition upon local environmental effects in the host media to be elucidated. The polymers used
were polyethylene glycol, polymethylmethacrylate and polyethylene. Each matrix was also characterized with respect to microstructure,
morphology and pore size via the use of X-ray diffractometry and scanning electron microscopy.
The results show that is was possible to obtain, in a controlled way, mixed silica–calcite matrices with a wide range of porosities
(important if the material is to be used for scaffold or drug release applications, for example). The spectroscopic behaviour
of Nile red when incorporated has confirmed the existence of distinct and specific local polarities within each type of matrix
that may determine to a large extent the mechanism of interaction between these matrices and biological molecules.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
993.
Phillip Hamer Gabrielle Bourret‐Sicotte George Martins Alison Wenham Ruy S. Bonilla Peter Wilshaw 《固体物理学:研究快报》2017,11(5)
Palladium membranes have been used for decades for the separation of hydrogen from other gasses. In this letter the use of thin palladium leaves to act as sources of atomic hydrogen for silicon samples is explored. It has been assumed in the past that although hydrogen diffuses through palladium in atomic form, the atoms recombine to form molecular hydrogen at the surface. In this letter it is shown that hydrogen supplied to one surface of a palladium leaf can result in atomic hydrogen being released from the opposite surface at low pressure. This is demonstrated through the use of a palladium leaf in a direct plasma system which allows for atomic hydrogen to be supplied to a sample while avoiding exposure to UV radiation from the plasma and high energy charged particles. This method is shown to provide significant atomic hydrogen to silicon samples and improve passivation of silicon surfaces. Method of Shielded Hydrogen Passivation: Schematic of direct plasma chamber with a shield inserted between the plasma and the silicon sample. 相似文献
994.
R.M.S. Martins N. Schell A. Mücklich H. Reuther M. Beckers R.J.C. Silva L. Pereira F.M. Braz Fernandes 《Applied Physics A: Materials Science & Processing》2008,91(2):291-299
In-situ X-ray diffraction (XRD) was employed to study the effect of the deliberate change of the Ti/Ni ratio during the deposition
of Ni-Ti films. Thus, graded films were deposited exhibiting distinctive composition and crystalline structure along the growth
direction. The as-sputtered films were ex-situ characterized by Auger electron spectroscopy (AES), cross-sectional transmission
electron microscopy (XTEM), and electrical resistivity (ER) measurements (during thermal cycling). In this paper results are
presented concerning a film (thickness of ≈ 420 nm) with a Ti-rich composition in the central part (ranging from 50 to ≈60 at. %)
and near-equiatomic composition in the extremities, following four distinct deposition periods (different Ti target powers).
During the initial deposition step (near-equiatomic composition) the Ni-Ti B2 phase starts by stacking onto (h00) planes on
the naturally oxidized Si(100) substrate due to the presence of the native Si oxide (2–3 nm). The increase of the power of
the Ti target in the second and third steps induced the precipitation of Ti2Ni. When stopping the Ti co-sputtering, Ti2Ni dissolves and, thus, plays the role of a Ti reservoir for the formation of B2 phase now preferentially stacking onto (110)
with the system approaching again the equiatomic composition. The ex-situ study of the morphology of the interface has shown
the presence of NiSi2 silicides (A-NiSi2 and B-NiSi2), Ti4Ni4Si7, Ti2Ni and a non-identified phase constituted by Ni, Ti and Si, most likely amorphous. During thermal cycling, ER measurements
revealed phase transitions associated with the B2, R-phase and B19′ phases. These type of studies allow the identification of intermediate states during deposition and annealing, and the correlation
with the final structure of the film, being useful for the optimisation of the deposition parameters in order to fabricate
films with a two-way reversible actuation.
PACS 81.15.Cd; 61.10.Nz; 68.55.Jk 相似文献
995.
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
996.
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
997.
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
998.
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
999.
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
1000.
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