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Hussein Hijazi Thomas Langlinay Hermann Rothard Philippe Boduch Frédéric Ropars Amine Cassimi Lucio S. Farenzena Enio F. da Silveira 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2014,68(7):1-6
Electronic sputtering of lithium fluoride by swift heavy ions was studied as a function of electronic energy loss (dE/dx) e . The single crystal targets were irradiated with swift heavy ion beams (166Z P 692; 46E P /M P (MeV/u) 611). This allowed varying the deposited energy by a factor of 20 (1.86dE/dx (keV/nm) 632). The sputtered secondary ions were measured from well controlled LiF targets without surface contaminations, by means of the time-of-flight technique (TOF-SIMS). The mass spectrum reveals an important contribution of clusters (over single ions), which increases with (dE/dx) e . Another observation for the strongest perturbation at high dE/dx (>8 keV/nm) is that the secondary ion yields saturate: Y(dE/dx) = constant. In contrast, at lower dE/dx (<8 keV/nm) for weaker perturbation, the yield Y scales with (dE/dx)2. This quadratic increase would rather point towards a thermal evaporation-like mechanism leading to electronic sputtering, however, the origin of the yield saturation remains an open finding. 相似文献
54.
In this study the behaviour of two different types of shock absorbers, symmetrical (linear) and asymmetrical (nonlinear) is compared for use on passenger vehicles. The analyses use different standard road inputs and include variation of the severity parameter, the asymmetry ratio and the velocity of the vehicle. Performance indices and acceleration values are used to assess the efficacy of the asymmetrical systems. The comparisons show that the asymmetrical system, with nonlinear characteristics, tends to have a smoother and more progressive performance, both for vertical and angular movements. The half-car front asymmetrical system was introduced, and the simulation results show that the use of the asymmetrical system only at the front of the vehicle can further diminish the angular oscillations. As lower levels of acceleration are essential for improved ride comfort, the use of asymmetrical systems for vibrations and impact absorption can be a more advantageous choice for passenger vehicles. 相似文献
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Daniel M. Silveira Pedro A. S. Salgueiro M. Filomena G. F. C. Cam?es Ricardo J. N. Bettencourt da Silva 《Accreditation and quality assurance》2012,17(2):115-127
Tear gases are the most widely used non-lethal weapons, both by security forces and by the general public. The pepper spray,
whose active agent is capsaicin, is the only self-defence aerosol allowed in Portugal, where capsaicin concentration must
be below 5 g/100 mL. The cost-effective evaluation of the compliance of self-defence weapons with legislation involves the
use of two measurement procedures with increasing quantitative capability. Samples are first assessed by preliminary measurement
procedure based on single-point GC–MS calibration. Whenever the measurement uncertainty from this assessment makes evaluation
inconclusive, the evaluation of sample compliance using multi-point GC–MS calibration is performed. Metrological models including
sound criteria for the evaluation of sample compliance with legislation were developed for both measurement procedures. Such
models include the evaluation of the impact of instrumental performance, calibration model, sample dilution and standards
preparation on measurement uncertainty. The relative expanded uncertainty, in the studied range (capsaicin 3–7 g/100 mL),
of measurements supported in single-point calibrations ranged from 10 to 22% and the ones supported on multi-point calibrations
from 8 to 12% depending on capsaicin concentration and daily GC–MS repeatability. Measurements are fit for the intended use
since they present a relative expanded uncertainty smaller than a target value of 30, or 15%, for measurements supported in
single- or multi-point calibrations, respectively. 相似文献
57.
Pereira-Netto AB Meneguin RG Biz A Silveira JL 《Applied biochemistry and biotechnology》2012,166(1):197-207
Agar is a complex mixture of gel-forming polysaccharides. Gelling agents are very often used to provide proper support for
plants grown in semisolid culture media. And agar is the most frequently used gelling agent in plant tissue culture media.
Galactomannans, another group of gel-forming polysaccharides, consists of a (1 → 4)-linked β-d-mannopyranosyl backbone partially substituted at O-6 with d-galactopyranosyl side groups. In this work, we demonstrate that a statistically significant 2.7-fold increase on the multiplication
rate (MR) for in vitro-grown Marubakaido (Malus prunifolia) shoots was associated with a 12.5% replacement of agar in the semi-solid culture media for a galactomannan obtained from
seeds of Schizolobium paraybae. This increase on MR was due mainly to a 1.9-fold increase in the number of main branches and an 8.6-fold increase in the
number of primary lateral branches. Gas liquid chromatography and thin layer chromatography analyzes demonstrated that the
galactomannan-driven enhancement of the in vitro multiplication rate of the Marubakaido apple rootstock was not related to
the galactomannan degradation. To the best of our knowledge, this is the first report on the successful use of partial replacement
of high quality agar by a galactomannan from S. paraybae in a micropropagation system for a tree species. 相似文献
58.
Silveira G de Morais A Villis PC Maroneze CM Gushikem Y Lucho AM Pissetti FL 《Journal of colloid and interface science》2012,369(1):302-308
A silica-cerium mixed oxide (SiCe) was prepared by the sol-gel process, using tetraethylorthosilicate and cerium nitrate as precursors and obtained as an amorphous solid possessing a specific surface area of 459 m(2) g(-1). Infrared spectroscopy of the SiCe material showed the formation of the Si-O-Ce linkage in the mixed oxide. Scanning electron microscopy/energy dispersive spectroscopy indicated that the cerium oxide particles were homogenously dispersed on the matrix surface. X-ray diffraction and (29)Si solid-state nuclear magnetic resonance implied non-crystalline silica matrices with chemical environments that are typical for silica-based mixed oxides. X-ray photoelectron spectroscopy showed that Ce was present in approximately equal amounts of both the 3+ and 4+ oxidation states. Cyclic voltammetry data of electrode prepared from the silica-cerium mixed oxide showed a peak for oxidation of Ce(3+)/Ce(4+) at 0.76 V and electrochemical impedance spectroscopy equivalent circuit indicated a porous structure with low charge transfer resistance. In the presence of nitrite, the SiCe electrode shows an anodic oxidation peak at 0.76 V with a linear response as the concentration of the analyte increases from 3×10(-5) at 3.9×10(-3) mol L(-1). 相似文献
59.
Luís Gustavo Cofani dos Santos Márcio Arruda Bacchi Elisabete A. De Nadai Fernandes Simone Silveira Nery da Silva Cofani dos Santos 《Journal of Radioanalytical and Nuclear Chemistry》2012,291(1):179-185
As a non-destructive and multi-element technique, with high-level metrological properties, instrumental neutron activation analysis (INAA) has an important role to determine chemical elements in food. However, its use may be limited when looking for mass fractions near the detection limits. The Compton scattering of higher energy gamma-rays raised the spectrum baseline thus impairing the determination of several elements. Therefore, the gamma-ray spectrometry with Compton suppression becomes an alternative for improving the performance of INAA, since it can reduce the uncertainty of measurements and the detection limits by increasing the proportion between photopeak area and baseline. Here the performance of a Compton suppression system set by Ortec, with 50% relative efficiency and 2.04?keV resolution (FWHM) for the 1,332?keV photopeak, was evaluated for food analysis. Samples of beans, chickpeas, lentils, peas, and rice were irradiated with neutrons and measured in the suppression system. Detection limits calculated from suppressed and unsuppressed spectra were compared. The suppression factor achieved by the system for 137Cs was 5.88?±?0.11 (n?=?20) in the plateau region (358 to 382?keV), which was stable along a 20?week period and similar to the data provided in literature for other systems. Amongst fifteen elements determined, the detection limits for Br, Co, La, Na, Sc, and Se were not improved by the use of Compton suppression. On the other hand, the variable improvement obtained for As, Ca, Cd, Cr, Fe, Hg, K, Rb, and Zn corroborated the idea that the performance of the Compton suppressor must be individually assessed for each type of sample. 相似文献
60.
Danielle da Silveira dos Santos Anna Carolina Camelo Kelly Cristina Pedro Rodrigues Luís Cláudio Carlos Nei Pereira Jr. 《Applied biochemistry and biotechnology》2010,161(1-8):93-105
Considerable efforts have been made to utilize agricultural and forest residues as biomass feedstock for the production of second-generation bioethanol as an alternative fuel. Fermentation utilizing strains of Zymomonas mobilis and the use of simultaneous saccharification and fermentation (SSF) process has been proposed. Statistical experimental design was used to optimize the conditions of SSF, evaluating solid content, enzymatic load, and cell concentration. The optimum conditions were found to be solid content (30%), enzymatic load (25 filter paper units/g), and cell concentration (4 g/L), resulting in a maximum ethanol concentration of 60 g/L and a volumetric productivity of 1.5 g L?1?h?1. 相似文献