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71.
The detection of explosives for the purpose of aviation security is an important task for preventing terrorism acts and smuggling. A number of methods for explosive screening have been developed. For the purpose of aviation security, the inspections are performed on passengers, their carry-on luggage, checked baggage, and cargo containers. An effective explosive detection system should be capable of reporting the type of energetic material, the mass, the object shape and its location within the volume being scanned. Quadrupole resonance (QR) is a mature technique for detecting and classifying explosives concealed in unopened containers. We report recent research on threat localization techniques, aimed to enhance the efficiency of QR-based baggage scanner systems. The methods investigated for threat localization are based on the effect of inhomogeneous static magnetic fields, nonuniform radio-frequency excitation, and the use of spatially selective radio-frequency coils for one- and two-dimensional mapping. 相似文献
72.
L. A. S. De A. Prado H. Wittich K. Schulte G. Goerigk Vasil M. Garamus R. Willumeit S. Vetter B. Ruffmann S. P. Nunes 《Journal of Polymer Science.Polymer Physics》2004,42(3):567-575
The morphology and distribution of zirconium oxide and zirconium phosphates in a matrix of sulfonated poly(ether ether ketone) (SPEEK) were investigated with anomalous small‐angle X‐ray scattering (ASAXS) and electron microscopy. ASAXS revealed that ZrO2 was distributed in the SPEEK matrix in the form of nanoparticles smaller than 13 Å. A decrease in the conductivity suggested that the sulfonic groups were bound to the zirconium oxo species at the particle surface. Furthermore, two kinds of membranes containing zirconium phosphate were investigated. In one case, the phosphate was directly dispersed in the polymer solution for the casting of the membrane. In the other case, the phosphate was previously treated with n‐propyl ammonium and polybenzimidazole. From ASAXS data, the fractal dimension could be estimated. Mass‐fractal behavior was confirmed for the SPEEK membrane containing previously exfoliated zirconium phosphate, with aggregates of 6.3–165 Å. Surface‐fractal behavior was detected for membranes with untreated phosphates, with aggregates of 6.4–185 Å. The untreated phosphates caused an increase in the permeability, without changing the proton conductivity much. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 567–575, 2004 相似文献
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75.
Vandenberghe LP Soccol CR Prado FC Pandey A 《Applied biochemistry and biotechnology》2004,118(1-3):293-303
Studies were conducted to evaluate citric acid production by solid-state fermentation (SSF) using cassava bagasse as substrate
employing a fungal culture of Aspergillus niger LPB 21 at laboratory and semipilot scale. Optimization of the process parameters temperature, pH, initial humidity, aeration,
and nutritive composition was conducted in flasks and column fermentors. The results showed that thermal treatment of cassava
bagasse enhanced fungal fermentation efficacy, resulting in 220 g of citric acid/kg of dry cassava bagasse with only treated
cassava bagasse as substrate. The results obtained from the factorial experimental design in a column bioreactor showed that
an aeration rate of 60 mL/min (3 mL/[g·min]) and 60% initial humidity were optimum, resulting in 265.7 g/kg of dry cassava
bagasse citric acid production. This was almost 1.6 times higher than the quantities produced under unoptimized conditions
(167.4 g of citric acid/kg of dry cassava bagasse). The defined parameters were transferred to semipilot scale, which showed
high promise for large-scale citric acid production by SSF with cassava bagasse. Respirometry assays were carried out in order
to follow indirectly the biomass evolution of the process. Citric acid production reached 220, 309, 263, and 269 g/kg of dry
cassava bagasse in Erlenmeyer flasks, column fermentors, a tray bioreactor, and a horizontal drum bioreactor, respectively. 相似文献
76.
García Rodenas LA Weisz AD Magaz GE Blesa MA 《Journal of colloid and interface science》2000,230(1):181-185
The electrokinetic behavior of titanium dioxide particles (Degussa P25, mainly composed of anatase) put in contact with chromium(VI) aqueous solutions is highly sensitive to light exposure under normal laboratory conditions. In the dark, adsorption of Cr(VI) gives rise to substantial decrements in the mobilities, especially in the acidic branch, and, at higher concentrations, to shifts in the isoelectric point (pH(piep)) to lower values, as expected for anionic chemisorption. A two-mode adsorption model accounts qualitatively for the results. Under light, pH(piep) shifts in the opposite direction as the Cr(VI) concentration increases. A maximum value is attained at [Cr(VI)] approximately 10(-3) mol dm(-3), pH(piep) 8.2, which coincides with values reported for hydrous chromium(III) oxides. At higher concentrations, Cr(VI) adsorption defines a shift of pH(piep) to lower values. It is concluded that light absorption by titanium dioxide promotes the reduction of Cr(VI) and the surface precipitation of the hydrous Cr(III) oxide. The values of pH(piep) for partially covered surfaces are well described by a simple model of surface ionization derived earlier. FTIR/ATR analysis of the surfaces supports this interpretation, and further suggests that one of the modes of Cr(VI) adsorption implies surface dimerization to yield adsorbed dichromate. Copyright 2000 Academic Press. 相似文献
77.
Ma Prado García-Aparicio Ignacio Ballesteros Alberto González José Miguel Oliva Mercedes Ballesteros Ma José Negro 《Applied biochemistry and biotechnology》2006,129(1-3):278-288
The influence of the liquid fraction (prehydrolysate) generated during steam-explosion pretreatment (210°C, 15 min) of barley
straw on the enzymatic hydrolysis was determined. Prehydrolysate was analyzed for degradation compounds and sugars' content
and used as a medium for enzymatic hydrolysis tests after pH adjusting to 4.8. Our results show that the presence of the compounds
contained in the prehydrolysate strongly affects the hydrolysis step (a 25% decrease in cellulose conversion compared with
control). Sugars are shown to be more potent inhibitors of enzymatic hydrolysis than degradation products. 相似文献
78.
Sandee AJ van Der Veen LA Reek JN Kamer PC Lutz M Spek AL van Leeuwen PW 《Angewandte Chemie (International ed. in English)》1999,38(21):3231-3235
By a sol-gel process a rhodium complex containing a diphosphane with a large natural P-Rh-P bite angle is covalently anchored in a silica matrix (see picture). The immobilized catalyst is a very selective hydroformylation catalyst that is completely and conveniently separated from the product and can be reused in numerous cycles. 相似文献
79.
Fernanda M. Prado Alexsandra C. Scalfo Sayuri Miyamoto Marisa H.G. Medeiros Paolo Di Mascio 《Photochemistry and photobiology》2020,96(3):560-569
Singlet molecular oxygen is a reactive species involved in biological oxidative processes. The major cellular targets of singlet molecular oxygen are unsaturated fatty acids in the membrane, as well as nucleic acids and proteins. The aim of this study was to investigate whether lipids and commercial hydroperoxides generate singlet molecular oxygen, in presence of nitronium and activated nitronium ion. For this purpose, monomol light emitted in the near-infrared region (λ = 1270 nm) was used to monitor singlet molecular oxygen decay in different solvents, with different hydroperoxides and in the presence of azide. Direct measurements of the singlet molecular oxygen spectrum at 1270 nm recorded during the reaction between lipids and commercial hydroperoxides and nitronium ions unequivocally demonstrated the formation of this excited species. 相似文献
80.
Monteiro Thatyara Oliveira dos Santos Clenilton Costa do Prado Thiago Martimiano Damos Flávio Santos Luz Rita de Cássia Silva Fatibello-Filho Orlando 《Journal of Solid State Electrochemistry》2020,24(8):1801-1809
Journal of Solid State Electrochemistry - A novel label-free photoelectrochemical immunosensor was developed for the determination of prostate-specific antigen (PSA) based on fluorine-doped tin... 相似文献