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91.
Leonardo S. Lopes Filipe S. Q. Silva Adriana S. Silva Isabella F. Delgado 《Journal of surfactants and detergents》2013,16(3):445-448
Enzymatic detergents are widely used in health services. These products should be controlled to ensure their activity. In this paper, a UV spectrophotometric method for the determination of proteolytic activity in enzymatic detergents was validated. An artificial substrate (azocasein) was used to quantify the enzyme activity at 340 nm. The results showed that the method was satisfactory in respect to its specificity, linearity, precision, accuracy and robustness. This method fulfills both ICH’s and Brazilian criteria, demonstrating its suitability for routine analysis as well as its potential application for regulatory purposes. 相似文献
92.
93.
We derive a simple analytical correction of a well-known standard formulation of the gravity wave height produced in a prismatic channel due to a sudden discharge stoppage at the downstream end of the channel. The proposed analytical correction considers the vertical growth of the wave and, as a result, takes into account the effect of the channel bed slope on the wave height. This simple correction is useful to be considered in preliminary designs of relatively long channels subject to unsteady flow conditions. 相似文献
94.
Pablo A. Corzo-Valladares Álvaro Fernández-Cuesta José M. Fernández-Martínez Leonardo Velasco 《Journal of the American Oil Chemists' Society》2013,90(11):1713-1718
Jatropha curcas L. has great potential for biofuel and phytosterol production. The objective of this research was to evaluate G × E variability for kernel phytosterol content and composition in Jatropha germplasm. Freshly matured seeds from 21 accessions grown in Málaga, Spain were collected at two stages of development. Significant genetic variation was detected for total kernel phytosterol content, which ranged from 2,246 to 2,883 mg kg?1; and stigmasterol concentration, which ranged from 7.6 to 11.5 % of the total phytosterols. An accession with 9.2 % Δ5‐avenasterol was also identified. The coefficient of variation for kernel phytosterol content and stigmasterol concentration was 6.2 and 14.0 % respectively between accessions and 7.2 and 10.2 % respectively within accessions. Accordingly, evaluation of plant to plant variation is advisable. The existence of variability for kernel phytosterol content and composition in Jatropha will enable breeding for enhanced levels of these compounds. 相似文献
95.
Leonardo I. Farfán-Cabrera Cesar D. Reséndiz-Calderón Cesar Sedano de la Rosa 《摩擦学汇刊》2018,61(4):640-647
This article aims to investigate the degradation of physical and tribological properties (friction coefficients and wear resistance) of a dynamic sealing material (silicone rubber [VMQ]) exposed to Jatropha oil (JO), engine mineral oil (EMO), and a blend (B20; 80% EMO–20% JO), separately. JO has demonstrated better lubricating properties than EMO in various mechanical applications; however, the degradation of elastomers by using this oil has not been studied yet, nor have its effect on their tribological properties. The physical degradation was evaluated by conducting static immersion tests (670 h at 25 °C) based on ASTM-D471 and ASTM-D7216 methods. Hence, the changes in mass, volume, tensile and tear strengths, and hardness of VMQ were measured. In addition, creep compliance tests were conducted to determine the changes in viscoelastic properties and the changes in morphology and topography were measured by scanning electron microscopy (SEM) and optical profilometry, respectively. In addition, the compositional changes were determined by Fourier transform infrared (FTIR) analyses to complement the degradation examination. Changes in the friction coefficients were determined by ball-on-disk tests and changes in wear resistance were obtained by accelerated wear tests (microabrasion tests). Finally, VMQ exhibited no significant physical and compositional degradation due to immersion in the three lubricants. However, considerable changes in the friction coefficients and wear resistance were observed; the change in the friction coefficients was minimal using JO. In addition, the coefficients using JO were 50% lower than those for EMO and the changes in wear resistance were lowest after immersion in JO. 相似文献
96.
97.
Jichun Ye Leonardo Ajdelsztajn Julie M. Schoenung 《Metallurgical and Materials Transactions A》2006,37(8):2569-2579
Dense, bulk nanocrystalline aluminum 5083 alloy was fabricatedvia a combined technique: cryomilling (mechanical milling at cryogenic temperature) to achieve the nanocrystalline Al 5083 powder
and spark plasma sintering (SPS) to consolidate the cryomilled powder. The results of X-ray diffraction analysis indicate
that the average grain size in the SPS consolidated material is 51 nm, one of the smallest grain sizes ever reported in bulk
Al alloys produced by powder metallurgy derived methods. In contrast, transmission electron microscopy (TEM) analysis revealed
a bimodal grain size distribution, with an average grain size of 47 nm in the fine-grained regions and approximately 300 nm
in the coarse-grained regions. Nanoindentation was used to evaluate the mechanical properties and the uniformity of the consolidated
nanocrystalline Al 5083. The hardness of the material is greatly improved over that of the conventional equivalent, due to
the fine grain size. The mechanisms for spark plasma sintering and the microstructural evolution are discussed on the basis
of the experimental findings. 相似文献
98.
F. Delfino R. Procopio A. Andreotti L. Verolino 《Electrical Engineering (Archiv fur Elektrotechnik)》2002,84(1):41-50
An inverse procedure is presented for identifying and reconstructing the waveform of the lightning return stroke current.
It is based only on the acquisition of the electromagnetic field radiated by the discharge channel in various locations on
the ground and at various frequencies, and requires no information about the channel base current. The fundamental idea is
shown to come from an electrostatic problem in which the linear charge density of a vertical thin wire is determined starting
from the measured field. Three versions of this procedure have been developed: in the first, the identification is carried
out by means of the measurement of the electric field at various distances from the lightning channel at a given frequency;
in the second, only two sensors for the electric field are necessary, but various sampling frequencies; in the third, only
one observation point is needed, for the measurement of both the electric and the magnetic field. A simulated validation of
all the approaches is provided as well as a detailed analysis of their numerical accuracy.
Received: 4 April 2001/Accepted: 30 April 2001 相似文献
99.
Estevez, L., Kehtarnavaz, N., and Wendt, R. III, Interactive Selective and Adaptive Clustering for Detection of Microcalcifications in Mammograms,Digital Signal Processing6(1996), 224–232.This paper presents a clustering algorithm, called interactive selective and adaptive clustering (Isaac), to assist radiologists in looking for small clusters of microcalcifications in mammograms. Isaac is developed to identify suspicious microcalcification regions which are missed by other classification techniques due to false positive samples in the feature space. It comprises two parts: (i) selective clustering and (ii) interactive adaptation. The first part reduces the number of false positives by identifying the microcalcification subspace or domains in the feature space. The second part allows the radiologist to improve results by interactively identifying additional false positive or true negative samples. Clinical evaluations of mammograms indicate the potential of using this algorithm as an effective tool to bring microcalcification areas to the attention of the radiologist during a routine reading session of mammograms. 相似文献
100.
n-Heptane, 2- and 3-methylhexane, ethylcyclopentane, and cycloheptane were passed in the presence of hydrogen at 500 °C over “nonacidic” platinum-alumina catalyst containing 3% by weight of platinum. The conversion ranged between 12 and 26%, depending on the interval of time the product was removed for analysis. In the case of cycloheptane, however, the conversion amounted to 98% during the first 30 min on stream and with time, during the approximate period between 2 and 3 h, it decreased to 69%. The products from the reaction contained besides toluene, also hydrocarbons resulting from a skeletal isomerization and dehydrocyclization of the original hydrocarbons, and to a smaller extent from a bond shift process, and a repetitive 1,5-ring closure followed by hydrogenolysis. Using 1,1-dimethylcyclohexane as a model compound, it was shown that the skeletal isomerization accompanying the aromatization of the seven-carbon hydrocarbons does not proceed through cationic intermediates. A survey of the literature relating to the mechanism of aromatization of hydrocarbon over “nonacidic” chromia-alumina and platinum-alumina catalysts is presented, and the differences between the two mechanisms are discussed. 相似文献