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71.
The present study investigates the utility of composite beads of nano-particles of iron oxide and chitosan for removing Ni (II) ions from aqueous solution by batch and column adsorption techniques. In the batch mode experiment, the influence of pH, concentration, adsorbent dose, temperature, column mode, bed height, flow rate and initial concentration were studied on the adsorption profiles of nickel ions. The maximum uptake of Ni (II) ions was obtained at pH 4.0 in 30 min at room temperature. 相似文献
72.
An unprecedented conversion of thioalkyl/aryl glycoside to the corresponding 1‐O‐acetates has been described using acetic anhydride and HClO4‐SiO2 at rt. Although this transformation does not play an important role in the oligosaccharide synthesis in comparison to its reverse transformation, this gives useful information in selecting the reaction condition for the synthesis of oligosaccharides. The yields were excellent in all cases. 相似文献
73.
Manoj Kumar Santosh Kumar Tiwari Sheela Srivastava 《Applied biochemistry and biotechnology》2010,160(1):40-49
Enterocin LR/6, a bacteriocin obtained from the culture filtrate of Enterococcus faecium strain LR/6, has been purified to homogeneity using ammonium sulfate precipitation, cation-exchange chromatography, gel-filtration,
and checked on reverse-phase high-performance liquid chromatography. It is active at high temperatures (boiling as well as
autoclaving) and over a wide range of pH (2.0–8.0). Also, it is sensitive to a number of proteolytic enzymes but is stable
in the presence of surfactants and organic solvents. The protein could be stored at least up to 1 year at low temperatures
(4 °C and −20 °C) without any loss of activity. The N-terminal sequence of enterocin LR/6 showed no homology with known enterocins
or other bacteriocins present in the database, suggesting it to be a novel enterocin. Matrix-assisted laser desorption/ionization-time-of-flight
mass spectrometry and tricine sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed its mass to be ∼6.1 kDa.
It showed a bactericidal mode of action against indicator strain, Micrococcus luteus. 相似文献
74.
The purpose of a cruise control system is to accurately maintain the driver’s desired set speed, without intervention from the driver, by actuating the throttle-accelerator pedal linkage. Over the past five years, owners of a particular cruise control have complained that it did not operate properly. Complaints ranged from not engaging upon command, to the cruise unexpectedly accelerating past the desired speed. A common thread among all the complaints was the intermittent nature of the problems. More than 96% of the reported failed modules removed from vehicles and returned to the company, passed bench tests.This paper presents a physics-of-failure process to identify, induce and analyze failure mechanisms causing intermittent failures, high warranty returns and cannot duplicate (CND) problems of the digital electronic cruise control module (CCM). In addition, we explain why the manufacturer’s tests were not representative of the actual automotive environments, nor were they conducted in a manner to access actual failures. We conclude with a recommendation for a physics-of-failure approach for future product development. 相似文献
75.
76.
Incident primary beam divergence is a source of systematic error in X-ray standing wave (XSW) characterization of single and multilayer thin films. Primary beam divergence significantly alters the XSW profile of a layered material and can lead to large errors when used with higher excitation energies. The present study suggests that when one uses Mo-Kalpha excitation, the primary beam divergence should be in range of 0.005(0). On the other hand, in the case of Cu-Kalpha excitation, primary beam divergence can be relaxed up to 0.01(0). 相似文献
77.
The influence of analyte mass concentration on determination of detection limits in X-ray fluorescence spectrometry has been investigated experimentally. Both the total reflection X-ray fluorescence (TXRF) and the conventional energy-dispersive X-ray fluorescence techniques have been used to derive the dependence of analyte mass concentration on the values of detection limits. Results obtained indicate that values of detection limits are optimum, or in other words, they are closer to the true detection limit of the technique, when analyte concentrations are in the range of 10 times of the detection limit. 相似文献
78.
A class of tests for the increasing failure rate average (IFRA) alternatives under random censoring is proposed. The tests are based on a function of the Kaplan-Meier estimator. Most of the IFRA tests in the literature depend on the (nuisance) parameter that appears in the definition of IFRA, and the choice of this parameter is crucial in performing the tests. The proposed class of tests does not have this disadvantage. Under some regularity conditions, the asymptotic normality of the tests is established and asymptotically distribution-free tests are obtained by using estimators for the null standard deviations. The efficacies of the tests under the proportional hazard censoring model are studied. The proposed test is most efficient for the Weibull family of IFRA alternatives among the existing tests available for the censored data. The test is applied to published appliance data 相似文献
79.
Origin of room-temperature ferromagnetism in cobalt-doped ZnO 总被引:1,自引:0,他引:1
Thin films of ZnO doped with cobalt have been grown by the pulsed laser deposition (PLD) technique in different temperatures
ranging from 500°C to 650°C. The films grown on sapphire c-plane single crystal were found to be highly epitaxial. Magnetic
properties of these films were studied, and the films exhibited ferromagnetic characteristics at room temperature. Detailed
structural and microstructural characterization was performed to correlate the fate of the magnetic impurities, i.e., cobalt,
and the cause of magnetic properties. It is established from this work that the magnetic properties of these films are inherent
to the system, and any presence of second phase/nanoclusters/precipitates are ruled out as the cause of magnetic properties.
The techniques used to establish these were conventional and high-resolution transmission electron microscopy (HRTEM) along
with electron-energy loss spectroscopy (EELS) and scanning transmission electron microscopy-atomic number (STEM-Z) contrast
studies. 相似文献
80.
A. K. Rastogi S. Mishra M. Nigam A. K. Tiwari 《International Journal of Infrared and Millimeter Waves》1994,15(10):1709-1720
Dispersion characteristics and wave impedance of trapped coupled image guides are computed by using mode matching techniques. Dispersion curves for trapped coupled image guide are plotted for various dielectric materials and dimensional parameters. The hybrid directional couplers in the above configuration have been theoretically designed by computing the normalization propagation constant. 相似文献