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71.
The performance of La2−xCexCu1−yZnyO4 perovskites as catalysts for the high temperature water-gas shift reaction (HT-WGSR) was investigated. The catalysts were characterized by EDS, XRD, BET surface area, TPR, and XANES. The results showed that all the perovskites exhibited the La2CuO4 orthorhombic structure, so the Pechini method is suitable for the preparation of pure perovskite. However, the La1.90Ce0.10CuO4 perovskite alone, when calcined at 350/700 °C, also showed a (La0.935Ce0.065)2CuO4 perovskite with tetragonal structure, which produced a surface area higher than the other perovskites. The perovskites that exhibited the best catalytic performance were those calcined at 350/700 °C and, among these, La1.90Ce0.10CuO4 was outstanding, probably because of the high surface area associated with the presence of the (La0.935Ce0.065)2CuO4 perovskite with tetragonal structure and orthorhombic La2CuO4 phase. 相似文献
72.
The classical weighted minsum scheduling and due-date assignment problem (with earliness, tardiness and due-date costs) was shown to be polynomially solvable on a single machine, more than two decades ago. Later, it was shown to have a polynomial time solution in the case of identical processing time jobs and parallel identical machines. We extend the latter setting to parallel uniform machines. We show that the two-machine case is solved in constant time. Furthermore, the problem remains polynomially solvable for a given (fixed) number of machines. 相似文献
73.
The excitation of large amplitude nonlinear waves is achieved via parametric autoresonance of Faraday waves. We experimentally demonstrate that phase locking to low amplitude driving can generate persistent high-amplitude growth of nonlinear waves in a dissipative system. The experiments presented are in excellent agreement with theory. 相似文献
74.
A. M. Glezer M. A. Libman I. A. Timshin I. V. Shchetinin E. S. Savchenko A. A. Tomchuk 《JETP Letters》2018,108(1):54-58
The effect of large plastic deformations at room temperature in a Bridgman anvil cell on the specific saturation magnetization of the DO3-type ordered (Fe–24 at % Al) alloy has been revealed. It has been found that torsion at high pressure and certain deformation parameters results in the complete suppression of long-range order in the alloy and in the corresponding increase in the specific saturation magnetization by 11% with respect to the equilibrium state. A theoretical model qualitatively describing the revealed phenomenon has been proposed. 相似文献
75.
Lahini Y Avidan A Pozzi F Sorel M Morandotti R Christodoulides DN Silberberg Y 《Physical review letters》2008,100(1):013906
We experimentally investigate the evolution of linear and nonlinear waves in a realization of the Anderson model using disordered one-dimensional waveguide lattices. Two types of localized eigenmodes, flat-phased and staggered, are directly measured. Nonlinear perturbations enhance localization in one type and induce delocalization in the other. In a complementary approach, we study the evolution on short time scales of delta-like wave packets in the presence of disorder. A transition from ballistic wave packet expansion to exponential (Anderson) localization is observed. We also find an intermediate regime in which the ballistic and localized components coexist while diffusive dynamics is absent. Evidence is found for a faster transition into localization under nonlinear conditions. 相似文献
76.
We study theoretically the dynamics of a beam launched inside an amplifying trap potential. Raising the amplification transforms the dynamics from linear tunneling at low amplification to periodic ejection of a sequence of identical solitons (when the amplification rate exceeds the tunneling rate) and, at strong amplification, to nonperiodic multisoliton ejection. 相似文献
77.
A. Assaf C. B. Y. Cordella G. Thouand 《Analytical and bioanalytical chemistry》2014,406(20):4899-4910
Food safety is a major concern for suppliers in the food chain to ensure the safety of their products. The identification procedure requested by norms is tedious, and it often requires systematic controls and qualified staff to perform the necessary analyses. Raman spectroscopy offers new opportunities to rapidly and efficiently ascertain the presence of pathogens in samples. Nevertheless, this technique requires a standardized procedure to be applied in the industrial context. Our study shows that the variability between spectral fingerprints is related to the physiological state of the microbial species and the growth phase of the bacteria plays a crucial role in its identification by Raman spectroscopy. To improve the discrimination between closely related bacterial species, a procedure based on the selection of bacterial spectra in the exponential growth phase was proposed. Different ways to introduce Raman spectroscopy in the ISO 6579:2002 standards are also proposed from the entire process to a shorter protocol. In the latter case, the identification of bacterial colonies after the selective enrichment step was proposed with the advantages of this path in terms of simplicity and rapidity (analysis time is reduced up to 50 h from the 100 h required by the standard). The protocol validated using six food categories from industrial partners have presented a good correlation by confirmation with other laboratory classical methods. In the future, this procedure could be introduced to the control system of the food production chain with a reliable database for various microorganisms encountered in this field. 相似文献
78.
Summary The concentration effect in size-exclusion chromatographic analysis of hyaluronans of various relative molecular masses (RMM) has been studied. A critical concentration has been found that is negatively dependent on the hyaluronan molecular mass; the higher the biopolymer molecular mass, the smaller the injected sample where the concentration effect should be taken into account for accurate evaluation of molecular mass distribution. At higher temperatures, however, the concentration effect diminishes significantly. 相似文献
79.
M. S. Al-Masri H. Mukallati A. Al-Hamwi H. Khalili M. Hassan H. Assaf Y. Amin A. Nashawati 《Journal of Radioanalytical and Nuclear Chemistry》2004,260(2):405-412
More than one hundred different food stuffs (meat, vegetables cereals, seafood,..) have been collected during 1998, 1999 and
2000 and analyzed for radioactivity as part of the National Food Monitoring Program in Syria. Results have shown that most
of the observed concentrations were within the range of the worldwide values with the exception of relatively high levels
of 210Po being observed in fish, vegetables, mushrooms, herbs and flowers. The daily intakes of the radionuclides studied have been
evaluated. Relatively high values, in comparison with some countries, were found for 210Po (1.9 Bq/day). This is due to high content of 210Po in wheat (2.3 Bq/kg) consumed by Syrians, the daily consumption of wheat by Syrians is about 526 g. In addition, natural
and artificial radionuclides in some manufactured food of Syrian infant and their intake rates have been determined. Seventeen
manufactured food and eleven types of canned milk were collected from the local market and their radioactivity analyzed. 210Po activity concentration varied between 0.38 and 2.89 Bq/kg dry wt. in canned milk while the highest concentration in infant
food was found to be 1.69 Bq/kg dry wt. Other radionuclide concentrations were below the limit of detection of 3 Bq/kg dry
wt. and 4 Bq/kg dry wt. for 226Ra and 228Ra, respectively, while uranium concentration varied between 2.2 and 10.5 μg/kg dry wt. in milk samples and 0.78-6.0 μg/kg
dry wt. in other food samples.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
80.
Amphipathic alpha-helical peptides are often ascribed an ability to induce curvature stress in lipid membranes. This may lead directly to a bending deformation of the host membrane, or it may promote the formation of defects that involve highly curved lipid layers present in membrane pores, fusion intermediates, and solubilized peptide-micelle complexes. The driving force is the same in all cases: peptides induce a spontaneous curvature in the host lipid layer, the sign of which depends sensitively on the peptide's structural properties. We provide a quantitative account for this observation on the basis of a molecular-level method. To this end, we consider a lipid membrane with peptides interfacially adsorbed onto one leaflet at high peptide-to-lipid ratio. The peptides are modeled generically as rigid cylinders that interact with the host membrane through a perturbation of the conformational properties of the lipid chains. Through the use of a molecular-level chain packing theory, we calculate the elastic properties, that is, the spontaneous curvature and bending stiffness, of the peptide-decorated lipid membrane as a function of the peptide's insertion depth. We find a positive spontaneous curvature (preferred bending of the membrane away from the peptide) for small penetration depths of the peptide. At a penetration depth roughly equal to half-insertion into the hydrocarbon core, the spontaneous curvature changes sign, implying negative spontaneous curvature (preferred bending of the membrane toward the peptide) for large penetration depths. Despite thinning of the membrane upon peptide insertion, we find an increase in the bending stiffness. We discuss these findings in terms of how the peptide induces elastic stress. 相似文献