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排序方式: 共有1004条查询结果,搜索用时 15 毫秒
41.
42.
A gel filtration chromatographic method has been developed which is capable of fractionating amylose and amylopectin in starch. Three GFC columns (2 × 4000 A and 1 × 300A PL Separation Sciences, Polymer Laboratories Ltd,) are used in series using sodium chloride solution as eluent. Minimal sample preparation is involved which includes a preliminary wetting of powder starch with ethanol followed by dissolution with sodium hydroxide. Since the solvent system is aqueous, cooked starch samples are analysed by direct dissolution with sodium hydroxide. The method shows promise as a rapid technique in elucidating starch structure. 相似文献
43.
Simon Barquera Fabricio Campirano Anabelle Bonvecchio Lucia Hernández-Barrera Juan A Rivera Barry M Popkin 《Nutrition journal》2010,9(1):47
Background
Mexico has seen a very steep increase in child obesity level. Little is known about caloric beverage intake in this country as well as all other countries outside a few high income countries. This study examines overall patterns and trends in all caloric beverages from two nationally representative surveys from Mexico. 相似文献44.
Rebecca Braslau Frank Rivera Chittreeya Tansakul 《Reactive and Functional Polymers》2013,73(4):624-633
Monomers or N-alkoxyamine initiators containing protected thiol groups are utilized to prepare polymers via nitroxide-mediated radical polymerization. Following thiol deprotection, the macromolecular properties of these polymers are manipulated, by adjusting the redox conditions to either form or cleave disulfide bonds, or irreversibly cap free thiols by the rapid addition to a maleimide Michael acceptor. Formation of disulfide bonds under dilute conditions results in intramolecular disulfide formation, resulting in internal polymer collapse. Alternatively, disulfide formation under high concentration results in intermolecular crosslinking of polymers to form networked macromolecular assemblies. 相似文献
45.
A total of 260 samples from six food groups (grains and grain products, tree nuts, dried fruits, fresh produce, fruit juice, and dairy products) were tested for levels of fungal contamination using the SimPlate Yeast and Mould Color Indicator (YM-CI) and the FDA official (BAM) method. Results showed that the SimPlate, in most cases, gave higher yeast and mould (YM) counts than the FDA (reference) method. Statistical analysis of the data (paired t-test) revealed that there were significant differences (α = 0.05) between the two methods for several foods tested. The SimPlate was easy to use, saved time during sample preparation and inoculation and gave results faster than the reference method. Some difficulties were encountered when spreading moulds were present. 相似文献
46.
María D. Perez-Godoy Antonio J. Rivera Francisco J. Berlanga María José Del Jesus 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2010,14(9):953-971
This paper presents a new evolutionary cooperative–competitive algorithm for the design of Radial Basis Function Networks
(RBFNs) for classification problems. The algorithm, CO2RBFN, promotes a cooperative–competitive environment where each individual represents a radial basis function (RBF) and the
entire population is responsible for the final solution. The proposal considers, in order to measure the credit assignment
of an individual, three factors: contribution to the output of the complete RBFN, local error and overlapping. In addition,
to decide the operators’ application probability over an RBF, the algorithm uses a Fuzzy Rule Based System. It must be highlighted
that the evolutionary algorithm considers a distance measure which deals, without loss of information, with differences between
nominal features which are very usual in classification problems. The precision and complexity of the network obtained by
the algorithm are compared with those obtained by different soft computing methods through statistical tests. This study shows
that CO2RBFN obtains RBFNs with an appropriate balance between accuracy and simplicity, outperforming the other methods considered. 相似文献
47.
E.P. Rivero P. Granados F.F. Rivera M. Cruz I. González 《Chemical engineering science》2010,65(10):3042-3049
This work presents the numerical simulation of a laboratory reactor with rotating cylinder electrode (RCE) and a six-plate counter electrode that is used in studies on heavy metal recovery. The rate of electrode rotation and the potential applied are of such magnitude that the electrochemical reactor works in conditions of mass transport control under turbulent flow to obtain high recovery rates and formation of dendritic metal deposits. For hydrodynamics, the Reynolds averaged Navier–Stokes (RANS) equations were solved using the standard k–ε turbulence model, as well as wall functions based on the universal velocity distribution in the near-wall region. Results of 3-D simulations of the velocity field show clearly the formation of the turbulence Taylor vortex flow. For mass transfer, convection–diffusion equation was solved using the Kays–Crawford model for turbulent Schmidt number and Launder–Spalding wall functions adapted for mass transfer. Kinetics of copper recovery from aqueous solutions containing 0.019 M CuSO4 and 1 M H2SO4, in the range of rotation speed of 400–1100 rpm, was adequately fit (error <8%) during the electrolysis time to achieve a final recovery of 85% for potentiostatic and 60% for galvanostatic experiments. The fitting parameter of the concentration wall function used in all experiments was A=2.9. 相似文献
48.
Prediction of overall glucose yield in hydrolysis of pretreated sugarcane bagasse using a single artificial neural network: good insight for process development
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49.
Optimisation of rancidity stability in long‐chain PUFA concentrates obtained from a rainbow trout (Oncorhynchus mykiss) by‐product
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Mª Macarena Berríos Alicia Rodriguez Matías Rivera Mª Elsa Pando Mª Antonieta Valenzuela Santiago P. Aubourg 《International Journal of Food Science & Technology》2017,52(6):1463-1472
This research was focused on the production of polyunsaturated fatty acid concentrates from a farmed rainbow trout (Oncorhynchus mykiss) by‐product (i.e. belly muscle). The effect of different process variables (urea/fatty acids (FA) contents ratio, crystallisation time and temperature and stirring speed of the urea/FA mixture) on the lipid oxidation development during the urea complexation process was investigated. For this purpose, an experimental design (26 runs) following the response‐surface methodology was developed. As a result, peroxide value and TOTOX index showed to be dependent on the crystallisation time and temperature and the urea/FA ratio, while no influence of the crystallisation stirring speed was detected on both indices; additionally, polyene index was affected by the urea/FA ratio and its interaction with the crystallisation time. An optimised desirability score near 1.0 was attained provided values of 2.8 °C, 3.05 h and 3.57 were applied for crystallisation temperature, crystallisation time and urea/FA ratio, respectively. 相似文献
50.
A quadratic cost functional for reconstruction of a high-resolution wave front from a coarse wave front is presented. The functional uses as data the position and the direction of the coarse wave front that had previously been computed with a ray-tracing method. This functional uses an optical relationship between the ray information and the wave front's shape to reconstruct a high-density wave front. The performance of the proposed functional is illustrated by reconstruction of complicated wave fronts for which this functional has an accuracy that is superior to that of conventional interpolation methods. 相似文献