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31.
Neela Badrie Frances Bekele Elzbieta Sikora Marek Sikora 《Critical reviews in food science and nutrition》2015,55(5):620-659
The history of cocoa and chocolate including the birth and the expansion of the chocolate industry was described. Recent developments in the industry and cocoa economy were briefly depicted. An overview of the classification of cacao as well as studies on phenotypic and genetic diversity was presented. Cocoa agronomic practices including traditional and modern propagation techniques were reviewed. Nutrition-related health benefits derived from cocoa consumption were listed and widely reviewed. The specific action of cocoa antioxidants was compared to those of teas and wines. Effects of adding milk to chocolate and chocolate drinks versus bioavailability of cocoa polyphenols were discussed. Finally, flavor, sensory, microbiological, and toxicological aspects of cocoa consumption were presented. 相似文献
32.
Anil Kumar B. Ravikumar I. Chattoraj S. Mukherjee A. Basumallick 《Metallurgical and Materials Transactions B》2004,35(6):1123-1128
Plasma source ion implantation of nitrogen on a high-strength steel substrate carried out at relatively low temperatures produced
no discernible nitrides. The hardness increase caused by these treatments was discernible. There was indirect evidence of
nitrogen in solid solution. The plasma treatments produced changes in the hydrogen permeation through the substrate as a result
of alteration in the subsurface hydrogen solubility as well as the hydrogen diffusivity. The alteration in hydrogen permeation
behavior depended on the time and temperature of plasma treatment. 相似文献
33.
The electrochemical response of melt‐spun Al‐Ni‐La alloys with partial substitution of Ni after different stages of devitrification was studied. The base alloy was found to have the best corrosion resistance. It was observed that primary crystallization caused minimal deterioration in the corrosion resistance of the base alloy as compared to its amorphous state. The substitute alloys had different corrosion resistance dependent on the substituting element with the Ag containing alloy having the least resistance. This could be attributed to the operation of local galvanic cells, enhanced by chemical heterogeneities in the alloys. Secondary crystallization caused a reduction in the corrosion resistance of all the alloys due to the creation of intermetallic phases that increased the galvanic activity. 相似文献
34.
RepA, the initiator protein of plasmid P1, binds to multiple sites (iterons) in the origin. The binding normally requires participation of chaperones, DnaJ, DnaK and GrpE. When purified, RepA appears dimeric and is inactive in iteron binding. On reaction with chaperones, a species active in iteron binding is formed and found to be monomeric. To test whether the chaperones can reduce dimerization, RepA was used to replace the dimerization domain of the lambda repressor. The hybrid protein repressed the lambda operator efficiently, indicating that RepA can dimerize in vivo. A further increase in repressor activity was seen in dnaJ mutant cells. These results are consistent with a chaperone-mediated reduction of RepA dimerization. We also found that RepA mutants defective in dimerization still depend on DnaJ for iteron binding. Conversely, RepA mutants that no longer require chaperones for iteron binding remain dimerization proficient. These results indicate that the chaperone dependence of RepA activity is not solely owing to RepA dimerization. Our results are most simply explained by a chaperone-mediated conformational change in RepA protomer that activates iteron binding. This conformational change also results in reduced RepA dimerization. 相似文献
35.
The effects of cold working on sensitization and intergranular corrosion behavior of AISI 304 stainless steel 总被引:1,自引:0,他引:1
Raghuvir Singh I. Chattoraj A. Kumar B. Ravikumar P. K. Dey 《Metallurgical and Materials Transactions A》2003,34(11):2441-2447
The effects of prior cold rolling of up to an 80 pct reduction in thickness on the sensitization-desensitization behavior
of Type AISI 304 stainless steel and its susceptibility to intergranular corrosion have been studied by electrochemical potentiokinetic
reactivation (EPR) and Strauss-test methods. The results indicate that the prior deformation accelerated the sensitization
as compared to the undeformed stainless steel. The deformed Type 304 stainless steel experienced desensitization at higher
temperatures and times, and it was found to be enhanced by increased cold deformation. This could be attributed to the increased
long-range chromium diffusion, possibly brought on by increasing pipe diffusion and vacancies. The role of the deformation-induced
martensite (DIM) and texture, introduced by uniaxial cold rolling, on the sensitization-desensitization kinetics has also
been discussed. This study could not reveal any systematic relationship between texture and the degree of sensitization (DOS)
obtained. The effect of DIM on DOS seems to be pronounced at 500 °C when the steel retained significant amounts of DIM; however,
the retained DIM is insignificant at higher sensitization times and temperatures. 相似文献
36.
Raghuvir Singh S. Ghosh Chowdhury Gautam Das P. K. Singh I. Chattoraj 《Metallurgical and Materials Transactions A》2012,43(3):986-1003
This study investigates the sensitization behavior of AISI 304LN deformed previously by cold rolling (CR) to 5 pct to 25 pct
reduction in thickness and aged at 673 K to 873 K (400 °C to 600 °C). The emphasis was on revealing the degree of sensitization
(DOS) resulting from low-temperature sensitization (LTS) on the orthogonal surfaces and correlation thereof with the changes
in various metallurgical properties caused by cold rolling. It was found that the DOS differs among the orthogonal surfaces
such as the rolling surface (RS), transverse surface (TS), and cross transverse surface (CTS). RS showed lower DOS compared
with CTS and TS. The differences in the DOS were attributed to the combined effect of deformation-induced martensite (DIM),
grain size, and slip band formation. A deformation of 5 pct was critical to the susceptibility of AISI 304LN to intergranular
(IGC) and transgranular corrosion (TGC). The sensitization kinetics was slow or saturated leading to desensitization beyond
5pct deformations at 773 K (500 °C) and 873 K (600 °C). It was, however, uniformly accelerated over 5 to 25 pct deformation
when aged at 673 K (400 °C). 相似文献
37.
Precise Manipulation and Patterning of Protein Crystals for Macromolecular Crystallography Using Surface Acoustic Waves 下载免费PDF全文
Feng Guo Weijie Zhou Peng Li Zhangming Mao Neela H. Yennawar Jarrod B. French Tony Jun Huang 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(23):2733-2737
Advances in modern X‐ray sources and detector technology have made it possible for crystallographers to collect usable data on crystals of only a few micrometers or less in size. Despite these developments, sample handling techniques have significantly lagged behind and often prevent the full realization of current beamline capabilities. In order to address this shortcoming, a surface acoustic wave‐based method for manipulating and patterning crystals is developed. This method, which does not damage the fragile protein crystals, can precisely manipulate and pattern micrometer and submicrometer‐sized crystals for data collection and screening. The technique is robust, inexpensive, and easy to implement. This method not only promises to significantly increase efficiency and throughput of both conventional and serial crystallography experiments, but will also make it possible to collect data on samples that were previously intractable. 相似文献
38.
Seema Kumari I. Chattoraj S. K. Pal A. Mitra 《Materials and Manufacturing Processes》2006,21(7):683-686
Giant magneto-impedance (GMI) behavior have been studied in melt spun Co71-XFeXCr7Si8B14 (X = 0, 2, 3.2, 4, 6, 8, and 12 at%) alloys. The addition of Fe in the system changed the saturation magnetostriction constant from negative to positive values. The GMI property was measured with a driving current of 5 mA and 4 MHz frequency using a spectrum analyzer. The GMI ratio increased with the increase of the applied dc field and became maximum at a field Hk known as the anisotropy field of the materials. The maximum of GMI ratio (GMImax) depended on the Fe content and was maximum (12%) for Fe = 4 at% for the alloys in the as-melt spun state. Substantial increase of GMImax to 66% for Fe = 4 at% was observed after annealing the sample at 673 K. 相似文献
39.
FeNbCuSiB based materials were produced in the form of ribbons by rapid solidification techniques. The crystallization, magnetic,
mechanical and corrosion behaviour were studied for the prepared materials as a function of quenching rate from liquid to
the solid state. Higher quench rates produced a more amorphous structure exhibiting superior soft magnetic properties with
improved corrosion resistance. 相似文献
40.
I. Chattoraj S. K. Das S. Jana S. P. Chakraborty A. K. Bhattamishra 《Journal of Materials Science》1995,30(20):5313-5320
Discontinuous precipitation in a 21Cr-10Mn-5Ni steel was found to result in breakdown of passivity when tested in a 0.5 m H2SO4 + 0.01 m KSCN solution. The electrochemical response was similar to that due to sensitization of conventional stainless steels. The ageing time and temperature affected the resistance of the passive film, with lower ageing temperatures being more severe in terms of passivity breakdown. The effect of interlamellar spacing on the chromium depletion, the effect of volume diffusion on the healing of the matrix, and the solubility product reaction for precipitation, were considered to explain the observed different strengths of passive films formed on specimens aged at different temperatures and times. The observance of good corrosion protection in spite of the presence of profuse precipitates was in contrast to the effect of grain-boundary carbide proliferation on the corrosion resistance of conventional stainless steels. 相似文献