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91.
Survival rate analysis of freeze-dried lactic acid bacteria using the arrhenius and z-value models 总被引:1,自引:0,他引:1
The survival rate of five freeze-dried bacteria species, Lactobacillus plantarum, Lactobacillus pentosus, Weisella paramesenteroides, Leuconostoc mesenteroides, and Lactobacillus fermentum, was described in terms of reaction rate constants (D or k) and temperature sensitivity of rate constants (z or Ea). The freeze-dried strains were stored under vacuum at 55, 37, and 4 degrees C for 168 h, 17 days, and 2 months, respectively. D-values decreased and k increased with an increase of the storage temperature. Neither the z-value nor the inactivation energy (Ea) of the reaction was significantly different (P > 0.05) for all the strains, suggesting that thermal inactivation of the freeze-dried lactic acid bacteria may occur by the same mechanism. Therefore, it was possible to compare rate constants of survival for the freeze-dried strains studied. 相似文献
92.
Sheela Berchmans Paulraj Arunkumar Shrikanth Lalitha Venkatraman Yegnaraman Santanu Bera 《Applied catalysis. B, Environmental》2009,88(3-4):557-563
In this work we demonstrate the preparation of highly catalytically active Pt formed by the galvanic replacement of the copper adlayer on Au substrates, modified by the self-assembly of fourth generation amine terminated PAMAM dendrimer (G4NH2). The copper adlayer was formed on the dendrimer-modified gold substrate by chemical preconcentration of copper ions followed by electrochemical reduction. The Pt overlayer was characterized by SEM, XPS and by cyclic voltammetry. The catalytic efficiency of the modified film thus prepared through soft route was evaluated by the electro catalytic oxidation of methanol using cyclic voltammetry, chronoamperometry and AC impedance techniques. This work also demonstrates that the copper adlayer formed on the dendrimer-modified electrode can undergo galvanic replacement by nobler metals like Au and Ag, besides Pt. An elegant soft route involving a new three-step protocol to build the concentration of active Pt on the Au surface has been developed. Concentration of the same metal (Pt) or two different metals (Pt–Au) can be built at the interface in a stepwise manner at ambient temperature. 相似文献
93.
Polycrystalline sample of Pb(Li1/4Eu1/4Mo1/2)O3 was prepared by usual ceramic route. X-ray diffraction, SEM and EDAX were used to check the formation, homogeneity and elements
present in the compound. The measurement of dielectric constant (ɛ), dielectric loss (tanδ), hysteresis loop parameters (e.g. spontaneous polarization) as function of frequency and temperature suggest that the compound
is a ferroelectric one and has a ferro-paraelectric phase transition at 112 ± 2°C. The measurement of dc resistivity both
as function of biasing electric field and temperature of the compound suggests that the compound has negative temperature
coefficient (NTC) of resistance above 100°C. 相似文献
94.
Experiments were performed at X band with GaAs f.e.t.s used as mixer elements. These studies show that an f.e.t. mixer may exhibit a conversion gain approaching that of the corresponding amplifier. Conversion gains as high as 6 dB were measured. Low noise and high signal-handling capabilities were also demonstrated. 相似文献
95.
96.
Formation of zinc ferrite by solid-state reaction and its characterization by XRD and XPS 总被引:3,自引:0,他引:3
S. Bera A. A. M. Prince S. Velmurugan P. S. Raghavan R. Gopalan G. Panneerselvam S. V. Narasimhan 《Journal of Materials Science》2001,36(22):5379-5384
A dry mixture of ZnO and -Fe2O3was annealed at 1200°C; the progress of the formation of the ferrite was monitored by XRD and XPS analyses at different time intervals. The presence of octahedral zinc cation was observed along with the regular tetrahedral Zn in the sample that had undergone 30 minute heat treatment. After three hours of heating, pure normal zinc ferrite was formed. The Zn 2p3/2peak binding energy, intensity and line shape were analyzed extensively to show the diffusion of ZnO and the growth of ferrite at different stages of heat treatment. Analysis of the Fe 2p3/2line-shape supported the substitution of Fe2+by zinc cations during ferrite formation. The binding energy values of the Zn 2p levels for stoichiometric and non-stoichiometric ferrites were also determined and surface segregation of the zinc was observed by XPS in the non-stoichiometric ferrites. 相似文献
97.
Bera L.K. Loh W.Y. Guo L.H. Zhang X.W. Lo G.Q. Balasubramanian N. Kwong D.-L. 《Electron Device Letters, IEEE》2006,27(1):58-61
For the first time, this letter presents a novel post-backend strain applying technique and the study of its impact on MOSFET device performance. By bonding the Si wafer after transistor fabrication onto a plastic substrate (a conventional packaging material FR-4), a biaxial-tensile strain (/spl sim/0.026%) was achieved globally and uniformly across the wafer due to the shrinkage of the bonded adhesive. A drain-current improvement (average /spl Delta/I/sub d//I/sub d//spl sim/10%) for n-MOSFETs uniformly across the 8-in wafer is observed, independent of the gate dimensions (L/sub g//spl sim/55 nm -0.530 /spl mu/m/W /spl sim/2-20 /spl mu/m). The p-MOSFETs also exhibited I/sub d/-improvement by /spl sim/7% under the same biaxial-tensile strain. The strain impact on overall device characteristics was also studied, including increased gate-induced drain leakage and short-channel effects. 相似文献
98.
Abhinandan Rana Madhusudan Bera Durga Sankar Chowdhuri Debdoot Hazari Raymond J. Butcher Sudipta Dalai 《Journal of Inorganic and Organometallic Polymers and Materials》2011,21(4):747-753
Abstract
A coordination polymer of formula [Pb0.5(pyc)] n , 1, where Hpyc = pyridine-3-carboxylic acid, has been synthesized and structurally characterized by X-ray single crystal diffraction analysis. Every Pb(II) centre demonstrate trigonal dodecahedron geometry. The ligand i.e. pyridine-3-carboxylate offers μ 3 - η 2 : η 1 coordination pattern using its hetero donor centres. The complex initially forms an infinite 1D chain (c-axis) which is turned to 2D sheet and finally a 3D network is recognized through ligand connectivity. Stabilization of 3D structure is further reinforced by π–π stacking interaction. An open channel is identified along c-axis. TG analysis has been performed for the complex. Emission study demonstrates the existence of intraligand and metal-to-ligand charge transfer transition in 1. 相似文献99.
S.K. Ghosh T. Bera O. Karacasu A. Swarnakar J.G. Buijnsters J.P. Celis 《Electrochimica acta》2011,56(5):2433
The in situ electrochemical deposition of nanostructured MoSx (x = 1.5–1.7) based thin films on various substrates from aqueous solutions is reported. The as-deposited amorphous films transform on annealing into crystalline ones as revealed by a stepwise high temperature X-ray diffraction (XRD). Both Raman spectroscopy and XRD crystal structure analyses confirmed the formation of inorganic fullerene-MoSx nanoparticles (IF-MoSx). The as-deposited thin films have a featureless surface morphology, but after annealing either a nanotube or a nanorod structure along with numerous smaller nanoballs appear at the surface. An investigation by transmission electron microscopy unearths the presence of nanoballs, nanoribbons, and nanotubes throughout the annealed MoSx thin films. The size of the nanoballs is in the range of 5–10 nm. The nanotubes have a diameter of 10–400 nm, and a length of up to several micrometers as evidenced by SEM. The catalytic effect of transition metals on the growth of nanotubes is noticed. The temperature-induced transformation from amorphous to crystalline structured MoSx films results in a large lowering of the coefficient of friction under sliding against corundum in ambient air of 50% relative humidity. 相似文献
100.
Chengqian Zhang Lan Wu Anjin Tao Hriday Bera Xing Tang Dongmei Cun Mingshi Yang 《材料科学技术学报》2021,63(4):133-144
The present study aimed to formulate triptorelin acetate(TA)into poly(D,L-lactic-co-glycolic)acid(PLGA)based injectable sustained-release microspheres(TA-PLGA-MS)by usingdouble emulsion solvent extraction/evaporation(DESE)technique and investigate the effects of various material attributes and process parameters on the quality attributes such as size,shape,surface morphology,encapsulation efficiency(EE)and in vitro release behavior of these microspheres.Variable compositions of the outer water phase,type of the organic solvents,volume ratios of inner water phase to oil phase,PLGA concentrations,and the powers for emulsification in the preparation of the microspheres showed an influence on their quality attributes.An optimal formulation(F-2)obtained from this univariate approach possess an excellent EE value of 63.5%±3.4%and an average volumetric particle size of 35.3±1.8μm.This formulation was further accomplished with different solidification rates assisted by variable incubation temperatures,which exhibited an impact on the shape/surface and inner morphology of the microspheres.The resultant microspheres also displayed different in vitro release patterns.The matrices processed with a high incubation temperature conferred the fastest and the most complete drug release profile over the period of 63 days.Thus,the solidification rate could be identified as one of the critical process parameters that affected the quality of the PLGA based injectable microspheres specifically designed for the prolonged delivery of TA. 相似文献