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31.
Desouza Arun H. G. Tanner Robert D. Effler W. T. 《Applied biochemistry and biotechnology》1991,(1):655-666
Studies were conducted to establish the effect of the variation of environmental factors on the separation occurring in protein
systems, resulting from bubble fractionation in a bioreactor. The measure of separation was selected to be the separation
ratio. This is defined to be the ratio of either the top or the middle position concentration in the vessel to the bottom
concentration of the vessel. Invertase and α-amylase were the two “model” enzymes considered. It was observed that, under
certain conditions, i.e., a combination of the nature of the sparging gas and the medium pH, varying degrees of protein separation
were achieved. The pH of the system dramatically influenced the separation. It was found that the best separation occurred
at a certain pH, assumed to be at or close to thepI of the protein in question. Furthermore, it was observed that systems sparged with CO2 exhibited greater separation than systems sparged with air. In fact, in the case of invertase, almost threefold separation
was observed at the top port when the solution was sparged with CO2. 相似文献
32.
Kariate Sudhakara Prasad A. B. Arun P. D. Rekha Chiu‐Chung Young Jen‐Lin Chang Jyh‐Myng Zen 《Electroanalysis》2009,21(14):1646-1650
Aerobically grown Shewanella sp. bacterial suspension drop‐coated on a disposable screen‐printed carbon electrode was found to possess electroactivity without the aid of redox mediator. Cyclic voltammetric studies revealed the characteristics of a mixed diffusion adsorption‐controlled electrochemical process for direct electron transfer at the bacteria‐modified electrode. Both FE‐SEM and ATR FT‐IR experiments were carried out to investigate the surface characteristics. The electroanalytical applicability was further demonstrated for electrocatalytic reduction of arsenite, hydrogen peroxide and nitrite. Low cost and very simple manufacturing procedure allow for the proposed bacterial sensor to be applied as disposable devices. 相似文献
33.
Effect of annealing on hydrophobic stability of plasma deposited fluoropolymer coatings 总被引:1,自引:0,他引:1
Arun Kumar Gnanappa Cian O'Murchu Frank Peters Syed A.M. Tofail 《Polymer Degradation and Stability》2008,93(12):2119-2126
Fluorinated amorphous carbon (a-C:F) films e.g. plasma polymerised perfluorocyclobutane have long attracted much consideration due to their low surface energy, hydrophobicity, low refractive index, good electrical and thermal insulation and good thermal stability. Although a-C:F films have many advantages, hydrophobic stability over time in air and water remains a major concern. In this study, the effects of weathering conditions on the hydrophobicity of fluorocarbon films prepared from perfluorocyclobutane precursors were examined using water contact angle measurements. It was found that the high initial hydrophobicity of as-deposited films degrades rapidly in humid conditions. The stability of hydrophobicity can be significantly improved when a suitable treatment such as annealing is employed. The mechanism of weathering was explained with the help of a number of morphological and chemical characterisation techniques such as Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS). In particular, XPS results demonstrated that a reduction in the overall amount of -CF3 radical, oxygenation of surface fluorides and the formation of an overlayer all influence the degradation of fluorocarbon in aquatic environment. 相似文献
34.
35.
An efficient stereoselective synthesis of C4-12 fragment of the cembranoids, sarcophytonolides E-G and L and C5-11 fragment of sarcophytonolide L is described. The C4-12 building block is efficiently assembled starting from chiral pool material (R)-carvone employing the Baeyer-Villiger oxidation, modified Knoevenagel condensation and asymmetric dihydroxylation as the key steps. The synthesis of C5-11 fragment is based on orthoester Johnson-Claisen rearrangement as the key step. 相似文献
36.
Base-modified fluorescent ribonucleoside-analogue probes are valuable tools in monitoring RNA structure and function because they closely resemble the structure of natural nucleobases. Especially, 2-aminopurine, a highly environment-sensitive adenosine analogue, is the most extensively utilized fluorescent nucleoside analogue. However, only a few isosteric pyrimidine ribonucleoside analogues that are suitable for probing the structure and recognition properties of RNA molecules are available. Herein, we describe the synthesis and photophysical characterization of a small series of base-modified pyrimidine ribonucleoside analogues derived from tagging indole, N-methylindole, and benzofuran onto the 5-position of uracil. One of the analogues, based on a 5-(benzofuran-2-yl)pyrimidine core, shows emission in the visible region with a reasonable quantum yield and, importantly, displays excellent solvatochromism. The corresponding triphosphate substrate is effectively incorporated into oligoribonucleotides by T7 RNA polymerase to produce fluorescent oligoribonucleotide constructs. Steady-state and time-resolved spectroscopic studies with fluorescent oligoribonucleotide constructs demonstrate that the fluorescent ribonucleoside photophysically responds to subtle changes in its environment brought about by the interaction of the chromophore with neighboring bases. In particular, the emissive ribonucleoside, if incorporated into an oligoribonucleotide, positively reports the presence of a DNA abasic site with an appreciable enhancement in fluorescence intensity. The straightforward synthesis, amicability to enzymatic incorporation, and sensitivity to changes in the microenvironment highlight the potential of the benzofuran-conjugated pyrimidine ribonucleoside as an efficient fluorescent probe to investigate nucleic acid structure, dynamics, and recognition events. 相似文献
37.
A preliminary assessment of microstructural and compositional characteristics of two variants of precarbonated and postcarbonated concrete mixes 下载免费PDF全文
The hydration, precarbonation, and postcarbonation microstructural and compositional attributes of 2 variants of concrete were studied using scanning electron microscope, energy dispersive spectroscopy, and X‐ray diffraction techniques. Results obtained showed presence of large number of diffraction peaks indicative of SiO2 as major phase. Higher pH, alkalinity, and absence of effects of carbonation were suggested from the presence of portlandite peaks. Evidence of effect of carbonation was studied through the analysis of the experimental diffraction peaks obtained postexposure to accelerated carbonation in a controlled environment. Presence of all the 3 polymorphs of calcium carbonate (CaCO3) such as aragonite, vaterite, and calcite depending upon the moisture content and the material constituting the concrete sample were envisaged signifying carbonation. Precipitation of these CaCO3 crystals was responsible for depletion of CH as well as calcium–silicate–hydrate, ettringite with the progress of carbonation as suggested by their absence in the X‐ray diffraction diffractograms of the carbonated samples. The crystal structure of the newly formed minerals in both the variants of concrete sample was highly controlled by the stages of carbonation, with development of amorphous CaCO3 (amalgamated with that of calcium hydrates) in early stages of carbonation as well as fully developed rhombohedral CaCO3 crystals in later stages. 相似文献
38.
Hard sphere diameters of liquid alkali metal alloys (Na-Cs and K-Rb) are calculated at 373 K ensuring the minimum Helmholtz
free energy of the system. These diameters are then used to fix the packing density of the alloy. On alloying, the hard sphere
diameters of Na in Na-Cs and K in K-Rb alloys expand whereas those of Cs and Rb contract. 相似文献
39.
Tathe Shraddha V. Deshmukh Prashant R. Kashid Arun M. Gaikwad Shubhangee 《平面色谱法杂志一现代薄层色谱法》2019,32(6):495-500
JPC – Journal of Planar Chromatography – Modern TLC - This paper includes the development of a novel, systematic, quality by design (QbD)-based high-performance thin-layer... 相似文献
40.
Experiments were carried out to observe the effect of a magnetic field and grid biasing voltage in presence of a plasma bubble in a magnetized, filamentary discharge plasma system. A spherical mesh grid of 80% optical transparency was negatively biased and introduced into the plasma for creating a plasma bubble. Diagnostics via an electrical Langmuir probe and a hot emissive probe were extensively used for scanning the plasma bubble. Plasma floating potential fluctuations were measured at three different positions of the plasma bubble. The instability in the pattern showed the dynamic transition from periodic to chaotic for increasing magnetic fields. Time scale analysis using continuous wavelet transform was carried out to identify the presence of non‐linearity from the contour plots. The mechanisms of the low‐frequency instabilities along with the transition to chaos could be qualitatively explained. Non‐linear techniques such as fast Fourier transform, phase space plot, and recurrence plot were used to explore the dynamics of the system appearing during plasma fluctuations. In order to demonstrate the observed chaotic phenomena in this study, characteristics of chaos such as the Lyapunov exponent were obtained from experimental time series data. The experimentally observed potential structure is confirmed with numerical analysis based on fluid hydrodynamics. 相似文献