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751.
Analytical investigation of the lightwave propagation through dielectric elliptical fibers with conducting helical windings on the core-clad boundary is presented under the consideration of slow-wave approximation. The analysis essentially requires the use of elliptical coordinate system. Mathieu and the modified Mathieu functions are used as the representatives of the electromagnetic fields within the structure. Field components in the different sections of the guide are presented, and the characteristic dispersion relations for the system are deduced for 0° and 90° pitch angles. The investigation reveals that the pitch angle has ultimately no effect on the dispersion relations for their selected values. The effect of core ellipse eccentricity on the dispersion characteristics is presented for two different operating wavelengths, and considering different values of the core major axis length. 相似文献
752.
Long Han Deepak Doraiswamy Rakesh K. Gupta 《Journal of Thermal Analysis and Calorimetry》2011,106(1):305-312
Light emitting devices containing conjugated polymers are conveniently fabricated using ink-jet printing. A common problem
in the processing of these materials is that the Newtonian viscosity of the polymer solution is not sufficient to describe
the jetting performance because the molecular weights and concentrations employed are such that the resulting solutions are
elastic. These differences in fluid elasticity levels cannot be measured using traditional techniques like dynamic mechanical
experiments or the first normal stress difference in shear, but strongly impact the jetting behavior of the liquid. In this
study, a variety of polystyrene solutions in DECALIN having a shear viscosity of ~5 mPa s but different elasticity levels
were examined for their jetting behavior. The jetting behavior of these solutions was studied visually using drop-on-demand
jetting equipment and their rheology was characterized using a custom extensional rheometer designed for measuring the elasticity
of such low viscosity liquids. If elasticity effects are absent as in Newtonian liquids (corresponding to a Trouton ratio
of 3) satellite drops are formed resulting in loss of liquid and poor positioning. On the other hand, if elasticity effects
are very large (Trouton ratios ≫4) separation problems occur at the nozzle with undesirable “tailing.” The optimum range for
stable, efficient jetting occurs at Trouton ratios in a narrow band between 3 and ~5. A very slight degree of elasticity corresponding
to a Trouton Ratio around four thus seems to be optimum for the jetting process. This appears to be the first time that such
a design criterion has been outlined for this process. Such an approach complements thermal techniques for elucidating the
role of molecular and flow properties on the processing behavior of polymeric systems. 相似文献
753.
Deepak Chopra T. P. Mohan B. Vishalakshi T. N. Guru Row 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(12):o704-o710
In the molecular structures of a series of substituted chalcones, namely (2E)‐3‐(2‐fluoro‐4‐phenoxyphenyl)‐1‐phenylprop‐2‐en‐1‐one, C21H15FO2, (I), (2E)‐3‐(2‐fluoro‐4‐phenoxyphenyl)‐1‐(4‐fluorophenyl)prop‐2‐en‐1‐one, C21H14F2O2, (II), (2E)‐1‐(4‐chlorophenyl)‐3‐(2‐fluoro‐4‐phenoxyphenyl)prop‐2‐en‐1‐one, C21H14ClFO2, (III), (2E)‐3‐(2‐fluoro‐4‐phenoxyphenyl)‐1‐(4‐methylphenyl)prop‐2‐en‐1‐one, C22H17FO2, (IV), and (2E)‐3‐(2‐fluoro‐4‐phenoxyphenyl)‐1‐(4‐methoxyphenyl)prop‐2‐en‐1‐one, C22H17FO3, (V), the configuration of the keto group with respect to the olefinic double bond is s‐cis. The molecules pack utilizing weak C—H...O and C—H...π intermolecular contacts. Identical packing motifs involving C—H...O interactions, forming both chains and dimers, along with C—H...π dimers and π–π aromatic interactions are observed in the fluoro, chloro and methyl derivatives. 相似文献
754.
Satish V. Patil Rahul B. Salunkhe Chandrashekhar D. Patil Deepak M. Patil Bipinchandra K. Salunke 《Applied biochemistry and biotechnology》2010,162(4):1095-1108
Efficacy of Azotobacter indicus ATCC 9540 strain for production exopolysaccharide (EPS) bioflocculant was investigated. Mahua flower extract (Madhuca latifolia L), a natural substrate at the concentration of 20 g L?1, gave maximum recovery of EPS followed by sucrose and mannitol as compared to other carbon sources after 172 h. Yeast extract was found to be the most effective nitrogen source as compared to beef extract, sodium nitrate, ammonium sulfate, casein hydrolysate, and urea for the production of EPS. EPS production was increased in presence of nitrogen (5.51 g L?1) as compared to nitrogen-free medium (3.51 g L?1), and fermentation time was also reduced by 28 h. Maximum EPS production (6.10 g L?1) was found in the presence of 20 g L?1 flower extract and 0.5 g L?1 yeast extract containing Ashby’s media with 180 rpm at 30 °C at 144 h, under controlled conditions in 2.5 L fermenter using optimized medium. The isolated EPS showed cation-dependent flocculating activity. Concentration of EPS played an important role in bioflocculating activity which increased in a concentration-dependent manner up to a certain limit, with the maximum flocculation of 72% at 500 mg L?1 concentration but remained almost static after this concentration. Extracted polymer was characterized by different chemical tests, FT-IR spectroscopy, and TLC which showed presence of uronic acids, O-acetyl groups, and Orcinol with suggestive indication of alginate like polymer. This study suggests that use of M. latifolia L. flowers can be a potential alternative bioresource for production of exopolysaccharide. 相似文献
755.
Deepak Bandyopadhyay Jun Huan Jan Prins Jack Snoeyink Wei Wang Alexander Tropsha 《Journal of computer-aided molecular design》2009,23(11):785-797
Protein function prediction is one of the central problems in computational biology. We present a novel automated protein
structure-based function prediction method using libraries of local residue packing patterns that are common to most proteins
in a known functional family. Critical to this approach is the representation of a protein structure as a graph where residue
vertices (residue name used as a vertex label) are connected by geometrical proximity edges. The approach employs two steps.
First, it uses a fast subgraph mining algorithm to find all occurrences of family-specific labeled subgraphs for all well
characterized protein structural and functional families. Second, it queries a new structure for occurrences of a set of motifs
characteristic of a known family, using a graph index to speed up Ullman’s subgraph isomorphism algorithm. The confidence
of function inference from structure depends on the number of family-specific motifs found in the query structure compared
with their distribution in a large non-redundant database of proteins. This method can assign a new structure to a specific
functional family in cases where sequence alignments, sequence patterns, structural superposition and active site templates
fail to provide accurate annotation. 相似文献
756.
Deepak Bandyopadhyay Jun Huan Jan Prins Jack Snoeyink Wei Wang Alexander Tropsha 《Journal of computer-aided molecular design》2009,23(11):773-784
Protein function prediction is one of the central problems in computational biology. We present a novel automated protein structure-based function prediction method using libraries of local residue packing patterns that are common to most proteins in a known functional family. Critical to this approach is the representation of a protein structure as a graph where residue vertices (residue name used as a vertex label) are connected by geometrical proximity edges. The approach employs two steps. First, it uses a fast subgraph mining algorithm to find all occurrences of family-specific labeled subgraphs for all well characterized protein structural and functional families. Second, it queries a new structure for occurrences of a set of motifs characteristic of a known family, using a graph index to speed up Ullman’s subgraph isomorphism algorithm. The confidence of function inference from structure depends on the number of family-specific motifs found in the query structure compared with their distribution in a large non-redundant database of proteins. This method can assign a new structure to a specific functional family in cases where sequence alignments, sequence patterns, structural superposition and active site templates fail to provide accurate annotation. 相似文献
757.
758.
Aromatic and hetero-aromatic acyl chlorides were efficiently cross-coupled with triarylbismuths as atom-efficient nucleophilic organometallic coupling reagents in sub-stoichiometric amounts using catalytic Pd(0)/C. Thus, the coupling reactions of various triarylbismuths with a variety of acyl chlorides furnished a plethora of both symmetrical/unsymmetrical aromatic and hetero-aromatic ketones in high yields. 相似文献
759.
Jyoti Prasad Chakraborty Deepak Kunzru 《Journal of Analytical and Applied Pyrolysis》2009,86(1):44-52
Pyrolysis of n-heptane was investigated in a tubular reactor in the temperature range of 793–953 K and pressure range of 0.1–2.93 MPa. At all conditions, the main products were methane, ethylene, ethane, propylene, 1-butene, 1-pentene and 1-hexene. With an increase in pressure, the selectivities of hydrogen, methane, ethylene and propylene decreased and that of propane, n-butane and 1-butene increased. To explain the product distribution at high pressure, the Rice–Kossiakoff theory was modified by including the bimolecular reactions of alkyl radicals with the parent hydrocarbon. The initial product selectivities, calculated using the modified R–K mechanism, were in good agreement with the experimental selectivities. The overall kinetics of n-heptane pyrolysis was determined by non-linear analysis. The optimum values of the kinetic parameters at each pressure were determined by minimizing the difference between the calculated and experimental conversions. At each pressure, the reaction order was close to unity and the activation energy ranged between 209 and 219 kJ mol−1. 相似文献
760.
Single nucleotide polymorphism (SNP) is the most common genetic variation among individuals. The association of SNP with individual's response to pathogens, phenotypic variations, and gene functions emphasizes the importance of sensitive and reliable SNP detection for biomedical diagnosis and therapy. To increase sensitivity, most approaches employ amplification steps, such as PCR, to generate detectable signals that are usually ensemble-averaged. Introduction of amplification steps increases the complexity of a system, whereas ensemble averaging of signals often suffers from background interference. Here, we have exploited the stochastic behavior of a single-molecule probe to recognize SNP sequence in a microfluidic platform using a laser-tweezers instrument. The detection relies on on-off mechanical signals that provide little background interference and high specificity between wild type and SNP sequences. The microfluidic setting allows multiplex sensing and in situ recycling of the SNP probe. As a proof-of-concept, we have detected as low as 100 pM of an SNP target associated with coronary heart diseases within half an hour without any amplification steps. The mechanical signal permits the detection of single mutations involving either G/C or A/T pairs. We anticipate this system has the capacity to function as a highly sensitive generic biosensor after incorporation of a specific recognition element, such as an aptamer for example. 相似文献