Thermoelectric power in ultrathin films, quantum wires and carbon nanotubes under classically large magnetic field: Simplified theory and relative comparison

We study the thermoelectric power under classically large magnetic field (TPM) in ultrathin films (UFs), quantum wires (QWs) of non-linear optical materials on the basis of a newly formulated electron dispersion law considering the anisotropies of the effective electron masses, the spin-orbit splitting constants and the presence of the crystal field splitting within the framework of k.p formalism. The results of quantum confined III-V compounds form the special cases of our generalized analysis. The TPM has also been studied for quantum confined II-VI, stressed materials, bismuth and carbon nanotubes (CNs) on the basis of respective dispersion relations. It is found taking quantum confined CdGeAs2, InAs, InSb, CdS, stressed n-InSb and Bi that the TPM increases with increasing film thickness and decreasing electron statistics exhibiting quantized nature for all types of quantum confinement. The TPM in CNs exhibits oscillatory dependence with increasing carrier concentration and the signature of the entirely different types of quantum systems are evident from the plots. Besides, under certain special conditions, all the results for all the materials gets simplified to the well-known expression of the TPM for non-degenerate materials having parabolic energy bands, leading to the compatibility test. (C) 2009 Elsevier B.V. All rights reserved.

Elastic Properties of Boron Nitride Nanotubes and Their Comparison with Carbon Nanotubes

Boron Nitride Nanotubes (BNNTs) have alternating boron and nitrogen atoms in graphite like network and are strongly polar in nature due to a large charge on boron and nitrogen atoms. Hence electrostatic interactions are expected to play an important role in determining the elastic properties of BNNTs. In the absence of specific partial atomic charge information for boron and nitrogen, we have studied the elastic properties BNNTs varying the partial atomic charges on boron and nitrogen. We have computed Young modulus (Y) and Shear modulus (G) of BNNT as a function of the tube radius and number of walls using molecular mechanics calculation. Our calculation shows that Young modulus of BNNTs increases with increase in magnitude of the partial atomic charge on B and N and can be larger than the Young modulus of CNTs of same radius. This is in contrast to the earlier finding that CNTs has the largest tensile strength (PRL, 80, 4502, 1998). Shear modulus, on the other hand depends weakly on the magnitude of partial atomic charge and is less than the shear modulus of the CNT. The values obtained for Young modulus and Shear modulus are in excellent agreement with the available experimental results.

Thermoelectric Power Under Strong Magnetic Field in Quantum Dots and Quantized Superlattices: Simplified Theory and Relative Comparison

In this paper, we study the thermoelectric power under strong magnetic field (TPSM) in quantum dots (QDs) of nonlinear optical, III-V, II-VI, GaP, Ge, Te, Graphite, PtSb2, zerogap, Lead Germanium Telluride, GaSb, stressed materials, Bismuth, IV-VI, II-V, Zinc and Cadmium diphosphides, Bi2Te3 and Antimony respectively. The TPSM in III-V, II-VI, IV-VI, HgTe/CdTe quantum well superlattices with graded interfaces and effective mass superlattices of the same materials together with the quantum dots of aforementioned superlattices have also been investigated in this context on the basis of respective carrier dispersion laws. It has been found that the TPSM for the said quantum dots oscillates with increasing thickness and decreases with increasing electron concentration in various manners and oscillates with film thickness, inverse quantizing magnetic field and impurity concentration for all types of superlattices with two entirely different signatures of quantization as appropriate in respective cases of the aforementioned quantized structures. The well known expression of the TPSM for wide-gap materials has been obtained as special case for our generalized analysis under certain limiting condition, and this compatibility is an indirect test of our generalized formalism. Besides, we have suggested the experimental method of determining the carrier contribution to elastic constants for nanostructured materials having arbitrary dispersion laws.

The Photoemission from Quantum Wells, Wires and Carbon Nanotubes:Simplified Theory and Relative Comparison

We investigate the photoemission from quantum wells (QWs) in ultrathin films (UFs) and quantum well wires (QWWs) of non-linear optical materials on the basis of a newly formulated electron dispersion law considering the anisotropies of the effective electron masses, the spin-orbit splitting constants and the presence of the crystal field splitting within the framework of k.p formalism. The results of quantum confined Ill-V compounds form the special cases of our generalized analysis. The photoemission has also been studied for quantum confined II-VI, n-GaP, n-Ge, PtSb2, stressed materials and Bismuth on the basis of respective dispersion relations. It has been found taking quantum confined CdGeAS(2), InAs, InSb, CdS, GaP, Ge, PtSb2, stressed n-InSb and B1 that the photoemission exhibits quantized variations with the incident photon energy, changing electron concentration and film thickness, respectively, for all types of quantum confinement. The photoemission from CNs exhibits oscillatory dependence with increasing normalized electron degeneracy and the signature of the entirely different types of quantum systems are evident from the plots. Besides, under certain special conditions, all the results for all the materials gets simplified to the well-known expression of photoemission from non-degenerate semiconductors and parabolic energy bands, leading to the compatibility test.

Structure of basic winged-bean lectin and a comparison with its saccharide-bound form

The crystal structure of the saccharide-free form of the basic form of winged-bean agglutinin (WBAI) has been solved by the molecular-replacement method and refined at 2.3 Angstrom resolution The final R factor is 19.74b for all data in the resolution range 8.0-2.3 Angstrom. The asymmetric unit contains two half-dimers, each located on a crystallographic twofold axis. The structure of the saccharide-free form is compared with that of the complex of WBAI wi th methyl-alpha-D-galactoside. The complex is composed of two dimers in the asymmetric unit. The intersubunit interactions in the dimer are nearly identical in the two structures The binding site of the saccharide-free structure contains three ordered water molecules at positions similar to those of the hydroxyl groups of the carbohydrate which an hydrogen bonded to the protein. Superposition of the saccharide-binding sites of the two structures shows that the major changes involve expulsion of these ordered water molecules and a shift of about 0.6 Angstrom of the main-chain atoms of the variable loop.

Sandwich propellant combustion: Modeling and experimental comparison

This paper reports reacting fluid dynamics calculations for an ammonium percholrate binder sandwich and extracts experimentally observed features including surface profiles and maximum regression rates as a function of pressure and binder thickness. These studies have been carried out by solving the two-dimensional unsteady Navier-Stokes equations with energy and species conservation equations and a kinetic model of three reaction steps (ammonium perchlorate decomposition flame, primary diffusion flame, and final diffusion flame) in the gas phase. The unsteady two-dimensional conduction equation is solved in the condensed phase. The regressing surface is unsteady and two dimensional. Computations have been carried out for a binder thickness range of 25-125 mum and a pressure range of 1.4 to 6.9 MPa. Good comparisons at several levels of detail are used to demonstrate the need for condensed-phase two-dimensional unsteady conduction and three-step gas-phase reactions. The choice of kinetic and thermodynamic parameters is crucial to good comparison with experiments. The choice of activation energy parameters for ammonium percholrate combustion has been made with stability of combustion in addition to experimentally determined values reported in literature. The choice of gas-phase parameters for the diffusion flames are made considering that (a) primary diffusion flame affects the low-pressure behavior and (b) final diffusion flame affects high-pressure behavior. The predictions include the low-pressure deflagration limit of the sandwich apart from others noted above. Finally, this study demonstrates the possibility of making meaningful comparisons with experimental observations on sandwich propellant combustion.

Identification of a core promoter and a novel isoform of the human TSCI gene transcript and structural comparison with mouse homolog

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder with loci on chromosome 9q34.12 (TSC1) and chromosome 16p13.3 (TSC2). Genes for both loci have been isolated and characterized. The promoters of both genes have not been characterized so far and little is known about the regulation of these genes. This study reports the characterization of the human TSC1 promoter region for the first time. We have identified a novel alternative isoform in the 5' untranslated region (UTR) of the TSC1 gene transcript involving exon 1. Alternative isoforms in the 5' UTR of the mouse Tsc1 gene transcript involving exon I and exon 2 have also been identified. We have identified three upstream open reading frames (uORFs) in the 5' UTR of the TSC1/Tsc1 gene. A comparative study of the 5' UTR of TSC1/Tsc1 gene has revealed that there is a high degree of similarity not only in the sequence but also in the splicing pattern of both human and mouse TSC1 genes. We have used PCR methodology to isolate approximately 1.6 kb genomic DNA 5' to the TSC1 cDNA. This sequence has directed a high level of expression of luciferase activity in both HeLa and HepG2 cells. Successive 5' and 3' deletion analysis has suggested that a -587 bp region, from position +77 to -510 from the transcription start site (TSS), contains the promoter activity. Interestingly, this region contains no consensus TATA box or CAAT box. However, a 521-bp fragment surrounding the TSS exhibits the characteristics of a CpG island which overlaps with the promoter region. The identification of the TSC1 promoter region will help in designing a suitable strategy to identify mutations in this region in patients who do not show any mutations in the coding regions. It will also help to study the regulation of the TSC1 gene and its role in tumorigenesis. (C) 2003 Elsevier B.V. All rights reserved.

New possibilities in amplitude- and phase-comparison techniques for distance relays

The paper reports further work on the amplitude-comparison technique described by the same authors in a previous paper. This technique is extended to develop improved polar characteristics. Discontinuous polar characteristics, like directional parallelograms, are obtained by a single measuring gate with a simple mode of relay circuitry, whereas two measuring gates are required to provide a directional-quadrilateral characteristic of potentially general application. The paper also describes some new possibilities in phase-comparison methods for distance-protection schemes. Comparator models which effect the amplitude and phase comparison of the relaying signals are described in their schematic form. A comprehensive theoretical basis for comparison is also presented.

On the two dimensional effective electron mass in quantum wells, inversion layers and NIPI superlattices of Kane type semiconductors in the presence of strong light waves: Simplified theory and relative comparison

An attempt is made to study the two dimensional (2D) effective electron mass (EEM) in quantum wells (Qws), inversion layers (ILs) and NIPI superlattices of Kane type semiconductors in the presence of strong external photoexcitation on the basis of a newly formulated electron dispersion laws within the framework of k.p. formalism. It has been found, taking InAs and InSb as examples, that the EEM in Qws, ILs and superlattices increases with increasing concentration, light intensity and wavelength of the incident light waves, respectively and the numerical magnitudes in each case is band structure dependent. The EEM in ILs is quantum number dependent exhibiting quantum jumps for specified values of the surface electric field and in NIPI superlattices; the same is the function of Fermi energy and the subband index characterizing such 2D structures. The appearance of the humps of the respective curves is due to the redistribution of the electrons among the quantized energy levels when the quantum numbers corresponding to the highest occupied level changes from one fixed value to the others. Although the EEM varies in various manners with all the variables as evident from all the curves, the rates of variations totally depend on the specific dispersion relation of the particular 2D structure. Under certain limiting conditions, all the results as derived in this paper get transformed into well known formulas of the EEM and the electron statistics in the absence of external photo-excitation and thus confirming the compatibility test. The results of this paper find three applications in the field of microstructures. (C) 2011 Elsevier Ltd. All rights reserved.

THE EFFECTS OF SURFACTANT ON SIMPLEX NOZZLE SPRAY BEHAVIOR AND ITS COMPARISON TO LIQUID FUELS

Pressure-swirl nozzles (simplex nozzles) are used in various field applications such as aero-engines, power generation, spray painting and agricultural irrigation. For this particular nozzle, research in the past decade has dealt with the development of numerical models for predicting droplet distribution profiles. Although these results have been valuable, the experimental results have been contradictory, therefore fundamental understanding of the influence of properties in nozzle is important. This paper experimentally investigates the effect of surfactants on breakup and coalescence. Since most of the fuels and biofuels have low surface tension compared to water, a comparative analysis between a surfactant solution and a liquid fuel is imperative. For this experimental study, a simplex nozzle characterized as flow number 0.4 will be utilized. The injection pressures will range from 0.3 - 4Mpa while altering the surface tension from 72 to 28mN/m. By applying Phase Doppler Particle Anemometry (PDPA) which is a non-intrusive laser diagnostic technique, the differences in spray characteristics due to spray surface tension can be highlighted. The average droplet diameter decreases for a low surface tension fluid in the axial direction in comparison to pure water. The average velocity of droplets is surprisingly lower in the same spray zone. Measurements made in the radial direction show no significant changes, but at the locations close to the nozzle, water droplets have larger diameter and velocity. The results indicate the breakup and coalescence regimes have been altered when surface tension is lowered. A decrease in surface tension alters the breakup length while increasing the spray angle. Moreover, higher injection pressure shortens the breakup length and decrease in overall diameter of the droplets. By performing this experimental study the fundamentals of spray dynamics, such as spray formation, liquid breakup length, and droplet breakup regimes can be observed as a function of surface tension and how a surrogate fuel compares with a real fuel for experimental purposes. This knowledge potentially will lead to designing a better atomizer or new biofuels.

Scientometric analysis of some disciplines: Comparison of Indian institutions with other international institutions

We have carried out a three-part study comparing the research performance of Indian institutions with that of other international institutions. In the first part, the publication profiles of various Indian institutions were examined and ranked based on the h-index and p-index. We found that the institutions of national importance contributed the highest in terms of publications and citations per institution. In the second part of the study, we looked at the publication profiles of various Indian institutions in the high-impact journals and compared these profiles against that of the top Asian and US universities. We found that the number of papers in these journals from India was miniscule compared to the US universities. Recognizing that the publication profiles of various institutions depend on the field/departments, we studied the publication profiles of many science and engineering departments at the Indian Institute of Science (IISc), Bangalore, the Indian Institutes of Technology, as well as top Indian universities. Because the number of faculty in each department varies widely, we have computed the publications and citations per faculty per year for each department. We have also compared this with other departments in various Asian and US universities. We found that the top Indian institution based on various parameters in various disciplines was IISc, but overall even the top Indian institutions do not compare favourably with the top US or Asian universities.

Experimental analysis of composite single-lap joints using digital image correlation and comparison with theoretical models

The demand for energy efficient, low weight structures has boosted the use of composite structures assembled using increased quantities of structural adhesives. Bonded structures may be subjected to severe working environments such as high temperature and moisture due to which the adhesive gets degraded over a period of time. This reduces the strength of a joint and leads to premature failure. Measurement of strains in the adhesive bondline at any point of time during service may be beneficial as an assessment can be made on the integrity of a joint and necessary preventive actions may be taken before failure. This paper presents an experimental approach of measuring peel and shear strains in the adhesive bondline of composite single-lap joints using digital image correlation. Different sets of composite adhesive joints with varied bond quality were prepared and subjected to tensile load during which digital images were taken and processed using digital image correlation software. The measured peel strain at the joint edge showed a rapid increase with the initiation of a crack till failure of the joint. The measured strains were used to compute the corresponding stresses assuming a plane strain condition and the results were compared with stresses predicted using theoretical models, namely linear and nonlinear adhesive beam models. A similar trend in stress distribution was observed. Further comparison of peel and shear strains also exhibited similar trend for both healthy and degraded joints. Maximum peel stress failure criterion was used to predict the failure load of a composite adhesive joint and a comparison was made between predicted and actual failure loads. The predicted failure loads from theoretical models were found to be higher than the actual failure load for all the joints.

Performance comparison for 12 V lead-carbon hybrid ultracapacitors with substrate-integrated and conventional pasted positive plates

Lead-carbon hybrid ultracapacitors comprise positive lead dioxide plates of the lead-acid battery and negative plates of carbon-based electrical double-layer capacitors (EDLCs). Accordingly, a lead-carbon hybrid ultracapacitor has the features of both the battery and that of an EDLC. In this study, the development and performance comparison between the two types of lead-carbon hybrid ultracapacitors, namely those with substrate-integrated and conventional pasted positive plates, is presented as such a study is lacking in the literature. The study suggests that the faradaic efficiencies for both types of lead-carbon hybrid ultracapacitors are comparable. However, their capacitance values as well as energy and power densities differ significantly. For substrate-integrated positive plate hybrid ultracapacitor, capacitance and energy density values are lower, but power density values are higher than pasted positive plate lead-carbon hybrid ultracapacitors due to their shorter response time. Accordingly, internal resistance values are also lower for substrate-integrated lead-carbon hybrid ultracapacitors. Both types of lead-carbon hybrid ultracapacitors exhibit good cycle life of 100,000 pulse charge-discharge cycles with only a nominal loss in their capacitance values.