Thermal gap conductance at low contact pressures (<1 MPa): Effect of gold plating and plating thickness

Thermal contact conductance (TCC) measurements are made on bare and gold plated (<= 0.5 mu m) oxygen free high conductivity (OFHC) Cu and brass contacts in vacuum, nitrogen, and argon environments. It is observed that the TCC in gaseous environment is significantly higher than that in vacuum due to the enhanced thermal gap conductance. It is found that for a given contact load and gas pressure, the thermal gap conductance for bare OFHC Cu contacts is higher than that for gold plated contacts. It is due to the difference in the molecular weights of copper and gold, which influences the exchange of kinetic energy between the gas molecules and contact surfaces. Furthermore, the gap conductance is found to increase with increasing thickness of gold plating. Topography measurements and scanning electron microscopy (SEM) analysis of contact surfaces revealed that surfaces become smoother with increasing gold plating thickness, thus resulting in smaller gaps and consequently higher gap conductance. (C) 2010 Elsevier Ltd. All rights reserved.

Superconducting gap in Nb seen by point contact spectroscopy

The nonlinear current voltage characteristics of a point contact convey information about various excitations in the metal. We have made a poin~ contact study on a superconductor to see the band gap and on a normal metal to see Ihe transport characteristics.

Doing marriage and parenthood: The division of household labour across two life course events

The current study is a longitudinal investigation into changes in the division of household labour across transitions to marriage and parenthood in the UK. Previous research has noted a more traditional division of household labour, with women performing the majority of housework, amongst spouses and couples with children. However, the bulk of this work has been cross-sectional in nature. The few longitudinal studies that have been carried out have been rather ambiguous about the effect of marriage and parenthood on the division of housework. Theoretically, this study draws on gender construction theory. The key premise of this theory is that gender is something that is performed and created in interaction, and, as a result, something fluid and flexible rather than fixed and stable. The idea that couples 'do gender' through housework has been a major theoretical breakthrough. Gender-neutral explanations of the division of household labour, positing rational acting individuals, have failed to explicate why women continue to perform an unequal share of housework, regardless of socioeconomic status. Contrastingly, gender construction theory situates gender as the key process in dividing household labour. By performing and avoiding certain housework chores, couples fulfill social norms of what it means to be a man and a woman although, given the emphasis on human agency in producing and contesting gender, couples are able to negotiate alternative gender roles which, in turn, feed back into the structure of social norms in an ever-changing societal landscape. This study adds extra depth to the doing gender approach by testing whether or not couples negotiate specific conjugal and parent roles in terms of the division of household labour. Both transitions hypothesise a more traditional division of household labour. Data comes from the British Household Panel Survey, a large, nationally representative quantitative survey that has been carried out annually since 1991. Here, data tracks the same 776 couples at two separate time points - 1996 and 2005. OLS regression is used to test whether or not transitions to marriage and parenthood have a significant impact on the division of household labour whilst controlling for host of relevant socio-economic factors. Results indicate that marriage has no significant effect on how couples partition housework. Those couples making the transition from cohabitation to marriage do not show significant changes in housework arrangements from those couples who remain cohabiting in both waves. On the other hand, becoming parents does lead to a more traditional division of household labour whilst controlling for socio-economic factors which accompany the move to parenthood. There is then some evidence that couples use the site of household labour to 'do parenthood' and generate identities which both use and inform socially prescribed notions of what it means to be a mother and a father. Support for socio-economic explanations of the division of household labour was mixed although it remains clear that they, alone, cannot explain how households divide housework.

Choosing the Arranged One, Arranging the Chosen One – Imagining an Indian Modernity: Reconciling Love, Marriage and Family On and Off the Screen

This is a study on the changing practices of kinship in Northern India. The change in kinship arrangements, and particularly in intermarriage processes, is traced by analysing the reception of Hindi popular cinema. Films and their role and meaning in people´s lives in India was the object of my research. Films also provided me with a methodology for approaching my other subject-matters: family, marriage and love. Through my discussion of cultural change, the persistence of family as a core value and locus of identity, and the movie discourses depicting this dialogue, I have looked for a possibility of compromise and reconciliation in an Indian context. As the primary form of Indian public culture, cinema has the ability to take part in discourses about Indian identity and cultural change, and alleviate the conflicts that emerge within these discourses. Hindi popular films do this, I argue, by incorporating different familiar cultural narratives in a resourceful way, thus creating something new out of the old elements. The final word, however, is the one of the spectator. The “new” must come from within the culture. The Indian modernity must be imaginable and distinctively Indian. The social imagination is not a “Wild West” where new ideas enter the void and start living a life of their own. The way the young women in Dehra Dun interpreted family dramas and romantic movies highlights the importance of family and continuity in kinship arrangements. The institution of arranged marriage has changed its appearance and gained new alternative modes such as love cum arranged marriage. It nevertheless remains arranged by the parents. In my thesis I have offered a social description of a cultural reality in which movies act as a built-in part. Movies do not work as a distinct realm, but instead intertwine with the social realities of people as a part of a continuum. The social imagination is rooted in the everyday realities of people, as are the movies, in an ontological and categorical sense. According to my research, the links between imagination and social life were not so much what Arjun Appadurai would call global and deterritorialised, but instead local and conventional.

Fluorescence and topological gap of conjugated phenylene polymers

We propose that strong fluorescence in conjugated polymers requires a dipole-allowed state to be the lowest singlet. Hückel theory for para-conjugated phenyl rings yields an extended, topologically one-dimensional ?-system with increased alternation, states localized on each ring, and charge-transfer excitations between them. Exact Pariser�Parr�Pople results and molecular spectra for oligomers support a topological contribution and a lowest dipole-allowed singlet in phenylene polymers.

Pressure-induced band gap reduction, orientational ordering and reversible amorphization in single crystals of C70: Photoluminescence and Raman studies

Photoluminescence and Raman scattering experiments have been carried out on single crystals of C70 up to 31 GPa to investigate the effect of pressure on the optical band gap, vibrational modes and stability of the molecule. The photoluminescence band shifts to lower energies and the pressure dependence of the band maxima yields the hydrostatic deformation potential to be 2.15 eV. The slope changes in the pressure dependence of peak positions and linewidths of the Raman modes associated with the intramolecular vibrations at 1 GPa mark the known face-centred cubic-->rhombohedral orientational ordering transition. The reversible amorphization in C70 at P > 20 GPa has been compared with the irreversible amorphization in C60 at P > 22 GPa in terms of carbon-carbon distance between the neighbouring molecules at the threshold transition pressures, in conjunction with the interplay between the intermolecular and intramolecular interactions.

Non-Marcus energy gap dependence of electron transfer rate in contact ion pairs. Novel interplay between relaxation and reaction in solution

Electron transfer reactions between donor-acceptor pairs in solution and in organized media exhibit diverse behaviour. Recent experiments have indicated an interesting breakdown of the Marcus parabolic energy gap dependence in the normal regime for back electron transfer from contact ion pairs. A novel explanation of this breakdown has recently been proposed (M. Tachiya and S. Murata, J. Am. Chem. Sec., 116(1994) 2434) which attributes the breakdown to the interplay between the relaxation in the reactant well and the reaction. A particularly interesting aspect of the model is that it envisages the electron transfer in the normal regime to take place from a completely non-equilibrium condition. In this article a time dependent solution of the model is presented for the first time, after generalizing it to include a realistic initial population distribution. The decay of the contact ion pair population is completely non-exponential. This can be used to check the validity of the Tachiya-Murata model. The dynamics of electron transfer from the solvent separated ion pair, which seem to obey the Marcus relation, is exponential.

Solid-state miscibility gap and thermodynamics of the system BaO–SrO

A solid-state miscibility gap in the pseudo-binary system BaO-SrO is delineated by X-ray diffraction studies on samples equilibrated either in vacuum or under flowing inert gas at temperatures between 1073 and 1423 K. For the SrxBa1-xO solid solution an asymmetric phase boundary, characterized by a critical temperature of 1356 (+/-4) K and composition x=0.55 (+/-0.008), is obtained. Thermodynamic mixing properties of the solid solution, derived from the experimental phase boundary compositions and temperatures, can be represented by the expression: Delta G(E)=x(1-x){33 390-7.09T)x+(29 340-6.23T)(1-x)} J mol(-1)It is necessary to include excess entropy terms to obtain a good fit to the experimental data. The chemical spinodal curve is computed from the thermodynamic parameters

Zn incorporation and band gap shrinkage in p-type GaAs

Dimethylzine (DMZn) was used as a p-type dopant in GaAs grown by low pressure metalorganic vapor phase epitaxy using trimethylgallium and arsine (AsH3) as source materials, The hole carrier concentrations and zinc (Zn) incorporation efficiency are studied by using the Hall effect, electrochemical capacitance voltage profiler and photoluminescence (PL) spectroscopy, The influence of growth parameters such as DMZn mole fraction, growth temperature, and AsH, mole fraction on the Zn incorporation have been studied. The hole concentration increases with increasing DMZn and AsH3 mole fraction and decreases with increasing growth temperature. This can be explained by vacancy control model. The PL experiments were carried out as a function of hole concentration (10(17)-1.5 x 10(20) cm(-3)). The main peak shifted to lower energy and the full width at half maximum (FWHM) increases with increasing hole concentrations. We have obtained an empirical relation for FWHM of PL, Delta E(p)(eV) = 1.15 x 10(-8)p(1/3). We also obtained an empirical relation for the band gap shrinkage, Delta E-g in Zn doped GaAs as a function of hole concentration. The value of Delta E-g(eV) = -2.75 x 10(-8)p(1/3), indicates a significant band gap shrinkage at high doping levels, These relations are considered to provide a useful tool to determine the hole concentration in Zn doped GaAs by low temperature PL measurement. The hole concentration increases with increasing AsH3 mole fraction and the main peak is shifted to a lower energy side. This can be explained also by the vacancy control model. As the hole concentration is increased above 3.8 x 10(18) cm(-3), a shoulder peak separated from the main peak was observed in the PL spectra and disappears at higher concentrations. (C) 1997 American Institute of Physics.

Raman evidence for the superconducting gap and spin-phonon coupling in the superconductor Ca( Fe0.95Co0.05)(2)As-2

Inelastic light scattering studies on a single crystal of electron-doped Ca(Fe0.95Co0.05)(2)As-2 superconductor, covering the tetragonal-to-orthorhombic structural transition as well as the magnetic transition at T-SM similar to 140 K and the superconducting transition temperature T-c similar to 23 K, reveal evidence for superconductivity-induced phonon renormalization. In particular, the phonon mode near 260 cm(-1) shows hardening below T-c, signaling its coupling with the superconducting gap. All three Raman active phonon modes show anomalous temperature dependence between room temperature and T-c, i.e. the phonon frequency decreases with lowering temperature. Further, the frequency of one of the modes shows a sudden change in temperature dependence at TSM. Using first-principles density functional theory based calculations, we show that the low temperature phase (T-c < T < T-SM) exhibits short-ranged stripe antiferromagnetic ordering, and estimate the spin-phonon couplings that are responsible for these phonon anomalies.

Trends in consanguineous marriage in Karnataka, South India, 1980–89

Analysis of data on 106,848 marriages in the cities of Bangalore and Mysore, South India, between 1980 and 1989 showed that levels of consanguineous marriage varied between cities through time and by religion. The average coefficient of inbreeding was higher in Bangalore (F = 0·0339) than in Mysore (F = 0·0203), principally reflecting large-scale, post-Independence rural migration into Bangalore. Although there was some evidence of a decline in consanguineous marriages in Mysore, there was no convincing support in either city for earlier projections of a rapid reduction in the popularity of unions between close biological relatives.

PL due to Discrete Gap Levels in Some Chalcogenide Glasses- A Configurational Coordinate Diagram Illustration

Photoluminescence (PL) studies were carried out on a-Se and a few Ge20Se80−xBix and Ge20Se70−xBixTe10 bulk glassy semiconductors at 4.2 K with Ar+ laser as excitation source. While a-Se and samples with lesser at% of Bi show fine structured PL with a large Stokes shift, samples with higher at% of Bi did not show any detectable PL. The investigations show at least three radiative recombination transitions. Features extracted by deconvoluting the experimental spectra show that the discrete gap levels associated with the inherent coordination defects are involved in the PL transitions. Absence of PL in samples with higher Bi at% are explained on the basis of nonradiative transition mechanisms. Overall PL mechanism involving gap levels in chalcogenide glasses is illustrated with the help of a configurational coordinate diagram.