Micromechanical tuning elements in a 620-GHz monolithic integrated circuit

While monolithic integrated-circuit technology promises a practical means for realizing reliable reproducible planar millimeter and submillimeter-wave circuits, conventional planar circuits do not allow for critical post-fabrication optimization of performance. A 620-GHz quasi-optical monolithic detector circuit is used here to demonstrate the performance of two integrated micromechanical planar tuning elements. This is the first reported demonstration of integrated micromechanical tuning at submillimeter wavelengths. The tuning elements, called sliding planar backshorts (SPBs), are used to adjust the electrical length of planar transmission-line tuning stubs to vary the power delivered between a substrate-lens coupled planar antenna and a thin-film bismuth detector over a range of nearly 15 dB. The circuit performance agrees with theoretical calculations and microwave measurements of a -0.06-dB reflection coefficient made for a scale model of the integrated tuners. The demonstrated tuning range for the SPB tuners indicates that they can be valuable for characterizing components in developmental circuits and for optimizing the in-use performance of various millimeter and submillimeter-wave integrated circuits

Child mortality in rural Malawi: HIV closes the survival gap between the socio-economic strata

As HIV-related deaths increase in a population the usual association between low socioeconomic status and child mortality may change, particularly as death rates from other causes decline.METHODS/PRINCIPAL FINDINGS: As part of a demographic surveillance system in northern Malawi in 2002-6, covering a population of 32,000, information was collected on socio-economic status of the households. Deaths were classified as HIV/AIDS-related or not by verbal autopsy. Poisson regression models were used to assess the association of socio-economic indicators with all-cause mortality, AIDS-mortality and non-AIDS mortality among children. There were 195 deaths in infants, 109 in children aged 1-4 years, and 38 in children aged 5-15. All-cause child mortality in infants and 1-4 year olds was similar in households with higher and lower socio-economic status. In infants 13% of deaths were attributed to AIDS, and there were no clear trends with socio-economic status for AIDS or non-AIDS causes. For 1-4 year olds 27% of deaths were attributed to AIDS. AIDS mortality was higher among those with better built houses, and lowest in those with income from farming and fishing, whereas non-AIDS mortality was higher in those with worse built houses, lowest in those with income from employment, and decreased with increasing household assets.CONCLUSIONS/SIGNIFICANCE: In this population, since HIV infection among adults was initially more common among the less poor, childhood mortality patterns have changed. The usual gap in survival between the poor and the less poor has been lost, but because the less poor have been disproportionately affected by HIV, rather than because of relative improvement in the survival of the poorest

Rethinking the employability of international graduate migrants: reflections on the experiences of Zimbabweans with degrees from England

The last decade has seen the rise of literatures that have focused on the rapid expansion of the numbers of international students in higher education globally and the growing policy discourse around improving graduate employability. However, both, inevitably, have limitations. Together, they tend to homogenise international learners and see them narrowly as simply economic actors. More recently, however, there have been signs of important new developments in both literatures, drawing on interactive employability and capability accounts that stress both agency and structure in more satisfactory ways. We seek to further the development of an account that bridges the new wave of student mobility research and the capability-employability account. In doing so, we offer two further elements to the literature. First, we aim to bridge the gap between international higher education accounts and those of migration and diasporic studies. Second, we deliberately focus on a group that is marginal to the mainstream discourse but who are migrants that have engaged in international higher education in order to improve their labour market prospects, amongst other motivations. We do this through examining the stories of five Zimbabweans who embarked on additional higher educational studies in England after migrating to the country. Through this unique approach, we offer an important new perspective on how the debates on international higher education, employability and migration can be taken forward through closer articulation between these accounts

The Assembly of the Red Sequence at z ~ 1: The Color and Spectral Properties of Galaxies in the Cl1604 Supercluster

We investigate the properties of the 525 spectroscopically confirmed members of the Cl1604 supercluster at z ~ 0.9 as part of the Observations of Redshift Evolution in Large Scale Environments survey. In particular, we focus on the photometric, stellar mass, morphological, and spectral properties of the 305 member galaxies of the eight clusters and groups that comprise the Cl1604 supercluster. Using an extensive Keck Low-Resolution Imaging Spectrometer (LRIS)/DEep Imaging Multi-Object Spectrograph (DEIMOS) spectroscopic database in conjunction with ten-band ground-based, Spitzer, and Hubble Space Telescope imaging, we investigate the buildup of the red sequence in groups and clusters at high redshift. Nearly all of the brightest and most massive red-sequence galaxies present in the supercluster environment are found to lie within the bounds of the cluster and group systems, with a surprisingly large number of such galaxies present in low-mass group systems. Despite the prevalence of these red-sequence galaxies, we find that the average cluster galaxy has a spectrum indicative of a star-forming galaxy, with a star formation rate between those of z ~ 1 field galaxies and moderate-redshift cluster galaxies. The average group galaxy is even more active, exhibiting spectral properties indicative of a starburst. The presence of massive, red galaxies and the high fraction of starbursting galaxies present in the group environment suggest that significant processing is occurring in group environments at z ~ 1 and earlier. There is a deficit of low-luminosity red-sequence galaxies in all Cl1604 clusters and groups, suggesting that such galaxies transition to the red sequence at later times. Extremely massive (~10^(12)M_☉) red-sequence galaxies routinely observed in rich clusters at z ~ 0 are also absent from the Cl1604 clusters and groups. We suggest that such galaxies form at later times through merging processes. There are significant populations of transition galaxies at intermediate stellar masses (log(M_*)=10.25-10.75) present in the group and cluster environments, suggesting that this range is important for the buildup of the red-sequence mass function at z ~ 1. Through a comparison of the transitional populations present in the Cl1604 cluster and group systems, we find evidence that massive blue-cloud galaxies are quenched earliest in the most dynamically relaxed systems and at progressively later times in dynamically unrelaxed systems

Magellanic Cloud X-ray Sources: III. Completion of a ROSAT Survey

This paper concludes a series of three papers presenting ROSAT High-Resolution Imager (HRI) observations of unidentified Einstein and serendipitous ROSAT X-ray sources in the direction of the Magellanic Clouds. Accurate positions and fluxes have been measured for these sources. Optical photometry and spectroscopy were obtained to search for identifications in order to determine the physical nature of these sources. The present paper includes new data for 24 objects; identifications are given or confirmed for 30 sources. For six sources optical finding charts showing the X-ray positions are provided. The results from this program are summarized, showing the populations of luminous X-ray sources in the Magellanic Clouds are quite different from those in the Galaxy.Comment: 28 pages, 2 figures; to appear in Astronomical Journa

The surface science of quasicrystals

The surfaces of quasicrystals have been extensively studied since about 1990. In this paper we review work on the structure and morphology of clean surfaces, and their electronic and phonon structure. We also describe progress in adsorption and epitaxy studies. The paper is illustrated throughout with examples from the literature. We offer some reflections on the wider impact of this body of work and anticipate areas for future development. (Some figures in this article are in colour only in the electronic version

What other's disappointment may do to selfish people: Emotion and social value orientation in a negotiation context

The authors examined whether individual differences in social value orientation moderate responses to other’s expressions of disappointment in negotiation. The literature suggested competing hypotheses: First, prosocials are more responsive to other’s disappointment because they have a greater concern for other; second, proselfs are more responsive because they see other’s disappointment as a threat to their own outcomes. Results of a computer-mediated negotiation in which a simulated opponent expressed disappointment, no emotion, or anger supported the second prediction: Proselfs conceded more to a disappointed opponent than to a neutral or angry one, whereas prosocials were unaffected by the other’s emotion. This effect was mediated by participants’ motivation to satisfy the other’s needs, which disappointment triggered more strongly in proselfs than in prosocials. Implications for theorizing on emotion, social value orientation, and negotiation are discussed

Synthesis And Properties Of Clay-ZrO2-Cellulose Fibre-Reinforced Polymeric Nano-Hybrids

Epoxy nano-hybrids reinforced with cellulose fibre (CF), nano-kaolinite (K), and micro-ZrO2 (Z) have been synthesized. The influence of CF/K/Z dispersions on the mechanical properties of these hybrids have been characterized in terms of elastic modulus, hardness, flexural strength, fracture toughness and indentation responses. This new but cost-effective approach has been developed to improve the physical and mechanical properties of polymeric materials without adversely affecting their processing characteristics. The mechanism of reinforcement in these organic/inorganic nanohybrid materials has been investigated. The micromechanisms of toughening and failure processes are identified and discussed in the light of observed nano- and micro-structures

The Force-Velocity Relation for Growing Biopolymers

The process of force generation by the growth of biopolymers is simulated via a Langevin-dynamics approach. The interaction forces are taken to have simple forms that favor the growth of straight fibers from solution. The force-velocity relation is obtained from the simulations for two versions of the monomer-monomer force field. It is found that the growth rate drops off more rapidly with applied force than expected from the simplest theories based on thermal motion of the obstacle. The discrepancies amount to a factor of three or more when the applied force exceeds 2.5kT/a, where a is the step size for the polymer growth. These results are explained on the basis of restricted diffusion of monomers near the fiber tip. It is also found that the mobility of the obstacle has little effect on the growth rate, over a broad range.Comment: Latex source, 9 postscript figures, uses psfig.st