The plasma dynamics of hypersonic spacecraft: Applications of laboratory simulations and active in situ experiments

Attempts to gain an understanding of spacecraft plasma dynamics via experimental investigation of the interaction between artificially synthesized, collisionless, flowing plasmas and laboratory test bodies date back to the early 1960's. In the past 25 years, a number of researchers have succeeded in simulating certain limited aspects of the complex spacecraft-space plasma interaction reasonably well. Theoretical treatments have also provided limited models of the phenomena. Several active experiments were recently conducted from the space shuttle that specifically attempted to observe the Orbiter-ionospheric interaction. These experiments have contributed greatly to an appreciation for the complexity of spacecraft-space plasma interaction but, so far, have answered few questions. Therefore, even though the plasma dynamics of hypersonic spacecraft is fundamental to space technology, it remains largely an open issue. A brief overview is provided of the primary results from previous ground-based experimental investigations and the preliminary results of investigations conducted on the STS-3 and Spacelab 2 missions. In addition, several, as yet unexplained, aspects of the spacecraft-space plasma interaction are suggested for future research

Space Complexity of Perfect Matching in Bounded Genus Bipartite Graphs

We investigate the space complexity of certain perfect matching problems over bipartite graphs embedded on surfaces of constant genus (orientable or non-orientable). We show that the problems of deciding whether such graphs have (1) a perfect matching or not and (2) a unique perfect matching or not, are in the logspace complexity class \SPL. Since \SPL\ is contained in the logspace counting classes \oplus\L (in fact in \modk\ for all $k\geq 2$), \CeqL, and \PL, our upper bound places the above-mentioned matching problems in these counting classes as well. We also show that the search version, computing a perfect matching, for this class of graphs is in \FL^{\SPL}. Our results extend the same upper bounds for these problems over bipartite planar graphs known earlier. As our main technical result, we design a logspace computable and polynomially bounded weight function which isolates a minimum weight perfect matching in bipartite graphs embedded on surfaces of constant genus. We use results from algebraic topology for proving the correctness of the weight function.Comment: 23 pages, 13 figure

Board Interlocks and Their Impact on Corporate Governance: The Indian Experience - Coping with Corporate Cholesterol

Board interlocks occur when a director of one organization sits on the board of directors of another organization. The causes and consequences of these interlocks have been much debated in the western literature but comparatively little is known about interlocks in Indian corporate boards. Board interlocks are essentially analogous to cholesterol. Both are facts of life. Like good cholesterol, there are aspects of interlocking directorates that are beneficial and there are others that are detrimental to the corporation and its stakeholders and their respective interests. In this study, we find that board interlocks are quite widespread in India. Taking a (numerically) small but nevertheless (in terms of market capitalization) an important slice of available corporate data, we observed that in 2010, ‘highly boarded’ directors (defined as those on the board of 5 or more listed NSE companies) who constitute just 6 percent of the overall pool of directors among NSE100 companies are associated with 486 NSE listed companies which account for a whopping 66 percent of the total market capitalization of all NSE listed companies. Interestingly, there appears to be a marked increase in market capitalization of these ‘highly boarded’ companies, which these ‘highly boarded’ directors are linked to over the last several years. For instance, for the 3 years from 2001 to 2003, the market capitalization of ‘highly boarded’ companies ranged between 33 percent to 43 percent; it moved up to peak of 70 percent in 2007 and was at 66 percent in 2010 (the latest year in the study period). The substantive rise in market capitalization of these ‘highly boarded’ companies has coincided with only a marginal increase (from 5% to 6%) in the proportion of ‘highly boarded’ directorships. These trends suggest that despite the well-intentioned regulatory reforms (a) the extent of over-boarding/interlocking among directors has not come down (there is actually a marginal increase) and (b) there appears to be increasing concentration of power among key individuals. Given the general view that concentration of power in a few individuals or entities is not desirable in the larger interests of society, it would appear that the observed trends in the concentration of power among a handful of the country’s corporate elite is a matter for substantive public policy concern. Finally, the regression analysis indicates a positive impact on Return on Assets (ROA) for ‘highly boarded’ directors signifying a negation of the agency centric conceptualization on the role of multiple directors. Instead, connectedness variables (Eigen vector) which proxy for the Resource dependency hypothesis are quite strongly supported. In a nutshell, from public policy perspective, the analysis potentially reflects the ‘bad cholesterol’ elements of multiple directorships in terms of a tiny segment of ‘highly boarded’ directors controlling a significant portion of the country’s economic prowess, whereas the positive influences on company performance provide some evidence of the ‘good cholesterol’.

Plethysmography Phenotype QTL in Mice Before and After Allergen Sensitization and Challenge

Allergic asthma is common airway disease that is characterized in part by enhanced airway constriction in response to nonspecific stimuli. Genome-wide association studies have identified multiple loci associated with asthma risk in humans, but these studies have not accounted for gene–environment interactions, which are thought to be important factors in asthma. To identify quantitative trait loci (QTL) that regulate responses to a common human allergen, we applied a house dust mite mouse (HDM) model of allergic airway disease (AAD) to 146 incipient lines of the Collaborative Cross (CC) and the CC founder strains. We employed a longitudinal study design in which mice were phenotyped for response to the bronchoconstrictor methacholine both before and after HDM sensitization and challenge using whole body plethysmography (WBP). There was significant variation in methacholine responsiveness due to both strain and HDM treatment, as reflected by changes in the WBP parameter enhanced pause. We also found that distinct QTL regulate baseline [chromosome (Chr) 18] and post-HDM (Chr 19) methacholine responsiveness and that post-HDM airway responsiveness was correlated with other features of AAD. Finally, using invasive measurements of airway mechanics, we tested whether the Chr 19 QTL affects lung resistance per se using C57BL/6J mice and a consomic strain but found that QTL haplotype did not affect lung resistance. We conclude that aspects of baseline and allergen-induced methacholine responsiveness are associated with genetic variation, and that robust detection of airway resistance QTL in genetically diverse mice will be facilitated by direct measurement of airway mechanics

Swelling behaviour of nitrile rubber in organic liquids

This research is concerned with the interaction of elastomers and liquids, more specifically with volume changes of rubber in liquids, particularly with nitrile rubbers and mineral oils; with free swelling and the effect of compressive strain on swelling and set. [Continues.

First observation of electric-quadrupole infrared transitions in water vapour

Molecular absorption of infrared radiation is generally due to ro-vibrational electric-dipole transitions. Electric-quadrupole transitions may still occur, but they are typically a million times weaker than electric-dipole transitions, rendering their observation extremely challenging. In polyatomic or polar diatomic molecules, ro-vibrational quadrupole transitions have never been observed. Here, we report the first direct detection of quadrupole transitions in water vapor. The detected quadrupole lines have intensity largely above the standard dipole intensity cut-off of spectroscopic databases and thus are important for accurate atmospheric and astronomical remote sensing

Nearby Microlensing Events - Identification of the Candidates for the SIM

The Space Interferometry Mission (SIM) is the instrument of choice when it comes to observing astrometric microlensing events where nearby, usually high-proper-motion stars (``lenses''), pass in front of more distant stars (``sources''). Each such encounter produces a deflection in the source's apparent position that when observed by SIM can lead to a precise mass determination of the nearby lens star. We search for lens-source encounters during the 2005-2015 period using Hipparcos, ACT and NLTT to select lenses, and USNO-A2.0 to search for the corresponding sources, and rank these by the SIM time required for a 1% mass measurement. For Hipparcos and ACT lenses, the lens distance and lens-source impact parameter are precisely determined so the events are well characterized. We present 32 candidates beginning with a 61 Cyg A event in 2012 that requires only a few minutes of SIM time. Proxima Centauri and Barnard's star each generate several events. For NLTT lenses, the distance is known only to a factor of 3, and the impact parameter only to 1''. Together, these produce uncertainties of a factor ~10 in the amount of SIM time required. We present a list of 146 NLTT candidates and show how single-epoch CCD photometry of the candidates could reduce the uncertainty in SIM time to a factor of ~1.5.Comment: ApJ accepted, 31 pages (inc. 5 tables), 5 figures. t SIM refine