44,867 research outputs found
Leak test system
System for quantitative determination of leak rates in large pressurized compartments is described. Method uses pressure reference cylinder placed in thermal contact with internal environment of compartment. Construction of equipment and details of operational procedure are reported. Illustration of equipment is included
Endurance testing of downstream cathodes on a low-power MPD thruster
A low-power MPD thruster with downstream cathode was tested for endurance with a series of hollow cathode designs. Failure modes and failure mechanisms were identified. A new hollow cathode (with rod inserts) has emerged which shows promise for long life. The downstream positioning of the cathode was also changed from an on-axis location to an off-axis location. Data are presented for a 1332-hour life test of this new hollow cathode located at the new off-axis location. Xenon propellant was used
Time evolution of the Partridge-Barton Model
The time evolution of the Partridge-Barton model in the presence of the
pleiotropic constraint and deleterious somatic mutations is exactly solved for
arbitrary fecundity in the context of a matricial formalism. Analytical
expressions for the time dependence of the mean survival probabilities are
derived. Using the fact that the asymptotic behavior for large time is
controlled by the largest matrix eigenvalue, we obtain the steady state values
for the mean survival probabilities and the Malthusian growth exponent. The
mean age of the population exhibits a power law decayment. Some Monte
Carlo simulations were also performed and they corroborated our theoretical
results.Comment: 10 pages, Latex, 1 postscript figure, published in Phys. Rev. E 61,
5664 (2000
Alcohol consumption is associated with increased all-cause mortality in Russian men and women: a cohort study based on the mortality of relatives
Objectives: To examine the relationships between frequency of alcohol consumption and of binge drinking and adult mortality in Russian men and women.Methods : Using modified indirect demographic techniques, a convenience cohort was constructed based on survey respondents? information about their close relatives. A random sample general population of the Russian Federation of 7172 respondents (response rate 61%) provided information on 10475 male and 3129 female relatives, including age, vital status and frequency of alcohol consumption and binge drinking. These relatives formed the cohort analysed in this report. The outcome measure was all-cause mortality after the age of 30 years.Findings: There was a strong linear relationship between frequency of drinking and of binge drinking and all-cause mortality in men; after controlling for smoking and calendar period of birth, the relative risk of death in daily drinkers compared to occasional drinkers was 1.52 (95% CI 1.33 ?1.75). Male binge drinkers had higher mortality than drinkers who did not binge, which persisted after adjustment for drinking frequency (adjusted RR 1.09 (1.00-1.19). In women, the increased mortality was confined to a small group of those who binged at least once a month (adjusted relative risk 2.68, 1.54-4.66). Conclusions: The results suggest a positive association between alcohol and mortality in Russia. There was no evidence for the protective effect of drinking seen in western populations. Alcohol appears to have contributed to the high long-term mortality rates in Russian men, but it is unlikely to be a major cause of female mortality. Objectives: To examine the relationships between frequency of alcohol consumption and of binge drinking and adult mortality in Russian men and women.Methods : Using modified indirect demographic techniques, a convenience cohort was constructed based on survey respondents? information about their close relatives. A random sample general population of the Russian Federation of 7172 respondents (response rate 61%) provided information on 10475 male and 3129 female relatives, including age, vital status and frequency of alcohol consumption and binge drinking. These relatives formed the cohort analysed in this report. The outcome measure was all-cause mortality after the age of 30 years.Findings: There was a strong linear relationship between frequency of drinking and of binge drinking and all-cause mortality in men; after controlling for smoking and calendar period of birth, the relative risk of death in daily drinkers compared to occasional drinkers was 1.52 (95% CI 1.33 ?1.75). Male binge drinkers had higher mortality than drinkers who did not binge, which persisted after adjustment for drinking frequency (adjusted RR 1.09 (1.00-1.19). In women, the increased mortality was confined to a small group of those who binged at least once a month (adjusted relative risk 2.68, 1.54-4.66). Conclusions: The results suggest a positive association between alcohol and mortality in Russia. There was no evidence for the protective effect of drinking seen in western populations. Alcohol appears to have contributed to the high long-term mortality rates in Russian men, but it is unlikely to be a major cause of female mortality
Collective multipole-like signatures of entanglement in symmetric N-qubit systems
A cogent theory of collective multipole-like quantum correlations in
symmetric multiqubit states is presented by employing SO(3) irreducible
spherical tensor representation. An arbitrary bipartite division of this system
leads to a family of inequalities to detect entanglement involving averages of
these tensors expressed in terms of the total system angular momentum operator.
Implications of this theory to the quantum nature of multipole-like
correlations of all orders in the Dicke states are deduced. A selected set of
examples illustrate these collective tests. Such tests detect entanglement in
macroscopic atomic ensembles, where individual atoms are not accessible.Comment: REVTEX, 4 pages with 1 figure; To appear in Phys. Rev.
Recombination in polymer-fullerene bulk heterojunction solar cells
Recombination of photogenerated charge carriers in polymer bulk
heterojunction (BHJ) solar cells reduces the short circuit current (Jsc) and
the fill factor (FF). Identifying the mechanism of recombination is, therefore,
fundamentally important for increasing the power conversion efficiency. Light
intensity and temperature dependent current-voltage measurements on polymer BHJ
cells made from a variety of different semiconducting polymers and fullerenes
show that the recombination kinetics are voltage dependent and evolve from
first order recombination at short circuit to bimolecular recombination at open
circuit as a result of increasing the voltage-dependent charge carrier density
in the cell. The "missing 0.3V" inferred from comparison of the band gaps of
the bulk heterojunction materials and the measured open circuit voltage at room
temperature results from the temperature dependence of the quasi-Fermi-levels
in the polymer and fullerene domains - a conclusion based upon the fundamental
statistics of Fermions.Comment: Accepted for publication in Physical Review B.
http://prb.aps.org/accepted/B/6b07cO3aHe71bd1b149e1425e58bf2868cda2384d?ajax=1&height=500&width=50
What Have We Learned from Policy Transfer Research? Dolowitz and Marsh Revisited
Over the last decade, policy transfer has emerged as an important concept within public policy analysis, guiding both theoretical and empirical research spanning many venues and issue areas. Using Dolowitz and Marsh's 1996 stocktake as its starting point, this article reviews what has been learned by whom and for what purpose. It finds that the literature has evolved from its rather narrow, state-centred roots to cover many more actors and venues. While policy transfer still represents a niche topic for some researchers, an increasing number have successfully assimilated it into wider debates on topics such as globalisation, Europeanisation and policy innovation. This article assesses the concept's position in the overall ‘tool-kit’ of policy analysis, examines some possible future directions and reflects on their associated risks and opportunities
Comments on Anomaly Cancellations by Pole Subtractions and Ghost Instabilities with Gravity
We investigate some aspects of anomaly cancellation realized by the
subtraction of an anomaly pole, stressing on some of its properties in
superspace. In a local formulation these subtractions can be described in terms
of a physical scalar, an axion and related ghosts. They appear to be necessary
for the unitarization of the theory in the ultraviolet, but they may generate
an infrared instability of the corresponding effective action, signalled by
ghost condensation. In particular the subtraction of the superanomaly multiplet
by a pole in superspace is of dubious significance, due to the different nature
of the chiral and conformal anomalies. In turn, this may set more stringent
constraints on the coupling of supersymmetric theories to gravity.Comment: 18 pages. Revised version. To appear in "Classical and Quantum
Gravity
A wireless multi-sensor subglacial probe: design and preliminary results
This paper introduces a new way to investigate in situ processes, the wireless multi-sensor probe, as part of an environmental sensor network. Instruments are housed within a 'probe' which can move freely and so behave like a clast. These were deployed in the ice and till at Briksdalsbreen, Norway. The sensors measure temperature, resistivity, case stress, tilt angle and water pressure and send their data to a base station on the glacier surface via radio links. These data are then forwarded by radio to a reference station with mains power 2.5 km away, from where they are sent to a web server in the UK. The system deployed during 2004/05 was very successful and a total of 859 probe days worth of data from the ice and till were collected, along with GPS, weather and diagnostic data about the system
The limits of process: On (re)reading Henri Bergson
This article offers a reading of the work of Henri Bergson as it pertains to organizations through the lens of ideas drawn from critical realism. It suggests an alternative to interpretations based on a stark division between process and realist perspectives. Much of the existing literature presents a rather partial view of Bergson’s work. A review suggests some interesting parallels with themes in critical realism, notably the emergence of mind. Critical realism has a focus on process at its heart, but is also concerned with how the products of such processes become stabilized and form the conditions for action. This suggests that attention might usefully be paid to the relationship between organizational action and the sedimented practices grouped under the heading of ‘routines’. More attention to Bergson’s account of the relationship between instinct, intuition and intelligence provides a link to the social character of thought, something which can be mapped on to Archer’s work on reflexivity and the ‘internal conversation’. This suggests that our analyses need to pay attention to both memory and history, to building and dwelling, rather than the one-sided focus found in some process theory accounts
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