20,182 research outputs found

    The development and test of ultra-large-format multi-anode microchannel array detector systems

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    The specific tasks that were accomplished with each of the key elements of the multi-anode microchannel array detector system are described. The modes of operation of position-sensitive electronic readout systems for use with high-gain microchannel plates are described and their performance characteristics compared and contrasted. Multi-anode microchannel array detector systems with formats as large as 256 x 1024 pixels are currently under evaluation. Preliminary performance data for sealed ultraviolet and visible-light detector tubes show that the detector systems have unique characteristics which make them complementary to photoconductive array detectors, such as CCDs, and superior to alternative pulse-counting detector systems employing high-gain MCPs

    The evaluation of a deformable diffraction grating for a stigmatic EUV spectroheliometer

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    Two crucial areas in the development of the high resolution EUV spectroheliometer are the elastically deformable toroidal diffraction grating and the open-structure imaging pulse counting detector system. The optical performance of a high frequency toroidal grating at EUV wavelengths was verified with a 3600 groove/mm master grating on a spherical concave blank. An open-structure (256 x 1024) pixel, multi-anode microchannel array was developed and tested as a pulse counting detector system. These two systems verify the proof of concept of the spectroheliometer design

    The development and test of multi-anode microchannel array detector systems. 2: Soft X-ray detectors

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    The techniques and procedures for producing very-large-format pulse-counting array detector systems for use in forthcoming high-energy astrophysics facilities were defined, and the structures and performance characteristics of high-sensitivity photocathodes for use at soft X-ray wavelengths between 100 and 1 A were determined. The progress made to date in each of these areas are described and the tasks that will be undertaken when the program is continued are summarized

    The measurement of solar spectral irradiances at wavelengths between 40 and 4000 A

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    Two 1/8-meter Ebert-Fastie spectrometers were refurbished and upgraded in order to measure the solar spectral irradiances between 1160 A and 3100 A. An evacuated 1/4-meter normal-incidence spectrometer was also fabricated for spectral irradiance measurements over the wavelength range from 1250 A to 250 A. Procedures were developed for the calibration of all three instruments utilizing standards at the National Bureau of Standards. The two 1/8-meter spectrometers were flown to measure the solar spectral irradiances near solar maximum on two different dates. Data from these flights were analyzed. The performance of the spectrometers, and the results of an analysis of the variabilities of the solar spectral irradiances over the solar cycles 20 and 21 are discussed

    Gender Composition of Occupations and Earnings: Why Enter a Female Dominated Occupation?

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    Given the inverse relationship between the proportion of females employed in an occupation and earnings, why enter a female-dominated occupation? It has been argued that an individual’s total compensation from work is a combination of wage compensation plus non-pecuniary compensation associated with job characteristics, and when choosing an occupation, one selects the utility-maximizing combination of wages and job characteristics. Our findings support the theory that employee and job characteristics are rewarded differently in non-female dominated (NFD) and female dominated (FD) occupations, and that people choose occupations that reward their attributes more or penalize them less. Comparison of the variables significantly related to salary among FD occupations, NFD occupations and the full sample reveals that 9 of 13 variables significantly related to salary among NFD occupations are also significantly related to salary, with the same sign, among the full sample. However, none of these 13 variables is related to salary among FD occupations. This suggests that an individual’s labor force attributes are rewarded differently in FD occupations compared to NFD occupations and therefore any individual with a particular set of attributes can expect to be rewarded differently in a NFD occupation than in a FD occupation

    Electronic Reverse Auctions: Spawning Procurement Innovation in the Context of Arab Culture

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    Government e-procurement initiatives have the potential to transform local institutions, but few studies have been published of strategies for implementing specific e-procurement tools, particularly involving procurement by a foreign government adapting to local culture in the Middle East/North Africa (MENA). This case describes procurement at a forward operating base (FOB) in Kuwait in support of operations in Iraq. The government procurers had to deal with a phenomenon unique to the MENA region: wasta. Wasta is a form of social capital that bestows power, influence, and connection to those who possess it, similar to guanxi in China. This study explores the value proposition and limitations of electronic reverse auctions (eRA) with the purpose of sharing best practices and lessons learned for government procurement in a MENA country. The public value framework provides valuable theoretical insights for the implementation of a new government e-procurement tool in a foreign country. In a culture dominated by wasta, the suppliers enjoyed the transparency and merit-based virtues of eRA’s that transferred successfully into the new cultural milieu: potential to increase transparency, competition, efficiency, and taxpayer savings. The practices provided herein are designed specifically to help buyers overcome structural barriers including training, organizational inertia, and a lack of eRA policy and guidance while implementing a new e-procurement tool in a foreign country

    What Fundamentals Drive World Migration?

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    OECD governments note rising immigration with alarm and grapple with policies aimed at selecting certain migrants and keeping out others. Economists appear to be well armed to advise governments since they are responsible for an impressive literature that examines the characteristics of individual immigrants, their absorption and the consequences of their migration on both sending and receiving regions. Economists are, however, much less well armed to speak to the determinants of the world migrations that give rise to public alarm. This paper offers a quantitative assessment of the economic and demographic fundamentals that have driven and are driving world migration, across different historical epochs and around the world. The paper is organized around three questions: How do the standard theories of migration perform when confronted with evidence drawn from more than a century of world migration experience? How do inequality and poverty influence world migration? Is it useful to distinguish between migration pressure and migration ex-post, or between the potential demand for visas and the actual use of them?

    TRADE LIBERALIZATION AND JAPANESE AGRICULTURAL IMPORT POLICIES

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    This analysis empirically evaluates a subset of Japanese agricultural policies during the 1970s and 1980s using the Trade Restrictiveness Index recently developed by Anderson and Neary. This index, though theoretically rigorous, is empirically demanding, resulting in relatively few applications. Inferences obtained from the index are in general accordance with policy changes and economic events over the period of analysis. Using 1970 as the base, the estimated TRI suggests that policy changes during 1970-87 resulted in moderately liberalized trade. Comparison with a conventional measure of trade distortion- producer and consumer subsidy equivalents (PSEs and CSEs)- reveals contrasting inference. This suggests the choice of empirical measures in evaluating trade policies in nontrivial.International Relations/Trade,

    International Migration in the Long-Run: Positive Selection, Negative Selection and Policy

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    Most labor scarce overseas countries moved decisively to restrict their immigration during the first third of the 20th century. This autarchic retreat from unrestricted and even publicly-subsidized immigration in the first global century before World War I to the quotas and bans introduced afterwards was the result of a combination of factors: public hostility towards new immigrants of lower quality public assessment of the impact of those immigrants on a deteriorating labor market, political participation of those impacted, and, as a triggering mechanism, the sudden shocks to the labor market delivered by the 1890s depression, the Great War, postwar adjustment and the great depression. The paper documents the secular drift from very positive to much more negative immigrant selection which took place in the first global century after 1820 and in the second global century after 1950, and seeks explanations for it. It then explores the political economy of immigrant restriction in the past and seeks historical lessons for the present.

    Giving subjects the eye and showing them the finger: socio-biological cues and saccade generation in the anti-saccade task.

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    Pointing with the eyes or the finger occurs frequently in social interaction to indicate direction of attention and one's intentions. Research with a voluntary saccade task (where saccade direction is instructed by the colour of a fixation point) suggested that gaze cues automatically activate the oculomotor system, but non-biological cues, like arrows, do not. However, other work has failed to support the claim that gaze cues are special. In the current research we introduced biological and non-biological cues into the anti-saccade task, using a range of stimulus onset asynchronies (SOAs). The anti-saccade task recruits both top ^ down and bottom^ up attentional mechanisms, as occurs in naturalistic saccadic behaviour. In experiment 1 gaze, but not arrows, facilitated saccadic reaction times (SRTs) in the opposite direction to the cues over all SOAs, whereas in experiment 2 directional word cues had no effect on saccades. In experiment 3 finger pointing cues caused reduced SRTs in the opposite direction to the cues at short SOAs. These findings suggest that biological cues automatically recruit the oculomotor system whereas non- biological cues do not. Furthermore, the anti-saccade task set appears to facilitate saccadic responses in the opposite direction to the cues
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