613 research outputs found

    RURAL INFRASTRUCTURE, TRANSACTIONS COSTS, AND MARKETED SURPLUS IN KENYA

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    We develop a conceptual framework for quantifying fixed transactions costs facing semisubsistence households. Using household survey data from a sample of 324 Kenyan maize farmers, we generate estimates of household supply and demand schedules, as well as the price bands that they face. Our econometric results indicate that on average the ad valorem tax equivalent of the fixed transactions costs facing the households in our sample is 28%. Additional analysis indicates that both remoteness and infrastructure quality have significant impacts on the size of the transactions costs facing farm households. To the best of our knowledge, ours are the first empirical estimates of the magnitude of transactions costs.Marketing,

    The geometry of quantum learning

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    Concept learning provides a natural framework in which to place the problems solved by the quantum algorithms of Bernstein-Vazirani and Grover. By combining the tools used in these algorithms--quantum fast transforms and amplitude amplification--with a novel (in this context) tool--a solution method for geometrical optimization problems--we derive a general technique for quantum concept learning. We name this technique "Amplified Impatient Learning" and apply it to construct quantum algorithms solving two new problems: BATTLESHIP and MAJORITY, more efficiently than is possible classically.Comment: 20 pages, plain TeX with amssym.tex, related work at http://www.math.uga.edu/~hunziker/ and http://math.ucsd.edu/~dmeyer

    American Eel: A Symposium. Session Two

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    Session Two\u27s panel focuses on the socio-economic and cultural significance of American eels. The discussion covers an overview of eel fisheries, socio-economic uses, international eel markets, dominance of Asian aquaculture, and the role of the American eel for aquaculture seed stock and for the consumption market

    American Eel: A Symposium. Session Two

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    Session Two\u27s panel focuses on the socio-economic and cultural significance of American eels. The discussion covers an overview of eel fisheries, socio-economic uses, international eel markets, dominance of Asian aquaculture, and the role of the American eel for aquaculture seed stock and for the consumption market

    Gravity-Assist Mechanical Simulator for Outreach

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    There is no convenient way to demonstrate mechanically, as an outreach (or inreach) topic, the angular momentum trade-offs and the conservation of angular momentum associated with gravityassist interplanetary trajectories. The mechanical concepts that underlie gravity assist are often misunderstood or confused, possibly because there is no mechanical analog to it in everyday experience. The Gravity Assist Mech - anical Simulator is a hands-on solution to this longstanding technical communications challenge. Users intuitively grasp the concepts, meeting specific educational objectives. A manually spun wheel with high angular mass and low-friction bearings supplies momentum to an attached spherical neodymium magnet that represents a planet orbiting the Sun. A steel bearing ball following a trajectory across a glass plate above the wheel and magnet undergoes an elastic collision with the revolving magnet, illustrating the gravitational elastic collision between spacecraft and planet on a gravity-assist interplanetary trajectory. Manually supplying the angular momentum for the elastic collision, rather than observing an animation, intuitively conveys the concepts, meeting nine specific educational objectives. Many NASA and JPL interplanetary missions are enabled by the gravity-assist technique

    Pando: Personal Volunteer Computing in Browsers

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    The large penetration and continued growth in ownership of personal electronic devices represents a freely available and largely untapped source of computing power. To leverage those, we present Pando, a new volunteer computing tool based on a declarative concurrent programming model and implemented using JavaScript, WebRTC, and WebSockets. This tool enables a dynamically varying number of failure-prone personal devices contributed by volunteers to parallelize the application of a function on a stream of values, by using the devices' browsers. We show that Pando can provide throughput improvements compared to a single personal device, on a variety of compute-bound applications including animation rendering and image processing. We also show the flexibility of our approach by deploying Pando on personal devices connected over a local network, on Grid5000, a French-wide computing grid in a virtual private network, and seven PlanetLab nodes distributed in a wide area network over Europe.Comment: 14 pages, 12 figures, 2 table

    Role of Doctoral Studies on the Relationships Between Select Doctoral Students and Their Partners: A Collective Case Study

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    Students who enter post-baccalaureate studies face numerable challenges during their tenure in graduate school. Although researchers have studied these inherent challenges, a gap exists in the literature concerning doctoral students and the impact of their studies on their personal relationships. As such, the purpose of this collective case study was to examine the effect that doctoral studies have on the relationships between select doctoral students and their partners. Semi-structured interviews of six participants, selected via convenience sampling (i.e., current doctoral students who have been in relationships during their doctoral studies), generated data concerning challenges, coping mechanisms, personal emotions, and relationship concerns. These findings provided a composite understanding of the potential inherent struggles of doctoral students and the corresponding role that their doctoral studies have on the relationships of these specific doctoral students and their partners that matched much of the findings noted in the literature. It is the researchers’ hope that the results will help guide future researchers but urge caution concerning the generalizability of the information gained from this study due to its small sample size

    Over-expression of copper/zinc superoxide dismutase in the median preoptic nucleus attenuates chronic angiotensin II-induced hypertension in the rat.

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    The brain senses circulating levels of angiotensin II (AngII) via circumventricular organs, such as the subfornical organ (SFO), and is thought to adjust sympathetic nervous system output accordingly via this neuro-hormonal communication. However, the cellular signaling mechanisms involved in these communications remain to be fully understood. Previous lesion studies of either the SFO, or the downstream median preoptic nucleus (MnPO) have shown a diminution of the hypertensive effects of chronic AngII, without providing a clear explanation as to the intracellular signaling pathway(s) involved. Additional studies have reported that over-expressing copper/zinc superoxide dismutase (CuZnSOD), an intracellular superoxide (O2·-) scavenging enzyme, in the SFO attenuates chronic AngII-induced hypertension. Herein, we tested the hypothesis that overproduction of O2·- in the MnPO is an underlying mechanism in the long-term hypertensive effects of chronic AngII. Adenoviral vectors encoding human CuZnSOD (AdCuZnSOD) or control vector (AdEmpty) were injected directly into the MnPO of rats implanted with aortic telemetric transmitters for recording of arterial pressure. After a 3 day control period of saline infusion, rats were intravenously infused with AngII (10 ng/kg/min) for ten days. Rats over-expressing CuZnSOD (n = 7) in the MnPO had a blood pressure increase of only 6 ± 2 mmHg after ten days of AngII infusion while blood pressure increased 21 ± 4 mmHg in AdEmpty-infected rats (n = 9). These results support the hypothesis that production of O2·- in the MnPO contributes to the development of chronic AngII-dependent hypertension
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