1,340 research outputs found

    Changes in Food, Alcohol and Cigarettes Consumption during Transition: Evidence from Russia

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    This paper examines the changes in nutritional behavior of Russian adults over the ten-year transition period, between 1994 and 2004. We present evidence on the impact of individual as well as regional characteristics on changes in fat, protein, alcohol and cigarette consumption, and on diversity of diet. The results from a dynamic empirical model suggest that among microeconomic determinants, initial levels of consumption, gender, holding a university degree, and having access to a garden plot have a significant impact on the changes in consumption behavior in Russia. Regarding the macroeconomic variables, economic growth has a significant impact on changes in fat and protein consumption and on alcohol use, while unemployment changes significantly impact protein intake, alcohol consumption and the diversity of diet.consumption, smoking, alcohol, economic transition, Russia, Consumer/Household Economics, Food Consumption/Nutrition/Food Safety,

    Reconstitution of Listeria motility: implications for the mechanism of force transduction

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    AbstractListeria monocytogenes and some other infectious bacteria polymerize their host cell’s actin into tails that propel the bacteria through the cytoplasm. Here we show that reconstitution of this behavior in simpler media resolves two aspects of the mechanism of force transduction. First, since dilute reconstitution media have no cytoskeleton, we consider what keeps the tail from being pushed backward rather than the bacterium being propelled forward. The dependence of the partitioning of motion on the friction coefficient of the tail is derived. Consistent with experiments, we find that the resistance of the tail to motion is sensitive to its length. That even small tails are stationary in intact cells is attributed to anchoring to the cytoskeleton. Second, the comparatively low viscosity of some reconstitution media magnifies the effects of diffusion, such that a large gap will develop between the bacterium and its tail if they are unattached. At the viscosities of diluted platelet extracts, steady-state gaps of several bacterium lengths are predicted. Since such gaps are not observed, we conclude that Listeria must be attached to their tails. We consider what purposes such attachments might serve under physiological conditions. The implications for related pathogens and amoeboid locomotion are also discussed

    Vibrational origin of the fast relaxation processes in molecular glass-formers

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    We study the interaction of the relaxation processes with the density fluctuations by molecular dynamics simulation of a flexible molecule model for o-terphenyl (oTP) in the liquid and supercooled phases. We find evidence, besides the structural relaxation, of a secondary vibrational relaxation whose characteristic time, few ps, is slightly temperature dependent. This i) confirms the result by Monaco et al. [Phys. Rev, E 62, 7595 (2000)] of the vibrational nature of the fast relaxation observed in Brillouin Light Scattering (BLS) experiments in oTP; and ii) poses a caveat on the interpretation of the BLS spectra of molecular systems in terms of a purely center of mass dynamics.Comment: RevTeX, 5 pages, 4 eps figure

    Dipole Interactions and Electrical Polarity in Nanosystems -- the Clausius-Mossotti and Related Models

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    Point polarizable molecules at fixed spatial positions have solvable electrostatic properties in classical approximation, the most familiar being the Clausius-Mossotti (CM) formula. This paper generalizes the model and imagines various applications to nanosystems. The behavior is worked out for a sequence of octahedral fragments of simple cubic crystals, and the crossover to the bulk CM law is found. Some relations to fixed moment systems are discussed and exploited. The one-dimensional dipole stack is introduced as an important model system. The energy of interaction of parallel stacks is worked out, and clarifies the diverse behavior found in different crystal structures. It also suggests patterns of self-organization which polar molecules in solution might adopt. A sum rule on the stack interaction is found and tested. Stability of polarized states under thermal fluctuations is discussed, using the one-dimensional domain wall as an example. Possible structures for polar hard ellipsoids are considered. An idea is formulated for enhancing polarity of nanosystems by intentionally adding metallic coatings.Comment: 18 pages (includes 6 embedded figures and 3 tables). New references, and other small improvements. Scheduled for publication by J. Chem. Phys., Jan. 200

    A 250 GHz gyrotron with a 3 GHz tuning bandwidth for dynamic nuclear polarization

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    We describe the design and implementation of a novel tunable 250 GHz gyrotron oscillator with >10 W output power over most of a 3 GHz band and >35 W peak power. The tuning bandwidth and power are sufficient to generate a >1 MHz nutation frequency across the entire nitroxide EPR lineshape for cross effect DNP, as well as to excite solid effect transitions utilizing other radicals, without the need for sweeping the NMR magnetic field. Substantially improved tunability is achieved by implementing a long (23 mm) interaction cavity that can excite higher order axial modes by changing either the magnetic field of the gyrotron or the cathode potential. This interaction cavity excites the rotating TE[subscript 5,2,q] mode, and an internal mode converter outputs a high-quality microwave beam with >94% Gaussian content. The gyrotron was integrated into a DNP spectrometer, resulting in a measured DNP enhancement of 54 on the membrane protein bacteriorhodopsin.National Institutes of Health (U.S.) (Grant EB002804)National Institutes of Health (U.S.) (Grant EB003151)National Institutes of Health (U.S.) (Grant EB002026)National Institutes of Health (U.S.) (Grant EB001960)National Institutes of Health (U.S.) (Grant EB001035)National Institutes of Health (U.S.) (Grant EB001965)National Institutes of Health (U.S.) (Grant EB004866)National Science Foundation (U.S.). Graduate Research Fellowshi

    Statistical-mechanical theory of ultrasonic absorption in molecular liquids

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    We present results of theoretical description of ultrasonic phenomena in molecular liquids. In particular, we are interested in the development of microscopical, i.e., statistical-mechanical framework capable to explain the long living puzzle of the excess ultrasonic absorption in liquids. Typically, ultrasonic wave in a liquid can be generated by applying the periodically alternating external pressure with the angular frequency that corresponds to the ultrasound. If the perturbation introduced by such process is weak - its statistical-mechanical treatment can be done with the use of the linear response theory. We treat the liquid as a system of interacting sites, so that all the response/aftereffect functions as well as the energy dissipation and generalized (wave-vector and frequency dependent) ultrasonic absorption coefficient are obtained in terms of familiar site-site static and time correlation functions such as static structure factors or intermediate scattering functions. To express the site-site intermediate scattering functions we refer to the site-site memory equations in the mode-coupling approximation for the first-order memory kernels, while equilibrium properties such as site-site static structure factors, direct and total correlation functions are deduced from the integral equation theory of molecular liquids known as RISM or one of its generalizations. All the formalism is phrased in a general manner, hence the obtained results are expected to work for arbitrary type of molecular liquid including simple, ionic, polar, and non-polar liquids.Comment: 14 pages, 1 eps-figure, RevTeX4-forma

    Continuously Tunable 250 GHz Gyrotron with a Double Disk Window for DNP-NMR Spectroscopy

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    In this paper, we describe the design and experimental results from the rebuild of a 250 GHz gyrotron used for Dynamic Nuclear Polarization enhanced Nuclear Magnetic Resonance spectroscopy on a 380 MHz spectrometer. Tuning bandwidth of approximately 2 GHz is easily achieved at a fixed magnetic field of 9.24 T and a beam current of 95 mA producing an average output power of >10 W over the entire tuning band. This tube incorporates a double disk output sapphire window in order to maximize the transmission at 250.58 GHz. DNP Signal enhancement of >125 is achieved on a [superscript 13]C-Urea sample using this gyrotron.National Institutes of Health (U.S.) (Grant EB002804)National Institutes of Health (U.S.) (Grant EB003151)National Institutes of Health (U.S.) (Grant EB002026)National Institutes of Health (U.S.) (Grant EB001960)National Institutes of Health (U.S.) (Grant EB001035)National Institutes of Health (U.S.) (Grant EB001965)National Institutes of Health (U.S.) (Grant EB004866
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