3,118 research outputs found

    Design definition of a mechanical capacitor

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    A design study and analyses of a 10 kW-hr, 15 kW mechanical capacitor system was studied. It was determined that magnetically supported wheels constructed of advanced composites have the potential for high energy density and high power density. Structural concepts are analyzed that yield the highest energy density of any structural design yet reported. Particular attention was paid to the problem of 'friction' caused by magnetic and I to the second power R losses in the suspension and motor-generator subsystems, and low design friction levels have been achieved. The potentially long shelf life of this system, and the absence of wearing parts, provide superior performance over conventional flywheels supported with mechanical bearings. Costs and economies of energy storage wheels were reviewed briefly

    How Gigging Musicians Utilize Social Media

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    Gigging musicians will exhaust their resources to get more audience members and music lovers at their show and active on their social media outlets. I will be conducting a survey in the Tri-State area to discover how local gigging musicians utilize social media to promote themselves and their shows. I hope to uncover what varying local musicians have found most useful in the age of social media. In doing so, local musicians and gigging musicians in smaller music scenes across the United States will be able to benefit in their promotions from my study

    Decreases in Plasma Membrane Ca2+-ATPase in Brain Synaptic Membrane Rafts from Aged Rats

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    Precise regulation of free intracellular Ca2+ concentrations [Ca2+]i is critical for normal neuronal function, and alterations in Ca2+ homeostasis are associated with brain aging and neurodegenerative diseases. One of the most important proteins controlling [Ca2+]i is the plasma membrane Ca2+-ATPase (PMCA), the high affinity transporter that fine tunes the cytosolic nanomolar levels of Ca2+. We previously found that PMCA protein in synaptic plasma membranes (SPMs) is decreased with advancing age and the decrease in enzyme activity is much greater than that in protein levels. In the present study, we isolated raft and non-raft fractions from rat brain SPMs and used quantitative mass spectrometry to show that the specialized lipid microdomains in SPMs, the rafts, contain 60% of total PMCA, comprised of all four isoforms. The raft PMCA pool had the highest specific activity and this decreased progressively with age. The reduction in PMCA protein could not account for the dramatic activity loss. Addition of excess CaM to the assay did not restore PMCA activity to that in young brains. Analysis of the major raft lipids revealed a slight age-related increase in cholesterol levels and such increases might enhance membrane lipid order and prevent further loss of PMCA activity

    Effects of Gangliosides on the Activity of the Plasma Membrane Ca2+-ATPase

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    Control of intracellular calcium concentrations ([Ca2+]i) is essential for neuronal function, and the plasma membrane Ca2+-ATPase (PMCA) is crucial for the maintenance of low [Ca2+]i. We previously reported on loss of PMCA activity in brain synaptic membranes during aging. Gangliosides are known to modulate Ca2+ homeostasis and signal transduction in neurons. In the present study, we observed age-related changes in the ganglioside composition of synaptic plasma membranes. This led us to hypothesize that alterations in ganglioside species might contribute to the age-associated loss of PMCA activity. To probe the relationship between changes in endogenous ganglioside content or composition and PMCA activity in membranes of cortical neurons, we induced depletion of gangliosides by treating neurons with D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (D-PDMP). This caused a marked decrease in the activity of PMCA, which suggested a direct correlation between ganglioside content and PMCA activity. Neurons treated with neuraminidase exhibited an increase in GM1 content, a loss in poly-sialoganglioside content, and a decrease in PMCA activity that was greater than that produced by D-PDMP treatment. Thus, it appeared that poly-sialogangliosides had a stimulatory effect whereas mono-sialogangliosides had the opposite effect. Our observations add support to previous reports of PMCA regulation by gangliosides by demonstrating that manipulations of endogenous ganglioside content and species affect the activity of PMCA in neuronal membranes. Furthermore, our studies suggest that age-associated loss in PMCA activity may result in part from changes in the lipid environment of this Ca2+ transporter

    Michaelis-Menten dynamics in protein subnetworks

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    To understand the behaviour of complex systems it is often necessary to use models that describe the dynamics of subnetworks. It has previously been established using projection methods that such subnetwork dynamics generically involves memory of the past, and that the memory functions can be calculated explicitly for biochemical reaction networks made up of unary and binary reactions. However, many established network models involve also Michaelis-Menten kinetics, to describe e.g. enzymatic reactions. We show that the projection approach to subnetwork dynamics can be extended to such networks, thus significantly broadening its range of applicability. To derive the extension we construct a larger network that represents enzymes and enzyme complexes explicitly, obtain the projected equations, and finally take the limit of fast enzyme reactions that gives back Michaelis-Menten kinetics. The crucial point is that this limit can be taken in closed form. The outcome is a simple procedure that allows one to obtain a description of subnetwork dynamics, including memory functions, starting directly from any given network of unary, binary and Michaelis-Menten reactions. Numerical tests show that this closed form enzyme elimination gives a much more accurate description of the subnetwork dynamics than the simpler method that represents enzymes explicitly, and is also more efficient computationally

    Toward an ecological aesthetics: music as emergence

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    In this article we intend to suggest some ecological based principles to support the possibility of develop an ecological aesthetics. We consider that an ecological aesthetics is founded in concepts as “direct perception”, “acquisition of affordances and invariants”, “embodied embedded perception” and so on. Here we will purpose that can be possible explain especially soundscape music perception in terms of direct perception, working with perception of first hand (in a Gibsonian sense). We will present notions as embedded sound, detection of sonic affordances and invariants, and at the end we purpose an experience with perception/action paradigm to make soundscape music as emergence of a self-organized system

    Crop Yields: Stripper Header Technology vs. Conventional Header Technology

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    The purpose of this paper is to compare crop yields on acres where stripper header technology was used to those where conventional header technology was used in a dryland cropping system. The results are based on experimental data collected at the USDA-ARS Central Great Plains Research Station, and include information on Northeastern Colorado wheat, millet, and sorghum yields. This analysis is important to demonstrate the benefits of using stripper header technology in a dryland cropping system. In the next section, the approaches and major findings of the previous literature are reviewed

    Lie bialgebras of generalized Witt type

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    In a paper by Michaelis a class of infinite-dimensional Lie bialgebras containing the Virasoro algebra was presented. This type of Lie bialgebras was classified by Ng and Taft. In this paper, all Lie bialgebra structures on the Lie algebras of generalized Witt type are classified. It is proved that, for any Lie algebra WW of generalized Witt type, all Lie bialgebras on WW are coboundary triangular Lie bialgebras. As a by-product, it is also proved that the first cohomology group H1(W,W⊗W)H^1(W,W \otimes W) is trivial.Comment: 14 page
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