1,053 research outputs found

    The sodium-potassium pump controls the intrinsic firing of the cerebellar Purkinje neuron

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    In vitro, cerebellar Purkinje cells can intrinsically fire action potentials in a repeating trimodal or bimodal pattern. The trimodal pattern consists of tonic spiking, bursting, and quiescence. The bimodal pattern consists of tonic spiking and quiescence. It is unclear how these firing patterns are generated and what determines which firing pattern is selected. We have constructed a realistic biophysical Purkinje cell model that can replicate these patterns. In this model, Na+/K+ pump activity sets the Purkinje cell's operating mode. From rat cerebellar slices we present Purkinje whole cell recordings in the presence of ouabain, which irreversibly blocks the Na+/K+ pump. The model can replicate these recordings. We propose that Na+/K+ pump activity controls the intrinsic firing mode of cerbellar Purkinje cells

    Missing GRB host galaxies in deep mid-infrared observations: implications on the use of GRBs as star formation tracers

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    We report on the first mid-infrared observations of 16 GRB host galaxies performed with the Spitzer Space Telescope, and investigate the presence of evolved stellar populations and dust-enshrouded star-forming activity associated with GRBs. Only a very small fraction of our sample is detected by Spitzer, which is not consistent with recent works suggesting the presence of a GRB host population dominated by massive and strongly-starbursting galaxies (SFR >~ 100M[sun]yr^–1). Should the GRB hosts be representative of star-forming galaxies at high redshift, models of galaxy evolution indicate that >~ 50% of GRB hosts would be easily detected at the depth of our mid-infrared observations. Unless our sample suffers from a strong observational bias which remains to be understood, we infer in this context that the GRBs identified with the current techniques can not be directly used as unbiased probes of the global and integrated star formation history of the Universe

    Markov counting models for correlated binary responses

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    We propose a class of continuous-time Markov counting processes for analyzing correlated binary data and establish a correspondence between these models and sums of exchangeable Bernoulli random variables. Our approach generalizes many previous models for correlated outcomes, admits easily interpretable parameterizations, allows different cluster sizes, and incorporates ascertainment bias in a natural way. We demonstrate several new models for dependent outcomes and provide algorithms for computing maximum likelihood estimates. We show how to incorporate cluster-specific covariates in a regression setting and demonstrate improved fits to well-known datasets from familial disease epidemiology and developmental toxicology

    William Allen Rogers Articles, unknown

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    Two articles discussing William Allen Rogers and his contributions of western life. One article is a chapter from Artists and Illustrators of the Old West 1850-1900 by Robert Taft and the other is from North Dakota History, Journal of the Plains Vol. 43, Summer 1976, No. 3

    Infrared and visible photometry of the gravitational lens systems 2237 + 030

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    As part of a program of high spatial resolution imaging of gravitationally lensed sources in the visible and IR, images of 2237 + 030 were obtained in the Gunn r and infrared J, H, K, and 3.3 micron filters. The results of the photometry of the four bright quasar components provide evidence of extinction through the lens and a determination of the extinction law in the galaxy is made. The energy distribution shows evidence of a sharp decrease of the spectral index at wavelengths longer than a rest wavelength of 1 micron. Assuming that microlensing amplification in the IR is of similar strength as in the visible, the data constrain the suggested microlensing event of August-September 1988 to a time scale of 100 days

    Dual Input Microinverter for Tandem Cells

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    For every solar panel, there is an inverter which transforms the harvested DC electricity into AC electricity so that it can connect to the grid and power household appliances. In this project, we examined a tandem solar cell being designed by Iris Photovoltaics which has two layers with two distinct outputs, and we explored several solutions to create a microinverter which can handle dual inputs from the tandem PV and combine them into a single AC output. To examine the viability of such a microinverter, we designed and simulated the DC-DC combination portion of the specialized dual input microinverter, resulting in a working circuit simulation using flyback transformers which can take two DC inputs at different voltage and current levels and combine them together into a single high voltage on the DC bus, ready to be transformed into AC. We also purchased an already existing dual input microinverter and tested it by connecting it with two different solar panels and measuring its performance, however we could not obtain useful results because it did not function as intended. Overall the dual input microinverter is an interesting technology involving maximum power point tracking, DC combination, and power electronics. It has a multitude of applications, and it fits perfectly with the 4-terminal tandem solar module being developed by Iris Photovoltaics

    Pharmacokinetic and Pharmacodynamic Principles of Anti-infective Dosing

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    An understanding of the pharmacokinetic (PK) and pharmacodynamic (PD) principles that determine response to antimicrobial therapy can provide the clinician with better-informed dosing regimens. Factors influential on antibiotic disposition and clinical outcome are presented, with a focus on the primary site of infection. Techniques to better understand antibiotic PK and optimize PD are acknowledged
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