2,573 research outputs found

    A novel method of combining blood oxygenation and blood flow sensitive magnetic resonance imaging techniques to measure the cerebral blood flow and oxygen metabolism responses to an unknown neural stimulus.

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    Simultaneous implementation of magnetic resonance imaging methods for Arterial Spin Labeling (ASL) and Blood Oxygenation Level Dependent (BOLD) imaging makes it possible to quantitatively measure the changes in cerebral blood flow (CBF) and cerebral oxygen metabolism (CMRO(2)) that occur in response to neural stimuli. To date, however, the range of neural stimuli amenable to quantitative analysis is limited to those that may be presented in a simple block or event related design such that measurements may be repeated and averaged to improve precision. Here we examined the feasibility of using the relationship between cerebral blood flow and the BOLD signal to improve dynamic estimates of blood flow fluctuations as well as to estimate metabolic-hemodynamic coupling under conditions where a stimulus pattern is unknown. We found that by combining the information contained in simultaneously acquired BOLD and ASL signals through a method we term BOLD Constrained Perfusion (BCP) estimation, we could significantly improve the precision of our estimates of the hemodynamic response to a visual stimulus and, under the conditions of a calibrated BOLD experiment, accurately determine the ratio of the oxygen metabolic response to the hemodynamic response. Importantly we were able to accomplish this without utilizing a priori knowledge of the temporal nature of the neural stimulus, suggesting that BOLD Constrained Perfusion estimation may make it feasible to quantitatively study the cerebral metabolic and hemodynamic responses to more natural stimuli that cannot be easily repeated or averaged

    Full Court Press: Northwestern University, A New Challenge To The NCAA

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    In recent years, a host of issues have arisen between the National Collegiate Athletic Association (NCAA) and the college athletes who provide the labor from which the NCAA and its member universities derive their profits. Many of these issues have been heavily publicized and have spurred a heated debate over the status of college athletes and the future of the collegiate athletic system. This Article primarily focuses on the issue of college athletes’ status as employees for purposes of federal labor law. The significant increase in the popularity of college sports in recent years has led to conference realignment, facility building and arms race, governance issues and litigation. The student-athletes, the players in the highly lucrative college football and basketball games have been left behind. They have resorted to challenging the NCAA’s system in many different ways. Recently, football players at Northwestern University successfully petitioned their local Regional Director of the National Labor Relations Board for a union representation election, arguing that they are employees of the University and as such are entitled to collective bargaining rights and other protections under the National Labor Relations Act. Northwestern University has rejected this argument and has appealed the Regional Director’s decision to the National Labor Relations Board in Washington, D.C. This Article provides a background for the highly contested dispute, refutes some of the common arguments made against the potential unionization of college athletics, and discusses some of the potential implications if players can and do form a union

    Sashimi plots: Quantitative visualization of RNA sequencing read alignments

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    We introduce Sashimi plots, a quantitative multi-sample visualization of mRNA sequencing reads aligned to gene annotations. Sashimi plots are made using alignments (stored in the SAM/BAM format) and gene model annotations (in GFF format), which can be custom-made by the user or obtained from databases such as Ensembl or UCSC. We describe two implementations of Sashimi plots: (1) a stand-alone command line implementation aimed at making customizable publication quality figures, and (2) an implementation built into the Integrated Genome Viewer (IGV) browser, which enables rapid and dynamic creation of Sashimi plots for any genomic region of interest, suitable for exploratory analysis of alternatively spliced regions of the transcriptome. Isoform expression estimates outputted by the MISO program can be optionally plotted along with Sashimi plots. Sashimi plots can be used to quickly screen differentially spliced exons along genomic regions of interest and can be used in publication quality figures. The Sashimi plot software and documentation is available from: http://genes.mit.edu/burgelab/miso/docs/sashimi.htmlComment: 2 figure

    Carbon nanotube switches for memory, RF communications and sensing applications, and methods of making the same

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    Switches having an in situ grown carbon nanotube as an element thereof, and methods of fabricating such switches. A carbon nanotube is grown in situ in mechanical connection with a conductive substrate, such as a heavily doped silicon wafer or an SOI wafer. The carbon nanotube is electrically connected at one location to a terminal. At another location of the carbon nanotube there is situated a pull electrode that can be used to elecrostatically displace the carbon nanotube so that it selectively makes contact with either the pull electrode or with a contact electrode. Connection to the pull electrode is sufficient to operate the device as a simple switch, while connection to a contact electrode is useful to operate the device in a manner analogous to a relay. In various embodiments, the devices disclosed are useful as at least switches for various signals, multi-state memory, computational devices, and multiplexers

    Precise B, B_s and B_c meson spectroscopy from full lattice QCD

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    We give the first accurate results for BB and BsB_s meson masses from lattice QCD including the effect of uu, dd and ss sea quarks, and we improve an earlier value for the BcB_c meson mass. By using the Highly Improved Staggered Quark action for u/du/d, ss and cc quarks and NRQCD for the bb quarks, we are able to achieve an accuracy in the masses of around 10 MeV. Our results are: mBm_B = 5.291(18) GeV, mBsm_{B_s} = 5.363(11) GeV and mBcm_{B_c} = 6.280(10) GeV. Note that all QCD parameters here are tuned from other calculations, so these are parameter free tests of QCD against experiment. We also give scalar, Bs0∗B_{s0}^*, and axial vector, Bs1B_{s1}, meson masses. We find these to be slightly below threshold for decay to BKBK and B∗KB^*K respectively.Comment: 22 pages, 19 figure

    Constraints on the Atmospheric Circulation and Variability of the Eccentric Hot Jupiter XO-3b

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    We report secondary eclipse photometry of the hot Jupiter XO-3b in the 4.5~μ\mum band taken with the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. We measure individual eclipse depths and center of eclipse times for a total of twelve secondary eclipses. We fit these data simultaneously with two transits observed in the same band in order to obtain a global best-fit secondary eclipse depth of 0.1580±0.0036%0.1580\pm 0.0036\% and a center of eclipse phase of 0.67004±0.000130.67004\pm 0.00013 . We assess the relative magnitude of variations in the dayside brightness of the planet by measuring the size of the residuals during ingress and egress from fitting the combined eclipse light curve with a uniform disk model and place an upper limit of 0.05%\%. The new secondary eclipse observations extend the total baseline from one and a half years to nearly three years, allowing us to place an upper limit on the periastron precession rate of 2.9×10−32.9\times 10^{-3} degrees/day the tightest constraint to date on the periastron precession rate of a hot Jupiter. We use the new transit observations to calculate improved estimates for the system properties, including an updated orbital ephemeris. We also use the large number of secondary eclipses to obtain the most stringent limits to date on the orbit-to-orbit variability of an eccentric hot Jupiter and demonstrate the consistency of multiple-epoch Spitzer observations.Comment: 14 pages, 11 figures, published by Ap

    3.6 and 4.5 μ\mum Spitzer{\it Spitzer} Phase Curves of the Highly-Irradiated Hot Jupiters WASP-19b and HAT-P-7b

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    We analyze full-orbit phase curve observations of the transiting hot Jupiters WASP-19b and HAT-P-7b at 3.6 and 4.5 μ\mum obtained using the Spitzer Space Telescope. For WASP-19b, we measure secondary eclipse depths of 0.485%±0.024%0.485\%\pm 0.024\% and 0.584%±0.029%0.584\%\pm 0.029\% at 3.6 and 4.5 μ\mum, which are consistent with a single blackbody with effective temperature 2372±602372 \pm 60 K. The measured 3.6 and 4.5 μ\mum secondary eclipse depths for HAT-P-7b are 0.156%±0.009%0.156\%\pm 0.009\% and 0.190%±0.006%0.190\%\pm 0.006\%, which are well-described by a single blackbody with effective temperature 2667±572667\pm 57 K. Comparing the phase curves to the predictions of one-dimensional and three-dimensional atmospheric models, we find that WASP-19b's dayside emission is consistent with a model atmosphere with no dayside thermal inversion and moderately efficient day-night circulation. We also detect an eastward-shifted hotspot, suggesting the presence of a superrotating equatorial jet. In contrast, HAT-P-7b's dayside emission suggests a dayside thermal inversion and relatively inefficient day-night circulation; no hotspot shift is detected. For both planets, these same models do not agree with the measured nightside emission. The discrepancies in the model-data comparisons for WASP-19b might be explained by high-altitude silicate clouds on the nightside and/or high atmospheric metallicity, while the very low 3.6 μ\mum nightside planetary brightness for HAT-P-7b may be indicative of an enhanced global C/O ratio. We compute Bond albedos of 0 (<0.08<0.08 at 1σ1\sigma) and 0.38±0.060.38\pm 0.06 for WASP-19b and HAT-P-7b, respectively. In the context of other planets with thermal phase curve measurements, we show that WASP-19b and HAT-P-7b fit the general trend of decreasing day-night heat recirculation with increasing irradiation.Comment: 22 pages, 29 figures, accepted by Ap

    A systematic review of covered balloon-expandable stents for treating aortoiliac occlusive disease

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    Objective: To evaluate and compare studies reporting the outcomes of the use of covered balloon-expandable (CBE) stents for the treatment of aortoiliac occlusive disease. Methods: A systematic literature search was conducted to identify studies that investigated the use of CBE stents for the treatment of aortoiliac occlusive disease and were published between 2000 and 2019. Baseline demographic data, procedural variables, and long-term outcomes were extracted from publications for analysis. Results: A total of 15 published articles about 14 studies were included in the review. Of these, eight studies were prospective clinical trials and six studies were retrospective real-world studies. The articles included data regarding five different CBE stents, namely, the iCast/Advanta V12, Viabahn VBX, BeGraft, LifeStream, and JOSTENT. Lesion severity was higher in real-world studies, with more TransAtlantic Inter-Society Consensus Classification class D lesions and a higher percentage of occlusions. All studies showed high rates of technical success and patency over the course of 12 months. Long-term data were only available for the iCast/Advanta V12 device, which had a primary patency rate of 74.7% at 5 years. Conclusions: CBE stents are a viable treatment option for patients with complex aortoiliac lesions because of their high rates of technical success and favorable patency across all devices at 12 months. However, long-term data are only available for a single device, the iCast/Advanta V12. The results of using this device were favorable over the course of 5 years
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