2,415 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.
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
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
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
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
We give the first accurate results for and meson masses from
lattice QCD including the effect of , and sea quarks, and we improve
an earlier value for the meson mass. By using the Highly Improved
Staggered Quark action for , and quarks and NRQCD for the
quarks, we are able to achieve an accuracy in the masses of around 10 MeV. Our
results are: = 5.291(18) GeV, = 5.363(11) GeV and =
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, , and axial vector, , meson masses. We find
these to be slightly below threshold for decay to and respectively.Comment: 22 pages, 19 figure
Constraints on the Atmospheric Circulation and Variability of the Eccentric Hot Jupiter XO-3b
We report secondary eclipse photometry of the hot Jupiter XO-3b in the
4.5~m 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 and a center of
eclipse phase of . 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 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 m Phase Curves of the Highly-Irradiated Hot Jupiters WASP-19b and HAT-P-7b
We analyze full-orbit phase curve observations of the transiting hot Jupiters
WASP-19b and HAT-P-7b at 3.6 and 4.5 m obtained using the Spitzer Space
Telescope. For WASP-19b, we measure secondary eclipse depths of and at 3.6 and 4.5 m, which are consistent
with a single blackbody with effective temperature K. The
measured 3.6 and 4.5 m secondary eclipse depths for HAT-P-7b are
and , which are well-described by a
single blackbody with effective temperature 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 m nightside planetary brightness for
HAT-P-7b may be indicative of an enhanced global C/O ratio. We compute Bond
albedos of 0 ( at ) and 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
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
- …