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Chemical, structural, and electrical characterization of poly(p-phenylene vinylene)/
A 100-element HBT grid amplifier
A 100-element 10-GHz grid amplifier has been developed. The active devices in the grid are chips with heterojunction-bipolar-transistor (HBT) differential pairs. The metal grid pattern was empirically designed to provide effective coupling between the HBTs and free space. Two independent measurements, one with focusing lenses and the other without, were used to characterize the grid. In each case, the peak gain was 10 dB at 10 GHz with a 3-dB bandwidth of 1 GHz. The input and output return losses were better than 15 dB at 10 GHz. The maximum output power was 450 mW, and the minimum noise figure was 7 dB. By varying the bias, a signal could be amplitude modulated with a modulation index as large as 0.65. Tests show that the grid was quite tolerant of failures-the output power dropped by only 1 dB when 10% of the inputs were detuned. The grid amplifier is a multimode device that amplifies beams of different shapes and angles. Beams with incidence angles up to 30° were amplified with less than a 3-dB drop in gain
Fluid-Induced Propulsion of Rigid Particles in Wormlike Micellar Solutions
In the absence of inertia, a reciprocal swimmer achieves no net motion in a
viscous Newtonian fluid. Here, we investigate the ability of a reciprocally
actuated particle to translate through a complex fluid that possesses a network
using tracking methods and birefringence imaging. A geometrically polar
particle, a rod with a bead on one end, is reciprocally rotated using magnetic
fields. The particle is immersed in a wormlike micellar (WLM) solution that is
known to be susceptible to the formation of shear bands and other localized
structures due to shear-induced remodeling of its microstructure. Results show
that the nonlinearities present in this WLM solution break time-reversal
symmetry under certain conditions, and enable propulsion of an artificial
"swimmer." We find three regimes dependent on the Deborah number (De): net
motion towards the bead-end of the particle at low De, net motion towards the
rod-end of the particle at intermediate De, and no appreciable propulsion at
high De. At low De, where the particle time-scale is longer then the fluid
relaxation time, we believe that propulsion is caused by an imbalance in the
fluid first normal stress differences between the two ends of the particle
(bead and rod). At De~1, however, we observe the emergence of a region of
network anisotropy near the rod using birefringence imaging. This anisotropy
suggests alignment of the micellar network, which is "locked in" due to the
shorter time-scale of the particle relative to the fluid
Daily Step Count Predicts Acute Exacerbations in a US Cohort with COPD
Background: COPD is characterized by variability in exercise capacity and physical activity (PA), and acute exacerbations (AEs). Little is known about the relationship between daily step count, a direct measure of PA, and the risk of AEs, including hospitalizations. Methods: In an observational cohort study of 169 persons with COPD, we directly assessed PA with the StepWatch Activity Monitor, an ankle-worn accelerometer that measures daily step count. We also assessed exercise capacity with the 6-minute walk test (6MWT) and patient-reported PA with the St. George's Respiratory Questionnaire Activity Score (SGRQ-AS). AEs and COPD-related hospitalizations were assessed and validated prospectively over a median of 16 months. Results: Mean daily step count was 5804±3141 steps. Over 209 person-years of observation, there were 263 AEs (incidence rate 1.3±1.6 per person-year) and 116 COPD-related hospitalizations (incidence rate 0.56±1.09 per person-year). Adjusting for FEV1 % predicted and prednisone use for AE in previous year, for each 1000 fewer steps per day walked at baseline, there was an increased rate of AEs (rate ratio 1.07; 95%CI = 1.003â1.15) and COPD-related hospitalizations (rate ratio 1.24; 95%CI = 1.08â1.42). There was a significant linear trend of decreasing daily step count by quartiles and increasing rate ratios for AEs (P = 0.008) and COPD-related hospitalizations (P = 0.003). Each 30-meter decrease in 6MWT distance was associated with an increased rate ratio of 1.07 (95%CI = 1.01â1.14) for AEs and 1.18 (95%CI = 1.07â1.30) for COPD-related hospitalizations. Worsening of SGRQ-AS by 4 points was associated with an increased rate ratio of 1.05 (95%CI = 1.01â1.09) for AEs and 1.10 (95%CI = 1.02â1.17) for COPD-related hospitalizations. Conclusions: Lower daily step count, lower 6MWT distance, and worse SGRQ-AS predict future AEs and COPDârelated hospitalizations, independent of pulmonary function and previous AE history. These results support the importance of assessing PA in patients with COPD, and provide the rationale to promote PA as part of exacerbation-prevention strategies
Valproate Protein Binding Is Highly Variable in ICU Patients and Not Predicted by Total Serum Concentrations: A Case Series and Literature Review
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136503/1/phar1912-sup-0001-SupInfo.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136503/2/phar1912_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136503/3/phar1912.pd
Phase diagram of insulating crystal and quantum Hall states in ABC-stacked trilayer graphene
In the presence of a perpendicular magnetic field, ABC-stacked trilayer
graphene's chiral band structure supports a 12-fold degenerate N=0 Landau level
(LL). Along with the valley and spin degrees of freedom, the zeroth LL contains
additional quantum numbers associated with the LL orbital index .
Remote inter-layer hopping terms and external potential difference
between the layers lead to LL splitting by introducing a gap
between the degenerate zero-energy triplet LL orbitals. Assuming that the spin
and valley degrees of freedom are frozen, we study the phase diagram of this
system resulting from competition of the single particle LL splitting and
Coulomb interactions within the Hartree-Fock approximation at integer filling
factors. Above a critical value of the external potential
difference i,e, for , the ground state is a
uniform quantum Hall state where the electrons occupy the lowest unoccupied LL
orbital index. For (which corresponds to large
positive or negative values of ) the uniform QH state is unstable
to the formation of a crystal state at integer filling factors. This phase
transition should be characterized by a Hall plateau transition as a function
of at a fixed filling factor. We also study the properties of
this crystal state and discuss its experimental detection.Comment: 16 pages with 13 figure
KELT-20b: A Giant Planet with a Period of P ~ 3.5 days Transiting the V ~ 7.6 Early A Star HD 185603
We report the discovery of KELT-20b, a hot Jupiter transiting a V ~ 7.6 early A star, HD 185603, with an orbital period of P â
3.47 days. Archival and follow-up photometry, Gaia parallax, radial velocities, Doppler tomography, and AO imaging were used to confirm the planetary nature of KELT-20b and characterize the system. From global modeling we infer that KELT-20 is a rapidly rotating (Îœ sin I* â 120 km s^(-1)) A2V star with an effective temperature of T_(eff) = 8730^(+250)_(-260) K, mass of, M* = ^(+0.14)_(-0.20) Mâ radius of, R* = 1.561^(+0.058)_(-0.064) Râ surface gravity of, log g* = 4.292^(+0.017)_(-0.020), and age of âŸ600 Myr. The planetary companion has a radius of R_P = 1.735^(+0.070)_(-0.075) R_J, a semimajor axis of a = 0.0542^(+0.0014)_(-0.0021) au, and a linear ephemeris of BJD_(TDB) = 2457503.120049 ± 0.000190 + E(3.4741070 ± 0.0000019). We place a 3Ï upper limit of ~3.5 M_J on the mass of the planet. Doppler tomographic measurements indicate that the planetary orbit normal is well aligned with the projected spin axis of the star (λ = 3.°4± 2.°1). The inclination of the star is constrained to 24.°4 < I* < 155.°6, implying a three-dimensional spinâorbit alignment of 1.°3 < Ï < 69.°8. KELT-20b receives an insolation flux of ~8 x 10^9 erg s^(-1) cm^(-2), implying an equilibrium temperature of of ~2250 K, assuming zero albedo and complete heat redistribution. Due to the high stellar T_(eff), KELT-20b also receives an ultraviolet (wavelength d â©œ 91.2 nm) insolation flux of ~9.1 x 10^4 erg s^(-1) cm^(-2), possibly indicating significant atmospheric ablation. Together with WASP-33, Kepler-13 A, HAT-P-57, KELT-17, and KELT-9, KELT-20 is the sixth A star host of a transiting giant planet, and the third-brightest host (in V) of a transiting planet
Plasticity in the antipredator behavior of the orange-footed sea cucumber under shifting hydrodynamic forces
Marine invertebrates that move too slowly to evade unfavorable environmental change may instead exhibit phenotypic plasticity, allowing them to adjust to varying conditions. The orange-footed sea cucumber Cucumaria frondosa is a slow-moving suspension feeder that is preyed on by the purple sunstar Solaster endeca. The sea cucumberâs antipredator behavior involves changing shape and detaching from the substratum, which might increase its probability of being displaced by water motion into an unsuitable environment. We hypothesized that sea cucumbersâ antipredator responses
would be diminished under stronger hydrodynamic forces, and that behavioral strategies would be
flexible so that individuals could adjust to frequent changes in water flows. In a natural orange-footed
sea cucumber habitat, individuals lived along a pronounced hydrodynamic gradient, allowing us to
measure antipredator behavior under different water flow strengths. We placed purple sunstars in physical contact with sea cucumbers living at various points along the gradient to elicit antipredator responses. We then repeated this procedure in a laboratory mesocosm that generated weak and strong hydrodynamic forces similar to those observed at the field site. Subjects in the mesocosm experiment were tested in both wave conditions to determine if their antipredator behavior would change in response to sudden environmental change, as would be experienced under deteriorating sea conditions.
Antipredator responses did not covary with hydrodynamic forces in the field. However, antipredator responses in the mesocosm experiment increased when individuals were transplanted from strong to weak forces and decreased when transplanted from weak to strong forces. Overall, our results indicate environmentally induced plasticity in the antipredator behavior of the orange-footed sea cucumber
The script concordance test in radiation oncology: validation study of a new tool to assess clinical reasoning
<p>Abstract</p> <p>Background</p> <p>The Script Concordance test (SCT) is a reliable and valid tool to evaluate clinical reasoning in complex situations where experts' opinions may be divided. Scores reflect the degree of concordance between the performance of examinees and that of a reference panel of experienced physicians. The purpose of this study is to demonstrate SCT's usefulness in radiation oncology.</p> <p>Methods</p> <p>A 90 items radiation oncology SCT was administered to 155 participants. Three levels of experience were tested: medical students (n = 70), radiation oncology residents (n = 38) and radiation oncologists (n = 47). Statistical tests were performed to assess reliability and to document validity.</p> <p>Results</p> <p>After item optimization, the test comprised 30 cases and 70 questions. Cronbach alpha was 0.90. Mean scores were 51.62 (± 8.19) for students, 71.20 (± 9.45) for residents and 76.67 (± 6.14) for radiation oncologists. The difference between the three groups was statistically significant when compared by the Kruskall-Wallis test (p < 0.001).</p> <p>Conclusion</p> <p>The SCT is reliable and useful to discriminate among participants according to their level of experience in radiation oncology. It appears as a useful tool to document the progression of reasoning during residency training.</p
A SAS macro for a clustered logrank test
The clustered logrank test is a nonparametric method of significance testing for correlated survival data. Examples of its application include cluster randomized trials where groups of patients rather than individuals are randomized to either a treatment or control intervention. We describe a SAS macro that implements the 2-sample clustered logrank test for data where the entire cluster is randomized to the same treatment group. We discuss the theory and applications behind this test as well as details of the SAS code
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