479 research outputs found
Electrowetting at the nanoscale
Using molecular simulations of nano-sized aqueous droplets on a model graphite surface we demonstrate remarkable sensitivity of water contact angles to the applied electric field polarity and direction relative to the liquid/solid interface. The effect is explained by analyzing the influence of the field on interfacial hydrogen bonding in the nanodrop, which in turn affects the interfacial tensions. The observed anisotropy in droplet wetting is a new nanoscale phenomenon that has so far been elusive as, in current experimental setups, surface molecules represent a very low fraction of the total number affected by the field. Our findings may have important implications for the design of electrowetting techniques in fabrication and property tuning of nanomaterials
Crossover between two different magnetization reversal modes in arrays of iron oxide nanotubes
The magnetization reversal in ordered arrays of iron oxide nanotubes of 50 nm
outer diameter grown by atomic layer deposition is investigated theoretically
as a function of the tube wall thickness, . In thin tubes (
nm) the reversal of magnetization is achieved by the propagation of a vortex
domain boundary, while in thick tubes ( nm) the reversal is driven by
the propagation of a transverse domain boundary. Magnetostatic interactions
between the tubes are responsible for a decrease of the coercive field in the
array. Our calculations are in agreement with recently reported experimental
results. We predict that the crossover between the vortex and transverse modes
of magnetization reversal is a general phenomenon on the length scale
considered.Comment: 8 pages, 7 figure
ACBAR: The Arcminute Cosmology Bolometer Array Receiver
We describe the Arcminute Cosmology Bolometer Array Receiver (ACBAR); a
multifrequency millimeter-wave receiver designed for observations of the Cosmic
Microwave Background (CMB) and the Sunyaev-Zel'dovich effect in clusters of
galaxies. The ACBAR focal plane consists of a 16-pixel, background-limited, 240
mK bolometer array that can be configured to observe simultaneously at 150,
220, 280, and 350 GHz. With 4-5' FWHM Gaussian beam sizes and a 3 degree
azimuth chop, ACBAR is sensitive to a wide range of angular scales. ACBAR was
installed on the 2 m Viper telescope at the South Pole in January 2001. We
describe the design of the instrument and its performance during the 2001 and
2002 observing seasons.Comment: 59 pages, 16 figures -- updated to reflect version published in ApJ
Monitoring External Training Loads and Neuromuscular Performance for Division I Basketball Players over the Preseason
Limited research has paralleled concomitant changes in external training load (eTL) and countermovement jump (CMJ) performance. Therefore, this investigation characterized eTL and CMJ performance changes across preseason training in Division 1 male collegiate basketball athletes, while examining the influence of position (Guard vs. Forward/Center) and scholarship status (Scholarship = S vs. Walk-on = WO). During 22 practices, eTL was monitored in 14 male athletes, with weekly CMJs performed to quantify neuromuscular performance (Jump Height [JH], Flight Time:Contraction Time [FT:CT], Reactive Strength Index Modified [RSIMod ]). PlayerLoad per minute was significantly higher during W1 and W2 (5.4 ± 1.3au and 5.3 ± 1.2au, respectively; p < 0.05) compared to subsequent weeks, but no additional differences in eTL parameters across time were observed. Scholarship athletes displayed greater PlayerLoad (S = 777.1 ± 35.6, WO = 530.1 ± 56.20; Inertial Movement Analysis (IMA) IMA_High (S = 70.9 ± 15.2, WO = 41.3 ± 15.2); IMA_Medium (S = 159.9 ± 30.7, WO = 92.7 ± 30.6); and IMA_Low (S = 700.6 ± 105.1, WO = 405 ± 105.0;) (p < 0.05), with no observed differences in eTL by position. Moderate decreases in FT:CT and RSIMod paralleled increased eTL. Significant increases in practice intensity (W1 and W2) did not impact CMJ performance, suggesting athletes could cope with the prescribed training loads. However, moderate perturbations in FT:CT and RSIMod paralleled the weeks with intensified training. Cumulatively, scholarship status appears to influence eTL while player position does not.The authors would like to thank Mr. Brady Brown and Mr. Keldon Peak for their assistance with this project. Additionally, the authors thank the Basketball Programs at the University of Oklahoma for their continued support of research directed at enhancing athlete performance, while also improving overall student-athlete welfare. Finally, the authors would also like to thank all of the student-athletes that graciously volunteered their time to enroll and participate in this study. The experiments comply with the current laws of the country in which they were performed. The authors have no conflict of interest to declare.
Open Access fees paid for in whole or in part by the University of Oklahoma Libraries.Ye
High resolution CMB power spectrum from the complete ACBAR data set
In this paper, we present results from the complete set of cosmic microwave
background (CMB) radiation temperature anisotropy observations made with the
Arcminute Cosmology Bolometer Array Receiver (ACBAR) operating at 150 GHz. We
include new data from the final 2005 observing season, expanding the number of
detector-hours by 210% and the sky coverage by 490% over that used for the
previous ACBAR release. As a result, the band-power uncertainties have been
reduced by more than a factor of two on angular scales encompassing the third
to fifth acoustic peaks as well as the damping tail of the CMB power spectrum.
The calibration uncertainty has been reduced from 6% to 2.1% in temperature
through a direct comparison of the CMB anisotropy measured by ACBAR with that
of the dipole-calibrated WMAP5 experiment. The measured power spectrum is
consistent with a spatially flat, LambdaCDM cosmological model. We include the
effects of weak lensing in the power spectrum model computations and find that
this significantly improves the fits of the models to the combined ACBAR+WMAP5
power spectrum. The preferred strength of the lensing is consistent with
theoretical expectations. On fine angular scales, there is weak evidence (1.1
sigma) for excess power above the level expected from primary anisotropies. We
expect any excess power to be dominated by the combination of emission from
dusty protogalaxies and the Sunyaev-Zel'dovich effect (SZE). However, the
excess observed by ACBAR is significantly smaller than the excess power at ell
> 2000 reported by the CBI experiment operating at 30 GHz. Therefore, while it
is unlikely that the CBI excess has a primordial origin; the combined ACBAR and
CBI results are consistent with the source of the CBI excess being either the
SZE or radio source contamination.Comment: Submitted to ApJ; Changed to apply a WMAP5-based calibration. The
cosmological parameter estimation has been updated to include WMAP
- …