Observation of fast stochastic ion heating by drift waves

Anomalously fast ion heating has been observed in the Caltech Encore tokamak [Phys. Rev. Lett. 59, 1436 (1987)], with the use of laser-induced fluorescence. This heating was found to be independent of electron temperature, but was well correlated with the presence of large-amplitude drift-Alfvén waves. Evidence is presented that suggests that the heating is stochastic and occurs when the ion displacement due to polarization drift becomes comparable to the perpendicular wavelength, i.e., when k[perpendicular] (mik[perpendicular] phi0/qB^2)~1. Stochastic heating may also be the cause of the anomalously high ion temperatures observed in reversed-field pinches

Rural Hospital Nursing Skill Mix and Work Environment Associated with Frequency of Adverse Events.

Introduction: Though rural hospitals serve about one fifth of the United States (U.S.), few studies have investigated relationships among nursing resources and rural hospital adverse events. Objectives: The purpose was to determine relationships among nursing skill mix (proportion of Registered Nurses (RNs) to all nursing staff), the work environment and adverse events (medication errors, patient falls with injury, pressure ulcers, and urinary tract infections) in rural hospitals. Methods: Using a cross-sectional design, nurse survey data from a large study examining nurse organizational factors, patient safety, and quality from four U.S. states were linked to the 2006 American Hospital Association data. The work environment was measured using the Practice Environment Scale of the Nursing Work Index (PES-NWI). Nurses reported adverse event frequency. Data analyses were descriptive and inferential. Results: On average, 72% of nursing staff were RNs (range = 45% to 100%). Adverse event frequency ranged from 0% to 67%, across 76 hospitals. In regression models, a 10-point increase in the proportion of RNs among all nursing staff and a one standard deviation increase in the PES-NWI score were significantly associated with decreased odds of frequent adverse events. Conclusion: Rural hospitals that increase the nursing skill mix and improve the work environment may achieve reduced adverse event frequency

Anderson Transition in Disordered Graphene

We use the regularized kernel polynomial method (RKPM) to numerically study the effect disorder on a single layer of graphene. This accurate numerical method enables us to study very large lattices with millions of sites, and hence is almost free of finite size errors. Within this approach, both weak and strong disorder regimes are handled on the same footing. We study the tight-binding model with on-site disorder, on the honeycomb lattice. We find that in the weak disorder regime, the Dirac fermions remain extended and their velocities decrease as the disorder strength is increased. However, if the disorder is strong enough, there will be a {\em mobility edge} separating {\em localized states around the Fermi point}, from the remaining extended states. This is in contrast to the scaling theory of localization which predicts that all states are localized in two-dimensions (2D).Comment: 4 page

Temperature fluctuations and heat transport in the edge regions of a tokamak

Electron temperature fluctuations have been investigated in the edge region of the Caltech research tokamak [S. J. Zweben and R. W. Gould, Nucl. Fusion 25, 171 (1985)], and an upper limit to this fluctuation level was found at Te/Te <~ 15%. This measurement, together with previous measurements of density and electric and magnetic field fluctuations, allows a unique comparison of the heat transport resulting from three basic turbulent mechanisms: (1) heat flux from the particle flux resulting from microscopic density and electric field fluctuations; (2) thermal conduction resulting from microscopic temperature and electric field fluctuations; and (3) thermal conduction resulting from microscopic magnetic field fluctuations. The measurements indicate that, in the edge regions, the electron heat transport caused by the measured turbulence-induced particle flux is comparable to or greater than that caused by the thermal conduction associated with the electron temperature and electric field fluctuations, and is significantly greater than that resulting from the measured magnetic fluctuations. This electron heat loss caused by the plasma turbulence is found to be an important electron energy loss mechanism in the edge regions

The Interaction of Fast Alpha Particles with Pellet Ablation Clouds

The energy spectra of energetic confined alpha particles are being measured using the pellet charge exchange method [R. K. Fisher, J. S. Leffler, A. M. Howald, and P. B. Parks, Fusion Technol. 13, 536 (1988)]. The technique uses the dense ablation cloud surrounding an injected impurity pellet to neutralize a fraction of the incident alpha particles, allowing them to escape from the plasma where their energy spectrum can be measured using a neutral particle analyzer. The signal calculations given in the above-mentioned reference disregarded the effects of the alpha particles\u27 helical Larmor orbits, which causes the alphas to make multiple passes through the cloud. Other effects such as electron ionization by plasma and ablation cloud electrons and the effect of the charge state composition of the cloud, were also neglected. This report considers these issues, reformulates the signal level calculation, and uses a Monte-Carlo approach to calculate the neutralization fractions. The possible effects of energy loss and pitch angle scattering of the alphas are also considered. © 1997 American Institute of Physics

Ultracold Neutron Production in a Pulsed Neutron Beam Line

We present the results of an Ultracold neutron (UCN) production experiment in a pulsed neutron beam line at the Los Alamos Neutron Scattering Center. The experimental apparatus allows for a comprehensive set of measurements of UCN production as a function of target temperature, incident neutron energy, target volume, and applied magnetic field. However, the low counting statistics of the UCN signal expected can be overwhelmed by the large background associated with the scattering of the primary cold neutron flux that is required for UCN production. We have developed a background subtraction technique that takes advantage of the very different time-of-flight profiles between the UCN and the cold neutrons, in the pulsed beam. Using the unique timing structure, we can reliably extract the UCN signal. Solid ortho-D$_2$ is used to calibrate UCN transmission through the apparatus, which is designed primarily for studies of UCN production in solid O$_2$. In addition to setting the overall detection efficiency in the apparatus, UCN production data using solid D$_2$ suggest that the UCN upscattering cross-section is smaller than previous estimates, indicating the deficiency of the incoherent approximation widely used to estimate inelastic cross-sections in the thermal and cold regimes

The Effects of Functional Fatigue on Ground Reaction Forces of a Jump, Land, and Cut Task

Rapid acceleration, deceleration, landing and change of direction have been implicated as mechanisms of noncontact anterior cruciate ligament (ACL) injury. PURPOSE: To examine the ground reaction forces occurring to the knee during non-fatigued and fatigued jump, land and cut maneuvers in three unplanned cutting directions. METHODS: Eleven healthy, adult female collegiate soccer athletes participated in this study (age= 20.3±0.9 years; height= 167.4±4.8 cm; mass= 63.7±7.7 kg). Each subject was instructed to perform 9 jump, land, and cut maneuvers in a pre-fatigued state and fatigued state. The protocols were randomly assigned to include 3 cuts in each of the three directions. The functional fatigue protocol consisted of rapid acceleration, deceleration, and change of direction activities. A 2x2 ANOVA design was used to compare groups (fatigue state) and (leg dominance). RESULTS: Differences were noted in the medial direction during the left cut land (p=0.049). Differences in the anterior-posterior forces occurred during fatigued landing tasks for all three cutting directions (left, p=0.049; center, p=0.000; right, p=0.009), and for the center cut push off (p=0.020). Fatigue appeared to have a significant impact on the vertical push off of all three directions (left, p=0.023; center, p=0.000; right, p=0.047). CONCLUSION: Fatigue has an important impact on jump, land and cut maneuvers regardless of cutting direction. Fatigue was noted to impact the anterior-posterior direction the most during landing which is significant as the primary purpose of the ACL is to prevent anterior shear force of the tibia on the femur during motion. Fatigue may prove to be a predominant risk factor for ACL injuries