Preferences for self-service meat among household consumers in metropolitan St. Louis

Also available online.Digitized 2007 AES

Simulated Galactic Cosmic Radiation Exposure Impairs Mouse Vertebral Bone Adaptations to Exercise During Recovery From Partial Weightbearing

Partial weightbearing that simulates Lunar gravity (1/6th of Earth’s gravitational force) results in a loss of bone volume. High energy radiation like that found in galactic cosmic radiation exposure also negatively affects the skeleton. Because resistance training is the most effective exercise mode to counteract disuse-induced bone loss, this experiment combined low-dose, high-energy simulated galactic cosmic radiation (GCR) exposure, followed by a period of partial weightbearing (PWB), and then a period of resistance exercise or normal cage activity during recovery. Young adult female BALB/c mice were randomly assigned to age-matched cage controls (CC) or PWB (G/6) groups. From there, animals were further divided into 0.5 Gy 36Fe radiation exposure (RAD) or sham exposure (SHAM) groups. Radiation exposure was performed at NASA’s Space Radiation Laboratory at Brookhaven National Laboratory before shipping to Texas A&M. GCR was followed by a 21-day period of PWB, equivalent to being placed in a simulated lunar gravity environment. A 21-day recovery period began on Day 22, during which PWB animals were assigned to one of two groups: recovery with normal cage activity (G/6 + Rec) or resistance training during recovery (G/6 + RecEX). The latter group was trained three times every four days with a tower climbing training regimen, climbing a 1-meter wire mesh tower at an 85° angle. This training was repeated for a total of 15 climb sessions. As the exercise period progressed, weights were taped on to the mice tails. Ex vivo micro-computed tomography (μCT) scans were performed by Matthew Allen, PhD at the Indiana University School of Medicine to quantify cancellous bone microarchitecture in the 4th lumbar vertebral body. Means for cancellous bone volume (%BV/TV), trabecular thickness (Tb.Th), and trabecular number (Tb.N) from Day 42 of the experiment were compared to Day 21 means by 2-way ANOVA to determine the changes occurring through the recovery period. RecEX had no significant affect on ∆BV/TV or ∆Tb.Th, but ∆BV/TV and ∆Tb.Th were significantly lower in RAD groups than in SHAM groups (p\u3c0.001). ∆Tb.N was significantly higher in exercised groups than non-exercised groups (p\u3c0.05), but no significant differences in ∆Tb.N were shown between RAD and SHAM groups. These data suggest that GCR exposure diminishes the ability of bone to respond to exercise during recovery form a period of reduced weightbearing

Stick-slip motion of solids with dry friction subject to random vibrations and an external field

We investigate a model for the dynamics of a solid object, which moves over a randomly vibrating solid surface and is subject to a constant external force. The dry friction between the two solids is modeled phenomenologically as being proportional to the sign of the object's velocity relative to the surface, and therefore shows a discontinuity at zero velocity. Using a path integral approach, we derive analytical expressions for the transition probability of the object's velocity and the stationary distribution of the work done on the object due to the external force. From the latter distribution, we also derive a fluctuation relation for the mechanical work fluctuations, which incorporates the effect of the dry friction.Comment: v1: 23 pages, 9 figures; v2: Reference list corrected; v3: Published version, typos corrected, references adde

Direct Hopf Bifurcation in Parametric Resonance of Hybridized Waves

We study parametric resonance of interacting waves having the same wave vector and frequency. In addition to the well-known period-doubling instability we show that under certain conditions the instability is caused by a Hopf bifurcation leading to quasiperiodic traveling waves. It occurs, for example, if the group velocities of both waves have different signs and the damping is weak. The dynamics above the threshold is briefly discussed. Examples concerning ferromagnetic spin waves and surface waves of ferro fluids are discussed.Comment: Appears in Phys. Rev. Lett., RevTeX file and three postscript figures. Packaged using the 'uufiles' utility, 33 k

Development and validation of the ACE tool: Assessing medical trainees' competency in evidence based medicine

BACKGROUND: While a variety of instruments have been developed to assess knowledge and skills in evidence based medicine (EBM), few assess all aspects of EBM - including knowledge, skills attitudes and behaviour - or have been psychometrically evaluated. The aim of this study was to develop and validate an instrument that evaluates medical trainees’ competency in EBM across knowledge, skills and attitude. METHODS: The ‘Assessing Competency in EBM’ (ACE) tool was developed by the authors, with content and face validity assessed by expert opinion. A cross-sectional sample of 342 medical trainees representing ‘novice’, ‘intermediate’ and ‘advanced’ EBM trainees were recruited to complete the ACE tool. Construct validity, item difficulty, internal reliability and item discrimination were analysed. RESULTS: We recruited 98 EBM-novice, 108 EBM-intermediate and 136 EBM-advanced participants. A statistically significant difference in the total ACE score was observed and corresponded to the level of training: on a 0-15-point test, the mean ACE scores were 8.6 for EBM-novice; 9.5 for EBM-intermediate; and 10.4 for EBM-advanced (p < 0.0001). Individual item discrimination was excellent (Item Discrimination Index ranging from 0.37 to 0.84), with internal reliability consistent across all but three items (Item Total Correlations were all positive ranging from 0.14 to 0.20). CONCLUSION: The 15-item ACE tool is a reliable and valid instrument to assess medical trainees’ competency in EBM. The ACE tool provides a novel assessment that measures user performance across the four main steps of EBM. To provide a complete suite of instruments to assess EBM competency across various patient scenarios, future refinement of the ACE instrument should include further scenarios across harm, diagnosis and prognosis

Direct Observations of Rapid Diffusion of Cu in Au Thin Films using In-Situ X-ray Diffraction

In-situ x-ray diffraction was performed while annealing thin-film Au/Cu binary diffusion couples to directly observe diffusion at elevated temperatures. The temperature dependence of the interdiffusion coefficient was determined from isothermal measurements at 700 C, 800 C, and 900 C, where Cu and Au form a disordered continuous face centered cubic solid solution. Large differences in the lattice parameters of Au and Cu allowed the initial diffraction peaks to be easily identified, and later tracked as they merged into one diffraction peak with increased diffusion time. Initial diffusion kinetics were studied by measuring the time required for the Cu to diffuse through the Au thin film of known thickness. The activation energy for interdiffusion was measured to be 65.4 kJ/mole during this initial stage, which is approximately 0.4x that for bulk diffusion and 0.8x that for grain boundary diffusion. The low activation energy is attributed to the high density of columnar grain boundaries combined with other defects in the sputter deposited thin film coatings. As interdiffusion continues, the two layers homogenize with an activation energy of 111 kJ/mole during the latter stages of diffusion. This higher activation energy falls between the reported values for grain boundary and bulk diffusion, and may be related to grain growth occurring at these temperatures which accounts for the decreasing importance of grain boundaries on diffusion

Long-term NIR Variability in the UKIDSS Ultra Deep Survey:a new probe of AGN activity at high redshift

We present the first attempt to select AGN using long-term NIR variability. By analysing the K-band light curves of all the galaxies in the UKIDSS Ultra Deep Survey, the deepest NIR survey over ~1 sq degree, we have isolated 393 variable AGN candidates. A comparison to other selection techniques shows that only half of the variable sources are also selected using either deep Chandra X-ray imaging or IRAC colour selection, suggesting that using NIR variability can locate AGN that are missed by more standard selection techniques. In particular, we find that long-term NIR variability identifies AGN at low luminosities and in host galaxies with low stellar masses, many of which appear relatively X-ray quiet.Comment: 12 pages, 18 figures, accepted for publication in MNRAS, an error in Equation 1 has been fixed in this versio

Brownian motion with dry friction: Fokker-Planck approach

We solve a Langevin equation, first studied by de Gennes, in which there is a solid-solid or dry friction force acting on a Brownian particle in addition to the viscous friction usually considered in the study of Brownian motion. We obtain both the time-dependent propagator of this equation and the velocity correlation function by solving the associated time-dependent Fokker-Planck equation. Exact results are found for the case where only dry friction acts on the particle. For the case where both dry and viscous friction forces are present, series representations of the propagator and correlation function are obtained in terms of parabolic cylinder functions. Similar series representations are also obtained for the case where an external constant force is added to the Langevin equation.Comment: 18 pages, 13 figures (in color

Phase Diffusion in Localized Spatio-Temporal Amplitude Chaos

We present numerical simulations of coupled Ginzburg-Landau equations describing parametrically excited waves which reveal persistent dynamics due to the occurrence of phase slips in sequential pairs, with the second phase slip quickly following and negating the first. Of particular interest are solutions where these double phase slips occur irregularly in space and time within a spatially localized region. An effective phase diffusion equation utilizing the long term phase conservation of the solution explains the localization of this new form of amplitude chaos.Comment: 4 pages incl. 5 figures uucompresse