Microscopic mechanisms of thermal and driven diffusion of non rigid molecules on surfaces

The motion of molecules on solid surfaces is of interest for technological applications such as catalysis and lubrication, but it is also a theoretical challenge at a more fundamental level. The concept of activation barriers is very convenient for the interpretation of experiments and as input for Monte Carlo simulations but may become inadequate when mismatch with the substrate and molecular vibrations are considered. We study the simplest objects diffusing on a substrate at finite temperature $T$, namely an adatom and a diatomic molecule (dimer), using the Langevin approach. In the driven case, we analyse the characteristic curves, comparing the motion for different values of the intramolecular spacing, both for T=0 and $T\ne 0$. The mobility of the dimer is higher than that of the monomer when the drift velocity is less than the natural stretching frequency. The role of intramolecular excitations is crucial in this respect. In the undriven case, the diffusive dynamics is considered as a function of temperature. Contrary to atomic diffusion, for the dimer it is not possible to define a single, temperature independent, activation barrier. Our results suggest that vibrations can account for drastic variations of the activation barrier. This reveals a complex behaviour determined by the interplay between vibrations and a temperature dependent intramolecular equilibrium length.Comment: 6 pages, 5 figures, Proceeding of the EMRS 2002 Conference, to be published in Thin Solid Film

Development of Replacement Heifers using Combinations of Three Forage Types and Feed Supplements (with or without Broiler Litter)

The proper management of replacement heifers is an essential component of successful cow/calf operations. The level of management and nutrition applied to replacement heifers as calves and yearlings can impact their subsequent reproductive performance and productivity

Impact of Velcro Cuff Closure on Forearm Skin Temperature In Surfers Wearing a 2mm and 3mm Wetsuit

International Journal of Exercise Science 13(6): 1574-1582, 2020. Surfing is a worldwide sport that often requires participants to wear a wetsuit to assist in thermoregulation. In a recent study, forearm skin temperature decreased by approximately 3 °C while wearing a wetsuit during recreational surfing. The purpose of this study was to test the hypothesis that reducing water flow in and out of the wetsuit by cuffing the wetsuit at the wrist, with a novel cuff closure system (Velcro cuff), would result in greater forearm skin temperature while surfing. One hundred and twelve (94 male, 18 female) recreational surfers between the ages of 18-50 participated in this study. Forearm skin temperature was measured at 1-minute intervals across the surf session in both arms with four wireless iButton thermal sensors located two inches from the styloid process (wrist) and olecranon process (elbow). Following instrumentation, all subjects had one of their wrists randomly cuffed with a one-inch wide Velcro cuff that was tightened to 2 cm less than the circumference of the wrist plus wetsuit. Subjects were then instructed to engage in regular recreational surfing activities for a minimum of 30 minutes at seven beaches in North San Diego County from October to April. No significant differences were found between the average cuffed wrist skin temperature and the average uncuffed wrist skin temperature (p = 0.06). However, average cuffed forearm skin temperature was significantly higher than average uncuffed forearm skin temperature (p = 0.01). Results from this study suggest that cuffing the wrist of wetsuits is a simple technique that can be utilized by surfers to significantly improve forearm skin temperature during surfing. These findings may also have an implication on future wetsuit designs

A comparison of spectral element and finite difference methods using statically refined nonconforming grids for the MHD island coalescence instability problem

A recently developed spectral-element adaptive refinement incompressible magnetohydrodynamic (MHD) code [Rosenberg, Fournier, Fischer, Pouquet, J. Comp. Phys. 215, 59-80 (2006)] is applied to simulate the problem of MHD island coalescence instability (MICI) in two dimensions. MICI is a fundamental MHD process that can produce sharp current layers and subsequent reconnection and heating in a high-Lundquist number plasma such as the solar corona [Ng and Bhattacharjee, Phys. Plasmas, 5, 4028 (1998)]. Due to the formation of thin current layers, it is highly desirable to use adaptively or statically refined grids to resolve them, and to maintain accuracy at the same time. The output of the spectral-element static adaptive refinement simulations are compared with simulations using a finite difference method on the same refinement grids, and both methods are compared to pseudo-spectral simulations with uniform grids as baselines. It is shown that with the statically refined grids roughly scaling linearly with effective resolution, spectral element runs can maintain accuracy significantly higher than that of the finite difference runs, in some cases achieving close to full spectral accuracy.Comment: 19 pages, 17 figures, submitted to Astrophys. J. Supp

Magnetic Surfaces in Stationary Axisymmetric General Relativity

In this paper a new method is derived for constructing electromagnetic surface sources for stationary axisymmetric electrovac spacetimes endowed with non-smooth or even discontinuous Ernst potentials. This can be viewed as a generalization of some classical potential theory results, since lack of continuity of the potential is related to dipole density and lack of smoothness, to monopole density. In particular this approach is useful for constructing the dipole source for the magnetic field. This formalism involves solving a linear elliptic differential equation with boundary conditions at infinity. As an example, two different models of surface densities for the Kerr-Newman electrovac spacetime are derived.Comment: 15 page

Characterization of Adult Heart Rate Responses During Recreational Skateboarding at Community Skateparks

International Journal of Exercise Science 13(2): 501-510, 2020. Youth participating in recreational skating at community skate parks attain exercise intensities and durations that are comparable with the CDC’s exercise recommendations for cardiovascular fitness for their age group. However, it is currently unclear if adults who skateboard in the same environment also achieve the recommended intensities and durations for cardiovascular fitness. Therefore, the purpose of this study was to test the hypothesis that skateboarding would elicit heart rates and durations consistent with the CDC’s recommendations for cardiovascular fitness in adults. Fifty-five subjects between ages 18-55 were recruited from six community skateparks for this study. Subjects completed a questionnaire and were instrumented with a Polar V800 heart rate receiver on the left wrist and an H7 Bluetooth heart rate transmitter around the chest below the pectoralis major. Participants were instructed to engage in a typical skateboarding session on their own board with the duration and intensity of activity to be determined by the participant. The mean age of the participants was 27.4 ± 8.5 years, and participants reported skateboarding at a community skate park a mean of 3.1 ± 1.8 days/week. Participants had a mean heart rate of 138.2 ± 21.9 beats per minute (71.7% of age predicted maximum), skated for 65.5 ± 36.2 minutes, and traveled 4.56 ± 4.5 kilometers. Subjects spent 70% of their total duration at moderate-intensity or above and 30% within the low, and below low-intensity range. Results from this study suggest that adults participating in recreational skateboarding in community skateparks achieve the CDC’s exercise recommendations for cardiovascular fitness. These findings may have implications for community skatepark design and professional training programs for adult skateboarding athletes

An intraorganizational model for developing and spreading quality improvement innovations

BACKGROUND Recent policy reforms encourage quality improvement (QI) innovations in primary care, but practitioners lack clear guidance regarding spread inside organizations. PURPOSE We designed this study to identify how large organizations can facilitate intraorganizational spread of QI innovations. METHODOLOGY/APPROACH We conducted ethnographic observation and interviews in a large, multispecialty, community-based medical group that implemented three QI innovations across 10 primary care sites using a new method for intraorganizational process development and spread. We compared quantitative outcomes achieved through the group's traditional versus new method, created a process model describing the steps in the new method, and identified barriers and facilitators at each step. FINDINGS The medical group achieved substantial improvement using its new method of intraorganizational process development and spread of QI innovations: standard work for rooming and depression screening, vaccine error rates and order compliance, and Pap smear error rates. Our model details nine critical steps for successful intraorganizational process development (set priorities, assess the current state, develop the new process, and measure and refine) and spread (develop support, disseminate information, facilitate peer-to-peer training, reinforce, and learn and adapt). Our results highlight the importance of utilizing preexisting organizational structures such as established communication channels, standardized roles, common workflows, formal authority, and performance measurement and feedback systems when developing and spreading QI processes inside an organization. In particular, we detail how formal process advocate positions in each site for each role can facilitate the spread of new processes. PRACTICE IMPLICATIONS Successful intraorganizational spread is possible and sustainable. Developing and spreading new QI processes across sites inside an organization requires creating a shared understanding of the necessary process steps, considering the barriers that may arise at each step, and leveraging preexisting organizational structures to facilitate intraorganizational process development and spread.This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial License 4.0 (CCBY-NC), where it is permissible to download, share, remix, transform, and buildup the work provided it is properly cited. The work cannot be used commercially