Quantifying the Significance of Abrasion and Selective Transport for Downstream Fluvial Grain Size Evolution

It is well known that pebble diameter systematically decreases downstream in rivers. The contribution of abrasion is uncertain, in part because (1) diameter is insufficient to characterize pebble mass loss due to abrasion and (2) abrasion rates measured in laboratory experiments cannot be easily extrapolated to the field. A recent geometric theory describes abrasion as a curvature-dependent process that produces a two-phase evolution: in Phase I, initially blocky pebbles round to smooth, convex shapes with little reduction in axis dimensions; then, in Phase II, smooth, convex pebbles slowly reduce their axis dimensions. Here we provide strong evidence that two-phase abrasion occurs in a natural setting, by examining downstream evolution of shape and size of thousands of pebbles over ~10 km in a tropical montane stream. The geometric theory is verified in this river system using a variety of manual and image-based shape parameters, providing a generalizable method for quantifying the significance of abrasion. Phase I occurs over ~1 km, in upstream bedrock reaches where abrasion is dominant and sediment storage is limited. In downstream alluvial reaches, where Phase II occurs, we observe the expected exponential decline in pebble diameter. Using a discretized abrasion model (the so-called “box equations”) with deposition, we deduce that abrasion removes more than one third of the mass of a pebble but that size-selective sorting dominates downstream changes in pebble diameter. Overall, abrasion is the dominant process in the downstream diminution of pebble mass (but not diameter) in the studied river, with important implications for pebble mobility and the production of fine sediments

Generalized Sorting Profile of Alluvial Fans

Alluvial rivers often exhibit self-similar gravel size distributions and abrupt gravel-sand transitions. Experiments suggest that these sorting patterns are established rapidly, but how—and how fast—this convergence occurs in the field is unknown. We examine the establishment of downstream sorting patterns in a kilometer-scale alluvial fan. The sharp transition from canyon to unconfined, channelized fan provides a well-defined boundary condition. The channel changes from deep and entrenched at the fan apex to shallow and depositional over a short distance, exhibiting nonequilibrium behavior. The resulting gravel-fining profile is not self-similar; the particle size distribution narrows until approximate equal mobility is achieved. Downfan, the gravel-sand transition appears to exhibit a self-similar form; field and laboratory data collapse when downstream distance is normalized by the location of the transition. Results suggest a generalized sorting profile for alluvial fans as a consequence of the threshold of motion and nonequilibrium channels

Effects of regional differences and demography in modelling foot-and-mouth disease in cattle at the national scale

Foot-and-mouth disease (FMD) is a fast-spreading viral infection that can produce large and costly outbreaks in livestock populations. Transmission occurs at multiple spatial scales, as can the actions used to control outbreaks. The US cattle industry is spatially expansive, with heterogeneous distributions of animals and infrastructure. We have developed a model that incorporates the effects of scale for both disease transmission and control actions, applied here in simulating FMD outbreaks in US cattle. We simulated infection initiating in each of the 3049 counties in the contiguous US, 100 times per county. When initial infection was located in specific regions, large outbreaks were more likely to occur, driven by infrastructure and other demographic attributes such as premises clustering and number of cattle on premises. Sensitivity analyses suggest these attributes had more impact on outbreak metrics than the ranges of estimated disease parameter values. Additionally, although shipping accounted for a small percentage of overall transmission, areas receiving the most animal shipments tended to have other attributes that increase the probability of large outbreaks. The importance of including spatial and demographic heterogeneity in modelling outbreak trajectories and control actions is illustrated by specific regions consistently producing larger outbreaks than others

Sex and Gender in Medical Education, and proceedings from the 2015 Sex and Gender Education Summit

The Sex and Gender Medical Education Summit: a roadmap for curricular innovation was a collaborative initiative of the American Medical Women\u27s Association, Laura W. Bush Institute for Women’s Health, Mayo Clinic, and Society for Women\u27s Health Research (www.sgbmeducationsummit.com). It was held on October 18–19, 2015 to provide a unique venue for collaboration among nationally and internationally renowned experts in developing a roadmap for the incorporation of sex and gender based concepts into medical education curricula. The Summit engaged 148 in-person attendees for the 1 1/2-day program. Pre- and post-Summit surveys assessed the impact of the Summit, and workshop discussions provided a framework for informal consensus building. Sixty-one percent of attendees indicated that the Summit had increased their awareness of the importance of sex and gender specific medicine. Other comments indicate that the Summit had a significant impact for motivating a call to action among attendees and provided resources to initiate change in curricula within their home institutions. These educational efforts will help to ensure a sex and gender basis for delivery of health care in the future

Engaging Volunteers with Disabilities: A Qualitative Study

Many volunteer administrators often wonder what they can do to increase their volunteer base and improve the efficiency, longevity, and morale of their current volunteers and staff. One virtually untapped, and certainly underutilized, population from which new volunteers may be recruited comprises individuals with disabilities. Volunteer coordinators with limited-to-no experience engaging volunteers with disabilities may be concerned, however, that increased time and money to supervise may be required, or special accommodations may be needed, to engage this population. These concerns are commonly cited by volunteer coordinators as barriers to successfully engaging volunteers with disabilities (CSV's Retired and Senior Volunteer Programme, 2000; Graff & Vedell, 2003; Miller, Schleien, & Bedini, 2003). Nevertheless, many agencies have deemed these barriers worthy of addressing and overcoming

Community for all: The therapeutic recreation practitioner’s role in inclusive volunteering

Participation in volunteerism has great potential in helping individuals reach their desired goals such as improving self-esteem, sense of purpose, social connectedness, happiness, quality of life, and community inclusion. A rationale for the facilitation of inclusive volunteering is discussed, including the current status of volunteering, the multitude of benefits that can be reaped from volunteerism, and a synopsis of the literature on individuals with disabilities as volunteers. Additionally, we review the vital role that therapeutic recreation practitioners could play in assisting individuals with disabilities to incorporate volunteering into their leisure repertoires

What's in it for Me and My Agency? A Survey on the Benefits of Engaging Volunteers with Disabilities

In 1998, the Association for Volunteer Administration adopted a formal Statement of Inclusiveness (AVA Board of Directors, 1999) that defines diversity in its broadest terms, and proclaimed the value of inclusiveness in volunteering and throughout the profession. This followed a 1995 process that identified professional ethics in volunteer administration. Among the professional ethics identified were citizenship and respect

Teaming Up for Inclusive Volunteering: A Case Study of a Volunteer Program for Youth with and without Disabilities

Volunteerism is a recreational activity that may hold the key to greater social inclusion for individuals with disabilities into our communities. Facilitating inclusive volunteering opportunities for youth with and without disabilities has a potential scope of impact that must not be ignored, including benefits to the youth and our communities. A case study of an inclusive youth volunteer program is described. Out-comes for participants included increased knowledge of volunteerism, increased social interaction, and psychosocial outcomes such as increased belief in self and increased sense of responsibility. The feasibility and sustainability of inclusive volunteer programs, as well as future programming and research needs are also discussed

Controlled cardiac reoxygenation does not improve myocardial function following global myocardial ischemia

AbstractBackgroundIt has been shown that abrupt re-exposure of ischemic myocardium to oxygen can lead to increased peroxidative damage to myocytes (oxygen paradox). Controlled cardiac reoxygenation, as an adjunct to substrate-enhanced cardioplegia, has been shown to improve myocardial function and limit reperfusion injury when utilizing standardized hyperoxic cardiopulmonary bypass (CPB). The objective of our study was to evaluate the effect of controlled reoxygenation on myocardial function following global ischemia employing normoxic CPB.Study designNineteen female swine (30–40kg) were placed on vented, normoxic CPB. They were subjected to 45–50min of unprotected global ischemia (aortic cross clamping) followed by 30min of controlled cardiac reperfusion utilizing substrate-enhanced cardioplegia. Group 1 maintained normoxic pO2 (O2 tension of 90–110mmHg). In Group 2, reoxygenation was titrated gradually and increased from venous to arterial levels (O2 tensions from 40 to 110mmHg over 15min). We measured coronary sinus blood samples for CK, CK-MB, nitric oxide, and conjugated dienes at baseline, 5min into the cardioplegic resuscitation, 5min after the cross clamp removal, and just prior to the termination of the study. Hearts were pathologically studied and scored for evidence of tissue peroxidation.ResultsAlthough not significantly different, Group 1 (normoxic reperfusion) animals were more likely to wean from CPB (p=0.141) and had a higher mean arterial pressure (p=0.556). In Group 1, conjugated dienes were significantly higher 5min into the resuscitative protocol (p=0.018) and at the termination of bypass (p=0.035). Five of six animals in Group 1 eventually attained normal sinus rhythm as opposed to three out of 13 in Group 2 (p=0.041). There was no significant difference in histology scoring between the two groups for tissue peroxidation.ConclusionThis study of controlled cardiac reoxygenation in a lethal ischemic swine model failed to demonstrate that the use of controlled reoxygenation on the myocardial function following global ischemia was better with maintained normoxic pO2 (with O2 tensions of 90–110mmHg) than when reoxygenation was titrated gradually and increased from venous to arterial levels (O2 tensions from 40 to 110mmHg over 15min)