Dry Friction due to Adsorbed Molecules

Using an adiabatic approximation method, which searches for Tomlinson model-like instabilities for a simple but still realistic model for two crystalline surfaces in the extremely light contact limit, with mobile molecules present at the interface, sliding relative to each other, we are able to account for the virtually universal occurrence of "dry friction." The model makes important predictions for the dependence of friction on the strength of the interaction of each surface with the mobile molecules.Comment: four pages of latex, figure provide

Issues in Forest Restoration: Forest Service Contracting: A Basic Guide for Restoration Practitioners

During the past ten years, the array of administrative tools available to the Forest Service for restoration has changed and been enhanced. This guide provides an overview of the contracts, agreements, and permits available to pursue restoration work on national forests, and provides contractors with information on how to find and bid on restoration contracts

Barriers to innovation and knowledge generation: The challenges of conducting business and social research in an emerging country context

© 2018 Journal of Innovation & Knowledge The Middle East, as a region, contributes proportionally less to new knowledge generation than other parts of the world. The United Arab Emirates (UAE) has sought to correct this imbalance through efforts to promote a knowledge-based economy and through educational investment. In light of these advances, significant challenges still remain in the promotion and production of high quality research in the social sciences, including business. The current monograph highlights the vital importance of such research to the social and economic development of the UAE. Reflecting on nearly a decade of conducting research in the UAE with varying degrees of success the authors highlight critical incidents, experiences and observations which serve to illustrate the challenges of new knowledge creation in the business and social sciences. Discussions focus on identifiable barriers to high quality research at both the micro and macro levels, within and outside the UAE, with specific recommendations on how such barriers can be overcome

University ‘Pay-for-grades’: the bait and switch search engine optimization strategies of contract cheating websites in the United States

This paper presents the first systematic investigation into the search engine optimization practices of major contract cheating websites in the United States. From a business perspective, visibility in organic search engine results is considered one of the top client recruitment tools. The current understanding of student recruitment strategies by these companies remains largely unexplored in both academic literature and popular press. Replicating the business research practices used in the search engine optimization industry, comprehensive search engine ranking and traffic data was obtained for the 38 largest contract cheating websites in the US. The overall objective was to illuminate the strategies that these companies take to get their services at the top of the search results of as many students as possible – not just the relatively small proportion of students actively cheating. The results show that these companies dominate the search results for not just students searching to cheat, but also for naïve search efforts, when students are simply doing genuine research or classwork. These nefarious companies use highly sophisticated search engine manipulation strategies to bait naïve student searchers onto their sites, thus enabling the potential to switch them to cheaters. Higher education institutions, armed with the specific details provided in this study, can use the strategies outlined in the discussion to directly and negatively impact on the success of these contract cheating services

Effects of a multi-component exercise program and calcium–vitamin-D3-fortified milk on bone mineral density in older men : a randomised controlled trial

Summary We examined the independent and combined effects of a multi-component exercise program and calcium&ndash;vitamin-D3-fortified milk on bone mineral density (BMD) in older men. Exercise resulted in a 1.8% net gain in femoral neck BMD, but additional calcium&ndash;vitamin D3 did not enhance the response in this group of older well-nourished men.Introduction This 12-month randomised controlled trial assessed whether calcium&ndash;vitamin-D3-fortified milk could enhance the effects of a multi-component exercise program on BMD in older men.Methods Men (n&thinsp; =&thinsp;180) aged 50&ndash;79 years were randomised into: (1) exercise + fortified milk; (2) exercise; (3) fortified milk; or (4) controls. Exercise consisted of high intensity progressive resistance training with weight-bearing impact exercise. Men assigned to fortified milk consumed 400 mL/day of low fat milk providing an additional 1,000 mg/day calcium and 800 IU/day vitamin D3. Femoral neck (FN), total hip, lumbar spine and trochanter BMD and body composition (DXA), muscle strength 25-hydroxyvitamin D and parathyroid hormone (PTH) were assessed.Results There were no exercise-by-fortified milk interactions at any skeletal site. Exercise resulted in a 1.8% net gain in FN BMD relative to no-exercise (p&thinsp;&lt;&thinsp;0.001); lean mass (0.6 kg, p&thinsp;&lt;&thinsp;0.05) and muscle strength (20&ndash;52%, p&thinsp;&lt;&thinsp;0.001) also increased in response to exercise. For lumbar spine BMD, there was a net 1.4&ndash;1.5% increase in all treatment groups relative to controls (all p&thinsp;&lt;&thinsp;0.01). There were no main effects of fortified milk at any skeletal site.Conclusion A multi-component community-based exercise program was effective for increasing FN BMD in older men, but additional calcium&ndash;vitamin D3 did not enhance the osteogenic response.<br /

Model-independent determination of the cosmic expansion rate. I. Application to type-Ia supernovae

Aims: In view of the substantial uncertainties regarding the possible dynamics of the dark energy, we aim at constraining the expansion rate of the universe without reference to a specific Friedmann model and its parameters. Methods: We show that cosmological observables integrating over the cosmic expansion rate can be converted into a Volterra integral equation which is known to have a unique solution in terms of a Neumann series. Expanding observables such as the luminosity distances to type-Ia supernovae into a series of orthonormal functions, the integral equation can be solved and the cosmic expansion rate recovered within the limits allowed by the accuracy of the data. Results: We demonstrate the performance of the method applying it to synthetic data sets of increasing complexity, and to the first-year SNLS data. In particular, we show that the method is capable of reproducing a hypothetical expansion function containing a sudden transition.Comment: 9 pages, 8 figures; accepted by A&A; subsection 3.6 added, new references and minor change

Crater Morphometry and Scaling in Coarse, Rubble-Like Targets: Insights from Impact Experiments

Spacecraft images reveal that the asteroids Itokawa, Ryugu, and Bennu are covered with coarse, boulder-rich material [13]. Impactors that collide with these bodies encounter a target with extreme physical heterogeneity. Other bodies can also possess significant physical heterogeneity (e.g., megaregolith, layering, etc.). Such heterogeneities establish free surfaces and impedance contrasts that can affect shock propagation and attenuation. Therefore, such heterogeneities may also affect crater formation and excavation [4], melt generation [57] and crater scaling [4]. As described by [8,9], the extent to which target heterogeneity affects crater formation likely depends on how the length scale, d, of the heterogeneity (e.g., boulder size on a rubble-pile asteroid) compares to the width of the shock, w, generated by impact. Here we further test this hypothesis using impact experiments across a broad range of impact velocities and target grain sizes to systematically vary the ratio between the width of the shock and the diameter of target grains

Investigating Women's Experiences of Asthma Care in Pregnancy: A Qualitative Study.

Background : Most asthmatic women have normal pregnancies and complications are infrequent when their asthma is well-controlled. Symptom control and medical treatment are concerning to pregnant asthma suffers, as is the impact that their illness and treatment might have on their unborn baby. The aim was to investigate in a qualitative study the thoughts and feelings of women's experiences of asthma in pregnancy. Twenty-two women with asthma who had a pregnancy within two years were asked to participate. Seven women were interviewed when data saturation was achieved. Interviews were transcribed and analysed using the 'Framework' Method, independently analysed by two researchers and consensus reached concerning the construction of themes. The key themes that emerged were Asthma and pregnancy; Pregnancy and post-natal experiences; and Health professionals. These findings are globally interesting because of the prevalence of maternal asthma and they illustrate participants' experiences concerning their asthma care and their views on its improvement. Pregnant asthmatic women have concerns about their care and treatment which might be alleviated by outreach, joint working between respiratory doctors and nurse specialists, midwives and General Practice nurses. Targeted educational activities could form a part of this care delivery