Auto-calibration of ultrasonic lubricant-film thickness measurements

The measurement of oil film thickness in a lubricated component is essential information for performance monitoring and design. It is well established that such measurements can be made ultrasonically if the lubricant film is modelled as a collection of small springs. The ultrasonic method requires that component faces are separated and a reference reflection recorded in order to obtain a reflection coefficient value from which film thickness is calculated. The novel and practically useful approach put forward in this paper and validated experimentally allows reflection coefficient measurement without the requirement for a reference. This involves simultaneously measuring the amplitude and phase of an ultrasonic pulse reflected from a layer. Provided that the acoustic properties of the substrate are known, the theoretical relationship between the two can be fitted to the data in order to yield reflection coefficient amplitude and phase for an infinitely thick layer. This is equivalent to measuring a reference signal directly, but importantly does not require the materials to be separated. The further valuable aspect of this approach, which is demonstrated experimentally, is its ability to be used as a self-calibrating routine, inherently compensating for temperature effects. This is due to the relationship between the amplitude and phase being unaffected by changes in temperature which cause unwanted changes to the incident pulse. Finally, error analysis is performed showing how the accuracy of the results can be optimized. A finding of particular significance is the strong dependence of the accuracy of the technique on the amplitude of reflection coefficient input data used. This places some limitations on the applicability of the technique. © 2008 IOP Publishing Ltd

The 5-HT(4) receptor agonist, tegaserod, is a potent 5-HT(2B) receptor antagonist in vitro and in vivo

1. Tegaserod (Zelnorm®) is a potent 5-hydroxytryptamine(4) (5-HT(4)) receptor agonist with clinical efficacy in disorders associated with reduced gastrointestinal motility and transit. The present study investigated the interaction of tegaserod with 5-HT(2) receptors, and compared its potency in this respect to its 5-HT(4) receptor agonist activity. 2. Tegaserod had significant binding affinity for human recombinant 5-HT(2A), 5-HT(2B) and 5-HT(2C) receptors (pK(i)=7.5, 8.4 and 7.0, respectively). The 5-HT(2B) receptor-binding affinity of tegaserod was identical to that at human recombinant 5-HT(4(c)) receptors (mean pK(i)=8.4) in human embryonic kidney-293 (HEK-293) cells stably transfected with the human 5-HT(4(c)) receptor. 3. Tegaserod (0.1–3 μM) inhibited 5-HT-mediated contraction of the rat isolated stomach fundus potently (pA(2)=8.3), consistent with 5-HT(2B) receptor antagonist activity. Tegaserod produced, with similar potency, an elevation of adenosine 3′,5′ cyclic monophosphate in HEK-293 cells stably transfected with the human 5-HT(4(c)) receptor (mean pEC(50)=8.6), as well as 5-HT(4) receptor-mediated relaxation of the rat isolated oesophagus (mean pEC(50)=8.2) and contraction of the guinea-pig isolated colon (mean pEC(50)=8.3). 4. Following subcutaneous administration, tegaserod (0.3 or 1 mg kg(−1)) inhibited contractions of the stomach fundus in anaesthetized rats in response to intravenous dosing of α-methyl 5-HT (0.03 mg kg(−1)) and BW 723C86 (0.3 mg kg(−1)), selective 5-HT(2B) receptor agonists. At similar doses, tegaserod (1 and 3 mg kg(−1) subcutaneously) evoked a 5-HT(4) receptor-mediated increase in colonic transit in conscious guinea-pigs. 5. The data from this study indicate that tegaserod antagonizes 5-HT(2B) receptors at concentrations similar to those that activate 5-HT(4) receptors. It remains to be determined whether this 5-HT(2B) receptor antagonist activity of tegaserod contributes to its clinical profile

Alternative Professional Roles in Health Care Delivery: Leadership Patterns in Self-Help Groups

The increasing professionalization of health care delivery systems, improved client awareness, funding cutbacks, and an emphasis on voluntarism have led recipients of health services to turn increasingly to self-help groups. This article examines the leadership and organizational pattern of such groups, using a study of 43 self-help groups from around the U.S. whose members are parents of children with cancer. Three leadership patterns emerged: groups were independent and parent-led, were led by professionals, or had a shared leadership of parents and professionals. Data indicate that the professionally led groups were the smallest, leastformal, and had the narrowest range of activities. The groups with shared leadership had the greatest longevity, tended most often to retain as members parents of deceased children. The authors conclude that such coalitions of clients and professionals are vital for ensuring proper service delivery at a time when health care systems will likely remain bureaucratic and public resources for professional care are being reduced.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66640/2/10.1177_002188638502100407.pd

Proposed new industry code on unhealthy food marketing to children and young people: will it make a difference?

Reducing the exposure of children and young people to the marketing of unhealthy foods is a core strategy for reducing the high overweight and obesity prevalence in this population. The Advertising Standards Authority (ASA) has recently reviewed its self-regulatory codes and proposed a revised single code on advertising to children. This article evaluates the proposed code against eight criteria for an effective code, which were included in a submission to the ASA review process from over 70 New Zealand health professors. The evaluation found that the proposed code largely represents no change or uncertain change from the existing codes, and cannot be expected to provide substantial protection for children and young people from the marketing of unhealthy foods. Government regulations will be needed to achieve this important outcome