Search

The Kirchhoff approximation is widely used to describe the scatter of elastodynamic waves. It simulates the scattered field as the convolution of the free-space Green’s tensor with the geometrical elastodynamics approximation to the total field on the scatterer surface and, therefore, cannot be used to describe nongeometrical phenomena, such as head waves. The aim of this paper is to demonstrate that an alternative approximation, the convolution of the far-field asymptotics of the Lamb’s Green’s tensor with incident surface tractions, has no such limitation. This is done by simulating the scatter of a critical Gaussian beam of transverse motions from an infinite plane. The results are of interest in ultrasonic nondestructive testing.

It is unknown whether insulin therapy can delay or prevent diabetes in nondiabetic relatives of patients with diabetes.In a randomized, controlled, nonblinded clinical trial, we screened 84,228 first-degree and second-degree relatives of patients with diabetes for islet-cell antibodies; 3152 tested positive; 2103 of the 3152 underwent genetic, immunologic, and metabolic staging to quantify their risk; 372 of the 2103 had a projected five-year risk of more than 50 percent; 339 of the 372 (median age, 11.2 years) were randomly assigned to undergo either close observation or an intervention that consisted of low-dose subcutaneous ultralente insulin, administered twice daily for a total dose of 0.25 unit per kilogram of body weight per day, plus annual four-day continuous intravenous infusions of insulin. Oral glucose-tolerance tests were performed every six months. Median follow-up was 3.7 years. The primary end point was a diagnosis of diabetes.Diabetes was diagnosed in 69 subjects in the intervention group and 70 subjects in the observation group. The annualized rate of progression to diabetes was 15.1 percent in the intervention group and 14.6 percent in the observation group. The cumulative incidence of diabetes was similar in the two groups (relative risk in the intervention group as compared with the observation group, 0.96). Most subjects in whom diabetes developed were asymptomatic. Progression to diabetes occurred at a faster rate among subjects with abnormal base-line glucose tolerance (22 percent per year) than among those with normal base-line glucose tolerance (10 percent per year, P0.001). There were no episodes of severe hypoglycemia. The incidence of chemical hypoglycemia, assessed without ascertainment bias, was similar in the two groups.In persons at high risk for diabetes, insulin at the dosage used in this study does not delay or prevent type 1 diabetes.

The causes and geographic distribution of 267 cases of iatrogenic Creutzfeldt-Jakob disease (CJD) are here updated at the millennium. Small numbers of still-occurring cases result from disease onsets after longer and longer incubation periods following infection by cadaveric human growth hormone or dura mater grafts manufactured and distributed before the mid-1980s. The proportion of recipients acquiring CJD from growth hormone varies from 0.3 to 4.4% in different countries, and acquisition from dura mater varies between 0.02 and 0.05% in Japan (where most cases occurred). Incubation periods can extend up to 30 years, and cerebellar onsets predominate in both hormone and graft recipients (in whom the site of graft placement had no effect on the clinical presentation). Homozygosity at codon 129 of the PRNP gene is over-represented in both forms of disease; it has no effect on the incubation period of graft recipients, but may promote shorter incubation periods in hormone cases. Knowledge about potential high-risk sources of contamination gained during the last quarter century, and the implementation of methods to circumvent them, should minimize the potential for iatrogenic contributions to the current spectrum of CJD.

Horton et al. (1987) have developed a guiding centre model for turbulent electron diffusion in 'quiet' discharges in tokamaks. They have argued that the electron diffusion in this regime may be due to a spectrum of electromagnetic drift fluctuations. They have studied by numerical means the dependence of the corresponding diffusion coefficient on amplitude and steepness of the spectrum as well as on other parameters of the model. The authors discuss the statistical significance of the results obtained with the type of computation used by Horton et al. They show that when the dependence of the computed diffusivity on computer, model and integrator parameters is taken into account, the corresponding estimation errors may be larger than the 'convergence error bars' calculated in Horton et al. The error bars in question have been designed to show only how well the running diffusivity had settled down to a constant for a particular choice of the parameter set. The authors study how these parameters might influence the value of the constant itself, and as a consequence propose a half-way time-reversing procedure to assess the possible deviation, often referred to as 'numerical diffusion'. They demonstrate, by the way, that an implicit version of the Runge-Kutta integrator that leads to the same numerical diffusion as its explicit counterpart is 10 to 20 times faster.

OBJECTIVE To examine the persistence of the original treatment effects 10 years after the Diabetes Control and Complications Trial (DCCT) in the follow-up Epidemiology of Diabetes Interventions and Complications (EDIC) study. In the DCCT, intensive therapy aimed at near-normal glycemia reduced the risk of microvascular complications of type 1 diabetes mellitus compared with conventional therapy. METHODS Retinopathy was evaluated by fundus photography in 1211 subjects at EDIC year 10. Further 3-step progression on the Early Treatment Diabetic Retinopathy Study scale from DCCT closeout was the primary outcome. RESULTS After 10 years of EDIC follow-up, there was no significant difference in mean glycated hemoglobin levels (8.07% vs 7.98%) between the original treatment groups. Nevertheless, compared with the former conventional treatment group, the former intensive group had significantly lower incidences from DCCT close of further retinopathy progression and proliferative retinopathy or worse (hazard reductions, 53%-56%; P < .001). The risk (hazard) reductions at 10 years of EDIC were attenuated compared with the 70% to 71% over the first 4 years of EDIC (P < .001). The persistent beneficial effects of former intensive therapy were largely explained by the difference in glycated hemoglobin levels during DCCT. CONCLUSION The persistent difference in diabetic retinopathy between former intensive and conventional therapy ("metabolic memory") continues for at least 10 years but may be waning. TRIAL REGISTRATION (clinicaltrials.gov) Identifiers: NCT00360815 and NCT00360893.

The TOFD (Time of Flight Diffraction) Technique is commonly used to detect and to characterize embedded disoriented flaws using their edge diffraction echoes. We present a TOFD simulation module which includes GTD coefficients allowing to predict diffraction echoes from embedded planar flaws. Other dedicated development have been added in the CIVA software platform to simulate lateral surface waves, backwall echoes and shadowing effects from flaws. Experimental validations have been performed on various specimen containing rectangular and CAD contour planar flaws with different possible disorientations (tilt, vertical misorientation, skew) and show an overall good agreement between simulation and measure.

The practice of warming up prior to exercise is advocated in injury prevention programs, but this is based on limited clinical evidence. It is hypothesised that warming up will reduce the number of injuries sustained during physical activity.A systematic review was undertaken. Relevant studies were identified by searching Medline (1966-April 2005), SPORTDiscus (1966-April 2005) and PubMed (1966-April 2005). This review included randomised controlled trials that investigated the effects of warming up on injury risk. Studies were included only if the subjects were human, and only if they utilised other activities than simply stretching. Studies reported in languages other than English were not included. The quality of included studies was assessed independently by two assessors.Five studies, all of high quality (7-9 (mean=8) out of 11) reported sufficient data (quality score7) on the effects of warming up on reducing injury risk in humans. Three of the studies found that performing a warm-up prior to performance significantly reduced the injury risk, and the other two studies found that warming up was not effective in significantly reducing the number of injuries.There is insufficient evidence to endorse or discontinue routine warm-up prior to physical activity to prevent injury among sports participants. However, the weight of evidence is in favour of a decreased risk of injury. Further well-conducted randomised controlled trials are needed to determine the role of warming up prior to exercise in relation to injury prevention.

Three reported cases of Creutzfeldt-Jakob disease (CJD) in young adults who had received human growth hormone (hGH) raised concerns that pituitary-derived GH had been contaminated. Subsequently reported cases have confirmed this suspicion. The US Public Health Service is conducting an investigation to determine the extent of the problem of CJD in recipients of National Hormone Pituitary Program (NHPP) GH. In addition, other possible adverse effects of GH use including leukemia are being investigated. The design, conduct and current status of the study are the subject of this report. Interview data are now available on 5,240 of the 6,284 subjects treated by the NHPP for growth problems. Analysis is underway.