Relationships Between Ultrasonic Noise and Macrostructure of Titanium Alloys

The complex microstructure of two-phase titanium alloys can produce considerable ultrasonic backscattering noise. The noise introduces problems in detecting small flaws, such as hard-alpha inclusions, by forming a background which can mask the flaw signals. Therefore better understanding of grain noise is required to quantify and increase the detectability of the small flaws. As an aid to understanding the grain noise, an independent scattering model was constructed and studied during last two years by Margetan and Thompson. In that model for the backscattered noise generated by a tone burst, the grain noise is described by following equation (1) N(t)=FOM×M(t) where N(t) is the rms grain noise, FOM is a material characteristic parameter and M is a factor that depends on the detailed description of the experimental configuration as well as the ultrasonic attenuation. The argument, t, is the time delay at which the noise is observed and can be related to a spatial position within the material. Since the model gives an explicit functional form for M, it is possible to use Eq. (1) to infer the FOM from a measurement of N(t).1 Figure 1 presents the results of such a measurement in which the noise was observed, through each of three orthogonal sides of a set of four Ti-6246 specimens, whose history of heat treatment is summarized in Table 1.2 The FOM’s of each of specimens A1, A2 and B2 varied by an order of magnitude, depending on the side of the measurement. However, on specimen C1, which was annealed above the beta transus of 1775 °F, the noise was nearly isotropic. The purpose of this paper is to understand the origin of this anisotropy

Theory of Ultrasonic Backscatter From Multiphase Polycrystalline Solids

Ultrasound scatters from the microscopic single crystals that constitute polycrystalline solids. The scattering originates from crystallite-crystallite variations in the density and elastic constants. For single-phase materials, each crystallite has the same density and the same crystalline symmetry. Hence, in single-phase materials scattering arises from the variation in velocity, which in turn is due to the anisotropy of the elastic constants and the more or less random orientation of the crystallites [1,2]. The situation is considerably more complicated in multiphase alloys where the density, the crystal symmetry and the elastic constants vary from crystallite to crystallite

The Inverse Born Approximation: Exact Determination of Shape of Convex Voids

The Inverse Born Approximation (IBA) to the elastic wave inverse scattering problem is known to give highly accurate results for the shape of complex voids. In this paper we present an argument demonstrating that the IBA is, in fact, exact for determining the size, shape and orientation of a wide class of these scatterers given infinite bandwidth and unlimited aperture information. Essentially, our argument demonstrates how the IBA algorithm picks out the singular contribution to the impulse response function and correctly relates it to the shape of the scatterer. Some specific examples will be used to illustrate the more intuitive aspects of the discussion

Effects of Short-Term Training of Community-Dwelling Elderly with Modular Interactive Tiles

Objective: The objective of this study is to test for the increased mobility, agility, balancing, and general fitness of community-dwelling elderly individuals as a result of short-term training involving playing with modular interactive tiles (Entertainment Robotics, Odense, Denmark) at two community activity centers for the elderly. Three different tests from the Senior Fitness Test were used in order to test a variety of health parameters of the community-dwelling elderly, including those parameters related to fall prevention. Materials and Methods: Eighteen community-dwelling elderly individuals (63–95 years of age; mean, 83.2 years of age) were assessed in one intervention group without the use of a control group. The intervention group performed nine group sessions (1–1.5 hours each) of playful training with the modular interactive tiles over a 12-week period in two community activity centers for the elderly. Data were collected using pre-tests and post-tests of the 6-Minute Walk Test (6MWT), the 8-foot Timed Up & Go Test (TUG), and the Chair-Stand Test (CS). Data were analyzed for statistically significant differences and increases of means. Results: The 6MWT, TUG, and CS measurements showed statistically significant differences and increases of means between the pre-tests and post-tests with the 6MWT (P<0.001) (means difference, 22.4 percent), TUG (P<0.001) (means difference, 15 percent), and CS (P<0.002) (means difference, 14 percent). Fifty-six percent of the elderly progressed from one health risk level to a better level, according to the three tests. Conclusions: Statistically significant increases in scores were found across all tests, suggesting an improvement of many different health parameters for the elderly. Well-established research has shown the relationship between such test scores and fall incidents, balancing, mobility, agility, etc. This significant improvement in the health status of the elderly is obtained in as few as nine training sessions over a 12-week period of “playing” exergames with the modular interactive tiles

The microbiological quality of air improves when using air conditioning systems in cars

<p>Abstract</p> <p>Background</p> <p>Because of better comfort, air conditioning systems are a common feature in automobiles these days. However, its impact on the number of particles and microorganisms inside the vehicle - and by this its impact on the risk of an allergic reaction - is yet unknown.</p> <p>Methods</p> <p>Over a time period of 30 months, the quality of air was investigated in three different types of cars (VW Passat, VW Polo FSI, Seat Alhambra) that were all equipped with a automatic air conditioning system. Operation modes using fresh air from outside the car as well as circulating air from inside the car were examined. The total number of microorganisms and the number of mold spores were measured by impaction in a high flow air sampler. Particles of 0.5 to 5.0 μm diameter were counted by a laser particle counter device.</p> <p>Results</p> <p>Overall 32 occasions of sampling were performed. The concentration of microorganisms outside the cars was always higher than it was inside the cars. Few minutes after starting the air conditioning system the total number of microorganisms was reduced by 81.7%, the number of mold spores was reduced by 83.3%, and the number of particles was reduced by 87.8%. There were no significant differences neither between the types of cars nor between the types of operation mode of the air conditioning system (fresh air vs. circulating air). All parameters that were looked for in this study improved during utilization of the car's air conditioning system.</p> <p>Conclusions</p> <p>We believe that the risk of an allergic reaction will be reduced during use also. Nevertheless, we recommend regular maintenance of the system and replacement of older filters after defined changing intervals.</p

A Generalized Model of the Effects of Microstructure on Ultrasonic Backscattering and Flaw Detection

The influence of microstructure on ultrasonic inspection is well known. Familiar examples include the attenuation of ultrasound due to scattering from grain boundaries and the anisotropies in velocity that are associated with preferred grain orientation. Less commonly discussed are the creation of backscattered noise, which can mask flaw signals, and the modification of transducer radiation patterns, e.g. the modulation of the phase fronts in a beam, which can cause fluctuations in signals reflected from surfaces [1]. The latter influence the measurement of attenuation as well as the strength of signals reflected from flaws. The goal of this work is to develop a unified basis for understanding these phenomena, as can be used in the analysis of the performance of ultrasonic flaw detection systems. Of interest are correlations of noise in time as well as the variance of noise signals (about their mean of zero) and reflected signals (about a non-zero mean).</p

Field Application of a Subunit Vaccine against an Enteric Protozoan Disease

Background: Coccidiosis is a major global veterinary health problem in intensively reared chickens. It is caused by apicomplexan parasites of the genus Eimeria. Principal Findings: A subunit vaccine composed of purified antigens from the gametocytes of Eimeria maxima was used to stimulate the production and transfer of maternal antibodies between breeding hens and their hatchlings. The vaccine was injected into hens twice before they began laying eggs. Immunization had no adverse affects on egg laying or health of the hens and resulted in high antibody levels throughout the life of the hens. Progeny of immunized hens excreted significantly less oocysts of various species of Eimeria in their faeces than chicks from unvaccinated hens. Furthermore, the offspring of vaccinated hens developed stronger natural immunity to Eimeria, so that they were resistant to challenge infection even at 8 weeks of age, well after all maternal antibodies had left their circulation. Field trials were conducted in South Africa, Brazil and Thailand, involving at least 1 million progeny of vaccinated hens and at least 1 million positive control birds (raised on feed containing anticoccidial drugs or immunized with a live vaccine) in each country. Additionally, trials were carried out in Israel involving 60 million progeny of vaccinated hens and 112 million positive control birds. There were no significant differences in growth rate, feed conversion ratios or mortality in the offspring of vaccinated hens compared with the positive control chickens in any of these countries regardless of different management practices, different breeds of chickens or climate. Conclusions: These results demonstrate that a vaccine composed of antigens purified from the gametocytes of Eimeria can be used safely and effectively to prevent the deleterious effects of coccidiosis. It is the first subunit vaccine against any protozoan parasite to be successfully applied on a commercial scale. © 2008 Wallach et al

Prevalence of Oral Pain and Barriers to use of Emergency Oral Care Facilities Among Adult Tanzanians.

Oral pain has been the major cause of the attendances in the dental clinics in Tanzania. Some patients postpone seeing the dentist for as long as two to five days. This study determines the prevalence of oral pain and barriers to use of emergency oral care in Tanzania. Questionnaire data were collected from 1,759 adult respondents aged 18 years and above. The study area covered six urban and eight rural study clusters, which had been selected using the WHO Pathfinder methodology. Chi-square tests and logistic regression analyses were performed to identify associations.\ud Forty two percent of the respondents had utilized the oral health care facilities sometimes in their lifetime. About 59% of the respondents revealed that they had suffered from oral pain and/or discomfort within the twelve months that preceded the study, but only 26.5% of these had sought treatment from oral health care facilities. The reasons for not seeking emergency care were: lack of money to pay for treatment (27.9%); self medication (17.6%); respondents thinking that pain would disappear with time (15.7%); and lack of money to pay for transport to the dental clinic (15.0%). Older adults were more likely to report that they had experienced oral pain during the last 12 months than the younger adults (OR = 1.57, CI 1.07-1.57, P < 0.001). Respondents from rural areas were more likely report dental clinics far from home (OR = 5.31, CI = 2.09-13.54, P < 0.001); self medication at home (OR = 3.65, CI = 2.25-5.94, P < 0.001); and being treated by traditional healer (OR = 5.31, CI = 2.25-12.49, P < 0.001) as reasons for not seeking emergency care from the oral health care facilities than their counterparts from urban areas. Oral pain and discomfort were prevalent among adult Tanzanians. Only a quarter of those who experienced oral pain or discomfort sought emergency oral care from oral health care facilities. Self medication was used as an alternative to using oral care facilities mainly by rural residents. Establishing oral care facilities in rural areas is recommended

Chapter 4: Effective Search Strategies for Systematic Reviews of Medical Tests

This article discusses techniques that are appropriate when developing search strategies for systematic reviews of medical tests. This includes general advice for searching for systematic reviews and issues specific to systematic reviews of medical tests. Diagnostic search filters are currently not sufficiently developed for use when searching for systematic reviews. Instead, authors should construct a highly sensitive search strategy that uses both controlled vocabulary and text words. A comprehensive search should include multiple databases and sources of grey literature. A list of subject-specific databases is included in this article