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Biomedical subjects

R E Newnham

Publications and source records attributed to R E Newnham.

8 recordsLinked to original sources
PubMed2001

A miniature class V flextensional cymbal transducer with directional beam patterns: the double-driver.

The "double-driver" cymbal, a directional class V flextensional transducer, is described in this paper. Its basic structure is a bilaminar piezoelectric disk with metal caps as mechanical transformers and amplifiers. The directivity was accomplished by exciting the double-driver in a combined flexural and bending mode causing the sound pressure to add in one direction and cancel in the opposite direction. The cardioid beam pattern predicted by finite element modeling agreed well with the experimental measurements. A 3 x 3 double-driver array was constructed to demonstrate that under optimal conditions the array can provide a directional beam pattern with a front-to-back ratio of more than 20 dB.

Ceramics↗
PubMed2001

Modeling and underwater characterization of cymbal transducers and arrays.

The cymbal is a miniaturized class V flextensional transducer that was developed for potential use as a shallow water sound projector and receiver. Single elements are characterized by high Q, low efficiency, and medium power output capability. Its low cost and thin profile allow the transducer to be assembled into large flexible arrays. Efforts were made to model both single element and transducer arrays by coupling finite element analysis (ATILA) and the integral equation formulation (EQI). The pressure and velocity distributions on the surface elements were calculated by ATILA and later used with EQI to calculate the far field properties of the transducer element and arrays. It eliminates the mesh of the fluid domain and makes the 3-D model of a transducer possible. Three-dimensional models of a cymbal transducer and a 3 x 3 cymbal array were developed in the modeling. Very good agreement was obtained between modeling and measurement for single element transducers. By coupling finite element analysis with the integral equation method using boundary elements, acoustic interaction effects were taken into account. Reasonable agreement was obtained between calculation and measurement for a 3 x 3 array.

Journal Article↗
PubMed2000

Cymbal array: a broad band sound projector.

A prototype 3 x 3 planar cymbal transducer array was built and tested. The array has a radiating area of 5.5 cm x 5.5 cm and a thickness of less than 8 mm. The measured transmitting voltage response was above 134 dB re 1 microPa/V @ 1 m and flat over the frequency range of 16 and 100 kHz. Array interaction was analyzed using an equivalent circuit model. The array interaction leads to variations in radiation resistance and velocity of the transducers in the array according to their surroundings in the array. The effect is enhanced overall efficiency and a flat response.

Equipment Design↗
PubMed1994

Essentiality of boron for healthy bones and joints.

Since 1963, evidence has accumulated that suggests boron is a safe and effective treatment for some forms of arthritis. The initial evidence was that boron supplementation alleviated arthritic pain and discomfort of the author. This was followed by findings from numerous other observations epidemiologic and controlled animal and human experiments. These findings included a) analytical evidence of lower boron concentrations in femur heads, bones, and synovial fluid from people with arthritis than from those without this disorder; b) observation evidence that bones of patients using boron supplements are much harder to cut than those of patients not using supplements; c) epidemiologic evidence that in areas of the world where boron intakes usually are 1.0 mg or less/day the estimated incidence of arthritis ranges from 20 to 70%, whereas in areas of the world where boron intakes are usually 3 to 10 mg, the estimated incidence of arthritis ranges from 0 to 10%; d) experimental evidence that rats with induced arthritis benefit from orally or intraperitoneally administered boron; e) experimental evidence from a double-blind placebo-boron supplementation trial with 20 subjects with osteoarthritis. A significant favorable response to a 6 mg boron/day supplement was obtained; 50% of subjects receiving the supplement improved compared to only 10% receiving the placebo. The preceding data indicate that boron is an essential nutrient for healthy bones and joints, and that further research into the use of boron for the treatment or prevention of arthritis is warranted.

Aged↗
PubMed1991

Agricultural practices affect arthritis.

It has been suggested that boron deficiency in food may be a cause of some arthritis (Newnham 1979). Epidemiological studies were done to try to ascertain why some countries have more or less arthritis than other countries. Jamaica, Mauritius, Fiji and Israel were visited with a view to ascertaining the boron levels of locally consumed food as it was suspected that excessive use of soluble chemical fertilizers had damaged the soils of the sugar producing lands. Food grown on these soils were found to have low boron levels. By contrast the foods consumed in Israel had high boron concentrations associated with a low incidence of arthritis. South African work has shown that people who eat mostly maize have more arthritis when eating processed maize grown with fertilizer. Brief reference is made to the role of boron in human diets. There are bound to be geographical differences in dietary boron, but even in the USA levels have dropped considerably in 50 years. Arthritis is increasing, especially juvenile arthritis. The increased use of fertilizers and genetic selection of plants has led to a wide range of changes in the quality of foodstuffs and their nutrient content. The identification of the parallel loss of boron may reflect vital changes in trace elements and other nutrients.

Agriculture↗