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Biomedical subjects

S H Evans

Publications and source records attributed to S H Evans.

11 recordsLinked to original sources
PubMed1991

Measurement of small-angle photon scattering for some breast tissues and tissue substitute materials.

For photon energies encountered in diagnostic radiology the shape of the scattering distributions for low-atomic-number media exhibits peaks in intensity close to the forward direction that are not predicted by conventional theoretical models. The positions and shapes of the peaks depend upon the interatomic and intermolecular configurations of the scatterers. The phenomenon is of particular interest because of its relevance to the understanding and modelling of x-ray imaging processes and the possibility that the peaking may be characteristic of tissue type. In the present study, peaks in the forward scattering distributions have been demonstrated for 19 samples of breast tissue and three tissue substitute materials using a position-sensitive photon detector and a 60 kVp x-ray source. Prominent features were observed for all samples investigated. Large differences were found in the shapes of the distributions between adipose and fibroglandular tissues and only small differences were found between carcinomas and fibroglandular tissues.

Adenofibroma↗
PubMed1989

A comparison of radiation doses to the breast in computed tomographic chest examinations for two scanning protocols.

Compared with other radiological examinations in which the breasts are directly exposed, the breast doses involved in computed tomographic (CT) chest examinations are high. A CT protocol which reduces such breast dose has been investigated. Breast doses have been measured for contiguous 10 mm scans and interspaced 3 mm scans. Differences in the breast doses were found between the left and right breasts for both scanning protocols. The dose associated with the interspaced scans was lower by a factor of about two compared with that for the contiguous scans.

Breast↗
PubMed1988

A quantitative analysis of the spatial relationships of grouped microcalcifications demonstrated on xeromammography in benign and malignant breast disease.

The mammograms of 444 patients who had a breast biopsy leading to a definitive histological diagnosis were reviewed. In 21 cases (4.7%) grouped microcalcifications were identified as the only mammographic abnormality. These groups of microcalcifications were analysed to determine whether there was any quantitative difference between benign and malignant lesions with respect to a shape parameter of the group, the spatial frequency of the particles and neighbour-to-neighbour relationships of the particles. This analysis did not reveal any significant difference between the spatial relationships of the grouped microcalcifications found in benign and malignant breast disease.

Biopsy↗
PubMed1984

Taxonomic abstraction in psychobiology.

If a body of knowledge in a scientific discipline is to be extended beyond empirical observation and into the realm of laws and principles, one of the fundamental requirements is a taxonomy which supports the systematic integration of observations. Psychobiology benefits from taxonomies provided by biology and chemistry, which include not only object oriented taxonomies such as species or chemical elements, but also process oriented taxonomies, such as oxidation, metabolism, phototaxis, or predation. Psychobiology has yet to provide equivalent taxonomies for its behavioral observations, although the common use of terms such as fear, anger, arousal, stress, and memory might lead one to suppose that these are based on a well established taxonomy of behavioral measures. In this report the logical and quantitative requirements for treating behavioral measures in terms of taxonomic classes are reviewed. A sample of studies representing recent research in psychobiology was examined to assess interest in such a taxonomy and to identify elements of current practice which might contribute to its development. Recent practice displays some evidence of interest in behavioral classes, in choice of language, and in frequent use of multiple dependent measures. Multivariate methods, which might elicit from such data evidence contributing to the development of a taxonomy, are rarely used. Recommendations are given on some appropriate analytic methods for data resulting from current practice and for new exploratory paradigms which could aim directly at the establishment of taxonomic classes for behaviors.

Animals↗
PubMed1981

Biochemical specificity of septal hyperreactivity: a behavioral discrimination.

Intra-septal injections of specific monoamine and cell body neurotoxins were used to determine the anatomical and biochemical elements critical to both short and longer term changes in reactivity normally seen after septal lesions. A multivariate discrimination performed on the basis of tactile, foot-shock and heat responsiveness revealed that septal lesions have a unique effect not accounted for by specific monoamine induced degeneration. Injections of 6-hydroxydopa and monosodium glutamate had slight effects on heat and shock responsiveness not at all comparable in degree or kind to septal lesion effects. Decreased hippocampal, but not hypothalamic, levels of norepinephrine may be associated with the longer term increased responsiveness to shock and heat in animals with septal lesions.

5,7-Dihydroxytryptamine↗
PubMed1980

Apparently changing patterns of inheritance in Alport's hereditary nephritis: genetic heterogeneity versus altered diagnostic criteria.

With the use of more stringent diagnostic criteria, it has recently been shown that some large pedigrees of Alport's and non-Alport's hereditary nephritis fit sex-linked dominant inheritance (O'Neill et al. 1978). We have used similar diagnostic criteria and have studied a number of Michigan pedigrees in order to see if this hypothesis would be confirmed. We found one small pedigree which definitely shows male-to-male transmission, while one large pedigree is tentatively compatible with sex-linked dominant inheritance. Many of the other pedigrees suggested male-to-male transmission. This Michigan experience is compared to other published reports and found to be consistent, although a trend of fewer reports of male-to-male transmission is seen. We conclude that genetic heterogeneity of Alport's hereditary nephritis is likely.

Female↗
PubMedDate not supplied

Quantitative measurement of small-angle gamma ray scattering from water, nylon, and Lucite.

The small-angle (2 degrees-10 degrees) total-differential-scattering cross sections of water, methyl methacrylate, and nylon 6 have been measured at a photon energy of 59.54 keV. An annular target geometry has been used with an acceptance of +/- 0.5 degrees and an experimental uncertainty of approximately 4% achieved. The experimental methods and data corrections necessary to obtain this accuracy are discussed in detail. The results demonstrate clearly the contribution of intermolecular effects to the scattering process and allow critical comparison with calculations using molecular form factors for water obtained from interpolated x-ray diffractometer data; agreement is obtained within the experimental uncertainties. They also support earlier Monte Carlo predictions of scattering in water at angles of the order of 2 degrees which are in disagreement with certain published experimental data.

Caprolactam↗