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Results for “Physical Phenomena”

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At least 19 recordsLinked to original sources
PubMed2002

A review of physical phenomena associated with ultrasonic contrast agents and illustrative clinical applications.

Successful clinical applications of contrast agents involve an understanding of the physical interaction of ultrasound (US) with contrast agents. This paper reviews the physical phenomena involved in these interactions and discusses the relevant theoretical background for modeling US-contrast agent interactions. Measurement techniques using US to obtain information regarding contrast agents are summarized. Illustrative clinical applications are given in the second part of the paper. Recent developments in nonlinear imaging techniques and transient techniques are reviewed. New methods, such as depletion perfusion measurement, and high-frequency applications are included.

Contrast Media↗
PubMed1998

First steps in eukaryogenesis: physical phenomena in the origin and evolution of chromosome structure.

Our present understanding of the origin and evolution of chromosomes differs considerably from current understanding of the origin and evolution of the cell itself. Chromosome origins have been less prominent in research, as the emphasis has not shifted so far appreciably from the phenomenon of primeval nucleic acid encapsulation to that of the origin of gene organization, expression, and regulation. In this work we discuss some reasons why preliminary steps in this direction are being taken. We have been led to examine properties that have contributed to raise the ancestral prokaryotic programmes to a level where we can appreciate in eukaryotes a clear departure from earlier themes in the evolution of the cell from the last common ancestor. We shift our point of view from evolution of cell morphology to the point of view of the genes. In particular, we focus attention on possible physical bases for the way transmission of information has evolved in eukaryotes, namely, the inactivation of whole chromosomes. The special case of the inactivation of the X chromosome in mammals is discussed, paying particular attention to the physical process of the spread of X inactivation in monotremes (platypus and echidna). When experimental data is unavailable some theoretical analysis is possible based on the idea that in certain cases collective phenomena in genetics, rather than chemical detail, are better correlates of complex chemical processes.

Animals↗
PubMedDate not supplied

Depressive phenomena, physical symptom distress, and functional status among women with breast cancer.

The nature and scope of depression and its relationship to physical symptom distress and functional status were examined in 79 women 3 to 7 months after breast cancer diagnosis. Psychiatric diagnostic criteria for depressive disorders and a depression rating scale were used to measure depression. Nine percent of the sample had depressive disorder, and 24% had elevated depressive symptoms. Women with elevated depressive symptoms had more physical symptom distress (p < .0001) and more impaired functioning (p < .0001) than subjects with depressive disorders and without depression. Multiple regression was used to examine the contribution of key variables to functional status. Two variables accounted for 35% of the variance in functional status: symptom distress (28%) and depressive symptoms (7%).

Adult↗