Biomedical subjects

R P Hammond

Publications and source records attributed to R P Hammond.

9 recordsLinked to original sources

PubMed2002

Observation of Kossel and Kikuchi lines in thermal neutron incoherent scattering.

In this Letter we report the observation of K lines (representing collectively, Kossel and Kikuchi lines) produced by monochromatic thermal neutrons interacting with a KDP (potassium dihydrogen phosphate) single crystal. Since K lines contain phase information, these observations establish the experimental basis for direct crystallographic phasing of atomic structures containing incoherent scatterers, such as hydrogen, via thermal neutron "inside source" holography.

Journal Article↗

PubMed2001

Atomic structure holography using thermal neutrons.

The idea of atomic-resolution holography has its roots in the X-ray work of Bragg and in Gabor's electron interference microscope. Gabor's lensless microscope was not realized in his time, but over the past twelve years there has been a steady increase in the number of reports on atomic-resolution holography. All of this work involves the use of electrons or hard X-rays to produce the hologram. Neutrons are often unique among scattering probes in their interaction with materials: for example, the relative visibility of hydrogen and its isotopes is a great advantage in the study of polymers and biologically relevant materials. Recent work proposed that atomic-resolution holography could be achieved with thermal neutrons. Here we use monochromatic thermal neutrons, adopting the inside-source concept of Szöke, to image planes of oxygen atoms located above and below a single hydrogen atom in the oxide mineral simpsonite.

Journal Article↗

PubMed1983

A calcium hypothesis of antidepressant action.

The biogenic amine hypothesis of affective disorders has served as a valuable model for investigations concerning the mechanism of action of antidepressant drugs. Despite numerous publications on the subject, the manner in which tricyclic antidepressants elicit their therapeutic effect remains unknown. Recent findings which involve tricyclic antidepressant interactions with thyroid hormone, along with an appraisal of the older literature concerned with dyscalcemias and affective disorders, provides the basis for an hypothesis featuring a role for calcium in mediating antidepressant responses.

Animals↗

PubMed1977

Thyroid cold acclimation influences on norepinephrine metabolism in brown fat.

Norepinephrine turnover rates and tyrosine hydroxylase activities were determined in the interscapular brown fat pad of the rat during cold acclimation, hyperthyroxinism, and after thyroidectomy. Rats were cold acclimated by placement in a cold room, one rat to a cage, for a period of 6 wk. Hyperthyroxinism was induced by daily subcutaneous injections of L-thyroxine (1 mg/kg) for 6 days. Norepinephrine turnover rate and enzyme activity were determined at the end of each experimental period and at 8 wk after thyroidectomy. The rate of norepinephrine turnover increased during cold acclimation and hyperthyroxinism and decreased after thyroidectomy. Cold acclimation resulted in a significant increase in tyrosine hydroxylase activity, whereas no significant effect on enzyme activity was observed in hyperthyroxinism or after thyroidectomy. None of the conditions produced a change compared to controls in the apparent Km of tyrosine hydroxylase for L-tyrosine. Cold acclimation resulted in a significant decrease in the apparent Km of tyrosine hydroxylase for pterin cofactor, whereas thyroxine treatment and thyroidectomy had no effect.

Acclimatization↗

PubMed1973