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Biomedical subjects

R L Armstrong

Publications and source records attributed to R L Armstrong.

32 records · Page 2Linked to original sources
PubMed1979

Comparison of Dycal and formocresol pulpotomies in young permanent teeth in monkeys.

This study compared Dycal and formocresol pulpotomies on young healthy permanent teeth with respect to continued dentinogenesis and root end development. Pulpotomy was performed on a total of forty permanent teeth with incompletely developed roots in three young stump-tailed monkeys (Macaca speciosa). Twenty teeth were treated with Dycal and twenty with formocresol. At the end of the experimental periods the animals were killed and the specimens were prepared and sectioned en bloc for histologic examination. The interval between treatment and death ranged between 7 and 797 days. Before each experimental procedure a Procion vital dye was administered as a marking agent for continued root development. Twelve of twenty teeth treated with Dycal and seventeen of twenty teeth treated with formocresol were judged to be successful as evidenced by continued root development, absence of periapical pathoses, and the presence of noninflamed or only mildly inflamed pulps. Brown and Brenn staining showed bacteria within the pulps of the teeth that failed. All but one of the teeth in this study showed evidence of continued root development as confirmed by Procion labeling.

Animals↗
PubMed1972

Biosynthesis of 50S ribosomal proteins during the outgrowth of Bacillus subtilis spores.

The biosynthesis of 14 protein bands from 50S ribosomes was studied during the outgrowth of Bacillus subtilis W23 spores. The time at which the synthesis of each protein band begins and the patterns of synthesis that each displays were determined by comparing the incorporation of (3)H-phenylalanine during five intervals throughout the first hour of outgrowth with the incorporation of (14)C-phenylalanine between 145 and 150 min. The majority of the proteins in the 14 bands analyzed were synthesized as early as 5 to 10 min. The bands could be grouped on the basis of their labeling patterns as well as the time required for them to achieve a high rate of synthesis. Three bands did not achieve a high rate of synthesis until after 30 min of outgrowth, and at least one of the proteins from these bands appeared to be located on the exterior of the 50S subunit. The significance of the proteins from these three bands is discussed in terms of the late formation of new, mature 50S subunits during outgrowth.

Bacillus subtilis↗
PubMedDate not supplied

Concrete/mortar water phase transition studied by single-point MRI methods.

A series of magnetic resonance imaging (MRI) water density and T2* profiles in hardened concrete and mortar samples has been obtained during freezing conditions (-50 degrees C < T < 11 degrees C). The single-point ramped imaging with T1 enhancement (SPRITE) sequence is optimal for this study given the characteristic short relaxation times of water in this porous media (T2* < 200 microseconds and T1 < 3.6 ms). The frozen and evaporable water distribution was quantified through a position based study of the profile magnitude. Submillimetric resolution of proton-density and T2*-relaxation parameters as a function of temperature has been achieved.

Cementation↗
PubMedDate not supplied

Near-field optical studies of local photomodification in nanostructured materials.

Fractal aggregates of silver nanoparticles are studied experimentally using atomic force microscopy and photon scanning tunnelling microscopy. Large changes in the near-field optical response of fractal aggregates are observed after the irradiation of samples with nanosecond laser pulses. The threshold energy density for photomodification using a 532 nm laser is measured to be 9 mJ cm(-2). It is shown that photomodification-induced changes in the local optical response can be two orders of magnitude larger than changes in far-field absorption.

Journal Article↗