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Biomedical subjects

J C Roberts

Publications and source records attributed to J C Roberts.

15 recordsLinked to original sources
PubMed1977

Wear of dental amalgam.

The wear of cental amalgam was studied by single- and double-pass sliding and by a silicon carbide abrasion test. A dispersed amalgam showed significantly better resistance to two-body abrasion than the spherical amalgams tested. The wear amalgam was determined by resistance to penetration and by a ductile mode of surface failure over the load range studied. Differences in the wear of amalgam and restorative resins and composites are discussed.

Composite Resins↗
PubMed1977

Temperature acclimation in the Mongolian gerbil (Meriones unguiculatus): biochemical and organ weight changes.

1. Adult Mongolian gerbils (Meriones unguiculatus) were acclimated to 5 +/- 1, 24 +/- 1 and 34 +/- 1 degrees C for 6-8 weeks. 2. Body weights of temperature acclimated gerbils did not differ significantly from controls. Organ wt/body wt ratios of liver, kidney and heart increased in cold-acclimated and decreased in heat-acclimated gerbils. Adrenal wt/body wt ratio increased in the cold and was unchanged in the heat. Relative weights of brain, spleen, lungs, brown fat and ovaries + uterus did not change with temperature acclimation. 3. Cold acclimation produced significant increases in specific and total activity of brown fat alpha GPO and liver SO and AAO and in total activity of kidney SO; a significant decrease in liver mitochondrial ADP/O ratio with succinate as substrate; and no change in brown fat SO or liver alpha KGO. 4. Heat acclimation produced significant decreases in specific and total activity of liver and kidney SO, and in total activity of brown fat SO and alpha GPO, and liver AAO and alpha KGO. 5. The combined biochemical and organ wt changes seen in temperature-acclimated gerbils suggest that this species is capable of altering its metabolic thermogenic potential in response to a wide range of ambient temperatures.

Acclimatization↗
PubMed1977

Fracture toughness of composite and unfilled restorative resins.

Fracture toughness, critical strain energy release rate, and critical stress intensity factor were determined for experimental and commercial restorative resins. A composite resin had lower resistance to crack initiation than an unfilled acrylic resin. The data were consistent with surface failure observed in single-pass wear studies of these resins.

Acrylic Resins↗
PubMed1976

Obstruction due to prepyloric mucosal diaphragm.

Antral mucosal diaphragm is uncommon, and presents with manifestations of obstruction to the pyloric outlet. The diagnosis is usually established only by gastrotomy. Excision of the diaphragm or pylorophasty affords permanent cure and unnecessary partial gastrectomy should be avoided.

Adult↗
PubMed1976

Giant leiomyoma of the stomach.

A giant smooth muscle tumour of the stomach was excised in a 58-year-old man. Although small leiomyomas are not rare, the giant gastric leiomyoma is not common, and may present diagnostic and operative difficulties. It is an essentially benign tumour, unlike the "bizarre" leiomyoma or leiomyoblastoma.

Humans↗
PubMed1976

Marine sterols. III--The sterol compositions of oceanic jellyfish. The use of gas chromatographic mass spectrometric techniques to identify unresolved components.

The sterol compositions of three oceanic jellyfish have been determined using gas chromatographic mass spectrometric techniques involving the use of two separate gas chromatographic column systems. The components in overlapping peaks have been identified by comparison of the mass spectra of peaks in the two column systems using subtractive techniques. A mid-water animal, Periphylla periphylla, was found to contain a very complex and unusual sterol profile including rare 5alpha-stanols, whereas two other oceanic jellyfish Pelagia noctiluca and Atolla wyvillei contained similar mixtures of delta5 sterols to those previously isolated from coastal species.

Chromatography, Gas↗
PubMed1976

Host--dose--time: a concept for atherosclerosis.

Advances in knowledge about atherosclerosis in the past 25 years were discussed. Areas of disagreement and agreement were identified. A concept of HOST-DOSE-TIME was introduced for the skeptical analysis of past, present, and future observation and treatment of atherosclerosis.

Age Factors↗
PubMed1975

Sterols of the cockle Cerastoderma edule. Evaluation of thermostable liquid phases for the gas-liquid chromatographic-mass spectrometric analysis of the trimethylsilyl ethers of marine sterols.

Some recent liquid phases for gas-liquid chromatography with improved thermostability have been evaluated for their use in the gas-liquid chromatographic-mass spectrometric (GC-MS) analysis of the complex mixtures of sterol trimethylsilyl ethers obtained, often in small amounts, from marine organisms. A combination of Dexsil 300 GC, SE-30 "ultraphase" and Silar 5CP is recommended for use in this technique because of the excellent separating efficiency and the very low substrate bleed. GC-MS analysis of the sterol trimethylsilyl ethers obtained from the cockle Cerastoderma edule has established the identity and relative proportions of the eleven sterols present.

Chromatography, Gas↗
PubMed1975

Traumatic pancreatitis and pleural effusion.

Two cases of pleural effusion are described, both of which were associated with pancreatitis of traumatic origin. It is suggested that in some cases of unexplained pleural effusion, concomitant pancreatitis should be sought as a possible cause.

Adult↗
PubMedDate not supplied

Surface failure of commercial and experimental restorative resins.

A single-pass test was used to study the surface failure of commercial and experimental restorative resins and composites. The surface failure observed for unfilled diacrylate resins was more severe than that seen for an unfilled acrylic resin. Addition of nonsilanated filler to the diacrylate resins increased the resistance to penetration but did not dramatically change the mode of surface failure. The surface failure of the commercial composite resins, which contain silanated filler, was ductile in mode and the resistance to penetration of the diamond slider was the highest of the materials studied. The wear of restorative resins and composites is determined, therefore, by resistance to penetration as well as mode of deformation during sliding.

Acrylic Resins↗