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Biomedical subjects

J T Guthrie

Publications and source records attributed to J T Guthrie.

17 recordsLinked to original sources
PubMed2005

Preferential interactions in pigmented, polymer blends - C.I. Pigment Blue 15:4 and C.I. Pigment Red 122 - as used in a poly(carbonate)-poly(butylene terephthalate) polymer blend.

Some important characteristics of selected pigments have been evaluated, using the inverse gas chromatography (IGC) technique, that indicate the occurrence of preferential interactions in pigmented polymer blends. Attention has been given to copper phthalocyanine pigments and to quinacridone pigments incorporated in polycarbonate-poly(butylene terephthalate) blends. Selected supporting techniques were used to provide supplementary information concerning the pigments of interest, C.I. Pigment Blue 15:4 and C.I. Pigment Red 122. For C.I. Pigment Red 122 and for C.I. Pigment Blue, the dispersive component of the surface free energy decreases as the temperature increases, indicating the relative ease with which the molecules can be removed from the surface.

Azo Compounds↗
PubMed2005

Study of a core-shell type impact modifier by inverse gas chromatography.

Inverse gas chromatography (IGC) has been used to study the Lewis acid-base properties of a technologically and commercially important core-shell type elastomer (MBS rubber). The parameters determined were the dispersive component of the surface tension, the surface free energy, the enthalpy and the entropy of adsorption of polar and apolar probes, the surface Lewis acidity constant (Ka), and the surface Lewis basicity constant (Kb). The results show that the MBS rubber is amphoteric but strongly Lewis basic. It is weakly Lewis acidic. The results are in accord with the analysis of the molecular structure of PMMA, the shell component of this impact modifier (IM). The interactivity of this elastomer with the remaining materials in multicomponent polymeric systems is expected to be strongly influenced by the particular surface energetic properties of the MBS rubber. The results presented would contribute to the interpretation, forecast and optimization of the adhesion properties and phase preferences shown by this impact modifier when incorporated in such complex polymeric systems as polymer blends and composites.

Chromatography, Gas↗
PubMed2002

Characterisation of the surface Lewis acid-base properties of poly(butylene terephthalate) by inverse gas chromatography.

The surface of poly(butylene terephthalate) (PBT) was analysed by means of inverse gas chromatography (IGC). The specific component of the adsorption of polar probes on the surface of poly(butylene terephthalate) was found to be endothermic, and the change in the entropy of the system, positive, which is not a common case in IGC. An interpretation is given, based on the contribution of cleavage of hydrogen bonds in the PBT and formation of hydrogen bonds between the probe-molecules and the polymer. The surface Lewis acidity and basicity constants, Ka and Kb, respectively, were determined and found to correlate well with an analysis of the repeating unit and end-groups in this polymer.

Acids↗
PubMed2002

Characterisation of the surface Lewis acid-base properties of the components of pigmented, impact-modified, bisphenol A polycarbonate-poly(butylene terephthalate) blends by inverse gas chromatography-phase separation and phase preferences.

Inverse gas chromatography was used to study the surface Lewis acid-base properties of the major components of pigmented, impact-modified, polycarbonate-poly(butylene terephthalate) blends. An investigation of the Lewis acid-base interactions in these polymeric systems has been carried out, based on the values determined for the surface Lewis acidity constant (Ka), surface Lewis basicity constant (Kb) and on the chemical and physical structure of the materials involved. This analysis provided the rationale for an interpretation of the phase separation and the phase preference that exist in these polymer blends, and of the consequences to their physical and mechanical properties.

Acids↗
PubMed1986

Investigation into the use of graft copolymer-based cibacron blue F3GA columns for the purification of proteins.

The graft copolymers Nylon-co-hydroxyethylmethacrylate and poly(ethylene)-co-hydroxyethylmethacrylate coupled to Cibacron blue F3GA at wet volume levels similar to those obtained with Sepharose 4B. However, the graft copolymers removed protein from human serum to a far lesser extent than did Sepharose 4B. Further investigations involved the preparation of hydrolyzed poly(vinyl acetate) copolymers of nylon and polyethylene and of cellulose-co-hydroxyethylmethacrylate and study of the ability of the copolymers to remove human serum albumin and lactic dehydrogenase. Comparisons were made with Sepharose 4B-, Sephadex G15-, and G25-based Cibacron blue F3GA systems. The effectiveness of Sepharose 4B-Cibacron blue F3GA is thought to be due to the manner in which the dye is located within the pores of the gel.

Adsorption↗
PubMed1980

Immobilization of beta-galactosidase and other enzymes onto p-amino-carbanilated cellulose derivatives.

beta-Galactosidase and other enzymes were immobilized on p-amino-carbanilated derivatives of cellulose and methylol cellulose using the diazo method and through glutaraldehyde. The optimum conditions for coupling cellulose tri-(p-amino-carbanilate) (CTAC) to beta-galactosidase were established. The diazo coupling method with CTAC gave greater activity than with glutaraldehyde when coupled to beta-galactosidase (Escherichia coli). The stability of the CTAC-beta--galactosidase system was examined. The disubstituted p-amino-carbanilate derivative (CDAC) gave a lower activity, whereas the methylol analog (MCTAC) gave slightly greater activity. The CTAC was also used to immobilize glucose oxidase, trypsin, pepsin, and papain.

Amines↗
PubMed1978

Reading ability and efficiency of graphemic-phonemic encoding.

It was hypothesized that children with a specific reading disability differ from children of normal reading ability because the former are impaired in extracting speech-like representations from graphemes. Three groups of 12 each of grade school boys and girls participated in timed word comparison tasks which required a "same-different" response. One group was specifically reading deficient, the other groups were matched either on age or on reading level to a deficient group. Monosyllabic word pairs were presented simultaneously by a slide projector. The deficient readers were slower than the two control groups only in a vowel phoneme comparison task and produced response times similar to the control groups for graphemic and visual symbol comparisons. The results are consistent with the hypothesis that the problem in learning to read is due to multiple relationships between spelling (graphemes) and sound (phonemes).

Child↗
PubMed1976

The genetics of specific reading disability.

Members of the immediate families of twenty children with specific reading disability were examined to determine the prevalence of reading disability within the families. A procedure was developed for identifying adults who may have compensated for a disability manifested more clearly in childhood. Forty-five percent of 75 first-degree relatives of the parents were affected and there was a significantly greater number of affected male relatives than females. No single mode of genetic transmission is evident after inspection of the pedigrees. It is suggested that the disorder is genetically heterogeneous and that subgroups of disabled readers should be looked for.

Adult↗