Showing papers by "University College Cork published in 1978"

Heat stability of milk: influence of denaturable proteins and detergents on pH sensitivity

Abstract: α-Lactalbumin and SDS in addition to β-lactoglobulin introduced pH sensitivity to the heat stability–pH curve of serum protein free casein micelles particularly by increasing stability in the pH range 6·4–6·7. Bovine serum albumin, ovalbumin and lysozyme caused marked destabilization of milk and casein micelle suspensions throughout the pH range 6·4–7·4. Tetramethyl ammonium bromide caused destabilization of milk at pH values > 7·0, but had no effect in the region of maximum stability while the non-ionic detergents Triton X-100 and Tween 80 had no effect on heat stability.

Heat stability of milk: influence of dilution and dialysis against water

Abstract: The marked precipitation of Ca phosphate found to occur at ~ pH 6·8 when milk is heated to high temperatures may account for the minimum in the heat coagulation time (HCT)–pH curve at ~ pH 6·8. Dialysis of milk against water for about 3 h converted a normal type A milk to one with type B heat stability characteristics by reducing stability in the region of the HCT maximum while increasing stability in the region of the minimum. Reduction of the concentration of urea, lactose, Na or chloride did not cause these changes and gross micelle structure appeared to be intact following short dialysis as indicated by turbidity and sedimentability. Dilution of milk with water increased stability at the minimum without significantly affecting stability at the maximum. Pre-heating at 80°C for 10 min precluded the effect of dilution but not of dialysis.

Search for high energy |[gamma]|-ray bursts from evaporation of primordial black holes

Abstract: PRIMORDIAL black holes (PBH) have been predicted by Hawking1. Density fluctuations in an early Universe might have given rise to a power law spectrum of low mass black holes which would evaporate by a thermal radiation process. Holes of initial mass 1012 kg might now be entering the terminal stages of evaporation, culminating in an explosion. The total energy liberated in particle emission and the corresponding radiation time scales depend critically on the nuclear models adopted2. The composite particle (CP) model predicts the liberation of 1027 J during the final 10−7 s of the explosion. About 10% of the total energy goes into γ rays with the spectrum peaked at 250 MeV. The elementary particle (EP) model predicts the liberation of 1030 photons during the final 0.1 s of the explosion at energies around 5 × 1012 eV (refs 3,4). We report here the results of a search for γ rays associated with the evaporation of PBHs, and upper limits are presented based on the latter model.

Heat stability of milk: influence of κ-casein hydrolysis

Abstract: The release of 12% (w/v) TCA-soluble N-acetylneuraminic acid from casein at 5 temperatures between 110 and 150°C was determined and showed a Q10 °C about 3; coagulation occurred when about 20% of the κ-casein was hydrolysed. Renneting of milk or colloidal calcium phosphate-free milk rendered the caseinate very heat-labile at its normal pH when more than about 20% of the κ-casein had been hydrolysed. Heat stability at the pH of maximum stability was not significantly decreased until after very prolonged renneting, but stability at pH values alkaline to the minimum was very sensitive to such hydrolysis suggesting that κ-casein is the principal factor responsible for heat stability in that region. Systems which do not have a maximum or minimum in the heat coagulation time–pH profile, i.e. serum protein-free casein micelles in milk diffusate, or milk which had been dialysed against water, were destabilized by renneting throughout the pH range 6·4–7·4.

Carcinoid tumour of the gall bladder associated with a meningioma.

Abstract: A case is reported of a patient with a carcinoid tumour of the gall bladder with metastasis in the liver and complicated by a posterior cranial fossa meningioma Both tumours were dealt with successfully by surgery A review of the other 15 cases of carcinoid tumours of the biliary tree is made The association of carcinoid tumours and second primary tumours is stressed

Butter: technology to control rheology

Abstract: Different approaches to increasing the liquid continuous fat phase of butter, by fractionation, by production of polyunsaturated milk fat through feeding of protected lipids and by direct addition of liquid vegetable fat are considered. The dispersed phases consisting of fat crystals, water droplets and air bubbles play a role in butter rheology. Thixotropic changes, which occur when butter sets, are partly reversed on reworking. Normal variations in the moisture and gas met with in commercial practice are not likely to have a significant influence on the physical properties of butter. Their role in the plasticity of dairy based spreads may be much more important.

Measurements of Earth-Space Attenuation at 230 GHz

Abstract: Measurements of attenuation at 230 GHz through the total atmosphere due to the presence of oxygen and water vapor molecules, clouds, and rain are presented and discussed. The measurements were carried out using a specially designed superhetrodyne receiver mounted on a sun tracker. Simultaneons measurements were also carried out at 13 GHz. For a measuring site close to sea level at Holmdel, NJ, the "clear-sky" zenith attenuation was found to be given by A (dB) = 0.35 rho, where rho was the measured ground water vapor density in g/m/sup 3/. When the ground temperature was below about 7/spl deg/C, most cloud and overcast gave < 0.5 -dB attenuation whereas with a ground temperature greater than 13/spl deg/C, cloud attenuation was 8-10 times greater. Calculations of zenith attenuation in the 230-GHz atmospheric window were also made using the Gross analytic line shape, Schulze-Tolbert empirical line shape, and an empirically modified Gross line shape. These calculations were based on determinations of water vapor density and temperature made at the measurement site, and on radiosonde measurements made at a distance of 80 km away. Measured and calculated results are graphically compared. It is concluded that either the modified Gross line shape or the Schulze-Tolbert line shape gives conservative estimates of zenith attenuation at 230 GHz for clear days, while the Gross line shape gives fair agreement with measured results.

A rapid sensitive bioassay for determination of paraquat and diquat in water

Abstract: Summary: Resume: Zusammenfassung The change in cell-membrane permeability as indicated by leakage of electrolytes from treated fronds of Lemna minor was the criterion used to detect the presence of diquat and paraquat in solution. The minimum herbicide concentrations that could be detected ranged from 1.8 and 1.7 μg/ml diquat and paraquat cation respectively after 3 h treatment to 0.00018 and 0.000017 μg/ml after 72 h. Paraquat was more active than diquat in all treatments. Increase in cell-membrane permeability occurred without the appearance of injury such as, chlorosis or bleaching of fronds. Light was necessary for these herbicides to alter cell-membrane permeability, though a little herbicidal activity could be detected after 48 h in the dark at concentrations above 0.17μg/ml. Un test biologique rapide et sensible pour la recherche du paraquat et du diquat dans l'eau Des modifications de la permeabilite de la membrane cellulaire, revelees par la deperdition d'electrolytes a partir de frondes de Lemna minor, ont ete utilisees comme criteres pour reveler la presence de diquat et de paraquat dans des solutions. Les concentrations minimales d'herbicides qui ont pu etre decelees se sont situees entre 1,8 μg/ml et 1,7 μg/ml des cations diquat et paraquat respectivement, apres 3 heures de traitement, jusqua 0,00018 et 0,000017 μg/ml apres 72 heures. Le paraquat s'est montre plus actif que le diquat dans tous les traitements. Un accroissement de la permeabilite cellulaire s'est produit sans qu'il soit apparu de degâts tels que la chlorose ou le blanchissement des frondes. La lumiere a ete necessaire pour que ces herbicides alterent la permeabilite de la membrane cellulaire, bien qu'une faible activite herbicide ait pu etre decelee apres 48 heures a l'obscurite, a des concentrations superieures a 0,17 μg/ml. Ein schneller und empindlicher Biotest fur den Nachweis von Paraquat und Deiquat in Wasser Veranderungen in der Permeabilitat der Zellmembran in Form des Austretens von Elektrolyten aus behandelten Wedeln von Lemna minor wurden als Kriterium fur den Nachweis von Deiquat und Paraquat in wasseriger Losung benutzt. Die geringsten Herbizidkonzentrationen, die festgestellt werden konnten, lagen nach 3 h nach der Applikation bei 1,8 und 1,7 μg/ml Deiquatbzw. Paraquat-Kation und nach 72 h bei 0,00018 und 0,000017 (μg/ml). In allen Behandlungen war Paraquat wirksamer als Deiquat. Der Anstieg in der Zellmembran-Per-meabilitat war nichi mit ausseren Symptomen wie Chlorose oder Ausbleichen der Wedel verbunden. Fur die Herbizidbedingte Veranderung der Zellmembran-Permeabilitat war Licht notwendig, doch konnte auch eine geringfugige Herbizidwirkung nach einer 48-h-Dunkelperiode bei Konzenlrationen > 0,17 μg/ml festgestellt werden.

Low temperature electroplated Au-SnNi-Au ohmic contacts on n type GaAs

Abstract: A method is described for fabricating ohmic contacts on n type GaAs by alloying electroplated layers of Au-SnNi-Au at 300°C, resulting in a contact resistance of approximately 3 x 10 -5 Ω cm 2 . In applications for which this resistance is adequate, the technique has the advantage of requiring low-temperature alloying for short times.

The western isle of Ireland and the Eastern seaboard of America ‐ England's first frontiers

Abstract: This paper outlines the basis for a comparative analysis of the origins processes and geographical impact of British colonisation in both Ireland and North America from c. 1550 to c. 1800. While recognising the fundamental differences in scale, location, environments and native population densities between the two study areas, the available evidence suggests that in terms of general strategies of colonisation, some genuine parallels can be inferred. Likewise, in the actual processes of colonisation, similar patterns of early settlement dispersal and the exploitative competitive nature of both frontiers can be documented. The differences in the colonial geographies of the two regions were, however, more profound. Here, the fundamental contrasts between a more densely settled and more developed pre‐colonial Ireland and the sparsely settled extensive territories of the eastern seaboard of America were crucial. In Ireland, a colonial society was generally superimposed upon long‐developed settlement, ...

A bilateral antidiuresis to renal artery infusion of prostaglandin E1 in dogs treated with phenylbutazone.

Abstract: 1. In acute experiments, high levels of endogenous prostaglandins, provoked by operative stress, could obscure or alter the actions of infused prostaglandins on the kidney. For this reason we decided to compare the effects of infusing prostaglandin E1 into the renal artery of the dog before and after the administration of phenylbutazone, a prostaglandin synthetase inhibitor. 2. Infusion of prostaglandin E1 into the left renal artery of the pre-phenylbutazone treated dog undergoing a mannitol diuresis increased renal plasma flow, glomerular filtration rate and the excretion of salt and water. The findings are in general agreement with those reported by others. 3. Following phenylbutazone administration the vascular and saluretic actions of prostaglandin E1 were unchanged but a reduced diuretic effect was observed. The response to a low dose of prostaglandin E1 (0·05 μg/min) was reduced from 1·46 ± 0·15 to 0·96 ± 0·16 ml./min (P < 0·001) and the response to a high dose (0·5 μg/min) from 1·82 ± 0·19 to 0·99 ± 0·31 ml./min (P < 0·002). 4. A significantly less dilute urine was excreted during prostaglandin infusion in the dog after phenylbutazone treatment than before. The reduction in the diuretic response was of the same order as the decrease in the free water clearance response, while the increase in osmolar clearance was unchanged. 5. In water-loaded dogs treated with phenylbutazone, infusion of prostaglandin E1 into the left renal artery had a biphasic effect on urine output from the left kidney. An initial diuretic response to a low dose of prostaglandin E1 disappeared with the infusion of higher doses, and antidiuresis developed in the immediate post-infusion period. 6. As prostaglandin was infused into the left kidney progressive antidiuresis was seen in the non-infused right kidney. 7. It is concluded that endogenous prostaglandins do not obscure or alter the vascular and saluretic actions of intrarenal prostaglandin E1. The findings question the proposed link between the vascular and saluretic actions of this compound. 8. It is suggested that the reduced diuretic effect of prostaglandin E1 in series no. 1, and the antidiuresis in the water-loaded dogs, are caused by the release of endogenous ADH. It is further suggested that phenylbutazone unmasks this release by removing the endogenous prostaglandins. If these deductions are correct, the findings support the anti-ADH role assigned to endogenous prostaglandins by Anderson, Berl, McDonald & Schrier (1975).

A Superhetrodyne Receiver from 350 - 400 GHz

Abstract: A superhetrodyne receiver operating in the frequenCY range 350 - 400 GHz has been constructed. The mixer consists of a low capacitance GaAs Schottky barrier diode, contacted by means of an ultra small inductance spring, mounted across a reduced height waveguide which is fed by a corrugated horn. The quasi-optical diplexer consists of a modified polarization rotating Michelson interferometer and the local oscillator is a Carcinatron. The overall receiver design is discussed and results of measured performance will be presented.

The pathogenesis of essential hypertension.

Abstract: Essential hypertension is a quantitative abnormality, the pathological effects and risks increasing with the blood pressure level. In Western countries blood pressure rises with age in most individuals, so essential hypertension is more frequent in middle and older age groups. It is likely that an individual's blood pressure level is determined by many interacting factors. These include heredity, which probably acts multifactorially, and many environment influences, including psychological stress and obesity. Specific factors may be of varying importance in different individuals and in different populations. Several physiological mechanisms control the blood pressure level and may be altered in essential hypertension. In early hypertension sympathetic nervous activity is sometimes increased, although in long-standing hypertension this is less marked. Cardiac output may be increased in borderline hypertension but is normal in established hypertension, when total peripheral resistance is increased. Total exchangeable sodium is normal, while the renal pressure-natriuresis balance is altered, so that for a given pressure the hypertension kidney excretes less sodium. In some patients, plasma renin is low, probably as a result of renal adaption to prolonged hypertension. The pathogenic sequence in essential hypertension is uncertain. Increased autonomic activity may cause vasoconstriction in renal and other arterioles and increase cardiac output, leading to a rise in blood pressure. Elevated pressure itself produces structural changes in the resistance vessels, including those of the kidney, which eventually maintain the hypertension even when the initiating stimulus is removed. The way in which heredity and environment influence pathogenic mechanism is also uncertain. Heredity might, for example, influence the autonomic response to stress or the liability to irreversible changes in the resistance vessels or in the kidney. Environmental factors may also increase autonomic activity, enhance vascular reactivity or alter renal function.

The strange physics of moving bones

Abstract: The centripetal force in a bone moving at a joint is a consequence, not a cause, of the bone's curved motion. That it is centripetal and a consequence of the motion follow from the need of a force to prevent physiological dislocation of the joint, and from a complete revision of Newtonian mechanics in this field.