Showing papers by "Newcastle University published in 1981"

The discrimination of mean directions drawn from Fisher distributions

Abstract: Summary An acceptably accurate approximation for the sampling distribution of the angle between two sample mean directions, conditional on the observed lengths of the vector resultants, is derived for samples drawn from Fisher populations sharing a common true mean direction. From this a test is given for the null hypothesis that two populations (with a common precision parameter) share a common true mean direction. This test is then compared with the unconditional test derived by Watson. The conditional test is then extended to an approximate test for the case where the two populations do not share a common precision parameter. The conditional test for populations with a common precision parameter is then extended to the case where it is desired to test simultaneously whether several samples could have been drawn from populations sharing a common true mean direction. The pooled, unbiased estimate for the inverse of the precision parameter is determined. From this a test for homogeneity of the precision parameter is derived for the case of several samples having unequal sample sizes.

The Distribution of Queuing Network States at Input and Output Instants

Abstract: Queuing networks are studied at selected points in the steady state, namely, at the moments when jobs of a given class arrive into a given node (either from the outside or from other nodes) and at the moments when jobs of a given class leave a given node (either for the outside or for other nodes). The processes defined by these points are known to be, in general, non-Potsson, interdependent, and serially correlated; therefore the relation between the distribution of the system state embedded at those moments and the steady-state (or random point) distribution is not obvious a priori. For a large class of networks having product-form equihbrium distribnttons it is shown that (a) if the given job class belongs to an open subchain, the state distributions at input pomts, output points, and random points are identical, and (b) if the job class belongs to a closed subchain, the distribution at input and output points ts the same as the steady-state distribution of a network with one less job in that subchain.

Cyclosporin A promotes spontaneous outgrowth in vitro of Epstein-Barr virus-induced B-cell lines.

Abstract: Cyclosporin A (CSA) is a fungal metabolite which exerts profound effects on the immune system and has potential as a selective immuno-suppressive agent1. Clinical trials with human renal allograft recipients have confirmed this potential but there have been disturbing reports of lymphoma in a significant number of patients2,3. Despite extensive animal studies, the specificity of this drug for human lymphocyte subpopulations is largely unknown4. We demonstrate here that in vitro CSA has no apparent effect on Epstein-Barr virus (EBV)-induced B-lymphocyte activation, but totally inhibits the T-cell dependent pokeweed mitogen (PWM) B-cell response. In addition, CSA markedly facilitates the outgrowth of B-lymphoblastoid cell lines from both EBV-infected and non-infected lymphocytes of EBV immune donors cultured in vitro. These results indicate that CSA can interfere with the lymphocytes normally responsible for maintaining the life-long carrier state initiated by primary infection with EBV, allowing outgrowth of the persistently infected cells circulating in the peripheral blood.

Alopecia areata and auto-immunity.

Abstract: SUMMARY The prevalence of auto-antibodies against thyroid constituents, gastric parietal cells, smooth muscle cells, mitochondria, reticulin, nuclear constituents and rheumatoid factor in 108 patients with alopecia areata was compared with that found in a previous survey of the local population. Female patients had a significantly increased prevalence of anti-thyroid antibodies which were present in 30% overall and in 44% of the youngest age group (11–17 years). Smooth muscle antibodies were more frequent in female patients but the increase was not significant. Male patients had a significantly increased prevalence of thyroid and gastric parietal cell antibodies (11.4% each). In females, antithyroid antibodies were associated with extensive hair loss: they were found in 42% of female patients with total alopecia and only 20% of males with total hair loss. A family history of alopecia areata was obtained from 24% of patients; 10% had relatives with thyroid disease and 10% had diabetic relatives. These findings confirm the association between alopecia areata and the other auto-immune diseases.

Nonlinear Taylor vortices and their stability

Abstract: Axisymmetric numerical solutions of the Navier-Stokes equations for flow between rotating cylinders are obtained. The stability of these solutions to non-axisymmetric perturbations is considered and the results of these calculations are compared with recent experiments.

Selective isolation and enumeration of actinomycetes using rifampicin

Abstract: Addition of rifampicin (5µg/ml) to a number of media allowed the selective isolation of Actinomadura strains from soil and enabled large numbers of ‘Thermomonospora (Thm.) chromogena’ and Streptomyces (St.) albus to be isolated from hay and straw. Saccharomonospora (S.) viridis was also tolerant to the antibiotic but was often inhibited by other isolates, while other bacteria including Micropolyspora faeni, ‘Thm. fusca’, Thermoactinomyces (Tha.) vulgaris and some other Streptomyces spp. were mostly sensitive, even to 2·5 µg/ml. Heating soil samples at 100°C for 15 min further decreased the number of unwanted bacteria growing on glucose-yeast extract agar supplemented with 5 µg/ml of rifampicin.

Growth Cycles with Induced Technical Change

Abstract: This paper concerns itself with two related topics: the relative shares of workers and capitalists in the national income and the labour augmenting bias of technical change. Both have been dealt with, in contrasting fashion, in two seminal papers on distribution theory. Kennedy (I964) attempts to explain the then observed constancy of relative shares with the help of the now famous invention possibility frontier. However, the wage and profit rates are exogeneous to his model. Goodwin (I967), on the other hand, presents a model of cycles in growth rates in which the share of labour, the wage rate and the profit rate are endogenously determined. However, unlike the Kennedy analysis, technical change is assumed to be constant and exogeneously given. Given that these pioneering works have addressed themselves to important questions, it seems a worthwhile task to build a model in which the shares of labour and capital, the wage rate, the profit rate, and technical change are all endogenously determined. The perspective we have chosen here introduces the key element of Kennedy's perception, induced technical change, into the Goodwin scheme and the consequences of so doing are traced out in the following terse account. There are two classes in the economy, workers and capitalists. Only one good q(t) is produced and it can be either consumed or invested. Capital stock k(t) is homogeneous and, for simplicity, also assumed to be non-depreciating. The capital-output ratio at time t is denoted by o(t). Labour, I(t) is also homogeneous and its productivity at time t, a(t) = q(t)/l(t), improves at the rate ac(t). Labour's share in the national income denoted by u(t) is

A formal model of atomicity in asynchronous systems

Abstract: We propose a generalisation of occurrence graphs as a formal model of computational structure. The model is used to define the "atomic occurrence" of a program, to characterise "interference freeness" between programs, and to model error recovery in a decentralised system.

The effect of calcium on cadmium toxicity in the freshwater amphipod, Gammarus pulex (L.).

Abstract: Adult intermoltGammarus pulex were exposed to a range of cadmium concentrations in an artificial stream water containing 20 mg calcium l−1. 96 hr and 48 hr LC-50 values obtained were 0.12 and 0.68 mg Cd l−1, respectively.

Interaction of light and temperature on the germination of Rumex obtusifolius L.

Abstract: Germination of Rumex obtusifolius L. seeds (nutlets) is low in darkness at 25° C. Germination is stimulated by exposure to 10 min red light (R) and also by a 10-min elevation of temperature to 35° C. A 10-min exposure to far-red light (FR) can reverse the effect of both R (indicating phytochrome control) and 35° C treatment. Fluence-response curves for this reversal of the effect of R and 35° C treatments are quantitatively identical. Treatment for 10 min with light of wavelenght 680, 700, 710 and 730 nm, after R and 35° C treatment, demonstrates that germination induced by 35° C treatment results from increased sensitivity to a pre-existing, active, far-red-absorbing form of phytochrome (Pfr) in the seeds.

Surface Vorticity Modelling of Separated Flows from Two-Dimensional Bluff Bodies of Arbitrary Shape

Abstract: A method is presented for the computation of separated flows past two-dimensional bodies of arbitrary shape. The surface vorticity technique is used to model the body flow and is combined with vorticity generation, shedding, and convection schemes which simulate the separation regime. The method is applied here especially to bluff body flows and illustrative examples have been limited to symmetrical or half plane flows only. An extension of the technique to free streamline flows is described and illustrated by comparison with the classical solution for free streamline separation from a flat plate.

Impaired contact hypersensitivity in untreated psoriasis and the effects of photochemotherapy and dithranol/UV-B.

Abstract: Cell mediated immune reactivity was studied in eighty-five psoriasis patients and twenty-five healthy controls by an improved (quantitative) method for measuring contact hypersensitivity to 2,4 dinitrochlorobenzene (DNCB). Patients were sensitized with 50 micrograms DNCB, the lowest dose found to sensitize all healthy subjects. Responses to epicutaneous challenge with a series of concentrations of DNCB were measured as volumes calculated from diameter and thickness and the various groups were compared by the differences in the log dose-response curves. Patients with untreated psoriasis were less responsive than healthy controls; responses were less still in patients treated with dithranol/UV-B/tar and they were least of all in patients treated with photochemotherapy with 8-methoxypsoralen and UV-A (PUVA), particularly in those who pigmented least. Sensitization and challenge at different stages of treatment showed that both induction and elicitation of sensitization were impaired by PUVA. The possible relationship of these changes to DNCB metabolism, Langerhans cell damage and a decrease in circulating T cells is discussed. Although the clinical significance of the findings is unknown, treatment with dithranol/UV-B/tar has proved safe over many years of use.

Disturbances in lactate metabolism in patients with liver damage due to paracetamol overdose

Abstract: Six patients with liver damage following paracetamol overdose, one patient with viral hepatitis and six control subjects were infused with sodium L(+) lactate. In controls the results were analysed using a single compartment model while in paracetamol patients a two compartment system was used to derive the fractional rate removal constant and lactate distribution volume. Forearm arterio-venous differences of lactate were also determined in order to assess the role of voluntary muscle in removal of a lactate load. In paracetamol patients with fractional rate removal constant was decreased to less than half the control value (P less than 0.001) while total distribution volume was similar to the two groups. Fasting lactate concentrations were significantly increased in paracetamol patients due to diminished lactate removal since the endogenous production rate of lactate was not significantly different from controls. A greater proportion of the lactate load was removed in voluntary muscle in paracetamol patients (39%) than controls (17%). Since the balance of lactate removal occurs principally in the liver, the decrease in the fractional rate removal constant in patients following paracetamol overdose indicates a severe derangement of hepatic lactate metabolism with a compensatory increase in lactate metabolism in voluntary muscle.

Pharmacokinetics of parenteral paracetamol and its analgesic effects in post-operative dental pain.

Abstract: A double-blind, randomised, crossover trial was undertaken to compare the analgesic effects of a single dose of paracetamol (1000 mg i.v.) with placebo in the immediate post-operative period following removal of impacted lower third molars. There was no significant difference in the pain relief between paracetamol and placebo in the first hour following injection. Thereafter, there was significantly less pain (P less than 0.05) after treatment with paracetamol than after placebo. Plasma concentrations of paracetamol were measured and pharmacokinetic variables were determined. Over the four hour period of investigation there was no clear relationship between analgesia and paracetamol concentration in either central or peripheral compartments.

Pubertal induction of sweat gland activity.

Abstract: 1. To study the difference in sweat rate between men and women the rates of cholinergic-induced sweating were measured in normal people before and after puberty and in response to androgens and anti-androgens. 2. Sweat rate in men was more than double that in women. 3. This difference did not occur in prepubertal boys and girls in whom the rate, corrected for surface area, was comparable with that in women. 4. Application or injection of androgen locally did not stimulate sweat production in the adult female. 5. Anti-androgen topically or systemically did not decrease sweat rate in men. 6. It is concluded that the rate of sweat rate in men is caused by androgen-induced gene expression at puberty and not by androgen modulation in adult life.

Control of postoperative pain by interactive demand analgesia

Abstract: A demand analgesia apparatus is described. It communicates with the patient by means of spoken messages in any desired language, so that preliminary instruction is unnecessary. Dosage is limited by a reduction in respiratory rate, and by a series of electronic fail-safe circuits. Operation of the system is illustrated in a series of 10 patients given fentanyl "on demand" for the first 12 h after operation. The mean dose rate 0.73±0.49 μg min −1 . There was no evidence of cumulation or tolerance during the period of study.

The Effects of Alloying Additions to Ferritic Steels upon Stress Corrosion Cracking Resistance

Abstract: The effects of Al, Cr, Cu, Ni, Mo, Si, and Ti additions in varying amounts to ferritic steels upon the stress corrosion cracking susceptibilities in a nitrate, a hydroxide, and a carbonate-bicarbonate solution have been determined for the steels in the annealed condition. The effects of the alloying additions vary with the environment, but Cr and Ti, in sufficient amounts, most frequently produced improvements in cracking resistance in the different solutions. The influences of the various alloying additions are mostly dependent upon their effects on dissolution and passivation characteristics, although their effects upon carbon distribution in the steel and mechanical properties are also of importance.

Decreased lymphocyte reactivity and auto-immunity in alopecia areata.

Abstract: SUMMARY T lymphocyte numbers and functions were measured in forty-six patients with alopecia areata and thirty healthy controls. In patients with alopecia areata, lymphocyte reactivity to extracts of scalp and hair follicles was not detected by 3H thymidine incorporation. 3H Thymidine incorporation by lymphocytes cultured with PPD, Varidasc and C. albicans was significantly reduced in cells from patients compared with controls and correlated with the extent of hair loss and the presence of antithyroid antibodies. Decreased lymphocyte responses to PPD and Varidase were not due to the presence of suppressor monocytes because removal of monocytes with carbonyl iron did not increase lymphocyte reactivity. However, responsiveness to C albicans was augmented by removal of monocytes. T cell numbers were significantly lower than in controls (P<0.005); patients with auto-antibodies had fewer T cells than patients without them. The relationship of reduced T cell function and auto-immunity to alopecia areata is discussed.