The fabrication of metal matrix composites by a pressureless infiltration technique

A novel technique for fabricating metal matrix composites by the spontaneous (pressureless) infiltration of filler preforms with molten aluminium alloys is described. Numerous reinforcing materials, including Al₂O₃ and SiC of various configurations, such as particles, agglomerates, and fibres, have been incorporated as fillers. The effects of processing variables, such as alloy chemistry, process temperature, and filler material, on the infiltration kinetics and resultant microstructures are discussed. Comparisons with existing infiltration technology and preliminary composite properties are presented.     

Compliance with cardiovascular disease prevention strategies: a review of the research

The efficacy of cardiovascular risk-reduction programs has been established. However, the extent to which risk-reduction interventions are effective may depend on adherence. Non-compliance, or non-adherence, may occur with any of the recommended or prescribed regimens and may vary across the treatment course. Compliance problems, whether occurring early or late in the treatment course, are clinically significant, as adherence is one mediator of the clinical outcome. This article, which is based on a review of the empirical literature of the past 20 years, addresses compliance across four regimens of cardiovascular risk reduction: pharmacological therapy, exercise, nutrition, and smoking cessation. The criteria for inclusion of a study in this review were: (a) focus on cardiovascular disease risk reduction; (b) report of a quantitative measure of compliance behavior; and (c) use of a randomized controlled design. Forty-six studies meeting these criteria were identified. A variety of self-report, objective, and electronic measurement methods were used across these studies. The interventions employed diverse combinations of cognitive, educational, and behavioral strategies to improve compliance in an array of settings. The strategies demonstrated to be successful in improving compliance included behavioral skill training, self-monitoring, telephone/mail contact, self-efficacy enhancement, and external cognitive aids. A series of tables summarize the intervention strategies, compliance measures, and findings, as well as the interventions demonstrated to be successful. This review reflects the progress made over two decades in compliance measurement and research and, further, advances made in the application of behavioral strategies to the promotion of cardiovascular risk reduction.     

Nutritional practices of elite female surfers during training and competition

Inhaled beryllium (Be) can induce a range of adverse pulmonary responses in animals and humans including acute pneumonitis, chronic granulomatous lung disease, and cancer. To facilitate comparisons with our previous data describing Be toxicity in rats, we evaluated the toxic effects of inhaled Be metal in mice. Groups of 34 strain C3H/HeJ mice were acutely exposed by the nose-only route to aerosolized Be metal to achieve measured initial lung burdens of 0, 1.7, 2.6, 12, or 34 microg. All mice received aerosolized 85 Sr-labeled fused aluminosilicate particles (85 Sr-FAPs) immediately before their Be exposure so that the influence of Be on lung retention of these poorly soluble tracer particles could be externally quantitated. Groups of mice were euthanized at 8, 15, 40, 90, 210, and 350 days after exposure for evaluation of histopathological changes and for cytologic and biochemical indicators of lung damage measured in bronchoalveolar lavage fluid. Clearance of 85 Sr-FAP tracer particles through 196 days after exposure was delayed in mice receiving the 12 and 34 microg Be lung burdens, but not the 1.7 or 2.6 microg lung burdens. Increased total cell numbers, increased percentage of neutrophils, and elevated levels of total protein and the activities of beta-glucuronidase and lactate dehydrogenase in bronchoalveolar lavage fluid were observed in the two highest Be lung burden groups compared with controls. Lung lesions included particle-containing macrophages, granulomatous pneumonia, lymphocytic interstitial aggregates, and mononuclear interstitial infiltrates. These lesions were occasionally seen in mice receiving the 2.6 microg lung burden, were present in most of the mice receiving 12 or 34 microg lung burdens, and were generally increased in severity with time and lung burden. Thus, we have demonstrated that a single, acute inhalation exposure to Be metal can chronically retard particle clearance and induce lung damage in mice. The initial lung burdens used caused responses ranging from no apparent effects to significant Be-induced responses. A comparison of these data with our previous data from rats indicates that the mass of Be metal required to induce lung damage in mice is similar to that needed for rats. When expressed on a lung weight-normalized basis, mice appeared to be more resistant to the toxic effects of inhaled Be than rats.     

Psychotherapeutic agents in older adults. Sedative hypnotics and sleep

Complaints about sleep are prominent among geriatric patients. Insomnia is a prominent feature of many psychiatric and general medical conditions. The physiologic effects of aging and primary sleep disorders also contribute to insomnia, sleep pattern changes, daytime sleepiness, and dozing. The clinical approach to insomnia requires a thorough diagnostic assessment as well as study of sleep habits and hygiene. Hypnotic agents may be useful in providing short-term relief. Pharmacologic intervention is best combined with nonpharmacologic approaches that improve the efficiency of sleep.     

Properties of xanthine dehydrogenase variants from rosy mutant strains of Drosophila melanogaster and their relevance to the enzyme's structure and mechanism

Xanthine dehydrogenase, a molybdenum, iron-sulfur flavoenzyme encoded in the fruit fly Drosophila melanogaster by the rosy gene, has been characterised both from the wild-type and mutant files. Enzyme assays, using a variety of different oxidising and reducing substrates were supplemented by limited molecular characterisation. Four rosy strains showed no detectable activity in any enzyme assay tried, whereas from four wild-type and three rosy mutant strains, those for the [E89K], [L127F] and [L157P]xanthine dehydrogenases (in all of which the mutation is in the iron-sulfur domain), the enzyme molecules, although present at different levels, had extremely similar or identical properties. This was confirmed by purification of one wild-type and one mutant enzyme. [E89K]xanthine dehydrogenase. These both had ultraviolet-visible absorption spectra similar to milk xanthine oxidase. Both were found to be quite stable molecules, showing very high catalytic-centre activities and with little tendency to become degraded by proteolysis or modified by conversion to oxidase or desulfo forms. In three further rosy strains, giving [G353D]xanthine dehydrogenase and [S357F]xanthine dehydrogenase mutated in the flavin domain, and [G1011E]xanthine dehydrogenase mutated in the molybdenum domain, enzyme activities were selectively diminished in certain assays. For the G353D and S357F mutant enzymes activities to NAD+ as oxidising substrate were diminished, to zero for the latter. In addition for [G353D]xanthine dehydrogenase, there was an increase in apparent Km values both for NAD+ and NADH. These findings indicate involvement of this part of the sequence in the NAD(+)-binding site. The G1011E mutation has a profound effect on the enzyme. As isolated and as present in crude extracts of the files, this xanthine dehydrogenase variant lacks activity to xanthine or pterin as reducing substrate, indicating an impairment of the functioning of its molybdenum centre. However, it retains full activity to NADH with dyes as oxidising substrate. Mild oxidation of the enzyme converts it, apparently irreversibly, to a form showing full activity to xanthine and pterin. The nature of the group that is oxidised is discussed in the light of redox potential data. It is proposed that the process involves oxidation of the pterin of the molybdenum cofactor from the tetrahydro to a dihydro oxidation state. This conclusion is fully consistent with recent information [Rom?o, M. J., Archer, M., Moura, I., Moura. J.J.G., LeGall, J., Engh, R., Schneider, M., Hof, P. & Huber, R. (1995) Science 270. 1170-1176) from X-ray crystallography on the structure of a closely related enzyme from Desulfovibrio gigas. It is proposed, that apparent irreversibility of the oxidative activating process for [G1011E]xanthine dehydrogenase, is due to conversion of its pterin to the tricyclic derivative detected by these workers. The data thus provide the strongest evidence available, that the oxidation state of the pterin can have a controlling influence on the activity of a molybdenum cofactor enzyme. Implications regarding pterin incorporation into xanthine dehydrogenase and in relation to other molybdenum enzymes are discussed.     

Identification of a BRCA1-associated kinase with potential biological relevance

A biochemical approach was used to identify proteins which interact with human BRCA1. Through this work, a kinase activity which co-purifies with BRCA1 has been identified. This kinase activity, which phosphorylates BRCA1 in vitro, was originally identified in Sf9 insect cells but is also present in cells of human origin including breast and ovarian carcinoma cell lines. The BRCA1 kinase activity in vitro is associated with a fragment of BRCA1 encompassing amino acids 329-435. This peptide is also phosphorylated in various human cell lines. A computer-assisted sequence analysis revealed that this peptide was a potential substrate for phosphorylation by PKA, PKC, or CKII. However, phosphorylation by these kinases could not be demonstrated in vitro indicating the presence of another kinase activity. Phosphorylation in vitro requires a minimal domain of BRCA1 encompassing amino acids 379-408. Notably, deletion of this minimal domain abolishes growth suppression by BRCA1 indicating that this domain, as well as phosphorylation within this domain, may be important for BRCA1 function.     

Relationship between ApoE, MRI findings, and cognitive function in the Cardiovascular Health Study

BACKGROUND AND PURPOSE: We determined the relationship between apolipoprotein (Apo)E, MRI, and low cognitive scores. METHODS: The relationship between age, education, ApoE genotype, MRI examination of the brain, subclinical and clinical cardiovascular disease, and low (<80) score on the Modified Mini-Mental State Examination (3MSE, as modified by Teng and Chui) was evaluated for 3469 black and white participants in the Cardiovascular Health Study (CHS) in years 5 and 6 of the study. The participants were followed for up to 3 years. RESULTS: The prevalence of scores <80 in years 5 and 6 of the CHS was 8.2% for participants without and 20.4% for those with prior history of stroke. Age, race, and education were important determinants of low 3MSE scores. The prevalence of ApoE-4 (odds ratio [OR], 1.6 [1.1 to 2.1]) was directly related to scores <80, as was high ventricular volume (OR, 1.6 [1.2 to 2.3]), high white matter grade (OR, 1.4 [1.1 to 1.9]), and infarctlike lesions (OR, 1.6 [1.2 to 2.1]) on the MRI in the multivariate analysis. A five-point or greater decline in scores over up to 3 years was more often observed for participants with low 3MSE scores at year 5, at older ages, with lower education, and experiencing incident stroke (OR, 3.6 [1.2 to 10.6]), ApoE-4 genotype (OR, 1.8 [1.4 to 2.3]), and with MRI findings of high ventricular volume (OR, 2.0 [1.5 to 2.7]), and infarctlike lesions (OR, 1.2 [0.9 to 1.5]). CONCLUSIONS: These results demonstrate that vascular changes on MRI, measures of brain atrophy, ApoE-4, and age, education, and race are associated with low cognitive scores among older individuals. The MRI of the brain provides valuable information related to cognitive tests and decline over time. The potential exists for using MRI measurements to identify high-risk individuals for dementia and to test potential interventions to reduce the risk of dementia.     

Interferometric measurement of dispersion of a single-mode optical fibre

The methods of Fourier transform spectroscopy are applied to the measurement of the dispersion of short lengths of a single-mode optical fibre. The fibres used were one metre or less in length.     

Exact polarised rib waveguide analysis

An exact Fourier operator transform method (F-OPT) is presented for finding the polarised mode propagation constants of a rib waveguide with any number of supporting layers and an arbitrary cladding. The implementation is of the order of one hundred times faster than the finite difference method for the same accuracy of the normalised propagation constant     

The contribution of a bacterially isolated environment to the prevention of infection in seriously burned patients

A new system of patient protection from bacterial crossinfection called the Bacteria Controlled Nursing Unit (BCNU) is described, based on strict environmental control of a 6 x 10 foot area surrounding the patient's bed rather than the entire patient room or isolation ward, plus the ability to deliver all medical care without entering the protective environment and maintaining all monitoring, life support, and i.v. equipment outside the controlled environment. The clinical effectiveness of this system in the treatment of burn patients has been studied and compared with the effectiveness of single room isolation on a burn isolation ward and conventional isolation techniques on an open burn ward. The studies show that the BCNU is significantly more effective in preventing bacterial cross-contamination than conventional precautions (3.8% vs. 13.1%, P < 0.001; and 8% vs. 22.8%, P < 0.001) over a two and four week period. The studies also indicate that there was a significant increase in the probability of infection occurring following cross-contamination than occurring after auto-contamination (65% vs. 39%, P < 0.005), emphasizing the importance of preventing cross-contamination in reducing the overall infection rate in seriously burned patients. Clinical evaluation of the unit proved it to be compatible with intensive nursing and medical care without increasing the nurse to patient ratio. The unit provided sufficient control of bacterial cross-infection to allow reduction in mortality and improvement in the effectiveness of burn care through routine prompt excision of burn eschar and immediate wound closure to be carried out in severe and massively burned patients without a limiting threat of bacterial burn wound sepsis.