Spinodal decomposition in a model colloid-polymer mixture in microgravity

We study phase separation in a deeply quenched colloid-polymer mixture in microgravity on the International Space Station using small-angle light scattering and direct imaging. We observe a clear crossover from early-stage spinodal decomposition to late-stage, interfacial-tension-driven coarsening. Data acquired over 5 orders of magnitude in time show more than 3 orders of magnitude increase in domain size, following nearly the same evolution as that in binary liquid mixtures. The late-stage growth approaches the expected linear growth rate quite slowly.

Time-dependent strength of colloidal gels

Colloidal silica gels are shown to stiffen with time, as demonstrated by both dynamic light scattering and bulk rheological measurements. Their elastic moduli increase as a power law with time, independent of particle volume fraction; however, static light scattering indicates that there are no large-scale structural changes. We propose that increases in local elasticity arising from bonding between neighboring colloidal particles can account for the strengthening of the network, while preserving network structure.

Limits to gelation in colloidal aggregation

We show that the dynamics of large fractal colloid aggregates are well described by a combination of translational and rotational diffusion and internal elastic fluctuations, allowing both the aggregate size and internal elasticity to be determined by dynamic light scattering. The comparison of results obtained in microgravity and on Earth demonstrates that cluster growth is limited by gravity-induced restructuring. In the absence of gravity, thermal fluctuations ultimately inhibit fractal growth and set the fundamental limitation to the lowest volume fraction which will gel.

Performance of power assisted respirators during simulated asbestos removal

Protection factors were measured on full face mask power assisted respirators when worn by experienced asbestos removal operatives under simulated asbestos removal work conditions. The sulfur hexafluoride test method as defined in European Standards was employed to determine the leakage into the respirators. Protection factors were measured on a total of 21 test volunteers. The test method allowed protection factors to be related to wearer activities and practices. Poor fitting techniques and simulated reduction in the respirator's performance resulted in a reduction in the protection factor. Visual inspection of the RPE usually worn by the volunteers identified inadequate maintenance. This study re-emphasises that careful selection, facepiece fit testing and correct use and maintenance of RPE are essential to ensure optimum protection to the wearer.

Trends in hospital activity, morbidity and case fatality related to atrial fibrillation in Scotland, 1986--1996

AIMS

Atrial fibrillation is a common and important cause of cardiovascular morbidity and mortality that may become more prevalent due to an ageing population and more prolonged exposure to predisposing cardiovascular disease states. This study examines recent trends in hospitalizations related to atrial fibrillation in Scotland.

METHODS AND RESULTS

Scotland (population 5.1 million) has a well described system for recording hospitalization data. All hospital discharges (and death) can be linked for each individual patient. We examined the period 1986--1996, during which time a total of 103,085 hospitalizations with a principal or secondary diagnosis of atrial fibrillation were recorded. The number of hospitalizations with a principal diagnosis of atrial fibrillation increased threefold from 1869 in 1986 to 5757 in 1996; the number with a secondary diagnosis rose from 3577 to 11,522. Similar increases were seen in the number of patients hospitalized, in those having a 'first-ever' hospitalization and in population hospitalization rates overall. The average age of patients rose, in men from 63.8 (SD 13.2) to 65.0 (13.2) years and in women from 72.2 (12.2) to 73.2 (11.4) years. The proportion of those aged >75 years rose from 33% to 35% in men and from 56% to 60% in women. Average length of stay and case fatality fell during this period, but, because of the overall increase in hospitalizations, atrial fibrillation contributed to a growing proportion of cardiovascular-related bed-days utilized (from 18% to 37% with atrial fibrillation coded in any diagnostic position).

CONCLUSION

The number of hospitalizations for atrial fibrillation has increased dramatically (two- to threefold) in recent years. These findings may be due to a real increase in atrial fibrillation prevalence, changing medical practice (e.g. coding or admission thresholds) or both. Consequently, the public health burden of atrial fibrillation is enormous. Moreover, the observed increase in atrial fibrillation-related hospital activity shows no sign of abating.

Trends in hospitalization for heart failure in Scotland, 1990-1996. An epidemic that has reached its peak?

AIMS

Studies in the 1980s and early 1990s showed striking increases in hospitalization rates for heart failure. This report describes contemporary trends in hospitalization for heart failure.

METHODS

Scotland (population of 5.1 million) has a well described system for recording details of all hospitalizations. All hospital discharges (and deaths) can be linked to each patient. We examined the period 1990-1996 (158 989 hospitalizations with a principal or secondary diagnosis of heart failure).

RESULTS

Compared to 1990, the number of hospitalizations with a principal diagnosis of heart failure increased in men (by 16%) and women (by 12%), although the highest numbers were recorded in 1993 in women (21%) and in 1994 in men (24%). Similar trends were seen for the number of patients hospitalized overall and those having a 'first ever' hospitalization. Hospitalizations with a secondary diagnosis of heart failure increased much more strikingly (by 110% and 60% in men and women, respectively). Re-hospitalization became more common, increasing by 53% and representing 23% of all hospitalizations in 1996. Median length of stay fell (from 9 to 8 days in men and 13 to 10 days in women with a principal diagnosis of heart failure), resulting in 100 877 fewer inpatient days. Heart failure (principal diagnosis) still, however, accounted for 4.2% of all inpatient medicine/geriatric bed-days in 1996. Although inpatient case fatality fell slightly, the total number of deaths due to heart failure (principal diagnosis) increased slightly.

CONCLUSIONS

Heart failure continues to be a common cause of hospitalization. The previously reported 'epidemic' of increasing rates of hospitalization for heart failure in Scotland and elsewhere between 1980 and 1990, however, seems to have peaked (in about 1993/4).

Biosynthesis of ganefromycin: results from blocked mutants and bioconversion experiments

The biosynthetic pathway of ganefromycin alpha (8) was investigated using blocked mutants of Streptomyces lydicus spp. tanzanius, the ganefromycin alpha producer, in conjunction with bioconversion experiments with the products of these mutants. Compounds 1-7 and 9-15, which are structurally related to ganefromycin alpha, were produced by cultures of secretor mutants showing blockage or diminished production of 8. These compounds were isolated, characterized, and subjected to bioconversion experiments using converter and other secretor mutants. Some of the compounds were shown to be products resulting from blocks at various stages in the biosynthetics pathway beyond construction of the polyketide skeleton (e.g., furan ring closure, hydroxylation, glycosylation, etc.). Other compounds were not bioconverted by biosynthetically capable mutants and were deemed shunt products. A mutant's metabolites and bioconverting ability were used to surmise the location of the block. A picture of the later sequence of events leading to the synthesis of ganefromycin alpha emerged, including C23-hydroxylation, C13a-O-methylation, C21a-hydroxylation, and C21a-O-glycosylation. Some of the later steps in the biosynthetic pathway for ganefromycin alpha are proposed.

A comparison of nifedipine once daily (Adalat LA), isosorbide mononitrate once daily, and isosorbide dinitrate twice daily in patients with chronic stable angina

The efficacy of nifedipine gastrointestinal therapeutic system (GITS), 60-90 mg o.d., isosorbide dinitrate, 40-60 mg b.d., and isosorbide mononitrate slow-release, 50-100 mg o.d. was assessed in a six week double-blind, parallel-group study in patients with stable angina on chronic beta-blocker treatment. Of 339 patients who entered the study, 229 were eligible for the valid case analysis of efficacy and 335 for the safety analysis. Nifedipine GITS was significantly better than isosorbide dinitrate (P < or = 0.025) in prolonging time to 1 mm ST-segment depression, time to maximum ST-segment depression, time to occurrence of angina and total exercise duration, in addition to reducing the number of angina attacks and glyceryl trinitrate consumption after six weeks therapy. Nifedipine GITS was also significantly better than isosorbide mononitrate (P < or = 0.025) in prolonging time to occurrence of angina and time to 1 mm ST-segment depression after six weeks therapy. The incidence of headache was considerably higher in both the isosorbide dinitrate and isosorbide mononitrate groups (40% and 41%, respectively) than in the nifedipine GITS group (9.5%, P < or = 0.001), and was the main reason for withdrawal from the study (isosorbide dinitrate 18/99, isosorbide mononitrate 17/99, nifedipine GITS 2/95). Peripheral oedema was more common in patients treated with nifedipine GITS (12.5%) compared to nitrates (2% in both groups, P < or = 0.01), but resulted in withdrawal of only one patient (treated with nifedipine GITS). This study suggests that the efficacy and tolerability of nifedipine GITS is superior to long acting nitrates as second-line therapy to beta-blockade in the treatment of chronic stable angina.

Base-catalyzed isomerism in elfamycin antibiotics. Structures of ganefromycins epsilon and epsilon 1

The structures of ganefromycins epsilon (2a) and epsilon 1 (2b) have been determined by spectroscopic techniques. The compounds are isomeric deoxygenated precursors of the parent antibiotics ganefromycins alpha and beta. The nature of the isomerism was determined by chemical interconversion experiments and spectroscope analysis to be a change in configuration at C-21. Evidence is provided for other cases of this type of isomerism in the elfamycin class of antibiotics.