Response of the unattached 218Po activity size distribution in H2O-SO2-N2 atmospheres.

The response of the unattached 218Po activity size distribution to variations in H2O and SO2 concentration was investigated in a high-purity N2 atmosphere. Lognormal size distributions were reconstructed from screen diffusion battery data using a random search and optimization procedure. For relative humidities of 1% to 90%, SO2 concentrations of 0-6 ppm, and residence times of 38 s, median diameters of the unattached mode ranged from 0.50 (+/- 0.04) to 0.80 (+/- 0.06) nm, corresponding to diffusion coefficients of 0.1-0.05 cm2 s-1. Increases in water vapor concentration resulted in an enhanced rate of ion neutralization and suppression of ion cluster formation. Decreases in cluster diameter with increasing humidity were therefore observed. Addition of SO2 at constant relative humidity resulted in an initial increase in diameter, with a subsequent decrease. Geometric standard deviations averaged 1.05 (+/- 0.01) to 1.06 (+/- 0.01) in all cases, with the unattached fraction comprising 83% to 88% of the total distribution. Results suggest that increases in water vapor concentration enhance neutralization in the immediate vicinity of the recoil path through water radiolysis. Conversion of OH to H2OSO4 on addition of SO2 provides a binary condensable phase capable of clustering around the ion at low relative humidities, increasing particle size. High H2O and SO2 concentrations enhance neutralization through electron scavenging and subsequent ion collision near the end of the recoil path, decreasing the number of available cluster sites and suppressing cluster formation. This reduction is more significant than the increasing size of the stable ion cluster, with increasing H2O and H2SO4 concentrations as predicted by Raes, resulting in decreases in both median diameter and distribution spread.     

Comparison of two treatment schedules for combined timolol and dipivefrin therapy

In a prospective, randomized, single-masked, cross-over study, 18 patients with primary open-angle glaucoma were treated for one month with each of the following regimens: timolol 0.5% twice daily, timolol 0.5% plus dipivefrin 0.1% twice daily given ten minutes apart, and timolol 0.5% plus dipivefrin 0.1% given twice daily four hours apart. An eight-hour intraocular pressure curve was obtained before treatment and at the end of each monthly regimen. When added to timolol therapy, dipivefrin produced a small but statistically significant additional mean decrease in intraocular pressure. The difference in intraocular pressure reduction between the two regimens for combined timolol and dipivefrin therapy was not statistically significant.     

Maintenance of Toscana virus in Phlebotomus perniciosus by vertical transmission

Toscana virus was maintained in a laboratory colony of Phlebotomus perniciosus by vertical (transovarial) transmission for 13 consecutive generations over a 23-month period. No significant biological changes were noted in the virus after prolonged vertical passage in the sand flies, and transovarially infected females were able to transmit the agent by bite to susceptible animals. Chronic infection of Ph. perniciosus with Toscana virus had no apparent effect on the insects' rate of eclosion. In the absence of selection and with random matings, the virus infection rates in each subsequent generation of the colony decreased, suggesting that Toscana virus cannot be maintained in Ph. perniciosus by transovarial transmission alone. Alternative mechanisms for virus maintenance are discussed.     

The Application of Number Needed to Treat (NNT) to Clinical Problems in Radiotherapy

The goals of this report are: 1) to review the number needed to treat (NNT) concept, which, although well established in many sectors of medicine, is still relatively new to the radiotherapy community; 2) to discuss several clinical radiotherapy examples illustrating the inherent advantages of the NNT approach; and 3) to discuss potential future roles of the NNT concept within radiotherapy.     

Small proportions: what to report for confidence intervals?

The original article to which this Erratum refers was published in Pharmacoepidemiology and Drug Safety 2005; 14: 239–247.     

Long-term anticoagulant therapy in patients with coronary artery disease.

Secondary prevention of coronary events in coronary artery disease (CAD) patients with aspirin is generally accepted because of ease of administration, predictable safety, and proven efficacy. The use of long-term anticoagulant therapy with heparins, vitamin-K antagonists (VKAs), or thrombin inhibitors is, however, more controversial. During the last 40 years, several trials have been conducted in order to evaluate the role of anticoagulant therapy in patients with CAD as a protection against subsequent death and thrombo-embolic complications. The conducted trials are heterogeneous in many ways, concerning comparative medications, patient populations, endpoints and follow-up, which makes a standardized recommendation on the basis of these studies difficult. This review is an overview of the largest and best studies on this topic and discusses the scientific background for a possible use of VKA or an alternative anticoagulant treatment in CAD patients, looking at both the beneficial effects and the risk of bleeding.