Transient natural ventilation of a space with localised heating

The natural ventilation of a well mixed, pre-heated room with a point source of heating, and openings at the base and roof is investigated. The transient draining associated with the room being warmer than the exterior combined with the convective flow produced by the point source of heat leads to a fascinating series of transient flow regimes as the system evolves to the two-layer steady-state regime described by Linden, Lane-Serff and Smeed [1]. As the room begins to ventilate, a turbulent plume rises from the point source of heat to the ceiling, and typically forms a deepening layer of hot air. However, with a weak heat source, then at some point the ascending plume will intrude beneath the layer of original fluid. Otherwise, the ascending plume always reaches the top of the room as the system evolves to a steady state. We develop a simplified model of the transient evolution and test this with some new laboratory experiments. We conclude with a discussion of the implications of our results for real buildings.     

An electrochemical investigation of the suppression of silver dissolution in aqueous cyanide by 2-mercaptobenzothiazole

Triangular potential sweep voltammetry, potentiokinetic generation of polarization curves, and coupon corrosion tests have been carried out to determine the influence of 2-mercaptobenzothiazole (MBT) on the dissolution of silver in cyanide solutions at pH 11. MBT has been shown to be an effective inhibitor for silver dissolution at concentrations similar to those used when MBT is applied as a flotation collector. The inhibition efficiency (i.e., [1 – the ratio of the corrosion rates in the presence and absence of MBT], expressed as a percentage) in 10^–2 and 10^–3 mol dm^–3 CN was found to increase with increase in MBT concentration in the range 10^–6 to 10^–4 mol dm^–3, and with increase in time of exposure of the silver to the MBT solution. The inhibition efficiency found for 10^–4 mol dm^–3 MBT in quiescent 10^–2 mol dm^–3 CN^– solution at 23 °C was 98.9%, 99.4% and 99.99% for exposure times of 10 min, 2 h and 5 days, respectively. Surface enhanced Raman spectroscopy showed that inhibition was associated with adsorption of MBT displacing cyanide from the silver surface.     

Gain-coupled DFB lasers with truncated quantum well second-ordergratings

Static and dynamic properties of in-phase gain-coupled multiple quantum well distributed feedback (DFB) lasers with second-order gratings have been measured at 1.55 μm. Devices with both facets antireflection coated and with a κL product between 4 and 5 have achieved a sidemode suppression ratio of over 63 dB. Relative intensity noise measurements have confirmed that the dynamic properties of second-order truncated well gain-coupled (GC)-DFB lasers are comparable to those with first-order truncated-well gratings     

Therapists, therapist variables, and cognitive-behavioral therapy outcome in a multicenter trial for panic disorder.

The relationship between therapists and treatment outcome was examined in 14 highly trained therapists who participated in the Multicenter Collaborative Study for the Treatment of Panic Disorder. Overall, therapists yielded positive outcomes in their caseloads; yet, therapists significantly differed in the magnitude of change among caseloads. Effect sizes for therapist impact on outcome measures varied from 0% to 18%. Overall experience in conducting psychotherapy was related to outcome on some measures, whereas age, gender, gender match, and experience with cognitive-behavioral therapy (CBT) were not. Therapists with above- and below-average outcomes were rated similarly on measures of adherence and competency. The results suggest that therapists make a contribution to outcome in CBT for panic disorder, even when patients are relatively uniform, treatment is structured, and outcome is positive. Implications for future clinical outcome studies and for training clinicians are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The parameter stability of a high dk rigid lens material.

The use of rigid materials with high oxygen permeability (Dk) is on the increase, their major benefit being the reduction of hypoxia. However, there is a reluctance to use these materials possibly due to increased surface scratching, reduced wettability, increased deposition, reduced life expectancy and parameter instability. Considering parameter stability, various studies have demonstrated contradictory results or used high Dk materials based on the silicone acrylate polymer. This study was designed to investigate whether the parameters of a high Dk rigid fluorocarbon contact lens material changed during daily wear and extended wear schedules. Thirty five subjects, divided into group groups, Group I wore the lens on a daily wear basis, whereas those in Group II wore the lens on a monthly extended wear basis. The parameters and integrity of the lenses were monitored in both groups every 3 months. For lens integrity a statistically significant increase in surface scratching was demonstrated for the lenses worn by the subjects of both groups over the time of the study (Group I, F=7.990, P <0.0001 [ANCOVA]; Group II, F=6.241, P=0.003 [ANCOVA]). The only parameter to show a statistically significant variation over the study period was that of centre thickness for the lenses worn by the subjects in Group I (F=3.976, P=0.0063 [ANCOVA]), with a mean reduction in centre thickness of 0.022 mm at the 12 month visit. No change was noted for either group or between groups for the other parameters measured. This study demonstrates that the parameters of rigid contact lenses manufactured from high Dk fluorocarbons are stable with only a non-clinically significant reduction in centre thickness for the contact lenses worn by the subjects in Group I.     

US regulatory considerations for low field magnetic resonance imaging systems

Although there has been a resurgence of interest in low field magnetic resonance imaging (MRI) systems in recent years, low field MRI is not a new concept. FDA has a long history of evaluating the safety and effectiveness of MRI systems encompassing a wide range of field strengths. Many systems seeking marketing authorization today include new technological features (such as artificial intelligence), but this does not fundamentally change the regulatory paradigm for MR systems. In this review, we discuss some of the US regulatory considerations for low field magnetic resonance imaging (MRI) systems, including applicability of existing laws and regulations and how the U.S. Food and Drug Administration (FDA) evaluates low field MRI systems for market authorization. We also discuss regulatory considerations in the review of low field MRI systems incorporating novel AI technology. We foresee that MRI systems of all field strengths intended for general diagnostic use will continue to be evaluated for marketing clearance by the metric of substantial equivalence set forth in the premarket notification pathway.