FEM investigation of leaky modes in hollow core photonic crystal fibers

Hollow-core holey fibers are promising candidates for low-loss guidance of light in various applications, e.g., for the use in laser guide star adaptive optics systems in optical astronomy. We present an accurate and fast method for the computation of light modes in arbitrarily shaped waveguides. Maxwell's equations are discretized using vectorial finite elements (FEM). We discuss how we utilize concepts like adaptive grid refinement, higher-order finite elements, and transparent boundary conditions for the computation of leaky modes in photonic crystal fibers. Further, we investigate the convergence behavior of our methods. We employ our FEM solver to design hollow-core photonic crystal fibers (HCPCF) whose cores are formed from 19 omitted cladding unit cells. We optimize the fiber geometry for minimal attenuation using multidimensional optimization taking into account radiation loss (leaky modes).Comment: 8 page

Two-stage fan. 3: Data and performance with rotor tip casing treatment, uniform and distorted inlet flows

A two stage fan with a 1st-stage rotor design tip speed of 1450 ft/sec, a design pressure ratio of 2.8, and corrected flow of 184.2 lbm/sec was tested with axial skewed slots in the casings over the tips of both rotors. The variable stagger stators were set in the nominal positions. Casing treatment improved stall margin by nine percentage points at 70 percent speed but decreased stall margin, efficiency, and flow by small amounts at design speed. Treatment improved first stage performance at low speed only and decreased second stage performance at all operating conditions. Casing treatment did not affect the stall line with tip radially distorted flow but improved stall margin with circumferentially distorted flow. Casing treatment increased the attenuation for both types of inlet flow distortion

Filter cassette for high volume air sampler

Filter cassette eliminates or substantially reduces contamination of filter media by extraneous material and facilitates handling

Inhalation therapy during acute asthma : the role of a combined steroid and beta-stimulant preparation

CITATION: Joubert, J. R., Burger, G. & Shephard, E. 1985. Inhalation therapy during acute asthma : the role of a combined steroid and beta-stimulant preparation. South African Medical Journal, 68:381-384.The original publication is available at http://www.samj.org.zaA compound consisting of a β-stimulant, salbutamol (100 μg/puff), and a steroid, beclomethasone diproprionate (50 μg/puff), was studied to test the hypothesis that the corticosteroid could enhance the bronchodilator proporties of the β-stimulant during chronic asthma and simulated acute attacks (antigen challenge). Conventional doses (200 μg and 100 μg of salbutamol and beclomethasone respectively) were compared using a schedule which included a second administration 1 hour later. The results obtained on the baseline bronchial responsiveness of chronic asthmatics and during the delayed asthmatic response (simulated acute asthma) were similar. The compound was as effective as salbutamol alone but not more so. A significantly greater bronchodilator response was recorded in all patients after the second administration of both the compound and salbutamol alone. The practical advantages of having one rather than two inhalers are evident, but the appropriate application of this compound agent, probably in a prophylactic role, must be defined.Publisher’s versio

Inappropriate medicine prescribing in older South Africans: A cross-sectional analysis of medicine claims data

Background. Prescribing for older patients is a well-recognised problem, and inappropriate items are prescribed frequently. Several tools and criteria are available to promote rational prescribing in older patients.Objective. To determine the prevalence of potentially inappropriate prescriptions (PIPs) in older South African patients.Methods. A retrospective drug utilisation review was conducted using medicine claims data over a 1-year period. Patients aged ≥65 years with at least one paid claim for any medicine item during this period were included. The prevalence of PIPs was identified by applying the 2012-Beers criteria list.Results. A total of 103 420 patients, mean age 74.0 years (standard deviation 6.7), 57.1% female, were included in the analysis. The number of PIPs identified was 562 852 in 71 206 patients (68.9%). The most common medicines inappropriately prescribed were oestrogen (oral and patch formulations only) (12.4%), meloxicam (7.3%), amitriptyline and combinations thereof (6.5%), diclofenac (6.4%), ibuprofen (6.1%), alprazolam (5.3%), meprobamate and combinations thereof (5.0%), sliding-scale insulin (3.3%), amiodarone (3.1%) and doxazosin (2.6%). Medicines were inappropriately prescribed to women statistically significantly more often than to men (1.9:1; p<0.001), although this difference was not of practical significance (Cramér’s V=0.06).Conclusions. Medicine use in older patients must be appropriate and evaluated regularly. According to explicit criteria, PIPs were found to be common in older patients registered on the database. Monitoring of PIPs may increase the quality of prescribing, but explicit criteria cannot substitute for clinical judgement based on the individual patient

Characterisation of different GLRaV-3 variant infections by determining virus concentration ratios and miRNA expression profiles

Grapevine leafroll disease (GLD) is present in all grape-growing regions of the world and is considered the most significant grapevine viral disease. Grapevine leafroll-associated virus 3 (GLRaV-3) is considered the primary cause of GLD and in South African vineyards five genetic variant groups (I, II, III, VI and VII) have been confirmed. Biological distinctions between GLRaV-3 variants have not been fully validated. By characterising virus concentration and stress-responsive microRNA expression in GLRaV-3 infected plants, this study aimed to glean a better understanding of the possible biological distinctions between GLRaV-3 variants. Quantitative reverse transcription PCR was utilised for virus concentration ratio (VCR) determination and miRNA quantitation in GLRaV-3 positive and negative grapevines grown under greenhouse and field conditions. This study found statistically significant differences in VCRs in plants singly infected with different GLRaV-3 variants. Interestingly, no difference in mean VCRs were observed between data sets, despite notable differences in plant age, duration of GLRaV-3 infection, scion/rootstock combination and growing conditions. Several miRNAs showed statistically significant expression modulation between infected and healthy samples. miRNA expression between data sets varied substantially and a greater overall miRNA response was observed in plants with more established GLRaV-3 infections. The lack of significant differences in mean VCRs between data sets, coupled with the consistent modulation of certain miRNAs in plants that have likely been infected for longer is a promising result. This finding could indicate that successful inhibition of further virus replication by plant defence mechanisms occurred, and that these miRNAs are implicated in this response