Thermal Expansion of 3C-SiC Obtained from In-Situ X-ray Diffraction at High Temperature and First-Principal Calculations

In situ X-ray crystallography powder diffraction studies on beta silicon carbide (3C-SiC) in the temperature range 25–800 °C at the maximum peak (111) are reported. At 25 °C, it was found that the lattice parameter is 4.596 Å, and coefficient thermal expansion (CTE) is 2.4 ×10−6/°C. The coefficient of thermal expansion along a-direction was established to follow a second order polynomial relationship with temperature (α11=−1.423×10−12T2+4.973×10−9T+2.269×10−6). CASTEP codes were utilized to calculate the phonon frequency of 3C-SiC at various pressures using density function theory. Using the Gruneisen formalism, the computational coefficient of thermal expansion was found to be 2.2 ×10−6/°C. The novelty of this work lies in the adoption of two-step thermal expansion determination for 3C-SiC using both experimental and computational techniques.     

Abnormal expression of MHC class II and ICAM-1 by melanocytes in vitiligo

The relationship between damage to cutaneous melanocytes and antimelanocyte autoimmunity in vitiligo is unclear. We have demonstrated abnormal expression of MHC class II molecules by perilesional melanocytes in 13/21 patients with vitiligo and a six-fold increase in the number expressing the intercellular adhesion molecule ICAM-1. These molecules have important roles in normal antigen presentation and activation of helper T lymphocytes, and their expression by melanocytes may contribute to the abnormal immune response in vitiligo. MHC class II is not expressed by melanocytes in psoriasis and is unlikely to be induced in vitiligo by cytokines released from activated non-melanocyte-specific T lymphocytes.     

Bathers as a possible source of contamination for swimming‐associated illness at marine bathing beaches

The results of a prospective, follow‐up epidemiological study conducted at three Israeli coastal beaches in 1983 showed that enteric, respiratory and ear symptomatology were higher among swimmers than nonswimmers, especially for young children. The enterococcus levels and the swimming‐associated rates for enteric and respiratory symptoms at one of the beaches (Gordon) were at least twice those at another beach (Rishon Lezion). The higher swimming‐associated symptom rates at Gordon Beach, however, were largely attributable to individuals who swam on Saturdays, which are non‐working days in Israel, as opposed to Fridays and Sundays. The absence of extrinsic sources of pollution, the restricted water exchange due to horizontal surf‐breakers, the greater bather density and higher indicator levels (including those of Staphylococcus aureus) on Saturdays and the better correlation of S. aureus than enterococcus (or Escherichia cofi) levels to swimming‐associated enteric and respiratory symptoms, suggests that contamination from the bathers themselves is the source of the indicators and swimming‐associated illness at Gordon Beach.     

Release of 19-nor-testosterone type of contraceptive steroids through different drug delivery systems into serum and breast milk of lactating women

The release of contraceptive steroids through different drug delivery systems into serum and breast milk was investigated in a group of lactating women. Four women in each group were taking either a low dosage progestogen compound like norethisterone (NET) 350 μg or d-norgestrel (d-Ng) 50 μg alone or low dosage combination pills containing NET 1 mg or d-Ng 150 μg with 30 μg ethinyl estradiol (EE₂) or a biodegradable implant containing 25 mg NET or d-Ng. Peak levels in plasma and milk were seen in oral contraceptive users around 2 hours. Of the two low dosage progestogen compounds, d-Ng was below the detection limit in milk within 4 hours whereas NET was still detectable at the 24-hour interval. In contrast to this, because of the larger quantity of steroids in the combination pills, the NET/d-Ng levels in serum as well as in milk were high throughout the 24-hour period. With the subdermal route because of the sustained low release of the drug from the biodegradable implants, the levels in milk were below the detection limit within a day with d-Ng and within a week with NET.     

Application of surfactant modified zeolite membrane electrode towards potentiometric determination of perchlorate

Potentiometric electrodes based on the incorporation of surfactant-modified zeolite Y (SMZ) particles into poly vinyl chloride (PVC) membranes were described. The electrode characteristics were evaluated regarding the response towards perchlorate ions. PVC membranes plasticized with dioctyl phthalate and without lipophilic additives (co-exchanger) are used throughout this study. The influence of membrane composition on the electrode response was studied. The electrode exhibited a Nernstian response towards perchlorate in the concentration range of 7.9 × 10⁻⁶–8.0 × 10⁻² M with a slope of 59.7 ± 0.9 mV per decade of perchlorate concentration with a working pH range of 1.7–9.5 with a fast response time of ≤10 s. The lower and upper detection limits were 4.07 × 10⁻⁷ and 0.13 M, respectively. The electrode response to perchlorate remains constant in the temperature range of 20–40 °C and in the presence of 2.5 × 10⁻⁶–1 × 10⁻² M NaNO₃. The selectivity coefficients for perchlorate anion as test species with respect to other anions were determined. The proposed modified zeolite-PVC electrode can be used for at least 30 days without any considerable divergence in potential. It was applied as indicator electrode in water samples with satisfactory results. The results of this study and our previous work show HDTMA plays different roles according to the zeolite type and matrix, as HDTMA-zeolite Y in a carbon paste matrix showed a good Nernstian behavior towards phosphate anion.     

When to initiate highly active antiretroviral therapy in sub-Saharan Africa? A South African cost-effectiveness study

BACKGROUND: Large-scale programmes increasing access to highly active antiretroviral therapy (HAART) are being implemented in sub-Saharan Africa. However, cost-effectiveness of initiating treatment at different CD4 count thresholds has not been explored in resource-poor settings. METHODS: A cost-effectiveness analysis was conducted from a public health perspective using primary treatment outcomes, healthcare utilisation and cost data (Jan 2004 local prices; US dollars 1=7.6 Rands) derived from the Cape Town AIDS Cohort. A Markov state-transition model was developed to estimate life-expectancy, lifetime costs, quality-adjusted life-years (QALYs), cost per life-year and QALY gained for initiating HAART at three CD4 cell count thresholds (<200/microl, 200-350/microl and >350/microl), including the no antiretroviral therapy (No-ART) alternative. Each treatment option was compared with the next most effective undominated option. RESULTS: Mean life-expectancy was 6.2, 18.8, 21.0 and 23.3 years; discounted (8%) QALYs were 3.1, 6.2, 6.7 and 7.4; and discounted lifetime costs were US dollars 5,250, US dollars 5,434, US dollars 5,740, US dollars 6,588 for No-ART, and therapy initiation at <200/microl, 200-350/microl and >350/microl scenarios respectively. Clinical benefits increased significantly with early therapy initiation. Initiating therapy at <200/microl had an incremental cost-effectiveness ratio (ICER) of US dollars 54 per QALY versus No-ART, 200-350/microl had an ICER of US dollars 616 versus therapy initiation at <200/microl, and >350/microl had an ICER of US dollars 1,137 versus therapy initiation at 200-350/microl. ICERs were sensitive to HAART cost. CONCLUSIONS: HAART is reasonably cost-effective for HIV-infected patients in South Africa, and most effective if initiated when CD4 count >200/microl. Deferring treatment to <200/microl would reduce the aggregate cost of treatment, but this should be balanced against the significant clinical benefits associated with early therapy.