12 research outputs found
Rheological characterization of linear low-density polyethylene-Fischer-Tropsch wax blends
No full textDATA AVAILABILITY STATEMENT :
The data that support the findings of this study are available
from the corresponding author, Shatish Ramjee,
upon request.Please read abstract in the article.Sasol.http://wileyonlinelibrary.com/journal/vnlam2024Chemical EngineeringSDG-09: Industry, innovation and infrastructur
Erratum
No full textIn the letter entitled 'Vaginal insertion and douching practices among sex workers at truck stops in KwaZuluNatal', which appeared on p. 470 of the April 1998 SAMJ, the name of the second author, Gita Ramjee, was inadvertently omitted. We apologise to Or Ramjee and her co-authors for this unfortunate error.
Synthesis and coordination of a neutral phosphaguanidine and comparison of its basicity with a guanidine
No full textA phosphaguanidine [Me2NC(PPh2)=NiPr], the analogous guanidine [Me2NC(NPh2)=NiPr], and their hydrochloride (HCl) salts were prepared to study the influence of substituting a phosphorus atom for a nitrogen atom on the basicity of the two compounds and the bonding in their conjugate acids. The pKa values of both HCl salts were measured in acetonitrile by NMR titration. Surprisingly, the substitution of P for N has essentially no effect on basicity even though the geometry at that atom is changed. The presence of phenyl substituents in the protonated guanidine reduces the resonance in the CN3 core, whereas poor orbital overlap between P and C reduces the resonance in the N2CP core of the protonated phosphaguanidine. The neutral phosphaguanidine binds to a Cu(I) halide through both the Nimine and the P, which suggested that the basic N atom on the bound ligand may have little utility as a Brønsted base. Fortunately, however, a Cu(I) halide complex of the protonated phosphaguanidine is stable. Thus, the tendency of the basic N to bind to metals does not proscribe it serving as a metal-proximate Brønsted base.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
Geographical Clustering of High Risk Sexual Behaviors in “Hot-Spots” for HIV and Sexually Transmitted Infections in Kwazulu-Natal, South Africa
No full textWe investigated geographical variations of three sexually transmitted infections (STIs) namely chlamydia, gonorrhea and syphilis in the greater Durban area, so as to optimize intervention strategies. The study population was a cohort of sexually active women who consented to be screened in one of three biomedical studies conducted in Durban. A total of nine local regions collectively formed three clusters at screening, five of which were previously defined as HIV hot-spots. STI cases were geo-coded at the census level based on residence at the time of screening. Spatial SaTScan Statistics software was employed to identify the areas with a disproportionate prevalence and incidence of STI infection when compared to the neighboring areas under study. Both prevalence and incidence of STIs were collectively clustered in several localized areas, and the majority of these locations overlapped with high HIV clusters and shared the same characteristics: younger age, not married/cohabitating and multiple sex partners. © 2013 The Author(s)
Development of Single Crystal CsPbBr3 Radiation Detectors from Low-Cost Solution Synthesized Material
No full textThe all-inorganic perovskite CsPbBr3 is a strong candidate for room-temperature, semiconducting radiation detecting applications. With a high stopping power, a large bandgap, and a high mobility-lifetime (μτ) product for both holes and electrons, CsPbBr3 contains all the desirable properties of a room temperature radiation detector. Unfortunately, the production of detector-grade single crystal samples requires high quality starting materials, which must be further processed to achieve the desired purity for semiconducting operation. We have developed a modified zone refining method combining the continuous purification of ternary CsPbBr3 and the subsequent crystal growth step. Taking advantage of this technique, low-cost polycrystalline CsPbBr3 synthesized via solution chemistry processes can be directly used in the production of high-purity, detector-grade crystals. Semi-cylindrical CsPbBr3 single crystal ingots up to 120 mm in length and 22 mm in diameter were obtained. The final product exhibited good chemical stoichiometry and high trace metal purity (2.34 ppm across 73 elements). Detector devices fabricated from the crystal wafers displayed resistivities > 2.0 × 108 Ω·cm and high photocurrent responses. The radiation detectors were able to produce spectroscopy responses to 241Am α-particle. The hole mobility-lifetime (μτH) product of the detectors was determined to be in the range of 1.45 × 10−3 cm2/V
Stabilization and Solvent Driven Crystal-to-Crystal Transition between New Bismuth Halides
No full textHIV transmission risk through anal intercourse: systematic review, meta-analysis and implications for HIV prevention.
No full textBACKGROUND: The human immunodeficiency virus (HIV) infectiousness of anal intercourse (AI) has not been systematically reviewed, despite its role driving HIV epidemics among men who have sex with men (MSM) and its potential contribution to heterosexual spread. We assessed the per-act and per-partner HIV transmission risk from AI exposure for heterosexuals and MSM and its implications for HIV prevention. METHODS: Systematic review and meta-analysis of the literature on HIV-1 infectiousness through AI was conducted. PubMed was searched to September 2008. A binomial model explored the individual risk of HIV infection with and without highly active antiretroviral therapy (HAART). RESULTS: A total of 62,643 titles were searched; four publications reporting per-act and 12 reporting per-partner transmission estimates were included. Overall, random effects model summary estimates were 1.4% [95% confidence interval (CI) 0.2-2.5)] and 40.4% (95% CI 6.0-74.9) for per-act and per-partner unprotected receptive AI (URAI), respectively. There was no significant difference between per-act risks of URAI for heterosexuals and MSM. Per-partner unprotected insertive AI (UIAI) and combined URAI-UIAI risk were 21.7% (95% CI 0.2-43.3) and 39.9% (95% CI 22.5-57.4), respectively, with no available per-act estimates. Per-partner combined URAI-UIAI summary estimates, which adjusted for additional exposures other than AI with a 'main' partner [7.9% (95% CI 1.2-14.5)], were lower than crude (unadjusted) estimates [48.1% (95% CI 35.3-60.8)]. Our modelling demonstrated that it would require unreasonably low numbers of AI HIV exposures per partnership to reconcile the summary per-act and per-partner estimates, suggesting considerable variability in AI infectiousness between and within partnerships over time. AI may substantially increase HIV transmission risk even if the infected partner is receiving HAART; however, predictions are highly sensitive to infectiousness assumptions based on viral load. CONCLUSIONS: Unprotected AI is a high-risk practice for HIV transmission, probably with substantial variation in infectiousness. The significant heterogeneity between infectiousness estimates means that pooled AI HIV transmission probabilities should be used with caution. Recent reported rises in AI among heterosexuals suggest a greater understanding of the role AI plays in heterosexual sex lives may be increasingly important for HIV prevention
Thermal and rheological properties of Fischer-Tropsch wax/high-flow LLDPE blends
No full textDATA AVAILABILITY STATEMENT :
The data that support the findings of this study are available from the corresponding author upon reasonable request.Waxes find use as processing aids in filled compounds and polyethylene-based masterbatches. In such applications, the thermal and physical property changes they impart to the polymer matrix are important. Therefore, this study details results obtained for blends prepared by mixing a Fischer–Tropsch (F–T) wax with a high-flow linear low-density polyethylene (LLDPE). The melting and crystallization behavior are studied using hot-stage polarized optical microscopy (POM) and differential scanning calorimetry (DSC). The calorimetry results are consistent with partial cocrystallization of the two components. The melting and crystallization exo- and endotherms for the wax- and LLDPE-rich phases remained separate. However, they change in shape and shift toward higher- and lower temperature ranges, respectively. It is found that increasing the wax content delays the crystallization, decreases the overall crystallinity, and reduces the size of the crystallites of the polyethylene-rich phase. Rotational viscosity is measured at 170 °C in the Newtonian shear-rate range. The variation of the zero-shear viscosity with blend composition is consistent with the assumption of a homogeneous melt in which the chains are in an entangled state. Therefore, it is concluded that the wax and LLDPE are, in effect, miscible in the melt and partially compatible in the solid state.Ministerio de Ciencia e Innovación and Sasol.http://www.mame-journal.de/hj2024Chemical EngineeringSDG-09: Industry, innovation and infrastructureSDG-12:Responsible consumption and productio
Single-Crystal Bismuth Thiophosphate, BiPS4, as a Nontoxic and Mechanically Robust Xray Detector
No full textBismuth
thiophosphate, BiPS4, is a promising nontoxic,
high-density ternary chalcogenide semiconductor. Polycrystalline BiPS4 was synthesized from the stoichiometric melt of Bi, P, and
S. Phosphorus was purified via an in-situ sublimation method. Single
crystals of BiPS4 were grown using a modified vertical
Bridgman method with a thermal gradient of 18 °C/cm. The material
exhibits an electrical resistivity of 2 × 109 Ω·cm.
The Knoop hardness of the single crystals is 128 ± 0.8 kg mm–2. A blocking contact behavior was observed with asymmetric
contacts of Ga/BiPS4/Ag. A clear photocurrent response
was observed from a BiPS4 crystal under an electric field
as low as 1.14 V mm–1. Using a tungsten X-ray source,
an X-ray sensitivity of 52 μ Gy–1 cm–2 was measured under an electric field of 80 V mm–1. When a single-crystal BiPS4 radiation detector device
was used in a pulse-height radiation detection system, a clear charge
collection response was observed under a 241Am α-particle
radiation source
Continuous metadata flows for distributed multimedia
No full textThe practical use of temporal multimedia has increased markedly in recent years as enabling technologies for the distribution and streaming of media have become available. As a part of this trend, hypermedia systems and models have adapted accordingly to incorporate such distributed multimedia for presentation. Structured interpretation of information has long been a fundamental feature of both open hypermedia systems and knowledge systems. Metadata, in its many forms, has become the cornerstone for providing this structured knowledge above and beyond basic data and information. This thesis presents the rationale and requirements for continuous metadata, which supports the metadata accompanying distributed multimedia throughout the lifecycle of streamed media, from generation, through distribution, to presentation. Throughout this process it is the temporal and continuous nature of the metadata which is paramount. A conceptual framework for continuous metadata is proposed to encapsulate these principles and ideas. Continuous metadata and the associated framework enable the development, in particular, of real-time, collaborative, semantically enriched distributed multimedia applications. Experience building one such system using continuous metadata is evaluated within the framework. An ontology is developed for the system to enable the collation, distribution, and presentation of structure aiding navigation of multimedia, and it is shown how continuous metadata utilising the ontology can be distributed using multicas
