Fracture behavior of boehmite-filled polypropylene block copolymer nanocomposites as assessed by the essential work of fracture concept

The essential work of fracture (EWF) method was adapted to determine the fracture toughness of poly(propylene-block-ethylene) (EPBC) based nanocomposites with different amounts (from 0 up to 5 wt.%) of synthetic boehmite alumina (BA). The dispersion of BA in the matrix was studied by transmission and scanning electron microscopies. Agglomerated micronscale along with well dispersed nanoscale BA particles were present in the EPBC matrix. By contrast to the neat EPBC, all nanocomposites failed by unstable necking. Therefore the energy partitioning concept of the EWF was adapted and attention paid to the yielding-related term. Both specific yielding-related essential and non-essential work of fracture parameters increased linearly with the product of the yield stress and elongation at yield derived from static tensile tests

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Profile dynamics of the South African banking sector

Abstract: A firm’s level of debt versus its level of equity has important implications for its value as well as its cost of capital. However, there are opposing views among many researchers and corporate finance experts pertaining to a firm’s optimal capital structure. Banks are responsible for providing liquidity as demanded by depositors, and to extend credit as well as liquidity to their borrowers through lines of credit. Given this central role that banks play in an economy, banks have always been concerned with both solvency and liquidity. This study explored the capital structure of the big four banks in South Africa by undertaking a descriptive analysis of the debt and equity dynamics of the big four banks during the period 2007 to 2016. The study employed secondary data which was obtained from various sources such as Bloomberg, online databases, Banks Act-returns, financial statements and reports of the big four banks in South Africa. The data collected was only restricted to Absa Bank, FirstRand Bank, Nedbank and Standard Bank. The study found that FirstRand has the best funding structure among the big four South African banks. ABSA has the second-best funding components with the highest ratio of retail funding to total funding. The study further analysed that Nedbank is by far the most reliant on institutional funding, leaving it particularly vulnerable to re-pricing in this market. Standard Bank has the lowest ratios of long-term and retail funding to total funding and is most reliant on foreign funding.M.Com. (Finance

Characterization of polypropylene/polystyrene boehmite alumina nanocomposites: Impact of filler surface modification on the mechanical, thermal, and rheological properties

The influences of surface treatment and the concentration of boehmite alumina (BA) particles on polypropylene and polystyrene (PS) (80/20) blends produced via melt compounding were examined. The results show that p-toluene sulfonic acid-treated BA particles yielded the highest stiffness improvement (27.5%), followed by untreated particles (25.7%), and dodecylbenzene sulfonic acid-treated BA particles (8.5%). Transmission electron microscopy revealed that p-toluene sulfonic acid-treated BA particle agglomerates were dispersed in the PS phase, whereas untreated particles formed agglomerations at the interfaces. Dodecylbenzene sulfonic acid-treated particles were poorly dispersed in both matrices. Differential scanning calorimetry showed that both untreated and p-toluene sulfonic acid-treated BA particles acted as nucleating agents in the blend because of the shifting of crystallization peaks to higher temperatures by 12 and 8 °C, respectively. A significant increase in decomposition temperatures occurred upon 7 wt % loading of all types of BA particles into the blend. Heat deflection temperature measurements showed that all types of BA particles improved the thermal properties of the blend

Curdlan-Conjugated PLGA Nanoparticles Possess Macrophage Stimulant Activity and Drug Delivery Capabilities

Research Article published by SpringerPurpose There is significant interest in the application of nanoparticles to deliver immunostimulatory signals to cells.We hypothesized that curdlan (immune stimulating polymer) could be conjugated to PLGA and nanoparticles from this copolymer would possess immunostimulatory activity, be non-cytotoxic and function as an effective sustained drug release system. Methods Carbodiimide chemistry was employed to conjugate curdlan to PLGA. The conjugate (C-PLGA) was characterized using 1H and 13C NMR, FTIR, DSC and TGA. Nanoparticles were synthesized using an emulsion-solvent evaporation technique. Immunostimulatory activity was characterized in THP-1 derived macrophages. MTTassay and real-time impedance measurements were used to characterize polymer and nanoparticle toxicity and uptake in macrophages. Drug delivery capability was assessed across Caco-2 cells using rifampicin as a model drug. Results Spectral characterization confirmed successful synthesis of C-PLGA. C-PLGA nanoparticles enhanced phosphorylated ERK production in macrophages indicating cell stimulation. Nanoparticles provided slow release of rifampicin across Caco-2 cells. Polymers but not nanoparticles altered the adhesion profiles of the macrophages. Impedance measurements suggested Ca2+ dependent uptake of nanoparticles by the macrophages. Conclusions PLGA nanoparticles with macrophage stimulating and sustained drug delivery capabilities have been prepared. These nanoparticles can be used to stimulate macrophages and concurrently deliver drug in infectious disease therapy

Listening to diverse community voices: the tensions of responding to community expectations in developing a male circumcision program for HIV prevention in Papua New Guinea

Background: The success of health programs is influenced not only by their acceptability but also their ability to meet and respond to community expectations of service delivery. The World Health Organization (WHO) and the Joint United Nations Programme on HIV/AIDS (UNAIDS) have recommended medical male circumcision (MC) as an essential component of comprehensive HIV prevention programs in high burden settings. This study investigated community-level perceptions of MC for HIV prevention in Papua New Guinea (PNG), a setting where diverse traditional and contemporary forms of penile foreskin cutting practices have been described