Rockbursts and mud

It has been observed that the presence of water or mud on the floor of a mining tunnel seems to reduce tunnel failure associated with remote seismic events. We examine two mechanisms that could explain this phenomenon. The investigations suggest that lubrication effects due to the presence of water within cracks could well affect the occurrence of spalling, and the results obtained suggest that coating the tunnel walls with moisture containing semi-liquid pastes may be effective for tunnel wall stabilization

Survival Analysis on Undergraduate Students� Persistence- Case study

A longitudinal study on 1,998 undergraduate students in the four-year program was conducted in one of the universities in Kenya. These were students who had been admitted in the years 2012, 2013 and 2014. Data collected was for 64 months, from January 1, 2012 to May 27, 2017.Survival analysis was used to model and analyze the persistence of these students at the university. It was found that majority of the students who withdrew from the university did so in the first 12 months of study. There was a significant difference in the persistence of the male and female students, with the female students having a higher survival rate than the male students. It was also found that the persistence of the Kenyan and Non-Kenyan students was significantly different, with the Kenyan students having a higher survival rate than the Non-Kenyan students. Gender had a significant effect on the survival of these students with the risk of a male student withdrawing being 2 times higher than that of a female student

TWO-PHASE FRICTION FACTOR IN GAS-LIQUID PIPE FLOW

An improved friction factor prediction model for two-phase gas-liquid pipe flow is proposed. The model is based on a previous no-slip formulation where a mixture Reynolds number was defined. In this study, the mixture Reynolds number is modified by introducing slip-ratio information through the inclusion of void-fraction and flow-pattern dependent models. An experimental database reconstituted from the available literature and new frictional pressure-drop data for air-water horizontal flow in an I.D. 0.0204m pipe are also presented. The full database considers several different flow conditions for horizontal two-phase flow of refrigerants and air-water mixtures. It was compared to predictions of models from the literature as well as the new proposed model. We found that the proposed and Müller-Steinhagen-and-Heck methods provide better agreement for the current experimental database. It is shown that the inclusion of void-fraction information on the previous mixture Reynolds definition improves the friction-factor predictio

Local Knowledge on the Changes in Vegetation Composition and Abundance in Rusinga Island, Homa Bay County, Kenya

Local communities have been coping with environmental dynamics since time immemorial, and they often possess considerable knowledge about environmental change, as well as mechanisms of coping with the consequences of such changes. Local knowledge on the changes in vegetation composition and abundance is therefore fundamental for the development of management strategies aimed at sustainable use and conservation of natural vegetation resources. Household interviews (n=150), Key informant interviews (n=30) and Focus group discussions (n=4) were used in this study to extract information on the communities’ perceptions on the status of vegetation in Rusinga Island of Homa Bay County of Kenya, and the suggested management strategies for the environment, particularly the vegetation resources for posterity. Rusinga Island is a biodiversity hotspot and an ancient historic area with numerous archeological sites that have given the World fossils dating back millions of years but the area has been experiencing downward trend in its ecosystems. Majority (86%) of the respondents reported having observed changes in vegetation composition and abundance in the study area. The changes were attributed to deforestation, high human population, overgrazing, inadequate rainfall, and soil erosion. Most (68%) of the respondents perceived the changes had occurred mainly in the forests/hills, in the entire Island (15.3%) and in the homesteads (2.7 %). To reverse the changes, the local community proposed tree planting, protection of existing trees, use of alternative sources of fuel, increased awareness creation on environmental conservation and controlled livestock grazing as the best strategies to reduce vegetation degradation. Besides sensitization and building capacity of the communities to engage in sustainable management of vegetation resources, land restoration interventions in the study area should target the plants species at risk through re-introduction and re-afforestation practices

Woody Plant Species Composition and Diversity in Rusinga Island, Homa Bay County, Kenya

Information on the state of woody vegetation of Rusinga Island is urgently needed in order to develop appropriate and effective conservation guidelines. Rusinga Island is an ancient historic area with numerous archeological sites and a bountiful of birdlife. However, the Island is characterized by highly degraded ecosystems from human disturbances such as cutting down of trees for fuel, construction poles, and overgrazing resulting in a remarkable degradation of flora, alteration of the ecosystems and loss of biodiversity. This study sought to determine the composition and diversity of woody plant species in Rusinga Island to understand the current status in order to develop appropriate and effective conservation measures since no such study has been conducted in the area before. Three hills (Ligongo, Agiro and Wanyama) were selected for sampling and demarcated into three study zones differentiated by the slope gradient and land use. A systematic random sampling approach was adopted to establish 98 sampling plots measuring 20 m x20 m (400m2) for recording tree species and subplots of 10 m by 10 m within the main plots for recording shrubs and lianas across the three study zones at an interval of 200m. A total of 63 woody plant species belonging to 32 families and 51 genera were recorded, out of which 66.7% were trees, 31.7% shrubs and 1.6% lianas. The upper zones had significantly higher species diversity, species richness, evenness and abundance compared to the middle and lower zones. The lower zones depicted a lower abundance of plants and least similarities of species compared to the middle and upper zones. Development of appropriate conservation and management strategies is required in order to protect the woody plant resources from unsustainable human activities and to improve the natural diversity of the Island

Identification of Niches for Integration of Brachiaria Grasses in Smallholder Mixed Crop-Livestock Farming Systems in Kenya

Inadequate quantity and quality of feed is the major constraint to livestock productivity in Kenya. Low rainfall, lack of adapted forages and poor management of sown forages are major factors that affect feed resources production. In most of the farming systems, forages are relegated to the less fertile and degraded soils resulting into poor growth. As a result the growth is poor resulting in deficient in minerals content, low crude protein (CP) and energy. The situation in exacerbated by climate variability and frequent drought. On the other hand, feed resources derived from crop residues, particularly cereals are of poor quality and not sufficient to meet animal production (Njarui and Mureithi, 2006). A research programme was initiated in 2012 to explore superior feed resources and increase availability of high quality forages to increase livestock productivity in East Africa. The program focuses on evaluation of drought and marginal soil adapted improved Brachiaria cultivars from South America. The genus Brachiaria is predominantly an African grass with about 100 species. The Brachiaria grasses are the most widely grown forages in South America (Miles et al., 2004). These grasses produce high biomass, enhance soil fertility and reduce greenhouse gas emission (Peters et al., 2012), are highly nutritious and are known to increase milk (Njarui, pers. comm.) thus suitable for different farming systems of Kenya. However, before integration of these grasses into farming systems, it was imperative to identify suitable niches suitable for growing these grasses. The knowledge gained from the study will facilitate development of suitable approaches for promoting these grasses across diverse production systems of Kenya

Mode-Locking in Driven Disordered Systems as a Boundary-Value Problem

We study mode-locking in disordered media as a boundary-value problem. Focusing on the simplest class of mode-locking models which consists of a single driven overdamped degree-of-freedom, we develop an analytical method to obtain the shape of the Arnol'd tongues in the regime of low ac-driving amplitude or high ac-driving frequency. The method is exact for a scalloped pinning potential and easily adapted to other pinning potentials. It is complementary to the analysis based on the well-known Shapiro's argument that holds in the perturbative regime of large driving amplitudes or low driving frequency, where the effect of pinning is weak.Comment: 6 pages, 7 figures, RevTeX, Submitte

Distinct genital tract HIV-specific antibody profiles associated with tenofovir gel

The impact of topical antiretrovirals for pre-exposure prophylaxis on humoral responses following HIV infection is unknown. Using a binding antibody multiplex assay, we investigated HIV-specific IgG and IgA responses to envelope glycoproteins, p24 Gag and p66, in the genital tract (GT) and plasma following HIV acquisition in women assigned to tenofovir gel (n=24) and placebo gel (n=24) in the CAPRISA 004 microbicide trial to assess if this topical antiretroviral had an impact on mucosal and systemic antibody responses. Linear mixed effect modeling and partial least squares discriminant analysis was used to identify multivariate antibody signatures associated with tenofovir use. There were significantly higher response rates to gp120 Env (P=0.03), p24 (P=0.002), and p66 (P=0.009) in plasma and GT in women assigned to tenofovir than placebo gel at multiple time points post infection. Notably, p66 IgA titers in the GT and plasma were significantly higher in the tenofovir compared with the placebo arm (P<0.05). Plasma titers for 9 of the 10 HIV-IgG specificities predicted GT levels. Taken together, these data suggest that humoral immune responses are increased in blood and GT of individuals who acquire HIV infection in the presence of tenofovir gel.United States. National Institutes of Health (AI51794)United States. National Institutes of Health (AI104387)United States. National Institutes of Health (AI115981)United States. National Institutes of Health (AI116086)United States. Agency for International Development (GP00-08-00005-00 subproject agreement PPA-09-046

Prognostic value of biochemical parameters among severe COVID-19 patients admitted to an intensive care unit of a tertiary hospital in South Africa

Background: Data on biochemical markers and their association with mortality rates in patients with severe coronavirus disease 2019 (COVID-19) admitted to intensive care units (ICUs) in sub-Saharan Africa are scarce. An evaluation of baseline routine biochemical parameters was performed in COVID-19 patients admitted to the ICU, in order to identify prognostic biomarkers. Methods: Demographic, clinical, and laboratory data were collected prospectively from patients with PCR-confirmed COVID-19 admitted to the adult ICU of a tertiary hospital in Cape Town, South Africa, between October 2020 and February 2021. Robust Poisson regression methods and the receiver operating characteristic (ROC) curve were used to explore the association of biochemical parameters with severity and mortality. Results: A total of 82 patients (median age 53.8 years, interquartile range 46.4–59.7 years) were enrolled, of whom 55 (67%) were female and 27 (33%) were male. The median duration of ICU stay was 10 days (interquartile range 5–14 days); 54/82 patients died (66% case fatality rate). Baseline lactate dehydrogenase (LDH) (adjusted relative risk 1.002, 95% confidence interval 1.0004–1.004; P = 0.016) and N-terminal pro B-type natriuretic peptide (NT-proBNP) (adjusted relative risk 1.0004, 95% confidence interval 1.0001–1.0007; P = 0.014) were both found to be independent risk factors of a poor prognosis, with optimal cut-off values of 449.5 U/l (sensitivity 100%, specificity 43%) and 551 pg/ml (sensitivity 49%, specificity 86%), respectively. Conclusions: LDH and NT-proBNP appear to be promising predictors of a poor prognosis in COVID-19 patients in the ICU. Studies with a larger sample size are required to confirm the validity of this combination of biomarkers

Acquisition of pneumococci specific effector and regulatory Cd4+ T cells localising within human upper respiratory-tract mucosal lymphoid tissue

The upper respiratory tract mucosa is the location for commensal Streptococcus (S.) pneumoniae colonization and therefore represents a major site of contact between host and bacteria. The CD4(+) T cell response to pneumococcus is increasingly recognised as an important mediator of immunity that protects against invasive disease, with data suggesting a critical role for Th17 cells in mucosal clearance. By assessing CD4 T cell proliferative responses we demonstrate age-related sequestration of Th1 and Th17 CD4(+) T cells reactive to pneumococcal protein antigens within mucosal lymphoid tissue. CD25(hi) T cell depletion and utilisation of pneumococcal specific MHCII tetramers revealed the presence of antigen specific Tregs that utilised CTLA-4 and PDL-1 surface molecules to suppress these responses. The balance between mucosal effector and regulatory CD4(+) T cell immunity is likely to be critical to pneumococcal commensalism and the prevention of unwanted pathology associated with carriage. However, if dysregulated, such responses may render the host more susceptible to invasive pneumococcal infection and adversely affect the successful implementation of both polysaccharide-conjugate and novel protein-based pneumococcal vaccines