Motion of a sphere through an aging system

We have investigated the drag on a sphere falling through a clay suspension that has a yield stress and exhibits rheological aging. The drag force increases with both speed and the rest time between preparation of the system and the start of the experiment, but there exists a nonzero minimum speed below which steady motion is not possible. We find that only a very thin layer of material around the sphere is fluidized when it moves, while the rest of suspension is deformed elastically. This is in marked contrast to what is found for yield-stress fluids that do not age.Comment: latex, 4 figure

Appraisal of some methods of weed control during initial establishment of cocoa in a semi-deciduous forest zone of Ghana

In appraising the effects of the quantum and quality of weed control required in establishment of young cocoa, six manual methods of controlling weeds were compared with chemical weed control at two stations of the Cocoa Research Institute of Ghana. Growth of cocoa seedlings after 2 years in the field was superior (P < 0.05) in plots which were clean-weeded two or four times per year or treated with paraquat four times per year than when plots were slashed two or four times per year. There was strong evidence to suggest that treatments which ensured a weed-free environment to the cocoa over a long period were favourable to girth increments in the seedlings. Death of seedlings during establishment was generally lower in plots which were either clean-weeded or treated with paraquat. Labour requirement for controlling weeds with paraquat was considerably lower than that required for the other treatments. Considering the equipment and chemical input, paraquat application was expensive compared to high slashing with or without clean-line weeding two times a year, or clean weeding two times a year; but by virtue of its efficacy, it is recommended for cocoa establishment. En évaluant les effets du quatum et de la qualité de désherbage exigé dans la culture de jeune cacao, six méthodes de désherbage manuel étaient comparées avec le désherbage chimique à deux stations de l'Institut de Recherche en cacao du Ghana. La croissance de semis de cacao, après deux années, dans le champ était supérieure (P £ 0.05 ) dans les lots qui étaient complètement désherbés 2 ou 4 fois/an ou traités avec le paraquat 4 fois/an que dans les lots qui étaient entaillés 2 ou 4 fois/an. Il y avait de nombreuses preuves qui laissent penser que les traitements qui assuraient un environnement sans mauvaise herbe pour le cacao sur une longue période étaient favorables aux augmentations de circonférence des semis. La mort de semis pendant la culture était dans l'ensemble plus faible dans les lots, qui étaient soit complètement désherbés soit traités avec le paraquat. L'exigence de main-d'oeuvre pour maîtriser les mauvaises herbes avec le paraquat était considérablement plus faible que celle exigée pour les autres traitements. En ce qui concerne les matériels et les intrants chimiques, l'application de paraquat était chère que les entailles élevées avec ou sans le désherbage complet en ligne deux fois par an ou le désherbage complet deux fois par an mais en vertu de son efficacité il est recommandé pour la culture de cacao. Ghana Journal of Agricultural Science Vol. 40 (1) 2007: pp. 67-7

A Quantitative Assessment of Relationship between Urban Green Parks and Self-Esteem of Urban Children and Adolescents (Teenage Group) in Ghana

The importance of urban green parks in sustainable urban design development has gained currency in recent times, not only because urban parks do enhance the visual image of the city, or ameliorate its harsh climatic conditions, or purify its air, but they help develop high self-esteem of children and adolescents.  The study examines the correlation between the presence of green parks and self-esteem development among urban adolescents in Kumasi, the second largest city and Accra, the largest and the capital city of Ghana as case studies. The Children and adolescents used as respondents had their ages ranging from 13 to 19 years (teenage group). Using the Rosenberg Self-Esteem Scale as a measure, the study revealed that the lack of green parks at Tafo (Kumasi) has significantly impacted the self-esteem of Tafo adolescents; {t (59) =13.178, P=0.000 (two-tailed)}. And, Respondents who socialize in green parks at Cantonments (Accra had high self-esteem levels, whereas respondents who have no access to green parks at Tafo (Kumasi) had low self-esteem. Keywords: Green parks, Socialization, Self-esteem, Urban, Tennage Group, Kumasi and Accra

Mircorheology and jamming in a yield-stress fluid

Abstract We study the onset of a yield stress in a polymer microgel dispersion using a combination of particle-tracking microrheology and shear rheometry. On the bulk scale, the dispersion changes from a predominantly viscous fluid to a stiff elastic gel as the concentration of the microgel particles increases. On the microscopic scale, the tracer particles see two distinct microrheological environments over a range of concentrations-one being primarily viscous, the other primarily elastic. The fraction of the material that is elastic on the microscale increases from zero to one as the concentration increases. Our results indicate that the yield stress appears as the result of jamming of the microgel particles, and we infer a model for the small-scale structure and interactions within the dispersion and their relationship to the bulk viscoelastic properties

Effect of Gamma Irradiation on Chlorophyll Content in the Cowpea (Vigna unguiculata (L.) Walp)

The experiment was conducted to study the mutagenic effect of gamma rays on chlorophyll content at three different physiological stages in the cowpea: pre-flowering, flowering and post-flowering. Five sets of cowpea seeds were subjected to individual doses of gamma rays: 400 Gy, 450 Gy, 500 Gy, 600 Gy and 0 Gy. The seeds were sown to raise the M1 generation. The M1 generation seeds were collected and sown in the next season to raise the M2 generation. Leaf chlorophyll content was measured for M2 generation plants. Mean chlorophyll content for pre-flowering stage ranged between 38.9 ± 8.17 (control) and 64.2 ± 6.16 (400 Gy). Flowering stage mean chlorophyll content ranged from 48.3 ± 14.4 (600 Gy) to 99.4 ± 6.22 (450 Gy). Post-harvest chlorophyll mean content ranged between 13.1&nbsp;±0.98 (600 Gy) and 38.0 ±1.90 (400 Gy). There were significant differences in treatment effects for pre-flowering (P = 0.021), flowering (P = 0.005) and harvest (P = 0.000). At pre-flowering treatment, treatment 400 Gy scored a significant increase of 64 percent (P = 0.02) above the control. The optimum dose for useful induced mutation for increases in chlorophyll concentration in the cowpea was 400 Gy

The impact of the COVID-19 pandemic on deaf adults, children and their families in Ghana

This paper investigates the impact of the COVID-19 pandemic on deaf adults, children, and their families in Ghana, focusing on issues of inclusion. We ask what it takes to ‘make cities and human settlements inclusive, safe, resilient and sustainable’ (United Nations Strategic Development Goal 11) for deaf people in the context of the global pandemic in a low-resource context. The exceptional challenge to inclusion posed by COVID-19 is examined in terms of issues for deaf children and their families, and from the point of view of deaf adults in advocacy and support organisations. The pivotal language and communication issues are shown through a bioecological analysis that illuminates the interdependent dynamics of development and context, and their influence on access to, and understanding of, crucial information. It is argued that the global crisis of COVID-19 exposes and deepens issues of societal exclusion for deaf adults, children, and their families, and provokes wider questions about what inclusion means, and how it can be realised, in different cultural contexts

SSR-Based Genetic Structure Study of Seventy-Eight Cowpea (Vigna unguiculata (L.) Walp) Genotypes

Seventy-eight cowpea accessions were studied using short sequence repeats (SSR) technique. Genetic structure of these accessions was studied using three SSR polymorphic primers, SSR-6206, SSR-6218 and SSR-6219. A total of eight loci were scored for the three primers with a total of ten alleles. Bayesian clustering method grouped the cowpea genotypes into 4 sub-populations. Ancestral allele frequencies ranged between 0.128 and 0.802, while allele frequencies within sub-populations ranged from 0.001 and 0.997. Allele frequency divergence among sub-populations ranged from 0.145 to 0.406. Expected heterozygosity between individuals in the same sub-population ranged from 0.084 and 0.26, Mean genetic differentiation among sub-populations ranged from 0.374 and 0.687, with a mean geneflow ranging from 0.228 and 0.837. There was relative uniformity within the sub-populations which can be accounted for by independent random genetic drift

Prevalence of Giardia species in Cattle Faecal Matter in Selected Farms in Weija and Kpong Major Water Supply Heads to Accra, Ghana.

In developing countries including Ghana, giardiasis plays a major role in gastroenteritis in vertebrate. It poses health and socio-economic burden, and continues to be one of the causes of infant and calf mortality. Their infection continues to thrive in humans due to the zoonotic transmission of infected domesticated animals including cattle, dogs and cats, and their con­tinual presence in water bodies. The objective of this study was to establish their presence and evaluate the prevalence of Giardia sp. in cattle faecal matter in the environment in the Kpong and Weija communities. The Iron-haematoxylin staining techniques was used to analyze the faecal samples in order to identify Giardia sp. (Student t- test and Chi square were the statistical analyses) used for the studies. About five percent (5.3%) prevalence was obtained in both com­munities and this was significant (p&gt; 0.05). The parasite was found to be most prevalent (9.4%) in calves less than 3 months old and this decreased with age of calf. It was also observed that Giardia plays an important role in the cause of diarrhoea in cattle. There is the need to educate people on the disease and its implication on the quality of water from the treatment plants. Keywords: Giardia sp, water, contamination, diarrhoea, infant mortality

Quasiparticle Lifetime of the Repulsive Fermi Polaron

We investigate the metastable repulsive branch of a mobile impurity coupled to a degenerate Fermi gas via short-range interactions. We show that the quasiparticle lifetime of this repulsive Fermi polaron can be experimentally probed by driving Rabi oscillations between weakly and strongly interacting impurity states. Using a time-dependent variational approach, we find that we can accurately model the impurity Rabi oscillations that were recently measured for repulsive Fermi polarons in both two and three dimensions. Crucially, our theoretical description does not include relaxation processes to the lower-lying attractive branch. Thus, the theory-experiment agreement demonstrates that the quasiparticle lifetime is dominated by many-body dephasing within the upper repulsive branch rather than by relaxation from the upper branch itself. Our findings shed light on recent experimental observations of persistent repulsive correlations, and have important consequences for the nature and stability of the strongly repulsive Fermi gas