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

Comparison of methods of field planting on cocoa seedling survival and early growth in a marginal cocoa-growing area of Ghana

Cocoa seeds were planted at stake at different times to determine the best time for optimum establishment at the Cocoa Research Institute of Ghana substation at Afosu, considered as a marginal cocoa-growing area owing to its prolonged dry season. The treatments evaluated were planting hybrid cocoa seeds at stake in either April, May, June, July or September; and polythene bag or bareroot transplanting of 5-month-old hybrid cocoa seedlings in May or June, respectively. The trial was laid out as randomized complete block with seven treatments and five replicates. Each plot measured 24 m × 18 m and contained 48 plants. The results recorded over 3 years (1999-2001) showed significantly higher (P< 0.01) seedling survival rates in the polythene bag-transplanted seedlings than in seedlings from seeds sown at stake. There were no significant differences between the survival rates of seedlings from seeds sown at stake from April to July. The average percentage seedling survival after the first dry season for seeds sown at stake from April to July over the 3-year period (1999-2001) was 60 per cent compared to 57 per cent for bare-root and 81 per cent for polythene bag-transplanted seedlings. There were no significant differences between the girth increments of the seedlings, implying that once established, there may be no differences in the rates of growth of transplanted seedlings and those sown at stake. It is concluded that bare-root transplanting of cocoa seedlings and planting cocoa seeds at stake are feasible options in marginal cocoa-growing areas if such activity is properly timed to coincide with the rains. However, the polythene bag method of transplanting cocoa seedlings remains the best option for field planting of cocoa in marginal cocoagrowing areas of Ghana.Les féves de cacao étaient semées et soutenues à l'aide d'un tuteur aux moments différents à Afosu, une sous-station de l'Institut de Recherche en Cacao du Ghana qui est considérée une zone marginale de la culture de cacao en raison de la longue durée de sa saison sèche pour déterminer le meilleur temps pour l'enracinement optimum. Les traitements évalués étaient; la plantation de fèves de cacao hybride soutenues à l'aide d'un tuteur soit en avril, mai, juin, juillet soit en septembre et le repiquage à sachet en plastique ou à racine-nue de semis de cacao hybride âgé de 5 mois respectivement en mai ou en juin. L'essai était dessiné comme un bloc complet choisi au hasard avec sept traitements et cinq replicatifs. Chaque lot avait une mesure de 24 m × 18 m et contenait quarante-huit plantes. Les résultats obtenus sur une période de trois ans (1999-2001) montraient un taux de survie de semis considérablement plus élevé (P £ 0.01) dans les semis repiqués à sachet en plastique que dans les semis de fèves semées et soutenues à l'aide d'un tuteur d'avril à juillet. Le pourcentage moyen de la survie de semis après la première saison sèche pour les fèves semèes et soutenues à l'aide d'un tuteur d'avril à juillet sur la pèriode de 3 ans (1999, 2000, 2001) était 60% comparé à 57% et 81% respectivement pour les semis repiqués à racine-nue et à sachet en plastique. Il n'y avaient pas des différences considérables entre les augmentations de circonférence des semis, signifiant qu'une fois établi, il n'y aura pas, peut-être, de différences entre les taux de croissance de semis repiqués et les semis semés et soutenus à l'aide d'un tuteur. La conclusion est tirée que le repiquage de semis de cacao à racine-nue et la plantation de fèves de cacao et soutenue à l'aide d'un tuteur sont des options faisables dans les zones marginales de la culture de cacao si cette activité est bien exécutée avec un bon timing pour coïncider avec la saison des pluies. Toutefois, le repiquage de semis de cacao par la méthode de sachet en plastique reste la meilleure option pour la plantation de cacao sur le terrain dans les zones marginales de la culture de cacao au Ghana. Ghana Journal of Agricultural Science Vol. 40 (2) 2008: pp. 199-20

Genetic Diversity of Wild Rice (Oryza longistaminata) in Ghana

Oryza longistaminata is a wild rice taxon and an excellent source of genetic variation that remains largely unexploited. This study was conducted to understand the genetic diversity between and within O. longistaminata populations, collected from different geographic locations in Ghana. In this study, SSR markers were used to determine the intra-specific variability in O. longistaminata, and how the variation is partitioned within and between different populations. Analysis of molecular variance revealed high levels of polymorphism (95.9%) within the populations. The overall genetic diversity for all the loci in the six populations was high (Shannon's Information Index I = 0.579, Nei's unbiased expected heterozygosity, He = 0.405). Hierarchical partitioning also indicated a high genetic diversity between and within populations, with some level of relatedness between samples taken from the Savannah agroecological area. The high genetic diversity observed in this study offer a great opportunity for screening useful traits among the populations of O. longistaminata in Ghana for rice breeding programs

Chemical Composition and Nutritive Value of an Invasive Exotic Species Broussonetia Papyrifera in Ghana

The study was done to determine the chemical composition and nutritive value of Broussonetia papyrifera with the aim of determining its potential for forage in Ghana. Due to its prolific regeneration pattern it has invaded large canopy gaps and degraded farm lands with a lot of ecological consequences.  Foliage samples of Broussonetia papyrifera were collected from wild stands in the Tano South District of the Brong Ahafo Region, Ghana, together with samples of Ficus exasperata and Leucaena leucocephala for comparison. The nutrient content (proximate composition, cell wall content and macro-mineral composition), anti-nutritive factor (condensed tannin) and digestibility of the test species were analysed. Results of the study showed that for a cheaper source of plant crude protein (27.17% DM), ether extract (6.45% DM), carbohydrate (25.37% DM), ash (11.54% DM), calcium (2.54% DM), phosphorus (0.23% DM), potassium (0.73% DM), magnesium (0.86% DM) and in vitro organic matter digestibility (50.88% DM), B. papyrifera appears good potential forage in ruminant nutrition. However, the level of condensed tannin (CT) in B. papyrifera (6.96% - 7.09% DM) may interfere with animal performance since they exceed 5.0% DM concentration which may reduce the digestibility of forage as a result of the nitrogen-condensed tannin (N-CT) complex formation that reduces their solubility and degradation by rumen bacteria. The results suggest that B. papyrifera could be a good candidate for forage, especially during the dry season for resource-poor farmers with stalled-fed animals in the B. papyrifera invaded areas in Ghana. Keywords: Invasive species, chemical composition, nutritive value, forage, Broussonetia papyrifera, Ghana

Assessment of the resettlement compensation satisfaction of wood workers at Sokoban, Kumasi

Resettlement has been one of the strategies used to pave way for development and redevelopment of infrastructure in major cities of Ghana in the past few decades. Resettlement is usually characterized by displacement of people and their livelihoods. In Kumasi, resettlement has physicallydisplaced over 10,000 people mostly traders, in and around the Central Business District. Kumasi has undergone significant development in the past two decades in the areas of road and housing construction, resulting in the resettlement of some commercial neighborhoods including the wood merchants from Anloga to allow for the construction of the south-eastern section of the ring road from Oforikrom (Anloga) to Nhyiaeso. This study assessed the outcome of involuntary resettlement of wood merchants from Anloga to Sokoban Wood Village in terms of compensation, improvement in working space and the impact on the timber trade. The study used mixedmethods: it relied on the administration of questionnaires and interviews to gather data from respondents for analysis as well as the use of dependent sample T-test for hypothesis testing to evaluate the change in livelihood that resulted from the resettlement programme. The study revealeda significant improvement in the livelihood of the displaced workers after the resettlement.Keywords: Resettlement, Infrastructure, Compensation, Satisfaction, Livelihood

The effectiveness of medroxyprogesterone acetate (MAP) in synchronizing oestrus and its influence on lambing rate and litter size in crossbred ewes

Oestrus was synchronized in crossbred ewes (Djallonke x Sahel F2 generation) on the Ghana Government /UNDPI FAO Sheep and Goat Project Farm at Ejura. Medroxyprogesterone acetate (MAP), 60 mg, was applied in an antibiotic-treated intravaginal sponge and allowed to remain for 14 days. Pregnant mare serum gonadotropin (PMSG; 500 LU) was injected intramuscularly in one group of ewes on the day of sponge withdrawal. A control group (D) had no treatment. TIle progestaten was effective in synchronizing oestrus and resulted in a compact batch lambing interval. PMSG shortened the interval between sponge withdrawal and the onset of oestrus. It also increased the incidence of multiple births. About 80 per cent of animals in MAP treated groups exhibited oestrus within a three-day period as compared to 33 per cent in the control group and the difference was significant (P&lt;0.01). About 90 pcr cent of animals in the treated groups lambed within a 6-day period as opposed to 45 per cent in the control group. The difference was significant (P&lt;0.01) Fertility was 100 per cent for all the animals

Effect of polybag size and foliar application of urea on cocoa seedling growth

The effects of different polybag sizes and foliar application of urea on the growth of cocoa seedlings in the nursery were studied at the Cocoa Research Institute of Ghana substation at Afosu in the Eastern Region of Ghana between June 2004 and May 2005. Hybrid cocoa seeds were sown in polybags measuring 17.5 cm × 25 cm, 12.5 cm × 25 cm, 12.5 cm × 20 cm, and 12.5 cm × 15 cm filled with top soil. From the four-leaf stage, half of the seedlings in the different polybags received fortnightly foliar application of 2 per cent urea solution, while the other half did not receive foliar application of urea. Each treatment consisted of 50 cocoa seedlings. There were significant differences (P< 0.01) in girth and height between the cocoa seedlings in the different sizes of polybags at 3, 4 and 5 months after sowing. Leaf number and tap root length were also significantly influenced by polybag size at 4 and 5 months after sowing. Generally, seedlings raised in 17.5 cm × 25 cm polybags produced bigger and taller seedlings, more leaves, longer tap root length, and had significantly higher (P< 0.01) total dry matter per seedling than those raised in 12.5 cm × 15 cm polybags. Foliar application of 2 per cent urea improved the growth of cocoa seedlings in all the different polybag sizes. The results suggest that smaller polybag sizes (12.5 cm × 25 cm, 12.5 cm × 20 cm, and 12.5 cm × 15 cm) could be used to nurse cocoa seedlings and transplanted early at 3 months after sowing instead of the recommended practice of nursing in 17.5 cm × 25 cm polybags and transplanting at 5 to 6 months after sowing. More cocoa seedlings raised in smaller polybags could, therefore, be transported per trip for field planting at reduced cost to the farmer.Les effets de différentes dimensions de sac en plastique et d\'application foliaire d\'urée sur la croissance de semis de Cacao dans les pépinières étaient étudiés à Afosu, une sous-station de l\'Institut de Recherche en Cacao du Ghana dans la région de l\'Est du Ghana entre juin 2004 et mai 2005. Les fèves de cacao hybride étaient semées dans les sacs en plastique qui mesuraient 17.5 cm × 25 cm, 12.5 cm × 25 cm, 12.5 cm × 20 cm, et 12.5 cm × 15 cm remplis de couche arable. De la phase de 4-feuille, une demie de semis dans les différents sacs en plastique recevaient tous les quinze jours l\'application foliaire de 2% de solution d\'urée alors que l\'autre demie ne recevaient pas d\'application foliaire d\'urée. Chaque traitement consistait en cinquant de semis de cacao. Il y avaient des différences considérables (P £ 0.01) en circonférence et en taille entre les semis de cacao dans les différentes dimensions de sacs en plastique à 3, 4 et 5 mois après la semaille. Nombre de feuille et la longueur de racine pivotante étaient aussi considérablement influencés par la dimension du sac en plastique à 4 et 5 mois après la semaille. En général les semis élevés dans les sacs en plastique de 17.5 cm × 25 cm produisaient des semis plus gros et plus grands, plus de feuilles, de longueur de racine pivotante plus longue et avaient une totalité de matière sèche par semis considérablement plus élevées (P £ 0.01) que ceux élevés dans les sacs en plastique de 12.5 cm × 15 cm. L\'application foliaire de 2% d\'urée améliorait la croissance de semis de cac ao dans toutes les différentes dimensions de sacs en plastique. Les résultats suggèrent que les sacs en plastique de dimensions plus petites (12.5 cm × 25 cm, 12.5 cm × 20 cm, et 12.5 cm × 15 cm) pourraient être utilisés pour soigner les semis de cacao et repiqués précoces à 3 mois après la semaille plutôt que la pratique actuelle recommandée de soigner dans les sacs en plastique de 17.5 cm × 25 cm et repiquer à 5-6 mois après la semaille. Plus de semis de cacao élevés dans les plus petites sacs en plastique pourraient donc être transporter par trajet pour le repiquage sur le terrain à coût réduit à l\'agriculteur. Ghana Journal of Agricultural Science Vol. 40 (2) 2008: pp. 207-21

ENHANCING PRE-SERVICE TEACHERS’ UNDERSTANDING AND ATTITUDES TOWARD NAMING AND REACTIONS OF ORGANIC COMPOUNDS USING JIGSAW APPROACH

This study aimed at enhancing pre-service teachers’ understanding and attitudes toward naming and reactions of organic compounds using the jigsaw approach. It was a descriptive study that used a quantitative approach in collecting the data for analysis. The research design was a quasi-experimental one, which adapted the non-randomised control group pre-test/post-test intact class design. A sample of 144 pre-service teachers, comprising 72 in the experimental group and 72 in the control group were engaged in the study. Intact classes were used for the study; thus, the sample selection was non-randomised. ‘Organic Chemistry Concept Understanding Test’ (OCCUT) in the form of a pre-test and a post-test as well as an ‘Organic Chemistry Attitude Scale’ (OCAS) were the instruments used for the study. The reliability indices of the pre-test and the post-test were 0.721 and 0.724 respectively, whereas, Cronbach’s alpha reliability coefficient of the ‘OCAS’ was 0.899. This study found that in terms of the pre-service teachers’ prior knowledge on naming and reactions of organic compounds, the experimental group and the control group both had more misunderstanding and partial understanding than a sound understanding of the concepts. The findings further revealed that the majority of the pre-service teachers in the experimental group had a sound understanding of the naming and reactions of organic compounds after they were taught through the jigsaw approach. Nevertheless, quite a large number of the pre-service teachers in the control group continue to show a misunderstanding of the concepts after they were taught through the traditional lecture-method. Again, the study found that the jigsaw approach enhanced the pre-service teachers’ attitudes toward the organic chemistry concepts than the traditional lecture-method.  Article visualizations

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

Performance Characteristics of Lactating Djallonké Ewes Fed Rice Straw Basal Diets Supplemented With Stylosanthes Hamata

A 7-week feed intake and growth performance study involving thirty lactating Djallonké ewes and their lambs was conducted. The ewes were randomly assigned to 3 dietary treatment groups resulting in 10 replications. The ewes were individually housed and offered 1000 g rice straw basal diet daily; Stylosanthes hamata given as a supplement at one of the 3 rates, which formed the treatments; i.e. 180 g/d [T180], 240 g/d[T240] or 360 g/d [T360]. Feed intake of the ewes and liveweight changes of the ewes and their lambs were recorded. Intake of rice straw was similar amongst the ewes on the different treatments (P>0.05). However, the ewes consumed more supplement as the amount offered increased resulting in a significant improvement in total feed intake as the supplement offered increased (P0.05) in the body weights of the ewes that could be attributable to treatment effects. The average daily gains (ADG) at day 49 for the lambs were, 47.5 [T180], 63.4 [T240] and 76 g [T360]. This result suggest that supplementation of ewes had a significant effect (