HIV and orientation of subsistence and commercial home gardens in rural Ghana: Crop composition, crop diversity and food security

An empirical study was conducted to explore differences and similarities in biodiversity in subsistence and commercial home gardens of HIV-positive and HIV-negative rural households in the Eastern Region of Ghana and their significance in household food security. Data were obtained through a household and home garden survey of a purposive sample of 32 HIV-positive and a random sample of 48 HIV-negative rural households and through in-depth interviews. A higher proportion of species common to all four home garden types consisted of food crops: vegetables, staples and fruits. In HIV-positive households, commercial home gardens were significantly larger, had significantly more species and individual plants, more perennial food crops and more species that were harvested all year round and evenness was lower, but there was no significant difference in species diversity compared with subsistence home gardens. Significantly, more HIV-positive and HIV-negative households with a commercial home garden consumed a staple crop cultivated in the home garden in the 24-h period prior to the survey than HIV-positive households with subsistence home gardens. Rural households with HIV that manage commercial home gardens cultivate a dual purpose home garden which supplies subsistence food and also provides cash income; such households may have better food security than households that cultivate subsistence home garden

Internal waves produced by a submerged slender body moving in a stratified fluid

Solutions are obtained for the velocity components generated by a singularity moving horizontally in a fluid of constant Brunt-Väisälä frequency. A radiation condition is enforced using an artificial damping mechanism. Two solutions are combined to produce a Rankine ovoid and a continuous line distribution is used to model a prolate spheroid. The distribution velocity field generated by the body displays the characteristics associated with the propagation of internal waves. The disturbance velocities calculated on the fluid’s surface are compared with those obtained from a three layer model. The patterns produced display significant differences

Interfacial waves produced by a submerged body moving in a layered fluid

Velocity potential solutions are derived for an arbitrary shaped body moving horizontally in a fluid system consisting of three layers, the lower layer of infinite depth. The body may be located in any one of the three layers. The boundary conditions on the free surface and interface are linearised and a radiation condition imposed. Expressions for the far field free surface and interface elevations are derived. A three dimensional extension of Lagally's theory provides a method which allows the wave resistance of the body to be determined. The application of a slender body approximation permits the derivation of analytical expressions for the elevations and wave resistance. Plots of the far field free surface and interface wave systems are presented when the body is located in each layer. The wave resistance of a prolate spheroid length L to diameter d for a series of L/d ratios is calculated over a Froude number range. The "dead water" effect being apparent in every case. The results of other parametric studies are also included

Trapped internal waves produced by a submerged slender body moving in a stratified fluid

Analytical solutions are obtained for the disturbance generated by a singularity moving horizontally in a layer of a three layer fluid, each layer possessing a constant Brunt-Väisälä frequency. A radiation condition is enforced using an artificial damping mechanism. The singularity solution is developed into a continuous source/sink line distribution which is used to model a prolate spheroid. The disturbance velocity field generated by the body displays the characteristics associated with the propagation of trapped internal waves. The disturbance calculated on the fluid's surface is compared with those obtained using a constant density three layer fluid model and a constant Brunt-Väisälä frequency model. The patterns produced by the current model described herein display significant departures from previous patterns

Layer dynamics of a freely standing smectic-A film

We study the hydrodynamics of a freely-standing smectic-A film in the isothermal, incompressible limit theoretically by analyzing the linearized hydrodynamic equations of motion with proper boundary conditions. The dynamic properties for the system can be obtained from the response functions for the free surfaces. Permeation is included and its importance near the free surfaces is discussed. The hydrodynamic mode structure for the dynamics of the system is compared with that of bulk systems. We show that to describe the dynamic correlation functions for the system, in general, it is necessary to consider the smectic layer displacement $u$ and the velocity normal to the layers, $v_z$, together. Finally, our analysis also provides a basis for the theoretical study of the off-equilibrium dynamics of freely-standing smectic-A films.Comment: 22 pages, 4 figure

Constraints on the ecomorphological convergence of zooplanktivorous butterflyfishes

Whether distantly related organisms evolve similar strategies to meet the demands of a shared ecological niche depends on their evolutionary history and the nature of form–function relationships. In fishes, the visual identification and consumption of microscopic zooplankters, selective zooplanktivory, is a distinct type of foraging often associated with a suite of morphological specializations. Previous work has identified inconsistencies in the trajectory and magnitude of morphological change following transitions to selective zooplanktivory, alluding to the diversity and importance of ancestral effects. Here we investigate whether transitions to selective zooplanktivory have influenced the morphological evolution of marine butterflyfishes (family Chaetodontidae), a group of small-prey specialists well known for several types of high-precision benthivory. Using Bayesian ancestral state estimation, we inferred the recent evolution of zooplanktivory among benthivorous ancestors that hunted small invertebrates and browsed by picking or scraping coral polyps. Traits related to the capture of prey appear to be functionally versatile, with little morphological distinction between species with benthivorous and planktivorous foraging modes. In contrast, multiple traits related to prey detection or swimming performance are evolving toward novel, zooplanktivore-specific optima. Despite a relatively short evolutionary history, general morphological indistinctiveness, and evidence of constraint on the evolution of body size, convergent evolution has closed a near significant amount of the morphological distance between zooplanktivorous species. Overall, our findings describe the extent to which the functional demands associated with selective zooplanktivory have led to generalizable morphological features among butterflyfishes and highlight the importance of ancestral effects in shaping patterns of morphological convergence

Assessing the levels of food shortage using the traffic light metaphor by analyzing the gathering and consumption of wild food plants, crop partsand crop residues in Konso, Ethiopia

Background Humanitarian relief agencies use scales to assess levels of critical food shortage to efficiently target and allocate food to the neediest. These scales are often labor-intensive. A lesser used approach is assessing gathering and consumption of wild food plants. This gathering per se is not a reliable signal of emerging food stress. However, the gathering and consumption of some specific plant species could be considered markers of food shortage, as it indicates that people are compelled to eat very poor or even health-threatening food. Methods We used the traffic light metaphor to indicate normal (green), alarmingly low (amber) and fully depleted (red) food supplies and identified these conditions for Konso (Ethiopia) on the basis of wild food plants (WFPs), crop parts (crop parts not used for human consumption under normal conditions; CPs) and crop residues (CRs) being gathered and consumed. Plant specimens were collected for expert identification and deposition in the National Herbarium. Two hundred twenty individual households free-listed WFPs, CPs, and CRs gathered and consumed during times of food stress. Through focus group discussions, the species list from the free-listing that was further enriched through key informants interviews and own field observations was categorized into species used for green, amber and red conditions. Results The study identified 113 WFPs (120 products/food items) whose gathering and consumption reflect the three traffic light metaphors: red, amber and green. We identified 25 food items for the red, 30 food items for the amber and 65 food items for the green metaphor. We also obtained reliable information on 21 different products/food items (from 17 crops) normally not consumed as food, reflecting the red or amber metaphor and 10 crop residues (from various crops), plus one recycled stuff which are used as emergency foods in the study area clearly indicating the severity of food stress (red metaphor) households are dealing with. Our traffic light metaphor proved useful to identify and closely monitor the types of WFPs, CPs, and CRs collected and consumed and their time of collection by subsistence households in rural settings. Examples of plant material only consumed under severe food stress included WFPs with health-threatening features like Dobera glabra (Forssk.) Juss. ex Poir. and inkutayata, parts of 17 crops with 21 food items conventionally not used as food (for example, maize tassels, husks, empty pods), ten crop residues (for example bran from various crops) and one recycled food item (tata). Conclusions We have complemented the conventional seasonal food security assessment tool used by humanitarian partners by providing an easy, cheap tool to scale food stress encountered by subsistence farmers. In cognizance of environmental, socio-cultural differences in Ethiopia and other parts of the globe, we recommend analogous studies in other parts of Ethiopia and elsewhere in the world where recurrent food stress also occurs and where communities intensively use WFPs, CPs, and CRs to cope with food stress

The arrow of time: from universe time-asymmetry to local irreversible processes

In several previous papers we have argued for a global and non-entropic approach to the problem of the arrow of time, according to which the ''arrow'' is only a metaphorical way of expressing the geometrical time-asymmetry of the universe. We have also shown that, under definite conditions, this global time-asymmetry can be transferred to local contexts as an energy flow that points to the same temporal direction all over the spacetime. The aim of this paper is to complete the global and non-entropic program by showing that our approach is able to account for irreversible local phenomena, which have been traditionally considered as the physical origin of the arrow of time.Comment: 48 pages, 8 figures, revtex4. Accepted for publication in Foundations of Physic

Spatial infinity in higher dimensional spacetimes

Motivated by recent studies on the uniqueness or non-uniqueness of higher dimensional black hole spacetime, we investigate the asymptotic structure of spatial infinity in n-dimensional spacetimes($n \geq 4$). It turns out that the geometry of spatial infinity does not have maximal symmetry due to the non-trivial Weyl tensor {}^{(n-1)}C_{abcd} in general. We also address static spacetime and its multipole moments P_{a_1 a_2 ... a_s}. Contrasting with four dimensions, we stress that the local structure of spacetimes cannot be unique under fixed a multipole moments in static vacuum spacetimes. For example, we will consider the generalized Schwarzschild spacetimes which are deformed black hole spacetimes with the same multipole moments as spherical Schwarzschild black holes. To specify the local structure of static vacuum solution we need some additional information, at least, the Weyl tensor {}^{(n-2)}C_{abcd} at spatial infinity.Comment: 6 pages, accepted for publication in Physical Review D, published versio