Urban Flooding in Kenya From a Psychosocial Perspective

There are legislative and engineering interventions coupled with increased community participation to mitigate urban flooding. However, there is an observed increase in flood events and their impact in these environments globally; and participation by individual home and property owners in community-driven initiatives to mitigate flooding in urban and peri-urban areas is reportedly low. The major objective of this study was to provide an understanding of urban flooding in Kenya from a psycho-social perspective. The specific objectives were: to establish a basis for a study associating the onset of flooding with environmental attitude and behaviour; to set ground for an investigation relating the effect of flooding on households to environmental attitude and behaviour; provide a background for analysis to correlate the level of humanitarian support during flooding with environmental attitude and behaviour; provide a basis for evaluation of possible attitude and behavioural change approaches to enhance urban flood disaster interventions; and to develop a conceptual framework the study of urban flooding in Kenya from an environmental attitude and behavioural perspective. This was a desk-top survey that involved a review of the literature covering urban flooding onset triggers, effects, and interventions; human attitudes and behaviour; environmental abuse, degradation, and conservation; as well as urban populations' livelihood practices. The study concludes that there exist gaps that provide an opportunity for investigation of urban flooding in Kenya from a psycho-social perspective

Econometrics of Domestication of the African Palm Weevil (<em>Rhynchophorus phoenicis</em> F.) Production as Small-Scale Business in Ghana

A reconnaissance survey of the domestication of the African palm weevil (APW) (Rhynchophorus phoenicis), which produces the edible larvae that are cherished as a delicacy among many tribes in Ghana, was conducted. Out of a total number of 560 semi-trained farmers, 271 (48.39%) were actively engaged in R. phoenicis farming near their homes or gardens, while 289 (51.61%) were non-active. Economic viability analyses showed that the active farmers would break even and repay their loans of GH¢1000 when they produce 3020 larvae at unit selling price of GH¢0.33, within a period of 4 months and 7 days (17 weeks). In a year, a farmer would have three production cycles and generate a total revenue of GH¢3018.79, at average monthly production of 755 edible larvae, net cash availability of GH¢1448.79, and projected net profit of GH¢448.79 in the first year of production. The farmer would make more profit and become wealthy in business in subsequent years. The pilot scheme of palm weevil farming was viable and ameliorated poverty and malnutrition of rural farmers in Ghana

Human Time-Frequency Acuity Beats the Fourier Uncertainty Principle

The time-frequency uncertainty principle states that the product of the temporal and frequency extents of a signal cannot be smaller than $1/(4\pi)$. We study human ability to simultaneously judge the frequency and the timing of a sound. Our subjects often exceeded the uncertainty limit, sometimes by more than tenfold, mostly through remarkable timing acuity. Our results establish a lower bound for the nonlinearity and complexity of the algorithms employed by our brains in parsing transient sounds, rule out simple "linear filter" models of early auditory processing, and highlight timing acuity as a central feature in auditory object processing.Comment: 4 pages, 2 figures; Accepted at PR

Bounds for graph regularity and removal lemmas

We show, for any positive integer k, that there exists a graph in which any equitable partition of its vertices into k parts has at least ck^2/\log^* k pairs of parts which are not \epsilon-regular, where c,\epsilon>0 are absolute constants. This bound is tight up to the constant c and addresses a question of Gowers on the number of irregular pairs in Szemer\'edi's regularity lemma. In order to gain some control over irregular pairs, another regularity lemma, known as the strong regularity lemma, was developed by Alon, Fischer, Krivelevich, and Szegedy. For this lemma, we prove a lower bound of wowzer-type, which is one level higher in the Ackermann hierarchy than the tower function, on the number of parts in the strong regularity lemma, essentially matching the upper bound. On the other hand, for the induced graph removal lemma, the standard application of the strong regularity lemma, we find a different proof which yields a tower-type bound. We also discuss bounds on several related regularity lemmas, including the weak regularity lemma of Frieze and Kannan and the recently established regular approximation theorem. In particular, we show that a weak partition with approximation parameter \epsilon may require as many as 2^{\Omega(\epsilon^{-2})} parts. This is tight up to the implied constant and solves a problem studied by Lov\'asz and Szegedy.Comment: 62 page

Population Dynamics and Non-Hermitian Localization

We review localization with non-Hermitian time evolution as applied to simple models of population biology with spatially varying growth profiles and convection. Convection leads to a constant imaginary vector potential in the Schroedinger-like operator which appears in linearized growth models. We illustrate the basic ideas by reviewing how convection affects the evolution of a population influenced by a simple square well growth profile. Results from discrete lattice growth models in both one and two dimensions are presented. A set of similarity transformations which lead to exact results for the spectrum and winding numbers of eigenfunctions for random growth rates in one dimension is described in detail. We discuss the influence of boundary conditions, and argue that periodic boundary conditions lead to results which are in fact typical of a broad class of growth problems with convection.Comment: 19 pages, 11 figure

Black hole polarization and new entropy bounds

Zaslavskii has suggested how to tighten Bekenstein's bound on entropy when the object is electrically charged. Recently Hod has provided a second tighter version of the bound applicable when the object is rotating. Here we derive Zaslavskii's optimized bound by considering the accretion of an ordinary charged object by a black hole. The force originating from the polarization of the black hole by a nearby charge is central to the derivation of the bound from the generalized second law. We also conjecture an entropy bound for charged rotating objects, a synthesis of Zaslavskii's and Hod's. On the basis of the no hair principle for black holes, we show that this last bound cannot be tightened further in a generic way by knowledge of ``global'' conserved charges, e.g., baryon number, which may be borne by the object.Comment: 21 pages, RevTex, Regularization of potential made clearer. Error in energy of the particle corrected with no consequence for final conclusions. New references adde

Spatio-selection in Expanding Bacterial Colonies

Segregation of populations is a key question in evolution theory. One important aspect is the relation between spatial organization and the population's composition. Here we study a specific example -- sectors in expanding bacterial colonies. Such sectors are spatially segregated sub-populations of mutants. The sectors can be seen both in disk-shaped colonies and in branching colonies. We study the sectors using two models we have used in the past to study bacterial colonies -- a continuous reaction-diffusion model with non-linear diffusion and a discrete ``Communicating Walkers'' model. We find that in expanding colonies, and especially in branching colonies, segregation processes are more likely than in a spatially static population. One such process is the establishment of stable sub- population having neutral mutation. Another example is the maintenance of wild-type population along side with sub-population of advantageous mutants. Understanding such processes in bacterial colonies is an important subject by itself, as well as a model system for similar processes in other spreading populations