FARM-LEVEL PERSPECTIVES ON THE IMPACT OF DOMESTIC SUPERMARKETS ON KENYA'S FRESH FRUITS AND VEGETABLES SUPPLY SYSTEM

The rise of supermarkets in Kenya has given rise to a new group of medium-sized farms managed by well-educated farmers. Focusing on kale, the essay shows that nearly all supermarket-channel farmers have the capacity to supply larger volumes year round and have transportation vehicles, an irrigation system, a packing shed, a cellular phone, and so on, pointing to the existence of a threshold capital vector which farmers must have in order to access supermarkets. Especially farm size and irrigation were found to be significant determinants of participation in the supermarket channel. Kale suppliers to supermarkets use more capital intensive production technologies, leading to average labor and land productivities which are 60-70% higher than in the traditional channel. Eighty percent of labor consists of hired workers, indicating that these farmers could be important in alleviating poverty for rural households with little or no land. While most traditional-channel kale farmers sell to brokers and get a price that lets them break-even at best, supermarket-channel farmers have a 40% gross profit margin. These margins and lower market risks in the supermarket channel have resulted in a strong growth dynamic of supermarket-channel farmers which have doubled the size of their operations over the last five years.Marketing,

On Pebble Automata for Data Languages with Decidable Emptiness Problem

In this paper we study a subclass of pebble automata (PA) for data languages for which the emptiness problem is decidable. Namely, we introduce the so-called top view weak PA. Roughly speaking, top view weak PA are weak PA where the equality test is performed only between the data values seen by the two most recently placed pebbles. The emptiness problem for this model is decidable. We also show that it is robust: alternating, nondeterministic and deterministic top view weak PA have the same recognition power. Moreover, this model is strong enough to accept all data languages expressible in Linear Temporal Logic with the future-time operators, augmented with one register freeze quantifier.Comment: An extended abstract of this work has been published in the proceedings of the 34th International Symposium on Mathematical Foundations of Computer Science (MFCS) 2009}, Springer, Lecture Notes in Computer Science 5734, pages 712-72

Design, synthesis, and pharmacological screening of β-amino-, thiadiazole/thiadiazine-phosphonate based triazole motifs as antimicrobial/cytotoxic agents

Three different series of phosphonate derivatives, β-amino- and fused thiadiazolo/thiadiazine-phosphonates have been synthesized using addition and/or addition-cyclization protocol of Horner-Wadsworth-Emmons (HWE) reagents to 1,2,4-triazole-3-thiols. The design of potentially antimicrobial and anticancer phosphor esters relied on the results of computer-assisted molecular modeling. All synthesized phosphonates were evaluated for their in vitro antimicrobial activities while anticancer properties were determined for eight out of twenty new phosphonates. The tested phosphonates, except for compounds that have a nitrile moiety, exhibited from moderate to significant antimicrobial activity. Nevertheless, the most active compounds were fused thiadiazole-phosphonates, which inhibited the growth of both Gram-negative and Gram-positive bacteria better than β-aminophosphonates and fused thiadiazolophosphonates. In parallel, the antitumor activity screenings of selected phosphonates from each series and the substrate 1 was also tested. Their antitumor properties against ten carcinoma cell lines, including breast (MCF7, MDA-MB- 231/ATCC, MDA-MB-435, BT-549), ovarian (IGROVI, OVCAR-3, SK-OV-3), prostate (PX-3, PU-145), and liver (HEPG2) were investigated. The results showed that all synthesized compounds reflected remarkable antitumor activity against breast (especially MDA-MB-231/ATCC and BT-549), and prostate carcinoma cell lines (PC-3 and DU-145), whereas a moderate to good effect on ovarian and liver cancer cells was observed

An automaton over data words that captures EMSO logic

We develop a general framework for the specification and implementation of systems whose executions are words, or partial orders, over an infinite alphabet. As a model of an implementation, we introduce class register automata, a one-way automata model over words with multiple data values. Our model combines register automata and class memory automata. It has natural interpretations. In particular, it captures communicating automata with an unbounded number of processes, whose semantics can be described as a set of (dynamic) message sequence charts. On the specification side, we provide a local existential monadic second-order logic that does not impose any restriction on the number of variables. We study the realizability problem and show that every formula from that logic can be effectively, and in elementary time, translated into an equivalent class register automaton

Logics for Unranked Trees: An Overview

Labeled unranked trees are used as a model of XML documents, and logical languages for them have been studied actively over the past several years. Such logics have different purposes: some are better suited for extracting data, some for expressing navigational properties, and some make it easy to relate complex properties of trees to the existence of tree automata for those properties. Furthermore, logics differ significantly in their model-checking properties, their automata models, and their behavior on ordered and unordered trees. In this paper we present a survey of logics for unranked trees

Relativistic Acoustic Geometry

Sound wave propagation in a relativistic perfect fluid with a non-homogeneous isentropic flow is studied in terms of acoustic geometry. The sound wave equation turns out to be equivalent to the equation of motion for a massless scalar field propagating in a curved space-time geometry. The geometry is described by the acoustic metric tensor that depends locally on the equation of state and the four-velocity of the fluid. For a relativistic supersonic flow in curved space-time the ergosphere and acoustic horizon may be defined in a way analogous the non-relativistic case. A general-relativistic expression for the acoustic analog of surface gravity has been found.Comment: 14 pages, LaTe