The Effects of Government Maize Marketing Policies on Maize Market Prices in Kenya

The Government of Kenya pursues maize marketing policy objectives through the National Cereals and Produce Board (NCPB) which procures and sells maize at administratively determined prices, and stores maize as a contingency against future shortages. A private sector marketing channel competes with the NCPB and prices in this channel are set by supply and demand forces. This paper estimates the effects of NCPB activities on the historical path of private sector maize market prices in Kenya between 1989 and 2004. Results provide important insights into the historical effects of the NCPB, and will provide useful input into deliberations on the appropriate role for the NCPB in the future. It was not possible to use a fully structural econometric model to estimate the historical policy effects because of data limitations in Kenya, which are typical of many developing countries. Instead we use a reduced form vector autoregression model (VAR) and show how policy simulation results can be obtained from a fairly parsimonious VAR that can be estimated with sparse data and imposes only minimal identification restrictions. Results show that NCPB activities have stabilized maize market prices in Kenya, reduced price levels in the early 1990s, and raised price levels by roughly 20 percent between 1995 and 2004. Because roughly 60 percent of Kenya's rural households purchase maize while less than 30 percent sell maize, the government's maize marketing board operations have transferred income from urban consumers and most small rural households to maize selling farmers.Kenya, income transfers, maize policy, price stabilization, VAR, International Development, C22, O2, Q13, Q18,

Contraceptive Vaginal Rings: Do They Pose an Increased Risk of Venous Thromboembolism in Aesthetic Surgery?

Nuvaring (Organon, Kenilworth, NJ) is a vaginal contraception ring inserted by the patient. It was approved by the Food and Drug Administration in 2001 for the prevention of pregnancy. The intent of this paper is to increase the awareness of Nuvaring among plastic surgeons, and to explore the risks associated with its use. We report the cases of two cosmetic surgery patients. These patients developed deep venous thrombosis and pulmonary emboli in the postoperative period while using Nuvaring. The very advantages of the Nuvaring—the ease of use, the avoidance of daily administration, and the insertion and removal of the device by the patient—may lead to the failure of patients to recollect being on a vaginal ring for contraception. Level of Evidence 4 Ris

HIV/AIDS and Agrarian Livelihoods in Zambia: a Test of the New Variant Famine Hypothesis.

1. Consistent with the New Variant Famine (NVF) hypothesis, the negative impact of drought on crop output and output per hectare is further exacerbated where HIV prevalence rates are relatively high, particularly in the low- and medium rainfall zones of the country (agro-ecological regions I and II). 2. HIV prevalence rates and AIDS-related mortality rates in Zambia are highest in the lowest rainfall and most drought-prone zone of the country (agro-ecological region I). 3. Only for districts in agro-ecological region I do we find evidence of a robust negative effect of HIV/AIDS on agrarian livelihood indicators. Relatively stable food production zones and/or areas with relatively low HIV prevalence rates appear to be less vulnerable to the adverse effects predicted by the NVF hypothesis, which suggests that HIV/AIDS exacerbates the effects of drought and other shocks on agrarian communities. 4. HIV/AIDS reduces the crop production gains associated with fertilizer subsidy increases in the highest rainfall areas. 5. Increases in the percentage of female-headed households in a district are related to declines in agricultural production indicators, but these effects do not appear to worsen when the HIV/AIDS epidemic is severe. 6. Only in districts whose borders encompass both agro-ecological regions II and III do we consistently find weak evidence that HIV/AIDS reduces the contribution of productive assets to crop output and output per unit of land as would be expected under the NVF hypothesis.food security, food policy, Zambia, HIV/AIDS, Food Security and Poverty, Health Economics and Policy, Q20,

Seeing a c-theorem with holography

There is no known model in holography exhibiting a $c$-theorem where the central charges of the dual CFT are distinct. We examine a holographic model of RG flows in a framework where the bulk gravity theory contains higher curvature terms. The latter allows us to distinguish the flow of the central charges $a$ and $c$ in the dual field theories in four dimensions. One finds that the flow of $a$ is naturally monotonic but that of $c$ is not. Extending the analysis of holographic RG flows to higher dimensions, we are led to formulate a novel c-theorem in arbitrary dimensions for a universal coefficient appearing in the entanglement entropy of the fixed point CFT's.Comment: 5 pages, 1 figure, v2: minor change

Syntactic Minimization Of Nondeterministic Finite Automata

Nondeterministic automata may be viewed as succinct programs implementing deterministic automata, i.e. complete specifications. Converting a given deterministic automaton into a small nondeterministic one is known to be computationally very hard; in fact, the ensuing decision problem is PSPACE-complete. This paper stands in stark contrast to the status quo. We restrict attention to subatomic nondeterministic automata, whose individual states accept unions of syntactic congruence classes. They are general enough to cover almost all structural results concerning nondeterministic state-minimality. We prove that converting a monoid recognizing a regular language into a small subatomic acceptor corresponds to an NP-complete problem. The NP certificates are solutions of simple equations involving relations over the syntactic monoid. We also consider the subclass of atomic nondeterministic automata introduced by Brzozowski and Tamm. Given a deterministic automaton and another one for the reversed language, computing small atomic acceptors is shown to be NP-complete with analogous certificates. Our complexity results emerge from an algebraic characterization of (sub)atomic acceptors in terms of deterministic automata with semilattice structure, combined with an equivalence of categories leading to succinct representations

Holographic Quantum Critical Transport without Self-Duality

We describe general features of frequency-dependent charge transport near strongly interacting quantum critical points in 2+1 dimensions. The simplest description using the AdS/CFT correspondence leads to a self-dual Einstein-Maxwell theory on AdS_4, which fixes the conductivity at a frequency-independent self-dual value. We describe the general structure of higher-derivative corrections to the Einstein-Maxwell theory, and compute their implications for the frequency dependence of the quantum-critical conductivity. We show that physical consistency conditions on the higher-derivative terms allow only a limited frequency dependence in the conductivity. The frequency dependence is amenable to a physical interpretation using transport of either particle-like or vortex-like excitations.Comment: 42 pages, 7 figures. A new figure showing the frequency dependence of EM dual conductivity and few references added. Abstract, introduction, section 5 and discussion extended. To appear in Phys.Rev.

Measuring Integration and Efficiency in Maize Grain Markets: The Case of South Africa and Mozambique

Price transmission between the South African market and other regional markets is not as straightforward, despite South Africa’s role of a surplus producer for the region. There appears to be a host of local factors that must be taken into account in order to anticipate the likely level of regional food prices. This article assesses the degree of market integration and the speed of price adjustment to spatial price differentials between the SAFEX maize price in South Africa and maize grain and maize meal prices in Maputo, Mozambique. The findings of this study indicate that under certain trading regimes, there is no evidence of a long-run relationship between Mozambican and South African maize grain prices. This implies that any large deviations, within these regimes, which exceed transaction costs, could continue to grow with no tendency towards equilibrium. However, the trade volume data indicates maize grain exports from South Africa into Mozambique in every month except for three within the sample set. Hence, the empirical findings of this paper are unexpected given a simple arbitrage argument. Possible reasons for these findings are highlighted in the article. It is interesting to note that when the same empirical analysis is undertaken for the SAFEX maize prices and maize meal prices in Maputo then there is in fact evidence of a long-run relationship between these prices in a high import regime. These findings are not surprising and are what we would expect since two of the largest milling companies, located in Maputo are responsible for the majority of the volume of maize grain imported into the country from South Africa.price transmission, market integration, cointegration, trade regimes, Crop Production/Industries,

Black Rings, Boosted Strings and Gregory-Laflamme

We investigate the Gregory-Laflamme instability for black strings carrying KK-momentum along the internal direction. We demonstrate a simple kinematical relation between the thresholds of the classical instability for the boosted and static black strings. We also find that Sorkin's critical dimension depends on the internal velocity and in fact disappears for sufficiently large boosts. Our analysis implies the existence of an analogous instability for the five-dimensional black ring of Emparan and Reall. We also use our results for boosted black strings to construct a simple model of the black ring and argue that such rings exist in any number of space-time dimensions.Comment: 26 pages, 6 figure