The Effects of Market Reform on Maize Marketing Margins in South Africa: An Empirical Study

This paper determines the effect of market reform and price decontrol on the size of maize milling/retail margins in South Africa. Regression models of monthly milling/retail margins are run over the period May 1976 to September 2003. To assess the robustness of our findings, we estimate several different model specifications for representing structural change, vary the sample period to examine the sensitivity of findings to unusual weather and market conditions in the region during the 2001-2003 period, and use different estimation techniques, OLS with Newey-West robust estimators and Feasible General Least Squares. In virtually all models, the results indicate that real maize milling/retailing margins in South Africa have increased since the market deregulation in 1997. Controlling for disturbances in weather, wages, exchange rate levels and volatility, inflation-adjusted margins accruing to millers and retailers have risen 29 to 42 percent between 1997 and 2003. Unlike experiences elsewhere in the region, maize market reform in South Africa has not benefited consumers.Maize milling/retailing marketing margins, Market Reform, Ordinary Least Squares, Feasible General Least Squares., Crop Production/Industries, Marketing,

GABA-enhanced collective behavior in neuronal axons underlies persistent gamma-frequency oscillations

Gamma (30–80 Hz) oscillations occur in mammalian electroencephalogram in a manner that indicates cognitive relevance. In vitro models of gamma oscillations demonstrate two forms of oscillation: one occurring transiently and driven by discrete afferent input and the second occurring persistently in response to activation of excitatory metabotropic receptors. The mechanism underlying persistent gamma oscillations has been suggested to involve gap-junctional communication between axons of principal neurons, but the precise relationship between this neuronal activity and the gamma oscillation has remained elusive. Here we demonstrate that gamma oscillations coexist with high-frequency oscillations (>90 Hz). High-frequency oscillations can be generated in the axonal plexus even when it is physically isolated from pyramidal cell bodies. They were enhanced in networks by nonsomatic -aminobutyric acid type A (GABAA) receptor activation, were modulated by perisomatic GABAA receptor-mediated synaptic input to principal cells, and provided the phasic input to interneurons required to generate persistent gamma-frequency oscillations. The data suggest that high-frequency oscillations occurred as a consequence of random activity within the axonal plexus. Interneurons provide a mechanism by which this random activity is both amplified and organized into a coherent network rhythm

Major Loss of the 28-kD Protein of Gap Junction in Proliferating Hepatocytes

There is a reduction in the 28-kD gap junction protein detectable by immunofluorescence in livers of partially hepatectomized rats and in cultured hepatocytes stimulated to proliferate. By the coordinate use of antibodies directed to the hepatic junction protein (HJP28) and the use of a monoclonal antibody that recognizes bromodeoxyuridine (BrdU) incorporated into DNA, we have been able to study the relationship between detectable gap junction protein and cell division. Hepatocytes that label with BrdU in the regenerating liver and in cell culture show a significant reduction of HJP28. Cells that do not synthesize DNA, on the other hand, show normal levels and distribution of immunoreactive gap junction protein. We postulate that the quantitative changes in gap junction expression might play an important role in the control of proliferation in the liver

Rational Choice and the Relevance of Irrelevant Alternatives

This experimental study investigates the inuence of irrelevant or phantom al- ternatives on subjects' choices in sequential decision making. Using experimental data from 45 subjects, we found that irrelevant alternatives bear significant rele- vance for decision making. We observe that only 38% of our subjects make the same choice after two phantom alternatives, as compared with the same decision problem when analyzed from scratch. Even allowing for a natural error rate as high as 25%, we find that between 40% and 60% of our subjects are led astray by the presence of phantom alternatives. Testing then basic postulates of rational choice, we find moderate violations of contraction monotonicity and static preference consistency, and substantial viola- tions of dynamic preference consistency. Finally we find that subjects exhibiting rational choice behaviour are far less susceptible to dependence on irrelevant alternatives than subjects which violate rational choice behaviour. Rational choice behaviour is thus a good proxy for the independence of a subject's choices of irrelevant alternatives.

Testing Decision Rules for Multiattribute Decision Making

This paper investigates the existence of an editing phase and studies the com- pliance of subjects' behaviour with the most popular multiattribute decision rules. We observed that our data comply well with the existence of an editing phase, at least if we allow for a natural error rate of some 25%. We also found a satis- factory performance of certain groups of subjects for the conjunctive rule, for the elimination{by{aspects rule, for the majority rule, and for the maximin rule. Our data suggest, however, rejection of the prominence hypothesis and of the maximax rule. Thus, our experiment sheds light on the existence of an editing phase and on the use of various multiattribute decision rules.

Phosphine Functionalization of GaAs(111)A Surfaces

Phosphorus-functionalized GaAs surfaces have been prepared by exposure of Cl-terminated GaAs(111)A surfaces to triethylphosphine (PEt3) or trichlorophosphine (PCl3), or by the direct functionalization of the native-oxide terminated GaAs(111)A surface with PCl3. The presence of phosphorus on each functionalized surface was confirmed by X-ray photoelectron spectroscopy. High-resolution, soft X-ray photoelectron spectroscopy was used to evaluate the As and Ga 3d regions of such surfaces. On PEt3 treated surfaces, the Ga 3d spectra exhibited a bulk Ga peak as well as peaks that were shifted to 0.35, 0.92 and 1.86 eV higher binding energy. These peaks were assigned to residual Cl-terminated Ga surface sites, surficial Ga2O and surficial Ga2O3, respectively. For PCl3-treated surfaces, the Ga 3d spectra displayed peaks ascribable to bulk Ga(As), Ga2O, and Ga2O3, as well as a peak shifted 0.30 eV to higher binding energy relative to the bulk signal. A peak corresponding to Ga(OH)3, observed on the Cl-terminated surface, was absent from all of the phosphine-functionalized surfaces. After reaction of the Cl-terminated GaAs(111)A surface with PCl3 or PEt3, the As 3d spectral region was free of As oxides and As0. Although native oxide-terminated GaAs surfaces were free of As oxides after reaction with PCl3, such surfaces contained detectable amounts of As0. Photoluminescence measurements indicted that phosphine-functionalized surfaces prepared from Cl-terminated GaAs(111)A surfaces had better electrical properties than the native-oxide capped GaAs(111)A surface, while the native-oxide covered surface treated with PCl3 showed no enhancement in PL intensity

Hair-cell-specific Genes in the Embryonic Chicken Inner Ear by Overexpression

The inner ear houses organs used for hearing and balance that use hair cells to accomplish their tasks. Inner ear development remains to be fully understood, and advancing knowledge in development could lead to therapies and treatments for hearing problems. A gene called Atoh1 is necessary for hair cell formation and has been shown to increase hair cell number when overexpressed. Importantly, microRNAs from the 183 family (miRs-183, -182, and -96) are also expressed in developing hair cells. MicroRNAs are small RNA molecules that bind to messenger RNAs and prevent translation. MicroRNAs have been associated with cellular functions such as programmed cell death, cell division, and differentiation. In 2009, miR-96 was implicated in a congenital form of human deafness. Like Atoh1, miR-96 increases hair cell number when over-expressed. However, we do not know if the effects of overexpressing these genes will be additive. To address this, we plan to inject the inner ears of chicken embryos with a virus that causes overexpression of miRNAs from the 183 family and Atoh1. In order to establish the effects of injecting this virus, we are gathering data on control embryos injected with a non-bioactive virus to acquire a baseline for hair cell quantification. Hair cells will be quantified using image-analysis software after injection of the virus. The data collection methods are still being refined and we do not yet have any data. Further research potentially could utilize these results to develop therapeutic treatments for deafness

Dynamically-Coupled Oscillators -- Cooperative Behavior via Dynamical Interaction --

We propose a theoretical framework to study the cooperative behavior of dynamically coupled oscillators (DCOs) that possess dynamical interactions. Then, to understand synchronization phenomena in networks of interneurons which possess inhibitory interactions, we propose a DCO model with dynamics of interactions that tend to cause 180-degree phase lags. Employing an approach developed here, we demonstrate that although our model displays synchronization at high frequencies, it does not exhibit synchronization at low frequencies because this dynamical interaction does not cause a phase lag sufficiently large to cancel the effect of the inhibition. We interpret the disappearance of synchronization in our model with decreasing frequency as describing the breakdown of synchronization in the interneuron network of the CA1 area below the critical frequency of 20 Hz.Comment: 10 pages, 3 figure

Rational Choice and the Relevance of Irrelevant Alternatives

This experimental study investigates the inuence of irrelevant or phantom al- ternatives on subjects' choices in sequential decision making. Using experimental data from 45 subjects, we found that irrelevant alternatives bear significant rele- vance for decision making. We observe that only 38% of our subjects make the same choice after two phantom alternatives, as compared with the same decision problem when analyzed from scratch. Even allowing for a natural error rate as high as 25%, we find that between 40% and 60% of our subjects are led astray by the presence of phantom alternatives. Testing then basic postulates of rational choice, we find moderate violations of contraction monotonicity and static preference consistency, and substantial viola- tions of dynamic preference consistency. Finally we find that subjects exhibiting rational choice behaviour are far less susceptible to dependence on irrelevant alternatives than subjects which violate rational choice behaviour. Rational choice behaviour is thus a good proxy for the independence of a subject's choices of irrelevant alternatives.Independence of Irrelevant Alternatives;Phantom Alternatives;Sequential Decision Making;Rational Choice;Multiattribute Decision Making