The changing organizational basis of African agricultural research:

National agricultural research systems in Africa increased markedly in size throughout the past three decades, but from an especially small base. In 1961, public systems in 33 of 48 African countries employed fewer than 25 full-time equivalent (fte) researchers, by 1991 there were only 8 such systems (and 23 countries employed more than 100 fte researchers, compared with only 4 countries in 1961). Despite this overall growth, and the efforts that began in the late 1980s to consolidate the conduct of agricultural research, most African agencies are still very small and fragmented by international standards, making it difficult to realize the scale and scope economies that seem increasingly evident in agricultural R&D conducted elsewhere. This study reports a range of institutional indicators for 341 agricultural research agencies located in 39 African countries. In 1991, 236 agencies (nearly 70 percent of our sample total) employed less than 20 fte researchers. Most public research in Africa is still done by government agencies; they employed 87 percent of the total number of researchers in 1991. University research has grown the most rapidly, but still accounted for only 10 percent of the total number of African researchers in 1991. Partly in response to the small, fragmented, and comparatively isolated structure of agricultural R&D agencies, but partly from local political and, especially, donor pressure too, there has been a proliferation of research networks in recent years. We identified 86 networks, of which 72 involved Africans linked to Africans, a rather parochial strategy in an increasingly interdependent world. Regional approaches to the conduct and funding of agricultural R&D have been revived in more recent years, a feature of much of the regions's research in earlier, colonial times, as we describe here. However, the political and economic realities of today bear little relationship to those of colonial times, and it remains unclear how these regional approaches will prosper and effect meaningful research given the organizational uncertainties that still abound.Research Economic aspects., Research institutes., Africa., Agriculture Research.,

Investments in African agricultural research:

Over the past three decades the development of agricultural research staff in sub-Saharan Africa has been impressive. Developments in agricultural research expenditures were less positive. Many of the developments of the past decade in personnel, expenditures, and sources of support for public-sector R&D in Africa are not sustainable. The rapid buildup of research staff is not paralleled by an equal growth in financial resources. Spending per scientist has continuously declined during the past 30 years, but most dramatically during the 1980s. Resources are spread increasingly thin over a growing group of researchers, which has negative effects on the efficiency and effectiveness of agricultural research.Agriculture Research., Research Economic aspects Africa, Sub-Saharan.,

Monte Carlo Markov Chain parameter estimation in semi-analytic models of galaxy formation

We present a statistical exploration of the parameter space of the De Lucia and Blaizot version of the Munich semi-analytic (SA) model built upon the Millennium dark matter simulation. This is achieved by applying a Monte Carlo Markov Chain method to constrain the six free parameters that define the stellar and black hole mass functions at redshift zero. The model is tested against three different observational data sets, including the galaxy K-band luminosity function, B - V colours and the black hole-bulge mass relation, separately and combined, to obtain mean values, confidence limits and likelihood contours for the best-fitting model. Using each observational data set independently, we discuss how the SA model parameters affect each galaxy property and find that there are strong correlations between them. We analyse to what extent these are simply reflections of the observational constraints, or whether they can lead to improved understandings of the physics of galaxy formation. When all the observations are combined, we find reasonable agreement between the majority of the previously published parameter values and our confidence limits. However, the need to suppress dwarf galaxy formation requires the strength of the supernova feedback to be significantly higher in our best-fitting solution than in previous work. To balance this, we require the feedback to become ineffective in haloes of lower mass than before, so as to permit the formation of sufficient high-luminosity galaxies: unfortunately, this leads to an excess of galaxies around L*. Although the best fit is formally consistent with the data, there is no region of parameter space that reproduces the shape of galaxy luminosity function across the whole magnitude range. For our best fit, we present the model predictions for the bJ-band luminosity and stellar mass functions. We find a systematic disagreement between the observed mass function and the predictions from the K-band constraint, which we explain in light of recent works that suggest uncertainties of up to 0.3 dex in the mass determination from stellar population synthesis models. We discuss modifications to the SA model that might simultaneously improve the fit to the observed mass function and reduce the reliance on excessive supernova feedback in small haloes

Cost aspects of African agricultural research:

Spending per scientist declined precipitously within African agricultural R&D agencies over the past several decades. In 1991, average cost per researcher across 147 R&D agencies was $119,300 in 1985 international dollars — or US$59,500 when measured in United States rather than international dollars — 34 percent below the corresponding 1961 figure. This trend reflects the rapid growth in numbers of scientific staff compared with the slow growth in funds to support them. Comparatively low, and often shrinking, real salaries per scientist are a factor too. African scientists were paid an average of US$5,000 in 1991 (or roughly US$7,500 with fringe benefits included), while comparable average salaries for academic staff working in large public universities in the United States were $58,889 (or$72,667 with fringe benefits included. The new, agency-level data reported in this paper reveal significant variation in the costs per scientist not apparent from the country averages. There were 67 agencies (46 percent) that spent less than $100,000 per scientist per annum. Simple econometric procedures were applied to a sub-sample of 107 agencies in 21 countries to investigate reasons for the large variation in costs per scientist. The intensity of support staff per scientist and the intensity with which expatriate researchers are used are important sources of variation. Larger stations lowered the costs and having more stations raised costs, but not significantly so. An agency's organizational type had a significant influence on its costs. Semipublic agencies typically spent considerably more per scientist than government agencies with 1991 figures of$207,700 for the former, compared with around $104,600 for the latter (in 1985 international dollars). GDP per capita and various other unspecified, country-specific effects also accounted for much of the observed variation in costs per scientist.Research institutes., Research Economic aspects.,

Sensory Mechanisms of Perceptual Uniformity

BACKGROUND AND AIMS: Visual experience appears rich in detail despite the poor performance of the vast majority of the visual field, as a result of the integration of coarse peripheral signals with the information of the comparatively tiny fovea. We examined the mechanisms of this integration by employing the uniformity illusion, in which a pattern with different properties in fovea and periphery uniformly takes the appearance of the fovea. We developed an adaptation paradigm to investigate whether the direction of an after-effect in the visual periphery followed the local, physical stimulation or the perception that arose under the Uniformity Illusion. We employed two different perceptual dimensions (orientation and spatial density) to investigate the extent to which the uniformity illusion is associated with changes in sensory encoding. RESULTS AND CONCLUSIONS: Experiments performed on two visual domains indicate that the uniformity illusion is not associated with a change in the sensory encoding on a local basis. Specifically, in our orientation experiments, the (V1-based) tilt after-effect only ever followed the local, physically presented orientation rather than the global orientation perceived under the illusion of uniformity. This was not due to insufficient exposure to the global pattern to produce an after-effect as presentation of physical uniformity for the same durations as participant reports of the illusion did produce an after-effect to the global orientation. Results on spatial-density based experiments showed an intermediate level of adaptation between (physical) low and high density, which could be consistent with an adaptation exerted by the illusory pattern. Thus, we could not rule out that the Uniformity Illusion might directly modify more abstract dimensions (such as numerosity, akin to our formalization of spatial density). However, the time invariance of the effect makes alternative explanations more likely and therefore, suggests that the uniformity illusion arises from high-level perceptual processes

Serial Dependence in Visual Variance

The recent history of perceptual experience has been shown to influence subsequent perception. Classically, this dependence on perceptual history has been examined in sensory adaptation paradigms, wherein prolonged exposure to a particular stimulus (e.g. a vertically oriented grating) produces changes in perception of subsequently presented stimuli (e.g. the tilt aftereffect). More recently, several studies have investigated the influence of shorter perceptual exposure with effects, referred to as serial dependence, being described for a variety of low and high-level perceptual dimensions. In this study, we examined serial dependence in the processing of dispersion statistics, namely variance - a key descriptor of the environment and indicative of the precision and reliability of ensemble representations. We found two opposite serial dependencies operating at different timescales, and likely originating at different processing levels: A positive, Bayesian-like bias was driven by the most recent exposures, dependent on feature-specific decision-making and appearing only when high confidence was placed in that decision; and a longer-lasting negative bias - akin to an adaptation after-effect - becoming manifest as the positive bias declined. Both effects were independent of spatial presentation location and the similarity of other close traits, such as mean direction of the visual variance stimulus. These findings suggest that visual variance processing occurs in high-level areas, but is also subject to a combination of multi-level mechanisms balancing perceptual stability and sensitivity, as with many different perceptual dimensions.</p