A New Estimate of the Extragalactic Gamma-Ray Background from EGRET Data

We use the GALPROP model for cosmic-ray (CR) propagation to obtain our best prediction of the Galactic component of gamma rays, and show that away from the Galactic plane it gives an accurate prediction of the observed EGRET intensities. On this basis we re-evaluate the isotropic extragalactic gamma-ray background (EGRB). We find that for some energies previous work underestimated the Galactic contribution and hence overestimated the background. Our new EGRB spectrum shows a positive curvature similar to that expected for models of the extragalactic emission based on the blazar population.Comment: 4 pages, 1 ps-figures, tsukuba.sty, to appear in the Proc. 28th International Cosmic Ray Conference (Tsukuba, Japan 2003). More details can be found at http://www.gamma.mpe-garching.mpg.de/~aws/aws.htm

Evidence on Imperfect Competition and Strategic Trade Theory

Strategic trade theory shows that government intervention in markets with small numbers of traders can boost the welfare of a country relative to free trade. This survey critically assesses the empirical evidence regarding this possibility. One finding is that while many international food and agricultural markets are characterized by oligopoly, price-cost markups tend to be small, and the potential gains from intervention are modest at best. In turn, existing government interventions such as agricultural export subsidies are generally not optimal in a strategic trade sense. The evidence suggests that oligopoly by itself is not a sufficient rationale for deviating from free trade in international markets.

Propagation in 3D spiral-arm cosmic-ray source distribution models and secondary particle production using PICARD

We study the impact of possible spiral-arm distributions of Galactic cosmic-ray sources on the flux of various cosmic-ray nuclei throughout our Galaxy. We investigate model cosmic-ray spectra at the nominal position of the sun and at different positions within the Galaxy. The modelling is performed using the recently introduced numerical cosmic ray propagation code \textsc{Picard}. Assuming non-axisymmetric cosmic ray source distributions yields new insights on the behaviour of primary versus secondary nuclei. We find that primary cosmic rays are more strongly confined to the vicinity of the sources, while the distribution of secondary cosmic rays is much more homogeneous compared to the primaries. This leads to stronger spatial variation in secondary to primary ratios when compared to axisymmetric source distribution models. A good fit to the cosmic-ray data at Earth can be accomplished in different spiral-arm models, although leading to decisively different spatial distributions of the cosmic-ray flux. This results in very different cosmic ray anisotropies, where even a good fit to the data becomes possible. Consequently, we advocate directions to seek best fit propagation parameters that take into account the higher complexity introduced by the spiral-arm structure on the cosmic-ray distribution. We specifically investigate whether the flux at Earth is representative for a large fraction of the Galaxy. The variance among possible spiral-arm models allows us to quantify the spatial variation of the cosmic-ray flux within the Galaxy in presence of non-axisymmetric source distributions.Comment: 38 pages, 16 figures, accepted for publication in Astroparticle Physic

Market Segmentation Practices of Retail Crop Input Firms

The farmers targeted by crop input retailers may be divided into distinct groups or segments, but retail crop input firms vary in their ability to implement strategies to serve individual segments. In this study, segmentation practices among cooperatives and independently owned crop input retailers were explored. Addressing gaps between Best’s seven-step market segmentation framework and retailer practices will help practitioners serve evolving farmer-customers.market segmentation, target marketing, crop inputs, distribution channel, retailer, Marketing, Q10, Q13,

INCORPORATING COMMODITY STOCKHOLDING BEHAVIOR INTO A SHORT-RUN GENERAL EQUILIBRIUM MODEL OF THE GLOBAL ECONOMY

This paper incorporates commodity stockholding into a short run, stochastic global general equilibrium model. A mix of econometric and calibration techniques are used to reconcile model outcomes with historical stockholding and price behavior. The resulting framework is useful for analyzing policies in the short run or presence of production variability.Agribusiness,

Re-Evaluation of the Diatom Species Nitzschia frustulum (Kutz.) Grun.

As in almost every other facet of science, the diatom taxonomist is constantly faced with the problem of merging phenomena. With the introduction of quantitative, mass, or population studies on various forms of plant life, lines of distinction between closely related species and varieties have often disappeared, thus indicating a single variable taxon. On the other hand, such studies have upheld the individuality of two or more similar taxa. It is now amply apparent that many of the presently accepted species of diatoms must be re-examined with such concepts in mind, for the purpose of determining, in other than a purely arbitrary fashion, the limits of specific variation. This becomes especially important in group. The most common method is asexual in which case the size of the frustule frequently becomes gradually smaller, until a certain size range is reached. Sometimes other taxonomic features are altered as well. If in a single ecological habitat intergrades are found between two entities, it usually is a good indication that a genetic difference does not actually exist, and that the investigator is dealing with a single entity

TRADE POLICY, FOOD PRICE VARIABILITY, AND THE VULNERABILITY OF LOW-INCOME HOUSEHOLDS

We utilize a global trade model to generate distributions of commodity and factor prices based on observed uncertainty in rice production. This is done for three trade policy regimes. We then assess their impact on domestic price variability and the likelihood of marginal households falling into poverty in four countries.Food Security and Poverty, International Relations/Trade,