Chemolithotrophy and physiology of bacterial nutrient limitation

An overview of the physiology of chemolithotrophic bacteria, particularly the thiobacilli, was presented. In these bacteria unique physiological traits are expressed during nutrient limited growth. Different physiological types of chemolithotrophs, pathways of sulfur oxidation, and electron transport in the thiobacilli, problems encountered by chemolithotrophs in the generation of reducing power, and some explanations of the phenomenon of obligate chemolithotrophy were considered. Mixotrophy in the thiobacilli has been studied extensively both under nutrient excess and limitation. In nature, bacteria usually grow under nutrient limitation. Yet the bulk of our knowledge of microbial metabolic function is derived from bacteria grown in laboratory batch cultures containing a great abundance of nutrients. Microbial behavior in these two types of environments can be very different, indicating the need for basing an understanding of microbial ecology on studies that rely on cultivation of microorganisms under nutrient limitation. Nutrient limited bacteria differ in several ways from those growing in large quantities of nutrients. They have different surface structures and make a much fuller use of their metabolic potential, especially by the synthesis of unique pathways of catabolic enzymes

Openness and economic performance in sub-Saharan Africa : evidence from time-series cross-country analysis

In a cross-country study for 1967-87, the author tests whether the finding that increased openness improves performance holds true for sub-Saharan Africa as a subgroup among developing countries. Econometric analysis - based on the augmented production function that includes labor, capital stock, and a measure of openness - shows that openness exerts a significant positive impact on economic performance of countries in sub-Saharan Africa. The relationship is especially strong in fixed-effect estimates that use annual panel data with country dummies to capture unobserved country-specific differences. The author finds the evidence of a positive link between openness and performance surprisingly robust to different measures of openness, to different periods, and to the inclusion of other policy variables. All four measures of openness, for example, are significant for 1967-87. For the shorter period, 1980-87, three are significant. Also, the size and significance of the openness coefficients do not change when one controls for macroeconomic policy.TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Economic Theory&Research,Environmental Economics&Policies,Achieving Shared Growth,Inequality

Competition, Kinship or Reciprocity? Village Experiments in Alternative Modes of Exchange

In this paper, detailed data on transactions in a village commodity market are used to explain the puzzle of sluggish agricultural supply response. We show that existence of reciprocity among sellers exhibits multiple equilibria and creates trade diversion. Large volumes of the commodity are sold to a trader who does not offer the best price, but on whom sellers depend through transactions in other markets. An implication of this trader-idiosyncratic effect on supply is that policies that affect prices may result in different supply responses.Reciprocity, Kinship, Neighborhood effects, Trader idiosyncrasy, Equilibrium, Consumer/Household Economics,

Analyzing nutritional impacts of policies

Widespread malnutrition in developing countries calls for appropriate strategies, presupposing good knowledge about nutritional impacts of policies. Little previous work has been carried out in this direction, especially with respect to micronutrients. We use representative household data from Malawi and develop a demand systems approach to estimate income and price elasticities of food demand and nutrient consumption. These estimates are applied for policy simulations. Given multiple nutritional deficiencies, income-related policies are better suited than price policies to improve nutrition. Although consumer price subsidies for maize improve calorie and mineral consumption, they can worsen vitamin consumption in urban areas.income and price elasticities, micronutrient deficiency, nutrient consumption, quadratic almost ideal demand system,

Income and Price Elasticities of Food Demand and Nutrient Consumption in Malawi

Widespread malnutrition in developing countries calls for appropriate interventions, presupposing good knowledge about the nutritional impacts of policies. Little previous work has been carried out in this direction. We present a comprehensive analytical framework, which we apply for Malawi. Using household data and a demand systems approach, we estimate income and price elasticities of food, calorie, and micronutrient consumption. These estimates are used for policy simulations. Given multiple nutrient deficiencies, income-related policies are better suited than price policies to improve nutrition. While consumer subsidies for maize increase calorie and mineral consumption, they contribute to a higher prevalence of vitamin deficiencies.quadratic almost ideal demand system, food security, micronutrient malnutrition, calorie elasticities, nutrient elasticities, Malawi, Food Consumption/Nutrition/Food Safety,

Smallholder Farmers and Collective Action: What Determines the Intensity of Participation?

Farm Management,

Conformal Extensions of the Standard Model with Veltman Conditions

Using the renormalisation group framework we classify different extensions of the standard model according to their degree of naturality. A new relevant class of perturbative models involving elementary scalars is the one in which the theory simultaneously satisfies the Veltman conditions and is conformal at the classical level. We term these extensions perturbative natural conformal (PNC) theories. We show that PNC models are very constrained and thus highly predictive. Among the several PNC examples that we exhibit, we discover a remarkably simple PNC extension of the standard model in which the Higgs is predicted to have the experimental value of the mass equal to 126 GeV. This model also predicts the existence of one more standard model singlet scalar boson with a mass of 541 GeV and the Higgs self-coupling to emerge radiatively. We study several other PNC examples that generally predict a somewhat smaller mass of the Higgs to the perturbative order we have investigated them. Our results can be a useful guide when building extensions of the standard model featuring fundamental scalars.Comment: 18 pages, updated to match published versio

Hidden Conformal Symmetry in Tree-Level Graviton Scattering

We argue that the scattering of gravitons in ordinary Einstein gravity possesses a hidden conformal symmetry at tree level in any number of dimensions. The presence of this conformal symmetry is indicated by the dilaton soft theorem in string theory, and it is reminiscent of the conformal invariance of gluon tree-level amplitudes in four dimensions. To motivate the underlying prescription, we demonstrate that formulating the conformal symmetry of gluon amplitudes in terms of momenta and polarization vectors requires manifest reversal and cyclic symmetry. Similarly, our formulation of the conformal symmetry of graviton amplitudes relies on a manifestly permutation symmetric form of the amplitude function.Comment: 35 pages, 3 figure

A natural Coleman-Weinberg theory explains the diphoton excess

It is possible to delay the hierarchy problem, by replacing the standard Higgs-sector by the Coleman-Weinberg mechanism, and at the same time ensure perturbative naturalness through the so-called Veltman conditions. As we showed in a previous study, minimal models of this type require the introduction of an extra singlet scalar further coupled to new fermions. In this constrained setup the Higgs mass was close to the observed value and the new scalar mass was below a TeV scale. Here we first extend the previous analysis by taking into account the important difference between running mass and pole mass of the scalar states. We then investigate whether these theories can account for the 750 GeV excess in diphotons observed by the LHC collaborations. New QCD-colored fermions in the TeV mass range coupled to the new scalar state are needed to describe the excess. We further show, by explicit computation of the running of the couplings, that the model is under perturbative control till just above the masses of the heaviest states of the theory. We further suggest related testable signatures and thereby show that the LHC experiments can test these models.Comment: Discussion on the perturbative limits of the model is added, Fig.1 updated and new Fig.2 is added; References update