2,311 research outputs found
Determinants of Well-Being: Applying the Easterlin Paradox, Life Expectancy, Carbon Emissions, and Education across Countries
This study estimates well-being as a function of Gross Domestic Product (GDP) per capita, life expectancy, primary education completion rates, and carbon dioxide emissions per capita using panel data from 78 countries from 2006 and 2009. We find that well-being increases at a decreasing rate as GDP per capita increases, which is consistent with the Easterlin Paradox. We also find a statistically significant, positive relationship between well-being and life expectancy and a negative relationship between well-being and carbon dioxide emissions
Uptake of branched-chain alpha-keto acids in \u3ci\u3eBacillus subtilis\u3c/i\u3e
Bacillus subtilis has a constitutive system for the uptake of alpha-keto-beta-methylvalerate, alpha-ketoisovalerate, and (probably) alpha-ketoisocaproate. A mutation, kauA1, which blocks the uptake of alpha-keto-beta-methylvalerate and alpha-ketoisovalerate, is located between metB and citK on the B. subtilis chromosome
New exports from emerging markets: do followers benefit from pioneers ?
Since Arrow (1962), spillovers from pioneer to follower in non-excludable innovations are central to our understanding of endogenous economic growth. Nonetheless, evidence of these spillovers in less-developed economies has been elusive. Our paper contributes by showing novel facts consistent with externalities in new export products. To avoid biases towards ex-post successes, we use data on the universe of customs transactions from Chile (1990- 2006). We find that, first, follower firms are more likely to enter a product if the pioneer firm survives exporting. More importantly, we also find that pioneers enter and remain smaller than followers, which is indicative that the first exporter may not be the firm that benets the most from the discovery. This fact is inconsistent with the currently standard view in international trade, in which the largest firm would be the first willing to pay a homogeneous sunk cost of exporting. In contrast, our facts are consistent with the view that smaller pioneer exporters are data producers, whose spillovers benet larger followers. We offer a simple model to formalize this intuition, based on the idea that large exporters have more choices on how to allocate their managerial capacity. This real option makes large exporters wait, as to assign their marginal manager on the best possible project. In contrast, smaller and more focused firms prefer to be pioneers.economic growth; innovation; externalities; first-mover-advantage
Gravity and extended gravity: estimating a structural model of export entry
Exporters continuously enter and exit individual foreign markets. Although a given firm's status as an exporter tends to be persistent, the set of destination countries that a firm serves changes frequently. In this paper we empirically examine the determinants of a firm's choice of destination countries and show that their export paths follow systematic patterns. We develop a model of export dynamics where firms decide in each period the countries to which they sell. Our model allows prots from each possible destination country to depend on: (a) how similar it is to the firm's home country (gravity), and (b) how similar it is to other destinations to which the firm has previously exported (extended gravity). Given the enormous number of possible export paths from which firms may choose, conventional estimation approaches based on discrete choice models are unfeasible. Instead, we use a moment inequalities approach. Our inequalities come from applying an analogue of Euler's perturbation method to a discrete choice setting. We show that standard gravity forces have a much larger influence on sunk costs than on fixed costs of exporting and that extended gravity effects can be substantial.gravity; extended gravity; export dynamics; moment inequalities
Gap-junctional coupling between neutrophils and endothelial cells
Communication between leukocytes and endothelial cells is crucial for inflammatory reactions. Paracrine cross-talk and outside-in signaling (via adhesion molecules) have been characterized as communication pathways to date. As leukocytes and endothelial cells express connexins, we considered intercellular communication via gap junctions an intriguing additional concept. We found that gap-junctional coupling between neutrophils and endothelium occurred in a time-dependent, bidirectional manner and was facilitated by adhesion. After blockade of connexins, transmigration of neutrophils through the endothelial layer was enhanced, and the barrier function of cell monolayers was reduced during transmigration. Tumor necrosis factor α decreased coupling. In the presence of connexins, transmigration of neutrophils did not alter permeability. Thus, neutrophils couple to endothelium via gap junctions, functionally modulating transmigration and leakiness. Gapjunctional coupling may be a novel way of leukocyte-
endothelial communication
Nitric oxide enhances de novo formation of endothelial gap junctions
Objective: Gap junctions (formed by connexins, Cx) are important for functional coordination of cells in the vascular wall. However, little is known about their physiological regulation in this tissue. We examined the effects of nitric oxide (NO), an important mediator of vasomotion, wound healing and angiogenesis, on the formation of gap junctions in endothelial cells (human umbilical vein endothelial cells, HUVEC). Methods: Flow cytometry was used to determine dye transfer through newly formed gap junctions between acutely coincubated HUVECs. Parallel experiments in wild-type HeLa cells (no connexins) and transfected HeLa cells exclusively expressing Cx43, Cx40 or Cx37 were performed to determine the specific role of Cx subtypes. The intracellular distribution of Cx40 was examined after fractionation with triton by Western blotting. Intracellular levels of cGMP and cAMP were measured by radioimmunoassay. Results: The NO donor SNAP (1 μM) enhanced gap-junctional coupling in HUVECs by about 40%. This was associated with an enhanced incorporation of Cx40 into the membrane. Both effects were restricted to Cx40 as analyzed in experiments with Cx-selective HeLa cells. The NO-induced increase in cell coupling was elicited by a corresponding rise of cGMP, which secondarily increased intracellular cAMP levels. The latter was an integral part of the signal cascade, since the protein kinase A (PKA) inhibitor H89 blocked the SNAP-induced incorporation of Cx40 into the plasma membrane. Conclusions: We conclude that NO is a potent modulator of gap-junctional coupling in endothelial cells. It enhances de novo formation of endothelial gap junctions by increasing incorporation of Cx40 into the plasma membrane due to PKA activation
Decomposing world export growth and the relevance of new destinations
Looking to understand what drives countries' export growth
in practice, I provide a decomposition of world export growth at the product variety level between new destinations, new products, and growth in value of old varieties. New destinations play a significant role, accounting for 37 percent of the growth in developing countries. By comparison, entry into new product
categories -a margin that has received considerable attention- explains just 7 percent of export growth. Exploring the nature of destination expansion reveals it is neither automatic nor permanent. Even relatively competitive sectors face difficulties penetrating new destinations, and these difficulties are negatively correlated with population size and GDP per capita. Consistent with pervasive experimentation and failure, more than a third of all products in new destinations exported only once to a destination in the sixteen years studied
Stimulation of endothelial adenosine Al receptors enhances adhesion of neutrophils in the intact guinea pig coronary system
Objective: The primary aim was to determine the action of pathophysiologically relevant adenosine concentrations (0.1-1 μM) on adhesion of neutrophils to coronary endothelium. Further aims were to evaluate the nature and localisation of the adenosine receptor involved. and to assess the effect of endogenous adenosine.
Methods: Adhesion was studied in isolated perfused guinea pig hearts by determining the number of cells emerging in the coronary effluent after intracoronary bolus injections of 600 000 neutrophils prepared from guinea pig or human blood. The system was characterised by the use of the proadhesive stimulus thrombin.
Results: A 5 rnin infusion of adenosine (0.1-0.3 μM) or the A1 receptor agonist N6-cyclopentyladenosine (CPA, 0.01 μM) significantly increased adhesion from about 20% (control) to 30%. This effect was prevented by the A1 receptor antagonist dipropyl-8-cyclopentylxanthine (DPCPX. 0.1 μM). It was not diminished by cessation of adenosine infusion 90 s prior to neutrophil injection. At a higher concentration of adenosine (1 μM), adhesion did not seem to be enhanced. However, coinfusion of the A2 receptor antagonist 3,7-dimethyl-1-propargylxanthine (DMPX. 0.1 μM) with 1 μM adenosine unmasked the A1 action, adhesion rising to 39%. Adenosine had a quantitatively identical effect on adhesion of human neutrophils. Total ischaemia of 15 min duration raised adhesion of subsequently applied neutrophils to 35%. This effect was completely blocked by DPCPX, as well as by ischaemic preconditioning (3 X 3 min). Preconditioning raised initial postischaemic coronary effluent adenosine from about 0.8 μM to 1.5 μM.
Conclusions: The findings suggest a bimodal participation of adenosine in the development of postischaemic dysfunction by an endothelium dependent modulation of neutrophil adhesion. Stimulation occurs via endothelial A1 receptors at submicromolar adenosine levels, whereas cardioprotection by adenosine may in part relate to the use of pharmacologically high concentrations of adenosine or enhanced endogenous production after preconditioning
Improving the Nutritional Characteristics of Plant Feedstuff By-Products Using Fungal Metabolism
Plant feedstuff by-products such as soy processing wastewater, guar korma meal, and sorghum hominy are very different, however, all possess a rich nutrient profile. Lessening their value is the presence of lignocellulose, plant anti-nutritional factors, and unfavorable protein profiles. Fungal conversion processes are an attractive approach to improving the value of these by-products by degrading detrimental fractions of each while simultaneously creating nutrient-rich cell mass. The aim of this research was to improve the value of each by-product for potential application in monogastric diets such as fish. Fungal organisms, both yeast and filamentous fungi, were examined for their ability to enhance the nutritional value of each by-product. Soybean processing supernatant contains a high amount of organic matter (carbohydrates and proteins) resulting in a high chemical oxygen demand (~55,000 mg/L), meaning that this by-product cannot be disposed of without treatment. Typically evaporation is used to concentrate the material from 7-10% solids to 40-50% solids which can be used in animal feeds. To improve the nutritional value of this material, eight fungal strains were tested for their ability to metabolize the soluble nutrients in the wastewater and produce protein-rich cell mass for potential application in animal feeds. Flask incubations trials of 100 ml total volume were conducted at 30°C and 150 rpm. Trichoderma reesei, Paecilomyces variotii and Neurospora crassa produced 51.7, 47.1 and 43.2 g/L of biomass while reducing solids present by 46.5, 48.9, and 49.1% respectively. The two best performing strains were further examined in fermenters using 3 L total volume. Trichoderma reesei and Neurospora crassa produced 55.5 and 62.0 g/L of protein-rich biomass while simultaneously reducing chemical oxygen demand levels by 10.53 and 23.04% respectively. Microbial processing produced a protein-rich animal feed ingredient while concurrently reducing organic matter present in the wastewater. Sorghum hominy contains a high amount of starch (34.5%), fiber (7.6%), and low amount of protein (12.9%) which inhibits its inclusion into higher value feed industries such as aquafeeds. To improve the nutritional value of the sorghum hominy, eight fungal strains were assessed for their ability to degrade the carbohydrate fractions of the sorghum hominy while simultaneously improving the protein profile for potential use in aquadiets. Flask incubations were performed using 100 ml total volume at 30°C and 150 rpm. Trichoderma reesei, Rhizopus oligosporus, Neurospora crassa and Aurebasidium pullulans were the best performing fungi in flask trials, increasing the protein titer of sorghum hominy by 53.6, 48.0, 47.8, and 41.5% compared to the raw material. T. reesei and A. pullulans were further tested in 5 L benchtop reactors, where biomass yields of 65.1 and 73.6 g/L were obtained with similar increases in protein to the previous flask trials. Lastly, T. reesei was examined in 70 L and 150 L fermenters, increasing all amino acids in the range of 33.3-152.3%. Thus, T. reesei submerged fermentation effectively increased the nutritional value of sorghum hominy. Guar korma meal contains a high amount of protein (55.6%), but also contains fiber (6.6%) and residual guar gum (0.77%) which inhibits its effectiveness as a feed ingredient in monogastric diets. To improve the nutritional value of guar korma meal, the prospect of subjecting the guar korma meal to a centrifugal wash pre-fungal incubation was examined. For both the washed concentrate and washed solubles, five fungal strains were examined for their ability to create a protein-rich biomass for potential application as a feed ingredient, while degrading detrimental fractions of the washed concentrate. Flask incubations of 100 ml total volume were conducted at 30°C and 150 rpm. T. reesei was the most effective treatment on the washed guar korma meal as it reduced guar gum levels to 0.17% and increased the protein titer to 66.8% yielding 65.8 g/L of biomass. A. pullulans was the most effective treatment on the guar korma meal solubles, producing 12.8 g/L of protein-rich (40.6%) biomass. Together the two-step fungal incubation process yielded 78.6 g/L of biomass containing 61.5% protein
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