ENTREPRENEURSHIP AND LIQUIDITY CONSTRAINTS IN DEPRIVED AREAS: EVIDENCE FROM THE SLUMS OF RIO DE JANEIRO

Several economic models have described the theoretical causes and onsequences of 'credit rationing' and 'under-investment'; one string of this literature shows the long-run effects of initial wealth distribution and entrepreneurial ability on the process of occupational choice and performance, and its consequences on inequality. Surprisingly, there is very little micro-level evidence on the existence and effects of 'credit rationing' in the context of developing countries. This is the contribution of the current paper. Using a survey of 4,553 entrepreneurs in 51 slums in Rio de Janeiro, this paper uses mean and quantile regression estimates to shows the effects of the type of initial capital, credit constraints, and human capital factors on entrepreneurs' performance. The main findings of the the paper are that entrepreneurs that were able to self-finance their business start-up presented earnings 16% greater than entrepreneurs that had to borrow their initial capital. In addition, entrepreneurs that explicitly claimed to be credit constrained performed substantially worse than their observationally identical counterparts, even if they were credit worthy. Both, initial source of funding and liquidity constraint presented greater effects on the highest quantiles. In terms of human capital, the current study shows positive and statistically significant returns for both years of schooling and experience, with higher returns on the lowest quantiles, indicating the potential role of these factors on inequality reduction.

Stability of antiphase line defects in nanometer-sized boron-nitride cones

We investigate the stability of boron nitride conical sheets of nanometer size, using first-principles calculations. Our results indicate that cones with an antiphase boundary (a line defect that contains either B-B or N-N bonds) can be more stable than those without one. We also find that doping the antiphase boundaries with carbon can enhance their stability, leading also to the appearance of localized states in the bandgap. Among the structures we considered, the one with the smallest formation energy is a cone with a carbon-modified antiphase boundary that presents a spin splitting of about 0.5 eV at the Fermi level.Comment: 5 two-column pages with 2 figures Accepted for publication in Physical Review B (vol 70, 15 Nov.

Charge pumping in magnetic tunnel junctions: Scattering theory

We study theoretically the charge transport pumped by magnetization dynamics through epitaxial FIF and FNIF magnetic tunnel junctions (F: Ferromagnet, I: Insulator, N: Normal metal). We predict a small but measurable DC pumping voltage under ferromagnetic resonance conditions for collinear magnetization configurations, which may change sign as function of barrier parameters. A much larger AC pumping voltage is expected when the magnetizations are at right angles. Quantum size effects are predicted for an FNIF structure as a function of the normal layer thickness.Comment: 4 pages, 3 figures. to be published on Physical Review B Rapid Communicatio

Tracking persistence of Helicobacter pylori in potable water biofilms using novel 16S rRNA peptide nucleic acid probes

A two stage chemostat system was used to study the pathogenic bacteria H. pylori association to drinking water biofilms. After allowing one week old biofilms to be grown on stainless steel coupons the system was inoculated with the pathogen that was detected using the recently established technique of 16S rRNA peptide nucleic acid (PNA) fluorescence in situ hybridization (FISH). Results show that H. pylori can successfully incorporate within biofilms and its presence was detected for up to five days, either in the basal layer or inside typical biofilm structures such as stacks or fronds. The PNA FISH protocol appears to be a promising new technique for the in situ visualization of microorganisms in biofilms, especially because the hydrophobic nature of the PNA molecule allows a better diffusion through the constituents of the biofilm matrix allowing an improved discrimination of microorganisms inside these naturally occurring structures. A setback in the application of this methodology was the presence of autofluorescent microorganisms. This problem can be minimized by comparing the morphologic characteristics of these suspected false positives with typical H. pylori morphology. If questions subsist, the visualization of the biofilm under different filter blocks can also improve the degree of certainty in the identification, since the reporter probe has usually a very distinctive pattern of fluorescence when compared to the autofluorescent microorganisms

Development of an optimized technique for the recovery of H. pylori from water and drinking water biofilms

At present, the route of transmission is perhaps one of the most controversialareas of Helicobacter pylori research. Drinking water and associated biofilms have been suggested as possible environmental reservoirs for the bacterium, however, successful and consistent detection of the bacterium in real systems has not yet been accomplished. A new protocol that offers improved recovery ratings of H. pylori from water and associated-biofilms has been developed and evaluated. This protocol includes optimized incubation atmospheres and a new recovery culture medium, as well as an assessmentof existing techniques for the detachment of H. pylori from surfaces. Even though obvious advantages in terms of cell counts are obtained using this method, certain problems, such as contamination by faster-growing species of the culture medium in heavily contaminated waters may still hinder a successful recovery of the pathogen.Future research will involve further improvement of the protocol and monitoring of real drinking water distribution systems.Unit of Helicobacter/Campylobacter of the Center of Bacteriology of INSA para a Ciência e a Tecnologia (FCT) ; European Commission Research Project SAFER

Efeito de formulações de Bacillus Thuringiensis (Berliner) aplicados em diferentes substratos alimentares sobre Grapholita Molesta (Busck) (Lepidoptera: Tortricidae).

Grapholita molesta (Busck, 1916) (Lepidoptera: Tortricidae) é uma das principais pragas das rosáceas de clima temperado. Neste trabalho, foi avaliado o efeito de dois produtos comerciais à base de Bacillus thuringiensis sobre lagartas neonatas (1°instar) de G. molesta aplicados sobre diferentes substratos alimentares: dieta artificial (Arioli 2007), ponteiros e frutos de ameixeira (cv. Leticia) e macieira (cv. Gala). Os tratamentos avaliados foram (1) Bacillus thuringiensis var. kurstaki (Dipel®, 100g.100L-1); (2) B. thuringieses var. aizawai e kurstaki (Agree 100g.100L-1), comparados com (3) Clorantraniliprole (Altacor® 10g.100L-1) e uma (4) testemunha (água). Ponteiros e frutos de ameixeira e macieira foram mergulhados nas caldas dos respectivos tratamentos e deixados à sombra por três horas para secagem. Em seguida os ponteiros foram transferidos para recipientes plásticos (300 ml) com ágar no fundo para a fixação e manutenção da turgidez e os frutos foram colocados em copos plásticos (250ml). Em cada ponteiro e fruto foi inoculada uma lagarta recém-eclodida de G. molesta criada em dieta artificial, em seguida os recipientes foram fechados com tecido tipo "voil". Para a dieta artificial a mesma foi preparada e vertida em poços das placas de cultura celular (24 poços COSTAR®) aplicando-se 30μL em cada célula, inoculando-se uma lagarta por poço. A mortalidade das lagartas foi avaliada 7 dias após a inoculação. O delineamento experimental foi inteiramente casualizado com 50 repetições (frutos e ponteiros) e 96 repetições (dieta artificial) empregando-se uma lagarta por repetição. Os resultados foram submetidos à análise de variância e as médias comparadas pelo teste de Tukey (PB. thuringiensis aplicados na dieta artificial apresentaram mortalidade de lagartas de G. molesta de 73% e 79% para Agree e Dipel, respectivamente, indicando que a espécie é suscetível a bactéria. A mortalidade em ponteiros e frutos foi de aproximadamente 50% e 20% respectivamente. O inseticida Clorantraniliprole causou mortalidade acima de 90% independente do substrato no qual o produto foi aplicado. Não foi observado diferença significativa na mortalidade causada pelos dois produtos à base de B. thuringiensis em função dos substratos aplicados. Conclui-se que a mortalidade de G. molesta causada por B. thuringiensis é dependente do substrato em que o produto é aplicado

Labeling energy cost on light bulbs lowers implicit discount rates

Lighting accounts for nearly 20% of overall U.S. electricity consumption and 18% of U.S. residential electricity consumption. A transition to alternative energy-efficient technologies could reduce this energy consumption considerably. To quantify the influence of factors that drive consumer choices for light bulbs, we conducted a choice-based conjoint field experiment with 183 participants. We estimated discrete choice models from the data, and found that politically liberal consumers have a stronger preference for compact fluorescent lighting technology and for low energy consumption. Greater willingness to pay for lower energy consumption and longer life was observed in conditions where estimated operating cost information was provided. Providing estimated annual cost information to consumers reduced their implicit discount rate by a factor of five, lowering barriers to adoption of energy efficient alternatives with higher up-front costs; however, even with cost information provided, consumers continued to use implicit discount rates of around 100%, which is larger than that experienced for other energy technologies

A STEADY PSEUDO-COMPRESSIBILITY APPROACH BASED ON UNSTRUCTURED HYBRID FINITE VOLUME TECHNIQUES APPLIED TO TURBULENT PREMIXED FLAME PROPAGATION

A pseudo-compressibility method for zero Mach number turbulent reactive flows with heat release is combined with an unstructured finite volume hybrid grid scheme. The spatial discretization is based on an overlapped cell vertex approach. An infinite freely planar flame propagating into a turbulent medium of premixed reactants is considered as a test case. The recourse to a flamelet combustion modeling for which the reaction rate is quenched in a continuous way ensures the uniqueness of the turbulent flame propagation velocity. To integrate the final form of discretized governing equations, a three-stage hybrid time-stepping scheme is used and artificial dissipation terms are added to stabilize the convergence path towards the final steady solution. The results obtained with such a numerical procedure prove to be in good agreement with those reported in the literature on the very same flow geometry. Indeed, the flame structure as well as its propagation velocity are accurately predicted thus confirming the validity of the approach followed and demonstrating that such a numerical procedure will be a valuable tool to deal with complex reactive flow geometries