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23 result(s) for "Ribas, Rafael P."
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Liquidity constraints, spillovers, and entrepreneurship
This paper exploits a liquidity shock from a welfare program in Brazil to investigate the role of financial constraints, in opposition to general equilibrium mechanisms, in explaining entrepreneurship. Previous research focuses exclusively on how liquidity changes recipients’ behavior through direct effects on reducing constraints. However, liquidity shocks may also produce spillovers from recipients to others and thereby indirectly affect entrepreneurial decisions. This paper presents a method for decomposing the liquidity shock into direct effects associated with relieving individual constraints, and indirect effects associated with spillovers to other individuals. Results suggest that the program, which assists 20 percent of Brazilian households, increased the number of small entrepreneurs by 10 percent. However, this increase is entirely driven by the indirect effect. Further tests suggest that this effect is associated with an increase in private transfers between households. Thus, entrepreneurship tends to respond more to the interaction between households than to financial constraints.
The effect of age at school entry on college admission and earnings: A regression-discontinuity approach
This paper provides evidence of the effect of age at school entry on college admission and earnings. It does so by exploiting a number of features in the application process to one of the major flagship universities in Brazil. By comparing applicants with different ages at school entry depending on whether they were born on December 31 or on January 1, our estimates show that applicants who delayed first-grade enrollment present higher aptitude test scores and probability of admission. Our results further suggest that advantaged applicants also earn more early in their careers.
Direct and Indirect Effects of Cash Transfers on Entrepreneurship
This paper exploits a liquidity shock from a large-scale welfare program in Brazil to investigate the importance of credit constraints and informal financial assistance in explaining entrepreneurship. Previous research focuses exclusively on how liquidity shocks change recipients' behavior through direct effects on reducing financial constraints. However, the shock may also produce spillovers from recipients to others through private transfers and thereby indirectly affect decisions to be an entrepreneur. This paper presents a method for decomposing the liquidity shock into direct effects associated with relieving financial constraints, and indirect effects associated with spillovers to other individuals. Results suggest that the program, which assists 20 percent of Brazilian households, has increased the number of small entrepreneurs by 10 percent. However, this increase is almost entirely driven by the indirect effect, which is related to an increase in private transfers among poor households. Thus the creation of small businesses seems to be more responsive to the opportunity cost of mutual assistance between households than to financial constraints.
Is the Stock Market Just a Side Show? Evidence from a Structural Reform
The 2005 split-share reform in China mandated the conversion of nontradable stocks into tradable status. This paper examines the effects of stock markets on corporate outcomes exploiting multiple institutional features of the Chinese conversion program. Using a generalized propensity score matching approach, we identify increases in corporate profitability, investment, value, and productivity as a result of the reform. We also identify changes in firms' likelihood to issue shares and engage in mergers, as well as changes in dividend and capital structure policies. Our findings provide insights on the role of stock markets in shaping corporate activity and on the impact of regulation on economic growth.
Prognostic evaluation of severe sepsis and septic shock: Procalcitonin clearance vs Δ Sequential Organ Failure Assessment
The purpose of the study is to compare the clearance of procalcitonin (PCT-c) in the first 24 and 48 hours of treatment of severe sepsis and septic shock with another early prognostic marker represented by the 48-hour Δ Sequential Organ Failure Assessment (SOFA). Prospective, observational cohort study conducted in a general intensive care unit including patients with severe sepsis and septic shock. The PCT-c was determined at the diagnosis of sepsis and after 24 and 48 hours. The SOFA score was determined at the time of intensive care unit admission and after 48 hours. One hundred thirty adult patients with severe sepsis and septic shock were studied over an 18-month period. The 24- and 48-hour PTC-c scores were significantly higher in survivors (P < .0001). In nonsurvivors, the initial SOFA was significantly higher, and the 48-hour Δ SOFA was significantly smaller (P = .01). The area under the receiver operating characteristic curve was 0.68 for Δ SOFA and 0.76 for 24- and 48-hour PCT-c. The 48-hour Δ SOFA score and the clearance of 24- and 48-hour PCT are useful markers of prognosis in patients with severe sepsis and septic shock. A decrease in PCT-c in the first 24 hours of treatment should prompt the reassessment of the appropriateness and adequacy of treatment.
High Expression of GABAA Receptor β Subunit Genes Is Associated with Longer Overall Survival in Medulloblastoma
Background/Objectives: Most of the rapid inhibitory neurotransmission in the brain is mediated through activation of the γ-aminobutyric acid (GABA) type A (GABAA) receptor, which is a ligand-gated ion channel. GABAA receptor activation via GABA binding allows for an intracellular influx of Cl− ions, thus inducing cellular hyperpolarization. Each GABAA receptor consists of a combination of five subunits, and several subunits have been proposed as biomarkers and therapeutic targets in cancer. Here, we show the expression of genes encoding β subunits of the GABAA receptor, namely GABRB1, GABRB2, and GABRB3, across the four different molecular subgroups of medulloblastoma (MB), which is the most common malignant pediatric brain tumor. We also show the associations of GABAA receptor β subunits with MB patients’ overall survival (OS). Methods: The expression of genes encoding GABAA receptor β subunits was analyzed using a previously described dataset comprising 763 MB tumor samples. Patients were classified into high- and low-gene-expression groups, and the Kaplan–Meier estimate was used to examine the relationship between gene expression levels and patient OS. Results: High GABRB1 expression was associated with better OS within each of the four molecular subgroups. The GABRB2 gene showed higher transcript levels in Group 3 MB compared to all other subgroups, and high expression was associated with better prognosis in Group 3 tumors. GABRB3 expression was significantly higher in Group 3 and Group 4 MB, and high expression of GABRB3 genes was associated with longer OS in the sonic hedgehog (SHH) subgroup. The high expression of GABRB1, GABRB2, and GABRB3 is associated with longer patient OS in a subgroup-specific manner. Conclusions: These results indicate a role for GABAA receptors containing β subunits in influencing MB progression.
The role of environmental filtering, geographic distance and dispersal barriers in shaping the turnover of plant and animal species in Amazonia
To determine the effect of rivers, environmental conditions, and isolation by distance on the distribution of species in Amazonia. Location: Brazilian Amazonia. Time period: Current. Major taxa studied: Birds, fishes, bats, ants, termites, butterflies, ferns + lycophytes, gingers and palms. We compiled a unique dataset of biotic and abiotic information from 822 plots spread over the Brazilian Amazon. We evaluated the effects of environment, geographic distance and dispersal barriers (rivers) on assemblage composition of animal and plant taxa using multivariate techniques and distance- and raw-data-based regression approaches. Environmental variables (soil/water), geographic distance, and rivers were associated with the distribution of most taxa. The wide and relatively old Amazon River tended to determine differences in community composition for most biological groups. Despite this association, environment and geographic distance were generally more important than rivers in explaining the changes in species composition. The results from multi-taxa comparisons suggest that variation in community composition in Amazonia reflects both dispersal limitation (isolation by distance or by large rivers) and the adaptation of species to local environmental conditions. Larger and older river barriers influenced the distribution of species. However, in general this effect is weaker than the effects of environmental gradients or geographical distance at broad scales in Amazonia, but the relative importance of each of these processes varies among biological groups.
High Expression of GABA A Receptor β Subunit Genes Is Associated with Longer Overall Survival in Medulloblastoma
Most of the rapid inhibitory neurotransmission in the brain is mediated through activation of the γ-aminobutyric acid (GABA) type A (GABA ) receptor, which is a ligand-gated ion channel. GABA receptor activation via GABA binding allows for an intracellular influx of Cl ions, thus inducing cellular hyperpolarization. Each GABA receptor consists of a combination of five subunits, and several subunits have been proposed as biomarkers and therapeutic targets in cancer. Here, we show the expression of genes encoding β subunits of the GABA receptor, namely , , and , across the four different molecular subgroups of medulloblastoma (MB), which is the most common malignant pediatric brain tumor. We also show the associations of GABA receptor β subunits with MB patients' overall survival (OS). The expression of genes encoding GABA receptor β subunits was analyzed using a previously described dataset comprising 763 MB tumor samples. Patients were classified into high- and low-gene-expression groups, and the Kaplan-Meier estimate was used to examine the relationship between gene expression levels and patient OS. High expression was associated with better OS within each of the four molecular subgroups. The gene showed higher transcript levels in Group 3 MB compared to all other subgroups, and high expression was associated with better prognosis in Group 3 tumors. expression was significantly higher in Group 3 and Group 4 MB, and high expression of genes was associated with longer OS in the sonic hedgehog (SHH) subgroup. The high expression of , , and is associated with longer patient OS in a subgroup-specific manner. These results indicate a role for GABA receptors containing β subunits in influencing MB progression.
Randomized comparison of oblique and perpendicular stabilizers for minimally invasive repair of pectus excavatum
OBJECTIVES Bar dislocation is one of the most feared complications of the minimally invasive repair of pectus excavatum. METHODS Prospective randomized parallel-group clinical trial intending to assess whether oblique stabilizers can reduce bar displacement in comparison with regular stabilizers used in minimally invasive repair of pectus excavatum. Additionally, we evaluated pain, quality of life and other postoperative complications. Participants were randomly assigned to surgery with perpendicular (n = 16) or oblique stabilizers (n = 14) between October 2017 and September 2018 and followed for 3 years. Bar displacements were evaluated with the bar displacement index. Pain scores were evaluated through visual analogue scale and quality of life through the Pectus Excavatum Evaluation Questionnaire. RESULTS Control group average displacement index was 17.7 (±26.7) and intervention group average displacement index was 8.2 (±10.9). There was 1 reoperation in each group that required correction with 2 bars. Bar displacement was similar among groups (P = 0.12). No other complications were recorded. There was no statistically significant difference on pain score. There was a significant difference between pre- and postoperative composite scores of the participants’ body image domain and psycho-social aspects in both groups. The difference between the pre- and postoperative participants’ perception of physical difficulties was greater and statistically significant in the intervention group. CONCLUSIONS There was no statistical difference in the use of perpendicular or oblique stabilizers, but the availability of different models of stabilizers during the study suggested that this can be advantageous. The trial is registered at ClinicalTrials.gov, number NCT03087734. Pectus excavatum (PE) is associated with shortness of breath, exercise intolerance, low self-esteem and depression [1–3] and to date there is no effective non-invasive treatment [4].