Social ties and economic development

We develop a parsimonious general equilibrium model where agents allocate time across three activities: production, trade, and leisure. Leisure includes time spent socializing, which economizes transaction costs. Our framework yields multiple equilibria in terms of the number of social ties and predicts that the number of social ties is positively associated with development, a relationship we observe in cross-country data. The model captures additional dimensions of data, namely: (i) increasing income inequality, but converging growth rates; (ii) an association between weak social ties and development; and (iii) an association between number of social ties and size of the transaction sector.social capital; development; transaction costs; networks

Notch signaling in the regulation of hematopoietic stem cell

Purpose of Review Understanding the signaling pathways that govern hematopoietic stem and progenitor cells (HSPCs) is fundamental to uncover their regulation and how this is skewed in hematological malignancies. Whether Notch is necessary for the regulation of mammalian HSPCs is still unclear. We therefore critically review the current literature on the role of Notch in HSPCs. Recent Findings HSPCs have shown different requirements for Notch signals in vitro and in vivo and at different stages of differentiation. Additionally, bone marrow niche cells activate Notch signaling in HSPCs enhancing their regenerative and self-renewal capacity. Summary Despite the controversy, adequate levels of Notch signaling appear necessary to avoid the development of hematological malignancies. Contrary to early studies, recent research suggests that Notch signaling may play a role in homeostatic and regenerative hematopoiesis but further investigation is necessary to understand how it is regulated by the different ligand/receptor pairings and the molecular mechanisms that are triggered

Criptococose cutânea causada por Cryptococcus gattii em um paciente sob corticoterapia crônica

Cryptococcus gattii é agente causador de uma micose endêmica que afeta principalmente os pulmões e o sistema nervoso central de pacientes imunocompetentes em regiões tropicais e subtropicais do globo. Relato de caso. Um paciente de 66 anos, portador de doença pulmonar obstrutiva crônica, não infectado pelo vírus HIV, em corticoterapia sistêmica prolongada, desenvolveu extensa ulceração do antebraço esquerdo, associada a adenomegalia supraclavicular ipsilateral, em conseqüência à infecção por Cryptococcus gattii. O paciente foi tratado com fluconazol 400mg/dia durante 8 meses, obtendo resolução completa da lesão. Este caso enfatiza que, ainda que raramente, C. gattii pode causar infecção cutâneo-linfática oportunista, em paciente imunocomprometido pelo uso sistêmico de corticosteróides vivendo na região sudeste do Brasil.Cryptococcus gattii causes a form of endemic mycosis that most commonly affects the lungs and central nervous system of immunocompetent patients living in tropical and subtropical areas of the world. Case report. A 66-year-old man who had chronic obstructive pulmonary disease without HIV infection and had been on systemic corticotherapy for several years developed extensive ulceration of the left forearm that was associated with ipsilateral supraclavicular adenomegaly, consequent to infection with Cryptococcus gattii. The patient was treated with fluconazole 400mg/day for eight months, which led to complete healing of the lesion. This case emphasizes that, although rare, C. gattii may cause opportunistic cutaneous-lymphatic infection in patients living in the southeastern region of Brazil who are immunocompromised through chronic corticotherapy

Perturbed hematopoiesis in mice lacking ATMIN

The ATM-interacting protein ATMIN mediates non-canonical ATM signaling in response to oxidative and replicative stress conditions. Like ATM, ATMIN can function as a tumor suppressor in the hematopoietic system: deletion of Atmin under the control of CD19-Cre results in B cell lymphomas in aging mice. ATM signaling is essential for lymphopoiesis and hematopoietic stem cell (HSC) function; however, little is known about the role of ATMIN in hematopoiesis. We thus sought to investigate if the absence of ATMIN would affect primitive hematopoietic cells in an ATM-dependent or -independent manner. Apart from its role in B cell development, we show that ATMIN has an ATM-independent function in the common myeloid progenitors (CMPs) by deletion of Atmin in the entire hematopoietic system using Vav-Cre. Despite the lack of lymphoma formation, ATMIN-deficient mice developed chronic leukopenia as a result of high levels of apoptosis in B cells and CMPs and induced a compensatory mechanism in which HSCs displayed enhanced cycling. Consequently, ATMIN-deficient HSCs showed impaired regeneration ability, with the induction of the DNA oxidative stress response, especially when aged. ATMIN therefore has multiple roles in different cell types and its absence results in perturbed hematopoiesis, especially during stress conditions and aging

Technological specialization and the decline of diversified firms

We document a strong decline in corporate-diversification activity since the late 1970s, and we develop a dynamic model that explains this pattern, both qualitatively and quantitatively. The key feature of the model is that synergies endogenously decline with technological specialization, leading to fewer diversified firms in equilibrium. The model further predicts that segments inside a conglomerate should become more related over time, which is consistent with the data. Finally, the calibrated model also matches other empirical magnitudes well: output growth rate, market-to-book ratios, diversification discount, frequency and returns of diversifying mergers, and frequency of refocusing activity.otherpublishe

an agent-based model of optimal exploitation

Using an agent-based simulation, we illustrate how goal-seeking behavior affects network formation, learning, and performance. Our organization has one manager, who decides where to invest financial capital; individual workers, who decide where to work and prefer projects with larger budgets; and projects, which vary in quality. Our manager discovers high-quality projects from interactions with workers and allocates more capital to high-quality projects. When given an opportunity, our workers move to bigger-budget projects. We let our manager vary in terms of how much she exploits what she learns and allow our workers vary in terms of how sensitive they are to differences in capital. Our results highlight a contingency which shapes how goal-seeking behavior affects learning. The contingency is network fragility. Fragile connections decay quickly when individuals are not working together, while robust relationships decay more slowly. When relationships are robust, exploitation by our manager leads to a dense organizational network, improving information quality, and performance. Decisions by self-interested individuals (our manager and our workers) produce a virtuous learning cycle. When relationships are fragile, exploitation by our manager produces a sparse network, reducing information quality, and undermining performance. When network connections are fragile, the manager must find the right balance of exploitation and exploration, a balance which limits the rate at which workers move from one project to the next, allowing the manager to exploit some of what she knows, without undermining the very network which allows for useful information to be obtained.publishersversionpublishe

Social ties and economic development

We develop a parsimonious general equilibrium model where agents allocate time across three activities: production, trade, and leisure. Leisure includes time spent socializing, which economizes transaction costs. Our framework yields multiple equilibria in terms of the number of social ties and predicts that the number of social ties is positively associated with development, a relationship we observe in cross-country data. The model captures additional dimensions of data, namely: (i) increasing income inequality, but converging growth rates; (ii) an association between weak social ties and development; and (iii) an association between number of social ties and size of the transaction sector

Social ties and economic development

We develop a parsimonious general equilibrium model where agents allocate time across three activities: production, trade, and leisure. Leisure includes time spent socializing, which economizes transaction costs. Our framework yields multiple equilibria in terms of the number of social ties and predicts that the number of social ties is positively associated with development, a relationship we observe in cross-country data. The model captures additional dimensions of data, namely: (i) increasing income inequality, but converging growth rates; (ii) an association between weak social ties and development; and (iii) an association between number of social ties and size of the transaction sector

Educação em sustentabilidade : proposta metodológica de incentivo a prática de quintais domésticos

Orientador :Monografia (especialização) - Universidade Federal do Paraná, Setor de ..., Curso de Especialização em ...Inclui referência