Contrastive learning and neural oscillations

The concept of Contrastive Learning (CL) is developed as a family of possible learning algorithms for neural networks. CL is an extension of Deterministic Boltzmann Machines to more general dynamical systems. During learning, the network oscillates between two phases. One phase has a teacher signal and one phase has no teacher signal. The weights are updated using a learning rule that corresponds to gradient descent on a contrast function that measures the discrepancy between the free network and the network with a teacher signal. The CL approach provides a general unified framework for developing new learning algorithms. It also shows that many different types of clamping and teacher signals are possible. Several examples are given and an analysis of the landscape of the contrast function is proposed with some relevant predictions for the CL curves. An approach that may be suitable for collective analog implementations is described. Simulation results and possible extensions are briefly discussed together with a new conjecture regarding the function of certain oscillations in the brain. In the appendix, we also examine two extensions of contrastive learning to time-dependent trajectories

Genetic parameters and relationships between growth traits and scrotal circumference measured at different ages in Nellore cattle

Records from 106,212 Nellore animals, born between 1998 and 2006, were used to estimate (co)variance components and genetic parameters for birth weight (BW), average weight gains from birth to weaning (GBW), average weight gains from weaning to after yearling (GWAY), weaning hip height (WHH), postweaning hip height (PHH) and scrotal circumferences at 9 (SC9), 12 (SC12) and 15 (SC15) months of age. (Co)variance components were estimated by an animal model using multi-trait analysis. Heritability estimates for BW, GBW, GWAY, WHH, PHH, SC9, SC12 and SC15 were 0.31 ± 0.01; 0.25 ± 0.02; 0.30 ± 0.04; 0.51 ± 0.04; 0.54 ± 0.04; 0.39 ± 0.01; 0.41 ± 0.01 and 0.44 ± 0.02, respectively. Genetic correlations between growth traits ranged from 0.09 ± 0.01 to 0.88 ± 0.01, thereby implying that, at any age, selection to increase average weight gains will also increase stature. Genetic correlations between BW and average weight gains with scrotal circumferences were all positive and moderate (0.15 ± 0.03 to 0.38 ± 0.01). On the other hand, positive and low genetic associations were estimated between hip height and scrotal circumference at different ages (0.09 ± 0.01 to 0.17 ± 0.02). The results of this study pointed out that selection to larger scrotal circumferences in males will promote changes in average weight gains. In order to obtain Nellore cattle with the stature and size suitable for the production system, both weight gain and hip height should be included in a selection index

Histaminergic ligands injected into the nucleus basalis magnocellularis differentially affect fear conditioning consolidation

Abstract The role of the nucleus basalis magnocellularis (NBM) in fear conditioning encoding is well established. In the present report, we investigate the involvement of the NBM histaminergic system in consolidating fear memories. The NBM was injected bilaterally with ligands of histaminergic receptors immediately after contextual fear conditioning. Histaminergic compounds, either alone or in combination, were stereotaxically administered to different groups of adult male Wistar rats and memory was assessed as conditioned freezing duration 72 h after administration. This protocol prevents interference with NBM function during either acquisition or retrieval phases, hence restricting the effect of pharmacological manipulations to fear memory consolidation. The results presented here demonstrate that post-training H3 receptors (H3R) blockade with the antagonist/inverse agonist thioperamide or activation with immepip in the NBM potentiates or decreases, respectively, freezing response at retrieval. Thioperamide induced memory enhancement seems to depend on H2R, but not H1R activation, as the H2R antagonist zolantidine blocked the effect of thioperamide, whereas the H1R antagonist pyrilamine was ineffective. Furthermore, the H2R agonist ampthamine improved fear memory expression independently of the H3R agonist effect. Our results indicate that activation of post-synaptic H2R within the NBM by endogenous histamine is responsible for the potentiated expression of fear responses. The results are discussed in terms of activation of H3 auto- and heteroreceptors within the NBM and the differential effect of H3R ligands on fear memory consolidation in distinct brain regions

Parceria no agronegócio da carcinicultura na perspectiva da imersão estrutural – o caso da Camanor Produtos Marinhos Ltda

This article investigates the partnerships of Camanor, an agribusiness company of farmed shrimp, highlighting the importance of trust, reputation and the role played by strong ties in the formation of these arrangements. It analyzes Camanor’s partnerships with Aquatec and Carrefour and their influences on the company’s competitive behavior. It employs a theoretical framework based on the perspective of embeddedness, particularly structural embeddedness (Zukin and Dimaggio, 1990). According to Gnyawali and Madhavan (2001), there are three types of resources flowing in a network: flow of assets, information and status. The article combines primary data obtained through in-depth interviews and secondary data to explore how the differences between the previous ties and the position in the network affected the flow of resources. The partnership with Aquatec, which is based on previous and strong ties, indicates a constant flow of information and a not-hierarchical relationship. On the other hand, the partnership with Carrefour is characterized by a more hierarchical relationship, with less exchange of information. While the former is predominantly based on trust, the latter is predominantly based on economic reciprocity. In both cases there was a significant flow of assets, such as money, technology and organizational skills; a significant flow of status in terms of an increase of Camanor’s legitimacy and reputation in the international market, as well as among its suppliers; and finally a major flow of information on advances in the techniques of shrimp production and market trends. This flow of resources is a consequence of the partners’ position in the international network of shrimp distribution and production. Key words: partnerships, inter-actors networks, internationalization.Esse artigo investiga as parcerias da Camanor, empresa de agronegócio de camarão cultivado, destacando a importância da confiança, da reputação e do papel dos laços fortes na formação desses arranjos. São analisadas as parcerias com a Aquatec e com o Carrefour e suas influências no comportamento competitivo da Camanor. Utilizou-se uma estrutura teórica baseada na perspectiva da imersão social, particularmente o mecanismo estrutural (Zukin e Dimaggio, 1990). Segundo Gnyawali e Madhavan (2001), há três tipos de recursos fluindo em uma rede: ativos, informações e status. Foram combinados dados de entrevistas em profundidade com dados secundários para explorar como as diferenças entre os laços prévios e a posição na rede afetaram o fluxo de recursos. A parceria com a Aquatec, a qual é baseada em laços prévios e fortes, indica um fluxo constante de informação. De forma contrária, a parceria com o Carrefour se caracteriza por uma relação mais hierárquica, com menor troca de informação. Enquanto a primeira é baseada predominantemente na confiança, a segunda é baseada predominantemente na reciprocidade econômica. Em ambos os casos, verificou-se um fluxo significativo de ativos, tais como dinheiro, tecnologia e habilidades organizacionais; um fluxo também significativo de status, observado em termos de aumento de legitimidade e reputação da Camanor no mercado internacional e junto aos seus fornecedores; e, finalmente, um fluxo importante de informações sobre avanços na área de produção de camarão, bem como informações sobre condições e tendências de mercado. Esse fluxo foi observado no trabalho como conseqüência da posição das organizações parceiras na rede internacional de produção e distribuição de camarão. Palavras-chave: parcerias, redes interatores, internacionalização

Long-term satellite NDVI data sets: evaluating their ability to detect ecosystem functional changes in South America

In the last decades, South American ecosystems underwent important functional modifications due to climate alterations and direct human intervention on land use and land cover. Among remotely sensed data sets, NOAA-AVHRR "Normalized Difference Vegetation Index" (NDVI) represents one of the most powerful tools to evaluate these changes thanks to their extended temporal coverage. In this paper we explored the possibilities and limitations of three commonly used NOAA-AVHRR NDVI series (PAL, GIMIMS and FASIR) to detect ecosystem functional changes in the South American continent. We performed pixel-based linear regressions for four NDVI variables (average annual, maximum annual, minimum annual and intra-annual coefficient of variation) for the 1982-1999 period and (1) analyzed the convergences and divergences of significant multi-annual trends identified across all series, (2) explored the degree of aggregation of the trends using the O-ring statistic, and (3) evaluated observed trends using independent information on ecosystem functional changes in five focal regions. Several differences arose in terms of the patterns of change (the sign, localization and total number of pixels with changes). FASIR presented the highest proportion of changing pixels (32.7%) and GIMMS the lowest (16.2%). PAL and FASIR data sets showed the highest agreement, with a convergence of detected trends on 71.2% of the pixels. Even though positive and negative changes showed substantial spatial aggregation, important differences in the scale of aggregation emerged among the series, with GIMMS showing the smaller scale (11 pixels). The independent evaluations suggest higher accuracy in the detection of ecosystem changes among PAL and FASIR series than with GIMMS, as they detected trends that match expected shifts. In fact, this last series eliminated most of the long term patterns over the continent. For example, in the "Eastern Paraguay" and "Uruguay River margins" focal regions, the extensive changes due to land use and land cover change expansion were detected by PAL and FASIR, but completely ignored by GIMMS. Although the technical explanation of the differences remains unclear and needs further exploration, we found that the evaluation of this type of remote sensing tools should not only be focused at the level of assumptions (i.e. physical or mathematical aspects of image processing), but also at the level of results (i.e. contrasting observed patterns with independent proofs of change). We finally present the online collaborative initiative "Land ecosystem change utility for South America", which facilitates this type of evaluations and helps to identify the most important functional changes of the continent.Fil: Baldi, Germán. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; ArgentinaFil: Nosetto, Marcelo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; ArgentinaFil: Aragón, Myriam Roxana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; Argentina. Universidad de Buenos Aires. Facultad de Agronomía; ArgentinaFil: Aversa, Fernando. Universidad Nacional de San Luis; ArgentinaFil: Paruelo, José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Jobbagy Gampel, Esteban Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; Argentin

Arranjos cooperativos sob a ótica da imersão social e da economia dos custos de transação: um estudo de caso

The creation of cooperative arrangements is a strategy increasingly used by organizations around the world as a way to be more competitive in highly dynamic markets. Thus, it becomes increasingly important to understand these new organizational structures. This article analyzes the formation and development of two partnerships established through cooperatives of shrimp producers in the state of Rio Grande do Norte: Coopercam and Unipesca. Both were analyzed from the perspective of Transaction Cost Economics (TCE) and Embeddedness. Gulati’s work (1998) was used to identify the steps needed to understand the creation and development of cooperative arrangements: the decision to start an alliance and the choice of partners, the decision about the governance structure, the evolution of the alliance and the performance of the companies which established the partnership. The research methodology used was the case study (Yin, 2005). The data collection was of exploratory and qualitative nature. For purposes of data analysis, the methodology used in the case study was the content and document analysis proposed by Bardin (1977). The survey results showed that the partnerships brought improvements in competitiveness in both cases. However, these gains were more relevant to Unipesca due to the smaller number of partners in this cooperative, which enabled an increase in social ties and trust between partners. In the case of Coopercam, this was limited by the large number of members.Key words: partnerships, transaction cost economics, embeddedness.A formação de arranjos cooperativos é uma estratégia cada vez mais utilizada por organizações em todo o mundo como forma de obter ganhos de competitividade em mercados altamente dinâmicos. Assim, torna-se cada vez mais importante a compreensão sobre esses novos tipos de arranjos organizacionais. Este artigo analisa a formação e o desenvolvimento de duas parcerias, formadas através de cooperativas de produtores de camarão no estado do Rio Grande do Norte: a Coopercam e a Unipesca. Ambas foram analisadas sob a ótica da Economia dos Custos de Transação (ECT) e da Imersão Social (embeddedness). Utilizou-se o trabalho de Gulati (1998) com o objetivo de identificar as fases para a compreensão da formação e do desenvolvimento de arranjos cooperativos: a decisão de entrar e a escolha dos parceiros, a decisão sobre a estrutura do arranjo, a evolução da aliança e a influência no desempenho daqueles que ingressaram nessa parceria. O método empregado na pesquisa foi o estudo de caso (Yin, 2005). A coleta de dados se caracterizou por ser de natureza exploratório-qualitativa. Já no que se refere à análise de dados, utilizou-se da técnica de análise de conteúdo e análise documental proposta por Bardin (1977). Os resultados da pesquisa mostraram que a formação das parcerias trouxe, em ambos os casos, ganhos de competitividade. Contudo, esses ganhos foram mais relevantes no caso da Unipesca em função do menor número de parceiros, o que possibilitou um incremento dos laços sociais e da confiança existentes entre os parceiros. No caso da Coopercam, isso foi limitado pelo grande número de cooperados.Palavras-chave: parcerias, economia dos custos de transação, imersão social

Arranjos cooperativos sob a ótica da imersão social e da economia dos custos de transação: um estudo de caso

The creation of cooperative arrangements is a strategy increasingly used by organizations around the world as a way to be more competitive in highly dynamic markets. Thus, it becomes increasingly important to understand these new organizational structures. This article analyzes the formation and development of two partnerships established through cooperatives of shrimp producers in the state of Rio Grande do Norte: Coopercam and Unipesca. Both were analyzed from the perspective of Transaction Cost Economics (TCE) and Embeddedness. Gulati’s work (1998) was used to identify the steps needed to understand the creation and development of cooperative arrangements: the decision to start an alliance and the choice of partners, the decision about the governance structure, the evolution of the alliance and the performance of the companies which established the partnership. The research methodology used was the case study (Yin, 2005). The data collection was of exploratory and qualitative nature. For purposes of data analysis, the methodology used in the case study was the content and document analysis proposed by Bardin (1977). The survey results showed that the partnerships brought improvements in competitiveness in both cases. However, these gains were more relevant to Unipesca due to the smaller number of partners in this cooperative, which enabled an increase in social ties and trust between partners. In the case of Coopercam, this was limited by the large number of members.Key words: partnerships, transaction cost economics, embeddedness.A formação de arranjos cooperativos é uma estratégia cada vez mais utilizada por organizações em todo o mundo como forma de obter ganhos de competitividade em mercados altamente dinâmicos. Assim, torna-se cada vez mais importante a compreensão sobre esses novos tipos de arranjos organizacionais. Este artigo analisa a formação e o desenvolvimento de duas parcerias, formadas através de cooperativas de produtores de camarão no estado do Rio Grande do Norte: a Coopercam e a Unipesca. Ambas foram analisadas sob a ótica da Economia dos Custos de Transação (ECT) e da Imersão Social (embeddedness). Utilizou-se o trabalho de Gulati (1998) com o objetivo de identificar as fases para a compreensão da formação e do desenvolvimento de arranjos cooperativos: a decisão de entrar e a escolha dos parceiros, a decisão sobre a estrutura do arranjo, a evolução da aliança e a influência no desempenho daqueles que ingressaram nessa parceria. O método empregado na pesquisa foi o estudo de caso (Yin, 2005). A coleta de dados se caracterizou por ser de natureza exploratório-qualitativa. Já no que se refere à análise de dados, utilizou-se da técnica de análise de conteúdo e análise documental proposta por Bardin (1977). Os resultados da pesquisa mostraram que a formação das parcerias trouxe, em ambos os casos, ganhos de competitividade. Contudo, esses ganhos foram mais relevantes no caso da Unipesca em função do menor número de parceiros, o que possibilitou um incremento dos laços sociais e da confiança existentes entre os parceiros. No caso da Coopercam, isso foi limitado pelo grande número de cooperados.Palavras-chave: parcerias, economia dos custos de transação, imersão social

Genetic Factors that Determine the Meat Fatty Acids Composition

In relation the nutritional attributes of beef meat quality, the composition of fatty acid is important not only because it affects the meat palatability, but also it can affect the human health. The fatty acids harmful to human health have received attenuating attention in recent years. Some studies, with taurine breed, have shown that there is a genetic variation for the trait fatty acid profile of the meat and, therefore, the possibility of genetic improvement of this trait in beef cattle. Meantime, in zebu cattle, the genetic parameter estimates for fatty acid profile are scarce. Furthermore, the trait meat fatty acid profile is something difficult and costly to measure and for this kind of trait is indicated the use of genomic selection, which is a type of marker-assisted selection. The objective of this chapter is showing the genetic variability of meat fatty acid profile different cattle breeds and makes an approach of the implement models and methods that use genomic information to improve the fatty acid composition of beef meat

Associação entre os achados ecocardiográficos e por ventriculografia radioisotópica e níveis plasmáticos de troponina I no diagnóstico de disfunção ventricular esquerda secundária a cardiotoxidade por adriamicina

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Case report: First documented case of cerebral angiostrongyliasis caused by Angiostrongylus costaricensis in a free-ranging opossum

Angiostrongylus costaricensis is a metastrongyloid nematode that primarily infects the mesenteric arteries of wild rodents. This parasite is endemic in several regions of the American continent, and in humans, causes a disease known as abdominal angiostrongyliasis. Despite the important health implications of this nematode, there are limited studies investigating the involvement of wild animals in its life cycle. In this study, we present the clinical manifestations, pathologic findings, and molecular diagnosis, to the best of our current knowledge, of the first documented onset of cerebral angiostrongyliasis because of A. costaricensis infection in a juvenile free-ranging opossum (Didelphis marsupialis). Histopathological findings stress the presence of eosinophilic meningoencephalitis with nematodes present within the lesions, and PCR was positive for cox1 and ITS1 reactions. The obtained sequences for a 279 bp fragment of ITS1 were 100% identical to A. costaricensis from Costa Rica. This case highlights the substantial difficulties in diagnosing neuroangiostrongyliasis, yet underscores the importance of considering A. costaricensis as a potential culprit behind neurological conditions in wild marsupials. It acts as an urgent call to action to improve surveillance programs tracking infectious and parasitic diseases causing mortality in wildlife populations