989 resultados para EVOLUTION REACTION


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ABSTRACT This paper provides evidence on the market reaction to corporate investment decisions whose shareholder value is largely attributed to growth options. The exploratory research raised pre-operational companies and their operational pairs on the same economy segments. It had the purpose of investigating the existence of statistical differentiation from financial indicators that reflect the installed assets and growth assets, and then study the market reaction to changes in fixed assets as a signaling element about investment decisions. The formation process of operational assets and shareholder value almost exclusively dependent on asset growth stands out in the pre-operational companies. As a result, differentiation tests confirmed that the pre-operational companies had their value especially derived on growth options. The market reaction was particularly bigger in pre-operational companies with abnormal negative stock returns, while the operational companies had positive returns, which may indicate that the quality of the investment is judged based on the financial disclosure. Additionally, operational companies' investors await the disclosure to adjust their prices. We conclude that the results are consistent with the empirical evidence and the participants in financial markets to long-term capital formation investments should give that special attention.

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ABSTRACT This paper addresses the changes in university-industry relations in Brazil regarding innovation activities. It is based on a survey of articles published in major national journals or presented at the most relevant Brazilian and regional conferences, between 1980 and 2012. The year 1980 was chosen due to the creation of the Technological Innovation Offices (NITs), which was the first government initiative to encourage knowledge transfer from universities to companies; the second was the Innovation Act of 2004. Our assumption was that after the Act the number of academic papers on this subject would increase, bringing new ideas and propositions of models to enhance this relationship. The methodology employed a qualitative, exploratory approach, using bibliographical research and a bibliometric analysis of 247 papers. Literature review of international studies shows the discussion of problems and suggestions for improvements, while in Brazil there is still a debate on whether this collaboration should occur, and if this is a legitimate role for the university. Despite the numerical growth, the content analysis showed few papers on new configurations and procedures for partnership management. We conclude that university-industry relations are not a regular and totally accepted process in Brazilian public universities, which reflect an ideological bias against cooperation with firms.

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Using game theory, we developed a kin-selection model to investigate the consequences of local competition and inbreeding depression on the evolution of natal dispersal. Mating systems have the potential to favor strong sex biases in dispersal because sex differences in potential reproductive success affect the balance between local resource competition and local mate competition. No bias is expected when local competition equally affects males and females, as happens in monogamous systems and also in polygynous or promiscuous ones as long as female fitness is limited by extrinsic factors (breeding resources). In contrast, a male-biased dispersal is predicted when local mate competition exceeds local resource competition, as happens under polygyny/promiscuity when female fitness is limited by intrinsic factors (maximal rate of processing resources rather than resources themselves). This bias is reinforced by among-sex interactions: female philopatry enhances breeding opportunities for related males, while male dispersal decreases the chances that related females will inbreed. These results meet empirical patterns in mammals: polygynous/promiscuous species usually display a male-biased dispersal, while both sexes disperse in monogamous species. A parallel is drawn with sex-ratio theory, which also predicts biases toward the sex that suffers less from local competition. Optimal sex ratios and optimal sex-specific dispersal show mutual dependence, which argues for the development of coevolution models.

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The Himalayan orogen is the result of the collision between the Indian and Asian continents that began 55-50 Ma ago, causing intracontinental thrusting and nappe formation. Detailed mapping as well as structural and microfabric analyses on a traverse from the Tethyan Himalaya southwestward through the High Himalayan Crystalline and the Main Central Thrust zone (MCT zone) to the Lesser Himalayan Sequence in the Spiti-eastern Lahul-Parvati valley area reveal eight main phases of deformation, a series of late stage phases and five stages of metamorphic crystallization. This sequence of events is integrated into a reconstruction of the tectonometamorphic evolution of the Himalayan orogen in northern Himachal Pradesh. The oldest phase D-1 is preserved as relies in the High Himalayan Crystalline. Its deformational conditions are poorly known, but the metamorphic evolution is well documented by a prograde metamorphism reaching peak conditions within the upper amphibolite facies. This indicates that D-1 was an important tectonometamorphic event including considerable crustal thickening. The structural, metamorphic and sedimentary record suggest that D-1 most probably represents an early stage of continental collision. The first event clearly attributed to the collision between India and Asia is documented by two converging nappe systems, the NE-verging Shikar Beh Nappe and the SW-verging north Himalayan nappes. The D-2 Shikar Beh Nappe is characterized by isoclinal folding and top-to-the NE shearing, representing the main deformation in the High Himalayan Crystalline. D-2 also caused the main metamorphism in the High Himalayan Crystalline that was of a Barrovian-type, reaching upper amphibolite facies peak conditions. The Shikar Beh Nappe is interpreted to have formed within the Indian crust SW of the subduction zone. Simultaneously with NE-directed nappe formation, incipient subduction of India below Asia caused stacking of the SW-verging north Himalayan Nappes, that were thrust from the northern edge of the subducted continent toward the front of the Shikar Beh Nappe. As a result, the SW-verging folds of the D-3 Main Fold Zone formed in the Tethyan Himalaya below the front of the north Himalayan nappes. D-3 represents the main deformation in the Tethyan Himalaya, associated with a greenschist facies metamorphism. Folding within the Main Fold Zone subsequently propagated toward SW into the High Himalayan Crystalline, where it overprinted the preexisting D-2 structures. After subduction at the base of the north Himalayan nappes, the subduction zone stepped to the base of the High Himalayan Crystalline, where D-3 folds were crosscut by SW-directed D-4 thrusting. During D-4, the Crystalline Nappe, comprising the Main Fold Zone and relies of the Shikar Beh Nappe was thrust toward SW over the Lesser Himalayan Sequence along the 4 to 5 kms thick Main Central Thrust zone. Thrusting was related to a retrograde greenschist facies overprint at the base of the Crystalline Nappe and to pro-grade greenschist facies conditions in the Lesser Himalayan Sequence. Simultaneously with thrusting at the base of the Crystalline Nappe, higher crustal levels were affected by NE-directed D-5 normal extensional shearing and by dextral strike-slip motion, indicating that the high-grade metamorphic Crystalline Nappe was extruded between the low-grade metamorphic Lesser Himalayan Sequence at the base and the north Himalayan nappes at the top. The upper boundary of the Crystalline Nappe is not clearly delimited and passes gradually into the low-grade rocks at the front of the north Himalayan nappes. Extrusion of the Crystalline Nappe was followed by the phase D-6, characterized by large-scale, upright to steeply inclined, NE-verging folds and by another series of normal and extensional structures D-7+D-8 that may be related to ongoing extrusion of the Crystalline Nappe. The late stage evolution is represented by the phases D-A and D-B that indicate shortening parallel to the axis of the mountain chain and by D-C that is interpreted to account for the formation of large-scale domes with NNW-SSE-trending axes, an example of which is exposed in the Larji-Kullu-Rampur tectonic window.

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In colonies of social Hymenoptera (which include all ants, as well as some wasp and bee species), only queens reproduce whereas workers generally perform other tasks. The evolution of worker's reproductive altruism can be explained by kin selection, which states that workers can indirectly transmit copies of their genes by helping the reproduction of relatives. The relatedness between queens and workers may however be low, particularly when there are multiple queens per colony, which limits the transmission of copies of workers genes and increases potential conflicts between colony members. In this thesis, we investigated the link between social structure variations and conflicts, and explored the mechanisms involved in variation of colony queen number in ants. According to kin selection, workers should rear the brood they are most related to. In social Hymenoptera, males are haploid whereas females (workers and queens) are diploid. As a result, workers can be up to three times more related to females than males in some colonies, where they should consequently favour the production of females. In contrast, queens are equally related to daughters and sons in all types of colonies and therefore should favour a balanced sex ratio. In a meta-analysis across all studies of social Hymenoptera, we showed that colony sex ratio is generally largely influenced by workers. Hence, the evolution of social structures where queens and workers are equally related to males and females may contribute to decrease the conflict between the two castes over colony sex ratio. Another conflict between queens and workers can occur over male production. Many species contain workers that still have the ability to lay haploid eggs. In some social structures, workers are on average more related to sons of queens than to sons of other workers. As a result, workers should eliminate worker-laid eggs to favour queen-laid eggs. We showed that in the ant Formica selysi, workers eliminate more worker-laid than queen-laid eggs, independently of colony social structure. These results therefore suggest that worker policing can evolve independently from relatedness, potentially because of costs of worker reproduction at the colony-level. Colony queen number is a key parameter that influences relatedness between group members. Queen body size is generally linked to the success of independent colony foundation by single queens and may influence the number of queens in the new colony. In the ant F. selysi, single-queen colonies produce larger queens than multiple-queen colonies. We showed that this association results from genes or maternal effects transmitted to the eggs. However, we also found that queens produced in colonies of the two social forms did not differ in their general ability to found new colonies independently. Queen body size may also influence queen dispersal ability and constrain small queens to be re-adopted in their original nest after mating at proximity. We tested the acceptance of new queens in another ant species, Formica paralugubris, which has numerous queens per colony. Our results show that workers do not discriminate between nestmate and foreign queens, and more generally accept new queens at a limited rate. To conclude, this thesis shows that mechanisms influencing variation in colony queen number and the influence of these changes on conflict resolution are complex. Data gathered in this thesis therefore constitute a solid background for further research on the evolution and the maintenance of complex organisations in insect societies.

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PURPOSE: To compare the apparent diffusion coefficient (ADC) values of malignant liver lesions on diffusion-weighted MRI (DWI) before and after successful radiofrequency ablation (RF ablation). MATERIALS AND METHODS: Thirty-two patients with 43 malignant liver lesions (23/20: metastases/hepatocellular carcinomas (HCC)) underwent liver MRI (3.0T) before (<1month) and after RF ablation (at 1, 3 and 6months) using T2-, gadolinium-enhanced T1- and DWI-weighted MR sequences. Jointly, two radiologists prospectively measured ADCs for each lesion by means of two different regions of interest (ROIs), first including the whole lesion and secondly the area with the visibly most restricted diffusion (MRDA) on ADC map. Changes of ADCs were evaluated with ANOVA and Dunnett tests. RESULTS: Thirty-one patients were successfully treated, while one patient was excluded due to focal recurrence. In metastases (n=22), the ADC in the whole lesion and in MRDA showed an up-and-down evolution. In HCC (n=20), the evolution of ADC was more complex, but with significantly higher values (p=0.013) at 1 and 6months after RF ablation. CONCLUSION: The ADC values of malignant liver lesions successfully treated by RF ablation show a predictable evolution and may help radiologists to monitor tumor response after treatment.

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The great majority of plant species in the tropics require animals to achieve pollination, but the exact role of floral signals in attraction of animal pollinators is often debated. Many plants provide a floral reward to attract a guild of pollinators, and it has been proposed that floral signals of non-rewarding species may converge on those of rewarding species to exploit the relationship of the latter with their pollinators. In the orchid family (Orchidaceae), pollination is almost universally animal-mediated, but a third of species provide no floral reward, which suggests that deceptive pollination mechanisms are prevalent. Here, we examine floral colour and shape convergence in Neotropical plant communities, focusing on certain food-deceptive Oncidiinae orchids (e.g. Trichocentrum ascendens and Oncidium nebulosum) and rewarding species of Malpighiaceae. We show that the species from these two distantly related families are often more similar in floral colour and shape than expected by chance and propose that a system of multifarious floral mimicry-a form of Batesian mimicry that involves multiple models and is more complex than a simple one model-one mimic system-operates in these orchids. The same mimetic pollination system has evolved at least 14 times within the species-rich Oncidiinae throughout the Neotropics. These results help explain the extraordinary diversification of Neotropical orchids and highlight the complexity of plant-animal interactions.

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BACKGROUND: Evolutionary analysis may serve as a useful approach to identify and characterize host defense and viral proteins involved in genetic conflicts. We analyzed patterns of coding sequence evolution of genes with known (TRIM5alpha and APOBEC3G) or suspected (TRIM19/PML) roles in virus restriction, or in viral pathogenesis (PPIA, encoding Cyclophilin A), in the same set of human and non-human primate species. RESULTS AND CONCLUSION: This analysis revealed previously unidentified clusters of positively selected sites in APOBEC3G and TRIM5alpha that may delineate new virus-interaction domains. In contrast, our evolutionary analyses suggest that PPIA is not under diversifying selection in primates, consistent with the interaction of Cyclophilin A being limited to the HIV-1M/SIVcpz lineage. The strong sequence conservation of the TRIM19/PML sequences among primates suggests that this gene does not play a role in antiretroviral defense.

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We developed a procedure that combines three complementary computational methodologies to improve the theoretical description of the electronic structure of nickel oxide. The starting point is a Car-Parrinello molecular dynamics simulation to incorporate vibrorotational degrees of freedom into the material model. By means ofcomplete active space self-consistent field second-order perturbation theory (CASPT2) calculations on embedded clusters extracted from the resulting trajectory, we describe localized spectroscopic phenomena on NiO with an efficient treatment of electron correlation. The inclusion of thermal motion into the theoretical description allowsus to study electronic transitions that, otherwise, would be dipole forbidden in the ideal structure and results in a natural reproduction of the band broadening. Moreover, we improved the embedded cluster model by incorporating self-consistently at the complete active space self-consistent field (CASSCF) level a discrete (or direct) reaction field (DRF) in the cluster surroundings. The DRF approach offers an efficient treatment ofelectric response effects of the crystalline embedding to the electronic transitions localized in the cluster. We offer accurate theoretical estimates of the absorption spectrum and the density of states around the Fermi level of NiO, and a comprehensive explanation of the source of the broadening and the relaxation of the charge transferstates due to the adaptation of the environment

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We present the derivation of the continuous-time equations governing the limit dynamics of discrete-time reaction-diffusion processes defined on heterogeneous metapopulations. We show that, when a rigorous time limit is performed, the lack of an epidemic threshold in the spread of infections is not limited to metapopulations with a scale-free architecture, as it has been predicted from dynamical equations in which reaction and diffusion occur sequentially in time

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The speed of front propagation in fractals is studied by using (i) the reduction of the reaction-transport equation into a Hamilton-Jacobi equation and (ii) the local-equilibrium approach. Different equations proposed for describing transport in fractal media, together with logistic reaction kinetics, are considered. Finally, we analyze the main features of wave fronts resulting from this dynamic process, i.e., why they are accelerated and what is the exact form of this acceleration

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The effect of initial conditions on the speed of propagating fronts in reaction-diffusion equations is examined in the framework of the Hamilton-Jacobi theory. We study the transition between quenched and nonquenched fronts both analytically and numerically for parabolic and hyperbolic reaction diffusion. Nonhomogeneous media are also analyzed and the effect of algebraic initial conditions is also discussed

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The enzyme glutamate dehydrogenase (GDH) is important for recycling the chief excitatory neurotransmitter, glutamate, during neurotransmission. Human GDH exists in housekeeping and brain-specific isotypes encoded by the genes GLUD1 and GLUD2, respectively. Here we show that GLUD2 originated by retroposition from GLUD1 in the hominoid ancestor less than 23 million years ago. The amino acid changes responsible for the unique brain-specific properties of the enzyme derived from GLUD2 occurred during a period of positive selection after the duplication event.