962 resultados para Covariantization on the light-cone gauge
Resumo:
While a remarkable continuity in smallholder agricultural production has been identified, the shift from subsistence orientation towards more wage dependence appears in a different light when analysed under a gender perspective. "Feminisation" has been a catchphrase to characterise some of these processes; however, the debate has been subject to overgeneralisation, and can only inadequately grasp the gender dynamics in what has been referred to as "new ruralities". Illustrated for high-value crop production as an expression of agricultural transition in the Global South, this contribution offers a critical account of the feminisation thesis. Instead of discarding the notion of feminisation, it advocates a reassessment of its potential as a comprehensive framework against which empirical findings can be reflected. While conventional uses of the feminisation thesis have, in their great majority, come up with the conclusion that for women it can always only get worse, I propose a perspective which reveals gains and risks and how they are shared between men and women as they engage in new agricultural labour markets. This perspective rests on a methodology for case-based, comparative studies developed in this paper as a contribution for assessing the nature of agricultural transition and to investigate the qualitative change associated with new ruralities. A distinctive appreciation of the substance of agricultural change for different members of the rural society – namely men and women, but also different men, and different women – is the premise for overcoming barriers to shared development, and for framing effective governance in the context of global development.
Resumo:
Recent studies provide promising methodological advances in the use of pupillometry as on-line measurement of cognitive processes and show that visual attention allocation, mind-wandering, mental imagery, and even rhyme expectations can influence the size of the human pupil.
Resumo:
In this article I argue that the shift from a private to a public–social understanding of religion raises new ontological and epistemological questions for the scientific study of religion\s. These questions are deeply related to three central features of the emic– etic debate, namely the problems of intentionality, objectivity, and comparison. Focusing on these interrelated issues, I discuss the potential of John Searle’s philoso- phy of society for the scientific study of religion\s. Considering the role of intentional- ity at the social level, I present Searle’s concept of “social ontology” and discuss its epistemological implications. To clarify Searle’s position regarding the objectivity of the social sciences, I propose a heuristic model contrasting different stances within the scientific study of religion\s. Finally, I explore some problematic aspects of Searle’s views for a comparative study of religion\s, and sketch a solution within his frame- work. I shall argue that a distinction between the epistemological and ontological dimensions of religious affairs would help clarify the issues at stake in the past and future of the emic–etic debate.
Resumo:
Recently, it has been suggested that there are conditions under which some coral species appear to be resistant to the effects of ocean acidification. To test if such resistance can be explained by environmental factors such as light and food availability, the present study investigated the effect of 3 feeding regimes crossed with 2 light levels on the response of the coral Porites rus to 2 levels of pCO2 at 28 °C. After 1, 2, and 3 weeks of incubation under experimental conditions, none of the factors-including pCO2-significantly affected area-normalized calcification and biomass-normalized calcification. Biomass also was unaffected during the first 2 weeks, but after 3 weeks, corals that were fed had more biomass per unit area than starved corals. These results suggest that P. rus is resistant to short-term exposure to high pCO2, regardless of food availability and light intensity. P. rus might therefore represent a model system for exploring the genetic basis of tolerance to OA.
Resumo:
Global change leads to a multitude of simultaneous modifications in the marine realm among which shoaling of the upper mixed layer, leading to enhanced surface layer light intensities, as well as increased carbon dioxide (CO2) concentration are some of the most critical environmental alterations for phytoplankton. In this study, we investigated the responses of growth, photosynthetic carbon fixation and calcification of the coccolithophore Gephyrocapsa oceanica to elevated inline image (51 Pa, 105 Pa, and 152 Pa) (1 Pa ~ 10 µatm) at a variety of light intensities (50-800 µmol photons/m**2/s). By fitting the light response curve, our results showed that rising inline image reduced the maximum rates for growth, photosynthetic carbon fixation and calcification. Increasing light intensity enhanced the sensitivity of these rate responses to inline image, and shifted the inline image optima toward lower levels. Combining the results of this and a previous study (Sett et al. 2014) on the same strain indicates that both limiting low inline image and inhibiting high inline image levels (this study) induce similar responses, reducing growth, carbon fixation and calcification rates of G. oceanica. At limiting low light intensities the inline image optima for maximum growth, carbon fixation and calcification are shifted toward higher levels. Interacting effects of simultaneously occurring environmental changes, such as increasing light intensity and ocean acidification, need to be considered when trying to assess metabolic rates of marine phytoplankton under future ocean scenarios.
Resumo:
The effects of light and elevated pCO2 on the growth and photochemical efficiency of the critically endangered staghorn coral, Acropora cervicornis, were examined experimentally. Corals were subjected to high and low treatments of CO2 and light in a fully crossed design and monitored using 3D scanning and buoyant weight methodologies. Calcification rates, linear extension, as well as colony surface area and volume of A. cervicornis were highly dependent on light intensity. At pCO2 levels projected to occur by the end of the century from ocean acidification (OA), A. cervicornis exhibited depressed calcification, but no change in linear extension. Photochemical efficiency (F v /F m ) was higher at low light, but unaffected by CO2. Amelioration of OA-depressed calcification under high-light treatments was not observed, and we suggest that the high-light intensity necessary to reach saturation of photosynthesis and calcification in A. cervicornis may limit the effectiveness of this potentially protective mechanism in this species. High CO2 causes depressed skeletal density, but not linear extension, illustrating that the measurement of extension by itself is inadequate to detect CO2 impacts. The skeletal integrity of A. cervicornis will be impaired by OA, which may further reduce the resilience of the already diminished populations of this endangered species.
Resumo:
The marine diazotrophic cyanobacterium Trichodesmium responds to elevated atmospheric CO2 partial pressure (pCO2) with higher N2 fixation and growth rates. To unveil the underlying mechanisms, we examined the combined influence of pCO2(150 and 900 µatm) and light (50 and 200 µmol photons m-2 s-1) on TrichodesmiumIMS101. We expand on a complementary study that demonstrated that while elevated pCO2 enhanced N2 fixation and growth, oxygen evolution and carbon fixation increased mainly as a response to high light. Here, we investigated changes in the photosynthetic fluorescence parameters of photosystem II, in ratios of the photosynthetic units (photosystem I:photosystem II), and in the pool sizes of key proteins involved in the fixation of carbon and nitrogen as well as their subsequent assimilation. We show that the combined elevation in pCO2 and light controlled the operation of the CO2-concentrating mechanism and enhanced protein activity without increasing their pool size. Moreover, elevated pCO2 and high light decreased the amounts of several key proteins (NifH, PsbA, and PsaC), while amounts of AtpB and RbcL did not significantly change. Reduced investment in protein biosynthesis, without notably changing photosynthetic fluxes, could free up energy that can be reallocated to increase N2 fixation and growth at elevated pCO2 and light. We suggest that changes in the redox state of the photosynthetic electron transportchain and posttranslational regulation of key proteins mediate the high flexibility in resources and energy allocation in Trichodesmium. This strategy should enableTrichodesmium to flourish in future surface oceans characterized by elevated pCO2, higher temperatures, and high light.
Resumo:
Measuring the shadow economy is inherently difficult, but critical for understanding economic development. Using census data on formal and informal sectors in Cambodia, we document that 96.6% of non-farm establishments do not formally register with the government, and their sales accounted for 76.6% of total sales in 2011. We estimate a relationship between nighttime light and sales across regions separately for formal and informal firms for 2011, and estimate their past sales from changes in nighttime light for 1993-2010. Both formal and informal firms increased their estimated sales, and the share of informal sales increased from 68.8% in 1993 to 76.6% in 2011, suggesting that the informal sector increased quantitatively in both absolute and relative terms throughout the economic development of the Cambodian economy.
Resumo:
Interlinking text documents with Linked Open Data enables the Web of Data to be used as background knowledge within document-oriented applications such as search and faceted browsing. As a step towards interconnecting the Web of Documents with the Web of Data, we developed DBpedia Spotlight, a system for automatically annotating text documents with DBpedia URIs. DBpedia Spotlight allows users to congure the annotations to their specic needs through the DBpedia Ontology and quality measures such as prominence, topical pertinence, contextual ambiguity and disambiguation condence. We compare our approach with the state of the art in disambiguation, and evaluate our results in light of three baselines and six publicly available annotation systems, demonstrating the competitiveness of our system. DBpedia Spotlight is shared as open source and deployed as a Web Service freely available for public use.
Resumo:
Interlinking text documents with Linked Open Data enables the Web of Data to be used as background knowledge within document-oriented applications such as search and faceted browsing. As a step towards interconnecting the Web of Documents with the Web of Data, we developed DBpedia Spotlight, a system for automatically annotating text documents with DBpedia URIs. DBpedia Spotlight allows users to configure the annotations to their specific needs through the DBpedia Ontology and quality measures such as prominence, topical pertinence, contextual ambiguity and disambiguation confidence. We compare our approach with the state of the art in disambiguation, and evaluate our results in light of three baselines and six publicly available annotation systems, demonstrating the competitiveness of our system. DBpedia Spotlight is shared as open source and deployed as a Web Service freely available for public use.