909 resultados para Causal nexus
Resumo:
Genes underlying mutant phenotypes can be isolated by combining marker discovery, genetic mapping and resequencing, but a more straightforward strategy for mapping mutations would be the direct comparison of mutant and wild-type genomes. Applying such an approach, however, is hampered by the need for reference sequences and by mutational loads that confound the unambiguous identification of causal mutations. Here we introduce NIKS (needle in the k-stack), a reference-free algorithm based on comparing k-mers in whole-genome sequencing data for precise discovery of homozygous mutations. We applied NIKS to eight mutants induced in nonreference rice cultivars and to two mutants of the nonmodel species Arabis alpina. In both species, comparing pooled F2 individuals selected for mutant phenotypes revealed small sets of mutations including the causal changes. Moreover, comparing M3 seedlings of two allelic mutants unambiguously identified the causal gene. Thus, for any species amenable to mutagenesis, NIKS enables forward genetics without requiring segregating populations, genetic maps and reference sequences.
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In this paper we compare two historical scenarios very different one to each other bothin institutional and geographical terms. What they have in common is the situation ofrelative poverty of most of the population. On the one side we are dealing withhistorical industrializing Catalonia in the North East of Spain, a country exhibiting pooreconomic yields in the context of European and non European industrializing nations inthe 19th century. We compare children s work patterns in 19th century Catalonia withthose of current developing countries in Latin America, Africa and South and East Asia.This kind of exercise in which the nexus of the comparison are the levels of wealth ofcountries that are unsuccessful to achieve high standards of economic growth allows usto combine the micro historical analysis (in the Catalan case) with the macrocomparative approach in current developing countries. By means of both, the microhistorical analysis and the macro regression analysis we obtain the result that adultwomen s skills and real wages are a key factor when we want to explain the patterns ofchildren work. While female real wages increased a sharp rate in 19th century Cataloniawe obtain very different results in the case of developing countries. This differentgender bias helps to explain why in some cases children continue to work and also whysome parts of the world continue to be poor according to our regression analysis.
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Pollination syndromes involve convergent evolution towards phenotypes composed of specific scents, colours or floral morphologies that attract or restrict pollinator access to reward. How these traits might influence the distributions of plant species in interaction with pollinators has rarely been investigated. We sampled 870 vegetation plots in the western Swiss Alps and classified the plant species into seven blossom types according to their floral morphology (wind, disk, funnel, tube, bilabiate, head or brush). We investigated the environmental features of plots with functional diversity (FD) lower than expected by chance alone to detect potential pollination filtering and related the proportions of the seven blossom types to a combination of environmental descriptors. From these results, we inferred the potential effect of the pollinator on the spatial distribution of plant species. The vegetation plots with significantly lower FD of blossom types than expected by chance were found at higher altitudes, and the proportions of blossom types were strongly patterned along the same gradient. These results support a biotic filtering effect on plant species assemblages through pollination: disk blossoms became dominant at higher altitudes, resulting in a lower FD. In harsh conditions at high altitudes, pollinators usually decrease in activity, and the openness of the disk blossom grants access to any available pollinator. Inversely, bilabiate blossoms, which are mostly pollinated by bees, were more abundant at lower elevations, which are characterised by greater abundance and diversity of bees. Generalisation through openness of the blossom could be advantageous at high elevations, while specialisation could be a successful alternative strategy at lower elevations. The approach used in this study is purely correlative, and further investigations should be conducted to infer the nature of the causal relationship between plant and pollinator distributions.
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I study the impact of a universal child benefit on fertility and family well-being. I exploitthe unanticipated introduction of a new, sizeable, unconditional child benefit in Spain in2007, granted to all mothers giving birth on or after July 1, 2007. The regressiondiscontinuity-type design allows for a credible identification of the causal effects. I find thatthe benefit did lead to a significant increase in fertility, as intended, part of it coming froman immediate reduction in abortions. On the unintended side, I find that families whoreceived the benefit did not increase their overall expenditure or their consumption ofdirectly child-related goods and services. Instead, eligible mothers stayed out of the laborforce significantly longer after giving birth, which in turn led to their children spending lesstime in formal child care and more time with their mother during their first year of life. Ialso find that couples who received the benefit were less likely to break up the year afterhaving the child, although this effect was only short-term. Taken together, the resultssuggest that child benefits of this kind may successfully increase fertility, as well asaffecting family well-being through their impact on maternal time at home and familystability.
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This paper provides empirical evidence of the persistent effect of exposure to political violence on humancapital accumulation. I exploit the variation in conflict location and birth cohorts to identify the longandshort-term effects of the civil war on educational attainment. Conditional on being exposed toviolence, the average person accumulates 0.31 less years of education as an adult. In the short-term,the effects are stronger than in the long-run; these results hold when comparing children within thesame household. Further, exposure to violence during early childhood leads to permanent losses. I alsoexplore the potential causal mechanisms.
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We study the determinants of comparative advantage in polluting industries. We combine dataon environmental policy at the country level with data on pollution intensity at the industry levelto show that countries with laxer environmental regulation have a comparative advantage in polluting industries. Further, we address the potential problem of reverse causality. We propose aninstrument for environmental regulation based on meteorological determinants of pollution dispersion identified by the atmospheric pollution literature. We find that the effect of environmentalregulation on the pattern of trade is causal and comparable in magnitude to the effect of physicaland human capital.
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BACKGROUND: Human immunodeficiency virus (HIV) takes advantage of multiple host proteins to support its own replication. The gene ZNRD1 (zinc ribbon domain-containing 1) has been identified as encoding a potential host factor that influenced disease progression in HIV-positive individuals in a genomewide association study and also significantly affected HIV replication in a large-scale in vitro short interfering RNA (siRNA) screen. Genes and polymorphisms identified by large-scale analysis need to be followed up by means of functional assays and resequencing efforts to more precisely map causal genes. METHODS: Genotyping and ZNRD1 gene resequencing for 208 HIV-positive subjects (119 who experienced long-term nonprogression [LTNP] and 89 who experienced normal disease progression) was done by either TaqMan genotyping assays or direct sequencing. Genetic association analysis was performed with the SNPassoc package and Haploview software. siRNA and short hairpin RNA (shRNA) specifically targeting ZNRD1 were used to transiently or stably down-regulate ZNRD1 expression in both lymphoid and nonlymphoid cells. Cells were infected with X4 and R5 HIV strains, and efficiency of infection was assessed by reporter gene assay or p24 assay. RESULTS: Genetic association analysis found a strong statistically significant correlation with the LTNP phenotype (single-nucleotide polymorphism rs1048412; [Formula: see text]), independently of HLA-A10 influence. siRNA-based functional analysis showed that ZNRD1 down-regulation by siRNA or shRNA impaired HIV-1 replication at the transcription level in both lymphoid and nonlymphoid cells. CONCLUSION: Genetic association analysis unequivocally identified ZNRD1 as an independent marker of LTNP to AIDS. Moreover, in vitro experiments pointed to viral transcription as the inhibited step. Thus, our data strongly suggest that ZNRD1 is a host cellular factor that influences HIV-1 replication and disease progression in HIV-positive individuals.
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Using historical data for all Swiss cantons from 1890 to 2000, we estimate the causal effect of direct democracy on government spending. The main innovation in this paper is that we use fixed effects to control for unobserved heterogeneity and instrumental variables to address the potential endogeneity of institutions. We find that the budget referendum and lower costs to launch a voter initiative are effective tools in reducing canton level spending. However, we find no evidence that the budget referendum results in more decentralized government or a larger local government. Our instrumental variable estimates suggest that a mandatory budget referendum reduces the size of canton spending between 13 and 19 percent. A 1 percent lower signature requirement for the initiative reduces canton spending by up to 2 percent.
Resumo:
Highly competitive environments are leading companies to implement SupplyChain Management (SCM) to improve performance and gain a competitiveadvantage. SCM involves integration, co-ordination and collaborationacross organisations and throughout the supply chain. It means that SCMrequires internal (intraorganisational) and external (interorganisational)integration. This paper examines the Logistics-Production and Logistics-Marketing interfaces and their relation with the external integrationprocess. The study also investigates the causal impact of these internaland external relationships on the company s logistical service performance.To analyse this, an empirical study was conducted in the Spanish Fast MovingConsumer Goods (FMCG) sector.
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A 41-year-old woman who worked in a furniture plant was admitted to hospital for acute dyspnea that had developed a few hours she marked pieces of "Alcantara" material with a heated metallic blade. The chest x-ray showed a restrictive syndrome. The lymphocyte count was high in the bronchioalveolar lavage fluid with a CD4/CD8 ratio of 0.11, leading to the diagnosis of alveolitis. Investigations at the work place allowed identification and evaluation of the causal agent. Alcantara is a synthetic fabric composed of 70% polyurethane fibers, which when burned produces isocyanate monomers. After eliminating exposure and institution of corticosteroid therapy, the outcome was good with complete recovery. The risk was eliminated by changing the work procedure. This risk has not been reported earlier for furniture manufacture.
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We formulate performance assessment as a problem of causal analysis and outline an approach based on the missing data principle for its solution. It is particularly relevant in the context of so-called league tables for educational, health-care and other public-service institutions. The proposed solution avoids comparisons of institutions that have substantially different clientele (intake).
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This paper studies the effect of changes in foreign competition on the structureof compensation and incentives of U.S. executives. We measure foreign competitionas import penetration and use tariffs and exchange rates as instrumental variables toestimate its causal effect on pay. We find that higher foreign competition leads tomore incentive provision in a variety of ways. First, it increases the sensitivity of payto performance. Second, it increases whithin-firm pay differentials between executivelevels, with CEOs typically experiencing the largest wage increases, partly becausethey receive the steepest incentive contracts. Finally, higher foreign competition is alsoassociated with a higher demand for talent. These results indicate that increased foreigncompetition can explain some of the recent trends in compensation structures.
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In spite of increasing representation of women in politics, little is known about their impact onpolicies. Comparing outcomes of parliaments with different shares of female members does not identifytheir causal impact because of possible differences in the underlying electorate. This paper usesa unique data set on voting decisions to sheds new light on gender gaps in policy making. Ouranalysis focuses on Switzerland, where all citizens can directly decide on a broad range of policiesin referendums and initiatives. We show that there are large gender gaps in the areas of health,environmental protection, defense spending and welfare policy which typically persist even conditionalon socio-economic characteristics. We also find that female policy makers have a substantial effect onthe composition of public spending, but a small effect on the overall size of government.
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Ontic structural realism is the view that structures are what is real in the first place in the domain of fundamental physics. The structures are usually conceived as including a primitive modality. However, it has not been spelled out as yet what exactly that modality amounts to. This paper proposes to fill this lacuna by arguing that the fundamental physical structures possess a causal essence, being powers. Applying the debate about causal vs. categorical properties in analytic metaphysics to ontic structural realism, I show that the standard argument against categorical and for causal properties holds for structures as well. Structural realism, as a position in the metaphysics of science that is a form of scientific realism, is committed to causal structures. The metaphysics of causal structures is supported by physics, and it can provide for a complete and coherent view of the world that includes all domains of empirical science.
Resumo:
Intuitively, we think of perception as providing us with direct cognitive access to physical objects and their properties. But this common sense picture of perception becomes problematic when we notice that perception is not always veridical. In fact, reflection on illusions and hallucinations seems to indicate that perception cannot be what it intuitively appears to be. This clash between intuition and reflection is what generates the puzzle of perception. The task and enterprise of unravelling this puzzle took, and still takes, centre stage in the philosophy of perception. The goal of my dissertation is to make a contribution to this enterprise by formulating and defending a new structural approach to perception and perceptual consciousness. The argument for my structural approach is developed in several steps. Firstly, I develop an empirically inspired causal argument against naïve and direct realist conceptions of perceptual consciousness. Basically, the argument says that perception and hallucination can have the same proximal causes and must thus belong to the same mental kind. I emphasise that this insight gives us good reasons to abandon what we are instinctively driven to believe - namely that perception is directly about the outside physical world. The causal argument essentially highlights that the information that the subject acquires in perceiving a worldly object is always indirect. To put it another way, the argument shows that what we, as perceivers, are immediately aware of, is not an aspect of the world but an aspect of our sensory response to it. A view like this is traditionally known as a Representative Theory of Perception. As a second step, emphasis is put on the task of defending and promoting a new structural version of the Representative Theory of Perception; one that is immune to some major objections that have been standardly levelled at other Representative Theories of Perception. As part of this defence and promotion, I argue that it is only the structural features of perceptual experiences that are fit to represent the empirical world. This line of thought is backed up by a detailed study of the intriguing phenomenon of synaesthesia. More precisely, I concentrate on empirical cases of synaesthetic experiences and argue that some of them provide support for a structural approach to perception. The general picture that emerges in this dissertation is a new perspective on perceptual consciousness that is structural through and through.