970 resultados para modèle causal contrefactuel


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Mode of access: Internet.

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Symptoms associated with pistachio dieback in Australia include decline (little or no current season growth), xylem staining in shoots two or more years old, trunk mu and limb lesions (often covered by black, superficial fungal growth), excessive exudation of resin, dieback and death of the tree. Bacteria belonging to the genus Xanthomonas have been suggested as the causal agent. To confirm the constant association between these bacteria and the disease syndrome, the absence of other pathogens and the identity of the pathogen, we performed a series of isolations and pathogenicity tests. The only microorganism consistently isolated from diseased tissue was a bacterium that produced yellow, mucoid colonies and displayed morphological and cultural characteristics typical of the genus Xanthomonas. Database comparisons of the fatty acid and whole-cell protein profiles of five representative pistachio isolates indicated that they all belonged to X. translucens, but it was not possible to allocate the isolates to pathovar. Pathogenicity tests on cereals and grasses supported this identification. However, Koch's postulates have been only partially fulfilled because not all symptoms associated with pistachio dieback were reproduced on inoculated two-year-old pistachio trees. While discolouration was observed, dieback, excessive resinous exudate and trunk and limb lesions were not produced; expression of these symptoms may be delayed, and long-term monitoring of a small number of inoculated trees is in progress.

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Individuals seeking compensation following traumatic brain injury (TBI) are often found to report a disproportionately high level of symptoms relative to objective indicators of impairment. Previous studies highlight that level of symptom reporting is also related to self-awareness, causal attribution, and emotional wellbeing. Therefore, the reasons for high symptom reporting in the context of compensation are generally unclear. This study aimed to identify whether self-awareness, causal attribution, and emotional wellbeing are significantly associated with level of symptom reporting after controlling for compensation status. A sample of 54 participants with TBI comprised two groups, namely, claimants (n = 27) and non-claimants (n = 27), who were similar in terms of demographic and neuro-cognitive variables. Participants completed the Symptom Expectancy Checklist, Hospital Anxiety Depression Scale, Awareness Questionnaire and a causal attribution scale. A series of independent t tests and Pearson's correlations identified that a higher level of symptom reporting was associated with the following: seeking compensation, less severe TBI, increased age, greater self-awareness, increased post-injury changes reported by relatives, a higher level of mood symptoms, and a tendency to blame other people. Multivariate analysis identified that after controlling for demographic, injury, and compensation status variables, level of mood symptoms and self-awareness were significantly associated with level of symptom reporting. The findings suggest that mood symptoms and heightened self-awareness are significantly related to high symptom reporting independent of compensation status, thus supporting the need for clinicians to interpret symptom reporting within a biopsychosocial context.

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An international collection of the sugarcane ratoon stunting disease pathogen, Leifsonia xyli subsp. xyli, was analysed to assess genetic diversity. DNA fingerprinting using BOX primers was performed on 105 isolates, comprising 65 Australian isolates and an additional 40 isolates from Indonesia (n = 8), Japan (n = 1), USA (n = 3), Brazil (n = 2), Mali (n = 2), Zimbabwe (n = 13), South Africa (n = 9) and Reunion (n = 2). Sixty-two of these isolates were also screened using ERIC primers. No variation was found among any of the isolates. The intergenic spacer (IGS) region of the ribosomal RNA genes from 54 isolates was screened for sequence variation using single-stranded conformational polymorphism (SSCP), but none was observed. Direct sequencing of the IGS from a subset of nine isolates, representing all of the countries sampled in this study, confirmed the results of the SSCP analysis. Likewise, no sequence variation was found in the 16S ribosomal RNA genes of the same subset. Four Colombian isolates from sugarcane, morphologically similar to L. xyli subsp. xyli, were putatively shown to be an undescribed Agrococcus species of unknown pathogenicity. The lack of genetic variation among L. xyli subsp. xyli isolates, independent of time of sampling, cultivar of isolation, or country of origin, suggests the worldwide spread of a single pathogenic clone, and further suggests that sugarcane cultivars resistant to ratoon stunting disease in one area should retain this property in other regions.

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Twelve years ago our understanding of ratoon stunting disease (RSD) was confined almost exclusively to diagnosis of the disease and control via farm hygiene, with little understanding of the biology of the interaction between the causal agent (Leifsonia xyli subsp. xyli) and the host plant sugarcane (Saccharum spp. hybrids). Since then, research has focused on developing the molecular tools to dissect L. xyli subsp. xyli, so that better control strategies can be developed to prevent losses from RSD. Within this review, we give a brief overview of the progression in research on L. xyli subsp. xyli and highlight future challenges. After a brief historical background on RSD, we discuss the development of molecular tools such as transformation and transposon mutagenesis and discuss the apparent lack of genetic diversity within the L. xyli subsp. xyli world population. We go on to discuss the sequencing of the genome of L. xyli subsp. xyli, describe the key findings and suggest some future research based on known deficiencies that will capitalise on this tremendous knowledge base to which we now have access.

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Tubercularia lateritia was recorded for the first time as causing canker, characterised by a sunken centre surrounded by galls or callus, on macadamia. The fungus was isolated and inoculated on young macadamia trees in the glasshouse and produced characteristic disease symptoms from which the fungus was successfully reisolated.

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This paper investigates the simultaneous causal relationship between investments in information and communication technology (ICT) and flows of foreign direct investment (FDI), with reference to its implications on economic growth. For the empirical analysis we use data from 23 major countries with heterogeneous economic development for the period 1976-99. Our causality test results suggest that there is a causal relationship from ICT to FDI in developed countries, which means that a higher level of ICT investment leads to an increase inflow of FDI. ICT may contribute to economic growth indirectly by attracting more FDI. Contrarily, we could not find significant causality from ICT to FDI in developing countries. Instead, we have partial evidence of opposite causality relationship: the inflow of FDI causes further increases in ICT investment and production capacity. © United Nations University 2006.

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Causal mapping can help managers to think through the causal influence between issues, enabling them to base a decision on a more structured consideration. Even in regular meetings, learning and the integration of knowledge from diverse stakeholders can benefit from causal mapping. Four causal mapping meetings with management teams are analysed to assess how managers thought causally about their environment when strategy-making. We found that although managers can use other views to expand their environmental knowledge, some prefer to use familiar information rather than less familiar information. Despite this preference, many managers thought systemically about a raft of related issues. We discuss our findings in the context of regular meetings and offer improvements to the facilitation of group causal mapping.

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This paper proposes, and begins to evaluate, a format of brainstorming-type activity which aims to release the creativity of participants and encourage them to learn about a wider range of issues in more detail. The format does this through providing a two-stage brainstorming session. After the first brainstorm, participants have an opportunity to both piggy-back off other peoples ideas (i.e. create new ideas by synthesising other peoples' ideas into their own perspectives), and share causal links to build a causal map with the brainstormed ideas. Five causal mapping sessions with organisations have been analysed. Findings suggest that ideas shared when piggy-backing are often highly creative and unique for the participant who shared them. Also piggy-backing and causal linking seem to provide effective opportunities for individual learning as participants have time to reflect upon other peoples' perspectives and share their own views on those.

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. FDI, Trade and Growth, a Causal Link? (RP0710) Prof Nigel DRIFFIELD Dr Rakesh BISSOONDEEAL Mayang Pramadhani Non-technical Summary This paper explores the relationship between imports, exports, foreign direct investment and growth. For some time there has been a good deal of debate whether trade and foreign direct investment) FDI are substitutes and complements, with the existing literature generating some rather contradictory findings. We show, for Indonesia that inward FDI and both imports and exports are complementary, and further that FDI causes an increase in trade. This is of particular interest for a country such as Indonesia, that has attracted a high proportion of export-orientated inward investment. This, theoretically at least is associated with an increase in imports, in the form of capital goods and components, but a reduction in imports. We show that the previous literature that fails to find such a relationship does so because both trade and FDI are associated with growth, and previous work ignores these growth effects when seeking to isolate the relationship between trade and FDI.

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Neuroimaging studies have consistently shown that working memory (WM) tasks engage a distributed neural network that primarily includes the dorsolateral prefrontal cortex, the parietal cortex, and the anterior cingulate cortex. The current challenge is to provide a mechanistic account of the changes observed in regional activity. To achieve this, we characterized neuroplastic responses in effective connectivity between these regions at increasing WM loads using dynamic causal modeling of functional magnetic resonance imaging data obtained from healthy individuals during a verbal n-back task. Our data demonstrate that increasing memory load was associated with (a) right-hemisphere dominance, (b) increasing forward (i.e., posterior to anterior) effective connectivity within the WM network, and (c) reduction in individual variability in WM network architecture resulting in the right-hemisphere forward model reaching an exceedance probability of 99% in the most demanding condition. Our results provide direct empirical support that task difficulty, in our case WM load, is a significant moderator of short-term plasticity, complementing existing theories of task-related reduction in variability in neural networks. Hum Brain Mapp, 2013. © 2013 Wiley Periodicals, Inc.