Demographic bottlenecks in tropical plant regeneration: A comparative analysis of causal influences

Mortality factors that act sequentially through the demographic transitions from seed to sapling may have critical effects on recruitment success. Understanding how habitat heterogeneity influences the causal factors that limit propagule establishment in natural populations is central to assess these demographic bottlenecks and their consequences. Bamboos often influence forest structure and dynamics and are a major factor in generating landscape complexity and habitat heterogeneity in tropical forests. To understand how patch heterogeneity influences plant recruitment we studied critical establishment stages during early recruitment of Euterpe edulis, Sloanea guianensis and Virola bicuhyba in bamboo and non-bamboo stands in the Brazilian Atlantic forest. We combined observational studies of seed rain and seedling emergence with seed addition experiments to evaluate the transition probabilities among regeneration stages within bamboo and non-bamboo stands. The relative importance of each mortality factor was evaluated by determining how the loss of propagules affected stage-specific recruitment success. Our results revealed that the seed addition treatment significantly increased seedling survivorship for all three species. E. edulis seedling survival probability increased in the addition treatment in the two stand types. However, for S. guianensis and V. bicuhyba this effect depended strongly on artificially protecting the seeds, as both species experienced increased seed and seedling losses due to post-dispersal seed predators and herbivores. Propagules of all three species had a greater probability of reaching subsequent recruitment stages when protected. The recruitment of large-seeded V. bicuhyba and E. edulis appears to be much more limited by post-dispersal factors than by dispersal limitation, whereas the small-seeded S. guianensis showed an even stronger effect of post-dispersal factors causing recruitment collapse in some situations. We demonstrated that E. edulis, S. guianensis and V. bicuhyba are especially susceptible to predation during early compared with later establishment stages and this early stage mortality can be more crucial than stand differences as determinants of successful regeneration. Among-species differences in the relative importance of dispersal vs. establishment limitation are mediated by variability in species responses to patch heterogeneity. Thus, bamboo effects on the early recruitment of non-bamboo species are patchy and species-specific, with successional bamboo patches exerting a far-reaching influence on the heterogeneity of plant species composition and abundance. © 2012 Perspectives in Plant Ecology, Evolution and Systematics.

Caracterização de Rhizoctonia solani Kühn, agente causal da mela da soja (Glycine max (L.) Merrill), seleção de genótipos e controle químico

Pós-graduação em Agronomia (Proteção de Plantas) - FCA

Effects of UV-B radiation on Lecanicillium spp., biological control agents of the coffee leaf rust pathogen

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A sequential Cox approach for estimating the causal effect of treatment in the presence of time-dependent confounding applied to data from the Swiss HIV Cohort Study

When estimating the effect of treatment on HIV using data from observational studies, standard methods may produce biased estimates due to the presence of time-dependent confounders. Such confounding can be present when a covariate, affected by past exposure, is both a predictor of the future exposure and the outcome. One example is the CD4 cell count, being a marker for disease progression for HIV patients, but also a marker for treatment initiation and influenced by treatment. Fitting a marginal structural model (MSM) using inverse probability weights is one way to give appropriate adjustment for this type of confounding. In this paper we study a simple and intuitive approach to estimate similar treatment effects, using observational data to mimic several randomized controlled trials. Each 'trial' is constructed based on individuals starting treatment in a certain time interval. An overall effect estimate for all such trials is found using composite likelihood inference. The method offers an alternative to the use of inverse probability of treatment weights, which is unstable in certain situations. The estimated parameter is not identical to the one of an MSM, it is conditioned on covariate values at the start of each mimicked trial. This allows the study of questions that are not that easily addressed fitting an MSM. The analysis can be performed as a stratified weighted Cox analysis on the joint data set of all the constructed trials, where each trial is one stratum. The model is applied to data from the Swiss HIV cohort study.

The Effects of Self-Esteem and Expectancies for Success on Affective Reactions to Achievement

Affective reactions to academic performance appear to be influenced by performance outcome, self-esteem, and causal attributions. We investigated whether expectancies for success and the confirmation or disconfirmation of epectancies also influenced students' affective reactions and causal attributions in achievement settings. Subjects were 132 university students. Causal attributions and affective reactions to an achievement-related situation were assessed and related to students' self-esteem, expectancies for success, and confirmation or disconfirmation of expectancies. Results indicated that causal attributions were related to confirmation or disconfirmation of expectancies for success and to self-esteem. Affective reactions were related to the interaction of self-esteem, expectancies for success, and confirmation or disconfirmation of expectancies. Further analysis suggested that students' affective reactions to performance may serve to maintain existing levels of self-esteem. The role of self-referent and other-referent emotions in self-esteem maintenance was also discussed.

On Causal Mediation Analysis with a Survival Outcome

Suppose that having established a marginal total effect of a point exposure on a time-to-event outcome, an investigator wishes to decompose this effect into its direct and indirect pathways, also know as natural direct and indirect effects, mediated by a variable known to occur after the exposure and prior to the outcome. This paper proposes a theory of estimation of natural direct and indirect effects in two important semiparametric models for a failure time outcome. The underlying survival model for the marginal total effect and thus for the direct and indirect effects, can either be a marginal structural Cox proportional hazards model, or a marginal structural additive hazards model. The proposed theory delivers new estimators for mediation analysis in each of these models, with appealing robustness properties. Specifically, in order to guarantee ignorability with respect to the exposure and mediator variables, the approach, which is multiply robust, allows the investigator to use several flexible working models to adjust for confounding by a large number of pre-exposure variables. Multiple robustness is appealing because it only requires a subset of working models to be correct for consistency; furthermore, the analyst need not know which subset of working models is in fact correct to report valid inferences. Finally, a novel semiparametric sensitivity analysis technique is developed for each of these models, to assess the impact on inference, of a violation of the assumption of ignorability of the mediator.

[Effects of tobacco use on systemic health: relevant information for dentistry (II)--part 2: cardiovascular diseases and public health issues]

This is the sixth and concluding part of a series of publications from the Swiss task force named "Smoking - Intervention in the private dental office" on the topic "tobacco use and dental medicine". The focus of this review is the effects of smoking for the development of atherosclerosis as pathohistological correlate for acute coronary syndrome (ACS), arterial occlusive disease, and cerebrovascular diseases (stroke). Additionally, a causal relationship between tobacco use and an increased rate for complications during pregnancy and child birth will be discussed. Next to causal therapy of local and systemic diseases in general, an emphasis must be given to tobacco use prevention and cessation. Finally, important public health issues concerning smoking and tobacco use will be demonstrated, and options to improve the current situation will be presented.

[Effects of tobacco use on general health: relevant information for dentistry (I)--part 1: pulmonary diseases and other malignancies]

This fifth part of a series of publications from the Swiss task force named "Smoking--Intervention in the private dental office" on the topic "tobacco use and dental medicine" focuses on the effects of tobacco use on general health. A significant increase of tobacco use associated morbidity and mortality for many cardiovascular and pulmonary diseases has been well documented in the literature. In this review, the epidemiologic background as well as the pathophysiological fundamentals for tobacco-mediated pulmonary diseases is presented, focusing especially on chronic obstructive pulmonary disease (COPD) and lung cancer. In addition, a causal relationship between nicotine abuse and an increased carcinoma incidence for other malignancies but lung cancer will be discussed. Regarding the evidence in the present literature, it is undisputable that smoking is the most preventable cause for COPD and lung cancer.

Fit between situational and dispositional goal orientation, and its effects on flow experience and affective well-being during sports.

Flow represents an optimal psychological state that is intrinsically rewarding. However, to date only a few studies have investigated the conditions for flow in sports. The present research aims to expand our understanding of the psychological factors that promote the flow experience in sports, focusing on the person-goal fit, or more precisely on the athletes’ situational and dispositional goal orientations. We hypothesize that a fit between an athlete’s situational and dispositional approach versus avoidance goal orientation should promote flow, whereas a non-fit will hinder flow during sports. In addition to the flow experience, we hypothesize that an athlete’s affective well-being is also affected by the person-goal fit. Here our assumptions are theoretically rooted in research on person-environment fit. An experimental study in an ecologically valid sport setting was conducted in order to draw causal conclusions and derive useful strategies for the practice of sports. Specifically, we investigated 67 male soccer players from a regional amateur league during a regular training session. They were randomly assigned to an approach or avoidance goal group and asked to take five penalty shots. Immediately afterwards, their flow experience and affective well-being during the penalty shootout were measured. As predicted, soccer players with a strong dispositional approach goal orientation experienced more flow and reported higher affective well-being when they were assigned to the approach goal. In contrast, soccer players with a strong dispositional avoidance goal orientation benefited from being assigned an avoidance goal in terms of their flow experience and affective well-being. The results are discussed critically with respect to their theoretical and practical implications.

Status and Causal Pathway Assessments Supporting River Basin Management

The European Water Framework Directive (WFD) requires a status assessment of all water bodies. If that status is deteriorated, the WFD urges the identification of its potential causes in order to be able to suggest appropriate management measures. The instrument of investigative monitoring allows for such identification, provided that appropriate tools are available to link the observed effects to causative stressors, while unravelling confounding factors. In this chapter, the state of the art of status and causal pathway assessment is described for the major stressors responsible for the deterioration of European water bodies, i.e. toxicity, acidification, salinisation, eutrophication and oxygen depletion, parasites and pathogens, invasive alien species, hydromorphological degradation, changing water levels as well as sediments and suspended matter. For each stressor, an extensive description of the potential effects on the ecological status is given. Secondly, stressor-specific abiotic and biotic indicators are described that allow for a first indication of probable causes, based on the assessment of available monitoring data. Subsequently, more advanced tools for site-specific confirmation of stressors at hand are discussed. Finally, the local status assessments are put into the perspective of the risk for downstream stretches in order to be able to prioritise stressors and to be able to select appropriate measures for mitigation of the risks resulting from these stressors.

The Democratizing Effects of Multilateral Organizations: A Cautionary Note on the WTO

The field of international relations has been obsessed with democracy and democratization and its effects on international cooperation for a long time. More recently, research has turned its focus on how international organizations enhance democracy. This article contributes to this debate and applies a prominent liberal framework to study the ‘outside-in’ effects of the World Trade Organization. The article offers a critical reading of democratization through IO membership. It provides for an assessment of the dominant framework put forward by Keohane et al. (2009). In doing so, it develops a set of empirical strategies to test conjectured causal mechanisms with respect to the WTO, and illustrates the potential application by drawing on selected empirical evidence from trade politics. Finally, it proposes a number of analytical revisions to the liberal framework and outlines avenues for future research.

Time-course of "off-line" prefrontal rTMS effects--a PET study.

Low-frequency "off-line" repetitive transcranial magnetic stimulation (rTMS) over the course of several minutes has attained considerable attention as a research tool in cognitive neuroscience due to its ability to induce functional disruptions of brain areas. This disruptive rTMS effect is highly valuable for revealing a causal relationship between brain and behavior. However, its influence on remote interconnected areas and, more importantly, the duration of the induced neurophysiological effects, remain unknown. These aspects are critical for a study design in the context of cognitive neuroscience. In order to investigate these issues, 12 healthy male subjects underwent 8 H(2)(15)O positron emission tomography (PET) scans after application of long-train low-frequency rTMS to the right dorsolateral prefrontal cortex (DLPFC). Immediately after the stimulation train, regional cerebral blood flow (rCBF) increases were present under the stimulation site as well as in other prefrontal cortical areas, including the ventrolateral prefrontal cortex (VLPFC) ipsilateral to the stimulation site. The mean increases in rCBF returned to baseline within 9 min. The duration of this unilateral prefrontal rTMS effect on rCBF is of particular interest to those who aim to influence behavior in cognitive paradigms that use an "off-line" approach.

Survival effects of inferior vena cava filter in patients with acute symptomatic venous thromboembolism and a significant bleeding risk.

OBJECTIVES The purpose of this study was to investigate the survival effects of inferior vena cava filters in patients with venous thromboembolism (VTE) who had a significant bleeding risk. BACKGROUND The effectiveness of inferior vena cava filter use among patients with acute symptomatic VTE and known significant bleeding risk remains unclear. METHODS In this prospective cohort study of patients with acute VTE identified from the RIETE (Computerized Registry of Patients With Venous Thromboembolism), we assessed the association between inferior vena cava filter insertion for known significant bleeding risk and the outcomes of all-cause mortality, pulmonary embolism (PE)-related mortality, and VTE rates through 30 days after the initiation of VTE treatment. Propensity score matching was used to adjust for the likelihood of receiving a filter. RESULTS Of the 40,142 eligible patients who had acute symptomatic VTE, 371 underwent filter placement because of known significant bleeding risk. A total of 344 patients treated with a filter were matched with 344 patients treated without a filter. Propensity score-matched pairs showed a nonsignificant trend toward lower risk of all-cause death for filter insertion compared with no insertion (6.6% vs. 10.2%; p = 0.12). The risk-adjusted PE-related mortality rate was lower for filter insertion than no insertion (1.7% vs. 4.9%; p = 0.03). Risk-adjusted recurrent VTE rates were higher for filter insertion than for no insertion (6.1% vs. 0.6%; p < 0.001). CONCLUSIONS In patients presenting with VTE and with a significant bleeding risk, inferior vena cava filter insertion compared with anticoagulant therapy was associated with a lower risk of PE-related death and a higher risk of recurrent VTE. However, study design limitations do not imply a causal relationship between filter insertion and outcome.

Cage-induced stereotypies, perseveration and the effects of environmental enrichment in laboratory mice.

When kept in barren and restrictive cages, animals frequently develop stereotypic behaviour patterns that are characterized by high repetition rates, conspicuous invariance and an apparent lack of function. Although millions of animals are affected, the underlying causes and mechanisms are still unclear. Growing evidence suggests that cage-induced stereotypies may reflect pathological dysfunction within basal ganglia circuitry expressed by perseverative behaviour. In order to assess whether variation in stereotypy performance and variation in perseverative behaviour may have a common cause in ICR CD-1 mice, we assessed the effects of environmental enrichment on both phenomena. We raised 48 female ICR CD-1 mice in standard or enriched cages from three weeks to either 6 or 11 months of age and measured stereotypy level in the home cage and perseveration on an extinction task. We further examined whether enriched rearing conditions (early enrichment) protect mice from the developing stereotypies later in life and whether stereotypies developed in barren cages would persist in an enriched environment (late enrichment) by transferring standard mice to enriched cages and vice versa for 14 weeks after completion of the extinction task. We found no evidence for a causal relation between stereotypy and perseveration in mice. However, transfer to enriched cages reduced stereotypy levels significantly both at 6 and 11 months of age indicating that stereotypies had not become established yet. Finally, we found that removing enrichments at both ages did not induce higher stereotypy levels, thereby confirming earlier reports of a neuroprotective effect of early enrichment.

Effects of congressional modernization laws on public access to innovative medical device technologies

The Federal Food and Drug Administration (FDA) and the Centers for Medicare and Medicaid (CMS) play key roles in making Class III, medical devices available to the public, and they are required by law to meet statutory deadlines for applications under review. Historically, both agencies have failed to meet their respective statutory requirements. Since these failures affect patient access and may adversely impact public health, Congress has enacted several “modernization” laws. However, the effectiveness of these modernization laws has not been adequately studied or established for Class III medical devices. ^ The aim of this research study was, therefore, to analyze how these modernization laws may have affected public access to medical devices. Two questions were addressed: (1) How have the FDA modernization laws affected the time to approval for medical device premarket approval applications (PMAs)? (2) How has the CMS modernization law affected the time to approval for national coverage decisions (NCDs)? The data for this research study were collected from publicly available databases for the period January 1, 1995, through December 31, 2008. These dates were selected to ensure that a sufficient period of time was captured to measure pre- and post-modernization effects on time to approval. All records containing original PMAs were obtained from the FDA database, and all records containing NCDs were obtained from the CMS database. Source documents, including FDA premarket approval letters and CMS national coverage decision memoranda, were reviewed to obtain additional data not found in the search results. Analyses were conducted to determine the effects of the pre- and post-modernization laws on time to approval. Secondary analyses of FDA subcategories were conducted to uncover any causal factors that might explain differences in time to approval and to compare with the primary trends. The primary analysis showed that the FDA modernization laws of 1997 and 2002 initially reduced PMA time to approval; after the 2002 modernization law, the time to approval began increasing and continued to increase through December 2008. The non-combined, subcategory approval trends were similar to the primary analysis trends. The combined, subcategory analysis showed no clear trends with the exception of non-implantable devices, for which time to approval trended down after 1997. The CMS modernization law of 2003 reduced NCD time to approval, a trend that continued through December 2008. This study also showed that approximately 86% of PMA devices do not receive NCDs. ^ As a result of this research study, recommendations are offered to help resolve statutory non-compliance and access issues, as follows: (1) Authorities should examine underlying causal factors for the observed trends; (2) Process improvements should be made to better coordinate FDA and CMS activities to include sharing data, reducing duplication, and establishing clear criteria for “safe and effective” and “reasonable and necessary”; (3) A common identifier should be established to allow tracking and trending of applications between FDA and CMS databases; (4) Statutory requirements may need to be revised; and (5) An investigation should be undertaken to determine why NCDs are not issued for the majority of PMAs. Any process improvements should be made without creating additional safety risks and adversely impacting public health. Finally, additional studies are needed to fully characterize and better understand the trends identified in this research study.^