198 resultados para Individual-based modeling
Resumo:
Recent studies have pointed out a similarity between tectonics and slope tectonic-induced structures. Numerous studies have demonstrated that structures and fabrics previously interpreted as of purely geodynamical origin are instead the result of large slope deformation, and this led in the past to erroneous interpretations. Nevertheless, their limit seems not clearly defined, but it is somehow transitional. Some studies point out continuity between failures developing at surface with upper crust movements. In this contribution, the main studies which examine the link between rock structures and slope movements are reviewed. The aspects regarding model and scale of observation are discussed together with the role of pre-existing weaknesses in the rock mass. As slope failures can develop through progressive failure, structures and their changes in time and space can be recognized. Furthermore, recognition of the origin of these structures can help in avoiding misinterpretations of regional geology. This also suggests the importance of integrating different slope movement classifications based on distribution and pattern of deformation and the application of structural geology techniques. A structural geology approach in the landslide community is a tool that can greatly support the hazard quantification and related risks, because most of the physical parameters, which are used for landslide modeling, are derived from geotechnical tests or the emerging geophysical approaches.
Resumo:
BACKGROUND AND AIMS: Data from the literature reveal the contrasting influences of family members and friends on the survival of old adults. On one hand, numerous studies have reported a positive association between social relationships and survival. On the other, ties with children may be associated with an increased risk of disability, whereas ties with friends or other relatives tend to improve survival. A five-year prospective, population-based study of 295 Swiss octogenarians tested the hypothesis that having a spouse, siblings or close friends, and regular contacts with relatives or friends are associated with longer survival, even at a very old age. METHODS: Data were collected through individual interviews, and a Cox regression model was applied to assess the effects of kinship and friendship networks on survival, after adjusting for socio-demographic and health-related variables. RESULTS: Our analyses indicate that the presence of a spouse in the household is not significantly related to survival, whereas the presence of siblings at baseline improves the oldest old's chances of surviving five years later. Moreover, the existence of close friends is a central component in the patterns of social relationships of oldest adults, and one which is significantly associated with survival. Overall, the protective effect of social relationships on survival is more related to the quality of those relationships (close friends) than to the frequency of relationships (regular contacts). CONCLUSIONS: We hypothesize that the existence of siblings or close friends may beneficially affect survival, due to the potential influence on the attitudes of octogenarians regarding health practices and adaptive strategies.
Resumo:
Individuals need to adapt to their local environment in order to survive. When selection pressures differ in local populations, polymorphism can evolve. Colour polymorphism is one of the most obvious polymorphisms since it is readily observable. Different sources of colouration exist, but melanin-based colouration is one of the most common in birds. The melanocortin system produces this colouration and because the melanocortin system has pleiotropic effects on behavioural and physiological traits, it is a good candidate to be an underlying mechanism to explain the maintenance of colour polymorphism. In this thesis I studied three different raptors which all display melanin-based colouration; barn owls (Tyto alba), tawny owls (Strix aluco) and Eurasian kestrels (Falco tinnunculus). The main question was if there was a relationship between melanin-based colouration and individual behavioural differences. The underlying hypothesis is that colour could be a signal of certain adaptive traits. Our goal was to find evolutionary explanations for the persistence of colour polymorphism. I found that nestling kestrels and barn owls differ in anti-predatory behaviour, with respect to their melanic colouration (chapters 1 and 2). Darker individuals show less reaction to human handling, but in kestrels aggression and colouration are related in opposite ways than in barn owls. More reddish barn owls travel greater distances in natal dispersal and this behaviour is repeatable between parents and same sex offspring (chapter 3). Dark reddish tawny owls defend their nests more intensely against intruders and appear to suffer less from nest predation (chapter 4). Finally I show that polymorphism in the Melanocortin 1 receptor gene (MC1R), which is strongly correlated with reddish colouration in the barn owl, is related to natal dispersal distance, providing a first indication for a genetic basis of the relation between this behaviour and colouration (chapter 5). My results demonstrate a clear link between melanin-based colouration and animal personality traits. I demonstrated this relation in three different species, which shows there is most likely a general underlying mechanism responsible. Different predation pressures might have shaped the reactions to predation, but also differences in sex-related colouration. Male-like and female-like colouration might signal more or less aggressive behaviour. Fluctuating environmental conditions might cause different individual strategies to produce equal reproductive success. The melanocortin system with its pleiotropic effects might be an underlying mechanism, as suggested by the results from the genetic polymorphism, the similar results found in these three species and by the similar relations reported in other species. This thesis demonstrates that colouration and individual differences are correlated and it provides the first glimpse of an underlying system. We can now conduct a more directed search for underlying mechanisms and evolutionary explanations with the use of quantitative genetic methods.
Resumo:
In the context of the investigation of the use of automated fingerprint identification systems (AFIS) for the evaluation of fingerprint evidence, the current study presents investigations into the variability of scores from an AFIS system when fingermarks from a known donor are compared to fingerprints that are not from the same source. The ultimate goal is to propose a model, based on likelihood ratios, which allows the evaluation of mark-to-print comparisons. In particular, this model, through its use of AFIS technology, benefits from the possibility of using a large amount of data, as well as from an already built-in proximity measure, the AFIS score. More precisely, the numerator of the LR is obtained from scores issued from comparisons between impressions from the same source and showing the same minutia configuration. The denominator of the LR is obtained by extracting scores from comparisons of the questioned mark with a database of non-matching sources. This paper focuses solely on the assignment of the denominator of the LR. We refer to it by the generic term of between-finger variability. The issues addressed in this paper in relation to between-finger variability are the required sample size, the influence of the finger number and general pattern, as well as that of the number of minutiae included and their configuration on a given finger. Results show that reliable estimation of between-finger variability is feasible with 10,000 scores. These scores should come from the appropriate finger number/general pattern combination as defined by the mark. Furthermore, strategies of obtaining between-finger variability when these elements cannot be conclusively seen on the mark (and its position with respect to other marks for finger number) have been presented. These results immediately allow case-by-case estimation of the between-finger variability in an operational setting.
Resumo:
Objectives: The study objective was to derive reference pharmacokinetic curves of antiretroviral drugs (ART) based on available population pharmacokinetic (Pop-PK) studies that can be used to optimize therapeutic drug monitoring guided dosage adjustment.¦Methods: A systematic search of Pop-PK studies of 8 ART in adults was performed in PubMed. To simulate reference PK curves, a summary of the PK parameters was obtained for each drug based on meta-analysis approach. Most models used one-compartment model, thus chosen as reference model. Models using bi-exponential disposition were simplified to one-compartment, since the first distribution phase was rapid and not determinant for the description of the terminal elimination phase, mostly relevant for this project. Different absorption were standardized for first-order absorption processes.¦Apparent clearance (CL), apparent volume of distribution of the terminal phase (Vz) and absorption rate constant (ka) and inter-individual variability were pooled into summary mean value, weighted by number of plasma levels; intra-individual variability was weighted by number of individuals in each study.¦Simulations based on summary PK parameters served to construct concentration PK percentiles (NONMEM®).¦Concordance between individual and summary parameters was assessed graphically using Forest-plots. To test robustness, difference in simulated curves based on published and summary parameters was calculated using efavirenz as probe drug.¦Results: CL was readily accessible from all studies. For studies with one-compartment, Vz was central volume of distribution; for two-compartment, Vz was CL/λz. ka was directly used or derived based on the mean absorption time (MAT) for more complicated absorption models, assuming MAT=1/ka.¦The value of CL for each drug was in excellent agreement throughout all Pop-PK models, suggesting that minimal concentration derived from summary models was adequately characterized. The comparison of the concentration vs. time profile for efavirenz between published and summary PK parameters revealed not more than 20% difference. Although our approach appears adequate for estimation of elimination phase, the simplification of absorption phase might lead to small bias shortly after drug intake.¦Conclusions: Simulated reference percentile curves based on such an approach represent a useful tool for interpretating drug concentrations. This Pop-PK meta-analysis approach should be further validated and could be extended to elaborate more sophisticated computerized tool for the Bayesian TDM of ART.
Resumo:
The generation of an antigen-specific T-lymphocyte response is a complex multi-step process. Upon T-cell receptor-mediated recognition of antigen presented by activated dendritic cells, naive T-lymphocytes enter a program of proliferation and differentiation, during the course of which they acquire effector functions and may ultimately become memory T-cells. A major goal of modern immunology is to precisely identify and characterize effector and memory T-cell subpopulations that may be most efficient in disease protection. Sensitive methods are required to address these questions in exceedingly low numbers of antigen-specific lymphocytes recovered from clinical samples, and not manipulated in vitro. We have developed new techniques to dissect immune responses against viral or tumor antigens. These allow the isolation of various subsets of antigen-specific T-cells (with major histocompatibility complex [MHC]-peptide multimers and five-color FACS sorting) and the monitoring of gene expression in individual cells (by five-cell reverse transcription-polymerase chain reaction [RT-PCR]). We can also follow their proliferative life history by flow-fluorescence in situ hybridization (FISH) analysis of average telomere length. Recently, using these tools, we have identified subpopulations of CD8+ T-lymphocytes with distinct proliferative history and partial effector-like properties. Our data suggest that these subsets descend from recently activated T-cells and are committed to become differentiated effector T-lymphocytes.
Resumo:
Many antidepressants have been introduced as racemic drugs, the enantiomers of which may differ in some of their pharmacodynamic and pharmacokinetic properties. This review argues that each enantiomer of a chiral antidepressant should be evaluated according to its individual characteristics rather than by extrapolation from the racemate, or by assumptions based on the stereoselective characteristics of other enantiomeric drugs. For example, in some cases the enantiomers' pharmacodynamic and therapeutic properties can be complementary, which suggests that the racemate should be used clinically. In other cases where enantiomers show qualitatively similar but quantitatively different properties to the racemate, using a single enantiomer might be more appropriate. In yet further cases, a distomer may induce the metabolism of the eutomer, enantiomers may be metabolised by different enzymes, there may be a different profile of drug-drug interactions, and therapeutic drug monitoring may be simpler. Therefore, this review exemplifies the principle that each enantiomer of a chiral antidepressant should be evaluated according to its individual pharmacological, pharmacokinetic and pharmacogenetic characteristics. These factors are discussed in relation to five chiral antidepressants: trimipramine, mianserin, mirtazapine, fluoxetine and citalopram. It is hoped that an appreciation of the stereoselective differences between enantiomers will facilitate improvements in the benefit:risk ratio of drugs used in the management of depression.
Resumo:
ABSTRACT: BACKGROUND: The prevalence of obesity has increased in societies of all socio-cultural backgrounds. To date, guidelines set forward to prevent obesity have universally emphasized optimal levels of physical activity. However there are few empirical data to support the assertion that low levels of energy expenditure in activity is a causal factor in the current obesity epidemic are very limited. METHODS: The Modeling the Epidemiologic Transition Study (METS) is a cohort study designed to assess the association between physical activity levels and relative weight, weight gain and diabetes and cardiovascular disease risk in five population-based samples at different stages of economic development. Twenty-five hundred young adults, ages 25-45, were enrolled in the study; 500 from sites in Ghana, South Africa, Seychelles, Jamaica and the United States. At baseline, physical activity levels were assessed using accelerometry and a questionnaire in all participants and by doubly labeled water in a subsample of 75 per site. We assessed dietary intake using two separate 24-h recalls, body composition using bioelectrical impedance analysis, and health history, social and economic indicators by questionnaire. Blood pressure was measured and blood samples collected for measurement of lipids, glucose, insulin and adipokines. Full examination including physical activity using accelerometry, anthropometric data and fasting glucose will take place at 12 and 24 months. The distribution of the main variables and the associations between physical activity, independent of energy intake, glucose metabolism and anthropometric measures will be assessed using cross-section and longitudinal analysis within and between sites. DISCUSSION: METS will provide insight on the relative contribution of physical activity and diet to excess weight, age-related weight gain and incident glucose impairment in five populations' samples of young adults at different stages of economic development. These data should be useful for the development of empirically-based public health policy aimed at the prevention of obesity and associated chronic diseases.
Resumo:
Initial topography and inherited structural discontinuities are known to play a dominant role in rock slope stability. Previous 2-D physical modeling results demonstrated that even if few preexisting fractures are activated/propagated during gravitational failure all of those heterogeneities had a great influence on mobilized volume and its kinematics. The question we address in the present study is to determine if such a result is also observed in 3-D. As in 2-D previous models we examine geologically stable model configuration, based upon the well documented landslide at Randa, Switzerland. The 3-D models consisted of a homogeneous material in which several fracture zones were introduced in order to study simplified but realistic configurations of discontinuities (e.g. based on natural example rather than a parametric study). Results showed that the type of gravitational failure (deep-seated landslide or sequential failure) and resulting slope morphology evolution are the result of the interplay of initial topography and inherited preexisting fractures (orientation and density). The three main results are i) the initial topography exerts a strong control on gravitational slope failure. Indeed in each tested configuration (even in the isotropic one without fractures) the model is affected by a rock slide, ii) the number of simulated fracture sets greatly influences the volume mobilized and its kinematics, and iii) the failure zone involved in the 1991 event is smaller than the results produced by the analog modeling. This failure may indicate that the zone mobilized in 1991 is potentially only a part of a larger deep-seated landslide and/or wider deep seated gravitational slope deformation.
Resumo:
This review on intra-individual factors affecting drug metabolism completes our series on the biochemistry of drug metabolism. The article presents the molecular mechanisms causing intra-individual differences in enzyme expression and activity. They include enzyme induction by transcriptional activation and enzyme inhibition on the protein level. The influencing factors are of physiological, pathological, or external origin. Tissue characteristics and developmental age strongly influence enzyme-expression patterns. Further influencing factors are pregnancy, disease, or biological rhythms. Xenobiotics, drugs, constituents of herbal remedies, food constituents, ethanol, and tobacco can all influence enzyme expression or activity and, hence, affect drug metabolism.
Resumo:
Doping with natural steroids can be detected by evaluating the urinary concentrations and ratios of several endogenous steroids. Since these biomarkers of steroid doping are known to present large inter-individual variations, monitoring of individual steroid profiles over time allows switching from population-based towards subject-based reference ranges for improved detection. In an Athlete Biological Passport (ABP), biomarkers data are collated throughout the athlete's sporting career and individual thresholds defined adaptively. For now, this approach has been validated on a limited number of markers of steroid doping, such as the testosterone (T) over epitestosterone (E) ratio to detect T misuse in athletes. Additional markers are required for other endogenous steroids like dihydrotestosterone (DHT) and dehydroepiandrosterone (DHEA). By combining comprehensive steroid profiles composed of 24 steroid concentrations with Bayesian inference techniques for longitudinal profiling, a selection was made for the detection of DHT and DHEA misuse. The biomarkers found were rated according to relative response, parameter stability, discriminative power, and maximal detection time. This analysis revealed DHT/E, DHT/5β-androstane-3α,17β-diol and 5α-androstane-3α,17β-diol/5β-androstane-3α,17β-diol as best biomarkers for DHT administration and DHEA/E, 16α-hydroxydehydroepiandrosterone/E, 7β-hydroxydehydroepiandrosterone/E and 5β-androstane-3α,17β-diol/5α-androstane-3α,17β-diol for DHEA. The selected biomarkers were found suitable for individual referencing. A drastic overall increase in sensitivity was obtained. The use of multiple markers as formalized in an Athlete Steroidal Passport (ASP) can provide firm evidence of doping with endogenous steroids.
Resumo:
While the past decades were marked by an increased interest for the existential situation of man suffering from disease, the mechanisms alienating the patient from himself and from his context have been poorly investigated. These mechanisms, though operating in a dynamic interaction, will be discussed here sequentially. The first part of this article focuses on individual mechanisms of alienation emerging from the relationship the patient establishes with his body and psyche and on those related to his relational context. The aim is not to comprehensively describe these phenomena, but to discuss--based on clinical vignettes--some examples and their implications. The second part of the article describes some mechanisms of alienation that are incorporated in the medical apparatus and the dominant discourses.
Resumo:
Mountains and mountain societies provide a wide range of goods and services to humanity, but they are particularly sensitive to the effects of global environmental change. Thus, the definition of appropriate management regimes that maintain the multiple functions of mountain regions in a time of greatly changing climatic, economic, and societal drivers constitutes a significant challenge. Management decisions must be based on a sound understanding of the future dynamics of these systems. The present article reviews the elements required for an integrated effort to project the impacts of global change on mountain regions, and recommends tools that can be used at 3 scientific levels (essential, improved, and optimum). The proposed strategy is evaluated with respect to UNESCO's network of Mountain Biosphere Reserves (MBRs), with the intention of implementing it in other mountain regions as well. First, methods for generating scenarios of key drivers of global change are reviewed, including land use/land cover and climate change. This is followed by a brief review of the models available for projecting the impacts of these scenarios on (1) cryospheric systems, (2) ecosystem structure and diversity, and (3) ecosystem functions such as carbon and water relations. Finally, the cross-cutting role of remote sensing techniques is evaluated with respect to both monitoring and modeling efforts. We conclude that a broad range of techniques is available for both scenario generation and impact assessments, many of which can be implemented without much capacity building across many or even most MBRs. However, to foster implementation of the proposed strategy, further efforts are required to establish partnerships between scientists and resource managers in mountain areas.
Resumo:
During the year 2011, Chile has been scenario of several student's demonstrations claiming for more equity in the access to the higher education. The high support to the protests by the side of the general population (nearly 89% of approval in public opinion polls) seems to suggest the existence of a large consensus about the weaknesses of the Chilean educative model, a model that would challenge the traditional ideals of meritocracy and social mobility that are at the core of the educational systems in modern societies. In this context, a question that remains open is to what extent these claims are mostly based on consensual equality ideals, or whether they are influenced by individual socio-economic determinants vis-à-vis rational motives. Using data of the social inequality module International Social Survey Program (ISSP) of 2009, this research analyzes perceptions and beliefs about education and the distributive system as well as the influence of income and educational variables, through a structural equation modeling framework. Preliminary results indicate the presence of socioeconomic cleavages in relation to the fairness of the educational system, questioning the assumption about a normative consensus.
Resumo:
Abstract Sexual selection theory posits that ornaments can signal the genetic quality of an individual. Eumelanin-based coloration is such an ornament and can signal the ability to cope with a physiological stress response because the melanocortin system regulates eumelanogenesis as well as physiological stress responses. In the present article, we experimentally investigated whether the stronger stress sensitivity of light than dark eumelanic individuals stems from differential regulation of stress hormones. Our study shows that darker eumelanic barn owl nestlings have a lower corticosterone release after a stressful event, an association, which was also inherited from the mother (but not the father) to the offspring. Additionally, nestlings sired by darker eumelanic mothers more quickly reduced experimentally elevated corticosterone levels. This provides a solution as to how ornamented individuals can be more resistant to various sources of stress than drab conspecifics. Our study suggests that eumelanin-based coloration can be a sexually selected signal of resistance to stressful events.