Renin inhibition by aliskiren prevents atherosclerosis progression: comparison with irbesartan, atenolol, and amlodipine.

Hypertension is associated with increased risk of cardiovascular diseases. Antihypertensive treatment, particularly blockade of the renin-angiotensin system, contributes to prevent atherosclerosis-mediated cardiovascular events. Direct comparison of different antihypertensive treatments on atherosclerosis and particularly plaque stabilization is sparse. ApoE(-/-) mice with vulnerable (2-kidney, 1-clip renovascular hypertension model) or stable (1-kidney, 1-clip renovascular hypertension model) atherosclerotic plaques were used. Mice were treated with aliskiren (renin inhibitor), irbesartan (angiotensin-receptor blocker), atenolol (beta-blocker), or amlodipine (calcium channel blocker). Atherosclerosis characteristics were assessed. Hemodynamic and hormonal parameters were measured. Aliskiren and irbesartan significantly prevented atherosclerosis progression in 2-kidney, 1-clip mice. Indeed, compared with untreated animals, plaques showed thinner fibrous cap (P<0.05); smaller lipid core (P<0.05); decreased media degeneration, layering, and macrophage content (P<0.05); and increased smooth muscle cell content (P<0.05). Interestingly, aliskiren significantly increased the smooth muscle cell compared with irbesartan. Despite similar blood pressure lowering, only partial plaque stabilization was attained by atenolol and amlodipine. Amlodipine increased plaque smooth muscle cell content (P<0.05), whereas atenolol decreased plaque inflammation (P<0.05). This divergent effect was also observed in 1-kidney, 1-clip mice. Normalizing blood pressure by irbesartan increased the plasma renin concentration (5932+/-1512 ng/mL per hour) more than normalizing it by aliskiren (16085+/-5628 ng/mL per hour). Specific renin-angiotensin system blockade prevents atherosclerosis progression. First, evidence is provided that direct renin inhibition mediates atherosclerotic plaque stabilization. In contrast, beta-blocker and calcium channel blocker treatment only partially stabilize plaques differently influencing atherogenesis. Angiotensin II decisively mediates plaque vulnerability. The plasma renin concentration measurement by an indirect method did not confirm the excessive increase of plasma renin concentration reported in the literature during aliskiren compared with irbesartan or amlodipine treatment.

Stressing schizotypy: The modulating role of stress-relieving behaviours and intellectual capacity on functional hemispheric asymmetry.

Relative cognitive impairments are common along the schizophrenia spectrum reflecting potential psychopathological markers. Yet stress, a vulnerability marker in schizophrenia (including its spectrum), is likewise related to cognitive impairments. We investigated whether one such cognitive marker (attenuated functional hemispheric asymmetry) during stressful life periods might be linked to individuals' schizotypal features or rather to individuals' stress-related experiences and behaviours. A total of 58 students performed a left hemisphere dominant (lateralised lexical decisions) and right hemisphere dominant (sex decisions on composite faces) task. In order to account for individual differences in stress sensitivity we separated participants into groups of high or low cognitive reserve according to their average current marks. In addition, participants filled in questionnaires on schizotypy (short O-LIFE), perceived stress, stress response, and a newly adapted questionnaire that enquired about potential stress compensation behaviour (elevated substance use). The most important finding was that enhanced substance use and cognitive disorganisation contributed to a right and left hemisphere shift in language dominance, respectively. We discuss that (i) former reports on right hemisphere shifts in language dominance with positive schizotypy might be explained by an associated higher substance use and (ii) cognitive disorganisation relates to unstable cognitive functioning that depend on individuals' life circumstances, contributing to published reports on inconsistent laterality-schizotypy relationships.

Suboptimal access to primary healthcare among street-based sex workers in southwest Switzerland.

OBJECTIVES: Street-based sex workers (SSWs) in Lausanne, Switzerland, are poorly characterised. We set out to quantify potential vulnerability factors in this population and to examine SSW healthcare use and unmet healthcare requirements. METHODS: We conducted a cross-sectional questionnaire-based survey among SSWs working in Lausanne's red light district between 1 February and 31 July 2010, examining SSW socio-demographic characteristics and factors related to their healthcare. RESULTS: We interviewed 50 SSWs (76% of those approached). A fifth conducted their interviews in French, the official language in Lausanne. 48 participants (96%) were migrants, of whom 33/48 (69%) held no residence permit. 22/50 (44%) had been educated beyond obligatory schooling. 28/50 (56%) had no health insurance. 18/50 (36%) had been victims of physical violence. While 36/50 (72%) had seen a doctor during the preceding 12 months, only 15/50 (30%) were aware of a free clinic for individuals without health insurance. Those unaware of free services consulted emergency departments or doctors outside Switzerland. Gynaecology, primary healthcare and dental services were most often listed as needed. Two individuals (of 50, 4%) disclosed positive HIV status; of the others, 24/48 (50%) had never had an HIV test. CONCLUSIONS: This vulnerable population comprises SSWs who, whether through mobility, insufficient education or language barriers, are unaware of services they are entitled to. With half the participants reporting no HIV testing, there is a need to enhance awareness of available facilities as well as to increase provision and uptake of HIV testing.

Perineuronal nets protect fast-spiking interneurons against oxidative stress.

A hallmark of schizophrenia pathophysiology is the dysfunction of cortical inhibitory GABA neurons expressing parvalbumin, which are essential for coordinating neuronal synchrony during various sensory and cognitive tasks. The high metabolic requirements of these fast-spiking cells may render them susceptible to redox dysregulation and oxidative stress. Using mice carrying a genetic redox imbalance, we demonstrate that extracellular perineuronal nets, which constitute a specialized polyanionic matrix enwrapping most of these interneurons as they mature, play a critical role in the protection against oxidative stress. These nets limit the effect of genetically impaired antioxidant systems and/or excessive reactive oxygen species produced by severe environmental insults. We observe an inverse relationship between the robustness of the perineuronal nets around parvalbumin cells and the degree of intracellular oxidative stress they display. Enzymatic degradation of the perineuronal nets renders mature parvalbumin cells and fast rhythmic neuronal synchrony more susceptible to oxidative stress. In parallel, parvalbumin cells enwrapped with mature perineuronal nets are better protected than immature parvalbumin cells surrounded by less-condensed perineuronal nets. Although the perineuronal nets act as a protective shield, they are also themselves sensitive to excess oxidative stress. The protection might therefore reflect a balance between the oxidative burden on perineuronal net degradation and the capacity of the system to maintain the nets. Abnormal perineuronal nets, as observed in the postmortem patient brain, may thus underlie the vulnerability and functional impairment of pivotal inhibitory circuits in schizophrenia.

Big brother is watching you: eavesdropping to resolve family conflicts

Adult animals can eavesdrop on behavioral interactions between potential opponents to assess their competitive ability and motivation to contest resources without interacting directly with them. Surprisingly, eavesdropping is not yet considered as an important factor used to resolve conflicts between family members. In this study, we show that nestling barn owls (Tyto alba) competing for food eavesdrop on nestmates' vocal interactions to assess the dominance status and food needs of opponents. During a first training playback session, we broadcasted to singleton bystander nestlings a simulated vocal interaction between 2 prerecorded individuals, 1 relatively old (i.e., senior) and 1 younger nestling (i.e., junior). One playback individual, the "responder," called systematically just after the "initiator" playback individual, hence displaying a higher hunger level. To test whether nestlings have eavesdropped on this interaction, we broadcasted the same prerecorded individuals separately in a subsequent playback test session. Nestlings vocalized more rapidly after former initiators' than responders' calls and they produced more calls when the broadcasted individual was formerly a junior initiator. They chiefly challenged vocally juniors and initiators against whom the likelihood of winning a vocal contest is higher. Owlets, therefore, identified the age hierarchy between 2 competitors based on their vocalizations. They also memorized the dynamics of competitors' previous vocal interactions, and used this information to optimally adjust signaling level once interacting with only 1 of the competitor. We conclude that siblings eavesdrop on one another to resolve conflicts over parental resources.

Le trouble de l'adaptation, un diagnostic anodin ? : une étude comparative avec le trouble dépressif majeur

Résumé Le trouble de l'adaptation est un diagnostic très fréquent, mais étonnamment peu étudié et controversé. Il est, selon les études, considéré comme une forme mineure d'un trouble psychiatrique spécifique, comme une fragilité psychologique révélée par un événement stressant pour le sujet ou encore comme une forme précoce annonçant un trouble psychiatrique majeur. Ces trois points de vue ramènent en fait tous à la question de fond concernant son étiologie. L'objectif de cette étude est de montrer si le trouble de l'adaptation est un diagnostic clairement différencié dont l'existence est justifiée. Afin de tenter de répondre à cette question, il nous est apparu intéressant de comparer cette catégorie diagnostique à une autre catégorie diagnostique psychiatrique importante, le trouble dépressif majeur. Dans cette étude rétrospective nous avons sélectionné tous les patients avec un diagnostic de trouble de l'adaptation ou un trouble dépressif majeur parmi les patients hospitalisés à l'hôpital psychiatrique de Malévoz en Valais en 1993 (580). Elle est basée sur des diagnostics cliniques. Nous avons comparé leurs données socio-démographiques (âge, sexe, nationalité, état civil, activité professionnelle), leurs antécédents psychiatriques (hospitalisations antérieures, suivi psychiatrique ambulatoire, antécédents de tentamen), leurs hospitalisations ultérieures dans les 5 ans, leur hospitalisation actuelle (durée, tentamens, comorbidité) et les traitements médicamenteux prescrits (leur nombre et leur classe). Notre étude met en évidence certaines distinctions entre le trouble de l'adaptation et le trouble dépressif majeur: les patients souffrant de trouble de l'adaptation diffèrent des troubles dépressifs majeurs par le fait qu'ils sont plus fréquemment des hommes, célibataires et plus jeunes que ceux souffrant de trouble dépressif majeur; leur durée d'hospitalisation est plus courte, leur évolution entre les hospitalisations est meilleure et ils reçoivent moins de psychotropes. Nous ne pouvons cependant pas conclure à une distinction claire de ces deux catégories diagnostiques, ni que le trouble de l'adaptation n'est pas simplement lié à une moindre gravité. Nos résultats confirment par contre que ce diagnostic n'est pas non plus un diagnostic anodin (nombre élevé d'antécédents psychiatriques, de tentamens, d'hospitalisations psychiatriques ultérieures, importance des comorbidités de même que la lourdeur des traitements psychotropes prescrits (notamment la fréquence des neuroleptiques). A notre avis, les trois hypothèses étiologiques (forme mineure, trouble précoce ou fragilité psychologique spécifique révélée par un événement stressant) qui ont été évoquées peuvent être considérées comme plausibles suivant le point de vue que l'on choisit. Le diagnostic de trouble de l'adaptation révèle une des limitations de l'approche du DSM-Ill-R qui se veut athéorique. Le fait que dans sa définition même, le DSM-111-R évoque "qu'il faut souvent se référer au seul jugement clinique" le montre bien, un tel diagnostic renvoie inévitablement à une référence psychopathologique. Nous pensons qu'il est illusoire de vouloir se passer d'une telle référence qui elle seule permet d'appréhender justement la portée symbolique d'un événement donné pour un individu. Summary In this retrospective study we selected all the patients with a diagnosis of adjustment disorder (77) or major depressive disorder (125) among the patients hospitalised in the psychiatric hospital of Malevoz in Valais during the year 1993 (580). It is based on clinical diagnosis. Their social and demographic characteristics (age, sex, nationality, marital status, professional activity), their past psychiatric history (earlier psychiatric hospitalisations, ambulatory treatment and attempted suicide), their hospitalisations during the next 5 years, their index hospitalisation (length, attempted suicide, comorbidity) and their drug treatment (number and class of prescribed drugs) were compared. This survey confirms certain differences be-tween adjustment disorder and major depression disorder: patients suffering from adjustment disorder were more often men, not married, younger than those suffering from major depression; their hospitalisations were shorter with a better evolution between hospitalisations and they received less medication. However, the study does not allow to clearly distinguish between the two diagnoses or to conclude that adjustment disorder is not only a minor form of a specific psychiatric disorder. Yet it confirms that adjustment disorder is not a light diagnosis (importance of the psychiatric past, high number of past attempted suicides, rehospitalisations, number of comorbid disorders and weight of the prescribed psychotropic treatments among which neuroleptics were frequent). The three aetiological hypotheses that have been proposed (minor form of a specific disorder, specific psychological vulnerability revealed by a stress factor or precursor manifestation of a major psychiatric disorder) can still be considered as plausible. The diagnosis of adjustment disorder points to methodological limitations of the atheoretical approach of the DSM-III-R. The fact that, in its DSM-III-R definition, it is stated that the diagnosis of adjustment disorder has often to be based only on clinical judgment shows very well that such a diagnosis inevitably refers to a psychopathological theory. Indeed, the authors consider an approach without such a reference as difficult, a reference which remains the only way to appreciate accurately the symbolic weight of a given event for an individual person.

Redox dysregulation, neurodevelopment, and schizophrenia.

In schizophrenia, a developmental redox dysregulation constitutes one 'hub' on which converge genetic impairments of glutathione synthesis and environmental vulnerability factors generating oxidative stress. Their timing at critical periods of neurodevelopment could play a decisive role in inducing impairment of neural connectivity and synchronization as observed in schizophrenia. In experimental models, such redox dysregulation induces anomalies strikingly similar to those observed in patients. This is mediated by hypoactive NMDA receptors, impairment of fast-spiking parvalbumin GABA interneurons and deficit in myelination. A treatment restoring the redox balance without side effects yields improvements of negative symptoms in chronic patients. Novel interventions based on these mechanisms if applied in early phases of the disease hold great therapeutic promise.

Disaster Risk, Livelihoods and Natural Barriers, Strengthening Decision-Making Tools for Disaster Risk Reduction: A case study from northern Pakistan

The goal of this interdisciplinary study is to better understand the land use factors that increase vulnerability of mountain areas in northern Pakistan. The study will identify and analyse the damages and losses caused by the October 2005 earthquake in two areas of the same valley: one "low-risk" watershed with sound natural resources management, the other, "high-risk" in an ecologically degraded watershed. Secondly, the study will examine natural and man-made causes of secondary hazards in the study area, especially landslides; and third it will evaluate the cost of the earthquake damage in the study areas on the livelihoods of local communities and the sub-regional economy. There are few interdisciplinary studies to have correlated community land use practices, resources management, and disaster risk reduction in high-risk mountain areas. By better understanding these linkages, development- humanitarian- and donor agencies focused on disaster reduction can improve their risk reduction programs for mountainous regions.

The Lausanne cohort Lc65+: a population-based prospective study of the manifestations, determinants and outcomes of frailty

BACKGROUND: Frailty is a relatively new geriatric concept referring to an increased vulnerability to stressors. Various definitions have been proposed, as well as a range of multidimensional instruments for its measurement. More recently, a frailty phenotype that predicts a range of adverse outcomes has been described. Understanding frailty is a particular challenge both from a clinical and a public health perspective because it may be a reversible precursor of functional dependence. The Lausanne cohort Lc65+ is a longitudinal study specifically designed to investigate the manifestations of frailty from its first signs in the youngest old, identify medical and psychosocial determinants, and describe its evolution and related outcomes. METHODS/DESIGN: The Lc65+ cohort was launched in 2004 with the random selection of 3054 eligible individuals aged 65 to 70 (birth year 1934-1938) in the non-institutionalized population of Lausanne (Switzerland). The baseline data collection was completed among 1422 participants in 2004-2005 through questionnaires, examination and performance tests. It comprised a wide range of medical and psychosocial dimensions, including a life course history of adverse events. Outcomes measures comprise subjective health, limitations in activities of daily living, mobility impairments, development of medical conditions or chronic health problems, falls, institutionalization, health services utilization, and death. Two additional random samples of 65-70 years old subjects will be surveyed in 2009 (birth year 1939-1943) and in 2014 (birth year 1944-1948). DISCUSSION: The Lc65+ study focuses on the sequence "Determinants --> Components --> Consequences" of frailty. It currently provides information on health in the youngest old and will allow comparisons to be made between the profiles of aging individuals born before, during and at the end of the Second World War.

Evolutionary history and its relevance in understanding and conserving southern African biodiversity

Abstract : Understanding how biodiversity is distributed is central to any conservation effort and has traditionally been based on niche modeling and the causal relationship between spatial distribution of organisms and their environment. More recently, the study of species' evolutionary history and relatedness has permeated the fields of ecology and conservation and, coupled with spatial predictions, provides useful insights to the origin of current biodiversity patterns, community structuring and potential vulnerability to extinction. This thesis explores several key ecological questions by combining the fields of niche modeling and phylogenetics and using important components of southern African biodiversity. The aims of this thesis are to provide comparisons of biodiversity measures, to assess how climate change will affect evolutionary history loss, to ask whether there is a clear link between evolutionary history and morphology and to investigate the potential role of relatedness in macro-climatic niche structuring. The first part of my thesis provides a fine scale comparison and spatial overlap quantification of species richness and phylogenetic diversity predictions for one of the most diverse plant families in the Cape Floristic Region (CFR), the Proteaceae. In several of the measures used, patterns do not match sufficiently to argue that species relatedness information is implicit in species richness patterns. The second part of my thesis predicts how climate change may affect threat and potential extinction of southern African animal and plant taxa. I compare present and future niche models to assess whether predicted species extinction will result in higher or lower V phylogenetic diversity survival than what would be experienced under random extinction processes. l find that predicted extinction will result in lower phylogenetic diversity survival but that this non-random pattern will be detected only after a substantial proportion of the taxa in each group has been lost. The third part of my thesis explores the relationship between phylogenetic and morphological distance in southern African bats to assess whether long evolutionary histories correspond to equally high levels of morphological variation, as predicted by a neutral model of character evolution. I find no such evidence; on the contrary weak negative trends are detected for this group, as well as in simulations of both neutral and convergent character evolution. Finally, I ask whether spatial and climatic niche occupancy in southern African bats is influenced by evolutionary history or not. I relate divergence time between species pairs to climatic niche and range overlap and find no evidence for clear phylogenetic structuring. I argue that this may be due to particularly high levels of micro-niche partitioning. Résumé : Comprendre la distribution de la biodiversité représente un enjeu majeur pour la conservation de la nature. Les analyses se basent le plus souvent sur la modélisation de la niche écologique à travers l'étude des relations causales entre la distribution spatiale des organismes et leur environnement. Depuis peu, l'étude de l'histoire évolutive des organismes est également utilisée dans les domaines de l'écologie et de la conservation. En combinaison avec la modélisation de la distribution spatiale des organismes, cette nouvelle approche fournit des informations pertinentes pour mieux comprendre l'origine des patterns de biodiversité actuels, de la structuration des communautés et des risques potentiels d'extinction. Cette thèse explore plusieurs grandes questions écologiques, en combinant les domaines de la modélisation de la niche et de la phylogénétique. Elle s'applique aux composants importants de la biodiversité de l'Afrique australe. Les objectifs de cette thèse ont été l) de comparer différentes mesures de la biodiversité, 2) d'évaluer l'impact des changements climatiques à venir sur la perte de diversité phylogénétique, 3) d'analyser le lien potentiel entre diversité phylogénétique et diversité morphologique et 4) d'étudier le rôle potentiel de la phylogénie sur la structuration des niches macro-climatiques des espèces. La première partie de cette thèse fournit une comparaison spatiale, et une quantification du chevauchement, entre des prévisions de richesse spécifique et des prédictions de la diversité phylogénétique pour l'une des familles de plantes les plus riches en espèces de la région floristique du Cap (CFR), les Proteaceae. Il résulte des analyses que plusieurs mesures de diversité phylogénétique montraient des distributions spatiales différentes de la richesse spécifique, habituellement utilisée pour édicter des mesures de conservation. La deuxième partie évalue les effets potentiels des changements climatiques attendus sur les taux d'extinction d'animaux et de plantes de l'Afrique australe. Pour cela, des modèles de distribution d'espèces actuels et futurs ont permis de déterminer si l'extinction des espèces se traduira par une plus grande ou une plus petite perte de diversité phylogénétique en comparaison à un processus d'extinction aléatoire. Les résultats ont effectivement montré que l'extinction des espèces liées aux changements climatiques pourrait entraîner une perte plus grande de diversité phylogénétique. Cependant, cette perte ne serait plus grande que celle liée à un processus d'extinction aléatoire qu'à partir d'une forte perte de taxons dans chaque groupe. La troisième partie de cette thèse explore la relation entre distances phylogénétiques et morphologiques d'espèces de chauves-souris de l'Afrique australe. ll s'agit plus précisément de déterminer si une longue histoire évolutive correspond également à des variations morphologiques plus grandes dans ce groupe. Cette relation est en fait prédite par un modèle neutre d'évolution de caractères. Aucune évidence de cette relation n'a émergé des analyses. Au contraire, des tendances négatives ont été détectées, ce qui représenterait la conséquence d'une évolution convergente entre clades et des niveaux élevés de cloisonnement pour chaque clade. Enfin, la dernière partie présente une étude sur la répartition de la niche climatique des chauves-souris de l'Afrique australe. Dans cette étude je rapporte temps de divergence évolutive (ou deux espèces ont divergé depuis un ancêtre commun) au niveau de chevauchement de leurs niches climatiques. Les résultats n'ont pas pu mettre en évidence de lien entre ces deux paramètres. Les résultats soutiennent plutôt l'idée que cela pourrait être I dû à des niveaux particulièrement élevés de répartition de la niche à échelle fine.

Taking care of the most vulnerable : a descriptive study of patients with 12 attendances or more at a Swiss university hospital emergency department in 2009

Introduction: Patients who repeatedly attend the Emergency Department (ED) often have a distinct and complex vulnerability profile that includes poor somatic, psychological, and social indicators. This profile has an impact on the patients' well-being as well as on hospital costs. The objective of the study was to specify the characteristics of hyper users (HU) and explore the connection with ED care and hospital costs. Methods: The study sample comprised all adult patients with 12 or more attendances at the ED of the Lausanne University Hospital in 2009. The data were collected by retrospectively searching internal databases to identify the patients concerned and then analysing the profiles of these patients. Information gathered included demographic, somatic, psychological, at-risk behaviour, and social indicators, and health system consumption including costs. Results: In 2009, 23 patients (0.1%) attended 12 times or more (425 attendances, 0.8%). The average age was about 43 years, 60.9% were female, and 47.8% single. Of these 95.7% had basic insurance, 87.0% had a general practitioner, and 30.4% were under legal guardianship. The majority attended in the evening or at night (67.1%), and almost one quarter of these attendances resulted in inpatient treatment (24.0%). Most HU had attended the ED in previous years too (95.7% in 2008). The most prevalent diagnoses concerned 'mental disorders' (87.0%). About 30.4% of patients had attempted suicide (all were female patients). Other frequent diagnoses concerned 'trauma' (65.2%), and the 'digestive' and the 'nervous system' (each 56.5%). At-risk behaviour such as severe alcohol consumption (34.8%), or excessive use of medicines (26.1%) was very frequent, and some patients used illicit drugs (21.7%). There was only a weak association between the number of ED attendances and the resulting costs. However, a reduction of one outpatient visit per patient would have decreased ED outpatient costs by 8.5%. Conclusions: HU often have a particularly vulnerable profile. Mental problems are prevalent among them, as are at-risk behaviour and severe somatic conditions. The complexity of the patients' profiles demands specific care that cannot be guaranteed within an everyday ED routine. The use of an interdisciplinary case management team might be a promising approach in diminishing the number of attendances and the associated costs, although the profiles of HU are such that they probably cannot completely give up ED attendance.

Alzheimer's disease: the amyloid hypothesis and the Inverse Warburg effect.

Epidemiological and biochemical studies show that the sporadic forms of Alzheimer's disease (AD) are characterized by the following hallmarks: (a) An exponential increase with age; (b) Selective neuronal vulnerability; (c) Inverse cancer comorbidity. The present article appeals to these hallmarks to evaluate and contrast two competing models of AD: the amyloid hypothesis (a neuron-centric mechanism) and the Inverse Warburg hypothesis (a neuron-astrocytic mechanism). We show that these three hallmarks of AD conflict with the amyloid hypothesis, but are consistent with the Inverse Warburg hypothesis, a bioenergetic model which postulates that AD is the result of a cascade of three events-mitochondrial dysregulation, metabolic reprogramming (the Inverse Warburg effect), and natural selection. We also provide an explanation for the failures of the clinical trials based on amyloid immunization, and we propose a new class of therapeutic strategies consistent with the neuroenergetic selection model.

Les coûts des dommages éléments naturels aux bâtiments et l'influence des facteurs du risque dans un contexte d'assurance immobilière : analyse de cas des innondations et de la grêle en Suisse

In Switzerland, the annual cost of damage by natural elements has been increasing for several years despite the introduction of protective measures. Mainly induced by material destruction building insurance companies have to pay the majority of this cost. In many European countries, governments and insurance companies consider prevention strategies to reduce vulnerability. In Switzerland, since 2004, the cost of damage due to natural hazards has surpassed the cost of damage due to fire; a traditional activity of the Cantonal Insurance company (EGA). Therefore, the strategy for efficient fire prevention incorporates a reduction of the vulnerability of buildings. The thesis seeks to illustrate the relevance of such an approach when applied to the damage caused by natural hazards. It examines the role of insurance place and its involvement in targeted prevention of natural disasters. Integrated risk management involves a faultless comprehension of all risk parameters The first part of the thesis is devoted to the theoretical development of the key concepts that influence risk management, such as: hazard, vulnerability, exposure or damage. The literature on this subject, very prolific in recent years, was taken into account and put in perspective in the context of this study. Among the risk parameters, it is shown in the thesis that vulnerability is a factor that we can influence efficiently in order to limit the cost of damage to buildings. This is confirmed through the development of an analysis method. This method has led to the development of a tool to assess damage to buildings by flooding. The tool, designed for the property insurer or owner, proposes several steps, namely: - Vulnerability and damage potential assessment; - Proposals for remedial measures and risk reduction from an analysis of the costs of a potential flood; - Adaptation of a global strategy in high-risk areas based on the elements at risk. The final part of the thesis is devoted to the study of a hail event in order to provide a better understanding of damage to buildings. For this, two samples from the available claims data were selected and analysed in the study. The results allow the identification of new trends A second objective of the study was to develop a hail model based on the available data The model simulates a random distribution of intensities and coupled with a risk model, proposes a simulation of damage costs for the determined study area. Le coût annuel des dommages provoqués par les éléments naturels en Suisse est conséquent et sa tendance est en augmentation depuis plusieurs années, malgré la mise en place d'ouvrages de protection et la mise en oeuvre de moyens importants. Majoritairement induit par des dégâts matériels, le coût est supporté en partie par les assurances immobilières en ce qui concerne les dommages aux bâtiments. Dans de nombreux pays européens, les gouvernements et les compagnies d'assurance se sont mis à concevoir leur stratégie de prévention en termes de réduction de la vulnérabilité. Depuis 2004, en Suisse, ce coût a dépassé celui des dommages dus à l'incendie, activité traditionnelle des établissements cantonaux d'assurance (ECA). Ce fait, aux implications stratégiques nombreuses dans le domaine public de la gestion des risques, résulte en particulier d'une politique de prévention des incendies menée efficacement depuis plusieurs années, notamment par le biais de la diminution de la vulnérabilité des bâtiments. La thèse, par la mise en valeur de données actuarielles ainsi que par le développement d'outils d'analyse, cherche à illustrer la pertinence d'une telle approche appliquée aux dommages induits par les phénomènes naturels. Elle s'interroge sur la place de l'assurance et son implication dans une prévention ciblée des catastrophes naturelles. La gestion intégrale des risques passe par une juste maîtrise de ses paramètres et de leur compréhension. La première partie de la thèse est ainsi consacrée au développement théorique des concepts clés ayant une influence sur la gestion des risques, comme l'aléa, la vulnérabilité, l'exposition ou le dommage. La littérature à ce sujet, très prolifique ces dernières années, a été repnse et mise en perspective dans le contexte de l'étude, à savoir l'assurance immobilière. Parmi les paramètres du risque, il est démontré dans la thèse que la vulnérabilité est un facteur sur lequel il est possible d'influer de manière efficace dans le but de limiter les coûts des dommages aux bâtiments. Ce raisonnement est confirmé dans un premier temps dans le cadre de l'élaboration d'une méthode d'analyse ayant débouché sur le développement d'un outil d'estimation des dommages aux bâtiments dus aux inondations. L'outil, destiné aux assurances immobilières, et le cas échéant aux propriétaires, offre plusieurs étapes, à savoir : - l'analyse de la vulnérabilité et le potentiel de dommages ; - des propositions de mesures de remédiation et de réduction du risque issues d'une analyse des coûts engendrés par une inondation potentielle; - l'adaptation d'une stratégie globale dans les zones à risque en fonction des éléments à risque. La dernière partie de la thèse est consacrée à l'étude d'un événement de grêle dans le but de fournir une meilleure compréhension des dommages aux bâtiments et de leur structure. Pour cela, deux échantillons ont été sélectionnés et analysés parmi les données de sinistres à disposition de l'étude. Les résultats obtenus, tant au niveau du portefeuille assuré que de l'analyse individuelle, permettent de dégager des tendances nouvelles. Un deuxième objectif de l'étude a consisté à élaborer une modélisation d'événements de grêle basée sur les données à disposition. Le modèle permet de simuler une distribution aléatoire des intensités et, couplé à un modèle d'estimation des risques, offre une simulation des coûts de dommages envisagés pour une zone d'étude déterminée. Les perspectives de ce travail permettent une meilleure focalisation du rôle de l'assurance et de ses besoins en matière de prévention.

The contribution of patch topology and demographic parameters to PVA predictions: the case of the European tree frog

Population viability analyses (PVA) are increasingly used in metapopulation conservation plans. Two major types of models are commonly used to assess vulnerability and to rank management options: population-based stochastic simulation models (PSM such as RAMAS or VORTEX) and stochastic patch occupancy models (SPOM). While the first set of models relies on explicit intrapatch dynamics and interpatch dispersal to predict population levels in space and time, the latter is based on spatially explicit metapopulation theory where the probability of patch occupation is predicted given the patch area and isolation (patch topology). We applied both approaches to a European tree frog (Hyla arborea) metapopulation in western Switzerland in order to evaluate the concordances of both models and their applications to conservation. Although some quantitative discrepancies appeared in terms of network occupancy and equilibrium population size, the two approaches were largely concordant regarding the ranking of patch values and sensitivities to parameters, which is encouraging given the differences in the underlying paradigms and input data.