Generalized linear and generalized additive models in studies of species distributions: setting the scene

An important statistical development of the last 30 years has been the advance in regression analysis provided by generalized linear models (GLMs) and generalized additive models (GAMs). Here we introduce a series of papers prepared within the framework of an international workshop entitled: Advances in GLMs/GAMs modeling: from species distribution to environmental management, held in Riederalp, Switzerland, 6-11 August 2001.We first discuss some general uses of statistical models in ecology, as well as provide a short review of several key examples of the use of GLMs and GAMs in ecological modeling efforts. We next present an overview of GLMs and GAMs, and discuss some of their related statistics used for predictor selection, model diagnostics, and evaluation. Included is a discussion of several new approaches applicable to GLMs and GAMs, such as ridge regression, an alternative to stepwise selection of predictors, and methods for the identification of interactions by a combined use of regression trees and several other approaches. We close with an overview of the papers and how we feel they advance our understanding of their application to ecological modeling.

L'hémodialyse intermittente aux soins intensifs = [Intermittent hemodialysis in the intensive care setting]

Acute renal failure is a frequent and potentially lethal disease in intensive care units. Renal replacement therapy (RRT) is often required. Either intermittent or continuous methods of RRT can be used. When to start a RRT and which method to use is not always clearly defined and a global evaluation of the clinical situation is required. The choice of the modality of RRT will be up to the general clinical context, hemodynamic stability, the type of molecules to be cleared and the haemorrhagic risk as much as habits and available resources. No study currently showed a superiority of either continuous or intermittent renal replacement therapy. The collaboration between intensive care specialists and nephrologists allows an optimized choice for a given patient and allow better move from one technic to another if required.

Residual antimalarials in malaria patients from Tanzania--implications on drug efficacy assessment and spread of parasite resistance.

Repeated antimalarial treatment for febrile episodes and self-treatment are common in malaria-endemic areas. The intake of antimalarials prior to participating in an in vivo study may alter treatment outcome and affect the interpretation of both efficacy and safety outcomes. We report the findings from baseline plasma sampling of malaria patients prior to inclusion into an in vivo study in Tanzania and discuss the implications of residual concentrations of antimalarials in this setting. In an in vivo study conducted in a rural area of Tanzania in 2008, baseline plasma samples from patients reporting no antimalarial intake within the last 28 days were screened for the presence of 14 antimalarials (parent drugs or metabolites) using liquid chromatography-tandem mass spectrometry. Among the 148 patients enrolled, 110 (74.3%) had at least one antimalarial in their plasma: 80 (54.1%) had lumefantrine above the lower limit of calibration (LLC = 4 ng/mL), 7 (4.7%) desbutyl-lumefantrine (4 ng/mL), 77 (52.0%) sulfadoxine (0.5 ng/mL), 15 (10.1%) pyrimethamine (0.5 ng/mL), 16 (10.8%) quinine (2.5 ng/mL) and none chloroquine (2.5 ng/mL). The proportion of patients with detectable antimalarial drug levels prior to enrollment into the study is worrying. Indeed artemether-lumefantrine was supposed to be available only at government health facilities. Although sulfadoxine-pyrimethamine is only recommended for intermittent preventive treatment in pregnancy (IPTp), it was still widely used in public and private health facilities and sold in drug shops. Self-reporting of previous drug intake is unreliable and thus screening for the presence of antimalarial drug levels should be considered in future in vivo studies to allow for accurate assessment of treatment outcome. Furthermore, persisting sub-therapeutic drug levels of antimalarials in a population could promote the spread of drug resistance. The knowledge on drug pressure in a given population is important to monitor standard treatment policy implementation.

Setting up a Common European Asylum System : Report on the application of existing instruments and proposals for the new system

The study assesses firstly the evaluation process of the first generation of asylum instruments while underlining the possibilities to improve it. It analyses secondly the asylum "acquis" regarding distribution of refugees between Member States, the eligibility for protection, the status of protected persons regarding detention and vulnerability, asylum procedures and the external dimension by formulating short-term recommendations of each area. Its last part is devoted to the long term evolution of the Common European Asylum System regarding the legal context including the accession of the EU to the Geneva Convention, the institutional perspectives including the new European Support Office, the jurisdictional perspective, the substantive perspective, the distributive perspective and the external perspective.

L'orientation du patient souffrant d'un syndrome douloureux abdominal aigu a domicile [Hospitalisation criteria for the acute abdominal pain patient seen at home or in an ambulatory setting].

Dealing at patient's home with an acute abdominal pain may be particularly challenging for the primary care physician. In such a clinical situation, the part of laboratory and radiological investigations is increasing in the diagnostic process. The decision to keep the patient at home based on a clinical evaluation alone may represent a great medical responsibility for the physician. Emergency departments (ED) are of course in charge of investigating such patients with a wide panel of investigation techniques. But these structures are chronically overcrowded resulting frequently in long and difficult periods of waiting. Based on a literature review, a description of useful clinical symptoms and signs is summarized and should help the decision process for the orientation of the patient.

Comment on "Geochemistry, petrogenesis and tectonic setting of the Samothraki mafic suite, NE Greece: Trace-element, isotopic and zircon age constraints'' by N. Koglin, D. Kostopoulos & T. Reischmann [Tectonophysics 473, 53-68 (doi:10.1016/j.tecto.2008.10.028)]

The work by Koglin et al. (Koglin, N., Kostopoulos, D., Reichmann, T., 2009. Geochemistry, petrogenesis and tectonic setting of the Samothraki mafic Suite, NE Greece: Trace-element, isotopic and zircon age constraints. Tectonophysics 473, 53-68. doi: 10.1016/j.tecto.2008.10.028), where the authors have proposed to nullify the scenario presented by Bonev and Stampfli (Bonev, N., Stampfli, G., 2008. Petrology, geochemistry and geodynamic implications of Jurassic island arc magmatism as revealed by mafic volcanic rocks in the Mesozoic low-grade sequence, eastern Rhodope, Bulgaria. Lithos 100, 210-233) is here Put under discussion. The arguments for this proposal are reviewed in the light of available stratigraphic and radiometric age constraints, geochemical signature and tectonics of highly relevant Jurassic ophiolitic suites occurring immediately north of the Samothraki mafic suite. Our conclusion is that the weak arguments and the lack of knowledge on the relevant constraints from the regional geologic information make inconsistent the Proposal and the model of these authors. (C) 2009 Elsevier B.V. All rights reserved.

A health behaviour cross-sectional study of immigrants and non-immigrants in a Swiss urban general-practice setting.

BACKGROUND: Little is known about smoking, unhealthy use of alcohol, and risk behaviours for sexually transmitted diseases (STDs) in immigrants from developed and developing countries. METHOD: We performed a cross-sectional study of 400 patients who consulted an academic emergency care centre at a Swiss university hospital. The odds ratios for having one or more risk behaviours were adjusted for age, gender, and education level. RESULTS: Immigrants from developing countries were less likely to use alcohol in an unhealthy manner (OR = 0.35, 95% CI 0.22-0.57) or practise risk behaviours for STDs (OR = 0.31, 95% CI 0.13-0.74). They were also less likely to have any of the three studied risk behaviours (OR = 2.5, 95% CI 1.5-4.3). DISCUSSION: In addition to the usual determinants, health behaviours are also associated with origin; distinguishing between immigrants from developing and developed countries is useful in clinical settings. Surprisingly, patients from developing countries tend to possess several protective characteristics.

Measurement of ß-tryptase in postmortem serum, pericardial fluid, urine and vitreous humor in forensic setting

L'activation des mastocytes se produit dans plusieurs conditions pathologiques et est principalement observée chez des patients développant une réaction anaphylactique. Dans la pratique clinique, la mesure de l'histamine et de ses métabolites dans le plasma et dans l'urine du patient peut être effectuée et montre parfois des résultats aussi précis que la mesure de la beta-tryptase dans le sang lorsqu'il est nécessaire de confirmer une activation mastocytaire. En revanche, la mesure de la beta tryptase dans l'urine dans un but diagnostic n'a que rarement été effectuée sur des personnes vivantes et a montré des résultats contradictoires. Dans le domaine de la médecine légale, la mesure de la beta-tryptase dans un but diagnostic est effectuée dans le sérum postmortem obtenu à partir de sang prélevé au niveau fémoral. Cependant, le sang peut être partiellement ou complètement indisponible dans certains cas spécifiques, dans les autopsies de nourrissons ou de corps sévèrement mutilés par exemple. Un des buts de notre étude est d'évaluer la pertinence de la mesure de la beta-tryptase dans des échantillons biologiques alternatifs, à savoir dans l'urine, l'humeur vitrée et le liquide péricardique. Pour cela nous avons sélectionné 94 cas d'autopsies comprenant 6 cas de réaction anaphylactique suite à l'administration de produits de contraste radiologique, 10 cas d'hypothermie, 10 cas d'acidocétose diabétique, 10 cas de suicide par arme à feu, 18 cas de décès consécutif à une injection d'héroïne, 10 cas de décès traumatiques, 10 cas de mort subite avec peu ou pas d'athérosclérose coronarienne, 10 cas de décès avec une athérosclérose coronarienne sévère mais sans signe d'infarctus du myocarde et 10 cas de décès consécutif à un infarctus du myocarde avec une athérosclérose coronarienne sévère. Dans tous les cas de réaction anaphylactique suite à l'administration de produit de contraste radiologique, les concentrations de beta-tryptase, mesurées dans le sérum postmortem et dans le liquide péricardique, ont montré des valeurs plus élevées que le seuil clinique de référence (11 ng/l) et le seuil postmortem de référence (45 ng/l). La concentration de beta-tryptase mesurée dans l'urine et l'humeur vitrée a montré des valeurs inférieures au seuil clinique dans tous les cas de notre étude. La mesure de la concentration de beta tryptase dans le liquide péricardique semble donc une alternative valable à la mesure dans le sérum postmortem, lorsque le sang fémoral n'est pas disponible durant l'autopsie, afin de poser un diagnostic de réaction anaphylactique.

Impact of physical activity on energy balance, food intake and choice in normal weight and obese children in the setting of acute social stress: a randomized controlled trial.

BACKGROUND: Psychological stress negatively influences food intake and food choices, thereby contributing to the development of childhood obesity. Physical activity can also moderate eating behavior and influence calorie intake. However, it is unknown if acute physical activity influences food intake and overall energy balance after acute stress exposure in children. We therefore investigated the impact of acute physical activity on overall energy balance (food intake minus energy expenditure), food intake, and choice in the setting of acute social stress in normal weight (NW) and overweight/obese (OW/OB) children as well as the impact of psychological risk factors. METHOD: After receiving written consent from their parents, 26 NW (BMI < 90(th) percentile) and 24 7-to 11-year-old OW (n = 5)/OB (n = 19, BMI ≥ 90(th) percentile) children were randomly allocated using computer-generated numbers (1:1, after stratification for weight status) to acute moderate physical or to sedentary activity for 30 min. Afterwards, all children were exposed to an acute social stressor. Children and their parents completed self-report questionnaires. At the end of the stressor, children were allowed to eat freely from a range of 12 different foods (6 sweet/6 salty; each of low/high caloric density). Energy balance, food intake/choice and obesity-related psychological risk factors were assessed. RESULTS: Lower overall energy balance (p = 0.019) and a decreased choice of low density salty foods (p < 0.001) in NW children compared with OW/OB children was found after acute moderate physical activity but not sedentary activity. Independent of their allocation, OW/OB children ate more high density salty foods (104 kcal (34 to 173), p = 0.004) following stress. They scored higher on impulsive behavior (p = 0.005), restrained eating (p < 0.001) and parental corporal punishment (p = 0.03), but these psychological factors were not related to stress-induced food intake/choice. Positive parenting tended to be related to lower intake of sweet high density food (-132 kcal, -277 to 2, p = 0.054). CONCLUSIONS: In the setting of stress, acute moderate physical activity can address energy balance in children, a benefit which is especially pronounced in the OW/OB. Positive parenting may act as a protective factor preventing stress-induced eating of comfort food. TRIAL REGISTRATION: clinicaltrials.gov NCT01693926 The study was a pilot study of a project funded by the Swiss National Science Foundation (CRSII3_147673).

Quality assessment of cardiovascular magnetic resonance in the setting of the European CMR registry: description and validation of standardized criteria.

BACKGROUND: Cardiovascular magnetic resonance (CMR) has become an important diagnostic imaging modality in cardiovascular medicine. However, insufficient image quality may compromise its diagnostic accuracy. We aimed to describe and validate standardized criteria to evaluate a) cine steady-state free precession (SSFP), b) late gadolinium enhancement (LGE), and c) stress first-pass perfusion images. These criteria will serve for quality assessment in the setting of the Euro-CMR registry. METHODS: Thirty-five qualitative criteria were defined (scores 0-3) with lower scores indicating better image quality. In addition, quantitative parameters were measured yielding 2 additional quality criteria, i.e. signal-to-noise ratio (SNR) of non-infarcted myocardium (as a measure of correct signal nulling of healthy myocardium) for LGE and % signal increase during contrast medium first-pass for perfusion images. These qualitative and quantitative criteria were assessed in a total of 90 patients (60 patients scanned at our own institution at 1.5T (n=30) and 3T (n=30) and in 30 patients randomly chosen from the Euro-CMR registry examined at 1.5T). Analyses were performed by 2 SCMR level-3 experts, 1 trained study nurse, and 1 trained medical student. RESULTS: The global quality score was 6.7±4.6 (n=90, mean of 4 observers, maximum possible score 64), range 6.4-6.9 (p=0.76 between observers). It ranged from 4.0-4.3 for 1.5T (p=0.96 between observers), from 5.9-6.9 for 3T (p=0.33 between observers), and from 8.6-10.3 for the Euro-CMR cases (p=0.40 between observers). The inter- (n=4) and intra-observer (n=2) agreement for the global quality score, i.e. the percentage of assignments to the same quality tertile ranged from 80% to 88% and from 90% to 98%, respectively. The agreement for the quantitative assessment for LGE images (scores 0-2 for SNR <2, 2-5, >5, respectively) ranged from 78-84% for the entire population, and 70-93% at 1.5T, 64-88% at 3T, and 72-90% for the Euro-CMR cases. The agreement for perfusion images (scores 0-2 for %SI increase >200%, 100%-200%,<100%, respectively) ranged from 81-91% for the entire population, and 76-100% at 1.5T, 67-96% at 3T, and 62-90% for the Euro-CMR registry cases. The intra-class correlation coefficient for the global quality score was 0.83. CONCLUSIONS: The described criteria for the assessment of CMR image quality are robust with a good inter- and intra-observer agreement. Further research is needed to define the impact of image quality on the diagnostic and prognostic yield of CMR studies.

Setting in motion the immune mechanisms underlying genetically determined resistance and susceptibility to infection with Leishmania major.

The murine model of infection with Leishmania major has allowed the demonstration of a causal relationship between, on the one hand, genetically determined resistance to infection and the development of a Th1 CD4+ cell response, and on the other hand, genetically determined susceptibility and Th2 cell maturation. Using this murine model of infection, the role of cytokines in directing the functional differentiation pathway of CD4+ T cell precursors, has been demonstrated in vivo. Thus, IL-12 and IFN-gamma have been shown to favour Th1 cell development and IL-4 is crucial for the differentiation of Th2 responses. Maturation of a Th2 response in susceptible BALB/c mice following infection with L. major is triggered by the IL-4 produced during the first two days after parasite inoculation. This IL-4 rapidly renders parasite specific CD4+ T cells precursors unresponsive to IL-12. A restricted population of CD4+ T cells expressing the V beta 4V alpha 8 TCR heterodimer and recognizing a single epitope on the LACK (Leishmania Activated C-Kinase) antigen of L. major is responsible for this rapid production of IL-4, instructing subsequent differentiation towards the Th2 phenotype of CD4+ T cells specific for several parasite antigens.

An evolutionary model explaining the Neolithic transition from egalitarianism to leadership and despotism.

The Neolithic was marked by a transition from small and relatively egalitarian groups to much larger groups with increased stratification. But, the dynamics of this remain poorly understood. It is hard to see how despotism can arise without coercion, yet coercion could not easily have occurred in an egalitarian setting. Using a quantitative model of evolution in a patch-structured population, we demonstrate that the interaction between demographic and ecological factors can overcome this conundrum. We model the coevolution of individual preferences for hierarchy alongside the degree of despotism of leaders, and the dispersal preferences of followers. We show that voluntary leadership without coercion can evolve in small groups, when leaders help to solve coordination problems related to resource production. An example is coordinating construction of an irrigation system. Our model predicts that the transition to larger despotic groups will then occur when: (i) surplus resources lead to demographic expansion of groups, removing the viability of an acephalous niche in the same area and so locking individuals into hierarchy; (ii) high dispersal costs limit followers' ability to escape a despot. Empirical evidence suggests that these conditions were probably met, for the first time, during the subsistence intensification of the Neolithic.