Limits on the validity of infinite length assumptions for modelling shallow landslides

The infinite slope method is widely used as the geotechnical component of geomorphic and landscape evolution models. Its assumption that shallow landslides are infinitely long (in a downslope direction) is usually considered valid for natural landslides on the basis that they are generally long relative to their depth. However, this is rarely justified, because the critical length/depth (L/H) ratio below which edge effects become important is unknown. We establish this critical L/H ratio by benchmarking infinite slope stability predictions against finite element predictions for a set of synthetic two-dimensional slopes, assuming that the difference between the predictions is due to error in the infinite slope method. We test the infinite slope method for six different L/H ratios to find the critical ratio at which its predictions fall within 5% of those from the finite element method. We repeat these tests for 5000 synthetic slopes with a range of failure plane depths, pore water pressures, friction angles, soil cohesions, soil unit weights and slope angles characteristic of natural slopes. We find that: (1) infinite slope stability predictions are consistently too conservative for small L/H ratios; (2) the predictions always converge to within 5% of the finite element benchmarks by a L/H ratio of 25 (i.e. the infinite slope assumption is reasonable for landslides 25 times longer than they are deep); but (3) they can converge at much lower ratios depending on slope properties, particularly for low cohesion soils. The implication for catchment scale stability models is that the infinite length assumption is reasonable if their grid resolution is coarse (e.g. >25?m). However, it may also be valid even at much finer grid resolutions (e.g. 1?m), because spatial organization in the predicted pore water pressure field reduces the probability of short landslides and minimizes the risk that predicted landslides will have L/H ratios less than 25. Copyright (c) 2012 John Wiley & Sons, Ltd.

Molecular epidemiology of pseudomonas aeruginosae in intensive care units (ICUs) over a 10-year period (1998-2007)

Pseudomonas aeruginosa, une bactérie environnementale ubiquitaire, est un des pathogènes nosocomiaux les plus fréquents aux soins intensifs. La source de ce microorganisme peut être soit endogène, 2,6 à 24 % des patients hospitalisés étant colonisés au niveau digestif, soit exogène. La proportion des cas d'infections à P. aeruginosa d'origine exogène, donc secondaires à une transmission par manuportage ou par l'eau du réseau utilisée pour la toilette ou d'autres soins, reste débattue. Or une meilleure évaluation du taux d'infections exogènes est importante pour la mise en place de mesures de contrôle appropriées. Le but de cette étude était de déterminer sur une période de 10 ans les rôles respectifs des sources exogènes (robinets, autres patients) et endogène dans la colonisation et/ou l'infection par P.aeruginosa chez les patients des Soins Intensifs, ainsi que de documenter les variations épidémiologiques au cours du temps. L'étude a été menée dans les unités de Soins Intensifs du Centre Hospitalier Universitaire Vaudois (CHUV). Les patients colonisés et/ou infectés par P. aeruginosa entre 1998 et 2007ont été identifiés via la base de données du laboratoire de microbiologie. Ils ont été inclus dans l'étude s'ils étaient hospitalisés dans une des unités de Soins Intensifs, Durant cette période, des prélèvements pour recherche de P. aeruginosa ont été effectués sur des robinets des soins intensifs. Un typage moléculaire a été effectué sur toutes les souches cliniques et environnementales isolées en 1998, 2000, 2003, 2004 et 2007. Les patients inclus dans l'étude ont été répartis en quatre catégories (A-D) selon le résultat du typage moléculaire leur souche de P. aeruginosa. La catégorie A inclut les cas pour lesquels le génotype de P. aeruginosa est identique à un des génotypes retrouvé dans l'environnement. La catégorie B comprend les cas pour lesquels le génotype est identique à celui d'au moins un autre patient. La catégorie C comprend les cas avec un génotype unique et la catégorie D comprend les cas pour lesquels la souche était non disponible pour le typage. Les cas des catégories A et B sont considérés comme ayant une origine exogène. Au cours des années de l'étude, le nombre d'admissions aux soins intensifs est resté stable. En moyenne, 86 patients par année ont été identifiés colonisés ou infectés par P. aeruginosa aux Soins Intensifs. Durant la première année d'investigation, un grand nombre de patients colonisés par une souche de P. aeruginosa identique à une de celles retrouvées dans l'environnement a été mis en évidence. Par la suite, possiblement suite à l'augmentation de la température du réseau d'eau chaude, le nombre de cas dans la catégorie A a diminué. Dans la catégorie B, le nombre de cas varie de 1,9 à 20 cas/1000 admissions selon les années. Ce nombre est supérieur à 10 cas/1000 admissions en 1998, 2003 et 2007 et correspond à des situations épidémiques transitoires. Tout au long des 10 ans de l'étude, le nombre de cas dans la catégorie C (source endogène) est demeuré stable et indépendant des variations du nombre de cas dans les catégories A et B. En conclusion, la contribution relative des réservoirs endogène et exogène dans la colonisation et/ou l'infection des patients de soins Intensifs varie au cours du temps. Les facteurs principaux qui contribuent à de telles variations sont probablement le degré de contamination de l'environnement, la compliance des soignants aux mesures de contrôle des infections et la génétique du pathogène lui-même. Etant donné que ce germe est ubiquitaire dans l'environnement aqueux et colonise jusqu'à 15% des patients hospitalisés, la disparition de son réservoir endogène semble difficile. Cependant, cette étude démontre que son contrôle est possible dans l'environnement, notamment dans les robinets en augmentant la température de l'eau. De plus, si une souche multi-résistante est retrouvée de manière répétée dans l'environnement, des efforts doivent être mis en place pour éliminer cette souche. Des efforts doivent être également entrepris afin de limiter la transmission entre les patients, qui est une cause importante et récurrente de contamination exogène. - Pseudomonas aeruginosa is one of the leading nosocomial pathogens in intensive care units (ICUs). The source of this microorganism can be either endogenous or exogenous. The proportion of cases as a result of transmission is still debated, and its elucidation is important for implementing appropriate control measures. To understand the relative importance of exogenous vs. endogenous sources of P. aeru¬ginosa, molecular typing was performed on all available P. aeruginosa isolated from ICU clinical and environmental specimens in 1998, 2000, 2003, 2004 and 2007. Patient samples were classified according to their P. aeruginosa genotypes into three categories: (A) identical to isolate from faucet; (B) identical to at least one other patient sample and not found in faucet; and (C) unique genotype. Cases in cat¬egories A and Β were considered as possibly exogenous, and cases in category C as possibly endogenous. A mean of 34 cases per 1000 admissions per year were found to be colonized or infected by P. aeruginosa. Higher levels of faucet contamination were correlated with a higher number of cases in category A. The number of cases in category Β varied from 1.9 to 20 cases per 1000 admissions. This num¬ber exceeded 10/1000 admissions on three occasions and was correlated with an outbreak on one occasion. The number of cases con¬sidered as endogenous (category C) was stable and independent of the number of cases in categories A and B. The present study shows that repeated molecular typing can help identify variations in the epidemiology of P. aeruginosa in ICU patients and guide infection control measures.

Modelling the effect of minor orthopaedic day surgery on patient mood at the early post-operative period: a prospective population-based cohort study.

OBJECTIVE: The effect of minor orthopaedic day surgery (MiODS) on patient's mood. METHODS: A prospective population-based cohort study of 148 consecutive patients with age above 18 and less than 65, an American Society of Anaesthesiology (ASA) score of 1, and the requirement of general anaesthesia (GA) were included. The Medical Outcomes Study - Short Form 36 (SF-36), Beck Anxiety Inventory (BAI) and Beck Depression Inventory (BDI) were used pre- and post-operatively. RESULTS: The mean physical component score of SF-36 before surgery was 45.3 (SD=+/-10.1) and 8 weeks following surgery was 44.9 (SD=+/-11.04) [n=148, p=0.51, 95% CI=(-1.03 to 1.52)]. For the measurement of the changes in mood using BDI, BAI and SF-36, latent construct modelling was employed to increase validity. The covariance between mood pre- and post-operatively (cov=69.44) corresponded to a correlation coefficient, r=0.88 indicating that patients suffering a greater number of mood symptoms before surgery continue to have a greater number of symptoms following surgery. When the latent mood constructs were permitted to have different means the model fitted well with chi(2) (df=1)=0.86 for which p=0.77, thus the null hypothesis that MiODS has no effect on patient mood was rejected. CONCLUSIONS: MiODS affects patient mood which deteriorates at 8 weeks post-operatively regardless of the pre-operative patient mood state. More importantly patients suffering a greater number of mood symptoms before MiODS continue to have a greater number of symptoms following surgery.

Calceology : an introduction to North Western European archaeological leather footwear (Neolithic period to c. AD 1600)

Calceology is the study of recovered archaeological leather footwear and is comprised of conservation, documentation and identification of leather shoe components and shoe styles. Recovered leather shoes are complex artefacts that present technical, stylistic and personal information about the culture and people that used them. The current method in calceological research for typology and chronology is by comparison with parallel examples, though its use poses problems by an absence of basic definitions and the lack of a taxonomic hierarchy. The research findings of the primary cutting patterns, used for making all leather footwear, are integrated with the named style method and the Goubitz notation, resulting in a combined methodology as a basis for typological organisation for recovered footwear and a chronology for named shoe styles. The history of calceological research is examined in chapter two and is accompanied by a review of methodological problems as seen in the literature. Through the examination of various documentation and research techniques used during the history of calceological studies, the reasons why a standard typology and methodology failed to develop are investigated. The variety and continual invention of a new research method for each publication of a recovered leather assemblage hindered the development of a single standard methodology. Chapter three covers the initial research with the database through which the primary cutting patterns were identified and the named styles were defined. The chronological span of each named style was established through iterative cross-site sedation and named style comparisons. The technical interpretation of the primary cutting patterns' consistent use is due to constraints imposed by the leather and the forms needed to cover the foot. Basic parts of the shoe patterns and the foot are defined, plus terms provided for identifying the key points for pattern making. Chapter four presents the seventeen primary cutting patterns and their sub-types, these are divided into three main groups: six integral soled patterns, four hybrid soled patterns and seven separately soled patterns. Descriptions of the letter codes, pattern layout, construction principle, closing seam placement and list of sub-types are included in the descriptions of each primary cutting pattern. The named shoe styles and their relative chronology are presented in chapter five. Nomenclature for the named styles is based on the find location of the first published example plus the primary cutting pattern code letter. The named styles are presented in chronological order from Prehistory through to the late 16th century. Short descriptions of the named styles are given and illustrated with examples of recovered archaeological leather footwear, reconstructions of archaeological shoes and iconographical sources. Chapter six presents documentation of recovered archaeological leather using the Goubitz notation, an inventory and description of style elements and fastening methods used for defining named shoe styles, technical information about sole/upper constructions and the consequences created by the use of lasts and sewing forms for style identification and fastening placement in relation to the instep point. The chapter concludes with further technical information about the implications for researchers about shoemaking, pattern making and reconstructive archaeology. The conclusion restates the original research question of why a group of primary cutting patterns appear to have been used consistently throughout the European archaeological record. The quantitative and qualitative results from the database show the use of these patterns but it is the properties of the leather that imposes the use of the primary cutting patterns. The combined methodology of primary pattern identification, named style and artefact registration provides a framework for calceological research.

Fick's law adapted to cationic diffusion in a semi-infinite solid: application to spinel megacrystals

In alkaline lavas, the chemical zoning of megacrystals of spinel is due to the cationic exchange between the latter and the host lava. The application of Fick's law to cationic diffusion profiles allows to calculate the time these crystals have stayed in the lava. Those which are in a chemical equilibrium were in contact with the lava during 20 to 30 days, whereas megacrystals lacking this equilibrium were in contact only for 3 or 4 days. The duration of the rise of an ultrabasic nodule in the volcanic chimney was calculated by applying Stokes' law.

Composition of weight gain during the neonatal period and longitudinal growth follow-up in premature babies.

Changes in the rate of growth and adiposity index (Quetelet index), calculated as weight/(length)2, kg/m2, were monitored from birth to 3 years in 19 premature babies (post-conceptional age 31.2 +/- 2 weeks) who were subjected during rapid growth (16 +/- 4 g/kg.day) to initial metabolic balance studies in the first weeks of life. These studies showed that the rate of fat accretion in these infants (3.3 +/- 0.9 g/kg.day) was substantially greater than that observed in fetuses of the same gestational age (2 g/kg.day) but the adiposity index was lower (9.6 +/- 1 kg/m2) than intrauterine values (11 kg/m2). Since at 6 months of age (corrected for gestational age at birth) the adiposity index was close to normality (103% of standard), the greater rate of fat accretion in early life contributed to progressively restore total body fat in premature babies. It is concluded that despite substantial fat deposition during the first weeks of life, the future evolution of these premature babies is favourable as judged from the normalization of adiposity index within the first 2 years of life.

ON THE ROLE OF PERIOD-2 IN THE CIRCADIAN AND HOMEOSTATIC REGULATION OF SLEEP

Humans spend one third of their life sleeping, then we could raise the basic question: Why do we sleep? Despite the fact that we still don't fully understand its function, we made much progress in understanding at different levels how sleep is regulated. One model suggests that sleep is regulated by two processes: a homeostatic process that tracks the need for sleep and by a circadian rhythm that determines the preferred time-of-day sleep occurs. At the molecular level circadian rhythms are a property of interlocking transcriptional regula-tors referred to as clock genes. The heterodimeric transcription factors BMAL1::CLOCK/NPAS2 drive the transcription of many target genes including the clock genes Cryptochome1 (Cry1), Cry2, Period1 (Per1), and Per2. The encoded CRY/PER proteins are transcriptional inhibitors of BMAL1::CLOCK/NPAS2 thereby providing negative feedback to their own transcription. These genes seem, however, also involved in sleep homeostasis because the brain expression of clock genes, es-pecially that of Per2, increase as a function of time-spent-awake and because mice lacking clock genes display altered sleep homeostasis. The aim of first part of my doctoral work has been to advance our understanding the link that exists between sleep homeostasis and circadian rhythms investigating a possible mechanism by which sleep deprivation could alter clock gene expression by quantifying DNA-binding of the core-clock genes BMAL1, CLOCK and NPAS2 to their target chromatin loci including the E-box enhancers of the Per2 promoter. We made use of chromatin immunoprecipitation (ChIP) and quantitative poly-merase chain reaction (qPCR) to show that DNA-binding of CLOCK and BMAL1 to their target genes changes as a function of time-of-day in both liver and cerebral cortex. We then performed a 6h sleep deprivation (SD) and observed a significant decrease in DNA-binding of CLOCK and BMAL1 to Dbp. This is consistent with a decrease in Dbp mRNA levels after SD. The DNA-binding of NPAS2 and BMAL1 to Per2 was similarly decreased following SD. However, SD has been previously shown to in-crease Per2 expression in the cortex which seems paradoxical. Our results demonstrate that sleep-wake history can affect the molecular clock machinery directly at the level of the chromatin thereby altering the cortical expression of Dbp and Per2, and likely other targets. However, the precise dy-namic relationship between DNA-binding and mRNA expression, especially for Per2, remains elusive. The second aim of my doctoral work has been to perform an in depth characterization of cir-cadian rhythmicity, sleep architecture, analyze the response to SD in full null-Per2 knock-out (Per2-/-) mice, and Per1-/- mice, as well as their double knock-out offspring (Per1,2-/-) and littermate wildtype (Wt) mice. The techniques used include locomotor activity recording by passive infrared (PIR) sen-sors, EEG/EMG surgery, recording, and analysis, and cerebral cortex extraction and quantification of mRNA levels by qPCR. Under standard LD12:12 conditions, we found that wakefulness onset, as well as the time courses of clock gene expression in the brain and corticosterone plasma levels were ad-vanced by about 2h in Per2-/- mice compared to Wt mice. When released under constant dark condi-tions almost all Per2-/- mice (97%) became arrhythmic immediately. From these observations, we conclude that while Per2-/- mice seem to be able to anticipate dark onset, this does not result from a self-sustained circadian clock. Our results suggest instead that the earlier onset of activity results from a labile, not-self sustained 22h rhythm linked to light onset suggesting the existence of a light-driven rhythm. Analyses of sleep under LD12:12 conditions revealed that in both Per2-/- and Per1,2-/- mice the same sleep phenotypes are observed compared to Wt mice: increased NREM sleep frag-mentation and inability to adequately compensate the loss of NREM sleep. That suggests a possible role of PER2 in sleep consolidation and recovery.

Stent-assisted coiling of bifurcation aneurysms may improve endovascular treatment: a critical evaluation in an experimental model.

BACKGROUND AND PURPOSE: Endovascular treatment of wide-neck bifurcation aneurysms often results in incomplete occlusion or aneurysm recurrence. The goals of this study were to compare results of coil embolization with or without the assistance of self-expandable stents and to examine how stents may influence neointima formation. MATERIALS AND METHODS: Wide-neck bifurcation aneurysms were constructed in 24 animals and, after 4-6 weeks, were randomly allocated to 1 of 5 groups: 1) coil embolization using the assistance of 1 braided stent (n = 5); 2) coil embolization using the assistance of 2 braided stents in a Y configuration (n = 5); 3) coil embolization without stent assistance (n = 6); 4) Y-stenting alone (n = 4); and 5) untreated controls (n = 4). Angiographic results were compared at baseline and at 12 weeks, by using an ordinal scale. Neointima formation at the neck at 12 weeks was compared among groups by using a semiquantitative grading scale. Bench studies were performed to assess stent porosities. RESULTS: Initial angiographic results were improved with single stent-assisted coiling compared with simple coiling (P = .013). Angiographic results at 12 weeks were improved with any stent assistance (P = .014). Neointimal closure of the aneurysm neck was similar with or without stent assistance (P = .908), with neointima covering coil loops but rarely stent struts. Y-stent placement alone had no therapeutic effect. Bench studies showed that porosities can be decreased with stent compaction, but a relatively stable porous transition zone was a limiting factor. CONCLUSIONS: Stent-assisted coiling may improve results of embolization by allowing more complete initial coiling, but these high-porosity stents did not provide a scaffold for more complete neointimal closure of aneurysms.

Development of a high throughput PCR to detect Coxiella burnetii and its application in a diagnostic laboratory over a 7-year period.

Q fever is a worldwide zoonotic infectious disease due to Coxiella burnetii. The clinical presentation may be acute (pneumonia and/or hepatitis) or chronic (most commonly endocarditis). Diagnosis mainly relies on serology and PCR. We therefore developed a quantitative real-time PCR. We first tested blindly its performance on various clinical samples and then, when thoroughly validated, we applied it during a 7-year period for the diagnosis of both acute and persistent C. burnetii infection. Analytical sensitivity (< 10 copies/PCR) was excellent. When tested blindly on 183 samples, the specificity of the PCR was 100% (142/142) and the sensitivity was 71% (29/41). The sensitivity was 88% (7/8) on valvular samples, 69% (20/29) on blood samples and 50% (2/4) on urine samples. This new quantitative PCR was then successfully applied for the diagnosis of acute Q fever and endovascular infection due to C. burnetii, allowing the diagnosis of Q fever in six patients over a 7-year period. During a local small cluster of cases, the PCR was also applied to blood from 1355 blood donors; all were negative confirming the high specificity of this test. In conclusion, we developed a highly specific method with excellent sensitivity, which may be used on sera for the diagnosis of acute Q fever and on various samples such as sera, valvular samples, aortic specimens, bone and liver, for the diagnosis of persistent C. burnetii infection.

Temporal distribution and magnitude of the vulnerability period around stroke depend on stroke subtype.

Background: We aimed to analyze the rate and time distribution of pre- and post-morbid cerebrovascular events in a single ischemic stroke population, and whether these depend on the etiology of the index stroke. Methods: In 2,203 consecutive patients admitted to a single stroke center registry (ASTRAL), the ischemic stroke that led to admission was considered the index event. Frequency distribution and cumulative relative distribution graphs of the most recent and first recurrent event (ischemic stroke, transient ischemic attack, intracranial or subarachnoid hemorrhage) were drawn in weekly and daily intervals for all strokes and for all stroke types. Results: The frequency of events at identical time points before and after the index stroke was mostly reduced in the first week after (vs. before) stroke (1.0 vs. 4.2%, p < 0.001) and the first month (2.7 vs. 7.4%, p < 0.001), and then ebbed over the first year (8.4 vs. 13.1%, p < 0.001). On daily basis, the peak frequency was noticed at day -1 (1.6%) with a reduction to 0.7% on the index day and 0.17% 24 h after. The event rate in patients with atherosclerotic stroke was particularly high around the index event, but 1-year cumulative recurrence rate was similar in all stroke types. Conclusions: We confirm a short window of increased vulnerability in ischemic stroke and show a 4-, 3- and 2-fold reduction in post-stroke events at 1 week, 1 month and 1 year, respectively, compared to identical pre-stroke periods. This break in the 'stroke wave' is particularly striking after atherosclerotic and lacunar strokes.

Effects of age, birth cohort and period of death on Swiss cancer mortality, 1951-1984.

Swiss death certification data over the period 1951-1984 for total cancer mortality and 30 major cancer sites in the population aged 25 to 74 years were analysed using a log-linear Poisson model with arbitrary constraints on the parameters to isolate the effects of birth cohort, calendar period of death and age. The overall pattern of total cancer mortality in males was stable for period values and showed some moderate decreases in cohort values restricted to the generations born after 1930. Cancer mortality trends were more favourable in females, with steady, though moderate, declines in both cohort and period values. According to the estimates from the model, the worst affected generation for male lung cancer was that born around 1910, and a flattening of trends or some moderate decline was observed for more recent cohorts, although this decline was considerably more limited than in other European countries. There were decreases in cohort and period values for stomach, intestine and oesophageal cancer in both sexes and (cervix) uteri in females. Increases were observed in both cohort and period trends for pancreas and liver in males and for several other neoplasms, including prostate, brain, leukaemias and lymphomas, restricted, however, for the latter sites, to the earlier cohorts and hence partly attributable to improved diagnosis and certification in the elderly. Although age values for lung cancer in females were around 10-times lower than in males, upward trends in female lung cancer cohort values were observed in subsequent cohorts and for period values from the late 1960's onwards. Therefore, future trends in female lung cancer mortality should continue to be monitored. The application of these age/period/cohort models thus provides a summary guide for the reading and interpretation of cancer mortality trends, although it cannot replace careful inspection of single age-specific rates.

Flow structures at an idealized bifurcation : a numerical experiment

River bifurcations are key nodes within braided river systems controlling the flow and sediment partitioning and therefore the dynamics of the river braiding process. Recent research has shown that certain geometrical configurations induce instabilities that lead to downstream mid-channel bar formation and the formation of bifurcations. However, we currently have a poor understanding of the flow division process within bifurcations and the flow dynamics in the downstream bifurcates, both of which are needed to understand bifurcation stability. This paper presents results of a numerical sensitivity experiment undertaken using computational fluid dynamics (CFD) with the purpose of understanding the flow dynamics of a series of idealized bifurcations. A geometric sensitivity analysis is undertaken for a range of channel slopes (0.005 to 0.03), bifurcation angles (22 degrees to 42 degrees) and a restricted set of inflow conditions based upon simulating flow through meander bends with different curvature on the flow field dynamics through the bifurcation. The results demonstrate that the overall slope of the bifurcation affects the velocity of flow through the bifurcation and when slope asymmetry is introduced, the flow structures in the bifurcation are modified. In terms of bifurcation evolution the most important observation appears to be that once slope asymmetry is greater than 0.2 the flow within the steep bifurcate shows potential instability and the potential for alternate channel bar formation. Bifurcation angle also defines the flow structures within the bifurcation with an increase in bifurcation angle increasing the flow velocity down both bifurcates. However, redistributive effects of secondary circulation caused by upstream curvature can very easily counter the effects of local bifurcation characteristics. Copyright (C) 2011 John Wiley & Sons, Ltd.

Circadian clock-coordinated 12 Hr period rhythmic activation of the IRE1alpha pathway controls lipid metabolism in mouse liver.

The mammalian circadian clock plays a fundamental role in the liver by regulating fatty acid, glucose, and xenobiotic metabolism. Impairment of this rhythm has been shown to lead to diverse pathologies, including metabolic syndrome. Currently, it is supposed that the circadian clock regulates metabolism mostly by regulating expression of liver enzymes at the transcriptional level. Here, we show that the circadian clock also controls hepatic metabolism by synchronizing a secondary 12 hr period rhythm characterized by rhythmic activation of the IRE1alpha pathway in the endoplasmic reticulum. The absence of circadian clock perturbs this secondary clock and provokes deregulation of endoplasmic reticulum-localized enzymes. This leads to impaired lipid metabolism, resulting in aberrant activation of the sterol-regulated SREBP transcription factors. The resulting aberrant circadian lipid metabolism in mice devoid of the circadian clock could be involved in the appearance of the associated metabolic syndrome.