Optimal culture incubation time in orthopedic device-associated infections: a retrospective analysis of prolonged 14-day incubation.

Accurate diagnosis of orthopedic device-associated infections can be challenging. Culture of tissue biopsy specimens is often considered the gold standard; however, there is currently no consensus on the ideal incubation time for specimens. The aim of our study was to assess the yield of a 14-day incubation protocol for tissue biopsy specimens from revision surgery (joint replacements and internal fixation devices) in a general orthopedic and trauma surgery setting. Medical records were reviewed retrospectively in order to identify cases of infection according to predefined diagnostic criteria. From August 2009 to March 2012, 499 tissue biopsy specimens were sampled from 117 cases. In 70 cases (59.8%), at least one sample showed microbiological growth. Among them, 58 cases (82.9%) were considered infections and 12 cases (17.1%) were classified as contaminations. The median time to positivity in the cases of infection was 1 day (range, 1 to 10 days), compared to 6 days (range, 1 to 11 days) in the cases of contamination (P < 0.001). Fifty-six (96.6%) of the infection cases were diagnosed within 7 days of incubation. In conclusion, the results of our study show that the incubation of tissue biopsy specimens beyond 7 days is not productive in a general orthopedic and trauma surgery setting. Prolonged 14-day incubation might be of interest in particular situations, however, in which the prevalence of slow-growing microorganisms and anaerobes is higher.

The lower Triassic anachronistic carbonate facies in space and time

The end-Permian mass extinction greatly affected the sedimentary record, but the sedimentary response was not limited to the Permian-Triassic boundary interval. This transformation extended to sedimentation that spanned the entire Early Triassic. Calcimicrobialites play an important role throughout this time interval, and at least four main events of anomalous carbonate deposition can be shown. A post-extinction calcimicrobial unit occurs above the extensive Permian skeletal carbonate platform exposed in the Taurus Mountains (southern Turkey), in south Armenia, north-west north and Central Iran along the Zagros Mountains. The calcimicrobial unit formed during the flooding of the platform that took place during the earliest Triassic. A similar calcimicrobialite formed during late Griesbachian to Dienerian time atop the shallow Permian skeletal carbonate platform largely exposed in south China. A third event occurred during the Early Olenekian on the first Mesozoic isolated pelagic plateau (Baid seamount, Oman Mountains). Here the change in carbonate sedimentation is reflected in the occurrence of thrombolites and carbonate seafloor fans. Near the end of Early Triassic time, unusual carbonate deposition is recorded both on an isolated pelagic plateau of the Western Tethys (Halstatt limestone of Dobrogea, Romania) and on the eastern Panthalassa margin of the western United States. In the western United States, the event is represented by stromatolites and thrombolites in the Virgin Limestone of the Moenkopi Formation and by seafloor fans in the middle and upper members of the Union Wash Formation. These unusual episodes of anomalous carbonate deposition illustrate a fundamental change in sedimentation that occurred in the aftermath of the end-Permian mass extinction.

Predicting the physicochemical profile of diastereoisomeric histidine-containing dipeptides by property space analysis.

OBJECTIVES: This study aimed at measuring the lipophilicity and ionization constants of diastereoisomeric dipeptides, interpreting them in terms of conformational behavior, and developing statistical models to predict them. METHODS: A series of 20 dipeptides of general structure NH(2) -L-X-(L or D)-His-OMe was designed and synthetized. Their experimental ionization constants (pK(1) , pK(2) and pK(3) ) and lipophilicity parameters (log P(N) and log D(7.4) ) were measured by potentiometry. Molecular modeling in three media (vacuum, water, and chloroform) was used to explore and sample their conformational space, and for each stored conformer to calculate their radius of gyration, virtual log P (preferably written as log P(MLP) , meaning obtained by the molecular lipophilicity potential (MLP) method) and polar surface area (PSA). Means and ranges were calculated for these properties, as was their sensitivity (i.e., the ratio between property range and number of rotatable bonds). RESULTS: Marked differences between diastereoisomers were seen in their experimental ionization constants and lipophilicity parameters. These differences are explained by molecular flexibility, configuration-dependent differences in intramolecular interactions, and accessibility of functional groups. Multiple linear equations correlated experimental lipophilicity parameters and ionization constants with PSA range and other calculated parameters. CONCLUSION: This study documents the differences in lipophilicity and ionization constants between diastereoisomeric dipeptides. Such configuration-dependent differences are shown to depend markedly on differences in conformational behavior and to be amenable to multiple linear regression. Chirality 24:566-576, 2012. © 2012 Wiley Periodicals, Inc.

Where and how family members spend time at home? A quantitative analysis of the observational tracking on the everyday lives of Italian families

This paper examines a dataset that derives from an observational tracking, in order to analyze where and how middle-class working families spend time at home. We use an ethnographic approach to study the everyday lives of Italian dual-income middle-class families, with the aim to analyze quantitatively the use of home spaces and the types of activities of family members on weekday afternoons and evenings. The different analyses (multiple correspondence analysis, agglomerative hierarchical cluster, discriminant analysis) show how particular spaces and activities in these spaces are dominated by certain family members. We suggest a combination of qualitative and quantitative methodologies as useful tools to explore in detail the everyday lives of families, and to understand how family members use the domestic spaces. In particular, we consider relevant the use of quantitative analyses to examine ethnographic data, especially in connection with the methodological reflexivity among researchers

Analysis of TNF-antagonist switch over time and associated risk factors in the Swiss Inflammatory Bowel Disease Cohort.

Abstract Background and aims. Limited data from large cohorts are available on tumor necrosis factor (TNF) antagonists (infliximab, adalimumab, certolizumab pegol) switch over time. We aimed to evaluate the prevalence of switching from one TNF antagonist to another and to identify associated risk factors. Methods. Data from the Swiss Inflammatory Bowel Diseases Cohort Study (SIBDCS) were analyzed. Results. Of 1731 patients included into the SIBDCS (956 with Crohn's disease [CD] and 775 with ulcerative colitis [UC]), 347 CD patients (36.3%) and 129 UC patients (16.6%) were treated with at least one TNF antagonist. A total of 53/347 (15.3%) CD patients (median disease duration 9 years) and 20/129 (15.5%) of UC patients (median disease duration 7 years) needed to switch to a second and/or a third TNF antagonist, respectively. Median treatment duration was longest for the first TNF antagonist used (CD 25 months; UC 14 months), followed by the second (CD 13 months; UC 4 months) and third TNF antagonist (CD 11 months; UC 15 months). Primary nonresponse, loss of response and side effects were the major reasons to stop and/or switch TNF antagonist therapy. A low body mass index, a short diagnostic delay and extraintestinal manifestations at inclusion were identified as risk factors for a switch of the first used TNF antagonist within 24 months of its use in CD patients. Conclusion. Switching of the TNF antagonist over time is a common issue. The median treatment duration with a specific TNF antagonist is diminishing with an increasing number of TNF antagonists being used.

Gliotransmitters Travel in Time and Space.

The identification of the presence of active signaling between astrocytes and neurons in a process termed gliotransmission has caused a paradigm shift in our thinking about brain function. However, we are still in the early days of the conceptualization of how astrocytes influence synapses, neurons, networks, and ultimately behavior. In this Perspective, our goal is to identify emerging principles governing gliotransmission and consider the specific properties of this process that endow the astrocyte with unique functions in brain signal integration. We develop and present hypotheses aimed at reconciling confounding reports and define open questions to provide a conceptual framework for future studies. We propose that astrocytes mainly signal through high-affinity slowly desensitizing receptors to modulate neurons and perform integration in spatiotemporal domains complementary to those of neurons.

Artificial evolution on network structures : how time and space influence dynamics

Abstract The main objective of this work is to show how the choice of the temporal dimension and of the spatial structure of the population influences an artificial evolutionary process. In the field of Artificial Evolution we can observe a common trend in synchronously evolv¬ing panmictic populations, i.e., populations in which any individual can be recombined with any other individual. Already in the '90s, the works of Spiessens and Manderick, Sarma and De Jong, and Gorges-Schleuter have pointed out that, if a population is struc¬tured according to a mono- or bi-dimensional regular lattice, the evolutionary process shows a different dynamic with respect to the panmictic case. In particular, Sarma and De Jong have studied the selection pressure (i.e., the diffusion of a best individual when the only selection operator is active) induced by a regular bi-dimensional structure of the population, proposing a logistic modeling of the selection pressure curves. This model supposes that the diffusion of a best individual in a population follows an exponential law. We show that such a model is inadequate to describe the process, since the growth speed must be quadratic or sub-quadratic in the case of a bi-dimensional regular lattice. New linear and sub-quadratic models are proposed for modeling the selection pressure curves in, respectively, mono- and bi-dimensional regu¬lar structures. These models are extended to describe the process when asynchronous evolutions are employed. Different dynamics of the populations imply different search strategies of the resulting algorithm, when the evolutionary process is used to solve optimisation problems. A benchmark of both discrete and continuous test problems is used to study the search characteristics of the different topologies and updates of the populations. In the last decade, the pioneering studies of Watts and Strogatz have shown that most real networks, both in the biological and sociological worlds as well as in man-made structures, have mathematical properties that set them apart from regular and random structures. In particular, they introduced the concepts of small-world graphs, and they showed that this new family of structures has interesting computing capabilities. Populations structured according to these new topologies are proposed, and their evolutionary dynamics are studied and modeled. We also propose asynchronous evolutions for these structures, and the resulting evolutionary behaviors are investigated. Many man-made networks have grown, and are still growing incrementally, and explanations have been proposed for their actual shape, such as Albert and Barabasi's preferential attachment growth rule. However, many actual networks seem to have undergone some kind of Darwinian variation and selection. Thus, how these networks might have come to be selected is an interesting yet unanswered question. In the last part of this work, we show how a simple evolutionary algorithm can enable the emrgence o these kinds of structures for two prototypical problems of the automata networks world, the majority classification and the synchronisation problems. Synopsis L'objectif principal de ce travail est de montrer l'influence du choix de la dimension temporelle et de la structure spatiale d'une population sur un processus évolutionnaire artificiel. Dans le domaine de l'Evolution Artificielle on peut observer une tendence à évoluer d'une façon synchrone des populations panmictiques, où chaque individu peut être récombiné avec tout autre individu dans la population. Déjà dans les année '90, Spiessens et Manderick, Sarma et De Jong, et Gorges-Schleuter ont observé que, si une population possède une structure régulière mono- ou bi-dimensionnelle, le processus évolutionnaire montre une dynamique différente de celle d'une population panmictique. En particulier, Sarma et De Jong ont étudié la pression de sélection (c-à-d la diffusion d'un individu optimal quand seul l'opérateur de sélection est actif) induite par une structure régulière bi-dimensionnelle de la population, proposant une modélisation logistique des courbes de pression de sélection. Ce modèle suppose que la diffusion d'un individu optimal suit une loi exponentielle. On montre que ce modèle est inadéquat pour décrire ce phénomène, étant donné que la vitesse de croissance doit obéir à une loi quadratique ou sous-quadratique dans le cas d'une structure régulière bi-dimensionnelle. De nouveaux modèles linéaires et sous-quadratique sont proposés pour des structures mono- et bi-dimensionnelles. Ces modèles sont étendus pour décrire des processus évolutionnaires asynchrones. Différentes dynamiques de la population impliquent strategies différentes de recherche de l'algorithme résultant lorsque le processus évolutionnaire est utilisé pour résoudre des problèmes d'optimisation. Un ensemble de problèmes discrets et continus est utilisé pour étudier les charactéristiques de recherche des différentes topologies et mises à jour des populations. Ces dernières années, les études de Watts et Strogatz ont montré que beaucoup de réseaux, aussi bien dans les mondes biologiques et sociologiques que dans les structures produites par l'homme, ont des propriétés mathématiques qui les séparent à la fois des structures régulières et des structures aléatoires. En particulier, ils ont introduit la notion de graphe sm,all-world et ont montré que cette nouvelle famille de structures possède des intéressantes propriétés dynamiques. Des populations ayant ces nouvelles topologies sont proposés, et leurs dynamiques évolutionnaires sont étudiées et modélisées. Pour des populations ayant ces structures, des méthodes d'évolution asynchrone sont proposées, et la dynamique résultante est étudiée. Beaucoup de réseaux produits par l'homme se sont formés d'une façon incrémentale, et des explications pour leur forme actuelle ont été proposées, comme le preferential attachment de Albert et Barabàsi. Toutefois, beaucoup de réseaux existants doivent être le produit d'un processus de variation et sélection darwiniennes. Ainsi, la façon dont ces structures ont pu être sélectionnées est une question intéressante restée sans réponse. Dans la dernière partie de ce travail, on montre comment un simple processus évolutif artificiel permet à ce type de topologies d'émerger dans le cas de deux problèmes prototypiques des réseaux d'automates, les tâches de densité et de synchronisation.

Sex-chromosome evolution of Palearctic tree frogs in space and time

Sexual reproduction is nearly universal in eukaryotes and genetic determination of sex prevails among animals. The astonishing diversity of sex-determining systems and sex chromosomes is yet bewildering. Some taxonomic groups possess conserved and dimorphic sex chromosomes, involving a functional copy (e.g. mammals' X, birds' Z) and a degenerated copy (mammals' Y, birds' W), implying that sex- chromosomes are expected to decay. In contrast, others like amphibians, reptiles and fishes yet maintained undifferentiated sex chromosomes. Why such different evolutionary trajectories? In this thesis, we empirically test and characterize the main hypotheses proposed to prevent the genetic decay of sex chromosomes, namely occasional X-Y recombination and frequent sex-chromosome transitions, using the Palearctic radiation of Hyla tree frogs as a model system. We take a phylogeographic and phylogenetic approach to relate sex-chromosome recombination, differentiation, and transitions in a spatial and temporal framework. By reconstructing the recent evolutionary history of the widespread European tree frog H. arborea, we showed that sex chromosomes can recombine in males, preventing their differentiation, a situation that potentially evolves rapidly. At the scale of the entire radiation, X-Y recombination combines with frequent transitions to prevent sex-chromosome degeneration in Hyla: we traced several turnovers of sex-determining system within the last 10My. These rapid changes seem less random than usually assumed: we gathered evidences that one chromosome pair is a sex expert, carrying genes with key role in animal sex determination, and which probably specialized through frequent reuse as a sex chromosome in Hyla and other amphibians. Finally, we took advantage of secondary contact zones between closely-related Hyla lineages to evaluate the consequences of sex chromosome homomorphy on the genetics of speciation. In comparison with other systems, the evolution of sex chromosomes in Hyla emphasized the existence of consistent evolutionary patterns within the chaotic diversity of flexibility of cold-blooded vertebrates' sex-determining systems, and provides insights into the evolution of recombination. Beyond sex-chromosome evolution, this work also significantly contributed to speciation, phylogeography and applied conservation research. -- La reproduction sexuée est quasi-universelle chez les eucaryotes et le sexe est le plus souvent déterminé génétiquement au sein du règne animal. L'incroyable diversité des systèmes de reproduction et des chromosomes sexuels est particulièrement étonnante. Certains groupes taxonomiques possèdent des chromosomes sexuels dimorphiques et très conservés, avec une copie entièrement fonctionnelle (ex : le X des mammifères, le Z des oiseaux) et une copie dégénérée (ex : le Y des mammifères, le W des oiseaux), suggérant que les chromosomes sexuels sont voués à se détériorer. Cependant les chromosomes sexuels d'autres groupes tels que les amphibiens, les reptiles et les poissons sont pour la plupart indifférenciés. Comment expliquer des trajectoires évolutives si différentes? Au cours de cette thèse, nous avons étudié empiriquement les processus évolutifs pouvant maintenir les chromosomes sexuels intacts, à savoir la recombinaison X-Y occasionnel ainsi que les substitutions fréquentes de chromosomes sexuels, en utilisant les rainettes Paléarctiques du genre Hyla comme modèle d'étude. Nous avons adopté une approche phylogéographique et phylogénétique pour appréhender les événements de recombinaison, de différenciation et de transitions de chromosomes sexuels dans un contexte spatio-temporel. En retraçant l'histoire évolutive récente de la rainette verte H. arborea, nous avons mis en évidence que les chromosomes sexuels pouvaient recombiner chez les mâles, empêchant ainsi leur différenciation, et que ce processus avait le potentiel d'évoluer très rapidement. A l'échelle plus globale de la radiation, il apparait que les phénomènes de recombinaison X-Y soient également accompagnés de substitutions de chromosomes sexuels, et participent de concert au maintien de chromosomes sexuels intacts dans les populations: le système de détermination du sexe des rainettes a changé plusieurs fois au cours des 10 derniers millions d'années. Ces transitions fréquentes ne semblent pas aléatoires: nous avons identifié une paire de chromosomes qui présente des caractéristiques présageant d'une spécialisation dans le déterminisme du sexe (notamment car elle possède des gènes importants pour cette fonction), et qui a été réutilisée plusieurs fois comme tel chez les rainettes ainsi que d'autres amphibiens. Enfin, nous avons étudié l'hybridation entre différentes espèces dans leurs zones de contact, afin d'évaluer si l'absence de différenciation entre X et Y jouaient un rôle dans les processus génétiques de spéciation. Outre son intérêt pour la compréhension de l'évolution des chromosomes sexuels, ce travail contribue de manière significative à d'autres domaines de recherche tels que la spéciation, la phylogéographie, ainsi que la biologie de la conservation.

Risk Factors for Incisional and Organ Space Surgical Site Infections After Liver Resection are Different.

BACKGROUND: Surgical site infection (SSI) is a common cause of major morbidity after liver resection. This study aimed to identify the risk factors for incisional and organ/space SSIs after liver resection. METHODS: Our liver surgery database was retrospectively analyzed for patients treated between January 2009 and November 2012 in a tertiary care Swiss hospital. Univariate and multivariate analyses were conducted on preoperative, intraoperative, and postoperative variables to identify risk factors for incisional and organ/space SSIs. RESULTS: In a total of 226 patients, SSI incidences were 12.8 % (incisional), 4.0 % (organ/space), and 1.8 % (both). Univariate analysis showed that incisional SSIs were associated with high American Society of Anesthesiologists (ASA) scores, preoperative anemia, hypoalbuminemia, low prothrombin time, viral or alcoholic chronic hepatitis, liver cirrhosis, and prolonged operation times. Organ/space SSIs were associated with high rates of red blood cell transfusions, concomitant bowel surgery, and prolonged operation times. Multivariate analysis revealed that risk factors for incisional SSIs were anemia [odds ratio (OR) 2.82], high ASA scores (OR 2.88), presence of hepatitis or cirrhosis (OR 5.07), and prolonged operation times (OR 9.61). The only risk factor for organ/space SSIs was concomitant bowel surgery (OR 5.53). Hospital stays were similar in organ/space and incisional SSI groups, but significantly longer for those with both organ/space and incisional SSIs. CONCLUSIONS: High ASA scores, anemia, chronic hepatitis or liver cirrhosis, and prolonged operations increased the risk of incisional SSIs; concomitant bowel surgery increased the risk of organ/space SSI. Specific precautions to prevent organ/space and incisional SSIs may shorten hospital stays.

Analysis of flow dynamics in right ventricular outflow tract.

BACKGROUND: The mechanism behind early graft failure after right ventricular outflow tract (RVOT) reconstruction is not fully understood. Our aim was to establish a three-dimensional computational fluid dynamics (CFD) model of RVOT to investigate the hemodynamic conditions that may trigger the development of intimal hyperplasia and arteriosclerosis. METHODS: Pressure, flow, and diameter at the RVOT, pulmonary artery (PA), bifurcation of the PA, and left and right PAs were measured in 10 normal pigs with a mean weight of 24.8 ± 0.78 kg. Data obtained from the experimental scenario were used for CFD simulation of pressure, flow, and shear stress profile from the RVOT to the left and right PAs. RESULTS: Using experimental data, a CFD model was obtained for 2.0 and 2.5-L/min pulsatile inflow profiles. In both velocity profiles, time and space averaged in the low-shear stress profile range from 0-6.0 Pa at the pulmonary trunk, its bifurcation, and at the openings of both PAs. These low-shear stress areas were accompanied to high-pressure regions 14.0-20.0 mm Hg (1866.2-2666 Pa). Flow analysis revealed a turbulent flow at the PA bifurcation and ostia of both PAs. CONCLUSIONS: Identified local low-shear stress, high pressure, and turbulent flow correspond to a well-defined trigger pattern for the development of intimal hyperplasia and arteriosclerosis. As such, this real-time three-dimensional CFD model may in the future serve as a tool for the planning of RVOT reconstruction, its analysis, and prediction of outcome.

Improving anterior deltoid activity in a musculoskeletal shoulder model - an analysis of the torque-feasible space at the sternoclavicular joint.

Modelling the shoulder's musculature is challenging given its mechanical and geometric complexity. The use of the ideal fibre model to represent a muscle's line of action cannot always faithfully represent the mechanical effect of each muscle, leading to considerable differences between model-estimated and in vivo measured muscle activity. While the musculo-tendon force coordination problem has been extensively analysed in terms of the cost function, only few works have investigated the existence and sensitivity of solutions to fibre topology. The goal of this paper is to present an analysis of the solution set using the concepts of torque-feasible space (TFS) and wrench-feasible space (WFS) from cable-driven robotics. A shoulder model is presented and a simple musculo-tendon force coordination problem is defined. The ideal fibre model for representing muscles is reviewed and the TFS and WFS are defined, leading to the necessary and sufficient conditions for the existence of a solution. The shoulder model's TFS is analysed to explain the lack of anterior deltoid (DLTa) activity. Based on the analysis, a modification of the model's muscle fibre geometry is proposed. The performance with and without the modification is assessed by solving the musculo-tendon force coordination problem for quasi-static abduction in the scapular plane. After the proposed modification, the DLTa reaches 20% of activation.