Orthotropic active strain models for the numerical simulation of cardiac biomechanics

An active strain formulation for orthotropic constitutive laws arising in cardiac mechanics modeling is introduced and studied. The passive mechanical properties of the tissue are described by the Holzapfel-Ogden relation. In the active strain formulation, the Euler-Lagrange equations for minimizing the total energy are written in terms of active and passive deformation factors, where the active part is assumed to depend, at the cell level, on the electrodynamics and on the specific orientation of the cardiac cells. The well-posedness of the linear system derived from a generic Newton iteration of the original problem is analyzed and different mechanical activation functions are considered. In addition, the active strain formulation is compared with the classical active stress formulation from both numerical and modeling perspectives. Taylor-Hood and MINI finite elements are employed to discretize the mechanical problem. The results of several numerical experiments show that the proposed formulation is mathematically consistent and is able to represent the main key features of the phenomenon, while allowing savings in computational costs.

Probabilistic evidential assessment of gunshot residue particle evidence (Part II) : Bayesian parameter estimation for experimental count data.

Part I of this series of articles focused on the construction of graphical probabilistic inference procedures, at various levels of detail, for assessing the evidential value of gunshot residue (GSR) particle evidence. The proposed models - in the form of Bayesian networks - address the issues of background presence of GSR particles, analytical performance (i.e., the efficiency of evidence searching and analysis procedures) and contamination. The use and practical implementation of Bayesian networks for case pre-assessment is also discussed. This paper, Part II, concentrates on Bayesian parameter estimation. This topic complements Part I in that it offers means for producing estimates useable for the numerical specification of the proposed probabilistic graphical models. Bayesian estimation procedures are given a primary focus of attention because they allow the scientist to combine (his/her) prior knowledge about the problem of interest with newly acquired experimental data. The present paper also considers further topics such as the sensitivity of the likelihood ratio due to uncertainty in parameters and the study of likelihood ratio values obtained for members of particular populations (e.g., individuals with or without exposure to GSR).

Determinants sociodemogràfics, incentius i rendiments econòmics de l'aprenentage de l'idioma Català per part de la població immigrant a Catalunya

En aquest projecte s’han estudiat diferents aspectes relacionats amb l’aprenentatge del català per part de la població immigrant. Aquest es un tema rellevant donat que les habilitats idiomàtiques dels immigrants es una altra forma de capital humà, que no només facilita la seva integració social, sinó que també incrementa les seves oportunitats laborals. En aquest estudi s’ha enfocat l’aprenentatge de l’idioma català per part de la població immigrant com una inversió de la qual es deriven costos i beneficis. Una qüestió rellevant és quins son els incentius que els immigrants que ja parlen el castellà, bé per que és la seva llengua materna o per que l’han après amb posterioritat, tenen per aprendre la llengua catalana. Aquest estudi es encara més interessant si considerem aquells immigrants que no tenen un nivell fluït del castellà, i encara més els que arriben a Catalunya sense conèixer cap de les dues llegües oficials. Aquest estudi es centra en els determinants econòmics i demogràfics del nivell de coneixement del català entre els immigrants a Catalunya. En aquest sentit, és clau determinar el rol que juguen variables com el grau d’exposició, eficiència i els incentius econòmics, com per exemple les conseqüències laborals (salaris i oportunitat de treball). Tanmateix, també es important determinar si viure en entorns on hi ha una gran concentració d’immigrants d’un mateix país exerceix un efecte depressor en l’aprenentatge del català per part dels immigrants. La segona part del projecte ha consistit en estimar un model per contrastar la hipòtesi de si el coneixement del català per part dels immigrants implica un millor salari. Per altra banda, també analitzarem si aquest coneixement del català implícita tenir accés a millors oportunitats de treball. La confirmació d’aquestes hipòtesis implicaria que els immigrants realment tenen un incentiu econòmic per invertir en l’aprenentatge del català.     

THE ADULA NAPPE: STRATIGRAPHY, STRUCTURE AND KINEMATICS OF AN EXHUMED HIGH-PRESSURE NAPPE

This study analyses the stratigraphy, structure and kinematics of the northern part of the Adula nappe of the Central Alps. The Adula nappe is one of the highest basement nappes in the Lower Penninic nappe stack of the Lepontine Dome. This structural position makes possible the investigation of the transition between the Helvetic and North Penninic paleogeographic domains. The Adula nappe is principally composed of crystalline basement rocks. The investigation of the pre-Triassic basement shows that it contains several Palaeozoic detrital metasedimentary formations dated from the Cambrian to the Ordovician. These formations contain also some volcanic or intrusive magmatic rocks. Ordovician metagranites dated at ~450 Ma are also a common rock-type of the Adula basement. These formations underwent Alpine and Variscan deformation and metamorphism. Permian granites (Zervreila orthogneiss, dated at ~290 Ma) have intruded this pre-structured basement in a post-orogenic geodynamic context. Due to their age, the Zervreila orthogneiss are good markers for alpine deformation. The stratigraphy of the Mesozoic and Paleogene sedimentary cover of the Adula nappe is essential to unraveling its pre- orogenic history. The autochthonous cover is assigned to a North Penninic Triassic series that testifies for a transition between the Helvetic and Briançonnais Triassic domains. The Adula domain goes through an emersion during the Middle Jurassic, and is part of a topographic high during the first phase of the Alpine rift. The sediments of the late Middle Jurassic show a drowning phase associated with a tectonic activity and a breccia formation. In the neighbouring domains, coeval with the drowning phase in the Adula domain, a strong extensional crustal delamination and a scattered magmatic activity is associated with the main opening of the North Penninic domain. The Upper Jurassic of the Adula nappe is characterized by a carbonate formation comparable with those in the Helvetic or Subbriaçonnais domains. Flysch s.l. deposition starts probably at the end of the Cretaceous. These sediments are deposited on a large unconformity testifying for a Cretaceous sedimentary gap. The Adula nappe exhibits a very complex structure. This structure is formed by several deformation phases. Two ductile deformations are responsible for the nappe emplacement. The first deformation phase is associated with a folding compatible with a top-to-south movement at the top of the nappe. The second phase is dominant and pervasive throughout the whole nappe. It goes with a strong north vergent folding and the main nappe emplacement. These two phases cause the exhumation and emplacement of a coherent, although pre-structured, piece of continental crust. Two further deformation phases postdate the nappe emplacement. - Ce travail concerne l'étude géologique de la partie nord de la nappe de l'Adula dans les Alpes centrales. La nappe de l'Adula est l'une des nappes cristallines la plus élevée dans la pile des nappes du Pennique inférieur des Alpes lepontines. Cette position particulière permet d'étudier la transition entre les nappes des domaines helvétique et pennique inférieur. La nappe de l'Adula est principalement composée de socle cristallin : l'étude de l'histoire géologique du socle est donc l'un des thèmes de cette recherche. Ce socle contient plusieurs formations métasédimentaires paléozoïques du Cambrien à I'Ordovicien. Ces métasédiments sont issus de formations clastiques comprenant souvent des roches magmatiques volcaniques et intrusives. Ces métasédiments ont subi les cycles orogéniques varisque et alpin. La nappe de l'Adula contient plusieurs corps magmatiques granitiques métamorphisés. Les premiers métagranites sont Ordovicien et témoignent d'un environnement de marge active. Ces granites sont aussi polymétamorphiques. Les deuxièmes métagranites sont représentés par les orthogneiss de type Zervreila. Ce métagranite est d'âge permien (-290 Ma). Il est mis en place dans un contexte tectonique post-orogénique. Ce granite est un maqueur de la déformation alpine car il n'est pas affecté par les orogenèses précédentes, flippy Le contenu stratigraphique des roches mésozoïques et cénozoiques de la couverture sédimentaire de la nappe de l'Adula est'important pour en étudier son histoire pré-alpine. La couverture autochtone est composée d'une série d'âge triasique d'affinité nord-pennique, un faciès qui marque la transition entre les domaines helvétiques et briançonnais au Trias. Le domaine paléogéographique représenté dans la nappe de l'Adula connaît une émersion pendant le Jurassique moyen. Cette émersion marque le commencement du rift dans le domaine alpin. La sédimentation de la fin du Jurassique moyen est marquée par une transgression marine accompagnée par des mouvements tectoniques et la formation d'une brèche. Cette transgression est contemporaine des importants mouvements tectoniques et des manifestations magmatiques dans les unités voisines qui marquent la phase principale d'ouverture du bassin nord-pennique. Le Jurassique supérieur est caractérisé par l'instauration d'une sédimentation carbonatée comparable à celle du domaine helvétique ou subbriançonnais. Une sédimentation flyschoïde, probablement du Crétacé à Tertiaire, est déposée sur une importante discordance qui témoigne d'une lacune au Crétacé. La structure complexe de la nappe de l'Adula témoigne de nombreuses phases de déformation. Ces phases de déformation sont en partie issues de la mise en place de la nappe et de déformations plus tardives. La mise en place de la nappe produit deux phases de déformation ductile : la première produit un plissement compatible avec un cisaillement top-vers-le sud dans la partie supérieure de la nappe; la deuxième produit un intense plissement qui accompagne la mise en place de la nappe vers le nord. Ces deux phases de déformation témoignent d'un mécanisme d'exhumation par déformation ductile d'un bloc cohérent.

Temporal diffeomorphic free-form deformation: application to motion and strain estimation from 3D echocardiography

This paper presents a new registration algorithm, called Temporal Di eomorphic Free Form Deformation (TDFFD), and its application to motion and strain quanti cation from a sequence of 3D ultrasound (US) images. The originality of our approach resides in enforcing time consistency by representing the 4D velocity eld as the sum of continuous spatiotemporal B-Spline kernels. The spatiotemporal displacement eld is then recovered through forward Eulerian integration of the non-stationary velocity eld. The strain tensor iscomputed locally using the spatial derivatives of the reconstructed displacement eld. The energy functional considered in this paper weighs two terms: the image similarity and a regularization term. The image similarity metric is the sum of squared di erences between the intensities of each frame and a reference one. Any frame in the sequence can be chosen as reference. The regularization term is based on theincompressibility of myocardial tissue. TDFFD was compared to pairwise 3D FFD and 3D+t FFD, bothon displacement and velocity elds, on a set of synthetic 3D US images with di erent noise levels. TDFFDshowed increased robustness to noise compared to these two state-of-the-art algorithms. TDFFD also proved to be more resistant to a reduced temporal resolution when decimating this synthetic sequence. Finally, this synthetic dataset was used to determine optimal settings of the TDFFD algorithm. Subsequently, TDFFDwas applied to a database of cardiac 3D US images of the left ventricle acquired from 9 healthy volunteers and 13 patients treated by Cardiac Resynchronization Therapy (CRT). On healthy cases, uniform strain patterns were observed over all myocardial segments, as physiologically expected. On all CRT patients, theimprovement in synchrony of regional longitudinal strain correlated with CRT clinical outcome as quanti ed by the reduction of end-systolic left ventricular volume at follow-up (6 and 12 months), showing the potential of the proposed algorithm for the assessment of CRT.

Dynamic estimation of three-dimensional cerebrovascular deformation from rotational angiography

Purpose: The objective of this study is to investigate the feasibility of detecting and quantifying 3D cerebrovascular wall motion from a single 3D rotational x-ray angiography (3DRA) acquisition within a clinically acceptable time and computing from the estimated motion field for the further biomechanical modeling of the cerebrovascular wall. Methods: The whole motion cycle of the cerebral vasculature is modeled using a 4D B-spline transformation, which is estimated from a 4D to 2D + t image registration framework. The registration is performed by optimizing a single similarity metric between the entire 2D + t measured projection sequence and the corresponding forward projections of the deformed volume at their exact time instants. The joint use of two acceleration strategies, together with their implementation on graphics processing units, is also proposed so as to reach computation times close to clinical requirements. For further characterizing vessel wall properties, an approximation of the wall thickness changes is obtained through a strain calculation. Results: Evaluation on in silico and in vitro pulsating phantom aneurysms demonstrated an accurate estimation of wall motion curves. In general, the error was below 10% of the maximum pulsation, even in the situation when substantial inhomogeneous intensity pattern was present. Experiments on in vivo data provided realistic aneurysm and vessel wall motion estimates, whereas in regions where motion was neither visible nor anatomically possible, no motion was detected. The use of the acceleration strategies enabled completing the estimation process for one entire cycle in 5-10 min without degrading the overall performance. The strain map extracted from our motion estimation provided a realistic deformation measure of the vessel wall. Conclusions: The authors' technique has demonstrated that it can provide accurate and robust 4D estimates of cerebrovascular wall motion within a clinically acceptable time, although it has to be applied to a larger patient population prior to possible wide application to routine endovascular procedures. In particular, for the first time, this feasibility study has shown that in vivo cerebrovascular motion can be obtained intraprocedurally from a 3DRA acquisition. Results have also shown the potential of performing strain analysis using this imaging modality, thus making possible for the future modeling of biomechanical properties of the vascular wall.

Characterization of myocardial deformation in patients with different etiologies of left ventricular hypertrophy by using strain distribution from Magnetic Resonance Imaging

Introducción y objetivos. Se ha señalado que, en la miocardiopatía hipertrófica (MCH), la desorganización de las fibras regionales da lugar a segmentos en los que la deformación es nula o está gravemente reducida, y que estos segmentos tienen una distribución no uniforme en el ventrículo izquierdo (VI). Esto contrasta con lo observado en otros tipos de hipertrofia como en el corazón de atleta o la hipertrofia ventricular izquierda hipertensiva (HVI-HT), en los que puede haber una deformación cardiaca anormal, pero nunca tan reducida como para que se observe ausencia de deformación. Así pues, proponemos el empleo de la distribución de los valores de strain para estudiar la deformación en la MCH. Métodos. Con el empleo de resonancia magnética marcada (tagged), reconstruimos la deformación sistólica del VI de 12 sujetos de control, 10 atletas, 12 pacientes con MCH y 10 pacientes con HVI-HT. La deformación se cuantificó con un algoritmo de registro no rígido y determinando los valores de strain sistólico máximo radial y circunferencial en 16 segmentos del VI. Resultados. Los pacientes con MCH presentaron unos valores medios de strain significativamente inferiores a los de los demás grupos. Sin embargo, aunque la deformación observada en los individuos sanos y en los pacientes con HVI-HT se concentraba alrededor del valor medio, en la MCH coexistían segmentos con contracción normal y segmentos con una deformación nula o significativamente reducida, con lo que se producía una mayor heterogeneidad de los valores de strain. Se observaron también algunos segmentos sin deformación incluso en ausencia de fibrosis o hipertrofia. Conclusiones. La distribución de strain caracteriza los patrones específicos de deformación miocárdica en pacientes con diferentes etiologías de la HVI. Los pacientes con MCH presentaron un valor medio de strain significativamente inferior, así como una mayor heterogeneidad de strain (en comparación con los controles, los atletas y los pacientes con HVI-HT), y tenían regiones sin deformación.

Morphodynamic analysis of cerebral aneurysm pulsation from time-resolved rotational angiography

This paper presents a technique to estimate and model patient-specific pulsatility of cerebral aneurysms over onecardiac cycle, using 3D rotational X-ray angiography (3DRA) acquisitions. Aneurysm pulsation is modeled as a time varying-spline tensor field representing the deformation applied to a reference volume image, thus producing the instantaneousmorphology at each time point in the cardiac cycle. The estimated deformation is obtained by matching multiple simulated projections of the deforming volume to their corresponding original projections. A weighting scheme is introduced to account for the relevance of each original projection for the selected time point. The wide coverage of the projections, together with the weighting scheme, ensures motion consistency in all directions. The technique has been tested on digital and physical phantoms that are realistic and clinically relevant in terms of geometry, pulsation and imaging conditions. Results from digital phantomexperiments demonstrate that the proposed technique is able to recover subvoxel pulsation with an error lower than 10% of the maximum pulsation in most cases. The experiments with the physical phantom allowed demonstrating the feasibility of pulsation estimation as well as identifying different pulsation regions under clinical conditions.

Multiuser detection in a dynamic environment — Part II: Joint user identification and parameter estimation

The problem of jointly estimating the number, the identities, and the data of active users in a time-varying multiuser environment was examined in a companion paper (IEEE Trans. Information Theory, vol. 53, no. 9, September 2007), at whose core was the use of the theory of finite random sets on countable spaces. Here we extend that theory to encompass the more general problem of estimating unknown continuous parameters of the active-user signals. This problem is solved here by applying the theory of random finite sets constructed on hybrid spaces. We doso deriving Bayesian recursions that describe the evolution withtime of a posteriori densities of the unknown parameters and data.Unlike in the above cited paper, wherein one could evaluate theexact multiuser set posterior density, here the continuous-parameter Bayesian recursions do not admit closed-form expressions. To circumvent this difficulty, we develop numerical approximationsfor the receivers that are based on Sequential Monte Carlo (SMC)methods (“particle filtering”). Simulation results, referring to acode-divisin multiple-access (CDMA) system, are presented toillustrate the theory.

Investigation into Improved Pavement Curing Materials and Techniques: Part 2 - Phase III, March 2003

Appropriate curing is important for concrete to obtain the designed properties. This research was conducted to evaluate the curing effects of different curing materials and methods on pavement properties. At present the sprayed curing compound is a common used method for pavement and other concrete structure construction. Three curing compounds were selected for testing. Two different application rates were employed for the white-pigmented liquid curing compounds. The concrete properties of temperature, moisture content, conductivity, and permeability were examined at several test locations. It was found, in this project, that the concrete properties varied with the depth. Of the tests conducted (maturity, sorptivity, permeability, and conductivity), conductivity appears to be the best method to evaluate the curing effects in the field and bears potential for field application. The results indicated that currently approved curing materials in Iowa, when spread uniformly in a single or double application, provide adequate curing protection and meet the goals of the Iowa Department of Transportation. Experimental curing methods can be compared to this method through the use of conductivity testing to determine their application in the field.

Investgiation into Improved Pavement Curing Materials and Techniques: Part 1 - Phases I and II, April 2002

Concrete curing is closely related to cement hydration, microstructure development, and concrete performance. Application of a liquid membrane-forming curing compound is among the most widely used curing methods for concrete pavements and bridge decks. Curing compounds are economical, easy to apply, and maintenance free. However, limited research has been done to investigate the effectiveness of different curing compounds and their application technologies. No reliable standard testing method is available to evaluate the effectiveness of curing, especially of the field concrete curing. The present research investigates the effects of curing compound materials and application technologies on concrete properties, especially on the properties of surface concrete. This report presents a literature review of curing technology, with an emphasis on curing compounds, and the experimental results from the first part of this research—lab investigation. In the lab investigation, three curing compounds were selected and applied to mortar specimens at three different times after casting. Two application methods, single- and double-layer applications, were employed. Moisture content, conductivity, sorptivity, and degree of hydration were measured at different depths of the specimens. Flexural and compressive strength of the specimens were also tested. Statistical analysis was conducted to examine the relationships between these material properties. The research results indicate that application of a curing compound significantly increased moisture content and degree of cement hydration and reduced sorptivity of the near-surface-area concrete. For given concrete materials and mix proportions, optimal application time of curing compounds depended primarily upon the weather condition. If a sufficient amount of a high-efficiency-index curing compound was uniformly applied, no double-layer application was necessary. Among all test methods applied, the sorptivity test is the most sensitive one to provide good indication for the subtle changes in microstructure of the near-surface-area concrete caused by different curing materials and application methods. Sorptivity measurement has a close relation with moisture content and degree of hydration. The research results have established a baseline for and provided insight into the further development of testing procedures for evaluation of curing compounds in field. Recommendations are provided for further field study.

Réadaptation cardiovasculaire, un- bien sous-utilisé [Cardiac rehabilitation, a proven intervention underutilized in the French-speaking part of Switzerland].

Cardiac rehabilitation is associated with a reduced risk of recurrence and mortality after an acute coronary syndrome. Cardiac rehabilitation is a multidisciplinary approach which starts during the acute hospital phase, then followed by a four to six weeks home-based or stationary program, in order to maintain long-term lifestyle changes. Despite the important health benefits of cardiac rehabilitation and its cost-effectiveness, only half of the patients in Europe will achieve a cardiovascular prevention program after an acute coronary syndrome. In the French part of Switzerland, one explanation for this low adherence might be the lack of both stationary and home-based program facilities.

Théâtre itinéraire de la Guerre actuelle entre les Turcs, d'une part, les Russes et les Impériaux, d'autre part : carte relative aussi au partage éventuel d'une partie de l'Empire Othoman / par M[onsieur Louis] Brion de la Tour, Ing[énieu]r Géographe du Roi

Échelle(s) : [1:3 400 000 ca] Échelle de Lieues d'une heure, ou de 20 au Degré 80 = [10,4 cm] (d'après échelles graphiques).

Théâtre itinéraire de la Guerre actuelle entre les Turcs, d'une part, les Russes et les Impériaux, d'autre part : carte relative aussi au partage éventuel d'une partie de l'Empire Othoman / par M[onsieur Louis] Brion de la Tour, Ing[énieu]r Géographe du Roi

Échelle(s) : [1:3 400 000 ca] Échelle de Lieues d'une heure, ou de 20 au Degré 80 = [10,4 cm] (d'après échelles graphiques).