The Use of Epicardial Electrogram as a Simple Guide to Select the Optimal Site of Left Ventricular Pacing in Cardiac Resynchronization Therapy

Cardiac resynchronization therapy (CRT) has been demonstrated to improve symptoms and survival in patients with left ventricular (LV) systolic dysfunction and dyssynchrony. To achieve this goal, the LV lead should be positioned in a region of delayed contraction. We hypothesized that pacing at the site of late electrical activation was also associated with long-term response to CRT. We conducted a retrospective study on 72 CRT patients. For each patient, we determined the electrical delay (ED) from the onset of QRS to the epicardial EGM and the ratio of ED to QRS duration (ED/QRS duration). After a followup of 30 ± 20 months, 47 patients responded to CRT. Responders had a significantly longer ED and greater ratio of ED/QRS duration than nonresponders. An ED/QRS duration ≥0.38 predicted a response to CRT with 89% specificity and 53% sensitivity

Producción, procesado y caracterización de aleaciones de Ti de grano fino

La presente tesis trata del desarrollo de nuevas aleaciones de Ti que por su comportamiento mecánico, resistencia a la oxidación, estabilidad térmica o características multifuncionales pudieran sustituir con ventaja a algunas de las aleaciones comerciales de Ti, o extender el rango de aplicaciones de las aleaciones de Ti. Como aleación de tipo α que pudiera tener un buen comportamiento mecánico a altas temperaturas y una buena resistencia a la oxidación se ha investigado la aleación Ti-0,6wt%Y₂O₃. Como aleaciones estables de tipo β con posibilidad de adquirir características multifuncionales mediante deformación plástica severa se han investigado aleaciones de Ti-Nb-Ta-Zr-(V) de diferentes composiciones. Ambas aleaciones se han fabricado mediante técnicas de pulvimetalurgia (P/M) consistentes en una fase de mezclado y aleado mecánico, seguida de compactación en frío, sinterización en alto vacío y un tratamiento final de compresión isostática a alta temperatura y presión (HIP: Hot Isostatic Pressing). Las aleaciones de Ti-Nb-Ta-Zr también se fabricaron mediante fundición y colada. Se ha desarrollado y optimizado el método de preparación de estas aleaciones, investigando el efecto de las condiciones del aleado mecánico, de sinterización y del tratamiento final de HIP sobre la microestructura, composición y propiedades de las aleaciones obtenidas. Las aleaciones se han sometido a diferentes tratamientos térmicos y termomecánicos: forjado, templado y extrusión angular de sección constante (ECAP: Equal Channel Angular Pressing), con el objeto de optimizar su microestructura y propiedades mecánicas. Estas aleaciones, que son consideradas como difíciles de procesar mediante ECAP, han requerido la investigación de las condiciones específicas para realizar con éxito su procesado ECAP. La microestructura de las aleaciones en las distintas etapas de su procesado se analizó mediante diferentes técnicas: difracción de rayos X, metalografía, y microscopía electrónica de barrido y de transmisión. Además, se investigó la textura inducida por el procesado ECAP. La caracterización mecánica se realizó mediante medidas del módulo de Young, microdureza y ensayos de tracción hasta fractura a diferentes temperaturas. Las características de la fractura de estas aleaciones también se investigaron. Además, las características de la oxidación de las aleaciones de Ti-0,6wt%Y₂O₃ y de Ti P/M entre 973 y 1173 K se han investigado mediante termogravimetría y microscopia electrónica de barrido.-------------------------------------------------------------------------------------------------------------------------------------------------------The present PhD thesis is about the development of new Ti-based alloys that, by virtue of their mechanical behaviour, resistance to oxidation, thermal stability or multifunctional characteristics could extend their field of application or substitute advantageously the actual commercial Ti alloys. In the α range the focus was set on Ti-0,6wt%Y₂O₃, alloy which should have a good mechanical behaviour at high temperatures and a good oxidation resistance. In the β range the investigation was focused on different Ti-Nb-Ta-Zr-(V) alloys with enhanced mechanical properties and possible multifunctional characteristics obtained through severe plastic deformation. Both alloys were produced by powder metallurgy (P/M) techniques consisting in a phase of blending and mechanical alloying, followed by compaction by cold isostatic pressing (CIP), high vacuum sintering and a final hot isostatic pressing (HIP) treatment. The Ti-Nb-Ta-Zr alloys were also prepared by casting. The preparation methods for these alloys were optimized by investigating the effect of the milling, sintering and HIP-treatment conditions on the microstructure, composition and properties of the materials produced. The alloys were subjected to different thermal and thermomechanical treatments: forging, quenching and equal channel angular pressing (ECAP), to enhance their microstructure and mechanical properties. With this objective and to avoid failure of the billets during the ECAP, specific process conditions for these alloys have been investigated. The microstructure of the alloys in the course of the successive processing stages was analysed using the techniques of X-ray diffraction, metallography and scanning and transmission electron microscopy. The crystallographic texture induced by the ECAP process was also investigated. The mechanical properties were determined by Young modulus and microhardness measurements and tensile tests up to fracture at different temperatures. The fracture characteristics of the alloys were also analysed. The oxidation resistance of the Ti-0,6wt%Y₂O₃ and of P/M Ti was also investigated by thermogravimetry and scanning electron microscopy

Di-tert-butyl 2-benzoyl­hydrazine-1,1-dicarboxyl­ate

The crystal structure of the title compound, C17H24N2O5, was determined in the course of our studies on the preparation of two families of pseudopeptides, viz. hydrazino- and N-amino- peptides. The most significant inter­action in the crystal structure is a bifurcated inter­molecular N—H⋯O hydrogen bond

Sensitivity of chloride ingress modelling in concrete to input parameter variability

The Rosenblueth point estimator method is used to propagate uncertainty on stochastic parameters in a multi-ionic reactive transport model for concrete degradation. The degradation mechanism that was analysed is the ingress of chlorides into concrete. This point estimator method is used because it requires a minimum number of simulations to compute means, standard deviations and skewness for the solution of the transport model. Two exposure cases are considered in this article: the first is a saturated case, and the second is an unsaturated case with wetting (4 days) and drying (3 days at 50 % relative humidity) cycles. The sodium chloride exposure during the wetting cycle of both cases was 500 mmol/L. In both cases, predictions from the model were compared to experimental results. The Rosenblueth approach yielded results comparable to Monte Carlo simulations for both saturated and unsaturated cases. The relative sensitivity of model parameters on prediction results are investigated through a sensitivity analysis. The sensitivity results show the high importance of ionic diffusion parameters and of exposure conditions, while the calculated initial mineral phases in the hydrated paste have lower importance

Statistical analysis of concrete transport properties

Results of a statistical analysis of transport properties measurements carried out on a number of concrete mixtures are presented. Migration and drying experiments were performed to evaluate the ionic diffusion coefficients and permeability of concrete mixtures. Seven concrete mixtures were tested. The mixtures were either batched under laboratory conditions or sampled from construction sites. For each mixture, approximately eighty concrete samples from a single batch were tested. Ionic diffusion coefficients were calculated by analyzing the evolution of the electrical current passing through concrete samples during the migration tests. Calculations took into account the volume of permeable pores of the materials and the pore solution chemistry. Permeability was calculated from mass loss measured during drying tests. The study indicates that the coefficient of variation of ionic diffusion coefficients is 11.1 % on average, with a maximum of 23.5 %, and that the coefficient of variation of permeability is 20.6 % on average, with a maximum of 37.3 %

L’impact des pratiques scolaires d’évalution sur les motivations et le concept de soi des élèves

Le type de pratiques d'évaluation mises en oeuvre par un enseignant influence-t-il le style motivationnel et l'image de soi de ses élèves ? Pour répondre à cette question, 240 élèves de 5' et 6' primaire ont rempli une adaptation française du questionnaire de Nicholls (1989) relatif aux orientations motivationnelles, ainsi qu'un questionnaire portant sur leur concept de soi. Dans le même temps, leurs enseignants ont répondu à un questionnaire sur leurs pratiques d'évaluation. Les résultats soutiennent la fiabilité et la validité de l'adaptation française du questionnaire de Nicholls. Concernant les relations entre motivations et concept de soi, les résultats indiquent que l'orientation vers l'apprentissage est positivement liée à toutes les dimensions du concept de soi, sauf en mathématiques où la relation se marque davantage avec l'orientation vers la performance. Mais surtout, les résultats montrent un effet du type de pratiques d'évaluation rapportées par l'enseignant sur les orientations motivationnelles et le concept de soi en lecture. Les implications éducatives de ces résultats sont discutées.Does the kind of evaluation practices implemented by a teacher have an effect on students goal orientations and sen-concept ? To answer this question, 240 fifth and sixth graders completed a French version of the motivational orientation scales (Nichons, 1989) and a measure of sen-concept. At the saine time, their teachers completed a questionnaire on evaluation practices. Results support globaly the reliability and validity of the French adaptation of motivational orientation scales. Concerning relations between goal orientation and self-concept, task orienta­tion shows a positive association with ail self-concept dimensions, except for mathematics. For this dimension, the relation is more pronounced with ego orientation. Above all, the results indicate an impact of evaluation practices reported by teachers on students' motivational orientations and self-concept. Educational implications of these results are discussed

Influence of yttria additions on the oxidation behaviour of titanium prepared by powder metallurgy

The yttria dispersion effect on the oxidation resistance of titanium prepared by powder metallurgy has been evaluated between 700 and 900º C. Yttria additions slightly increase the oxidation rate up to 800ºC and decrease it considerably at 900º C. The multilayered rutile scale formed on pure titanium prepared by conventional techniques is replaced by a denser rutile scale in the case of Titanium prepared by powder metallurgy. Yttria additions raise the temperature at which a more protective dense rutile scale is formedThis work was supported by the Dirección General de Investigación (Ministerio de Ciencia e Innovación of Spain) under grant MAT2006-13005-C03-02, and the Dirección General de Universidades (Comunidad de Madrid) through the program ESTRUMAT-CM (Grant S-0505/MAT/0077).Publicad