Form-finding of pierced vaults and digital fabrication of scaled prototype

The new serious consideration to masonry and non-metallic structures evidenced their direct prospective to be, even in the present days, advanced architectural and engineering solutions. In the present paper, a form finding for a cement based tessellated pierced vault is studied. The multi-body rope approach (MRA) was used to define compression-only vault optimal shapes. Successively, the thrust network analysis (TNA) was implemented by Rhino-vault for a further validation of the shape and the definition of different tessellation meshes of the surfaces, according to different hole pattern configuration. Different piercing percentage of the vaults were considered and compared for the best solution identification. In addition, the geometrical solutions were analyzed by means of global stability analysis, taking into account the different positions of the holes. Furthermore, 3D printing with a Fuse Deposition Modeling (FDM) technique in polylactide (PLA) material (completely eco-friendly) is used for the construction of the formworks of the cement based blocks (dowels) useful for the assembly of a vault scaled prototype. The prototype of the vault, characterized by a certain piercing percentage was subjected to different loading conditions and monitored by a non-contact device based on the Digital Image Correlation (DIC) technique. The 3D-DIC was performed to recognize the structural behavior during the loading process of the model (prototype). DIC measurements were used to recognize in advance the critical condition of the vault under loading and the displacement measurements were correlated to the different loading phases up to the collapse condition

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The aim of this study was the assessment of the Regional Myocardial Work (RMW) by measuring the stress-strain relationships in the left myocardium, under basic and ischemic conditions. In 11 swines, 4 Sonometrics crystals were placed in the region perfused by the left anterior descending artery (LAD) circumscribing a tetrahedral myocardial volume (TMV). The 1st crystal was situated 45mm below the pulmonary artery, beside the LAD. Under control of the acquisition device, the 2nd was placed 10mm below the 1st following the LAD, the 3rd 10mm at the left side of the 1st and the 4th in equidistant point between the 1st and the 2nd, 5mm deep within the myocardium. A Millar, omnidirectional pressure catheter was placed within the TMV. The 6 distances and intramyocardial pressure measured were digitized and mathematically synthesized. The variation in TMV strain (µv) and stress (µp) was calculated throughout the cardiac cycle, resulting in 2 equations. The relationships between µp and µv result in a stress-strain loop, from which RMW was calculated. Simultaneously, Pulsed Doppler Tissue Imaging (DTI) assessed systolic (VS), early-diastolic (VE) and latediastolic (VA) myocardial velocities. Measurements were performed under basic (B), during ischemia by occlusion LDA for 40 seconds, after 1 and 15 minutes of reperfusion (Occlusion (O), Reperfusion1 (R1) and 2 (R2) periods). The average of RMW, under basic conditions, wa

Usefulness and limitations of transthoracic echocardiography in heart transplantation recipients

Transthoracic echocardiography is a primary non-invasive modality for investigation of heart transplant recipients. It is a versatile tool which provides comprehensive information about cardiac structure and function. Echocardiographic examinations can be easily performed at the bedside and serially repeated without any patient's discomfort. This review highlights the usefulness of Doppler echocardiography in the assessment of left ventricular and right ventricular systolic and diastolic function, of left ventricular mass, valvular heart disease, pulmonary arterial hypertension and pericardial effusion in heart transplant recipients. The main experiences performed by either standard Doppler echocardiography and new high-tech ultrasound technologies are summarised, pointing out advantages and limitations of the described techniques in diagnosing acute allograft rejection and cardiac graft vasculopathy. Despite the sustained efforts of echocardiographic technique in predicting the biopsy state, endocardial myocardial biopsies are still regarded as the gold standard for detection of acute allograft rejection. Conversely, stress echocardiography is able to identify accurately cardiac graft vasculopathy and has a recognised prognostic in this clinical setting. A normal stress-echo justifies postponement of invasive studies. Another use of transthoracic echocardiography is the monitorisation and the visualisation of the catheter during the performance of endomyocardial biopsy. Bedside stress echocardiography is even useful to select appropriately heart donors with brain death. The ultrasound monitoring is simple and effective for monitoring a safe performance of biopsy procedures

On the Deformation of Dendrites During Directional Solidification of a Nickel-Based Superalloy

Abstract: Synchrotron X-ray imaging has been used to examine in situ the deformation of dendrites that takes place during the solidification of a nickel-based superalloy. By combining absorption and diffraction contrast imaging, deformation events could be classified by their localization and permanence. In particular, a deformation mechanism arising from thermal contraction in a temperature gradient was elucidated through digital image correlation. It was concluded that this mechanism may explain the small misorientations typically observed in single crystal castings

Efecto de la topografía, las labranzas y el pastoreo de los rastrojos sobre el carbono orgánico y la estructura del suelo

This study reports the effect of topography, stubble grazing, tillage and the addition of fertilizer on the organic carbon content and structural stability of a typic Hapludoll topsoil under mixed agricultural production. The organic carbon content was significantly higher in the lower area of the slope when harvest residues were not grazed and when conservation tillage was performed. The interaction tillage x residue showed the highest carbon content to be attained with reduced tillage and no stubble grazing, and the lowest to be attained with conventional tillage with stubble grazing. Comparisons with minimally altered soil showed the loss of organic carbon to oscillate between 80% with conventional tillage when residues were grazed and 77% when conservation tillage systems were used. With respect to quantities of water-stable aggregates available (four diameter ranges), minimal alteration led to the highest percentages of the most coarse aggregates, while with the different treatments the finest and most coarse aggregates showed the highest percentages. The exception was under direct seeding where the distribution was similar to that for minimal soil alteration, though the percentage of the most coarse aggregates was lower. A linear, positive relationship was found between organic carbon and macroaggregate content. These results may help in the choice of technologies that can improve soil quality.Se estudió el efecto de la topografía, pastoreo de rastrojos, labranzas y fertilización sobre el contenido de carbono orgánico y la estabilidad estructural del horizonte superficial de un Hapludoll típico bajo producción mixta, y se comparó con el mismo suelo con mínima alteración. El contenido de carbono orgánico fue significativamente más elevado en la posición más baja de la pendiente, cuando no se pastorearon los residuos de cosecha y se usaron labranzas conservacionistas. La interacción labranza x residuo indicó que el mayor contenido de carbono se observa en labranza reducida no pastoreada y el menor en labranza convencional con pastoreo de rastrojos. La comparación con la situación de mínima alteración indicó que la pérdida de carbono orgánico oscila entre el 80% en labranza convencional cuando se pastorean los rastrojos y el 77% en labranzas conservacionistas. En cuanto a la cantidad de agregados estables al agua de cuatro rangos de diámetros, se observó que en la situación de mínima alteración los porcentajes más elevados se encontraron en los agregados más gruesos, mientras que en los tratamientos estudiados la distribución fue bimodal, con porcentajes más elevados en los agregados más finos y más gruesos, excepto en siembra directa, que tuvo una distribución semejante a mínima alteración, aunque con valores inferiores de agregados más gruesos. Se encontró relación lineal y positiva entre el carbono orgánico y los macroagregados. Los resultados obtenidos pueden contribuir a la elección de tecnologías para iniciar un proceso que llevaría al suelo a un nuevo estado de equilibrio tendiente a una mayor calidad

The effect of topography, tillage and stubble grazing on soil structure and organic carbon levels

Se estudió el efecto de la topografía, pastoreo de rastrojos, labranzas y fertilización sobre el contenido de carbono orgánico y la estabilidad estructural del horizonte superficial de un Hapludoll típico bajo producción mixta, y se comparó con el mismo suelo con mínima alteración. El contenido de carbono orgánico fue significativamente más elevado en la posición más baja de la pendiente, cuando no se pastorearon los residuos de cosecha y se usaron labranzas conservacionistas. La interacción labranza X residuo indicó que el mayor contenido de carbono se observa en labranza reducida no pastoreada y el menor en labranza convencional con pastoreo de rastrojos. La comparación con la situación de mínima alteración indicó que la pérdida de carbono orgánico oscila entre el 80% en labranza convencional cuando se pastorean los rastrojos y el 77% en labranzas conservacionistas. En cuanto a la cantidad de agregados estables el agua de cuatro rangos de diámetro, se observó que en la situación de mínima alteración los porcentajes más elevados se encontraron en los agregados más gruesos, mientras que en los tratamientos estudiados la distribución fue bimodal, con porcentajes más elevados en los agregados más finos y más gruesos, excepto en siembra directa, que tuvo una distribución semejante a mínima alteración, aunque con valores inferiores de agregados más gruesos. Se encontró relación lineal y positiva entre el carbono orgánico y los macroagregados. Los resultados obtenidos pueden contribuir a la elección de tecnologías para iniciar un proceso que llevaría al suelo a un nuevo estado de equilibrio tendente a una mayor calidad