Conserving time-integration of beams under contact constrains using B-Spline interpolation

The design of energy-momentum algorithms for geometrically exact beams has been achieved more than 15 years ago. However, many of the desired conserivng propeties do not carry over into constrained systems such as beams subjected to sliding contact conditions. We here model such situation and derive a sliding contact conditions that conserves energy and momenta. Basic ingredients of the resulting formulation is the inteprolation of incremental tangent-scaled rotations and a relaxation of the exact sliding condition. We also combine this formulation with a B-Spline interpolation of the beam centroid axis. In this manner, we achieve to smooth the contact loads thrughout the analysis and consequently increase the stability of the numerical model. We demonstrate these advantages and the conserving properties of the algorithm with a set of two-dimensional numerical examples.Peer ReviewedPostprint (published version

Explicit parametric solutions of lattice structures with proper generalized decomposition (PGD): applications to the design of 3D-printed architectured materials

The final publication is available at Springer via http://dx.doi.org/10.1007/s00466-017-1534-9Architectured materials (or metamaterials) are constituted by a unit-cell with a complex structural design repeated periodically forming a bulk material with emergent mechanical properties. One may obtain specific macro-scale (or bulk) properties in the resulting architectured material by properly designing the unit-cell. Typically, this is stated as an optimal design problem in which the parameters describing the shape and mechanical properties of the unit-cell are selected in order to produce the desired bulk characteristics. This is especially pertinent due to the ease manufacturing of these complex structures with 3D printers. The proper generalized decomposition provides explicit parametic solutions of parametric PDEs. Here, the same ideas are used to obtain parametric solutions of the algebraic equations arising from lattice structural models. Once the explicit parametric solution is available, the optimal design problem is a simple post-process. The same strategy is applied in the numerical illustrations, first to a unit-cell (and then homogenized with periodicity conditions), and in a second phase to the complete structure of a lattice material specimen.Peer ReviewedPostprint (author's final draft

Explicit parametric solutions of lattice structures with proper generalized decomposition (PGD)

Architectured materials (or metamaterials) are constituted by a unit-cell with a complex structural design repeated periodically forming a bulk material with emergent mechanical properties. One may obtain specific macro-scale (or bulk) properties in the resulting architectured material by properly designing the unit-cell. Typically, this is stated as an optimal design problem in which the parameters describing the shape and mechanical properties of the unit-cell are selected in order to produce the desired bulk characteristics. This is especially pertinent due to the ease manufacturing of these complex structures with 3D printers. The proper generalized decomposition provides explicit parametic solutions of parametric PDEs. Here, the same ideas are used to obtain parametric solutions of the algebraic equations arising from lattice structural models. Once the explicit parametric solution is available, the optimal design problem is a simple post-process. The same strategy is applied in the numerical illustrations, first to a unit-cell (and then homogenized with periodicity conditions), and in a second phase to the complete structure of a lattice material specimen

Appendicitis and diverticulitis of the colon: Misleading forms

AbstractAppendicitis and diverticulitis of the colon are the two main causes of febrile acute abdomen in adults. Diagnosis from imaging (ultrasound and CT) is usually easy. However, an imaging procedure which is not suitable for the clinical situation and an examination performed with the wrong protocol are sources of error and must be avoided. Anatomical variants, inflammatory cancers, complicated forms (perforation, secondary occlusion of the small intestine, peripheral abscesses, fistulae, pylephlebitis, liver abscesses) and associated signs related to a peritoneal inflammatory reaction (reflex ileus, reactive ileitis or salpingitis) can also lead to a wrong diagnosis

Aciertos y desaciertos en la gobernanza medioambiental internacional

This article seeks to analyze, from an international law point of view, the history of the construction of global environmental architecture, a global environmental authority that solves environmental degradation.\nAmid the discussions on how this international authority went from\nbeing considered a useful institution to not being one\nFil: Devia, Leila. Universidad de Buenos Aires. Facultad de Derecho. Cátedra Derecho Ambiental. Buenos Aires, ArgentinaFil: Sibileau, Agnès. Universidad de Buenos Aires. Facultad de Derecho. Buenos Aires, ArgentinaFil: Ulla, María Carolina. Universidad Nacional de Córdoba. Cátedra Derecho de los Recursos Naturales y Ambiental. Córdoba, ArgentinaEn el presente artículo nos proponemos reflexionar, a partir del derecho internacional, sobre la historia de la construcción de la arquitectura global medioambiental, es decir, de la construcción de una autoridad mundial ambiental a los fines de buscar soluciones a los problemas ambientales. El eje central del ensayo girará en torno a las reflexiones y pensamientos sobre cómo la autoridad mundial ambiental pasó de considerarse una ya no sólo en un problema, sino en una institución en la búsqueda de nuevas soluciones para enfrentar los problemas ambientales, buscando poner énfasis, no sólo en los Estados, sino en los distintos niveles de toma de decisión (local, nacional y transnacional) y en la multiplicidad de los actores (sociedad civil, empresas privadas y actores públicos o estatales) que inciden en la solución de estas problemáticas.\

Malignant rhabdoid tumors of the liver: an exceptional tumor in adults - a case report and literature review

Malignant rhabdoid tumor (MRT) is a very rare liver tumor, with only a few cases reported in the literature. MRT generally occurs in pediatric patients and prognosis is usually very poor. Here we report a very rare case of MRT occurring in a young adult who is still alive with no sign of recurrence at 41 months of follow-up. MRI and computed tomography scans revealed a voluminous heterogeneous mass in the left liver with no specific pattern. The mass included necrotic and fibrous components. Histology showed fusiform, loosely cohesive cells with abundant eosinophilic cytoplasm resulting in eccentric nuclei, thus creating the characteristic rhabdoid appearance. Immunohistochemical studies revealed a lack of nuclear INI1 protein expression. The patient\u27s treatment included a major left liver resection associated with chemotherapy. A thorough search of the literature revealed one case of MRT in a young adult who died at 48 months of follow-up. A less malignant nature of the tumor in young adults may be suspected, but a longer disease-free survival may also be the fruit of aggressive surgical and oncological treatment

Applications of phase-contrast velocimetry sequences in cardiovascular imaging.

AIMS: To describe and illustrate the main applications of phase-contrast flow quantification in cardiovascular imaging. CONCLUSION: Phase-contrast velocimetry sequences provide an accurate, reliable, reproducible and non-invasive study of blood flow, information which is sometimes not available from other investigation methods. The haemodynamic information obtained from these complement MRI angiography images. They appear to have a range of clinical applications, firstly improving pathophysiological understanding but also contributing to the treatment and follow-up strategy after surgical or endovascular treatment

Accuracy of water-enema multidetector computed tomography (WE-MDCT) in colon cancer staging: a prospective study

Purpose To assess the accuracy of water-enema multidetector computed tomography (WE-MDCT) in extra-rectal colon cancer staging. Materials and methods Fifty-three patients (mean age 70 years) with extra-rectal colon cancer proven by colonoscopy and biopsy were prospectively evaluated by preoperative WE-MDCT. CT scans were both intraluminal (water enema or WE) and intravenous (iodinated) contrast enhanced (CE). All patients underwent surgery. Tumors were classified with the TNM staging system. Noted CT features were: tumor size and location; tumor form and edges; spread to the pericolic fat or neighboring organs; thickening of retroperitoneal fascia; number, size, and enhancement of the peritumoral lymph nodes. Tumors were classified on CT into 3 T-stage groups: T1/T2, T3, and T4. Lymph nodes were classified by their density after injection [positive over 100 Hounsfield units (HU)]. Results Tumor localization to the specific colon segment was correct in all the cases. The agreement between WE-MDCT staging and histopathology staging was good (k = 0.64). An irregular and bowl-shaped aspect of the external edges of tumor provided excellent sensitivity for T3/T4 inclusion (Se 97.7%, NPV 85.7%). Thickening of a fascia or the abdominal wall provided good specificity for T4 stage (Sp 88.1%, NPV 94.9%). Enhancement over 100 HU of at least one peritumoral lymph node was the best criterion of N+ staging (Sp 67.7%, NPV 87.5%). Conclusion WE-MDCT permits good staging of colon cancer based on objective features

Colorectal carcinoma: Ex vivo evaluation using q-space imaging; Correlation with histopathologic findings

BACKGROUND: Although the prognosis of colorectal carcinoma (CRC) patients depends on the histologic grade (HG) and lymph node metastasis (LNM), accurate preoperative assessment of these prognostic factors is often difficult. PURPOSE: To assess the HG and extent of LNM by q-space imaging (QSI) for preoperative diagnosis of CRC. STUDY TYPE: Prospective. SPECIMEN: A total of 20 colorectal tissue samples containing adenocarcinomas and resected lymph nodes (LNs). FIELD STRENGTH/SEQUENCE: QSI was performed with a 3T MRI system using a diffusion-weighted echo-planar imaging sequence: repetition time, 10,000 msec; echo time, 216 or 210 msec; field of view, 113 x 73.45 mm; matrix, 120 x 78; section thickness, 4 mm; and 11 b values ranging from 0 to 9000 s/mm(2) . ASSESSMENT: The mean displacement (MDP; mum), zero-displacement probability (ZDP; arbitrary unit [a.u.]), kurtosis (K; a.u.), and apparent diffusion coefficient (ADC) were analyzed by two observers and compared with histopathologic findings. STATISTICAL TESTS: Spearman\u27s rank correlation coefficient, Mann-Whitney U-test, and ROC curve analyses. RESULTS: For all 20 carcinomas, the MDP, ZDP, K, and ADC were 8.87 +/- 0.37 mum, 82.0 +/- 6.2 a.u., 74.3 +/- 3.0 a.u., and 0.219 +/- 0.040 x 10(-3) mm(2) /s, respectively. The MDP (r = -0.768; P < 0.001), ZDP (r = 0.768; P < 0.001), and K (r = 0.785; P < 0.001) were significantly correlated with the HG of CRC, but not the ADC (r = 0.088; P = 0.712). There were also significant differences in the MDP, ZDP, and K between metastatic and nonmetastatic LNs (all, P < 0.001), but not the ADC (P = 0.082). In the HG of CRC and LNM, the area under the curve was significantly greater for MDP, ZDP, and K than for ADC. DATA CONCLUSION: QSI provides useful diagnostic information to assess the HG and extent of LNM in CRC. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;48:1059-1068

A legitimization undertaking of arabic grammar : the Ḫaṣāʾiṣ of Ibn Ğinnī (d. 392/1002)

Cette thèse s'inscrit dans le domaine de l'histoire de la grammaire arabe. Elle prend pour objet un traité sur la langue arabe du 4e/10e siècle intitulé al-Ḫaṣāʾiṣ, du grammairien Ibn Ğinnī (m. 392/1002), se focalisant sur les énoncés qui visent à expliquer les faits linguistiques. La thèse tient compte de la spécificité énonciative du discours d’Ibn Ğinnī qui ne s’adresse pas seulement à des grammairiens, mais aussi à des théologiens, juristes, philosophes, lettrés, et secrétaires de chancellerie. Nous soutenons que cette particularité énonciative, va de pair avec une réorganisation taxinomique des données grammaticales ainsi qu’une nouvelle approche du langage. La première partie de la thèse prend pour objet la notion métalinguistique de ʿilla (cause, explication) ainsi que les réflexions d’Ibn Ğinnī sur la structure logico-sémantique des énoncés explicatifs. Notre enquête nous conduit à établir une connexion forte avec le discours naissant des principes de la jurisprudence incarné par le Fuṣūl fī l-Uṣūl d’al-Ğaṣṣāṣ (m. 370/981), mais aussi avec le discours explicatif de la théologie, ainsi que celui de la logique. La seconde partie étudie les arguments mobilisés par Ibn Ğinnī afin de montrer le caractère homogène de l’arabe au moyen de l’analogie et du principe aristotélicien de non-contradiction, ainsi que sa contribution au développement de la rhétorique dont nous retrouvons notamment la trace chez le rhétoricien al-Ğurğānī (m. 471/1078). Enfin la troisième partie est consacrée à l’analyse des explications relatives à la variation linguistique, au sein desquelles la diachronie occupe une place centrale.This thesis falls within the scope of the history of arabic grammar. It studies a treatise of arabic language dated back to the 4th/10th century entitled al-Ḫaṣāʾiṣ, of the grammarian Ibn Ğinnī (d. 392/1002), especially the utterances which aim at explaining the linguistic facts. The thesis takes into account the enunciative specificity of Ibn Ğinnī's discourse who does not only speak to grammarians, but to theologians, lawyers, philosophers, lettered persons, and secretaries of chancellery too. We argue that this enunciative peculiarity goes along with a reorganization of the grammatical datas and a new approach of language. The first part of the thesis examines the metalinguistic notion of ʿilla (cause, explanation) and the reflections of Ibn Ğinnī on the logico-semantic structure of the explanatory utterances. Our inquiry leads us to establish a strong connexion with the beginnings of the discourse of the principals of jurisprudence with al-Fuṣūl fī l-Uṣūl of al-Ğaṣṣāṣ (d. 370/981). It also leads us to establish a strong connexion with the explanatory discourse of theology, as well as logic. The second part studies the arguments gathered by Ibn Ğinnī in order to show the homogeneous character of arabic by the mean of analogy and the aristotelian law of non-contradiction, as his contribution to the development of rhetoric of which we find the trace with the rhetorician al-Ğurğānī (d. 471/1078). Finally, the third part is devoted to the analysis of the explanations related to linguistic variation, in which diachrony holds a special rank