A study on block flexible iterative solvers with applications to Earth imaging problem in geophysics

Les travaux de ce doctorat concernent le développement de méthodes itératives pour la résolution de systèmes linéaires creux de grande taille comportant de nombreux seconds membres. L’application visée est la résolution d’un problème inverse en géophysique visant à reconstruire la vitesse de propagation des ondes dans le sous-sol terrestre. Lorsque de nombreuses sources émettrices sont utilisées, ce problème inverse nécessite la résolution de systèmes linéaires complexes non symétriques non hermitiens comportant des milliers de seconds membres. Dans le cas tridimensionnel ces systèmes linéaires sont reconnus comme difficiles à résoudre plus particulièrement lorsque des fréquences élevées sont considérées. Le principal objectif de cette thèse est donc d’étendre les développements existants concernant les méthodes de Krylov par bloc. Nous étudions plus particulièrement les techniques de déflation dans le cas multiples seconds membres et recyclage de sous-espace dans le cas simple second membre. Des gains substantiels sont obtenus en terme de temps de calcul par rapport aux méthodes existantes sur des applications réalistes dans un environnement parallèle distribué. ABSTRACT : This PhD thesis concerns the development of flexible Krylov subspace iterative solvers for the solution of large sparse linear systems of equations with multiple right-hand sides. Our target application is the solution of the acoustic full waveform inversion problem in geophysics associated with the phenomena of wave propagation through an heterogeneous model simulating the subsurface of Earth. When multiple wave sources are being used, this problem gives raise to large sparse complex non-Hermitian and nonsymmetric linear systems with thousands of right-hand sides. Specially in the three-dimensional case and at high frequencies, this problem is known to be difficult. The purpose of this thesis is to develop a flexible block Krylov iterative method which extends and improves techniques already available in the current literature to the multiple right-hand sides scenario. We exploit the relations between each right-hand side to accelerate the convergence of the overall iterative method. We study both block deflation and single right-hand side subspace recycling techniques obtaining substantial gains in terms of computational time when compared to other strategies published in the literature, on realistic applications performed in a parallel environment

Dammarane Triterpenoids from Carnauba, Copernicia prunifera (Miller) H. E. Moore (Arecaceae), Wax

Phytochemical investigation from carnauba (Copernicia prunifera) wax led to the identification of sixteen dammarane-type triterpenes, including thirteen new characterized as: (24R*)-methyldammara-20,25-dien-3 alpha-ol and a mixture of alkyl (24R*)-methyldammar-25-en- 20-ol-3 beta-carboxylates, together with three previously described triterpenes: carnaubadiol, (24R*)-methyldammara-20,25-dien-3 beta-ol and (24R*)-24-methyldammara-20,25-dien-3-one. Moreover, four fatty alcohols (eicosanol, docosanol, tetracosanol and hexacosanol) as well as four sterols (cholesterol, campesterol, stigmasterol, and sitosterol) were also obtained. These compounds were isolated using classical chromatographic methods and their structures were determined by spectroscopic and chemical methods.Univ Fed Piaui, Dept Quim, BR-64049550 Teresina, PI, BrazilUniv Fed Sao Paulo, Inst Ciencias Ambientais Quim & Farmaceut, BR-09972270 Diadema, SP, BrazilUniv Fed ABC, Ctr Ciencias Nat & Humanas, BR-09210180 Santo Andre, SP, BrazilUniv Fed Sao Paulo, Inst Ciencias Ambientais Quim & Farmaceut, BR-09972270 Diadema, SP, BrazilWeb of Scienc

Starch and total soluble sugar content in torch ginger postharvest

Floral opening stage during harvest and use of postharvest techniques, such as inflorescence coating with carnauba wax, may influence quality maintenance for commercialization. The aim was to evaluate the carbohydrate content of torch ginger inflorescences harvested at two different opening stages and treated with different concentrations of carnauba wax. The inflorescences were harvested with semi-open (basal bracts beginning their expansion process) and open bracts (fully expanded basal bracts and opening of the smaller bracts on interior of the inflorescence) and received the application of carnauba wax at concentrations of 0.75%; 1.5% or 3.0%, in addition to a control treatment, without wax application. After the treatment, the floral stems were maintained at 16 and 21 oC for 20 days. During the storage period, five bracts samples (external and internal bracts separately - in open inflorescences, external and internal bracts together - in semi-open inflorescences) were carried out every three days for evaluation of total soluble sugars and starch content. Contents of total soluble sugars and starch differed between the different types of bracts collected and throughout the storage period evaluated, and could indicate a remobilization of reserves. The concentration of 3.0% carnauba wax induced higher total soluble sugar content. However, this content does not affect the longevity of torch ginger at the two evaluated floral opening stages

Ethics Committee experience during COVID-19 emergency. A brief report

La crisis sanitaria motivada por el COVID-19 hace necesaria la puesta en marcha, con celeridad, de investigaciones encaminadas a generar evidencias científicas que incidan en el control de sus devastadores efectos. Por ello, fue necesario realizar ajustes en la dinámica de trabajo de los Comités de Ética de la Investigación así como priorizar y agilizar la evaluación de los proyectos relacionados con dicha enfermedad. Este trabajo pretende analizar la actividad la actividad evaluadora del Comité de Ética de la Investigación con Medicamentos de Galicia (CEIm-G) durante dicho período de emergencia sanitaria. Se evaluaron 81 proyectos de investigación, 73 de ellos de ámbito autonómico (62 unicéntricos), 4 nacionales y 4 internacionales. En 57 proyectos el dictamen fue favorable, 4 fueron retirados por los promotores, en 6 no procedía dictamen y 14 no respondieron a las aclaraciones solicitadas hasta la fecha del cierre del estudio. La causas más frecuentes de solicitud de aclaraciones estaban relacionadas con la metodología y a continuación con la hoja de información al paciente y el consentimiento informado. También es imprescindible abordar los aspectos relacionados con la intimidad de los datos personales y las muestras y tener en cuenta la carga de trabajo de los investigadores. Como propuesta de mejora, consideramos que se debe incidir en una mayor coordinación entre los diferentes equipos de investigación para tratar de obtener resultados más robustos