Search results for "ORAC"

Modified hemi-Fontan procedure on the beating heart

1998

the heart by infusing the cardioplegic solution under aortic occlusion by means of the balloon throughout the procedure. Even though the balloon catheter passes through the aortic valve, significant aortic valve insufficiency is not likely to occur because of the small caliber of the balloon catheter. We believe that the clinical application of this double-lumen aortic occlusion catheter will protect the myocardium in patients with a thoracoabdominal aortic aneurysm or distal descending aortic aneurysm who undergo the operation through the left thoracotomy with DHCA.

Deep learning approach for the segmentation of aneurysmal ascending aorta.

2020

Diagnosis of ascending thoracic aortic aneurysm (ATAA) is based on the measurement of the maximum aortic diameter, but size is not a good predictor of the risk of adverse events. There is growing interest in the development of novel image-derived risk strategies to improve patient risk management towards a highly individualized level. In this study, the feasibility and efficacy of deep learning for the automatic segmentation of ATAAs was investigated using UNet, ENet, and ERFNet techniques. Specifically, CT angiography done on 72 patients with ATAAs and different valve morphology (i.e., tricuspid aortic valve, TAV, and bicuspid aortic valve, BAV) were semi-automatically segmented with Mimic…

On the severity of aortic stenosis in ascending aortic aneurysm: A computational tool to examine ventricular-arterial interaction and aortic wall str…

2020

Abstract An ascending thoracic aortic aneurysm (ATAA) is a life-threatening cardiovascular consequence of vessel dilatation that portends adverse events and death. From a clinical perspective, ATAA should not be treated as an isolated disease, and surgery is often carried out in the presence of AS, aortic insufficiency or a calcified valve leaflet. Aortic stenosis (AS) is common in ATAAs and leads to both vessel rigidity and left ventricular (LV) impairment. In this study, lumped-parameter modeling and computational analysis were used to assess the change in the wall shear stress (WSS) and intramural wall stress of patient-specific ATAA models with different degrees of AS (i.e., mild to sev…

Constitutive modeling of ascending thoracic aortic aneurysms using microstructural parameters.

2016

Ascending thoracic aortic aneurysm (ATAA) has been associated with diminished biomechanical strength and disruption in the collagen fiber microarchitecture. Additionally, the congenital bicuspid aortic valve (BAV) leads to a distinct extracellular matrix structure that may be related to ATAA development at an earlier age than degenerative aneurysms arising in patients with the morphological normal tricuspid aortic valve (TAV). The purpose of this study was to model the fiber-reinforced mechanical response of ATAA specimens from patients with either BAV or TAV. This was achieved by combining image-analysis derived parameters of collagen fiber dispersion and alignment with tensile testing dat…

2016

Background Transcatheter aortic valve implantation (TAVI) has become the treatment of choice in patients with severe aortic valve stenosis who are not eligible for operative replacement and an alternative for those with high surgical risk. Due to high age and smoking history in a high proportion of TAVI patients, suspicious findings are frequently observed in pre-procedural chest computer tomography (CCT).

Statistical shape analysis of ascending thoracic aortic aneurysm: Correlation between shape and biomechanical descriptors

2020

An ascending thoracic aortic aneurysm (ATAA) is a heterogeneous disease showing different patterns of aortic dilatation and valve morphologies, each with distinct clinical course. This study aimed to explore the aortic morphology and the associations between shape and function in a population of ATAA, while further assessing novel risk models of aortic surgery not based on aortic size. Shape variability of n = 106 patients with ATAA and different valve morphologies (i.e., bicuspid versus tricuspid aortic valve) was estimated by statistical shape analysis (SSA) to compute a mean aortic shape and its deformation. Once the computational atlas was built, principal component analysis (PCA) allow…

Vascular Activity of (-)-Anonaine, (-)-Roemerine and (-)-Pukateine, Three Natural 6a(R)-1,2-Methylenedioxyaporphines with Different Affinities for α1…

2004

We have studied the mechanism of action of three 6a( R)-1,2-methylenedioxyaporphines as vasorelaxant compounds. The alkaloids assayed showed different affinities for the three human cloned alpha (1)-adrenoceptor (AR) subtypes stably expressed in rat-1 fibroblasts, showing lower affinity for alpha(1B)-AR with regard to the alpha(1A)- or alpha(1D)-subtypes. These three natural compounds are more potent inhibitors of [ (3)H]-prazosin binding than of [ (3)H]-diltiazem binding to rat cerebral cortical membranes. As all these alkaloids inhibited noradrenaline (NA)-induced [ (3)H]-inositol phosphate formation in cerebral cortex and rat tail artery, they may be safely viewed as alpha (1)-AR antagon…

Educar

2015

El presente artículo describe una experiencia de formación en alternancia en un contexto de educación superior; en concreto, a partir de la iniciativa desarrollada por Florida Universitaria, centro adscrito a la Universidad de Valencia. La formación en alternancia implica alternar el aprendizaje entre períodos desarrollados en el centro educativo y momentos desarrollados en el contexto laboral. El objetivo del presente trabajo es identificar una iniciativa que, de forma empírica, muestre cómo estos periodos impactan en el aprendizaje de competencias de los estudiantes. La metodología que se ha aplicado en la experiencia de formación en alternancia se basa en el aprendizaje basado en problem…

Guided collaboration and computers: Some of its effects on learning outcome

2004

The purpose of the study was to investigate the effects of different treatments on learning outcome, into a collaborative learning context. It was used a factorial design, consisting of two factors, each one with two categories. The first factor was to give students specific roles to play to guide the kinds of interactions and activities that students engage in, versus to allow students to make their own decisions about when and how to use the teacher instructions. The second one was to develop a simple hypertext, versus to write an extended essay. It was found that the factor 'specific roles' favored the learning outcome, whereas the factor 'hypertext development' was not statistically sig…

Estado de la investigación sobre la colaboración en Entornos Virtuales de Aprendizaje

2019

El aprendizaje colaborativo posee una tradición teórica y práctica amplia en la educación general, como en la educación superior. No obstante, la actividad de coordinación entre personas que buscan aprender no es sencilla de gestionar. Esta complejidad aumenta cuando entre la actividad colaborativa surge un nuevo componente, la tecnología. ¿Qué se ha avanzado sobre el aprendizaje colaborativo mediado tecnológicamente? Este trabajo tiene como objetivo analizar el estado de la investigación sobre aprendizaje colaborativo en Educación Superior en los Entornos Virtuales de Aprendizaje (EVA). Para ello se realiza un análisis bibliométrico de las publicaciones indexadas de la base de datos SCOPUS…