1,720,991 research outputs found
Linac Based STereotactic Arrhythmia Radioablation (STAR) of Atrial fibrillation
No full textBackground and Aims: Stereotactic arrhythmia radioablation (STAR) is a novel therapeutic
approach for cardiac arrhythmias. The aim of this trial is to investigate the feasibility of STAR for the
treatment of paroxysmal atrial fibrillation (AF) in elderly patients.
Method: inclusion criteria were: age > 70 years, symptomatic AF, antiarrhythmic drugs failure or
intolerance. All patients underwent to 4D cardiac Computed Tomography simulation. The clinical
target volume was identified in the area around pulmonary veins (PV). STAR was performed with a
total dose of 25Gy (single fraction) delivered in 3 minutes.
Results: Twenty patients were enrolled and 18 underwent STAR. One patient withdrew informed
consent before treatment and 1 patient was excluded due to unfavorable esophagus position. With a
median follow-up (FU) of 16 months (range 12-23), no acute toxicity more than grade 3 was reported.
Five patients had a grade 1 esophagitis 24 hours after STAR; eight patients had an asymptomatic
grade 1 pericardial effusion, one patient had a torsade de pointes treated effectively by electrical
cardioversion and subsequent cardiac ICD implantation. Most patients had a significant reduction in
AF episodes. Five patients, due to arrhythmias recurrences after STAR, performed
electrophysiological study documenting successful PV isolation. Finally, a significant improvement
of quality of life was documented (48±15 at enrollment vs 75±15 at 12 months FU; p<0.001).
Conclusion: The present phase II trial demonstrated the feasibility of STAR in paroxysmal AF elderly
patients and its potential role in increasing the quality of life. Surely, more robust data are needed
about safety and efficacy
SPH modeling of solid boundaries through a semi-analytic approach
No full textThis paper presents a general semi-analytic approach for modeling solid boundaries in the SPH method: boundaries are here considered as a material continuum with a suitable distribution of velocity and pressure; their contributions to each term of the SPH mass and momentum equations can be expressed in terms of a suitable integral extended to the part of the sphere of influence of the particle delimited by the boundary surface. Analytical details with reference to a slightly compressible viscous Newtonian fluid in three dimensions are given. The validity of the method is checked by comparing the obtained numerical results with available experimental data in a
benchmark flow case
Smoothed particle hydrodynamics method for simulating sediment scouring
No full textSediment scouring due to free-surface water flows represents a topic of great concern in several fields of the applied engineering such as operation of an artificial reservoir, design and maintenance of partially submerged structures.
Even if traditional CFD techniques are commonly adopted for modeling such problems, they suffer from some intrinsic limitations owing to the difficulty to mimic surface separation and wave breaking; furthermore, high computational effort is
generally needed for simulating moving boundaries and interfaces that often require cumbersome adaptive mesh rezoning to avoid numerical degradation related to large deformation induced mesh distortion.
Due to its peculiar features of meshless method, Smoothed Particle Hydrodynamics (SPH) handles easily those problems and gives the chance for setting up a reliable tool that can predict the relevant engineering aspects of the water-sediment coupled
dynamics in presence of rapidly varied free-surface flows.
In this work, recent implementations in modeling of non-cohesive sediment scouring by SPH are illustrated: two different approaches to the problem are discussed, showing the basics of the theoretical formulation and numerical results for some test
case of interest
SPH Modeling of Rapid Sediment Scour Induced by Water Flow
No full textThe numerical modeling of the scour rapidly induced by a water flow in a saturated layer of noncohesive
sediment at the bottom of an experimental reservoir is carried out on the basis of the
Smoothed Particle Hydrodynamics (SPH) method. Two alternative approaches have been followed
for describing such a phenomenon: liquid and granular phases are treated as slightly compressible
fluids whose motion results from the numerical solution of the continuity and momentum equations
in Lagrangian form; the evolution of the interface between the two phases (i.e. the scouring process)
is described as a transport-diffusion phenomenon. The main features of the model set up are
presented and the numerical results for some representative 2D and 3D experimental test cases are
discussed
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Simulating rapid sediment scour by water flow with SPH
No full textThe present paper deals with the SPH numerical modelling of the interaction between fluid and non-cohesive bed sediments whose scour is induced by a rapid water outflow from the bottom of an experimental reservoir. The dynamic behaviour of the liquid and granular phases is simulated by following two alternative approaches: either by treating them as slightly compressible fluids whose motion results from the numerical solution of the continuity and momentum equations according to the standard SPH formulation; or by describing the evolution of the interface between the two phases (i.e. the scouring process) as a transport-diffusion phenomenon. The main features of the model are presented first and then the numerical results for representative experimental test cases are discussed and compared with available experimental data
A semi-analytic approach for SPH modelling of solid boundaries
No full textA general semi-analytic approach for modelling solid boundaries in the SPH method is presented: they are considered as a material continuum with suitable distribution of velocity and pressure. Boundary contribution to each term of the SPH mass and momentum balance equations can be expressed in terms of a suitable integral extended to the volume intersection of the influence sphere of the particle with the boundary surface. Analytical details with reference to a slightly compressible viscous Newtonian fluid in three-dimensional geometry are given
Clinical correlates and prognostic value of flow mediated dilation in patients with non-ST segment elevation acute coronary syndromes
No full textEndothelial dysfunction can predict cardiovascular outcomes in several populations of patients. The aim of this study was to assess the severity, time course, and clinical implications of endothelial dysfunction in patients with non-ST-segment elevation (NSTE) acute coronary syndromes (ACS). Sixty patients with NSTE ACS (mean age 62 ± 8 years, 44 men) and 40 controls with stable coronary artery disease (CAD) (mean age 63 ± 10 years, 27 men) were studied. In patients with NSTE ACS and in those with stable CAD, endothelial function was assessed <12 hours after admission and at 3-month follow-up by measuring right brachial artery dilation after 5 minutes of forearm ischemia (flow-mediated dilation [FMD]). Clinical outcomes were assessed after a median follow-up period of 32 months (range 14 to 36). The primary end point was a combination of cardiac death or readmission for new ACS or recurrence of angina pectoris. FMD on admission was significantly lower in patients with NSTE ACS compared to those with stable CAD (2.1 ± 1.2% vs 4.8 ± 1.9%, p <0.001). FMD improved significantly at 3-month follow-up in patients with NSTE ACS, becoming comparable to that in patients with stable CAD (5.7 ± 2.6% vs 5.5 ± 1.7%, p = 0.93). During follow-up, 14 cardiac events (23%) occurred in patients with NSTE ACS. On multivariate analysis, only diabetes (hazard ratio 18.1, 95% confidence interval 3.9 to 83.9, p <0.001) and FMD at 3 months (hazard ratio 0.78, 95% confidence interval 0.61 to 0.99, p = 0.04) were independent predictors of the primary end point in patients with NSTE ACS. In conclusion, endothelial function is markedly impaired in the acute phase of NSTE ACS but improves significantly at 3-month follow-up. In patients with NSTE ACS, FMD at 3 months after the acute event is a significant independent predictor of cardiac outcomes
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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