1,220 research outputs found

    Carotid Artery Stent Continued Expansion Days After Deployment, Without Post Stent Deployment Angioplasty.

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    This is a carotid artery stent (CAS) case report, which avoids post-stent deployment angioplasty (Post-SDA), with duplex confirmed continued stent expansion at 1, 3 and 30-day post deployment. This report confirms that self-expanding nitinol stents in the carotid artery may not require Post-SDA. We believe CAS can be performed without Post-SDA, which helps reduce the occurrence of intraoperative hemodynamic depression

    Parallel image restoration

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    Cataloged from PDF version of article.In this thesis, we are concerned with the image restoration problem which has been formulated in the literature as a system of linear inequalities. With this formulation, the resulting constraint matrix is an unstructured sparse-matrix and even with small size images we end up with huge matrices. So, to solve the restoration problem, we have used the surrogate constraint methods, that can work efficiently for large size problems and are amenable for parallel implementations. Among the surrogate constraint methods, the basic method considers all of the violated constraints in the system and performs a single block projection in each step. On the other hand, parallel method considers a subset of the constraints, and makes simultaneous block projections. Using several partitioning strategies and adopting different communication models we have realized several parallel implementations of the two methods. We have used the hypergraph partitioning based decomposition methods in order to minimize the communication costs while ensuring load balance among the processors. The implementations are evaluated based on the per iteration performance and on the overall performance. Besides, the effects of different partitioning strategies on the speed of convergence are investigated. The experimental results reveal that the proposed parallelization schemes have practical usage in the restoration problem and in many other real-world applications which can be modeled as a system of linear inequalities.Malas, TahirM.S

    "La nef dans la tempête". La leggenda di Helsin tra dogma e realtà politica

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    Traditionally, ships were linked to the underworld and water was seen as the border between the world of the living and the one of the dead. This symbology dates back to the Egyptians, when the boat was a symbol of the passing of time and of the soul’s journey to the afterlife. For Christians, the boat was the image of safety amidst perils, hence its identification with the Church. In 1150 the Norman amanuensis Robert Wace translated "De Conceptione Mariae" into his dialect. The text, written by St. Anselm of Canterbury, narrates the troubles monk Helsin had to face before going back to William the Conqueror’s court after a difficult mission in Denmark. The ship was about to sink, when Helsin had the vision of an angel promising to save him and his crew in exchange for a vow: Helsin had to add the fest of the Immaculate Conception to the other festivals dedicated to the Virgin Mary. The essay discusses the political implications of the text by Wace, since the author added a real event (the White Ship tragedy, a shipwreck in which the heirs of Henry Beauclerc, son of William Rufus, died) to the legend. Over time, the motif of the ship in a storm at sea became a literary scheme. In the essay, the case of the “Puys” of Northern France with their poetic competitions in which the theme of the Immaculate Conception was compulsory, is mentioned – along with some examples centred on the image of the sea and navigation

    Influencia del miedo en las teorías de conspiración contra las vacunas y el comportamiento frente a la vacunación

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    Pandemics are a global threat, with vaccination being the main weapon of control. Fear, an unplea-sant emotional state caused by a threatening stimulus perception, is known to be behind inhibitory be-haviours; being, with mistrust, the basis of anti-vaccine conspiracy theories (CTs). It would be appropria-te to know the fear influence on these theories. In this way, a cross-sectional online survey was applied to 2.987 subjects, in a COVID-19 context, characterized by high levels of uncertainty and mistrust, with the aims of analyse the relationship between some anti-vaccine CTs and vaccination intention (VI), also the influence of fear to vaccination (VF) on CTs and VI in this context. As result, all CTs were positive predictors of VF and negative predictors of VI. The correlations were significant (p <0.001), from mode-rate to high, for all analysed variables, with a significant and moderate directionality and size of associa-tion. Regression analysis indicated a moderate and significant explained variance (r2 = 0.54) of CTs + VF in VI. The analysis also indicates that safety and security CTs were more strongly associated with VF (r2 = 0.347) and VI (r2 = 0.46) than other CTs. Obtained results were more significant than those found by other researchers. Knowing in each case the main anti-vaccine CTs and the associated fear can help to plan programs to increase vaccination levels. Keywords: Fear, Conspiracy Theories, Vaccination avoidance, Vaccines, Anti-vaccines.ResumenLas pandemias son una amenaza global, siendo la vacunación la principal arma de control. Se sabe que el miedo, un estado emocional desagradable causado por la percepción de un estímulo amenazan-te, está detrás de las conductas inhibitorias; siendo, con la desconfianza, la base de las teorías de la conspiración antivacunas (CTs por sus siglas en inglés) Sería oportuno conocer la influencia del miedo en estas teorías. Con esta intención, se aplicó una encuesta transversal online a 2.987 sujetos, en un contexto COVID-19, caracterizado por altos niveles de incertidumbre y desconfianza, con el objetivo de analizar la relación entre algunas CTs antivacunas y la intención de vacunación (VI), así como la influen-cia del miedo a la vacunación (VF) en las CTs y la VI, en dicho contexto. Como resultado, todos las CTs fueron predictores positivos de VF y predictores negativos de VI. Las correlaciones fueron significativas (p <0,001), de moderada a alta, para todas las variables analizadas, con una direccionalidad y tamaño de asociación significativa y moderada. El análisis de regresión indicó una varianza explicada moderada y significativa (r2 = 0.54) de CTs + VF en VI. El análisis también indica que los CTs de seguridad y eficacia estaban más fuertemente asociados con VF (r2 = 0,347) y VI (r2 = 0,46) que otras CTs. Los resultados obtenidos fueron más significativos que los hallados por otros investigadores. Conocer en cada caso los principales CTs antivacunas y el miedo asociado puede ayudar a planificar programas para aumentar los niveles de vacunación.Palabras clave: Miedo, Teorías de la Conspiración, Evitación de la vacunación, Vacunas, Antivacu-nas.Las pandemias son una amenaza global, siendo la vacunación la principal arma de control. Se sabe que el miedo, un estado emocional desagradable causado por la percepción de un estímulo amenazan-te, está detrás de las conductas inhibitorias; siendo, con la desconfianza, la base de las teorías de la conspiración antivacunas (CTs por sus siglas en inglés) Sería oportuno conocer la influencia del miedo en estas teorías. Con esta intención, se aplicó una encuesta transversal online a 2.987 sujetos, en un contexto COVID-19, caracterizado por altos niveles de incertidumbre y desconfianza, con el objetivo de analizar la relación entre algunas CTs antivacunas y la intención de vacunación (VI), así como la influen-cia del miedo a la vacunación (VF) en las CTs y la VI, en dicho contexto. Como resultado, todos las CTs fueron predictores positivos de VF y predictores negativos de VI. Las correlaciones fueron significativas (p <0,001), de moderada a alta, para todas las variables analizadas, con una direccionalidad y tamaño de asociación significativa y moderada. El análisis de regresión indicó una varianza explicada moderada y significativa (r2 = 0.54) de CTs + VF en VI. El análisis también indica que los CTs de seguridad y eficacia estaban más fuertemente asociados con VF (r2 = 0,347) y VI (r2 = 0,46) que otras CTs. Los resultados obtenidos fueron más significativos que los hallados por otros investigadores. Conocer en cada caso los principales CTs antivacunas y el miedo asociado puede ayudar a planificar programas para aumentar los niveles de vacunació

    Schur complement preconditioners for surface integral-equation formulations of dielectric problems solved with the multilevel fast multipole algorithm

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    Cataloged from PDF version of article.Surface integral-equation methods accelerated with the multilevel fast multipole algorithm (MLFMA) provide a suitable mechanism for electromagnetic analysis of real-life dielectric problems. Unlike the perfect-electric-conductor case, discretizations of surface formulations of dielectric problems yield 2 x 2 partitioned linear systems. Among various surface formulations, the combined tangential formulation (CTF) is the closest to the category of first-kind integral equations, and hence it yields the most accurate results, particularly when the dielectric constant is high and/or the dielectric problem involves sharp edges and corners. However, matrix equations of CTF are highly ill-conditioned, and their iterative solutions require powerful preconditioners for convergence. Second-kind surface integral-equation formulations yield better conditioned systems, but their conditionings significantly degrade when real-life problems include high dielectric constants. In this paper, for the first time in the context of surface integral-equation methods of dielectric objects, we propose Schur complement preconditioners to increase their robustness and efficiency. First, we approximate the dense system matrix by a sparse near-field matrix, which is formed naturally by MLFMA. The Schur complement preconditioning requires approximate solutions of systems involving the (1,1) partition and the Schur complement. We approximate the inverse of the (1,1) partition with a sparse approximate inverse (SAI) based on the Frobenius norm minimization. For the Schur complement, we first approximate it via incomplete sparse matrix-matrix multiplications, and then we generate its approximate inverse with the same SAI technique. Numerical experiments on sphere, lens, and photonic crystal problems demonstrate the effectiveness of the proposed preconditioners. In particular, the results for the photonic crystal problem, which has both surface singularity and a high dielectric constant, shows that accurate CTF solutions for such problems can be obtained even faster than with second-kind integral equation formulations, with the acceleration provided by the proposed Schur complement preconditioners

    Multicore-optimized wavefront diamond blocking for optimizing stencil updates

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    The importance of stencil-based algorithms in computational science has focused attention on optimized parallel implementations for multilevel cache-based processors. Temporal blocking schemes leverage the large bandwidth and low latency of caches to accelerate stencil updates and approach theoretical peak performance. A key ingredient is the reduction of data traffic across slow data paths, especially the main memory interface. In this work we combine the ideas of multi-core wavefront temporal blocking and diamond tiling to arrive at stencil update schemes that show large reductions in memory pressure compared to existing approaches. The resulting schemes show performance advantages in bandwidth-starved situations, which are exacerbated by the high bytes per lattice update case of variable coefficients. Our thread groups concept provides a controllable trade-off between concurrency and memory usage, shifting the pressure between the memory interface and the CPU. We present performance results on a contemporary Intel processor
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