A Jacobi-Davidson type method with a correction equation tailored for integral operators

The final publication is available at Springer via http://dx.doi.org/10.1007/s11075-012-9656-9We propose two iterative numerical methods for eigenvalue computations of large dimensional problems arising from finite approximations of integral operators, and describe their parallel implementation. A matrix representation of the problem on a space of moderate dimension, defined from an infinite dimensional one, is computed along with its eigenpairs. These are taken as initial approximations and iteratively refined, by means of a correction equation based on the reduced resolvent operator and performed on the moderate size space, to enhance their quality. Each refinement step requires the prolongation of the correction equation solution back to a higher dimensional space, defined from the infinite dimensional one. This approach is particularly adapted for the computation of eigenpair approximations of integral operators, where prolongation and restriction matrices can be easily built making a bridge between coarser and finer discretizations. We propose two methods that apply a Jacobi–Davidson like correction: Multipower Defect-Correction (MPDC), which uses a single-vector scheme, if the eigenvalues to refine are simple, and Rayleigh–Ritz Defect-Correction (RRDC), which is based on a projection onto an expanding subspace. Their main advantage lies in the fact that the correction equation is performed on a smaller space while for general solvers it is done on the higher dimensional one. We discuss implementation and parallelization details, using the PETSc and SLEPc packages. Also, numerical results on an astrophysics application, whose mathematical model involves a weakly singular integral operator, are presented.This work was partially supported by European Regional Development Fund through COMPETE, FCT-Fundacao para a Ciencia e a Tecnologia through CMUP-Centro de Matematica da Universidade do Porto and Spanish Ministerio de Ciencia e Innovacion under projects TIN2009-07519 and AIC10-D-000600.Vasconcelos, PB.; D'almeida, FD.; Román Moltó, JE. (2013). A Jacobi-Davidson type method with a correction equation tailored for integral operators. Numerical Algorithms. 64(1):85-103. doi:10.1007/s11075-012-9656-9S85103641Absil, P.A., Mahony, R., Sepulchre, R., Dooren, P.V.: A Grassmann–Rayleigh quotient iteration for computing invariant subspaces. SIAM Rev. 44(1), 57–73 (2002)Ahues, M., Largillier, A., Limaye, B.V.: Spectral Computations with Bounded Operators. 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A influência da transgressão e da raiva do consumidor na avaliação de provedores de serviços de Susi d’Almeida Garrett e Paulo H. M. Prado

O objetivo geral da pesquisa foi verificar a influência da emoção da raiva dos consumidores, decorrente de uma situação de transgressão (violação de conduta, falha), na percepção de qualidade do relacionamento consumidor-empresa. A pesquisa também analisa a eficiência das ações de recuperação. A raiva surgiu como a emoção mais sentida pelos participantes após as falhas de serviço, e depois das ações de recuperação, as médias das emoções negativas caíram, em especial as médias da raiva.El objetivo general de la investigación fue verificar la influencia de la emoción de la rabia de los consumidores, debido a una situación de transgresión (violación de conducta, fallo), en la percepción de calidad de la relación cliente-empresa. La investigación analiza también la eficacia de las acciones de recuperación. La rabia surgió como la emoción más sentida por los participantes después de las fallas en el servicio, y después de las acciones de recuperación, el promedio de las emociones negativas cayeron, en particular los promedios de la rabia.The overall purpose of this research was to verify the influence of the anger emotion in consumers, resulting from a transgression situation (violation of conduct, failure), on the perception of quality of the consumer-company relationship. The research also analyses the efficiency of recovery actions. Anger appeared as the most felt emotion after the service failures, and after the recovery actions, the averages of negative emotions fell, specially the averages of anger

Imagerie Des Retars Psychomoteurs De L’enfant A Lome

Objective: To determine by radiology the different etiologies of psychomotor delays (PMD) in Lomé (Togo). Material and Method: Retrospective study of 12 months in the radiology department of CAMPUS Teaching Hospital, concerned images of CT and MRI scans of children 0-16 years of age with PMD. Results: The mean age was 4.4 years +/- 4.35. The result was pathological in 69.63% of the cases.Cerebral atrophy was the most frequent lesion (40.50%), followed by hydrocephalus (23.14%). The congenital stenosis of the Sylvius aqueduct was the most frequent malformation (37.93%). Triventricular hydrocephalus accounted for 45.61% of hydrocephalus. The most common tumor lesions were choroid plexus carcinoma and craniopharyngioma (28.57% each). Meningo-encephalitis accounted for half of infectious cases. Conclusion: PMD is most often the consequence of several cerebral pathologies. The most frequent of which is cerebral atrophy

Enzymatic One-Pot Synthesis of Renewable and Biodegradable Surfactants in Supercritical Carbon Dioxide (scCO2)

We seek to expand the opportunities to exploit glycerol, a largely untapped renewable feedstock, by exploiting enzymatic catalysis in supercritical carbon dioxide (scCO2). This work highlights a promising and clean approach to bio-renewable amphiphilic polyester-based biodegradable surfactants. We have developed a low temperature (40, 50 and 60 °C), low energy melt processing route to biodegradable, renewable poly(glycerol succinate) (PGLSA) polymers that importantly have a low degree of branching (3% 85%) or insoluble crosslinked materials. We have exploited these linear PGLSA materials to create a library of ‘green’ surfactants by end-capping with lauric acid or poly(ethylene glycol). Our approach avoids pre-modification of the monomers and fewer synthetic steps are required. Finally, we evaluate the performance of these new surfactants, focussing upon surface tension, critical aggregation concentration (CAC) and water contact angle

Effects of the reaction cavity on metastable optical excitation in ruthenium-sulfur dioxide complexes

We report photoexcited-state crystal structures for two new members of the [Ru(SO_2)(NH_3)_4X]Y family: 1:X=H2O, Y=(+/-)-camphorsulfonate_2; 2:X=isonicotinamide, Y=tosylate_2. The excited states are metastable at 100 K, with a photoconversion fraction of 11.1(7)% achieved in 1, and 22.1(10)% and 26.9(10)% at the two distinct sites in 2.We further show using solid-state density-functional-theory calculations that the excited-state geometries achieved are strongly influenced by the local crystal environment. This result is relevant to attempts to rationally design related photoexcitation systems for optical data-storage applications.Comment: 6 pages, 5 figure

Deformation of canonical morphisms and the moduli of surfaces of general type

In this article we study the deformation of finite maps and show how to use this deformation theory to construct varieties with given invariants in a projective space. Among other things, we prove a criterion that determines when a finite map can be deformed to a one--to--one map. We use this criterion to construct new simple canonical surfaces with different $c_1^2$ and $\chi$. Our general results enable us to describe some new components of the moduli of surfaces of general type. We also find infinitely many moduli spaces $\mathcal M_{(x',0,y)}$ having one component whose general point corresponds to a canonically embedded surface and another component whose general point corresponds to a surface whose canonical map is a degree 2 morphism.Comment: 32 pages. Final version with some simplifications and clarifications in the exposition. To appear in Invent. Math. (the final publication is available at springerlink.com

Forecast of Healthcare Facilities and Health Workforce Requirements for the Public Sector in Ghana, 2016–2026

Abstract Background: Ghana is implementing activities towards universal health coverage (UHC) as well as the attainment of the health-related Sustainable Development Goals (SDGs) by the health sector by the year 2030. Aside lack of empirical forecast of the required healthcare facilities to achieve these mandates, health workforce deficits are also a major threat. We therefore modelled the needed healthcare facilities in Ghana and translated it into year-by-year staffing requirements based on established staffing standards. Methods: Two levels of modelling were used. First, a predictive model based on Markov processes was used to estimate the future healthcare facilities needed in Ghana. Second, the projected healthcare facilities were translated into aggregate staffing requirements using staffing standards developed by Ghana’s Ministry of Health (MoH). Results: The forecast shows a need to expand the number/capacity of healthcare facilities in order to attain UHC. All things being equal, the requisite healthcare infrastructure for UHC would be attainable from 2023. The forecast also shows wide variations in staffing-need-availability rate, ranging from 15% to 94% (average being 68%) across the various staff types. Thus, there are serious shortages of staff which are worse amongst specialists. Conclusion: Ghana needs to expand and/or increase the number of healthcare facilities to facilitate the attainment of UHC. Also, only about 68% of the health workforce (HWF) requirements are employed and available for service delivery, leaving serious shortages of the essential health professionals. Immediate recruitment of unemployed but qualified health workers is therefore imperative. Also, addressing health worker productivity, equitable distribution of existing workers, and attrition may be the immediate steps to take whilst a long-term commitment to comprehensively address HWF challenges, including recruitments, expansion and streamlining of HWF training, is pursued