On the non-local geometry of turbulence

A multi-scale methodology for the study of the non-local geometry of eddy structures in turbulence is developed. Starting from a given three-dimensional field, this consists of three main steps: extraction, characterization and classification of structures. The extraction step is done in two stages. First, a multi-scale decomposition based on the curvelet transform is applied to the full three-dimensional field, resulting in a finite set of component three-dimensional fields, one per scale. Second, by iso-contouring each component field at one or more iso-contour levels, a set of closed iso-surfaces is obtained that represents the structures at that scale. The characterization stage is based on the joint probability density function (p.d.f.), in terms of area coverage on each individual iso-surface, of two differential-geometry properties, the shape index and curvedness, plus the stretching parameter, a dimensionless global invariant of the surface. Taken together, this defines the geometrical signature of the iso-surface. The classification step is based on the construction of a finite set of parameters, obtained from algebraic functions of moments of the joint p.d.f. of each structure, that specify its location as a point in a multi-dimensional ‘feature space’. At each scale the set of points in feature space represents all structures at that scale, for the specified iso-contour value. This then allows the application, to the set, of clustering techniques that search for groups of structures with a common geometry. Results are presented of a first application of this technique to a passive scalar field obtained from 5123 direct numerical simulation of scalar mixing by forced, isotropic turbulence (Reλ = 265). These show transition, with decreasing scale, from blob-like structures in the larger scales to blob- and tube-like structures with small or moderate stretching in the inertial range of scales, and then toward tube and, predominantly, sheet-like structures with high level of stretching in the dissipation range of scales. Implications of these results for the dynamical behaviour of passive scalar stirring and mixing by turbulence are discussed

Geometry of enstrophy and dissipation, grid resolution effects and proximity issues in turbulence

We perform a multi-scale non-local geometrical analysis of the structures extracted from the enstrophy and kinetic energy dissipation-rate, instantaneous fields of a numerical database of incompressible homogeneous isotropic turbulence decaying in time obtained by DNS in a periodic box. Three different resolutions are considered: 256^3, 512^3 and 1024^3 grid points, with k_(max)η(overbar) approximately 1, 2 and 4, respectively, the same initial conditions and Re_λ ≈ 77. This allows a comparison of the geometry of the structures obtained for different resolutions. For the highest resolution, structures of enstrophy and dissipation evolve in a continuous distribution from blob-like and moderately stretched tube-like shapes at the large scales to highly stretched sheet-like structures at the small scales. The intermediate scales show a predominance of tube-like structures for both fields, much more pronounced for the enstrophy field. The dissipation field shows a tendency towards structures with lower curvedness than those of the enstrophy, for intermediate and small scales. The 256^3 grid resolution case (k_(max)η(overbar) ≈ 1) was unable to detect the predominance of highly stretched sheet-like structures at the smaller scales in both fields. The same non-local methodology for the study of the geometry of structures, but without the multi-scale decomposition, is applied to two scalar fields used by existing local criteria for the eduction of tube- and sheet-like structures in turbulence, Q and [A_ij]_+, respectively, obtained from invariants of the velocity-gradient tensor and alike in the 1024^3 case. This adds the non-local geometrical characterization and classification to those local criteria, assessing their validity in educing particular geometries. Finally, we introduce a new methodology for the study of proximity issues among structures of different fields, based on geometrical considerations and non-local analysis, by taking into account the spatial extent of the structures. We apply it to the four fields previously studied. Tube-like structures of Q are predominantly surrounded by sheet-like structures of [A_ij]_+, which appear at closer distances. For the enstrophy, tube-like structures at an intermediate scale are primarily surrounded by sheets of smaller scales of the enstrophy and structures of dissipation at the same and smaller scales. A secondary contribution results from tubes of enstrophy at smaller scales appearing at farther distances. Different configurations of composite structures are presented

Multi-scale geometric analysis of Lagrangian structures in isotropic turbulence

We report the multi-scale geometric analysis of Lagrangian structures in forced isotropic turbulence and also with a frozen turbulent field. A particle backward-tracking method, which is stable and topology preserving, was applied to obtain the Lagrangian scalar field φ governed by the pure advection equation in the Eulerian form ∂_tφ + u · ∇φ = 0. The temporal evolution of Lagrangian structures was first obtained by extracting iso-surfaces of φ with resolution 1024^3 at different times, from t = 0 to t = T_e, where T_e is the eddy turnover time. The surface area growth rate of the Lagrangian structure was quantified and the formation of stretched and rolled-up structures was observed in straining regions and stretched vortex tubes, respectively. The multi-scale geometric analysis of Bermejo-Moreno & Pullin (J. Fluid Mech., vol. 603, 2008, p. 101) has been applied to the evolution of φ to extract structures at different length scales and to characterize their non-local geometry in a space of reduced geometrical parameters. In this multi-scale sense, we observe, for the evolving turbulent velocity field, an evolutionary breakdown of initially large-scale Lagrangian structures that first distort and then either themselves are broken down or stretched laterally into sheets. Moreover, after a finite time, this progression appears to be insensible to the form of the initially smooth Lagrangian field. In comparison with the statistical geometry of instantaneous passive scalar and enstrophy fields in turbulence obtained by Bermejo-Moreno & Pullin (2008) and Bermejo-Moreno et al. (J. Fluid Mech., vol. 620, 2009, p. 121), Lagrangian structures tend to exhibit more prevalent sheet-like shapes at intermediate and small scales. For the frozen flow, the Lagrangian field appears to be attracted onto a stream-surface field and it develops less complex multi-scale geometry than found for the turbulent velocity field. In the latter case, there appears to be a tendency for the Lagrangian field to move towards a vortex-surface field of the evolving turbulent flow but this is mitigated by cumulative viscous effects

The XMM-Newton Slew Survey: towards the XMMSL1 catalogue

The XMM-Newton satellite is the most sensitive X-ray observatory flown to date due to the great collecting area of its mirrors coupled with the high quantum efficiency of the EPIC detectors. It performs slewing manoeuvers between observation targets tracking almost circular orbits through the ecliptic poles due to the Sun constraint. Slews are made with the EPIC cameras open and the other instruments closed, operating with the observing mode set to the one of the previous pointed observation and the medium filter in place. Slew observations from the EPIC-pn camera in FF, eFF and LW modes provide data, resulting in a maximum of 15 seconds of on-source time. These data can be used to give a uniform survey of the X-ray sky, at great sensitivity in the hard band compared with other X-ray all-sky surveys.Comment: 2 pages, 2 figures, to appear in the proceedings of "The X-ray Universe 2005", San Lorenzo de El Escorial (Spain), 26-30 September 200

Extended sources in the XMM-Newton slew survey

The low background, good spatial resolution and great sensitivity of the EPIC-pn camera on XMM-Newton give useful limits for the detection of extended sources even during the short exposures made during slewing maneouvers. In this paper we attempt to illustrate the potential of the XMM-Newton slew survey as a tool for analysing flux-limited samples of clusters of galaxies and other sources of spatially extended X-ray emission.Comment: 2 pages, 4 figures, to appear in the proceedings of "The X-ray Universe 2005", San Lorenzo de El Escorial (Spain), 26-30 September 200

The Boomerang Effect: How Nurses' Regulation of Patients' Affect Associates With Their Own Emotional Exhaustion and Affective Experiences

Recent research has shown that the intentional regulation of others’ affect has effects not only on the target (e.g., a patient) of the regulation, but also on the agent (e.g., a nurse). In particular, the use of intentional interpersonal affect regulation strategies has been found to predict employees’ emotional exhaustion (EEx). Use of affect-worsening strategies is associated with an increase in EEx, whereas the effect of using affect-improving strategies is less clear. Another relevant consequence of interpersonal affect regulation is its effect on affective experiences, which is one of the main determinants of job attitudes. This study tests the relationships between the interpersonal affect regulation strategies that nurses use to regulate their patients’ affect and the nurses’ EEx and affective experiences. A longitudinal 2-wave field study was conducted in sample of nurses. Participants completed a questionnaire on 2 different occasions, 2 months apart (Time 1 [T1], Time 2 [T2]). Of the 141 participants at T1, 103 also completed the survey at T2. Longitudinal hierarchical regression analyses showed that using affect-worsening strategies was a significant predictor of nurse’s EEx, whereas using affect-improving strategies did not significantly predict their EEx. For affective experiences, use of affect-worsening strategies was related to nurses experiencing low-activation negative affect (e.g., feeling depressed); whereas affect-improving strategies was related to them experiencing low-activation positive affect (e.g., feeling calm). Results support the view that intentional regulation of patients’ affect needs to be considered not only in relation to the patients’ perception of service quality but also from the perspective of nurses’ well-being

Una contribución al estudio racial del cerdo Mamellado Uruguayo

In spite of the persistence in Uruguay of pigs belonging to the wattled pig breed, no adequate attention had ever been paid to them. The wattles appear associated with ancestries of the Iberian pig (Spanish and Portuguese) and to other breeds pertaining to the Mediterranean trunk, being rare in the Celtic trunk. This scientific peculiarity, together with reasons of adaptation and rusticity (production), environmental (association with specific ecosystems) and historical-cultural role makes the study of this genetic resource justifiable. The Team of the Red XII-H CYTED of Uruguay was established and has made a series of consultations and interviews to locate the farms in which this type of pig is established and other information that will help clarify their present situation, origin and historical evolution. Preliminary information obtained in the census indicates that the Uruguayan Wattled Pigs (UWP) whilst critical in terms of numbers are widely distributed geographically, living in varying ecosystems and living together with small and medium producers that have maintained the animals as a novelty as well as for self consumption (sausage making). Within the framework of a complete racial study the Team is planning to carry out the morphologic characterization of the animals and a genetic study, in order to determine the distance between the Uruguayan wattled pig and other breeds from the Mediterranean trunk. Productive parameters and the most favourable exploitation conditions for obtaining high quality products in sustainable systems that make geographically unfavourable areas more profitable, will also be analysed.A pesar de que aún persisten en el Uruguay cerdos de la raza Mamellado Uruguayo, nunca se les ha dedicado la atención adecuada. Las mamellas aparecen asociadas a variedades ancestrales del cerdo Ibérico (español y portugués) y a otras razas pertenecientes al tronco Mediterráneo, siendo muy raras en el tronco Celta. Esta peculiaridad específica, junto con razones de adaptación y rusticidad (producción), ambiente (asociación con ambientes específicos) y el papel histórico-cultural justifican sobradamente este estudio. El equipo uruguayo dela Red CYTED XII-H ha realizado una serie de consultas y entrevistas para localizar las granjas donde estos cerdos están establecidos así como otra información que nos ayudará a clarificar su situación actual, su origen y su evolución histórica. La información preliminar obtenida sobre sus censos indica que el Cerdo Mamellado Uruguayo se encuentra en estado crítico. Además se encuentra distribuido geográficamente de una manera amplia habitando variados ecosistemas en explotaciones medias y pequeñas que han mantenido a estos animales por afición o para autoconsumo (fabricación de chacinados). Dentro de la tarea de un estudio racial completo nuestro equipo está planeando llevar a cabo la caracterización morfológica de estos animales y su estudio genético, en orden a determinar la distancia entre esta raza y otros miembros del Tronco Mediterráneo. También son analizados los parámetros productivos y las condiciones de explotación más favorables para obtener productos de alta calidad en sistemas sostenibles que hacen rentables a las áreas más desfavorecidas

Population-based study of baseline ethanol consumption and risk of incident essential tremor

Recent postmortem studies have demonstrated pathological changes, including Purkinje cell loss, in the cerebellum in essential tremor (ET). Toxic exposures that compromise cerebellar tissue could lower the threshold for developing ET. Ethanol is a well-established cerebellar toxin, resulting in Purkinje cell loss

Population-based prospective study of cigarette smoking and risk of incident essential tremor

Background: Smoking cigarettes is associated with lower risk of Parkinson disease (PD). Despite the clinical links between PD and essential tremor (ET), there are few data on smoking in ET. One study showed an association between smoking and lower ET prevalence. We now study whether baseline smoking is associated with lower risk of incident ET. Methods: Using a population-based, cohort design, baseline cigarette smoking habits were assessed in 3,348 participants in an epidemiologic study in Spain, among whom 77 developed incident ET. Results: There were 3,348 participants, among whom 397 (11.9%) were smokers at baseline. Five (6.5%) of 77 incident ET cases had been smokers at baseline, compared with 392 (12.0%) of 3,271 controls (p = 0.14). Baseline pack-years were lower in incident ET cases than in controls (9.2 ± 17.7 vs 15.7 ± 28.4, p = 0.002). Participants were stratified into baseline pack-year tertiles, and few incident ET cases were in the highest tertile (4 [5.2%] cases vs 431 [13.2%] controls, p = 0.039). In Cox proportional hazards models, the highest baseline pack-year tertile was associated with lower risk of incident ET; those in the highest pack-year tertile were one-third as likely to develop ET when compared with nonsmokers (relative risk [RR] 0.37, 95% CI 0.14—1.03, p = 0.057 [unadjusted model] and RR 0.29, 95% CI 0.09—0.90, p = 0.03 [adjusted model]). Conclusions: We demonstrated an association between baseline heavy cigarette smoking and lower risk of incident essential tremor. The biologic basis for this association requires future investigation