Numerical and modeling error assessment of large-eddy simulation using direct-numerical-simulation-aided large-eddy simulation

We study the numerical errors of large-eddy simulation (LES) in isotropic and wall-bounded turbulence. A direct-numerical-simulation (DNS)-aided LES formulation, where the subgrid-scale (SGS) term of the LES is computed by using filtered DNS data is introduced. We first verify that this formulation has zero error in the absence of commutation error between the filter and the differentiation operator of the numerical algorithm. This method allows the evaluation of the time evolution of numerical errors for various numerical schemes at grid resolutions relevant to LES. The analysis shows that the numerical errors are of the same order of magnitude as the modeling errors and often cancel each other. This supports the idea that supervised machine learning algorithms trained on filtered DNS data might not be suitable for robust SGS model development, as this approach disregards the existence of numerical errors in the system that accumulates over time. The assessment of errors in turbulent channel flow also identifies that numerical errors close to the wall dominate, which has implications for the development of wall models

Avalanche statistics and time-resolved grain dynamics for a driven heap

We probe the dynamics of intermittent avalanches caused by steady addition of grains to a quasi-two dimensional heap. To characterize the time-dependent average avalanche flow speed v(t), we image the top free surface. To characterize the grain fluctuation speed dv(t), we use Speckle-Visibility Spectroscopy. During an avalanche, we find that the fluctuation speed is approximately one-tenth the average flow speed, and that these speeds are largest near the beginning of an event. We also find that the distribution of event durations is peaked, and that event sizes are correlated with the time interval since the end of the previous event. At high rates of grain addition, where successive avalanches merge into smooth continuous flow, the relationship between average and fluctuation speeds changes to dv Sqrt[v]

Desde la etnobotánica a la reconstrucción de identidades en localidades de la Quebrada de Humahuaca, Jujuy.

En las comunidades de la Quebrada de Humahuaca, debido a los procesos migratorios sucesivos hacia zonas de producción demandantes de mano de obra; y a los cambios de hábito de consumo como consecuencia de la globalización, se ha producido una pérdida de conocimiento tradicional asociado al uso de los recursos vegetales. Este último, asumido como componente del patrimonio local resulta de gran importancia a la hora de reconstruir la identidad de los pueblos. Este planteo ha sido central en el desarrollo de una investigación etnobotánica realizada en Juella desde el año 2004 al 2008; el trabajo obtenido ha permitido replicar la experiencia en Hornaditas y Coctaca desde el año 2010. El objetivo fue documentar y fortalecer el conocimiento local sobre el uso de los recursos vegetales. Se trabajó con investigación participativa que involucró talleres, caminatas etnobotánicas y  co-presencia; complementándose con la colección de cada ejemplar involucrado; registrándose cada una de las percepciones particulares. Éstos  cuentan con su nombre vulgar, fotos y han sido identificados a gabinete con el uso de claves dicotómicas. Como consecuencia, se han sistematizado 85 especies en Juella, 50 en Coctaca y unas 20 en Hornaditas, las que serán devueltas en forma de catálogos locales. Se reconoce la pervivencia de un conocimiento tradicional de transmisión horizontal y vertical que asegura el uso del recurso local. Además, la comunidad y el equipo de investigación (estudiantes de Ingeniería Agronómica y Lic. en Ciencias Biológicas) debieron construir un canal de comunicación que posibilitara a través del diálogo la explicitación de los saberes locales como un aporte al fortalecimiento de las identidades locales. Palabras claves: conocimiento tradicional–catálogos-saberes locales.    

Space and time behaviour of the temperature second-order structure function in Rayleigh-Bénard convection

One of the most peculiar aspects of turbulence in wall bounded-flows is the ability of the turbulent fluctuations to regenerate themselves through self-sustained processes. The dynamics of these self-sustaining mechanisms has been extensively investigated in the past via two complementary approaches. From one side, the possibility to identify very robust kinematic features within the flow feeds the hope of the scientific community to obtain a complete and consistent dynamical description of the physics of the turbulent regeneration cycles in terms of the so-called coherent structures. From the other side, the multi-scale and inhomogeneous features of the self-sustaining mechanisms of turbulence have been addressed by means of global statistical quantities based on two-point averages such as second-order structure functions. The present work attempts to link these two approaches, by identifying how turbulent cycle mechanisms and turbulent structures reflect on the global statistical properties of second-order structure function. To this aim we use Direct Numerical Simulation data of thermally driven turbulence in the Rayleigh-Bénard convection and we analyse for the first time the behaviour of the second-order structure function of temperature in the complete four-dimensional space of spatio-temporal scales and wall-distances. The observed behaviour is then interpreted in terms of the dynamics of coherent thermal structures and of their commonly accepted model of life-cycle

Assessment of Public Hospital Governance in Romania: Lessons From 10 Case Studies

Background: The Government of Romania commissioned international technical assistance to help unpacking the causes of arrears in selected public hospitals. Emphases were placed on the governance-related determinants of the hospital performance in the context of the Romanian health system. Methods: The assessment was structured around a public hospital governance framework examining 4 dimensions: institutional arrangements, financing arrangements, accountability arrangements and correspondence between responsibility and decision-making capacity. The framework was operationalized using a 2-pronged approach: (i) a policy review of broader health system governance arrangements influencing hospital performance; and (ii) a series of 10 case-studies of public hospitals experiencing financial hardship. Data were collected during 2016-2017 through key informant interviews with central authorities and hospital management teams, exhaustive semi-structured questionnaires filled in by hospitals, as well as the review of documentary sources where feasible.Results: Overall, the governance landscape of Romanian public hospitals includes a large number of seemingly modern legislative provisions and management instruments. Over the past 30 years substantial efforts have been made to put in place standardised hospital classification, hospital governance structures, management and service purchasing contracts with key performance indicators, modern reimbursement mechanisms based on diagnosis-related groups (DRGs), and regulatory requirements for accountability, including internal and external audit. Nevertheless, their application appears to have been challenging for a range of reasons, pointing to the misalignment between the responsibility and decision-making capacity given to hospitals in a questionably conducive context. Incoherent policy design, outdated and often disjointed regulatory frameworks, and cumbersome administrative procedures limit managerial autonomy and obstruct efficiency gains. In a context of chronic insufficient funding, misaligned incentives, and overly rigid service procurement processes, hospitals seem to struggle to adjust service baskets to the population’s health needs or to overcoming financial hardship. External challenges, combined with the limited strategic, operational, and financial management capacity within hospitals, make it difficult to exhibit good financial and general performance.Conclusion: Existing governance arrangements for Romanian public hospitals appear conducive to poor financial performance. The suggested framework for hospital governance assessment has proved a powerful tool for identifying system and hospital-specific challenges contributing to sub-optimal hospital performance

Molecular Identification of Mycobacterium Species of Public Health and Veterinary Importance from Cattle in the South State of México

Mycobacterium genus causes a variety of zoonotic diseases. The best known example is the zoonotic tuberculosis due to M. bovis. Much less is known about “nontuberculous mycobacteria (NTM),” which are also associated with infections in humans. The Mexican standard NOM-ZOO-031-1995 regulates the presence of M. bovis in cattle; however, no regulation exists for the NTM species. The objective of this study was to isolate and identify nontuberculous mycobacteria species from cattle of local herds in the south region of the State of Mexico through the identification and detection of the 100 bp molecular marker in the 23S rRNA gene with subsequent sequencing of the 16S rRNA gene.Milk samples (35) and nasal exudate samples (68) were collected. From the 108 strains isolated, 39 were selected for identification. Thirteen strains isolated from nasal exudates amplified the 100 bp molecular marker and were identified as M. neoaurum (six strains), M. parafortuitum (four strains), M. moriokaense (two strains), and M. confluentis (one strain). Except M. parafortuitum, the other species identified are of public health and veterinary concern because they are pathogenic to humans, especially those with underlying medical conditions