On constraint preservation and strong hyperbolicity

We use partial differential equations (PDEs) to describe physical systems. In general, these equations include evolution and constraint equations. One method used to find solutions to these equations is the Free-evolution approach, which consists in obtaining the solutions of the entire system by solving only the evolution equations. Certainly, this is valid only when the chosen initial data satisfies the constraints and the constraints are preserved in the evolution. In this paper, we establish the sufficient conditions required for the PDEs of the system to guarantee the constraint preservation. This is achieved by considering quasi-linear first-order PDEs, assuming the sufficient condition and deriving strongly hyperbolic first-order partial differential evolution equations for the constraints. We show that, in general, these constraint evolution equations correspond to a family of equations parametrized by a set of free parameters. We also explain how these parameters fix the propagation velocities of the constraints. As application examples of this framework, we study the constraint conservation of the Maxwell electrodynamics and the wave equations in arbitrary space-times. We conclude that the constraint evolution equations are unique in the Maxwell case and a family in the wave equation case

Variability in upwelling across the tropical tropopause and correlations with tracers in the lower stratosphere

Temporal variability of the upwelling near the tropical tropopause on daily to annual timescales is investigated using three different estimates computed from the ERA-Interim reanalysis. These include upwelling archived by the reanalysis, plus estimates derived from thermodynamic and momentum balance calculations. Substantial variability in upwelling is observed on both seasonal and sub-seasonal timescales, and the three estimates show reasonably good agreement. Tropical upwelling should exert strong influence on temperatures and on tracers with large vertical gradients in the lower stratosphere. We test this behavior by comparing the calculated upwelling estimates with observed temperatures in the tropical lower stratosphere, and with measurements of ozone and carbon monoxide (CO) from the Aura Microwave Limb Sounder (MLS) satellite instrument. Time series of temperature, ozone and CO are well correlated in the tropical lower stratosphere, and we quantify the influence of tropical upwelling on this joint variability. Strong coherent annual cycles observed in each quantity are found to reflect the seasonal cycle in upwelling. Statistically significant correlations between upwelling, temperatures and tracers are also found for sub-seasonal timescales, demonstrating the importance of upwelling in forcing transient variability in the lower tropical stratosphere

Urban art, public authorities and territorial development: a reflection from three case studies

This article comes from different researches recently developed by its authors, which deal with urban art and its relationship with the contemporary city. Of particular relevance is the focus on the articulation between urban art and local public authorities in what we can define as policies for urban art. In the last two decades, a path has been taken that points precisely to a certain consensus regarding the role and importance of urban art, which goes through clear processes of legitimation and institutionalization. In this article we intend to discuss these issues from research carried out in different geographical contexts. The research, of qualitative and ethnographic nature, was developed in the last years, centered in emblematic urban art projects developed in the cities of Lisbon and Loures (Portugal) and Porto Alegre (Brazil). The conclusions reveal a tendency to understand urban art from a strategic and utilitarian point of view, considered as a relevant instrument for the production of the urban landscape.info:eu-repo/semantics/publishedVersio

Variability and trends in dynamical forcing of tropical lower stratospheric temperatures

The contribution of dynamical forcing to variations and trends in tropical lower stratospheric 70 hPa temperature for the period 1980–2011 is estimated based on ERA-Interim and Modern-Era Retrospective Analysis for Research and Applications (MERRA) reanalysis data. The dynamical forcing is estimated from the tropical mean residual upwelling calculated with the momentum balance equation, and with a simple proxy based on eddy heat fluxes averaged between 25° and 75° in both hemispheres. The thermodynamic energy equation with Newtonian cooling is used to relate the dynamical forcing to temperature. The deseasonalised, monthly mean time series of all four calculations are highly correlated (~ 0.85) with temperature for the period 1995–2011 when variations in radiatively active tracers are small. All four calculations provide additional support to previously noted prominent aspects of the temperature evolution 1980–2011: an anomalously strong dynamical cooling (~ −1 to −2 K) following the Pinatubo eruption that partially offsets the warming from enhanced aerosol, and a few years of enhanced dynamical cooling (~ −0.4 K) after October 2000 that contributes to the prominent drop in water entering the stratosphere at that time. The time series of dynamically forced temperature calculated with the same method are more highly correlated and have more similar trends than those from the same reanalysis but with different methods. For 1980–2011 (without volcanic periods), the eddy heat flux calculations give a dynamical cooling of ~ −0.1 to ~ −0.25 K decade−1 (magnitude sensitive to latitude belt considered and reanalysis), largely due to increasing high latitude eddy heat flux trends in September and December–January. The eddy heat flux trends also explain the seasonality of temperature trends very well, with maximum cooling in January–February. Trends derived from momentum balance calculations show near-zero annual mean dynamical cooling, with weaker seasonal trends especially in December–January. These contradictory results arising from uncertainties in data and methods are discussed and put in context to previous analyses

Is children’s education associated with parental health? Evidence from the Philippines

This study examines the association between children’s education and parental health using data from the 2007 Philippine Study on Ageing. It employs a broad, more comprehensive, definition of health to capture the different health dimensions. By employing multiple indicators of health, this study is able to examine whether the influence of children's education is consistent across different health indicators. It also investigates whether parental behavior and receipt of support from children serve as pathways that mediate the relationship between children’s education and parental health. Findings show that older women whose children completed tertiary education have lower odds of reporting IADL or ADL difficulty compared with their counterparts whose children attained below tertiary education. These findings contribute to the growing evidence that education is not only an individual resource; rather it could be a household or family resource that could benefit other family members

A systematic review of the impact of educational programs on factors that affect nurses' post-operative pain management for children

Despite extensive research in the international arena into pain and its management, there is, as yet, little research on the topic of pain in children in Saudi Arabia and in the Gulf countries generally. A systematic review was conducted to explore the impact of education programs on factors affecting paediatric nurses’ postoperative pain management practice. This was done in order to advise the creation of an educational program for nurses in Saudi Arabia. Knowledge about pain, attitudes towards pain, beliefs about children’s pain, perceptions of children’s reports of pain, self-efficacy with regard to pain management, and perceptions of barriers to optimal practice were all considered to be relevant factors. The review was restricted to randomized controlled trials and quasi-experimental designs, excluding studies focussed on chronic pain or populations other than solely children. Studies published in English between 2000 and 2016 were identified using CINAHL, MEDLINE, Ovid SP, The Cochrane Library, ProQuest, and Google Scholar databases. Of 499 published studies identified by the search, 14 met the inclusion criteria and were included in the review. There was evidence of educational programs exerting a postive impact on enhancing pediatric nurses’ knowledge of pain and modifing their attitudes towards it, but only limited evidence was available about the impact on nurses’ beliefs and perceptions of children’s reports of pain, nurses’ self-efficacy, or barriers to optimal practice. None of the studies was conducted in Saudi Arabia. Studies were needed to address additional aspects of preparedness for effective postperative pain management. Details of educational programs used as experimental intervention must be included in reports

A review and meta-analysis of mitigation measures for nitrous oxide emissions from crop residues

Crop residues are of crucial importance to maintain or even increase soil carbon stocks and fertility, and thereby to address the global challenge of climate change mitigation. However, crop residues can also potentially stimulate emissions of the greenhouse gas nitrous oxide (N$_{2}$O) from soils. A better understanding of how to mitigate N$_{2}$O emissions due to crop residue management while promoting positive effects on soil carbon is needed to reconcile the opposing effects of crop residues on the greenhouse gas balance of agroecosystems. Here, we combine a literature review and a meta-analysis to identify and assess measures for mitigating N$_{2}$O emissions due to crop residue application to agricultural fields. Our study shows that crop residue removal, shallow incorporation, incorporation of residues with C:N ratio > 30 and avoiding incorporation of residues from crops terminated at an immature physiological stage, are measures leading to significantly lower N$_{2}$O emissions. Other practices such as incorporation timing and interactions with fertilisers are less conclusive. Several of the evaluated N$_{2}$O mitigation measures implied negative side-effects on yield, soil organic carbon storage, nitrate leaching and/or ammonia volatilization. We identified additional strategies with potential to reduce crop residue N$_{2}$O emissions without strong negative side-effects, which require further research. These are: a) treatment of crop residues before field application, e.g., conversion of residues into biochar or anaerobic digestate, b) co-application with nitrification inhibitors or N-immobilizing materials such as compost with a high C:N ratio, paper waste or sawdust, and c) use of residues obtained from crop mixtures. Our study provides a scientific basis to be developed over the coming years on how to increase the sustainability of agroecosystems though adequate crop residue management