769 research outputs found
A family of triaxial modified Hubble mass models: effects of the additional radial functions
The projected properties of triaxial generalization of the modified Hubble
mass models are studied. These models are constructed by adding the additional
radial functions, each multiplied by a low-order spherical harmonic, to the
models of \citet{ct00}. The projected surface density of mass models can be
calculated analytically which allows us to derive the analytic expressions of
axial ratio and position angles of major axis of constant density elliptical
contours at asymptotic radii. The models are more general than those studied
earlier in the sense that the inclusions of additional terms in density
distribution, allows one to produce varieties of the radial profile of axial
ratio and position angle, in particular, their small scale variations at inner
radii. Strong correlations are found to exist between the observed axial ratio
evaluated at and at which occupy well-separated regions
in the parameter space for different choices of the intrinsic axial ratios.
These correlations can be exploited to predict the intrinsic shape of the mass
model, independent of the viewing angles. Using Bayesian statistics, the result
of a test case launched for an estimation of the shape of a model galaxy is
found to be satisfactory.Comment: 23 pages, 8 figures, accepted for publication in New Astronom
Optimization of water distribution networks using a deterministic approach
Water distribution networks (WDNs) are the main component of industrial and urban water distribution systems and are currently formed by pipes, nodes and loops. In this article, a deterministic mathematical programming approach is proposed, aiming to minimize the cost of looped WDNs, considering known pipe lengths and a discrete set of commercially available diameters. The optimization model constraints are mass balances in nodes, energy balances in loops and hydraulic equations, in such a way that no additional software is needed to find the appropriate pressure drops and water velocities. Generalized disjunctive programming is used to reformulate the discrete optimization problem to a mixed-integer nonlinear programming (MINLP) problem. The GAMS (General Algebraic Modeling System) environment is used to solve the problem. Four cases are studied to test the applicability of the model and the results show compatibility with the literature.This study was financially supported by the Coordination for the Improvement of Higher Education Personnel (CAPES) (Brazil) [processes 88887.217374/2018-00 and 88881.171419/2018-01] and the National Council for Scientific and Technological Development (CNPq) (Brazil) [processes 428650/2018-0 and 440047/2019-6]; and by the Conselho Nacional de Desenvolvimento Científico e Tecnológico and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Design Optimization of 3D Steel Frameworks Under Constraints of Natural Frequencies of Vibration
Steel multistorey 3D frames are commonly used in business and residential buildings, industrial sheds, warehouses, etc. The design optimization of tall steel buildings is usually governed by horizontal loadings, such as, wind load, as well as its dynamic behavior, for which the structure must have the stiffness and stability in accordance with the safety criteria established by codes. This chapter deals with sizing structural optimization problems, concerning weight minimization of 3D steel frames, considering natural frequencies of vibration as well as allowable displacements as the constraints of the optimization problem. The discrete design variables are to be chosen from commercial profiles tables. A differential evolution (DE) is the search algorithm adopted coupled to an adaptive penalty method (APM) to handle the constraints. Three different 3D frames are optimized, presenting very interesting results
Impact of methodological approaches in the agreement between subjective and objective methods for assessing screen time and sedentary behavior in pediatric population: a systematic review
Introduction: sedentary behavior is an important target for health promotion. In this systematic review, we aimed to provide evidence to support decisions about measurement approach choices for subjectively assessing sedentary behavior in pediatric population, adopting objective methods as the reference.
Methods: in this systematic review with meta-analysis, published studies were retrieved from electronic databases: Medline (PubMed), Web of Science, Embase, SPORTDiscus, BioMed Central and SCOPUS. We considered studies evaluating sedentary behavior agreement through questionnaire and/or diary in comparison with an objective measure. A total of six inclusion criteria v, rere used. We synthesized the data using correlation coefficients (r) as an indicator of agreement estimates. The review protocol is registered in the PROSPERO database (CRD42014015138).
Results: a total of 14 studies met the inclusion criteria with ages ranging from 3 to 17.5 years and provided 17 agreement analyses. Thirteen of these agreement analyses (76.5%) reported correlation coefficients. We found two major groups of sedentary activities: screen time (47.1%) and sedentary behaviors (52.9%). The pooled agreement between questionnaires and accelerometers for assessing self-reported screen time was negative (r =-0.15; Cl 95%:-0.17 to-0.13). Conversely, when the sedentary behavior was assessed by questionnaires and accelerometers, the pooled agreement, vas positive for parent-reporting (r = 0.09; Cl 95%; 0.04 to 0.13) and self-reporting (r = 0.43; CI 95%: 0.40 to 0.47) in children and adolescents, respectively.
Conclusion: questionnaires have positive agreement with accelerometers for assessing sedentary behavior, whereas the agreement is negative for assessing screen time. Self-reported questionnaires are recommended methods to measure sedentary behavior in adolescents
Prevalence of cardiovascular risk factors, the association with socioeconomic variables in adolescents from Low-Income region
Objectives: To estimate the prevalence of obesity, overweight, abdominal obesity and high blood pressure in a sample of adolescents from a low-income city in Brazil and to estimate the relationship with the socioeconomic status of the family, the education level of the family provider and the type of school.
Methods: This cross-sectional study randomly sampled 1,014 adolescents (54.8% girls), between 14-19 years of age, attending high school from Imperatriz (MA). The outcomes of this study were: obesity and overweight, abdominal obesity and high blood pressure (systolic and/ or diastolic). The independent variables were: socioeconomic status (SES) of the family, education level of the family provider (ELFP) and type of school. The confounding variables were: gender, age and physical activity level. Prevalence was estimated, and the association between the endpoints and the independent variables was analyzed using a prevalence ratio (PR), with a 95% confidence interval, estimated by Poisson regression.
Results: The overall prevalence of obesity was 3.8%, overweight, 13.1%, abdominal obesity, 22.7% and high blood pressure, 21.3%. The adjusted analysis indicated that girls with high SES showed an increased likelihood to be overweight (PR=1.71 [95% IC: 1.13-2.87]), while private school boys had an increased likelihood of obesity (PR=1.79 [95% CI: 1.04-3.08]) and abdominal obesity (PR =1.64 [95% CI: 1.06-2.54]).
Conclusion: The prevalence of CVDR is high in adolescents from this low-income region. Boys from private schools are more likely to have obesity and abdominal obesity, and girls with high SES are more likely to be overweight
Impact of Caffeine Consumption on Type 2 Diabetes-Induced Spatial Memory Impairment and Neurochemical Alterations in the Hippocampus.
Diabetes affects the morphology and plasticity of the hippocampus, and leads to learning and memory deficits. Caffeine has been proposed to prevent memory impairment upon multiple chronic disorders with neurological involvement. We tested whether long-term caffeine consumption prevents type 2 diabetes (T2D)-induced spatial memory impairment and hippocampal alterations, including synaptic degeneration, astrogliosis, and metabolic modifications. Control Wistar rats and Goto-Kakizaki (GK) rats that develop T2D were treated with caffeine (1 g/L in drinking water) for 4 months. Spatial memory was evaluated in a Y-maze. Hippocampal metabolic profile and glucose homeostasis were investigated by <sup>1</sup> H magnetic resonance spectroscopy. The density of neuronal, synaptic, and glial-specific markers was evaluated by Western blot analysis. GK rats displayed reduced Y-maze spontaneous alternation and a lower amplitude of hippocampal long-term potentiation when compared to controls, suggesting impaired hippocampal-dependent spatial memory. Diabetes did not impact the relation of hippocampal to plasma glucose concentrations, but altered the neurochemical profile of the hippocampus, such as increased in levels of the osmolites taurine (P < 0.001) and myo-inositol (P < 0.05). The diabetic hippocampus showed decreased density of the presynaptic proteins synaptophysin (P < 0.05) and SNAP25 (P < 0.05), suggesting synaptic degeneration, and increased GFAP (P < 0.001) and vimentin (P < 0.05) immunoreactivities that are indicative of astrogliosis. The effects of caffeine intake on hippocampal metabolism added to those of T2D, namely reducing myo-inositol levels (P < 0.001) and further increasing taurine levels (P < 0.05). Caffeine prevented T2D-induced alterations of GFAP, vimentin and SNAP25, and improved memory deficits. We conclude that caffeine consumption has beneficial effects counteracting alterations in the hippocampus of GK rats, leading to the improvement of T2D-associated memory impairment
Water Distribution Networks Optimization Using Disjunctive Generalized Programming
Water Distribution Networks (WDN) are systems of water distribution used in industrial processes and urban centers. The optimal WDN design can be very effective in saving energy, specifically in pumping service, to carry water to nodes of demand, at appropriated velocities and pressures. Indirectly, it can contribute in reducing liquid pollution and accidents caused by pressure overestimation in nodes. The design of WDN can be treated as an optimization problem with a Mixed Integer Nonlinear Programming (MINLP) formulation. The objective function, to be minimized is the WDN cost, given by the product of the pipe diameters and their lengths. The problem constraints are the mass balances in each node, the energy balances in the WDN loops and pressure and velocities limits. A set of commercial diameters is available, with proper costs and rugosity coefficients. The majority of paper published in this research field use external hydraulic simulators and meta-heuristic methods to solve the optimization problem. In the current paper a mathematical model using a deterministic Mathematical Programming approach is proposed and all variables are simultaneously optimized, avoiding the use of external software for pressure and velocities calculations. Two case studies were used to test the model applicability and coded in GAMS, using the global optimization solver BARON. Results showed that for both cases global optima was achieved, proving that it is possible to solve the problem, independently of external hydraulic simulator.The authors gratefully acknowledge the financial support from the National Council for Scientific and Technological Development - CNPq (Brazil), the Coordination for the Improvement of Higher Education Personnel - Process 88881.171419/2018-01- CAPES (Brazil) and the Spanish Ministerio de Economía, Industria y Competitividad CTQ2016-77968-C3-02-P (FEDER, UE)
Reliability and validity of body weight and body image perception in children and adolescents from the South American Youth/Child Cardiovascular and Environmental (SAYCARE) Study
Objective: To assess the reliability and validity of body weight (BW) and body image (BI) perception reported by parents (in children) and by adolescents in a South American population.
Design: Cross-sectional study. BW perception was evaluated by the question, "Do you think you/your child are/is: severely wasted, wasted, normal weight, overweight, obese?" BI perception was evaluated using the Gardner scale. To evaluate reliability, BW and BI perceptions were reported twice, two weeks apart. To evaluate validity, the BW and BI perceptions were compared with WHO BMI Z-scores. Kappa and Kendall's tau-c coefficients were obtained.
Setting: Public and private schools and high schools from six countries of South America (Argentina, Peru, Colombia, Uruguay, Chile, Brazil).
Participants: Children aged 3-10 years (n 635) and adolescents aged 11-17 years (n 400).
Results: Reliability of BW perception was fair in children's parents (k=0·337) and substantial in adolescents (k=0·709). Validity of BW perception was slight in children's parents (k=0·176) and fair in adolescents (k=0·268). When evaluating BI, most children were perceived by parents as having lower weight. Reliability of BI perception was slight in children's parents (k=0·124) and moderate in adolescents (k=0·599). Validity of BI perception was poor in children's parents (k=-0·018) and slight in adolescents (k=0·023).
Conclusions: Reliability of BW and BI perceptions was higher in adolescents than in children's parents. Validity of BW perception was good among the parents of the children and adolescents with underweight and normal weight
Vibrational properties of SrVO2 H with large spin-phonon coupling
The antiferromagnetic transition metal oxyhydride SrVO2H is distinguished by its stoichiometric composition and an ordered arrangement of H atoms. The tetragonal structure is related to the cubic perovskite and consists of alternating layers of VO2 and SrH. d2 V(III) attains a sixfold coordination by four O and two H atoms. The latter are arranged in a trans fashion, which produces H-V-H chains along the tetragonal axis. Here, we investigate the vibrational properties of SrVO2H by inelastic neutron scattering and infrared spectroscopy combined with phonon calculations based on density functional theory. The H-based vibrational modes divide into a degenerate bending motion perpendicular to the H-V-H chain direction and a highly dispersed stretching motion along the H-V-H chain direction. The bending motion, with a vibrational frequency of approximately 800 cm-1, is split into two components separated by about 50 cm-1, owing to the doubled unit cell from the antiferromagnetic structure. Interestingly, spin-phonon coupling stiffens the H-based modes by 50-100cm-1 although super-exchange coupling via H is very small. Frequency shifts of the same order of magnitude also occur for V-O modes. It is inferred that SrVO2H displays the hitherto largest recognized coupling between magnetism and phonons in a material
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