1,371 research outputs found
A near-IR line of Mn I as a diagnostic tool of the average magnetic energy in the solar photosphere
We report on spectropolarimetric observations of a near-IR line of Mn I
located at 15262.702 A whose intensity and polarization profiles are very
sensitive to the presence of hyperfine structure. A theoretical investigation
of the magnetic sensitivity of this line to the magnetic field uncovers several
interesting properties. The most important one is that the presence of strong
Paschen-Back perturbations due to the hyperfine structure produces an intensity
line profile whose shape changes according to the absolute value of the
magnetic field strength. A line ratio technique is developed from the intrinsic
variations of the line profile. This line ratio technique is applied to
spectropolarimetric observations of the quiet solar photosphere in order to
explore the probability distribution function of the magnetic field strength.
Particular attention is given to the quietest area of the observed field of
view, which was encircled by an enhanced network region. A detailed theoretical
investigation shows that the inferred distribution yields information on the
average magnetic field strength and the spatial scale at which the magnetic
field is organized. A first estimation gives ~250 G for the mean field strength
and a tentative value of ~0.45" for the spatial scale at which the observed
magnetic field is horizontally organized.Comment: 42 pages, 17 figures, accepted for publication in the Astrophysical
Journal. Figures 1 and 9 are in JPG forma
Inexact restoration method for derivative-free optimization with smooth constraints
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)A new method is introduced for solving constrained optimization problems in which the derivatives of the constraints are available but the derivatives of the objective function are not. The method is based on the inexact restoration framework, by means of which each iteration is divided in two phases. In the first phase one considers only the constraints, in order to improve feasibility. In the second phase one minimizes a suitable objective function subject to a linear approximation of the constraints. The second phase must be solved using derivative-free methods. An algorithm introduced recently by Kolda, Lewis, and Torczon for linearly constrained derivative-free optimization is employed for this purpose. Under usual assumptions, convergence to stationary points is proved. A computer implementation is described and numerical experiments are presented.A new method is introduced for solving constrained optimization problems in which the derivatives of the constraints are available but the derivatives of the objective function are not. The method is based on the inexact restoration framework, by means of23211891213CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPERJ - FUNDAÇÃO CARLOS CHAGAS FILHO DE AMPARO À PESQUISA DO ESTADO DO RIO DE JANEIROFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)CNPq [E-26/171.164/2003-APQ1]FAPESP [FAPESP 2011-51305-0]FAPESP [03/09169-6, 06/53768-0, 07/06663-0, 08/00468-4]E-26/171.164/2003–APQ12011-51305-0; 03/09169-6; 06/53768-0; 07/06663-0; 08/00468-4sem informaçãoWe are indebted to associate editor Prof. Margaret Wright and two anonymous referees for many useful comments and remarks that led to significant improvement of this pape
Assessment of the corneal collagen organization after chemical burn using second harmonic generation microscopy
The organization of the corneal stoma is modified due to different factors, including pathology, surgery or external damage. Here the changes in the organization of the corneal collagen fibers during natural healing after chemical burn are investigated using second harmonic generation (SHG) imaging. Moreover, the structure tensor (ST) was used as an objective tool for morphological analyses at different time points after burn (up to 6 months). Unlike control corneas that showed a regular distribution, the collagen pattern at 1 month of burn presented a non-organized arrangement. SHG signal levels noticeably decreased and individual fibers were hardly visible. Over time, the healing process led to a progressive re-organization of the fibers that could be quantified through the ST. At 6 months, the stroma distribution reached values similar to those of control eyes and a dominant direction of the fibers re-appeared. The present results show that SHG microscopy imaging combined with the ST method is able to objectively monitor the temporal regeneration of the corneal organization after chemical burn. Future implementations of this approach into clinically adapted devices would help to diagnose and quantify corneal changes, not only due to chemical damages, but also as a result of disease or surgical procedures
The Effect of Physical Activity Interventions on Glycosylated Haemoglobin (HbA1c) in Non-diabetic Populations: A Systematic Review and Meta-analysis
Introduction Epidemiological evidence suggests that physical activity has a positive effect on reducing glycated haemoglobin A1c (HbA1c) levels not only in diabetics, but also in healthy subjects. Moreover, a positive association of HbA1c levels with cardiovascular disease and mortality in non-diabetic populations has recently been reported. This is a protocol for a systematic review and meta-analysis aiming to estimate the effects of physical activity on glycaemic control measured by HbA1c levels in non-diabetic populations; and to determine which type of physical activity has a greater influence on glycaemic control.
Methods and analysis The search will be conducted using MEDLINE, EMBASE, the Cochrane Library and Web of Science databases from inception to mid-2017. Randomised controlled trials, non-randomised experimental studies and controlled pre–post studies written in English, Portuguese, French or Spanish will be included. The Cochrane Collaboration’s tool and The Quality Assessment Tool for Quantitative Studies will be used to assess the risk of bias for studies included in the systematic review. Standardised pre–post intervention mean differences of HbA1c will be calculated as the primary outcome. Subgroup analyses will be performed based on the characteristics of physical activity intervention and population included in the studies.
Ethics and dissemination This systematic review will synthesise evidence on the association of physical activity and HbA1c in non-diabetic populations. This study is important from the clinical and public health point because it will estimate the effect of physical activity on the glycemic control, and it will also examine which is the type of physical activity that should be recommended for preventing type 2 diabetes and its complications. The results will be disseminated by publication in a peer-reviewed journal. Ethical approval will not be required because the data used for this systematic review will be obtained from published studies and there will be no concerns about privacy
The effects of physical activity interventions on glycated haemoglobin A1c in non-diabetic populations: a protocol for a systematic review and meta-analysis
Introduction Epidemiological evidence suggests that physical activity has a positive effect on reducing glycated haemoglobin A1c (HbA1c) levels not only in diabetics, but also in healthy subjects. Moreover, a positive association of HbA1c levels with cardiovascular disease and mortality in non-diabetic populations has recently been reported. This is a protocol for a systematic review and meta-analysis aiming to estimate the effects of physical activity on glycaemic control measured by HbA1c levels in non-diabetic populations; and to determine which type of physical activity has a greater influence on glycaemic control.
Methods and analysis The search will be conducted using MEDLINE, EMBASE, the Cochrane Library and Web of Science databases from inception to mid-2017. Randomised controlled trials, non-randomised experimental studies and controlled pre–post studies written in English, Portuguese, French or Spanish will be included. The Cochrane Collaboration’s tool and The Quality Assessment Tool for Quantitative Studies will be used to assess the risk of bias for studies included in the systematic review. Standardised pre–post intervention mean differences of HbA1c will be calculated as the primary outcome. Subgroup analyses will be performed based on the characteristics of physical activity intervention and population included in the studies.This research received no specific grant from any funding agency in the public, commercial or not for profit sectors. IC-R is supported by a grant from the Universidad de Castilla-La Mancha (FPU13/01582). BP is supported by a grant from the Portuguese Foundation for Science and Technology (SFRH/BPD/108751/2015). CA-B and MG-M are supported by a grant from the Spanish Ministry of Ministry of Education, Culture and Sport (FPU13/03137 and FPU15/03847, respectively)
Prevalence and trends of thinness, overweight and obesity among children and adolescents aged 3-18 years across Europe: a protocol for a systematic review and meta-analysis
Introduction Increasing prevalence of both thinness and excess weight during childhood and adolescence is a significant public health issue because of short-term health consequences and long-term tracking of weight status. Monitoring weight status in Europe may serve to identify countries and regions where rates of these disorders are either slowing down or increasing to evaluate recent policies aimed at appropriate body weight, and to direct future interventions. This study protocol provides a standardised and transparent methodology to improve estimating trends of thinness, overweight and obesity in children aged 3-18 years and adolescents across the European region between 2000 and 2017. Methods and analysis This protocol is guided by the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P) and the Cochrane Collaboration Handbook. To identify relevant studies, a search will be conducted in MEDLINE, EMBASE, Cochrane Library, CINAHL and Web of Science databases. From the selected studies, relevant references will be screened as supplemental sources. Finally, open search in websites from health institutions will be conducted to identify weight status data not published in scientific journals. Cross-sectional, follow-up studies and panel surveys reporting weight status (objectively measured height and weight) according to the International Obesity Task Force criteria, and written in English or Spanish will be included. Subgroup analyses will be carried out by gender, age, study year and country or European region. Discussion This study will provide a comprehensive description of weight status of children and adolescents across Europe from 2000 to 2017. The results will be disseminated in a peer-reviewed journal. This study will use data exclusively from published research or institutional literature, so institutional ethical approval is not required
Evolution of the threshold temperature definition of a heat wave vs. evolution of the minimum mortality temperature: a case study in Spain during the 1983–2018 period
An area of current study concerns analysis of the possible adaptation of the population to heat, based on the temporal evolution of the minimum mortality temperature (MMT). It is important to know how is the evolution of the threshold temperatures (Tthreshold) due to these temperatures provide the basis for the activation of public health prevention plans against high temperatures. The objective of this study was to analyze the temporal evolution of threshold temperatures (Tthreshold) produced in different Spanish regions during the 1983–2018 period and to compare this evolution with the evolution of MMT. The dependent variable used was the raw rate of daily mortality due to natural causes ICD X: (A00-R99) for the considered period. The independent variable was maximum daily temperature (Tmax) during the summer months registered in the reference observatory of each region. Threshold values were determined using dispersion diagrams (annual) of the prewhitened series of mortality temperatures and Tmax. Later, linear fit models were carried out between the different values of Tthreshold throughout the study period, which permitted detecting the annual rate of change in Tthreshold.This research project was funded by the Carlos III Health Institute (ISCIII) under file number ENPY 470/19 and is supported by the Biodiversity Foundation of the Ministry for Ecological Transition and Demographic Challenge, in addition to the research projects ISCIII: ENPY107/18 and ENPY 376/1
Characterization and Enhancement of Non-Invasive Recordings of Intestinal Myoelectrical Activity
Non
Evaluation of antimicrobial activity against Enterococcus faecalis of activated chelating agents in different final rinse protocols : an ex vivo study
To evaluate the antimicrobial activity of the following chelating agents against Enterococcus faecalis using quantitative polymerase chain reaction (qPCR) analysis: 1% peracetic acid (PA), 1% peracetic acid with 0.1% cetrimide (PAC), and 17% ethylenediam
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