6 resultados para Nano-dimensions

em Repositório Científico do Instituto Politécnico de Lisboa - Portugal


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Childhood excessive weight and obesity are a major public health concern from early childhood. Early childhood is an important period of development for developing healthy eating habits, that may be associated with an adequate present/future BMI. There is extensive evidence that children’s food intake is shaped by early experiences, suggesting ways in which parenting practices may be promoting obesity. But what leads parents to endorse healthier or detrimental educational practices and routines needs further study. 1. Perception of children’s weight: parents of overweight or obese children often fail to correctly perceive their children as overweight; failing to recognize their children’s excessive weight may impeach parents from implementing the best educational practices. 2. Concern: relation between the adequacy of mothers perception of their children’s weight and the level of concern - parental concern is be associated with parental practices. 3. Attribution of control: also, if parents do not consider their children’s eating behavior at least partially controllable by them, they may relinquish some of their responsibility in this area. Self-efficacy: evidence linking parental self-efficacy to parent competence and to parenting practices and behaviors; low parental self-efficacy related to the control of everyday behavior of young children may lead parents to abandon more consistent health practices and endorse permissive and inconsistent strategies. We designed 2 sequential studies that aim to contribute to the understanding of cognitive determinants of children’s eating patterns.

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Obesidade é uma preocupação de saúde pública. Objetivos OMS - Redução a zero da taxa de crescimento da obesidade e uma redução em 10% na prevalência de atividade física insuficiente. Em Portugal, os estudos de prevalência apontam para valores entre 24% e os 34% de crianças e jovens pré-obesos e obesos. Extensa confirmação da obesidade infantil como preditor da obesidade na idade adulta. Em alguns países há indicadores de que a taxa de obesidade infantil começa a ter uma ligeira diminuição, provavelmente fruto de intervenções no macrosistema. Necessidade de intervenção direta nos microssistemas familiar e escolar da criança para uma intervenção mais abrangente e eficaz. Existe um ampla confirmação da influência parental nos comportamentos alimentares da criança. Os comportamentais parentais relacionados com a alimentação da criança são influenciados por variáveis cognitivas parentais. A maioria dos pais de crianças com excesso de peso subavalia o peso do seu filho, mas não de outras crianças. Os pais das crianças pré-escolares distorcem mais o peso do que os pais de crianças mais velhas. Os pais com uma perceção correta utilizam mais estratégias de restrição alimentar.

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Micro- and nano-patterned materials are of great importance for the design of new nanoscale electronic, optical and mechanical devices, ranging from sensors to displays. A prospective system that can support a designed functionality is elastomeric polyurethane thin films with nano- or micromodulated surface structures ("wrinkles"). These wrinkles can be induced on different lengthscales by mechanically stretching the films, without the need for any sophisticated lithographic techniques. In the present article we focus on the experimental control of the wrinkling process. A simple model for wrinkle formation is also discussed, and some preliminary results reported. Hierarchical assembly of these tunable structures paves the way for the development of a new class of materials with a wide range of applications, from electronics to biomedicine.

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We show that suspended nano and microfibres electrospun from liquid crystalline cellulosic solutions will curl into spirals if they are supported at just one end, or, if they are supported at both ends, will twist into a helix of one handedness over half of its length and of the opposite handedness over the other half, the two halves being connected by a short straight section. This latter phenomenon, known as perversion, is a consequence of the intrinsic curvature of the fibres and of a topological conservation law. Furthermore, agreement between theory and experiment can only be achieved if account is taken of the intrinsic torsion of the fibres. Precisely the same behaviour is known to be exhibited by the tendrils of climbing plants such as Passiflora edulis, albeit on a lengthscale of millimetres, i.e., three to four orders of magnitude larger than in our fibres. This suggests that the same basic, coarse-grained physical model is applicable across a range of lengthscales.

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This paper presents the design methodology for the creation of corrugated horn antennas for the CosmoGal satellite. The mission will collect the radiation of the cosmic microwave background, by a radiometer in three different radio astronomy frequency bands (10.6-10.7GHz; 15.35-15.4GHz; 23.6-24GHz). It is discussed the design of several types of horns, simulated with the CST software. The best result points to a choked Gaussian corrugated horn antenna, with directivity of 23 dBi, side lobes 35 dB below and cross polarization better than -45 dB. Plus, with the advantage of having a small dimension, with a total length of only 7.43λ © 2014 IEEE.

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Resumo: Cement, as well as the remaining constituents of self-compacting mortars, must be carefully selected, in order to obtain an adequate composition with a granular mix as compact as possible and a good performance in the fresh state (self-compacting effect) and the hardened state (mechanical and durability-related behavior). Therefore in this work the possibility of incorporating nano particles in self-compacting mortars was studied. Nano materials are very reactive due mostly to their high specific surface and show a great potential to improve the properties of these mortars, both in mechanical and durability terms. In this work two nano materials were used, nano silica (nano SiO2) in colloidal state and nano titanium (nano TiO2) in amorphous state, in two types of self-compacting mortars (ratio binder:sand of 1:1 and 1:2). The self-compacting mortar mixes have the same water/cement ratio and 30% of replacement of cement with fly ashes. The influence of nano materials nano-SiO2 and nano-TiO2 on the fresh and hardened state properties of these self-compacting mortars was studied. The results show that the use of nano materials in repair and rehabilitation mortars has significant potential but still needs to be optimized. (C) 2015 Elsevier Ltd. All rights reserved.