Resumen Introducción: El gateo representa la primera forma de locomoción autónoma. Se han mencionado las implicaciones de la adquisición del gateo para lograr la marcha independiente y el control motor en el niño, pero son pocos los estudios relacionados con el gateo y sus efectos en el niño de alto riesgo biológico. Por eso se intentó conocer la relación entre la adquisición del gateo y la marcha independiente en una población de niños nacidos de alto riesgo en un programa de seguimiento pediátrico. Material y métodos: Estudio observacional, retrospectivo y descriptivo de una cohorte de niños de alto riesgo que acuden al seguimiento pediátrico, en el cual se revisó el periodo de adquisición del patrón de gateo y la marcha independiente. Resultados: Se integraron cuatro grupos: gateo normal, gateo limítrofe, gateo con retraso y gateo nulo. Se estudió a 558 lactantes; los grupos se integraron con gateo normal, 238 niños; gateo limítrofe, 96 lactantes; retraso en la adquisición del gateo, 207 niños; y gateo nulo, 17 niños. Por género, las niñas gatean mejor, con peso y edad gestacional mayores y predominio en los gateadores. La escala de Bayley señala mejores puntuaciones para los gateadores. En los niños con gateo normal, la marcha independiente se adquirió en el periodo normal a diferencia del grupo con retraso en el gateo en el cual la marcha independiente apareció con retraso. Conclusiones: En este estudio se identificó una relación entre la edad de inicio del gateo con la edad de adquisición de la marcha independiente, con mejor evolución en los niños gateadores.

Abstract Background: Crawling represents the first form of autonomous human locomotion. Much has been said about the implications that an adequate acquisition of crawling has on development in order to achieve independent gait in the short term and the child’s motor control in the long term. There are few studies related to crawling and its implications in children who were high biologic risk newborns. Therefore, we wanted to know the relation between crawling acquisition and independent gait in a population of children who were high risk at birth in our Pediatric Follow up clinic. Material and Methods: An observational, retrospective, and analytical study of a cohort of children who were high risk at birth, and attended our pediatric follow-up clinic was done. The period between crawling acquisition and independent gait was reviewed. Results: 4 groups were integrated; normal crawling, borderline crawling, delayed crawling and null crawling. 558 infants were studied; the groups were integrated by: normal crawling 238 children; borderline crawling with 96 infants; delayed crawling with 207 children and null crawling with 17 children. By gender distribution, girls achieved better crawling. Weight and higher gestational age predominated in children with normal crawling. Crawlers had the best scores in the Bayley Scale. In children with normal crawling, independent gait was acquired within the normal period unlike the group with delay in crawling where independent gait was behind. Conclusions: In this study, we found a relation between the age of onset of crawling with the age of acquisition of the independent gait, with better skill in children who crawled.

Nanocompósitos de poliamida 6/argila organofílica foram preparados pelo método de intercalação por fusão. A argila foi tratada com o sal quaternário de amônio (Cetremide) visando-se à obtenção da argila organofílica (OMMT). Esta foi caracterizada por fluorescência de raio X (FRX), Espectroscopia no Infravermelho (FTIR) e Difração de Raio X (DRX). Os resultados dessas análises evidenciaram incorporação do sal entre as camadas da argila, tornando-a organofílica. Os nanocompósitos foram obtidos em extrusora de rosca dupla corrotacional, com 3% em peso de argila, e estes foram posteriormente injetados. A caracterização dos nanocompósitos por DRX mostrou uma estrutura esfoliada e/ou parcialmente esfoliada. As análises por Calorimetria Exploratória Diferencial (DSC) foram realizadas nas regiões da pele (superfície) e do núcleo (centro) dos corpos de prova e, mostraram as fases cristalinas α e γ na pele e apenas a fase α no núcleo e que o grau de cristalinidade na pele foi menor do que no núcleo.

Polyamide 6/organoclay nanocomposites were prepared using the melt intercalation technique. The clay was treated with a quaternary ammonium salt (Cetremide) to obtain the organoclay (OMMT), which was characterized with X ray fluorescence (XRF), Infrared Spectroscopy (FTIR) and X ray diffraction (XRD). The results of these analyses showed the incorporation of the salt in the clay structure, confirming the organophilization. The nanocomposites were obtained in a co-rotational twin screw extruder with 3 wt. (%) of clay, and then the pellets were injection molded. The characterization by XRD of the nanocomposites showed an exfoliated and/or partially exfoliated structure. The analysis by DSC were made in the skin and core regions of the samples, showing the α and γ-crystalline forms in the skin and only the α-form in the core region. The degree of crystallinity in the skin was lower than in the core.

Nanocompósitos de poliamida 6/argila organofílica foram preparados pelo método de intercalação por fusão. A argila foi tratada com o sal quaternário de amônio (Genamin) visando-se a obtenção da argila organofílica (OMMT). Ela foi caracterizada por fluorescência de raio X (FRX) e difração de raio X (DRX) e, os resultados dessas análises mostraram a incorporação do sal entre as camadas da argila, tornando-a organofílica. Os nanocompósitos foram obtidos em extrusora de rosca dupla contra-rotacional, com 3% em peso de argila e, foram caracterizados por difração de raio X (DRX), microscopia eletrônica de transmissão (MET), caracterização mecânica sob tração, análise térmica dinâmico-mecânica (DMTA) e temperatura de deflexão térmica (HDT). Os resultados de DRX e MET mostraram estrutura esfoliada e/ou parcialmente esfoliada. As propriedades mecânicas sob tração dos nanocompósitos foram superiores às da poliamida 6 e, a análise por DMTA e HDT mostrou que a incorporação da argila organofílica na matriz polimérica, aumentou a rigidez (módulo de armazenamento) e a HDT do sistema, confirmando o efeito reforçante da argila no polímero.

Polyamide 6/organoclay nanocomposites were prepared by the melt intercalation technique. The clay was treated with a quaternary ammonium salt (Genamin) to obtain the organoclay (OMMT), being characterized by X ray fluorescence (XRF) and X ray diffraction (XRD). The results confirmed the incorporation of the salt into the clay structure, i.e. the organophilization. The nanocomposites were obtained with a counter-rotational twin screw extruder with 3 wt.% of clay and characterized by XRD, transmission electron microscopy (TEM), tensile testing, dynamical-mechanical thermal analysis (DMTA) and heat deflection temperature (HDT). The XRD and TEM results showed exfoliated and/or partially exfoliated structures. The tensile properties were superior to those of the pure polyamide 6.The analysis with DMTA and HDT also showed that the incorporation of the organoclay into the polymer matrix increased the rigidity (storage modulus) of the system, confirming the reinforcing effect of the clay on the polymer.

O objetivo deste trabalho foi avaliar o efeito do compatibilizante PE-g-MA (5 e 10%) no comportamento reológico de nanocompósitos de poliamida6/polietileno/argila organofílica, onde a argila foi tratada com um sal quaternário de amônio (Cetremide). Em geral, observou-se que a presença do compatibilizante aumentou o torque da mistura de PA6/PE e que a presença da argila organofílica (2%) sem o compatibilizante não pareceu alterar o comportamento do torque da mistura. Por outro lado, para o nanocompósito com 10% em peso de compatibilizante e com a argila organofílica, verificou-se um aumento significativo do torque em relação às outras misturas, evidenciando maior interação da argila organofílica com as matrizes poliméricas, isto é, maior viscosidade do sistema, promovida provavelmente pela presença do compatibilizante. Os resultados de difração de raio X mostraram que os sistemas apresentaram estrutura intercalada e/ou esfoliada.

The aim of this work was to evaluate the effect of PE-g-MA (5 and 10 wt.%) compatibilizer on the rheological behavior of polyamide6/polyethylene/organoclay nanocomposites. The organoclay was treated with a quaternary ammonium salt (Cetremide). In general, it was observed that the presence of compatibilizer increased the torque of PA6/PE blend and that the presence of organoclay (2 wt.%) did not appear to affect the torque behavior of the blend without compatibilizer. On the other hand, for the nanocomposite with 10 wt.% of compatibilizer and with the organoclay, a significant increase in torque was observed in comparison with other mixtures, thus pointing to strong interaction between the caly and the polymer matrices, i.e. a larger viscosity of the system, probably due to the presence of compatibilizer. The results from X ray diffraction showed that the systems presented intercalated and/or exfoliated structure.