Forças manuais e o design de produtos: uma revisão

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Correlação entre os questionários dash, qualidade de vida SF-36 e avaliação física nas afecções do punho e da mão

Pós-graduação em Bases Gerais da Cirurgia - FMB

Influência do zinco suplementar na maturação biológica e no crescimento de jovens atletas de futebol do sexo masculino

Introdução O zinco é um importante elemento traço que auxilia na capacidade antioxidante, além de participar da maturação biológica. Em atletas, a suplementação de zinco tem efeito positivo nos parâmetros hematológicos e pode melhorar o rendimento esportivo. Sua deficiência é comumente observada nesses grupo e pode estar associada à diminuição da força física assim como da massa corporal, além de ter efeito significativo no crescimento. Assim os objetivos do presente estudo foram: comparar os métodos de avaliação da maturidade biológica e suas relações com variáveis antropométricas e de rendimento físico de acordo com o estado de zinco em jovens jogadores de futebol; comparar diferentes métodos de avaliação da composição corporal em jovens jogadores de futebol esratificados de acordo com os níveis plasmáticos de zinco e investigar o efeito do zinco suplementar na maturação biológica, no crescimento, na composição corporal e na força muscular de jogadores de futebol púberes do sexo masculino. Materiais e métodos Foram avaliados em dois momentos 48 jovens do sexo masculino (13±1 anos, massa corporal de 48±10kg, estatura de 160±10cm e zinco plasmático de 12,1±2,2 μmol/L). Todos eram jogadores de futebol de um tradicional clube do Rio de Janeiro e foram divididos aleatoriamente em dois grupos. Durante 12 semanas o grupo placebo (n=28) recebeu cápsulas de amido de milho e o grupo suplementado (n=20) recebeu cápsulas de gluconato de Zn (22mg/dia). O valor de 11,0 μmol/L foi considerado como ponto de corte para classificação dos jovens em normozincêmicos ou hipozincêmicos. No início da manhã, após jejum noturno, foram coletados sangue e urina para determinação da concentração de zinco. A massa corporal, alturas (do vértex, acromial, dactiloidal, iliocristal, trocantérica e sentado), composição corporal, força e maturidade esquelética (TW3) também foram determinadas por metodologias validadas. Resultados As comparações entre as categorias maturacionais definidas por cada método de avaliação mostraram que a idade óssea foi o único método que permitiu a identificação de diferenças entre as três categorias, em ao menos duas variáeis relacionadas ao rendimento (massa livre de gordura (MLG) e força na mão dominante (FMD) – p<0,0001). O método da pilosidade axilar foi capaz de discriminar apenas para a FMD (p<0,0001). Embora tenha fornecido quatro categorias maturacionais, o método por dosagem da testosterona não possibilitou a identificação de diferenças entre as categorias relativas a MLG, a FMD e as dobras cutâneas(DC). Quando observamos os métodos de avaliação da composição corporal não foram identificadas diferenças sigificativas entre os grupos hipozincêmico e normozincêmico no percentagem de gordura(PG) nem na MLG obtidas através dos métodos da absortometria de dupla energia (DXA) (p=0,06076 e p=0,5638 respectivamente), das DC (p=0,6840 and 0,5087) e através da bioimpedância elétrica (BIA) (p=0,3475 and p=0,3475). Entre os diferentes métodos também não foi encontrada diferenças significativas (PG: p=0,1272 e p=0,3231 - MLG: p=0,9229 and p=0,8933 para os grupos hipozincêmico e normozincêmico, respectivamente). As correlações entre os métodos foram significativas (PG: r= 0,3414 a 0,9765 e p<0,0001 a 0,0133 - MLG: r=0,9533 a 0,9998 e p<0,0001). Fortes coeficientes de determinação foram obtidos nas regressões múltiplas dos valores do DXA com a equação de Slaughter na estimativa da PG (r=0,86; r2=0,928 e SEE=2,37%) e ainda maiores para MLG (r=0,98; r2=0,990 e SEE=1,18kg). Valores menores foram encontrados para as outras equações com DC e para BIA. Ao analisar os efeitos da suplementação de zinco sobre o crescimento, a maturação, a composição corporal e a força, observou-se que somente as alterações ocorridas nos indicadores de crescimento foram significativas (p=0,0312), sendo que todas as demais não foram significativas - idade óssea (p=0,1391), massa livre de gordura (p=0,0593), percentual de massa gorda (p=0,2212) e força na mão dominante (p=0,6569). Conclusões Observando diferentes métodos de avaliação da maturidade biológica e as categorias por eles definidas, o método da idade óssea (IO) mostrou ser melhor, visto que ele permitiu identificar diferenças entre as três categorias possíveis, nas variáveis MLG e FMD, ao contrário dos outros métodos. Para a avaliação da composição corporal, os métodos baseados nas DC foram melhores que BIA, quando DXA não estiver disponível. A comparação entre os métodos baseados nas DC mostrou que a melhor associação foi obtida com a equação de Slaughter, seguida pela equação de Lohman com a utilização da IO ao invés da idade cronológica. Os níveis de zinco plasmático parecem não serem influenciados pela composição corporal, o que certamente justifica mais estudos. Os resultados da análise dos efeitos da suplementação de zinco no crescimento, na maturação, na composição corporal e na força, nos levam a concluir que o crescimento teve alteração positiva significativa e que os valores das demais variáveis estudadas (maturação, composição corporal e força muscular) não sofreram alterações significativas relacionadas à suplementação de zinco nos jovens jogadores de futebol do sexo masculino, na faixa etária dos 12 aos 14 anos.

Properties of hand-made clay balls used as a novel filter media

Filtration using granular media such as quarried sand, anthracite and granular activated carbon is a well-known technique used in both water and wastewater treatment. A relatively new prefiltration method called pebble matrix filtration (PMF) technology has been proved effective in treating high turbidity water during heavy rain periods that occur in many parts of the world. Sand and pebbles are the principal filter media used in PMF laboratory and pilot field trials conducted in the UK, Papua New Guinea and Serbia. However during first full-scale trials at a water treatment plant in Sri Lanka in 2008, problems were encountered in sourcing the required uniform size and shape of pebbles due to cost, scarcity and Government regulations on pebble dredging. As an alternative to pebbles, hand-made clay pebbles (balls) were fired in a kiln and their performance evaluated for the sustainability of the PMF system. These clay balls within a filter bed are subjected to stresses due to self-weight and overburden, therefore, it is important that clay balls should be able to withstand these stresses in water saturated conditions. In this paper, experimentally determined physical properties including compression failure load (Uniaxial Compressive Strength) and tensile strength at failure (theoretical) of hand-made clay balls are described. Hand-made clay balls fired between the kiln temperatures of 875oC to 960oC gave failure loads of between 3.0 kN and 7.1 kN. In another test when clay balls were fired to 1250oC the failure load was 35.0 kN compared to natural Scottish cobbles with an average failure load of 29.5 kN. The uniaxial compressive strength of clay balls obtained by experiment has been presented in terms of the tensile yield stress of clay balls. Based on the effective stress principle in soil mechanics, a method for the estimation of maximum theoretical load on clay balls used as filter media is proposed and compared with experimental failure loads.

Molecular dynamics simulation of fracture strength and morphology of defective graphene

Different types of defects can be introduced into graphene during material synthesis, and significantly influence the properties of graphene. In this work, we investigated the effects of structural defects, edge functionalisation and reconstruction on the fracture strength and morphology of graphene by molecular dynamics simulations. The minimum energy path analysis was conducted to investigate the formation of Stone-Wales defects. We also employed out-of-plane perturbation and energy minimization principle to study the possi-ble morphology of graphene nanoribbons with edge-termination. Our numerical results show that the fracture strength of graphene is dependent on defects and environmental temperature. However, pre-existing defects may be healed, resulting in strength recovery. Edge functionalization can induce compressive stress and ripples in the edge areas of gra-phene nanoribbons. On the other hand, edge reconstruction contributed to the tensile stress and curved shape in the graphene nanoribbons.

Molecular dynamics simulation of fracture strength and morphology of defective graphene

Different types of defects can be introduced into graphene during material synthesis, and significantly influence the properties of graphene. In this work, we investigated the effects of structural defects, edge functionalisation and reconstruction on the fracture strength and morphology of graphene by molecular dynamics simulations. The minimum energy path analysis was conducted to investigate the formation of Stone-Wales defects. We also employed out-of-plane perturbation and energy minimization principle to study the possible morphology of graphene nanoribbons with edge-termination. Our numerical results show that the fracture strength of graphene is dependent on defects and environmental temperature. However, pre-existing defects may be healed, resulting in strength recovery. Edge functionalization can induce compressive stress and ripples in the edge areas of graphene nanoribbons. On the other hand, edge reconstruction contributed to the tensile stress and curved shape in the graphene nanoribbons.

Strength properties of composite clay balls containing additives from industry wastes as new filter media in water treatment

Pebble matrix filtration (PMF) is a water treatment technology that can remove suspended solids in highly turbid surface water during heavy storms. PMF typically uses sand and natural pebbles as filter media. Hand-made clay pebbles (balls) can be used as alternatives to natural pebbles in PMF treatment plants, where natural pebbles are not readily available. Since the high turbidity is a seasonal problem that occurs during heavy rains, the use of newly developed composite clay balls instead of pure clay balls have the advantage of removing other pollutants such as natural organic matter (NOM) during other times. Only the strength properties of composite clay balls are described here as the pollutant removal is beyond the scope of this paper. These new composite clay balls must be able to withstand dead and live loads under dry and saturated conditions in a filter assembly. Absence of a standard ball preparation process and expected strength properties of composite clay balls were the main reasons behind the present study. Five different raw materials from industry wastes: Red Mud (RM), Water Treatment Alum Sludge (S), Shredded Paper (SP), Saw Dust (SD), and Sugar Mulch (SM) were added to common clay brick mix (BM) in different proportions. In an effort to minimize costs, in this study clay balls were fired to 1100 0C at a local brick factory together with their bricks. A comprehensive experimental program was performed to evaluate crushing strength of composite hand-made clay balls, using uniaxial compression test to establish the best material combination on the basis of strength properties for designing sustainable filter media for water treatment plants. Performance at both construction and operating stages were considered by analyzing both strength properties under fully dry conditions and strength degradation after saturation in a water bath. The BM-75% as the main component produced optimum combination in terms of workability and strength. With the material combination of BM-75% and additives-25%, the use of Red Mud and water treatment sludge as additives produced the highest and lowest strength of composite clay balls, with a failure load of 5.4 kN and 1.4 kN respectively. However, this lower value of 1.4 kN is much higher than the effective load on each clay ball of 0.04 kN in a typical filter assembly (safety factor of 35), therefore, can still be used as a suitable filter material for enhanced pollutant removal.

Diabetic charcot neuroarthropathy of the hand: Clinical course, diagnosis, and treatment options

During the treatment of diabetic Charcot neuroarthropathy (CN) of the foot in two young patients, we discovered atypical alterations of their hands with loss of strength and paresthesia combined with atypical and nonhealing bone alterations and instability. Whereas CN of the foot is a serious and well-known complication of diabetes, CN of the hand is only mentioned in four articles (1–4).

Designing copper-zirconium based nanowires for improving yield strength and plasticity by configuring surface atoms

Epitaxial-Bain-Path and Uniaxial-Bain-Path studies reveal that a B2-CuZr nanowire with Zr atoms on the surface is energetically more stable compared to a B2-CuZr nanowire with Cu atoms on the surface. Nanowires of cross-sectional dimensions in the range of similar to 20-50 are considered. Such stability is also correlated with the initial state of stress in the nanowires. It is also demonstrated here that a more stable structure, i.e., B2-CuZr nanowire with Zr atoms at surface shows improved yield strength compared to B2-CuZr nanowire with Cu atoms at surface site, over range of temperature under both the tensile and the compressive loadings. Nearly 18% increase in the average yield strength under tensile loading and nearly 26% increase in the averaged yield strength under compressive loading are observed for nanowires with various cross-sectional dimensions and temperatures. It is also observed that the B2-CuZr nanowire with Cu atom at the surface site shows a decrease in failure/plastic strain with an increase in temperature. On the other hand, B2-CuZr nanowires with Zr at the surface site shows an improvement in failure/plastic strain, specially at higher temperature as compared to the B2-CuZr nanowires which are having Cu atoms at the surface site. Finally, a possible design methodology for an energetically stable nano-structure with improved thermo-mechanical properties via manipulating the surface atom configuration is proposed.

Strength of hot pressed ZrB2-SiC composite after exposure to high temperatures (1000-1700 degrees C)

Residual strength (room temperature strength after exposure in air at high temperatures) of hot pressed ZrB2-SiC composites was evaluated as function of SiC contents (10-30 vol%) as well as exposure temperatures for 5 h (1000-1700 degrees C). Multilayer oxide scale structures were found after exposures. The composition and thickness of these multilayered oxide scale structure was dependent on exposure temperature and SiC contents in composites. After exposure to 1000 degrees C for 5 h, the residual strength of ZrB2-SiC composites improved by nearly 60% compared to the as-hot pressed composites with 20 and 30 vol% SiC. On the other hand, the residual strength of these composites remained unchanged after 1500 degrees C for 5 h. A drastic degradation in residual strength was observed in composites with 20 and 30 vol% SiC after exposure to 1700 degrees C for 5 h in ZrB2-SiC. An attempt was made to correlate the microstructural changes and oxide scales with residual strength with respect to variation in SiC content and temperature of expsoure. (C) 2012 Elsevier Ltd. All rights reserved.

Division of Labor in Hand Usage in Free- Ranging Bonnet Macaques, Macaca radiata

Primates exhibit laterality in hand usage either in terms of (a) hand with which an individual solves a task or while solving a task that requires both hands, executes the most complex action, that is, hand preference, or (b) hand with which an individual executes actions most efficiently, that is, hand performance. Observations from previous studies indicate that laterality in hand usage might reflect specialization of the two hands for accomplishing tasks that require maneuvering dexterity or physical strength. However, no existing study has investigated handedness with regard to this possibility. In this study, we examined laterality in hand usage in urban free-ranging bonnet macaques, Macaca radiata with regard to the above possibility. While solving four distinct food extraction tasks which varied in the number of steps involved in the food extraction process and the dexterity required in executing the individual steps, the macaques consistently used one hand for extracting food (i.e., task requiring maneuvering dexterity)the maneuvering hand, and the other hand for supporting the body (i.e., task requiring physical strength)the supporting hand. Analogously, the macaques used the maneuvering hand for the spontaneous routine activities that involved maneuvering in three-dimensional space, such as grooming, and hitting an opponent during an agonistic interaction, and the supporting hand for those that required physical strength, such as pulling the body up while climbing. Moreover, while solving a task that ergonomically forced the usage of a particular hand, the macaques extracted food faster with the maneuvering hand as compared to the supporting hand, demonstrating the higher maneuvering dexterity of the maneuvering hand. As opposed to the conventional ideas of handedness in non-human primates, these observations demonstrate division of labor between the two hands marked by their consistent usage across spontaneous and experimental tasks requiring maneuvering in three-dimensional space or those requiring physical strength. Am. J. Primatol. 76:576-585, 2014. (c) 2013 Wiley Periodicals, Inc.

Stiffness and strength of tridimensional periodic lattices

This paper presents a method for the linear analysis of the stiffness and strength of open and closed cell lattices with arbitrary topology. The method hinges on a multiscale approach that separates the analysis of the lattice in two scales. At the macroscopic level, the lattice is considered as a uniform material; at the microscopic scale, on the other hand, the cell microstructure is modelled in detail by means of an in-house finite element solver. The method allows determine the macroscopic stiffness, the internal forces in the edges and walls of the lattice, as well as the global periodic buckling loads, along with their buckling modes. Four cube-based lattices and nine cell topologies derived by Archimedean polyhedra are studied. Several of them are characterized here for the first time with a particular attention on the role that the cell wall plays on the stiffness and strength properties. The method, automated in a computational routine, has been used to develop material property charts that help to gain insight into the performance of the lattices under investigation. © 2012 Elsevier B.V.

Strength and drying shrinkage of reactive MgO modified alkali-activated slag paste

Conventional alkali-activated slag (AAS) cements suffer from significant drying shrinkage which hinders their widespread application. This paper investigates the potential of using commercial reactive MgO to reduce the drying shrinkage of AAS. Two different reactive MgOs were added at a content of 2.5-7.5 wt% of the slag, which was activated by sodium hydroxide and water-glass. The strength and the drying shrinkage of those reactive MgO modified AAS (MAAS) pastes were measured up to 90 days. It is found that MgO with high reactivity accelerated the early hydration of AAS, while MgO with medium reactivity had little effect. The drying shrinkage was significantly reduced by highly reactive MgO but it also generated severe cracking under the dry condition. On the other hand, medium-reactive MgO only showed observable shrinkage-reducing effect after one month, but the cement soundness was improved. The hydration products, analysed by X-ray diffraction, thermogravimetric analysis and scanning electron microscopy techniques, showed that Mg was mainly incorporated in the hydrotalcite-like phases. It is concluded that the curing conditions and the time of hydrotalcite-like phases formation and their quantity are crucial to the developed strength and shrinkage reduction properties of MAAS, which are highly dependent on the reactivity and content of reactive MgO. Crown Copyright © 2013 Published by Elsevier Ltd. All rights reserved.