Mechanics and force transmission in soft composites of rods in elastic gels

We report detailed theoretical investigations of the micro-mechanics and bulk elastic properties of composites consisting of randomly distributed stiff fibers embedded in an elastic matrix in two and three dimensions. Recent experiments published in Physical Review Letters [102, 188303 (2009)] have suggested that the inclusion of stiff microtubules in a softer, nearly incompressible biopolymer matrix can lead to emergent compressibility. This can be understood in terms of the enhancement of the compressibility of the composite relative to its shear compliance as a result of the addition of stiff rod-like inclusions. We show that the Poisson's ratio $\nu$ of such a composite evolves with increasing rod density towards a particular value, or {\em fixed point}, independent of the material properties of the matrix, so long as it has a finite initial compressibility. This fixed point is $\nu=1/4$ in three dimensions and $\nu=1/3$ in two dimensions. Our results suggest an important role for stiff filaments such as microtubules and stress fibers in cell mechanics. At the same time, our work has a wider elasticity context, with potential applications to composite elastic media with a wide separation of scales in stiffness of its constituents such as carbon nanotube-polymer composites, which have been shown to have highly tunable mechanics.Comment: 10 pages, 8 figure

Recovery of burned forest soil by organic residue application - substrate induced respiration in soil

RAMIRAN International ConferenceThe Mediterranean is one of the most vulnerable regions to climatic changes. One of the impacts of these changes is a substantial increase in the meteorological risk of fire. The forest fire regime instantaneously responds to climatic changes and may become the dominant factor of alteration in forest communities (Santos & Miranda, 2006). Therefore, understanding the impact of fire on natural ecosystems may be important in the recovery of post-fire ecosystems, hence allowing a better forest restoration. A fire impacted soil can recover, namely through soil organic matter (OM) correction by the application of organic residues. Applying agricultural (e.g. pig slurry) and municipal solid wastes as organic matter sources to soil may represent a good way to recycle these wastes. Fire leads to important changes in the physical, chemical and biological properties of soils, which are relevant for the future productivity and sustainability of ecosystems (Neary et al., 2005). The extent and duration of these effects on soil properties depend on the intensity and residence time, ergo fire severity (Certini, 2005). Soil microorganisms perform an important and essential role in soil biological processes. Biological properties however, are extremely sensitive to soil warming, where lethal temperature thresholds for most organisms are below 100 oC. Biological diversity represents a sensitive means to determine soil quality. This is related to functional diversity, which comprises the ability of organisms to use a vast range of carbon substrates and be able to perform several biochemical reactions. Soil health and quality can be assessed by microbial community level physiological profiles (CLPP), using different carbon substrates. MicroRespTM can be applied to a vast range of soils and has good sensibility to detect changes in microbial communities, offering a rapid and sensitive method to determine CLPP (Chapman et al., 2007). Soil (Litosol) was collected in Sintra Mountain (Portugal), on a Pinus Pinaster forest, 11 days after a forest fire. The impact on recovery of burned soil by organic residue application and its influence on soil microorganisms was studied using the MicroRespTM method, concerning fire effects on soil microorganisms and the need to recycle wastes

Shifts in the structure of a mine contaminated soil (Pb, Cu, As) following different organic and inorganic treatments

RAMIRAN International ConferenceSoil microbial community structure is increasingly being marketed as ecologically-relevant endpoint and it can realistically be incorporated for assessing the potential risks associated with anthropogenic disturbances and soil amendment strategies on sustainability of soil ecosystems. In Portugal, additional research is needed if technologies based on the combined action of plants and the microbial communities they support within the rhizosphere are to be adopted in large-scale remediation actions (Nabais et al., 2008). The information about this fact in mine soils is scarce and had focused on soil biochemical properties, producing no clear results. Furthermore, the effects of phytoremediation as soil remediation technique and metal contamination on microbial community structural would be achieved by PLFA studies. By phospholipid fatty acid analysis it is possible to examine broad scale patterns in microbial community structure (Bååth et al. 2005) and generally, after the application of multivariate statistical analyses, whole community fatty acids profiles indicate which communities are similar or different. Determination both microbial community composition and biomass size by this direct method gives results that very closely represent the in situ soil conditions and is currently used for soil monitoring purposes (Nielsen and Winding, 2002). The present investigation studies the medium-term response in the soil microbial community structure after the application of different remediation technologies including several organic and inorganic treatments

The immediate effects of Therasuit® on the gait pattern of a child with unilateral spastic cerebral palsy

Aims: This study analyzes the immediate effects of using TheraSuit® (TS) on the gait of a child with left spastic hemiplegia level II (GMFCS). Methods: Spatiotemporal gait parameters and kinematic variables in the sagittal plane were compared between baseline and TS conditions. Results: Positive effects were noted on temporal parameters in the TS condition, such as a reduced gait cadence. The analysis of angular displacements in joint angles showed that at initial contact there was a reduction in the: (i) Plantarflexion on the paretic side; (ii) Dorsiflexion on the non-paretic side; and (iii) Knee flexion angles in both limbs. Furthermore, an increase in hip and knee extension angles during stance, and a decrease in knee and hip flexion on the non-paretic limb during swing were also detected. Conclusions: Further investigations with larger samples are necessary to confirm these effects of wearing TS on gait kinematics, aiming toward providing a more functional and safer gait pattern in children with spastic hemiplegia.info:eu-repo/semantics/publishedVersio

Learning to cycle: from training wheels to balance bike

Background: Learning to cycle is an important milestone in a child’s life, so it is important to allow them to explore cycling as soon as possible. The use of a bicycle with training wheels (BTW) for learning to cycling is an old approach practiced worldwide. Most recently, a new approach using the balance bike (BB) has received increased attention, and several entities believe that this could be most efficient. Drawing on the work of Bronfenbrenner (1995) and Newel (1986), this study aimed to analyse the effect of BB’s use on the learning process of cycling independently. Methods: Data were collected in Portugal from an online structured survey between November 2019 and June 2020. Results: A total of 2005 responses were obtained for adults and children (parental response). Results revealed that when the BB’s approach was used, learning age (LA) occurred earlier (M = 4.16 ± 1.34 years) than with the BTW’s approach (M = 5.97 ± 2.16 years) (p < 0.001); or than when there was only the single use of the traditional bicycle (M =7.27 ± 3.74 years) (p < 0.001). Conclusions: Children who used the BB as the first bike had a significantly lower LA than children who did not use it (p < 0.001). To maximize its effects, the BB should be used in the beginning of the learning process.info:eu-repo/semantics/publishedVersio

Correlates of children's physical activity during the COVID-19 confinement in Portugal

Objectives: The aim of the study was to understand the role of household variables on the percentage of physical activity (%PA) during the coronavirus disease 2019 (COVID-19) confinement in Portugal. Study design: A cross-sectional study design using an anonymous online survey was launched to assess how Portuguese families with children aged younger than 13 years adjusted their daily routines to the confinement. Methods: Separate analyses of variance were performed to investigate how factors such as the number of children, age, sex, the housing characteristics, and the adults' job situation can affect the percentage of time for PA (%PA). Results: Findings, based on data from 2159 children, indicate that (1) boys and girls did not differ in the %PA on any of the age-groups; (2) children with an outdoor space and who had other children in the household were significantly more active (P < .001); (3) children from families with all adults working from home showed lower levels of %PA; and (4) being younger, having a big outdoor space, having other children in the household, and having at least one adult free from working from home were significant positive predictors of children's %PA, explaining 21% of the overall variance. Conclusion: Time allocated for PA during this period is reduced compared with what is usually reported on normal days. It is necessary to find strategies to increase children's PA, especially in families in which both parents are working and have no outdoor space.4811-99FE-2ECD | Luis Paulo RodriguesN/

The immediate effects of a dynamic orthosis on gait patterns in children with unilateral spastic cerebral palsy: a kinematic analysis

This study analyzes the immediate effects of wearing a Therasuit on sagittal plane lower limb angular displacements during gait in children with unilateral spastic cerebral palsy (US-CP). Seven participants (median age = 7.00 years; ranging from 5.83 to 9.00 years) with US-CP, levels I and II of the Gross Motor Function Classification System, were assessed with kinematic gait analysis in three different conditions: (A) Baseline; (B) Therasuit without elastics and (C) Therasuit with elastics. Significant improvements were observed at the hip joint of both lower limbs during most of the gait cycle in participants wearing a Therasuit, including a decrease in the flexion pattern at the initial contact and swing phase in both lower limbs, and an increase in the extension pattern in the paretic lower limb during the stance phase. At the knee joint in the paretic lower limb, significant differences were found between the baseline and Therasuit with elastics conditions on the knee angle at initial contact, and between baseline and both Therasuit conditions on the flexion angle at swing phase. However, the inter-individual variability in kinematic patterns at the knee joint was high. At the ankle joint, decreased plantar flexion at initial contact and increased dorsiflexion during stance and swing phases were observed at the Therasuit with elastics condition, helping to correct the equinus-foot in the paretic lower limb during the whole gait cycle. The Z-values showed large effect sizes particularly for most of the angular hip variables in both lower limbs and for the angular ankle variables in the paretic lower limb. The Therasuit seems to have some positive immediate effects on gait kinematics in children with spastic unilateral cerebral palsy by providing a more functional and safer gait pattern. Future investigations with larger samples are recommended to further support these findings.info:eu-repo/semantics/publishedVersio

Siblings’ influence on the motor competence of preschoolers

The number of single-child families has been rising steadily in recent years, resulting in a childhood absent of sibling relationships. Being an only child has been shown to have a negative impact on physical fitness, somatic fitness, and motor development. In this study, we aimed to understand how living with and without siblings can impact the motor competence of children. One hundred and sixty-one children (87 boys, 74 girls) from 3.0 to 6.0 years of age (34 only children, 125 siblings) and with no known motor or cognitive disability were assessed using the Motor Competence Assessment (MCA). Their standardized results on the three MCA subscales (stability, locomotor, and manipulative) and total MCA were used to group them into high, average, and low motor competence groups. Motor competence percentile distribution of the sibling and only child group condition was compared using chi-square tests. Results showed a significative and positive association between the sibling condition and the distribution between the three MC groups (chi-square = 6.29; p = 0.043), showing that children in a household with siblings, independent of their age and sex, show a clear tendency for developing better motor competence.L.P.R. and V.P.L. were partly supported by the Portuguese Science Foundation (FCT), under Grant UID04045/2020. R.C. was partly supported by the Portuguese Science Foundation (FCT), under Grant UIDB/00447/2020 (unit 447). The research project was funded by the European Regional Development Fund (ERDF) through the Regional Operational Program North 2020, within the scope of Project TECH-Technology, Environment, Creativity and Health, Norte-01-0145-FEDER-000043.info:eu-repo/semantics/publishedVersio