Feasibility of Barley Straw Fibers as Reinforcement in Fully Biobased Polyethylene Composites: Macro and Micro Mechanics of the Flexural Strength.

Awareness on deforestation, forest degradation, and its impact on biodiversity and global warming, is giving rise to the use of alternative fiber sources in replacement of wood feedstock for some applications such as composite materials and energy production. In this category, barley straw is an important agricultural crop, due to its abundance and availability. In the current investigation, the residue was submitted to thermomechanical process for fiber extraction and individualization. The high content of holocellulose combined with their relatively high aspect ratio inspires the potential use of these fibers as reinforcement in plastic composites. Therefore, fully biobased composites were fabricated using barley fibers and a biobased polyethylene (BioPE) as polymer matrix. BioPE is completely biobased and 100% recyclable. As for material performance, the flexural properties of the materials were studied. A good dispersion of the reinforcement inside the plastic was achieved contributing to the elevate increments in the flexural strength. At a 45 wt.% of reinforcement, an increment in the flexural strength of about 147% was attained. The mean contribution of the fibers to the flexural strength was assessed by means of a fiber flexural strength factor, reaching a value of 91.4. The micromechanical analysis allowed the prediction of the intrinsic flexural strength of the fibers, arriving up to around 700 MPa, and coupling factors between 0.18 and 0.19, which are in line with other natural fiber composites. Overall, the investigation brightness on the potential use of barley straw residues as reinforcement in fully biobased polymer composites.

A randomized controlled trial to evaluate the effectiveness of a brief motivational intervention to improve exclusive breastfeeding rates: Study protocol.

AIMS: To estimate the effectiveness of a brief motivational intervention (BMI) in increasing the duration of exclusive breastfeeding in the first 6 months postpartum. A complementary aim was to examine a potential mediating role of breastfeeding self-efficacy in the effectiveness of the BMI. BACKGROUND: Breastfeeding is associated with benefits for babies and mothers' health. Among the pool of techniques used to encourage healthy behaviours, BMI is highlighted based on the principles of motivational interviewing. One of the main components of these interventions is the promotion of self-efficacy, which, in fact, is a key factor for breastfeeding success. DESIGN: A multi-centre randomized controlled clinical trial of parallel groups. METHODS: Women who begin to breastfeed in the first hour after birth will be randomly assigned to the intervention group (receiving a BMI at immediate postpartum plus a telephone booster at the 1st and 3rd month postpartum) or the control group (receiving standard breastfeeding education at the same time). Outcome measures include the following: breastfeeding, breastfeeding self-efficacy, general self-efficacy, and postnatal depression. Data will be collected before the intervention and at the 1st, 3rd, and 6th month after birth. The study protocol has been approved by Badajoz Ethics Committee of Clinical Research in October 2017. DISCUSSION: This study will identify the effectiveness of BMI in improving exclusive breastfeeding rates. The findings will give useful evidence to health professionals about how to support breastfeeding. IMPACT: This study will address the low-exclusive breastfeeding rates, that in our country are far lower than World Health Organization's recommendation.

Exploration adhesion properties of Liquorilactobacillus and Lentilactobacillus isolated from two different sources of tepache kefir grains.

Due to the distinctive characteristics of probiotics, it is essential to pinpoint strains originating from diverse sources that prove efficacious in addressing a range of pathologies linked to dysfunction of the intestinal barrier. Nine strains of lactic acid bacteria were isolated from two different sources of tepache kefir grains (KAS2, KAS3, KAS4, KAS7, KAL4, KBS2, KBS3, KBL1 and KBL3), and were categorized to the genus Lacticaseibacillus, Liquorilactobacillus, and Lentilactobacillus by 16S rRNA gene. Kinetic behaviors of these strains were evaluated in MRS medium, and their probiotic potential was performed: resistance to low pH, tolerance to pepsin, pancreatin, bile salts, antibiotic resistance, hemolytic activity, and adhesion ability. KAS7 strain presented a higher growth rate (0.50 h-1) compared with KAS2 strain, who presented a lower growth rate (0.29 h-1). KBS2 strain was the only strain that survived the in vitro stomach simulation conditions (29.3%). Strain KBL1 demonstrated significantly higher viability (90.6%) in the in vitro intestine simulation conditions. Strain KAS2 demonstrated strong hydrophilic character with chloroform (85.6%) and xylol (57.6%) and a higher percentage of mucin adhesion (87.1%). However, strains KBS2 (84.8%) and KBL3 (89.5%) showed the highest autoaggregation values. In terms of adhesion to the intestinal epithelium in rats, strains KAS2, KAS3 and KAS4 showed values above 80%. The growth of the strains KAS2, KAS3, KAS4, KBS2, and KBL3 was inhibited by cefuroxime, cefotaxime, tetracycline, ampicillin, erythromycin, and cephalothin. Strains KBS2 (41.9% and 33.5%) and KBL3 (42.5% and 32.8%) had the highest co-aggregation values with S. aureus and E. coli. The results obtained in this study indicate that lactic acid bacteria isolated from tepache can be considered as candidates for potentially probiotic bacteria, laying the foundations to evaluate their probiotic functionality in vivo and thus to be used in the formulation of functional foods.

Respectful Children's Shoes: A Systematic Review.

BACKGROUND: Child footwear, both in pathologies and in normal situations, can affect the foot in various ways depending on its characteristics. Below, some features of child footwear are described, and how they can influence the foot, including suitable size, shape and design, flexibility, and transpirable material; inadequate footwear includes situations with flat foot, equine foot, and hammer toes. It is important to highlight that each child is unique and may have different footwear needs. In case of specific pathologies or concerns, it is recommended to consult a specialist in podology or foot medicine for personalized assessment and recommendations. METHODS: The present systematic review was conducted in accordance with the guidelines outlined in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. RESULTS: Children's footwear must adapt to all stages of children's growth, starting from when they begin to walk, to promote the correct evolution of their musculoskeletal system. For up to six months, they do not need to wear shoes; socks and similar clothing are enough to warm your feet like a second skin. The flexibility of respectful footwear is essential between six months and three or four years. From that age onwards, the soles can be somewhat thicker, and the buttress can have a certain firmness, but the shoes should remain flexible. CONCLUSIONS: Eco-friendly footwear, which typically comes from small businesses and factories, is sometimes described as "ergonomic footwear". However, there is some reluctance towards this term. When choosing this type of footwear for children, it is important to not just look at the label; rather, one should verify that it meets all the necessary characteristics to be considered respectful.

Simulated Environmental Conditioning of PHB Composites Reinforced with Barley Fibres to Determine the Viability of Their Use as Plastics for the Agriculture Sector.

Nowadays, the search for new materials with a sustainable character to reduce the production of residues is under continuous research. In this sense, fully biodegradable composites based on polyhydroxybutyrate and different pretreated fibres coming from barley straw have been fabricated, and their resistance to environmental controlled conditions have been characterized. The materials were already compounded in a kinetic mixer and injection-moulded as specimens for tensile assay to be aged in a Xenotest chamber so as to simulate environmental conditioning. The samples, after accelerated aging, were characterized thus: mechanical characterization (tensile assay), water uptake (immersion and contact angle), and surface observation (optical and SEM microscopy). The incorporation of the fibres helps the composite to keep its structure for a longer time. On the other hand, the presence of the fibres increases the water uptake capacity to allow water permeation in the composite, which allows final degradation, characterised by a significant drop in properties after one month of exposure to simulated environmental conditions.

Effect of Extruder Type in the Interface of PLA Layers in FDM Printers: Filament Extruder Versus Direct Pellet Extruder.

FDM (Fused Deposition Modeling) is one of the most used and industrially applied additive manufacturing processes due to its fast prototyping and manufacturing, simplicity, and low cost of the equipment. However, the mechanical properties of the printed products have a large dependence on orientation and interface strength between layers which is mainly related to the thermal union obtained. This thermal union has a large dependence on the melting and cooling down process. Additionally, the materials used must be extruded in a continuous filament before their use, which limits the materials used. However, a pellet extruder could be used directly in the printing equipment, avoiding filament extrusion. In this work, specimens of PLA (Poly(lactic acid)) with different bead orientations have been produced via filament or pellet extrusion to compare the effect of the different melting processes in the manufacturing methodology. Pellet extruded specimens showed higher infill and mechanical properties. These results were related to better adhesion between layers due to the longer melting and cooling process. The result was confirmed using DSC and XRD techniques, where a higher crystallinity was observed. A bicomponent specimen (50% pellet-50% filament) was prepared and tested, showing higher mechanical results than expected, which was, again, due to the better thermal union obtained in the pellet extruder.

Evaluation of the Interface Strength in the Abaca-Fiber-Reinforced Bio-Polyethylene Composites.

Bio-based polymers, with any of their constituents based on nonrenewable sources, can answer the demands of society and regulations regarding minimizing the environmental impact. The more similar such biocomposites are to oil-based composites, the easier the transition, especially for companies that do not like the uncertainty. A BioPE matrix, with a structure similar to that of a high-density polyethylene (HDPE), was used to obtain abaca-fiber-reinforced composites. The tensile properties of these composites are displayed and compared with commercial glass-fiber-reinforced HDPE. Since the strength of the interface between the reinforcements and the matrix is responsible for the exploitation of the strengthening abilities of the reinforcements, several micromechanical models were used to obtain an estimation of the strength of the interface and the intrinsic tensile strength of the reinforcements. Biocomposites require the use of a coupling agent to strengthen their interface, and once an 8 wt.% of such coupling agent was added to the composites, these materials returned tensile properties in line with commercial glass-fiber-reinforced HDPE composites.

Comparative Evaluation of the Stiffness of Abaca-Fiber-Reinforced Bio-Polyethylene and High Density Polyethylene Composites.

The use of bio-based matrices together with natural fibers as reinforcement is a strategy for obtaining materials with competitive mechanical properties, costs, and environmental impacts. However, bio-based matrices, unknown by the industry, can be a market entry barrier. The use of bio-polyethylene, which has properties similar to polyethylene, can overcome that barrier. In this study, composites reinforced with abaca fibers used as reinforcement for bio-polyethylene and high density polyethylene are prepared and tensile tested. A micromechanics analysis is deployed to measure the contributions of the matrices and reinforcements and to measure the evolution of these contributions regarding AF content and matrix nature. The results show that the mechanical properties of the composites with bio-polyethylene as a matrix were slightly higher than those of the composites with polyethylene as a matrix. It was also found that the contribution of the fibers to the Young's moduli of the composites was susceptible to the percentage of reinforcement and the nature of the matrices. The results show that it is possible to obtain fully bio-based composites with mechanical properties similar to those of partially bio-based polyolefin or even some forms of glass fiber-reinforced polyolefin.

Methodologies to Evaluate the Micromechanics Flexural Strength Properties of Natural-Fiber-Reinforced Composites: The Case of Abaca-Fiber-Reinforced Bio Polyethylene Composites.

There is growing emphasis on developing green composites as a substitute for oil-based materials. In the pursuit of studying and enhancing the mechanical properties of these composites, tensile tests are predominantly employed, often overlooking the flexural properties. This study focuses on researching the flexural properties of abaca-fiber-reinforced bio-based high-density polyethylene (BioPE) composites. Specifically, composites containing 30 wt% of abaca fiber (AF) were treated with a coupling agent based on polyethylene functionalized with maleic acid (MAPE). The test results indicate that incorporating 8 wt% of the coupling agent significantly improved the flexural strength of the composites. Thereafter, composites with AF content ranging from 20 to 50 wt% were produced and subjected to flexural testing. It was observed that flexural strength was positively correlated with AF content. A micromechanics analysis was conducted to evaluate the contributions of the phases. This analysis involved assessing the mechanical properties of both the reinforcement and matrix to facilitate the modeling of flexural strength. The findings of this study demonstrate the feasibility of replacing oil-based matrices, such as high-density polyethylene (HDPE), with fully bio-based composites that exhibit comparable flexural properties to their oil-based counterparts.

Effects of simulated climate change conditions of increased temperature and [CO2] on the early growth and physiology of the tropical tree crop, Theobroma cacao L.

Despite multiple studies of the impact of climate change on temperate tree species, experiments on tropical and economically important tree crops, such as cacao (Theobroma cacao L.), are still limited. Here, we investigated the combined effects of increased temperature and atmospheric carbon dioxide concentration ([CO2]) on the growth, photosynthesis and development of juvenile plants of two contrasting cacao genotypes: SCA 6 and PA 107. The factorial growth chamber experiment combined two [CO2] treatments (410 and 700 p.p.m.) and three day/night temperature regimes (control: 31/22 °C, control + 2.5 °C: 33.5/24.5 °C and control + 5.0 °C: 36/27 °C) at a constant vapour pressure deficit (VPD) of 0.9 kPa. At elevated [CO2], the final dry weight and the total and individual leaf areas increased in both genotypes, while the duration for individual leaf expansion declined in PA 107. For both genotypes, elevated [CO2] also improved light-saturated net photosynthesis (Pn) and intrinsic water-use efficiency (iWUE), whereas leaf transpiration (E) and stomatal conductance (gs) decreased. Under a constant low VPD, increasing temperatures above 31/22 °C enhanced the rates of Pn, E and gs in both genotypes, suggesting that photosynthesis responds positively to higher temperatures than previously reported for cacao. However, dry weight and the total and individual leaf areas declined with increases in temperature, which was more evident in SCA 6 than PA 107, suggesting the latter genotype was more tolerant to elevated temperature. Our results suggest that the combined effect of elevated [CO2] and temperature is likely to improve the early growth of high temperature-tolerant genotypes, while elevated [CO2] appeared to ameliorate the negative effects of increased temperatures on growth parameters of more sensitive material. The evident genotypic variation observed in this study demonstrates the scope to select and breed cacao varieties capable of adapting to future climate change scenarios.

Evaluation of the Strength of the Interface for Abaca Fiber Reinforced Hdpe and Biope Composite Materials, and Its Influence over Tensile Properties.

In this study, tensile properties of abaca-reinforced HDPE and BioPE composites have been researched. The strength of the interface between the matrix and the reinforcement of a composite material noticeably impacts its mechanical properties. Thus, the strength of the interface between the reinforcements and the matrices has been studied using micromechanics models. Natural fibers are hydrophilic and the matrices are hydrophobic, resulting in weak interfaces. In the study, a coupling agent based on polyethylene functionalised with maleic acid was used, to increase the strength of the interface. The results show that 8 wt% coupling agent contents noticeably increased the tensile strength of the composites and the interface. Tensile properties obtained for HDPE and BioPE-based coupled composites were statistically similar or better for BioPE-based materials. The use of bio-based matrices increases the possibility of decreasing the environmental impact of the materials, obtaining fully bio-based composites. The article shows the ability of fully bio-based composites to replace others using oil-based matrices.

Effective Tensile Strength Estimation of Natural Fibers through Micromechanical Models: The Case of Henequen Fiber Reinforced-PP Composites.

The performance of henequen fibers and polypropylene composites obtained by injection molding with and without coupling agent was evaluated. Henequen fibers are natural non-wood fibers mainly used in textile sector or in thermosetting matrix composites. In this work, henequen fibers have been used as a possible substitute reinforcement material for sized glass fibers. The surface charge density of the materials used was evaluated, as well as the morphology of the fibers inside the material. A significant reduction in the length of the fibers was observed as a consequence of the processing. The use of a 4% coupling agent based on fiber content was found to be effective in achieving significant improvements in the tensile strength of the composites in the reinforcement range studied. The influence of the aspect ratio on the coupling factor was determined, as well as the evaluation of the interface quality. The results obtained demonstrate the great potential of henequen fibers as reinforcement of composite materials, giving rise to strong interfaces with coupling. Finally, the comparison of henequen fiber composites with sized glass fiber composites showed that it is possible to substitute polypropylene composites with 20 wt.% glass fiber for 50 wt.% henequen fibers.

Tensile Strength of Poly(lactic acid)/Bleached Short Hemp Fiber Fully Green Composites as Replacement for Polypropylene/Glass Fiber.

The compatibility between poly(lactic acid) (PLA) and natural fibers to develop bio-sourced, recyclable, and biodegradable composites remains a commonplace issue. This work highlights that, at least in the case of hemp, pulping and bleaching towards delignified short fibers attained remarkable improvements over untreated hemp strands. This approach differs from usual proposals of chemically modifying hydroxyl groups. Soda-bleached hemp fibers (SBHFs) granted a relatively large bonding surface area and a satisfactory quality of the interphase, even in the absence of any dispersant or compatibilizer. To attain satisfactory dispersion, the matrix and the fibers were subjected to kinetic mixing and to a moderately intensified extrusion process. Then, dog-bone specimens were prepared by injection molding. Up to a fiber content of 30 wt.%, the tensile strength increased linearly with the volume fraction of the dispersed phase. It reached a maximum value of 77.8 MPa, signifying a relative enhancement of about 52%. In comparison, the tensile strength for PLA/hemp strands was 55.7 MPa. Thence, based on the modified rule of mixtures and the Kelly & Tyson modified equation, we analyzed this performance at the level of the constituent materials. The interfacial shear strength (over 28 MPa) and other micromechanical parameters were computed. Overall, this biocomposite was found to outperform a polypropylene/sized glass fiber composite (without coupling agent) in terms of tensile strength, while fulfilling the principles of green chemistry.

Nanoclay Effect into the Biodegradation and Processability of Poly(lactic acid) Nanocomposites for Food Packaging.

One of the most promising expectations in the design of new materials for food packaging is focused on the development of biodegradable systems with improved barrier character. In this sense PLA reinforced with nanoclay is a potential alternative to the use of conventional oil-derivative polymers due to the synergetic effect of the biodegradable character of PLA and the barrier-induced effect derived from the dispersion of nanoparticles. In this work, composite materials based on PLA and reinforced with bentonite nanoparticles (up to 4% w/w) (NC) have been prepared to produce films with improved barrier character against water vapor transportation. Additionally, the biodegradable character of the composites depending on the crystallinity of the polymer and percentage of NC have been evaluated in the presence of an enzymatic active medium (proteinase K). Finally, a study of the capacity to film production of the composites has been performed to determine the viability of the proposals. The dispersion of the nanoparticles induced a tortuous pathway of water vapor crossing, reducing this diffusion by more than 22%. Moreover, the nanoclays materials were in all the cases acceptable for food packing in terms of migration. A migration lower than 1 mg/m2 was obtained in all the materials. Nonetheless, the presence of the nanoclays in decreased biodegradable capacity was observed. The time was enlarged to more than 15 days for the maximum content (4% w/w). On the other hand, the incorporation of NC does not avoid the processability of the material to obtain film-shaped processed materials.

Technical and Environmental Viability of a Road Bicycle Pedal Part Made of a Fully Bio-Based Composite Material.

Glass fibre is the most widely used material for reinforcing thermoplastic matrices presently and its use continues to grow. A significant disadvantage of glass fibre, however, is its impact on the environment, in particular, due to the fact that glass fibre-reinforced composite materials are difficult to recycle. Polyamide 6 is an engineering plastic frequently used as a matrix for high-mechanical performance composites. Producing polyamide monomer requires the use of a large amount of energy and can also pose harmful environmental impacts. Consequently, glass fibre-reinforced Polyamide 6 composites cannot be considered environmentally friendly. In this work, we assessed the performance of a road cycling pedal body consisting of a composite of natural Polyamide 11 reinforced with lignocellulosic fibres from stone-ground wood, as an alternative to the conventional glass fibre-reinforced Polyamide 6 composite (the most common material used for recreational purposes). We developed a 3D model of a pedal with a geometry based on a combination of two existing commercial choices and used it to perform three finite-element tests in order to assess its strength under highly demanding static and cyclic conditions. A supplementary life cycle analysis of the pedal was also performed to determine the ecological impact. Based on the results of the simulation tests, the pedal is considered to be mechanically viable and has a significantly lower environmental impact than fully synthetic composites.

Nanocomposites Materials of PLA Reinforced with Nanoclays Using a Masterbatch Technology: A Study of the Mechanical Performance and Its Sustainability.

Packaging consumes around 40% of the total plastic production. One of the most important fields with high requirements is food packaging. Food packaging products have been commonly produced with petrol polymers, but due to environmental concerns, the market is being moved to biopolymers. Poly (lactic acid) (PLA) is the most promising biopolymer, as it is bio-based and biodegradable, and it is well established in the market. Nonetheless, its barrier properties need to be enhanced to be competitive with other polymers such as polyethylene terephthalate (PET). Nanoclays improve the barrier properties of polymeric materials if correct dispersion and exfoliation are obtained. Thus, it marks a milestone to obtain an appropriate dispersion. A predispersed methodology is proposed as a compounding process to improve the dispersion of these composites instead of common melt procedures. Afterwards, the effect of the polarity of the matrix was analyzing using polar and surface modified nanoclays with contents ranging from 2 to 8% w/w. The results showed the suitability of the predispersed and concentrated compound, technically named masterbatch, to obtain intercalated structures and the higher dispersion of polar nanoclays. Finally, the mechanical performance and sustainability of the prepared materials were simulated in a food tray, showing the best assessment of these materials and their lower fingerprint.

Experimental Behavior of Thin-Tile Masonry under Uniaxial Compression. Multi-Leaf Case Study.

In this study, experimental analysis on the compressive strength of multi-leaf thin-tile masonry is presented. A compressive strength test was carried out on thin-tile, mortar and 48 specimens with two- and three-leaf thin-tile masonry. The results obtained were compared with literature on brick masonry loaded parallel to a bed joint. Based on the results of this study, the failure mode presented the first crack in the vertical interface; this crack grew until the leaf was detached. From this point until collapse, lateral buckling of the leaves was generally observed. Therefore, the detachment compressive strength value was considered relevant. Up to this point, both masonries exhibit similar stress-strain behavior. The experimental values of the detachment compressive strength were compared with the values calculated from the equation generally used in the literature to evaluate the compressive strength of brick masonry. From the results obtained, the following conclusion can be drawn: This equation is only suitable for tree-leaf thin-tile masonry but with more relevant influence on the compressive strength of the mortar. This study concluded that only three-leaf specimens behave similarly to brick masonry loaded parallel to a bed joint. Finally, whether the failure mode was due to shear or tensile stresses in the vertical thin-tile-mortar interface cannot be identified.

Association between the Use of Backpack and Static Foot Posture in Schoolchildren with Static Pronated Foot Posture: A 36-Month Cohort Study.

Background: Schoolchildren often spend a lot of time carrying a backpack with school equipment, which can be very heavy. The impact a backpack may have on the pronated feet of schoolchildren is unknown. Aims: The objective of this study was to evaluate the association of the backpack use on static foot posture in schoolchildren with a pronated foot posture over 36 months of follow-up. Methods: This observational longitudinal prospective study was based on a cohort of consecutive healthy schoolchildren with pronated feet from fifteen different schools in Plasencia (Spain). The following parameters were collected and measured in all children included in the study: sex, age, height, weight, body mass index, metatarsal formula, foot shape, type of shoes, and type of schoolbag (non-backpack and backpack). Static foot posture was determined by the mean of the foot posture index (FPI). The FPI was assessed again after 36 months. Results: A total of 112 participants used a backpack when going to school. Over the 36-month follow-up period, 76 schoolchildren who had a static pronated foot posture evolve a neutral foot posture. Univariate analysis showed that the schoolchildren using backpacks were at a greater risk of not developing neutral foot (odds ratio [OR]: 2.09; 95% CI: 1.08-4.09). The multivariate analysis provided similar results, where the schoolchildren using a backpack (adjusted OR [aOR]: 1.94; 95% CI: 1.02-3.82) had a significantly greater risk of not developing a neutral foot posture. Conclusions: A weak relationship was found between backpack use and schoolchildren aged from five to eleven years with static pronated feet not developing a neutral foot posture over a follow-up period of 36 months.

Myasthenia gravis presenting as bilateral pseudointernuclear ophthalmoplegia in a patient with an incidental prolactinoma.

Myasthenia gravis (MG) is a rare and potentially dangerous autoimmune condition, which affects the acetylcholine receptors at the neuromuscular junction of skeletal muscle. MG's diverse symptomatology may readily masquerade as other neurological conditions, posing a diagnostic challenge to clinicians. We describe a 24-year old man who presented to the emergency department with a new onset internuclear ophthalmoplegia. After a series of investigations, we eventually arrived at a diagnosis of MG with pseudointernuclear ophthalmoplegia with an incidentally detected prolactinoma. We explore the literature regarding the pathophysiology of pseudointernuclear ophthalmoplegia, the link between prolactin and autoimmunity and the association between prolactinoma and MG.