Low Fiber Content Research Articles

Study of the chemical composition of Urochloa brizantha using the SPAD index, neural networks, multiple linear models, principal components and cluster analysis

The objectives of this study were to explore the relationship between plant variables using correlation and principal component analysis; to explore the chemical composition patterns in a subgroup of plants using cluster analysis; and to compare the prediction ability between a linear model using only the SPAD index as a predictor with multiple linear regression and neural networks with the SPAD index, morphological and climatic measurements as predictors of the chemical composition of Urochloa brizantha leaves and stems. The experimental design was in blocks (three blocks) with five treatments, totaling 15 experimental units. Chlorophyll measurements and forage sampling were performed every 28 d. The variables used in the statistical analysis were: percentage of leaves, stems and dead plant material; plant height; relative chlorophyll (SPAD); percentage of acid detergent fibre in leaves and stems (ADF.L, ADF.S); percentage of neutral detergent fibre in leaves and stems (NDF.L, NDF.S); lignin percentage in leaves and stems (LIG.L, LIG.S); and nitrogen content in leaves and stems (N.L, N.S). The climatic variables were monthly average minimum and maximum temperatures and monthly rainfall. The correlation between SPAD with N.L and N.S was 0.56 and 0.49, respectively, and between N.L with N.S was 0.87. The correlation between the observed and predicted responses using simple linear regression, with SPAD as the predictor, ranged from 0.198 for ADF.L to 0.577 for N.L. However, the correlations ranged from 0.497 for LIG.L to 0.759 for N.S when multiple regression was used with other predictors, besides SPAD. The prediction accuracy using neural networks ranged from 0.501 for LIG.L to 0.863 for N.S and was higher than multiple regression for all characteristics except LIG.L and LIG.S. Principal component analysis efficiently condensed the most important information of the 13 original variables measured in the plants into three principal components due to the redundancy of information of the variables. According to the cluster analysis, plants with higher nitrogen content in their leaves and stems presented lower fibre contents and dead plant material, and were denser than those with lower nitrogen content. Multiple linear regression can be used to predict lignin content in leaves and stems and neural networks must be used to predict nitrogen and the other fibre contents. SPAD is an important predictor of nitrogen content in tropical pastures, but it is not the only predictor that must be used in regression models and neural networks; morphological characteristics and climatic conditions increase the prediction accuracy of the models.

Valorisation Approach for the Soybean By-Product Okara Using High Hydrostatic Pressure

Okara is a perishable, cheap and abundant by-product derived from soybean after extracting the soluble fraction for tofu or soybean drink, mainly known as soymilk, production. Nowadays, Okara is mostly discarded: landfill and incineration, but a useful alternative for valorisation would be to use it as a valuable source of dietary fibre. However, it presents low soluble dietary fibre (SDF) content responsible for prebiotic and anti-carcinogenic effects, so an easy industrial transformation to maximize its SDF content would be most interesting for this purpose. Different approaches can be used to increase SDF content, such as chemical or enzymatic treatments with food-grade enzymes at atmospheric pressure, but these conventional methods present some disadvantages as that the chemical procedures are pollutant and the extractions normally are incomplete, and the enzymatic methods could be expensive to scale-up. On the other hand, currently, consumers are demanding for safer, more natural and minimally-processed foods. This request has led researchers and manufacturers to develop new technologies, and within these, high hydrostatic pressure (HHP) is one of the top-10 most popular emerging technologies applied in the field of food science. The effect of HHP, and more recently, the combined effect of HHP and enzymatic treatment on okara by-product have been studied, showing that this novel approach, should also be considered in order to stabilise other agro-food byproducts -due to their perishable character- as well as to improve the functionality of the rich-ininsoluble dietary fibre from vegetable residues.

The Role of Diet in the Pathogenesis of Cholesterol Gallstones.

Cholesterol gallstone disease is a major health problem in Westernized countries and depends on a complex interplay between genetic factors, lifestyle and diet, acting on specific pathogenic mechanisms. Overweigh, obesity, dyslipidemia, insulin resistance and altered cholesterol homeostasis have been linked to increased gallstone occurrence, and several studies point to a number of specific nutrients as risk- or protective factors with respect to gallstone formation in humans. There is a rising interest in the identification of common and modifiable dietetic factors that put the patients at risk of gallstones or that are able to prevent gallstone formation and growth. In particular, dietary models characterized by increased energy intake with highly refined sugars and sweet foods, high fructose intake, low fiber contents, high fat, consumption of fast food and low vitamin C intake increase the risk of gallstone formation. On the other hand, high intake of monounsaturated fats and fiber, olive oil and fish (ω-3 fatty acids) consumption, vegetable protein intake, fruit, coffee, moderate alcohol consumption and vitamin C supplementation exert a protective role. The effect of some confounding factors (e.g., physical activity) cannot be ruled out, but general recommendations about the multiple beneficial effects of diet on cholesterol gallstones must be kept in mind, in particular in groups at high risk of gallstone formation.

Preparation of β‐glucan and antioxidant‐rich fractions by stone milling of hull‐less barley

SummaryStone milling of hull‐less barley in combination with size‐based separation of the milled fractions was used for preparation of flours with different compositions of macronutrients and bioactive compounds. According to similar compositions, specific milled fractions were combined to define three flours. The flour with the largest mass fraction (~70%) comprised particle sizes < 124 μm, which showed lower fibre, residual ash and antioxidant contents than the unfractionated flour. The flour with particles from 124 to 250 μm (~20% mass fraction) had >twofold greater β‐glucan content, and the flour with particles > 250 μm (~10% mass fraction) had >threefold greater content of antioxidants than unfractionated flour. Each of these three flour fractions represents valuable material that can be incorporated into bakery products to enhance functional and health‐related properties. Large enrichment factors of bioactive compounds in barley flours can be obtained using small‐scale and widely available milling equipment.

Nutritional quality of baby corn fodder as influenced by tillage practices and nitrogen management

An experiment was conducted at Karnal, Haryana to evaluate the effect of tillage practices and nitrogen management on yield and quality of baby corn fodder. The experiment was laid out in a split plot design with three replications having a combination of three contrasting tillage practices as main plots and six nitrogen management practices as sub plot treatments. Among tillage practices, significantly higher green fodder and dry matter (DM) yield was observed in raised bed (RB) over zero tillage (ZT) and conventional tillage (CT). Significantly higher cell content and lower neutral detergent fibre (NDF) content was observed in ZT over CT and RB, while significantly higher DM% and lower amount of neutral detergent insoluble crude protein (NDICP) and acid detergent insoluble crude protein (ADICP) were observed in RB and ZT over CT. Among nitrogen management options, significantly higher fodder and DM yield, DM%, total ash, CP, NDICP and ADICP was recorded in 125% N over 0, 75, 75 + Azotobacter and 100% N alone. However, 125% N was statistically at par with 100% N + Azotobacter. Significantly higher ether extract (EE) and lower NDF and cellulose content were observed in 100% N + Azotobacter and 125% N. The significant interaction effect was observed in green fodder and dry matter yield and RB with 125% N and 100% N + Azotobacter were superior over rest of the treatments. Among fodder quality parameters, significantly lower NDICP was observed in ZT with 125% N and 100% N + Azotobacter over rest of the treatments. Baby corn grown in RB/ZT with 100% N and seed inoculation with Azotobacter was a better strategy for higher yield and better fodder quality.

Friction plug welding of glass fiber reinforced PA6 sheets using a newly designed tool

In the present investigation, a new tool was designed and utilized to friction plug weld glass fiber reinforced polyamide sheets. The welding process was divided into two steps: the plug nut generation and the plug weld production. Sound joints were obtained with appropriate welding parameters and the corresponding microstructure was analyzed and the joint mechanical performance was tested. Results showed that the plug nut was composed of three regions with different fiber distributions. The stir zone generated between the unsoftened plug zone and the workpiece base material showed obvious glass fiber orientation towards the rotational direction. At the bottom corner of the plug weld, a banded region with low fiber content was observed. The thermal mechanically affected zone at the weld bottom was more apparent due to the larger axial force resulted from plug plunging. Lap-shear tensile test showed that a steep drop of tensile force occurred at about 850 N and the maximum fracture load reached 1600 N. The joint failed with lower weld pulling out together with partial nugget tearing at the bottom corner of the plug weld. Through SEM, regular fiber orientation was observed on the surface of the pulled-out lower weld.

Effect of design parameters on the properties of ultra-high performance fibre-reinforced concrete in the fresh state

The properties of Ultra-High Performance Fibre-Reinforced Concrete (UHPFRC) in the fresh state were studied and analysed. The design parameters were the nature of the mineral admixture (metakaolin or silica fume), the fibre content and the paste content. Workability tests (mini slump-flow and mini L-box) were carried out immediately after mixing and after different resting times. Rheological tests were performed in order to evaluate the shear-dependent properties as well as the time-dependent ones. Workability results showed that the self-compacting ability targeted at the end of mixing was maintained up to 20 min after mixing for all UHPFRCs. Highlighting some significant relationships between workability measurements and rheological parameters enabled the flow properties to be analysed depending on the mixture composition. In particular, at given fibre and paste contents, UHPFRC incorporating metakaolin displayed higher plastic viscosity and structuration rate than UHPFRC containing silica fume. Furthermore, even if designed with lower fibre content or lower paste content, UHPFRC made with metakaolin was always more thixotropic than UHPFRC with silica fume. For the case of UHPFRC, having the highest metakaolin and fibre contents, a practical solution is proposed to prevent distinct-layer casting from occurring in the precast factory.

Intake of Vegetables and Fruits Through Young Adulthood Is Associated with Better Cognitive Function in Midlife in the US General Population

Vegetables and fruits (VF) may differentially affect cognitive functions, presumably due to their various nutrient contents, but evidence from epidemiologic studies is limited. The aim of this study was to examine the long-term association between VF intakes, including VF subgroups, in young adulthood and cognitive function in midlife. A biracial cohort of 3231 men and women aged 18-30 y at baseline in 1985-1986 were followed up for 25 y in the Coronary Artery Risk Development in Young Adults Study. Diet was measured at baseline, and in examination years 7 and 20. Cognitive function was assessed at examination year 25 through the use of 3 tests: the Rey Auditory Verbal Learning Test (RAVLT), the Digit Symbol Substitution Test (DSST), and the Stroop test. The mean differences (MDs) with 95% CIs in cognitive scores across intake categories were estimated through the use of the multivariable-adjusted general linear regression model. Excluding potatoes, intake of whole vegetables was significantly associated with a better cognitive performance after adjustment for potential confounders in all 3 cognitive tests (quintile 5 compared with quintile 1-RAVLT, MD: 0.33; 95% CI: 0.01, 0.64; P-trend = 0.08; DSST, MD: 2.84; 95% CI: 0.93, 4.75; P-trend<0.01; Stroop test, MD: -2.87; 95% CI: -4.24, -1.50; P-trend<0.01]. Similarly, intake of fruits, except fruit juices, was significantly related to a better cognitive performance (quintile 5 compared with quintile 1-DSST, MD: 2.41; 95% CI: 0.70, 4.12; P-trend = 0.03). This study supports the long-term benefits of VF consumption on cognitive performance, except those VF with relatively low fiber content such as potatoes and fruit juices, among the middle-aged US general population.

Effects of Fiber Dimension and Its Distribution on the Properties of Lyocell and Ramie Fibers Reinforced Polylactide Composites

The regenerated cellulose fiber (Lyocell) and natural cellulose fiber (ramie) with different initial lengths were used to reinforce polylactide (PLA) by melt compounding and injection molding. The fiber dimension and its distribution in composites after injection molding were analyzed by high-resolution Fiber Quality Analyzer (FQA). Moreover, the contents of small fibers with length < 0.2 mm were also provided by FQA. Then the influences of fiber dimension and its distribution on the mechanical properties of the composites were investigated. The results showed that fiber length was reduced during compounding and injection molding processes, and the longer the initial fiber length, the more severe the length declined. Compared with ramie fiber, Lyocell fiber showed a longer fiber length, smaller diameter and narrower width distribution in composite after injection molding. Additionally, the content of small fiber played an important role in the analysis of the relation between the fiber dimension and mechanical properties of composites owing to its smaller aspect ratio. The different mechanical characteristics of the PLA composites were attributed predominantly to the fiber aspect ratio and the small fiber content. By comparison, Lyocell fiber exhibited better reinforcement for PLA due to the higher aspect ratio and lower small fiber content. The tensile strength, tensile modulus and impact strength of Lyocell/PLA composite were increased by 8.61 %, 75.43 % and 26.9 %, respectively.

The Combination of Whey Protein and Dietary Fiber Does Not Alter Low-Grade Inflammation or Adipose Tissue Gene Expression in Adults with Abdominal Obesity.

Abdominal obesity is characterized by low-grade inflammation and plays a central role in the development of type 2 diabetes and cardiovascular diseases. Dietary factors can influence low-grade inflammation and affect adipose tissue function. To investigate the separate and combined effects of whey protein and cereal fiber on inflammatory markers and adipose tissue gene expression in abdominal obesity. We performed a 12-week, double-blind, randomized controlled dietary intervention in 65 adults with abdominal obesity. The participants were randomized to 4 groups using a 2 × 2 factorial design; they received either 60 g/day of whey protein or maltodextrin in combination with high-fiber wheat bran products (30 g fiber/day) or low-fiber refined wheat products (10 g fiber/day). Plasma concentrations of tumor necrosis factor α (TNF-α), high-sensitivity C-reactive protein (hs-CRP), monocyte chemoattractant protein-1 (MCP-1), interleukin 1 receptor antagonist (IL-1Ra), and adiponectin were measured before and after intervention. Changes in gene expression related to inflammation, insulin signaling, and lipid metabolism were measured in abdominal subcutaneous adipose tissue. After intervention, TNF-α was reduced for both high-fiber groups compared with baseline, but did not significantly differ from the low-fiber groups. There were no differences in fasting or postprandial inflammatory markers between the groups. The relative gene expression of ribosomal protein S6 kinase B1 (S6K1) was increased after whey protein compared with maltodextrin consumption. Intake of whey protein in combination with high cereal fiber content did not differentially affect low-grade inflammation or adipose tissue gene expression compared with maltodextrin and low fiber content in individuals with abdominal obesity.

Uniaxial tensile behavior of aligned steel fibre reinforced cementitious composites

By applying an external uniform magnetic field to a fresh cement mixture during casting, an aligned steel fibre reinforced cementitious composites (ASFRC) was prepared. This investigation compares the performance of ASFRC with its counterpart—ordinary steel fibre reinforced cementitious composite (SFRC) containing randomly distributed steel fibres. First, the orientation of the steel fibres in ASFRC and SFRC specimens was examined using X-ray computed tomography analysis; this confirmed that the steel fibres were effectively aligned in the ASFRC. Then, uniaxial tensile tests were performed to allow a comparison of the uniaxial tensile stress–strain curves of the ASFRC and SFRC; and to determine the advantages, if any of ASFRC over SFRC in terms of uniaxial tensile strength (fUtu), ultimate strain (εUtu) and energy dissipation (Gf-A). The uniaxial tensile test results were also used to show that, if the tensile strength of ASFRC is equal to that of SFRC (actually slightly exceeding) using the aligned steel fibre technology, the dosage of steel fibres can be reduced at least 40%. It was also found that the alignment of the steel fibres affects the strain-hardening and multiple cracking behavior of the composites during uniaxial tension testing. Finally, the multiple cracking behavior of the composites was analyzed using a digital image correlation method. These results show that ASFRC exhibits a multiple cracking pattern at a much lower fibre content compared to SFRC.

Dual Purpose Barley Production in the Mediterranean Climate: Effect of Seeding Rate and Age at Forage Cutting

Barley cutting in the late winter season is a strategy to provide good amount of high quality forage in the Mediterranean region. A 2-year field study was conducted in Alexandria, Egypt, to explore the variations in forage and grain yields and their characteristics of barley seeded with 100, 125, and 150 kg ha−1 and cut at 45, 55, and 65 days after sowing (DAS). The highest significant forage and grain yields were obtained with highest seeding rate (150 kg ha−1), amounting to 18.91, and 4.38 t ha−1, respectively. Cutting barley at early growth stages (45 and 55 DAS) resulted in the production of higher forage yield with higher quality, in terms of high crude protein and low fiber content, compared to late forage cut at 65 DAS. Meanwhile, early forage cutting resulted in the least amount of reduction in the final grain yield and, thus, grain income. The percentage reduction in grain income associated with forage cutting at 45, 55, and 65 DAS, amounted to 5.7, 19.6, and 31.0%, respectively. However, the net returns obtained from the dual purpose system, when forage was cut at 45 and 55 DAS were $104.27 (11.4%), and $67.91 (7.4%), respectively, greater than that obtained in the grain-only system. Economic analysis showed that the extra income from early forage cutting was sufficient to compensate the grain yield reduction in the dual purpose system. Dual purpose barley production, thus, proved to be highly feasible in the region due to the good price of the barley forage.

Nutrient Enhancement of Corn Distillers Dried Grains by Addition of Coproducts of the Enzyme‐Assisted Aqueous Extraction Process of Soybeans in Corn Fermentation

AbstractCorn distillers dried grains with solubles (DDGS) are not nutritionally complete as a nonruminant ingredient owing to poor essential amino acid profile, and high fat and fiber contents. Coproducts of soybean enzyme‐assisted aqueous extraction process, skim (wastewater) and insoluble fiber (IF; solid residue), and/or enzymes (pectinase, cellulase, and acid protease; referred to as PCF) were evaluated as distillers dried grains (DDG) nutritional quality enhancers in corn fermentation. Corn‐soy DDG had ~10% higher protein, ~3% lower fat, and ~2% lower fiber contents compared to corn DDG; fiber content was further reduced with PCF treatment (~4% total decrease). Concentrations of all essential amino acids in corn‐soy DDG showed at least a threefold increase, except for allo‐isoleucine and tryptophan, compared to corn DDG. Corn‐soy DDG had ~25% decrease in total fatty acid (TFA) and ~6% decrease in free fatty acid (FFA) contents compared to corn DDG; TFA and FFA contents further decreased with PCF treatment. Corn‐soy DDG had ~15%, 3%, and 1.7% lower hemicellulose, cellulose, and lignin contents, respectively, compared to corn DDG; hemicellulose content further decreased with PCF treatment. Mineral composition of corn‐soy DDG was in the recommended range, except Na and S were out of range by 0.79% and 0.74%, respectively. All results, except for Na and S, suggest strong potential of using skim and IF as DDG nutritional quality enhancers.

Stability, correlation and path coefficient analysis for yield and quality traits in betelvine (Piper betle L.) genotypes under three different sets of conditions

Betelvine (Piper betle L.) is commonly consumed as betel quid or paan with areca nut and/or tobacco; and also utilized in Indian medicine systems and in religious ceremonies. The betel production is highly erratic and so is the income of farmers due to natural climatic factors and spoilage during transport. It is therefore important to improve its productivity per vine and per unit area to meet the demand. Correlation, path coefficient and stability analysis was carried out in fifteen genotypes of betelvine including 3 checks under three protected structures, namely, Bareja (E1), Poly tunnel (E2) and Net tunnel (E3). Among the three structures, Net tunnel was found suitable for the cultivation of betelvine in Chhattisgarh. With respect to quality parameters, Meetha paan (2.65 g/100g) followed by Billori (2.23 g/100g) found to have high protein content. Meetha paan (5.89g/100g) followed by Meetha-cum-bangla (5.36g/100g) was also found to possess high starch content. However, low fiber content was recorded in Meetha pan (1.83g/100g), whereas high potassium content was found in Ramtake meetha (933mg/100g) followed by Bidhan pan (991mg/100g). The genotype, Karapaku possessed high potassium content (2.67mg/g). Hedonic five point scale for organolaptic test showed Meetha paan (2.3/5) followed by Bali paan (2.4/5) were less pungent among genotype studied. Highest shelf life was found in genotype Karapaku and Bhaichigudi (18days). The results indicated that number of leaves per vein were positively correlated with leaf width (0.802 and 0.819) followed by leaf area (0.790 and 0.808), leaf area index (0.782 and 0.800), leaf length (0.745 and 0.759), specific leaf weight (0.681 and 0.709), petiole length (0.658 and 0.705), diameter of internodes (0.484 and 0.559) and R-value (0.112 and 0.110) at both phenotypic and genotypic level, respectively. Path analysis identified leaf width (0.8772) and leaf length (0.4712) had direct effects on leaf yield at phenotypic level. Highest positive direct effect on leaf yield was exerted by leaf area (1.3544) followed by leaf width (0.8986) at genotypic level. These characters can be used as selection criterion in a breeding programme to develop varieties of betelvine with high leaf yield. The stability analysis under three different protected structures viz; E1, E2, E3 indicated that the genotypes, Karapaku, Bhaichigudi and Maghai pan are stable across the environment for leaf yield.

Nutritional Composition of Brazilian Food Products Marketed to Children.

Most food industry marketing in products targeted at children is found in packages of foods containing either excessive fat, sugar, or salt. This study audited all 5620 packaged foods available in a store of a large Brazilian supermarket chain and retrieved information from the nutrition facts tables on package labels. Products were photographed for further visual analysis to determine the presence of marketing strategies directed at children. Comparison of nutrient content per 100 g between children’s and non-children’s food products employed the Student t-test or the Mann–Whitney U-test (p-value < 0.05), due to the non-normal distribution of the nutritional composition data as verified through the Shapiro–Wilk test. Brazilian children’s food products from groups 4, 5, and 7 presented higher carbohydrate content than similar non-children’s products, while children’s food products from groups 1 and 7 presented lower fiber content. Results indicate that regulation on food labeling needs revising as it has not been effective in stopping the marketing of energy-dense nutrient-poor foods towards children.

Unripe plantain flour as a dietary fiber source in gluten‐free spaghetti with moderate glycemic index

Gluten-free products generally have low dietary fiber (DF) content. The aim of this study was to prepare a DF-rich gluten-free spaghetti and to evaluate the influence of the DF source on the chemical composition, cooking quality, texture, starch digestibility, and predicted glycemic index of the product. Unripe plantain flour (UPF) and Hi-Maize 260 were used as DF sources. The total DF in the uncooked samples was higher in the spaghetti with Hi-Maize 260 (17.4%) than in the UPF-containing one (9.6%), but no difference was observed between the two kinds of pastas (31%). Spaghetti with UPF showed shorter cooking time and lower cooking loss than the Hi-Maize 260-based sample. Microscopy observations revealed the presence of central zones containing ungelatinized starch granules. The predicted glycemic index of both spaghetti preparations was similar (66) and typical of medium GI products. UPF may be used as DF source in gluten-free pasta. Practical applications Unripe plantain flour (UPF) is a source of indigestible carbohydrates (dietary fiber), including resistant starch. The consumption of starchy foods, like spaghetti, produce glucose peaks that are associated with the risk of cardiovascular diseases, obesity, and diabetes. Spaghetti with moderate glycemic index can be elaborate with the blend of other gluten-free flours as chickpea and maize. The study showed the factibility of UPF as source of dietary fiber in a gluten-free spaghetti at a lower cost than the commercial source (Hi-Maize 260).

A Novel Route to Fabricate High-Performance 3D Printed Continuous Fiber-Reinforced Thermosetting Polymer Composites.

Recently, 3D printing of fiber-reinforced composites has gained significant research attention. However, commercial utilization is limited by the low fiber content and poor fiber–resin interface. Herein, a novel 3D printing process to fabricate continuous fiber-reinforced thermosetting polymer composites (CFRTPCs) is proposed. In brief, the proposed process is based on the viscosity–temperature characteristics of the thermosetting epoxy resin (E-20). First, the desired 3D printing filament was prepared by impregnating a 3K carbon fiber with a thermosetting matrix at 130 °C. The adhesion and support required during printing were then provided by melting the resin into a viscous state in the heating head and rapidly cooling after pulling out from the printing nozzle. Finally, a powder compression post-curing method was used to accomplish the cross-linking reaction and shape preservation. Furthermore, the 3D-printed CFRTPCs exhibited a tensile strength and tensile modulus of 1476.11 MPa and 100.28 GPa, respectively, a flexural strength and flexural modulus of 858.05 MPa and 71.95 GPa, respectively, and an interlaminar shear strength of 48.75 MPa. Owing to its high performance and low concentration of defects, the proposed printing technique shows promise in further utilization and industrialization of 3D printing for different applications.

Intensifying soluble dietary fiber production and properties of soybean curd residue via autoclaving treatment

Soybean curd residue (SCR) contains rich dietary fiber, but the low content of soluble dietary fiber (SDF) limits its development and utilization. To fully utilize SCR, autoclaving treatment (AT) was used to enhance the yield and properties of SDF. The results indicated that when SCR was treated under the condition of 128 °C for 10 min and solid liquid ratio 1:3, the yield of SDF increased to 23.60% compared with the original 11.13%. Under the optimized condition, SDF degraded into low molecular mass products by AT. Meanwhile, referred to the glucose, monosaccharide molar ratios in ASDF were increased except mannose. ASDF has a viscosity of 23.6 Pa·S when the concentration was 35 mg/mL. When the temperature reaches to 90 °C, the solubility of ASDF is 9.24 g/100 mL. The results indicated that AT is a potential pathway to improve yield and properties of SDF in SCR.

Investigation of the Mechanical Properties of Engineered Cementitious Composites with Low Fiber Content and with Crumb Rubber and High Fly Ash Content

Engineered cementitious composites (ECCs) are a type of micromechanically-designed cementitious composite reinforced with a moderate volume fraction of short fiber, typically 2% by volume. ECCs form steady-state multiple cracking that considerably improves the tensile strength and ductility of traditional concrete. In this study, the properties of matrix and the interface of ECCs were tailored through the use of crumb rubber, different types of sand, and different replacement levels of cement with fly ash. The study examined the effect of sand replacement with crumb rubber (20% by volume), two types of river sands (coarse and fine), increasing the content of class F fly ash (up to 75% cement replacement), and low fiber content (1.75%) on the mechanical properties of ECCs. Compressive strength, uniaxial tensile, and third-point bending tests were performed to characterize the properties of ECC mixes. Experimental results demonstrated that increasing fly ash content and using crumb rubber favored ductility of the composites. However, higher fly ash contents and a low water-to-binder (W/B) ratio produced lower strengths as these limited the pozzolanic reaction of fly ash making it act partially as a filler. While incorporation of crumb rubber showed adverse effects on the tensile strength of ECC materials (up to 26% decrease), the tensile ductility of ECC materials improved significantly (up to 434% improvement). Moreover, the implementation of different types of sand produced minor effects on the mechanical properties of ECCs. Overall, a tradeoff between the strength and ductility of the composites was detected, which highlights the implications of matrix/interface tailoring in the overall performance of ECC.

A viscoelastic model for time-dependent behavior of pultruded GFRP

Abstract Several works in the literature have investigated creep of pultruded glass-fiber reinforced polymer (pGFRP), but mainly to characterize the material in longitudinal direction. Moreover, the empirical Findley Power Law has been widely used to describe the creep response, but this approach is particular for each case and may result in little predictive capacity for different loading conditions, resin types and fiber architecture. In this work, a linear viscoelastic model combining elastic behavior of fiber and viscoelastic nature of matrix is proposed to represent the long-term behavior of pGFRP material. To validate the model, flexural creep and recovery experimental tests were carried out for vinyl ester (VE) and orthopolyester (OPE)-based composites for specimens oriented parallel and perpendicular to pultrusion direction. To reduce uncertainties with respect to the degree of curing of resin during fabrication, tests were conducted for two different conditions: as supplied and post-cured. Dynamic mechanical analyses (DMA) were performed to evaluate qualitatively the degree of cross-linking and the fiber architecture was studied by stereomicroscopy. Tests revealed greater compliances for OPE resulting from lower viscoelastic properties of this resin, as well as by lower fiber content and less effective fiber architecture. For transverse direction, matrix dominates the behavior and compliances were more pronounced. The thermal treatment adopted for post-curing resulted in damage formation or propagation, increasing the compliances. Satisfactory agreement was achieved between proposed model and experiments.