Influence of Design Parameters on Mechanical Behavior of Multi-Bolt, Countersunk C/SiC Composite Joint Structure.

Aerospace vehicle connection constructions are in urgent need of joint structures with excellent aerodynamic profiles and environmental adaptability. To address issues such as poor aerodynamic profile, material thermal expansion coefficient mismatch, and limited joint structure evaluation indexes, a multi-bolt, countersunk C/SiC composite joint structure is presented in this study. The development of a 3D Hashin progressive damage model and its dedicated solver code is presented. The validity of the model is confirmed by comparing simulation results with experimental data. Three evaluation indexes are proposed, peak load, weight increment efficiency, and bolt load distribution, to thoroughly evaluate the mechanical performance of multi-bolt, countersunk C/SiC composite joint structures. Using the proposed model and evaluation indices, we evaluate sixteen different designs of multi-bolt, countersunk C/SiC composite joint structures and analyze how design parameters affect their mechanical properties and damage patterns. The results show that the best mechanical properties of the joint structure are achieved when the ratio of bolt pitch to through hole diameter is 3, the ratio of bolt spacing between columns to through hole diameter is 4, the ratio of the distance between the free edge of the substrate to through hole diameter is 1.5, the ratio of through hole diameter to specimen thickness is 1.7, and the ratio of the distance between the edge of the substrate to through hole diameter is 1.5.

An efficient protocol for preparing linear ß-manno-oligosaccharides.

Linear ß-manno-oligosaccharides (l-ß-MOS) are widely used to investigate oligo- and poly-saccharide structures and mannanolytic enzyme activities. l-ß-MOS are also being used as prebiotic agents with potential bio-active properties. In this study, we developed an efficient protocol to prepare a series of l-ß-MOS by hydrolyzing cassia gum (CG) using mannanolytic enzymes (endo-1,4-ß-mannanase, α-galactosidases and ß-glucosidases). By using medium pressure liquid chromatography (MPLC), we purified l-ß-MOS with different degrees of polymerization (DPs). HPAEC-PAD, MALDI-TOF-MS and NMR studies confirmed that these l-ß-MOS species ranged from 1,4-ß-d-mannobiose to 1,4-ß-d-mannononaose (DP 2-9) with >95% purity. Our results provide a robust approach to preparing l-ß-MOS, thus enabling l-ß-MOS to be further used in the fields of chemistry, life science, and nutritional food.

Structure and antioxidant activity of six mushroom-derived heterogalactans.

Heterogalactans with weight-average molecular weights ~20 kDa were purified from several species of mushroom: Hypsizygus marmoreus, Pleurotus ostreatus, Pholiota nameko, Agrocybe cylindracea, Hygrophorus lucorum and Hericium erinaceus, and structurally characterized and assessed for antioxidant activity in vitro. Methylation analysis, combined with NMR spectral analysis, indicates that these glycans have a common backbone composed of (1 â†’ 6)-linked-α-D-galactopyranosyl residues that are substituted at O-2. The (1 â†’ 6)-α-D-galactans, branched primarily with ß-D-mannopyranosyl (Manp) or α-L-fucopyranosyl (Fucp) residues, have been assigned to mannogalactans or fucogalactans, respectively, as well as to ß-D-Manp and α-L-Fucp residues attached in tandem to the main chain as fucomannogalactans. In addition, 3-O-methylated-α-D-galactopyranosyl (3-O-Me-Galp) residues within the mannogalactan chains, exhibit strong reducing power and radical scavenging activity suggesting that this sugar moiety functions as an antioxidant. Our results provide important structural information on mushroom heterogalactans and prompt further investigations into their structure-activity relationships.

[Improvement on compactibility of the alcoholic extract of Zingiberis Rhizoma by co-spray drying with HPMC].

Aiming to solve the poor compactibility of the alcoholic extract of Zingiberis Rhizoma(ZR), this study explored the feasibility of its physical modification using co-spray drying with a small amount of hydroxypropyl methyl cellulose(HPMC). Based on the univariate analysis, the influence of two independent variables(the HPMC content in the product and the solid content of spray material) on the powder properties and tablet properties of the dried product was investigated by the central composite design. With the tensile strength and disintegration time of the tablets as the evaluation indexes, the optimal prescription was determined as follows: the HPMC content was 15% and the solid content of spray material was 25.6%. The accuracy of the regression model established for predicting tensile strength and disintegration time of tablets was verified, and the results revealed that the measured values were close to the predicted ones with deviations of 0.47% and-8.2%, indicating good prediction and reproducibility of the model. The tensile strength(4.24 MPa) of tablets prepared with the optimal prescription was 3.59 times that(1.18 MPa, far lower than the baseline of 2 MPa for qualified tablets) with the spray-dried powder of the ZR. On the other hand, due to the addition of HPMC, the disintegration time of tablets increased from 7.3 min to 24.6 min. On the whole, this study provided a new strategy to solve the common problem of poor compactibility of raw Chinese medicinal materials, which facilitated the successful preparation of Chinese medicinal tablets with high drug loads.

Structural analyses of the HG-type pectin from notopterygium incisum and its effects on galectins.

In the manuscript, water-soluble polysaccharides WPNI was extracted from notopterygium incisum roots and separated into two homogeneous fractions WPNI-A-a and WPNI-A-b. WPNI-A-a was an arabinogalactan (AG). WPNI-A-b belonged to HG type pectin. The structure of WPNI-A-b was analyzed by FT-IR, NMR, enzymatic hydrolysis (Endo-PG) and UPLC-FLD-MSn. WPNI-A-b was dominated by HG domain, covalently linked with AG and RG-II domains. Oligogalacturonides produced by Endo-PG from HG domain were non-, mono-, di- or tri-methyl esterified with degree of polymerization (DP) from 1 to 6. The distribution of methyl-ester groups was in a block-wise manner. The interaction of WPNI-A-b and its enzymatic hydrolysis products with galectin-1, galectin-3, galectin-7 and galectin-8 showed that AG domain exhibited stronger binding avidity to galectins than RG-II and HG domain, while oligogalacturonides showed no binding activities to galectins. The results would be useful for the application of the pectin from notopterygium incisum.

Box-Behnken design based statistical modeling for the extraction and physicochemical properties of pectin from sunflower heads and the comparison with commercial low-methoxyl pectin.

A natural low-methoxyl pectin (LAHP), was extracted with oxalic acid solution from dried heads of sunflower (Helianthus annuus L.). The single-factor experiments and response surface methodology (RSM) were used to optimize LAHP extraction conditions. The extraction yield of LAHP was 18.83 ± 0.21%, and the uronic acid content was 85.43 ± 2.9% obtained under the optimized conditions (temperature of 96 °C, time of 1.64 h, oxalic acid concentration of 0.21%). Experimentally obtained values were in agreement with those predicted by RSM model, indicating suitability of the employed model and the success of RSM in optimizing the extraction conditions. LAHP has been characterized by ash content, degree of esterification (DE), galacturonic acid (GalA) content, molecular weight and intrinsic viscosity meanwhile commercial low-methoxyl pectin (CLMP) as comparison. This study finds out a potential source of natural LMP which expands the application scope of sunflower heads. It is an efficient reuse of waste resources and provides a novel thought to explore the natural resources for food and pharmaceutical applications.

Analyses of active antioxidant polysaccharides from four edible mushrooms.

Four water-soluble polysaccharides were extracted from Pleurotus eryngii, Flammulina velutipes, Pleurotus ostreatus and white Hypsizygus marmoreus. Using anion exchange and gel permeation chromatography, a neutral and an acidic fraction were purified from each water-soluble polysaccharide. Their molecular weights were all around 20 kDa except that the acidic polysaccharide from Pleurotus ostreatus (named WPOPA) had a lower molecular weight of 5 kDa. Four neutral polysaccharides were mainly composed of galactose (42.7%-69.1%), followed by Man (19.4%-39.3%) and Glc (1.1%-15.9%). Four acidic polysaccharides contained glucose (59.0%-81.8%) as major sugar and minor glucuronic acid (4.5%-9.5%). Acidic polysaccharides exhibited stronger antioxidant activities than neutral fractions, and WPOPA showed the best antioxidant effects. Structural analysis indicated WPOPA had ß-(1 → 6)-glucan backbone branched at O-3 by ß-1,3-d-Glcp, t-ß-d-Glcp and t-ß-d-GlcpA. This investigation would be useful for screening natural antioxidants and significant in developing mushroom polysaccharides as functional foods.

A 3-O-methylated heterogalactan from Pleurotus eryngii activates macrophages.

Mushroom-derived polysaccharides exhibit various biological activities owing to their diverse structural features. Here, we purified a 3-O-methylated heterogalactan (WPEP-N-b, Mw 21.4 kDa) from the fruiting bodies of Pleurotus eryngii. WPEP-N-b is composed primarily of galactose (43.8%), mannose (39.3%), methyl-galactose (11.7%) and glucose (9.2%) residues, with the main chain being composed of α-1,6-linked D-Galp and 3-O-Me-D-Galp, branched at O-2 with single t-ß-D-Manp as major the side chain. ß-1,6-D-Glcp residues are present as minor components either in side-chains or backbone. WPEP-N-b increases macrophage phagocytosis and secretion of NO, TNF-α, IL-6 and IL-1ß. Mechanistic studies demonstrate that WPEP-N-b promotes the degradation of IκB-α, and enhances phosphorylation of MAPKs and the NF-κB p65 subunit. Our results also indicate that this polysaccharide activates RAW264.7 cells via MAPK and NF-κB signaling pathways and the Toll-like receptor 2(TLR2). These results increase our understanding as to how mushroom-derived polysaccharides modulate the immunologic process.

Cholesteryl-modification of a glucomannan from Bletilla striata and its hydrogel properties.

A glucomannan-type polysaccharide, named BSP, was obtained from the tubers of Bletilla striata by ultrasonic-assisted extraction, ethanol precipitation, deproteination and gel-permeation chromatography. HPLC analysis revealed that BSP contained mannose and glucose in the molar ratio of 3.5:1. Its molecular weight (Mw) was estimated to be 20 kDa. Methylation analysis, FT-IR and NMR analyses indicated that BSP consisted of (1→4)-linked ß-D-glucopyranosyl residues and (1→4)-linked ß-D-mannopyranosyl residues. Cholesteryl succinate was linked to BSP to make it more amphiphilic and the degree of substitution of cholesteryl succinate-BSP was 3.2%. The critical micelle concentration of modified BSP was 0.001 mg/mL, suggesting it could self-assemble into nanoparticles in aqueous solution.