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• Keratin filaments were developed from poultry feather wastes. • Dual-functional dithiols endow filaments with higher ductility than feathers. • Filament regeneration potentially creates more than 100-billion-dollar revenue. • Poultry wastes can be substantially reduced. Technology for the transformation of waste feathers to quality regenerated filaments has been developed. Regardless of superior properties of natural keratin materials, previously developed regenerated materials from keratin had tensile properties much lower than their natural counterparts due to backbone hydrolysis and inefficient reconstruction of disulfide crosslinkages. In this work, tough keratin filaments have been regenerated from white duck feathers via efficient restoration of disulfide crosslinkages using a dithiol reducing agent. Dithiol substantially reserves free thiol groups in the extraction and formed lengthy intermolecular crosslinkages in regenerated keratin filaments. Due to the high degree of intermolecular reconstruction of disulfide bonds and formation of lengthy crosslinkages via dithiol chain-extension, the keratin filaments exhibited considerable improvements in mechanical properties, especially for ductility and water stability. The tenacity and elongation at break were 160.7 MPa and 14%, respectively. The filaments retained about 80% of the tenacity of natural feathers at either dry or wet conditions and demonstrated stretchability 150% higher than natural feathers. The fiber regeneration technology makes it possible to substitute primary fiber sources by renewable poultry feathers. Successful filament substitution or addition can bring more than 88-billion-dollar revenue. The technology not only contributes to a sustainable fiber and poultry industry but adds substantial values to poultry feathers. [ABSTRACT FROM AUTHOR]

• The ultimate load-carrying capacity tests were carried out on the curved CFRP thin-walled pipe truss. • Linear and non-linear buckling analysis of the structure. • Methods for the introduction of initial geometric imperfections were investigated. • Parametric analysis of the ply orientation was carried out. This paper investigates the stability performance of a large-scale carbon fiber reinforced composite (CFRP) truss used in the keel structure of a stratospheric airship. An ultimate load-bearing test was performed on an approximately 4 m long curved CFRP thin-walled pipe truss, which was reduced to sliding supports at both ends to simulate force conditions in the normal service phase. A modified initial geometric imperfection (GI) simulation method was employed to conduct a linear and nonlinear finite element (FE) buckling analysis of the structure, considering the composite lay-up of the thin-walled pipe. Parametric analysis studies were also conducted to improve simulation accuracy and lightweight design. Results show that the structure exhibits linear behavior under the ultimate load level, with failure occurring at the span position of the lower chord. The FE model predicts the ultimate load capacity and stiffness of the structure accurately, and the parametric analysis reveals the significance of choosing a reasonable imperfection form and amplitude for the FE analysis, as well as the significant effect of ply orientation on structural performance. This study provides valuable insights into the design and optimization of CFRP trusses used in the keel structure of stratospheric airships. [ABSTRACT FROM AUTHOR]

• Keratin films were reinforced by interfacially-compatible nano-cysteine particles. • Cysteine particles with smaller sizes showed better reinforcing effects. • The keratin composite films were tough, pliant and stable in high humidity. • Keratin composite films demonstrated good biocompatibility in vitro study. Keratin films with wet stability and strength suitable for biomedical applications were developed via reinforcement with submicron cysteine particles for improved interfaces. Keratin products regenerated from wool or human hair were widely investigated as wound dressing and tissue engineering scaffolds for their satisfactory biomedical properties. However, regenerated keratin scaffolds usually did not have good mechanical properties, and also could not stand humid or wet biological environment due to poor moisture stability. Reinforcements for keratin materials were usually polysaccharides or synthetic polymers, and thus usually had non-ideal interfacial properties due to limited compatibility. In this research, submicron cystine particles were employed to reinforce keratin films for their high compatibility with keratin and bio-safety. Transition of primary and secondary structures of keratin due to matrix-reinforcement interaction was analyzed. The keratin films showed unprecedented pliancy, good tensile properties under humid conditions and biocompatibility, and thus had good potential for biomedical engineering applications. [ABSTRACT FROM AUTHOR]

• A new large-scale modular CFRP wheel-spoke-shaped stiffening ring is proposed. • A CFRP wheel-spoke-shaped stiffening ring with a diameter of 40.0 m was integrated through modular assembly technology. • The buckling failure position and buckling load of the CFRP wheel-spoke-shaped stiffening ring are determined by a multi-point loading static stability test. • A refined multi-layered shell model based on the combined eigenmode imperfection method is proposed and established. To enhance the hoop stiffness of the rigid-flexible integrated airship, a new large-scale wheel-spoke-shaped stiffening ring composed of modular carbon fiber reinforced polymer (CFRP) standard trusses was designed in this work. Particularly, by using the modular assembly technology, the CFRP stiffening ring with a diameter of 40.0 m was integrated assembly, which verified the feasibility of the proposed structural design method. Based on the applied uniformly distributed load form of the CFRP wheel-spoke-shaped stiffening ring during the flight of the rigid-flexible integrated airship, the standard truss module was subjected to a multi-point loading static stability test through a self-developed loading device, while the in-plane buckling failure position and buckling load of the CFRP wheel-spoke-shaped stiffening ring were also determined. Based on the refined multi-layered shell model, the combined eigenmode imperfection method was used for the nonlinear buckling analysis of the CFRP truss module. The buckling failure mode and the buckling load obtained from the simulation results were in good agreement with the test results. The proposed and verified large-scale modular CFRP wheel-spoke-shaped stiffening ring improved the hoop stiffness of the rigid-flexible integrated airship and achieved structural weight reduction and the design goal of the large-scale structure. The refined multi-layered shell model based on the combined eigenmode imperfection method has an important application value and guiding significance for investigating the buckling property of CFRP wheel-spoke-shaped stiffening rings, which provides valuable technical support for the structural design of rigid-flexible integrated airships. [ABSTRACT FROM AUTHOR]

The Asian hydroclimate variability during the early and middle Marine Isotope Stage (MIS) 3 was reconstructed from a high-resolution stalagmite δ18O record from Qixing Cave in southern China, which exhibited an extraordinarily strong precessional cycle. When compared with other cave records (mostly) from East Asia, covering a latitudinal transect from 23° to 38°N, it can be found that the magnitude of precessional-scale stalagmite δ18O variations decreases when the latitude increases, approximately from 3‰ to 1‰. In contrast, the amplitude of Heinrich stadials (HSs) in these stalagmite δ18O records enhances with increasing latitudes, from 1‰ to 2‰, reflecting an alleviated effect of high-latitude climate changes on the low-latitude hydroclimate, or a relative contribution from Westerlies-borne and near-sourced 18O-enriched moisture at northern China. In southern China, orbital-scale changes in stalagmite δ18O closely match variations of the atmospheric CH 4 concentration and δ18O of the atmospheric O 2 , suggesting a coherent response of low-latitude ecological and hydrological processes. In addition, a weaker precessional cycle in northern China is possibly related to the relative supply of near-sourced moisture source, where the Westerly wind can exert a substantial role. Therefore, precessional to millennial-scale changes in East Asian stalagmite δ18O records could be further modulated by local processes, rendering them a spatially contrasting trait. A pervasive imprint of muted precessional rainfall changes in loess records from northern China suggests a regionally distinct rhythm of moisture availability, in agreement with the stalagmite records from higher latitudes. • An increase of HS amplitude but weakening of the precessional cycle with increasing latitudes. • The role of low-latitude processes on alleviating the HS amplitude in southern China. • A dividing role of the latitudinal band ∼30°N on controlling the moisture supply in East Asia. • The barrier effect of Westerly jet and different moisture sources modulate precessional hydroclimate changes in northern China. [ABSTRACT FROM AUTHOR]

Abstract: The population size structure, growth dynamics and mode of competition among adult trees (≥4 cm DBH) of six abundant tree species in a 5 ha study plot of a temperate deciduous forest in the Dongling Mountains in northern China were investigated using diffusion and growth dynamics models. In the year of 2000, two dominant species, Quercus liaotungensis and Betula dahurica accounted for ca. 68.69% of the total basal area and 52.71% of the total density of adult plants. Q. liaotungensis, Populus davidiana and Acer mono exhibited inverse J-shaped DBH distributions whereas Betula dahurica, B. platyphylla and Salix caprea had unimodal DBH distributions. One-sided interspecific competition was detected between some species combinations at the scale of the 5 ha study plot, and the competitive effect was mainly size-dependent rather than from species-specific interactions with large individuals in the canopy layer out competing smaller individuals in the understory. Symmetric competition was found between Q. liaotungensis and A. mono only. However, considering the straight line relationship of G (t, x) –, which suggests that competitive asymmetry is very low or absent, combined with the relatively low mortality of trees with a DBH larger than 4 cm, we speculate that asymmetric interspecific competition was not important in structuring this tree community. Regeneration characteristics of each species are most likely important in regulating species coexistence and stand dynamics in this forest. [Copyright &y& Elsevier]

• Crosslinkers were developed from oligosaccharides for valorization of keratin wastes. • Oligosaccharide crosslinkers were more effective than other non-toxic crosslinkers. • Crosslinking simultaneously improved strength and elongation of keratin films. • Reaction mechanism between sugar crosslinker and keratin was revealed using analogs. • Relationship between tensile properties and crosslinking degree was quantified. Oligosaccharide derivatives were developed to crosslink keratin materials from poultry feathers, swine bristles and ox hairs to valorize these major wastes from meat industry. Global butchery generates more than 8,600,000 tons of keratinous wastes annually. Keratin was considered a promising resource for developing bio-based products as alternatives to petroleum products. Regenerated keratin products, such as films, usually showed insufficient mechanical properties, and required external crosslinking. However, most crosslinkers for proteins are either toxic, expensive, or with low efficiencies under mild conditions. In this research, regenerated keratin films were crosslinked by oxidized sucrose, a safe and potent bio-polyaldehyde. The crosslinker with verified low toxicity improved both tensile strength and elongation of keratin films, surpassing many other safe crosslinkers. Mechanism of the crosslinking reaction was proposed as forming Schiff bases and aminals and verified via 1H NMR and 13C NMR. Relationship between tensile properties and crosslinking degree of keratin films was also quantified. [ABSTRACT FROM AUTHOR]

• A new modular design scheme for large-scale modular CFRP wheel-spoke-shaped pre-tensioned structures is proposed. • The design scheme of the CFRP wheel-spoke-shaped pre-tensioned structure is verified. • A single-point synchronous graded tensioning method was proposed. • The stiffening ring structure achieves a self-equilibrium at the designed prestress level. The development of large-scale space flight platforms and space vehicles has led to the definition of ultra-lightweight and large-span structural design requirements for backbone structures. Taking the large-scale production, lightweight, modularization, and rapid assembly requirements as the optimization design goals, the modularization technology, connection method, and assembly mode of a carbon fiber reinforced polymer (CFRP) truss structure are studied; leading to the proposal of a new modular design scheme for large-scale modular CFRP wheel-spoke-shaped pre-tensioned structure. Based on the single-point synchronous graded tensioning method, an integrated tension test of the large-scale modular CFRP wheel-spoke-shaped structure is carried out with an integrated tension equipment. The consistency of the strain changed when the upper and lower radial cables was tested, the strain characteristics of the triangular joint frame and the CFRP truss during the push-tensioning process were analyzed, and the overall deformation of the large-scale modular CFRP wheel-spoke-shaped structure was studied. The proposed single-point synchronous graded tensioning method can simply and efficiently perform tensioning consistency in the prestressed cables, and therefore solve the engineering issues of low precision, complex tension application, and assembly difficulties in existing circular multi-point synchronous graded tensioning method. The large-scale modular CFRP wheel-spoke-shaped pre-tensioned structure achieves both structural weight reduction and large-scale structural design goals, while having broad application prospects in various aerospace vehicles and space structures. The proposed modular technology, wheel-spoke structure design scheme, and single-point synchronous graded tensioning method have high a scientific contribution, while providing technical support for the development of new spacecrafts. [ABSTRACT FROM AUTHOR]

High-resolution stalagmite δ18O records, representing Asian summer monsoon (ASM) intensity, were reconstructed from Wulu and Xiao caves, southwestern China, over Chinese Interstadials (CIS) 25 and 22. A most prominent feature of these stalagmite records is a persistent ASM strengthening throughout the entire event, different from a gradual cooling in corresponding events at Greenland and Antarctica. It implicates that the cooling in the Southern Hemisphere may intensify the ASM circulation through increased cross-equatorial flow, which overwhelms the northern high-latitude impact. Combined with previous published records over the past two interglacial-glacial cycles, diverse trends of CIS events generally match with changes in North Hemisphere summer insolation (NHSI). Accordingly, three modes of CIS ASM variability can be observed, i.e., ASM strengthening when NHSI increases, weakening when NHSI decreases, and a relatively stable ASM during NHSI peak. We argue that NHSI variability or interhemispheric gradient could change the strength of cross-equatorial flow, and in turn, alter the landward transport of monsoonal moisture. The mean isotopic composition of moisture, inherited by stalagmite δ18O signal especially in southern China, is likely a reflection of energy balance between hemispheres. [ABSTRACT FROM AUTHOR]

• An experimental system is developed to conduct vibration experiments on large films in air. • The dynamic equivalent methodology has been demonstrated for a larger rectangular membrane. • Vibration test results show that added masses affect the dynamic equivalence of grid membranes. While the dynamic equivalent methodology of substituting grid membranes for rectangular membranes in air vibration testing has been validated at small scales, scaling up to large rectangular membranes presents challenges such as gravity, uneven stress, and low-frequency identification. This paper uses numerical and experimental methods to explore the dynamic equivalence of a large rectangular membrane and a grid membrane. An experimental system is designed to conduct vibration tests of grid membranes in air, with the vertically arranged, bi-directionally tensioned grid membranes reducing the influence of gravity and flexible tensioning devices, eliminating shear stresses, and facilitating the realization of a uniform stress field. Additionally, the grid membrane is excited using rapid sinusoidal sweep excitation with an exciter, which effectively excites the low-order modes. At the same time, a laser vibrometer is utilized to accurately measure the velocity time history data at the observation points. Combining the observation points' velocity time history data with the exciter's force time history data, signal processing, and modal analysis techniques effectively identify the low-order modes. A series of grid membranes with various added masses are compared with the numerical results of rectangular membranes with respect to frequency and mode shape. The first three modes show a consistent frequency and mode shape between the large rectangular and grid membranes, while the mode correlation decreases with higher modes. Increasing the additional mass at the intersection of the grid membrane enhances frequency consistency without altering mode correlation. [ABSTRACT FROM AUTHOR]

A rigid-flexible tensegrity airship structure is proposed through the systematic research and design of the wheel spoke–shaped stiffening ring, carbon fiber–reinforced polymer slender cable, central longitudinal compression truss, and spherical multi-part integration assemblage. This structure aimed to fully utilize the structural performance advantages of a semi-rigid airship and the self-equilibrating characteristics of a tensegrity structure. The design of the spherical multi-part integration assemblage facilitates the rotation of a wheel spoke–shaped stiffening ring and enhances the installation efficiency of longitudinal cables. The tensegrity system is applied to the rigid-flexible integrated airship structure to make the main compression-bearing shaft bear the compressive stress and the longitudinal cables bear the tensile stress, thereby creating a rigid-flexible tensegrity airship structure with the self-equilibrating system. The feasibility of the structural design, component preparation, and integrated assembly technology of the rigid-flexible tensegrity airship has been effectively verified and evaluated by the integral assembly procedure, which ensures the assembly safety and reliability of the airship structure. The rigid-flexible tensegrity airship structure exhibits a clear load transfer path, high stiffness, bearing capacity, and strong shape retention capacity under low pressure conditions, which provides an ideal structural form for the stratospheric airship. • A new modular large-scale CFRP wheel spoke–shaped stiffening ring is proposed. • A CFRP slender cable with a geometric locking end-fitting is designed and developed. • A new type of spherical multi-part integration assemblage is designed to facilitate the installation of longitudinal cables. • Two types of large-span central longitudinal compression trusses are designed and developed. • The tensegrity system is applied to create a rigid-flexible tensegrity airship structure. [ABSTRACT FROM AUTHOR]

Based on the "light-weight, heavy-load, and large-span" composite truss design goal for the load-bearing structures of large aircraft, the joint construction pattern, modular integration approach, unique connection method for rear connection-rings, and structural design of composite trusses are studied in detail; a novel carbon-fiber-reinforced polymer (CFRP) truss supporting rear connection-ring is proposed. Based on the force characteristics of different section positions and the advantages of different joint types, three different joint types have been adopted: plate-shell-integrated joint (only single-K and double-K patterns), aluminum alloy joints, and butt joints. This can help fully analyze the advantages of different joint types and achieve the optimal design of composite trusses. Each truss module can be designed separately based on the specific functional and usability requirements, which increases the design freedom of the composite truss, and gives the composite truss an aesthetic three-dimensional structure. Based on the unique construction characteristics of the truss ends, axial compression performance tests were carried out on the designed and fabricated 1:1 CFRP truss prototype, with a span of 18.5 m, using specific axial loading equipment. The research results show that the unique connection method of the rear connection-ring achieved uniform load transfer from the rear connection-ring to the truss; the CFRP truss prototype meets two design requirements (bearing capacity ≥ 55.0 kN, axial compression deformation <1/1500), and is particularly suitable for the rear connection-ring to transmit large loads effectively. The proposed novel CFRP truss supporting rear connection-ring has the advantages of efficient structure assemblage, high design freedom, and flexible construction, which meets the design requirements in terms of truss functionality and realizes the "large-span, heavy-load, and light-weight" structural design goal. • A novel carbon-fiber-reinforced polymer (CFRP) truss supporting rear connection-ring is proposed. • The joint construction pattern, modular integration approach, unique connection method, and structural design were effectively verified. • The axial compression behavior of the CFRP truss supporting rear connection-ring is systematically studied. • Three different joints are adopted to leverage the performance advantages of each joint and optimize the overall performance of the composite truss. [ABSTRACT FROM AUTHOR]

Stratospheric airships require a lightweight envelope to contain lighter-than-air (LTA) buoyancy gas, making the lightweight design and pressure-bearing performance of the envelope structure a key research issue. This paper proposes a structural design scheme for a sliding poly-p-phenylene benzobisoxazole (PBO) fiber-rope-reinforced spherical envelope. The aims were to reduce envelope weight and improve pressure-bearing performance while solving the challenges of envelope structural strength. Two types of spherical envelope structures were constructed from Vectran fabric with PBO rope placed in various positions for reinforcement, and subjected to inflatable burst tests. Strain in the seam tape and envelope gores were measured by digital image correlation. A refined envelope structure model was established to simulate the bursting process with consideration of the cutting pattern effect and the mechanical properties of the weld seams. Comparison of the simulation and test results, combined with observations of the tear textures of damaged envelopes, enabled the determination of failure positions. The envelope material at the failure point was disassembled and the micromorphology and microstructure of the bearing layer were observed by scanning electron microscopy (SEM). The process and characteristics of damage origination, propagation, and collection in the envelope material are explained, and the stress behavior and state of the damage positions are analyzed. Based on the study of the mechanical behavior at the failure position, design suggestions for PBO-rope-reinforced spherical envelopes are provided. A strength criterion to incorporate tensile–shear coupling is proposed, which bridges the gap between the uniaxial tensile strength (UTS) and biaxial tensile mechanical properties of the envelope structure. • A structural design scheme using a sliding PBO-rope-reinforced airship envelope structure was proposed. • A sliding PBO-rope-reinforced spherical airship envelope structural model was established. • The stress behavior and state of the damage position were analyzed. • Design suggestions for PBO-rope-reinforced spherical envelopes are provided. • A novel idea of incorporating tensile–shear coupling into a strength criterion was proposed. [ABSTRACT FROM AUTHOR]

Serum is an important component in cell culture medium. It also possesses potent antioxidant properties. Therefore, the conventional protocols for detecting reactive oxygen species (ROS) in cultured cells with fluorescent probes include washing and suspending cells with serum-free buffers, such as PBS. This transient serum deprivation is essential for the ROS detecting. Unfortunately, it may also cause unexpected results, which push us to choose more optimal experiment conditions. In the present study, we found an acute lytic cell death induced by xanthohumol (XN), which obstructed ROS detecting in human leukemia cell line HL-60 cells. XN induced ROS burst, caused cell swelling, membrane permeability increase, LDH release, and ultimately an acute lytic cell death and cell rupture. These effects could be alleviated by the antioxidant N-Acetyl-L-cysteine (NAC). Apoptosis, pyroptosis or necroptosis were not observed in this process. Results also indicated that 2% serum addition had already completely scavenged ROS induced by 10 μM XN. Taken together, it is strongly suggested to detecting ROS in a serum-free medium when studying where and how ROS generated in cells. The concentration at the ROS maximum point (10 μM XN in this study) can be selected as the optimal concentration. Unlabelled Image • XN induced ROS, caused cell swelling and damaged cell membrane integrity. • An acute lytic cell death was induced by XN treatment ultimately. • This ROS-induced acute lytic cell death was not apoptosis, pyroptosis or necroptosis. • Help to explain the unusual decrease of ROS generation found in pro-oxidant studies. [ABSTRACT FROM AUTHOR]