Anisotropic Composition and Mechanical Behavior of a Natural Thin-Walled Composite: Eagle Feather Shaft.

Flight feather shafts are outstanding bioinspiration templates due to their unique light weight and their stiff and strong characteristics. As a thin wall of a natural composite beam, the keratinous cortex has evolved anisotropic features to support flight. Here, the anisotropic keratin composition, tensile response, dynamic properties of the cortex, and fracture behaviors of the shafts are clarified. The analysis of Fourier transform infrared (FTIR) spectra indicates that the protein composition of calamus cortex is almost homogeneous. In the middle and distal shafts (rachis), the content of the hydrogen bonds (HBs) and side-chain is the highest within the dorsal cortex and is consistently lower within the lateral wall. The tensile responses, including the properties and dominant damage pattern, are correlated with keratin composition and fiber orientation in the cortex. As for dynamic properties, the storage modulus and damping of the cortex are also anisotropic, corresponding to variation in protein composition and fibrous structure. The fracture behaviors of bent shafts include matrix breakage, fiber dissociation and fiber rupture on compressive dorsal cortex. To clarify, 'real-time' damage behaviors, and an integrated analysis between AE signals and fracture morphologies, are performed, indicating that calamus failure results from a straight buckling crack and final fiber rupture. Moreover, in the dorsal and lateral walls of rachis, the matrix breakage initially occurs, and then the propagation of the crack is restrained by 'ligament-like' fiber bundles and cross fiber, respectively. Subsequently, the further matrix breakage, interface dissociation and induced fiber rupture in the dorsal cortex result in the final failure.

EMI Shielding Nanocomposite Laminates with High Temperature Resistance, Hydrophobicity and Anticorrosion Properties.

High-performance multifunctional EMI shielding composite fabricated by low-cost method is increasingly required. Herein, novel EMI shielding nanocomposite laminates, consisting of composite prepreg of carbon fiber/epoxy resin/carbon nanotube film, were manufactured by facile electric heating of carbon nanotube film. The results indicated that composite with excellent specific shielding effectiveness of 0.07 dB/µm, 47 dB cm3/g and metamaterial properties can be designed by composite prepreg, and the primary shielding mechanism of it was reflection loss, along with interface polarization loss and conductive loss, which was superior to lots of shielding materials including carbon nanotube-based, carbon black-based, carbon nanofiber-based and graphene-based materials reported previously. Meanwhile, highly required excellent properties, including the thermostability with initial decomposition temperature up to 300 °C, hydrophobicity over contact angle of 115°, corrosion resistance of the composite with metal-free modification, and function as structural laminate compared with previous studies were demonstrated, which suggested tremendous potentials of the multifunctional EMI shielding composites in harsh environment.

Effect of Equal Channel Angular Pressing on the Dynamic Softening Behavior of Ti-6Al-4V Alloy in the Hot Deformation Process.

To investigate the effect of equal channel angular pressing (ECAP) on the deformation of Ti-6Al-4V alloy at a higher temperature, hot compression tests were conducted on alloys having two different initial microstructures (the original alloy (Pre-ECAP) and ECAP-deformed alloy (Post-ECAP)). Post-ECAP, the alloy showed a higher degree of dynamic softening during the hot deformation process due to its finer grain size and higher distortion energy. The flow stress of Post-ECAP alloy was higher than the Pre-ECAP alloy at 500 °C when ε˙= 0.003 s-1. However, the stress of the Post-ECAP alloy decreased rapidly with increasing temperature and strain rate, until the stress value was much lower than that of Pre-ECAP at 700 °C when ε˙= 0.03 s-1. The value of the dynamic softening coefficient revealed that the dynamic softening behavior of Post-ECAP was more pronounced than that of Pre-ECAP in the hot compression deformation process. The main dynamic softening mechanism of Pre-ECAP is dynamic recovery, while the dynamic recrystallization process plays a more important role in the deformation process of Post-ECAP alloy. The microstructures observation results showed that dynamic recrystallization was more likely to occur to Post-ECAP alloys under the same deformation condition. Almost fully dynamic recrystallization had occurred in the deformation process of Post-ECAP at 700 °C and a strain rate of ε˙= 0.01 s-1. The grains of Post-ECAP alloys were further refined. The Post-ECAP alloy exhibits better plastic deformation at temperatures higher than 600 °C due to its significant dynamic recrystallization.

Efficient biosynthesis of cinnamyl alcohol by engineered Escherichia coli overexpressing carboxylic acid reductase in a biphasic system.

BACKGROUND: Cinnamyl alcohol is not only a kind of flavoring agent and fragrance, but also a versatile chemical applied in the production of various compounds. At present, the preparation of cinnamyl alcohol depends on plant extraction and chemical synthesis, which have several drawbacks, including limited scalability, productivity and environmental impact. It is therefore necessary to develop an efficient, green and sustainable biosynthesis method. RESULTS: Herein, we constructed a recombinant Escherichia coli BLCS coexpressing carboxylic acid reductase from Nocardia iowensis and phosphopantetheine transferase from Bacillus subtilis. The strain could convert cinnamic acid into cinnamyl alcohol without overexpressing alcohol dehydrogenase or aldo-keto reductase. Severe product inhibition was found to be the key limiting factor for cinnamyl alcohol biosynthesis. Thus, a biphasic system was proposed to overcome the inhibition of cinnamyl alcohol via in situ product removal. With the use of a dibutyl phthalate/water biphasic system, not only was product inhibition removed, but also the simultaneous separation and concentration of cinnamyl alcohol was achieved. Up to 17.4 mM cinnamic acid in the aqueous phase was totally reduced to cinnamyl alcohol with a yield of 88.2%, and the synthesized cinnamyl alcohol was concentrated to 37.4 mM in the organic phase. This process also demonstrated robust performance when it was integrated with the production of cinnamic acid from L-phenylalanine. CONCLUSION: We developed an efficient one-pot two-step biosynthesis system for cinnamyl alcohol production, which opens up possibilities for the practical biosynthesis of natural cinnamyl alcohol at an industrial scale.

Diffusion Bonding of 1420 Al-Li Alloy Assisted by Pure Aluminum Foil as Interlayer.

The Al-Li alloy is becoming popular for aerospace application owing to their low density, high specific strength, good corrosion resistance, etc. The diffusion bonding/superplastic forming (DB/SPF) structure of titanium alloy has been widely used in the aerospace industry. In order to broaden the application of Al-Li alloy, it is necessary to develop its diffusion bonding and superplastic forming (DB/SPF) technology. In the present study, diffusion bonding of 1420 Al-Li alloy assisted by pure aluminum foil was conducted on Gleeble-3500 thermal simulation system under different bonding parameters, the results show that the bonding temperatures have direct influence on the interface microstructure and bond strength of joints. Meanwhile, when the pure aluminum interlayer was introduced into the diffusion bonding process, the alloying element diffusion across the bond can improve the interface integrity and the mechanical properties. The joint formation mechanism with interlayer was investigated in detail, the development and application of this method was explored.

The effect of pulsed current on the shear deformation behavior of Ti-6Al-4V alloy.

Pulse current-assisted forming is a new technology to improve the plastic deformability of titanium alloy. In this work, Shearing tests of Ti-6Al-4V alloy were conducted using hat-shaped specimens under pulsed current (electroplastic shearing) and constant temperature (isothermal shearing). The actual deformation in shear zone of electroplastic shearing was larger than that of isothermal shearing. The shear load is also decreased by the pulsed current. Microstructure variation in the shear zone was investigated by scanning electron microscopy. An evident straight shear band was observed in the electroplastic shearing specimens. The deformation model of shear zone was established. Intracrystalline deformation was markedly easier for the grains with the pulsed current and induced larger deformation of the grains along the shear direction. Microcracks were observed in the shear zone of isothermal shearing, but none were found in the shear zone of electroplastic shearing. Evident crack healing was found in the crack tip of the shear zone of electroplastic shearing.

Effect of Alloying Elements Gradient on Solid-State Diffusion Bonding between Aerospace Aluminum Alloys.

Three different bonding couples assembled by two commonly used aerospace aluminum alloys were bonded within the temperature range of 460⁻520 °C under 6 MPa for 60 min in vacuum atmosphere. The interface microstructure and alloying elements distribution of the bonded joints were determined by scanning electron microscope (SEM) and Energy Dispersive Spectroscope (EDS); the bond strength was evaluated by tensile-shear strength test. The results show the bond quality improved effectively as the bonding temperature increased. Compared with the 1420-1420 and 7B04-7B04 bonding couples, the 1420-7B04 couples obtained better interface integrity and higher bond strength, the highest shear strength for 1420-7B04 couple can be as high as 188 MPa when bonded at 520 °C. Special attention was focused on the 1420-7B04 couple, the diffusion coefficient of Mg at the original interface under different temperatures were investigated, the results show the diffusion coefficient increased obviously as the bonding temperature increased. A diffusion affected zone (DAZ) without continuous intermetallic phases formed due to the diffusion of alloying elements across the bonding interface. The combined action of temperature and alloying elements gradient resulted in the increase of alloying elements diffusion fluxes, which in turn promote the bonding quality through the accelerated shrinkage of interfacial voids.

Bone marrow stromal cells with a combined expression of BMP-2 and VEGF-165 enhanced bone regeneration.

Bone graft substitutes with osteogenic factors alone often exhibit poor bone regeneration due to inadequate vascularization. Combined delivery of osteogenic and angiogenic factors from biodegradable scaffolds may enhance bone regeneration. We evaluated the effects of bone morphogenetic protein 2 (BMP2) and vascular endothelial growth factor (VEGF), combined with natural coral scaffolds, on the repair of critical-sized bone defects in rabbit orbits. In vitro expanded rabbit bone marrow stromal cells (BMSCs) were transfected with human BMP2 and VEGF165 genes. Target protein expression and osteogenic differentiation were confirmed after gene transduction. Rabbit orbital defects were treated with a coral scaffold loaded with BMP2-transduced and VEGF-transduced BMSCs, BMP2-expressing BMSCs, VEGF-expressing BMSCs, or BMSCs without gene transduction. Volume and density of regenerated bone were determined by micro-computed tomography at 4, 8, and 16 weeks after implantation. Neovascularity, new bone deposition rate, and new bone formation were measured by immunostaining, tetracycline and calcein labelling, and histomorphometric analysis at different time points. The results showed that VEGF increased blood vessel formation relative to groups without VEGF. Combined delivery of BMP2 and VEGF increased new bone deposition and formation, compared with any single factor. These findings indicate that mimicking the natural bone development process by combined BMP2 and VEGF delivery improves healing of critical-sized orbital defects in rabbits.

Repair of orbital wall defects using biocoral scaffolds combined with bone marrow stem cells enhanced by human bone morphogenetic protein-2 in a canine model.

Repair of orbital bone defects caused by trauma, infection or cancer is a continuous challenge in reconstructive surgery. Few studies have reported the application of tissue engineering for the repair of orbital bone defects in large animal models. Thus, we investigated the effects of tissue-engineered bone enhanced by the human bone morphogenetic protein-2 (BMP2) on the repair of orbital wall defects in a canine model. Autologous bone marrow stromal cells (BMSCs) from 16 Beagle dogs were isolated and cultured in vitro. Passage 2 cells were transfected with adenovirus containing human BMP2 (adv-BMP2) and tissue-engineered bone was constructed using BMP2-expressing BMSCs seeded on a biocoral scaffold. Circular defects (12-mm diameter) created bilaterally in the canine medial orbital wall, were treated with one of the following: adv-BMP2-transfected BMSC/coral composite (group I, n=8), BMSC/coral composite (group II, n=8), biocoral alone (group III, n=8), or were left untreated (group IV, n=8). Four samples from each group were harvested at 12 and 24 weeks after surgery, and the volume and density of newly regenerated bone were determined by micro-computed tomographic (micro-CT) measurement. The rate of new bone deposition and regeneration was measured by tetracycline/calcein labeling and histomorphometric analysis. The results showed that a canine 12-mm circular orbital defect was a critical-sized defect, and the micro-CT and histomorphometry detection results indicated that the combined delivery of BMSCs and BMP2 (group I) resulted in the highest regenerative effects on orbital bone defects, compared to the other groups without BMP2. Biocoral scaffolds combined with BMSCs enhanced by BMP2 could improve the healing of critical-sized medial orbital wall defects in canines.

Causes of infection after earthquake, China, 2008.

To determine which organisms most commonly cause infection after natural disasters, we cultured specimens from injured earthquake survivors in Wenchuan, China, 2008. Of 123 cultures, 46 (59%) grew only 1 type of pathogenic bacteria. Smear was more effective than culture for early diagnosis of gas gangrene. Early diagnosis and treatment of wounds are crucial.

Enhancement of bone formation by genetically-engineered bone marrow stromal cells expressing BMP-2, VEGF and angiopoietin-1.

To explore the potential of combined delivery of osteogenic and angiogenic factors to bone marrow stromal cells (BMSCs) for repair of critical-size bone defects, we followed the formation of bone and vessels in tissue-engineered constructs in nude mice and rabbit bone defects upon introducing different combinations of BMP-2, vascular endothelial growth factor (VEGF) and angiopoietin-1 (Ang-1) to BMSCs with adenoviral vectors. Better osteogenesis and angiogenesis were found in co-delivery group of BMP-2, VEGF and angiopoietin-1 than any other combination of these factors in both animal models, indicating combined gene delivery of angiopoietin-1 and VEGF165 into a tissue-engineered construct produces an additive effect on BMP-2-induced osteogenesis.