Biomimetic heat-localized and solar absorption-enhanced hollow structural nanofibrous membrane for clean water production from saline water and dye wastewater.

The rational design of material structures can be an effective approach to enhance the performance of solar-driven clean water production. In this study, a hollow structural nanofibrous membrane was developed by mimicking the hollow structure of polar bear hair using coaxial electrospinning. The shell layer consisted of carbon nanoparticles (C NPs) decorated CuO nanosheets (C@CuO), that exhibited photothermal conversion capacity. Meanwhile, the core layer containing hydrophilic polyvinylpyrrolidone (PVP) was eliminated to generate the hollow structure. The C NPs enhanced the membrane's light absorption to increase thermal energy harvesting, while the CuO nanosheets improved the membrane's wettability enhancing the water supply. Furthermore, the hollow structure limited air convection, prevented heat conduction, and minimized heat radiation, enabling heat localization to be achieved inside the membrane to suppress heat loss during evaporation. For 3.5 wt% saline water and actual dye wastewater, the C@CuO nanofibrous membrane achieved high evaporation rates of 1.36 kg·m-2·h-1 and 1.31 kg·m-2·h-1, respectively, under 1 sun illumination. Moreover, even after continuous 6-h evaporation tests, the evaporation rate of the C@CuO membrane remained virtually unchanged, highlighting its long-term stability with regard to salt resistance in real-world applications. Additionally, the remarkable flexibility of the C@CuO membrane offers convenience during operation and guarantees dimensional stability when it is subjected to external stresses. These discoveries should inspire subsequent research on developing delicate architectural materials and exploring their potential applications in various fields, including energy generation, clean water production, and thermal insulation.

Membrane technology as a promising alternative in biodiesel production: a review.

In recent years, environmental problems caused by the use of fossil fuels and the depletion of petroleum reserves have driven the world to adopt biodiesel as an alternative energy source to replace conventional petroleum-derived fuels because of biodiesel's clean and renewable nature. Biodiesel is conventionally produced in homogeneous, heterogeneous, and enzymatic catalysed processes, as well as by supercritical technology. All of these processes have their own limitations, such as wastewater generation and high energy consumption. In this context, the membrane reactor appears to be the perfect candidate to produce biodiesel because of its ability to overcome the limitations encountered by conventional production methods. Thus, the aim of this paper is to review the production of biodiesel with a membrane reactor by examining the fundamental concepts of the membrane reactor, its operating principles and the combination of membrane and catalyst in the catalytic membrane. In addition, the potential of functionalised carbon nanotubes to serve as catalysts while being incorporated into the membrane for transesterification is discussed. Furthermore, this paper will also discuss the effects of process parameters for transesterification in a membrane reactor and the advantages offered by membrane reactors for biodiesel production. This discussion is followed by some limitations faced in membrane technology. Nevertheless, based on the findings presented in this review, it is clear that the membrane reactor has the potential to be a breakthrough technology for the biodiesel industry.

Effect of cutting and functionalization of single-walled carbon nanotubes on their dispersion behaviors.

Cutting of single-walled carbon nanotubes (SWCNTs) and their modification with poly (ethylene glycol) and polystyrene were successfully performed through a treatment of the SWCNTs with piranha solutions and monoamine terminated polymers. The shortening and functionalization of SWCNTs were confirmed through size exclusion chromatography and Raman spectroscopy observations. The shortened SWCNTs exhibited more aggregated morphology than as-prepared SWCNTs in scanning electron microscope and atomic force microscope observations. Cutting and functionalization of SWCNTs with different polymer chains effectively tailored their dispersion behaviors in solvents. Polystyrene composite films exhibited improved transparency employing shortened SWCNTs, suggesting that the size of SWCNTs are critical factors in controlling the transparency of polymer composite films.

Calcium phosphate-based composites as injectable bone substitute materials.

A major weakness of current orthopedic implant materials, for instance sintered hydroxyapatite (HA), is that they exist as a hardened form, requiring the surgeon to fit the surgical site around an implant to the desired shape. This can cause an increase in bone loss, trauma to the surrounding tissue, and longer surgical time. A convenient alternative to harden bone filling materials are injectable bone substitutes (IBS). In this article, recent progress in the development and application of calcium phosphate (CP)-based composites use as IBS is reviewed. CP materials have been used widely for bone replacement because of their similarity to the mineral component of bone. The main limitation of bulk CP materials is their brittle nature and poor mechanical properties. There is significant effort to reinforce or improve the mechanical properties and injectability of calcium phosphate cement (CPC) and this review resumes different alternatives presented in this specialized literature.

A numerical study of the effect of axial acceleration on the responses of the cervical spine during low-speed rear-end impact.

A detailed, three-dimensional, head-neck (vertebral segments CO to C7) finite element model - developed and validated previously on the basis of the actual geometry of a cadaveric specimen - was used to evaluate the effect of cranial acceleration on the response of the cervical spine during low-speed, rear-end impact. Analyses were carried out to compare the predicted overall and segmental rotations, peak disc stresses, and capsular ligament strains of each motion segment during whiplash with or without cranial acceleration applied on the C7 inferior surface. The results show that, in the first 150 ms, the variation curves of predicted segmental rotational angles, disc stresses, and capsular strains for each motion segment overlapped well under the two conditions. However, after 150 ms, the capsular strains of C2 to C6 without cranial acceleration applied on C7 were all obviously lower than those with cranial acceleration applied, but the segmental rotational angles and disc stresses remain unaffected. It was implied that, although without cranial acceleration applied on C7, the relatively simple head-neck model could be used to reflect effectively the biomechanical response of the cervical spine during the initial stage (i.e. 150 ms) under low-speed, rear-end impact as well as the whole-human-body dummy model.

Finite element analysis of head-neck kinematics under simulated rear impact at different accelerations.

The information on the variation of ligament strains over time after rear impact has been seldom investigated. In the current study, a detailed three-dimensional C0-C7 finite element model of the whole head-neck complex developed previously was modified to include T1 vertebra. Rear impact of half sine-pulses with peak values of 3.5g, 5g, 6.5g and 8g respectively were applied to the inferior surface of the T1 vertebral body to validate the simulated variations of the intervertebral segmental rotations and to investigate the ligament tensions of the cervical spine under different levels of accelerations. The simulated kinematics of the head-neck complex showed relatively good agreement with the experimental data with most of the predicted peak values falling within one standard deviation of the experimental data. Under rear impact, the whole C0-T1 structure formed an S-shaped curvature with flexion at the upper levels and extension at the lower levels at early stage after impact, during which the lower cervical levels might experience hyperextensions. The predicted high resultant strain of the capsular ligaments, even at low impact acceleration compared with other ligament groups, suggests their susceptibility to injury. The peak impact acceleration has a significant effect on the potential injury of ligaments. Under higher accelerations, most ligaments will reach failure strain in a much shorter time immediately after impact.

Effects of bone materials on the screw pull-out strength in human spine.

A three-dimensional finite element model simulating the threaded connections including detailed helix curve for the bone and surgical screw was constructed. Validation of the FE model was conducted by comparing the predicted screw pull-out strength in different foam materials against experimental study. The FE model was then further analyzed to investigate the interaction of bone material and purchase length on the screw pull-out strength. The results show that failure of the connection was due to bone shearing which occurred along a cylindrical surface determined by the outer perimeter of the screw. The cortical shell resists around 50% of the pull-out strength for a screw of 4mm in major diameter and 22 mm in length. The effects of purchase length on the pull-out strength were different for different bone material. It is the bone material that determines the stability of the inserted surgical screw. The significance of the purchase length on the pull-out strength of cortical screw will be much lower than that in cancellous bone screw.

Second metatarsophalangeal joint: biomechanics and reconstruction potential.

A damaged distal radioulnar joint results in instability, pain, and loss of motion. This amounts to function loss. Of the many proposed reconstructive procedures, only a vascularized joint transfer offers growth potential in children and durability. The well-studied vascular anatomy and minimal donor morbidity of the second metatarsophalangeal joint makes it a potentially useful source. The authors evaluated various biomechanical aspects of the second metatarsophalangeal joint, which included the mediolateral arc of movement of the second metatarsophalangeal joint in hyperextension when subjected to lateral stress loading; the different patterns of disruption at peak load; and the flexion and extension range of movement. Twenty-six cadaveric specimens were tested with a customized jig. The results showed that the mediolateral arc of movement of 114 degrees approximates that of the flexion and extension range of movement of 114.2 degrees. However, it differed in that it was equal in both directions, compared with an extension arc that was greater than a flexion arc. The peak load was approximately 100 N, and this resulted in fracture, avulsion, and ligament tear. These biomechanical results may be useful to reconstructive surgeons.