Correlation between MWCNT aspect ratio and the mechanical properties of composites of PMMA and MWCNTs

The correlation between MWCNT aspect ratio and the quasi-static and dynamic mechanical properties of composites of MWCNTs and PMMA was studied for relatively long MWCNT lengths, in the range 0.3mm to 5mm (aspect ratios up to 5 x 105) and at low loading (0.15wt%). The height of the MWCNTs prepared were modulated by controlling the amount of water vapour introduced in the reactor limiting Ostwald ripening of the catalyst, the formation of amorphous carbon and any increase in CNT diameter. The Tg of PMMA increased by up to 4 ºC on addition of the longest tubes as they have the ability to form physical junctions with the polymer chains which lead to enhanced PMMA-MWCNTs interactions and increased mechanical properties, Young's modulus by 20% on addition of 5mm long MWCNTs. Predictions of the Young's modulus of the composites of PMMA and MWCNT with the Mori-Tanaka theory show that future micromechanical models should account for MWCNT agglomeration and polymer-nanotube interactions as a function of CNT length

Construction of a Food-grade Expression Vector Based on pyrF Gene in Lactococcus lactis

In this study, the pyrF screening marker and the genomic DNA fragments were used to construct the expression vectors in food-grade Lactococcus lactis (L. lactis). Such expression system could potentially be used to express and produce food-grade and medicinal polypeptides. Firstly, the NZ3900 ΔpyrF auxotrophic strain was created from the homologous recombination mutant cassette. Secondly, the repA and repC genes were used as the replication elements, the pyrF gene as the screening marker, the P32 and P8 elements from L. lactis as the promoters, and the Tusp45 and TpepN from L. lactis as the terminators, all of which were constructed in the expression plasmid pLD. Finally, the reporter gene ZsGreen (a fluorescent protein) was used to verify the expression of recombinant protein in the NZ3900 ΔpyrF mutant strain and the genetic stability of pLD-ZsG plasmid. The result showed that the prototrophic ZsGreen positive transformants could grow normally in common Elliker culture medium, and the green fluorescent signal was observed under a fluorescence microscope. In addition, ZsGreen protein could be highly expressed in NZ3900 ΔpyrF and the expression plasmid could be stably transmitted through at least 30 generations, according to the results of the PCR and Western blotting, indicating that the recombinant protein was expressed in L. lactis in a stable manner. Based on the above results, the approach for creating an L. lactis expression vector (without antibiotic resistance gene) based on the pyrF auxotrophic marker is feasible and offers a basis for further investigation into the use of L. lactis to manufacture food- and pharmaceutical-grade polypeptides

Thermal conductivity of 2D nano-structured graphitic materials and their composites with epoxy resins

Abstract The outstanding thermal conductivity (λ) of graphene and its derivatives offers a potential route to enhance the thermal conductivity of epoxy resins. Key challenges still need to be overcome to ensure effective dispersion and distribution of 2D graphitic fillers throughout the epoxy matrix. 2D filler type, morphology, surface chemistry and dimensions are all important factors in determining filler thermal conductivity and de facto the thermal conductivity of the composite material. To achieve significant enhancement in the thermal conductivity of epoxy composites, different strategies are required to minimise phonon scattering at the interface between the nano-filler and epoxy matrix, including chemical functionalisation of the filler surfaces such that interactions between filler and matrix are promoted and interfacial thermal resistance (ITR) reduced. The combination of graphitic fillers with dimensions on different length scales can potentially form an interconnected multi-dimensional filler network and, thus contribute to enhanced thermal conduction. In this review, we describe the relevant properties of different 2D nano-structured graphitic materials and the factors which determine the translation of the intrinsic thermal conductivity of these 2D materials to epoxy resins. The key challenges and perspectives with regard achieving epoxy composites with significantly enhanced thermal conductivity on addition of 2D graphitic materials are presented

The effect of multi-walled carbon nanotubes on the thermo-physical properties of shape stabilised phase change materials for buildings based on high density polyethylene and paraffin wax

The inherent low thermal conductivity and inferior mechanical properties of polymer based shape stabilised phase change materials (SSPCMs) restrict their wide applications in building sections. Multi-walled carbon nanotubes (MWCNTs) with excellent thermal and mechanical properties were incorporated into SSPCMs based on blends of a low molecular weight HDPE (lv-HDPE) and paraffin waxes by extrusion. Their suitability for latent heat thermal energy storage was evaluated. The MWCNTs were uniformly distributed within the SSPCM matrix and were wetted by the SSPCM. The SSPCMs with MWCNTs had latent heats up to 53 J g−1 with 0.5 wt% MWCNTs. Both the Young's moduli and yield stress of lv-HDPE50H-PW50 with MWCNTs composites were lower than that of unfilled lv-HDPE50H-PW50 at low MWCNT loading (≤1 wt%). They then went up with an increase in MWCNT loading (from 1 wt% to 3 wt%). This is due to the formation of an inter-connected network of MWCNTs. Similar results were obtained for both flexural moduli and stress. However, there is no significant difference of the compression moduli between unfilled lv-HDPE50H-PW50 blend and those MWCNT blends. The thermal conductivity increased with increasing MWCNTs content and the greatest enhancement was 29 % for SSPCM with 3 wt% MWCNTs. It will therefore contribute to the decarbonisation of buildings

Recycled cement

Cement recycling can reduce the environmental impact caused by the landfills of demolished concrete and the demand of raw materials for producing cement because the waste cement paste in demolished concrete could be used to produce recycled cement. Recycled cement was produced through burning a 2-year-old waste cement paste at 4 different temperatures (120 °C, 450 °C, 750 °C and 1150 °C) and then grinding into powder. The selected temperatures were the temperatures where there was a significant weight loss based on the thermogravimetric analysis (TGA) result of the old cement paste. The results show that the highest compressive strength happened at 450 °C and the recycled cement paste had a similar strength as OPC paste but with a poor workability which was even beyond the measurement range of a rheometer. Increasing the particle size of recycled cement powder and partially replacing the cement powder with ground-granulated blast-furnace slag (GGBS) were found to be able to improve the workability of recycled cement paste effectively and at same time without reducing the compressive strength

Shape stabilised phase change materials (SSPCMs) : high density polyethylene and hydrocarbon waxes

Shape stabilised phase change materials (SSPCMs) based on high density polyethylene (HDPE) with high (HPW, Tm=56-58 °C) and low (L-PW, Tm=18-23 °C) melting point waxes were prepared by melt-mixing in a twin-screw extruder and their potential in latent heat thermal energy storage (LHTES) applications for housing assessed. The structure and morphology of these blends were investigated by scanning electron microscopy (SEM). Both H-PW and L-PW were uniformly distributed throughout the HDPE matrix. The melting point and latent heat of the SSPCMs were determined by differential scanning calorimetry (DSC). The results demonstrated that both H-PW and L-PW have a plasticisation effect on the HDPE matrix. The tensile and flexural properties of the samples were measured at room temperature (RT, 20±2 °C) and 70 °C, respectively. All mechanical properties of HDPE/H-PW and HDPE/L-PW blends decreased from RT to 70 °C. In all instances at RT, modulus and stress, irrespective of the mode of deformation was greater for the HDPE/H-PW blends. However, at 70 °C, there was no significant difference in mechanical properties between the HDPE/H-PW and HDPE/L-PW blends

Three dimensional printed electronic devices realised by selective laser melting of copper/high-density-polyethylene powder mixtures

A manufacturing process with the capability to integrate electronics into 3D structures is of great importance to the development of next-generation miniaturised devices. In this study, Selective Laser Melting (SLM) was used to process copper/high-density-polyethylene (HDPE) powder mixtures to build conductive tracks in a 3D circuit system. The effects of copper/HDPE volume ratio, laser input power and scanning speed on the resistivity of CO 2 laser processed tracks were investigated. The resistivity of the tracks decreased from 26.6 ± 0.6 × 10 −4 Ωcm to 1.9 ± 0.1 × 10 −4 Ωcm as the copper volume ratio increased from 30% to 60%. However, further increasing the copper ratio to 100% resulted in poor conductivity. The lowest resistivity was achieved with an input power of 20 W and scanning speed of 80 mm/s. Additionally, processing using single-track-scanning and raster-scanning programs was compared; the overall energy distribution on the surface was more uniform using a raster-scanning program, which further reduced the resistivity to 0.35 ± 0.04 × 10 −4 Ωcm. Based on the results, a 3D multi-layered circuit system was manufactured with the HDPE as the substrate/matrix material and copper/HDPE mixture as the conductive-track material. This circuit system was successfully manufactured, demonstrating the possibility of using SLM technology to manufacture dissimilar materials towards 3D electronic applications

Systematic gene therapy derived from an investigative study of AAV2/8 vector gene therapy for Fabry disease

Abstract Background Fabry disease (FD) is a progressive multisystemic disease characterized by a lysosomal enzyme deficiency. A lack of α-galactosidase A (α-Gal A) activity results in the progressive systemic accumulation of its substrates, including globotriaosylceramide (Gb3) and globotriaosylsphingosine (Lyso-Gb3), which results in renal, cardiac, and/or cerebrovascular disease and early death. Enzyme replacement therapy (ERT) is the current standard of care for FD; however, it has important limitations, including a low half-life, limited distribution, and requirement of lifelong biweekly infusions of recombinant enzymes. Methods Herein, we evaluated a gene therapy approach using an episomal adeno-associated viral 2/8 (AAV2/8) vector that encodes the human GLA cDNA driven by a liver-specific expression cassette in a mouse model of FD that lacks α-Gal A activity and progressively accumulates Gb3 and Lyso-Gb3 in plasma and tissues. Results A pharmacology and toxicology study showed that administration of AAV2/8-hGLA vectors (AAV2/8-hGLA) in FD mice without immunosuppression resulted in significantly increased plasma and tissue α-Gal A activity and substantially normalized Gb3 and Lyso-Gb3 content. Conclusions Moreover, the plasma enzymatic activity of α-Gal A continued to be stably expressed for up to 38 weeks and sometimes even longer, indicating that AAV2/8-hGLA is effective in treating FD mice, and that α-Gal A is continuously and highly expressed in the liver, secreted into plasma, and absorbed by various tissues. These findings provide a basis for the clinical development of AAV2/8-hGLA

Development of Lanzyme as the Potential Enzyme Replacement Therapy Drug for Fabry Disease

Fabry disease (FD) is a progressive multisystemic disease characterized by lysosomal enzyme deficiency. Enzyme replacement therapy (ERT) is one of the most significant advancements and breakthroughs in treating FD. However, limited resources and the high cost of ERT might prevent patients from receiving prompt and effective therapy, thereby resulting in severe complications. Future progress in ERT can uncover promising treatment options. In this study, we developed and validated a recombinant enzyme (Lanzyme) based on a CHO-S cell system to provide a new potential option for FD therapy. Our results indicated that Lanzyme was heavily glycosylated, and its highest activity was similar to a commercial enzyme (Fabrazyme®). Our pharmacokinetic assessment revealed that the half-life of Lanzyme was up to 11 min, which is nearly twice that of the commercial enzyme. In vivo experiments revealed that Lanzyme treatment sharply decreased the accumulation levels of Gb3 and lyso-Gb3 in various tissues of FD model mice, with superior or comparable therapeutic effects to Fabrazyme®. Based on these data, Lanzyme may represent a new and promising treatment approach for FD. Building this enzyme production system for ERT can offer additional choice, potentially with enhanced efficacy, for the benefit of patients with FD