Composite films of polyacrylonitrile (PAN) and multiwalled carbon nanotubes (MWNTs) have been prepared by gelation/crystallization from solution. The contents of MWNTs were 5–10 wt.‐%, measured ...against PAN. The electrical and mechanical properties have been studied in comparison with those of the homopolymer PAN films prepared from the same method. Furthermore, stabilization and the carbonization have been carried out by using the drawn PAN–MWNTs as a new precursor to prepare carbon films with a cross‐sectional area much larger than that of a commercial carbon fiber (> 3000 times). The MWNTs within the PAN matrix promote the formation of a condensed aromatic ladder structure during the stabilization process and play an important role in preparing PAN‐based carbon material with high carbon quality and high mechanical properties. When the stabilized composites with 10 wt.‐% MWNTs are carbonized at 1000 °C, the Young's modulus reaches 37.5 GPa, and the electrical conductivity reaches 102 S cm–1. The carbonized PAN homopolymer does not form an adequately robust bulk film for the mechanical properties to be measured.
Composite films of polyacrylonitrile (PAN) and multiwalled carbon nanotubes (MWNTs) have been prepared via gelation/crystallization from solution and their electrical and mechanical properties are studied. Stabilization and carbonization have additionally been carried out (using the drawn PAN–MWNT composite as a new precursor) in order to prepare carbon films with a cross‐sectional area ∼3000 times larger than that of commercial carbon fibers (see Figure).
Electric field sensing has various real-life applications, such as early prediction of lightning. In this study, we effectively used graphene as an electric field sensor that can detect both positive ...and negative electric fields. The response of the sensor is recorded as the change in drain current under the application of an electric field. In addition, by systematic analysis, we established the mechanism of the graphene electric field sensor, and it is found to be different from the previously proposed one. The mechanism relies on the transfer of electrons between graphene and the traps at the SiO2/graphene interface. While the direction of charge transfer depends on the polarity of the applied electric field, the amount of charge transferred depends on the magnitude of the electric field. Such a charge transfer changes the carrier concentration in the graphene channel, which is reflected as the change in drain current.
After the radioactive material leak accident at the J-PARC hadron experimental facility on May 23, 2013, we designed a new production target, which is capable of a primary proton beam with the energy ...of 30 GeV and power of 50 kW. It is made of gold and cooled by water through a copper block. For the countermeasures of the recurrence of the accident, the target is enclosed by an airtight chamber and helium gas is circulated to monitor the target soundness. In this paper, technical details of the new target design are presented.
The methylotrophic yeast, Pichia pastoris, has been genetically engineered to produce many heterologous proteins for industrial and research purposes. In order to secrete proteins for easier ...purification from the extracellular medium, the coding sequence of recombinant proteins is initially fused to the Saccharomyces cerevisiae α-mating factor secretion signal leader. Extensive site-directed mutagenesis of the prepro-region of the α-mating factor secretion signal sequence was performed in order to determine the effects of various deletions and substitutions on expression. Though some mutations clearly dampened protein expression, deletion of amino acids 57–70, corresponding to the predicted 3rd alpha helix of α-mating factor secretion signal, increased secretion of reporter proteins horseradish peroxidase and lipase at least 50% in small-scale cultures. These findings raise the possibility that the secretory efficiency of the leader can be further enhanced in the future.
► Mutations of the MATα pre-pro-leader affected protein secretion in P. pastoris. ► Many deletions in α-mating factor pre-pro-secretion signal reduced secretion. ► A deletion of amino acids 57–70 increased protein secretion at least 50%. ► Deletions had similar quantitative effects on two different reporters. ► Results were used to create a 3D model of the MATα leader.
Vascular endothelial growth factor (VEGF) has been shown to display neuroprotective effects on dopaminergic (DA) neurons. Here, we investigated the neurorescue effects of VEGF on 6-hydroxydopamine ...(6-OHDA)-treated DA neurons in vitro and in vivo. Initially, we examined in vitro whether 1, 10, or 100 ng/ml of VEGF administration at 2 or 4 h after 6-OHDA treatment rescued DA neurons derived from E14 murine ventral mesencephalon. The earlier treatment of VEGF suppressed 6-OHDA-induced loss of DA neurons more than the delayed treatment. Next, we examined whether the continuous infusion of VEGF had neurorescue effects in a rat model of Parkinson's disease. We established a human VEGF secreting cell line (BHK-VEGF) and encapsulated the cells into hollow fibers. The encapsulated cells were unilaterally transplanted into the striatum of adult rats at 1 or 2 weeks after 6-OHDA lesions, and animals subsequently underwent behavioral and immunohistochemical evaluations. Compared to lesioned rats that received BHK-Control capsules, lesioned rats transplanted with BHK-VEGF capsules showed a significant reduction in the number of amphetamine-induced rotations, a significant preservation of TH-positive neurons in the substantia nigra pars compacta, and a remarkable glial proliferation in the striatum, with the earlier transplantation exerting much more benefits than the delayed transplantation. Parallel studies revealed that the observed in vitro and in vivo neurorescue effects were likely mediated by VEGF's angiogenic and glial proliferative effects, as well as its direct effects on the neurons. Our results suggest that VEGF is a highly potent neurorescue molecule for Parkinson's disease therapy.
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