High-Performance Electroabsorption Modulators Utilizing Microwave Reflection Control Technique

A microwave reflection control technique that improves the performance of electroabsorption modulators (EAMs) is presented. The technique exploits the superposition of incident and reflected electrical signals as a modulation signal to enhance the modulation signal voltage applied to EAMs and therefore differs from conventional impedance matching techniques in terms of operating principle. A nearly flat electrical-to-optical frequency response up to 50 GHz and significant improvement in eye openings at 40 Gbit/s have been achieved with the technique. The effects of the technique are demonstrated through both experimental and computational investigations.     

Colored Fluorescent Silk Made by Transgenic Silkworms

Silk is a protein fiber used to weave fabrics and as a biomaterial in medical applications. Recently, genetically modified silks have been produced from transgenic silkworms. In the present study, transgenic silkworms for the mass production of three colors of fluorescent silks, (green, red, and orange) are generated using a vector originating from the fibroin H chain gene and a classical breeding method. The suitability of the recombinant silks for making fabrics is investigated by harvesting large amounts of the cocoons, obtained from rearing over 20 thousand silkworms. The application of low temperature and a weakly alkaline solution for cooking and reeling enables the production of silk fiber without loss of color. The maximum strain tolerated and Young's modulus of the fluorescent silks are similar to those of ordinary silk, although the maximum stress value of the recombinant silk is slightly lower than that of the control. Fabrics with fluorescent color are demonstrated using the recombinant silk, with the color persisting for over two years. The results indicate that large amounts of genetically modified silk can be made by transgenic silkworms, and the silk is applicable as functional silk fiber for making fabrics and for use in medical applications.     

Nanowrinkled and Nanoporous Polyethylene Membranes Via Entanglement Arrangement Control

Crystalline homopolymers, including polyethylene (PE), which has the simplest architecture, form a nanometer‐sized combination of crystalline and amorphous components, but their arrangement control, similar to self‐assembled phase‐separation of block‐copolymers, is usually difficult. However, molecular entanglements trapped between crystalline and amorphous components of homopolymers coincide with the segmental linking points on the interfaces of the microphase separation for block copolymers. Nanowrinkled PE membranes are prepared with a network of 30 nm‐thick homogeneous lamellae using a novel entanglement control technique composed of biaxial melt‐drawing and melt‐shrinking procedures, which are limited for highly entangled ultrahigh molecular weight materials. Such a network arrangement of nanowrinkling lamellae spreading on membrane surface and also across the membrane thickness improves the mechanical properties of both tensile strength and tearing strength. Subsequent cold‐drawing causes delamination of the lamellar interfaces, leading to the resultant nanoporous morphology composed of passing‐through channels that are several tens of nanometers in diameter, without any solvent processing.     

Sodium‐Ion Batteries: Building Effective Layered Cathode Materials with Long‐Term Cycling by Modifying the Surface via Sodium Phosphate

Surface stabilization of cathode materials is urgent for guaranteeing long‐term cyclability, and is important in Na cells where a corrosive Na‐based electrolyte is used. The surface of P2‐type layered Na_2/3[Ni_1/3Mn_2/3]O₂ is modified with ionic, conducting sodium phosphate (NaPO₃) nanolayers, ≈10 nm in thickness, via melt‐impregnation at 300 °C; the nanolayers are autogenously formed from the reaction of NH₄H₂PO₄ with surface sodium residues. Although the material suffers from a large anisotropic change in the c‐axis due to transformation from the P2 to O2 phase above 4 V versus Na⁺/Na, the NaPO₃‐coated Na_2/3[Ni_1/3Mn_2/3]O₂/hard carbon full cell exhibits excellent capacity retention for 300 cycles, with 73% retention. The surface NaPO₃ nanolayers positively impact the cell performance by scavenging HF and H₂O in the electrolyte, leading to less formation of byproducts on the surface of the cathodes, which lowers the cell resistance, as evidenced by X‐ray photoelectron spectroscopy and time‐of‐flight secondary‐ion mass spectroscopy. Time‐resolved in situ high‐temperature X‐ray diffraction study reveals that the NaPO₃ coating layer is delayed for decomposition to Mn₃O₄, thereby suppressing oxygen release in the highly desodiated state, enabling delay of exothermic decomposition. The findings presented herein are applicable to the development of high‐voltage cathode materials for sodium batteries.     

A tunable waveguide CO2 laser with expanded tuning range

A method of expanding the tuning range of the CW CO₂ waveguide laser making use of a Fabry-Perot type light modulator is proposed. A preliminary experiment has been done to confirm the workability of the proposed scheme.     

Identification of a methanol-inducible promoter from Rhodococcus erythropolis PR4 and its use as an expression vector

The genus Rhodococcus exhibits a broad range of catalytic activity and is tolerant to various kinds of organic solvents. This property makes rhodococci suitable for use as a whole-cell catalyst. Various tools for genetic engineering have been developed to use Rhodococcus erythropolis as a host for bioconversion. In this study, we investigated the protein expression responses of R. erythropolis strains and found that isocitrate lyase production in R. erythropolis PR4 (ICL(Re)) was induced by methanol. By analyzing the regulation mechanisms of icl(Re) expression, the ~200-bp upstream region from the first nucleotide of the translation initiation codon of icl(Re) was shown to be sufficient for the methanol-inducible expression. Also, the ~100-bp upstream region exhibited strong constitutive promoter activity by an unknown mechanism(s). By investigating proteins that bound to the upstream region of icl(Re)in vitro, a RamB homologue of R. erythropolis PR4 (RamB(Re)) was identified. Moreover, 2 putative RamB(Re) binding sites were identified in the upstream region of icl(Re) through pull-down assays. A ramB(Re) knockout experiment suggested that RamB(Re) negatively controlled the expression of icl(Re) and that RamB(Re) regulation was dependent on the availability of a carbon source. On the basis of these findings, we were able to create novel methanol-inducible and strong constitutive expression vectors.     

Identification of HLA-A24-restricted epitopes with high affinities to Hsp70 using peptide arrays

Heat shock protein 70 (Hsp70) family members are known as facilitators of immune responses by interacting with receptors on antigen-presenting cells leading to Hsp70-peptide uptake and antigen cross priming. Here, identification of human leukocyte antigen (HLA)-A24-restricted epitopes was achieved using peptide arrays for evaluation of their affinities to Hsp70 and HLA-A24 binding prediction tools. Using Hsp70 as the model antigen, the GYPVTNAVI and VFQHGKVEI peptides were identified as antigens. These peptides actually bound to HLA-A24 in the stabilization assay using T2-A*2402 cells, and induced a strong peptide-reactive cytotoxic T lymphocyte response in HLA-A24 transgenic mice after vaccination.     

Successfully operated case of posterior fossa tuberculoma in childhood (author's transl)

A case of intracerebellar tuberculoma is described in which a tuberculoma was removed successfully through the administration of antituberculous agents, and a full recovery was obtained. The patient was a 3-year-old boy who had been receiving antituberculous agents for about 4 months because of acute inflammation followed by osteomyelitis of his right big toe, which was suspected to be tuberculous, and because of pulmonary tuberculosis diagnosed in a chest roentgenogram taken about 1 month after osteomyelitis was cured. While his osteomyelitis was being treated, disturbance in his gait, due to progressive spastic paraparesis, was not iced, and thereafter left cerebellar symptoms with impairment of equilibrium appeared additionally. Then, he was reffered to our clinic for further neurosurgical examination, and was admitted on November 1, 1974 after right carotid and vertebral angiography was performed via the right axillar artery, in which findings suggesting left cerebellar tumor and internal hydrocephalus were obtained. After he was admitted to our clinic, a diagnosis of tumor of the left cerebellum and internal hydrocephalus was more precisely confirmed by pneumoventriculography. Suboccipital craniectomy was then carried out and the tumor, weighing 60 gm, was completely removed from the left cerbellar hemisphere. The tumor was confirmed as tuberculoma not only by histological findings but also by the vertification of tuberculous bacilli in it. Though, moderate fever lasted for about 2 weeks postoperatively, no obvious meningitic signs or new neurological deficits were noted. The patient showed marked improvement especially in his gait disturbance, and was discharged ambulatory 40 days after the operation, and has since been asymptomatic except for slight ataxic gait. The antituberculous agents have been continuously administered postoperatively.