Polarization dependence of multipath propagation and high-speedtransmission characteristics of indoor millimeter-wave channel at 60 GHz

Measurements of polarization dependence of multipath-propagation characteristics were conducted at 60 GHz in a room within a modern office building. Delay profiles were measured using a swept frequency method with a high time-delay resolution of 2 ns. Directions of arrival of the multipath components reflected from walls were analyzed by rotating a narrow-beam receiving antenna with an angular resolution of 5 degrees. Results of this experiment showed that multipath delayed waves due to wall reflection can be effectively suppressed by employing circular polarization instead of linear polarization. Based on this experimental result, a computer simulation was made to clarify the polarization dependence of the high-speed transmission characteristics of an indoor communications system operating at 60 GHz     

Wurtzite-type ZnS nanoparticles by pulsed electric discharge

The synthesis of wurtzite-type ZnS nanoparticles by an electric discharge submerged in molten sulfur is reported. Using a pulsed plasma between two zinc electrodes of diameter 5 mm in molten sulfur, we have synthesized high-temperature phase (wurtzite-type) ZnS nanocrystals with an average size of about 20 nm. The refined lattice parameters of the synthesized wurtzite-type ZnS nanoparticles were found to be larger than those of the reported ZnS (JCPDS card no 36-1450). Synthesis of ZnMgS (solid solution of ZnS and MgS) was achieved by using ZnMg alloys as both cathode and anode electrodes. UV-visible absorption spectroscopy analysis showed that the absorption peak of the as-prepared ZnS sample (319 nm) displays a blue-shift compared to the bulk ZnS (335 nm). Photoluminescence spectra of the samples revealed peaks at 340, 397, 423, 455 and 471 nm, which were related to excitonic emission and stoichiometric defects.     

Stiff and hierarchical chain nature of atactic and stereoregular poly(substituted methylene)s

In this study, we estimated the chain nature of atactic and stereoregular poly(substituted methylene)s containing a phenylmethoxy side chain at each main‐chain backbone carbon atom using synchrotron X‐ray scattering to understand the topological and conformational properties of these rigid polymers. The atactic poly(substituted methylene) showed a linear chain nature. Contrastingly, the stereoregular poly(substituted methylene) exhibited a random coil structure. © 2018 Society of Chemical Industry     

Identification of novel derivative of helvolic acid from Metarhizium anisopliae grown in medium with insect component

Entomopathogenic fungi are unique owing to their versatile ability to produce many bioactive compounds and from the dependence of their morphological differentiation on the presence of insect-derived materials. An entomopathogenic fungus, Metarhizium anisopliae HF293, was found to show insect-material-dependent production of antibacterial compounds, which were purified to homogeneity from 10-d culture broth when the production reached maximum. Two compounds were isolated: the major compound was determined to be helvolic acid and the minor one was a novel derivative of helvolic acid (1,2-dihydrohelvolic acid). Discovery of a novel bioactive compound indicated that insect-derived material would be a useful factor for enhancing the diversity of compounds produced by entomopathogenic fungi.     

Synthesis of silica-coated AgI nanoparticles and immobilization of proteins on them

This paper describes a method for preparing silica-coated silver iodide (AgI/SiO2) particles and immobilizing proteins on the AgI/SiO2 particles. Colloid solution of AgI particles was prepared by mixing AgClO4 aqueous solution and KI aqueous solution. Silica-coating of the AgI particles was performed by adding 3-mercaptopropyltrimethoxysilane, tetraethylorthosilicate/ethanol solution and NaOH aqueous solution successively to the AgI colloid solution. TEM observation revealed that the AgI nanoparticles were coated with uniform silica shell. The AgI/SiO2 particles were surface-modified with 3-aminopropyltrimethoxysilane and succinic anhydride. It was confirmed by XPS measurement that amino group or carboxyl group was introduced onto the AgI/SiO2 particles. Protein-immobilization was performed in aqueous solution with bovine serum albumin (BSA) in the presence of the surface-modified AgI/SiO2 particles. UV-VIS absorption spectroscopy revealed that the BSA was adsorbed on the surface-modified particles.     

Packaging technology for a 10-Gb/s photoreceiver module

We designed a 10-Gb/s photoreceiver module integrating a flip-chip avalanche photodiode (APD), a Si-preamplifier IC, and a slant-ended fiber (SEF). Flip-chip bonding minimizes parasitic reactances in the interconnect between the photodiode and the preamplifier IC. The optical coupling system consists of a slant-ended fiber and a microlens monolithically fabricated on the photodiode. This gives a flat IC-package assembly, which enables stripline interfaces to extract high-speed signals, increases misalignment tolerances, and lowers package height. Tolerances of over ±9 μm were obtained in every direction, which matched our theoretical predictions. To attach and hermetically seal the optical coupling, the fiber ferrule was directly laser-welded to the package wall with a double ring structure. The module withstood shock and vibration tests and had a 10-GHz bandwidth and -23-dBm minimum photosensitivity at 10 Gb/s     

Development of a novel rat mutant with spontaneous limbic-like seizures

A new epileptic rat mutant with spontaneous seizures was developed by successive mating and selection from an inherited cataract rat. The procedures for developing the mutant and the symptomatology, electroencephalographic correlates, and neuropathology of the mutant are reported. It is possible that this rat stain will provide a useful animal model for human temporal lobe epilepsy. The seizures of the rat usually begin with face and head myoclonus, followed by rearing, and generalized clonic and tonic convulsions, all of which are symptomatologically the same as limbic seizures. Electrographic recording during generalized convulsive seizures demonstrated that sustained spike discharges emerged at the hippocampus and then propagated to the neocortex. Seizures occurred spontaneously without any artificial stimuli. Furthermore, external stimuli such as auditory, flashing light, or vestibular stimulations could not elicit epileptic attacks. Almost all of the male animals had generalized convulsions, mostly from 5 months after birth, and the frequency of the seizures increased with aging. Generalized convulsions developed in approximately 20% of the female rats. Microdysgenesis, such as abnormal neuronal clustering, neuronal disarrangement, or interruption of pyramidal neurons in the hippocampal formation, was found in the young rats that had not yet had generalized seizures. This microdysgenesis, which is though to be genetically programmed, was very interesting from the aspect of the relationship between structural abnormalities and epileptogenesis in this mutant. In addition to microdysgenesis, there was sprouting of mossy fibers into the inner molecular layer of the dentate gyrus in those adult rats that had repeated generalized convulsions. An increase of glial-fibrillary-acidic-protein-positive astrocytes with thickened and numerous processes, ie, astrogliosis, was also found in the cerebral cortex, amygdala region, and hippocampus of these adult animals. Judging from the characteristics of the symptomatology, electroencephalographic correlates, and neuropathology, this epileptic mutant can be expected to be a useful animal model for studying human temporal lobe epilepsy.