Syntheses and conformational studies of poly(S-menthyloxycarbonylmethyl l- and d-cysteines)

S-menthyloxycarbonylmethyl l- and d-cysteines were prepared by the reaction of l- or d-cysteine and (?)-menthyl chloroacetate in liquid ammonia and were then polymerized to poly(S-menthyloxycarbonylmethyll- and d-cysteines) by the N-carboxyanhydride (NCA) method. From the results obtained by means of infra-red spectra, X-ray diffractions, optical rotatory dispersions (o.r.d.), and circular dichroisms (c.d.), $\text{poly}\text{(S-}\text{menthyloxycarbonylmethyl-}\text{l}\text{-cysteine}\text{)}$ was found to be a right-handed α-helix in the solid state and in ethyl ether/chloroform and chloroform solutions. Similarly, $\text{poly}\text{(S-}\text{menthyloxycarbonylmethyl-}\text{d}\text{-cysteine}\text{)}$ was a left-handed α-helix. The helix-coil transition of these polymers was observed in the vicinity of 3–4% trifluoroacetic acid (TFA) in chloroform/TFA mixtures.     

Optimum clearance design for a loose optical-fiber cable based on suppression of fiber strain

Theoretical and experimental investigations were made for fiber strain in a loose-type optical-fiber cable. Calculation formulae were derived for strain evaluation, including clearance in a loose-tube. Loose-type optical cables composed of five-fiber ribbons were manufactured and the strain characteristics were measured under tensile force, bending, and temperature change. The theoretical and experimental results were compared and strain reduction was confirmed due to the clearance. By using the results, a design procedure for optimum clearance has been shown, based on strain suppression under an allowable value for long-term use.     

Water activity-adjusted enzymatic partial hydrolysis of phospholipids to concentrate polyunsaturated fatty acids

Selective partial hydrolyses of egg yolk phospholipid and squid skin phospholipid were carried out. By keeping the water activity (a _w) of Lipozyme IM at an intermediate level, it was easy to concentrate docosahexaenoic acid (DHA). It was also possible to concentrate both DHA and arachidonic acid (AA) simultaneously to a certain level under this a _w range. However, it was impossible to concentrate AA alone when DHA was present. Though there is a limitation in concentrating AA exclusively, the proposed a _w-adjusted hydrolytic reaction is a promising way for preparing phospholipids rich in DHA.     

Corneal critical barrier against the penetration of dexamethasone and lomefloxacin hydrochloride: evaluation by the activation energy for drug partition and diffusion in cornea

The cornea is a solid barrier against drug permeation. We searched the critical barrier of corneal drug permeation using a hydrophobic drug, dexamethasone (DM), and a hydrophilic drug, lomefloxacin hydrochloride (LFLX). The activation energies for permeability of DM and LFLX across the intact cornea were 88.0 and 42.1 kJ/mol, respectively. Their activation energies for permeability across the cornea without epithelium decreased to 33.1 and 16.6 kJ/mol, respectively. The results show that epithelium is the critical barrier on the cornea against the permeation of a hydrophobic drug of DM as well as a hydrophilic drug of LFLX. The activation energy of partition for DM (66.8 kJ/mol) was approximately 3-fold larger than that of diffusion (21.2 kJ/mol). The results indicate that the partition for the hydrophobic drug of DM to the corneal epithelium is the primary barrier. Thermodynamic evaluation of activation energy for the drug permeation parameters is a good approch to investigate the mechanism of drug permeability.     

Resistance switch employing a simple metal nanogap junction

In recent years, several researchers have reported the occurrence of reversible resistance switching effects in simple metal nanogap junctions. A large negative resistance is observed in the I-V characteristics of such a junction when high-bias voltages are applied. This phenomenon is characteristic behaviour on the nanometre scale; it only occurs for gap widths slightly under 13?nm. Furthermore, such a junction exhibits a non-volatile resistance hysteresis when the bias voltage is reduced very rapidly from a high level to around 0?V, and when the bias voltage is reduced slowly. This non-volatile resistance change occurs as a result of changes in the gap width between the metal electrodes, brought about by the applied bias voltage.     

Preparation of calcium-doped boron nitride by pulsed laser deposition

Calcium-doped BN thin films Ca_xBN_y (x = 0.05–0.1, y = 0.7–0.9) were grown on α-Al₂O₃(0 0 1) substrates by pulsed laser deposition (PLD) using h-BN and Ca₃N₂ disks as the targets under nitrogen radical irradiation. Infrared ATR spectra demonstrated the formation of short range ordered structure of BN hexagonal sheets, while X-ray diffraction gave no peak indicating the absence of long-range order structure in the films. It was notable that Ca-doped film had 5.45–5.55 eV of optical band gap, while the band gap of Ca-free films was 5.80–5.85 eV. This change in the band gap is ascribed to interaction of Ca with the BN sheets; first principle calculations on h-BN structure indicated that variation of inter-plane distance between the BN layers did not affect the band gap. This study highlights that PLD could prepare BN having short-range structure of h-BN sheets and being doped with electropositive cation which varies the optical band gap of the films.     

Possible Alterations in ��-Synuclein, the Non-Amyloidogenic Homologue of ��-Synuclein, during Progression of Sporadic ��-Synucleinopathies

α-Synucleinopathies are neurodegenerative disorders that are characterized by progressive decline of motor and non-motor dysfunctions. α-Synuclein (αS) has been shown to play a causative role in neurodegeneration, but the pathogenic mechanisms are still unclear. Thus, there are no radical therapies that can halt or reverse the disease’s progression. β-Synuclein (βS), the non-amyloidogenic homologue of αS, ameliorates the neurodegeneration phenotype of αS in transgenic (tg) mouse models, as well as in cell free and cell culture systems, which suggests that βS might be a negative regulator of neurodegeneration caused by αS, and that “loss of function” of βS might be involved in progression of α-synucleinopathies. Alternatively, it is possible that “toxic gain of function” of wild type βS occurs during the pathogenesis of sporadic α-synucleinopathies, since tg mice expressing dementia with Lewy bodies-linked P123H βS develop progressive neurodegeneration phenotypes, such as axonal pathology and dementia. In this short review, we emphasize the aspects of “toxic gain of function” of wild type βS during the pathogenesis of sporadic α-synucleinopathies.     

Synthesis of calcium carbonate vaterite crystals and their effect on stabilization of suspension polymerization of MMA

Spherical calcium carbonate vaterite crystals were synthesized and the effect of them on stabilization of suspension polymerization of methyl methacrylate was investigated. Suspension polymerization of methyl methacrylate could be stabilized with calcium carbonate vaterite crystals and sodium dodecylbenzene sulfonate of the concentrations from 25 to 100 ppm. Poly(methyl methacrylate) beads coated with spherical calcium carbonate vaterite crystals were prepared. With an increase in the concentration of sodium dodecylbenzene sulfonate from 25 to 100 ppm, the amount of calcium carbonate vaterite crystals adhered on the surface of poly methyl methacrylate bead increased and the mean diameters of the polymer beads decreased.     

Spatial distribution of corticospinal potentials following transcranial electric and magnetic stimulation in human spinal cord

To search for concomitant anomalies among babies with congenital hypothyroidism, 120 newborn babies with confirmed congenital hypothyroidism were studied at the Veterans General Hospital, Taipei. The incidence of concomitant anomalies was estimated to be 11.67% (14/120). Among these anomalies, cardiac and gastrointestinal systems were the most commonly involved, comprising 35.7% (5/14) and 28.6% (4/14) of all anomalies, respectively. The type (i.e. agenesis, ectopia or eutopic goiter) as well as the severity of hypothyroidism were analyzed between groups of babies with or without concomitant anomalies. No differences existed between the two groups of babies regarding these two aspects.     

Simple-structure optical fiber cables manufactured withoutstranding processes

The design and characteristics of an optical-fiber cable which can be manufactured in one tandem process have been described. The structural design has been made in view of attaining stable transmission characteristics and long-term reliability. The relation between excess fiber length and cable structure was investigated. Optical loss increase due to excess fiber length was clarified. The fabricated cable has the following advantageous characteristics: (1) fiber strain did not occur when the cable was elongated by less than 0.2%; (2) the loss changes were less than 0.1 dB/km due to manufacturing and temperature changes within a range of -20-60°C; and (3) the cable exhibited excellent mechanical characteristics