Athermal silica-based arrayed-waveguide grating multiplexer

A temperature dependent channel wavelength shift in a silica-based arrayed-waveguide grating multiplexer is successfully suppressed from 0.95 to 0.05 nm in the 0-85°C temperature range, which means that it can be used in practical WDM systems without the need for temperature control     

Flexural properties of moldings of rigid polyurethane made by reaction injection molding

Flexural properties of moldings made by Reaction Injection Molding (RIM), which are structural foams consisting of high density skin and low density core, were investigated by three-point bending tests. Two failure modes were observed in bending tests of the moldings made by RIM, and they are classified as follows according to the density ratio of skin layer to core layer: the opposite side of the skin layer to which load was subjected failed by tensile stress: and the same side of the skin layer to which load was subjected failed by compressive stress, causing wrinkling or buckling. Then the conventional composite beam theory was applied to the former failure mode and Hoff s buckling theory to the latter, and equations were derived to predict the flexural properties of the structural foams, which involved buckling from the flexural properties of solid construction. In addition, it has been shown that there exists a density distribution that maximizes the flexural strength of the moldings made by RIM with a given overall density. The results obtained here should be useful to the optimum structural design of moldings made by RIM.     

Patterns of expression for the mRNA corresponding to the four isoforms of phospholipase Cbeta in mouse brain

Ligand binding to neurotransmitter and hormone receptors which couple to the Gq subclass of GTP-binding protein leads to the activation of phospholipase Cbeta (PLCbeta) which hydrolyses phosphatidyl-inositol 4,5-bisphosphate, yielding a pair of second messengers, diacylglycerol and inositol 1,4,5-trisphosphate (IP3). The expression of PLCbeta1-4 mRNAs was comparatively examined by in situ hybridization in the mouse brain. In adults, PLCbeta1 mRNA was expressed predominantly in the telencephalon, including the cerebral cortex, hippocampus, amygdala, lateral septum and olfactory bulb, with little expression in most thalamic nuclei. PLCbeta2 mRNA was distributed in the white matter, suggesting its expression in non-neuronal cells, most likely oligodendrocytes. PLCbeta3 mRNA was specifically expressed in cerebellar Purkinje cells. The highest levels of PLCbeta4 mRNA were detected in Purkinje cells. High levels of PLCbeta4 mRNA were also found in the thalamus and medial septum, whereas weak signals were detected in most telencephalic regions, thus showing an expression pattern almost reciprocal to that of PLCbeta1 mRNA. During development, such characteristic regional expression of PLCbeta1 and PLCbeta4 were observed starting in late foetal stages, while specific expression of PLCbeta2 and PLCbeta3 appeared in early postnatal stages. We conclude that despite the existence of four PLCbeta isoforms, only one or two of them is expressed in individual neurons and glial cells. The distinct expression of PLCbetas provides a molecular basis for analysing the nature of the specific signal transduction pathway leading to the production of diacylglycerol and IP3 in distinct cell types and in different regions of the brain.     

Changes of biochemical markers during fracture healing

Clinical diagnosis of canine nasal mite (Pneumonyssoides caninum) infection is difficult due to the mite's location in the caudal nasal cavity and frontal sinuses. The current study was performed to evaluate the efficacy of milbemycin oxime in treating dogs with nasal mite infection. A prospective open uncontrolled study included 20 dogs with case histories indicating possible nasal mite infection. Inclusion criteria consisted of either nasal mites being demonstrated (group 1, four dogs), or suspicious clinical signs with no other apparent causes, combined with eosinophilia (group 2, 16 dogs). Milbemycin oxime 1 mg/kg was given orally three times at 10-day intervals. In 17 (85 per cent) dogs, clinical signs resolved completely following milbemycin therapy; within 10 days of the first treatment in 13 cases (group 1, four dogs; group 2, nine dogs) and within 14 days in four cases. In the remaining three dogs clinical signs persisted but were diminished.     

Novel UV absorbers prepared from 2,4-dihydroxybenzophenone and hexachlorocyclotriphosphazene

The UV-stabilizing ability and thermal loss from the polystyrene film of novel UV absorbers, 2-[(3-hydroxy-4-benzoyl) phenoxy] pentachlorocyclotriphosphazene (HBPC) and hexakis[ (2-hydroxy-4-benzoyl) phenoxy] cyclotriphosphazene (HBPP), were investigated. The UV-stabilizing ability of HBPC estimated by the formation of carbonyl groups in polystyrene was comparable to that of 2,4-dihydroxybenzophenone (DHB), suggesting that the phosphazene moiety does not affect the efficiency of the stabilizing ability of DHB units. No significant difference of efficiency per stabilizing units between HBPC and HBPP was observed. HBPC and HBPP are noteworthy for their low thermal losses from the polystyrene film, i.e., the thermal loss of HBPP was completely suppressed and the diffusion coefficient of HBPC at 160°C was two orders of magnitude smaller than that of DHB. The thermogravimetric analysis and differential scanning calorimetry measurement showed that HBPC and HBPP are nonvolatile and stable up to 230 and 300°C, respectively. © 1993 John Wiley & Sons, Inc.     

Large magnetoresistivity of sputtered Al-(O or N)-Bi alloys

Application of the sputtering technique to (Al₂O₃)_xBi_100–x and (AIN)_x Bi_100–x (x = 0 to 100%) has been found to result in the formation of a duplex material consisting of hexagonal bismuth particles dispersed finely and homogeneously in amorphous Al_xO_y and Al_xN_y matrices. The particle size and interparticle distance of the bismuth phase were about 5 to 140nm and 5 to 35 nm. The duplex alloys have high electrical resistivities ranging from 1.82 × 10³ to 3.16 × 10⁵ cm combined with a negative temperature-dependent resistivity of 148 to 342% of ₂₇₃. Furthermore, all the Al-O-Bi and Al-N-Bi alloys have been found to exhibit a positive magnetoresistive change and the maximum value, (H), at 4.2 K and 7.5T reaches 5.85 × 10⁴ cm for (Al-O)_65.7Bi_34.3 and 1.99 × 10⁵ cm for (Al-N)_69.7 Bi_30.3. The large magnetoresistivities are probably due to the unique sputtered structure consisting of metallic bismuth particles with a long mean free path of electrons embedded finely and homogeneously in amorphous Al_xO_y or Al_xN_y matrix, resulting in the large difference of the relaxation times (different mobilities) of electron carriers. It has thus been demonstrated that the oxide- or nitride-based composite materials exhibiting large magnetoresistivities, which cannot be achieved in metallic composite materials, are obtained by sputtering simultaneously Al₂O₃ or AIN and bismuth which is immiscible to aluminium.     

Microstructure and mechanical properties of metastable lath martensite wires in the Fe-Ni-Cr-Al-C system produced by melt spinning in rotating water

Metastable lath martensite ( _L ) phase wires with high strengths have been produced in the Fe-Ni-Cr-Al-C alloy system by melt spinning in rotating water. These wires have a circular cross section and a white lustre and the wire diameter is in the range of 100 to 140m. The width and length of each lath in the _L phase are as small as about 0.3 and 2m, respectively. The _y, _f and _p are about 900 and 1650 MPa and 2.0% for the _L wires. The subsequent annealing causes an increase in _p as well as _y and _f and the attained values are about 1000 and 1700 MPa and 3.0% for Fe-10Ni-10Cr-6.5 Al-1.0C wire annealed at 773 K for 1 h owing to the precipitation strengthening of a very fine unidentified carbide and to a high density of dislocations and lath boundaries in the _L phase. Further annealing causes a significant decrease in _p through decomposition of _L to+M₇C₃+M₂₃C₆. Therefore, the high strength combined with relatively good ductility for the _L wires is interpreted as due to the suppression of the phase transformation of _L to a mixed structure of+M₇C₃+M₂₃C₆ by melt quenching.