On the electric resistance of solid soap

Summary Electrical resistance values are reported for soaps of various moisture contents. Marked changes in resistance were found at 40–50°C. Below this temperature the logarithm of conductivity is a linear function of inverse temperature, and the slope of the curve is practically independent of water content. Above 40° resistance is markedly affected by the water content of the soap. For soaps containing 12–30% water, heating and cooling curves show definite maxima and minima in electrical resistance values. This effect is less obvious in soaps containing more than 30% water. The phase transition points estimated from resistance measurements are in good agreement with those deduced from other physical measurements.     

Novel free-space optical interconnection architecture employing array devices

A novel architecture for free-space optical interconnections is proposed. The architecture named LISA (lightwave interconnections employing spatial addressing) enables the construction of a high speed and large fanout 1*N switch. A 1*16 LISA switch is implemented and demonstrated at 200 Mbit/s.<>     

Real-time digital simulator for power system analysis on ahypercube computer

A digital simulator based on a hypercube-type massively parallel computer, the NCube2, has been developed. The simulator features: real-time simulation of a large power system which covers transient stability through long-term behavior with constant accuracy level in root mean square values; user-friendly man-machine interfaces which mimic the actual operating environment including interactive setting of several system parameters and real-time data presentation on a CRT; and high-speed A/D (analog to digital) converters, D/A (digital to analog) converters, and D/IO (digital input and digital output) interfaces are used to connect the digital simulator (power system dynamic model) to actual equipment. The authors describe the basic characteristics of the digital simulator and present results obtained in real-time simulations     

1.55 mu m polarization-insensitive high-gain tensile-strained-barrier MQW optical amplifier

A polarization-insensitive semiconductor optical amplifier was realized at a wavelength of 1.55 mu m. The active layer consisted of a tensile-strained-barrier multiple quantum well (MQW) structure. At a driving current of 150 mA, no dependence of the saturation characteristics on modes was obtained. The saturation output power at which the gain decreases 3 dB is 13.3 dBm. A slightly higher saturation output power of 14 dBm was measured at a driving current of 200 mA. No large difference was observed between transverse-electric (TE) and transverse-magnetic (TM) modes. A high gain of 27.5 dB at a polarization sensitivity of 0.5 dB and a high saturation output of 14 dBm were realized simultaneously by using a longer device with reduced residual facet reflectivities.<>     

Development of lung and soft tissue substitutes for photons

The use of solid tissue substitutes is a well-accepted and common practice in dosimetric studies and in the production of counting standards for radiological protection. However, only a few solid tissue substitutes simulating a particular body tissue with respect to a set of physical characteristics are commercially available. Hence, we have developed polyurethane-based tissue substitutes simulating soft tissue, muscle, muscle-adipose mixture tissue (90% muscle + 10% adipose), brain, cartilage, larynx, thyroid, trachea, liver, kidney, skin and lungs. Tissue substitutes for photons were formulated using the basic data method together with an equation for calculating the optimum relative mass of corrective additives. The tissue substitutes were formulated to be phantom materials in the photon energy range of at least 8 keV-10 MeV. In particular, they were designed to match the body tissues with linear attenuation coefficients for low photon energy (13.6, 17.2 and 20.2 keV from 239Pu) and to have the same mass densities as the tissues. The tissue substitutes developed in the present study were examined for the photon transmissions using 16.6 keV KX rays from 93Nb(m). The experimental transmission curves of the tissue substitutes were found to be consistent with those derived from data on the body tissues in ICRP Publication 23. It was found that the developed tissue substitutes are suitable to the corresponding body tissues defined by ICRP.     

Characterisation of radionuclides formed by high-energy neutron irradiation

The physicochemical properties of radionuclides suspended in the air are important parameters in order to evaluate internal doses due to the inhalation of the airborne radionuclides and to develop the air-monitoring system in high-energy proton accelerator facilities. This study focuses on the property of radioactive airborne chlorine (38Cl and 39Cl) and sulphur (38S) produced in Ar gas by irradiation with high-energy neutrons. As a result of the irradiation of a mixture of Ar gas and dry air, 38Cl and 39Cl existed as non-acidic gas and 38S was present as acidic gas. Furthermore, it has been found that in the high-energy neutron irradiation of aerosol containing Ar gas, the higher the amount of radioactive aerosols, the lower will be the amount of radioactive acidic gas.     

Bhc-cNMPs as either water-soluble or membrane-permeant photoreleasable cyclic nucleotides for both one- and two-photon excitation

Cyclic nucleoside monophosphates (cNMPs) play key roles in many cellular regulatory processes, such as growth, differentiation, motility, and gene expression. Caged derivatives that can be activated by irradiation could be powerful tools for studying such diverse functions of intracellular second messengers, since the spatiotemporal dynamics of these molecules can be controlled by irradiation with appropriately focused light. Here we report the synthesis, photochemistry, and biological testing of 6-bromo-7-hydroxycoumarin-4-ylmethyl esters of cNMP (Bhc-cNMP) and their acetyl derivatives (Bhc-cNMP/Ac) as new caged second messengers. Irradiation of Bhc-cNMPs quantitatively produced the parent cNMPs with one-photon uncaging efficiencies (Phiepsilon) of up to one order of magnitude better than those of 2-nitrophenethyl (NPE) cNMPs. In addition, two-photon induced photochemical release of cNMP from Bhc-cNMPs (7 and 8) can be observed with the two-photon uncaging action cross-sections (delta(u)) of up to 2.28 GM (1 GM=10(-50) cm(4) s photon(-1)), which is the largest value among those of the reported Bhc-caged compounds. The wavelength dependence of the delta(u) values of 7 revealed that the peak wavelength was twice that of the one-photon absorption maximum. Bhc-cNMPs showed practically useful water solubility (nearly 500 microM), whereas 7-acetylated derivatives (Bhc-cNMPs/Ac) were expected to have a certain membrane permeability. Their advantages were demonstrated in two types of biological systems: the opening of cAMP-mediated transduction channels in newt olfactory receptor cells and cAMP-mediated motility responses in epidermal melanophores in scales from medaka fish. Both examples showed that Bhc and Bhc/Ac caged compounds have great potential for use in many cell biological applications.     

Very wide spectrum multiquantum well superluminescent diode at 1.5 mu m

An InGaAs-InGaAsP multiquantum well superluminescent diode (SLD) emitting at 1.5 mu m has been studied. Broad spectral widths exceeding 100 nm are achieved under a wide injection current range. The maximum spectral width is 170 nm, which gives a calculated coherence length of 13 mu m, approximately one third that of 1.5 mu m conventionally available bulk SLDs.<>