Conductivity measurements on liquid sulphur

The electrical conductivity of liquid sulphur has been measured from the melting point to 900° C, evaporation of the sulphur being prevented by use of an atmosphere of argon at elevated pressure. With rise in temperature, the conductivity increases except at the polymerization maximum near 170° C where a minimum in the conductivity is confirmed. Above 400° C the plot of log versus 1/T is linear, and on the assumption that the conductivity at these temperatures is intrinsic, a value of 3.1 eV is obtained for the energy gap. Although the rise in conductivity above 400° C is accompanied by a decrease in mean chain length in the liquid, there is no simple relationship between the two properties. The behaviour of sulphur is compared with that of liquid selenium.     

Synthetic pyrethroid insecticides as replacements for chlorinated hydrocarbons for the control of wood-boring insects

The need for effective contact insecticides to replace γ-HCH and dieldrin is discussed. Four synthetic pyrethroids, permethrin, cypermethrin, decamethrin and fenvalerate were evaluated for control of the house longhorn beetle,Hylotrupes bajulus and the common furniture beetleAnobium punctatum. Permethrin was also tested againssLyctus brunneus and the termiteReticulitermes santonensis. Initial toxic effectiveness of all 4 pyrethroids was similar to or in the case of decamethrin, markedly better than γ-HCH and with the exception of fenvalerate their persistence in wood was superior to γ-HCH. They offer hopeful potential replacements for chlorinated hydrocarbons but further evaluation is necessary.     

A Digitally Controlled Stimulator for Neurophysiological Applications

A stimulator circuit is presented which is capable of generating pulse train waveforms suitable for neurophysiological experiments are available, as well as special test conditions such as dishabituation. Digital and linear integrated circuits are used to provide precise control over the stimulus parameters.     

Precise lattice parameter determination of dislocation-free gallium arsenide—II: Chemical and electrical measurements

Precise lattice parameter measurements on dislocation-free gallium arsenide were described in Part I (preceding paper).² Detailed chemical and electrical analyses of the same samples are described here. The predictions of simple chemical models are developed in the light of the analytical results. The significant observed increase in lattice parameter due to silicon doping, in contrast to the predicted decrease, is discussed.     

Noise-shaping sense amplifier for MRAM cross-point arrays

A sensing technique using a voltage-mode architecture, noise-shaping modulator, and digital filter (a counter) is presented for use with cross-point MRAM arrays and magnetic tunnel junction memory cells. The presented technique eliminates the need for precision components, the use of calibrations, and reduces the effects of power supply noise. To obviate the effects of cell-to-cell variations in the array, a digital self-referencing scheme using the counter is presented. Measured experimental results in a 180-nm CMOS process indicate an RMS sensing noise of 20 /spl mu/V for a 5-/spl mu/s sense time. Further increases in sense time are shown to increase the signal-to-noise ratio. The current used by the sense amplifier and counter was measured as 10 /spl mu/A when running at 100 MHz or 10 mA when 1000 sense amplifiers are used with a memory subarray having 1000 bitlines.     

Kreinovich,V., Lakeyev,A., Rohn,J., and Kahl,P.: Computational Complexity and Feasibility of Data Processing and Interval Computations

Reliable Computing -     

Nonlinear Mohr Envelopes Based on Triaxial Data

A substantial amount of experimental evidence suggests that Mohr envelopes of many soils are not linear, particularly in the range of small normal stresses. This departure from linearity is significant for slope stability calculations since for a wide range of practical stability problems, critical slip surfaces are shallow and normal stresses acting on such surfaces are small. The present work presents a procedure for estimating parameters of the Mohr form of Hoek and Brown empirical failure criterion, based on triaxial data. This nonlinear Mohr envelope provides significantly better representation of experimental information than the Mohr–Coulomb criterion in cases when the data set includes tests at small enough normal stress. Application of the estimation procedure to published data sets shows that effective cohesive strength of most soils is close to zero, and Mohr envelopes are continuous at the tensile strength limit.     

Dislocation identification and in situ straining in the spinodal Fe30Ni20Mn25Al25 alloy

Dislocations in the spinodal alloy Fe(30)Ni(20)Mn(25)Al(25), which is composed of alternating BCC and B2 (ordered BCC) phases, have been investigated using weak-beam transmission electron microscopy (TEM). The alloy was compressed at room temperature in an as-hot-extruded state to strains of approximately 3% for post-mortem dislocation analysis. Dislocations with a/2<111> Burgers vectors were found to glide in pairs on both {110} and {112} slip planes. TEM in situ straining experiments were also performed on both the as-extruded alloy and an arc-melted alloy. The in situ straining observations confirmed that dislocations were able to pass between both spinodal phases. Partial dislocation separations were relatively wide in the BCC phase and narrow in the B2 phase. Dislocation glide, as opposed to twinning (both of which have been observed in other BCC-based spinodals), was also found to be the only room temperature deformation mechanism.