On the superconductivity in β-beryllium and related phases

Two high temperature beryllium allotropes have been stabilized at room temperature through the addition of transition elements. Superconductivity has been observed in almost all of them. Beryllium films reported superconducting in the past appear in all probability to require the presence of transition element impurities, in order to show the phenomenon.     

Technology showcase electronic penetrometer for field tests

The design and construction of a cone penetrometer for field use is described. The penetrometer is mounted on a frame to which two wheels are fitted for towing the device from one test site to the next. An electric motor drives the penetrometer during the test and simultaneous readings are performed of both cone depth and penetration resistance. The device weighs 70 kg and the maximum force on the cone typically exceeds 1.2 kN. The acquired data are transferred to a microcomputer and after each penetration the result is presented to the operator in graphic form. The microcomputer is equipped with a fairly large RAM memory which serves as storage medium for data during measuring work. Afterwards, data are easily moved to a mainframe computer for analysis.     

Electron-transfer reactions and conformational changes associated with the reduction of substituted bianthrones

The electrochemical reduction of several substituted bianthrones is similar to that of the parent compound. 3,3′-Dimethylbianthrone (II), 3,3′-di-n-heptylbianthrone (III). 3,3′-dimethoxybianthrone (IV) and 1,1′-dimethylbianthrone -(V) were studied in dimethylformamide using cyclic voltammetry and transmission mode spectroelectrochemistry. For each compound the low temperature A form is reduced in a two-electron irreversible reaction to a twisted dianion, B^2?. Upon oxidation, B^2? forms first B, then B, whose spectral properties are identical to those of the high-temperature thermochromic form of the bianthrones. Rate constants for the B-A reaction were determined for each compound. The reduction of 2,3,2′,3′-dibenzo-7,7′-dimethylbianthrone (VI) showed somewhat different features which were tentatively interpreted in terms of redox catalysis.     

The effect of sintering on the mineralogy of a synthetic heavy mineral concentrate base prepared by mixing together specpure oxides

Synthetic heavy mineral concentrate standards for calibrating a d.c. arc emission spectrometer were prepared from specpure oxides and compounds. X-ray diffraction and scanning electron microscope studies of the heat-treated synthetic matrix showed that minerals which occurred in natural heavy mineral concentrates were formed. An optimum sintering time of 4 hr was established by monitoring X-ray diffraction peaks of minerals undergoing alteration or being formed in the synthetic base.     

Anomalous low energy Kα lines in Al and Si from high energy oxygen bombardments

Three prominant peaks are observed in Kα X-ray spectra of both Al and Si at energies below the characteristic Kα_1,2 lines. These emission lines were produced by 30 MeV oxygen bombardment and recorded with a crystal spectrometer. The exact origin of these lines is not understood.     

Threshold electron impact excitation of argon in the region of the M1 edge

The threshold electron impact spectrum of argon has been obtained in the energy range 24–35 eV using the sulphur hexafluoride electron scavenging technique. Structure is observed which may be due to single excitation, double excitation and temporary negative ion states.     

Beta relaxation in the shear mechanics of viscous liquids: Phenomenology and network modeling of the alpha-beta merging region

The phenomenology of the beta relaxation process in the shear-mechanical response of glass-forming liquids is summarized and compared to that of the dielectric beta process. Furthermore, we discuss how to model the observations by means of standard viscoelastic modeling elements. Necessary physical requirements to such a model are outlined, and it is argued that physically relevant models must be additive in the shear compliance of the alpha and beta parts. A model based on these considerations is proposed and fitted to data for Polyisobutylene 680.     

A combined measurement of thermal and mechanical relaxation

In order to describe relaxation the thermodynamic coefficient can be generalized into a complex frequency-dependent cross response function. We explore theoretically the possibility of measuring for a supercooled liquid near the glass transition. This is done by placing a thermistor in the middle of the liquid which itself is contained in a spherical piezoelectric shell. The piezoelectric voltage response to a thermal power generated in the thermistor is found to be proportional to but factors pertaining to heat diffusion and adiabatic compressibility κ_S(ω) do also intervene. We estimate a measurable piezoelectric voltage of 1 mV to be generated at 1 Hz for a heating power of 0.3 mW. Together with κ_S(ω) and the longitudinal specific heat c_l(ω) which may also be found in the same setup a complete triple of thermoviscoelastic response functions may be determined when supplemented with shear modulus data.