Materials Literature
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The present review is devoted to discussion of the principal stages of development of mirror electron microscopy. In the mirror electron microscope (MEM) the electron beam is reflected in a retarding electric field near the sample surface, and as a result the object being studied is not subjected to bombardment by the…
Light scattering has been used to study phase separation near the critical point in a binary mixture of methanol and cyclohexane. The intensity measurements are in conformity with the spinodal decomposition theory of Cahn. Measurements were also made of the spectral width of the scattered light in the phase separation…
The previously termed "anomalous" properties of the various polytypes of ${d}^{1}$ Ta${\mathrm{S}}_{2}$, Ta${\mathrm{Se}}_{2}$, etc. are attributed to charge-density waves, their periodic structure distortions, and the superlattices they induce.
The paramagnetic spectra of Gd 3+ and Fe 3+ in monoclinic zirconia single crystals have been investigated in the Q-band. In both cases a unique type of defect was observed, thus confirming that the trivalent ion has no O 2- vacancy in nearest-neighbour positions. The spectra were fitted to the most general spin hamilt…
The optical absorption coefficients and the temperature dependence of the edge in amorphous As 2 S 3 have been measured at temperatures down to 10 K. The temperature coefficients of the gap at a fixed absorption level ( delta E/ delta T) alpha , can be separated into two components. The first is attributed to electron…
The published data on the specific heat and susceptibility of Fe(NH 4 ) 2 (SO 4 ) 2 6H 2 O are analysed to find the energies, wavefunctions and magnetic axes appropriate to the Fe 2+ ions at temperatures below 20 K. Two ambiguities are solved by experiment. The dependence on temperature of the crystal susceptibility a…
Data necessary to determine the activation energy and volume of the creep process in zinc have been obtained in the temperature range 1.5 to 80 °K by means of a differential technique. While calculating the activation parameters the influence of quantum phenomena on fluctuation-induced dislocation motion over local ba…
The authors have discussed earlier the photomagnetoelectric effect in graded-band-gap semiconductors assuming symmetrical band-edge gradients. The present paper rewrites the continuity equation under asymmetric band-edge gradients, and includes the effects of position-dependent minority carrier lifetime, electron and…
The heat and entropy of the transformation ice III–IX has been measured by a differential calorimetric technique as −0.32 cal K−1 mol, compared with the value −0.805 cal K−1 mol expected if ice III were fully disordered and ice IX were fully ordered within the limitations of the ice rules. It seems likely that there i…
Contrary to recent claims, no correlation of useful predicting power exists between the tendency of a nematic liquid to align transverse to a solid surface and the difference between the surface free energies of the nematic liquid and of the substrate. Observations that lead to this conclusion are reported for systems…
The ion-pair interaction potentials obtained by using the modle presented in our previous paper are applied to some ionic crystals. The calculated lattice properties of alkali-halide and alkaline-earth-dihalide crystals agree quite well with experimental data. The polymorphic transitions of alkali-halide crystals at h…
We determine bandwidths and critical-point positions with respect to the valence-band edge for the valence bands of several extensively studied semiconductors (with an accuracy of about 0.3 eV) by using photoemission densities of states derived from photoemission spectra obtained in the 24-78-eV photon energy range. T…
Electronic transport has been investigated in ${\mathrm{As}}_{2}$(${\mathrm{Se}}_{1/3}$ ${\mathrm{Te}}_{2/3}$${)}_{3}$ and Ge(${\mathrm{Se}}_{1/3}$${\mathrm{Te}}_{2/3}$ ${)}_{2}$ amorphous semiconductors through measurements of photoconductivity, optical absorption, dark conductivity, thermoelectric power, and field e…
Mutant adenylosuccinate lyases of Bacillus subtilis were prepared by site-directed mutagenesis with replacements for His141, previously identified by affinity labeling as being in the active site [Lee, T. T., Worby, C., Dixon, J. E., and Colman, R. F. (1997) J. Biol. Chem. 272, 458-465]. Four substitutions (A, L, E, Q…
The spectra of corona discharges in air at atmospheric pressure, in a 0·6 m point-plane gap under positive impulse voltage, have been measured in the near-ultraviolet and visible regions. Two types of corona discharges have been investigated: the first corona which develops from the electrode tip; and the leader coron…
A technique is presented which enables the recovery of the probability distribution for single scattering from plural-scattering electron energy loss data. Neither the scattering parameter t/λ nor details of the component processes need be known. The computational method uses Fourier series in order to overcome a numb…
Luminescence at 368 nm from crystals containing ${\mathrm{Eu}}^{2+}$ exhibits the small spectral shifts from host to host typical of a parity-forbidden rare-earth transition, and yet has the emission oscillator strength ($f\ensuremath{\gtrsim}1$) of a highly allowed transition. It is improbable that this anomaly can b…
In the layer structure MoS 2 , the oscillatory inter-band magneto-optic absorption has revealed a mass ratio of the order of 0.01. Theory is presented to show that this mass may be associated with the H-point of the Brillouin zone. Moreover, it is proposed that the origin of the mass is an instability of the equally-s…
Comparative powder Raman studies on zircon (ZrSiO 4 ) and hafnon (HfSiO 4 ) are reported. It is shown that rotational and translational modes of the same symmetry can be identified by comparing the spectra of these two crystals in a similar way as could be done by means of isotopic substitution. The authors also show…
We report a method for operating twisted nematic devices with rapid turnoff times by using a nematic material with variable dielectric anisotropy. These are useful as fast shutters and colour switches, and can be operated at a 25 Hz repetition rate.