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Notes: Hydrogenated amorphous germanium carbide (a-Ge1−xCx@B:H ) films were prepared by rf sputtering, at various rf power levels and mixtures of Ar, H2, and propane. As in the case of a-Si:H rf sputtered under similar conditions, the concentration of Ge–H bond, as determined by the IR absorption spectra, and the Tauc determined optical gap, generally increase as the rf power is decreased. The optical gap of the a-Ge1−xCx@B:H films range from 0.85–2.3 eV, and the electron-spin-resonance defect spin densities from 6.5×1017 to 3×1018 spins/cm3. Auger spectroscopy was used to determine the C/Ge ratio and indicated that in most of the samples, this ratio was (approximately-less-than)0.15. Isochronal annealing up to 400 °C indicated that (i) Ge-C segregation effects already initiated at 100 °C are greatly enhanced above 300 °C, (ii) at 300 °C C–H bonds are formed at the expense of Ge–H ones, and (iii) all of the hydrogen bonded to Ge and most of that bonded to carbon evolve out of the sample at or slightly below 400 °C.

Notes: In this paper a new circuit design for automatic electrostatic vibroscopes is presented. Previously, the component which stabilized the self-oscillatory motion of the filament in the feedback loop of electrostatic vibroscopes was a negative temperature coefficient thermistor. In the present system this device is replaced with a programmable analog compander. This modification represents an improvement because response time is faster, the steady-state conditions are more stable, and the overall performance of the vibroscope is less susceptible to errors caused by changes in environmental conditions.

Notes: Abstract Vicia faba plants grown under water deficit were found to have guard cells considerably smaller than those of plants grown under well-watered conditions. Stomala of plants adapted to drought conditions have been observed in past studies to maintain opening at plant water potentials lower than those of plants not so adapted. By employing the geometric interpretation of the mechanical advantage (Wu, Sharpe & Spence, 1985), an anatomical/mechanical basis was found that helps explain how such opening in drought conditions can occur. The geometry and resulting mechanical properties of small stomata, in contrast to larger stomata, give them the capability of opening or maintaining open pores with lower guard cell turgor pressures, relative to the turgor of the surrounding epidermal cells.

Notes: Abstract. Previous mathematical analyses of stomatal mechanics have demonstrated, and experimental measurements have confirmed, that the turgor-generated force of the epidermal cells dominates that of the guard cells in determining aperture. DcMichele & Sharpe (1973) termed the phenomenon the mechanical advantage of the epidermal cells, while Cooke et al. (1976) expressed it as an antagonism ratio. Both of these formulations, however, have theoretical or practical limitations. This study presents a biophysical analysis demonstrating that the effective forces in the stomatal system may be studied in terms of simple stomatal geometry. From this analysis, the mechanical advantage can be redefined and interpreted based upon simple geometric relationships calculated from measurable anatomical dimensions.

Notes: The relation between the form of the scattering particles and the outer part of the small-angle X-ray scattering curve has been studied. The particles are assumed to be independent, identical, and randomly oriented and to have a uniform electron density and a smooth, strictly convex boundary surface. The electron density of the solvent is also assumed to be uniform. As earlier calculations by the authors and others have shown, the effects of the particle shape on the scattered intensity can often be conveniently described by a function called the chord, or intersect, distribution G(M). A chord, or intersect, is a straight line that has both ends on the particle boundary surface, and G(M) is defined to have the property that G(M)dM is the probability that the chord length will lie between M and M+ dM. The outer part of the scattering curve is shown to depend on the form of G(M) only in the neighborhoods of M = 0 and of any M values at which G(M) or G′(M) are discontinuous. Methods are developed for finding where these discontinuities occur and for calculating the form of G(M) in the neighborhood of these M values. In the outer part of the scattering curve, the intensity I(h) is shown to have the limiting form I(h) = \pi I_{e}\rho^{2}h^{-4}\Bigg[2A+j_{-2}h^{-2}+ \sum_{i=0}^{N+1} j_{i} {{sin (hD_i + \phi _{i})}\over (hD_{i})^{\mu}_{\kern4pt i}}\Bigg] where h = 4πλ −1 sin (&thgr;/2), 2 is the X-ray wavelength, &thgr; is the scattering angle, Ie is the intensity scattered by a single electron, A is the particle surface area, the Di are the values of M at which G(M) or G′(M) is discontinuous, and j−2 and the ji, &phgr;i, and μi are quantities which can be calculated from the principal curvatures and other properties of the surface at the two points where it contacts the chord with length Di. The values of the μi are shown to lie in the interval 0 ≤ μi ≤ 1. In this equation the assumption is made that only the term or terms which vanish least rapidly as h increases are to be retained. In addition to the assumptions which conventionally are made in the analysis of the small-angle X-ray scattering from dilute suspensions, the limiting expression for the intensity for large h requires only that the particle boundary be smooth and strictly convex. This approximation is useful for determining the effect of the particle shape on the outer part of the scattering curve. In addition, the equation can be employed for numerical calculations for large h, where other methods of computation often are unwieldy or inapplicable.

Notes: An expression is developed for the intersect distribution function G(M) for an ellipsoid. The intersect distribution is useful for studying how the intensity of small-angle X-ray scattering is affected by the shape of the scattering particles in suspensions of identical, independent, randomly oriented particles when both the particles and the solvent have constant electron densities. The expression for G(M) for an ellipsoid can be employed in numerical calculations of the scattered intensity. In addition, the techniques and concepts developed to obtain G(M) for an ellipsoid can be useful in finding this function for other particles less symmetrical than a sphere or a solid of revolution.

Notes: A new method has been developed for calculating the intersect distribution function G(M) which is used in the theory of the small-angle X-ray scattering from suspensions of identical non-interacting randomly oriented particles with uniform electron density. Intersects, or chords, are straight lines which have both ends on the particle boundary, and G(M)dM is the probability that an intersect has a length between M and M+ dM. Since G(M) can be shown to contain all information about these suspensions which is obtainable from small-angle X-ray scattering measurements, the intersect distribution function can be used to study the relation between the scattered intensity and the particle shape and dimensions. The new calculation technique, which employs some results from integral geometry, is much simpler than methods previously used to find G(M) or the characteristic function γ0(r), which contains essentially equivalent information. For particles with a smooth convex boundary, the first two terms are obtained in the expansion of G(M) in powers of M and are evaluated for a plane lamina and a three-dimensional particle. The approximate expressions for G(M) are used to determine some properties of the scattered intensity in the outer part of the scattering curve.