Comparison of the Galactic Cepheid Open Cluster and Surface Brightness Distance Scales

We compare the best determined Baade-Wesselink (BW) period-luminosity (PL) relation for 100 galactic Cepheids to the PL relation derived for 32 open cluster and association Cepheids by the ZAMS-fitting method. Eighteen stars in common lead to the conclusion that BW and ZAMS-fitting distances can agree to better than 0.1 mag, after proper allowance of systematic effects in both methods.

Banded Contour Charts

The proposal by A. J. Wright (this Journal, vol. 34, no. 1, p. 142) that banded contour charts should be introduced, appears attractive at first sight. It appears to provide immediately recognizable indication of safe areas for the navigation of those ships whose draught is within certain limits. However, I feel that the system as proposed suffers from some major weaknessesAllowance for height of tide. Tidal ranges of several metres are by no means uncommon. Failure to make proper allowance for this could result in a wrong assessment by the user of where navigationally safe water lies. Such tidal ranges frequently occur in areas of high-density traffic. Here, the pressures on the mariner are such that the temptation to ‘eye-ball the navigation’ is greatest – yet it is in such areas that positional accuracy based on sound chartwork procedures is vital.

The Departure From Nucleate Boiling in Rod Bundles During Pressure Blowdown

Tests were performed in a high pressure heat transfer loop to determine the behavior of transient DNB during pressure blowdown in rod bundles. Water flowed along a 21 rod, 5-ft-long electrically heated rod bundle with a radially nonuniform heat flux distribution. Both steady-state and transient DNB tests were conducted over the following range of operating parameters: 1 Pressure—750 to 1500 psia; 2 Inlet temperature—480 to 540 deg F; 3 Mass velocity—1 × 106 to 3 × 106 lb/hr ft2; 4 Grid configurations—2. The data were analyzed using calculated subchannel local velocity and enthalpy as a function of time with proper allowance for the mixing and cross flow within the bundle. Results show that the inception of transient DNB during pressure blowdown can be predicted on the basis of steady-state data.

Effect of temperature on the Hg6(3P1) photosensitized decomposition of propane

The relative yields of n-propyl and isopropyl radicals from the primary step of the Hg6(3P1) photosensitization of propane have been measured as a function of temperature between 0 and 202 °C. The ratio of n-propyl to isopropyl yield increases with increasing temperature according to the equation[Formula: see text]The primary yields of the propyl radicals were determined from the measured yields of the hexane and pentane products in ethylene scavenging experiments and from the yields of the isomeric hexane products in pure propane, after making proper allowance in the kinetics for all secondary reactions.

Paper 1: Skidding of Vehicles Due to Locked Wheels

The present paper combines older work by the first author with more recent research by the second author. A basic simplifying assumption of the entire investigation is that the height of the centre of gravity of the vehicle above the road surface has been neglected, such that the vertical wheel reactions remain constant. In the earlier analysis it was also assumed that the drift angle of rolling wheels under lateral forces may be neglected, and the possibility of lateral skidding of rolling wheels was also ignored. The equations of motion may then be reduced to a comparatively simple non-linear second-order system of ordinary differential equations. The equations may be given a non-dimensional form in several ways, and two such methods are employed to reveal some characteristic properties of the skidding phenomenon. The more recent analysis has been refined considerably by proper allowance for the drift angle of rolling wheels under the action of lateral forces, for the possibility of sideways skidding of rolling wheels, and for braking action on the rolling wheels. The equations of motion then reduce to a third-order system which may be solved in closed form in the linear case of small deviations from a rectilinear motion. It appears that the drift angle of rolling wheels under the action of lateral forces leads to a small increase of the critical speed and to a significant reduction of the danger when the critical speed is exceeded. The non-linear equations for larger deviations from a rectilinear motion cannot so easily be discussed qualitatively, but detailed results have been obtained by means of a digital computer.

INFRARED ABSORPTION LINES IN BORON-DOPED SILICON

In boron-doped silicon, optical absorption takes place through the excitation of bound holes from the ground state to excited states. This leads to a line spectrum. Because of a lack of sufficient resolution and a failure to make proper allowance for line distortion by the finite spectrometer slit width, previous authors gave a misleading picture of the low-temperature half-width, the temperature dependence of this half-width, and the onset of concentration broadening at low temperatures.New experimental data are presented and explained by introducing the mechanism of statistical Stark broadening due to ionized impurities, and by modifying Baltensperger's (1953) theory for concentration broadening. At low impurity concentration the width is attributed to phonon broadening (Barrie and Nishikawa 1963) and internal strains (Kohn 1957).

Electron capture by fast protons and α-particles in hydrogen

Cross-sections are calculated for the accidental resonance reaction, He 2+ + H(ls) -> He + (2s or 2p) + H + , and the non-resonance reaction, H + + H (ls)-> H(2s or 2p) + H + by means of the method due to Bates in which account is taken of the non-orthogonality of the wave functions describing the initial and final states. Proper allowance is made for the effects of distortion and of momentum transfer. The calculations are carried out for incident ion energies in the range 25 to 800 keV. In the accidental resonance case, the cross-section is small at low velocities of relative motion, and tends rapidly towards zero as the velocity is decreased in accordance with the prediction of Bates & Lynn. In all processes investigated the effect of distortion is considerable. Using the results of McCarroll & McElroy and of McCarroll for capture into the ground states of He + and H, the cross-sections for capture into all states are estimated. Comparisons are made with the experimental data of Fite, Smith & Stebbings for the incident alpha particle case and with that of Fite, Stebbings, Hummer & Brackman for the incident proton case. The highest energy for which cross-sections are measured in either case is however only 40 keV.

TEMPERATURE DEPENDENCE OF ABSORPTION LINE WIDTH IN BORON-DOPED SILICON

In boron-doped silicon, optical absorption takes place through the excitation of bound holes from the ground to excited states. This leads to a line spectrum. Due to a lack of sufficient resolution and a failure to make proper allowance for line distortion by the finite spectrometer slit width, previous authors gave incorrect values for both the low temperature half-width and the temperature dependence of this half-width. In re-evaluating these quantities, two of three previously known lines were found to be doublets. It is found that presently available theory does not explain the results adequately.