The influence of adsorption and step reconstruction on the growth and etching vectors of silicon (111)

The lateral growth and etching vectors which are published for silicon and related materials appear to differ between the vacuum (or gas)-solid systems and the liquid-solid system: the vectors are 180° rotated with respect to each other. A theoretical analysis based on a first order broken bond model and assuming either unaffected dangling bonds or completely saturated dangling bonds, leads to growth and etching vectors consistent with the vector orientations observed in the liquid-solid system. When step reconstruction is taken into account a similar treatment leads to the 180° rotated vector orientations which are found in the vacuum (or gas)-solid systems.     

A high sensitivity DC thermometric circuit using operational amplifiers and a hybrid combination of NTC and PTC thermistors

Equations predicting the response of thermometric circuits constructed from operational amplifiers with NTC and NTC—PTC hybrid thermistors are derived and tested. Sensitivities and time constants were determined experimentally and are compared with theoretical predictions. The circuit with the NTC—PTC hybrid is characterized by greater sensivity than a NTC circuit and greater linearity than a PTC circuit.     

Ghost interactions from auxiliary fields in d = 11 supergravity

By introducing auxiliary boson fields in 11-dimensional supergravity we can close the commutator linearly on the gravitino. Although the algebra is not closed on the boson fields, the auxiliary fields replace the four-ghost interactions.     

Relativistic kinetic theory of quantum systems: III. Transport equation for a neutrino system

On the basis of the quantum-mechanical equations of motion and the statistical assumption that dynamical correlations present in the initial state may be ignored, a kinetic equation for a dilute neutrino system is derived. If the system is sufficiently uniform in space this equation reduces to the relativistic Boltzmann equation for massless particles with a quantum-mechanical transition probability.     

The determination of selenium in water samples from the environment

A method for the determination of selenium by preconcentration and thermal neutron activation is presented. Selenium is adsorbed on active charcoal after reduction to the elemental state. By varying the conditions of the reduction, it is possible to measure the total selenium content and tetravalent selenium separately. The contribution of hexavalent selenium is obtained by substraction. The lower limit of determination is 5 ng°1⁻¹. About 40 samples per day can be handled by one analyst. The preconcentration can be performed at the sampling site resulting in samples, which can be stored easily for later analyses by neutron activation.     

Pulse polarography: VIII. A new digital to analog pulse polarograph

A new pulse polarograph for normal mode instantaneous current sampling with digital control of timing and of potential generation, is described. Pulse times and delay times are independently variable over a wide range. Pulse times can be varied in 10 ms intervals. The performance of the instrument has been tested in the determination of pulse-polarographic diffusion coefficients of Tl⁺, Cd²⁺, Co(III)(en)₃³⁺ and Co(NH₃)₆³⁺. The reproducibility was found to be excellent.     

Ω− produced in K−p reactions at 4.2 GeV/c

Forty $\text{Ω}{}^{\mathrm{?}}$ events have been observed in a large (133 events/βb) experiment at 4.2 GeV/c incident K^? momentum. Thirty nine of the events come from the three-body reaction $\text{K}{}^{\mathrm{?}}\text{p}\text{→Ω}{}^{\mathrm{?}}\text{K}{}^{\mathrm{+}}\text{K}{}^0$. The $\text{Ω}{}^{\mathrm{?}}$ is mainly produced in the forward hemisphere (direction of the incident K^?). The lifetime is measured to be τ = (0.75 _+0.14?0.11 × 10^?10 sec substantially less than the Particle Data Group value of (1.3 _?0.3^+0.2) × 10^?10 sec. The mass is determined to be 1671.7 ± 0.6 MeV, in good agreement with other determinations. The decay asymmetry parameter α (for the decay mode $\text{Ω}{}^{\mathrm{?}}\text{→ Λ}\text{K}{}^{\mathrm{?}}$) is found to be ?0.2 ± 0.4.