Investigation on the feasibility of using an Ulbricht sphere for the absolute calibration of an ICP or other source at specific wavelengths

The short term and long term stability of an Ulbricht sphere was investigated by comparing its radiation at four Balmer wavelengths with those of two Sylvania projector lamps. A slight positive trend in the radiation intensity of the Ulbricht sphere was observed. This was attributed to a change in the molecular structure of the paint used to cover the inside of the sphere. However, the radiance varied less than 3% for 14 h burning time. The uncertainty in the primary calibration of the Tungsten standard lamp was given as ±3% in the wavelength range 400–600 nm. It was hence concluded that the sphere is suitable for spectral calibration purposes for a period of 14 h operational time without being recalibrated.     

Galvanomagnetic study of the quantum-well valence band of germanium in the Ge<Subscript>1−x</Subscript>Si<Subscript>x</Subscript>/Ge/Ge<Subscript>1−x</Subscript>Si<Subscript>x</Subscript> potential well

The structure of the quantum-well valence band in a Ge(111) two-dimensional layer is calculated by the self-consistent method. It is shown that the effective mass characterizing the motion of holes along the germanium layer is almost one order of magnitude smaller than the mass for the motion of heavy holes along the [111] direction in a bulk material (this mass is responsible for the formation of quantum-well levels). This creates a unique situation in which a large number of subbands appear to be populated at moderate values of the layer thickness d _w and the hole concentration p _s . The depopulation of two or more upper subbands in a 38-nm-thick germanium layer at a hole concentration p _s = 5 × 10¹⁵ m^?2 is revealed from the results of measuring the magnetoresistance in a strong magnetic field aligned parallel to the germanium layers. The destruction of the quantum Hall state at a filling factor ν = 1 indicates that the two lower subbands merge together in a self-formed potential profile of the double quantum well. It is demonstrated that, in a quasi-two-dimensional hole gas, the latter effect should be sensitive to the layer strain.     

Stereospecific oxidation by compound I of cytochrome P450 does not proceed in a concerted synchronous manner

Calculations show that the transition structure for the synchronous oxygen transfer by Compound I is a second order saddle point. The process is unlikely.     

A reciprocity inequality for Gaussian Schell-model beams and some of its consequences

A reciprocity inequality is derived, involving the effective size of a planar, secondary, Gaussian Schell-model source and the effective angular spread of the beam that the source generates. The analysis is shown to imply that a fully spatially coherent source of that class (which generates the lowest-order Hermite-Gaussian laser mode) has certain minimal properties.     

Evidence for a two component magnetic response in UPt3

The magnetic response of the heavy fermion superconductor UPt3 has been investigated on a microscopic scale by muon Knight shift studies. Two distinct and isotropic Knight shifts have been found for the field in the basal plane. While the volume fractions associated with the two Knight shifts are approximately equal at low and high temperatures, they show a dramatic and opposite temperature dependence around T(N). Our results are independent on the precise muon localization site. We conclude that UPt3 is characterized by a two component magnetic response.     

Zum Nachweis und zur Bestimmung von salicylsaurem Natron bei Gegenwart von Ichthyol

Ohne Zusammenfassung     

Cryotrapping gas chromatography-Fourier transform infrared spectrometry in environmental analysis: A pilot study

The potential applicability of cryotrapping gas chromatography-Fourier transform infrared spectrometry in environmental analysis was studied. First results of on-the-flight measurements on pesticides and polynuclear aromatic hydrocarbons show detection limits in the 100–500 pg range. The low-temperature spectra obtained appear to be closely comparable to conventionally recorded spectra. Library search procedures based on existing solid-phase spectra appear to be useful.