Heavily carbon-doped GaAs grown on various oriented GaAs substrates by MOMBE

Heavily carbon-doped GaAs epitaxial layers have been grown simultaneously on (100), (111)A, (111)B, (411)A, (411)B and (711)A semi-insulating (SI) GaAs substrates by metalorganic molecular beam epitaxy (MOMBE) using trimethylgallium (TMG) and elemental As (As₄). The hole concentration and surface flatness strongly depend on the substrate orientation. The highest carbon incorporation was observed for the layers grown on a (411)A substrate with a hole concentration of 1.0 × 10²¹ cm^{− 3} and a lattice mismatch of Δd/d = −0.48%. Atomic force microscope (AFM) images reveal that the epilayers grown on (411)A substrates exhibit extremely flat surfaces, although these layers contain the highest carbon concentration.     

Influence of growth related thickness fluctuations on the spectral and lateral luminescence intensity distribution in GaAs quantum wells

The effect of low energy exciton sinks on the spectral and spatial luminescence intensity distribution has been investigated in a single quantum well (QW) and a multiple QW structure prepared by growth interrupted molecular beam epitaxy (MBE). Both samples contain growth-related lateral variations of the exciton confinement energy on the order of the exciton diffusion length, which cause a lateral and spectral intensity distribution in cathodoluminescence images.     

Determination of drugs by direct injection of plasma into a biocompatible extraction column based on a protein-entrapped hydrophobic phase

Drugs were determined by direct injection of plasma samples into a biocompatible extraction column. The column is based on particles with a biocompatible external surface and a hydrophobic internal surface. The pores of the particles are small enough to exclude the protein molecules; the drug molecules can penetrate the porous particle and are retained on the hydrophobic internal surface. Biocompatibility of the particles was obtained by reaction of the external surface with the human plasma protein ₁-acid glycoprotein. The surface within the pores of the particles contains hydrophobic C₈ or C₁₈ groups. The biocompatible extraction column was used in a fully automated system for the determination of ibuprofen, naproxen, propranolol, carbamazepine and phenytoin in plasma. No pressure increase was observed during the analysis of several hundred plasma samples. Plasma concentrations of propranolol in the range 4.5–125 ng/ml were determined with a precision (R.S.D.) of 0.75–1.8%. Linear calibration graphs were observed for the five drugs, and correlation coefficients of 1.0000 were obtained for four of the five model compounds.     

13C-NMR-Spektren von γ-substituierten pentamethincyanin-farbstoffen mit indolenin-endgruppen

The ¹³C-resonances of fourteen γ-substituted pentamethincyanine dyes 1 with indolenine nuclei have been measured and assigned. The effect of the γ-substituents R on the ¹³C chemical shifts is compared with the corresponding effect of substituents R of monosubstituted benzenes and 1-substituted trans-butadienes. The chemical shifts of the C²-methincarbons, which are separated by four bonds from R, correlate with Hammett's substituent parameters σ_para. A significant substituent effect through nine covalent bonds has been observed.     

Lifetime measurement in 195Po

The lifetime of the 17/2⁺ yrast state in ¹⁹⁵Po has been measured using the recoil distance Doppler-shift technique to be = 43(11) ps. The lifetime was extracted from the singles -ray spectra obtained by using the recoil-decay tagging method. The present work provides more information of the coupling schemes, shapes and configuration mixing in neutron-deficient odd-mass Po nuclei.     

Structure of rotational bands in 253No

In-beam gamma-ray and conversion electron spectroscopic studies have been performed on the ²⁵³ No nucleus. A strongly coupled rotational band has been identified and the improved statistics allows an assignment of the band structure as built on the $\ensuremath 9/2^-[734]_{\nu}$ ground state. The results agree with previously known transition energies but disagree with the tentative structural assignments made in earlier work.