Elucidation of codoping effects on the solubility enhancement of Er3+ in SiO2 glass: striking difference between Al and P codoping

The codoping effect mechanism of Al and P on the solubility enhancement of Er(3+) ion in SiO(2) glass was clarified by electron spin-echo envelope modulation spectroscopy. It turned out that doped P ions preferentially coordinate to the Er(3+) ion to form a "solvation shell structure", and the environment is similar to that in phosphate glass, while doped Al ions do not form such a selective solvation structure, taking octahedral coordination. This striking difference indicates that the primary roles of the P-doping and the Al-doping are attributed to "enthalpy of mixing" and to "entropy of mixing", respectively.     

Uncertainty of determination of palladium in road dust sample by inductively coupled plasma mass spectrometry

The determination of palladium in a road dust sample taken close to the highway (w _Pd=450 ng g⁻¹) was carried out by the ICP-MS method after sample decomposition by aqua-regia. Analyses were evaluated by two methods: external calibration accompanied with mathematical correction of spectral interferences (EC) and isotope dilution measurement after separation of Pd by extraction to dibutyl sulfide solution (ID). In both cases, the uncertainties and accuracy of results were investigated. Although in the case of ideally homogeneous sample the repeatability of EC results (11 ng g⁻¹ Pd) was somewhat lower than those of ID results (16 ng g⁻¹ Pd), the uncertainties of results of both techniques were almost the same and they reached the level of 19 ng g⁻¹ Pd. The main uncertainty source of the EC method is represented by the correction of spectral interferences. In case of real non-homogeneous sample, the main uncertainty component represents the soil sampling. The uncertainty of results (approx. 75 ng g⁻¹ Pd) only slightly exceeded the repeatability (approx. 70 ng g⁻¹ Pd). The accuracy of results was proven by analyses of CRM TDB–1 Diabas Rock (in case of ID) and by the standard addition method (in case of EC).     

Optically controlled confined potential of a vertically aligned double-dot array system

In a vertically coupled dot, it is expected that generalized Kohn theorem is invalid. Then electron–electron interaction can be observed in far-infrared absorption. This interaction depends on the coupling between dots. We fabricated a vertically aligned double-dot array using a double heterostructure to investigate the coupling. The strength of the coupling depends on the confine potential of the dot. In far-infrared magneto-optical absorption measurements under pulsed photoexcitation, we observed peak shift of asymmetry states and increasing of absorption intensity of symmetry states of the dot. This is a result of the confined potential modulation by light. This indicates the possibility of optical control of the coupling.     

L p-discrepancy and statistical independence of sequences

We characterize statistical independence of sequences by the L ^p-discrepancy and the Wiener L ^p-discrepancy. Furthermore, we find asymptotic information on the distribution of the L ²-discrepancy of sequences     

Preparation and testing of standard solutions of cadmium, copper and lead

 Solutions of Cd, Cu and Pb at concentrations of about 1000 mg/l were prepared by dissolving the pure metals in HNO₃. Their concentration was verified by complexometric titration and by gravimetric analysis (Cu with salicylaldoxime, Cd with quinaldinic acid and Pb with 8-hydroxyquinoline). The results of the two methods were very similar and the uncertainty values were equal. However, the gravimetric determination can be regarded as more reliable, because titrimetric analysis is more prone to error due to inaccurate end-point reading. The expanded uncertainty of the concentrations of Cd and Cu attained 1 mg/l, which is half the value typically obtained for similar solutions from commercial manufacturers. To achieve such precise results, the bias had to be reduced by the highest possible extent, particularly by calibrating both the balance and the volumetric glassware. In addition to the uncertainty of the basic operations (volumetric and gravimetric), the uncertainty of the atomic and molecular weights constituted an appreciable component in the combined standard uncertainty; this manifested itself in the determination of Pb, where the expanded uncertainty was 2 mg/l. Received: 24 September 1998 / Accepted: 25 January 1999     

In-plane and perpendicular magnetic fields dependence of cyclotron resonance in two-dimensional electron systems

The cyclotron resonance of two-dimensional electron systems (2DES) of GaAs/AlGaAs heterostructures is investigated in a tilted magnetic field. In this study, the perpendicular (B) and in-plane (B_||) magnetic fields are changed systematically. More than two cyclotron resonances caused by B_|| are observed. Further, the enhancement of cyclotron mass by B_|| and its dependence on B and electron concentration of 2DES are also investigated in detail. These phenomena are well explained by the resonant subband Landau level coupling model.     

Determination of zinc in plant samples by isotope dilution inductively coupled plasma mass spectrometry

Determination of zinc involved spiking with (68)Zn enriched solution, digestion by HNO(3)+H(2)O(2) in microwave decomposition unit, off-line separation of zinc on Chelex-100 column and measurement of ((64)Zn+(66)Zn)/(68)Zn isotope ratio on ICP-MS spectrometer with a quadrupole mass filter. After optimization of standard operation procedure (details are given) the method was validated. LOD was found to be 0.3 mug g(-1) for the procedure without zinc separation and 3.6 mug g(-1) for the procedure involving zinc separation, respectively. The accuracy of results was proved by analyses of several CRM and a primary solution of zinc, the concentration of which was verified by gravimetry and complexometric titration. Barium is the only element causing serious interferences and it must be removed from samples. The uncertainty budget is given together with the scheme of combined uncertainty calculation. The main uncertainty components are contamination during zinc separation and uncertainty of isotopic composition of natural zinc.     

Determination of 7,12-dimethylbenz[a]anthracene in orally treated rats by high-performance liquid chromatography and transfer stripping voltammetry

A number of polycyclic aromatic hydrocarbons (PAHs) have been shown to be toxicants, and induce carcinogenic and immunotoxic effects. As a model PAH agent, 7,12-dimethylbenz[a]anthracene (DMBA) was the strongest one tested in terms of its biological activities and biotransformation. A new and simple high-performance liquid chromatographic (HPLC) method with diode-array detection at 290 nm was developed and validated for monitoring of DMBA in different matrices (serum, liver and kidney) of rats orally treated with DMBA. Furthermore, the applicability of adsorptive transfer stripping voltammetry (AdTSV) on the pencil-lead graphite electrode to these samples was illustrated using our previously reported data for bulk aqueous solutions of DMBA. HPLC and AdTSV methods, which were compatible with each other, allowed DMBA to be detected down to the levels of 3.82x10-9 M (0.98 ppb) and 6.73x10-9 M (1.73 ppb), respectively. Olive oil solutions of DMBA in dose 50 mg/kg were orally administered. 60 days after a single dose of DMBA, its concentrations in these biological samples from rats were measured by means of both methods. Because of rapid biotransformation, DMBA could not be detected in serum. Only low levels of the compounds were deposited unchanged in kidney whereas its levels were considerably higher in liver. These methods were also applied to the assay whether there is an influence of the intake of aqueous extracts of Hypericum Perforatum L. plant on the parent DMBA levels accumulated in rat tissues.     

(+)-(5R,6S)-2-(1′-Aminoalkyl)-6-(hydroxyalkyl)penem-3-carboxylic Acids

In continuation of our work on penem antibiotics, novel chiral (5R,6S)-2-(1′-aminoalkyl)-6-(hydroxyalkyl)-derivatives 1 have been synthesized by two essentially different strategies. Whereas the starting materials for 1a - f , azetidinones 2 and 5 , were obtained from chiral building blocks (6-aminopenicillanic acid and L-threonine, resp.), the one for 1g , azetidinone 9 , was derived from racemic 4-acetoxyazetidinone and, as chiral auxiliary, (2R)-2-mercaptopropan-1-ol. The 2-aminomethyl derivatives 1a (CGP 30 779) and 1f (CGP 31 608) proved the most potent compounds in the antibacterial tests in vitro and showed a well-balanced spectrum of activity by comparison with that of established β-lactams.     

L2‐estimates for the DG IIPG‐0 scheme

We discuss the optimality in L² of a variant of the Incomplete Discontinuous Galerkin Interior Penalty method (IIPG) for second order linear elliptic problems. We prove optimal estimate, in two and three dimensions, for the lowest order case under suitable regularity assumptions on the data and on the mesh. We also provide numerical evidence, in one dimension, of the necessity of the regularity assumptions. © 2011 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2012