Comparison of tungsten and gold radiation from beam-foil excitation and tokamak-produced plasmas

Spectra in the 30–80 Å wavelength region of tungsten and gold ions, with charge states ranging from 20–33, and 25–38, respectively, have been measured in beam-foil excitation and compared with similar spectra from tokamak-produced plasmas.     

Determination of chlorophenols in urine of children and suggestion of reference values

During the course of a human biomonitoring project (Biebesheim in Hessen, Germany) we elaborated a simple but sensitive method for the determination of tri- (TCP), tetra- (TeCP) and pentachlorophenol (PCP) in human urine. Urine samples, spiked with internal standards, were treated by acid hydrolysis. After a steam bath distillation the distillates were extracted using solid phase extraction. Derivatization of the chlorophenols was not carried out. GC/ECD system was used for detection. Detection limits of the chlorophenols were found in the range of 0.02 μg/L urine (detection limits of the ECD: 0.52 to 2.76 μg/L). By this method mono- and dichlorophenols cannot be detected. We investigated 24h-urine samples of 339 pupils (age 10 to 12 years). The children live either in the surroundings of a hazardous waste incinerator (SVA) in Biebesheim (n = 193), or controls (i.e. regions without waste incinerator) in the non polluted areas of Odenwald (n = 90) and Rheintal (n = 56). Between these three groups we did not find statistically significant differences in chlorophenol concentrations of the urine samples. The 95-percentiles of the analyzed samples are 0.74 μg/L (2,3,4-TCP), 1.24 μg/L (2,3,5-TCP), 0.70 μg/L (2,3,6–TCP), 1.10 μg/L (2,4,5–TCP), 1.74 μg/L (2,4,6–TCP), 2.84 μg/L (3,4,5–TCP), 4.78 μg/L (2,3,4,5-TeCP), 1.86 μg/L (2,3,4,6-TeCP), 2.90 μg/L (2,3,5,6-TeCP) and 4.39 μg/L (PCP). Received: 24 February 1999 / Revised: 3 May 1999 / Accepted: 6 May 1999     

Determination of total arsenic and speciation of arseno-betaine in marine fish by means of reaction — headspace gas chromatography utilizing flame-ionization detection and element specific spectrometric detection

Marine organisms contain amounts of arsenic ranging from less than 1 μg/g to more than 10 μg/g. In food examinations usually total arsenic is determined, rarely As(III) and As(V) additionally. Rating marine food according to its total arsenic contents without further speciation, would involve an overcritical assessment. Due to the lack of suitable methods for routine analysis in food-control, the “organic” moiety remains unspecified. Only after performing a systematic research onto the real existence of arsenic and its compounds relevant to marine organisms, a toxicological evaluation can be carried out. As to its quantitative occurrence and its negligible toxic relevance arsenobetaine is of decisive importance. Therefore a reliable method has been developed based on headspace gas chromatography after chemical reaction. The predominant role of arsenobetaine in the organic arsenic moiety as well as in total arsenic in marine fish could thus be demonstrated.     

Rheology behavior of nematic side-chain polymers in blends with thermoplasts

Peculiarities of the rheological behavior of blends composed of thermoplasts and side-chain nematic polymers have been studied. The strong role of interface interactions associated with the polymer chemical structure on the effect of rheology is shown. The influence of the nematic ordering is shown to be effective in the mechanical characteristics of blend extrudates whereas the rheology effect does not depend on the liquid crystal ordering.     

Effect of coupled oscillations on microbubble behavior

Ultrasound contrast agents are encapsulated microbubbles whose nonlinear acoustic scattering signatures have been the foundation of their use in diagnostic imaging. The coupled oscillations of microbubbles along their lines of center are investigated theoretically using radial equations in the monopole approximation and an energy balance, which is obtained for the system. Coupled microbubble pairs of different initial radii are investigated numerically relative to the normal modes for the linearized system. For microbubble pairs of different size bubbles driven below the mode of the smaller bubble and above the mode of the larger bubble, it is shown that oscillations of the smaller agent are affected substantially more by the coupling than those of the larger one. For separation distances of 10 and 500 microns, a difference of approximately 10 dB occurs in the second harmonic output of a 1.0-micron radius agent coupled with a 2.2-micron radius agent forced at 2.0 MHz and 0.3 MPa. The subharmonic spectral peak is shown to decrease approximately 19 dB for the coupling of 1.5- and 2.2-micron radius agents at 10- and 500-micron distances under the same acoustic forcing conditions. These coupling effects on the radiated pressure and its spectral power are highlighted for contrast agent imaging applications.     

Investigating inclusion complexes using quantum chemical methods

Quantum chemistry has firmly established itself as a reliable method for investigating present-day problems in biological and materials chemistry. Understanding inclusion complexes represents one of the cutting edges of simulation sciences. In this tutorial review, we focus on the role and composition of non-covalent interactions, which are essential when studying inclusion complexes. A selected set of recently developed pragmatic methods used to study inclusion complexes are then surveyed including e.g. dispersion corrected DFT, double-hybrid functionals and spin-component scaled MP2. Finally, three case studies are outlined: (a) endohedral fullerene complexes, (b) buckyball catcher and (c) resorcinarene capsule. These case studies were carefully chosen to help illustrate how one may accurately investigate inclusion complexes, at a modest computational cost, using state-of-the-art quantum chemical methods (67 references).