The determination of cadmium in microgram amounts of pancreatic tissue by electrothermal atomic absorption spectometry

Cadmium was determined either by direct insertion of freeze-dried biological samples (1–13 μg) or by injection of 2-μl samples of perifusion medium into the graphite furnace. At 228.8 nm ? 10 fmol of cadmium could be measured. The endogenous cadmium contents in the endocrine and exocrine parts of the pancreas were 8.5 ± 2.0 and 15.1 ± 1.4 μ mol (dry wt.), respectively. A less sensitive wavelength (326.1 nm) was employed for measuring the larger amounts obtained after specimens had been incubated in the presence of cadmium.     

Ready-made matrix-assisted laser desorption/ionization target plates coated with thin matrix layer for automated sample deposition in high-density array format.

The methodology for ready-made matrix-assisted laser desorption/ionization (MALDI) target plates covered with an optimized thin layer consisting of matrix and nitrocellulose has been developed. Piezoelectric microdispensing enabled sample depositions in a high-density array format of 2000 sample depositions on a conventionally sized target plate (45 x 47 mm). The sample depositions were made reproducibly in a fully automated mode by using an in-house developed computer-controlled piezoelectric flow-through microdispenser. Additionally, the piezoelectric technique facilitated significant analyte enrichment that increased the detection sensitivity. The MS signal was obtained rapidly, generally within ten laser pulses. An airbrush device was used to generate a fine spray of matrix and nitrocellulose dissolved in acetone. The acetone evaporated instantly when reaching the target plate leaving the entire surface with a thin and uniform matrix/nitrocellulose coating consisting of very small crystals of matrix embedded in the nitrocellulose. These crystals acted as a seed-layer on subsequent analyte depositions, rendering homogeneous sample spots when using alpha-cyano-4-hydroxycinnamic acid (CHCA) as matrix. The relative standard deviation of the signal intensity between spots was (20-30)% (n = 30). The detection sensitivity was improved by restricting the sample spot diameter to 300 microm. The spot size was affected by the deposition rate and the evaporation rate of the dispensed sample volume. Mass spectra of a 25-amol peptide mixture deposition were successfully recorded.     

A multiple grating flame photometer for the simultaneous determination of five elements

A flame emission spectrometer for the simultaneous determination of five elements has been constructed. The instrument is built around a special holographic diffraction grating, built up from several smaller gratings with different ruling characteristics, each covering a different spectral range. It is provided with automatic background correction and a photon counting system. Sensitivity and precision are good. The instrument is compared with other multichannel flame emission systems. Construction of the spectrometer including electronics is described.     

The effects of some laboratory designs and mounting conditions on reduction index measurements

The effects of typical transmission laboratory designs on measured reduction indices are investigated. First the influences of test frames, test openings with deep apertures and mounting conditions are examined separately for some common wall types. The result of a limited test series is then discussed. The test was run in five laboratories. The reduction indices were measured for two lightweight walls, each one mounted in two different ways.     

The absorption spectrum of the hydrated electron at high pressures. A calculation of the pressure shift of the absorption peak

The structure of the excess electron localization center in water has been identified with the structure of the dodecahedral cavities in hexagonal ice. Based on this model the pressure shift of the optical absorption peak, the oscillator strength and the photoconductivity threshold energy of the excess electron have been calculated.     

A phenomenological investigation of the shower particle pseudorapidity fluctuations in hadron-nucleus collisions

From the experimental matrix $\text{?(N}{}_{\mathrm{<mtext>g</mtext>}}\text{; n}{}_{\mathrm{<mtext>s</mtext>}}\text{, Δη}{}_{\mathrm{i}}\text{)}$ (the number of events with a given number N_g of particles with velocity 0.3c<v<0.7c, and n_s, the number of shower particles (v > 0.7c) in a pseudo-rapidity interval Δη_i) obtained from the Heidelberg-Igel hadron-nucleus experiment at CERN, we extract the shower particle multiplicity distributions as a function of ν, the number of nucleons that interacted with the projectile. We use a theoretically justified statistical correlation between ν and N_g (recoil protons) and the assumption that the correlation between n_s and N_g is given merely through ν. The data used are for incoming energies 50 and 150 GeV with a proton or pion as the projectile and Cu or Pb as the target. We find that the shower particle multiplicity distributions are of a Poissonian character in each η bin and for each value of ν. The average multiplicities $\text{〈n}{}_{\mathrm{<mtext>s</mtext>}}\text{〉(ν)}\text{Δη}{}_{\mathrm{i}}$ are approximately the same for the two targets and for the different projectile, possibly with a small excess for the pion projectile.The results are compared to a rather general theoretical model of the soft interaction type. The predictions from this model for the shower particle pseudorapidity distributions are very close to the derived values.     

Carbon-13 NMR studies of twenty-four methyl-substituted morpholines

Carbon-13 NMR spectra of all the isomers of monomethyl-, 2,3-, 2,5-, 2,6-, 3,5-dimethyl-, 2,3,5-, 2,3,6-trimethyl- and 2,3,5,6-tetramethylmorpholine have been obtained at both ambient (25 °C) and low temperature (～ ?100 to ?120 °C). The ring carbon shifts appear to be additive with respect to the position of the methyl groups. A good correlation between predicted and experimental shift values was obtained (r = 0.998₉). The values were used in an attempt to assign, conformationally, the ‘all cis’ isomer 2,3,5,6-tetramethylmorpholine, which from ¹HNMR spin–spin coupling studies has been unsuccessful. Methyl carbon shifts to high field were found for axially oriented carbons. The extracted ‘steric shift’ values for such carbons were compared to their corresponding proton shift data.     

Angular dependences in u.v.-photoemission from single crystals of Au

Photoemitted electron energy distributions from single crystals of Au at a photon energy of 16.8 eV are reported. Measurements have been taken for different surface orientations and electron emission angles. An anisotropic version of the three step model can describe the main features of the observed data.     

Many-body effects in the appearance potential spectrum of barium

The appearance potential spectrum of barium has been measured in the energy range 20–150 eV. Broad peaks are observed which are attributed to giant dipole resonances.