Lifetimes of excited states in164Hf

Lifetimes of excited states in¹⁶⁴Hf were measured using the Doppler-shift recoil-distance method. Gamma-gamma coincidences at eleven target-stopper distances were measured using the twelve Compton-suppressed Ge-detectors of the OSIRIS spectrometer. From the coincidence spectra the intensities of the Doppler-shifted and unshiftedγ-lines were determined. The quadrupole momentsQ _tof transitions within the rotational bands derived from the lifetimes are constant within the experimental uncertainties up to the 18⁺ state. TheQ _tvalue for the transition between the ground- and the neutroni ₁₃ ^2/2 band (s-band) which is strongly reduced compared to the values of the in-band transitions is used to deduce a band interaction energy of 34 keV ≦V≦57 keV.     

ISOLTRAP: A tandem penning trap mass spectrometer for radioactive isotopes

The masses of over sixty short-lived Rb, Sr, Cs, Ba, Fr and Ra isotopes have been measured at the on-line mass separator ISOLDE at CERN/Geneva by determination of their cyclotron frequency in the tandem Penning trap system ISOLTRAP. Resolving powers exceedingm/m(FWHM)=10⁶ and accuracies of typically m/m=10^–7 could be achieved. ISOLTRAP can also act as an isomer separator, as proven for the cases of⁸⁴Rb and⁷⁸Rb.     

New chromogens of the ferroin-type-I. Substituted triazines related to 6-cyano-2,2'-bipyridine

A spectrophotometric study has been made of the iron(II), cobalt(II), nickel(II) and copper(I) chelates of seven new compounds that contain the ferroin functional grouping. None of the new compounds proved to be superior to chromogenic reagents currently in use, but the results are of interest in designing new chromogens.     

Characterization of the chemical homogeneity of solid-state standard materials by chemometric methods

Summary For characterizing the homogeneity of a copper standard for optical emission spectrometry, the results of spark source mass spectrographic (SSMS) milliprobing have been treated by diverse chemometric methods. The proposed strategy includes visualization of the data, global homogeneity testing for each element, testing the anisotropy of elemental distributions, search for correlation between elements, and statements on the homogeneity with respect to other analytical procedures. The copper standard was proved to be non-homogeneous for SSMS but homogeneous for techniques of optical emission spectroscopy having larger sampling volumes.

---

Homogenitätscharakterisierung fester Standardproben unter Verwendung chemometrischer Methoden

---

Dedicated to Prof. Dr. G. Tölg on the occasion of his 60th birthday     

Reinforcing Silk Scaffolds with Silk Particles

Silk fibroin is a useful protein polymer for biomaterials and tissue engineering. In this work, porogen leached scaffolds prepared from aqueous and HFIP silk solutions were reinforced through the addition of silk particles. This led to about 40 times increase in the specific compressive modulus and the yield strength of HFIP‐based scaffolds. This increase in mechanical properties resulted from the high interfacial cohesion between the silk matrix and the reinforcing silk particles, due to partial solubility of the silk particles in HFIP. The porosity of scaffolds was reduced from ≈90% (control) to ≈75% for the HFIP systems containing 200% particle reinforcement, while maintaining pore interconnectivity. The presence of the particles slowed the enzymatic degradation of silk scaffolds.