Die Reaktion10B(d,α)8Be im Energiebereich von 0,5 bis 2 MeV

The differential magnetic susceptibility X=X′-iX″ of HoCl₃, Ho(Y)Cl₃, and Ho(La)Cl₃ has been measured with a mutual inductance bridge with frequencies from 5.3 c/s to 5.12 kc/s at temperatures between 1.1 and 4.2 °K, and in constant magnetic fields up to 3 kOe. — In monoclinic HoCl₃ a magnetic transition has been observed atT=2.15 °K (maximum of X″). No transition occurs for 0.5 and 5% Ho³⁺ in isomorphic YCl₃. — The results for nominal concentrations of 1, 2, and 5% Ho³⁺ in hexagonal LaCl₃ indicate, that there is a considerable precipitation of monoclinic HoCl₃ during crystal growth. Relaxation measurements on Ho³⁺ in hexagonal sites are interpreted in terms of a phonon-bottleneck in the temperature region 1.1 °K≦T≦2.0⁰K with a hot-phonon equilibration time of about 0.2 μs.     

A single-channel microparticle sieve based on Brownian ratchets

We present a novel device for the separation of microparticles in a single channel, which is made of inversely asymmetric Brownian ratchets. It enables separation into two different fractions with an adjustable threshold and can be modeled with good agreement. This device serves as proof of concept for an extremely compact class of microsieves.     

Aligning 3D time-of-flight MRA datasets for quantitative longitudinal studies: evaluation of rigid registration techniques

Objective

3D Time-of-flight (TOF) magnetic resonance angiography is commonly used for vascular analyses. A quantification of longitudinal morphological changes usually requires the registration of TOF image sequences acquired at different time points. The aim of this study was to evaluate the precision of different 3D rigid registration setups such that an optimal quantification of morphological changes can be achieved.

Methods

Eight different rigid registration techniques were implemented and evaluated in this study using the target registration error (TRE) calculated based on 554 landmarks defined in twenty TOF datasets. The registration techniques differed in integration of brain and vessel segmentation masks and usage of a multi-resolution framework. Furthermore, the benefit of a prior volume-of-interest definition for registration accuracy was evaluated.

Results

The results revealed that the highest registration accuracies can be achieved using a multi-resolution framework and a cerebrovascular segmentation as mask. Numerically, a mean TRE of 1.1 mm was calculated. If applicable, a prior definition of a volume-of-interest allows a reduction of the TRE to only 0.6 mm.

Conclusion

TOF datasets should be registered using vessel segmentations as mask, multi-resolution framework and previous volume-of-interest definition if possible to obtain the highest registration precision. This is especially the case for longitudinal datasets that are separated by several months while the registration technique seems less important for datasets that are only separated by a few days.     

Die Reaktion11B(d, α)9Be im Energiebereich von 0,7 bis 2,2 MeV

Excitation functions were measured from 0.7 to 2.2 MeV for the α₀ -, α₁-, α₂- and α₃-groups at an angle ofθ _L=90°. Two broad maxima were found in all four cases, suggesting the existance of resonances in the¹³C-compound nucleus. A problem, however, arises, as the first maximum appears at a bombarding energy of 1.15 MeV for the α₀- and α₁-groups, whilst it is shifted to 1.35 MeV in the excitation curves for the α₂- and α₃-groups. The second maximum appears at 1.85 MeV in all curves. Angular distributions were measured at 7 energies between 1.0 and 2.2 MeV for the α₀- and α₂-transitions. The coefficients of the first four Legendre polinomials, describing these distributions, are given.

     

Elastische Streuung von Deuteronen an10B bei niedrigen Energien

The excitation curve for the elastic scattering of deuterons from¹⁰B in the energy range from 1.0 to 2.0 MeV has been measured atθ _L =135°. Strong indications for compound nucleus resonances in¹²C at bombarding energies of approximately 1.0 and 1.9 MeV were observed. Angular distributions from 80 to 175° were determined in 200 keV steps from 1.0 to 2.0 MeV. Optical model analysis were made both for volume absorption and surface absorption potentials. Reasonable fits were obtained at energies up to 1.6 MeV with one set of parameters in both cases, whilst for the higher energies strong deviations were found with the same parameters.