Fluorides or hydrides? 41Ca performance at VERA’s 3-MV AMS facility

Recent improvements in isobaric suppression for medium-mass isotopes, e.g. ⁴¹Ca, offer new possibilities for tandem accelerators with terminal voltages of 3 MV or lower; i.e. when dealing with particle energies ?1 MeV/amu. In particular, detection of ⁴¹Ca requires sufficient discrimination of the stable isobar ⁴¹K. We explored the limits of ⁴¹Ca detection at our 3-MV AMS facility by means of different types of particle detectors: The ΔTOF method, which is based on the different flight-time of isobars after passing a thick absorber foil. The second method makes use of a new type of compact ionization chamber: ⁴¹K and ⁴¹Ca are separated in energy due to their different energy loss in the detector entrance foil and the detector gas, which is measured via a segmented anode.At VERA we measured ⁴¹Ca/Ca ratios below 10^?13 for commercial CaF₂ material serving as blank samples. CaH₂ sputter targets, with the extraction of ${\text{CaH}}_3^{-}$, yielded background ratios as low as ⁴¹Ca/Ca = 1 × 10^?15. The typical measurement precision at VERA for ⁴¹Ca measurements was between 2% and 5%. These results demonstrate that AMS facilities based on 3-MV tandems have reached the sensitivity level of larger AMS facilities for a wide range of applications, with the advantage of high overall efficiency and sample throughput.     

Comparison of detector systems for the separation of 36Cl and 36S with a 3-MV tandem

The possibility of detecting ³⁶Cl for geological exposure dating has been explored for several years at VERA (the Vienna Environmental Research Accelerator). First results on real samples were obtained with an ionization chamber (developed at the ETH/PSI, Zürich, Switzerland) with two anodes. To improve the suppression of ³⁶S, we equipped the ionization chamber with an exit window and added a Time-of-Flight (TOF) system with a double-sided silicon strip detector (50 × 50 mm²) as stop detector. We optimized the TOF setup by using silicon nitride foils to reduce scattering tails in the energy spectra.At 3 MV terminal voltage, corresponding to a particle energy of 24 MeV of ³⁶Cl⁷⁺, we achieved a ³⁶S⁷⁺-suppression of 21,500 (50% ³⁶Cl-detector-efficiency).     

Color-coded sleep EEG power density spectra

The colour-coded representation of transformed sleep EEG power density spectra makes it possible to demonstrate changes in sleep architecture. With the aid of this method, spectral changes in physical units can be shown. The present study also shows that sleep is a continuous process which, for clinical interpretation, urgently needs to be processed with this in mind, in particular for the investigation of the effects of psychopharmaceuticals. The method is derived mathematically, and illustrated by convincing examples. It is to be hoped that the method will be accepted without delay and its use spread rapidly.     

Effect of alloying elements on recovery and damage rates in zirconium

Pure Zr and Zr-X (where $\text{X = Cr, Fe, Ce and Sn}$) alloys have been irradiated to a fast neutron fluence of $\text{1.8 × 10}{}^{22}\text{nm}{}^{\mathrm{?2}}$ at 4.6 K. The radiation induced resistivity has been measured in situ as a function of dose. It was observed that compared to pure zirconium the radiation induced resistivity and hence the initial damage accumulation rate increases in the Zr-Sn alloy whereas it was practically unchanged by the other alloy elements. The irradiated samples were also subjected to isochronal annealing in the temperature range of 20–400 K and different annealing stages in pure zirconium and its alloys were studied. It was concluded that tin acts as a good trap for interstitials in stage I and for vacancies in stage III.     

Human and rodent MaxiK channel beta-subunit genes: cloning and characterization

Fifty years after the advent of antibiotics for clinical use, the rates of morbidity and mortality associated with bacterial meningitis remain high. The unfavourable clinical outcome is often due to intracranial complications including cerebrovascular insults, raised intracranial pressure, hydrocephalus, and brain edema. Reactive oxygen species (ROS) are known effector molecules in the antimicrobial armature of polymorphonuclear and mononuclear phagocytes. However, over the last decade, there has been a substantial body of work implicating a central role of ROS in the development of intracranial complications and brain damage in bacterial meningitis. Recently, it also became evident that reactive nitrogen species (RNS), especially nitric oxide, are important mediators of meningitis-associated pathophysiological changes, at least during the early phase of the disease. There is now substantial evidence that much of the oxidative injury associated by simultaneous production of superoxide and nitric oxide is mediated by the strong oxidant peroxynitrite. ROS and peroxynitrite can be cytotoxic via a number of independent mechanisms. Their cytotoxic effects include initiation of lipid peroxidation and induction of DNA single strand breakage. Damaged DNA activates poly(ADP-ribose) polymerase (PARP). Recent experimental data propose a role of lipid peroxidation and PARP activation in the development of meningitis-associated intracranial complications and brain injury. Agents which interfere with the production of ROS and peroxynitrite, as well as with PARP activation and lipid peroxidation may represent novel, therapeutic strategies to limit meningitis-associated brain damage, and, thus, to improve the outcome of this serious disease.     

Hydrogen-fueled internal combustion engines

The threat posed by climate change and the striving for security of energy supply are issues high on the political agenda these days. Governments are putting strategic plans in motion to decrease primary energy use, take carbon out of fuels and facilitate modal shifts.     

Structure–property correlations of flexible clear coats

In this paper thermomechanical and mechanical properties of various free clear coat films for coil-coated steel sheets were studied by dynamic mechanical analysis and tensile testing. To establish structure–property correlations, polyacrylate and polyester binder resins with varying molar mass and functionality were investigated. The clear coat films based on polyacrylate binders exhibited higher glass transitions values, crosslinking densities, elastic modulus and tensile strength values. For both resin types, a relationship of the properties glass transition temperature, crosslinking density, stiffness and tensile strength and the functionality considering the molar mass and the hydroxyl value of the resins was obtained. The elastic strain energy of the investigated brittle clear coat films depended mainly on the elastic modulus.     

Flexible clear coats—Effect of curing conditions

The effect of curing at different conditions was investigated for flexible model clear coat films for coil coating applications. Based on a commercial polyester binder two formulations with isocyanate based crosslinking agents (hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI)) were prepared. The clear coats were baked at laboratory (145 °C) and industrial processing (300 °C) conditions. While for high temperature curing the baking time was kept constant at 30 s, the curing time at 145 °C, which is above the deblocking temperature of the crosslinking agents, was varied from 10 to 90 min. The clear coat films were characterized as to their thermomechanical and mechanical properties by dynamic mechanical analysis (DMA) and by tensile testing. Regarding DMA loading in tensile and penetration mode was performed.     

Structural Characterization of Metallurgical Coke by Raman Spectroscopy

To investigate the factors influencing the structural order of metallurgical coke, several coke samples were treated by temperatures between 850 °C and 1300 °C and analyzed by Raman Spectroscopy. A quantitative Raman-parameter is proposed to reflect the structural state of a coke sample.