Metallic Magnetic Calorimeters for X-Ray Spectroscopy

An increasing number of experiments employ low-temperature radiation/particle detectors which are based on a calorimetric detection scheme and operate at temperatures below 100 mK. Metallic magnetic calorimeters use a metallic paramagnetic temperature sensor in tight thermal contact with the X-ray absorber. The magnetization of the sensor is used to monitor the temperature change of the detector upon the absorption of single photons, which is proportional to the absorbed energy. Low-noise high-bandwidth dc superconducting quantum interference devices read out the small changes in magnetization. An energy resolution of DeltaE _FWHM = 2.7 eV was obtained for X-ray energies up to 6 keV.     

Separation of chiral biodegradation intermediates of linear alkylbenzenesulfonates by capillary electrophoresis

High-performance capillary electrophoresis (HPCE) with α-cyclodextrin as the chiral selector was applied to separate the enantiomers of p-sulfophenyl-2-butyrate (SP2B) and p-sulfophenyl-3-butyrate (SP3B), which occur as biodegradation intermediates of linear alkylbenzenesulfonates (LAS), the widely used anionic surfactants. With this analytical method, we studied the transformation of both SP3B enantiomers in a laboratory batch incubation with activated sewage sludge of a municipal wastewater treatment plant. (S)-(+)-SP3B and (R)-(-)-SP3B could be detected in mechanically treated sewage effluent. After enrichment on graphitized carbon black (Carbopack B), the extracts were analyzed by HPLC with UV diode array and fluorescence detection as well as by HPCE with UV diode array detection. Quantification of SP3B in a 24-h composite sample of primary sewage effluent yielded 34 μg/L (limit of detection, 0.1 μg/L) of the racemic mixture determined by HPLC and 18 μg/L of each enantiomer measured by HPCE (limit of detection, 1 μg/L).     

Engineering the Interlayer Spacing by Pre-Intercalation for High Performance Supercapacitor MXene Electrodes in Room Temperature Ionic Liquid

MXenes exhibit excellent capacitance at high scan rates in sulfuric acid aqueous electrolytes, but the narrow potential window of aqueous electrolytes limits the energy density. Organic electrolytes and room-temperature ionic liquids (RTILs) can provide higher potential windows, leading to higher energy density. The large cation size of RTIL hinders its intercalation in-between the layers of MXene limiting the specific capacitance in comparison to aqueous electrolytes. In this work, different chain lengths alkylammonium (AA) cations are intercalated into Ti₃C₂T_x, producing variation of MXene interlayer spacings (d-spacing). AA-cation-intercalated Ti₃C₂T_x (AA-Ti₃C₂), exhibits higher specific capacitances, and cycling stabilities than pristine Ti₃C₂T_x in 1 m 1-ethly-3-methylimidazolium bis-(trifluoromethylsulfonyl)-imide (EMIMTFSI) in acetonitrile and neat EMIMTFSI RTIL electrolytes. Pre-intercalated MXene with an interlayer spacing of ≈2.2 nm, can deliver a large specific capacitance of 257 F g⁻¹ (1428 mF cm⁻² and 492 F cm⁻³) in neat EMIMTFSI electrolyte leading to high energy density. Quasi elastic neutron scattering and electrochemical impedance spectroscopy are used to study the dynamics of confined RTIL in pre-intercalated MXene. Molecular dynamics simulations suggest significant differences in the structures of RTIL ions and AA cations inside the Ti₃C₂T_x interlayer, providing insights into the differences in the observed electrochemical behavior.     

Cone calorimeter — an alternative calibration constant calculation

This paper focuses on an alternative method of calculating the calibration constant, C, used in the cone calorimeter. The alternative method is derived from the principles of thermochemistry. It is based on carbon dioxide measurements and implicit knowledge of water vapour and fuel mass loss and is independent of the oxygen concentration. In the final form, the equation for the alternative calibration constant is much simpler than the standard equation. An uncertainty analysis of the alternative technique is also presented in this paper and the alternative method was found to a have marginally lower uncertainty than the Standard method. Notwithstanding these advantages, the Standard method remains the preferred technique for calculating the calibration constant as it is based on the operating principle of the apparatus and includes an oxygen measurement term. However, the alternative method can be easily incorporated into software and act as a means for checkin/troubleshooting the cone calorimeter. Copyright © 2000 John Wiley & Sons Ltd.     

Numerische Berechnung von Holzkonstruktionen unter Verwendung eines orthotropen elasto-plastischen Werkstoffmodells

To be able to perform more realistic simulations of timber constructions with modern numerical simulation methods like the finite element method (FEM), a suitable constitutive material model is required. Such a material model was developed by Mackenzie-Helnwein et al. (2005) for clear spruce wood. This paper presents an application-oriented adaption and usage of the mentioned material model, its implementation in a FE software as well as performing ultimate load analyses using FEM and the validation of the material model by means of the comparison of results of FE Simulations and experiments on the structure level (Fleischmann 2005). Further, some aspects with respect to the standardisation are discussed in one of the two examples.     

A mechanistic method for scrutinising LIFT ignition data

The lateral ignition and flame spread test (LIFT) standard (ASTM E 1321‐97a) requires the Thermal Response correlation to be scrutinized for data points that violate the zero heat loss requirement, but the standard gives no guidance on how this should be done. The fundamentals of linear regression were reviewed and an unbiased and mechanistic algorithm for scrutinising LIFT ignition data without human intervention was developed. The algorithm produced reasonable results compared with human interpretation of exemplar test data taken from the literature. Copyright © 2010 John Wiley & Sons, Ltd.     

Single‐step synthesis of a radically polymerizable 1,1′‐bi‐2‐naphthol derivative for asymmetric catalysis

A new polymerizable 1,1′‐bi‐2‐naphthol derivative for polymer‐supported catalytic asymmetric synthesis is presented. The synthesis is conducted within a single reaction step, which is a major advantage over other approaches presented in the literature. The ligand‐bearing polymer is prepared through copolymerization with N‐isopropylacrylamide. Preliminary experiments on the utility in catalytic asymmetric alkylation reactions reveal the accessibility and activity of the polymer‐attached catalysts. The stereoselectivity of the reaction is found to be somewhat lower than for reactions performed in the presence of free 1,1′‐bi‐2‐naphthol, and thus requires further optimization. The enantiomeric excess of the reaction products was determined via ¹H NMR spectroscopy after chiral derivatization with (R)‐α‐methylbenzyl isocyanate. © 2015 Society of Chemical Industry     

Performance of bipolar trickle reactors

The performance of the bipolar trickle reactor has been studied using the electrochemical tracer technique. The theoretical equations for a semi-infinite dispersion model have been fitted to the experimental responses for the reactor with and without electrochemical reaction. Hydrodynamic parameters and reaction rate constants for copper deposition as functions of both the film Reynolds number and the dimensions of the bipolar trickle reactor have been derived and are interpreted in this paper.List of Symbols (Bo) Bodenstein number (uL _p/D) - C amplitude of the response curve (dimen sionless) - C ⁰ area under the response curve (mol cm^–3 s) - D dispersion coefficient (cm²s^–1) - h film thickness (cm) - k/h first order reaction rate constant (s^–1) - L length of the reactor (cm) - L _p length of the ring (cm) - n _r number of rings in a single layer - (Pe) Peclét number (uL/D) - (Re)_f film Reynolds number - r _i,r _o inner and outer radii of the ring (cm) - t time (s) - u mean liquid velocity (cm s^–1) - v volumetric liquid velocity (cm³ s^–1) - residence time (s) - kinematic viscosity (cm²s^–1)     

maXs: Microcalorimeter Arrays for High-Resolution X-Ray Spectroscopy at GSI/FAIR

Highly-charged heavy ions like U⁹¹⁺ provide unique conditions for the investigation of relativistic and quantum electrodynamical effects in strong electromagnetic fields. We present two X-ray detectors developed for high-resolution spectroscopy on highly-charged heavy ions. Both detectors consist of metallic magnetic calorimeters (MMCs) forming linear eight-pixel arrays. The first detector, maXs-20, is developed for the detection of X-rays up to 20?keV with an energy resolution below 3?eV. The second device, maXs-200, is designed for X-ray energies up to 200?keV with an energy resolution of 40?eV. The results of characterization measurements of single detectors of both arrays will be shown and discussed. In both cases, the performance of the detectors agrees well with their design values. Furthermore, we present a prototype MMC for soft X-rays with improved magnetic flux coupling. In first characterization measurements the energy resolution of this device was 2.0?eV (FWHM) for X-rays up to 6?keV.     

Microstructured Magnetic Calorimeter with Meander-Shaped Pickup Coil

In the last years metallic magnetic calorimeters (MMC) showed an energy resolution of a few eV for x-rays up to 10 keV. This makes MMCs a promising and powerful tool for many applications where photons or energetic massive particles have to be detected—like absolute activity measurements of radioactive isotopes, high resolution x-ray spectroscopy and x-ray fluorescence material analysis. However, in order to fulfill all requirements of these applications and to allow to reach the maximum resolving power a consequent micro-fabrication of the MMC detectors is needed. The micro-fabrication of metallic magnetic calorimeters requires reliable deposition and patterning processes for niobium structures with high critical currents and for paramagnetic sensors. As one result of our advances in microstructuring a fully microfabricated MMC which consists of a meander shaped niobium thin film pickup coil and a 3 μm thick sputter deposited paramagnetic Au:Er temperature sensor will be presented. Deposition of energy in the paramagnetic sensor causes a rise in temperature and results in a change of magnetization, which is measured by a low noise high bandwidth dc-SQUID. The sputter deposited Au:Er films we report on are working well and show thermodynamic properties close to the ones known from bulk material down to temperatures of 45 mK.