Discovery and Structure Determination of an Unusual Sulfide Telluride through an Effective Combination of TEM and Synchrotron Microdiffraction

The structure elucidation of the novel sulfide telluride Pb₈Sb₈S₁₅Te₅ demonstrates a new versatile procedure that exploits the synergism of electron microscopy and synchrotron diffraction methods for accurate structure analyses of side‐phases in heterogeneous microcrystalline samples. Suitable crystallites of unknown compounds can be identified by transmission electron microscopy and relocated and centered in a microfocused synchrotron beam by means of X‐ray fluorescence scans. The refined structure model is then confirmed by simulating HRTEM images of the same crystallite. Pb₈Sb₈S₁₅Te₅ consists of chains of heterocubane‐like units. Cation coordination polyhedra form unusually entwined chains of edge‐ and face‐sharing bicapped trigonal prisms. The structure data are precise enough for bond‐valence calculations, which confirm the disordered atom distribution. On this basis, optimization of physical properties becomes feasible.     

Peak assignment in multi-capillary column–ion mobility spectrometry using comparative studies with gas chromatography–mass spectrometry for VOC analysis

Over the past years, ion mobility spectrometry (IMS) as a well established method within the fields of military and security has gained more and more interest for biological and medical applications. This highly sensitive and rapid separation technique was crucially enhanced by a multi-capillary column (MCC), pre-separation for complex samples. In order to unambiguously identify compounds in a complex sample, like breath, by IMS, a reference database is mandatory. To obtain a first set of reference data, 16 selected volatile organic substances were examined by MCC-IMS and comparatively analyzed by the standard technique for breath research, thermal desorption–gas chromatography–mass spectrometry. Experimentally determined MCC and GC retention times of these 16 compounds were aligned and their relation was expressed in a mathematical function. Using this function, a prognosis of the GC retention time can be given very precisely according to a recorded MCC retention time and vice versa. Thus, unknown MCC-IMS peaks from biological samples can be assigned—after alignment via the estimated GC retention time—to analytes identified by GC/MS from equivalent accomplished data. One example of applying the peak assignment strategy to a real breath sample is shown in detail.     

A novel epitaxially grown LSO‐based thin‐film scintillator for micro‐imaging using hard synchrotron radiation

The efficiency of high‐resolution pixel detectors for hard X‐rays is nowadays one of the major criteria which drives the feasibility of imaging experiments and in general the performance of an experimental station for synchrotron‐based microtomography and radiography. Here the luminescent screen used for the indirect detection is focused on in order to increase the detective quantum efficiency: a novel scintillator based on doped Lu₂SiO₅ (LSO), epitaxially grown as thin film via the liquid phase epitaxy technique. It is shown that, by using adapted growth and doping parameters as well as a dedicated substrate, the scintillation behaviour of a LSO‐based thin crystal together with the high stopping power of the material allows for high‐performance indirect X‐ray detection. In detail, the conversion efficiency, the radioluminescence spectra, the optical absorption spectra under UV/visible‐light and the afterglow are investigated. A set‐up to study the effect of the thin‐film scintillator's temperature on its conversion efficiency is described as well. It delivers knowledge which is important when working with higher photon flux densities and the corresponding high heat load on the material. Additionally, X‐ray imaging systems based on different diffraction‐limited visible‐light optics and CCD cameras using among others LSO‐based thin film are compared. Finally, the performance of the LSO thin film is illustrated by imaging a honey bee leg, demonstrating the value of efficient high‐resolution computed tomography for life sciences.     

Detection of emissions from surfaces using ion mobility spectrometry

Emissions from surfaces (from furniture, wall paintings or floor coverings for instance) significantly influence indoor air quality and therefore the wellbeing or even the health of the occupants. Together with metabolites from mold they are responsible for the well-known “sick building syndrome”. Therefore, it is in the interest of the manufacturer as well as of the occupants to have a fast and accurate method for the detection of substances relevant to this syndrome in order to be able to monitor and control product quality and indoor air quality. The use of small and easy-to-transport ion mobility spectrometers that use UV light as the ionization source enables rapid in situ detection of such substances with high selectivity and sensitivity (detection limits in the lower ppb range). If a multicapillary column is used for preseparation as well, the selectivity is increased and the unwanted influence of humidity on the spectra can be eliminated, thus enabling the use of the instruments under normal ambient conditions. Furthermore, the use of air as carrier gas avoids the need for other sources of high-purity gas. An emission cell with a homogeneous and constant air flow over the surface to be investigated was developed in order to ensure reproducible results. Investigations of emissions from wooden surfaces with and without additional contamination as well as from complex mixtures are presented. The results demonstrate that relevant emissions can be identified and quantified with high sensitivity and selectivity in under five minutes. Therefore, the method is useful for indoor air quality monitoring, especially when miniaturized instruments are applied. Figure     

Signals in human breath related to Sarcoidosis. — Results of a feasibility study using MCC/IMS

Using a ⁶³Ni—Ion Mobility Spectrometer (IMS) coupled with a Multi-Capillary Column (MCC) the signals obtained are considered to identify characteristic peaks of volatile compounds in exhaled human breath samples of 10 mL volume. The breath of 20 patients with sarcoidosis and suspicion of sarcoidosis because of mediastinal lymp node enlargement was investigated. It could be shown that a procedure related to a single peak in the IMS-chromatogram delivers a differentiation into the two groups of patients with confirmed sarcoidosis and such suffering no sarcoidosis. The potential biomarker is characterised by the following parameters inverse mobility (1/K₀) 0.53 ± 0.01 Vs/cm²—retention time 22 ± 5 s. These results are a first step in breath analysis by MCC/IMS in patients with sarcoidosis.     

One-year time series of investigations of analytes within human breath using ion mobility spectrometry

Ion mobility Spectrometry is used to detect volatile analytes within human breath directly. Many volatile organic compounds (VOC) show significant day-to-day variation in the signal height related to the concentration of the analyte, although the breath collection had been performed under the same conditions with respect to similar sampling procedure, similar dead volume, similar measurement time, and measurement conditions. Variations of 8 different analytes are investigated over a time period of 11 months in the exhaled breath of the same person in the same room environment. The individual variability is reported for Benzothiazole; D-Limonene; Eucalyptol; Decamethylcyclopentasiloxane; Decanal; 1-Hexanol, 2-ethyl-; Cyclohexanone, 5-methyl-2-(1-methylethyl) and Nonanal. The paper shows, that the individual variability must be taken into consideration to relate the findings to medical questions. Therefore, the room air concentration of VOCs must be taken into account, so that the difference between exhaled and inhaled air has to be used as indicator. Finally, starting with individual variabilities, the normal variation related to the specific analyte should be considered in addition.     

Synthesis of Boc protected block copolymers based on para-hydroxystyrene via NMRP

Nitroxide mediated free radical polymerization (NMRP) was used for the preparation of orthogonally protected block copolymers based on para-hydroxystyrene. The polymers have a low polydispersity and an active chain end. By a series of polymer analogous reactions, a partly deprotected block copolymer was synthesized consisting of a block with unprotected phenolic OH groups and a further block which is protected by the thermolabile Boc group.     

Changes in lithium isotopic composition in hydrogen-enriched Ti/Al systems

Changes in the isotopic composition of electrolyte lithium are studied experimentally when thin-film titanium-aluminum systems are enriched in hydrogen. Strong deviations of the lithium isotope concentration from their natural abundances are observed both in the surface titanium layer and at the titanium-aluminum interface. Analysis of the experimental results permits us to conclude that isotope-induced transformations occur in materials enriched in hydrogen due to cold diffusion of impurity atoms stimulated by hydrogen migration and non-equilibrium chemical reactions. Tomsk Polytechnical University and Fraunhofer Institute for Non-Destructive Testing, Germany. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 29–33, November 1999.     

Coherence in microchip traps

We report the coherent manipulation of internal states of neutral atoms in a magnetic microchip trap. Coherence lifetimes exceeding 1 s are observed with atoms at distances of 5-130 microm from the microchip surface. The coherence lifetime in the chip trap is independent of atom-surface distance within our measurement accuracy and agrees well with the results of similar measurements in macroscopic magnetic traps. Because of the absence of surface-induced decoherence, a miniaturized atomic clock with a relative stability in the 10(-13) range can be realized. For applications in quantum information processing, we propose to use microwave near fields in the proximity of chip wires to create potentials that depend on the internal state of the atoms.