Anisotropic long-range spin transport in canted antiferromagnetic orthoferrite YFeO3.

In antiferromagnets, the efficient transport of spin-waves has until now only been observed in the insulating antiferromagnet hematite, where circularly (or a superposition of pairs of linearly) polarized spin-waves diffuse over long distances. Here, we report long-distance spin-transport in the antiferromagnetic orthoferrite YFeO3, where a different transport mechanism is enabled by the combined presence of the Dzyaloshinskii-Moriya interaction and externally applied fields. The magnon decay length is shown to exceed hundreds of nanometers, in line with resonance measurements that highlight the low magnetic damping. We observe a strong anisotropy in the magnon decay lengths that we can attribute to the role of the magnon group velocity in the transport of spin-waves in antiferromagnets. This unique mode of transport identified in YFeO3 opens up the possibility of a large and technologically relevant class of materials, i.e., canted antiferromagnets, for long-distance spin transport.

Mechanism of Néel Order Switching in Antiferromagnetic Thin Films Revealed by Magnetotransport and Direct Imaging.

We probe the current-induced magnetic switching of insulating antiferromagnet-heavy-metal systems, by electrical spin Hall magnetoresistance measurements and direct imaging, identifying a reversal occurring by domain wall (DW) motion. We observe switching of more than one-third of the antiferromagnetic domains by the application of current pulses. Our data reveal two different magnetic switching mechanisms leading together to an efficient switching, namely, the spin-current induced effective magnetic anisotropy variation and the action of the spin torque on the DWs.

Application of proton-transfer-reaction-mass-spectrometry for Indoor Air Quality research.

In the field of Indoor Air Quality research, the measurement of volatile organic compounds (VOCs) demands instruments that are rapid, mobile, robust, highly sensitive and allow for simultaneous monitoring of multiple compounds. These instruments should also compensate for possible interferences from permanent gases and air humidity. Proton-transfer-reaction-mass-spectrometry (PTR-MS) has proved to be a valuable and promising technique that fits the mentioned requirements for a suitable online measuring device. In this study, five exemplary applications of PTR-MS are described: (i) release of paint additives during drying process, (ii) emission of VOCs from active hardcopy devices, (iii) reference material evaluation, (iv) diffusion studies, and (v) emission testing of building products. The examples are selected to illustrate possibilities and limitations of the PTR technique in this field of research. The quadruple-based PTR-QMS was able to determine the emission characteristics during the experiments, especially in case of depleting emission sources (e.g., reference material). This allows for chemometrical analysis of the measured release patterns and detection of underlying processes. However, PTR-QMS reaches a functional limit in case of compound identification. If identification of VOCs is necessary, the measurements need to be accompanied by GC/MS analytics or a PTR instrument with higher mass-resolution (e.g., PTR-TOF-MS).

Photocatalytic surface reactions on indoor wall paint.

The reduction of indoor air pollutants by air cleaning systems has received considerable interest, and a number of techniques are now available. So far, the method of photocatalysis was mainly applied by use of titanium dioxide (TiO2) in flow reactors under UV light of high intensity. Nowadays, indoor wall paints are equipped with modified TiO2 to work as a catalyst under indoor daylight or artificial light. In chamber experiments carried out under indoor related conditions itwas shown thatthe method works for nitrogen dioxide with air exchange and for formaldehyde without air exchange at high concentrations. In further experiments with volatile organic compounds (VOCs), a small effect was found for terpenoids with high kOH rate constants. For other VOCs and carbon monoxide there was no degradation at all or the surface acted as a reversible sink. Secondary emissions from the reaction of paint constituents were observed on exposure to light. From the results it is concluded that recipes of photocatalytic wall paints need to be optimized for better efficiency under indoor conditions.

Flame retardants in the indoor environment -- Part II: release of VOCs (triethylphosphate and halogenated degradation products) from polyurethane.

Organophosphate esters, halogenated and non-halogenated, are frequently used for fire protection of building materials. With regard to toxicological profiles it is desired to avoid human exposure in the indoor environment. Moreover, some hazardous volatile organic compounds detected in indoor air are directly linked to the utilization of flame retardants. In this study, different polyurethane (PUR) products for building and indoor use treated with organophosphate flame retardants were tested in 1 m(3) emission test chambers. Emissions of flame retardants and degradation products were measured under living conditions. A PUR hard foam sample showed area-specific emission rates >100 microg/m(2) h for the compound triethylphosphate. During the tests several chlorinated degradation products of organophophorous flame retardants could be identified in the chamber air.

Phthalic esters in the indoor environment--test chamber studies on PVC-coated wallcoverings.

Phthalic acid esters are important additives in polyvinyl chloride (PVC) products. Since PVC plastisoles for the production of wallcoverings contain about 30% phthalic acid esters, it is a crucial question whether these products can contribute to the pollution of the indoor environment. In this study, the emission of several technically relevant phthalates from PVC-coated wallcoverings were measured in emission test chambers under standard room conditions. During a 14-day test period, both the chamber air concentrations and the condensation on a cooled plate (fogging) were determined. In the chamber air, maximum concentrations of 5.1 micrograms/m3 for di-n-butylphthalate (DBP), 2.08 micrograms/m3 for di-pentylphthalate (DPP) and 0.94 microgram/m3 for di-(2-ethylhexyl)phthalate (DEHP) were found. After 14 days of exposure, up to 60.4 micrograms DEHP and 17.7 micrograms DPP could be quantified on the cooled plates of the fogging apparatus. The amounts of DBP and DIBP were significantly lower. A simple exposure calculation indicated no specific risk of an increased phthalate exposure in rooms with PVC wallcoverings.

Release of acetic acid and furfural from cork products.

Cork samples were exposed to different temperatures and volatile ingredients were analyzed using gas chromatography/mass spectrometry (GC/MS). Thermal treatment at 180 degrees C yielded considerable amounts of furfural and acetic acid. In accordance with previous investigations it was concluded that both compounds are produced under thermal stress from degradation of polyoses.

A routine method for the determination of the TVOC content in wallcoverings using headspace gas-chromatography.

A method for the fast routine analysis of the total content of volatile organic compounds in wallcoverings and paper products was developed, using headspace gas-chromatography for quantification. 57 wallcoverings of different types were investigated. Typical components were toluene, methyl-ethyl ketone, methyl-iso-butyl ketone, n-butyl acetate and iso-butyl acetate, all compounds being used as industrial solvents. The TVOC concentrations are calculated in toluene-carbon equivalents and ranged from 0.31 microg/g to 1789 microg/g with an average value of 123.22 microg/g and a median of 20.37 microg/g. To obtain an estimation of VOC-concentrations in indoor air, 10 selected wallcoverings were also analyzed in a 1 m(3) climate test chamber. A correlation between headspace data and chamber concentrations could not be observed, which might be a result of increased analytical uncertainties at low emission rates under chamber conditions.

Topical mosquito repellents XIII: Cyclic analogs of lactic acid.

Numerous cyclic analogs of lactic acid were synthesized to ascertain whether they might act as agonists of antagonists of lactic acid, a known attractant for mosquitoes. These compounds were evaluated with an in vitro blood-feeding test system and an in vivo cloth test. Two of the compounds in the blood-feeding test system showed biphasic results, acting as attractants at low concentrations and as repellents at higher concentrations. Several compounds (III, V, VII, and X) repelled Aedes aegypti mosquitoes in the blood-feeding test system. However, in the in vivo cloth test system, only III repelled the mosquitoes significantly.