Molekulargewichtsbestimmungsmethoden unter Anwendung kleiner Substanzmengen

Ohne Zusammenfassung     

Fortschritte in der Kryoskopie und Ebullioskopie

Ohne Zusammenfassung     

Zur Bestimmung von Siedepunkten unter konstanten Bedingungen

Ohne Zusammenfassung     

Raman spectra of mirabilite,Na2SO4·10H2O and the rediscovered metastable heptahydrate,Na2SO4·7H2O

Salt crystallisation in pores is known to cause serious damage to masonry. Sodium sulphate, often regarded as one of the most damaging salts, has a rich hydrate chemistry including one rediscovered metastable hydrate and a new high pressure octahydrate plus five known polymorphs of the anhydrous phase. The difficulty in working with these hydrates lies in their strong tendency to dehydrate or to convert to the stable phase, in the case of the heptahydrate. We present Raman spectra and a table of peak wavenumbers for randomly oriented crystals of mirabilite and the metastable heptahydrate, sufficient to distinguish between these phases that have SO₄ν₁ values of 989.3 and 987.6 cm⁻¹, respectively. Mirabilite has a Raman spectrum very similar to the free sulphate anion in solution, which is probably due to the mobility of oxygen atoms within the sulphate tetrahedron. The oxygen atoms in the heptahydrate sulphate groups have no partial occupancy, and predicted peak splitting is observed in the region 400–1200 cm⁻¹. Copyright © 2010 John Wiley & Sons, Ltd.     

High sensitivity detection of trace gases at atmospheric pressure using tunable diode lasers

A detailed study of the detection of trace gases at atmospheric pressure using tunable diode lasers is described. The influence of multipass cells, retroreflectors and topographical targets is examined. The minimum detectable infrared absorption ranges from 0.1% for a pathlength of 1.2 km to 0.01% over short pathlengths. The factors which limit this sensitivity are discussed, and the techniques are illustrated by monitoring atmospheric CO₂ and CH₄.     

Nanostructured ZrO2-Coated TiO2 Electrodes for Dye-Sensitised Solar Cells

Thin films of ZrO₂ were deposited on nanostructured anatase TiO₂ electrodes via sol-gel route and utilised in the assembly of a dye-sensitised solar cells (DSSCs) forming nanostructured core-shell networks. The ZrO₂-coated TiO₂ electrodes were characterised by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and constructing a DSSC. The characterisation concluded that core-shell morphologies were produced with varying ZrO₂ shell thickness without altering the anatase TiO₂ core. When a DSSC was constructed from the ZrO₂:TiO₂ core-shell electrode, the efficiency increased to 2.27% from 0.42% for the uncoated TiO₂ electrode. As the ZrO₂ shell thickness increased, the cell efficiency was reduced.     

Behaviors producing photodispersal in Stentor coeruleus

The ciliate Stentor coeruleus exhibits photodispersal, that is, these cells swim away from light sources and collect in dimly lighted areas. We imaged and reconstructed the tracks of 48 Stentor to determine which swimming behaviors produced their photodispersal. We observed that their photodispersal is not due to a change in their swimming speed but rather to a change in the frequency with which they reorient their swimming direction. Therefore, their photodispersal must be due to either (1) a gradual reorientation of the organism's swimming direction determined by the direction of the light beam (phototaxis) or (2) multiple randomly directed reorientations in swimming direction that occur less frequently when the cell is swimming away from the light source (biased random walk). Sixteen (19%) of the 83 observed forward swimming tracks lasting three or more seconds exhibited a gradual bending away from the light source consistent with a phototaxis. However, most tracks were interrupted repeatedly by abrupt reorientations resulting from ciliary reversals and "smooth turns" that caused cells to reorient through 5.4 times as many degrees as were needed to direct them away from the light source. When cells were swimming away from the light source, their probability of reorienting was reduced and photodispersal resulted.