Zur tritrimetrischen Bestimmung des Quecksilberchlorids in Sublimatpastillen

Ohne Zusammenfassung     

Theorie der Elemententripel einstufiger Elementargebilde

Annali di Matematica Pura ed Applicata (1867-1897) -     

Über die Inhaltsstoffe der Wurzel von Pimpinella saxifraga I

Ohne Zusammenfassung     

Über die Inhaltsstoffe der Wurzel von Pimpinella saxifraga II

Ohne Zusammenfassung     

Buchbesprechungen

Ohne Zusammenfassung     

Combining UK and German emissions monitoring proficiency testing data based on stack simulator facilities to determine whether increasingly stringent EU emission limits are enforceable

Accreditation and Quality Assurance - We report an examination of the capability of the existing measurement infrastructure in the industrial emissions sector for successfully enforcing emission...     

Particle Sizes of Fumed Silica

Fumed silica is a synthetic amorphous silicon dioxide produced by burning silicon tetrachloride in an oxygen-hydrogen flame. Surface areas range from 50 up to 400 m²/g. Using particle sizing techniques, fumed silica shows micro-sized particles leading to surface areas markedly lower than expected. Fumed silica appears as a fluffy solid with bulk densities down to 0.03 g/cm³, being invariant over the wide range of surface areas. Attempts to relate the variation of the surface area directly to the performance of fumed silica in technical applications, such as its thickening efficiency in fluids, mainly fail and remain ambiguous. The aim of this work was to investigate the particle sizes and structures of fumed silica aggregates and agglomerates, using different particle dispersion and sizing techniques.     

A structural study of the retinal photoreceptor, plexiform and ganglion cell layers following exposure to UV-B and UV-C radiation in the albino rat

Over the last two decades, ultraviolet radiation levels (UV), reaching the Earth's surface, have been increasing at a rate of 1.5% per each 1% loss of the ozone layer. Moreover, artificial UV-sources have also proliferated and contributed to the rising UV-stress that many organisms have to face. To assess how the vertebrate retina responds to an exposure of short wavelength UV, we focused our attention on the rat retina, observing photoreceptor (containing outer and inner segments of rods and cones), inner plexiform, and ganglion cell layers by light and transmission electron microscopy using conventional and cytochemical techniques. We analyzed how cells of the layers in question responded to a 30 min exposure to UV-C and UV-B radiation with doses of 7200 and 590 J/cm², respectively. The results show that there are significant changes in the nuclei and cytoplasmic organelles of the exposed retinae when compared with those of the unexposed controls. The changes include an increase in heterochromatin, distension of rough endoplasmic reticulum, mitochondrial disruptions, and increases in the number of myelin bodies. The recorded morphological changes, especially those of the ganglion cells, are suggestive of apoptotic processes and show that the exposure of vertebrate retina to wavelengths ranging from 254 to 312 nm can produce alterations that are likely to impact negatively on the retina's proper functioning.     

Influence of different extraction parameters on a solid-phase dynamic extraction for the gas chromatographic determination of d-limonene degradation products by using a fractional factorial design

Through the application of a solid-phase dynamic extraction (SPDE) method for the determination of volatile substances, different parameters may influence the extraction and desorption process and are, therefore, vital for the determination of the extracted substances via gas chromatography (GC). In this study, the influence of extraction und desorption parameters of an SPDE-GC method for the determination of the d-limonene degradation products, namely, alpha-terpineol, (-)-carveol, and (S)-carvone, in an aqueous model system was evaluated using a factorial fractional design. The aim was to reduce the number of factors that should be considered for the optimization of an SPDE procedure for different applications. It could be shown that the extraction efficiency of alpha-terpineol, (-)-carveol, and (S)-carvone is significantly influenced by the extraction parameters incubation temperature, number of extraction strokes, and amount of added NaCl. All 3 parameters have a positive effect on the extraction and determination of the examined d-limonene degradation products. Due to the identification of significant factors on the basis of an experimental design, the results of this study can be very useful for further development of SPDE methods for different applications.