Prins-Reaktionen mit Arylaldehyden, 3. Mitt.

By reaction of excess benzaldehyde with cyclohexene in presence of sulfuric acid besider-2,c-4-diphenyl-(t-4aH,c-8aH)-hexahydro-4H-1,3-benzodioxin (2) andr-4-phenyl-(t-4aH,c-8aH)-hexahydro-4H-1,3,2-benzodioxathiin-2,2-dioxide (3),trans-2-benzyloxycyclohexyl phenyl ketone (5) and (E)-3-benzylidene-1-cyclohexenyl phenyl ketone (6) are obtained. The formation of5 and6 is shown to proceed via an acid catalyzedCannizzaro reaction of benzaldehyde.

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2. Mitt.:H. Griengl undK. P. Geppert, Mh. Chem.107, 675 (1976).     

Hydrothermal deamidation of 4-N-acylcytosine nucleoside derivatives: efficient synthesis of uracil nucleoside esters

[reaction: see text] N,O-Peracylated cytidine and 2'-deoxycytidine derivatives in superheated water/DME solutions (oil bath at 125 degrees C) undergo hydrolytic deamidation (and/or N-deacylation). Acylated starting materials derived from arylcarboxylic acids give the corresponding uridine esters cleanly, and such derivatives crystallize selectively from the cooled reaction mixtures in high yields.     

Pattern generation with cesium atomic beams at nanometer scales

We have demonstrated that a cesium atomic beam can be used to pattern a gold surface using a self assembling monolayer (SAM) as a resist. A 12.5 m period mesh was used as a proximity mask for the atomic beam. The cesium atoms locally change the wetability of the SAM, which allows a wet etching reagent to remove the underlying gold in the exposed regions. An edge resolution of better than 100 nm was obtained. The experiment suggests that this method can either be used as a sensitive position detector with nanometer resolution in atom optics, or for nanostructuring in a resist technique.     

Fabrication and dielectric properties of modified calcium (Pb<Subscript>0.75</Subscript>Ba<Subscript>0.25</Subscript>)(Zr<Subscript>0.7</Subscript>Ti<Subscript>0.3</Subscript>)O<Subscript>3</Subscript> ceramics

The aim of the present work is to report investigations concerning the influence of homovalent modificators on relaxor properties of PBZT 25/70/30 ceramics. The selection of the proper homovalent additive was very important. Literature reports as well as data taken from the periodic table indicated, that calcium ions substitute themselves for lead ions with high likelihood of occurrence. The investigations showed that the substitution significantly changed the microstructure of ceramics – with grains of calcium modified ceramics decreasing and density increasing. The XRD measurements indicate that the pure PBZT ceramics as well as calcium dopant were characterised by tetragonal structure with space group I4 /mmm. Addition of calcium leads to a slight decrease in the lattice constant and crystal structure. The calcium modification also changes the dielectric properties. The temperature characteristic of the dielectric constant achieved a broadened maximum at temperature T_m, which decreases with increasing Ca content. The properties typical for ferroelectric relaxors weaken with increasing calcium dopant.     

Sorptive properties of aluminium ions containing mesoporous silica towards <Emphasis Type="SmallCaps">l</Emphasis>-histidine

The applicability of aluminium-containing mesoporous materials as carriers for l-histidine has been evaluated for the first time. The modified mesoporous silica such as SBA-15 and SBA-16 were synthesised by hydrothermal method and characterised by low-temperature nitrogen sorption, transmission and scanning microscopy, X-ray and laser diffraction methods. The results of these studies confirmed the ordered mesoporous structures of all materials obtained. The modification of mesoporous materials with aluminium ions changed the textural parameters and particle size distribution relative to those in the pristine material. Aluminium-modified SBA-15 exhibited higher release rate of amino acid than the pure material. The opposite phenomenon was observed when l-His was released from pristine and modified SBA-16 materials. The kinetics of amino acid release from all mesoporous materials followed the Korsmeyer–Peppas model. The results proved that the structural parameters of mesoporous materials and the percentage content of aluminium strongly influenced the release rate of l-His.     

Uncertainty of carboxyhaemoglobin determination in putrefied blood by headspace gas chromatography

The uncertainty of carboxyhaemoglobin (COHb) determination in post-mortem blood samples by headspace gas chromatography with the use of methanizer and flame ionization detector was estimated. Four main components of uncertainty were identified, i.e. calibration, measurement repeatability, standard solutions preparation and sample preparation, and their contributions to the combined uncertainty were determined. The calibration step was the dominating source of uncertainty, counting for more than 39 % of overall variance. The contribution of remaining sources to the combined uncertainty was lower than 31 % (measurement repeatability), 21 % (standards preparation) and 12 % (sample preparation). The calculated absolute expanded uncertainty in samples containing 3.8–82 % mass fraction of COHb ranged between 2.2 % and 2.6 % (coverage factor 2), depending only slightly on the analyte level in the analysed sample.     

Development of a microwave-assisted extraction of atropine and scopolamine from Solanaceae family plants followed by a QuEChERS cleanup procedure

In this work, a novel method based on the microwave-assisted extraction (MAE), the QuEChERS dispersive solid-phase extraction and gas chromatography–mass spectrometry was developed for the determination of atropine and scopolamine in plant samples from Datura and Brugmansia genera, which belong to the Solanaceae family. The experimental conditions for MAE, such as temperature, time of extraction, and volume of the extracting solvent as well as extract purification procedure parameters were optimized by the Doehlert uniform shell design and the response surface methodology. For quantitative analysis and validation, a standard addition calibration method was used to reduce the matrix effect. The limits of detection from 3.0 to 3.4 µg g^?1 of dry matter and the linearity of the calibration dependence were suitable for the analysis of plant extracts. The repeatability and intermediate precision for both analytes were found to be acceptable (<15%). The developed method was successfully applied to the samples of leaves and seeds of Datura and Brugmansia.     

A Family of Partial Geometric Designs from Three‐Class Association Schemes

In this paper, we show that partial geometric designs can be constructed from certain three‐class association schemes and ternary linear codes with dual distance three. In particular, we obtain a family of partial geometric designs from the three‐class association schemes introduced by Kageyama, Saha, and Das in their article [“Reduction of the number of associate classes of hypercubic association schemes,” Ann Inst Statist Math 30 (1978)]. We also give a list of directed strongly regular graphs arising from the partial geometric designs obtained in this paper.