Asymmetric hydrogenation of alkyl(vinyl)thioethers: a promising approach to α-chiral thioethers

This paper describes the enantioselective hydrogenation of vinylthioethers. We show that thioether derivatives of maleic esters can be hydrogenated with full conversion and up to 60% ee, and that α-thioether cinnamic acids can be hydrogenated in 51% ee with modest conversion.     

Thiazolylazo dyestuffs as coordinating ligands : Part I. the stability constants for 4-(2-thiazolylazo)-resorcinol and related compounds

The complex forming properties of the thiazole azo dyestuffs and related compounds have been studied in order to try to ascertain the role of importance of the donor atoms present in thiazolylazo-resorcinol. Potentiometric titrations were employed for these determinations, although in many cases meaningful stability constants could not be obtained because of reagent instability or insolubility of the complexes formed on chelation.     

1,3-Oxazolidin-4-ones. Synthesis and configuration of cis and trans isomers

Mixtures of cis and trans 1,3-oxazolidin-4-ones were obtained by cyclodehydration, in the presence of p-toluenesulfonic acid or boron trifluoride etherate, of lactamide and N-methyl-lactamide with aromatic and aliphatic aldehydes. The products were separated by column (silica) chromatography and their configurations were determined.     

The development of nuclear microprobe techniques for the spatial determination of13C and13C/12C ratios

Sensitive and selective nuclear reaction methods have been sought for the nuclear microprobe measurement of the spatial distributions of¹³C and¹³C/¹²C ratios. The¹³C(α, n)¹⁶O reaction, with neutron detection, is the most selective for¹³C, and has a sensitivity of ca. 100 ppm. The reactions¹³C(d, p)¹⁴C and¹²C(d, p)¹³C, with proton detection, are the most sensitive for the simultaneous measurement of¹³C and¹²C, with detection limits of 30 and 2 ppm respectively. Less sensitive alternative reaction pairs are;¹³C(³He, p)¹⁵N and¹²C(³He, p)¹⁴N;¹³C(d, nγ)¹⁴N and¹²C(d, pγ)¹³C;¹³C(³He, pγ)¹⁵N and¹²C(³He, pγ)¹⁴N. The conditions governing their use, particularly light element interferences, are detailed.     

Platin

Ohne Zusammenfassung     

Method development and inter-laboratory comparison about the determination of titanium from titanium dioxide nanoparticles in tissues by inductively coupled plasma mass spectrometry

Nanosized titanium dioxide (TiO₂) is one of the most interesting and valuable nanomaterials for the construction industry but also in health care applications, food, and consumer goods, e.g., cosmetics. Therefore, the properties associated with this material are described in detail. Despite its widespread use, the analytical determination and characterization of nanosized metal oxides is not as straightforward as the comparatively easy-to-detect metallic nanoparticles (e.g., silver or gold). This study presents the method development and the results of the determination of tissue titanium (Ti) levels after treatment of rats with the nanosized TiO₂. Total Ti levels were chosen to evaluate the presence and distribution of TiO₂ nanoparticles. A procedure consisting of incubation with a mixture of nitric acid (HNO₃) and hydrofluoric acid (HF), and heating was developed to digest tissues and TiO₂ nanomaterials in order to determine the total Ti content by inductively coupled plasma mass spectrometry (ICPMS). For the inter-laboratory comparison, altogether four laboratories analyzed the same samples upon digestion using the available ICPMS equipment. A major premise for any toxicokinetic study is the possibility to detect the chemical under investigation in biological samples (tissues). So, the study has to be performed with a dose high enough to allow for subsequent tissue level measurement of the chemical under investigation. On the other hand, dose of the chemical applied should not induce over toxicity in the animal as this may affect its absorption, distribution, metabolism, and excretion. To determine a non-toxic TiO₂ dosage, an acute toxicity study in rats was performed, and the organs obtained were evaluated for the presence of Ti by ICPMS. Despite the differences in methodology and independent of the sample preparation and the ICPMS equipment used, the results obtained for samples with Ti concentrations >4 μg Ti/g tissue agreed well.

Maximal inequalities via bracketing with adaptive truncation

The paper provides a recursive interpretation for the technique known as bracketing with adaptive truncation. By way of illustration, a simple bound is derived for the expected value of the supremum of an empirical process, thereby leading to a simpler derivation of a functional central limit theorem due to Ossiander. The recursive method is also abstracted into a framework that consists of only a small number of assumptions about processes and functionals indexed by sets of functions. In particular, the details of the underlying probability model are condensed into a single inequality involving finite sets of functions. A functional central limit theorem of Doukhan, Massart and Rio, for empirical processes defined by absolutely regular sequences, motivates the generalization.     

A review and tutorial discussion of noise and signal-to-noise ratios in analytical spectrometry—II. Fundamental principles of signal-to-noise ratios

This part of the review links up with the tutorial discussion in Part I and gives general signal-to-noise expressions for emission and luminescence spectrometric systems. Tabular presentations are used for the expressions and for comparison of noise sources.