Note on maximal split-stable subgraphs

A multigraph G=(V,R∪B) with red and blue edges is an R/B-split graph if V is the union of a red and a blue stable set. Gavril has shown that R/B-split graphs yield a common generalization of split graphs and König-Egerváry graphs. Moreover, R/B-split graphs can be recognized in linear time. In this note, we address the corresponding optimization problem: identify a set of vertices of maximal cardinality that decomposes into a red and a blue stable set. This problem is NP-hard in general. We investigate the complexity of special and related cases (e.g., (anti-)chains in partial orders and stable matroid bases) and exhibit some NP-hard cases as well as polynomial ones.     

Determination of organotin compounds in marine sediments using graphite furnace atomic absorption spectrometry

Organotin compounds, especially tributyltin, began to cause concern 10 years ago due to a high toxicity towards marine organisms. Several methods of analysing organotin compounds in various matrices have already been developed to determine organotin species simultaneously, but these are quite expensive as special equipment and specialized staff are needed. A simple screening method, which determines the organic tin compounds in the sediment, has therefore been developed and validated. The method can easily be implemented in laboratories accustomed to tracelement analyses; the sediment is extracted by a two-phase extraction and the organic extract is analysed using graphite furnace atomic absorption spectrometry (GF AA.) The screening method has been validated using high-pressure liquid chromatography-inductively coupled plasma mass spectrometry (HPLC–ICP MS).     

Sterisch gehinderte Alkene,VII Röntgenstrukturanalyse und Reaktionen des Tetrakis-(2-formyl-2-propyl)ethens

The tetraaldehyde {=1} was synthesized by ozonation of the triene {=3}. The C=C-bond in {=1} is twisted by 28.6° and the CC-bond and the allylic bond lengths are significantly elongated to 135.7 and 155.5–159.7 pm, resp.     

Pulsed laser deposition of metals in various inert gas atmospheres

The changes in the properties of laser deposited metal thin films were investigated in different inert gas atmospheres (He, Ne, Ar and Xe). With increasing inert gas pressure, the reduction of particle energy is accompanied by a strong increase of the deposition rate (especially in He atmosphere), a transition from compressive to tensile stress, and changes in structure and texture. This is explained by a reduction of surface mobility of the deposited particles, a decrease of implantation, resputtering and shot-peening effects. At high gas pressures, deposition conditions similar to sputtering or even thermal deposition are obtained. PACS 68.55.-a; 81.15.Fg