Comparison of separation performances of amylose- and cellulose-based stationary phases in the high-performance liquid chromatographic enantioseparation of stereoisomers of β-lactams

High-performance liquid chromatographic methods were developed for the separation of the enantiomers of 19 β-lactams. The direct separations were performed on chiral stationary phases containing either amylose tris(3,5-dimethylphenylcarbamate), (Kromasil® AmyCoat? column) or cellulose tris(3,5-dimethylphenylcarbamate), (Kromasil® CelluCoat? column) as chiral selector. The different methods were compared in systematic chromatographic examinations. The separations were carried out with good selectivity and resolution. The AmyCoat? and CelluCoat? columns appear to be highly complementary. The best separations of bi- and tricyclic β-lactam stereoisomers were obtained with the AmyCoat? column, while the 4-aryl-substituted β-lactams were better separated on the CelluCoat? column. The elution sequence was determined in all cases; no general rule could be established.     

Solving some NP-complete problems using split decomposition

We show how to use the split decomposition to solve some NP-hard optimization problems on graphs. We give algorithms for clique problem and domination-type problems. Our main result is an algorithm to compute a coloration of a graph using its split decomposition. Finally we show that the clique-width of a graph is bounded if and only if the clique-width of each representative graph in its split decomposition is bounded.     

Chemical bonding in view of electron charge density and kinetic energy density descriptors

Stalke's dilemma, stating that different chemical interpretations are obtained when one and the same density is interpreted either by means of natural bond orbital (NBO) and subsequent natural resonance theory (NRT) application or by the quantum theory of atoms in molecules (QTAIM), is reinvestigated. It is shown that within the framework of QTAIM, the question as to whether for a given molecule two atoms are bonded or not is only meaningful in the context of a well‐defined reference geometry. The localized‐orbital‐locator (LOL) is applied to map out patterns in covalent bonding interaction, and produces results that are consistent for a variety of reference geometries. Furthermore, LOL interpretations are in accord with NBO/NRT, and assist in an interpretation in terms of covalent bonding. © 2008 Wiley Periodicals, Inc.J Comput Chem, 2009.     

Über den indirekten Nachweis und die Bestimmung der Alkali sulfate

Analytical and Bioanalytical Chemistry -     

Notiz über eine allgemeine Integralformel

Ohne Zusammenfassung     

Structuring production planning systems for computer applications

Activities in a job shop type mechanical company can be split in production, product cycle and production cycle. The corresponding flow in each of these are materials, manufacturing specifications and product requirements. Production planning will plan and control these flows. Basic data structures are a product model and a corresponding hierarchy linked to production resources. A planning system may be designed by combining a set of operation or building blocks. These are three types: user communication, data base management and basic operations. The basic operations cover all processing necessary in production planning and represent the fundamental building blocks. A list of basic operations is suggested.