Problems, Models and Complexity. Part II: Application to the DLSP

In Part I of this study, we suggest to identify an operations research (OR) problem with the equivalence class of models describing the problem and enhance the standard computer-science theory of computational complexity to be applicable to this situation of an often model-based OR context. The Discrete Lot-sizing and Scheduling Problem (DLSP) is analysed here in detail to demonstrate the difficulties which can arise if these aspects are neglected and to illustrate the new theoretical concept. In addition, a new minimal model is introduced for the DLSP which makes this problem eventually amenable to a rigorous analysis of its computational complexity.     

GnRH binding RNA and DNA Spiegelmers: a novel approach toward GnRH antagonism

Mirror-image oligonucleotide ligands (Spiegelmers) that bind to the pharmacologically relevant target gonadotropin-releasing hormone I (GnRH) with high affinity and high specificity have been identified using the Spiegelmer technology. GnRH is a decapeptide that plays an important role in mammalian reproduction and sexual maturation and is associated with several benign and malignant diseases. First, aptamers that bind to D-GnRH with dissociation constants of 50-100 nM were isolated out of RNA and DNA libraries. The respective enantiomers of the DNA and RNA aptamers were synthesized, and their binding to L-GnRH was shown. These Spiegelmers bind to L-GnRH with similar affinity to that of the corresponding aptamers that bind to D-GnRH. We further demonstrated dose-dependent inhibition of GnRH-induced Ca(2+) release in Chinese hamster ovary cells that were stably transfected with the human GnRH receptor.     

Simultaneous determination of alkylphenol ethoxylates and their biotransformation products by liquid chromatography/electrospray ionisation tandem mass spectrometry

Reversed-phase LC-MS/MS is used to determine major estrogenic alkylphenol ethoxylates (APEOs) and their biotransformation products. It allows the simultaneous analysis of eight APEOs, alkylphenoxy carboxylates (APECs) and alkylphenols (APs) in sewage treatment plant (STP) effluents in the same extract after solid-phase enrichment on polymeric Oasis HLB. As precursor ions, [APEO + NH4]+, [APEC - H]- and [AP - H]- were monitored. Instrumental limits of detection (LOD) were 2-600 pg, corresponding to sample concentrations of 0.04-12 ng l(-1), without correction for overall method recoveries. Matrix-induced signal suppression during electrospray ionisation (ESI) and extraction as well as overall method recoveries were assessed and the suitability of deuterated surrogates as internal standards was evaluated.     

Über halogen- und stickstoffhaltige Derivate aliphatischer Carbonsäuren, 10. Mitt. (Über Reaktionen mit Aluminiumalkylen, 13. Mitt.): Über die Reduktion von tertiären α-Nitrocarbonsäureestern mit LiAlH4, Diisobutylaluminiumhydrid und Diäthylaluminiumhydrid

Zusammenfassung Die Reduktion tertiärer -Nitroester mit LiAlH₄ verläuft anomal. Infolge Abspaltung der Carboxylgruppe sind Aminoalkane Hauptprodukte dieser Reduktion. Daneben entstehen in geringer Menge unter Erhaltung des Kohlenstoffgerüstes -Hydroxylaminoalkohole. Diese Reaktion wird mit der Reduktion von sekundären -Nitroestern und von -Oximinoestern verglichen.Mit Dialkylaluminiumhydriden erleiden die tertiären Nitroester ebenfalls in der Hauptsache Reduktion unter C-C-Spaltung zu Aminoalkanen. Eine Nebenreaktion führt jedoch über die Stufe der Hydroxylaminoalkohole hinaus zu Aminoalkoholen. Außerdem tritt alkylierung am Stickstoffatom zu Alkylaminoalkanen bzw.-alkoholen auf.

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Halogen and nitrogen containing derivatives of aliphatic carboxylic acids, X (reactions with aluminium alkyls, XIII): Reduction of tertiary -nitro carboxylic acid esters with LiAlH₄, diisobutyl aluminium hydride, and diethyl aluminium hydride

The reduction of tertiary -nitro esters with LiAlH₄ proceeds anomalously. As a result of a decarboxylation amino alkanes are the main products of this reductions. Besides -hydroxylamino alcohols are obtained in small amounts by conservation of the carbon skeleton. This reaction is compared with the reduction of secondary -nitro esters and of -oximino esters.Tertiary -nitro esters are reduced by dialkyl aluminium hydrides to amino alkanes under cleavage of the C-C-bond. In a side-reaction one obtains amino alcohols via the stage of hydroxylamino alcohols. Besides the nitrogen atom is alkylated leading to alkylamino alkanes respectively alkohols.

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9. Mitt.:H. Reinheckel, Mh. Chem.99, 2215 (1968).

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12. Mitt.:H. Reinheckel undR. Gensike, J. Organometal. Chem.13, 45 (1968).     

Experimental separation of virtual photon exchange and electron transfer in interatomic coulombic decay of neon dimers

We investigate the interatomic Coulombic decay (ICD) of neon dimers following photoionization with simultaneous excitation of the ionized atom (shakeup) in a multiparticle coincidence experiment. We find that, depending on the parity of the excited state, which determines whether ICD takes place via virtual dipole photon emission or overlap of the wave functions, the decay happens at different internuclear distances, illustrating that nuclear dynamics heavily influence the electronic decay in the neon dimer.     

Comparison of models and lattice-gas simulations for Liesegang patterns

For more than a century Liesegang patterns – self-organized, quasi-periodic structures occurring in diffusion-limited chemical reactions with two components – have been attracting scientists. The pattern formation can be described by four basic empirical laws. In addition to many experiments, several models have been devised to understand the formation of the bands and rings. Here we review the most important models and complement them with detailed three-dimensional lattice-gas simulations. We show how the mean-field predictions can be reconciled with experimental data by a redefinition of the distances suggested by our lattice-gas simulations.