Adsorption of 1-octanol at the free water surface as studied by Monte Carlo simulation

The adsorption of 1-octanol at the free water surface has been investigated by Monte Carlo computer simulation. Six different systems, built up by an aqueous and a vapor phase, the latter also containing various number of octanol molecules, have been simulated. The number of the octanol molecules has been chosen in such a way that the octanol surface density varies in a broad range, between 0.27 and 7.83 micromol/m(2) in the six systems simulated. For reference, the interfacial system containing bulk liquid octanol in the apolar phase has also been simulated. The results have shown that the formation of hydrogen bonds between the interfacial water and adsorbed octanol molecules is of key importance in determining the properties of the adsorbed layer. At low octanol surface concentration values all the octanol molecules are strongly (i.e., by hydrogen bonds) bound to the aqueous phase, whereas their interaction with each other is negligibly small. Hence, they are preferentially oriented in such a way that their own binding energy (and thus their own free energy) is minimized. In this preferred orientation the O-H bond of the octanol molecule points flatly toward the aqueous phase, declining by about 30 degrees from the interfacial plane, irrespectively from whether the octanol molecule is the H-donor or the H-acceptor partner in the hydrogen bond. Hence, in its preferred orientation the octanol molecule can form at least two low energy hydrogen bonds with water: one as a H-donor and another one as a H-acceptor. Moreover, the preferred orientation of the hydrogen bonded water partners is close to one of the two preferred interfacial water alignments, in which the plane of the water molecule is parallel with the interface. When increasing the octanol surface density, the water surface gets saturated with hydrogen bonded octanols, and hence any further octanol molecule can just simply condense to the layer of the adsorbed octanols. The surface density value at which this saturation occurs is estimated to be about 1.7 micromol/m(2). Above this surface density value the hydrogen bonded octanols and their water partners are oriented in such a way that the number of the water-octanol hydrogen bonds is maximized. Hence, the preferred alignment of the O...O axes of these hydrogen bonds is perpendicular to the interface. This orientation is far from the optimal alignment of the individual octanol molecules, which is also reflected in the observed fact that, unlike in the case of many other adsorbents, the average molecular binding energy of the adsorbed octanol molecules increases (i.e., becomes less negative) with increasing octanol surface density.     

Triangle Factors In Sparse Pseudo-Random Graphs

The goal of the paper is to initiate research towards a general, Blow-up Lemma type embedding statement for pseudo-random graphs with sublinear degrees. In particular, we show that if the second eigenvalue of a d-regular graph G on 3n vertices is at most cd ³/n ² log n, for some sufficiently small constant c > 0, then G contains a triangle factor. We also show that a fractional triangle factor already exists if < 0.1d ²/n. The latter result is seen to be best possible up to a constant factor, for various values of the degree d = d(n).* Supported by a USA-Israeli BSF grant, by a grant from the Israel Science Foundation and by a Bergmann Memorial Award. Research supported in part by NSF grants DMS-0106589, CCR-9987845 and by the State of New Jersey. Research supported in part by NSF grant DMS 99-70270 and by the joint Berlin/Zurich graduate program Combinatorics, Geometry, Computation, financed by the German Science Foundation (DFG) and ETH Zürich.     

Synthesis of D-Glucose-based Azacrown Ethers with Phosphinoxidoalkyl Side Chains and Their Application to an Enantioselective Reaction

Five chiral -D-glucose-based monoaza-15-crown-5 ethers with phosphinoxidoalkyl side chains of one to five carbon atoms (5a–e)have been synthesised. The cation binding ability of the new lariat ethers was evaluated bythe picrate extraction method. The substituents at the nitrogen atom were not a major influenceon the cation extraction ability of the azacrown ether; the compounds showed, however, a significant asymmetric induction as phase transfer catalysts in the Michael addition of2-nitropropane to chalcone (95% ee).     

Glycoform Heterogeneity of Human Serum α1-Acid Glycoprotein Determined by CZE in Malignant Diseases

A novel capillary zone electrophoresis method was developed to investigate the glycoform heterogeneity of human serum α1-acid glycoprotein (AGP). The simultaneous application of a dimethyl polysiloxane coated capillary and oligoamine additives, particularly spermidine resulted in a more detailed separation of AGP glycoforms than reported previously. The relative distribution of AGP glycoforms in CZE was determined by baseline integration of peak areas and verified by peak-fitting analysis. Providing high purity of AGP samples suitable for CZE a schedule of isolation and purification steps including sample preparation and an improved technique of ion exchange chromatography was applied. Based on data obtained by CZE and on the serum AGP levels measured the serum concentrations of AGP glycoforms were calculated in cancer patients with Hodgkin and non-Hodgkin lymphoma, ovary carcinoma and melanoma compared to healthy donors. Results presented here demonstrated a significant increase in the serum concentration of the more acidic AGP fractions also indicating the overproduction of these glycoforms in cancer. In conclusion, our observations may raise the clinical diagnostic relevance of changes in the molecular heterogeneity of AGP detected by CZE in the various forms of malignant diseases.

     

On multiplicity functions associated with Lebesgue area

Rendiconti del Circolo Matematico di Palermo Series 2 -     

Über die erste Randwertaufgabe für Δu=0

Ohne Zusammenfassung     

Efficient interval partitioning for constrained global optimization

A new efficient interval partitioning approach to solve constrained global optimization problems is proposed. This involves a new parallel subdivision direction selection method as well as an adaptive tree search. The latter explores nodes (intervals in variable domains) using a restricted hybrid depth-first and best-first branching strategy. This hybrid approach is also used for activating local search to identify feasible stationary points. The new tree search management technique results in improved performance across standard solution and computational indicators when compared to previously proposed techniques. On the other hand, the new parallel subdivision direction selection rule detects infeasible and suboptimal boxes earlier than existing rules, and this contributes to performance by enabling earlier reliable deletion of such subintervals from the search space.     

Adsorption des Pseudoisozyanin-N-N′-diäthylchlorids am Glimmer

Ohne ZusammenfassungD 91 (München 1941). XV. Mitteilung über reversible Polymerisate von G. Scheibe und Mitarbeitern. — Bisher sind erschienen: I. Angew. Chem.49, 563 (1936); II. Angew. Chem.50, 51 und 212 (1937); III. Angew. Chem.52, 631 (1939); IV. Naturwiss.25, 75 (1937); V. Naturwiss.25, 474 (1937); VI. Naturwiss.25, 795 (1937); VII. Naturwiss.26, 412/413 (1938); VIII. Naturwiss.27, 499 (1939); IX. Kolloid-Z.82, 1 (1938); X. Z. wiss. Photogr.38, 1 (1939); XI. Kolloid-Z.92, 35 (1940) [H. Ecker]; XII. Kolloid-Z.92, 299 (1940) und93, 28. (1940) [F. Katheder]; XIII. Z. wiss. Photogr.39, 18 (1940) [A. Schöntag]; XIV. Z. Elektrochem.47, 73 (1941).