Strictly locally order affine complete lattices

We call a latticeL strictly locally order-affine complete if, given a finite subsemilatticeS ofL ⁿ, every functionf: S L which preserves congruences and order, is a polynomial function. The main results are the following: (1) all relatively complemented lattices are strictly locally order-affine complete; (2) a finite modular lattice is strictly locally order-affine complete if and only if it is relatively complemented. These results extend and generalize the earlier results of D. Dorninger [2] and R. Wille [9, 10].     

The quickest flow problem

Consider a network =(G, c, ) whereG=(N, A) is a directed graph andc _ij and _ij , respectively, denote the capacity and the transmission time of arc (i, j) A. The quickest flow problem is then to determine for a given value the minimum numberT() of time units that are necessary to transmit (send) units of flow in from a given sources to a given sinks.In this paper we show that the quickest flow problem is closely related to the maximum dynamic flow problem and to linear fractional programming problems. Based on these relationships we develop several polynomial algorithms and a strongly polynomial algorithm for the quickest flow problem.Finally we report computational results on the practical behaviour of our metholds. It turns out that some of them are practically very efficient and well-suited for solving large problem instances.Partial financial support by the Air Force Office of Scientific Research under grants AFOSR-89-0512 and AFOSR-90-0008 is gratefully acknowledged by the first author.     

Experimental and theoretical investigations of the Knight shift of Pd and Ag in the alloy system Ag x Pd1−x

The Knight shift of Pd in Ag _x Pd_1–x has been determined for concentrationsx0.2. In full accordance with the expectations based on the behaviour of the magnetic susceptibility, it was found that the Knight shift of Pd is rapidly reduced in magnitude by adding Ag to Pd. To allow for a detailed interpretation of this finding, we have performed Korringa-Kohn-Rostoker coherent potential approximation (KKR-CPA) band structure calculations for Ag _x Pd_1–x . These calculations clearly demonstrate that the decrease in spin susceptibility with increasingx is accompanied with a decrease in core polarization. In contrast to Pd, the negative Knight shift of Ag on the Pd-rich side of the system is caused by the valence band contribution, as it is demonstrated by our calculations. This is caused by an intersite effect in analogy to the transferred hyperfine field found for non-magnetic elements dissolved in a magnetic host.     

5-Methylnaioxone and 5-Methylnaltrexone: Synthesis and Pharmacological Evaluation

Starting from 5-methyl-oxycodone ( 6 ), 5-methylnaloxone ( 4 ), and 5-methylnaltrexone ( 5 ) have been prepared in several steps. Both 4 and 5 behaved as partial agonists in the AcOH writhing agonism and antagonism test in mice.     

Glycosylphosphonates of 2-Amino-2-deoxy-aldoses. Synthesis of a Phosphonate Analogue of Lipid X

A preparation of glycosylphosphonates ( 27 , 28 , 36 , 38 , and 39 ) from 2-azido-2-deoxy-glycoses ( 26 , 35 , and 37 ) and the synthesis of the non-isosteric phosphonate analogue 3a of lipid X( 2 ) are described. The 2-azido group was introduced by azidonitration. Treatment of the 1-O-acetyl-2-azido-2-deoxy-β-D-galactopyranose 22 with 1.5-3 equiv. of P(OMe)₃ and 1.2-2.5 equiv. of TfOSiMe₃ gave mainly recovered starting material. In P(OMe)₃ as the solvent, the dimethyl phosphoramidate 24 was obtained by way of a Staudinger reaction, even in the presence of TfOSiMe₃. Treatment of the benzylated α-D-galacto-trichloroacetimidate 26 , however, with P(OMe)₃ and TfOSiMe₃ gave a 1:1 mixture of the α- and β-D-galacto-phosphonates 27 and 28 , while the acetylated α-D-gluco- imidate 35 led to the α-D-gluco-configurated phosphonate 36 . The stereoselectivity of the phosphonate formation is related to the relative ease of formation of oxonium-ion intermediates from 26 and 35 . Starting from the phosphonate 36 , deacetylation, benzylidenation, reduction of the azido group, acylation with (R)-3-(benzyloxy)tetradecanoic acid and deprotection yielded the desired compound 3a which was crystallized in the presence of 2 equiv. of (aminomethylidyne)trimethanol (Tris.). The structure of the phosphonates was deduced from their ¹H-, ¹³C-, and ³¹P-NMR spectra.     

Exploration of the electrophoretic behaviour of borane cluster anions and of the capability of capillary electrophoresis to separate them chirally

Mobilities of investigated boron cluster compounds in 3-(N-morpholino)propanesulfonic and phosphate buffers adjusted to pH 7 either with sodium hydroxide or with tris(hydroxymethyl)aminomethane depend on both buffer ions. The zone width and zone asymmetry, which are usually markedly higher than those of organic or common inorganic ions of comparable size, depend on the type of the borane cluster anion. Unusual shapes of zones of two investigated compounds have been found in tris phosphate buffer. Acetonitrile was superior to methanol as an organic additive to separation systems from the viewpoint of the zone symmetry and separation speed. Narrow trigonal zones, typical of organic ions non-interacting with the capillary wall, have been observed for some bridged sandwich cobalt complexes in run buffers with the addition of acetonitrile. The interaction of borane cluster anions with beta-cyclodextrin cavity is excessively strong in purely aqueous solutions. Methanol and acetonitrile, which generally weaken the interaction, sometimes affect the separation enantioselectivity of various compounds in different ways in addition to the weakening effect. Chiral discrimination was reached for all ten investigated anions, which belong to four different structural types of cluster boranes. Stability constants estimated for some analyte-beta-cyclodextrin complexes range between 100 and 1800 l/mol in acceptable separations. The relative difference of the constants was from 3 to 20%.     

Characterisation of natural polysaccharides (plant gums) used as binding media for artistic and historic works by capillary zone electrophoresis

The monosaccharide constituents of plant gums were separated by capillary electrophoresis at pH 12.1 and detected with indirect UV absorbance. The plant gums investigated were gum arabic, gum acacia, gum tragacanth, cherry gum and locust bean gum (carob gum). The monosaccharides obtained after hydrolysis with 2M trifluoroacetic acid and lyophilisation of the hydrolysate were arabinose, galactose, mannose, rhamnose, xylose, fucose, and glucose, and the two sugar acids galacturonic and glucuronic acid, in accordance with the literature. They were separated in a background electrolyte consisting of NaOH to adjust the pH, 20 mM 2,6-pyridinedicarboxylic acid as chromophore for detection and 0.5 mM cetyltrimethylammonium bromide as additive to reverse the electroosmotic flow. Based on their electropherograms, the plant gums could be identified by their typical composition (depicted in a decision scheme) as follows: a peak of glucuronic acid, together with that of rhamnose, is indicative for gum arabic. Peaks of galacturonic acid and fucose point to gum tragacanth. Locust bean gum shows a major peak for mannose (with the concomitant galactose peak in ratio 4-1), whereas a glucuronic acid and a mannose peak together with a prominent arabinose peak indicates cherry gum. The method was applied to identify the plant gums in samples like watercolours and in several paint layers like gum tempera or those with egg white or drying oils as additives. Artificial aging experiments of thin layers of gum arabic on paper or glass carried out with UV-A radiation (366 nm) did not result in changes of the saccharide patterns, in contrast to the simultaneously conducted aging of a drying oil layer.     

Micellar affinity gradient focusing: a new method for electrokinetic focusing

This report describes a new method for the concentration and separation of neutral and/or hydrophobic analytes based on a combination of the analytes' electrophoretic mobility, and affinity for partitioning into a micellar phase. Micellar affinity gradient focusing (MAGF) works by creating a gradient in the micellar retention factor. An electric field is applied along the channel to cause the (negatively charged) micelles to move from the region of high retention to the region of low retention, and the mobile phase is forced to move from the region of low retention to the region of high retention. Consequently, the analyte moves into the gradient region from both directions where it is concentrated at a point where its total velocity is zero. Different analytes, which interact differently with the micelles, will have zero total velocity at different points along the gradient, and will thereby be simultaneously concentrated and separated.     

Derivate des 4-Hydroxy-3-thiosemicarbazides

The synthesis of 4-alkyl- and 4-aryl-substituted 4-hydroxy-3-thiosemicarbazides (2 a-e) and their condensation products with several carbonyl compounds are described.2 a-e can also be employed for the synthesis of the 2-hydroxylamino-1.3.4-thiadiazoles4 a-g.