[N,N′‐Bis(5‐bromo­salicyl­idene)‐1,3‐di­amino­propane]­nickel(II) and [N,N′‐­bis(5‐chloro­salicyl­idene)‐1,3‐­di­amino­propane]copper(II)

The title compounds, {4,4′‐di­bromo‐2,2′‐[1,3‐propane­diyl­bis(nitrilo­methyl­idyne‐N)]­diphenolato‐O,O′}nickel(II), [Ni(C₁₇­H₁₄­Br₂­N₂O₂)], and {4,4′‐di­chloro‐2,2′‐[1,3‐pro­pane­diyl­bis­(ni­trilo­methyl­idyne‐N)]­di­phen­ol­ato‐O,O′}­copper(II), [Cu­(C₁₇­H₁₄­Cl₂­N₂O₂)], lie on crystallographic twofold axes. In both structures, the metal coordination sphere is a tetrahedrally distorted square plane formed by the four‐coordinate N₂O₂ donor set of the Schiff base imine–phenol ligands. In the Ni compound, the Ni—O and Ni—N distances are 1.908 (3) and 1.959 (4) Å, respectively, while in the Cu compound, the Cu—O and Cu—N distances are 1.907 (2) and 1.960 (2) Å, respectively. The two Schiff base moieties, which themselves are nearly planar, are inclined at an angle of 29.26 (7)° for the Ni compound and 29.26 (5)° for the Cu compound.     

Quantitavive Proton Magnetic Resonance Analysis of Ranitidine in Solid Dosage Forms

A rapid and specific proton magnetic resonance (PMR) spectroscopic method was developed for determining ranitidine hydrochloride in tablets. 2-Choloroacetophenon was used as the internal standard and DMSO-d₆ served as the PMR solvent. The concentration of drug per unit dose was calculated from the integration values for the resonance signals of ranitidine hydrochloride at 4.32 δ ppm and int. st. at 5.19 δ ppm. The method using commercial products gave comparable results to those obtained by the methods of UV spectroscopy and USP XXIII.     

Polymethacrylate-based monolithic capillary column with weak cation exchange functionalities for capillary electrochromatography

Polymethacrylate-based monolith with weak cation exchange functionalities was prepared in capillary column (i.d. 100 μm, o.d. 375 μm) by in situ polymerization of butyl methacrylate, ethylene dimethacrylate and N-methacryloyl-L-glutamic acid in presence of porogens. The porogen mixture included N,N-dimethyl formamide and phosphate buffer. The preparation procedure of stationary phase contained the synthesis of monomer, silanization of capillary inner wall and in situ polymerization. The use of amino acid based monomer for the monolith synthesis is one of the originalities of this novel approach. N-methacryloyl-L-glutamic acid has two carboxyl functionalities. The separation of the solutes were performed at different acetonitrile/phosphate buffer and acetonitrile/sodium hydroxide contents. The applied voltage for the alkyl benzenes was changed between +5 and +30 kV. CEC separations of alkyl benzenes, acidic, basic, phenolic and some polycylic aromatic compounds were succesfully performed under capillary-electrochromatography mode with cathodic electroosmotic flow.     

A simple and sensitive LC-ESI-MS (ion trap) method for the determination of bupropion and its major metabolite, hydroxybupropion in rat plasma and brain microdialysates

A specific and highly sensitive liquid chromatography-electrospray mass spectrometry (LC-ESI-MS) method for the direct determination of bupropion (BUP) and its main metabolite hydroxybupropion (HBUP) in rat plasma and brain microdialysate has been developed and validated. The analysis was performed on a Bonus RP C18 (100 mm × 2.1 mm i.d., 3.5 μm particles) column using gradient elution with the mobile phase consisting of acetonitrile and ammonium formate buffer (10 mM, pH 4). Plasma samples were analyzed after a simple, one-step protein precipitation clean-up with trichloroacetic acid (TCA), however clean-up for microdialysis samples was not necessary, enabling direct injection of the samples into the LC-ESI-MS system. Signals of the compounds were monitored under the multiple reaction monitoring (MRM) mode of the LC-ESI-MS (ion trap) for quantification. The precursor to product ion transitions of m/z 240-184 and m/z 256-238 were used to measure BUP and HBUP, respectively. The method was validated in both plasma and microdialysate samples, and the obtained lower limit of quantification (LLOQ) was 1.5 ng mL⁻¹ for BUP and HBUP in both matrices. The intra- and inter-day assay variability was less than 15% for both analytes. This LC-ESI-MS method provided simple sampling, rapid clean-up and short analysis time (<9 min), applicable to the routine therapeutic monitoring and pharmacokinetic studies of BUP and HBUP.     

On the Interplay among Entropy, Variable Metrics and Potential Functions in Interior-Point Algorithms

We are motivated by the problem of constructing aprimal-dual barrier function whose Hessian induces the (theoreticallyand practically) popular symmetric primal and dual scalings forlinear programming problems. Although this goal is impossible toattain, we show that the primal-dual entropy function may provide asatisfactory alternative. We study primal-dual interior-pointalgorithms whose search directions are obtained from a potentialfunction based on this primal-dual entropy barrier. We providepolynomial iteration bounds for these interior-point algorithms. Thenwe illustrate the connections between the barrier function and areparametrization of the central path equations. Finally, we considerthe possible effects of more general reparametrizations oninfeasible-interior-point algorithms.     

Crystal structure of [N,N'-bis(5-chlorosalicylidene)-1,3-diaminopropane]iron(II).

The crystal structure of the title compound has been determined. The coordination geometry about the iron(II) center is a tetrahedrally distorted square plane formed by the four-coordinate N2O2 donor set of the Schiff-base imine-phenol ligand. Molecules of the title compound are not planar. The two Schiff-base moieties, which themselves are reasonably planar, are inclined at an angle of 31.5(1) degrees.     

Boundary measures of Markov chains

It is known that each Markov chain has associated with it a polytope and a family of Markov measures indexed by the interior points of the polytope. Measure-preserving factor maps between Markov chains must preserve the associated families. In the present paper, we augment this structure by identifying measures corresponding to points on the boundary of the polytope. These measures are also preserved by factor maps. We examine the data they provide and give examples to illustrate the use of this data in ruling out the existence of factor maps between Markov chains. E. Cawley was partially supported by the Modern Analysis joint NSF grant in Berkeley. S. Tuncel was partially supported by NSF Grant DMS-9303240.