Conditional independence models for seemingly unrelated regressions with incomplete data

We consider normal ≡ Gaussian seemingly unrelated regressions (SUR) with incomplete data (ID). Imposing a natural minimal set of conditional independence constraints, we find a restricted SUR/ID model whose likelihood function and parameter space factor into the product of the likelihood functions and the parameter spaces of standard complete data multivariate analysis of variance models. Hence, the restricted model has a unimodal likelihood and permits explicit likelihood inference. In the development of our methodology, we review and extend existing results for complete data SUR models and the multivariate ID problem.     

On a Formula for the Kostka Numbers

From Kostant’s multiplicity formula for general linear groups, one can derive a formula for the Kostka numbers. In this note we give a combinatorial proof of this formula. Received January 7, 2005     

Synthesis and characterization of a semiflexible liquid crystalline polyester with a broad nematic region

In this paper, we report on the synthesis and detailed characterization of a new semiflexible nematic liquid crystalline polyester which could serve as a 'model' polyester for a variety of physical and physico-chemical investigations. The polymer is a nematic liquid over a wide temperature range-from the glass transition temperature at ∼95°C to the isotropic transition at ∼240°C. We expect this polyester to be particularly useful for studying the effect of flow on the orientation of liquid crystalline polymers, as well as the production and removal of disclinations.     

Oxygen on Fe(100) and Fe(110)

Investigations of the electronic and magnetic properties of oxygen adsorbed on magnetized iron films have been carried out by means of angle and spin resolving photoelectron spectroscopy. Iron, epitaxially grown on W(100) and W(110) crystals, served as the ferromagnetic substrate. Exchange splittings of the O 2p_x derived level have been detected, demonstrating a magnetic coupling between the chemisorbate and the iron layer. Variations of the exchange splitting have occurred as a function of the oxygen coverage, photon energy, and emission angle. High oxygen exposures have lead to a FeO overlayer at the surface.     

Synthesis and antibacterial activities of water‐soluble methacrylate polymers containing quaternary ammonium compounds

New water‐soluble methacrylate polymers with pendant quaternary ammonium (QA) groups were synthesized and used as antibacterial materials. The polymers with pendant QA groups were obtained by the reaction of the alkyl halide groups of a previously synthesized functional methacrylate homopolymer with various tertiary alkyl amines containing 12‐, 14‐, or 16‐carbon alkyl chains. The structures of the functional polymer and the polymers with QA groups were confirmed with Fourier transform infrared and ¹H and ¹³C NMR. The degree of conversion of alkyl halides to QA sites in each polymer was determined by ¹H NMR to be over 90% in all cases. The number‐average molecular weight and polydispersity of the functional polymer were determined by size exclusion chromatography to be 32,500 g/mol and 2.25, respectively. All polymers were thermally stable up to 180 °C according to thermogravimetric analysis. The antibacterial activities of the polymers with pendant QA groups against Staphylococcus aureus and Escherichia coli were determined with broth‐dilution and spread‐plate methods. All the polymers showed excellent antibacterial activities in the range of 32–256 μg/mL. The antibacterial activity against S. aureus increased with an increase in the alkyl chain length for the ammonium groups, whereas the antibacterial activity against E. coli decreased with increasing alkyl chain length. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5965–5973, 2006     

CHLORINATION OF ISOLATED CHLOROPHYLLS in vitro

Abstract— It was shown that chlorophyll a and its epimer chlorophyll a' are chlorinated and hydroxyl-ated during thin layer chromatography with silica gel plates. Hydroxylated chlorophyll a could not be chlorinated. Chlorinated and non chlorinated chlorophylls could be separated and determined by high performance liquid chromatography, because chlorophylls do not alter during this procedure. These findings support the assumption that Chi RC I is a preparation artifact. The extent of chlorination depends on chloride availability on the thin layer and on time. Chlorination and hydroyxlation do not take place under nitrogen atmosphere. The mechanism of chlorination during the thin layer chromatography procedure is discussed.     

Evaluation of different tubing geometries for high-speed counter-current chromatography

Different tubing geometries were evaluated for use in high-speed counter-current chromatography. Standard round tubing was compared to rectangular and twisted rectangular tubing. The number of theoretical plates for a standard anthocyanin mixture from black currant was determined for each experiment. The results of twisted rectangular tubing were superior to a standard setup.