Characterizing binary simplical matroids

In an earlier paper we defined a class of matroids whose circuit are combinatorial generalizations of simple polytopes; these matroids are the binary analogue of the simplical geometrics of Crapo and Rota. Here we find necessary and sufficient conditions for a matroid to be isomorphic to such a binary simplical matroid.     

A constructive proof of Tucker's combinatorial lemma

Tucker's combinatorial lemma is concerned with certain labellings of the vertices of a triangulation of the n-ball. It can be used as a basis for the proof of antipodal-point theorems in the same way that Sperner's lemma yields Brouwer's theorem. Here we give a constructive proof, which thereby yields algorithms for antipodal-point problems. Our method is based on an algorithm of Reiser.     

Investigation of the cell-wall loosening protein expansin as a possible additive in the enzymatic saccharification of lignocellulosic biomass

Applied Biochemistry and Biotechnology -     

Promoting Preservice Elementary Teachers' Awareness of Learning and Teaching Mathematics Conceptually Through KTEM

In this article, we describe preservice elementary teachers' reactions to Liping Ma's (1999) book, Knowing and Teaching Elementary Mathematics (KTEM), from five universities. Ma's discussion of solely teaching elementary mathematics procedurally and its consequences awakens the preservice teachers' memories of learning elementary mathematics. Ma's analysis of and solution to the problem ignites strong emotions in the preservice elementary teachers and promotes a desire to teach elementary mathematics conceptually. Through the analysis of writing assignments, we summarize how reading and reflecting on KTEM gives preservice teachers an opportunity to examine their beliefs about teaching and learning elementary mathematics conceptually.     

In vivo and in vitro lipid peroxidation of arachidonate esters: the effect of fish oil omega-3 lipids on product distribution

The effect of lipid composition on the distribution of free radical oxidation products derived from arachidonic acid (20:4) esters has been studied in vitro and in vivo. Pro-inflammatory prostaglandin (PG) F2-like compounds, termed F2-isoprostanes (IsoPs), are produced in vivo and in vitro by the free radical-catalyzed peroxidation of arachidonic acid. Controlled free radical oxidation of mixtures of fatty acid esters in vitro showed that the formation of IsoPs from arachidonate is dramatically influenced by the presence of other fatty acid esters in the reaction mixture. Thus, three lipid mixtures containing the same arachidonate concentration but different amounts of other fatty esters (16:0; 18:1; 18:2; 20:5, and 22:6) were oxidized, and the product yields were determined by GC and LC/MS/MS analysis. The yield of F2-IsoP formed after 1 h of oxidation was 18% (based on arachidonate consumed) for mixtures containing arachidonate as the only oxidizable PUFA, but yields of these biologically active compounds dropped to 6% in polyunsaturated fatty acid (PUFA) mixtures typical of those found in tissues of fish oil-fed animals. F2-IsoP levels were also monitored in the livers of mice on diets supplemented with eicosapentaenoic acid (C20:5 omega-3; EPA), the PUFA most abundant in fish oil. While the level of arachidonic acid present in livers was not significantly different from that in control animals, levels of IsoPs in the liver were reduced in the EPA-fed mice compared to those in controls under conditions of oxidative stress (60 +/- 25% reduction, n = 5) or at baseline (48 +/- 14% reduction, n = 5). These results suggest that dietary omega-3 PUFAs may influence the formation of bio-active peroxidation products derived from omega-6 PUFAs by channeling the free radical pathway away from the F2-IsoPs.     

Study and characterization of tobacco mosaic virus head-to-tail assembly assisted by aniline polymerization

One-dimensional composite nanofibres with narrow dispersity, high aspect ratio and high processibility have been fabricated by head-to-tail self-assembly of rod-like tobacco mosaic virus assisted by aniline polymerization, which can promote many potential applications including electronics, optics, sensing and biomedical engineering.     

2,3-Anhydrosugars in glycoside bond synthesis. Application to alpha-D-galactofuranosides

We report here the use of 2,3-anhydro-D-gulofuranosyl thioglycosides and glycosyl sulfoxides in the synthesis of alpha-D-galactofuranosidic bonds, which are present in a range of bacterial and fungal glycoconjugates. This two-step method involves a stereoselective glycosylation in which a 2,3-anhydro-alpha-D-gulofuranoside is obtained either as the sole or as the major product, followed by a regioselective opening of the epoxide ring using lithium benzylate in the presence of (-)-sparteine. In exploring the scope of the method, donors protected at O5 and O6 with an isopropylidene acetal, benzyl ethers, or benzoate esters were studied. Overall, the glycosyl sulfoxides provided the products in slightly higher yields and selectivity, with the best results being obtained with benzylated and benzoylated substrates. In the epoxide ring-opening reactions, the acetal- and ether-protected donors afforded poor to modest regioselectivity, whereas the benzoylated products gave good yields of the desired alpha-D-galactofuranosides. The benzoyl-protected species are, therefore, the donors of choice for these reactions. The utility of the approach was demonstrated through the synthesis of three alpha-D-galactofuranosyl-containing oligosaccharides.     

Enantioselective synthesis of the farnesyltransferase inhibitor, A-345665.0

The stereoselective synthesis of A-345665.0 1, a novel farnesyl transferase inhibitor, is described. The key step involves a stereoselective addition of an imidazolyl Grignard reagent to aldehyde 8 in the presence of an external chiral auxiliary. Crystallization of the product as the dimeric zinc complex 12 facilitates the isolation of product in >98:2 er. The biaryl linkage is formed by the use of a Suzuki coupling, employing boronic acid 4 prepared by the directed ortho-lithiation of benzonitrile 6. The overall yield for the six step sequence is 21%.     

Method development and validation for zotarolimus concentration determination in stented swine arteries by liquid chromatography/tandem mass spectrometry detection

Drug-eluting stents have attracted significant attention in the medical community and pharmaceutical industry due to their proven success in significantly reducing restenosis. Abbott Laboratories is developing a drug-eluting stent coated with zotarolimus and swine was recently used as an animal model for the pre-clinical study of stent implantation. In this article, we present a detailed experimental design and results for the validation and sample analysis of zotarolimus drug concentration in stented swine artery samples. Introduction of tissue quality control (QC) samples allows evaluation of the entire analytical process as well as the stability of the drug in both original tissue and homogenized tissue samples. In addition, a novel approach using 100% swine blood as the homogenization solution was developed for the consistency of the liquid-liquid extraction recovery and stability of the zotarolimus in tissue homogenates. Standards were prepared by spiking zotarolimus working solution in swine blood and tissue QC samples were used along with the artery samples during the sample analysis. The linear dynamic range of blood standard samples is from 0.61 to 333.20 ng/mL to accommodate the predicted artery homogenate concentrations. Overall tissue QC %CV during the method validation was from 4.4% to 8.6%. The overall %bias of tissue QC samples during the method validation was from -7.3% to 16.6%. The method was successfully applied for the analysis of swine artery samples. A similar approach for method validation and sample analysis has been successfully applied for the analysis of swine myocardium, kidney and liver tissue samples.