Pulsed laser deposition of silicate phosphor thin films

Three types of silicate phosphor thin films, emitting in the red-green-blue (RGB) primary colors, were fabricated by pulsed laser deposition, including manganese and lead doped calcium silicate (CaSiO₃:MnPb) for red color, manganese doped zinc silicate (Zn₂SiO₄:Mn) for green color and cerium doped yttrium silicate (Y₂SiO₅:Ce) for blue color. A correlation was observed between photoluminescence intensity with film crystallinity and surface morphology. RGB phosphor thin films with excellent color saturation were obtained. Luminescence mechanisms for these phosphor thin films are discussed.     

Tight Lower Bounds on the Size of a Maximum Matching in a Regular Graph

In this paper we study tight lower bounds on the size of a maximum matching in a regular graph. For k ≥3, let G be a connected k-regular graph of order n and let α′(G) be the size of a maximum matching in G. We show that if k is even, then , while if k is odd, then . We show that both bounds are tight. Research supported in part by the South African National Research Foundation and the University of KwaZulu-Natal.     

Applying Direct Yellow 11 to a modified Simons’ staining assay

For quantification of overall fiber accessibility of lignocellulosic substrates, Direct Yellow 11 (C.I. 40000) is a suitable alternative to the discontinued Pylam Products’ dye Direct Orange 15 (C.I. 40002/40003). In this study we present a side-by-side comparison between the two azo-stilbene dyes. We characterize individual dye fractions and provide equations to determine individual concentrations. We present a modified Simons’ staining protocol incorporating the high molecular weight fraction of Direct Yellow 11. We perform tests on lignin, cellulosic, and lignocellulosic materials. In all tests, the two dyes perform similarly and satisfy many accessibility measurement criteria. We demonstrate that the adsorption of Direct Yellow 11 onto a substrate correlates with that substrate’s propensity for enzymatic hydrolysis. We confirm this correlation on a series of organic solvent pretreatments and on a series of lignocellulosic substrates. Finally, we outline the inherent limitations of performing adsorption experiments with Direct Yellow 11 and other high molecular weight dyes.     

Quantitation of surface-bound proteins on biochips using MALDI-TOF MS

We report on a novel method for the quantitation of proteins specifically bound on a ligand-presenting biochip by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS). The bound protein was digested by trypsin, and the resulting peptide fragments were analyzed by MALDI-TOF MS in the presence of an isotope-labeled internal standard (IS). The IS has the same sequence as a reference peptide (RP) of the target protein digest, but a different molecular weight. The absolute amount of the specifically bound protein on a biochip is then quantitated by comparison of mass intensities between the RP and the IS. Because they have the same molecular milieu, the mass intensities of these two analytes represent the real amounts of analytes on the chip. As a model system, we tested glutathione s-transferase (GST) and a GST-fusion protein, which were captured on glutathione-presenting biochips. We observed that the glutathione densities on biochips showed a good correlation with the absolute quantity of the proteins. We believe that our method will provide an alternative to currently existing tools for the absolute quantitation of surface-bound proteins.     

Copper-catalyzed highly regioselective silylcupration of terminal alkynes to form α-vinylsilanes

A highly regioselective synthesis of branched vinylsilanes through silicon-copper additions to terminal alkynes catalyzed by copper(I) was developed using methanol as additive. The corresponding vinylsilanes were obtained with excellent branched to linear selectivity of up to 99/1 in good yields.     

Perfect Matchings in Total Domination Critical Graphs

A graph is total domination edge-critical if the addition of any edge decreases the total domination number, while a graph with minimum degree at least two is total domination vertex-critical if the removal of any vertex decreases the total domination number. A 3 _t EC graph is a total domination edge-critical graph with total domination number 3 and a 3 _t VC graph is a total domination vertex-critical graph with total domination number 3. A graph G is factor-critical if G − v has a perfect matching for every vertex v in G. In this paper, we show that every 3 _t EC graph of even order has a perfect matching, while every 3 _t EC graph of odd order with no cut-vertex is factor-critical. We also show that every 3 _t VC graph of even order that is K _1,7-free has a perfect matching, while every 3 _t VC graph of odd order that is K _1,6-free is factor-critical. We show that these results are tight in the sense that there exist 3 _t VC graphs of even order with no perfect matching that are K _1,8-free and 3 _t VC graphs of odd order that are K _1,7-free but not factor-critical.     

Synthesis and multiple reuse of eccentric Au@TiO2 nanostructures as catalysts

In this work, we have synthesized eccentric Au@TiO(2) core-shell nanostructures and demonstrated their multiple reuse in the catalytic reduction of 4-nitrophenol.