Preparation of a Novel Polymer‐Modified Si Surface for DNA Immobilization

The design of a novel polymer‐modified overlayer composed of PPAPE and GPMS on a silicon wafer for immobilization of DNA molecules is described. After hydroxylation of Si(100) surfaces, GPMS molecules were self‐assembled onto these surfaces. PPAPE molecules were then covalently attached to the epoxy‐terminated surfaces. The incubation time and concentration of PPAPE was found to effect both layer thickness and water CA. The type of organic solvent and the pH were found to change the nature of the PPAPE‐modified surface for DNA immobilization. It is concluded that PPAPE‐modified surfaces show advantages for DNA immobilization by electrostatic interactions between DNA molecules and positively charged free amino groups of the PPAPE‐modified surfaces at the appropriate pH values.

     

Simple Functors of Admissible Linear Categories

Generalizing an idea used by Bouc, Thévenaz, Webb and others, we introduce the notion of an admissible R-linear category for a commutative unital ring R. Given an R-linear category \(\mathcal {L}\), we define an \(\mathcal {L}\)-functor to be a functor from \(\mathcal {L}\) to the category of R-modules. In the case where \(\mathcal {L}\) is admissible, we establish a bijective correspondence between the isomorphism classes of simple functors and the equivalence classes of pairs (G, V) where G is an object and V is a module of a certain quotient of the endomorphism algebra of G. Here, two pairs (F, U) and (G, V) are equivalent provided there exists an isomorphism F ← G effecting transport to U from V. We apply this to the category of finite abelian p-groups and to a class of subcategories of the biset category.     

Synthesis,Characterization and Redox Properties of Three New <Emphasis Type="Italic">vic</Emphasis>-dioximes and their Nickel(II) Metal Complexes

Three novel vic-dioximes: cyclohexylamine-p-tolylglyoxime (L₁H₂), t-butylamine-p-tolylglyoxime (L₂H₂) and sec-butylamine-p-tolylglyoxime (L₃H₂) were prepared by the reaction of anti-p-tolylchloroglyoxime with cyclohexylamine, t-butylamine and sec-butylamine in absolute THF. The detection of H-bonding in all of the Ni(II) complexes by i.r. revealed the square-planar MN₄ coordination of mononuclear complexes. MN₄ coordination of the [(L₁H)₂Ni] complex was also determined by ¹H and ¹³C-n.m.r spectroscopy. Mononuclear complexes with a 1:2 metal-ligand ratio were prepared using Ni(II) salts. All Ni(II) complexes are insoluble in common solvents. The ligands and complexes were characterized by elemental analyses, FT-i.r., u.v.–vis., ¹H and ¹³C-n.m.r. spectra, magnetic susceptibility measurements, thermogravimetric analyses (t.g.a.) and cyclic voltammetry.     

Comparative mechanical property characterization of three indirect composite resin materials compared with two direct composites

Various new indirect composite materials have been developed with required advantages. In this study three indirect composite material (Artglass, Belleglass HP, Targis) were tested for flexural strength, fracture toughness, wear resistance and hardness against Filtek P60 and Z‐100. Five specimens of each material were fabricated according to the manufacturer's directions. The flexural strength and fracture toughness was measured using the bending test. The wear test was performed to accelerated wear in a toothbrushing apparatus. Vickers hardness was measured for each of the tested materials. The statistical tests used for flexural strength, fracture toughness, wear and hardness were One‐way ANOVA and Kruskal–Wallis test. The level of statistical significance chosen was p = 0.05. Results of the study showed that Filtek P60 was superior to the other composites in all tests. Significant differences were found among the materials. The differences in flexural strength, fracture toughnes, wear and hardness may have been due to differences in chemistry or method of polymerization of the composites. Copyright © 2003 John Wiley & Sons, Ltd.     

Spatially organized free-standing poly(p-xylylene) nanowires fabricated by vapor deposition

Thin films of poly(chloro-p-xylylene) (PPXC) grown by the pyrolysis and evaporation of chloro-[2.2]paracyclophane in an evacuated chamber contain free-standing, slanted, parallel columns that are 50 mum long and are assemblies of 50- to 100-nm-diameter nanowires, which thus can have an unprecedented aspect ratio as high as 1000:1. The nanostructured thin films organize spatially with a chemical structure similar to that of planar PPXC thin films, but the former also possess nanostructured morphology. Nanostructured thin films of poly(p-xylylene) (PPX) and its derivatives shall be useful as functionalized interfaces for antifouling coatings and biomedical devices.     

Controlling the wettability and adhesion of nanostructured poly-(p-xylylene) films

The hydrophobic surface properties of structured poly-(p-xylylene) (PPX) films, as measured by water wettability, are studied as functions of surface chemistry, film composition, and surface roughness. We demonstrate the fabrication of very hydrophobic surfaces and control over adhesion properties via nanoscale modulation of roughness, changes in composition, and alteration of the surface chemistry of PPX films. The formation of superhydrophobic surfaces through the chemisorption of fluoroalkylsiloxane coatings to hydroxyl sites created on the nanostructured PPX surface is also illustrated. The ability to control both hydrophobicity and adhesion using nanostructured PPX films is a promising development because it may lead to a new generation of coatings with applicability ranging from self-cleaning surfaces to robotics.     

Raman lasing near 630 nm from stationary glycerol-water microdroplets on a superhydrophobic surface

We demonstrate, for the first time to our knowledge, Raman lasing from stationary microdroplets on a superhydrophobic surface. In the experiments, glycerol-water microdroplets with radii in the 11-15 microm range were pumped at 532 nm with a pulsed, frequency-doubled Nd:YAG laser. Two distinct operation regimes of the microdroplets were observed: cavity-enhanced Raman scattering and Raman lasing. In the latter case, the Raman lasing signal was higher than the background by more than 30 dB. Investigation of the Raman spectra of various glycerol-water mixtures indicates that lasing occurs within the glycerol Raman band. Raman lasing was not sustained; rather, oscillation would occur in temporally separated bursts. Increasing the rate of convective cooling by nitrogen purging improved the lasing performance and reduced the average interburst separation from 2.3 to 0.4 s.     

Secondary metabolites from the aerial parts of <Emphasis Type="Italic">Verbascum dudleyanum</Emphasis> and their biological activities

From the overground parts of Verbascum dudleyanum, six iridoid glycosides, aucubin, ajugol, catalpol, 6-O-α-L-rhamnopyranosylcatalpol, saccatoside, and 6-O-(3″-O-trans-p-coumaroyl)-α-L-rhamnopyranosylcatalpol, and two saponins, ilwensisaponin A and C, as well as a flavonoid, luteolin-7-O-β-glucopyranoside, together with an acetophenone glucoside, picein, were isolated. The structures of isolated compounds were elucidated by spectroscopic methods. These compounds showed biological acitivites. __________ Published in Khimiya Prirodnykh Soedinenii, No. 3, pp. 232–234, May–June, 2008.     

An efficient boundary element method for two-dimensional transient wave propagation problems

The boundary element method (BEM) has been recognized by its unique feature of requiring neither internal cells nor their associated domain integrals in the computation. The method preserves its elegance for transient problems by means of a certain time-stepping scheme that initiates the time integration always from the initial time. Unfortunately, this time-marching scheme becomes rather difficult to apply, because the computation time and storage requirement grow dramatically with the increasing number of time steps. This paper shows that a reduction of one half of the computation time as well as the storage requirement can be achieved by an efficient truncation scheme for two-dimensional transient wave propagation problems. In particular, a guiding parameter for the determination of the truncation limit is proposed, and the overall measure of the error with respect to the truncation guide parameter is established.