A thermogravimetric method for assessing the substantivity of polymer films on dentally relevant substrates

A thermogravimetric (TG) method is described for evaluating the substantivity of multi-functional polymeric materials that may be used as protective coatings for teeth. Applied to poly(butyl methacrylate) and poly(octadecyl methacrylate) film structures deposited onto model tooth surfaces from aqueous latex formulations, the method shows that while the latter polymer exhibits little substantivity, the former may be a suitable candidate material for dental-care applications.     

Incorporation of phosphorus oxyacids into layered double hydroxides

Four phosphonate anions (methyl-, ethyl-, phenyl- and benzylphosphonate) were successfully incorporated into [Cu₂Cr(OH)₆]Cl·yH₂O. It was found that two phases exist for the phenylphosphonate intercalate; one in which the anions are arranged perpendicular to the layers, and one with a tilted orientation. Systematic variation of the reaction conditions allowed the former to be isolated with phase purity, but not the latter. The solid-state ³¹P NMR data suggest that proton transfer may occur between host and guest. Some neutral guest is incorporated in the case of phenylphosphonate and benzylphosphonate, presumably owing to relatively poor solvation of these guests. Heat treatments only resulted in the formation of a covalent bond between host and guest in the case of the methylphosphonate intercalate. The intercalation of the related and redox-active phenylphosphinate into a range of LDHs is also reported. Time-resolved in situ diffraction techniques were used to both monitor and quantify the intercalation of phenylphosphonate into [Cu₂Cr(OH)₆]Cl·yH₂O and phenylphosphinate into the hexagonal form of [LiAl₂(OH)₆]Cl·yH₂O. Kinetic and mechanistic parameters have been determined from the diffraction data.     

Layer guided-acoustic plate mode biosensors for monitoring MHC-peptide interactions

The transduction signals from the immobilisation of a class I heavy chain, HLA-A2, on a layer guided acoustic plate mode device, followed by binding of beta(2)-microglobulin and subsequent selective binding of a target peptide are reported.     

Synthesis and characterization of imidocubanes with exocube Ge(IV) and Sn(IV) substituents: [M(mu3-NGeMe3)]4 (M = Sn, Ge, Pb); [Sn(mu3-NSnMe3)]4

The heteroleptic lithium amide, [(Me3Sn)(Me3Ge)NLi.(Et2O)]2 (2), reacts with MCl(2) (M = Sn, Ge, Pb) to yield the corresponding cubane complexes [M(mu3-NGeMe3)]4 [M = Sn (3), Ge (4), Pb (5)]. In an analogous reaction with SnCl2, the lithium stannylamide, [(Me3Sn)2NLi.(Et2O)]2 (1), produces the mixed-valent Sn congener [Sn(mu3-NSnMe3)]4 (6). All imidocubanes contain both di- and tetravalent group 14 metals that are bridged by N. These structures are comprised of M4N4 (M = Sn, Pb, Ge) cores that possess varying distortion from perfect cube geometry. The Pb derivative (5) exhibits enhanced volatility and vapor-phase integrity.     

First-principles studies of chiral step reconstructions of Cu(100) by adsorbed glycine and alanine

Adsorption of amino acids on Cu(100) is known experimentally to induce surface reconstructions featuring intrinsically chiral Cu(3,1,17) facets, but no information about the geometry of the molecules on these chiral facets is available. We present density-functional theory calculations for the structure of glycine and alanine at moderate coverages on Cu(3,1,17). As might be expected, molecules prefer to bind at the step edges on this surface rather than on the surface's (100)-oriented terraces. The adsorption of enantiopure alanine on Cu(3,1,17) is predicted to be weakly enantiospecific, with S-alanine being more stable on Cu(3,1,17)(S) than R-alanine. By comparing the surface energies of Cu(100) and Cu(3,1,17) in the presence of adsorbed glycine or alanine, our calculations provide insight into the driving force for chiral reconstructions of Cu(100) by amino acids.     

Block‐triangular preconditioners for PDE‐constrained optimization

In this paper we investigate the possibility of using a block‐triangular preconditioner for saddle point problems arising in PDE‐constrained optimization. In particular, we focus on a conjugate gradient‐type method introduced by Bramble and Pasciak that uses self‐adjointness of the preconditioned system in a non‐standard inner product. We show when the Chebyshev semi‐iteration is used as a preconditioner for the relevant matrix blocks involving the finite element mass matrix that the main drawback of the Bramble–Pasciak method—the appropriate scaling of the preconditioners—is easily overcome. We present an eigenvalue analysis for the block‐triangular preconditioners that gives convergence bounds in the non‐standard inner product and illustrates their competitiveness on a number of computed examples. Copyright © 2010 John Wiley & Sons, Ltd.     

Spectrophotometric determination of platinum in experimental catalysts

Conditions have been established and procedures are described for the colorimetric determination of platinum in experimental catalysts and miscellaneous materials. The methods are based on the measurement of the intensity of colour produced by the reaction of chloroplatinic acid with tin(II) chloride. Interference from metals such as chromium, molybdenum and nickel, which are often also present in catalysts, is overcome by selective extraction of the complex into isoamyl alcohol followed by measurement of the absorbance of the alcohol layer.     

Synthesis and characterization of a series of zinc bis[(alkyl)(trimethylsilyl)amide] compounds

A series of 21 secondary (alkyl)(trimethylsilyl)amines HNR(TMS) [R = n-propyl (1), i-propyl (2), n-butyl (3), i-butyl (4), s-butyl (5), tert-butyl (6), c-pentyl (7), n-pentyl (8), i-pentyl (9), l-methylbutyl (10), 2-methylbutyl (11), 1-ethylpropyl (12), 1,2-dimethylpropyl (13), tert-pentyl (14), phenyl (15), c-hexyl (16), n-hexyl (17), N,N-dimethyl-3-aminopropyl (18), benzyl (19), n-heptyl (20), 1,1,3,3-tert-butyl (21); TMS = Si(CH3)3] has been prepared and fully characterized by elemental analyses, multinuclear (1H, 13C, 29Si, 14N) NMR, IR, UV/vis, MS, and boiling point. A new method for determination of boiling points of milligram-size samples, based on DSC (differential scanning calorimetry), is described. Each amine has been converted to the corresponding zinc bis(amide) compound Zn[N(TMS)(R)]2 [R = n-propyl (22), i-propyl (23), n-butyl (24), i-butyl (25), s-butyl (26), tert-butyl (27), c-pentyl (28), n-pentyl (29), i-pentyl (30), 1-methylbutyl (31), 2-methylbutyl (32), 1-ethylpropyl (33), 1,2-dimethylpropyl (34), tert-pentyl (35), phenyl (36), c-hexyl (37), n-hexyl (38), N,N-dimethyl-3-aminopropyl (39), benzyl (40), n-heptyl (41), 1,1,3,3-tert-butyl (42); TMS = Si(CH3)3] and subsequently fully characterized by elemental analyses, multinuclear (1H, 13C, 29Si, 14N) NMR, IR, UV/vis, MS, and TGA. The experimental IR has been compared to the computationally calculated one for compound 27. Observed trends in volatility of the compounds are discussed in the context of the dominant intermolecular forces present in the condensed phase.     

Acetylene Sorption Dynamics in Carbon Nanotubes

Single‐walled and multi‐walled carbon nanotubes (SWNT and MWNT, resp.) were prepared by applying the catalytic chemical vapor deposition (CCVD) technique. Different nanotube samples were obtained from the as‐synthesized carbon/catalyst composites by treatments applied to remove the catalyst and the amorphous carbon. The dynamic and equilibrium adsorption properties of the samples were compared. Acetylene was used as an adsorptive probe. The sorption mass‐transport properties have been characterized by applying the frequency response (FR) technique. Results reflected that the surface functional groups, generated by an oxidative treatment, have significant influence on both the static and the dynamic acetylene sorption properties of the carbon nanotube materials. The rate of acetylene mass transport was governed by the rate of sorption in all the samples, except in MWNT after oxidative treatment, where the intracrystalline diffusion in the nanotubes was the rate‐controlling process.     

The effect of hydration on the thermal behaviour of hydrophilic non-aqueous gels stabilised by Carbopol 974P

A thermal analysis of the effect of hydration of non-aqueous polymer-stabilised gels was investigated using differential scanning calorimetry (DSC). The interaction of water with the polymer and its distribution within the gel are critical to the physicochemical behaviour of the gel, and consequently affects the utility of the gel matrix as a drug delivery vehicle. Addition of water at levels up to and including 50% (w/w) did not result in an observable freezing event in the thermogram. However, at 60 and 80% (w/w) water, phase transitions were observed, the magnitude of which were found to be independent of the annealing time within the range used. The observed melting enthalpies increased as the water concentration increased for all formulations, but were always smaller than that of pure water. There was no evidence of multiple transitions that might be attributed to different populations of water molecules. However, the results demonstrate that DSC can be employed to differentiate between freezable and non-freezable water, in these particular formulations.