The reaction of sulphur and nitrogen nucleophiles with [Pt(dien)Cl]+

The reaction of a variety of sulphur nucleophiles [thiourea, S-ethyl mercaptoethylamine (EMEA), glutathione (GSH), dimethylsulphoxide (DMSO) and methionine] with the platinum(II) complex [Pt(dien)Cl]+ has been studied at 25°C using the nucleophiles in large excess. The measurements confirm that the sulphur nucleophiles react directly with the platinum complex and that the solvolytic pathway makes little contribution to the reaction. The reactions were monitored by a combination of conductometric and spectrophotometric methods. The oxygen and nitrogen nucleophiles water and imidazole respectively have also been studied. Reagents such as thiourea, EMEA, methionine and glutathione are some 101–102 more reactive than the nitrogen nucleophile imidazole and some 102–103 more reactive than oxygen nucleophile. In a direct competition between sulphur (kS) and nitrogen (kN) nucleophiles for the platinum substrate, as will occur under biological conditions, the kS/kN ratio is at least 10 so that little of the nitrogen-substituted product will be formed in the reaction.     

Supercritical fluid extraction of nylon 6,6 oligomers and their characterization via liquid chromatography coupled with mass spectrometry.

This research extends previous studies regarding the application of supercritical fluid extraction (SFE) for the analysis of oligomers from nylon 6,6 fibers. The effects of CO2 pressure, extraction temperature, CO2-modifier percentage, static extraction time and dynamic extraction time on the SFE efficiency of nylon 6,6 oligomers were examined. Results from the SFE methods for oligomer extractions were compared to results from conventional solvent extraction. The extracted oligomers were identified by high-performance liquid chromatography (HPLC) with coupled on-line atmospheric pressure chemical ionization mass spectrometry and HPLC fractionation coupled with off-line liquid secondary ion mass spectrometry.     

Mid-infrared absorption measurements of liquid hydrocarbon fuels near

Quantitative absorption spectra for several hydrocarbon fuels in the liquid phase at are presented. Measurements of toluene, n-dodecane, n-decane, and three samples of gasoline were made over the spectral region 2700–3200 to support the development of mid-infrared laser-absorption diagnostics for measurements of fuel vapor in the presence of liquid films and aerosols. A procedure for quantitative Fourier transform infrared (FTIR) absorption measurements of strongly absorbing liquids is described and the resulting absorption spectra are compared with previously measured absorption spectra in the vapor phase. The measured absorption spectra for liquid gasoline are shown to scale with the volume percent of olefin, alkane, and aromatic hydrocarbons in each sample. Finally, the observed frequency shift of in the spectra of vapor and liquid hydrocarbons is discussed, including the potential for measurements of fuel vapor in the presence of liquid films.     

Mikanolide from Jamaican Mikania micrantha

Mikanolide [systematic names: 1,10:2,3‐di­epoxy‐6,8‐di­hy­droxy‐11‐vinyl­germacr‐4‐ene 12,14‐di‐γ‐lactone and 7,10a‐di­methyl‐1a,1b,2a,6a,7,9a,10,10a‐octa­hydro‐4H‐6,3‐metheno­furo­[3,2‐c]­bisoxireno­[f,h]­oxa­cyclo­undecin‐4,8(6H)‐dione], C₁₅H₁₄O₆, derived from a variety of Mikania micrantha growing in Portland, Jamaica, contains a methyl­cyclo­decane ring fused to an unsaturated planar α,γ‐lactone, an envelope‐type near‐planar vinyl‐β,γ‐lactone and two epoxide moieties. The crystal packing shows stacks of mikanolide mol­ecules interlocked via a network of non‐classical C—H⋯O hydrogen bonds between the lactone units.     

Synthesis of tubular gold and silver nanoshells using silica nanowire core templates

We report the synthesis of tubular gold and silver nanoshells on silica nanowire core templates in solution. Silica nanowires were synthesized and characterized with optical and NMR methods. Gold nanoparticle seeds (2 to 3 nm) with weak repulsive surfactants such as tetrakis-hydroxymethyl-phosphonium chloride (THPC) were conjugated to the surface of these nanowires. A regrowth process was initiated from these nanoparticles on the surface of the silica nanowires dispersed in gold or silver stock solutions in the presence of reducing agents. Micrometers-long gold and silver tubular nanoshells (80-150 nm o.d.) were made, fully covering the silica nanowires.     

Fast gradient elution reversed-phase liquid chromatography with diode-array detection as a high-throughput screening method for drugs of abuse. II. Data analysis

In Part I of this work, we developed a method for the detection of drugs of abuse in biological samples based on fast gradient elution liquid-chromatography coupled with diode array spectroscopic detection (LC-DAD). In this part of the work, we apply the chemometric method of target factor analysis (TFA) to the chromatograms. This algorithm identifies the target compounds present in chromatograms based on a spectral library, resolves nearly co-eluting components, and differentiates between drugs with similar spectra. The ability to resolve highly overlapped peaks using the spectral data afforded by the DAD is what distinguishes the present method from conventional library searching methods. Our library has a mean list length (MLL) of 1.255 and a discriminating power of 0.997 when both retention index and spectral factors are considered. The algorithm compares a library of 47 different compounds of toxicological relevance to unknown samples and identifies which compounds are present based on spectral and retention index matching. The application of a corrected retention index for identification rather than raw retention times compensates for long-term and column-to-column retention time shifts and allows for the use of a single library of spectral and retention data. Training data sets were used to establish the search and identification parameters of the method. A validation data set of 70 chromatograms was used to calculate the sensitivity (correct identification of positives) and specificity (correct identification of negatives) of the method, which were found to be 92% and 94%, respectively.     

Nanoscale characterization of the interface between bone and hydroxyapatite implants and the effect of silicon on bone apposition

Silicon plays an important role in bone mineralization and formation and is therefore incorporated into a wide variety of medical implants and bone grafts used today. The significance of silicon (Si) can be understood through an analysis of the mechanisms of bone bonding to calcium containing biomaterials and through comparisons of hydroxyapatite (HA) and silicon-substituted hydroxyapatite (Si–HA). The addition of Si to HA causes a decrease in grain size that subsequently affects surface topography, dissolution–reprecipitation rates and the bone apposition process. Through the use of high-resolution transmission electron microscopy (HR-TEM) studies, the interactions between bone and silicon hydroxyapatite (Si–HA) at interfaces are reviewed and related to their impact on bone apposition and ultimately the performance of medical implants.     

One-particle and few-particle billiards

We study the dynamics of one-particle and few-particle billiard systems in containers of various shapes. In few-particle systems, the particles collide elastically both against the boundary and against each other. In the one-particle case, we investigate the formation and destruction of resonance islands in (generalized) mushroom billiards, which are a recently discovered class of Hamiltonian systems with mixed regular-chaotic dynamics. In the few-particle case, we compare the dynamics in container geometries whose counterpart one-particle billiards are integrable, chaotic, and mixed. One of our findings is that two-, three-, and four-particle billiards confined to containers with integrable one-particle counterparts inherit some integrals of motion and exhibit a regular partition of phase space into ergodic components of positive measure. Therefore, the shape of a container matters not only for noninteracting particles but also for interacting particles.     

Trapped modes due to narrow cracks in thin simply-supported elastic plates

We consider an elastic plate of infinite length and constant width supported simply along its two parallel edges and having a finite length crack along its centreline. In particular, we look for and find trapped modes (localised oscillations) in the presence of the crack. An explicit wide-spacing approximation based on the Wiener–Hopf technique applied to incident wave scattering by semi-infinite cracks is complemented by an exact formulation of the problem in the form of integro-differential equations. An application of a Galerkin method for the numerical calculation of results from the latter method leads to a novel explicit ‘small-spacing’ approximation. In combination with the wide-spacing results this is shown to provide accurate results for all lengths of crack.