A glow discharge device for atomic emission spectrometry of microliter solution samples

A novel glow discharge device designed specifically for solution analysis is described. The detection limits obtained are comparable to those obtained with demountable hollow cathode lamps, but with better precision. Rotational and excitation temperatures are examined as functions of fill gas pressure and discharge current. A sputtering constant is presented and the technique for measuring this parameter is described.     

Substrate-based design of the first class of angiotensin-converting enzyme-related carboxypeptidase (ACE2) inhibitors

Angiotensin-converting enzyme-related carboxypeptidase (ACE2) is a recently identified zinc metalloprotease with carboxypeptidase activity that was identified using our genomics platform. We implemented a rational design approach to identify potent and selective ACE2 inhibitors. To this end, picomolar inhibitors of ACE2 were designed and synthesized.     

Investigation of Progesterone Loaded Poly(D,L-Lactide) Microspheres Using TMDSC,SEM and PXRD

Poly(d,l-lactide) microspheres with progesterone loadings of 0, 10, 20, 30 and 50% w/w were manufactured using an interrupted solvent evaporation process. Spherical microspheres with loadings close to the theoretical values were produced. The glass transition of the polymer could be identified by a step change in the heat capacity measured by TMDSC. Progesterone was found to plasticise the glass transition temperature at contents of 20% w/w or less. At a 30% loading, cold crystallisation of progesterone was seen indicating that an amorphous form of the drug was present; these microspheres were found to exhibit a pitted surface. TMDSC of the 50% progesterone samples suggested that most of the drug was present as crystals. This was supported by the SEM and PXRD results. This revised version was published online in July 2006 with corrections to the Cover Date.     

High-performance liquid chromatographic determination of arecoline in human saliva

Arecoline (methyl-1,2,5,6-tetrahydro-1-methyl nicotinate) is an alkaloid found in the areca catechu nut which is a major component of the 'betel quid' chewed by a large proporation of the population in India, South Asia and the South Pacific islands. It is commonly associated with the development of oral leukoplakia, oral submucous fibrosis and oral cancer. We have developed a new ion-pairing reversed-phase high-performance liquid chromatographic (HPLC) method for the determination of arecoline in saliva, using arecaidine (1,2,5,6-tetrahydro-1-methylnicotinic acid) as an internal standard. The optimal wavelength was established using UV absorbance scans. It was showed that 215 nm is the optimal wavelength to maximise the signal in detecting arecoline in the mobile phase. Arecoline was extracted from saliva with hexane-isoamyl alcohol (1%) and reconstituted with mobile phase for HPLC analysis. The developed method is an easy and reliable method of determining arecoline concentrations in saliva. Sensitivity, specificity, precision, accuracy and reproducibility of the method were demonstrated to be satisfactory for measuring the arecoline level.     

Promotion of iridium-catalyzed methanol carbonylation: mechanistic studies of the cativa process

The iridium/iodide-catalyzed carbonylation of methanol to acetic acid is promoted by carbonyl complexes of W, Re, Ru, and Os and simple iodides of Zn, Cd, Hg, Ga, and In. Iodide salts (LiI and Bu(4)NI) are catalyst poisons. In situ IR spectroscopy shows that the catalyst resting state (at H(2)O levels > or = 5% w/w) is fac,cis-[Ir(CO)(2)I(3)Me](-), 2. The stoichiometric carbonylation of 2 into [Ir(CO)(2)I(3)(COMe)](-), 6, is accelerated by substoichiometric amounts of neutral promoter species (e.g., [Ru(CO)(3)I(2)](2), [Ru(CO)(2)I(2)](n), InI(3), GaI(3), and ZnI(2)). The rate increase is approximately proportional to promoter concentration for promoter:Ir ratios of 0-0.2. By contrast anionic Ru complexes (e.g., [Ru(CO)(3)I(3)](-), [Ru(CO)(2)I(4)](2)(-)) do not promote carbonylation of 2 and Bu(4)NI is an inhibitor. Mechanistic studies indicate that the promoters accelerate carbonylation of 2 by abstracting an iodide ligand from the Ir center, allowing coordination of CO to give [Ir(CO)(3)I(2)Me], 4, identified by high-pressure IR and NMR spectroscopy. Migratory CO insertion is ca. 700 times faster for 4 than for 2 (85 degrees C, PhCl), representing a lowering of Delta G(++) by 20 kJ mol(-1). Ab initio calculations support a more facile methyl migration in 4, the principal factor being decreased pi-back-donation to the carbonyl ligands compared to 2. The fac,cis isomer of [Ir(CO)(2)I(3)(COMe)](-), 6a (as its Ph(4)As(+) salt), was characterized by X-ray crystallography. A catalytic mechanism is proposed in which the promoter [M(CO)(m)I(n)] (M = Ru, In; m = 3, 0; n = 2, 3) binds I(-) to form [M(CO)(m)I(n+1)](-)H(3)O(+) and catalyzes the reaction HI(aq) + MeOAc --> MeI + HOAc. This moderates the concentration of HI(aq) and so facilitates catalytic turnover via neutral 4.     

Chlorination of isothiocyanates. VIII. Reaction of S-chloroisothiocarbamoyl chlorides with aliphatic and cycloaliphatic ketones

Reported is the synthesis of various derivatives of 2-imino-5-chloro-1,3-oxathiolanes, 2-imino-1,3-oxathioles and 1,3-thiazolin-2-ones from N-aryl- and N-alkyl-S-chloroisothiocarbamoyl chlorides and ketones.     

Determination of Particle Size and Shape during the Hydrolysis of Pb(Zr0.3Ti0.7)O3 Precursor Solutions

The formation and growth of polymeric particles during the hydrolysis and condensation of PbZr_0.3Ti_0.7 O₃ (PZT 30/70) sol-gel precursor solutions have been investigated by using photon correlation spectroscopy (PCS), small angle X-ray scattering (SAXS) and by measuring their rheological properties. The measurements showed that the growth of the particles in the transition of PZT sol to gel followed a simple polymerisation process. Solution A (containing by-products) and Solution B (by-products removed) displayed a similar plot of logarithmic viscosity against logarithmic time, indicating that the particles in both solutions have similar structures after hydrolysis. The changes in viscosity and particle size with time were described by single logarithmic growth models. However, the increasing rate of logarithmic particle size in Solution B is higher than that in Solution A. A model for the form of the aggregates is discussed which is applicable to PZT organometal-particle aggregation process in systems with acetic acid as a modifier.     

Synthesis and characterization of cubic cobalt oxide nanocomposite fluids

Narrow size distribution cubic Co₃O₄ nanoparticles were synthesized and rheological properties of suspensions of the cubes in oligomeric polyethylene glycol (PEG) were explored over a range of particle volume fractions and rotational shear flow conditions. At low and high particle volume fractions, the relative viscosity of the suspensions is described by a Krieger–Dougherty formula with an intrinsic viscosity consistent with expectations for suspensions of ideal cuboids. At intermediate to high particle loadings, the suspensions manifest complex rheological behavior, including shear thinning and shear-thickening features. These observations are discussed in terms of the charge carried by the cubes and the shear rate/volume fraction dependency of the transition from shear thinning to shear thickening.     

A Comparison of the Nanostructure of Lead Zirconate,Lead Titanate and Lead Zirconate Titanate Sols

Sol-gel processing has been widely used for the fabrication of lead zirconate titanate (PZT) thin films. To successfully and consistently make high quality thin films for different applications, we must develop a fundamental understanding of the structures of the sols. In this study, the characters of lead titanate (PT) and lead zirconate (PZ)sols were studied by measuring the rheological properties and particle sizes in them and comparing their behaviours. The average particle sizes in unhydrolysed PT, PZ and PZT sols are 11.5, 1.0, and 6.0 nm, respectively. PT sol has the highest rate of hydrolysis. It gels at about 24 h after hydrolysis. PZ and PZT sols have a quite similar feature in hydrolysis. The reasons for the differences in the hydrolysis behaviour of the different types of sol are discussed in terms of a model which indicates that the inhomogeneous sols consist of 5 to 6 nm PT particles surrounded by much smaller PZ particles, which tend to dominate the sol behaviour.