Preparation of carbon-11 labelled acetate and palmitic acid for the study of myocardial metabolism by emission-computerised axial tomography

Methods have been developed for the labelling of acetate and palmitic acid with the positron-emitting radionuclide,¹¹C (T=20.4 min). Labelling was achieved via carbonation of the appropriate alkyl magnesium bromide (methyl magnesium bromide or n-pentadecyl magnesium bromide) with¹¹C-labelled carbon dioxide produced by the¹⁴N(p, α)¹¹C nuclear reaction. The radiochemical yield and speed of each method of labelling are such that a radiochemically pure product is obtained in injectable form and in activity (>10 mCi) suitable for the study of myocardial metabolism by emission-computerised axial tomography. High pressure liquid chromatography and thin layer chromatography were used to assess the radiochemical purity of each radiopharmaceutical. The specific activity of¹¹C-labelled acetate was estimated by an enzymic procedure to be greater than 0.5 Ci/μmole.     

Multiresidue method for the determination of residues of 251 pesticides in fruits and vegetables by gas chromatography/mass spectrometry and liquid chromatography with fluorescence detection

A method is described for the determination of 251 pesticide and degradation product residues in fruit and vegetable samples. Extraction of the sample with acetonitrile is followed by a salting-out step. Co-extractives are removed by passing a portion of the acetonitrile extract through an octadecyl (C18) solid-phase extraction cleanup cartridge and then, in a second cleanup, through a carbon cartridge coupled to an amino propyl cartridge. Determination is by gas chromatography with mass-selective detection in the selected-ion monitoring mode, and by liquid chromatography with post-column reaction and fluorescence detection for N-methyl carbamates. The method has been used for analysis of various fruits and vegetables, such as apple, banana, cabbage, carrot, cucumber, lettuce, orange, pear, pepper, and pineapple. Limits of detection range between 0.02 and 1.0 mg/kg for most compounds. Over 80% of the compounds have a limit of detection of < or = 0.04 mg/kg.     

Cationic palladacycles as catalyst precursors for phenyl acetylene polymerization

Novel cationic palladacycles based on benzylidene-2,6-diisopropylphenylimines were prepared via C-H activation using Pd(CH₃CN)₂Cl₂ as metal precursor. The complexes were fully characterized by IR and NMR spectroscopy, mass spectrometry and elemental analysis. The cationic palladacycles were found to be active catalysts for the polymerization of phenylacetylene producing largely trans-cisoidal PPA.     

Production of the NH radical from the catalytic decomposition of NH3 on polycrystalline Pt and Fe surfaces at high temperatures

Decomposition of NH₃ on polycrystalline platinum at temperatures >1200 K was found to result in desorption of the NH radical into the gas phase. The gaseous NH radical was detected by means of the laser-induced fluorescence technique. The desorption process is one of several possible steps involving the surface-adsorbed NH radical. NH₂ was not observed to desorb from the catalyst at all temperatures studied. The measured activation energy for NH desorption is 66 ± 3 kcal/mol and appears to be independent of NH₃ or H₂ gas phase concentration over the range studied. Addition of H₂ to NH₃ enhances the yield of NH desorbed; however, addition of D₂ to NH₃ enhances the desorption yield of both ND and NH. A mechanism for NH₃ decomposition is proposed to account for these observations and the results of other studies. A similar but brief study of NH₃ decomposition on polycrystalline Fe surfaces was also made. Similarly NH, but not NH₂, was found to desorb from the Fe surface above 1000 K.     

Neutral palladium(II) complexes with P,N Schiff-base ligands: Synthesis, characterization and catalytic oligomerisation of ethylene

New N-functionalised 2-phosphinobenzaldimino (P^N) ligands bearing 3-picolyl, furfuryl, thiophene-2-methyl, thiophene-2-ethyl, and benzyl groups have been prepared in good yield. The 2-phosphinobenzaldimino ligands were reacted with PdCl₂(COD) to give the corresponding metal complexes of the type Pd(L)Cl₂ (L = 2-phosphinobenzaldimino (P^N) ligand). All compounds were fully characterized using spectroscopic and analytical techniques, including ¹H, ¹³C, and ³¹P NMR and IR spectroscopies, mass spectrometry and elemental analysis. Selected neutral palladium complexes were evaluated as catalyst precursors in ethylene oligomerisation reactions, after activation with a co-catalyst (MMAO, EtAlCl₂, or Et₂AlCl).     

The atmospheric-pressure plasma jet: a review and comparison toother plasma sources

Atmospheric-pressure plasmas are used in a variety of materials processes. Traditional sources include transferred arcs, plasma torches, corona discharges, and dielectric barrier discharges. In arcs and torches, the electron and neutral temperatures exceed 3000°C and the densities of charge species range from 10¹⁶-10¹⁹ cm^-3. Due to the high gas temperature, these plasmas are used primarily in metallurgy. Corona and dielectric barrier discharges produce nonequilibrium plasmas with gas temperatures between 50-400°C and densities of charged species typical of weakly ionized gases. However, since these discharges are nonuniform, their use in materials processing is limited. Recently, an atmospheric-pressure plasma jet has been developed, which exhibits many characteristics of a conventional, low-pressure glow discharge. In the jet, the gas temperature ranges from 25-200°C, charged-particle densities are 10 ¹¹-10¹² cm^-3, and reactive species are present in high concentrations, i.e., 10-100 ppm. Since this source may be scaled to treat large areas, it could be used in applications which have been restricted to vacuum. In this paper, the physics and chemistry of the plasma jet and other atmospheric-pressure sources are reviewed     

RFID-generated traceability for contaminated product recall in perishable food supply networks

As perishable food supply networks become more complex, incidents of contamination in these supply networks have become fairly common. Added to this complexity is the fact that there have been long delays in identifying the contamination source in several such incidents. Even when the contamination source was identified, there have been cases where the ultimate destination of all contaminated products were not known with complete certainty due, in part, to dispersion in these supply networks. We study the recall dynamics in a three-stage perishable food supply network through three different visibility levels in the presence of contamination. Specifically, we consider allocation of liability among the different players in the perishable supply network based on the accuracy with which the contamination source is identified. We illustrate the significance of finer levels of granularity both upstream and downstream as well as determine appropriate visibility levels and recall policies.     

Should retail stores also RFID-tag ‘cheap’ items?

Despite their implementations in a wide variety of applications, there are very few instances where every item sold at a retail store is RFID-tagged. While the business case for expensive items to be RFID tagged may be somewhat clear, we claim that even ‘cheap’ items (i.e., those that cost less than an RFID tag) should be RFID tagged for retailers to benefit from efficiencies associated with item-level visibility. We study the relative price premiums a retailer with RFID tagged items can command as well as the retailer’s profit to illustrate the significance of item-level RFID-tagging both cheap and expensive items at a retail store. Our results indicate that, under certain conditions, item-level RFID tagging of items that cost less than an RFID tag has the potential to generate significant benefits to the retailer. The retailer is also better off tagging all items regardless of their relative price with respect to that of an RFID tag compared to the case where only the expensive item is RFID-tagged.     

Inorganic coordination polymers. VII. Zinc(II) dimethyl-, methylphenyl-, and diphenylphosphinates

Zinc dimethyl-, methylphenyl-, and diphenylphosphinate have been prepared by the reaction of Zn(C₂H₃O₂)₂·2H₂O with the appropriate acid or salt and found to exist in amorphous and crystalline forms. Zinc methylphenylphosphinate, the most tractable, exhibits many of the physical attributes of polymeric materials, both in solution and bulk form, supporting our earlier suggestion that these compounds are double-bridged coordination polymers. Thermogravimetric analysis indicates initial decomposition temperatures of 440, 425, and 490°C., respectively, for the three polymers, but long-term studies show initiation of decomposition at somewhat lower temperatures.     

The synthesis,characterization and polycondensation of metal‐containing diols: crystal structure of [(η5‐C5H5)(CO)2Fe(CH2)3O‐{2,6‐(CH2OH)2‐4‐CH3?C6H2}]

The synthesis of two new transition‐metal‐containing polyesters is described. The precursors are bifunctional organometallic monomers that were synthesized using 2,6‐bis(hydroxymethyl)‐p‐cresol as the key reagent. This was achieved by simple coupling reactions between the appropriate organometallic alkyl halide and the cresol reagent. Polycondensation reactions were carried out with terephthaloyl chloride using ambient temperature solution techniques. The new low molecular weight oligomeric polyesters were characterized using Fourier transform infrared and ¹HNMR spectroscopy, differential scanning calorimetry, thermogravimetric analysis and size‐exclusion chromatography analyses. Copyright © 2002 John Wiley & Sons, Ltd.