Evaluation of the dark-medium objective lens in counting asbestos fibers by phase-contrast microscopy.

A Japanese round-robin study revealed that analysts who used a dark-medium (DM) objective lens reported higher fiber counts from American Industrial Hygiene Association (AIHA) Proficiency Analytical Testing (PAT) chrysotile samples than those using a standard objective lens, but the cause of this difference was not investigated at that time. The purpose of this study is to determine any major source of this difference by performing two sets of round-robin studies. For the first round-robin study, 15 AIHA PAT samples (five each of chrysotile and amosite generated by water-suspended method, and five chrysotile generated by aerosolization method) were prepared with relocatable cover slips and examined by nine laboratories.

Comparison of lead and tin concentrations in air at a solder manufacturer from the closed-face 37-mm cassette with and without a custom cellulose-acetate cassette insert.

A polyvinyl chloride (PVC) cassette insert with PVC filter (ACCU-CAP) in a 37-mm closed-face cassette (CFC) was designed for gravimetric analysis. A customized version of the ACCU-CAP, also to be used in the CFC, was manufactured from an acid-digestible cellulose-acetate cassette insert joined to a mixed cellulose ester (MCE) filter for wet chemical analysis. The aim of this study was to compare metal particle concentrations as sampled by the customized insert (CI) in a CFC sampler with the traditional sampling method using only a MCE filter in the CFC.

Phosphaallyl complexes of Ru(II) derived from dicyclohexylvinylphosphine (DCVP).

The complexes [(eta5-RC5H4)Ru(CH3CN)3]PF6(R = H, CH3) react with DCVP (DCVP = Cy2PCH=CH2) at room temperature to produce the phosphaallyl complexes [(eta5-C5H5)Ru(eta1-DCVP)(eta3-DCVP)]PF6 and [(eta5-MeC5H4)Ru(eta1-DCVP)(eta3-DCVP)]PF6. Both compounds react with a variety of two-electron donor ligands displacing the coordinated vinyl moiety. In contrast, we failed to prepare the phosphaallyl complexes [(eta5-C5Me5)Ru(eta1-DCVP)(eta3-DCVP)]PF6, [(eta5-MeC5H4)Ru(CO)(eta3-DCVP)]PF6 and [(eta5-C5Me5)Ru(CO)(eta3-DPVP)]PF6(DPVP = Ph2PCH=CH2).

Chloride Substitution Reactions of Cycloruthenated (R)(C)-(+)-N,N-Dimethyl(1-phenylethyl)amine with Pseudohalides: Ruthenium Atom Stereochemistry.

The diastereoselectivity of chloride substitution by the pseudohalides azide, nitrite, thiocyanate, and cyanate in has been determined by a combination of (1)H and (13)C{(1)H} NMR spectroscopy, UV-visible spectroscopy, circular dichroism, infrared spectroscopy, and single-crystal X-ray crystallography. These chloride substitution reactions proceed with predominant retention of configuration at ruthenium. For the ambidentate ligands thiocyanate and nitrite, the major bonding mode is through their nitrogen donor atoms.

Single-Crystal (31)P NMR and X-ray Diffraction Study of a Molybdenum Phosphine Complex: (5-Methyldibenzophosphole)pentacarbonylmolybdenum(0).

The molecular structure of (5-methyldibenzophosphole)pentacarbonylmolybdenum(0), 1, has been determined by X-ray crystallography. The crystal is monoclinic C2/c, Z = 8, with unit cell dimensions of: a = 31.113(2) Å, b =7.

Phosphorus Chemical Shift Tensors of Phosphole Derivatives Determined by (31)P NMR Spectroscopy of Powder Samples.

The results of a systematic solid-state (31)P NMR study of 5-phenyldibenzophosphole, DBP, its chalcogenides, and some of its transition metal complexes are reported. Phosphorus chemical shift tensors have been obtained from (31)P NMR spectra of stationary samples and of samples spinning about the magic angle. The spans of the phosphorus chemical shift tensors for DBP and its chalcogenides are comparable to those of the corresponding compounds of triphenylphosphine; however, the asymmetry of the tensors for the DBP series reflects the reduced local symmetry at phosphorus.

Thermal Coupling Reactions of 1-Phenyl-3,4-dimethylphosphole within the Coordination Sphere of Palladium(II).

The thermolyses of dihalobis(1-phenyl-3,4-dimethylphosphole)palladium(II) complexes [(DMPP)(2)PdX(2), X = Cl, Br, I] were investigated in 1,1,2,2-tetrachloroethane solutions at 145 degrees C and in the crystalline state at 140 degrees C. For cis-(DMPP)(2) PdCl(2) and cis- or trans-(DMPP)(2) PdBr(2) four types of products were formed: (1) [4 + 2] cycloaddition products, (2) [2 + 2] cycloaddition products, (3) compounds that result from 1,5-hydrogen migration from a methyl group on one phosphole to the beta-carbon of an adjacent phosphole (exo-methylene), and (4) products that result from an intermolecular [4 + 2] coupling of two phospholes followed sequentially by phosphinidene elimination and intramolecular [4 + 2] cycloaddition to another phosphole to give diphosphatetracyclotetradecatrienes (DPTCT). trans-(DMPP)(2)PdBr(2) undergoes thermal isomerization to cis-(DMPP)(2)PdBr(2) in the solid state, and cis- and trans-(DMPP)(2)PdBr(2) give the same products in both their solid- and solution-state thermolyses.

Comparison of the Properties of SnCl(3)(-) and SnBr(3)(-) Complexes of Platinum(II).

The complexes M(3)[Pt(SnX(3))(5)] (M = Bu(4)N(+), PhCH(2)PPh(3)(+); X = Cl, Br), cis-M(2)[PtX(2)(SnX(3))(2)] (M = Bu(4)N(+), PhCH(2)PPh(3)(+), CH(3)PPh(3)(+), Pr(4)N(+); X = Cl, Br), and [PhCH(2)PPh(3)](2)[PtBr(3)(SnBr(3))] have been prepared and characterized by (119)Sn and (195)Pt NMR, far-infrared, and electronic absorption and emission spectroscopies. In acetone solutions the [Pt(SnX(3))(5)](3)(-) ions retain their trigonal bipyramidal structures but are stereochemically nonrigid as evidenced by (119)Sn and (195)Pt NMR spectroscopy. For [Pt(SnCl(3))(5)](3)(-) spin correlation is preserved between 183 and 363 K establishing that the nonrigidity is due to intramolecular tin site exchange, probably via Berry pseudorotation.

Behavior of Listeria monocytogenes and Salmonella heidelberg in Rennet Whey Containing Added Sodium and/or Potassium Chloride.

The behavior of Listeria monocytogenes and Salmonella heidelberg in rennet whey salted with sodium chloride, potassium chloride, or a 55/45 mixture of these two salts was evaluated. Other variables included initial whey pH, 4.8 or 5.

Microbiological Safety of Cheese Made from Heat-Treated Milk, Part III. Technology, Discussion, Recommendations, Bibliography.

Heat treatment or pasteurization does not adversely affect the cheesemaking process or the resulting physical properties of the cheese. Both types of heat-treatments can correct chemical changes that occur in cold stored raw milk. Thermization on the farm may help control psychrotrophic bacteria in cold stored milk.

Microbiological Safety of Cheese Made from Heat-Treated Milk, Part II. Microbiology.

A review of epidemiological literature identified six illness outbreaks transmitted via U.S. produced cheese during 40 years, 1948-1988.

Microbiological Safety of Cheese Made from Heat-Treated Milk, Part I. Executive Summary, Introduction and History.

Research on pasteurization of milk for cheesemaking was begun in the late 1800's. Early equipment was crude and control devices non-existent. Consequently, early pasteurization processes were not well verified.