Chemical Subgroup Research Articles

Flavouring Group Evaluation 210: alpha, beta‐Unsaturated alicyclic ketones and precursors from chemical subgroup 2.4 of FGE.19

Flavouring Group Evaluation 210: alpha, beta‐Unsaturated alicyclic ketones and precursors from chemical subgroup 2.4 of FGE.19

Occupational exposure to potential endocrine disruptors: further development of a job exposure matrix

Objectives:The aim was to develop a new up-to-date and comprehensive job exposure matrix (JEM) for estimating exposure to potential endocrine disruptors in epidemiological research.Methods:Chemicals with endocrine disrupting properties were identified...

Interprovincial Variation in Access to Publicly Funded Pharmaceuticals

Introduction: Government-funded drug programs provide prescription medications for many Canadian residents, including senior citizens and social assistance recipients. Pharmaceuticals available for beneficiaries are typically listed in federal, provincial, and territorial formularies. We analyzed six Canadian drug formularies (for the provinces of Alberta, British Columbia, Manitoba, Nova Scotia, Ontario, and Quebec) and report the extent of interprovincial variation in Canadians' access to publicly funded pharmaceuticals at the chemical subgroup (CSG) level of the World Health Organization Anatomical Therapeutic Chemical (WHO ATC) classification system. Methods: A database profiling provincial formulary listings of CSGs was compiled to enable a cross-sectional analysis of drug benefits at a clinically meaningful level. The comprehensiveness of provincial drug reimbursement plans was evaluated in a quantitative comparison of CSGs. Therapeutic distribution of CSGs within anatomical main groups of the WHO ATC classification system was also investigated. Interprovincial formulary agreement of CSG listings (full, restricted, or not listed) was determined on the basis of kappa coefficients. Results: British Columbia and Nova Scotia provided residents with access to the greatest number of full-listing CSGs, 336 each. Manitoba had the fewest full-listing CSGs, 268. Kappa coefficients, representing agreement in provincial listing decisions, ranged from 0.23 (between British Columbia and Quebec) to 0.45 (between Alberta and Manitoba). All of these coefficients represent a fair-to-poor level of interprovincial agreement in CSG listing status. Conclusion: A large degree of variation is present in Canadian provincial drug formularies, even at the CSG level. This reflects differences in provincial listing decisions and has therapeutic implications for patients, in that there is differential access to entire categories of drug products across provincial drug plans.

Chemical mapping of patterned polymer photoresists by near-field infrared microscopy

Latent images obtained by deep-ultraviolet (DUV) patterning and post-exposure bake in the polymer system poly(t-butylmethacrylate) (PTBMA) resist/triphenyl sulfonium photoacid generator are characterized by infrared near-field microscopy (IR-NSOM). Chemical sub-group specificity is achieved in the infrared near-field images by using wavelengths tuned on the OH absorption band of the poly(methacrylate acid) (PMAA) resulting from the photoacid-catalyzed decomposition of t-butoxycarbonyl groups. The experimental images of the patterned thin polymer film are compared with predictions based on scalar diffraction theory calculations for the initial light illumination step through the mask. Partial disagreement between the theory and the experiment is observed, but only for certain line/space dimensions of the pattern. The results suggest a structure-dependent chemistry during the latent image development.

Contents and enantiomeric compositions of monoterpene hydrocarbons in xylem oleoresins from four Pinus species growing in Cuba. Comparison of trees unattacked and attacked by Dioryctria horneana

Monoterpene hydrocarbons from the xylem oleoresins of Pinus tropicalis, P. caribaea var. caribaea, P. cubensis and P. maestrensis growing in Cuba were investigated. A large number of oleoresin samples from trees, attacked and unattacked by the moth Dioryctria horneana, as well as from trees growing in different localities, were analyzed. In each sample, the relative amounts of the volatiles and the enantiomeric compositions of six chiral monoterpene hydrocarbons were determined using a two-dimensional gas chromatographic (2D-GC) system. The GC-data were evaluated using two methods for multivariate data analysis, PCA (principal components analysis) and PLS-DA (projections to latent structures-discriminant analysis). PC-plots based on the relative amounts of the monoterpenes present in the volatile oleoresin fractions analyzed, showed that P. tropicalis and P. cubensis formed one group, separated from P. caribaea, while pines belonging to the species P. maestrensis were found in both groups. The species P. tropicalis and P. maestrensis, both of which are resistant to D. horneana, and the subgroups within the species P. caribaea and P. cubensis, that had not been attacked by D. horneana, showed no signs of constituting a chemical subgroup. No significant difference was found between the attacked and the unattacked P. cubensis trees. In P. caribaea, on the other hand, the composition of volatiles in attacked trees was significantly different from that in unattacked trees. However, an influence of monoterpenes on the oviposition of D. horneana was not proved.

Asbestos inhalation and nonmalignant abnormalities of the chest

The term asbestos refers to a group of hydrated fibrous silicates containing the chemical subgroup silica (SiO,), combined with a variety of other metallic cations such as zinc, aluminum, calcium, magnesium, and iron. Whereas other mineral substances also share these chemical compositions, the fibrous character of asbestos, defined as a length-to-width ratio (aspect ratio) of at least 3:1, distinguishes asbestos from other silicates such as talc, kaolin, and mica which have similar chemical composition but form flat, platelike structures. Silicates such as asbestos and talc must be distinguished from crystalline silica, another potentially pathogenic material, inasmuch as silica is not combined with other cations and produces tetrahedral crystals known as quartz, tridymite, and crystobalite. Both chemistry and configuration define the physical properties of the different types of asbestos fibers. Two major subgroups of asbestos are recognized according to their physical appearance.’ Serpentine asbestos has a curved or curly fiber shape, whereas amphibole asbestos fibers are perfectly straight. There is only one member of the serpentine group, chrysotile asbestos, but this type accounts for about 90% of the fiber that has been used commercially in the United States. The amphibole group consists of crocidolite, amosite, anthophylite, tremolite, and actinolite (Fig 1). From a commercial standpoint, the most important amphibole types are crocidolite and amosite. Not only are there differences among the various types of asbestos fibers with regard to their chemical composition and commercial uses, there are also differences in their propensity to cause specific types of biological reactions. For instance, crocidolite is recognized as the most powerful producer of malignant mesothelioma, although the other types of asbestos have also been reported to cause this disease at a lower frequency.2

Comparative Toxicology of Laboratory Organisms for Assessing Hazardous Waste Sites

AbstractMulti‐media/multi‐trophic level bioassays have been proposed to determine the extent and severity of environmental contamination at hazardous waste sites. Comparative toxicological profiles for algae (Selenastrum capricornutum), daphnia (Daphnia magna), earthworms (Eisenia foetida), microbes (Photobacterium fisherii, mixed sewage microorganisms) and plants; wheat “Stephens,” (Triticum aestivum), lettuce, butter crunch, (Lactuca sativa L.), radish, “Cherry Belle,” (Raphanus sativa L.), red clover, “Kenland,” (Trifolium pratense L.) and cucumber, “Spartan Valor,” (Cucumis sativa L.) are presented for selected heavy metals, herbicides and insecticides. Specific chemical EC50 values are presented for each test organism. Differences in standard deviations were compared between each individual test organism, as well as for the chemical subgroup assayed. Algae and daphnia are the most sensitive test organisms to heavy metals and insecticides followed in order of decreasing sensitivity by Microtox (Photobacterium fisherii), DO depletion rate, seed germination and earthworms. Higher plants were most sensitive to 2,4‐D, (2,4‐Dichlorophenoxy acetic acid) followed by algae, Microtox, daphnia and earthworms. Differences in toxicity of 2,4‐D chemical formulations and commercial sources of insecticides were observed with algae and daphnia tests.

ADELAIDE AND BENCH CRATER — MEMBERS OF A NEW SUBGROUP OF THE CARBONACEOUS CHONDRITES

The composition and mineralogy of Bench Crater and a new carbonaceous chondrite (Adelaide) are compared. They, Kakangari and possibly certain carbonaceous xenoliths from other meteorites constitute a distinct chemical subgroup of the carbonaceous chondrites characterized primarily by a calcium‐to‐aluminium ratio (atomic) of about 0.5. It is proposed to call this group the Kakangari (CK) group

A second tektite fall in Australia

A chemical subgroup of tektites found in Australia (Chapman's “high sodium” tektites) have fission track ages of approximately 4 m.y. and hence are part of a distinct tektite fall, one that preceded the formation of the well known Australasian strewn field 0.7 m.y. ago.