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1.
Environ Res ; 110(1): 1-11, 2010 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-19926083

RESUMO

A prior study in New York City observed that airborne concentrations of three metals found in steel - iron, manganese, and chromium - are more than 100 times higher in the subway system than in aboveground air. To investigate the potential for health effects of exposure at these levels, we conducted a pilot study of subway workers comparing personal exposures to steel dust with biomarkers of metal exposure, oxidative stress, and DNA damage in blood and urine samples. Workers wore a personal air sampler operating at 4L/m for one to three work shifts with blood and urine samples collected at the end of the final shift. We found that PM(2.5) exposures varied among subway workers on the basis of job title and job activity. The subway workers' mean time-weighted PM(2.5) exposure was 52 microg/m3, with a median of 27 microg/m3, and a range of 6-469 microg/m3. The observed concentrations of PM(2.5), iron, manganese, and chromium fell well below occupational standards. Biomarker concentrations among the 39 subway workers were compared with a group of 11 bus drivers, and a group of 25 suburban office workers. Concentrations of DNA-protein crosslinks and chromium in plasma were significantly higher in subway workers than in bus drivers, but no significant difference was observed for these biomarkers between subway workers and office workers. Urinary isoprostane concentrations were significantly correlated with the number of years working in the subway system, and were detected at higher, though not significantly higher, concentrations in subway workers than in bus drivers or office workers. At the group level, there was no consistent pattern of biomarker concentrations among subway workers significantly exceeding those of the bus drivers and office workers. At the individual level, steel dust exposure was not correlated with any of the biomarkers measured.


Assuntos
Poluentes Ocupacionais do Ar/análise , Monitoramento Ambiental , Exposição por Inalação/análise , Metais Pesados/análise , Material Particulado/análise , Ferrovias , Adulto , Poluentes Ocupacionais do Ar/sangue , Poluentes Ocupacionais do Ar/toxicidade , Poluentes Ocupacionais do Ar/urina , Dano ao DNA , Poeira , Humanos , Metais Pesados/sangue , Metais Pesados/toxicidade , Metais Pesados/urina , Microscopia Eletrônica de Varredura , Pessoa de Meia-Idade , Cidade de Nova Iorque , Estresse Oxidativo/efeitos dos fármacos , Tamanho da Partícula , Material Particulado/sangue , Material Particulado/toxicidade , Material Particulado/urina , Projetos Piloto , Ferrovias/normas , Aço , Propriedades de Superfície , Local de Trabalho/normas
2.
J Am Chem Soc ; 131(24): 8425-33, 2009 Jun 24.
Artigo em Inglês | MEDLINE | ID: mdl-19473007

RESUMO

The solution photochemistry of bis(phenylpyrrolidinonyl)ketones (R,R)-1b and (S,S)-1b exhibited a remarkably high memory of chirality. Stereospecific decarbonylation to products (R,R)-3b and (S,S)-3b, respectively, occurred with an ee of ca. 80%. The reaction is thought to occur along the single state manifold by sequential Norrish type-I alpha-cleavage, decarbonylation, and radical-radical combination in a time scale that is comparable to that required for the radical intermediate to expose its other enantiotopic face by rotation about an axis perpendicular to that of the p orbital (ca. 3-7 ps). The absolute configuration of a key intermediate and that of ketone (R,R)-1b were determined by single-crystal X-ray diffraction and the ee values of the photochemical products with the help of chiral shift reagent (+)-Eu(tfc)(3) and chiral LC-MS/MS. On the basis of the ee and de values at 25 degrees C, it could be determined that ca. 70% of the bond forming events occur with double memory of chirality, ca. 21% occur after rotation of one radical to form the meso product (R,S)-3b, and only 9% occur after double rotation to form the opposite enantiomer. This report represents the first example of a doubly enantiospecific Norrish type-I and decarbonylation reaction in solution and illustrates potentially efficient ways to obtain compounds with adjacent stereogenic quaternary centers.

3.
J Org Chem ; 74(6): 2476-80, 2009 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-19222209

RESUMO

Here we report the crystallization and solid photochemistry of six quaternary ammonium salts of 2,4-di-p-carboxyphenyl-2,4-dimethyl pentanone. While salt formation resulted in solids with different melting temperatures and crystallinities, photochemical excitation in the solid state resulted in the chemoselective formation of a single product arising from the homolytic loss of CO followed by combination of the intermediate radical pair. Photochemical experiments in solution led to the product mixtures formed by combination and disproportionation of the corresponding free radical intermediates. The crystallinity of all salts was documented by DSC, 13C CP-MAS NMR, and XRPD.


Assuntos
Ácidos Dicarboxílicos/química , Compostos de Amônio Quaternário/química , Monóxido de Carbono , Cristalização , Descarboxilação , Pentanonas , Processos Fotoquímicos
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