1,720,973 research outputs found
The contribution of occupational exposure vs. cigarette smoking in determining the internal dose of 1,3-butadiene in Italian workers
No full textAims: The aim of this study was to compare the contribution of occupational exposure and smoking habit in determining the total intake of 1,3-butadiene (BD), a probable carcinogen to humans, in chemical workers.
Methods: Forty-two BD healthy male petrochemical workers (W), and forty-three internal controls (C) entered the study. Personal exposure to airborne BD was evaluated as time weighted average value during the work-shift. BD in exhaled air, blood and urine was measured in specimens collected both at the beginning and at the end of the work-shift. Information on cigarette smoking was obtained by questionnaire.
Results: Median exposure to BD was 1.5 (ranging from <0.1-201 ) μg/m3 in W, and 0.4 (<0.1-10) μg/m3 in C. BD in exhaled air, blood and urine was about 1.5-3 times higher in W then in C (p<0.05). Correlations between these biomarkers and airborne BD (0.28<Pearson r<0.39) and between the biomarkers themselves (0.78<Pearson r<0.90) were significant. Cigarette smoke had a great impact on internal dose: an increase of BD up to 20 folds was found in biological fluids of smokers compared to non-smokers. Multiple linear regression analysis correlated BD in exhaled air, in blood or in urine with personal exposure and cigarette smoking (0.72R0.77), explaining up to 59% of the observed variability.
Conclusion: In the present study airborne BD exposure was very low. Notwithstanding, the levels of BD in exhaled air, blood and urine were positively associated with personal exposure and showed that cigarette smoke, rather then occupational exposure, was the major source of BD exposure in the investigated subjects
Determination of low level methyl tert-butyl ether, ethyl tert-butyl ether and methyl tert-amyl ether in human urine by HS-Spme gaschromatography/mass spectrometry
No full textMethyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE) and tert-amyl methyl ether (TAME) are oxygenated compounds added to gasoline to enhance octane rating and to improve combustion. They may be found as pollutants of living and working environments. In this work a robotized method for the quantification of low level MTBE, ETBE and TAME in human urine was developed and validated. The analytes were sampled in the headspace of urine by SPME in the presence of MTBE-d12 as internal standard. Different fibers were compared for their linearity and extraction efficiency: carboxen/polydimethylsiloxane, polydimethylsiloxane/divinylbenzene, and polydimethylsiloxane. The first, although highly efficient, was discarded due to deviation of linearity for competitive displacement, and the polydimethylsiloxane/divinylbenzene fiber was chosen instead. The analysis was performed by GC/MS operating in the electron impact mode. The method is very specific, with range of linearity 30-4600 ng L(-1), within- and between-run precision, as coefficient of variation, <22 and <16%, accuracy within 20% the theoretical level, and limit of detection of 6 ng L(-1) for all the analytes. The influence of the matrix on the quantification of these ethers was evaluated analysing the specimens of seven traffic policemen exposed to autovehicular emissions: using the calibration curve and the method of standard additions comparable levels of MTBE (68-528 ng L(-1)), ETBE (<6 ng L(-1)), and TAME (<6 ng L(-1)) were obtained
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Dalla riflessione su oralità e scrittura alla redazione di testi scritti efficaci: uno studio sperimentale
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Comparison between urinary o-cresol and toluene as biomarkers for assessing toluene exposure
No full textAim: In the present research the characteristics of urinary o-cresol and toluene as biomarkers of exposure to toluene were comparatively evaluated.
Methods: 100 healthy male rotogravure-printing workers (P) and 87 male and female control subjects (C) were investigated. Personal exposure to toluene during the shift was determined. Simple and sensible analytical procedures based on solid phase micro-extraction followed by GC/MS analysis were developed and applied to the determination of end-shift urinary o-cresol and toluene.
Results: Median exposure to airborne toluene, as time weighted average, was 48 (in the range 6-162) mg/m3 in P and 0.03 (0.01-0.14) mg/m3 in C. o-Cresol was 0.19 (0.03-0.95) mg/g creatinine in P and 0.03 (0.002-0.330) mg/g creatinine in C. Urinary toluene was 8 (2-24) μg/l in P and <1 μg/l in C. Accordingly with all indices, exposure to toluene was higher in P than in C. Nevertheless the distributions of o-cresol in the two groups were partially overlapped, whereas such behaviour was not found in urinary toluene. Both urinary o-cresol and toluene were correlated with personal exposure (Pearson r 0.64 and 0.82 respectively) and among them. Smoking habit significantly increased the excretion of o-cresol, but not of toluene.
Conclusion: Urinary toluene, although presents constrains in sample handling and sampling time, has low background values, is not affected by smoking habit, has lower inter-individual variability, higher specificity and sensitivity in comparison with o-cresol; for such reasons we recommend its use as biomarker of short term exposure to toluene
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Determination of urinary ortho- and meta-cresol in humans by headspace SPME gas chromatography-mass spectrometry
No full textortho-Cresol (o-C) and meta-cresol (m-C) are minor urinary metabolites of toluene, a widely used chemical with neurotoxicological properties. A new assay for their determination in human urine is here proposed. Urinary cresol sulphates and glucuronates are submitted to acid hydrolysis, urine is neutralized, added with o-cresols-d8, and analytes are sampled in the headspace of urine by SPME using a polydimethylsiloxane fiber. Analysis is performed by GC/MS using, for separation, either a SupelcoWax10 (for o-C) or a chiral CP Cresol (for o-C and m-C) column. The method is very specific, with a range of linearity 0-5.0 mg/l, within- and between-run precision, as coefficient of variation, <15% and <19%, limit of detection of 0.006 mg/l for o-C and 0.007 mg/l for m-C. The procedure is applied to the quantification of cresols in urine from workers exposed to toluene and from subjects belonging to the general population
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