Search results for "Benzene"

A Chemical Index Inspired by Biological Plastic Evolution:  Valence-Isoelectronic Series of Aromatics

2004

Plastic evolution is a new perspective of the evolutionary process conjugating the effect, on one hand, of the acquired characters and, on the other, of the relationships that emerge among the principle of evolutionary indeterminacy, the principle of morphologic determination, and natural selection. Plastic evolution is applied to design the coordination index Ic. Ic is used to characterize the valence-isoelectronic series of cyclopentadiene, benzene, toluene, and styrene and compared to charge indices for dipole moment. The parameters needed to calculate Ic are minus the standard enthalpy of formation T, molecular surface area S, and molecular weight W. With the exception of the O heteromo…

Structural Approaches to Explain the Selectivity of COX-2 Inhibitors: Is There a Common Pharmacophore?

2000

The identification and characterisation of the isoenzyme cyclooxygenase 2 (COX-2) stimulated investigations to develop efficient non-steroidal anti-inflammatory drugs with reduced side effects compared to standard NSAIDs. This review will focus on the structural features needed to achieve COX-2 selectivity. Five structural classes can be identified together with a class bearing little or no resemblance to one another in their molecular structure. The most interesting point is the very distinct structure/activity relationship. On the one hand only minor modifications to a particular compound induce a drastic change in its COX selectivity and on the other hand the structural prerequisites in …

Outdoor NO2 and benzene exposure in the INMA (Environment and Childhood) Asturias cohort (Spain)

2011

Air pollution exposure during pregnancy has been linked to a wide range of negative health effects. NO2, a traffic pollution marker, and benzene, an industrial pollution indicator, stand out among the types of air pollution linked to these effects. The aim of this work is to show the methodology used to assign exposure levels for both pollutants and preliminary reports in the INMA (Environment and Childhood) Asturias cohort in Spain. This cohort consists of 494 pregnant women and their children, who have been recruited and followed since 2004. Air pollution levels were measured at 67 points by means of passive samplers. The mean NO2 measured value was 21.2 mu g m(-3) (range 3.5 mu g m(-3) t…

Evaluation of the Soil Contamination of Tangier (Morocco) by the Determination of BTEX, PCBs, and PAHs

2009

Benzene, toluene, ethylbenzene, and xylenes (BTEX), twelve polycyclic aromatic hydrocarbons (PAHs) and seven polychlorinated biphenyls (PCBs), were selected as pollutants to evaluate the contamination of soils in the urban and industrial areas of Tangier (Morocco). PAHs and PCBs were determined by gas chromatography-mass spectrometry (GC-MS) after a microwave-assisted extraction (MAE) and gel permeation chromatography (GPC) clean-up. BTEX were directly determined by head-space GC-MS. Results obtained in this study show the presence of high levels of BTEX and PAHs in the soil near the urban waste deposit. However, the analysis of pollutants in the other sampling sites provided comprehensive …

The Seasonality Impact of the BTEX Pollution on the Atmosphere of Arad City, Romania

2021

Benzene, toluene, and total BTEX (benzene, toluene, ethylbenzene, and xylene) concentrations registered for one year (2016) have been determined every month for one high-density traffic area. The assessment was performed in Arad City, Romania, to evaluate these pollutants and their influence on the inhabitants’ health. The contaminants were sampled using a static sampling method and analyzed by gas chromatography coupled with mass spectrometry. Benzene was the most dominant among the BTEX compounds—the average concentrations ranged from 18.00 ± 1.32 µg m−3 in December to 2.47 ± 0.74 µg m−3 in August. The average toluene concentration over the year was 4.36 ± 2.42 µg m−3 (with a maximum of 9…

Annoyance Caused by Noise and Air Pollution during Pregnancy: Associated Factors and Correlation with Outdoor NO2 and Benzene Estimations

2015

This study aimed to describe the degree of annoyance among pregnant women in a Spanish cohort and to examine associations with proximity to traffic, NO2 and benzene exposure. We included 2457 participants from the Spanish Childhood and Environment study. Individual exposures to outdoor NO2 and benzene were estimated, temporally adjusted for pregnancy. Interviews about sociodemographic variables, noise and air pollution were carried out. Levels of annoyance were assessed using a scale from 0 (none) to 10 (strong and unbearable)

Determining exhaust fumes exposure in chainsaw operations

2016

Abstract The objective of this study was to investigate the inhalation exposure of forest operators to polycyclic aromatic hydrocarbons (PAHs) and BTEX (benzene, toluene, ethylbenzene and total xylenes) contained in the exhaust fumes released from chainsaws and to suggest possible countermeasures. The study was carried out in four silvicultural treatments (coppice clearcut, conifer thinning, conifer pruning, and sanitary cut), using three types of chainsaw fuel (normal two-stroke petrol mix and two alkylate fuels). Eighty personal air samples were collected; IOM samplers combined with Amberlite XAD-2 sorbent tubes were used for collecting PAHs and Radiello® samplers were used for BTEX. Resu…

Highly selective and sensitive chromo-fluorogenic detection of the Tetryl explosive using functional silica nanoparticles

2011

Silica nanoparticles containing polyamines and thiol groups have been used as probes for the selective detection of Tetryl. © 2011 The Royal Society of Chemistry.

1992

The synthesis of a new type of combined polymers containing both disc- and rod-like mesogens is reported. The polyesters, having a triphenylene derivative as a discotic mesogen in the side group and azobenzene or biphenyl derivatives as rod-like mesogens in the main chain were characterized by polarizing microscopy, differential scanning calorimetry, and X-ray scattering studies. The homopolymer 7 is highly crystalline, while the copolymer 8 is amorphous, both, however, do not form liquid-crystalline phases.

Manipulation of the ferroelectricity in LC polymers via photomechanical isomerization of azobenzene moieties

1996

We report the synthesis and characterization of a new ferroelectric liquid crystalline side chain copolymer containing photoisomerizable chromophores and non-photoisomerizable mesogenic units. On illumination with UV-light a suppression of the polar order is obtained as indicated by a substantial drop of the spontaneous polarization (Ps) compared to the dark state. We interpret this as the phase order being disrupted by the cis-isomer of the chromophore. After illumination with VIS-light only the major part of Ps is restored. The photochemical cis-trans back-isomerization (restoration of the phase) leads to a different stationary state than the dark state of the material. The thermal reisom…