EVALUATION OF THE USE OF 1-NITROPYRENE,PYRENE, AND 1-HYDROXYPYRENE AS MARKERS OF DIESEL EXHAUST EXPOSURE IN UNDERGROUND MINING: RESULTS FROM THE BIOMODEM STUDY

The exposure to diesel exhaust was studied in underground mining of oil shale in Estonia. The purpose of this study was to evaluate different approaches to exposure assessment. Fifty men who drove diesel-powered excavators underground were compared with 50 surface workers who had no known occupational exposure to diesel exhaust. Samples of respirable air were analyzed for 1-nitropyrene and pyrene. Urine samples were collected at the start and after the first and the last shift of the same week, and were analyzed for 1-hydroxypyrene. Although ambient monitoring of 1-nitropyrene indicated a relatively high exposure of underground workers to diesel exhaust compared to surface workers (approximately 10-fold higher), only a small increase in the excretion of 1-hydroxypyerene was observed. Nonoccupational exposures such as smoking, recent consumption of grilled food, and recent proximity to an open fire had a greater impact on urinary excretion of 1-hydroxypyrene than occupational exposure to diesel exhaust.     

Modeling transdermal permeation. Part 2. Predicting the dermatopharmacokinetics of percutaneous solute

The prediction of percutaneous absorption and bioavailability in vivo, using the recently reported “bricks‐and‐mortar” model is discussed. Two sets of in vivo data have been simulated: the tape‐striping data of 4‐cyanophenol and Raman spectrometry data of transretinol. The predicted transdermal permeation using theoretically derived properties agreed well with the experimental data. The prediction shows that about 2/3 of the 4‐cynophenol in the SC partitioned into the corneocytes, indicating diffusion of moderately hydrophobic solutes across the corneocytes is also important. Only for highly hydrophobic solute like transretinol, diffusion across the corneocytes is negligibly small. The study demonstrates that with the mechanism‐based computer model, many dermatopharmacokinetic parameters can be derived, providing much insight into how vehicle formulation and topical administration affects the absorption and distribution of solute in the SC, as well as its bioavailability in epidermis/dermis. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

Microsecond time-resolved Fourier transform infrared analytics in a low pressure glow discharge reactor

A low pressure glow discharge reactor has been designed to allow time-resolved infrared spectroscopic investigation of the discharge zone in practical conditions. The benefits of such reactor are demonstrated through the study of the evolution in the infrared spectra of air/CO(2) gas mixture at the microsecond time-scale. It has been shown that the spectra are greatly affected by the electrical discharge in the 2400-2200?cm(-1) region, where the asymmetric stretch mode of CO(2) falls. The CO(2) molecules are excited through a collision with excited N(2) molecules, where the transfer of energy occurs by a resonant effect. The mechanisms involved are reversible and following plasma pulses.     

Probing the electronic properties of self-organized poly(3-dodecylthiophene) monolayers by two-dimensional scanning tunneling spectroscopy imaging at the single chain scale

Regioregular poly(3-dodecylthiophene) films self-organized on highly oriented pyrolytic graphite have been investigated by scanning tunneling microscopy and two-dimensional scanning tunneling spectroscopy (STS). Simulated spectra in very good agreement with the experimental data have been obtained by a method combining ab initio and semiempirical approaches, which allows a careful discussion of the polymer electronic states. From the experimental data, with the support of modeling, it is shown that the STS spectra give a direct access to the polymer semiconducting band gap without noticeable charge-transfer effects from the substrate. Spectroscopic images are achieved at the single chain scale, which allows scrutinizing the electronic consequences of chain folds and pi-stacking effects through spectroscopic contrasts. While chain folds do not locally increase the polymer band gap more than a few tens of millielectonvolt, a striking widening of the STS conductance gap is observed in the case of electronic tunneling through two interacting polymer layers. Scenarios based on nonplanar configuration of thiophene cycles within the second layer or variations of the charge screening effects are proposed to explain this phenomenon.     

Direct phase projection and transcranial focusing of ultrasound for brain therapy

Ultrasound can be used to noninvasively treat the human brain with hyperthermia by focusing through the skull. To obtain an accurate focus, especially at high frequencies (>500 kHz), the phase of the transmitted wave must be modified to correct the aberrations introduced by the patient's individual skull morphology. Currently, three-dimensional finite-difference time-domain simulations are used to model a point source at the target. The outward-propagating wave crosses the measured representation of the human skull and is recorded at the therapy array transducer locations. The signal is then time reversed and experimentally transmitted back to its origin. These simulations are resource intensive and add a significant delay to treatment planning. Ray propagation is computationally efficient because it neglects diffraction and only describes two propagation parameters: the wave's direction and the phase. We propose a minimal method that is based only on the phase. The phase information is projected from the external skull surface to the array locations. This replaces computationally expensive finite-difference computations with an almost instantaneous direct phase projection calculation. For the five human skull samples considered, the phase distribution outside of the skull is shown to vary by less than λ/20 as it propagates over a 5 cm distance and the validity of phase projection is established over these propagation distances. The phase aberration introduced by the skull is characterized and is shown to have a good correspondence with skull morphology. The shape of this aberration is shown to have little variation with propagation distance. The focusing quality with the proposed phase-projection algorithm is shown to be indistinguishable from the gold-standard full finite-difference simulation. In conclusion, a spherical wave that is aberrated by the skull has a phase propagation that can be accurately described as radial, even after it has been distorted. By combining finite-difference simulations with a phase-projection algorithm, the time required for treatment planning is significantly reduced. The correlation length of the phase is used to validate the algorithm and it can also be used to provide guiding parameters for clinical array transducer design in terms of transducer spacing and phase error.     

Stratified jet flames in a heated (1390 K) air cross-flow with autoignition

Measurements are reported of the heat release profiles, the flame lengths, flame structure and other properties of a reacting jet-in-cross-flow (JICF) for two fuels. The air was heated to a static temperature of 1390 K, which is above the autoignition temperature, and the air velocity was 468 m/s, which is much larger than values that were considered previously. Aerodynamic strain rates are so large that the flame was expected to fall into either the “distributed reaction”, “thickened flamelet”, or “shredded flamelet” regimes. Fluorescence images of CH, OH and formaldehyde identified the flame structure. The jet-in-cross-flow is a unit physics problem that occurs in turbojets and scramjets. While scaling relations are known for the non-reacting case, more information about the reacting case is needed, especially when autoignition and strain rates become important. Three regions were identified. In the liftoff region autoignition reactions occur which create a strong formaldehyde PLIF signal. However, flames and heat release do not occur in the liftoff region since CH and CH¹ signals were negligible. The second region is the lifted flame base, which has the character of a premixed flame, as evidenced by a very rapid rise in the heat release rate as indicated by the CH¹ and OH¹ signals. The third region contains a turbulent non-premixed flame and the CH images indicate the presence of thickened and shredded flamelets. The 2–3 mm thickness of each CH layer is more than 10 times the laminar flamelet thickness. In the third region the heat release rate decays slowly downstream, which is typical of a non-premixed flame. Because both upstream autoignition and downstream thickened flamelets were observed, we classify this combustion to be an “autoignition-assisted flame”. Flame lengths increase linearly with fuel mass flow rate, indicating that mixing is controlled by the air velocity rather than the fuel velocity.     

Synergetic Use of Principal Component Analysis Applied to Normed Physicochemical Measurements and GC × GC‐MS to Reveal the Stabilization Effect of Selected Essential Oils on Heated Rapeseed Oil

Lipid oxidation leads to the formation of volatile compounds and very often to off‐flavors. In the case of the heating of rapeseed oil, unpleasant odors, characterized as a fishy odor, are emitted. In this study, 2 different essential oils (coriander and nutmeg essential oils) were added to refined rapeseed oil as odor masking agents. The aim of this work was to determine a potential antioxidant effect of these essential oils on the thermal stability of rapeseed oil subject to heating cycles between room temperature and 180 °C. For this purpose, normed determinations of different parameters (peroxide value, anisidine value, and the content of total polar compounds, free fatty acids and tocopherols) were carried out to examine the differences between pure and degraded oil. No significant difference was observed between pure rapeseed oil and rapeseed oil with essential oils for each parameter separately. However, a stabilizing effect of the essential oils, with a higher effect for the nutmeg essential oil was highlighted by principal component analysis applied on physicochemical dataset. Moreover, the analysis of the volatile compounds performed by GC × GC showed a substantial loss of the volatile compounds of the essential oils from the first heating cycle.     

Cartographie distribuée du cœur de l’Internet

The study of the Internet topology allows us to discover properties that can be beneficial to the performances of network protocols and applications. Thus, Internet mapping is very useful to simulation software focusing on network protocols. Unfortunately Internet mapping has two major drawbacks. First it takes a lot of time to be carried out and second it is often incomplete. To solve these two problems, we have developed a fast mapping software whose aim is to map the heart of the Internet as fast as possible with the highest attainable precision. In this paper, we describe our software and evaluate its performances compared to an existing and freely available mapping software. We assess the completeness of the router level maps by creating overlays with an autonomous system topology. We also assess its use inIpv6 and the evolution of its performances inIpv4 when increasing the size of the input parameter set. We conclude with a detailed study on the delay of the paths and links in the Internet.