Chemical Compounds Responsible for Skin Allergy to Complex Mixtures: How to Identify Them?

International audienceIn the cosmetics industry, various natural complex mixtures such as botanical extracts or essential oils are used. In addition to that, finished consumer products may contain a number of constituents of natural origin but many products derived from organic synthesis too. Hence, finding skin sensitizers within this myriad of chemicals is an arduous task. Nowadays, methods validated by European dedicated instances to evaluate the allergenicity of chemicals are incapable to predict the sensitization potential of complex mixtures, even if research has progressed a lot in this direction recently. Accordingly and in this context, to identify precisely the culprit(s) responsible for skin sensitization to the mixtures is essential for risk assessment. This review is a short summary of approaches that allow identifying allergens in chemical mixtures such as bioassay-guided chemical fractionation, structure-activity relationships studies and recent methods allowing identification of reactive intermediates in natural extracts exposed to air oxidation. It is shown that a big progress has been accomplished, even if the identification of sensitizers in complex mixtures continues to be puzzling

Next-to-leading order renormalization of the ΔB=2\Delta B=2 operators in the static theory

The renormalization, at the next-to-leading order in $\alpha_s$, of the $\Delta B=2$ operators at the lowest order in the heavy quark expansion, namely in the static theory, is computed taking into account previously missed contributions. These operators are relevant for the calculation of the $B^0$--$\bar B^0$ mixing on the lattice.Comment: Latex, 8 pages, 1 figur

Association of radio polar cap brightening with bright patches and coronal holes

Radio-bright regions near the solar poles are frequently observed in Nobeyama Radioheliograph (NoRH) maps at 17 GHz, and often in association with coronal holes. However, the origin of these polar brightening has not been established yet. We propose that small magnetic loops are the source of these bright patches, and present modeling results that reproduce the main observational characteristics of the polar brightening within coronal holes at 17 GHz. The simulations were carried out by calculating the radio emission of the small loops, with several temperature and density profiles, within a 2D coronal hole atmospheric model. If located at high latitudes, the size of the simulated bright patches are much smaller than the beam size and they present the instrument beam size when observed. The larger bright patches can be generated by a great number of small magnetic loops unresolved by the NoRH beam. Loop models that reproduce bright patches contain denser and hotter plasma near the upper chromosphere and lower corona. On the other hand, loops with increased plasma density and temperature only in the corona do not contribute to the emission at 17 GHz. This could explain the absence of a one-to-one association between the 17 GHz bright patches and those observed in extreme ultraviolet. Moreover, the emission arising from small magnetic loops located close to the limb may merge with the usual limb brightening profile, increasing its brightness temperature and width.Comment: 8 pages, 6 figures, 1 table. Accepted for publication in The Astrophysical Journa

On the Relationship between Violent Conflict and Wages in Colombia

We analyse how forced displacements caused by violent conflict are related to the wages of workers in Colombia. Using data from the Quality of Life Survey (2011–2014), we analyse the differences in wages between those forced by violence to move to other regions, and those who moved for other reasons. We apply Propensity Score Matching techniques to compare workers from the two groups, finding that forced displacement is related to decreases of between 10 and 29 per cent in the wages of males, and between 18 and 37 per cent in the wages of females, relative to their counterparts. Thus, forced displacements are related to poorer labour market outcomes in terms of wages

Depth of interaction and bias voltage depenence of the spectral response in a pixellated CdTe detector operating in time-over-threshold mode subjected to monochromatic X-rays

High stopping power is one of the most important figures of merit for X-ray detectors. CdTe is a promising material but suffers from: material defects, non-ideal charge transport and long range X-ray fluorescence. Those factors reduce the image quality and deteriorate spectral information. In this project we used a monochromatic pencil beam collimated through a 20μm pinhole to measure the detector spectral response in dependance on the depth of interaction. The sensor was a 1mm thick CdTe detector with a pixel pitch of 110μm, bump bonded to a Timepix readout chip operating in Time-Over-Threshold mode. The measurements were carried out at the Extreme Conditions beamline I15 of the Diamond Light Source. The beam was entering the sensor at an angle of \texttildelow20 degrees to the surface and then passed through \texttildelow25 pixels before leaving through the bottom of the sensor. The photon energy was tuned to 77keV giving a variation in the beam intensity of about three orders of magnitude along the beam path. Spectra in Time-over-Threshold (ToT) mode were recorded showing each individual interaction. The bias voltage was varied between -30V and -300V to investigate how the electric field affected the spectral information. For this setup it is worth noticing the large impact of fluorescence. At -300V the photo peak and escape peak are of similar height. For high bias voltages the spectra remains clear throughout the whole depth but for lower voltages as -50V, only the bottom part of the sensor carries spectral information. This is an effect of the low hole mobility and the longer range the electrons have to travel in a low field

The Mass of the Convective Zone in FGK Main Sequence Stars and the Effect of Accreted Planetary Material on Apparent Metallicity Determinations

The mass of the outer convective zone in FGK main sequence stars decreases dramatically with stellar mass. Therefore, any contamination of a star's atmosphere by accreted planetary material should affect hotter stars much more than cool stars. If recent suggestions that high metal abundances in stars with planets are caused by planetesimal accretion are correct, then metallicity enhancements in earlier-type stars with planets should be very pronounced. No such trend is seen, however.Comment: Submitted ApJ Letters March 26th; accepted April 30th. 12 pages, 2 figure