Influence of the volume fraction on the electrokinetic properties of maghemite nanoparticles in suspension

Special issue in Honour of Pierre TURQInternational audienceWe used several complementary experimental and theoretical tools to characterise the charge properties of well-definedmaghemite nanoparticles in solution as a function of the volume fraction. The radius of the nanoparticles is equal to 6 nm.The structural charge was measured from chemical titration and was found high enough to expect some counterions tobe electrostatically attracted to the surface, decreasing the apparent charge of the nanoparticle. Direct-current conductivitymeasurements were interpreted by an analytical transport theory to deduce the value of this apparent charge, denoted here by‘dynamic effective charge’. This dynamic effective charge is found to decrease strongly with the volume fraction. In contrast,the ‘static’ effective charge, defined thanks to the Bjerrum criterion and computed from Monte Carlo simulations turns outto be almost independent of the volume fraction. In the range of Debye screening length and volume fraction investigatedhere, double layers around nanoparticles actually interact with each other. This strong interaction between nanocolloidalmaghemite particles is probably responsible for the experimental dependence of the electrokinetic properties with the volumefraction

Chemical characterization of inks in skin reactions to tattoo

Skin reactions are well described complications of tattooing, usually provoked by red inks. Chemical characterizations of these inks are usually based on limited subjects and techniques. This study aimed to determine the organic and inorganic composition of inks using X-ray fluorescence spectroscopy (XRF), X-ray absorption spectroscopy (XANES) and Raman spectroscopy, in a cohort of patients with cutaneous hypersensitivity reactions to tattoo. A retrospective multicenter study was performed, including 15 patients diagnosed with skin reactions to tattoos. Almost half of these patients developed skin reactions on black inks. XRF identified known allergenic metals - titanium, chromium, manganese, nickel and copper - in almost all cases. XANES spectroscopy distinguished zinc and iron present in ink from these elements in endogenous biomolecules. Raman spectroscopy showed the presence of both reported (azo pigments, quinacridone) and unreported (carbon black, phtalocyanine) putative organic sensitizer compounds, and also defined the phase in which Ti was engaged. To the best of the authors' knowledge, this paper reports the largest cohort of skin hypersensitivity reactions analyzed by multiple complementary techniques. With almost half the patients presenting skin reaction on black tattoo, the study suggests that black modern inks should also be considered to provoke skin reactions, probably because of the common association of carbon black with potential allergenic metals within these inks. Analysis of more skin reactions to tattoos is needed to identify the relevant chemical compounds and help render tattoo ink composition safer.Peer reviewe

Skyrmion Hall Effect Revealed by Direct Time-Resolved X-Ray Microscopy

Magnetic skyrmions are highly promising candidates for future spintronic applications such as skyrmion racetrack memories and logic devices. They exhibit exotic and complex dynamics governed by topology and are less influenced by defects, such as edge roughness, than conventionally used domain walls. In particular, their finite topological charge leads to a predicted "skyrmion Hall effect", in which current-driven skyrmions acquire a transverse velocity component analogous to charged particles in the conventional Hall effect. Here, we present nanoscale pump-probe imaging that for the first time reveals the real-time dynamics of skyrmions driven by current-induced spin orbit torque (SOT). We find that skyrmions move at a well-defined angle {\Theta}_{SH} that can exceed 30{\deg} with respect to the current flow, but in contrast to theoretical expectations, {\Theta}_{SH} increases linearly with velocity up to at least 100 m/s. We explain our observation based on internal mode excitations in combination with a field-like SOT, showing that one must go beyond the usual rigid skyrmion description to unravel the dynamics.Comment: pdf document arxiv_v1.1. 24 pages (incl. 9 figures and supplementary information

Genome-wide association and HLA fine-mapping studies identify risk loci and genetic pathways underlying allergic rhinitis

Allergic rhinitis is the most common clinical presentation of allergy, affecting 400 million people worldwide, with increasing incidence in westernized countries1,2. To elucidate the genetic architecture and understand the underlying disease mechanisms, we carried out a meta-analysis of allergic rhinitis in 59,762 cases and 152,358 controls of European ancestry and identified a total of 41 risk loci for allergic rhinitis, including 20 loci not previously associated with allergic rhinitis, which were confirmed in a replication phase of 60,720 cases and 618,527 controls. Functional annotation implicated genes involved in various immune pathways, and fine mapping of the HLA region suggested amino acid variants important for antigen binding. We further performed genome-wide association study (GWAS) analyses of allergic sensitization against inhalant allergens and nonallergic rhinitis, which suggested shared genetic mechanisms across rhinitis-related traits. Future studies of the identified loci and genes might identify novel targets for treatment and prevention of allergic rhinitis

A genetic variation map for chicken with 2.8 million single-nucleotide polymorphisms

We describe a genetic variation map for the chicken genome containing 2.8 million single-nucleotide polymorphisms ( SNPs). This map is based on a comparison of the sequences of three domestic chicken breeds ( a broiler, a layer and a Chinese silkie) with that of their wild ancestor, red jungle fowl. Subsequent experiments indicate that at least 90% of the variant sites are true SNPs, and at least 70% are common SNPs that segregate in many domestic breeds. Mean nucleotide diversity is about five SNPs per kilobase for almost every possible comparison between red jungle fowl and domestic lines, between two different domestic lines, and within domestic lines - in contrast to the notion that domestic animals are highly inbred relative to their wild ancestors. In fact, most of the SNPs originated before domestication, and there is little evidence of selective sweeps for adaptive alleles on length scales greater than 100 kilobases

Venus Observations at 40 and 90 GHz with CLASS

Using the Cosmology Large Angular Scale Surveyor, we measure the disk-averaged absolute Venus brightness temperature to be 432.3 $\pm$ 2.8 K and 355.6 $\pm$ 1.3 K in the Q and W frequency bands centered at 38.8 and 93.7 GHz, respectively. At both frequency bands, these are the most precise measurements to date. Furthermore, we observe no phase dependence of the measured temperature in either band. Our measurements are consistent with a CO$_2$-dominant atmospheric model that includes trace amounts of additional absorbers like SO$_2$ and H$_2$SO$_4$.Comment: 7 pages, 3 figures, published in PS