Magnetic domain structure and dynamics in interacting ferromagnetic stacks with perpendicular anisotropy

The time and field dependence of the magnetic domain structure at magnetization reversal were investigated by Kerr microscopy in interacting ferromagnetic Co/Pt multilayers with perpendicular anisotropy. Large local inhomogeneous magnetostatic fields favor mirroring domain structures and domain decoration by rings of opposite magnetization. The long range nature of these magnetostatic interactions gives rise to ultra-slow dynamics even in zero applied field, i.e. it affects the long time domain stability. Due to this additionnal interaction field, the magnetization reversal under short magnetic field pulses differs markedly from the well-known slow dynamic behavior. Namely, in high field, the magnetization of the coupled harder layer has been observed to reverse more rapidly by domain wall motion than the softer layer alone.Comment: 42 pages including 17 figures. submitted to JA

Development of RT-semi-nested PCR for detection of hepatitis A virus in stool in epidemic conditions.

The purpose of this study was to determine the efficiency of semi-nested PCR in detecting hepatitis A virus (HAV) RNA. During a 2-year period (1990-1991), HAV RNA was searched for in shellfish from the French Brittany coasts using cRNA and vRNA probes. In January 1992, at the time of a hepatitis A outbreak, 28 stool samples were collected from infected patients (18 adults, 10 children) with anti-HAV IgM. Four samples from subjects with negative HAV serology were used as negative controls. Nucleic acid amplification (reverse-transcription-semi-nested PCR) was performed to detect HAV in stool. HAV RNA was purified by phenol-chloroform extraction and converted to cDNA using reverse transcriptase (Mu-MLV). After amplification, PCR products were visualized on an ethidium-bromide-stained gel and confirmed by hybridization with a specific digoxigenin-labelled oligoprobe. Samples were also studied by molecular hybridization with cRNA and vRNA probes. After onset of the illness, HAV RNA was detected over a longer time period by semi-nested PCR (16/28) than by hybridization (0/28). Even though biological diagnosis of hepatitis A will continue to rely on the detection of anti-HAV IgM, PCR should be useful in certain clinical cases (diagnosis of relapse) and for epidemiological and environmental monitoring of viruses

Highly asymmetric magnetic domain wall propagation due to coupling to a periodic pinning potential

Magneto-optical microscopy and magnetometry have been used to study 19 magnetization reversal in an ultrathin magnetically soft [Pt/Co]2 ferromagnetic film 20 coupled to an array of magnetically harder [Co/Pt]4 nanodots via a predominantly 21 dipolar interaction across a 3 nm Pt spacer. This interaction generates a spatially 22 periodic pinning potential for domain walls propagating through the continuous 23 magnetic film. When reversing the applied field with respect to the static nanodot 24 array magnetization orientation, strong asymmetries in the wall velocity and switching 25 fields are observed. Asymmetric switching fields mean that the hysteresis of the film is 26 characterized by a large bias field of dipolar origin which is linked to the wall velocity 27 asymmetry. This latter asymmetry, though large at low fields, vanishes at high fields 28 where the domains become round and compact. A field-polarity-controlled transition 29 from dendritic to compact faceted domain structures is also seen at low field and a 30 model is proposed to interpret the transition

Understanding the Effect of the Adatoms in the Formic Acid Oxidation Mechanism on Pt(111) Electrodes

The engineered search for new catalysts requires a deep knowledge about reaction mechanisms. Here, with the support of a combination of computational and experimental results, the oxidation mechanism of formic acid on Pt(111) electrodes modified by adatoms of the p block is elucidated for the first time. DFT calculations reveal that some adatoms, such as Bi and Pb, have positive partial charge when they are adsorbed on the bare surface, whereas others, such as Se and S, remain virtually neutral. When the partial charge is correlated with previously reported experimental results for the formic acid oxidation reaction, it is found that the partial positive charge is directly related to the increase in catalytic activity of the modified surface. Further, it is obtained that such a positive partial charge is directly proportional to the electronegativity difference between the adatom and Pt. Thus, the electronegativity difference can be used as an effective descriptor for the expected electrocatalytic activity. This partial positive charge on the adatom drives the formic acid oxidation reaction, since it favors the formation and adsorption of formate on the adatom. Once adsorbed, the neighboring platinum atoms assist in the C–H bond cleavage. Finally, it is found that most of the steps involved in the proposed oxidation mechanism are barrierless, which implies a significant diminution of the activation barriers in comparison to that of the unmodified Pt(111) electrode. This diminution in the activation barrier has been experimentally corroborated for the Bi–Pt(111) electrode, supporting the proposed mechanism.This work has been financially supported by the MINECO (Spain) (project CTQ2013-44083-P) and Generalitat Valenciana (project PROMETEOII/2014/013)

A spontaneous gravity prior: newborn chicks prefer stimuli that move against gravity

To investigate whether upward movement is attractive already at birth, before any previosu visual experience, we tested the early preferences of dark-hatched chicks (Gallus gallus) for upward vs downward moving visual stimuli. The results are published in Bliss et al. 2023, Biology Letters “A spontaneous gravity prior: Newborn chicks prefer stimuli that move against gravity" This entry contains experimental data (output from DeepLabCut tracking, python pre-processed data, summary .csv files of results) and data analysis scripts used in the publication. A readme file is also provided

P18-01. Exquisite specificity of CTL response to the M184V mutation

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Direct sequencing of hepatitis A virus strains isolated during an epidemic in France

Direct sequencing of PCR products was used to study the VP1 region of the hepatitis A virus (HAV) genome (position 2199 to 2356) of nine strains isolated from human stools collected during a hepatitis A epidemic (western France, 1992), three strains from environmental samples (1990, 1991, and 1992), and two HAV cell culture isolates (the French strain CF53/Lyon and strain CLF). These viruses differed from CF53/Lyon (genotype I) by between 1 and 10.3%, and results indicated the existence of two groups of strains belonging to two different subgenotypes (IA and IB). With this sequencing technique it was possible to monitor the epidemiology of HAV and study its relations

An Aza-Fused pi-Conjugated Microporous Framework Catalyzes the Production of Hydrogen Peroxide

"This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Catalysis, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://pubs.acs.org/page/policy/articlesonrequest/index.html"[EN] In order to produce hydrogen peroxide in small-scale electrochemical plants, selective catalysts for the oxygen reduction reaction (ORR) toward the desired species are required. Here, we report about the synthesis, characterization, ORR electrochemical behavior, and reaction mechanism of an aza-fused pi-conjugated microporous polymer, which presents high selectivity toward hydrogen peroxide. It was synthesized by polycondensation of 1,2,4,5-benzenetetramine tetrahydrochloride and triquinoyl octahydrate. A cobalt-modified version of the material was also prepared by a simple postsynthesis treatment with a Co(II) salt. The characterization of the material is consistent with the formation of a conductive robust porous covalent laminar polyaza structure. The ORR properties of these catalysts were investigated using rotating disk and rotating disk ring arrangements. The results indicate that hydrogen peroxide is almost exclusively produced at very low overpotentials on these materials. Density functional theory calculations provide key elements to understand the reaction mechanism. It is found that, at the relevant potential for the reaction, half of the nitrogen atoms of the material would be hydrogenated. This hydrogenation process would destabilize some carbon atoms in the lattice and would provide segregated charge. On the destabilized carbon atoms, molecular oxygen would be chemisorbed with the aid of charge transferred from the hydrogenated nitrogen atoms and solvation effects. Due to the low destabilization of the carbon sites, the resulting molecular oxygen chemisorbed state, which would have the characteristics of a superoxide species, would be only slightly stable, promoting the formation of hydrogen peroxide.This work has been financially supported by the MCINN-FEDER (projects CTQ2016-76221-P, MAT2013-46753-C2-1-P, and MAT2014-52305-P) and Generalitat Valenciana (project PROMETEO/2014/013).Briega-Martos, V.; Ferre Vilaplana, A.; De La Peña, A.; Segura, J.; Zamora, F.; Feliu, J.; Herrero, E. (2017). An Aza-Fused pi-Conjugated Microporous Framework Catalyzes the Production of Hydrogen Peroxide. ACS Catalysis. 7(2):1015-1024. https://doi.org/10.1021/acscatal.6b03043S101510247

Physical activity and sedentary behavior from 6 to 11 years

OBJECTIVES: Physical activity (PA) is presumed to decline during childhood and adolescence, but only few long-term studies about PA development during this period of life exist. We assessed PA and sedentary behavior (SB) over a 5-year period to gain a better understanding of the extent of change in activity and potential influencing factors. METHODS: PA and SB of 600 children from the Childhood Obesity Project were objectively measured with the SenseWear Armband 2 at the ages of 6, 8, and 11 years, resulting in 1254 observations. Longitudinal changes of total PA, moderate-to-vigorous physical activity (MVPA), light physical activity (LPA), and SB were modeled with mixed-effects models. RESULTS: Total PA revealed a significant quadratic decline with age (P < .001), resulting in a change of total PA by -75.3 minutes per day from 6 to 11 years. LPA linearly declined (P < .001) by 44.6 minutes per day, MVPA quadratically declined (P < .001) by an overall 30.7 minutes, whereas SB increased significantly (+107 minutes; P = .001). Boys showed a steeper decline in LPA (P = .003) and MVPA (P < .001) than did girls. Higher fat mass index and BMI z scores were associated with lower levels of total PA and MVPA and higher levels of SB (all P < .001). CONCLUSIONS: We showed that PA decreased, and SB increased in earlier years than previously thought. MVPA remained relatively stable until 8 years, but revealed a drop-off at 11 years, identifying this period as a crucial time for intervention