333 research outputs found
Extended skyrmion lattice scattering and long-time memory in the chiral magnet FeCoSi
Small angle neutron scattering measurements on a bulk single crystal of the
doped chiral magnet FeCoSi with =0.3 reveal a pronounced effect
of the magnetic history and cooling rates on the magnetic phase diagram. The
extracted phase diagrams are qualitatively different for zero and field cooling
and reveal a metastable skyrmion lattice phase outside the A-phase for the
latter case. These thermodynamically metastable skyrmion lattice correlations
coexist with the conical phase and can be enhanced by increasing the cooling
rate. They appear in a wide region of the phase diagram at temperatures below
the -phase but also at fields considerably smaller or higher than the fields
required to stabilize the A-phase
Contribution of toxicological analysis to the care of dimethyl fumarate dermatitis
Background:
Dimethyl fumarate (DMFu) is a fungicide which is used in Chinese manufactures of furniture and shoes to avoid mould spoiling of fabrics. In 2008, DMFu was found the responsible allergen for several cases of contact dermatitis from armchairs and shoes observed in Europe. In France a national toxicovigilance survey was set up and importation of products containing dimethyl fumarate is now forbidden. Case report: a 36 year-old woman, with no history of previous allergy, was hospitalized because of a severe acute eczema of her feet after wearing a new pair of boots inside which she had noticed desiccant sachets. She strongly reacted on patch testing to DMFu and to the content of a sachet which was identified as DMFu, both at 0.01%, 0.1%, 1% in petrolatum, and also to a piece of the fabric of her boots, patch tested as is.
Materials and method:
Boot fabrics and mould-proof sachets found in the boots were analysed by HPLC/UV/DAD and GC/MS after methanol extraction. Further samples of anti mould agent sachets or shoe fabrics from 5 other patients with suspicion of DMFu dermatitis were analysed with the same procedure. Some of them were transferred to the laboratory several months after healing of the dermatitis.
Results:
DMFu was found in all the samples from 1 to 100% in sachets or from 20 to 2000 μg/g in the fabrics of shoes, even after one year. These findings contributed to ensure the responsibility of DMFu in the dermatitis of the patients and demonstrate that DMFu may remain a long time in the contaminated fabrics after removal of the sachets. This study also points out the usefulness of the collaboration between dermatologists, biologists and poison centre practitioners
Universality of the helimagnetic transition in cubic chiral magnets: Small angle neutron scattering and neutron spin echo spectroscopy studies of FeCoSi
We present a comprehensive Small Angle Neutron Scattering (SANS) and Neutron
Spin Echo Spectroscopy (NSE) study of the structural and dynamical aspects of
the helimagnetic transition in FeCoSi with = 0.30. In contrast
to the sharp transition observed in the archetype chiral magnet MnSi, the
transition in FeCoSi is gradual and long-range helimagnetic
ordering coexists with short-range correlations over a wide temperature range.
The dynamics are more complex than in MnSi and involve long relaxation times
with a stretched exponential relaxation which persists even under magnetic
field. These results in conjunction with an analysis of the hierarchy of the
relevant length scales show that the helimagnetic transition in
FeCoSi differs substantially from the transition in MnSi and
question the validity of a universal approach to the helimagnetic transition in
chiral magnets
The magnitude of nephron number reduction mediates intrauterine growth-restriction-induced long term chronic renal disease in the rat. A comparative study in two experimental models.
Intrauterine growth restriction (IUGR) is a risk factor for hypertension (HT) and chronic renal disease (CRD). A reduction in the nephron number is proposed to be the underlying mechanism; however, the mechanism is debated. The aim of this study was to demonstrate that IUGR-induced HT and CRD are linked to the magnitude of nephron number reduction, independently on its cause.
Systolic blood pressure (SBP), glomerular filtration rate (GFR), proteinuria, nephron number, and glomerular sclerosis were compared between IUGR offspring prenatally exposed to a maternal low-protein diet (9% casein; LPD offspring) or maternal administration of betamethasone (from E17 to E19; BET offspring) and offspring with a normal birth weight (NBW offspring).
Both prenatal interventions led to IUGR and a similar reduction in birth weight. In comparison to NBW offspring, BET offspring had a severe nephron deficit (-50% in males and -40% in females, p < 0.01), an impaired GFR (-33%, p < 0.05), and HT (SBP+ 17 mmHg, p < 0.05). Glomerular sclerosis was more than twofold higher in BET offspring than in NBW offspring (p < 0.05). Long-term SBP, GFR, and glomerular sclerosis were unchanged in LPD offspring while the nephron number was moderately reduced only in males (-28% vs. NBW offspring, p < 0.05).
In this study, the magnitude of nephron number reduction influences long term renal disease in IUGR offspring: a moderate nephron number is an insufficient factor. Extremely long-term follow-up of adults prenatally exposed to glucocorticoids are required
Intoxications aiguës par le pentobarbital: un vieux produit toujours d'actualité
National audienc
Effective dynamics using conditional expectations
The question of coarse-graining is ubiquitous in molecular dynamics. In this
article, we are interested in deriving effective properties for the dynamics of
a coarse-grained variable , where describes the configuration of
the system in a high-dimensional space , and is a smooth function
with value in (typically a reaction coordinate). It is well known that,
given a Boltzmann-Gibbs distribution on , the equilibrium
properties on are completely determined by the free energy. On the
other hand, the question of the effective dynamics on is much more
difficult to address. Starting from an overdamped Langevin equation on , we propose an effective dynamics for using conditional
expectations. Using entropy methods, we give sufficient conditions for the time
marginals of the effective dynamics to be close to the original ones. We check
numerically on some toy examples that these sufficient conditions yield an
effective dynamics which accurately reproduces the residence times in the
potential energy wells. We also discuss the accuracy of the effective dynamics
in a pathwise sense, and the relevance of the free energy to build a
coarse-grained dynamics
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