Investigating the kinetics of the formation of a C Cottrell atmosphere around a screw dislocation in bcc iron: a mixed-lattice atomistic kinetic Monte-Carlo analysis.

We present a mixed-lattice atomistic kinetic Monte-Carlo algorithm (MLKMC) that integrates a rigid-lattice AKMC approach with the kinetic activation-relaxation technique (k-ART), an off-lattice/self-learning AKMC. This approach opens the door to study large and complex systems adapting the cost of identification and evaluation of transition states to the local environment. To demonstrate its capacity, MLKMC is applied to the problem of the formation of a C Cottrell atmosphere decorating a screw dislocation in α-Fe. For this system, transitions that occur near the dislocation core are searched by k-ART, while transitions occurring far from the dislocation are computed before the simulation starts using the rigid-lattice AKMC. This combination of the precision of k-ART and the speed of the rigid-lattice makes it possible to follow the onset of the C Cottrell atmosphere and to identify interesting mechanisms associated with its formation.

A single typical trichoscopic feature is predictive of tinea capitis: a prospective multicentre study.

BACKGROUND: Specific trichoscopic signs of tinea capitis (TC) were first described in 2008. The accuracy of this diagnostic tool has not been evaluated. OBJECTIVES: To assess the diagnostic accuracy of trichoscopy. METHODS: A prospective, multicentre study was done between March 2015 and March 2017 at the dermatology departments of four French university medical centres. Patients with a presumed diagnosis of TC were included. Trichoscopy was considered to be positive if at least one specific trichoscopic sign was observed. Trichoscopy results were compared with the gold standard for diagnosis of TC (mycological culture). RESULTS: One hundred patients were included. Culture was positive for 53 patients and negative for 47. The sensitivity of trichoscopy was 94% [95% confidence interval (CI) 88-100], specificity was 83% (95% CI 72-94), positive predictive value was 92% and negative predictive value was 86%. Comma hairs, corkscrew hairs, zigzag hairs, Morse-code-like hairs and whitish sheath were significantly more frequent in patients with a positive mycological culture (P < 0·001). Comma hairs were more frequent in patients with Trichophyton TC (P = 0·026), and zigzag hairs were more frequent in patients with Microsporum TC (P < 0·001). Morse-code-like hair was not observed in any patients with Trichophyton TC and therefore appears to be highly specific for Microsporum TC. CONCLUSIONS: The presence of a single trichoscopic finding is predictive of TC. Trichoscopy is a useful, rapid, painless, highly sensitive tool for the diagnosis of TC - even for dermoscopists with little experience of trichoscopy. It enhances physicians' ability to make treatment decisions. What's already known about this topic? Tinea capitis (TC) must be confirmed by a mycological culture that may take up to 6 weeks, delaying treatment. Specific trichoscopic signs of TC were first described in 2008, but the accuracy of trichoscopy for diagnosing TC has not previously been evaluated. What does this study add? The present series is the largest yet on the use of trichoscopy in the diagnosis of TC. Our results demonstrated that the presence of a single feature (comma hair, corkscrew hair, zigzag hair, Morse-code-like hair or whitish sheath) is predictive of TC. Trichoscopy is painless and highly sensitive. Morse-code-like hair appears to be highly specific for Microsporum TC.

A model of defect cluster creation in fragmented cascades in metals based on morphological analysis.

The impacts of ions and neutrons in metals cause cascades of atomic collisions that expand and shrink, leaving microstructure defect debris, i.e. interstitial or vacancy clusters or loops of different sizes. In De Backer et al (2016 Europhys. Lett. 115 26001), we described a method to detect the first morphological transition, i.e. the cascade fragmentation in subcascades, and a model of primary damage combining the binary collision approximation and molecular dynamics (MD). In this paper including W, Fe, Be, Zr and 20 other metals, we demonstrate that the fragmentation energy increases with the atomic number and decreases with the atomic density following a unique power law. Above the fragmentation energy, the cascade morphology can be characterized by the cross pair correlation functions of the multitype point pattern formed by the subcascades. We derive the numbers of pairs of subcascades and observed that they follow broken power laws. The energy where the power law breaks indicates the second morphological transition when cascades are formed by branches decorated by chaplets of small subcascades. The subcascade interaction is introduced in our model of primary damage by adding pairwise terms. Using statistics obtained on hundreds of MD cascades in Fe, we demonstrate that the interaction of subcascades increases the proportion of large clusters in the damage created by high energy cascades. Finally, we predict the primary damage of 500 keV Fe ion in Fe and obtain cluster size distributions when large statistics of MD cascades are not feasible.

Interaction between interstitial carbon atoms and a ½ 〈1 1 1〉 self-interstitial atoms loop in an iron matrix: a combined DFT, off lattice KMC and MD study.

A static and kinetic study of the interaction between a 19 ½ 〈1 1 1〉 self-interstitial atoms loop and C atoms in body-centred cubic iron is presented in this work. An empirical potential matching the density functional theory calculations is used to study the static properties of the system. The usual kinetic Monte-Carlo (KMC) on-lattice restriction is not valid when the material is highly distorted, especially in the presence of a dislocation loop. Therefore, the dynamics of the system are investigated using both molecular dynamics simulations and k-ART, a self-learning/off-lattice atomic kinetic monte-carlo. The presented work is thus a full study of the C-loop and the C2-loop systems. A good agreement is observed between the statics and the kinetics (e.g. the discovery of a zone of stability of the C atom around the Fe cluster where the C can almost freely move), even though the kinetics show some unexpected behaviours of the studied systems. The pinning time of the loop induced by the C atoms is also estimated.

An empirical potential for simulating vacancy clusters in tungsten.

We present an empirical interatomic potential for tungsten, particularly well suited for simulations of vacancy-type defects. We compare energies and structures of vacancy clusters generated with the empirical potential with an extensive new database of values computed using density functional theory, and show that the new potential predicts low-energy defect structures and formation energies with high accuracy. A significant difference to other popular embedded-atom empirical potentials for tungsten is the correct prediction of surface energies. Interstitial properties and short-range pairwise behaviour remain similar to the Ackford-Thetford potential on which it is based, making this potential well-suited to simulations of microstructural evolution following irradiation damage cascades. Using atomistic kinetic Monte Carlo simulations, we predict vacancy cluster dissociation in the range 1100-1300 K, the temperature range generally associated with stage IV recovery.

Extensive levamisole-induced vasculitis.

Levamisole (an increasingly frequent contaminant of cocaine) can cause antineutrophil cytoplasmic antibody-associated vasculitis. Dermatologists should consider a diagnosis of cocaine/levamisole-associated cutaneous vasculopathy syndrome in cases of purpura of the ears and/or extensive retiform purpura in drug users. We report a case of particularly severe levamisole-induced necrotic purpura and immunological abnormalities in a 40-year-old woman.

[Bacillus cereus endocarditis and a probable cutaneous gateway]. / Endocardite à Bacillus cereus avec probable porte d'entrée cutanée.

BACKGROUND: Bacillus cereus is a ubiquitous telluric organism. B. cereus endocarditis is a rare condition seen mostly in prosthetic heart valves and among intravenous drug users. We report a new case of a patient without risk factors and with a good clinical outcome not requiring valve replacement. CASE REPORT: In October 2014, a 50-year-old woman was referred to the dermatology department of Lille University Hospital for lower-limb wounds developing 6 months earlier. She presented fever without clinical signs of infection, except for the lower-limbs wounds. Blood cultures revealed the presence of B. cereus. Transesophageal echocardiography was performed and revealed two foci of aortic valve vegetation with a diameter of 5mm. After bacterial sensitivity testing, rifampicin and levofloxacin treatment was given for six weeks, with complete remission. A skin graft was performed and good improvement was seen. DISCUSSION: Nineteen cases of B. cereus endocarditis have been described previously, only one of which was without risk factors. We described a case of complete remission after a 6-week course of antibiotics. Our case demonstrates that BC should not be considered as a blood culture contamination, and that treatment may be complex due to antibiotic resistance.

Severe scurvy: an underestimated disease.

Scurvy is one of the oldest diseases in human history. Nowadays, although scurvy tends to become a forgotten disease in developed country, rare cases still occur, especially in people undergoing extreme diet, old people or children with poor diet and patients with malabsorption. We describe three cases of scurvy. The first case is a patient diagnosed with Crohn's disease, the second one is in a context of anorexia nervosa and drug addiction, and the third case is in a context of social isolation. Early recognition of scurvy can be difficult because symptoms may appear nonspecific and can mimic more common conditions. In any patient with spontaneous hematoma and purpura, in the context of nutritional disorder, scurvy should be systematically considered. As this disease can lead to severe complications, such as bone pain, heart failure or gastrointestinal symptoms, nothing should delay vitamin C supplementation, which is a simple and rapidly effective treatment.

[Massive panniculectomy and bilateral subtotal mastectomy in a case of calciphylaxis: A case report and up date]. / Dermolipectomie abdominale et mastectomie bilatérale subtotale dans le cadre d'une calciphylaxie: à propos d'un cas et mise au point.

Calciphylaxis or calcific arteriolopathy is a rare, life-threatening obstructive pathology of the small cutaneous and subcutaneous vessels. It mainly affects patients with chronic renal failure but it also has been described in patients with normal renal function. The principal risks factors apart from renal failure and phosphocalcic metabolism imbalance are: the female sex, obesity, peripheral vascular disease, diabetes and oral anti-coagulation. We present a very rare case of abdominal, mammarian and upper thighs calciphylaxis in a patient with normal renal function. She presented a severe obesity with a recent important loss of weight and had been treated by oral anticoagulants for a long time. She benefited of a multidisciplinary approach with dermatologists, plastic surgeons and anesthesists permitting a recovery in fourteen weeks. Multidisciplinary approach is necessary but the place of the surgery is not well defined. We report a case in which early and wide surgical approach permitted to obtain a favourable evolution of the pathology. Then, we propose a therapeutic strategy after review of the literature.

[Limbic encephalitis: a new paraneoplastic auto-immune manifestation associated with metastatic melanoma?]. / Encéphalite limbique : une nouvelle manifestation auto-immune paranéoplasique associée au mélanome métastatique ?

BACKGROUND: Several studies indicate an association between immune-related manifestations and prolonged survival in metastatic melanoma. Limbic encephalitis driven by immune-mediated disorders may also be observed during the course of certain cancers. PATIENTS AND METHODS: In November 2009, a 60-year-old woman followed up for metastatic melanoma since July 2005 developed rapidly progressive cognitive disorder. Clinical, biological, MRI and electroencephalogram abnormalities resulted in diagnosis of probably paraneoplastic limbic encephalitis in a context of immune-related manifestations although chemotoxicity could not be ruled out. Auto-immunity with hypothyroidism and thrombocytopenia were seen concomitantly. DISCUSSION: To the best of our knowledge, this is the first reported case of probably paraneoplastic limbic encephalitis associated with melanoma, a new example of an immune-related condition associated with prolonged survival in metastatic melanoma.

Atomistic modeling of carbon Cottrell atmospheres in bcc iron.

Atomistic simulations with an EAM interatomic potential were used to evaluate carbon-dislocation binding energies in bcc iron. These binding energies were then used to calculate the occupation probability of interstitial sites in the vicinity of an edge and a screw dislocation. The saturation concentration due to carbon-carbon interactions was also estimated by atomistic simulations in the dislocation core and taken as an upper limit for carbon concentration in a Cottrell atmosphere. We obtained a maximum concentration of 10 ± 1 at.% C at T = 0 K within a radius of 1 nm from the dislocation lines. The spatial carbon distributions around the line defects revealed that the Cottrell atmosphere associated with an edge dislocation is denser than that around a screw dislocation, in contrast with the predictions of the classical model of Cochardt and colleagues. Moreover, the present Cottrell atmosphere model is in reasonable quantitative accord with the three-dimensional atom probe data available in the literature.

Density functional calculations on structural materials for nuclear energy applications and functional materials for photovoltaic energy applications (abstract only).

Ab initio density functional theory calculations are carried out in order to predict the evolution of structural materials under aggressive working conditions such as cases with exposure to corrosion and irradiation, as well as to predict and investigate the properties of functional materials for photovoltaic energy applications. Structural metallic materials used in nuclear facilities are subjected to irradiation which induces the creation of large amounts of point defects. These defects interact with each other as well as with the different elements constituting the alloys, which leads to modifications of the microstructure and the mechanical properties. VASP (Vienna Ab initio Simulation Package) has been used to determine the properties of point defect clusters and also those of extended defects such as dislocations. The resulting quantities, such as interaction energies and migration energies, are used in larger scale simulation methods in order to build predictive tools. For photovoltaic energy applications, ab initio calculations are used in order to search for new semiconductors and possible element substitutions for existing ones in order to improve their efficiency.