Coupled atomistic spin-lattice simulations of ultrafast demagnetization in 3d ferromagnets.

Despite decades of research, the role of the lattice and its coupling to the magnetisation during ultrafast demagnetisation processes is still not fully understood. Here we report on studies of both explicit and implicit lattice effects on laser induced ultrafast demagnetisation of bcc Fe and fcc Co. We do this using atomistic spin- and lattice dynamics simulations following a heat-conserving three-temperature model. We show that this type of Langevin-based simulation is able to reproduce observed trends of the ultrafast magnetization dynamics of fcc Co and bcc Fe. The parameters used in our models are all obtained from electronic structure theory, with the exception of the lattice dynamics damping term, where a range of parameters were investigated. It was found that while the explicit spin-lattice coupling in the studied systems does not impact the demagnetisation process notably, the lattice damping has a large influence on the details of the magnetization dynamics. The dynamics of Fe and Co following the absorption of a femtosecond laser pulse are compared with previous results for Ni and similarities and differences in the materials' behavior are analysed. For all elements investigated so far with this model, we obtain a linear relationship between the value of the maximally demagnetized state and the fluence of the laser pulse , which is in agreement with experiments. Moreover, we demonstrate that the demagnetization amplitude is largest for Ni and smallest for Co. This holds over a wide range of the reported electron-phonon couplings, and this demagnetization trend is in agreement with recent experiments.

Validación del método de cuantificación del área corporal afectada por la psoriasis mediante lápiz óptico / Validation of an Optical Pencil Method to Estimate the Affected Body Surface Area in Psoriasis

INTRODUCCIÓN: La determinación de la superficie corporal afectada, Body Surface Area (BSA), es una de las escalas de medida más empleadas en la evaluación de la gravedad de la psoriasis, pero no está exenta de inconvenientes. OBJETIVO: Validación de un nuevo sistema de medida del BSA. MATERIAL Y MÉTODO: Estudio multicéntrico, prospectivo, que incluyó 56 pacientes con psoriasis. Cada paciente fue evaluado en 2 visitas por 2 dermatólogos del mismo Centro que valoraron BSA mediante 2 procedimientos: método visual «tradicional» (MT), palma mano=1%; y el método «lápiz óptico» (LO), lápiz capacitivo puntero sobre pantalla táctil con medición de la superficie mediante software específico. RESULTADOS: Se observó una concordancia aceptable entre ambos métodos, con coeficiente de correlación intraclase (CCI) de 0,87, pero con unos límites de acuerdo excesivamente grandes y un sesgo sistemático consistente en mayores medidas de BSA con MT que con LO. La concordancia entre métodos fue superior en el tronco y las extremidades inferiores (CCI > 0,8). La fiabilidad intraobservador fue excelente con ambos métodos (CCI: MT, 0,97; LO, 0,98). La fiabilidad interobservador fue elevada (CCI: MT, 0,91; LO, 0,94), pero el BSA medio difirió significativamente entre observadores. Además, el CCI se redujo drásticamente cuando se consideró la cabeza exclusivamente. CONCLUSIONES: El presente estudio valida el método LO para la medición de la superficie corporal afectada en pacientes con psoriasis. Muestra una buena concordancia con el MT, presentando menos variabilidad y mayor fiabilidad interobservador

INTRODUCTION: Body surface area (BSA) affected by psoriasis is one of the most often used measures for assessing severity, but this method has shortcomings. OBJECTIVE: To validate a new way to estimate BSA. MATERIAL AND METHOD: Prospective, multicenter study in 56 patients with psoriasis. Each patient was evaluated by 2 dermatologists in 2 visits to the same hospital. Each dermatologist used 2 methods for estimating BSA: the traditional visual estimation in which the area of the palm equals 1% of the total body surface and an optical pencil (OP) method in which the affected area is drawn on a touch screen. Software in the application then calculates the BSA. RESULTS: Overall concordance between the 2 methods was acceptable according to an intraclass correlation coefficient (ICC) of 0.87. However, the limits of agreement were unacceptably large and there was systematic bias: traditional estimates were consistently greater than OP calculations. Concordance between the methods was better (ICC > 0.8) on the trunk and lower extremities. Intraobserver reliability was excellent with both methods (ICCs, 0.97 and 0.98 for the traditional and OP estimates, respectively). Interobserver reliability was also high (ICCs, 0.91 and 0.94 for the traditional and OP methods), although the mean BSA differed significantly between observers. The ICCs were much lower for BSA estimates on the head. CONCLUSIONS: This study to validate the OP method for estimating the affected BSA in patients with psoriasis shows good agreement between the OP and traditional approaches. The OP calculations also showed less variance and better interobserver reliability

Validation of an Optical Pencil Method to Estimate the Affected Body Surface Area in Psoriasis. / Validación del método de cuantificación del área corporal afectada por la psoriasis mediante lápiz óptico.

INTRODUCTION: Body surface area (BSA) affected by psoriasis is one of the most often used measures for assessing severity, but this method has shortcomings. OBJECTIVE: To validate a new way to estimate BSA. MATERIAL AND METHOD: Prospective, multicenter study in 56 patients with psoriasis. Each patient was evaluated by 2 dermatologists in 2 visits to the same hospital. Each dermatologist used 2 methods for estimating BSA: the traditional visual estimation in which the area of the palm equals 1% of the total body surface and an optical pencil (OP) method in which the affected area is drawn on a touch screen. Software in the application then calculates the BSA. RESULTS: Overall concordance between the 2 methods was acceptable according to an intraclass correlation coefficient (ICC) of 0.87. However, the limits of agreement were unacceptably large and there was systematic bias: traditional estimates were consistently greater than OP calculations. Concordance between the methods was better (ICC>0.8) on the trunk and lower extremities. Intraobserver reliability was excellent with both methods (ICCs, 0.97 and 0.98 for the traditional and OP estimates, respectively). Interobserver reliability was also high (ICCs, 0.91 and 0.94 for the traditional and OP methods), although the mean BSA differed significantly between observers. The ICCs were much lower for BSA estimates on the head. CONCLUSIONS: This study to validate the OP method for estimating the affected BSA in patients with psoriasis shows good agreement between the OP and traditional approaches. The OP calculations also showed less variance and better interobserver reliability.

Multi-polaron solutions, nonlocal effects and internal modes in a nonlinear chain.

Multipolaron solutions were studied in the framework of the Holstein one-dimensional molecular crystal model. The study was performed in the continuous limit where the crystal model maps into the nonlinear Schrödinger equation for which a new periodic dnoidal solution was found for the multipolaron system. In addition, the stability of the multi-polaron solutions was examined, and it was found that cnoidal and dnoidal solutions stabilize in different ranges of the parameter space. Moreover, the model was studied under the influence of nonlocal effects and the polaronic dynamics was described in terms of internal solitonic modes.

A survey among dermatologists: diagnostics of superficial fungal infections - what is used and what is needed to initiate therapy and assess efficacy?

BACKGROUND: Superficial fungal infections are common. It is important to confirm the clinical diagnosis by mycological laboratory methods before initiating systemic antifungal treatment, especially as antifungal sensitivity and in vitro susceptibility may differ between different genera and species. For many years, the gold standard for diagnosis of superficial fungal infections has been direct fungal detection in the clinical specimen (microscopy) supplemented by culturing. Lately, newer molecular based methods for fungal identification have been developed. OBJECTIVE: This study was initiated to focus on the current usage of mycological diagnostics for superficial fungal infections by dermatologists. It was designed to investigate whether it was necessary to differentiate between initial diagnostic tests and those used at treatment follow-up in specific superficial fungal infections. METHODS: An online questionnaire was distributed among members of the EADV mycology Task Force and other dermatologists with a special interest in mycology and nail disease. RESULTS: The survey was distributed to 62 dermatologists of whom 38 (61%) completed the whole survey, 7 (11%) partially completed and 17 (27%) did not respond. Nearly, all respondents (82-100%) said that ideally they would use the result of direct microscopy (or histology) combined with a genus/species directed treatment of onychomycosis, dermatophytosis, Candida- and Malassezia-related infections. The majority of the dermatologists used a combination of clinical assessment and direct microscopy for treatment assessment and the viability of the fungus was considered more important at this visit than when initiating the treatment. Molecular based methods were not available for all responders. CONCLUSION: The available diagnostic methods are heterogeneous and their usage differs between different practices as well as between countries. The survey confirmed that dermatologists find it important to make a mycological diagnosis, particularly prior to starting oral antifungal treatment in order to confirm the diagnose and target the therapy according to genus and species.

Lesión tumoral de reciente aparición en paciente inmunodeprimido / New-Onset Mass in an Immunosuppressed Patient

No disponible

A two-population analysis of the magnetic dipolar interaction in superparamagnetic systems: a Monte Carlo study.

To understand the influence of the magnetic dipolar interaction on the blocking temperature (T(B)) of superparamagnetic systems, usual models treat the dipolar energy as an additional term to the single-particle anisotropy energy barrier. However, such approaches cannot describe non-monotonic T(B)(c) dependences as reported both experimental and theoretically. Therefore, alternative approaches should be explored. For such a purpose, in this work we investigate a simple approach based on splitting the total population of the system into two subgroups, depending on its relative orientation (parallel- or antiparallel-aligned) with respect to the applied magnetic field direction. The suitability of such approach was explored by means of a Monte Carlo technique that provided us with a good insight into the properties of the system. Our results indicate that this two-population analysis can be a promising way to understand the SPM behaviour of interacting nanomagnetic systems.

A first-principles study of the influence of helium atoms on the optical response of small silver clusters.

Optical excitation spectra of Ag(n) and Ag(n)@He(60) (n = 2, 8) clusters are investigated in the framework of the time-dependent density functional theory (TDDFT) within the linear response regime. We have performed the ab initio calculations for two different exact exchange functionals (GGA-exact and LDA-exact). The computed spectra of Ag(n)@He(60) clusters with the GGA-exact functional accounting for exchange-correlation effects are found to be generally in a relatively good agreement with the experiment. A strategy is proposed to obtain the ground-state structures of the Ag(n)@He(60) clusters and in the initial process of the geometry optimization, the He environment is simulated with buckyballs. A redshift of the silver clusters spectra is observed in the He environment with respect to the ones of bare silver clusters. This observation is discussed and explained in terms of a contraction of the Ag-He bonding length and a consequent confinement of the s valence electrons in silver clusters. Likewise, the Mie-Gans predictions combined with our TDDFT calculations also show that the dielectric effect produced by the He matrix is considerably less important in explaining the redshifting observed in the optical spectra of Ag(n)@He(60) clusters.

Density functional study of the magnetic properties of Bi4Mn clusters: discrepancy between theory and experiment.

We have performed collinear and noncollinear calculations on neutral Bi(4)Mn and collinear ones on ionized Bi(4)Mn with charges +1 and -1 to find out why theoretical calculations will not predict the magnetic state found in the experiment. We have used the density functional theory to find a fit between the theoretical prediction of the magnetic moment and the experimental value. Our calculations have consisted in a structural search of local energy minima, and the lowest energy magnetic state for each resulting isomer. The geometry optimization found three local minima whose fundamental state is the doublet spin state. These isomers could not be found in previous theoretical works, but they are higher in energy than the lowest-lying isomer by ≈1.75 eV. This magnetic state could help understand the experiment. Calculations of noncollinear magnetic states for the Bi(4)Mn do not lower the total magnetic moment. We conclude arguing how the three isomers with doublet state could actually be the ones measured in the experiment.

Magnetocaloric effect in magnetic nanoparticle systems: how to choose the best magnetic material?

Magnetic nanoparticles with controlled magnetocaloric properties are a good candidate to lower the temperature of nanosized systems: they are easy to manipulate and to distribute into different geometries, as wires or planes. Using a Monte Carlo technique we study the entropy change and refrigerant capacity of an assembly of fine magnetic particles as a function of their anisotropy and magnetization, key-parameters of the magnetic behavior of the system. We focus our attention on the anisotropy energy/dipolar energy ratio by means of the related parameter c0 = 2K/M(S)2, where K is the anisotropy constant and M(S) is the saturation magnetization of the nanoparticles. Making to vary the value of co parameter by choosing different K-M(S) combinations, allows us to discuss how the magnetocaloric response of an assembly of magnetic nanoparticles may be tuned by an appropriate choice of the magnetic material composition.

Density functional study of the oxidation of small neutral and charged silver clusters.

We have studied the energetic and structural stability of the interaction of molecular oxygen with small neutral, anionic and cationic silver clusters, Ag(n) (3 < or = n < or = < 8). The calculations have been carried out using a linear combination of atomic Gaussian-type orbitals within the density functional theory as it is implemented in the demon-ks3.5 code. The O2 molecule has been placed in different positions surrounding the cluster, in order to increase the configurational space of the structural minima. We have found that the oxidized cation and neutral clusters undergo a 2D-3D structural transition even before than the nonoxidized counterparts. Moreover, our results show that the adsorption energies on the cationic and neutral silver oxide clusters manifest an odd-even alternation pattern. Likewise, the average magnetic moment of the O2 radical in the charged and neutral silver environment tends to be greater than the charged and neutral bare diatomic oxygen molecule.

Role of the dipolar interaction on the macroscopic state of magnetic nanoparticle systems: a Monte Carlo study.

We have performed Monte Carlo simulations to treat the effect of the dipolar interaction in assemblies of superparamagnetic nanoparticles. Our simulations reproduce correctly the increase of the blocking temperature (T(B)) as the concentration increases, as observed experimentally. Interestingly, we have observed a progressive displacement of the M2 versus H/M isotherms (Arrott plots) from the origin as the concentration of nanoparticles increases. Moreover, the curvature of the isotherms at T > T(B) changes from positive to negative slope at high sample concentrations, resembling the shape of a first order phase transition. These results are surprisingly similar to that found in a conventional magnetic phase transition under the effect of a random anisotropy or a random field.

Small Au clusters oxidation: an ab initio study.

We have performed ab initio calculations in the Density Functional Theory framework on unsupported small gold clusters with size ranging from three to seven atoms. In our calculations we have introduced a single O2 molecule on different places around the cluster surface, and in both parallel and perpendicular position with respect to the cluster surface. We have found that the oxygen molecule bonds in-plane with the bidimensional Au cluster when the number of Au atoms is even, and it will be adsorbed off-plane if the number of Au atoms is odd. The latter case, despite not presenting a true chemical bonding, has great stability due to spin pairing and electrostatic interactions, and the structures will be distorted respect to the geometry of their pure Au cluster equivalents.

[Our experience with infliximab in reclacitrant cases of psoriasis]. / Nuestra experiencia con infliximab en psoriasis recalcitrante.

Present report is focused in our personal experience with the anti TNF-alpha infliximab. There is a short, four case series, but they are a very representative sample of the clinical conditions that we can solve with infliximab.

Nuestra experiencia con infliximab en psoriasis recalcitrante / Our experience with infliximab in reclacitrant cases of psoriasis

En el presente artículo, detallamos nuestra experiencia personal con el anticuerpo TNF-α (factor de necrosis tumoral alfa), infliximab. Se trata de cuatro casos que creemos que ilustran adecuadamente varias de las situaciones con las que nos podemos encontrar en el manejo de pacientes con psoriasis y algunos de los contextos clínicos en los que podemos recurrir a infliximab (AU)

Present report is focused in our personal experience with the anti TNF-α infliximab. There is a short, four case series, but they are a very representative sample of the clinical conditions that we can solve with infliximab (AU)

[Recurrent vulvovaginitis: diagnostic assessment and therapeutic management]. / Vulvovaginitis de repetición. Valoración diagnóstica y manejo terapéutico.

Recurrent vulvovaginitis is a common problem in clinical practice. Management is often complicated by a long history of inappropriate treatments based on tentative diagnoses after an incomplete diagnostic workup. We review the most common causes of recurrent vulvovaginitis; the appropriate steps with which to establish a diagnosis, from the medical history through to the additional tests needed; and, finally, the best therapeutic options. We will focus on infectious, irritant, allergic, and hormonal causes as the ones of most interest to the dermatologist. Given that infection is the most frequent cause of these processes and also a common reason for inopportune treatment, we will pay particular attention to infectious etiologies and their differential diagnosis.

[Chronic recurrent neutrophilic dermatosis: a possible variant in the spectrum of neutrophilic dermatoses]. / Dermatosis neutrofílica crónica recurrente: una posible variante en el espectro de las dermatosis neutrofílicas.

Neutrophilic dermatoses constitute a clinically heterogeneous group of diseases that share a common histological substrate, consisting of a dense dermal inflammatory infiltrate of mature polymorphonuclear neutrophils and no evidence of vasculitis. We describe the case of a 56-year-old man with a 6-month history of painful generalized erythematous edematous plaques. Histopathology indicated neutrophilic dermatosis but the patient did not have fever, elevated white blood cell count, or systemic involvement. Tests to rule out possible inflammatory, neoplastic, or infectious processes were negative. We consider the term chronic recurrent annular neutrophilic dermatosis, first used by Christensen et al, to be the most appropriate to define this variant with clinical findings that differ from classic Sweet syndrome.