Fast-to-Alfv\'en mode conversion mediated by Hall current. II Application to the solar atmosphere

Coupling between fast magneto-acoustic and Alfv\'en waves can be observe in fully ionized plasmas mediated by stratification and 3D geometrical effects. In Paper I, Cally & Khomenko (2015) have shown that in a weakly ionized plasma, such as the solar photosphere and chromosphere, the Hall current introduces a new coupling mechanism. The present study extends the results from Paper I to the case of warm plasma. We report on numerical experiments where mode transformation is studied using quasi-realistic stratification in thermodynamic parameters resembling the solar atmosphere. This redresses the limitation of the cold plasma approximation assumed in Paper I, in particular allowing the complete process of coupling between fast and slow magneto-acoustic modes and subsequent coupling of the fast mode to the Alfv\'en mode through the Hall current. Our results confirm the efficacy of the mechanism proposed in Paper I for the solar case. We observe that the efficiency of the transformation is a sensitive function of the angle between the wave propagation direction and the magnetic field, and of the wave frequency. The efficiency increases when the field direction and the wave direction are aligned for increasing wave frequencies. After scaling our results to typical solar values, the maximum amplitude of the transformed Alfv\'en waves, for a frequency of 1 Hz, corresponds to an energy flux (measured above the height of peak Hall coupling) of $\sim10^3$ $\rm W\,m^{-2}$, based on an amplitude of 500 $\rm m\,s^{-1}$ at $\beta=1$, which is sufficient to play a major role in both quiet and active region coronal heating

MHDSTS: a new explicit numerical scheme for simulations of partially ionised solar plasma

The interaction of plasma with magnetic field in the partially ionised solar atmosphere is frequently modelled via a single-fluid approximation, which is valid for the case of a strongly coupled collisional media, such as solar photosphere and low chromosphere. Under the single-fluid formalism the main non-ideal effects are described by a series of extra terms in the generalised induction equation and in the energy conservation equation. These effects are: Ohmic diffusion, ambipolar diffusion, the Hall effect, and the Biermann battery effect. From the point of view of the numerical solution of the single-fluid equations, when ambipolar diffusion or Hall effects dominate can introduce severe restrictions on the integration time step and can compromise the stability of the numerical scheme. In this paper we introduce two numerical schemes to overcome those limitations. The first of them is known as Super Time-Stepping (STS) and it is designed to overcome the limitations imposed when the ambipolar diffusion term is dominant. The second scheme is called the Hall Diffusion Scheme (HDS) and it is used when the Hall term becomes dominant. These two numerical techniques can be used together by applying Strang operator splitting. This paper describes the implementation of the STS and HDS schemes in the single-fluid code Mancha3D. The validation for each of these schemes is provided by comparing the analytical solution with the numerical one for a suite of numerical tests

Candida dubliniensis, a new fungal pathogen

There is a high interest in Candida species other than Candida albicans because of the rise and the epidemiological shifts in candidiasis. These emerging Candida species are favored by the increase of immunocompromised patients and the use of new medical practices, and m. Most oropharyngeal candidiasis can be foundare observed in those HIV-infected patients infected with human immunodeficiency virus (HIV). Candida dubliniensis is a recently described opportunistic pathogen that is closely related to C. albicans but differs from it with respect to epidemiology, certain virulence characteristics, and the ability to develop fluconazole resistance in vitro. C. dubliniensis has been linked to oral candidiasis in AIDS patients, although it has recently been associated to invasive disease. C. dubliniensis shares diagnostic characteristics with C. albicans, as germ tube- and chlamydospore-production, and it is generally misclassified as C. albicans by standard diagnostic procedures. Several recent studies have attempted to elucidate useful phenotypic and genotypic characteristics for separating both species. A large variety of methods have been developed with the aim of facilitating rapid and, accurate identification of this species. These have included differential chromogenic isolation platesculture media, direct immunological tests, and enhanced manual and automated biochemical and enzymatic panels. Chromogenic isolation media, as CHROMagar Candida, demonstrate better detection rates than traditional media, and allow the presumptive identification of C. dubliniensis by means of colony color (dark-green colonies). API 20 C AUX system is considered a reference method, but ID 32 C strip, the VITEK Yeast Biochemical Card and the VITEK 2 ID-YST system correctly identify most C. dubliniensis isolates, being the latter the most accurate. Spectroscopic methods, such as Fourier transformed-infrared spectroscopy, offer potential advantages. However, many authors consider that standard methods for differentiation of Candida species are time-consuming, often insensitive and can fail to distinguish C. dubliniensis. To overcome these low sensitivity, poor specificity and intolerable delay,drawbacks, molecular tools have been developed to discriminate C. dubliniensis, and particularly those based on the polymerase chain reaction. But, molecular tools prove difficult and too complex for routine use in the clinical laboratory setting and new developments are necessary. Moreover, an increased resistance to antifungal drugs has been described. Although preliminary studies indicate that most strains of C. dubliniensis are susceptible to antifungal agents, fluconazole-resistant strains have been detected. Furthermore, fluconazole-resistant strains are easily derived in vitro, showing an increased expression of multidrug resistance transporters, as MDR1

Chronic Elevation of Liver Enzymes in Acute Intermittent Porphyria Initially Misdiagnosed as Autoimmune Hepatitis

Autoimmune hepatitis is a disease characterized by an elevation of liver enzymes, as well as specific autoantibodies. It is more common in women than men. We describe a 32-year-old woman with elevated transaminases, autoantibodies, and a liver biopsy result suggestive of autoimmune hepatitis. The indicated treatment was administered without showing a satisfactory response. The patient had a family history of acute intermittent porphyria (AIP) so we decided to begin treatment with hematin, achieving a complete remission of the symptoms. Acute intermittent porphyria is a rare condition characterized by neurovisceral symptoms, abdominal pain being the most common of them. The disease has a higher prevalence among young women and certain European countries such as Sweden, Great Britain, and Spain. A correct diagnosis and prompt treatment are essential because patients affected by AIP must have a strict followup due to the fatal outcome of the outbreaks

Kinematics of the ionized-to-neutral interfaces in Monoceros R2

Context. Monoceros R2 (Mon R2), at a distance of 830 pc, is the only ultra-compact H ii region (UC H ii) where its associated photon-dominated region (PDR) can be resolved with the Herschel Space Observatory. Aims. Our aim is to investigate observationally the kinematical patterns in the interface regions (i.e., the transition from atomic to molecular gas) associated with Mon R2. Methods. We used the HIFI instrument onboard Herschel to observe the line profiles of the reactive ions CH+, OH+ and H2O+ toward different positions in Mon R2. We derive the column density of these molecules and compare them with gas-phase chemistry models. Results. The reactive ion CH+ is detected both in emission (at central and red-shifted velocities) and in absorption (at blue-shifted velocities). OH+ is detected in absorption at both blue- and red-shifted velocities, with similar column densities. H2O+ is not detected at any of the positions, down to a rms of 40 mK toward the molecular peak. At this position, we find that the OH+ absorption originates in a mainly atomic medium, and therefore is associated with the most exposed layers of the PDR. These results are consistent with the predictions from photo-chemical models. The line profiles are consistent with the atomic gas being entrained in the ionized gas flow along the walls of the cavity of the H ii region. Based on this evidence, we are able to propose a new geometrical model for this region. Conclusions. The kinematical patterns of the OH+ and CH+ absorption indicate the existence of a layer of mainly atomic gas for which we have derived, for the first time, some physical parameters and its dynamics.Comment: 6 pages, 5 figures. Accepted for publication in A&

Pseudoartrosis de escafoides carpiano tratadas mediante la técnica de Matti-Russe: estudio retrospectivo de 36 casos

Presentamos un estudio retrospectivo de una serie de 36 pacientes con pseudoartrosis de escafoides operados mediante la técnica de Matti-Russe entre 1985 y 1991. Utilizamos injerto córtico esponjoso obtenido del radio (50%), cresta ilíaca (42%) y cúbito (8%) sin diferencias en la incorporación. La tasa de curación fue mayor en las pseudoartrosis medias y distales (80%) que en las de localización proximal (54%). El 80% de los fracasos de curación en la localización media y distal eran pseudoartrosis de más de 30 meses de evolución. Los cambios degenerativos en el carpo de las pseudoartrosis no curadas fueron significativamente mayores (p< 0,001) que en las que se obtuvo la consolidación. La localización y la antiguedad de la pseudoartrosis parecen ser dos importantes factores pronósticos. La técnica de Matti-Russe presenta limitaciones en la pseudoartrosis de localización proximal y en los carpos muy degenerados.We reported a retrospective study of 36 patients with a pseudoarthrosis of the carpal scaphoid bone treated by the Matti-Russe operation from 1985 to 1991. We used radial (50%), iliac (42%) or ulnar (8%) autogenous grafts without any difference in the rate of incorporation. The rate of healing of the pseudoarthrosis was higher in mid and distal location (80%) than in proximal location (54%). In 80% of cases, healing failures in the mid and distal location occurred in old pseudoarthrosis ( >3 0 months evolution). Carpal degenerative changes were significantly higher (p < 0,01) in patients with not healed pseudoarthrosis. The location and the age of the pseudoarthrosis appear to be important prognostic factors. The Matti-Russe technique has limitations when is performed either in proximal pseudoarthrosis or in the presence of advanced radiocarpal osteoarthritis

Relación entre la presencia de Malassezia Pachydermatis y los signos clínicos encontrados en cuadros de otitis crónicas caninas en una población de perros de raza Podenco canarios

El papel que desempeña Malassezia pachydermatis como factor perpetuante en las otitis externas caninas ha sido muy discutido. Dada la problemática que presentan las otitis en la clínica veterinaria, hemos intentado determinar la relación existente entre las manifestaciones clínicas de otitis externas crónicas caninas, y la presencia de esta levadura en los oídos de perros de raza Podenco canario. A los perros se les realizó una exploración física general, toma de muestras de ambos conductos auditivos externos, video otoscopia, y toma de biopsias de dichos conductos. Se realizó un contaje de M. pachydermatis por campo en cada una de las muestras a mil aumentos, y con objetivo de inmersión. Los resultados citológicos fueron comparados con los obtenidos de los cultivos en placa, los signos y lesiones encontrados en la exploración y con los hallados en las biopsias. Más de la mitad dé los perros estudiados padecían otitis crónica, siendo la forma eritematosa-ceruminosa la más comúnmente diagnosticada. Se aisló M. pachydermatis en el 54'28% de los conductos auditivos externos(CAE) con signos clínicos o lesiones. Como conclusión, comprobamos que el contaje por campos de esta levadura a mil aumentos en los frotis de las muestras, es un método bastante fiable para determinar el papel patógeno de M. pachydermatis en los cuadros de otitis crónicas caninas, y para decidir si instaurar o no un tratamiento antifúngica frente a las mismas a la espera de pruebas diagnósticas más concluyentes

Deuteration around the ultracompact HII region Mon R2

The massive star-forming region Mon R2 hosts the closest ultra-compact HII region that can be spatially resolved with current single-dish telescopes. We used the IRAM-30m telescope to carry out an unbiased spectral survey toward two important positions (namely IF and MP2), in order to studying the chemistry of deuterated molecules toward Mon R2. We found a rich chemistry of deuterated species at both positions, with detections of C2D, DCN, DNC, DCO+, D2CO, HDCO, NH2D, and N2D+ and their corresponding hydrogenated species and isotopologs. Our high spectral resolution observations allowed us to resolve three velocity components: the component at 10 km/s is detected at both positions and seems associated with the layer most exposed to the UV radiation from IRS 1; the component at 12 km/s is found toward the IF position and seems related to the molecular gas; finally, a component at 8.5 km/s is only detected toward the MP2 position, most likely related to a low-UV irradiated PDR. We derived the column density of all the species, and determined the deuterium fractions (Dfrac). The values of Dfrac are around 0.01 for all the observed species, except for HCO+ and N2H+ which have values 10 times lower. The values found in Mon R2 are well explained with pseudo-time-dependent gas-phase model in which deuteration occurs mainly via ion-molecule reactions with H2D+, CH2D+ and C2HD+. Finally, the [H13CN]/[HN13C] ratio is very high (~11) for the 10 km/s component, which also agree with our model predictions for an age of ~0.01-0.1 Myr. The deuterium chemistry is a good tool for studying star-forming regions. The low-mass star-forming regions seem well characterized with Dfrac(N2H+) or Dfrac(HCO+), but it is required a complete chemical modeling to date massive star-forming regions, because the higher gas temperature together with the rapid evolution of massive protostars.Comment: 14 pages of manuscript, 17 pages of apendix, 7 figures in the main text, accepted for publication in A&

Interplay of Surface Diffusion and Surface Tension in the Evolution of Solid/Liquid Interfaces : Dealloying of β-Brass in Aqueous Sodium Chloride

The dealloying of β-brass in 0.5 M aqueous NaCl was studied by electrochemical techniques at different temperatures in the range 278 K ≤ T ≤ 318 K, complemented with in situ scanning tunneling microscopy (STM) imaging. In the potential region where the electrodissolution of zinc and the formation of vacancies and copper islands take place, two different roughness regimes were distinguished. When dealloying involves only a few monolayers (ML) the process approaches a quasiuniform alloy electrodissolution, whereas after electrodissolution of more than 20 ML, void formation takes place. In both regimes the interface evolution was analyzed by applying the dynamic scaling method to in situ STM imaging data. The first roughness regime exhibits a stable interface consisting of copper-rich islands that coarsen with time according to a surface diffusion controlled process. The second roughness regime exhibits an unstable interface due to a curvature dependent corrosion rate enhancing zinc electrodissolution at cavities. The overall interface evolution is well-described by a differential stochastic equation containing an electrodissolution term and surface rearrangement terms related to surface diffusion and negative surface tension effect.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada