Magnetic properties and domain structure of (Ga,Mn)As films with perpendicular anisotropy

The ferromagnetism of a thin GaMnAs layer with a perpendicular easy anisotropy axis is investigated by means of several techniques, that yield a consistent set of data on the magnetic properties and the domain structure of this diluted ferromagnetic semiconductor. The magnetic layer was grown under tensile strain on a relaxed GaInAs buffer layer using a procedure that limits the density of threading dislocations. Magnetometry, magneto-transport and polar magneto-optical Kerr effect (PMOKE) measurements reveal the high quality of this layer, in particular through its high Curie temperature (130 K) and well-defined magnetic anisotropy. We show that magnetization reversal is initiated from a limited number of nucleation centers and develops by easy domain wall propagation. Furthermore, MOKE microscopy allowed us to characterize in detail the magnetic domain structure. In particular we show that domain shape and wall motion are very sensitive to some defects, which prevents a periodic arrangement of the domains. We ascribed these defects to threading dislocations emerging in the magnetic layer, inherent to the growth mode on a relaxed buffer

Magnetic patterning of (Ga,Mn)As by hydrogen passivation

We present an original method to magnetically pattern thin layers of (Ga,Mn)As. It relies on local hydrogen passivation to significantly lower the hole density, and thereby locally suppress the carrier-mediated ferromagnetic phase. The sample surface is thus maintained continuous, and the minimal structure size is of about 200 nm. In micron-sized ferromagnetic dots fabricated by hydrogen passivation on perpendicularly magnetized layers, the switching fields can be maintained closer to the continuous film coercivity, compared to dots made by usual dry etch techniques

Orbital Optimized Density Functional Theory for Electronic Excited States

Density functional theory (DFT) based modeling of electronic excited states is of importance for investigation of the photophysical/photochemical properties and spectroscopic characterization of large systems. The widely used linear response time-dependent DFT (TDDFT) approach is however not effective at modeling many types of excited states, including (but not limited to) charge-transfer states, doubly excited states and core-level excitations. In this perspective, we discuss state-specific orbital optimized (OO) DFT approaches as an alterative to TDDFT for electronic excited states. We motivate the use of OO-DFT methods and discuss reasons behind their relatively restricted historical usage (vs TDDFT). We subsequently highlight modern developments that address these factors and allow efficient and reliable OO-DFT computations. Several successful applications of OO-DFT for challenging electronic excitations are also presented, indicating their practical efficacy. OO-DFT approaches are thus increasingly becoming a useful route for computing excited states of large chemical systems. We conclude by discussing the limitations and challenges still facing OO-DFT methods, as well as some potential avenues for addressing them

Registro de neoplasias caninas diagnosticadas en la Unidad de Prácticas Veterinarias, Universidad Maza, Mendoza, Argentina, 2006-2020

This study aims to present the relative frequency of canine tumors diagnosed at a Veterinary Practice Unit, University service with regional scope, in the period 2006- 2020. A retrospective analysis was carried out based on the information extracted from the medical records. In total, 4500 clinical histories were consulted, among which 238 cases of canine tumors were diagnosed. Information about epidemiological aspects was recorded. Neoplasms were confirmed by histological or cytological analysis in 49% of the cases, which were mostly malignant (60%). In the canine population under study, the animals manifested tumors primarily between 9 and 10 years of age. The 49.5% of the animals with neoplasia were of purebreds, represented mostly by Argentinian Dogo with squamous cell carcinoma and hemangiosarcoma, and boxer with mast cell tumor and multicentric lymphoma, which suggests a predisposition of certain breeds to some type of neoplasms. The most common tumor was Transmissible Venereal Tumor TVT (16% of the total neoplasms), presented mainly in mixed breeds. Next in order of frequency, mast cell tumors and hemangiosarcoma (8.4% each), followed by squamous cell carcinoma (7.6%). The registration of animal tumors is important to delineate the behavior of cancer in the canine population and to provide data that can be compared with human ones, useful for identifying possible risk factors. This study constitutes a preliminary step to characterize and understand the occurrence of canine tumors in the region.Este estudio tiene como objetivo presentar la frecuencia relativa de tumores caninos diagnosticados en una Unidad de Prácticas Veterinarias, servicio universitario de ámbito regional, en el periodo 2006- 2020. El análisis retrospectivo se realizó a partir de la información extraída de las historias clínicas, se consultaron 4500 en total, que evidenciaron 238 casos de tumores caninos. Se registró la información disponible acerca de aspectos epidemiológicos. Las neoplasias se confirmaron mediante análisis histológico o citológico en el 49% de los casos, los que en su mayoría fueron malignos (60%). En la población canina objeto de estudio, los animales manifestaron tumores principalmente entre los 9 y 10 años de edad. El 49,5% de los animales con neoplasia eran de raza pura, representados en su mayoría por Dogo Argentino con carcinoma de células escamosas y hemangiosarcoma, y bóxer con mastocitoma y linfoma multicéntrico, lo que sugiere una predisposición de ciertas razas a algún tipo de neoplasias. El tumor más frecuente fue el Tumor Venéreo Transmisible TVT (16% del total), presentado principalmente en mestizos. Le siguen en orden de frecuencia el mastocitoma y el hemangiosarcoma (8,4% cada uno), seguidos del carcinoma de células escamosas (7,6%). El registro de tumores en animales es importante para delinear el comportamiento del cáncer en la población canina y proporcionar datos que puedan compararse con los humanos, lo cual es útil para identificar posibles factores de riesgo. Este estudio constituye un paso preliminar para caracterizar y comprender la ocurrencia de tumores caninos en la región

New Insights into the Geochemical Processes Occurring on the Surface of Stuccoes Made of Slaked Lime Putty

The fresco technique performed with slaked lime putty as binding material has been well known since Antiquity. However, the geochemical processes that occur on the surface have been generally described as part of the carbonation process of the intonaco itself. When approaching this technique from experimental archaeology, it has been observed for the first time that during the execution period (from 0 to 20 h, approximately) the processes occurring on the surface of the stucco are different from those occurring inside. Furthermore, these processes lead to the formation of an epigenetic film of specific texture, stiffness and compactness. This study investigates the formation and evolution of this surface film using a series of slaked lime putty stucco test tubes. Samples were extracted at different intervals and subsequently analyzed by polarized optical microscopy, scanning electron microscopy, and Fourier transform infrared spectroscopy. Results indicate that the development of the film, composed of an amorphous gel-like stratum and a micro-crystalline stratum, occurs in parallel to the carbonation occurring inside the stucco. Moreover, this process does not respond to the classical geological processes of calcium carbonate formation. It was also observed that its presence slows down the carbonation in the underlying strata (intonaco, intonachino, arriccio, etc.) and that the surface becomes more crystalline over time. The identification of this film has implications for the field of the conservation-restoration of fresco paintings and lime-based wall paintings

Growth mode, magnetic and magneto-optical properties of pulsed-laser-deposited Au/Co/Au(111) trilayers

The growth mode, magnetic and magneto-optical properties of epitaxial Au/Co/Au(111) ultrathin trilayers grown by pulsed-laser deposition (PLD) under ultra-high vacuum are presented. Sapphire wafers buffered with a single-crystalline Mo(110) bilayer were used as substrates. Owing to PLD-induced interfacial intermixing at the lower Co/Au(111) interface, a layer-by-layer growth mode is promoted. Surprisingly, despite this intermixing, ferromagnetic behavior is found at room temperature for coverings starting at 1 atomic layer (AL). The films display perpendicular magnetization with anisotropy constants reduced by 50% compared to TD-grown or electrodeposited films, and with a coercivity more than one order of magnitude lower ($\lesssim$ 5 mT). The magneto-optical (MO) response in the low Co thickness range is dominated by Au/Co interface contributions. For thicknesses starting at 3 AL Co, the MO response has a linear dependence with the Co thickness, indicative of a continuous-film-like MO behavior

Tres generaciones de serpentina en el perfil laterítico niquelífero del Ne de Cuba)

Los yacimientos lateríticos de Ni-Co producen actualmente alrededor del 40% del Ni mundial. Sin embargo, el conocimiento sobre la distribución de Ni en las distintas fases minerales presentes en estos depósitos es sólo a un nivel muy genérico y de poco detalle composicional y estructural

Taking SPARQL 1.1 extensions into account in the SWIP system

International audienceThe SWIP system aims at hiding the complexity of expressing a query in a graph query language such as SPARQL. We propose a mechanism by which a query expressed in natural language is translated into a SPARQL query. Our system analyses the sentence in order to exhibit concepts, instances and relations. Then it generates a query in an internal format called the pivot language. Finally, it selects pre-written query patterns and instantiates them with regard to the keywords of the initial query. These queries are presented by means of explicative natural language sentences among which the user can select the query he/she is actually interested in. We are currently focusing on new kinds of queries which are handled by the new version of our system, which is now based on the 1.1 version of SPARQL

Molecular characterization of corona radiata cells from patients with diminished ovarian reserve using microarray and microfluidic-based gene expression profiling

BACKGROUND: Diminished ovarian reserve (DOR) is one of the causes of infertility in young women. In this prospective study, gene expression profiling (GEP) of corona radiata cells (CRC) was performed to identify genes deregulated in DOR patients. METHODS: Microarray-based GEP of CRC isolated from eight women undergoing IVF was performed to identify genes differentially expressed between patients with normal ovarian reserve and DOR patients. Microfluidic-based quantitative RT-PCR assays were used to validate selected transcripts on 40 independent patients. A principal component analysis was used to identify more homogeneous subgroups of DOR patients. In silico analyses focusing on cis-regulation were performed to refine the interactions between patient\u27s biological characteristics and their GEP. RESULTS: Forty-eight transcripts were differentially expressed, including CXXC finger protein 5 (CXXC5), forkhead box C1 (FOXC1) (down-regulated in DOR) as well as connective tissue growth factor (CTGF), follistatin-like 3 (FSTL3), prostaglandin-endoperoxide synthase 2 (PTGS2) and suppressor of cytokine signaling 2 (SOCS2) (up-regulated in DOR). According to these transcripts, two DOR patients\u27 subgroups (DOR Gr1 and Gr2) were identified. In DOR Gr2 patients, C-terminal domain 2 (CITED2), CTGF, growth arrest-specific 1 (GAS1), insulin receptor substrate 2 (IRS2), PTGS2, SOCS2 and Versican (VCAN) were expressed at significantly higher levels and CXXC5, FOXC1, guanylate-binding protein 2 (GBP2) and zinc finger MIZ-domain containing 1 (ZMIZ1) at significantly lower levels. Higher baseline estradiol (E(2)) levels were observed in DOR Gr2 patients (P < 0.006). The in silico analyses suggested that all 11 genes differentially expressed between DOR Gr1 and DOR Gr2 subgroups could be transcriptional targets of estrogen. CONCLUSIONS: Despite small sample size limitations, 12 genes deregulated in the CRC of DOR patients were identified, which could be involved in DOR pathogenesis. A DOR patient\u27s subgroup with high baseline E(2) levels and deregulated estrogen-responsive genes was also identified

Kinetic Monte Carlo Simulations of a Model for Heat-assisted Magnetization Reversal in Ultrathin Films

To develop practically useful systems for ultra-high-density information recording with densities above terabits/cm$^2$, it is necessary to simultaneously achieve high thermal stability at room temperature and high recording rates. One method that has been proposed to reach this goal is heat-assisted magnetization reversal (HAMR). In this method, one applies a high-coercivity material, whose coercivity is temporarily lowered during the writing process through localized heating. Here we present kinetic Monte Carlo simulations of a model of HAMR for ultrathin films, in which the temperature in the central part of the film is momentarily increased above the critical temperature, for example by a laser pulse. We observe that the speed-up achieved by this method, relative to the switching time at a constant, subcritical temperature, is optimal for an intermediate strength of the writing field. This effect is explained using the theory of nucleation-induced magnetization switching in finite systems. Our results should be particularly relevant to recording media with strong perpendicular anisotropy, such as ultrathin Co/Pt or Co/Pd multilayers.Comment: 8 pp., 7 fig