State-of-the-art techniques for calculating spectral functions in models for correlated materials

The dynamical mean field theory (DMFT) has become a standard technique for the study of strongly correlated models and materials overcoming some of the limitations of density functional approaches based on local approximations. An important step in this method involves the calculation of response functions of a multiorbital impurity problem which is related to the original model. Recently there has been considerable progress in the development of techniques based on the density matrix renormalization group (DMRG) and related matrix product states (MPS) implying a substantial improvement to previous methods. In this article we review some of the standard algorithms and compare them to the newly developed techniques, showing examples for the particular case of the half-filled two-band Hubbard model.Comment: 8 pages, 4 figures, to be published in EPL Perspective

Extended WKB method, resonances and supersymmetric radial barriers

Semiclassical approximations are implemented in the calculation of position and width of low energy resonances for radial barriers. The numerical integrations are delimited by t/T<<8, with t the period of a classical particle in the barrier trap and T the resonance lifetime. These energies are used in the construction of `haired' short range potentials as the supersymmetric partners of a given radial barrier. The new potentials could be useful in the study of the transient phenomena which give rise to the Moshinsky's diffraction in time.Comment: 12 pages, 4 figures, 3 table

Doping and temperature dependence of Mn 3d states in A-site ordered manganites

We present a systematic study of the electronic structure in A-site ordered manganites as function of doping and temperature. The energy dependencies observed with soft x-ray resonant diffraction (SXRD) at the Mn L_{2,3} edges are compared with structural investigations using neutron powder diffraction as well as with cluster calculations. The crystal structures obtained with neutron powder diffraction reflect the various orbital and charge ordered phases and show an increase of the Mn-O-Mn bond angle as function of doping and temperature. Cluster calculations show that the observed spectral changes in SXRD as a function of doping are more pronounced than expected from an increase in bandwitdh due to the increase in Mn-O-Mn bond angle, and are best described by holes that are distributed at the neighbouring oxygen ions. These holes are not directly added to the Mn 3d shell, but centered at the Mn site. In contrast, the spectral changes in SXRD as function of temperature are best described by an increase of magnetic correlations. This demonstrates the strong correlations between orbitals and magnetic moments of the 3d states

Theoretical Kinetics Study of the F(2P) + NH3 Hydrogen Abstraction Reaction

The hydrogen abstraction reaction of fluorine with ammonia represents a true chemical challenge because it is very fast, is followed by secondary abstraction reactions, which are also extremely fast, and presents an experimental/theoretical controversy about rate coefficients. Using a previously developed full-dimensional analytical potential energy surface, we found that the F + NH3 → HF + NH2 system is a barrierless reaction with intermediate complexes in the entry and exit channels. In order to understand the reactivity of the title reaction, thermal rate coefficidents were calculated using two approaches: ring polymer molecular dynamics and quasi-classical trajectory calculations, and these were compared with available experimental data for the common temperature range 276–327 K. The theoretical results obtained show behavior practically independent of temperature, reproducing Walther–Wagner’s experiment, but in contrast with Persky’s more recent experiment. However, quantitatively, our results are 1 order of magnitude larger than those of Walther–Wagner and reasonably agree with the Persky at the lowest temperature, questioning so Walther−Wagner’s older data. At present, the reason for this discrepancy is not clear, although we point out some possible reasons in the light of current theoretical calculationsThis work was partially supported by Gobierno de Extremadura, Spain, and FEDER (Project No. IB10001). Y.V.S. acknowledges the support of a Combustion Energy Research Fellowship through the Combustion Energy Frontier Research Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Basic Energy Sciences under Award Number DE-SC0001198. A.F-.R. thanks Xunta de Galicia through Grant No. 2012/314 para a consolidación e a estruturación de unidades de investigación competitivas do Sistema Universitario de Galicia, 2012S

Biomarkers in ocular chronic graft versus host disease: tear cytokine- and chemokine-based predictive model.

Producción CientíficaPurpose: To develop a tear molecule level-based predictive model based on a panel of tear cytokines and their correlation with clinical features in ocular chronic graft versus host disease (cGVHD). Methods: Twenty-two ocular cGVHD patients and 21 healthy subjects were evaluated in a controlled environmental research laboratory (CERLab). Clinical parameters were recorded, and tears were collected. Levels of 15 molecules (epidermal growth factor [EGF], IL receptor antagonist [IL-1Ra], IL-1β, IL-2, IL-6, IL-8/CXCL8, IL-10, IL-12p70, IL-17A, interferon inducible protein [IP]-10/CXCL10, IFN-γ, VEGF, TNF-α, eotaxin 1, and regulated on activation normal T cell expressed and secreted [RANTES]) were measured by multiplex-bead assay and correlated with clinical parameters. Logistic regression was used to develop a predictive model. Leave-one-out cross-validation was applied. Classification capacity was evaluated in a cohort of individuals with dry eye (DE) of other etiologies different from GVHD. Results: Epidermal growth factor and IP-10/CXCL10 levels were significantly decreased in ocular cGVHD, positively correlating with tear production and stability and negatively correlating with symptoms, hyperemia, and vital staining. Interleukin-1Ra, IL-8/CXCL8, and IL-10 were significantly increased in ocular cGVHD, and the first two correlated positively with symptoms, hyperemia, and ocular surface integrity while negatively correlating with tear production and stability. Predictive models were generated, and the best panel was based on IL-8/CXCL8 and IP-10/CXCL10 tear levels along with age and sex, with an area under the receiving operating curve of 0.9004, sensitivity of 86.36%, and specificity of 95.24%. Conclusions: A predictive model based on tear levels of IL-8/CXCL8 and IP-10/CXCL10 resulted in optimal sensitivity and specificity. These results add further knowledge to the search for potential biomarkers in this devastating ocular inflammatory disease.Ministry of Economy and Competitiveness, Madrid, Spain, SAF-2010 15631 (AES)

Estudio comparativo de diferentes técnicas de implantación de stents en bifurcaciones coronarias

ResumenEl objetivo de este trabajo es el análisis comparativo de los cambios hemodinámicos locales producidos en una bifurcación coronaria por el implante de stents mediante 3 técnicas diferentes: stent simple en la arteria principal, stent simple en la arteria principal con orificio de comunicación con la arteria secundaria para el paso de un balón de inflado («kissing») y «culotte». Para ello se ha utilizado la geometría ideal de una bifurcación coronaria a 45 y 90°.En primer lugar se simularon los modelos en régimen estacionario mediante el código comercial ANSYS Fluent, y a continuación se validaron con las medidas experimentales tomadas en el laboratorio mediante velocimetría de imagen de partículas (particle image velocimetry [PIV]). Una vez obtenida una buena concordancia de resultados entre ambos estudios en régimen permanente, se abordó el flujo pulsátil. Los parámetros que se consideraron para comparar las diferentes técnicas en este régimen fueron los esfuerzos cortantes y la caída de presión promediados en el tiempo, así como el índice de esfuerzos cortantes oscilatorios (oscillatory shear index [OSI]). Las conclusiones finales fueron que el stent simple presenta los peores resultados, en términos de caída de presión, y la técnica «kissing», los mejores. Esto sería aplicable a los stents liberadores de fármacos, donde la reestenosis no es tan crucial como el restablecimiento del flujo sanguíneo. En cuanto al criterio basado en el valor menor de los esfuerzos cortantes (<0,4Pa) y un OSI elevado (>0,1), la técnica «culotte» presenta el peor comportamiento. Esto sería aplicable a los stents sin recubrimiento, en que la mejor opción sería el stent simple.AbstractThe objective of this work is to analyze the local hemodynamic changes caused in a coronary bifurcation by three different stenting techniques: simple stenting of the main vessel, simple stenting of the main vessel with kissing balloon in the side branch and culotte. To carry out this study an idealized geometry of a coronary bifurcation is used, and two bifurcation angles, 45° and 90°, are chosen as representative of the wide variety of real configurations. Both numerical simulations and experimental measurements are performed. First, steady simulations are carried out with the commercial code ANSYS Fluent, then, experimental measurements with PIV (Particle Image Velocimetry), obtained in the laboratory, are used to validate the numerical simulations. The steady computational simulations show a good overall agreement with the experimental data. Second, pulsatile flow is considered to take into account the transient effects. The time averaged wall shear stress, oscillatory shear index (OSI) and pressure drop obtained numerically are used to compare the behavior of the stenting techniques. As conclusions obtained, simple stenting technique shows the worst results in terms of pressure drop, and kissing the best ones. This criterion could be applied for DES (Drug Eluting Stents) where the restenosis is not as critical as the reestablishment of the blood flow. But considering the regions of low wall shear stress (<0.4Pa) and elevated OSI (>0.1), the culotte procedure shows the worst performance and the simple stent, the best. This could be applied to BMS (Bare Metal Stents)

Magnetic and electronic Co states in layered cobaltate GdBaCo2O5.5-x

We have performed non-resonant x-ray diffraction, resonant soft and hard x-ray magnetic diffraction, soft x-ray absorption and x-ray magnetic circular dichroism measurements to clarify the electronic and magnetic states of the Co3+ ions in GdBaCo2O5.5. Our data are consistent with a 3+ Py Co HS state at the pyramidal sites and a 3+ Oc Co LS state at the octahedral sites. The structural distortion, with a doubling of the a axis (2ap x 2ap x 2ap cell), shows alternating elongations and contractions of the pyramids and indicates that the metal-insulator transition is associated with orbital order in the t2g orbitals of the 3+ Py Co HS state. This distortion corresponds to an alternating ordering of xz and yz orbitals along the a and c axes for the 3+ Py Co . The orbital ordering and pyramidal distortion lead to deformation of the octahedra, but the 3+ Oc Co LS state does not allow an orbital order to occur for the 3+ Oc Co ions. The soft x-ray magnetic diffraction results indicate that the magnetic moments are aligned in the ab plane but are not parallel to the crystallographic a or b axes. The orbital order and the doubling of the magnetic unit cell along the c axis support a non-collinear magnetic structure. The x-ray magnetic circular dichroism data indicate that there is a large orbital magnetic contribution to the total ordered Co moment

Las guerras astur-cántabras: estrategias y armamento

El carácter de los pueblos astures y cántabros y las características del territorio norte de Hispania condicionarían enormemente las guerras astur-cántabras llevadas a cabo del 29 al 19 a.C., llegando a ser dirigidas las operaciones romanas por el propio Augusto. De este modo, las diferentes tribus que conformaban estos pueblos tuvieron que hacer frente a un numeroso ejército que pretendía acabar con su preciada independencia. Estos enfrentamientos supusieron el fin de la larga conquista de la Península Ibérica y tuvieron una gran repercusión en un momento de inestabilidad política para Roma. Este trabajo pretende estudiar el conflicto astur-cántabro mostrando las principales estrategias de conquista del territorio astur, así como de la invasión y ocupación del territorio cántabro. Además, se expone el armamento que pudieron utilizar los guerreros de ambos bandos durante estos enfrentamientos y cuyos restos han sido encontrados a través de la arqueología, lo que ha permitido, junto con las estructuras halladas y las fuentes clásicas, dar una visión renovada de este conflicto bélico.The character of the Asturian and Cantabrian peoples and the geographical features of the northern Hispania would greatly condition the Asturian-Cantabrian Wars carried out between 29 and 19 BC, with Augustus leading the Roman campaigns in person. In this way, the different tribes that made up these towns had to face a large army that tried to end their precious independence. These clashes were the final stage of the long conquest of the Iberian Peninsula and had a great impact at a time of political instability for Rome. This work aims to study the Asturian-Cantabrian conflict showing the main strategies of conquest of the Asturian territory, as well as of the invasion and occupation of the Cantabrian territory. In addition, the weapons that the warriors of both sides could use during these confrontations are shown and whose remains have been found through archaeology, which has allowed, together with the structures found and the classical sources, to give a renewed vision of this war conflict.Departamento de Prehistoria, Arqueología, Antropología Social y Ciencias y Técnicas HistoriográficasGrado en Histori

Osteitis condensante de clavícula

La osteítis condensante de clavícula es una lesión ósea infrecuente, benigna y de etiología desconocida. Se caracteriza por esclerosis densa y homogénea de la porción infero-medial clavicular con obliteración de la cavidad medular sin afectación de la articulación esternoclavicular. Hasta ahora sólo se había descrito en mujeres, en el presente trabajo presentamos un caso en un paciente varón. Se discute el diagnóstico diferencial con otras entidades que producen afectación similar y proponemos la TC como método diagnóstico de elección, defendiendo el tratamiento conservador.Condensing osteitis of the clavicle is a benign and uncommon bone lesion of unknown cause, characterized by homogeneously dense sclerotic patch with obliteration of the marrow cavity at the medial end of the clavicle without involvement of the sternoclavicular joint. To date it had been described only in women. In this work we report a case in a male patient. The differential diagnosis with other disorders of similar findings is discussed. We propose CT-scan as the elective diagnostic test and we defend the conservative treatment