Phase‐amplitude coupling profiles differ in frontal and auditory cortices of bats

Neural oscillations are at the core of important computations in the mammalian brain. Interactions between oscillatory activities in different frequency bands, such as delta (1–4 Hz), theta (4–8 Hz) or gamma (>30 Hz), are a powerful mechanism for binding fundamentally distinct spatiotemporal scales of neural processing. Phase‐amplitude coupling (PAC) is one such plausible and well‐described interaction, but much is yet to be uncovered regarding how PAC dynamics contribute to sensory representations. In particular, although PAC appears to have a major role in audition, the characteristics of coupling profiles in sensory and integration (i.e. frontal) cortical areas remain obscure. Here, we address this question by studying PAC dynamics in the frontal‐auditory field (FAF; an auditory area in the bat frontal cortex) and the auditory cortex (AC) of the bat Carollia perspicillata. By means of simultaneous electrophysiological recordings in frontal and auditory cortices examining local‐field potentials (LFPs), we show that the amplitude of gamma‐band activity couples with the phase of low‐frequency LFPs in both structures. Our results demonstrate that the coupling in FAF occurs most prominently in delta/high‐gamma frequencies (1‐4/75‐100 Hz), whereas in the AC the coupling is strongest in the delta‐theta/low‐gamma (2‐8/25‐55 Hz) range. We argue that distinct PAC profiles may represent different mechanisms for neuronal processing in frontal and auditory cortices, and might complement oscillatory interactions for sensory processing in the frontal‐auditory cortex network

Ab initio study of intrinsic profiles of liquid metals and their reflectivity

The free surfaces of liquid metals are known to exhibit a stratified profile that, in favourable cases, shows up in experiments as a peak in the ratio between the reflectivity function and that of an ideal step-like profile. This peak is located at a wave-vector related to the distance between the layers of the profile. In fact the surface roughness produced by thermally induced capillary waves causes a depletion of the previous so called intrinsic reflectivity by a damping factor that may hinder the observation of the peak. The behaviour of the intrinsic reflectivity below the layering peak is however far from being universal, with systems as Ga or In where the reflectiviy falls uniformly towards the q → 0 value, others like Sn or Bi where a shoulder appears at intermediate wavevectors, and others like Hg which show a minimum. We have performed extensive ab initio simulations of the free liquid surfaces of Bi, Pb and Hg, that yield direct information on the structure of the profiles and found that the macroscopic capillary wave theory usually employed in order to remove the capillary wave components fails badly in some cases for the typical sample sizes affordable in ab initio simulations. However, a microscopic method for the determination of the intrinsic profile is shown to be succesful in obtaining meaningful intrinsic profiles and corresponding reflectivities which reproduce correctly the qualitative behaviour observed experimentally

La gestión de los Social Media en los medios informativos iberoamericanos

En este estudio se examina cómo gestionan los Social Media 22 medios locales en 12 regiones de Argentina, Colombia, Perú, Portugal, España y Venezuela. A través de 22 entrevistas semi-estructuradas realizadas a los responsables de su gestión, hemos podido observar cómo, en la actualidad, los Social Media son considerados recursos que ayudan al aumento de las capacidades de comunicación y desarrollo informativo, a pesar del poco auge que aún tienen los nuevos perfiles profesionales y del estado inicial de empoderamiento que hay a la fecha de los Social Media, dentro de estos medios. ----------------------------------------------------------------------------------------------------------------In this study we analyze how the social networks are being managed in 22 local digital media of 12 regions of Argentina, Colombia, Peru, Portugal, Spain and Venezuela. Through 22 semi-structured interviews made to their manager, which allow us to appreciate how, at present, the Social Media are seen like resources that help to increase the media capacities around communication and informative channels in spite of the little short development that exist, until now, about new professional profiles dedicated to the social networks management and initial state of empowerment of social media within the media

Electronic and crystallographic structure of apatites

An ab initio study of four different stoichiometric apatites (oxyapatite, hydroxyapatite, fluorapatite, and chlorapatite) is presented. The calculations were performed using density-functional theory with the local-density approximation for exchange and correlation, and a full relaxation of the electronic structure, the atomic arrangement, and the unit cell. Hexagonal unit cells were obtained for all four apatites, and the calculated atomic arrangements are in close agreement with observation in those cases for which the structure is firmly established. A zero-temperature structure is predicted for oxyapatite, and two possible configurations were found for the Cl- ions in chlorapatite. The possibility of the monoclinic structure in hydroxyapatite and chlorapatite was also studied but no indication of greater stability with respect to the hexagonal structure was found. A relationship between the structure of the apatites and that of pure calcium is discussed.This work was supported by a CRD grant of the NSERC of Canada and Millenium Biologix Inc. L.C. also acknowledges W.A. Miller Materials and Manufacturing Ontario Ph.D. Graduate Award. A.R. acknowledges support from DGES, Basque University, and EC-RTN program NANOPHASE (Contract No. HPRN-CT-2000-00167) and COMELCAN (Contract No. HPRN-CT-2000-00128).Peer reviewe

Kubo–Greenwood electrical conductivity formulation and implementation for projector augmented wave datasets

As the foundation for a new computational implementation, we survey the calculation of the complex electrical conductivity tensor based on the Kubo-Greenwood (KG) formalism (Kubo, 1957; Greenwood, 1958), with emphasis on derivations and technical aspects pertinent to use of projector augmented wave datasets with plane wave basis sets (BIlichl, 1994). New analytical results and a full implementation of the KG approach in an open-source Fortran 90 post-processing code for use with Quantum Espresso (Giannozzi et al., 2009) are presented. Named KGEC ([K]ubo [G]reenwood [E]lectronic [C]onductivity), the code calculates the full complex conductivity tensor (not just the average trace). It supports use of either the original KG formula or the popular one approximated in terms of a Dirac delta function. It provides both Gaussian and Lorentzian representations of the Dirac delta function (though the Lorentzian is preferable on basic grounds). KGEC provides decomposition of the conductivity into intra- and inter band contributions as well as degenerate state contributions. It calculates the dc conductivity tensor directly. It is MPI parallelized over k-points, bands, and plane waves, with an option to recover the plane wave processes for their use in band parallelization as well. It is designed to provide rapid convergence with respect to k-point density. Examples of its use are given.U.S. Dept. of Energy [DE-SC0002139]Pre-print submitted, no embargo.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Ciprofloxacin, an antibiotic with cardiac actions on isolated rat hearts

Context: Ciprofloxacin is the most commonly used fluoroquinolone and is prescribed as the antibiotic of choice in the treatment of several microbial infections. Some clinical reports have suggested that ciprofloxacin may induce QT-interval prolongation and Torsades de Pointes arrhythmias. This drug is a weak inhibitor of a rapid component of the cardiac delayed rectifier potassium current IKr, but there are few electrophysiological data available to assess whether ciprofloxacin has the potency to provoke QT prolongation and subsequent Torsades de Pointes arrhythmias. Aims: To evaluate the effect of ciprofloxacin on the contractile and electrical activity of isolated rat hearts. Methods: The Langendorff technique was performed in rat hearts, and the effects of ciprofloxacin (0.001 – 100 μM) were measured on the cardiac force of contraction and on the RR, QRS and QTc intervals. The arrhythmogenic potential and the ventricular fibrillation threshold were evaluated with ciprofloxacin. Results: Ciprofloxacin decreased the force of contraction of all hearts studied, in a concentration-dependent manner. The estimated IC50 for the inotropic negative effect was 0.15 ± 0.04 μM. Ciprofloxacin significantly prolonged the QRS complex, QTc and RR interval. Significant arrhythmic effects with ciprofloxacin were shown and the ventricular fibrillation threshold was decreased. Conclusions: These results suggest that ciprofloxacin exerted effects on cardiac Na+, K+ and Ca2+ channels. The actions of ciprofloxacin require further studies at the cellular level. These conclusions may account for clinical data that have been reported previously

Esplenectomía laparoscópica

La esplenectomía laparoscópica (EL) ofrece las ventajas de la cirugía laparoscópica. La mejor indicación de la EL la constituyen las enfermedades hematológicas benignas. Desde octubre de 1996 hasta agosto del 2000 se intentaron realizar 22 esplenectomías por el método laparoscópico. Las indicaciones más frecuentes fueron las enfermedades hematológicas benignas: la púrpura trombocitopénica idiopática en 9 pacientes, la microesferocitosis hereditaria en 4, la anemia hemolítica autoinmune en 5, la estadiación del linfoma de Hodgkin en 2, 1 caso de tumor quístico del bazo y 1 caso de hiperesplenismo sin causa demostrada. Se analizan los resultados en estos primeros 22 casos y se describe la técnica quirúrgica. La edad promedio fue de 34,3 años, con rango de 16 a 73 años. El tiempo quirúrgico promedio fue de 147 min. Se convirtieron a cirugía abierta 4 pacientes por sangrado transoperatorio. Ocurrieron accidentes operatorios en 4 pacientes. No se presentaron complicaciones posoperatorias. El proceder se asoció con colecistectomía laparoscópica en 6 pacientes y biopsia de ganglio mesentérico con biopsia hepática en 2 pacientes. El sangrado transoperatorio promedio fue de 467 mL. La EL es una técnica reproducible y segura que brinda las ventajas de la cirugía laparoscópica (menor morbilidad y mortalidad posoperatoria), sobre todo en las enfermedades hematológicas benignas con bazo de tamaño normal o esplenomegalia no mayor de 25 cm, a pesar del efecto negativo de la curva de aprendizajeThe laparoscopic splenectomy (LS) offers the advantages of the laparoscopic surgery. The best indication of LS are the bening hematological diseases. 22 splenectomies were performed by the laparoscopic method from October, 1996, to August, 2000. The most frequent indications were the bening hematological diseases: idiopathic thrombocytopenic purpura in 9 patients, hereditary microspherocytosis in 4, autoimmune hemolitic anaemia in 5, Hodgkin lymphoma staging in 2, 1 case of cystic spleen tumor and 1 case of hypersplenism of undemonstrated cause. The results obtained in these first 22 cases are analyzed and the surgical technique is described. The average age was 34.3 years old with a range from 16 to 73 years old. The average surgical time was 147 min. Open surgery was performed in 4 patients due to postoperative bleeding. Surgical accidents occurred in 4 patients. No postoperative complications were reported. The procedure was associated with laparoscopic cholecystectomy in 6 patients and with biopsy of mesenteric ganglion with liver biopsy in 2 patients. The average transoperative bleeding was 467 mL. The LS is a reproducible and safe technique having the advantages of laparoscopic surgery (lower morbidity and postoperative mortality), mainly in the bening hematologic diseases with spleen of normal size or splenomegaly not exceeding 25 cm, in spite of the negative effect of the learning curv

Prevalencia de hipovitaminosis D e hiperparatiroidismo secundario en la Unidad de Lesionados Medulares de Gran Canaria. Estudio preliminar

Fundamento: La deficiencia de vitamina D es muy frecuente, y se ha puesto en evidencia en múltiples estudios realizados tanto en la población general como en pacientes con diferentes patologías. Sin embargo, ha sido poco estudiada en los pacientes afectos de lesión medular. Objetivo: Estudiar la prevalencia de hipovitaminosis D y el posible desarrollo de un hiperparatiroidismo secundario en una población de pacientes con lesión medular. Material y método: Estudio descriptivo transversal realizado en 104 pacientes afectos de lesión medular. A todos se les efectuó una historia clínica y una exploración física detallada, y se les extrajo sangre en ayunas, con la menor compresión posible. Los parámetros analíticos fueron analizados por técnicas automatizadas y la determinación de la 25-hidroxivitamina D (25HCC) y la hormona paratiroidea (PTH) se efectuó por electroinmunoquimioluminiscencia (EIQL). Resultados: El valor medio global de 25-hidroxivitamina D fue 20,1 ± 11,6 ng/ml. El 84,6% de los pacientes tenían unos valores séricos de 25-hidroxivitamina D inferiores a 30 ng/ml y el 62,5% del total de pacientes, mostraron valores inferiores a 20 ng/ml. La prevalencia de insuficiencia de vitamina D fue similar en hombres y mujeres. Sin embargo, aunque encontramos una correlación inversa entre los niveles de PTH y de 25-hidroxivitamina D, sólo el 5,8% de los pacientes llegaron a desarrollar un hiperparatiroidismo secundario. Conclusiones: Existe una elevada prevalencia de hipovitaminosis D en los pacientes con lesión medular. Es aconsejable, por tanto, la inclusión del estudio de este metabolito en el protocolo de atención de estos pacientes para corregir las deficiencias en cuando se objetiven