1,418 research outputs found
Electronic Instabilities of the AA-Honeycomb Bilayer
We use a functional renormalization group approach to study the instabilities
due to electron-electron interactions in a bilayer honeycomb lattice model with
AA stacking, as it might be relevant for layered graphene with this structure.
Starting with a tight- binding description for the four -bands, we
integrate out the modes of the dispersion by successively lowering an infrared
cutoff and determine the leading tendencies in the effective interactions. The
antiferromagnetic spin-density wave is an expected instability for dominant
local repulsion among the electrons, but for nonlocal interaction terms also
other instabilities occur. We discuss the phase diagrams depending on the model
parameters. We compare our results to single-layer graphene and the more common
AB-stacked bilayer, both qualitatively and quantitatively.Comment: 9 pages, 3 figures, Annalen der Physik, online available (2014
Pricing tranched credit products with generalized multifactor models
The market for tranched credit products (CDOs, Itraxx tranches) is one of the fastest growing
segments in the credit derivatives industry. However, some assumptions underlying the standard
Gaussian onefactor
pricing model (homogeneity, single factor, Normality), which is the pricing
standard widely used in the industry, are probably too restrictive. In this paper we generalize the
standard model by means of a two by two model (two factors and two asset classes). We assume
two driving factors (business cycle and industry) with independent tStudent
distributions,
respectively, and we allow the model to distinguish among portfolio assets classes. In order to
illustrate the estimation of the parameters of the model, an empirical application with Moody's
data is also included
Milk production estimation in goats by the Fleischmann method
Four adaptations of Fleischmann"s method, utilized for the calculus of accumulated milk production at complete lactation are compared. 551 lactations of the Florida breed goat were employed from the first to the tenth lactation with monthly controls. The mean reference productions obtained with the adaptations were different (p<0.05). These differences obey to a different way in which the milk production is calculated principally from calving to first control and, from the last control to drying.Se comparan cuatro adaptaciones del método Fleischmann para el cálculo de la producción de leche acumulada a lactación completa. Se emplearon 551 lactaciones de cabras de raza Florida de primera a décima lactación con controles mensuales. Las producciones medias de referencia obtenidas con las adaptaciones fueron diferentes (p<0,05) debido a la distinta manera de plantear el cálculo de la producción de leche, principalmente desde el parto al primer control y del último control al secado
Effect of zinc intake on growth in infants: A meta-analysis
A systematic review and meta-analysis of available randomized controlled trials (RCTs) was conducted to evaluate the effect of zinc (Zn) intake on growth in infants. Out of 5500 studies identified through electronic searches and reference lists, 19 RCTs were selected after applying the exclusion/inclusion criteria. The influence of Zn intake on growth was considered in the overall meta-analysis. Other variables were also taken into account as possible effect modifiers: doses of Zn intake, intervention duration, nutritional status, and risk of bias. From each select growth study, final measures of weight, length, mid upper arm circumference (MUAC), head circumference, weight for age z-score (WAZ), length for age z-score (LAZ), and weight for length z-score (WLZ) were assessed. Pooled β and 95% confidence interval (CI) were calculated. Additionally, we carried out a sensitivity analysis. Zn intake was not associated with weight, length, MUAC, head circumference, and LAZ in the pooled analyses. However, Zn intake had a positive and statistically effect on WAZ (β = 0.06; 95%CI 0.02 to 0.10) and WLZ (β = 0.05; 95%CI 0.01 to 0.08). The dose–response relationship between Zn intake and these parameters indicated that a doubling of Zn intake increased WAZ and WLZ by approximately 4%. Substantial heterogeneity was present only in length analyses (I2 = 45%; p = 0.03). Zn intake was positively associated with length values at short time (four to 20 weeks) (β = 0.01; CI 95% 0 to 0.02) and at medium doses of Zn (4.1 to 8 mg/day) (β = 0.003; CI 95% 0 to 0.01). Nevertheless, the effect magnitude was small. Our results indicate that Zn intake increases growth parameters of infants. Nonetheless, interpretation of these results should be carefully considered
The Effects of Technology Entrepreneurship on Customers and Society: A Case Study of a Spanish Pharmaceutical Distribution Company
Laser-assisted surface melting of Al2O3-YSZ eutectic ceramics
[ES] Se presenta un procedimiento para la densificación y/o texturado superficial de cerámicas de Al2O3-YSZ (circona
estabilizada con itria) con composición eutéctica mediante fusión zonal asistida por láser. Haciendo un barrido con la
radiación proveniente de un láser de potencia sobre piezas cerámicas conseguimos modificar la microestructura y densificar
completatmente la capa superficial, con un espesor que va de 30 a 1000 μm. Por ejemplo, con lÃnea estrecha de láser de
diodo, fluencia de 1.23 kW/cm2 y velocidades de barrido de 0.14 mm/s, solidificamos capas de 560 μm. El resultado es una
superficie de baja rugosidad y no porosa. La microestructura de la muestra es fina debido a su composición eutéctica. La
interfase sólido-lÃquido en el proceso de crecimiento determina la orientación de la microestructura. Se estudia la forma de
esta interfase tanto en cortes transversales como longitudinales, lo que permite analizar el efecto que sobre la microestructura
tiene la superposición de barridos, que es una alternativa para tratar superficies extensas. Macroscópicamente la frontera
entre barridos contiguos es suave. Sin embargo, su microestructura presenta discontinuidad en el espaciado entre las fases
debido a la evolución microestructural en la región no fundida sometida a altas temperaturas y a la nucleación preferencial
de Al2O3 al comenzar el crecimiento cristalino. Se analizan distintas posibilidades para disminuir el choque térmico inherente
al proceso y que conduce a la formación de grietas paralelas a la dirección de procesado y de delaminación. Se observa una
mejora importante cuando se precalienta la pieza a tratar, de modo que es posible procesar superficies de cerámicas eutécticas
99% densas.[EN] A procedure for surface densification and/or texturing of Al2O3-YSZ (yttria stabilised zirconia) ceramics with eutectic
composition by means of laser surface melting is presented. By scanning a high-power laser beam on a ceramic surface, we
achieve a textured and fully dense surface layer from 30 to 1000 microns thick. For example, using a thin diode laser line
with fluence 1.23 kW/cm2 and 0.14 mm/s scan rate, the solidified layer has 560 μm depth. We get a low roughness and
dense surface. The microstructure is fine (micron size) due to the eutectic composition. The orientation of the microstructure
is determined by the shape of the solid-liquid interface in the solidification process. We study the shape of this interface
in transverse and longitudinal cross-sections in single as well as overlapping scans, which are required to process large
surfaces. From the macroscopic point of view, the transition between adjacent scans is smooth. However, the microstructure
presents discontinuity in the interphase spacing due to microstructural evolution in the heat affected region as well as the
nucleation of an Al2O3 layer at the beginning of the crystal growth. The thermal shock inherent to the procedure generates
cracks longitudinal and transverse to the scanning direction, as well as delaminating cracks. We analyse different possibilities
to reduce this thermal shock. The best results are obtained by preheating the substrate, allowing us to process surfaces of
Al2O3-YSZ eutectic ceramics 99% dense.Financiación del Ministerio de Ciencia y TecnologÃa a través de los proyectos MAT2000-1495 y MAT2000-1533-C03-02.Peer reviewe
Cognitive and functional differences in aging with and without intellectual disabilities: Observational study
The lifespan of people with cognitive disabilities (ID) has increased significantly, but the cognitive aspects together with the functional ones comparing normal aging and those with intellectual disabilities had not been previously studied. Objective: This study analyzed the cognitive and functional differences in older adults aging with ID (and with DS), compared with their peers without disabilities, in order to identify the most adapted interventions. Methodology: This study evaluated the outcome variables of MEC, Set-Test, Barthel, Lawton–Brody, and Tinetti with 247 participants: 146 without ID and 101 ID (29 with DS and 72 without DS). Results: At the cognitive level, older people with ID presented lower scores both in MEC (p < 0.01), globally and in each cognitive domain (except in short-term memory), and in verbal fluency (Set-Test) than older people without ID; however, the diagnosis of cognitive impairment and dementia is higher in people without ID. At the functional level, there are no differences in ABDL, but there are in AIDL and Tinetti (p < 0.01), where participants without ID obtain higher scores. The most frequent pathologies in people with ID were obesity and epilepsy. Conclusions: The lower cognitive and functional performance in ID is associated with the disability itself, the low educational level, the neurocognitive underdiagnosis, and the use of poorly adapted assessment tools. The cognitive and functional results indicated the importance of interventions adapted to the characteristics of this population, in their aging process. © 2021 by the author. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/)
Dynamic changes in the lower Gállego River (Ebro Basin, NE Spain) and their relationship with anthropic activities and the quaternary substrate
The lower Gállego River has been strongly degraded since the 1960s due to human activity (gravel mining, dump accumulation, channeling works), which has produced a deep channel incision. Although these humandriven processes are usually reported in fluvial bibliography, in this case, more complex results are observable. For instance, regarding the depth and incision rates, we observed no relationship between the most anthropically impacted areas and the sections with the deepest incisions; moreover, the deepening process continues 40 years after the human interventions ceased. The reason for this maladjustment is the role played by the exhumation of the underlying Pleistocene substrate, affected by the synsedimentary processes of karstification. The appearance of paleodolines filled with fine sediments on the incision bottom and sides is the main factor conditioning the continuity and magnitude of the process. Besides, these paleodepressions direct the river dynamics and course, thus favoring its widening when they appear and causing the development of a new riverbed (Qt13) while the 1960s floodplain (Qt12) is becoming an old terrace located between 5 and 11 m above the new alluvial bottom. There are no previous records about this kind of consequences in the regional fluvial dynamics.
El curso bajo del rÃo Gállego ha sido fuertemente degradado desde los años 1960 por la actividad antrópica (extracción de áridos, acumulaciones de escombros, obras de encauzamiento) que ha conducido a una fuerte incisión. Aunque este tipo de procesos inducidos por el hombre son habituales en la bibliografÃa fluvial, en este caso se aprecian efectos más complejos. Son, por ejemplo, la profundidad y velocidad de la incisión, la falta de relación entre puntos de máxima intervención y los de mayor incisión o la continuidad del proceso cuarenta años después de cesar ese tipo de acciones. La respuesta a estos desajustes está en el papel que está jugando la exhumación del sustrato pleistoceno infrayacente, afectado por procesos sinsedimentarios de karstificación. La aparición de paleodolinas rellenas de sedimentos finos en el fondo y laterales de la incisión es actualmente el principal determinante de su importancia y continuidad. Además, estas paleodepresiones dirigen la dinámica y trazado del rÃo y puntualmente favorecen ensanchamientos laterales. Esto propicia la aparición de un nuevo lecho (Qt13) a medida que el lecho de los años 1960 (Qt12) va quedando como una terraza colgada entre 5 y 11 m sobre el nuevo fondo aluvial. No hay antecedentes de este tipo de consecuencias en la dinámica fluvial regional
Inhibition of hyaluronidase activity by high-pressure treated onion
Onions exert their effects on human health via multiple different functions, including antioxidant,
antiinflammatory, and antibacterial properties. Upregulation of hyaluronidase activity occurs in
chronic inflammatory conditions. High hydrostatic pressure food processing offers the chance of
producing functional foods, in the sense that not only preserve the nutritional, microbiological
and sensorial quality of foods, but also can improve the extraction of potentially health-related
compounds due to the effects of this technology on plant food structure. Onions are a good
source of bioactive compounds, such as phenolic compounds and organosulfur compounds,
which have been related to beneficial health effects mainly due to their antioxidant and
antiinflammatory properties. In this study we evaluated the ability of onion treated by highpressure
to inhibit in vitro hyaluronidase activity, as an in vitro measurement of its
antiinflammatory activity.Peer Reviewe
Pore water chemistry of a Paleogene continental mudrock in Spain and a Jurassic marine mudrock in Switzerland: Sampling methods and geochemical interpretation
Este trabajo resume una serie de metodologÃas y aproximaciones desarrolladas en CIEMAT durante los últimos 10 años con el objetivo de obtener información del agua intersticial de dos formaciones arcillosas: la Opalinus Clay procedente de Suiza y una formación de edad Oligoceno Mioceno española. Ambas tienen caracterÃsticas bastante diferentes tanto desde el punto de vista de la metodologÃa aplicada para su estudio como del origen sedimentario en sà mismo de las dos formaciones. La arcilla Suiza se estudió a través de la participación en el experimento DI-B en el laboratorio subterráneo de Mont Terri, en Suiza, uno de cuyos objetivos fue el muestreo y análisis in situ del agua intersticial de la arcilla. Las muestras de agua se recogieron después de desarrollar equipos y metodologÃas para conseguir una alteración mÃnima de los parámetros crÃticos del agua de la arcilla: pH, Eh, pCO2, Fe(II) y alcalinidad. La modelización geoquÃmica se utilizó como herramienta para interpretar y entender los principales procesos geoquÃmicos que controlan la quÃmica del agua y el estado actual del sistema. En relación con la arcilla española, el artÃculo muestra el desarrollo de una metodologÃa integrada para caracterizar el agua intersticial de la formación arcillosa a partir de muestras de testigos correspondientes a un sondeo, denominados S1. El estudio trata de integrar todos los datos disponibles sobre la composición del agua intersticial obtenida mediante la técnica de compresión bajo presión (squeezing) y mediante extractos acuosos, con la caracterización mineralógica y geoquÃmica de los testigos. La modelización geoquÃmica se utilizó con dos objetivos principales: para valorar la consistencia de los datos analÃticos del agua intersticial y para determinar la importancia relativa de los principales procesos que gobiernan la quÃmica del agua intersticial. EspecÃficamente, la modelización se utilizó para simular los procesos que controlan la evolución redox del sistema. Se consideró equilibrio para los minerales reactivos como la calcita, dolomita, yeso y ferrihidrita. Además, se trató la degradación de la materia orgánica y la disolución oxidativa de la pirita desde un punto de vista cinético
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