University of Córdoba (Spain)

About: University of Córdoba (Spain) is a education organization based out in Cordova, Spain. It is known for research contribution in the topics: Population & Catalysis. The organization has 12006 authors who have published 22998 publications receiving 537842 citations. The organization is also known as: University of Córdoba (Spain) & Universidad de Córdoba.

The stability of P2-layered sodium transition metal oxides in ambient atmospheres

Abstract: Air-stability is one of the most important considerations for the practical application of electrode materials in energy-harvesting/storage devices, ranging from solar cells to rechargeable batteries. The promising P2-layered sodium transition metal oxides (P2-NaxTmO2) often suffer from structural/chemical transformations when contacted with moist air. However, these elaborate transitions and the evaluation rules towards air-stable P2-NaxTmO2 have not yet been clearly elucidated. Herein, taking P2-Na0.67MnO2 and P2-Na0.67Ni0.33Mn0.67O2 as key examples, we unveil the comprehensive structural/chemical degradation mechanisms of P2-NaxTmO2 in different ambient atmospheres by using various microscopic/spectroscopic characterizations and first-principle calculations. The extent of bulk structural/chemical transformation of P2-NaxTmO2 is determined by the amount of extracted Na+, which is mainly compensated by Na+/H+ exchange. By expanding our study to a series of Mn-based oxides, we reveal that the air-stability of P2-NaxTmO2 is highly related to their oxidation features in the first charge process and further propose a practical evaluating rule associated with redox couples for air-stable NaxTmO2 cathodes. Air-stability is a critical challenge faced by layered sodium transition metal oxide cathodes. Here, the authors depict a general and in-depth model of the structural/chemical evolution of P2-type layered oxides in air and propose an evaluation rule for the air-stability of layered sodium cathodes.

Cellular Location and Hormonal Regulation of Ghrelin Expression in Rat Testis

Abstract: Ghrelin, the endogenous ligand for the growth hormone-secretagogue receptor, is a recently cloned 28-amino acid peptide, expressed primarily in the stomach and hypothalamus, with the ability to stimulate growth hormone (GH) release and food intake. However, the possibility of additional, as yet unknown biological actions of ghrelin has been suggested. As a continuation of our recent findings on the expression and functional role of ghrelin in rat testis, we report here the pattern of cellular expression of ghrelin peptide in rat testis during postnatal development and after selective Leydig cell elimination, and we assess hormonal regulation of testicular ghrelin expression, at the mRNA and/or protein levels, in different experimental models. Immunohistochemical analyses along postnatal development demonstrated selective location of ghrelin peptide within rat testis in mature fetal- and adult-type Leydig cells. In good agreement, ghrelin protein appeared undetectable in testicular interstitium after selective Leydig cell withdrawal. In terms of hormonal regulation, testicular ghrelin mRNA and protein expression decreased to negligible levels after long-term hypophysectomy, whereas replacement with human chorionic gonadotropin (CG) (as superagonist of LH) partially restored ghrelin mRNA and peptide expression. Furthermore, acute administration of human CG (25 IU) to intact rats resulted in a transient increase in testicular ghrelin mRNA levels, with peak values 4 h after injection, an effect that was not mimicked by FSH (12.5 IU/rat). In contrast, testicular expression of ghrelin mRNA remained unaltered in GH-deficient rats, under hyper- and hypothyroidism conditions, as well as in adrenalectomized animals. In conclusion, our results demonstrate that mature Leydig cells are the source of ghrelin expression in rat testis, the protein being expressed in both fetal- and adult-type Leydig cells. In addition, our data indicate that testicular expression of ghrelin is hormonally regulated and is at least partially dependent on pituitary LH.

Diffuse Reflectance Spectroscopy

Abstract: The appearance of a soil results from the interaction of its different constituents with incident light. Color and various other attributes of the appearance of soil are highly sensitive to the nature, proportion, particle size and morphology, and spatial association of its mineral and organic components. In fact, color has been used for more than 75 yr to obtain information about these soil properties with a goal of characterizing and distinguishing soil types. The demand for a standardized method to describe soil color was met by the adoption of the Munsell notation by the USA Soil Survey Program in 1949 and, about 10 yr later, by the International Society of Soil Science (Simonson, 1993). Since then, Munsell Soil Color Charts (Munsell Color, 1975) have been systematically used by pedologists. Visual estimation of soil color, however, is subject to substantial error due to various psychophysical and physical factors. For this reason, the use of colorimeters and spectrophotometers has gained widespread acceptance among soil scientists as a means to measure color accurately and precisely. Moreover, different types of spectrophotometers afford the elucidation of the spectrum of light reflected by a soil illuminated in various ways. Reflectance, which is the base quantity that characterizes the process of reflection, is defined as the ratio of the reflected radiant flux (or power) to the incident radiant flux (or power) (Wyszecki and Stiles, 1982). Generally, the reflectance of a soil at any wavelength λ can be considered to be the sum of two components: regular (or specular, or mirror) reflectance and diffuse (or volume or nondirectional) reflectance (defined in more detail below). Reflectance measurements in the field are usually made on relatively large areas (>10 cm2). Under these conditions, both specular and diffuse reflectance usually contribute to the total reflectance of a soil surface, the magnitude of which depends on particle size, structure, microrelief, and other properties that define the “surface state” (Escadafal, 1989). In contrast, laboratory measurements of soil reflectance are usually made on small areas (<10 cm2) of disturbed soil materials that are usually sieved or ground to a small size. In this case diffuse reflectance predominates, which depends mainly on soil composition. This chapter describes available laboratory methods for recording diffuse reflectance spectra for soil materials and ways to handle the information to identify and characterize soil minerals. Only the visible and narrow vicinal ultraviolet (UV) and infrared (IR) regions of the spectrum are considered here because reflectance in the IR region is the subject of another chapter (Johnston and Aochi, 1996)).

Detecting People Looking at Each Other in Videos

Abstract: The objective of this work is to determine if people are interacting in TV video by detecting whether they are looking at each other or not. We determine both the temporal period of the interaction and also spatially localize the relevant people. We make the following four contributions: (i) head detection with implicit coarse pose information (front, profile, back); (ii) continuous head pose estimation in unconstrained scenarios (TV video) using Gaussian process regression; (iii) propose and evaluate several methods for assessing whether and when pairs of people are looking at each other in a video shot; and (iv) introduce new ground truth annotation for this task, extending the TV human interactions dataset (Patron-Perez et al. 2010) The performance of the methods is evaluated on this dataset, which consists of 300 video clips extracted from TV shows. Despite the variety and difficulty of this video material, our best method obtains an average precision of 87.6 % in a fully automatic manner.