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.

Pathophysiology of Calcium, Phosphorus, and Magnesium Dysregulation in Chronic Kidney Disease

Abstract: Calcium, phosphorus, and magnesium homeostasis is altered in chronic kidney disease (CKD). Hypocalcemia, hyperphosphatemia, and hypermagnesemia are not seen until advanced CKD because adaptations develop. Increased parathyroid hormone (PTH) secretion maintains serum calcium normal by increasing calcium efflux from bone, renal calcium reabsorption, and phosphate excretion. Similarly, renal phosphate excretion in CKD is maintained by increased secretion of fibroblast growth factor 23 (FGF23) and PTH. However, the phosphaturic effect of FGF23 is reduced by downregulation of its cofactor Klotho necessary for binding FGF23 to FGF receptors. Intestinal phosphate absorption is diminished in CKD due in part to reduced levels of 1,25 dihydroxyvitamin D. Unlike calcium and phosphorus, magnesium is not regulated by a hormone, but fractional excretion of magnesium increases as CKD progresses. As 60-70% of magnesium is reabsorbed in the thick ascending limb of Henle, activation of the calcium-sensing receptor by magnesium may facilitate magnesium excretion in CKD. Modification of the TRPM6 channel in the distal tubule may also have a role. Besides abnormal bone morphology and vascular calcification, abnormalities in mineral homeostasis are associated with increased cardiovascular risk, increased mortality and progression of CKD.

Hydromaghemite, an intermediate in the hydrothermal transformation of 2-line ferrihydrite into hematite

Abstract: The hydrothermal transformation of 2-line ferrihydrite into hematite proceeds slowly if a suffi- cient quantity of some strongly adsorbing ligand, such as phosphate or citrate, is sorbed on the starting product. In this work, we studied such transformation at temperatures ranging from 125 to 200 ∞C, a molar P/Fe ratio of 0-6%, and a molar citrate/Fe ratio of 3%. The products were character- ized by X-ray diffraction (XRD), infrared spectroscopy, Mossbauer spectroscopy (MS) at various temperatures and in an applied field of 60 kOe, magnetic and thermal analysis, and transmission electron microscopy (TEM). At 150 ∞C, pure 2-line ferrihydrite transformed rapidly into hematite. The products of transformation of 2-line ferrihydrite with P/Fe = 2.75% or citrate/Fe = 3% had a magnetic susceptibility of >240 ∞ 10 -6 m 3 /kg and were, according to XRD and MS data, mixtures of hematite with structural P, 6-line ferrihydrite, and a magnetic phase. This phase exhibited most of the characteristic reflections and MS features of maghemite, and occurred as 7-30 nm subrounded particles with lattice fringes corresponding to the maghemite (310) and (220) planes. It was desig- nated "hydromaghemite" because it lost >3% water between 110 and ~350 ∞C. At 150 ∞C, complete transformation into hematite occurred in <120 days.

Designed multimetallic Pd nanosponges with enhanced electrocatalytic activity for ethylene glycol and glycerol oxidation

Abstract: We report an effective synthesis of surfactant-free multimetallic Pd nanosponges with tunable compositions using EDTA as the structure-directing reagent and NaBH4 as the reducing reagent. Among the mono-metallic Pd, binary PdNi and PdAu, ternary PdAuNi nanosponges and commercial Pt/C catalysts studied, Pd62Au21Ni17 nanosponges exhibit excellent activities and are the most efficient nanoparticle catalysts ever reported for both ethylene glycol and glycerol oxidation reactions.

Fertilizer Nitrogen Efficiency in Durum Wheat under Rainfed Mediterranean Conditions: Effect of Split Application

Abstract: Efficient N fertilizer management is critical for the economic production of wheat and the long-term protection of environmental quality. A 3-yr field experiment on a rainfed Vertisol was designed to study the effects of N fertilizer timing on the efficiency of N in durum wheat (Triticum turgidum L. var. durum Desf.). A single rate of 150 kg N ha -1 was used with different fractions being applied at planting, tillering, and stem elongation. A 15 N experiment was also conducted within the main experiment area, with microplots, to quantify N uptake from fertilizer and soil. Mean wheat recovery of N fertilizer ranged from 12.7% when applied at sowing to 41.6% when applied as a topdressing at the beginning of stem elongation. The mean annual contribution of soil residual N and mineralization was 167 kg N ha -1 , representing a considerable proportion of total wheat N uptake-ranging from 80.4% when N fertilizer was applied in the fall to 56.3% when it was applied at stem elongation. This would account for the poor and inconsistent response of grain yield and N efficiency indices, and for the importance of soil N in Vertisols for predicting wheat N fertilizer requirements, due to the carryover effect. It is recommended that N fertilizer be applied mainly as a topdressing in durum wheat, between tillering and stem elongation, to enhance crop N use efficiency (NUE) and reduce losses through leaching and runoff.