University of Extremadura

About: University of Extremadura is a education organization based out in Badajoz, Spain. It is known for research contribution in the topics: Population & Hyperspectral imaging. The organization has 7856 authors who have published 18299 publications receiving 396126 citations. The organization is also known as: Universidad de Extremadura.

Toughening of super-hard ultra-fine grained B4C densified by spark-plasma sintering via SiC addition

Abstract: Toughening of super-hard B 4 C ceramics with ultra-fine grained microstructures via the addition of SiC (15 wt.%) or the simultaneous addition of SiC (15 wt.%) and graphite (2 wt.%) is reported. The ultra-fine grained B 4 C–SiC and B 4 C–SiC–C composites prepared by spark-plasma sintering from powder mixtures subjected to high-energy co-ball-milling are found to be remarkably tougher (i.e., ∼65% and 50%) than the pure B 4 C ceramic with a coarsened microstructure. Crack bridging by the homogenously dispersed SiC grains can give an explanation for the improvement in toughness. Also, the addition of SiC to the B 4 C matrix was found to change the fracture mode from purely transgranular to a mixture of intergranular and transgranular fracture. This is derived from the weakness of the B 4 C–SiC interfaces due to the existence of residual thermo-elastic stresses. It was also found that despite SiC is softer than B 4 C, the B 4 C–SiC are yet extremely hard if densified appropriately, with the hardness even reaching 36 GPa.

Neoproterozoic-early Cambrian geology and palaeontology of Iberia

Abstract: Neoproterozoic-early Cambrian successions in Iberia are reexamined. A gradual transition across the Neoproterozoic-Cambrian boundary is present in Central Iberia, whereas in the Cantabrian region and the Iberian Chains Lower Cambrian arenaceous successions rest with profound angular unconformity on Neoproterozoic turbidites. In Central Iberia, the Neoproterozoic sedimentary succession is referred to the informal Domo Extremeno group, representing mostly basinal facies, and the overlying Rio Huso group consisting of slope deposits and proximal turbidites that grade into shallower marine deposits. The latter is inferred to represent distal slope to outer platform depositional conditions and contains widespread carbonate olistostromic units. The position of the Precambrian-Cambrian boundary is within the Pusa shale of the Rio Huso group and can be correlated at the regional level by the occurrence of trace fossils, acritarchs, and in particular the abundant shelly metazoan Cloudina. The succession also yielded megascopic carbonaceous fossils, such as vendotaenids and Beltanelioides? sp. ind., and Sabellidites. Contrary to former interpretations assuming transport of older platform carbonates from the Ibor region into ‘younger’ olistostromic beds of the Rio Huso group, we interpret sedimentary and fossil evidence to suggest that shallower platform deposits of the informal Ibor group were penecontemporaneously incorporated in the olistostromic lower part of the Rio Huso group. Hence, the olistostromes are not believed to mark a major erosive unconformity. Based on the ichnofossil record and recent U-Pb age determinations, we argue that a proposed disconformity between Lower and Upper ‘Alcudian’ strata is neither regional nor does it mark a significant hiatus. Neoproterozoic-early Cambrian deposition in Central Iberia can be accommodated in a model that implies a generalized stretching of the crust during an extensional event which closely followed the Cadomian phase of the Pan-African Orogeny and which eventually could have included transcurrent components. An extensional phase with transcurrent components during the deposition of the Ibor and lower Rio Huso groups is regarded as a probable cause of widespread ponding resulting in the juxtaposition of platform and basinal successions, eventually leading to anoxic conditions in Pusa shale deposition times. A possible cause for repeated collapse events developing olistostromes and intra-sequential folding could be sought in this tectonic context.

Prevalence of overweight and obesity in non‐institutionalized people aged 65 or over from Spain: the elderly EXERNET multi‐centre study

Abstract: Coupled with the growth of the older population, an increase in the prevalence of overweight and obesity in this age group has occurred in the last decades. The main aims of the present study were (i) to provide an updated prevalence of overweight and obesity in a representative sample of the Spanish elderly population; (ii) to calculate the prevalence of sarcopenic obesity (SO) and (iii) to analyse the relationships between adiposity measurements and lifestyle. A cross-sectional study was carried out in a sample of 3136 persons representative of the non-institutionalized population ≥65 years of age. Anthropometric measurements were obtained using standardized techniques and equipment. Overall, 84% of the population can be categorized as overweight and/or obese. The present study indicates that 67% of the Spanish elderly population has an increased percentage of fat mass and more than 56% suffer from central obesity. Moreover, SO is present in 15% of the Spanish elderly population. Finally, a strong relationship between both physically active and sedentary lifestyles and the level of adiposity was found. Prevalence of overweight and obesity among elderly people in Spain is very high and is still increasing. Lifestyle seems to be a determinant factor in the development of obesity among elderly people.

Human NK cells in acute myeloid leukaemia patients: analysis of NK cell-activating receptors and their ligands

Abstract: Natural killer (NK) cell activation is strictly regulated to ensure that healthy cells are preserved, but tumour-transformed or virus-infected cells are recognized and eliminated. To carry out this selective killing, NK cells have an ample repertoire of receptors on their surface. Signalling by inhibitory and activating receptors by interaction with their ligands will determine whether the NK cell becomes activated and kills the target cell. Here, we show reduced expression of NKp46, NKp30, DNAM-1, CD244 and CD94/NKG2C activating receptors on NK cells from acute myeloid leukaemia patients. This reduction may be induced by chronic exposure to their ligands on leukaemic blasts. The analysis of ligands for NK cell-activating receptors showed that leukaemic blasts from the majority of patients express ligands for NK cell-activating receptors. DNAM-1 ligands are frequently expressed on blasts, whereas the expression of the NKG2D ligand MICA/B is found in half of the patients and CD48, a ligand for CD244, in only one-fourth of the patients. The decreased expression of NK cell-activating receptors and/or the heterogeneous expression of ligands for major receptors on leukaemic blasts can lead to an inadequate tumour immunosurveillance by NK cells. A better knowledge of the activating receptor repertoire on NK cells and their putative ligands on blasts together with the possibility to modulate their expression will open new possibilities for the use of NK cells in immunotherapy against leukaemia.