Polytechnic University of Valencia

About: Polytechnic University of Valencia is a education organization based out in Valencia, Spain. It is known for research contribution in the topics: Catalysis & Population. The organization has 16282 authors who have published 40162 publications receiving 850234 citations.

Two Chloroplastic Viroids Induce the Accumulation of Small RNAs Associated with Posttranscriptional Gene Silencing

Abstract: In plants, posttranscriptional gene silencing (PTGS) has been reported for cytoplasmic RNAs from endogenous nuclear genes, transgenes, viruses, and, recently, for a viroid with nuclear replication and accumulation. However, phenomena of this kind have not been described for mitochondrial or chloroplastic RNAs. Here we show that viroids that replicate and accumulate in the chloroplast are also targets of PTGS and this process may control viroid titer.

Optimization of conventional and ultrasound assisted extraction of flavonoids from grapefruit (Citrus paradisi L.) solid wastes

Abstract: Flavonoid compounds from grapefruit wastes were obtained by conventional solid–liquid extraction (CE) and ultrasound assisted extraction (USE). Naringin was by far the most abundant flavonoid in the extracts ranging from 18 to 28 mg/g dw for CE and 24–36 mg/g dw for USE. Response surface methodology allowed obtaining predictive models for total phenolic content (TPC) and total antioxidant activity (TAA) as a function of the process variables ethanol concentration (EtC) (defined as weight of ethanol/weight of solution), temperature (T) and time (t) with reasonable success (CE-TPC, R2 = 0.86, CE-TAA, R2 = 0.85; USE-TPC, R2 = 0.82; USE, TAA, R2 = 0.86). USE was very effective when compared with conventional solvent extraction, allowing higher extraction yields (on average TPC 50% and TAA 66% higher) with lower temperatures and extraction times. Although the optimum process conditions indicate the use of a low ethanol concentration and ultrasounds (T = 25 °C, EtC = 0.4 (g/g) (40 g/100 g) and t = 55 min leading to TPC = 80.0 mg GAE/g dw and TAA = 38.3 mmol trolox/g dw), it has been proved that an USE treatment free of organic solvent (EtC = 0 g/g), at moderate temperature (25 °C) and short time (t = 3 min) leads to similar results (TPC = 75.3 mg GAE/g dw and TAA = 31.9 mmol trolox/g dw), suggesting its use for economic and environmental purposes.

High-pressure structural study of the scheelite tungstates CaWO 4 and SrWO 4

Abstract: Angle-dispersive x-ray-diffraction and x-ray-absorption near-edge structure measurements have been performed on ${\mathrm{CaWO}}_{4}$ and ${\mathrm{SrWO}}_{4}$ up to pressures of approximately 20 GPa. Both materials display similar behavior in the range of pressures investigated in our experiments. As in the previously reported case of ${\mathrm{CaWO}}_{4}$, under hydrostatic conditions ${\mathrm{SrWO}}_{4}$ undergoes a pressure-induced scheelite-to-fergusonite transition around 10 GPa. Our experimental results are compared to those found in the literature and are further supported by ab initio total-energy calculations, from which we also predict the instability at larger pressures of the fergusonite phases against an orthorhombic structure with space group Cmca. Finally, a linear relationship between the charge density in the $A{\mathrm{O}}_{8}$ polyhedra of $AB{\mathrm{O}}_{4}$ scheelite-related structures and their bulk modulus is discussed and used to predict the bulk modulus of other materials, like hafnon.