Search results for "vanA"

Melting curve and phase diagram of vanadium under high-pressure and high-temperature conditions

2019

Melting curve and phase diagram of vanadium under high-pressure and high-temperature conditions We report a combined experimental and theoretical study of the melting curve and the structural behavior of vanadium under extreme pressure and temperature. We performed powder x-ray-diffraction experiments up to 120 GPa and 4000 K, determining the phase boundary of the body-centered cubic-to-rhombohedral transition and melting temperatures at different pressures. Melting temperatures have also been established from the observation of temperature plateaus during laser heating, and the results from the density-functional theory calculations. Results obtained from our experiments and calculations a…

High-pressure phase transformations in NdVO4 under hydrostatic, conditions: a structural powder x-ray diffraction study

2019

Room temperature angle dispersive powder x-ray diffraction experiments on zircon-type NdVO4 were performed for the first time under quasi-hydrostatic conditions up to 24.5 GPa. The sample undergoes two phase transitions at 6.4 and 19.9 GPa. Our results show that the first transition is a zircon-to-scheelite-type phase transition, which has not been reported before, and contradicts previous non-hydrostatic experiments. In the second transition, NdVO4 transforms into a fergusonite-type structure, which is a monoclinic distortion of scheelite-type. The compressibility and axial anisotropy of the different polymorphs of NdVO4 are reported. A direct comparison of our results with former experime…

New polymorph of InVO4: A high-pressure structure with six-coordinated vanadium

2013

A new wolframite-type polymorph of InVO4 is identified under compression near 7 GPa by in situ high-pressure (HP) X-ray diffraction (XRD) and Raman spectroscopic investigations on the stable orthorhombic InVO4. The structural transition is accompanied by a large volume collapse (Delta V/V = -14%) and a drastic increase in bulk modulus (from 69 to 168 GPa). Both techniques also show the existence of a third phase coexisting with the low- and high-pressure phases in a limited pressure range close to the transition pressure. XRD studies revealed a highly anisotropic compression in orthorhombic InVO4. In addition, the compressibility becomes nonlinear in the HP polymorph. The volume collapse in…

Analysis of the Diffusion-Induced Stress Effect on the Oxidation in Finely Divided Vanadium Ferrites

1999

L'oxydation isotherme des cations fer(II), vanadium(II) et vanadium(III) pour les ferrites spinelles finement divises, lesquels sont oxydes en phases deficitaires en cations, a ete etudiee par thermogravimetrie. La faible temperature de cinetique d'oxydation de chaque cation oxydable a ete expliquee en considerant que l'oxydation genere des contraintes qui en modifie la cinetique ou les cations a la surface sont plus oxydes que dans le volume. Pour cela, il at ete considere que le coefficient de diffusion chimique est donne par la relation D = D 0 exp [-(E' a + pV a )/RT] ou D 0 represente le facteur pre-exponentiel, E' a l'energie d'activation, V a le volume d'activation et p la pression i…

Enterokoku antibakteriālās rezistences un VAN gēnu noteikšana

2019

Aktualitāte: Pēdējo gadu laikā pasaulē strauji pieaug enterokoku rezistence pret antibakteriālajiem līdzekļiem. Tas rada nopietnas problēmas pacientu ārstēšanā. Ierosinātāji ir grampozitīvas baktērijas. Infekciju ierosinātāji visbiežāk ir grampozitīvas baktērijas, tajā skaitā arī enterokoki. Tāpēc, autores Maģistra darba mērķis bija: noteikt no klīniskā materiāla izolēto enterokoku antibakteriālo jutību, kā arī noteikt vankomicīna rezistences (van) gēnus. Darba uzdevumi bija: Noteikt antibakteriālo jutību Enterococcus sp. celmiem, izmantojot Kirby-Bauer disku difūzijas metodi, bet vankomicīna rezistences gēni enterokokos tika identificēti izmantojot Genotype Enterococcus testu. Laikā no 01.…

Toxicity of vanadium during development of sea urchin embryos: bioaccumulation, calcium depletion, ERK modulation and cell-selective apoptosis

2022

Vanadium toxicology is a topic of considerable importance as this metal is widely used in industrial and biomedical fields. However, it represents a potential emerging environmental pollutant because wastewater treatment plants do not adequately remove metal compounds that are subsequently released into the environment. Vanadium applications are limited due to its toxicity, so it is urgent to define this aspect. This metal is associated with sea urchin embryo toxicity as it perturbs embryogenesis and skeletogenesis, triggering several stress responses. Here we investigated its bioaccumulation and the correlation with cellular and molecular developmental pathways. We used cytotoxic concentra…

Technical-economical evaluation for distributed storage applications. An Italian case study for a medium-scale public facility

2014

Time-of-use energy cost management involves the use of storage by customers to reduce their electricity bills. This can be accomplished by charging the storage during off-peak time periods, when electricity energy prices are low, and discharging it during times when on-peak energy prices are applied. This article addresses the question whether it is economically viable to install medium-scale distributed storage devices in the power system designed to lower the electricity cost for a customer-side application, assuming flexible electricity tariffs. The technical/economical evaluation is carried out referring to Lithium ion (Li-ion), Sodium Sulphur (NaS) and Vanadium Redox Battery (VRB) tech…

Fabrication of cobalt and cobalt oxide/graphene composites: towards high-performance anode materials for lithium ion batteries.

2010

Comparative study of the high-pressure behavior of ZnV2O6, Zn2V2O7, and Zn3V2O8

2020

We report a study of the high-pressure structural behavior of ZnV2O6, Zn2V2O2, and Zn3V2O8, which has been explored by means of synchrotron powder x-ray diffraction. We found that ZnV2O6 and Zn3V2O8 remain in the ambient-pressure structure up to 15 GPa. In contrast, in the same pressure range, Zn2V2O2 undergoes three phase transitions at 0.7, 3.0, and 10.8 GPa, respectively. Possible crystal structures for the first and second high-pressure phases are proposed. Reasons for the distinctive behavior of Zn2V2O2 are discussed. The compressibility of the different polymorphs has been determined. The response to pressure is found to be anisotropic in all the considered compounds and the room-temp…

Sol–gel material as a support of organometallic catalyst for ethylene polymerization

2008

Abstract The sol–gel procedure was applied to obtain powdery materials with different structures and morphology. It was possible to produce almost non-porous silica powder, with an extremely low surface area (ca. 4 m 2 /g) and very high uniformity of spherical particles as well as materials with various uniformity of particles and different porosity, most likely associated with increasing pore volume. Dependent on the properties of the carrier, the resulting supported vanadium catalysts (VOCl 3 /AlEt 2 Cl) showed significant differences concerning activity and stability. It was confirmed that improved hydrophobicity of the carrier’s surface may be useful and improve the activity of the syst…