University of Valencia

About: University of Valencia is a education organization based out in Valencia, Spain. It is known for research contribution in the topics: Population & Context (language use). The organization has 27096 authors who have published 65669 publications receiving 1765689 citations. The organization is also known as: Universitat de València & UV.

Microbial responses to environmental arsenic.

Abstract: Microorganisms have evolved dynamic mechanisms for facing the toxicity of arsenic in the environment. In this sense, arsenic speciation and mobility is also affected by the microbial metabolism that participates in the biogeochemical cycle of the element. The ars operon constitutes the most ubiquitous and important scheme of arsenic tolerance in bacteria. This system mediates the extrusion of arsenite out of the cells. There are also other microbial activities that alter the chemical characteristics of arsenic: some strains are able to oxidize arsenite or reduce arsenate as part of their respiratory processes. These type of microorganisms require membrane associated proteins that transfer electrons from or to arsenic (AoxAB and ArrAB, respectively). Other enzymatic transformations, such as methylation-demethylation reactions, exchange inorganic arsenic into organic forms contributing to its complex environmental turnover. This short review highlights recent studies in ecology, biochemistry and molecular biology of these processes in bacteria, and also provides some examples of genetic engineering for enhanced arsenic accumulation based on phytochelatins or metallothionein-like proteins.

Molecular Electron Density Theory: A Modern View of Reactivity in Organic Chemistry

Abstract: A new theory for the study of the reactivity in Organic Chemistry, named Molecular Electron Density Theory (MEDT), is proposed herein. MEDT is based on the idea that while the electron density distribution at the ground state is responsible for physical and chemical molecular properties, as proposed by the Density Functional Theory (DFT), the capability for changes in electron density is responsible for molecular reactivity. Within MEDT, the reactivity in Organic Chemistry is studied through a rigorous quantum chemical analysis of the changes of the electron density as well as the energies associated with these changes along the reaction path in order to understand experimental outcomes. Studies performed using MEDT allow establishing a modern rationalisation and to gain insight into molecular mechanisms and reactivity in Organic Chemistry.

Lateralized effect of rapid-rate transcranial magnetic stimulation of the prefrontal cortex on mood

Abstract: We studied the effects of rapid-rate transcranial magnetic stimulation (rTMS) of different scalp positions on mood Ten normal volunteers rated themselves before and after rTMS on five analog scales labeled ``Tristeza99 (Sadness), ``Ansiedad99 (Anxiety), ``Alegria99 (Happiness), ``Cansancio99 (Tiredness), and ``Dolor/Malestar99 (Pain/Discomfort). rTMS was applied to the right lateral prefrontal, left prefrontal, or midline frontal cortex in trains of 5 seconds9 duration at 10 Hz and 110% of the subject9s motor threshold intensity. Each stimulation position received 10 trains separated by a 25-second pause. No clinically apparent mood changes were evoked by rTMS to any of the scalp positions in any subject. However, left prefrontal rTMS resulted in a significant increase in the Sadness ratings (Tristeza) and a significant decrease in the Happiness ratings (``Alegria99) as compared with right prefrontal and midfrontal cortex stimulation. These results show differential effects of rTMS of left and right prefrontal cortex stimulation on mood and illustrate the lateralized control of mood in normal volunteers. NEUROLOGY 1996,46 499-502.