Hidrólisis del ácido salicilsalicílico en medio fuertemente básico

Se ha estudiado la hidrólisis del ácido salicilsalicílico en medio acuoso fuertemente básico (pH = 11,6), a las temperaturas de 10, 20, 25, 30, 35, 40, 45 y 50°C. La citada reacción ha sido seguida por espectro fotometría. Se han calculado los valores de la costante de velocidad así como los parámetros termodinámicos correspondientes al proceso global

Hidrólisis del ácido salicilsalicílico en medio fuertemente básico

Se ha estudiado la hidrólisis del ácido salicilsalicílico en medio acuoso fuertemente básico (pH = 11,6), a las temperaturas de 10, 20, 25, 30, 35, 40, 45 y 50°C. La citada reacción ha sido seguida por espectro fotometría. Se han calculado los valores de la costante de velocidad así como los parámetros termodinámicos correspondientes al proceso global

I-mode studies at ASDEX Upgrade: L-I and I-H transitions, pedestal and confinement properties

The I-mode is a plasma regime obtained when the usual L-H power threshold is high, e.g. with unfavourable ion B ∇ direction. It is characterised by the development of a temperature pedestal while the density remains roughly as in the L-mode. This leads to a confinement improvement above the L-mode level which can sometimes reach H-mode values. This regime, already obtained in the ASDEX Upgrade tokamak about two decades ago, has been studied again since 2009 taking advantage of the development of new diagnostics and heating possibilities. The I-mode in ASDEX Upgrade has been achieved with different heating methods such as NBI, ECRH and ICRF. The I-mode properties, power threshold, pedestal characteristics and confinement, are independent of the heating method. The power required at the L-I transition exhibits an offset linear density dependence but, in contrast to the L-H threshold, depends weakly on the magnetic field. The L-I transition seems to be mainly determined by the edge pressure gradient and the comparison between ECRH and NBI induced L-I transitions suggests that the ion channel plays a key role. The I-mode often evolves gradually over a few confinement times until the transition to H-mode which offers a very interesting situation to study the transport reduction and its link with the pedestal formation. Exploratory discharges in which n = 2 magnetic perturbations have been applied indicate that these can lead to an increase of the I-mode power threshold by flattening the edge pressure at fixed heating input power: more heating power is necessary to restore the required edge pressure gradient. Finally, the confinement properties of the I-mode are discussed in detail.European Commission (EUROfusion 633053

Polarografía de complejos de ácido acetilsalicílico con Zn(II)

Polarographic waves of Zn(II) and acetysalicylic acid Zn(II) complexes in CIK 1 M (ph = 6,5) are reported. Electrochemical reduction of metallic cation has been analyzed by means conventional and oscilopolarographic methods. The formation constants of comple.xes (ASA)Zn + and (ASA)2 Zn have been calculated.Se ha realizado un estudio polarográfico de complejos del ácido acetilsalicílico con Zn(II) en Clk 1 M (ph = 6,5). El proceso de reducción del catión metálico es analizado por medidas polarográficas convencionales y oscilopolarográficas. Se han calculado los valores de las constantes de formación de los complejos (ASA) Zn + y (ASA)2 Zn

The unusual persistence of an ozone hole over a southern mid-latitude station during the Antarctic spring 2009: a multi-instrument study

International audienceRecord-low ozone column densities (with a minimum of 212 DU) persisted over three weeks at the Río Gallegos NDACC (Network for the Detection of Atmospheric Composition Change) station (51.5° S, 69.3° W) in November 2009. Total ozone remained two standard deviations below the climatological mean for five consecutive days during this period. The statistical analysis of 30 years of satellite data from the Multi Sensor Reanalysis (MSR) database for Río Gallegos revealed that such a long-lasting low-ozone episode is a rare occurrence. The event is examined using height-resolved ozone lidar measurements at Río Gallegos, and observations from satellite and ground-based instruments. The computed relative difference between the measured total ozone and the climatological monthly mean shows reductions varying between 10 and 30% with an average decrease of 25%. The mean absolute difference of total ozone column with respect to climatological monthly mean ozone column is around 75 DU. Extreme values of the UV index (UVI) were measured at the ground for this period, with the daily maximum UVI of around 13 on 15 and 28 November. The high-resolution MIMOSA-CHIM (Modélisation Isentrope du transport Méso-échelle de l'Ozone Stratosphérique par Advection) model was used to interpret the ozone depletion event. An ozone decrease of about 2 ppmv was observed in mid-November at the 550 K isentropic level (~22 km). The position of Río Gallegos relative to the polar vortex was classified using equivalent latitude maps. During the second week of November, the vortex was over the station at all isentropic levels, but after 20 November and until the end of the month, only the 10 lower levels in the stratosphere were affected by vortex overpasses with ozone poor air masses. A rapid recovery of the ozone column density was observed later, due to an ozone rich filament moving over Río Gallegos between 18 and 24 km in the first two weeks of December 2009

Polarografía de complejos de ácido acetilsalicílico con Zn(II)

Se ha realizado un estudio polarográfico de complejos del ácido acetilsalicílico con Zn(II) en Clk 1 M (ph = 6,5). El proceso de reducción del catión metálico es analizado por medidas polarográficas convencionales y oscilopolarográficas. Se han calculado los valores de las constantes de formación de los complejos (ASA) Zn + y (ASA)2 Zn.Polarographic waves of Zn(II) and acetysalicylic acid Zn(lI) complexes in CIK 1 M (ph = 6,5) are reported. Electrochemical reduction of metallic cation has been analyzed by means conventional and oscilopolarographic methods. The formation constants of comple.xes (ASA)Zn + and (ASA)z Zn have been calculated

Single-Molecule Analysis of the Human Telomerase RNA·Dyskerin Interaction and the Effect of Dyskeratosis Congenita Mutations†

It has been proposed that human telomerase RNA (hTR) interacts with dyskerin, prior to assembly of the telomerase holoenzyme. The direct interaction of dyskerin and hTR has not been demonstrated and is an experimentally challenging research problem because of difficulties in expressing and purifying dyskerin in quantities that are useful for biophysical analysis. By orthogonally labeling dyskerin and hTR, we have been able to employ single-molecule two-color coincidence detection (TCCD) to observe directly the formation of a dyskerin·hTR complex. By systematic deletion of hTR subdomains, we have gained insights into the RNA sites required for interaction with dyskerin. We then investigated mutated forms of hTR and dyskerin that are associated with dyskeratosis congenita (DC), on the basis of clinical genetics studies, for their effects on the dyskerin·hTR interaction. Dyskerin mutations associated with X-linked DC resulted in significant impairment of the dyskerin·hTR interaction, whereas mutations in hTR associated with autosomal dominant (AD) DC did not affect the interaction. We propose that disruption of the dyskerin·hTR interaction may contribute to X-linked DC

Evaluating Nuclei Concentration in Amyloid Fibrillation Reactions Using Back-Calculation Approach

Background: In spite of our extensive knowledge of the more than 20 proteins associated with different amyloid diseases, we do not know how amyloid toxicity occurs or how to block its action. Recent contradictory reports suggest that the fibrils and/or the oligomer precursors cause toxicity. An estimate of their temporal concentration may broaden understanding of the amyloid aggregation process. Methodology/Principal Findings: Assuming that conversion of folded protein to fibril is initiated by a nucleation event, we back-calculate the distribution of nuclei concentration. The temporal in vitro concentration of nuclei for the model hormone, recombinant human insulin, is estimated to be in the picomolar range. This is a conservative estimate since the back-calculation method is likely to overestimate the nuclei concentration because it does not take into consideration fibril fragmentation, which would lower the amount of nuclei Conclusions: Because of their propensity to form aggregates (non-ordered) and fibrils (ordered), this very low concentration could explain the difficulty in isolating and blocking oligomers or nuclei toxicity and the long onset time for amyloid diseases