7,482 research outputs found
Lanthanide(III) complexes are more active inhibitors of the Fenton reaction than pure ligands
OBJECTIVES:
This study is an extension to our finding of direct anti-oxidant activities of lanthanide(III) complexes with the heterocyclic compound, 5-aminoorotic acid (AOA). In this experiment, we used AOA and coumarin-3-carboxylic acid as the two heterocyclic compounds with anti-oxidant potential, to produce the complexes with different lanthanides.
METHODS:
Lanthanide(III) complexes were tested on the iron-driven Fenton reaction. The product of this reaction, the hydroxyl radical, was detected by HPLC.
RESULTS:
All complexes as well as their ligands had positive or neutral effect on the Fenton reaction but their behavior was different. Both pure ligands in low concentration ratio to iron were inefficient in contrast to some of their complexes. Complexes of neodymium, samarium, gadolinium, and partly of cerium blocked the Fenton reaction at very low ratios (in relation to iron) but the effect disappeared at higher ratios. In contrast, lanthanum complexes appeared to be the most promising. Both blocked the Fenton reaction in a dose-dependent manner.
CONCLUSION:
Lanthanide(III) complexes were proven to block the iron-driven production of the hydroxyl radical. Second, the lanthanide(III) element appears to be crucial for the anti-oxidant effect. Overall, lanthanum complexes may be promising direct anti-oxidants for future testing
Garigliano nuclear power plant: seismic evaluation of the turbine building
The Italian Garigliano Nuclear Power Plant (NPP) started its energy production in 1963. At present it is in the decommissioning stage. In order to get a proper management of the radioactive waste that will be produced during the dismantling operations it has been considered convenient to convert the turbine building of the plant into a temporary waste repository. This decision posed a remarkable seismic safety assessment issue. As a matter of fact, the challenge was to extend, in satisfactory safety conditions, the use of an important facility that has reached the end of its designed lifetime and to have this extended use approved by nuclear safety agencies. In this context many tasks have been accomplished, of which the most important are:
(a) a new appraisal of site seismic hazard;
(b) the execution of many investigations and testing on the
construction materials;
(c) the set up of a detailed 3D finite element model including the explicit representation of foundation piles and soil;
(d) consideration of soil structure kinematic and dynamic nteraction effects.
This paper describes the adopted seismic safety assessment criteria which are based on a performance objectives design approach. While performance based design is the approach currently recommended by European Regulations to manage seismic risk and it is fully incorporated in the Italian code for conventional buildings, bridges and plants, NPP are not explicitly considered. Therefore it was necessary to delineate a consistent interpretation of prescribed rules in order to properly select the maximum and operating design earthquakes on one side and corresponding acceptable limit states on the other side. The paper further provides an outline of the numerical analyses carried out, of the main results obtained and of the principal retrofitting actions that will be realized
The luminosity evolution over the EQuiTemporal Surfaces in the prompt emission of Gamma-Ray Bursts
Due to the ultrarelativistic velocity of the expanding "fireshell" (Lorentz
gamma factor \gamma \sim 10^2 - 10^3), photons emitted at the same time from
the fireshell surface do not reach the observer at the same arrival time. In
interpreting Gamma-Ray Bursts (GRBs) it is crucial to determine the properties
of the EQuiTemporal Surfaces (EQTSs): the locus of points which are source of
radiation reaching the observer at the same arrival time. In the current
literature this analysis is performed only in the latest phases of the
afterglow. Here we study the distribution of the GRB bolometric luminosity over
the EQTSs, with special attention to the prompt emission phase. We analyze as
well the temporal evolution of the EQTS apparent size in the sky. We use the
analytic solutions of the equations of motion of the fireshell and the
corresponding analytic expressions of the EQTSs which have been presented in
recent works and which are valid for both the fully radiative and the adiabatic
dynamics. We find the novel result that at the beginning of the prompt emission
the most luminous regions of the EQTSs are the ones closest to the line of
sight. On the contrary, in the late prompt emission and in the early afterglow
phases the most luminous EQTS regions are the ones closest to the boundary of
the visible region. This transition in the emitting region may lead to specific
observational signatures, i.e. an anomalous spectral evolution, in the rising
part or at the peak of the prompt emission. We find as well an expression for
the apparent radius of the EQTS in the sky, valid in both the fully radiative
and the adiabatic regimes. Such considerations are essential for the
theoretical interpretation of the prompt emission phase of GRBs.Comment: 11 pages, 5 figures, in the Proceedings of the 1st Galileo-Xu GuangQi
Meeting, October 26-30, 2009, Shangha
Is arrhythmogenic right ventricular cardiomyopathy a paediatric problem too?
Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a heart muscle disease
that is often familial, characterized by arrhythmias of right ventricular origin, due to
transmural fatty or fibrofatty replacement of atrophic myocardium. ARVC is usually
diagnosed in the clinical setting between 20 and 40 years of age. The disease is
seldom recognised in infancy or under the age of 10, probably because the clinical
expression of the disease is normally postponed to youth and adulthood. This review
focuses its attention to the pediatric age, defined as the period of life raging from birth
to 18 years. During this span of life, ARVC is not so rare as previously supposed and
can be identified by applying the same diagnostic criteria proposed for the adult.
Ventricular arrhythmias range from isolated ventricular arrhythmias to sustained
ventricular tachycardia and fibrillation. Children and adolescents with ARVC must be
carefully evaluated and followed-up especially when a family positive history is
present, taking into account the high probability during this life-period that
asymptomatic affected patients become symptomatic or that arrhythmias worsen
during follow-up. The recent identification of the first defective gene opens new
avenues for the early identification of affected subjects even when asymptomatic.peer-reviewe
Topology and Dynamics in Complex Networks: The Role of Edge Reciprocity
A key issue in complex systems regards the relationship between topology and
dynamics. In this work, we use a recently introduced network property known as
steering coefficient as a means to approach this issue with respect to
different directed complex network systems under varying dynamics. Theoretical
and real-world networks are considered, and the influences of reciprocity and
average degree on the steering coefficient are quantified. A number of
interesting results are reported that can assist the design of complex systems
exhibiting larger or smaller relationships between topology and dynamics
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