Correlation between synthesis conditions, coherently diffracting domain size and cubic phase stabilization in barium titanate

The Constant Rate Thermal Analysis method has been used under different experimental conditions to obtain barium titanate powder of very small grain size. Both a crystallographic and a dielectric study ham been carried out on samples sintered at different temperatures. It is deduced that the formation of small coherently diffracting domains is improved by the generation of oxygen vacancies and the cubic phase stabilization depends on the coherently diffracting domain size rather than on the particle size.     

Medium and substitution pattern effects on the action of hydroxyflavones as photoprotectors against singlet molecular oxygen-mediated photooxidation of fats

The ability of mono-, di-, tri-and tetra-hydroxyflavones (7-and 3-hy-droxyflavones, 7, 8-dihydroxyflavone, baicalein and fisetin) to act as photoprotectors against singlet molecular oxygen [O²(Δ_g)]-initiated photooxidation of fats has been established by a kinetic study. The overall quenching rate constants for a series of five hydroxyflavones perfectly parallel their respective behaviour as inhibitors of the sensitized photooxidation of linoleic acid. The best antioxidative effect was exerted by 7-hydroxyflavone which does not chemically react with O²(¹Δ_g). Nevertheless for the remaining flavonoids of the series, the physical deactivation of O²(¹Δ_g) largely prevails over the chemical process. As for the cases of phenols and related hydroxy-aromatic derivatives, the ionization of the -OH group in the flavones, dramatically accelerates the rate of photooxidation. Under these conditions, the 7-hydroxyflavone also reacts effectively with O²(¹Δ_g). Given that flavonoids are natural oil components, this medium effect should be taken into account during the oil-refining process, in order to avoid the flavonoid photodestruction.     

Ridge hypoplasia and ridge dissociation: minor physical anomalies in autistic children

Ten term newborns underwent CT of the brain 12-24 h following vacuum extractor delivery. Haemorrhage in the area of the tentorium was demonstrated in all of them, with similar findings in all cases. CT 1 week later demonstrated reabsorption of the blood without demonstrating any other brain pathology. Clinical and CT examination a year after delivery did not reveal any abnormality. The haemorrhage appears to be a benign condition.     

Kinetics of the Initial Stage of Sintering from Shrinkage Data: Simultaneous Determination of Activation Energy and Kinetic Model from a Single Nonisothermal Experiment

A new method for the kinetic analysis of the initial stage of sintering for constant-heating-rate data has been proposed. Unlike all of the methods previously reported in the literature, this new method proposed here allows the simultaneous determination of the activation energy and the kinetic model from a single dilatometric curve recorded under a linear-heating-rate program. The proposed method has been tested with simulated sintering curves and experimental results have been obtained for the sintering of a rutile sample.     

Mechanosynthesis of complex oxides and preparation of mixed conducting nanocomposites for catalytic membrane reactors

Nanopowders of LaGaO₃- and LaMnO₃-based complex perovskites (P) and ceria-based fluorites (F) were prepared by mechanosynthesis. Compatible nanocomposites F + P and P + P with mixed ion and electron conducting (MIEC) properties were prepared and sintered at moderate temperatures up to dense ceramics. The obtained materials were studied by means of XRD, SEM, TEM, electrical conductivity measurements, temperature programmed (TP) reduction/oxidation and preliminary estimations of permeability were obtained. A new strategy based on the advantages of the mechanochemical ceramic approach is proposed to design multilayer ceramic membranes for CMR. Casting technology and one-step sintering were used for the production of thin film membranes with MIEC properties on porous substrates. The coarse fraction of as-milled powders from agglomerates with density 70% was used for the porous substrate, and fine fractions of aggregates with sizes <1 μm were used in preparation of composites for thin dense films. Ceria-based composites prepared by the Pechini route and/or mechanochemical method are proposed as materials for protecting thin films.     

A coherence maximisation process for solving normative inconsistencies

Norms can be used in multi-agent systems for defining patterns of behaviour in terms of permissions, prohibitions and obligations that are addressed to agents playing a specific role. Agents may play different roles during their execution and they may even play different roles simultaneously. As a consequence, agents may be affected by inconsistent norms; e.g., an agent may be simultaneously obliged and forbidden to reach a given state of affairs. Dealing with this type of inconsistency is one of the main challenges of normative reasoning. Existing approaches tackle this problem by using a static and predefined order that determines which norm should prevail in the case where two norms are inconsistent. One main drawback of these proposals is that they allow only pairwise comparison of norms; it is not clear how agents may use the predefined order to select a subset of norms to abide by from a set of norms containing multiple inconsistencies. Furthermore, in dynamic and non-deterministic environments it can be difficult or even impossible to specify an order that resolves inconsistencies satisfactorily in all potential situations. In response to these two problems, we propose a mechanism with which an agent can dynamically compute a preference order over subsets of its competing norms by considering the coherence of its cognitive and normative elements. Our approach allows flexible resolution of normative inconsistencies, tailored to the current circumstances of the agent. Moreover, our solution can be used to determine norm prevalence among a set of norms containing multiple inconsistencies.     

Adoption of beta structure by the inactivating "ball" peptide of the Shaker B potassium channel

The conformation of the inactivating peptide of the Shaker B K+ channel (ShB peptide) and that of a noninactivating mutant (ShBL7E peptide) have been studied. Under all experimental conditions explored, the mutant peptide remains in a predominantly nonordered conformation. On the contrary, the inactivating ShB peptide has a great tendency to adopt a highly stable beta structure, particularly when challenged "in vitro" by anionic phospholipid vesicles. Because the putative peptide binding elements at the inner mouth of the channel comprise a ring of anionic residues and a hydrophobic pocket, we hypothesize that the conformational restrictions imposed on the ShB peptide by its interaction with the anionic lipid vesicles could partly imitate those imposed by the above ion channel elements. Thus, we propose that adoption of beta structure by the inactivating peptide may also occur during channel inactivation. Moreover, the difficulties encountered by the noninactivating ShBL7E peptide mutant to adopt beta structure and the observation that trypsin hydrolysis of the ShB peptide prevent both structure formation and channel inactivation lend further support to the hypothesis that adoption of beta structure by the inactivating peptide in a hydrophobic environment is important in determining channel blockade.     

Catalytic Decomposition of Formic Acid on Metal Oxides

Studies on the decomposition of formic acid were initiated during the first decade of the present century by Mailhe and Sabatier [1], using metals and metal oxides. These authors were concerned primarily with the selectivity of their catalysts, i.e., their ability to favor one of the reactions possible for the decomposition of formic acid (Eq. 1).     

MaNEA: A distributed architecture for enforcing norms in open MAS

Norms have been promoted as a coordination mechanism for controlling agent behaviours in open MAS. Thus, agent platforms must provide normative support, allowing both norm-aware and non-norm-aware agents to take part in MAS that are controlled by norms. In this paper, the most relevant proposals on the definition of norm enforcement mechanisms are analyzed. These proposals present several drawbacks that make them unsuitable for open MAS. In response to these problems, this paper describes a new Norm-Enforcing Architecture aimed at controlling norms in open MAS. Specifically, this architecture supports the creation and deletion of norms on-line as well as the dynamic activation and expiration of instances. Finally, it can dynamically adapt to different scale MAS. The efficiency of this architecture has been experimentally evaluated and the results are shown in this paper.