Eduardo Martinez

NF-κB activation but not PI3K/Akt is required for dexamethasone dependent protection against TNF-α cytotoxicity in L929 cells

Tumor necrosis factor alpha (TNF‐α) is one of the best‐described cell death promoters. In murine L929 fibroblasts, dexamethasone inhibits TNF‐α‐induced cytotoxicity. Since phosphatidyl inositol 3 kinase (PI3K) and nuclear factor kappa B (NF‐κB) proteins regulate several survival pathways, we evaluated their participation in dexamethasone protection against TNF‐α cell death. We interfered with these pathways by overexpressing a negative dominant mutant of PI3K or a non‐degradable mutant of inhibitor of NF‐κB alpha (IκBα) (the cytoplasmic inhibitor of NF‐κB) in L929 cells. The mutant IκB, but not the mutant PI3K, abrogated dexamethasone‐mediated protection. The loss of dexamethasone protection was associated with a diminished accumulation in XIAP and c‐IAP proteins.

Termoluminescent Properties of High Sensitive ZrO2+PTFE for UV Radiation Dosimetry

This paper presents the preparation method, luminescent characteristics and the results of studying the thermoluminescence (TL) properties of zirconium oxide (ZrO2) exposed to 260 nm ultraviolet radiation. The glow curve of ZrO2+PTFE pellets exhibited one peak centered at 180°C about 30°C lower than that the commercially available aluminum oxide peak (Al2O3:C). TL response as a function of spectral irradiance showed good linear in the range from 2.4 to 3000 µJ/cm2 of spectral irradiance. Experimental results of studying the thermoluminescent (TL) properties of ZrO2+PTFE exposed to ultraviolet radiation allow to propose zirconium oxide as an excellent candidate as ultraviolet radiation dosimeter.

Evidence of short-range antiferroelectric local states in lanthanum- and titanium-modified Sr0.3Ba0.7Nb2O6 ferroelectric ceramics

Structural and electrical measurements were performed on lanthanum- and titanium-modified Sr0.3Ba0.7Nb2O6 ferroelectric (FE) ceramics. Dielectric properties show a well-defined relaxor anomaly around −50 °C with double-loop hysteresis curves from this point to the transition temperature. The thesis of short-range antiferroelectric (AFE) local states having incommensurate (INC) structure embedded in the FE polar matrix is proposed to explain the observed behavior. Structural lattice parameters show negative expansion coefficients and INC superlattice diffraction spots were observed through the selected-area diffraction patterns in the [110] zone for this minority local states. The titanium modification of this system seems to be the key fact in the coupling of the INC structure to the AFE local states in the FE–AFE coexistence region.

FERROELECTRIC CHARACTERIZATION AND AC-CONDUCTIVITY PROPERTIES OF Bi4 − xPrxTi3O12 POLYCRYSTALS

ABSTRACT Effects of Praseodymium doping on the ferroelectric properties of Bi4Ti3O12 using dense ceramics were systematically investigated from room temperature to 730°C. DRX studies show that Aurivillius structure can accept low amounts of praseodymium without the precipitation of second phases. Thermoelectric analysis and ferroelectric hysteresis measurements were performed and show that the incorporation of praseodymium modified the transition temperature (Tc) and slightly the polarization values. The incorporation of praseodymium resulted in a variation in the permittivity and in the remnant polarization. The polarization characteristics of the doped samples were different to those of Bi4Ti3O12. AC-conductivity was calculated for each sample and different conduction mechanisms are identified using the typical Arrhenius law.

High Pressure Deposition of Epitaxial PZT Thin Films on Sr(Nb)TiO 3

Epitaxial thin ferroelectric films of Pb(Zr 0.53 Ti 0.47 ) (PZT) were successfully grown on Sr(Nb)TiO 3 (SNTO) single crystal substrates by high-pressure rf sputtering. Pure O 2 was used as working gas at a pressure above 1 Torr. Deposition temperature was varied from 550°C to 600°C. Under these conditions we were able to deposit films at a rate of 2.7 A/min. Their crystalline properties, evaluated by Θ/2Θ, ω and φ scans, showed both in-plane and out of plane orientation. Film composition and film-substrate interface characteristics were studied by Rutherford Backscattering Spectroscopy (RBS). For RBS data the composition ratios for the films were calculated having obtained the expected values for a stoichiometric composition. A very thin diffusion layer of Pb at the film-substrate interface was also introduced. However, the deficiency in Pb, which is correlated to the presence of oxygen vacancies, is lower in our films produced at high O2 pressure than those reported for films produced by sputtering at lower pressures. The ferroelectric hysteresis loops measured in the Pt/PZT/SNTO heterostructures show good ferroelectric behavior with remanent polarizations of 12μ Ccm -2 and coercive field of 50kVcm -1 at 5V. The high-pressured technique representing a useful and capable method capable of obtaining in situ epitaxial, fully oxygenated, pyrochlore-free ferroelectric thin film with high quality structural, compositional and dielectric properties, without post deposit treatment.

Preparation and characterization of 0.5PMN-0.5PFN ceramics using [Fe0.6, Mg0.4]NbO4 as precursor

A study of the calcination and sintering processes of 0.5PMN-0.5PFN ceramics prepared starting from the specifically designed precursor compound [Fe0.6, Mg0.4]NbO4, is presented. The microstructural characteristics are determined using X-ray diffraction and scanning electron microscopy. The resulting dielectric properties of the PMN-PFN samples thus obtained were very good when compared with those reported in the literature, for samples prepared at higher calcination temperatures. The dielectric properties as functions of temperature and the hysteresis loops (P vs. E) under different external applied electric fields are reported.

Formation of the La0.03Sr0.255Ba0.7Nb2–yTiyO6–y/2 ferroelectric ceramic system

The study of the formation of the Sr0.255La0.03Ba0.7Nb2 − yTiyO6 − y/2 ferroelectric ceramic system and the influence of the sintering conditions and titanium concentration on the densification process is reported. A single-phase compound is observed for low titanium content (y ≤ 0.1) in the XRD spectra, being isostructural with the tetragonal tungsten bronze SBN phase. For high titanium concentrations (y > 0.1) the XRD patterns show, besides the tetragonal phase reflections, several small peaks evidencing an additional phase in the compound. This second phase was identified as isostructural to hexagonal Ba6Nb9Ti7O42. The grain size shows a linear increase with titanium content in the region of monophasic compositions and a possible liquid phase aided sintering process is analyzed.

Non-Linear Step-by-Step Seismic Response and the Push-Over Analysis Comparison of a Reinforced Concrete of Ductile Frames 15 Level Building

Based on a ductile frames 15 level building, a non-linear analysis with increased monotonically lateral loads (Push-Over) was made in order to determine its collapse and its principal responses were compared against the elastic and inelastic time-history seismic responses determined with the SCT-EW-85 record. The seismic-resistance design and faced to gravitational loads was made according to the Complementary Technical Norms of Concrete Structures Design (NTC-Concrete) and the NTC-Seismic of the Mexico City Code (RDF-04), satisfying the limit service states (relative lateral displacement between story height maximum relations, story drifts ≤ 0.012) and failure (seismic behavior factor, Q= 3). The compressible (soft) seismic zone IIIb and the office use type (group B) were considered. The non-linear responses were determined with nominal and over-resistance effects. The comparison were made with base shear force–roof lateral displacement relations, global distribution of plastic hinges, failure mechanics tendency, lateral displacements and story drift and its distribution along the height of the building, local and global ductility demands, etc. For the non-linear static analysis with increased monotonically lateral loads, it was important to select the type of lateral forces distribution.

Non Linear Step By Step Seismic Response and the Push Over Analysis Comparison of a Reinforced Concrete of Ductile Frames 25 Level Building

Based on a ductile frames 25 level building, a non‐linear analysis with increased monotonically lateral loads (Push‐Over) was made in order to determine its collapse and its principal responses were compared against the time‐history seismic responses determined with the SCT‐EW‐85 record. The seismic‐resistance design and faced to gravitational loads was made according to the Complementary Technical Norms of Concrete Structures Design (NTC‐Concrete) and the NTC‐Seismic of the Mexico City Code (RDF‐04), satisfying the limit service states (relative lateral displacement between story height maximum relations, story drifts ⩽0.012) and failure (seismic behavior factor, Q = 3). The compressible (soft) seismic zone IIIb and the office use type (group B) were considered. The non‐lineal responses were determined with nominal and over‐resistance effects. The comparison were made with base shear force‐roof lateral displacement relations, global distribution of plastic hinges, failure mechanics tendency, lateral disp...

Determination of ZrO2 Thermoluminescence Kinetic Parameters after UV Irradiation Using Peak Shape Methods

Various experimental methods are currently employed for the determination of the trap parameters. Methods based on the glow curve shape extract information from a glow peak utilizing the temperature at the maximum emission, TM, the temperature on the ascending part of the peak ,T1, which corresponding to half peak intensity and the temperature on the descending part of the peak, T2, also corresponding to the half peak intensity; as well as, the half width parameters and the symmetry properties. In order to obtain the kinetic order b and the trap parameters, ZrO2 samples were exposed to 260 nm ultraviolet radiation (UVR). The trapping kinetics parameters of the ZrO2 dosimetric peak using the shape of the glow curve were then determined. The order of kinetics followed by the main peak was also determined using the same method. The values of activation energy E and frequency factor ,s, for the main peak of ZrO2 obtained by the above mentioned methods, showed a good agreement among them.