Anomaly in the dielectric response at the charge orbital ordering transition of crystalline Pr0.67Ca0.33MnO3

The complex impedance of a Pr0.67Ca0.33MnO3 crystal has been measured. The frequency dependence is studied for a wide range of temperatures (50K-403K) and is found to be characteristic of relaxation process with a single Debye time relaxation constant, which is interpreted as a dielectric constant of the material. A strong peak is observed in this dielectric constant (up to two millions) at the charge ordering transition suggesting an interpretation in terms of ordering of electric dipoles at TCO or in term of phase separation. Comparison with Pr0.63Ca0.37MnO3 - in which the phase separation is much smaller and the peak in the dielectric constant is absent - suggests an interpretation in term of phase separation between insulating and metallic states.Comment: pdf fil

Disruption of Yarrowia lipolytica TPS1 Gene Encoding Trehalose-6-P Synthase Does Not Affect Growth in Glucose but Impairs Growth at High Temperature

We have cloned the Yarrowia lipolytica TPS1 gene encoding trehalose-6-P synthase by complementation of the lack of growth in glucose of a Saccharomyces cerevisiae tps1 mutant. Disruption of YlTPS1 could only be achieved with a cassette placed in the 3′half of its coding region due to the overlap of its sequence with the promoter of the essential gene YlTFC1. The Yltps1 mutant grew in glucose although the Y. lipolytica hexokinase is extremely sensitive to inhibition by trehalose-6-P. The presence of a glucokinase, insensitive to trehalose-6-P, that constitutes about 80% of the glucose phosphorylating capacity during growth in glucose may account for the growth phenotype. Trehalose content was below 1 nmol/mg dry weight in Y. lipolytica, but it increased in strains expressing YlTPS1 under the control of the YlTEF1promoter or with a disruption of YALI0D15598 encoding a putative trehalase. mRNA levels of YlTPS1 were low and did not respond to thermal stresses, but that of YlTPS2 (YALI0D14476) and YlTPS3 (YALI0E31086) increased 4 and 6 times, repectively, by heat treatment. Disruption of YlTPS1 drastically slowed growth at 35°C. Homozygous Yltps1 diploids showed a decreased sporulation frequency that was ascribed to the low level of YALI0D20966 mRNA an homolog of the S. cerevisiae MCK1 which encodes a protein kinase that activates early meiotic gene expression

LOS PROCESOS DE APRENDIZAJE COMO PROPULSORES DEL CAMBIO EN LAS PYMES FORESTO INDUSTRIALES EN MISIONES

El presente trabajo tiene como objetivo analizar las conductas y acciones de los agentes, relacionadas con los cambios producidos por la aparición y difusión de elementos dinamizadores de dicho cambio de las Pequeñas y Medianas Empresas (PyMEs) del sector de la Foresto-industria y actividades relacionadas, los procesos de aprendizaje, que facilitarían el ingreso a un proceso de asociatividad dentro del sector. Se trata de una investigación cualitativa, en la que se recolectó información por medio de entrevistas a doce empresarios del sector de la Foresto-industria y actividades relacionadas, de la zona norte de la Provincia de Misiones (zona del Alto Paraná). Tal información fue analizada por medio del Programa Atlas ti versión 4.1. Para el análisis de los procesos de aprendizaje, se plantearon categorías previas que permitieron simplificar el procedimiento, a costa de condicionar la lectura. En primer término, por una cuestión de orden, se construyeron los marcos teóricos a partir de la praxis y la reflexión sobre el corpus estudiado, así como sobre los obstáculos y las dificultades encontradas. Ello exigió reunir una serie de conceptualizaciones y miradas alrededor de lo relevado y analizado. Sin pretender agotar las referencias, se recorrieron los numerosos aportes pluridisciplinarios respecto al comportamiento de las empresas para poder situar, con mayor precisión, el marco conceptual en que se encuadraban los casos encontrados para la presente investigación; desde allí se podría caracterizar los territorios y observar la relación entre los mismos, los actores locales y las empresas

Hand metastases from urothelial tumor.

Metastases to the hand are rare, particularly those of soft tissues. As a rule they arise in lung, breast, or kidney but other primary sites such as the bladder, have been described. We report a silent primary malignant tumor of the bladder, which came to light as soft tissue hand metastases

Photodynamically induced cytotoxicity of hypericin dye on human fibroblast cell line MRC5

The possible application of hypericin (hyp) in the photodynamic therapy (PDT) of cancer was investigated using the human fibroblast cell line MRC5. In aerobic conditions, at pH 7.4, irradiation of MRCS cells was carried out with different doses of visible light and different doses of hyp. A low concentration of hyp (5x10(-9) M) was highly toxic to MRC5 cells, producing 15% survival for an irradiation period of 40 min. In the dark, no cytotoxicity was observed in the range 10(-9)-10(-7) M hyp. The mechanism of cell killing by hyp was also examined. Significant inhibition of MRCS killing was observed on addition of 1,4-diazabicyclo[2,2,2]octane (DABCO) or histidine, known quenchers of type II mechanisms. In addition, the photodynamic effect of hyp was enhanced by deuterium oxide. The addition of desferrioxamine, catalase or superoxide dismutase (SOD), known scavenging agents of the type I mechanism, had a significant inhibitory effect on the rate of photodynamic action of hyp. The experimental results suggest that hyp has considerable potential for use as a sensitizer in the PDT of cancer