Totes les vacances són diferents. És més beneficiós fer el descans anual sempre a la mateixa època i recordar-lo

Les vacances, el descans mensual, ens influeixen des del punt de vista psicològic i fisiològic, en vista de dos treballs científics recents que analitzen minuciosament els seus efectes.

Isothermal sections of the Ru-Si-Ge, Ru-Ge-Sn and Ru-Si-Sn systems at 900°C

The ternary systems Ruthenium-Silicon-Germanium, Ruthenium-Germanium-Tin and Ruthenium-Silicon-Tin were investigated by powder X-ray diffraction and electron microprobe analysis. Relations at 900 degrees C between solid phases are given and no ternary compound was found. Solubilities and evolution of lattice parameters have been correlated. Maximum mutual solubilities in the Si-Sn and Ge-Sn systems are given. (C) 1998 Elsevier Science S.A.

Galvanomagnetic effects in strongly doped p-Bi2Te3:Sn crystals

Magnetic field dependencies of Hall coefficient and magnetoresistivity are investigated in classical and quantizing magnetic fields in p-Bi2Te3 crystals heavily doped with Sn grown by Czochralsky method. Magnetic field was parallel to the trigonal axis C3. Shubnikov-de Haas effect and quantum oscillations of the Hall coefficient were measured at temperatures 4.2 K and 11 K. On the basis of the magnetic field dependence of the Hall coefficient a method of estimation of the Hall factor and Hall mobility using the Drabble- Wolf six ellipsoid model is proposed. Shubnikov-de Haas effect and quantum oscillations of the Hall coefficient were observed at 4.2 K and 11 K. New evidence for the existence of the narrow band of Sn impurity states was shown. This band is partly filled by electrons and it is overlapping with the valence states of the light holes. Parameters of the impurity states, their energy ESn - 15 meV, band broadening ¿<< k0T and localization radius of the impuritystate R - 30 Å were obtained.

Els enciams no són només per a l'amanida, també tenen cautxú

El cautxú és un polímer d'origen biològic que s'obté del làtex, un fluid d'aspecte lletós que es pot extreure de diverses plantes i que es fa servir com a primera matèria per manufacturar molts productes. També es pot produir de manera sintètica a partir de derivats del petroli, però de moment el natural presenta avantatges importants, com ara que és més elàstic i resistent a l'abrasió. Un nou estudi ha trobat una nova font de làtex: els enciams. L'hortalissa mediterrània podria passar de ser només un producte per a l'amanida a tenir un interès industrial, com ara fer rodes.

Les universitats són meritocràtiques o no són

La universitat catalana no és dolenta. No està en els millors llocs dels rànquings, però tampoc està ensorrada a la cua d'Europa. No és satisfactori no tenir cap universitat entre les 100 primeres, però hi ha raons que impedeixen millorar. Un finançament insuficient i, més determinant, una legislació que pretén que totes les universitats de l'Estat espanyol siguin iguals, que impedeix que es governin adequadament i que siguin eficaces. Retiment de comptes, zero

Són els símptomes de la fibromiàlgia la histèria del segle XXI?

Nowadays, fribromialgya is one of the nervous diseases with the highest comorbidity and chronic index. The peculiarity of this symptomatology is becausephysiological pain goes to different parts of the body. The symptomatology of fribromialgya and hysteria could have relation between them and even, sharing many similar simptoms. Therefore, we will focus on studyng two cases to resolve these questions and we will be able to see if fibromialgya has histerical symptoms.

Preparation and characterization oF Ru-Sn/Al2O3 catalysts for the hydrogenation of fatty acid methyl esters

Ru-Sn/Al2O3 catalysts with different Sn loadings were prepared by the coimpregnation method. Several characterization techniques such as TPR, pyridine TPD and catalytic tests for dehydrogenation and hydrogenolysis were used to evaluate and compare such catalysts. TPR results indicate that Sn is deposited both onto the support and as species strongly interacting with Ru. Such non selective deposition modifies the acid and metallic functions of the catalysts. Both total acidity and acid strength distribution are affected: total acidity decreases and new sites of lower acid strength are created. Both dehydrogenating and hydrogenolytic activities are strongly diminished by the addition of Sn. Results of catalytic tests for methyl oleate hydrogenation indicate that methyl stearate is the main product, with only minute amounts of oleyl alcohol produced, and that the addition of Sn diminishes the hydrogenation activity.

Utilization of Sn/Nb2O5 composite for the removal of methylene blue

In this work, the oxidation of methylene blue textile dye in the presence of hydrogen peroxide, using niobium oxide impregnated with different proportions of tin (1, 5 and 10% in mass) as catalyst was studied. The materials were characterized by TPR, XPS, XRD and FTIR. The oxidation tests monitored by ESI-MS showed that the composite containing the higher amount of tin was the most efficient in the removal of the dye. The XRD, XPS, and TPR data presented evidence of the formation of the tin-niobium oxide composite containing Sn0 and supported SnO2.

Determinação seletiva de tributilestanho na presença de Sn(IV) em amostras ambientais usando HG-ICP OES e Saccharomyces cerevisiae como material sorvente

A method for selective determination of tributyltin in the presence of Sn(IV) by combining hydride generation inductively coupled plasma optical emission spectrometry (HG-ICP OES) and solid phase extraction (SPE) using baker's yeast is proposed. The procedure is based on selective retention of TBT by the yeast at pH = 6. Detection limit of 1.9 µg L-1 and quantification limit of 6.3 µg L-1 were obtained. TBT and San(IV) were determined in the range of 0-25 µg L-1 and the proposed approach was applied to analyze river water, sea water and biological extracts, with recoveries of 114, 101 and 86%, respectively.

Síntesis de cúmulos de galio estabilizados por heterociclos de Ge (II) y Sn (II) análogos al carbeno con potenciales propiedades de semiconductores

Tesis (Maestría en Ciencias con Orientación en Química de los Materiales) UANL, 2011

Síntesis y caracterización de complejos de Sn(IV) derivados de ?-Amidofosfonatos . Evaluación de su efecto tóxico sobre artemia salina.

Tesis (Maestría en Ciencias con Orientación en Farmacia) UANL, 2012.

Ruta panorámica descriptiva del Ferrocarril Nacional de México y album mercantil, monumental y pintoresco de la ciudad de Querétaro para la exposición universal de Sn. Luis Missouri en 1904.

UANL