Large Amplitude Photocurrent In Photo-emf Experiments In Pure And Doped Absorbing Photorefractive Crystals

We report a mathematical formulation that successfully describes the holographic photocurrent produced in photo-emf experiments, with large oscillation amplitudes, in strongly absorbing photorefractive materials. The large amplitude produces a sensible enhancement of the photocurrent signal and in this way facilitates measurements. Accounting for bulk light absorption of the sample is essential in order to adequately describe the experiment. We measure pure and doped photorefractive Bi12TiO20 (BTO) crystals and show that these data are in excellent agreemnt with theory. From data fitting we are able to determine some material's parameters.4829 II953954Trofimov, G.S., Stepanov, S.I., (1986) Sov. Phys. Solid State, 28, pp. 1559-1562Petrov, M.P., Sokolov, I.A., Stepanov, S.I., Trofimov, G.S., (1990) J. Appl. Phys., 68, pp. 2216-2225Bittner, R., Meerholz, K., Stepanov, S., (1999) Appl. Phys. Lett., 74, pp. 3723-3725Korneev, N.A., Stepanov, S., (1993) J. Appl. Phys., 74, pp. 2736-2741Bryushinin, M.A., Dubrovsky, G.B., Sokolov, L.A., (1999) Appl. Phys. B, 68, pp. 871-87

Effect of silver on the phase transition and wettability of titanium oxide films

The effect of silver on the phase transition and microstructure of titanium oxide films grown by pulsed cathodic arc had been investigated by XRD, SEM and Raman spectroscopy. Following successive thermal annealing up to 1000 °C, microstructural analysis of annealed Ag-TiO2 films reveals that the incorporation of Ag nanoparticles strongly affects the transition temperature from the initial metastable amorphous phase to anatase and stable rutile phase. An increase of silver content into TiO2 matrix inhibits the amorphous to anatase phase transition, raising its temperature boundary and, simultaneously reduces the transition temperature to promote rutile structure at lower value of 600 °C. The results are interpreted in terms of the steric effects produced by agglomeration of Ag atoms into larger clusters following annealing which hinders diffusion of Ti and O ions for anatase formation and constrains the volume available for the anatase lattice, thus disrupting its structure to form rutile phase. The effect of silver on the optical and wetting properties of TiO2 was evaluated to demonstrate its improved photocatalytic performance

La Enseñanza y el aprendizaje de la química en el contexto de un currículo articulado desde concepciones científicas de interacción

En el presente trabajo se muestra la construcción, desarrollo y aplicación de unidades didácticas innovadoras abordando conceptos estructurantes como naturaleza corpuscular de la materia, cambio químico y cuantificación de relaciones, orientadas por un eje didáctico de resolución de problemas teniendo en cuenta los estándares curriculares nacionales y concepciones científicas de interacción. Las unidades didácticas derivadas de la conjugación de estas perspectivas científicas y educativas fueron aplicadas con estudiantes de educación media de varios Colegios de la ciudad de Bogotá

Treatment of sunitinib-induced hypertension in solid tumor by nitric oxide donors

[Abstract] Vascular endothelial growth factor (VEGF) and its receptor (VEGFR) are overexpressed in the majority of renal cell carcinomas. This characteristic has supported the rationale of targeting VEGF-driven tumour vascularization, especially in clear cell RCC. VEGF-inhibiting strategies include the use of tyrosine kinase inhibitors (sunitinib, axitinib, pazopanib, and sorafenib) and neutralizing antibodies such as bevacizumab. Hypertension (HTN) is one of the most common adverse effects of angiogenesis inhibitors. HTN observed in clinical trials appears to correlate with the potency of VEGF kinase inhibitor against VEGFR-2: agents with higher potency are associated with a higher incidence of HTN. Although the exact mechanism by tyrosine kinase inhibitors induce HTN has not yet been completely clarified, two key hypotheses have been postulated. First, some studies have pointed to a VEGF inhibitors-induced decrease in nitric oxide synthase (NOS) and nitric oxide (NO) production, that can result in vasoconstriction and increased blood pressure. VEGF, mediated by PI3K/Akt and MAPK pathway, upregulates the endothelial nitric oxide synthase enzyme leading to up-regulation of NO production. So inhibition of signaling through the VEGF pathway would lead to a decrease in NO production, resulting in an increase in vascular resistance and blood pressure. Secondly a decrease in the number of microvascular endothelial cells and subsequent depletion of normal microvessel density (rarefaction) occurs upon VEGF signaling inhibition. NO donors could be successfully used not only for the treatment of developed angiogenesis-inhibitor-induced hypertension but also for preventive effects

Refractometric Sensor Based On All-fiber Coaxial Michelson And Mach-zehnder Interferometers For Ethanol Detection In Fuel

A refractometric sensor based on mechanically induced interferometers formed with long period gratings is reported. It is also shown two different setups based on a Michelson and Mach-Zender interferometer and its application to measure ethanol concentration in gasoline.2741OSA,SPIE,ICO,JPCS,Quantel,CIOAshish, M.V., Lemaire, P.J., Judkins, J.B., Bhatia, V., Turan, E., Sipe, J.E., (1996) J. Lightwave Tech., 14 (1)James, S.W., Tatam, R.P., (2003) Meas. Sci. Technol., 14, pp. R49-R61Chomát, M., Berková, D., Matejec, V., Kasík, I., Kanka, J., Slavík, R., Jancárek, A., Bittner, P., (2006) Mater. Sci. Eng. C, 26, pp. 457-461Petrovic, J.S., Dobb, H., Mezentsev, V.K., Kyriacos, K., Webb, D.J., Bennion, I., (2007) J. Lightwave Tech., 25 (5)Chan, H.M., Fares, A., Tomov, I.V., Lee, H.P., (2008) IEEE Photon. Technol. Lett., 20 (8)Dürr, F., Rego, G., Marques, P.V.S., Semjonov, S.L., Dianov, E.M., Limberger, H.G., Salathé, R.P., (2005) J. Lightwave Tech., 23 (11)Smietana, M., Bock, W.J., Mikulic, P., (2010) Meas. Sci. Technol., 21Savin, S., Digonnet, M.J.F., Kino, G.S., Shaw, H.J., (2000) Optic. Lett., 25 (10)Xiaojun, Z., Chen, C., Zhang, Z., Qin, Z., Liu, Y., (2009) 14th OptoElectronics and Communications Conf. OECC, , art. No 5218070Swart, P.L., (2004) Meas. Sci. Technol., 15, pp. 1576-1580Barrios, P., Sáez, R.D., Rodríguez, A., Cruz, J.L., Díez, A., Andrés, M.V., (2009) J. Sensors, , ID 815409Liu, Y., Williams, J.A.R., Zhang, L., Bennion, I., (1999) Opt. Commun., 164, pp. 27-31Wei, T., Lan, X., Xiao, H., (2009) IEEE Photon. Technol. Lett., 21 (10), pp. 669-671Young-Geun, H., Lee, B.H., Won-Taek, H., Paek, U.C., Chung, Y., (2001) Meas. Sci. Technol., 12, pp. 778-781Falate, R., Kamikawachi, R.C., Fabris, J.L., Müller, M., Kalinowski, H.J., Ferri, F.A.S., Czelusniak, L.K., (2003) Proc. Microwave and Optoelectronics Conference (20-23 Sept 2003), 2, pp. 907-91

A Consistent Picture Emerges: A Compact X-ray Continuum Emission Region in the Gravitationally Lensed Quasar SDSS J0924+0219

We analyze the optical, UV, and X-ray microlensing variability of the lensed quasar SDSS J0924+0219 using six epochs of Chandra data in two energy bands (spanning 0.4-8.0 keV, or 1-20 keV in the quasar rest frame), 10 epochs of F275W (rest-frame 1089A) Hubble Space Telescope data, and high-cadence R-band (rest-frame 2770A) monitoring spanning eleven years. Our joint analysis provides robust constraints on the extent of the X-ray continuum emission region and the projected area of the accretion disk. The best-fit half-light radius of the soft X-ray continuum emission region is between 5x10^13 and 10^15 cm, and we find an upper limit of 10^15 cm for the hard X-rays. The best-fit soft-band size is about 13 times smaller than the optical size, and roughly 7 GM_BH/c^2 for a 2.8x10^8 M_sol black hole, similar to the results for other systems. We find that the UV emitting region falls in between the optical and X-ray emitting regions at 10^14 cm < r_1/2,UV < 3x10^15 cm. Finally, the optical size is significantly larger, by 1.5*sigma, than the theoretical thin-disk estimate based on the observed, magnification-corrected I-band flux, suggesting a shallower temperature profile than expected for a standard disk.Comment: Replaced with accepted version to Ap

Magnetic contributions in Bekenstein type models

In this work, we analyze the spatial and time variation of the fine structure constant (α) upon the theoretical framework developed by Bekenstein (Phys. Rev. D 66, 123514 (2002)PRVDAQ0556-282110.1103/PhysRevD.66.123514). We have computed the field ψ related to α at first order of the weak-field approximation and have also improved the estimation of the nuclear magnetic energy and, therefore, their contributions to the source term in the equation of motion of ψ. We obtained that the results are similar to the ones published in L. Kraiselburd and H. Vucetich, Int. J. Mod. Phys. E 20, 101 (2011) which were computed using the zero order of the approximation, showing that one can neglect the first order contribution to the variation of the fine structure constant. Through the comparison between our theoretical results and the observational data of the Eötvös-type experiments or the time variation of α over the cosmological time scale, we set constraints on the free parameter of the Bekenstein model, namely the Bekenstein length.Fil: Kraiselburd, Lucila. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Área Física Teórica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Castillo, Florencia L.. Universidad de Valencia; España. Consejo Superior de Investigaciones Científicas; EspañaFil: Mosquera, Mercedes Elisa. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Vucetich, Hector. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Área Física Teórica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentin

Pasture Production After Sewage Sludge and Liming Application on Highlands in North West Spain

In recent years, a sewage sludge surplus has been created in the EU countries, due to the Urban Waste Water Treatment Directive 91/271/CEE. Therefore, it is necessary to find adequate disposal for these residues in accordance with EU policy. Organic matter and nutrient sewage sludge contain principally N, indicating that it could be used as fertiliser. The main risk of this residue is its heavy metal content, whose solubility is usually increased as soil pH declines. The objective of this experiment was to determine the effect of liming and sewage sludge application on pasture production in a silvopastoral system located on acid soi