High frequency magnetic behavior through the magnetoimpedance effect in CoFeB/(Ta, Ag, Cu) multilayered ferromagnetic thin films

We studied the dynamics of magnetization through an investigation of the magnetoimpedance effect in CoFeB/(Ta, Ag, Cu) multilayered thin films grown by magnetron sputtering. Impedance measurements were analyzed in terms of the mechanisms responsible for their variations at different frequency intervals and the magnetic and structural properties of the multilayers. Analysis of the mechanisms responsible for magnetoimpedance according to frequency and external magnetic field showed that for the CoFeB/Cu multilayer, ferromagnetic resonance (FMR) contributes significantly to the magnetoimpedance effect at frequencies close to 470 MHz. This frequency is low when compared to the results obtained for CoFeB/Ta and CoFeB/Ag multilayers and is a result of the anisotropy distribution and non-formation of regular bilayers in this sample. The MImax values occurred at different frequencies according to the used non-magnetic metal. Variations between 25% and 30% were seen for a localized frequency band, as in the case of CoFeB/Ta and CoFeB/Ag, as well as for a wide frequency range, in the case of CoFeB/Cu.Comment: 14 pages, 5 figure

Light Controlled Spin Polarization In Asymmetric N -type Resonant Tunneling Diode

The authors have observed a strong dependence of the circular polarization degree from the quantum well emission in an asymmetric n -type GaAsAlAsAlGaAs resonant tunneling diode on both the laser excitation intensity and the applied bias voltage. The sign of the circular polarization can be reversed by increasing the light excitation intensity when the structure is biased with voltages slightly larger than the first electron resonance. The variation of polarization is associated with a large density of photogenerated holes accumulated in the quantum well, which is enhanced due to the asymmetry of the structure. © 2007 American Institute of Physics.917Hanbicki, A., Van Erve, O.M.J., Magno, R., Kioseoglou, G., Li, C.H., Jonker, B.T., Itskos, G., Petrou, A., (2003) Appl. Phys. Lett., 82, p. 4092Jiang, X., Wang, R., Shelby, R.M., MacFarlane, R.M., Bank, S.R., Harris, J.S., Parkin, S.S.P., (2005) Phys. Rev. Lett., 94, p. 056601Motsnyi, V.F., Van Dorpe, P., Van Roy, W., Goovaerts, E., Safarov, V.I., Borghs, G., De Boeck, J., (2003) Phys. Rev. B, 68, p. 245319Fiederling, R., Keim, M., Reuscher, G., Ossau, W., Schmidt, G., Waag, A., Molenkamp, L.W., (1999) Nature (London), 402, p. 787Ohno, Y., Young, D.K., Beschoten, B., Matsukura, F., Ohno, H., Awschalom, D., (1999) Nature (London), 402, p. 790Oestreich, M.J., Hübner, M.J., Hägele, D., Klar, P.J., Heimbrodt, W., Rühle, W.W., Ashenford, D.E., Lunn, B., (1999) Appl. Phys. Lett., 74, p. 1251Jonker, B.T., Park, Y.D., Bennett, B.R., Cheong, H.D., Kioseoglou, G., Petrou, A., (2000) Phys. Rev. B, 62, p. 8180Braden, J.G., Parker, J.S., Xiong, P., Chun, S.H., Samarth, N., (2003) Phys. Rev. Lett., 91, p. 056602Mattana, R., George, J.-M., Jaffr̀s, H., Nguyen Van Dau, F., Fert, A., Ĺpine, B., Guivarc'H, A., J́źquel, G., (2003) Phys. Rev. Lett., 90, p. 166601Gruber, Th., Keim, M., Fiederling, R., Reuscher, G., Ossau, W., Schmidt, G., Molenkamp, M., Waag, A., (2001) Appl. Phys. Lett., 78, p. 1101Slobodskyy, A., Gould, C., Slobodskyy, T., Becker, C.R., Schmidt, G., Molenkamp, L.W., (2003) Phys. Rev. Lett., 90, p. 246601De Carvalho, H.B., Galvão Gobato, Y., Brasil, M.J.S.P., Lopez-Richard, V., Marques, G.E., Camps, I., Henini, M., Hill, G., (2006) Phys. Rev. B, 73, p. 155317De Carvalho, H.B., Brasil, M.J.S.P., Galvão Gobato, Y., Marques, G.E., Galeti, H.V.A., Henini, M., Hill, G., (2007) Appl. Phys. Lett., 90, p. 62120Buhmann, H., Mansouri, L., Wang, J., Beton, P.H., Mori, N., Eaves, L., Henini, M., Potemski, M., (1995) Phys. Rev. B, 51, p. 7969Teran, F.J., Eaves, L., Mansouri, L., Buhmann, H., Maude, D.K., Potemski, M., Henini, M., Hill, G., (2005) Phys. Rev. B, 71, p. 161309Glasberg, S., Finkelstein, G., Shtrikman, H., Bar-Joseph, I., (1999) Phys. Rev. B, 59, p. 10425Vanhoucke, T., Hayne, M., Henini, M., Moshchalkov, V.V., (2002) Phys. Rev. B, 65, p. 041307Marie, X., Amand, T., Le Jeune, P., Paillard, M., Renucci, P., Golub, L.E., Dymnikov, V.D., Ivchenko, E.L., (1999) Phys. Rev. B, 60, p. 5811Van Kesteren, H.W., Cosman, E.C., Van Der Poel, W.A.J.A., Foxon, C.T., (1990) Phys. Rev. B, 41, p. 528

Polarization Resolved Luminescence In Asymmetric N -type Gaasalgaas Resonant Tunneling Diodes

We have investigated the polarized emission from a n -type GaAsAlGaAs resonant tunneling diode under magnetic field. The GaAs contact layer emission shows a large constant negative circular polarization. A similar result is observed for the quantum well, but only when electrons are injected from the substrate, while for inverted biases, the polarization tends to become positive for small voltages and large laser excitation intensities. We believe that the quantum well polarization may be associated to the partial thermalization of minority carriers on the well subbands and is thus critically dependent on the bias-controlled density of carriers accumulated in the well. © 2008 American Institute of Physics.9214Hanbicki, A., Van Erve, O.M.J., Magno, R., Kioseoglou, G., Li, C.H., Jonker, B.T., Itskos, G., Petrou, A., (2003) Appl. Phys. Lett., 82, p. 4092Jiang, X., Wang, R., Shelby, R.M., MacFarlane, R.M., Bank, S.R., Harris, J.S., Parkin, S.S.P., (2005) Phys. Rev. Lett., 94, p. 056601Motsnyi, V.F., Van Dorpe, P., Van Roy, W., Goovaerts, E., Safarov, V.I., Borghs, G., De Boeck, J., (2003) Phys. Rev. B, 68, p. 245319Fiederling, R., Keim, M., Reuscher, G., Ossau, W., Schmidt, G., Waag, A., Molenkamp, L.W., (1999) Nature (London), 402, p. 787Ohno, Y., Young, D.K., Beschoten, B., Matsukura, F., Ohno, H., Awschalom, D., (1999) Nature (London), 402, p. 790Oestreich, M.J., Hübner, M.J., Hägele, D., Klar, P.J., Heimbrodt, W., Rühle, W.W., Ashenford, D.E., Lunn, B., (1999) Appl. Phys. Lett., 74, p. 1251Jonker, B.T., Park, Y.D., Bennett, B.R., Cheong, H.D., Kioseoglou, G., Petrou, A., (2000) Phys. Rev. B, 62, p. 8180Braden, J.G., Parker, J.S., Xiong, P., Chun, S.H., Samarth, N., (2003) Phys. Rev. Lett., 91, p. 056602Mattana, R., George, J.-M., Jaffr̀s, H., Nguyen Van Dau, F., Fert, A., Ĺpine, B., Guivarc'H, A., J́źquel, G., (2003) Phys. Rev. Lett., 90, p. 166601Gruber, T., Keim, M., Fiederling, R., Reuscher, G., Ossau, W., Schmidt, G., Molenkamp, M., Waag, A., (2001) Appl. Phys. Lett., 78, p. 1101Slobodskyy, A., Gould, C., Slobodskyy, T., Becker, C.R., Schmidt, G., Molenkamp, L.W., (2003) Phys. Rev. Lett., 90, p. 246601De Carvalho, H.B., Galvão Gobato, Y., Brasil, M.J.S.P., Lopez-Richard, V., Marques, G.E., Camps, I., Henini, M., Hill, G., (2006) Phys. Rev. B, 73, p. 155317De Carvalho, H.B., Brasil, M.J.S.P., Galvão Gobato, Y., Marques, G.E., Galeti, H.V.A., Henini, M., Hill, G., (2007) Appl. Phys. Lett., 90, p. 062120Dos Santos, L.F., Galvão Gobato, Y., Marques, G.E., Brasil, M.J.S.P., Henini, M., Airey, R., (2007) Appl. Phys. Lett., 91, p. 073520Snelling, M.J., Blackwood, E., MacDonagh, C.J., Harley, R.T., Foxon, C.T.B., (1992) Phys. Rev. B, 45, p. 392

A novel enzymatically-mediated drug delivery carrier for bone tissue engineering applications: combining biodegradable starch-based microparticles and differentiation agents

In many biomedical applications, the performance of biomaterials depends largely on their degradation behavior. For instance, in drug delivery applications, the polymeric carrier should degrade under physiological conditions slowly releasing the encapsulated drug. The aim of this work was, therefore, to develop an enzymaticmediated degradation carrier system for the delivery of differentiation agents to be used in bone tissue engineering applications. For that, a polymeric blend of starch with polycaprolactone (SPCL) was used to produce a microparticle carrier for the controlled release of dexamethasone (DEX). In order to investigate the effect of enzymes on the degradation behavior of the developed system and release profile of the encapsulated osteogenic agent (DEX), the microparticles were incubated in phosphate buffer solution in the presence of a-amylase and/or lipase enzymes (at physiological concentrations), at 37 C for different periods of time. The degradation was followed by gravimetric measurements, scanning electron microscopy (SEM) and Fourier transformed infrared (FTIR) spectroscopy and the release of DEX was monitored by high performance liquid chromatography (HPLC). The developed microparticles were shown to be susceptible to enzymatic degradation, as observed by an increase in weight loss and porosity with degradation time when compared with control samples (incubation in buffer only). For longer degradation times, the diameter of the microparticles decreased significantly and a highly porous matrix was obtained. The in vitro release studies showed a sustained release pattern with 48% of the encapsulated drug being released for a period of 30 days. As the degradation proceeds, it is expected that the remaining encapsulated drug will be completely released as a consequence of an increasingly permeable matrix and faster diffusion of the drug. Cytocompatibility results indicated the possibility of the developed microparticles to be used as biomaterial due to their reduced cytotoxic effects

Metastatic deaths in retinoblastoma patients treated with intraarterial chemotherapy (ophthalmic artery chemosurgery) worldwide.

Ophthalmic artery chemosurgery [OAC, intra-arterial chemotherapy (IAC)] was introduced in 2006 as treatment modality for intraocular retinoblastoma. The purpose of this commentary is to retrospectively review the incidence of metastatic deaths in retinoblastoma patients treated with OAC worldwide over a 10 year period. Retrospective data regarding metastatic deaths was collected from six international retinoblastoma centers (New York City USA, Philadelphia USA, Sao Paulo Brazil, Siena Italy, Lausanne Switzerland and Buenos Aires Argentina). All retinoblastoma patients from these centers (naive and recurrent, unilateral and bilateral) treated with OAC/IAC since 2006 have been included in this study. Data regarding number of patients, number of OAC/IAC infusions, number unilateral and bilateral, number treated for naive disease or salvage and number of metastatic deaths have been assessed. Over a 10-year period of time 1139 patients received OAC/IAC for 4396 infusions. At last follow-up there were only three metastatic deaths (all treated in Buenos Aires). The current survey assessed the recorded risk of metastatic deaths in six retinoblastoma centers worldwide in children with retinoblastoma (unilateral or bilateral) treated with OAC/IAC as primary or secondary therapy. Overall, the observed risk for metastatic deaths from retinoblastoma was <1% in OAC/IAC treated children