Capacitance Measurements for Subcell Characterization in Multijunction Solar Cells.

On this paper we present an alternative way to analyze de electronic properties of each subcell from the complete device. By illuminating the cell with light sources which energy is near one of the subcell bandgaps, it is possible to “erase” the presence of such subcell on the CV curve. The main advantages of this technique are that it is not destructive, it can be measured on the complete cell so can be easily implemented as a diagnostic technique for controlling electronic deviations

Subaru and Swift observations of V652 Herculis: resolving the photospheric pulsation

High-resolution spectroscopy with the Subaru High Dispersion Spectrograph, and Swift ultraviolet photometry are presented for the pulsating extreme helium star V652 Her. Swift provides the best relative ultraviolet photometry obtained to date, but shows no direct evidence for a shock at ultraviolet or X-ray wavelengths. Subaru has provided high spectral and high temporal resolution spectroscopy over six pulsation cycles (and eight radius minima). These data have enabled a line-by-line analysis of the entire pulsation cycle and provided a description of the pulsating photosphere as a function of optical depth. They show that the photosphere is compressed radially by a factor of at least 2 at minimum radius, that the phase of radius minimum is a function of optical depth and the pulse speed through the photosphere is between 141 and 239 km s−1 (depending how measured) and at least 10 times the local sound speed. The strong acceleration at minimum radius is demonstrated in individual line profiles; those formed deepest in the photosphere show a jump discontinuity of over 70 kms−1 on a time-scale of 150 s. The pulse speed and line profile jumps imply a shock is present at minimum radius. These empirical results provide input for hydrodynamical modelling of the pulsation and hydrodynamical plus radiative transfer modelling of the dynamical spectra

Sub-Nanosecond Switching of HV SiC MOS Transistors for Impact Ionisation Triggering

Pulse generators with multi kV/kA pulses are necessary for the particle accelerator environment for beam transfer magnets. Traditionally these generators are using thyratrons - until recently the only switches capable of switching such pulses within tens of ns. There is a strong demand to replace thyratrons with semiconductor switches to avoid their future obsolescence. Very promising candidates are components from the family of fast ionization dynistors triggered by impact ionization. Their sub-nanosecond switching time and extreme current densities can provide performances superior to that of thyratrons. Recent investigations showed that impact ionization triggering is feasible also in cheap industrial thyristors. The main issue is the generation of triggering pulses with slew rates in the multi kV/ns region and with the required output current for charging the parasitic capacitance of the thyristor. We present an approach of generating > 1 kV/ns pulses by ultra-boosted gate driving of HV SiC MOS transistors. We found that the MOS lifetime under these extreme triggering conditions can still reach more than 10⁸ pulses, enough for kicker generator applications

Ultra-Fast Generator for Impact Ionization Triggering

Impact ionization triggering can be successfully applied to standard thyristors, thus boosting their dI/dt capability by up to 1000x. This groundbreaking triggering requires applying significant overvoltage on the anode-cathode of thyristor with a slew rate > 1kV/ns. Compact pulse generators based on commercial off-the-shelf (COTS) components would allow the spread of this technology into numerous applications, including fast kicker generators for particle accelerators. In our approach, the beginning of the triggering chain is a HV SiC MOS with an ultra-fast super-boosting gate driver. The super boosting of a 1.7kV rated SiC MOS allows to reduce the MOS rise time by a factor of > 25 (datasheet tr = §I{20}{ns} vs. measured tr 1kV/ns and an amplitude > 1kV. Additional boosting is obtained by a Marx generator with GaAs diodes, reaching an output voltage slew rate > 11kV/ns. The final stage will be a Marx generator with medium size thyristors triggered in impact ionization mode with sufficient voltage and current rating necessary for the triggering of a big thyristor. This paper presents the impact ionization triggering of a small size thyristor

Semantic Construction and Form: Foundations of the Communicative Dimension in Contemporary Architecture

Aquest article investiga les característiques de la concepció simbòlica de l’arquitectura al panorama que sorgeix de la crisi de la modernitat i evoluciona fins als nostres dies, així com els aspectes més significatius en relació amb la seva comprensió semàntica. Per això aborda els conceptes relacionats amb el signe i utilitza la semiòtica com a metodologia original d’anàlisi amb l’objectiu d’interpretar els elements visuals que transmeten un significat. En aquest sentit, les eines semiòtiques com a símbol, metàfora o icona, entre d’altres, interpreten l’expressió de formes arquitectòniques i formulen la seva comprensió posterior i les converteixen en eines de comunicació. Aquesta visió de l’arquitectura contemporània situa el seu llenguatge en el context de la teoria dels signes, contribuint a explicar, amb una nova metodologia, les emocions que transmet un objecte arquitectònic i la seva relació amb lintèrpret (usuari).This paper examines the characteristics of the symbolic conception of architecture in the panorama that arises from the crisis of modernity and evolves to the present day, as well as the most significant aspects in relation to its semantic understanding. To this end, the research addresses the concepts related to the sign and uses Semiotics as an original analysis methodology with the aim of interpreting the visual elements that convey a meaning. Therefore, semiotic tools such as symbol, metaphor, or icon, among others, interpret the expression of architectural forms and formulate their subsequent understanding, turning them into communication tools. This approach of contemporary architecture takes place in the context of the theory of signs, helping to explain, with a new methodology, the emotions transmitted by an architectural object and its relationship with the interpreter (user).Este artículo investiga las características de la concepción simbólica de la arquitectura en el panorama que surge de la crisis de la modernidad y evoluciona hasta nuestros días, así como los aspectos más significativos en relación con su comprensión semántica. Para ello aborda los conceptos relacionados con el signo y utiliza la Semiótica como metodología original de análisis con el objetivo de interpretar los elementos visuales que transmiten un significado. En este sentido, las herramientas semióticas como símbolo, metáfora o icono, entre otras, interpretan la expresión de formas arquitectónicas y formulan su comprensión posterior convirtiéndolas en herramientas de comunicación. Esta visión de la arquitectura contemporánea sitúa su lenguaje en el contexto de la teoría de los signos, contribuyendo a explicar, con una nueva metodología, las emociones que transmite un objeto arquitectónico y su relación con el intérprete (usuario).Peer Reviewe

Continuous intraocular pressure monitoring in patients with obstructive sleep apnea syndrome using a contact lens sensor

Purpose To analyse nocturnal intraocular pressure (IOP) fluctuations in patients with obstructive sleep apnea syndrome (OSAS) using a contact lens sensor (CLS) and to identify associations between the OSAS parameters determined by polysomnographic study (PSG) and IOP changes. Method Prospective, observational study. Twenty participants suspected of having OSAS were recruited. During PSG study, IOP was monitored using a CLS placed in the eye of the patient. The patients were classified according to the apnea-hypopnea index (AHI) in two categories, severe (>30) or mild/moderate (<30) OSAS. We evaluated several parameters determined by the IOP curves, including nocturnal elevations (acrophase) and plateau times in acrophase (PTs) defined by mathematical and visual methods. Results The IOP curves exhibited a nocturnal acrophase followed by PTs of varying extents at which the IOP remained higher than daytime measurement with small variations. We found significant differences in the length of the PTs in patients with severe OSAS compared to those with mild/moderate disease (P = 0.032/P = 0.028). We found a positive correlation between PTs and OSAS severity measured by the total number of apneic events (r = 0.681/ 0.751 P = 0.004/0.001) and AHI (r = 0.674/0.710, P = 0.004/0.002). Respiratory-related arousal and oxygen saturation also were associated significantly with the IOP PT length. Conclusions Periods of nocturnal IOP elevation lasted longer in severe OSAS patients than those with mild/moderate OSAS and correlate with the severity of the disease. The length of the nocturnal PT is also associated to respiratory parameters altered in patients with OSAS

Effluents from the copper electrorefining as a secondary source of antimony: Role of mass transfer on the recovery by electrodeposition

The limited availability of antimony has increased the need for exploiting alternative sources to its direct extraction from stibnite deposits. Furthermore, introducing recovery techniques in industries where antimony is released in wastewaters leads to more responsible production routes. In this work, electrodeposition is employed to recover the antimony present in a secondary waste effluent of the copper electrorefining that is highly concentrated in hydrochloric acid. The electrochemical characterization of the system was conducted by voltammetry to identify a range of suitable operating conditions for the potentiostatic and galvanostatic electro-recovery of antimony. In potentiostatic mode, the progress of the secondary electrode reactions of hydrogen and chlorine evolution at potentials more cathodic than −0.38 V vs. Ag/AgCl causes the detachment and redissolution of the deposited antimony. Operating under galvanostatic control, similar effects were observed when the limiting current density is exceeded. Current efficiency and specific energy consumption values above 50 % and below 65 kW·h·kg−1, were achieved below the limiting current density (1.265 mA·cm−2). The operational range where electrodeposition of antimony is accelerated at increasing current densities can be broadened at intensified hydrodynamic conditions and higher concentrations of antimony. The detrimental effect of the hydrogen evolution reaction on the recovery of antimony decreases at high HCl concentrations

Voltammetric and electrodeposition study for the recovery of antimony from effluents generated in the copper electrorefining process

Antimony is a metalloid with limited availability as a primary resource, but it is commonly found as an impurity in effluents generated in the copper metallurgy. Thus, the development of clean and selective processes to recover antimony from these wastewaters would improve the sustainability of the copper production. In this work, an emulated effluent of the copper electrorefining industry that contains antimony and hydrochloric acid was characterized by means of voltammetric and electrodeposition tests using two different cell configurations: a static cell, and a dynamic cell with a rotating disk electrode (RDE). Voltammograms were obtained at varying hydrochloric acid and antimony concentrations, inversion potentials, scan rates and RDE rotation rates. Two main conclusions were drawn: (a) the deposition of antimony is a mass transfer-controlled process; and (b) an increase in hydrochloric acid concentration improves the deposition of antimony. The diffusion coefficient of antimony species was obtained applying the Randles-ˇ Sevˇcík and the Levich equations; both of them providing very similar values (5.29 ± 0.20 ⋅ 10− 6 cm2 s − 1). The effective electrodeposition of antimony from highly concentrated hydrochloric acid solutions was demonstrated. The surface examination of the electrodes revealed that compact and adherent deposits of antimony could be obtained under operating conditions that minimize the hydrogen evolution reaction in both potentiostatic and galvanostatic modes. Intensified convective regimes by using the RDE improve the supply of dissolved antimony towards the electrode surface, thus leading to a notorious increase in current density and, consequently, in the rate of antimony deposition

Low-Loss multilayered metamaterial exhibiting a negative index of refraction at visible wavelengths

We experimentally demonstrate a low-loss multilayered metamaterial exhibiting a double-negative refractive index in the visible spectral range. To this end, we exploit a second-order magnetic resonance of the so-called fishnet structure. The low-loss nature of the employed magnetic resonance, together with the effect of the interacting adjacent layers, results in a figure of merit as high as 3.34. A wide spectral range of negative index is achieved, covering the wavelength region between 620 and 806 nm with only two different designs. © 2011 American Physical Society.Financial support by the Spanish MICINN (Contracts No. CSD2008-00066 and No. TEC2008-06871-C02) and by the Valencian government (Contract No. PROMETEO-2010-087) is acknowledged. C.G.-M. acknowledges financial support from Grant FPU of MICINN. W.D. and A.Z. acknowledge financial support from EPSRC (U.K.).García Meca, C.; Hurtado Montañés, J.; Martí Sendra, J.; Martínez Abietar, AJ.; Dickson, W.; Zayats, AV. (2011). Low-Loss multilayered metamaterial exhibiting a negative index of refraction at visible wavelengths. Physical Review Letters. 106(6). https://doi.org/10.1103/PhysRevLett.106.067402S1066Veselago, V. G. (1968). THE ELECTRODYNAMICS OF SUBSTANCES WITH SIMULTANEOUSLY NEGATIVE VALUES OF $\epsilon$ AND μ. Soviet Physics Uspekhi, 10(4), 509-514. doi:10.1070/pu1968v010n04abeh003699Shelby, R. A. (2001). Experimental Verification of a Negative Index of Refraction. Science, 292(5514), 77-79. doi:10.1126/science.1058847Pendry, J. B. (2000). Negative Refraction Makes a Perfect Lens. Physical Review Letters, 85(18), 3966-3969. doi:10.1103/physrevlett.85.3966Tsakmakidis, K. L., Boardman, A. D., & Hess, O. (2007). ‘Trapped rainbow’ storage of light in metamaterials. Nature, 450(7168), 397-401. doi:10.1038/nature06285Soukoulis, C. M., Linden, S., & Wegener, M. (2007). PHYSICS: Negative Refractive Index at Optical Wavelengths. Science, 315(5808), 47-49. doi:10.1126/science.1136481Depine, R. A., & Lakhtakia, A. (2004). A new condition to identify isotropic dielectric-magnetic materials displaying negative phase velocity. Microwave and Optical Technology Letters, 41(4), 315-316. doi:10.1002/mop.20127Dolling, G., Wegener, M., Soukoulis, C. M., & Linden, S. (2006). Negative-index metamaterial at 780 nm wavelength. Optics Letters, 32(1), 53. doi:10.1364/ol.32.000053Chettiar, U. K., Kildishev, A. V., Yuan, H.-K., Cai, W., Xiao, S., Drachev, V. P., & Shalaev, V. M. (2007). Dual-band negative index metamaterial: double negative at 813 nm and single negative at 772 nm. Optics Letters, 32(12), 1671. doi:10.1364/ol.32.001671Xiao, S., Chettiar, U. K., Kildishev, A. V., Drachev, V. P., & Shalaev, V. M. (2009). Yellow-light negative-index metamaterials. Optics Letters, 34(22), 3478. doi:10.1364/ol.34.003478Mary, A., Rodrigo, S. G., Garcia-Vidal, F. J., & Martin-Moreno, L. (2008). Theory of Negative-Refractive-Index Response of Double-Fishnet Structures. Physical Review Letters, 101(10). doi:10.1103/physrevlett.101.103902García-Meca, C., Ortuño, R., Rodríguez-Fortuño, F. J., Martí, J., & Martínez, A. (2009). Negative refractive index metamaterials aided by extraordinary optical transmission. Optics Express, 17(8), 6026. doi:10.1364/oe.17.006026Ortuño, R., García-Meca, C., Rodríguez-Fortuño, F. J., Martí, J., & Martínez, A. (2009). Role of surface plasmon polaritons on optical transmission through double layer metallic hole arrays. Physical Review B, 79(7). doi:10.1103/physrevb.79.075425Zayats, A. V., Smolyaninov, I. I., & Maradudin, A. A. (2005). Nano-optics of surface plasmon polaritons. Physics Reports, 408(3-4), 131-314. doi:10.1016/j.physrep.2004.11.001Dickson, W., Wurtz, G. A., Evans, P. R., Pollard, R. J., & Zayats, A. V. (2008). Electronically Controlled Surface Plasmon Dispersion and Optical Transmission through Metallic Hole Arrays Using Liquid Crystal. Nano Letters, 8(1), 281-286. doi:10.1021/nl072613gMinovich, A., Neshev, D. N., Powell, D. A., Shadrivov, I. V., Lapine, M., McKerracher, I., … Kivshar, Y. S. (2010). Tilted response of fishnet metamaterials at near-infrared optical wavelengths. Physical Review B, 81(11). doi:10.1103/physrevb.81.115109García-Meca, C., Ortuño, R., Rodríguez-Fortuño, F. J., Martí, J., & Martínez, A. (2009). Double-negative polarization-independent fishnet metamaterial in the visible spectrum. Optics Letters, 34(10), 1603. doi:10.1364/ol.34.001603Zhou, J., Koschny, T., & Soukoulis, C. M. (2008). An efficient way to reduce losses of left-handed metamaterials. Optics Express, 16(15), 11147. doi:10.1364/oe.16.011147Zhang, S., Fan, W., Panoiu, N. C., Malloy, K. J., Osgood, R. M., & Brueck, S. R. (2006). Optical negative-index bulk metamaterials consisting of 2D perforated metal-dielectric stacks. Optics Express, 14(15), 6778. doi:10.1364/oe.14.006778Valentine, J., Zhang, S., Zentgraf, T., Ulin-Avila, E., Genov, D. A., Bartal, G., & Zhang, X. (2008). Three-dimensional optical metamaterial with a negative refractive index. Nature, 455(7211), 376-379. doi:10.1038/nature07247Drachev, V. P., Chettiar, U. K., Kildishev, A. V., Yuan, H.-K., Cai, W., & Shalaev, V. M. (2008). The Ag dielectric function in plasmonic metamaterials. Optics Express, 16(2), 1186. doi:10.1364/oe.16.001186Kriegler, C. E., Rill, M. S., Linden, S., & Wegener, M. (2010). Bianisotropic Photonic Metamaterials. IEEE Journal of Selected Topics in Quantum Electronics, 16(2), 367-375. doi:10.1109/jstqe.2009.2020809Rockstuhl, C., Paul, T., Lederer, F., Pertsch, T., Zentgraf, T., Meyrath, T. P., & Giessen, H. (2008). Transition from thin-film to bulk properties of metamaterials. Physical Review B, 77(3). doi:10.1103/physrevb.77.035126Xiao, S., Drachev, V. P., Kildishev, A. V., Ni, X., Chettiar, U. K., Yuan, H.-K., & Shalaev, V. M. (2010). Loss-free and active optical negative-index metamaterials. Nature, 466(7307), 735-738. doi:10.1038/nature0927