Optical Modeling of Microcrystalline Silicon Deposited by Plasma-Enhanced Chemical Vapor Deposition on Low-Cost Iron-Nickel Substrates for Photovoltaic Applications

AbstractThis paper deals with the optical modeling of thin hydrogenated microcrystalline silicon films grown on flexible low-cost iron-nickel alloy substrates by low-temperature (175°C) plasma-enhanced chemical vapor deposition. This material serves as the absorber in solar cells and hence it has direct impact on the resulting solar cell performance. Since the crystallinity and the material quality of hydrogenated microcrystalline silicon films evolve during the growth, the deposited film is inhomogeneous, with a rather complex structure. Real-time spectroscopic ellipsometry has been used to trace the changing composition of the films. In-situ ellipsometric data taken for photon energies from 2.8 to 4.5eV every 50seconds enabled us to study the evolution of the monocrystalline silicon fraction of the hydrogenated microcrystalline silicon films

Wavelength tuning of fiber lasers using multimode interference effects

We report on a novel scheme to fabricate a simple, cheap, and compact tunable fiber laser. The tuning is realized by splicing a piece of single-mode fiber to one end of an active double-clad fiber, while the other end of the single-mode fiber is spliced to a 15 mm long section of 105/125 multimode fiber. The fluorescence signal entering into the multimode fiber will be reproduced as single images at periodic intervals along the propagation direction of the fiber. The length of the multimode fiber is chosen to be slightly shorter than the first re-imaging point, such that the signal coming out from the single mode fiber is obtained in free space, where a broadband mirror retroreflects the fluorescence signal. Since the position of the re-imaging point is wavelength dependent, different wavelengths will be imaged at different positions. Therefore, wavelength tuning is easily obtained by adjusting the distance between the broadband mirror and the multimode fiber facet end. Using this principle, the tunable fiber laser revealed a tunability of 8 nm, ranging from 1088-1097 nm, and an output power of 500 mW. The simplicity of the setup makes this a very cost-effective tunable fiber laser

Lung emphysema and lung cancer: what do we know about it?

Emphysema and lung cancer (LC) are two diseases which share common risk factors, e.g., smoking. In recent years, many studies have sought to analyse this association. By way of illustration, we conducted a review of the scientific literature of the studies published to date, whose main designated aim was to demonstrate the relationship between emphysema and LC, and this association's influence on the histology, prognosis and molecular mechanisms responsible. We included over 40 studies (ranging from case-control and cohort studies to systematic reviews and meta-analyses), which highlight the association between emphysema and LC, independently of smoking habit. These studies also report a possible influence on histology, with adenocarcinoma being the most frequent lineage, and an association with poor prognosis, which affects both survival and post-operative complications. Oxidative stress, which generates chronic inflammatory status as well as the presence of certain polymorphisms in various genes (CYP1A1, TERT, CLPTM1L, ERK), gives rise-in the case of patients with emphysema-to alteration of cellular repair mechanisms, which in turn favours the proliferation of neoplastic epithelial cells responsible for the origin of LC

Relación de los niveles de testosterona sérica y el tamaño testicular en alpacas según grupo etario y mes del año en Tacna, Perú

El objetivo del presente estudio fue evaluar la relación del tamaño testicular con los niveles de testosterona sérica en alpacas según la edad y mes del año. Se trabajó con ocho machos (4 jóvenes y 4 adultos). Las mediciones del tamaño testicular se realizaron con una regla Vernier y la determinación de los niveles de testosterona en suero se realizó mediante una prueba de quimioluminiscencia. Los adultos presentaron mayor tamaño testicular en los meses de abril, octubre, noviembre y en jóvenes en abril y noviembre. Así mismo, se encontró una diferencia significativa (t=3.17; p=0.009) entre adultos (8.41 cm2) y jóvenes (6.57 cm2). Con relación al nivel de testosterona, tanto en adultos y jóvenes, los niveles más altos fueron en el mes de abril. La comparación entre jóvenes y adultos no presentó diferencias significativas (t=0.23; p=0.81).  Además, la concentración de testosterona no presentó una relación significativa con el largo (r = 0.41), ancho (r = 0.21) y área testicular (r = 0.32)

Comportamiento de cuarenta frutales tropicales no explotados comercialmente en Colombia.

"Colombia posee una amplia variedad de condiciones ecológicas apropiadas para el cultivo de frutales tropicales, nativos y exóticos. Muchos de ellos, a pesar de no ser explotados extensivamente, sobresalen por su consumo tradicional, por su alto valor alimenticio y como alternativa para ser cultivados en un futuro. En 1957, el Programa de Frutales del Instituto Colombiano Agropecuaro, plantó un huerto en el Centro Nacional de Investigaciones Palmira con 40 especies nativas y foráneas, no explotadas comercialmente, con el fin de observar su comportamiento bajo las condiciones del Valle del Cauca. En el presente trabajo se suministran datos sobre su crecimiento y producción y sobre su desarrollo a los 25 años de edad. También se determinó la distribución de los períodos de floraciópn y fructificación durante el año y su relación con las épocas de lluvia y seaquía. Se encontró que en los meses secos, enero a marzo y julio a septiembre, ocurren con mayor frecuencia las cosechas en los frutales evaluados. Entres las especies estudiadas, se presentan como promisorias para ser sembradas en el Valle del Cauca, las siguientes: guanábana, anona blanca, grosella, cereza de Ceylán, madroño, caimarón, carambola ""Icambola"", mamey, níspero, nispero-zapote, guayaba coronilla, jabóticaba, árbol del pan y acerola

A Radial Velocity Survey of the Cygnus OB2 Association

We conducted a radial velocity survey of the Cygnus OB2 Association over a 6 year (1999 - 2005) time interval to search for massive close binaries. During this time we obtained 1139 spectra on 146 OB stars to measure mean systemic radial velocities and radial velocity variations. We spectroscopically identify 73 new OB stars for the first time, the majority of which are likely to be Association members. Spectroscopic evidence is also presented for a B3Iae classification and temperature class variation (B3 - B8) on the order of 1 year for Cygnus OB2 No. 12. Calculations of the intial mass function with the current spectroscopic sample yield Gamma = -2.2 +/- 0.1. Of the 120 stars with the most reliable data, 36 are probable and 9 are possible single-lined spectroscopic binaries. We also identify 3 new and 8 candidate double-lined spectroscopic binaries. These data imply a lower limit on the massive binary fraction of 30% - 42%. The calculated velocity dispersion for Cygnus OB2 is 2.44 +/- km/s, which is typical of open clusters. No runaway OB stars were found.Comment: 56 pages, 23 figures, 5 tables, accepted for publication in the Astrophysical Journa