87,799 research outputs found
Effetto dello Yag laser sulla vascolarizzazione dello pterigio.
No full textGli AA evidenziano in casi selezionati di pterigio le possibilità e i limiti nel trattamento della componente neovascolare tramite applicazione con Yag laser
Microwave synthesis of YAG : Eu by sol-gel methodology
No full textYttrium-aluminum oxides are interesting compounds and they have been extensively used as host for lasers and phosphors, due to their stable physical and chemical properties. The fabrication of yttrium-aluminum garnet (YAG) has been investigated thoroughly. Single-crystal YAG is expensive and to produce it a new way has been investigated. This process consists of modifying the methodology of reagents mixture and the process of heating them. The microwave irradiation is used to heat-treat the oxide mixture. The traditional synthesis of YAG powders occurs through the reaction of aluminum and yttrium powders at high temperatures. With this work we investigated the preparation of YAG by non-hydrolytic sol-gel route as an alternative methodology to obtain yttrium-aluminum matrix from inorganic precursors (yttrium and aluminum chloride). The preparation of the gel was carried out in an oven-dried glassware. The AlCl3, YCl3 and ethanol were reacted in reflux under argon atmosphere. Europium III chloride was added as a structural probe. The powder was dried and heat-treated in modified microwaves. The samples were pre-treated at 50 and 800 C during I h and then heated in microwaves for 30 s, 2 and 4 min. The formation process and structure of the powders were studied by means of X-ray diffraction (XRD), photoluminescence (PL) and transmission electronic microscopy (TEM). XRD presents only picks corresponding to the YAG phase and confirmed by TEM. PL date showed that the YAG phase was formed in 2 min with the samples pre-treated at 50 C. For the samples pretreated at 800 degrees C, the YAG phase appears in 30s. The excitation spectra present a maximum of 394 nm corresponding to the L-5(6) level and emission spectra of Eu III ion present bands characteristic transitions arising from the D-5(0) -> F-7(J) (J= 1, 2, 3, 4) monifolds excited at their maximum. The magnetic dipole D-5(0) -> F-7(1) transition presents more intensity than the electric dipole D-5(0) -> F-7(2) transition. This methodology showed efficiency in obtaining YAG phase. (c) 2006 Elsevier B.V. All rights reserved.Univ Franca, BR-14404600 Franca, SP, BrazilUniv Estadual Paulista, Inst Quim, BR-14801970 Araraquara, SP, BrazilUniv Estadual Paulista, Inst Quim, BR-14801970 Araraquara, SP, Brazi
HIGH SPEED JOINING OF POLYMERIC PLASTICS USING DIFFERENT LASER SOURCES (CO2, ND-YAG AND HPDL)
No full textHIGH SPEED JOINING OF POLYMERIC PLASTICS USING DIFFERENT LASER SOURCES (CO2, ND-YAG AND HPDL
Fabrication and plasma resistance properties of transparent YAG ceramics
No full textHigh quality transparent yttrium aluminum garnet (YAG) ceramics with an average grain size of about 12 μm have been fabricated by a solid state reactive sintering method. Plasma resistance property of the fabricated YAG ceramics was studied and compared with that of the Y2O3 ceramics, silicate glass and quartz. The YAG ceramics showed an excellent plasma resistance as well as Y2O3 ceramics. After etching in F-plasma for 6 h, the eroded depth of YAG ceramics was about 100 nm. The plasma resistance of YAG ceramics was far better than that of silicate glass and quartz
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Nd: YAG Laser Posterior Capsulotomy Rates in Myopic Eyes after Implantation of Capsular Tension Ring
No full textBackground: The aim f this study was to evaluate the effect of capsular tension ring implantation during cataract surgery on the incidence of neodymium: YAG (Nd: YAG) laser posterior capsulotomy in myopic (axial length [AL] >= 25.00 mm) eyes
Luminescence Temperature Quenching for and d-f Emission in YAG and LuAG
No full textThe d-f emission from Ce3+ and Pr3+ in garnets is attracting considerable attention, especially in relation to application in white light LEDs and scintillators. An important aspect is the luminescence quenching temperature TQ. It is not trivial to determine TQ and to unravel the quenching mechanism. In this paper the TQ of d-f emission for Ce3+ and Pr3+ are determined by temperature dependent lifetime measurements. The results show a TQ for Pr3+ of 340 K for Y3Al5O12:Pr3+ (YAG:Pr) and 680 K for Lu3Al5O12:Pr3+ (LuAG:Pr). For Ce3+ the TQ is too high to measure. An onset of quenching above 600 K (YAG:Ce) or 700 K (LuAG:Ce) is observed. The differences in TQ between YAG and LuAG are explained by a smaller Stokes shift for the d-f emission in LuAG (∼2300 cm−1) compared to YAG (∼2750 cm−1) derived from low temperature luminescence spectra. The large difference in TQ between Ce3+ and Pr3+ is related to the smaller energy difference between the lowest energetic fd state of Pr3+ and the next lower 4f2 state (3P2) compared to the 5d – 4f1(2F7/2) energy difference for Ce3+. Both observations are consistent with luminescence temperature quenching by non-radiative relaxation from the 5d state to the 4f state described by a configurational coordinate diagram and not by thermally induced photoionization
Effect of Carbon Doping on F-Type Defects in YAG and YAG:Ce Crystals
No full textCe-doped yttrium aluminum garnet (YAG) is among the efficient rare-earth garnet scintillators and phosphors. This paper addresses a computational and experimental study of complex F-type defect centers formed in YAG by doping with cerium and carbon. The formation energies determined by ab initio calculations of different defects and atomic chemical potentials in YAG:Ce,C are discussed in O-poor and O-rich conditions corresponding to the crystal growth under Ar+CO reducing atmosphere, and post-growth annealing in air. It is shown that as-grown crystals contain numerous positively charged defects responsible for F-type center formation, whereas mainly negative charged defects are remained after the annealing in air. The negatively charged defects located nearby Ce luminescence center occupying Y site may stabilize cerium in the tetravalent state and promote a hole transport to this luminescence center. This describes a high scintillation efficiency of Ce,C-doped garnets. Furthermore, YAG:C and YAG:Ce,C with a high carbon concentration, besides of luminescence peaked at 400 ns ascribed to F+-type centers, possess a fast luminescence peaked around 650 nm that may be attributed to the complex defect centers. These unveiled features of the luminescence process in rare-earth garnets may contribute to the development of efficient luminescence materials
IDENTIFIKASI UNSUR NIKEL DENGAN TEKNIK LASER INDUCED PLASMA (LIP)
No full textThe line spectral of Ni element has been obtained for high and low concentration using Laser Induced Plasma (LIP) method. Focusing of high power pulse laser without pre treatment on the sample generates the Ni plasma contributed to atomic emission. From this experiment, the limit detection is obtained at about 76,61 ppm by Ni (I) 279,7 nm-emission
Oxidkeramische Verbundwerkstoffe auf der Basis von Yttrium-Aluminium-Granat (YAG)
No full textS.285-291Oxidkeramische Verbundwerkstoffe auf der Basis von Yttrium-Aluminium-Granat (YAG). YAG ist aufgrund der Kriechbeständigkeit und inhärenten Oxidationsbeständigkeit ein vielversprechender Kandidat für den Einsatz als Matrixmaterial in oxidkeramischen Verbundwerkstoffen (Oxide Fiber Composites, OFC). YAG kann ausgehend von den Oxiden (Aluminiumoxid und Yttriumoxid) synthetisiert werden. Dadurch wurde eine Möglichkeit geschaffen, das Material auf eine kostengünstigere Weise zu erzeugen. Um dichten YAG bei Temperaturen unterhalb von 1600 °C herstellen zu können, müssen Sinteradditive eingesetzt werden. Hier stellte sich heraus, dass vor allem Siliziumoxid und Kobaltoxid sowie deren Kombination eine sehr gute Verdichtung der Matrix bewirken. Im weiteren Verlauf wurde das auf der Verwendung von Gelatine basierende Gelcasting erfolgreich durchgeführt
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