Efficient Laser Performance Of Ndgdlif4: A New Laser Crystal

Laser action of Nd3+ doped GdLiF4 (GLF) has been demonstrated for both pulsed and cw laser pumped operation. A slope efficiency of 60% was obtained in either manner of operation. The spectroscopic properties and laser performance of Nd:GLF are very similar to those of Nd:YLF. GLF, on the other hand, can be doped with much higher Nd3+ concentration

Tensile bond strength and SEM analysis of enamel etched with Er:YAG laser and phosphoric acid: a comparative study In vitro

Er:YAG laser has been studied as a potential tool for restorative dentistry due to its ability to selectively remove oral hard tissue with minimal or no thermal damage to the surrounding tissues. The purpose of this study was to evaluate in vitro the tensile bond strength (TBS) of an adhesive/composite resin system to human enamel surfaces treated with 37% phosphoric acid, Er:YAG laser (lambda=2.94 mum) with a total energy of 16 J (80 mJ/pulse, 2Hz, 200 pulses, 250 ms pulse width), and Er:YAG laser followed by phosphoric acid etching. Analysis of the treated surfaces was performed by scanning electron microscopy (SEM) to assess morphological differences among the groups. TBS means (in MPa) were as follows: Er:YAG laser + acid (11.7 MPa) > acid (8.2 MPa) > Er:YAG laser (6.1 MPa), with the group treated with laser+acid being significantly from the other groups (p=0.0006 and p= 0.00019, respectively). The groups treated with acid alone and laser alone were significantly different from each other (p=0.0003). The SEM analysis revealed morphological changes that corroborate the TBS results, suggesting that the differences in TBS means among the groups are related to the different etching patterns produced by each type of surface treatment. The findings of this study indicate that the association between Er:YAG laser and phosphoric acid can be used as a valuable resource to increase bond strength to laser-prepared enamel.A tecnologia a laser tem sido estudada como uma ferramenta potencial para uso em odontologia devido à sua habilidade em remover tecido ósseo com um mínimo ou nenhum dano aos tecidos vizinhos. O objetivo deste estudo é comparar in vitro a resistência à tração do sistema adesivo em esmalte tratado com ácido fosfórico a 37 %, laser Er:YAG (lambda=2,94 mim) com energia total de 16 J (80 mJ/pulso, 2 Hz, 200 pulsos e largura de pulso de 250 ms) e com a combinação laser Er:YAG seguido por ácido fosfórico. O teste de resistência à tração foi usado para comparar a resistência à tração em cada grupo. Foi também realizada microscopia eletrônica de varredura para permitir a análise das diferenças morfológicas entre os grupos. Foram obtidos os seguintes valores médios de resistência para os grupos tratados com: laser (6,1 MPa), ácido fosfórico (8,2 MPa) e laser mais ácido (11,7 Mpa). Amostras tratadas com laser e ácido apresentaram valores maiores de resistência do que amostras com laser ou ácido isoladamente. A análise da microscopia eletrônica revelou diferenças que corroboram os resultados, demonstrando que diferenças de resistência entre os grupos são devidas às diferenças entre os padrões superficiais resultantes. Nossos resultados sugerem que a combinação do laser Er:YAG com ácido fosfórico pode ser usada como um método para aumentar a resistência à tração do sistema esmalte resina

Spectroscopy And Laser Performance Of Nd Doped Gadolinium Lithium-Fluoride

A comprehensive investigation on the spectroscopic Properties and laser performance of Nd3+ doped GdLiF4 (GLF), a new laser crystal, is reported. Our high resolution absorption and emission spectra for GLF are nearly identical to those of Nd:LiYF4 (YLF), a well known laser crystal, strongly suggesting that the two crystals are isostructural. The laser performance of Nd:GLF is very similar to that of Nd:YLF. A maximum laser-pump-laser slope efficiency of 68% and 67% was obtained for low (1.0 at. %) and high (4.0 at. %) Nd concentration GLF respectively. Concentration quenching of the fluorescence decay time was observed and appears to be due to the dipole-dipole interaction between the isolated Nd3+ ions and Nd3+ ion pairs

Room-Temperature Optical-Absorption in Undoped Alpha-AL2O3

Optical absorption over a large dynamic range obtained by two different experimental techniques is reported for an undoped α‐Al2 O3 single crystal. Absorption data are presented in two energy ranges: 0.94–3.5 eV and 4.5–8.6 eV. Vacuum ultraviolet (vuv) absorption measurements were performed on three boules of Czochralski‐grown single‐crystal Al2 O3 with differing starting material purities. The initial powder purities were 99.99%, 99.999%, and 99.999999%. In addition to the vuv measurements, calorimetric absorption results obtained in the visible and near‐infrared (ir) are presented. An empirical formula is obtained that provides an estimate of the absorption coefficient from the near‐ir to the vuv for undoped Al2 O3 . Detailed impurity analyses and sample histories are given for the optical‐quality α‐Al2 O3 utilized herein

Fiscal developments and financial stress : a threshold VAR analysis

We use a threshold VAR analysis to study the linkages between changes in the debt ratio, economic activity and financial stress within different financial regimes. We use quarterly data for the US, the UK, Germany and Italy, for the period 1980:4– 2014:1, encompassing macro, fiscal and financial variables, and use nonlinear impulse responses allowing for endogenous regime-switches in response to structural shocks. The results show that output reacts mostly positively to an increase in the debt ratio in both financial stress regimes; however, the differences in estimated multipliers across regimes are relatively small. Furthermore, a financial stress shock has a negative effect on output and worsens the fiscal situation. The large time-variation and the estimated nonlinear impulse responses suggest that the size of the fiscal multipliers was higher than average in the 2008–2009 crisis.info:eu-repo/semantics/publishedVersio

Data-driven reverse engineering of signaling pathways using ensembles of dynamic models

Signaling pathways play a key role in complex diseases such as cancer, for which the development of novel therapies is a difficult, expensive and laborious task. Computational models that can predict the effect of a new combination of drugs without having to test it experimentally can help in accelerating this process. In particular, network-based dynamic models of these pathways hold promise to both understand and predict the effect of therapeutics. However, their use is currently hampered by limitations in our knowledge of the underlying biochemistry, as well as in the experimental and computational technologies used for calibrating the models. Thus, the results from such models need to be carefully interpreted and used in order to avoid biased predictions. Here we present a procedure that deals with this uncertainty by using experimental data to build an ensemble of dynamic models. The method incorporates steps to reduce overfitting and maximize predictive capability. We find that by combining the outputs of individual models in an ensemble it is possible to obtain a more robust prediction. We report results obtained with this method, which we call SELDOM (enSEmbLe of Dynamic lOgic-based Models), showing that it improves the predictions previously reported for several challenging problems.JRB and DH acknowledge funding from the EU FP7 project NICHE (ITN Grant number 289384). JRB acknowledges funding from the Spanish MINECO project SYNBIOFACTORY (grant number DPI2014-55276-C5-2-R). AFV acknowledges funding from the Galician government (Xunta de Galiza) through the I2C postdoctoral fellowship ED481B2014/133-0. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.info:eu-repo/semantics/publishedVersio

HIV Epidemic Appraisals for Assisting in the Design of Effective Prevention Programmes: Shifting the Paradigm Back to Basics

To design HIV prevention programmes, it is critical to understand the temporal and geographic aspects of the local epidemic and to address the key behaviours that drive HIV transmission. Two methods have been developed to appraise HIV epidemics and guide prevention strategies. The numerical proxy method classifies epidemics based on current HIV prevalence thresholds. The Modes of Transmission (MOT) model estimates the distribution of incidence over one year among risk-groups. Both methods focus on the current state of an epidemic and provide short-term metrics which may not capture the epidemiologic drivers. Through a detailed analysis of country and sub-national data, we explore the limitations of the two traditional methods and propose an alternative approach.We compared outputs of the traditional methods in five countries for which results were published, and applied the numeric and MOT model to India and six districts within India. We discovered three limitations of the current methods for epidemic appraisal: (1) their results failed to identify the key behaviours that drive the epidemic; (2) they were difficult to apply to local epidemics with heterogeneity across district-level administrative units; and (3) the MOT model was highly sensitive to input parameters, many of which required extraction from non-regional sources. We developed an alternative decision-tree framework for HIV epidemic appraisals, based on a qualitative understanding of epidemiologic drivers, and demonstrated its applicability in India. The alternative framework offered a logical algorithm to characterize epidemics; it required minimal but key data.Traditional appraisals that utilize the distribution of prevalent and incident HIV infections in the short-term could misguide prevention priorities and potentially impede efforts to halt the trajectory of the HIV epidemic. An approach that characterizes local transmission dynamics provides a potentially more effective tool with which policy makers can design intervention programmes