Fluorescence Decay Characteristics of the Green Emission From CaF2:Ho3+

Variations in the decay times of the characteristic green emissions at 522.7, 551.3, 549.6, 547.6, 542.2, 540.2, 535.9 and 533.5nm from CaF2 :H03+ with concentration are studied at RT and LNT. A pulsed N2 laser beam of power density 1.5 MW cm-2 is used for the excitation. Temperature dependent concentration quenching of the decay times are observed for all the emission bands. But an increase in the decay time due to the reabsorption process is also observed for a few of the above bands.

X-ray and gamma irradiation effects on dipole defects in CaF2 : La, Yb, Al

Impurity-interstitial dipoles in calcium fluoride solutions with Al3+, Yb3+ and La3+ fluorides were studied using the thermally stimulated depolarization current (TSDC) technique. The dipolar complexes are formed by substitutional trivalent ions in Ca2+ sites and interstitial fluorine in nearest neighbor sites. The relaxations observed at 150 K are assigned to dipoles nnR(S)(3+)- F-i(-) (R-S = La or Yb). The purpose of this work is to study the processes of energy storage in the fluorides following X-ray and gamma irradiation. Computer modelling techniques are used to obtain the formation energy of dipole defects. (C) 2007 Elsevier Ltd. All rights reserved.

Effect of Er:YAG laser on CaF2 formation and its anticariogenic action on human enamel: An in vitro study

Objective: The objective of this study was to evaluate the effect of Er: YAG laser on the formation of CaF2, after the application of acidulated phosphate fluoride (APF), and its influence on the anti-cariogenic action in human dental enamel. Background Data: Er:YAG laser was designed to promote ablation of the enamel. However, the possibility of using this energy to increase the enamel's resistance to caries has hardly been explored, and neither has its interaction with the use of fluorides. Materials and Methods: One hundred and twenty blocks of enamel were allocated to four groups of 30 blocks each: (1) C, control group; (2) Er:YAG, laser; (3) APF; and (4) Er:YAG+APF. Of these, 80 blocks were submitted to pH cycling for 14 days. In the other 40 blocks, fluoride (CaF2) was measured before cycling. After pH cycling, surface microhardness (SMH), microhardness in cross-section (converted to mineral contents % vol. min.), and fluoride after cycling (40 blocks) were also determined. Results: SMH decreased in all groups. The control group showed the highest decrease, and Er:YAG+APF showed the lowest decrease (p < 0.05). Groups APF and Er:YAG showed the same results (p > 0.05). Mineral content at depths 10, 20, and 40 μm was lower in the control and Er:YAG groups, and higher in groups APF and Er:YAG+APF. CaF2 (μgF/cm2) deposited before pH cycling was higher in the APF group when compared to the Er:YAG+APF group. Control and Er:YAG groups showed the lowest values (p > 0.05). Conclusion: It was concluded that Er:YAG laser influenced the deposition of CaF2 on the enamel and showed a superficial anti-cariogenic action, but not in depth.

Factors affecting the use of CaF2 : Mn thermoluminescent dosimeters for low-level environmental radiation monitoring /

Mode of access: Internet.

Efeito do fluoreto de cálcio e do carbonato de cálcio na composição química da solução percolada de um solo ácido

Durante oito meses, foram estudados, em casa de vegetação, os efeitos da aplicação de CaF2 (p.a.) e de CaCO3 (p.a.) sobre a concentração de Al e de outros elementos químicos na solução percolada de amostras de um solo ácido, coletado na região de Piracicaba, SP. Os valores de pH aumentaram na solução percolada de amostras de solos que receberam tanto CaCO3 como CaF2. Os tratamentos com CaF2 foram mais eficientes na retirada de Al do solo do que os tratamentos com CaCO3. Na testemunha e nos tratamentos com CaCO3, a maior parte do Al estava, respectivamente, na forma livre Al3+ ou formando complexos Al-OH, ao passo que, nos tratamentos com CaF2 , mais de 99,5% do Al estava complexado com o fluoreto.

Roughness and light scattering of ion-beam-sputtered fluoride coatings for 193 nm

Scattering characteristics of multilayer fluoride coatings for 193 nm deposited by ion beam sputtering and the related interfacial roughnesses are investigated. Quarter- and half-wave stacks of MgF2 and LaF3 with increasing thickness are deposited onto CaF2 and fused silica and are systematically characterized. Roughness measurements carried out by atomic force microscopy reveal the evolution of the power spectral densities of the interfaces with coating thickness. Backward-scattering measurements are presented, and the results are compared with theoretical predictions that use different models for the statistical correlation of interfacial roughnesses.

Ultraviolet optical and microstructural properties of MgF2 and LaF3 coatings deposited by ion-beam sputtering and boat and electron-beam evaporation

Single layers of MgF2 and LaF3 were deposited upon superpolished fused-silica and CaF2 substrates by ion-beam sputtering (IBS) as well as by boat and electron beam (e-beam) evaporation and were characterized by a variety of complementary analytical techniques. Besides undergoing photometric and ellipsometric inspection, the samples were investigated at 193 and 633 nm by an optical scatter measurement facility. The structural properties were assessed with atomic-force microscopy, x-ray diffraction, TEM techniques that involved conventional thinning methods for the layers. For measurement of mechanical stress in the coatings, special silicon substrates were coated and analyzed. The dispersion behavior of both deposition materials, which was determined on the basis of various independent photometric measurements and data reduction techniques, is in good agreement with that published in the literature and with the bulk properties of the materials. The refractive indices of the MgF2 coatings ranged from 1.415 to 1.440 for the wavelength of the ArF excimer laser (193 nm) and from 1.435 to 1.465 for the wavelength of the F2 excimer laser (157 nm). For single layers of LaF3 the refractive indices extended from 1.67 to 1.70 at 193 nm to ~1.80 at 157 nm. The IBS process achieves the best homogeneity and the lowest surface roughness values (close to 1 nmrms) of the processes compared in the joint experiment. In contrast to MgF2 boat and e-beam evaporated coatings, which exhibit tensile mechanical stress ranging from 300 to 400 MPa, IBS coatings exhibit high compressive stress of as much as 910 MPa. A similar tendency was found for coating stress in LaF3 single layers. Experimental results are discussed with respect to the microstructural and compositional properties as well as to the surface topography of the coatings.

Fungicidal synergism of fluconazole and cyclosporine in Candida albicans is not dependent on multidrug efflux transporters encoded by the CDR1, CDR2, CaMDR1, and FLU1 genes.

The combination of fluconazole (FLC) and cyclosporine (CY) is fungicidal in FLC-susceptible C. albicans (O. Marchetti, P. Moreillon, M. P. Glauser, J. Bille, and D. Sanglard, Antimicrob. Agents Chemother. 44:2373-2381, 2000). The mechanism of this synergism is unknown. CY has several cellular targets including multidrug efflux transporters. The hypothesis that CY might inhibit FLC efflux was investigated by comparing the effect of FLC-CY in FLC-susceptible parent CAF2-1 (FLC MIC, 0.25 mg/liter) and in FLC-hypersusceptible mutant DSY1024 (FLC MIC, 0.03 mg/liter), in which the CDR1, CDR2, CaMDR1, and FLU1 transporter genes have been selectively deleted. We postulated that a loss of the fungicidal effect of FLC-CY in DSY1024 would confirm the roles of these efflux pumps. Time-kill curve studies showed a more potent fungistatic effect of FLC (P = 0.05 at 48 h with an inoculum of 10(3) CFU/ml) and a more rapid fungicidal effect of FLC-CY (P = 0.05 at 24 h with an inoculum of 10(3) CFU/ml) in the FLC-hypersusceptible mutant compared to those in the parent. Rats with experimental endocarditis were treated for 2 or 5 days with high-dose FLC, high-dose CY, or both drugs combined. FLC monotherapy for 5 days was more effective against the hypersusceptible mutant than against the parent. However, the addition of CY to FLC still conferred a therapeutic advantage in animals infected with mutant DSY1024, as indicated by better survival (P = 0.04 versus the results obtained with FLC) and sterilization of valves and kidneys after a very short (2-day) treatment (P = 0.009 and 0.002, respectively, versus the results obtained with FLC). Both in vitro and in vivo experiments consistently showed that the deletion of the four membrane transporters in DSY1024 did not result in loss of the fungicidal effect of FLC-CY. Yet, the accelerated killing in the mutant suggested a "dual-hit" mechanism involving FLC hypersusceptibility due to the efflux pump elimination and fungicidal activity conferred by CY. Thus, inhibition of multidrug efflux transporters encoded by CDR1, CDR2, CaMDR1, and FLU1 genes is not responsible for the fungicidal synergism of FLC-CY. Other cellular targets must be considered.

Fluoriditasetarkastelu ja päästöjen hallinta ferrokromi- ja terästeollisuudessa

Työn alkuosassa kartoitettiin AvestaPolarit –yhtiöiden Tornion tehtaiden keskeiset fluoridilähteet kuten fluspaatti, valukuonat, valupulverit ja fluorivetyhappo. Valupulverien ja kuonien haihtumis- ja liukoisuuskäyttäytymistä valaistiin kotimaisten ja kansainvälisten tutkimusten avulla. Tutkimustuloksia sovellettiin pääpiirteittäin Tornion tehtaiden tilanteeseen ottamalla huomioon tekijät, jotka saattoivat lieventää tai vahvistaa fluoridien vaikutusta ympäristöön. Yleisesti fluoridien ympäristö- ja terveysvaikutukset arvioitiin vähäisiksi. Työn kokeellisessa osassa määritettiin Tornion tehtaiden ferrokromitehtaan, terässulaton, kuumavalssaamon ja kylmävalssaamon fluoriditaseet. Jokaisen osastojen syötteiden fluoridipitoisuudet selvitettiin tuottajien ilmoittamien tuotekoostumuksien, spesifikaatioiden ja fluoridianalyysien perusteella. Fluoridien kokonaismäärät laskettiin jokaiselle syötteelle ja ne suhteutettiin kunkin osaston vuoden 2001 tuotantotasoon. Tasetarkastelussa suurimpina fluoridisyötteinä nousivat odotetusti esiin terässulaton käyttämä kuonanmuodostaja-aine fluspaatti (CaF2) ja kylmävalssaamon peittaushappo, 70 prosenttinen fluorivetyhappo (HF). Lisäksi muita merkittäviä syötteitä olivat kylmävalssaamon käyttämä kalkkipitoinen sekakuona ja ferrokromitehtaan sulatuskoksi. Tuotoksien eli päästöjen fluoridipitoisuudet saatiin selville päästömittauksin. Jätevesistä otettiin pääosin viikoittaisia kokoomanäytteitä, jotka analysoitiin tehtaan laboratoriossa. Kaasumaiset tuotokset oli määritetty kertamittauksien perusteella. Kiinteiden tuotoksien eli sakkojen ja kuonien fluoridimittaukset suoritettiin 3 sulatuksen kuonanäytteistä ja sakan vuosinäytteestä. Tuotoksista suurimmat ominaispäästökertoimet olivat juuri terässulaton AOD-konvertterin ja senkkauunin kuonilla ja kylmävalssaamon neutraloidulla regenerointisakalla ja neutralointisakoilla. Näistä ei aiheutunut varsinaista päästöä lähiympäristöön, koska sakat ja kuonat loppusijoitetaan tehtaan kaatopaikalle tai niitä käytetään liukenemattomassa muodossa. Tornion tehtaiden fluoridisyötteiden ja -tuotoksien mittausepätarkkuudet vaikuttivat fluoriditaseeseen. Ferrokromitehtaan fluoridisyötteet olivat kokonaismäärältään selvästi suurempia kuin tuotokset. Terässulaton fluoriditaseen tuotokset olivat suurempia kuin syötteet ja kylmävalssaamon syötteet sekä tuotokset olivat karkeasti arvioiden samaa suuruusluokkaa. Kuumavalssaamon fluoridisyötteet ja -tuotokset olivat mitättömiä. Fluoriditaseen epävarmuustekijöitä voidaan vähentää suorittamalla esimerkiksi useita fluoridimittauksia kaasumaisista päästöistä.

Obtencion de recubrimientos autolubricados por proyeccion termica de plasma atmosferico (APS) como alternativa a los lubricantes liquidos

La obtención de recubrimientos con bajos coeficientes de fricción, es una innovadora respuesta a la creciente demanda industrial de alternativas para los tradicionales sistemas lubricados con aceites. Para este fin, la introducción de un sólido lubricante, en una matriz con buenas propiedades mecánicas, ha de conferir al conjunto un bajo coeficiente de fricción y mejorar la resistencia al desgaste del recubrimiento, favoreciendo además, la utilización a elevadas temperaturas, en las que los lubricantes líquidos convencionales presentan limitaciones. En el Centro de Proyección Térmica (CPT) de la Universidad de Barcelona se han obtenido mediante proyección de Plasma Atmosférico (APS) recubrimientos autolubricados de Ni-Grafito y Cr2O3-CaF2, estudiando con especial interés las propiedades y el efecto que produce el grafito y el CaF2 en las matrices metálica y cerámica respectivamente. Se ha determinado en los dos casos que el desgaste originado en los recubrimientos es bajo, si bien los coeficientes de fricción varían ostensiblemente en función del sistema indicado. Los resultados obtenidos indican que el recubrimiento de Ni-Grafito posee un comportamiento idóneo capaz de competir con los tradicionales lubricantes líquidos.

Nitrogen laser excited fluorescence of some rare earth doped alkaline earth fluorides

The present study is mainly concéntrated on the visible fluorescence of Ho3+ ,nd 3+ and Er 3+rare earths in alkaline earth fluoride hosts(caF2,srF2,BaF2) using a nitrogen laser excitation. A nitrogen laser was fabricated and its parametric studies were first carried out.

Effect of rinsing with water immediately after neutral gel and foam fluoride topical application on enamel remineralization: An in situ study

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)