Morphological and luminescent studies on nanosized Er, Yb-Yttrium oxide up-converter prepared from different precursors

In this paper, we report luminescent and morphological studies with yttrium oxide samples doped with ytterbium and erbium. The samples were prepared by the combustion method and also from different precursors: oxalate, basic carbonate and polymeric resin. All powders were identified Lis being an yttrium oxide with a C-form structure, independent of the employed precursor. From mean crystallite size measurements, it was verified that oxides prepared through the polymeric precursor and combustion methods lead to the smallest crystallite size. Particle shape and size were investigated by SEM and TEM, and showed that both the oxalate precursor and the combustion methods do not provide oxide materials of suitable shape or size, on the other hand. The basic carbonate and polymeric precursors resulted in spherically shaped particles with an average diameter of 90 and 15 run. respectively, Upon 980 run diode laser excitation, green and red emission lines were detected for all samples and were assigned to the H-2(11/2) S-4(3/2) -> I-4(15/2) and (4)Fg(9/2) -> 4I(15/12) transitions, respectively. Such transitions are characteristic for Er3+ and result from energy transfer from Yb3+ energy levels, F-2(7/2) -> F-2(5/2). A relationship between the decrease in the mean crystallite size and the enhancement in red emission was also established as well as the influence of the presence of a high percentage of Yb-3 Both factors promote ET from Yb3+ (F-2(5/2)) to Er3+ (I-4(11/2)). (c) 2004 Elsevier B.V. All rights reserved.

A new beta-diketone complex with high color purity

In this work a new europium (III) complex with the following formula NH(4) [Eu(bmdm)(4)] was synthesized and characterized. The bmdm (butyl methoxy-dibenzoyl-methane) is a P-diketone molecule used as UV radiation absorber in sunscreen formulations. Coordination of this ligand to the Eu(3+) ion was confinned by FT-IR, while the Raman spectrum suggests the presence of NH(4)(+) ions. The photoluminescence spectra present narrow lines arising from f-f intra-configurational transitions (5)D(0-)(7)F(0,1,2,3,4), dominated by the hypersensitive (5)D(0)-(7)F(2) transition. In the spectrum recorded at 77 K, all transitions split into 2J + 1 lines suggesting that there is just one symmetry site around Eu(3+) ion. This symmetry is not centrosymmetric. The calculated intensity parameters are ohm(2) = 30.5 x 10(-20) cm(2) and ohm(4) = 5.91 x 10(-20) cm(2) for this complex. The CIE chromaticity coordinates (x = 0.67 and y = 0.32) show a dominant wavelength of 615 nm. The color gamut achieved by this complex is a 100% in the CIE color space. (c) 2005 Elsevier B.V. All rights reserved.

Langmuir-Blodgett films incorporating an ionic europium complex

Langmuir-Blodgett (LB) technique is a powerful tool to fabricate ultrathin films with highly ordered structures and controllable molecular array for efficient energy and electron transfer, allowing the construction of devices at molecular level. One method to obtain LB films consists in the mixture of classical film-forming molecules, for example Stearic Acid (SA) and functional metal complex. In this work NH(4)[Eu(bmdm)(4)], where the organic ligand bmdm is (butyl methoxy-dibenzoyl-methane) or (1-(4-methoxyphenyl)-3-(4-tert-butylphenyl)propane-1,3-dione) was used to build up Langmuir and LB films. Langmuir isotherms were obtained from (i) NH(4)[Eu(bmdm)(4)] complex and (ii) NH(4)[Eu(bmdm)(4)]/SA (1:1). Results indicated that (i) form multilayer structure; however the surface pressure was insufficient to obtain LB films, and (ii) can easily reproduce and build LB films. The dependence of number of layers in the UV absorption spectra suggest that the complex did not hydrolyze or show decomposition, UV spectral differences observed between the solution and the LB film indicate that the complex has a highly ordered arrangement in the film and the complex has an interaction with SA. Excitation spectra confirm a ligand-europium energy transfer mechanism. The transition lines of Eu(3+) ion were observed in emission spectra of all films, the photoluminescence spectra indicate a fluorescence enhanced effect with the number of LB layers. (C) 2009 Elsevier B.V. All rights reserved.

UVC emitting phosphors obtained by spray pyrolysis

The broadband inter-configurational (4f(1)5d(1)-->4f(2)) emission of Pr(3+) doped in lanthanum orthophosphate (LaPO(4)) and in calcium pyrophosphate (Ca(2)P(2)O(7)) has been investigated under plasma excitation. The synthesis by spray pyrolysis at moderate temperature followed by a controlled annealing proves to be a very efficient way to produce good quality UVC emitting phosphor Ca(1.92)Pr(0.04)Na(0.04)P(2)O(7) (alpha phase). The emission of this phosphor in the wavelength range 200-350 nm has been measured with a prototype device, which can be employed for anti-microbial testing. (C) 2010 Elsevier B.V. All rights reserved.

Digital radiographic evaluation of optical density of porcelains used for fabrication of inlay/onlay prosthesis

The purpose of this article was to compare the mean value of optical density of four porcelains commonly used for fabrication of inlay/ onlay prostheses using direct digital radiograph. The sample consisted of 20 2-mm thick porcelain specimens (measured by digital pachymeter): Empress (Ivoclair), Simbios (Degussa), Vita Omega 900 and Vitadur Alpha (Vita Zahnfabrik). The values of optical density of the specimens were expressed in millimeters aluminum equivalent (mm eq Al). The samples were X-rayed using two charge coupled devices (CCD) - RVG (Trophy) - Visualix (Gendex) and a phosphor plate system - Digora (Soredex). The optical density reading was performed with Image Tool 1.28 in a total of 110 measurements. Statistical analysis showed that there were statistically significant differences in all materials studied (p < 0.05) regardless of the radiographic system used. The highest optical density value was found for Omega 900 (1.8988 mmeqAl - Visualix - Gendex) and the lowest for Vitadur Alpha (0.8647 - Visualix - Gendex). Thus, the material presenting the highest degree of optical density was Omega 900, Empress and Simbios presented intermediate optical density values, Vitadur Alpha presented the lowest value, and the optical density of porcelains was not influenced by the digital radiography systems.

Radiopacity of restorative materials using digital images

The radiopacity of esthetic restorative materials has been established as an important requirement, improving the radiographic diagnosis. The aim of this study was to evaluate the radiopacity of six restorative materials using a direct digital image system, comparing them to the dental tissues (enamel-dentin), expressed as equivalent thickness of aluminum (millimeters of aluminum). Five specimens of each material were made. Three 2-mm thick longitudinal sections were cut from an intact extracted permanent molar tooth (including enamel and dentin). An aluminum step wedge with 9 steps was used. The samples of different materials were placed on a phosphor plate together with a tooth section, aluminum step wedge and metal code letter, and were exposed using a dental x-ray unit. Five measurements of radiographic density were obtained from each image of each item assessed (restorative material, enamel, dentin, each step of the aluminum step wedge) and the mean of these values was calculated. Radiopacity values were subsequently calculated as equivalents of aluminum thickness. Analysis of variance (ANOVA) indicated significant differences in radiopacity values among the materials (P<0.0001). The radiopacity values of the restorative materials evaluated were, in decreasing order: TPH, F2000, Synergy, Prisma Flow, Degufill, Luxat. Only Luxat had significantly lower radiopacity values than dentin. One material (Degufill) had similar radiopacity values to enamel and four (TPH, F2000, Synergy and Prisma Flow) had significantly higher radiopacity values than enamel. In conclusion, to assess the adequacy of posterior composite restorations it is important that the restorative material to be used has enough radiopacity, in order to be easily distinguished from the tooth structure in the radiographic image. Knowledge on the radiopacity of different materials helps professionals to select the most suitable material, along with other properties such as biocompatibility, adhesion and esthetic.

Detection of cavitated approximal surfaces using cone beam CT and intraoral receptors

Objectives: The aim of this study was to compare cone beam CT (CBCT) in a small field of view (FOV) with a solid-state sensor and a photostimulable phosphor plate system for detection of cavitated approximal surfaces. Methods: 257 non-filled approximal surfaces from human permanent premolars and molars were recorded by two intraoral digital receptors, a storage phosphor plate (Digora Optime, Soredex) and a solid-state CMOS sensor (Digora Toto, Soredex), and scanned in a cone beam CT unit (3D Accuitomo FPD80, Morita) with a FOV of 4 cm and a voxel size of 0.08 mm. Image sections were carried out in the axial and mesiodistal tooth planes. Six observers recorded surface cavitation in all images. Validation of the true absence or presence of surface cavitation was performed by inspecting the surfaces under strong light with the naked eye. Differences in sensitivity, specificity and agreement were estimated by analysing the binary data in a generalized linear model using an identity link function. Results: A significantly higher sensitivity was obtained by all observers with CBCT (p,0.001), which was not compromised by a lower specificity. Therefore, a significantly higher overall agreement was obtained with CBCT (p,0.001). There were no significant differences between the Digora Optime phosphor plate system and the Digora Toto CMOS sensor for any parameter. Conclusions: CBCT was much more accurate in the detection of surface cavitation in approximal surfaces than intraoral receptors. The differences are interpreted as clinically significant. A CBCT examination performed for other reasons should also be assessed for approximal surface cavities in teeth without restorations. �� 2013 The British Institute of Radiology.

Avalia����o da rela����o entre as atividades de engorda e pesque-pague e as caracter��sticas limnol��gicas destes ambientes aqu��ticos

P��s-gradua����o em Aquicultura - FCAV

Obten����o de esp��cies moleculares e supramoleculares a partir de rea����es de auto-montagem entre ��ons lantan��deos e mol��culas org��nicas multil��picas

Conselho Nacional de Desenvolvimento Cient��fico e Tecnol��gico (CNPq)

Biocompatibilidade in vitro em amostras densas e porosas de tit��nio-35ni��bio submetidas a tratamento biomim��tico

Coordena����o de Aperfei��oamento de Pessoal de N��vel Superior (CAPES)

Mineralogy and chemistry of archaeological ceramic fragments from archaeological Dark Earth site in Colombian Amazon

V��rios s��tios arqueol��gicos de Terra Preta Arqueol��gica (TPA) encontrados na floresta Amaz��nica Colombiana tamb��m cont��m alto conte��do de fragmentos cer��micos semelhantes aqueles da Amaz��nia Brasileira, como mostra o s��tio Quebrada Tacana. Seus fragmentos cer��micos s��o amarelo a cinza, exibem matriz argilosa calcinada envolvendo fragmentos de cariap��, carv��o e part��culas de cinza, gr��os de quartzo e micas. A matriz �� composta de metacaulinita a material amorfo, quartzo, folhas de micas, clorita e sepiolita. Cariap�� e cauixi s��o constitu��dos de cristobalita, da mesma forma o carv��o e as cinzas. Embora n��o detectados pela difra����o de raios x, os fosfatos devem estar presentes, pois foram detectados teores de P2O5 de at�� 2,90 %, possivelmente como fosfatos de alum��nio, j�� que o conte��do de Ca est�� abaixo 0,1 %, o que elimina a possibilidade da presen��a de apatita. Estas caracter��sticas mineral��gicas e qu��micas permitem relacionar estes fragmentos cer��micos com aqueles encontrados nos s��tios de TPA no Brasil e refor��a o f��sforo como um importante componente qu��mico, originado pelo contato dos vasos cer��micos com os alimentos do cotidiano dos povos amaz��nicos pr��-hist��ricos.

The ceramic artifacts in archaeological black earth (terra preta) from lower Amazon region, Brazil: Mineralogy

S��tios arqueol��gicos com Terra Preta, denominados de Terra Preta de ��ndio ou ainda Terra Preta Arqueol��gica (TPA) s��o muito freq��entes na Amaz��nia. As TPA geralmente cont��m fragmentos de vasos cer��micos, por vezes abundantes, al��m de l��ticos, que s��o materiais de grande import��ncia para os estudos arqueol��gicos. Para consubstanciar esses estudos, realizou-se pesquisas mineral��gicas e qu��micas em fragmentos cer��micos provenientes de dois s��tios arqueol��gicos da regi��o de Cachoeira-Porteira, Estado do Par��. Os fragmentos foram classificados segundo seus principais temperos em: cauixi, cariap��, areia+feldspatos e caco de vaso cer��mico. Mineralogicamente s��o compostos de quartzo, minerais de argila calcinados (especialmente caulinita), feldspatos (albita e microcl��nio), hematita, goethita, maghemita, variscita-estrengita, fosfatos amorfos, anat��sio, e raramente apatita, rhabdophana e ��xidos de Mn e Ba. Cauixi e cariap�� s��o componentes org��nicos silicosos e amorfos a DRX. A composi����o mineral��gica e a morfologia dos seus gr��os indicam sapr��lito (material argiloso rico em quartzo) derivado de rochas ��gneas f��lsicas de granula����o fina ou rochas sedimentares ricas em argilominerais como mat��ria-prima dos vasos cer��micos. Neste material argiloso cauixi, cariap�� e/ou areias, ricas em s��lica, foram intencionalmente adicionados. O elevado conte��do de fosfatos de Al-Fe, amorfos ou como de baixa cristalinidade, originou-se a partir do contato entre a matriz argilosa da parede do vaso cer��mico com a solu����o aquosa quente durante o cozimento di��rio de alimentos de origem animal (principal fonte de f��sforo). A cristaliza����o dos fosfatos deve ter prosseguida mesmo depois que os vasos foram descartados, e juntos com os restos de mat��ria org��nica vegetal e animal incorporaram-se aos solos residuais. Participaram desta forma na forma����o dos solos tipo TPA.

Impacto ambiental e agron��mico do uso de condicionadores org��nicos no cultivo de Cymbopogon citratus

Conselho Nacional de Desenvolvimento Cient��fico e Tecnol��gico (CNPq)

C��lulas solares de ZnO:Ga nanocristalino sensibilizado por corante

Coordena����o de Aperfei��oamento de Pessoal de N��vel Superior (CAPES)

Par��metros espectrosc��picos te��ricos e experimentais do cintilador 'GD IND.2''O IND.2''S':'CE POT.3+', 'PR POT.3+'

Coordena����o de Aperfei��oamento de Pessoal de N��vel Superior (CAPES)