Energy transfer processes in Yb(3+)-Tm(3+) co-doped sodium alumino-phosphate glasses with improved 1.8 mu m emission

Sodium alumino-phosphate glasses co-doped with Yb(3+) and Tm(3+) ions have been prepared with notably low OH(-) content, and characterized from the viewpoint of their spectroscopic properties. In these glasses, Yb(3+) acts as an efficient sensitizer of excitation energy at 0.98 mu m - which can be provided by high power and low cost diode lasers, and subsequently undergoes non-resonant energy transfer to Tm(3+) ions ((2)F(5/2), (3)H(6) --> (2)F(7/2), (3)H(5)). Through this process, the emitting level (3)F(4) is rapidly populated, generating improved emission at 1.8 mu m ((3)F(4) --> (3)H(6)). In order to guarantee the efficiency of such favorable energy transfer, energy losses via multiphonon decay, Yb-Yb radiative trapping, and non- radiative transfer to OH(-) groups were evaluated, and minimized when possible. The dipole - dipole energy transfer microscopic parameters corresponding to Yb(3+) --> Tm(3+), Yb(3+) --> Yb(3+) and Tm(3+) --> Tm(3+) transfers, calculated by the Forster-Dexter model, are C(Yb-Tm) = 2.9 x 10(-40) cm(6) s(-1), C(Yb-Yb) = 42 x 10(-40) cm(6) s(-1) and C(Tm-Tm) = 43 x 10(-40) cm(6) s(-1), respectively.

A TRIPLE-MODE BANDPASS FILTER USING A MODIFIED CIRCULAR PATCH RESONATOR

This article presents a triple-mode bandpass filter using a modified circular patch resonator. Etched slots in the resonator split the TM(1, 1, 0)(z) degenerate fundamental modes and also perturb the TM(2, 1, 0)(z) mode, approximating their resonant frequencies to form a third-order bandpass filter. A 2.42 GHz centered filter was designed and fabricated. Experimental results showed a fractional bandwidth of 29%, return loss better than 16 dB, insertion loss of 0.5 dB, and good second harmonic band rejection. The filter exhibited a size reduction of 51% compared with a filter using an unperturbed circular patch resonator at the same frequency. (C) 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 178-182, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23950

Frequency upconversion luminescence from Yb(+3)-Tm(+3) codoped PbO-GeO(2) glasses containing silver nanoparticles

Infrared-to-visible and infrared-to-infrared frequency upconversion processes in Yb(3+)-Tm(3+) doped PbO-GeO(2) glasses containing silver nanoparticles (NPs) were investigated. The experiments were performed by exciting the samples with a diode laser operating at 980 nm (in resonance with the Yb(3+) transition (2)F(7/2)->(2)F(5/2)) and observing the photoluminescence (PL) in the visible and infrared regions due to energy transfer from Yb(3+) to Tm(3+) ions followed by excited state absorption in the Tm3+ ions. The intensified local field in the vicinity of the metallic NPs contributes for enhancement in the PL intensity at 480 nm (Tm(3+) :(1)G(4)->(3)H(6)) and at 800 nm (Tm(3+) : (3)H(4) -> (3)H(6)). (C) 2009 American Institute of Physics. [doi:10.1063/1.3211300]

Influence of the heat treatment on the nucleation of silver nanoparticles in Tm(3+) doped PbO-GeO(2) glasses

Nucleation of silver nanoparticles (NPs) in Tm(3+) doped PbO-GeO(2) (PGO) glass is reported. The influence of the heat treatment on the nucleation of silver NPs is studied by means of transmission electron microscopy and optical spectroscopy. Two heat treatment procedures were applied in order to compare their performance. Observation of infrared-to-visible frequency upconversion (UC) luminescence of Tm(3+) ions is reported and correlated with the heat-treatment procedure. Enhancement of the UC emission for samples heat treated during various time intervals is attributed to the increased local field in the vicinity of the NPs. Quenching of the UC signal was also observed and correlated with the growth of NPs amount and size.

COMPARATIVE STUDY OF THE SENSITIVITY OF DIABETIC LOWER EXTREMITIES WITH AND WITHOUT ULCERS USING THE PSSD (TM)

Introduction To determine and compare thresholds of cutaneous sensitivity of lower extremities in diabetic patients with an ulcer on only one lower extremity Methods and Materials The study group included 20 patients with mean age of 61 6 and average time with diabetes of 12 4 years All patients were previously tested using Semmes-Weinstein monofilament 5 07 Sensitivity was evaluated using the two point discrimination test and the PSSD (TM) (Pressure-Specified Sensory Device) in order to assess touch thresholds in a quantitative manner, in g/mm(2) Three skin areas were tested hallux pulp, dorsum of foot and medial heel, including four tests 1 point static, 1 point moving, 2 points static and 2 points moving Results Mean 2 point discrimination distance in mm was higher in feet with ulcers, but the difference between extremities was only statistically significant for the hallux. With the PSSD (TM), all patients had higher pressure thresholds in feet with ulcers when compared with feet without ulcers, in all tests, with statistical significance Conclusion The PSSD (TM) was able to differentiate levels of sensation between extremities with and without ulcers in diabetic patients, with statistical significance

Reverse Microemulsion Synthesis, Structure, and Luminescence of Nanosized REPO(4):Ln(3+) (RE = La, Y, Gd, or Yb, and Ln = Eu, Tm, or Er)

A surfactant-mediated solution route for the obtainment of nanosized rare-earth orthophosphates of different compositions (LaPO(4):Eu(3+), (Y,Gd)PO(4):Eu(3+),LaPO(4):Tm(3+), YPO(4):Tm(3+), and YbPO(4):Er(3+)) is presented, and the implications of the morphology control on the solids properties are discussed. The solids are prepared in water-in-heptane microemulsions, using cetyltrimethylammonium bromide and 1-butanol as the surfactant and cosurfactant; the alteration of the starting microemulsion composition allows the obtainment of similar to 30 nm thick nanorods with variable length. The morphology and the structure of the solids were evaluated through scanning electron microscopy and through powder X-ray diffractometry; dynamic light scattering and thermal analyses were also performed. The obtained materials were also characterized through vibrational (FTIR) and luminescence spectroscopy (emission/excitation, luminescence lifetimes, chromaticity, and quantum efficiency), where the red, blue, and upconversion emissions of the prepared phosphors were evaluated.

PM(2.5) and PM(10): The influence of sugarcane burning on potential cancer risk

In Brazil, sugarcane fields are often burned to facilitate manual harvesting, and this burning causes environmental pollution from the large amounts of soot released into the atmosphere. This material contains numerous organic compounds such as PAHs. In this study, the concentrations of PAHs in two particulate-matter fractions (PM(2.5) and PM(10)) in the city of Araraquara (SE Brazil, with around 200,000 inhabitants and surrounded by sugarcane plantations) were determined during the sugarcane harvest (HV) and non-harvest (NHV) seasons in 2008 and 2009. The sampling strategy included four campaigns, with 60 samples in the NHV season and 220 samples in the HV season. The PM(2.5) and PM(10) fractions were collected using a dichotomous sampler (10 L min(-1), 24 h) with Teflon (TM) filters. The filter sets were extracted (ultrasonic bath with hexane/acetone (1:1 v/v)) and analyzed by HPLC/Fluorescence. The median concentration for total PAHs (PM(2.5) in 2009) was 0.99 ng m(-3) (NHV) and 3.3 ng m(-3) (HV). In the HV season, the total concentration of carcinogenic PAHs (benz(a)anthracene, benzo(b)fluoranthene, benzo(k)fluoranthene, and benzo(a)pyrene) was 5 times higher than in the NHV season. B(a)P median concentrations were 0.017 ng m(-3) and 0.12 ng m(-3) for the NHV and HV seasons, respectively. The potential cancer risk associated with exposure through inhalation of these compounds was estimated based on the benzo[a]pyrene toxic equivalence (BaP(eq)), where the overall toxicity of a PAR mixture is defined by the concentration of each compound multiplied by its relative toxic equivalence factor (TEF). BaP(eq) median (2008 and 2009 years) ranged between 0.65 and 1.0 ng m(-3) and 1.2-1.4 ng m(-3) for the NHV and HV seasons, respectively. Considering that the maximum permissible BaPeq in ambient air is 1 ng m(-3), related to the increased carcinogenic risk, our data suggest that the level of human exposure to PAHs in cities surrounded by sugarcane crops where the burning process is used is cause for concern. (C) 2010 Published by Elsevier Ltd.

Essential role of TM V and VI for binding the C-terminal sequences of Des-Arg-kinins

In the kallikrein-kinin and renin-angiotensin systems the main receptors, B-1 and B-2 (kinin receptors) and AT(1) and AT(2) (angiotensin receptors) respectively, are seven-transmembrane domain G-protein-coupled receptors. Considering that the B, agonists Des-Arg(9)-BK (Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe), Lys-desArg(9)-BK or Des-Arg(10)-KD (Lys-Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe) and the AT, agonist (Asp-Arg-Val-Tyr-lle-His-Pro-Phe) have the same two residues at the C-terminal region (i.e. Pro-Phe), we hypothesized that TM V and TM VI of the B-1 receptor could play an essential role in agonist binding and activity, being these regions receptor sites for binding the C-terminal sequences of Des-Arg-kinins similarly to that observed to AT, receptor. To investigate this hypothesis, we replaced Arg(212) for Ala at the top of the TM V and the sequence 274-282 (CPYHFFAFL) in TM VI of the rat kinin B, receptor by the 32 receptor homologous sequence, 289-297 (FPFQISTFL) and subsequently analyzed the consequences of these mutations by competition binding and functional assays. Despite correct expression, observed at the mRNA and protein level by RT-PCR and confocal microscopy, respectively, no agonist binding and function was verified for the mutated receptors. Therefore, our results suggest an important role for Arg(212) in the TM V and a region of TM VI of rat B, receptor in the interaction with the C-terminal residues of Des-Arg-kinins, similar to that observed with AngII. (c) 2007 Elsevier B.V. All rights reserved.

Canine visceral leishmaniasis: Performance of a rapid diagnostic test (Kalazar Detect (TM)) in dogs with and without signs of the disease

Current visceral leishmaniasis (VL) control programs in Brazil include the infected dog elimination but, despite this strategy, the incidence of human VL is still increasing. One of the reasons is the long delay between sample collection, analysis, control implementation and the low sensitivity of diagnostic tests. Due to the high prevalence of asymptomatic dogs, the diagnosis of these animals is important considering their vector infection capacity. Hence, a rapid and accurate diagnosis of canine visceral leishmaniasis is essential for an efficient surveillance program. In this study we evaluated the performance of rK39 antigen in an immunochromatographic format to detect symptomatic and asymptomatic Leishmania chagasi infection in dogs and compared the results with those using a crude antigen ELISA. The sensitivity of rK39 dipstick and ELISA were 83% vs. 95%, respectively, while the specificity was both 100%. Our results also demonstrated that the dipstick test was able to detect infected dogs presenting different clinical forms. (C) 2008 Elsevier B.V. All rights reserved.

Bond strength of Epiphany (TM) Sealer combined with different adhesive systems photo-activated with LED and QTH

The Epiphany (TM) Sealer is a new dual-curing resin-based sealer and has been introduced as an alternative to gutta-percha and traditional root canal sealers. The canal filling is claimed to create a seal with the dentinal tubules within the root canal system producing a `monoblock` effect between the sealer and dentinal tubules. Therefore, considering the possibility to incorporate the others adhesive systems, it is important to study the bond strength of the resulting cement. Forty-eight root mandibular canines were sectioned 8-mm below CEJ. The dentine discs were prepared using a tapered diamond bur and irrigated with 1% NaOCl and 17% EDTA. Previous the application Epiphany (TM) Sealer, the Epiphany (TM) Primer, AdheSE, and One Up Bond F were applied to the root canal walls. The LED and QTH (Quartz Tungsten Halogen) were used to photo-activation during 45 s with power density of 400 and 720 mW/cm(2), respectively. The specimens were performed on a universal testing machine at a cross-head speed of 1 mm/min until bond failure occurred. The force was recorded and the debonding values were used to calculate Push-out bond strength. The analysis of variance (ANOVA) and Tukey`s post-hoc tests showed significant statistical differences (P < 0.05) to Epiphany (TM) Sealer/Epiphany (TM) Primer/QTH and EpiphanyTM Sealer/AdheSE/QTH, which had the highest mean values of bond strength. The efficiency of resin-based filling materials are dependent the type of light curing unit used including the power density, the polymerization characteristics of these resin-based filling materials, depending on the primer/adhesive used.

Synthesis and magnetic characterization of TmCo(2)B(2)C

A new quaternary intermetallic borocarbide TmCo(2)B(2)C has been synthesized via rapid-quench of an arc-melted ingot. Elemental and powder-diffraction analyses established its correct stoichiometry and single-phase character. The crystal structure is isomorphous with that of TmNi(2)B(2)C (I4/mmm) and is stable over the studied temperature range. Above 7 K, the paramagnetic state follows modified Curie-Weiss behavior (chi = C/(T - theta) + chi(0)) wherein chi(0) = 0.008(1) emu mol(-1) with the temperature-dependent term reflecting the paramagnetism of the Tm subsystem: mu(eff) = 7.6(2) mu(B) (in agreement with the expected value for a free Tm(3+) ion) and theta = -4.5(3) K. Long-range ferromagnetic order of the Tm sublattice is observed to develop around similar to 1 K. No superconductivity is detected in TmCo(2)B(2)C down to 20 mK, a feature which is consistent with the general trend in the RCo(2)B(2)C series. Finally, the influence of the rapid-quench process on the magnetism (and superconductivity) of TmNi(2)B(2)C will be discussed and compared to that of TmCo(2)B(2)C.

Comparison between blue and green stimulated luminescence of Al(2)O(3):C

This paper presents a systematic comparison of OSL signals from Al(2)O(3):C when stimulated with blue and green light. Al(2)O(3):C detectors were irradiated with various doses and submitted to various bleaching regimes using yellow, green and blue light. Most of the investigations were carried out using Luxel (TM)-type detectors used in the commercial Luxet (TM) and InLight (TM) dosimetry systems (Landauer Inc.). Al(2)O(3):C single crystals and Al(2)O(3):C powder were also used to complement the investigations. The results show that, although blue stimulation provides faster readout times (OSL curves that decayed faster) and higher initial OSL intensity than green stimulation, blue stimulation introduced complicating factors. These include incomplete bleaching of the dosimetric trap when the Al(2)O(3):C detectors are bleached with yellow or green light and the OSL is recorded with blue light stimulation, and an increased residual level due to stimulation of charge carriers from deep traps. The results warrant caution when using blue stimulation to measure the OSL signal from Al(2)O(3):C detectors, particularly if the doses involved are low and the detectors have been previously exposed to high doses. (C) 2010 Elsevier Ltd. All rights reserved.

Structural and optical properties on thulium-doped LHPG-grown Ta(2)O(5) fibres

Structural, spectroscopic and dielectric properties of thulium-doped laser-heated pedestal Ta(2)O(5) as-grown fibres were studied. Undoped samples grow preferentially with a single crystalline monoclinic structure. The fibre with the lowest thulium content (0.1 at%) also shows predominantly a monoclinic phase and no intra-4f(12) Tm(3+) recombination was observed. For sample with the highest thulium amount (1.0 at%), the appearance of a dominant triclinic phase as well as intraionic optical activation was observed. The dependence of photoluminescence on excitation energy allows identification of different site locations of Tm(3+) ions in the lattice. The absence of recombination between the first and the ground-state multiplets as well as the temperature dependence of the observed transitions was justified by an efficient energy transfer between the Tm(3+) ions. Microwave dielectric properties were investigated using the small perturbation theory. At a frequency of 5 GHz, the undoped material exhibits a dielectric permittivity of 21 and for thulium-doped Ta(2)O(5) samples it decreases to 18 for the highest doping concentration. Nevertheless, the dielectric losses maintain a very low value. (C) 2008 Elsevier Ltd. All rights reserved.

Mg(2+) Ions Bind at the C-Terminal Region of Skeletal Muscle alpha-Tropomyosin

Tropomyosin (Tm) is a dimeric coiled-coil protein that polymerizes through head-to-tail interactions. These polymers bind along actin filaments and play an important role in the regulation of muscle contraction. Analysis of its primary structure shows that Tm is rich in acidic residues, which are clustered along the molecule and may from sites for divalent cation binding. In a previous study, we showed that the Mg(2+)-induced increase in stability of the C-terminal half of Tin is sensitive to imitations near the C-terminus. In the present report, we study the interaction between Mg(2+) and full-length Tin and smaller fragments corresponding to the last 65 and 26 Tin residues. Although the smaller Tin peptide (Tm(259-284(W269))) is flexible and to large extent unstructured, the larger Tm(220-284(W269)) fragments forms a coiled coil in solution whose stability increases significantly in the presence of Mg(2+). NMR analysis shows thin Mg(2+) induces chemical shift perturbations in both Tm(220-284(W269)) and Tm(259-284(W269)) in the vicinity of His276, in which are located several negatively charged residues. (C) 2009 Wiley Periodicals, Inc. Biopolymers 91: 583-590, 2009.

Desmistificando os braquetes autoligáveis

Atualmente, os braquetes autoligáveis têm sido associados a tratamentos mais rápidos e eficazes, o que desperta a curiosidade em compará-los ao sistema convencional. Ao contrário dos braquetes tradicionais, os autoligáveis não necessitam de ligaduras, sejam elásticas ou metálicas. A literatura é farta em concluir que essa característica diminui, ostensivamente, a resistência do atrito durante as mecânicas de deslize. Além disso, existem alegações sobre a dimimuição da necessidade de extrações e de expansão maxilar com o uso desses acessórios. Portanto, o objetivo dessa revisão de literatura foi buscar os mais novos estudos a respeito dos aparelhos autoligáveis atualmente utilizados nos tratamentos ortodônticos, confirmando ou retificando as especulações vigentes.