Influence of energy and pulse repetition rate of Er : YAG laser on enamel ablation ability and morphological analysis of the laser-irradiated surface

Objective: To assess the influence of energy and pulse repetition rate of Er:YAG laser on the enamel ablation ability and substrate morphology. Methods: Fifteen crowns of molars were sectioned in four fragments, providing 60 samples, which were ground to flatten the enamel surface. The initial mass was obtained by weighing the fragments. The specimens were hydrated for I h, fixed, and a 3-mm-diameter area was delimited. Twelve groups were randomly formed according to the combination of laser energies (200, 250, 300, or 350 mJ) and pulse repetition rates (2, 3, or 4 Hz). The final mass was obtained and mass loss was calculated by the difference between the initial and final mass. The specimens were prepared for SEM. Data were submitted to ANOVA and Scheffe test. Results: The 4 Hz frequency resulted in higher mass loss and was statistically different from 2 and 3 Hz (p < 0.05). The increase of frequency produced more melted areas, cracks, and unselective and deeper ablation. The 350 mJ energy promoted greater mass loss, similar to 300 mJ. Conclusions: The pulse repetition rate influenced more intensively the mass loss and morphological alteration. Among the tested parameters, 350 mJ/3 Hz improved the ability of enamel ablation with less surface morphological alterations. (C) 2007 Wiley Periodicals, Inc. J Biomed Mater Res.

Bond durability in erbium:yttrium-aluminum-garnet laser-irradiated enamel

This study sought to evaluate the influence of thermocycling and water storage on the microtensile bond strength of composite resin bonded to erbium:yttrium-aluminum-garnet (Er:YAG)-irradiated and bur-prepared enamel. Eighty bovine incisors were selected and sectioned. Specimens were ground to produce a flat enamel surface. Samples were randomly assigned according to cavity preparation device: (I) Er:YAG laser and (II) high-speed turbine, and were subsequently restored with composite resin. They were subdivided according to the duration of water storage (WS)/number of thermocycles (TCs): 24 h WS/no TCs; 7 days WS/500 TCs; 1 month WS/2,000 TCs; 6 months WS/12,000 TCs. The teeth were sectioned into 1.0 mm(2)-thick slabs and subjected to tensile stress in a universal testing machine. Data were submitted to two-way analysis of variance (ANOVA) and Tukey`s test at a 0.05 significance level. The different periods of water storage and thermocycling did not influence the microtensile bond strength (A mu TBS) values in the Er:YAG laser-prepared groups. In bur-prepared enamel, the group submitted to 12,000 TCs/6 months` WS (IID) showed a significant decrease in bond strength values when compared to the group stored in water for 24 h and not submitted to thermocycling (IIA), but values were statistically similar to those obtained in all Er:YAG laser groups and in the bur- prepared groups degraded with 500 TCs/1 week WS (IIB) or 2,000 TCs/1 month WS (IIC). It may be concluded that adhesion of an etch-and-rinse adhesive to Er:YAG laser-irradiated enamel was not affected by the methods used to simulate degradation of the adhesive interface and was similar to adhesion in the bur-prepared groups in all periods of water storage and thermocycling.

Influence of NaHCO(3) Powder on Translucency of Microfilled Composite Resin Immersed in Different Mouthrinses

The regular use of mouthrinses, particularly when combined with the use of air-powder polishing, could affect the appearance of tooth-colored restorations. The current study sought to evaluate the effect of NaHCO(3) powder on translucency of a microfilled composite resin immersed in different mouthrinses, at distinct evaluation periods. Eighty disk-shaped specimens of composite resin (Durafill VS, Heraeus Kulzer GmbH & Co. KG, Hanau, Germany) were prepared. The composite specimens were then randomly allocated into two groups according to the surface treatment: exposure to NaHCO(3) powder (10 seconds) or nonexposure, and they were randomly assigned into four subgroups, according to the mouthrinses employed (N = 10): Periogard (Colgate/Palmolive, Sao Bernardo do Campo, SP, Brazil), Cepacol (Aventis Pharma, Sao Paulo, SP, Brazil), Plax (Colgate/Palmolive), and distilled water (control group). The samples were immersed for 2 minutes daily, 5 days per week, over a 4-month test period. Translucency was measured with a transmission densitometer at seven evaluation periods. Statistical analyses (analysis of variance and Tukey`s test) revealed that: distilled water presented higher translucency values (86.72%); Periogard demonstrated the lowest translucency values (72.70%); and Plax (74.05%) and Cepacol (73.32%) showed intermediate translucency values, which were statistically similar between them (p > 0.01). NaHCO(3) air-powder polishing increased the changes in translucency associated with the mouthrinses. Air-powder polishing alone had no effect on material translucency. Translucency percent was gradually decreased from 1 week of immersion up to 4 months. It may be concluded that the NaHCO(3) powder and the tested mouthrinses have affected the translucency of microfilled composite resin, according to the tested time. CLINICAL SIGNIFICANCE During the last decade, the demand for composite resin restorations has grown considerably, however, controversy persists regarding the effect of surface roughness on color stability.

Influence of water flow rate on shear bond strength of resin composite to Er : YAG cavity preparation

Purpose: To evaluate in vitro the influence of water flow rate on shear bond strength of a resin composite to enamel and dentin after Er:YAG cavity preparation. Methods: Ten bovine incisors were selected and roots removed. Crowns were sectioned in four pieces, resulting in 40 samples that were individually embedded in polyester resin (n=10), and ground to plane the enamel and expose the dentin. The bonding site was delimited and samples were randomly assigned according to cavity preparation: (1) Er:YAG/1.0 mL/minute; (2) Er:YAG/1.5 mL/minute; (3) Er:YAG/2.0 mL/minute and (4) High speed handpiece/bur (control group). Samples were fixed to a metallic device, where composite resin cylinders were prepared. Subsequently, they were stored for 24 hours and subjected to a shear bond strength test (500N at 0.5 mm/minute). Results: Means (MPa) were: enamel: 1: 12.8; 2: 16.8; 3: 17.5; 4: 36.0 and Dentin: 1: 13.6; 2: 18.7; 3: 12.1; 4: 21.3. Data were submitted to ANOVA and Tukey`s test. Adhesion to enamel was more efficient than for dentin. The cavities prepared with conventional bur (control) presented higher statistically significant bond strength values (P<0.05) than for Er:YAG laser for both enamel and dentin. No significant differences were observed between water flow rates employed during enamel ablation. For dentin, the shear bond strength of 2.0 mL/minute water flow rate was lower than for 1.5 mL/minute and 1.0 mL/minute rates. The Er:YAG laser adversely affected shear bond strength of resin composite to both enamel and dentin, regardless of the water flow rate used.

Adhesion to Er : YAG laser-prepared dentin after long-term water storage and thermocycling

This in vitro study evaluated the microtensile bond strength of a resin composite to Er:YAG-prepared dentin after long-term storage and thermocycling. Eighty bovine incisors were selected and their roots removed. The crowns were ground to expose superficial dentin. The samples were randomly divided according to cavity preparation method (I-Er:YAG laser and II-carbide bur). Subsequently, an etch & rinse adhesive system was applied and the samples were restored with a resin composite. The samples were subdivided according to time of water storage (WS)/number of thermocycles (TC) performed: A) 24 hours WS/no TC; B) 7 days WS/500 TC; C) 1 month WS/2,000 TC; D) 6 months WS/12,000 TC. The teeth were sectioned in sticks with a cross-sectional area of 1.0-mm(2), which were loaded in tension in a universal testing machine. The data were subjected to two-way ANOVA, Scheffe and Fisher`s tests at a 5% level. In general, the bur-prepared group displayed higher microtensile bond strength values than the laser-treated group. Based on one-month water storage and 2,000 thermocycles, the performance of the tested adhesive system to Er:YAG-laser irradiated dentin was negatively affected (Group IC), while adhesion of the bur-prepared group decreased only within six months of water storage combined with 12,000 thermocycles (Group IID). It may be concluded that adhesion to the Er:YAG laser cavity preparation was more affected by the methods used for simulating degradation of the adhesive interface.

SURFACE ALFVEN WAVE DAMPING IN A THREE-DIMENSIONAL SIMULATION OF THE SOLAR WIND

Here we investigate the contribution of surface Alfven wave damping to the heating of the solar wind in minima conditions. These waves are present in the regions of strong inhomogeneities in density or magnetic field (e.g., the border between open and closed magnetic field lines). Using a three-dimensional (3D) magnetohydrodynamics (MHD) model, we calculate the surface Alfven wave damping contribution between 1 and 4 R(circle dot) (solar radii), the region of interest for both acceleration and coronal heating. We consider waves with frequencies lower than those that are damped in the chromosphere and on the order of those dominating the heliosphere: 3 x 10(-6) to 10(-1) Hz. In the region between open and closed field lines, within a few R(circle dot) of the surface, no other major source of damping has been suggested for the low frequency waves we consider here. This work is the first to study surface Alfven waves in a 3D environment without assuming a priori a geometry of field lines or magnetic and density profiles. We demonstrate that projection effects from the plane of the sky to 3D are significant in the calculation of field line expansion. We determine that waves with frequencies >2.8 x 10(-4) Hz are damped between 1 and 4 R(circle dot). In quiet-Sun regions, surface Alfven waves are damped at further distances compared to active regions, thus carrying additional wave energy into the corona. We compare the surface Alfven wave contribution to the heating by a variable polytropic index and find it as an order of magnitude larger than needed for quiet-Sun regions. For active regions, the contribution to the heating is 20%. As it has been argued that a variable gamma acts as turbulence, our results indicate that surface Alfven wave damping is comparable to turbulence in the lower corona. This damping mechanism should be included self-consistently as an energy driver for the wind in global MHD models.

Sediment-contact fish embryo toxicity assay with Danio rerio to assess particle-bound pollutants in the Tiete River Basin (Sao Paulo, Brazil)

The Tiete River and its tributary Pinheiros River receive a highly complex organic and inorganic pollutants load from sanitary sewage and industrial sources, as well as agricultural and agroindustrial activities. The aim of the present study was to evaluate the embryotoxic and teratogenic effects of sediments from selected locations in the Tiete River Basin by means of the sediment contact embryo toxicity assay with Danio rerio, in order to provide a comprehensive and realistic insight into the bioavailable hazard potential of these sediment samples. Lethal and sub-lethal effects were recorded, and high embryo toxicity could be found in the samples not only in the vicinity of the megacity Sao Paulo (Billings reservoir and Pinheiros River samples), but also downstream (in the reservoirs Barra Bonita, Promissao and Tres Irmaos). Results confirm that most toxicity is due to the discharges of the metropolitan area of Sao Paulo. However, they also indicate additional sources of pollutants along the river course, probably from industrial, agricultural and agroindustrial residues, which contribute to the degradation of each area. The sediment contact fish embryo test showed to be powerful tool to detect embryo toxicity in sediments, not only by being a sensitive method, but also for taking into account bioavailability. This test provides an ecological highly realistic and relevant exposure scenario, and should therefore be added in ecotoxicological sediment quality assessments. (C) 2011 Elsevier Inc. All rights reserved.

Five vicarious genera from Gondwana: the Velloziaceae as shown by molecules and morphology

Background and Aims The amount of data collected previously for Velloziaceae neither clarified relationships within the family nor helped determine an appropriate classification, which has led to huge discordance among treatment by different authors. To achieve an acceptable phylogenetic result and understand the evolution and roles of characters in supporting groups, a total evidence analysis was developed which included approx. 20 % of the species and all recognized genera and sections of Velloziaceae, plus outgroups representatives of related families within Pandanales. Methods Analyses were undertaken with 48 species of Velloziaceae, representing all ten genera, with DNA sequences from the atpB-rbcL spacer, trnL-trnF spacer, trnL intron, trnH-psbA spacer, ITS ribosomal DNA spacers and morphology. Key Results Four groups consistently emerge from the analyses. Persistent leaves, two phloem strands, stem cortex divided in three regions and violet tepals support Acanthochlamys as sister to Velloziaceae s. s., which are supported mainly by leaves with marginal bundles, transfusion tracheids and inflorescence without axis. Within Velloziaceae s. s., an African Xerophyta + Talbotia clade is uniquely supported by basal loculicidal capsules; an American clade, Barbacenia s. l. + Barbaceniopsis + Nanuza + Vellozia, is supported by only homoplastic characters. Barbacenia s. l. (Aylthonia + Barbacenia + Burlemarxia + Pleurostima) is supported by a double sheath in leaf vascular bundles and a corona; Barbaceniopsis + Nanuza + Vellozia is not supported by an unambiguous character, but Barbaceniopsis is supported by five characters, including diclinous flowers, Nanuza + Vellozia is supported mainly by horizontal stigma lobes and stem inner cortex cells with secondary walls, and Vellozia alone is supported mainly by pollen in tetrads. Conclusions The results imply recognition of five genera (Acanthochlamys (Xerophyta (Barbacenia (Barbaceniopsis, Vellozia)))), solving the long-standing controversies among recent classifications of the family. They also suggest a Gondwanan origin for Velloziaceae, with a vicariant pattern of distribution.

Craniosynostosis in Pycnodysostosis: Broadening the Spectrum of the Cranial Flat Bone Abnormalities

Pycnodysostosis is a rare autosomal recessive skeletal dysplasia caused by the absence of active cathepsin K, which is a lysosomal cysteine protease that plays a role in degrading the organic matrix of bones, acting in bone resorption and bone remodeling. The disease is primarily characterized by osteosclerosis, bone fragility, short stature, acro-osteolysis, and delayed closure of the cranial sutures. A differing feature, cranial synostosis, has occasionally been described in this disorder. We reviewed six unrelated patients with pycnodysostosis (mean age of 10 years and 4 months) in order to evaluate the presence of craniosynostosis. In addition to the typical findings of the condition, they all presented premature fusion of the corona! suture. Although none of them showed signs of cranial hypertension, one patient had had the craniosynostosis surgically corrected previously. These data suggest that the cranial sutures in pycnodysostosis can display contradictory features: wide cranial sutures, which are commonly described, and craniosynostosis. The clinical impact of this latter finding still remains to be elucidated. Further studies are necessary to address more precisely the role of cathepsin K in suture patency. (C) 2010 Wiley-Liss, Inc.

Identification of geodesic chirping Alfven modes and q-factor estimation in hot core tokamak plasmas in ASDEX Upgrade

Alfven eigenmodes (AE) driven by ion cyclotron resonance heating are usually registered by different diagnostic channels in the hot core plasmas of large tokamaks like JET and ASDEX Upgrade. These AE appear very near to the extremum points of Alfven wave continuum, which is modified by the geodesic effect due to poloidal mode coupling. It is shown that the AE spectrum may be explored as the magnetic spectroscopy (like Alfven cascades by Sharapov et al 2001 Phys. Lett. A 289 127) to determine the q-factor minimum and geodesic frequency at the magnetic axis in standard sawtoothed discharges without reversed shear.

Temporal behaviour of toroidal rotation velocity in the TCABR tokamak

A new method for determining the temporal evolution of plasma rotation is reported in this work. The method is based upon the detection of two different portions of the spectral profile of a plasma impurity line, using a monochromator with two photomultipliers installed at the exit slits. The plasma rotation velocity is determined by the ratio of the two detected signals. The measured toroidal rotation velocities of C III (4647.4 angstrom) and C VI (5290.6 angstrom), at different radial positions in TCABR discharges, show good agreement, within experimental uncertainty, with previous results (Severo et al 2003 Nucl. Fusion 43 1047). In particular, they confirm that the plasma core rotates in the direction opposite to the plasma current, while near the plasma edge (r/a > 0.9) the rotation is in the same direction. This technique was also used to investigate the dependence of toroidal rotation on the poloidal position of gas puffing. The results show that there is no dependence for the plasma core, while for plasma edge (r/a > 0.9) some dependence is observed.

Anisotropy of thermal stresses in confined dusty plasmas

Anisotropy of thermal stresses in confined dusty plasmas is considered. It is shown that in a multi-component low-temperature plasma containing electrons, ions and dust, the complicated dependence of the ion viscosity on ion temperature gradients leads to a plasma equilibrium state with anisotropic pressure. This pressure anisotropy can be of the order of the ion pressure in some limiting cases, in which the ion Larmor radius or the ion mean free path are of the order of the characteristic length of the plasma nonuniformity. For a sufficiently large dust number density, they contribute to the plasma pressure anisotropy and to its spatial dependence. Currently, it is not yet clear whether this equilibrium state is stable or not. Under these conditions, some convective plasma flows can arise in confinement devices. Therefore, this question needs special consideration.

Ionized-air-treated curaua fibers as reinforcement for phenolic matrices

Curaua fibers were treated with ionized air to improve the fiber/phenolic matrix adhesion.The treatment with ionized air did not change the thermal stability of the fibers. The impact strength increased with increase in the fiber treatment time. SEM micrographs of the fibers showed that the ionized air treatment led to separation of the fiber bundles. Treatment for 12 h also caused a partial degradation of the fibers, which prompted the matrix to transfer the load to a poorer reinforcing agent during impact, thereby decreasing the impact strength of the related composite. The composites reinforced with fibers treated with ionized air absorbed less water than those reinforced with untreated fibers.

1983 Yearbook Innervisions

128 p. b&w, color photographs TOC: LaGuardia the Man…4/Cooperative Education…12/Faculty and Staff…20/College Wide Events and Activities…37/Recreation…45/Nursery Program…51/Student Government…55/Student Activities…59/Dedication to Graduates…71/Graduates…81 YEARBOOK CREDITS: Project Director, VINCENT BANREY; Committee Chairperson, WALTER JACKSON; Copy /Caption Writer and Editor, UMOJA KWANGUVU; Photographers: ROBERT BROWN, WALTER JACKSON, RANDY FADER-SMITH, MARK SEALY, CLASSIC STUDIOS; Designed by VINCENT BANREY; Layout: VINCENT BANREY, SANDRA BRADLEY, BRIDGET DAVIS, REINALDO DENNY, UMOJA KWANGUVU, KEVIN RILEY; Typesetting, AUDREY WILLIAMS; Typing: SANDRA BRADLEY, TANYA BUSH-CORONA, BRIDGET DAVIS, ROSALIE NIEVES; Graphics: VINCENT BANREY, GEORGE BERMUDEZ, REINALDO DENNY, WALTER JACKSON.

Uncertainty Characterization Of A Conceptual Rainfall-Runoff Model By Using Grey Numbers

A procedure for characterizing global uncertainty of a rainfall-runoff simulation model based on using grey numbers is presented. By using the grey numbers technique the uncertainty is characterized by an interval; once the parameters of the rainfall-runoff model have been properly defined as grey numbers, by using the grey mathematics and functions it is possible to obtain simulated discharges in the form of grey numbers whose envelope defines a band which represents the vagueness/uncertainty associated with the simulated variable. The grey numbers representing the model parameters are estimated in such a way that the band obtained from the envelope of simulated grey discharges includes an assigned percentage of observed discharge values and is at the same time as narrow as possible. The approach is applied to a real case study highlighting that a rigorous application of the procedure for direct simulation through the rainfall-runoff model with grey parameters involves long computational times. However, these times can be significantly reduced using a simplified computing procedure with minimal approximations in the quantification of the grey numbers representing the simulated discharges. Relying on this simplified procedure, the conceptual rainfall-runoff grey model is thus calibrated and the uncertainty bands obtained both downstream of the calibration process and downstream of the validation process are compared with those obtained by using a well-established approach, like the GLUE approach, for characterizing uncertainty. The results of the comparison show that the proposed approach may represent a valid tool for characterizing the global uncertainty associable with the output of a rainfall-runoff simulation model.