Effect of Different Radiopacifying Agents on the Physicochemical Properties of White Portland Cement and White Mineral Trioxide Aggregate

Introduction: The aim of this study was to evaluate the pH, calcium ion release, setting time, and solubility of white mineral trioxide aggregate (WMTA) and white Portland cement (WPC) combined with the following radiopacifying agents: bismuth oxide (BO), calcium tungstate (CT), and zirconium oxide (ZO). Methods: Fifty acrylic teeth with root-end filling material were immersed in ultrapure water for measurement of pH and calcium release (atomic absorption spectrophotometry) at 3, 24, 72, and 168 hours. For evaluation of setting time, each material was analyzed according to the American Society for Testing and Materials guidelines 266/08. The solubility test was performed according to American National Standards Institute/American Dental Association specification no. 57/2000. Solubility, setting time, and pH values were compared by using analysis of variance and Tukey test, and the values of calcium release were compared by the Kruskal-Wallis and Miller tests. The significance level was set at 5%. Results: The pH and calcium release were higher at 3 and 24 hours. WPC was the material with the higher values for both properties. WMTA had the greatest solubility among all materials (P < .05). All radiopacifiers increased the setting time of WPC, and WMTA had the shortest setting time among all materials (P < .05). Conclusions: All materials released calcium ions. Except for WPC/CT at 168 hours, all materials promoted an alkaline pH. On the basis of the obtained results, ZO and CT can be considered as potential radiopacifying agents to be used in combination with Portland cement. (J Endod 2012;38:394-397)

Effect of surface area and air-drying distance on shear bond strength of etch-and-rinse adhesive

We evaluated the effects of air-drying distance and bond surface area on the shear bond strength of a 2-step etch-and-rinse adhesive. A total of 120 bovine anterior teeth were equally divided into 6 main groups based on bonding surface area. The main groups were divided into sub-groups (n = 5) according to air-drying distance. The shear strength was determined using a universal testing machine at a crosshead speed of 0.5 mm/min. The averaged results were subjected to two-way ANOVA and Tukey's test (alpha = 0.05). Two-way ANOVA testing identified no significant cross-product interactions (p > 0.05), but the main factors of area (p < 0.0001) and air-drying distance (p < 0.00001) significantly affected the mean bond strength. Shorter air-drying distances improved bond strength, and increased surface area decreased the bond strength.

The effect of Antarctic sea ice on the Southern Hemisphere atmosphere during the southern summer

This study examines the influence of Antarctic sea ice distribution on the large scale circulation of the Southern Hemisphere using a fully coupled GCM where the sea ice submodel is replaced by a climatology of observed extremes in sea ice concentration. Three 150-year simulations were completed for maximum, minimum and average sea ice concentrations and the results for the austral summer (January-March) were compared using the surface temperatures forced by the sea ice distributions as a filter for creating the composite differences. The results indicate that in the austral summer the polar cell expands (contracts) under minimum (maximum) sea ice conditions with corresponding shifts in the midlatitude Ferrell cell. We suggest that this response occurs because sea ice lies in the margin between the polar and midlatitude cells. The polarity of the Southern Hemisphere Annular (SAM) mode is also influenced such that when sea ice is at a minimum (maximum) the polarity of the SAM tends to be negative (positive).

Effect of different restorative procedures on the fracture resistance of teeth submitted to internal bleaching

The aim of this study was to evaluate the influence of different restorative procedures on the fracture resistance of endodontically treated teeth submitted to intracoronal bleaching. Fifty upper central incisors were distributed into 5 groups: GI - healthy teeth; GII - endodontically treated teeth sealed with Coltosol; GIII - endodontically treated teeth bleached and sealed with Coltosol; GIV - endodontically treated teeth bleached and restored with composite resin; and GV - endodontically treated teeth bleached and restored with a fiberglass post and composite resin. In the bleached specimens, a cervical seal was made prior to bleaching with 38% hydrogen peroxide. The gel was applied on the buccal surface and in the pulp chamber, and was then light-activated for 45 s. This procedure was repeated three times per session for four sessions, and each group was submitted to the restorative procedures described above. The specimens were submitted to fracture resistance testing in a universal testing machine. There were statistically significant differences among the groups (p < 0.05). The mean value found for GIII was the lowest (0.32 kN) and was significantly different from the values found for GI (0.75 kN), GII (0.67 kN), GIV (0.70 kN), and GV (0.72 kN), which were not significantly different from each other (p > 0.05). The restorative procedures using composite resin were found to successfully restore the fracture resistance of endodontically treated and bleached teeth.

An optimization study of PtSn/C catalysts applied to direct ethanol fuel cell: Effect of the preparation method on the electrocatalytic activity of the catalysts

The aim of this work was to perform a systematic study of the parameters that can influence the composition, morphology, and catalytic activity of PtSn/C nanoparticles and compare two different methods of nanocatalyst preparation, namely microwave-assisted heating (MW) and thermal decomposition of polymeric precursors (DPP). An investigation of the effects of the reducing and stabilizing agents on the catalytic activity and morphology of Pt75Sn25/C catalysts prepared by microwave-assisted heating was undertaken for optimization purposes. The effect of short-chain alcohols such as ethanol, ethylene glycol, and propylene glycol as reducing agents was evaluated, and the use of sodium acetate and citric acid as stabilizing agents for the MW procedure was examined. Catalysts obtained from propylene glycol displayed higher catalytic activity compared with catalysts prepared in ethylene glycol. Introduction of sodium acetate enhanced the catalytic activity, but this beneficial effect was observed until a critical acetate concentration was reached. Optimization of the MW synthesis allowed for the preparation of highly dispersed catalysts with average sizes lying between 2.0 and 5.0 nm. Comparison of the best catalyst prepared by MW with a catalyst of similar composition prepared by the polymeric precursors method showed that the catalytic activity of the material can be improved when a proper condition for catalyst preparation is achieved. (C) 2012 Elsevier B.V. All rights reserved.

Effect of Nitrogen Ion Implantation on the Flexibility of Rotary Nickel-Titanium Instruments

Introduction: The aim of this study was to assess the effect of nitrogen ion implantation on the flexibility of rotary nickel-titanium (NiTi) instruments as measured by the load required to bend implanted and nonimplanted instruments at a 30 degrees angle. Methods: Thirty K3 files, size #40, 0.02 taper and 25-mm length, were allocated into 2 groups as follows: group A, 15 files exposed to nitrogen ion implantation at a dose of 2.5 x 10(17) ions/cm(2), voltage 200 KeV, current density 1 mu A/cm(2), temperature 130 degrees C, and vacuum conditions of 10 x 10(-6) mm Hg for 6 hours; and group B, 15 nonimplanted files. One extra file was used for process control. All instruments were subjected to bend testing on a modified troptometer, with measurement of the load required for flexure to an angle of 30 degrees. The Mann-Whitney U test was used for statistical analysis. Findings with P <.05 were considered significant. Results: The mean load required to bend instruments at a 30 degrees angle was 376.26 g for implanted instruments and 383.78 g for nonimplanted instruments. The difference was not statistically significant. Conclusions: Our findings show that nitrogen ion implantation has no appreciable effect on the flexibility of NiTi instruments. (J Endod 2012;38:673-675)

Self-Assembly of Poly(4-vynil-N-alkylpyridinium) Bromide onto Silica: Effect of Side-Chain Length on Structural Aspects at a Molecular Level

Self-assembly of poly(4-vynil-N-alkyl)pyridinium bromide with alkyl side chains of 2, 5, 7, 10, or 16 carbons from ethanolic solutions onto flat silica surfaces was studied by means of ellipsometry, atomic force microscopy (AFM), contact angle measurements, and sum-frequency generation (SFG) vibrational spectroscopy in the CH3 and CH2 stretch region. Ab initio quantum-chemical calculations on the N-alkylpyridinium side-group with restricted Hartree-Fock (RHF) method and 6-311G (d,p) basis set were C one to estimate the charge distribution along the pyridinium ring and the alkyl side-chain. SFG results showed that longer side chains promote the disorientation of the alkyl groups at the surface, corroborating with the contact angle values. AFM images revealed film homogeneity, regardless the alkyl side group. However, after 24 h contact with water, ringlike structures appeared on the film surfaces, when the polycation alkyl side chain had 7 or less carbons, and as the alkyl chain increased to 10 or 16 carbons, the films dewetted because the hydrophobic interactions prevailed over the electrostatic interactions between the pyridinium charged groups and the negatively charged SiO2 surface. Under acid conditions (HCl 0.1 mol.L-1), the film mean thickness values decreased up to 50% of original values when the alkyl side chains were ethyl or pentyl groups due to ion-pair disruption, but for longer groups they remained unchanged. Quantum-chemical optimization and Mulliken electron population showed that (i) from C2 to C15 the positive charge at the headgroup (HG) decreased 0.025, while the charge at combined HG + alpha-CH2 increased 0.037; and (ii) for C6 or longer, the alkyl side group presents a tilt in the geometry, moving away from the plane. Such effects summed up over the whole polymer chain give support to suggest that when the side chains are longer than 7 carbons, the hydrophobic interaction decreases film stability and increases acid resistance.

Effect of pH and temperature on the global compactness, structure, and activity of cellobiohydrolase Cel7A from Trichoderma harzianum

Due to its elevated cellulolytic activity, the filamentous fungus Trichoderma harzianum (T. harzianum) has considerable potential in biomass hydrolysis application. Cellulases from Trichoderma reesei have been widely used in studies of cellulose breakdown. However, cellulases from T. harzianum are less-studied enzymes that have not been characterized biophysically and biochemically as yet. Here, we examined the effects of pH and temperature on the secondary and tertiary structures, compactness, and enzymatic activity of cellobiohydrolase Cel7A from T. harzianum (Th Cel7A) using a number of biophysical and biochemical techniques. Our results show that pH and temperature perturbations affect Th Cel7A stability by two different mechanisms. Variations in pH modify protonation of the enzyme residues, directly affecting its activity, while leading to structural destabilization only at extreme pH limits. Temperature, on the other hand, has direct influence on mobility, fold, and compactness of the enzyme, causing unfolding of Th Cel7A just above the optimum temperature limit. Finally, we demonstrated that incubation with cellobiose, the product of the reaction and a competitive inhibitor, significantly increased the thermal stability of Th Cel7A. Our studies might provide insights into understanding, at a molecular level, the interplay between structure and activity of Th Cel7A at different pH and temperature conditions.

Effect of nAellore cows ciclicity on conception and pregnant rates after synchronization protocols for fixed timed artificial insemination

Palhano H.B., Jesus V.L.T., Abidu-Figueiredo M., Baldrighi J.M. & Mello M.R.B. [Effect of nAellore cows ciclicity on conception and pregnant rates after synchronization protocols for fixed timed artificial insemination]. Efeito da ciclicidade de vacas Nelore sobre as taxas de concepcao e de prenhez apos protocolos de sincronizacao para inseminacao artificial em tempo fixo. Revista Brasileira de Medicina Veterinaria, 34(1):63-68, 2012. Departamento de Biologia Animal, Universidade Federal Rural do Rio de Janeiro, BR 465 km 7, Seropedica, RJ 23890-000, Brasil. Email: hbpalhano@gmail.com The present study evaluated the effect on conception and pregnancy rates of Nellore cows selected for Fixed Timed Artificial Insemination (FTAI) program, submitted to four synchronization protocols. Four hundred and ninety lactating females were used and assigned to eight groups: I-OvSynch, n=68, with selection of cycling cows; II-OvSynch + progesterone (P-4), n=67, after selection of non-cycling animals; III-OvSynch, without selection, n=68; IV-OvSynch + P-4, without selection, n=67; V-Co-Synch, n=55, with selection of cycling cows; VI-Co-Synch + P-4, n=55, with selection non-cycling cows; VII- Co-Synch without selection, n=55; VIII- Co-Synch + P-4, without selection, n=55. The conception and pregnancy rates were, respectively, 45.6%, 27.9% and 82.4%, 48.5% for groups I and III; 61.2%, 37.3% and 85.1%, 58.2% for groups II and IV; 43.6%, 25.5% and 80%, 41.8% for groups V and VII; 52.7%, 32.7% and 83.6%, 50.9% for groups VI and VIII. When compared these rates, the results after chi-square test showed significant difference (P < 0.05) among protocols with or without selection. There was no significant difference (P > 0.05) between OvSynch and Co-Synch protocols, with or without P-4 and with selection, considering Co-Synch a viable option for optimization of FTAI. In conclusion, the selection of cows before FTAI program contributed significantly to improve the conception and pregnancy rates.

Direct effect of PGF2 alpha pulses on PRL pulses, based on inhibition of PRL or PGF2 alpha secretion in heifers

The relationships between PRL and PGF(2 alpha) and their effect on luteolysis were studied. Heifers were treated with a dopamine-receptor agonist (bromocriptine; Bc) and a Cox-1 and -2 inhibitor (flunixin meglumine [FM]) to inhibit PRL and PGF(2 alpha), respectively. The Bc was given (Hour 0) when ongoing luteolysis was indicated by a 12.5% reduction in CL area (cm(2)) from the area on Day 14 postovulation, and FM was given at Hours 0, 4, and 8. Blood samples were collected every 8-h beginning on Day 14 until Hour 48 and hourly for Hours 0 to 12. Three groups of heifers in ongoing luteolysis were used: control (n = 7), Bc (n = 7), and FM (n = 4). Treatment with Bc decreased (P < 0.003) the PRL concentrations averaged over Hours 1 to 12. During the greatest decrease in PRL (Hours 2-6), LH concentrations were increased. Progesterone concentrations averaged over hours were greater (P < 0.05) in the Bc group than in the controls. In the FM group, no PGFM pulses were detected, and PRL concentrations were reduced. Concentrations of PGFM were not reduced in the Bc group, despite the reduction in PRL. Results supported the hypothesis that a decrease (12.5%) in CL area (cm(2)) is more efficient in targeting ongoing luteolysis (63%) than using any day from Days 14 to >= 19 (efficiency/day, 10-24%). The hypothesis that PRL has a role in luteolysis was supported but was confounded by the known positive effect of LH on progesterone. The hypothesis was supported that the synchrony of PGFM and PRL pulses represents a positive effect of PGF(2 alpha), on PRL, rather than an effect of PRL on PGF(2 alpha). (C) 2012 Elsevier Inc. All rights reserved.

Effect of cold-working process on corrosion behavior of copper

The microstructure, microhardness, texture and corrosion resistance of cold-swaged and cold-wiredrawn copper rods were evaluated. Elongated grains along the deformation direction were observed for both materials and the width of these grains decreased with the increase of reduction in area. Wiredrawn copper rods have higher microhardness than the swaged rods for the same reduction in area. The copper grains in both cold-worked rods presented a preferential orientation in the [1 1 0] crystallographic direction but this trend was more pronounced for swaged rods. The corrosion resistance of wiredrawn copper rods investigated in H(2)SO(4) solutions was lower than that of swaged rods, and for both deformed materials the corrosion resistance decreased with the deformation degree. (C) 2011 Elsevier Ltd. All rights reserved.

The Effect of Adenoidectomy or Adenotonsillectomy on Occlusal Features in Mouth-breathing Preschoolers

Purpose: The purpose of this study was to evaluate mouth-breathing and nasal-breathing children prior to surgical intervention and 28 months postoperatively, comparing the occlusal features obtained pre- and postoperatively through orthodontic study costs. Methods: The mouth-breathing (MB) group consists of 33 MB children who underwent surgery and presented a nasal-breathing (NB) pattern after surgery The control group comprised 22 NB children. The orthodontic examinations were accomplished prior to surgery (77) and an average of 28 months postoperatively (T2). Results: At T1, the MB and NB children presented no statistically significant difference in any analyzed occlusal features and measurements. At T2, the MB presented larger overjet comparing to NB children (P<.05). MB and NB groups presented statistically similar results (P>.05) concerning intercanine and intermolor distances, second primary molar terminal plane and canine relationship, overbite, crossbite, and open bite. From T1 to T2, the MB and NB groups showed a statistically significant difference in the molar terminal plane. Conclusion: Neither the breathing pattern nor the surgery had any effect on occlusal features in 3- to 6-year-olds. (Pediatr Dent 2012;34:10842) Received May 14, 2010 vertical bar Last Revision April 11, 2010 vertical bar Accepted April 12, 2010

Effect of hydrogen bond formation on the elastic molecular scattering: a case study with methanol

Rayleigh optical activities of small hydrogen-bonded methanol clusters containing two to five molecules are reported. For the methanol trimer, tetramer, and pentamer both cyclic and linear structures are considered. After the geometry optimizations, the dipole moments and the dipole polarizabilities (mean, interaction, and anisotropic components) are calculated using HF, MP2 and DFT (B3LYP, B3P86 and BH&HLYP) with aug-cc-pVDZ extended basis set. The polarizabilities are used to analyse the depolarization ratios and the Rayleigh scattering activities. The variations in the activity and in the depolarization for Rayleigh scattered radiation with the increase in the cluster size for both cyclic and linear structures are analysed.

Effect of sample storage time on detection of hybridization signals in Checkerboard DNA-DNA hybridization

Long-term sample storage can affect the intensity of the hybridization signals provided by molecular diagnostic methods that use chemiluminescent detection. The aim of this study was to evaluate the effect of different storage times on the hybridization signals of 13 bacterial species detected by the Checkerboard DNA-DNA hybridization method using whole-genomic DNA probes. Ninety-six subgingival biofilm samples were collected from 36 healthy subjects, and the intensity of hybridization signals was evaluated at 4 different time periods: (1) immediately after collecting (n = 24) and (2) after storage at -20 degrees C for 6 months (n = 24), (3) for 12 months (n = 24), and (4) for 24 months (n = 24). The intensity of hybridization signals obtained from groups 1 and 2 were significantly higher than in the other groups (p < 0.001). No differences were found between groups 1 and 2 (p > 0.05). The Checkerboard DNA-DNA hybridization method was suitable to detect hybridization signals from all groups evaluated, and the intensity of signals decreased significantly after long periods of sample storage.

Effect of Brazil Nut Supplementation on Plasma Levels of Selenium in Hemodialysis Patients: 12 Months of Follow-up

Background: Large amounts of reactive oxygen species are produced in hemodialysis (HD) patients, and, at higher concentrations, reactive oxygen species are thought to be involved in the pathogenesis of cardiovascular disease. It has been proposed that selenium (Se) may exert an antiatherogenic influence by reducing oxidative stress. The richest known food source of Se is the Brazil nut (Bertholletia excelsa, family Lecythidaceae), found in the Amazon region. Objective: The objective of this work was to determine if Se plasma levels in HD patients submitted to a program of supplementation during 3 months with 1 Brazil nut by day could be sustained after 12 months. Methods: A total of 21 HD patients (54.2 +/- 15.2 years old; average time on dialysis, 82.3 +/- 51.6 months; body mass index, 24.4 +/- 3.8 kg/m(2)) from the RenalCor Clinic in Rio de Janeiro, Brazil, were followed up 12 months after the supplementation study ended. The Se plasma levels were determined by atomic absorption spectrophotometry with hydride generation. Results: The Se Plasma levels (17.3 +/- 19.9 mg/L) were below the normal range (60 to 120 mu g/L) before nut supplementation, and after 3 months of supplementation, the levels increased to 106.8 +/- 50.3 mu g/L (P < .0001). Twelve months after supplementation, the plasma Se levels decreased to 31.9 +/- 14.8 mu g/L (P < .0001). Conclusions: The data showed that these patients were Se deficient and that the consumption of Brazil nut was effective to increase the Se parameters of nutritional status. Se levels 12 months after the supplementation period were not as low as presupplementation levels but yet significantly lower, and we needed to motivate patients to adopt different dietary intake patterns. (C) 2012 by the National Kidney Foundation, Inc. All rights reserved.