Caracterização textural e estrutural de V 2O 5/TiO 2 obtidos via sol-gel: Comparação entre secagem convencional e supercrítica

This work describes a modified sol-gel method for the preparation of V 2O 5/TiO 2 catalysts. The samples have been characterized by N 2 adsorption at 77K, x-ray diffractometry (XRD) and Fourier Transform Infrared (FT-IR). The surface area increases with the vanadia loading from 24 m 2 g -1, for pure TiO 2, to 87 m 2 g -1 for 9wt.% of V 2O 5. The rutile form is predominant for pure TiO 2 but became enriched with anatase phase when vanadia loading is increased. No crystalline V 2O 5 phase was observed in the catalysts diffractograms. Two species of surface vanadium observed by FT-IR spectroscopy a monomeric vanadyl and polymeric vanadates, the vanadyl/vanadate ratio remains practically constant.

Contribution of oxygen related defects to the electronic transport in SnO2 sol-gel films

SnO2 deposited by sol-gel is a polycrystalline film with small grain size. Oxygen present at a less grain boundary traps electrons and then the depletion layer around the potential barrier of the grain boundary becomes wider, comparable to the grain size. We have modeled the conductivity taking into account the trapped charge at the depletion layer of the grain boundary and other scattering mechanisms such as ionized impurity and polar optical. Experimental data of photoconductivity of SnO2 sol-gel films are simulated considering the dominant scattering at grain boundary and crystallite bulk. The fraction of trapped charge at the grain boundary depends on temperature and wavelength of irradiating light, being as high as 50% for illumination in the range 500-600 nm for SnO2-2%Nb as grown sample annealed in air to 550°C. This fraction can be quite reduced depending on exposure to light and annealing under different oxygen partial pressure conditions.

Dietary electrolyte balance for broiler chickens under moderately high ambient temperatures and relative humidities

Cobb male broiler chicks (1,000) on new litter were used to evaluate effects of dietary electrolyte balance [DEB; Na+K-Cl, milliequivalents (mEq) per kilogram] under tropical summer conditions. Corn-soybean meal-based mash diets had salt (NaCl) alone or in combination with one or more supplements: sodium bicarbonate (NaHCO3), ammonium chloride (NH4Cl), or potassium bicarbonate (KHCO3). A completely randomized design, with five starter and grower feed treatments (control: 145, then 130 mEq/kg; or 0, 120, 240, or 360 mEq/kg throughout) and four replicate pens (1.5 x 3.2 m) per treatment (50 chicks per pen), was used. Diets were analyzed for Na, K, and Cl for confirmation. There were no significant (P < 0.05) effects of treatments on mortality or processing parameters. Water intake increased linearly with increasing DEB, giving higher litter moistures and lower rectal temperatures. Blood HCO3 and pH increased with the highest DEB (360 mEq/kg) causing respiratory alkalosis. The DEB of 240 mEg/kg gave best weight gain and feed conversion ratio, and ideal DEB predicted by regression analyses were 186 and 197 mEq/kg from 0 to 21 d of age and 236 and 207 mEq/kg of feed from 0 to 42 d, respectively. These DEB corresponded to estimated (interpolated) values in predicted optimal 186 to 197 mEq/kg starter of Na 0.38 to 0.40% and Cl 0.405 to 0.39% (K = 0.52%), in 207 to 236 mEq/kg starter, Na 0.409 to 0.445% and Cl 0.326 to 0.372% Cl (K = 0.52%), and in grower Na 0.41 to 0.445%, Cl 0.315 to 0.267% (K = 0.47%).

Dietary electrolyte balance for broiler chickens exposed to thermoneutral or heat-stress environments

Ross male broiler chicks (n = 480) on new litter were used in a randomized block design with two blocks (environmental rooms) and four treatments having four replicate pens (1.0 × 2.5 m; 15 chicks) each to evaluate dietary electrolyte balance (DEB; P < 0.05). Two rooms were 1) thermoneutral (Weeks 1 through 6, with decreasing maximum from 32 to 25°C and minimum from 28 to 19°C; relative humidity 49 to 58%) and 2) cyclic daily heat stress (Weeks 1 and 2, thermoneutral; Weeks 2 through 6, maximum temperatures 35, 35, 33, and 33°C, respectively; and minimum temperatures 23, 20, 19, and 19°C, respectively; relative humidity 51 to 54%). The DEB treatments (0, 140, 240, or 340 mEq Na + K - Cl/kg) had NaHCO3 plus NH4Cl, or KHCO3, or both added to corn-soybean meal mash basal diets with 0.30% salt (NaCl). In the thermoneutral room, DEB 240 increased 42-d weight gain and 44-d lymphocyte percentage and decreased heterophil percentage and heterophil to lymphocyte ratio compared to the DEB 40 treatment. The DEB 240 diets had 0.35 and 0.35% Na and 0.37% and 0.29% Cl in starter (0.75% K) and grower (0.67% K) diets, respectively. No DEB treatment differences were found in the heat stress room. For combined rooms, 42-d feed intake was higher for DEB 240 than for DEB 40. The 21-d weight gain was higher for DEB 240 than for DEB 40 or 140; and 21-d feed/gain was lower for DEB 40 than for DEB 340. The predicted maximum point of inflection for 21- and 42-d weight gains were DEB 250 and 201, with highest 42-d feed intake at 220.

Fluoride release by restorative materials before and after a topical application of fluoride gel

The release of fluoride from restorative materials (Vitremer, Ketac-Fil, Fuji II LC and Freedom) was evaluated during two 15-day periods, before and after a topical application of acidulated phosphate fluoride gel (APF). For each material, 6 specimens were made, which were immersed in 2 ml of deionized water. The fluoride concentration dosages in the solutions were read at intervals of 24 hours for 15 days. After this period, the specimens of each material received treatment with APF gel for 4 minutes and the fluoride released was analyzed at 24-hour intervals during the following 15 days. The analysis of variance and the Tukey test (p < 0.05) showed that the total mean fluoride released during the initial 15 days was greater for Vitremer and Ketac-Fil and lower for Fuji II LC and Freedom; and in the final 15 days there was a difference in release readings, with the greatest value for Vitremer, followed by Fuji II LC, Ketac-Fil and Freedom. The comparison of the results between the 1st day and the 16th day (after gel application) showed a greater fluoride release on the 16th day for Vitremer, Fuji II LC and Freedom and was equal for Ketac-Fil. Although all the materials evaluated gained fluoride with the application of APF, the data suggest that the resin-modified ionomers are more efficient in releasing fluoride to the medium than the other materials.

Sol-Gel Erbium-Doped Silica-Hafnia Planar and Channel Waveguides

Erbium activated SiO2 -HfO2 planar waveguides, doped with Er3+ concentrations ranging from 0.01 to 4 mol%, were prepared by sol-gel method. The films were deposited on v-SiO2 and silica-on-silicon substrates using dip-coating technique. The waveguides show high densification degree, effective intermingling of the two film components, and uniform surface morphology. The waveguide deposited on silica-on-silicon substrates shows one single propagation mode at 1.5μm, with a confinement coefficient of 0.81 and an attenuation coefficient of 0.8 dB/cm at 632.8nm. Emission in the C-telecommunication band was observed at room temperature for all the samples upon continuouswave excitation at 980 nm or 514.5 nm. The shape of the emission band corresponding to the 4I13/2 → 4I15/2 transition is found to be almost independent both on erbium content and excitation wavelength, with a FWHM between 44 and 48 nm. The 4I13/2 level decay curves presented a single-exponential profile, with a lifetime ranging between 1.1 - 6.6 ms, depending on the erbium concentration. Infrared to visible upconversion luminescence upon continuous-wave excitation at 980 nm was observed for all the samples. Channel waveguide in rib configuration was obtained by etching the active film in order to have a well confined mode at 1.5 μm.

Determination of cadmium in river water samples by flame AAS after on-line preconcentration in mini-column packed with 2-aminothiazole-modified silica gel

A rapid and sensitive method was developed to determine trace levels of Cd2+ ions in an aqueous medium by flame atomic absorption spectrometry, using on-line preconcentration in a mini-column packed with 100 mg of 2-aminothiazol modified silica gel (SiAT). The Cd2+ ions were sorbed at pH 5.0. The preconcentrated Cd2+ ions were directly eluted from the column to the spectrometer's nebulizer-burner system using 100 μL of 2 mol L-1 hydrochloric acid. A retention efficiency of over 95% was achieved. The enrichment factor (calculated as the ratio of slopes of the calibration graphs) obtained with preconcentrations in a mini-column packed with SiAT (A = -1.3 × 10-3 + 1.8 × 10-3 [Cd2+]) and without preconcentrations (A = 4 × 10-5 + 3.5 × 10-3[Cd2+]), was 51 and the detection limit calculated was 0.38 μg L-1. The preconcentration procedure was applied to determine trace levels of Cd in river water samples. The optimum preconcentration conditions are discussed herein.

Determination of Cu, Ni and Pb in Aqueous Medium by FAAS after Pre-Concentration on 2-Aminothiazole Modified Silica Gel

This work describes the synthesis and characterization of 2-aminothiazole modified silica gel (SiAT), and the results of a study of the adsorption and pre-concentration (in batch and using a flow-injection system coupled to an absorption atomic spectrometer) of Cu(II), Ni(II) and Pb(II) in aqueous medium. The adsorption capacities for each metal ions in mmol g -1 were: Cu(II)= 1.18, Ni(II)= 1.15 and Pb(II)= 1.10. The results obtained in the flow experiments showed a recovery of practically 100% of the metal ions adsorbed in a mini-column packed with 100 mg of SiAT, using 100 μL of 2.0 mol L -1 HCl solution as eluent. The sorption-desorption of the metal ions made possible the application of a flow-injection system for the pre-concentration and quantification by FAAS of metal ions at trace level in natural water samples digested and not digest by an oxidizing UV photolysis.

Physiological responses of broiler chickens to heat stress and dietary electrolyte balance (sodium plus potassium minus chloride, milliequivalents per kilogram)

Individually caged male Cobb broilers (24), 44 d of age, were used to evaluate effects of heat stress (1 d of data collection) and dietary electrolyte balance (DEB; Na + K - Cl, mEq/kg from 1 d of age). During summer rearing, mortality was variable, but DEB 240 improved growth, feed conversion ratio, water intake, and waterrfeed ratio vs. DEB 0. The temperature sequence for heat stress was 24 to 32°C in 30 min, 32 to 36°C in 30 min, 36 to 37°C in 15 min, and 37 to 41°C in 45 min. Maximum temperature was held for 15, 60, 90, or 360 min for data collection (relative humidity averaged 42 ± 7%). Results from the same room before and after heat stress were analyzed by DEB (1-factor ANOVA) and before vs. after heat stress compared across DEB (2-sample t-test). Heat stress decreased blood Na, K, and pCO2, and lymphocytes but increased heterophils. Blood HCO3 rose, Cl declined, and hematocrit gave a concave pattern (lowest at DEB 120) as DEB increased. After heat stress, DEB O decreased blood Na and K, and DEB O and 120 levels decreased blood HCO3. After heat stress blood pCO2 and hemoglobin decreased with DEB 240, but it had highest pCO2, a key factor. The DEB 120 gave longest times to panting and prostration with DEB O and 240 results lower but similar statistically. In heat stress, DEB 360 was excessive, DEB 120 and 240 were favorable, and DEB 0 was intermediate based on hematology, panting, and prostration responses.

Effect of 0.4% stannous fluoride gel on Streptococci mutans in relation to elastomeric rings and steel ligatures in orthodontic patients

Background: Patients with fixed orthodontic appliances often experience an absolute increase in the number of Streptococci mutans colony-forming units (cfu). The aim of this investigation was to study the development of biofilm and S. mutans cfu in connection with stainless steel ligatures and elastomeric rings in orthodontic patients treated with and without 0.4% stannous fluoride gel (SFG). Material: Forty-seven patients were divided into 2 groups: those treated with 0.4% SFG for 4 minutes (experimental) and those without 0.4% SFG (control). In each patient, elastomeric rings were used for ligation on 1 side of the dental arch midline, and stainless steel ligatures were used on the opposite side. Saliva samples were collected before and after appliance placement. At 15 and 30 days after appliance placement, biofilm samples from the stainless steel ligatures and the elastomeric rings were collected and subjected to microbiologic procedures and scanning electron microscopy (SEM) analysis. Results: The numbers of S. mutans cfu in the saliva and biofilm were not statistically different between the teeth fitted with elastomeric rings and stainless steel ligatures, or between the experimental and control groups. SEM analysis showed biofilm formation on both ligature ties. Conclusions: Topical application of 0.4% SFG in orthodontic patients with elastomeric rings or stainless steel ligatures does not cause a significant decrease in S. mutans cfu in the saliva and biofilm. Copyright © 2005 by the American Association of Orthodontists.

Blood cell attachment to root surfaces treated with EDTA gel.

Root debridement generates a smear layer which contains microorganisms and toxins that could interfere in periodontal healing. For this reason, different substances have been used to remove it and to expose collagen fibers at the tooth surface. Blood element adhesion to demineralized roots and clot stabilization by collagen fibers are extremely important for the success of periodontal surgery. The aim of this study was to evaluate the different patterns of blood element adsorption and adhesion to root surfaces only irrigated with distilled water and after application of a manipulated or an industrialized EDTA gel. Thirty samples were planed, equally divided into three groups and treated with distilled water (control), a manipulated EDTA gel or an industrialized one. Immediately after, samples were exposed to fresh blood and prepared for scanning electron microscopy. Untreated planed dentin presented the best results with blood cells entrapped in a thick web of fibrin. In the manipulated EDTA group, the web of fibrin was thick with sparse blood elements. The worst result was seen with the industrialized EDTA group, in which no blood elements could be seen. Statistical difference was obtained between control and industrialized EDTA groups. Surfaces only irrigated presented the most organized fibrin network and cell entrapment.

Efficacy of EDTA-T gel for smear layer removal at root surfaces

Objective: The purpose of this in vitro study was to investigate the efficacy of EDTA gel preparation, associated with texapon detergent (EDTA-T), for removing the smear layer at human root surfaces. Method and materials: An experimental smear layer was produced by scaling using periodontal curettes, and the root surfaces were etched with the following concentrations of EDTA-T: 5%, 10%, 15%, 20%, 24%, and negative control (saline solution) for 1, 2, or 3 minutes using both passive and active methods. The surfaces were evaluated by scanning electron microscopy, and photomicrographs were evaluated in relation to smear removal. Results: All EDTA-T groups were more effective than the control group (P < .0001). EDTA-T at 15% was more effective when applied by the passive method, although this difference was not observed for the active method. The active method was statistically better than the passive method (P < .0001). Conclusion: The etching of the root surface with EDTA-T gel by active application, independently of the other factors evaluated, was effective for smear layer removal.

Preconcentration and determination of mercury(II) at a chemically modified electrode containing 3-(2-thioimidazolyl)propyl silica gel

A mercury-sensitive chemically modified graphite paste electrode was constructed by incorporating modified silica gel into a conventional graphite paste electrode. The functional group attached to the (3-chloropropyl) silica gel surface was 2-mercaptoimidazole, giving a new product denoted by 3-(2-thioimidazolyl)propyl silica gel, which is able to complex mercury ions. Mercury was chemically adsorbed on the modified graphite paste electrode containing 3-(2-thioimidazolyl)propyl silica (TIPSG GPE) by immersion in a Hg(II) solution, and the resultant surface was characterized by cyclic and differential pulse anodic stripping voltammetry. One cathodic peak at 0.1 V and other anodic peak at 0.34 V were observed on scanning the potential from -0.1 to 0.8 V (0.01 M KNO3; ν = 2.0 mV s-1 νs. Ag/AgCl). The anodic peak at 0.34 V show an excellent sensitivity for Hg(II) ions in the presence of several foreign ions. A calibration graph covering the concentration range from 0.02 to 2 mg L-1 was obtained. The detection limit was estimated to be 5 μg L-1. The precision for six determinations of 0.05 and 0.26 mg L-1 Hg(II) was 3.0 and 2.5% (relative standard deviation), respectively. The method can be used to determine the concentration of mercury(II) in natural waters contaminated by this metal. 2005 © The Japan Society for Analytical Chemistry.

Solubilization of proteins from human lymph node tissue and two-dimensional gel storage.

In the present study, we compared six different solubilization buffers and optimized two-dimensional electrophoresis (2-DE) conditions for human lymph node proteins. In addition, we developed a simple protocol for 2-D gel storage. Efficient solubilization was obtained with lysis buffers containing (a) 8 M urea, 4% CHAPS (3-[(3-cholamidopropyl) dimethylammonio]-1-propanesulfonate), 40 mM Tris base, 65 mM DTT (dithiothreitol) and 0.2% carrier ampholytes; (b) 5 M urea, 2 M thiourea, 2% CHAPS, 2% SB 3-10 (N-decyl-N,N-dimethyl-3-ammonio-1-propanesulfonate), 40 mM Tris base, 65 mM DTT and 0.2% carrier ampholytes or (c) 7 M urea, 2 M thiourea, 4% CHAPS, 65 mM DTT and 0.2% carrier ampholytes. The optimal protocol for isoelectric focusing (IEF) was accumulated voltage of 16,500 Vh and 0.6% DTT in the rehydration solution. In the experiments conducted for the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), best results were obtained with a doubled concentration (50 mM Tris, 384 mM glycine, 0.2% SDS) of the SDS electrophoresis buffer in the cathodic reservoir as compared to the concentration in the anodic reservoir (25 mM Tris, 192 mM glycine, 0.1% SDS). Among the five protocols tested for gel storing, success was attained when the gels were stored in plastic bags with 50% glycerol. This is the first report describing the successful solubilization and 2D-electrophoresis of proteins from human lymph node tissue and a 2-D gel storage protocol for easy gel handling before mass spectrometry (MS) analysis.