Influence of the oxygen adsorbed on tin varistors doped with Co, Mn and Cr oxides

The non-ohmic properties of the 98.90% SnO2+(1-x)%CoO+0.05% Cr2O3+0.05% Nb2O5+x% MnO2 varistor system (all of them in mol %), as well as the influence of the oxidizing and reducing atmosphere on this system were studied in this work. Experimental evidence indicates that the electrical properties of the varistor depend on the defects that occur at the grain boundary and on the adsorbed oxygen species such as O''(2), O'(2), O in this region. Thermal treatments at 900 degreesC in oxygen and nitrogen atmospheres indicated such a dependence with the values of the non-linearity coefficient (alpha) increasing under oxygen atmosphere, being reduced in nitrogen atmosphere and restored after a new treatment in oxygen atmosphere, presenting a reversibility in the process. EDS analysis accomplished by SEM showed the distribution of the oxides in the varistor matrix. (C) 2002 Kluwer Academic Publishers.

Qualidade do melão ‘Orange Flesh’ minimamente processado armazenado sob atmosfera modificada

This work aimed at evaluate the effect of the fresh cut 'Orange Flesh' melon stored under modified atmosphere. The cubes of melons were sanitizationed with 100 mg L-1 of hypoclorite of sodium for one minute, washed, drained and wrapped with different concentrations of O-2 and CO2 in plastic bags of polyethylene (Nylon Polished). They were appraised every other day for ten days as regards the firmness, total pectin, soluble pectin and activity of the polifenoloxidase and peroxidase. At the end of the conservation period, it was verified that melons sustained the firmest texture of the vegetable products under modified atmosphere, and the concentration of 5%O-2 + 3% CO2 showed smaller content of total pectin and together with the concentration of 100% N-2 the smallest content of soluble pectin, the polifenoloxidase activity was not verified as well as of the peroxidase.

Small-angle X-ray scattering and X-ray absorption near-edge structure study of iron-doped siloxane-polyoxyethylene nanocomposites

The local and medium-range structures of siloxane-POE hybrids doped with Fe(III) ions and prepared by the sol-gel process were investigated by X-ray absorption near-edge structure (XANES)/extended X-ray absorption fine structure (EXAFS) and small-angle X-ray scattering (SAXS), respectively. The experimental results show that the structure of these composites depends on the doping level. EXAFS data reveal that, for low doping levels ([O]/[Fe] > 40, oxygens being of the ether-type of the POE chains), Fe(III) ions are surrounded essentially by a shell of chlorine atoms, suggesting the formation of FeCl4- anions. At high doping levels ([O]/[Fe] < 20), Fe(III) ions interacts mainly with oxygen atoms and form FeOx species. The relative proportion of FeOx species increases with iron concentration, this result being consistent with the results of SAXS measurements showing that increasing iron doping induces the formation of iron-rich nanodomains embedded in the polymer matrix.

Kinetic of thermal decomposition of residues from different kinds of composting

Non-isothermal kinetic parameters regarding to the thermal decomposition of the ligninocellulosic fraction present in compost from urban solid residues (USR) obtained through stack covered (SC) with composted material, comes from the usine in composing of Araraquara city, São Paulo state, Brazil, and from stack containing academic restaurant organic solid residues (SAR). The samples were periodically revolved round 132 days of composting.Results from TG, DTG and DSC curves obtained on inert atmosphere indicated that the lignocellulosic fraction present, despite the slow degradation during the composting process, is thermally less stable than other substances originated during that process. The lignocellulosic fraction decomposition, between 200 and 400degreesC, were kinetically evaluated through non-isothermal methods of analysis.By using the Flynn-Wall and Ozawa isoconversional method, the medium activation energy, E-a, and pre-exponential factor, IgA, were 283.0+/-4.6, 257.6+/-1.3 U mol(-1) and 25.4+/-0.8, 23.2+/-0.2 min(-1),to the SC and SAR, respectively, at 95% confidence level.From E-a, and IgA values and DSC curves, Malek procedure could be applied, Suggesting that the SB (Sestik-Berggren) kinetic model is suitable for the first thermal decomposition step.

Validation of hysteroscopic view in cases of endometrial hyperplasia and cancer in patients with abnormal uterine bleeding

STUDY OBJECTIVE: To validate hysteroscopic view with histology in cases of endometrial hyperplasia and cancer in patients with abnormal uterine bleeding (AUB)DESIGN: Retrospective study.(Canadian Task Force classification II-3).SETTING: University teaching hospitals in Rio de Janeiro and São Paulo, and private office in Rio de Janeiro.PATIENTS: Four thousand and fifty-four patients with AUB in whom hysteroscopic views were complete and the histologic result was conclusive.INTERVENTION: Four thousand and fifty-four office hysteroscopies with complete views and conclusive histologic results. The material for histologic examination was obtained through biopsy of the lesion in an outpatient unit or through the resection of the entire lesion in patients who underwent surgery. Histology was considered the gold standard and compared with the hysteroscopic view.MEASUREMENTS AND MAIN RESULTS: In the histology of the 4054 examinations, 613 (15.2%) were endometrial hyperplasia, and 105 (2.6%) were endometrial cancer. The most frequent hysteroscopic finding was endometrial polyps (31.2%). In endometrial hyperplasia, the sensitivity of the hysteroscopic view was 56.3% (95% CI 52.21-60.2%), specificity was 89.1% (95% CI 88.0%-90.1%), positive predictive value (PPV) was 48.0% (95% CI 44.3%-51.7%), negative predictive value (NPV) was 92.0% (95% Cl 90.1%-92.9%), and accuracy was 72.7% (95% CI 70.7%-74.7%). Accuracy was defined as the proportion of correct results among the hysteroscopic examinations. In endometrial cancer, the sensitivity of the hysteroscopic view was 80.0% (95% Cl 71.1%-87.2%), specificity was 99.5% (95% CI 99.2%-99.7%), PPV was 81.5% (95% Cl 72.7%-88.5%), NPV was 99.5% (95% CI 99.2%-99.7%), and accuracy was 89.8% (95% CI, 85.9%-93.6%). In the 814 patients (20.0%) in whom the hysteroscopic view was normal, there were no false negatives for endometrial cancer; however, there were 37 (4.5%) false negatives for endometrial hyperplasia. In the histologic cases of endometrial cancer, 101 (96.2%) hysteroscopic views were compatible with cancer or hyperplasia (80.0% and 16.2%, respectively). Ninety-seven out of 103 hysteroscopic views with cancer findings (94.2%) had histologic diagnosis of cancer or hyperplasia (81.5% and 12.6%, respectively).CONCLUSION: It seems that even in face of good validity of hysteroscopic view for endometrial hyperplasia and cancer, histologic study is mandatory in the presence of any lesion as the hysteroscopic view cannot completely replace the histologic study in patients with AUB. (C) 2006 AAGL. All rights reserved.

Low-temperature synthesis of single-phase Co7Sb2O12

Polycrystalline Co7Sb2O12 compounds have been synthesized by a chemical route, which is based on a modified polymeric precursor method. In order to study the physical properties of the samples, X-ray diffraction (XRD), thermal analyses (TG and DSC), infrared spectroscopy (IR), specific surface area (BET), and magnetization measurements were performed on these materials. Characterization through XRD revealed that the samples are single-phase after a heat-treatment at 1100degreesC for 2h, while the X-ray patterns of the samples heat-treated at lower temperatures revealed the presence of additional Bragg reflections belonging to the Co6Sb2O6 phase. These data were analyzed by means of Rietveld refinement and further analyze showed that Co7Sb2O12 displays an inverse spinel crystalline structure. In this structure, the Co2+ ions occupy the eight tetrahedral positions, and the sixteen octahedral positions are randomly occupied by the Sb5+ and Co2+ ions. IR studies disclosed two strong absorption bands, v(1) and v(2), in the expected spectral range for a spinel-type binary oxide with space group Fd3m. Exploratory studies concerning the magnetic properties indicated that this sample presents a spin-glass transition at T-f similar to 64 K. (C) 2004 Elsevier B.V. All rights reserved.

Bayesian approximations in randomized response model

Practical Bayesian inference depends upon detailed examination of posterior distribution. When the prior and likelihood are conjugate, this is easily carried out; however, in general, one must resort to numerical approximation. In this paper, our aim is to solve, using MAPLE, the Bayesian paradigm, for a very special data collecting procedure, known as the randomized-response technique. This allows researchers to obtain sensitive information while guaranteeing privacy to respondents. This approach intends to reduce false responses on sensitive questions. Exact methods and approximations will be compared from the accuracy point of view as well as for the computational effort.

Potencial alelopático de Ipomoea fistulosa sobre a germinação de alface e tomate

The objective of the present research was to determine the allelopathic potential of Ipomoea fistulosa plants on germination and growth of seedlings. In laboratory, lettuce and tomato seeds were placed to germinate in the presence of water or Ipomoea fistulosa leaf extract, in the concentrations of 5, 10 e 15% (p/v). In greenhouse, seeds were placed to germinate in trays containing Plantmax (R) substrate and Plantmax (R) substrate + Ipomoea fistulosa dry leaf residue, at 3% (w/w). The aqueous extract inhibited germination, raised the mean germination time of the seeds and reduced the radicle and hypocotyl growth in all used concentrations. In greenhouse, the plant height, leaf number, and dry mass accumulation also were reduced in the presence of the leaf residue in the substrate. The results suggest the presence of allelochemicals in Ipomoea fistulosa and demonstrate the highest sensitivity of lettuce that tomato to these compounds.

Solid-state reactions of mercury with pure noble metals - Part 2. Mercury-iridium system

Thermogravimetry, cyclic voltammetry and other analytical techniques were used to study the reactions of mercury with pure iridium. The results allowed to suggest when subjected to heat or anodic stripping voltammetry an electrodeposited mercury film reacts with Ir substrate and at least three mass loss steps and three peaks appear in the mercury desorption process. The first two were attributed to Hg(0) species removal like a mercury bulk and a mercury monolayer. The last can be ascribed to the mercury removal from a solid solution with iridium.

Resposta do abacaxizeiro 'Vitória' a doses de nitrogênio em solos de tabuleiros costeiros da Paraíba

Informations about fertilization and mineral nutrition of the new fusariosis-resistant pineapple cultivars are still scarce, despite the importance of this crop. The purpose of this study was to evaluate the effect of increasing doses of N on fruit yield and quality of the pineapple cultivar 'Vitoria' grown on a 'Humiluvico Espodossolo' in the region of Tabuleiros Costeiros, in the state of Paraiba. The experiment was arranged in a randomized block design, using five N doses (100, 200, 300, 500 and 600 kg ha(-1)N, as urea) applied 60, 180 and 270 days after planting (dap) with three replications. The following variables were evaluated: length and fresh matter of the 'D' leaf; contents of N, P and K in the portions with and without chlorophyll, 300 and 420 dap; average weight, yield, physical properties (fruit weight, length and medium diameter; crown weight and length) and chemical properties (pH, soluble solids -SS, titrable acidity - AT, and the SS/AT ratio) of the fruits at harvest. Increasing N doses linearly increased length and fresh matter of the 'D' leaf and N content and decrease both P and K contents of the chlorophyll portion 300 dap, but did not affect nutrient contents 420 dap; in the chlorophyll-free portion. Increasing N doses, also, led to an increase in K contents 320 dap, but to reductions 420 dap. Individual fruit weight and total yield increased with increasing N doses, as maximum values of 1.0 kg and 37.9 t ha(-1) were estimated at doses of 409.0 and 439.0 kg ha(-1) N, respectively. The N doses did not affect the fruit quality properties, which were compatible with the characteristics described for this cultivar.

Épocas de aplicação de nitrogênio para híbridos de mamona no sistema plantio direto em safrinha

The castor bean cultivation has a high demand for nitrogen, in addition, the efficiency of nitrogen fertilization in most cases is low, so that this essential nutrient is provided at the appropriate time. The objective was to study the time nitrogen application in castor bean hybrids under no-till system in off-season. The experiment was carried out in an experimental area located in Botucatu, São Paulo State, Brazil, for two growing off-seasons (2006 and 2007). The experimental design was a randomized block in split plot design, with four replications. The plots were constituted by two castor bean hybrids (Lyra/Savana in 2006 and Lyra/Sara in 2007). Six combination of times out rates (0-0, 0-100, 100-0, 30-70, 70-30, 50-50 kg ha-1 of N) side dressing nitrogen fertilization constituted the subplots. The N source used was ammonium nitrate, applied 20 days after emergence and 40 days after emergence. Measurements were carried out: dry matter production of shoots, nitrate and ammonium leaf, leaf analysis, yield components and nitrogen factor utilization. The highest grain yield was obtained to the hybrid Lyra with nitrogen fertilization. In 2006 the highest nitrogen utilization factor to the hybrid Lyra was obtained with the form 70-30 and in the 2007 with 50-50.

The respiratory responses of an amphibious snail Pomacea lineata (spix, 1827), to temperature and oxygen tension variations

1. 1. The respiratory responses of Pomacea lineata to short-term (or acute) exposure to temperature and oxygen tension variations were investigated in animals acclimated to 25°C. 2. 2. The respiratory rates increased with rising temperatures; this increase was sharper between 15 and 25°C than at any other temperature interval; a tendency to a plateau in the RT curve was recorded between 25 and 35°C. 3. 3. All animals survived well to 1 hr exposure to the extreme temperatures used (5 and 40°C). 4. 4. In two different experimental approaches, the animals showed ability to regulate the respiratory rate in declining oxygen tensions, at least down to 10% (70.8 mmHg) oxygen. 5. 5. After 1 hr exposure to hypoxic conditions, P. lineata exhibited the pattern of underpayment of the oxygen debt acquired. 6. 6. Six out of ten animals survived after 40 days in anoxia (100% nitrogen). © 1987.

Chaotic and nonchaotic behaviour in the mixmaster dynamics

We show that the mixmaster universe is nonchaotic with respect to the intrinsic time but chaotic with respect to the synchronous time. No appeal to any numerical simulation or other arguments are made, apart from the well known properties of the model. © 1991.

Helicity amplitudes for matter-coupled gravity

The great simplicity attained by the Weyl-van der Waerden spinor technique in the evaluation of helicity invariant amplitudes is shown to apply in the cumbersome calculations within the framework of linearized gravitation. Once the graviton couplings to spin-0, 1/2, 1, and 3/2 particles are given, we exhibit the reach of this method by evaluating, as an example, the helicity amplitudes for the process electron + positron → photon + graviton in a very straightforward way. © 1994 Plenum Publishing Corporation.