Raman scattering, differential scanning calorimetry and Nd3+ spectroscopy in alkali niobium tellurite glasses

Alkali niobium tellurite glasses have been prepared and some of their properties measured by differential scanning calorimetry and Raman scattering. The vitreous domain was established in the pseudo ternary phases diagram for the system TeO2-Nb2O5-(0.5K(2)O-0.5Li(2)O). Raman scattering shows that for samples in the TeO2 rich part of the phase diagram the vitreous structure is composed essentially of (TeO4) units connected by the vertices, as in the alpha-TeO2 crystal. The addition of alkali and niobium oxides causes depolymerization to occur with structures composed essentially of (TeO3) and (NbO6) units. Samples with the composition (mol%) 80TeO(2)-10Nb(2)O(5)-5K(2)O-5Li(2)O, stable against crystallization, were prepared containing up to 10% mol Nd3+. The addition of this oxide increases the rigidity of the vitreous network shifting characteristic temperatures to higher temperatures. For the 10% Nd3+ sample amorphous phase separation is assumed to exist from the observation of two glass transition temperatures. Spectroscopic properties such as Judd-Ofelt Omega(lambda) intensity parameters, radiative emission probabilities, and induced emission cross sections were calculated. From these results and also from the emission quenching observed as a function of Nd3+ concentration, we suggest that these glasses could be utilized in optical amplifying devices. (C) 1999 Elsevier B.V. B.V. All rights reserved.

Linear relationship between potential and concentration in flow potentiometry

In potentiometric-flow systems, linear-potential responses for logarithmic concentrations can be attained for first-(or pseudo-first-) order reactions in which the monitored chemical species react with the analyte during a fixed time interval. To demonstrate this property, the determination of glycerol based on its oxidation by periodate and potentiometric monitoring of the remaining periodate was selected. Influence of reagent concentration and timing on the linearity of the analytical curve were investigated. A mathematical treatment was derived, and potentialities/limitations of the approach were outlined. The system was applied to analysis of soap and lixivia samples. The analytical curve within 200 and 2000 mg L-1 (r = 0.99975; n = 5) was described as E = 8.166 + 0.0478 (glycerol). The sample throughput was 100 h(-1), and a measurement repeatability within 0.5 mV was always observed. By applying a t-test, there was no statistical difference between the results obtained by the proposed procedure and by iodimetric titration at the 95% confidence level. (C) 2000 John Wiley & Sons, Inc. Lab Robotics and Automation 12:41-45, 2000.

A CALORIMETRIC STUDY OF THE ULTRASOUND-STIMULATED HYDROLYSIS OF SOLVENTLESS TEOS-WATER MIXTURES

The kinetics of ultrasound-stimulated and HCl-catalyzed hydrolysis of solventless TEOS-water mixtures was studied as a function of temperature ranging from 10 degrees C up to 65 degrees C by means of flux calorimetry measurements. A specially designed device was utilized for this purpose. The exothermic peak arising few minutes after sonication began has been attributed mainly to the hydrolysis reaction. The overall hydrolysis process, which was measured through the irradiation time up to the hydrolysis peak, was found to be thermally activated, with an apparent activation energy Delta E = 36.4 kJ/mol. The alcohol produced at the early hydrolysis due to sonication seems to further enhance the reaction, via a parallel autocatalytic path, which is controlled by a faster pseudo second order rate constant (k'). Our modeling yielded k' = 6.3 x 10(-2) M(-1) min(-1) at 20 degrees C, which is in a reasonable agreement with the literature, and an activation energy Delta E = 40.4 kJ/mol for the specific process of hydrolysis in presence of alcohol.

Influence of pH and precipitation temperature on the structural characteristics of aluminium hydroxides prepared form nitrate aqueous solutions

Aluminium Hydroxides were precipitated from Aluminium Nitrate and Ammonium Hydroxide, at the temperatures 64 degrees C (hot) and 25 degrees C (cold), under the pH conditions 5, 7 and 9. The samples were characterized by X-Ray Diffraction (XRD) and Differential Thermal Analysis (DTA). The hydroxide precipitated at pH 9 and 64 degrees C is built up by pseudoboehmite and a minor share of others apparently amorphous hydroxides. The crystallinity of the hot yielded pseudoboehmite diminishes with the pH. The crystallite size was evaluated as about 40 Angstrom for the best crystallized sample. The cold precipitated product is apparently composed by amorphous or very poorly crystallized hydroxides. Upon heating, the cold precipitated hydroxides, and the low pH and hot precipitated hydroxide, release their structural water before the occurrence, about 430 degrees C, of the transition of the pseudoboehmite to gamma-alumina, and exhibit a shifting (towards low temperature side) and a broadening in the peak of the transition to alpha-alumina, which occurs at 1200 degrees C in the pseudoboehmite pattern. The yielded pseudo-boehmite peptized by HNO3, addition and gelified by evaporation in a critical concentration approximately 0.17 gcm(-3).

Photoexpansion and photorefraction in oxysulphide glasses

Oxysulphide glasses have been prepared in the pseudo binary system GeS(2.6)-Ga(2)O(3). The effect of addition of gallium oxide has been evaluated in term of thermal and optical properties. Structural behavior has been studied using Raman spectroscopy. Samples have been exposed above band gap energy (3.52 eV) varying power density and exposure time. Giant photoexpansion and photorefraction is obtained for samples containing 20% of Ga(2)O(3). (C) 2009 Elsevier B.V. All rights reserved.

Development of Intra- and Interxylary Secondary Phloem in Coccinia indica (Cucurbitaceae)

Stern anatomy and the development of intraxylary phloem were investigated in six to eight years old Coccinia indica L. (Cucurbitaceae). Secondary growth in the stems was achieved by the normal cambial activity. In the innermost part of the thicker stems, xylem parenchyma and pith cells dedifferentiated into meristematic cells at several points. In some of the wider rays, ray cells dedifferentiate and produce secondary xylem and phloem with different orientations and sometimes a complete bicollateral vascular bundle. The inner cambial segments of the bicollateral vascular bundle (of primary growth) maintained radial arrangement even in the mature stems but in most places the cambia were either inactive or showed very few cell divisions. Concomitant with the obliteration and collapse of inner phloem (of bicollateral vascular bundles), parenchyma cells encircling the phloem became meristematic forming a circular sheath of internal cambia. These internal cambia produce only intraxylary secondary phloem centripetally and do not produce any secondary xylem. In the stem, secondary xylem consisted mainly of axial parenchyma, small strands of thick-walled xylem derivatives, i.e. vessel elements and fibres embedded in parenchymatous ground mass, wide and tall rays along with exceptionally wide vessels characteristic of lianas. In thick stems, the axial parenchyma de-differentiated into meristem, which later re-differentiated into interxylary phloem. Fibre dimorphism and pseudo-vestured pits in the vessels are also reported.

Determinação bromatológica de Pleurotus ostreatus cultivado em resíduos de diferentes cultivares de bananeira

The objective of this work was to evaluate the nutritional composition (raw protein, ether extract, raw fiber, FDA, FDN and ash) of the POS 09/100 strain of Pleurotus ostreatus grown in three combinations of residues (pseudo-stem, leave and pseudo-stem + leaf) and four banana tree cultivars (Thap maeo, Prata ana, Pelipita and Caipira). The basidiomata harvested were submitted to dehydration in a forced ventilation stove with temperature adjusted to 40 degrees C until reaching constant weight, being then grinded in a knife mill. The method proposed by Kjeldahl (1883) was used to determine total nitrogen. The Weende method (AOAC, 1997) was employed to determine crude fiber, acid-detergent fiber (ADF) and neutral detergent fiber (NDF). According to the results obtained, crude protein, ash, ADF and NDF contents varied with the kind of residue and banana tree cultivar; the substrate prepared with leaves of banana tree (Prata Ana cultivar) yielded the highest crude protein (35.4%) and ash (6.7%) contents in the basidiomata of P. streams; the substrate prepared with pseudo-stein of banana tree (Prata Ana cultivar) provided the highest ADF (31.6%) and NDF (41.9%) contents in the basidiomata of P. ostreatus. Ether extract and crude fiber contents of P. ostreatus didn't vary in function of the treatments, with averages of 2.45 and 11.27%, respectively.

Structural deformation monitored by vibrational properties and orbital modeling in (Pb,Sm)TiO3 systems

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Use of Biopolymeric Membranes for Adsorption of Paraquat Herbicide from Water

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Spin-orbit coupling for tidally evolving super-Earths

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

On discrete symmetries of the multi-boson KP hierarchies

We show that the multi-boson KP hierarchies possess a class of discrete symmetries linking them to discrete Toda systems. These discrete symmetries are generated by the similarity transformation of the corresponding Lax operator. This establishes a canonical nature of the discrete transformations. The spectral equation, which defines both the lattice system and the corresponding Lax operator, plays a key role in determining pertinent symmetry structure. We also introduce the concept of the square root lattice leading to a family of new pseudo-differential operators with covariance under additional Bäcklund transformations.

Spectroscopy of InF3 based glasses containing a large amount of GdF3

Glass formation in the pseudo ternary system ZnF2-GdF3-BaF2-InF3 and other complex systems stabilized by NaF, CaF2, AlF3 and YF3 have been investigated. Samples with greater stability have been prepared and their properties measured. Optical absorption and emission spectra of Gd3+ ions doped glasses with 2, 4, 10 and 20% concentrations have been measured. Using the Judd-Ofelt theory and the experimental oscillator strengths, the Judd-Ofelt parameters have been calculated. The emission of Gd3+ ions from 6I and 6P has been detected and the lifetime has been measured.

Residues of Some Pesticides in Fresh and Dried Apricots

The persistence of three pesticides (fenitrothion, dimethoate, and ziram) in apricots in field conditions and their fate during the drying process were studied. After the treatments, the pesticides showed fast decay rates with pseudo-first-order kinetics and half-lives ranging from 6.9 to 9.9 days. The drying process showed a different effect on residue concentrations in dried apricots: omethoate (metabolite of dimethoate) and ziram residues had almost doubled, while fenitrothion disappeared and dimethoate remained constant.

Ticks associated with wild animals in the Nhecolândia Pantanal, Brazil

A study of ticks associated with wild animals was carried out from September 1996 to April 1998 at the Fazenda Alegria (21,000 ha), in the Nhecolândia Pantanal, State of Mato Grosso do Sul, Brazil, a sunken plain bordering the upper Paraguay river, located 19 × 08′S; 56 × 46′W. A total of 81 wild animals (13 species, 6 orders) were captured with the aid of nets, and ticks were found on 63 (78%). Tick species identified included Boophilus microplus (Canestrini), Amblyomma cajennense (F.), A. parvum (Aragão), A. pseudo-concolor (Aragão), A. scalpturatum (Neumann), A. nodosum (Neumann), A. ovale (Koch), and A. tigrinum (Koch). Dragging from grasslands (campos) yielded negative results compared to the high concentration of ticks, mainly nymphs, that were collected from leaves in the forests (capão). Predominance of immature instars (Amblyomma genera) was observed in the end of winter (August-September). Ticks were associated mainly with coatis, deer (Mazama gouazoubira) and anteater, and these animals may play a role in the epidemiology of tick-transmitted pathogens in the Pantanal if one considers their coexistence with local domestic animals.

Short-chain di-ureasil ormolytes doped with potassium triflate: Phase diagram and conductivity behavior

Di-urea cross-linked poly(oxyethylene)/siloxane hybrids, synthesized by the sol-gel process and containing a wide concentration range of potassium triflate, KCF3SO3, have been analyzed by x-ray diffraction and differential scanning calorimetry. The pseudo-phase diagram proposed has been taken into account in the interpretation of the complex impedance measurements. The xerogels prepared are obtained as transparent, thin monoliths. At room temperature the highest conductivity found was 2 × 10-6 Ω-1 cm-1.