Drug-matrix interaction of sodium diclofenac incorporated into ureasilpoly(ethylene oxide) hybrid materials

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Corrosion protection of stainless steel by polysiloxane hybrid coatings prepared using the sol-gel process

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Cryopreservation of Dendrobium hybrid seeds and protocorms as affected by phloroglucinol and Supercool X1000

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Single-phase high power factor hybrid rectifier suitable for high-power applications

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effects of Synthesis Conditions on the Nanostructure of Hybrid Sols Produced by the Hydrolytic Condensation of (3-Methacryloxypropyl)trimethoxysilane

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Ligand Exchange Inducing Efficient Incorporation of CisPt Derivatives into Ureasil-PPO Hybrid and Their Interactions with the Multifunctional Hybrid Network

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Controlled Cisplatin Delivery from Ureasil-PEO1900 Hybrid Matrix

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Application of dissociation curve analysis to radiation hybrid panel marker scoring: generation of a map of river buffalo (B-bubalis) chromosome 20

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

Molecular evidence of ribosomal DNA (rDNA) amplification of a minichromosome derived from Drosophila arizonae in D. mulleri-D. arizonae hybrid males

We present data supporting cytogenetic observations on nucleolar dominance in hybrids between Drosophila arizonae and D. mulleri. Our approach was to compare the rDNA restriction patterns between the parental species and their hybrids. Results demonstrated that the minichromosome attached to the nucleolus in hybrid males is derived from D. arizonae.

Study of Hybrid Silica-Polyethyleneglycol Xerogels by Eu3+ Luminescence Spectroscopy

Good optical quality Eu3+-doped silica-polyethyleneglycol hybrids were prepared by the sol-gel process. Thermomechanical analysis showed an increase of the glass transition temperature, due to the stiffness of the polymeric network, as the amount of Eu3+ increased. Europium luminescent properties were used to study structural evolution during the sol-gel transition. For lower doping concentrations dried gels present statistical distributions of Eu3+, typical of an amorphous environment, while for higher concentrations a crystalline-like environment of Eu3+ was observed. A broad emission band was observed in the visible part of the electromagnetic spectrum and assigned to the intrinsic emission from the hybrid polymeric network.

White light emission of Eu3+-based hybrid xerogels

The luminescence spectra and extended x-ray-absorption fine-structure (EXAFS) measurements of a series of Eu3+-based organic/inorganic xerogels were reported and related to the local coordination of the lanthanide cations. The hybrid matrix of these organically modified silicates, classed as U(2000) ureasils, is a siliceous network to which short organic chains containing oxyethylene units are covalently grafted by means of urea bridges. The luminescent centers were incorporated as europium triflate, Eu(CF3SO3)3, and europium bromide, EuBr3, with concentrations 200≥n≥20 and n=80, 40, and 30, respectively - where n is the number of ether oxygens in the polymer chains per Eu3+ cation. EXAFS measurements were carried out in some of the U(2000)nEu(CF3SO3)3 xerogels (n=200, 80, 60, and 40). The obtained coordination numbers N ranging from 12.8, n=200, to 9.7, n=40, whereas the average Eu3+ first neighbors distance R is 2.48-2.49 Å. The emission spectra of these multiwavelength phosphors superpose a broad green-blue band to a series of yellow-red narrow 5D0→7F0-4 Eu3+ lines and to the eye the hybrids appeared to be white, even at room temperature. The ability to tune the emission of the xerogels to colors across the chromaticity diagram is achieved by changing the excitation wavelength and the amount of salt incorporated in the hybrid host. The local environment of Eu3+ is described as a continuous distribution of closely similar low-symmetry network sites. The cations are coordinated by the carbonyl groups of the urea moieties, water molecules, and, for U(2000)nEu(CF3SO3)3, by the SO3 end groups of the triflate anions. No spectral evidences have been found for the coordination by the ether oxygens of the polyether chains. A mean radius for the first coordination shell of Eu3+ is calculated on the basis of the emission energy assignments. The results obtained for U(2000)nEu(CF3SO3)3, 2.4 Å for 90 ≥n≥40 and 2.6 and 2.5 Å for n=30 and 20, respectively, are in good agreement with the values calculated from EXAFS measurements. The energy of the intraconfigurational charge-transfer transitions, the redshift of the 5D0→7F0 line, with respect to the value calculated for gaseous Eu3+, and the hypersensitive ratio between the 5D0→7F2 and 5D0→7F1 transitions, point out a rather low covalency nature of the Eu3+ first coordination shell in these xerogels, comparing to the case of analogous polymer electrolytes modified by europium bromide. ©1999 The American Physical Society.

Cytogenetical and histological studies in testis of Tayassu tajacu (Cateto), Tayassu pecari (Queixada) and a natural interspecific hybrid

The karyotype, the histological structure of the testis and the synaptonemal complex (SC) of the mammalian species Tayassu tajacu, Tayassu pecari and of an interspecific male hybrid captured in nature were analysed. The specimens of T. tajacu (2n = 30) and T. pecan (2n = 26) exhibited seminiferous tubules with germ cells in all sperma to genesis stages. In the SC studies both species had a regular structure, easily identified in the autosomes and in the sex chromosomes. The hybrid (2n = 28) had seminiferous tubules with almost all germinal cells in the spermatogonium stage and only a few cells in the primary spermatocyte stage. Gross abnormalities in SC were observed. A few lateral elements showed regular or partially regular synapsis, other lateral elements were synapsed as multivalents, and most axial elements remained unsynapsed. The results suggest that the karyotypes of the parental species have sufficient differentiation to avoid chromosome synapsis. Alternatively, the hypothesis of the existence of genetic incompatibilities between the parental species is discussed.

Transient stability indices from a hybrid approach

This paper deals with hybrid method for transient stability analysis combining time domain simulation and a direct method. Nowadays, the step-by-step simulation is the best available tool for allowing the uses of detailed models and for providing reliable results. The main limitation of this approach involves the large time of computational simulations and the absence of stability margin. On the other hand, direct methods, that demand less CPU time, did not show ample reliability and applicability yet. The best way seems to be using hybrid solutions, in which a direct method is incorporated in a time domain simulation tool. This work has studied a direct method using the transient potential and kinetic energy of the critical machine only. In this paper the critical machine is identified by a fast and efficient method, and the proposal is new for using to get stability margins from hybrid approaches. Results from systems, like 16-machine, show stability indices to dynamic security assessment. © 2001 IEEE.

Paternity study of an interspecific natural hybrid of the genus Eucalyptus L'Hér (Myrtaceae) based on cytogenetic data

Three species of the genus Eucalyptus (E. dunni, E. grandis, E. saligna) and interspecific hybrid were studied cytogenetically. The Eucalyptus species and the hybrid showed a symmetrical karyotype with 2n=22 chromosomes, with chromosome length ranging from 0.67 to 1.39 μm. Karyotypic analysis indicated a homogenous morphology and chromosome number for the species and the hybrid studied here. Based on the karyotype asymmetry data, together with the chromosome morphology results, the hybrid presented close similarity to E. saligna, suggesting that the latter is one of the parental species involved in the production of the hybrid.

Synaptonemal complex analysis in the fish species Piaractus mesopotamicus and Colossoma macropomum, and in their interspecific hybrid

The surface-spreading technique for visualization of whole cell synaptonemal complex (SC) complements was employed to study the chromosome synapsis in spermatocytes of P. mesopotamicus, C. macropomum and in their interspecific hybrid (tambacu) with the main objective to analyze possible errors in chromosome pairing that could result in hybrid sterility. SC analysis showed that the parental species P. mesopotamicus and C. macropomum have 27 bivalents homogeneously synapsed. The SC in spermatocytes from the hybrid tambacu showed gross meiotic configurations in all cells analyzed. The spermatocytes exhibited a few chromosomes or well synapsed chromosome segments, while many chromosome segments did not have any synapsis. This result, allied to other genetical and cytogenetical evidence, reinforces the hypothesis that the hybrid tambacu is sterile. Further studies involving other aspects, such as behavior and physiology, should be conduced before the introduction of these hybrids in rivers and lakes.