Stabilization of fluoroindate glasses by magnesium fluoride and other heavy metal fluorides

Their extended transparency in the IR makes them attractive for use as optical fibers for CO laser power delivery and optical amplification. This paper firstly describes the spectacular stabilizing effect of MgF2 on the binary system InF3-BaF2. The investigation of the InF3-BaF2-MgF2 system led to samples up to 5mm in thickness. Further optimization of this system was achieved by incorporation of limited amounts of other fluorides and resulted in increased resistence to devitrification. The second approach of this work was concerned to the investigation of the pseudo-ternary system InF3-GdF3-GaF3 at constant concentrations of ZnF2-SrF2-BaF2-NaF. Several compositions were studied in this system. The samples presented a better thermal stability when compared to other families of fluoride glasses. Therefore, these glasses seem to be very promising for the fabrication of special optical fibers. Thermal data are reported.

In vitro PHYTOTHERAPY OF VECTOR SNAILS BY BINARY COMBINATIONS OF LARVICIDAL ACTIVE COMPONENTS IN EFFECTIVE CONTROL OF FASCIOLIASIS

SUMMARY A food-borne trematode infection fascioliasis is one among common public health problems worldwide. It caused a great economic loss for the human race. Control of snail population below a certain threshold level is one of the important methods in the campaign to reduce the incidence of fascioliasis. The life cycle of the parasite can be interrupted by killing the snail or Fasciola larva redia and cercaria inside of the snail Lymnaea acuminata. In vitro toxicity of different binary combinations (1:1 ratio) of plant-derived larvicidal active components such as citral, ferulic acid, umbelliferone, azadirachtin and allicin against Fasciola redia and cercaria were tested. The mortality of larvae was observed at 2h, 4h, 6h and 8h of treatment. In in vitro condition azadirachtin + allicin (1:1 ratio) was highly toxic against redia and cercaria (8h LC50 0.006 and 0.005 mg/L). Toxicity of citral + ferulic acid was lowest against redia and cercaria larvae.

EFFECTS OF SINGLE, BINARY AND TERTIARY COMBINATIONS WITH Jatropha gossypifolia AND OTHER PLANT-DERIVED MOLLUSCICIDES ON REPRODUCTION AND SURVIVAL OF THE SNAIL Lymnaea acuminata

The effect of sub-lethal doses (40% and 80% of LC50/24h) of plant derived molluscicides of singly, binary (1:1) and tertiary (1:1:1) combinations of the Rutin, Ellagic acid, Betulin and taraxerol with J. gossypifolia latex, leaf and stem bark powder extracts and their active component on the reproduction of freshwater snail Lymnaea acuminata have been studied. It was observed that the J. gossypifolia latex, stem bark, individual leaf and their combinations with other plant derived active molluscicidal components caused a significant reduction in fecundity, hatchability and survival of young snails. It is believed that sub-lethal exposure of these molluscicides on snail reproduction is a complex process involving more than one factor in reducing the reproductive capacity.

New compositions of fluoroindate glasses with higher chemical resistance

In this paper, glasses in the systems In-Ba-Mg and In-Ba-Zn-Sr-Mg were water leachead at 80ºC showing surface degradation after 72 hours of leaching. The extent of such degradation is determined by the solubility and the concentration of the elemental fluorides that constitute the glasses. The formation of a layer of crystallized phases on the surface of the samples was observed. Small weight losses were registered and the absence of water on the glass matrix after the attack suggested that the use of MgF2 in the systems studied can lead to better results against moisture corrosion when compared to other fluoride glasses such as the fluorozirconates.

Optical characterization of sol-gel glasses derived from Eu3+ complex-forming precursors

Fabrication of new optical devices based upon the incorporation of rare earth ions via sol-gel methods depends on elimination of dopant ion clusters and residual hydroxyl groups from the final material. The optical absorption and/or luminescence properties of luminescent rare earth ions are influenced by the local bonding environment and the distribution of the rare-earth dopants in the matrix. Typically, dopants are incorporated into gel via dissolution of soluble species into the initial precursor sol. In this work, Eu3+ is used as optical probe, to assess changes in the local environment. Results of emission, excitation, fluorescence line narrowing and lifetimes studies of Eu3+-doped gels derived from Si(OCH3)4 and fluorinated/chelate Eu3+ precursors are presented. The precursors used in the sol-gel synthesis were: tris (6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate) Eu(III), Eu (III) trifluoromethanesulfonate, Eu(III) acetylacetonate hydrate, Eu (III) trifluoroacetate trihidrate, tris (2,2,6,6-tetramethyl-3,5- heptanedionate) Eu(III) and Eu(NO3)3.6H2O. The results were interpreted in terms of the evolution of the Eu3+ fluorescence in systems varying from solution to the gels densified to 800ºC. The lifetimes studies indicate that the fluorinated precursors are effective at reducing the water content in densified gels.

Connectivity in sol-gel silica glasses

In this work it is carried out a review on structural parameters related to the evaluation of pore connectivity of nanostructures. The work describes parameters and methods of evaluation of geometric parameters. The concepts of connectivity are applied to silica gels and glasses obtained from sol-gel process. The study of pores connectivity was carried out using a combination of geometric modeling and experimental evaluation of specific surface area and pore volume. The permeability of the pore structure is evaluated and a permeability geometric factor, Pg, is proposed.

Preparation of glasses and glass ceramics of heavy metal oxides containing silver: optical, structural and electrochemical properties

Silver containing heavy metal oxide glasses and glass ceramics of the system WO3-SbPO4-PbO-AgCl with different AgCl contents have been prepared and their thermal, structural and optical properties characterized. Glass ceramics containing metallic silver nanoparticles have been prepared by annealing glass samples at temperatures above the glass transition and analyzed by transmission electron microscopy and energy dispersive X-ray microanalysis. The presence of the metallic clusters has been also confirmed by the observation of a surface plasmon resonance band in the visible range. Cyclic voltammetric measurements indicated the presence of metallic silver into the glasses, even before to perform the thermal treatment.

Stability-indicating RP-HPLC method for simultaneous determination of gatifloxacin and flurbiprofen in binary combination

A stability-indicating RP-HPLC method is presented for determination of gatifloxacin and flurbiprofen in binary combination. Gatifloxacin, flurbiprofen and their degradation products were detected at 254 nm using a BDS Hypersil C8 (250 X 4.6 mm, 5 µm) column and mixture of 20 mM phosphate buffer (pH 3.0) and methanol 30:70 v/v as mobile phase. Response was linear over the range of 15-105 mg mL-1 for gatifloxacin (r² > 0.998) and of 1.5-10.5 mg mL-1 for flurbiprofen (r² > 0.999). The developed method efficiently separated the analytical peaks from degradation products (peak purity index > 0.9999). The method developed can be applied successfully for determination of gatifloxacin and flurbiprofen in human serum, urine, pharmaceutical formulations, and their stability studies.