The influence of Y-TZP surface treatment on topography and ceramic/resin cement interfacial fracture toughness.

OBJECTIVE: Consider the efficacy of glass infiltration etching (SIE) treatment as a procedure to modify the zirconia surface resulting in higher interfacial fracture toughness. METHODS: Y-TZP was subjected to 5 different surface treatments conditions consisting of no treatment (G1), SIE followed by hydrofluoric acid treatment (G2), heat treated at 750°C (G3), hydrofluoric acid treated (G4) and airborne-particle abrasion with alumina particles (G5). The effect of surface treatment on roughness was evaluated by Atomic Force Microscopy providing three different parameters: Ra, Rsk and surface area variation. The ceramic/resin cement interface was analyzed by Fracture Mechanics KI test with failure mode determined by fractographic analysis. Weibull's analysis was also performed to evaluate the structural integrity of the adhesion zone. RESULTS: G2 and G4 specimens showed very similar, and high Ra values but different surface area variation (33% for G2 and 13% for G4) and they presented the highest fracture toughness (KIC). Weibull's analysis showed G2 (SIE) tendency to exhibit higher KIC values than the other groups but with more data scatter and a higher early failure probability than G4 specimens. SIGNIFICANCE: Selective glass infiltration etching surface treatment was effective in modifying the zirconia surface roughness, increasing the bonding area and hence the mechanical imbrications at the zirconia/resin cement interface resulting in higher fracture toughness (KIC) values with higher KIC values obtained when failure probability above 20% was expected (Weibull's distribution) among all the experimental groups.

Layer-preferential substitutions and magnetic properties of pyrrhotite-type Fe7-yMyX8 chalcogenides (X = S, Se; M = Ti, Co).

A comparative study of four series of pyrrhotite-type chalcogenide compounds Fe(7-y)M(y)X(8) (X = S, Se) with substitution of Ti or Co for iron has been performed by means of x-ray and neutron powder diffraction, and by magnetization measurements. In Fe(7-y)M(y)X(8) compounds having a ferrimagnetic order at y = 0, the substitution of either Ti or Co for iron is observed to result in a monotonous decrease of the magnetic ordering temperature, while the resultant magnetization shows a non-monotonous behavior with a minimum around y = 1.0-1.5 in all the Fe(7-y)M(y)X(8) families except Fe(7-y)Co(y)Se(8). Suppression of a magnetically ordered state with substitutions in Fe(7-y)M(y)X(8) is ascribed to nearly zero values of Ti and Co magnetic moments, while the non-monotonous changes of the resultant magnetization are explained by the compensation of the sublattice magnetizations due to the non-random substitutions in alternating metallic layers. The difference in the cation partitioning observed in Fe(7-y)Ti(y)X(8) and Fe(7-y)Co(y)X(8) is attributed to the difference in the spatial extension of Ti and Co 3d orbitals. High coercive field values (20-24 kOe) observed at low temperatures in the Ti-containing compounds Fe(7-y)Ti(y)X(8) with y ⩾ 3 are suggested to result from the enhancement of Fe orbital moment due to the Ti for Fe substitution.

Características gerais dos espermatozóides em homens oligozoospérmicos com e sem varicocele clínica / General chararacteristics of the spermatozoa in oligozoospermic men with and without clinical varicocele

Pacientes com oligozoospermia apresentam uma reduçao na qualidade do sêmen, independente da etiologia do distúrbio. Objetivo. Investigar o papel da varicocele na reduçao da qualidade do sêmen, em homens oligozoospérmicos. Métodos. Foram estudados dez pacientes portadores de varicocele clínica esquerda (PCV) e 21 pacientes nao-portadores desta entidade (PSV), atendidos em um laboratório privado, em Petrópolis, RJ. Foram analisados os seguintes parâmetros seminais: contagem de espermatozóides, vitalidade, motilidade e morfologia espermática. PCV e PSV foram comparados entre si e com um grupo-controle (n=15) de pacientes sem varicocele clínica e com espermograma normal. Resultados. PCV e PSV apresentaram uma reduçao significativa na vitalidade (43,9 por cento e 34,9 por cento versus 73,0 por cento no grupo-controle), nos graus (a) (5,3 por cento e 2,4 por cento versus 32,4 por cento) e (d) (76,7 por cento e 83,8 por cento versus 44,9 por cento) de progressao espermática e nos percentuais de espermatozóides ovais (25,5 por cento e 22,9 por cento versus 61,2 por cento), amorfos (25,4 por cento e 23,8 por cento versus 12,5 por cento) e outras anomalias (23,8 por cento e 30,5 por cento versus 13,0 por cento). PCV ainda apresentou diferença significativa no percentual de espermatozóides fusiformes (10,9 por cento versus 1,3 por cento) e PSV no grau (b) de progressao espermática (11,0 por cento versus 22,0 por cento), em relaçao ao grupo-controle. Entre PCV e PSV, nao foram encontradas diferenças significativas. Conclusao. A varicocele reduz a qualidade de semens oligozoospérmicos, mas esta reduçao também ocorre em oligozoospermias de outras etiologias.

Eruption of the nevado del ruiz volcano, Colombia, on 13 november 1985: gas flux and fluid geochemistry.

The 13 November 1985 eruption of Nevado del Ruiz volcano, in Colombia, released a small volume of pyroclastic material and a disproportionately large volume of volcanic gas. Before the eruption, summit fumarole gases became less water-rich, and the sulfur/chlorine ratio increased. Remote measurements of sulfur dioxide flux after the eruption indicated active degassing at levels associated with eruptive or inter-eruptive stages of other volcanoes. Thermal water analyses revealed increases in magnesium, calcium, and potassium and an increase in the magnesium/chlorine ratio, suggesting that these elements may have been leached from new magma. Ash leachate data showed sulfate and chloride concentrations and ratios that would be expected for the late stages ofa major Plinian eruption. Water from the lahar contained high concentrations of sulfate and had a sulfur/chlorine ratio of 4.67, suggesting that water ejected from the crater lake and turbulent mixing of pyroclasts and glacial ice triggered the lahar. Microprobe analyses of pumice from this eruption and the most recent previous event showed similar mixed andesites. The uniform composition of the pumices and the unusually high ratio of gas to magma suggest that, although a new batch of magma triggered this eruption, the pumice that erupted may actually be old. Large volumes of new magma and glacial ice make the volcano dangerous and should stimulate development of an integrated long-term monitoring program to include Tolima volcano, 25 kilometers to the south.