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Poor mechanical properties of biological tissue are known to cause wear, leading to the failure of cardiac bioprostheses made of calf pericardium. Different chemical agents such as sodium dodecyl sulfate (SDS) are presently being tested as possible inhibitors of the calcification process. The objective of this report was to determine the mechanical behavior of calf pericardium treated with SDS for 24 h and the influence of the suture on the mechanical properties of the tissue. Forty-eight samples were tested: 24 subjected to a standard treatment with glutaraldehyde (12 sewn with 4/0 silk suture thread) and 24 incubated with SDS for 24 h (12 sewn with the same suture thread). Each sutured and nonsutured sample was cut into two strips to yield paired samples. All were subjected to tensile stress to breaking point. The mean stress at breaking point in the nonsutured series treated with glutaraldehyde alone was 16.42 and 13.85 MPa, depending on the region of the pericardium, while in the sutured samples subjected to glutaraldehyde the mean stress was 7.50 and 7.63 MPa, respectively, differences which were statistically significant (p=0.03 and p=0.003, respectively) when the means for nonsutured samples from equivalent regions treated with glutaraldehyde were compared. The stress at breaking point was lower in the SDS-treated series, ranging between 2.60 and 3.56 MPa. The mathematical functions that govern the stress/strain or deformation were obtained. In the series of pericardium treated with SDS, deformations of 10% were produced with stresses of under 0.4 MPa, an outcome that is intolerable from the constructive point of view. We established a regression model that enabled us to determine the mechanical behavior of a sutured sample by testing a contiguous piece of tissue, with a high correlation coefficient (r > 0.99). We consider this finding to be of interest in the selection of pericardium for use in the construction of leaflets for cardiac bioprostheses. ©2000 Kluwer Academic Publishers

Lead-bismuth eutectic (LBE) is of interest as a coolant in the design of fast reactors and also as both a coolant and a spallation target in proposed transmutation schemes for radioactive waste. However, liquid metal corrosion to the structural materials can proceed via various processes: species dissolution, formation of the inter-metallic compounds at the steels/liquid metal interface... It is known that the formation of an oxide scale on a steel surface can protect it dissolution attack by liquid LBE. The variables that play an important role on the feasibility of the formation of an oxide layer and on its protective characteristics for steels in contact with LBE are oxygen content, temperature, materials composition and evolution with time, but also surface state of steels prior to testing or weld joints, being these parameters not very widely studied. For the study of the influence of the surface finishing, specimens with different surface states were prepared (as-received, grinded, grinded and polished and electrolitically polished). These treatments gave to the materials a different degree of cold working, the higher for the mechanised samples and the lowest for the electrolitically polished. Tests were carried out at 500 and 550°C from 100 to 2000 hours with two different H2 /H2 O ratios: 3 and 0.03. The general conclusion is that the effect of surface finishing on the corrosion/protection processes is not significant for the conditions tested.Copyright © 2009 by ASME

Alloy 22 is a nickel base alloy highly resistant to all forms of corrosion. In very aggressive conditions (e.g. hot concentrated chloride containing brines) Alloy 22 could suffer localized attack, namely pitting and crevice corrosion. The occurrence of localized corrosion in a given environment is governed by the values of the critical potential (E{sub crit}) for crevice corrosion and the corrosion potential (E{sub corr}) that the alloy may establish in the studied environment. If E{sub corr} is equal or higher than E{sub crit}, localized corrosion may be expected. This paper discusses the evolution of E{sub corr} of Alloy 22 specimens in 5 m CaCl{sub 2} + 5 m Ca(NO{sub 3}){sub 2} brines at 100 C and 120 C. Two types of specimens were used, polished as-welded (ASW) creviced and noncreviced specimens and as-welded plus solution heat-treated (ASW+SHT) creviced specimens. The latter contained the black annealing oxide film on the surface. Results show that, for all types of Alloy 22 specimens the E{sub corr} was higher at 120 C than at 100 C, probably because a more protective film formed at the higher temperature. Specimens with the black oxide film on the surface showed more oscillations in the potential. None ofmore » the tested specimens suffered crevice corrosion probably because of the relatively high concentration of nitrate in the electrolyte, R = [NO3]/[Cl] = 1.« less

One of the two acetone ligands in the complex [IrH2(Me2CO)2(PPh3)2]BF4 (1) is displaced by pyrazole (Hpz) to give [IrH2(Me2CO)(Hpz)(PPh3)2]BF4 (2). Treatment of2 with methyl propiolate and acetylenedicar☐ylic dimethyl ester leads to the cationic complexes [I¯rH(C(CO¯OCH3)=CH2)(Hpz)(PPh3)2]BF4 (3), [I¯rH(CH= CHCO¯OCH3)(Hpz)(PPh3)2]BF4 (4) and [I¯rH(C(CO¯OCH3)=CH(CO2CH3))(Hpz)(PPh3)2]BF4 (5). The molecular structure of3 has been determined by X-ray analysis.3 crystallizes with an acetone molecule in the lattice, in the space groupP21/m witha = 9.661(3)A˚,b = 22.903(3)A˚,c = 11.056(3)A˚and β = 99.82(1)°. The coordination around the iridium atom is a distorted octahedron with the two phosphorus atoms of the triphenylphosphine ligands occupyingtrans positions. The equatorial plane is formed by the α-C atom, the oxygen atom of the carbonyl group of the ester, the hydride and a nitrogen atom of the pyrazole ligand.3 reacts with [Rh(μ-OMe)(η4-1,5-COD)2] to give, via a redistribution reaction, [I¯r¯H¯(¯C¯H=¯¯C¯H¯C¯OOCH3)(MeOH)(PPh3)2]BF4 (6) and [Rh(μ-pz)(η4-1,5-COD)2]. The methanol molecule of6 is displaced by P(OMe)3 and CO to yield [I¯rH(CH=CH¯COOCH3)L(PPh3)2]BF4 (L = P(OMe)3 (7) or CO (8)). The vinyl complexes [IrH(C(CO2CH3)=CH2)(Hpz)(P(OMe)3)(PPh3)2]BF4 (9) and [IrH(C(CO2CH3)=CH2)Cl(Hpz)(PPh3)2] (10) were prepared by reaction of3 with P(OMe)3 and Cl− respectively. Complex10 reacts with [Rh(μ-OMe)(η4- 1,5-COD)2] to afford the heterobimetallic compound [H(C(CO2CH3)=CH2)(PPh3)2Ir(μ-pz)(μ-Cl)Rh(η4-1,5-COD)] (11)., We thank the DGICYT (Project PB 92-0092, Programa de Promocion General del Conocimiento) and EEC (Small Molecules: Selective Processes and Catalysis project) for financial support. M.M. thanks the Diputacion General de Aragon for a grant.

Parathyroid hormone (PTH) has been known to produce phosphaturia in a variety of species (Agus et al., 1971; Amiel et al., 1970; Bell et al., 1972). This response is most strikingly demonstrated in individuals with primary hyperparathyroidism, in whom excess phosphaturia and hypophosphatemia correlate closely with measured elevations in serum PTH levels (Aurbach and Heath, 1974). On the other hand, the role of PTH in the regulation of phosphate (PO4) homeostasis in normal subjects has been more difficult to ascertain. For example, studies from several laboratories have revealed that a variety of agents may influence the urinary excretion of PO4 in the absence of PTH including extracellular fluid volume expansion (Amiel et al., 1970), diuretics (Fulop and Brazeau, 1968), the level of dietary PO4 intake (Steele, 1976), insulin (DeFronzo et al., 1976), mild hyperglycemia (DeFronzo et al., 1976), phlorizin infusion (Nussbaum et al., 1978), and changes in systemic pH (Fulop and Brazeau, 1968; Puschett and Goldberg, 1969).