Recent observations suggest that increased silicon levels improve ladle desulfurization of aluminum-killed steel. A kinetic model was developed and presented in part I of this paper, demonstrating that increased silicon levels in steel suppress the consumption of aluminum by parasitic reactions like silica reduction and FeO/MnO reduction, thus making more aluminum available at the interface for desulfurization. The results are increases in the rate and the extent of desulfurization. Predictions were compared with laboratory induction furnace melts using 1 kg of steel and 0.1 kg slag. The experimental results demonstrate the beneficial effect of silicon on the desulfurization reaction and that alumina can be reduced out of the slag and aluminum picked up by the steel, if the silicon content in the steel is high enough. The experimental results are in close agreement with the model predictions. Plant trials also show that with increased silicon content, both the rate and extent of desulfurization increase; incorporating silicon early into the ladle desulfurization process leads to considerable savings in aluminum consumption.

Sulphur control is an essential part of steel production. This paper summarises two aspects of sulphur in secondary metallurgy. First, it is shown that silicon can contribute to ladle desulphurisation if the ladle slag is low in silica; the effect of silicon is primarily on the equilibrium sulphur level, rather than a specific kinetic effect. Second, sulphur is shown to capture calcium (as calcium sulphide) upon calcium injection to modify inclusions. In steels with less than approximately 100 ppm sulphur, the calcium sulphide subsequently back-reacts with alumina inclusions, to modify the oxide inclusions to calcium aluminates.

Recent observations suggest that increased silicon levels improve ladle desulfurization of aluminum-killed steel. While the overall desulfurization reaction of Al-killed steels does not show a direct role of silicon in desulfurization, model calculations are presented which test the idea that silicon suppresses the reduction of silica which can consume aluminum at the slag/metal interface. Consumption of aluminum would increase the oxygen potential at the slag/metal interface and decrease the sulfur partition coefficient between slag and metal. The model considers the coupled reactions of the reduction of silica, iron oxide, and manganese oxide in the slag and desulfurization of the steel by aluminum. The results show that silicon can indeed suppress consumption of aluminum at the slag/metal interface by side reactions other than desulfurization, with silicon affecting both the kinetics and the equilibrium of desulfurization.

Constant stress amplitude fatigue life of an austenitic Ni (55.88wt.%)–Ti shape memory alloy (SMA) within the stress amplitude range of 180–450MPa was evaluated. The stress–strain hysteresis loops were monitored throughout the fatigue loading. They reveal that with the increasing number of fatigue cycles, the critical stress required for the stress-induced martensitic transformation, width of the hysteresis loop, recoverable and frictional energies of each cycle, all decrease while accumulated plastic strain increases. Post-mortem characterization of the fatigued specimens by employing differential scanning calorimetry (DSC), X-ray diffraction (XRD), and fractography were carried out, in order to understand the fatigue micromechanisms. Results indicate that the progressive accumulation of stress-induced martensite in the alloy is the source for the fatigue failure. Implications of these observations are discussed within the context of fatigue performance of SMAs and other materials that undergo stress-induced transformations.

An investigation into the thermo-mechanical response of trained Ni–Ti shape memory alloy (SMA) wires with two-way shape memory effect (TWSME) induced into them was conducted in order to examine the influence of the cold work on quasi-static and fatigue behavior of SMAs. Use of dynamic mechanical analyzer (DMA) for such tests on thin wires was examined and successfully utilized. Quasi-static stress–strain responses of the wires at different temperatures were obtained to determine the critical stresses for forward as well as reverse transformations. Mechanical stress-controlled fatigue tests were conducted on the wires in the austenitic state (130°C). They showed a two-stage deterioration of fatigue life—a rapid decay when the maximum stress of the fatigue cycle is higher than the critical transformation stress, and a more gradual deterioration at stress levels considerably lower than the critical stress. The fatigue life of the wires was found to increase with the load ratio, R, whereas the frequency of cyclic loading had only a marginal effect. Differential scanning calorimetry (DSC) of the fatigued austenite specimens indicated the presence of residual stress-induced martensite in the austenitic state. The high concentration of the austenite–martensite interfaces act as potential sites for stress-concentration and are the main source of the drastic decrease of the fatigue life in the two-phase region.

Lenses from rat or calf were exposed in vitro to UV radiation from a nitrogen laser operated at 337.1 nm or from an excimer laser operated at 3.8 nm. Visible light transmission was monitored during calf lens irradiations at 308 nm and found to decrease. Proteins were extracted from the irradiated rat or calf lenses, separated into water soluble and insoluble fractions, and analysed using SDS-PAGE. Comparison of these gels with dark controls showed that, following photolysis, there was loss of polypeptide material in the 20-30 kDa region and concomitant formation of polymers at 40 and 60 kDa, and at greater than 100 kDa in calf lens (308 nm irradiation) and rat lenses (337.1 nm irradiation) in vitro. In addition, there was evidence for formation of lower molecular weight polypeptides at 10 kDa in the protein from irradiated rat lenses. The rat SDS-PAGE gels were challenged against anti-calf gamma crystallin serum. There was clear evidence that the polymeric material, in the water insoluble protein fraction from the 337.1 nm photolyzed rat lenses was derived in part from gamma crystallin. The macromolecular changes detected in these photolyzed rat and calf lens proteins were similar to those previously reported to accompany aging in the human lens. Biochemical changes of the type observed in UV irradiated rat and calf lenses may be responsible for the loss of visible light transmission seen in calf lenses.

Hematoporphyrin (HP), a drug used for the treatment of tumors including intraocular tumors, is an efficient photosensitizer. In addition to its therapeutic value, it also produces a phototoxic side effect in the skin. To test whether such effects may also occur in the eye, calf lens fiber membranes were photolyzed in the presence and absence of 1 mM HP. A marked increase (ca 5 times) in the photopolymerization of the calf lens membrane main intrinsic protein (MP26) was found in the presence of HP. Tenfold increases in destruction rates were found in losses of histidine. The MP26 was also photolyzed after tryptic and chymotryptic digestion to MP21, this resulted in an increased photopolymerization in the presence of 1 mM HP. These data suggest an age related increase in sensitivity of the lens fiber membrane proteins to such photoprocesses. The addition of both azide and penicillamine reduces the photosensitized loss of the main intrinsic protein.

Calf lens fiber membranes were photolyzed in the presence and absence of sensitizers and scavengers. Photolytic damage was assessed by SDS-polyacrylamide gel electrophoresis, UV and fluorescence spectra and amino acid analyses. With irradiation, there is an apparent polymerization of the major membrane polypeptide (MP26) and the formation of material which does not enter SDS-polyacrylamide gels. Some degradation was also observed. These changes are accompanied by losses of histidine and tryptophan and changes in the UV spectra. The rate of photolysis is enhanced in the presence of the glucoside of 3-hydroxykynurenine (3-OH-KYN), a compound endogenous to the lens. The reaction is retarded in the presence of sulfhydryl-containing compounds such as glutathione.

The water-soluble 43,000-dalton fraction (WS43) of the human lens has been shown to be heterogeneous. It appears to contain, in addition to actin, components related to the crystallins. Immunoblot reactions indicate that this polypeptide fraction is composed of dimers containing beta- and gamma-crystallin components. It has been estimated that 10-30% of this fraction arises by dimerization of gamma-crystallin. A possible route for the formation of the 43,000-dalton fraction is suggested by the observation that photolysis of gamma-crystallin with light greater than 295 nm leads to polymer formation, including the 43,000-dalton fraction. The polymerization products react with anti-WS43. The results suggest that photochemical reactions may lead to the accumulation of polymers of some of the crystallins with aging of the human lens. Similar covalently linked polypeptides have previously been shown to be present in the high molecular weight aggregates associated with cataract formation.

Two of the major in vitro phosphorylated polypeptides of the bovine lens have been identified. Analysis by means of two-dimensional gel electrophoresis (IEF) has demonstrated that the lens phosphorylated 57,000 and 43,000 dalton polypeptides correspond in mobility to purified phosphorylated bovine lens vimentin and chicken gizzard actin, respectively. Purified actin and vimentin were phosphorylated by a partially purified cAMP-dependent protein kinase isolated from the outer cortex water soluble fraction. All detectable bovine lens vimentin isoelectric variants were phosphorylated. In both the lens fiber cell and chicken gizzard actin preparations, the phosphorylated actin isoelectric variants did not correspond in mobility to the major actin isoelectric variant, but were more acidic. Phosphorylation in all preparations occurred at serine residues.

The lens has been shown to contain a Ca+2 activated proteinase specific for vimentin. The proteinase is present in the soluble fraction of the cortex but not in the epithelium. It is suggested that this proteinase is expressed during terminal differentiation of the epithelial cells and may be responsible for degradation of the intermediate filaments in the fiber cells. The proteinase is inhibited by EGTA but not by several proteinase inhibitors.

The polyamine composition of normal and cataractous human lenses has been studied. Polyamines (putrescine, spermidine and spermine) have been shown to occur in the unbound form in the acid-soluble fraction and in the bound form in the acid-insoluble fraction of the lens. It has also been shown that only putrescine occurs in both conjugated and non-conjugated states in the lens, while putrescine as well as spermidine occur in both forms in the aqueous fluid. Estimation of the polyamine content in cataractous lenses indicates elevated levels of both bound and unbound polyamines in these lenses in comparison to the normal lenses. Evidence is presented which indicates an increase in the level of polyamines covalently bound to protein, in a gamma-glutamyl linkage, in the cataractous lens.

The photolysis of lens protein leads to the destruction of a number of amino acids. In addition to tryptophan; methionine, histidine and cysteine are destroyed upon irradiation. The latter three amino acids are not photolyzed directly but are degraded after an initial absorption of light by tryptophan. At least part of this mediated damage is probably due to singlet oxygen. The photo-destruction of tryptophan was found to be concentration dependent. As the concentration of lens proteins increases, the photolability decreases.

Changes in the protein chemistry of the Nakano lens with age and developing cataract and comparison with normal mouse lens protein are reported. It was found that significant differences exist between the protein of the normal and the cataractous lens. In Nakano lenses high molecular weight disulfide-linked aggregates, disulfide-linked cytosol polypeptides to the fiber membrane, an apparent increase in the concentration of degraded polypeptides, disulfide crosslinking of low molecular weight species and marked differences in membrane polypeptide profiles were observed. A striking similarity was found between these observations with the Nakano cataract and previous reports of the changes in protein chemistry in the development of senile human cataract. It can be concluded that although the initiating event for induction of the cataract may differ, the sequence of events following such insult may be similar.

Using antibodies to both the 26000 dalton and 22000 dalton fractions of the human lens membrane, it is shown that in the normal aging process there is cleavage of the 26000 dalton chain to products with molecular weights of 22000 and 16000 daltons. Furthermore, the human lens membrane contains at least one other 22000 dalton chain which is immunochemically unrelated to the 26000 dalton component.

Na/K ATPase activity has been determined in normal and cataractous human lenses using labeled ATP as a substrate. The enzyme is distributed throughout the lens with approximately 1/3 of the total activity in the capsule-epithelium and 1/2 of the activity in the cortex. Furthermore, the activity of Na/K ATPase decreases with increasing age and this decrease occurs primarily in the inner nuclear region. In severe cataractous lenses, a marked decrease in the Na/K ATPase activity has been demonstrated in all parts of the lens, in contrast to immature cataracts, where the decrease in the enzyme activity occurs primarily in the cortical and nuclear regions.

Lens plasma membrane from different animal lenses has been prepared by the acylation procedure. Using three different criteria: heat aggregation of intrinsic membrane polypeptides, immunochemistry and solubilization of intrinsic proteins at low (40 mM) LIS concentration, it has been shown that these preparations are essentially free of cytoplasmic contaminants. Using the results obtained with acylated membrane as the reference of purity, it has been shown that both sucrose gradient centrifugation of bovine WI protein and urea washing of old human lenses give impure membrane preparations. The main intrinsic polypeptides (mol. wt 26 000 and 22 000) of human lens membrane have been purified and characterized. It has been shown by enzymatic digestion and amino terminal analysis of the residual membrane-bound fragments that the amino terminal halves of the polypeptides are embedded in the lipid bilayer and are probably blocked at their amino terminal sites. Lipid analyses of human and bovine lens membranes suggest that the protein to total lipid ratio is 1:1. Carbohydrate analyses of chromatographically separated intrinsic membrane polypeptides indicate the presence of 1 mol glucose/1 mol protein.

Biochemical evidence is presented for the disintegration of the lens fiber plasma membrane in human cataracts. The intrinsic membrane proteins are found in both the water-soluble and water-insoluble nonmembrane fractions of the cataract lens but not in the normal tissue. Furthermore, in contrast to the normal lens, not all of the lipid found in the cataractous lens is isolated with the membrane fraction. In cataracts, both the membrane and membrane fragments are involved in covalent high molecular weight aggregates with an extrinsic membrane protein (43,000 daltons) and a cytoplasmic protein (gamma-crystallin).