Dissolution-resistant

Event II was the main plankton extinction and productivity crisis coimected to the rapid collapse of the surface-to-deep water carbon isotope gradient and drops in barium and carbonate accumulation rates. Curiously, there was a hundredfold increase in the concentration of foraminifera relative to total carbonate. It could be due to intensified deep circulation with winnowing of the fine fraction. Or possibly to better the preservation of the dissolution-prone planktonic forms through deepening of the CCD and/or lowered rates of in situ dissolution caused by decreased decay of organic carbon in sediment pore waters. There is support for this idea from the fact that coccoHths tend to be more dissolution-resistant than foraminifera, also from calcite dissolution above the calcite saturation horizon is driven mainly by titration by metabolic carbon dioxide derived from organic carbon decay at or near the sediment-water interface. 

Refractory metals and alloys are generally dissolution-resistant in liquid metals and corrosion is often controlled by reactions with impurity/interstitial elements [13,14,27]. In the case of refractory metal alloys based on niobium or tantalum, the concentration of oxygen in the alloy is an important parameter with respect to corrosion in alkali metals, particularly lithium [34-38]. As little as 300 wppm of oxygen in niobium will induce catastrophic penetration of the niobium by lithium. Interstitial oxygen will also cause penetration of niobium tmd tantalum by sodium or potassium, but the threshold of oxygen concentration is higher. 

Ramrrez-Caballero GE, BalbucmaPB (2010) Dissolution-resistant COTe-shell materials for acid medium oxygen reduction electrocatalysts. J Phys Chem Lett 1 724-728... 

Dissolution/Precipitation Quantitative analyte transfer Some polymeric matrices are dissolution resistant... 

Strategies to improve the durability of the cathode catalyst are being considered. They are application of oxidation-resistant carbon support, and application of dissolution-resistant platinum alloy catalyst. 

From polarization curves the protectiveness of a passive film in a certain environment can be estimated from the passive current density in figure C2.8.4 which reflects the layer s resistance to ion transport tlirough the film, and chemical dissolution of the film. It is clear that a variety of factors can influence ion transport tlirough the film, such as the film s chemical composition, stmcture, number of grain boundaries and the extent of flaws and pores. The protectiveness and stability of passive films has, for instance, been based on percolation arguments [67, 681, stmctural arguments [69], ion/defect mobility [56, 57] and charge distribution [70, 71]. 

Positive-Tone Photoresists based on Dissolution Inhibition by Diazonaphthoquinones. The intrinsic limitations of bis-azide—cycHzed mbber resist systems led the semiconductor industry to shift to a class of imaging materials based on diazonaphthoquinone (DNQ) photosensitizers. Both the chemistry and the imaging mechanism of these resists (Fig. 10) differ in fundamental ways from those described thus far (23). The DNQ acts as a dissolution inhibitor for the matrix resin, a low molecular weight condensation product of formaldehyde and cresol isomers known as novolac (24). The phenoHc stmcture renders the novolac polymer weakly acidic, and readily soluble in aqueous alkaline solutions. In admixture with an appropriate DNQ the polymer s dissolution rate is sharply decreased. Photolysis causes the DNQ to undergo a multistep reaction sequence, ultimately forming a base-soluble carboxyHc acid which does not inhibit film dissolution. Immersion of a pattemwise-exposed film of the resist in an aqueous solution of hydroxide ion leads to rapid dissolution of the exposed areas and only very slow dissolution of unexposed regions. In contrast with crosslinking resists, the film solubiHty is controUed by chemical and polarity differences rather than molecular size. 

Numerous studies have probed how novolac microstmcture influences resist hthographic properties. In one example, a series of resists were formulated from novolacs prepared with varying feed ratios ofpara-jmeta-cmso. These researchers found that the dissolution rate decreased, and the resist contrast increased, as thepara-jmeta-cmso feed ratio increased (33). Condensation can only occur at the ortho position ofpara-cmso but can occur at both the ortho- and i ra-positions of meta-cmso. It is beheved that increased steric factors and chain rigidity that accompany increasedpara-cmso content modify the polymer solubihty. 

The solubHity properties of the PAG itself can play an important role in the overaH resist performance as weU (50). SolubHity differences between the neutral onium salt and the acidic photoproducts can be quite high and wHl affect the resist contrast. In fact onium salts can serve as dissolution inhibitors in novolac polymers, analogous to diazonaphthoquinones, even in the absence of any acid-sensitive chemical function (51). 

Positive resists have as the photoreactive component a dissolution inhibitor that is destroyed in the regions exposed to the light. The resist is developed in an aqueous solution, where the exposed region dissolves away. The resists do not swell as much in the aqueous developer, allowing higher resolution. 

The success of thrombus lysis depends mainly on how large the thrombus is and whether any blood flow stiU remains. The outcome is better the larger the surface of the entire thrombus exposed to the thrombolytic agent. As the clot ages, the polymerization of fibria cross-linking and other blood materials iacreases and it becomes more resistant to lysis. Therefore, the eadier the thrombolysis therapy starts, the higher the frequency of clot dissolution. Thrombolytic agents available are Hsted ia Table 7 (261—276). 

Cr2 03 - 112 0, of indefinite composition occurs. This compound is commonly misnamed as chromic or chromium (ITT) hydroxide [1308-14-1], Cr(OH)2. A tme hydroxide, chromium (ITT) hydroxide trihydrate [41646-40-6], Cr(OH)2 3H20, does exist and is prepared by the slow addition of alkaU hydroxide to a cold aqueous solution of hexaaquachromium(III) ion (40). The fresh precipitate is amphoteric and dissolves in acid or in excess of hydroxide to form the metastable Cr(OH). This ion decomposes upon heating to give the hydrous chromium (ITT) oxide. However, if the precipitate is allowed to age, it resists dissolution in excess hydroxide. 

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