No abstract

No abstract

Results suggest that EIPH is associated with impaired performance in Thoroughbred racehorses not medicated with furosemide and not using nasal dilator strips.

Interlayering of 2: 1 layer silicates varies as a function of chemical weathering from the simple, homogeneous K or Na interlayers of micas to the heterogeneous systems of mica intercalated with expanded 2: 1 layer silicates. “Frayed edge” type of weathering at dislocation planes of mica is collated with K release and preferential cation-exchange uptake of K relative to Ca by such expansible layer silicate systems; mica islands maintain alignment of the silica sheet cavities, which facilitates recapture of lattice K. Intercalation of the expanded 2: 1 layer silicates with alumina interlayers appears to be a characteristic function of chemical weathering in soils, with the formation of 2: 1–2: 2 intergrades not only of 14 Å spacing but also of swelling 18 Å types that give small 12, 14, 18 Å and higher spacing peaks (along with the 10 Å peak) at 550°C. Interlayer precipitates appear to be characteristic of soil clays, contrasting with “pure” minerals of deposits developed in less “open” environments than those of soils. The “2: 2 lattice building” phenomenon in expansible 2: 1 layer silicates relates to layer charge density and crystal size, and frequently tends to inhibit the formation of free gibbsite in soil chemical weathering so long as there are expansible layer silicates present to become intercalated with aluminum hydroxide—a weathering phenomenon that may be called an “antigibbsite effect”. Accumulation of alumina (possibly with some iron, magnesium, and allophane) as interlayers in 2: 1 minerals of soils is seen as a genetic stage in the 2: 2 → 1: 1 weathering sequence through which kaolinite and halloysite develop in soils.

Freshly precipitated Fe and Al gels (points of zero change at pH 8.1 and 9.4, respectively) strongly specifically adsorb divalent cations from 1M NaNO3 solution. Adsorption from a mixed solution of eight divalent cations (each 0.125 × 10‐3M) in suspensions of freshly precipitated Fe and Al gels (0.093M with respect to Fe or Al) was measured as a function of pH in 1M NaNO3. The selectivity sequence (lower pH = greater selectivity) for the retention of the alkaline earth cations by Fe gel was Ba > Ca > Sr > Mg, but for the Al gel was Mg > Ca > Sr > Ba. The selectivity sequence (Figures in parentheses indicate pH ± 0.2 for 50% retention) for the Fe gel was: Pb (3.1) > Cu(4.4) > Zn(5.4) > Ni(5.6) > Cd(5.8) > Co(6.0) > Sr(7.4) > Mg(7.8), whereas the sequence for the Al gel was: Cu(4.8) > Pb(5.2) > Zn(5.6) > Ni(6.3) > Co(6.5) > Cd(6.6) > Mg(8.1) > Sr(9.2). Significant adsorption occurred even when the extent of cation hydrolysis was much < 1%, and invariably occurred at a pH lower than that for hydroxide precipitation. Although the adsorption‐pH sequences are related to cation hydrolysis and hydroxide precipitation pH values, the relationship is far from perfect, as is evidenced by the different sequences for the two gels. On aging of the Al gel in the presence of alkaline earth cations, the retention of Mg increased, while that of Ca, Sr, and Ba decreased. This result was thought to result from the structural incorporation of some Mg and the exclusion of the other cations.

Results indicated that interobserver reliability of tracheobronchoscopic assessment of EIPH in Thoroughbred racehorses is high when the examination is conducted by experienced veterinarians. Concordance among investigators is sufficient to justify use of this grading system for further studies and clinical descriptions of EIPH.

No abstract

The aluminum ion bonds through oxygen to form a variety of functional groups underlying diverse properties of soils. One aluminum-bond functional group provides the cation exchange site of soil layer silicate clays. Pauling's m-rule of acid strength for oxy-acids, (HO) n O m C, applied to the 2:1 layer silicate clay formula of beidellite, considering all structural cations, yields m = 1.6, characteristic of a medium to strong acid strength (on an m-scale: 1 = weak; 2 = strong). The solubility product of A1(OH) 3 , k T of A1(OH.,),, 3 +, and the Pauling k^k;, ratio of 10 5 are applied to calculate concentrations of aluminohydronium monomeric cation species of valence of 3, 2, and 1. These concentrations relate to cation exchange and interlayer aluminum polymerization reactions in soils during chemical weathering. The latter and mineral colloid composition changes are summarized in the generalized bonding equation: Al -O ±^ Al -OH, which provides the ultimate buffer, setting the lower and upper limits of the pH range of soils except in the presence of strong acidforming compounds such as S and FeS 2 . Aluminum bonding is central to soil acidity, through not only the acidic aluminohexahydronium monomeric cations, but also through the weakly acid Al-OH 2 . . . OH pair at edges of polymerized ("precipitated") hydroxy aluminum structures. The aluminum toxicity of soil acidity may involve aluminum bonding and solubility product relations at the soil-root interface and in solutions in soil and sap. Retention by soils of anions such as phosphate and sulfate is closely related to aluminum bonding of these anions (OH replacement). Some aspects of soil aggregate structure involve hydroxy aluminum bonding; loss of aggregates follows intensive cheluviation in the A2 horizon. Aluminum bonding in a real sense supplies a unifying principle for