Lability definition

Compounds of this type possess a definite Aj-selenazoline structure, while homologous compounds with at least one labile hydrogen on the 2-amino group can exist as a tautomeric equilibrium (Scheme 64). 

The exotoxin reported by Smirnoff (31) is definitively different from other soluble toxins, as indicated by its reported heat lability. This soluble toxin was obtained from the supernatant of a sporulated B. thuringiensis culture. In testing, it was found to be very toxic by ingestion to 18 species of larch sawfly larvae. No further studies on this toxin have been reported at this time. 

The term bioavailability has different meanings in different contexts and disciplines. Numerous definitions of bioavailability exist. Research on the relationship between bioavailability and chemical speciation (forms) originated in the field of soil fertility in the search for a good predictor for the bioavailability of essential plant nutrients (Traina and Laperche 1999). It is well accepted that dissolved nutrients are more labile and bioavailable to plants than solid-phase forms (including sorbed species). The same has been considered to be true for organic contaminants and their availability for microbial degradation. 

Shuman and Michael [10] applied a rotating disk electrode to the measurement of copper complex dissociation rate constants in marine coastal waters. An operational definition for labile and non-labile metal complexes was established on kinetic criteria. Samples collected off the mid-Atlantic coast of USA showed varying degrees of copper chelation. It is suggested that the technique should be useful for metal toxicity studies because of its ability to measure both equilibrium concentrations and kinetic availability of soluble metal. 

Several comprehensive texts [164-166] and papers [167-170] have been published on complexation reaction kinetics in aqueous, including environmental, solutions. In this section, we shall briefly examine the Eigen-Wilkins mechanism as a starting point for estimating the rates of metal complexation reactions in environmental aqueous systems (Sections 4.3.2-4.3.3) and as a basis for the definition of the lability criteria (Section 7.2). 

Another striking characteristic of aversive memories is their abiUty to reconsolidate on reactivation. By definition, memories should be insensitive to disruption, for instance by electroconvulsive shocks or drugs, once they have been consohdated. This is, in fact, the case as long as the treatments do not coincide with memory recall. Reactivation of a memory, however, makes it labile again because of reconsoUdation processes (Sara 2000 Nader 2003). Reconsolidation resembles consolidation in that similar cascades of molecular... 

The 2,3-dideoxy sugars have received the most attention among the remaining classes of dideoxy sugars. This interest stems from the fact that ethyl 2,3-dideoxy-a-D-er2/fAro-hexopyrano8ide 07 is a readily available compound it was found to be more labile to N hydrochloric acid at 18° than the 2-deoxy analog, and it was concluded 08 that an increase in the number of methylene groups in the chain definitely increases the lability of the... 

Some evidence234 for Zn—OH attack in anhydride hydrolysis has been obtained using the complex (65) (Section 61.4.11) but the evidence is not definitive, and other mechanisms could apply. Large rate enhancements occur in the Zn11- and Cu -promoted hydrolysis of the lactam (66) (Section 61.4.10). Rates increase commensurate with the ionization of a metal-bound water molecular and sigmoidal pH-rate profiles are observed. Rate enhancements of 9 x 105 and 1 x 103 occur with (66)—Cu—OH and (66)—Zn—OH compared with the free ligand. A number of other reactions which are believed to proceed via M—OH species, in kinetically labile systems, are considered in Section 61.4.3. 

Solid iodine monochloride exists in two forms. The brownish-red tablets of the j8 form (m. 13.9°C.) are labile and pass readily into the ruby-red needles of the a form (m. 27.19°C.). Since iodine monochloride dissociates on boiling at atmospheric pressure, its boiling point is not definite. The literature gives values from 94.7° to 102°C. Calculations from vapor-pressure data give 33.4 cal. as the value of the entropy of vaporization at a vapor concentration of 0.00507 mol per liter. Iodine monochloride must therefore be an associated or polar liquid. 

Attempts have been made to use stress-testing results to classify compounds as extremely labile, very labile, labile, and stable (71). The basis for this classification system was the personal experience of the authors. In this section we will attempt to outline and discuss some of the factors that need to be considered when attempting to interpret the results of stress testing, and to provide references to other resources. It is our opinion that insufficient information has been gathered to provide a definitive classification system. 

Thus, an interaction between reactions may be performed both with the help of stable IP (consecutive reactions), intermediate compounds (initiation, conjugated reactions, etc.), and in their absence (a definite type of parallel reactions). Of special interest for us are interrelated reactions performed with the help of labile, highly reactive intermediate compounds. This question will also be discussed below. 

Main drivers for membrane emulsification development include high product quality - especially when labile molecules are involved, precise definition of droplet-size distribution, low energy input, equipment modularity and easy scale-up, and low equipment footprint. 

Diastereoisomerism is observed when two or more chiral elements appear in the same system. Isolation and characterization of enantiomers or diastereoisomers depend on the structural stability of the chiral element. Therefore the conformation of a chelate ring must generally be considered as labile. The structural stability of the configuration around the metal center and the stability of an asymmetric coordination atom depends on the nature of the central metal atom. In most cases an optically active ligand molecule can be considered as configurationally stable. The presence of a stable chiral element can induce definite chirality in another element which, taken separately, would be labile. 

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