Constraints anomalies

Accretion Li abundances can be altered in two ways by accretion. During PMS Li depletion the additional mass will lead to increased Li depletion at a given Teff when the star reaches the ZAMS [26], If accretion occurs after Li-burning has ceased then the convective zone is enriched with Li. Too much accretion is required to be compatible with observations of disks around PMS stars unless the accreted material is H/He-deficient. But then accretion of sufficient H/He depleted material to explain the Li abundance scatter would also lead to (for instance) Fe abundance anomalies of order 0.2-0.3dex - much higher than allowed by current observational constraints [38]. 

The measurements of isotopic anomalies in meteorites has contributed greatly to the understanding of mixing processes and time scales in the formation of the solar system as well as strong constraints on presolar stellar evolution but it also left unanswered questions and revealed new complexities which are discussed here. 

The constraint index test revisited anomalies based upon new zeolite structure types. Micropor. Mesopor. Mater., 35-36, 31 5. 

ABSTRACT Constraints that abundance anomalies observed on main sequence stars put on turbulence, meridional circulation and mass loss are reviewed. The emphasis is on recent observations of Li abundances. 

McKay G., Le L., and Wagstaff J. (1991) Constraints on the origin of the mare basalt europium anomaly REE partition coefficients for pigeonite. In Lunar Planet. Sci. XXII. The Lunar and Planetary Institute, Houston, (CD-ROM), pp. 883-884. 

The rationale for using Hg as a pathfinder element in mineral exploration is attractive. Because of its volatility, Hg is presumed to form broader halos in the hypogene environment than most elements. It is envisaged that both vapour-phase and solution transport are responsible for a wide dispersion of the element. In the secondary environment it is well known that Hg exerts a measurable vapour pressure at ambient temperatures and possesses redox properties that allow the metal to exist in the elemental state under a range of natural conditions. Therefore it has been claimed that, as a host sulphide-body weathers, it can be expected that Hg will be converted partly to the vapour state, thereby overcoming the constraint of hydromorphic or solution dispersion that applies to other target and indicator elements. Vapour-phase dispersion through permeable rock or cover would allow Hg to be detected in soil or soil gas, and perhaps as an atmospheric anomaly. 

Given the complexity of excimer behaviour believed to be present in all the decays measured it is perhaps not surprising that there are shortcomings in the different kinetic interpretations offered by Equations 3 and 4. Indeed, particularly for BuPBD which is reluctant to form an intermolecular excimer, it is possible to envisage that there exists in Poly(VBuPBD) a distribution of preformed excimer conformations each with differing overlap, molecular constraint, chromophore separation and decay rate. What is interesting is that these features also look to be apparent in Poly (VPPO) even though PPO itself readily forms an intermolecular excimer. Even if just two excimer conformations are present in these polymers the apparent anomalies of Tables I, II and III now start to appear more rational. 

The factors controlling the regioselectivity appear to be more subtle than simple steric hindrance. For example, in the formation of a 6,7-bicycle, the opposite regioselectivity from that observed in path a in Equation 1.52 occurs, as illustrated in Equation 1.54 [49a]. The conformational constraints imposed in forming the six-membered ring may account for this anomaly. 

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