Abstract-New data are reported from five previously unanalyzed Apollo 12 mare basalts that are incorporated into an evaluation of previous petrogenetic modelsand classification schemes for these basalts. This paper proposes a classification for Apollo 12 mare basalts on the basis of whole-rock Mg# [molar 100·(MgI(Mg+Fe»] and RbiSr ratio (analyzed by isotope dilution), whereby the ilmenite,.olivine, and pigeonite basalt groups are readily distinguished from each other. Scrutiny ofthe Apollo 12 feldspathic "suite" demonstrates thl¢ two of the three basalts previously assigned to this group (12031, 12038, 12072) can be reclassified: 12031 is a plagioclase-rich pigeonite basah (Nyquist et al., 1979); and 12072 is an olivine basalt, Only basah 12038 stands out as a unique sample (Nyquist et al., 1981) to the Apollo 12 site, but whether this represents a single sample from another flow at the Apollo 12 site or is exotic to this site is equivocal.The question of whether the olivine and pigeonite basalt suites are co-magmatic is addressed by incompatible trace-elernent chemistry: the trends defined by these two suites when Co/Sm andSmIEu ratios are plotted against RblSr ratio demonstrate that these two basaltic types cannot be co-magmatic. Crystal fractionation/accumulation paths have been calculated and show that neither the pigeonite, olivine, or ilmenite basalts are related by this process. Each suite requires a distinct andseparate source region. This study also examines sample heterogeneity and the degree to which whole-rock analyses are representative, which is critical when petrogenetic interpretation is undertaken. Sample heterogeneity has been investigated petrographically (inhomogeneous mineral distribution) with consideration of duplicate analyses, and whether a specific sample (using average data) plots consistently upon a fractionation trend when a number of different compositional parameters are considered. Using these criteria, four basalts have been identified where reported analyses are not representative ofthe whole-rock composition: 12005, an ilmenite basalt; 12006 and 12036, olivine basalts; and 12031 previously classified as a feldspathic basalt, but reclassified as part ofthepigeonite suite (Nyquist et al., 1979).

This paper is devoted to the global practical tracking by output-feedback for a class of uncertain nonlinear systems with only the tracking error measurable. Different from the closely related works, the systems have unmeasured states dependent growth with unknown constant rate, and the reference signal, as well as its first order derivative, has unknown bound. Mainly because of these, the tracking problem can hardly be solved by straightforwardly extending the existing results. In the paper, motivated by the related stabilization results, and flexibly using the ideas of universal control and dead zone, an adaptive output-feedback controller is designed to make the tracking error prescribed arbitrarily small after a finite time while keeping all the states of the closed-loop system bounded. A numerical example demonstrates the effectiveness of the theoretical results.

Polychlorinated biphenyls (PCBs) are important persistent environmental contaminants. PCBs can be metabolically converted to their hydroxylated metabolites (OHPCBs), and in recent years, these OHPCBs have been observed to inhibit human sulfotransferases (SULTs) such as the phenol SULTs (SULT family-1) involved in the metabolism of estrogen and various other endogenous and xenobiotic phenols. In the present study, we have investigated the hypothesis that OHPCBs interact with family 2 hydroxysteroid (alcohol) SULTs (e.g., human SULT2A1), enzymes that are physiologically important for the metabolic transformations of several key endogenous hydroxysteroids as well as xenobiotic alcohols. We have examined the interactions of three OHPCBs with purified recombinant human SULT2A1 (also known as either human DHEA-ST or ST2A3). These studies with SULT2A1 were carried out on 4'-hydroxy-2,5-dichlorobiphenyl (4'-OH PCB 9), 4-hydroxy-2',3,5-trichlorobiphenyl (4-OH PCB 34), and 4'-hydroxy-2,3',4,5'-tetrachlorobiphenyl (4'-OH PCB 68). Our results showed that 4-OH PCB 34 and 4'-OH PCB 68 were substrates for SULT2A1, and 4-OH PCB 34 exhibited substrate inhibition similar to that seen with the physiological substrate dehydroepiandrosterone (DHEA). Although the sulfation of 4-OH PCB 34 and 4'-OH PCB 68 represents a potential metabolic route for these compounds, these OHPCBs may also compete with other xenobiotic substrates as well as endogenous substrates for SULT2A1. The third OHPCB studied, 4'-OH PCB 9, was not a substrate for SULT2A1 but was an inhibitor of the enzyme. Thus, the interactions of OHPCBs with human SULT2A1 represent both a potential route of metabolism and a possible source of interference with sulfation reactions catalyzed by this enzyme.

This paper addresses the design problem of practical (or satisfaction) output-feedback controls for stochastic strict-feedback nonlinear systems in observer canonical form with stable zerodynamics under long-term average tracking risk-sensitive cost criteria. The cost function adopted here is of the quadratic-integral type usually encountered in practice, rather than the quartic-integral one used to avoid difficulty in control design and performance analysis of the closed-loop system. A sequence of coordinate diffeomorphisms is introduced to separate the zero-dynamics from the entire system, so that the transformed system has an appropriate form suitable for integrator backstepping design. For any given risk-sensitivity parameter and desired cost value, by using the integrator backstepping methodology, an output-feedback control is constructively designed such that (a) the closed-loop system is bounded in probability and (b) the long-term average risk-sensitive cost is upper bounded by the desired value. In addition, this paper does not require the uniform boundedness of the gain functions of the system noise. Furthermore, an example is given to show the effectiveness of the theory.

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