Instrumental neutron activation analyses of the most Earth-like meteorites

C1-carbonaceous chondrites are known to have the highest meteoritic content of volatile elements. Nevertheless, most volatile elements, such as H, He, N and O, are excluded from the accordance with the solar photosphere. In meteoritic material, which condensed closer to the sun, even moderately volatile elements could not completely condense and their C1-normalized concentration ratios with refractory elements are typically depleted. In primitive terrestrial samples these ratios of (lithophile) moderately volatile to refractory elements are even lower. This suggests an accretion of our planet from material, which condensed closer to the sun than all available meteorites surviving in significantly farer distances in the asteroid belt. Evidence to that may come from agreements between most Earth-like meteorites with the depletion pattern of moderately volatile elements in the Earth’s mantle or rather related bulk data. Therefore, two samples from Hammadah al Hamra 073 and Sahara 0182, supposed to be further members of the most Earth-like Coolidge-Loongana grouplet, have been analysed by INAA. Together with two earlier analysed samples from the grouplet the results have been used in fingerprint studies with terrestrial data. In spite of internal spreading due to sampling of inhomogeneous material, the results are in accordance with a volatility-dependent model of depletion. Abundance ratios of Fe relative to Mn, Cr, and Si measured from the grouplet-abundances are depleted relative to calculated data from the total Earth, what can be explained with a 30 %-mantle-stripping from an impact of a Mars-sized body.     

1H NMR detection of immobilized water molecules within a strong distal hydrogen-bonding network of substrate-bound human heme oxygenase-1

Solution 1H NMR is used to probe the environments of the donor protons of eight strong hydrogen bonds on the distal side of the heme substrate in the cyanide-inhibited, substrate-bound complex of human heme oxygenase, hHO. It is demonstrated that significant magnetization transfer from the bulk water signal to the eight labile protons does not result from chemical exchange, but from direct nuclear Overhauser effect due to the dipolar interaction of these labile protons with "ordered" water molecules. The enzyme labile proton to water proton distances are estimated at approximately 3 A. It is proposed that the role of the strong hydrogen-bonding network is to immobilize numerous water molecules which both stabilize the activated hydroperoxy species and funnel protons to the active site.     

Asymptotisches Verhalten der Maxima der Lösungen gewisser Differentialgleichungen

Eine oszillatorische Lösung u der Gleichung u" + qu = 0u' + qu = 0 hat die Wintner-Eigenschaft, wenn die relativen Maxima von q^1/4 |u|q^{1/4} |u| für t ? ￥t \to \infty gegen einen positiven endlichen Grenzwert streben. In Verallgemeinerung eines Satzes von Hartman werden neue Methoden zum Nachweis der Wintner-Eigenschaft beschrieben. Andererseits werden Funktionen q konstruiert, die belegen, daß i.a. das Verhalten von q^1/4 uq^{1/4} u fast beliebig ist. Durch Methoden aus dem Bereich der universellen Funktionen wird die Residualität solcher Funktionen q bewiesen.     

Symmetries of Surface Singularities

The study of reductive group actions on a normal surface singularityX is facilitated by the fact that the group Aut X of automorphismsof X has a maximal reductive algebraic subgroup G which containsevery reductive algebraic subgroup of Aut X up to conjugation.If X is not weighted homogeneous then this maximal group G isfinite (Scheja, Wiebe). It has been determined for cusp singularitiesby Wall. On the other hand, if X is weighted homogeneous butnot a cyclic quotient singularity then the connected componentG₁ of the unit coincides with the C* defining the weighted homogeneousstructure (Scheja, Wiebe, Wahl). Thus the main interest liesin the finite group G/G₁. Not much is known about G/G₁. Ganterhas given a bound on its order valid for Gorenstein singularitieswhich are not log-canonical. Aumann-Körber has determinedG/G₁ for all quotient singularities. We propose to study G/G₁ through the action of G on the minimalgood resolution of X. If X is weightedhomogeneous but not a cyclic quotient singularity, let E₀ bethe central curve of the exceptional divisor of . We show that the natural homomorphism GAut E₀ haskernel C* and finite image. In particular, this re-proves therest of Scheja, Wiebe and Wahl mentioned above. Moreover, itallows us to view G/G₁ as a subgroup of Aut E₀. For simple ellipticsingularities it equals (Z_bxZ_b)Aut₀ E₀ where –b is theself-intersection number of E₀, Z_bxZ_b is the group of b-torsionpoints of the elliptic curve E₀ acting by translations, andAut₀ E₀ is the group of automorphisms fixing the zero elementof E₀. If E₀ is rational then G/G₁ is the group of automorphismsof E₀ which permute the intersection points with the branchesof the exceptional divisor while preserving the Seifert invariantsof these branches. When there are exactly three branches weconclude that G/G₁ is isomorphic to the group of automorphismsof the weighted resolution graph. This applies to all non-cyclicquotient singularities as well as to triangle singularities.We also investigate whether the maximal reductive automorphismgroup is a direct product GG₁xG/G₁. This is the case, for instance,if the central curve E₀ is rational of even self-intersectionnumber or if X is Gorenstein such that its nowhere-zero 2-form has degree ±1. In the latter case there is a ‘natural’section G/G₁G of GG/G₁ given by the group of automorphisms inG which fix . For a simple elliptic singularity one has GG₁xG/G₁if and only if –E₀ · E₀ = 1.     

Cut sharing for multistage stochastic linear programs with interstage dependency

Multistage stochastic programs with interstage independent random parameters have recourse functions that do not depend on the state of the system. Decomposition-based algorithms can exploit this structure by sharing cuts (outer-linearizations of the recourse function) among different scenario subproblems at the same stage. The ability to share cuts is necessary in practical implementations of algorithms that incorporate Monte Carlo sampling within the decomposition scheme. In this paper, we provide methodology for sharing cuts in decomposition algorithms for stochastic programs that satisfy certain interstage dependency models. These techniques enable sampling-based algorithms to handle a richer class of multistage problems, and may also be used to accelerate the convergence of exact decomposition algorithms. Research leading to this work was partially supported by the Department of Energy Contract DE-FG03-92ER25116-A002; the Office of Naval Research Contract N00014-89-J-1659; the National Science Foundation Grants ECS-8906260, DMS-8913089; and the Electric Power Research Institute Contract RP 8010-09, CSA-4O05335. This author's work was supported in part by the National Research Council under a Research Associateship at the Naval Postgraduate School, Monterey, California.     

λ-definierbare Funktionen auf Peanoalgebren

Ohne Zusammenfassung