4,783 research outputs found
Hyperkähler cones and instantons on quaternionic Kähler manifolds
We present a novel approach to the study of Yang-Mills instantons on quaternionic Kähler manifolds, based on an extension of the harmonic space method of constructing instantons on hyperk\"ahler manifolds. Our results establish a bijection between local equivalence classes of instantons on quaternionic Kähler manifolds M and equivalence classes of certain holomorphic maps on an appropriate SL_2(C)-bundle over the Swann bundle of M
A randomized trial comparing doxorubicin, cyclophosphamide, methotrexate with leucovorin rescue, vincristine, and cytarabine (ACOMLA), with doxorubicin, cyclophosphamide, vincristine, prednisone, and bleomycin (CHOP-B) in the treatment of diffuse histiocytic lymphoma
Investment rigidity and policy measures
This paper assesses the impacts of decoupled government transfers on production decisions of a sample of Kansas farms observed from 1996 to 2001. Our model allows for risk, risk attitudes and the intertemporal investment decisions. We also allow for different adjustments of the decision variables depending on the predominant economic conditions. The theoretical model is estimated using the threshold regression methods proposed by Hansen (1999). Threshold effects are allowed to characterize the behavior of output supply and quasi-fixed and variable input demand.. The econometric results support the existence of three regimes characterized by different economic behavior. Our analysis suggests that in a dynamic setting with risk and non-risk neutral economic agents, decoupled transfers can have a powerful influence on decisions taken by economic agents. The dynamics of the stock of capital cause this influence to grow over time.Investment, Decoupling, Threshold Behaviour, Farm Management, Risk and Uncertainty,
Subunit-Selective Interrogation of CO Recombination in Carbonmonoxy Hemoglobin by Isotope-Edited Time-Resolved Resonance Raman Spectroscopy
Hemoglobin (Hb) is an allosteric tetrameric protein made up of αβ heterodimers. The α and β chains are similar, but are chemically and structurally distinct. To investigate dynamical differences between the chains, we have prepared tetramers in which the chains are isotopically distinguishable, via reconstitution with 15N-heme. Ligand recombination and heme structural evolution, following HbCO dissociation, was monitored with chain selectivity by resonance Raman (RR) spectroscopy. For α but not for β chains, the frequency of the ν4 porphyrin breathing mode increased on the microsecond time scale. This increase is a manifestation of proximal tension in the Hb T-state, and its time course is parallel to the formation of T contacts, as determined previously by UVRR spectroscopy. Despite the localization of proximal constraint in the α chains, geminate recombination was found to be equally probable in the two chains, with yields of 39 ± 2%. We discuss the possibility that this equivalence is coincidental, in the sense that it arises from the evolutionary pressure for cooperativity, or that it reflects mechanical coupling across the αβ interface, evidence for which has emerged from UVRR studies of site mutants
On pseudo-hyperk\"ahler prepotentials
An explicit surjection from a set of (locally defined) unconstrained
holomorphic functions on a certain submanifold of (Sp_1(C) \times C^{4n}) onto
the set HK_{p,q} of local isometry classes of real analytic
pseudo-hyperk\"ahler metrics of signature (4p,4q) in dimension 4n is
constructed. The holomorphic functions, called prepotentials, are analogues of
K\"ahler potentials for K\"ahler metrics and provide a complete
parameterisation of HK_{p,q}. In particular, there exists a bijection between
HK_{p,q} and the set of equivalence classes of prepotentials. This affords the
explicit construction of pseudo-hyperk\"ahler metrics from specified
prepotentials. The construction generalises one due to Galperin, Ivanov,
Ogievetsky and Sokatchev. Their work is given a coordinate-free formulation and
complete, self-contained proofs are provided. An appendix provides a vital tool
for this construction: a reformulation of real analytic G-structures in terms
of holomorphic frame fields on complex manifolds.Comment: 53 pages; v2: minor amendments to Def.4.1 and Theorem 4.5; a
paragraph inserted in the proof of the latter; V3: minor changes; V4: minor
changes/ typos corrected for journal versio
LB O-014. Increasing trans-hepatic caval pressure gradient is associated with acute kidney injury after liver transplantation, irrespective of surgical technique
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