Forward-backward asymmetry in tt production from flavor symmetries

We show that the forward-backward asymmetry in top quark pair production can be enhanced by fields that transform nontrivially under the flavor group and satisfy minimal flavor violation, while at the same time the constraints from associated effects on the dσ(tt)/dM(tt) distribution, dijet resonance searches, same-sign top-pair production, and other phenomenology are satisfied. We work out two examples in detail: one where a scalar color antisextet field that is also an antisextet of SU(3)(U) enhances the forward-backward asymmetry and one where the enhancement arises from a vector color octet field that is also an octet of SU(3)(U).     

Reversal of the Stereochemical Course of 1‐Methyl‐1H‐indole Addition to Cinnamaldehyde with cis‐5‐Benzyl‐(2‐fluoromethyl)‐2,3‐dimethylimidazolidin‐4‐ones as Catalysts – a Puzzling ‘Fluorine Effect’

Replacement of the cis‐Me group by CH₂F in the imidazolidinone organocatalyst specified in the title (so‐called McMillan generation‐I catalyst) leads to reversal of the product configuration in the title reaction. The topicity reversal in the nucleophilic addition step must arise either from cis‐addition with respect to the benzylic substituent of an (E)‐iminium ion intermediate or from trans‐addition to the corresponding (Z)‐iminium ion. Mechanistic investigations have not provided evidence for either one of these two possibilities, so far.     

Asymptotic relations betweenL- andM-estimators in the linear model

We obtain Bahadur-type representations for one-stepL-estimators,M- and one-stepM-estimators in the linear model. The order of the remainder terms in these representations depends on the smooth-ness of the weight function forL-estimators and on the smoothness of the ψ-function forM- and one-stepM-estimators. We use the representations to investigate the asymptotic relations between these estimators. In particular, we show that asymptotically equivalentL- andM-estimators of the slope parameter exist even when the underlying distribution is asymmetric. It is important to consider the asymmetric case for both practical and robustness reasons: first, there is no compelling argument which precludes asymmetric distributions from arising in practice, and, secondly, even if a symmetric model can be posited, it is important to allow for the possibility of mild (and therefore difficult to detect) departures from the symmetric model.     

Effect of the initial estimator on the asymptotic behavior of one-step M-estimator

For a general (real) parameter, let M _nbe the M-estimator and M _n ⁽¹⁾ be its one-step version (based on a suitable initial estimator M _n ⁽⁰⁾). It is known that, under certain regularity conditions, n(M _n ⁽¹⁾-M _n)=O _p(1). The asymptotic distribution of n(M _n ⁽¹⁾-M _n) is studied; it is typically non-normal and it reveals the role of the initial estimator M _n ⁽⁰⁾.Work of this author was partially supported by the Office of Naval Research, Contract No. N00014-83-K-0387     

Reversible interconversion of thiazolidine-tetrahydrothiazine in the thiadiazabicyclooctanone system

Summary The interconversion of thiazolidine-tetrahydrothiazine in some derivatives of thiadiazabicyclooctanone in aqueous HCl has been studied. In the case of 6- and 7-substituted hydroxy or methoxy thiadiazabicyclooctanone a reversible rearrangement was found. The sulfoxide of thiadiazabicyclooctanone under the same reaction conditions undergoes epimerisation, while reaction with PCl₅ — via a corresponding sulfenyl chloride — affords a mixture of 6-and 7-substituted hydroxy or methoxy derivatives of thiadiazabicyclooctanone.The authors dedicate this paper to Dr. B. Gapert for his 60th birthday     

Observation of condensed phases of quasiplanar core-softened colloids

We experimentally study the condensed phases of repelling core-softened spheres in two dimensions. The dipolar pair repulsion between superparamagnetic spheres trapped in a thin cell is induced by a transverse magnetic field and softened by suitably adjusting the cell thickness. We scan a broad density range and we materialize a large part of the theoretically predicted phases in systems of core-softened particles, including expanded and close-packed hexagonal, square, chainlike, stripe or labyrinthine, and honeycomb phase. Further insight into their structure is provided by Monte Carlo simulations.     

Representations of étale Lie groupoids and modules over Hopf algebroids

The classical Serre-Swan’s theorem defines an equivalence between the category of vector bundles and the category of finitely generated projective modules over the algebra of continuous functions on some compact Hausdorff topological space. We extend these results to obtain a correspondence between the category of representations of an étale Lie groupoid and the category of modules over its Hopf algebroid that are of finite type and of constant rank. Both of these constructions are functorially defined on the Morita category of étale Lie groupoids and we show that the given correspondence represents a natural equivalence between them.     

Novel inhibitors of trihydroxynaphthalene reductase with antifungal activity identified by ligand-based and structure-based virtual screening

Curvularia lunata is a dark pigmented fungus that is the causative agent of several diseases in plants and in both immunodeficient and immunocompetent patients. 1,8-Dihydroxynaphthalene-melanin is found in the cell wall of C. lunata and is believed to be the important virulence factor of dematiaceous fungi. Trihydroxynaphthalene reductase is an enzyme of the 1,8-dihydroxynaphthalene-melanin biosynthetic pathway, and it thus represents an emerging target for the development of novel fungicides and antimycotics. In the present study, we describe novel inhibitors of trihydroxynaphthalene reductase from C. lunata. These inhibitors were identified by ligand-based three-dimensional similarity searching and docking to a homology-built model and by subsequent biochemical and antifungal evaluation. Discovery of competitive inhibitors with K(i) values in low micromolar and even nanomolar concentration range proves the aplicability of homology-built model of 3HNR for hit finding by virtual screening methods.