5,739 research outputs found
Higgs production at future colliders in the Georgi-Machacek model
We study how the dominant single and double SM-like Higgs () production at
future colliders is modified in the Georgi-Machacek (GM) model. On
imposing theoretical, indirect and direct constraints, significant deviations
of -couplings from their SM values are still possible; for instance, the
Higgs-gauge coupling coupling can be corrected by a factor
in the allowed parameter space. For the
Higgs-strahlung and vector boson fusion processes , the cross section could increase by or decrease
by . In the case of associated production with a top quark pair
, the cross section can be enhanced up to several times
when the custodial triplet scalar is resonantly produced. In the
meanwhile, the double Higgs production can be
maximally enhanced by one order of magnitude at the resonant
production. We also include exclusion limits expected from future LHC runs at
higher energy and luminosity and discuss their further constraints on the
relevant model parameters. We find that the GM model can result in likely
measurable deviations of Higgs production from the SM at future
colliders.Comment: 31 pages, 17 figures, published in JHE
Evolving P450pyr Monooxygenase for Regio- and Stereoselective Hydroxylations
P450pyr monooxygenase from Sphingomonas sp. HXN-200 catalysed the regio- and stereoselective hydroxylation at a non-activated carbon atom, a useful but challenging reaction in classic chemistry, with unique substrate specificity for a number of alicyclic compounds. New
P450pyr mutants were developed by directed evolution with improved catalytic performance, thus significantly extending the application of the P450pyr monooxygenase family in biohydroxylation to prepare useful and valuable chiral alcohols. Directed evolution of P450pyr created new enzymes with
improved S-enantioselectivity or R-enantioselectivity for the hydroxylation of N-benzyl pyrrolidine, enhanced regioselectivity for the hydroxylation of N-benzyl pyrrolidinone, and increased enantioselectivity for the hydroxylation of N-benzyl piperidinone,
respectively. Directed evolution of P450pyr generated also mutants with fully altered regioselectivity (from terminal to subterminal) and newly created excellent S-enantioselectivity for the biohydroxylation of n-octane and propylbenzene, respectively, providing new opportunities
for the regio- and enantioselective alkane functionalization. New P450pyr mutants were engineered as the first catalyst for highly selective terminal hydroxylation of n-butanol to 1,4-butanediol. Several novel, accurate, sensitive, simple, and HTS assays based on colorimetric or MS
detection for measuring the enantio- and/or regioselectivity of hydroxylation were developed and proven to be practical in directed evolution. The P450pyr X-ray structure was obtained and used to guide the evolution. In silico modelling and substrate docking provided some insight into
the influence of several important amino acid mutations of the engineered P450pyr mutants on the altered or enhanced regio- and enantioselectivity as well as new substrate acceptance. The obtained information and knowledge is useful for further engineering of P450pyr for other hydroxylations and oxidations
Topological Protection from Random Rashba Spin-Orbit Backscattering: Ballistic Transport in a Helical Luttinger Liquid
The combination of Rashba spin-orbit coupling and potential disorder induces
a random current operator for the edge states of a 2D topological insulator. We
prove that charge transport through such an edge is ballistic at any
temperature, with or without Luttinger liquid interactions. The solution
exploits a mapping to a spin 1/2 in a time-dependent field that preserves the
projection along one randomly undulating component (integrable dynamics). Our
result is exact and rules out random Rashba backscattering as a source of
temperature-dependent transport, absent integrability-breaking terms.Comment: 6+3 pages, 2+1 figure
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