323 research outputs found
Understanding Jet Scaling and Jet Vetos in Higgs Searches
Jet counting and jet vetos are crucial analysis tools for many LHC searches.
We can understand their properties from the distribution of the exclusive
number of jets. LHC processes tend to show either a distinct staircase scaling
or a Poisson scaling, depending on kinematic cuts. We illustrate our approach
in a detailed study of jets in weak boson fusion Higgs production.Comment: 5 pages, 4 figures, 1 table. Text clarified to reflect that we
applied forward-backward tagging jet selectio
Coibacins A D, Antileishmanial Marine Cyanobacterial Polyketides with Intriguing Biosynthetic Origins
Four unsaturated polyketide lactone derivatives, coibacins A-D, were isolated from a Panamanian marine cyanobacterium, cf. Oscillatoria sp. The two different types of termini observed in these co-occurring metabolites, either a methyl cyclopropyl ring as seen in curacin A or a methyl vinyl chloride similar to that observed in the jamaicamides, suggest an intriguing flexibility in the “beta branch” forming biosynthetic process. The coibacins possess selective antileishmanial activity as well as potent anti-inflammatory activity.Four unsaturated polyketide lactone derivatives, coibacins A-D, were isolated from a Panamanian marine cyanobacterium, cf. Oscillatoria sp. The two different types of termini observed in these co-occurring metabolites, either a methyl cyclopropyl ring as seen in curacin A or a methyl vinyl chloride similar to that observed in the jamaicamides, suggest an intriguing flexibility in the “beta branch” forming biosynthetic process. The coibacins possess selective antileishmanial activity as well as potent anti-inflammatory activity
Ghost wave-function renormalization in Asymptotically Safe Quantum Gravity
Motivated by Weinberg's asymptotic safety scenario, we investigate the
gravitational renormalization group flow in the Einstein-Hilbert truncation
supplemented by the wave-function renormalization of the ghost fields. The
latter induces non-trivial corrections to the beta-functions for Newton's
constant and the cosmological constant. The resulting ghost-improved phase
diagram is investigated in detail. In particular, we find a non-trivial
ultraviolet fixed point in agreement with the asymptotic safety conjecture,
which also survives in the presence of extra dimensions. In four dimensions the
ghost anomalous dimension at the fixed point is , supporting
space-time being effectively two-dimensional at short distances.Comment: 23 pages, 4 figure
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Synergism of anisotropic and computational NMR methods reveals the likely configuration of phormidolide A.
Characterization of the complex molecular scaffold of the marine polyketide natural product phormidolide A represents a challenge that has persisted for nearly two decades. In light of discordant results arising from recent synthetic and biosynthetic reports, a rigorous study of the configuration of phormidolide A was necessary. This report outlines a synergistic effort employing computational and anisotropic NMR investigation, that provided orthogonal confirmation of the reassigned side chain, as well as supporting a further correction of the C7 stereocenter
Scaling Patterns for QCD Jets
Jet emission at hadron colliders follows simple scaling patterns. Based on
perturbative QCD we derive Poisson and staircase scaling for final state as
well as initial state radiation. Parton density effects enhance staircase
scaling at low multiplicities. We propose experimental tests of our theoretical
findings in Z+jets and QCD gap jets production based on minor additions to
current LHC analyses.Comment: 36 pages, 16 figure
Unitary Standard Model from Spontaneous Dimensional Reduction and Weak Boson Scattering at the LHC
Spontaneous dimensional reduction (SDR) is a striking phenomenon predicted by
a number of quantum gravity approaches which all indicate that the spacetime
dimensions get reduced at high energies. In this work, we formulate an
effective theory of electroweak interactions based upon the standard model,
incorporating the spontaneous reduction of space-dimensions at TeV scale. The
electroweak gauge symmetry is nonlinearly realized with or without a Higgs
boson. We demonstrate that the SDR ensures good high energy behavior and
predicts unitary weak boson scattering. For a light Higgs boson of mass 125GeV,
the TeV-scale SDR gives a natural solution to the hierarchy problem. Such a
light Higgs boson can have induced anomalous gauge couplings from the TeV-scale
SDR. We find that the corresponding WW scattering cross sections become unitary
at TeV scale, but exhibit different behaviors from that of the 4d standard
model. These can be discriminated by the WW scattering experiments at the LHC.Comment: 38pp, Eur.Phys.J.(in Press); extended discussions for testing non-SM
Higgs boson(125GeV) via WW scattering; minor clarifications added; references
added; a concise companion is given in the short PLB letter arXiv:1301.457
Les Houches 2013: Physics at TeV Colliders: Standard Model Working Group Report
This Report summarizes the proceedings of the 2013 Les Houches workshop on
Physics at TeV Colliders. Session 1 dealt primarily with (1) the techniques for
calculating standard model multi-leg NLO and NNLO QCD and NLO EW cross sections
and (2) the comparison of those cross sections with LHC data from Run 1, and
projections for future measurements in Run 2.Comment: Proceedings of the Standard Model Working Group of the 2013 Les
Houches Workshop, Physics at TeV Colliders, Les houches 3-21 June 2013. 200
page
Brevianes Revisited
Breviones are a new family of secondary metabolites that were originally isolated from the New Zealand endemic fungus Penicillium brevicompactum var. Dierckx. These compounds are generally characterized by a new carbon skeleton, known as breviane, which that has three possible structural variations, such as breviane, abeo-breviane, and abeo-norbreviane. Brevianes present a basic diterpenic tricyclic core that is mevalonic in origin and is similar to that of perhydrophenanthrene. The core bears four methyl groups at positions C4, C8, C10, and C13 and has defined stereochemistry at positions C5, C8, C9, C10, and C14. The C1'-C7' side chain has been proposed to have a polyketide biosynthetic origin and is joined to the diterpenic moiety through carbons C2'-C15'. The cyclization and lactonization of this part of the molecule leads to the characteristic breviane spiranic ring fused to the α-pyrone
Single Cell Genome Amplification Accelerates Identification of the Apratoxin Biosynthetic Pathway from a Complex Microbial Assemblage
Filamentous marine cyanobacteria are extraordinarily rich sources of structurally novel, biomedically relevant natural products. To understand their biosynthetic origins as well as produce increased supplies and analog molecules, access to the clustered biosynthetic genes that encode for the assembly enzymes is necessary. Complicating these efforts is the universal presence of heterotrophic bacteria in the cell wall and sheath material of cyanobacteria obtained from the environment and those grown in uni-cyanobacterial culture. Moreover, the high similarity in genetic elements across disparate secondary metabolite biosynthetic pathways renders imprecise current gene cluster targeting strategies and contributes sequence complexity resulting in partial genome coverage. Thus, it was necessary to use a dual-method approach of single-cell genomic sequencing based on multiple displacement amplification (MDA) and metagenomic library screening. Here, we report the identification of the putative apratoxin. A biosynthetic gene cluster, a potent cancer cell cytotoxin with promise for medicinal applications. The roughly 58 kb biosynthetic gene cluster is composed of 12 open reading frames and has a type I modular mixed polyketide synthase/nonribosomal peptide synthetase (PKS/NRPS) organization and features loading and off-loading domain architecture never previously described. Moreover, this work represents the first successful isolation of a complete biosynthetic gene cluster from Lyngbya bouillonii, a tropical marine cyanobacterium renowned for its production of diverse bioactive secondary metabolites
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