8,034 research outputs found
Dark Left-Right Gauge Model: SU(2)_R Phenomenology
In the recently proposed dark left-right gauge model of particle
interactions, the left-handed fermion doublet is connected to its
right-handed counterpart through a scalar bidoublet, but
couples to only through which has no vacuum expectation value.
The usual R parity, i.e. , can be defined for this
nonsupersymmetric model so that both and are odd together with
. The lightest is thus a viable dark-matter candidate (scotino).
Here we explore the phenomenology associated with the gauge group of
this model, which allows it to appear at the TeV energy scale. The exciting
possibility of charged leptons is discussed.Comment: 12 pages, 2 figure
Neutral SU(2) Gauge Extension of the Standard Model and a Vector-Boson Dark-Matter Candidate
If the standard model of particle interactions is extended to include a
neutral SU(2)_N gauge factor, with SU(3)_C x SU(2)_L x U(1)_Y x SU(2)_N
embedded in E_6 or [SU(3)]^3, a conserved generalized R parity may appear. As a
result, we have the first example of a possible dark-matter candidate X_1 which
is a non-Abelain vector boson. Using current data, its mass is predicted to be
less than about 1 TeV. The associated Z' of this model, as well as some
signatures of the Higgs sector, should then be observable at the LHC (Large
Hadron Collider).Comment: 10 pages, 1 figure; version accepted in PL
gem-Dibromocyclopropanes and enzymatically derived cis-1,2-dihydrocatechols as building blocks in alkaloid synthesis
The application of the title building blocks, the 6,6-dibromobicyclo[3.1.0]hexanes
and the cis-1,2-dihydrocatechols, to the total synthesis of crinine and lycorinine alkaloids is
described.We thank the Australian Research Council and the Institute of Advanced Studies for generous financial
support
The c-terminal extension of a hybrid immunoglobulin A/G heavy chain is responsible for its Golgi-mediated sorting to the vacuole
We have assessed the ability of the plant secretory pathway to handle the expression of complex heterologous proteins by investigating the fate of a hybrid immunoglobulin A/G in tobacco cells. Although plant cells can express large amounts of the antibody, a relevant proportion is normally lost to vacuolar sorting and degradation. Here we show that the synthesis of high amounts of IgA/G does not impose stress on the plant secretory pathway. Plant cells can assemble antibody chains with high efficiency and vacuolar transport occurs only after the assembled immunoglobulins have traveled through the Golgi complex. We prove that vacuolar delivery of IgA/G depends on the presence of a cryptic sorting signal in the tailpiece of the IgA/G heavy chain. We also show that unassembled light chains are efficiently secreted as monomers by the plant secretory pathway
Topological Protection of Coherence in Noisy Open Quantum Systems
We consider topological protection mechanisms in dissipative quantum systems
in the presence of quenched disorder, with the intent to prolong coherence
times of qubits. The physical setting is a network of qubits and dissipative
cavities whose coupling parameters are tunable, such that topological edge
states can be stabilized. The evolution of a fiducial qubit is entirely
determined by a non-Hermitian Hamiltonian which thus emerges from a bona-fide
physical process. It is shown how even in the presence of disorder winding
numbers can be defined and evaluated in real space, as long as certain
symmetries are preserved. Hence we can construct the topological phase diagrams
of noisy open quantum models, such as the non-Hermitian disordered
Su-Schrieffer- Heeger dimer model and a trimer model that includes longer-range
couplings. In the presence of competing disorder parameters, interesting
re-entrance phenomena of topologically non-trivial sectors are observed. This
means that in certain parameter regions, increasing disorder drastically
increases the coherence time of the fiducial qubit
Chiral mononuclear lanthanide complexes derived from chiral Schiff bases: Structural and magnetic studies
A new family of mononuclear lanthanide complexes with formula [LnIII(L)Cl3] (Ln = Eu (1), Tb (2), Dy (3), Er (4), Yb (5)) and L = N,N0-bis((1,2-diphenyl-(pyridine-2-yl)methylene)-(R,R/S,S)-ethane-1,2-diamine has been obtained employing enantiomerically pure Schiff bases. The complexes have been structurally characterized using X-ray single crystal and powder diffraction. Their dynamic magnetic properties have been studied showing that this family presents slow relaxation of the magnetization under certain conditions and confirms the different behavior of each LnIII cations in isostructural complexes: only the Er one possibly relaxing via an overbarrier Orbach process, while Raman process dominates for Dy and Yb derivative
One- and two-dimensional higher-point conformal blocks as free-particle wavefunctions in AdS
We establish that all of the one- and two-dimensional global conformal blocks
are, up to some choice of prefactor, free-particle wavefunctions in tensor
products of AdS or limits thereof. Our first core observation is that the
six-point comb-channel conformal blocks correspond to free-particle
wavefunctions on an AdS constructed directly in cross-ratio space. This
construction generalizes to blocks for a special class of diagrams, which are
determined as free-particle wavefunctions in tensor products of AdS.
Conformal blocks for all the remaining topologies are obtained as limits of the
free wavefunctions mentioned above. Our results show directly that the
integrable models associated with all one- and two-dimensional conformal blocks
can be seen as limits of free theory, and manifest a relation between AdS and
CFT kinematics that lies outside of the standard AdS/CFT dictionary. We
complete the discussion by providing explicit Feynman-like rules that can be
used to work out blocks for all topologies, as well as a Mathematica notebook
that allows simple computation of Casimir equations and series expansions for
blocks, by requiring just an OPE diagram as input.Comment: 39 pages + an appendix, 18 figures, Mathematica notebook attache
Lie symmetries of nonlinear boundary value problems
Nonlinear boundary value problems (BVPs) by means of the classical Lie
symmetry method are studied. A new definition of Lie invariance for BVPs is
proposed by the generalization of existing those on much wider class of BVPs. A
class of two-dimensional nonlinear boundary value problems, modeling the
process of melting and evaporation of metals, is studied in details. Using the
definition proposed, all possible Lie symmetries and the relevant reductions
(with physical meaning) to BVPs for ordinary differential equations are
constructed. An example how to construct exact solution of the problem with
correctly-specified coefficients is presented and compared with the results of
numerical simulations published earlier.Comment: Published versio
Genetic and biochemical analyses of chromosome and plasmid gene homologues encoding ICL and ArCP domains in Vibrioanguillarum strain 775
Anguibactin, the siderophore produced by Vibrio anguillarum 775 is synthesized from 2,3-dihydroxybenzoic acid (DHBA), cysteine and hydroxyhistamine via a nonribosomal peptide synthetase (NRPS) mechanism. Most of the genes encoding anguibactin biosynthetic proteins are harbored by the pJM1 plasmid. In this work we report the identification of a homologue of the plasmid-encoded angB on the chromosome of strain 775. The product of both genes harbor an isochorismate lyase (ICL) domain that converts isochorismic acid to 2,3-dihydro-2,3-dihydroxybenzoic acid, one of the steps of DHBA synthesis. We show in this work that both ICL domains are functional in the production of DHBA in V. anguillarum as well as in E. coli. Substitution by alanine of the aspartic acid residue in the active site of both ICL domains completely abolishes their isochorismate lyase activity in vivo. The two proteins also carry an aryl carrier protein (ArCP) domain. In contrast with the ICL domains only the plasmid encoded ArCP can participate in anguibactin production as determined by complementation analyses and site-directed mutagenesis in the active site of the plasmid encoded protein, S248A. The site-directed mutants, D37A in the ICL domain and S248A in the ArCP domain of the plasmid encoded AngB were also tested in vitro and clearly show the importance of each residue for the domain function and that each domain operates independently.
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