340 research outputs found
The Regulatory Mechanisms Controlling Zinc Content in Wheat
Cereals such as wheat serve as staples for a large proportion of the world’s population. However, they contain relatively low concentrations of essential micronutrients such as zinc (Zn) in their edible tissues. This is a major issue for human nutrition and food security. The process of Zn uptake and partitioning in plants is highly controlled, with systems present for sensing and responding to Zn status. In the model plant, Arabidopsis thaliana, two transcription factors, bZIP19 and bZIP23, are thought to act as Zn sensors mediating the increased expression of Zn membrane transporters, ZIPs (Zrt/Irt-like proteins), in response to low Zn status. In this thesis the identification and characterisation of homologous bZIP transcription factors and ZIP transporters in wheat are described. TabZIP sequence analysis confirmed the presence of motifs characteristic to the F-group of bZIP transcription factors. Expression of these wheat bZIPs in an Atbzip19 bzip23 line showed a conservation of function between the Arabidopsis and wheat group F bZIPs. A key question is whether the wheat bZIP transcription factors and ZIP transporters are regulated by Zn. Gene-expression analysis indicated that the wheat transcription factors TabZIP1, 3a, 3b, 4 & 5, and the wheat ZIP transporters, TaZIP1, 4, 5, 6 & 7 are induced by Zn-deficient conditions. The Zn-transport capability of TaZIP1, 5, 6, 7 & 8 was confirmed using heterologous yeast expression. Additionally, the binding ability of TabZIPs to regulatory-elements in the promoters of TaZIPs was demonstrated. This links TabZIPs and TaZIPs in the Zn-regulatory mechanism of wheat. This research has identified key genes involved in the regulation, uptake and distribution of Zn in wheat. The molecular mechanisms elucidated will be important in the development of Zn biofortified wheat varieties as well as cultivars which maintain high yield in Zn-deficient conditions. These may prove vital in achieving global food security
Relativistically Covariant Symmetry in QED
We construct a relativistically covariant symmetry of QED. Previous local and
nonlocal symmetries are special cases. This generalized symmetry need not be
nilpotent, but nilpotency can be arranged with an auxiliary field and a certain
condition. The Noether charge generating the symmetry transformation is
obtained, and it imposes a constraint on the physical states.Comment: Latex file, 9 page
The quantization of the symplectic groupoid of the standard Podles sphere
We give an explicit form of the symplectic groupoid that integrates the
semiclassical standard Podles sphere. We show that Sheu's groupoid, whose
convolution C*-algebra quantizes the sphere, appears as the groupoid of the
Bohr-Sommerfeld leaves of a (singular) real polarization of the symplectic
groupoid. By using a complex polarization we recover the convolution algebra on
the space of polarized sections. We stress the role of the modular class in the
definition of the scalar product in order to get the correct quantum space.Comment: 33 pages; minor correction
Cohomology of skew-holomorphic Lie algebroids
We introduce the notion of skew-holomorphic Lie algebroid on a complex
manifold, and explore some cohomologies theories that one can associate to it.
Examples are given in terms of holomorphic Poisson structures of various sorts.Comment: 16 pages. v2: Final version to be published in Theor. Math. Phys.
(incorporates only very minor changes
On localization in holomorphic equivariant cohomology
We prove a localization formula for a "holomorphic equivariant cohomology"
attached to the Atiyah algebroid of an equivariant holomorphic vector bundle.
This generalizes Feng-Ma, Carrell-Liebermann, Baum-Bott and K. Liu's
localization formulas.Comment: 16 pages. Completely rewritten, new title. v3: Minor changes in the
exposition. v4: final version to appear in Centr. Eur. J. Mat
Poisson sigma model on the sphere
We evaluate the path integral of the Poisson sigma model on sphere and study
the correlators of quantum observables. We argue that for the path integral to
be well-defined the corresponding
Poisson structure should be unimodular. The construction of the finite
dimensional BV theory is presented and we argue that it is responsible for the
leading semiclassical contribution. For a (twisted) generalized Kahler manifold
we discuss the gauge fixed action for the Poisson sigma model. Using the
localization we prove that for the holomorphic Poisson structure the
semiclassical result for the correlators is indeed the full quantum result.Comment: 38 page
A heterotic sigma model with novel target geometry
We construct a (1,2) heterotic sigma model whose target space geometry
consists of a transitive Lie algebroid with complex structure on a Kaehler
manifold. We show that, under certain geometrical and topological conditions,
there are two distinguished topological half--twists of the heterotic sigma
model leading to A and B type half--topological models. Each of these models is
characterized by the usual topological BRST operator, stemming from the
heterotic (0,2) supersymmetry, and a second BRST operator anticommuting with
the former, originating from the (1,0) supersymmetry. These BRST operators
combined in a certain way provide each half--topological model with two
inequivalent BRST structures and, correspondingly, two distinct perturbative
chiral algebras and chiral rings. The latter are studied in detail and
characterized geometrically in terms of Lie algebroid cohomology in the
quasiclassical limit.Comment: 83 pages, no figures, 2 references adde
Early and Late Complications Associated with Busulfan, Cyclophosphamide, and Etoposide (Bu/Cy/VP-16) Conditioning Followed by Allogeneic or Autologous Stem Cell Transplantation in Relapsed/Refractory Non-Hodgkin'S Lymphoma
Support varieties for selfinjective algebras
Support varieties for any finite dimensional algebra over a field were
introduced by Snashall-Solberg using graded subalgebras of the Hochschild
cohomology. We mainly study these varieties for selfinjective algebras under
appropriate finite generation hypotheses. Then many of the standard results
from the theory of support varieties for finite groups generalize to this
situation. In particular, the complexity of the module equals the dimension of
its corresponding variety, all closed homogeneous varieties occur as the
variety of some module, the variety of an indecomposable module is connected,
periodic modules are lines and for symmetric algebras a generalization of
Webb's theorem is true
Multiplicative slices, relativistic Toda and shifted quantum affine algebras
We introduce the shifted quantum affine algebras. They map homomorphically
into the quantized -theoretic Coulomb branches of SUSY
quiver gauge theories. In type , they are endowed with a coproduct, and they
act on the equivariant -theory of parabolic Laumon spaces. In type ,
they are closely related to the open relativistic quantum Toda lattice of type
.Comment: 125 pages. v2: references updated; in section 11 the third local Lax
matrix is introduced. v3: references updated. v4=v5: 131 pages, minor
corrections, table of contents added, Conjecture 10.25 is now replaced by
Theorem 10.25 (whose proof is based on the shuffle approach and is presented
in a new Appendix). v6: Final version as published, references updated,
footnote 4 adde
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