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Gil L.,Hebrew University of Jerusalem | Yaron I.,Hebrew University of Jerusalem | Shalitin D.,Hebrew University of Jerusalem | Sauer N.,FAU Erlangen Nurnberg | And 2 more authors.
Plant Journal | Year: 2011

Based on the high density of plasmodesmata interconnecting the intermediary cells and their neighboring phloem parenchyma or bundle-sheath cells, and based on the insensitivity to the sucrose transport inhibitor p- chloromercuribenzenesulfonic acid (PCMBS), cucurbits have been concluded to be symplastic loaders. In the present study, we identified and characterized the full-length sequence of sucrose transporter gene (CmSUT1) from melon (Cucumis melo L. cv. Hale's best jumbo). In vitro experiments confirmed that the identified gene product has sucrose transporter activity in baker's yeast. Healthy and cucumber mosaic virus (CMV)-infected melon plants were employed to examine sucrose transporter activity in planta. Pretreatment with PCMBS inhibited loading of newly fixed 14CO2 into minor veins of CMV-infected plants. Moreover, CMV infection caused significant increase in CmSUT1 transcripts expression, mainly in vascular bundles of minor veins, which was associated with elevated sucrose content in phloem sap collected from source-leaf petioles. We propose that cucurbit plants contain the machinery for apoplastic phloem loading and that CMV infection causes a quantitative shift in the mode by which photoassimilates are loaded into the sieve tube. © 2011 Blackwell Publishing Ltd.

Neeb K.-H.,FAU Erlangen Nurnberg | Olafsson G.,Louisiana State University
Journal of Physics: Conference Series | Year: 2015

In this note we characterize those unitary one-parameter groups (Utc)t∈R which admit euclidean realizations in the sense that they are obtained by the analytic continuation process corresponding to reflection positivity from a unitary representation U of the circle group. These are precisely the ones for which there exists an anti-unitary involution J commuting with Uc. This provides an interesting link with the modular data arising in Tomita-Takesaki theory. Introducing the concept of a positive definite function with values in the space of sesquilinear forms, we further establish a link between KMS states and reflection positivity on the circle. © Published under licence by IOP Publishing Ltd.

Foersch S.,FAU Erlangen Nurnberg | Neurath M.F.,FAU Erlangen Nurnberg
Cellular and Molecular Life Sciences | Year: 2014

Crohn's disease and ulcerative colitis are both associated with an increased risk of inflammation-associated colorectal carcinoma. Colitis-associated cancer (CAC) is one of the most important causes for morbidity and mortality in patients with inflammatory bowel diseases (IBD). Colitis-associated neoplasia distinctly differs from sporadic colorectal cancer in its biology and the underlying mechanisms. This review discusses the molecular mechanisms of CAC and summarizes the most important genetic alterations and signaling pathways involved in inflammatory carcinogenesis. Then, clinical translation is evaluated by discussing new endoscopic techniques and their contribution to surveillance and early detection of CAC. Last, we briefly address different types of concepts for prevention (i.e., anti-inflammatory therapeutics) and treatment (i.e., surgical intervention) of CAC and give an outlook on this important aspect of IBD. © 2014 Springer.

Meusburger C.,FAU Erlangen Nurnberg | Noui K.,CNRS Laboratory for Theoretical Physics
Advances in Theoretical and Mathematical Physics | Year: 2010

We relate three-dimensional loop quantum gravity to the combinatorial quantization formalism based on the Chern-Simons formulation for three-dimensional Lorentzian and Euclidean gravity with vanishing cosmological constant. We compare the construction of the kinematical Hilbert space and the implementation of the constraints. This leads to an explicit and very interesting relation between the associated operators in the two approaches and sheds light on their physical interpretation. We demonstrate that the quantum group symmetries arising in the combinatorial formalism, the quantum double of the three-dimensional Lorentz and rotation group are also present in the loop formalism. We derive explicit expressions for the action of these quantum groups on the space of cylindrical functions associated with graphs. This establishes a direct link between the two quantization approaches and clarifies the role of quantum group symmetries in three-dimensional gravity. © 2011 International Press.

Krasnov K.,University of Nottingham | Scarinci C.,FAU Erlangen Nurnberg
Journal of High Energy Physics | Year: 2013

Hodge's formula represents the gravitational MHV amplitude as the determinant of a minor of a certain matrix. When expanded, this determinant becomes a sum over weighted trees, which is the form of the MHV formula first obtained by Bern, Dixon, Perelstein, Rozowsky and rediscovered by Nguyen, Spradlin, Volovich and Wen. The gravity MHV amplitude satisfies the Britto, Cachazo, Feng and Witten recursion relation. The main building block of the MHV amplitude, the so-called half-soft function, satisfies a different, Berends-Giele-type recursion relation. We show that all these facts are illustrations to a more general story. We consider a weighted Laplacian for a complete graph of n vertices. The matrix tree theorem states that its diagonal minor determinants are all equal and given by a sum over spanning trees. We show that, for any choice of a cocycle on the graph, the minor determinants satisfy a Berends-Giele as well as Britto-Cachazo-Feng-Witten type recursion relation. Our proofs are purely combinatorial. © SISSA 2013.

Martin A.,FAU Erlangen Nurnberg | Muller J.C.,FAU Erlangen Nurnberg | Pokutta S.,Georgia Institute of Technology
Optimization Methods and Software | Year: 2014

The European power grid can be divided into several market areas where the price of electricity is determined in a day-ahead auction. Market participants can provide continuous hourly bid curves and combinatorial bids with associated quantities given the prices. The goal of our auction is to maximize the economic surplus of all participants subject to quantity constraints and price constraints. The price constraints ensure that no one incurs a loss. Only traders who submitted a combinatorial bid might miss a not-realized profit. The resulting problem is a large-scale mathematical program with equilibrium constraints (MPEC) and binary variables that cannot be solved efficiently by standard solvers. We present an exact algorithm and a fast heuristic for this type of problem. Both algorithms decompose the MPEC into a master problem (a mixed-integer quadratic program) and pricing subproblems (linear programs). The modelling technique and the algorithms are applicable to a wide variety of combinatorial auctions that are based on mixed-integer programs. © 2014 Taylor & Francis.

Wise D.K.,FAU Erlangen Nurnberg
Journal of Physics: Conference Series | Year: 2014

We study the dynamics of gauge theory and general relativity using fields of local observers, thus maintaining local Lorentz symmetry despite a space/time splitting of fields. We start with Yang-Mills theory, where observer fields are defined as normalized future-timelike vector fields. We then define observers without a fixed geometry, and find these play two related roles in general relativity: splitting fields into spatial and temporal parts, and 'breaking' gauge symmetry, effectively reducing the spacetime SO(n, 1) connection to an observer-dependent spatial SO(n) connection. In both gauge theory and gravity, the observer field reduces the action to canonical form, without using gauge fixing. In the 4d gravity case, the result is a manifestly Lorentz covariant counterpart of the Ashtekar-Barbero formulation. We also explain how this leads geometrically to a picture of general relativity in terms of 'observer space' rather than spacetime-a setting where both spacetime symmetry and the dynamical description are simultaneously available.

Winner B.,The Interdisciplinary Center | Winkler J.,FAU Erlangen Nurnberg
Cold Spring Harbor Perspectives in Biology | Year: 2015

Adult neurogenesis is limited to specific brain regions in the mammalian brain, such as the hippocampal dentate gyrus and the subventricular zone/olfactory bulb system. Alterations in adult neurogenesis appear to be a common hallmark in different neurodegenerative diseases including Parkinson’s disease (PD), Alzheimer’s disease (AD), and Huntington’s disease (HD). This is remarkable, because the distinct pathological proteins responsible for the different diseases induce the loss of different neural populations. Impaired adult neurogenesis was shown in numerous animal models of neurodegenerative diseases; however, only few post-mortem studies have been performed. We will review concepts related to the interplay between cellular plasticity in regions of adult neurogenesis with a specific focus on cell-autonomous and non-cell-autonomous factors. Furthermore, various strategies aimed to stimulate neuronal plasticity will be discussed within the context of a potential translation into therapeutic approaches for neuropsychiatric symptoms associated with PD, HD, and AD. © 2015 Cold Spring Harbor Laboratory Press; all rights reserved.

Fairbairn W.J.,FAU Erlangen Nurnberg | Meusburger C.,FAU Erlangen Nurnberg
Journal of Mathematical Physics | Year: 2012

We construct the q-deformed version of two four-dimensional spin foam models, the Euclidean and Lorentzian versions of the Engle, Pereira, Rovelli and Livine (EPRL) model. The q-deformed models are based on the representation theory of two copies of U q(su(2)) at a root of unity and on the quantum Lorentz group with a real deformation parameter. For both models, we give a definition of the quantum EPRL intertwiners, study their convergence and braiding properties, and construct an amplitude for the four-simplexes. We find that both of the resulting models are convergent. © 2012 American Institute of Physics.

Ballesteros A.,University of Burgos | Herranz F.J.,University of Burgos | Meusburger C.,FAU Erlangen Nurnberg
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

We show that the Drinfel'd double associated to the standard quantum deformation slη(2,R) is isomorphic to the (2 + 1)-dimensional AdS algebra with the initial deformation parameter η related to the cosmological constant Λ = - η2. This gives rise to a generalisation of a non-commutative Minkowski spacetime that arises as a consequence of the quantum double symmetry of (2 + 1) gravity to non-vanishing cosmological constant. The properties of the AdS quantum double that generalises this symmetry to the case Λ ≠ 0 are sketched, and it is shown that the new non-commutative AdS spacetime is a nonlinear Λ-deformation of the Minkowskian one. © 2014 The Authors.

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