TY - JOUR
AB - The mitochondrial respiratory chain, also known as the electron transport chain (ETC), is crucial to life, and energy production in the form of ATP is the main mitochondrial function. Three proton-translocating enzymes of the ETC, namely complexes I, III and IV, generate proton motive force, which in turn drives ATP synthase (complex V). The atomic structures and basic mechanisms of most respiratory complexes have previously been established, with the exception of complex I, the largest complex in the ETC. Recently, the crystal structure of the entire complex I was solved using a bacterial enzyme. The structure provided novel insights into the core architecture of the complex, the electron transfer and proton translocation pathways, as well as the mechanism that couples these two processes.
AU - Sazanov, Leonid A
ID - 1638
IS - 6
JF - Nature Reviews Molecular Cell Biology
TI - A giant molecular proton pump: structure and mechanism of respiratory complex I
VL - 16
ER -
TY - JOUR
AB - In this paper the optimal transport and the metamorphosis perspectives are combined. For a pair of given input images geodesic paths in the space of images are defined as minimizers of a resulting path energy. To this end, the underlying Riemannian metric measures the rate of transport cost and the rate of viscous dissipation. Furthermore, the model is capable to deal with strongly varying image contrast and explicitly allows for sources and sinks in the transport equations which are incorporated in the metric related to the metamorphosis approach by Trouvé and Younes. In the non-viscous case with source term existence of geodesic paths is proven in the space of measures. The proposed model is explored on the range from merely optimal transport to strongly dissipative dynamics. For this model a robust and effective variational time discretization of geodesic paths is proposed. This requires to minimize a discrete path energy consisting of a sum of consecutive image matching functionals. These functionals are defined on corresponding pairs of intensity functions and on associated pairwise matching deformations. Existence of time discrete geodesics is demonstrated. Furthermore, a finite element implementation is proposed and applied to instructive test cases and to real images. In the non-viscous case this is compared to the algorithm proposed by Benamou and Brenier including a discretization of the source term. Finally, the model is generalized to define discrete weighted barycentres with applications to textures and objects.
AU - Maas, Jan
AU - Rumpf, Martin
AU - Schönlieb, Carola
AU - Simon, Stefan
ID - 1639
IS - 6
JF - ESAIM: Mathematical Modelling and Numerical Analysis
TI - A generalized model for optimal transport of images including dissipation and density modulation
VL - 49
ER -
TY - JOUR
AB - Auxin and cytokinin are key endogenous regulators of plant development. Although cytokinin-mediated modulation of auxin distribution is a developmentally crucial hormonal interaction, its molecular basis is largely unknown. Here we show a direct regulatory link between cytokinin signalling and the auxin transport machinery uncovering a mechanistic framework for cytokinin-auxin cross-talk. We show that the CYTOKININ RESPONSE FACTORS (CRFs), transcription factors downstream of cytokinin perception, transcriptionally control genes encoding PIN-FORMED (PIN) auxin transporters at a specific PIN CYTOKININ RESPONSE ELEMENT (PCRE) domain. Removal of this cis-regulatory element effectively uncouples PIN transcription from the CRF-mediated cytokinin regulation and attenuates plant cytokinin sensitivity. We propose that CRFs represent a missing cross-talk component that fine-tunes auxin transport capacity downstream of cytokinin signalling to control plant development.
AU - Šimášková, Mária
AU - O'Brien, José
AU - Khan-Djamei, Mamoona
AU - Van Noorden, Giel
AU - Ötvös, Krisztina
AU - Vieten, Anne
AU - De Clercq, Inge
AU - Van Haperen, Johanna
AU - Cuesta, Candela
AU - Hoyerová, Klára
AU - Vanneste, Steffen
AU - Marhavy, Peter
AU - Wabnik, Krzysztof T
AU - Van Breusegem, Frank
AU - Nowack, Moritz
AU - Murphy, Angus
AU - Friml, Jiřĺ
AU - Weijers, Dolf
AU - Beeckman, Tom
AU - Benková, Eva
ID - 1640
JF - Nature Communications
TI - Cytokinin response factors regulate PIN-FORMED auxin transporters
VL - 6
ER -
TY - JOUR
AB - The Hanani-Tutte theorem is a classical result proved for the first time in the 1930s that characterizes planar graphs as graphs that admit a drawing in the plane in which every pair of edges not sharing a vertex cross an even number of times. We generalize this result to clustered graphs with two disjoint clusters, and show that a straightforward extension to flat clustered graphs with three or more disjoint clusters is not possible. For general clustered graphs we show a variant of the Hanani-Tutte theorem in the case when each cluster induces a connected subgraph. Di Battista and Frati proved that clustered planarity of embedded clustered graphs whose every face is incident to at most five vertices can be tested in polynomial time. We give a new and short proof of this result, using the matroid intersection algorithm.
AU - Fulek, Radoslav
AU - Kynčl, Jan
AU - Malinovič, Igor
AU - Pálvölgyi, Dömötör
ID - 1642
IS - 4
JF - Electronic Journal of Combinatorics
TI - Clustered planarity testing revisited
VL - 22
ER -
TY - CONF
AB - Increasing the computational complexity of evaluating a hash function, both for the honest users as well as for an adversary, is a useful technique employed for example in password-based cryptographic schemes to impede brute-force attacks, and also in so-called proofs of work (used in protocols like Bitcoin) to show that a certain amount of computation was performed by a legitimate user. A natural approach to adjust the complexity of a hash function is to iterate it c times, for some parameter c, in the hope that any query to the scheme requires c evaluations of the underlying hash function. However, results by Dodis et al. (Crypto 2012) imply that plain iteration falls short of achieving this goal, and designing schemes which provably have such a desirable property remained an open problem. This paper formalizes explicitly what it means for a given scheme to amplify the query complexity of a hash function. In the random oracle model, the goal of a secure query-complexity amplifier (QCA) scheme is captured as transforming, in the sense of indifferentiability, a random oracle allowing R queries (for the adversary) into one provably allowing only r < R queries. Turned around, this means that making r queries to the scheme requires at least R queries to the actual random oracle. Second, a new scheme, called collision-free iteration, is proposed and proven to achieve c-fold QCA for both the honest parties and the adversary, for any fixed parameter c.
AU - Demay, Grégory
AU - Gazi, Peter
AU - Maurer, Ueli
AU - Tackmann, Björn
ID - 1644
TI - Query-complexity amplification for random oracles
VL - 9063
ER -