742 research outputs found
Computing Hilbert Class Polynomials
We present and analyze two algorithms for computing the Hilbert class
polynomial . The first is a p-adic lifting algorithm for inert primes p
in the order of discriminant D < 0. The second is an improved Chinese remainder
algorithm which uses the class group action on CM-curves over finite fields.
Our run time analysis gives tighter bounds for the complexity of all known
algorithms for computing , and we show that all methods have comparable
run times
A comparison and a combination of SST and AGM algorithms for counting points of elliptic curves in characteristic 2
International audienceSince the first use of a p-adic method for counting points of elliptic curves, by Satoh in 1999, several variants of his algorithm have been proposed. In the current state, the AGM algorithm, proposed by Mestre is thought to be the fastest in practice, and the algorithm by Satoh-Skjernaa-Taguchi has the best asymptotic complexity but requires precomputations. We present an amelioration of the SST algorithm, borrowing ideas from the AGM. We make a precise comparison between this modified SST algorithm and the AGM, thus demonstrating that the former is faster by a significant factor, even for small cryptographic sizes
Simulation of the Deformation for Cycling Chemo-Mechanically Coupled Battery Active Particles with Mechanical Constraints
Next-generation lithium-ion batteries with silicon anodes have positive
characteristics due to higher energy densities compared to state-of-the-art
graphite anodes. However, the large volume expansion of silicon anodes can
cause high mechanical stresses, especially if the battery active particle
cannot expand freely. In this article, a thermodynamically consistent continuum
model for coupling chemical and mechanical effects of electrode particles is
extended by a change in the boundary condition for the displacement via a
variational inequality. This switch represents a limited enlargement of the
particle swelling or shrinking due to lithium intercalation or deintercalation
in the host material, respectively. For inequality constraints as boundary
condition a smaller time step size is need as well as a locally finer mesh. The
combination of a primal-dual active set algorithm, interpreted as semismooth
Newton method, and a spatial and temporal adaptive algorithm allows the
efficient numerical investigation based on a finite element method. Using the
example of silicon, the chemical and mechanical behavior of one- and
two-dimensional representative geometries for a charge-discharge cycle is
investigated. Furthermore, the efficiency of the adaptive algorithm is
demonstrated. It turns out that the size of the gap has an significant
influence on the maximal stress value and the slope of the increase. Especially
in two dimension, the obstacle can cause an additional region with a
lithium-poor phase
Simulation of the Deformation for Cycling Chemo-Mechanically Coupled Battery Active Particles with Mechanical Constraints
Next-generation lithium-ion batteries with silicon anodes have positive characteristics due to higher energy densities compared to state-of-the-art graphite anodes. However, the large volume expansion of silicon anodes can cause high mechanical stresses, especially if the battery active particle cannot expand freely. In this article, a thermodynamically consistent continuum model for coupling chemical and mechanical effects of electrode particles is extended by a change in the boundary condition for the displacement via a variational inequality. This switch represents a limited enlargement of the particle swelling or shrinking due to lithium intercalation or deintercalation in the host material, respectively. For inequality constraints as boundary condition a smaller time step size is need as well as a locally finer mesh. The combination of a primal-dual active set algorithm, interpreted as semismooth Newton method, and a spatial and temporal adaptive algorithm allows the efficient numerical investigation based on a finite element method. Using the example of silicon, the chemical and mechanical behavior of one- and two-dimensional representative geometries for a charge-discharge cycle is investigated. Furthermore, the efficiency of the adaptive algorithm is demonstrated. It turns out that the size of the gap has an significant influence on the maximal stress value and the slope of the increase. Especially in two dimension, the obstacle can cause an additional region with a lithium-poor phase
The PlaNet Consortium: A Network of European Plant Databases Connecting Plant Genome Data in an Integrated Biological Knowledge Resource
The completion of the Arabidopsis genome and the large collections of other plant
sequences generated in recent years have sparked extensive functional genomics
efforts. However, the utilization of this data is inefficient, as data sources are
distributed and heterogeneous and efforts at data integration are lagging behind.
PlaNet aims to overcome the limitations of individual efforts as well as the
limitations of heterogeneous, independent data collections. PlaNet is a distributed
effort among European bioinformatics groups and plant molecular biologists to
establish a comprehensive integrated database in a collaborative network. Objectives
are the implementation of infrastructure and data sources to capture plant genomic
information into a comprehensive, integrated platform. This will facilitate the
systematic exploration of Arabidopsis and other plants. New methods for data
exchange, database integration and access are being developed to create a highly
integrated, federated data resource for research. The connection between the
individual resources is realized with BioMOBY. BioMOBY provides an architecture
for the discovery and distribution of biological data through web services. While
knowledge is centralized, data is maintained at its primary source without a need for
warehousing. To standardize nomenclature and data representation, ontologies and
generic data models are defined in interaction with the relevant communities.Minimal
data models should make it simple to allow broad integration, while inheritance allows
detail and depth to be added to more complex data objects without losing integration.
To allow expert annotation and keep databases curated, local and remote annotation
interfaces are provided. Easy and direct access to all data is key to the project
Some genus 3 curves with many points
Using an explicit family of plane quartic curves, we prove the existence of a
genus 3 curve over any finite field of characteristic 3 whose number of
rational points stays within a fixed distance from the Hasse-Weil-Serre upper
bound. We also provide an intrinsic characterization of so-called Legendre
elliptic curves
Dataset for the proteomic inventory and quantitative analysis of the breast cancer hypoxic secretome associated with osteotropism
The cancer secretome includes all of the macromolecules secreted by cells into their microenvironment. Cancer cell secretomes are significantly different to that of normal cells reflecting the changes that normal cells have undergone during their transition to malignancy. More importantly, cancer secretomes are known to be active mediators of both local and distant host cells and play an important role in the progression and dissemination of cancer. Here we have quantitatively profiled both the composition of breast cancer secretomes associated with osteotropism, and their modulation under normoxic and hypoxic conditions. We detect and quantify 162 secretome proteins across all conditions which show differential hypoxic induction and association with osteotropism. Mass Spectrometry proteomics data have been deposited to the ProteomeXchange Consortium with the dataset identifier PXD000397 and the complete proteomic, bioinformatic and biological analyses are reported in Cox et al. (2015) [1]
Computing the Characteristic Polynomial of a Finite Rank Two Drinfeld Module
Motivated by finding analogues of elliptic curve point counting techniques,
we introduce one deterministic and two new Monte Carlo randomized algorithms to
compute the characteristic polynomial of a finite rank-two Drinfeld module. We
compare their asymptotic complexity to that of previous algorithms given by
Gekeler, Narayanan and Garai-Papikian and discuss their practical behavior. In
particular, we find that all three approaches represent either an improvement
in complexity or an expansion of the parameter space over which the algorithm
may be applied. Some experimental results are also presented
Conference Review The PlaNet consortium: a network of European plant databases connecting plant genome data in an integrated biological knowledge resource
Abstract The completion of the Arabidopsis genome and the large collections of other plant sequences generated in recent years have sparked extensive functional genomics efforts. However, the utilization of this data is inefficient, as data sources are distributed and heterogeneous and efforts at data integration are lagging behind. PlaNet aims to overcome the limitations of individual efforts as well as the limitations of heterogeneous, independent data collections. PlaNet is a distributed effort among European bioinformatics groups and plant molecular biologists to establish a comprehensive integrated database in a collaborative network. Objectives are the implementation of infrastructure and data sources to capture plant genomic information into a comprehensive, integrated platform. This will facilitate the systematic exploration of Arabidopsis and other plants. New methods for data exchange, database integration and access are being developed to create a highly integrated, federated data resource for research. The connection between the individual resources is realized with BioMOBY. BioMOBY provides an architecture for the discovery and distribution of biological data through web services. While knowledge is centralized, data is maintained at its primary source without a need for warehousing. To standardize nomenclature and data representation, ontologies and generic data models are defined in interaction with the relevant communities. Minimal data models should make it simple to allow broad integration, while inheritance allows detail and depth to be added to more complex data objects without losing integration. To allow expert annotation and keep databases curated, local and remote annotation interfaces are provided. Easy and direct access to all data is key to the project
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