Side-Information Coding with Turbo Codes and its Application to Quantum Key Distribution

Turbo coding is a powerful class of forward error correcting codes, which can achieve performances close to the Shannon limit. The turbo principle can be applied to the problem of side-information source coding, and we investigate here its application to the reconciliation problem occurring in a continuous-variable quantum key distribution protocol.Comment: 3 pages, submitted to ISITA 200

Computing Graph Roots Without Short Cycles

Graph G is the square of graph H if two vertices x, y have an edge in G if and only if x, y are of distance at most two in H. Given H it is easy to compute its square H2, however Motwani and Sudan proved that it is NP-complete to determine if a given graph G is the square of some graph H (of girth 3). In this paper we consider the characterization and recognition problems of graphs that are squares of graphs of small girth, i.e. to determine if G = H2 for some graph H of small girth. The main results are the following. - There is a graph theoretical characterization for graphs that are squares of some graph of girth at least 7. A corollary is that if a graph G has a square root H of girth at least 7 then H is unique up to isomorphism. - There is a polynomial time algorithm to recognize if G = H2 for some graph H of girth at least 6. - It is NP-complete to recognize if G = H2 for some graph H of girth 4. These results almost provide a dichotomy theorem for the complexity of the recognition problem in terms of girth of the square roots. The algorithmic and graph theoretical results generalize previous results on tree square roots, and provide polynomial time algorithms to compute a graph square root of small girth if it exists. Some open questions and conjectures will also be discussed

Nonparametric estimation of the fragmentation kernel based on a PDE stationary distribution approximation

We consider a stochastic individual-based model in continuous time to describe a size-structured population for cell divisions. This model is motivated by the detection of cellular aging in biology. We address here the problem of nonparametric estimation of the kernel ruling the divisions based on the eigenvalue problem related to the asymptotic behavior in large population. This inverse problem involves a multiplicative deconvolution operator. Using Fourier technics we derive a nonparametric estimator whose consistency is studied. The main difficulty comes from the non-standard equations connecting the Fourier transforms of the kernel and the parameters of the model. A numerical study is carried out and we pay special attention to the derivation of bandwidths by using resampling

Time-dependent magnetotransport of a wave packet in a quantum wire with embedded quantum dots

We consider wave packet propagation in a quantum wire with either an embedded antidot or an embedded parallel double open quantum dot under the influence of a uniform magnetic field. The magnetoconductance and the time evolution of an electron wave packet are calculated based on the Lippmann-Schwinger formalism. This approach allows us to look at arbitrary embedded potential profiles and illustrate the results by performing computational simulations for the conductance and the time evolution of the electron wave packet through the quantum wire. In the double-dot system we observe a long-lived resonance state that enhances the spatial spreading of the wave packet, and quantum skipping-like trajectories are induced when the envelop function of the wave packet covers several subbands in appropriate magnetic fields.Comment: RevTeX, 9 pages with 8 included postscript figure

An illustrative recovery approach for stateful interaction failures of orchestrated processes

During a stateful interaction, a partner service may become unavailable because of a server crash or a temporary network failure. Once the failed service becomes available again, the interaction partners do not have any knowledge about each other’s state, possibly resulting in errors or deadlocks. This paper proposes an approach to the recovery of stateful interactions based on service interaction patterns and process transformations. Our recovery approach works without a central management node and without additional communication protocols. We also minimize the changes to the description of the service supported by the recovery-enabled process. Our approach allows one partner process to be modified in order to support failures in a way that interaction with the other (unchanged) processes is still possible

Modeling the reaction mechanism of membrane penetration by striated amphiphitic gold nanoparticles

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2009.Cataloged from PDF version of thesis.Includes bibliographical references (p. 37-38).The desire to desire targeted drug delivery devices capable of releasing therapeutic payloads within the cytosol of cells has led to research on nanoparticles as suitable drug carriers. Recently, it was shown that gold nanoparticles coated in striped, alternating layers of hydrophobic and hydrophilic ligands are capable of non-disruptively penetrating a lipid bilayer, a discovery with potential implications in drug delivery. While the reaction mechanism is not known, initial experimental results indicate that endocytosis and membrane poration could be ruled as possible mechanisms. In this work, we explore the reaction mechanism of membrane penetration using a coarse-grained Brownian Dynamics model. We also define a Monte Carlo simulation for modeling ligand motion on the nanoparticle surface based on a single order parameter, and describe a method for approximating the interaction energy with the bilayer as a function of this parameter. Our simulations demonstrate the dependence of nanoparticles penetration on the surface mobility, not explicit conformation, of coated ligands. They demonstrate that while nanoparticles with static ligands in a striped conformation are unable to penetrate the bilayer, enabling surface mobility allows penetration by the induced formation of a small, transient pore of a comparable size to the nanoparticle. Our results offer an enhanced understanding of the nanoparticles-bilayer interaction and an identification of the property necessary for membrane penetration.by Reid Chi Van Lehn.S.B

MolabIS: A Labs Backbone for Storing, Managing and Evaluating Molecular Genetics Data

Using paper lab books and spreadsheets to store and manage growing datasets in a file system is inefficient, time consuming and error-prone. Therefore, the overall purpose of this study is to develop an integrated information system for small laboratories conducting Sanger sequencing and microsatellite genotyping projects. To address this, the thesis has investigated the following three issues. First, we proposed a uniform solution using the workflow approach to efficiently collect and store data items in different labs. The outcome is the design of the formalized data framework which is the basic to create a general data model for biodiversity studies. Second, we designed and implemented a web-based information system (MolabIS) allowing lab people to store all original data at each step of their workflow. MolabIS provides essential tools to import, store, organize, search, modify, report and export relevant data. Finally, we conducted a case study to evaluate the performance of MolabIS with typical operations in a production mode. Consequently, we can propose the use of virtual appliance as an efficient solution for the deployment of complex open-source information systems like MolabIS. The major result of this study, along with the publications, is the MolabIS software which is freely released under GPL license at http://www.molabis.org. With its general data model, easy installation process and additional tools for data migration, MolabIS can be used in a wide range of molecular genetics labs