Phase Clocks for Transient Fault Repair

Phase clocks are synchronization tools that implement a form of logical time in distributed systems. For systems tolerating transient faults by self-repair of damaged data, phase clocks can enable reasoning about the progress of distributed repair procedures. This paper presents a phase clock algorithm suited to the model of transient memory faults in asynchronous systems with read/write registers. The algorithm is self-stabilizing and guarantees accuracy of phase clocks within O(k) time following an initial state that is k-faulty. Composition theorems show how the algorithm can be used for the timing of distributed procedures that repair system outputs.Comment: 22 pages, LaTe

The Arabidopsis thaliana checkpoint kinase WEE1 protects against premature vascular differentiation during replication stress

A sessile lifestyle forces plants to respond promptly to factors that affect their genomic integrity. Therefore, plants have developed checkpoint mechanisms to arrest cell cycle progression upon the occurrence of DNA stress, allowing the DNA to be repaired before onset of division. Previously, the WEE1 kinase had been demonstrated to be essential for delaying progression through the cell cycle in the presence of replication-inhibitory drugs, such as hydroxyurea. To understand the severe growth arrest of WEE1-deficient plants treated with hydroxyurea, a transcriptomics analysis was performed, indicating prolonged S-phase duration. A role for WEE1 during S phase was substantiated by its specific accumulation in replicating nuclei that suffered from DNA stress. Besides an extended replication phase, WEE1 knockout plants accumulated dead cells that were associated with premature vascular differentiation. Correspondingly, plants without functional WEE1 ectopically expressed the vascular differentiation marker VND7, and their vascular development was aberrant. We conclude that the growth arrest of WEE1-deficient plants is due to an extended cell cycle duration in combination with a premature onset of vascular cell differentiation. The latter implies that the plant WEE1 kinase acquired an indirect developmental function that is important for meristem maintenance upon replication stress

NASA/ESACV-990 spacelab simulation. Appendix B: Experiment development and performance

Eight experiments flown on the CV-990 airborne laboratory during the NASA/ESA joint Spacelab simulation mission are described in terms of their physical arrangement in the aircraft, their scientific objectives, developmental considerations dictated by mission requirements, checkout, integration into the aircraft, and the inflight operation and performance of the experiments

On Cancer Cell Cycle and Universal Apoptosis Parameters Signaling Unravelled In Silico

Here, cell cycle in higher eukaryotes and their molecular networks signals both in G1/S and G2/M transitions are in silico replicated. Systems control theory is employed to design multi-nestled digital layers to simulate protein-toprotein activation and inhibition in the cancer cell cycle dynamics in presence of damaged genome. Sequencing and controlling the digital process of four micro-scale species networks (p53/Mdm2/DNA damage; p21mRNA/cyclin-CDK complex; CDK/CDC25/wee1/SKP2/APC/CKI and apoptosis target genes system) paved the way for unravelling the participants and their by-products having the task to execute (or not) cell death. The results of the proposed cell digital multi-layers give reason to believe in the existence of an universal apoptotic mechanism. We identified and selected cell checkpoints, sizers, timers and specific target genes dynamics both for influencing mitotic process and avoiding cancer proliferation as much as for leading the cancer cell(s) to collapse into a steady stable apoptosis phase

Self-stabilizing inter-domain policy routing

As the complexity of the networked systems increases, the likelihood of experiencing unanticipated faults grows. Self-stabilization is the most general technique to design fault tolerant systems. This paradigm was introduced by Dijkstra in 1974. A self-stabilizing system guarantees that starting from an arbitrary state, the system converges to a legal state in a finite number of steps and remains in a legal state until another fault occurs. Such a system after any unexpected perturbation eventually recovers without any outside intervention; The goal of this thesis research is to design a self-stabilizing Inter Domain Policy Routing Algorithm in order to make the policy routing procedure resistant to failures. We propose two algorithms. Our first algorithm sets up a path from a source to a destination, where the source and destination belong to different autonomous systems. It uses the Path Control Protocol (PCP). This algorithm can handle path failures, but cannot cope with message losses. Our second solution takes care of this problem by using the Control Message Transport Protocol (CMTP). (Abstract shortened by UMI.)

Study of extravehicular protection and operations

Extravehicular protection and operation

A RPL based adaptive and scalable data-collection protocol module for NS-3 simulation platform

International audienceThis paper presents data-collection protocol framework based on RPL (IPv6 Routing Protocol for Low Power and Lossy Networks) for NS-3 (Network Simulator 3) simulation platform. Its design, implementation, simple examples of operations and evaluations will also be demonstrated. The conclusions and future developments are located in the final part of this paper