1,838 research outputs found
Dynamix on the Frame VM: Declarative dynamic semantics on a VM using scopes as frames
No full textOver the years virtual machines (VMs) have been created to abstract over computer hardware. This simplified code generation and allowed for easy portability between hardware platforms. These VMs are however highly tailored to a particular runtime model. This improves the execution speed, but places restrictions on the types of languages that the VM supports. In this thesis the Frame VM was developed as a VM that supports many different types of languages in a principled way. Achieving this is done by basing the VM on language independent models of memory and control flow. Usage of the scopes-as-frames paradigm and control frames resulted in an instruction set that is relatively small at its core, but does allow for the construction of complex control flow. As an effect, many different programming languages can be compiled to the Frame VM. In addition to this VM, a Domain Specific Language (DSL) for executable semantics of programming languages was created. This language, Dynamix, allows for a modular approach to writing the semantics of a language. Additionally, Dynamix provides a meta-compiler that uses these semantics of a language to compile programs to the Frame VM. To validate the Frame VM, direct compilers for Rust and Prolog have been created in a student project and compilers for Scheme and Tiger were created using Dynamix. Using these semantics of Scheme and Tiger, it was possible to execute programs containing usage of call/cc and a suite of Tiger benchmark programs. Furthermore, the control flow of Tiger was extended with exceptions and generator functions. This extension did not require any changes to the existing semantics, showing the modularity of control achieved when using Dynamix and the Frame VM.Computer Scienc
Fast VM Replication on Heterogeneous Hypervisors for Robust Fault Tolerance
No full textJean-Baptiste Decourcelle, Tu Dinh Ngoc, Boris Teabe, and Daniel Hagimont. 2023. Fast VM Replication on Heterogeneous Hypervisors for Robust Fault Tolerance. In 24th International Middleware Conference (Middleware ’23), December 11–15, 2023, Bologna, Italy. ACM, New York, NY, USA, 14 pages. https://doi.org/10.1145/3590140.3592849International audienceThe reliability of virtualization infrastructures in the face of availability issues is a long-standing problem. Current fault tolerance approaches such as live VM replication are effective at addressing external, accidental issues (e.g. hardware failures, power cuts, environmental disasters); however, against an active attacker exploiting zero-day denial-of-service (DoS) vulnerabilities in the hypervisor itself, these approaches do not address the root cause of said vulnerabilities, and therefore cannot protect against these issues. This is made more relevant by the prevalence of DoS vulnerabilities among many widely used hypervisors. We introduce heterogeneous replication, a new solution that enhances live VM replication so that VMs can be replicated across different hypervisors. We show that heterogeneous replication not only mitigates accidental failures from the external operational environment, but also mitigates DoS attacks arising from hypervisor vulnerabilities. We further show that heterogeneous replication can be used to increase the security of virtualized infrastructures without sacrificing availability. We build HERE, our implementation of the heterogeneous replication concept for replicating a protected VM across hypervisor boundaries. We describe the implementation of HERE, including details on the necessary VM state replications, as well as a dynamic checkpoint interval adjustment scheme that maximizes VM protection based on load levels. We evaluate HERE using various benchmarks to show that HERE meets the goal of protecting VMs from availability issues while adapting to the VM's computing load
Autonomous DRL-based energy efficient VM consolidation for cloud data centers
No full textThe exponential data growth and demands for high computing resources lead to excessive resource use in cloud data centers, which cause an increase in energy consumption and high carbon emissions in the environment. So, the high energy consumption, inefficient resource usage, and quality of service assurance (QoS) are major challenges for cloud data centers. The dynamic consolidation of Virtual Machines (VMs) is proven to be an efficient way to tackle these issues while reducing energy consumption and improving resource utilization in data centers. It reduces the number of active hosts for energy efficiency by switching under-utilized and idle hosts into lower power mode. So, several heuristics and Artificial Intelligence (AI) based VM consolidation approaches have been published in papers. Most existing approaches rely on the aggressive consolidation of VMs for energy efficiency, thus causing performance degradation and high SLA violation. However, an automated solution is needed to reduce energy consumption and SLA violation by ensuring efficient resource usage in the cloud data center environment. Therefore, this article proposes an energy-efficient autonomous VM consolidation (AVMC) mechanism that has Deep Reinforcement Learning (DRL) based agent for performing VM consolidation decisions. The DRL agent learns the optimal distribution of VMs in the data center, considering energy efficiency and QoS assurance. The real-time workload traces from PlanetLab have been used to validate the proposed mechanism. Experimental results reveal the superiority of the proposed AVMC system over the existing models. AVMC reduced the energy consumption and SLA violation rate significantly.11Nsciescopusothe
The <i>Valsa Mali</i> effector Vm1G-1794 protects the aggregated MdEF-Tu from autophagic degradation to promote infection in apple
No full textMacroautophagy/autophagy is a conserved degradation pathway in eukaryotes that is required for recycling unwanted intracellular components, maintaining homeostasis, and coping with biotic and abiotic stresses. Pathogens have evolved to subvert autophagic machinery by secreting host cell-entering effector proteins. Here, we provided evidence that an apple autophagy-related gene MdATG8i, activated autophagy and contributed to resistance against Valsa canker caused by Valsa Mali (Vm) when being overexpressed in apple. MdATG8i interacted with a plastid elongation factor Tu (MdEF-Tu) which became insoluble and aggregated during Vm infection and was degraded through the autophagy pathway. Intriguingly, we identified a highly-induced effector secreted from Vm, Vm1G-1794, which competitively interacted with MdATG8i, suppressed autophagy, and depleted MdEF-Tu out of MdATG8i complexes. The formation of stable MdEF-Tu aggregates caused by Vm1G-1794 promoted the susceptibility of apple to Vm. Overall, our study demonstrated that MdATG8i contributed to Vm resistance by targeting and degrading MdEF-Tu, and Vm1G-1794 competed with MdEF-Tu to target MdATG8i and prevent MdEF-Tu degradation, thus favoring infection. Abbreviations: 35S: cauliflower mosaic virus 35S promoter; AIM: ATG8-interacting motif; ATG8–PE: ATG8 conjugated with phosphatidylethanolamine; BiFC: biomolecular fluorescence complementation; Con A: concanamycin A; Co-IP: co-immunoprecipitation; DEPs: differentially expressed proteins; DMSO: dimethyl sulfoxide; GFP: green fluorescent protein; hpt: hours post-treatment; LCI: luciferase complementation imaging; MdATG8i: autophagy-related protein 8i in Malus domestica; MDC: monodansylcadaverine; MdEF-Tu: elongation factor Tu in Malus domestica; MdNBR1: neighbor of BRCA1 in Malus domestica; N. benthamiana: Nicotiana benthamiana; OE: overexpression; PAMP: pathogen-associated molecular pattern; PTI: pattern-triggered immunity; qRT-PCR: quantitative reverse transcription PCR; RFP: red fluorescent protein; RNAi: RNA interference; ROS: reactive oxygen species; Ub: ubiquitin; V. Mali: Valsa Mali; WT: wild-type plant; YFP: yellow fluorescent protein</p
Flow compensation in a MEMS dual-thermal conductivity detector for hydrogen sensing in natural gas
No full textConventional thermal conductivity detectors (TCDs) demonstrate a flow dependence. The approach presented here to reduce the flow dependence is based on the on-line flow compensation using two thin-film sensors on membranes in parallel on the same chip that are differentially operated. These are laterally identically, but with a different depth of the detection chamber, resulting in different quasi-static sensitivities to the thermal conductivity of the sample gas. The effects of conduction and convection in the structure have been studied using COMSOL Multiphysics. First prototypes have been fabricated and are presently tested.Accepted Author ManuscriptElectronic Instrumentatio
The diverse functional roles of elongation factor tu (Ef-tu) in microbial pathogenesis
No full text© 2019 Harvey, Jarocki, Charles and Djordjevic. Elongation factor thermal unstable Tu (EF-Tu) is a G protein that catalyzes the binding of aminoacyl-tRNA to the A-site of the ribosome inside living cells. Structural and biochemical studies have described the complex interactions needed to effect canonical function. However, EF-Tu has evolved the capacity to execute diverse functions on the extracellular surface of both eukaryote and prokaryote cells. EF-Tu can traffic to, and is retained on, cell surfaces where can interact with membrane receptors and with extracellular matrix on the surface of plant and animal cells. Our structural studies indicate that short linear motifs (SLiMs) in surface exposed, non-conserved regions of the molecule may play a key role in the moonlighting functions ascribed to this ancient, highly abundant protein. Here we explore the diverse moonlighting functions relating to pathogenesis of EF-Tu in bacteria and examine putative SLiMs on surface-exposed regions of the molecule
Elongation factor Tu is a multifunctional and processed moonlighting protein
No full text© 2017 The Author(s). Many bacterial moonlighting proteins were originally described in medically, agriculturally, and commercially important members of the low G + C Firmicutes. We show Elongation factor Tu (Ef-Tu) moonlights on the surface of the human pathogens Staphylococcus aureus (SaEf-Tu) and Mycoplasma pneumoniae (MpnEf-Tu), and the porcine pathogen Mycoplasma hyopneumoniae (MhpEf-Tu). Ef-Tu is also a target of multiple processing events on the cell surface and these were characterised using an N-terminomics pipeline. Recombinant MpnEf-Tu bound strongly to a diverse range of host molecules, and when bound to plasminogen, was able to convert plasminogen to plasmin in the presence of plasminogen activators. Fragments of Ef-Tu retain binding capabilities to host proteins. Bioinformatics and structural modelling studies indicate that the accumulation of positively charged amino acids in short linear motifs (SLiMs), and protein processing promote multifunctional behaviour. Codon bias engendered by an A + T rich genome may influence how positively-charged residues accumulate in SLiMs
Multisize Electrode Field-of-View: Validation by High Resolution Gadolinium-Enhanced Cardiac Magnetic Resonance
No full textBackground: Voltage mapping to detect ventricular scar is important for guiding catheter ablation, but the field-of-view of unipolar, bipolar, conventional, and microelectrodes as it relates to the extent of viable myocardium (VM) is not well defined. Objectives: The purpose of this study was to evaluate electroanatomic voltage-mapping (EAVM) with different-size electrodes for identifying VM, validated against high-resolution ex-vivo cardiac magnetic resonance (HR-LGE-CMR). Methods: A total of 9 swine with early-reperfusion myocardial infarction were mapped with the QDOT microcatheter. HR-LGE-CMR (0.3-mm slices) were merged with EAVM. At each EAVM point, the underlying VM in multisize transmural cylinders and spheres was quantified from ex vivo CMR and related to unipolar and bipolar voltages recorded from conventional and microelectrodes. Results: In each swine, 220 mapping points (Q1, Q3: 216, 260 mapping points) were collected. Infarcts were heterogeneous and nontransmural. Unipolar and bipolar voltage increased with VM volumes from >175 mm3 up to >525 mm3 (equivalent to a 5-mm radius cylinder with height >6.69 mm). VM volumes in subendocardial cylinders with 1- or 3-mm depth correlated poorly with all voltages. Unipolar voltages recorded with conventional and microelectrodes were similar (difference 0.17 ± 2.66 mV) and correlated best to VM within a sphere of radius 10 and 8 mm, respectively. Distance-weighting did not improve the correlation. Conclusions: Voltage increases with transmural volume of VM but correlates poorly with small amounts of VM, which limits EAVM in defining heterogeneous scar. Microelectrodes cannot distinguish thin from thick areas of subendocardial VM. The field-of-view for unipolar recordings for microelectrodes and conventional electrodes appears to be 8 to 10 mm, respectively, and unexpectedly similar.ImPhys/Tao grou
Application of Value Methodology to Improve Preservation of Infrastructural Assets in Rijkswaterstaat
No full textValue Methodology (VM) is proposed by Dr. Frits Willems from Grontmij, as a possible way to help solve the problems. VM is a strong problem-analyzing and decision-making tool which matches the problem framework. Besides, based on an insight of its development and applications in other Government agencies, and comparisons with other relative methods, a conclusion is drawn that it is worthwhile researching on VM to see how it can help. VM is the starting point of this thesis research. The objective is to develop a framework of the application of Value Methodology, in order to identify maintenance improvements on infrastructural assets and guide decision-making on renewal and modification projects.BouwprocessenBouwCivil Engineering and Geoscience
MIME Configurations for Using VM on Emacs
No full textP(論文)Emacsは単なる文書編集アプリケーションではなく、様々な機能をマクロとして附加することができる。本稿では、このEmacsでメールを読み書きするための追加マクロとしてVMを取り上げる。VMでは電子メール本文におけるMIME対応はなされているが、ヘッダにおけるMIME対応はなされていない。本稿では、VMからSEMIを利用し、電子メールヘッダに日本語を利用するためのMIME設定について述べる。当初の目的であるEmacsとVMによる電子メールヘッダにおける日本語のMIME処理は実現できた。ただし、Emacsの版によってはうまく実現できないという情報もある。汎用的な方法を確立するためには、更なる調査が必要である。Emacs is an application software that can be used not only for editing plain texts but also for many other purposes by adding facilities as macros. In this study, VM was used as auxiliary macro for reading and writing e-mails by Emacs. VM has MIME reading and writing ability in the body part of e-mail messages but not in the header part. In this paper, MIME configurations for using SEMI from VM for processingJapanese characters in e-mail headers are described. The goal of this study, i.e., reading and writing MIME messages in header parts, was achieved. However, the author has information that the method described in this paper does not work well with one version of Emacs (Emacs 22). Establishment of a general method is a subject of future work.departmental bulletin pape
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