Restart-Based Fault-Tolerance: System Design and Schedulability Analysis

Embedded systems in safety-critical environments are continuously required to deliver more performance and functionality, while expected to provide verified safety guarantees. Nonetheless, platform-wide software verification (required for safety) is often expensive. Therefore, design methods that enable utilization of components such as real-time operating systems (RTOS), without requiring their correctness to guarantee safety, is necessary. In this paper, we propose a design approach to deploy safe-by-design embedded systems. To attain this goal, we rely on a small core of verified software to handle faults in applications and RTOS and recover from them while ensuring that timing constraints of safety-critical tasks are always satisfied. Faults are detected by monitoring the application timing and fault-recovery is achieved via full platform restart and software reload, enabled by the short restart time of embedded systems. Schedulability analysis is used to ensure that the timing constraints of critical plant control tasks are always satisfied in spite of faults and consequent restarts. We derive schedulability results for four restart-tolerant task models. We use a simulator to evaluate and compare the performance of the considered scheduling models

Safety and security of cyber-physical systems

The number of embedded controllers in charge of physical systems has rapidly increased over the past years. Embedded controllers are present in every aspect of our lives, from our homes to our vehicles and factories. The complexity of these systems is also more than ever. These systems are expected to deliver many features and high performance without trading off in robustness and assurance. As systems increase in complexity, however, the cost of formally verifying their correctness and eliminating security vulnerabilities can quickly explode. On top of the unintentional bugs and problems, malicious attacks on cyber-physical systems (CPS) can also lead to adverse outcomes on physical plants. Some of the recent attacks on CPS are focused on causing physical damage to the plants or the environment. Such intruders make their way into the system using cyber exploits but then initiate actions that can destabilize and even damage the underlying (physical) systems. Given the reality mentioned above and the reliability standards of the industry, there is a need to embrace new CPS design paradigms where faults and security vulnerabilities are the norms rather than an anomaly. Such imperfections must be assumed to exist in every system and component unless it is formally verified and scanned. Faults and vulnerabilities should be safely handled and the CPS must be able to recover from them at run-time. Our goal in this work is to introduce and investigate a few designs compatible with this paradigm. The architectures and techniques proposed in this dissertation do not rely on the testing and complete system verification. Instead, they enforce safety at the highest level of the system and extend guaranteed safety from a few certified components to the entire system. These solutions are carefully curated to utilize unverified components and provide guaranteed performance

The effect of adding Rosmarinic and Ascorbic acids to vitrification media on fertilization rate of the mice oocyte: An experimental study

Background: Oocytes vitrification is a pivotal step for the widespread and safekeeping of animal genetic resources. Oocytes endure notable morphological and functional damage during cryopreservation. Oxidative stress is one of the adverse effects that vitrification imparts on oocytes.Objective: In the present study, we investigated the antioxidant effect of Rosmarinic and Ascorbic acids on the quality and fertilizing ability of frozen-thawed mice oocyte.Materials and Methods: In this experimental study, germinal vesicle oocytes obtained from two-months-old (30–40gr) NMRI mice were randomly divided into four groups. The basic cryoprotectants were 7.5% (v/v) ethylene glycol+7.5% (v/v) Propanediol as an equilibration media. Vitrification medium contained 15% (v/v) ethylene glycol+15% (v/v) propanediol, and 0.5 M sucrose. In the first group (Control), nothing was addedto vitrification mediums, whereas, in the second and third groups, 0.5 mmol/L of Ascorbic acid and 105 µmol/L of Rosmarinic acid were added into vitrification medium, respectively. The cumulative concentration of Rosmarinic and Ascorbic acids were added to group 4. Mouse oocytes were vitrified and preserved for one month. The thawed oocytes were transferred into the α-MEM medium (Alpha Minimum Essential Medium) and maintained in this medium for 24 hr, to be matured and reach the metaphase II stage.Results: The addition of Rosmarinic and Ascorbic acids to the vitrification solution improved the survival, maturation of Germinal vesicles, fertilization rate, and finally development to 4-cell stage. Maturation rates to 4-cell stage for Ascorbic acid, Rosmarinic acid, and both of them together were 80%, 80.76%, and 86.61%, respectively.Conclusion: These results indicate that the addition of a cumulative concentration of 0.5 mmol/L Ascorbic acid and 105 µmol/L of Rosmarinic acid to the cryopreservation solution for the mouse immature oocytes would be of significant value (p< 0.01)

Metformin therapy attenuates pro-inflammatory Microglia by inhibiting NF-κB in cuprizone demyelinating mouse model of multiple Sclerosis

Multiple sclerosis (MS) is a chronic disorder characterized by reactive gliosis, inflammation, and demyelination. Microglia plays a crucial role in the pathogenesis of MS and has the dynamic plasticity to polarize between pro-inflammatory (M1) and anti-inflammatory (M2) phenotypes. Metformin, a glucose-lowering drug, attenuates inflammatory responses by activating adenosine monophosphate protein kinase (AMPK) which suppresses nuclear factor kappa B (NF-κB). In this study, we indirectly investigated whether metformin therapy would regulate microglia activity in the cuprizone (CPZ)-induced demyelination mouse model of MS via measuring the markers associated with pro- and anti-inflammatory microglia. Evaluation of myelin by luxol fast blue staining revealed that metformin treatment (CPZ + Met) diminished demyelination, in comparison to CPZ mice. In addition, metformin therapy significantly alleviated reactive microgliosis and astrogliosis in the corpus callosum, as measured by Iba-1 and GFAP staining. Moreover, metformin treatment significantly downregulated the expression of pro-inflammatory associated genes (iNOS, H2-Aa, and TNF-α) in the corpus callosum, whereas expression of anti-inflammatory markers (Arg1, Mrc1, and IL10) was not promoted, compared to CPZ mice. Furthermore, protein levels of iNOS (pro-inflammatory marker) were significantly decreased in the metformin group, while those of Trem2 (anti-inflammatory marker) were increased. In addition, metformin significantly increased AMPK activation in CPZ mice. Finally, metformin administration significantly reduced the activation level of NF-κB in CPZ mice. In summary, our data revealed that metformin attenuated pro-inflammatory microglia markers through suppressing NF-κB activity. The positive effects of metformin on microglia and remyelination suggest that it could be used as a promising candidate to lessen the incidence of inflammatory neurodegenerative diseases such as MS

Preserving safety in distributed cyber physical systems with unreliable communication channels

Cyber-physical systems (CPS) may interact and manipulate objects in the physical world with the aid of communication channels. Additionally, due to their nature, most CPS are safety-critical systems where there are safety invariant that need to be preserved. The big challenge is that communication channels are unreliable meaning that there may not be bounds on message delays. this will pose a threat to the safety of system. Guaranteeing safety for these systems can be even further complicated as physical components with which these systems interact may not have accurate physical models available. In this Thesis we discuss two approaches to solve the safety problem. In the first part, we discuss a general methodology and architecture for distributed CPS design in order to increase the resiliency to communication faults. In this approach, each node exploits physical connections between nodes to estimate some of the state parameters of the remote nodes in order to detect the faults and also to maintain stability of system after fault occurrence. Finally, as a case study, a fault-resilient decentralized voltage control algorithm is presented and evaluated. In the second part of the thesis, we address the challenge of proving safety and progress in distributed CPS communicating over an unreliable commu- nication layer. This is done in two parts. First, we show that system safety can be verified by partially relying upon run-time checks, and that dropping messages if the run-time checks fail will maintain safety. Second, we use a notion of compatible action chains to guarantee system progress, despite un- bounded message delays. We demonstrate the effectiveness of our approach on a multi-agent vehicle flocking system, and show that the overhead of the proposed run-time checks is not overbearing

DIAGNOSTIC UTILITY OF ADENOSINE DEAMINASE IN SERUM AND BRONCHOALVEOLAR LAVAGE FLUID FOR SCREENING LUNG CANCER IN WESTERN IRAN DIJAGNOSTI^KA KORIST ADENOZIN-DEAMINAZE U SERUMU I BRONHOALVEOLARNOM LAVA@U ZA SKRINING RAKA PLU]A U ZAPADNOM IRANU

Summary Background: This study aimed to determine adenosine deaminase (ADA) activity as a possible screening tool in lung cancer patients. Methods: Blood samples were collected from 30 subjects with positive pathological tests and 62 patients with negative pathological tests as a control group. The enzymatic activity of total ADA and its isoenzymes was determined. Results: tADA and ADA2 isoenzyme activity was significantly higher in cancerous patients compared to benign controls in serum and BAL fluid. Using a cut-off level of respectively 35.22 U/L and 31.80 U/L for BAL total ADA and ADA2, sensitivity and specificity were 100% and 81% for total ADA and 95% and 98% for ADA2. Conclusions: Adenosine deaminase may play important roles in the pathophysiology of lung cancer and because of it