746 research outputs found
Risk-based Security Measure Allocation Against Injection Attacks on Actuators
This article considers the problem of risk-optimal allocation of security
measures when the actuators of an uncertain control system are under attack. We
consider an adversary injecting false data into the actuator channels. The
attack impact is characterized by the maximum performance loss caused by a
stealthy adversary with bounded energy. Since the impact is a random variable,
due to system uncertainty, we use Conditional Value-at-Risk (CVaR) to
characterize the risk associated with the attack. We then consider the problem
of allocating the security measures which minimize the risk. We assume that
there are only a limited number of security measures available. Under this
constraint, we observe that the allocation problem is a mixed-integer
optimization problem. Thus we use relaxation techniques to approximate the
security allocation problem into a Semi-Definite Program (SDP). We also compare
our allocation method across different risk measures: the worst-case
measure, the average (nominal) measure, and across different search
algorithms: the exhaustive and the greedy search algorithms. We depict the
efficacy of our approach through numerical examples.Comment: Submitted to IEEE Open Journal of Control Systems (OJ-CSYS
Security Allocation in Networked Control Systems under Stealthy Attacks
This paper considers the problem of security allocation in a networked
control system under stealthy attacks in which the system is comprised of
interconnected subsystems represented by vertices. A malicious adversary
selects a single vertex on which to conduct a stealthy data injection attack to
maximally disrupt the local performance while remaining undetected. On the
other hand, a defender selects several vertices on which to allocate defense
resources against the adversary. First, the objectives of the adversary and the
defender with uncertain targets are formulated in probabilistic ways, resulting
in an expected worst-case impact of stealthy attacks. Next, we provide a
graph-theoretic necessary and sufficient condition under which the cost for the
defender and the expected worst-case impact of stealthy attacks are bounded.
This condition enables the defender to restrict the admissible actions to a
subset of available vertex sets. Then, we cast the problem of security
allocation in a Stackelberg game-theoretic framework. Finally, the contribution
of this paper is highlighted by utilizing the proposed admissible actions of
the defender in the context of large-scale networks. A numerical example of a
50-vertex networked control system is presented to validate the obtained
results.Comment: 11 pages, 3 figures, and 1 table, journal submissio
Risk Assessment of Stealthy Attacks on Uncertain Control Systems
In this article, we address the problem of risk assessment of stealthy
attacks on uncertain control systems. Considering data injection attacks that
aim at maximizing impact while remaining undetected, we use the recently
proposed output-to-output gain to characterize the risk associated with the
impact of attacks under a limited system knowledge attacker. The risk is
formulated using a well-established risk metric, namely the maximum expected
loss. Under this setups, the risk assessment problem corresponds to an
untractable infinite non-convex optimization problem. To address this
limitation, we adopt the framework of scenario-based optimization to
approximate the infinite non-convex optimization problem by a sampled
non-convex optimization problem. Then, based on the framework of dissipative
system theory and S-procedure, the sampled non-convex risk assessment problem
is formulated as an equivalent convex semi-definite program. Additionally, we
derive the necessary and sufficient conditions for the risk to be bounded.
Finally, we illustrate the results through numerical simulation of a
hydro-turbine power system
A Zero-Sum Game Framework for Optimal Sensor Placement in Uncertain Networked Control Systems under Cyber-Attacks
This paper proposes a game-theoretic approach to address the problem of
optimal sensor placement against an adversary in uncertain networked control
systems. The problem is formulated as a zero-sum game with two players, namely
a malicious adversary and a detector. Given a protected performance vertex, we
consider a detector, with uncertain system knowledge, that selects another
vertex on which to place a sensor and monitors its output with the aim of
detecting the presence of the adversary. On the other hand, the adversary, also
with uncertain system knowledge, chooses a single vertex and conducts a
cyber-attack on its input. The purpose of the adversary is to drive the attack
vertex as to maximally disrupt the protected performance vertex while remaining
undetected by the detector. As our first contribution, the game payoff of the
above-defined zero-sum game is formulated in terms of the Value-at-Risk of the
adversary's impact. However, this game payoff corresponds to an intractable
optimization problem. To tackle the problem, we adopt the scenario approach to
approximately compute the game payoff. Then, the optimal monitor selection is
determined by analyzing the equilibrium of the zero-sum game. The proposed
approach is illustrated via a numerical example of a 10-vertex networked
control system.Comment: 8 pages, 3 figues, Accepted to the 61st Conference on Decision and
Control, Cancun, December 202
Design of multiplicative watermarking against covert attacks
This paper addresses the design of an active cyberattack detection
architecture based on multiplicative watermarking, allowing for detection of
covert attacks. We propose an optimal design problem, relying on the so-called
output-to-output l2-gain, which characterizes the maximum gain between the
residual output of a detection scheme and some performance output. Although
optimal, this control problem is non-convex. Hence, we propose an algorithm to
design the watermarking filters by solving the problem suboptimally via LMIs.
We show that, against covert attacks, the output-to-output l2-gain is unbounded
without watermarking, and we provide a sufficient condition for boundedness in
the presence of watermarks.Comment: 6 page conference paper accepted to the 60th IEEE Conference on
Decision and Contro
Hydrogen peroxide production regulates the mitochondrial function in insulin resistant muscle cells: Effect of catalase overexpression
AbstractThe mitochondrial redox state plays a central role in the link between mitochondrial overloading and insulin resistance. However, the mechanism by which the ROS induce insulin resistance in skeletal muscle cells is not completely understood. We examined the association between mitochondrial function and H2O2 production in insulin resistant cells. Our hypothesis is that the low mitochondrial oxygen consumption leads to elevated ROS production by a mechanism associated with reduced PGC1α transcription and low content of phosphorylated CREB. The cells were transfected with either the encoded sequence for catalase overexpression or the specific siRNA for catalase inhibition. After transfection, myotubes were incubated with palmitic acid (500μM) and the insulin response, as well as mitochondrial function and fatty acid metabolism, was determined. The low mitochondrial oxygen consumption led to elevated ROS production by a mechanism associated with β-oxidation of fatty acids. Rotenone was observed to reduce the ratio of ROS production. The elevated H2O2 production markedly decreased the PGC1α transcription, an effect that was accompanied by a reduced phosphorylation of Akt and CREB. The catalase transfection prevented the reduction in the phosphorylated level of Akt and upregulated the levels of phosphorylated CREB. The mitochondrial function was elevated and H2O2 production reduced, thus increasing the insulin sensitivity. The catalase overexpression improved mitochondrial respiration protecting the cells from fatty acid-induced, insulin resistance. This effect indicates that control of hydrogen peroxide production regulates the mitochondrial respiration preventing the insulin resistance in skeletal muscle cells by a mechanism associated with CREB phosphorylation and β-oxidation of fatty acids
Portuguese Football Federation consensus statement 2020: nutrition and performance in football
Nutrition is an undeniable part of promoting health and performance among football (soccer) players. Nevertheless, nutritional strategies adopted in elite football can vary significantly depending on culture, habit and practical constraints and might not always be supported by scientific evidence. Therefore, a group of 28 Portuguese experts on sports nutrition, sports science and sports medicine sought to discuss current practices in the elite football landscape and review the existing evidence on nutritional strategies to be applied when supporting football players. Starting from understanding football's physical and physiological demands, five different moments were identified: preparing to play, match-day, recovery after matches, between matches and during injury or rehabilitation periods. When applicable, specificities of nutritional support to young athletes and female players were also addressed. The result is a set of practical recommendations that gathered consensus among involved experts, highlighting carbohydrates periodisation, hydration and conscious use of dietary supplements.info:eu-repo/semantics/publishedVersio
The Portuguese Society of Rheumatology position paper on the use of biosimilars
Biotechnological drugs have become a fundamental resource for the treatment of rheumatic patients. Patent expiry of some of these drugs created the opportunity for biopharmaceutical manufacturers to develop biosimilar drugs intended to be as efficacious as the originator product but with a lower cost to healthcare systems. Due to the complex manufacturing process and highly intricate structure of biologicals, a biosimilar can never be an exact copy of its reference product. Consequently, regulatory authorities issued strict preclinical and clinical guidelines to ensure safety and efficacy equivalence and, in September 2013, the biosimilar of infliximab was the first biosimilar monoclonal antibody to be authorized for use in the European Union. The current document is a position statement of the "Sociedade Portuguesa de Reumatologia" (Portuguese Society of Rheumatology) on the use of biosimilar drugs in rheumatic diseases. Two systematic literature reviews were performed, one concerning clinical trials and the other one concerning international position papers on biosimilars. The results were presented and discussed in a national meeting and a final position document was discussed, written and approved by Portuguese rheumatologists. Briefly, this position statement is contrary to automatic substitution of the originator by the biosimilar, defends either a different INN or the prescription by brand name, supports that switching between biosimilars and the originator molecule should be done after at least 6 months of treatment and based on the attending physician decision and after adequate patient information, recommends the registration of all biosimilar treated patients in Reuma.pt for efficacy, safety and immunogenicity surveillance, following the strategy already ongoing for originators, and opposes to extrapolation of indications approved to the originator to completely different diseases and/or age groups without adequate pre-clinical, safety or efficacy data.info:eu-repo/semantics/publishedVersio
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