Evaluating Cascading Impact of Attacks on Resilience of Industrial Control Systems: A Design-Centric Modeling Approach

A design-centric modeling approach was proposed to model the behaviour of the physical processes controlled by Industrial Control Systems (ICS) and study the cascading impact of data-oriented attacks. A threat model was used as input to guide the construction of the CPS model where control components which are within the adversary's intent and capabilities are extracted. The relevant control components are subsequently modeled together with their control dependencies and operational design specifications. The approach was demonstrated and validated on a water treatment testbed. Attacks were simulated on the testbed model where its resilience to attacks was evaluated using proposed metrics such as Impact Ratio and Time-to-Critical-State. From the analysis of the attacks, design strengths and weaknesses were identified and design improvements were recommended to increase the testbed's resilience to attacks

Carbon-fiber tips for scanning probe microscopes and molecular electronics experiments

We fabricate and characterize carbon-fiber tips for their use in combined scanning tunneling and force microscopy based on piezoelectric quartz tuning fork force sensors. An electrochemical fabrication procedure to etch the tips is used to yield reproducible sub-100-nm apex. We also study electron transport through single-molecule junctions formed by a single octanethiol molecule bonded by the thiol anchoring group to a gold electrode and linked to a carbon tip by the methyl group. We observe the presence of conductance plateaus during the stretching of the molecular bridge, which is the signature of the formation of a molecular junction.Comment: Conference Proceeding (Trends in NanoTechnology 2011, Tenerife SPAIN); Nanoscale Research Letters, (2012) 7:25

Finite Size Effects in Separable Recurrent Neural Networks

We perform a systematic analytical study of finite size effects in separable recurrent neural network models with sequential dynamics, away from saturation. We find two types of finite size effects: thermal fluctuations, and disorder-induced `frozen' corrections to the mean-field laws. The finite size effects are described by equations that correspond to a time-dependent Ornstein-Uhlenbeck process. We show how the theory can be used to understand and quantify various finite size phenomena in recurrent neural networks, with and without detailed balance.Comment: 24 pages LaTex, with 4 postscript figures include

Controlling the quality factor of a tuning-fork resonance between 9 K and 300 K for scanning-probe microscopy

We study the dynamic response of a mechanical quartz tuning fork in the temperature range from 9 K to 300 K. Since the quality factor Q of the resonance strongly depends on temperature, we implement a procedure to control the quality factor of the resonance. We show that we are able to dynamically change the quality factor and keep it constant over the whole temperature range. This procedure is suitable for applications in scanning probe microscopy.Comment: 5 pages, 6 figure

The effect of contextual risk factors on the effectiveness of brief personality‐targeted interventions for adolescent alcohol use and misuse : a cluster‐randomized trial

Background A range of school‐based prevention programs has been developed and used to prevent, delay, or reduce alcohol use among adolescents. Most of these programs have been evaluated at the community‐level impact. However, the effect of contextual risk factors has rarely been considered in the evaluation of these programs. The aim of this study was to investigate the potential moderating effects of 2 important contextual risk factors (i.e., socioeconomic status [SES] and peer victimization) on the effectiveness of the school‐based personality‐targeted interventions (Preventure program) in reducing adolescent alcohol use over a 2‐year period using a cluster‐randomized trial. Methods High‐risk adolescents were identified using personality scores on the Substance Use Risk Profile Scale and randomized to intervention and control groups. Two 90‐minute cognitive behavioral therapy‐based group sessions targeted 1 of 4 personality risk profiles: Anxiety Sensitivity, Hopelessness, Impulsivity, or Sensation Seeking. Multilevel linear modeling of alcohol use, binge drinking, and drinking‐related harm was conducted to assess the moderating effect of baseline peer victimization and SES. Results Results indicated that the Preventure program was equally beneficial to all adolescents, regardless of SES and victimization history, in terms of their alcohol outcomes and related harm. Receiving the intervention was additionally beneficial for adolescents reporting peer victimization regarding their alcohol‐related harm compared to nonvictimized youth (β = −0.29, SE = 0.11, p = 0.014). Conclusions Findings suggest that the content of personality‐targeted interventions is beneficial for all high‐risk youth regardless of their SES or experience of peer victimization. The current study suggests that using targeted approaches, such as targeting underlying personality risk factors, may be the most appropriate substance use prevention strategy for high‐risk youth, as it is beneficial for all high‐risk youth regardless of their contextual risk factors

Photoinduced polycyclic aromatic hydrocarbon dehydrogenation: Molecular hydrogen formation in dense PDRs

The physical and chemical conditions in photodissociation regions (PDRs) are largely determined by the influence of far ultraviolet radiation. Far-UV photons can efficiently dissociate molecular hydrogen, a process that must be balanced at the HI/H2 interface of the PDR. Given that reactions involving hydrogen atoms in the gas phase are highly inefficient under interstellar conditions, H2 formation models mostly rely on catalytic reactions on the surface of dust grains. Additionally, molecular hydrogen formation in polycyclic aromatic hydrocarbons (PAHs) through the Eley-Rideal mechanism has been considered as well, although it has been found to have low efficiency in PDR fronts. In a previous work, we have described the possibility of efficient H2 release from medium to large sized PAHs upon photodissociation, with the exact branching between H-/H2-loss reactions being molecule dependent. Here we investigate the astrophysical relevance of this process, by using a model for the photofragmentation of PAHs under interstellar conditions. We focus on three PAHs cations (coronene, ovalene and circumcoronene), which represent three possibilities in the branching of atomic and molecular hydrogen losses. We find that, for ovalene (H2-loss dominated) the rate coefficient for H2 formation reaches values of the same order as H2 formation in dust grains. This result suggests that this hitherto disregarded mechanism can account, at least partly, for the high level of molecular hydrogen formation in dense PDRs.Comment: 6 pages, 4 figures, accepted for publication in A&