Models and Algorithms for Graph Watermarking

We introduce models and algorithmic foundations for graph watermarking. Our frameworks include security definitions and proofs, as well as characterizations when graph watermarking is algorithmically feasible, in spite of the fact that the general problem is NP-complete by simple reductions from the subgraph isomorphism or graph edit distance problems. In the digital watermarking of many types of files, an implicit step in the recovery of a watermark is the mapping of individual pieces of data, such as image pixels or movie frames, from one object to another. In graphs, this step corresponds to approximately matching vertices of one graph to another based on graph invariants such as vertex degree. Our approach is based on characterizing the feasibility of graph watermarking in terms of keygen, marking, and identification functions defined over graph families with known distributions. We demonstrate the strength of this approach with exemplary watermarking schemes for two random graph models, the classic Erd\H{o}s-R\'{e}nyi model and a random power-law graph model, both of which are used to model real-world networks

Capacitance measurements of bulk salinity and brine movement in first-year sea ice

Thesis (M.S.) University of Alaska Fairbanks, 2007Sea ice is an important component of the global climate system, as it changes the properties of the ocean-atmosphere interface. Understanding sea ice requires detailed knowledge of its temperature and bulk salinity. To measure these attributes using non-destructive in-situ techniques, instruments were frozen into first-year sea ice, and analysed jointly with ice-core, mass balance and climate data. The bulk salinity of the ice is calculated from measurements of temperature and complex dielectric permittivity at 50 MHz in landfast ice in McMurdo Sound, Antarctica, the Chukchi Sea, Alaska, and in an outdoor tank experiment in Fairbanks, Alaska. A simple relation for estimating brine volume fraction and bulk salinity in columnar, bubble-free ice from the real part of the complex dielectric permittivity was derived. For relative brine volumes below 50-70 % the error in the derived bulk salinity was below 15%. The observed brine movement events are analyzed. The data clearly indicate the extent and impact of brine movement on ice temperature and salinity. The analysis of a drainage event recorded by both the temperature and dielectric permittivity probe provided insight into gravity drainage of brine driven by a large brine reservoir in the freeboard layer.1. Capacitance probe measurements of brine volume and bulk salinity in first-year sea ice -- 1.1. Abstract -- 1.2. Introduction -- 1.3. Methodology -- 1.3.1. Complex dialectric permittivity of sea ice -- 1.3.2. Instrumentation -- 1.3.3. Laboratory and field experiments -- 1.3.3.1. Measurements in Landfast sea ice in McMurdo Sound, Antarctica, July 10 -- November 11, 2002 -- 1.3.3.2. Measurements in landfast sea ice off Barrow, Alaska, February 2 -- June 4, 2003 -- 1.3.3.3. Outdoor ice tank experiment, Fairbanks, Alaska, February 8-April 20, 2003 -- 1.4. Results and analysis -- 1.4.1. Field data -- 1.4.1.1. McMurdo Sound -- 1.4.1.2. Barrow -- 1.4.1.3. Ice tank experiment -- 1.4.2. Deriving the bulk salinity of the ice from complex dielectric permittivity measurements -- 1.4.2.1. Apparent aspect ratio of brine inclusions in sea ice -- 1.4.2.2. Establishing the relation between the real part of the complex dielectric permittivity and bulk salinity of sea ice -- 1.4.2.3. Salinity change in the landfast sea ice at Barrow, Alaska, 2003 -- 1.4.2.4. Sources of error -- 1.5. Conclusions -- 1.6. Figures -- 1.7. Tables -- 1.8. References -- 2. Analysis of brine movement in first-year sea ice based on a case study of temperature and dielectric permittivity data -- 2.1. Abstract -- 2.2. Introduction -- 2.2.1. Aims -- 2.2.2. Theory -- 2.3. Study area and instrumentation -- 2.4. Results and analysis -- 2.4.1. Analysis of individual events -- 2.4.2. Analysis of heat flow -- 2.5. Discussion and conclusion -- 2.6. Figures -- 2.7. Tables -- 2.8. References -- General conclusions -- References

Incidence, management, and outcomes of cardiovascular insufficiency in critically ill term and late preterm newborn infants

OBJECTIVE: The objective of this study was to characterize the incidence, management, and short-term outcomes of cardiovascular insufficiency (CVI) in mechanically ventilated newborns, evaluating four separate prespecified definitions. STUDY DESIGN: Multicenter, prospective cohort study of infants ≥34 weeks gestational age (GA) and on mechanical ventilation during the first 72 hours. CVI was prospectively defined as either (1) mean arterial pressure (MAP) < GA; (2) MAP < GA + signs of inadequate perfusion; (3) any therapy for CVI; or (4) inotropic therapy. Short-term outcomes included death, days on ventilation, oxygen, and to full feedings and discharge. RESULTS: Of 647 who met inclusion criteria, 419 (65%) met ≥1 definition of CVI. Of these, 98% received fluid boluses, 36% inotropes, and 17% corticosteroids. Of treated infants, 46% did not have CVI as defined by a MAP < GA ± signs of inadequate perfusion. Inotropic therapy was associated with increased mortality (11.1 vs. 1.3%; p < 0.05). CONCLUSION: More than half of the infants met at least one definition of CVI. However, almost half of the treated infants met none of the definitions. Inotropic therapy was associated with increased mortality. These findings can help guide the design of future studies of CVI in newborn

Meta-Reinforcement Learning for the Tuning of PI Controllers: An Offline Approach

Meta-learning is a branch of machine learning which trains neural network models to synthesize a wide variety of data in order to rapidly solve new problems. In process control, many systems have similar and well-understood dynamics, which suggests it is feasible to create a generalizable controller through meta-learning. In this work, we formulate a meta reinforcement learning (meta-RL) control strategy that can be used to tune proportional--integral controllers. Our meta-RL agent has a recurrent structure that accumulates "context" to learn a system's dynamics through a hidden state variable in closed-loop. This architecture enables the agent to automatically adapt to changes in the process dynamics. In tests reported here, the meta-RL agent was trained entirely offline on first order plus time delay systems, and produced excellent results on novel systems drawn from the same distribution of process dynamics used for training. A key design element is the ability to leverage model-based information offline during training in simulated environments while maintaining a model-free policy structure for interacting with novel processes where there is uncertainty regarding the true process dynamics. Meta-learning is a promising approach for constructing sample-efficient intelligent controllers.Comment: 23 pages; postprin

Safety and pharmacokinetics of multiple dose myo-inositol in preterm infants

BACKGROUND: Preterm infants with respiratory distress syndrome (RDS) given inositol had reduced bronchopulmonary dysplasia (BPD), death and severe retinopathy of prematurity (ROP). We assessed the safety and pharmacokinetics of daily inositol to select a dose providing serum levels previously associated with benefit, and to learn if accumulation occurred when administered throughout the normal period of retinal vascularization. METHODS: Infants ≤ 29 wk GA (n = 122, 14 centers) were randomized and treated with placebo or inositol at 10, 40, or 80 mg/kg/d. Intravenous administration converted to enteral when feedings were established, and continued to the first of 10 wk, 34 wk postmenstrual age (PMA) or discharge. Serum collection employed a sparse sampling population pharmacokinetics design. Inositol urine losses and feeding intakes were measured. Safety was prospectively monitored. RESULTS: At 80 mg/kg/d mean serum levels reached 140 mg/l, similar to Hallman's findings. Levels declined after 2 wk, converging in all groups by 6 wk. Analyses showed a mean volume of distribution 0.657 l/kg, clearance 0.058 l/kg/h, and half-life 7.90 h. Adverse events and comorbidities were fewer in the inositol groups, but not significantly so. CONCLUSION: Multiple dose inositol at 80 mg/kg/d was not associated with increased adverse events, achieves previously effective serum levels, and is appropriate for investigation in a phase III trial

Understanding the interplay between social and spatial behaviour

According to personality psychology, personality traits determine many aspects of human behaviour. However, validating this insight in large groups has been challenging so far, due to the scarcity of multi-channel data. Here, we focus on the relationship between mobility and social behaviour by analysing trajectories and mobile phone interactions of ∼1000 individuals from two high-resolution longitudinal datasets. We identify a connection between the way in which individuals explore new resources and exploit known assets in the social and spatial spheres. We show that different individuals balance the exploration-exploitation trade-off in different ways and we explain part of the variability in the data by the big five personality traits. We point out that, in both realms, extraversion correlates with the attitude towards exploration and routine diversity, while neuroticism and openness account for the tendency to evolve routine over long time-scales. We find no evidence for the existence of classes of individuals across the spatio-social domains. Our results bridge the fields of human geography, sociology and personality psychology and can help improve current models of mobility and tie formation

Grappling with the social dimensions of novel ecosystems

The novel ecosystem concept has emerged in response to the increasing prevalence of modified ecosystems. Traditional conservation and restoration strategies have been deemed inadequate to guide the management of ecosystems that are the product of anthropogenic environmental change and have no “natural” analogs. Opinions about novel ecosystems are currently divided between those who embrace the flexibility offered by the concept and those who see it as a shift toward the abandonment of traditional strategies. However, the debate is missing a key element: recognition that all conservation decisions are socially constructed and that the concept of novel ecosystems is most practicable within a decision or management context. Management of novel ecosystems should be framed in such a context, and the concept evaluated for its capacity to meet social, ecological, and economic objectives

Neurosteroid Activation of GABA-A Receptors: A Potential Treatment Target for Symptoms in Primary Biliary Cholangitis?

\ua9 2022 Aaron Wetten et al. Background and Aims. A third of patients with primary biliary cholangitis (PBC) experience poorly understood cognitive symptoms, with a significant impact on quality of life (QOL), and no effective medical treatment. Allopregnanolone, a neurosteroid, is a positive allosteric modulator of gamma-aminobutyricacid-A (GABA-A) receptors, associated with disordered mood, cognition, and memory. This study explored associations between allopregnanolone and a disease-specific QOL scoring system (PBC-40) in PBC patients. Method. Serum allopregnanolone levels were measured in 120 phenotyped PBC patients and 40 age and gender-matched healthy controls. PBC subjects completed the PBC-40 at recruitment. Serum allopregnanolone levels were compared across PBC-40 domains for those with none/mild symptoms versus severe symptoms. Results. There were no overall differences in allopregnanolone levels between healthy controls (median = 0.03 ng/ml (IQR = 0.025)) and PBC patients (0.031 (0.42), p=0.42). Within the PBC cohort, higher allopregnanolone levels were observed in younger patients (r (120) = -0.53, p&lt;0.001) but not healthy controls (r (39) = -0.21, p=0.21). Allopregnanolone levels were elevated in the PBC-40 domains, cognition (u = 1034, p=0.02), emotional (u = 1374, p=0.004), and itch (u = 795, p=0.03). Severe cognitive symptoms associated with a younger age: severe (50 (12)) vs. none (60 (13); u = 423 p=0.001). Conclusion. Elevated serum allopregnanolone is associated with severe cognitive, emotional, and itch symptoms in PBC, in keeping with its known action on GABA-A receptors. Existing novel compounds targeting allopregnanolone could offer new therapies in severely symptomatic PBC, satisfying a significant unmet need