582 research outputs found
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
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
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
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
The effects of continued azacitidine treatment cycles on response in higher risk patients with myelodysplastic syndromes: an update
The international, phase III, multi-centre AZA-001 trial demonstrated azacitidine (AZA) is the first treatment to significantly extend overall survival (OS) in higher risk myelodysplastic syndromes (MDS) patients (Fenaux (2007) Blood 110 817). The current treatment paradigm, which is based on a relationship between complete remission (CR) and survival, is increasingly being questioned (Cheson (2006) Blood 108 419). Results of AZA-001 show CR is sufficient but not necessary to prolong OS (List (2008) Clin Oncol 26 7006). Indeed, the AZA CR rate in AZA-001 was modest (17%), while partial remission (PR, 12%) and haematological improvement (HI, 49%) were also predictive of prolonged survival. This analysis was conducted to assess the median number of AZA treatment cycles associated with achievement of first response, as measured by IWG 2000-defined CR, PR or HI (major + minor). The number of treatment cycles from first response to best response was also measured
Azacitidine prolongs overall survival and reduces infections and hospitalizations in patients with WHO-defined acute myeloid leukaemia compared with conventional care regimens: an update
Azacitidine (AZA), as demonstrated in the phase III trial (AZA-001), is the first MDS treatment to significantly prolong overall survival (OS) in higher risk MDS pts ((2007) Blood 110 817). Approximately, one-third of the patients (pts) enrolled in AZA-001 were FAB RAEB-T (≥20–30% blasts) and now meet the WHO criteria for acute myeloid leukaemia (AML) ((1999) Blood 17 3835). Considering the poor prognosis (median survival <1 year) and the poor response to chemotherapy in these pts, this sub-group analysis evaluated the effects of AZA versus conventional care regimens (CCR) on OS and on response rates in pts with WHO AML
Luspatercept for myelodysplastic syndromes/myeloproliferative neoplasm with ring sideroblasts and thrombocytosis
Activation of the G-protein-coupled receptor GPR30 induces anxiogenic effects in mice, similar to oestradiol
Seats, Votes, and Gerrymandering: Estimating Representation and Bias in State Legislative Redistricting
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