Joint Centrality Distinguishes Optimal Leaders in Noisy Networks

We study the performance of a network of agents tasked with tracking an external unknown signal in the presence of stochastic disturbances and under the condition that only a limited subset of agents, known as leaders, can measure the signal directly. We investigate the optimal leader selection problem for a prescribed maximum number of leaders, where the optimal leader set minimizes total system error defined as steady-state variance about the external signal. In contrast to previously established greedy algorithms for optimal leader selection, our results rely on an expression of total system error in terms of properties of the underlying network graph. We demonstrate that the performance of any given set of leaders depends on their influence as determined by a new graph measure of centrality of a set. We define the $joint \; centrality$ of a set of nodes in a network graph such that a leader set with maximal joint centrality is an optimal leader set. In the case of a single leader, we prove that the optimal leader is the node with maximal information centrality. In the case of multiple leaders, we show that the nodes in the optimal leader set balance high information centrality with a coverage of the graph. For special cases of graphs, we solve explicitly for optimal leader sets. We illustrate with examples.Comment: Conditionally accepted to IEEE TCN

On pore-scale modeling and simulation of reactive transport in 3D geometries

Pore-scale modeling and simulation of reactive flow in porous media has a range of diverse applications, and poses a number of research challenges. It is known that the morphology of a porous medium has significant influence on the local flow rate, which can have a substantial impact on the rate of chemical reactions. While there are a large number of papers and software tools dedicated to simulating either fluid flow in 3D computerized tomography (CT) images or reactive flow using pore-network models, little attention to date has been focused on the pore-scale simulation of sorptive transport in 3D CT images, which is the specific focus of this paper. Here we first present an algorithm for the simulation of such reactive flows directly on images, which is implemented in a sophisticated software package. We then use this software to present numerical results in two resolved geometries, illustrating the importance of pore-scale simulation and the flexibility of our software package.Comment: 15 pages, 6 figure

Development of oyster resources

During the 3-year project period, augmentation of cultch material and transplanting of seed oysters as a means of increasing oyster production was used. Sites were selected for the planting and transplanting. These sites were evaluated based on several criteria. One of the major considerations is the relative abundance of previous spatfall or production in a given area. Several additional factors reviewed for selection included approximate date of peak setting, substrate type (muddy, sandy, rocky, etc. bottom), impact of MSX, estimate of bar potential, gross fishing efforts and salinity regimes. It is important to plant a week or two prior to peake setting, because if shells are planted much too early or late, they may become so fouled with marine organisms that spat or larvae will not set

A Transect Through the Foreland and Transitional Zone of Western Vermont

Guidebook for field trips in Vermont: New England Intercollegiate Geological Conference, 79th annual meeting, October 16, 17 and 18, 1987: Trips A-

Modeling Expert Opinions on Food Healthiness: A Nutrition Metric

Background Research over the last several decades indicates the failure of existing nutritional labels to substantially improve the healthiness of consumers' food and beverage choices. The difficulty for policy-makers is to encapsulate a wide body of scientific knowledge in a labeling scheme that is comprehensible to the average shopper. Here, we describe our method of developing a nutrition metric to fill this void. Methods We asked leading nutrition experts to rate the healthiness of 205 sample foods and beverages, and after verifying the similarity of their responses, we generated a model that calculates the expected average healthiness rating that experts would give to any other product based on its nutrient content. Results The form of the model is a linear regression that places weights on 12 nutritional components (total fat, saturated fat, cholesterol, sodium, total carbohydrate, dietary fiber, sugars, protein, vitamin A, vitamin C, calcium, and iron) to predict the average healthiness rating that experts would give to any food or beverage. We provide sample predictions for other items in our database. Conclusions Major benefits of the model include its basis in expert judgment, its straightforward application, the flexibility of transforming its output ratings to any linear scale, and its ease of interpretation. This metric serves the purpose of distilling expert knowledge into a form usable by consumers so that they are empowered to make healthier decisions.

A Systematic Literature Review on Image Information Needs and Behaviors

Purpose: With ready access to search engines and social media platforms, the way people find image information has evolved and diversified in the past two decades. The purpose of this paper is to provide an overview of the literature on image information needs and behaviors. Design/methodology/approach: Following an eight-step procedure for conducting systematic literature reviews, the paper presents an analysis of peer-reviewed work on image information needs and behaviors, with publications ranging from the years 1997 to 2019. Findings: Application of the inclusion criteria led to 69 peer-reviewed works. These works were synthesized according to the following categories: research methods, users targeted, image types, identified needs, search behaviors, and search obstacles. The reviewed studies show that people seek and use images for multiple reasons, including entertainment, illustration, aesthetic appreciation, knowledge construction, engagement, inspiration, and social interactions. The reviewed studies also report that common strategies for image searches include keyword searches with short queries, browsing, specialization, and reformulation. Observed trends suggest common deployment of query analysis, survey questionnaires, and undergraduate participant pools to research image information needs and behavior. Originality: At this point, after more than two decades of image information needs research, a holistic systematic review of the literature was long overdue. The way users find image information has evolved and diversified due to technological developments in image retrieval. By synthesizing this burgeoning field into specific foci, this systematic literature review provides a foundation for future empirical investigation. With this foundation set, the paper then pinpoints key research gaps to investigate, particularly the influence of user expertise, a need for more diverse population samples, a dearth of qualitative data, new search features, and information and visual literacies instruction

Depression in Right Hemisphere Disorder

Between 25-79% of stroke survivors suffer depression, which can lead to limited recovery, decreased quality of life, and increased mortality. In adults with right hemisphere disorder (RHD), the cause(s) of depression have been unclear. Our results showed that significantly more adults with RHD were depressed than normal controls, and that adults with RHD were significantly more depressed than normal controls. In both groups, depression was significantly related with loneliness. In adults with RHD, depression was also significantly related with social support. No demographic or lesion-related variables were associated with increased depression in our samples. Suggestions for treatment research are offered

Anomalous accumulation rates in the Vostok ice-core resulting from ice flow over Lake Vostok

The accumulation rate of snow is crucial to the development of accurate age-depth models for ice-cores. The dating of the Vostok ice-core assumes that accumulation rates generally vary linearly between the core site and the ice divide 250 km to the west [Jouzel et al., 1996; Lorius et al., 1985; Petit et al., 1999], an assumption which impacts the timing of prominent climatic transitions. We present evidence for a local accumulation rate anomaly at the ice surface above the western shoreline of Lake Vostok. A significant thickening between isochronous layers results from this geographically fixed high accumulation zone which can be stratigraphically traced to a depth of 820 – 1100 m in the Vostok ice-core, a portion known for its high accumulation rates and paleoclimate records that deviate from other Antarctic ice-core records. This non-climatic accumulation anomaly in the Vostok ice-core impacts the flow dependent age models and subsequent interpretations of sequencing of global climate shifts during the last glacial. These previously unreported geographically fixed accumulation rate anomalies are introduced into ice-cores drilled away from ice domes (e.g., Byrd and Vostok) and should be considered in age depth models