Spatiotemporal dynamics of complex ecological networks: Power-law scaling and implications for conservation planning

Spatial constraints on the topology of complex networks are just beginning to be appreciated, both theoretically and in concrete examples like the Internet and global air transportation network. Ecological networks, composed of habitat patches connected by species dispersal, are intrinsically spatial and show promise as a tool for conservation planning; but while habitat-loss effects on ecological networks have been simulated, such effects have not been directly measured in ecological networks varying over time. In this study, I used satellite remote sensing to study ecological networks composed of wetland habitat in the Prairie Pothole Region (PPR) of North America. I find power-law scaling of important topological properties as a function of dispersal ability and as wetland density varies with climate. Prairie wetland networks are 'meso-worlds' with mean topological distance increasing faster with network size than small-world networks, but slower than regular lattices. While similar dynamics have been shown in random spatial networks, these results emphasize the importance of processes determining locations of nodes in a spatial network, with possible implications in other areas like wireless communication networks or disease transmission networks. Wetland networks establish a climate envelope for landscape connectivity in the PPR, and I show that wetland-dependent species face a 'crisis of connectivity' with climate change. The global biodiversity crisis requires that conservation planners act quickly over large areas using limited resources; a network-based approach to coarse-filter conservation planning in dynamic landscapes should be broadly applicable to this problem

Downward trends in violence among adolescents in the United States: Evidence from the NSDUH 2002-2014

OBJECTIVE: To examine trends and correlates of fighting and violence among youth from the nation's three largest racial/ethnic groups in the US. METHODS: A population-based study (National Survey on Drug Use and Health, 2002-2014) of youth ages 12-17 (n = 209,393) provided prevalence estimates for fighting, group fighting, and attacks with the intent to harm by race/ethnicity. RESULTS The prevalence of youth fighting and violence decreased significantly for all racial/ethnic groups, dropping from a high of 33.6% in 2003 to a low of 23.7% in 2014, reflecting a 29% decrease in the relative proportion of young people involved in these behaviors. However, we also see a clear severity gradient in which year-by-year point estimates for fighting and violence are consistently highest among African-American youth followed by Hispanic and then non-Hispanic white youth. CONCLUSIONS Among youth in general and across racial/ethnic subgroups, fighting and violence are on the decline but with a stable pattern of disparities in youth involvement in these behaviors

Anal signs of child sexual abuse: a case–control study

Background: There is uncertainty about the nature and specificity of physical signs following anal child sexual abuse. The study investigates the extent to which physical findings discriminate between children with and without a history of anal abuse.<p></p> Methods: Retrospective case note review in a paediatric forensic unit.<p></p> Cases: all eligible cases from 1990 to 2007 alleging anal abuse.<p></p> Controls: all children examined anally from 1998 to 2007 with possible physical abuse or neglect with no identified concern regarding sexual abuse. Fisher’s exact test (two-tailed) was performed to ascertain the significance of differences for individual signs between cases and controls. To explore the potential role of confounding, logistic regression was used to produce odds ratios adjusted for age and gender.<p></p> Results: A total of 184 cases (105 boys, 79 girls), average age 98.5 months (range 26 to 179) were compared with 179 controls (94 boys, 85 girls) average age 83.7 months (range 35–193). Of the cases 136 (74%) had one or more signs described in anal abuse, compared to 29 (16%) controls. 79 (43%) cases and 2 (1.1%) controls had >1 sign. Reflex anal dilatation (RAD) and venous congestion were seen in 22% and 36% of cases but <1% of controls (likelihood ratios (LR) 40, 60 respectively), anal fissure in 14% cases and 1.1% controls (LR 13), anal laxity in 27% cases and 3% controls (LR 10).<p></p> Novel signs seen significantly more commonly in cases were anal fold changes, swelling and twitching. Erythema, swelling and fold changes were seen most commonly within 7 days of last reported contact; RAD, laxity, venous congestion, fissure and twitching were observed up to 6 months after the alleged assault.<p></p> Conclusions: Anal findings are more common in children alleging anal abuse than in those presenting with physical abuse or neglect with no concern about sexual abuse. Multiple signs are rare in controls and support disclosed anal abuse

A Hadwiger Theorem for Simplicial Maps

We define the notion of valuation on simplicial maps between geometric realizations of simplicial complexes in $\mathbb{R}^n$. Valuations on simplicial maps are analogous to valuations on sets. In particular, we define the Lefschetz volumes, which are analogous to the intrinsic volumes of subsets of $\mathbb{R}^n$. Our definition not only provides a generalization of the Lefschetz number, but also yields a Hadwiger-style classification theorem for all such valuations.Comment: 11 pages, 3 figure

Using Matching Estimators to Evaluate the Effect of Unit-Based Pricing on Municipal Solid Waste Disposal

The delivery of municipal services for the collection, transfer, and disposal of household solid waste is often provided by local governmental units; typically at the town or city level. Unit-based pricing, also known as pay-as-you-throw (PAYT), is a residential solid waste collection program requiring households to pay a fee per bag of trash disposed. Unit-based pricing represents a significant departure from the historical practice of financing solid waste service from property tax revenues in which the marginal cost to a household for disposing solid waste is effectively zero. Local governments are motivated to adopt unit-based pricing for the purpose of creating a financial incentive for households to reduce the quantity of solid waste disposed and concurrently increasing the level of recycled materials. The objective of this study is to evaluate the impact of unit-based pricing of household solid waste disposal. A counter-factual model is used to estimate the program effect. The study area for this paper consists of the 234 incorporated towns and cities in the state of New Hampshire. As of 2008, 40 towns had adopted a form of unit-based pricing of household solid waste. Results from propensity score matching suggest there is an average annual reduction of 466 pounds of household solid waste due to unit-based pricing.Propensity score matching, unit-based pricing, pay-as-you-throw, municipal solid waste, Environmental Economics and Policy,

Marijuana use among young people in an era of policy change: what does recent evidence tell us?

R25 DA030310 - National Institute on Drug Abus

Introduction to the macroeconomic dynamics: special issues on money, credit, and liquidity

We motivate and provide an overview to New Monetarist Economics. We then briefly describe the individual contributions to the Macroeconomics Dynamics special issues on money, credit and liquidity.Macroeconomics - Econometric models

Microbial Interactions with Nanostructures and their Importance for the Development of Electrospun Nanofibrous Materials used in Regenerative Medicine and Filtration

The growing use of electrospinning to fabricate nanofibrous structures for use in wound dressings, tissue engineering and filtration processes has increased the need for an understanding of the interactions between bacteria and nanostructures. The adhesion characteristics and colonisation of bacteria on these materials is still not completely understood but is essential to aid their future development. This review presents the state of current research on microbial attachment at materials with micro- and nano- structures and how this research has been developed and adapted to study the interactions of bacteria with nanofibres. The few studies to date are discussed with the view to identifying the future studies required to increase understanding and allow the technology and application of electrospun nanofibres to move forward