Factors Influencing Common Raven Occurrence and Density Across Cold-Desert Sagebrush Ecosystems of the Southwestern U.S.

Common ravens (Corvus corax) are a predator of eggs and chicks of numerous species including greater sage-grouse (Centrocercus urophasianus). Raven abundance and distribution is increasing within sagebrush ecosystems as a result of anthropogenic resource subsidies. Despite concerns about subsequent predation pressure on sage-grouse, broad-scale spatial information about raven populations remains lacking. We used hierarchical occupancy and distance sampling models to map raven density and distribution in response to natural and anthropogenic landscape covariates using \u3e15,000 point count surveys occurring within the Great Basin region since 2007. Anthropogenic factors contributing to greater raven occurrence included increased road density, presence of transmission lines, agricultural activity, and presence of roadside rest areas. Natural landscape characteristics included lower elevations with greener vegetation (NDVI), greater stream and habitat edge densities, and lower percentages of big sagebrush (A. tridentate spp.). Many of these same environmental factors influenced spatial variation in raven density, although the effects varied by field site. Both raven occurrence and density tended to increase in valleys with networks of agricultural fields, ranches, roads, and distribution lines. These features likely subsidize local raven populations, which then move into more remote shrubland environments with negative consequences for sage-grouse populations. We used the relationships identified in our model to make predictions of raven density and distribution across the Great Basin landscape. We show how these model outputs can be used to guide management decisions where raven distributions overlap with breeding sage-grouse concentration areas. Findings are preliminary and provided for timely best science

Position estimating in peer-to-peer networks

We present two algorithms for indoor positioning estimation in peer-to-peer networks. The setup is a network of two types of devices: reference devices with a known location and blindfolded devices that can determine distances to reference devices and each other. From this information the blindfolded devices try to estimate their positions. A typical scenario is navigation inside a shopping mall where devices in the parking lot can make contact with GPS satellites, whereas devices inside the building make contact with each other, devices on the parking lot, and devices fixed to the building. The devices can measure their in-between distances, with some measurement error, and exchange positioning information. However, other devices might only know their position with some error. We present two algorithms for positioning estimation in such a peer-to-peer network. The first one is purely geometric and is based on Euclidean geometry and intersecting spheres. We rewrite the information to a linear system, which is typically overdetermined. We use least squares to ??nd the best estimate for a device its position. The second approach can be considered as a probabilistic version of the geometric approach. We estimate the probability density function that a device is located at a position given a probability density function for the positions of the other devices in the network, and a probability density function of the measured distances. First we study the case with a distance measurement to a single other user, then we focus on multiple other users. We give an approximation algorithm that is the probabilistic analogue of the intersecting spheres method. We show some simulated results where ambiguous data lead to well defined probability distributions for the position of a device. We conclude with some open questions

Effects of Common Ravens on Greater Sage-Grouse in the Great Basin, Region, USA

Anthropogenic modification to ecosystems can result in the redistribution of species at higher trophic levels. Humans have re-organized predator-prey dynamics, namely by removing top predators and subsidizing more generalist mesocarnivore species. As a result, some mid-level predator species have increased in abundance and distribution, often to the detriment of lower-level species that are not adapted to increased predation rates. One example of a native avian predator that has experienced population increase following increased anthropogenic subsidization is the common raven (Corvus corax; hereafter, raven).The raven is an ubiquitous predator within sagebrush ecosystems in the western U.S.,and may contribute to suppressed population growth in greater sage-grouse (Centrocercus urophasianus) through disruptions to lekking behavior and top-down influences on nest success and recruitment. Ravens have expanded in distribution and abundance, in large part due to increased resource subsidies from human infrastructure and land use activities. Concurrently, some sage-grouse populations appear to be in decline where habitat conditions should be promoting species persistence. Using long-term monitoring data on sage-grouse and ravens in the northern Great Basin region, we show that ravens disrupt sage-grouse lekking behavior, increased raven density is associated with reduced sage-grouse nest success, and that negative trends in lek counts may be related to elevated raven occurrence and density. Taken together, these results suggest the need to address a growing problem, as ravens continue to expand their distribution, facilitated by anthropogenic subsidies. These findings are preliminary and provided to meet the need for timely best science

PU(2) monopoles and links of top-level Seiberg-Witten moduli spaces

This is the first of two articles in which we give a proof - for a broad class of four-manifolds - of Witten's conjecture that the Donaldson and Seiberg-Witten series coincide, at least through terms of degree less than or equal to c-2, where c is a linear combination of the Euler characteristic and signature of the four-manifold. This article is a revision of sections 1-3 of an earlier version of the article dg-ga/9712005, now split into two parts, while a revision of sections 4-7 of that earlier version appears in a recently updated dg-ga/9712005. In the present article, we construct virtual normal bundles for the Seiberg-Witten strata of the moduli space of PU(2) monopoles and compute their Chern classes.Comment: Journal fur die Reine und Angewandte Mathematik, to appear; 64 page

A Rapid Assessment Function to Estimate Common Raven Population Densities: Implications for Targeted Management

Common raven (Corvus corax; raven) populations have increased over the past 5 decades within the western United States. Raven population increases have been largely attributed to growing resource subsidies from expansion of human enterprise. Concomitantly, managers are becoming increasingly concerned about elevated adverse effects on multiple sensitive prey species, damage to livestock and agriculture, and human safety. Managers could benefit from a rapid but reliable method to estimate raven densities across spatiotemporal scales to monitor raven populations more efficiently and inform targeted and adaptive management frameworks. However, obtaining estimates of raven density is data- and resource-intensive, which renders monitoring within an adaptive framework unrealistic. To address this need, we developed a rapid survey protocol for resource managers to estimate site-level density based on the average number of ravens per survey. Specifically, we first estimated raven densities at numerous field sites with robust distance sampling procedures and then used regression to investigate the relationship between those density estimates and the number of ravens per survey, which revealed a strong correlation (R2 = 0.86). For management application, we provide access to R function software through a web-based interface to estimate density using number of ravens per survey, which we refer to as a Rapid Assessment Function (RAF). Then, using a simulation analysis of data from sites with abundant surveys and the RAF, we estimated raven density based on different numbers of surveys to help inform how many surveys are needed to achieve reliable estimates within this rapid assessment. While more robust procedures of distance sampling are the preferred methods for estimating raven densities from count surveys, the RAF tool presented herein provides a reliable approximation for informing management decisions when managers are faced with resource and small sample size constraints

Spatial Modeling of Common Raven Density and Occurrence Helps Guide Landscape Management Within Great Basin Sagebrush Ecosystems

Common ravens (Corvus corax; ravens) are a behaviorally flexible nest predator of several avian species, including species of conservation concern. Movement patterns based on life history phases, particularly territoriality of breeding birds and transiency of nonbreeding birds, are thought to influence the frequency and efficacy of nest predation. As such, predicting where on the landscape territorial resident and non-territorial transient birds may be found in relation to the distribution of sensitive prey is of increasing importance to managers and conservationists. From 2007 to 2019, we conducted raven point count surveys between mid-March and mid-September across 43 different field sites representing typical sagebrush (Artemisia spp.) ecosystems of the Great Basin, USA. The surveys conducted during 2007–2016 were used in previously published maps of raven occurrence and density. Here, we examined the relationship between occurrence and density of ravens using spatially explicit predictions from 2 previously published studies and differentiate areas occupied by higher concentrations of resident ravens as opposed to transients. Surveys conducted during 2017–2019 were subsequently used to evaluate the predicted trends from our analytical approach. Specifically, we used residuals from a generalized linear regression to establish the relationship between occurrence and density, which ultimately resulted in a spatially explicit categorical map that identifies areas of resident versus transient ravens. We evaluated mapped categories using independently collected observed raven group sizes from the 2017–2019 survey data, as well as an independent dataset of global positioning system locations of resident and transient individuals monitored during 2019–2020. We observed moderate agreement between the mapped categories and independent datasets for both evaluation approaches. Our map provides broad inference about spatial variation in potential predation risk from ravens for species such as greater sage-grouse (Centrocercus urophasianus) and can be used as a valuable spatial layer for decision support tools aimed at guiding raven management decisions and, ultimately, improving survival and reproduction of sensitive prey within the Great Basin

Binding kinetics of ZM241385 derivatives at the human adenosine A(2A) receptor

Medicinal Chemistr

Are mice good models for human neuromuscular disease? Comparing muscle excursions in walking between mice and humans

The mouse is one of the most widely used animal models to study neuromuscular diseases and test new therapeutic strategies. However, findings from successful pre-clinical studies using mouse models frequently fail to translate to humans due to various factors. Differences in muscle function between the two species could be crucial but often have been overlooked. The purpose of this study was to evaluate and compare muscle excursions in walking between mice and humans

Controlled Radical Polymerization of Vinyl Acetate Mediated by a Bis(imino)pyridine Vanadium Complex

Source type: Prin