Aggregating the conceptualisation of movement data better captures real world and simulated animal-environment relationships

Habitat selection analysis is a widely applied statistical framework used in spatial ecology. Many of the methods used to generate movement and couple it with the environment are strongly integrated within GIScience. The choice of movement conceptualisation and environmental space can potentially have long-lasting implications on the spatial statistics used to infer movement–environment relationships. The aim of this study was to explore how systematically altering the conceptualisation of movement, environmental space and temporal resolution affects the results of habitat selection analyses using both real-world case studies and a virtual ecologist approach. Model performance and coefficient estimates did not differ between the finest conceptualisations of movement (e.g. vector and move), while substantial differences were found for the more aggregated representations (e.g. segment and area). Only segments modelled the expected movement–environment relationship with increasing linear feature resistance in the virtual ecologist approach and altering the temporal resolution identified inversions in the movement–environment relationship for vectors and moves. The results suggest that spatial statistics employed to investigate movement–environment relationships should advance beyond conceptualising movement as the (relatively) static conceptualisation of vectors and moves and replace these with (more) dynamic aggregations of longer-lasting movement processes such as segments and areal representations

Simulating movement-related resource dynamics to improve species distribution models: a case study with oilbirds in northern South America

A better understanding of the current and future distributions of organisms is a critical facet of biodiversity conservation, and species distribution models (SDMs) are an important framework for achieving this. Despite the potential of SDMs to address an array of biogeography questions, they are subject to a number of conceptual and methodological uncertainties, such as the role of animal movement processes in determining geographic ranges. Movement processes have only recently been incorporated in SDMs, predominantly conceptualized as broad-scale movement processes (e.g., dispersal), while finer scale ambulatory movements of mobile animals (e.g., foraging) have been omitted. This research addresses this gap by developing a model that simulates the dynamic relationship between movement and biotic resources (e.g., food sources) for oilbirds (Steatornis caripensis) in Venezuela. This simulation represented the sustainability of an oilbird’s neighborhood, based on the connectivity, accessibility, and viability of its biotic resources. These dynamic variables improved the accuracy and ecological realism of the SDM projection compared to other commonly applied SDM scenarios. Integration of a Lagrangian (individual-level) form of movement in SDM with step-selection functions to parameterize biased-correlated random walks provides a new empirical framework for applying geographic context to simulation

Evaluation of the role of the melanocortin receptor system in ischemia-reperfusion induced leukocyte endothelium interaction in the brain microcirculation

Leukocyte recruitment following cerebral ischemia reperfusion (I/R) has been shown to amplify inflammatory processes and enhance brain injury. Potent anti-inflammatory and neuro-protective properties have been attributed to the melanocortin receptor system, thus targeting this system may provide a novel therapeutic strategy for the treatment of stroke. Melanocortin receptor (MC) subtypes MC1, MC3 and MC4 have previously been shown to mediate MC anti-inflammatory actions, however their relative importance is poorly understood and may differ with the pathophysiological environment. In this study the bilateral common carotid artery occlusion (BCCAo) mouse model of global stroke was used with intravital microscopy to investigate the potential of melanocortin targeted compounds in modulating cerebral I/R induced leukocyte recruitment. While under basal conditions the cerebral microcirculation provides a poor substrate for leukocyte recruitment, BCCAo induced significant leukocyte recruitment by 40 min of reperfusion, with leukocyte rolling increasing from 21.5 cells/mm2/min to 191.0 cells/mm2/min and adhesion from 42.1 cells/mm2/min to 282.3 cells/mm2/min. Extending reperfusion to 2 h resulted in further increases in adhesion to 1500% of sham levels. Treatment with the non-selective melanocortin agonist, α-MSH, significantly reduced I/R induced leukocyte recruitment (Rolling by 80% at 40 min and 68% at 2 h and adhesion by 68% at 40 min and 82% at 2 h). The relative contributions of the melanocortin receptor subtypes were investigated in this model using MC selective compounds and receptor mutant mice. The MC1 selective BMS-470,539 provided most potent inhibition of leukocyte recruitment at 40 min with the MC1 mutant e/e mice also showing enhanced leukocyte rolling and circulating TNF-α, while MC3-/- mice showed no inflammatory phenotype. However by 2 h the inhibitory effects of BMS-470,539 subsided and e/e mice no longer showed abnormalities in leukocyte recruitment. On the other hand MC3 targeted compounds were highly effective at this later time point. These investigations reveal an important role for MC1 immediately following BCCAo with a later shift toward MC3 mediated processes by 2 h. Due to no observed changes in receptor mRNA and that by 2 h α-MSH treatment was found to reduce NF-κβ related gene expression but not at 40min. It is likely the apparent shift in receptor importance is due to the activation of distinct signalling pathways rather than change in receptor expression.Open Acces

Can rock-rubble groynes support similar intertidal ecological communities to natural rocky shores?

© 2020 by the authors. Despite the global implementation of rock-rubble groyne structures, there is limited research investigating their ecology, much less than for other artificial coastal structures. Here we compare the intertidal ecology of urban (or semi-urban) rock-rubble groynes and more rural natural rocky shores for three areas of the UK coastline. We collected richness and abundance data for 771 quadrats across three counties, finding a total of 81 species, with 48 species on the groynes and 71 species on the natural rocky shores. We performed three-way analysis of variance (ANOVA) on both richness and abundance data, running parallel analysis for rock and rock-pool habitats. We also performed detrended correspondence analysis on all species to identify patterns in community structure. On rock surfaces, we found similar richness and abundance across structures for algae, higher diversity and abundance for lichen and mobile animals on natural shores, and higher numbers of sessile animals on groynes. Rock-pool habitats were depauperate on groynes for all species groups except for sessile animals, relative to natural shores. Only a slight differentiation between groyne and natural shore communities was observed, while groynes supported higher abundances of some 'at risk' species than natural shores. Furthermore, groynes did not differ substantially from natural shores in terms of their presence and abundance of species not native to the area. We conclude that groynes host similar ecological communities to those found on natural shores, but differences do exist, particularly with respect to rock-pool habitats

Uncertainty analysis of step-selection functions: The effect of model parameters on inferences about the relationship between animal movement and the environment

As spatio-temporal movement data is becoming more widely available for analysis in GIS and related areas, new methods to analyze them have been developed. A step-selection function (SSF) is a recently developed method used to quantify the effect of environmental factors on animal movement. This method is gaining traction as an important conservation tool; however there have been no studies that have investigated the uncertainty associated with subjective model decisions. In this research we used two types of animals – oilbirds and hyenas – to examine how systematically altering user decisions of model parameters influences the main outcome of an SSF, the coefficients that quantify the movement-environment relationship. We found that user decisions strongly influence the results of step-selection functions and any subsequent inferences about animal movement and environmental interactions. Differences were found between categories for every variable used in the analysis and the results presented here can help to clarify the sources of uncertainty in SSF model decisions

A quantitative synthesis of how movement has been incorporated within species distribution modelling

Movement is a ubiquitous ecological process that influences the distribution of all species. In spite of this ecological significance, the incorporation of movement in species distribution models (SDMs) has lagged in comparison with other methodological and conceptual advancements. Many studies still ignore movement processes in applications inherently linked to movement (e.g. tracking changes in climate), and moreover, finer scale movements (e.g. foraging) have been neglected even more severely. We reviewed almost 600 research articles published in the last decade to identify important trends in the way that movement has been explicitly incorporated in SDM. We note that the conceptual differences associated with the ‘object’ whose movement is of interest, as well as subtler differences among taxon groups (e.g. plants v animals) and levels of organization (e.g. individuals, populations, species) that have significant implications for how movement processes occur, have hindered more substantial integration of these concepts. Finally, we highlight novel and unique methodological issues such as the use of successive telemetry data as response data in these correlative models. The gaps and trends identified in this review should foster future research in this burgeoning research area

Reactor Start‐up and Control Methodologies: Consideration of the Space Radiation Environment

The use of fission energy in space power and propulsion systems offers considerable advantages over chemical propulsion. Fission provides over six orders of magnitude higher energy density, which translates to higher vehicle specific impulse and lower specific mass. These characteristics enable the accomplishment of ambitious space exploration missions. The natural radiation environment in space provides an external source of protons and high energy, high Z particles that can result in the production of secondary neutrons through interactions in reactor structures. Initial investigation using MCNPX 2.5.b for proton transport through the SAFE‐400 reactor indicates a secondary neutron net current of 1.4×107 n/s at the core‐reflector interface, with an incoming current of 3.4×106 n/s due to neutrons produced in the Be reflector alone. This neutron population could provide a reliable startup source for a space reactor. Additionally, this source must be considered in developing a reliable control strategy during reactor startup, steady‐state operation, and power transients. An autonomous control system is developed and analyzed for application during reactor startup, accounting for fluctuations in the radiation environment that result from changes in vehicle location (altitude, latitude, position in solar system) or due to temporal variations in the radiation field, as may occur in the case of solar flares. One proposed application of a nuclear electric propulsion vehicle is in a tour of the Jovian system, where the time required for communication to Earth is significant. Hence, it is important that a reactor control system be designed with feedback mechanisms to automatically adjust to changes in reactor temperatures, power levels, etc., maintaining nominal operation without user intervention. This paper will evaluate the potential use of secondary neutrons produced by proton interactions in the reactor vessel as a startup source for a space reactor and will present a potential control methodology for reactor startup procedures in the event of source fluctuations. © 2004 American Institute of PhysicsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87576/2/614_1.pd

Advancing beyond static representations of movement in spatial analysis

Methods used to generate movement and couple it with the environment are strongly integrated within GIScience. This study explores how systematically altering the conceptualisation of movement, environmental space, and temporal resolution affects the results of habitat selection analyses using both real-world case studies and simulated data. Only segment conceptualisations modelled the expected movement-environment relationship with increasing linear feature resistance. This suggests that spatial statistics employed to investigate movement-environment relationships should advance beyond conceptualising movement as the (relatively) static conceptualisation of vectors and moves and replace these with (more) dynamic aggregations of longer-lasting movement processes such as segments and areal representations

Miniature Neutron‐Alpha Activation Spectrometer

We are developing a miniature neutron‐alpha activation spectrometer for in‐situ analysis of chem‐bio samples, including rocks, fines, ices, and drill cores, suitable for a lander or Rover platform for Mars or outer‐planet missions. In the neutron‐activation mode, penetrating analysis will be performed of the whole sample using a γ spectrometer and in the α‐activation mode, the sample surface will be analyzed using Rutherford‐backscatter and x‐ray spectrometers. Novel in our approach is the development of a switchable radioactive neutron source and a small high‐resolution γ detector. The detectors and electronics will benefit from remote unattended operation capabilities resulting from our NEAR XGRS heritage and recent development of a Ge γ detector for MESSENGER. Much of the technology used in this instrument can be adapted to portable or unattended terrestrial applications for detection of explosives, chemical toxins, nuclear weapons, and contraband. © 2002 American Institute of PhysicsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87580/2/101_1.pd