Mechanics of extended masses in general relativity

The "external" or "bulk" motion of extended bodies is studied in general relativity. Compact material objects of essentially arbitrary shape, spin, internal composition, and velocity are allowed as long as there is no direct (non-gravitational) contact with other sources of stress-energy. Physically reasonable linear and angular momenta are proposed for such bodies and exact equations describing their evolution are derived. Changes in the momenta depend on a certain "effective metric" that is closely related to a non-perturbative generalization of the Detweiler-Whiting R-field originally introduced in the self-force literature. If the effective metric inside a self-gravitating body can be adequately approximated by an appropriate power series, the instantaneous gravitational force and torque exerted on it is shown to be identical to the force and torque exerted on an appropriate test body moving in the effective metric. This result holds to all multipole orders. The only instantaneous effect of a body's self-field is to finitely renormalize the "bare" multipole moments of its stress-energy tensor. The MiSaTaQuWa expression for the gravitational self-force is recovered as a simple application. A gravitational self-torque is obtained as well. Lastly, it is shown that the effective metric in which objects appear to move is approximately a solution to the vacuum Einstein equation if the physical metric is an approximate solution to Einstein's equation linearized about a vacuum background.Comment: 39 pages, 2 figures; fixed equation satisfied by the Green function used to construct the effective metri

The Strategic Development of Irish Livestock Marts.

End of Project ReportA study of co-operative livestock marts revealed that cumulative marts turnover decreased by 26% from 1990 to 1999: Commission income as a percentage of turnover increased from 2% in 1990 to 3.2% in 1999. However operating expenses increased by 25% from 1990 to 1999. Operating expenses have since 1997, surpassed commision income, thus putting co-op marts in a collective loss making situation from their mart activities. However overall profit from co-op mart societies (including profit generated from all business activities) almost doubled between 1990 and 1999. While overall profitability of livestock marts societies has increased, twelve of thirty nine marts were in a loss making situation in 1999. Four of these marts have been in a permanent loss - making situation since 1990. All loss making societies in 1999 have little or no involvement in non-mart activities and almost all operate from just one site. In general, the large diversified societies are showing profitability. A number of strategic alternatives to deal with their situation were placed before mart executives. A diversification strategy is by far the most likely strategy to be adopted by marts for the future Most marts are unlikely to consider merging with other societies. Most marts have no plans to downsize and exit from the industry is not considered an option by any society. There is a recognition that there is an urgent need to rationalise the industry, but this strategy is likely to meet with a strong resistance from marts . A problem with rationalisation is that there are no incentives to make this strategy a reality. On the one hand, management would be reluctant to follow this approach, as it may be perceived to reflect badly on their own performance or may result in them being forced to seek alternative employment. On the other hand, the shareholders have little to gain and much to lose if the mart closes. Projections of past trends and impact of new policies would suggest continuing decline in turnover and profitability in the co-operative mart sector. Rationalisation is therefore absolutely essential. The industry cannot sustain the present number of marts. Diversification seems the most obvious option for the future of the industry. In general marts that have diversified are profitable and there is no reason why this trend cannot continue into the future

How geckos stick in nature: ecology and biomechanics of gecko feet

Phenotype and performance play a fundamental role in evolution and ecology. Studies of form and function often use correlations between morphology, performance, and habitat use to examine patterns of ecomorphology and morphological adaptation. Geckos, of the taxonomic group Gekkota, are an understudied yet diverse clade of lizards in which studies of form and function would greatly improve our understanding of their evolution. Geckos have the rather unique trait of adhesive toe pads, enabling them to use arboreal and rocky environments in a way few other creatures can. Gecko toe pad morphology and adhesive abilities are highly variable across species, suggesting ecological adaptations may have driven their evolution, yet few studies has considered gecko adhesive morphology and performance in an ecological context. In this study, we quantified morphology, adhesive performance, and habitat use of 13 gecko species from Queensland, Australia including tropical, arid, arboreal, and rock-dwelling species. We found toe detachment angle to be correlated with residual limb length. We also found residual limb length to be correlated with the use of arboreal and rock microhabitats as well as negatively correlated with perch diameter. This study is one of the first examples investigating gecko adhesive performance and specific microhabitat parameters. We suggest additional comparative studies investigating gecko limb kinematics and setal mechanics to corroborate our observational results

Spatial Scaling in Model Plant Communities

We present an analytically tractable variant of the voter model that provides a quantitatively accurate description of beta-diversity (two-point correlation function) in two tropical forests. The model exhibits novel scaling behavior that leads to links between ecological measures such as relative species abundance and the species area relationship.Comment: 10 pages, 3 figure

Altered fMRI restingâ state connectivity in individuals with fibromyalgia on acute pain stimulation

BackgroundFibromyalgia is a chronic widespread pain condition, with patients commonly reporting other symptoms such as sleep difficulties, memory complaints and fatigue. The use of magnetic resonance imaging (MRI) in fibromyalgia has allowed for the detection of neural abnormalities, with alterations in brain activation elicited by experimental pain and alterations in resting state connectivity related to clinical pain.MethodsIn this study, we sought to monitor state changes in resting brain connectivity following experimental pressure pain in fibromyalgia patients and healthy controls. Twelve fibromyalgia patients and 15 healthy controls were studied by applying discrete pressure stimuli to the thumbnail bed during MRI. Restingâ state functional MRI scanning was performed before and immediately following experimental pressure pain. We investigated changes in functional connectivity to the thalamus and the insular cortex.ResultsAcute pressure pain increased insula connectivity to the anterior cingulate and the hippocampus. Additionally, we observed increased thalamic connectivity to the precuneus/posterior cingulate cortex, a known part of the default mode network, in patients but not in controls. This connectivity was correlated with changes in clinical pain.ConclusionsThese data reporting changes in restingâ state brain activity following a noxious stimulus suggest that the acute painful stimuli may contribute to the alteration of the neural signature of chronic pain.What does this study/add?In this study acute pain application shows an echo in functional connectivity and clinical pain changes in chronic pain.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/122449/1/ejp832_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/122449/2/ejp832.pd

Resting state connectivity correlates with drug and placebo response in fibromyalgia patients

AbstractFibromyalgia is a chronic pain syndrome characterized by widespread pain, fatigue, and memory and mood disturbances. Despite advances in our understanding of the underlying pathophysiology, treatment is often challenging. New research indicates that changes in functional connectivity between brain regions, as can be measured by magnetic resonance imaging (fcMRI) of the resting state, may underlie the pathogenesis of this and other chronic pain states. As such, this parameter may be able to be used to monitor changes in brain function associated with pharmacological treatment, and might also be able to predict treatment response.We performed a resting state fcMRI trial using a randomized, placebo-controlled, cross-over design to investigate mechanisms of action of milnacipran (MLN), a selective serotonin and norepinephrine reuptake inhibitor (SNRI), in fibromyalgia patients. Our aim was to identify functional connectivity patterns at baseline that would differentially predict treatment response to MLN as compared to placebo. Since preclinical studies of MLN suggest that this medication works by augmenting antinociceptive processes, we specifically investigated brain regions known to be involved in pain inhibition.15 fibromyalgia patients completed the study, consisting of 6 weeks of drug and placebo intake (order counterbalanced) with an interspersed 2 week wash out period. As a main finding we report that reductions in clinical pain scores during MLN were associated with decreased functional connectivity between pro-nociceptive regions and antinociceptive pain regions at baseline, specifically between the rostral part of the anterior cingulate cortex (ACC) and the insular cortex (IC), as well as between the periaqueductal gray (PAG) and the IC: patients with lower preexisting functional connectivity had the greatest reduction in clinical pain. This pattern was not observed for the placebo period. However a more robust placebo response was associated with lower baseline functional connectivity between the ACC and the dorsolateral prefrontal cortex.This study indicates that ACC–IC connectivity might play a role in the mechanism of action of MLN, and perhaps more importantly fcMRI might be a useful tool to predict pharmacological treatment response