Space race functional responses

We derive functional responses under the assumption that predators and prey are engaged in a space race in which prey avoid patches with many predators and predators avoid patches with few or no prey. The resulting functional response models have a simple structure and include functions describing how the emigration of prey and predators depend on interspecific densities. As such, they provide a link between dispersal behaviors and community dynamics. The derived functional response is general but is here modeled in accordance with empirically documented emigration responses. We find that the prey emigration response to predators has stabilizing effects similar to that of the DeAngelis-Beddington functional response, and that the predator emigration response to prey has destabilizing effects similar to that of the Holling type II response. A stabiliy criterion describing the net effect of the two emigration responses on a Lotka-Volterra predator-prey system is presented. The winner of the space race (i.e. whether predators or prey are favoured) is determined by the relationship between the slopes of the species- migration responses. It is predicted that predators win the space race in poor habitats, where predator and prey densities are low, and that prey are more successful in richer habitats

Predicting the number of COVID-19 cases from the reported number of deaths

The new corona virus disease 2019 (COVID-2019) is rapidly spreading through the world. With insufficient testing, available case data may underestimate the total number of infections. We statistically estimated the cumulative number of cases with confidence intervals from the reported number of deaths, assuming that the number of infections grow exponentially with a constant doubling time. Our findings indicate that the number of unreported infections is likely at least one order of magnitude higher than the reported cases, in particular in the United States and the United Kingdom. This finding is supported by a recent mass screening for SARS-CoV-2 in Iceland which found that the actual case numbers may be about 20 times higher than the officially reported number

The Formation of Structured Cooperative Communities

A society relying upon public goods must avoid a tragedy of the commons; it will otherwise wither owing to the collapse of cooperative enterprises. This long recognized phenomenon has repeatedly caught the attention of thinkers across a variety of fields. Game theory has, through stylized quantitative models, served to unfold core processes governing the nature of cooperation on public goods. While caught between oversimplification and intractability, research is pushing to understand cooperation in complex systems. Large organizational units, such as whole communities, are typically subdivided into a multiple of different localized groups between which individuals may transfer. Although the group structure of such heterogeneous units is known to be important to the success of cooperation, knowledge on how group structures dynamically unfold and develop jointly with cooperative efforts is limited. Public economist Charles Tiebout suggested in 1956 that foot voting as an inter-group migration behavior could constitute a powerful bottom-up solution to the free-rider problem in local governance, as he believed that large communities would self-organize into an optimal type of group-structure. We apply evolutionary game-theory to social group-formation, and find that foot voting spontaneously emerges in large self-organized, public-goods communities. In turn, the emergence of foot voting makes way for cooperation to develop in non-cooperative communities which transform into highly cooperative group-structured societies. As such, the Tiebout hypothesis gets support in evolutionary game theory, and at the same time is revealed as an example of a wider concept, as it builds on a sorting principle that appears inevitable and that may represent a general mechanism for triggering invasion of altruism, potentially at many, and much more basic, levels of social and biological organization

Insertion and Deletion Processes in Recent Human History

Background: Although insertions and deletions (indels) account for a sizable portion of genetic changes within and among species, they have received little attention because they are difficult to type, are alignment dependent and their underlying mutational process is poorly understood. A fundamental question in this respect is whether insertions and deletions are governed by similar or different processes and, if so, what these differences are. Methodology/Principal Findings: We use published resequencing data from Seattle SNPs and NIEHS human polymorphism databases to construct a genomewide data set of short polymorphic insertions and deletions in the human genome (n = 6228). We contrast these patterns of polymorphism with insertions and deletions fixed in the same regions since the divergence of human and chimpanzee (n = 10546). The macaque genome is used to resolve all indels into insertions and deletions. We find that the ratio of deletions to insertions is greater within humans than between human and chimpanzee. Deletions segregate at lower frequency in humans, providing evidence for deletions being under stronger purifying selection than insertions. The insertion and deletion rates correlate with several genomic features and we find evidence that both insertions and deletions are associated with point mutations. Finally, we find no evidence for a direct effect of the local recombination rate on the insertion and deletion rate. Conclusions/Significance: Our data strongly suggest that deletions are more deleterious than insertions but that insertion

On a modified-Lorentz-transformation based gravity model confirming basic GRT experiments

Implementing Poincar\'e's `geometric conventionalism' a scalar Lorentz-covariant gravity model is obtained based on gravitationally modified Lorentz transformations (or GMLT). The modification essentially consists of an appropriate space-time and momentum-energy scaling ("normalization") relative to a nondynamical flat background geometry according to an isotropic, nonsingular gravitational `affecting' function Phi(r). Elimination of the gravitationally `unaffected' S_0 perspective by local composition of space-time GMLT recovers the local Minkowskian metric and thus preserves the invariance of the locally observed velocity of light. The associated energy-momentum GMLT provides a covariant Hamiltonian description for test particles and photons which, in a static gravitational field configuration, endorses the four `basic' experiments for testing General Relativity Theory: gravitational i) deflection of light, ii) precession of perihelia, iii) delay of radar echo, iv) shift of spectral lines. The model recovers the Lagrangian of the Lorentz-Poincar\'e gravity model by Torgny Sj\"odin and integrates elements of the precursor gravitational theories, with spatially Variable Speed of Light (VSL) by Einstein and Abraham, and gravitationally variable mass by Nordstr\"om.Comment: v1: 14 pages, extended version of conf. paper PIRT VIII, London, 2002. v2: section added on effective tensorial rank, references added, appendix added, WEP issue deleted, abstract and other parts rewritten, same results (to appear in Found. Phys.

A Method for Estimating the Number of Infections From the Reported Number of Deaths

At the outset of an epidemic, available case data typically underestimate the total number of infections due to insufficient testing, potentially hampering public responses. Here, we present a method for statistically estimating the true number of cases with confidence intervals from the reported number of deaths and estimates of the infection fatality ratio; assuming that the time from infection to death follows a known distribution. While the method is applicable to any epidemic with a significant mortality rate, we exemplify the method by applying it to COVID-19. Our findings indicate that the number of unreported COVID-19 infections in March 2020 was likely to be at least one order of magnitude higher than the reported cases, with the degree of underestimation among the countries considered being particularly high in the United Kingdom

Population-level consequences of heterospecific density-dependent movements in predator-prey systems

In this paper we elucidate how small-scale movements, such as those associated with searching for food and avoiding predators, affect the stability of predator-prey dynamics. We investigate an individual-based Lotka-Volterra model with density dependent movement, in which the predator and prey populations live in a very large number of coupled patches. The rates at which individuals leave patches depend on the local densities of heterospecifics, giving rise to one reaction norm for each of the two species. Movement rates are assumed to be much faster than demographics rates. A spatial structure of predators and prey emerges which affects the global population dynamics. We derive a criterion which reveals how demograhic stability depends on the relationships between the per capita covariance and densities of predators and prey. Specifically we establish that a positive relationship with prey density and a negative relationship with predator density tend to be stabilizig. On a more mechanistic level we show how these relationships are linked to the movement reaction norms of predators and prey. Numerical results show that these findings hold both for local and global movements, i.e., both when migration is biased towards neighboring patches and when all patches are reached with equal probability

Objectively measured movement asymmetry in yearling Standardbred trotters

Background Lameness evaluation of Standardbred trotters can be challenging due to discrepancies in observed movement asymmetry between in-hand and track exercise, and between different trotting speeds. There are few studies on objective measurement of movement in Standardbreds, and little knowledge regarding biological variation and clinical significance of measured movement asymmetry in this breed. Objectives To quantify the prevalence and magnitude of objectively measured movement asymmetry in young Standardbred trotters, and identify associations with trainer, sex, height, track type and in-hand measurement prior to or after track trials. Study design Cross-sectional, observational study. Methods A total of 114 Standardbred yearlings were evaluated with a wireless inertial sensor system during trot in-hand and when driven on a track. After exclusions relating to lameness or technical difficulties, 103 horses were included in the study; 77 were evaluated in-hand and on the track, 24 only in-hand and 2 only on the track. Results Front and/or hindlimb parameters were above asymmetry thresholds previously established for other breeds during in-hand trials for 94 (93%) horses and during track trials for 74 (94%) horses. Most horses showed mild asymmetry. A minority of horses (20%) switched side of the asymmetry for one or more parameters between in-hand and track trials. Mixed model analyses revealed no significant effects of trial mode (in-hand or track trial, in-hand trial pre- or post-track trial, straight or oval track), trainer or horse height. Females had a significant but small reduction in asymmetry in one front limb parameter (HDmax) compared with males (1.7 mm, 95% CI 0.18-3.28,P = .03). Main limitations High data variability, reflected in large trial standard deviations, relating mainly to a lack of horse compliance. Conclusions A high proportion of Standardbred yearlings showed movement asymmetries. There was no group-level effect between in-hand and track trials, however, considerable individual variation was observed

Endo-lysosomal proteins and ubiquitin CSF concentrations in Alzheimer's and Parkinson's disease

BACKGROUND: Increasing evidence implicates dysfunctional proteostasis and the involvement of the autophagic and endo-lysosomal system and the ubiquitin-proteasome system in neurodegenerative diseases. In Alzheimer's disease (AD), there is an accumulation of autophagic vacuoles within the neurons. In Parkinson's disease (PD), susceptibility has been linked to genes encoding proteins involved in autophagy and lysosomal function, as well as mutations causing lysosomal disorders. Furthermore, both diseases are characterized by the accumulation of protein aggregates. METHODS: Proteins associated with endocytosis, lysosomal function, and the ubiquitin-proteasome system were identified in the cerebrospinal fluid (CSF) and targeted by combining solid-phase extraction and parallel reaction monitoring mass spectrometry. In total, 50 peptides from 18 proteins were quantified in three cross-sectional cohorts including AD (N = 61), PD (N = 21), prodromal AD (N = 10), stable mild cognitive impairment (N = 15), and controls (N = 68). RESULTS: A pilot study, including subjects selected based on their AD CSF core biomarker concentrations, showed increased concentrations of several targeted proteins in subjects with core biomarker levels indicating AD pathology compared to controls. Next, in a clinically characterized cohort, lower concentrations in CSF of proteins in PD were found compared to subjects with prodromal AD. Further investigation in an additional clinical study again revealed lower concentrations in CSF of proteins in PD compared to controls and AD. CONCLUSION: In summary, significantly different peptide CSF concentrations were identified from proteins AP2B1, C9, CTSB, CTSF, GM2A, LAMP1, LAMP2, TCN2, and ubiquitin. Proteins found to have altered concentrations in more than one study were AP2B1, CTSB, CTSF, GM2A, LAMP2, and ubiquitin. Interestingly, given the genetic implication of lysosomal function in PD, we did identify the CSF concentrations of CTSB, CTSF, GM2A, and LAMP2 to be altered. However, we also found differences in proteins associated with endocytosis (AP2B1) and the ubiquitin-proteasome system (ubiquitin). No difference in any peptide CSF concentration was found in clinically characterized subjects with AD compared to controls. In conclusion, CSF analyses of subjects with PD suggest a general lysosomal dysfunction, which resonates well with recent genetic findings, while such changes are minor or absent in AD

Adaptation strategies of the Icelandic horse with induced forelimb lameness at walk, trot and tölt

Background and objective Lameness assessment in the gaited Icelandic horse is complex. We aimed to describe their kinematic and temporal adaptation strategies in response to forelimb lameness at walk, trot and tolt.Study designIn vivo experiment.Methods Ten clinically non-lame Icelandic horses were measured before and after reversible forelimb lameness induction. Upper body and limb kinematics were measured using 11 inertial measurement units mounted on the poll, withers, pelvis (tubera sacrale) and all four limbs and hoofs (Equimoves (R), 500 Hz). Horses were measured on a straight line at walk and trot in-hand and at walk, trot and tolt while ridden. Linear mixed models were used to compare baseline and lame conditions (random factor = 'horse'), and results are presented as the difference in estimated marginal means or percentage of change.Results Lameness induction significantly (p < 0.05) increased head vertical movement asymmetry at walk (HDmin/HDmaxHAND: 18.8/5.7 mm, HDmin/HDmaxRIDDEN: 9.8/0.3 mm) and trot (HDmin/HDmaxHAND: 18.1/7.8 mm, HDmin/HDmaxRIDDEN: 24.0/9.3 mm). At the tolt, however, HDmin did not change significantly (1.1 mm), but HDmax increased by 11.2 mm (p < 0.05). Furthermore, pelvis vertical movement asymmetry (PDmax) increased by 4.9 mm, sound side dissociation decreased (-8.3%), and sound diagonal dissociation increased (6.5%). Other temporal stride variables were also affected, such as increased stance duration of both forelimbs at walk, tolt and in-hand trot.Main limitations Only one degree of lameness (mild) was induced with an acute lameness model.Conclusions Classical forelimb lameness metrics, such as vertical head and withers movement asymmetry, were less valuable at tolt compared to walk and trot, except for HDmax. Therefore, it is advised to primarily use the walk and trot to detect and quantify forelimb lameness in the Icelandic horse