Methodological Problems in the Modeling and Analysis of Ecological Systems

I would like to give you an overview of basic ecological modeling and analysis problems by discussing three things. First, I will try to explain the general attitude of systems-oriented ecologists towards their subject matter. This is a different perspective from that of many here, and we will almost certainly fail to understand each other if you imagine us to be, say, economists with an interest in animals. Second, I will review those structural characteristics of ecological systems which have made their analysis particularly difficult. We like to think that it is at least in part these difficulties which have kept us rather behind the rest of you in a number of methods-related areas. Finally, I'll give a brief picture of the kinds of dynamic and stability behavior which we encounter in real and model ecological systems, using as examples cases presently under investigation at IIASA and' available for study at this workshop

Exploring joint hypermobility syndrome, developmental coordination disorder and pain

INTRODUCTION Floppy, clumsy, hypermobile children are increasingly referred to occupational and physical therapy under the label of dyspraxia. Motor impairments associated with the umbrella diagnosis of developmental coordination disorder (DCD) have been reported as persisting into adolescence and adulthood and subsequently affecting functional abilities (Cousins and Smyth 2003). Within this heterogeneous condition the underlying mechanisms causing the motor difficulties remains unclear. Ayers (1985) hypothesised that some individuals might have somatosensory processing issues contributing to their poor motor planning and coordination difficulties. Similarities in functional difficulties have been noted in children with a diagnosis of DCD and joint hypermobility syndrome (JHS) (Kirby and Davies 2006). There is limited understanding of the relationship between the two conditions. JHS is a multisystemic inherited connective tissue disorder, in which hypermobile joints, pain, clumsiness, poor proprioception and dislocations are familiar features (Grahame and Hakim 2006; Adib et al 2005). It has been suggested that adults with JHS show poor movement patterns which contribute to biomechanical dysfunction and continuing pain (Clark et al 2009). Pain and disability reported in adults with JHS often leads to anxiety, depression, work incapacity and social isolation (Grahame and Hakim 2006). The purpose of this study was to explore the association between adults with JHS and DCD and long term pain. METHODOLOGY/ METHODS A mixed methods design influenced by a pragmatic paradigm was utilised. Subjects: 90 patients with JHS (18-65 years) recruited from a hypermobility clinic were compared, using a questionnaire, with 113 healthy volunteers (18-65 years) with no pain recruited from a university. Analysis: Quantitative data were described and examined by regression, odds ratios were calculated. Qualitative data was analysed thematically FINDINGS The percentage of subjects who reported DCD in patients with JHS and healthy volunteers were 56% and 19% respectively. A significant association between patients with JHS and DCD was noted, chi square = 30.11, p < .001. Patients with JHS were 6 times [95% CI 2.9 – 10.3] more likely to report DCD than healthy volunteers. Pain was a significant feature with an average of 9.8 pain sites reported (out of a total of 17). Open ended questions revealed many patients recalling pain starting in early childhood and adolescence. DISCUSSION These results suggest a significant association between patients with JHS and DCD and the reporting of long term pain. Early recognition and understanding of the needs of children with DCD who present with somatosensory impairment, pain modulation and JHS is therefore essential. Sensory integration therapy as part of a comprehensive early intervention program has the potential to mitigate long term problems. A multidisciplinary approach which involves health professionals and teachers is also recommended. CONCLUSION This research may be considered an early step in the identification of an association of DCD and JHS. Further studies are required to explore somatosensory processing issues experienced by those with DCD and JHS as this might be an important underlying mechanism

Fibroblast migration and collagen deposition during dermal wound healing: mathematical modelling and clinical implications,

The extent to which collagen alignment occurs during dermal wound healing determines the severity of scar tissue formation. We have modelled this using a multiscale approach, in which extracellular materials, for example collagen and fibrin, are modelled as continua, while fibroblasts are considered as discrete units. Within this model framework, we have explored the effects that different parameters have on the alignment process, and we have used the model to investigate how manipulation of transforming growth factor-β levels can reduce scar tissue formation. We briefly review this body of work, then extend the modelling framework to investigate the role played by leucocyte signalling in wound repair. To this end, fibroblast migration and collagen deposition within both the wound region and healthy peripheral tissue are considered. Trajectories of individual fibroblasts are determined as they migrate towards the wound region under the combined influence of collagen/fibrin alignment and gradients in a paracrine chemoattractant produced by leucocytes. The effects of a number of different physiological and cellular parameters upon the collagen alignment and repair integrity are assessed. These parameters include fibroblast concentration, cellular speed, fibroblast sensitivity to chemoattractant concentration and chemoattractant diffusion coefficient. Our results show that chemoattractant gradients lead to increased collagen alignment at the interface between the wound and the healthy tissue. Results show that there is a trade-off between wound integrity and the degree of scarring. The former is found to be optimized under conditions of a large chemoattractant diffusion coefficient, while the latter can be minimized when repair takes place in the presence of a competitive inhibitor to chemoattractants

Exploiting orbital constraints from optical data to detect binary gamma-Ray pulsars

It is difficult to discover pulsars via their gamma-ray emission because current instruments typically detect fewer than one photon per million rotations. This creates a significant computing challenge for isolated pulsars, where the typical parameter search space spans wide ranges in four dimensions. It is even more demanding when the pulsar is in a binary system, where the orbital motion introduces several additional unknown parameters. Building on earlier work by Pletsch & Clark, we present optimal methods for such searches. These can also incorporate external constraints on the parameter space to be searched, for example, from optical observations of a presumed binary companion. The solution has two parts. The first is the construction of optimal search grids in parameter space via a parameter space metric, for initial semicoherent searches and subsequent fully coherent follow-ups. The second is a method to demodulate and detect the periodic pulsations. These methods have different sensitivity properties than traditional radio searches for binary pulsars and might unveil new populations of pulsars. © 2020. The Author(s). Published by the American Astronomical Society

Abstract: Pain poses a significant health burden in those with Joint Hypermobility Syndrome

Background Joint hypermobility Syndrome (JHS) is a complex multisystemic connective tissue disorder. JHS is acknowledged as a common clinical entity in musculoskeletal medicine with a prevalence of between 30%-60% in those presenting with musculoskeletal pain. It is more prevalent in females than males may present in childhood and shares symptom overlap with Ehlers-Danlos Syndrome, Marfan Syndrome and Ostegenesis Imperfecta. Patients with JHS report a variety of symptoms associated with this condition. These symptoms include: chronic pain, dislocations, impaired coordination, autonomic nervous system (ANS) and Gastrointestinal (GI) symptoms. Aims The purpose of this study was to investigate the health burden in those with JHS and to understand which symptoms are considered to be most troublesome. Methods A sample of 89 patients with JHS (mean age 34.6 ± 9.9 years, 82 female), diagnosed by a consultant rheumatologist according to the Brighton Criteria were compared with 113 healthy volunteers (mean age 35.7 ± 12.9, 82 female) with no musculoskeletal pain. Information relating to dislocations, ANS, GI symptoms and impaired coordination was collected by means of a self-report questionnaire. Data relating to the reporting of pain for >3 months was collected on a pain chart and the SF-12 was employed for assessing quality of life. SF-12 data is reported as Physical Component Summary (PCS) scores and Mental Component Summary (MCS) Scores. A difference in either the PCS or MCS scores of 5 points is considered to be a clinically important difference. Numerical data were analysed using independent sample t-tests and regression analysis. Results Patients with JHS reported significantly lower mean PCS scores (M = 29.70 SD 10.63) than healthy volunteers (M = 54.45 SD 5.74), t (127.701) = 19.81, p<0.001 (2-tailed). The mean difference was 24.75 points [95%CI 22.44 - 27.06] - a statistically significant and clinically important difference. Patients with JHS were significantly more likely to report the following than healthy volunteers; subluxations/dislocations, GI and ANS symptoms and impaired coordination. The average number of pain sites reported was 10/17. Regression analysis of the reported symptoms revealed the number of pain sites as the only significant predictor of a lowered PCS score (p< 0.01) in a model explaining 23% of the variance. MCS scores of patients with JHS (M = 41.13 SD 11.60) were significantly lower than those of healthy volunteers (M = 45.64 SD 10.95), t (200) = 2.65, p<0.01. The mean difference was <5 points - this might not be clinically important. Conclusion Patients with JHS in this study reported a statistically significant reduction in both PCS and MCS scores compared with healthy volunteers. The large difference in PCS scores is likely to be clinically important. Although multisystemic symptoms were reported multisite pain was the only symptom which contributed significantly to a lowered PCS score of the SF-12. This study high lights the health and personal burden of those with JHS and the importance of recognising and understanding the contribution of multisite pain in this population

Correlation of the Functional Difficulties Questionnaire (FDQ-9) with dynamic balance using the SMART instrumented wobbleboard

Objectives : To investigate concurrent validity of the Functional Difficulties Questionnaire (FDQ-9) using balance tasks on the SMARTwobbleboard . Poor balance is associated with reduced physical activity which may impact on quality of life. There is a requirement to use simple tests to assess balance so that suitable interventions can be employed to ameliorate poor balance and enhance uptake of physical activity. Design: Observational study employing 30 healthy volunteers who completed the FDQ-9 and undertook three balance tasks on the SMARTwobbleboard: double leg stance eyes open (DLSEO); double leg stance eyes closed (DLSEC) and single leg stance eyes open (SLSEO). Results: There were moderate significant correlations between the FDQ-9 and DLSEO and SLSEO. There were significant between group differences in dynamic balance for participants with FDQ-9 ≤ 18 (indicative of no functional difficulties) and FDQ-9 ≥ 19 (indicative of one or more functional difficulties) for DLSEO and SLSEO. Conclusions: Significant moderate correlations were recorded between the FDQ-9 and the SMARTwobbleboard in healthy adults indicating a relationship between dynamic balance and questionnaire scores (DLSEO and SLSEO). Initial findings contribute to the concurrent validity of the FDQ-9 which could also be used as a simple tool for assessing balance

Self-consistent description of nuclear compressional modes

Isoscalar monopole and dipole compressional modes are computed for a variety of closed-shell nuclei in a relativistic random-phase approximation to three different parametrizations of the Walecka model with scalar self-interactions. Particular emphasis is placed on the role of self-consistency which by itself, and with little else, guarantees the decoupling of the spurious isoscalar-dipole strength from the physical response and the conservation of the vector current. A powerful new relation is introduced to quantify the violation of the vector current in terms of various ground-state form-factors. For the isoscalar-dipole mode two distinct regions are clearly identified: (i) a high-energy component that is sensitive to the size of the nucleus and scales with the compressibility of the model and (ii) a low-energy component that is insensitivity to the nuclear compressibility. A fairly good description of both compressional modes is obtained by using a ``soft'' parametrization having a compression modulus of K=224 MeV.Comment: 28 pages and 10 figures; submitted to PR

First measurement of the total gravitational quadrupole moment of a black widow companion

We present the first measurement of the gravitational quadrupole moment of the companion star of a spider pulsar, namely the black widow PSR J2051–0827. To this end, we have re-analysed radio timing data using a new model that is able to account for periastron precession caused by tidal and centrifugal deformations of the star as well as by general relativity. The model allows for a time-varying component of the quadrupole moment, thus self-consistently accounting for the ill-understood orbital period variations observed in these systems. Our analysis results in the first detection of orbital precession in a spider system at ω˙=−68∘.6+0∘.9−0∘.5 yr−1 and the most accurate determination of orbital eccentricity for PSR J2051–0827 with e = (4.2 ± 0.1) × 10−5. We show that the variable quadrupole component is about 100 times smaller than the average quadrupole moment Q¯=−2.2+0.6−1×1041 kgm2⁠. We discuss how accurate modelling of high-precision optical light curves of the companion star will allow its apsidal motion constant to be derived from our results

Is the Black-widow Pulsar PSR J1555-2908 in a Hierarchical Triple System?

The 559 Hz black-widow pulsar PSR J1555-2908, originally discovered in radio, is also a bright gamma-ray pulsar. Timing its pulsations using 12 yr of Fermi-Large Area Telescope gamma-ray data reveals long-term variations in its spin frequency that are much larger than is observed from other millisecond pulsars. While this variability in the pulsar rotation rate could be intrinsic "timing noise,"here we consider an alternative explanation: the variations arise from the presence of a very-low-mass third object in a wide multiyear orbit around the neutron star and its low-mass companion. With current data, this hierarchical-triple-system model describes the pulsar's rotation slightly more accurately than the best-fitting timing noise model. Future observations will show if this alternative explanation is correct. © 2022. The Author(s). Published by the American Astronomical Society

An Exploration of Neurophysiological Symptoms in Patients with Joint Hypermobility Syndrome and their Impact on Quality of Life.

Purpose: The purpose of this study was to explore the prevalence of neurophysiological symptoms in patients with Joint Hypermobility Syndrome (JHS) and their impact on quality of life. Relevance: Clinical experience suggests patients with JHS suffer from neurophysiological symptoms contributing to skill and health impairments affecting quality of life. MethodsA sample of 90 JHS-patients (mean age 34.7 ± 9.9 years), diagnosed according to the Brighton Criteria were compared with 113 healthy volunteers (mean age 35.7 ± 12.9) with no musculoskeletal pain. Neurophysiological symptoms were collected in a self report questionnaire. The Functional Difficulties Questionnaire was used for the assessment of developmental coordination disorder (DCD). A pain chart was employed to collect data relating to musculoskeletal pain. The SF-12 medical outcomes questionnaire was used for assessing quality of life. Analysis: Chi-square was employed to compare group proportions. Continuous numerical data comparisons were analysed using independent sample t-tests. Regression analysis was employed to analyse multiple variables. Results: Patients with JHS were significantly more likely to report the following than healthy volunteers; autonomic symptoms (70%, 12%); gastrointestinal symptoms (71%, 9%); DCD (56%, 19%) and chronic fatigue syndrome (31%, 1%). The mean number of pain sites reported for patients with JHS were 9.83 ± 4.18. Patients with JHS reported significantly lower physical component summary scores (PCS) of the SF-12 than healthy volunteers (p < 0.001). Pain was a significant predictor of reduced PCS of the SF-12 (p < 0.001) in a model that explained 23% of the variance. Conclusions Neurophysiological symptoms were common. Pain was a significant contributor to the health burden of patients with JHS. Research is required to explore the connectivity and implications of these symptoms in relation to the central nervous system. Implications: There is a requirement to acknowledge and understand the multidimensional nature of JHS