Effects of periodic forcing on a Paleoclimate delay model

This is final version. Available from SIAM via the DOI in this record.We present a study of a delay differential equation (DDE) model for the Mid-Pleistocene Transition. We investigate the behavior of the model when subjected to periodic forcing. The unforced model has a bistable region consisting of a stable equilibrium along with a large amplitude stable periodic orbit. We are interested in how forcing affects solutions in this region. The results here are compared to what is found when the model is forced with the quasiperiodic insolation. The quasiperiodic forcing displays a threshold behavior when the forcing amplitude is increased - moving the model from a non-transitioning regime to a transitioning regime. Similar threshold behavior is found when the periodic forcing amplitude is increased. A bifurcation analysis shows that the threshold is not due to a bifurcation but instead to a shifting basin of attraction.European Union Horizon 2020Engineering and Physical Sciences Research Council (EPSRC

Passivity-Based Trajectory Tracking and Formation Control of Nonholonomic Wheeled Robots Without Velocity Measurements

This note proposes a passivity-based control method for trajectory tracking and formation control of nonholonomic wheeled robots without velocity measurements. Coordinate transformations are used to incorporate the nonholonomic constraints, which are then avoided by controlling the front end of the robot rather than the center of the wheel axle into the differential equations. Starting from the passivity-based coordination design, the control goals are achieved via an internal controller for velocity tracking and heading control and an external controller for formation in the port-Hamiltonian framework. This approach endows the resulting controller with a physical interpretation. To avoid unavailable velocity measurements or unreliable velocity estimations, we derive the distributed control law with only position measurements by introducing a dynamic extension. In addition, we prove that our approach is suitable not only for acyclic graphs but also for a class of non-acyclic graphs, namely, ring graphs. Simulations are provided to illustrate the effectiveness of the approach

A dynamic Bayesian Markov model for health economic evaluations of interventions against infectious diseases

Health economic evaluations of interventions against infectious diseases are commonly based on the predictions of compartmental models such as ordinary differential equation (ODE) systems and Markov models. In contrast to standard Markov models which are static, ODE systems are dynamic by definition and therefore able to account for the effects of herd immunity. This is crucial in pathogens which are transmissible between humans to prevent incorrect model outcomes. The computational effort of fully probabilistic ODE systems is considerably high. Thus, most ODE-based models in the literature are deterministic; they do not account for parameter uncertainty and probabilistic sensitivity analysis cannot be conducted straightforwardly. Yet, it is an essential part of health economic evaluations to investigate the impact of parameter uncertainty on decision making. We present an innovative approach of a dynamic Markov model with Bayesian inference. We extend a static Markov model by directly incorporating the force of infection of the pathogen into the health state allocation algorithm, accounting for the effects of herd immunity. As a consequence, the output of our fully probabilistic Bayesian Markov model is based on dynamic interactions between individuals, and at the same time eligible to conduct probabilistic sensitivity analysis straightforwardly. We introduce a case study of a fictional chronic sexually transmitted infection. By means of this constructed example, we show that our methodology produces results which are comparable to a Bayesian ODE system, yet at lower cost of implementation and computation. In contrast to probabilistic methodology, deterministic models tend to underestimate disease prevalence and thus the benefits of vaccination

Abdominal symptoms in general practice: Frequency, cancer suspicions raised, and actions taken by GPs in six European countries. Cohort study with prospective registration of cancer

Background Abdominal symptoms are diagnostically challenging to general practitioners (GPs): although common, they may indicate cancer. In a prospective cohort of patients, we examined abdominal symptom frequency, initial diagnostic suspicion, and actions of GPs in response to abdominal symptoms. Methods Over a 10-day period, 493 GPs in Norway, Denmark, Sweden, Belgium, the Netherlands, and Scotland, recorded consecutive consultations: sex, date of birth and any specified abdominal symptoms. For patients with abdominal symptoms, additional data on non-specific symptoms, GPs’ diagnostic suspicion, and features of the consultation were noted. Data on all cancer diagnoses among all included patients were requested from the GPs eight months later. Findings Consultations with 61802 patients were recorded. Abdominal symptoms were recorded in 6264 (10.1%) patients. A subsequent malignancy was reported in 511 patients (0.8%): 441 (86.3%) had a new cancer, 70 (13.7%) a recurrent cancer. Abdominal symptoms were noted in 129 (25.2%) of cancer patients (P < 0.001), rising to 34.5% for the 89 patients with cancer located in the abdominal region. PPV for any cancer given any abdominal symptom was 2.1%. In symptomatic patients diagnosed with cancer, GPs noted a suspicion of cancer for 85 (65.9%) versus 1895 (30.9%) when there was no subsequent cancer (P < 0.001). No suspicion was noted in 32 (24.8%) cancer patients. The GP's intuitive cancer suspicion was independently associated with a subsequent new cancer diagnosis (OR 2.11, 95% CI 1.15–3.89). Laboratory tests were ordered for 45.4% of symptomatic patients, imaging for 10.4%, referral or hospitalization for 20.0%: all were more frequent in subsequent cancer patients (P < 0.001). Interpretation Abdominal symptoms pointed to abdominal cancers rather than to other cancers. However, the finding of abdominal symptoms in only one third of patients with an abdominal cancer, and the lack of cancer suspicion in a quarter of symptomatic cancer patients, provide challenges for GPs’ diagnostic thinking and referral practices

Proximity to Sports Facilities and Sports Participation for Adolescents in Germany

Objectives - To assess the relationship between proximity to specific sports facilities and participation in the corresponding sports activities for adolescents in Germany. Methods - A sample of 1,768 adolescents aged 11–17 years old and living in 161 German communities was examined. Distances to the nearest sports facilities were calculated as an indicator of proximity to sports facilities using Geographic Information Systems (GIS). Participation in specific leisure-time sports activities in sports clubs was assessed using a self-report questionnaire and individual-level socio-demographic variables were derived from a parent questionnaire. Community-level socio-demographics as covariates were selected from the INKAR database, in particular from indicators and maps on land development. Logistic regression analyses were conducted to examine associations between proximity to the nearest sports facilities and participation in the corresponding sports activities. Results - The logisitic regression analyses showed that girls residing longer distances from the nearest gym were less likely to engage in indoor sports activities; a significant interaction between distances to gyms and level of urbanization was identified. Decomposition of the interaction term showed that for adolescent girls living in rural areas participation in indoor sports activities was positively associated with gym proximity. Proximity to tennis courts and indoor pools was not associated with participation in tennis or water sports, respectively. Conclusions - Improved proximity to gyms is likely to be more important for female adolescents living in rural areas

Global human frequencies of predicted nuclear pathogenic variants and the role played by protein hydrophobicity in pathogenicity potential

Mitochondrial proteins are coded by nuclear (nDNA) and mitochondrial (mtDNA) genes, implying a complex cross-talk between the two genomes. Here we investigated the diversity displayed in 104 nuclear-coded mitochondrial proteins from 1,092 individuals from the 1000 Genomes dataset, in order to evaluate if these genes are under the effects of purifying selection and how that selection compares with their mitochondrial encoded counterparts. Only the very rare variants (frequency < 0.1%) in these nDNA genes are indistinguishable from a random set from all possible variants in terms of predicted pathogenicity score, but more frequent variants display distinct signs of purifying selection. Comparisons of selection strength indicate stronger selection in the mtDNA genes compared to this set of nDNA genes, accounted for by the high hydrophobicity of the proteins coded by the mtDNA. Most of the predicted pathogenic variants in the nDNA genes were restricted to a single continental population. The proportion of individuals having at least one potential pathogenic mutation in this gene set was significantly lower in Europeans than in Africans and Asians. This difference may reflect demographic asymmetries, since African and Asian populations experienced main expansions in middle Holocene, while in Europeans the main expansions occurred earlier in the post-glacial period

Early and Middle Holocene Hunter-Gatherer Occupations in Western Amazonia: The Hidden Shell Middens

We report on previously unknown early archaeological sites in the Bolivian lowlands, demonstrating for the first time early and middle Holocene human presence in western Amazonia. Multidisciplinary research in forest islands situated in seasonally-inundated savannahs has revealed stratified shell middens produced by human foragers as early as 10,000 years ago, making them the oldest archaeological sites in the region. The absence of stone resources and partial burial by recent alluvial sediments has meant that these kinds of deposits have, until now, remained unidentified. We conducted core sampling, archaeological excavations and an interdisciplinary study of the stratigraphy and recovered materials from three shell midden mounds. Based on multiple lines of evidence, including radiocarbon dating, sedimentary proxies (elements, steroids and black carbon), micromorphology and faunal analysis, we demonstrate the anthropogenic origin and antiquity of these sites. In a tropical and geomorphologically active landscape often considered challenging both for early human occupation and for the preservation of hunter-gatherer sites, the newly discovered shell middens provide evidence for early to middle Holocene occupation and illustrate the potential for identifying and interpreting early open-air archaeological sites in western Amazonia. The existence of early hunter-gatherer sites in the Bolivian lowlands sheds new light on the region's past and offers a new context within which the late Holocene "Earthmovers" of the Llanos de Moxos could have emerged. © 2013 Lombardo et al

Neighborhood socioeconomic status, Medicaid coverage and medical management of myocardial infarction: Atherosclerosis risk in communities (ARIC) community surveillance

<p>Abstract</p> <p>Background</p> <p>Pharmacologic treatments are efficacious in reducing post-myocardial infarction (MI) morbidity and mortality. The potential influence of socioeconomic factors on the receipt of pharmacologic therapy has not been systematically examined, even though healthcare utilization likely influences morbidity and mortality post-MI. This study aims to investigate the association between socioeconomic factors and receipt of evidence-based treatments post-MI in a community surveillance setting.</p> <p>Methods</p> <p>We evaluated the association of census tract-level neighborhood household income (nINC) and Medicaid coverage with pharmacologic treatments (aspirin, beta [β]-blockers and angiotensin converting enzyme [ACE] inhibitors; optimal therapy, defined as receipt of two or more treatments) received during hospitalization or at discharge among 9,608 MI events in the ARIC community surveillance study (1993-2002). Prevalence ratios (PR, 95% CI), adjusted for the clustering of hospitalized MI events within census tracts and within patients, were estimated using Poisson regression.</p> <p>Results</p> <p>Seventy-eight percent of patients received optimal therapy. Low nINC was associated with a lower likelihood of receiving β-blockers (0.93, 0.87-0.98) and a higher likelihood of receiving ACE inhibitors (1.13, 1.04-1.22), compared to high nINC. Patients with Medicaid coverage were less likely to receive aspirin (0.92, 0.87-0.98), compared to patients without Medicaid coverage. These findings were independent of other key covariates.</p> <p>Conclusions</p> <p>nINC and Medicaid coverage may be two of several socioeconomic factors influencing the complexities of medical care practice patterns.</p

Diabetes care: reasons for missing HbA1c measurements in general practice

<p>Abstract</p> <p>Background</p> <p>Glycated haemoglobin (HbA_1c) is often used as one of the indicators to measure the quality of diabetes care. Complete registration is difficult to obtain. This study investigated the reasons for missing HbA_1cmeasurements.</p> <p>Findings</p> <p>HbA_1cmeasurements for 1485 patients with diabetes mellitus type 2 who were attended by 19 general practitioners at 4 primary care health centres in south-east Amsterdam were studied. HbA_1cmeasurements were missing for 356 (23.9%) of the patients. The main reason stated in 50% of the cases was that the patient was under specialized care.</p> <p>Conclusions</p> <p>The general practitioners provided multiple reasons for the missing HbA_1cmeasurements. This study provides insight into why HbA_1cmeasurements were not present in the patients' electronic medical record.</p