Properties of an invariant set of weights of perceptrons

In this paper, the dynamics of weights of perceptrons are investigated based on the perceptron training algorithm. In particular, the condition that the system map is not injective is derived. Based on the derived condition, an invariant set that results to a bijective invariant map is characterized. Also, it is shown that some weights outside the invariant set will be moved to the invariant set. Hence, the invariant set is attracting. Computer numerical simulation results on various perceptrons with exhibiting various behaviors, such as fixed point behaviors, limit cycle behaviors and chaotic behaviors, are illustrated

Global convergence and limit cycle behavior of weights of perceptron

In this paper, it is found that the weights of a perceptron are bounded for all initial weights if there exists a nonempty set of initial weights that the weights of the perceptron are bounded. Hence, the boundedness condition of the weights of the perceptron is independent of the initial weights. Also, a necessary and sufficient condition for the weights of the perceptron exhibiting a limit cycle behavior is derived. The range of the number of updates for the weights of the perceptron required to reach the limit cycle is estimated. Finally, it is suggested that the perceptron exhibiting the limit cycle behavior can be employed for solving a recognition problem when downsampled sets of bounded training feature vectors are linearly separable. Numerical computer simulation results show that the perceptron exhibiting the limit cycle behavior can achieve a better recognition performance compared to a multilayer perceptro

Is acupuncture effective in controlling gagging when taking an alginate impressions?

Our community health project aimed to (1) identify the prevalence of gagging among patients attending the Prince Philip Dental Hospital; and to identify socio-demographic variations in reported gagging experiences; and (2) perform a pilot study to evaluate the effectiveness of acupuncture in the control of gagging in the dental setting. Methods: A survey on reported gagging experiences was conducted among patients attending our hospital involving a convenience sample of 225 patients. Participants who reported to previously gag in the dental setting were invited to participate in a pilot study to evaluate the effectiveness of acupuncture in controlling gagging when taking an upper alginate impression. Participants were randomized to receive acupuncture stimulation at a site reported to be effective in the control of gagging on the lower lip (point CV 24) or at a sham site on the upper lip (point GV 26) on their first visit and at their second visit to receive the alternative acupuncture stimulation. Results: The response rate to the survey was 81.3% (183/225). Approximately a third (58/183) reported to have experienced gagging in the dental setting and most frequently encountered this when having a dental impression (among approximately a quarter of participants - 44/183). Half (95/183) reported gagging while performing oral self-care. Four in ten participants (73/183) reported some stress visiting the dentist related to gagging. Sociodemographic variations in reported gagging experiences were evident with respect to age, gender and education level. The response rate to the pilot study was 92.3% (36/39). There was no significant difference in the prevalence of gagging when acupuncture was applied to the test site compared to when acupuncture was applied to the sham site on dental examination (p>0.05) or when taking an upper alginate impression (p>0.05). Conclusions: Gagging in a relative common experience reported by patients attending our hospital – in daily life, in the dental setting and in performing oral self-care. Socio-demographic variations in the prevalence of gagging were apparent. The pilot study does not support the use of acupuncture in controlling gagging in the dental setting.published_or_final_versio

Retrospective cohort study to investigate the 10-year trajectories of disease patterns in patients with hypertension and/or diabetes mellitus on subsequent cardiovascular outcomes and health service utilisation: a study protocol.

INTRODUCTION: Hypertension (HT) and diabetes mellitus (DM) and are major disease burdens in all healthcare systems. Given their high impact on morbidity, premature death and direct medical costs, we need to optimise effectiveness and cost-effectiveness of primary care for patients with HT/DM. This study aims to find out the association of trajectories in disease patterns and treatment of patients with HT/DM including multimorbidity and continuity of care with disease outcomes and service utilisation over 10 years in order to identify better approaches to delivering primary care services. METHODS AND ANALYSIS: A 10-year retrospective cohort study on a population-based primary care cohort of Chinese patients with documented doctor-diagnosed HT and/or DM, managed in the Hong Kong Hospital Authority (HA) public primary care clinics from 1 January 2006 to 31 December 2019. Data will be extracted from the HA Clinical Management System to identify trajectory patterns of patients with HT/DM. Complications defined by ICPC-2/International Classification of Diseases-Ninth Revision, Clinical Modification diagnosis codes, all-cause mortality rates and public service utilisation rates are included as independent variables. Changes in clinical parameters will be investigated using a growth mixture modelling analysis with standard quadratic trajectories. Dependent variables including effects of multimorbidity, measured by (1) disease count and (2) Charlson's Comorbidity Index, and continuity of care, measured by the Usual Provide Continuity Index, on patient outcomes and health service utilisation will be investigated. Multivariable Cox proportional hazards regression will be conducted to estimate the effect of multimorbidity and continuity of care after stratification of patients into groups according to respective definitions. ETHICS AND DISSEMINATION: This study was approved by the institutional review board of the University of Hong Kong-the HA Hong Kong West Cluster, reference no: UW 19-329. The study findings will be disseminated through peer-reviewed publications and international conferences. TRIAL REGISTRATION NUMBER: NCT04302974

Risk factors and prediction models for incident heart failure with reduced and preserved ejection fraction

Abstract: Aims: This study aims to develop the first race‐specific and sex‐specific risk prediction models for heart failure with preserved (HFpEF) and reduced ejection fraction (HFrEF). Methods and results: We created a cohort of 1.8 million individuals who had an outpatient clinic visit between 2002 and 2007 within the Veterans Affairs (VA) Healthcare System and obtained information on HFpEF, HFrEF, and several risk factors from electronic health records (EHR). Variables were selected for the risk prediction models in a ‘derivation cohort’ that consisted of individuals with baseline date in 2002, 2003, or 2004 using a forward stepwise selection based on a change in C‐index threshold. Discrimination and calibration were assessed in the remaining participants (internal ‘validation cohort’). A total of 66 831 individuals developed HFpEF, and 92 233 developed HFrEF (52 679 and 71 463 in the derivation cohort) over a median of 11.1 years of follow‐up. The HFpEF risk prediction model included age, diabetes, BMI, COPD, previous MI, antihypertensive treatment, SBP, smoking status, atrial fibrillation, and estimated glomerular filtration rate (eGFR), while the HFrEF model additionally included previous CAD. For the HFpEF model, C‐indices were 0.74 (SE = 0.002) for white men, 0.76 (0.005) for black men, 0.79 (0.015) for white women, and 0.77 (0.026) for black women, compared with 0.72 (0.002), 0.72 (0.004), 0.77 (0.017), and 0.75 (0.028), respectively, for the HFrEF model. These risk prediction models were generally well calibrated in each race‐specific and sex‐specific stratum of the validation cohort. Conclusions: Our race‐specific and sex‐specific risk prediction models, which used easily obtainable clinical variables, can be a useful tool to implement preventive strategies or subtype‐specific prevention trials in the nine million users of the VA healthcare system and the general population after external validation

Early initiation of prophylactic anticoagulation for prevention of coronavirus disease 2019 mortality in patients admitted to hospital in the United States: cohort study.

OBJECTIVE: To evaluate whether early initiation of prophylactic anticoagulation compared with no anticoagulation was associated with decreased risk of death among patients admitted to hospital with coronavirus disease 2019 (covid-19) in the United States. DESIGN: Observational cohort study. SETTING: Nationwide cohort of patients receiving care in the Department of Veterans Affairs, a large integrated national healthcare system. PARTICIPANTS: All 4297 patients admitted to hospital from 1 March to 31 July 2020 with laboratory confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and without a history of anticoagulation. MAIN OUTCOME MEASURES: The main outcome was 30 day mortality. Secondary outcomes were inpatient mortality, initiating therapeutic anticoagulation (a proxy for clinical deterioration, including thromboembolic events), and bleeding that required transfusion. RESULTS: Of 4297 patients admitted to hospital with covid-19, 3627 (84.4%) received prophylactic anticoagulation within 24 hours of admission. More than 99% (n=3600) of treated patients received subcutaneous heparin or enoxaparin. 622 deaths occurred within 30 days of hospital admission, 513 among those who received prophylactic anticoagulation. Most deaths (510/622, 82%) occurred during hospital stay. Using inverse probability of treatment weighted analyses, the cumulative incidence of mortality at 30 days was 14.3% (95% confidence interval 13.1% to 15.5%) among those who received prophylactic anticoagulation and 18.7% (15.1% to 22.9%) among those who did not. Compared with patients who did not receive prophylactic anticoagulation, those who did had a 27% decreased risk for 30 day mortality (hazard ratio 0.73, 95% confidence interval 0.66 to 0.81). Similar associations were found for inpatient mortality and initiation of therapeutic anticoagulation. Receipt of prophylactic anticoagulation was not associated with increased risk of bleeding that required transfusion (hazard ratio 0.87, 0.71 to 1.05). Quantitative bias analysis showed that results were robust to unmeasured confounding (e-value lower 95% confidence interval 1.77 for 30 day mortality). Results persisted in several sensitivity analyses. CONCLUSIONS: Early initiation of prophylactic anticoagulation compared with no anticoagulation among patients admitted to hospital with covid-19 was associated with a decreased risk of 30 day mortality and no increased risk of serious bleeding events. These findings provide strong real world evidence to support guidelines recommending the use of prophylactic anticoagulation as initial treatment for patients with covid-19 on hospital admission

Towards a global partnership model in interprofessional education for cross-sector problem-solving

Objectives A partnership model in interprofessional education (IPE) is important in promoting a sense of global citizenship while preparing students for cross-sector problem-solving. However, the literature remains scant in providing useful guidance for the development of an IPE programme co-implemented by external partners. In this pioneering study, we describe the processes of forging global partnerships in co-implementing IPE and evaluate the programme in light of the preliminary data available. Methods This study is generally quantitative. We collected data from a total of 747 health and social care students from four higher education institutions. We utilized a descriptive narrative format and a quantitative design to present our experiences of running IPE with external partners and performed independent t-tests and analysis of variance to examine pretest and posttest mean differences in students’ data. Results We identified factors in establishing a cross-institutional IPE programme. These factors include complementarity of expertise, mutual benefits, internet connectivity, interactivity of design, and time difference. We found significant pretest–posttest differences in students’ readiness for interprofessional learning (teamwork and collaboration, positive professional identity, roles, and responsibilities). We also found a significant decrease in students’ social interaction anxiety after the IPE simulation. Conclusions The narrative of our experiences described in this manuscript could be considered by higher education institutions seeking to forge meaningful external partnerships in their effort to establish interprofessional global health education