Mark Joy

Results concerning the absolute stability of delayed neural networks

We report on results concerning the global asymptotic stability (GAS) and absolute stability (ABST) of delay models of continuous-time neural networks. These results present sufficient conditions for GAS and in case the network has instantaneous signalling as well as delay signalling (for example, a delayed cellular neural network (DCNN)), are milder than previously known criteria; they apply to neural networks with a broad range of activation functions assuming neither differentiability nor strict monotonicity. We are therefore able to interpret the results as guarantees of absolute stability of the network with respect to the wide class of admissible activation functions. Furthermore, these results do not assume symmetry of the connection matrices. We also present a sufficient condition for absolute stability in the presence of nonconstant delays.

Forecasting demand of emergency care.

This paper describes a model that can forecast the daily number of occupied beds due to emergency admissions in an acute hospital. Out of sample forecasts 32 day days in advance, have an RMS error of 3% of the mean number of beds used for emergency admissions. We find that the number of occupied beds due to emergency admissions is related to both air temperature and PHLS data on influenza like illnesses. We find that a period of high volatility, indicated by GARCH errors, will result in an increase in waiting times in the A&E Department. Furthermore, volatility gives more warning of waiting times in A&E than total bed occupancy.

A new parameter range for the stability of opposite-sign cellular neural networks

Complete stability of cellular neural networks and their associated dynamical system precludes the possibility of any periodic or chaotic behavior and is an important property to establish. The authors establish complete stability of the opposite-sign cellular neural network (CNN) provided that the template values fall within the range (p-1)/2 >

Circulant matrices and the stability of a class of CNNs

In this paper we show that feedback matrices of ring CNNs are block circulants; as special cases, for example, feedback matrices of one-dimensional ring CNNs are circulant matrices. Circulants and their close relations the block circulants possess many pleasant properties which allow one to describe their spectrum completely. After deriving the spectrum of the feedback operator, we discuss conditions for a CNN to be contractive, ensuring global asymptotic stability.

An equilibrium analysis of CNNs

In this paper, we study the equilibrium set of cellular neural networks (CNNs). We establish new conditions for the stability of equilibria in delayed cellular neural networks (DCNNs), and we also study the topology of the equilibrium set-whether equilibria are isolated.

Cohort analysis of outcomes in 69 490 emergency general surgical admissions across an international benchmarking collaborative

Objective This study aims to use the Dr Foster Global Comparators Network (GC) database to examine differences in outcomes following high-risk emergency general surgery (EGS) admissions in participating centres across 3 countries and to determine whether hospital infrastructure factors can be linked to the delivery of high-quality care. Design A retrospective cohort analysis of high-risk EGS admissions using GCs international administrative data set. Setting 23 large hospitals in Australia, England and the USA. Methods Discharge data for a cohort of high-risk EGS patients were collated. Multilevel hierarchical logistic regression analysis was performed to examine geographical and structural differences between GC hospitals. Results 69 490 patients, admitted to 23 centres across Australia, England and the USA from 2007 to 2012, were identified. For all patients within this cohort, outcomes defined as: 7-day and 30-day inhospital mortality, readmission and length of stay appeared to be superior in US centres. A subgroup of 19 082 patients (27%) underwent emergency abdominal surgery. No geographical differences in mortality were seen at 7 days in this subgroup. 30-day mortality (OR=1.47, p<0.01) readmission (OR=1.42, p<0.01) and length of stay (OR=1.98, p<0.01) were worse in English units. Patient factors (age, pathology, comorbidity) were significantly associated with worse outcome as were structural factors, including low intensive care unit bed ratios, high volume and interhospital transfers. Having dedicated EGS teams cleared of elective commitments with formalised handovers was associated with shorter length of stay. Conclusions Key factors that influence outcomes were identified. For patients who underwent surgery, outcomes were similar at 7 days but not at 30 days. This may be attributable to better infrastructure and resource allocation towards EGS in the US and Australian centres.

Reconciliation of international administrative coding systems for comparison of colorectal surgery outcome.

Significant variation in colorectal surgery outcomes exists between different countries. Better understanding of the sources of variable outcomes using administrative data requires alignment of differing clinical coding systems. We aimed to map similar diagnoses and procedures across administrative coding systems used in different countries.

Stability of a three cell cellular neural network

Complete stability of a cellular neural network (CNN) is a strong form of stability where almost all solution curves of the associated differential equations tend to a stable equilibrium point. For the three cell system considered here the state space is the three-dimensional Euclidean space R/sup 3/ which allows following the evolution of trajectories geometrically. The author carries out a stability analysis by studying the vector field associated with the state equations. Specifically he notes the directions of the vector field in certain convex, compact subregions of the state space, capitalizing on the fact that the differential equations are piecewise-linear and actually linear in the regions considered. A three cell CNN with an opposite-sign template is described by differential equations. Complete stability of the opposite-sign cellular neural network is established for a certain parameter range. The proof is geometric in nature and provides an example of a qualitative analysis of a nonlinear differential equation.<<ETX>>

Conurbation, urban and rural living are contributing determinants of allergic and infectious disease: Royal College of General Practitioners (RCGP) Research and Surveillance Centre (RSC) Annual Report 2016-2017 (Preprint)

Background Living in a conurbation, urban, or rural environment is an important determinant of health. For example, conurbation and rural living is associated with increased respiratory and allergic conditions, whereas a farm or rural upbringing has been shown to be a protective factor against this. Objective The objective of the study was to assess differences in general practice presentations of allergic and infectious disease in those exposed to conurbation or urban living compared with rural environments. Methods The population was a nationally representative sample of 175 English general practices covering a population of over 1.6 million patients registered with sentinel network general practices. General practice presentation rates per 100,000 population were reported for allergic rhinitis, asthma, and infectious conditions grouped into upper and lower respiratory tract infections, urinary tract infection, and acute gastroenteritis by the UK Office for National Statistics urban-rural category. We used multivariate logistic regression adjusting for age, sex, ethnicity, deprivation, comorbidities, and smoking status, reporting odds ratios (ORs) with 95% CIs. Results For allergic rhinitis, the OR was 1.13 (95% CI 1.04-1.23; P=.003) for urban and 1.29 (95% CI 1.19-1.41; P<.001) for conurbation compared with rural dwellers. Conurbation living was associated with a lower OR for both asthma (OR 0.70, 95% CI 0.67-0.73; P<.001) and lower respiratory tract infections (OR 0.94, 95% CI 0.90-0.98; P=.005). Compared with rural dwellers, the OR for upper respiratory tract infection was greater in urban (OR 1.06, 95% CI 1.03-1.08; P<.001) but no different in conurbation dwellers (OR 1.00, 95% CI 0.97-1.03; P=.93). Acute gastroenteritis followed the same pattern: the OR was 1.13 (95% CI 1.01-1.25; P=.03) for urban dwellers and 1.04 (95% CI 0.93-1.17; P=.46) for conurbation dwellers. The OR for urinary tract infection was lower for urban dwellers (OR 0.94, 95% CI 0.89-0.99; P=.02) but higher in conurbation dwellers (OR 1.06, 95% CI 1.00-1.13; P=.04). Conclusions Those living in conurbations or urban areas were more likely to consult a general practice for allergic rhinitis and upper respiratory tract infection. Both conurbation and rural living were associated with an increased risk of urinary tract infection. Living in rural areas was associated with an increased risk of asthma and lower respiratory tract infections. The data suggest that living environment may affect rates of consultations for certain conditions. Longitudinal analyses of these data would be useful in providing insights into important determinants.

14 The use of prehospital 12-lead electrocardiograms in acute stroke patients

AIM Emergency medical services (EMS) play a vital role in the recognition, management and transportation of acute stroke patients. UK guidelines recommend clinicians consider performing a prehospital 12-lead electrocardiogram (PHECG) in patients with suspected stroke , but this recommendation is based on expert consensus, rather than robust evidence. The aim of this study was to investigate the association between PHECG and modified Rankin scale (mRS). Secondary outcomes included in-hospital mortality, EMS and in-hospital time intervals and rates of thrombolysis received. Method A multicentre retrospective cohort study was undertaken. The data collection period spanned from 29/12/2013 – 30/01/2017. Participants were identified through secondary analysis of hospital data routinely collected as part of the Sentinel Stroke National Audit Programme (SSNAP) and linked to EMS clinical records (PCRs) via EMS incident number. Results PHECG was performed in 558 (48%) of study patients. PHECG was associated with an increase in mRS (aOR 1.44, 95% CI: 1.14 to 1.82, p=0.002) and in-hospital mortality (aOR 2.07, 95% CI: 1.42 to 3.00, p=0.0001). There was no association between PHECG and administration of thrombolysis (aOR 0.92, 95% CI: 0.65 to 1.30, p=0.63). Patients who had a PHECG recorded spent longer under the care of EMS (median 49 vs 43 min, p=0.007). No difference in times to receiving brain scan (Median 28 with PHECG vs 29 min no PHECG, p=0.14) or thrombolysis (median 46 min vs 48 min, p=0.82) were observed. Conclusion This is the first study of its kind to investigate the association between PHECG and functional outcome in stroke patients attended by EMS. Although there are limitations in regard to the retrospective study design, the findings challenge current guideline recommendations regarding PHECG in patients with acute stroke. Conflict of interest None Funding University of Surrey School of Health Sciences PhD scholarship.