Stochastic modelling of urban structure

The building of mathematical and computer models of cities has a long history. The core elements are models of flows (spatial interaction) and the dynamics of structural evolution. In this article, we develop a stochastic model of urban structure to formally account for uncertainty arising from less predictable events. Standard practice has been to calibrate the spatial interaction models independently and to explore the dynamics through simulation. We present two significant results that will be transformative for both elements. First, we represent the structural variables through a single potential function and develop stochastic differential equations to model the evolution. Second, we show that the parameters of the spatial interaction model can be estimated from the structure alone, independently of flow data, using the Bayesian inferential framework. The posterior distribution is doubly intractable and poses significant computational challenges that we overcome using Markov chain Monte Carlo methods. We demonstrate our methodology with a case study on the London, UK, retail system.

Chlorhexidine vaginal preparation versus standard treatment at caesarean section to reduce endometritis and prevent sepsis-a feasibility study protocol (the PREPS trial)

BACKGROUND

Worldwide caesarean section (CS) delivery is the most common major operation. Approximately 25% of pregnant women undergo a CS in the UK for delivery of their babies. Sepsis and post-natal infection constitute significant maternal mortality and morbidity. Infection following a CS has a number of primary sources including endometritis occurring in 7-17% of women. Sepsis reduction and reduction in antibiotic use have been identified as a national and international priority. The overarching aim of this research is to reduce infectious morbidity from caesarean sections.

METHODS

This is a parallel group feasibility randomised controlled trial comparing vaginal cleansing using chlorhexidine gluconate versus no cleansing (standard practice) at CS to reduce infection. Women will be recruited from four National Health Service maternity units. Two hundred fifty women (125 in each arm) undergoing elective or emergency CS, who are aged 16 years and above, and at least 34 weeks pregnant will be randomised. Allocation to treatment will be on a 1:1 ratio. The study includes a qualitative aspect to develop women centred outcomes of wellbeing after delivery.

DISCUSSION

The success of the feasibility study will be assessed by criteria related to the feasibility measurements to ascertain if a larger study is feasible in its current format, needs modification or is unfeasible, and includes recruitment, adherence, follow-up and withdrawal measures.

TRIAL REGISTRATION

The PREPS trial has been registered with ISRCTN (ISRCTN 33435996).

Economic evidence for nonpharmacological asthma management interventions: A systematic review

Asthma management, education and environmental interventions have been reported as cost‐effective in a previous review (Pharm Pract (Granada), 2014;12:493), but methods used to estimate costs and outcomes were not discussed in detail. This review updates the previous review by providing economic evidence on the cost‐effectiveness of studies identified after 2012, and a detailed assessment of the methods used in all identified studies. Twelve databases were searched from 1990 to January 2016, and studies included economic evaluations, asthma subjects and nonpharmacological interventions written in English. Sixty‐four studies were included. Of these, 15 were found in addition to the earlier review; 53% were rated fair in quality and 47% high. Education and self‐management interventions were the most cost‐effective, in line with the earlier review. Self‐reporting was the most common method used to gather resource‐use data, accompanied by bottom‐up approaches to estimate costs. Main outcome measures were asthma‐related hospitalizations (69%), quality of life (41%) and utility (38%), with AQLQ and the EQ‐5D being the most common questionnaires measured prospectively at fixed time points. More rigorous costing methods are needed with a more common quality of life tool to aid greater replicability and comparability amongst asthma studies.

Computational modelling for decision-making: where, why, what, who and how

In order to deal with an increasingly complex world, we need ever more sophisticated computational models that can help us make decisions wisely and understand the potential consequences of choices. But creating a model requires far more than just raw data and technical skills: it requires a close collaboration between model commissioners, developers, users and reviewers. Good modelling requires its users and commissioners to understand more about the whole process, including the different kinds of purpose a model can have and the different technical bases. This paper offers a guide to the process of commissioning, developing and deploying models across a wide range of domains from public policy to science and engineering. It provides two checklists to help potential modellers, commissioners and users ensure they have considered the most significant factors that will determine success. We conclude there is a need to reinforce modelling as a discipline, so that misconstruction is less likely; to increase understanding of modelling in all domains, so that the misuse of models is reduced; and to bring commissioners closer to modelling, so that the results are more useful.

Adult-born dentate granule cell excitability depends on the interaction of neuron age, ontogenetic age and experience

Early during their maturation, adult-born dentate granule cells (aDGCs) are particularly excitable, but eventually develop the electrophysiologically quiet properties of mature cells. However, the stability versus plasticity of this quiet state across time and experience remains unresolved. By birthdating two populations of aDGCs across different animal ages, we found for 10-month-old rats the expected reduction in excitability across cells aged 4-12 weeks, as determined by Egr1 immunoreactivity. Unexpectedly, cells 35 weeks old (after genesis at an animal age of 2 months) were as excitable as 4-week-old cells, in the dorsal hippocampus. This high level of excitability at maturity was specific for cells born in animals 2 months of age, as cells born later in life did not show this effect. Importantly, excitability states were not fixed once maturity was gained, but were enhanced by enriched environment exposure or LTP induction, indicating that any maturational decrease in excitability can be compensated by experience. These data reveal the importance of the animal's age for aDGC excitability, and emphasize their prolonged capability for plasticity during adulthood.

Roderick S. F. Campbell

With a vital role in developing veterinary education in Australia, he became one of the country's most outstanding veterinarians.

Examining the association between adverse childhood experiences and smoking-exacerbated illnesses

OBJECTIVES

Adults who smoke increase their likelihood of death from smoking-exacerbated illnesses. The presence of illnesses exacerbated by smoking can be a powerful incentive to quit smoking. However, having a smoking-exacerbated illness does not stop all patients from smoking. Understanding that smoking may be a coping mechanism for stress, this study examined the association between the experiences of adverse events in childhood with continued smoking in adulthood among individuals and a smoking-exacerbated illness.

STUDY DESIGN

This retrospective observational study used 2014-2015 data from the South Carolina Behavioral Risk Factor Surveillance System survey.

METHODS

We used multivariable logistic regression to examine the impact of adverse childhood experience (ACE) exposure on current smoking status.

RESULTS

A total of 6321 respondents reported having a smoking-exacerbated illness. The most frequently reported categories of smoking-exacerbated illnesses were current asthma (63.9%), previous asthma (13.0%), and diabetes (12.3%). Overall, 62.4% of respondents had at least one ACE, with 20.3% of respondents having four or more ACEs. Respondents with one to three ACEs (adjusted odds ratio [aOR] 1.38; 95% confidence interval [CI] 1.37-1.40) and four or more ACEs (aOR 2.89; CI 2.86-2.92) were both significantly more likely to smoke than respondents with no ACEs, even in the presence of illnesses exacerbated by smoking.

CONCLUSIONS

Results suggest that ACE exposure may influence risky health behaviors in adulthood, such as continued smoking even in the presence of illnesses that are exacerbated by smoking. Given that smoking has been found to be a coping mechanism for adversity, anti-smoking efforts might benefit from designing interventions and treatment plans that address ACE exposure.

HLA-DQA1-HLA-DRB1 polymorphism is a major predictor of azathioprine-induced pancreatitis in patients with inflammatory bowel disease

BACKGROUND

Azathioprine (AZA)-induced pancreatitis is an unpredictable and dose-independent adverse event affecting 2%-7% of patients with inflammatory bowel disease (IBD) patients treated with AZA. There are no tools in clinical practice to identify at-risk individuals; however, a genome wide association study (GWAS) identified a strong association between the Class II HLA gene region polymorphism (rs2647087) and thiopurine-induced pancreatitis.

AIM

To independently confirm the findings of the GWAS in an IBD cohort, to evaluate its utility in clinical practice and to offer a novel AZA treatment algorithm for IBD based on pharmacogenomic principles.

METHODS

A retrospective cohort study evaluated 373 AZA-exposed IBD patients from a tertiary care academic centre in London, Canada. Due to the limited number of patients taking mercaptopurine (MP), such patients were not included this cohort. All subjects underwent screening for the single nucleotide polymorphism (SNP) rs2647087 mapped to the HLA-DQA1*02:01-HLA-DRB1*07:01 haplotype and were sub-divided based on the presence (n = 13) or absence (n = 360) of an AZA-induced pancreatitis diagnosis. The risk of AZA-induced pancreatitis was assessed based on rs2647087 genotype.

RESULTS

The risk of pancreatitis during AZA-therapy was highly predictable and genotype dependent: 0.53% for wild type (A/A), 4.25% (OR = 4.19, 95% CI 1.02-36.45, P = 0.044) for heterozygous (A/C), and 14.63% (OR = 15.83, 95% CI 3.80-145.26, P = 0.0001) for homozygous variant (C/C) patients.

CONCLUSIONS

The class II HLA region (at rs2647087) is an important marker of AZA-induced pancreatitis risk. We propose a simple and clinically implementable algorithm based on rs2647087 and TPMT genotypes for AZA selection and dosing for patients with IBD.

Correction to: Recommendations from Two Citizens' Juries on the Surgical Management of Obesity

The spelling of the name of author K. Chalkidou was incorrect in the original article. It is correct here.

A review of international clinical practice guidelines for the use of oxygen in the delivery room resuscitation of preterm infants

AIM

To collate and assess international clinical practice guidelines (CPG) to determine current recommendations guiding oxygen management for respiratory stabilisation of preterm infants at delivery.

METHODS

A search of public databases using the terms 'clinical practice guidelines', 'preterm', 'oxygen' and 'resuscitation' was made and complemented by direct query to consensus groups, resuscitation expert committees and clinicians. Data were extracted to include the three criteria for assessment: country of origin, gestation and initial FiO₂ and target SpO₂ for the first 10 minutes of life.

RESULTS

A total of 45 CPGs were identified: 36 provided gestation specific recommendations (<28 to <37 weeks) while eight distinguished only between 'preterm' and 'term'. The most frequently recommended initial FiO₂ were between 0.21 and 0.3 (n = 17). Most countries suggested altering FiO₂ to meet SpO₂ targets recommended by expert committees, However, specific five-minute SpO₂ targets differed by up to 20% (70-90%) between guidelines. Five countries did not specify SpO₂ targets.

CONCLUSION

CPG recommendations for delivery room oxygen management of preterm infants vary greatly, particularly in regard to gestational ages, initial FiO₂ and SpO₂ targets and most acknowledge the lack of evidence behind these recommendations. Sufficiently large and well-designed randomised studies are needed to inform on this important practice.

Urban retail location: Insights from percolation theory and spatial interaction modeling

Characterising road networks has been the focus of a large body of research due to it being the main driver of activities in an urban ecosystem and the structuring factor in the dynamics of the city. One of these activities, and one with the largest economical impact in a city, is retail dynamics and its evolution. Therefore, the mathematical modeling of the location of retail activities and of the emergence of clustering in retail centers has as well generated a large number of works. Despite these two interwoven components strongly depending on one another and their fundamental importance in understanding cities, little work has been done in order to compare their local and global properties. Here we compare the road network's hierarchical structure, unveiled through a percolation analysis of the network, with the retail location distribution defined by exploiting a gravity-based retail model. We interpret the great agreement in the city's organizations as it emerges from both methodologies as new evidence of the interdependence of these two crucial dimensions of a city's life.