On Measuring Social Dynamics of Online Social Media

Due to the complex nature of human behaviour and to our inability to directly measure thoughts and feelings, social psychology has long struggled for empirical grounding for its theories and models. Traditional techniques involving groups of people in controlled environments are limited to small numbers and may not be a good analogue for real social interactions in natural settings due to their controlled and artificial nature. Their application as a foundation for simulation of social processes suffers similarly. The proliferation of online social media offers new opportunities to observe social phenomena “in the wild” that have only just begun to be realised. To date, analysis of social media data has been largely focussed on specific, commercially relevant goals (such as sentiment analysis) that are of limited use to social psychology, and the dynamics critical to an understanding of social processes is rarely addressed or even present in collected data. This thesis addresses such shortfalls by: (i) presenting a novel data collection strategy and system for rich dynamic data from communities operating on Twitter; (ii) a data set encompassing longitudinal dynamic information over two and a half years from the online pro-ana (pro-anorexia) movement; and (iii) two approaches to identifying active social psychological processes in collections of online text and network metadata: an approach linking traditional psychometric studies with topic models and an algorithm combining community detection in user networks with topic models of the social media text they generate, enabling identification of community specific topic usage

Four-year experience with methotrexate exposures.

INTRODUCTION: Unintentional methotrexate (MTX) acute oral overdose is rarely reported. METHODS: We conducted a retrospective chart review of all human exposure calls (\u3e150,000 charts) for MTX ingestions reported to our Poison Center during 2000-2003. RESULTS: Thirteen patients met the criteria. The average amount of MTX ingested was 13.03 mg (data from 7 cases), and the average patient age was 43 years (20 months to 80 years). No significant toxicities occurred. DISCUSSION: Although intravenous MTX toxicity can be severe, this does not appear to be a phenomenon associated with either acute unintentional or suicidal oral ingestion

Are the benefits of clickers due to the enforcement of good pedagogy?

Milperra NS

Stable synchronous propagation of signals by feedforward networks

We analyze the dynamics of networks in which a central pattern generator (CPG) transmits signals along one or more feedforward chains in a synchronous or phase-synchronous manner. Such propagating signals are common in biology, especially in locomotion and peristalsis, and are of interest for continuum robots. We construct such networks as feedforward lifts of the CPG. If the CPG dynamics is periodic, so is the lifted dynamics. Synchrony with the CPG manifests as a standing wave, and a regular phase pattern creates a traveling wave. We discuss Liapunov, asymptotic, and Floquet stability of the lifted periodic orbit and introduce transverse versions of these conditions that imply stability for signals propagating along arbitrarily long chains. We compare these notions to a simpler condition, transverse stability of the synchrony subspace, which is equivalent to Floquet stability when nodes are 1 dimensional

Inequalities in the dental health needs and access to dental services among looked after children in Scotland: a population data linkage study

Background: There is limited evidence on the health needs and service access among children and young people who are looked after by the state. The aim of this study was to compare dental treatment needs and access to dental services (as an exemplar of wider health and well-being concerns) among children and young people who are looked after with the general child population. Methods: Population data linkage study utilising national datasets of social work referrals for ‘looked after’ placements, the Scottish census of children in local authority schools, and national health service’s dental health and service datasets. Results: 633 204 children in publicly funded schools in Scotland during the academic year 2011/2012, of whom 10 927 (1.7%) were known to be looked after during that or a previous year (from 2007–2008). The children in the looked after children (LAC) group were more likely to have urgent dental treatment need at 5 years of age: 23%vs10% (n=209/16533), adjusted (for age, sex and area socioeconomic deprivation) OR 2.65 (95% CI 2.30 to 3.05); were less likely to attend a dentist regularly: 51%vs63% (n=5519/388934), 0.55 (0.53 to 0.58) and more likely to have teeth extracted under general anaesthesia: 9%vs5% (n=967/30253), 1.91 (1.78 to 2.04). Conclusions: LAC are more likely to have dental treatment needs and less likely to access dental services even when accounting for sociodemographic factors. Greater efforts are required to integrate child social and healthcare for LAC and to develop preventive care pathways on entering and throughout their time in the care system

Association between hypertensive disorders of pregnancy and later risk of cardiovascular outcomes

Funder: Homerton College, University of Cambridge (GB)BACKGROUND: Hypertensive disorders of pregnancy are common pregnancy complications that are associated with greater cardiovascular disease risk for mothers. However, risk of cardiovascular disease subtypes associated with gestational hypertension or pre-eclampsia is unclear. The present study aims to compare the risk of cardiovascular disease outcomes for women with and without a history of gestational hypertension and pre-eclampsia using national hospital admissions data. METHODS: This was a retrospective cohort study of national medical records from all national health service hospitals in England. Women who had one or more singleton live births in England between 1997 and 2015 were included in the analysis. Risk of total cardiovascular disease and 19 pre-specified cardiovascular disease subtypes, including stroke, coronary heart disease, cardiomyopathy and peripheral arterial disease was calculated separately for women with a history of gestational hypertension and pre-eclampsia compared to normotensive pregnancies. RESULTS: Amongst 2,359,386 first live births there were 85,277 and 74,542 hospital admissions with a diagnosis of gestational hypertension and pre-eclampsia, respectively. During 18 years (16,309,386 person-years) of follow-up, the number and incidence of total CVD for normotensive women, women with prior gestational hypertension and women with prior pre-eclampsia were: n=8668, 57.1 (95% CI:55.9-58.3) per 100,000 person-years; n=521, 85.8 (78.6-93.5) per 100,000 person-years and n=518, 99.3 (90.9-108.2) per 100,000 person-years, respectively. Adjusted HRs (aHR) for total CVD were: aHR (95% CI) = 1.45 (1.33-1.59) for women with prior gestational hypertension and, aHR=1.62 (1.48-1.78) for women with prior pre-eclampsia. Gestational hypertension was strongly associated with dilated cardiomyopathy, aHR=2.85 (1.67-4.86), and unstable angina, aHR=1.92 (1.33-2.77). Pre-eclampsia was strongly associated with hypertrophic cardiomyopathy, aHR=3.27 (1.49-7.19), and acute myocardial infarction, aHR=2.46 (1.72-3.53). Associations were broadly homogenous across cardiovascular disease subtypes and increased with a greater number of affected pregnancies. CONCLUSIONS: Women with either previous gestational hypertension or pre-eclampsia are at greater risk of a range of cardiovascular outcomes. These women may benefit from clinical risk assessment or early interventions to mitigate their greater risk of various cardiovascular outcomes.Cambridge BHF Centre of Research Excellence (RE/13/6/30180

Effects of dispersal mode on the environmental and spatial correlates of nestedness and species turnover in pond communities

Advances in metacommunity theory have made a significant contribution to understanding the drivers of variation in biological communities. However, there has been limited empirical research exploring the expression of metacommunity theory for two fundamental components of beta diversity: nestedness and species turnover. In this paper, we examine the influence of local environmental and a range of spatial variables (hydrological connectivity, proximity and overall spatial structure) on total beta diversity and the nestedness and turnover components of beta diversity for the entire macroinvertebrate community and active and passively dispersing taxa within pond habitats. High beta diversity almost entirely reflects patterns of species turnover (replacement) rather than nestedness (differences in species richness) in our dataset. Local environmental variables were the main drivers of total beta diversity, nestedness and turnover when the entire community was considered and for both active and passively dispersing taxa. The influence of spatial processes on passively dispersing composition, total beta diversity and nestedness was significantly greater than for actively dispersing taxa. Our results suggest that species sorting (local environmental variables) operating through niche processes was the primary mechanism driving total beta diversity, nestedness and turnover for the entire community and active and passively dispersing taxa. In contrast, spatial factors (hydrological connectivity, proximity and spatial eigenvectors) only exerted a secondary influence on the nestedness and turnover components of beta diversity

Unintended Memorization and Timing Attacks in Named Entity Recognition Models

Named entity recognition models (NER), are widely used for identifying named entities (e.g., individuals, locations, and other information) in text documents. Machine learning based NER models are increasingly being applied in privacy-sensitive applications that need automatic and scalable identification of sensitive information to redact text for data sharing. In this paper, we study the setting when NER models are available as a black-box service for identifying sensitive information in user documents and show that these models are vulnerable to membership inference on their training datasets. With updated pre-trained NER models from spaCy, we demonstrate two distinct membership attacks on these models. Our first attack capitalizes on unintended memorization in the NER's underlying neural network, a phenomenon NNs are known to be vulnerable to. Our second attack leverages a timing side-channel to target NER models that maintain vocabularies constructed from the training data. We show that different functional paths of words within the training dataset in contrast to words not previously seen have measurable differences in execution time. Revealing membership status of training samples has clear privacy implications, e.g., in text redaction, sensitive words or phrases to be found and removed, are at risk of being detected in the training dataset. Our experimental evaluation includes the redaction of both password and health data, presenting both security risks and privacy/regulatory issues. This is exacerbated by results that show memorization with only a single phrase. We achieved 70% AUC in our first attack on a text redaction use-case. We also show overwhelming success in the timing attack with 99.23% AUC. Finally we discuss potential mitigation approaches to realize the safe use of NER models in light of the privacy and security implications of membership inference attacks.Comment: This is the full version of the paper with the same title accepted for publication in the Proceedings of the 23rd Privacy Enhancing Technologies Symposium, PETS 202