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Binary branching processes with Moran type interactions
Get PDFThe aim of this paper is to study the large population limit of a binary branching particle system with Moran type interactions: we introduce a new model where particles evolve, reproduce and die independently and, with a probability that may depend on the configuration of the whole system, the death of a particle may trigger the reproduction of another particle, while a branching event may trigger the death of an other one. We study the occupation measure of the new model, explicitly relating it to the Feynman-Kac semigroup of the underlying Markov evolution and quantifying the L2 distance between their normalisations. This model extends the fixed size Moran type interacting particle system discussed in [18, 19, 6, 7, 57] and we will indeed show that our model outperforms the latter when used to approximate a birth and death process. We discuss several other applications of our model including the neutron transport equation [36, 15] and population size dynamics
Do children (and adults) benefit from a prediction error boost in one-shot word learning?
Get PDFInfluential theories and computational models suggest error-based learning plays an important role in language acquisition: Children learn new words by generating predictions about upcoming utterances and revising those predictions when they are erroneous. Critically, revising stronger (rather than weaker) predictions should further enhance learning. Although previously demonstrated in adults, such prediction error boost has not been conclusively shown in children. To close this gap, we tested 107 participants between the ages of 5 and 10. We found little evidence that word learning in this age group benefits from a prediction error boost. Moreover, we also failed to replicate previous evidence for such an effect in adults. Based on a detailed task analysis, we suggest the variation in adult findings may be partly explained by differences in encoding strategies and that, relatedly, the protracted development of the episodic memory system might explain why children do not experience robust benefits from having stronger (rather than weaker) predictions disconfirmed
Sexual victimisation, peer victimisation, and mental health outcomes among adolescents in Burkina Faso : a prospective cohort study
Get PDFBackground
Sexual victimisation and peer victimisation are pervasive and increase risk for mental illness. Longitudinal studies that compare their unique and cumulative effects are scarce and have been done predominantly in high-income countries. The aims of this study were to examine the prevalence, prospective associations, and gender differences in sexual and peer victimisation and mental health in a low-income, African setting.
Methods
In this prospective cohort study, data were obtained from the 2017 ARISE Adolescent Health Study, a population-representative, two-wave, prospective study of adolescents (aged 12–20 years) from Burkina Faso. A random sample of adolescents was drawn from ten villages, selected to capture the five main ethnic groups, and from one of the seven sectors of Nouna town, Burkina Faso, at two timepoints: Nov 12 to Dec 27, 2017, and Nov 15 to Dec 20, 2018. Standardised interviews were conducted in French or a local language by trained researchers. We measured victimisation exposure as sexual victimisation, peer victimisation, and polyvictimisation, using lifetime frequency of exposure, and we measured mental health symptoms and disorders using the Kutcher Adolescent Depression Scale, the Primary Care Post-Traumatic Stress Disorder screen IV and 5, and a question on lifetime self-harm and number of incidents in the past year. We calculated prevalence of victimisation and mental health symptoms and disorders at the two timepoints, and we used lifetime victimisation at the first timepoint to predict mental health at the second timepoint using logistic and negative binomial regressions. Gender differences were examined using interaction terms.
Findings
Of 2544 eligible adolescents, 1644 participated at time 1 and 1291 participated at time 2. The final sample with data at both timepoints included 1160 adolescents aged 12–20 years (mean 15·1, SE 0·2), of whom 469 (40·4%) were girls and 691 (59·6%) were boys. The majority ethnic group was Dafin (626 [39·1%]), followed by Bwaba (327 [20·5%]), Mossi (289 [16·0%]), Samo (206 [13·0%]), Peulh (166 [9·7%]), and other (30 [1·6%]). After survey weight adjustment, sexual victimisation (weighted percentages, time 1, 256 [13·8%] of 1620; time 2, 93 [7·2%] of 1264) and peer victimisation (weighted percentages, time 1, 453 [29·9%] of 1620; time 2, 272 [21·9%] of 1264) were common, whereas polyvictimisation was more rare (weighted percentages, time 1, 116 [6·6%] of 1620; time 2, 76 [5·7%] of 1264). Longitudinally, sexual victimisation was associated with probable clinical disorder (adjusted odds ratio 2·59, 95% CI 1·15–5·84), depressive symptoms (adjusted incidence rate ratio [aIRR] 1·39, 95% CI 1·12–1·72), and symptoms of post-traumatic stress disorder (aIRR 2·34, 1·31–4·16). Peer victimisation was associated with symptoms of post-traumatic stress disorder (aIRR 1·89, 1·13–3·17) and polyvictimisation was associated with depressive symptoms (aIRR 1·34, 1·01–1·77). Girls reported more sexual victimisation (weighted percentages, 130 [17·3%] of 681 vs 126 [11·4%] of 939), boys reported more peer victimisation (weighted percentages, 290 [33·1%] of 939 vs 163 [25·2%] of 681), and there was a significant interaction between lifetime victimisation and gender for probable clinical disorder (F [degrees of freedom 7, sample 376] 2·16; p=0·030).
Interpretation
Sexual and peer victimisation were common in the study setting and increased risk for mental health problems. Adolescent girls who have been sexually victimised are especially at risk of mental health problems. Interventions targeting sexual and peer violence in low-income settings are needed
The evolution and delivery of rocky extra-solar materials to white dwarfs
No full textUnderstanding stellar evolution and its effect on planetary systems is crucial for correctly interpreting the chemical constraints of exo-planetary material that can be given to us by white dwarfs. This article will describe how asteroids, moons, and comets, as well as boulders, pebbles and dust, evolve into eventual targets for chemical spectroscopy, and how planets and companion stars play a vital role in reshaping system architectures for this purpose
Sunbeds, dihydroxyacetone (DHA) fake tan and MelanoTan injections : a history of ‘safe’ tanning technologies
No full textBy the early 1990s, a drastic increase in malignant melanoma rates—mainly in the UK, Europe, America, and Australia—sparked significant concern about skin cancer. Medical experts and the media attempted to curtail overall sunbed use in Britain but failed. Skincare providers and research institutions, on the other hand, realized that they could capitalise on people’s concerns by providing the most advanced “UV-free” tanning technologies. This chapter focuses on two of these technologies: dihydroxyacetone (DHA) fake tanning serums and the entirely novel invention of MelanoTan injections. An evaluation of media coverage and publications in medical journals demonstrates how such “UV-free” technologies were introduced as entirely “safe” alternatives to sunbeds and sunbathing. As Creed argues, both products counterintuitively promoted former risk-laden practices and reinvigorated tanning culture overall. Tanning injections, moreover, introduced a new host of health risks for twenty-first-century consumers. Such technologies, therefore, provide insight into the history of controversial health, beauty, and risk reduction technologies. They also demonstrate the extent to which commercial industries have simultaneously taken the lead in resolving and profiting from public health concerns since the second half of the twentieth century.
Keywords: ultraviolet, tanning, cancer, sunbeds, health and beauty
A fast ceramic mixed OH − /H + ionic conductor for low temperature fuel cells
Get PDFLow temperature ionic conducting materials such as OH− and H+ ionic conductors are important electrolytes for electrochemical devices. Here we show the discovery of mixed OH−/H+ conduction in ceramic materials. SrZr0.8Y0.2O3-δ exhibits a high ionic conductivity of approximately 0.01 S cm−1 at 90 °C in both water and wet air, which has been demonstrated by direct ammonia fuel cells. Neutron diffraction confirms the presence of OD bonds in the lattice of deuterated SrZr0.8Y0.2O3-δ. The OH− ionic conduction of CaZr0.8Y0.2O3-δ in water was demonstrated by electrolysis of both H218O and D2O. The ionic conductivity of CaZr0.8Y0.2O3-δ in 6 M KOH solution is around 0.1 S cm−1 at 90 °C, 100 times higher than that in pure water, indicating increased OH− ionic conductivity with a higher concentration of feed OH− ions. Density functional theory calculations suggest the diffusion of OH− ions relies on oxygen vacancies and temporarily formed hydrogen bonds. This opens a window to discovering new ceramic ionic conducting materials for near ambient temperature fuel cells, electrolysers and other electrochemical devices
Life in a random universe : Sciama's argument reconsidered
Get PDFRandom sampling in high dimensions has successfully been applied to phenomena as diverse as nuclear resonances, neural networks, and black hole evaporation. Here we revisit an elegant argument by the British physicist Dennis Sciama, who demonstrated that were our Universe random, it would almost certainly have a negligible chance for life. Under plausible assumptions, we show that a random universe can masquerade as “intelligently designed,” with the fundamental constants instead appearing to be fined tuned to achieve the highest probability for life to occur. For our Universe, this mechanism may only require there to be around a dozen currently unknown fundamental constants. We speculate on broader applications for the mechanism we uncover
Two kinds of vaccine hesitancy
Get PDFWe ask whether it is reasonable to delay or refuse to take COVID-19 vaccines that have been shown in clinical trials to be safe and effective against infectious diseases. We consider two kinds of vaccine hesitancy. The first is geared to scientifically informed open questions about vaccines. We argue that in cases where the data is not representative of relevant groups, such as pregnant women and ethnic minorities, hesitancy can be reasonable on epistemic grounds. However, we argue that hesitancy is not reasonable if a vaccine has passed well-conducted clinical trials. The second kind of hesitancy is to do with beliefs about the institutions offering a successfully trialled vaccine, and the justifiability of cooperating with those institutions. For example, in the UK, distrust of the UK Government or the National Health Service is identified as a factor in the vaccine hesitancy of minority ethnic populations. We ask whether this sort of hesitation is reasonable given normative requirements of fair cooperation, both with those institutions and the wider population. We suggest that the answer is not straightforward. Sometimes the hesitation is unreasonable but understandable
The performance of wearable AI in detecting stress among students : systematic review and meta-analysis
Get PDFBackground:
Students usually encounter stress throughout their academic path. Ongoing stressors may lead to chronic stress, adversely affecting their physical and mental well-being. Thus, early detection and monitoring of stress among students are crucial. Wearable artificial intelligence (AI) has emerged as a valuable tool for this purpose. It offers an objective, noninvasive, nonobtrusive, automated approach to continuously monitor biomarkers in real time, thereby addressing the limitations of traditional approaches such as self-reported questionnaires.
Objective:
This systematic review and meta-analysis aim to assess the performance of wearable AI in detecting and predicting stress among students.
Methods:
Search sources in this review included 7 electronic databases (MEDLINE, Embase, PsycINFO, ACM Digital Library, Scopus, IEEE Xplore, and Google Scholar). We also checked the reference lists of the included studies and checked studies that cited the included studies. The search was conducted on June 12, 2023. This review included research articles centered on the creation or application of AI algorithms for the detection or prediction of stress among students using data from wearable devices. In total, 2 independent reviewers performed study selection, data extraction, and risk-of-bias assessment. The Quality Assessment of Diagnostic Accuracy Studies–Revised tool was adapted and used to examine the risk of bias in the included studies. Evidence synthesis was conducted using narrative and statistical techniques.
Results:
This review included 5.8% (19/327) of the studies retrieved from the search sources. A meta-analysis of 37 accuracy estimates derived from 32% (6/19) of the studies revealed a pooled mean accuracy of 0.856 (95% CI 0.70-0.93). Subgroup analyses demonstrated that the accuracy of wearable AI was moderated by the number of stress classes (P=.02), type of wearable device (P=.049), location of the wearable device (P=.02), data set size (P=.009), and ground truth (P=.001). The average estimates of sensitivity, specificity, and F1-score were 0.755 (SD 0.181), 0.744 (SD 0.147), and 0.759 (SD 0.139), respectively.
Conclusions:
Wearable AI shows promise in detecting student stress but currently has suboptimal performance. The results of the subgroup analyses should be carefully interpreted given that many of these findings may be due to other confounding factors rather than the underlying grouping characteristics. Thus, wearable AI should be used alongside other assessments (eg, clinical questionnaires) until further evidence is available. Future research should explore the ability of wearable AI to differentiate types of stress, distinguish stress from other mental health issues, predict future occurrences of stress, consider factors such as the placement of the wearable device and the methods used to assess the ground truth, and report detailed results to facilitate the conduct of meta-analyses
A multi-agent reinforcement learning-based method for server energy efficiency optimization combining DVFS and dynamic fan control
No full textWith the rapid development of the digital economy and intelligent industry, the energy consumption of data centers (DCs) has increased significantly. Various optimization methods are proposed to improve the energy efficiency of servers in DCs. However, existing solutions usually adopt model-based heuristics and best practices to select operations, which are not universally applicable. Moreover, existing works primarily focus on the optimization methods for individual components, with a lack of work on the joint optimization of multiple components. Therefore, we propose a multi-agent reinforcement learning-based method, named MRDF, combining DVFS and dynamic fan control to achieve a trade-off between power consumption and performance while satisfying thermal constraints. MRDF is model-free and learns by continuously interacting with the real server without prior knowledge. To enhance the stability of MRDF in dynamic environments, we design a data-driven baseline comparison method to evaluate the actual contribution of a single agent to the global reward. In addition, an improved Q-learning is proposed to deal with the large state and action space of the multi-core server. We implement MRDF on a Huawei Taishan 200 server and verify the effectiveness by running benchmarks. Experimental results show that the proposed method improves energy efficiency by an average of 3.9% compared to the best baseline solution, while flexibly adapting to different thermal constraints