Entropic measure of wave-packet spreading and ionization in laser-driven atoms

Published versio

Seroepidemiological investigations of Salmonella enterica serovar Typhi infection and the potential role of vaccination in the control of typhoid fever in Fiji

Typhoid fever is a potentially-life threatening systemic disease caused by Salmonella Typhi, a human-restricted bacterium, spread through the faecal-oral route. Following a sustained rise in observed incidence in Fiji from 2004, in 2013, I undertook a nationally-representative cross-sectional serological survey of 1,531 participants to determine infection by age, assess putative risk factors, and quantify social contact patterns. These data were utilised in the development of a transmission dynamic model. The literature indicated that typhoid transmission models are relatively under-utilised, particularly in economic evaluation, with little to guide use of vaccination in place of or alongside water, sanitation and hygiene (WASH). The serosurvey found that iTaukei and non-iTaukei Fijians have similar risk of raised IgG antibodies to the Vi antigen expressed by S. Typhi. Seroprevalence increased with age, suggestive of endemic transmission or declining incidence. Unimproved sanitation may increase risk of seropositivity. Geospatial analysis suggested rainfall, proximity to major rivers and creeks, or flood-prone areas were risk factors for acquisition of anti-Vi IgG antibodies. Social mixing was assortative by ethnicity and age when assessed by mealtime contacts and highest in school-age children. Increasing number of age-adjusted contacts increases the odds ratio for being seropositive, though substantial uncertainties remain around the specificity and sensitivity of serological thresholds as indicators of past typhoid infection. An age- and ethnicity-structured transmission dynamic model fitted the serology and case surveillance data well when including a substantially reduced force of infection for high-dose infection being passed to non-iTaukei Fijians, and high generation of asymptomatic non-infectious cases per new infectious case. Surveillance reporting of infectious cases was estimated as one in five infectious adult cases and one in twelve infectious child cases. The fit to the data suggested endemic rather than declining transmission, and there was better fit with age-ethnic assortative mixing than with ethnically-assortative or homogeneous mixing. Vaccine scenarios suggested that of single dose routine programmes, school entry could be more effective than school leaver vaccination, reflecting age-contact transmission probabilities in the model. Modest reduction (10%) in per-case infectious transmission through effective WASH programmes offered substantial incidence reductions of around 25%, comparable to two-dose (school entry and exit) ViPS vaccination programmes. Potential benefits of conjugate vaccines were projected to be similar to more effective WASH programmes, with administration alongside other vaccines in the second year of life projected to offer approximately 50% incidence reduction, the most benefit of any single dose regimen; with the impact being greater if typhoid carrier daily infectious risk is lower than the daily infectiousness of acute typhoid fever cases

The effect of ambient sounds on decision-making and heart rate variability in autism.

Many autistic people report difficulties making decisions during everyday tasks, such as shopping. To examine the effect of sounds on decision-making, we developed a supermarket task where people watched a film shown from the shopper's perspective and were asked to make decisions between different products. The task was divided into three sections and participants completed each section in a different auditory environment: (1) no sounds, (2) non-social sounds (e.g. fridges humming) and (3) social sounds (e.g. people talking). Thirty-eight autistic and 37 neurotypical adults took part. We measured decision-making by examining how long it took to make a decision and how consistent people were with their decisions. We also measured heart rate variability because this biological response provides a measure of anxiety. After the supermarket shopping task, participants told us in their own words about their experiences. Autistic participants said that they found the non-social and social sound conditions more difficult than the no sound condition, and autistic participants found the social sound condition more negative than neurotypical participants. However, decision-making and heart rate variability were similar for autistic and neurotypical participants across the sound conditions, suggesting that these measures may not have been sensitive enough to reflect the experiences the autistic participants reported. Further research should consider alternative measures to explore the experiences reported by autistic people to help us understand which specific aspects of the environment autistic people are sensitive to. This, in turn, may enable more specific and evidence-based autism-friendly changes to be made.Anonymous donatio

Understanding self-reported difficulties in decision-making by people with autism spectrum disorders.

Autobiographical accounts and a limited research literature suggest that adults with autism spectrum disorders can experience difficulties with decision-making. We examined whether some of the difficulties they describe correspond to quantifiable differences in decision-making when compared to adults in the general population. The participants (38 intellectually able adults with autism spectrum disorders and 40 neurotypical adults) were assessed on three tasks of decision-making (Iowa Gambling Task, Cambridge Gamble Task and Information Sampling Task), which quantified, respectively, decision-making performance and relative attention to negative and positive outcomes, speed and flexibility, and information sampling. As a caution, all analyses were repeated with a subset of participants ( nASD = 29 and nneurotypical = 39) who were not taking antidepressant or anxiolytic medication. Compared to the neurotypical participants, participants with autism spectrum disorders demonstrated slower decision-making on the Cambridge Gamble Task, and superior performance on the Iowa Gambling Task. When those taking the medications were excluded, participants with autism spectrum disorders also sampled more information. There were no other differences between the groups. These processing tendencies may contribute to the difficulties self-reported in some contexts; however, the results also highlight strengths in autism spectrum disorders, such as a more logical approach to, and care in, decision-making. The findings lead to recommendations for how adults with autism spectrum disorders may be better supported with decision-making.The research reported here was carried out by the first author (Lydia Vella, née Luke) as part of her PhD in the Department of Psychiatry, University of Cambridge, and was supported by a Pinsent Darwin Studentship in Mental Health; University of Cambridge Domestic Research Studentship; the Charles Slater Fund; and the Marmaduke Sheild Fund. IC was supported during the preparation of this paper by the National Institute of Health Research (NIHR) Collaboration for Applied Health Research and Care (CLAHRC) East of England at Cambridgeshire & Peterborough NHS Foundation Trust. We are grateful to all our funders for their support. The paper describes independent research and the views expressed are those of the authors and not necessarily those of the NHS, the NIHR, or the Department of Health

Specific Heat Study on a Novel Spin-Gapped System : (CH_3)_2NH_2CuCl_3

Specific heat measurements down to 120mK have been performed on a quasi-one-dimensional $S=1/2$ spin-gapped system (CH$_3$)$_2$NH$_2$CuCl$_3$ in a magnetic field up to 8 T. This compound has a characteristic magnetization curve which shows a gapless ground state and a plateau at 1/2 of the saturation value. We have observed a spontaneous antiferromagnetic ordering and a field-induced one below and above the 1/2 plateau field range, respectively. The field versus temperature phase diagram is quite unusual and completely different from those of the other quantum spin systems investigated so far. In the plateau field range, a double-structure in the specific heat is observed, reflecting the coexistence of ferromagnetic and antiferromagnetic excitations. These behaviors are discussed on the basis of a recently proposed novel quantum spin chain model consisting of weakly coupled ferromagnetic and antiferromagnetic dimers.Comment: 4 pages, 3 figures, submitted to J. Phys. Soc. Jp

Real-time dynamic modelling for the design of a cluster-randomized phase 3 Ebola vaccine trial in Sierra Leone.

BACKGROUND: Declining incidence and spatial heterogeneity complicated the design of phase 3 Ebola vaccine trials during the tail of the 2013-16 Ebola virus disease (EVD) epidemic in West Africa. Mathematical models can provide forecasts of expected incidence through time and can account for both vaccine efficacy in participants and effectiveness in populations. Determining expected disease incidence was critical to calculating power and determining trial sample size. METHODS: In real-time, we fitted, forecasted, and simulated a proposed phase 3 cluster-randomized vaccine trial for a prime-boost EVD vaccine in three candidate regions in Sierra Leone. The aim was to forecast trial feasibility in these areas through time and guide study design planning. RESULTS: EVD incidence was highly variable during the epidemic, especially in the declining phase. Delays in trial start date were expected to greatly reduce the ability to discern an effect, particularly as a trial with an effective vaccine would cause the epidemic to go extinct more quickly in the vaccine arm. Real-time updates of the model allowed decision-makers to determine how trial feasibility changed with time. CONCLUSIONS: This analysis was useful for vaccine trial planning because we simulated effectiveness as well as efficacy, which is possible with a dynamic transmission model. It contributed to decisions on choice of trial location and feasibility of the trial. Transmission models should be utilised as early as possible in the design process to provide mechanistic estimates of expected incidence, with which decisions about sample size, location, timing, and feasibility can be determined

Phase separation due to quantum mechanical correlations

Can phase separation be induced by strong electron correlations? We present a theorem that affirmatively answers this question in the Falicov-Kimball model away from half-filling, for any dimension. In the ground state the itinerant electrons are spatially separated from the classical particles.Comment: 4 pages, 1 figure. Note: text and figure unchanged, title was misspelle

Charge and Orbital Ordering in Pr_{0.5} Ca_{0.5} MnO_3 Studied by ^{17}O NMR

The charge and orbital ordering in Pr_{0.5} Ca_{0.5} MnO_3 is studied for the first time by ^{17}O NMR. This local probe is sensitive to spin, charge and orbital correlations. Two transitions exist in this system: the charge and orbital ordering at T_{CO} = 225 K and the antiferromagnetic (AF) transition at T_N = 170 K. Both are clearly seen in the NMR spectra measured in a magnetic field of 7T. Above T_{CO} there exists only one NMR line with a large isotropic shift, whose temperature dependence is in accordance with the presence of ferromagnetic (FM) correlations. This line splits into two parts below T_{CO}, which are attributed to different types of oxygen in the charge/orbital ordered state. The interplay of FM and AF spin correlations of Mn ions in the charge ordered state of Pr_{0.5} Ca_{0.5} MnO_3 is considered in terms of the hole hopping motion that is slowed down with decreasing temperature. The developing fine structure of the spectra evidences, that there still exist charge-disordered regions at T_{CO} > T > T_N and that the static (t > 10^{-6}s) orbital order is established only on approaching T_N. The CE-type magnetic correlations develop gradually below T_{CO}, so that at first the AF correlations between checkerboard ab-layers appear, and only at lower temperature - CE correlations within the ab-planes

Segregation and charge-density-wave order in the spinless Falicov-Kimball model

The spinless Falicov-Kimball model is solved exactly in the limit of infinite-dimensions on both the hypercubic and Bethe lattices. The competition between segregation, which is present for large U, and charge-density-wave order, which is prevalent at moderate U, is examined in detail. We find a rich phase diagram which displays both of these phases. The model also shows nonanalytic behavior in the charge-density-wave transition temperature when U is large enough to generate a correlation-induced gap in the single-particle density of states.Comment: 10 pages, 10 figure