Effect of quantum nuclear motion on hydrogen bonding

This work considers how the properties of hydrogen bonded complexes, D-H....A, are modified by the quantum motion of the shared proton. Using a simple two-diabatic state model Hamiltonian, the analysis of the symmetric case, where the donor (D) and acceptor (A) have the same proton affinity, is carried out. For quantitative comparisons, a parametrization specific to the O-H....O complexes is used. The vibrational energy levels of the one-dimensional ground state adiabatic potential of the model are used to make quantitative comparisons with a vast body of condensed phase data, spanning a donor-acceptor separation (R) range of about 2.4-3.0 A, i.e., from strong to weak bonds. The position of the proton and its longitudinal vibrational frequency, along with the isotope effects in both are discussed. An analysis of the secondary geometric isotope effects, using a simple extension of the two-state model, yields an improved agreement of the predicted variation with R of frequency isotope effects. The role of the bending modes in also considered: their quantum effects compete with those of the stretching mode for certain ranges of H-bond strengths. In spite of the economy in the parametrization of the model used, it offers key insights into the defining features of H-bonds, and semi-quantitatively captures several experimental trends.Comment: 12 pages, 8 figures. Notation clarified. Revised figure including the effect of bending vibrations on secondary geometric isotope effect. Final version, accepted for publication in Journal of Chemical Physic

A L\'evy input fluid queue with input and workload regulation

We consider a queuing model with the workload evolving between consecutive i.i.d.\ exponential timers $\{e_q^{(i)}\}_{i=1,2,...}$ according to a spectrally positive L\'evy process $Y_i(t)$ that is reflected at zero, and where the environment $i$ equals 0 or 1. When the exponential clock $e_q^{(i)}$ ends, the workload, as well as the L\'evy input process, are modified; this modification may depend on the current value of the workload, the maximum and the minimum workload observed during the previous cycle, and the environment $i$ of the L\'evy input process itself during the previous cycle. We analyse the steady-state workload distribution for this model. The main theme of the analysis is the systematic application of non-trivial functionals, derived within the framework of fluctuation theory of L\'evy processes, to workload and queuing models

A Ten Year Review of Civilian Iliac Vessel Injuries from a Single Trauma Centre

AbstractObjectiveTo report the surgical management and outcome of iliac vessel (IV) injuries in a civilian trauma centre with a high incidence of penetrating trauma.Design, patients and methodsA retrospective record review of patients with IV injuries treated between January 2000 and December 2009.ResultsSixty nine patients, 59 with gunshot wounds, sustained 108 iliac vessel injuries. Mean revised trauma and injury severity scores was 7.06 and 28.4, respectively. Twenty nine patients required damage control laparotomy. Common or external iliac arteries were repaired by primary repair (10), temporary shunt with delayed graft (6), interposition graft (5) or ligation if limb non-viable (3). Forty-seven patients had injuries to the common or external iliac vein, 42 were ligated. Mortality was 25% and 6 survivors required amputation.ConclusionsIn a stable patient a primary arterial repair is preferred but a temporary shunt can be a life and limb saving option in the unstable patient. Ligating the common or external iliac veins is associated with a low incidence of prolonged leg swelling

Applications of discrete choice experiments in COVID-19 research:Disparity in survey qualities between health and transport fields

Published choice experiments linked to various aspects of the COVID-19 pandemic are analysed in a rapid review. The aim is to (i) document the diversity of topics as well as their temporal and geographical patterns of emergence, (ii) compare various elements of design quality across different sectors of applied economics, and (iii) identify potential signs of convergent validity across findings of comparable experiments. Of the N = 43 published choice experiments during the first two years of the pandemic, the majority identifies with health applications (n = 30), followed by transport-related applications (n = 10). Nearly 100,000 people across the world responded to pandemic-related discrete choice surveys. Within health applications, while the dominant theme, up until June 2020, was lockdown relaxation and tracing measures, the focus shifted abruptly to vaccine preference since then. Geographical origins of the health surveys were not diverse. Nearly 50% of all health surveys were conducted in only three countries, namely US, China and The Netherlands. Health applications exhibited stronger pre-testing and larger sample sizes compared to transport applications. Limited signs of convergent validity were identifiable. Within some applications, issues of temporal instability as well as hypothetical bias attributable to social desirability, protest response or policy consequentiality seemed likely to have affected the findings. Nevertheless, very few of the experiments implemented measures of hypothetical bias mitigation and those were limited to health studies. Our main conclusion is that swift administration of pandemic-related choice experiments has overall resulted in certain degrees of compromise in study quality, but this has been more so the case in relation to transport topics than health topics

An attempt to decrease social desirability bias:The effect of cheap talk mitigation on internal and external validity of discrete choice experiments

Discrete choice experiments (DCEs) have been used extensively to elicit preferences. However, the hypothetical nature of choices induces socially desirable behaviour and endangers internal and external validity of DCEs. This study experimentally investigated social desirability bias in DCEs and whether it can be mitigated using the cheap talk mitigation method in the context of food choices. Respondents (N = 1027) were randomly allocated to one of four questionnaire versions: default without manipulation, priming socially desirable behaviour, cheap talk mitigation, or both. The effect on internal validity was assessed by comparing respondent-reported characteristics, DCE results, and prediction accuracy for a holdout task between questionnaire versions. The effect on external validity was assessed by comparing stated and revealed preferences. Social desirability bias, if present, was hardly affected by cheap talk mitigation. Respondent-reported characteristics, DCE results and prediction accuracy for the holdout task and actual food choice did not strongly differ between questionnaire versions. Prediction accuracy for the holdout task was lowest in the default version. Prediction accuracy for actual food choice was slightly better among respondents in the versions that were exposed to cheap talk mitigation. Social desirability bias was hard to detect and mitigate in this study, potentially due to limited social desirability, the effectiveness of the cheap talk mitigation method, and other sources of hypothetical bias. The differences in prediction accuracy indicates that cheap talk mitigation slightly improved external validity at minimum cost to internal validity. Recommendations for future research are provided.</p

Pan computed tomography for blunt polytrauma: Are we doing too many?

Background. Pan computed tomography (CT) is widely used in the evaluation of  patients with blunt polytrauma, but there is growing concern about the radiation risks imposed.Objectives. To ascertain whether we were possibly overutilising pan CT in our  trauma service, and whether we could safely cut down on scans without missing significant injuries.Methods. We audited all pan scans performed in the Metropolitan Trauma Service, Pietermaritzburg, South Africa, during the 12-month period 1 January - 31  December 2012. An analysis was done to determine what injuries were identified and how these findings influenced our management.Results. Of the 140 pan scans, 108 (77.1%) influenced management. These  included the following components: 62 brain scans (44.3%), 16 cervical spine scans (11.4%), 50 chest scans (35.7%) and 31 abdominal scans (22.1%). The remaining 32 pan scans (22.9%) did not influence management. However, it turned out that many of these ‘clinically negative’ scans were in fact clinically important, ruling out injury in patients in whom clinical assessment was regarded as unreliable: 3 patients (2.1%) were hypoxic and had to be sedated, intubated and ventilated; 14 (10.0%) had a Glasgow Coma Score (GCS) of &lt;15; and 9 (6.4%) had major  distracting injuries. This left only 6 pan scans (4.3%) that were not regarded as clinically helpful.Conclusion. In our setting, the majority of pan scans influence management. By  ruling out significant injuries, clinically negative scans are valuable in patients who are obtunded, intubated and ventilated, or have major distracting injuries. In  patients with a GCS of 15, not sedated and ventilated and with no major distracting injuries, clinical assessment and alternative imaging modalities may suffice

Optical spectroscopy of complex open 4dd-shell ions Sn7+^{7+}-Sn10+^{10+}

We analyze the complex level structure of ions with many-valence-electron open [Kr] 4$d^\textrm{m}$ sub-shells ($\textrm{m}$=7-4) with ab initio calculations based on configuration-interaction many-body perturbation theory (CI+MBPT). Charge-state-resolved optical and extreme ultraviolet (EUV) spectra of Sn$^{7+}$-Sn$^{10+}$ ions were obtained using an electron beam ion trap. Semi-empirical spectral fits carried out with the orthogonal parameters technique and Cowan code calculations lead to 90 identifications of magnetic-dipole transitions and the determination of 79 energy ground-configuration levels, questioning some earlier EUV-line assignments. Our results, the most complete data set available to date for these ground configurations, confirm the ab initio predictive power of CI+MBPT calculations for the these complex electronic systems.Comment: 18 pages, 5 figure

Public Preferences for Introducing a COVID-19 Certificate:A Discrete Choice Experiment in the Netherlands

Objective: Here we investigate public preferences for coronavirus disease 2019 (COVID-19) certificates in the Netherlands, and whether these preferences differ between subgroups in the population. Methods: A survey including a discrete choice experiment was administered to 1500 members of the adult population of the Netherlands. Each participant was asked to choose between hypothetical COVID-19 certificates that differed in seven attributes: the starting date, and whether the certificate allowed gathering with multiple people, shopping without appointment, visiting bars and restaurants, visiting cinemas and theatres, attending events, and practising indoor sports. Latent class models (LCMs) were used to determine the attribute relative importance and predicted acceptance rate of hypothetical certificates. Results: Three classes of preference patterns were identified in the LCM. One class a priori opposed a certificate (only two attributes influencing preferences), another class was relatively neutral and included all attributes in their decision making, and the final class was positive towards a certificate. Respondents aged &gt; 65 years and those who plan to get vaccinated were more likely to belong to the latter two classes. Being allowed to shop without appointment and to visit bars and restaurants was most important to all respondents, increasing predicted acceptance rate by 12 percentage points. Conclusions: Preferences for introduction of a COVID-19 certificate are mixed. A certificate that allows for shopping without appointment and visiting bars and restaurants is likely to increase acceptance. The support of younger citizens and those who plan to get vaccinated seems most sensitive to the specific freedoms granted by a COVID-19 certificate

Autonomy deficits as vulnerability for anxiety:Evidence from two laboratory-based studies

Background Autonomous individuals are characterized by self-governance; awareness of and capacity to realize one’s wishes and needs, while being connected with and sensitive towards others. In line with earlier research showing consistent associations between autonomy-connectedness deficits and anxiety, we tested in two studies whether autonomy deficits predict anxious responses to acute stressors. Methods In Study 1, participants (N = 177) viewed an anxiety-inducing film fragment and reported anxiety before and after viewing the clip. In experimental Study 2, participants (N = 100) were randomly allocated to one of two conditions: giving a short presentation to an audience (impromptu speech task) or watching another person’s presentation (control condition). Anxiety was measured at baseline, after a preparation period and directly after the presentation. Results In Study 1, individuals’ anxiety in reaction to watching the movie was positively associated with the autonomy-connectedness component sensitivity to others. In Study 2, individuals’ anxiety in reaction to preparing the presentation was negatively associated with the autonomy-connectedness component self-awareness. Conclusions Specific autonomy components may be related to experiencing anxiety in differing situations (i.e., related to others’ distress or presenting one’s personal views). Collectively these results indicate that autonomy-connectedness deficits may form a vulnerability factor for experiencing anxiety