First-passage theory of exciton population loss in single-walled carbon nanotubes reveals micron-scale intrinsic diffusion lengths

One-dimensional crystals have long range translational invariance which manifests as long exciton diffusion lengths, but such intrinsic properties are often obscured by environmental perturbations. We use a first-passage approach to model single-walled carbon nanotube (SWCNT) exciton dynamics (including exciton-exciton annihilation and end effects) and compare it to results from both continuous-wave and multi-pulse ultrafast excitation experiments to extract intrinsic SWCNT properties. Excitons in suspended SWCNTs experience macroscopic diffusion lengths, on the order of the SWCNT length, (1.3-4.7 um) in sharp contrast to encapsulated samples. For these pristine samples, our model reveals intrinsic lifetimes (350-750 ps), diffusion constants (130-350 cm^2/s), and absorption cross-sections (2.1-3.6 X 10^-17 cm^2/atom) among the highest previously reported.and diffusion lengths for SWCNTs.Comment: 6 pages, 3 figure

A new tunnel assessment procedure integrating smoke dispersion and evacuation models

International audienceThis paper focuses on a new risk assessment procedure for tunnel. This procedure is based on the coupling between smoke dispersion models and evacuation models. It has been developed inside the UPGRADE procedure put in place in the UPTUN project. The method is based on two heat and mass flow (HMF) models for the calculation of tenability conditions due to a fire event: NewVendis for the 1D calculation and the global equilibrium of the tunnel network and FASIT for the calculation in the vicinity of the fire. Tenability conditions are used as input data for the evacuation calculation carried out by the evacuation model CRISP . All results (smoke dispersion and evacuation) are then combined in tenability diagrams which are a superposition of HMF tenability conditions and users' location in the tunnel. This kind of presentation can then be used to help understand injuries or people casualties and to take efficient safety measures to increase safety level in tunnel

A position sensitive phoswich hard X-ray detector system

A prototype position sensitive phoswich hard X-ray detector, designed for eventual astronomical usage, was tested in the laboratory. The scintillation crystal geometry was designed on the basis of a Monte Carlo simulation of the internal optics and includes a 3mm thick NaI(T1) primary X-ray detector which is actively shielded by a 20 mm thick CsI(T1) scintillation crystal. This phoswich arrangement is viewed by a number two inch photomultipliers. Measured values of the positional and spectral resolution of incident X-ray photons are compared with calculation

Spatially generalizable representations of facial expressions: Decoding across partial face samples

A network of cortical and sub-cortical regions is known to be important in the processing of facial expression. However, to date no study has investigated whether representations of facial expressions present in this network permit generalization across independent samples of face information (e.g. eye region Vs mouth region). We presented participants with partial face samples of five expression categories in a rapid event-related fMRI experiment. We reveal a network of face sensitive regions that contain information about facial expression categories regardless of which part of the face is presented. We further reveal that the neural information present in a subset of these regions: dorsal prefrontal cortex (dPFC), superior temporal sulcus (STS), lateral occipital and ventral temporal cortex, and even early visual cortex, enables reliable generalization across independent visual inputs (faces depicting the 'eyes only' versus 'eyes removed'). Furthermore, classification performance was correlated to behavioral performance in STS and dPFC. Our results demonstrate that both higher (e.g. STS, dPFC) and lower level cortical regions contain information useful for facial expression decoding that go beyond the visual information presented, and implicate a key role for contextual mechanisms such as cortical feedback in facial expression perception under challenging conditions of visual occlusion

Sensor-steered fire simulation

A sensor-linked modelling tool for live prediction of uncontrolled compartment fires, K-CRISP, has been developed in order to facilitate emergency response via novel systems such as FireGrid. The modelling strategy is an extension of the Monte-Carlo fire model, CRISP, linking simulations to sensor inputs which controls evolution of the parametric space in which new scenarios are generated, thereby representing real-time “learning” about the fire. CRISP itself is based on a zone model representation of the fire, with linked capabilities for egress modelling and failure prediction for structural members, thus providing a major advantage over more detailed approaches in terms of flexibility and practicality, though with the conventional limitations of zone models. Large numbers of scenarios are required, but computational demands are mitigated to some extent by various procedures to limit the parameters which need to be varied. HPC (high performance computing) resources are exploited in “urgent computing” mode. The approach adopted for steering is shown to be effective in directing the evolution of the fire parameters, thereby driving the fire predictions towards the measurements. Moreover, the availability of probabilistic information in the output assists in providing potential end users with an indication of the likelihood of various hazard scenarios. The best forecasts are those for the immediate future, or for relatively simple fires, with progressively less confidence at longer lead times and in more complex scenarios. Given the uncertainties in real fire development the benefits of more detailed model representations may be marginal and the system developed thus far is considered to be an appropriate engineering approach to the problem, providing information of potential benefit in emergency response

An Economic Analysis of Twitching Behaviour and Species Rarity

Avid birdwatchers, or ‘twitchers’, expend a considerable amount of money and time pursuing viewing experiences of rare or vagrant species. By vagrant species we mean a species found outside its normal range/distribution. To enhance our understanding of this form of behaviour, we present results from a UK survey of twitchers. First, we examine the relationship between cost and rarity based on actual viewing experiences. Our statistical results reveal that the relationship between cost and rarity is positive and very inelastic. Second, we present results from a hypothetical Best-Worst Scaling exercise examining aspects of species rarity. We find that rarity is a more nuanced construct than simply the frequency with which a vagrant species has appeared. Our results provide insights into the meaning of rarity, as well as the economic value attach to it and why

The impact of deliberate reflection with WISE-MD modules on surgical clerkship students\u27 critical thinking: a prospective, randomized controlled pilot study

Purpose: Critical thinking underlies several Association of American Medical Colleges (AAMC)-defined core entrustable professional activities (EPAs). Critical-thinking ability affects health care quality and safety. Tested tools to teach, assess, improve, and nurture good critical-thinking skills are needed. This prospective randomized controlled pilot study evaluated the addition of deliberate reflection (DR), guidance with Web Initiative in Surgical Education (WISE-MD) modules, to promote surgical clerks\u27 critical-thinking ability. The goal was to promote the application of reflective awareness principles to enhance learning outcomes and critical thinking about the module content. Participants and methods: Surgical clerkship (SC) students were recruited from two different blocks and randomly assigned to a control or intervention group. The intervention group was asked to record responses using a DR guide as they viewed two selected WISE-MD modules while the control group was asked to view two modules recording free thought. We hypothesized that the intervention group would show a significantly greater pre- to postintervention increase in critical-thinking ability than students in the control group. Results: Neither group showed a difference in pre- and posttest free-thought critical-thinking outcomes; however, the intervention group verbalized more thoughtful clinical reasoning during the intervention. Conclusion: Despite an unsupported hypothesis, this study provides a forum for discussion in medical education. It took a sponsored tool in surgical education (WISE-MD) and posed the toughest evaluation criteria of an educational intervention; does it affect the way we think? and not just what we learn, but how we learn it? The answer is significant and will require more resources before we arrive at a definitive answer

GPs’ role in caring for children and young people with life-limiting conditions: a retrospective cohort study

Background: GPs are rarely actively involved in healthcare provision for children and young people (CYP) with life-limiting conditions (LLCs). This raises problems when these children develop minor illness or require management of other chronic diseases. Aim: To investigate the association between GP attendance patterns and hospital urgent and emergency care use. Design and setting: Retrospective cohort study using a primary care data source (Clinical Practice Research Datalink) in England. The cohort numbered 19 888. Method: CYP aged 0–25 years with an LLC were identified using Read codes (primary care) or International Classification of Diseases 10 th Revision (ICD-10) codes (secondary care). Emergency inpatient admissions and accident and emergency (A&E) attendances were separately analysed using multivariable, two-level random intercept negative binomial models with key variables of consistency and regularity of GP attendances. Results: Face-to-face GP surgery consultations reduced, from a mean of 7.12 per person year in 2000 to 4.43 in 2015. Those consulting the GP less regularly had 15% (95% confidence interval [CI] = 10% to 20%) more emergency admissions and 5% more A&E visits (95% CI = 1% to 10%) than those with more regular consultations. CYP who had greater consistency of GP seen had 10% (95% CI = 6% to 14%) fewer A&E attendances but no significant difference in emergency inpatient admissions than those with lower consistency. Conclusion: There is an association between GP attendance patterns and use of urgent secondary care for CYP with LLCs, with less regular GP attendance associated with higher urgent secondary healthcare use. This is an important area for further investigation and warrants the attention of policymakers and GPs, as the number of CYP with LLCs living in the community rises

Model thrombi formed under flow reveal the role of factor XIII-mediated cross-linking in resistance to fibrinolysis

Background: Activated factor XIII (FXIIIa), a transglutaminase, introduces fibrin-fibrin and fibrin-inhibitor cross-links, resulting in more mechanically stable clots. The impact of cross-linking on resistance to fibrinolysis has proved challenging to evaluate quantitatively. Methods: We used a whole blood model thrombus system to characterize the role of cross-linking in resistance to fibrinolytic degradation. Model thrombi, which mimic arterial thrombi formed in vivo, were prepared with incorporated fluorescently labeled fibrinogen, in order to allow quantification of fibrinolysis as released fluorescence units per minute. Results: A site-specific inhibitor of transglutaminases, added to blood from normal donors, yielded model thrombi that lysed more easily, either spontaneously or by plasminogen activators. This was observed both in the cell/platelet-rich head and fibrin-rich tail. Model thrombi from an FXIII-deficient patient lysed more quickly than normal thrombi; replacement therapy with FXIII concentrate normalized lysis. In vitro addition of purified FXIII to the patient's preprophylaxis blood, but not to normal control blood, resulted in more stable thrombi, indicating no further efficacy of supraphysiologic FXIII. However, addition of tissue transglutaminase, which is synthesized by endothelial cells, generated thrombi that were more resistant to fibrinolysis; this may stabilize mural thrombi in vivo. Conclusions: Model thrombi formed under flow, even those prepared as plasma 'thrombi', reveal the effect of FXIII on fibrinolysis. Although very low levels of FXIII are known to produce mechanical clot stability, and to achieve ?-dimerization, they appear to be suboptimal in conferring full resistance to fibrinolysis