Bounds on Information Propagation in Disordered Quantum Spin Chains

We investigate the propagation of information through the disordered XY model. We find, with a probability that increases with the size of the system, that all correlations, both classical and quantum, are suppressed outside of an effective lightcone whose radius grows at most polylogarithmically with |t|.Comment: 4 pages, pdflatex, 1 pdf figure. Corrected the bound for the localised propagator and quantified the probability it bound occur

Developing content for a process-of-care checklist for use in intensive care units: a dual-method approach to establishing construct validity

Background: In the intensive care unit (ICU), checklists can be used to support the delivery of quality and consistent clinical care. While studies have reported important benefits for clinical checklists in this context, lack of formal validity testing in the literature prompted the study aim; to develop relevant `process-of-care? checklist statements, using rigorously applied and reported methods that were clear, concise and reflective of the current evidence base. These statements will be sufficiently instructive for use by physicians during ICU clinical rounds. Methods: A dual-method approach was utilized; semi-structured interviews with local clinicians; and rounds of surveys to an expert Delphi panel. The interviews helped determine checklist item inclusion/exclusion prior to the first round Delphi survey. The panel for the modified-Delphi technique consisted of local intensivists and a state- wide ICU quality committee. Minimum standards for consensus agreement were set prior to the distribution of questionnaires, and rounds of surveys continued until consensus was achieved. Results: A number of important issues such as overlap with other initiatives were identified in interviews with clinicians and integrated into the Delphi questionnaire, but no additional checklist items were suggested, demonstrating adequate checklist coverage sourced from the literature. These items were verified by local clinicians as being relevant to ICU and important elements of care that required checking during ward rounds. Two rounds of Delphi surveys were required to reach consensus on nine checklist statements: nutrition, pain management, sedation, deep vein thrombosis and stress ulcer prevention, head-of-bed elevation, blood glucose levels, readiness to extubate, and medications. Conclusions: Statements were developed as the most clear, concise, evidence-informed and instructive statements for use during clinical rounds in an ICU. Initial evidence in support of the checklist?s construct validity was established prior to further prospective evaluation in the same ICU

Post-fire Recruitment Failure as a Driver of Forest to Non-forest Ecosystem Shifts in Boreal Regions

Climate change and land-use are driving large changes in forest ecosystems around the globe. In the boreal biome it is likely that increases in temperature and the associated lengthening of the growing season will cause the forest to expand into the northern tundra and upwards in elevation, whilst potentially contracting at its southern limits. This increase in temperature is also driving an increase in the frequency and severity of boreal forest fires. A growing number of studies have observed the failure of forest species to re-establish after a standreplacing fire event, which results in the shift to a non-forested ecosystem. In this chapter, this process is referred to as post-fire recruitment failure. We provide multiple lines of evidence for boreal forests, and more specifically for southern Siberia forests, that a possible regional tipping point is unfolding, which could lead to the rapid replacement of large areas of forest ecosystems with low-stature non-forest ecosystems. This change would come with significant consequences for the carbon balance, surface albedo and the resulting altered energy balanc

Condensation of microturbulence-generated shear flows into global modes

In full flux-surface computer studies of tokamak edge turbulence, a spectrum of shear flows is found to control the turbulence level and not just the conventional (0,0)-mode flows. Flux tube domains too small for the large poloidal scale lengths of the continuous spectrum tend to overestimate the flows, and thus underestimate the transport. It is shown analytically and numerically that under certain conditions dominant (0,0)-mode flows independent of the domain size develop, essentially through Bose-Einstein condensation of the shear flows.Comment: 5 pages, 4 figure

Non-Destructive Evaluation of Grain Structure Using Air-Coupled Ultrasonics

Cast material has a grain structure that is relatively non-uniform. There is a desire to evaluate the grain structure of this material non-destructively. Traditionally, grain size measurement is a destructive process involving the sectioning and metallographic imaging of the material. Generally, this is performed on a representative sample on a periodic basis. Sampling is inefficient and costly. Furthermore, the resulting data may not provide an accurate description of the entire part's average grain size or grain size variation. This project is designed to develop a non-destructive acoustic scanning technique, using Chirp waveforms, to quantify average grain size and grain size variation across the surface of a cast material. A Chirp is a signal in which the frequency increases or decreases over time (frequency modulation). As a Chirp passes through a material, the material's grains reduce the signal (attenuation) by absorbing the signal energy. Geophysics research has shown a direct correlation with Chirp wave attenuation and mean grain size in geological structures. The goal of this project is to demonstrate that Chirp waveform attenuation can be used to measure grain size and grain variation in cast metals (uranium and other materials of interest). An off-axis ultrasonic inspection technique using air-coupled ultrasonics has been developed to determine grain size in cast materials. The technique gives a uniform response across the volume of the component. This technique has been demonstrated to provide generalized trends of grain variation over the samples investigated

Axisymmetric equilibria of a gravitating plasma with incompressible flows

It is found that the ideal magnetohydrodynamic equilibrium of an axisymmetric gravitating magnetically confined plasma with incompressible flows is governed by a second-order elliptic differential equation for the poloidal magnetic flux function containing five flux functions coupled with a Poisson equation for the gravitation potential, and an algebraic relation for the pressure. This set of equations is amenable to analytic solutions. As an application, the magnetic-dipole static axisymmetric equilibria with vanishing poloidal plasma currents derived recently by Krasheninnikov, Catto, and Hazeltine [Phys. Rev. Lett. {\bf 82}, 2689 (1999)] are extended to plasmas with finite poloidal currents, subject to gravitating forces from a massive body (a star or black hole) and inertial forces due to incompressible sheared flows. Explicit solutions are obtained in two regimes: (a) in the low-energy regime $\beta_0\approx \gamma_0\approx \delta_0 \approx\epsilon_0\ll 1$, where $\beta_0$, $\gamma_0$, $\delta_0$, and $\epsilon_0$ are related to the thermal, poloidal-current, flow and gravitating energies normalized to the poloidal-magnetic-field energy, respectively, and (b) in the high-energy regime $\beta_0\approx \gamma_0\approx \delta_0 \approx\epsilon_0\gg 1$. It turns out that in the high-energy regime all four forces, pressure-gradient, toroidal-magnetic-field, inertial, and gravitating contribute equally to the formation of magnetic surfaces very extended and localized about the symmetry plane such that the resulting equilibria resemble the accretion disks in astrophysics.Comment: 12 pages, latex, to be published in Geophys. Astrophys. Fluid Dynamic

A progressive postresection walking program significantly improves fatigue and health-related quality of life in pancreas and periampullary cancer patients.

BACKGROUND: As patients with pancreas and periampullary cancer (PPC) experience improved survival rates and longevity, the focus shifts toward living life while surviving cancer. Fatigue is the most commonly reported symptom in all cancer patients. Exercise has been found to effectively decrease fatigue levels and improve physical functioning in cancer patients. STUDY DESIGN: One hundred two patients with resected PPC consented to participate in this study and were randomized to either an intervention group (IG) or a usual care group (UCG). Subjects completed visual analog scales, the FACIT-Fatigue Scale and the Short Form-36v2 after surgery and again 3 to 6 months after hospital discharge. RESULTS: Patients in the IG and UCG were comparable with regard to demographics, comorbidities, cancer type and staging, type of resection, preoperative fatigue and pain levels, adjuvant therapy, and baseline walking distance. Patients in the IG had significantly improved scores on the FACIT-Fatigue Scale at study completion, improved fatigue and pain scores, as well as overall physical functioning and mental health composite scores. At study completion, participants in the IG were walking twice as far and were significantly more likely to have continued walking or another form of exercise as compared with the UCG. Using hierarchical cluster analysis, 3 mutually exclusive symptom groupings were identified in the cohort. Kaplan-Meier survival analysis did not indicate an overall survival benefit for the IG. CONCLUSIONS: This is the first prospective, randomized controlled trial to report that participation in a home walking program confers a significant benefit in resected PPC patients with regard to fatigue levels, physical functioning, and health-related quality of life

Children and young people’s experiences of completing mental health and wellbeing measures for research: learning from two school-based pilot projects

BACKGROUND: In recent years there has been growing interest in child and adolescent mental health and wellbeing, alongside increasing emphasis on schools as a crucial site for research and intervention. This has coincided with an increased use of self-report mental health and wellbeing measures in research with this population, including in school-based research projects. We set out to explore the way that children and young people perceive and experience completing mental health and wellbeing measures, with a specific focus on completion in a school context, in order to inform future measure and research design. METHODS: We conducted semi-structured interviews and focus groups with 133 participants aged 8–16 years following their completion of mental health and wellbeing measures as part of school-based research programmes, using thematic analysis to identify patterns of experience. FINDINGS: We identified six themes: Reflecting on emotions during completion; the importance of anonymity; understanding what is going to happen; ease of responding to items; level of demand; and interacting with the measure format. CONCLUSIONS: Our findings offer greater insight into children and young people’s perceptions and experiences in reporting on their mental health and wellbeing. Such understanding can be used to support more ethical and robust data collection procedures in child and adolescent mental health research, both for data quality and ethical purposes. We offer several practical recommendations for researchers, including facilitating this in a school context