One-Dimensional Directed Sandpile Models and the Area under a Brownian Curve

We derive the steady state properties of a general directed ``sandpile'' model in one dimension. Using a central limit theorem for dependent random variables we find the precise conditions for the model to belong to the universality class of the Totally Asymmetric Oslo model, thereby identifying a large universality class of directed sandpiles. We map the avalanche size to the area under a Brownian curve with an absorbing boundary at the origin, motivating us to solve this Brownian curve problem. Thus, we are able to determine the moment generating function for the avalanche-size probability in this universality class, explicitly calculating amplitudes of the leading order terms.Comment: 24 pages, 5 figure

The effect of free-stream turbulence on heat transfer to a strongly accelerated turbulent boundary layer

Free-stream turbulence effects on heat transfer to strongly accelerated turbulent boundary laye

Distribution of the time at which the deviation of a Brownian motion is maximum before its first-passage time

We calculate analytically the probability density $P(t_m)$ of the time $t_m$ at which a continuous-time Brownian motion (with and without drift) attains its maximum before passing through the origin for the first time. We also compute the joint probability density $P(M,t_m)$ of the maximum $M$ and $t_m$. In the driftless case, we find that $P(t_m)$ has power-law tails: $P(t_m)\sim t_m^{-3/2}$ for large $t_m$ and $P(t_m)\sim t_m^{-1/2}$ for small $t_m$. In presence of a drift towards the origin, $P(t_m)$ decays exponentially for large $t_m$. The results from numerical simulations are in excellent agreement with our analytical predictions.Comment: 13 pages, 5 figures. Published in Journal of Statistical Mechanics: Theory and Experiment (J. Stat. Mech. (2007) P10008, doi:10.1088/1742-5468/2007/10/P10008

Effective mass and quantum lifetime in a Si/Si0.87Ge0.13/Si two-dimensional hole gas

Measurements of Shubnikov de Haas oscillations in the temperature range 0.3–2 K have been used to determine an effective mass of 0.23 m0 in a Si/Si0.87Ge0.13/Si two-dimensional hole gas. This value is in agreement with theoretical predictions and with that obtained from cyclotron resonance measurements. The ratio of the transport time to the quantum lifetime is found to be 0.8. It is concluded that the 4 K hole mobility of 11 000 cm2 V−1 s−1 at a carrier sheet density of 2.2×1011 cm−2 is limited by interface roughness and short-range interface charge scattering

Development of a post-fall multidisciplinary checklist to evaluate the in-patient fall

Background: Falls suffered by hospitalized patients are an important reportable event. Approximately 4 - 6 % of inpatient falls result in serious injury. Recurrent falls or delayed recognition of injury can harm patients and represents a medico-legal risk. In 2010, our tertiary-care academic medical center reviewed current practice regarding falls prevention and assessment to develop a comprehensive falls prevention program. The committee found that there was no consistent practice in the assessment by nurses or physicians of inpatients who had fallen, either for injury or for conditions which might have led to the fall. A new systematic checklist for evaluation of the hospital faller was developed by a team consisting of nursing, hospitalists, and a medical unit director. Purpose: To develop an evidence-based multi-disciplinary checklist to facilitate evaluation, implementation of secondary prevention interventions and documentation following a hospital fall. Description: The hospitalist and the general medical unit director reviewed relevant literature, consulted national experts, and drafted a multidisciplinary checklist, the UNMH Post-Fall/Huddle Tool, to be used by nurses and physicians in post-fall patient evaluation. The checklist was reviewed and revised with further input from key stakeholders including hospitalists, housestaff, and the adult Medical/Surgical Shared Governance Committee. It was implemented as part of a comprehensive falls prevention program 3 month pilot. The checklist prompts a three step process: (1) an initial 7-item assessment by nursing staff to determine factors which would necessitate immediate evaluation by cross-covering physicians versus deferring evaluation to the primary team; (2) a 5-item focused physical examination to be performed by a physician to assess the likelihood of injury and suggested diagnostic tests based on this examination; and (3) an interdisciplinary face-to-face meeting between the evaluating physician and nurse to review 7 specific possible precipitating events and implement potential interventions. The UNMH Post-Fall/Huddle Tool will be adapted into the electronic health record after pilot completion and evaluation. An educational presentation about falls and how to use the checklist was developed for residents and hospitalists. Use of the checklist was implemented in November, 2010. To date, nurses and residents report that the checklist is easy to use and that it facilitates a timely, multidisciplinary evaluation of patients who have fallen in the hospital. Conclusion: A multi-disciplinary post-fall checklist facilitates a consistent and evidence-based evaluation and treatment of patients who have fallen in the hospital

Changes in Pasture Growth Rate Due to Fertiliser and Grazing Management

It is imperative that sheep production systems in southern Australia continue to be refined so producers remain financially viable but at the same time the environment is not degraded. As part of a national thrust for development and promotion of better production systems, one research site has been established in Victoria where pastures and animal production are measured together with water and nutrient movement. Results for pasture growth rates over two years are presented here and will be used to develop best industry practice at completion of the project

Area distribution and the average shape of a L\'evy bridge

We consider a one dimensional L\'evy bridge x_B of length n and index 0 < \alpha < 2, i.e. a L\'evy random walk constrained to start and end at the origin after n time steps, x_B(0) = x_B(n)=0. We compute the distribution P_B(A,n) of the area A = \sum_{m=1}^n x_B(m) under such a L\'evy bridge and show that, for large n, it has the scaling form P_B(A,n) \sim n^{-1-1/\alpha} F_\alpha(A/n^{1+1/\alpha}), with the asymptotic behavior F_\alpha(Y) \sim Y^{-2(1+\alpha)} for large Y. For \alpha=1, we obtain an explicit expression of F_1(Y) in terms of elementary functions. We also compute the average profile < \tilde x_B (m) > at time m of a L\'evy bridge with fixed area A. For large n and large m and A, one finds the scaling form = n^{1/\alpha} H_\alpha({m}/{n},{A}/{n^{1+1/\alpha}}), where at variance with Brownian bridge, H_\alpha(X,Y) is a non trivial function of the rescaled time m/n and rescaled area Y = A/n^{1+1/\alpha}. Our analytical results are verified by numerical simulations.Comment: 21 pages, 4 Figure

Adapting to the digital age: a narrative approach

The article adopts a narrative inquiry approach to foreground informal learning and exposes a collection of stories from tutors about how they adapted comfortably to the digital age. We were concerned that despite substantial evidence that bringing about changes in pedagogic practices can be difficult, there is a gap in convincing approaches to help in this respect. In this context, this project takes a “bottom-up” approach and synthesises several life-stories into a single persuasive narrative to support the process of adapting to digital change. The project foregrounds the small, every-day motivating moments, cultural features and environmental factors in people's diverse lives which may have contributed to their positive dispositions towards change in relation to technology enhanced learning. We expect that such narrative approaches could serve to support colleagues in other institutions to warm up to ever-changing technological advances

Appropriate timing of the 14 C-urea breath test to establish eradication of Helicobacter pylori infection

The aim of this study was to determine the performance characteristics of the 14 C-urea breath test (UBT) performed 2 wk after the completion of therapy for Helicobacter pylori using a 4 to 6 wk study as the gold standard. METHODS : Patients with active Helicobacter pylori infection at four medical centers received proton pump inhibitor-based triple or quadruple therapy for 10–14 days. Patients underwent the 14 C-UBT 2 and 4–6 wk after the completion of therapy. A positive test was defined as 14 CO 2 excretion of >200 dpm, a negative test as 50 but <200 dpm. Performance characteristics of the 2-wk UBT were calculated using the 4 to 6-wk result as a gold standard. RESULTS : Eighty-five patients were enrolled and 82 patients (mean ± SD age, 62 ± 15 yr; 15 women) completed the protocol. Four patients had equivocal UBT results and were excluded from the analysis. Of the 78 patients, 68 (87%) had a negative 4 to 6-wk UBT. The 2-week UBT yielded a sensitivity of 90% (95% confidence interval 72–100%), specificity of 99% (97–100%), and accuracy of 97% (93–100%). In patients with a persistently positive UBT, 14 CO 2 excretion at 2 wk was significantly lower than at 4–6 wk after therapy ( p = 0.03 ). CONCLUSIONS : A UBT performed 2 wk after therapy yielded results comparable to 4 to 6 wk testing. Further studies to evaluate the optimal time of confirmatory testing in the age of more effective proton pump inhibitor-based triple therapies are warranted.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73434/1/j.1572-0241.2000.02005.x.pd