Physical Constraints to Aquatic Plant Growth in New Zealand Lakes

The nature of aquatic plant communities often defines benthic habitat within oligotrophic and mesotrophic lakes and lake management increasingly recognizes the importance of maintaining plant diversity in order to sustain biological diversity and capacity within lakes. We have developed simple statistical relationships between key physical and vegetation variables that define the habitat requirements, or “habitat-templates”, of key vegetation types to facilitate management of plant communities in New Zealand lakes. Statistical relationships were derived from two datasets. The first was a multi-lake dataset to determine the effects of water level fluctuation and water clarity. The second dataset was from a comprehensive shoreline survey of Lake Wanaka, which allowed us to examine within-lake variables such as beach slope and wave action. Sufficient statistical relationships were established to develop a habitat template for each of the major species or assemblages. The relationships suggested that the extent and diversity of shallow-growing species was related to a combination of the extent of water level fluctuation and wave exposure. (PDF contains 9 pages.

A slow and dark atomic beam

We demonstrate a method to produce a very slow atomic beam from a vapour cell magneto-optical trap. Atoms are extracted from the trap using the radiation pressure imbalance caused by a push beam. An additional transfer beam placed near the center of the trap transfers the atomic beam into an off-resonant state. The velocity of the atomic beam has been varied by changing the intensity of the push beam or the position of the transfer beam. The method can be used to generate a continuous, magnetically guided atomic beam in a dark state.Comment: 14 page

Short-term mortality after perforated or bleeding peptic ulcer among elderly patients: a population-based cohort study

<p>Abstract</p> <p>Background</p> <p>Mortality after perforated and bleeding peptic ulcer increases with age. Limited data exist on how the higher burden of comorbidity among elderly patients affects this association. We aimed to examine the association of age with short-term mortality after perforated and bleeding peptic ulcer and to determine the impact of comorbidity on this association.</p> <p>Methods</p> <p>In this population-based cohort study in three Danish counties between 1991 and 2003 we identified two cohorts of patients: those hospitalized with a first-time discharge diagnosis of perforated peptic ulcer and those with bleeding peptic ulcer. The diagnoses were ascertained from hospital discharge registries and mortality through the Danish Civil Registration System. Information on comorbidity and use of ulcer-related drugs was obtained through administrative medical databases. We computed age-, gender- and comorbidity-standardized 30-day mortality rates and used Cox's regression to estimate adjusted 30-day mortality rate ratios (MRR) for elderly compared with younger patients.</p> <p>Results</p> <p>Among 2,061 patients with perforated peptic ulcer, 743 (36%) were 65–79 years old and 513 patients (25%) were aged 80+ years. Standardized 30-day mortality was 8.9% among patients younger than 65 years rising to 44.6% among patients aged 80+ years, corresponding to an adjusted MRR of 5.3 (95% CI: 4.0–7.0). Among 7,232 patients with bleeding peptic ulcer 2,372 (33%) were aged 80+ years. Standardized 30-day mortality among patients younger than 65 was 4.3% compared with 16.9% among patients aged 80+ years, corresponding to an adjusted MRR of 3.7 (95% CI: 2.9–4.7). Analyses stratified by comorbidity consistently showed high MRRs among elderly patients, regardless of comorbidity level.</p> <p>Conclusion</p> <p>Ageing is a strong predictor for a poor outcome after perforated and bleeding peptic ulcer independently of comorbidity.</p

Explainable Metamodels for ATM Performance Assessment

Fast-time simulation constitutes a well-known and long-established technique within the Air Traffic Management (ATM) community. However, it is often the case that simulation input and output spaces are underutilized, limiting the full understandability, transparency, and interpretability of the obtained results. In this paper, we propose a methodology that combines simulation metamodeling and SHapley Additive exPlanations (SHAP) values, aimed at uncovering the intricate hidden relationships among the input and output variables of a simulated ATM system in a rather practical way. Whereas metamodeling provides explicit functional approximations mimicking the behavior of the simulators, the SHAP-based analysis delivers a systematic framework for improving their explainability. We illustrate our approach using a state-of-the-art ATM simulator across two case studies in which two delay-centered performance metrics are analyzed. The results show that the proposed methodology can effectively make simulation and its results more explainable, facilitating the interpretation of the obtained emergent behavior, and additionally opening new opportunities towards novel performance assessment processes within the ATM research field

Scalable Group Level Probabilistic Sparse Factor Analysis

Many data-driven approaches exist to extract neural representations of functional magnetic resonance imaging (fMRI) data, but most of them lack a proper probabilistic formulation. We propose a group level scalable probabilistic sparse factor analysis (psFA) allowing spatially sparse maps, component pruning using automatic relevance determination (ARD) and subject specific heteroscedastic spatial noise modeling. For task-based and resting state fMRI, we show that the sparsity constraint gives rise to components similar to those obtained by group independent component analysis. The noise modeling shows that noise is reduced in areas typically associated with activation by the experimental design. The psFA model identifies sparse components and the probabilistic setting provides a natural way to handle parameter uncertainties. The variational Bayesian framework easily extends to more complex noise models than the presently considered.Comment: 10 pages plus 5 pages appendix, Submitted to ICASSP 1