Finite element analysis of elasto-plastic soils. Report no. 4: Finite element analysis of elasto-plastic frictional materials for application to lunar earth sciences

The behavior of finite element models employing different constitutive relations to describe the stress-strain behavior of soils is investigated. Three models, which assume small strain theory is applicable, include a nondilatant, a dilatant and a strain hardening constitutive relation. Two models are formulated using large strain theory and include a hyperbolic and a Tresca elastic perfectly plastic constitutive relation. These finite element models are used to analyze retaining walls and footings. Methods of improving the finite element solutions are investigated. For nonlinear problems better solutions can be obtained by using smaller load increment sizes and more iterations per load increment than by increasing the number of elements. Suitable methods of treating tension stresses and stresses which exceed the yield criteria are discussed

Study of the use of auxiliary electrodes in silver cells

Auxiliary electrodes in silver-cadmium and silver zinc cells for hydrogen and oxygen recombination, and hydrogen combination cell desig

Aging in a Long-Lived Clonal Tree

Using genetic estimates of clone age in trembling aspen, this study demonstrates a significant decline in male sexual fitness with increasing age, showing that long-lived clonal organisms are vulnerable to aging

Five-years surveillance of invasive aspergillosis in a university hospital

<p>Abstract</p> <p>Background</p> <p>As the most common invasive fungal infection, invasive aspergillosis (IA) remains a serious complication in immunocompromised patients, leading to increased mortality. Antifungal therapy is expensive and may result in severe adverse effects.</p> <p>The aim of this study was to determine the incidence of invasive aspergillosis (IA) cases in a tertiary care university hospital using a standardized surveillance method.</p> <p>Methods</p> <p>All inpatients at our facility were screened for presence of the following parameters: positive microbiological culture, pathologist's diagnosis and antifungal treatment as reported by the hospital pharmacy. Patients fulfilling one or more of these indicators were further reviewed and, if appropriate, classified according to international consensus criteria (EORTC).</p> <p>Results</p> <p>704 patients were positive for at least one of the indicators mentioned above. Applying the EORTC criteria, 214 IA cases were detected, of which 56 were proven, 25 probable and 133 possible. 44 of the 81 (54%) proven and probable cases were considered health-care associated. 37 of the proven/probable IA cases had received solid organ transplantation, an additional 8 had undergone stem cell transplantation, and 10 patients were suffering from some type of malignancy. All the other patients in this group were also suffering from severe organic diseases, required long treatment and experienced several clinical complications. 7 of the 56 proven cases would have been missed without autopsy. After the antimycotic prophylaxis regimen was altered, we noticed a significant decrease (p = 0.0004) of IA during the investigation period (2003-2007).</p> <p>Conclusion</p> <p>Solid organ and stem cell transplantation remain important risk factors for IA, but several other types of immunosuppression should also be kept in mind. Clinical diagnosis of IA may be difficult (in this study 13% of all proven cases were diagnosed by autopsy only). Thus, we confirm the importance of IA surveillance in all high-risk patients.</p

A Federated Design for a Neurobiological Simulation Engine: The CBI Federated Software Architecture

Simulator interoperability and extensibility has become a growing requirement in computational biology. To address this, we have developed a federated software architecture. It is federated by its union of independent disparate systems under a single cohesive view, provides interoperability through its capability to communicate, execute programs, or transfer data among different independent applications, and supports extensibility by enabling simulator expansion or enhancement without the need for major changes to system infrastructure. Historically, simulator interoperability has relied on development of declarative markup languages such as the neuron modeling language NeuroML, while simulator extension typically occurred through modification of existing functionality. The software architecture we describe here allows for both these approaches. However, it is designed to support alternative paradigms of interoperability and extensibility through the provision of logical relationships and defined application programming interfaces. They allow any appropriately configured component or software application to be incorporated into a simulator. The architecture defines independent functional modules that run stand-alone. They are arranged in logical layers that naturally correspond to the occurrence of high-level data (biological concepts) versus low-level data (numerical values) and distinguish data from control functions. The modular nature of the architecture and its independence from a given technology facilitates communication about similar concepts and functions for both users and developers. It provides several advantages for multiple independent contributions to software development. Importantly, these include: (1) Reduction in complexity of individual simulator components when compared to the complexity of a complete simulator, (2) Documentation of individual components in terms of their inputs and outputs, (3) Easy removal or replacement of unnecessary or obsoleted components, (4) Stand-alone testing of components, and (5) Clear delineation of the development scope of new components

The Importance of the Pathologist’s Role in Assessment of the Quality of the Mesorectum

Total mesorectal excision (TME) is considered standard of care for rectal cancer treatment. Failure to remove the mesorectal fat envelope entirely may explain part of observed local and distant recurrences. Several studies suggest quality of the mesorectum after TME surgery as determined by pathological evaluation may influence prognosis. We aimed to determine the prognostic value of the plane of surgery as well as factors influencing the likelihood of a high-quality specimen by reviewing the literature. A pooled meta-analysis of relevant outcome data was performed where appropriate. A muscularis propria resection plane was found to increase the risk of local recurrence (RR 2.72 [95 % CI 1.36 to 5.44]) and overall recurrence (RR 2.00 [95 % CI 1.17 to 3.42]) compared to an (intra)mesorectal plane. Plane of surgery is an important factor in rectal cancer treatment and the documentation by pathologists is essential for the improvement of TME quality and patient outcome

Towards neuro-inspired symbolic models of cognition: linking neural dynamics to behaviors through asynchronous communications

A computational architecture modeling the relation between perception and action is proposed. Basic brain processes representing synaptic plasticity are first abstracted through asynchronous communication protocols and implemented as virtual microcircuits. These are used in turn to build mesoscale circuits embodying parallel cognitive processes. Encoding these circuits into symbolic expressions gives finally rise to neuro-inspired programs that are compiled into pseudo-code to be interpreted by a virtual machine. Quantitative evaluation measures are given by the modification of synapse weights over time. This approach is illustrated by models of simple forms of behaviors exhibiting cognition up to the third level of animal awareness. As a potential benefit, symbolic models of emergent psychological mechanisms could lead to the discovery of the learning processes involved in the development of cognition. The executable specifications of an experimental platform allowing for the reproduction of simulated experiments are given in “Appendix”

Economic evaluation of posaconazole versus fluconazole prophylaxis in patients with graft-versus-host disease (GVHD) in the Netherlands

The objective of this study was to evaluate the cost-effectiveness of posaconazole versus fluconazole for the prevention of invasive fungal infections (IFI) in graft-versus-host disease (GVHD) patients in the Netherlands. A decision analytic model was developed based on a double-blind randomized trial that compared posaconazole with fluconazole antifungal prophylaxis in recipients of allogeneic HSCT with GVHD who were receiving immunosuppressive therapy (Ullmann et al., N Engl J Med 356:335–347, 2007). Clinical events were modeled with chance nodes reflecting probabilities of IFIs, IFI-related death, and death from other causes. Data on life expectancy, quality-of-life, medical resource consumption, and costs were obtained from the literature. The total cost with posaconazole amounted to €9,428 (95% uncertainty interval €7,743–11,388), which is €4,566 (€2,460–6,854) more than those with fluconazole. Posaconazole prophylaxis resulted in 0.17 (0.02–0.36) quality adjusted life year (QALY) gained compared to fluconazole prophylaxis, corresponding to an incremental cost effectiveness ratio (ICER) of €26,225 per QALY gained. A scenario analysis demonstrated that at an increased background IFI risk (from 9% to 15%) the ICER was €13,462 per QALY. Given the underlying data and assumptions, posaconazole prophylaxis is expected to be cost-effective relative to fluconazole in recipients of allogeneic HSCT developing GVHD in the Netherlands. The cost-effectiveness of posaconazole depends on the IFI risk, which can vary by hospital

People Efficiently Explore the Solution Space of the Computationally Intractable Traveling Salesman Problem to Find Near-Optimal Tours

Humans need to solve computationally intractable problems such as visual search, categorization, and simultaneous learning and acting, yet an increasing body of evidence suggests that their solutions to instantiations of these problems are near optimal. Computational complexity advances an explanation to this apparent paradox: (1) only a small portion of instances of such problems are actually hard, and (2) successful heuristics exploit structural properties of the typical instance to selectively improve parts that are likely to be sub-optimal. We hypothesize that these two ideas largely account for the good performance of humans on computationally hard problems. We tested part of this hypothesis by studying the solutions of 28 participants to 28 instances of the Euclidean Traveling Salesman Problem (TSP). Participants were provided feedback on the cost of their solutions and were allowed unlimited solution attempts (trials). We found a significant improvement between the first and last trials and that solutions are significantly different from random tours that follow the convex hull and do not have self-crossings. More importantly, we found that participants modified their current better solutions in such a way that edges belonging to the optimal solution (“good” edges) were significantly more likely to stay than other edges (“bad” edges), a hallmark of structural exploitation. We found, however, that more trials harmed the participants' ability to tell good from bad edges, suggesting that after too many trials the participants “ran out of ideas.” In sum, we provide the first demonstration of significant performance improvement on the TSP under repetition and feedback and evidence that human problem-solving may exploit the structure of hard problems paralleling behavior of state-of-the-art heuristics