Application of quasi-Monte Carlo methods to PDEs with random coefficients -- an overview and tutorial

This article provides a high-level overview of some recent works on the application of quasi-Monte Carlo (QMC) methods to PDEs with random coefficients. It is based on an in-depth survey of a similar title by the same authors, with an accompanying software package which is also briefly discussed here. Embedded in this article is a step-by-step tutorial of the required analysis for the setting known as the uniform case with first order QMC rules. The aim of this article is to provide an easy entry point for QMC experts wanting to start research in this direction and for PDE analysts and practitioners wanting to tap into contemporary QMC theory and methods.Comment: arXiv admin note: text overlap with arXiv:1606.0661

A Dimension-Adaptive Multi-Index Monte Carlo Method Applied to a Model of a Heat Exchanger

We present an adaptive version of the Multi-Index Monte Carlo method, introduced by Haji-Ali, Nobile and Tempone (2016), for simulating PDEs with coefficients that are random fields. A classical technique for sampling from these random fields is the Karhunen-Lo\`eve expansion. Our adaptive algorithm is based on the adaptive algorithm used in sparse grid cubature as introduced by Gerstner and Griebel (2003), and automatically chooses the number of terms needed in this expansion, as well as the required spatial discretizations of the PDE model. We apply the method to a simplified model of a heat exchanger with random insulator material, where the stochastic characteristics are modeled as a lognormal random field, and we show consistent computational savings

Hot new directions for quasi-Monte Carlo research in step with applications

This article provides an overview of some interfaces between the theory of quasi-Monte Carlo (QMC) methods and applications. We summarize three QMC theoretical settings: first order QMC methods in the unit cube $[0,1]^s$ and in $\mathbb{R}^s$, and higher order QMC methods in the unit cube. One important feature is that their error bounds can be independent of the dimension $s$ under appropriate conditions on the function spaces. Another important feature is that good parameters for these QMC methods can be obtained by fast efficient algorithms even when $s$ is large. We outline three different applications and explain how they can tap into the different QMC theory. We also discuss three cost saving strategies that can be combined with QMC in these applications. Many of these recent QMC theory and methods are developed not in isolation, but in close connection with applications

Guidance on Noncorticosteroid Systemic Immunomodulatory Therapy in Noninfectious Uveitis : Fundamentals Of Care for UveitiS (FOCUS) Initiative

Supplemental material available at www.aaojournal.org. Supported by AbbVie, Inc., and the Fundamentals of Care for Uveitis Initiative National Faculty. This manuscript was developed subsequent to an AbbVie-sponsored literature review of noninfectious, nonanterior uveitis. The meeting was conducted to understand the available literature regarding the management of patients with noninfectious, nonanterior uveitis. The program involved a total of 139 experts from 28 countries, who were selected for participation by AbbVie. However, AbbVie was not involved in the development of the manuscript. The authors maintained complete control over the content and this manuscript reflects the opinions of the authors. AbbVie selected the discussion participants and reviewed the final manuscript draft for scientific accuracy, but the authors determined the final content. All authors made substantial contributions to the article or critically revised it for important intellectual content and approved the final manuscript. AbbVie provided funding to invited participants, including honoraria for their attendance at the meetings. Travel to and from the meetings was reimbursed. No payments were made to the authors for the development of this manuscript. Dhinakaran Sambandan, PhD, and Shula Sarner, PhD, of Lucid Partners, Burleighfield House, Buckinghamshire, United Kingdom, provided medical writing and editorial support to the authors in the development of this manuscript; financial support for these services was provided by AbbVie. AbbVie reviewed the manuscript, but was not involved in the methodology, data collection and analysis, or completion of this manuscript.Peer reviewedPublisher PD

Reef sponges facilitate the transfer of coral-derived organic matter to their associated fauna via the sponge loop

The high biodiversity of coral reefs results in complex trophic webs where energy and nutrients are transferred between species through a multitude of pathways. Here, we hypothesize that reef sponges convert the dissolved organic matter released by benthic primary producers (e.g. corals) into particulate detritus that is transferred to sponge-associated detritivores via the sponge loop pathway. To test this hypothesis, we conducted stable isotope (13C and15N) tracer experiments to investigate the uptake and transfer of coral-derived organic matter from the sponges Mycale fistulifera and Negombata magnifica to 2 types of detritivores commonly associated with sponges: ophiuroids (Ophiothrix savignyi and Ophiocoma scolopendrina) and polychaetes (Polydorella smurovi). Findings revealed that the organic matter naturally released by the corals was indeed readily assimilated by both sponges and rapidly released again as sponge detritus. This detritus was subsequently consumed by the detritivores, demonstrating transfer of coral-derived organic matter from sponges to their associated fauna and confirming all steps of the sponge loop. Thus, sponges provide a trophic link between corals and higher trophic levels, thereby acting as key players within reef food webs

Studie zu Dispozinsen / Ratenkrediten - Forschungsvorhaben zur Bereitstellung wissenschaftlicher Entscheidungshilfe für das Bundesministerium für Ernährung, Landwirtschaft und Verbraucherschutz (BMELV)

Studie zu Dispozinsen / Ratenkrediten Aktenzeichen: 514-06.01-2810HS034 Laufzeit 8/2011 – 5/2012 - Zusammenfassung – In Deutschland verfügen etwa 80 Prozent der Haushalte über einen Dispositionskredit. Bei beträchtlicher Variation liegt der eingeräumte Kreditrahmen bei knapp dem 3-fachen des Nettoeinkommens. Arbeitslose, Alleinerziehende, Paare mit Kindern und Selbständige nutzen den Dispositionskredit häufiger. Einer Stichprobe unter Banken zufolge wurde bei 29 Prozent der Konten mit Dispositionsrahmen der Kredit zum Befragungstag in Anspruch genommen. Insgesamt werden die Zinssätze für Überziehungskredite von Experten der Verbraucherorganisationen als zu hoch angesehen. Die im Vergleich zu Ratenkrediten höheren Zinsen für Dispositionskredite erscheinen nicht durch höhere Ausfallquoten gerechtfertigt. Das Fortbestehen hoher Zinsen wird dadurch begünstigt, dass Konsumenten ihre Kontenwahl nur in geringem Maße von den Preisen der Dispokredite abhängig machen. Raten- und Abrufkredite sind nach Meinung von Experten der Verbraucherorganisationen und Schuldnerberatung selten als Alternative für einen kurzfristigen Liquiditätsausgleich geeignet. Anders sei dies bei dauerhafter Nutzung des Dispositionskredits als Ersatz für einen Ratenkredit zu beurteilen. Teilweise werden dadurch die Schutzvorschriften des Verzugs ausgehebelt. Die Studie diskutiert die Vor- und Nachteile verschiedener rechtlicher Regelungen, die darauf abzielen, die Höhe der Dispozinsen zu begrenzen und Fehlnutzungen zu vermeiden: hierzu gehören eine klare Wucher- bzw. Preisobergrenze und eine hervorgehobene Preisangabe in der Werbung, Hinweisschreiben bei exzessiver Nutzung, die Begrenzung preistreibender Faktoren und eine jährlichen Berichtspflicht. Erfahrungen im Ausland und in anderen Rechtsgebieten zeigen, dass solche Mittel wirkungsvoll sein können. Je nach Stärke des Eingriffs besteht für die Politik hierbei ein Zielkonflikt zwischen der Versorgung mit Dispositionskrediten und günstigen Konditionen. Es ist möglich, dass klare Wucher- bzw. Preisobergrenzen zu einer Kostenverlagerung führen; dies kann anhand dieser Studie jedoch nicht abschließend beurteilt werden. Ein Ende der Quersubventionierung der Kontoführung durch Dispozinsen kann aus Verteilungs- und Preisgerechtigkeitsgründen politisch gewollt sein. Es würde die betroffenen Haushalte entlasten und zu mehr Preisgerechtigkeit führen. Aktuelle Beispiele aus der Praxis zeigen, dass günstigere Konditionen auf dem Niveau von Konsumentenkrediten und ein fairer Umgang mit dem Verbraucher bei Überziehungskrediten grundsätzlich möglich sind.Study on Overdraft and Instalment Credit Reference No: 514-06.01-2810HS034 Duration 8/2011 – 5/2012 - Executive Summary - In Germany, about 80 per cent of private households dispose of a bank account with an overdraft facility. On average, the authorised credit limit on a facility amounts to a multiple of three times an individual’s net monthly income, a figure that is subject to large variation. Unemployed persons, lone parents, couples with children and the self-employed use the credit offered by the overdraft facility more frequently than the average household. From the research sample of banks covered by the study, approximately 29 per cent of all personal bank accounts with an authorised credit line were overdrawn at the time of the survey. Experts from consumer organisations consider interest rates charged for overdraft credit as too expensive. In comparison with instalment credit, the high interest rates do not appear to be justified by a high default rate. According to the same experts instalment credit and callable loans are only a better alternative to the use of the overdraft facility in cases when the funds from the overdraft are used exhaustively. The study discusses the advantages and disadvantages of different legal rules, among such possible regulations are clear usury ceilings, prominent price disclosure in advertisements, the obligation to inform the consumer in instances of excessive use of overdraft credit, rules to constrain other price determinant factors, and the duty of a governmental report on overdraft credit on an annual basis. Experiences from abroad and from other jurisdictions show the effectiveness such measures can have. Depending on the level of constraint exercised, policy may face a trade-off between the extent of consumer access to overdraft credit and reasonable prices. It is possible that usury ceilings or other limitations lead to cost transfers; however, a final assessment of such effects is beyond the scope of this study. Measures aimed at reducing the cross-subsidisation of the costs of current accounts by high interest on overdrafts may be desirable from a policy point of view to establish fair pricing and to grant relief to vulnerable households. Examples of better practice from credit markets show that more favourable pricing conditions for overdrafts (i.e. at a more similar level of interest rate to those observed for a consumer loan) and a fairer treatment of consumers are possible

The disruption of proteostasis in neurodegenerative diseases

Cells count on surveillance systems to monitor and protect the cellular proteome which, besides being highly heterogeneous, is constantly being challenged by intrinsic and environmental factors. In this context, the proteostasis network (PN) is essential to achieve a stable and functional proteome. Disruption of the PN is associated with aging and can lead to and/or potentiate the occurrence of many neurodegenerative diseases (ND). This not only emphasizes the importance of the PN in health span and aging but also how its modulation can be a potential target for intervention and treatment of human diseases.info:eu-repo/semantics/publishedVersio

Autoimmune and autoinflammatory mechanisms in uveitis

The eye, as currently viewed, is neither immunologically ignorant nor sequestered from the systemic environment. The eye utilises distinct immunoregulatory mechanisms to preserve tissue and cellular function in the face of immune-mediated insult; clinically, inflammation following such an insult is termed uveitis. The intra-ocular inflammation in uveitis may be clinically obvious as a result of infection (e.g. toxoplasma, herpes), but in the main infection, if any, remains covert. We now recognise that healthy tissues including the retina have regulatory mechanisms imparted by control of myeloid cells through receptors (e.g. CD200R) and soluble inhibitory factors (e.g. alpha-MSH), regulation of the blood retinal barrier, and active immune surveillance. Once homoeostasis has been disrupted and inflammation ensues, the mechanisms to regulate inflammation, including T cell apoptosis, generation of Treg cells, and myeloid cell suppression in situ, are less successful. Why inflammation becomes persistent remains unknown, but extrapolating from animal models, possibilities include differential trafficking of T cells from the retina, residency of CD8(+) T cells, and alterations of myeloid cell phenotype and function. Translating lessons learned from animal models to humans has been helped by system biology approaches and informatics, which suggest that diseased animals and people share similar changes in T cell phenotypes and monocyte function to date. Together the data infer a possible cryptic infectious drive in uveitis that unlocks and drives persistent autoimmune responses, or promotes further innate immune responses. Thus there may be many mechanisms in common with those observed in autoinflammatory disorders

A qualitative study of independent fast food vendors near secondary schools in disadvantaged Scottish neighbourhoods

Background: Preventing and reducing childhood and adolescent obesity is a growing priority in many countries. Recent UK data suggest that children in more deprived areas have higher rates of obesity and poorer diet quality than those in less deprived areas. As adolescents spend a large proportion of time in school, interventions to improve the food environment in and around schools are being considered. Nutrient standards for school meals are mandatory in the UK, but many secondary pupils purchase foods outside schools at break or lunchtime that may not meet these standards. Methods: Qualitative interviews were conducted with fast food shop managers to explore barriers to offering healthier menu options. Recruitment targeted independently-owned shops near secondary schools (pupils aged c.12-17) in low-income areas of three Scottish cities. Ten interviews were completed, recorded, and transcribed for analysis. An inductive qualitative approach was used to analyse the data in NVivo 10. Results: Five themes emerged from the data: pride in what is sold; individual autonomy and responsibility; customer demand; profit margin; and neighbourhood context. Interviewees consistently expressed pride in the foods they sold, most of which were homemade. They felt that healthy eating and general wellbeing are the responsibility of the individual and that offering what customers want to eat, not necessarily what they should eat, was the only way to stay in business. Most vendors felt they were struggling to maintain a profit, and that many aspects of the low-income neighbourhood context would make change difficult or impossible. Conclusions: Independent food shops in low-income areas face barriers to offering healthy food choices, and interventions and policies that target the food environment around schools should take the neighbourhood context into consideration