92 research outputs found
The cathedral and the bazaar of e-repository development: encouraging community engagement with moving pictures and sound
No full textThis paper offers an insight into the development, use and governance of e‐repositories for learning and teaching, illustrated by Eric Raymond's bazaar and cathedral analogies and by a comparison of collection strategies that focus on content coverage or on the needs of users. It addresses in particular the processes that encourage and achieve community engagement. This insight is illustrated by one particular e‐repository, the Education Media On‐Line (EMOL) service. This paper draws analogies between the bazaar approach for open source software development and its possibilities for developing e‐repositories for learning and teaching. It suggests in particular that the development, use and evaluation of online moving pictures and sound objects for learning and teaching can benefit greatly from the community engagement lessons provided by the development, use and evaluation of open source software. Such lessons can be underpinned by experience in the area of learning resource collections, where repositories have been classified as ‘collections‐based’ or ‘user‐based’. Lessons from the open source movement may inform the development of e‐repositories such as EMOL in the future
Higher S-dualities and Shephard-Todd groups
No full textAbstract: Seiberg and Witten have shown that in N=2 SQCD with Nf = 2Nc = 4 the S-duality group PSL2ℤ acts on the flavor charges, which are weights of Spin(8), by triality. There are other N=2 SCFTs in which SU(2) SYM is coupled to strongly-interacting non-Lagrangian matter: their matter charges are weights of E6, E7 and E8 instead of Spin(8). The S-duality group PSL2ℤ acts on these weights: what replaces Spin(8) triality for the E6, E7, E8root lattices? In this paper we answer the question. The action on the matter charges of (a finite central extension of) PSL2ℤ factorizes trough the action of the exceptional Shephard-Todd groups G4 and G8 which should be seen as complex analogs of the usual triality group S3≃WeylA2. Our analysis is based on the identification of S-duality for SU(2) gauge SCFTs with the group of automorphisms of the cluster category of weighted projective lines of tubular type. © 2015, The Author(s)
INTEGRATING NATIONAL INITIATIVES AND LOCAL DEVELOPMENTS: STREAMING VIDEO TO SUPPORT NURSE EDUCATION IN THE UK
No full textEconomic incentives and point source emissions : choice of modeling platform
No full textThe purpose of this study is to identify the best modeling platform for the analysis of alternative environmental policy instruments designed to reduce the emission of pollutants from point sources, most notably, central power generating stations and manufacturing facilities. The primary analysis of concern is a cost-effectiveness investigation of the policy; where for the most part, the cost of compliance is a multidimensional variable that includes the private costs incurred by the owners of the facility, measures of the change in the cost of providing the facility's product, and estimates of the change in facility capacity factors. The range of pollutants under consideration include the usual menu of air- and waterborne emissions as well as solid and liquid wastes finding their way to landfills and other such disposal options. The range of policies considered include: (a) tariffs on the emission of pollutants; (b) tariffs and subsidies applied to the inputs or the outputs of the point source activities under consideration; (c) limits on the pollutant emissions themselves; and (d) directives regarding the installation of particular equipment and/or the alteration of process activities. The paper also discusses a nonexhaustive set of issues associated with the modeling of point source emissions and policies for their control.Economic Theory&Research,Access to Markets,Markets and Market Access,Consumption,Environmental Economics&Policies
Computationally-intensive Econometrics using a Distributed Matrix-programming Language
No full textThis paper reviews the need for powerful facilities in econometrics, focusing on concrete problems which arise in financial economics and in macroeconomics. We argue that the profession is being held back by the lack of easy to use generic software which is able to exploit the availability of cheap clusters of distributed computers. Our response is to extend, in a number of directions, the well known matrix-programming interpreted language Ox developed by the first author. We note three possible levels of extensions: (i) Ox with parallelization explicit in the Ox code; (ii) Ox with a parallelized run-time library; (iii) Ox with a parallelized interpreter. This paper studies and implements the first case, emphasizing the need for deterministic computing in science. We give examples in the context of financial economics and time-series modelling.Distributed computing; Econometrics; High-performance computing; Matrix-programming language
Time series analysis of count data with an application to the incidence of cholera
No full textIncludes bibliographical references (leaves 88-93).This dissertation comprises a study into the application of count data time series models to weekly counts of cholera cases that have been recorded in Beira, Mozambique. The study specifically looks at two classes of time series models for count data, namely observation-driven and parameter-driven, and two models from each of these classes are investigated. The autoregressive conditional Poisson (ACP) and double autoregressive conditional Poisson (DACP) are considered under the observation-driven class, while the parameter-driven models used are the Poisson-gamma and stochastic autoregressive mean (SAM) model. An in-depth case study of the cholera counts is presented in which the four selected count data time series models are compared. In addition the time series models are compared to static Poisson and negative binomial regression, thereby indicating the benefits gained in using count data time series models when the counts exhibit serial correlation. In the process of comparing the models, the effect of environmental drivers on the outbreaks of cholera are observed and discussed
Environmental toxicity, redox signaling and lung inflammation:the role of glutathione
No full textGlutathione (gamma-glutamyl-cysteinyl-glycine, GSH) is the most abundant intracellular antioxidant thiol and is central to redox defense during oxidative stress. GSH metabolism is tightly regulated and has been implicated in redox signaling and also in protection against environmental oxidant-mediated injury. Changes in the ratio of the reduced and disulfide form (GSH/GSSG) can affect signaling pathways that participate in a broad array of physiological responses from cell proliferation, autophagy and apoptosis to gene expression that involve H(2)O(2) as a second messenger. Oxidative stress due to oxidant/antioxidant imbalance and also due to environmental oxidants is an important component during inflammation and respiratory diseases such as chronic obstructive pulmonary disease, idiopathic pulmonary fibrosis, acute respiratory distress syndrome, and asthma. It is known to activate multiple stress kinase pathways and redox-sensitive transcription factors such as Nrf2, NF-kappaB and AP-1, which differentially regulate the genes for pro-inflammatory cytokines as well as the protective antioxidant genes. Understanding the regulatory mechanisms for the induction of antioxidants, such as GSH, versus pro-inflammatory mediators at sites of oxidant-directed injuries may allow for the development of novel therapies which will allow pharmacological manipulation of GSH synthesis during inflammation and oxidative injury. This article features the current knowledge about the role of GSH in redox signaling, GSH biosynthesis and particularly the regulation of transcription factor Nrf2 by GSH and downstream signaling during oxidative stress and inflammation in various pulmonary diseases. We also discussed the current therapeutic clinical trials using GSH and other thiol compounds, such as N-acetyl-l-cysteine, fudosteine, carbocysteine, erdosteine in environment-induced airways disease
Model Dependency of the Digital Option Replication – Replication under an Incomplete Model (in English)
No full textThe paper focuses on the replication of digital options under an incomplete model. Digital options are regularly applied in the hedging and static decomposition of many path-dependent options. The author examines the performance of static and dynamic replication. He considers the case of a market agent for whom the right model of the underlying asset-price evolution is not available. The observed price dynamic is supposed to follow four distinct models: (i) the Black and Scholes model, (ii) the Black and Scholes model with stochastic volatility driven by Hull and White model, (iii) the variance gamma model, defined as time changed Brownian motion, and (iv) the variance gamma model set in a stochastic environment modelled as the rate of time change via a Cox-Ingersoll-Ross model. Both static and dynamic replication methods are applied and examined within each of these settings. The author verifies the independence of the static replication on underlying processes.digital options, dynamic and static replication, internal time, Lévy models, replication error, stochastic environment, stochastic volatility, variance gamma process
The Impact of Immigration on the Labour Market Outcomes of New Zealanders
No full textThis paper uses data from the 1996, 2001 and 2006 New Zealand Census to examine how the supply of immigrants in particular skill-groups affects the employment and wages of the New Zealand-born and of earlier migrants. We first estimate simple CES production functions that allow for substitutability between workers from different skill-groups, but assume that, within skill-groups, migrants are perfect substitutes for non-migrants. We next estimate hierarchical CES production functions that allow for substitutability between immigrant and non-immigrant workers within skillgroups, but constrain the patterns of wage impacts on different factors in response to changing factor shares, and that natives and migrants are not substitutable across skill-groups. Then, we extend the previous literature by estimating a Generalised Leontief production function that allows for a less restrictive relationship between changes in factors shares and changes in wages within a particular level of the production function and for substitution and complementarity between immigrant and nonimmigrant workers both between and across skill-groups. Regardless of the model being estimated, we find little evidence that immigrants negatively affect either the wages or employment opportunities of the average New Zealand-born worker. However, we find some evidence that increases in the number of high-skilled recent migrants have small negative impacts on the wages of high-skilled New Zealand-born workers, which are offset by small positive impacts on the wages of medium-skilled New Zealanders.Immigration, Wage Impacts, New Zealand, Labour Market Areas
Des coloriages de pavages super et superbes
No full textII existe une vaste littérature sur le sujet des groupes de couleurs et des coloriages des motifs dans le plan [2, chapitre 8], [6], [8]. II est toutefois étrange qu’aucun de ces travaux ne semble porter directement sur les problèmes du coloriage des pavages comme tel. Plus particulièrernent, bien que les groupes de couleurs soient
souvent présentés comme des groupes de symétrie de couleurs
des pavages, un examen approfondi révélera que ce ne sont que
les motifs des pavés du pavage qui sont considérés; d’autres
propriétés essentielles d’un pavage tel que son type topologique
et I’adjacence de certaines paires de pavés sont ignorées. Si, par
contre, on en tient compte, plusieurs problèmes intéressants (et
complexes) se présentent. Le but de cet article est d’aborder
quelques-uns de ces problèmes.
On s’intéressera plus particulièrement à ce qu’on appelle les super
coloriages de pavages isoédriques. (On expliquera ci-dessous les
termes essentiels.) Au-delà de I’intérêt mathématique, les super
coloriages sont très attrayants d’un point devue esthétique et, à ce
titre, ils ont été utilisés par des artistes comme M.C. Escher. En fait
dans I’ensemble des collections publiées d’oeuvres d’Escher, tous
les coloriages de pavages isoédriques sont super. (On peut
consulter, par exemple, [ 1 , Planches E2-E23, E32-E31, E36-E51,
E55, E62-E66, E70, E73-E79, E86, E88-E92, E94-E98, E l 02-E109,
E116-E119, E124, E127, E128].) Ce fait fut à I’origine du présent article, il est la suite d’une présentation de I’auteur au Escher
Symposium de Rome en mars 1985 (un rapport en a été donné dans les Comptes-rendus de cette rencontre [7]). Toutefois, dans
I’intérêt du lecteur, on répétera ici la terminologie jugée essentielle
et cette présentation sera auto-suffisante. L’auteurtient à exprimer
sa reconnaissance à Marjorie Senechal et à Tom Wieting pour hi avoir suggéré les corrections à [6], et, plus particulièrement a Branko Grünbaum pour nos discussions utiles et les commentaires qu’il porta sur les versions préliminaires de cet article,
commentaires qui menèrent à plusieurs améliorations.There exists an extensive literature concerning colour groups and the related colourings of the motifs of a plane pattern [2, Chapter 81, [6], [8]. It is strange that none of this work seems to refer directly to the problems of colouring tilings as such. To be more specific, though colour groups are often displayed as the colour symmetry groups of tilings, careful examination will show that it is only the patterns of the tiles in the tilings which are under consideration; other essential properties of a tiling such as its topological type, and the adjacencies of certain pairs of tiles, are ignored. If the latter are taken into account, several interesting (and difficult) problems emerge. It is the purpose of the present paper to consider some of these.
In particular, we shall be concerned with what are called super colourings of isohedral tilings. (These words and other essential terminology, will be explained shortly.) Besides being mathematically interesting, super colourings are very attractive from an aesthetic point of view, and have been used by artists such as
M.C. Escher. In fact, in the published collections of Escher’s works, all his colourings of isohedral tilings are super. (See, for example, [ l , Plates E2-E23, E32-E31, E36-E51, E55, E62-E66, E70, E73-E79, E86, E88-E92, E94-E98, E102-E109, E l 16-El 19, E 124, E 127, E 1281.) This fact motivated the present paper, which
isasequel to the talkgiven bythe authoratthe ExherSymposium in Rome in March 1985, and reported in the Proceedings of that meeting [7]. However, for the convenience of the reader, essential terminology will be repeated here and the presentation will be self-contained. The author wishes to express his gratitude to Marjorie Senechal and Tom Wieting for supplying him with corrections to
[6], and, more especially to Branko Grunbaum for helpful discussions and for his comments on preliminary versions of this paper which led to many improvements.Peer Reviewe
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