Non-standard Features Research Articles

Nonparametric Bayesian estimation of the three‐way receiver operating characteristic surface

We describe a nonparametric Bayesian approach for estimating the three-way ROC surface based on mixtures of finite Polya trees (MFPT) priors. Mixtures of finite Polya trees are robust models that can handle nonstandard features in the data. We address the difficulties in modeling continuous diagnostic data with skewness, multimodality, or other nonstandard features, and how parametric approaches can lead to misleading results in such cases. Robust, data-driven inference for the ROC surface and for the volume under the ROC surface is obtained. A simulation study is performed to assess the performance of the proposed method. Methods are applied to data from a magnetic resonance spectroscopy study on human immunodeficiency virus patients.

Non-standard features in English in Anglophone Cameroon New Writing: dilemmas for the education system

One of the ways a language is learned, especially a foreign language, is by personal extensive reading. When people read widely, they are exposed to the linguistic structure of what they read and so learn it consciously or unconsciously. What they come across in their reading remains in their minds and adds to their general knowledge. This includes knowledge of the language they read. General wide reading reinforces the language students have been formally taught in their language classes. Exposure to grammatically correct language would improve their language skills. On the other hand, exposure to incorrect language would negatively affect the language skills of foreign learners and cause them to use wrong language comfortably, not knowing that they are erroneous in their usage.

Investigating the impact of SMS speak on the written work of English first language and English second language high school learners

This study examined the impact of SMS speak on the written work of English first language (L1) and English second language (L2) grade 8s and 11s. The aim was to establish whether these learners make use of features of SMS speak in their English written work. The participants, 88 learners from an English-Afrikaans dual medium school, completed questionnaires from which the frequency and volume of their SMS use were determined, as well as the features of SMS speak they reportedly use while SMSing. In addition, samples of their English essays were examined for the following features of SMS speak: (deliberate) spelling errors; lack of punctuation; over-punctuation; omission of function words; and use of abbreviation, acronyms, emoticons and rebus writing. The questionnaires indicated that these learners are avid users of the SMS. All participants reported using features of SMS speak in their SMSes, and more than 40% reported using SMS speak in their written school work. Despite this, features of SMS speak infrequently occurred in the written work of the learners, which could indicate that the learners are able to assess when it is and is not appropriate to use a certain variety of language. That said, a number of SMS speak features were indeed present in the samples, which indicates that SMS speak had some impact on the written work of these learners. Not all of the nonstandard features of their written English could, however, necessarily be attributed to the influence of SMS speak; specifically some of the spelling and punctuation errors could have occurred in the written English of high school learners from before the advent of cell phones.

Consistent reductions from [formula omitted] beyond Sasaki–Einstein

The most general class of warped AdS5×M6w supersymmetric solutions in D=11 supergravity permits a consistent truncation to D=5N=2 minimal gauged supergravity. Here we extend this truncation, for a particular subclass of M6 manifolds, to D=5N=4 gauged supergravity coupled to two vector multiplets. We obtain the reduction ansatz by T-duality of a recently discussed type IIB truncation on a generic Sasaki–Einstein five-fold, which becomes non-trivial in D=11 and displays non-standard features due to the G-structure of the internal M6. Using this truncation, we construct two new classes of warped and unwarped non-supersymmetric AdS5 M-theory backgrounds. We also comment on possible extensions of the reduction ansatz to the general class of M6 geometries.

Drawdown-at-Risk Monte Carlo Optimization

We present a portfolio construction approach with two interesting non-standard features: First, the risk measure used is “drawdown-at-risk”, an interesting concept combining attractive features of drawdown and value-at-risk measures. Second, the efficient frontier is calculated from “random portfolios”, i.e. portfolios containing random constituent weights. We call this “Monte Carlo optimization”. Both features would deserve a detailed analysis. The goal of this note is to provide an overview and illustrate the potential of the approach with two examples: Asset allocation in a small universe consisting of three assets (Indian stocks and bonds as well as gold in INR) and drawdown optimization on single-stock level across the full S&P 500 universe.

Partial evaluation of Maple

Having been convinced of the potential benefits of partial evaluation, we wanted to apply these techniques to code written in Maple, our Computer Algebra System of choice. Maple is a very large language, with a number of non-standard features. When we tried to implement a partial evaluator for it, we ran into a number of difficulties for which we could find no solution in the literature. Undaunted, we persevered and ultimately implemented a working partial evaluator with which we were able to very successfully conduct our experiments, first on small codes, and now on actual routines taken from Maple’s own library. Here, we document the techniques we had to invent or adapt to achieve these results.

Interactional renegotiations of educational discourses in recreational learning contexts

In this paper I focus on sequences of interaction among youth where the participants engage in classroom related activities (such as spelling, discussion of essays, etc.). My paper is based on interactional and ethnographic data collected among youth in two different leisure contexts. I discuss how the participants by employment of various interactional and linguistic means, including the use of non-standard linguistic features, integrate different cultural frames by bringing out-of-classroom practices into educationally focused interactions, as well as by bringing classroom related activities outside the classroom and into recreational contexts. In these interactional sequences, the participants challenge and renegotiate dominant assumptions characteristic of educational discourses, of a contradiction between mainstream-societally accepted behaviour valued in school contexts, and semiotic measures of social peer-credibility among late modern urban youth. I consider how the adolescents’ interactional practices and their situated use of particular linguistic features reflect as well as contribute to ongoing enregisterment ( Agha, 2007) of a speech style in contemporary Copenhagen. Finally, I discuss to what extent the bringing together of peer-culture and school orientation can be viewed as re-negotiations of social class relations. This discussion involves a comparison to the British context and to work by Rampton (2006, 2008).

Discrimination Power of Short-Term Heart Rate Variability Measures for CHF Assessment

In this study, we investigated the discrimination power of short-term heart rate variability (HRV) for discriminating normal subjects versus chronic heart failure (CHF) patients. We analyzed 1914.40 h of ECG of 83 patients of which 54 are normal and 29 are suffering from CHF with New York Heart Association (NYHA) classification I, II, and III, extracted by public databases. Following guidelines, we performed time and frequency analysis in order to measure HRV features. To assess the discrimination power of HRV features, we designed a classifier based on the classification and regression tree (CART) method, which is a nonparametric statistical technique, strongly effective on nonnormal medical data mining. The best subset of features for subject classification includes square root of the mean of the sum of the squares of differences between adjacent NN intervals (RMSSD), total power, high-frequencies power, and the ratio between low- and high-frequencies power (LF/HF). The classifier we developed achieved sensitivity and specificity values of 79.3 % and 100 %, respectively. Moreover, we demonstrated that it is possible to achieve sensitivity and specificity of 89.7 % and 100 %, respectively, by introducing two nonstandard features ΔAVNN and ΔLF/HF, which account, respectively, for variation over the 24 h of the average of consecutive normal intervals (AVNN) and LF/HF. Our results are comparable with other similar studies, but the method we used is particularly valuable because it allows a fully human-understandable description of classification procedures, in terms of intelligible "if … then …" rules.

What are people really saying in World of Warcraft® chat?

Internet usage continues to increase and people spend more time chatting and forming friendships online. Out of this phenomenon, a new way of speaking is emerging. This poster reports on a pilot study that examines nonstandard English features in World of Warcraft chat.

Parallelism generics for Ada 2005 and beyond

The Ada programming language is seemingly well-positioned to take advantage of emerging multi-core technologies. While it has always been possible to write parallel algorithms in Ada, there are certain classes of problems however, where the level of effort to write parallel algorithms outweighs the ease and simplicity of a sequential approach. This can result in lost opportunities for parallelism and slower running software programs. Languages such as Cilk++ and OpenMB provide expressive mechanisms to add parallelism to code using a C++ based syntax by adding special syntactic directives where parallelism is desired. This paper explores Ada's concurrency features to see whether it is possible to easily inject similar iterative and recursive parallelism to code written in Ada, without having to resort to special language extensions or non-standard language features. This paper identifies a "work-seeking" technique, which can be viewed as a form of compromise between work-sharing and work-stealing, two other existing strategies. The paper presents performance results to illustrate the benefits of use for the generics and goes on to suggest how parallelism pragmas could possibly be added to the Ada language to further facilitate writing parallel applications.

A dynamic principal-agent problem as a feedback Stackelberg differential game

We consider situations in which a principal tries to induce an agent to spend effort on accumulating a state variable that affects the well-being of both parties. The only incentive mechanism that the principal can use is a state-dependent transfer of her own utility to the agent. Formally, the model is a Stackelberg differential game in which the players use feedback strategies. Whereas in general Stackelberg differential games with feedback strategy spaces the leader’s optimization problem has non-standard features that make it extremely hard to solve, in the present case this problem can be rewritten as a standard optimal control problem. A linear-quadratic example is used to illustrate our approach.

Emergence of geometry: A two-dimensional toy model

We review the similarities between the effective chiral lagrangrian, relevant for low-energy strong interactions, and the Einstein-Hilbert action. We use these analogies to suggest a specific mechanism whereby gravitons would emerge as Goldstone bosons of a global SO(D) X GL(D) symmetry broken down to SO(D) by fermion condensation. We propose a two-dimensional toy model where a dynamical zwei-bein is generated from a topological theory without any pre-existing metric structure, the space being endowed only with an affine connection. A metric appears only after the symmetry breaking; thus the notion of distance is an induced effective one. In spite of several non-standard features this simple toy model appears to be renormalizable and at long distances is described by an effective lagrangian that corresponds to that of two-dimensional gravity (Liouville theory). The induced cosmological constant is related to the dynamical mass M acquired by the fermion fields in the breaking, which also acts as an infrared regulator. The low-energy expansion is valid for momenta k >M, i.e. for supra-horizon scales. We briefly discuss a possible implementation of a similar mechanism in four dimensions.

A features-based approach for teaching Singapore English

: Research into Singapore English (SgE) has undergone many paradigm shifts from the 1970s to the present. This paper first begins with a consideration of how variation in the English language used in Singapore has been studied. It then identifies the two main varieties of English commonly described in Singapore, namely, Standard SgE (SSE) and Singapore Colloquial English (SCE). The existence of these two varieties poses problems in language teaching as student teachers are not always confident in their own use and when to execute the two varieties appropriately and they may also lack the linguistic tools to help them distinguish between the two varieties. This paper examines the level of effectiveness of a particular course known as ‘Features of SgE’ has in introducing and helping undergraduate student teachers to distinguish between standard and non-standard features of SgE. Consequently, the features that need to be addressed in the classroom are identified. The results of a questionnaire administered at the start of the course and again at the end of the course designed to test students’ knowledge of the differences between SSE and SCE are analysed. Finally, the main findings from the course feedback are discussed in order to ascertain whether the course has been effective in fulfilling its objectives.

“It ain't Nothing to do with my School.” Variation and Pragmatic Uses of ain't in the Language of British English Teenagers

The negative form ain't has been regarded as one of the most typical non-standard features of modern English. Although traditionally highly stigmatised, it is widely present in most geographical and social varieties, both in British and in American English. In fact, the linguistic changes that this contracted negative has undergone have been extensively researched; however, its variation and use have received much less attention. This paper is concerned with the analysis of ain't in the speech of British English teenagers on the basis of the COLT corpus. It starts by considering its origin and development. It then describes not only the syntactic functions that ain't fulfils in teenagers' language but it also considers the sociological factors that condition this grammatical feature and its pragmatic meanings.

A Bayesian Nonparametric Approach to Inference for Quantile Regression

We develop a Bayesian method for nonparametric model–based quantile regression. The approach involves flexible Dirichlet process mixture models for the joint distribution of the response and the covariates, with posterior inference for different quantile curves emerging from the conditional response distribution given the covariates. An extension to allow for partially observed responses leads to a novel Tobit quantile regression framework. We use simulated data sets and two data examples from the literature to illustrate the capacity of the model to uncover nonlinearities in quantile regression curves, as well as nonstandard features in the response distribution.

MASSIVE HALOS IN MILLENNIUM GAS SIMULATIONS: MULTIVARIATE SCALING RELATIONS

The joint likelihood of observable cluster signals reflects the astrophysical evolution of the coupled baryonic and dark matter components in massive halos, and its knowledge will enhance cosmological parameter constraints in the coming era of large, multi-wavelength cluster surveys. We present a computational study of intrinsic covariance in cluster properties using halo populations derived from Millennium Gas Simulations (MGS). The MGS are re-simulations of the original 500 Mpc/h Millennium Simulation performed with gas dynamics under two different physical treatments: shock heating driven by gravity only (GO) and a second treatment with cooling and preheating (PH). We examine relationships among structural properties and observable X-ray and Sunyaev-Zel'dovich (SZ) signals for samples of thousands of halos with M_200 > 5 \times 10^{13} Msun/h and z < 2. While the X-ray scaling behavior of PH model halos at low-redshift offers a good match to local clusters, the model exhibits non-standard features testable with larger surveys, including weakly running slopes in hot gas observable--mass relations and ~10% departures from self-similar redshift evolution for 10^14 Msun/h halos at redshift z ~ 1. We find that the form of the joint likelihood of signal pairs is generally well-described by a multivariate, log-normal distribution, especially in the PH case which exhibits less halo substructure than the GO model. At fixed mass and epoch, joint deviations of signal pairs display mainly positive correlations, especially the thermal SZ effect paired with either hot gas fraction (r=0.88/0.69 for PH/GO at z=0) or X-ray temperature (r=0.62/0.83). We discuss halo mass selection by signal pairs, and find a minimum mass scatter of 4% in the \PH model by combining thermal SZ and gas fraction measurements.

Discussion of the paper “A rational expectations model for simulation and policy evaluation of the Spanish economy”

Rational expectations model for simulation (REMS) is a state-of-the-art DynamicStochastic General Equilibrium model (DSGE model) of the kind used in many pol-icy institutions throughout the world. It shares a number of common features withstandard models along this line of research, but also displays a number of specificfeatures that makes it appealing for fiscal policy simulations. Indeed, among otherparticular features REMS encompasses: (i) a wider coverage of fiscal variables thanin standard DSGE models, and (ii) a labour market specified along the lines of the“search”framework.WhileIthinkthatthemodelis,ingeneral,arelevantcontributionto the literature, in my discussion I will hinge upon some weaknesses and problemswith the modelling approach and the interpretation of the results that can be identified.For the sake of brevity I will focus on just a few points, grouped in two blocks. First, Iwill comment on non-standard features of REMS, as any critique to features standardin the relevant literature will make no justice to this particular model. Second, I willdiscuss some additional issues.

Nigerian English in informal email messages

This study applies a sociolinguistic and discourse-analytical methodology to the study of features and manifestations of Nigerian English in computer-mediated communication, particularly informal emails. The data comprise 133 email samples consisting of messages received or sent within a seven-year period, i.e. between 2002 and 2009, from typical Nigerian environments, as well as by the youth, adults and the elderly. Analyses reveal that the rise of new media technologies and digital communication has provided a resource for the use and dissemination of Nigerian English alongside Nigerian cultures. The study shows that Nigerian English in informal emails comprises the construction of local thoughts through a range of characteristic properties. In non-standard Nigerian English features like misuse of words, grammatical inconsistencies and a mixture of local pidgin also exist. The study of Nigerian English in informal emails reveals that email samples provide resourceful data for the study of English regional varieties in computer-mediated communication. It also shows that a variety of English is a cultural medium for expressing language habits and socio-cultural practices.

Estimation of synthetic accessibility score of drug-like molecules based on molecular complexity and fragment contributions

BackgroundA method to estimate ease of synthesis (synthetic accessibility) of drug-like molecules is needed in many areas of the drug discovery process. The development and validation of such a method that is able to characterize molecule synthetic accessibility as a score between 1 (easy to make) and 10 (very difficult to make) is described in this article.ResultsThe method for estimation of the synthetic accessibility score (SAscore) described here is based on a combination of fragment contributions and a complexity penalty. Fragment contributions have been calculated based on the analysis of one million representative molecules from PubChem and therefore one can say that they capture historical synthetic knowledge stored in this database. The molecular complexity score takes into account the presence of non-standard structural features, such as large rings, non-standard ring fusions, stereocomplexity and molecule size. The method has been validated by comparing calculated SAscores with ease of synthesis as estimated by experienced medicinal chemists for a set of 40 molecules. The agreement between calculated and manually estimated synthetic accessibility is very good with r2 = 0.89.ConclusionA novel method to estimate synthetic accessibility of molecules has been developed. This method uses historical synthetic knowledge obtained by analyzing information from millions of already synthesized chemicals and considers also molecule complexity. The method is sufficiently fast and provides results consistent with estimation of ease of synthesis by experienced medicinal chemists. The calculated SAscore may be used to support various drug discovery processes where a large number of molecules needs to be ranked based on their synthetic accessibility, for example when purchasing samples for screening, selecting hits from high-throughput screening for follow-up, or ranking molecules generated by various de novo design approaches.

Searching for Lepton Flavor Violation with the MEG experiment (or looking for flying pigs)

As the Standard Model encounters several philosophical problems, New Physics is expected to be found slightly above the mass scale currently probed. Effects due to non-Standard Model features can be easily tagged by the observation of Charged Lepton Flavor Violation. Thus the MEG experiment has been designed and is currently in an advanced phase having started data taking in summer 2008 and is expected to give at least an upper limit on the μ → e + γ decay two order of magnitude better than the current limit [A. Baldini, [MEG Collaboration], at http://meg.psi.ch/docs/prop_infn/nproposal.ps ] set by the MEGA collaboration [M. Ahmed et al. , Phys. Rev. D 65 (2002) 112002, arXiv:hep-ex/0111030 ]. Here all experimental challenges are shown together with the main detector features.