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Appendicularians are abundant planktonic filter feeders that play a significant role in the pelagic food web due to their high clearance rates. Their diet and feeding rates have typically been measured as bulk chlorophyll or cell removal, with some attention given to prey size but no differentiation between the microbial phylotypes. Using a combination of in situ and laboratory incubations with flow cytometry and next-generation sequencing, we found species-specific differences in clearance rates and diet compositions of 4 common species: Oikopleura albicans, O. fusiformis, O. longicauda, and O. dioica. While O. albicans most efficiently removed nano-eukaryotic algae, the other smaller species preferentially removed micron-sized pico-eukaryotic algae. Pico- and nano-eukaryotic cells constituted the major food source of the studied appendicularians despite their occurrence in oligotrophic water dominated by prokaryotic cells. Across species, pico- and nano-planktonic microalgae biomass comprised 45 to 75% of the appendicularian diets. Although non-photosynthetic bacteria were removed at lower rates than all other prey groups, their total contribution to the appendicularian diet was not trivial, representing 5 to 19% of the planktonic carbon in the appendicularian diet; pico-cyanobacteria contributed an additional 9 to 18%. Removal rates and efficiencies of pico-eukaryotes were higher than those of prokaryotes of similar size. Strikingly different clearance rates were observed for different prokaryotic phylotypes, indicating that factors other than size are involved in determining the capturability of the cells. Collectively, our findings provide additional evidence for differential retention of microbial prey among mucous-mesh grazers and its substantial effect on the upper-ocean microbial community.

Practitioners in various fields are often confronted with the task of assessing the ability of a diagnostic test to correctly assign one of two labels (healthy/diseased or low/high credit risk) to each observation in a collection of observations. An ordinal dominance curve (ODC) describes the functional relationship between the proportions of correct assignments to the labels. In this paper we derive a semi-parametric confidence band for the ODC and evaluate some of its properties by Monte Carlo simulation. The methodology is illustrated by application to data from a credit risk environment. Keywords: Confidence band, Ordinal dominance curve, Semi-parametric

We develop CUSUMs based on sequential ranks of the observations to detect changes over time in the location and dispersion of a distribution. The CUSUMs are distribution free in the sense that the appropriate control limits do not depend on the form or any parameters of the unknown underlying distribution. As such the CUSUMs are fully self starting. The inand out-of-control average run length properties of the CUSUMs are gauged qualitatively via theory-based calculations and quantitatively by Monte Carlo simulation. The CUSUMS are shown to perform very well when compared to some existing parametric and nonparametric CUSUMS. Implementation of the CUSUMs is illustrated in an application based on real data from an industrial environment.

A cumulative sum (CUSUM) control chart has desirable properties for checking whether a distribution has changed from an in-control to an out-of-control setting. Distribution-free CUSUMs based on sequential ranks to detect changes in the mean direction and dispersion of angular data are developed and some of their properties are illustrated by theoretical calculations and Monte Carlo simulation. Three applications to sequentially observed angular data from health science, industrial quality control and astrophysics are discussed.

The von Mises distribution is widely used for modeling angular data. When such data are seen in a quality control setting, there may be interest in checking whether the values are in statistical control or have gone out of control. A cumulative sum (cusum) control chart has desirable properties for checking whether the distribution has changed from an in-control to an out-of-control setting. This paper develops cusums for a change in the mean direction and concentration of angular data and illustrates some of their properties.

Two random variables X and Y are said to belong to the same location-scale family when Y=Dμ+σX with unknown constants μ∈R and σ>0. Given iid observations Xi, i=1,…,n and Yi, i=1,…,m satisfying this location-scale assumption, we wish to estimate μ and σ with high efficiency in the absence of knowledge of the functional form of the underlying common family of distributions of X and Y. Here, ‘high efficiency’ means that the estimator is asymptotically unbiased and that its asymptotic variance is close to the asymptotic variance of the maximum likelihood estimator that would be used had the form of the underlying location-scale family of distributions been known. We propose in the present paper two methods for estimating these parameters based on the empirical characteristic function (ECF). The first approach considered minimizes a weighted L2 distance between the ECFs of the X and Y data. The second approach constructs a quadratic form comparing the real and imaginary parts of the X- and Y-sample ECF...

International audience; Angiostrongyliasis, the leading cause worldwide of eosinophilic meningitis, is an emergent disease due to Angiostrongylus cantonensis larvae, transmitted accidentally to humans. Contamination of children usually occurs by direct contact with an infected mollusk. Eosinophilic meningoencephalitis is the major clinical feature of this parasitic infection in humans. It is usually benign for adults, but more severe for children. Clinical symptoms usually combine fever, meningitis, and neurological signs (somnolence, moaning, hypotonia, convulsions, and increased intracranial pressure). Presumptive diagnosis of human angiostrongyliasis is based on epidemiologic characteristics, clinical symptoms, medical history, and laboratory findings, in particular, hypereosinophilia in blood and cerebrospinal fluid. Treatment is based on corticosteroids associated with anthelmintics. This work reviews the diagnosis and treatment of this life-threatening (especially in children) parasitic disease and the need for preventive action.

CUSUMs based on the signed sequential ranks of observations are developed for detecting location and scale changes in symmetric distributions. The CUSUMs are distribution-free and fully self-starting: given a specified in-control median and nominal in-control average run length, no parametric specification of the underlying distribution is required in order to find the correct control limits. If the underlying distribution is normal with unknown variance, a CUSUM based on the Van der Waerden signed rank score produces out-of-control average run lengths that are commensurate with those produced by the standard CUSUM for a normal distribution with known variance. For heavier tailed distributions, use of a CUSUM based on the Wilcoxon signed rank score is indicated. The methodology is illustrated by application to real data from an industrial environment.

Circular data – data whose values lie in the interval [0,2π) – are important in a number of application areas. In some, there is a suspicion that a sequence of circular readings may contain two or more segments following different models. An analysis may then seek to decide whether there are multiple segments, and if so, to estimate the changepoints separating them. This paper presents an optimal method for segmenting sequences of data following the von Mises distribution. It is shown by example that the method is also successful in data following a distribution with much heavier tails.

International audience; OBJECTIVE:To describe the disability status of non-selected hospitalized persons.METHODS AND FINDINGS:We conducted a cross-sectional survey to assess activity limitations of every person older than 18 years hospitalized in a regional university hospital covering all medical fields. Evaluators rated, on a scale from 0 to 4, 22 selected items of the International Classification of Functioning (ICF), covering the 6 following domains: learning and applying knowledge, general tasks and demands, communication, mobility, self-care, and interpersonal interactions and relationships. Univariate and multivariate analyses were performed to analyze the prevalence, severity and profile of the handicap in terms of sociodemographic characteristics and care pathways.RESULTS:Among 1572 eligible persons, 1267 (81%) were surveyed (mean age 62.7±20.4years; 655 males [51.7%]). Overall, 82% showed at least one activity limitation. For 52%, disability was severe or total for at least one ICF item. Prevalence of disabilities was higher for mobility (75%) and self-care domains (63%). Disability was strongly related to age: age older than 80years versus 18 to 44years (OR=12.8 95% CI 6.4-27.9]; P

Motivated by two applications in the mining industry, we introduce a new approach to testing the hypothesis that two-sampled distributions are simply location and scale changes of one another. The test, applicable to both paired data and two-sample data, is based on the empirical characteristic function. More conventional techniques founded on the empirical distribution function suffer from serious drawbacks when used to test for location-scale families. In the motivating applications, knowing that the distributions differ only in location and scale has significant operational and economic advantages, enabling protocols for one type of data to be applied directly to another. Supplementary material in the form of Matlab code is available online.

Two random variables X and Y belong to the same location-scale family if there are constants @m and @s such that Y and @[email protected] have the same distribution. In this paper we consider non-parametric estimation of the parameters @m and @s under minimal assumptions regarding the form of the distribution functions of X and Y. We discuss an approach to the estimation problem that is based on asymptotic likelihood considerations. Our results enable us to provide a methodology that can be implemented easily and which yields estimators that are often near optimal when compared to fully parametric methods. We evaluate the performance of the estimators in a series of Monte Carlo simulations.

Approximate normality and unbiasedness of the maximum likelihood estimate (MLE) of the long-memory parameter H of a fractional Brownian motion hold reasonably well for sample sizes as small as 20 if the mean and scale parameter are known. We show in a Monte Carlo study that if the latter two parameters are unknown the bias and variance of the MLE of H both increase substantially. We also show that the bias can be reduced by using a parametric bootstrap procedure. In very large samples, maximum likelihood estimation becomes problematic because of the large dimension of the covariance matrix that must be inverted. To overcome this difficulty, we propose a maximum likelihood method based upon first differences of the data. These first differences form a short-memory process. We split the data into a number of contiguous blocks consisting of a relatively small number of observations. Computation of the likelihood function in a block then presents no computational problem. We form a pseudo-likelihood function ...

Particle size analyses of a raw material are commonplace in the mineral processing industry. Knowledge of particle size distributions is crucial in planning milling operations to enable an optimum degree of liberation of valuable mineral phases, to minimize plant losses due to an excess of oversize or undersize material or to attain a size distribution that fits a contractual specification. The problem addressed in the present paper is how to test the equality of two or more underlying size distributions. A distinguishing feature of these size distributions is that they are not based on counts of individual particles. Rather, they are mass size distributions giving the fractions of the total mass of a sampled material lying in each of a number of size intervals. As such, the data are compositional in nature, using the terminology of Aitchison [1] that is, multivariate vectors the components of which add to 100%. In the literature, various versions of Hotelling's T 2 have been used to compare matched pairs...

We consider estimation of the precision of a measuring instrument without the benefit of replicate observations on heterogeneous sampling units. Grubbs (1948) proposed an estimator which involves the use of a second measuring instrument, resulting in a pair of observations on each sampling unit. Since the precisions of the two measuring instruments are generally different, these observations cannot be treated as replicates. Very large sample sizes are often required if the standard error of the estimate is to be within reasonable bounds and if negative precision estimates are to be avoided. We show that the two instrument Grubbs estimator can be improved considerably if fairly reliable preliminary information regarding the ratio of sampling unit variance to instrument variance is available. Our results are presented in the context of the evaluation of on-line analyzers. A data set from an analyzer evaluation is used to illustrate the methodology.

The aims of this study were to examine whether use of tobacco, alcohol, and illicit drugs predicts dropout among secondary school students in Cape Town, South Africa. A self‐report instrument was administered to 1,470 Grade 8 students. The proportion of students that dropped out of school between the onset of the study and 4 years later was 54.9%. After adjusting for a range of confounders, dropout was significantly predicted by absenteeism, poverty (as assessed by a possession index), and past month cigarette use, but not by past month alcohol use and lifetime illicit drug use. Contrary to findings from developed countries, alcohol and illicit drug use did not predict dropout. It is possible that predictors of dropout documented elsewhere may not be pertinent in developing countries.

This study investigated the prevalence and correlates of sexual risk behaviour among high school students in two rural settings in the Eastern Cape, South Africa, using a cross-sectional survey design. One thousand six hundred and thirteen randomly-selected adolescents (58% female) in Grade 11 completed a self-report questionnaire that asked about demographic characteristics and participation in a range of health risk behaviours. The results indicated a high prevalence of sexual risk behaviours, and suggested that rural adolescents are initiating intercourse at a younger age than their urban counterparts and are less likely to use condoms. Socioeconomic status, grade repetition and having lived in a city were inconsistently related to sexual risk behaviour. The findings suggest a particular need for intervention efforts aimed at young people in rural settings.

In a recent paper, Puech and co-workers compared K-band Tully–Fisher relations derived for nearby and distant galaxies, respectively. They concluded that the two relations differ, and deduced that there is evolution in the Tully–Fisher relations. The statistical comparison between the two regression lines is re-examined, and it is shown that the statistical test used gives non-significant results. It is argued that better results can be obtained by comparing the ‘inverse’ Tully–Fisher relations, and it is demonstrated by two different methods that the nearby- and distant-sample relations do indeed differ at a very high significance level. One of the statistical methods described is non-parametric, and can be applied very generally to compare linear regressions from two different samples.

The dependence of [Fe/H] on galactocentric distance, distance from the galactic mid-plane and age is studied. Both ordinary least-squares and non-parametric regression in the form of a ‘generalized additive model’ are used. The radial metallicity slope is found to be shallower than previously claimed in the literature, and there is a significant abundance gradient perpendicular to the galactic plane. There may be a tendency for metallicity to increase with cluster age.

Summary We report the results of a period change analysis of time series observations for 378 pulsating variable stars. The null hypothesis of no trend in expected periods is tested for each of the stars. The tests are non-parametric in that potential trends are estimated by local linear smoothers. Our testing methodology has some novel features. First, the null distribution of a test statistic is defined to be the distribution that results in repeated sampling from a population of stars. This distribution is estimated by means of a bootstrap algorithm that resamples from the collection of 378 stars. Bootstrapping in this way obviates the problem that the conditional sampling distribution of a statistic, given a particular star, may depend on unknown parameters of that star. Another novel feature of our test statistics is that one-sided cross-validation is used to choose the smoothing parameters of the local linear estimators on which they are based. It is shown that doing so results in tests that are tremendously more powerful than analogous tests that are based on the usual version of cross-validation. The positive false discovery rate method of Storey is used to account for the fact that we simultaneously test 378 hypotheses. We ultimately find that 56 of the 378 stars have changes in mean pulsation period that are significant when controlling the positive false discovery rate at the 5% level.

A two-sided cumulative sum (cusum) scheme for a normal mean involves running two one-sided schemes, one to control upward and the other to control downward changes in the mean. We show that the two-sided scheme can be replaced by a single upward cusum scheme that has the same in-control average run length (ARL) and a smaller out-of-control ARL. The benefits of the new scheme are especially apparent at small mean shifts.

Alignment is defined as the tendency of the distribution of pointing angles between the major axes of clusters and their nearest neighbours to be more concentrated towards small values for small nearest neighbour distances, whereas the distribution is expected to be uniform over all angles at larger distances. Conflicting pronouncements on the reality of this effect have been published in the astronomy literature. A re-assessment of the evidence for alignment is presented, based on three recently published X-ray data sets. We find that whereas there is evidence for alignment, it is not as convincing as previously claimed. In particular, the scale to which the effect has been claimed to extend seems to have been severely overstated.

Resume Objectif Evaluer la faisabilite clinique de la communication visiophonique, entre un malade a son domicile et les equipes soignantes d’un reseau d’Hospitalisation a domicile (HAD). Methodes Etude cas-temoins, concernant les secteurs adulte, maternite et pediatrie du reseau HAD. Apres accord de participation, les patients qui remplissaient les criteres d’inclusion ont ete tires au sort pour leur appartenance au groupe telemedecine (appareil de visiophonie au domicile) ou au groupe temoin (prise en charge habituelle en HAD). Le groupe telemedecine comportait 16 patients apparies a 16 autres qui constituaient le groupe temoin. Les criteres d’appariement etaient l’âge, l’indice de Karnofsky et l’objectif d’admission en HAD. Resultats La duree de communication visiophonique a ete en moyenne de 6 minutes. Le nombre moyen d’appels a ete de 23 par patient, soit 0,7 appels par jour ouvrable. La visiophonie a permis une coordination en temps reel et un meilleur suivi des plaies avec prise de photos. C’etait un apport pour le suivi de patients douloureux, les soins techniques infirmiers, l’education du patient ou de son entourage. Le score d’anxiete a l’echelle HAD ( Hospital Anxiety Depression scale ) a diminue significativement au cours de la prise en charge des patients du groupe telemedecine contrairement a ceux du groupe temoin (p = 0,048). Dans le groupe telemedecine, tous les patients et leur entourage ont ete tres satisfaits ou satisfaits de la prise en charge et de la communication (15 cas sur 15), alors que 88 % des soignants le sont (14 cas sur 16), sans difference significative avec le groupe temoin. Conclusion Le programme ViSaDom a confirme la faisabilite et l’acceptabilite de la communication visiophonique. C’est un outil prometteur pour la qualite et l’efficacite des soins en HAD.

This article develops statistical methods useful for comparing the marginals F and G of a bivariate distribution. Such comparisons are appropriate in the analysis of matched-pair data involving a treatment and a control (or two treatments). The quantile comparison functionq = G−1(F), proposed by Lehmann as a generalized measure of treatment effect in fully randomized experiments, is shown to be applicable and also useful in the analysis of matched-pair data. Nonparametric simultaneous confidence bands for q are constructed using asymptotic and permutation methods. The copula of the bivariate distribution plays a significant role in the methodology. Application of the results is illustrated on a dataset from an industrial experiment.

It has been found that the near-infrared flux variations of Seyfert galaxies satisfy relations of the form Fi≈αij+βijFj, where Fi, Fj are the fluxes in filters i and j; and αi,j, βi,j are constants. These relations have been used to estimate the constant contributions of the non-variable underlying galaxies. The paper attempts a formal treatment of the estimation procedure, allowing for the possible presence of a third component, namely non-variable hot dust. In an analysis of a sample of 38 Seyfert galaxies, inclusion of the hot dust component improves the model fit in approximately half the cases. All derived dust temperatures are below 300 K, in the range 540–860 K or above 1300 K. A noteworthy feature is the estimation of confidence intervals for the component contributions: this is achieved by bootstrapping. It is also pointed out that the model implies that such data could be fruitfully analysed in terms of principal components.

Different enzymatic routes for the production of (R)-seudenol were investigated. The Novozym 435-catalyzed reaction of racemic seudenol with vinyl butyrate proved to be the most promising route. By using vinyl laurate as an acyl donor, (R)-seudenol laurate could be separated from (S)-seudenol by an extractive work-up procedure. A nonaqueous hydrolysis allowed the isolation of pure (R)-seudenol. Scaling up to 7 kg resulted in a robust reproducible process.

On-line gauges are used in many industries to measure characteristics of raw material destined for a production process. In the coal industry, which is the focus of interest in this paper, the traditional method for determining coal characteristics has been the assay of coal samples. This method requires a great deal of work on a day-to-day basis. It has the further drawback that there is generally a time lag of at least 1 day between sampling of the coal and obtaining numerical measures of its quality characteristics. An interesting recent development is that nuclear gauges, which are capable of producing estimates of coal quality in real time, are now available commercially. The present paper demonstrates how bootstrap methods can be used to obtain a confidence interval for gauge precision using gauge output data alone. No specially constructed reference values from a sampling and assay operation are required. As such, the method is potentially an attractive alternative to the methodology set out in ISO 15239. It is also shown how gauge calibration can be checked using gauge output and one set of reference samples obtained under normal operating conditions. The method, which again uses the bootstrap, involves the construction of a simultaneous confidence band for a calibration function that relates gauge values to reference values.

X nonlinear rank statistic is proposed to test whether a location or scale parameter of a continuous distribution has remained constant over time. The test is based on frequency domain characteristics of the data and uses the periodogram of appropriate rank scores. The test has good power against alternatives involving multiple abrupt up and down changes

The use of on-line analyzers which are capable of producing a quality index for raw material in real time provides an economically viable alternative to traditional laboratory assays. Such analyzers are, in principle, capable of making quality determinations to a substantially higher order of precision. In this paper some statistical methods useful in assessing precision and bias of an analyzer relative to one or two reference instruments are considered. In particular, the roles of preparation variance and of scale bias between reference instruments are highlighted. A large preparation variance and/or substantial scale bias between reference instruments effectively precludes proper evaluation of an analyzer. Precision estimates proposed by Grubbs [F.E. Grubbs, J. Am. Stat. Assoc. 43 (1948) 243–264] and by Hahn and Nelson [G.J. Hahn, W. Nelson, Technometrics 12 (1970) 95–102] in an analogous context are shown to be numerically identical. A test for scale bias between analyzer and reference instruments is also proposed.

Cook and Stefanski have described a computer-intensive method, the SIMEX method, for approximately consistent estimation in regression problems with additive measurement error. In this article we derive the asymptotic distribution of their estimators and show how to compute estimated standard errors. These standard error estimators can either be used alone or as prepivoting devices in a bootstrap analysis. We also give theoretical justification to some of the phenomena observed by Cook and Stefanski in their simulations.

We propose a sequential cumulative sum procedure to detect deviations from uniformity in angular data. The method is motivated by a problem in high-energy astrophysics and is illustrated by an application to data. http://dx.doi.org/10.1080/02664763.2012.683857 http://www.tandfonline.com/doi/pdf/10.1080/02664763.2012.683857

Monokaryotic isolates of Phellinus sulphurascens, a fungus originally described from the Primorsk Territory, Russia, are compatible with monokaryotic isolates of, what has been called in North Amer...

A new approach is presented for easily testable two-dimensional iterative arrays. It is an improvement on GI-testability (Group Identical testability) and is referred to as GID-testability (Group Identical and Different testability). In a GID-testable two-dimensional array, the primaryx andy outputs are organized into groups and every group has more than one output. This is similar to the GI-testable arrays. However, GID-testability not only ensures that identical test responses can be obtained from every output in the same group when an array is fault free, but also ensures that at least one output has different test responses (from the other outputs in a group) when a cell in the array is faulty. Therefore, all faults can be detected under the assumption of a single faulty cell model. It is proved that an arbitrary two-dimensional iterative array is GID-testable if sevenx-states and seveny-states are added to the original flow table of the basic cell of the array.