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Sample Numbers (sample + number)
Selected AbstractsMinimizing errors in identifying Lévy flight behaviour of organismsJOURNAL OF ANIMAL ECOLOGY, Issue 2 2007DAVID W. SIMS Summary 1Lévy flights are specialized random walks with fundamental properties such as superdiffusivity and scale invariance that have recently been applied in optimal foraging theory. Lévy flights have movement lengths chosen from a probability distribution with a power-law tail, which theoretically increases the chances of a forager encountering new prey patches and may represent an optimal solution for foraging across complex, natural habitats. 2An increasing number of studies are detecting Lévy behaviour in diverse organisms such as microbes, insects, birds, and mammals including humans. A principal method for detecting Lévy flight is whether the exponent (µ) of the power-law distribution of movement lengths falls within the range 1 < µ , 3. The exponent can be determined from the histogram of frequency vs. movement (step) lengths, but different plotting methods have been used to derive the Lévy exponent across different studies. 3Here we investigate using simulations how different plotting methods influence the µ-value and show that the power-law plotting method based on 2k (logarithmic) binning with normalization prior to log transformation of both axes yields low error (1·4%) in identifying Lévy flights. Furthermore, increasing sample size reduced variation about the recovered values of µ, for example by 83% as sample number increased from n = 50 up to 5000. 4Simple log transformation of the axes of the histogram of frequency vs. step length underestimated µ by c.40%, whereas two other methods, 2k (logarithmic) binning without normalization and calculation of a cumulative distribution function for the data, both estimate the regression slope as 1 , µ. Correction of the slope therefore yields an accurate Lévy exponent with estimation errors of 1·4 and 4·5%, respectively. 5Empirical reanalysis of data in published studies indicates that simple log transformation results in significant errors in estimating µ, which in turn affects reliability of the biological interpretation. The potential for detecting Lévy flight motion when it is not present is minimized by the approach described. We also show that using a large number of steps in movement analysis such as this will also increase the accuracy with which optimal Lévy flight behaviour can be detected. [source] Survey augmentation using commercial vessels in the Mid-Atlantic Bight: Sampling density and relative catchabilityJOURNAL OF APPLIED ICHTHYOLOGY, Issue 6 2006E. N. Powell Summary A series of side-by-side tows was conducted between a survey vessel and a commercial vessel in two seasons, spring and fall (autumn), to examine the use of commercial vessels to increase sampling density in trawl-based stock surveys. Both vessels caught more fish offshore in the spring. The commercial vessel caught more fish than the survey vessel in both seasons. Catches of nearly all species were contagiously distributed in the spring. Most were contagiously distributed in the fall; however, somewhat more species were characterized by random or even distributions. The variance-to-mean ratio was consistently higher for most species for commercial vessel catches, regardless of season. As both vessels sampled in the same region at the same time, the increased predilection for the survey vessel to assess the distribution pattern as less patchy than the commercial vessel must accrue from some difference in sampling dynamics rather than variation in species distribution. A simulated decrease in sampling effort from 59 to 30 or 15 hauls increased the variance-to-mean ratio. Reduced sampling effort increased the tendency for occasional large catches to vary the estimate of domain biomass. The sampling program included an onshore,offshore gradient in station density. Domain biomass was considerably underestimated with reduced station density for six species characterized by large catches offshore in that portion of the survey domain characterized by low station density. In this study, a factor of two variation in domain biomass became more likely in 40% of species when sampling effort was reduced to 15 hauls from 59. A factor of two in biomass may distinguish a sustainable fishery from one in which a species is overfished. As survey sampling effort in this area was 18 hauls, increasing sample number by inclusion of commercial vessel tows would be advantageous. A regression between paired tows failed to adequately predict catches of one vessel from catches of the other. Standardization of vessel catches by the ratio-of-mean catches provided a more realistic comparison because large catches accounted for a significant fraction of domain biomass; however, a single conversion coefficient between boats could not be used for both sampling periods. The underlying impediment in developing a general conversion factor between the two vessels seems to be rooted in the differential in variance-to-mean ratios of the catches; this differential exists despite sampling of the same distribution of fish. [source] Evaluation by scanning acoustic microscopy (SAM) on glomerular lesion of IgA nephropathyNEPHROLOGY, Issue 2001H Kiyomoto IgA nephropathy (IgAN) is known to commonly cause of end-stage renal failure in Japan. The glomerular lesions of IgAN have histological variations. The determination of prognosis and therapeutic strategy should be carefully done by experts because morphological information from renal biopsies using ordinary optical microscopy is usually qualitative and subjective. Moreover, the histological items for the evaluation of glomerular lesions seems to be unsatisfactory for expression of the disease condition of IgAN. The beneficial properties of scanning acoustic microscopy (SAM) include not only observation of microstructure but also quantitative measurement of acoustic propagation speed (APS), indicating the tissue elasticity. In the present study we compared the APS of glomeruli with the pathological scores that were determined by ordinary light microscopy. We used stocked human renal biopsy specimens diagnosed as IgAN (n = 12) and normal/minimal changes (n = 5). All samples were taken by renal biopsy in Kagawa Medical University Hospital during 1997,2000 under informed consent of the patients. The obtained renal tissue were immersed in 10% formalin and embedded in paraffin. A fixed specimen was consecutively cut into 4 ,m slices. One of the deparaffinized 4 ,m-specimens was directly utilized for SAM without any staining, and the others were stained with haematoxylin-eosin and Masson Trichrome for counting cell number and evaluation of collagen accumulation. For the measurement of glomerular APS, the sample line was set on the equator of the glomerulus and then scanning of the X,Z axis was carried out to obtain the interference fringes that were analysed with a computer imaging software in order to calculate the APS. In light microscopic study, pathological scores were evaluated semiquantitatively by two independent investigators who were unaware of the sample number. Glomerular lesions were scored into five grades and glomerular cell number was also counted in individual glomerulus. The computer-assisted imaging analyser Win ROOF (Mitani, Fukui, Japan) was also used for the determination of glomerular collagen content in specimens stained by Masson Trichrome. A two-dimensional image (C-mode scanning) of SAM enabled imaging of glomerulus in renal biopsy specimen compatible with findings of ordinary light microscopy without staining dye. The glomerular APS in IgAN was significantly higher than in normal/minimal changes. This alteration of glomerular APS in IgAN was positively correlated to both semiquantitative pathological scores and glomerular collagen content determined by light microscopy. However, the cell number of glomelurus did not change between IgAN and normal/minimal change. As a result, we conclude that the glomerular lesion, especially matrix expansion in IgAN, was comparable with the absolute value among specimens. Therefore, it is suggested that SAM method is a novel and useful technique for quantitative evaluation of glomerular lesion in IgAN. [source] A class of sequential tests for two-sample composite hypothesesTHE CANADIAN JOURNAL OF STATISTICS, Issue 2 2006Edit Gombay Abstract The authors propose a class of statistics based on Rao's score for the sequential testing of composite hypotheses comparing two treatments (populations). Asymptotic approximations of the statistics lead them to propose sequential tests and to derive their monitoring boundaries. As special cases, they construct sequential versions of the two-sample t-test for normal populations and two-sample z-score tests for binomial populations. The proposed algorithms are simple and easy to compute, as no numerical integration is required. Furthermore, the user can analyze the data at any time regardless of how many inspections have been made. Monte Carlo simulations allow the authors to compare the power and the average stopping time (also known as average sample number) of the proposed tests to those of nonsequential and group sequential tests. A two-armed comparative clinical trial in patients with adult leukemia allows them to illustrate the efficiency of their methods in the case of binary responses. Une classe de tests séquentiels pour des hypothèses composites sur deux échantillons Les auteurs proposent une classe de statistiques, basées sur le score de Rao, pouvant servir à tester séquentiellement des hypothèses composites comparant deux traitements (ou populations). Des approximations asymptotiques les conduisent à proposer des tests séquentiels dont ils déterminent les zones de rejet. Comme cas particulier, ils construisent des versions séquentielles du test de Student pour deux échantillons normaux et du test du score z pour deux populations binomiales. Les algorithmes proposés sont simples et faciles à mettre en ,uvre, puisqu'ils ne nécessitent aucune intégration numérique. De plus, l'utilisateur peut analyser ses données à n'importe quel moment, sans égard au nombre d'inspections déjà effectuées. Des simulations de Monte-Carlo permettent aux auteurs de comparer la puissance et le temps d'arr,t moyen (aussi appelé l'effectif moyen) des tests proposés à ceux de tests non séquentiels ou séquentiels groupés. Une étude clinique comparative à deux bras effectuée sur des patients atteints de leucémie adulte leur permet d'illustrer l'efficacité de leurs méthodes pour des réponses binaires. [source] Occupancy frequency distributions: patterns, artefacts and mechanismsBIOLOGICAL REVIEWS, Issue 3 2002MELODIE A. McGEOCH ABSTRACT Numerous hypotheses have been proposed to explain the shape of occupancy frequency distributions (distributions of the numbers of species occupying different numbers of areas). Artefactual effects include sampling characteristics, whereas biological mechanisms include organismal, niche-based and metapopulation models. To date, there has been little testing of these models. In addition, although empirically derived occupancy distributions encompass an array of taxa and spatial scales, comparisons between them are often not possible because of differences in sampling protocol and method of construction. In this paper, the effects of sampling protocol (grain, sample number, extent, sampling coverage and intensity) on the shape of occupancy distributions are examined, and approaches for minimising artefactual effects recommended. Evidence for proposed biological determinants of the shape of occupancy distributions is then examined. Good support exists for some mechanisms (habitat and environmental heterogeneity), little for others (dispersal ability), while some hypotheses remain untested (landscape productivity, position in geographic range, range size frequency distributions), or are unlikely to be useful explanations for the shape of occupancy distributions (species specificity and adaptation to habitat, extinction,colonization dynamics). The presence of a core (class containing species with the highest occupancy) mode in occupancy distributions is most likely to be associated with larger sample units, and small homogenous sampling areas positioned well within and towards the range centers of a sufficient proportion of the species in the assemblage. Satellite (class with species with the lowest occupancy) modes are associated with sampling large, heterogeneous areas that incorporate a large proportion of the assemblage range. However, satellite modes commonly also occur in the presence of a core mode, and rare species effects are likely to contribute to the presence of a satellite mode at most sampling scales. In most proposed hypotheses, spatial scale is an important determinant of the shape of the observed occupancy distribution. Because the attributes of the mechanisms associated with these hypotheses change with spatial scale, their predictions for the shape of occupancy distributions also change. To understand occupancy distributions and the mechanisms underlying them, a synthesis of pattern documentation and model testing across scales is thus needed. The development of null models, comparisons of occupancy distributions across spatial scales and taxa, documentation of the movement of individual species between occupancy classes with changes in spatial scale, as well as further testing of biological mechanisms are all necessary for an improved understanding of the distribution of species and assemblages within their geographic ranges. [source] Quantifying uncertainty in estimates of C emissions from above-ground biomass due to historic land-use change to cropping in AustraliaGLOBAL CHANGE BIOLOGY, Issue 8 2001Damian J. Barrett Abstract Quantifying continental scale carbon emissions from the oxidation of above-ground plant biomass following land-use change (LUC) is made difficult by the lack of information on how much biomass was present prior to vegetation clearing and on the timing and location of historical LUC. The considerable spatial variability of vegetation and the uncertainty of this variability leads to difficulties in predicting biomass C density (tC ha,1) prior to LUC. The issue of quantifying uncertainties in the estimation of land based sources and sinks of CO2, and the feasibility of reducing these uncertainties by further sampling, is critical information required by governments world-wide for public policy development on climate change issues. A quantitative statistical approach is required to calculate confidence intervals (the level of certainty) of estimated cleared above-ground biomass. In this study, a set of high-quality observations of steady state above-ground biomass from relatively undisturbed ecological sites across the Australian continent was combined with vegetation, topographic, climatic and edaphic data sets within a Geographical Information System. A statistical model was developed from the data set of observations to predict potential biomass and the standard error of potential biomass for all 0.05° (approximately 5 × 5 km) land grid cells of the continent. In addition, the spatial autocorrelation of observations and residuals from the statistical model was examined. Finally, total C emissions due to historic LUC to cultivation and cropping were estimated by combining the statistical model with a data set of fractional cropland area per land grid cell, fAc (Ramankutty & Foley 1998). Total C emissions from loss of above-ground biomass due to cropping since European colonization of Australia was estimated to be 757 MtC. These estimates are an upper limit because the predicted steady state biomass may be less than the above-ground biomass immediately prior to LUC because of disturbance. The estimated standard error of total C emissions was calculated from the standard error of predicted biomass, the standard error of fAc and the spatial autocorrelation of biomass. However, quantitative estimates of the standard error of fAc were unavailable. Thus, two scenarios were developed to examine the effect of error in fAc on the error in total C emissions. In the first scenario, in which fAc was regarded as accurate (i.e. a coefficient of variation, CV, of fAc = 0.0), the 95% confidence interval of the continental C emissions was 379,1135 MtC. In the second scenario, a 50% error in estimated cropland area was assumed (a CV of fAc = 0.50) and the estimated confidence interval increased to between 350 and 1294 MtC. The CV of C emissions for these two scenarios was 25% and 29%. Thus, while accurate maps of land-use change contribute to decreasing uncertainty in C emissions from LUC, the major source of this uncertainty arises from the prediction accuracy of biomass C density. It is argued that, even with large sample numbers, the high cost of sampling biomass carbon may limit the uncertainty of above-ground biomass to about a CV of 25%. [source] Non-pharmacological approaches for dementia that informal carers might try or access: a systematic reviewINTERNATIONAL JOURNAL OF GERIATRIC PSYCHIATRY, Issue 7 2010Claire Hulme Abstract Objective To review non-drug treatments for dementia; to provide a source of evidence for informal carers who want ideas about non-drug approaches for dementia, that they might try or that they could try to access. The systematic review addresses: what non-drug treatments work and what do they work for? What non-drug treatments might work and what for? What non-drug treatments do not work? Methods Literature searches of seven electronic databases (AMED, CINAHL, EMBASE, MEDLINE, PSYCINFO, Cochrane Library of Systematic Reviews and DARE) were carried out in November 2007 using the following search terms (or derivatives): dementia/Alzheimer's AND Review AND non-drug therapies and aimed at finding systematic reviews. Results Thirty-three reviews were identified; 25 were judged to be high or good quality. Studies within these systematic reviews were characterised by weak study designs with small sample numbers. Three interventions were found to be effective for use with particular symptoms of dementia: music or music therapy, hand massage or gentle touch and physical activity/exercise. Conclusions Whilst informal carers can apply some of the interventions highlighted in the home setting at little or no cost to themselves or to health or social care services, others are likely to require training or instruction. Service providers and commissioners should explore current and future provision of more structured group activities for people with dementia; in particular the provision of group music therapy and group exercise activities that meet the needs of both the person with dementia and their carer. Copyright © 2009 John Wiley & Sons, Ltd. [source] Educational Attainments of Immigrant Offspring: Success or Segmented Assimilation?,INTERNATIONAL MIGRATION REVIEW, Issue 4 2002Monica Boyd In this article, I study the educational attainments of the adult offspring of immigrants, analyzing data from the 1996 panel of the Survey of Labour and Income Dynamics (SLID). Fielded annually since 1993 by Statistics Canada, respondents are asked for the first time in 1996 to report the birthplaces of their parents, making it possible to define and study not only the foreign-born population (the first generation), but also the second generation (Canadian born to foreign-born parents) and the third-plus generation (Canadian born to Canadian-born parents). The survey also asked respondents to indicate if they are members of a visible minority group, thus permitting a limited assessment of whether or not color conditions educational achievements of immigrant offspring. I find that "1.5" and second generation adults, age 20,64 have more years of schooling and higher percentages completing high school compared with the third-plus generation. Contrary to the segmented "underclass" assimilation model found in the United States, adult visible minority immigrant offspring in Canada exceed the educational attainments of other not-visible-minority groups. Although the analysis is hampered by small sample numbers, the results point to country differences in historical and contemporary race relations, and call for additional national and cross-national research. [source] Negative and positive ion matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and positive ion nano-electrospray ionization quadrupole ion trap mass spectrometry of peptidoglycan fragments isolated from various Bacillus speciesJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2001Gerold Bacher Abstract A general approach for the detailed characterization of sodium borohydride-reduced peptidoglycan fragments (syn. muropeptides), produced by muramidase digestion of the purified sacculus isolated from Bacillus subtilis (vegetative cell form of the wild type and a dacA mutant) and Bacillus megaterium (endospore form), is outlined based on UV matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) and nano-electrospray ionization (nESI) quadrupole ion trap (QIT) mass spectrometry (MS). After enzymatic digestion and reduction of the resulting muropeptides, the complex glycopeptide mixture was separated and fractionated by reversed-phase high-performance liquid chromatography. Prior to mass spectrometric analysis, the muropeptide samples were subjected to a desalting step and an aliquot was taken for amino acid analysis. Initial molecular mass determination of these peptidoglycan fragments (ranging from monomeric to tetrameric muropeptides) was performed by positive and negative ion MALDI-MS using the thin-layer technique with the matrix ,-cyano-4-hydroxycinnamic acid. The results demonstrated that for the fast molecular mass determination of large sample numbers in the 0.8,10 pmol range and with a mass accuracy of ±0.07%, negative ion MALDI-MS in the linear TOF mode is the method of choice. After this kind of muropeptide screening often a detailed primary structural analysis is required owing to ambiguous data. Structural data could be obtained from peptidoglycan monomers by post-source decay (PSD) fragment ion analysis, but not from dimers or higher oligomers and not with the necessary sensitivity. Multistage collision-induced dissociation (CID) experiments performed on an nESI-QIT instrument were found to be the superior method for structural characterization of not only monomeric but also of dimeric and trimeric muropeptides. Up to MS4 experiments were sometimes necessary to obtain unambiguous structural information. Three examples are presented: (a) CID MSn (n = 2,4) of a peptidoglycan monomer (disaccharide-tripeptide) isolated from B. subtilis (wild type, vegetative cell form), (b) CID MSn (n = 2,4) of a peptidoglycan dimer (bis-disaccharide-tetrapentapeptide) obtained from a B. subtilis mutant (vegetative cell form) and (c) CID MS2 of a peptidoglycan trimer (a linear hexasaccharide with two peptide side chains) isolated from the spore cortex of B. megaterium. All MSn experiments were performed on singly charged precursor ions and the MS2 spectra were dominated by fragments derived from interglycosidic bond cleavages. MS3 and MS4 spectra exhibited mainly peptide moiety fragment ions. In case of the bis-disaccharide-tetrapentapeptide, the peptide branching point could be determined based on MS3 and MS4 spectra. The results demonstrate the utility of nESI-QIT-MS towards the facile determination of the glycan sequence, the peptide linkage and the peptide sequence and branching of purified muropeptides (monomeric up to trimeric forms). The wealth of structural information generated by nESI-QIT-MSn is unsurpassed by any other individual technique. Copyright © 2001 John Wiley & Sons, Ltd. [source] Highly automated and fast determination of raffinose family oligosaccharides in Lupinus seeds using pressurized liquid extraction and high-performance anion-exchange chromatography with pulsed amperometric detectionJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 11 2008David Bansleben Abstract BACKGROUND: Taking into account several requirements for the determination of raffinose family oligosaccharides (RFOs) from Lupinus seeds,e.g., conducting plant breeding projects or food product development,a reasonable combination of efficient automated sample preparation and reliable analysis need to be developed and validated. RESULTS: In this regard pressurized liquid extraction was applied to extract the RFOs from ground and defatted lupin flour. Compared to many other publications, no further pretreatment, such as protein precipitation, was necessary to obtain satisfactory results applying ion chromatography with pulsed amperometric detection. The oligosaccharide content for the examined Lupinus albus samples were in the range 5.19,9.25 g kg,1 and for Lupinus angustifolius RFOs 3.49,4.75 g kg,1. Stachyose has always been the main component followed by raffinose and verbascose. CONCLUSION: The developed sample preparation and analytical method is suited to quantify raffinose, stachyose, verbascose and the disaccharide sucrose and, owing to a high degree of automation for sample preparation and relatively short analysis times by pretty peak separation, particularly high sample numbers can be accomplished. Copyright © 2008 Society of Chemical Industry [source] Adaptive charting schemes based on double sequential probability ratio testsQUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 1 2009Yan Li Abstract Sequential probability ratio test (SPRT) control charts are shown to be able to detect most shifts in the mean or proportion substantially faster than conventional charts such as CUSUM charts. However, they are limited in applications because of the absence of the upper bound on the sample size and possibly large sample numbers during implementation. The double SPRT (2-SPRT) control chart, which applies a 2-SPRT at each sampling point, is proposed in this paper to solve some of the limitations of SPRT charts. Approximate performance measures of the 2-SPRT control chart are obtained by the backward method with the Gaussian quadrature in a computer program. On the basis of two industrial examples and simulation comparisons, we conclude that the 2-SPRT chart is competitive in that it is more sensitive and economical for small shifts and has advantages in administration because of fixed sampling points and a proper upper bound on the sample size. Copyright © 2008 John Wiley & Sons, Ltd. [source] Living donation: focus on public concernsCLINICAL TRANSPLANTATION, Issue 5 2005Consensus statement Abstract:, In December 2002, a conference was held in Philadelphia to discuss public concerns about living organ transplantation with the goal of reaching a consensus about new strategies for such transplants. The conference was hosted by the Hospital of the University of Pennsylvania and the Center for Bioethics. A multidisciplinary group of leading experts and stakeholders was called to assess the current status of living donation and suggest productive changes to ensure safer and more ethically sound procedures for both donors and recipients. Prior to the meeting, the research team from the University of Pennsylvania, Center for Bioethics, conducted literature reviews and extensive background research on living organ transplantation. Summary briefs were prepared for all conference participants. Issues were divided into four subcategories; two or three experts led the discussion on each topic. At the conclusion of the conference, the points raised were summarized and discussed, and additional comments were offered before general agreement was reached on each subject. Transcribed minutes and summary statements were reviewed and circulated among participants to allow for additional comments and clarification. All feedback was incorporated into the statement, and a draft of the article was recirculated. Participants who have endorsed the following statements have agreed that these points represent the intent and spirit of the discussion, yet each participant reserves the right to disclaim the document in its entirety. The views represented in the consensus points are held by members of the consensus group and do not necessarily represent the views of the sponsor. A consensus was reached to propose new strategies and make improvements on existing practices and protocols. Specific attention was paid to the widely accepted needs of consistent and responsible communication with the public and press, standardization in donor assessment, a national living donor registry and new research focusing on larger sample numbers and long-term donor follow-up. These consensus points support the work carried out by other advisory transplant organizations and should assist in advocating for living organ donors, the live donor transplant process and the concerns of the public. [source] | ||||||||||||||||