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Sampling Strategy (sampling + strategy)
Kinds of Sampling Strategy Selected AbstractsSampling Strategies for Volatile Organic Compounds at Three Karst Springs in TennesseeGROUND WATER MONITORING & REMEDIATION, Issue 1 2006Shannon D. Williams The influence of different sampling strategies on characterizing volatile organic compound (VOC) concentrations and estimating VOC loads was evaluated at three karst springs in Tennessee. During a 6-month period, water samples for VOC analyses were collected weekly at all three springs and as frequently as every 20 min during storms at the two springs with variable water quality conditions. Total 6-month loads for selected VOCs were calculated, and VOC data were systematically subsampled to simulate and evaluate several potential sampling strategies. Results from the study indicate that sampling strategies for karst springs need to be developed on a site-specific basis. The use of fixed sampling intervals (as infrequently as quarterly or semiannually) produced accurate concentration and load estimates at one of the springs; however, additional sampling was needed to detect storm-related changes at a second spring located in a similar hydrogeologic setting. Continuous discharge data and high-frequency or flow-controlled sampling were needed at the third spring, which had the most variable flow and water quality conditions. The lack of continuous discharge data at the third spring would substantially affect load calculations, and the use of fixed sampling intervals would affect load calculations and the ability to detect pulses of high contaminant concentrations that might exceed toxicity levels for aquatic organisms. [source] Mixed stream channel morphologies: implications for fish community diversityAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 2 2009Christina M. Cianfrani Abstract 1.Stream classification systems are widely used in stream management and restoration. Whereas the principal morphological types of these classification systems are increasingly recognized for their ecological connections, the roles of intermediate and mixed morphologies are still poorly understood, yet may be biologically significant. 2.Twenty-five stream reaches in north-western Vermont were classified by channel morphology to determine whether fish community diversity differed among pool-riffle, mixed (i.e. pool-riffle/cascade, pool-riffle/other) and forced pool-riffle stream morphological groups. Stream reach surveys included cross-sectional surveys, longitudinal profiles, bed substrate characterization, and fish surveys. 3.Three fish community diversity measures were calculated: (1) species richness (S); (2) Shannon,Weaver Index (H,); and (3) Simpson's Index (1/D). Multivariate analysis of covariance (MANCOVA) followed by analysis of variance (ANOVA) were used to explore potential differences in fish diversity among stream morphological groups. Fish diversity was significantly different for all three community diversity measures (P,0.05), with pool-riffle/cascade morphology consistently exhibiting the greatest fish diversity and forced pool-riffle the lowest. 4.These results suggest that fish community diversity is significantly associated with distinct channel morphologies. Generally, pool-riffle/cascade and pool-riffle/other stream morphological groups supported habitats that fostered greater species diversity than more homogeneous and uniform pool-riffle reaches. The observed patterns of diversity are likely to be the result of habitat patches created by variations in flow and other physical characteristics in reaches of mixed morphologies. 5.These results support fish sampling schemes that incorporate morphological heterogeneity, such as proportional-distance designation. Sampling strategies that focus on homogeneous reaches may underestimate diversity, and misrepresent stream condition when fish community data are used in indices of biological integrity (IBIs). Reaches of mixed stream morphologies should be recognized as areas of biological importance in stream and catchment management and in conservation efforts. Copyright © 2008 John Wiley & Sons, Ltd. [source] Spatial Autocorrelation Analysis and the Identification of Operational Units for Conservation in Continuous PopulationsCONSERVATION BIOLOGY, Issue 4 2002José Alexandre Felizola Diniz-Filho We show that spatial autocorrelation analysis, applied to phenotypic or molecular data, can be used to describe the geographic structure and therefore can help define optimum strategies for conserving genetic variability within species. We propose that the intercept of a spatial correlogram can be an indication of the minimum distance between samples that can conserve and assess genetic diversity with maximum efficiency at lower costs. This parameter can be used both to define units and to establish sampling strategies for conservation programs. We illustrate the utility of this approach by autocorrelation analyses applied to three data sets: isozyme variability among Eugenia dysenterica populations in Brazilian Cerrado and within populations of Adenophora glandiflora in Korea, and microsatellite variation among Ursus arctos populations in North America. Our results suggest that the intercept of spatial correlograms is a useful parameter for establishing operational units for intraspecific conservation in continuous populations, based on overall genetic or phenotypic variability, by defining the minimum geographic distance at which samples are independent. Resumen: A pesar de los avances recientes en la identificación de la estructura genética poblacional mediante la tecnología de marcadores moleculares, la definición de las unidades intraespecíficas para la conservación es aún problemática. Esto sucede particularmente cuando la variación genética y fenotípica se encuentra distribuida de manera continua en un espacio geográfico. Demostramos que el análisis de autocorrelación espacial, aplicado a los datos fenotípicos o moleculares puede ser usado para describir la estructura geográfica y, por lo tanto, puede ayudar a definir estrategias óptimas para la conservación de la variabilidad genética en las especies. Proponemos que el intercepto de un correlograma espacial puede ser un indicador de la distancia mínima entre muestras que pueden conservar y evaluar la diversidad genética con mayor eficiencia a un costo más bajo. Este parámetro puede ser usado tanto para definir unidades como para establecer estrategias de muestreo para los programas de conservación. Ejemplificamos la utilidad de este método mediante la aplicación de análisis de autocorrelación a tres grupos de datos: variabilidad de isozomas entre poblaciones de Adenophora dysenterica en el cerrado brasileño, dentro de poblaciones de Adenophora glandiflora en Korea y variación microsatélite entre poblaciones de Ursus arctos en América del Norte. Nuestros resultados sugieren que el intercepto de los correlogramas espaciales son un parámetro útil que puede establecer unidades operacionales para conservación intraespecífica en poblaciones continuas, en base a la variabilidad general genética o fenótipica, al definir la distancia geográfica mínima a la cual las muestras son independientes. [source] Investigating the evolution of floras: problems and progress , An introductionDIVERSITY AND DISTRIBUTIONS, Issue 1 2006H. P. Linder ABSTRACT The Cape flora of southern Africa is a remarkable hotspot for plant species diversity and endemism. At a meeting in Zurich in 2004 progress in understanding the evolution of this diversity was reviewed. In this symposium, four papers presenting several of the methods used in this investigation were reported. These papers deal with molecular dating methods, the reconstruction of ancestral habitats, with possible speciation scenarios for the Cape flora, and the importance of the correct sampling strategies. [source] Landings, logbooks and observer surveys: improving the protocols for sampling commercial fisheriesFISH AND FISHERIES, Issue 2 2007A J R Cotter Abstract The sampling of commercial marine fisheries for management purposes often displays a key weakness in the form of poor documentation of the scientific basis of sampling and estimation, the assumptions made, and the practical constraints. This paper reviews systematically the theoretical and practical options that can remedy this situation and recommends that decisions be archived in regularly updated ,Sampling Approach and Modifications' (SAM) documents. Defining the target population, the observable population (usually a subset of the target), and the assumed links between them is important, along with the distinction between design- and model-based sampling approaches. Fleet-targeted and stock-targeted sampling strategies are contrasted, the latter being much harder to implement. Sampling protocols aimed at estimating quantities of fish landed and discarded, length,frequency distributions, length-related variables such as age, weight and maturity, and ratio variables such as catch per unit of effort and the proportions of discards are discussed, together with the raising of estimates to fleet and/or stock levels. The ideas are summarized in the specific contexts of landings sampling, logbook schemes and sea-going observer surveys. SAMs are commended for enhancing the scientific value of fishery sampling, and for encouraging methodological discussions among users and producers of the data. [source] Functional trait variation and sampling strategies in species-rich plant communitiesFUNCTIONAL ECOLOGY, Issue 1 2010Christopher Baraloto Summary 1. ,Despite considerable interest in the application of plant functional traits to questions of community assembly and ecosystem structure and function, there is no consensus on the appropriateness of sampling designs to obtain plot-level estimates in diverse plant communities. 2. ,We measured 10 plant functional traits describing leaf and stem morphology and ecophysiology for all trees in nine 1-ha plots in terra firme lowland tropical rain forests of French Guiana (N = 4709). 3. ,We calculated, by simulation, the mean and variance in trait values for each plot and each trait expected under seven sampling methods and a range of sampling intensities. Simulated sampling methods included a variety of spatial designs, as well as the application of existing data base values to all individuals of a given species. 4. ,For each trait in each plot, we defined a performance index for each sampling design as the proportion of resampling events that resulted in observed means within 5% of the true plot mean, and observed variance within 20% of the true plot variance. 5. ,The relative performance of sampling designs was consistent for estimations of means and variances. Data base use had consistently poor performance for most traits across all plots, whereas sampling one individual per species per plot resulted in relatively high performance. We found few differences among different spatial sampling strategies; however, for a given strategy, increased intensity of sampling resulted in markedly improved accuracy in estimates of trait mean and variance. 6. ,We also calculated the financial cost of each sampling design based on data from our ,every individual per plot' strategy and estimated the sampling and botanical effort required. The relative performance of designs was strongly positively correlated with relative financial cost, suggesting that sampling investment returns are relatively constant. 7. ,Our results suggest that trait sampling for many objectives in species-rich plant communities may require the considerable effort of sampling at least one individual of each species in each plot, and that investment in complete sampling, though great, may be worthwhile for at least some traits. [source] The effects of temporal and spatial patterns of Holocene erosion and alluviation on the archaeological record of the Central and Eastern Great Plains, U.S.A.GEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 2 2002E. Arthur Bettis III Patterns of erosion and deposition act as a filter that strongly influences the disposition of the archaeological record of the Central and Eastern Plains of the North American Midcontinent. Detailed studies of alluvial valley stratigraphy in four drainage basins in the region reveal temporal and spatial patterns of fluvial system behavior that control the preservation and visibility of past human activity. These basins are located on a 600-km-long longitudinal gradient extending from semiarid southwestern Kansas to moist-subhumid central Iowa. Despite significant environmental variability along this transect, basin-wide patterns of Holocene erosion and deposition are similar across the study area. From ca. 11,000 to 8000 yr B.P., aggradation, punctuated by slow alluviation and/or stability around 10,000 yr B.P., was the dominant process in large and some small valleys. The early and middle Holocene (ca. 8000,5000 yr B.P.) was a period of net erosion and sediment movement in small valleys, sediment storage in large valleys, and episodic aggradation on alluvial fans. During the late Holocene (post-5000 yr B.P.), alluvial fans stabilized, small valleys became zones of net sediment storage, and aggradation slowed in large valleys. Basin-wide aggradation followed by entrenchment and channel migration characterizes fluvial activity during the Historic period. Consideration of the effects of these temporal and spatial patterns of Holocene erosion and alluviation on the archaeological record is crucial for developing efficient cultural resource sampling strategies and for accurately interpreting the archaeological record. © 2002 John Wiley & Sons, Inc. [source] Sampling Strategies for Volatile Organic Compounds at Three Karst Springs in TennesseeGROUND WATER MONITORING & REMEDIATION, Issue 1 2006Shannon D. Williams The influence of different sampling strategies on characterizing volatile organic compound (VOC) concentrations and estimating VOC loads was evaluated at three karst springs in Tennessee. During a 6-month period, water samples for VOC analyses were collected weekly at all three springs and as frequently as every 20 min during storms at the two springs with variable water quality conditions. Total 6-month loads for selected VOCs were calculated, and VOC data were systematically subsampled to simulate and evaluate several potential sampling strategies. Results from the study indicate that sampling strategies for karst springs need to be developed on a site-specific basis. The use of fixed sampling intervals (as infrequently as quarterly or semiannually) produced accurate concentration and load estimates at one of the springs; however, additional sampling was needed to detect storm-related changes at a second spring located in a similar hydrogeologic setting. Continuous discharge data and high-frequency or flow-controlled sampling were needed at the third spring, which had the most variable flow and water quality conditions. The lack of continuous discharge data at the third spring would substantially affect load calculations, and the use of fixed sampling intervals would affect load calculations and the ability to detect pulses of high contaminant concentrations that might exceed toxicity levels for aquatic organisms. [source] Accuracy and precision of different sampling strategies and flux integration methods for runoff water: comparisons based on measurements of the electrical conductivityHYDROLOGICAL PROCESSES, Issue 2 2006Patrick Schleppi Abstract Because of their fast response to hydrological events, small catchments show strong quantitative and qualitative variations in their water runoff. Fluxes of solutes or suspended material can be estimated from water samples only if an appropriate sampling scheme is used. We used continuous in-stream measurements of the electrical conductivity of the runoff in a small subalpine catchment (64 ha) in central Switzerland and in a very small (0·16 ha) subcatchment. Different sampling and flux integration methods were simulated for weekly water analyses. Fluxes calculated directly from grab samples are strongly biased towards high conductivities observed at low discharges. Several regressions and weighted averages have been proposed to correct for this bias. Their accuracy and precision are better, but none of these integration methods gives a consistently low bias and a low residual error. Different methods of peak sampling were also tested. Like regressions, they produce important residual errors and their bias is variable. This variability (both between methods and between catchments) does not allow one to tell a priori which sampling scheme and integration method would be more accurate. Only discharge-proportional sampling methods were found to give essentially unbiased flux estimates. Programmed samplers with a fraction collector allow for a proportional pooling and are appropriate for short-term studies. For long-term monitoring or experiments, sampling at a frequency proportional to the discharge appears to be the best way to obtain accurate and precise flux estimates. Copyright © 2006 John Wiley & Sons, Ltd. [source] Potential biases in sampling design and interpretation of intra-tooth isotope analysisINTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 1-2 2003M. BalasseArticle first published online: 30 JAN 200 Abstract An increasing number of studies dealing with environmental and dietary reconstruction involve measurement of intra-tooth variation of isotope ratios. The sampling procedure typically consists of collecting a sequence of horizontal bands perpendicular to the growth axis of the tooth. The objective is to obtain a temporal sequence of the changes recorded in dental tissues during tooth development. This paper examines some issues associated with this sampling strategy and consequences for interpretation of the data. Time resolution is influenced by the pattern and duration of enamel mineralization, in a way that might, however, depend on the species and the tooth analysed. Although it may be impossible to sample discrete amounts of time, a chronological order seems to be respected, which should be well enough when the objective is to detect changes in isotope ratios with time. Absolute data must be interpreted with caution. Such issues do not affect studies of inter-individual variability as long as the sampling procedure applied to the compared specimens is consistent. A new sampling strategy is tested on modern goat teeth, involving drilling in an oblique direction. The results obtained from obliquely drilled samples are very similar to those obtained from the horizontal sampling procedure. More work is still needed to determine the value of alternative sampling strategies. Copyright © 2003 John Wiley & Sons, Ltd. [source] The bacterial flora of vacuum-packed cold-smoked salmon stored at 7°C, identified by direct 16S rRNA gene analysis and pure culture techniqueJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2007T.C. Olofsson Abstract Aims:, The indigenous flora of freshly chilled cold-smoked salmon just after the vacuum packaging, and the spoilage flora after storage, in vacuum package at 7°C for 19 days, were to be investigated with two different sampling strategies. Methods and Results:, Identification was performed using 16S rRNA sequencing of both isolated bacteria and bacterial DNA from tissue extract. The indigenous flora of fresh cold-smoked vacuum-packed salmon was dominated by, in order, Brochothrix thermosphacta, Yersinia ruckeri, Photobacterium and Carnobacterium, whereas the spoilage flora of the same product stored at 7°C for 19 days was dominated by Lactobacillus and Photobacterium. The two sampling strategies showed similar results on the fish flora. Several new types of Photobacterium sequences, closely related to Photobacterium iliopiscarium and Photobacterium phosphoreum, were found from both the freshly processed and the stored salmon, indicating that smoked salmon harbours at least three different, as yet unknown, Photobacterium species. Conclusions:, Ten per cent of the bacterial flora multiplying on chilled, vacuum-packed, cold-smoked salmon comprised unknown species. The two sampling strategies complement each other. Significance and Impact of the Study:, As cold-smoked salmon is consumed without heat-treatment, the presence of undefined bacteria in high numbers should be considered in public health assessments. [source] Nonlinear optimization of autonomous undersea vehicle sampling strategies for oceanographic data-assimilationJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 6 2007Kevin D. Heaney The problem of how to optimally deploy a suite of sensors to estimate the oceanographic environment is addressed. An optimal way to estimate (nowcast) and predict (forecast) the ocean environment is to assimilate measurements from dynamic and uncertain regions into a dynamical ocean model. In order to determine the sensor deployment strategy that optimally samples the regions of uncertainty, a Genetic Algorithm (GA) approach is presented. The scalar cost function is defined as a weighted combination of a sensor suite's sampling of the ocean variability, ocean dynamics, transmission loss sensitivity, modeled temperature uncertainty (and others). The benefit of the GA approach is that the user can determine "optimal" via a weighting of constituent cost functions, which can include ocean dynamics, acoustics, cost, time, etc. A numerical example with three gliders, two powered AUVs, and three moorings is presented to illustrate the optimization approach in the complex shelfbreak region south of New England. © 2007 Wiley Periodicals, Inc. [source] Calcite,graphite isotope thermometry in amphibolite facies marble, Bancroft, OntarioJOURNAL OF METAMORPHIC GEOLOGY, Issue 9 2005S. R. DUNN Abstract This study presents calcite,graphite carbon isotope fractionations for 32 samples from marble in the northern Elzevir terrane of the Central Metasedimentary Belt, Grenville Province, southern Ontario, Canada. These results are compared with temperatures calculated by calcite,dolomite thermometry (15 samples), garnet,biotite thermometry (four samples) and garnet,hornblende thermometry (three samples). ,cal-gr values vary regularly across the area from >6.5, in the south to 4.0, in the north, which corresponds to temperatures of 525 °C in the south to 650 °C in the north. Previous empirical calibration of the calcite,graphite thermometer agrees very well with calcite,dolomite, garnet,biotite and garnet,hornblende thermometry, whereas, theoretical calibrations compare less well with the independent thermometry. Isograds in marble based on the reactions rutile + calcite + quartz =titanite and tremolite + calcite + quartz = diopside, span temperatures of 525,600 °C and are consistent with calculated temperature,X(CO2) relations. Results of this study compare favourably with large-scale regional isotherms, however, local variation is greater than that revealed by large-scale sampling strategies. It remains unclear whether the temperature,,cal-gr relationship observed in natural materials below 650 °C represents equilibrium fractionations or not, but the regularity and consistency apparent in this study demonstrate its utility for thermometry in amphibolite facies marble. [source] MASS LOAD ESTIMATION ERRORS UTILIZING GRAB SAMPLING STRATEGIES IN A KARST WATERSHED,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 6 2003Alex W. Fogle ABSTRACT: Developing a mass load estimation method appropriate for a given stream and constituent is difficult due to inconsistencies in hydrologic and constituent characteristics. The difficulty may be increased in flashy flow conditions such as karst. Many projects undertaken are constrained by budget and manpower and do not have the luxury of sophisticated sampling strategies. The objectives of this study were to: (1) examine two grab sampling strategies with varying sampling intervals and determine the error in mass load estimates, and (2) determine the error that can be expected when a grab sample is collected at a time of day when the diurnal variation is most divergent from the daily mean. Results show grab sampling with continuous flow to be a viable data collection method for estimating mass load in the study watershed. Comparing weekly, biweekly, and monthly grab sampling, monthly sampling produces the best results with this method. However, the time of day the sample is collected is important. Failure to account for diurnal variability when collecting a grab sample may produce unacceptable error in mass load estimates. The best time to collect a sample is when the diurnal cycle is nearest the daily mean. [source] Validation of limited sampling strategy for the estimation of mycophenolic acid exposure in Chinese adult liver transplant recipientsLIVER TRANSPLANTATION, Issue 12 2007Chen Hao Mycophenolate mofetil (MMF) is indicated as immunosuppressive therapy in liver transplantation. The abbreviated models for the estimation of mycophenolic acid (MPA) area under the concentration-time curve (AUC) have been established by limited sampling strategies (LSSs) in adult liver transplant recipients. In the current study, the performance of the abbreviated models to predict MPA exposure was validated in an independent group of patients. A total of 30 MPA pharmacokinetic profiles from 30 liver transplant recipients receiving MMF in combination with tacrolimus were used to compare 8 models' performance with a full 10 time-point MPA-AUC. Linear regression analysis and Bland-Altman analysis were used to compare the estimated MPA-AUC0-12h from each model against the measured MPA-AUC0-12h. A wide range of agreement was shown when estimated MPA-AUC0-12h was compared with measured MPA-AUC0-12h, and the range of coefficient of determination (r2) was from 0.479 to 0.936. The model based on MPA pharmacokinetic parameters C1h, C2h, C6h, and C8h had the best ability to predict measured MPA-AUC0-12h, with the best coefficient of determination (r2 = 0.936), the excellent prediction bias (2.18%), the best prediction precision (5.11%), and the best prediction variation (2SD = ±7.88 mg · h/L). However, the model based on MPA pharmacokinetic sampling time points C1h, C2h, and C4h was more suitable when concerned with clinical convenience, which had shorter sampling interval, an excellent coefficient of determination (r2 = 0.795), an excellent prediction bias (3.48%), an acceptable prediction precision (14.37%), and a good prediction variation (2SD = ±13.23 mg · h/L). Measured MPA-AUC0-12h could be best predicted by using MPA pharmacokinetic parameters C1h, C2h, C6h, and C8h. The model based on MPA pharmacokinetic parameters C1h, C2h, and C4h was more feasible in clinical application. Liver Transpl 13:1684,1693, 2007. © 2007 AASLD. [source] Optimal acquisition schemes for in vivo quantitative magnetization transfer MRIMAGNETIC RESONANCE IN MEDICINE, Issue 4 2006Mara Cercignani Abstract This paper uses the theory of Cramer-Rao lower bounds (CRLB) to obtain optimal acquisition schemes for in vivo quantitative magnetization transfer (MT) imaging, although the method is generally applicable to any multiparametric MRI technique. Quantitative MT fits a two-pool model to data collected at different sampling points or settings of amplitude and offset frequency in the MT saturation pulses. Here we use simple objective functions based on the CRLB to optimize sampling strategies for multiple parameters simultaneously, and use simulated annealing to minimize these objective functions with respect to the sampling configuration. Experiments compare optimal schemes derived for quantitative MT in the human white matter (WM) at 1.5T with previously published schemes using both synthetic and human-brain data. Results show large reductions in error of the fitted parameters with the new schemes, which greatly increases the clinical potential of in vivo quantitative MT. Since the sampling-scheme optimization requires specific settings of the MT parameters, we also show that the optimum schemes are robust to these settings within the range of MT parameters observed in the brain. Magn Reson Med, 2006. © 2006 Wiley-Liss, Inc. [source] How to track and assess genotyping errors in population genetics studiesMOLECULAR ECOLOGY, Issue 11 2004A. BONIN Abstract Genotyping errors occur when the genotype determined after molecular analysis does not correspond to the real genotype of the individual under consideration. Virtually every genetic data set includes some erroneous genotypes, but genotyping errors remain a taboo subject in population genetics, even though they might greatly bias the final conclusions, especially for studies based on individual identification. Here, we consider four case studies representing a large variety of population genetics investigations differing in their sampling strategies (noninvasive or traditional), in the type of organism studied (plant or animal) and the molecular markers used [microsatellites or amplified fragment length polymorphisms (AFLPs)]. In these data sets, the estimated genotyping error rate ranges from 0.8% for microsatellite loci from bear tissues to 2.6% for AFLP loci from dwarf birch leaves. Main sources of errors were allelic dropouts for microsatellites and differences in peak intensities for AFLPs, but in both cases human factors were non-negligible error generators. Therefore, tracking genotyping errors and identifying their causes are necessary to clean up the data sets and validate the final results according to the precision required. In addition, we propose the outline of a protocol designed to limit and quantify genotyping errors at each step of the genotyping process. In particular, we recommend (i) several efficient precautions to prevent contaminations and technical artefacts; (ii) systematic use of blind samples and automation; (iii) experience and rigor for laboratory work and scoring; and (iv) systematic reporting of the error rate in population genetics studies. [source] Sampling within the genome for measuring within-population diversity: trade-offs between markersMOLECULAR ECOLOGY, Issue 7 2002S. Mariette Abstract Experimental results of diversity estimates in a set of populations often exhibit contradictory patterns when different marker systems are used. Using simulations we identified potential causes for these discrepancies. These investigations aimed also to detect whether different sampling strategies of markers within the genome resulted in different estimates of the diversity at the whole genome level. The simulations consisted in generating a set of populations undergoing various evolutionary scenarios which differed by population size, migration rate and heterogeneity of gene flow. Population diversity was then computed for the whole genome and for subsets of loci corresponding to different marker techniques. Rank correlation between the two measures of diversity were investigated under different scenarios. We showed that the heterogeneity of genetic diversity either between loci (genomic heterogeneity, GH) or among populations (population heterogeneity, PH) varied greatly according to the evolutionary scenario considered. Furthermore, GH and PH were major determinants of the level of rank correlation between estimates of genetic diversities obtained using different kinds of markers. We found a strong positive relationship between the level of the correlation and PH, whatever the marker system. It was also shown that, when GH values were constantly low during generations, a reduced number of microsatellites was enough to predict the diversity of the whole genome, whereas when GH increased, more loci were needed to predict the diversity and amplified fragment length polymorphism markers would be more recommended in this case. Finally the results are discussed to recommend strategies for gene diversity surveys. [source] Encoding and reconstruction in parallel MRINMR IN BIOMEDICINE, Issue 3 2006Klaas P. Pruessmann Abstract The advent of parallel MRI over recent years has prompted a variety of concepts and techniques for performing parallel imaging. A main distinguishing feature among these is the specific way of posing and solving the problem of image reconstruction from undersampled multiple-coil data. The clearest distinction in this respect is that between k -space and image-domain methods. The present paper reviews the basic reconstruction approaches, aiming to emphasize common principles along with actual differences. To this end the treatment starts with an elaboration of the encoding mechanisms and sampling strategies that define the reconstruction task. Based on these considerations a formal framework is developed that permits the various methods to be viewed as different solutions of one common problem. Besides the distinction between k -space and image-domain approaches, special attention is given to the implications of general vs lattice sampling patterns. The paper closes with remarks concerning noise propagation and control in parallel imaging and an outlook upon key issues to be addressed in the future. Copyright © 2006 John Wiley & Sons, Ltd. [source] Amplified fragment length polymorphism among Rhynchosporium secalis isolates collected from a single barley field in SyriaANNALS OF APPLIED BIOLOGY, Issue 3 2005A KIROS-MELES Summary AFLP markers were used to measure the amount and distribution of genetic variation among Rhynchosporium secalis isolates on a microgeographical scale in Syria. Forty isolates hierarchically sampled from a single barley field were assayed for AFLP variation using primer combinations not previously tested in populations of the pathogen from Syria. In contrast to a previous study, which showed high clonality within field populations of R. secalis in Syria, the present study revealed a much higher level of genetic diversity, stressing the important roles that sampling strategies and the choice of primers/primer combinations play in the evaluation of genetic variation in R. secalis populations at a microgeographical scale. A high level of genetic variation was found to occur on a fine scale throughout the pathogen population examined, with 40 different haplotypes being identified among the 40 isolates sampled. Data were consistent with the hypothesis that the primary inoculum originated from a genetically diverse founding population, which may have consisted of ascospores of an as yet undescribed teleomorph and/or asexual spores of a highly mutable local population. [source] Combining molecular, morphological and ecological data to infer species boundaries in a cryptic tropical pitviperBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2006KATE L. SANDERS Few operational methods exist for delimiting species boundaries, and these usually require sampling strategies that are unrealistic for widespread organisms that occur at low densities. Here we apply molecular, morphological and ecological species delimitation criteria to a wide-ranging, fragmented group of Asian green pitvipers, the Popeia popeiorum complex. A mitochondrial DNA phylogeny for the group indicates two well-differentiated clades, corresponding mainly to northern and southern parts of its range. Strong phylogeographical structure within each clade suggests isolation in forest refugia during the Pliocene and a southward colonization of the Sunda islands during the Pleistocene. Multivariate analysis of morphological characters reveals a generally conserved pattern of geographical variation, incongruent with the recovered phylogenetic history. We compare groups delineated by mtDNA variation to morphological and ecological divisions in the complex, and discuss the implications of these for the taxonomy of the group. Discordance between species boundaries inferred from different criteria suggests that combining independent sources of data provides the most reliable estimation of species boundaries in organisms that are difficult to sample in large numbers. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 87, 343,364. [source] A limited sampling strategy for tacrolimus in renal transplant patientsBRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 4 2008Binu S. Mathew WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT , Tacrolimus trough concentration is being currently used for dose individualization. , Limited sampling strategies (LSS) have been developed and validated for renal transplant patients. , Earlier literature has suggested that measurement of tacrolimus AUC is more reliable than trough with respect to both rejection and nephrotoxicity. WHAT THIS STUDY ADDS , Four thousand renal transplants take place annually in India, with many patients prescribed tacrolimus in combination with mycophenolate and steroid. , In this study a LSS with two points, i.e. trough and 1.5 h postdose was developed and validated to estimate AUC0,12. , The added benefit of only a single additional sample with completion of blood collection in 1.5 h and minimum additional cost makes this a viable LSS algorithm in renal transplant patients. , In patients having tacrolimus trough concentrations outside the recommended range (<3 and >10 ng ml,1 in the treatment protocol in our institution) or having side-effects in spite of trough concentrations in the desired range, we can estimate AUC using this LSS for a better prediction of exposure. AIMS To develop and validate limited sampling strategy (LSS) equations to estimate area under the curve (AUC0,12) in renal transplant patients. METHODS Twenty-nine renal transplant patients (3,6 months post transplant) who were at steady state with respect to tacrolimus kinetics were included in this study. The blood samples starting with the predose (trough) and collected at fixed time points for 12 h were analysed by microparticle enzyme immunoassay. Linear regression analysis estimated the correlations of tacrolimus concentrations at different sampling time points with the total measured AUC0,12. By applying multiple stepwise linear regression analysis, LSS equations with acceptable correlation coefficients (R2), bias and precision were identified. The predictive performance of these models was validated by the jackknife technique. RESULTS Three models were identified, all with R2 , 0.907. Two point models included one with trough (C0) and 1.5 h postdose (C1.5), another with trough and 4 h postdose. Increasing the number of sampling time points to more than two increased R2 marginally (0.951 to 0.990). After jackknife validation, the two sampling time point (trough and 1.5 h postdose) model accurately predicted AUC0,12. Regression coefficient R2 = 0.951, intraclass correlation = 0.976, bias [95% confidence interval (CI)] 0.53% (,2.63, 3.69) and precision (95% CI) 6.35% (4.36, 8.35). CONCLUSION The two-point LSS equation [AUC0,12 = 19.16 + (6.75.C0) + (3.33.C1.5)] can be used as a predictable and accurate measure of AUC0,12 in stable renal transplant patients prescribed prednisolone and mycophenolate. [source] A new model Gondwanan taxon: systematics and biogeography of the harvestman family Pettalidae (Arachnida, Opiliones, Cyphophthalmi), with a taxonomic revision of genera from Australia and New ZealandCLADISTICS, Issue 4 2007Sarah L. Boyer The phylogeny of the temperate Gondwanan harvestman family Pettalidae is investigated by means of a new morphological matrix of 45 characters, and DNA sequence data from five markers, including two nuclear ribosomal genes (18S rRNA and 28S rRNA), one nuclear protein coding gene (histone H3), and two mitochondrial genes,one protein coding (cytochrome c oxidase subunit I) and one ribosomal (16S rRNA). Phylogenetic analyses using an array of homology schemes (dynamic and static), criteria (parsimony and maximum likelihood), and sampling strategies (optimal trees versus Bayesian phylogenetics) all agree on the monophyly of Pettalidae as well as several of its subclades, each of which is restricted to a modern landmass. While most genera as traditionally defined are monophyletic, Rakaia and Neopurcellia, distributed across Queensland (Australia) and New Zealand, are not. Instead, the species from Queensland, previously described under three genera, constitute a well-supported clade, suggesting that in this case biogeography prevails over traditional taxonomy. A taxonomic emendation of the genera from Queensland and New Zealand is presented, and the new genus Aoraki is erected to include the species of the New Zealand denticulata group. A biogeographical hypothesis of the relationships of the former temperate Gondwana landmasses (with the exception of Madagascar) is presented, although ambiguity in the deep nodes of the pettalid tree renders such inference provisional. The data suggest that neither the South African fauna, the New Zealand fauna nor the Australian fauna is monophyletic but instead monophyly is found at smaller geographic scales (e.g., Western Australia, Queensland, NE South Africa). © The Willi Hennig Society 2007. [source] Changing risk factors for fluorosis among South Australian childrenCOMMUNITY DENTISTRY AND ORAL EPIDEMIOLOGY, Issue 3 2008A. John Spencer Abstract,,, Background:, Research in the last decade has shown changing exposure patterns to discretionary fluorides and declining prevalence of fluorosis among South Australian children, raising the question of how risk factors for fluorosis have changed. Objective:, To examine and compare risk factors for fluorosis among representative samples of South Australian children in 1992/1993 and 2002/2003. Methods:, Similar sampling strategies and data collection methods were employed in the Child Fluoride Study (CFS) Marks 1 (1992/1993) and 2 (2002/2003). Participants in each CFS round were examined for fluorosis using the Thylstrup and Fejerskov (TF) Index. Exposure history was collected for fluoride in water, toothpaste, fluoride supplements and infant formula, allowing for a fluorosis risk assessment analysis. Data were re-weighted to represent the child population at each time. Changes in prevalence of fluorosis, defined as having a TF score of 1+ on maxillary central incisors, fluoride exposure and risk factors between the two rounds were evaluated. Result:, A total of 375 and 677 children participated in the 1992/1993 and 2002/2003 rounds respectively. Prevalence of fluorosis declined significantly from 45.3% to 25.9%. Reduced use of fluoride supplements and increased use of 400,550-ppm children F toothpaste were the most substantial fluoride exposure changes. Early toothpaste use, residence in fluoridated areas and fluoride supplement use were the risk factors in 1992/1993. Early toothpaste use and fluoride supplement use were not risk factors, leaving fluoridated water as the only risk factor among the common variables in 2002/2003. In an analysis stratified by the type of fluoridated toothpaste in 2002/2003, the large amount of toothpaste used was a risk factor in those who used 1000-ppm fluoridated toothpaste, and eating/licking toothpaste when toothpaste use started was a risk factor among children who used either 1000-ppm or 400,550-ppm fluoridated toothpaste. Conclusion:, Introduction of the 400,550-ppm F toothpaste and use of smaller amount of toothpaste restricted risk associated with early toothpaste use. Less use and possibly a stricter fluoride supplements regimen also restricted fluorosis risk. Periodic monitoring of risk of fluorosis is required to adjust guidelines for fluoride use in caries prevention. [source] Geostatistics in fisheries survey design and stock assessment: models, variances and applicationsFISH AND FISHERIES, Issue 3 2001Pierre Petitgas Abstract Over the past 10 years, fisheries scientists gradually adopted geostatistical tools when analysing fish stock survey data for estimating population abundance. First, the relation between model-based variance estimates and covariance structure enabled estimation of survey precision for non-random survey designs. The possibility of using spatial covariance for optimising sampling strategy has been a second motive for using geostatistics. Kriging also offers the advantage of weighting data values, which is useful when sample points are clustered. This paper discusses, with fisheries applications, the different geostatistical models that characterise spatial variation, and their variance formulae for many different survey designs. Some anticipated developments of geostatistics related to multivariate structures, temporal variability and adaptive sampling are discussed. [source] Using human rights-based approaches to conceptualise lesbian and bisexual women's health inequalitiesHEALTH & SOCIAL CARE IN THE COMMUNITY, Issue 4 2010Julie Fish PhD, Social Sciences Abstract This article makes a contribution to current debates in human rights-based approaches to lesbian and bisexual (LB) women's health. With reference to concepts embodied in the Yogyakarta Principles, it is proposed that the right to health includes access to health information, participation, equity, equality and non-discrimination. Specifically, the article examines how LB women's health can be considered as a health inequality and discusses international developments to reduce disparities. Drawing on qualitative data collected in an online survey, the article reports on sexual minority women's experiences of health-care. Participants were recruited via a purposive sampling strategy; questionnaires were completed by 6490 respondents of whom 5909 met the study criteria of residence in the UK, sexual orientation and completing the survey once. Analysis revealed four broad themes: heteronormativity in health-care; improving attitudes among healthcare professionals; equality in access; raising awareness and informed communities. The accounts highlight the centrality of human rights principles: fairness, respect, equality, dignity and autonomy. The implications for healthcare policy and practice are discussed including ways to empower staff and service users with knowledge and skills and ensuring non-discrimination in health service delivery. [source] Post-wildfire changes in suspended sediment rating curves: Sabino Canyon, ArizonaHYDROLOGICAL PROCESSES, Issue 11 2007Sharon L. E. Desilets Abstract Wildfire has been shown to increase erosion by several orders of magnitude, but knowledge regarding short-term variations in post-fire sediment transport processes has been lacking. We present a detailed analysis of the immediate post-fire sediment dynamics in a semi-arid basin in the southwestern USA based on suspended sediment rating curves. During June and July 2003, the Aspen Fire in the Coronado National Forest of southern Arizona burned an area of 343 km2. Surface water samples were collected in an affected watershed using an event-based sampling strategy. Sediment rating parameters were determined for individual storm events during the first 18 months after the fire. The highest sediment concentrations were observed immediately after the fire. Through the two subsequent monsoon seasons there was a progressive change in rating parameters related to the preferential removal of fine to coarse sediment. During the corresponding winter seasons, there was a lower supply of sediment from the hillslopes, resulting in a time-invariant set of sediment rating parameters. A sediment mass-balance model corroborated the physical interpretations. The temporal variability in the sediment rating parameters demonstrates the importance of storm-based sampling in areas with intense monsoon activity to characterize post-fire sediment transport accurately. In particular, recovery of rating parameters depends on the number of high-intensity rainstorms. These findings can be used to constrain rapid assessment fire-response models for planning mitigation activities. Copyright © 2006 John Wiley & Sons, Ltd. [source] Potential biases in sampling design and interpretation of intra-tooth isotope analysisINTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 1-2 2003M. BalasseArticle first published online: 30 JAN 200 Abstract An increasing number of studies dealing with environmental and dietary reconstruction involve measurement of intra-tooth variation of isotope ratios. The sampling procedure typically consists of collecting a sequence of horizontal bands perpendicular to the growth axis of the tooth. The objective is to obtain a temporal sequence of the changes recorded in dental tissues during tooth development. This paper examines some issues associated with this sampling strategy and consequences for interpretation of the data. Time resolution is influenced by the pattern and duration of enamel mineralization, in a way that might, however, depend on the species and the tooth analysed. Although it may be impossible to sample discrete amounts of time, a chronological order seems to be respected, which should be well enough when the objective is to detect changes in isotope ratios with time. Absolute data must be interpreted with caution. Such issues do not affect studies of inter-individual variability as long as the sampling procedure applied to the compared specimens is consistent. A new sampling strategy is tested on modern goat teeth, involving drilling in an oblique direction. The results obtained from obliquely drilled samples are very similar to those obtained from the horizontal sampling procedure. More work is still needed to determine the value of alternative sampling strategies. Copyright © 2003 John Wiley & Sons, Ltd. [source] Causes and management of nursing practice errors: a questionnaire survey of hospital nurses in IranINTERNATIONAL NURSING REVIEW, Issue 3 2008M. Anoosheh rn Background:, Some human error in health care is inevitable. Research into the predisposing factors for these errors is an important step in their management. Aim:, To survey nurse perceptions of the contributing factors to nursing practice errors. Methods:, A descriptive survey was carried out in three selected educational hospitals in Tehran city. Data were collected by questionnaire and analysed using descriptive statistics. The study sample consisted of 96 nurses and nursing managers. A multistage sampling strategy was used. Results:, Results showed that from nurses' and nursing managers' perspectives, various factors could contribute to the occurrence of nursing errors in the ,management', ,environment' and ,nursing care' sections. In addition, there were differences between nurses working on various wards about the causes of nursing errors in each section. Conclusion:, A culture of safety recognizes that safety is ,no accident'. Rather, it requires a change in management practices, providing a suitable environment with the requisite supply of resources and infrastructure, and increasing nurses' knowledge. Outcomes that are identified from the process of practice error management should promote interventions designed to prevent future practice errors based on the above contributing factors. Limitations:, The study relied on self-report by a sample of nurses. These responses should now be tested by empirical research into actual nursing practice errors in order to test whether the nurses' perceived ideas of causation are substantiated. [source] Spatial and temporal variability in seed dynamics of machair sand dune plant communities, the Outer Hebrides, ScotlandJOURNAL OF BIOGEOGRAPHY, Issue 5 2001N. W. Owen Aim The subjects of seed banks and seed rain represent comparatively neglected areas of biogeography, yet at the community scale, exhibit interesting patterns in both space and time. This paper describes the seed bank and seed rain characteristics of the machair sand dune communities of the Outer Hebrides. As well as looking at individual species distributions and variability, the seed banks and seed rain are examined in terms of their detailed subcommunity composition and its local spatial and temporal variation. The machair plant (sub)communities show extensive degrees of anthropogenic modification because of past and present agricultural management, including cultivation for cereals over wide areas and for potatoes in large numbers of ,lazy beds' or small patches. Thus over the historical period, large areas of machair have undergone regular ploughing and cultivation, which have provided the opportunity for a patchwork of secondary succession to occur. This pattern continues to the present day. Furthermore, most other non-cultivated plant (sub)communities are intensively grazed, primarily by cattle and also by sheep and rabbits. Location South Uist, the Outer Hebrides, north-west Scotland. Methods At two carefully selected locations, a range of these various successional subcommunities have been sampled for their seed banks, by taking cores and for their seed rain, by using specially designed traps located where each seed bank sample was removed. This paired sampling strategy allowed direct comparison of the seed bank and the seed rain. Both individual species distributions and the community assemblages of seed bank/seed rain species are examined in space and time using techniques of numerical classification [two-way indicator species analysis (TWINSPAN)] and ordination [detrended correspondence analysis (DCA)]. Results and conclusions There is considerable heterogeneity within and between machair subcommunities in terms of seed bank and seed rain characteristics. The soil seed banks and seed rain of the agriculturally disturbed machair subcommunities are consistently more dense and more species rich than non-cultivated areas of the machair. Overall, machair seed banks are small and stable with no discernible seasonal trends in either size or species composition. In contrast, seed rain on the machair is characterized by a distinct temporal trend. Both seed banks and seed rain are potentially very poor sources of propagules for recolonization following disturbance, indicating that the majority of revegetation following anthropogenic and/or environmental interference is through vegetative reproduction. [source] | |||||||||||||||||||||||||||||||||||||