Size and modal analyses of fines and ultrafines from some Apollo 17 samples

NASA Technical Reports Server (NTRS)

Greene, G. M.; King, D. T., Jr.; Banholzer, G. S., Jr.; King, E. A.

1975-01-01

Scanning electron and optical microscopy techniques have been used to determine the grain-size frequency distributions and morphology-based modal analyses of fine and ultrafine fractions of some Apollo 17 regolith samples. There are significant and large differences between the grain-size frequency distributions of the less than 10-micron size fraction of Apollo 17 samples, but there are no clear relations to the local geologic setting from which individual samples have been collected. This may be due to effective lateral mixing of regolith particles in this size range by micrometeoroid impacts. None of the properties of the frequency distributions support the idea of selective transport of any fine grain-size fraction, as has been proposed by other workers. All of the particle types found in the coarser size fractions also occur in the less than 10-micron particles. In the size range from 105 to 10 microns there is a strong tendency for the percentage of regularly shaped glass to increase as the graphic mean grain size of the less than 1-mm size fraction decreases, both probably being controlled by exposure age.

Day and night variation in chemical composition and toxicological responses of size segregated urban air PM samples in a high air pollution situation

NASA Astrophysics Data System (ADS)

Jalava, P. I.; Wang, Q.; Kuuspalo, K.; Ruusunen, J.; Hao, L.; Fang, D.; Väisänen, O.; Ruuskanen, A.; Sippula, O.; Happo, M. S.; Uski, O.; Kasurinen, S.; Torvela, T.; Koponen, H.; Lehtinen, K. E. J.; Komppula, M.; Gu, C.; Jokiniemi, J.; Hirvonen, M.-R.

2015-11-01

Urban air particulate pollution is a known cause for adverse human health effects worldwide. China has encountered air quality problems in recent years due to rapid industrialization. Toxicological effects induced by particulate air pollution vary with particle sizes and season. However, it is not known how distinctively different photochemical activity and different emission sources during the day and the night affect the chemical composition of the PM size ranges and subsequently how it is reflected to the toxicological properties of the PM exposures. The particulate matter (PM) samples were collected in four different size ranges (PM10-2.5; PM2.5-1; PM1-0.2 and PM0.2) with a high volume cascade impactor. The PM samples were extracted with methanol, dried and thereafter used in the chemical and toxicological analyses. RAW264.7 macrophages were exposed to the particulate samples in four different doses for 24 h. Cytotoxicity, inflammatory parameters, cell cycle and genotoxicity were measured after exposure of the cells to particulate samples. Particles were characterized for their chemical composition, including ions, element and PAH compounds, and transmission electron microscopy (TEM) was used to take images of the PM samples. Chemical composition and the induced toxicological responses of the size segregated PM samples showed considerable size dependent differences as well as day to night variation. The PM10-2.5 and the PM0.2 samples had the highest inflammatory potency among the size ranges. Instead, almost all the PM samples were equally cytotoxic and only minor differences were seen in genotoxicity and cell cycle effects. Overall, the PM0.2 samples had the highest toxic potential among the different size ranges in many parameters. PAH compounds in the samples and were generally more abundant during the night than the day, indicating possible photo-oxidation of the PAH compounds due to solar radiation. This was reflected to different toxicity in the PM samples. Some of the day to night difference may have been caused also by differing wind directions transporting air masses from different emission sources during the day and the night. The present findings indicate the important role of the local particle sources and atmospheric processes on the health related toxicological properties of the PM. The varying toxicological responses evoked by the PM samples showed the importance of examining various particle sizes. Especially the detected considerable toxicological activity by PM0.2 size range suggests they're attributable to combustion sources, new particle formation and atmospheric processes.

Study of structural and magnetic properties of melt spun Nd2Fe13.6Zr0.4B ingot and ribbon

NASA Astrophysics Data System (ADS)

Amin, Muhammad; Siddiqi, Saadat A.; Ashfaq, Ahmad; Saleem, Murtaza; Ramay, Shahid M.; Mahmood, Asif; Al-Zaghayer, Yousef S.

2015-12-01

Nd2Fe13.6Zr0.4B hard magnetic material were prepared using arc-melting technique on a water-cooled copper hearth kept under argon gas atmosphere. The prepared samples, Nd2Fe13.6Zr0.4B ingot and ribbon are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) for crystal structure determination and morphological studies, respectively. The magnetic properties of the samples have been explored using vibrating sample magnetometer (VSM). The lattice constants slightly increased due to the difference in the ionic radii of Fe and that of Zr. The bulk density decreased due to smaller molar weight and low density of Zr as compared to that of Fe. Ingot sample shows almost single crystalline phase with larger crystallite sizes whereas ribbon sample shows a mixture of amorphous and crystalline phases with smaller crystallite sizes. The crystallinity of the material was highly affected with high thermal treatments. Magnetic measurements show noticeable variation in magnetic behavior with the change in crystallite size. The sample prepared in ingot type shows soft while ribbon shows hard magnetic behavior.

Influence of multidroplet size distribution on icing collection efficiency

NASA Technical Reports Server (NTRS)

Chang, H.-P.; Kimble, K. R.; Frost, W.; Shaw, R. J.

1983-01-01

Calculation of collection efficiencies of two-dimensional airfoils for a monodispersed droplet icing cloud and a multidispersed droplet is carried out. Comparison is made with the experimental results reported in the NACA Technical Note series. The results of the study show considerably improved agreement with experiment when multidroplet size distributions are employed. The study then investigates the effect of collection efficiency on airborne particle droplet size sampling instruments. The biased effect introduced due to sampling from different collection volumes is predicted.

Combining gas-phase electrophoretic mobility molecular analysis (GEMMA), light scattering, field flow fractionation and cryo electron microscopy in a multidimensional approach to characterize liposomal carrier vesicles.

PubMed

Urey, Carlos; Weiss, Victor U; Gondikas, Andreas; von der Kammer, Frank; Hofmann, Thilo; Marchetti-Deschmann, Martina; Allmaier, Günter; Marko-Varga, György; Andersson, Roland

2016-11-20

For drug delivery, characterization of liposomes regarding size, particle number concentrations, occurrence of low-sized liposome artefacts and drug encapsulation are of importance to understand their pharmacodynamic properties. In our study, we aimed to demonstrate the applicability of nano Electrospray Gas-Phase Electrophoretic Mobility Molecular Analyser (nES GEMMA) as a suitable technique for analyzing these parameters. We measured number-based particle concentrations, identified differences in size between nominally identical liposomal samples, and detected the presence of low-diameter material which yielded bimodal particle size distributions. Subsequently, we compared these findings to dynamic light scattering (DLS) data and results from light scattering experiments coupled to Asymmetric Flow-Field Flow Fractionation (AF4), the latter improving the detectability of smaller particles in polydisperse samples due to a size separation step prior detection. However, the bimodal size distribution could not be detected due to method inherent limitations. In contrast, cryo transmission electron microscopy corroborated nES GEMMA results. Hence, gas-phase electrophoresis proved to be a versatile tool for liposome characterization as it could analyze both vesicle size and size distribution. Finally, a correlation of nES GEMMA results with cell viability experiments was carried out to demonstrate the importance of liposome batch-to-batch control as low-sized sample components possibly impact cell viability. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Variations in the moisture content of several fuel size components of live and dead chamise

Treesearch

John D. Dell; Charles W. Philpot

1965-01-01

Samples taken May 25, Sept. 2, and Dec. 8, 1964, indicated that leaves were the only fuel components of live chamise with appreciable seasonal moisture fluctuation. A close relationship in fuel moistures existed between like components from the different shrubs sampled. Dead chamise showed little or no variation due to fuel size or season of the year.

Evaluation of the molecular lipid organization in millimeter-sized stratum corneum by synchrotron X-ray diffraction.

PubMed

Suzuki, T; Uchino, T; Hatta, I; Miyazaki, Y; Kato, S; Sasaki, K; Kagawa, Y

2018-04-29

The aim of this study was to investigate whether the lamellar and lateral structure of intercellular lipid of stratum corneum (SC) can be evaluated from millimeter-sized SC (MSC) by X-ray diffraction. A 12 mm × 12 mm SC sheet from hairless mouse was divided into 16 pieces measuring 3 mm × 3 mm square. From another sheet, 4 pieces of ultramillimeter-sized SC (USC:1.5 mm × 1.5 mm square) were prepared. Small and wide-angle X-ray diffraction (SAXD and WAXD) measurements were performed on each piece. For MSC and USC, changes in the lamellar and lateral structure after the application of d-limonene were measured. The intensity of SAXD peaks due to the lamellar phase of long periodicity phase (LPP) and WAXD peaks due to the lateral hydrocarbon chain-packing structures varied in MSC and USC pieces, although over the 12 mm × 12 mm SC sheet. These results indicated that the intercellular lipid components and their proportion appeared nearly uniform. Application of d-limonene on MSC and USC piece with strong peaks in SAXD and the WAXD resulted in the disappearance of peaks due to the lamellar phase of LPP and decrease in peak intensity for the lateral hydrocarbon chain-packing structures. These changes are consistent with normal-sized sample results. We found that the selection of a sample piece with strong diffraction peaks due to the lamellar and lateral structure enabled evaluation of the SC structure in small-sized samples by X-ray diffraction. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Simulation of Particle Size Effect on Dynamic Properties and Fracture of PTFE-W-Al Composites

NASA Astrophysics Data System (ADS)

Herbold, E. B.; Cai, J.; Benson, D. J.; Nesterenko, V. F.

2007-12-01

Recent investigations of the dynamic compressive strength of cold isostatically pressed composites of polytetrafluoroethylene (PTFE), tungsten (W) and aluminum (Al) powders show significant differences depending on the size of metallic particles. The addition of W increases the density and changes the overall strength of the sample depending on the size of W particles. To investigate relatively large deformations, multi-material Eulerian and arbitrary Lagrangian-Eulerian methods, which have the ability to efficiently handle the formation of free surfaces, were used. The calculations indicate that the increased sample strength with fine metallic particles is due to the dynamic formation of force chains. This phenomenon occurs for samples with a higher porosity of the PTFE matrix compared to samples with larger particle size of W and a higher density PTFE matrix.

Multi-passes warm rolling of AZ31 magnesium alloy, effect on evaluation of texture, microstructure, grain size and hardness

NASA Astrophysics Data System (ADS)

Kamran, J.; Hasan, B. A.; Tariq, N. H.; Izhar, S.; Sarwar, M.

2014-06-01

In this study the effect of multi-passes warm rolling of AZ31 magnesium alloy on texture, microstructure, grain size variation and hardness of as cast sample (A) and two rolled samples (B & C) taken from different locations of the as-cast ingot was investigated. The purpose was to enhance the formability of AZ31 alloy in order to help manufacturability. It was observed that multi-passes warm rolling (250°C to 350°C) of samples B & C with initial thickness 7.76mm and 7.73 mm was successfully achieved up to 85% reduction without any edge or surface cracks in ten steps with a total of 26 passes. The step numbers 1 to 4 consist of 5, 2, 11 and 3 passes respectively, the remaining steps 5 to 10 were single pass rolls. In each discrete step a fixed roll gap is used in a way that true strain per step increases very slowly from 0.0067 in the first step to 0.7118 in the 26th step. Both samples B & C showed very similar behavior after 26th pass and were successfully rolled up to 85% thickness reduction. However, during 10th step (27th pass) with a true strain value of 0.772 the sample B experienced very severe surface as well as edge cracks. Sample C was therefore not rolled for the 10th step and retained after 26 passes. Both samples were studied in terms of their basal texture, microstructure, grain size and hardness. Sample C showed an equiaxed grain structure after 85% total reduction. The equiaxed grain structure of sample C may be due to the effective involvement of dynamic recrystallization (DRX) which led to formation of these grains with relatively low misorientations with respect to the parent as cast grains. The sample B on the other hand showed a microstructure in which all the grains were elongated along the rolling direction (RD) after 90 % total reduction and DRX could not effectively play its role due to heavy strain and lack of plastic deformation systems. The microstructure of as cast sample showed a near-random texture (mrd 4.3), with average grain size of 44 & micro-hardness of 52 Hv. The grain size of sample B and C was 14μm and 27μm respectively and mrd intensity of basal texture was 5.34 and 5.46 respectively. The hardness of sample B and C came out to be 91 and 66 Hv respectively due to reduction in grain size and followed the well known Hall-Petch relationship.

Effects of sample size on estimates of population growth rates calculated with matrix models.

PubMed

Fiske, Ian J; Bruna, Emilio M; Bolker, Benjamin M

2008-08-28

Matrix models are widely used to study the dynamics and demography of populations. An important but overlooked issue is how the number of individuals sampled influences estimates of the population growth rate (lambda) calculated with matrix models. Even unbiased estimates of vital rates do not ensure unbiased estimates of lambda-Jensen's Inequality implies that even when the estimates of the vital rates are accurate, small sample sizes lead to biased estimates of lambda due to increased sampling variance. We investigated if sampling variability and the distribution of sampling effort among size classes lead to biases in estimates of lambda. Using data from a long-term field study of plant demography, we simulated the effects of sampling variance by drawing vital rates and calculating lambda for increasingly larger populations drawn from a total population of 3842 plants. We then compared these estimates of lambda with those based on the entire population and calculated the resulting bias. Finally, we conducted a review of the literature to determine the sample sizes typically used when parameterizing matrix models used to study plant demography. We found significant bias at small sample sizes when survival was low (survival = 0.5), and that sampling with a more-realistic inverse J-shaped population structure exacerbated this bias. However our simulations also demonstrate that these biases rapidly become negligible with increasing sample sizes or as survival increases. For many of the sample sizes used in demographic studies, matrix models are probably robust to the biases resulting from sampling variance of vital rates. However, this conclusion may depend on the structure of populations or the distribution of sampling effort in ways that are unexplored. We suggest more intensive sampling of populations when individual survival is low and greater sampling of stages with high elasticities.

The impact of sample size on the reproducibility of voxel-based lesion-deficit mappings.

PubMed

Lorca-Puls, Diego L; Gajardo-Vidal, Andrea; White, Jitrachote; Seghier, Mohamed L; Leff, Alexander P; Green, David W; Crinion, Jenny T; Ludersdorfer, Philipp; Hope, Thomas M H; Bowman, Howard; Price, Cathy J

2018-07-01

This study investigated how sample size affects the reproducibility of findings from univariate voxel-based lesion-deficit analyses (e.g., voxel-based lesion-symptom mapping and voxel-based morphometry). Our effect of interest was the strength of the mapping between brain damage and speech articulation difficulties, as measured in terms of the proportion of variance explained. First, we identified a region of interest by searching on a voxel-by-voxel basis for brain areas where greater lesion load was associated with poorer speech articulation using a large sample of 360 right-handed English-speaking stroke survivors. We then randomly drew thousands of bootstrap samples from this data set that included either 30, 60, 90, 120, 180, or 360 patients. For each resample, we recorded effect size estimates and p values after conducting exactly the same lesion-deficit analysis within the previously identified region of interest and holding all procedures constant. The results show (1) how often small effect sizes in a heterogeneous population fail to be detected; (2) how effect size and its statistical significance varies with sample size; (3) how low-powered studies (due to small sample sizes) can greatly over-estimate as well as under-estimate effect sizes; and (4) how large sample sizes (N ≥ 90) can yield highly significant p values even when effect sizes are so small that they become trivial in practical terms. The implications of these findings for interpreting the results from univariate voxel-based lesion-deficit analyses are discussed. Copyright © 2018 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Synthesis, characterization, and hydrogen uptake studies of magnesium nanoparticles by solution reduction method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rather, Sami ullah, E-mail: rathersami@gmail.com

2014-12-15

Graphical abstract: X-ray diffraction (XRD) pattern of magnesium nanoparticles synthesized by solution reduction method with and without TOPO. - Highlights: • Simple and convenient method of preparing Mg nanoparticles. • Characterized by XRD, SEM, FESEM and TEM. • Trioctylphosphine oxide offers a greater control over the size of the particles. • Hydrogen uptake of samples at different temperatures and pressure of 4.5 MPa. - Abstract: Facile and simple, surfactant-mediated solution reduction method was used to synthesize monodisperse magnesium nanoparticles. Little amount of magnesium oxide nanoparticles were also formed due to the presence of TOPO and easy oxidation of magnesium, eventhough,more » all precautions were taken to avoid oxidation of the sample. Precise size control of particles was achieved by carefully varying the concentration ratio of two different types of surfactants, – trioctylphosphine oxide and hexadecylamine. Recrystallized magnesium nanoparticle samples with and without TOPO were analyzed by X-ray diffraction, scanning electron microscope, field emission scanning electron microscope, and transmission electron microscope. The peak diameters of particles were estimated from size distribution analysis of the morphological data. The particles synthesized in the presence and absence of TOPO found to have diameters 46.5 and 34.8 nm, respectively. This observed dependence of particle size on the presence of TOPO offers a convenient method to control the particle size by simply using appropriate surfactant concentrations. Exceptional enhancement in hydrogen uptake and kinetics in synthesized magnesium nanoparticles as compared to commercial magnesium sample was due to the smaller particle size and improved morphology. Overall hydrogen uptake not affected by the little variation in particle size with and without TOPO.« less

Implications of sampling design and sample size for national carbon accounting systems

Treesearch

Michael Köhl; Andrew Lister; Charles T. Scott; Thomas Baldauf; Daniel Plugge

2011-01-01

Countries willing to adopt a REDD regime need to establish a national Measurement, Reporting and Verification (MRV) system that provides information on forest carbon stocks and carbon stock changes. Due to the extensive areas covered by forests the information is generally obtained by sample based surveys. Most operational sampling approaches utilize a combination of...

On the role of the grain size in the magnetic behavior of sintered permanent magnets

NASA Astrophysics Data System (ADS)

Efthimiadis, K. G.; Ntallis, N.

2018-02-01

In this work the finite elements method is used to simulate, by micromagnetic modeling, the magnetic behavior of sintered anisotropic magnets. Hysteresis loops were simulated for different grain sizes in an oriented multigrain sample. By keeping out other parameters that contribute to the magnetic microstructure, such as the sample size, the grain morphology and the grain boundaries mismatch, it has been found that the grain size affects the magnetic properties only if the grains are exchange-decoupled. In this case, as the grain size decreases, a decrease in the nucleation field of a reverse magnetic domain is observed and an increase in the coercive field due to the pinning of the magnetic domain walls at the grain boundaries.

Generalized SAMPLE SIZE Determination Formulas for Investigating Contextual Effects by a Three-Level Random Intercept Model.

PubMed

Usami, Satoshi

2017-03-01

Behavioral and psychological researchers have shown strong interests in investigating contextual effects (i.e., the influences of combinations of individual- and group-level predictors on individual-level outcomes). The present research provides generalized formulas for determining the sample size needed in investigating contextual effects according to the desired level of statistical power as well as width of confidence interval. These formulas are derived within a three-level random intercept model that includes one predictor/contextual variable at each level to simultaneously cover various kinds of contextual effects that researchers can show interest. The relative influences of indices included in the formulas on the standard errors of contextual effects estimates are investigated with the aim of further simplifying sample size determination procedures. In addition, simulation studies are performed to investigate finite sample behavior of calculated statistical power, showing that estimated sample sizes based on derived formulas can be both positively and negatively biased due to complex effects of unreliability of contextual variables, multicollinearity, and violation of assumption regarding the known variances. Thus, it is advisable to compare estimated sample sizes under various specifications of indices and to evaluate its potential bias, as illustrated in the example.

Size effect on atomic structure in low-dimensional Cu-Zr amorphous systems.

PubMed

Zhang, W B; Liu, J; Lu, S H; Zhang, H; Wang, H; Wang, X D; Cao, Q P; Zhang, D X; Jiang, J Z

2017-08-04

The size effect on atomic structure of a Cu 64 Zr 36 amorphous system, including zero-dimensional small-size amorphous particles (SSAPs) and two-dimensional small-size amorphous films (SSAFs) together with bulk sample was investigated by molecular dynamics simulations. We revealed that sample size strongly affects local atomic structure in both Cu 64 Zr 36 SSAPs and SSAFs, which are composed of core and shell (surface) components. Compared with core component, the shell component of SSAPs has lower average coordination number and average bond length, higher degree of ordering, and lower packing density due to the segregation of Cu atoms on the shell of Cu 64 Zr 36 SSAPs. These atomic structure differences in SSAPs with various sizes result in different glass transition temperatures, in which the glass transition temperature for the shell component is found to be 577 K, which is much lower than 910 K for the core component. We further extended the size effect on the structure and glasses transition temperature to Cu 64 Zr 36 SSAFs, and revealed that the T g decreases when SSAFs becomes thinner due to the following factors: different dynamic motion (mean square displacement), different density of core and surface and Cu segregation on the surface of SSAFs. The obtained results here are different from the results for the size effect on atomic structure of nanometer-sized crystalline metallic alloys.

77 FR 60671 - Notice of Intent To Request Revision and Extension of a Currently Approved Information Collection

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-04

... approved information collection, the List Sampling Frame Surveys. Revision to burden hours will be needed due to changes in the size of the target population, sampling design, and/or questionnaire length... Agriculture, (202) 720-4333. SUPPLEMENTARY INFORMATION: Title: List Sampling Frame Surveys. OMB Control Number...

Determining the sample size for co-dominant molecular marker-assisted linkage detection for a monogenic qualitative trait by controlling the type-I and type-II errors in a segregating F2 population.

PubMed

Hühn, M; Piepho, H P

2003-03-01

Tests for linkage are usually performed using the lod score method. A critical question in linkage analyses is the choice of sample size. The appropriate sample size depends on the desired type-I error and power of the test. This paper investigates the exact type-I error and power of the lod score method in a segregating F(2) population with co-dominant markers and a qualitative monogenic dominant-recessive trait. For illustration, a disease-resistance trait is considered, where the susceptible allele is recessive. A procedure is suggested for finding the appropriate sample size. It is shown that recessive plants have about twice the information content of dominant plants, so the former should be preferred for linkage detection. In some cases the exact alpha-values for a given nominal alpha may be rather small due to the discrete nature of the sampling distribution in small samples. We show that a gain in power is possible by using exact methods.

Recent advances of mesoporous materials in sample preparation.

PubMed

Zhao, Liang; Qin, Hongqiang; Wu, Ren'an; Zou, Hanfa

2012-03-09

Sample preparation has been playing an important role in the analysis of complex samples. Mesoporous materials as the promising adsorbents have gained increasing research interest in sample preparation due to their desirable characteristics of high surface area, large pore volume, tunable mesoporous channels with well defined pore-size distribution, controllable wall composition, as well as modifiable surface properties. The aim of this paper is to review the recent advances of mesoporous materials in sample preparation with emphases on extraction of metal ions, adsorption of organic compounds, size selective enrichment of peptides/proteins, specific capture of post-translational peptides/proteins and enzymatic reactor for protein digestion. Copyright © 2011 Elsevier B.V. All rights reserved.

Does the bathing water classification depend on sampling strategy? A bootstrap approach for bathing water quality assessment, according to Directive 2006/7/EC requirements.

PubMed

López, Iago; Alvarez, César; Gil, José L; Revilla, José A

2012-11-30

Data on the 95th and 90th percentiles of bacteriological quality indicators are used to classify bathing waters in Europe, according to the requirements of Directive 2006/7/EC. However, percentile values and consequently, classification of bathing waters depend both on sampling effort and sample-size, which may undermine an appropriate assessment of bathing water classification. To analyse the influence of sampling effort and sample size on water classification, a bootstrap approach was applied to 55 bacteriological quality datasets of several beaches in the Balearic Islands (Spain). Our results show that the probability of failing the regulatory standards of the Directive is high when sample size is low, due to a higher variability in percentile values. In this way, 49% of the bathing waters reaching an "Excellent" classification (95th percentile of Escherichia coli under 250 cfu/100 ml) can fail the "Excellent" regulatory standard due to sampling strategy, when 23 samples per season are considered. This percentage increases to 81% when 4 samples per season are considered. "Good" regulatory standards can also be failed in bathing waters with an "Excellent" classification as a result of these sampling strategies. The variability in percentile values may affect bathing water classification and is critical for the appropriate design and implementation of bathing water Quality Monitoring and Assessment Programs. Hence, variability of percentile values should be taken into account by authorities if an adequate management of these areas is to be achieved. Copyright © 2012 Elsevier Ltd. All rights reserved.

Three-year-olds obey the sample size principle of induction: the influence of evidence presentation and sample size disparity on young children's generalizations.

PubMed

Lawson, Chris A

2014-07-01

Three experiments with 81 3-year-olds (M=3.62years) examined the conditions that enable young children to use the sample size principle (SSP) of induction-the inductive rule that facilitates generalizations from large rather than small samples of evidence. In Experiment 1, children exhibited the SSP when exemplars were presented sequentially but not when exemplars were presented simultaneously. Results from Experiment 3 suggest that the advantage of sequential presentation is not due to the additional time to process the available input from the two samples but instead may be linked to better memory for specific individuals in the large sample. In addition, findings from Experiments 1 and 2 suggest that adherence to the SSP is mediated by the disparity between presented samples. Overall, these results reveal that the SSP appears early in development and is guided by basic cognitive processes triggered during the acquisition of input. Copyright © 2013 Elsevier Inc. All rights reserved.

Effect of sample inhomogeneity in KAr dating

USGS Publications Warehouse

Engels, J.C.; Ingamells, C.O.

1970-01-01

Error in K-Ar ages is often due more to deficiencies in the splitting process, whereby portions of the sample are taken for potassium and for argon determination, than to imprecision in the analytical methods. The effect of the grain size of a sample and of the composition of a contaminating mineral can be evaluated, and this provides a useful guide in attempts to minimize error. Rocks and minerals should be prepared for age determination with the effects of contaminants and grain size in mind. The magnitude of such effects can be much larger than intuitive estimates might indicate. ?? 1970.

Storage effects on quantity and composition of dissolved organic carbon and nitrogen of lake water, leaf leachate and peat soil water.

PubMed

Heinz, Marlen; Zak, Dominik

2018-03-01

This study aimed to evaluate the effects of freezing and cold storage at 4 °C on bulk dissolved organic carbon (DOC) and nitrogen (DON) concentration and SEC fractions determined with size exclusion chromatography (SEC), as well as on spectral properties of dissolved organic matter (DOM) analyzed with fluorescence spectroscopy. In order to account for differences in DOM composition and source we analyzed storage effects for three different sample types, including a lake water sample representing freshwater DOM, a leaf litter leachate of Phragmites australis representing a terrestrial, 'fresh' DOM source and peatland porewater samples. According to our findings one week of cold storage can bias DOC and DON determination. Overall, the determination of DOC and DON concentration with SEC analysis for all three sample types were little susceptible to alterations due to freezing. The findings derived for the sampling locations investigated here may not apply for other sampling locations and/or sample types. However, DOC size fractions and DON concentration of formerly frozen samples should be interpreted with caution when sample concentrations are high. Alteration of some optical properties (HIX and SUVA 254 ) due to freezing were evident, and therefore we recommend immediate analysis of samples for spectral analysis. Copyright © 2017 Elsevier Ltd. All rights reserved.

Influence of pore size distributions on decomposition of maize leaf residue: evidence from X-ray computed micro-tomography

NASA Astrophysics Data System (ADS)

Negassa, Wakene; Guber, Andrey; Kravchenko, Alexandra; Rivers, Mark

2014-05-01

Soil's potential to sequester carbon (C) depends not only on quality and quantity of organic inputs to soil but also on the residence time of the applied organic inputs within the soil. Soil pore structure is one of the main factors that influence residence time of soil organic matter by controlling gas exchange, soil moisture and microbial activities, thereby soil C sequestration capacity. Previous attempts to investigate the fate of organic inputs added to soil did not allow examining their decomposition in situ; the drawback that can now be remediated by application of X-ray computed micro-tomography (µ-CT). The non-destructive and non-invasive nature of µ-CT gives an opportunity to investigate the effect of soil pore size distributions on decomposition of plant residues at a new quantitative level. The objective of this study is to examine the influence of pore size distributions on the decomposition of plant residue added to soil. Samples with contrasting pore size distributions were created using aggregate fractions of five different sizes (<0.05, 0.05-0.1, 0.10-05, 0.5-1.0 and 1.0-2.0 mm). Weighted average pore diameters ranged from 10 µm (<0.05 mm fraction) to 104 µm (1-2 mm fraction), while maximum pore diameter were in a range from 29 µm (<0.05 mm fraction) to 568 µm (1-2 mm fraction) in the created soil samples. Dried pieces of maize leaves 2.5 mg in size (equivalent to 1.71 mg C g-1 soil) were added to half of the studied samples. Samples with and without maize leaves were incubated for 120 days. CO2 emission from the samples was measured at regular time intervals. In order to ensure that the observed differences are due to differences in pore structure and not due to differences in inherent properties of the studied aggregate fractions, we repeated the whole experiment using soil from the same aggregate size fractions but ground to <0.05 mm size. Five to six replicated samples were used for intact and ground samples of all sizes with and without leaves. Two replications of the intact aggregate fractions of all sizes with leaves were subjected to µ-CT scanning before and after incubation, whereas all the remaining replications of both intact and ground aggregate fractions of <0.05, 0.05-0.1, and 1.0-2.0 mm sizes with leaves were scanned with µ-CT after the incubation. The µ-CT image showed that approximately 80% of the leaves in the intact samples of large aggregate fractions (0.5-1.0 and 1.0-2.0 mm) was decomposed during the incubation, while only 50-60% of the leaves were decomposed in the intact samples of smaller sized fractions. Even lower percent of leaves (40-50%) was decomposed in the ground samples, with very similar leaf decomposition observed in all ground samples regardless of the aggregate fraction size. Consistent with µ-CT results, the proportion of decomposed leaf estimated with the conventional mass loss method was 48% and 60% for the <0.05 mm and 1.0-2.0 mm soil size fractions of intact aggregates, and 40-50% in ground samples, respectively. The results of the incubation experiment demonstrated that, while greater C mineralization was observed in samples of all size fractions amended with leaf, the effect of leaf presence was most pronounced in the smaller aggregate fractions (0.05-0.1 mm and 0.05 mm) of intact aggregates. The results of the present study unequivocally demonstrate that differences in pore size distributions have a major effect on the decomposition of plant residues added to soil. Moreover, in presence of plant residues, differences in pore size distributions appear to also influence the rates of decomposition of the intrinsic soil organic material.

Effect of calcination temperatures on microstructures and photocatalytic activity of tungsten trioxide hollow microspheres.

PubMed

Yu, Jiaguo; Qi, Lifang; Cheng, Bei; Zhao, Xiufeng

2008-12-30

Tungsten trioxide hollow microspheres were prepared by immersing SrWO4 microspheres in a concentrated HNO3 solution, and then calcined at different temperatures. The prepared tungsten oxide samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectra, differential thermal analysis-thermogravimetry, UV-visible spectrophotometry, scanning electron microscopy, N2 adsorption/desorption measurements. The photocatalytic activity of the samples was evaluated by photocatalytic decolorization of rhodamine B aqueous solution under visible-light irradiation. It was found that with increasing calcination temperatures, the average crystallite size and average pore size increased, on the contrary, Brunauer-Emmett-Teller-specific surface areas decreased. However, pore volume and porosity increased firstly, and then decreased. Increasing calcination temperatures resulted in the changes of surface morphology of hollow microspheres. The un-calcined and 300 degrees C-calcined samples showed higher photocatalytic activity than other samples. At 400 degrees C, the photocatalytic activity decreased greatly due to the decrease of specific surface areas. At 500 degrees C, the photocatalytic activity of the samples increased again due to the junction effect of two phases.

Spatially-explicit estimation of Wright's neighborhood size in continuous populations

Treesearch

Andrew J. Shirk; Samuel A. Cushman

2014-01-01

Effective population size (Ne) is an important parameter in conservation genetics because it quantifies a population's capacity to resist loss of genetic diversity due to inbreeding and drift. The classical approach to estimate Ne from genetic data involves grouping sampled individuals into discretely defined subpopulations assumed to be panmictic. Importantly,...

Particle size distributions of metal and non-metal elements in an urban near-highway environment

EPA Science Inventory

Determination of the size-resolved elemental composition of near-highway particulate matter (PM) is important due to the health and environmental risks it poses. In the current study, twelve 24 h PM samples were collected (in July-August 2006) using a low-pressure impactor positi...

Effect of resin infiltration on the thermal and mechanical properties of nano-sized silica-based thermal insulation.

PubMed

Lee, Jae Chun; Kim, Yun-Il; Lee, Dong-Hun; Kim, Won-Jun; Park, Sung; Lee, Dong Bok

2011-08-01

Several kinds of nano-sized silica-based thermal insulation were prepared by dry processing of mixtures consisting of fumed silica, ceramic fiber, and a SiC opacifier. Infiltration of phenolic resin solution into the insulation, followed by hot-pressing, was attempted to improve the mechanical strength of the insulation. More than 22% resin content was necessary to increase the strength of the insulation by a factor of two or more. The structural integrity of the resin-infiltrated samples could be maintained, even after resin burn-out, presumably due to reinforcement from ceramic fibers. For all temperature ranges and similar sample bulk density values, the thermal conductivities of the samples after resin burn-out were consistently higher than those of the samples obtained from the dry process. Mercury intrusion curves indicated that the median size of the nanopores formed by primary silica aggregates in the samples after resin burn-out is consistently larger than that of the sample without resin infiltration.

Rule-of-thumb adjustment of sample sizes to accommodate dropouts in a two-stage analysis of repeated measurements.

PubMed

Overall, John E; Tonidandel, Scott; Starbuck, Robert R

2006-01-01

Recent contributions to the statistical literature have provided elegant model-based solutions to the problem of estimating sample sizes for testing the significance of differences in mean rates of change across repeated measures in controlled longitudinal studies with differentially correlated error and missing data due to dropouts. However, the mathematical complexity and model specificity of these solutions make them generally inaccessible to most applied researchers who actually design and undertake treatment evaluation research in psychiatry. In contrast, this article relies on a simple two-stage analysis in which dropout-weighted slope coefficients fitted to the available repeated measurements for each subject separately serve as the dependent variable for a familiar ANCOVA test of significance for differences in mean rates of change. This article is about how a sample of size that is estimated or calculated to provide desired power for testing that hypothesis without considering dropouts can be adjusted appropriately to take dropouts into account. Empirical results support the conclusion that, whatever reasonable level of power would be provided by a given sample size in the absence of dropouts, essentially the same power can be realized in the presence of dropouts simply by adding to the original dropout-free sample size the number of subjects who would be expected to drop from a sample of that original size under conditions of the proposed study.

Effect of the three-dimensional microstructure on the sound absorption of foams: A parametric study.

PubMed

Chevillotte, Fabien; Perrot, Camille

2017-08-01

The purpose of this work is to systematically study the effect of the throat and the pore sizes on the sound absorbing properties of open-cell foams. The three-dimensional idealized unit cell used in this work enables to mimic the acoustical macro-behavior of a large class of cellular solid foams. This study is carried out for a normal incidence and also for a diffuse field excitation, with a relatively large range of sample thicknesses. The transport and sound absorbing properties are numerically studied as a function of the throat size, the pore size, and the sample thickness. The resulting diagrams show the ranges of the specific throat sizes and pore sizes where the sound absorption grading is maximized due to the pore morphology as a function of the sample thickness, and how it correlates with the corresponding transport parameters. These charts demonstrate, together with typical examples, how the morphological characteristics of foam could be modified in order to increase the visco-thermal dissipation effects.

Influences of Co doping on the structural and optical properties of ZnO nanostructured

NASA Astrophysics Data System (ADS)

Majeed Khan, M. A.; Wasi Khan, M.; Alhoshan, Mansour; Alsalhi, M. S.; Aldwayyan, A. S.

2010-07-01

Pure and Co-doped ZnO nanostructured samples have been synthesized by a chemical route. We have studied the structural and optical properties of the samples by using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), field-emission transmission electron microscope (FETEM), energy-dispersive X-ray (EDX) analysis and UV-VIS spectroscopy. The XRD patterns show that all the samples are hexagonal wurtzite structures. Changes in crystallite size due to mechanical activation were also determined from X-ray measurements. These results were correlated with changes in particle size followed by SEM and TEM. The average crystallite sizes obtained from XRD were between 20 to 25 nm. The TEM images showed the average particle size of undoped ZnO nanostructure was about 20 nm whereas the smallest average grain size at 3% Co was about 15 nm. Optical parameters such as absorption coefficient ( α), energy band gap ( E g ), the refractive index ( n), and dielectric constants ( σ) have been determined using different methods.

Experimental Effects on IR Reflectance Spectra: Particle Size and Morphology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beiswenger, Toya N.; Myers, Tanya L.; Brauer, Carolyn S.

For geologic and extraterrestrial samples it is known that both particle size and morphology can have strong effects on the species’ infrared reflectance spectra. Due to such effects, the reflectance spectra cannot be predicted from the absorption coefficients alone. This is because reflectance is both a surface as well as a bulk phenomenon, incorporating both dispersion as well as absorption effects. The same spectral features can even be observed as either a maximum or minimum. The complex effects depend on particle size and preparation, as well as the relative amplitudes of the optical constants n and k, i.e. the realmore » and imaginary components of the complex refractive index. While somewhat oversimplified, upward-going amplitude in the reflectance spectrum usually result from surface scattering, i.e. rays that have been reflected from the surface without penetration, whereas downward-going peaks are due to either absorption or volume scattering, i.e. rays that have penetrated or refracted into the sample interior and are not reflected. While the effects are well known, we report seminal measurements of reflectance along with quantified particle size of the samples, the sizing obtained from optical microscopy measurements. The size measurements are correlated with the reflectance spectra in the 1.3 – 16 micron range for various bulk materials that have a combination of strong and weak absorption bands in order to understand the effects on the spectral features as a function of the mean grain size of the sample. We report results for both sodium sulfate Na2SO4 as well as ammonium sulfate (NH4)2SO4; the optical constants have been measured for (NH4)2SO4. To go a step further from the field to the laboratory we explore our understanding of particle size effects on reflectance spectra in the field using standoff detection. This has helped identify weaknesses and strengths in detection using standoff distances of up 160 meters away from the Target. The studies have shown that particle size has an enormous influence on the measured reflectance spectra of such materials; successful identification requires sufficient, representative reflectance data to include the particle sizes of interest.« less

Geochemical and radiological characterization of soils from former radium processing sites

USGS Publications Warehouse

Landa, E.R.

1984-01-01

Soil samples were collected from former radium processing sites in Denver, CO, and East Orange, NJ. Particle-size separations and radiochemical analyses of selected samples showed that while the greatest contents of both 226Ra and U were generally found in the finest (< 45 ??m) fraction, the pattern was not always of progressive increase in radionuclide content with decreasing particle size. Leaching tests on these samples showed a large portion of the 225Ra and U to be soluble in dilute hydrochloric acid. Radon-emanation coefficients measured for bulk samples of contaminated soil were about 20%. Recovery of residual uranium and vanadium, as an adjunct to any remedial action program, appears unlikely due to economic considerations.

A Future Moon Mission: Curatorial Statistics on Regolith Fragments Applicable to Sample Collection by Raking

NASA Technical Reports Server (NTRS)

Allton, J. H.; Bevill, T. J.

2003-01-01

The strategy of raking rock fragments from the lunar regolith as a means of acquiring representative samples has wide support due to science return, spacecraft simplicity (reliability) and economy [3, 4, 5]. While there exists widespread agreement that raking or sieving the bulk regolith is good strategy, there is lively discussion about the minimum sample size. Advocates of consor-tium studies desire fragments large enough to support petrologic and isotopic studies. Fragments from 5 to 10 mm are thought adequate [4, 5]. Yet, Jolliff et al. [6] demonstrated use of 2-4 mm fragments as repre-sentative of larger rocks. Here we make use of cura-torial records and sample catalogs to give a different perspective on minimum sample size for a robotic sample collector.

Size Matters: FTIR Spectral Analysis of Apollo Regolith Samples Exhibits Grain Size Dependence.

NASA Astrophysics Data System (ADS)

Martin, Dayl; Joy, Katherine; Pernet-Fisher, John; Wogelius, Roy; Morlok, Andreas; Hiesinger, Harald

2017-04-01

The Mercury Thermal Infrared Spectrometer (MERTIS) on the upcoming BepiColombo mission is designed to analyse the surface of Mercury in thermal infrared wavelengths (7-14 μm) to investigate the physical properties of the surface materials [1]. Laboratory analyses of analogue materials are useful for investigating how various sample properties alter the resulting infrared spectrum. Laboratory FTIR analysis of Apollo fine (<1mm) soil samples 14259,672, 15401,147, and 67481,96 have provided an insight into how grain size, composition, maturity (i.e., exposure to space weathering processes), and proportion of glassy material affect their average infrared spectra. Each of these samples was analysed as a bulk sample and five size fractions: <25, 25-63, 63-125, 125-250, and <250 μm. Sample 14259,672 is a highly mature highlands regolith with a large proportion of agglutinates [2]. The high agglutinate content (>60%) causes a 'flattening' of the spectrum, with reduced reflectance in the Reststrahlen Band region (RB) as much as 30% in comparison to samples that are dominated by a high proportion of crystalline material. Apollo 15401,147 is an immature regolith with a high proportion of volcanic glass pyroclastic beads [2]. The high mafic mineral content results in a systematic shift in the Christiansen Feature (CF - the point of lowest reflectance) to longer wavelength: 8.6 μm. The glass beads dominate the spectrum, displaying a broad peak around the main Si-O stretch band (at 10.8 μm). As such, individual mineral components of this sample cannot be resolved from the average spectrum alone. Apollo 67481,96 is a sub-mature regolith composed dominantly of anorthite plagioclase [2]. The CF position of the average spectrum is shifted to shorter wavelengths (8.2 μm) due to the higher proportion of felsic minerals. Its average spectrum is dominated by anorthite reflectance bands at 8.7, 9.1, 9.8, and 10.8 μm. The average reflectance is greater than the other samples due to a lower proportion of glassy material. In each soil, the smallest fractions (0-25 and 25-63 μm) have CF positions 0.1-0.4 μm higher than the larger grain sizes. Also, the bulk-sample spectra mostly closely resemble the 0-25 μm sieved size fraction spectrum, indicating that this size fraction of each sample dominates the bulk spectrum regardless of other physical properties. This has implications for surface analyses of other Solar System bodies where some mineral phases or components could be concentrated in a particular size fraction. For example, the anorthite grains in 67481,96 are dominantly >25 μm in size and therefore may not contribute proportionally to the bulk average spectrum (compared to the <25 μm fraction). The resulting bulk spectrum of 67481,96 has a CF position 0.2 μm higher than all size fractions >25 microns and therefore does not represent a true average composition of the sample. Further investigation of how grain size and composition alters the average spectrum is required to fully understand infrared spectra of planetary surfaces. [1] - Hiesinger H., Helbert J., and MERTIS Co-I Team. (2010). The Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) for the BepiColombo Mission. Planetary and Space Science. 58, 144-165. [2] - NASA Lunar Sample Compendium. https://curator.jsc.nasa.gov/lunar/lsc/

Studies on Microstructure and Thermoelectric Properties of p-Type Bi-Sb-Te Based Alloys by Gas Atomization and Hot Extrusion Processes

NASA Astrophysics Data System (ADS)

Park, Ki-Chan; Madavali, Babu; Kim, Eun-Bin; Koo, Kyung-Wan; Hong, Soon-Jik

2017-05-01

p-Type Bi2Te3 + 75% Sb2Te3 based thermoelectric materials were fabricated via gas atomization and the hot extrusion process. The gas atomized powder showed a clean surface with a spherical shape, and expanded in a wide particle size distribution (average particle size 50 μm). The phase of the fabricated extruded and R-extruded bars was identified using x-ray diffraction. The relative densities of both the extruded and R-extruded samples were measured by Archimedes principle with ˜98% relative density. The R-extruded bar exhibited finer grain microstructure than that of single extrusion process, which was attributed to a recrystallization mechanism during the fabrication. The R-extruded sample showed improved Vickers hardness compared to the extruded sample due to its fine grain microstructure. The electrical conductivity improved for the extruded sample whereas the Seebeck coefficient decreases due to its high carrier concentration. The peak power factor, ˜4.26 × 10-3 w/mK2 was obtained for the single extrusion sample, which is higher than the R-extrusion sample owing to its high electrical properties.

Gaps in sampling and limitations to tree biomass estimation: a review of past sampling efforts over the past 50 years

Treesearch

Aaron Weiskittel; Jereme Frank; James Westfall; David Walker; Phil Radtke; David Affleck; David Macfarlane

2015-01-01

Tree biomass models are widely used but differ due to variation in the quality and quantity of data used in their development. We reviewed over 250 biomass studies and categorized them by species, location, sampled diameter distribution, and sample size. Overall, less than half of the tree species in Forest Inventory and Analysis database (FIADB) are without a...

Effects of sample size and sampling frequency on studies of brown bear home ranges and habitat use

USGS Publications Warehouse

Arthur, Steve M.; Schwartz, Charles C.

1999-01-01

We equipped 9 brown bears (Ursus arctos) on the Kenai Peninsula, Alaska, with collars containing both conventional very-high-frequency (VHF) transmitters and global positioning system (GPS) receivers programmed to determine an animal's position at 5.75-hr intervals. We calculated minimum convex polygon (MCP) and fixed and adaptive kernel home ranges for randomly-selected subsets of the GPS data to examine the effects of sample size on accuracy and precision of home range estimates. We also compared results obtained by weekly aerial radiotracking versus more frequent GPS locations to test for biases in conventional radiotracking data. Home ranges based on the MCP were 20-606 km2 (x = 201) for aerial radiotracking data (n = 12-16 locations/bear) and 116-1,505 km2 (x = 522) for the complete GPS data sets (n = 245-466 locations/bear). Fixed kernel home ranges were 34-955 km2 (x = 224) for radiotracking data and 16-130 km2 (x = 60) for the GPS data. Differences between means for radiotracking and GPS data were due primarily to the larger samples provided by the GPS data. Means did not differ between radiotracking data and equivalent-sized subsets of GPS data (P > 0.10). For the MCP, home range area increased and variability decreased asymptotically with number of locations. For the kernel models, both area and variability decreased with increasing sample size. Simulations suggested that the MCP and kernel models required >60 and >80 locations, respectively, for estimates to be both accurate (change in area <1%/additional location) and precise (CV < 50%). Although the radiotracking data appeared unbiased, except for the relationship between area and sample size, these data failed to indicate some areas that likely were important to bears. Our results suggest that the usefulness of conventional radiotracking data may be limited by potential biases and variability due to small samples. Investigators that use home range estimates in statistical tests should consider the effects of variability of those estimates. Use of GPS-equipped collars can facilitate obtaining larger samples of unbiased data and improve accuracy and precision of home range estimates.

Effect of high pressure processing on dispersive and aggregative properties of almond milk.

PubMed

Dhakal, Santosh; Giusti, M Monica; Balasubramaniam, V M

2016-08-01

A study was conducted to investigate the impact of high pressure (450 and 600 MPa at 30 °C) and thermal (72, 85 and 99 °C at 0.1 MPa) treatments on dispersive and aggregative characteristics of almond milk. Experiments were conducted using a kinetic pressure testing unit and water bath. Particle size distribution, microstructure, UV absorption spectra, pH and color changes of processed and unprocessed samples were analyzed. Raw almond milk represented the mono model particle size distribution with average particle diameters of 2 to 3 µm. Thermal or pressure treatment of almond milk shifted the particle size distribution towards right and increased particle size by five- to six-fold. Micrographs confirmed that both the treatments increased particle size due to aggregation of macromolecules. Pressure treatment produced relatively more and larger aggregates than those produced by heat treated samples. The apparent aggregation rate constant for 450 MPa and 600 MPa processed samples were k450MPa,30°C  = 0.0058 s(-1) and k600MPa,30°C  = 0.0095 s(-1) respectively. This study showed that dispersive and aggregative properties of high pressure and heat-treated almond milk were different due to differences in protein denaturation, particles coagulation and aggregates morphological characteristics. Knowledge gained from the study will help food processors to formulate novel plant-based beverages treated with high pressure. © 2015 Society of Chemical Industry. © 2015 Society of Chemical Industry.

In vitro and in vivo studies of biodegradable fine grained AZ31 magnesium alloy produced by equal channel angular pressing.

PubMed

Ratna Sunil, B; Sampath Kumar, T S; Chakkingal, Uday; Nandakumar, V; Doble, Mukesh; Devi Prasad, V; Raghunath, M

2016-02-01

The objective of the present work is to investigate the role of different grain sizes produced by equal channel angular pressing (ECAP) on the degradation behavior of magnesium alloy using in vitro and in vivo studies. Commercially available AZ31 magnesium alloy was selected and processed by ECAP at 300°C for up to four passes using route Bc. Grain refinement from a starting size of 46μm to a grain size distribution of 1-5μm was successfully achieved after the 4th pass. Wettability of ECAPed samples assessed by contact angle measurements was found to increase due to the fine grain structure. In vitro degradation and bioactivity of the samples studied by immersing in super saturated simulated body fluid (SBF 5×) showed rapid mineralization within 24h due to the increased wettability in fine grained AZ31 Mg alloy. Corrosion behavior of the samples assessed by weight loss and electrochemical tests conducted in SBF 5× clearly showed the prominent role of enhanced mineral deposition on ECAPed AZ31 Mg in controlling the abnormal degradation. Cytotoxicity studies by MTT colorimetric assay showed that all the samples are viable. Additionally, cell adhesion was excellent for ECAPed samples particularly for the 3rd and 4th pass samples. In vivo experiments conducted using New Zealand White rabbits clearly showed lower degradation rate for ECAPed sample compared with annealed AZ31 Mg alloy and all the samples showed biocompatibility and no health abnormalities were noticed in the animals after 60days of in vivo studies. These results suggest that the grain size plays an important role in degradation management of magnesium alloys and ECAP technique can be adopted to achieve fine grain structures for developing degradable magnesium alloys for biomedical applications. Copyright © 2015 Elsevier B.V. All rights reserved.

Design of Phase II Non-inferiority Trials.

PubMed

Jung, Sin-Ho

2017-09-01

With the development of inexpensive treatment regimens and less invasive surgical procedures, we are confronted with non-inferiority study objectives. A non-inferiority phase III trial requires a roughly four times larger sample size than that of a similar standard superiority trial. Because of the large required sample size, we often face feasibility issues to open a non-inferiority trial. Furthermore, due to lack of phase II non-inferiority trial design methods, we do not have an opportunity to investigate the efficacy of the experimental therapy through a phase II trial. As a result, we often fail to open a non-inferiority phase III trial and a large number of non-inferiority clinical questions still remain unanswered. In this paper, we want to develop some designs for non-inferiority randomized phase II trials with feasible sample sizes. At first, we review a design method for non-inferiority phase III trials. Subsequently, we propose three different designs for non-inferiority phase II trials that can be used under different settings. Each method is demonstrated with examples. Each of the proposed design methods is shown to require a reasonable sample size for non-inferiority phase II trials. The three different non-inferiority phase II trial designs are used under different settings, but require similar sample sizes that are typical for phase II trials.

Enhanced asymmetric magnetization reversal in nanoscale Co/CoO arrays: competition between exchange bias and magnetostatic coupling.

PubMed

Girgis, E; Portugal, R D; Loosvelt, H; Van Bael, M J; Gordon, I; Malfait, M; Temst, K; Van Haesendonck, C; Leunissen, L H A; Jonckheere, R

2003-10-31

Magnetization reversal was studied in square arrays of square Co/CoO dots with lateral size varying between 200 and 900 nm. While reference nonpatterned Co/CoO films show the typical shift and increased width of the hysteresis loop due to exchange bias, the patterned samples reveal a pronounced size dependence. In particular, an anomaly appears in the upper branch of the magnetization cycle and becomes stronger as the dot size decreases. This anomaly, which is absent at room temperature in the patterned samples, can be understood in terms of a competition between magnetostatic interdot interaction and exchange anisotropy during the magnetic switching process.

Geochemical and radiological characterization of soils from former radium processing sites.

PubMed

Landa, E R

1984-02-01

Soil samples were collected from former radium processing sites in Denver, CO, and East Orange, NJ. Particle-size separations and radiochemical analyses of selected samples showed that while the greatest contents of both 226Ra and U were generally found in the finest (less than 45 micron) fraction, the pattern was not always of progressive increase in radionuclide content with decreasing particle size. Leaching tests on these samples showed a large portion of the 226Ra and U to be soluble in dilute hydrochloric acid. Radon-emanation coefficients measured for bulk samples of contaminated soil were about 20%. Recovery of residual uranium and vanadium, as an adjunct to any remedial action program, appears unlikely due to economic considerations.

Characterization of Extracellular Vesicles by Size-Exclusion High-Performance Liquid Chromatography (HPLC).

PubMed

Huang, Tao; He, Jiang

2017-01-01

Extracellular vesicles (EVs) have recently attracted substantial attention due to the potential diagnostic and therapeutic relevance. Although a variety of techniques have been used to isolate and analyze EVs, it is still far away from satisfaction. Size-exclusion chromatography (SEC), which separates subjects by size, has been widely applied in protein purification and analysis. The purpose of this chapter is to show the applications of size-exclusion high-performance liquid chromatography (HPLC) as methods for EV characterization of impurities or contaminants of small size, and thus for quality assay for the purity of the samples of EVs.

Large exchange bias effect in NiFe2O4/CoO nanocomposites

NASA Astrophysics Data System (ADS)

Mohan, Rajendra; Prasad Ghosh, Mritunjoy; Mukherjee, Samrat

2018-03-01

In this work, we report the exchange bias effect of NiFe2O4/CoO nanocomposites, synthesized via chemical co-precipitation method. Four samples of different particle size ranging from 4 nm to 31 nm were prepared with the annealing temperature varying from 200 °C to 800 °C. X-ray diffraction analysis of all the samples confirmed the presence of cubic spinel phase of Nickel ferrite along with CoO phase without trace of any impurity. Sizes of the particles were studied from transmission electron micrographs and were found to be in agreement with those estimated from x-ray diffraction. Field cooled (FC) hysteresis loops at 5 K revealed an exchange bias (HE) of 2.2 kOe for the sample heated at 200 °C which decreased with the increase of particle size. Exchange bias expectedly vanished at 300 K due to high thermal energy (kBT) and low effective surface anisotropy. M-T curves revealed a blocking temperature of 135 K for the sample with smaller particle size.

Extraction of hydrocarbons from high-maturity Marcellus Shale using supercritical carbon dioxide

USGS Publications Warehouse

Jarboe, Palma B.; Philip A. Candela,; Wenlu Zhu,; Alan J. Kaufman,

2015-01-01

Shale is now commonly exploited as a hydrocarbon resource. Due to the high degree of geochemical and petrophysical heterogeneity both between shale reservoirs and within a single reservoir, there is a growing need to find more efficient methods of extracting petroleum compounds (crude oil, natural gas, bitumen) from potential source rocks. In this study, supercritical carbon dioxide (CO2) was used to extract n-aliphatic hydrocarbons from ground samples of Marcellus shale. Samples were collected from vertically drilled wells in central and western Pennsylvania, USA, with total organic carbon (TOC) content ranging from 1.5 to 6.2 wt %. Extraction temperature and pressure conditions (80 °C and 21.7 MPa, respectively) were chosen to represent approximate in situ reservoir conditions at sample depth (1920−2280 m). Hydrocarbon yield was evaluated as a function of sample matrix particle size (sieve size) over the following size ranges: 1000−500 μm, 250−125 μm, and 63−25 μm. Several methods of shale characterization including Rock-Eval II pyrolysis, organic petrography, Brunauer−Emmett−Teller surface area, and X-ray diffraction analyses were also performed to better understand potential controls on extraction yields. Despite high sample thermal maturity, results show that supercritical CO2 can liberate diesel-range (n-C11 through n-C21) n-aliphatic hydrocarbons. The total quantity of extracted, resolvable n-aliphatic hydrocarbons ranges from approximately 0.3 to 12 mg of hydrocarbon per gram of TOC. Sieve size does have an effect on extraction yield, with highest recovery from the 250−125 μm size fraction. However, the significance of this effect is limited, likely due to the low size ranges of the extracted shale particles. Additional trends in hydrocarbon yield are observed among all samples, regardless of sieve size: 1) yield increases as a function of specific surface area (r2 = 0.78); and 2) both yield and surface area increase with increasing TOC content (r2 = 0.97 and 0.86, respectively). Given that supercritical CO2 is able to mobilize residual organic matter present in overmature shales, this study contributes to a better understanding of the extent and potential factors affecting the extraction process.

Effects of crystallite size on the structure and magnetism of ferrihydrite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Xiaoming; Zhu, Mengqiang; Koopal, Luuk K.

2015-12-15

The structure and magnetic properties of nano-sized (1.6 to 4.4 nm) ferrihydrite samples are systematically investigated through a combination of X-ray diffraction (XRD), X-ray pair distribution function (PDF), X-ray absorption spectroscopy (XAS) and magnetic analyses. The XRD, PDF and Fe K-edge XAS data of the ferrihydrite samples are all fitted well with the Michel ferrihydrite model, indicating similar local-, medium- and long-range ordered structures. PDF and XAS fitting results indicate that, with increasing crystallite size, the average coordination numbers of Fe–Fe and the unit cell parameter c increase, while Fe2 and Fe3 vacancies and the unit cell parameter a decrease.more » Mössbauer results indicate that the surface layer is relatively disordered, which might have been caused by the random distribution of Fe vacancies. These results support Hiemstra's surface-depletion model in terms of the location of disorder and the variations of Fe2 and Fe3 occupancies with size. Magnetic data indicate that the ferrihydrite samples show antiferromagnetism superimposed with a ferromagnetic-like moment at lower temperatures (100 K and 10 K), but ferrihydrite is paramagnetic at room temperature. In addition, both the magnetization and coercivity decrease with increasing ferrihydrite crystallite size due to strong surface effects in fine-grained ferrihydrites. Smaller ferrihydrite samples show less magnetic hyperfine splitting and a lower unblocking temperature (T B) than larger samples. The dependence of magnetic properties on grain size for nano-sized ferrihydrite provides a practical way to determine the crystallite size of ferrihydrite quantitatively in natural environments or artificial systems.« less

Dry particle generation with a 3-D printed fluidized bed generator

DOE PAGES

Roesch, Michael; Roesch, Carolin; Cziczo, Daniel J.

2017-06-02

We describe the design and testing of PRIZE (PRinted fluidIZed bed gEnerator), a compact fluidized bed aerosol generator manufactured using stereolithography (SLA) printing. Dispersing small quantities of powdered materials – due to either rarity or expense – is challenging due to a lack of small, low-cost dry aerosol generators. With this as motivation, we designed and built a generator that uses a mineral dust or other dry powder sample mixed with bronze beads that sit atop a porous screen. A particle-free airflow is introduced, dispersing the sample as airborne particles. The total particle number concentrations and size distributions were measured duringmore » different stages of the assembling process to show that the SLA 3-D printed generator did not generate particles until the mineral dust sample was introduced. Furthermore, time-series measurements with Arizona Test Dust (ATD) showed stable total particle number concentrations of 10–150 cm -3, depending on the sample mass, from the sub- to super-micrometer size range. Additional tests with collected soil dust samples are also presented. PRIZE is simple to assemble, easy to clean, inexpensive and deployable for laboratory and field studies that require dry particle generation.« less

Dry particle generation with a 3-D printed fluidized bed generator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roesch, Michael; Roesch, Carolin; Cziczo, Daniel J.

We describe the design and testing of PRIZE (PRinted fluidIZed bed gEnerator), a compact fluidized bed aerosol generator manufactured using stereolithography (SLA) printing. Dispersing small quantities of powdered materials – due to either rarity or expense – is challenging due to a lack of small, low-cost dry aerosol generators. With this as motivation, we designed and built a generator that uses a mineral dust or other dry powder sample mixed with bronze beads that sit atop a porous screen. A particle-free airflow is introduced, dispersing the sample as airborne particles. The total particle number concentrations and size distributions were measured duringmore » different stages of the assembling process to show that the SLA 3-D printed generator did not generate particles until the mineral dust sample was introduced. Furthermore, time-series measurements with Arizona Test Dust (ATD) showed stable total particle number concentrations of 10–150 cm -3, depending on the sample mass, from the sub- to super-micrometer size range. Additional tests with collected soil dust samples are also presented. PRIZE is simple to assemble, easy to clean, inexpensive and deployable for laboratory and field studies that require dry particle generation.« less

An integrated approach to piezoactuator positioning in high-speed atomic force microscope imaging

NASA Astrophysics Data System (ADS)

Yan, Yan; Wu, Ying; Zou, Qingze; Su, Chanmin

2008-07-01

In this paper, an integrated approach to achieve high-speed atomic force microscope (AFM) imaging of large-size samples is proposed, which combines the enhanced inversion-based iterative control technique to drive the piezotube actuator control for lateral x-y axis positioning with the use of a dual-stage piezoactuator for vertical z-axis positioning. High-speed, large-size AFM imaging is challenging because in high-speed lateral scanning of the AFM imaging at large size, large positioning error of the AFM probe relative to the sample can be generated due to the adverse effects—the nonlinear hysteresis and the vibrational dynamics of the piezotube actuator. In addition, vertical precision positioning of the AFM probe is even more challenging (than the lateral scanning) because the desired trajectory (i.e., the sample topography profile) is unknown in general, and the probe positioning is also effected by and sensitive to the probe-sample interaction. The main contribution of this article is the development of an integrated approach that combines advanced control algorithm with an advanced hardware platform. The proposed approach is demonstrated in experiments by imaging a large-size (50μm ) calibration sample at high-speed (50Hz scan rate).

Internal pilots for a class of linear mixed models with Gaussian and compound symmetric data

PubMed Central

Gurka, Matthew J.; Coffey, Christopher S.; Muller, Keith E.

2015-01-01

SUMMARY An internal pilot design uses interim sample size analysis, without interim data analysis, to adjust the final number of observations. The approach helps to choose a sample size sufficiently large (to achieve the statistical power desired), but not too large (which would waste money and time). We report on recent research in cerebral vascular tortuosity (curvature in three dimensions) which would benefit greatly from internal pilots due to uncertainty in the parameters of the covariance matrix used for study planning. Unfortunately, observations correlated across the four regions of the brain and small sample sizes preclude using existing methods. However, as in a wide range of medical imaging studies, tortuosity data have no missing or mistimed data, a factorial within-subject design, the same between-subject design for all responses, and a Gaussian distribution with compound symmetry. For such restricted models, we extend exact, small sample univariate methods for internal pilots to linear mixed models with any between-subject design (not just two groups). Planning a new tortuosity study illustrates how the new methods help to avoid sample sizes that are too small or too large while still controlling the type I error rate. PMID:17318914

Passage of Campylobacter jejuni and Campylobacter coli subtypes through 0.45 and 0.65 µm pore size nitro-cellulose filters

USDA-ARS?s Scientific Manuscript database

Campylobacter can be difficult to recover from complex samples due to overgrowth by background bacteria. A 0.45 or 0.65 µm pore size filter overlaid on agar plates can be used as a means to separate Campylobacter from confounding non-Campylobacter cells, facilitating detection on solid plating medi...

Influence of Cr and Y Addition on Microstructure, Mechanical Properties, and Corrosion Resistance of SPSed Fe-Based Alloys

NASA Astrophysics Data System (ADS)

Muthaiah, V. M. Suntharavel; Mula, Suhrit

2018-03-01

Present work investigates the microstructural stability during spark plasma sintering (SPS) of Fe-Cr-Y alloys, its mechanical properties and corrosion behavior for its possible applications in nuclear power plant and petrochemical industries. The SPS was carried out for the Fe-7Cr-1Y and Fe-15Cr-1Y alloys at 800 °C, 900 °C, and 1000 °C due to their superior thermal stability as reported in Muthaiah et al. [Mater Charact 114:43-53, 2016]. Microstructural analysis through TEM and electron back scattered diffraction confirmed that the grain sizes of the sintered samples depicted a dual size grain distribution with >50 pct grains within a range of 200 nm and remaining grains in the range 200 nm to 2 µm. The best combination of hardness, wear resistance, and corrosion behavior was achieved for the samples sintered at 1000 °C. The high hardness (9.6 GPa), minimum coefficient of friction (0.25), and extremely low wear volume (0.00277 × 10-2 mm3) and low corrosion rate (3.43 mpy) are discussed in the light of solid solution strengthening, grain size strengthening, grain boundary segregation, excellent densification due to diffusion bonding, and precipitation hardening due to uniformly distributed nanosize Fe17Y2 phase in the alloy matrix. The SEM analysis of the worn surface and corroded features corroborated well with the wear resistance and corrosion behavior of the corresponding samples.

Monitoring landscape metrics by point sampling: accuracy in estimating Shannon's diversity and edge density.

PubMed

Ramezani, Habib; Holm, Sören; Allard, Anna; Ståhl, Göran

2010-05-01

Environmental monitoring of landscapes is of increasing interest. To quantify landscape patterns, a number of metrics are used, of which Shannon's diversity, edge length, and density are studied here. As an alternative to complete mapping, point sampling was applied to estimate the metrics for already mapped landscapes selected from the National Inventory of Landscapes in Sweden (NILS). Monte-Carlo simulation was applied to study the performance of different designs. Random and systematic samplings were applied for four sample sizes and five buffer widths. The latter feature was relevant for edge length, since length was estimated through the number of points falling in buffer areas around edges. In addition, two landscape complexities were tested by applying two classification schemes with seven or 20 land cover classes to the NILS data. As expected, the root mean square error (RMSE) of the estimators decreased with increasing sample size. The estimators of both metrics were slightly biased, but the bias of Shannon's diversity estimator was shown to decrease when sample size increased. In the edge length case, an increasing buffer width resulted in larger bias due to the increased impact of boundary conditions; this effect was shown to be independent of sample size. However, we also developed adjusted estimators that eliminate the bias of the edge length estimator. The rates of decrease of RMSE with increasing sample size and buffer width were quantified by a regression model. Finally, indicative cost-accuracy relationships were derived showing that point sampling could be a competitive alternative to complete wall-to-wall mapping.

Chemical Characterization of an Envelope A Sample from Hanford Tank 241-AN-103

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hay, M.S.

2000-08-23

A whole tank composite sample from Hanford waste tank 241-AN-103 was received at the Savannah River Technology Center (SRTC) and chemically characterized. Prior to characterization the sample was diluted to {approximately}5 M sodium concentration. The filtered supernatant liquid, the total dried solids of the diluted sample, and the washed insoluble solids obtained from filtration of the diluted sample were analyzed. A mass balance calculation of the three fractions of the sample analyzed indicate the analytical results appear relatively self-consistent for major components of the sample. However, some inconsistency was observed between results where more than one method of determination wasmore » employed and for species present in low concentrations. A direct comparison to previous analyses of material from tank 241-AN-103 was not possible due to unavailability of data for diluted samples of tank 241-AN-103 whole tank composites. However, the analytical data for other types of samples from 241-AN-103 we re mathematically diluted and compare reasonably with the current results. Although the segments of the core samples used to prepare the sample received at SRTC were combined in an attempt to produce a whole tank composite, determination of how well the results of the current analysis represent the actual composition of the Hanford waste tank 241-AN-103 remains problematic due to the small sample size and the large size of the non-homogenized waste tank.« less

The late Neandertal supraorbital fossils from Vindija Cave, Croatia: a biased sample?

PubMed

Ahern, James C M; Lee, Sang-Hee; Hawks, John D

2002-09-01

The late Neandertal sample from Vindija (Croatia) has been described as transitional between the earlier Central European Neandertals from Krapina (Croatia) and modern humans. However, the morphological differences indicating this transition may rather be the result of different sex and/or age compositions between the samples. This study tests the hypothesis that the metric differences between the Krapina and Vindija supraorbital samples are due to sampling bias. We focus upon the supraorbital region because past studies have posited this region as particularly indicative of the Vindija sample's transitional nature. Furthermore, the supraorbital region varies significantly with both age and sex. We analyzed four chords and two derived indices of supraorbital torus form as defined by Smith & Ranyard (1980, Am. J. phys. Anthrop.93, pp. 589-610). For each variable, we analyzed relative sample bias of the Krapina and Vindija samples using three sampling methods. In order to test the hypothesis that the Vindija sample contains an over-representation of females and/or young while the Krapina sample is normal or also female/young biased, we determined the probability of drawing a sample of the same size as and with a mean equal to or less than Vindija's from a Krapina-based population. In order to test the hypothesis that the Vindija sample is female/young biased while the Krapina sample is male/old biased, we determined the probability of drawing a sample of the same size as and with a mean equal or less than Vindija's from a generated population whose mean is halfway between Krapina's and Vindija's. Finally, in order to test the hypothesis that the Vindija sample is normal while the Krapina sample contains an over-representation of males and/or old, we determined the probability of drawing a sample of the same size as and with a mean equal to or greater than Krapina's from a Vindija-based population. Unless we assume that the Vindija sample is female/young and the Krapina sample is male/old biased, our results falsify the hypothesis that the metric differences between the Krapina and Vindija samples are due to sample bias.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saxena, Shailendra K., E-mail: phd1211512@iiti.ac.in; Sahu, Gayatri; Sagdeo, Pankaj R.

Quantum confinement effect has been studied in cheese like silicon nano-structures (Ch-SiNS) fabricated by metal induced chemical etching using different etching times. Scanning electron microscopy is used for the morphological study of these Ch-SiNS. A visible photoluminescence (PL) emission is observed from the samples under UV excitation at room temperature due to quantum confinement effect. The average size of Silicon Nanostructures (SiNS) present in the samples has been estimated by bond polarizability model using Raman Spectroscopy from the red-shift observed from SiNSs as compared to its bulk counterpart. The sizes of SiNS present in the samples decreases as etching timemore » increase from 45 to 75 mintunes.« less

A strategy for characterized aerosol-sampling transport efficiency.

NASA Astrophysics Data System (ADS)

Schwarz, J. P.

2017-12-01

A fundamental concern when sampling aerosol in the laboratory or in situ, on the ground or (especially) from aircraft, is characterizing transport losses due to particles contacting the walls of tubing used for transport. Depending on the size range of the aerosol, different mechanisms dominate these losses: diffusion for the ultra-fine, and inertial and gravitational settling losses for the coarse mode. In the coarse mode, losses become intractable very quickly with increasing particle size above 5 µm diameter. Here we present these issues, with a concept approach to reducing aerosol losses via strategic dilution with porous tubing including results of laboratory testing of a prototype. We infer the potential value of this approach to atmospheric aerosol sampling.

Impact of crystalline defects and size on X-ray line broadening: A phenomenological approach for tetragonal SnO{sub 2} nanocrystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muhammed Shafi, P.; Chandra Bose, A., E-mail: acbose@nitt.edu

2015-05-15

Nanocrystalline tin oxide (SnO{sub 2}) powders with different grain size were prepared by chemical precipitation method. The reaction was carried out by varying the period of hydrolysis and the as-prepared samples were annealed at different temperatures. The samples were characterized using X-ray powder diffractometer and transmission electron microscopy. The microstrain and crystallite size were calculated for all the samples by using Williamson-Hall (W-H) models namely, isotropic strain model (ISM), anisotropic strain model (ASM) and uniform deformation energy density model (UDEDM). The morphology and particle size were determined using TEM micrographs. The directional dependant young’s modulus was modified as an equationmore » relating elastic compliances (s{sub ij}) and Miller indices of the lattice plane (hkl) for tetragonal crystal system and also the equation for elastic compliance in terms of stiffness constants was derived. The changes in crystallite size and microstrain due to lattice defects were observed while varying the hydrolysis time and the annealing temperature. The dependence of crystallite size on lattice strain was studied. The results were correlated with the available studies on electrical properties using impedance spectroscopy.« less

Speeding Up Non-Parametric Bootstrap Computations for Statistics Based on Sample Moments in Small/Moderate Sample Size Applications

PubMed Central

Chaibub Neto, Elias

2015-01-01

In this paper we propose a vectorized implementation of the non-parametric bootstrap for statistics based on sample moments. Basically, we adopt the multinomial sampling formulation of the non-parametric bootstrap, and compute bootstrap replications of sample moment statistics by simply weighting the observed data according to multinomial counts instead of evaluating the statistic on a resampled version of the observed data. Using this formulation we can generate a matrix of bootstrap weights and compute the entire vector of bootstrap replications with a few matrix multiplications. Vectorization is particularly important for matrix-oriented programming languages such as R, where matrix/vector calculations tend to be faster than scalar operations implemented in a loop. We illustrate the application of the vectorized implementation in real and simulated data sets, when bootstrapping Pearson’s sample correlation coefficient, and compared its performance against two state-of-the-art R implementations of the non-parametric bootstrap, as well as a straightforward one based on a for loop. Our investigations spanned varying sample sizes and number of bootstrap replications. The vectorized bootstrap compared favorably against the state-of-the-art implementations in all cases tested, and was remarkably/considerably faster for small/moderate sample sizes. The same results were observed in the comparison with the straightforward implementation, except for large sample sizes, where the vectorized bootstrap was slightly slower than the straightforward implementation due to increased time expenditures in the generation of weight matrices via multinomial sampling. PMID:26125965

Sampling errors in the measurement of rain and hail parameters

NASA Technical Reports Server (NTRS)

Gertzman, H. S.; Atlas, D.

1977-01-01

Attention is given to a general derivation of the fractional standard deviation (FSD) of any integrated property X such that X(D) = cD to the n. This work extends that of Joss and Waldvogel (1969). The equation is applicable to measuring integrated properties of cloud, rain or hail populations (such as water content, precipitation rate, kinetic energy, or radar reflectivity) which are subject to statistical sampling errors due to the Poisson distributed fluctuations of particles sampled in each particle size interval and the weighted sum of the associated variances in proportion to their contribution to the integral parameter to be measured. Universal curves are presented which are applicable to the exponential size distribution permitting FSD estimation of any parameters from n = 0 to n = 6. The equations and curves also permit corrections for finite upper limits in the size spectrum and a realistic fall speed law.

Combining the boundary shift integral and tensor-based morphometry for brain atrophy estimation

NASA Astrophysics Data System (ADS)

Michalkiewicz, Mateusz; Pai, Akshay; Leung, Kelvin K.; Sommer, Stefan; Darkner, Sune; Sørensen, Lauge; Sporring, Jon; Nielsen, Mads

2016-03-01

Brain atrophy from structural magnetic resonance images (MRIs) is widely used as an imaging surrogate marker for Alzheimers disease. Their utility has been limited due to the large degree of variance and subsequently high sample size estimates. The only consistent and reasonably powerful atrophy estimation methods has been the boundary shift integral (BSI). In this paper, we first propose a tensor-based morphometry (TBM) method to measure voxel-wise atrophy that we combine with BSI. The combined model decreases the sample size estimates significantly when compared to BSI and TBM alone.

Threshold responses of Blackside Dace (Chrosomus cumberlandensis) and Kentucky Arrow Darter (Etheostoma spilotum) to stream conductivity

USGS Publications Warehouse

Hitt, Nathaniel P.; Floyd, Michael; Compton, Michael; McDonald, Kenneth

2016-01-01

Chrosomus cumberlandensis (Blackside Dace [BSD]) and Etheostoma spilotum (Kentucky Arrow Darter [KAD]) are fish species of conservation concern due to their fragmented distributions, their low population sizes, and threats from anthropogenic stressors in the southeastern United States. We evaluated the relationship between fish abundance and stream conductivity, an index of environmental quality and potential physiological stressor. We modeled occurrence and abundance of KAD in the upper Kentucky River basin (208 samples) and BSD in the upper Cumberland River basin (294 samples) for sites sampled between 2003 and 2013. Segmented regression indicated a conductivity change-point for BSD abundance at 343 μS/cm (95% CI: 123–563 μS/cm) and for KAD abundance at 261 μS/cm (95% CI: 151–370 μS/cm). In both cases, abundances were negligible above estimated conductivity change-points. Post-hoc randomizations accounted for variance in estimated change points due to unequal sample sizes across the conductivity gradients. Boosted regression-tree analysis indicated stronger effects of conductivity than other natural and anthropogenic factors known to influence stream fishes. Boosted regression trees further indicated threshold responses of BSD and KAD occurrence to conductivity gradients in support of segmented regression results. We suggest that the observed conductivity relationship may indicate energetic limitations for insectivorous fishes due to changes in benthic macroinvertebrate community composition.

Influences of spark plasma sintering temperature on the microstructures and thermoelectric properties of (Sr0.95Gd0.05)TiO3 ceramics

NASA Astrophysics Data System (ADS)

Li, Liang-Liang; Qin, Xiao-Ying; Liu, Yong-Fei; Liu, Quan-Zhen

2015-06-01

(Sr0.95Gd0.05)TiO3 (SGTO) ceramics are successfully prepared via spark plasma sintering (SPS) respectively at 1548, 1648, and 1748 K by using submicron-sized SGTO powders synthesized from a sol-gel method. The densities, microstructures, and thermoelectric properties of the SGTO ceramics are studied. Though the Seebeck coefficient shows no obvious difference in the case that SPS temperatures range from 1548 K to 1648 K, the electrical conductivity and the thermal conductivity increase remarkably due to the increase in grain size and density. The sample has a density higher than 98% theoretical density as the sintering temperature increases up to 1648 K and shows average grain sizes increasing from ˜ 0.7 μm to 7 μm until 1748 K. As a result, the maximum of the dimensionless figure of merit of ˜ 0.24 is achieved at ˜ 1000 K for the samples sintered at 1648 K and 1748 K, which was ˜ 71% larger than that (0.14 at ˜ 1000 K) for the sample sintered at 1548 K due to the enhancement of the power factor. Project supported by the National Natural Science Foundation of China (Grant Nos. 11174292, 51101150, and 11374306).

Size-Based Separation of Particles and Cells Utilizing Viscoelastic Effects in Straight Microchannels.

PubMed

Liu, Chao; Xue, Chundong; Chen, Xiaodong; Shan, Lei; Tian, Yu; Hu, Guoqing

2015-06-16

Viscoelasticity-induced particle migration has recently received increasing attention due to its ability to obtain high-quality focusing over a wide range of flow rates. However, its application is limited to low throughput regime since the particles can defocus as flow rate increases. Using an engineered carrier medium with constant and low viscosity and strong elasticity, the sample flow rates are improved to be 1 order of magnitude higher than those in existing studies. Utilizing differential focusing of particles of different sizes, here, we present sheathless particle/cell separation in simple straight microchannels that possess excellent parallelizability for further throughput enhancement. The present method can be implemented over a wide range of particle/cell sizes and flow rates. We successfully separate small particles from larger particles, MCF-7 cells from red blood cells (RBCs), and Escherichia coli (E. coli) bacteria from RBCs in different straight microchannels. The proposed method could broaden the applications of viscoelastic microfluidic devices to particle/cell separation due to the enhanced sample throughput and simple channel design.

Sample size and power considerations in network meta-analysis

PubMed Central

2012-01-01

Background Network meta-analysis is becoming increasingly popular for establishing comparative effectiveness among multiple interventions for the same disease. Network meta-analysis inherits all methodological challenges of standard pairwise meta-analysis, but with increased complexity due to the multitude of intervention comparisons. One issue that is now widely recognized in pairwise meta-analysis is the issue of sample size and statistical power. This issue, however, has so far only received little attention in network meta-analysis. To date, no approaches have been proposed for evaluating the adequacy of the sample size, and thus power, in a treatment network. Findings In this article, we develop easy-to-use flexible methods for estimating the ‘effective sample size’ in indirect comparison meta-analysis and network meta-analysis. The effective sample size for a particular treatment comparison can be interpreted as the number of patients in a pairwise meta-analysis that would provide the same degree and strength of evidence as that which is provided in the indirect comparison or network meta-analysis. We further develop methods for retrospectively estimating the statistical power for each comparison in a network meta-analysis. We illustrate the performance of the proposed methods for estimating effective sample size and statistical power using data from a network meta-analysis on interventions for smoking cessation including over 100 trials. Conclusion The proposed methods are easy to use and will be of high value to regulatory agencies and decision makers who must assess the strength of the evidence supporting comparative effectiveness estimates. PMID:22992327

Characterizing acoustic shocks in high-performance jet aircraft flyover noise.

PubMed

Reichman, Brent O; Gee, Kent L; Neilsen, Tracianne B; Downing, J Micah; James, Michael M; Wall, Alan T; McInerny, Sally Anne

2018-03-01

Acoustic shocks have been previously documented in high-amplitude jet noise, including both the near and far fields of military jet aircraft. However, previous investigations into the nature and formation of shocks have historically concentrated on stationary, ground run-up measurements, and previous attempts to connect full-scale ground run-up and flyover measurements have omitted the effect of nonlinear propagation. This paper shows evidence for nonlinear propagation and the presence of acoustic shocks in acoustical measurements of F-35 flyover operations. Pressure waveforms, derivatives, and statistics indicate nonlinear propagation, and the resulting shock formation is significant at high engine powers. Variations due to microphone size, microphone height, and sampling rate are considered, and recommendations for future measurements are made. Metrics indicating nonlinear propagation are shown to be influenced by changes in sampling rate and microphone size, and exhibit less variation due to microphone height.

Environmental Particle Emissions due to Automated Drilling of Polypropylene Composites and Nanocomposites Reinforced with Talc, Montmorillonite and Wollastonite

NASA Astrophysics Data System (ADS)

Starost, K.; Frijns, E.; Laer, J. V.; Faisal, N.; Egizabal, A.; Elizextea, C.; Nelissen, I.; Blazquez, M.; Njuguna, J.

2017-05-01

In this study, the effect on nanoparticle emissions due to drilling on Polypropylene (PP) reinforced with 20% talc, 5% montmorillonite (MMT) and 5% Wollastonite (WO) is investigated. The study is the first to explore the nanoparticle release from WO and talc reinforced composites and compares the results to previously researched MMT. With 5% WO, equivalent tensile properties with a 10 % weight reduction were obtained relative to the reference 20% talc sample. The materials were fabricated through injection moulding. The nanorelease studies were undertaken using the controlled drilling methodology for nanoparticle exposure assessment developed within the European Commission funded SIRENA Life 11 ENV/ES/506 project. Measurements were taken using CPC and DMS50 equipment for real-time characterization and measurements. The particle number concentration (of particles <1000nm) and particle size distribution (4.87nm - 562.34nm) of the particles emitted during drilling were evaluated to investigate the effect of the silicate fillers on the particles released. The nano-filled samples exhibited a 33% decrease (MMT sample) or a 30% increase (WO sample) on the average particle number concentration released in comparison to the neat polypropylene sample. The size distribution data displayed a substantial percentage of the particles released from the PP, PP/WO and PP/MMT samples to be between 5-20nm, whereas the PP/talc sample emitted larger particle diameters.

Will Outer Tropical Cyclone Size Change due to Anthropogenic Warming?

NASA Astrophysics Data System (ADS)

Schenkel, B. A.; Lin, N.; Chavas, D. R.; Vecchi, G. A.; Knutson, T. R.; Oppenheimer, M.

2017-12-01

Prior research has shown significant interbasin and intrabasin variability in outer tropical cyclone (TC) size. Moreover, outer TC size has even been shown to vary substantially over the lifetime of the majority of TCs. However, the factors responsible for both setting initial outer TC size and determining its evolution throughout the TC lifetime remain uncertain. Given these gaps in our physical understanding, there remains uncertainty in how outer TC size will change, if at all, due to anthropogenic warming. The present study seeks to quantify whether outer TC size will change significantly in response to anthropogenic warming using data from a high-resolution global climate model and a regional hurricane model. Similar to prior work, the outer TC size metric used in this study is the radius in which the azimuthal-mean surface azimuthal wind equals 8 m/s. The initial results from the high-resolution global climate model data suggest that the distribution of outer TC size shifts significantly towards larger values in each global TC basin during future climates, as revealed by 1) statistically significant increase of the median outer TC size by 5-10% (p<0.05) according to a 1,000-sample bootstrap resampling approach with replacement and 2) statistically significant differences between distributions of outer TC size from current and future climate simulations as shown using two-sample Kolmogorov Smirnov testing (p<<0.01). Additional analysis of the high-resolution global climate model data reveals that outer TC size does not uniformly increase within each basin in future climates, but rather shows substantial locational dependence. Future work will incorporate the regional mesoscale hurricane model data to help focus on identifying the source of the spatial variability in outer TC size increases within each basin during future climates and, more importantly, why outer TC size changes in response to anthropogenic warming.

Differential scanning calorimetry of coal

NASA Technical Reports Server (NTRS)

Gold, P. I.

1978-01-01

Differential scanning calorimetry studies performed during the first year of this project demonstrated the occurrence of exothermic reactions associated with the production of volatile matter in or near the plastic region. The temperature and magnitude of the exothermic peak were observed to be strongly affected by the heating rate, sample mass and, to a lesser extent, by sample particle size. Thermal properties also were found to be influenced by oxidation of the coal sample due to weathering effects.

Trophic accumulation of PSP toxins in zooplankton during Alexandrium fundyense blooms in Casco Bay, Gulf of Maine, April-June 1998. II. . Zooplankton abundance and size-fractionated community composition

NASA Astrophysics Data System (ADS)

Turner, Jefferson T.; Doucette, Gregory J.; Keafer, Bruce A.; Anderson, Donald M.

2005-09-01

During spring blooms of the toxic dinoflagellate Alexandrium fundyense in Casco Bay, Maine in 1998, we investigated vectorial intoxication of various zooplankton size fractions with PSP toxins, including zooplankton community composition from quantitative zooplankton samples (>102 μm), as well as zooplankton composition in relation to toxin levels in various size fractions (20-64, 64-100, 100-200, 200-500, >500 μm). Zooplankton abundance in 102 μm mesh samples was low (most values<10,000 animals m -3) from early April through early May, but increased to maxima in mid-June (cruise mean=121,500 animals m -3). Quantitative zooplankton samples (>102 μm) were dominated by copepod nauplii, and Oithona similis copepodites and adults at most locations except for those furthest inshore. At these inshore locations, Acartia hudsonica copepodites and adults were usually dominant. Larger copepods such as Calanus finmarchicus, Centropages typicus, and Pseudocalanus spp. were found primarily offshore, and at much lower abundances than O. similis. Rotifers, mainly present from late April to late May, were most abundant inshore. The marine cladoceran Evadne nordmani was sporadically abundant, particularly in mid-June. Microplankton in 20-64 μm size fractions was generally dominated by A. fundyense, non-toxic dinoflagellates, and tintinnids. Microplankton in 64-100 μm size fractions was generally dominated by larger non-toxic dinoflagellates, tintinnids, aloricate ciliates, and copepod nauplii, and in early May, rotifers. Some samples (23%) in the 64-100 μm size fractions contained abundant cells of A. fundyense, presumably due to sieve clogging, but most did not contain A. fundyense cells. This suggests that PSP toxin levels in those samples were due to vectorial intoxication of microzooplankters such as heterotrophic dinoflagellates, tintinnids, aloricate ciliates, rotifers, and copepod nauplii via feeding on A. fundyense cells. Dominant taxa in zooplankton fractions varied in size. Samples in the 100-200 μm size fraction were overwhelmingly dominated in most cases by copepod nauplii and small copepodites of O. similis, and during late May, rotifers. Samples in the 200-500 μm size fraction contained fewer copepod nauplii, but progressively more copepodites and adults of O. similis, particularly at offshore locations. At the most inshore stations, copepodites and adults of A. hudsonica were usual dominants. There were few copepod nauplii or O. similis in the>500 μm size fraction, which was usually dominated by copepodites and adults of C. finmarchicus, C. typicus, and Pseudocalanus spp. at offshore locations, and A. hudsonica inshore. Most of the higher PSP toxin concentrations were found in the larger zooplankton size fractions that were dominated by larger copepods such as C. finmarchicus and C. typicus. In contrast to our earlier findings, elevated toxin levels were also measured in numerous samples from smaller zooplankton size fractions, dominated by heterotrophic dinoflagellates, tintinnids and aloricate ciliates, rotifers, copepod nauplii, and smaller copepods such as O. similis and, at the most inshore locations, A. hudsonica. Thus, our data suggest that ingested PSP toxins are widespread throughout the zooplankton grazing community, and that potential vectors for intoxication of zooplankton assemblages include heterotrophic dinoflagellates, rotifers, protozoans, copepod nauplii, and small copepods.

The local environment of ice particles in arctic mixed-phase clouds

NASA Astrophysics Data System (ADS)

Schlenczek, Oliver; Fugal, Jacob P.; Schledewitz, Waldemar; Borrmann, Stephan

2015-04-01

During the RACEPAC field campaign in April and May 2014, research flights were made with the Polar 5 and Polar 6 aircraft from the Alfred Wegener Institute in Arctic clouds near Inuvik, Northwest Territories, Canada. One flight with the Polar 6 aircraft, done on May 16, 2014, flew under precipitating, stratiform, mid-level clouds with several penetrations through cloud base. Measurements with HALOHolo, an airborne digital in-line holographic instrument for cloud particles, show ice particles in a field of other cloud particles in a local three-dimensional sample volume (~14x19x130 mm3 or ~35 cm^3). Each holographic sample volume is a snapshot of a 3-dimensional piece of cloud at the cm-scale with typically thousands of cloud droplets per sample volume, so each sample volume yields a statistically significant droplet size distribution. Holograms are recorded at a rate of six times per second, which provides one volume sample approx. every 12 meters along the flight path. The size resolution limit for cloud droplets is better than 1 µm due to advanced sizing algorithms. Shown are preliminary results of, (1) the ice/liquid water partitioning at the cloud base and the distribution of water droplets around each ice particle, and (2) spatial and temporal variability of the cloud droplet size distributions at cloud base.

Trap configuration and spacing influences parameter estimates in spatial capture-recapture models

USGS Publications Warehouse

Sun, Catherine C.; Fuller, Angela K.; Royle, J. Andrew

2014-01-01

An increasing number of studies employ spatial capture-recapture models to estimate population size, but there has been limited research on how different spatial sampling designs and trap configurations influence parameter estimators. Spatial capture-recapture models provide an advantage over non-spatial models by explicitly accounting for heterogeneous detection probabilities among individuals that arise due to the spatial organization of individuals relative to sampling devices. We simulated black bear (Ursus americanus) populations and spatial capture-recapture data to evaluate the influence of trap configuration and trap spacing on estimates of population size and a spatial scale parameter, sigma, that relates to home range size. We varied detection probability and home range size, and considered three trap configurations common to large-mammal mark-recapture studies: regular spacing, clustered, and a temporal sequence of different cluster configurations (i.e., trap relocation). We explored trap spacing and number of traps per cluster by varying the number of traps. The clustered arrangement performed well when detection rates were low, and provides for easier field implementation than the sequential trap arrangement. However, performance differences between trap configurations diminished as home range size increased. Our simulations suggest it is important to consider trap spacing relative to home range sizes, with traps ideally spaced no more than twice the spatial scale parameter. While spatial capture-recapture models can accommodate different sampling designs and still estimate parameters with accuracy and precision, our simulations demonstrate that aspects of sampling design, namely trap configuration and spacing, must consider study area size, ranges of individual movement, and home range sizes in the study population.

Spatial sampling considerations of the CERES (Clouds and Earth Radiant Energy System) instrument

NASA Astrophysics Data System (ADS)

Smith, G. L.; Manalo-Smith, Natividdad; Priestley, Kory

2014-10-01

The CERES (Clouds and Earth Radiant Energy System) instrument is a scanning radiometer with three channels for measuring Earth radiation budget. At present CERES models are operating aboard the Terra, Aqua and Suomi/NPP spacecraft and flights of CERES instruments are planned for the JPSS-1 spacecraft and its successors. CERES scans from one limb of the Earth to the other and back. The footprint size grows with distance from nadir simply due to geometry so that the size of the smallest features which can be resolved from the data increases and spatial sampling errors increase with nadir angle. This paper presents an analysis of the effect of nadir angle on spatial sampling errors of the CERES instrument. The analysis performed in the Fourier domain. Spatial sampling errors are created by smoothing of features which are the size of the footprint and smaller, or blurring, and inadequate sampling, that causes aliasing errors. These spatial sampling errors are computed in terms of the system transfer function, which is the Fourier transform of the point response function, the spacing of data points and the spatial spectrum of the radiance field.

Effect of annealing temperature on the size and magnetic properties of CoFe2O4 nanoparticle

NASA Astrophysics Data System (ADS)

Sunny, Annrose; Akshay, V. R.; Vasundhara, M.

2018-05-01

CoFe2O4 (CFO) nanoparticles (NPs) are synthesized using sol gel method and are annealed at 400, 600 and 800 °C for 4h. The crystal structure and morphology of the NPs are investigated through XRD and TEM analysis. The X- ray diffraction analysis shows that all the samples are well formed and attain a cubic structure with Fd-3m space group. The morphology of the material is found to be polygonal and the particle size of the NPs is increased with increase of annealing temperature as 400, 600 and 800 to be 20 nm, 30 nm and 70 nm respectively. The magnetic properties of the NPs are investigated using VSM and observed that the curie temperature for 400, 600 and 800 °C annealing temperature are 762 K, 780 K, 769 K respectively. The Ms of 600 sample is 80 emu/g. The 400 and 800 sample shows lower Ms value this is due to poor crystalanity and exaggerated grain growth at the respective temperatures. The coercivity of the sample shows linear dependence with particle size of the material the highest coercivity is obtained for 400 sample and low value for 800 sample.

Thermal conductivity of nanocrystalline silicon: importance of grain size and frequency-dependent mean free paths.

PubMed

Wang, Zhaojie; Alaniz, Joseph E; Jang, Wanyoung; Garay, Javier E; Dames, Chris

2011-06-08

The thermal conductivity reduction due to grain boundary scattering is widely interpreted using a scattering length assumed equal to the grain size and independent of the phonon frequency (gray). To assess these assumptions and decouple the contributions of porosity and grain size, five samples of undoped nanocrystalline silicon have been measured with average grain sizes ranging from 550 to 64 nm and porosities from 17% to less than 1%, at temperatures from 310 to 16 K. The samples were prepared using current activated, pressure assisted densification (CAPAD). At low temperature the thermal conductivities of all samples show a T(2) dependence which cannot be explained by any traditional gray model. The measurements are explained over the entire temperature range by a new frequency-dependent model in which the mean free path for grain boundary scattering is inversely proportional to the phonon frequency, which is shown to be consistent with asymptotic analysis of atomistic simulations from the literature. In all cases the recommended boundary scattering length is smaller than the average grain size. These results should prove useful for the integration of nanocrystalline materials in devices such as advanced thermoelectrics.

The utility of point count surveys to predict wildlife interactions with wind energy facilities: An example focused on golden eagles

USGS Publications Warehouse

Sur, Maitreyi; Belthoff, James R.; Bjerre, Emily R.; Millsap, Brian A.; Katzner, Todd

2018-01-01

Wind energy development is rapidly expanding in North America, often accompanied by requirements to survey potential facility locations for existing wildlife. Within the USA, golden eagles (Aquila chrysaetos) are among the most high-profile species of birds that are at risk from wind turbines. To minimize golden eagle fatalities in areas proposed for wind development, modified point count surveys are usually conducted to estimate use by these birds. However, it is not always clear what drives variation in the relationship between on-site point count data and actual use by eagles of a wind energy project footprint. We used existing GPS-GSM telemetry data, collected at 15 min intervals from 13 golden eagles in 2012 and 2013, to explore the relationship between point count data and eagle use of an entire project footprint. To do this, we overlaid the telemetry data on hypothetical project footprints and simulated a variety of point count sampling strategies for those footprints. We compared the time an eagle was found in the sample plots with the time it was found in the project footprint using a metric we called “error due to sampling”. Error due to sampling for individual eagles appeared to be influenced by interactions between the size of the project footprint (20, 40, 90 or 180 km2) and the sampling type (random, systematic or stratified) and was greatest on 90 km2 plots. However, use of random sampling resulted in lowest error due to sampling within intermediate sized plots. In addition sampling intensity and sampling frequency both influenced the effectiveness of point count sampling. Although our work focuses on individual eagles (not the eagle populations typically surveyed in the field), our analysis shows both the utility of simulations to identify specific influences on error and also potential improvements to sampling that consider the context-specific manner that point counts are laid out on the landscape.

Surface-sediment grain-size distribution and sediment transport in the subaqueous Mekong Delta, Vietnam

NASA Astrophysics Data System (ADS)

Nguyen, T. T.; Stattegger, K.; Nittrouer, C.; Phung, P. V.; Liu, P.; DeMaster, D. J.; Bui, D. V.; Le, A. D.; Nguyen, T. N.

2016-02-01

Collected surface-sediment samples in coastal water around Mekong Delta (from distributary channels to Ca Mau Peninsula) were analyzed to determine surface-sediment grain-size distribution and sediment-transport trend in the subaqueous Mekong Delta. The grain-size data set of 238 samples was obtained by using the laser instrument Mastersizer 2000 and LS Particle Size Analyzer. Fourteen samples were selected for geochemical analysis (total-organic and carbonate content). These geochemical results were used to assist in interpreting variations of granulometricparamenters along the cross-shore transects. Nine transects were examined from CungHau river mouth to Ca Mau Peninsula and six thematic maps on the whole study area were made. The research results indicate that: (1) generally, the sediment becomes finer from the delta front downwards to prodelta and becomes coarser again and poorer sorted on the adjacent inner shelf due to different sources of sediment; (2) sediment-granulometry parameters vary among sedimentary sub-environments of the underwater part of Mekong Delta, the distance from sediment source and hydrodynamic regime controlling each region; (3) the net sediment transport is southwest toward the Ca Mau Peninsula.

Influence of surface treatments on micropore structure and hydrogen adsorption behavior of nanoporous carbons.

PubMed

Kim, Byung-Joo; Park, Soo-Jin

2007-07-15

The scope of this work was to control the pore sizes of porous carbons by various surface treatments and to investigate the relation between pore structures and hydrogen adsorption capacity. The effects of various surface treatments (i.e., gas-phase ozone, anodic oxidation, fluorination, and oxygen plasma) on the micropore structures of porous carbons were investigated by N(2)/77 K isothermal adsorption. The hydrogen adsorption capacity was measured by H(2) isothermal adsorption at 77 K. In the result, the specific surface area and micropore volume of all of the treated samples were slightly decreased due to the micropore filling or pore collapsing behaviors. It was also found that in F(2)-treated carbons the center of the pore size distribution was shifted to left side, meaning that the average size of the micropores decreased. The F(2)- and plasma-treated samples showed higher hydrogen storage capacities than did the other samples, the F(2)-treated one being the best, indicating that the micropore size of the porous carbons played a key role in the hydrogen adsorption at 77 K.

An Open-Source Storage Solution for Cryo-Electron Microscopy Samples.

PubMed

Ultee, Eveline; Schenkel, Fred; Yang, Wen; Brenzinger, Susanne; Depelteau, Jamie S; Briegel, Ariane

2018-02-01

Cryo-electron microscopy (cryo-EM) enables the study of biological structures in situ in great detail and to solve protein structures at Ångstrom level resolution. Due to recent advances in instrumentation and data processing, the field of cryo-EM is a rapidly growing. Access to facilities and national centers that house the state-of-the-art microscopes is limited due to the ever-rising demand, resulting in long wait times between sample preparation and data acquisition. To improve sample storage, we have developed a cryo-storage system with an efficient, high storage capacity that enables sample storage in a highly organized manner. This system is simple to use, cost-effective and easily adaptable for any type of grid storage box and dewar and any size cryo-EM laboratory.

Visual sensitivity to spatially sampled modulation in human observers

NASA Technical Reports Server (NTRS)

Mulligan, Jeffrey B.; Macleod, Donald I. A.

1991-01-01

Thresholds were measured for detecting spatial luminance modulation in regular lattices of visually discrete dots. Thresholds for modulation of a lattice are generally higher than the corresponding threshold for modulation of a continuous field, and the size of the threshold elevation, which depends on the spacing of the lattice elements, can be as large as a one log unit. The largest threshold elevations are seen when the sample spacing is 12 min arc or greater. Theories based on response compression cannot explain the further observation that the threshold elevations due to spatial sampling are also dependent on modulation frequency: the greatest elevations occur with higher modulation frequencies. The idea that this is due to masking of the modulation frequency by the spatial frequencies in the sampling lattice is considered.

Performance of a Line Loss Correction Method for Gas Turbine Emission Measurements

NASA Astrophysics Data System (ADS)

Hagen, D. E.; Whitefield, P. D.; Lobo, P.

2015-12-01

International concern for the environmental impact of jet engine exhaust emissions in the atmosphere has led to increased attention on gas turbine engine emission testing. The Society of Automotive Engineers Aircraft Exhaust Emissions Measurement Committee (E-31) has published an Aerospace Information Report (AIR) 6241 detailing the sampling system for the measurement of non-volatile particulate matter from aircraft engines, and is developing an Aerospace Recommended Practice (ARP) for methodology and system specification. The Missouri University of Science and Technology (MST) Center for Excellence for Aerospace Particulate Emissions Reduction Research has led numerous jet engine exhaust sampling campaigns to characterize emissions at different locations in the expanding exhaust plume. Particle loss, due to various mechanisms, occurs in the sampling train that transports the exhaust sample from the engine exit plane to the measurement instruments. To account for the losses, both the size dependent penetration functions and the size distribution of the emitted particles need to be known. However in the proposed ARP, particle number and mass are measured, but size is not. Here we present a methodology to generate number and mass correction factors for line loss, without using direct size measurement. A lognormal size distribution is used to represent the exhaust aerosol at the engine exit plane and is defined by the measured number and mass at the downstream end of the sample train. The performance of this line loss correction is compared to corrections based on direct size measurements using data taken by MST during numerous engine test campaigns. The experimental uncertainty in these correction factors is estimated. Average differences between the line loss correction method and size based corrections are found to be on the order of 10% for number and 2.5% for mass.

Orphan therapies: making best use of postmarket data.

PubMed

Maro, Judith C; Brown, Jeffrey S; Dal Pan, Gerald J; Li, Lingling

2014-08-01

Postmarket surveillance of the comparative safety and efficacy of orphan therapeutics is challenging, particularly when multiple therapeutics are licensed for the same orphan indication. To make best use of product-specific registry data collected to fulfill regulatory requirements, we propose the creation of a distributed electronic health data network among registries. Such a network could support sequential statistical analyses designed to detect early warnings of excess risks. We use a simulated example to explore the circumstances under which a distributed network may prove advantageous. We perform sample size calculations for sequential and non-sequential statistical studies aimed at comparing the incidence of hepatotoxicity following initiation of two newly licensed therapies for homozygous familial hypercholesterolemia. We calculate the sample size savings ratio, or the proportion of sample size saved if one conducted a sequential study as compared to a non-sequential study. Then, using models to describe the adoption and utilization of these therapies, we simulate when these sample sizes are attainable in calendar years. We then calculate the analytic calendar time savings ratio, analogous to the sample size savings ratio. We repeat these analyses for numerous scenarios. Sequential analyses detect effect sizes earlier or at the same time as non-sequential analyses. The most substantial potential savings occur when the market share is more imbalanced (i.e., 90% for therapy A) and the effect size is closest to the null hypothesis. However, due to low exposure prevalence, these savings are difficult to realize within the 30-year time frame of this simulation for scenarios in which the outcome of interest occurs at or more frequently than one event/100 person-years. We illustrate a process to assess whether sequential statistical analyses of registry data performed via distributed networks may prove a worthwhile infrastructure investment for pharmacovigilance.

Extreme sensitivity of magnetic properties on the synthesis routes in La{sub 0.7}Sr{sub 0.3}MnO{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Ashutosh, E-mail: ashutosh.pph13@iitp.ac.in; Sharma, Himanshu; Tomy, C. V.

2016-05-06

La{sub 0.7}Sr{sub 0.3}MnO{sub 3} polycrystalline samples have been prepared using different synthesis routes. X-ray Diffraction (XRD) confirms that the samples are of single phase with R-3c space group. The surface morphology and particle size has been observed using Field Emission Scanning Electron Microscopy (FESEM). Magnetic measurement shows that the magnetization in the materials are affected by low crystallite size which destroys the spin ordering due to strain at grain boundaries and this also leads to reduction in magnetization as well as high coercivity in the material.

78 FR 17921 - Notice of Intent To Seek Reinstatement of an Information Collection

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-25

... may be needed due to changes in the size of the target population, sampling design, and/or questionnaire length. DATES: Comments on this notice must be received by May 24, 2013 to be assured of...

Particle size distribution and perchlorate levels in settled dust from urban roads, parks, and roofs in Chengdu, China.

PubMed

Li, Yiwen; Shen, Yang; Pi, Lu; Hu, Wenli; Chen, Mengqin; Luo, Yan; Li, Zhi; Su, Shijun; Ding, Sanglan; Gan, Zhiwei

2016-01-01

A total of 27 settled dust samples were collected from urban roads, parks, and roofs in Chengdu, China to investigate particle size distribution and perchlorate levels in different size fractions. Briefly, fine particle size fractions (<250 μm) were the dominant composition in the settled dust samples, with mean percentages of 80.2%, 69.5%, and 77.2% for the urban roads, roofs, and the parks, respectively. Perchlorate was detected in all of the size-fractionated dust samples, with concentrations ranging from 73.0 to 6160 ng g(-1), and the median perchlorate levels increased with decreasing particle size. The perchlorate level in the finest fraction (<63 μm) was significantly higher than those in the coarser fractions. To our knowledge, this is the first report on perchlorate concentrations in different particle size fractions. The calculated perchlorate loadings revealed that perchlorate was mainly associated with finer particles (<125 μm). An exposure assessment indicated that exposure to perchlorate via settled road dust intake is safe to both children and adults in Chengdu, China. However, due to perchlorate mainly existing in fine particles, there is a potential for perchlorate to transfer into surface water and the atmosphere by runoff and wind erosion or traffic emission, and this could act as an important perchlorate pollution source for the indoor environment, and merits further study.

The albatross plot: A novel graphical tool for presenting results of diversely reported studies in a systematic review

PubMed Central

Jones, Hayley E.; Martin, Richard M.; Lewis, Sarah J.; Higgins, Julian P.T.

2017-01-01

Abstract Meta‐analyses combine the results of multiple studies of a common question. Approaches based on effect size estimates from each study are generally regarded as the most informative. However, these methods can only be used if comparable effect sizes can be computed from each study, and this may not be the case due to variation in how the studies were done or limitations in how their results were reported. Other methods, such as vote counting, are then used to summarize the results of these studies, but most of these methods are limited in that they do not provide any indication of the magnitude of effect. We propose a novel plot, the albatross plot, which requires only a 1‐sided P value and a total sample size from each study (or equivalently a 2‐sided P value, direction of effect and total sample size). The plot allows an approximate examination of underlying effect sizes and the potential to identify sources of heterogeneity across studies. This is achieved by drawing contours showing the range of effect sizes that might lead to each P value for given sample sizes, under simple study designs. We provide examples of albatross plots using data from previous meta‐analyses, allowing for comparison of results, and an example from when a meta‐analysis was not possible. PMID:28453179

Grain size statistics and depositional pattern of the Ecca Group sandstones, Karoo Supergroup in the Eastern Cape Province, South Africa

NASA Astrophysics Data System (ADS)

Baiyegunhi, Christopher; Liu, Kuiwu; Gwavava, Oswald

2017-11-01

Grain size analysis is a vital sedimentological tool used to unravel the hydrodynamic conditions, mode of transportation and deposition of detrital sediments. In this study, detailed grain-size analysis was carried out on thirty-five sandstone samples from the Ecca Group in the Eastern Cape Province of South Africa. Grain-size statistical parameters, bivariate analysis, linear discriminate functions, Passega diagrams and log-probability curves were used to reveal the depositional processes, sedimentation mechanisms, hydrodynamic energy conditions and to discriminate different depositional environments. The grain-size parameters show that most of the sandstones are very fine to fine grained, moderately well sorted, mostly near-symmetrical and mesokurtic in nature. The abundance of very fine to fine grained sandstones indicate the dominance of low energy environment. The bivariate plots show that the samples are mostly grouped, except for the Prince Albert samples that show scattered trend, which is due to the either mixture of two modes in equal proportion in bimodal sediments or good sorting in unimodal sediments. The linear discriminant function analysis is dominantly indicative of turbidity current deposits under shallow marine environments for samples from the Prince Albert, Collingham and Ripon Formations, while those samples from the Fort Brown Formation are lacustrine or deltaic deposits. The C-M plots indicated that the sediments were deposited mainly by suspension and saltation, and graded suspension. Visher diagrams show that saltation is the major process of transportation, followed by suspension.

Brief Report: Accuracy and Response Time for the Recognition of Facial Emotions in a Large Sample of Children with Autism Spectrum Disorders

ERIC Educational Resources Information Center

Fink, Elian; de Rosnay, Marc; Wierda, Marlies; Koot, Hans M.; Begeer, Sander

2014-01-01

The empirical literature has presented inconsistent evidence for deficits in the recognition of basic emotion expressions in children with autism spectrum disorders (ASD), which may be due to the focus on research with relatively small sample sizes. Additionally, it is proposed that although children with ASD may correctly identify emotion…

Use of ancillary data to improve the analysis of forest health indicators

Treesearch

Dave Gartner

2013-01-01

In addition to its standard suite of mensuration variables, the Forest Inventory and Analysis (FIA) program of the U.S. Forest Service also collects data on forest health variables formerly measured by the Forest Health Monitoring program. FIA obtains forest health information on a subset of the base sample plots. Due to the sample size differences, the two sets of...

An Investigation of the Measurement Properties of the Spot-the-Word Test In a Community Sample

ERIC Educational Resources Information Center

Mackinnon, Andrew; Christensen, Helen

2007-01-01

Intellectual ability is assessed with the Spot-the-Word (STW) test (A. Baddeley, H. Emslie, & I. Nimmo Smith, 1993) by asking respondents to identify a word in a word-nonword item pair. Results in moderate-sized samples suggest this ability is resistant to decline due to dementia. The authors used a 3-parameter item response theory model to…

Probing defects in chemically synthesized ZnO nanostrucures by positron annihilation and photoluminescence spectroscopy

NASA Astrophysics Data System (ADS)

Chaudhuri, S. K.; Ghosh, Manoranjan; Das, D.; Raychaudhuri, A. K.

2010-09-01

The present article describes the size induced changes in the structural arrangement of intrinsic defects present in chemically synthesized ZnO nanoparticles of various sizes. Routine x-ray diffraction and transmission electron microscopy have been performed to determine the shapes and sizes of the nanocrystalline ZnO samples. Detailed studies using positron annihilation spectroscopy reveals the presence of zinc vacancy. Whereas analysis of photoluminescence results predict the signature of charged oxygen vacancies. The size induced changes in positron parameters as well as the photoluminescence properties, has shown contrasting or nonmonotonous trends as size varies from 4 to 85 nm. Small spherical particles below a critical size (˜23 nm) receive more positive surface charge due to the higher occupancy of the doubly charge oxygen vacancy as compared to the bigger nanostructures where singly charged oxygen vacancy predominates. This electronic alteration has been seen to trigger yet another interesting phenomenon, described as positron confinement inside nanoparticles. Finally, based on all the results, a model of the structural arrangement of the intrinsic defects in the present samples has been reconciled.

The Petersen-Lincoln estimator and its extension to estimate the size of a shared population.

PubMed

Chao, Anne; Pan, H-Y; Chiang, Shu-Chuan

2008-12-01

The Petersen-Lincoln estimator has been used to estimate the size of a population in a single mark release experiment. However, the estimator is not valid when the capture sample and recapture sample are not independent. We provide an intuitive interpretation for "independence" between samples based on 2 x 2 categorical data formed by capture/non-capture in each of the two samples. From the interpretation, we review a general measure of "dependence" and quantify the correlation bias of the Petersen-Lincoln estimator when two types of dependences (local list dependence and heterogeneity of capture probability) exist. An important implication in the census undercount problem is that instead of using a post enumeration sample to assess the undercount of a census, one should conduct a prior enumeration sample to avoid correlation bias. We extend the Petersen-Lincoln method to the case of two populations. This new estimator of the size of the shared population is proposed and its variance is derived. We discuss a special case where the correlation bias of the proposed estimator due to dependence between samples vanishes. The proposed method is applied to a study of the relapse rate of illicit drug use in Taiwan. ((c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim).

Statistical aspects of genetic association testing in small samples, based on selective DNA pooling data in the arctic fox.

PubMed

Szyda, Joanna; Liu, Zengting; Zatoń-Dobrowolska, Magdalena; Wierzbicki, Heliodor; Rzasa, Anna

2008-01-01

We analysed data from a selective DNA pooling experiment with 130 individuals of the arctic fox (Alopex lagopus), which originated from 2 different types regarding body size. The association between alleles of 6 selected unlinked molecular markers and body size was tested by using univariate and multinomial logistic regression models, applying odds ratio and test statistics from the power divergence family. Due to the small sample size and the resulting sparseness of the data table, in hypothesis testing we could not rely on the asymptotic distributions of the tests. Instead, we tried to account for data sparseness by (i) modifying confidence intervals of odds ratio; (ii) using a normal approximation of the asymptotic distribution of the power divergence tests with different approaches for calculating moments of the statistics; and (iii) assessing P values empirically, based on bootstrap samples. As a result, a significant association was observed for 3 markers. Furthermore, we used simulations to assess the validity of the normal approximation of the asymptotic distribution of the test statistics under the conditions of small and sparse samples.

Characterization of the particulate emissions from the BP Deepwater Horizon surface oil burns.

PubMed

Gullett, Brian K; Hays, Michael D; Tabor, Dennis; Wal, Randy Vander

2016-06-15

Sampling of the smoke plumes from the BP Deepwater Horizon surface oil burns led to the unintentional collection of soot particles on the sail of an instrument-bearing, tethered aerostat. This first-ever plume sampling from oil burned at an actual spill provided an opportunistic sample from which to characterize the particles' chemical properties for polycyclic aromatic hydrocarbons (PAHs), organic carbon, elemental carbon, metals, and polychlorinated dibenzodioxins/dibenzofurans (PCDDs/PCDFs) and physical properties for size and nanostructure. Thermal-optical analyses indicated that the particulate matter was 93% carbon with 82% being refractory elemental carbon. PAHs accounted for roughly 68μg/g of the PM filter mass and 5mg/kg oil burned, much lower than earlier laboratory based studies. Microscopy indicated that the soot is distinct from more common soot by its aggregate size, primary particle size, and nanostructure. PM-bound metals were largely unremarkable but PCDD/PCDF formation was observed, contrary to other's findings. Levels of lighter PCDD/PCDF and PAH compounds were reduced compared to historical samples, possibly due to volatilization or photo-oxidation. Published by Elsevier Ltd.

Power/Sample Size Calculations for Assessing Correlates of Risk in Clinical Efficacy Trials

PubMed Central

Gilbert, Peter B.; Janes, Holly E.; Huang, Yunda

2016-01-01

In a randomized controlled clinical trial that assesses treatment efficacy, a common objective is to assess the association of a measured biomarker response endpoint with the primary study endpoint in the active treatment group, using a case-cohort, case-control, or two-phase sampling design. Methods for power and sample size calculations for such biomarker association analyses typically do not account for the level of treatment efficacy, precluding interpretation of the biomarker association results in terms of biomarker effect modification of treatment efficacy, with detriment that the power calculations may tacitly and inadvertently assume that the treatment harms some study participants. We develop power and sample size methods accounting for this issue, and the methods also account for inter-individual variability of the biomarker that is not biologically relevant (e.g., due to technical measurement error). We focus on a binary study endpoint and on a biomarker subject to measurement error that is normally distributed or categorical with two or three levels. We illustrate the methods with preventive HIV vaccine efficacy trials, and include an R package implementing the methods. PMID:27037797

Nano-Pore Size Analysis by SAXS Method of Cementitious Mortars Undergoing Delayed Ettringite Formation

NASA Astrophysics Data System (ADS)

Shekar, Yamini

This research investigates the nano-scale pore structure of cementitious mortars undergoing delayed ettringite formation (DEF) using small angle x-ray scattering (SAXS). DEF has been known to cause expansion and cracking during later ages (around 4000 days) in concrete that has been heat cured at temperatures of 70°C or above. Though DEF normally occurs in heat cured concrete, mass cured concrete can also experience DEF. Large crystalline pressures result in smaller pore sizes. The objectives of this research are: (1) to investigate why some samples expand early than later expansion, (2) to evaluate the effects of curing conditions and pore size distributions at high temperatures, and (3) to assess the evolution of the pore size distributions over time. The most important outcome of the research is the pore sizes obtained from SAXS were used in the development of a 3-stage model. From the data obtained, the pore sizes increase in stage 1 due to initial ettringite formation and in turn filling up the smallest pores. Once the critical pore size threshold is reached (around 20nm) stage 2 is formed due to cracking which tends to decrease in the pore sizes. Finally, in stage 3, the cracking continues, therefore increasing in the pore size.

Size exclusion chromatography-gradients, an alternative approach to polymer gradient chromatography: 2. Separation of poly(meth)acrylates using a size exclusion chromatography-solvent/non-solvent gradient.

PubMed

Schollenberger, Martin; Radke, Wolfgang

2011-10-28

A gradient ranging from methanol to tetrahydrofuran (THF) was applied to a series of poly(methyl methacrylate) (PMMA) standards, using the recently developed concept of SEC-gradients. Contrasting to conventional gradients the samples eluted before the solvent, i.e. within the elution range typical for separations by SEC, however, the high molar mass PMMAs were retarded as compared to experiments on the same column using pure THF as the eluent. The molar mass dependence on retention volume showed a complex behaviour with a nearly molar mass independent elution for high molar masses. This molar mass dependence was explained in terms of solubility and size exclusion effects. The solubility based SEC-gradient was proven to be useful to separate PMMA and poly(n-butyl crylate) (PnBuA) from a poly(t-butyl crylate) (PtBuA) sample. These samples could be separated neither by SEC in THF, due to their very similar hydrodynamic volumes, nor by an SEC-gradient at adsorbing conditions, due to a too low selectivity. The example shows that SEC-gradients can be applied not only in adsorption/desorption mode, but also in precipitation/dissolution mode without risking blocking capillaries or breakthrough peaks. Thus, the new approach is a valuable alternative to conventional gradient chromatography. Copyright © 2011 Elsevier B.V. All rights reserved.

Effect of Synthesis Parameter on Crystal Structures and Magnetic Properties of Magnesium Nickel Ferrite (Mg0.5Ni0.5Fe2O4) Nanoparticles

NASA Astrophysics Data System (ADS)

Maulia, R.; Putra, R. A.; Suharyadi, E.

2017-05-01

Mg0.5Ni0.5Fe2O4 nanoparticles have been successfully synthesized by using co-precipitation method and varying the synthesis parameter, i.e. synthesis temperature and NaOH concentration. X-ray Diffraction (XRD) pattern showed that nanoparticles have cubic spinel structures with an additional phase of γ-Fe2O3 and particle size varies within the range of 4.3 - 6.7 nm. This variation is due to the effect of various synthesis parameters. Transmission Electron Microscopy (TEM) image showed that the nanoparticles exhibited agglomeration. The observed diffraction ring from selected area electron diffraction showed that the sample was polycrystalline and confirmed the peak appearing in XRD. The coercivities showed an increasing trend with an increase in particle size from 44.7 Oe to 49.6 Oe for variation of NaOH concentration, and a decreasing trend with an increase in particle size from 46.8 to 45.1 Oe for variation of synthesis temperature. The maximum magnetization showed an increasing trend with an increase in the ferrite phase from 3.7 emu/g to 5.4 emu/g possessed in the sample with variations on NaOH concentration. The maximum magnetization for the sample with variations on synthesis temperature varied from 4.4 emu/g to 5.7 emu/g due to its crystal structures.

Cracks and nanodroplets produced on tungsten surface samples by dense plasma jets

NASA Astrophysics Data System (ADS)

Ticoş, C. M.; Galaţanu, M.; Galaţanu, A.; Luculescu, C.; Scurtu, A.; Udrea, N.; Ticoş, D.; Dumitru, M.

2018-03-01

Small samples of 12.5 mm in diameter made from pure tungsten were exposed to a dense plasma jet produced by a coaxial plasma gun operated at 2 kJ. The surface of the samples was analyzed using a scanning electron microscope (SEM) before and after applying consecutive plasma shots. Cracks and craters were produced in the surface due to surface tensions during plasma heating. Nanodroplets and micron size droplets could be observed on the samples surface. An energy-dispersive spectroscopy (EDS) analysis revealed that the composition of these droplets coincided with that of the gun electrode material. Four types of samples were prepared by spark plasma sintering from powders with the average particle size ranging from 70 nanometers up to 80 μm. The plasma power load to the sample surface was estimated to be ≈4.7 MJ m-2 s-1/2 per shot. The electron temperature and density in the plasma jet had peak values 17 eV and 1.6 × 1022 m-3, respectively.

At convenience and systematic random sampling: effects on the prognostic value of nuclear area assessments in breast cancer patients.

PubMed

Jannink, I; Bennen, J N; Blaauw, J; van Diest, P J; Baak, J P

1995-01-01

This study compares the influence of two different nuclear sampling methods on the prognostic value of assessments of mean and standard deviation of nuclear area (MNA, SDNA) in 191 consecutive invasive breast cancer patients with long term follow up. The first sampling method used was 'at convenience' sampling (ACS); the second, systematic random sampling (SRS). Both sampling methods were tested with a sample size of 50 nuclei (ACS-50 and SRS-50). To determine whether, besides the sampling methods, sample size had impact on prognostic value as well, the SRS method was also tested using a sample size of 100 nuclei (SRS-100). SDNA values were systematically lower for ACS, obviously due to (unconsciously) not including small and large nuclei. Testing prognostic value of a series of cut off points, MNA and SDNA values assessed by the SRS method were prognostically significantly stronger than the values obtained by the ACS method. This was confirmed in Cox regression analysis. For the MNA, the Mantel-Cox p-values from SRS-50 and SRS-100 measurements were not significantly different. However, for the SDNA, SRS-100 yielded significantly lower p-values than SRS-50. In conclusion, compared with the 'at convenience' nuclear sampling method, systematic random sampling of nuclei is not only superior with respect to reproducibility of results, but also provides a better prognostic value in patients with invasive breast cancer.

Impact of particle size on distribution and human exposure of flame retardants in indoor dust.

PubMed

He, Rui-Wen; Li, Yun-Zi; Xiang, Ping; Li, Chao; Cui, Xin-Yi; Ma, Lena Q

2018-04-01

The effect of dust particle size on the distribution and bioaccessibility of flame retardants (FRs) in indoor dust remains unclear. In this study, we analyzed 20 FRs (including 6 organophosphate flame retardants (OPFRs), 8 polybrominated diphenyl ethers (PBDEs), 4 novel brominated flame retardants (NBFRs), and 2 dechlorane plus (DPs)) in composite dust samples from offices, public microenvironments (PME), and cars in Nanjing, China. Each composite sample (one per microenvironment) was separated into 6 size fractions (F1-F6: 200-2000µm, 150-200µm, 100-150µm, 63-100µm, 43-63µm, and <43µm). FRs concentrations were the highest in car dust, being 16 and 6 times higher than those in offices and PME. The distribution of FRs in different size fractions was Kow-dependent and affected by surface area (Log Kow=1-4), total organic carbon (Log Kow=4-9), and FR migration pathways into dust (Log Kow>9). Bioaccessibility of FRs was measured by the physiologically-based extraction test, with OPFR bioaccessibility being 1.8-82% while bioaccessible PBDEs, NBFRs, and DPs were under detection limits due to their high hydrophobicity. The OPFR bioaccessibility in 200-2000µm fraction was significantly higher than that of <43µm fraction, but with no difference among the other four fractions. Risk assessment was performed for the most abundant OPFR-tris(2-chloroethyl) phosphate. The average daily dose (ADD) values were the highest for the <43µm fraction for all three types of dust using total concentrations, but no consistent trend was found among the three types of dust if based on bioaccessible concentrations. Our results indicated that dust size impacted human exposure estimation of FRs due to their variability in distribution and bioaccessibility among different fractions. For future risk assessment, size selection for dust sampling should be standardized and bioaccessibility of FRs should not be overlooked. Copyright © 2018 Elsevier Inc. All rights reserved.

Grindability and combustion behavior of coal and torrefied biomass blends.

PubMed

Gil, M V; García, R; Pevida, C; Rubiera, F

2015-09-01

Biomass samples (pine, black poplar and chestnut woodchips) were torrefied to improve their grindability before being combusted in blends with coal. Torrefaction temperatures between 240 and 300 °C and residence times between 11 and 43 min were studied. The grindability of the torrefied biomass, evaluated from the particle size distribution of the ground sample, significantly improved compared to raw biomass. Higher temperatures increased the proportion of smaller-sized particles after grinding. Torrefied chestnut woodchips (280 °C, 22 min) showed the best grinding properties. This sample was blended with coal (5-55 wt.% biomass). The addition of torrefied biomass to coal up to 15 wt.% did not significantly increase the proportion of large-sized particles after grinding. No relevant differences in the burnout value were detected between the coal and coal/torrefied biomass blends due to the high reactivity of the coal. NO and SO2 emissions decreased as the percentage of torrefied biomass in the blend with coal increased. Copyright © 2015 Elsevier Ltd. All rights reserved.

Measuring larval nematode contamination on cattle pastures: Comparing two herbage sampling methods.

PubMed

Verschave, S H; Levecke, B; Duchateau, L; Vercruysse, J; Charlier, J

2015-06-15

Assessing levels of pasture larval contamination is frequently used to study the population dynamics of the free-living stages of parasitic nematodes of livestock. Direct quantification of infective larvae (L3) on herbage is the most applied method to measure pasture larval contamination. However, herbage collection remains labour intensive and there is a lack of studies addressing the variation induced by the sampling method and the required sample size. The aim of this study was (1) to compare two different sampling methods in terms of pasture larval count results and time required to sample, (2) to assess the amount of variation in larval counts at the level of sample plot, pasture and season, respectively and (3) to calculate the required sample size to assess pasture larval contamination with a predefined precision using random plots across pasture. Eight young stock pastures of different commercial dairy herds were sampled in three consecutive seasons during the grazing season (spring, summer and autumn). On each pasture, herbage samples were collected through both a double-crossed W-transect with samples taken every 10 steps (method 1) and four random located plots of 0.16 m(2) with collection of all herbage within the plot (method 2). The average (± standard deviation (SD)) pasture larval contamination using sampling methods 1 and 2 was 325 (± 479) and 305 (± 444)L3/kg dry herbage (DH), respectively. Large discrepancies in pasture larval counts of the same pasture and season were often seen between methods, but no significant difference (P = 0.38) in larval counts between methods was found. Less time was required to collect samples with method 2. This difference in collection time between methods was most pronounced for pastures with a surface area larger than 1 ha. The variation in pasture larval counts from samples generated by random plot sampling was mainly due to the repeated measurements on the same pasture in the same season (residual variance component = 6.2), rather than due to pasture (variance component = 0.55) or season (variance component = 0.15). Using the observed distribution of L3, the required sample size (i.e. number of plots per pasture) for sampling a pasture through random plots with a particular precision was simulated. A higher relative precision was acquired when estimating PLC on pastures with a high larval contamination and a low level of aggregation compared to pastures with a low larval contamination when the same sample size was applied. In the future, herbage sampling through random plots across pasture (method 2) seems a promising method to develop further as no significant difference in counts between the methods was found and this method was less time consuming. Copyright © 2015 Elsevier B.V. All rights reserved.

Synthesis, structure and magnetic properties of nanostructured La1-xAxFe0.5Mn0.5O3 (A = Ca, Sr and Pb; x = 0 & 0.25) perovskites

NASA Astrophysics Data System (ADS)

Hossain, Aslam; Ghosh, Debamalya; Dutta, Uma; Walke, Pravin S.; Mordvinova, Natalia E.; Lebedev, Oleg I.; Sinha, Bhavesh; Pal, Kamalesh; Gayen, Arup; Kundu, Asish K.; Seikh, Md. Motin

2017-12-01

The effect of hole doping on magnetic properties of LaFe0.5Mn0.5O3 have been investigated. All the ceramics samples La1-xAxFe0.5Mn0.5O3 (A = Ca, Sr and Pb; x = 0 & 0.25) were synthesized at 500 °C by sol-gel method and the particles size were found to be in nanodimension. The samples were characterized by X-ray and electron diffraction, HRTEM and both dc and ac-magnetization measurements. The X-ray and electron diffraction patterns were indexed by cubic Pm-3m space group. The particle size of the LaFe0.5Mn0.5O3 is ∼100 nm, whereas the Pb-doped sample is ∼50 nm and for Ca or Sr doped samples the size is ∼10-30 nm. Both dc and ac-susceptibility measurements suggest that the effect of hole doping and A-site cationic radius in LaFe0.5Mn0.5O3 have no significant role on magnetic properties. However, the particle size plays an important role on magnetic property due to the development of surface ferromagnetic cluster at nanoscale. The competing interactions lead to magnetic phase separation where local ferromagnetic clusters coexist within the antiferromagentic matrix in all the samples.

Estimating the breeding population of long-billed curlew in the United States

USGS Publications Warehouse

Stanley, T.R.; Skagen, S.K.

2007-01-01

Determining population size and long-term trends in population size for species of high concern is a priority of international, national, and regional conservation plans. Long-billed curlews (Numenius americanus) are a species of special concern in North America due to apparent declines in their population. Because long-billed curlews are not adequately monitored by existing programs, we undertook a 2-year study with the goals of 1) determining present long-billed curlew distribution and breeding population size in the United States and 2) providing recommendations for a long-term long-billed curlew monitoring protocol. We selected a stratified random sample of survey routes in 16 western states for sampling in 2004 and 2005, and we analyzed count data from these routes to estimate detection probabilities and abundance. In addition, we evaluated habitat along roadsides to determine how well roadsides represented habitat throughout the sampling units. We estimated there were 164,515 (SE = 42,047) breeding long-billed curlews in 2004, and 109,533 (SE = 31,060) breeding individuals in 2005. These estimates far exceed currently accepted estimates based on expert opinion. We found that habitat along roadsides was representative of long-billed curlew habitat in general. We make recommendations for improving sampling methodology, and we present power curves to provide guidance on minimum sample sizes required to detect trends in abundance.

Dust generation in powders: Effect of particle size distribution

NASA Astrophysics Data System (ADS)

Chakravarty, Somik; Le Bihan, Olivier; Fischer, Marc; Morgeneyer, Martin

2017-06-01

This study explores the relationship between the bulk and grain-scale properties of powders and dust generation. A vortex shaker dustiness tester was used to evaluate 8 calcium carbonate test powders with median particle sizes ranging from 2μm to 136μm. Respirable aerosols released from the powder samples were characterised by their particle number and mass concentrations. All the powder samples were found to release respirable fractions of dust particles which end up decreasing with time. The variation of powder dustiness as a function of the particle size distribution was analysed for the powders, which were classified into three groups based on the fraction of particles within the respirable range. The trends we observe might be due to the interplay of several mechanisms like de-agglomeration and attrition and their relative importance.

A multi-particle crushing apparatus for studying rock fragmentation due to repeated impacts

NASA Astrophysics Data System (ADS)

Huang, S.; Mohanty, B.; Xia, K.

2017-12-01

Rock crushing is a common process in mining and related operations. Although a number of particle crushing tests have been proposed in the literature, most of them are concerned with single-particle crushing, i.e., a single rock sample is crushed in each test. Considering the realistic scenario in crushers where many fragments are involved, a laboratory crushing apparatus is developed in this study. This device consists of a Hopkinson pressure bar system and a piston-holder system. The Hopkinson pressure bar system is used to apply calibrated dynamic loads to the piston-holder system, and the piston-holder system is used to hold rock samples and to recover fragments for subsequent particle size analysis. The rock samples are subjected to three to seven impacts under three impact velocities (2.2, 3.8, and 5.0 m/s), with the feed size of the rock particle samples limited between 9.5 and 12.7 mm. Several key parameters are determined from this test, including particle size distribution parameters, impact velocity, loading pressure, and total work. The results show that the total work correlates well with resulting fragmentation size distribution, and the apparatus provides a useful tool for studying the mechanism of crushing, which further provides guidelines for the design of commercial crushers.

Formation of metallic clusters in oxide insulators by means of ion beam mixing

NASA Astrophysics Data System (ADS)

Talut, G.; Potzger, K.; Mücklich, A.; Zhou, Shengqiang

2008-04-01

The intermixing and near-interface cluster formation of Pt and FePt thin films deposited on different oxide surfaces by means of Pt+ ion irradiation and subsequent annealing was investigated. Irradiated as well as postannealed samples were investigated using high resolution transmission electron microscopy. In MgO and Y :ZrO2 covered with Pt, crystalline clusters with mean sizes of 2 and 3.5nm were found after the Pt+ irradiations with 8×1015 and 2×1016cm-2 and subsequent annealing, respectively. In MgO samples covered with FePt, clusters with mean sizes of 1 and 2nm were found after the Pt+ irradiations with 8×1015 and 2×1016cm-2 and subsequent annealing, respectively. In Y :ZrO2 samples covered with FePt, clusters up to 5nm in size were found after the Pt+ irradiation with 2×1016cm-2 and subsequent annealing. In LaAlO3 the irradiation was accompanied by a full amorphization of the host matrix and appearance of embedded clusters of different sizes. The determination of the lattice constant and thus the kind of the clusters in samples covered by FePt was hindered due to strong deviation of the electron beam by the ferromagnetic FePt.

Intra-class correlation estimates for assessment of vitamin A intake in children.

PubMed

Agarwal, Girdhar G; Awasthi, Shally; Walter, Stephen D

2005-03-01

In many community-based surveys, multi-level sampling is inherent in the design. In the design of these studies, especially to calculate the appropriate sample size, investigators need good estimates of intra-class correlation coefficient (ICC), along with the cluster size, to adjust for variation inflation due to clustering at each level. The present study used data on the assessment of clinical vitamin A deficiency and intake of vitamin A-rich food in children in a district in India. For the survey, 16 households were sampled from 200 villages nested within eight randomly-selected blocks of the district. ICCs and components of variances were estimated from a three-level hierarchical random effects analysis of variance model. Estimates of ICCs and variance components were obtained at village and block levels. Between-cluster variation was evident at each level of clustering. In these estimates, ICCs were inversely related to cluster size, but the design effect could be substantial for large clusters. At the block level, most ICC estimates were below 0.07. At the village level, many ICC estimates ranged from 0.014 to 0.45. These estimates may provide useful information for the design of epidemiological studies in which the sampled (or allocated) units range in size from households to large administrative zones.

EXAFS analysis of cations distribution in structure of Co1-xNixFe2O4 nanoparticles obtained by hydrothermal method in aloe vera extract solution

NASA Astrophysics Data System (ADS)

Wongpratat, Unchista; Maensiri, Santi; Swatsitang, Ekaphan

2016-09-01

Effect of cations distribution upon EXAFS analysis on magnetic properties of Co1-xNixFe2O4 (x = 0, 0.25, 0.50, 0.75 and 1.0) nanoparticles prepared by the hydrothermal method in aloe vera extract solution were studied. XRD analysis confirmed a pure phase of cubic spinel ferrite of all samples. Changes in lattice parameter and particle size depended on the Ni content with partial substitution and site distributions of Co2+, Ni2+ ions of different ionic radii at both tetrahedral and octahedral sites in the crystal structure. Particle sizes of samples estimated by TEM images were found to be in the range of 10.87-62.50 nm. The VSM results at room temperature indicated the ferrimagnetic behavior of all samples. Superparamagnetic behavior was observed in NiFe2O4 sample. The coercivity (Hc) and remanance (Mr) values were related to the particle sizes of samples. The saturation magnetization (Ms) was increased by a factor of 1.4 to a value of 57.57 emu/g, whereas the coercivity (Hc) was decreased by a factor of 20 to a value of 63.15 Oe for a sample with x = 0.75. In addition to the cations distribution, the increase of aspect ratio (surface to volume ratio) due to the decrease of particle size could significantly affect the magnetic properties of the materials.

Buoyancy-corrected gravimetric analysis of lightly loaded filters.

PubMed

Rasmussen, Pat E; Gardner, H David; Niu, Jianjun

2010-09-01

Numerous sources of uncertainty are associated with the gravimetric analysis of lightly loaded air filter samples (< 100 microg). The purpose of the study presented here is to investigate the effectiveness and limitations of air buoyancy corrections over experimentally adjusted conditions of temperature (21-25 degrees C) and relative humidity (RH) (16-60% RH). Conditioning (24 hr) and weighing were performed inside the Archimedes M3 environmentally controlled chamber. The measurements were performed using 20 size-fractionated samples of resuspended house dust loaded onto Teflo (PTFE) filters using a Micro-Orifice Uniform Deposit Impactor representing a wide range of mass loading (7.2-3130 microg) and cut sizes (0.056-9.9 microm). By maintaining tight controls on humidity (within 0.5% RH of control setting) throughout pre- and postweighing at each stepwise increase in RH, it was possible to quantify error due to water absorption: 45% of the total mass change due to water absorption occurred between 16 and 50% RH, and 55% occurred between 50 and 60% RH. The buoyancy corrections ranged from -3.5 to +5.8 microg in magnitude and improved relative standard deviation (RSD) from 21.3% (uncorrected) to 5.6% (corrected) for a 7.2 microg sample. It is recommended that protocols for weighing low-mass particle samples (e.g., nanoparticle samples) should include buoyancy corrections and tight temperature/humidity controls. In some cases, conditioning times longer than 24 hr may be warranted.

Infrared reflectance spectra: Effects of particle size, provenance and preparation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Su, Yin-Fong; Myers, Tanya L.; Brauer, Carolyn S.

2014-09-22

We have recently developed methods for making more accurate infrared total and diffuse directional - hemispherical reflectance measurements using an integrating sphere. We have found that reflectance spectra of solids, especially powders, are influenced by a number of factors including the sample preparation method, the particle size and morphology, as well as the sample origin. On a quantitative basis we have investigated some of these parameters and the effects they have on reflectance spectra, particularly in the longwave infrared. In the IR the spectral features may be observed as either maxima or minima: In general, upward-going peaks in the reflectancemore » spectrum result from strong surface scattering, i.e. rays that are reflected from the surface without bulk penetration, whereas downward-going peaks are due to either absorption or volume scattering, i.e. rays that have penetrated or refracted into the sample interior and are not reflected. The light signals reflected from solids usually encompass all such effects, but with strong dependencies on particle size and preparation. This paper measures the reflectance spectra in the 1.3 – 16 micron range for various bulk materials that have a combination of strong and weak absorption bands in order to observe the effects on the spectral features: Bulk materials were ground with a mortar and pestle and sieved to separate the samples into various size fractions between 5 and 500 microns. The median particle size is demonstrated to have large effects on the reflectance spectra. For certain minerals we also observe significant spectral change depending on the geologic origin of the sample. All three such effects (particle size, preparation and provenance) result in substantial change in the reflectance spectra for solid materials; successful identification algorithms will require sufficient flexibility to account for these parameters.« less

Characterization of the enhancement effect of Na2CO3 on the sulfur capture capacity of limestones.

PubMed

Laursen, Karin; Kern, Arnt A; Grace, John R; Lim, C Jim

2003-08-15

It has been known for a long time that certain additives (e.g., NaCl, CaCl2, Na2CO3, Fe2O3) can increase the sulfur dioxide capture-capacity of limestones. In a recent study we demonstrated that very small amounts of Na2CO3 can be very beneficial for producing sorbents of very high sorption capacities. This paper explores what contributes to these significant increases. Mercury porosimetry measurements of calcined limestone samples reveal a change in the pore-size from 0.04-0.2 microm in untreated samples to 2-10 microm in samples treated with Na2CO3--a pore-size more favorable for penetration of sulfur into the particles. The change in pore-size facilitates reaction with lime grains throughout the whole particle without rapid plugging of pores, avoiding premature change from a fast chemical reaction to a slow solid-state diffusion controlled process, as seen for untreated samples. Calcination in a thermogravimetric reactor showed that Na2CO3 increased the rate of calcination of CaCO3 to CaO, an effect which was slightly larger at 825 degrees C than at 900 degrees C. Peak broadening analysis of powder X-ray diffraction data of the raw, calcined, and sulfated samples revealed an unaffected calcite size (approximately 125-170 nm) but a significant increase in the crystallite size for lime (approximately 60-90 nm to approximately 250-300 nm) and less for anhydrite (approximately 125-150 nm to approximately 225-250 nm). The increase in the crystallite and pore-size of the treated limestones is attributed to an increase in ionic mobility in the crystal lattice due to formation of vacancies in the crystals when Ca is partly replaced by Na.

Infrared reflectance spectra: effects of particle size, provenance and preparation

NASA Astrophysics Data System (ADS)

Su, Yin-Fong; Myers, Tanya L.; Brauer, Carolyn S.; Blake, Thomas A.; Forland, Brenda M.; Szecsody, J. E.; Johnson, Timothy J.

2014-10-01

We have recently developed methods for making more accurate infrared total and diffuse directional - hemispherical reflectance measurements using an integrating sphere. We have found that reflectance spectra of solids, especially powders, are influenced by a number of factors including the sample preparation method, the particle size and morphology, as well as the sample origin. On a quantitative basis we have investigated some of these parameters and the effects they have on reflectance spectra, particularly in the longwave infrared. In the IR the spectral features may be observed as either maxima or minima: In general, upward-going peaks in the reflectance spectrum result from strong surface scattering, i.e. rays that are reflected from the surface without bulk penetration, whereas downward-going peaks are due to either absorption or volume scattering, i.e. rays that have penetrated or refracted into the sample interior and are not reflected. The light signals reflected from solids usually encompass all such effects, but with strong dependencies on particle size and preparation. This paper measures the reflectance spectra in the 1.3 - 16 micron range for various bulk materials that have a combination of strong and weak absorption bands in order to observe the effects on the spectral features: Bulk materials were ground with a mortar and pestle and sieved to separate the samples into various size fractions between 5 and 500 microns. The median particle size is demonstrated to have large effects on the reflectance spectra. For certain minerals we also observe significant spectral change depending on the geologic origin of the sample. All three such effects (particle size, preparation and provenance) result in substantial change in the reflectance spectra for solid materials; successful identification algorithms will require sufficient flexibility to account for these parameters.

Estimating Mutual Information for High-to-Low Calibration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michaud, Isaac James; Williams, Brian J.; Weaver, Brian Phillip

Presentation shows that KSG 2 is superior to KSG 1 because it scales locally automatically; KSG estimators are limited to a maximum MI due to sample size; LNC extends the capability of KSG without onerous assumptions; iLNC allows LNC to estimate information gain.

Relative efficiency of unequal versus equal cluster sizes in cluster randomized trials using generalized estimating equation models.

PubMed

Liu, Jingxia; Colditz, Graham A

2018-05-01

There is growing interest in conducting cluster randomized trials (CRTs). For simplicity in sample size calculation, the cluster sizes are assumed to be identical across all clusters. However, equal cluster sizes are not guaranteed in practice. Therefore, the relative efficiency (RE) of unequal versus equal cluster sizes has been investigated when testing the treatment effect. One of the most important approaches to analyze a set of correlated data is the generalized estimating equation (GEE) proposed by Liang and Zeger, in which the "working correlation structure" is introduced and the association pattern depends on a vector of association parameters denoted by ρ. In this paper, we utilize GEE models to test the treatment effect in a two-group comparison for continuous, binary, or count data in CRTs. The variances of the estimator of the treatment effect are derived for the different types of outcome. RE is defined as the ratio of variance of the estimator of the treatment effect for equal to unequal cluster sizes. We discuss a commonly used structure in CRTs-exchangeable, and derive the simpler formula of RE with continuous, binary, and count outcomes. Finally, REs are investigated for several scenarios of cluster size distributions through simulation studies. We propose an adjusted sample size due to efficiency loss. Additionally, we also propose an optimal sample size estimation based on the GEE models under a fixed budget for known and unknown association parameter (ρ) in the working correlation structure within the cluster. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Effect of Pixel Size on the Accuracy of Orthophoto Production

NASA Astrophysics Data System (ADS)

Kulur, S.; Yildiz, F.; Selcuk, O.; Yildiz, M. A.

2016-06-01

In our country, orthophoto products are used by the public and private sectors for engineering services and infrastructure projects, Orthophotos are particularly preferred due to faster and are more economical production according to vector digital photogrammetric production. Today, digital orthophotos provide an expected accuracy for engineering and infrastructure projects. In this study, the accuracy of orthophotos using pixel sizes with different sampling intervals are tested for the expectations of engineering and infrastructure projects.

Surface integrity and fatigue behaviour of electric discharged machined and milled austenitic stainless steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lundberg, Mattias, E-mail: mattias.lundberg@liu.se

Machining of austenitic stainless steels can result in different surface integrities and different machining process parameters will have a great impact on the component fatigue life. Understanding how machining processes affect the cyclic behaviour and microstructure are of outmost importance in order to improve existing and new life estimation models. Milling and electrical discharge machining (EDM) have been used to manufacture rectangular four-point bend fatigue test samples; subjected to high cycle fatigue. Before fatigue testing, surface integrity characterisation of the two surface conditions was conducted using scanning electron microscopy, surface roughness, residual stress profiles, and hardness profiles. Differences in cyclicmore » behaviour were observed between the two surface conditions by the fatigue testing. The milled samples exhibited a fatigue limit. EDM samples did not show the same behaviour due to ratcheting. Recrystallized nano sized grains were identified at the severely plastically deformed surface of the milled samples. Large amounts of bent mechanical twins were observed ~ 5 μm below the surface. Grain shearing and subsequent grain rotation from milling bent the mechanical twins. EDM samples showed much less plastic deformation at the surface. Surface tensile residual stresses of ~ 500 MPa and ~ 200 MPa for the milled and EDM samples respectively were measured. - Highlights: •Milled samples exhibit fatigue behaviour, but not EDM samples. •Four-point bending is not suitable for materials exhibiting pronounced ratcheting. •LAGB density can be used to quantitatively measure plastic deformation. •Grain shearing and rotation result in bent mechanical twins. •Nano sized grains evolve due to the heat of the operation.« less

Bright and multicolor luminescent colloidal Si nanocrystals prepared by pulsed laser irradiation in liquid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakamura, Toshihiro, E-mail: nakamura@el.gunma-u.ac.jp; Watanabe, Kanta; Adachi, Sadao

2016-01-11

We reported the preparation of bright and multicolor luminescent colloidal Si nanocrystal (Si-nc) by pulsed UV laser irradiation to porous Si (PSi) in an organic solvent. The different-luminescence-color (different-sized) colloidal Si-nc was produced by the pulsed laser-induced fragmentation of different-sized porous nanostructures. The colloidal Si-nc samples were found to have higher photoluminescence quantum efficiencies (20%–23%) than the PSi samples (1%–3%). The brighter emission of the colloidal Si-nc was attributed to an enhanced radiative band-to-band transition rate due to the presence of a surface organic layer formed by UV laser-induced hydrosilylation.

Lowering sample size in comparative analyses can indicate a correlation where there is none: example from Rensch's rule in primates.

PubMed

Lindenfors, P; Tullberg, B S

2006-07-01

The fact that characters may co-vary in organism groups because of shared ancestry and not always because of functional correlations was the initial rationale for developing phylogenetic comparative methods. Here we point out a case where similarity due to shared ancestry can produce an undesired effect when conducting an independent contrasts analysis. Under special circumstances, using a low sample size will produce results indicating an evolutionary correlation between characters where an analysis of the same pattern utilizing a larger sample size will show that this correlation does not exist. This is the opposite effect of increased sample size to that expected; normally an increased sample size increases the chance of finding a correlation. The situation where the problem occurs is when co-variation between the two continuous characters analysed is clumped in clades; e.g. when some phylogenetically conservative factors affect both characters simultaneously. In such a case, the correlation between the two characters becomes contingent on the number of clades sharing this conservative factor that are included in the analysis, in relation to the number of species contained within these clades. Removing species scattered evenly over the phylogeny will in this case remove the exact variation that diffuses the evolutionary correlation between the two characters - the variation contained within the clades sharing the conservative factor. We exemplify this problem by discussing a parallel in nature where the described problem may be of importance. This concerns the question of the presence or absence of Rensch's rule in primates.

Microstructural Characterization and Modeling of SLM Superalloy 718

NASA Technical Reports Server (NTRS)

Smith, Tim M.; Sudbrack, Chantal K.; Bonacuse, Pete; Rogers, Richard

2017-01-01

Superalloy 718 is an excellent candidate for selective laser melting (SLM) fabrication due to a combination of excellent mechanical properties and workability. Predicting and validating the microstructure of SLM-fabricated Superalloy 718 after potential post heat-treatment paths is an important step towards producing components comparable to those made using conventional methods. At present, obtaining accurate volume fraction and size measurements of gamma-double-prime, gamma-prime and delta precipitates has been challenging due to their size, low volume fractions, and similar chemistries. A technique combining high resolution distortion corrected SEM imaging and with x-ray energy dispersive spectroscopy has been developed to accurately and independently measure the size and volume fractions of the three precipitates. These results were further validated using x-ray diffraction and phase extraction methods and compared to the precipitation kinetics predicted by PANDAT and JMatPro. Discrepancies are discussed in context of materials properties, model assumptions, sampling, and experimental errors.

A closer look at the size of the gaze-liking effect: a preregistered replication.

PubMed

Tipples, Jason; Pecchinenda, Anna

2018-04-30

This study is a direct replication of gaze-liking effect using the same design, stimuli and procedure. The gaze-liking effect describes the tendency for people to rate objects as more likeable when they have recently seen a person repeatedly gaze toward rather than away from the object. However, as subsequent studies show considerable variability in the size of this effect, we sampled a larger number of participants (N = 98) than the original study (N = 24) to gain a more precise estimate of the gaze-liking effect size. Our results indicate a much smaller standardised effect size (d z  = 0.02) than that of the original study (d z  = 0.94). Our smaller effect size was not due to general insensitivity to eye-gaze effects because the same sample showed a clear (d z  = 1.09) gaze-cuing effect - faster reaction times when eyes looked toward vs away from target objects. We discuss the implications of our findings for future studies wishing to study the gaze-liking effect.

The albatross plot: A novel graphical tool for presenting results of diversely reported studies in a systematic review.

PubMed

Harrison, Sean; Jones, Hayley E; Martin, Richard M; Lewis, Sarah J; Higgins, Julian P T

2017-09-01

Meta-analyses combine the results of multiple studies of a common question. Approaches based on effect size estimates from each study are generally regarded as the most informative. However, these methods can only be used if comparable effect sizes can be computed from each study, and this may not be the case due to variation in how the studies were done or limitations in how their results were reported. Other methods, such as vote counting, are then used to summarize the results of these studies, but most of these methods are limited in that they do not provide any indication of the magnitude of effect. We propose a novel plot, the albatross plot, which requires only a 1-sided P value and a total sample size from each study (or equivalently a 2-sided P value, direction of effect and total sample size). The plot allows an approximate examination of underlying effect sizes and the potential to identify sources of heterogeneity across studies. This is achieved by drawing contours showing the range of effect sizes that might lead to each P value for given sample sizes, under simple study designs. We provide examples of albatross plots using data from previous meta-analyses, allowing for comparison of results, and an example from when a meta-analysis was not possible. Copyright © 2017 The Authors. Research Synthesis Methods Published by John Wiley & Sons Ltd.

Alteration of histological gastritis after cure of Helicobacter pylori infection.

PubMed

Hojo, M; Miwa, H; Ohkusa, T; Ohkura, R; Kurosawa, A; Sato, N

2002-11-01

It is still disputed whether gastric atrophy or intestinal metaplasia improves after the cure of Helicobacter pylori infection. To clarify the histological changes after the cure of H. pylori infection through a literature survey. Fifty-one selected reports from 1066 relevant articles were reviewed. The extracted data were pooled according to histological parameters of gastritis based on the (updated) Sydney system. Activity improved more rapidly than inflammation. Eleven of 25 reports described significant improvement of atrophy. Atrophy was not improved in one of four studies with a large sample size (> 100 samples) and in two of five studies with a long follow-up period (> 12 months), suggesting that disagreement between the studies was not totally due to sample size or follow-up period. Methodological flaws, such as patient selection, and statistical analysis based on the assumption that atrophy improves continuously and generally in all patients might be responsible for the inconsistent results. Four of 28 studies described significant improvement of intestinal metaplasia [corrected]. Activity and inflammation were improved after the cure of H. pylori infection. Atrophy did not improve generally among all patients, but improved in certain patients. Improvement of intestinal metaplasia was difficult to analyse due to methodological problems including statistical power.

Improving the accuracy of hyaluronic acid molecular weight estimation by conventional size exclusion chromatography.

PubMed

Shanmuga Doss, Sreeja; Bhatt, Nirav Pravinbhai; Jayaraman, Guhan

2017-08-15

There is an unreasonably high variation in the literature reports on molecular weight of hyaluronic acid (HA) estimated using conventional size exclusion chromatography (SEC). This variation is most likely due to errors in estimation. Working with commercially available HA molecular weight standards, this work examines the extent of error in molecular weight estimation due to two factors: use of non-HA based calibration and concentration of sample injected into the SEC column. We develop a multivariate regression correlation to correct for concentration effect. Our analysis showed that, SEC calibration based on non-HA standards like polyethylene oxide and pullulan led to approximately 2 and 10 times overestimation, respectively, when compared to HA-based calibration. Further, we found that injected sample concentration has an effect on molecular weight estimation. Even at 1g/l injected sample concentration, HA molecular weight standards of 0.7 and 1.64MDa showed appreciable underestimation of 11-24%. The multivariate correlation developed was found to reduce error in estimations at 1g/l to <4%. The correlation was also successfully applied to accurately estimate the molecular weight of HA produced by a recombinant Lactococcus lactis fermentation. Copyright © 2017 Elsevier B.V. All rights reserved.

Size effect on the structural, magnetic, and magnetotransport properties of electron doped manganite La0.15Ca0.85MnO3

NASA Astrophysics Data System (ADS)

Thomas, Rini; Das, Gangadhar; Mondal, Rajib; Pradheesh, R.; Mahato, R. N.; Geetha Kumary, T.; Nirmala, R.; Morozkin, A. V.; Lamsal, J.; Yelon, W. B.; Nigam, A. K.; Malik, S. K.

2012-04-01

Nanocrystalline La0.15Ca0.85MnO3 samples of various grain sizes ranging from ˜17 to 42 nm have been prepared by sol-gel technique. Phase purity and composition were verified by room temperature x-ray diffraction and SEM-EDAX analysis. The bulk La0.15Ca0.85MnO3 is known to order antiferromagnetically around 170 K and to undergo a simultaneous crystal structural transition. DC magnetization measurements on 17 nm size La0.15Ca0.85MnO3 show a peak at ˜130 K (TN) in zero-field-cooled (ZFC) state. Field-cooled magnetization bifurcates from ZFC data around 200 K hinting a weak ferromagnetic component near room temperature due to surface moments of the nanoparticle sample. Low temperature powder neutron diffraction experiments reveal that the incomplete structural transition from room temperature orthorhombic to low temperature orthorhombic-monoclinic state also occurs in the nanoparticle sample as in the bulk. Magnetization in the ordered state decreases as particle size increases, thus indicating the reduction of the competing ferromagnetic surface moments.

Particle size effect on strength, failure, and shock behavior in polytetrafluoroethylene-Al-W granular composite materials

NASA Astrophysics Data System (ADS)

Herbold, E. B.; Nesterenko, V. F.; Benson, D. J.; Cai, J.; Vecchio, K. S.; Jiang, F.; Addiss, J. W.; Walley, S. M.; Proud, W. G.

2008-11-01

The variation of metallic particle size and sample porosity significantly alters the dynamic mechanical properties of high density granular composite materials processed using a cold isostatically pressed mixture of polytetrafluoroethylene (PTFE), aluminum (Al), and tungsten (W) powders. Quasistatic and dynamic experiments are performed with identical constituent mass fractions with variations in the size of the W particles and pressing conditions. The relatively weak polymer matrix allows the strength and fracture modes of this material to be governed by the granular type behavior of agglomerated metal particles. A higher ultimate compressive strength was observed in relatively high porosity samples with small W particles compared to those with coarse W particles in all experiments. Mesoscale granular force chains of the metallic particles explain this unusual phenomenon as observed in hydrocode simulations of a drop-weight test. Macrocracks forming below the critical failure strain for the matrix and unusual behavior due to a competition between densification and fracture in dynamic tests of porous samples were also observed. Numerical modeling of shock loading of this granular composite material demonstrated that the internal energy, specifically thermal energy, of the soft PTFE matrix can be tailored by the W particle size distribution.

Multiple antiferromagnet/ferromagnet interfaces as a probe of grain-size-dependent exchange bias in polycrystalline Co/Fe 50Mn 50

NASA Astrophysics Data System (ADS)

Bolon, Bruce T.; Haugen, M. A.; Abin-Fuentes, A.; Deneen, J.; Carter, C. B.; Leighton, C.

2007-02-01

We have used ferromagnet/antiferromagnet/ferromagnet trilayers and ferromagnet/antiferromagnet multilayers to probe the grain size dependence of exchange bias in polycrystalline Co/Fe 50Mn 50. X-ray diffraction and transmission electron microscopy show that the Fe 50Mn 50 (FeMn) grain size increases with increasing FeMn thickness in the Co (30 Å)/FeMn system. Hence, in Co(30 Å)/FeMn( tAF Å)/Co(30 Å) trilayers the two Co layers sample different FeMn grain sizes at the two antiferromagnet/ferromagnet interfaces. For FeMn thicknesses above 100 Å, where simple bilayers have a thickness-independent exchange bias, we are therefore able to deduce the influence of FeMn grain size on the exchange bias and coercivity (and their temperature dependence) simply by measuring trilayer and multilayer samples with varying FeMn thicknesses. This can be done while maintaining the (1 1 1) orientation, and with little variation in interface roughness. Increasing the average grain size from 90 to 135 Å results in a fourfold decrease in exchange bias, following an inverse grain size dependence. We interpret the results as being due to a decrease in uncompensated spin density with increasing antiferromagnet grain size, further evidence for the importance of defect-generated uncompensated spins.

[Association between productivity, list size, patient and practice characteristics in general practice].

PubMed

Olsen, Kim Rose; Sørensen, Torben Højmark; Gyrd-Hansen, Dorte

2010-04-19

Due to shortage of general practitioners, it may be necessary to improve productivity. We assess the association between productivity, list size and patient- and practice characteristics. A regression approach is used to perform productivity analysis based on national register data and survey data for 1,758 practices. Practices are divided into four groups according to list size and productivity. Statistical tests are used to assess differences in patient- and practice characteristics. There is a significant, positive correlation between list size and productivity (p < 0.01). Nevertheless, 19% of the practices have a list size below and a productivity above mean sample values. These practices have relatively demanding patients (older, low socioeconomic status, high use of pharmaceuticals) and they are frequently located in areas with limited access to specialized care and have a low use of assisting personnel. 13% of the practices have a list size above and a productivity below mean sample values. These practices have relatively less demanding patients, are located in areas with good access to specialized care, and have a high use of assisting personnel. Lists and practice characteristics have substantial influence on both productivity and list size. Adjusting list size to external factors seems to be an effective tool to increase productivity in general practice.

Effect of Microstructural Interfaces on the Mechanical Response of Crystalline Metallic Materials

NASA Astrophysics Data System (ADS)

Aitken, Zachary H.

Advances in nano-scale mechanical testing have brought about progress in the understanding of physical phenomena in materials and a measure of control in the fabrication of novel materials. In contrast to bulk materials that display size-invariant mechanical properties, sub-micron metallic samples show a critical dependence on sample size. The strength of nano-scale single crystalline metals is well-described by a power-law function, sigma ∝ D-n, where D is a critical sample size and n is a experimentally-fit positive exponent. This relationship is attributed to source-driven plasticity and demonstrates a strengthening as the decreasing sample size begins to limit the size and number of dislocation sources. A full understanding of this size-dependence is complicated by the presence of microstructural features such as interfaces that can compete with the dominant dislocation-based deformation mechanisms. In this thesis, the effects of microstructural features such as grain boundaries and anisotropic crystallinity on nano-scale metals are investigated through uniaxial compression testing. We find that nano-sized Cu covered by a hard coating displays a Bauschinger effect and the emergence of this behavior can be explained through a simple dislocation-based analytic model. Al nano-pillars containing a single vertically-oriented coincident site lattice grain boundary are found to show similar deformation to single-crystalline nano-pillars with slip traces passing through the grain boundary. With increasing tilt angle of the grain boundary from the pillar axis, we observe a transition from dislocation-dominated deformation to grain boundary sliding. Crystallites are observed to shear along the grain boundary and molecular dynamics simulations reveal a mechanism of atomic migration that accommodates boundary sliding. We conclude with an analysis of the effects of inherent crystal anisotropy and alloying on the mechanical behavior of the Mg alloy, AZ31. Through comparison to pure Mg, we show that the size effect dominates the strength of samples below 10 microm, that differences in the size effect between hexagonal slip systems is due to the inherent crystal anisotropy, suggesting that the fundamental mechanism of the size effect in these slip systems is the same.

Gravity or turbulence? IV. Collapsing cores in out-of-virial disguise

NASA Astrophysics Data System (ADS)

Ballesteros-Paredes, Javier; Vázquez-Semadeni, Enrique; Palau, Aina; Klessen, Ralf S.

2018-06-01

We study the dynamical state of massive cores by using a simple analytical model, an observational sample, and numerical simulations of collapsing massive cores. From the analytical model, we find that cores increase their column density and velocity dispersion as they collapse, resulting in a time evolution path in the Larson velocity dispersion-size diagram from large sizes and small velocity dispersions to small sizes and large velocity dispersions, while they tend to equipartition between gravity and kinetic energy. From the observational sample, we find that: (a) cores with substantially different column densities in the sample do not follow a Larson-like linewidth-size relation. Instead, cores with higher column densities tend to be located in the upper-left corner of the Larson velocity dispersion σv, 3D-size R diagram, a result explained in the hierarchical and chaotic collapse scenario. (b) Cores appear to have overvirial values. Finally, our numerical simulations reproduce the behavior predicted by the analytical model and depicted in the observational sample: collapsing cores evolve towards larger velocity dispersions and smaller sizes as they collapse and increase their column density. More importantly, however, they exhibit overvirial states. This apparent excess is due to the assumption that the gravitational energy is given by the energy of an isolated homogeneous sphere. However, such excess disappears when the gravitational energy is correctly calculated from the actual spatial mass distribution. We conclude that the observed energy budget of cores is consistent with their non-thermal motions being driven by their self-gravity and in the process of dynamical collapse.

Accounting for treatment by center interaction in sample size determinations and the use of surrogate outcomes in the pessary for the prevention of preterm birth trial: a simulation study.

PubMed

Willan, Andrew R

2016-07-05

The Pessary for the Prevention of Preterm Birth Study (PS3) is an international, multicenter, randomized clinical trial designed to examine the effectiveness of the Arabin pessary in preventing preterm birth in pregnant women with a short cervix. During the design of the study two methodological issues regarding power and sample size were raised. Since treatment in the Standard Arm will vary between centers, it is anticipated that so too will the probability of preterm birth in that arm. This will likely result in a treatment by center interaction, and the issue of how this will affect the sample size requirements was raised. The sample size requirements to examine the effect of the pessary on the baby's clinical outcome was prohibitively high, so the second issue is how best to examine the effect on clinical outcome. The approaches taken to address these issues are presented. Simulation and sensitivity analysis were used to address the sample size issue. The probability of preterm birth in the Standard Arm was assumed to vary between centers following a Beta distribution with a mean of 0.3 and a coefficient of variation of 0.3. To address the second issue a Bayesian decision model is proposed that combines the information regarding the between-treatment difference in the probability of preterm birth from PS3 with the data from the Multiple Courses of Antenatal Corticosteroids for Preterm Birth Study that relate preterm birth and perinatal mortality/morbidity. The approach provides a between-treatment comparison with respect to the probability of a bad clinical outcome. The performance of the approach was assessed using simulation and sensitivity analysis. Accounting for a possible treatment by center interaction increased the sample size from 540 to 700 patients per arm for the base case. The sample size requirements increase with the coefficient of variation and decrease with the number of centers. Under the same assumptions used for determining the sample size requirements, the simulated mean probability that pessary reduces the risk of perinatal mortality/morbidity is 0.98. The simulated mean decreased with coefficient of variation and increased with the number of clinical sites. Employing simulation and sensitivity analysis is a useful approach for determining sample size requirements while accounting for the additional uncertainty due to a treatment by center interaction. Using a surrogate outcome in conjunction with a Bayesian decision model is an efficient way to compare important clinical outcomes in a randomized clinical trial in situations where the direct approach requires a prohibitively high sample size.

Probing the Magnetic Causes of CMEs: Free Magnetic Energy More Important Than Either Size Or Twist

NASA Technical Reports Server (NTRS)

Falconer, D. A.; Moore, R. L.; Gary, G. A.

2006-01-01

To probe the magnetic causes of CMEs, we have examined three types of magnetic measures: size, twist and total nonpotentiality (or total free magnetic energy) of an active region. Total nonpotentiality is roughly the product of size times twist. For predominately bipolar active regions, we have found that total nonpotentiality measures have the strongest correlation with future CME productivity (approx. 75% prediction success rate), while size and twist measures each have a weaker correlation with future CME productivity (approx. 65% prediction success rate) (Falconer, Moore, & Gary, ApJ, 644, 2006). For multipolar active regions, we find that the CME-prediction success rates for total nonpotentiality and size are about the same as for bipolar active regions. We also find that the size measure correlation with CME productivity is nearly all due to the contribution of size to total nonpotentiality. We have a total nonpotentiality measure that can be obtained from a line-of-sight magnetogram of the active region and that is as strongly correlated with CME productivity as are any of our total-nonpotentiality measures from deprojected vector magnetograms. We plan to further expand our sample by using MDI magnetograms of each active region in our sample to determine its total nonpotentiality and size on each day that the active region was within 30 deg. of disk center. The resulting increase in sample size will improve our statistics and allow us to investigate whether the nonpotentiality threshold for CME production is nearly the same or significantly different for multipolar regions than for bipolar regions. In addition, we will investigate the time rates of change of size and total nonpotentiality as additional causes of CME productivity.

Authoritarian Parenting and Asian Adolescent School Performance: Insights from the US and Taiwan

PubMed Central

Pong, Suet-ling; Johnston, Jamie; Chen, Vivien

2014-01-01

Our study re-examines the relationship between parenting and school performance among Asian students. We use two sources of data: wave I of the Adolescent Health Longitudinal Survey (Add Health), and waves I and II of the Taiwan Educational Panel Survey (TEPS). Analysis using Add Health reveals that the Asian-American/European-American difference in the parenting–school performance relationship is due largely to differential sample sizes. When we select a random sample of European-American students comparable to the sample size of Asian-American students, authoritarian parenting also shows no effect for European-American students. Furthermore, analysis of TEPS shows that authoritarian parenting is negatively associated with children's school achievement, while authoritative parenting is positively associated. This result for Taiwanese Chinese students is similar to previous results for European-American students in the US. PMID:24850978

Authoritarian Parenting and Asian Adolescent School Performance: Insights from the US and Taiwan.

PubMed

Pong, Suet-Ling; Johnston, Jamie; Chen, Vivien

2010-01-01

Our study re-examines the relationship between parenting and school performance among Asian students. We use two sources of data: wave I of the Adolescent Health Longitudinal Survey (Add Health), and waves I and II of the Taiwan Educational Panel Survey (TEPS). Analysis using Add Health reveals that the Asian-American/European-American difference in the parenting-school performance relationship is due largely to differential sample sizes. When we select a random sample of European-American students comparable to the sample size of Asian-American students, authoritarian parenting also shows no effect for European-American students. Furthermore, analysis of TEPS shows that authoritarian parenting is negatively associated with children's school achievement, while authoritative parenting is positively associated. This result for Taiwanese Chinese students is similar to previous results for European-American students in the US.

Size dependent exchange bias in single-phase Zn0.3Ni0.7Fe2O4 ferrite nanoparticles

NASA Astrophysics Data System (ADS)

Mohan, Rajendra; Ghosh, Mritunjoy Prasad; Mukherjee, Samrat

2018-07-01

We report the microstructural and magnetic characterization of single phase nanocrystalline partially inverted Zn0.3Ni0.7Fe2O4 mixed spinel ferrite. The samples were annealed at 200 °C, 400 °C, 600 °C, 800 °C and 1000 °C. X-ray diffraction results indicate phase purity of all the samples and application of Debye- Scherrer yielded a crystallite size variation from 5 nm to 33 nm for the different samples. Magnetic measurements have revealed the freezing of interfacial spins which were the cause of the large horizontal M-H loop shift causing large exchange bias with high anisotropy. The magnetic measurements show a hysteresis loop with high effective anisotropy constant due to highly magnetically disordered surface spin at 5 K.

Optimal Wavelength Selection on Hyperspectral Data with Fused Lasso for Biomass Estimation of Tropical Rain Forest

NASA Astrophysics Data System (ADS)

Takayama, T.; Iwasaki, A.

2016-06-01

Above-ground biomass prediction of tropical rain forest using remote sensing data is of paramount importance to continuous large-area forest monitoring. Hyperspectral data can provide rich spectral information for the biomass prediction; however, the prediction accuracy is affected by a small-sample-size problem, which widely exists as overfitting in using high dimensional data where the number of training samples is smaller than the dimensionality of the samples due to limitation of require time, cost, and human resources for field surveys. A common approach to addressing this problem is reducing the dimensionality of dataset. Also, acquired hyperspectral data usually have low signal-to-noise ratio due to a narrow bandwidth and local or global shifts of peaks due to instrumental instability or small differences in considering practical measurement conditions. In this work, we propose a methodology based on fused lasso regression that select optimal bands for the biomass prediction model with encouraging sparsity and grouping, which solves the small-sample-size problem by the dimensionality reduction from the sparsity and the noise and peak shift problem by the grouping. The prediction model provided higher accuracy with root-mean-square error (RMSE) of 66.16 t/ha in the cross-validation than other methods; multiple linear analysis, partial least squares regression, and lasso regression. Furthermore, fusion of spectral and spatial information derived from texture index increased the prediction accuracy with RMSE of 62.62 t/ha. This analysis proves efficiency of fused lasso and image texture in biomass estimation of tropical forests.

Sampling Errors in Monthly Rainfall Totals for TRMM and SSM/I, Based on Statistics of Retrieved Rain Rates and Simple Models

NASA Technical Reports Server (NTRS)

Bell, Thomas L.; Kundu, Prasun K.; Einaudi, Franco (Technical Monitor)

2000-01-01

Estimates from TRMM satellite data of monthly total rainfall over an area are subject to substantial sampling errors due to the limited number of visits to the area by the satellite during the month. Quantitative comparisons of TRMM averages with data collected by other satellites and by ground-based systems require some estimate of the size of this sampling error. A method of estimating this sampling error based on the actual statistics of the TRMM observations and on some modeling work has been developed. "Sampling error" in TRMM monthly averages is defined here relative to the monthly total a hypothetical satellite permanently stationed above the area would have reported. "Sampling error" therefore includes contributions from the random and systematic errors introduced by the satellite remote sensing system. As part of our long-term goal of providing error estimates for each grid point accessible to the TRMM instruments, sampling error estimates for TRMM based on rain retrievals from TRMM microwave (TMI) data are compared for different times of the year and different oceanic areas (to minimize changes in the statistics due to algorithmic differences over land and ocean). Changes in sampling error estimates due to changes in rain statistics due 1) to evolution of the official algorithms used to process the data, and 2) differences from other remote sensing systems such as the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave/Imager (SSM/I), are analyzed.

Evaluation of species richness estimators based on quantitative performance measures and sensitivity to patchiness and sample grain size

NASA Astrophysics Data System (ADS)

Willie, Jacob; Petre, Charles-Albert; Tagg, Nikki; Lens, Luc

2012-11-01

Data from forest herbaceous plants in a site of known species richness in Cameroon were used to test the performance of rarefaction and eight species richness estimators (ACE, ICE, Chao1, Chao2, Jack1, Jack2, Bootstrap and MM). Bias, accuracy, precision and sensitivity to patchiness and sample grain size were the evaluation criteria. An evaluation of the effects of sampling effort and patchiness on diversity estimation is also provided. Stems were identified and counted in linear series of 1-m2 contiguous square plots distributed in six habitat types. Initially, 500 plots were sampled in each habitat type. The sampling process was monitored using rarefaction and a set of richness estimator curves. Curves from the first dataset suggested adequate sampling in riparian forest only. Additional plots ranging from 523 to 2143 were subsequently added in the undersampled habitats until most of the curves stabilized. Jack1 and ICE, the non-parametric richness estimators, performed better, being more accurate and less sensitive to patchiness and sample grain size, and significantly reducing biases that could not be detected by rarefaction and other estimators. This study confirms the usefulness of non-parametric incidence-based estimators, and recommends Jack1 or ICE alongside rarefaction while describing taxon richness and comparing results across areas sampled using similar or different grain sizes. As patchiness varied across habitat types, accurate estimations of diversity did not require the same number of plots. The number of samples needed to fully capture diversity is not necessarily the same across habitats, and can only be known when taxon sampling curves have indicated adequate sampling. Differences in observed species richness between habitats were generally due to differences in patchiness, except between two habitats where they resulted from differences in abundance. We suggest that communities should first be sampled thoroughly using appropriate taxon sampling curves before explaining differences in diversity.

A Bayesian Perspective on the Reproducibility Project: Psychology

PubMed Central

Etz, Alexander; Vandekerckhove, Joachim

2016-01-01

We revisit the results of the recent Reproducibility Project: Psychology by the Open Science Collaboration. We compute Bayes factors—a quantity that can be used to express comparative evidence for an hypothesis but also for the null hypothesis—for a large subset (N = 72) of the original papers and their corresponding replication attempts. In our computation, we take into account the likely scenario that publication bias had distorted the originally published results. Overall, 75% of studies gave qualitatively similar results in terms of the amount of evidence provided. However, the evidence was often weak (i.e., Bayes factor < 10). The majority of the studies (64%) did not provide strong evidence for either the null or the alternative hypothesis in either the original or the replication, and no replication attempts provided strong evidence in favor of the null. In all cases where the original paper provided strong evidence but the replication did not (15%), the sample size in the replication was smaller than the original. Where the replication provided strong evidence but the original did not (10%), the replication sample size was larger. We conclude that the apparent failure of the Reproducibility Project to replicate many target effects can be adequately explained by overestimation of effect sizes (or overestimation of evidence against the null hypothesis) due to small sample sizes and publication bias in the psychological literature. We further conclude that traditional sample sizes are insufficient and that a more widespread adoption of Bayesian methods is desirable. PMID:26919473

A Bayesian Perspective on the Reproducibility Project: Psychology.

PubMed

Etz, Alexander; Vandekerckhove, Joachim

2016-01-01

We revisit the results of the recent Reproducibility Project: Psychology by the Open Science Collaboration. We compute Bayes factors-a quantity that can be used to express comparative evidence for an hypothesis but also for the null hypothesis-for a large subset (N = 72) of the original papers and their corresponding replication attempts. In our computation, we take into account the likely scenario that publication bias had distorted the originally published results. Overall, 75% of studies gave qualitatively similar results in terms of the amount of evidence provided. However, the evidence was often weak (i.e., Bayes factor < 10). The majority of the studies (64%) did not provide strong evidence for either the null or the alternative hypothesis in either the original or the replication, and no replication attempts provided strong evidence in favor of the null. In all cases where the original paper provided strong evidence but the replication did not (15%), the sample size in the replication was smaller than the original. Where the replication provided strong evidence but the original did not (10%), the replication sample size was larger. We conclude that the apparent failure of the Reproducibility Project to replicate many target effects can be adequately explained by overestimation of effect sizes (or overestimation of evidence against the null hypothesis) due to small sample sizes and publication bias in the psychological literature. We further conclude that traditional sample sizes are insufficient and that a more widespread adoption of Bayesian methods is desirable.

The Relationship between Organizational Culture Types and Innovation in Aerospace Companies

NASA Astrophysics Data System (ADS)

Nelson, Adaora N.

Innovation in the aerospace industry has proven to be an effective strategy for competitiveness and sustainability. The organizational culture of the firm must be conducive to innovation. The problem was that although innovation is needed for aerospace companies to be competitive and sustainable, certain organizational culture issues might hinder leaders from successfully innovating (Emery, 2010; Ramanigopal, 2012). The purpose of this study was to assess the relationship of hierarchical, clan, adhocracy and market organizational types and innovation in aerospace companies within the U.S while controlling for company size and length of time in business. The non-experimental quantitative study included a random sample of 136 aerospace leaders in the U.S. There was a significant relationship between market organizational culture and innovation, F(1,132) = 4.559, p = .035. No significant relationships were found between hierarchical organizational culture and innovation and between clan culture and innovation. The relationship between adhocracy culture and innovation was not significant, possible due to inadequate sample size. Company size was shown to be a justifiable covariate in the study, due to a significant relationship with innovative (F(1, 130) = 4.66, p < .1, r = .19). Length of time in business had no relationship with innovation. The findings imply that market organizational cultures are more likely to result in innovative outcomes in the aerospace industry. Organizational leaders are encouraged to adopt a market culture and adopt smaller organizational structures. Recommendations for further research include investigating the relationship between adhocracy culture and innovation using an adequate sample size. Research is needed to determine other variables that predict innovation. This study should be repeated at periodic intervals and across other industrial sectors and countries.

An Investigation of Community Attitudes Toward Blast Noise: Complaint Survey Protocol

DTIC Science & Technology

2010-10-11

increase complaints (Hume et al., 2003a). If an individual is already stressed by other non-noise factors, the source noise many be more annoying than...protocol (lab staffing, sampling and locating records, callback schedules) focused on completing the data collection for any given noise event within...relationship (e.g., increased feelings of importance of the installation tend to be associated with decreased annoyance). Due to the limited sample size only

Improved Statistical Sampling and Accuracy with Accelerated Molecular Dynamics on Rotatable Torsions.

PubMed

Doshi, Urmi; Hamelberg, Donald

2012-11-13

In enhanced sampling techniques, the precision of the reweighted ensemble properties is often decreased due to large variation in statistical weights and reduction in the effective sampling size. To abate this reweighting problem, here, we propose a general accelerated molecular dynamics (aMD) approach in which only the rotatable dihedrals are subjected to aMD (RaMD), unlike the typical implementation wherein all dihedrals are boosted (all-aMD). Nonrotatable and improper dihedrals are marginally important to conformational changes or the different rotameric states. Not accelerating them avoids the sharp increases in the potential energies due to small deviations from their minimum energy conformations and leads to improvement in the precision of RaMD. We present benchmark studies on two model dipeptides, Ace-Ala-Nme and Ace-Trp-Nme, simulated with normal MD, all-aMD, and RaMD. We carry out a systematic comparison between the performances of both forms of aMD using a theory that allows quantitative estimation of the effective number of sampled points and the associated uncertainty. Our results indicate that, for the same level of acceleration and simulation length, as used in all-aMD, RaMD results in significantly less loss in the effective sample size and, hence, increased accuracy in the sampling of φ-ψ space. RaMD yields an accuracy comparable to that of all-aMD, from simulation lengths 5 to 1000 times shorter, depending on the peptide and the acceleration level. Such improvement in speed and accuracy over all-aMD is highly remarkable, suggesting RaMD as a promising method for sampling larger biomolecules.

Calibration correction of an active scattering spectrometer probe to account for refractive index of stratospheric aerosols

NASA Technical Reports Server (NTRS)

Pueschel, R. F.; Overbeck, V. R.; Snetsinger, K. G.; Russell, P. B.; Ferry, G. V.

1990-01-01

The use of the active scattering spectrometer probe (ASAS-X) to measure sulfuric acid aerosols on U-2 and ER-2 research aircraft has yielded results that are at times ambiguous due to the dependence of particles' optical signatures on refractive index as well as physical dimensions. The calibration correction of the ASAS-X optical spectrometer probe for stratospheric aerosol studies is validated through an independent and simultaneous sampling of the particles with impactors; sizing and counting of particles on SEM images yields total particle areas and volumes. Upon correction of calibration in light of these data, spectrometer results averaged over four size distributions are found to agree with similarly averaged impactor results to within a few percent: indicating that the optical properties or chemical composition of the sample aerosol must be known in order to achieve accurate optical aerosol spectrometer size analysis.

Molecular-Size-Separated Brown Carbon Absorption for Biomass-Burning Aerosol at Multiple Field Sites.

PubMed

Di Lorenzo, Robert A; Washenfelder, Rebecca A; Attwood, Alexis R; Guo, Hongyu; Xu, Lu; Ng, Nga L; Weber, Rodney J; Baumann, Karsten; Edgerton, Eric; Young, Cora J

2017-03-21

Biomass burning is a known source of brown carbon aerosol in the atmosphere. We collected filter samples of biomass-burning emissions at three locations in Canada and the United States with transport times of 10 h to >3 days. We analyzed the samples with size-exclusion chromatography coupled to molecular absorbance spectroscopy to determine absorbance as a function of molecular size. The majority of absorption was due to molecules >500 Da, and these contributed an increasing fraction of absorption as the biomass-burning aerosol aged. This suggests that the smallest molecular weight fraction is more susceptible to processes that lead to reduced light absorption, while larger-molecular-weight species may represent recalcitrant brown carbon. We calculate that these large-molecular-weight species are composed of more than 20 carbons with as few as two oxygens and would be classified as extremely low volatility organic compounds (ELVOCs).

A general unified framework to assess the sampling variance of heritability estimates using pedigree or marker-based relationships.

PubMed

Visscher, Peter M; Goddard, Michael E

2015-01-01

Heritability is a population parameter of importance in evolution, plant and animal breeding, and human medical genetics. It can be estimated using pedigree designs and, more recently, using relationships estimated from markers. We derive the sampling variance of the estimate of heritability for a wide range of experimental designs, assuming that estimation is by maximum likelihood and that the resemblance between relatives is solely due to additive genetic variation. We show that well-known results for balanced designs are special cases of a more general unified framework. For pedigree designs, the sampling variance is inversely proportional to the variance of relationship in the pedigree and it is proportional to 1/N, whereas for population samples it is approximately proportional to 1/N(2), where N is the sample size. Variation in relatedness is a key parameter in the quantification of the sampling variance of heritability. Consequently, the sampling variance is high for populations with large recent effective population size (e.g., humans) because this causes low variation in relationship. However, even using human population samples, low sampling variance is possible with high N. Copyright © 2015 by the Genetics Society of America.

The effect of reaction temperature on the room temperature ferromagnetic property of sol-gel derived tin oxide nanocrystal

NASA Astrophysics Data System (ADS)

Sakthiraj, K.; Hema, M.; Balachandra Kumar, K.

2018-06-01

In the present study, nanocrystalline tin oxide materials were prepared using sol-gel method with different reaction temperatures (25 °C, 50 °C, 75 °C & 90 °C) and the relation between the room temperature ferromagnetic property of the sample with processing temperature has been analysed. The X-ray diffraction pattern and infrared absorption spectra of the as-prepared samples confirm the purity of the samples. Transmission electron microscopy images visualize the particle size variation with respect to reaction temperature. The photoluminescence spectra of the samples demonstrate that luminescence process in materials is originated due to the electron transition mediated by defect centres. The room temperature ferromagnetic property is observed in all the samples with different amount, which was confirmed using vibrating sample magnetometer measurements. The saturation magnetization value of the as-prepared samples is increased with increasing the reaction temperature. From the photoluminescence & magnetic measurements we accomplished that, more amount of surface defects like oxygen vacancy and tin interstitial are created due to the increase in reaction temperature and it controls the ferromagnetic property of the samples.

Effect of body size and body mass on δ 13 C and δ 15 N in coastal fishes and cephalopods

NASA Astrophysics Data System (ADS)

Vinagre, C.; Máguas, C.; Cabral, H. N.; Costa, M. J.

2011-11-01

Carbon and nitrogen isotopes have been widely used in the investigation of trophic relations, energy pathways, trophic levels and migrations, under the assumption that δ 13C is independent of body size and that variation in δ 15N occurs exclusively due to ontogenetic changes in diet and not body size increase per se. However, several studies have shown that these assumptions are uncertain. Data from food-webs containing an important number of species lack theoretical support on these assumptions because very few species have been tested for δ 13C and δ 15N variation in captivity. However, if sampling comprises a wide range of body sizes from various species, the variation of δ 13C and δ 15N with body size can be investigated. While correlation between body size and δ 13C and δ 15N can be due to ontogenetic diet shifts, stability in such values throughout the size spectrum can be considered an indication that δ 13C and δ 15N in muscle tissues of such species is independent of body size within that size range, and thus the basic assumptions can be applied in the interpretation of such food webs. The present study investigated the variation in muscle δ 13C and δ 15N with body size and body mass of coastal fishes and cephalopods. It was concluded that muscle δ 13C and δ 15N did not vary with body size or mass for all bony fishes with only one exception, the dragonet Callionymus lyra. Muscle δ 13C and δ 15N also did not vary with body size or mass in cartilaginous fishes and cephalopods, meaning that body size/mass per se have no effect on δ 13C or δ 15N, for most species analysed and within the size ranges sampled. The assumption that δ 13C is independent of body size and that variation in δ 15N is not affected by body size increase per se was upheld for most organisms and can be applied to the coastal food web studied taking into account that C. lyra is an exception.

Massively parallel rRNA gene sequencing exacerbates the potential for biased community diversity comparisons due to variable library sizes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gihring, Thomas; Green, Stefan; Schadt, Christopher Warren

2011-01-01

Technologies for massively parallel sequencing are revolutionizing microbial ecology and are vastly increasing the scale of ribosomal RNA (rRNA) gene studies. Although pyrosequencing has increased the breadth and depth of possible rRNA gene sampling, one drawback is that the number of reads obtained per sample is difficult to control. Pyrosequencing libraries typically vary widely in the number of sequences per sample, even within individual studies, and there is a need to revisit the behaviour of richness estimators and diversity indices with variable gene sequence library sizes. Multiple reports and review papers have demonstrated the bias in non-parametric richness estimators (e.g.more » Chao1 and ACE) and diversity indices when using clone libraries. However, we found that biased community comparisons are accumulating in the literature. Here we demonstrate the effects of sample size on Chao1, ACE, CatchAll, Shannon, Chao-Shen and Simpson's estimations specifically using pyrosequencing libraries. The need to equalize the number of reads being compared across libraries is reiterated, and investigators are directed towards available tools for making unbiased diversity comparisons.« less

Electrochemical Behavior Assessment of Micro- and Nano-Grained Commercial Pure Titanium in H2SO4 Solutions

NASA Astrophysics Data System (ADS)

Fattah-alhosseini, Arash; Ansari, Ali Reza; Mazaheri, Yousef; Karimi, Mohsen

2017-02-01

In this study, the electrochemical behavior of commercial pure titanium with both coarse-grained (annealed sample with the average grain size of about 45 µm) and nano-grained microstructure was compared by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and Mott-Schottky analysis. Nano-grained Ti, which typically has a grain size of about 90 nm, is successfully made by six-cycle accumulative roll-bonding process at room temperature. Potentiodynamic polarization plots and impedance measurements revealed that as a result of grain refinement, the passive behavior of the nano-grained sample was improved compared to that of annealed pure Ti in H2SO4 solutions. Mott-Schottky analysis indicated that the passive films behaved as n-type semiconductors in H2SO4 solutions and grain refinement did not change the semiconductor type of passive films. Also, Mott-Schottky analysis showed that the donor densities decreased as the grain size of the samples reduced. Finally, all electrochemical tests showed that the electrochemical behavior of the nano-grained sample was improved compared to that of annealed pure Ti, mainly due to the formation of thicker and less defective oxide film.

Marine sources of ice nucleating particles: results from phytoplankton cultures and samples collected at sea

NASA Astrophysics Data System (ADS)

Wilbourn, E.; Thornton, D.; Brooks, S. D.; Graff, J.

2016-12-01

The role of marine aerosols as ice nucleating particles is currently poorly understood. Despite growing interest, there are remarkably few ice nucleation measurements on representative marine samples. Here we present results of heterogeneous ice nucleation from laboratory studies and in-situ air and sea water samples collected during NAAMES (North Atlantic Aerosol and Marine Ecosystems Study). Thalassiosira weissflogii (CCMP 1051) was grown under controlled conditions in batch cultures and the ice nucleating activity depended on the growth phase of the cultures. Immersion freezing temperatures of the lab-grown diatoms were determined daily using a custom ice nucleation apparatus cooled at a set rate. Our results show that the age of the culture had a significant impact on ice nucleation temperature, with samples in stationary phase causing nucleation at -19.9 °C, approximately nine degrees warmer than the freezing temperature during exponential growth phase. Field samples gathered during the NAAMES II cruise in May 2016 were also tested for ice nucleating ability. Two types of samples were gathered. Firstly, whole cells were fractionated by size from surface seawater using a BD Biosciences Influx Cell Sorter (BD BS ISD). Secondly, aerosols were generated using the SeaSweep and subsequently size-selected using a PIXE Cascade Impactor. Samples were tested for the presence of ice nucleating particles (INP) using the technique described above. There were significant differences in the freezing temperature of the different samples; of the three sample types the lab-grown cultures tested during stationary phase froze at the warmest temperatures, followed by the SeaSweep samples (-25.6 °C) and the size-fractionated cell samples (-31.3 °C). Differences in ice nucleation ability may be due to size differences between the INP, differences in chemical composition of the sample, or some combination of these two factors. Results will be presented and atmospheric implications discussed.

Pre and post annealed low cost ZnO nanorods on seeded substrate

NASA Astrophysics Data System (ADS)

Nordin, M. N.; Kamil, Wan Maryam Wan Ahmad

2017-05-01

We wish to report the photonic band gap (where light is confined) in low cost ZnO nanorods created by two-step chemical bath deposition (CBD) method where the glass substrates were pre-treated with two different seeding thicknesses, 100 nm (sample a) and 150 nm (sample b), of ZnO using radio frequency magnetron sputtering. Then the samples were annealed at 600°C for 1 hour in air before and after immersed into the chemical solution for CBD process. To observe the presence of photonic band gap on the sample, UV-Visible-NIR spectrophotometer was utilized and showed that sample a and sample b both achieved wide band gap between 240 nm and 380 nm, within the UV range for typical ZnO, however sample b provided a better light confinement that may be attributed by the difference in average nanorods size. Field Emission Scanning Electron Microscope (FESEM) of the samples revealed better oriented nanorods uniformly scattered across the surface when substrates were coated with 100 nm of seeding layer whilst the 150 nm seeding sample showed a poor distribution of nanorods probably due to defects in the sample. Finally, the crystal structure of the ZnO crystallite is revealed by employing X-ray diffraction and both samples showed polycrystalline with hexagonal wurtzite structure that matched with JCPDS No. 36-1451. The 100 nm pre-seeded samples was recognized to have bigger average crystallite size, however sample b was suggested as having a higher crystalline quality. In conclusion, the sample b is recognized as a better candidate for future photonic applications due to its more apparent of photonic band gap and this may be contributed by more random distribution of the nanorods as observed in FESEM images as well as higher crystalline quality as suggested from XRD measurements.

Optimization of scat detection methods for a social ungulate, the wild pig, and experimental evaluation of factors affecting detection of scat

USGS Publications Warehouse

Keiter, David A.; Cunningham, Fred L.; Rhodes, Olin E.; Irwin, Brian J.; Beasley, James

2016-01-01

Collection of scat samples is common in wildlife research, particularly for genetic capture-mark-recapture applications. Due to high degradation rates of genetic material in scat, large numbers of samples must be collected to generate robust estimates. Optimization of sampling approaches to account for taxa-specific patterns of scat deposition is, therefore, necessary to ensure sufficient sample collection. While scat collection methods have been widely studied in carnivores, research to maximize scat collection and noninvasive sampling efficiency for social ungulates is lacking. Further, environmental factors or scat morphology may influence detection of scat by observers. We contrasted performance of novel radial search protocols with existing adaptive cluster sampling protocols to quantify differences in observed amounts of wild pig (Sus scrofa) scat. We also evaluated the effects of environmental (percentage of vegetative ground cover and occurrence of rain immediately prior to sampling) and scat characteristics (fecal pellet size and number) on the detectability of scat by observers. We found that 15- and 20-m radial search protocols resulted in greater numbers of scats encountered than the previously used adaptive cluster sampling approach across habitat types, and that fecal pellet size, number of fecal pellets, percent vegetative ground cover, and recent rain events were significant predictors of scat detection. Our results suggest that use of a fixed-width radial search protocol may increase the number of scats detected for wild pigs, or other social ungulates, allowing more robust estimation of population metrics using noninvasive genetic sampling methods. Further, as fecal pellet size affected scat detection, juvenile or smaller-sized animals may be less detectable than adult or large animals, which could introduce bias into abundance estimates. Knowledge of relationships between environmental variables and scat detection may allow researchers to optimize sampling protocols to maximize utility of noninvasive sampling for wild pigs and other social ungulates.

Optimization of scat detection methods for a social ungulate, the wild pig, and experimental evaluation of factors affecting detection of scat

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keiter, David A.; Cunningham, Fred L.; Rhodes, Jr., Olin E.

Collection of scat samples is common in wildlife research, particularly for genetic capture-mark-recapture applications. Due to high degradation rates of genetic material in scat, large numbers of samples must be collected to generate robust estimates. Optimization of sampling approaches to account for taxa-specific patterns of scat deposition is, therefore, necessary to ensure sufficient sample collection. While scat collection methods have been widely studied in carnivores, research to maximize scat collection and noninvasive sampling efficiency for social ungulates is lacking. Further, environmental factors or scat morphology may influence detection of scat by observers. We contrasted performance of novel radial search protocolsmore » with existing adaptive cluster sampling protocols to quantify differences in observed amounts of wild pig ( Sus scrofa) scat. We also evaluated the effects of environmental (percentage of vegetative ground cover and occurrence of rain immediately prior to sampling) and scat characteristics (fecal pellet size and number) on the detectability of scat by observers. We found that 15- and 20-m radial search protocols resulted in greater numbers of scats encountered than the previously used adaptive cluster sampling approach across habitat types, and that fecal pellet size, number of fecal pellets, percent vegetative ground cover, and recent rain events were significant predictors of scat detection. Our results suggest that use of a fixed-width radial search protocol may increase the number of scats detected for wild pigs, or other social ungulates, allowing more robust estimation of population metrics using noninvasive genetic sampling methods. Further, as fecal pellet size affected scat detection, juvenile or smaller-sized animals may be less detectable than adult or large animals, which could introduce bias into abundance estimates. In conclusion, knowledge of relationships between environmental variables and scat detection may allow researchers to optimize sampling protocols to maximize utility of noninvasive sampling for wild pigs and other social ungulates.« less

Optimization of Scat Detection Methods for a Social Ungulate, the Wild Pig, and Experimental Evaluation of Factors Affecting Detection of Scat.

PubMed

Keiter, David A; Cunningham, Fred L; Rhodes, Olin E; Irwin, Brian J; Beasley, James C

2016-01-01

Collection of scat samples is common in wildlife research, particularly for genetic capture-mark-recapture applications. Due to high degradation rates of genetic material in scat, large numbers of samples must be collected to generate robust estimates. Optimization of sampling approaches to account for taxa-specific patterns of scat deposition is, therefore, necessary to ensure sufficient sample collection. While scat collection methods have been widely studied in carnivores, research to maximize scat collection and noninvasive sampling efficiency for social ungulates is lacking. Further, environmental factors or scat morphology may influence detection of scat by observers. We contrasted performance of novel radial search protocols with existing adaptive cluster sampling protocols to quantify differences in observed amounts of wild pig (Sus scrofa) scat. We also evaluated the effects of environmental (percentage of vegetative ground cover and occurrence of rain immediately prior to sampling) and scat characteristics (fecal pellet size and number) on the detectability of scat by observers. We found that 15- and 20-m radial search protocols resulted in greater numbers of scats encountered than the previously used adaptive cluster sampling approach across habitat types, and that fecal pellet size, number of fecal pellets, percent vegetative ground cover, and recent rain events were significant predictors of scat detection. Our results suggest that use of a fixed-width radial search protocol may increase the number of scats detected for wild pigs, or other social ungulates, allowing more robust estimation of population metrics using noninvasive genetic sampling methods. Further, as fecal pellet size affected scat detection, juvenile or smaller-sized animals may be less detectable than adult or large animals, which could introduce bias into abundance estimates. Knowledge of relationships between environmental variables and scat detection may allow researchers to optimize sampling protocols to maximize utility of noninvasive sampling for wild pigs and other social ungulates.

Optimization of scat detection methods for a social ungulate, the wild pig, and experimental evaluation of factors affecting detection of scat

DOE PAGES

Keiter, David A.; Cunningham, Fred L.; Rhodes, Jr., Olin E.; ...

2016-05-25

Collection of scat samples is common in wildlife research, particularly for genetic capture-mark-recapture applications. Due to high degradation rates of genetic material in scat, large numbers of samples must be collected to generate robust estimates. Optimization of sampling approaches to account for taxa-specific patterns of scat deposition is, therefore, necessary to ensure sufficient sample collection. While scat collection methods have been widely studied in carnivores, research to maximize scat collection and noninvasive sampling efficiency for social ungulates is lacking. Further, environmental factors or scat morphology may influence detection of scat by observers. We contrasted performance of novel radial search protocolsmore » with existing adaptive cluster sampling protocols to quantify differences in observed amounts of wild pig ( Sus scrofa) scat. We also evaluated the effects of environmental (percentage of vegetative ground cover and occurrence of rain immediately prior to sampling) and scat characteristics (fecal pellet size and number) on the detectability of scat by observers. We found that 15- and 20-m radial search protocols resulted in greater numbers of scats encountered than the previously used adaptive cluster sampling approach across habitat types, and that fecal pellet size, number of fecal pellets, percent vegetative ground cover, and recent rain events were significant predictors of scat detection. Our results suggest that use of a fixed-width radial search protocol may increase the number of scats detected for wild pigs, or other social ungulates, allowing more robust estimation of population metrics using noninvasive genetic sampling methods. Further, as fecal pellet size affected scat detection, juvenile or smaller-sized animals may be less detectable than adult or large animals, which could introduce bias into abundance estimates. In conclusion, knowledge of relationships between environmental variables and scat detection may allow researchers to optimize sampling protocols to maximize utility of noninvasive sampling for wild pigs and other social ungulates.« less

Design considerations for case series models with exposure onset measurement error.

PubMed

Mohammed, Sandra M; Dalrymple, Lorien S; Sentürk, Damla; Nguyen, Danh V

2013-02-28

The case series model allows for estimation of the relative incidence of events, such as cardiovascular events, within a pre-specified time window after an exposure, such as an infection. The method requires only cases (individuals with events) and controls for all fixed/time-invariant confounders. The measurement error case series model extends the original case series model to handle imperfect data, where the timing of an infection (exposure) is not known precisely. In this work, we propose a method for power/sample size determination for the measurement error case series model. Extensive simulation studies are used to assess the accuracy of the proposed sample size formulas. We also examine the magnitude of the relative loss of power due to exposure onset measurement error, compared with the ideal situation where the time of exposure is measured precisely. To facilitate the design of case series studies, we provide publicly available web-based tools for determining power/sample size for both the measurement error case series model as well as the standard case series model. Copyright © 2012 John Wiley & Sons, Ltd.

Modeling misidentification errors that result from use of genetic tags in capture-recapture studies

USGS Publications Warehouse

Yoshizaki, J.; Brownie, C.; Pollock, K.H.; Link, W.A.

2011-01-01

Misidentification of animals is potentially important when naturally existing features (natural tags) such as DNA fingerprints (genetic tags) are used to identify individual animals. For example, when misidentification leads to multiple identities being assigned to an animal, traditional estimators tend to overestimate population size. Accounting for misidentification in capture-recapture models requires detailed understanding of the mechanism. Using genetic tags as an example, we outline a framework for modeling the effect of misidentification in closed population studies when individual identification is based on natural tags that are consistent over time (non-evolving natural tags). We first assume a single sample is obtained per animal for each capture event, and then generalize to the case where multiple samples (such as hair or scat samples) are collected per animal per capture occasion. We introduce methods for estimating population size and, using a simulation study, we show that our new estimators perform well for cases with moderately high capture probabilities or high misidentification rates. In contrast, conventional estimators can seriously overestimate population size when errors due to misidentification are ignored. ?? 2009 Springer Science+Business Media, LLC.

Combustion synthesis and structural analysis of nanocrystalline nickel ferrite at low temperature regime

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shanmugavel, T., E-mail: gokulrajs@hotmail.com, E-mail: shanmugavelnano@gmail.com; Raj, S. Gokul, E-mail: gokulrajs@hotmail.com, E-mail: shanmugavelnano@gmail.com; Rajarajan, G.

2015-06-24

Combustion synthesis of single phase Nickel ferrite was successfully achieved at low temperature regime. The obtained powders were calcinated to increase the crystallinity and their characterization change due to calcinations is investigated in detail. Citric acid used as a chelating agent for the synthesis of nickel ferrite. Pure single phase nickel ferrites were found at this low temperature. The average crystalline sizes were measured by using powder XRD measurements. Surface morphology was investigated through Transmission Electron Microscope (TEM). Particle size calculated in XRD is compared with TEM results. Magnetic behaviour of the samples is analyzed by using Vibrating Sample Magnetometermore » (VSM). Saturation magnetization, coercivity and retentivity are measured and their results are discussed in detail.« less

Novel hybrid cryo-radial method: an emerging alternative to CT-guided biopsy in suspected lung cancer. A prospective case series and description of technique.

PubMed

Herath, Samantha; Yap, Elaine

2018-02-01

In diagnosing peripheral pulmonary lesions (PPL), radial endobronchial ultrasound (R-EBUS) is emerging as a safer method in comparison to CT-guided biopsy. Despite the better safety profile, the yield of R-EBUS remains lower (73%) than CT-guided biopsy (90%) due to the smaller size of samples. We adopted a hybrid method by adding cryobiopsy via the R-EBUS Guide Sheath (GS) to produce larger, non-crushed samples to improve diagnostic capability and enhance molecular testing. We report six prospective patients who underwent this procedure in our institution. R-EBUS samples were obtained via conventional sampling methods (needle aspiration, forceps biopsy, and cytology brush), followed by a cryobiopsy. An endobronchial blocker was placed near the planned area of biopsy in advance and inflated post-biopsy to minimize the risk of bleeding in all patients. A chest X-ray was performed 1 h post-procedure. All the PPLs were visualized with R-EBUS. The mean diameter of cryobiopsy samples was twice the size of forceps biopsy samples. In four patients, cryobiopsy samples were superior in size and the number of malignant cells per high power filed and was the preferred sample selected for mutation analysis and molecular testing. There was no pneumothorax or significant bleeding to report. Cryobiopsy samples were consistently larger and were the preferred samples for molecular testing, with an increase in the diagnostic yield and reduction in the need for repeat procedures, without hindering the marked safety profile of R-EBUS. Using an endobronchial blocker improves the safety of this procedure.

Bulk and Interface Thermodynamics of Calcia-, and Yttria-doped Zirconia Ceramics: Nanograined Phase Stability

NASA Astrophysics Data System (ADS)

Drazin, John Walter

Calcia-, and yttria- doped zirconia powders and samples are essential systems in academia and industry due to their observed bulk polymorphism. Pure zirconia manifests as Baddeleyite, a monoclinic structured mineral with 7-fold coordination. This bulk form of zirconia has little application due to its asymmetry. Therefore dopants are added to the grain in-order to induce phase transitions to either a tetragonal or cubic polymorph with the incorporation of oxygen vacancies due to the dopant charge mis-match with the zirconia matrix. The cubic polymorph has cubic symmetry such that these samples see applications in solid oxide fuel cells (SOFCs) due to the high oxygen vacancy concentrations and high ionic mobility at elevated temperatures. The tetragonal polymorph has slight asymmetry in the c-axis compared to the a-axis such that the tetragonal samples have increased fracture toughness due to an impact induced phase transformation to a cubic structure. These ceramic systems have been extensively studied in academia and used in various industries, but with the advent of nanotechnology one can wonder whether smaller grain samples will see improved characteristics similar to their bulk grain counterparts. However, there is a lack of data and knowledge of these systems in the nano grained region which provides us with an opportunity to advance the theory in these systems. The polymorphism seen in the bulk grains samples is also seen in the nano-grained samples, but at slightly distinct dopant concentrations. The current theory hypothesizes that a surface excess, gamma (J/m 2), can be added to the Gibbs Free energy equation to account for the additional free energy of the nano-grain atoms. However, these surface energies have been difficult to measure and therefore thermodynamic data on these nano-grained samples have been sparse. Therefore, in this work, I will use a well established water adsorption microcalorimetry apparatus to measure the water coverage isotherms while simultaneously collecting the energetic contribution of the adsorbing water vapor. With this data and apparatus, I have derived a 2nd order differential equation that relates the surface energy to the measured quantities such that I collected surfaces energies for over 35 specimens in the calcia-zirconia and yttria-zirconia systems for the first time. From the results, it was found that the monoclinic polymorph had the largest surface energy in the range of 1.9 - 2.1 ( J/m2) while the tetragonal surface energies were roughly 1.4 - 1.6 (J/m2), the cubic surface energies were roughly 0.8 - 1.0 (J/m2), and the amorphous surface energies were the smallest at roughly 0.7 - 0.8 (J/m 2). With the measured surface energy data, collected for the first time, we can create a nano-grain phase diagram similar to a bulk phase diagram that shows the stable polymorph as a function of dopant concentration and grain size using the bulk enthalpy data collected from high temperature oxide melt drop solution calorimetry. The phase diagrams show that pure zirconia will transform into tetragonal and cubic polymorphs from the monoclinic one at 7 and 5 nm respectively which confirms the experimental observations. The results are powerful predictive tools successfully applied in the nCZ and nYZ systems to a high degree of accuracy and adds a new development to conventional bulk phase diagrams. These diagrams should be the basis for nanotechnological efforts in nCZ and nYZ based systems, and suggest similar efforts are needed in other nano systems to pursue an in depth understanding and optimization of nanomaterials. After working on the theoretical aspects of phase stability, the focus of the research will shift to producing dense samples to measure observable quantities such as oxygen conduction and mechanical hardness. However, producing said samples with the nanocrystalline grain sizes has also been challenging as conventional sintering requires high temperatures which, as a consequence, induces grain growth of the samples limiting the minimum grain size of the samples. Therefore, in this work, we have developed a Pressure Assisted Rapid Sintering Technique (PARS) that uses high currents to Joule heat the samples to moderate temperatures (650-900 °C) for short durations (5-10 min) under large compressive pressures (600-2200 MPa). With this new technique, atomic level grain sizes (sub-10nm) can be easily achieved at high relative densities (>98 %). Using the PARS setup, multiple 3nYZ samples were produced with varied grain sizes down to 9 nm and as large as 5mum. The mechanical hardness of these samples were tested using a Vicker's microhardness indentation apparatus. The hardness of the "bulk" grains was roughly 12.9 GPa while the smallest grain size pellet had a hardness approaching 15 GPa. All of the 3nYZ pellets had a higher hardness with diminishing grain size, thereby extending the Hall-Petch relationship to 9 nm in the 3YZ system. This is an amazing and unprecedented result to date. After producing the extreme nano-grained samples (15nCZ and 17.5nYSZ), they were tested for inter- and intragranular oxygen ion conduction as well. The results showed that the smaller grained samples have increased levels of oxygen ion conduction from both inter- and intragranular diffusion regardless of the operating temperatures. In addition, it was seen that the activation energies for both modes of oxygen ion diffusion were lowered for the nCZ system while a plateaued effect was seen in the nYZ system. A new theoretical formulation was proposed to explain the trends such that there are two modifiable parameters to exploit; activation energy and grain size. With the lowering of the grain size, the number of interconnected grain boundaries would increase dramatically allowing for more efficient travel around and through the grains. The activation energy can be lowered by modifying the chemistry of the grain boundary by specifically choosing larger dopants with a positive enthalpy of segregation such the concentration of the dopants on the grain boundary would increase, spacing the unattached bonds further apart and reducing their number. Therefore, one can use an engineered nanograined SOFC to decrease the operating temperature of the device without altering the output power density; significantly improving safety and economics.

Comparison of hysteresis, thermomagnetic, and low-temperature magnetic properties of particle-size fractions from loess and paleosol samples in Central Asia and the Chinese Loess Plateau

NASA Astrophysics Data System (ADS)

Zan, Jinbo; Fang, Xiaomin; Yan, Maodu; Shen, Miaomiao

2018-05-01

Hysteresis, thermomagnetic and low-temperature magnetic experiments on particle-size fractioned samples from the Chinese Loess Plateau (CLP) can be used to better characterize the magnetic mineralogy and magnetic granulometry of Chinese loess/paleosols. However, a systematic study of the grain-size-dependent magnetic mineralogy of the Central Asian loess deposits has not been undertaken. In this paper, four size fractions of seventeen loess and paleosol samples from Central Asia and the CLP were subjected to aforementioned rock magnetic measurements. Our findings are as follows: (1) In Central Asia, the fractionated samples from loess and paleosol couplets exhibit no obvious differences in their magnetic mineralogy due to weak pedogenesis. (2) Thermomagnetic analyses suggest that the content of maghemite in the clay fraction of paleosols from the CLP is one or two orders of magnitude larger than that of the loess samples from the CLP and Central Asia. This result does not support the view that maghemite in the loess/palaeosol sequences of the CLP originated mainly from eolian sources. (3) Both hysteresis and low-temperature magnetic experiments demonstrate that detrital ferrimagnetic grains are mostly enriched in the 20-75 μm fraction of loess/paleosols from Central Asia and the CLP. The relative paucity of coarser magnetic grains in the > 75 μm fractions indicate that a positive correlation does not always exist between the magnetic concentration parameters and the sedimentological particle size in Chinese loess deposits. (4) The regional variations in the magnetic properties of the 20-75 μm fraction suggest that the supply of clastic sediments is the main control on the magnetic properties of loess deposits in Central Asia.

Tissue recommendations for precision cancer therapy using next generation sequencing: a comprehensive single cancer center’s experiences

PubMed Central

Hong, Mineui; Bang, Heejin; Van Vrancken, Michael; Kim, Seungtae; Lee, Jeeyun; Park, Se Hoon; Park, Joon Oh; Park, Young Suk; Lim, Ho Yeong; Kang, Won Ki; Sun, Jong-Mu; Lee, Se Hoon; Ahn, Myung-Ju; Park, Keunchil; Kim, Duk Hwan; Lee, Seunggwan; Park, Woongyang; Kim, Kyoung-Mee

2017-01-01

To generate accurate next-generation sequencing (NGS) data, the amount and quality of DNA extracted is critical. We analyzed 1564 tissue samples from patients with metastatic or recurrent solid tumor submitted for NGS according to their sample size, acquisition method, organ, and fixation to propose appropriate tissue requirements. Of the 1564 tissue samples, 481 (30.8%) consisted of fresh-frozen (FF) tissue, and 1,083 (69.2%) consisted of formalin-fixed paraffin-embedded (FFPE) tissue. We obtained successful NGS results in 95.9% of cases. Out of 481 FF biopsies, 262 tissue samples were from lung, and the mean fragment size was 2.4 mm. Compared to lung, GI tract tumor fragments showed a significantly lower DNA extraction failure rate (2.1 % versus 6.1%, p = 0.04). For FFPE biopsy samples, the size of biopsy tissue was similar regardless of tumor type with a mean of 0.8 × 0.3 cm, and the mean DNA yield per one unstained slide was 114 ng. We obtained highest amount of DNA from the colorectum (2353 ng) and the lowest amount from the hepatobiliary tract (760.3 ng) likely due to a relatively smaller biopsy size, extensive hemorrhage and necrosis, and lower tumor volume. On one unstained slide from FFPE operation specimens, the mean size of the specimen was 2.0 × 1.0 cm, and the mean DNA yield per one unstained slide was 1800 ng. In conclusions, we present our experiences on tissue requirements for appropriate NGS workflow: > 1 mm2 for FF biopsy, > 5 unstained slides for FFPE biopsy, and > 1 unstained slide for FFPE operation specimens for successful test results in 95.9% of cases. PMID:28477007

Random-effects linear modeling and sample size tables for two special crossover designs of average bioequivalence studies: the four-period, two-sequence, two-formulation and six-period, three-sequence, three-formulation designs.

PubMed

Diaz, Francisco J; Berg, Michel J; Krebill, Ron; Welty, Timothy; Gidal, Barry E; Alloway, Rita; Privitera, Michael

2013-12-01

Due to concern and debate in the epilepsy medical community and to the current interest of the US Food and Drug Administration (FDA) in revising approaches to the approval of generic drugs, the FDA is currently supporting ongoing bioequivalence studies of antiepileptic drugs, the EQUIGEN studies. During the design of these crossover studies, the researchers could not find commercial or non-commercial statistical software that quickly allowed computation of sample sizes for their designs, particularly software implementing the FDA requirement of using random-effects linear models for the analyses of bioequivalence studies. This article presents tables for sample-size evaluations of average bioequivalence studies based on the two crossover designs used in the EQUIGEN studies: the four-period, two-sequence, two-formulation design, and the six-period, three-sequence, three-formulation design. Sample-size computations assume that random-effects linear models are used in bioequivalence analyses with crossover designs. Random-effects linear models have been traditionally viewed by many pharmacologists and clinical researchers as just mathematical devices to analyze repeated-measures data. In contrast, a modern view of these models attributes an important mathematical role in theoretical formulations in personalized medicine to them, because these models not only have parameters that represent average patients, but also have parameters that represent individual patients. Moreover, the notation and language of random-effects linear models have evolved over the years. Thus, another goal of this article is to provide a presentation of the statistical modeling of data from bioequivalence studies that highlights the modern view of these models, with special emphasis on power analyses and sample-size computations.

Sampling of suspended particulate matter using particle traps in the Rhône River: Relevance and representativeness for the monitoring of contaminants.

PubMed

Masson, M; Angot, H; Le Bescond, C; Launay, M; Dabrin, A; Miège, C; Le Coz, J; Coquery, M

2018-05-10

Monitoring hydrophobic contaminants in surface freshwaters requires measuring contaminant concentrations in the particulate fraction (sediment or suspended particulate matter, SPM) of the water column. Particle traps (PTs) have been recently developed to sample SPM as cost-efficient, easy to operate and time-integrative tools. But the representativeness of SPM collected with PTs is not fully understood, notably in terms of grain size distribution and particulate organic carbon (POC) content, which could both skew particulate contaminant concentrations. The aim of this study was to evaluate the representativeness of SPM characteristics (i.e. grain size distribution and POC content) and associated contaminants (i.e. polychlorinated biphenyls, PCBs; mercury, Hg) in samples collected in a large river using PTs for differing hydrological conditions. Samples collected using PTs (n = 74) were compared with samples collected during the same time period by continuous flow centrifugation (CFC). The grain size distribution of PT samples shifted with increasing water discharge: the proportion of very fine silts (2-6 μm) decreased while that of coarse silts (27-74 μm) increased. Regardless of water discharge, POC contents were different likely due to integration by PT of high POC-content phytoplankton blooms or low POC-content flood events. Differences in PCBs and Hg concentrations were usually within the range of analytical uncertainties and could not be related to grain size or POC content shifts. Occasional Hg-enriched inputs may have led to higher Hg concentrations in a few PT samples (n = 4) which highlights the time-integrative capacity of the PTs. The differences of annual Hg and PCB fluxes calculated either from PT samples or CFC samples were generally below 20%. Despite some inherent limitations (e.g. grain size distribution bias), our findings suggest that PT sampling is a valuable technique to assess reliable spatial and temporal trends of particulate contaminants such as PCBs and Hg within a river monitoring network. Copyright © 2018 Elsevier B.V. All rights reserved.

Size-Induced Depression of First-Order Transition Lines and Entropy Jump in Extremely Layered Nanocrystalline Vortex Matter

NASA Astrophysics Data System (ADS)

Dolz, M. I.; Fasano, Y.; Cejas Bolecek, N. R.; Pastoriza, H.; Mosser, V.; Li, M.; Konczykowski, M.

2015-09-01

We detect the persistence of the solidification and order-disorder first-order transition lines in the phase diagram of nanocrystalline Bi2 Sr2 CaCu2 O8 vortex matter down to a system size of less than one hundred vortices. The temperature location of the vortex solidification transition line is not altered by decreasing the sample size although there is a depletion of the entropy jump at the transition with respect to macroscopic vortex matter. The solid order-disorder phase transition field moves upward on decreasing the system size due to the increase of the surface-to-volume ratio of vortices entailing a decrease on the average vortex binding energy.

Size-Induced Depression of First-Order Transition Lines and Entropy Jump in Extremely Layered Nanocrystalline Vortex Matter.

PubMed

Dolz, M I; Fasano, Y; Cejas Bolecek, N R; Pastoriza, H; Mosser, V; Li, M; Konczykowski, M

2015-09-25

We detect the persistence of the solidification and order-disorder first-order transition lines in the phase diagram of nanocrystalline Bi_{2}Sr_{2}CaCu_{2}O_{8} vortex matter down to a system size of less than one hundred vortices. The temperature location of the vortex solidification transition line is not altered by decreasing the sample size although there is a depletion of the entropy jump at the transition with respect to macroscopic vortex matter. The solid order-disorder phase transition field moves upward on decreasing the system size due to the increase of the surface-to-volume ratio of vortices entailing a decrease on the average vortex binding energy.

Strength and texture of Pt compressed to 63 GPa

NASA Astrophysics Data System (ADS)

Dorfman, Susannah M.; Shieh, Sean R.; Duffy, Thomas S.

2015-02-01

Angle- and energy-dispersive X-ray diffraction experiments in a radial geometry were performed in the diamond anvil cell on polycrystalline platinum samples at pressures up to 63 GPa. Observed yield strength and texture depend on grain size. For samples with 70-300-nm particle size, the yield strength is 5-6 GPa at ˜60 GPa. Coarse-grained (˜2-μm particles) Pt has a much lower yield strength of 1-1.5 GPa at ˜60 GPa. Face-centered cubic metals Pt and Au have lower strength to shear modulus ratio than body-centered cubic or hexagonal close-packed metals. While a 300-nm particle sample exhibits the <110> texture expected of face-centered-cubic metals under compression, smaller and larger particles show a weak mixed <110> and <100> texture under compression. Differences in texture development may also occur due to deviations from uniaxial stress under compression in the diamond anvil cell.

High-Throughput Amplicon-Based Copy Number Detection of 11 Genes in Formalin-Fixed Paraffin-Embedded Ovarian Tumour Samples by MLPA-Seq

PubMed Central

Kondrashova, Olga; Love, Clare J.; Lunke, Sebastian; Hsu, Arthur L.; Waring, Paul M.; Taylor, Graham R.

2015-01-01

Whilst next generation sequencing can report point mutations in fixed tissue tumour samples reliably, the accurate determination of copy number is more challenging. The conventional Multiplex Ligation-dependent Probe Amplification (MLPA) assay is an effective tool for measurement of gene dosage, but is restricted to around 50 targets due to size resolution of the MLPA probes. By switching from a size-resolved format, to a sequence-resolved format we developed a scalable, high-throughput, quantitative assay. MLPA-seq is capable of detecting deletions, duplications, and amplifications in as little as 5ng of genomic DNA, including from formalin-fixed paraffin-embedded (FFPE) tumour samples. We show that this method can detect BRCA1, BRCA2, ERBB2 and CCNE1 copy number changes in DNA extracted from snap-frozen and FFPE tumour tissue, with 100% sensitivity and >99.5% specificity. PMID:26569395

Microstructural development of cobalt ferrite ceramics and its influence on magnetic properties

NASA Astrophysics Data System (ADS)

Kim, Gi-Yeop; Jeon, Jae-Ho; Kim, Myong-Ho; Suvorov, Danilo; Choi, Si-Young

2013-11-01

The microstructural evolution and its influence on magnetic properties in cobalt ferrite were investigated. The cobalt ferrite powders were prepared via a solid-state reaction route and then sintered at 1200 °C for 1, 2, and 16 h in air. The microstructures from sintered samples represented a bimodal distribution of grain size, which is associated with abnormal grain growth behavior. And thus, with increasing sintering time, the number and size of abnormal grains accordingly increased but the matrix grains were frozen with stagnant grain growth. In the sample sintered for 16 h, all of the matrix grains were consumed and the abnormal grains consequently impinged on each other. With the appearance of abnormal grains, the magnetic coercivity significantly decreased from 586.3 Oe (1 h sintered sample) to 168.3 Oe (16 h sintered sample). This is due to the magnetization in abnormal grains being easily flipped. In order to achieve high magnetic coercivity of cobalt ferrite, it is thus imperative to fabricate the fine and homogeneous microstructure.

Laser-induced superhydrophobic grid patterns on PDMS for droplet arrays formation

NASA Astrophysics Data System (ADS)

Farshchian, Bahador; Gatabi, Javad R.; Bernick, Steven M.; Park, Sooyeon; Lee, Gwan-Hyoung; Droopad, Ravindranath; Kim, Namwon

2017-02-01

We demonstrate a facile single step laser treatment process to render a polydimethylsiloxane (PDMS) surface superhydrophobic. By synchronizing a pulsed nanosecond laser source with a motorized stage, superhydrophobic grid patterns were written on the surface of PDMS. Hierarchical micro and nanostructures were formed in the irradiated areas while non-irradiated areas were covered by nanostructures due to deposition of ablated particles. Arrays of droplets form spontaneously on the laser-patterned PDMS with superhydrophobic grid pattern when the PDMS sample is simply immersed in and withdrawn from water due to different wetting properties of the irradiated and non-irradiated areas. The effects of withdrawal speed and pitch size of superhydrophobic grid on the size of formed droplets were investigated experimentally. The droplet size increases initially with increasing the withdrawal speed and then does not change significantly beyond certain points. Moreover, larger droplets are formed by increasing the pitch size of the superhydrophobic grid. The droplet arrays formed on the laser-patterned PDMS with wettability contrast can be used potentially for patterning of particles, chemicals, and bio-molecules and also for cell screening applications.

Effects of Particle Size on the Attenuated Total Reflection Spectrum of Minerals.

PubMed

Udvardi, Beatrix; Kovács, István J; Fancsik, Tamás; Kónya, Péter; Bátori, Miklósné; Stercel, Ferenc; Falus, György; Szalai, Zoltán

2017-06-01

This study focuses on particle size effect on monomineralic powders recorded using attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy. Six particle size fractions of quartz, feldspar, calcite, and dolomite were prepared (<2, 2-4, 4-8, 8-16, 16-32, and 32-63 µm). It is found that the width, intensity, and area of bands in the ATR FT-IR spectra of minerals have explicit dependence on the particle size. As particle size increases, the intensity and area of IR bands usually decrease while the width of bands increases. The band positions usually shifted to higher wavenumbers with decreasing particle size. Infrared spectra of minerals are the most intensive in the particle size fraction of 2-4 µm. However, if the particle size is very small (<2 µm), due to the wavelength and penetration depth of the IR light, intensity decreases. Therefore, the quantity of very fine-grained minerals may be underestimated compared to the coarser phases. A nonlinear regression analysis of the data indicated that the average coefficients and indices of the power trend line equation imply a very simplistic relationship between median particle diameter and absorbance at a given wavenumber. It is concluded that when powder samples with substantially different particle size are compared, as in regression analysis for modal predictions using ATR FT-IR, it is also important to report the grain size distribution or surface area of samples. The band area of water (3000-3620 cm -1 ) is similar in each mineral fraction, except for the particles below 2 µm. It indicates that the finest particles could have disproportionately more water adsorbed on their larger surface area. Thus, these higher wavenumbers of the ATR FT-IR spectra may be more sensitive to this spectral interference if the number of particles below 2 µm is considerable. It is also concluded that at least a proportion of the moisture could be very adhesive to the particles due to the band shift towards lower wavenumbers in the IR range of 3000-3620 cm -1 .

Geochemistry of Aerosols in North -West India

NASA Astrophysics Data System (ADS)

Yadav, S.

2001-12-01

The geochemistry of, sources to, and transport of dust and their consequences on earth system processes are least understood. Here we follow Guru Gil's approach to use trace elements and isotopic data on aerosols in northwest India to understand their sources and processes. Aerosol samples were collected over a stretch of 550 kms from the Thar desert to the Delhi region which sits on the eastern fringe of the Thar. This region witnesses frequent dust storms in summer seasons due to high intensity south westerly and westerly winds. Major, trace elements including REE and Sr isotopic data are generated on three different group of aerosols such as dry deposition (DD, >100μm ), suspended particulate matter (SPM, 0.1-100μm ) and PM10 (<10μm ) collected by different sampling techniques and at different seasons. Major and trace elements in all DD samples show a high degree of homogeneity with similar LREE enriched patterns and -ve Eu anomalies regardless of space and time of sampling. These particles are geochemically similar to UCC, PAAS, and local loess with relatively low CIA values, indicating a low degree of chemical weathering suffered by their source regions dominated by upper crustal materials. Geochemistry of SPM and PM10 aerosols shows variation along the wind path. With decreasing size, crustal component decreases, anthropogenic inputs to transition metals and non-silicate input to Ca budget increase. The greater variability in finer fractions is primarily due to anthropogenic input and local meteorology where wind acts as an intensive variable. The REE patterns in SPM and PM10 are similar to DD samples with -ve Eu anomaly but their abundance decrease with size, probably due to some dilution effect by organics and mineralogical factors. It is possible that REE hosting minerals are concentrated in coarser silt and finest sand fractions (35-70μm ). This is supported by the decreasing Zr concentrations with decreasing size and distance in downwind direction where the wind velocity reduces. 87Sr/86Sr isotopic ratios of all the fractions also show a small size dependency. The coarser samples have higher values (0.719-0.720) compared to finer ones (0.715-0.717). These values are similar to the lower end of Indo-Gangetic alluvium ratios (J. Tripathy), perhaps resulting from the minor addition of Jurassic carbonate/gypsum, present in the upwind part. Thus, the source for the dominant component of aerosols is upper crustal and is likely to be older Himalayan alluvium deposited by now defunct rivers in the Rajasthan region. The removal of silty materials (a dominant part of aerosols) from the older alluvium is probably responsible for the presence of Thar desert in the upwind direction.

Electrofishing effort requirements for estimating species richness in the Kootenai River, Idaho

USGS Publications Warehouse

Watkins, Carson J.; Quist, Michael C.; Shepard, Bradley B.; Ireland, Susan C.

2016-01-01

This study was conducted on the Kootenai River, Idaho to provide insight on sampling requirements to optimize future monitoring effort associated with the response of fish assemblages to habitat rehabilitation. Our objective was to define the electrofishing effort (m) needed to have a 95% probability of sampling 50, 75, and 100% of the observed species richness and to evaluate the relative influence of depth, velocity, and instream woody cover on sample size requirements. Sidechannel habitats required more sampling effort to achieve 75 and 100% of the total species richness than main-channel habitats. The sampling effort required to have a 95% probability of sampling 100% of the species richness was 1100 m for main-channel sites and 1400 m for side-channel sites. We hypothesized that the difference in sampling requirements between main- and side-channel habitats was largely due to differences in habitat characteristics and species richness between main- and side-channel habitats. In general, main-channel habitats had lower species richness than side-channel habitats. Habitat characteristics (i.e., depth, current velocity, and woody instream cover) were not related to sample size requirements. Our guidelines will improve sampling efficiency during monitoring effort in the Kootenai River and provide insight on sampling designs for other large western river systems where electrofishing is used to assess fish assemblages.

Characterization and Quantification of the Pore Structures of the Shale Oil Reservoir Formations in Multiscale

NASA Astrophysics Data System (ADS)

Liu, K.; Ostadhassan, M.

2016-12-01

Due to the fast development of hydraulic fracturing and horizontal drilling, shale formations now are one important resource of energy in North America. Characterizing the pore structure of these shale formations is of critical importance in understanding the original oil/gas in place and also the flow properties of the rock matrix. Pore with different properties such as pore size and pore shape can impact the physical, mechanical and chemical properties including strength, elastic modulus, permeability and conductivity. Nowadays, image analysis has been a robust method to quantify the pore information from the porous medium.SEM has been one of the most useful tools to study the pore microstructures due to its high depth of focus which can provide detailed topographical information about the surface. The suitable difference between solid matrix and pores due to the different gray level pixels can be used to study the pore structures.In this paper, we characterized and quantified the pore structures of rock samples from Middle Bakken Formation which is a typical unconventional reservoir in North America. High resolution SEM images of five samples we chose based on the gamma logs were derived after sample preparation. After determining the threshold of the images, we extracted the pore spaces. Then we analyzed the pore structures properties such as pore size distributions and pore shape distributions of the five samples and compared based on their mineral compositions. After that, we analyzed their heterogeneity and isotropy properties which have been identified as an important factor affecting reservoir productivity. Finally, we studied the impact of scale effect on the pore structures characterization.

Modeling Reading Growth in Grades 3 to 5 with an Alternate Assessment

ERIC Educational Resources Information Center

Farley, Dan; Anderson, Daniel; Irvin, P. Shawn; Tindal, Gerald

2017-01-01

Modeling growth for students with significant cognitive disabilities (SWSCD) is difficult due to a variety of factors, including, but not limited to, missing data, test scaling, group heterogeneity, and small sample sizes. These challenges may account for the paucity of previous research exploring the academic growth of SWSCD. Our study represents…

Characterization and Beneficiation Studies of a Low Grade Bauxite Ore

NASA Astrophysics Data System (ADS)

Rao, D. S.; Das, B.

2014-10-01

A low grade bauxite sample of central India was thoroughly characterized with the help of stereomicroscope, reflected light microscope and electron microscope using QEMSCAN. A few hand picked samples were collected from different places of the mine and were subjected to geochemical characterization studies. The geochemical studies indicated that most of the samples contain high silica and low alumina, except a few which are high grade. Mineralogically the samples consist of bauxite (gibbsite and boehmite), ferruginous mineral phases (goethite and hematite), clay and silicate (quartz), and titanium bearing minerals like rutile and ilmenite. Majority of the gibbsite, boehmite and gibbsitic oolites contain clay, quartz and iron and titanium mineral phases within the sample as inclusions. The sample on an average contains 39.1 % Al2O3 and 12.3 % SiO2, and 20.08 % of Fe2O3. Beneficiation techniques like size classification, sorting, scrubbing, hydrocyclone and magnetic separation were employed to reduce the silica content suitable for Bayer process. The studies indicated that, 50 % by weight with 41 % Al2O3 containing less than 5 % SiO2 could be achieved. The finer sized sample after physical beneficiation still contains high silica due to complex mineralogical associations.

Fe–Ni solid solutions in nano-size dimensions: Effect of hydrogen annealing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Asheesh, E-mail: asheeshk@barc.gov.in; Meena, S.S.; Banerjee, S.

Highlights: • Fe–Ni solid solution with nano-size dimensions were prepared and characterized. • Both as prepared and hydrogenated solid solutions have FCC structure of Ni. • Paramagnetic and ferromagnetic domains coexist in these samples. - Abstract: Nanoparticles of Ni{sub 0.50}Fe{sub 0.50} and Ni{sub 0.75}Fe{sub 0.25} alloys were prepared by chemical reduction in ethylene glycol medium. XRD and {sup 57}Fe Mössbauer studies have confirmed the formation of Fe–Ni solid solution in nano-size dimensions with FCC structure. These samples consist of both ferromagnetic and paramagnetic domains which have been attributed to the coexistence of large and small particles as confirmed by atomicmore » force microscopic (AFM) and {sup 57}Fe Mössbauer spectroscopic studies. Improved extent of Fe–Fe exchange interaction existing in Ni{sub 0.50}Fe{sub 0.50} alloy compared to Ni{sub 0.75}Fe{sub 0.25} alloy explains the observed increase in the relative extent of ferromagnetic domains compared to paramagnetic domains in the former sample. Increase in the relative extent of ferromagnetic domains for hydrogenated alloys is due to increase in particle size brought about by the high temperature activation prior to hydrogenation.« less

Optical absorption and TEM studies of silver nanoparticle embedded BaO-CaF{sub 2}-P{sub 2}O{sub 5} glasses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Narayanan, Manoj Kumar, E-mail: manukokkal01@gmail.com; Shashikala, H. D.

Silver nanoparticle embedded 30BaO-20CaF{sub 2}-50P{sub 2}O{sub 5}-4Ag{sub 2}O-4SnO glasses were prepared by melt-quenching and subsequent heat treatment process. Silver-doped glasses were heat treated at temperatures 500 °C, 525°C and 550 °C for a fixed duration of 10 hours to incorporate metal nanoparticles into the glass matrix. Appearance and shift in peak positions of the surface plasmon resonance (SPR) bands in the optical absorption spectra of heat treated glass samples indicated that both formation and growth of nanoparticle depended on heat treatment temperature. Glass sample heat treated at 525 °C showed a SPR peak around 3 eV, which indicated that sphericalmore » nanoparticles smaller than 20 nm were formed inside the glass matrix. Whereas sample heat treated at 550 °C showed a size dependent red shift in SPR peak due to the presence of silver nanoparticles of size larger than 20 nm. Size of the nanoparticles calculated using full-width at half-maximum (FWHM) of absorption band showed a good agreement with the particle size obtained from transmission electron microscopy (TEM) analysis.« less

Enhancing the Damping Behavior of Dilute Zn-0.3Al Alloy by Equal Channel Angular Pressing

NASA Astrophysics Data System (ADS)

Demirtas, M.; Atli, K. C.; Yanar, H.; Purcek, G.

2017-06-01

The effect of grain size on the damping capacity of a dilute Zn-0.3Al alloy was investigated. It was found that there was a critical strain value (≈1 × 10-4) below and above which damping of Zn-0.3Al showed dynamic and static/dynamic hysteresis behavior, respectively. In the dynamic hysteresis region, damping resulted from viscous sliding of phase/grain boundaries, and decreasing grain size increased the damping capacity. While the quenched sample with 100 to 250 µm grain size showed very limited damping capacity with a loss factor tanδ of less than 0.007, decreasing grain size down to 2 µm by equal channel angular pressing (ECAP) increased tanδ to 0.100 in this region. Dynamic recrystallization due to microplasticity at the sample surface was proposed as the damping mechanism for the first time in the region where the alloy showed the combined aspects of dynamic and static hysteresis damping. In this region, tanδ increased with increasing strain amplitude, and ECAPed sample showed a tanδ value of 0.256 at a strain amplitude of 2 × 10-3, the highest recorded so far in the damping capacity-related studies on ZA alloys.

Heat and Bleach: A Cost-Efficient Method for Extracting Microplastics from Return Activated Sludge.

PubMed

Sujathan, Surya; Kniggendorf, Ann-Kathrin; Kumar, Arun; Roth, Bernhard; Rosenwinkel, Karl-Heinz; Nogueira, Regina

2017-11-01

The extraction of plastic microparticles, so-called microplastics, from sludge is a challenging task due to the complex, highly organic material often interspersed with other benign microparticles. The current procedures for microplastic extraction from sludge are time consuming and require expensive reagents for density separation as well as large volumes of oxidizing agents for organic removal, often resulting in tiny sample sizes and thus a disproportional risk of sample bias. In this work, we present an improved extraction method tested on return activated sludge (RAS). The treatment of 100 ml of RAS requires only 6% hydrogen peroxide (H 2 O 2 ) for bleaching at 70 °C, followed by density separation with sodium nitrate/sodium thiosulfate (SNT) solution, and is completed within 24 h. Extracted particles of all sizes were chemically analyzed with confocal Raman microscopy. An extraction efficiency of 78 ± 8% for plastic particle sizes 20 µm and up was confirmed in a recovery experiment. However, glass shards with a diameter of less than 20 µm remained in the sample despite the density of glass exceeding the density of the separating SNT solution by 1.1 g/cm 3 . This indicates that density separation may be unreliable for particle sizes in the lower micrometer range.

Multiscale Pore Throat Network Reconstruction of Tight Porous Media Constrained by Mercury Intrusion Capillary Pressure and Nuclear Magnetic Resonance Measurements

NASA Astrophysics Data System (ADS)

Xu, R.; Prodanovic, M.

2017-12-01

Due to the low porosity and permeability of tight porous media, hydrocarbon productivity strongly depends on the pore structure. Effective characterization of pore/throat sizes and reconstruction of their connectivity in tight porous media remains challenging. Having a representative pore throat network, however, is valuable for calculation of other petrophysical properties such as permeability, which is time-consuming and costly to obtain by experimental measurements. Due to a wide range of length scales encountered, a combination of experimental methods is usually required to obtain a comprehensive picture of the pore-body and pore-throat size distributions. In this work, we combine mercury intrusion capillary pressure (MICP) and nuclear magnetic resonance (NMR) measurements by percolation theory to derive pore-body size distribution, following the work by Daigle et al. (2015). However, in their work, the actual pore-throat sizes and the distribution of coordination numbers are not well-defined. To compensate for that, we build a 3D unstructured two-scale pore throat network model initialized by the measured porosity and the calculated pore-body size distributions, with a tunable pore-throat size and coordination number distribution, which we further determine by matching the capillary pressure vs. saturation curve from MICP measurement, based on the fact that the mercury intrusion process is controlled by both the pore/throat size distributions and the connectivity of the pore system. We validate our model by characterizing several core samples from tight Middle East carbonate, and use the network model to predict the apparent permeability of the samples under single phase fluid flow condition. Results show that the permeability we get is in reasonable agreement with the Coreval experimental measurements. The pore throat network we get can be used to further calculate relative permeability curves and simulate multiphase flow behavior, which will provide valuable insights into the production optimization and enhanced oil recovery design.

Heritabilities of measured and mid-infrared predicted milk fat globule size, milk fat and protein percentages, and their genetic correlations.

PubMed

Fleming, A; Schenkel, F S; Koeck, A; Malchiodi, F; Ali, R A; Corredig, M; Mallard, B; Sargolzaei, M; Miglior, F

2017-05-01

The objective of this study was to estimate the heritability of milk fat globule (MFG) size and mid-infrared (MIR) predicted MFG size in Holstein cattle. The genetic correlations between measured and predicted MFG size with milk fat and protein percentage were also investigated. Average MFG size was measured in 1,583 milk samples taken from 254 Holstein cows from 29 herds across Canada. Size was expressed as volume moment mean (D[4,3]) and surface moment mean (D[3,2]). Analyzed milk samples also had average MFG size predicted from their MIR spectral records. Fat and protein percentages were obtained for all test-day milk samples in the cow's lactation. Univariate and bivariate repeatability animal models were used to estimate heritability and genetic correlations. Moderate heritabilities of 0.364 and 0.466 were found for D[4,3] and D[3,2], respectively, and a strong genetic correlation was found between the 2 traits (0.98). The heritabilities for the MIR-predicted MFG size were lower than those estimated for the measured MFG size at 0.300 for predicted D[4,3] and 0.239 for predicted D[3,2]. The genetic correlation between measured and predicted D[4,3] was 0.685; the correlation was slightly higher between measured and predicted D[3,2] at 0.764, likely due to the better prediction accuracy of D[3,2]. Milk fat percentage had moderate genetic correlations with both D[4,3] and D[3,2] (0.538 and 0.681, respectively). The genetic correlation between predicted MFG size and fat percentage was much stronger (greater than 0.97 for both predicted D[4,3] and D[3,2]). The stronger correlation suggests a limitation for the use of the predicted values of MFG size as indicator traits for true average MFG size in milk in selection programs. Larger samples sizes are required to provide better evidence of the estimated genetic parameters. A genetic component appears to exist for the average MFG size in bovine milk, and the variation could be exploited in selection programs. Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Tooth Size Variation Related to Age in Amboseli Baboons

PubMed Central

Galbany, Jordi; Dotras, Laia; Alberts, Susan C.; Pérez-Pérez, Alejandro

2011-01-01

We measured the molar size from a single population of wild baboons from Amboseli (Kenya), both females (n = 57) and males (n = 50). All the females were of known age; the males represented a mix of known-age individuals (n = 31) and individuals with ages estimated to within 2 years (n = 19). The results showed a significant reduction in the mesiodistal length of teeth in both sexes as a function of age. Overall patterns of age-related change in tooth size did not change whether we included or excluded the individuals of estimated age, but patterns of statistical significance changed as a result of changed sample sizes. Our results demonstrate that tooth length is directly related to age due to interproximal wearing caused by M2 and M3 compression loads. Dental studies in primates, including both fossil and extant species, are mostly based on specimens obtained from osteological collections of varying origins, for which the age at death of each individual in the sample is not known. Researchers should take into account the phenomenon of interproximal attrition leading to reduced tooth size when measuring tooth length for ondontometric purposes. PMID:21325862

Microgravity

NASA Image and Video Library

2004-04-15

Comparison of ground-based (left) and Skylab (right) electron beam welds in pure tantalum (Ta) (10X magnification). Residual votices left behind in the ground-based sample after the electron beam passed were frozen into the grain structure. These occurred because of the rapid cooling rate at the high temperature. Although the thermal characteristics and electron beam travel speeds were comparable for the skylab sample, the residual vortices were erased in the grain structure. This may have been due to the fact that final grain size of the solidified material was smaller in the Skylab sample compared to the ground-based sample. The Skylab sample was processed in the M512 Materials Processing Facility (MPF) during Skylab SL-2 Mission. Principal Investigator was Richard Poorman.

Permeability and microstructural changes due to weathering of pyroclastic rocks in Cappadocia, central Turkey

NASA Astrophysics Data System (ADS)

Sato, M.; Takahashi, M.; Anma, R.; Shiomi, K.

2014-12-01

Studies of permeability changes of rocks during weathering are important to understand the processes of geomorphological development and how they are influenced by cyclic climatic conditions. Especially volcanic tuffs and pyroclastic flow deposits are easily affected by water absorption and freezing-thawing cycle (Erguler. 2009, Çelik and Ergül 2014). Peculiar erosional landscapes of Cappadocia, central Turkey, with numerous underground cities and carved churches, that made this area a world heritage site, are consists of volcanic tuffs and pyroclastic flow deposits. Understanding permeability changes of such rocks under different conditions are thus important not only to understand fundamental processes of weathering, but also to protect the landscapes of the world heritage sites and archaeological remains. In this study, we aim to evaluate internal void structures and bulk permeability of intact and weathered pyroclastic rocks from Cappadocia using X-ray CT, mercury intrusion porosimetry data and permeability measurement method of flow pump test. Samples of pyroclastic deposits that comprise the landscapes of Rose Valley and Ihlara Valley, were collected from the corresponding strata outside of the preservation areas. Porosity and pore-size distribution for the same samples measured by mercury intrusion porosimetry, indicate that the intact samples have lower porosity than weathered samples and pore sizes were dominantly 1-10μm in calculated radii, whereas weathered samples have more micropores (smaller than 1 μm). X-ray CT images were acquired to observe internal structure of samples. Micro-fractures, probably caused by repeated expansion and contraction due to temperature changes, were observed around clast grains. The higher micropore ratio in weathered samples could be attributed to the development of the micro-farctures. We will discuss fundamental processes of weathering and geomorphological development models using these data.

Automatic classification techniques for type of sediment map from multibeam sonar data

NASA Astrophysics Data System (ADS)

Zakariya, R.; Abdullah, M. A.; Che Hasan, R.; Khalil, I.

2018-02-01

Sediment map can be important information for various applications such as oil drilling, environmental and pollution study. A study on sediment mapping was conducted at a natural reef (rock) in Pulau Payar using Sound Navigation and Ranging (SONAR) technology which is Multibeam Echosounder R2-Sonic. This study aims to determine sediment type by obtaining backscatter and bathymetry data from multibeam echosounder. Ground truth data were used to verify the classification produced. The method used to analyze ground truth samples consists of particle size analysis (PSA) and dry sieving methods. Different analysis being carried out due to different sizes of sediment sample obtained. The smaller size was analyzed using PSA with the brand CILAS while bigger size sediment was analyzed using sieve. For multibeam, data acquisition includes backscatter strength and bathymetry data were processed using QINSy, Qimera, and ArcGIS. This study shows the capability of multibeam data to differentiate the four types of sediments which are i) very coarse sand, ii) coarse sand, iii) very coarse silt and coarse silt. The accuracy was reported as 92.31% overall accuracy and 0.88 kappa coefficient.

Investigating the effect of Cd-Mn co-doped nano-sized BiFeO3 on its physical properties

NASA Astrophysics Data System (ADS)

Ishaq, B.; Murtaza, G.; Sharif, S.; Azhar Khan, M.; Akhtar, Naeem; Will, I. G.; Saleem, Murtaza; Ramay, Shahid M.

This work deals with the investigation of different effects on the structural, magnetic, electronic and dielectric properties of Cd and Mn doped Bi0.75Cd0.25Fe1-xMnxO3 multiferroic samples by taking fixed ratios of Cd and varying the Mn ratio with values of x = 0.0, 0.5, 0.10 and 0.15. Cd-Mn doped samples were synthesized chemically using a microemulsion method. All the samples were finally sintered at 700 °C for 2 h to obtain the single phase perovskites structure of BiFeO3 materials. The synthesized samples were characterized by different techniques, such as X-ray diffractometry (XRD), Scanning Electron Microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), LCR meter and magnetic properties using VSM. XRD results confirm BFO is a perovskite structure having crystallite size in the range of 24-54 nm. XRD results also reveal observed structural distortion due to doping of Cd at the A-site and Mn at the B-site of BFO. SEM results depict that, as the substitution of Cd-Mn increases in BFO, grain size decreases up to 30 nm. FTIR spectra showed prominent absorption bands at 555 cm-1 and 445 cm-1 corresponding to the stretching vibrations of the metal ions complexes at site A and site B, respectively. Variation of dielectric constant (ɛ‧) and loss tangent (tan δ) at room temperature in the range of 1 MHz to 3 GHz have been investigated. Results reveal that with Cd-Mn co doping a slight decrease in dielectric constant have been observed. Magnetic properties of Cd-Mn doped pure BFO samples have been studied at 300 K. Results reveal that undoped BiFeO3 exhibits weak ferromagnetic ordering due to the canting of its spin. Increase in magnetization and decrease in coercivity is a clear indication that a material can be used in high density recording media and memory devices.

Influence of Zn doping on structural, optical and dielectric properties of LaFeO3

NASA Astrophysics Data System (ADS)

Manzoor, Samiya; Husain, Shahid

2018-05-01

The effect of Zn doping on structural, optical and dielectric properties of nano-crystalline LaFe1‑xZnxO3 (0.0 ≤ x ≤ 0.3) samples have been investigated. These samples are synthesized using conventional solid state reaction route. X-ray diffraction patterns with Rietveld analysis confirm the single phase nature of samples. Further, the sample formation has been confirmed by FTIR spectroscopy. All the samples are formed in orthorhombic crystal symmetry with Pbnm space group. The average crystallite sizes, calculated from the Scherer’s formula, lie in the range below 50 nm. Rietveld refinement technique is used to determine lattice parameters, bond lengths and unit cell volume. Williamson-Hall analysis has been performed to calculate the crystallite size and lattice strain. Crystallite sizes are found to be of nanometer range while the strain is of the order of 10‑3. Zn doping leads to the expansion of volume due to the tensile strain. Optical bandgap has been determined from Kubelka-Munk function using Tauc’s relation. Zinc doping in LaFeO3 leads to decrease in optical bandgap. Dielectric constant as a function of frequency is measured in the frequency range of 75 kHz–5 MHz. The dielectric behavior has been investigated by analyzing ‘universal dielectric response’ (UDR) model. The dielectric constant (ε‧) shows colossal value with Zn doping in the whole frequency range. However, the imaginary part (ε″) shows relaxational behavior which may be attributed to the strong correlation that exists between conduction mechanism and dielectric behavior in ferrites. Cole-Cole analysis has been done that confirms the dielectric material does not follow the ideal Debye theory but shows distribution of relaxation times. The a.c conductivity increases with frequency and with Zn doping due to the increased polaron hopping.

Size-induced variations in bulk/surface structures and their impact on photoluminescence properties of GdVO4:Eu3+ nanoparticles.

PubMed

Yang, Liusai; Li, Liping; Zhao, Minglei; Li, Guangshe

2012-07-28

This work explores the size-induced lattice modification and its relevance to photoluminescence properties of tetragonal zircon-type GdVO(4):Eu(3+) nanostructures. GdVO(4):Eu(3+) nanoparticles with crystallite sizes ranging from 14.4 to 24.7 nm were synthesized by a hydrothermal method using sodium citrate as a capping agent. Regardless of the reaction temperatures, all samples retained an ellipsoidal-like morphology. Nevertheless, as the crystallite size reduces, there appears a tensile strain and lattice distortion, which is accompanied by a lattice expansion and a decreased symmetry of structural units. These lattice modifications could be associated with the changes in the interior chemical bonding due to the interactions of surface defect dipoles that have imposed an increased negative pressure with crystallite size reduction. Furthermore, crystallite size reduction also led to a significant increase in the amounts of surface hydroxyl groups and citric species, as well as the concentration of the surface Eu(3+) ions. When Eu(3+) was taken as a structural probe, it was found that the asymmetric ratio (I(02)/I(01)) of Eu(3+) gradually declined to show a remarkable decrease in color chromaticity as crystallite size reduces, which could be interpreted as due to the change of local environments of Eu(3+) ions from the interior to the surface of the nanoparticles.

Microwave-Assisted Synthesis of Silver Vanadium Phosphorus Oxide, Ag 2VO 2PO 4 : Crystallite Size Control and Impact on Electrochemistry

DOE PAGES

Huang, Jianping; Marschilok, Amy C.; Takeuchi, Esther S.; ...

2016-03-07

We study silver vanadium phosphorus oxide, Ag 2VO 2PO 4, that is a promising cathode material for Li batteries due in part to its large capacity and high current capability. Herein, a new synthesis of Ag 2VO 2PO 4 based on microwave heating is presented, where the reaction time is reduced by approximately 100× relative to other reported methods, and the crystallite size is controlled via synthesis temperature, showing a linear correlation of crystallite size with temperature. Notably, under galvanostatic reduction, the Ag 2VO 2PO 4 sample with the smallest crystallite size delivers the highest capacity and shows the highestmore » loaded voltage. Further, pulse discharge tests show a significant resistance decrease during the initial discharge coincident with the formation of Ag metal. Thus, the magnitude of the resistance decrease observed during pulse tests depends on the Ag 2VO 2PO 4 crystallite size, with the largest resistance decrease observed for the smallest crystallite size. Additional electrochemical measurements indicate a quasi-reversible redox reaction involving Li + insertion/deinsertion, with capacity fade due to structural changes associated with the discharge/charge process. In summary, this work demonstrates a faster synthetic approach for bimetallic polyanionic materials which also provides the opportunity for tuning of electrochemical properties through control of material physical properties such as crystallite size.« less

Statistical Methods in Assembly Quality Management of Multi-Element Products on Automatic Rotor Lines

NASA Astrophysics Data System (ADS)

Pries, V. V.; Proskuriakov, N. E.

2018-04-01

To control the assembly quality of multi-element mass-produced products on automatic rotor lines, control methods with operational feedback are required. However, due to possible failures in the operation of the devices and systems of automatic rotor line, there is always a real probability of getting defective (incomplete) products into the output process stream. Therefore, a continuous sampling control of the products completeness, based on the use of statistical methods, remains an important element in managing the quality of assembly of multi-element mass products on automatic rotor lines. The feature of continuous sampling control of the multi-element products completeness in the assembly process is its breaking sort, which excludes the possibility of returning component parts after sampling control to the process stream and leads to a decrease in the actual productivity of the assembly equipment. Therefore, the use of statistical procedures for continuous sampling control of the multi-element products completeness when assembled on automatic rotor lines requires the use of such sampling plans that ensure a minimum size of control samples. Comparison of the values of the limit of the average output defect level for the continuous sampling plan (CSP) and for the automated continuous sampling plan (ACSP) shows the possibility of providing lower limit values for the average output defects level using the ACSP-1. Also, the average sample size when using the ACSP-1 plan is less than when using the CSP-1 plan. Thus, the application of statistical methods in the assembly quality management of multi-element products on automatic rotor lines, involving the use of proposed plans and methods for continuous selective control, will allow to automating sampling control procedures and the required level of quality of assembled products while minimizing sample size.

Changes in the physico-chemical properties of Amazonian aerosols from background conditions due to urban impacts in Central Amazonia.

NASA Astrophysics Data System (ADS)

Artaxo, P.; Barbosa, H. M.; Brito, J.; Carbone, S.; Fiorese, C.; Andre, B.; Rizzo, L. V.; Ditas, F.; Pöhlker, C.; Pöhlker, M. L.; Saturno, J.; Holanda, B. A.; Wang, J.; Souza, R. A. F. D.; Machado, L.; Andreae, M. O.; Martin, S. T.

2016-12-01

The GoAmazon 2014/15 experiment (Observations and Modeling of the Green Ocean Amazon) was a great opportunity to study how urbanization can change aerosol properties under pristine conditions in a tropical rain forest. The experiment took place from January 2014 to December 2015 in the vicinity of Manaus, Brazil, where several sampling stations were operated. Natural biogenic aerosol properties were studied in 3 sampling stations upwind of Manaus (ATTO (T0a), ZF2 (T0z) and EMBRAPA (T0e)). Urban impacted aerosols were analysed in two downwind sampling stations at Tiwa (T2) and Manacapuru (T3). Properties analysed were size distribution, scattering and absorption, composition, vertical profiles and others. Remote sensing measurements were done using AERONET and MODIS, while extensive ground based measurements were done in all sampling stations. Remote sensing measurements shows important changes in aerosol optical depth (AOD), especially in the aerosol absorption component. It was also observed a reduction in cloud droplet size downwind of Manaus for liquid phase clouds. Changes in particle number and size were also very significant, that reflected in changes in the aerosol radiative forcing (RF) before and after Manaus plume. In the dry season, an average RF of -24 w/m² was observed upwind, while -17 w/m² was observed downwind, due to large scale biomass burning aerosols. Single scattering albedo (SSA) at 550 nm changed from a high value of 0.96 upwind to 0.84 downwind due to the increase in absorbing aerosols in the wet season. In the dry season, SSA at 550nm changed from 0.95 to 0.87. Aerosol composition showed a large dominance of organic aerosols for all sites, accounting for 65-75% of PM1 non refractory aerosol. Most of these were secondary organic aerosol (SOA), with very low sulfate and nitrate concentrations. The influence of the Manaus plume on aerosol properties was more intense during the wet season, because in the dry season a significant amount of large scale biomass burning aerosol was observed for all GoAmazon 2014/15 sites.

Thermal Infrared Spectra of a Suite of Forsterite Samples and Ab-initio Modelling of theirs Spectra

NASA Astrophysics Data System (ADS)

Maturilli, A.; Stangarone, C.; Helbert, J.; Tribaudino, M.; Prencipe, M.

2017-12-01

Forsterite is the dominating component in olivine, a major constituent in ultrafemic rocks, as well as planetary bodies. Messenger X-ray spectrometer has shown that Mg-rich silicate minerals, such as enstatite and forsterite, dominate Mercury's surface (Weider et al 2012). A careful and detailed acquaintance with the forsterite spectral features and their dependence wrt environmental conditions on Mercury is needed to interpret the remote sensing data from previous and forthcoming missions. We propose an experimental vs calculation approach to reproduce and describe the spectral features of forsterite. TIR emissivity measurements are performed by the Planetary Spectroscopy Laboratory (PSL) of DLR. PSL offers the unique capability to measure the emissivity of samples at temperature up to 1000K under vacuum conditions. TIR emissivity and reflectance measurements are performed on 11 olivine samples having a different composition within the forsterite-fayalite series. When available, the sample has been measured in 2 different grain sizes (<25µm and 125-250µm ranges). Emissivity measurements are taken for temperatures from 300K to 900K step 100K in the 1-100µm spectral range. Modelling is based on ab initio calculation techniques, which allow reproducing properties of crystals, at any P/T condition, with the least possible amount of a priori empirical information. Spectra are calculated evaluating vibrational frequencies at different volume cell, here 0K, 300K and 1000K (extreme situations), taking into account zero point effects. The aim of this work is to study experimentally the effects of temperature, composition and grain sizes on emissivity band minima shifts. The outcomes will benefit the modelling of emissivity spectra with ab initio methods, already successfully enabling to foresee the bands shift due to temperature and composition, but not taking into account band shape due to grain size variations. Considering the chameleon-like effects of Mercury surface already observed (Helbert et al. 2013), this study wants to point out the main spectral features due to the composition and temperature. Our results are used to create a theoretical background to interpret the high temperature infrared emissivity spectra from MERTIS onboard the ESA BepiColombo mission to Mercury (Helbert et al. 2010).

Annealing effects in plated-wire memory elements. II - Recrystallization in Permalloy films.

NASA Technical Reports Server (NTRS)

Marquardt, S. J.; Kench, J. R.

1971-01-01

Results of grain-size measurements in Permalloy platings suggest that recrystallization is possible at temperatures as low as 200 C, but that it is an extremely heterogeneous process. No worthwhile correlation was found to exist between observed grain size and magnetic dispersion in samples aged in the temperature range from 180 to 230 C. It is suggested that the magnetic aging which occurs under these conditions may be due to some other diffusion-controlled process than recrystallization; a process such as chemical homogenization is tentatively preferred.

Amplification volume reduction on DNA database samples using FTA™ Classic Cards.

PubMed

Wong, Hang Yee; Lim, Eng Seng Simon; Tan-Siew, Wai Fun

2012-03-01

The DNA forensic community always strives towards improvements in aspects such as sensitivity, robustness, and efficacy balanced with cost efficiency. Therefore our laboratory decided to study the feasibility of PCR amplification volume reduction using DNA entrapped in FTA™ Classic Card and to bring cost savings to the laboratory. There were a few concerns the laboratory needed to address. First, the kinetics of the amplification reaction could be significantly altered. Second, an increase in sensitivity might affect interpretation due to increased stochastic effects even though they were pristine samples. Third, statics might cause FTA punches to jump out of its allocated well into another thus causing sample-to-sample contamination. Fourth, the size of the punches might be too small for visual inspection. Last, there would be a limit to the extent of volume reduction due to evaporation and the possible need of re-injection of samples for capillary electrophoresis. The laboratory had successfully optimized a reduced amplification volume of 10 μL for FTA samples. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Hollow-fiber flow field-flow fractionation with multi-angle laser scattering detection for aggregation studies of therapeutic proteins.

PubMed

Reschiglian, P; Roda, B; Zattoni, A; Tanase, M; Marassi, V; Serani, S

2014-02-01

The rapid development of protein-based pharmaceuticals highlights the need for robust analytical methods to ensure their quality and stability. Among proteins used in pharmaceutical applications, an important and ever increasing role is represented by monoclonal antibodies and large proteins, which are often modified to enhance their activity or stability when used as drugs. The bioactivity and the stability of those proteins are closely related to the maintenance of their complex structure, which however are influenced by many external factors that can cause degradation and/or aggregation. The presence of aggregates in these drugs could reduce their bioactivity and bioavailability, and induce immunogenicity. The choice of the proper analytical method for the analysis of aggregates is fundamental to understand their (size) dimensional range, their amount, and if they are present in the sample as generated by an aggregation or as an artifact due to the method itself. Size exclusion chromatography is one of the most important techniques for the quality control of pharmaceutical proteins; however, its application is limited to relatively low molar mass aggregates. Among the techniques for the size characterization of proteins, field-flow fractionation (FFF) represents a competitive choice because of its soft mechanism due to the absence of a stationary phase and application in a broader size range, from nanometer- to micrometer-sized analytes. In this paper, the microcolumn variant of FFF, the hollow-fiber flow FFF, was online coupled with multi-angle light scattering, and a method for the characterization of aggregates with high reproducibility and low limit of detection was demonstrated employing an avidin derivate as sample model.

Effects of sintering atmosphere and temperature on structural and magnetic properties of Ni-Cu-Zn ferrite nano-particles: Magnetic enhancement by a reducing atmosphere

NASA Astrophysics Data System (ADS)

Gholizadeh, Ahmad; Jafari, Elahe

2017-01-01

In this work, effects of sintering atmosphere and temperature on structural and magnetic properties of Ni0.3Cu0.2Zn0.5Fe2O4 nanoparticles prepared by citrate precursor method have been studied. The structural characterization of the samples by X-ray powder diffraction and FT-IR spectroscopy is evidence for formation of a cubic structure with no presence of impurity phase. Calculated values of crystallite size and unit cell parameter show an increase with sintering temperature under different atmospheres. Variation of saturation magnetization with sintering temperature and atmosphere can be attributed to change of three factors: magnetic core size, inversion parameter and the change of Fe3+-ion concentration due to the presence of Fe4+ and Fe2+ ions. The saturation magnetization gradually grows with sintering temperature due to increase of magnetic core size and a maximum 63 emu/g was achieved at 600 °C under carbon monoxide-ambient atmosphere.

Effect of oxidizer to fuel molar ratio on particle size and DC conductivity of CeO{sub 2} nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harish, B. M.; Rajeeva, M. P.; Naveen, C. S.

2016-05-06

Cerium oxide nanoparticles were synthesized by solution combustion method with varying the oxidizer (cerium nitrate hexa hydrate) to fuel (Glycine) molar ratio. The prepared samples were characterized by UV-visible spectrometer, X-ray diffractometer (XRD), Scanning electron microscope (SEM) and Energy dispersive X-Ray analysis (EDAX). XRD pattern reveals the formation of cubic fluorite structure of CeO{sub 2}. It was observed that finest crystallites were found at extreme fuel-deficient condition and it is good enough to produce favorable powder characteristics. The average crystallite size was found to be 14.46 nm to 21.57 nm. The temperature dependent dc conductivity was carried out using Keithleymore » source meter between the temperature range from 300 K to 573 K. From this study it was found that the conductivity increases with increase of temperature due to semiconducting behavior of CeO{sub 2} and it decreases with particle size due to increase in the energy band gap.« less

Effect of freezing conditions on β-Tricalcium Phosphate /Camphene scaffold with micro sized particles fabricated by freeze casting.

PubMed

Singh, Gurdev; Soundarapandian, S

2018-03-01

The long standing need of the implant manufacturing industries is to fabricate multi-matrix, customized porous scaffold as cost-effectively. In recent years, freeze casting has shown greater opportunity in the fabrication of porous scaffolds (tricalcium phosphate, hydroxyapatite, bioglass, alumina, etc.) such as at ease and good control over pore size, porosity, a range of materials and economic feasibility. In particular, tricalcium phosphate (TCP) has proved as it possesses good biocompatible (osteoinduction, osteoconduction, etc.) and biodegradability hence beta-tricalcium phosphate (β-TCP, particle size of 10µm) was used as base material and camphene was used as a freezing vehicle in this study. Both freezing conditions such as constant freezing temperature (CFT) and constant freezing rate (CFR) were used for six different conditional samples (CFT: 30, 35 and 40vol% solid loading; similarly CFR: 30, 35 and 40vol% solid loading) to study and understand the effect of various properties (pore size, porosity and compressive strength) of the freeze-cast porous scaffold. It was observed that the average size of the pore was varying linearly as from lower to higher when the solid loading was varying higher to lower. With the help of scanning electron micrographs (SEM), it was observed that the average size of pore during CFR (9.7/ 6.5/ 4.9µm) was comparatively higher than the process of CFT (6.0/ 4.8/ 2.6µm) with respect to the same solid loading (30/ 35/ 40vol%) conditions. From the Gas pycnometer analysis, it was found that the porosity in both freezing conditions (CFT, CFR) were almost near values such as 32.8% and 28.5%. Further to be observed that with the increase in solid loading, the total porosity value has decreased due to the reduction in the concentration of the freezing vehicle. Hence, the freezing vehicle was found as responsible for the formation of appropriate size and orientation of pores during freeze casting. The compressive strength (CS) testing was clearly indicated that the CS was majorly depending on the size of pore which was depending on solid loading. The CS of CFT-based samples (smaller pore sizes and higher resistance to the propagation of crack) were higher due to the higher solid content (pore size) in compared with CFR-based samples on the similar solid loading conditions. As evidently, it was noted that the CFT-based sample with 40% solid loading has given the compressive strength which has come in the range of cancellous bone. The positive note was that the ratio of Ca/P has come as 1.68 (natural bone) after sintering and that was the required value recommended by the food and drug administration (FDI) for manufacturing of bone implants. Copyright © 2017 Elsevier Ltd. All rights reserved.

Extracting samples of high diversity from thematic collections of large gene banks using a genetic-distance based approach

PubMed Central

2010-01-01

Background Breeding programs are usually reluctant to evaluate and use germplasm accessions other than the elite materials belonging to their advanced populations. The concept of core collections has been proposed to facilitate the access of potential users to samples of small sizes, representative of the genetic variability contained within the gene pool of a specific crop. The eventual large size of a core collection perpetuates the problem it was originally proposed to solve. The present study suggests that, in addition to the classic core collection concept, thematic core collections should be also developed for a specific crop, composed of a limited number of accessions, with a manageable size. Results The thematic core collection obtained meets the minimum requirements for a core sample - maintenance of at least 80% of the allelic richness of the thematic collection, with, approximately, 15% of its size. The method was compared with other methodologies based on the M strategy, and also with a core collection generated by random sampling. Higher proportions of retained alleles (in a core collection of equal size) or similar proportions of retained alleles (in a core collection of smaller size) were detected in the two methods based on the M strategy compared to the proposed methodology. Core sub-collections constructed by different methods were compared regarding the increase or maintenance of phenotypic diversity. No change on phenotypic diversity was detected by measuring the trait "Weight of 100 Seeds", for the tested sampling methods. Effects on linkage disequilibrium between unlinked microsatellite loci, due to sampling, are discussed. Conclusions Building of a thematic core collection was here defined by prior selection of accessions which are diverse for the trait of interest, and then by pairwise genetic distances, estimated by DNA polymorphism analysis at molecular marker loci. The resulting thematic core collection potentially reflects the maximum allele richness with the smallest sample size from a larger thematic collection. As an example, we used the development of a thematic core collection for drought tolerance in rice. It is expected that such thematic collections increase the use of germplasm by breeding programs and facilitate the study of the traits under consideration. The definition of a core collection to study drought resistance is a valuable contribution towards the understanding of the genetic control and the physiological mechanisms involved in water use efficiency in plants. PMID:20576152

Magnetic hyperthermia in magnetic nanoemulsions: Effects of polydispersity, particle concentration and medium viscosity

NASA Astrophysics Data System (ADS)

Lahiri, B. B.; Ranoo, Surojit; Zaibudeen, A. W.; Philip, John

2017-11-01

Magnetic fluid hyperthermia (MFH) is a promising cancer treatment modality where alternating magnetic field is used for heating cancerous cells loaded with magnetic nanofluids. Of late, it is realized that magnetic nano-carriers in the size range ∼100-200 nm (e.g. magnetic nanocomposites, magnetic liposomes and magnetic nanoemulsions) are ideal candidates for multimodal MFH coupled with drug delivery or photodynamic therapy due to enhanced permeation and retention (EPR) in the leaky vasculature of cancerous tissues. Here, we study the radiofrequency alternating magnetic field induced heating in magnetically polarizable oil-in-water nanoemulsions of hydrodynamic diameter ∼200 nm, containing single domain superparamagnetic nanoparticles of average diameter ∼10 nm in the oil phase. We probe the effects of size polydispersity of the droplets and medium viscosity on the field induced heating efficiency. The contribution of Neel and Brown relaxation of the magnetic nanoparticles on specific absorption rate (SAR) of the magnetic nanoemulsions, was found to increase linearly with the square of the applied field, with a maximum value of 164.4 ± 4.3 W/gFe. In magnetic nanoemulsions, the heating is induced by the Neel-Brown relaxation of the MNP over a length scale of 10 nm, and the whole scale Brownian relaxation of the emulsion droplets has over a length scale of 200 nm. The magnetic nanoemulsion sample with lower polydispersity (σ = 0.2) exhibited a significantly higher SAR value (3.3 times higher) as compared to the sample with larger polydispersity (σ = 0.4). The SAR values of the samples with 4.6 and 1.7 wt.% of MNP loading with σ values 0.4 a 0.3, respectively were comparable, suggesting a higher heating efficiency in nanofluid containing particles of lower size polydispersity even at lower particle loading. The emulsion droplets, immobilized in an agar matrix (4 wt.%), gave a maximum SAR value of 41.7 ± 2.4 W/gFe as compared to 111.8 ± 3.4 W/gFe in the case of droplets dispersed in water, which indicate a ∼40-50% drop in SAR due to abrogation of whole scale Brownian relaxation of the emulsion droplets. This suggests the need for improving the heating efficiency during actual therapy in tissues. The residual SAR of the immobilized sample correlates well with the SAR of the magnetic nanofluid, albeit under a lower external field amplitude due to demagnetization effect of the clusters of MNP loaded inside the droplets. The observed heating efficiency of larger sized magnetic nanoemulsion offer new possibilities for multimodal therapy due to availability of large volume for loading anti-cancer drug or photodynamic agents.

Size effects on electrical properties of chemically grown zinc oxide nanoparticles

NASA Astrophysics Data System (ADS)

Rathod, K. N.; Joshi, Zalak; Dhruv, Davit; Gadani, Keval; Boricha, Hetal; Joshi, A. D.; Solanki, P. S.; Shah, N. A.

2018-03-01

In the present article, we study ZnO nanoparticles grown by cost effective sol–gel technique for various electrical properties. Structural studies performed by x-ray diffraction (XRD) revealed hexagonal unit cell phase with no observed impurities. Transmission electron microscopy (TEM) and particle size analyzer showed increased average particle size due to agglomeration effect with higher sintering. Dielectric constant (ε‧) decreases with increase in frequency because of the disability of dipoles to follow higher electric field. With higher sintering, dielectric constant reduced owing to the important role of increased formation of oxygen vacancy defects. Universal dielectric response (UDR) was verified by straight line fitting of log (fε‧) versus log (f) plots. All samples exhibit UDR behavior and with higher sintering more contribution from crystal cores. Impedance studies suggest an important role of boundary density while Cole–Cole (Z″ versus Z‧) plots have been studied for the relaxation behavior of the samples. Average normalized change (ANC) in impedance has been studied for all the samples wherein boundaries play an important role. Frequency dependent electrical conductivity has been understood on the basis of Jonscher’s universal power law. Jonscher’s law fits suggest that conduction of charge carrier is possible in the context of correlated barrier hopping (CBH) mechanism for lower temperature sintered sample while for higher temperature sintered ZnO samples, Maxwell–Wagner (M–W) relaxation process has been determined.

Methane Leaks from Natural Gas Systems Follow Extreme Distributions.

PubMed

Brandt, Adam R; Heath, Garvin A; Cooley, Daniel

2016-11-15

Future energy systems may rely on natural gas as a low-cost fuel to support variable renewable power. However, leaking natural gas causes climate damage because methane (CH 4 ) has a high global warming potential. In this study, we use extreme-value theory to explore the distribution of natural gas leak sizes. By analyzing ∼15 000 measurements from 18 prior studies, we show that all available natural gas leakage data sets are statistically heavy-tailed, and that gas leaks are more extremely distributed than other natural and social phenomena. A unifying result is that the largest 5% of leaks typically contribute over 50% of the total leakage volume. While prior studies used log-normal model distributions, we show that log-normal functions poorly represent tail behavior. Our results suggest that published uncertainty ranges of CH 4 emissions are too narrow, and that larger sample sizes are required in future studies to achieve targeted confidence intervals. Additionally, we find that cross-study aggregation of data sets to increase sample size is not recommended due to apparent deviation between sampled populations. Understanding the nature of leak distributions can improve emission estimates, better illustrate their uncertainty, allow prioritization of source categories, and improve sampling design. Also, these data can be used for more effective design of leak detection technologies.

Methane Leaks from Natural Gas Systems Follow Extreme Distributions

DOE PAGES

Brandt, Adam R.; Heath, Garvin A.; Cooley, Daniel

2016-10-14

Future energy systems may rely on natural gas as a low-cost fuel to support variable renewable power. However, leaking natural gas causes climate damage because methane (CH 4) has a high global warming potential. In this study, we use extreme-value theory to explore the distribution of natural gas leak sizes. By analyzing ~15,000 measurements from 18 prior studies, we show that all available natural gas leakage datasets are statistically heavy-tailed, and that gas leaks are more extremely distributed than other natural and social phenomena. A unifying result is that the largest 5% of leaks typically contribute over 50% of themore » total leakage volume. While prior studies used lognormal model distributions, we show that lognormal functions poorly represent tail behavior. Our results suggest that published uncertainty ranges of CH 4 emissions are too narrow, and that larger sample sizes are required in future studies to achieve targeted confidence intervals. Additionally, we find that cross-study aggregation of datasets to increase sample size is not recommended due to apparent deviation between sampled populations. Finally, understanding the nature of leak distributions can improve emission estimates, better illustrate their uncertainty, allow prioritization of source categories, and improve sampling design. Also, these data can be used for more effective design of leak detection technologies.« less

Methane Leaks from Natural Gas Systems Follow Extreme Distributions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brandt, Adam R.; Heath, Garvin A.; Cooley, Daniel

Future energy systems may rely on natural gas as a low-cost fuel to support variable renewable power. However, leaking natural gas causes climate damage because methane (CH 4) has a high global warming potential. In this study, we use extreme-value theory to explore the distribution of natural gas leak sizes. By analyzing ~15,000 measurements from 18 prior studies, we show that all available natural gas leakage datasets are statistically heavy-tailed, and that gas leaks are more extremely distributed than other natural and social phenomena. A unifying result is that the largest 5% of leaks typically contribute over 50% of themore » total leakage volume. While prior studies used lognormal model distributions, we show that lognormal functions poorly represent tail behavior. Our results suggest that published uncertainty ranges of CH 4 emissions are too narrow, and that larger sample sizes are required in future studies to achieve targeted confidence intervals. Additionally, we find that cross-study aggregation of datasets to increase sample size is not recommended due to apparent deviation between sampled populations. Finally, understanding the nature of leak distributions can improve emission estimates, better illustrate their uncertainty, allow prioritization of source categories, and improve sampling design. Also, these data can be used for more effective design of leak detection technologies.« less

Novel hybrid cryo‐radial method: an emerging alternative to CT‐guided biopsy in suspected lung cancer. A prospective case series and description of technique

PubMed Central

Yap, Elaine

2017-01-01

In diagnosing peripheral pulmonary lesions (PPL), radial endobronchial ultrasound (R‐EBUS) is emerging as a safer method in comparison to CT‐guided biopsy. Despite the better safety profile, the yield of R‐EBUS remains lower (73%) than CT‐guided biopsy (90%) due to the smaller size of samples. We adopted a hybrid method by adding cryobiopsy via the R‐EBUS Guide Sheath (GS) to produce larger, non‐crushed samples to improve diagnostic capability and enhance molecular testing. We report six prospective patients who underwent this procedure in our institution. R‐EBUS samples were obtained via conventional sampling methods (needle aspiration, forceps biopsy, and cytology brush), followed by a cryobiopsy. An endobronchial blocker was placed near the planned area of biopsy in advance and inflated post‐biopsy to minimize the risk of bleeding in all patients. A chest X‐ray was performed 1 h post‐procedure. All the PPLs were visualized with R‐EBUS. The mean diameter of cryobiopsy samples was twice the size of forceps biopsy samples. In four patients, cryobiopsy samples were superior in size and the number of malignant cells per high power filed and was the preferred sample selected for mutation analysis and molecular testing. There was no pneumothorax or significant bleeding to report. Cryobiopsy samples were consistently larger and were the preferred samples for molecular testing, with an increase in the diagnostic yield and reduction in the need for repeat procedures, without hindering the marked safety profile of R‐EBUS. Using an endobronchial blocker improves the safety of this procedure. PMID:29321931

A Dictionary Learning Approach for Signal Sampling in Task-Based fMRI for Reduction of Big Data

PubMed Central

Ge, Bao; Li, Xiang; Jiang, Xi; Sun, Yifei; Liu, Tianming

2018-01-01

The exponential growth of fMRI big data offers researchers an unprecedented opportunity to explore functional brain networks. However, this opportunity has not been fully explored yet due to the lack of effective and efficient tools for handling such fMRI big data. One major challenge is that computing capabilities still lag behind the growth of large-scale fMRI databases, e.g., it takes many days to perform dictionary learning and sparse coding of whole-brain fMRI data for an fMRI database of average size. Therefore, how to reduce the data size but without losing important information becomes a more and more pressing issue. To address this problem, we propose a signal sampling approach for significant fMRI data reduction before performing structurally-guided dictionary learning and sparse coding of whole brain's fMRI data. We compared the proposed structurally guided sampling method with no sampling, random sampling and uniform sampling schemes, and experiments on the Human Connectome Project (HCP) task fMRI data demonstrated that the proposed method can achieve more than 15 times speed-up without sacrificing the accuracy in identifying task-evoked functional brain networks. PMID:29706880

A Dictionary Learning Approach for Signal Sampling in Task-Based fMRI for Reduction of Big Data.

PubMed

Ge, Bao; Li, Xiang; Jiang, Xi; Sun, Yifei; Liu, Tianming

2018-01-01

The exponential growth of fMRI big data offers researchers an unprecedented opportunity to explore functional brain networks. However, this opportunity has not been fully explored yet due to the lack of effective and efficient tools for handling such fMRI big data. One major challenge is that computing capabilities still lag behind the growth of large-scale fMRI databases, e.g., it takes many days to perform dictionary learning and sparse coding of whole-brain fMRI data for an fMRI database of average size. Therefore, how to reduce the data size but without losing important information becomes a more and more pressing issue. To address this problem, we propose a signal sampling approach for significant fMRI data reduction before performing structurally-guided dictionary learning and sparse coding of whole brain's fMRI data. We compared the proposed structurally guided sampling method with no sampling, random sampling and uniform sampling schemes, and experiments on the Human Connectome Project (HCP) task fMRI data demonstrated that the proposed method can achieve more than 15 times speed-up without sacrificing the accuracy in identifying task-evoked functional brain networks.

(Sample) Size Matters: Best Practices for Defining Error in Planktic Foraminiferal Proxy Records

NASA Astrophysics Data System (ADS)

Lowery, C.; Fraass, A. J.

2016-02-01

Paleoceanographic research is a vital tool to extend modern observational datasets and to study the impact of climate events for which there is no modern analog. Foraminifera are one of the most widely used tools for this type of work, both as paleoecological indicators and as carriers for geochemical proxies. However, the use of microfossils as proxies for paleoceanographic conditions brings about a unique set of problems. This is primarily due to the fact that groups of individual foraminifera, which usually live about a month, are used to infer average conditions for time periods ranging from hundreds to tens of thousands of years. Because of this, adequate sample size is very important for generating statistically robust datasets, particularly for stable isotopes. In the early days of stable isotope geochemistry, instrumental limitations required hundreds of individual foraminiferal tests to return a value. This had the fortunate side-effect of smoothing any seasonal to decadal changes within the planktic foram population. With the advent of more sensitive mass spectrometers, smaller sample sizes have now become standard. While this has many advantages, the use of smaller numbers of individuals to generate a data point has lessened the amount of time averaging in the isotopic analysis and decreased precision in paleoceanographic datasets. With fewer individuals per sample, the differences between individual specimens will result in larger variation, and therefore error, and less precise values for each sample. Unfortunately, most (the authors included) do not make a habit of reporting the error associated with their sample size. We have created an open-source model in R to quantify the effect of sample sizes under various realistic and highly modifiable parameters (calcification depth, diagenesis in a subset of the population, improper identification, vital effects, mass, etc.). For example, a sample in which only 1 in 10 specimens is diagenetically altered can be off by >0.3‰ δ18O VPDB, or 1°C. Here, we demonstrate the use of this tool to quantify error in micropaleontological datasets, and suggest best practices for minimizing error when generating stable isotope data with foraminifera.

SOLAR SYSTEM MOONS AS ANALOGS FOR COMPACT EXOPLANETARY SYSTEMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kane, Stephen R.; Hinkel, Natalie R.; Raymond, Sean N., E-mail: skane@ipac.caltech.edu

2013-11-01

The field of exoplanetary science has experienced a recent surge of new systems that is largely due to the precision photometry provided by the Kepler mission. The latest discoveries have included compact planetary systems in which the orbits of the planets all lie relatively close to the host star, which presents interesting challenges in terms of formation and dynamical evolution. The compact exoplanetary systems are analogous to the moons orbiting the giant planets in our solar system, in terms of their relative sizes and semimajor axes. We present a study that quantifies the scaled sizes and separations of the solarmore » system moons with respect to their hosts. We perform a similar study for a large sample of confirmed Kepler planets in multi-planet systems. We show that a comparison between the two samples leads to a similar correlation between their scaled sizes and separation distributions. The different gradients of the correlations may be indicative of differences in the formation and/or long-term dynamics of moon and planetary systems.« less

Diagnosing hyperuniformity in two-dimensional, disordered, jammed packings of soft spheres.

PubMed

Dreyfus, Remi; Xu, Ye; Still, Tim; Hough, L A; Yodh, A G; Torquato, Salvatore

2015-01-01

Hyperuniformity characterizes a state of matter for which (scaled) density fluctuations diminish towards zero at the largest length scales. However, the task of determining whether or not an image of an experimental system is hyperuniform is experimentally challenging due to finite-resolution, noise, and sample-size effects that influence characterization measurements. Here we explore these issues, employing video optical microscopy to study hyperuniformity phenomena in disordered two-dimensional jammed packings of soft spheres. Using a combination of experiment and simulation we characterize the possible adverse effects of particle polydispersity, image noise, and finite-size effects on the assignment of hyperuniformity, and we develop a methodology that permits improved diagnosis of hyperuniformity from real-space measurements. The key to this improvement is a simple packing reconstruction algorithm that incorporates particle polydispersity to minimize the free volume. In addition, simulations show that hyperuniformity in finite-sized samples can be ascertained more accurately in direct space than in reciprocal space. Finally, our experimental colloidal packings of soft polymeric spheres are shown to be effectively hyperuniform.

The size, mass, and composition of plastic debris in the western North Atlantic Ocean.

PubMed

Morét-Ferguson, Skye; Law, Kara Lavender; Proskurowski, Giora; Murphy, Ellen K; Peacock, Emily E; Reddy, Christopher M

2010-10-01

This study reports the first inventory of physical properties of individual plastic debris in the North Atlantic. We analyzed 748 samples for size, mass, and material composition collected from surface net tows on 11 expeditions from Cape Cod, Massachusetts to the Caribbean Sea between 1991 and 2007. Particles were mostly fragments less than 10mm in size with nearly all lighter than 0.05 g. Material densities ranged from 0.808 to 1.24 g ml(-1), with about half between 0.97 and 1.04 g ml(-1), a range not typically found in virgin plastics. Elemental analysis suggests that samples in this density range are consistent with polypropylene and polyethylene whose densities have increased, likely due to biofouling. Pelagic densities varied considerably from that of beach plastic debris, suggesting that plastic particles are modified during their residence at sea. These analyses provide clues in understanding particle fate and potential debris sources, and address ecological implications of pelagic plastic debris. Copyright © 2010 Elsevier Ltd. All rights reserved.

Blood platelet counts, morphology and morphometry in lions, Panthera leo.

PubMed

Du Plessis, L

2009-09-01

Due to logistical problems in obtaining sufficient blood samples from apparently healthy animals in the wild in order to establish normal haematological reference values, only limited information regarding the blood platelet count and morphology of free-living lions (Panthera leo) is available. This study provides information on platelet counts and describes their morphology with particular reference to size in two normal, healthy and free-ranging lion populations. Blood samples were collected from a total of 16 lions. Platelet counts, determined manually, ranged between 218 and 358 x 10(9)/l. Light microscopy showed mostly activated platelets of various sizes with prominent granules. At the ultrastructural level the platelets revealed typical mammalian platelet morphology. However, morphometric analysis revealed a significant difference (P < 0.001) in platelet size between the two groups of animals. Basic haematological information obtained in this study may be helpful in future comparative studies between animals of the same species as well as in other felids.

Diagnosing hyperuniformity in two-dimensional, disordered, jammed packings of soft spheres

NASA Astrophysics Data System (ADS)

Dreyfus, Remi; Xu, Ye; Still, Tim; Hough, L. A.; Yodh, A. G.; Torquato, Salvatore

2015-01-01

Hyperuniformity characterizes a state of matter for which (scaled) density fluctuations diminish towards zero at the largest length scales. However, the task of determining whether or not an image of an experimental system is hyperuniform is experimentally challenging due to finite-resolution, noise, and sample-size effects that influence characterization measurements. Here we explore these issues, employing video optical microscopy to study hyperuniformity phenomena in disordered two-dimensional jammed packings of soft spheres. Using a combination of experiment and simulation we characterize the possible adverse effects of particle polydispersity, image noise, and finite-size effects on the assignment of hyperuniformity, and we develop a methodology that permits improved diagnosis of hyperuniformity from real-space measurements. The key to this improvement is a simple packing reconstruction algorithm that incorporates particle polydispersity to minimize the free volume. In addition, simulations show that hyperuniformity in finite-sized samples can be ascertained more accurately in direct space than in reciprocal space. Finally, our experimental colloidal packings of soft polymeric spheres are shown to be effectively hyperuniform.

Is there any consistency between the microplastics found in the field and those used in laboratory experiments?

PubMed

Phuong, Nam Ngoc; Zalouk-Vergnoux, Aurore; Poirier, Laurence; Kamari, Abderrahmane; Châtel, Amélie; Mouneyrac, Catherine; Lagarde, Fabienne

2016-04-01

The ubiquitous presence and persistency of microplastics (MPs) in aquatic environments are of particular concern since they represent an increasing threat to marine organisms and ecosystems. Great differences of concentrations and/or quantities in field samples have been observed depending on geographical location around the world. The main types reported have been polyethylene, polypropylene, and polystyrene. The presence of MPs in marine wildlife has been shown in many studies focusing on ingestion and accumulation in different tissues, whereas studies of the biological effects of MPs in the field are scarce. If the nature and abundance/concentrations of MPs have not been systematically determined in field samples, this is due to the fact that the identification of MPs from environmental samples requires mastery and execution of several steps and techniques. For this reason and due to differences in sampling techniques and sample preparation, it remains difficult to compare the published studies. Most laboratory experiments have been performed with MP concentrations of a higher order of magnitude than those found in the field. Consequently, the ingestion and associated effects observed in exposed organisms have corresponded to great contaminant stress, which does not mimic the natural environment. Medium contaminations are produced with only one type of polymer of a precise sizes and homogenous shape whereas the MPs present in the field are known to be a mix of many types, sizes and shapes of plastic. Moreover, MPs originating in marine environments can be colonized by organisms and constitute the sorption support for many organic compounds present in environment that are not easily reproducible in laboratory. Determination of the mechanical and chemical effects of MPs on organisms is still a challenging area of research. Among the potential chemical effects it is necessary to differentiate those related to polymer properties from those due to the sorption/desorption of organic compounds. Copyright © 2015 Elsevier Ltd. All rights reserved.

Facile and green synthesis of mesoporous Co3O4 nanocubes and their applications for supercapacitors

NASA Astrophysics Data System (ADS)

Liu, Xiangmei; Long, Qing; Jiang, Chunhui; Zhan, Beibei; Li, Chen; Liu, Shujuan; Zhao, Qiang; Huang, Wei; Dong, Xiaochen

2013-06-01

Nanostructured Co3O4 materials attracted significant attention due to their exceptional electrochemical (pseudo-capacitive) properties. However, rigorous preparation conditions are needed to control the size (especially nanosize), morphology and size distribution of the products obtained by conventional methods. Herein, we describe a novel one step shape-controlled synthesis of uniform Co3O4 nanocubes with a size of 50 nm with the existence of mesoporous carbon nanorods (meso-CNRs). In this synthesis process, meso-CNRs not only act as a heat receiver to directly obtain Co3O4 eliminating the high-temperature post-calcination, but also control the morphology of the resulting Co3O4 to form nanocubes with uniform distribution. More strikingly, mesoporous Co3O4 nanocubes are obtained by further thermal treatment. The structure and morphology of the samples were characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. A possible formation mechanism of mesoporous Co3O4 nanocubes is proposed here. Electrochemical tests have revealed that the prepared mesoporous Co3O4 nanocubes demonstrate a remarkable performance in supercapacitor applications due to the porous structure, which endows fast ion and electron transfer.Nanostructured Co3O4 materials attracted significant attention due to their exceptional electrochemical (pseudo-capacitive) properties. However, rigorous preparation conditions are needed to control the size (especially nanosize), morphology and size distribution of the products obtained by conventional methods. Herein, we describe a novel one step shape-controlled synthesis of uniform Co3O4 nanocubes with a size of 50 nm with the existence of mesoporous carbon nanorods (meso-CNRs). In this synthesis process, meso-CNRs not only act as a heat receiver to directly obtain Co3O4 eliminating the high-temperature post-calcination, but also control the morphology of the resulting Co3O4 to form nanocubes with uniform distribution. More strikingly, mesoporous Co3O4 nanocubes are obtained by further thermal treatment. The structure and morphology of the samples were characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. A possible formation mechanism of mesoporous Co3O4 nanocubes is proposed here. Electrochemical tests have revealed that the prepared mesoporous Co3O4 nanocubes demonstrate a remarkable performance in supercapacitor applications due to the porous structure, which endows fast ion and electron transfer. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00495c

Rock magnetic properties estimated from coercivity - blocking temperature diagram: application to recent volcanic rocks

NASA Astrophysics Data System (ADS)

Terada, T.; Sato, M.; Mochizuki, N.; Yamamoto, Y.; Tsunakawa, H.

2013-12-01

Magnetic properties of ferromagnetic minerals generally depend on their chemical composition, crystal structure, size, and shape. In the usual paleomagnetic study, we use a bulk sample which is the assemblage of magnetic minerals showing broad distributions of various magnetic properties. Microscopic and Curie-point observations of the bulk sample enable us to identify the constituent magnetic minerals, while other measurements, for example, stepwise thermal and/or alternating field demagnetizations (ThD, AFD) make it possible to estimate size, shape and domain state of the constituent magnetic grains. However, estimation based on stepwise demagnetizations has a limitation that magnetic grains with the same coercivity Hc (or blocking temperature Tb) can be identified as the single population even though they could have different size and shape. Dunlop and West (1969) carried out mapping of grain size and coercivity (Hc) using pTRM. However, it is considered that their mapping method is basically applicable to natural rocks containing only SD grains, since the grain sizes are estimated on the basis of the single domain theory (Neel, 1949). In addition, it is impossible to check thermal alteration due to laboratory heating in their experiment. In the present study we propose a new experimental method which makes it possible to estimate distribution of size and shape of magnetic minerals in a bulk sample. The present method is composed of simple procedures: (1) imparting ARM to a bulk sample, (2) ThD at a certain temperature, (3) stepwise AFD on the remaining ARM, (4) repeating the steps (1) ~ (3) with ThD at elevating temperatures up to the Curie temperature of the sample. After completion of the whole procedures, ARM spectra are calculated and mapped on the HC-Tb plane (hereafter called HC-Tb diagram). We analyze the Hc-Tb diagrams as follows: (1) For uniaxial SD populations, theoretical curve for a certain grain size (or shape anisotropy) is drawn on the Hc-Tb diagram. The curves are calculated using the single domain theory, since coercivity and blocking temperature of uniaxial SD grains can be expressed as a function of size and shape. (2) Boundary between SD and MD grains are calculated and drawn on the Hc-Tb diagram according to the theory by Butler and Banerjee (1975). (3) Theoretical predictions by (1) and (2) are compared with the obtained ARM spectra to estimate quantitive distribution of size, shape and domain state of magnetic grains in the sample. This mapping method has been applied to three samples: Hawaiian basaltic lava extruded in 1995, Ueno basaltic lava formed during Matsuyama chron, and Oshima basaltic lava extruded in 1986. We will discuss physical states of magnetic grains (size, shape, domain state, etc.) and their possible origins.

Height and seasonal growth pattern of jack pine full-sib families

Treesearch

Don E. Riemenschneider

1981-01-01

Total tree height, seasonal shoot elongation, dates of growth initiation and cessation, and mean daily growth rate were measured and analyzed for a population of jack pine full-sib families derived from inter-provenance crosses. Parental provenance had no effect on these variables although this may have been due to small sample size. Progenies differed significantly...

A Class of Population Covariance Matrices in the Bootstrap Approach to Covariance Structure Analysis

ERIC Educational Resources Information Center

Yuan, Ke-Hai; Hayashi, Kentaro; Yanagihara, Hirokazu

2007-01-01

Model evaluation in covariance structure analysis is critical before the results can be trusted. Due to finite sample sizes and unknown distributions of real data, existing conclusions regarding a particular statistic may not be applicable in practice. The bootstrap procedure automatically takes care of the unknown distribution and, for a given…

A model for estimating understory vegetation response to fertilization and precipitation in loblolly pine plantations

Treesearch

Curtis L. VanderSchaaf; Ryan W. McKnight; Thomas R. Fox; H. Lee Allen

2010-01-01

A model form is presented, where the model contains regressors selected for inclusion based on biological rationale, to predict how fertilization, precipitation amounts, and overstory stand density affect understory vegetation biomass. Due to time, economic, and logistic constraints, datasets of large sample sizes generally do not exist for understory vegetation. Thus...

Evaluating Classified MODIS Satellite Imagery as a Stratification Tool

Treesearch

Greg C. Liknes; Mark D. Nelson; Ronald E. McRoberts

2004-01-01

The Forest Inventory and Analysis (FIA) program of the USDA Forest Service collects forest attribute data on permanent plots arranged on a hexagonal network across all 50 states and Puerto Rico. Due to budget constraints, sample sizes sufficient to satisfy national FIA precision standards are seldom achieved for most inventory variables unless the estimation process is...

76 FR 6598 - Notice of Intent To Request Revision and Extension of a Currently Approved Information Collection

Federal Register 2010, 2011, 2012, 2013, 2014

2011-02-07

... Clearance for Survey Research Studies. Revision to burden hours may be needed due to changes in the size of the target population, sampling design, and/or questionnaire length. DATES: Comments on this notice... Survey Research Studies. OMB Control Number: 0535-0248. Type of Request: To revise and extend a currently...

77 FR 75120 - Notice of Intent To Request Revision and Extension of a Currently Approved Information Collection

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-19

... Clearance for Survey Research Studies. Revision to burden hours will be needed due to changes in the size of the target population, sampling design, and/or questionnaire length. DATES: Comments on this notice... Survey Research Studies. OMB Control Number: 0535-0248. Type of Request: To revise and extend a currently...

The impact of restorative treatment on tooth loss prevention.

PubMed

Caldas Junior, Arnaldo de França; Silveira, Renata Cimões Jovino; Marcenes, Wagner

2003-01-01

A cross-sectional study was carried out to analyze tooth loss resulting from caries in relation to the number of times the extracted tooth had been restored, the type of caries diagnosed (primary or secondary), and socioeconomic indicators of patients from the city of Recife, Brazil. Ten public health centres and ten centres associated with health insurance companies were randomly selected. The size of the sample was calculated using a standard error of 2.5%. A confidence interval of 95% and a 50% prevalence of reasons for extractions were used for calculating the sample. The minimum size of the sample for meeting these requirements was 381 patients. Patients were randomly selected from the list of adults registered at each centre. A total of 410 patients were invited to take part in the study. The response rate was 100%, but 6 patients were excluded due to incompleteness of data in the questionnaire applied. An assessment was made to obtain the number of decayed, missing or filled teeth (DMFT index) and the reasons for extraction. The results showed a highly significant (p < 0.001) relationship between the number of times the tooth indicated for extraction had been restored and the reason for extraction being caries. Furthermore, the majority of teeth extracted due to caries had been restored two or more times. A highly statistically significant association was also observed between one indicator of use of dental services (F/DMFT) and extraction due to caries (p < 0.001). The findings questioned the belief that tooth loss can be prevented in the general population by merely providing restorative treatment.

Magnetic and dielectric properties of Fe3BO6 nanoplates prepared through self-combustion method

NASA Astrophysics Data System (ADS)

Kumari, Kalpana

In the present investigation, a facile synthesis method is explored involving a self-combustion of a solid precursor mixture of iron oxide Fe2O3 and boric acid (H3BO3) using camphor (C10H16O) as fuel in ambient air in order to form a single phase Fe3BO6 crystallites. X-ray diffraction (XRD), Field emission electron microscopy (FESEM), magnetic, and dielectric properties of as prepared sample are studied. From XRD pattern, a single phase compound is observed with an orthorhombic crystal structure (Pnma space group), with average crystallite size of 42nm. A reasonably uniform size distribution of the plates and self-assemblies is retained in the sample. A magnetic transition is observed in dielectric permittivity (at ˜445K) and power loss (at ˜435K) when plotted against temperature. A weak peak occurs near 330K due to the charge reordering in the sample. For temperatures above the transition temperature, a sharp increase of the dielectric loss is observed which occurs due to the presence of thermally activated charge carriers. A canted antiferromagnetic Fe3+ ordering in a Fe3BO6 lattice with a localized charge surface layer is an apparent source of exhibiting a ferroelectric feature in this unique example of a centrosymmetric compound. An induced spin current over the Fe sites thus could give rise to a polarization hysteresis loop. Due to the presence of both ferromagnetic as well as polarization ordering, Fe3BO6 behaves like a single phase multiferroic ceramics.

Longitudinal design considerations to optimize power to detect variances and covariances among rates of change: Simulation results based on actual longitudinal studies

PubMed Central

Rast, Philippe; Hofer, Scott M.

2014-01-01

We investigated the power to detect variances and covariances in rates of change in the context of existing longitudinal studies using linear bivariate growth curve models. Power was estimated by means of Monte Carlo simulations. Our findings show that typical longitudinal study designs have substantial power to detect both variances and covariances among rates of change in a variety of cognitive, physical functioning, and mental health outcomes. We performed simulations to investigate the interplay among number and spacing of occasions, total duration of the study, effect size, and error variance on power and required sample size. The relation between growth rate reliability (GRR) and effect size to the sample size required to detect power ≥ .80 was non-linear, with rapidly decreasing sample sizes needed as GRR increases. The results presented here stand in contrast to previous simulation results and recommendations (Hertzog, Lindenberger, Ghisletta, & von Oertzen, 2006; Hertzog, von Oertzen, Ghisletta, & Lindenberger, 2008; von Oertzen, Ghisletta, & Lindenberger, 2010), which are limited due to confounds between study length and number of waves, error variance with GCR, and parameter values which are largely out of bounds of actual study values. Power to detect change is generally low in the early phases (i.e. first years) of longitudinal studies but can substantially increase if the design is optimized. We recommend additional assessments, including embedded intensive measurement designs, to improve power in the early phases of long-term longitudinal studies. PMID:24219544

Magnetic Force Microscopy Investigation of Magnetic Domains in Nd2Fe14B

NASA Astrophysics Data System (ADS)

Talari, Mahesh Kumar; Markandeyulu, G.; Rao, K. Prasad

2010-07-01

Remenance and coercivity in Nd2Fe14B materials are strongly dependent on the microstructural aspects like phases morphology and grain size. The coercivity (Hc) of a magnetic material varies inversely with the grain size (D) and there is a critical size below which Hc∝D6. Domain wall pinning by grain boundaries and foreign phases is the important mechanism in explaining the improvement in coercivity and remenance. Nd2Fe14B intermetallic compound with stochiometric composition was prepared from pure elements (Nd -99.5%, Fe—99.95%, B -99.99%) by arc melting in argon atmosphere. Magnetic Force Microscope (MFM) gives high-resolution magnetic domain structural information of ferromagnetic samples. DI-3100 Scanning Probe Microscope with MESP probes was used For MFM characterization of the samples. Magnetic domains observed in cast ingots were very long (up to 40 μm were observed) and approximately 1-5 μm wide due to high anisotropy of the compounds. Magnetic domains have displayed different image contrast and morphologies at different locations of the samples. The domain morphologies and image contrast obtained in this analysis were explained in this paper.

Portfolio of automated trading systems: complexity and learning set size issues.

PubMed

Raudys, Sarunas

2013-03-01

In this paper, we consider using profit/loss histories of multiple automated trading systems (ATSs) as N input variables in portfolio management. By means of multivariate statistical analysis and simulation studies, we analyze the influences of sample size (L) and input dimensionality on the accuracy of determining the portfolio weights. We find that degradation in portfolio performance due to inexact estimation of N means and N(N - 1)/2 correlations is proportional to N/L; however, estimation of N variances does not worsen the result. To reduce unhelpful sample size/dimensionality effects, we perform a clustering of N time series and split them into a small number of blocks. Each block is composed of mutually correlated ATSs. It generates an expert trading agent based on a nontrainable 1/N portfolio rule. To increase the diversity of the expert agents, we use training sets of different lengths for clustering. In the output of the portfolio management system, the regularized mean-variance framework-based fusion agent is developed in each walk-forward step of an out-of-sample portfolio validation experiment. Experiments with the real financial data (2003-2012) confirm the effectiveness of the suggested approach.

A comparison of solids collected in sediment traps and automated water samplers

USGS Publications Warehouse

Bartsch, L.A.; Rada, R.G.; Sullivan, J.F.

1996-01-01

Sediment traps are being used in some pollution monitoring programs in the USA to sample suspended solids for contaminant analyses. This monitoring approach assumes that the characteristics of solids obtained in sediment traps are the same as those collected in whole-water sampling devices. We tested this assumption in the upper Mississippi River, based on the inorganic particle-size distribution (determined with a laser particle- analyzer) and volatile matter content of solids (a surrogate for organic matter). Cylindrical sediment traps (aspect ratio 3) were attached to a rigid mooring device and deployed in a flowing side channel in Navigation Pool 7 of the upper Mississippi River. On each side of the mooring device, a trap was situated adjacent to a port of an autosampler that collected raw water samples hourly to form 2-d composite samples. Paired samples (one trap and one raw water, composite sample) were removed from each end of the mooring device at 2-d intervals during the 30-d study period and compared. The relative particle collection efficiency of paired samplers did not vary temporally. Particle-size distributions of inorganic solids from sediment traps and water samples were not significantly different. The volatile matter content of solids was lesser in sediment traps (mean, 9.5%) than in corresponding water samples (mean, 22.7%). This bias may have been partly due to under-collection of phytoplankton (mainly cyanobacteria), which were abundant in the water column during the study. The positioning of water samplers and sediment traps in the mooring device did not influence the particle-size distribution or total solids of samples. We observed a small difference in the amount of organic matter collected by water samplers situated at opposite ends of the mooring device.

Structural elucidation and magnetic behavior evaluation of Cu-Cr doped BaCo-X hexagonal ferrites

NASA Astrophysics Data System (ADS)

Azhar Khan, Muhammad; Hussain, Farhat; Rashid, Muhammad; Mahmood, Asif; Ramay, Shahid M.; Majeed, Abdul

2018-04-01

Ba2-xCuxCo2CryFe28-yO46 (x = 0.0, 0.1, 0.2, 0.3, 0.4, y = 0.0, 0.2, 0.4, 0.6, 0.8) X-type hexagonal ferrites were synthesized via micro-emulsion route. The techniques which were applied to characterize the prepared samples are as follows: X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Dielectric measurements and vibrating sample magnetometer (VSM). The structural parameters i.e. lattice constant (a, c), cell volume (V), X-ray density, bulk density and crystallite size of all the prepared samples were obtained using XRD analysis. The lattice parameters 'a' and 'c' increase from 5.875 Å to 5.934 Å and 83.367 Å to 83.990 Å respectively. The crystallite size of investigated samples lies in the range of 28-32 nm. The magnetic properties of all samples have been calculated by vibrating sample magnetometer (VSM) analysis. The increase in coercivity (Hc) was observed with the increase of doping contents. It was observed that the coercivity (Hc) of all prepared samples is inversely related to the crystalline size which reflects that all materials are super-paramagnetic. The dielectric parameters i.e. dielectric constant, dielectric loss, tangent loss etc were obtained in the frequency range of 1 MHz-3 GHz and followed the Maxwell-Wagner's model. The significant variation the dielectric parameters are observed with increasing frequency. The maximum Q value is obtained at ∼2 GHz due to which these materials are used for high frequency multilayer chip inductors.

Geotechnical characterization of mined clay from Appalachian Ohio: challenges and implications for the clay mining industry.

PubMed

Moran, Anthony R; Hettiarachchi, Hiroshan

2011-07-01

Clayey soil found in coal mines in Appalachian Ohio is often sold to landfills for constructing Recompacted Soil Liners (RSL) in landfills. Since clayey soils possess low hydraulic conductivity, the suitability of mined clay for RSL in Ohio is first assessed by determining its clay content. When soil samples are tested in a laboratory, the same engineering properties are typically expected for the soils originated from the same source, provided that the testing techniques applied are standard, but mined clay from Appalachian Ohio has shown drastic differences in particle size distribution depending on the sampling and/or laboratory processing methods. Sometimes more than a 10 percent decrease in the clay content is observed in the samples collected at the stockpiles, compared to those collected through reverse circulation drilling. This discrepancy poses a challenge to geotechnical engineers who work on the prequalification process of RSL material as it can result in misleading estimates of the hydraulic conductivity of the samples. This paper describes a laboratory investigation conducted on mined clay from Appalachian Ohio to determine how and why the standard sampling and/or processing methods can affect the grain-size distributions. The variation in the clay content was determined to be due to heavy concentrations of shale fragments in the clayey soils. It was also concluded that, in order to obtain reliable grain size distributions from the samples collected at a stockpile of mined clay, the material needs to be processed using a soil grinder. Otherwise, the samples should be collected through drilling.

Geotechnical Characterization of Mined Clay from Appalachian Ohio: Challenges and Implications for the Clay Mining Industry

PubMed Central

Moran, Anthony R.; Hettiarachchi, Hiroshan

2011-01-01

Clayey soil found in coal mines in Appalachian Ohio is often sold to landfills for constructing Recompacted Soil Liners (RSL) in landfills. Since clayey soils possess low hydraulic conductivity, the suitability of mined clay for RSL in Ohio is first assessed by determining its clay content. When soil samples are tested in a laboratory, the same engineering properties are typically expected for the soils originated from the same source, provided that the testing techniques applied are standard, but mined clay from Appalachian Ohio has shown drastic differences in particle size distribution depending on the sampling and/or laboratory processing methods. Sometimes more than a 10 percent decrease in the clay content is observed in the samples collected at the stockpiles, compared to those collected through reverse circulation drilling. This discrepancy poses a challenge to geotechnical engineers who work on the prequalification process of RSL material as it can result in misleading estimates of the hydraulic conductivity of the samples. This paper describes a laboratory investigation conducted on mined clay from Appalachian Ohio to determine how and why the standard sampling and/or processing methods can affect the grain-size distributions. The variation in the clay content was determined to be due to heavy concentrations of shale fragments in the clayey soils. It was also concluded that, in order to obtain reliable grain size distributions from the samples collected at a stockpile of mined clay, the material needs to be processed using a soil grinder. Otherwise, the samples should be collected through drilling. PMID:21845150

Biomagnification of PBDEs and PCBs in food webs from the Baltic Sea and the northern Atlantic Ocean.

PubMed

Burreau, Sven; Zebühr, Yngve; Broman, Dag; Ishaq, Rasha

2006-08-01

Biomagnification of polychlorinated biphenyls (PCBs) and polybrominated diphenylethers (PBDEs) in food webs from the Baltic Sea and the northern Atlantic Sea was investigated. For this, we used PCB and PBDE concentration data, together with data on fish body weight and delta15N of fish and zooplankton as a measure of trophic position. In the Baltic Sea material, consisting of zooplankton, sprat, herring and salmon, we report biomagnification of all PCB congeners but PCB #209 and of PBDEs with 3-6 or 7 bromine atoms. Higher brominated PBDEs and PCB 209 did not biomagnify likely due to their high molecular weights or sizes and subsequent inefficient dietary uptake in fish. If salmon was excluded from the statistical analysis, strong biomagnification of PCB #209 was evident, indicating species differences in biomagnification. In the Baltic Sea material delta15N and body weight covaried. In the Atlantic Sea material, consisting of fish samples (herring and salmon) of larger body sizes, we show positive correlation between concentrations of most PCBs and PBDEs and body weight without increasing delta15N. This shows that biomagnification in some cases depends on body size and not trophic position. We conclude that there probably is trophic position dependence in biomagnification, which was manifested in a food chain from zooplankton to piscivores, but no further trophic position influence on biomagnification in fish at the highest trophic levels. In these fish, there was a body size effect leading to biomagnification, probably due to slower clearance in larger fish. PCB concentrations were generally between 2 and 6 times higher in Baltic Sea salmon than in Atlantic Sea salmon. Higher PBDE concentrations in the Baltic compared to the Atlantic Sea salmon were also found, but with a larger variation between congeners. Nona- to deca-BDEs were found in most investigated samples, which illustrates the bioavailability of these compounds. Unidentified penta-, hexa-, hepta-, and octa- BDEs were found in several samples.

Bedload Rating and Flow Competence Curves Vary With Watershed and Bed Material Parameters

NASA Astrophysics Data System (ADS)

Bunte, K.; Abt, S. R.

2003-12-01

Bedload transport rating curves and flow competence curves (largest bedload size for specified flow) are usually not known for streams unless a large number of bedload samples has been collected and analyzed. However, this information is necessary for assessing instream flow needs and stream responses to watershed effects. This study therefore analyzed whether bedload transport rating and flow competence curves were related to stream parameters. Bedload transport rating curves and flow competence curves were obtained from extensive bedload sampling in six gravel- and cobble-bed mountain streams. Samples were collected using bedload traps and a large net sampler, both of which provide steep and relatively well-defined bedload rating and flow competence curves due to a long sampling duration, a large sampler opening and a large sampler capacity. The sampled streams have snowmelt regimes, steep (1-9%) gradients, and watersheds that are mainly forested and relatively undisturbed with basin area sizes of 8 to 105 km2. The channels are slightly incised and can contain flows of more than 1.5 times bankfull with little overbank flow. Exponents of bedload rating and flow competence curves obtained from these measurements were found to systematically increase with basin area size and decrease with the degree of channel armoring. By contrast, coefficients of bedload rating and flow competence curves decreased with basin size and increased with armoring. All of these relationships were well-defined (0.86 < r2 < 0.99). Data sets from other studies in coarse-bedded streams fit the indicated trend if the sampling device used allows measuring bedload transport rates over a wide range and if bedload supply is somewhat low. The existence of a general positive trend between bedload rating curve exponents and basin area, and a negative trend between coefficients and basin area, is confirmed by a large data set of bedload rating curves obtained from Helley-Smith samples. However, in this case, the trends only become visible as basin area sizes span a wide range (1 - 10,000 km2). The well-defined relationships obtained from the bedload trap and the large net sampler suggest that exponents and coefficients of bedload transport rating curves (and flow competence curves) are predictable from an easily obtainable parameter such as basin size. However, the relationships of bedload rating curve exponents and coefficients with basin size and armoring appear to be influenced by the sampling device used and the watershed sediment production.

Magnetotransport in heterostructures of transition metal dichalcogenides and graphene

NASA Astrophysics Data System (ADS)

Völkl, Tobias; Rockinger, Tobias; Drienovsky, Martin; Watanabe, Kenji; Taniguchi, Takashi; Weiss, Dieter; Eroms, Jonathan

2017-09-01

We use a van der Waals pickup technique to fabricate different heterostructures containing WSe2(WS2) and graphene. The heterostructures were structured by plasma etching, contacted by one-dimensional edge contacts, and a top gate was deposited. For graphene /WSe2/SiO2 samples we observe mobilities of ˜12 000 cm2V-1s-1 . Magnetic-field-dependent resistance measurements on these samples show a peak in the conductivity at low magnetic fields. This dip is attributed to the weak antilocalization (WAL) effect, stemming from spin-orbit coupling. Samples where graphene is encapsulated between WSe2(WS2) and hexagonal boron nitride show a much higher mobility of up to ˜120 000 cm2V-1s-1 . However, in these samples no WAL peak can be observed. We attribute this to a transition from the diffusive to the quasiballistic regime. At low magnetic fields a resistance peak appears, which we ascribe to a size effect due to boundary scattering. Shubnikov-de Haas oscillations in fully encapsulated samples show all integer filling factors due to complete lifting of the spin and valley degeneracies.

Insights into bioassessment of marine pollution using body-size distinctness of planktonic ciliates based on a modified trait hierarchy.

PubMed

Xu, Henglong; Jiang, Yong; Xu, Guangjian

2016-06-15

Based on a modified trait hierarchy of body-size units, the feasibility for bioassessment of water pollution using body-size distinctness of planktonic ciliates was studied in a semi-enclosed bay, northern China. An annual dataset was collected at five sampling stations within a gradient of heavy metal contaminants. Results showed that: (1) in terms of probability density, the body-size spectra of the ciliates represented significant differences among the five stations; (2) bootstrap average analysis demonstrated a spatial variation in body-size rank patterns in response to pollution stress due to heavy metals; and (3) the average body-size distinctness (Δz(+)) and variation in body-size distinctness (Λz(+)), based on the modified trait hierarchy, revealed a clear departure pattern from the expected body-size spectra in areas with pollutants. These results suggest that the body-size diversity measures based on the modified trait hierarchy of the ciliates may be used as a potential indicator of marine pollution. Copyright © 2016 Elsevier Ltd. All rights reserved.

The role of beaded activated carbon's surface oxygen groups on irreversible adsorption of organic vapors.

PubMed

Jahandar Lashaki, Masoud; Atkinson, John D; Hashisho, Zaher; Phillips, John H; Anderson, James E; Nichols, Mark

2016-11-05

The objective of this study is to determine the contribution of surface oxygen groups to irreversible adsorption (aka heel formation) during cyclic adsorption/regeneration of organic vapors commonly found in industrial systems, including vehicle-painting operations. For this purpose, three chemically modified activated carbon samples, including two oxygen-deficient (hydrogen-treated and heat-treated) and one oxygen-rich sample (nitric acid-treated) were prepared. The samples were tested for 5 adsorption/regeneration cycles using a mixture of nine organic compounds. For the different samples, mass balance cumulative heel was 14 and 20% higher for oxygen functionalized and hydrogen-treated samples, respectively, relative to heat-treated sample. Thermal analysis results showed heel formation due to physisorption for the oxygen-deficient samples, and weakened physisorption combined with chemisorption for the oxygen-rich sample. Chemisorption was attributed to consumption of surface oxygen groups by adsorbed species, resulting in formation of high boiling point oxidation byproducts or bonding between the adsorbates and the surface groups. Pore size distributions indicated that different pore sizes contributed to heel formation - narrow micropores (<7Å) in the oxygen-deficient samples and midsize micropores (7-12Å) in the oxygen-rich sample. The results from this study help explain the heel formation mechanism and how it relates to chemically tailored adsorbent materials. Copyright © 2016 Elsevier B.V. All rights reserved.

Does size matter? Statistical limits of paleomagnetic field reconstruction from small rock specimens

NASA Astrophysics Data System (ADS)

Berndt, Thomas; Muxworthy, Adrian R.; Fabian, Karl

2016-01-01

As samples of ever decreasing sizes are being studied paleomagnetically, care has to be taken that the underlying assumptions of statistical thermodynamics (Maxwell-Boltzmann statistics) are being met. Here we determine how many grains and how large a magnetic moment a sample needs to have to be able to accurately record an ambient field. It is found that for samples with a thermoremanent magnetic moment larger than 10-11Am2 the assumption of a sufficiently large number of grains is usually given. Standard 25 mm diameter paleomagnetic samples usually contain enough magnetic grains such that statistical errors are negligible, but "single silicate crystal" works on, for example, zircon, plagioclase, and olivine crystals are approaching the limits of what is physically possible, leading to statistic errors in both the angular deviation and paleointensity that are comparable to other sources of error. The reliability of nanopaleomagnetic imaging techniques capable of resolving individual grains (used, for example, to study the cloudy zone in meteorites), however, is questionable due to the limited area of the material covered.

Effect of size on structural, optical and magnetic properties of SnO2 nanoparticles

NASA Astrophysics Data System (ADS)

Thamarai Selvi, E.; Meenakshi Sundar, S.

2017-07-01

Tin Oxide (SnO2) nanostructures were synthesized by a microwave oven assisted solvothermal method using with and without cetyl trimethyl ammonium bromide (CTAB) capping agent. XRD confirmed the pure rutile-type tetragonal phase of SnO2 for both uncapped and capped samples. The presence of functional groups was analyzed by Fourier transform infrared spectroscopy. Scanning electron microscopy shows the morphology of the samples. Transmission electron microscopy images exposed the size of the SnO2 nanostructures. Surface defect-related g factor of SnO2 nanoparticles using fluorescence spectroscopy is shown. For both uncapped and capped samples, UV-visible spectrum shows a blue shift in absorption edge due to the quantum confinement effect. Defect-related bands were identified by electron paramagnetic resonance (EPR) spectroscopy. The magnetic properties were studied by using vibrating sample magnetometer (VSM). A high value of magnetic moment 0.023 emu g-1 at room temperature for uncapped SnO2 nanoparticles was observed. Capping with CTAB enhanced the saturation magnetic moment to high value of 0.081 emu g-1 by altering the electronic configuration on the surface.

Outlier Removal and the Relation with Reporting Errors and Quality of Psychological Research

PubMed Central

Bakker, Marjan; Wicherts, Jelte M.

2014-01-01

Background The removal of outliers to acquire a significant result is a questionable research practice that appears to be commonly used in psychology. In this study, we investigated whether the removal of outliers in psychology papers is related to weaker evidence (against the null hypothesis of no effect), a higher prevalence of reporting errors, and smaller sample sizes in these papers compared to papers in the same journals that did not report the exclusion of outliers from the analyses. Methods and Findings We retrieved a total of 2667 statistical results of null hypothesis significance tests from 153 articles in main psychology journals, and compared results from articles in which outliers were removed (N = 92) with results from articles that reported no exclusion of outliers (N = 61). We preregistered our hypotheses and methods and analyzed the data at the level of articles. Results show no significant difference between the two types of articles in median p value, sample sizes, or prevalence of all reporting errors, large reporting errors, and reporting errors that concerned the statistical significance. However, we did find a discrepancy between the reported degrees of freedom of t tests and the reported sample size in 41% of articles that did not report removal of any data values. This suggests common failure to report data exclusions (or missingness) in psychological articles. Conclusions We failed to find that the removal of outliers from the analysis in psychological articles was related to weaker evidence (against the null hypothesis of no effect), sample size, or the prevalence of errors. However, our control sample might be contaminated due to nondisclosure of excluded values in articles that did not report exclusion of outliers. Results therefore highlight the importance of more transparent reporting of statistical analyses. PMID:25072606

'Mitominis': multiplex PCR analysis of reduced size amplicons for compound sequence analysis of the entire mtDNA control region in highly degraded samples.

PubMed

Eichmann, Cordula; Parson, Walther

2008-09-01

The traditional protocol for forensic mitochondrial DNA (mtDNA) analyses involves the amplification and sequencing of the two hypervariable segments HVS-I and HVS-II of the mtDNA control region. The primers usually span fragment sizes of 300-400 bp each region, which may result in weak or failed amplification in highly degraded samples. Here we introduce an improved and more stable approach using shortened amplicons in the fragment range between 144 and 237 bp. Ten such amplicons were required to produce overlapping fragments that cover the entire human mtDNA control region. These were co-amplified in two multiplex polymerase chain reactions and sequenced with the individual amplification primers. The primers were carefully selected to minimize binding on homoplasic and haplogroup-specific sites that would otherwise result in loss of amplification due to mis-priming. The multiplexes have successfully been applied to ancient and forensic samples such as bones and teeth that showed a high degree of degradation.

Millimeter-Wave Absorption as a Quality Control Tool for M-Type Hexaferrite Nanopowders

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCloy, John S.; Korolev, Konstantin A.; Crum, Jarrod V.

2013-01-01

Millimeter wave (MMW) absorption measurements have been conducted on commercial samples of large (micrometer-sized) and small (nanometer-sized) particles of BaFe12O19 and SrFe12O19 using a quasi-optical MMW spectrometer and a series of backwards wave oscillators encompassing the 30-120 GHz range. Effective anisotropy of the particles calculated from the resonant absorption frequency indicates lower overall anisotropy in the nano-particles. Due to their high magnetocrystalline anisotropy, both BaFe12O19 and SrFe12O19 are expected to have spin resonances in the 45-55 GHz range. Several of the sampled BaFe12O19 powders did not have MMW absorptions, so they were further investigated by DC magnetization and x-ray diffractionmore » to assess magnetic behavior and structure. The samples with absent MMW absorption contained primarily iron oxides, suggesting that MMW absorption could be used for quality control in hexaferrite powder manufacture.« less

Degradation of radiator performance on Mars due to dust

NASA Technical Reports Server (NTRS)

Gaier, James R.; Perez-Davis, Marla E.; Rutledge, Sharon K.; Forkapa, Mark

1992-01-01

An artificial mineral of the approximate elemental composition of Martian soil was manufactured, crushed, and sorted into four different size ranges. Dust particles from three of these size ranges were applied to arc-textured Nb-1 percent Zr and Cu radiator surfaces to assess their effect on radiator performance. Particles larger than 75 microns did not have sufficient adhesive forces to adhere to the samples at angles greater than about 27 deg. Pre-deposited dust layers were largely removed by clear wind velocities greater than 40 m/s, or by dust-laden wind velocities as low as 25 m/s. Smaller dust grains were more difficult to remove. Abrasion was found to be significant only in high velocity winds (89 m/s or greater). Dust-laden winds were found to be more abrasive than clear wind. Initially dusted samples abraded less than initially clear samples in dust laden wind. Smaller dust particles of the simulant proved to be more abrasive than large. This probably indicates that the larger particles were in fact agglomerates.

Particle size dependence of alkali and alkaline earth metal enrichment in marine aerosols from Bermuda

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoffman, E.J.; Hoffman, G.L.; Duce, R.A.

1980-10-20

Three cascade impactor samples were collected from a 20-m-high tower on the southeastern coast of Bermuda. These samples were analyzed for Na, K, Ca, Mg, and Fe by atomic absorption spectrophotometry. When the alkali-alkakine earth metal concentrations are corrected for a soil-derived component, utilizing the atmospheric Fe concentrations, Mg, Ca, and Na are found to be present in the same relative abundances as in seawater for all particle sizes sampled. Potassium also shows no deviation from a bulk seawater composition for particles with radii greater than approx.0.5 ..mu..m. However, excess K above that expected from either a bulk seawater ormore » soil source is observed on particles with radii less than approx.0.5 ..mu..m. While oceanic chemical fractionation processes during bubble bursting may be responsible for this excess small particle K, it is most likely due to long-range transport of K-rich particles of terrestrial vegetative origin.« less

Superficial and deep changes of histology, texture and particle size distribution in broiler wooden breast muscle during refrigerated storage.

PubMed

Soglia, Francesca; Gao, Jingxian; Mazzoni, Maurizio; Puolanne, Eero; Cavani, Claudio; Petracci, Massimiliano; Ertbjerg, Per

2017-09-01

Recently the poultry industry faced an emerging muscle abnormality termed wooden breast (WB), the prevalence of which has dramatically increased in the past few years. Considering the incomplete knowledge concerning this condition and the lack of information on possible variations due to the intra-fillet sampling locations (superficial vs. deep position) and aging of the samples, this study aimed at investigating the effect of 7-d storage of broiler breast muscles on histology, texture, and particle size distribution, evaluating whether the sampling position exerts a relevant role in determining the main features of WB. With regard to the histological observations, severe myodegeneration accompanied by accumulation of connective tissue was observed within the WB cases, irrespective of the intra-fillet sampling position. No changes in the histological traits took place during the aging in either the normal or the WB samples. As to textural traits, although a progressive tenderization process took place during storage (P ≤ 0.001), the differences among the groups were mainly detected when raw meat rather than cooked was analyzed, with the WB samples exhibiting the highest (P ≤ 0.001) 80% compression values. In spite of the increased amount of connective tissue components in the WB cases, their thermally labile cross-links will account for the similar compression and shear-force values as normal breast cases when measured on cooked samples. Similarly, the enlargement of extracellular matrix and fibrosis might contribute in explaining the different fragmentation patterns observed between the superficial and the deep layer in the WB samples, with the superficial part exhibiting a higher amount of larger particles and an increase in particles with larger size during storage, compared to normal breasts. © 2017 Poultry Science Association Inc.

Genetic algorithms and MCML program for recovery of optical properties of homogeneous turbid media

PubMed Central

Morales Cruzado, Beatriz; y Montiel, Sergio Vázquez; Atencio, José Alberto Delgado

2013-01-01

In this paper, we present and validate a new method for optical properties recovery of turbid media with slab geometry. This method is an iterative method that compares diffuse reflectance and transmittance, measured using integrating spheres, with those obtained using the known algorithm MCML. The search procedure is based in the evolution of a population due to selection of the best individual, i.e., using a genetic algorithm. This new method includes several corrections such as non-linear effects in integrating spheres measurements and loss of light due to the finite size of the sample. As a potential application and proof-of-principle experiment of this new method, we use this new algorithm in the recovery of optical properties of blood samples at different degrees of coagulation. PMID:23504404

Body Size Correlates with Fertilization Success but not Gonad Size in Grass Goby Territorial Males

PubMed Central

Pujolar, Jose Martin; Locatello, Lisa; Zane, Lorenzo; Mazzoldi, Carlotta

2012-01-01

In fish species with alternative male mating tactics, sperm competition typically occurs when small males that are unsuccessful in direct contests steal fertilization opportunities from large dominant males. In the grass goby Zosterisessor ophiocephalus, large territorial males defend and court females from nest sites, while small sneaker males obtain matings by sneaking into nests. Parentage assignment of 688 eggs from 8 different nests sampled in the 2003–2004 breeding season revealed a high level of sperm competition. Fertilization success of territorial males was very high but in all nests sneakers also contributed to the progeny. In territorial males, fertilization success correlated positively with male body size. Gonadal investment was explored in a sample of 126 grass gobies collected during the period 1995–1996 in the same area (61 territorial males and 65 sneakers). Correlation between body weight and testis weight was positive and significant for sneaker males, while correlation was virtually equal to zero in territorial males. That body size in territorial males is correlated with fertilization success but not gonad size suggests that males allocate much more energy into growth and relatively little into sperm production once the needed size to become territorial is attained. The increased paternity of larger territorial males might be due to a more effective defense of the nest in comparison with smaller territorial males. PMID:23056415

Body size correlates with fertilization success but not gonad size in grass goby territorial males.

PubMed

Pujolar, Jose Martin; Locatello, Lisa; Zane, Lorenzo; Mazzoldi, Carlotta

2012-01-01

In fish species with alternative male mating tactics, sperm competition typically occurs when small males that are unsuccessful in direct contests steal fertilization opportunities from large dominant males. In the grass goby Zosterisessor ophiocephalus, large territorial males defend and court females from nest sites, while small sneaker males obtain matings by sneaking into nests. Parentage assignment of 688 eggs from 8 different nests sampled in the 2003-2004 breeding season revealed a high level of sperm competition. Fertilization success of territorial males was very high but in all nests sneakers also contributed to the progeny. In territorial males, fertilization success correlated positively with male body size. Gonadal investment was explored in a sample of 126 grass gobies collected during the period 1995-1996 in the same area (61 territorial males and 65 sneakers). Correlation between body weight and testis weight was positive and significant for sneaker males, while correlation was virtually equal to zero in territorial males. That body size in territorial males is correlated with fertilization success but not gonad size suggests that males allocate much more energy into growth and relatively little into sperm production once the needed size to become territorial is attained. The increased paternity of larger territorial males might be due to a more effective defense of the nest in comparison with smaller territorial males.

Size Effects in the Resistivity of Kondo and Spin-Glass Wires

NASA Astrophysics Data System (ADS)

van Haesendonck, Chris

1998-03-01

Recently, several experiments have focused on possible size effects for the Kondo scattering in thin-film structures of very dilute magnetic alloys (concentration ~ 100 ppm) (For an overview, see M.A. Blachly and N. Giordano, Phys. Rev. B 51), 12537 (1995).. Intuitively, one expects size effects to occur as soon as the sample dimensions become smaller than the size of the Kondo screening cloud which induces a compensation of the local magnetic moments below the Kondo temperature. Since the size of the Kondo cloud is predicted to be of the order of 1 μ m, one should be able to observe pronounced size effects in thin-film Kondo alloys which have been patterned by standard electron beam lithography. Experiments performed by other groups have indeed revealed an important reduction of the slope of the Kondo resistivity for samples with micrometer dimensions. These experiments also show that the size effects are affected by disorder. On the other hand, our experiments on AuFe wires, which have been prepared by flash evaporation as well as by ion implantation, indicate the absence of size effects for the Kondo scattering down to a width of 38 nm. Therefore, the existence of the Kondo cloud remains a controversial issue. The size effects have also been investigated for more concentrated spin-glass alloys (concentration ~ 1 at.%). The resistivity measurements of thin-film spin glasses indicate that intrinsic size effects may be present for length scales below 100 nm (K.R. Lane et al., Phys. Rev. B 51), 945 (1995); G. Neuttiens et al., Europhys. Lett. 34, 617 (1996).. Due to the damping of the RKKY interaction by elastic defect scattering, size effects in the spin-glass regime can be strongly affected by disorder.

Genealogical Properties of Subsamples in Highly Fecund Populations

NASA Astrophysics Data System (ADS)

Eldon, Bjarki; Freund, Fabian

2018-03-01

We consider some genealogical properties of nested samples. The complete sample is assumed to have been drawn from a natural population characterised by high fecundity and sweepstakes reproduction (abbreviated HFSR). The random gene genealogies of the samples are—due to our assumption of HFSR—modelled by coalescent processes which admit multiple mergers of ancestral lineages looking back in time. Among the genealogical properties we consider are the probability that the most recent common ancestor is shared between the complete sample and the subsample nested within the complete sample; we also compare the lengths of `internal' branches of nested genealogies between different coalescent processes. The results indicate how `informative' a subsample is about the properties of the larger complete sample, how much information is gained by increasing the sample size, and how the `informativeness' of the subsample varies between different coalescent processes.

Size-Tuned Plastic Flow Localization in Irradiated Materials at the Submicron Scale

NASA Astrophysics Data System (ADS)

Cui, Yinan; Po, Giacomo; Ghoniem, Nasr

2018-05-01

Three-dimensional discrete dislocation dynamics (3D-DDD) simulations reveal that, with reduction of sample size in the submicron regime, the mechanism of plastic flow localization in irradiated materials transitions from irradiation-controlled to an intrinsic dislocation source controlled. Furthermore, the spatial correlation of plastic deformation decreases due to weaker dislocation interactions and less frequent cross slip as the system size decreases, thus manifesting itself in thinner dislocation channels. A simple model of discrete dislocation source activation coupled with cross slip channel widening is developed to reproduce and physically explain this transition. In order to quantify the phenomenon of plastic flow localization, we introduce a "deformation localization index," with implications to the design of radiation-resistant materials.

The influence of landscape characteristics and home-range size on the quantification of landscape-genetics relationships

Treesearch

Tabitha A. Graves; Tzeidle N. Wasserman; Milton Cezar Ribeiro; Erin L. Landguth; Stephen F. Spear; Niko Balkenhol; Colleen B. Higgins; Marie-Josee Fortin; Samuel A. Cushman; Lisette P. Waits

2012-01-01

A common approach used to estimate landscape resistance involves comparing correlations of ecological and genetic distances calculated among individuals of a species. However, the location of sampled individuals may contain some degree of spatial uncertainty due to the natural variation of animals moving through their home range ormeasurement error in plant or animal...

Characterisation of Fine Ash Fractions from the AD 1314 Kaharoa Eruption

NASA Astrophysics Data System (ADS)

Weaver, S. J.; Rust, A.; Carey, R. J.; Houghton, B. F.

2012-12-01

The AD 1314±12 yr Kaharoa eruption of Tarawera volcano, New Zealand, produced deposits exhibiting both plinian and subplinian characteristics (Nairn et al., 2001; 2004, Leonard et al., 2002, Hogg et al., 2003). Their widespread dispersal yielded volumes, column heights, and mass discharge rates of plinian magnitude and intensity (Sahetapy-Engel, 2002); however, vertical shifts in grain size suggest waxing and waning within single phases and time-breaks on the order of hours between phases. These grain size shifts were quantified using sieve, laser diffraction, and image analysis of the fine ash fractions (<1 mm in diameter) of some of the most explosive phases of the eruption. These analyses served two purposes: 1) to characterise the change in eruption intensity over time, and 2) to compare the three methods of grain size analysis. Additional analyses of the proportions of components and particle shape were also conducted to aid in the interpretation of the eruption and transport dynamics. 110 samples from a single location about 6 km from source were sieved at half phi intervals between -4φ to 4φ (16 mm - 63 μm). A single sample was then chosen to test the range of grain sizes to run through the Mastersizer 2000. Three aliquots were tested; the first consisted of each sieve size fraction ranging between 0φ (1000 μm) and <4φ (<63 μm, i.e. the pan). For example, 0, 0.5, 1, …, 4φ, and the pan were ran through the Mastersizer and then their results, weighted according to their sieve weight percents, were summed together to produce a total distribution. The second aliquot included 3 samples ranging between 0-2φ (1000-250 μm), 2.5-4φ (249-63 μm), and the pan. A single sample consisting of the total range of grain sizes between 0φ and the pan was used for the final aliquot. Their results were compared and it was determined that the single sample consisting of the broadest range of grain sizes yielded an accurate grain size distribution. This data was then compared with the sieve weight percent data, and revealed that there is a significant difference in size characterisation between sieving and the Mastersizer for size fractions between 0-3φ (1000-125 μm). This is due predominantly to the differing methods that sieving and the Mastersizer use to characterise a single particle, to inhomogeneity in grain density in each grain-size fraction, and to grain-shape irregularities. This led the Mastersizer to allocate grains from a certain sieve size fraction into coarser size fractions. Therefore, only the Mastersizer data from 3.5φ and below were combined with the coarser sieve data to yield total grain size distributions. This high-resolution analysis of the grain size data enabled subtle trends in grain size to be identified and related to short timescale eruptive processes.

Three-Dimensional Characterization and Modeling of Microstructural Weak Links for Spall Damage in FCC Metals

DOE PAGES

Krishnan, Kapil; Brown, Andrew; Wayne, Leda; ...

2014-11-25

Local microstructural weak links for spall damage were investigated using three-dimensional (3-D) characterization in multicrystalline copper samples (grain size ≈ 450 µm) shocked with laser-driven plates at low pressures (2 to 4 GPa). The thickness of samples and flyer plates, approximately 1000 and 500 µm respectively, led to short pressure pulses that allowed isolating microstructure effects on local damage characteristics. Electron Backscattering Diffraction and optical microscopy were used to relate the presence, size, and shape of porosity to local microstructure. The experiments were complemented with 3-D finite element simulations of individual grain boundaries (GBs) that resulted in large damage volumesmore » using crystal plasticity coupled with a void nucleation and growth model. Results from analysis of these damage sites show that the presence of a GB-affected zone, where strain concentration occurs next to a GB, correlates strongly with damage localization at these sites, most likely due to the inability of maintaining strain compatibility across these interfaces, with additional effects due to the inclination of the GB with respect to the shock. Results indicate that strain compatibility plays an important role on intergranular spall damage in metallic materials.« less

Comparative study of magnetic ordering in bulk and nanoparticles of Sm0.65Ca0.35MnO3: Magnetization and electron magnetic resonance measurements

NASA Astrophysics Data System (ADS)

Goveas, Lora Rita; Anuradha, K. N.; Bhagyashree, K. S.; Bhat, S. V.

2015-05-01

To explore the effect of size reduction to nanoscale on the hole doped Sm0.65Ca0.35MnO3 compound, dc magnetic measurements and electron magnetic resonance (EMR) were done on bulk and nanoparticle samples in the temperature range 10 ≤ T ≤ 300 K. Magnetization measurement showed that the bulk sample undergoes a charge ordering transition at 240 K and shows a mixed magnetic phase at low temperature. However, the nanosample underwent a ferromagnetic transition at 75 K, and the charge ordered state was destabilized on size reduction down to nanoscale. The low-temperature ferromagnetic component is found to be enhanced in nanoparticles as compared to their bulk counterpart. Interestingly around room temperature, bulk particles show higher magnetization where as at low temperature nanoparticles show higher magnetization. Ferromagnetism in the bulk is due to super exchange where as ferromagnetism in nanoparticles is due to uncompensated spins of the surface layer. Temperature variation of EMR parameters correlates well with the results of magnetic measurements. The magnetic behaviour of the nanoparticles is understood in terms of the core shell scenario.

Nonresponse patterns in the Federal Waterfowl Hunter Questionnaire Survey

USGS Publications Warehouse

Pendleton, G.W.

1992-01-01

I analyzed data from the 1984 and 1986 Federal Waterfowl Hunter Questionnaire Survey (WHQS) to estimate the rate of return of name and address contact cards, to evaluate the efficiency of the Survey's stratification scheme, and to investigate potential sources of bias due to nonresponse at the contact card and questionnaire stages of the Survey. Median response at the contact card stage was 0.200 in 1984 and 0.208 in 1986, but was lower than 0.100 for many sample post offices. Large portions of the intended sample contributed little to the final estimates in the Survey. Differences in response characteristics between post office size strata were detected, but size strata were confounded with contact card return rates; differences among geographic zones within states were more pronounced. Large biases in harvest and hunter activity due to nonresponse were not found; however, consistent smaller magnitude biases were found. Bias in estimates of the proportion of active hunters was the most pronounced effect of nonresponse. All of the sources of bias detected would produce overestimates of harvest and activity. Redesigning the WHQS, including use of a complete list of waterfowl hunters and resampling nonrespondents, would be needed to reduce nonresponse bias.

Zipf's law and city size distribution: A survey of the literature and future research agenda

NASA Astrophysics Data System (ADS)

Arshad, Sidra; Hu, Shougeng; Ashraf, Badar Nadeem

2018-02-01

This study provides a systematic review of the existing literature on Zipf's law for city size distribution. Existing empirical evidence suggests that Zipf's law is not always observable even for the upper-tail cities of a territory. However, the controversy with empirical findings arises due to sample selection biases, methodological weaknesses and data limitations. The hypothesis of Zipf's law is more likely to be rejected for the entire city size distribution and, in such case, alternative distributions have been suggested. On the contrary, the hypothesis is more likely to be accepted if better empirical methods are employed and cities are properly defined. The debate is still far from to be conclusive. In addition, we identify four emerging areas in Zipf's law and city size distribution research including the size distribution of lower-tail cities, the size distribution of cities in sub-national regions, the alternative forms of Zipf's law, and the relationship between Zipf's law and the coherence property of the urban system.

Improved ASTM G72 Test Method for Ensuring Adequate Fuel-to-Oxidizer Ratios

NASA Technical Reports Server (NTRS)

Juarez, Alfredo; Harper, Susana A.

2016-01-01

The ASTM G72/G72M-15 Standard Test Method for Autogenous Ignition Temperature of Liquids and Solids in a High-Pressure Oxygen-Enriched Environment is currently used to evaluate materials for the ignition susceptibility driven by exposure to external heat in an enriched oxygen environment. Testing performed on highly volatile liquids such as cleaning solvents has proven problematic due to inconsistent test results (non-ignitions). Non-ignition results can be misinterpreted as favorable oxygen compatibility, although they are more likely associated with inadequate fuel-to-oxidizer ratios. Forced evaporation during purging and inadequate sample size were identified as two potential causes for inadequate available sample material during testing. In an effort to maintain adequate fuel-to-oxidizer ratios within the reaction vessel during test, several parameters were considered, including sample size, pretest sample chilling, pretest purging, and test pressure. Tests on a variety of solvents exhibiting a range of volatilities are presented in this paper. A proposed improvement to the standard test protocol as a result of this evaluation is also presented. Execution of the final proposed improved test protocol outlines an incremental step method of determining optimal conditions using increased sample sizes while considering test system safety limits. The proposed improved test method increases confidence in results obtained by utilizing the ASTM G72 autogenous ignition temperature test method and can aid in the oxygen compatibility assessment of highly volatile liquids and other conditions that may lead to false non-ignition results.

Chi-Squared Test of Fit and Sample Size-A Comparison between a Random Sample Approach and a Chi-Square Value Adjustment Method.

PubMed

Bergh, Daniel

2015-01-01

Chi-square statistics are commonly used for tests of fit of measurement models. Chi-square is also sensitive to sample size, which is why several approaches to handle large samples in test of fit analysis have been developed. One strategy to handle the sample size problem may be to adjust the sample size in the analysis of fit. An alternative is to adopt a random sample approach. The purpose of this study was to analyze and to compare these two strategies using simulated data. Given an original sample size of 21,000, for reductions of sample sizes down to the order of 5,000 the adjusted sample size function works as good as the random sample approach. In contrast, when applying adjustments to sample sizes of lower order the adjustment function is less effective at approximating the chi-square value for an actual random sample of the relevant size. Hence, the fit is exaggerated and misfit under-estimated using the adjusted sample size function. Although there are big differences in chi-square values between the two approaches at lower sample sizes, the inferences based on the p-values may be the same.

Instruction manual, Optical Effects Module, Model OEM

NASA Technical Reports Server (NTRS)

1975-01-01

The Optical Effects Module Model OEM-1, a laboratory prototype instrument designed for the automated measurement of radiation transmission and scattering through optical samples, is described. The system comprises two main components: the Optical Effects Module Enclosure (OEME) and the Optical Effects Module Electronic Controller and Processor (OEMCP). The OEM is designed for operation in the near UV at approximately 2540A, corresponding to the most intense spectral line activated by the mercury discharge lamp used for illumination. The radiation from this source is detected in transmission and reflection through a number of selectable samples. The basic objective of this operation is to monitor in real time the accretion of possible contamination on the surface of these samples. The optical samples are exposed outside of the OEME proper to define exposure conditions and to separate exposure and measurement environments. Changes in the transmissivity of the sample are attributable to surface contamination or to bulk effects due to radiation. Surface contamination will increase radiation scattering due to Rayleigh-Gans effect or to other phenomena, depending on the characteristics size of the particulate contaminants. Thus, also scattering from the samples becomes a part of the measurement program.

Experimental calibration of Phreatic and Hydrothermal Explosions: A case study on Lake Okaro, New Zealand

NASA Astrophysics Data System (ADS)

Foote, L. C.; Scheu, B.; kennedy, B.; Gravley, D.; Dingwell, D. B.

2011-12-01

Phreatic and hydrothermal eruptions, the most common on earth, frequently lead to magmatic eruptions. They often occur with little or no warning, representing a significant hazard. These eruptions occur over a range of temperature and pressure, and within widely differing rock types. Additionally, these eruptions may be triggered by earthquakes or landslides . Regardless of the trigger, they occur when hydrothermal/supercritical fluid rapidly flashes to steam due either to a heating or a decompression. Despite the frequency of these eruptions, previous studies have largely been focused exclusively on either the physical characteristics of the eruptions or experimental modelling of the trigger processes, with very few combining the two. Here, a new experimental procedure has been developed to model phreatic fragmentation based on the shock-tube experiments of magmatic fragmentation introduced by Alidibirov & Dingwell (1996). This technique uses water-saturated samples, producing fragmentation from a combination of argon gas overpressure and steam flashing, within the vesicles. By integrating measurements of the physical characteristics such as porosity, permeability and mineralogy in the analysis of the results of these experiments a model of phreatic fragmentation is proposed, to aid in future hazard modelling. The phreatic explosion crater forming Lake Okaro, within the Taupo Volcanic Zone of New Zealand was used as a case study. The eruption was triggered within the Rangitaiki Ignimbrite, which served as the sample material for these experiments. In order to evaluate the effects of alteration, both original, unaltered material and hydrothermally altered samples were analysed. As fragmentation is driven by gas overpressure/steam expansion within vesicles, porosity plays a critical role. For these samples average porosity values are 24 and 40% respectively. Experimental conditions were chosen primarily to reflect the conditions of the study location but also to study the effect of water saturation on the fragmentation behavior. Thus experiments were run at both room temperature and 300°C, and from 4 to 15 MPa. Pressure sensors were used to record the speed of fragmentation and fragments were recovered in order to determine grain-size distributions. First analyses of the fragmentation speed reveal no significant difference between dry and saturated samples; (14 - 42 m/s depending on applied energy). In contrast, the results of the grain size analysis show a clear shift to smaller grain sizes with saturated samples (independent of pressure or sample type) possibly reflecting the more efficient conversion of energy involved in phreatic eruptions most likely in combination with a strength reduction of the samples due to water weakening effects. We provide herewith a first parameterisation of conditions for phreatic and hydrothermal eruptions and offer an explanation for the reduction in grain size associated with phreatic eruptions.

Small Sample Performance of Bias-corrected Sandwich Estimators for Cluster-Randomized Trials with Binary Outcomes

PubMed Central

Li, Peng; Redden, David T.

2014-01-01

SUMMARY The sandwich estimator in generalized estimating equations (GEE) approach underestimates the true variance in small samples and consequently results in inflated type I error rates in hypothesis testing. This fact limits the application of the GEE in cluster-randomized trials (CRTs) with few clusters. Under various CRT scenarios with correlated binary outcomes, we evaluate the small sample properties of the GEE Wald tests using bias-corrected sandwich estimators. Our results suggest that the GEE Wald z test should be avoided in the analyses of CRTs with few clusters even when bias-corrected sandwich estimators are used. With t-distribution approximation, the Kauermann and Carroll (KC)-correction can keep the test size to nominal levels even when the number of clusters is as low as 10, and is robust to the moderate variation of the cluster sizes. However, in cases with large variations in cluster sizes, the Fay and Graubard (FG)-correction should be used instead. Furthermore, we derive a formula to calculate the power and minimum total number of clusters one needs using the t test and KC-correction for the CRTs with binary outcomes. The power levels as predicted by the proposed formula agree well with the empirical powers from the simulations. The proposed methods are illustrated using real CRT data. We conclude that with appropriate control of type I error rates under small sample sizes, we recommend the use of GEE approach in CRTs with binary outcomes due to fewer assumptions and robustness to the misspecification of the covariance structure. PMID:25345738

Evaluation of Particle Size Influence on Proximate Composition, Physicochemical, Techno-Functional and Physio-Functional Properties of Flours Obtained from Persimmon (Diospyros kaki Trumb.) Coproducts.

PubMed

Lucas-González, Raquel; Viuda-Martos, Manuel; Pérez-Álvarez, José Ángel; Fernández-López, Juana

2017-03-01

The aim of the work was to study the influence of particle size in the composition, physicochemical, techno-functional and physio-functional properties of two flours obtained from persimmon (Diospyros kaki Trumb. cvs. 'Rojo Brillante' (RBF) and 'Triump' (THF) coproducts. The cultivar (RBF and THF) and particle size significantly affected all parameters under study, although depending on the evaluated property, only one of these effects predominated. Carbohydrates (38.07-46.98 g/100 g) and total dietary fiber (32.07-43.57 g/100 g) were the main components in both flours (RBF and THF). Furthermore, insoluble dietary fiber represented more than 68% of total dietary fiber content. All color properties studied were influenced by cultivar and particle size. For both cultivars, the lower particle size, the higher lightness and hue values. RBF flours showed high values for emulsifying activity (69.33-74.00 mL/mL), while THF presented high values for water holding capacity (WHC: 9.47-12.19 g water/g sample). The bile holding capacity (BHC) and fat/oil binding values were, in general, higher in RBF (19.61-12.19 g bile/g sample and 11.98-9.07, respectively) than THF (16.12-12.40 g bile/g sample and 9.78-7.96, respectively). The effect of particle size was really evident in both WHC and BHC. Due to their dietary fiber content, techno-functional and physio-functional properties, persimmon flours seem to have a good profile to be used as potential functional ingredient.

Lab-on-a-disc agglutination assay for protein detection by optomagnetic readout and optical imaging using nano- and micro-sized magnetic beads.

PubMed

Uddin, Rokon; Burger, Robert; Donolato, Marco; Fock, Jeppe; Creagh, Michael; Hansen, Mikkel Fougt; Boisen, Anja

2016-11-15

We present a biosensing platform for the detection of proteins based on agglutination of aptamer coated magnetic nano- or microbeads. The assay, from sample to answer, is integrated on an automated, low-cost microfluidic disc platform. This ensures fast and reliable results due to a minimum of manual steps involved. The detection of the target protein was achieved in two ways: (1) optomagnetic readout using magnetic nanobeads (MNBs); (2) optical imaging using magnetic microbeads (MMBs). The optomagnetic readout of agglutination is based on optical measurement of the dynamics of MNB aggregates whereas the imaging method is based on direct visualization and quantification of the average size of MMB aggregates. By enhancing magnetic particle agglutination via application of strong magnetic field pulses, we obtained identical limits of detection of 25pM with the same sample-to-answer time (15min 30s) using the two differently sized beads for the two detection methods. In both cases a sample volume of only 10µl is required. The demonstrated automation, low sample-to-answer time and portability of both detection instruments as well as integration of the assay on a low-cost disc are important steps for the implementation of these as portable tools in an out-of-lab setting. Copyright © 2016 Elsevier B.V. All rights reserved.

Methods to increase reproducibility in differential gene expression via meta-analysis

PubMed Central

Sweeney, Timothy E.; Haynes, Winston A.; Vallania, Francesco; Ioannidis, John P.; Khatri, Purvesh

2017-01-01

Findings from clinical and biological studies are often not reproducible when tested in independent cohorts. Due to the testing of a large number of hypotheses and relatively small sample sizes, results from whole-genome expression studies in particular are often not reproducible. Compared to single-study analysis, gene expression meta-analysis can improve reproducibility by integrating data from multiple studies. However, there are multiple choices in designing and carrying out a meta-analysis. Yet, clear guidelines on best practices are scarce. Here, we hypothesized that studying subsets of very large meta-analyses would allow for systematic identification of best practices to improve reproducibility. We therefore constructed three very large gene expression meta-analyses from clinical samples, and then examined meta-analyses of subsets of the datasets (all combinations of datasets with up to N/2 samples and K/2 datasets) compared to a ‘silver standard’ of differentially expressed genes found in the entire cohort. We tested three random-effects meta-analysis models using this procedure. We showed relatively greater reproducibility with more-stringent effect size thresholds with relaxed significance thresholds; relatively lower reproducibility when imposing extraneous constraints on residual heterogeneity; and an underestimation of actual false positive rate by Benjamini–Hochberg correction. In addition, multivariate regression showed that the accuracy of a meta-analysis increased significantly with more included datasets even when controlling for sample size. PMID:27634930

Measuring missing heritability: Inferring the contribution of common variants

PubMed Central

Golan, David; Lander, Eric S.; Rosset, Saharon

2014-01-01

Genome-wide association studies (GWASs), also called common variant association studies (CVASs), have uncovered thousands of genetic variants associated with hundreds of diseases. However, the variants that reach statistical significance typically explain only a small fraction of the heritability. One explanation for the “missing heritability” is that there are many additional disease-associated common variants whose effects are too small to detect with current sample sizes. It therefore is useful to have methods to quantify the heritability due to common variation, without having to identify all causal variants. Recent studies applied restricted maximum likelihood (REML) estimation to case–control studies for diseases. Here, we show that REML considerably underestimates the fraction of heritability due to common variation in this setting. The degree of underestimation increases with the rarity of disease, the heritability of the disease, and the size of the sample. Instead, we develop a general framework for heritability estimation, called phenotype correlation–genotype correlation (PCGC) regression, which generalizes the well-known Haseman–Elston regression method. We show that PCGC regression yields unbiased estimates. Applying PCGC regression to six diseases, we estimate the proportion of the phenotypic variance due to common variants to range from 25% to 56% and the proportion of heritability due to common variants from 41% to 68% (mean 60%). These results suggest that common variants may explain at least half the heritability for many diseases. PCGC regression also is readily applicable to other settings, including analyzing extreme-phenotype studies and adjusting for covariates such as sex, age, and population structure. PMID:25422463

Creep of quartz by dislocation and grain boundary processes

NASA Astrophysics Data System (ADS)

Fukuda, J. I.; Holyoke, C. W., III; Kronenberg, A. K.

2015-12-01

Wet polycrystalline quartz aggregates deformed at temperatures T of 600°-900°C and strain rates of 10-4-10-6 s-1 at a confining pressure Pc of 1.5 GPa exhibit plasticity at low T, governed by dislocation glide and limited recovery, and grain size-sensitive creep at high T, governed by diffusion and sliding at grain boundaries. Quartz aggregates were HIP-synthesized, subjecting natural milky quartz powder to T=900°C and Pc=1.5 GPa, and grain sizes (2 to 25 mm) were varied by annealing at these conditions for up to 10 days. Infrared absorption spectra exhibit a broad OH band at 3400 cm-1 due to molecular water inclusions with a calculated OH content (~4000 ppm, H/106Si) that is unchanged by deformation. Rate-stepping experiments reveal different stress-strain rate functions at different temperatures and grain sizes, which correspond to differing stress-temperature sensitivities. At 600-700°C and grain sizes of 5-10 mm, flow law parameters compare favorably with those for basal plasticity and dislocation creep of wet quartzites (effective stress exponents n of 3 to 6 and activation enthalpy H* ~150 kJ/mol). Deformed samples show undulatory extinction, limited recrystallization, and c-axis maxima parallel to the shortening direction. Similarly fine-grained samples deformed at 800°-900°C exhibit flow parameters n=1.3-2.0 and H*=135-200 kJ/mol corresponding to grain size-sensitive Newtonian creep. Deformed samples show some undulatory extinction and grain sizes change by recrystallization; however, grain boundary deformation processes are indicated by the low value of n. Our experimental results for grain size-sensitive creep can be compared with models of grain boundary diffusion and grain boundary sliding using measured rates of silicon grain boundary diffusion. While many quartz mylonites show microstructural and textural evidence for dislocation creep, results for grain size-sensitive creep may apply to very fine-grained (<10 mm) quartz mylonites.

Lens-Aided Multi-Angle Spectroscopy (LAMAS) Reveals Small-Scale Outflow Structure in Quasars

NASA Astrophysics Data System (ADS)

Green, Paul J.

2006-06-01

Spectral differences between lensed quasar image components are common. Since lensing is intrinsically achromatic, these differences are typically explained as the effect of either microlensing, or as light path time delays sampling intrinsic quasar spectral variability. Here we advance a novel third hypothesis: some spectral differences are due to small line-of-sight differences through quasar disk wind outflows. In particular, we propose that variable spectral differences seen only in component A of the widest separation lens SDSS J1004+4112 are due to differential absorption along the sight lines. The absorber properties required by this hypothesis are akin to known broad absorption line (BAL) outflows but must have a broader, smoother velocity profile. We interpret the observed C IV emission-line variability as further evidence for spatial fine structure transverse to the line of sight. Since outflows are likely to be rotating, such absorber fine structure can consistently explain some of the UV and X-ray variability seen in AGNs. The implications are many: (1) Spectroscopic differences in other lensed objects may be due to this ``lens-aided multi-angle spectroscopy'' (LAMAS). (2) Outflows have fine structure on size scales of arcseconds, as seen from the nucleus. (3) Assuming either broad absorption line region sizes proposed in recent wind models, or typically assumed continuum emission region sizes, LAMAS and/or variability provide broadly consistent absorber size scale estimates of ~1015 cm. (4) Very broad smooth absorption may be ubiquitous in quasar spectra, even when no obvious troughs are seen.

Facultative adjustment of the offspring sex ratio and male attractiveness: a systematic review and meta-analysis.

PubMed

Booksmythe, Isobel; Mautz, Brian; Davis, Jacqueline; Nakagawa, Shinichi; Jennions, Michael D

2017-02-01

Females can benefit from mate choice for male traits (e.g. sexual ornaments or body condition) that reliably signal the effect that mating will have on mean offspring fitness. These male-derived benefits can be due to material and/or genetic effects. The latter include an increase in the attractiveness, hence likely mating success, of sons. Females can potentially enhance any sex-biased benefits of mating with certain males by adjusting the offspring sex ratio depending on their mate's phenotype. One hypothesis is that females should produce mainly sons when mating with more attractive or higher quality males. Here we perform a meta-analysis of the empirical literature that has accumulated to test this hypothesis. The mean effect size was small (r = 0.064-0.095; i.e. explaining <1% of variation in offspring sex ratios) but statistically significant in the predicted direction. It was, however, not robust to correction for an apparent publication bias towards significantly positive results. We also examined the strength of the relationship using different indices of male attractiveness/quality that have been invoked by researchers (ornaments, behavioural displays, female preference scores, body condition, male age, body size, and whether a male is a within-pair or extra-pair mate). Only ornamentation and body size significantly predicted the proportion of sons produced. We obtained similar results regardless of whether we ran a standard random-effects meta-analysis, or a multi-level, Bayesian model that included a correction for phylogenetic non-independence. A moderate proportion of the variance in effect sizes (51.6-56.2%) was due to variation that was not attributable to sampling error (i.e. sample size). Much of this non-sampling error variance was not attributable to phylogenetic effects or high repeatability of effect sizes among species. It was approximately equally attributable to differences (occurring for unknown reasons) in effect sizes among and within studies (25.3, 22.9% of the total variance). There were no significant effects of year of publication or two aspects of study design (experimental/observational or field/laboratory) on reported effect sizes. We discuss various practical reasons and theoretical arguments as to why small effect sizes should be expected, and why there might be relatively high variation among studies. Currently, there are no species where replicated, experimental studies show that mothers adjust the offspring sex ratio in response to a generally preferred male phenotype. Ultimately, we need more experimental studies that test directly whether females produce more sons when mated to relatively more attractive males, and that provide the requisite evidence that their sons have higher mean fitness than their daughters. © 2015 Cambridge Philosophical Society.

The Number of Patients and Events Required to Limit the Risk of Overestimation of Intervention Effects in Meta-Analysis—A Simulation Study

PubMed Central

Thorlund, Kristian; Imberger, Georgina; Walsh, Michael; Chu, Rong; Gluud, Christian; Wetterslev, Jørn; Guyatt, Gordon; Devereaux, Philip J.; Thabane, Lehana

2011-01-01

Background Meta-analyses including a limited number of patients and events are prone to yield overestimated intervention effect estimates. While many assume bias is the cause of overestimation, theoretical considerations suggest that random error may be an equal or more frequent cause. The independent impact of random error on meta-analyzed intervention effects has not previously been explored. It has been suggested that surpassing the optimal information size (i.e., the required meta-analysis sample size) provides sufficient protection against overestimation due to random error, but this claim has not yet been validated. Methods We simulated a comprehensive array of meta-analysis scenarios where no intervention effect existed (i.e., relative risk reduction (RRR) = 0%) or where a small but possibly unimportant effect existed (RRR = 10%). We constructed different scenarios by varying the control group risk, the degree of heterogeneity, and the distribution of trial sample sizes. For each scenario, we calculated the probability of observing overestimates of RRR>20% and RRR>30% for each cumulative 500 patients and 50 events. We calculated the cumulative number of patients and events required to reduce the probability of overestimation of intervention effect to 10%, 5%, and 1%. We calculated the optimal information size for each of the simulated scenarios and explored whether meta-analyses that surpassed their optimal information size had sufficient protection against overestimation of intervention effects due to random error. Results The risk of overestimation of intervention effects was usually high when the number of patients and events was small and this risk decreased exponentially over time as the number of patients and events increased. The number of patients and events required to limit the risk of overestimation depended considerably on the underlying simulation settings. Surpassing the optimal information size generally provided sufficient protection against overestimation. Conclusions Random errors are a frequent cause of overestimation of intervention effects in meta-analyses. Surpassing the optimal information size will provide sufficient protection against overestimation. PMID:22028777

Body mass estimates of hominin fossils and the evolution of human body size.

PubMed

Grabowski, Mark; Hatala, Kevin G; Jungers, William L; Richmond, Brian G

2015-08-01

Body size directly influences an animal's place in the natural world, including its energy requirements, home range size, relative brain size, locomotion, diet, life history, and behavior. Thus, an understanding of the biology of extinct organisms, including species in our own lineage, requires accurate estimates of body size. Since the last major review of hominin body size based on postcranial morphology over 20 years ago, new fossils have been discovered, species attributions have been clarified, and methods improved. Here, we present the most comprehensive and thoroughly vetted set of individual fossil hominin body mass predictions to date, and estimation equations based on a large (n = 220) sample of modern humans of known body masses. We also present species averages based exclusively on fossils with reliable taxonomic attributions, estimates of species averages by sex, and a metric for levels of sexual dimorphism. Finally, we identify individual traits that appear to be the most reliable for mass estimation for each fossil species, for use when only one measurement is available for a fossil. Our results show that many early hominins were generally smaller-bodied than previously thought, an outcome likely due to larger estimates in previous studies resulting from the use of large-bodied modern human reference samples. Current evidence indicates that modern human-like large size first appeared by at least 3-3.5 Ma in some Australopithecus afarensis individuals. Our results challenge an evolutionary model arguing that body size increased from Australopithecus to early Homo. Instead, we show that there is no reliable evidence that the body size of non-erectus early Homo differed from that of australopiths, and confirm that Homo erectus evolved larger average body size than earlier hominins. Copyright © 2015 Elsevier Ltd. All rights reserved.

A geostatistical analysis of small-scale spatial variability in bacterial abundance and community structure in salt marsh creek bank sediments

NASA Technical Reports Server (NTRS)

Franklin, Rima B.; Blum, Linda K.; McComb, Alison C.; Mills, Aaron L.

2002-01-01

Small-scale variations in bacterial abundance and community structure were examined in salt marsh sediments from Virginia's eastern shore. Samples were collected at 5 cm intervals (horizontally) along a 50 cm elevation gradient, over a 215 cm horizontal transect. For each sample, bacterial abundance was determined using acridine orange direct counts and community structure was analyzed using randomly amplified polymorphic DNA fingerprinting of whole-community DNA extracts. A geostatistical analysis was used to determine the degree of spatial autocorrelation among the samples, for each variable and each direction (horizontal and vertical). The proportion of variance in bacterial abundance that could be accounted for by the spatial model was quite high (vertical: 60%, horizontal: 73%); significant autocorrelation was found among samples separated by 25 cm in the vertical direction and up to 115 cm horizontally. In contrast, most of the variability in community structure was not accounted for by simply considering the spatial separation of samples (vertical: 11%, horizontal: 22%), and must reflect variability from other parameters (e.g., variation at other spatial scales, experimental error, or environmental heterogeneity). Microbial community patch size based upon overall similarity in community structure varied between 17 cm (vertical) and 35 cm (horizontal). Overall, variability due to horizontal position (distance from the creek bank) was much smaller than that due to vertical position (elevation) for both community properties assayed. This suggests that processes more correlated with elevation (e.g., drainage and redox potential) vary at a smaller scale (therefore producing smaller patch sizes) than processes controlled by distance from the creek bank. c2002 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.

Evaluation of Pump Pulsation in Respirable Size-Selective Sampling: Part II. Changes in Sampling Efficiency

PubMed Central

Lee, Eun Gyung; Lee, Taekhee; Kim, Seung Won; Lee, Larry; Flemmer, Michael M.; Harper, Martin

2015-01-01

This second, and concluding, part of this study evaluated changes in sampling efficiency of respirable size-selective samplers due to air pulsations generated by the selected personal sampling pumps characterized in Part I (Lee E, Lee L, Möhlmann C et al. Evaluation of pump pulsation in respirable size-selective sampling: Part I. Pulsation measurements. Ann Occup Hyg 2013). Nine particle sizes of monodisperse ammonium fluorescein (from 1 to 9 μm mass median aerodynamic diameter) were generated individually by a vibrating orifice aerosol generator from dilute solutions of fluorescein in aqueous ammonia and then injected into an environmental chamber. To collect these particles, 10-mm nylon cyclones, also known as Dorr-Oliver (DO) cyclones, were used with five medium volumetric flow rate pumps. Those were the Apex IS, HFS513, GilAir5, Elite5, and Basic5 pumps, which were found in Part I to generate pulsations of 5% (the lowest), 25%, 30%, 56%, and 70% (the highest), respectively. GK2.69 cyclones were used with the Legacy [pump pulsation (PP) = 15%] and Elite12 (PP = 41%) pumps for collection at high flows. The DO cyclone was also used to evaluate changes in sampling efficiency due to pulse shape. The HFS513 pump, which generates a more complex pulse shape, was compared to a single sine wave fluctuation generated by a piston. The luminescent intensity of the fluorescein extracted from each sample was measured with a luminescence spectrometer. Sampling efficiencies were obtained by dividing the intensity of the fluorescein extracted from the filter placed in a cyclone with the intensity obtained from the filter used with a sharp-edged reference sampler. Then, sampling efficiency curves were generated using a sigmoid function with three parameters and each sampling efficiency curve was compared to that of the reference cyclone by constructing bias maps. In general, no change in sampling efficiency (bias under ±10%) was observed until pulsations exceeded 25% for the DO cyclone. However, for three models of pumps producing 30%, 56%, and 70% pulsations, substantial changes were confirmed. The GK2.69 cyclone showed a similar pattern to that of the DO cyclone, i.e. no change in sampling efficiency for the Legacy producing 15% pulsation and a substantial change for the Elite12 producing 41% pulsation. Pulse shape did not cause any change in sampling efficiency when compared to the single sine wave. The findings suggest that 25% pulsation at the inlet of the cyclone as measured by this test can be acceptable for the respirable particle collection. If this test is used in place of that currently in European standards (EN 1232–1997 and EN 12919-1999) or is used in any International Organization for Standardization standard, then a 25% pulsation criterion could be adopted. This work suggests that a 10% criterion as currently specified in the European standards for testing may be overly restrictive and not able to be met by many pumps on the market. Further work is recommended to determine which criterion would be applicable to this test if it is to be retained in its current form. PMID:24064963

Evaluation of pump pulsation in respirable size-selective sampling: part II. Changes in sampling efficiency.

PubMed

Lee, Eun Gyung; Lee, Taekhee; Kim, Seung Won; Lee, Larry; Flemmer, Michael M; Harper, Martin

2014-01-01

This second, and concluding, part of this study evaluated changes in sampling efficiency of respirable size-selective samplers due to air pulsations generated by the selected personal sampling pumps characterized in Part I (Lee E, Lee L, Möhlmann C et al. Evaluation of pump pulsation in respirable size-selective sampling: Part I. Pulsation measurements. Ann Occup Hyg 2013). Nine particle sizes of monodisperse ammonium fluorescein (from 1 to 9 μm mass median aerodynamic diameter) were generated individually by a vibrating orifice aerosol generator from dilute solutions of fluorescein in aqueous ammonia and then injected into an environmental chamber. To collect these particles, 10-mm nylon cyclones, also known as Dorr-Oliver (DO) cyclones, were used with five medium volumetric flow rate pumps. Those were the Apex IS, HFS513, GilAir5, Elite5, and Basic5 pumps, which were found in Part I to generate pulsations of 5% (the lowest), 25%, 30%, 56%, and 70% (the highest), respectively. GK2.69 cyclones were used with the Legacy [pump pulsation (PP) = 15%] and Elite12 (PP = 41%) pumps for collection at high flows. The DO cyclone was also used to evaluate changes in sampling efficiency due to pulse shape. The HFS513 pump, which generates a more complex pulse shape, was compared to a single sine wave fluctuation generated by a piston. The luminescent intensity of the fluorescein extracted from each sample was measured with a luminescence spectrometer. Sampling efficiencies were obtained by dividing the intensity of the fluorescein extracted from the filter placed in a cyclone with the intensity obtained from the filter used with a sharp-edged reference sampler. Then, sampling efficiency curves were generated using a sigmoid function with three parameters and each sampling efficiency curve was compared to that of the reference cyclone by constructing bias maps. In general, no change in sampling efficiency (bias under ±10%) was observed until pulsations exceeded 25% for the DO cyclone. However, for three models of pumps producing 30%, 56%, and 70% pulsations, substantial changes were confirmed. The GK2.69 cyclone showed a similar pattern to that of the DO cyclone, i.e. no change in sampling efficiency for the Legacy producing 15% pulsation and a substantial change for the Elite12 producing 41% pulsation. Pulse shape did not cause any change in sampling efficiency when compared to the single sine wave. The findings suggest that 25% pulsation at the inlet of the cyclone as measured by this test can be acceptable for the respirable particle collection. If this test is used in place of that currently in European standards (EN 1232-1997 and EN 12919-1999) or is used in any International Organization for Standardization standard, then a 25% pulsation criterion could be adopted. This work suggests that a 10% criterion as currently specified in the European standards for testing may be overly restrictive and not able to be met by many pumps on the market. Further work is recommended to determine which criterion would be applicable to this test if it is to be retained in its current form.

Size distribution and growth rate of crystal nuclei near critical undercooling in small volumes

NASA Astrophysics Data System (ADS)

Kožíšek, Z.; Demo, P.

2017-11-01

Kinetic equations are numerically solved within standard nucleation model to determine the size distribution of nuclei in small volumes near critical undercooling. Critical undercooling, when first nuclei are detected within the system, depends on the droplet volume. The size distribution of nuclei reaches the stationary value after some time delay and decreases with nucleus size. Only a certain maximum size of nuclei is reached in small volumes near critical undercooling. As a model system, we selected recently studied nucleation in Ni droplet [J. Bokeloh et al., Phys. Rev. Let. 107 (2011) 145701] due to available experimental and simulation data. However, using these data for sample masses from 23 μg up to 63 mg (corresponding to experiments) leads to the size distribution of nuclei, when no critical nuclei in Ni droplet are formed (the number of critical nuclei < 1). If one takes into account the size dependence of the interfacial energy, the size distribution of nuclei increases to reasonable values. In lower volumes (V ≤ 10-9 m3) nucleus size reaches some maximum extreme size, which quickly increases with undercooling. Supercritical clusters continue their growth only if the number of critical nuclei is sufficiently high.

Estimating the Effective Sample Size of Tree Topologies from Bayesian Phylogenetic Analyses

PubMed Central

Lanfear, Robert; Hua, Xia; Warren, Dan L.

2016-01-01

Bayesian phylogenetic analyses estimate posterior distributions of phylogenetic tree topologies and other parameters using Markov chain Monte Carlo (MCMC) methods. Before making inferences from these distributions, it is important to assess their adequacy. To this end, the effective sample size (ESS) estimates how many truly independent samples of a given parameter the output of the MCMC represents. The ESS of a parameter is frequently much lower than the number of samples taken from the MCMC because sequential samples from the chain can be non-independent due to autocorrelation. Typically, phylogeneticists use a rule of thumb that the ESS of all parameters should be greater than 200. However, we have no method to calculate an ESS of tree topology samples, despite the fact that the tree topology is often the parameter of primary interest and is almost always central to the estimation of other parameters. That is, we lack a method to determine whether we have adequately sampled one of the most important parameters in our analyses. In this study, we address this problem by developing methods to estimate the ESS for tree topologies. We combine these methods with two new diagnostic plots for assessing posterior samples of tree topologies, and compare their performance on simulated and empirical data sets. Combined, the methods we present provide new ways to assess the mixing and convergence of phylogenetic tree topologies in Bayesian MCMC analyses. PMID:27435794

Identification of missing variants by combining multiple analytic pipelines.

PubMed

Ren, Yingxue; Reddy, Joseph S; Pottier, Cyril; Sarangi, Vivekananda; Tian, Shulan; Sinnwell, Jason P; McDonnell, Shannon K; Biernacka, Joanna M; Carrasquillo, Minerva M; Ross, Owen A; Ertekin-Taner, Nilüfer; Rademakers, Rosa; Hudson, Matthew; Mainzer, Liudmila Sergeevna; Asmann, Yan W

2018-04-16

After decades of identifying risk factors using array-based genome-wide association studies (GWAS), genetic research of complex diseases has shifted to sequencing-based rare variants discovery. This requires large sample sizes for statistical power and has brought up questions about whether the current variant calling practices are adequate for large cohorts. It is well-known that there are discrepancies between variants called by different pipelines, and that using a single pipeline always misses true variants exclusively identifiable by other pipelines. Nonetheless, it is common practice today to call variants by one pipeline due to computational cost and assume that false negative calls are a small percent of total. We analyzed 10,000 exomes from the Alzheimer's Disease Sequencing Project (ADSP) using multiple analytic pipelines consisting of different read aligners and variant calling strategies. We compared variants identified by using two aligners in 50,100, 200, 500, 1000, and 1952 samples; and compared variants identified by adding single-sample genotyping to the default multi-sample joint genotyping in 50,100, 500, 2000, 5000 and 10,000 samples. We found that using a single pipeline missed increasing numbers of high-quality variants correlated with sample sizes. By combining two read aligners and two variant calling strategies, we rescued 30% of pass-QC variants at sample size of 2000, and 56% at 10,000 samples. The rescued variants had higher proportions of low frequency (minor allele frequency [MAF] 1-5%) and rare (MAF < 1%) variants, which are the very type of variants of interest. In 660 Alzheimer's disease cases with earlier onset ages of ≤65, 4 out of 13 (31%) previously-published rare pathogenic and protective mutations in APP, PSEN1, and PSEN2 genes were undetected by the default one-pipeline approach but recovered by the multi-pipeline approach. Identification of the complete variant set from sequencing data is the prerequisite of genetic association analyses. The current analytic practice of calling genetic variants from sequencing data using a single bioinformatics pipeline is no longer adequate with the increasingly large projects. The number and percentage of quality variants that passed quality filters but are missed by the one-pipeline approach rapidly increased with sample size.

Increased Pouch Sizes and Resulting Changes in the Amounts of Nicotine and Tobacco-Specific N-Nitrosamines in Single Pouches of Camel Snus and Marlboro Snus

PubMed Central

Jensen, Joni; Biener, Lois; Bliss, Robin L.; Hecht, Stephen S.; Hatsukami, Dorothy K.

2012-01-01

Introduction: Initial analyses of the novel smokeless tobacco products Camel Snus and Marlboro Snus demonstrated that these products contain relatively low amounts of nicotine and the carcinogenic tobacco-specific nitrosamines N’-nitrosonornicotine (NNN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), as compared with traditional smokeless products. It is unknown whether the modifications in packaging, flavors, and pouch sizes that occurred for both Camel Snus and Marlboro Snus since their first introduction to the market were accompanied by any changes in nicotine or nitrosamine levels. Methods: We examined the available data on nicotine and NNN and NNK levels in 60 samples of Camel Snus and 87 samples of Marlboro Snus that were analyzed in our laboratory between 2006 and 2010. Results: Due to the increase in pouch size, the amounts of total nicotine, unprotonated nicotine, and the sum of NNN and NNK present in the large Camel Snus pouches released in 2010 are 1.9-fold, 2.4-fold, and 3.3-fold higher, respectively, than in the original smaller pouches that entered the market in 2006. Total and unprotonated nicotine content in the current version of Marlboro Snus pouches are 2.1-fold and 1.9-fold higher, respectively, and the sum of NNN and NNK is 1.5-fold lower than in the original version. Conclusions: We observed an increase in nicotine content in single portions of Camel Snus and Marlboro Snus, and an increase in tobacco-specific N-nitrosamine content in single portions of Camel Snus, due to the increases in pouch size that occurred between 2006 and 2010. This finding stresses the importance of tobacco product regulation and ingredient disclosures. PMID:22259150

Estimating relative decline in populations of subterranean termites (Isoptera: Rhinotermitidae) due to baiting.

PubMed

Evans, T A

2001-12-01

Although mark-recapture protocols produce inaccurate population estimates of termite colonies, they might be employed to estimate a relative change in colony size. This possibility was tested using two Australian, mound-building, wood-eating, subterranean Coptotermes species. Three different toxicants delivered in baits were used to decrease (but not eliminate) colony size, and a single mark-recapture protocol was used to estimate pre- and postbaiting population sizes. For both species, the numbers of termites retrieved from bait stations varied widely, resulting in no significant differences in the numbers of termites sampled between treatments in either the pre- or postbaiting protocols. There were significantly fewer termites sampled in all treatments, controls included, in the postbaiting protocol compared with the pre-, suggesting a seasonal change in forager numbers. The comparison of population estimates shows a large decrease in toxicant treated colonies compared with little change in control colonies, which suggests that estimating the relative decline in population size using mark-recapture protocols might to be possible. However, the change in population estimate was due entirely to the significantly lower recapture rate in the control colonies relative to the toxicant treated colonies, as numbers of unmarked termites did not change between treatments. The population estimates should be treated with caution because low recapture rates produce dubious population estimates and, in some cases, postbaiting mark-recapture population estimates could be much greater than those at prebaiting, despite consumption of bait in sufficient quantities to cause population decline. A possible interaction between fat-stain markers and toxicants should be investigated if mark-recapture population estimates are used. Alternative methods of population change are advised, along with other indirect measures.

4D Imaging of Salt Precipitation during Evaporation from Saline Porous Media Influenced by the Particle Size Distribution

NASA Astrophysics Data System (ADS)

Norouzi Rad, M.; Shokri, N.

2014-12-01

Understanding the physics of water evaporation from saline porous media is important in many processes such as evaporation from porous media, vegetation, plant growth, biodiversity in soil, and durability of building materials. To investigate the effect of particle size distribution on the dynamics of salt precipitation in saline porous media during evaporation, we applied X-ray micro-tomography technique. Six samples of quartz sand with different grain size distributions were used in the present study enabling us to constrain the effects of particle and pore sizes on salt precipitation patterns and dynamics. The pore size distributions were computed using the pore-scale X-ray images. The packed beds were saturated with NaCl solution of 3 Molal and the X-ray imaging was continued for one day with temporal resolution of 30 min resulting in pore scale information about the evaporation and precipitation dynamics. Our results show more precipitation at the early stage of the evaporation in the case of sand with the larger particle size due to the presence of fewer evaporation sites at the surface. The presence of more preferential evaporation sites at the surface of finer sands significantly modified the patterns and thickness of the salt crust deposited on the surface such that a thinner salt crust was formed in the case of sand with smaller particle size covering larger area at the surface as opposed to the thicker patchy crusts in samples with larger particle sizes. Our results provide new insights regarding the physics of salt precipitation in porous media during evaporation.

Effect of bait and gear type on channel catfish catch and turtle bycatch in a reservoir

USGS Publications Warehouse

Cartabiano, Evan C.; Stewart, David R.; Long, James M.

2014-01-01

Hoop nets have become the preferred gear choice to sample channel catfish Ictalurus punctatus but the degree of bycatch can be high, especially due to the incidental capture of aquatic turtles. While exclusion and escapement devices have been developed and evaluated, few have examined bait choice as a method to reduce turtle bycatch. The use of Zote™ soap has shown considerable promise to reduce bycatch of aquatic turtles when used with trotlines but its effectiveness in hoop nets has not been evaluated. We sought to determine the effectiveness of hoop nets baited with cheese bait or Zote™ soap and trotlines baited with shad or Zote™ soap as a way to sample channel catfish and prevent capture of aquatic turtles. We used a repeated-measures experimental design and treatment combinations were randomly assigned using a Latin-square arrangement. Eight sampling locations were systematically selected and then sampled with either hoop nets or trotlines using Zote™ soap (both gears), waste cheese (hoop nets), or cut shad (trotlines). Catch rates did not statistically differ among the gear–bait-type combinations. Size bias was evident with trotlines consistently capturing larger sized channel catfish compared to hoop nets. Results from a Monte Carlo bootstrapping procedure estimated the number of samples needed to reach predetermined levels of sampling precision to be lowest for trotlines baited with soap. Moreover, trotlines baited with soap caught no aquatic turtles, while hoop nets captured many turtles and had high mortality rates. We suggest that Zote™ soap used in combination with multiple hook sizes on trotlines may be a viable alternative to sample channel catfish and reduce bycatch of aquatic turtles.

Synthesis characterization and luminescence studies of gamma irradiated nanocrystalline yttrium oxide

NASA Astrophysics Data System (ADS)

Shivaramu, N. J.; Lakshminarasappa, B. N.; Nagabhushana, K. R.; Singh, Fouran

2016-02-01

Nanocrystalline Y2O3 is synthesized by solution combustion technique using urea and glycine as fuels. X-ray diffraction (XRD) pattern of as prepared sample shows amorphous nature while annealed samples show cubic nature. The average crystallite size is calculated using Scherrer's formula and is found to be in the range 14-30 nm for samples synthesized using urea and 15-20 nm for samples synthesized using glycine respectively. Field emission scanning electron microscopy (FE-SEM) image of 1173 K annealed Y2O3 samples show well separated spherical shape particles and the average particle size is found to be in the range 28-35 nm. Fourier transformed infrared (FTIR) and Raman spectroscopy reveals a stretching of Y-O bond. Electron spin resonance (ESR) shows V- center, O2- and Y2 + defects. A broad photoluminescence (PL) emission with peak at 386 nm is observed when the sample is excited with 252 nm. Thermoluminescence (TL) properties of γ-irradiated Y2O3 nanopowder are studied at a heating rate of 5 K s- 1. The samples prepared by using urea show a prominent and well resolved peak at 383 K and a weak one at 570 K. It is also found that TL glow peak intensity (Im1) at 383 K increases with increase in γ-dose up to 6.0 kGy and then decreases with increase in dose. However, glycine used Y2O3 shows a prominent TL glow with peaks at 396 K and 590 K. Among the fuels, urea used Y2O3 shows simple and well resolved TL glows. This might be due to fuel and hence particle size effect. The kinetic parameters are calculated by Chen's glow curve peak shape method and results are discussed in detail.

A screening of persistent organohalogenated contaminants in hair of East Greenland polar bears.

PubMed

Jaspers, Veerle L B; Dietz, Rune; Sonne, Christian; Letcher, Robert J; Eens, Marcel; Neels, Hugo; Born, Erik W; Covaci, Adrian

2010-10-15

In this pilot study, we report on levels of persistent organohalogenated contaminants (OHCs) in hair of polar bears (Ursus maritimus) from East Greenland sampled between 1999 and 2001. To our knowledge, this is the first study on the validation of polar bear hair as a non-invasive matrix representative of concentrations and profiles in internal organs and blood plasma. Because of low sample weights (13-140mg), only major bioaccumulative OHCs were detected above the limit of quantification: five polychlorinated biphenyl (PCB) congeners (CB 99, 138, 153, 170 and 180), one polybrominated diphenyl ether (PBDE) congener (BDE 47), oxychlordane, trans-nonachlor and β-hexachlorocyclohexane. The PCB profile in hair was similar to that of internal tissues (i.e. adipose, liver, brain and blood), with CB 153 and 180 as the major congeners in all matrices. A gender difference was found for concentrations in hair relative to concentrations in internal tissues. Females (n=6) were found to display negative correlations, while males (n=5) showed positive correlations, although p-values were not found significant. These negative correlations in females may reflect seasonal OHC mobilisation from periphery adipose tissue due to, for example, lactation and fasting. The lack of significance in most correlations may be due to small sample sizes and seasonal variability of concentrations in soft tissues. Further research with larger sample weights and sizes is therefore necessary to draw more definitive conclusions on the usefulness of hair for biomonitoring OHCs in polar bears and other fur mammals. Copyright © 2010 Elsevier B.V. All rights reserved.

Terrestrial in situ sampling of dust devils (relative particle loads and vertical grain size distributions) as an equivalent for martian dust devils.

NASA Astrophysics Data System (ADS)

Raack, J.; Dennis, R.; Balme, M. R.; Taj-Eddine, K.; Ori, G. G.

2017-12-01

Dust devils are small vertical convective vortices which occur on Earth and Mars [1] but their internal structure is almost unknown. Here we report on in situ samples of two active dust devils in the Sahara Desert in southern Morocco [2]. For the sampling we used a 4 m high aluminium pipe with sampling areas made of removable adhesive tape. We took samples between 0.1-4 m with a sampling interval of 0.5 m and between 0.5-2 m with an interval of 0.25 m, respectively. The maximum diameter of all particles of the different sampling heights were then measured using an optical microscope to gain vertical grain size distributions and relative particle loads. Our measurements imply that both dust devils have a general comparable internal structure despite their different strengths and dimensions which indicates that the dust devils probably represents the surficial grain size distribution they move over. The particle sizes within the dust devils decrease nearly exponential with height which is comparable to results by [3]. Furthermore, our results show that about 80-90 % of the total particle load were lifted only within the first meter, which is a direct evidence for the existence of a sand skirt. If we assume that grains with a diameter <31 μm can go into suspension [4], our results show that only less than 0.1 wt% can be entrained into the atmosphere. Although this amount seems very low, these values represent between 60 and 70 % of all lifted particles due to the small grain sizes and their low weight. On Mars, the amount of lifted particles will be general higher as the dust coverage is larger [5], although the atmosphere can only suspend smaller grain sizes ( <20 μm) [6] compared to Earth. During our field campaign we observed numerous larger dust devils each day which were up to several hundred meters tall and had diameters of several tens of meters. This implies a much higher input of fine grained material into the atmosphere (which will have an influence on the climate, weather, and human health [7]) compared to the relative small dust devils sampled during our field campaign. [1] Thomas and Gierasch (1985) Science 230 [2] Raack et al. (2017) Astrobiology [3] Oke et al. (2007) J. Arid Environ. 71 [4] Balme and Greeley (2006) Rev. Geophys. 44 [5] Christensen (1986) JGR 91 [6] Newman et al. (2002) JGR 107 [7] Gillette and Sinclair (1990) Atmos. Environ. 24

Detection of internal structure by scattered light intensity: Application to kidney cell sorting

NASA Technical Reports Server (NTRS)

Goolsby, C. L.; Kunze, M. E.

1985-01-01

Scattered light measurements in flow cytometry were sucessfully used to distinguish cells on the basis of differing morphology and internal structure. Differences in scattered light patterns due to changes in internal structure would be expected to occur at large scattering angles. Practically, the results of these calculations suggest that in experimental situations an array of detectors would be useful. Although in general the detection of the scattered light intensity at several intervals within the 10 to 60 region would be sufficient, there are many examples where increased sensitivity could be acheived at other angles. The ability to measure at many different angular intervals would allow the experimenter to empirically select the optimum intervals for the varying conditions of cell size, N/C ratio, granule size and internal structure from sample to sample. The feasibility of making scattered light measurements at many different intervals in flow cytometry was demonstrated. The implementation of simplified versions of these techniques in conjunction with independant measurements of cell size could potentially improve the usefulness of flow cytometry in the study of the internal structure of cells.

The Power of Low Back Pain Trials: A Systematic Review of Power, Sample Size, and Reporting of Sample Size Calculations Over Time, in Trials Published Between 1980 and 2012.

PubMed

Froud, Robert; Rajendran, Dévan; Patel, Shilpa; Bright, Philip; Bjørkli, Tom; Eldridge, Sandra; Buchbinder, Rachelle; Underwood, Martin

2017-06-01

A systematic review of nonspecific low back pain trials published between 1980 and 2012. To explore what proportion of trials have been powered to detect different bands of effect size; whether there is evidence that sample size in low back pain trials has been increasing; what proportion of trial reports include a sample size calculation; and whether likelihood of reporting sample size calculations has increased. Clinical trials should have a sample size sufficient to detect a minimally important difference for a given power and type I error rate. An underpowered trial is one within which probability of type II error is too high. Meta-analyses do not mitigate underpowered trials. Reviewers independently abstracted data on sample size at point of analysis, whether a sample size calculation was reported, and year of publication. Descriptive analyses were used to explore ability to detect effect sizes, and regression analyses to explore the relationship between sample size, or reporting sample size calculations, and time. We included 383 trials. One-third were powered to detect a standardized mean difference of less than 0.5, and 5% were powered to detect less than 0.3. The average sample size was 153 people, which increased only slightly (∼4 people/yr) from 1980 to 2000, and declined slightly (∼4.5 people/yr) from 2005 to 2011 (P < 0.00005). Sample size calculations were reported in 41% of trials. The odds of reporting a sample size calculation (compared to not reporting one) increased until 2005 and then declined (Equation is included in full-text article.). Sample sizes in back pain trials and the reporting of sample size calculations may need to be increased. It may be justifiable to power a trial to detect only large effects in the case of novel interventions. 3.

Analysis of Darwin Rainfall Data: Implications on Sampling Strategy

NASA Technical Reports Server (NTRS)

Rafael, Qihang Li; Bras, Rafael L.; Veneziano, Daniele

1996-01-01

Rainfall data collected by radar in the vicinity of Darwin, Australia, have been analyzed in terms of their mean, variance, autocorrelation of area-averaged rain rate, and diurnal variation. It is found that, when compared with the well-studied GATE (Global Atmospheric Research Program Atlantic Tropical Experiment) data, Darwin rainfall has larger coefficient of variation (CV), faster reduction of CV with increasing area size, weaker temporal correlation, and a strong diurnal cycle and intermittence. The coefficient of variation for Darwin rainfall has larger magnitude and exhibits larger spatial variability over the sea portion than over the land portion within the area of radar coverage. Stationary, and nonstationary models have been used to study the sampling errors associated with space-based rainfall measurement. The nonstationary model shows that the sampling error is sensitive to the starting sampling time for some sampling frequencies, due to the diurnal cycle of rain, but not for others. Sampling experiments using data also show such sensitivity. When the errors are averaged over starting time, the results of the experiments and the stationary and nonstationary models match each other very closely. In the small areas for which data are available for I>oth Darwin and GATE, the sampling error is expected to be larger for Darwin due to its larger CV.

Moessbauer Characterization of Magnetite/Polyaniline Magnetic Nanocomposite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rodriguez, Anselmo F. R.; Faria, Fernando S. E. D. V.; Lopez, Jorge L.

2010-12-02

Aniline surface coated Fe{sub 3}O{sub 4} nanoparticles have been successfully synthesized by UV irradiation varying the time and the acid media (HCl, HNO{sub 3}, or H{sub 2}SO{sub 4}). The synthesized material represents a promising platform for application in nerve regeneration. XRD patterns are consistent with the crystalline structure of magnetite. Nevertheless, for UV irradiation times longer than 2 h, extra XRD lines reveal the presence of goethite. The mean crystallite size of uncoated particles is estimated to be 25.4 nm, meanwhile that size is reduced to 19.9 nm for the UV irradiated sample in HCl medium for 4 h. Moessbauermore » spectra of uncoated nanoparticles reveal the occurrence of thermal relaxation at room temperature, while the 77 K-Moessbauer spectrum suggests the occurrence of electron localization effects similar to that expected in bulk magnetite. The Mossbauer spectra of UV irradiated sample in HCl medium during 4 h, confirms the presence of the goethite phase. For this sample, the thermal relaxation is more evident, since the room temperature spectrum shows larger spectral area for the nonmagnetic component due to the smaller crystallite size. Meanwhile, the 77 K-Moessbauer spectrum suggests the absence of the electron localization effect above 77 K.« less

Testing of commonly used mixing and sampling procedures to evaluate fertilizer blends prepared with matched and mismatched particle sizes.

PubMed

Hall, William L; Ramsey, Charles; Falls, J Harold

2014-01-01

Bulk blending of dry fertilizers is a common practice in the United States and around the world. This practice involves the mixing (either physically or volumetrically) of concentrated, high analysis raw materials. Blending is followed by bagging (for small volume application such as lawn and garden products), loading into truck transports, and spreading. The great majority of bulk blended products are not bagged but handled in bulk and transferred from the blender to a holding hopper. The product is then transferred to a transport vehicle, which may, or may not, also be a spreader. If the primary transport vehicle is not a spreader, then there is another transfer at the user site to a spreader for application. Segregation of materials that are mismatched due to size, density, or shape is an issue when attempting to effectively sample or evenly spread bulk blended products. This study, prepared in coordination with and supported by the Florida Department of Agriculture and Consumer Services and the Florida Fertilizer and Agrochemical Association, looks at the impact of varying particle size as it relates to blending, sampling, and application of bulk blends. The study addresses blends containing high ratios of N-P-K materials and varying (often small) quantities of the micronutrient Zn.

Radar volume reflectivity estimation using an array of ground-based rainfall drop size detectors

NASA Astrophysics Data System (ADS)

Lane, John; Merceret, Francis; Kasparis, Takis; Roy, D.; Muller, Brad; Jones, W. Linwood

2000-08-01

Rainfall drop size distribution (DSD) measurements made by single disdrometers at isolated ground sites have traditionally been used to estimate the transformation between weather radar reflectivity Z and rainfall rate R. Despite the immense disparity in sampling geometries, the resulting Z-R relation obtained by these single point measurements has historically been important in the study of applied radar meteorology. Simultaneous DSD measurements made at several ground sites within a microscale area may be used to improve the estimate of radar reflectivity in the air volume surrounding the disdrometer array. By applying the equations of motion for non-interacting hydrometers, a volume estimate of Z is obtained from the array of ground based disdrometers by first calculating a 3D drop size distribution. The 3D-DSD model assumes that only gravity and terminal velocity due to atmospheric drag within the sampling volume influence hydrometer dynamics. The sampling volume is characterized by wind velocities, which are input parameters to the 3D-DSD model, composed of vertical and horizontal components. Reflectivity data from four consecutive WSR-88D volume scans, acquired during a thunderstorm near Melbourne, FL on June 1, 1997, are compared to data processed using the 3D-DSD model and data form three ground based disdrometers of a microscale array.

DRME: Count-based differential RNA methylation analysis at small sample size scenario.

PubMed

Liu, Lian; Zhang, Shao-Wu; Gao, Fan; Zhang, Yixin; Huang, Yufei; Chen, Runsheng; Meng, Jia

2016-04-15

Differential methylation, which concerns difference in the degree of epigenetic regulation via methylation between two conditions, has been formulated as a beta or beta-binomial distribution to address the within-group biological variability in sequencing data. However, a beta or beta-binomial model is usually difficult to infer at small sample size scenario with discrete reads count in sequencing data. On the other hand, as an emerging research field, RNA methylation has drawn more and more attention recently, and the differential analysis of RNA methylation is significantly different from that of DNA methylation due to the impact of transcriptional regulation. We developed DRME to better address the differential RNA methylation problem. The proposed model can effectively describe within-group biological variability at small sample size scenario and handles the impact of transcriptional regulation on RNA methylation. We tested the newly developed DRME algorithm on simulated and 4 MeRIP-Seq case-control studies and compared it with Fisher's exact test. It is in principle widely applicable to several other RNA-related data types as well, including RNA Bisulfite sequencing and PAR-CLIP. The code together with an MeRIP-Seq dataset is available online (https://github.com/lzcyzm/DRME) for evaluation and reproduction of the figures shown in this article. Copyright © 2016 Elsevier Inc. All rights reserved.

Using Modern Statistical Methods to Analyze Demographics of Kansas ABE/GED Students Who Transition to Community or Technical College Programs

ERIC Educational Resources Information Center

Zacharakis, Jeff; Wang, Haiyan; Patterson, Margaret Becker; Andersen, Lori

2015-01-01

This research analyzed linked high-quality state data from K-12, adult education, and postsecondary state datasets in order to better understand the association between student demographics and successful completion of a postsecondary program. Due to the relatively small sample size compared to the large number of features, we analyzed the data…

The effect of plasma pre-treatment on NaHCO3 desizing of blended sizes on cotton fabrics

NASA Astrophysics Data System (ADS)

Li, Xuming; Qiu, Yiping

2012-03-01

The influence of the He/O2 atmospheric pressure plasma jet pre-treatment on subsequent NaHCO3 desizing of blends of starch phosphate and poly(vinyl alcohol) on cotton fabrics is investigated. Atomic force microscopy and scanning electron microscopy analysis indicate that the surface topography of the samples has significantly changed and the surface roughness increases with an increase in plasma exposure time. X-ray photoelectron spectroscopy analysis shows that a larger number of oxygen-containing polar groups are formed on the sized fabric surface after the plasma treatment. The results of the percent desizing ratio (PDR) indicate that the plasma pretreatment facilitated the blended sizes removal from the cotton fabrics in subsequent NaHCO3 treatment and the PDR increases with prolonging plasma treatment time. The plasma technology is a promising pretreatment for desizing of blended sizes due to dramatically reduced desizing time.

Etch pit investigation of free electron concentration controlled 4H-SiC

NASA Astrophysics Data System (ADS)

Kim, Hong-Yeol; Shin, Yun Ji; Kim, Jung Gon; Harima, Hiroshi; Kim, Jihyun; Bahng, Wook

2013-04-01

Etch pits were investigated using the molten KOH selective etching method to examine dependence of etch pit shape and size on free electron concentration. The free electron concentrations of highly doped 4H-silicon carbide (SiC) were controlled by proton irradiation and thermal annealing, which was confirmed by a frequency shift in the LO-phonon-plasmon-coupled (LOPC) mode on micro-Raman spectroscopy. The proton irradiated sample with 5×1015 cm-2 fluence and an intrinsic semi-insulating sample showed clearly classified etch pits but different ratios of threading screw dislocation (TSD) and threading edge dislocation (TED) sizes. Easily classified TEDs and TSDs on proton irradiated 4H-SiC were restored as highly doped 4H-SiC after thermal annealing due to the recovered carrier concentrations. The etched surface of proton irradiated 4H-SiC and boron implanted SiC showed different surface conditions after activation.

Volatility measurement with directional change in Chinese stock market: Statistical property and investment strategy

NASA Astrophysics Data System (ADS)

Ma, Junjun; Xiong, Xiong; He, Feng; Zhang, Wei

2017-04-01

The stock price fluctuation is studied in this paper with intrinsic time perspective. The event, directional change (DC) or overshoot, are considered as time scale of price time series. With this directional change law, its corresponding statistical properties and parameter estimation is tested in Chinese stock market. Furthermore, a directional change trading strategy is proposed for invest in the market portfolio in Chinese stock market, and both in-sample and out-of-sample performance are compared among the different method of model parameter estimation. We conclude that DC method can capture important fluctuations in Chinese stock market and gain profit due to the statistical property that average upturn overshoot size is bigger than average downturn directional change size. The optimal parameter of DC method is not fixed and we obtained 1.8% annual excess return with this DC-based trading strategy.

A random-sum Wilcoxon statistic and its application to analysis of ROC and LROC data.

PubMed

Tang, Liansheng Larry; Balakrishnan, N

2011-01-01

The Wilcoxon-Mann-Whitney statistic is commonly used for a distribution-free comparison of two groups. One requirement for its use is that the sample sizes of the two groups are fixed. This is violated in some of the applications such as medical imaging studies and diagnostic marker studies; in the former, the violation occurs since the number of correctly localized abnormal images is random, while in the latter the violation is due to some subjects not having observable measurements. For this reason, we propose here a random-sum Wilcoxon statistic for comparing two groups in the presence of ties, and derive its variance as well as its asymptotic distribution for large sample sizes. The proposed statistic includes the regular Wilcoxon rank-sum statistic. Finally, we apply the proposed statistic for summarizing location response operating characteristic data from a liver computed tomography study, and also for summarizing diagnostic accuracy of biomarker data.

Development of composite calibration standard for quantitative NDE by ultrasound and thermography

NASA Astrophysics Data System (ADS)

Dayal, Vinay; Benedict, Zach G.; Bhatnagar, Nishtha; Harper, Adam G.

2018-04-01

Inspection of aircraft components for damage utilizing ultrasonic Non-Destructive Evaluation (NDE) is a time intensive endeavor. Additional time spent during aircraft inspections translates to added cost to the company performing them, and as such, reducing this expenditure is of great importance. There is also great variance in the calibration samples from one entity to another due to a lack of a common calibration set. By characterizing damage types, we can condense the required calibration sets and reduce the time required to perform calibration while also providing procedures for the fabrication of these standard sets. We present here our effort to fabricate composite samples with known defects and quantify the size and location of defects, such as delaminations, and impact damage. Ultrasonic and Thermographic images are digitally enhanced to accurately measure the damage size. Ultrasonic NDE is compared with thermography.

The importance of particle size in porous titanium and nonporous counterparts for surface energy and its impact on apatite formation.

PubMed

Chen, Xiao-Bo; Li, Yun-Cang; Hodgson, Peter D; Wen, Cuie

2009-07-01

The importance of particle size in titanium (Ti) fabricated by powder metallurgy for the surface energy and its impact on the apatite formation was investigated. Four sorts of Ti powders of different mean particle size were realized through 20min, 2h, 5h and 8h of ball milling, respectively. Each sort of Ti powder was used to fabricate porous Ti and its nonporous counterparts sharing similar surface morphology, grain size and chemical composition, and then alkali-heat treatment was conducted on them. Surface energy was measured on the surfaces of the nonporous Ti counterparts due to the difficulty in measuring the porous surfaces directly. The surface energy increase on the alkali-heat-treated porous and nonporous Ti was observed due to the decrease in the particle size of the Ti powders and the presence of Ti-OH groups brought by the alkali-heat treatment. The apatite-inducing ability of the alkali-heat-treated porous and nonporous Ti with different surface energy values was evaluated in modified simulated body fluid and results indicated that there was a strong correlation between the apatite-inducing ability and the surface energy. The alkali-heat-treated porous and nonporous Ti discs prepared from the powders with an average particle size of 5.89+/-0.76microm possessed the highest surface energy and the best apatite-inducing ability when compared to the samples produced from the powders with the average particle size varying from 19.79+/-0.31 to 10.25+/-0.39microm.

Clay mineralogy of the ocean sediments from the Wilkes Land margin, east Antarctica: implications on the paleoclimate, provenance and sediment dispersal pattern

NASA Astrophysics Data System (ADS)

Verma, Kamlesh; Bhattacharya, Sanjeeb; Biswas, P.; Shrivastava, Prakash K.; Pandey, Mayuri; Pant, N. C.

2014-11-01

Core U1359 collected from the continental rise off Wilkes Land, east Antarctica, is analyzed for the clay mineralogy and carbon content. The temporal variation of the clay mineralogical data shows a dominance of illite with chlorite, smectite and kaolinite in decreasing concentration. Clay mineral illite is negatively correlated with smectite which shows enrichment during 6.2-6.8, 5.5-5.8, 4.5 and 2.5 Ma. The mineralogical analyses on the silt size fraction (2-53 μm) of some selected samples were also carried out. The combined result of both the size fractions shows the presence of chlorite and illite in both size fractions, smectite and kaolinite only in clay size fraction (<2 μm) and similarity in the crystallinity and chemistry of illite in both fractions. Similar nature of illite in both fractions suggests negligible role of sorting probably due to the deposition from the waxing ice sheet. During times of ice growth, nearby cratonic east Antarctica shield provided biotite-rich sediments to the depositional site. On the other hand, the presence of smectite, only in the clay size fraction, suggests the effective role of sorting probably due to the deposition from distal source in ice retreat condition. During times of ice retreat, smectite-rich sediment derived from Ross Orogen is transported to the core site through surface or bottom water currents. Poor crystallinity of illite due to degradation further corroborates the ice retreat condition. The ice sheet proximal sediments of U1359 show that in the eastern part of Wilkes Land, the `warming' was initiated during late Miocene.

Evaluating multi-level models to test occupancy state responses of Plethodontid salamanders

USGS Publications Warehouse

Kroll, Andrew J.; Garcia, Tiffany S.; Jones, Jay E.; Dugger, Catherine; Murden, Blake; Johnson, Josh; Peerman, Summer; Brintz, Ben; Rochelle, Michael

2015-01-01

Plethodontid salamanders are diverse and widely distributed taxa and play critical roles in ecosystem processes. Due to salamander use of structurally complex habitats, and because only a portion of a population is available for sampling, evaluation of sampling designs and estimators is critical to provide strong inference about Plethodontid ecology and responses to conservation and management activities. We conducted a simulation study to evaluate the effectiveness of multi-scale and hierarchical single-scale occupancy models in the context of a Before-After Control-Impact (BACI) experimental design with multiple levels of sampling. Also, we fit the hierarchical single-scale model to empirical data collected for Oregon slender and Ensatina salamanders across two years on 66 forest stands in the Cascade Range, Oregon, USA. All models were fit within a Bayesian framework. Estimator precision in both models improved with increasing numbers of primary and secondary sampling units, underscoring the potential gains accrued when adding secondary sampling units. Both models showed evidence of estimator bias at low detection probabilities and low sample sizes; this problem was particularly acute for the multi-scale model. Our results suggested that sufficient sample sizes at both the primary and secondary sampling levels could ameliorate this issue. Empirical data indicated Oregon slender salamander occupancy was associated strongly with the amount of coarse woody debris (posterior mean = 0.74; SD = 0.24); Ensatina occupancy was not associated with amount of coarse woody debris (posterior mean = -0.01; SD = 0.29). Our simulation results indicate that either model is suitable for use in an experimental study of Plethodontid salamanders provided that sample sizes are sufficiently large. However, hierarchical single-scale and multi-scale models describe different processes and estimate different parameters. As a result, we recommend careful consideration of study questions and objectives prior to sampling data and fitting models.

Splitting CO2 with a ceria‐based redox cycle in a solar‐driven thermogravimetric analyzer

PubMed Central

Takacs, M.; Ackermann, S.; Bonk, A.; Neises‐von Puttkamer, M.; Haueter, Ph.; Scheffe, J. R.; Vogt, U. F.

2016-01-01

Thermochemical splitting of CO2 via a ceria‐based redox cycle was performed in a solar‐driven thermogravimetric analyzer. Overall reaction rates, including heat and mass transport, were determined under concentrated irradiation mimicking realistic operation of solar reactors. Reticulated porous ceramic (RPC) structures and fibers made of undoped and Zr4+‐doped CeO2, were endothermally reduced under radiative fluxes of 1280 suns in the temperature range 1200–1950 K and subsequently re‐oxidized with CO2 at 950–1400 K. Rapid and uniform heating was observed for 8 ppi ceria RPC with mm‐sized porosity due to its low optical thickness and volumetric radiative absorption, while ceria fibers with μm‐sized porosity performed poorly due to its opacity to incident irradiation. The 10 ppi RPC exhibited higher fuel yield because of its higher sample density. Zr4+‐doped ceria showed increasing reduction extents with dopant concentration but decreasing specific CO yield due to unfavorable oxidation thermodynamics and slower kinetics. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1263–1271, 2017 PMID:28405030

Thin-plate spline analysis of treatment effects of rapid maxillary expansion and face mask therapy in early Class III malocclusions.

PubMed

Baccetti, T; Franchi, L; McNamara, J A

1999-06-01

An effective morphometric method (thin-plate spline analysis) was applied to evaluate shape changes in the craniofacial configuration of a sample of 23 children with Class III malocclusions in the early mixed dentition treated with rapid maxillary expansion and face mask therapy, and compared with a sample of 17 children with untreated Class III malocclusions. Significant treatment-induced changes involved both the maxilla and the mandible. Major deformations consisted of forward displacement of the maxillary complex from the pterygoid region and of anterior morphogenetic rotation of the mandible, due to a significant upward and forward direction of growth of the mandibular condyle. Significant differences in size changes due to reduced increments in mandibular dimensions were associated with significant shape changes in the treated group.

Size effects in olivine control strength in low-temperature plasticity regime

NASA Astrophysics Data System (ADS)

Kumamoto, K. M.; Thom, C.; Wallis, D.; Hansen, L. N.; Armstrong, D. E. J.; Goldsby, D. L.; Warren, J. M.; Wilkinson, A. J.

2017-12-01

The strength of the lithospheric mantle during deformation by low-temperature plasticity controls a range of geological phenomena, including lithospheric-scale strain localization, the evolution of friction on deep seismogenic faults, and the flexure of tectonic plates. However, constraints on the strength of olivine in this deformation regime are difficult to obtain from conventional rock-deformation experiments, and previous results vary considerably. We demonstrate via nanoindentation that the strength of olivine in the low-temperature plasticity regime is dependent on the length-scale of the test, with experiments on smaller volumes of material exhibiting larger yield stresses. This "size effect" has previously been explained in engineering materials as a result of the role of strain gradients and associated geometrically necessary dislocations in modifying plastic behavior. The Hall-Petch effect, in which a material with a small grain size exhibits a higher strength than one with a large grain size, is thought to arise from the same mechanism. The presence of a size effect resolves discrepancies among previous experimental measurements of olivine, which were either conducted using indentation methods or were conducted on polycrystalline samples with small grain sizes. An analysis of different low-temperature plasticity flow laws extrapolated to room temperature reveals a power-law relationship between length-scale (grain size for polycrystalline deformation and contact radius for indentation tests) and yield strength. This suggests that data from samples with large inherent length scales best represent the plastic strength of the coarse-grained lithospheric mantle. Additionally, the plastic deformation of nanometer- to micrometer-sized asperities on fault surfaces may control the evolution of fault roughness due to their size-dependent strength.

Monitoring of bioaerosol inhalation risks in different environments using a six-stage Andersen sampler and the PCR-DGGE method.

PubMed

Xu, Zhenqiang; Yao, Maosheng

2013-05-01

Increasing evidences show that inhalation of indoor bioaerosols has caused numerous adverse health effects and diseases. However, the bioaerosol size distribution, composition, and concentration level, representing different inhalation risks, could vary with different living environments. The six-stage Andersen sampler is designed to simulate the sampling of different human lung regions. Here, the sampler was used in investigating the bioaerosol exposure in six different environments (student dorm, hospital, laboratory, hotel room, dining hall, and outdoor environment) in Beijing. During the sampling, the Andersen sampler was operated for 30 min for each sample, and three independent experiments were performed for each of the environments. The air samples collected onto each of the six stages of the sampler were incubated on agar plates directly at 26 °C, and the colony forming units (CFU) were manually counted and statistically corrected. In addition, the developed CFUs were washed off the agar plates and subjected to polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE) for diversity analysis. Results revealed that for most environments investigated, the culturable bacterial aerosol concentrations were higher than those of culturable fungal aerosols. The culturable bacterial and fungal aerosol fractions, concentration, size distribution, and diversity were shown to vary significantly with the sampling environments. PCR-DGGE analysis indicated that different environments had different culturable bacterial aerosol compositions as revealed by distinct gel band patterns. For most environments tested, larger (>3 μm) culturable bacterial aerosols with a skewed size distribution were shown to prevail, accounting for more than 60 %, while for culturable fungal aerosols with a normal size distribution, those 2.1-4.7 μm dominated, accounting for 20-40 %. Alternaria, Cladosporium, Chaetomium, and Aspergillus were found abundant in most environments studied here. Viable microbial load per unit of particulate matter was also shown to vary significantly with the sampling environments. The results from this study suggested that different environments even with similar levels of total microbial culturable aerosol concentrations could present different inhalation risks due to different bioaerosol particle size distribution and composition. This work fills literature gaps regarding bioaerosol size and composition-based exposure risks in different human dwellings in contrast to a vast body of total bioaerosol levels.

Fabricating core (Au)-shell (different stimuli-responsive polymers) nanoparticles via inverse emulsion polymerization: Comparing DOX release behavior in dark room and under NIR lighting.

PubMed

Mazloomi-Rezvani, Mahsa; Salami-Kalajahi, Mehdi; Roghani-Mamaqani, Hossein

2018-06-01

Different core-shell nanoparticles with Au as core and stimuli-responsive polymers such as poly(acrylic acid) (PAA), poly(methacrylic acid) (PMAA), poly(N-isopropylacrylamide) (PNIPAAm), poly(N,N'-methylenebis(acrylamide)) (PMBA), poly(2-hydroxyethyl methacrylate) (PHEMA) and poly((2-dimethylamino)ethyl methacrylate) (PDMAEMA) as shells were fabricated via inverse emulsion polymerization. Dynamic light scattering (DLS) was used to investigate particles sizes and particle size distributions and transmission electron microscopy (TEM) was applied to observe the core-shell structure of Au-polymer nanoparticles. Also, surface charge of all samples was studied by measurement of zeta potentials. Synthesized core-shell nanoparticles were utilized as nanocarriers of DOX as anti-cancer drug and drug release behaviors were investigated in dark room and under irradiation of near-infrared (NIR) light. Results showed that all core-shell samples have particle sizes less than 100 nm with narrow particle size distributions. Moreover, amount of drug loading decreased by increasing zeta potential. In dark room, lower pH resulted in higher cumulative drug release due to better solubility of DOX in acidic media. Also, NIR lighting on DOX-loaded samples led to increasing cumulative drug release significantly. However, DOX-loaded Au-PAA and Au-PMAA showed higher drug release at pH = 7.4 compared to 5.3 under NIR lighting. Copyright © 2018 Elsevier B.V. All rights reserved.

Structural and morphological study of Zn0.9Mn0.05Fe0.05O synthesized by sol-gel wet chemical precipitation route

NASA Astrophysics Data System (ADS)

Jain, S. K.; Dolia, S. N.; Choudhary, B. L.; Prashant, B. L.

2018-04-01

Transition metal substituted Zinc oxide (ZnO) has drawn a great deal of attention due to its excellent properties. Zn0.9Mn0.05Fe0.05O sample synthesized was by Sol-gel wet chemical precipitation route at temperature 350°C. The crystallinity and the structure of Zn0.9Mn0.05Fe0.05O was determined by X-ray diffraction by Cu-Kα radiations operated at 40kV and 35mA in the range of 20° to 80°. The pattern gets indexed in wurtzite (hexagonal) structure with lattice constants a=b=3.2525Å and c=5.2071Å and approves the single phase material with no impurity. The values of particle size assessed by Debye Scherer’s (DS) formula lie in the range of 13nm to 33nm indicating the nano-crystalline nature of the sample. The morphological analysis of the sample was performed by Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) measurements. The observed size of Zn0.9Mn0.05Fe0.05O nanoparticles by TEM micrograph exhibits the similar trend with the size calculated by Debye-Scherer formula. TEM image show the irregular shape of the nanoparticles and particle size lies in the range of 10-35nm. Similar to SEM image, the slight agglomeration of the nanoparticles have been observed from TEM.

Online versus offline: The Web as a medium for response time data collection.

PubMed

Chetverikov, Andrey; Upravitelev, Philipp

2016-09-01

The Internet provides a convenient environment for data collection in psychology. Modern Web programming languages, such as JavaScript or Flash (ActionScript), facilitate complex experiments without the necessity of experimenter presence. Yet there is always a question of how much noise is added due to the differences between the setups used by participants and whether it is compensated for by increased ecological validity and larger sample sizes. This is especially a problem for experiments that measure response times (RTs), because they are more sensitive (and hence more susceptible to noise) than, for example, choices per se. We used a simple visual search task with different set sizes to compare laboratory performance with Web performance. The results suggest that although the locations (means) of RT distributions are different, other distribution parameters are not. Furthermore, the effect of experiment setting does not depend on set size, suggesting that task difficulty is not important in the choice of a data collection method. We also collected an additional online sample to investigate the effects of hardware and software diversity on the accuracy of RT data. We found that the high diversity of browsers, operating systems, and CPU performance may have a detrimental effect, though it can partly be compensated for by increased sample sizes and trial numbers. In sum, the findings show that Web-based experiments are an acceptable source of RT data, comparable to a common keyboard-based setup in the laboratory.

Data splitting for artificial neural networks using SOM-based stratified sampling.

PubMed

May, R J; Maier, H R; Dandy, G C

2010-03-01

Data splitting is an important consideration during artificial neural network (ANN) development where hold-out cross-validation is commonly employed to ensure generalization. Even for a moderate sample size, the sampling methodology used for data splitting can have a significant effect on the quality of the subsets used for training, testing and validating an ANN. Poor data splitting can result in inaccurate and highly variable model performance; however, the choice of sampling methodology is rarely given due consideration by ANN modellers. Increased confidence in the sampling is of paramount importance, since the hold-out sampling is generally performed only once during ANN development. This paper considers the variability in the quality of subsets that are obtained using different data splitting approaches. A novel approach to stratified sampling, based on Neyman sampling of the self-organizing map (SOM), is developed, with several guidelines identified for setting the SOM size and sample allocation in order to minimize the bias and variance in the datasets. Using an example ANN function approximation task, the SOM-based approach is evaluated in comparison to random sampling, DUPLEX, systematic stratified sampling, and trial-and-error sampling to minimize the statistical differences between data sets. Of these approaches, DUPLEX is found to provide benchmark performance with good model performance, with no variability. The results show that the SOM-based approach also reliably generates high-quality samples and can therefore be used with greater confidence than other approaches, especially in the case of non-uniform datasets, with the benefit of scalability to perform data splitting on large datasets. Copyright 2009 Elsevier Ltd. All rights reserved.

Publication Bias in Psychology: A Diagnosis Based on the Correlation between Effect Size and Sample Size

PubMed Central

Kühberger, Anton; Fritz, Astrid; Scherndl, Thomas

2014-01-01

Background The p value obtained from a significance test provides no information about the magnitude or importance of the underlying phenomenon. Therefore, additional reporting of effect size is often recommended. Effect sizes are theoretically independent from sample size. Yet this may not hold true empirically: non-independence could indicate publication bias. Methods We investigate whether effect size is independent from sample size in psychological research. We randomly sampled 1,000 psychological articles from all areas of psychological research. We extracted p values, effect sizes, and sample sizes of all empirical papers, and calculated the correlation between effect size and sample size, and investigated the distribution of p values. Results We found a negative correlation of r = −.45 [95% CI: −.53; −.35] between effect size and sample size. In addition, we found an inordinately high number of p values just passing the boundary of significance. Additional data showed that neither implicit nor explicit power analysis could account for this pattern of findings. Conclusion The negative correlation between effect size and samples size, and the biased distribution of p values indicate pervasive publication bias in the entire field of psychology. PMID:25192357

Publication bias in psychology: a diagnosis based on the correlation between effect size and sample size.

PubMed

Kühberger, Anton; Fritz, Astrid; Scherndl, Thomas

2014-01-01

The p value obtained from a significance test provides no information about the magnitude or importance of the underlying phenomenon. Therefore, additional reporting of effect size is often recommended. Effect sizes are theoretically independent from sample size. Yet this may not hold true empirically: non-independence could indicate publication bias. We investigate whether effect size is independent from sample size in psychological research. We randomly sampled 1,000 psychological articles from all areas of psychological research. We extracted p values, effect sizes, and sample sizes of all empirical papers, and calculated the correlation between effect size and sample size, and investigated the distribution of p values. We found a negative correlation of r = -.45 [95% CI: -.53; -.35] between effect size and sample size. In addition, we found an inordinately high number of p values just passing the boundary of significance. Additional data showed that neither implicit nor explicit power analysis could account for this pattern of findings. The negative correlation between effect size and samples size, and the biased distribution of p values indicate pervasive publication bias in the entire field of psychology.

Effect of Ar9+ irradiation on Zr-1Nb-1Sn-0.1Fe alloy characterized by Grazing Incidence X-ray diffraction technique

NASA Astrophysics Data System (ADS)

Dutta, Argha; Das, Kalipada; Gayathri, N.; Menon, Ranjini; Nabhiraj, P. Y.; Mukherjee, Paramita

2018-03-01

The microstructural parameters such as domain size and microstrain have been estimated from Grazing Incidence X-ray Diffraction (GIXRD) data for Ar9+ irradiated Zr-1Nb-1Sn-0.1Fe sample as a function of dpa (dose). Detail studies using X-ray Diffraction Line Profile Analysis (XRDLPA) from GIXRD data has been carried out to characterize the microstructural parameters like domain size and microstrain. The reorientation of the grains due to effect of irradiation at high dpa (dose) has been qualitatively assessed by the texture parameter P(hkl).

Aggregate size and structure determination of nanomaterials in physiological media: importance of dynamic evolution

NASA Astrophysics Data System (ADS)

Afrooz, A. R. M. Nabiul; Hussain, Saber M.; Saleh, Navid B.

2014-12-01

Most in vitro nanotoxicological assays are performed after 24 h exposure. However, in determining size and shape effect of nanoparticles in toxicity assays, initial characterization data are generally used to describe experimental outcome. The dynamic size and structure of aggregates are typically ignored in these studies. This brief communication reports dynamic evolution of aggregation characteristics of gold nanoparticles. The study finds that gradual increase in aggregate size of gold nanospheres (AuNS) occurs up to 6 h duration; beyond this time period, the aggregation process deviates from gradual to a more abrupt behavior as large networks are formed. Results of the study also show that aggregated clusters possess unique structural conformation depending on nominal diameter of the nanoparticles. The differences in fractal dimensions of the AuNS samples likely occurred due to geometric differences, causing larger packing propensities for smaller sized particles. Both such observations can have profound influence on dosimetry for in vitro nanotoxicity analyses.

Optimum sample size allocation to minimize cost or maximize power for the two-sample trimmed mean test.

PubMed

Guo, Jiin-Huarng; Luh, Wei-Ming

2009-05-01

When planning a study, sample size determination is one of the most important tasks facing the researcher. The size will depend on the purpose of the study, the cost limitations, and the nature of the data. By specifying the standard deviation ratio and/or the sample size ratio, the present study considers the problem of heterogeneous variances and non-normality for Yuen's two-group test and develops sample size formulas to minimize the total cost or maximize the power of the test. For a given power, the sample size allocation ratio can be manipulated so that the proposed formulas can minimize the total cost, the total sample size, or the sum of total sample size and total cost. On the other hand, for a given total cost, the optimum sample size allocation ratio can maximize the statistical power of the test. After the sample size is determined, the present simulation applies Yuen's test to the sample generated, and then the procedure is validated in terms of Type I errors and power. Simulation results show that the proposed formulas can control Type I errors and achieve the desired power under the various conditions specified. Finally, the implications for determining sample sizes in experimental studies and future research are discussed.

Particle size analysis of lamb meat: Effect of homogenization speed, comparison with myofibrillar fragmentation index and its relationship with shear force.

PubMed

Karumendu, L U; Ven, R van de; Kerr, M J; Lanza, M; Hopkins, D L

2009-08-01

The impact of homogenization speed on Particle Size (PS) results was examined using samples from the M.longissimus thoracis et lumborum (LL) of 40 lambs. One gram duplicate samples from meat aged for 1 and 5days were homogenized at five different speeds; 11,000, 13,000, 16,000, 19,000 and 22,000rpm. In addition to this LL samples from 30 different lamb carcases also aged for 1 and 5days were used to study the comparison between PS and myofibrillar fragmentation index (MFI) values. In this case, 1g duplicate samples (n=30) were homogenized at 16,000rpm and the other half (0.5g samples) at 11,000rpm (n=30). The homogenates were then subjected to respective combinations of treatments which included either PS analysis or the determination of MFI, both with or without three cycles of centrifugation. All 140 samples of LL included 65g blocks for subsequent shear force (SF) testing. Homogenization at 16,000rpm provided the greatest ability to detect ageing differences for particle size between samples aged for 1 and 5days. Particle size at the 25% quantile provided the best result for detecting differences due to ageing. It was observed that as ageing increased the mean PS decreased and was significantly (P<0.001) less for 5days aged samples compared to 1day aged samples, while MFI values significantly increased (P<0.001) as ageing period increased. When comparing the PS and MFI methods it became apparent that, as opposed to the MFI method, there was a greater coefficient of variation for the PS method which warranted a quality assurance system. Given this requirement and examination of the mean, standard deviation and the 25% quantile for PS data it was concluded that three cycles of centrifugation were not necessary and this also applied to the MFI method. There were significant correlations (P<0.001) within the same lamb loin sample aged for a given period between mean MFI and mean PS (-0.53), mean MFI and mean SF (-0.38) and mean PS and mean SF (0.23). It was concluded that PS analysis offers significant potential for streamlining determination of myofibrillar degradation when samples are measured after homogenization at 16,000rpm with no centrifugation.

Methodological issues concerning the application of reliable laser particle sizing in soils

NASA Astrophysics Data System (ADS)

de Mascellis, R.; Impagliazzo, A.; Basile, A.; Minieri, L.; Orefice, N.; Terribile, F.

2009-04-01

During the past decade, the evolution of technologies has enabled laser diffraction (LD) to become a much widespread means of particle size distribution (PSD), replacing sedimentation and sieve analysis in many scientific fields mainly due to its advantages of versatility, fast measurement and high reproducibility. Despite such developments of the last decade, the soil scientist community has been quite reluctant to replace the good old sedimentation techniques (ST); possibly because of (i) the large complexity of the soil matrix inducing different types of artefacts (aggregates, deflocculating dynamics, etc.), (ii) the difficulties in relating LD results with results obtained through sedimentation techniques and (iii) the limited size range of most LD equipments. More recently LD granulometry is slowly gaining appreciation in soil science also because of some innovations including an enlarged size dynamic range (0,01-2000 m) and the ability to implement more powerful algorithms (e.g. Mie theory). Furthermore, LD PSD can be successfully used in the application of physically based pedo-transfer functions (i.e., Arya and Paris model) for investigations of soil hydraulic properties, due to the direct determination of PSD in terms of volume percentage rather than in terms of mass percentage, thus eliminating the need to adopt the rough approximation of a single value for soil particle density in the prediction process. Most of the recent LD work performed in soil science deals with the comparison with sedimentation techniques and show the general overestimation of the silt fraction following a general underestimation of the clay fraction; these well known results must be related with the different physical principles behind the two techniques. Despite these efforts, it is indeed surprising that little if any work is devoted to more basic methodological issues related to the high sensitivity of LD to the quantity and the quality of the soil samples. Our work aims to both analyse and to suggest technical solutions to address the following key methodological problems: (i) sample representativeness due to the very small amount of soil sample required by LD (e.g. 0,2 g) as compared to ST (e.g. 40 g for densimetry); (ii) PSD reading variability caused by the large number of instantaneous reading on a very small volume of the solution, (iii) the varying soil mineralogy that in turn produce varying refractive indexes affecting PSD results, (iv) the determination of the mass density of the soil samples to compare results with those obtained from ST. Our results, referring to many different soil types (Vertisols, Regosols, Andosols, Calcisols, Luvisols) show that the listed major technical problems can be successfully addressed by the following set of solutions: (i) adequate subsampling in both solid and liquid phases (including a setup of a dilution system); (ii) preliminary study of the PSD variability to reasonably increase the number of readings per each sample; (iii, iv) preliminary sensitivity analysis of both refractive indexes and mass density in accordance to the specific soil mineralogy.

Analysis of Body Size Measurements for U.S. Navy Women’s Clothing and Pattern Design

DTIC Science & Technology

1979-03-01

due Charles E . Clauser, of the Aerospace Medical Research Laboratory at Wright-Patterson Air Force Base, Ohio and Robert M. White of the U.S. Army...Distribution of Samples by Race ..... e 155 6 Distribution of Samples by Handedness. 155 7 Number of Subjects at Each Site ....... 156 C FREQUENCY...20TH 7.86 -.. .. .. ... .. ... e - s ......... 7-65 15TH 7,* 77 ! ADJUSTED COMPOSITE VALUE 1 7.54 10TH 7,66 1 I 7,37 5TH 7.50 ! MEAN 8.23 1 7o26 3TH 7e40

A new facility for non-destructive assay using a 252Cf source.

PubMed

Stevanato, L; Caldogno, M; Dima, R; Fabris, D; Hao, Xin; Lunardon, M; Moretto, S; Nebbia, G; Pesente, S; Pino, F; Sajo-Bohus, L; Viesti, G

2013-03-01

A new laboratory facility for non-destructive analysis (NDA) using a time-tagged (252)Cf source is presented. The system is designed to analyze samples having maximum size of about 20 × 25 cm(2), the material recognition being obtained by measuring simultaneously total and energy dependent transmission of neutrons and gamma rays. The equipment technical characteristics and performances of the NDA system are presented, exploring also limits due to the sample thickness. Some recent applications in the field of cultural heritage are presented. Copyright © 2012 Elsevier Ltd. All rights reserved.

Reduction and structural modification of zirconolite on He+ ion irradiation

NASA Astrophysics Data System (ADS)

Gupta, Merry; Kulriya, P. K.; Shukla, Rishabh; Dhaka, R. S.; Kumar, Raj; Ghumman, S. S.

2016-07-01

The immobilization of minor actinides and alkaline-earth metal is a major concern in nuclear industry due to their long-term radioactive contribution to the high level waste (HLW). Materials having zirconolite, pyrochlore, and perovskite structure are promising candidates for immobilization of HLW. The zirconolite which exhibits high radiation stability and corrosion resistance behavior is investigated for its radiation stability against alpha particles in the present study. CaZrTi2O7 pellets prepared using solid state reaction techniques, were irradiated with 30 keV He+ ions for the ion fluence varying from 1 × 1017 to 1 × 1021 ions/m2. Scanning electron microscopy (SEM) images of the un-irradiated sample exhibited well separated grains with average size of about 6.8 μm. On the ion irradiation, value of the average grains size was about 7.1 μm, and change in the microstructure was insignificant. The X-ray photoelectron spectroscopy (XPS) studies showed a shift in the core level peak position (of Ca 2p, Ti 2p and Zr 3d) towards lower binding energy with respect to pristine sample as well as loss of oxygen was also observed for sample irradiated with the ion fluence of 1 × 1020 ions/m2. These indicate a decrease in co-ordination number and the ionic character of Msbnd O bond. Moreover, core level XPS signal was not detected for sample irradiated with ion fluence of 1 × 1021 ions/m2, suggesting surface damage of the sample at this ion fluence. However, X-ray diffraction (XRD) studies showed that zirconolite was not amorphized even on irradiation up to a fluence order of 1 × 1021 ion/m2. But, significant decrease in peak intensity due to creation of defects and a marginal positive peak shift due to tensile strain induced by irradiation, were observed. Thus, XRD along with XPS investigation suggests that reduction, decrease in co-ordination number, and increase in covalency are responsible for the radiation damage in zirconolite.

Spatial Distribution of Elemental Concentrations in Street Dust of Hanoi, Vietnam.

PubMed

Phi, Thai Ha; Chinh, Pham Minh; Hung, Nguyen The; Ly, Luong Thi Mai; Thai, Phong K

2017-02-01

Street dust samples were collected at 163 locations across four different zones of Hanoi, Vietnam, covering different traffic and population densities. Samples were sieved into three fractions of different particle sizes and analyzed for elemental concentrations (K, Ca, Mn, Fe, Zn, Pb) using an X-ray fluorescence (XRF) instrument. The metal concentrations in street dust were compared among different sampling zones and with samples from background to evaluate the degree of pollution. The smallest size particle fraction (diameter <75 μm) contained higher concentrations of metals than the coarser ones (diameters = 75-180 and >180 μm). While concentrations of metals like Ca and Fe are spatially similar, concentrations of Pb and Zn in street dust varied between different zones, with the highest concentrations observed in dust from the downtown area, and lowest levels in the new suburb areas. Overall, compared to studies from cities in other countries, the mean concentration of Pb in street dust in Hanoi was relatively low, suggesting a lower risk to human health due to inhalation or ingestion of Pb-containing dust particles than in cities where Pb concentrations were several times higher.

Structural studies on the substitution of Ag, Na doped LCSMO CMR manganites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Subhashini, P., E-mail: subhashinisvu@gmail.com; Krishnaiah, M.; Munirathinam, B.

2016-05-06

Synthesis and characterization of colossal magnetoresistance (CMR) materials has been a subject of scientific research due to the unique transport, magnetotransport, and magnetic properties. The single phase polycrystalline La{sub 0.7}Ca{sub 0.1}Sr{sub 0.1}M{sub 0.1}MnO{sub 3} (LCSMO) (M=Ag and Na) samples prepared using nitrate route method. The structural properties are studied at different dopants by X-ray diffraction. The surface morphology and elemental analysis of both samples were carried out by scanning electron microscopy (SEM) and energy dispersive X-ray technique (EDAX) respectively. The structural analysis shows that the LCSMO is crystallized in an orthorhombic perovskite structure belonging to Pnma space group. The crystalmore » size of the sample is calculated using Scherrer formula. The SEM images show that the polycrystalline grains are observed to be near spherical shape and uniform in size. EDAX spectra taken from the surface of the synthesized powders show a nominal composition near the desired one for M=Na sample where as some vacancies are present in the A-site in the case of Ag substitution as will be discussed in this paper.« less

Aged boreal biomass-burning aerosol size distributions from BORTAS 2011

NASA Astrophysics Data System (ADS)

Sakamoto, K. M.; Allan, J. D.; Coe, H.; Taylor, J. W.; Duck, T. J.; Pierce, J. R.

2015-02-01

Biomass-burning aerosols contribute to aerosol radiative forcing on the climate system. The magnitude of this effect is partially determined by aerosol size distributions, which are functions of source fire characteristics (e.g. fuel type, MCE) and in-plume microphysical processing. The uncertainties in biomass-burning emission number-size distributions in climate model inventories lead to uncertainties in the CCN (cloud condensation nuclei) concentrations and forcing estimates derived from these models. The BORTAS-B (Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellite) measurement campaign was designed to sample boreal biomass-burning outflow over eastern Canada in the summer of 2011. Using these BORTAS-B data, we implement plume criteria to isolate the characteristic size distribution of aged biomass-burning emissions (aged ~ 1-2 days) from boreal wildfires in northwestern Ontario. The composite median size distribution yields a single dominant accumulation mode with Dpm = 230 nm (number-median diameter) and σ = 1.5, which are comparable to literature values of other aged plumes of a similar type. The organic aerosol enhancement ratios (ΔOA / ΔCO) along the path of Flight b622 show values of 0.09-0.17 μg m-3 ppbv-1 (parts per billion by volume) with no significant trend with distance from the source. This lack of enhancement ratio increase/decrease with distance suggests no detectable net OA (organic aerosol) production/evaporation within the aged plume over the sampling period (plume age: 1-2 days), though it does not preclude OA production/loss at earlier stages. A Lagrangian microphysical model was used to determine an estimate of the freshly emitted size distribution corresponding to the BORTAS-B aged size distributions. The model was restricted to coagulation and dilution processes based on the insignificant net OA production/evaporation derived from the ΔOA / ΔCO enhancement ratios. We estimate that the young-plume median diameter was in the range of 59-94 nm with modal widths in the range of 1.7-2.8 (the ranges are due to uncertainty in the entrainment rate). Thus, the size of the freshly emitted particles is relatively unconstrained due to the uncertainties in the plume dilution rates.

Origin and heterogeneity of pore sizes in the Mount Simon Sandstone and Eau Claire Formation: Implications for multiphase fluid flow

DOE PAGES

Mozley, Peter S.; Heath, Jason E.; Dewers, Thomas A.; ...

2016-01-01

The Mount Simon Sandstone and Eau Claire Formation represent a principal reservoir - caprock system for wastewater disposal, geologic CO 2 storage, and compressed air energy storage (CAES) in the Midwestern United States. Of primary concern to site performance is heterogeneity in flow properties that could lead to non-ideal injectivity and distribution of injected fluids (e.g., poor sweep efficiency). Using core samples from the Dallas Center Structure, Iowa, we investigate pore structure that governs flow properties of major lithofacies of these formations. Methods include gas porosimetry and permeametry, mercury intrusion porosimetry, thin section petrography, and X-ray diffraction. The lithofacies exhibitmore » highly variable intra- and inter-informational distributions of pore throat and body sizes. Based on pore-throat size, samples fall into four distinct groups. Micropore-throat dominated samples are from the Eau Claire Formation, whereas the macropore-, mesopore-, and uniform-dominated samples are from the Mount Simon Sandstone. Complex paragenesis governs the high degree of pore and pore-throat size heterogeneity, due to an interplay of precipitation, non-uniform compaction, and later dissolution of cements. Furthermore, the cement dissolution event probably accounts for much of the current porosity in the unit. The unusually heterogeneous nature of the pore networks in the Mount Simon Sandstone indicates that there is a greater-than-normal opportunity for reservoir capillary trapping of non-wetting fluids — as quantified by CO 2 and air column heights — which should be taken into account when assessing the potential of the reservoir-caprock system for CO 2 storage and CAES.« less

Investigating textural controls on Archie's porosity exponent using process-based, pore-scale modelling

NASA Astrophysics Data System (ADS)

Niu, Q.; Zhang, C.

2017-12-01

Archie's law is an important empirical relationship linking the electrical resistivity of geological materials to their porosity. It has been found experimentally that the porosity exponent m in Archie's law in sedimentary rocks might be related to the degree of cementation, and therefore m is termed as "cementation factor" in most literatures. Despite it has been known for many years, there is lack of well-accepted physical interpretations of the porosity exponent. Some theoretical and experimental evidences have also shown that m may be controlled by the particle and/or pore shape. In this study, we conduct a pore-scale modeling of the porosity exponent that incorporates different geological processes. The evolution of m of eight synthetic samples with different particle sizes and shapes are calculated during two geological processes, i.e., compaction and cementation. The numerical results show that in dilute conditions, m is controlled by the particle shape. As the samples deviate from dilute conditions, m increases gradually due to the strong interaction between particles. When the samples are at static equilibrium, m is noticeably larger than its values at dilution condition. The numerical simulation results also show that both geological compaction and cementation induce a significant increase in m. In addition, the geometric characteristics of these samples (e.g., pore space/throat size, and their distributions) during compaction and cementation are also calculated. Preliminary analysis shows a unique correlation between the pore size broadness and porosity exponent for all eight samples. However, such a correlation is not found between m and other geometric characteristics.

Human body mass estimation: a comparison of "morphometric" and "mechanical" methods.

PubMed

Auerbach, Benjamin M; Ruff, Christopher B

2004-12-01

In the past, body mass was reconstructed from hominin skeletal remains using both "mechanical" methods which rely on the support of body mass by weight-bearing skeletal elements, and "morphometric" methods which reconstruct body mass through direct assessment of body size and shape. A previous comparison of two such techniques, using femoral head breadth (mechanical) and stature and bi-iliac breadth (morphometric), indicated a good general correspondence between them (Ruff et al. [1997] Nature 387:173-176). However, the two techniques were never systematically compared across a large group of modern humans of diverse body form. This study incorporates skeletal measures taken from 1,173 Holocene adult individuals, representing diverse geographic origins, body sizes, and body shapes. Femoral head breadth, bi-iliac breadth (after pelvic rearticulation), and long bone lengths were measured on each individual. Statures were estimated from long bone lengths using appropriate reference samples. Body masses were calculated using three available femoral head breadth (FH) formulae and the stature/bi-iliac breadth (STBIB) formula, and compared. All methods yielded similar results. Correlations between FH estimates and STBIB estimates are 0.74-0.81. Slight differences in results between the three FH estimates can be attributed to sampling differences in the original reference samples, and in particular, the body-size ranges included in those samples. There is no evidence for systematic differences in results due to differences in body proportions. Since the STBIB method was validated on other samples, and the FH methods produced similar estimates, this argues that either may be applied to skeletal remains with some confidence. 2004 Wiley-Liss, Inc.

Intrapopulation variation in stature and body proportions: social status and sex differences in an Italian medieval population (Trino Vercellese, VC).

PubMed

Vercellotti, Giuseppe; Stout, Sam D; Boano, Rosa; Sciulli, Paul W

2011-06-01

The phenotypic expression of adult body size and shape results from synergistic interactions between hereditary factors and environmental conditions experienced during growth. Variation in body size and shape occurs even in genetically relatively homogeneous groups, due to different occurrence, duration, and timing of growth insults. Understanding the causes and patterns of intrapopulation variation can foster meaningful information on early life conditions in living and past populations. This study assesses the pattern of biological variation in body size and shape attributable to sex and social status in a medieval Italian population. The sample includes 52 (20 female, 32 male) adult individuals from the medieval population of Trino Vercellese, Italy. Differences in element size and overall body size (skeletal height and body mass) were assessed through Monte Carlo methods, while univariate non-parametric tests and Principal Component Analysis (PCA) were employed to examine segmental and overall body proportions. Discriminant Analysis was employed to determine the predictive value of individual skeletal elements for social status in the population. Our results highlight a distinct pattern in body size and shape variation in relation to status and sex. Male subsamples exhibit significant postcranial variation in body size, while female subsamples express smaller, nonsignificant differences. The analysis of segmental proportions highlighted differences in trunk/lower limb proportions between different status samples, and PCA indicated that in terms of purely morphological variation high status males were distinct from all other groups. The pattern observed likely resulted from a combination of biological factors and cultural practices. Copyright © 2011 Wiley-Liss, Inc.

A Model of Thermal Conductivity for Planetary Soils: 1. Theory for Unconsolidated Soils

NASA Technical Reports Server (NTRS)

Piqueux, S.; Christensen, P. R.

2009-01-01

We present a model of heat conduction for mono-sized spherical particulate media under stagnant gases based on the kinetic theory of gases, numerical modeling of Fourier s law of heat conduction, theoretical constraints on the gas thermal conductivity at various Knudsen regimes, and laboratory measurements. Incorporating the effect of the temperature allows for the derivation of the pore-filling gas conductivity and bulk thermal conductivity of samples using additional parameters (pressure, gas composition, grain size, and porosity). The radiative and solid-to-solid conductivities are also accounted for. Our thermal model reproduces the well-established bulk thermal conductivity dependency of a sample with the grain size and pressure and also confirms laboratory measurements finding that higher porosities generally lead to lower conductivities. It predicts the existence of the plateau conductivity at high pressure, where the bulk conductivity does not depend on the grain size. The good agreement between the model predictions and published laboratory measurements under a variety of pressures, temperatures, gas compositions, and grain sizes provides additional confidence in our results. On Venus, Earth, and Titan, the pressure and temperature combinations are too high to observe a soil thermal conductivity dependency on the grain size, but each planet has a unique thermal inertia due to their different surface temperatures. On Mars, the temperature and pressure combination is ideal to observe the soil thermal conductivity dependency on the average grain size. Thermal conductivity models that do not take the temperature and the pore-filling gas composition into account may yield significant errors.

Fabrication and Magnetic Properties of Co₂MnAl Heusler Alloys by Mechanical Alloying.

PubMed

Lee, Chung-Hyo

2018-02-01

We have applied mechanical alloying (MA) to produce nanocrystalline Co2MnAl Heusler alloys using a mixture of elemental Co50Mn25Al25 powders. An optimal milling and heat treatment conditions to obtain a Co2MnAl Heusler phase with fine microstructure were investigated by X-ray diffraction, differential scanning calorimeter and vibrating sample magnetometer measurements. α-(Co, Mn, Al) FCC phases coupled with amorphous phase are obtained after 3 hours of MA without any evidence for the formation of Co2MnAl alloys. On the other hand, a Co2MnAl Heusler alloys can be obtained by the heat treatment of all MA samples up to 650 °C. X-ray diffraction result shows that the average grain size of Co2MnAl Heusler alloys prepared by MA for 5 h and heat treatment is in the range of 95 nm. The saturation magnetization of MA powders decreases with MA time due to the magnetic dilution by alloying with nonmagnetic Mn and Al elements. The magnetic hardening due to the reduction of the grain size with ball milling is also observed. However, the saturation magnetization of MA powders after heat treatment increases with MA time and reaches to a maximum value of 105 emu/g after 5 h of MA. It can be also seen that the coercivity of 5 h MA sample annealed at 650 °C is fairly low value of 25 Oe.

Numerical simulation based on core analysis of a single fracture in an Enhanced Geothermal System

NASA Astrophysics Data System (ADS)

Jarrahi, Miad; Holländer, Hartmut

2017-04-01

The permeability of reservoirs is widely affected by the presence of fractures dispersed within them, as they form superior paths for fluid flow. Core analysis studies the fractures characteristics and explains the fluid-rock interactions to provide the information of permeability and saturation of a hydraulic fracturing reservoir or an enhanced geothermal system (EGS). This study conducted numerical simulations of a single fracture in a Granite core obtained from a depth of 1890 m in borehole EPS1 from Soultz-sous-Forêts, France. Blaisonneau et al. (2016) designed the apparatus to investigate the complex physical phenomena on this cylindrical sample. The method of the tests was to percolate a fluid through a natural fracture contained in a rock sample, under controlled thermo-hydro-mechanical conditions. A divergent radial flow within the fracture occurred due to the injection of fluid into the center of the fracture. The tests were performed within a containment cell with a normal stress of 2.6, 4.9, 7.2 and 9.4 MPa loading on the sample perpendicular to the fracture plane. This experiment was numerically performed to provide an efficient numerical method by modeling single phase flow in between the fracture walls. Detailed morphological features of the fracture such as tortuosity and roughness, were obtained by image processing. The results included injection pressure plots with respect to injection flow rate. Consequently, by utilizing Hagen-Poiseuille's cubic law, the equivalent hydraulic aperture size, of the fracture was derived. Then, as the sample is cylindrical, to modify the Hagen-Poiseuille's cubic law for circular parallel plates, the geometric relation was applied to obtain modified hydraulic aperture size. Finally, intrinsic permeability of the fracture under each mechanical normal stress was evaluated based on modified hydraulic aperture size. The results were presented in two different scenarios, before and after reactive percolation test, to demonstrate the effect of chemical reactive flow. The fracture after percolation test showed larger equivalent aperture size and higher permeability. Additionally, the higher the normal stress, the lower permeability was investigated. This confirmed the permeability evolution due to chemical percolation and mechanical loading. All results showed good agreements with corresponding experimental results provided by Blaisonneau et al. (2016). Keyword: Core analysis, Hydraulic fracturing, Enhanced geothermal system, Permeability, Fluid-rock interactions.

The enhancement in electrical analysis of the nitrogen doped amorphous carbon thin films (a-C:N) prepared by aerosol-assisted CVD

NASA Astrophysics Data System (ADS)

Fadzilah, A. N.; Dayana, K.; Rusop, M.

2018-05-01

This paper reports on the deposition of Nitrogen doped amorphous carbon (a-C:N) by Aerosol-assisted Chemical Vapor Deposition (AACVD) using natural source of camphor oil as the precursor material. 5 samples were deposited at 5 different deposition times from 15 min to 90 min, with 15 min interval for each sample. The highest slope of linear graph was noted at the sample with 45 min deposition time, showing the lowest electrical resistance of the sample. From I-V characteristic, the sample deposited at 45 min has the highest electrical conductivity due to high sp2 carbon bonding ratio. Nanostructured behavior of N doped a-C:N was also investigated by FESEM micrograph resulting with the particle size less than 100nm.

A method for analysing small samples of floral pollen for free and protein-bound amino acids.

PubMed

Stabler, Daniel; Power, Eileen F; Borland, Anne M; Barnes, Jeremy D; Wright, Geraldine A

2018-02-01

Pollen provides floral visitors with essential nutrients including proteins, lipids, vitamins and minerals. As an important nutrient resource for pollinators, including honeybees and bumblebees, pollen quality is of growing interest in assessing available nutrition to foraging bees. To date, quantifying the protein-bound amino acids in pollen has been difficult and methods rely on large amounts of pollen, typically more than 1 g. More usual is to estimate a crude protein value based on the nitrogen content of pollen, however, such methods provide no information on the distribution of essential and non-essential amino acids constituting the proteins.Here, we describe a method of microwave-assisted acid hydrolysis using low amounts of pollen that allows exploration of amino acid composition, quantified using ultra high performance liquid chromatography (UHPLC), and a back calculation to estimate the crude protein content of pollen.Reliable analysis of protein-bound and free amino acids as well as an estimation of crude protein concentration was obtained from pollen samples as low as 1 mg. Greater variation in both protein-bound and free amino acids was found in pollen sample sizes <1 mg. Due to the variability in recovery of amino acids in smaller sample sizes, we suggest a correction factor to apply to specific sample sizes of pollen in order to estimate total crude protein content.The method described in this paper will allow researchers to explore the composition of amino acids in pollen and will aid research assessing the available nutrition to pollinating animals. This method will be particularly useful in assaying the pollen of wild plants, from which it is difficult to obtain large sample weights.

Dealing with non-unique and non-monotonic response in particle sizing instruments

NASA Astrophysics Data System (ADS)

Rosenberg, Phil

2017-04-01

A number of instruments used as de-facto standards for measuring particle size distributions are actually incapable of uniquely determining the size of an individual particle. This is due to non-unique or non-monotonic response functions. Optical particle counters have non monotonic response due to oscillations in the Mie response curves, especially for large aerosol and small cloud droplets. Scanning mobility particle sizers respond identically to two particles where the ratio of particle size to particle charge is approximately the same. Images of two differently sized cloud or precipitation particles taken by an optical array probe can have similar dimensions or shadowed area depending upon where they are in the imaging plane. A number of methods exist to deal with these issues, including assuming that positive and negative errors cancel, smoothing response curves, integrating regions in measurement space before conversion to size space and matrix inversion. Matrix inversion (also called kernel inversion) has the advantage that it determines the size distribution which best matches the observations, given specific information about the instrument (a matrix which specifies the probability that a particle of a given size will be measured in a given instrument size bin). In this way it maximises use of the information in the measurements. However this technique can be confused by poor counting statistics which can cause erroneous results and negative concentrations. Also an effective method for propagating uncertainties is yet to be published or routinely implemented. Her we present a new alternative which overcomes these issues. We use Bayesian methods to determine the probability that a given size distribution is correct given a set of instrument data and then we use Markov Chain Monte Carlo methods to sample this many dimensional probability distribution function to determine the expectation and (co)variances - hence providing a best guess and an uncertainty for the size distribution which includes contributions from the non-unique response curve, counting statistics and can propagate calibration uncertainties.

Agglomeration of Luminescent Porous Silicon Nanoparticles in Colloidal Solutions

NASA Astrophysics Data System (ADS)

Herynková, Kateřina; Šlechta, Miroslav; Šimáková, Petra; Fučíková, Anna; Cibulka, Ondřej

2016-08-01

We have prepared colloidal solutions of clusters composed from porous silicon nanoparticles in methanol, water and phosphate-buffered saline (PBS). Even if the size of the nanoclusters is between 60 and 500 nm, due to their highly porous "cauliflower"-like structure, the porous silicon nanoparticles are composed of interconnected nanocrystals having around 2.5 nm in size and showing strong visible luminescence in the orange-red spectral region (centred at 600-700 nm). Hydrophilic behaviour and good solubility of the nanoclusters in water and water-based solutions were obtained by adding hydrogen peroxide into the etching solution during preparation and 16 min long after-bath in hydrogen peroxide. By simple filtration of the solutions with syringe filters, we have extracted smaller nanoclusters with sizes of approx. 60-70 nm; however, these nanoclusters in water and PBS solution (pH neutral) are prone to agglomeration, as was confirmed by zeta potential measurements. When the samples were left at ambient conditions for several weeks, the typical nanocluster size increased to approx. 330-400 nm and then remained stable. However, both freshly filtered and aged samples (with agglomerated porous silicon nanoparticles) of porous silicon in water and PBS solutions can be further used for biological studies or as luminescent markers in living cells.

Cell segmentation in histopathological images with deep learning algorithms by utilizing spatial relationships.

PubMed

Hatipoglu, Nuh; Bilgin, Gokhan

2017-10-01

In many computerized methods for cell detection, segmentation, and classification in digital histopathology that have recently emerged, the task of cell segmentation remains a chief problem for image processing in designing computer-aided diagnosis (CAD) systems. In research and diagnostic studies on cancer, pathologists can use CAD systems as second readers to analyze high-resolution histopathological images. Since cell detection and segmentation are critical for cancer grade assessments, cellular and extracellular structures should primarily be extracted from histopathological images. In response, we sought to identify a useful cell segmentation approach with histopathological images that uses not only prominent deep learning algorithms (i.e., convolutional neural networks, stacked autoencoders, and deep belief networks), but also spatial relationships, information of which is critical for achieving better cell segmentation results. To that end, we collected cellular and extracellular samples from histopathological images by windowing in small patches with various sizes. In experiments, the segmentation accuracies of the methods used improved as the window sizes increased due to the addition of local spatial and contextual information. Once we compared the effects of training sample size and influence of window size, results revealed that the deep learning algorithms, especially convolutional neural networks and partly stacked autoencoders, performed better than conventional methods in cell segmentation.

Pattern of relative growth in cockle Anadara antiquata in Ihamahu coastal waters, Central Maluku

NASA Astrophysics Data System (ADS)

Siahainenia, L.; Tuhumury, S. F.; Uneputty, P. A.; Tuhumury, N. C.

2018-03-01

Anadara antiquata is economically important species for fisheries and belong to phylum mollusc which also found in Maluku. However, the density of population begins to decrease recently due to high exploitation by people. The objective of the present study was to analyze relative growth pattern of A. antiquata including size distribution and growth pattern based on shell dimensions. The study was conducted from December 2016 to February 2017 in Ihamahu coastal waters. Data were collected by using purposive random sampling. All the individuals of A. antiquata found were measured the length, width and height by using a vernier caliper to the nearest 0.01mm. Data were analyzed by using SPSS 20 and Microsoft Excel software. The results indicated that the A. antiquata mostly found in seagrass bed with a muddy substrate. The size distribution of shell dimensions was different during sampling. Overall, the length ranged from 15.87 mm to 57.5 mm, the width from 15.50 mm to 48.60 mm and the height was from 9.36 mm to 35.9 mm. The population of A. antiquata consisted of juvenile and mature size. The mature size (> 30 mm) was more dominant in the population. The A. antiquata showed allometric relative growth pattern based on shell dimensions.

Agglomeration of Luminescent Porous Silicon Nanoparticles in Colloidal Solutions.

PubMed

Herynková, Kateřina; Šlechta, Miroslav; Šimáková, Petra; Fučíková, Anna; Cibulka, Ondřej

2016-12-01

We have prepared colloidal solutions of clusters composed from porous silicon nanoparticles in methanol, water and phosphate-buffered saline (PBS). Even if the size of the nanoclusters is between 60 and 500 nm, due to their highly porous "cauliflower"-like structure, the porous silicon nanoparticles are composed of interconnected nanocrystals having around 2.5 nm in size and showing strong visible luminescence in the orange-red spectral region (centred at 600-700 nm). Hydrophilic behaviour and good solubility of the nanoclusters in water and water-based solutions were obtained by adding hydrogen peroxide into the etching solution during preparation and 16 min long after-bath in hydrogen peroxide. By simple filtration of the solutions with syringe filters, we have extracted smaller nanoclusters with sizes of approx. 60-70 nm; however, these nanoclusters in water and PBS solution (pH neutral) are prone to agglomeration, as was confirmed by zeta potential measurements. When the samples were left at ambient conditions for several weeks, the typical nanocluster size increased to approx. 330-400 nm and then remained stable. However, both freshly filtered and aged samples (with agglomerated porous silicon nanoparticles) of porous silicon in water and PBS solutions can be further used for biological studies or as luminescent markers in living cells.

Evaluation of sample holders designed for long-lasting X-ray micro-tomographic scans of ex-vivo soft tissue samples

NASA Astrophysics Data System (ADS)

Dudak, J.; Zemlicka, J.; Krejci, F.; Karch, J.; Patzelt, M.; Zach, P.; Sykora, V.; Mrzilkova, J.

2016-03-01

X-ray microradiography and microtomography are imaging techniques with increasing applicability in the field of biomedical and preclinical research. Application of hybrid pixel detector Timepix enables to obtain very high contrast of low attenuating materials such as soft biological tissue. However X-ray imaging of ex-vivo soft tissue samples is a difficult task due to its structural instability. Ex-vivo biological tissue is prone to fast drying-out which is connected with undesired changes of sample size and shape producing later on artefacts within the tomographic reconstruction. In this work we present the optimization of our Timepix equipped micro-CT system aiming to maintain soft tissue sample in stable condition. Thanks to the suggested approach higher contrast of tomographic reconstructions can be achieved while also large samples that require detector scanning can be easily measured.

Evaluation of sampling frequency, window size and sensor position for classification of sheep behaviour.

PubMed

Walton, Emily; Casey, Christy; Mitsch, Jurgen; Vázquez-Diosdado, Jorge A; Yan, Juan; Dottorini, Tania; Ellis, Keith A; Winterlich, Anthony; Kaler, Jasmeet

2018-02-01

Automated behavioural classification and identification through sensors has the potential to improve health and welfare of the animals. Position of a sensor, sampling frequency and window size of segmented signal data has a major impact on classification accuracy in activity recognition and energy needs for the sensor, yet, there are no studies in precision livestock farming that have evaluated the effect of all these factors simultaneously. The aim of this study was to evaluate the effects of position (ear and collar), sampling frequency (8, 16 and 32 Hz) of a triaxial accelerometer and gyroscope sensor and window size (3, 5 and 7 s) on the classification of important behaviours in sheep such as lying, standing and walking. Behaviours were classified using a random forest approach with 44 feature characteristics. The best performance for walking, standing and lying classification in sheep (accuracy 95%, F -score 91%-97%) was obtained using combination of 32 Hz, 7 s and 32 Hz, 5 s for both ear and collar sensors, although, results obtained with 16 Hz and 7 s window were comparable with accuracy of 91%-93% and F -score 88%-95%. Energy efficiency was best at a 7 s window. This suggests that sampling at 16 Hz with 7 s window will offer benefits in a real-time behavioural monitoring system for sheep due to reduced energy needs.

Evaluation of sampling frequency, window size and sensor position for classification of sheep behaviour

PubMed Central

Walton, Emily; Casey, Christy; Mitsch, Jurgen; Vázquez-Diosdado, Jorge A.; Yan, Juan; Dottorini, Tania; Ellis, Keith A.; Winterlich, Anthony

2018-01-01

Automated behavioural classification and identification through sensors has the potential to improve health and welfare of the animals. Position of a sensor, sampling frequency and window size of segmented signal data has a major impact on classification accuracy in activity recognition and energy needs for the sensor, yet, there are no studies in precision livestock farming that have evaluated the effect of all these factors simultaneously. The aim of this study was to evaluate the effects of position (ear and collar), sampling frequency (8, 16 and 32 Hz) of a triaxial accelerometer and gyroscope sensor and window size (3, 5 and 7 s) on the classification of important behaviours in sheep such as lying, standing and walking. Behaviours were classified using a random forest approach with 44 feature characteristics. The best performance for walking, standing and lying classification in sheep (accuracy 95%, F-score 91%–97%) was obtained using combination of 32 Hz, 7 s and 32 Hz, 5 s for both ear and collar sensors, although, results obtained with 16 Hz and 7 s window were comparable with accuracy of 91%–93% and F-score 88%–95%. Energy efficiency was best at a 7 s window. This suggests that sampling at 16 Hz with 7 s window will offer benefits in a real-time behavioural monitoring system for sheep due to reduced energy needs. PMID:29515862

Non-Destructive Study of Bulk Crystallinity and Elemental Composition of Natural Gold Single Crystal Samples by Energy-Resolved Neutron Imaging

PubMed Central

Tremsin, Anton S.; Rakovan, John; Shinohara, Takenao; Kockelmann, Winfried; Losko, Adrian S.; Vogel, Sven C.

2017-01-01

Energy-resolved neutron imaging enables non-destructive analyses of bulk structure and elemental composition, which can be resolved with high spatial resolution at bright pulsed spallation neutron sources due to recent developments and improvements of neutron counting detectors. This technique, suitable for many applications, is demonstrated here with a specific study of ~5–10 mm thick natural gold samples. Through the analysis of neutron absorption resonances the spatial distribution of palladium (with average elemental concentration of ~0.4 atom% and ~5 atom%) is mapped within the gold samples. At the same time, the analysis of coherent neutron scattering in the thermal and cold energy regimes reveals which samples have a single-crystalline bulk structure through the entire sample volume. A spatially resolved analysis is possible because neutron transmission spectra are measured simultaneously on each detector pixel in the epithermal, thermal and cold energy ranges. With a pixel size of 55 μm and a detector-area of 512 by 512 pixels, a total of 262,144 neutron transmission spectra are measured concurrently. The results of our experiments indicate that high resolution energy-resolved neutron imaging is a very attractive analytical technique in cases where other conventional non-destructive methods are ineffective due to sample opacity. PMID:28102285

How chip size impacts steam pretreatment effectiveness for biological conversion of poplar wood into fermentable sugars

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeMartini, Jaclyn D.; Foston, Marcus; Meng, Xianzhi

We report that woody biomass is highly recalcitrant to enzymatic sugar release and often requires significant size reduction and severe pretreatments to achieve economically viable sugar yields in biological production of sustainable fuels and chemicals. However, because mechanical size reduction of woody biomass can consume significant amounts of energy, it is desirable to minimize size reduction and instead pretreat larger wood chips prior to biological conversion. To date, however, most laboratory research has been performed on materials that are significantly smaller than applicable in a commercial setting. As a result, there is a limited understanding of the effects that largermore » biomass particle size has on the effectiveness of steam explosion pretreatment and subsequent enzymatic hydrolysis of wood chips. To address these concerns, novel downscaled analysis and high throughput pretreatment and hydrolysis (HTPH) were applied to examine whether differences exist in the composition and digestibility within a single pretreated wood chip due to heterogeneous pretreatment across its thickness. Heat transfer modeling, Simons’ stain testing, magnetic resonance imaging (MRI), and scanning electron microscopy (SEM) were applied to probe the effects of pretreatment within and between pretreated wood samples to shed light on potential causes of variation, pointing to enzyme accessibility (i.e., pore size) distribution being a key factor dictating enzyme digestibility in these samples. Application of these techniques demonstrated that the effectiveness of pretreatment of Populus tremuloides can vary substantially over the chip thickness at short pretreatment times, resulting in spatial digestibility effects and overall lower sugar yields in subsequent enzymatic hydrolysis. Finally, these results indicate that rapid decompression pretreatments (e.g., steam explosion) that specifically alter accessibility at lower temperature conditions are well suited for larger wood chips due to the non-uniformity in temperature and digestibility profiles that can result from high temperature and short pretreatment times. Furthermore, this study also demonstrated that wood chips were hydrated primarily through the natural pore structure during pretreatment, suggesting that preserving the natural grain and transport systems in wood during storage and chipping processes could likely promote pretreatment efficacy and uniformity.« less

How chip size impacts steam pretreatment effectiveness for biological conversion of poplar wood into fermentable sugars

DOE PAGES

DeMartini, Jaclyn D.; Foston, Marcus; Meng, Xianzhi; ...

2015-12-09

We report that woody biomass is highly recalcitrant to enzymatic sugar release and often requires significant size reduction and severe pretreatments to achieve economically viable sugar yields in biological production of sustainable fuels and chemicals. However, because mechanical size reduction of woody biomass can consume significant amounts of energy, it is desirable to minimize size reduction and instead pretreat larger wood chips prior to biological conversion. To date, however, most laboratory research has been performed on materials that are significantly smaller than applicable in a commercial setting. As a result, there is a limited understanding of the effects that largermore » biomass particle size has on the effectiveness of steam explosion pretreatment and subsequent enzymatic hydrolysis of wood chips. To address these concerns, novel downscaled analysis and high throughput pretreatment and hydrolysis (HTPH) were applied to examine whether differences exist in the composition and digestibility within a single pretreated wood chip due to heterogeneous pretreatment across its thickness. Heat transfer modeling, Simons’ stain testing, magnetic resonance imaging (MRI), and scanning electron microscopy (SEM) were applied to probe the effects of pretreatment within and between pretreated wood samples to shed light on potential causes of variation, pointing to enzyme accessibility (i.e., pore size) distribution being a key factor dictating enzyme digestibility in these samples. Application of these techniques demonstrated that the effectiveness of pretreatment of Populus tremuloides can vary substantially over the chip thickness at short pretreatment times, resulting in spatial digestibility effects and overall lower sugar yields in subsequent enzymatic hydrolysis. Finally, these results indicate that rapid decompression pretreatments (e.g., steam explosion) that specifically alter accessibility at lower temperature conditions are well suited for larger wood chips due to the non-uniformity in temperature and digestibility profiles that can result from high temperature and short pretreatment times. Furthermore, this study also demonstrated that wood chips were hydrated primarily through the natural pore structure during pretreatment, suggesting that preserving the natural grain and transport systems in wood during storage and chipping processes could likely promote pretreatment efficacy and uniformity.« less

Influence of Cu-Cr substitution on structural, morphological, electrical and magnetic properties of magnesium ferrite

NASA Astrophysics Data System (ADS)

Yonatan Mulushoa, S.; Murali, N.; Tulu Wegayehu, M.; Margarette, S. J.; Samatha, K.

2018-03-01

Cu-Cr substituted magnesium ferrite materials (Mg1 - xCuxCrxFe21 - xO4 with x = 0.0-0.7) have been synthesized by the solid state reaction method. XRD analysis revealed the prepared samples are cubic spinel with single phase face centered cubic. A significant decrease of ∼41.15 nm in particle size is noted in response to the increase in Cu-Cr substitution level. The room temperature resistivity increases gradually from 0.553 × 105 Ω cm (x = 0.0) to 0.105 × 108 Ω cm (x = 0.7). Temperature dependent DC-electrical resistivity of all the samples, exhibits semiconductor like behavior. Cu-Cr doped materials can be suitable to limit the eddy current losses. VSM result shows pure and doped magnesium ferrite particles show soft ferrimagnetic nature at room temperature. The saturation magnetization of the samples decreases initially from 34.5214 emu/g for x = 0.0 to 18.98 emu/g (x = 0.7). Saturation magnetization, remanence and coercivity are decreased with doping, which may be due to the increase in grain size.

Friction Stir Welding of Al Alloy 2219-T8: Part II-Mechanical and Corrosion

NASA Astrophysics Data System (ADS)

Kang, Ju; Feng, Zhi-Cao; Li, Ji-Chao; Frankel, G. S.; Wang, Guo-Qing; Wu, Ai-Ping

2016-09-01

In Part I of this series, abnormal agglomerations of θ particles with size of about 100 to 1000 µm were observed in friction stir welded AA2219-T8 joints. In this work, the effects of these agglomerated θ particles on the mechanical and corrosion properties of the joints are studied. Tensile testing with in situ SEM imaging was utilized to monitor crack initiation and propagation in base metal and weld nugget zone (WNZ) samples. These tests showed that cracks initiated in the θ particles and at the θ/matrix interfaces, but not in the matrix. The WNZ samples containing abnormal agglomerated θ particles had a similar ultimate tensile stress but 3 pct less elongation than other WNZ samples with only normal θ particles. Measurements using the microcell technique indicated that the agglomerated θ particles acted as a cathode causing the dissolution of adjacent matrix. The abnormal θ particle agglomerations led to more severe localized attack due to the large cathode/anode ratio. Al preferential dissolution occurred in the abnormal θ particle agglomerations, which was different from the corrosion behavior of normal size θ particles.

Problems in determining the surface density of the Galactic disk

NASA Technical Reports Server (NTRS)

Statler, Thomas S.

1989-01-01

A new method is presented for determining the local surface density of the Galactic disk from distance and velocity measurements of stars toward the Galactic poles. The procedure is fully three-dimensional, approximating the Galactic potential by a potential of Staeckel form and using the analytic third integral to treat the tilt and the change of shape of the velocity ellipsoid consistently. Applying the procedure to artificial data superficially resembling the K dwarf sample of Kuijken and Gilmore (1988, 1989), it is shown that the current best estimates of local disk surface density are uncertain by at least 30 percent. Of this, about 25 percent is due to the size of the velocity sample, about 15 percent comes from uncertainties in the rotation curve and the solar galactocentric distance, and about 10 percent from ignorance of the shape of the velocity distribution above z = 1 kpc, the errors adding in quadrature. Increasing the sample size by a factor of 3 will reduce the error to 20 percent. To achieve 10 percent accuracy, observations will be needed along other lines of sight to constrain the shape of the velocity ellipsoid.

XRD-based 40Ar/39Ar age correction for fine-grained illite, with application to folded carbonates in the Monterrey Salient (northern Mexico)

NASA Astrophysics Data System (ADS)

Fitz-Díaz, Elisa; Hall, Chris M.; van der Pluijm, Ben A.

2016-05-01

Due to their minute size, 40Ar/39Ar analysis of illite faces significant analytical challenges, including mineral characterization and, especially, effects of grain size and crystallography on 39Ar recoil. Quantifying the effects of 39Ar recoil requires the use of sample vacuum encapsulation during irradiation, which permits the measurement of the fraction of recoiled 39Ar as well as the 39Ar and 40Ar∗ retained within illite crystals that are released during step heating. Total-Gas Ages (TGA) are calculated by using both recoiled and retained argon, which is functionally equivalent to K-Ar ages, while Retention Ages (RA) only involve retained Ar in the crystal. Natural applications have shown that TGA fits stratigraphic constraints of geological processes when the average illite crystallite thickness (ICT) is smaller than 10 nm, and that RA matches these constraints for ICTs larger than 50 nm. We propose a new age correction method that takes into account the average ICT and corresponding recoiled 39Ar for a sample, with X-ray Corrected Ages (XCA) lying between Total-Gas and Retention Ages depending on ICT. This correction is particularly useful in samples containing authigenic illite formed in the anchizone, with typical ICT values between 10 and 50 nm. In three samples containing authigenic illite from Cretaceous carbonates in the Monterrey Salient in northern Mexico, there is a range in TGAs among the different size-fractions of 46-49, 36-43 and 40-52 Ma, while RAs range from 54-64, 47-52 and 53-54 Ma, respectively. XCA calculations produce tighter age ranges for these samples of 52.5-56, 45.5-48.5 and 49-52.5 Ma, respectively. In an apparent age vs ICT or %2M 1illite plot, authigenic illite grains show a slope that is in general slightly positive for TGA, slightly negative for RA, but close to zero for XCA, with thinner crystallites showing more dispersion than thicker ones. In order to test if dispersion is due to a different formation history or the result of retention capability, degassing spectra were modeled for site XCA averages and overall XCA average. Modeling shows that local site age average best match the measured spectra, instead of a global average age, indicating that illite growth reflects local deformation, and is not the result of regional metamorphism. Modeling also shows that Ar-degassing spectra are very sensitive to grain size, such that age interpretation based on Ar-plateaus is meaningless for most fine-grained clays.

Normalization and microbial differential abundance strategies depend upon data characteristics.

PubMed

Weiss, Sophie; Xu, Zhenjiang Zech; Peddada, Shyamal; Amir, Amnon; Bittinger, Kyle; Gonzalez, Antonio; Lozupone, Catherine; Zaneveld, Jesse R; Vázquez-Baeza, Yoshiki; Birmingham, Amanda; Hyde, Embriette R; Knight, Rob

2017-03-03

Data from 16S ribosomal RNA (rRNA) amplicon sequencing present challenges to ecological and statistical interpretation. In particular, library sizes often vary over several ranges of magnitude, and the data contains many zeros. Although we are typically interested in comparing relative abundance of taxa in the ecosystem of two or more groups, we can only measure the taxon relative abundance in specimens obtained from the ecosystems. Because the comparison of taxon relative abundance in the specimen is not equivalent to the comparison of taxon relative abundance in the ecosystems, this presents a special challenge. Second, because the relative abundance of taxa in the specimen (as well as in the ecosystem) sum to 1, these are compositional data. Because the compositional data are constrained by the simplex (sum to 1) and are not unconstrained in the Euclidean space, many standard methods of analysis are not applicable. Here, we evaluate how these challenges impact the performance of existing normalization methods and differential abundance analyses. Effects on normalization: Most normalization methods enable successful clustering of samples according to biological origin when the groups differ substantially in their overall microbial composition. Rarefying more clearly clusters samples according to biological origin than other normalization techniques do for ordination metrics based on presence or absence. Alternate normalization measures are potentially vulnerable to artifacts due to library size. Effects on differential abundance testing: We build on a previous work to evaluate seven proposed statistical methods using rarefied as well as raw data. Our simulation studies suggest that the false discovery rates of many differential abundance-testing methods are not increased by rarefying itself, although of course rarefying results in a loss of sensitivity due to elimination of a portion of available data. For groups with large (~10×) differences in the average library size, rarefying lowers the false discovery rate. DESeq2, without addition of a constant, increased sensitivity on smaller datasets (<20 samples per group) but tends towards a higher false discovery rate with more samples, very uneven (~10×) library sizes, and/or compositional effects. For drawing inferences regarding taxon abundance in the ecosystem, analysis of composition of microbiomes (ANCOM) is not only very sensitive (for >20 samples per group) but also critically the only method tested that has a good control of false discovery rate. These findings guide which normalization and differential abundance techniques to use based on the data characteristics of a given study.

Expression of Superparamagnetic Particles on FORC Diagrams

NASA Astrophysics Data System (ADS)

Hirt, A. M.; Kumari, M.; Crippa, F.; Petri-Fink, A.

2015-12-01

Identification of superparamagnetic (SP) particles in natural materials provides information on processes that lead to the new formation or dissolution of iron oxides. SP particles express themselves on first-order reversal curve (FORC) diagrams as a distribution centered near the origin of the diagram. Pike et al. (2001, GJI, 145, 721) demonstrated that thermal relaxation produces an upward shift in the FORC distribution, and attributed this to a pause encountered at each reversal field. In this study we examine the relationship between this upward shift and particles size on two sets of synthetic iron oxide nanoparticles. One set of coated magnetite particles have well-constrained particles size with 9, 16 and 20 nm as their diameter. A second set from the FeraSpin™ Series, consisting of FeraSpinXS, M and XL, were evaluated. Rock magnetic experiments indicate that the first set of samples is exclusively magnetite, whereas the FeraSpin samples contain predominantly magnetite with some degree of oxidation. Samples from both sets show that the upward shift of the FORC distribution at the origin increases with decreasing particle size. The amount of shift in the FeraSpin series is less when compared to the samples from the first set. This is attributed to the effect of interaction that counteracts the effect of thermal relaxation behavior of the SP particles. The FeraSpin series also shows a broader FORC distribution on the vertical axis that appears to be related to non-saturation of the hysteresis curve at maximum applied field. This non-saturation behavior can be due to spins of very fine particles or oxidation to hematite. AC susceptibility at low temperature indicates that particle interaction may affect the effective magnetic particle size. Our results suggest that the FORC distribution in pure SP particle systems provides information on the particle size distribution or oxidation, which can be further evaluated with low temperature techniques.

Increased Oxidative Burden Associated with Traffic Component of Ambient Particulate Matter at Roadside and Urban Background Schools Sites in London

PubMed Central

Godri, Krystal J.; Harrison, Roy M.; Evans, Tim; Baker, Timothy; Dunster, Christina; Mudway, Ian S.; Kelly, Frank J.

2011-01-01

As the incidence of respiratory and allergic symptoms has been reported to be increased in children attending schools in close proximity to busy roads, it was hypothesised that PM from roadside schools would display enhanced oxidative potential (OP). Two consecutive one-week air quality monitoring campaigns were conducted at seven school sampling sites, reflecting roadside and urban background in London. Chemical characteristics of size fractionated particulate matter (PM) samples were related to the capacity to drive biological oxidation reactions in a synthetic respiratory tract lining fluid. Contrary to hypothesised contrasts in particulate OP between school site types, no robust size-fractionated differences in OP were identified due high temporal variability in concentrations of PM components over the one-week sampling campaigns. For OP assessed both by ascorbate (OPAA m−3) and glutathione (OPGSH m−3) depletion, the highest OP per cubic metre of air was in the largest size fraction, PM1.9–10.2. However, when expressed per unit mass of particles OPAA µg−1 showed no significant dependence upon particle size, while OPGSH µg−1 had a tendency to increase with increasing particle size, paralleling increased concentrations of Fe, Ba and Cu. The two OP metrics were not significantly correlated with one another, suggesting that the glutathione and ascorbate depletion assays respond to different components of the particles. Ascorbate depletion per unit mass did not show the same dependence as for GSH and it is possible that other trace metals (Zn, Ni, V) or organic components which are enriched in the finer particle fractions, or the greater surface area of smaller particles, counter-balance the redox activity of Fe, Ba and Cu in the coarse particles. Further work with longer-term sampling and a larger suite of analytes is advised in order to better elucidate the determinants of oxidative potential, and to fuller explore the contrasts between site types. PMID:21818283

Pre-aging time dependence of microstructure and mechanical properties in nanostructured Al-2wt%Cu alloy

NASA Astrophysics Data System (ADS)

Azad, Bahram; Borhani, Ehsan

2016-03-01

This work is focused on the effect of pre-aging time on the properties of Al-2wt%Cu alloy processed by accumulative roll bonding (ARB) process. Following aged at 190 °C for 10 or 30 min, the samples were deformed up to a strain of 4.8 by the ARB process. The microstructure evolution was investigated by transmission electron microscope and electron backscattering diffraction analyzes. The results showed that the Al2Cu precipitates were formed with different sizes due to the different pre-aging times and the finer precipitates were more effective on the formation of high angle grain boundaries during the ARB process. The grain size of Aged-10 min and Aged-30 min specimens decreased to 400 nm and 420 nm, respectively, after 6 cycles of the ARB process. Also, the final texture after 6 cycles of the ARB process, shown in the {111} pole figure, were different depending on the starting microstructures. The mechanical properties of specimens were investigated by the Vickers microhardness measurements and the tensile tests. The results showed that the mechanical properties are affected by the starting microstructure. The mechanical properties of Aged-10 min specimen were different compared to Aged-30 min specimen due to the different size of the pre-existing precipitates. Although by continuing process, the precipitates were probably dissolved due to the heavy deformation.

Structural evolution of nanoporous silica thin films studied by positron annihilation spectroscopy and Fourier transform infrared spectroscopy

NASA Astrophysics Data System (ADS)

Patel, N.; Mariazzi, S.; Toniutti, L.; Checchetto, R.; Miotello, A.; Dirè, S.; Brusa, R. S.

2007-09-01

Three series of silica thin films with thicknesses in the 300 nm range were deposited by spin coating on Si substrates using different compositions of the sol precursors. Film samples were thermally treated in static air at temperatures ranging from 300 to 900 °C. The effect of sol precursors and thermal treatment temperature on the film porosity was analysed by Fourier transform infrared (FTIR) spectroscopy, depth profiling with positron annihilation spectroscopy (DP-PAS) and the analysis of the capacitance-voltage (C-V) characteristic. The maximum of the total porosity was found to occur at a temperature of 600 °C when removal of porogen and OH groups was completed. Film densification due to the collapsing of the pores was observed after drying at 900 °C. DP-PAS provides evidence that the increase in the total porosity is related to a progressive increase in the pore size. The increase in the pore size never gives rise to the onset of connected porosity. In the silica film samples prepared using a low acidity sol precursor, the pore size is always lower than 1 nm. By increasing the acid catalyst ratio in the sol, larger pores are formed. Pores with size larger than 2.3 nm can be obtained by adding porogen to the sol. In each series of silica film samples the shift of the antisymmetric Si-O-Si transversal optical (TO3) mode upon thermal treatment correlates with a change of the pore size as evidenced by DP-PAS analysis. The pore microstructure of the three series of silica films is different at all the examined treatment temperatures and depends on the composition of the precursor sol.

Key to enhance thermoelectric performance by controlling crystal size of strontium titanate

NASA Astrophysics Data System (ADS)

Wang, Jun; Ye, Xinxin; Yaer, Xinba; Wu, Yin; Zhang, Boyu; Miao, Lei

2015-09-01

One-step molten salt synthesis process was introduced to fabricate nano to micrometer sized SrTiO3 powders in which effects of synthesis temperature, oxide-to-flux ratios and raw materials on the generation of SrTiO3 powders were examined. 100 nm or above sized pure SrTiO3 particles were obtained at relatively lower temperature of 900∘C. Micro-sized rhombohedral crystals with a maximum size of approximately 12 μm were obtained from SrCO3 or Sr(NO3)2 strontium source with 1:1 O/S ratio. Controlled crystal size and morphology of Nb-doped SrTiO3 particles are prepared by using this method to confirm the performance of thermoelectric properties. The Seebeck coefficient obtained is significantly high when compared with the reported data, and the high ratio of nano particles in the sample has a positive effect on the increase of Seebeck coefficient too, which is likely due to the energy filtering effect at large numbers of grain boundaries resulting from largely distributed structure.

Development of Automated Objective Meteorological Techniques.

DTIC Science & Technology

1980-11-30

differences are due largely to the nature and spatial distribution of the atmospheric data chosen as input for the model . The data for initial values and...technique. This report fo,-uses on results of theoretical investigations and data analyses performed oy SASC during the period May, 1979 to June, 1980...the sampling period, at a given point in space, the various size particles composing the particle distribution ex- hibit different velocities from each

Draft Genome Sequence of Zobellia sp. Strain OII3, Isolated from the Coastal Zone of the Baltic Sea.

PubMed

Harms, Henrik; Poehlein, Anja; Thürmer, Andrea; König, Gabriele M; Schäberle, Till F

2017-09-07

Zobellia sp. strain OII3 was isolated from a marine environmental sample due to its heterotrophic lifestyle, i.e., using Escherichia coli cells as prey. It shows strong agar-lytic activity. The genome was assembled into 41 contigs with a total size of 5.4 Mb, revealing the genetic basis for natural product biosynthesis. Copyright © 2017 Harms et al.

Fit to Fight: Admin or Ethos? Embedding Fitness in Air Force Culture

DTIC Science & Technology

2009-02-12

including decreased levels of anxiety , depression , fatigue, and confusion, and improved memory and cognition.7 Maj Denise Hollywood highlighted...Ballaro also found a strong “statistically significant relationship between individuals who returned . . . early [from deployment] due to illness or...injuries and individuals who did not exercise while deployed.” Granted, sample size was small, but of the 89 early returners, 62--or 70 percent--did

A Direct Comparison of Two Densely Sampled HIV Epidemics: The UK and Switzerland

NASA Astrophysics Data System (ADS)

Ragonnet-Cronin, Manon L.; Shilaih, Mohaned; Günthard, Huldrych F.; Hodcroft, Emma B.; Böni, Jürg; Fearnhill, Esther; Dunn, David; Yerly, Sabine; Klimkait, Thomas; Aubert, Vincent; Yang, Wan-Lin; Brown, Alison E.; Lycett, Samantha J.; Kouyos, Roger; Brown, Andrew J. Leigh

2016-09-01

Phylogenetic clustering approaches can elucidate HIV transmission dynamics. Comparisons across countries are essential for evaluating public health policies. Here, we used a standardised approach to compare the UK HIV Drug Resistance Database and the Swiss HIV Cohort Study while maintaining data-protection requirements. Clusters were identified in subtype A1, B and C pol phylogenies. We generated degree distributions for each risk group and compared distributions between countries using Kolmogorov-Smirnov (KS) tests, Degree Distribution Quantification and Comparison (DDQC) and bootstrapping. We used logistic regression to predict cluster membership based on country, sampling date, risk group, ethnicity and sex. We analysed >8,000 Swiss and >30,000 UK subtype B sequences. At 4.5% genetic distance, the UK was more clustered and MSM and heterosexual degree distributions differed significantly by the KS test. The KS test is sensitive to variation in network scale, and jackknifing the UK MSM dataset to the size of the Swiss dataset removed the difference. Only heterosexuals varied based on the DDQC, due to UK male heterosexuals who clustered exclusively with MSM. Their removal eliminated this difference. In conclusion, the UK and Swiss HIV epidemics have similar underlying dynamics and observed differences in clustering are mainly due to different population sizes.

Branching, flowering and fruiting of Jatropha curcas treated with ethephon or benzyladenine and gibberellins.

PubMed

Costa, Anne P; Vendrame, Wagner; Nietsche, Sílvia; Crane, Jonathan; Moore, Kimberly; Schaffer, Bruce

2016-05-31

Jatropha curcas L. has been identified for biofuel production but it presents limited commercial yields due to limited branching and a lack of yield uniformity. The objective of this study was to evaluate the effects of single application of ethephon or a combination of 6-benzyladenine (BA) with gibberellic acid isomers A4 and A7 (GA4+7) on branch induction, flowering and fruit production in jatropha plants with and without leaves. Plants with and without leaves showed differences for growth and reproductive variables. For all variables except inflorescence set, there were no significant statistical interactions between the presence of leaves and plant growth regulators concentration. The total number of flowers per inflorescence was reduced as ethephon concentration was increased. As BA + GA4 +7 concentration increased, seed dry weight increased. Thus, ethephon and BA + GA4 +7 applications appeared to affect flowering and seed production to a greater extent than branching. The inability to discern significant treatment effects for most variables might have been due to the large variability within plant populations studied and thus resulting in an insufficient sample size. Therefore, data collected from this study were used for statistical estimations of sample sizes to provide a reference for future studies.

Mineralogy and Major Element Abundance of the Dust Particles Recovered from Muses-C Regio on the Asteroid Itokawa

NASA Technical Reports Server (NTRS)

Nakamura, T.; Noguchi, T.; Tanaka, M.; Zolensky, M. E.; Kimura, M.; Nakato, A.; Ogami, T.; Ishida, H.; Tsuchiyama, A.; Yada, T.;

Global complication rates of type 2 diabetes in Indigenous peoples: A comprehensive review.

PubMed

Naqshbandi, Mariam; Harris, Stewart B; Esler, James G; Antwi-Nsiah, Fred

2008-10-01

The world's Indigenous peoples are experiencing an unprecedented epidemic of type 2 diabetes [T2DM] but little has been published describing the complications burden. The objective of this paper was to conduct a systematic review of T2DM complications in Indigenous populations worldwide. A literature review was conducted using PubMed and EMBASE to examine available complications data. Country, Indigenous population, authors, publication year, total sample size, Indigenous sample size, age, methodology, and prevalence of nephropathy, end-stage renal disease, retinopathy, neuropathy, lower extremity amputations, cardiovascular disease, hospitalizations and mortality due to diabetes were recorded. One-hundred and eleven studies were selected. Results revealed a disproportionate burden of disease complications among all Indigenous peoples regardless of their geographic location. Complication rates were seen to vary widely across Indigenous groups. Gaps were found in the published literature on complications among Indigenous populations, especially those living in underdeveloped countries. These gaps may be in part due to the challenges caused by varying operational practices, research methodologies, and definitions of the term Indigenous, making documentation of rates among these peoples problematic. Comprehensive surveillance applying standardized definitions and methodologies is needed to design targeted prevention and disease management strategies for Indigenous peoples with T2DM.

Assessment of the influence of field size on maize gene flow using SSR analysis.

PubMed

Palaudelmàs, M; Melé, E; Monfort, A; Serra, J; Salvia, J; Messeguer, J

2012-06-01

One of the factors that may influence the rate of cross-fertilization is the relative size of the pollen donor and receptor fields. We designed a spatial distribution with four varieties of genetically-modified (GM) yellow maize to generate different sized fields while maintaining a constant distance to neighbouring fields of conventional white kernel maize. Samples of cross-fertilized, yellow kernels in white cobs were collected from all of the adjacent fields at different distances. A special series of samples was collected at distances of 0, 2, 5, 10, 20, 40, 80 and 120 m following a transect traced in the dominant down-wind direction in order to identify the origin of the pollen through SSR analysis. The size of the receptor fields should be taken into account, especially when they extend in the same direction than the GM pollen flow is coming. From collected data, we then validated a function that takes into account the gene flow found in the field border and that is very useful for estimating the % of GM that can be found in any point of the field. It also serves to predict the total GM content of the field due to cross fertilization. Using SSR analysis to identify the origin of pollen showed that while changes in the size of the donor field clearly influence the percentage of GMO detected, this effect is moderate. This study demonstrates that doubling the donor field size resulted in an approximate increase of GM content in the receptor field of 7%. This indicates that variations in the size of the donor field have a smaller influence on GM content than variations in the size of the receptor field.

Small-sized microplastics and pigmented particles in bottled mineral water.

PubMed

Oßmann, Barbara E; Sarau, George; Holtmannspötter, Heinrich; Pischetsrieder, Monika; Christiansen, Silke H; Dicke, Wilhelm

2018-09-15

Up to now, only a few studies about microparticle contamination of bottled mineral water have been published. The smallest analysed particle size was 5 μm. However, due to toxicological reasons, especially microparticles smaller than 1.5 μm are critically discussed. Therefore, in the present study, 32 samples of bottled mineral water were investigated for contamination by microplastics, pigment and additive particles. Due to the application of aluminium coated polycarbonate membrane filters and micro-Raman spectroscopy, a lowest analysed particle size of 1 μm was achieved. Microplastics were found in water from all bottle types: in single use and reusable bottles made of poly(ethylene terephthalate) (PET) as well as in glass bottles. The amount of microplastics in mineral water varied from 2649 ± 2857 per litre in single use PET bottles up to 6292 ± 10521 per litre in glass bottles. While in plastic bottles, the predominant polymer type was PET; in glass bottles various polymers such as polyethylene or styrene-butadiene-copolymer were found. Hence, besides the packaging itself, other contamination sources have to be considered. Pigment particles were detected in high amounts in reusable, paper labelled bottles (195047 ± 330810 pigment particles per litre in glass and 23594 ± 25518 pigment particles per litre in reusable paper labelled PET bottles). Pigment types found in water samples were the same as used for label printing, indicating the bottle cleaning process as possible contamination route. Furthermore, on average 708 ± 1024 particles per litre of the additive Tris(2,4-di-tert-butylphenyl)phosphite were found in reusable PET bottles. This additive might be leached out from the bottle material itself. Over 90% of the detected microplastics and pigment particles were smaller than 5 μm and thus not covered by previous studies. In summary, this is the first study reporting about microplastics, pigment and additive particles found in bottled mineral water samples with a smallest analysed particle size of 1 μm. Copyright © 2018 Elsevier Ltd. All rights reserved.

Seasonal dynamics of coarse atmospheric particulate matter between 2.5 μm and 80 μm in Beijing and the impact of 2008 Olympic Games

NASA Astrophysics Data System (ADS)

Norra, Stefan; Yu, Yang; Dietze, Volker; Schleicher, Nina; Fricker, Mathieu; Kaminski, Uwe; Chen, Yuan; Stüben, Doris; Cen, Kuang

2016-01-01

Beijing is well known as a megacity facing severe atmospheric pollution problems. One very important kind of pollution is the high amount of particles in Beijing's atmosphere. Numerous studies investigated the dynamics of fine particles smaller 10 μm. Less information is available on the coarse particle fraction larger 10 μm, although geogenic dusts, which often are composed by those coarser particles, frequently affect the air quality in Beijing. Therefore, systematic sampling and analysis of size fractionated particulate matter between 2.5 and 80 μm was performed in Beijing from April 2005 till October 2009. Atmospheric particles were collected in the North-West of Beijing using a cost-effective passive sampling method called Sigma-2. Altogether, 200 weeks could be analysed and assessed. Concentrations and size distribution of atmospheric coarse particles were determined by automated microscopic single particle analysis. Seasonal variability of the total mass of different size fractions was identified as follows: spring > winter > autumn > summer. High concentrations of transparent mineral particles indicate the activity of geogenic sources in spring and winter time, due to asian dust events and resuspension of soil from local bare land during dry and windy periods. The percentage of opaque particle components differs seasonally with relatively high values in winter, confirming combustion of fossil fuels for heating purposes as a predominant pollution source in this season. The influence of meteorological conditions on concentrations and size distribution of atmospheric particulate matter between 2.5 and 80 μm is demonstrated for the whole sampling period. Lowest pollution by coarse aerosols occurred during the period of the 2008 Olympic Summer Games. A general trend of decreasing total coarse particle mass concentrations was observed. Due to frequently observed high total coarse particle mass concentrations of several 100 μg·m-³ it is strongly recommended to enhance research and observation regarding these air pollutants to gain a better understanding of their dynamics, health effects, well being impacts on Beijing inhabitants and the effectiveness of mitigation measures.

[Effect sizes, statistical power and sample sizes in "the Japanese Journal of Psychology"].

PubMed

Suzukawa, Yumi; Toyoda, Hideki

2012-04-01

This study analyzed the statistical power of research studies published in the "Japanese Journal of Psychology" in 2008 and 2009. Sample effect sizes and sample statistical powers were calculated for each statistical test and analyzed with respect to the analytical methods and the fields of the studies. The results show that in the fields like perception, cognition or learning, the effect sizes were relatively large, although the sample sizes were small. At the same time, because of the small sample sizes, some meaningful effects could not be detected. In the other fields, because of the large sample sizes, meaningless effects could be detected. This implies that researchers who could not get large enough effect sizes would use larger samples to obtain significant results.

ALCHEMY: a reliable method for automated SNP genotype calling for small batch sizes and highly homozygous populations

PubMed Central

Wright, Mark H.; Tung, Chih-Wei; Zhao, Keyan; Reynolds, Andy; McCouch, Susan R.; Bustamante, Carlos D.

2010-01-01

Motivation: The development of new high-throughput genotyping products requires a significant investment in testing and training samples to evaluate and optimize the product before it can be used reliably on new samples. One reason for this is current methods for automated calling of genotypes are based on clustering approaches which require a large number of samples to be analyzed simultaneously, or an extensive training dataset to seed clusters. In systems where inbred samples are of primary interest, current clustering approaches perform poorly due to the inability to clearly identify a heterozygote cluster. Results: As part of the development of two custom single nucleotide polymorphism genotyping products for Oryza sativa (domestic rice), we have developed a new genotype calling algorithm called ‘ALCHEMY’ based on statistical modeling of the raw intensity data rather than modelless clustering. A novel feature of the model is the ability to estimate and incorporate inbreeding information on a per sample basis allowing accurate genotyping of both inbred and heterozygous samples even when analyzed simultaneously. Since clustering is not used explicitly, ALCHEMY performs well on small sample sizes with accuracy exceeding 99% with as few as 18 samples. Availability: ALCHEMY is available for both commercial and academic use free of charge and distributed under the GNU General Public License at http://alchemy.sourceforge.net/ Contact: mhw6@cornell.edu Supplementary information: Supplementary data are available at Bioinformatics online. PMID:20926420

Sample Size Estimation: The Easy Way

ERIC Educational Resources Information Center

Weller, Susan C.

2015-01-01

This article presents a simple approach to making quick sample size estimates for basic hypothesis tests. Although there are many sources available for estimating sample sizes, methods are not often integrated across statistical tests, levels of measurement of variables, or effect sizes. A few parameters are required to estimate sample sizes and…

Comparative analyses of basal rate of metabolism in mammals: data selection does matter.

PubMed

Genoud, Michel; Isler, Karin; Martin, Robert D

2018-02-01

Basal rate of metabolism (BMR) is a physiological parameter that should be measured under strictly defined experimental conditions. In comparative analyses among mammals BMR is widely used as an index of the intensity of the metabolic machinery or as a proxy for energy expenditure. Many databases with BMR values for mammals are available, but the criteria used to select metabolic data as BMR estimates have often varied and the potential effect of this variability has rarely been questioned. We provide a new, expanded BMR database reflecting compliance with standard criteria (resting, postabsorptive state; thermal neutrality; adult, non-reproductive status for females) and examine potential effects of differential selectivity on the results of comparative analyses. The database includes 1739 different entries for 817 species of mammals, compiled from the original sources. It provides information permitting assessment of the validity of each estimate and presents the value closest to a proper BMR for each entry. Using different selection criteria, several alternative data sets were extracted and used in comparative analyses of (i) the scaling of BMR to body mass and (ii) the relationship between brain mass and BMR. It was expected that results would be especially dependent on selection criteria with small sample sizes and with relatively weak relationships. Phylogenetically informed regression (phylogenetic generalized least squares, PGLS) was applied to the alternative data sets for several different clades (Mammalia, Eutheria, Metatheria, or individual orders). For Mammalia, a 'subsampling procedure' was also applied, in which random subsamples of different sample sizes were taken from each original data set and successively analysed. In each case, two data sets with identical sample size and species, but comprising BMR data with different degrees of reliability, were compared. Selection criteria had minor effects on scaling equations computed for large clades (Mammalia, Eutheria, Metatheria), although less-reliable estimates of BMR were generally about 12-20% larger than more-reliable ones. Larger effects were found with more-limited clades, such as sciuromorph rodents. For the relationship between BMR and brain mass the results of comparative analyses were found to depend strongly on the data set used, especially with more-limited, order-level clades. In fact, with small sample sizes (e.g. <100) results often appeared erratic. Subsampling revealed that sample size has a non-linear effect on the probability of a zero slope for a given relationship. Depending on the species included, results could differ dramatically, especially with small sample sizes. Overall, our findings indicate a need for due diligence when selecting BMR estimates and caution regarding results (even if seemingly significant) with small sample sizes. © 2017 Cambridge Philosophical Society.

Design of the value of imaging in enhancing the wellness of your heart (VIEW) trial and the impact of uncertainty on power.

PubMed

Ambrosius, Walter T; Polonsky, Tamar S; Greenland, Philip; Goff, David C; Perdue, Letitia H; Fortmann, Stephen P; Margolis, Karen L; Pajewski, Nicholas M

2012-04-01

Although observational evidence has suggested that the measurement of coronary artery calcium (CAC) may improve risk stratification for cardiovascular events and thus help guide the use of lipid-lowering therapy, this contention has not been evaluated within the context of a randomized trial. The Value of Imaging in Enhancing the Wellness of Your Heart (VIEW) trial is proposed as a randomized study in participants at low intermediate risk of future coronary heart disease (CHD) events to evaluate whether CAC testing leads to improved patient outcomes. To describe the challenges encountered in designing a prototypical screening trial and to examine the impact of uncertainty on power. The VIEW trial was designed as an effectiveness clinical trial to examine the benefit of CAC testing to guide therapy on a primary outcome consisting of a composite of nonfatal myocardial infarction, probable or definite angina with revascularization, resuscitated cardiac arrest, nonfatal stroke (not transient ischemic attack (TIA)), CHD death, stroke death, other atherosclerotic death, or other cardiovascular disease (CVD) death. Many critical choices were faced in designing the trial, including (1) the choice of primary outcome, (2) the choice of therapy, (3) the target population with corresponding ethical issues, (4) specifications of assumptions for sample size calculations, and (5) impact of uncertainty in these assumptions on power/sample size determination. We have proposed a sample size of 30,000 (800 events), which provides 92.7% power. Alternatively, sample sizes of 20,228 (539 events), 23,138 (617 events), and 27,078 (722 events) provide 80%, 85%, and 90% power. We have also allowed for uncertainty in our assumptions by computing average power integrated over specified prior distributions. This relaxation of specificity indicates a reduction in power, dropping to 89.9% (95% confidence interval (CI): 89.8-89.9) for a sample size of 30,000. Samples sizes of 20,228, 23,138, and 27,078 provide power of 78.0% (77.9-78.0), 82.5% (82.5-82.6), and 87.2% (87.2-87.3), respectively. These power estimates are dependent on form and parameters of the prior distributions. Despite the pressing need for a randomized trial to evaluate the utility of CAC testing, conduct of such a trial requires recruiting a large patient population, making efficiency of critical importance. The large sample size is primarily due to targeting a study population at relatively low risk of a CVD event. Our calculations also illustrate the importance of formally considering uncertainty in power calculations of large trials as standard power calculations may tend to overestimate power.

Design of the Value of Imaging in Enhancing the Wellness of Your Heart (VIEW) Trial and the Impact of Uncertainty on Power

PubMed Central

Ambrosius, Walter T.; Polonsky, Tamar S.; Greenland, Philip; Goff, David C.; Perdue, Letitia H.; Fortmann, Stephen P.; Margolis, Karen L.; Pajewski, Nicholas M.

2014-01-01

Background Although observational evidence has suggested that the measurement of CAC may improve risk stratification for cardiovascular events and thus help guide the use of lipid-lowering therapy, this contention has not been evaluated within the context of a randomized trial. The Value of Imaging in Enhancing the Wellness of Your Heart (VIEW) trial is proposed as a randomized study in participants at low intermediate risk of future coronary heart disease (CHD) events to evaluate whether coronary artery calcium (CAC) testing leads to improved patient outcomes. Purpose To describe the challenges encountered in designing a prototypical screening trial and to examine the impact of uncertainty on power. Methods The VIEW trial was designed as an effectiveness clinical trial to examine the benefit of CAC testing to guide therapy on a primary outcome consisting of a composite of non-fatal myocardial infarction, probable or definite angina with revascularization, resuscitated cardiac arrest, non-fatal stroke (not transient ischemic attack (TIA)), CHD death, stroke death, other atherosclerotic death, or other cardiovascular disease (CVD) death. Many critical choices were faced in designing the trial, including: (1) the choice of primary outcome, (2) the choice of therapy, (3) the target population with corresponding ethical issues, (4) specifications of assumptions for sample size calculations, and (5) impact of uncertainty in these assumptions on power/sample size determination. Results We have proposed a sample size of 30,000 (800 events) which provides 92.7% power. Alternatively, sample sizes of 20,228 (539 events), 23,138 (617 events) and 27,078 (722 events) provide 80, 85, and 90% power. We have also allowed for uncertainty in our assumptions by computing average power integrated over specified prior distributions. This relaxation of specificity indicates a reduction in power, dropping to 89.9% (95% confidence interval (CI): 89.8 to 89.9) for a sample size of 30,000. Samples sizes of 20,228, 23,138, and 27,078 provide power of 78.0% (77.9 to 78.0), 82.5% (82.5 to 82.6), and 87.2% (87.2 to 87.3), respectively. Limitations These power estimates are dependent on form and parameters of the prior distributions. Conclusions Despite the pressing need for a randomized trial to evaluate the utility of CAC testing, conduct of such a trial requires recruiting a large patient population, making efficiency of critical importance. The large sample size is primarily due to targeting a study population at relatively low risk of a CVD event. Our calculations also illustrate the importance of formally considering uncertainty in power calculations of large trials as standard power calculations may tend to overestimate power. PMID:22333998

The Relationship between Sample Sizes and Effect Sizes in Systematic Reviews in Education

ERIC Educational Resources Information Center

Slavin, Robert; Smith, Dewi

2009-01-01

Research in fields other than education has found that studies with small sample sizes tend to have larger effect sizes than those with large samples. This article examines the relationship between sample size and effect size in education. It analyzes data from 185 studies of elementary and secondary mathematics programs that met the standards of…

Pooling sheep faecal samples for the assessment of anthelmintic drug efficacy using McMaster and Mini-FLOTAC in gastrointestinal strongyle and Nematodirus infection.

PubMed

Kenyon, Fiona; Rinaldi, Laura; McBean, Dave; Pepe, Paola; Bosco, Antonio; Melville, Lynsey; Devin, Leigh; Mitchell, Gillian; Ianniello, Davide; Charlier, Johannes; Vercruysse, Jozef; Cringoli, Giuseppe; Levecke, Bruno

2016-07-30

In small ruminants, faecal egg counts (FECs) and reduction in FECs (FECR) are the most common methods for the assessment of intensity of gastrointestinal (GI) nematodes infections and anthelmintic drug efficacy, respectively. The main limitation of these methods is the time and cost to conduct FECs on a representative number of individual animals. A cost-saving alternative would be to examine pooled faecal samples, however little is known regarding whether pooling can give representative results. In the present study, we compared the FECR results obtained by both an individual and a pooled examination strategy across different pool sizes and analytical sensitivity of the FEC techniques. A survey was conducted on 5 sheep farms in Scotland, where anthelmintic resistance is known to be widespread. Lambs were treated with fenbendazole (4 groups), levamisole (3 groups), ivermectin (3 groups) or moxidectin (1 group). For each group, individual faecal samples were collected from 20 animals, at baseline (D0) and 14 days after (D14) anthelmintic administration. Faecal samples were analyzed as pools of 3-5, 6-10, and 14-20 individual samples. Both individual and pooled samples were screened for GI strongyle and Nematodirus eggs using two FEC techniques with three different levels of analytical sensitivity, including Mini-FLOTAC (analytical sensitivity of 10 eggs per gram of faeces (EPG)) and McMaster (analytical sensitivity of 15 or 50 EPG).For both Mini-FLOTAC and McMaster (analytical sensitivity of 15 EPG), there was a perfect agreement in classifying the efficacy of the anthelmintic as 'normal', 'doubtful' or 'reduced' regardless of pool size. When using the McMaster method (analytical sensitivity of 50 EPG) anthelmintic efficacy was often falsely classified as 'normal' or assessment was not possible due to zero FECs at D0, and this became more pronounced when the pool size increased. In conclusion, pooling ovine faecal samples holds promise as a cost-saving and efficient strategy for assessing GI nematode FECR. However, for the assessment FECR one will need to consider the baseline FEC, pool size and analytical sensitivity of the method. Copyright © 2016. Published by Elsevier B.V.

Phylogenetic effective sample size.

PubMed

Bartoszek, Krzysztof

2016-10-21

In this paper I address the question-how large is a phylogenetic sample? I propose a definition of a phylogenetic effective sample size for Brownian motion and Ornstein-Uhlenbeck processes-the regression effective sample size. I discuss how mutual information can be used to define an effective sample size in the non-normal process case and compare these two definitions to an already present concept of effective sample size (the mean effective sample size). Through a simulation study I find that the AICc is robust if one corrects for the number of species or effective number of species. Lastly I discuss how the concept of the phylogenetic effective sample size can be useful for biodiversity quantification, identification of interesting clades and deciding on the importance of phylogenetic correlations. Copyright © 2016 Elsevier Ltd. All rights reserved.

Bulk and nanocrystalline electron doped Gd0.15Ca0.85MnO3: Synthesis and magnetic characterization

NASA Astrophysics Data System (ADS)

Dhal, Lakshman; Chattarpal; Nirmala, R.; Santhosh, P. N.; Kumary, T. Geetha; Nigam, A. K.

2014-09-01

Polycrystalline Gd0.15Ca0.85MnO3 sample was prepared by solid state reaction method and nanocrystalline samples of different grain sizes of the same were prepared by sol-gel method. Phase purity and composition were verified by room temperature X-ray diffraction and SEM-EDAX analysis. Magnetization data of bulk Gd0.15Ca0.85MnO3 in 5 kOe field shows a peak at 119 K (TN) suggesting an antiferromagnetic transition. Nanocrystalline Gd0.15Ca0.85MnO3 sample ( 54 nm size) also shows a cusp at 107 K and a broad thermal hysteresis between field cooled cooling (FCC) and field cooled warming (FCW) data around this temperature. This thermal hysteresis suggests possible crystal structural transition. Field variation of magnetization of bulk Gd0.15Ca0.85MnO3 at 5 K shows a tendency to saturate, but yields a magnetic moment value of only 1.12 μB/f.u. in 70 kOe. The value of magnetization of nanocrystalline sample at 5 K in 70 kOe field is slightly larger and is 1.38 μB/f.u. which is probably due to the surface moments of the nanoparticle samples. Both the samples show Curie-Weiss-like behaviour in their paramagnetic state.

Dynamic relationships between body size, species richness, abundance, and energy use in a shallow marine epibenthic faunal community

PubMed Central

Labra, Fabio A; Hernández-Miranda, Eduardo; Quiñones, Renato A

2015-01-01

We study the temporal variation in the empirical relationships among body size (S), species richness (R), and abundance (A) in a shallow marine epibenthic faunal community in Coliumo Bay, Chile. We also extend previous analyses by calculating individual energy use (E) and test whether its bivariate and trivariate relationships with S and R are in agreement with expectations derived from the energetic equivalence rule. Carnivorous and scavenger species representing over 95% of sample abundance and biomass were studied. For each individual, body size (g) was measured and E was estimated following published allometric relationships. Data for each sample were tabulated into exponential body size bins, comparing species-averaged values with individual-based estimates which allow species to potentially occupy multiple size classes. For individual-based data, both the number of individuals and species across body size classes are fit by a Weibull function rather than by a power law scaling. Species richness is also a power law of the number of individuals. Energy use shows a piecewise scaling relationship with body size, with energetic equivalence holding true only for size classes above the modal abundance class. Species-based data showed either weak linear or no significant patterns, likely due to the decrease in the number of data points across body size classes. Hence, for individual-based size spectra, the SRA relationship seems to be general despite seasonal forcing and strong disturbances in Coliumo Bay. The unimodal abundance distribution results in a piecewise energy scaling relationship, with small individuals showing a positive scaling and large individuals showing energetic equivalence. Hence, strict energetic equivalence should not be expected for unimodal abundance distributions. On the other hand, while species-based data do not show unimodal SRA relationships, energy use across body size classes did not show significant trends, supporting energetic equivalence. PMID:25691966

Test Population Selection from Weibull-Based, Monte Carlo Simulations of Fatigue Life

NASA Technical Reports Server (NTRS)

Vlcek, Brian L.; Zaretsky, Erwin V.; Hendricks, Robert C.

2008-01-01

Fatigue life is probabilistic and not deterministic. Experimentally establishing the fatigue life of materials, components, and systems is both time consuming and costly. As a result, conclusions regarding fatigue life are often inferred from a statistically insufficient number of physical tests. A proposed methodology for comparing life results as a function of variability due to Weibull parameters, variability between successive trials, and variability due to size of the experimental population is presented. Using Monte Carlo simulation of randomly selected lives from a large Weibull distribution, the variation in the L10 fatigue life of aluminum alloy AL6061 rotating rod fatigue tests was determined as a function of population size. These results were compared to the L10 fatigue lives of small (10 each) populations from AL2024, AL7075 and AL6061. For aluminum alloy AL6061, a simple algebraic relationship was established for the upper and lower L10 fatigue life limits as a function of the number of specimens failed. For most engineering applications where less than 30 percent variability can be tolerated in the maximum and minimum values, at least 30 to 35 test samples are necessary. The variability of test results based on small sample sizes can be greater than actual differences, if any, that exists between materials and can result in erroneous conclusions. The fatigue life of AL2024 is statistically longer than AL6061 and AL7075. However, there is no statistical difference between the fatigue lives of AL6061 and AL7075 even though AL7075 had a fatigue life 30 percent greater than AL6061.

Test Population Selection from Weibull-Based, Monte Carlo Simulations of Fatigue Life

NASA Technical Reports Server (NTRS)

Vlcek, Brian L.; Zaretsky, Erwin V.; Hendricks, Robert C.

2012-01-01

Fatigue life is probabilistic and not deterministic. Experimentally establishing the fatigue life of materials, components, and systems is both time consuming and costly. As a result, conclusions regarding fatigue life are often inferred from a statistically insufficient number of physical tests. A proposed methodology for comparing life results as a function of variability due to Weibull parameters, variability between successive trials, and variability due to size of the experimental population is presented. Using Monte Carlo simulation of randomly selected lives from a large Weibull distribution, the variation in the L10 fatigue life of aluminum alloy AL6061 rotating rod fatigue tests was determined as a function of population size. These results were compared to the L10 fatigue lives of small (10 each) populations from AL2024, AL7075 and AL6061. For aluminum alloy AL6061, a simple algebraic relationship was established for the upper and lower L10 fatigue life limits as a function of the number of specimens failed. For most engineering applications where less than 30 percent variability can be tolerated in the maximum and minimum values, at least 30 to 35 test samples are necessary. The variability of test results based on small sample sizes can be greater than actual differences, if any, that exists between materials and can result in erroneous conclusions. The fatigue life of AL2024 is statistically longer than AL6061 and AL7075. However, there is no statistical difference between the fatigue lives of AL6061 and AL7075 even though AL7075 had a fatigue life 30 percent greater than AL6061.

The endothelial sample size analysis in corneal specular microscopy clinical examinations.

PubMed

Abib, Fernando C; Holzchuh, Ricardo; Schaefer, Artur; Schaefer, Tania; Godois, Ronialci

2012-05-01

To evaluate endothelial cell sample size and statistical error in corneal specular microscopy (CSM) examinations. One hundred twenty examinations were conducted with 4 types of corneal specular microscopes: 30 with each BioOptics, CSO, Konan, and Topcon corneal specular microscopes. All endothelial image data were analyzed by respective instrument software and also by the Cells Analyzer software with a method developed in our lab. A reliability degree (RD) of 95% and a relative error (RE) of 0.05 were used as cut-off values to analyze images of the counted endothelial cells called samples. The sample size mean was the number of cells evaluated on the images obtained with each device. Only examinations with RE < 0.05 were considered statistically correct and suitable for comparisons with future examinations. The Cells Analyzer software was used to calculate the RE and customized sample size for all examinations. Bio-Optics: sample size, 97 ± 22 cells; RE, 6.52 ± 0.86; only 10% of the examinations had sufficient endothelial cell quantity (RE < 0.05); customized sample size, 162 ± 34 cells. CSO: sample size, 110 ± 20 cells; RE, 5.98 ± 0.98; only 16.6% of the examinations had sufficient endothelial cell quantity (RE < 0.05); customized sample size, 157 ± 45 cells. Konan: sample size, 80 ± 27 cells; RE, 10.6 ± 3.67; none of the examinations had sufficient endothelial cell quantity (RE > 0.05); customized sample size, 336 ± 131 cells. Topcon: sample size, 87 ± 17 cells; RE, 10.1 ± 2.52; none of the examinations had sufficient endothelial cell quantity (RE > 0.05); customized sample size, 382 ± 159 cells. A very high number of CSM examinations had sample errors based on Cells Analyzer software. The endothelial sample size (examinations) needs to include more cells to be reliable and reproducible. The Cells Analyzer tutorial routine will be useful for CSM examination reliability and reproducibility.

Enhanced ferroelectric and piezoelectric properties in La-modified PZT ceramics

NASA Astrophysics Data System (ADS)

Kour, P.; Pradhan, S. K.; Kumar, Pawan; Sinha, S. K.; Kar, Manoranjan

2016-06-01

The effect of lanthanum (La) doping on ferroelectric and piezoelectric properties of lead zirconate titanate (PZT) sample has been investigated. Pb1- x La x Zr0.52Ti0.48O3 ceramics with x = 0.00, 0.02, 0.04, 0.06 and 0.10 were prepared by the sol-gel technique. Raman and Fourier transforms infrared spectroscopy have been employed to understand the structural modification due to ionic size mismatch. Raman spectra show the existence of both rhombohedral and tetragonal crystal symmetries. It also shows the dielectric relaxation with increase in La concentration in the sample. The increase in lattice strain due to La doping increases the remnant polarization and coercive field. The linear piezoelectric coefficient increases with the increase in La concentration. It reveals that La-substituted PZT is a better candidate for piezoelectric sensor applications as compared to that of PZT.

Structural and dielectric properties of Al x Zn1- x O ( x = 0, 0.02, 0.04, 0.06, 0.08 and 0.10) nanoparticles

NASA Astrophysics Data System (ADS)

Sharma, Neha; Kumar, Sanjay; Sharma, Varun

2018-05-01

The chemical precipitation method is followed for the synthesis of Al-doped ZnO nanoparticles (NPs) with varying doping concentrations (0, 0.02, 0.04, 0.06, 0.08, and 0.10 M). A single hexagonal crystalline phase of wurtzite structure has been confirmed for all the samples by X-ray diffraction. Crystalline size and microstrain of the un-doped and doped ZnO (NPs) is determined by the Williamson-Hall (W-H) analysis. The optical properties like band gap and Urbach energy are found out by the UV-visible spectroscopy. The functional bonds are detailed by Fourier transmission infrared spectroscopy. The dielectric properties have been shown by doped sample due to hopping mechanisms as compared to the undoped. The loss factor (tan δ) follows an inverse direction as correspond to frequency due to the presence of dielectric dispersion.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cole, K.C.; Noel, D.; Hechler, J.J.

Data are presented on physicochemical tests carried out on room-temperature aged samples of a commercially available carbon-epoxy composite prepreg system. The analytical methods used included Fourier transform IR (FTIR) spectroscopy, reverse-phase liquid chromatography (RPLC), high-speed RPLC, high-performance size-exclusion chromatography, differential scanning calorimetry and thermogravimetry, and pyrolysis/gas chromatography. All data indicated significant changes in these samples due to aging, with the most sensitive indices being those of FTIR and RPLC procedures. Results indicate that the number of unreacted epoxy groups decreased steadily at a rate of 0.34 percent per day, based on the initial amount, and the number of free amine-hardenermore » molecules decreased at a rate of 1.05 percent per day. The amount of initial epoxy-amine reaction product increased significantly over the first 30 days, but then declined, due to further reactions of these to give higher-molecular-weight products. 23 refs.« less

Structural and magnetic characterization of La{sub 0.8}Sr{sub 0.2}MnO{sub 3} nanoparticles prepared via a facile microwave-assisted method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moradi, J., E-mail: j_moradi@yahoo.com; Ghazi, M.E.; Ehsani, M.H., E-mail: mhe_ehsani@yahoo.com

2014-07-01

Nanoparticles of La{sub 0.8}Sr{sub 0.2}MnO{sub 3} (LSMO) with different particle sizes are synthesized by a very fast, inexpensive, reproducible, and environmentally friendly method: the microwave irradiation of the corresponding mixture of nitrates. The structural and magnetic properties of the samples are investigated by the X-Ray diffraction (XRD), Fourier transform infra-red (FT-IR) spectroscopy, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and magnetic (DC magnetization and AC susceptibility) measurements. The XRD study coupled with the Rietveld refinement show that all samples crystallize in a rhombohedral structure with the space group of R−3C. The FT-IR spectroscopy and FE-SEM images indicate formationmore » of the perovskite structure of LSMO. The DC magnetization measurements confirm the decrease in the particle size effects on the magnetic properties, e.g. reduction in the ferromagnetic (FM) moment and increase in the surface spin disorder. Magnetic dynamics of the samples studied by AC magnetic susceptibility shows that the magnetic behavior of the nanometer-sized samples is well-described by the Vogel-Fulcher and critical slowing down laws. Strong interaction between magnetic nanoparticles of LSMO was detected by fitting the experimental data with the mentioned models. - Graphical abstract: Temperature dependence of the magnetization M(T) was measured in the zero-field-cooling (ZFC) and field-cooling (FC) modes at the applied magnetic field of 100 Oe for the La{sub 0.8}Sr{sub 0.2}MnO{sub 3} with different size prepared via a facile microwave-assisted method. - Highlights: • Nanoparticles of La{sub 0.8}Sr{sub 0.2}MnO{sub 3} were synthesized by the microwave irradiation process. • The structural studies show that all samples crystallize in a rhombohedral structure with space group of R−3C. • The DC magnetic studies confirm tuning of the magnetic properties due to the particle size effects. • Magnetic dynamic studied by AC magnetic susceptibility indicate strong interaction between magnetic nanoparticles.« less

Sample size determination for mediation analysis of longitudinal data.

PubMed

Pan, Haitao; Liu, Suyu; Miao, Danmin; Yuan, Ying

2018-03-27

Sample size planning for longitudinal data is crucial when designing mediation studies because sufficient statistical power is not only required in grant applications and peer-reviewed publications, but is essential to reliable research results. However, sample size determination is not straightforward for mediation analysis of longitudinal design. To facilitate planning the sample size for longitudinal mediation studies with a multilevel mediation model, this article provides the sample size required to achieve 80% power by simulations under various sizes of the mediation effect, within-subject correlations and numbers of repeated measures. The sample size calculation is based on three commonly used mediation tests: Sobel's method, distribution of product method and the bootstrap method. Among the three methods of testing the mediation effects, Sobel's method required the largest sample size to achieve 80% power. Bootstrapping and the distribution of the product method performed similarly and were more powerful than Sobel's method, as reflected by the relatively smaller sample sizes. For all three methods, the sample size required to achieve 80% power depended on the value of the ICC (i.e., within-subject correlation). A larger value of ICC typically required a larger sample size to achieve 80% power. Simulation results also illustrated the advantage of the longitudinal study design. The sample size tables for most encountered scenarios in practice have also been published for convenient use. Extensive simulations study showed that the distribution of the product method and bootstrapping method have superior performance to the Sobel's method, but the product method was recommended to use in practice in terms of less computation time load compared to the bootstrapping method. A R package has been developed for the product method of sample size determination in mediation longitudinal study design.

Soft γ-ray selected radio galaxies: favouring giant size discovery

NASA Astrophysics Data System (ADS)

Bassani, L.; Venturi, T.; Molina, M.; Malizia, A.; Dallacasa, D.; Panessa, F.; Bazzano, A.; Ubertini, P.

2016-09-01

Using the recent INTEGRAL/IBIS and Swift/BAT surveys we have extracted a sample of 64 confirmed plus three candidate radio galaxies selected in the soft gamma-ray band. The sample covers all optical classes and is dominated by objects showing a Fanaroff-Riley type II radio morphology; a large fraction (70 per cent) of the sample is made of `radiative mode' or high-excitation radio galaxies. We measured the source size on images from the NRAO VLA Sky Survey, the Faint Images of the Radio Sky at twenty-cm and the Sydney University Molonglo Sky Survey images and have compared our findings with data in the literature obtaining a good match. We surprisingly found that the soft gamma-ray selection favours the detection of large size radio galaxies: 60 per cent of objects in the sample have size greater than 0.4 Mpc while around 22 per cent reach dimension above 0.7 Mpc at which point they are classified as giant radio galaxies (GRGs), the largest and most energetic single entities in the Universe. Their fraction among soft gamma-ray selected radio galaxies is significantly larger than typically found in radio surveys, where only a few per cent of objects (1-6 per cent) are GRGs. This may partly be due to observational biases affecting radio surveys more than soft gamma-ray surveys, thus disfavouring the detection of GRGs at lower frequencies. The main reasons and/or conditions leading to the formation of these large radio structures are still unclear with many parameters such as high jet power, long activity time and surrounding environment all playing a role; the first two may be linked to the type of active galactic nucleus discussed in this work and partly explain the high fraction of GRGs found in the present sample. Our result suggests that high energy surveys may be a more efficient way than radio surveys to find these peculiar objects.

Public Opinion Polls, Chicken Soup and Sample Size

ERIC Educational Resources Information Center

Nguyen, Phung

2005-01-01

Cooking and tasting chicken soup in three different pots of very different size serves to demonstrate that it is the absolute sample size that matters the most in determining the accuracy of the findings of the poll, not the relative sample size, i.e. the size of the sample in relation to its population.

Sample size in studies on diagnostic accuracy in ophthalmology: a literature survey.

PubMed

Bochmann, Frank; Johnson, Zoe; Azuara-Blanco, Augusto

2007-07-01

To assess the sample sizes used in studies on diagnostic accuracy in ophthalmology. Design and sources: A survey literature published in 2005. The frequency of reporting calculations of sample sizes and the samples' sizes were extracted from the published literature. A manual search of five leading clinical journals in ophthalmology with the highest impact (Investigative Ophthalmology and Visual Science, Ophthalmology, Archives of Ophthalmology, American Journal of Ophthalmology and British Journal of Ophthalmology) was conducted by two independent investigators. A total of 1698 articles were identified, of which 40 studies were on diagnostic accuracy. One study reported that sample size was calculated before initiating the study. Another study reported consideration of sample size without calculation. The mean (SD) sample size of all diagnostic studies was 172.6 (218.9). The median prevalence of the target condition was 50.5%. Only a few studies consider sample size in their methods. Inadequate sample sizes in diagnostic accuracy studies may result in misleading estimates of test accuracy. An improvement over the current standards on the design and reporting of diagnostic studies is warranted.

Facile and green synthesis of mesoporous Co3O4 nanocubes and their applications for supercapacitors.

PubMed

Liu, Xiangmei; Long, Qing; Jiang, Chunhui; Zhan, Beibei; Li, Chen; Liu, Shujuan; Zhao, Qiang; Huang, Wei; Dong, Xiaochen

2013-07-21

Nanostructured Co3O4 materials attracted significant attention due to their exceptional electrochemical (pseudo-capacitive) properties. However, rigorous preparation conditions are needed to control the size (especially nanosize), morphology and size distribution of the products obtained by conventional methods. Herein, we describe a novel one step shape-controlled synthesis of uniform Co3O4 nanocubes with a size of 50 nm with the existence of mesoporous carbon nanorods (meso-CNRs). In this synthesis process, meso-CNRs not only act as a heat receiver to directly obtain Co3O4 eliminating the high-temperature post-calcination, but also control the morphology of the resulting Co3O4 to form nanocubes with uniform distribution. More strikingly, mesoporous Co3O4 nanocubes are obtained by further thermal treatment. The structure and morphology of the samples were characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. A possible formation mechanism of mesoporous Co3O4 nanocubes is proposed here. Electrochemical tests have revealed that the prepared mesoporous Co3O4 nanocubes demonstrate a remarkable performance in supercapacitor applications due to the porous structure, which endows fast ion and electron transfer.

Caution regarding the choice of standard deviations to guide sample size calculations in clinical trials.

PubMed

Chen, Henian; Zhang, Nanhua; Lu, Xiaosun; Chen, Sophie

2013-08-01

The method used to determine choice of standard deviation (SD) is inadequately reported in clinical trials. Underestimations of the population SD may result in underpowered clinical trials. This study demonstrates how using the wrong method to determine population SD can lead to inaccurate sample sizes and underpowered studies, and offers recommendations to maximize the likelihood of achieving adequate statistical power. We review the practice of reporting sample size and its effect on the power of trials published in major journals. Simulated clinical trials were used to compare the effects of different methods of determining SD on power and sample size calculations. Prior to 1996, sample size calculations were reported in just 1%-42% of clinical trials. This proportion increased from 38% to 54% after the initial Consolidated Standards of Reporting Trials (CONSORT) was published in 1996, and from 64% to 95% after the revised CONSORT was published in 2001. Nevertheless, underpowered clinical trials are still common. Our simulated data showed that all minimal and 25th-percentile SDs fell below 44 (the population SD), regardless of sample size (from 5 to 50). For sample sizes 5 and 50, the minimum sample SDs underestimated the population SD by 90.7% and 29.3%, respectively. If only one sample was available, there was less than 50% chance that the actual power equaled or exceeded the planned power of 80% for detecting a median effect size (Cohen's d = 0.5) when using the sample SD to calculate the sample size. The proportions of studies with actual power of at least 80% were about 95%, 90%, 85%, and 80% when we used the larger SD, 80% upper confidence limit (UCL) of SD, 70% UCL of SD, and 60% UCL of SD to calculate the sample size, respectively. When more than one sample was available, the weighted average SD resulted in about 50% of trials being underpowered; the proportion of trials with power of 80% increased from 90% to 100% when the 75th percentile and the maximum SD from 10 samples were used. Greater sample size is needed to achieve a higher proportion of studies having actual power of 80%. This study only addressed sample size calculation for continuous outcome variables. We recommend using the 60% UCL of SD, maximum SD, 80th-percentile SD, and 75th-percentile SD to calculate sample size when 1 or 2 samples, 3 samples, 4-5 samples, and more than 5 samples of data are available, respectively. Using the sample SD or average SD to calculate sample size should be avoided.

Extinction-sedimentation inversion technique for measuring size distribution of artificial fogs

NASA Technical Reports Server (NTRS)

Deepak, A.; Vaughan, O. H.

1978-01-01

In measuring the size distribution of artificial fog particles, it is important that the natural state of the particles not be disturbed by the measuring device, such as occurs when samples are drawn through tubes. This paper describes a method for carrying out such a measurement by allowing the fog particles to settle in quiet air inside an enclosure through which traverses a parallel beam of light for measuring the optical depth as a function of time. An analytic function fit to the optical depth time decay curve can be directly inverted to yield the size distribution. Results of one such experiment performed on artificial fogs are shown as an example. The forwardscattering corrections to the measured extinction coefficient are also discussed with the aim of optimizing the experimental design so that the error due to forwardscattering is minimized.

Fragmentation and flow of grazed coastal Bermudagrass through the digestive tract of cattle.

PubMed

Pond, K R; Ellis, W C; Lascano, C E; Akin, D E

1987-08-01

Samples of forage fragments were obtained from the upper (RUS) and lower (RLS) strata of the reticulorumen and feces (F) of four Brahman X Jersey steers grazing Coastal bermudagrass (CB) of two maturities with dry matter digestibilities (DMD) of 54.8 and 64.3%. Forage fragments were separated by particle size and evaluated histochemically for tissue type and fragmentation pattern. Fragmentation pattern was similar to that previously observed due to ingestive mastication. There was longitudinal separation of vascular bundles (VB) and severing at VB ends. Microscopically, similar size fragments from RUS were indistinguishable from those of RLS. The major difference between RUS and RLS was the distribution of different size particles. Larger particles were associated with the RUS in cattle consuming immature and mature CB. More large particles were associated with mature compared with the immature CB in the RUS and RLS. The distribution of different size particles in the F was similar for both maturities, suggesting that similar particle size reduction was required regardless of maturity. Smaller particles in the rumen and F appeared to contain more lignin (determined histochemically) and were composed of indigestible fragments of cuticle and lignified vascular tissue. Cattle grazing mature CB had higher ruminal fills (2.40 vs 2.02 kg dry matter/100 kg body weight), reduced rates of passage and lower voluntary intake (2.50 vs 3.14 kg DM/100 kg body weight). Lower intake of mature CB may have resulted from a reduced rate of particle size reduction. Similarities in fragmentation patterns due to ingestive and ruminative mastication were interpreted to indicate that mastication was responsible for most of the particle size reduction of CB and that mastication facilitated digestion of potentially digestible tissues.

Dynamics of sediments along with their core properties in the Monastir-Bekalta coastline (Tunisia, Central Mediterranean)

NASA Astrophysics Data System (ADS)

Khiari, Nouha; Atoui, Abdelfattah; Khalil, Nadia; Charef, Abdelkrim; Aleya, Lotfi

2017-10-01

The authors report on two campaigns of high-resolution samplings along the shores of Monastir Bay in Tunisia: the first being a study of sediment dynamics, grain size and mineral composition in surface sediment, and the second, eight months later, using four sediment cores to study grain-size distribution in bottom sediments. Particle size analysis of superficial sediment shows that the sand in shallow depths is characterized by S-shaped curves, indicating a certain degree of agitation, possible transport by rip currents near the bottom and hyperbolic curves illustrating heterogeneity of sand stock. The sediments settle in a relatively calm environment. Along the bay shore (from 0 to 2 m depth), the bottom is covered by medium sand. Sediment transport is noted along the coast; from north to south and from south to north, caused by longshore drift and a rip current in the middle of the bay. These two currents are generated by wind and swell, especially by north to northeast waves which transport the finest sediment. Particle size analysis of bottom sediment indicates a mean grain size ranging from coarse to very fine sands while vertical distribution of grain size tends to decrease from surface to depth. The increase in particle size of sediment cores may be due to the coexistence of terrigenous inputs along with the sedimentary transit parallel to the coast due to the effect of longshore drift. Mineralogical analysis shows that Monastir's coastal sands and bottom sediment are composed of quartz, calcite, magnesium calcite, aragonite and hematite. The existence of a low energy zone with potential to accumulate pollutants indicates that managerial action is necessary to help preserve Monastir Bay.

Improved Time-Lapsed Angular Scattering Microscopy of Single Cells

NASA Astrophysics Data System (ADS)

Cannaday, Ashley E.

By measuring angular scattering patterns from biological samples and fitting them with a Mie theory model, one can estimate the organelle size distribution within many cells. Quantitative organelle sizing of ensembles of cells using this method has been well established. Our goal is to develop the methodology to extend this approach to the single cell level, measuring the angular scattering at multiple time points and estimating the non-nuclear organelle size distribution parameters. The diameters of individual organelle-size beads were successfully extracted using scattering measurements with a minimum deflection angle of 20 degrees. However, the accuracy of size estimates can be limited by the angular range detected. In particular, simulations by our group suggest that, for cell organelle populations with a broader size distribution, the accuracy of size prediction improves substantially if the minimum angle of detection angle is 15 degrees or less. The system was therefore modified to collect scattering angles down to 10 degrees. To confirm experimentally that size predictions will become more stable when lower scattering angles are detected, initial validations were performed on individual polystyrene beads ranging in diameter from 1 to 5 microns. We found that the lower minimum angle enabled the width of this delta-function size distribution to be predicted more accurately. Scattering patterns were then acquired and analyzed from single mouse squamous cell carcinoma cells at multiple time points. The scattering patterns exhibit angular dependencies that look unlike those of any single sphere size, but are well-fit by a broad distribution of sizes, as expected. To determine the fluctuation level in the estimated size distribution due to measurement imperfections alone, formaldehyde-fixed cells were measured. Subsequent measurements on live (non-fixed) cells revealed an order of magnitude greater fluctuation in the estimated sizes compared to fixed cells. With our improved and better-understood approach to single cell angular scattering, we are now capable of reliably detecting changes in organelle size predictions due to biological causes above our measurement error of 20 nm, which enables us to apply our system to future studies of the investigation of various single cell biological processes.

Improved tracking and resolution of bacteria in holographic microscopy using dye and fluorescent protein labeling

NASA Astrophysics Data System (ADS)

Nadeau, Jay; Cho, YongBin; Kühn, Jonas; Liewer, Kurt

2016-04-01

Digital holographic microscopy (DHM) is an emerging imaging technique that permits instantaneous capture of a relatively large sample volume. However, large volumes usually come at the expense of lower spatial resolution, and the technique has rarely been used with prokaryotic cells due to their small size and low contrast. In this paper we demonstrate the use of a Mach-Zehnder dual-beam instrument for imaging of labeled and unlabeled bacteria and microalgae. Spatial resolution of 0.3 micrometers is achieved, providing a sampling of several pixels across a typical prokaryotic cell. Both cellular motility and morphology are readily recorded. The use of dyes provides both amplitude and phase contrast improvement and is of use to identify cells in dense samples.

Increase in iodine deficiency disorder due to inadequate sustainability of supply of iodized salt in District Solan, Himachal Pradesh.

PubMed

Kapil, Umesh; Pandey, R M; Jain, Vandana; Kabra, Madhulika; Sareen, Neha; Bhadoria, Ajeet Singh; Vijay, Jyoti; Nigam, Sukirty; Khenduja, Preetika

2013-12-01

Himachal Pradesh is a known endemic area for iodine deficiency disorders. A study was conducted in district Solan with the objective of assessing the prevalence of iodine deficiency disorders in school-age children. Thirty clusters were selected by using the probability-proportionate-to-size cluster sampling methodology. Clinical examination of the thyroid of 1898 children in the age-group of 6-12 years was conducted. Urine and salt samples were collected. The total goiter rate was found to be 15.4%. Median urinary iodine excretion level was 62.5 μg/l. Only 39% of the salt samples had iodine content of ≥15 ppm. Mild iodine deficiency was present in the subjects studied.

Evidence of a chimpanzee-sized ancestor of humans but a gibbon-sized ancestor of apes.

PubMed

Grabowski, Mark; Jungers, William L

2017-10-12

Body mass directly affects how an animal relates to its environment and has a wide range of biological implications. However, little is known about the mass of the last common ancestor (LCA) of humans and chimpanzees, hominids (great apes and humans), or hominoids (all apes and humans), which is needed to evaluate numerous paleobiological hypotheses at and prior to the root of our lineage. Here we use phylogenetic comparative methods and data from primates including humans, fossil hominins, and a wide sample of fossil primates including Miocene apes from Africa, Europe, and Asia to test alternative hypotheses of body mass evolution. Our results suggest, contrary to previous suggestions, that the LCA of all hominoids lived in an environment that favored a gibbon-like size, but a series of selective regime shifts, possibly due to resource availability, led to a decrease and then increase in body mass in early hominins from a chimpanzee-sized LCA.The pattern of body size evolution in hominids can provide insight into historical human ecology. Here, Grabowski and Jungers use comparative phylogenetic analysis to reconstruct the likely size of the ancestor of humans and chimpanzees and the evolutionary history of selection on body size in primates.

Size-amplified acoustofluidic separation of circulating tumor cells with removable microbeads

NASA Astrophysics Data System (ADS)

Liu, Huiqin; Ao, Zheng; Cai, Bo; Shu, Xi; Chen, Keke; Rao, Lang; Luo, Changliang; Wang, Fu-Bin; Liu, Wei; Bondesson, Maria; Guo, Shishang; Guo, Feng

2018-06-01

Isolation and analysis of rare circulating tumor cells (CTCs) is of great interest in cancer diagnosis, prognosis, and treatment efficacy evaluation. Acoustofluidic cell separation becomes an attractive method due to its contactless, noninvasive, simple, and versatile features. However, the indistinctive physical difference between CTCs and normal blood cells limits the purity of CTCs using current acoustic methods. Herein, we demonstrate a size-amplified acoustic separation and release of CTCs with removable microbeads. CTCs selectively bound to size-amplifiers (40 μm-diameter anti-EpCAM/gelatin-coated SiO2 microbeads) have significant physical differences (size and mechanics) compared to normal blood cells, resulting in an amplification of acoustic radiation force approximately a hundredfold over that of bare CTCs or normal blood cells. Therefore, CTCs can be efficiently sorted out with size-amplifiers in a traveling surface acoustic wave microfluidic device and released from size-amplifiers by enzymatic degradation for further purification or downstream analysis. We demonstrate a cell separation from blood samples with a total efficiency (E total) of ∼ 77%, purity (P) of ∼ 96%, and viability (V) of ∼83% after releasing cells from size-amplifiers. Our method substantially improves the emerging application of rare cell purification for translational medicine.

Cloud water composition during HCCT-2010: Scavenging efficiencies, solute concentrations, and droplet size dependence of inorganic ions and dissolved organic carbon

NASA Astrophysics Data System (ADS)

van Pinxteren, Dominik; Wadinga Fomba, Khanneh; Mertes, Stephan; Müller, Konrad; Spindler, Gerald; Schneider, Johannes; Lee, Taehyoung; Collett, Jeffrey L.; Herrmann, Hartmut

2016-03-01

Cloud water samples were taken in September/October 2010 at Mt. Schmücke in a rural, forested area in Germany during the Lagrange-type Hill Cap Cloud Thuringia 2010 (HCCT-2010) cloud experiment. Besides bulk collectors, a three-stage and a five-stage collector were applied and samples were analysed for inorganic ions (SO42-,NO3-, NH4+, Cl-, Na+, Mg2+, Ca2+, K+), H2O2 (aq), S(IV), and dissolved organic carbon (DOC). Campaign volume-weighted mean concentrations were 191, 142, and 39 µmol L-1 for ammonium, nitrate, and sulfate respectively, between 4 and 27 µmol L-1 for minor ions, 5.4 µmol L-1 for H2O2 (aq), 1.9 µmol L-1 for S(IV), and 3.9 mgC L-1 for DOC. The concentrations compare well to more recent European cloud water data from similar sites. On a mass basis, organic material (as DOC × 1.8) contributed 20-40 % (event means) to total solute concentrations and was found to have non-negligible impact on cloud water acidity. Relative standard deviations of major ions were 60-66 % for solute concentrations and 52-80 % for cloud water loadings (CWLs). The similar variability of solute concentrations and CWLs together with the results of back-trajectory analysis and principal component analysis, suggests that concentrations in incoming air masses (i.e. air mass history), rather than cloud liquid water content (LWC), were the main factor controlling bulk solute concentrations for the cloud studied. Droplet effective radius was found to be a somewhat better predictor for cloud water total ionic content (TIC) than LWC, even though no single explanatory variable can fully describe TIC (or solute concentration) variations in a simple functional relation due to the complex processes involved. Bulk concentrations typically agreed within a factor of 2 with co-located measurements of residual particle concentrations sampled by a counterflow virtual impactor (CVI) and analysed by an aerosol mass spectrometer (AMS), with the deviations being mainly caused by systematic differences and limitations of the approaches (such as outgassing of dissolved gases during residual particle sampling). Scavenging efficiencies (SEs) of aerosol constituents were 0.56-0.94, 0.79-0.99, 0.71-98, and 0.67-0.92 for SO42-, NO3-, NH4+, and DOC respectively when calculated as event means with in-cloud data only. SEs estimated using data from an upwind site were substantially different in many cases, revealing the impact of gas-phase uptake (for volatile constituents) and mass losses across Mt. Schmücke likely due to physical processes such as droplet scavenging by trees and/or entrainment. Drop size-resolved cloud water concentrations of major ions SO42-, NO3-, and NH4+ revealed two main profiles: decreasing concentrations with increasing droplet size and "U" shapes. In contrast, profiles of typical coarse particle mode minor ions were often increasing with increasing drop size, highlighting the importance of a species' particle concentration size distribution for the development of size-resolved solute concentration patterns. Concentration differences between droplet size classes were typically < 2 for major ions from the three-stage collector and somewhat more pronounced from the five-stage collector, while they were much larger for minor ions. Due to a better separation of droplet populations, the five-stage collector was capable of resolving some features of solute size dependencies not seen in the three-stage data, especially sharp concentration increases (up to a factor of 5-10) in the smallest droplets for many solutes.

Cloud water composition during HCCT-2010: Scavenging efficiencies, solute concentrations, and droplet size dependence of inorganic ions and dissolved organic carbon

NASA Astrophysics Data System (ADS)

van Pinxteren, D.; Fomba, K. W.; Mertes, S.; Müller, K.; Spindler, G.; Schneider, J.; Lee, T.; Collett, J.; Herrmann, H.

2015-09-01

Cloud water samples were taken in September/October 2010 at Mt. Schmücke in a rural, forested area in Germany during the Lagrange-type Hill Cap Cloud Thuringia 2010 (HCCT-2010) cloud experiment. Besides bulk collectors, a 3-stage and a 5-stage collector were applied and samples were analysed for inorganic ions (SO42-, NO3-, NH4+, Cl-, Na+, Mg2+, Ca2+, K+), H2O2 (aq), S(IV), and dissolved organic carbon (DOC). Campaign volume-weighted mean concentrations were 191, 142, and 39 μmol L-1 for ammonium, nitrate, and sulfate, respectively, between 4 and 27 μmol L-1 for minor ions, 5.4 μmol L-1 for H2O2 (aq), 1.9 μmol L-1 for S(IV), and 3.9 mgC L-1 for DOC. The concentrations compare well to more recent European cloud water data from similar sites. On a mass basis, organic material (as DOC · 1.8) contributed 20-40 % (event means) to total solute concentrations and was found to have non-negligible impact on cloud water acidity. Relative standard deviations of major ions were 60-66 % for solute concentrations and 52-80 % for cloud water loadings (CWLs). Contrary to some earlier suggestions, the similar variability of solute concentrations and CWLs together with the results of back trajectory analysis and principal component analysis, suggests that concentrations in incoming air masses (i.e. air mass history), rather than cloud liquid water content (LWC) was the main factor controlling bulk solute concentrations at Mt. Schmücke. Droplet effective radius was found to be a somewhat better predictor for cloud water total ionic content (TIC) than LWC, even though no single explanatory variable can fully describe TIC (or solute concentration) variations in a simple functional relation due to the complex processes involved. Bulk concentrations typically agreed within a factor of 2 with co-located measurements of residual particle concentrations sampled by a counterflow virtual impactor (CV) and analysed by an aerosol mass spectrometer (AMS), with the deviations being mainly caused by systematic differences and limitations of the approaches (such as outgassing of dissolved gases during residual particle sampling). Scavenging efficiencies (SEs) of aerosol constituents were 0.56-0.94, 0.79-0.99, 0.71-98, and 0.67-0.92 for SO42-, NO3-, NH4+, and DOC, respectively, when calculated as event means with in-cloud data only. SEs estimated using data from an upwind site were substantially different in many cases, revealing the impact of gas-phase uptake (for volatile constituents) and mass losses across Mt. Schmücke likely due to physical processes such as droplet scavenging by trees and/or entrainment. Drop size-resolved cloud water concentrations of major ions SO42-, NO3-, and NH4+ revealed two main profiles: decreasing concentrations with increasing droplet size and "U"-shapes. In contrast, profiles of typical coarse particle mode minor ions were often increasing with increasing drop size, highlighting the importance of a species' particle concentration size distribution for the development of size-resolved solute concentration patterns. Concentration differences between droplet size classes were typically < 2 for major ions from the 3-stage collector and somewhat more pronounced from the 5-stage collector, while they were much larger for minor ions. Due to a better separation of droplet populations, the 5-stage collector was capable of resolving some features of solute size dependencies not seen in the 3-stage data, especially sharp concentration increases (up to a factor of 5-10) in the smallest droplets for many solutes.

Dispersion and sampling of adult Dermacentor andersoni in rangeland in Western North America.

PubMed

Rochon, K; Scoles, G A; Lysyk, T J

2012-03-01

A fixed precision sampling plan was developed for off-host populations of adult Rocky Mountain wood tick, Dermacentor andersoni (Stiles) based on data collected by dragging at 13 locations in Alberta, Canada; Washington; and Oregon. In total, 222 site-date combinations were sampled. Each site-date combination was considered a sample, and each sample ranged in size from 86 to 250 10 m2 quadrats. Analysis of simulated quadrats ranging in size from 10 to 50 m2 indicated that the most precise sample unit was the 10 m2 quadrat. Samples taken when abundance < 0.04 ticks per 10 m2 were more likely to not depart significantly from statistical randomness than samples taken when abundance was greater. Data were grouped into ten abundance classes and assessed for fit to the Poisson and negative binomial distributions. The Poisson distribution fit only data in abundance classes < 0.02 ticks per 10 m2, while the negative binomial distribution fit data from all abundance classes. A negative binomial distribution with common k = 0.3742 fit data in eight of the 10 abundance classes. Both the Taylor and Iwao mean-variance relationships were fit and used to predict sample sizes for a fixed level of precision. Sample sizes predicted using the Taylor model tended to underestimate actual sample sizes, while sample sizes estimated using the Iwao model tended to overestimate actual sample sizes. Using a negative binomial with common k provided estimates of required sample sizes closest to empirically calculated sample sizes.

Characterizing temporal changes of agricultural particulate matter number concentrations

NASA Astrophysics Data System (ADS)

Docekal, G. P.; Mahmood, R.; Larkin, G. P.; Silva, P. J.

2017-12-01

It is widely accepted among literature that particulate matter (PM) are of detriment to human health and the environment as a whole. These effects can vary depending on the particle size. This study examines PM size distributions and number concentrations at a poultry house. Despite much literature on PM concentrations at agricultural facilities, few studies have looked at the size distribution of particles at such facilities from the nucleation up through the coarse mode. Two optical particle counters (OPCs) were placed, one inside of a chicken house, and one on the outside of an exhaust fan to determine particle size distributions. In addition, a scanning mobility particle sizer (SMPS) and aerodynamic particle sizer (APS) sampled poultry house particles to give sizing information from a full size range of 10 nm - 20 mm. The data collected show several different types of events where observed size distributions changed. While some of these are due to expected dust generation events producing coarse mode particles, others suggest particle nucleation and accumulation events at the smaller size ranges that also occurred. The data suggest that agricultural facilities have an impact one the presence of PM in the environment beyond just generation of coarse mode dust. Data for different types of size distribution changes observed will be discussed.

Simple, Defensible Sample Sizes Based on Cost Efficiency

PubMed Central

Bacchetti, Peter; McCulloch, Charles E.; Segal, Mark R.

2009-01-01

Summary The conventional approach of choosing sample size to provide 80% or greater power ignores the cost implications of different sample size choices. Costs, however, are often impossible for investigators and funders to ignore in actual practice. Here, we propose and justify a new approach for choosing sample size based on cost efficiency, the ratio of a study’s projected scientific and/or practical value to its total cost. By showing that a study’s projected value exhibits diminishing marginal returns as a function of increasing sample size for a wide variety of definitions of study value, we are able to develop two simple choices that can be defended as more cost efficient than any larger sample size. The first is to choose the sample size that minimizes the average cost per subject. The second is to choose sample size to minimize total cost divided by the square root of sample size. This latter method is theoretically more justifiable for innovative studies, but also performs reasonably well and has some justification in other cases. For example, if projected study value is assumed to be proportional to power at a specific alternative and total cost is a linear function of sample size, then this approach is guaranteed either to produce more than 90% power or to be more cost efficient than any sample size that does. These methods are easy to implement, based on reliable inputs, and well justified, so they should be regarded as acceptable alternatives to current conventional approaches. PMID:18482055

RnaSeqSampleSize: real data based sample size estimation for RNA sequencing.

PubMed

Zhao, Shilin; Li, Chung-I; Guo, Yan; Sheng, Quanhu; Shyr, Yu

2018-05-30

One of the most important and often neglected components of a successful RNA sequencing (RNA-Seq) experiment is sample size estimation. A few negative binomial model-based methods have been developed to estimate sample size based on the parameters of a single gene. However, thousands of genes are quantified and tested for differential expression simultaneously in RNA-Seq experiments. Thus, additional issues should be carefully addressed, including the false discovery rate for multiple statistic tests, widely distributed read counts and dispersions for different genes. To solve these issues, we developed a sample size and power estimation method named RnaSeqSampleSize, based on the distributions of gene average read counts and dispersions estimated from real RNA-seq data. Datasets from previous, similar experiments such as the Cancer Genome Atlas (TCGA) can be used as a point of reference. Read counts and their dispersions were estimated from the reference's distribution; using that information, we estimated and summarized the power and sample size. RnaSeqSampleSize is implemented in R language and can be installed from Bioconductor website. A user friendly web graphic interface is provided at http://cqs.mc.vanderbilt.edu/shiny/RnaSeqSampleSize/ . RnaSeqSampleSize provides a convenient and powerful way for power and sample size estimation for an RNAseq experiment. It is also equipped with several unique features, including estimation for interested genes or pathway, power curve visualization, and parameter optimization.

Can mindfulness-based interventions influence cognitive functioning in older adults? A review and considerations for future research.

PubMed

Berk, Lotte; van Boxtel, Martin; van Os, Jim

2017-11-01

An increased need exists to examine factors that protect against age-related cognitive decline. There is preliminary evidence that meditation can improve cognitive function. However, most studies are cross-sectional and examine a wide variety of meditation techniques. This review focuses on the standard eight-week mindfulness-based interventions (MBIs) such as mindfulness-based stress reduction (MBSR) and mindfulness-based cognitive therapy (MBCT). We searched the PsychINFO, CINAHL, Web of Science, COCHRANE, and PubMed databases to identify original studies investigating the effects of MBI on cognition in older adults. Six reports were included in the review of which three were randomized controlled trials. Studies reported preliminary positive effects on memory, executive function and processing speed. However, most reports had a high risk of bias and sample sizes were small. The only study with low risk of bias, large sample size and active control group reported no significant findings. We conclude that eight-week MBI for older adults are feasible, but results on cognitive improvement are inconclusive due a limited number of studies, small sample sizes, and a high risk of bias. Rather than a narrow focus on cognitive training per se, future research may productively shift to investigate MBI as a tool to alleviate suffering in older adults, and to prevent cognitive problems in later life already in younger target populations.

The special case of the 2 × 2 table: asymptotic unconditional McNemar test can be used to estimate sample size even for analysis based on GEE.

PubMed

Borkhoff, Cornelia M; Johnston, Patrick R; Stephens, Derek; Atenafu, Eshetu

2015-07-01

Aligning the method used to estimate sample size with the planned analytic method ensures the sample size needed to achieve the planned power. When using generalized estimating equations (GEE) to analyze a paired binary primary outcome with no covariates, many use an exact McNemar test to calculate sample size. We reviewed the approaches to sample size estimation for paired binary data and compared the sample size estimates on the same numerical examples. We used the hypothesized sample proportions for the 2 × 2 table to calculate the correlation between the marginal proportions to estimate sample size based on GEE. We solved the inside proportions based on the correlation and the marginal proportions to estimate sample size based on exact McNemar, asymptotic unconditional McNemar, and asymptotic conditional McNemar. The asymptotic unconditional McNemar test is a good approximation of GEE method by Pan. The exact McNemar is too conservative and yields unnecessarily large sample size estimates than all other methods. In the special case of a 2 × 2 table, even when a GEE approach to binary logistic regression is the planned analytic method, the asymptotic unconditional McNemar test can be used to estimate sample size. We do not recommend using an exact McNemar test. Copyright © 2015 Elsevier Inc. All rights reserved.

Removal of Contaminant Nanoparticles from Wastewater Produced Via Hydrothermal Carbonization by SPIONs

NASA Astrophysics Data System (ADS)

Parsapour, Melika

Hydrothermal carbonization (HTC) is a chemical approach that can be defined as a combined dehydration and decarboxylation process in a wet state. Briefly, this process is performed by applying elevated temperature (between 180-250°C) and pressure (around 2MPa) to convert biomass from aqueous suspension (e.g. sludge, wastewater, natural products, among other) into three different phases and materials products, including biocoal. Further, during the wet conversion process the high residue content is transformed into nanoparticles that could present well-defined or heterogeneous nanostructure. Although HTC was known for years, it has been focused only recently due to exclusive products properties and cost-effective production. In fact, HTC has been used for sludge and wastewater treatment plants in some developed countries such as Germany. Nowadays, many scientific groups still investigate solid products (e.g. biocoal) from HTC. These studies are related to physico-chemical and biological characterization of HTC's generated materials, as well as their potential uses. However, aqueous products from HTC, which are rich in hydrocarbons derivatives and nanoparticles (NPs), are rarely studied. Thereby, our objective is to study the wastewater generated from HTC applied to samples of either glycerin or sugar. Furthermore, we propose a novel treatment strategy to remove the NPs from the wastewater. In this regard, we have used Superparamagnetic Iron Oxide (SPIONs) due to their unique physico-chemical properties (magnetic properties, adsorption capacity, biocompatibility and eco-friendly degradation) for decontamination of water and wastewater. In this regard, we synthesized two different nanocomposites based on SPIONs to carry out the magnetic removal of existent NPs in the wastewater. For the first case, we synthesized polyethylene-glycol (PEG) coated SPIONS (SPIONs PEG). The second one was a new nanocomposite (SPIONs/GO) obtained from in situ growth of SPIONS over purified graphene oxide (GO), which was afterwards coated with PEG (20000Da), resulting in SPIONs/GO PEG. As GO has various functional groups that have a high valence for absorption of contaminants due to their oxygen content, we assume that SPIONs/GO PEG improves the efficiency of the decontamination process compared to SPIONs PEG alone. Initially, we have characterized the synthetized SPIONs. Fourier Transform Infrared spectroscopy (FT-IR) was used to identify the present functional groups in the SPIONs samples. Atomic Force Microscopy (AFM) and Transmission Electronic Microscopy (TEM) were used to determine the topography and diameter size via high resolution images with fine details of the nanocomposites. Finally Dynamic Light Scattering (DLS) was used to evaluate the size distribution of the SPIONs in distilled water. Also, all wastewater samples were characterized before and after treatment. FT-IR was used to determine the functional groups in initial samples. Ultraviolet-visible spectroscopy (UV-vis) was used to observe the UV absorption of the chemicals. DLS was used for size distribution and density measurement, and morphology investigation was done by AFM technique. The SPIONs which involved the GO due to the presence of oxidizes groups showed a better ordered crystalline structure and a narrower diameter distribution. The glycerin samples treated by SPIONs PEG and SPIONs/GO PEG demonstrated 43% and 38% reduction in contaminant respectively. As for the sugar samples, the reductions were of 33% and 60% respectively. Thus, the obtained results confirm the capability of the nanocomposites to remove the nano contaminant from wastewater samples reasonably. However, the decontamination power of the nanocomposites differs accordingly to the chemical structure of the initial biomass.

Application of Response Surface Methods To Determine Conditions for Optimal Genomic Prediction

PubMed Central

Howard, Réka; Carriquiry, Alicia L.; Beavis, William D.

2017-01-01

An epistatic genetic architecture can have a significant impact on prediction accuracies of genomic prediction (GP) methods. Machine learning methods predict traits comprised of epistatic genetic architectures more accurately than statistical methods based on additive mixed linear models. The differences between these types of GP methods suggest a diagnostic for revealing genetic architectures underlying traits of interest. In addition to genetic architecture, the performance of GP methods may be influenced by the sample size of the training population, the number of QTL, and the proportion of phenotypic variability due to genotypic variability (heritability). Possible values for these factors and the number of combinations of the factor levels that influence the performance of GP methods can be large. Thus, efficient methods for identifying combinations of factor levels that produce most accurate GPs is needed. Herein, we employ response surface methods (RSMs) to find the experimental conditions that produce the most accurate GPs. We illustrate RSM with an example of simulated doubled haploid populations and identify the combination of factors that maximize the difference between prediction accuracies of best linear unbiased prediction (BLUP) and support vector machine (SVM) GP methods. The greatest impact on the response is due to the genetic architecture of the population, heritability of the trait, and the sample size. When epistasis is responsible for all of the genotypic variance and heritability is equal to one and the sample size of the training population is large, the advantage of using the SVM method vs. the BLUP method is greatest. However, except for values close to the maximum, most of the response surface shows little difference between the methods. We also determined that the conditions resulting in the greatest prediction accuracy for BLUP occurred when genetic architecture consists solely of additive effects, and heritability is equal to one. PMID:28720710

Size effects on magnetic actuation in Ni-Mn-Ga shape-memory alloys.

PubMed

Dunand, David C; Müllner, Peter

2011-01-11

The off-stoichiometric Ni(2)MnGa Heusler alloy is a magnetic shape-memory alloy capable of reversible magnetic-field-induced strains (MFIS). These are generated by twin boundaries moving under the influence of an internal stress produced by a magnetic field through the magnetocrystalline anisotropy. While MFIS are very large (up to 10%) for monocrystalline Ni-Mn-Ga, they are near zero (<0.01%) in fine-grained polycrystals due to incompatibilities during twinning of neighboring grains and the resulting internal geometrical constraints. By growing the grains and/or shrinking the sample, the grain size becomes comparable to one or more characteristic sample sizes (film thickness, wire or strut diameter, ribbon width, particle diameter, etc), and the grains become surrounded by free space. This reduces the incompatibilities between neighboring grains and can favor twinning and thus increase the MFIS. This approach was validated recently with very large MFIS (0.2-8%) measured in Ni-Mn-Ga fibers and foams with bamboo grains with dimensions similar to the fiber or strut diameters and in thin plates where grain diameters are comparable to plate thickness. Here, we review processing, micro- and macrostructure, and magneto-mechanical properties of (i) Ni-Mn-Ga powders, fibers, ribbons and films with one or more small dimension, which are amenable to the growth of bamboo grains leading to large MFIS, and (ii) "constructs" from these structural elements (e.g., mats, laminates, textiles, foams and composites). Various strategies are proposed to accentuate this geometric effect which enables large MFIS in polycrystalline Ni-Mn-Ga by matching grain and sample sizes.

Lesion Quantification in Dual-Modality Mammotomography

NASA Astrophysics Data System (ADS)

Li, Heng; Zheng, Yibin; More, Mitali J.; Goodale, Patricia J.; Williams, Mark B.

2007-02-01

This paper describes a novel x-ray/SPECT dual modality breast imaging system that provides 3D structural and functional information. While only a limited number of views on one side of the breast can be acquired due to mechanical and time constraints, we developed a technique to compensate for the limited angle artifact in reconstruction images and accurately estimate both the lesion size and radioactivity concentration. Various angular sampling strategies were evaluated using both simulated and experimental data. It was demonstrated that quantification of lesion size to an accuracy of 10% and quantification of radioactivity to an accuracy of 20% are feasible from limited-angle data acquired with clinically practical dosage and acquisition time

Birth order, family configuration, and verbal achievement.

PubMed

Breland, H M

1974-12-01

Two samples of National Merit Scholarship participants test in 1962 and the entire population of almost 800,000 participants tested in 1965 were examined. Consistent effects in all 3 groups were observed with respect to both birth order and family size (1st born and those of smaller families scored higher). Control of both socioeconomic variables and maternal age, by analysis of variance as well as by analysis of covariance, failed to alter the relationships. Stepdown analyses suggested that the effects were due to a verbal component and that no differences were attributable to nonverbal factors. Mean test scores were computed for detailed sibship configurations based on birth order, family size, sibling spacing, and sibling sex.

Considerations for successful cosmogenic 3He dating in accessory phases

NASA Astrophysics Data System (ADS)

Amidon, W. H.; Farley, K. A.; Rood, D. H.

2008-12-01

We have been working to develop cosmogenic 3He dating of phases other than the commonly dated olivine and pyroxene, especially apatite and zircon. Recent work by Dunai et al. underscores that cosmogenic 3He dating is complicated by 3He production via 6Li(n,α) 3H --> 3He. The reacting thermal neutrons can be produced from three distinct sources; nucleogenic processes (3Henuc), muon interactions (3Hemu), and by high-energy "cosmogenic" neutrons (3Hecn). Accurate cosmogenic 3He dating requires determination of the relative fractions of Li-derived and spallation derived 3He. An important complication for the fine-grained phases we are investigating is that both spallation and the 6Li reaction eject high energy particles, with consequences for redistribution of 3He among phases in a rock. Although shielded samples can be used to estimate 3Henuc, they do not conatin the 3Hecn component produced in the near surface. To calculate this component, we propose a procedure in which the bulk rock chemistry, helium closure age, 3He concentration, grain size and Li content of the target mineral are measured in a shielded sample. The average Li content of the adjacent minerals can then be calculated, which in turn allows calculation of the 3Hecn component in surface exposed samples of the same lithology. If identical grain sizes are used in the shielded and surface exposed samples, then "effective" Li can be calculated directly from the shielded sample, and it may not be necessary to measure Li at all. To help validate our theoretical understanding of Li-3He production, and to constrain the geologic contexts in which cosmogenic 3He dating with zircon and apatite is likely to be successful, results are presented from four different field locations. For example, results from ~18 Ky old moraines in the Sierra Nevada show that the combination of low Li contents and high closure ages (>50 My) creates a small 3Hecn component (2%) but a large 3Henuc component (40-70%) for zircon and apatite. In contrast the combination of high Li contents and a young closure age (0.6 My) in rhyolite from the Coso volcanic field leads to a large 3Hecn component (30%) and small 3Henuc component (5%) in zircon. Analysis of samples from a variety of lithologies shows that zircon and apatite tend to be low in Li (1-10 ppm), but are vulnerable to implantation of 3He from adjacent minerals due to their small grain size, especially from minerals like biotite and hornblende. This point is well illustrated by data from both the Sierra Nevada and Coso examples, in which there is a strong correlation between grain size and 3He concentration for zircons due to implantation. In contrast, very large zircons (150>125 um width) obtained from shielded samples of the Shoshone Falls rhyolite (SW Idaho) do not contain a significant implanted component. Thus, successful 3He dating of accessory phases requires low Li content (<10 ppm) in the target mineral and either 1) low Li in adjacent minerals, or 2) the use of large grain sizes (>100 um). In high-Li cases, the fraction of 3Henuc is minimized in samples with young helium closure ages or longer duration of exposure. However because the 3Hecn/3Hespall ratio is fixed for a given Li content, longer exposure will not reduce the fraction of 3Hecn.

Reporting of sample size calculations in analgesic clinical trials: ACTTION systematic review.

PubMed

McKeown, Andrew; Gewandter, Jennifer S; McDermott, Michael P; Pawlowski, Joseph R; Poli, Joseph J; Rothstein, Daniel; Farrar, John T; Gilron, Ian; Katz, Nathaniel P; Lin, Allison H; Rappaport, Bob A; Rowbotham, Michael C; Turk, Dennis C; Dworkin, Robert H; Smith, Shannon M

2015-03-01

Sample size calculations determine the number of participants required to have sufficiently high power to detect a given treatment effect. In this review, we examined the reporting quality of sample size calculations in 172 publications of double-blind randomized controlled trials of noninvasive pharmacologic or interventional (ie, invasive) pain treatments published in European Journal of Pain, Journal of Pain, and Pain from January 2006 through June 2013. Sixty-five percent of publications reported a sample size calculation but only 38% provided all elements required to replicate the calculated sample size. In publications reporting at least 1 element, 54% provided a justification for the treatment effect used to calculate sample size, and 24% of studies with continuous outcome variables justified the variability estimate. Publications of clinical pain condition trials reported a sample size calculation more frequently than experimental pain model trials (77% vs 33%, P < .001) but did not differ in the frequency of reporting all required elements. No significant differences in reporting of any or all elements were detected between publications of trials with industry and nonindustry sponsorship. Twenty-eight percent included a discrepancy between the reported number of planned and randomized participants. This study suggests that sample size calculation reporting in analgesic trial publications is usually incomplete. Investigators should provide detailed accounts of sample size calculations in publications of clinical trials of pain treatments, which is necessary for reporting transparency and communication of pre-trial design decisions. In this systematic review of analgesic clinical trials, sample size calculations and the required elements (eg, treatment effect to be detected; power level) were incompletely reported. A lack of transparency regarding sample size calculations may raise questions about the appropriateness of the calculated sample size. Copyright © 2015 American Pain Society. All rights reserved.

Facile synthesis of Li2S-P2S5 glass-ceramics electrolyte with micron range particles for all-solid-state batteries via a low-temperature solution technique (LTST)

NASA Astrophysics Data System (ADS)

Choi, Sunho; Lee, Sewook; Park, Jongyeop; Nichols, William T.; Shin, Dongwook

2018-06-01

A lithium ion conductive 75Li2Sṡ25P2S5 glass-ceramics electrolyte is, for the first time, successfully synthesized via a new low-temperature solution technique (LTST) and compared to the conventional mechanical-milling technique. Both samples are composed of the highly lithium ion conductive thio-LISICON III analog phase. Due to the uniform dispersion of reactants in an organic liquid, the use of LTST produced significantly smaller and more uniform particle sizes (2.2 ± 1.68 μm) resulting in a 6.5 times higher specific surface area compared to the mechanically-milled sample. A pronounced enhancement of both the rate capability and cyclability is demonstrated for the LTST solid electrolyte sample due to the more intimate contact with the LiCoO2 active material. Furthermore, the LTST sample shows excellent electrochemical stability throughout the potential range of -1 to 5 V. These results suggest that the proposed technique using the optimized LTST process is promising for the preparation of 75Li2Sṡ25P2S5 solid electrolytes for use in advanced Li-ion batteries.

Particle size effect on microwave absorbing of La{sub 0.67}Ba{sub 0.33}Mn{sub 0.94}Ti{sub 0.06}O{sub 3} powders prepared by mechanical alloying with the assistance of ultrasonic irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saptari, Sitti Ahmiatri, E-mail: siti-ahmiatri@yahoo.co.id; Manaf, Azwar; Kurniawan, Budhy

Doped manganites have attracted substantial interest due to their unique chemical and physics properties, which makes it possible to be used for microwave absorbing materials. In this paper we report synthesizes and characterization of La{sub 0.67}Ba{sub 0.33}Mn{sub 0.94}Ti{sub 0.06}O{sub 3} powders prepared by mechanical alloying with the assistance of a high power ultrasonic treatment. After solid state reaction, the presence of single phase was confirmed by X-ray Diffraction (XRD). Refinement results showed that samples are single phase with monoclinic structure. It was found that powder materials derived from mechanical alloying results in large variation in the particle size. A significantmore » improvement was obtained upon subjecting the mechanically milled powder materials to an ultrasonication treatment for a relatively short period of time. As determined by particle size analyzer (PSA), the mean particle size gradually decreased from the original size of 5.02 µm to 0.36 µm. Magnetic properties were characterized by VSM, and hysteresis loops results showed that samples are soft magnetic. It was found that when the mean particle size decreases, saturation was increases and coersitivity was decreases. Microwave absorption properties were investigated in the frequency range of 8-12 GHz using vector network analyzer. An optimal reflection loss of 24.44 dB is reached at 11.4 GHz.« less

Consistency of Pilot Trainee Cognitive Ability, Personality, and Training Performance in Undergraduate Pilot Training

DTIC Science & Technology

2013-09-09

multivariate correction method (Lawley, 1943) was used for all scores except the MAB FSIQ which used the univariate ( Thorndike , 1949) method. FSIQ... Thorndike , R. L. (1949). Personnel selection. NY: Wiley. Tupes, E. C., & Christal, R. C. (1961). Recurrent personality factors based on trait ratings... Thorndike , 1949). aThe correlations for 1995 were not corrected due to the small sample size (N = 17). *p< .05 Consistency of Pilot Attributes

Synthesis and optical properties of silver nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Jaiveer; Kaurav, Netram, E-mail: netramkaurav@yahoo.co.uk; Choudhary, K. K.

The preparation of stable, uniform silver nanoparticles by reduction of silver acetate by ethylene glycol (EG) is reported in the present paper. It is a simple process of recent interest for obtaining silver nanoparticles. The samples were characterized by X-Ray diffraction (XRD), which reveals an average particle size (D) of 38 nm. The UV/Vis spectra show that an absorption peak, occurring due to surface plasmon resonance (SPR), exists at 319 nm.

Acute, Five- and Ten-Day Inhalation Study of Hydroprocessed Esters and Fatty Acids-Mixed Fats (HEFA-F) Jet Fuel

DTIC Science & Technology

2012-09-01

Groups ...................18 Table 6. Urine Specific Gravity in the Ten-Day Duration Groups ...............................................19 Table 7...exposed rats were not consistently significant compared to control groups and were considered random due to small group sizes. In urine samples...sources. Alternative fuels may be developed by synthesis from simpler molecules (e.g., natural gas) or by refining from non-petroleum sources (e.g

Sediment laboratory quality-assurance project: studies of methods and materials

USGS Publications Warehouse

Gordon, J.D.; Newland, C.A.; Gray, J.R.

2001-01-01

In August 1996 the U.S. Geological Survey initiated the Sediment Laboratory Quality-Assurance project. The Sediment Laboratory Quality Assurance project is part of the National Sediment Laboratory Quality-Assurance program. This paper addresses the fmdings of the sand/fme separation analysis completed for the single-blind reference sediment-sample project and differences in reported results between two different analytical procedures. From the results it is evident that an incomplete separation of fme- and sand-size material commonly occurs resulting in the classification of some of the fme-size material as sand-size material. Electron microscopy analysis supported the hypothesis that the negative bias for fme-size material and the positive bias for sand-size material is largely due to aggregation of some of the fine-size material into sand-size particles and adherence of fine-size material to the sand-size grains. Electron microscopy analysis showed that preserved river water, which was low in dissolved solids, specific conductance, and neutral pH, showed less aggregation and adhesion than preserved river water that was higher in dissolved solids and specific conductance with a basic pH. Bacteria were also found growing in the matrix, which may enhance fme-size material aggregation through their adhesive properties. Differences between sediment-analysis methods were also investigated as pan of this study. Suspended-sediment concentration results obtained from one participating laboratory that used a total-suspended solids (TSS) method had greater variability and larger negative biases than results obtained when this laboratory used a suspended-sediment concentration method. When TSS methods were used to analyze the reference samples, the median suspended sediment concentration percent difference was -18.04 percent. When the laboratory used a suspended-sediment concentration method, the median suspended-sediment concentration percent difference was -2.74 percent. The percent difference was calculated as follows: Percent difference = (( reported mass - known mass)/known mass ) X 100.

Plasmonic and SERS performances of compound nanohole arrays fabricated by shadow sphere lithography

NASA Astrophysics Data System (ADS)

Skehan, Connor; Ai, Bin; Larson, Steven R.; Stone, Keenan M.; Dennis, William M.; Zhao, Yiping

2018-03-01

Several plasmonic compound nanohole arrays (CNAs), such as triangular nanoholes and fan-like nanoholes with multiple nanotips and nanogaps, are designed by a simple and efficient shadow sphere lithography technique by tuning the sphere mask size, the deposition and azimuthal angles, substrate temperature T S , and the number of deposition steps N. Compared with conventional circular nanohole arrays, the CNAs show more hot spots and exhibit new transmission speaks. Systematic finite-difference time-domain calculations indicate that different resonance modes excited by the various shaped and sized nanoholes are responsible for the enhanced plasmonic performances of CNAs. Compared to the CNA samples with only one circular hole in the unit cell, the Raman scattering intensity of the CNA with multiple triangular nanoholes, nanogaps, and nanotips can be enhanced up to 5-fold. These CNAs, due to the strong resonance due to the multiple structural features, are promising applications as optical filters, plasmonic sensors, and surface-enhanced spectroscopies.

Size and structure dependent ultrafast dynamics of plasmonic gold nanosphere heterostructures on poly (ethylene glycol) brushes

NASA Astrophysics Data System (ADS)

Karatay, Ahmet; Küçüköz, Betül; Pekdemir, Sami; Onses, Mustafa Serdar; Elmali, Ayhan

2017-11-01

We have investigated the plasmonic properties of heterostructures that consist of gold nanosphere (NSs) with average diameters of 60 nm, 40 nm and 20 nm on poly (ethylene glycol) (PEG) brushes by using ultrafast pump-probe spectroscopy experiments. Gold NSs start to behave like gold nanorods with increasing number of immobilization cycles due to the close proximity. Gold NSs immobilized by 3 and 5 deposition cycles show longitudinal modes of plasmon bands at long wavelengths which are characteristic behaviors for gold nanorods. Increasing the number of immobilization cycle also increase relaxation times of samples due to the close proximity. Linear absorption spectra and scanning electron microscopy images show that there are close packing assemblies for heterostructures containing 20 nm gold NSs as the small particle. Ultrafast electron transfer (<100 fs) occurs between transverse and longitudinal modes by exciting the samples at both 520 nm and 650 nm. Further, experimental results indicate that, heterostructures with the small particles have faster relaxation times than other heterostructures due to closed packing of 20 nm gold NSs.

Magnetic properties of atmospheric PMx in a small settlement during heating and non-heating season

NASA Astrophysics Data System (ADS)

Petrovsky, E.; Kotlik, B.; Zboril, R.; Kapicka, A.; Grison, H.

2012-04-01

Magnetic properties of environmental samples can serve as fast and relatively cheap proxy method to investigate occurrence of iron oxides. These methods are very sensitive in detecting strongly magnetic compounds such as magnetite and maghemite and can reveal concentration and assess grain-size distribution of these minerals. This information can be significant in estimating e.g. the source of pollutants, monitoring pollution load, or investigating seasonal and climatic effects. We studied magnetic properties of PM1, PM2.5 and PM10, collected over 32-48 hours in a small settlement in south Bohemia during heating and non-heating season. The site is rather remote, with negligible traffic and industrial contributions to air pollution. Thus, the suggested seasonal effect should be dominantly due to local (domestic) heating, burning wood or coal. In our contribution we show typical differences in PMx concentration, which is much higher in the winter (heating) sample, accompanied by SEM analyses and magnetic data oriented on concentration and grain-size distribution of magnetite/maghemite particles. While concentration of Fe-oxides does not vary that much, significant seasonal differences were observed in composition and grain-size distribution, reflecting different sources of the dust particles.

Enrichment and distribution of 24 elements within the sub-sieve particle size distribution ranges of fly ash from wastes incinerator plants.

PubMed

Raclavská, Helena; Corsaro, Agnieszka; Hartmann-Koval, Silvie; Juchelková, Dagmar

2017-12-01

The management of an increasing amount of municipal waste via incineration has been gaining traction. Fly ash as a by-product of incineration of municipal solid waste is considered a hazardous waste due to the elevated content of various elements. The enrichment and distribution of 24 elements in fly ash from three wastes incinerators were evaluated. Two coarse (>100 μm and <100 μm) and five sub-sieve (12-16, 16-23, 23-34, 34-49, and 49-100 μm) particle size fractions separated on a cyclosizer system were analyzed. An enhancement in the enrichment factor was observed in all samples for the majority of elements in >100 μm range compared with <100 μm range. The enrichment factor of individual elements varied considerably within the samples as well as the sub-sieve particle size ranges. These variations were attributed primarily to: (i) the vaporization and condensation mechanisms, (ii) the different design of incineration plants, (iii) incineration properties, (iv) the type of material being incinerated, and (v) the affinity of elements. Copyright © 2017 Elsevier Ltd. All rights reserved.

Determination of the optimal sample size for a clinical trial accounting for the population size.

PubMed

Stallard, Nigel; Miller, Frank; Day, Simon; Hee, Siew Wan; Madan, Jason; Zohar, Sarah; Posch, Martin

2017-07-01

The problem of choosing a sample size for a clinical trial is a very common one. In some settings, such as rare diseases or other small populations, the large sample sizes usually associated with the standard frequentist approach may be infeasible, suggesting that the sample size chosen should reflect the size of the population under consideration. Incorporation of the population size is possible in a decision-theoretic approach either explicitly by assuming that the population size is fixed and known, or implicitly through geometric discounting of the gain from future patients reflecting the expected population size. This paper develops such approaches. Building on previous work, an asymptotic expression is derived for the sample size for single and two-arm clinical trials in the general case of a clinical trial with a primary endpoint with a distribution of one parameter exponential family form that optimizes a utility function that quantifies the cost and gain per patient as a continuous function of this parameter. It is shown that as the size of the population, N, or expected size, N∗ in the case of geometric discounting, becomes large, the optimal trial size is O(N1/2) or O(N∗1/2). The sample size obtained from the asymptotic expression is also compared with the exact optimal sample size in examples with responses with Bernoulli and Poisson distributions, showing that the asymptotic approximations can also be reasonable in relatively small sample sizes. © 2016 The Author. Biometrical Journal published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Explanation of Two Anomalous Results in Statistical Mediation Analysis.

PubMed

Fritz, Matthew S; Taylor, Aaron B; Mackinnon, David P

2012-01-01

Previous studies of different methods of testing mediation models have consistently found two anomalous results. The first result is elevated Type I error rates for the bias-corrected and accelerated bias-corrected bootstrap tests not found in nonresampling tests or in resampling tests that did not include a bias correction. This is of special concern as the bias-corrected bootstrap is often recommended and used due to its higher statistical power compared with other tests. The second result is statistical power reaching an asymptote far below 1.0 and in some conditions even declining slightly as the size of the relationship between X and M , a , increased. Two computer simulations were conducted to examine these findings in greater detail. Results from the first simulation found that the increased Type I error rates for the bias-corrected and accelerated bias-corrected bootstrap are a function of an interaction between the size of the individual paths making up the mediated effect and the sample size, such that elevated Type I error rates occur when the sample size is small and the effect size of the nonzero path is medium or larger. Results from the second simulation found that stagnation and decreases in statistical power as a function of the effect size of the a path occurred primarily when the path between M and Y , b , was small. Two empirical mediation examples are provided using data from a steroid prevention and health promotion program aimed at high school football players (Athletes Training and Learning to Avoid Steroids; Goldberg et al., 1996), one to illustrate a possible Type I error for the bias-corrected bootstrap test and a second to illustrate a loss in power related to the size of a . Implications of these findings are discussed.

Multi-scale X-ray Microtomography Imaging of Immiscible Fluids After Imbibition

NASA Astrophysics Data System (ADS)

Garing, C.; de Chalendar, J.; Voltolini, M.; Ajo Franklin, J. B.; Benson, S. M.

2015-12-01

A major issue for CO2 storage security is the efficiency and long-term reliability of the trapping mechanisms occurring in the reservoir where CO2 is injected. Residual trapping is one of the key processes for storage security beyond the primary stratigraphic seal. Although classical conceptual models of residual fluid trapping assume that disconnected ganglia are permanently immobilized, multiple mechanisms exist which could allow the remobilization of residually trapped CO2. The aim of this study is to quantify fluid phases saturation, connectivity and morphology after imbibition using x-ray microtomography in order to evaluate potential changes in droplets organization due to differences in capillary pressure between disconnected ganglia. Particular emphasis is placed on the effect of image resolution. Synchrotron-based x-ray microtomographic datasets of air-water spontaneous imbibition were acquired in sintered glass beads and sandstone samples with voxel sizes varying from 0.64 to 4.44 μm. The results show that for both sandstones the residual air phase is homogeneously distributed within the entire pore space and consists of disconnected clusters of multiple sizes and morphologies. The multi-scale analysis of subsamples of few pores and throats imaged at the same location of the sample reveals significant variations in the estimation of connectivity, size and shape of the fluid phases. This is particularly noticeable when comparing the results from the images with voxel sizes above 1 μm with the results from the images acquired with voxel sizes below 1 μm.

Being stressed outside the park—conservation of African elephants (Loxodonta africana) in Namibia

PubMed Central

Ringstad, Iris H; Jackson, Craig R; May, Roel; Fossøy, Frode; Uiseb, Kenneth; Killian, Werner; Palme, Rupert; Røskaft, Eivin

2017-01-01

Abstract The conservation of the African savanna elephant (Loxodonta africana) is of prime importance for many African countries. Interactions between elephants and humans are known to induce stress and thereby have the potential to affect elephants’ fitness. In Namibia, anthropogenic disturbances are increasing due to increasing human population size and development, particularly near protected areas, such as national parks. In this study, we investigated elephant stress levels in relation to their land use, specifically their protection status, comparing elephants within Etosha National Park in Namibia with elephants residing outside the park. We noninvasively collected dung samples of 91 elephants and determined the concentration of faecal glucocorticoid metabolites (fGCM), an indicator of physiological stress. Elephants outside the park (N = 35) had significantly higher concentrations of fGCM than those inside ENP (N = 56), suggesting that, despite including community-based conservancies, unprotected areas are more stressful for elephants than protected areas, most likely due to increased interactions with humans. We also found that males had lower fGCM concentrations than females, but no significant effect of age, body size or group size was detected. Additionally, herd sizes were significantly smaller and calf recruitment was potentially lower in unprotected areas. These findings underpin the importance of protected areas such as ENP, while encouraging decision-makers to continue reducing and mitigating potential human-induced disturbances. PMID:29270294

Round-Trip Solar Electric Propulsion Missions for Mars Sample Return

NASA Technical Reports Server (NTRS)

Bailey, Zachary J.; Sturm, Erick J.; Kowalkowski, Theresa D.; Lock, Robert E.; Woolley, Ryan C.; Nicholas, Austin K.

2014-01-01

Mars Sample Return (MSR) missions could benefit from the high specific impulse of Solar Electric Propulsion (SEP) to achieve lower launch masses than with chemical propulsion. SEP presents formulation challenges due to the coupled nature of launch vehicle performance, propulsion system, power system, and mission timeline. This paper describes a SEP orbiter-sizing tool, which models spacecraft mass & timeline in conjunction with low thrust round-trip Earth-Mars trajectories, and presents selected concept designs. A variety of system designs are possible for SEP MSR orbiters, with large dry mass allocations, similar round-trip durations to chemical orbiters, and reduced design variability between opportunities.

Structural and optical characterizations of Ca2Al2SiO7:Ce3+, Mn2+ nanoparticles produced via a hybrid route

NASA Astrophysics Data System (ADS)

Teixeira, V. C.; Montes, P. J. R.; Valerio, M. E. G.

2014-07-01

Pure, Ce3+ doped and Ce3+ and Mn2+ co-doped Ca2Al2SiO7 ceramic powders were prepared by two different methodologies which are the proteic sol-gel process and a new hybrid route combining the proteic sol-gel with solid state reaction processes. The second one is an eco-friendly method because it uses natural raw materials in replacement of the metal alkoxides used in the traditional sol-gel routes. X-ray diffraction showed that Ca2Al2SiO7 crystalline phase was obtained for both preparations. Differential thermal analysis indicated that the exothermic event around 850 °C, for sample produced by proteic sol-gel method, and around 927 °C, for ceramics prepared by hybrid synthesis, can be associated to crystallization of Ca2Al2SiO7. Transmission electron microscope indicates that regular and spherical nanoparticles were obtained with average sizes of about 12 nm. The Scherrer's method was used to determine the average crystallite sizes and it was shown that nanometric crystallites were obtained of about 74 nm for samples produced via hybrid route. For all the single phase samples, the crystallite sizes are about the same and that agrees with TEM results. Diffuse optical reflectance measurements were used to estimate the Ca2Al2SiO7 optical band gap and the obtained value is about 6 eV, photoluminescence (PL) spectra presented typical emissions of Ce3+ and Mn2+ ions. Upon excitation at 352 nm the emission spectra showed a broad band centered at 415 nm due to the Ce3+ 4f1 → 5d1 typical transition. This emission is resonant with Mn2+ excitation and it transfers energy to Mn ions generating a second broad emission band centered at 620 nm due to the Mn2+. The PL results were used to obtain, as a fist approach, the Ce3+ energy levels diagram and, using the Tanabe-Sugano diagrams, the transitions due to the Mn2+ were calculated. X-ray excited optical luminescence measurements showed the same emission spectra as the PL emission spectra. Luminescence lifetime decay constants were measured for Ce and Mn co-doped and for Ce doped samples and the results indicate Ca2Al2SiO7:Ce3+, Mn2+ showed quite fast responses with main time constants below 30 ns.

Ash leachates from some recent eruptions of Mount Etna (Italy) and Popocatépetl (Mexico) volcanoes and their impact on amphibian living freshwater organisms

NASA Astrophysics Data System (ADS)

D'Addabbo, M.; Sulpizio, R.; Guidi, M.; Capitani, G.; Mantecca, P.; Zanchetta, G.

2015-12-01

Leaching experiments were carried out on fresh ash samples from Popocatépetl 2012, Etna 2011, and Etna 2012 eruptions, in order to investigate the release of compounds in both double-deionized and lake (Lake Ohrid, FYR of Macedonia) waters. The experiments were carried out using different grain sizes and variable stirring times (from 30 min to 7 days). Results were discussed in the light of changing pH and release of compounds for the different leachates. In particular, Etna samples induced alkalinization, and Popocatépetl samples induced acidification of the corresponding leachates. The release of different elements does not show correlation with the stirring time, with the measured maximum concentrations reached in the first hours of washing. General inverse correlation with grain size was observed only for Na+, K+, Cl-, Ca2+, Mg2+, SO42-, and Mn2+, while the other analysed elements show a complex, scattering relationship with grain size. Geochemical modelling highlights leachates' saturation only for F and Si, with Popocatépetl samples sometimes showing saturation in Fe. The analysed leachates are classified as undrinkable for humans on the basis of European laws, due to excess in F-, Mn2+, Fe, and SO42- (the latter only for Popocatépetl samples). Finally, the Etna 2012 and Popocatépetl leachates were used for toxicity experiments on living biota (Xenopus laevis). They are mildly toxic, and no significant differences exist between the toxic profiles of the two leachates. In particular, no significant embryo mortality was observed; while even at high dilutions, the leachates produced more than 20 % of malformed larvae.

Hydroxymethanesulfonic acid in size-segregated aerosol particles at nine sites in Germany

NASA Astrophysics Data System (ADS)

Scheinhardt, S.; van Pinxteren, D.; Müller, K.; Spindler, G.; Herrmann, H.

2013-12-01

In the course of two field campaigns, size-segregated particle samples were collected at nine sites in Germany, including traffic, urban, rural, marine, and mountain sites. During the chemical characterisation of the samples some of them were found to contain an unknown substance that was later on identified as hydroxymethanesulfonic acid (HMSA). HMSA is known to be formed during the reaction of S(IV) (HSO3- or SO32-) with formaldehyde in the aqueous phase. Due to its stability, HMSA may can act as a reservoir species for S(IV) in the atmosphere and is therefore of interest for the understanding of atmospheric sulphur chemistry. However, no HMSA data are available for atmospheric particles from Central Europe and even on a worldwide scale, data are scarce. Thus, the present study now provides a representative dataset with detailed information on HMSA concentrations in size-segregated Central European aerosol particles. HMSA mass concentrations in this dataset were highly variable: HMSA was found in 224 out of 738 samples (30%), sometimes in high mass concentrations exceeding those of oxalic acid. In average over all 154 impactor runs, 31.5 ng m-3 HMSA were found in PM10, contributing 0.21% to the total mass. The results show that the particle diameter, the sampling location, the sampling season and the air mass origin impact the HMSA mass concentration. Highest concentrations were found in the particle fraction 0.42-1.2 μm, at urban sites, in winter and with eastern (continental) air masses, respectively. The results suggest that HMSA is formed during aging of pollution plumes. A positive correlation of HMSA with sulphate, oxalate and PM is found (R2 > 0.4). The results furthermore suggest that the fraction of HMSA in PM slightly decreases with increasing pH.

Hydroxymethanesulfonic acid in size-segregated aerosol particles at nine sites in Germany

NASA Astrophysics Data System (ADS)

Scheinhardt, S.; van Pinxteren, D.; Müller, K.; Spindler, G.; Herrmann, H.

2014-05-01

In the course of two field campaigns, size-segregated particle samples were collected at nine sites in Germany, including traffic, urban, rural, marine and mountain sites. During the chemical characterisation of the samples some of them were found to contain an unknown substance that was later identified as hydroxymethanesulfonic acid (HMSA). HMSA is known to be formed during the reaction of S(IV) (HSO3- or SO32-) with formaldehyde in the aqueous phase. Due to its stability, HMSA can act as a reservoir species for S(IV) in the atmosphere and is therefore of interest for the understanding of atmospheric sulfur chemistry. However, no HMSA data are available for atmospheric particles from central Europe, and even on a worldwide scale data are scarce. Thus, the present study now provides a representative data set with detailed information on HMSA concentrations in size-segregated central European aerosol particles. HMSA mass concentrations in this data set were highly variable: HMSA was found in 224 out of 738 samples (30%), sometimes in high mass concentrations exceeding those of oxalic acid. On average over all 154 impactor runs, 31.5 ng m-3 HMSA was found in PM10, contributing 0.21% to the total mass. The results show that the particle diameter, the sampling location, the sampling season and the air mass origin impact the HMSA mass concentration. Highest concentrations were found in the particle fraction 0.42-1.2 μm, at urban sites, in winter and with eastern (continental) air masses, respectively. The results suggest that HMSA is formed during aging of pollution plumes. A positive correlation of HMSA with sulfate, oxalate and PM is found (R2 > 0.4). The results furthermore suggest that the fraction of HMSA in PM slightly decreases with increasing pH.

Cell-free DNA fragment-size distribution analysis for non-invasive prenatal CNV prediction.

PubMed

Arbabi, Aryan; Rampášek, Ladislav; Brudno, Michael

2016-06-01

Non-invasive detection of aneuploidies in a fetal genome through analysis of cell-free DNA circulating in the maternal plasma is becoming a routine clinical test. Such tests, which rely on analyzing the read coverage or the allelic ratios at single-nucleotide polymorphism (SNP) loci, are not sensitive enough for smaller sub-chromosomal abnormalities due to sequencing biases and paucity of SNPs in a genome. We have developed an alternative framework for identifying sub-chromosomal copy number variations in a fetal genome. This framework relies on the size distribution of fragments in a sample, as fetal-origin fragments tend to be smaller than those of maternal origin. By analyzing the local distribution of the cell-free DNA fragment sizes in each region, our method allows for the identification of sub-megabase CNVs, even in the absence of SNP positions. To evaluate the accuracy of our method, we used a plasma sample with the fetal fraction of 13%, down-sampled it to samples with coverage of 10X-40X and simulated samples with CNVs based on it. Our method had a perfect accuracy (both specificity and sensitivity) for detecting 5 Mb CNVs, and after reducing the fetal fraction (to 11%, 9% and 7%), it could correctly identify 98.82-100% of the 5 Mb CNVs and had a true-negative rate of 95.29-99.76%. Our source code is available on GitHub at https://github.com/compbio-UofT/FSDA CONTACT: : brudno@cs.toronto.edu. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Brief Communication: Buoyancy-Induced Differences in Soot Morphology

NASA Technical Reports Server (NTRS)

Ku, Jerry C.; Griffin, Devon W.; Greenberg, Paul S.; Roma, John

1995-01-01

Reduction or elimination of buoyancy in flames affects the dominant mechanisms driving heat transfer, burning rates and flame shape. The absence of buoyancy produces longer residence times for soot formation, clustering and oxidation. In addition, soot pathlines are strongly affected in microgravity. We recently conducted the first experiments comparing soot morphology in normal and reduced-gravity laminar gas jet diffusion flames. Thermophoretic sampling is a relatively new but well-established technique for studying the morphology of soot primaries and aggregates. Although there have been some questions about biasing that may be induced due to sampling, recent analysis by Rosner et al. showed that the sample is not biased when the system under study is operating in the continuum limit. Furthermore, even if the sampling is preferentially biased to larger aggregates, the size-invariant premise of fractal analysis should produce a correct fractal dimension.

Requirements for Minimum Sample Size for Sensitivity and Specificity Analysis

PubMed Central

Adnan, Tassha Hilda

2016-01-01

Sensitivity and specificity analysis is commonly used for screening and diagnostic tests. The main issue researchers face is to determine the sufficient sample sizes that are related with screening and diagnostic studies. Although the formula for sample size calculation is available but concerning majority of the researchers are not mathematicians or statisticians, hence, sample size calculation might not be easy for them. This review paper provides sample size tables with regards to sensitivity and specificity analysis. These tables were derived from formulation of sensitivity and specificity test using Power Analysis and Sample Size (PASS) software based on desired type I error, power and effect size. The approaches on how to use the tables were also discussed. PMID:27891446

Intrinsic speckle noise in in-line particle holography due to polydisperse and continuous particle sizes

NASA Astrophysics Data System (ADS)

Edwards, Philip J.; Hobson, Peter R.; Rodgers, G. J.

2000-08-01

In-line particle holography is subject to image deterioration due to intrinsic speckle noise. The resulting reduction in the signal to noise ratio (SNR) of the replayed image can become critical for applications such as holographic particle velocimetry (HPV) and 3D visualisation of marine plankton. Work has been done to extend the mono-disperse model relevant to HPV to include poly-disperse particle fields appropriate for the visualisation of marine plankton. Continuous and discrete particle fields are both considered. It is found that random walk statistics still apply for the poly-disperse case. The speckle field is simply the summation of the individual speckle patters due to each scatter size. Therefor the characteristic speckle parameter (which encompasses particle diameter, concentration and sample depth) is alos just the summation of the individual speckle parameters. This reduces the SNR calculation to the same form as for the mono-disperse case. For the continuous situation three distributions, power, exponential and Gaussian are discussed with the resulting SNR calcuated. The work presented here was performed as part of the Holomar project to produce a working underwater holographic camera for recording plankton.

Accurate condensed history Monte Carlo simulation of electron transport. II. Application to ion chamber response simulations.

PubMed

Kawrakow, I

2000-03-01

In this report the condensed history Monte Carlo simulation of electron transport and its application to the calculation of ion chamber response is discussed. It is shown that the strong step-size dependencies and lack of convergence to the correct answer previously observed are the combined effect of the following artifacts caused by the EGS4/PRESTA implementation of the condensed history technique: dose underprediction due to PRESTA'S pathlength correction and lateral correlation algorithm; dose overprediction due to the boundary crossing algorithm; dose overprediction due to the breakdown of the fictitious cross section method for sampling distances between discrete interaction and the inaccurate evaluation of energy-dependent quantities. These artifacts are now understood quantitatively and analytical expressions for their effect are given.

Sample size calculations for randomized clinical trials published in anesthesiology journals: a comparison of 2010 versus 2016.

PubMed

Chow, Jeffrey T Y; Turkstra, Timothy P; Yim, Edmund; Jones, Philip M

2018-06-01

Although every randomized clinical trial (RCT) needs participants, determining the ideal number of participants that balances limited resources and the ability to detect a real effect is difficult. Focussing on two-arm, parallel group, superiority RCTs published in six general anesthesiology journals, the objective of this study was to compare the quality of sample size calculations for RCTs published in 2010 vs 2016. Each RCT's full text was searched for the presence of a sample size calculation, and the assumptions made by the investigators were compared with the actual values observed in the results. Analyses were only performed for sample size calculations that were amenable to replication, defined as using a clearly identified outcome that was continuous or binary in a standard sample size calculation procedure. The percentage of RCTs reporting all sample size calculation assumptions increased from 51% in 2010 to 84% in 2016. The difference between the values observed in the study and the expected values used for the sample size calculation for most RCTs was usually > 10% of the expected value, with negligible improvement from 2010 to 2016. While the reporting of sample size calculations improved from 2010 to 2016, the expected values in these sample size calculations often assumed effect sizes larger than those actually observed in the study. Since overly optimistic assumptions may systematically lead to underpowered RCTs, improvements in how to calculate and report sample sizes in anesthesiology research are needed.

Long term evolution of distant retrograde orbits in the Earth-Moon system

NASA Astrophysics Data System (ADS)

Bezrouk, Collin; Parker, Jeffrey S.

2017-09-01

This work studies the evolution of several Distant Retrograde Orbits (DROs) of varying size in the Earth-Moon system over durations up to tens of millennia. This analysis is relevant for missions requiring a completely hands off, long duration quarantine orbit, such as a Mars Sample Return mission or the Asteroid Redirect Mission. Four DROs are selected from four stable size regions and are propagated for up to 30,000 years with an integrator that uses extended precision arithmetic techniques and a high fidelity dynamical model. The evolution of the orbit's size, shape, orientation, period, out-of-plane amplitude, and Jacobi constant are tracked. It has been found that small DROs, with minor axis amplitudes of approximately 45,000 km or less decay in size and period largely due to the Moon's solid tides. Larger DROs (62,000 km and up) are more influenced by the gravity of bodies external to the Earth-Moon system, and remain bound to the Moon for significantly less time.

Influence sample sizing of citrus hystrix essential oil from hydrodistillation extraction

NASA Astrophysics Data System (ADS)

Yahya, A.; Amadi, I.; Hashib, S. A.; Mustapha, F. A.

2018-03-01

Essential oil extracted from kaffir lime leaves through hydrodistillation. The objective of this study is to quantify the oil production rate by identify the significant influence of particle size on kaffir lime leaves. Kaffir lime leaves were ground and separated by using siever into 90, 150, 300 μm and other kaffir lime leaves. The mean essential oil yield of 0.87, 0.52, 0.41 and 0.3% was obtained. 90 μm of ground gives the highest yield compared to other sizes. Thus, it can be concluded that in quantifying oil production rate, the relevance of different size of particle is clearly affects the amount of oil yield. In analysing the composition of kaffir lime essential oil using GC-MS, there were 38 compounds found in the essential oil. Some of the major compounds of the kaffir lime leave oils were detected while some are not, may due to oil experience thermal degradation which consequently losing some significant compounds in controlled temperature.

Determination of lateral size distribution of type-II ZnTe/ZnSe stacked submonolayer quantum dots via spectral analysis of optical signature of the Aharanov-Bohm excitons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ji, Haojie; Dhomkar, Siddharth; Roy, Bidisha

2014-10-28

For submonolayer quantum dot (QD) based photonic devices, size and density of QDs are critical parameters, the probing of which requires indirect methods. We report the determination of lateral size distribution of type-II ZnTe/ZnSe stacked submonolayer QDs, based on spectral analysis of the optical signature of Aharanov-Bohm (AB) excitons, complemented by photoluminescence studies, secondary-ion mass spectroscopy, and numerical calculations. Numerical calculations are employed to determine the AB transition magnetic field as a function of the type-II QD radius. The study of four samples grown with different tellurium fluxes shows that the lateral size of QDs increases by just 50%, evenmore » though tellurium concentration increases 25-fold. Detailed spectral analysis of the emission of the AB exciton shows that the QD radii take on only certain values due to vertical correlation and the stacked nature of the QDs.« less

Optical, Magnetic and Photocatalytic Activity Studies of Li, Mg and Sr Doped and Undoped Zinc Oxide Nanoparticles.

PubMed

Shanthi, S I; Poovaragan, S; Arularasu, M V; Nithya, S; Sundaram, R; Magdalane, C Maria; Kaviyarasu, K; Maaza, M

2018-08-01

Nanoparticles of Li, Mg and Sr doped and undoped zinc oxide was prepared by simple precipitation method. The structural, optical, and magnetic properties of the samples were investigated by the Powder X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Fourier Transform Infrared (FTIR) spectroscopy, Ultra-violet Visible spectroscopy (UV-vis) spectra, Photoluminescence (PL) and Vibrational Sample Magnetometer (VSM). The Powder X-ray diffraction data confirm the formation of hexagonal wurtzite structure of all doped and undoped ZnO. The SEM photograph reveals that the pores availability and particles size in the range of 10 nm-50 nm. FTIR and UV-Visible spectra results confirm the incorporation of the dopant into the ZnO lattice nanostructure. The UV-Visible spectra indicate that the shift of blue region (lower wavelength) due to bandgap widening. Photoluminescence intensity varies with doping due to the increase of oxygen vacancies in prepared ZnO. The pure ZnO exist paramagnetic while doped (Li, Mg and Sr) ZnO exist ferromagnetic property. The photocatalytic activity of the prepared sample also carried out in detail.

Impact of hindcast length on estimates of seasonal climate predictability.

PubMed

Shi, W; Schaller, N; MacLeod, D; Palmer, T N; Weisheimer, A

2015-03-16

It has recently been argued that single-model seasonal forecast ensembles are overdispersive, implying that the real world is more predictable than indicated by estimates of so-called perfect model predictability, particularly over the North Atlantic. However, such estimates are based on relatively short forecast data sets comprising just 20 years of seasonal predictions. Here we study longer 40 year seasonal forecast data sets from multimodel seasonal forecast ensemble projects and show that sampling uncertainty due to the length of the hindcast periods is large. The skill of forecasting the North Atlantic Oscillation during winter varies within the 40 year data sets with high levels of skill found for some subperiods. It is demonstrated that while 20 year estimates of seasonal reliability can show evidence of overdispersive behavior, the 40 year estimates are more stable and show no evidence of overdispersion. Instead, the predominant feature on these longer time scales is underdispersion, particularly in the tropics. Predictions can appear overdispersive due to hindcast length sampling errorLonger hindcasts are more robust and underdispersive, especially in the tropicsTwenty hindcasts are an inadequate sample size to assess seasonal forecast skill.

TEM Analysis of Interfaces in Diffusion-Bonded Silicon Carbide Ceramics Joined Using Metallic Interlayers

NASA Technical Reports Server (NTRS)

Ozaki, T.; Tsuda, H.; Halbig, M. C.; Singh, M.; Hasegawa, Y.; Mori, S.; Asthana R.

2016-01-01

Silicon Carbide (SiC) is a promising material for thermo-structural applications due to its excellent high-temperature mechanical properties, oxidation resistance, and thermal stability. However, joining and integration technologies are indispensable for this material in order to fabricate large size and complex shape components with desired functionalities. Although diffusion bonding techniques using metallic interlayers have been commonly utilized to bond various SiC ceramics, detailed microstructural observation by Transmission Electron Microscopy (TEM) of the bonded area has not been carried out due to difficulty in preparing TEM samples. In this study, we tried to prepare TEM samples from joints of diffusion bonded SiC ceramics by Focused Ion Beam (FIB) system and carefully investigated the interfacial microstructure by TEM analysis. The samples used in this study were SiC fiber bonded ceramics (SA-Tyrannohex: SA-THX) diffusion bonded with metallic interlayers such as Ti, TiMo, and Mo-B. In this presentation, the result of microstructural analysis obtained by TEM observations and the influence of metallic interlayers and fiber orientation of SA-THX on the joint microstructure will be discussed.

TEM Analysis of Diffusion-Bonded Silicon Carbide Ceramics Joined Using Metallic Interlayers

NASA Technical Reports Server (NTRS)

Ozaki, T.; Tsuda, H.; Halbig, M. C.; Singh, M.; Hasegawa, Y; Mori, S.; Asthana, R.

2017-01-01

Silicon Carbide (SiC) is a promising material for thermostructural applications due to its excellent high-temperature mechanical properties, oxidation resistance, and thermal stability. However, joining and integration technologies are indispensable for this material in order to fabricate large size and complex shape components with desired functionalities. Although diffusion bonding techniques using metallic interlayers have been commonly utilized to bond various SiC ceramics, detailed microstructural observation by Transmission Electron Microscopy (TEM) of the bonded area has not been carried out due to difficulty in preparing TEM samples. In this study, we tried to prepare TEM samples from joints of diffusion bonded SiC ceramics by Focused Ion Beam (FIB) system and carefully investigated the interfacial microstructure by TEM analysis. The samples used in this study were SiC fiber bonded ceramics (SA-Tyrannohex: SA-THX) diffusion bonded with metallic interlayers such as Ti, TiMo, Mo-B and TiCu. In this presentation, we report the microstructure of diffusion bonded SA-THX mainly with TiCu interlayers obtained by TEM observations, and the influence of metallic interlayers on the joint microstructure and microhardness will be discussed.

Nonstoichiometry and phase stability of Al and Cr substituted Mg ferrite nanoparticles synthesized by citrate method

NASA Astrophysics Data System (ADS)

Ateia, Ebtesam. E.; Mohamed, Amira. T.

2017-03-01

The spinel ferrite Mg0.7Cr0.3Fe2O4, and Mg0.7Al0.3Fe2O4 were prepared by the citrate technique. All samples were characterized by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), High Resolution Transmission Electron Micrographs (HRTEM), Energy Dispersive X ray Spectroscopy (EDAX) and Atomic Force Microscope (AFM). XRD confirmed the formation of cubic spinel structure of the investigated samples. The average crystallite sizes were found to be between 24.7 and 27.5 nm for Al3+ and Mg2+ respectively. The substitution of Cr3+/Al3+ in place of Mg2+ ion initiates a crystalline anisotropy due to large size mismatch between Cr /Al and Mg2+, which creates strain inside the crystal volume. According to VSM results, by adding Al3+ or Cr3+ ions at the expense of Mg2+, the saturation magnetization increased. The narrow hysteresis loop of the samples indicates that the amount of dissipated energy is small, which is desirable for soft magnetic applications. Magnetic dynamics of the samples were studied by measuring magnetic susceptibility versus temperature at different magnetic fields. The band gap energy, which was calculated from near infrared (NIR) and visible (VIS) reflectance spectra using the Kubelka-Munk function, decreases with increasing the particle size. Furthermore, the band gaps were quite narrow (1.5-1.7 eV), hence the investigated samples could act as visible light driven photo catalysts. To sum up the addition of trivalent Al3+, and Cr3+ ions enhanced the optical, magnetic and structure properties of the samples. Mg0.7 Cr0.3Fe2O4 sample will be a better candidate for the optical applications and will also be a guaranteeing hopeful for technological applications.

Synthesis characterization and luminescence studies of gamma irradiated nanocrystalline yttrium oxide.

PubMed

Shivaramu, N J; Lakshminarasappa, B N; Nagabhushana, K R; Singh, Fouran

2016-02-05

Nanocrystalline Y2O3 is synthesized by solution combustion technique using urea and glycine as fuels. X-ray diffraction (XRD) pattern of as prepared sample shows amorphous nature while annealed samples show cubic nature. The average crystallite size is calculated using Scherrer's formula and is found to be in the range 14-30 nm for samples synthesized using urea and 15-20 nm for samples synthesized using glycine respectively. Field emission scanning electron microscopy (FE-SEM) image of 1173 K annealed Y2O3 samples show well separated spherical shape particles and the average particle size is found to be in the range 28-35 nm. Fourier transformed infrared (FTIR) and Raman spectroscopy reveals a stretching of Y-O bond. Electron spin resonance (ESR) shows V(-) center, O2(-) and Y(2+) defects. A broad photoluminescence (PL) emission with peak at ~386nm is observed when the sample is excited with 252 nm. Thermoluminescence (TL) properties of γ-irradiated Y2O3 nanopowder are studied at a heating rate of 5 K s(-1). The samples prepared by using urea show a prominent and well resolved peak at ~383 K and a weak one at ~570 K. It is also found that TL glow peak intensity (I(m1)) at ~383 K increases with increase in γ-dose up to ~6.0 kGy and then decreases with increase in dose. However, glycine used Y2O3 shows a prominent TL glow with peaks at 396 K and 590 K. Among the fuels, urea used Y2O3 shows simple and well resolved TL glows. This might be due to fuel and hence particle size effect. The kinetic parameters are calculated by Chen's glow curve peak shape method and results are discussed in detail. Copyright © 2015. Published by Elsevier B.V.

Cr3+ and Nb5+ co-doped Ti2Nb10O29 materials for high-performance lithium-ion storage

NASA Astrophysics Data System (ADS)

Yang, Chao; Yu, Shu; Ma, Yu; Lin, Chunfu; Xu, Zhihao; Zhao, Hua; Wu, Shunqing; Zheng, Peng; Zhu, Zi-Zhong; Li, Jianbao; Wang, Ning

2017-08-01

Ti2Nb10O29 is an advanced anode material for lithium-ion batteries due to its large specific capacity and high safety. However, its poor electronic/ionic conductivity significantly limits its rate capability. To tackle this issue, a Cr3+-Nb5+ co-doping is employed, and a series of CrxTi2-2xNb10+xO29 compounds are prepared. The co-doping does not change the Wadsley-Roth shear structure but increases the unit-cell volume and decreases the particle size. Due to the increased unit-cell volumes, the co-doped samples show increased Li+-ion diffusion coefficients. Experimental data and first-principle calculations reveal significantly increased electronic conductivities arising from the formation of impurity bands after the co-doping. The improvements of the electronic/ionic conductivities and the smaller particle sizes in the co-doped samples significantly contribute to improving their electrochemical properties. During the first cycle at 0.1 C, the optimized Cr0.6Ti0.8Nb10.6O29 sample delivers a large reversible capacity of 322 mAh g-1 with a large first-cycle Coulombic efficiency of 94.7%. At 10 C, it retains a large capacity of 206 mAh g-1, while that of Ti2Nb10O29 is only 80 mAh g-1. Furthermore, Cr0.6Ti0.8Nb10.6O29 shows high cyclic stability as demonstrated in over 500 cycles at 10 C with tiny capacity loss of only 0.01% per cycle.

Investigation of the effects of the macrophysical and microphysical properties of cirrus clouds on the retrieval of optical properties: Results for FIRE 2

NASA Technical Reports Server (NTRS)

Stackhouse, Paul W., Jr.; Stephens, Graeme L.

1993-01-01

Due to the prevalence and persistence of cirrus cloudiness across the globe, cirrus clouds are believed to have an important effect on the climate. Stephens et al., (1990) among others have shown that the important factor determining how cirrus clouds modulate the climate is the balance between the albedo and emittance effect of the cloud systems. This factor was shown to depend in part upon the effective sizes of the cirrus cloud particles. Since effective sizes of cirrus cloud microphysical distributions are used as a basis of parameterizations in climate models, it is crucial that the relationships between effective sizes and radiative properties be clearly established. In this preliminary study, the retrieval of cirrus cloud effective sizes are examined using a two dimensional radiative transfer model for a cirrus cloud case sampled during FIRE Cirrus 11. The purpose of this paper is to present preliminary results from the SHSG model demonstrating the sensitivity of the bispectral relationships of reflected radiances and thus the retrieval of effective sizes to phase function and dimensionality.

Sample Size and Statistical Conclusions from Tests of Fit to the Rasch Model According to the Rasch Unidimensional Measurement Model (Rumm) Program in Health Outcome Measurement.

PubMed

Hagell, Peter; Westergren, Albert

Sample size is a major factor in statistical null hypothesis testing, which is the basis for many approaches to testing Rasch model fit. Few sample size recommendations for testing fit to the Rasch model concern the Rasch Unidimensional Measurement Models (RUMM) software, which features chi-square and ANOVA/F-ratio based fit statistics, including Bonferroni and algebraic sample size adjustments. This paper explores the occurrence of Type I errors with RUMM fit statistics, and the effects of algebraic sample size adjustments. Data with simulated Rasch model fitting 25-item dichotomous scales and sample sizes ranging from N = 50 to N = 2500 were analysed with and without algebraically adjusted sample sizes. Results suggest the occurrence of Type I errors with N less then or equal to 500, and that Bonferroni correction as well as downward algebraic sample size adjustment are useful to avoid such errors, whereas upward adjustment of smaller samples falsely signal misfit. Our observations suggest that sample sizes around N = 250 to N = 500 may provide a good balance for the statistical interpretation of the RUMM fit statistics studied here with respect to Type I errors and under the assumption of Rasch model fit within the examined frame of reference (i.e., about 25 item parameters well targeted to the sample).

Towards well-defined gold nanomaterials via diafiltration and aptamer mediated synthesis

NASA Astrophysics Data System (ADS)

Sweeney, Scott Francis

Gold nanoparticles have garnered recent attention due to their intriguing size- and shape-dependent properties. Routine access to well-defined gold nanoparticle samples in terms of core diameter, shape, peripheral functionality and purity is required in order to carry out fundamental studies of their properties and to utilize these properties in future applications. For this reason, the development of methods for preparing well-defined gold nanoparticle samples remains an area of active research in materials science. In this dissertation, two methods, diafiltration and aptamer mediated synthesis, are explored as possible routes towards well-defined gold nanoparticle samples. It is shown that diafiltration has considerable potential for the efficient and convenient purification and size separation of water-soluble nanoparticles. The suitability of diafiltration for (i) the purification of water-soluble gold nanoparticles, (ii) the separation of a bimodal distribution of nanoparticles into fractions, (iii) the fractionation of a polydisperse sample and (iv) the isolation of [rimers from monomers and aggregates is studied. NMR, thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) measurements demonstrate that diafiltration produces highly pure nanoparticles. UV-visible spectroscopic and transmission electron microscopic analyses show that diafiltration offers the ability to separate nanoparticles of disparate core size, including linked nanoparticles. These results demonstrate the applicability of diafiltration for the rapid and green preparation of high-purity gold nanoparticle samples and the size separation of heterogeneous nanoparticle samples. In the second half of the dissertation, the identification of materials specific aptamers and their use to synthesize shaped gold nanoparticles is explored. The use of in vitro selection for identifying materials specific peptide and oligonucleotide aptamers is reviewed, outlining the specific requirements of in vitro selection for materials and the ways in which the field can be advanced. A promising new technique, in vitro selection on surfaces (ISOS), is developed and the discovery using ISOS of RNA aptamers that bind to evaporated gold is discussed. Analysis of the isolated gold binding RNA aptamers indicates that they are highly structured with single-stranded polyadenosine binding motifs. These aptamers, and similarly isolated peptide aptamers, are briefly explored for their ability to synthesize gold nanoparticles. This dissertation contains both previously published and unpublished co-authored material.

Temporal analysis of genetic structure to assess population dynamics of reintroduced swift foxes.

PubMed

Cullingham, Catherine I; Moehrenschlager, Axel

2013-12-01

Reintroductions are increasingly used to reestablish species, but a paucity of long-term postrelease monitoring has limited understanding of whether and when viable populations subsequently persist. We conducted temporal genetic analyses of reintroduced populations of swift foxes (Vulpes velox) in Canada (Alberta and Saskatchewan) and the United States (Montana). We used samples collected 4 years apart, 17 years from the initiation of the reintroduction, and 3 years after the conclusion of releases. To assess program success, we genotyped 304 hair samples, subsampled from the known range in 2000 and 2001, and 2005 and 2006, at 7 microsatellite loci. We compared diversity, effective population size, and genetic connectivity over time in each population. Diversity remained stable over time and there was evidence of increasing effective population size. We determined population structure in both periods after correcting for differences in sample sizes. The geographic distribution of these populations roughly corresponded with the original release locations, which suggests the release sites had residual effects on the population structure. However, given that both reintroduction sites had similar source populations, habitat fragmentation, due to cropland, may be associated with the population structure we found. Although our results indicate growing, stable populations, future connectivity analyses are warranted to ensure both populations are not subject to negative small-population effects. Our results demonstrate the importance of multiple sampling years to fully capture population dynamics of reintroduced populations. Análisis Temporal de la Estructura Genética para Evaluar la Dinámica Poblacional de Zorros (Vulpes velox) Reintroducidos. © 2013 Society for Conservation Biology.

Fabrication of superhydrophobic and antibacterial surface on cotton fabric by doped silica-based sols with nanoparticles of copper

PubMed Central

2011-01-01

The study discussed the synthesis of silica sol using the sol-gel method, doped with two different amounts of Cu nanoparticles. Cotton fabric samples were impregnated by the prepared sols and then dried and cured. To block hydroxyl groups, some samples were also treated with hexadecyltrimethoxysilane. The average particle size of colloidal silica nanoparticles were measured by the particle size analyzer. The morphology, roughness, and hydrophobic properties of the surface fabricated on cotton samples were analyzed and compared via the scanning electron microscopy, the transmission electron microscopy, the scanning probe microscopy, with static water contact angle (SWC), and water shedding angle measurements. Furthermore, the antibacterial efficiency of samples was quantitatively evaluated using AATCC 100 method. The addition of 0.5% (wt/wt) Cu into silica sol caused the silica nanoparticles to agglomerate in more grape-like clusters on cotton fabrics. Such fabricated surface revealed the highest value of SWC (155° for a 10-μl droplet) due to air trapping capability of its inclined structure. However, the presence of higher amounts of Cu nanoparticles (2% wt/wt) in silica sol resulted in the most slippery smooth surface on cotton fabrics. All fabricated surfaces containing Cu nanoparticles showed the perfect antibacterial activity against both of gram-negative and gram-positive bacteria. PMID:22085594

The Effect of Time, Roasting Temperature, and Grind Size on Caffeine and Chlorogenic Acid Concentrations in Cold Brew Coffee.

PubMed

Fuller, Megan; Rao, Niny Z

2017-12-21

The extraction kinetics and equilibrium concentrations of caffeine and 3-chlorogenic acid (3-CGA) in cold brew coffee were investigated by brewing four coffee samples (dark roast/medium grind, dark roast/coarse grind, medium roast/medium grind, medium roast/coarse grind) using cold and hot methods. 3-CGA and caffeine were found at higher concentrations in cold brew coffee made with medium roast coffees, rather than dark roast. The grind size did not impact 3-CGA and caffeine concentrations of cold brew samples significantly, indicating that the rate determining step in extraction for these compounds did not depend on surface area. Caffeine concentrations in cold brew coarse grind samples were substantially higher than their hot brew counterparts. 3-CGA concentrations and pH were comparable between cold and hot brews. This work suggests that the difference in acidity of cold brew coffee is likely not due to 3-CGA or caffeine concentrations considering that most acids in coffee are highly soluble and extract quickly. It was determined that caffeine and 3-CGA concentrations reached equilibrium according to first order kinetics between 6 and 7 hours in all cold brew samples instead of 10 to 24 hours outlined in typical cold brew methods.

[Potentials in the regionalization of health indicators using small-area estimation methods : Exemplary results based on the 2009, 2010 and 2012 GEDA studies].

PubMed

Kroll, Lars Eric; Schumann, Maria; Müters, Stephan; Lampert, Thomas

2017-12-01

Nationwide health surveys can be used to estimate regional differences in health. Using traditional estimation techniques, the spatial depth for these estimates is limited due to the constrained sample size. So far - without special refreshment samples - results have only been available for larger populated federal states of Germany. An alternative is regression-based small-area estimation techniques. These models can generate smaller-scale data, but are also subject to greater statistical uncertainties because of the model assumptions. In the present article, exemplary regionalized results based on the studies "Gesundheit in Deutschland aktuell" (GEDA studies) 2009, 2010 and 2012, are compared to the self-rated health status of the respondents. The aim of the article is to analyze the range of regional estimates in order to assess the usefulness of the techniques for health reporting more adequately. The results show that the estimated prevalence is relatively stable when using different samples. Important determinants of the variation of the estimates are the achieved sample size on the district level and the type of the district (cities vs. rural regions). Overall, the present study shows that small-area modeling of prevalence is associated with additional uncertainties compared to conventional estimates, which should be taken into account when interpreting the corresponding findings.

Microparticle sampling by electrowetting-actuated droplet sweeping.

PubMed

Zhao, Yuejun; Cho, Sung Kwon

2006-01-01

This paper describes a new microparticle sampler where particles can be efficiently swept from a solid surface and sampled into a liquid medium using moving droplets actuated by the electrowetting principle. We successfully demonstrate that super hydrophilic (2 microm and 7.9 microm diameter glass beads of about 14 degrees contact angle), intermediate hydrophilic (7.5 microm diameter polystyrene beads of about 70 degrees contact angle), and super hydrophobic (7.9 microm diameter Teflon-coated glass beads and 3 microm size PTFE particles of over 110 degrees contact angles) particles on a solid surface are picked up by electrowetting-actuated moving droplets. For the glass beads as well as the polystyrene beads, the sampling efficiencies are over 93%, in particular over 98% for the 7.9 microm glass beads. For the PTFE particles, however, the sampling efficiency is measured at around 70%, relatively lower than that of the glass and polystyrene beads. This is due mainly to the non-uniformity in particle size and the particle hydrophobicity. In this case, the collected particles staying (adsorbing) on the air-to-water interface hinder the droplet from advancing. This particle sampler requires an extremely small amount of liquid volume (about 500 nanoliters) and will thus be highly compatible and easily integrated with lab-on-a-chip systems for follow-up biological/chemical analyses.

The Influence of Hot-Rolled Temperature on Plasma Nitriding Behavior of Iron-Based Alloys

NASA Astrophysics Data System (ADS)

El-Hossary, F. M.; Khalil, S. M.; Lotfy, Kh.; Kassem, M. A.

2009-07-01

Experiments were performed with an aim of studying the effect of hot-rolled temperature (600 and 900°C) on radio frequency (rf) plasma nitriding of Fe93Ni4Zr3 alloy. Nitriding was carried out for 10 min in a nitrogen atmosphere at a base pressure of 10-2 mbarr. Different continuous plasma processing powers of 300-550 W in steps 50 W or less were applied. Nitrided hot-rolled specimens were characterized by optical microscopy (OM), X-ray diffraction (XRD) and microhardness measurements. The results reveal that the surface of hot-rolled rf plasma nitrided specimens at 600°C is characterized with a fine microstructure as a result of the high nitrogen solubility and diffusivity. Moreover, the hot-rolled treated samples at 600°C exhibit higher microhardness value than the associated values of hot-rolled treated samples at 900°C. The enhancement of microhardness is due to precipitation and predominance of new phases ( γ and ɛ phases). Mainly, this conclusion has been attributed to the high defect densities and small grain sizes of the samples hot-rolled at 600°C. Generally, the refinement of grain size plays a dramatic role in improvement of mechanical properties of tested samples.

On the analysis of very small samples of Gaussian repeated measurements: an alternative approach.

PubMed

Westgate, Philip M; Burchett, Woodrow W

2017-03-15

The analysis of very small samples of Gaussian repeated measurements can be challenging. First, due to a very small number of independent subjects contributing outcomes over time, statistical power can be quite small. Second, nuisance covariance parameters must be appropriately accounted for in the analysis in order to maintain the nominal test size. However, available statistical strategies that ensure valid statistical inference may lack power, whereas more powerful methods may have the potential for inflated test sizes. Therefore, we explore an alternative approach to the analysis of very small samples of Gaussian repeated measurements, with the goal of maintaining valid inference while also improving statistical power relative to other valid methods. This approach uses generalized estimating equations with a bias-corrected empirical covariance matrix that accounts for all small-sample aspects of nuisance correlation parameter estimation in order to maintain valid inference. Furthermore, the approach utilizes correlation selection strategies with the goal of choosing the working structure that will result in the greatest power. In our study, we show that when accurate modeling of the nuisance correlation structure impacts the efficiency of regression parameter estimation, this method can improve power relative to existing methods that yield valid inference. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Infrared thermal wave nondestructive technology on the defect in the shell of solid rocket motor

NASA Astrophysics Data System (ADS)

Zhang, Wei; Song, Yuanjia; Yang, Zhengwei; Li, Ming; Tian, Gan

2010-10-01

Based on the active infrared thermography nondestructive testing (NDT) technology, which is an emerging method and developed in the areas of aviation, spaceflight and national defence, the samples including glass fiber flat bottom hole sample, glass fiber inclusion sample and steel flat bottom hole sample that the shell materials of Solid Rocket Motor (SRM) were heated by a high energy flash lamp. The subsurface flaws can be detected through measuring temperature difference between flaws and materials. The results of the experiments show that: 1) the technique is a fast and effective inspection method, which is used for detecting the composites more easily than the metals. And it also can primarily identify the defect position and size according to the thermal image maps. 2) A best inspection time at when the area of hot spot is the same with that of defect is exited, which can be used to estimate the defect size. The bigger the defect area, the easier it could be detected and also the less of the error for estimating defect area. 3). The infrared thermal images obtained from experiments always have high noise, especially for metal materials due to high reflectivity and environmental factors, which need to be further processed.

Effect of electromagnetic interaction during fusion welding of AISI 2205 duplex stainless steel on the corrosion resistance

NASA Astrophysics Data System (ADS)

García-Rentería, M. A.; López-Morelos, V. H.; González-Sánchez, J.; García-Hernández, R.; Dzib-Pérez, L.; Curiel-López, F. F.

2017-02-01

The effect of electromagnetic interaction of low intensity (EMILI) applied during fusion welding of AISI 2205 duplex stainless steel on the resistance to localised corrosion in natural seawater was investigated. The heat affected zone (HAZ) of samples welded under EMILI showed a higher temperature for pitting initiation and lower dissolution under anodic polarisation in chloride containing solutions than samples welded without EMILI. The EMILI assisted welding process developed in the present work enhanced the resistance to localised corrosion due to a modification on the microstructural evolution in the HAZ and the fusion zone during the thermal cycle involved in fusion welding. The application of EMILI reduced the size of the HAZ, limited coarsening of the ferrite grains and promoted regeneration of austenite in this zone, inducing a homogeneous passive condition of the surface. EMILI can be applied during fusion welding of structural or functional components of diverse size manufactured with duplex stainless steel designed to withstand aggressive environments such as natural seawater or marine atmospheres.

Quantification of nanoparticle concentration in colloidal suspensions by a non-destructive optical method

NASA Astrophysics Data System (ADS)

Clement, Sandhya; Gardner, Brint; Razali, Wan Aizuddin W.; Coleman, Victoria A.; Jämting, Åsa K.; Catchpoole, Heather J.; Goldys, Ewa M.; Herrmann, Jan; Zvyagin, Andrei

2017-11-01

The estimation of nanoparticle number concentration in colloidal suspensions is a prerequisite in many procedures, and in particular in multi-stage, low-yield reactions. Here, we describe a rapid, non-destructive method based on optical extinction and dynamic light scattering (DLS), which combines measurements using common bench-top instrumentation with a numerical algorithm to calculate the particle size distribution (PSD) and concentration. These quantities were derived from Mie theory applied to measurements of the optical extinction spectrum of homogeneous, non-absorbing nanoparticles, and the relative PSD of a colloidal suspension. The work presents an approach to account for PSDs achieved by DLS which, due to the underlying model, may not be representative of the true sample PSD. The presented approach estimates the absolute particle number concentration of samples with mono-, bi-modal and broad size distributions with <50% precision. This provides a convenient and practical solution for number concentration estimation required during many applications of colloidal nanomaterials.

Preliminary investigation of bottlenose dolphins (Tursiops truncatus) for hfe gene-related hemochromatosis.

PubMed

Phillips, Brianne E; Venn-Watson, Stephanie; Archer, Linda L; Nollens, Hendrik H; Wellehan, James F X

2014-10-01

Hemochromatosis (iron storage disease) has been reported in diverse mammals including bottlenose dolphins (Tursiops truncatus). The primary cause of excessive iron storage in humans is hereditary hemochromatosis. Most human hereditary hemochromatosis cases (up to 90%) are caused by a point mutation in the hfe gene, resulting in a C282Y substitution leading to iron accumulation. To evaluate the possibility of a hereditary hemochromatosis-like genetic predisposition in dolphins, we sequenced the bottlenose dolphin hfe gene, using reverse transcriptase-PCR and hfe primers designed from the dolphin genome, from liver of affected and healthy control dolphins. Sample size included two case animals and five control animals. Although isotype diversity was evident, no coding differences were identified in the hfe gene between any of the animals examined. Because our sample size was small, we cannot exclude the possibility that hemochromatosis in dolphins is due to a coding mutation in the hfe gene. Other potential causes of hemochromatosis, including mutations in different genes, diet, primary liver disease, and insulin resistance, should be evaluated.

Driver gene classification reveals a substantial overrepresentation of tumor suppressors among very large chromatin-regulating proteins.

PubMed

Waks, Zeev; Weissbrod, Omer; Carmeli, Boaz; Norel, Raquel; Utro, Filippo; Goldschmidt, Yaara

2016-12-23

Compiling a comprehensive list of cancer driver genes is imperative for oncology diagnostics and drug development. While driver genes are typically discovered by analysis of tumor genomes, infrequently mutated driver genes often evade detection due to limited sample sizes. Here, we address sample size limitations by integrating tumor genomics data with a wide spectrum of gene-specific properties to search for rare drivers, functionally classify them, and detect features characteristic of driver genes. We show that our approach, CAnceR geNe similarity-based Annotator and Finder (CARNAF), enables detection of potentially novel drivers that eluded over a dozen pan-cancer/multi-tumor type studies. In particular, feature analysis reveals a highly concentrated pool of known and putative tumor suppressors among the <1% of genes that encode very large, chromatin-regulating proteins. Thus, our study highlights the need for deeper characterization of very large, epigenetic regulators in the context of cancer causality.

An Integrated Study on the Evolution of Inclusions in EH36 Shipbuilding Steel with Mg Addition: From Casting to Welding

NASA Astrophysics Data System (ADS)

Zou, Xiaodong; Zhao, Dapeng; Sun, Jincheng; Wang, Cong; Matsuura, Hiroyuki

2018-04-01

Inclusion evolution behaviors, in terms of composition, size, and number density, and associated influence on the microstructures of the as-cast slabs, rolled plates, and simulated welded samples of plain EH36 and EH36-Mg shipbuilding steels have been systematically investigated. The results indicate that the inclusions in the as-cast plain EH36 are almost Al-Ca-S-O-(Mn) complex oxides with sizes ranging from 1.0 to 2.0 μm. After Mg addition, a large amount of individually fine MnS precipitates and Mg-containing Ti-Al-Mg-O-(Mn-S) complex inclusions are generated, which significantly refine the microstructure and are conducive to the nucleation of acicular ferrite in the rolled and welded sample. Moreover, after rolling and welding thermal simulation, the number of individual MnS decreases gradually due to its precipitation on the surface of Ti-Al-Mg-O oxides.

First-Principles Determination of Ultralow Thermal Conductivity of monolayer WSe2

NASA Astrophysics Data System (ADS)

Zhou, Wu-Xing; Chen, Ke-Qiu

2015-10-01

By using first-principles calculations combined with the phonon Boltzmann transport equation, we systematically investigate the phonon transport of monolayer WSe2. Compared with other 2D materials, the monolayer WSe2 is found to have an ultralow thermal conductivity due to the ultralow Debye frequency and heavy atom mass. The room temperature thermal conductivity for a typical sample size of 1 μm is 3.935  W/m K, which is one order of magnitude lower than that of MoS2. And the room temperature thermal conductivity can be further decreased by about 95% in 10 nm sized samples. Moreover, we also find the ZA phonons have the dominant contribution to the thermal conductivity, and the relative contribution is almost 80% at room temperature, which is remarkably higher than that for monolayer MoS2. This is because the ZA phonons have longer lifetime than that of LA and TA phonons in monolayer WSe2.

Spatial distribution of heavy metals in surficial sediments from Guanabara Bay: Rio de Janeiro, Brazil

NASA Astrophysics Data System (ADS)

Neto, José Antônio Baptista; Gingele, Franz Xaver; Leipe, Thomas; Brehme, Isa

2006-04-01

Ninety-two surface sediment samples were collected in Guanabara Bay, one of the most prominent urban bays in SE Brazil, to investigate the spatial distribution of anthropogenic pollutants. The concentrations of heavy metals, organic carbon and particle size were examined in all samples. Large spatial variations of heavy metals and particle size were observed. The highest concentrations of heavy metals were found in the muddy sediments from the north western region of the bay near the main outlets of the most polluted rivers, municipal waste drainage systems and one of the major oil refineries. Another anomalous concentration of metals was found adjacent to Rio de Janeiro Harbour. The heavy metal concentrations decrease to the northeast, due to intact rivers and the mangrove systems in this area, and to the south where the sand fraction and open-marine processes dominate. The geochemical normalization of metal data to Li or Al has also demonstrated that the anthropogenic input of heavy metals have altered the natural sediment heavy metal distribution.

Evaluating manta ray mucus as an alternative DNA source for population genetics study: underwater-sampling, dry-storage and PCR success.

PubMed

Kashiwagi, Tom; Maxwell, Elisabeth A; Marshall, Andrea D; Christensen, Ana B

2015-01-01

Sharks and rays are increasingly being identified as high-risk species for extinction, prompting urgent assessments of their local or regional populations. Advanced genetic analyses can contribute relevant information on effective population size and connectivity among populations although acquiring sufficient regional sample sizes can be challenging. DNA is typically amplified from tissue samples which are collected by hand spears with modified biopsy punch tips. This technique is not always popular due mainly to a perception that invasive sampling might harm the rays, change their behaviour, or have a negative impact on tourism. To explore alternative methods, we evaluated the yields and PCR success of DNA template prepared from the manta ray mucus collected underwater and captured and stored on a Whatman FTA™ Elute card. The pilot study demonstrated that mucus can be effectively collected underwater using toothbrush. DNA stored on cards was found to be reliable for PCR-based population genetics studies. We successfully amplified mtDNA ND5, nuclear DNA RAG1, and microsatellite loci for all samples and confirmed sequences and genotypes being those of target species. As the yields of DNA with the tested method were low, further improvements are desirable for assays that may require larger amounts of DNA, such as population genomic studies using emerging next-gen sequencing.

Evaluating manta ray mucus as an alternative DNA source for population genetics study: underwater-sampling, dry-storage and PCR success

PubMed Central

Maxwell, Elisabeth A.; Marshall, Andrea D.; Christensen, Ana B.

2015-01-01

Sharks and rays are increasingly being identified as high-risk species for extinction, prompting urgent assessments of their local or regional populations. Advanced genetic analyses can contribute relevant information on effective population size and connectivity among populations although acquiring sufficient regional sample sizes can be challenging. DNA is typically amplified from tissue samples which are collected by hand spears with modified biopsy punch tips. This technique is not always popular due mainly to a perception that invasive sampling might harm the rays, change their behaviour, or have a negative impact on tourism. To explore alternative methods, we evaluated the yields and PCR success of DNA template prepared from the manta ray mucus collected underwater and captured and stored on a Whatman FTA™ Elute card. The pilot study demonstrated that mucus can be effectively collected underwater using toothbrush. DNA stored on cards was found to be reliable for PCR-based population genetics studies. We successfully amplified mtDNA ND5, nuclear DNA RAG1, and microsatellite loci for all samples and confirmed sequences and genotypes being those of target species. As the yields of DNA with the tested method were low, further improvements are desirable for assays that may require larger amounts of DNA, such as population genomic studies using emerging next-gen sequencing. PMID:26413431

Characterization of bottom sediments in the Río de la Plata estuary

NASA Astrophysics Data System (ADS)

Simionato, Claudia G.; Moreira, Diego

2016-04-01

Bottom sediments and surface water samples were collected in the intermediate and outer Río de la Plata Estuary during 2009-2010, in six repeated cruises, with 26 stations each. Samples were processed for grain size using a laser particle size analyzer, and water and organic matter contents. The aim of this work is to analyze this data set to provide a comprehensive and objective characterization of the bottom sediments distribution, to study their composition and to progress in the construction of a conceptual model of the involved physical mechanisms. Principal Components Analysis is applied to the bottom sediments size histograms to investigate the spatial patterns. Variations in grain-size parameters contain information on possible sediment transport patterns, which were analyzed by means of trend vectors. Sediments show a gradational arrangement of textures, sand dominant at the head, silt in the intermediate estuary and clayey silt and clay at its mouth; textures become progressively more poorly sorted offshore, and the water and organic matter contents increase. And seem to be strongly related to the geometry and the hydrodynamics. Along the Northern coast of the intermediate estuary, well sorted medium and fine silt predominates, whereas in the Southern coast, coarser and less sorted silt prevails, due to differences in tidal currents and/or in water pathways. Around Barra del Indio, clay prevails over silt and sand, and the water and organic matter contents reach a maximum, probably due flocculation, and the reduction of the currents. Immediately seawards the salt wedge, net transport reverses its direction and well sorted coarser sand from the adjacent shelf dominates. Relict sediment is observed around the Santa Lucía River, consisting of poorly sorted fine silt and clay. The inferred net transport suggests convergence at the Barra del Indio shoal, which is consistent with the constant growing of the banks.

Trends of Modern Contraceptive Use among Young Married Women Based on the 2000, 2005, and 2011 Ethiopian Demographic and Health Surveys: A Multivariate Decomposition Analysis

PubMed Central

Worku, Abebaw Gebeyehu; Tessema, Gizachew Assefa; Zeleke, Atinkut Alamirrew

2015-01-01

Introduction Accessing family planning can reduce a significant proportion of maternal, infant, and childhood deaths. In Ethiopia, use of modern contraceptive methods is low but it is increasing. This study aimed to analyze the trends and determinants of changes in modern contraceptive use over time among young married women in Ethiopia. Methods The study used data from the three Demographic Health Surveys conducted in Ethiopia, in 2000, 2005, and 2011. Young married women age 15–24 years with sample sizes of 2,157 in 2000, 1,904 in 2005, and 2,146 in 2011 were included. Logit-based decomposition analysis technique was used for analysis of factors contributing to the recent changes. STATA 12 was employed for data management and analyses. All calculations presented in this paper were weighted for the sampling probabilities and non-response. Complex sampling procedures were also considered during testing of statistical significance. Results Among young married women, modern contraceptive prevalence increased from 6% in 2000 to 16% in 2005 and to 36% in 2011. The decomposition analysis indicated that 34% of the overall change in modern contraceptive use was due to difference in women’s characteristics. Changes in the composition of young women’s characteristics according to age, educational status, religion, couple concordance on family size, and fertility preference were the major sources of this increase. Two-thirds of the increase in modern contraceptive use was due to difference in coefficients. Most importantly, the increase was due to change in contraceptive use behavior among the rural population (33%) and among Orthodox Christians (16%) and Protestants (4%). Conclusions Modern contraceptive use among young married women has showed a remarkable increase over the last decade in Ethiopia. Programmatic interventions targeting poor, younger (adolescent), illiterate, and Muslim women would help to maintain the increasing trend in modern contraceptive use. PMID:25635389

EX VIVO MODEL FOR THE CHARACTERIZATION AND IDENTIFICATION OF DRYWALL INTRAOCULAR FOREIGN BODIES ON COMPUTED TOMOGRAPHY.

PubMed

Syed, Reema; Kim, Sung-Hye; Palacio, Agustina; Nunery, William R; Schaal, Shlomit

2017-06-06

The study was inspired after the authors encountered a patient with a penetrating globe injury due to drywall, who had retained intraocular drywall foreign body. Computed tomography (CT) was read as normal in this patient. Open globe injury with drywall has never been reported previously in the literature and there are no previous studies describing its radiographic features. The case report is described in detail elsewhere. This was an experimental study. An ex vivo model of 15 porcine eyes with 1 mm to 5 mm fragments of implanted drywall, 2 vitreous only samples with drywall and 3 control eyes were used. Eyes and vitreous samples were CT scanned on Days 0, 1, and 3 postimplantation. Computed ocular images were analyzed by masked observers. Size and radiodensity of intraocular drywall were measured using Hounsfield units (HUs) over time. Intraocular drywall was hyperdense on CT. All sizes studied were detectable on Day 0 of scanning. Mean intraocular drywall foreign body density was 171 ± 52 Hounsfield units (70-237) depending on fragment size. Intraocular drywall foreign body decreased in size whereas Hounsfield unit intensity increased over time. Drywall dissolves in the eye and becomes denser over time as air in the drywall is replaced by fluid. This study identified Hounsfield Units specific to intraocular drywall foreign body over time.

Sample size determination for estimating antibody seroconversion rate under stable malaria transmission intensity.

PubMed

Sepúlveda, Nuno; Drakeley, Chris

2015-04-03

In the last decade, several epidemiological studies have demonstrated the potential of using seroprevalence (SP) and seroconversion rate (SCR) as informative indicators of malaria burden in low transmission settings or in populations on the cusp of elimination. However, most of studies are designed to control ensuing statistical inference over parasite rates and not on these alternative malaria burden measures. SP is in essence a proportion and, thus, many methods exist for the respective sample size determination. In contrast, designing a study where SCR is the primary endpoint, is not an easy task because precision and statistical power are affected by the age distribution of a given population. Two sample size calculators for SCR estimation are proposed. The first one consists of transforming the confidence interval for SP into the corresponding one for SCR given a known seroreversion rate (SRR). The second calculator extends the previous one to the most common situation where SRR is unknown. In this situation, data simulation was used together with linear regression in order to study the expected relationship between sample size and precision. The performance of the first sample size calculator was studied in terms of the coverage of the confidence intervals for SCR. The results pointed out to eventual problems of under or over coverage for sample sizes ≤250 in very low and high malaria transmission settings (SCR ≤ 0.0036 and SCR ≥ 0.29, respectively). The correct coverage was obtained for the remaining transmission intensities with sample sizes ≥ 50. Sample size determination was then carried out for cross-sectional surveys using realistic SCRs from past sero-epidemiological studies and typical age distributions from African and non-African populations. For SCR < 0.058, African studies require a larger sample size than their non-African counterparts in order to obtain the same precision. The opposite happens for the remaining transmission intensities. With respect to the second sample size calculator, simulation unravelled the likelihood of not having enough information to estimate SRR in low transmission settings (SCR ≤ 0.0108). In that case, the respective estimates tend to underestimate the true SCR. This problem is minimized by sample sizes of no less than 500 individuals. The sample sizes determined by this second method highlighted the prior expectation that, when SRR is not known, sample sizes are increased in relation to the situation of a known SRR. In contrast to the first sample size calculation, African studies would now require lesser individuals than their counterparts conducted elsewhere, irrespective of the transmission intensity. Although the proposed sample size calculators can be instrumental to design future cross-sectional surveys, the choice of a particular sample size must be seen as a much broader exercise that involves weighting statistical precision with ethical issues, available human and economic resources, and possible time constraints. Moreover, if the sample size determination is carried out on varying transmission intensities, as done here, the respective sample sizes can also be used in studies comparing sites with different malaria transmission intensities. In conclusion, the proposed sample size calculators are a step towards the design of better sero-epidemiological studies. Their basic ideas show promise to be applied to the planning of alternative sampling schemes that may target or oversample specific age groups.

Using known populations of pronghorn to evaluate sampling plans and estimators

USGS Publications Warehouse

Kraft, K.M.; Johnson, D.H.; Samuelson, J.M.; Allen, S.H.

1995-01-01

Although sampling plans and estimators of abundance have good theoretical properties, their performance in real situations is rarely assessed because true population sizes are unknown. We evaluated widely used sampling plans and estimators of population size on 3 known clustered distributions of pronghorn (Antilocapra americana). Our criteria were accuracy of the estimate, coverage of 95% confidence intervals, and cost. Sampling plans were combinations of sampling intensities (16, 33, and 50%), sample selection (simple random sampling without replacement, systematic sampling, and probability proportional to size sampling with replacement), and stratification. We paired sampling plans with suitable estimators (simple, ratio, and probability proportional to size). We used area of the sampling unit as the auxiliary variable for the ratio and probability proportional to size estimators. All estimators were nearly unbiased, but precision was generally low (overall mean coefficient of variation [CV] = 29). Coverage of 95% confidence intervals was only 89% because of the highly skewed distribution of the pronghorn counts and small sample sizes, especially with stratification. Stratification combined with accurate estimates of optimal stratum sample sizes increased precision, reducing the mean CV from 33 without stratification to 25 with stratification; costs increased 23%. Precise results (mean CV = 13) but poor confidence interval coverage (83%) were obtained with simple and ratio estimators when the allocation scheme included all sampling units in the stratum containing most pronghorn. Although areas of the sampling units varied, ratio estimators and probability proportional to size sampling did not increase precision, possibly because of the clumped distribution of pronghorn. Managers should be cautious in using sampling plans and estimators to estimate abundance of aggregated populations.

Design of an occulter testbed at flight Fresnel numbers

NASA Astrophysics Data System (ADS)

Sirbu, Dan; Kasdin, N. Jeremy; Kim, Yunjong; Vanderbei, Robert J.

2015-01-01

An external occulter is a spacecraft flown along the line-of-sight of a space telescope to suppress starlight and enable high-contrast direct imaging of exoplanets. Laboratory verification of occulter designs is necessary to validate the optical models used to design and predict occulter performance. At Princeton, we are designing and building a testbed that allows verification of scaled occulter designs whose suppressed shadow is mathematically identical to that of space occulters. Here, we present a sample design operating at a flight Fresnel number and is thus representative of a realistic space mission. We present calculations of experimental limits arising from the finite size and propagation distance available in the testbed, limitations due to manufacturing feature size, and non-ideal input beam. We demonstrate how the testbed is designed to be feature-size limited, and provide an estimation of the expected performance.

Dependence of Van-Vleck paramagnetism on the size of nanocrystals in superstoichiometric TiO{sub y}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Valeeva, A. A., E-mail: valeeva@ihim.uran.ru; Nazarova, S. Z.; Rempel, A. A.

2016-04-15

In situ measurements of the magnetic susceptibility of titanium monoxide nanocrystals with superstoichiometric composition TiO{sub y} (y > 1) in the 300–1200 K temperature range showed that this value depends not only on the structural state of a sample, but also on the size of crystals. Analysis of data obtained for both ordered and disordered TiO{sub y} showed that the Van-Vleck paramagnetism is inversely proportional to the nanocrystal size because of breakage of the symmetry of local environment of the near-surface atoms of titanium and oxygen. The Van-Vleck paramagnetism contribution due to atomic-vacancy disorder in superstoichiometric titanium monoxide nanocrystals, asmore » well as in the stoichiometric composition, is proportional to a deviation of the degree of long-range order from its maximum value.« less

Airframe integrity based on Bayesian approach

NASA Astrophysics Data System (ADS)

Hurtado Cahuao, Jose Luis

Aircraft aging has become an immense challenge in terms of ensuring the safety of the fleet while controlling life cycle costs. One of the major concerns in aircraft structures is the development of fatigue cracks in the fastener holes. A probabilistic-based method has been proposed to manage this problem. In this research, the Bayes' theorem is used to assess airframe integrity by updating generic data with airframe inspection data while such data are compiled. This research discusses the methodology developed for assessment of loss of airframe integrity due to fatigue cracking in the fastener holes of an aging platform. The methodology requires a probability density function (pdf) at the end of SAFE life. Subsequently, a crack growth regime begins. As the Bayesian analysis requires information of a prior initial crack size pdf, such a pdf is assumed and verified to be lognormally distributed. The prior distribution of crack size as cracks grow is modeled through a combined Inverse Power Law (IPL) model and lognormal relationships. The first set of inspections is used as the evidence for updating the crack size distribution at the various stages of aircraft life. Moreover, the materials used in the structural part of the aircrafts have variations in their properties due to their calibration errors and machine alignment. A Matlab routine (PCGROW) is developed to calculate the crack distribution growth through three different crack growth models. As the first step, the material properties and the initial crack size are sampled. A standard Monte Carlo simulation is employed for this sampling process. At the corresponding aircraft age, the crack observed during the inspections, is used to update the crack size distribution and proceed in time. After the updating, it is possible to estimate the probability of structural failure as a function of flight hours for a given aircraft in the future. The results show very accurate and useful values related to the reliability and integrity of airframes in aging aircrafts. Inspection data shown in this dissertation are not the actual data from known aircrafts and are only used to demonstrate the methodologies.

Observation of the sweating in lipstick by scanning electron microscopy.

PubMed

Seo, S Y; Lee, I S; Shin, H Y; Choi, K Y; Kang, S H; Ahn, H J

1999-06-01

The relationship between the wax matrix in lipstick and sweating has been investigated by observing the change of size and shape of the wax matrix due to sweating by Scanning Electron Microscopy (SEM). For observation by SEM, a lipstick sample was frozen in liquid nitrogen. The oil in the lipstick was then extracted in cold isopropanol (-70 degrees C) for 1-3 days. After the isopropanol was evaporated, the sample was sputtered with gold and examined by SEM. The change of wax matrix underneath the surface from fine, uniform structure to coarse, nonuniform structure resulted from the caking of surrounding wax matrix. The oil underneath the surface migrated to the surface of lipstick with sweating; consequently the wax matrix in that region was rearranged into the coarse matrix. In case of flamed lipstick, sweating was delayed and the wax matrix was much coarser than that of the unflamed one. The larger wax matrix at the surface region was good for including oil. The effect of molding temperature on sweating was also studied. As the molding temperature rose, sweating was greatly reduced and the size of the wax matrix increased. It was found that sweating was influenced by the compatibility of wax and oil. A formula consisting of wax and oil that have good compatibility has a tendency to reduce sweating and increase the size of the wax matrix. When pigments were added to wax and oil, the size of the wax matrix was changed, but in all cases sweating was increased due to the weakening of the binding force between wax and oil. On observing the thick membrane of wax at the surface of lipstick a month after molding it was also found that sweating was influenced by ageing. In conclusion, the structure of the wax matrix at the surface region of lipstick was changed with the process of flaming, molding temperature, compatibility of wax and oil, addition of pigment, and ageing. In most cases, as the size of the wax matrix was increased, sweating was reduced and delayed.

Sample Size Calculations for Population Size Estimation Studies Using Multiplier Methods With Respondent-Driven Sampling Surveys.

PubMed

Fearon, Elizabeth; Chabata, Sungai T; Thompson, Jennifer A; Cowan, Frances M; Hargreaves, James R

2017-09-14

While guidance exists for obtaining population size estimates using multiplier methods with respondent-driven sampling surveys, we lack specific guidance for making sample size decisions. To guide the design of multiplier method population size estimation studies using respondent-driven sampling surveys to reduce the random error around the estimate obtained. The population size estimate is obtained by dividing the number of individuals receiving a service or the number of unique objects distributed (M) by the proportion of individuals in a representative survey who report receipt of the service or object (P). We have developed an approach to sample size calculation, interpreting methods to estimate the variance around estimates obtained using multiplier methods in conjunction with research into design effects and respondent-driven sampling. We describe an application to estimate the number of female sex workers in Harare, Zimbabwe. There is high variance in estimates. Random error around the size estimate reflects uncertainty from M and P, particularly when the estimate of P in the respondent-driven sampling survey is low. As expected, sample size requirements are higher when the design effect of the survey is assumed to be greater. We suggest a method for investigating the effects of sample size on the precision of a population size estimate obtained using multipler methods and respondent-driven sampling. Uncertainty in the size estimate is high, particularly when P is small, so balancing against other potential sources of bias, we advise researchers to consider longer service attendance reference periods and to distribute more unique objects, which is likely to result in a higher estimate of P in the respondent-driven sampling survey. ©Elizabeth Fearon, Sungai T Chabata, Jennifer A Thompson, Frances M Cowan, James R Hargreaves. Originally published in JMIR Public Health and Surveillance (http://publichealth.jmir.org), 14.09.2017.

Size distribution of rare earth elements in coal ash

USGS Publications Warehouse

Scott, Clinton T.; Deonarine, Amrika; Kolker, Allan; Adams, Monique; Holland, James F.

2015-01-01

Rare earth elements (REEs) are utilized in various applications that are vital to the automotive, petrochemical, medical, and information technology industries. As world demand for REEs increases, critical shortages are expected. Due to the retention of REEs during coal combustion, coal fly ash is increasingly considered a potential resource. Previous studies have demonstrated that coal fly ash is variably enriched in REEs relative to feed coal (e.g, Seredin and Dai, 2012) and that enrichment increases with decreasing size fractions (Blissett et al., 2014). In order to further explore the REE resource potential of coal ash, and determine the partitioning behavior of REE as a function of grain size, we studied whole coal and fly ash size-fractions collected from three U.S commercial-scale coal-fired generating stations burning Appalachian or Powder River Basin coal. Whole fly ash was separated into , 5 um, to 5 to 10 um and 10 to 100 um particle size fractions by mechanical shaking using trace-metal clean procedures. In these samples REE enrichments in whole fly ash ranges 5.6 to 18.5 times that of feedcoals. Partitioning results for size separates relative to whole coal and whole fly ash will also be reported. 

Study the fragment size distribution in dynamic fragmentation of laser shock loding tin

NASA Astrophysics Data System (ADS)

He, Weihua; Xin, Jianting; Chu, Genbai; Shui, Min; Xi, Tao; Zhao, Yongqiang; Gu, Yuqiu

2017-06-01

Characterizing the distribution of fragment size produced from dynamic fragmentation process is very important for fundamental science like predicting material dymanic response performance and for a variety of engineering applications. However, only a few data about fragment mass or size have been obtained due to its great challenge in its dynamic measurement. This paper would focus on investigating the fragment size distribution from the dynamic fragmentation of laser shock-loaded metal. Material ejection of tin sample with wedge shape groove in the free surface is collected with soft recovery technique. Via fine post-shot analysis techniques including X-ray micro-tomography and the improved watershed method, it is found that fragments can be well detected. To characterize their size distributions, a random geometric statistics method based on Poisson mixtures was derived for dynamic heterogeneous fragmentation problem, which leads to a linear combinational exponential distribution. Finally we examined the size distribution of laser shock-loaded tin with the derived model, and provided comparisons with other state-of-art models. The resulting comparisons prove that our proposed model can provide more reasonable fitting result for laser shock-loaded metal.

Size Matters: Cerebral Volume Influences Sex Differences in Neuroanatomy

PubMed Central

Towler, Stephen; Welcome, Suzanne; Halderman, Laura K.; Otto, Ron; Eckert, Mark A.; Chiarello, Christine

2008-01-01

Biological and behavioral differences between the sexes range from obvious to subtle or nonexistent. Neuroanatomical differences are particularly controversial, perhaps due to the implication that they might account for behavioral differences. In this sample of 200 men and women, large effect sizes (Cohen's d > 0.8) were found for sex differences in total cerebral gray and white matter, cerebellum, and gray matter proportion (women had a higher proportion of gray matter). The only one of these sex differences that survived adjustment for the effect of cerebral volume was gray matter proportion. Individual differences in cerebral volume accounted for 21% of the difference in gray matter proportion, while sex accounted for an additional 4%. The relative size of the corpus callosum was 5% larger in women, but this difference was completely explained by a negative relationship between relative callosal size and cerebral volume. In agreement with Jancke et al., individuals with higher cerebral volume tended to have smaller corpora callosa. There were few sex differences in the size of structures in Broca's and Wernicke's area. We conclude that individual differences in brain volume, in both men and women, account for apparent sex differences in relative size. PMID:18440950

Relative efficiency and sample size for cluster randomized trials with variable cluster sizes.

PubMed

You, Zhiying; Williams, O Dale; Aban, Inmaculada; Kabagambe, Edmond Kato; Tiwari, Hemant K; Cutter, Gary

2011-02-01

The statistical power of cluster randomized trials depends on two sample size components, the number of clusters per group and the numbers of individuals within clusters (cluster size). Variable cluster sizes are common and this variation alone may have significant impact on study power. Previous approaches have taken this into account by either adjusting total sample size using a designated design effect or adjusting the number of clusters according to an assessment of the relative efficiency of unequal versus equal cluster sizes. This article defines a relative efficiency of unequal versus equal cluster sizes using noncentrality parameters, investigates properties of this measure, and proposes an approach for adjusting the required sample size accordingly. We focus on comparing two groups with normally distributed outcomes using t-test, and use the noncentrality parameter to define the relative efficiency of unequal versus equal cluster sizes and show that statistical power depends only on this parameter for a given number of clusters. We calculate the sample size required for an unequal cluster sizes trial to have the same power as one with equal cluster sizes. Relative efficiency based on the noncentrality parameter is straightforward to calculate and easy to interpret. It connects the required mean cluster size directly to the required sample size with equal cluster sizes. Consequently, our approach first determines the sample size requirements with equal cluster sizes for a pre-specified study power and then calculates the required mean cluster size while keeping the number of clusters unchanged. Our approach allows adjustment in mean cluster size alone or simultaneous adjustment in mean cluster size and number of clusters, and is a flexible alternative to and a useful complement to existing methods. Comparison indicated that we have defined a relative efficiency that is greater than the relative efficiency in the literature under some conditions. Our measure of relative efficiency might be less than the measure in the literature under some conditions, underestimating the relative efficiency. The relative efficiency of unequal versus equal cluster sizes defined using the noncentrality parameter suggests a sample size approach that is a flexible alternative and a useful complement to existing methods.