Use Of Composite Samples Research Articles

The microstructure and mechanical and corrosion properties of Mg matrix composites reinforced with bioactive glass: The combined effect of bioactive glass content and extrusion speed

This paper studies the influence of 64SiO2–31CaO–5P2O5 bioactive glass particles on the microstructure, and mechanical and corrosion characteristics of AZ91-bioactive glass composite wires fabricated by friction stir back extrusion (FSBE). According to the findings, the extruded composite mostly includes the α-Mg and β-Mg17Al12 phase, as well as the bioactive glass reinforcing phase with a gradient distribution in the AZ91 matrix. The hardness of the FSBE-processed composites increased to 81.32 HV with increasing bioactive glass phase content from 1 to 5 vol % and extrusion speed from 20 to 40 mm/min. In the FSBE-processed composite with 5 vol % bioactive glass particles, the maximum yield strength, ultimate tensile strength, and corrosion resistance of 253.34 ± 9.31 MPa, 298.73 ± 8.95 MPa, and 0.0457 mm/year were obtained, respectively. Compared to AZ91 alloy the polarization resistance in the simulated body fluid solution of AZ91-bioactive glass composite increased and reached 298.21 Ω.cm2. The use of composite samples in circumstances requiring biodegradable implants seems to be promising.

Use of composite samples and NIR spectroscopy to detect changes in SOC contents

Depending on the land management, soils can behave as sources or sinks of carbon. Thus, monitoring the changes in the SOC (ΔSOC) is of significance. However, this monitoring is often challenging because the value of ΔSOC is typically small in comparison with the spatial variability, and a large sample size is required, which may incur prohibitive costs. In the absence of the necessary sample size, hypothesis testing may be performed under deficient statistical conditions, which may result in misleading conclusions. In this study, we compared several cost-effective approaches to solve the aforementioned problems: i) using composites, as the number of samples to be analysed is smaller, and the costs using a reference method do not represent a substantial amount; ii) using NIR spectroscopy, which is a fast and cheap technique, and allows the analysis of massive number of samples; and iii) the combination of these approaches. In particular, the approaches were compared by evaluating the corrected minimum detectable difference (MDDC), which corresponds to the MDD after the errors of the methods have been accounted for. Bulking into the composites reduced the analysis costs, and the variance was reduced as the sample size reduced. However, a larger penalisation of the random measurement errors increased the MDDC. Biased predictions were obtained when an NIR spectroscopy based national scale model was used to predict the SOC at the local scale, resulting in extremely high values of the MDDC. By using composites to adapt that model to the local conditions through spiking with the extra-weighting technique, the bias was considerably reduced, along with the MDDC. In addition to their role as a spiking subset, the composites exhibited a desirable effect when combined with the NIR spectroscopy technique, since they allowed to find the model that was predicting SOC contents with the lowest bias, and hence measuring the ΔSOC with the highest accuracy. This analysis was highly specific and cannot be applied using any other spiking subsets, and allowed to identify a model that obtained an MDDC smaller than that obtained using only the composites. Therefore, the combination of the composites and NIR spectroscopy can be used to monitor ΔSOC since it is inexpensive, accurate and robust, and the spatial distribution of the SOC contents is not lost. Moreover, the cost efficiency of this combined approach probably improves along successive rounds in the monitoring process.

An alternative approach to testing of moisture susceptibility of recycled pavement materials

Recycling is one of the most sustainable methods of pavement construction. However, moisture entering through thin HMA surface layer(s) overlying recycled pavements has often caused their premature deterioration. This study was conducted to develop an alternative laboratory moisture conditioning and testing procedure for recycled layers, and recommend tests and structure to enhance the resistance against moisture damage. The study developed a unique way to utilize a dynamic moisture conditioning process to obtain a more realistic evaluation of the moisture resistance of recycled layers than the currently used static immersion tests. Instead of using samples of only recycled (Full Depth Reclaimed, FDR, with asphalt emulsion) layers, the study evaluated composite samples that are more representative of actual pavement structures. Composite samples were prepared by attaching HMA samples on top of FDR samples with tack coat. The samples were tested for permeability and modulus using Ultrasonic Pulse Velocity test, a nondestructive test (NDT) test. The samples were subjected to 2,000 cycles of the Moisture Induced Stress Test (MiST) and then retested for modulus. The conditioning process was able to simulate moisture damage in the composite samples, and the nondestructive test was able to detect moisture-induced damage. The samples with two HMA layers showed significantly lower loss (28%) in modulus than those with only one HMA layer with the same thickness (72%). Two layers of tack coat for the samples with the two HMA layers were more effective in reducing the ingress of water through the HMA layers into the FDR layer than the one layer of tack coat for one HMA layer samples. Use of composite samples and NDT, and the dynamic moisture conditioning process (MiST) are recommended for the design of recycled layers. The use of two separate HMA layers with intervening two tack coat layers instead of a single HMA layer with a single tack coat is recommended for the enhancement of moisture resistance of recycled pavements.

Human health risks related to the consumption of foodstuffs of animal origin contaminated by bisphenol A

Bisphenol A (BPA) is used in a wide variety of products and objects for consumers use (digital media such as CD's and DVD's, sport equipment, food and beverage containers, medical equipment). For humans, the main route of exposure to BPA is food. Based on previous estimates, almost 20% of the dietary exposure to BPA in the French population would be from food of animal origin. However, due to the use of composite samples, the source of the contamination had not been identified. Therefore, 322 individual samples of non-canned foods of animal origin were collected with the objectives of first updating the estimation of the exposure of the French population and second identifying the source of contamination of these foodstuffs using a specific analytical method. Compared to previous estimates in France, a decline in the contamination of the samples was observed, in particular with regard to meat. The estimated mean dietary exposures ranged from 0.048 to 0.050 μg (kg bw)−1 d−1 for 3–17 year children and adolescents, from 0.034 to 0.035 μg (kg bw)−1 d−1 for adults and from 0.047 to 0.049 μg (kg bw)−1 d−1 for pregnant women. The contribution of meat to total dietary exposure of pregnant women, adults and children was up to three times lower than the previous estimates. Despite this downward trend in contamination, the toxicological values were observed to have been exceeded for the population of pregnant women. With the aim of acquiring more knowledge about the origin the potential source(s) of contamination of non-canned foods of animal origin, a specific analytical method was developed to directly identify and quantify the presence of conjugated BPA (BPA-monoglucuronide, BPA-diglucuronide and sulphate forms) in 50 samples. No conjugated forms of BPAs were detected in the analysed samples, indicating clearly that BPA content in animal food was not due to metabolism but arise post mortem in food. This contamination may occur during food production. However, despite extensive sampling performed in several different shops (butcheries, supermarkets …. ) and in different conditions (fresh, prepared, frozen …), the source(s) of the contamination could not be specifically identified.

Utilization of composite fecal samples for detection of anthelmintic resistance in gastrointestinal nematodes of cattle

Recent reports indicate that anthelmintic resistance in gastrointestinal nematodes of cattle is becoming increasingly prevalent worldwide. Presently, the fecal egg count reduction test (FECRT) is the only means available for detection of resistance to anthelmintics in cattle herds at the farm level. However, the FECRT is labor and cost intensive, and consequently is only rarely performed on cattle farms unless for research purposes. If costs could be reduced, cattle producers might be more likely to pursue drug resistance testing on their farms. One approach to reducing the cost of the FECRT, is the use of composite fecal samples for performing fecal egg counts (FEC), rather than conducting FEC on fecal samples from 15 to 20 individual animals. In this study FECRT were performed on 14 groups of cattle using both individual and composite FEC methods To measure how well the results of composite sampling reproduce those of individual sampling, Lin’s Concordance Correlation Coefficient was utilized to describe both the linear relationship between methods and the slope and y-intercept of the line relating the data sets. There was little difference between the approaches with 98% agreement in mean FEC found between methods Mean FEC based on individual counts ranged between 0 and 670.6 eggs per gram of feces, indicating that the results of this study are applicable to a wide range of FEC levels. Standard error of the mean FEC and range of FEC are reported for each group prior to and following treatment to describe the variability of the data set. There was greater than 95% agreement in drug efficacy between individual and composite sampling methods, demonstrating composite sampling is appropriate to evaluate drug efficacy. Notably, for all groups tested the efficacy calculated by composite sampling was within the 95% confidence interval for efficacy calculated using individual sampling. The use of composite samples was shown to reduce the number of FEC required by 79%. These data demonstrate that pooling fecal samples from a group of cattle and then performing repeated FEC on that composite sample yields results very similar to performing individual FEC on those same animals, while substantially reducing the cost of performing a FECRT as compared to individual fecal samples. Furthermore, we have developed suggested methods for using composite samples in a FECRT, provided a cost comparison for this methodology, and described potential issues associated with the use of composite samples that must be considered.

Composite Sampling Approaches for Bacillus anthracis Surrogate Extracted from Soil.

Any release of anthrax spores in the U.S. would require action to decontaminate the site and restore its use and operations as rapidly as possible. The remediation activity would require environmental sampling, both initially to determine the extent of contamination (hazard mapping) and post-decon to determine that the site is free of contamination (clearance sampling). Whether the spore contamination is within a building or outdoors, collecting and analyzing what could be thousands of samples can become the factor that limits the pace of restoring operations. To address this sampling and analysis bottleneck and decrease the time needed to recover from an anthrax contamination event, this study investigates the use of composite sampling. Pooling or compositing of samples is an established technique to reduce the number of analyses required, and its use for anthrax spore sampling has recently been investigated. However, use of composite sampling in an anthrax spore remediation event will require well-documented and accepted methods. In particular, previous composite sampling studies have focused on sampling from hard surfaces; data on soil sampling are required to extend the procedure to outdoor use. Further, we must consider whether combining liquid samples, thus increasing the volume, lowers the sensitivity of detection and produces false negatives. In this study, methods to composite bacterial spore samples from soil are demonstrated. B. subtilis spore suspensions were used as a surrogate for anthrax spores. Two soils (Arizona Test Dust and sterilized potting soil) were contaminated and spore recovery with composites was shown to match individual sample performance. Results show that dilution can be overcome by concentrating bacterial spores using standard filtration methods. This study shows that composite sampling can be a viable method of pooling samples to reduce the number of analysis that must be performed during anthrax spore remediation.

Mapping geochemical patterns at regional to continental scales using composite samples to reduce the analytical costs

The use of composite samples to reduce the time and cost of chemical analysis is discussed. It is shown when composite samples can be used without affecting predefined project objectives. Furthermore, it is also demonstrated when they should not be used, and also how much information is lost due to their use.The study presents a comparison of data concentrations of some major (Al2O3, CaO, Fe2O3, K2O, P2O5, TiO2) and trace elements (Cd, Co, Cr, La, Rb, Sr, Th, Tl, U, Zn) in European topsoil and subsoil produced by FOREGS (Forum of European Geological Surveys) and two other data sets derived by compositing the five individual samples in each 160×160km cell of the Global Terrestrial Network (GTN); the first by physically compositing the samples, and analysing the composites, and the second by artificially compositing the samples in each GTN cell.The three soil databases were compared statistically and spatially to quantify the significance of the differences. The results of this study clearly demonstrate that composite samples can be used effectively to show broad continental-scale element distribution patterns; their use may not be effective if the goal is to highlight local geochemical anomalies. It is concluded that compositing samples for continental-scale surveys is a time- and cost-effective procedure, especially for reducing the costs for chemical analysis.

Use of post-stratification in composite sampling for estimating mean

We show with the results of a study conducted in the Hamadan Province, Iran as to how the use of composite sampling for estimating mean zinc concentration in the soil can help reduce analytical costs by reducing the number of analysis required. We also introduce post-stratification methodology in the composition step to take advantage of possible spatial dispersion. We speculate that the zinc concentration value depends on the sample location, we first stratified the sample set and then composite units from different strata randomly. The results of a simulation study show that the use of this approach not only reduces the total costs but also increases the precision of the estimator.

The Application of Cognitive-Behavioral Therapy for Psychosis in Clinical and Research Settings

This study compared the practice of cognitive-behavioral therapy (CBT) for psychosis across research and routine clinical settings. An observer-rated adherence measure was used to compare the content of 40 therapy sessions of clients with positive psychotic symptoms. Twenty therapist-client dyads came from a research setting in the United Kingdom and 20 from three clinical settings, two in the United Kingdom and one in the United States. In the research setting CBT was provided by research clinical psychologists and trained local therapists. In the clinical settings CBT was part of a case management service by trained therapists. Therapist adherence to CBT for psychosis did not differ between the research and clinical settings. However, clinicians in the research settings scored significantly higher on items for schema work (z=-1.98, p<.05), relapse prevention interventions (z=-2.08, p<.05), and formulating a model of relapse (z=-2.61, p<.01). CBT for psychosis conducted in clinical settings was more strongly characterized by assessment of symptoms and work on coping strategies and less so by relapse prevention and schema-level work. Relapse prevention interventions and schema work could be considered more challenging for therapists to undertake. The findings suggest that therapists working in routine clinical settings are able to establish good therapeutic relationships with people with psychosis and to work on assessing and coping with their psychotic symptoms. However, some therapeutic approaches may be more challenging in this context.

Comparison of Multiple Point and Composite Sampling for Monitoring Bathing Water Quality

The United States Environmental Protection Agency's Beaches Environmental Assessment and Coastal Health Act (BEACH Act) requires states to develop monitoring and notification programs for recreational waters using approved bacterial indicators. Implementation of an appropriate monitoring program can, under some circumstances, be expensive. This study explored the use of composite sampling at two Racine, Wisconsin beaches over a four month period (n = 68 days) to determine whether compositing can provide a valid, unbiased, and cost-effective measure of water quality. Multiple point sampling occurred throughout the bathing season, with water samples collected daily from three or four fixed locations along each beach. From each individual sample, well-mixed aliquots were combined to form a composite sample. Individual and composite samples were assayed identically for Escherichia coli using Colilert-18 and Quanti-Tray 2000 (IDEXX Laboratories, Inc., Westbrook, ME). Results from this study indicate a reasonable expectation of a simple 1:1 ratio between the composite samples and the arithmetic mean of the individual samples. Additionally, log variance of the composite sample results did not differ significantly from that of the single sample averages (p > 0.2). Empirical values for log standard deviations varied by no more than 7% between the composite sample and individually assayed samples. Thus compositing, as performed in this study, appears to introduce neither significant bias nor additional variability into the monitoring results and stands as a reasonable alternative to data sets derived from single-sample methods. Regulatory programs adopting this approach could maintain sample integrity while reducing costs associated with recreational water quality assessment.

Data Representativeness for Risk Assessment

Soil data collected to support a baseline human health or ecological risk assessment should be representative of the exposures likely to be encountered at the site. Representative data are produced when sampling plans consider the receptors, exposure areas, exposure media, exposure pathways, and habitat at the site. The number of soil samples required in each exposure area depends on the expected variability in sample concentrations and on providing adequate areal and depth coverage. Sampling designs that are probability based, such as simple random or grid sampling, provide the best data for risk assessment because they are unbiased, provide a reliable estimate of variability, and allow statistical inferences to be made from the data set of collected samples. The use of composite samples can reduce the total number of analyses needed to estimate the mean concentration. However, the main drawback to composites is that information about the variability in sample concentrations is lost, thus limiting their usefulness for estimating the 95% upper confidence limit (UCL) on the mean concentration, which is often the exposure point concentration used in risk assessment.

The Effects of Sieving and Spatial Variability of Estuarine Sediment Toxicity Samples on Sediment Chemistry

In 1998, we conducted a field-validation study of the chronic 28-day whole-sediment toxicity test with Leptocheirus plumulosus in Baltimore Harbor, MD, an area where this amphipod is indigenous. This study included an evaluation of the effect of sieving on sediment chemical concentrations and the use of field replicates, or separate grabs from the same site, which provided an estimation of within-site chemical and toxicologic variability. Six stations in Baltimore Harbor, MD, were included in this evaluation. Chemical analysis of two separate unsieved field replicates from the six sites indicated that, overall, the chemical concentrations of replicates within each site were similar, especially for metals. Organic contaminants particularly total PCBs, had the highest variability between replicates. Chemical variability did not appear to be related to differences in organic carbon content or grain size or to variability in toxicologic end points. Results supported the use of composite samples in sediment toxicity tests. In addition, in most cases, sieving had little effect on sediment chemistry. For the metals and trace elements, only selenium showed a substantial change after sieving, with some samples increasing after sieving and others decreasing. Concentrations of acid-volatile sulfide (AVS) increased 194.6% at one station after sieving, although in most other cases, AVS and simultaneously extracted metals remained relatively unchanged. As expected, concentrations of organics generally decreased after sieving, but in the majority of cases this decrease was small (i.e., coefficient of variation < or = 25%). Total benzene hexachloride and total chlordanes had the greatest changes, whereas polychlorinated biphenyl concentrations decreased at only two stations after sieving. Concentrations of polyaromatic hydrocarbons showed little change after sieving. These changes in sediment chemistry due to sieving must be viewed in the larger context of the potentially confounding effects that indigenous organisms may have on the interpretation of test results from whole-sediment toxicity tests.

The use of composite sampling in contaminated sites—a case study

Simulated composite sampling was carried out using data from a contaminated site. The values obtained by composite sampling were compared with the results obtained using discrete (individual) samples. It is appropriate to use a modified investigation level (MIL) when using composite samples. The MIL is lower than the standard investigation level, (IL). Various MILs were considered in this study. Too low an MIL will indicate that some composite samples require further investigation, when none of the discrete samples comprising the composite would have exceeded the IL. Too high an MIL will result in some discrete samples that exceed the IL being missed. A suggested MIL is IL/ $$\sqrt n $$ where n is the number of discrete samples in the composite sample. This MIL was found to give few false negatives but many fewer false positives than the IL/n rule. Although this MIL was effective on the test data it could be site specific. Some local areas of high concentration may be missed with composite samples if a lower investigation level is used. These however do not make a large contribution to the health risk because they will have a contaminant level only slightly higher than the IL, and the neighboring samples must have a low concentration of the contaminant. The increased risk due this cause may be more than offset by the higher sampling density made possible through the economies of composite sampling When composite sampling is used as the first phase of an adaptive cluster-sampling scheme, it must be augmented by additional samples to delineate the contaminated area to be cleaned up. Composite sampling can also be effectively used in a “clean up unit” technique, where a clean up unit is represented by one or more composite samples. Suggestions are given for when composite sampling can be used effectively.

Contributions to composite sampling

The initial use of composite sampling involved the analysis of many negative samples with relatively high laboratory cost (Dorfman sampling). We propose a method of double compositing and compare its efficiency with Dorfman sampling. The variability of composite measurement samples has environmental interest (hot spots). The precision of these estimates depends on the kurtosis of the distribution; leptokurtic distributions (γ2 > 0) have increased precision as the number of field samples is increased. The opposite effect is obtained for platykurtic distributions. In the lognormal case, coverage probabilities are reasonable for σ < 0.5. The Poisson distribution can be associated with temporal compositing, of particular interest where radioactive measurements are taken. Sample size considerations indicate that the total sampling effort is directly proportional to the length of time sampled. If there is background radiation then increasing levels of this radiation require larger sample sizes to detect the same difference in radiation.

Strategies for Sampling Spatially Heterogeneous Phenomena: the Example of River Gravels

ABSTRACT The paucity of critical results in the field sciences is partly the result of ineffective data collection. Multiple samples must be collected to take advantage of the power of inferential statistics, but the number of samples needed may be minimized by using efficient sampling methods. This study shows that for gravel river bars characterized by the presence of several unevenly distributed facies, the grid technique for sample selection is one of the best and easiest to use in the field. A special combination of grid and random techniques, known as systematic unaligned sampling, performs slightly better, but site selection and navigation in the field are more complex. Random sampling performs less well than either of the other methods. If the sampling question requires estimation of a statistic to represent the entire area or volume, rather than estimates of the variability within and between different zones of the area or volume, then the use of composite sampling further reduces the sampling effort required. A few replications of these composite samples will provide an estimate of the mean and standard deviation of a population statistic which can be used to construct confidence limits about the estimated statistic.

The beneficial use of composite samples in the energy-dispersive X-ray analysis of highly radioactive Nimonic PE16

A new technique for preparing 3 mm diameter disc samples for TEM is presented. It permits quantitative energy- dispersive X-ray (EDX) analysis of radioactive materials where otherwise high sample activity causes saturation of the EDX detector. The new composite sample geometry, comprising a small disc of radioactive material within an annulus of compatible unirradiated material, has up to ∼ 50 × reduced activity. Similar sample geometries may be used to minimize the mass of magnetic material in high-resolution TEM examinations or when samples from small diameter wires are required. Composite samples have been prepared from a Commercial Nimonic PE16 alloy containing 0.1 wt% Co after irradiation at 450° C under thermal reactor conditions. High-resolution EDX analysis in a field-emission gun STEM reveals significant irradiation-induced intergranular enrichment of nickel, silicon and phosphorus and depletion of chromium and iron. The observed changes are asymmetric with respect to the grain-boundary interface and extend over distances of 10 to 20 nm. The asymmetry may be explained by the presence of intergranular γ′ phase of mixed thermal and irradiation-induced origin. A coincident irradiation-induced deterioration in stress-rupture properties may be associated with intergranular γ′ and phosphorus. Future investigations should allow irradiation-induced changes in the mechanical properties of PE16 to be described in terms of coincident changes in grain-boundary microchemistry.