Conventional Sampling Methods Research Articles

Investigation of Initial Rock Damage and its Effects on Uniaxial Compressive Strength

This study investigated the initial rock damages and their effects on the uniaxial compressive strength of soft rock (claystone) and hard rock (marble) using Computerized Tomography (CT) scanning. The soft rock (claystone) samples were initially damaged before sampling. The samples were taken from three test areas with different levels of deterioration. These areas were initially subjected to different deteriorating conditions. In Area 1, the rock was exposed to natural air, called the uncovered test area; In Area 2, the rocks were wetted for three days by watering, drying, and exposing it to the sun/wind, called a wetting-drying test area. This process was conducted by wetting and drying the rocks for three days each; and in Area 3, the rock was covered with a concrete slab (in-place poured concrete), called a concrete covered test area. These different sampling methods damaged the hard rocks (marble). CT scanning experiments showed the recorded average CT numbers of the rock samples (from the highest to lowest) are: the concrete covered area, the uncovered area, and the wetting-drying area. The test results of the soft rock samples also demonstrated that a higher average CT number corresponded to a higher uniaxial compressive strength. In addition, the average CT number for soft rock undergoing different degrees of initial damage exhibits a certain regularity. The average CT number of the soft rock confirmed induced damages by the deteriorating condition. Using a nondestructive sampling method for the hard rock led to a significantly lower degree of initial damage than the samples obtained by the conventional sampling method. The marble samples obtained by the nondestructive sampling method exhibited higher average CT numbers and uniaxial compressive strength than the samples obtained by conventional sampling method.

Quantification of uncertainties due to manufacturing tolerances using deterministic sampling methods

The objective of this paper is to assess the applicability of three Deterministic Sampling (DS) methods (namely DS-Standard, DS-Simplex and DS-Hadamard) for uncertainty quantification of manufacturing tolerances for global safety parameters, such as the multiplicative factor (keff), and local quantities, such as the fission rate. More specifically, the IPEN/MB-01 research reactor (from LWR-RESR benchmark) has been modeled in the Monte Carlo code SERPENT to which the sampling methods have been applied. Twenty different input parameters (related to geometry and materials) were considered as sources of uncertainties. Uncertainty estimates for keff by DS were all compatible among the three methodologies (with a maximum nominal difference of 5 pcm) and in agreement with values reported in the benchmark (within the statistical Monte Carlo uncertainty of 15 pcm). Fission rate results obtained by DS showed full compatibility with results obtained by conventional stochastic sampling methods (such as Random Sampling or Latin Hypercube Sampling) and with those reported in the benchmark. The DS-Simplex showed the highest uncertainty in predicting the uncertainty on fission rate when compared to Random Sampling (with a maximum relative difference of 10% in the uncertainty estimate), whereas other DS methods showed a maximum deviation of 5%. The DS methods offer a remarkable reduction in the number of samples (from thousand to tens or hundreds according to the selected approach) required for an accurate uncertainty quantification for both global and local quantities.

Evaluation of seasonal dynamics of fungal DNA assemblages in a flow-regulated stream in a restored forest using eDNA metabarcoding.

Investigation of seasonal variation in fungal communities is essential for understanding biodiversity and ecosystem functions. However, the conventional sampling method, with substrate removal and high spatial heterogeneity of community composition, makes surveying the seasonality of fungal communities challenging. Recently, water environmental DNA (eDNA) analysis has been explored for its utility in biodiversity surveys. In this study, we assessed whether the seasonality of fungal communities can be detected by monitoring eDNA in a forest stream. We conducted monthly water sampling in a forest stream over 2 years and used DNA metabarcoding to identify fungal eDNA. The stream water contained DNA from functionally diverse aquatic and terrestrial fungi, such as plant decomposers, parasites and mutualists. The variation in the fungal assemblage showed a regular annual periodicity, meaning that the assemblages in a given season were similar, irrespective of the year or sampling. Furthermore, the strength of the annual periodicity varied among functional groups. Our results suggest that forest streams may act as a 'trap' for terrestrial fungal DNA derived from different habitats, allowing the analysis of fungal DNA in stream water to provide information about the temporal variation in fungal communities in both the aquatic and the surrounding terrestrial ecosystems.

A New Method for Standardizing Inland Fish Community Surveys: Characterizing Habitat Associated with Small-Bodied Fish Species, Abundance, and Size Distributions in a Highly Modified Estuary

Monitoring fish assemblages in estuary environments is often difficult to standardize due to habitat complexity and gear-specific selectivity. This is further compounded by conventional sampling methods which require fish handling that might cause stress or mortality. To ameliorate these issues, we developed the Single-Platform Aquatic Species and Habitat Sampling System (Platform), an integrated and mobile concentrator net and live box prototype, coupled with a range of physical monitoring equipment. The long-term goal of the Platform is to employ non-invasive sampling techniques such as video and eDNA; however, our aim in this study was to test the Platform’s ability to sample across different habitat types and detect differences in fish assemblages. We investigated the utility of the Platform over a short time period (2 mo) in a relatively small and complex embayment within the highly modified San Francisco Estuary, California. We were able to identify clear physical distinctions among estuary/delta habitat types and detect habitat segregation by ecological groups of sampled fishes with the Platform. The Platform also detected discernable ontogenetic shifts (i.e., size differences) within estuary habitats of commonly observed fish species. These initial results demonstrate the Platform’s ability to contrast fish density, size, and species diversity, which sets the stage to advance more passive monitoring techniques, including video and eDNA methods. The Platform has the potential to fill a methodological gap in non-invasive surveying of small-bodied fish across a range of estuarine habitats, warranting further investigation of potential applications.

Design & Characterization of Pb Electrode for Sensing Trichloroethylene in Ionic Liquid/Acetonitrile Co-Solvents

Design & Characterization of Pb Electrode for Sensing Trichloroethylene in Ionic Liquid/Acetonitrile Co-Solvents

Diagnostic Outcomes and Safety of Cryobiopsy Added to Conventional Sampling Methods: An Observational Study

Cryobiopsy enables specialists to perform high-quality, large, entirely circumferential biopsies; therefore, it may improve the diagnostic yield of peripheral pulmonary lesions (PPLs), as has been previously observed regarding endobronchial tumors and interstitial lung diseases. How do the diagnostic accuracy and safety change by cryobiopsy when performed alongside conventional biopsy for PPLs? Consecutive patients who underwent cryobiopsy in addition to conventional biopsies for PPL diagnosis at our institution between June 2017 and May 2018 were reviewed retrospectively. The target location was estimated and sampling was performed using conventional devices (ie, forceps, brush, aspiration needle), and cryobiopsy was performed at the same location. Diagnostic outcomes and cryobiopsy safety when performed in addition to conventional sampling methods were analyzed in this observational study. In total, 257 patients were analyzed, and the overall diagnostic yield was 89.9%. Among them, 22 lesions were diagnosable by cryobiopsy exclusively, which improved the rate of diagnosis by 8.6%. Advantages of the use of cryobiopsy were the most apparent when lesions were adjacent to areas assessed via radial endobronchial ultrasound (69.4%vs84.3%). Multivariable analysis identified bronchus sign (positive/negative, P= .001), lobe (other lobes/right upper lobe and left upper segment, P= .028), and visibility on radiograph (visible/invisible, P= .047) as factors that significantly affected diagnostic yield. On the other hand, three instances of severe hemorrhage (1.2%) and two of pneumothorax (0.8%) occurred. Although most complications were minor, two patients required hospitalization because of cerebral infarction and lung abscess. Cryobiopsy improves the diagnostic yield of PPLs when combined with other conventional sampling methods; however, caution is required because of the possibility of complications.

Common Differential Diagnostic Issues in Lung Cytopathology: 3 Case Reports and a Review

Abstract The diagnosis and staging of lung malignancies increasingly rely on the use of cytologic sampling techniques, particularly endobronchial ultrasound-guided transbronchial needle aspiration. Endobronchial ultrasound-guided transbronchial needle aspiration is minimally invasive and cost-effective and, most significantly, has been shown to be equivalent to conventional sampling methods. As the role of endobronchial ultrasound-guided transbronchial needle aspiration and other cytologic sampling methods, including transthoracic fine-needle aspiration and bronchoalveolar lavage, expands, diagnostic dilemmas arise that may pose a challenge to the cytopathologist. This review discusses 3 cases that illustrate 3 differential diagnoses, with an emphasis on distinguishing lung carcinoma from benign entities.

Event-triggered integral sliding mode fixed time control for trajectory tracking of autonomous underwater vehicle

In this paper, an event-triggered integral sliding mode fixed-time control method for trajectory tracking problem of autonomous underwater vehicle (AUV) with disturbance is investigated. Initially, the global fixed time stability is ensured with conventional periodic sampling method for reference trajectory tracking. By introducing fixed time integral sliding mode manifold, fixed time control strategy is expressed for the AUV, which can effectively eliminate the singularity. Correspondingly, in order to reduce the damage caused by chattering phenomenon, an adaptive fixed-time method is proposed based on the designed continuous integral terminal sliding mode (ITSM) to ensure that the trajectory tracking for AUV is achieved in fixed-time with external disturbance. In order to reduce resource consumption in the process of transmission network, the event-triggered sliding mode control strategy is designed which condition is triggered by an event. Also, Zeno behavior is avoided by proof of theoretical. It is shown that the upper bounds of settling time are only dependent on the parameters of controller. Theoretical analysis and simulation experiment results show that the presented methods can realize the control object.

Sequential and Binomial Sampling Plans to Estimate Thrips tabaci Population Density on Onion.

Simple SummaryThrips are tiny insects that cause significant damage to onion crops worldwide. They feed on the plants and can also transmit plant viral diseases. To prevent damage, it is necessary to estimate the population density (average number of insects per plant), through periodic sampling, and to apply a combination of control tactics to maintain thrips at acceptable levels. Conventional sampling methods are precise but require large investments of time and effort. In this study, binomial and sequential sampling plans were developed to estimate thrips population density in a precise and less time-consuming manner. More than 50 onion plots were sampled, and Thrips tabaci Lindeman was identified as the predominant pest species. The sampling plans reached acceptable levels of precision (D = 0.25) in less time than conventional sampling. Binomial and sequential sampling plans were reliable and easily implemented in practice, but sequential sampling showed better performance than binomial sampling under different field conditions. These findings may help to reduce time and work for T. tabaci sampling and, consequently, improve implementation of crop protection tactics on onion.Thrips tabaci Lindeman is a worldwide onion pest that causes economic losses of 10–60%, depending on many factors. Population sampling is essential for applying control tactics and preventing damage by the insect. Conventional sampling methods are criticized as time consuming, while fixed-precision binomial and sequential sampling plans may allow reliable estimations with a more efficient use of time. The aim of this work was to develop binomial and sequential sampling for fast reliable estimation of T. tabaci density on an onion. Forty-one commercial 1.0-ha onion plots were sampled (sample size n = 200) to characterize the spatial distribution of T. tabaci using Taylor’s power law (a = 2.586 and b = 1.511). Binomial and sequential enumerative sampling plans were then developed with precision levels of 0.10, 0.15 and 0.25. Sampling plans were validated with bootstrap simulations (1000 samples) using 10 independent data sets. Bootstrap simulation indicated that precision was satisfactory for all repetitions of the sequential sampling plan, while binomial sampling met the fixed precision in 80% of cases. Both methods reduced sampling time by around 80% relative to conventional sampling. These precise and less time-consuming sampling methods can contribute to implementation of control tactics within the integrated pest management approach.

Self‐training with one‐shot stepwise learning method for person re‐identification

SummaryPerson re‐identification (Re‐ID) aims at identifying the same person across multiple non‐overlapping camera views. A number of existing methods have been presented for this task in a fully‐supervised manner that requires a large amount of training annotations. However, obtaining high quality labels is extremely time consuming and expensive. In this article, we focus on the semi‐supervised person Re‐ID and propose a one‐shot stepwise learning method to address the above issue. It exploits only one labeled data along with additional unlabeled samples to gradually but steadily improving the discriminative capability of the feature representation. Specifically, we first construct labeled data portion to train Re‐ID model. Then we fine‐tune the overall system by the following two steps iteratively: (1) assigning the estimated labels to the unlabeled portion; (2) updating the network parameters according to the selected data. During the propagation process, different from conventional sampling method, we propose a novel dynamic sampling strategy to enlarge the pseudo‐labeled subset step by step to make the pseudo labels more reliable. On Market‐1501, DukeMTMC‐ReID and MARS datasets, we conducted extensively experiments to demonstrate that our proposed method contributes indispensably and achieves a very competitive Re‐ID performance.

Optimal sampling strategy of water quality monitoring at high dynamic lakes: A remote sensing and spatial simulated annealing integrated approach

Abstract An efficient and precise spatial sampling design is critical to capture spatial and temporal water quality variations under cost and labor constraints. Therefore, it is practically essential to optimize the sampling locations using limited sampling numbers to obtain the most comprehensive water quality monitoring results considering both the spatial and temporal dynamics. Existing sampling methods were restricted due to lacking pre-information and specific sampling objective function. This paper proposed an optimal sampling strategy using remote sensing (RS) big data and spatial sampling annealing (SSA) integrated approach for sampling design. The proposed method involved spatial-temporal clustering of the total suspended sediment (TSS) using long-term remote sensing data (Terra/Aqua MODIS, 2000–2014), determining the required sampling numbers using geostatistical analysis, and SSA simulation following the objective function of minimization of the spatial-temporal mean estimation error using remote sensing data as references. Taking total suspended sediment (TSS) observations at Poyang Lake, China, as the case study and application region. Results showed that the RS + SSA sampling approach is superior to conventional sampling methods such as systematic, stratified, and expert sampling, concerning spatial and temporal sampling accuracy. TSS estimation errors of the whole lake were reduced by 18.11% and 29.34% on average when compared to systematic and stratified sampling under the same sample size. The annual TSS estimation errors were dropped by approximately 50%. The sampling accuracy was affected by the synthetic effects of sampling strategy (station numbers and spatial distributions) and water quality variations (coefficient of variation, CV). Sampling optimization is more efficient to improve the sampling accuracy than increasing sampling size, which requires more cost and human resources. Remote sensing showed great potential as ideal means to provide spatially contiguous and comprehensive data as prior-knowledge for efficient sampling design. This paper provides solutions and recommendations for evaluating existing monitoring stations in their representation of water quality or optimizing a new sampling network for future implications of more efficient and precise water quality sampling and routine monitoring.

A practical guide to unbiased quantitative morphological analyses of the gills of rainbow trout (Oncorhynchus mykiss) in ecotoxicological studies.

Rainbow trout (Oncorhynchus mykiss) are frequently used as experimental animals in ecotoxicological studies, in which they are experimentally exposed to defined concentrations of test substances, such as heavy metals, pesticides, or pharmaceuticals. Following exposure to a broad variety of aquatic pollutants, early morphologically detectable toxic effects often manifest in alterations of the gills. Suitable methods for an accurate and unbiased quantitative characterization of the type and the extent of morphological gill alterations are therefore essential prerequisites for recognition, objective evaluation and comparison of the severity of gill lesions. The aim of the present guidelines is to provide practicable, standardized and detailed protocols for the application of unbiased quantitative stereological analyses of relevant morphological parameters of the gills of rainbow trout. These gill parameters inter alia include the total volume of the primary and secondary gill lamellae, the surface area of the secondary gill lamellae epithelium (i.e., the respiratory surface) and the thickness of the diffusion barrier. The featured protocols are adapted to fish of frequently used body size classes (300–2000 g). They include well-established, conventional sampling methods, probes and test systems for unbiased quantitative stereological analyses of light- and electron microscopic 2-D gill sections, as well as the application of modern 3-D light sheet fluorescence microscopy (LSFM) of optically cleared gill samples as an innovative, fast and efficient quantitative morphological analysis approach. The methods shown here provide a basis for standardized and representative state-of-the-art quantitative morphological analyses of trout gills, ensuring the unbiasedness and reproducibility, as well as the intra- and inter-study comparability of analyses results. Their broad implementation will therefore significantly contribute to the reliable identification of no observed effect concentration (NOEC) limits in ecotoxicological studies and, moreover, to limit the number of experimental animals by reduction of unnecessary repetition of experiments.

Applicability of Equilibrium Sampling in Informing Tissue Residues and Dietary Risks of Legacy and Current-Use Organic Chemicals in Aquaculture.

Equilibrium sampling based on silicone polydimethylsiloxane (PDMS) has been used to determine the concentrations of freely dissolved hydrophobic organic compounds (HOCs) and assess the thermodynamic potentials for bioaccumulation of these compounds in the aquatic environment. This allows the use of PDMS-based sampling techniques in assisting conventional sampling and extraction methods for the determination of the concentrations of HOCs in aquaculture products. The present study is an ex situ demonstration of how well PDMS can inform the tissue residues and dietary risks of legacy or current-use organic chemicals in aquaculture species from farm ponds in eastern China. For legacy contaminants such as polybrominated diphenyl ethers (PBDEs, n = 10), good agreement between the predicted concentrations based on PDMS and the measured lipid-normalized concentrations was observed for 60% of the studied biota, including both pelagic and benthic species. For pesticides currently used, such as pyrethroid (PE) (n = 4) and organophosphate pesticides (OPPs, n = 7), the measured tissue residues were consistently higher than those predicted by PDMS, possibly caused by the continuous input from the surroundings. For the organochlorine pesticides (OCPs, n = 5), the only detected chemical was also underestimated. Adjusted by ingestion rates of aquaculture products and toxicology data, the target hazard quotients of these chemicals predicted from PDMS were generally comparable to those derived from measured concentrations in tissue because of the predominance of PBDEs. Overall, PDMS-based equilibrium sampling offered an alternative approach for the prediction of tissue residues and dietary risks of PBDEs. Moreover, it should be applied with caution for PEs, OPPs, and OCPs. Improving the application of PDMS for these chemicals in farm ponds warrants future study. Environ Toxicol Chem 2021;40:79-87. © 2020 SETAC.

The role of sampling by cotton swab in the molecular diagnosis of cutaneous leishmaniasis.

An appreciated sampling technique is essential for achieving optimum results from diagnostic tests of cutaneous leishmaniasis (CL); conventional sampling methods, such as skin biopsy and dermal scrapping, are painful for the patients and require qualified staff and hospital facilities, while swabbing is patient-friendly more comfortable than invasive traditional techniques and can be carried out under field conditions. The aim of this study is to evaluate a non-invasive sampling method (swab) in the cutaneous leishmaniasis diagnosis, compared to microscopic examination. The recruitment of 205 patients was done during 3years in six regions known as endemic CL foci in the south-east, the centre, the south-west and the north of Morocco. The results showed that molecular detection of the nuclear marker ITS1 on swab materials is to be less sensitive than microscopic examination, and the difference was statistically significant (p-value=.036). Thereafter, 55 patients were randomly selected to compare the results of two molecular techniques (ITS1-PCR and nested KDNA-PCR), performed both on swab and on stained smears used for microscopic examination; ITS1-PCR results from stained smears reached 87% positivity against 65,2% for cotton swab; and it was statistically significant (p-value=.019); on the other hand for the KDNA marker, results from cotton swab reached 93% of positivity against 91% for stained smears; and statistically the difference was not significant (p-value=.5113). One can presume that rubbing over the lesion with cotton swab implies a low parasitic load collection, but the choice of the amplification target greatly influences the results obtained from cotton swab; on top of that swab remains useful in the cases of patients with multiples lesions or the latter are located in sensitive places difficult to reach with an invasive method such as the eyelids, the lips or other mucous areas.

Multispectral Interlaced Sparse Sampling Photoacoustic Tomography.

Multispectral photoacoustic tomography (PAT) is capable of resolving tissue chromophore distribution based on spectral un-mixing. It works by identifying the absorption spectrum variations from a sequence of photoacoustic images acquired at multiple illumination wavelengths. Due to multispectral acquisition, this inevitably creates a large dataset. To cut down the data volume, sparse sampling methods that reduce the number of detectors have been developed. However, image reconstruction of sparse sampling PAT is challenging because of insufficient angular coverage. During spectral un-mixing, these inaccurate reconstructions will further amplify imaging artefacts and contaminate the results. To solve this problem, we present the interlaced sparse sampling (ISS) PAT, a method that involved: 1) a novel scanning-based image acquisition scheme in which the sparse detector array rotates while switching illumination wavelength, such that a dense angular coverage could be achieved by using only a few detectors; and 2) a corresponding image reconstruction algorithm that makes use of an anatomical prior image created from the ISS strategy to guide PAT image computation. Reconstructed from the signals acquired at different wavelengths (angles), this self-generated prior image fuses multispectral and angular information, and thus has rich anatomical features and minimum artefacts. A specialized iterative imaging model that effectively incorporates this anatomical prior image into the reconstruction process is also developed. Simulation, phantom, and in vivo animal experiments showed that even under 1/6 or 1/8 sparse sampling rate, our method achieved comparable image reconstruction and spectral un-mixing results to those obtained by conventional dense sampling method.

Diagnostic accuracy of \u201csweeping\u201d method compared to conventional sampling in rapid urease test for Helicobacter pylori detection in atrophic mucosa

Although the rapid urease test (RUT) is a simple method for detecting Helicobacter pylori (H. pylori) infection, it requires sufficient biopsy samples and its sensitivity varies depending on the site and condition of H. pylori infection. We compared the diagnostic performance of a “sweeping method” for H. pylori detection with the conventional biopsy sampling method in atrophic gastric conditions which can reduce RUT accuracy. This prospective study included 279 patients who underwent upper endoscopy to determine the presence of H. pylori infection. Gastric mucosa of both the antrum and the corpus were swabbed, and we named this method the “sweeping method”. Biopsy sampling for the conventional method, histologic evaluation, and polymerase chain reaction were performed at the same time. The sensitivity, specificity, and accuracy of the sweeping method were 0.941, 0.826, and 0.903, respectively, compared to 0.685, 0.859, and 0.742, respectively, for the conventional biopsy method. The area under the receiver operating curve for the sweeping method was 0.884 versus 0.772 for the conventional method (P < 0.001). The sweeping method had a faster detection time than the conventional method. Compared to conventional biopsy sampling, the sweeping method with the RUT provided higher sensitivity and accuracy for the detection of H. pylori, with a faster detection time.

Encounter rates and abundance of humpback whales (Megaptera novaeangliae) in Gerlache and Bransfield Straits, Antarctic Peninsula

During the austral summer of 2006, the Projeto Baleias/Brazilian Antarctic Program (PROANTAR) conducted ship surveys for estimating whale encounter rates and abundance in Gerlache and Bransfield Straits, westward of the Antarctic Peninsula (edge between IWC Areas I and II). The encounter rate was higher in the Bransfield Strait (0.32 groups n. mile–1; 95% CI: 0.26–0.39) than in the Gerlache Strait (0.24 groups n. mile–1; 95% CI: 0.13–0.44), though the difference was not statistically evident. An abundance estimate using conventional distance sampling methods was computed only for the Bransfield Strait. The perpendicular distance data was best fitted by the half-normal model without adjustments. Derived abundance for the surveyed area was 865 humpback whales (95% CI = 656–1,141; CV = 14.13). This area represents only a small fraction of the Stock G feeding ground.

Biting and resting behaviour of malaria vectors in Bandar-Abbas County, Islamic Republic of Iran.

Blood feeding and resting behaviour of malaria vectors are the most influential factors in malaria transmission. To measure blood feeding and resting behaviour, conventional mosquito sampling methods were performed in an area with potential for malaria transmission. Adult mosquitoes were collected monthly from indoor/outdoor places by conventional sampling methods, and larval habitats were investigated. Enzyme-linked immunosorbent assay was used to measure the human blood index (HBI) of the mosquitoes. Anopheles stephensi, Anopheles culicifacies, Anopheles dthali and Anopheles fluviatilis, were collected. Overall, 1249 female Anopheles mosquitoes were captured on human and animal baits, but no human-vector contact occurred indoors. A. dthali, A. fluviatilis and A. culicifacies showed a greater tendency to outdoor resting places in contrast to A. stephensi, which had a propensity to indoor resting places. The seasonal biting activities of all species occurred at average temperatures between 23 and 27°C. HBI was measured as 27.2%, 20.7%, 19.1%, and 23.0% for A. fluviatilis, A. stephensi, A. culicifacies and A. dthali, respectively. Vector control strategy depends upon mosquito behaviour. Therefore, using appropriate sampling methods based on mosquito behaviour is critical for malaria control planning. Exophilic/exophagic habit of mosquito vectors leads to fewer human bites, resulting in biting protection. Exophilic behaviour also requires specific larvicidal operations in order to prevent and control malaria transmission.

Lognormal-Based Sampling for Fission Product Yields Uncertainty Propagation in Pebble-Bed HTGR

Uncertainty analyses of fission product yields are indispensable in evaluating reactor burnup and decay heat calculation credibility. Compared with neutron cross section, there are fewer uncertainty analyses conducted and it has been a controversial topic by lack of properly estimated covariance matrix as well as adequate sampling method. Specifically, the conventional normal-based sampling method in sampling large uncertainty independent fission yields could inevitably generate nonphysical negative samples. Cutting off these samples would introduce bias into uncertainty results. Here, we evaluate thermal neutron-induced U-235 independent fission yields covariance matrix by the Bayesian updating method, and then we use lognormal-based sampling method to overcome the negative fission yields samples issue. Fission yields uncertainty contribution to effective multiplication factor and several fission products’ atomic densities at equilibrium core of pebble-bed HTGR are quantified and investigated. The results show that the lognormal-based sampling method could prevent generating negative yields samples and maintain the skewness of fission yields distribution. Compared with the zero cut-off normal-based sampling method, the lognormal-based sampling method evaluates the uncertainty of effective multiplication factor and atomic densities are larger. This implies that zero cut-off effect in the normal-based sampling method would underestimate the fission yields uncertainty contribution. Therefore, adopting the lognormal-based sampling method is crucial for providing reliable uncertainty analysis results in fission product yields uncertainty analysis.

Profiling the Vertical Transport of Microplastics in the West Pacific Ocean and the East Indian Ocean with a Novel in Situ Filtration Technique.

A new technique involving large-volume (10 m3) samples of seawater was used to determine the abundance of microplastics (MPs) in the water column in the West Pacific Ocean and the East Indian Ocean. Compared to the conventional sampling methods based on smaller volumes of water, the new data yielded abundance values for the deep-water column that were at least 1-2 orders of magnitude lower. The data suggested that limited bulk volumes currently used for surface sampling are insufficient to obtain accurate estimates of MP abundance in deep water. Size distribution data indicated that the lateral movement of MPs into the water column contributed to their movement from the surface to the bottom. This study provides a reliable dataset for the water column to enable a better understanding of the transport and fate of plastic contamination in the deep-ocean ecosystem.