Innovative Sampling Method Research Articles

Mental Health Problems Among Indonesian Adolescents: Findings of a Cross-Sectional Study Utilising Validated Scales and Innovative Sampling Methods

PurposeThis study aimed to estimate the prevalence of mental health problems and identify potential risk and protective exposures for adolescents in Indonesia. MethodsAn innovative sampling approach was applied to simultaneously recruit school- and community-based adolescents aged 16–18 years old from Jakarta (urban megacity) and South Sulawesi (remote province). We used multistage cluster sampling for in-school (N = 1,337) and respondent driven sampling for out-of-school (N = 824) adolescents. Mental health was measured using two validated scales: Kessler-10 and Center for Epidemiologic Studies Depression Scale-Revised . Psychiatric interviews were conducted in a subsample (N = 196) of students from Jakarta to validate the self-report scales. ResultsThe estimated population prevalence of psychological distress and depression were 24.3% (95% CI = 21.5–27.2) and 12.6% (10.5–14.4) for in-school and 23.7% (20.7–26.7) and 23.5% (20.4–26.5) for out-of-school adolescents, respectively. In participants who completed a psychiatric interview, common psychiatric morbidities were social anxiety, depression, and suicidality. Compared to in-school females, male in-school adolescents reported a lower prevalence of psychological distress (16.9% (13.1–20.7) vs. 30.4% (26.4–34.4)) and depression (10.1% (7.2–13.1) vs. 14.6 (11.4–17.8)). By contrast, for out-of-school adolescents, males reported a higher prevalence of psychological distress (25.2% (21.6–28.9) vs. 20.2% (15.1–25.3)) and depression (26.3% (22.5–30.1) vs. 16.9% (11.8–21.9)). In-school adolescents who did not seek healthcare despite a perceived need were more likely to report psychological distress and depression. DiscussionAdolescent mental health problems are highly prevalent in Indonesia, with substantial variation by gender, geography, and school enrolment. This study and its approach to sampling and measurement may serve as a model to improving mental health surveillance across other settings.

EOFA: An Extended Version of the Optimal Foraging Algorithm for Global Optimization Problems

The problem of finding the global minimum of a function is applicable to a multitude of real-world problems and, hence, a variety of computational techniques have been developed to efficiently locate it. Among these techniques, evolutionary techniques, which seek, through the imitation of natural processes, to efficiently obtain the global minimum of multidimensional functions, play a central role. An evolutionary technique that has recently been introduced is the Optimal Foraging Algorithm, which is a swarm-based algorithm, and it is notable for its reliability in locating the global minimum. In this work, a series of modifications are proposed that aim to improve the reliability and speed of the above technique, such as a termination technique based on stochastic observations, an innovative sampling method and a technique to improve the generation of offspring. The new method was tested on a series of problems from the relevant literature and a comparative study was conducted against other global optimization techniques with promising results.

Vertical distribution of microplastics in a river water column using an innovative sampling method.

Due to limitations of sampling methods, subsurface water is usually a less well-investigated compartment of the water column when scientists assess microplastic contamination. In this study, microplastic (MP) contamination was assessed in a freshwater river both in surface and subsurface using an innovative sampling method. Microplastic contamination in the lower part of the water column, i.e., near-bottom water and in sediments, was also studied. Three sampling campaigns were carried out during different weather conditions: stormy, rainy, and dry in order to observe their influence on the microplastics vertical distribution. No significant difference was observed between the abundance and types of MPs in surface and subsurface water. The proportion of polymer with theoretical density < 1 (polypropylene d = 0.9, polyethylene d = 0.91-0.95) and polystyrene (d = 0.1-1.06) in the surface and subsurface samples was 73.5%, and this proportion drops to 40.8% for the samples located in the near-bottom water and the sediments. Our results indicate that the MP concentration of the different compartments analyzed can be significantly influenced by rainfall during and prior to the sampling day. This study highlights that in shallow rivers, surface water sampling is representative of the water column MP contamination, but that sampling without taking environmental conditions into account may lead to erroneous estimation of MPs concentration and flux entering the marine environment.

Respondent-driven sampling (RDS) method: Introduction and its potential use for social psychology research

Contrary to other non-probability sampling methods in which researchers actively recruit potential participants, respondent-driven sampling (RDS) relies on connection and trust within social networks to access hidden or hard-to-reach populations through a peer-to-peer recruitment process. These interdependency relations aligned with Indonesian communal culture. Personal network size calculation in the RDS method makes this innovative sampling method approximate random sampling methods, where findings from the sample could be generalized to the target population. Considering its superiority, the RDS method could be applied in social psychology research in Indonesia to explore current sensitive social issues among hidden or hard-to-reach Indonesian sub-populations, for instance, radical religious groups. The current article aimed to concisely describe the RDS method; discuss ethical considerations, strengths, and weaknesses of the RDS method; and outline the potential use of the RDS method in improving the contribution of social psychology research in Indonesia, for example, by advancing strategies for social intervention programs. It is followed by a brief step-by-step process to conduct a study using the RDS method.

A comparison of crude oil hydrocarbon mobilization by vaporization gas drive into methane, ethane, and carbon dioxide at 15.6 MPa and 42 °C

An innovative sampling method was developed that allowed crude oil hydrocarbons dissolved in the upper gas-rich phase to be collected and quantitatively measured while maintaining constant reservoir conditions of 15.6 MPa and 42 °C. Crude oil was allowed to come to equilibrium with the injected gas phase (ca. 1/1 vol ratio) prior to collecting the dissolved hydrocarbons via a heated flow restrictor and analyzing them using high-resolution gas chromatography. As solvents, the three fluids’ efficacy parallel their minimum miscibility pressures (MMPs) for the test crude oil. Methane (MMP = 28.1 MPa) was a very poor hydrocarbon solvent, and was only able to dissolve ca. 18 mg oil/g methane. In contrast, CO2 (MMP = 9.68 MPa) dissolved up to 133 mg oil/g CO2 and ethane (MMP = 5.27 MPa) dissolved 722 mg oil/g ethane. Sequential collections of the dissolved oil hydrocarbons in the gas-dominated phase showed progressively lower concentrations for ethane and CO2, which demonstrated that liquid/liquid partitioning (and not saturation solubility) between the gas-dominated and oil-dominated phases controls the amounts of dissolved hydrocarbons. Thus, the lower the ratio of injected ethane or CO2 to the bulk crude oil, the higher the dissolved hydrocarbon concentrations. Both methane and CO2 showed a bias against dissolving heavier hydrocarbons. Methane was only capable of dissolving the lightest hydrocarbons (up to about C12), while CO2 preferentially dissolved light and middle hydrocarbons (up to about C16), leaving a residual oil rich in higher molecular weight hydrocarbons with significantly higher viscosity and density (lower API gravity) than the original unexposed crude oil. In contrast, ethane was capable of efficiently dissolving the entire range of hydrocarbons, with only a small bias against the heavier hydrocarbons. These lab studies show that, at the constant reservoir pressure and temperature used, ethane is a far superior hydrocarbon solvent for crude oil hydrocarbons than CO2, while CO2 is far superior to methane. Thus, ethane may ultimately yield higher oil recovery efficiencies (used either instead of CO2 or after a CO2 flood), while reducing the deposition of paraffinic and other higher molecular weight hydrocarbons in the reservoir.

An Innovative Sampling Method for Determining the Scale Effect of Rock Joints

An Innovative Sampling Method for Determining the Scale Effect of Rock Joints

Women\u2019s experiences seeking informal sector abortion services in Cape Town, South Africa: a descriptive study

BackgroundIn settings where abortion is legally restricted, or permitted but not widely accessible, women face significant barriers to abortion access, sometimes leading them to seek services outside legal facilities. The advent of medication abortion has further increased the prevalence of informal sector abortion. This study investigates the reasons for attempting self-induction, methods used, complications, and sources of information about informal sector abortion, and tests a specific recruitment method which could lead to improved estimates of informal sector abortion prevalence among an at-risk population.MethodsWe recruited women who have sought informal sector abortion services in Cape Town, South Africa using respondent driven sampling (RDS). An initial seed recruiter was responsible for initiating recruitment using a structured coupon system. Participants completed face-to-face questionnaires, which included information about demographics, informal sector abortion seeking, and safe abortion access needs.ResultsWe enrolled 42 women, nearly one-third of whom reported they were sex workers. Thirty-four women (81%) reported having had one informal sector abortion within the past 5 years, 14% reported having had two, and 5% reported having had three. These women consumed home remedies, herbal mixtures from traditional healers, or tablets from an unregistered provider. Twelve sought additional care for potential warning signs of complications. Privacy and fear of mistreatment at public sector facilities were among the main reported reasons for attempting informal sector abortion. Most women (67%) cited other community members as their source of information about informal sector abortion; posted signs and fliers in public spaces also served as an important source of information.ConclusionsWomen are attempting informal sector abortion because they seek privacy and fear mistreatment and stigma in health facilities. Some were unaware how or where to seek formal sector services, or believed the cost was too high. Many informal methods are ineffective and unsafe, leading to potential warning signs of complications and continued pregnancy. Sex workers may be at particular risk of unsafe abortion. Based on these results, it is essential that future studies sample women outside of the formal health sector. The use of innovative sampling methods would greatly improve our knowledge about informal sector abortion in South Africa.

The decade of Roma Inclusion: did it make a difference to health and use of health care services?

ObjectivesWe investigated whether the severely disadvantaged health of Hungarian Roma adults living in segregated settlements changed by the Decade of Roma Inclusion program.MethodsWe compared the results of two paired health interview surveys that we carried out using the same methodology before and after the Decade, on the general Hungarian and Roma populations.ResultsSelf-perceived health status of younger Roma worsened, while it improved among older Roma. Reported experience of discrimination reduced considerably and health care utilization improved in general. Positive changes in smoking and nutrition, and negative changes in alcohol consumption and overweight were observed. Many of observed changes can plausibly be linked to various government policies, including a quadrupling of public works expenditure, banning smoking in public places, restricting marketing of tobacco products, increasing cigarette prices, and a new tax on unhealthy foods. Liberalization of rules on alcohol distillation coincided with worsening alcohol consumption.ConclusionsWe have shown that Roma remain severely disadvantaged and present an innovative sampling method which can be used to monitor changes in groups where identification is a challenge.

Early Minoan mortuary practices as evident by microarchaeological studies at Koumasa, Crete, applying new sampling procedures

Here we present the results of a micromorphological study conducted on the recently excavated layers in a tholos tomb - Tholos Beta - at the Minoan site at Koumasa, Crete, during the 2013–2014 excavation seasons. This was also a unique opportunity to conduct a detailed research on in situ unexcavated archaeological layers in a Minoan tholos tomb, applying new and innovative sampling methods in order to enable such research in remote locations. This is the first time a micromorphological study has ever been conducted at a Minoan tholos tomb. The micromorphological analysis of the archaeological layers demonstrates that a single and massive burning event of hundreds of disturbed burials took place throughout the structure. This was followed by sprinkling of burnt lime on top of the burnt bone layer. Later cycles of similar burning events are also implied. These results have significant implications on our understanding of Early Minoan mortuary practices and symbolic world.

Issues of Stream-Aquifer Interactions in Grout Lined Channels in Urban Watersheds

Grout lined storm drains are used worldwide to convey storm runoff away from urban areas. They also convey dry weather flows such as car wash runoff, lawn runoff, and other “nuisance flows” in urban centers. Areas in Southern California and elsewhere have shallow water tables where dry weather flows in grout lined storm drains consist primarily of perennial groundwater baseflows. In these areas, groundwater leaks through cracks, joints, weepholes, and intentional dewatering structures into storm drains and eventually flows into natural channels, coastal wetlands, and estuaries. The “lined” sections of these channels are not always impervious; in fact, the lining of the channels often affords excellent opportunities to collect groundwater samples at discrete points that are usually not present along unlined channels where well control is sparse or where technical or legal issues prevent installation of piezometers. Frequently, as much as 95% of the nutrient and trace element loading to urban catchments during dry weather is from seepage of groundwater that is laden with pollutants. This project presents several examples of our experiences in conducting stream/aquifer studies in lined and semi-lined channels in Southern California. Sub-projects include evolution of groundwater quality along flowpaths, detection of unwanted recharge mounds in shallow groundwater systems due to leaky water main pipes, and comparisons of water quality in lined and unlined sections of a creek. Tools that are utilized and described in the paper include isotopic tracers; trace element and standard inorganic constituents; and innovative sampling methods.

Evaluating the Effectiveness of Artificial Fish Habitat Designs in Turbid Reservoirs Using Sonar Imagery

AbstractArtificial fish habitats have been widely deployed by fisheries managers to increase the concentration of fish at known locations, often without any validation of how well they meet management goals. This study used an innovative sampling method, sonar imagery, to visually evaluate artificial fish habitat designs and their effectiveness in concentrating fish in two turbid North Carolina Piedmont reservoirs. Habitats encompassed equal volumes, but materials and general designs varied; cube habitats were constructed from PVC pipes, plastic barrels, and corrugated plastic pipes, a commercially available product called Porcupine, or evergreen trees. We found that all habitats held significantly more fish than the control sites that were lacking vertical structure. Among artificial habitats, the cubed, corrugated pipe design concentrated significantly more fish than the other designs, and the biodegradability of habitat provided by bundled evergreen trees was reflected in reduced concentrations of fish over time.Received January 28, 2016; accepted August 10, 2016 Published online November 10, 2016

LIBRA: Lightweight Data Skew Mitigation in MapReduce

MapReduce is an effective tool for parallel data processing. One significant issue in practical MapReduce applications is data skew: the imbalance in the amount of data assigned to each task. This causes some tasks to take much longer to finish than others and can significantly impact performance. This paper presents LIBRA, a lightweight strategy to address the data skew problem among the reducers of MapReduce applications. Unlike previous work, LIBRA does not require any pre-run sampling of the input data or prevent the overlap between the map and the reduce stages. It uses an innovative sampling method which can achieve a highly accurate approximation to the distribution of the intermediate data by sampling only a small fraction of the intermediate data during the normal map processing. It allows the reduce tasks to start copying as soon as the chosen sample map tasks (only a small fraction of map tasks which are issued first) complete. It supports the split of large keys when application semantics permit and the total order of the output data. It considers the heterogeneity of the computing resources when balancing the load among the reduce tasks appropriately. LIBRA is applicable to a wide range of applications and is transparent to the users. We implement LIBRA in Hadoop and our experiments show that LIBRA has negligible overhead and can speed up the execution of some popular applications by up to a factor of 4.

Using Shannon's entropy to sample heterogeneous and high‐dimensional atmospheric datasets

AbstractThe construction of diverse and synthetic datasets of atmospheric situations, used as first guesses or training bases for remote‐sensing algorithms, is still a challenge. Numerical constraints require the use of datasets with a limited number of representative situations, but keeping, as much as possible, the full diversity observed in nature. This study presents an innovative sampling method that allows extraction of a new, more limited, dataset from a large database of atmospheric situations. One major issue of such sampling concerns the heterogeneity of the input space variables: different units and ranges of temperatures and specific humidities, for instance, or locations from the lower troposphere to the higher stratosphere, can hardly be compared. We illustrate the fact that sampling using only one variable type is not optimal, since erroneous features can be observed in the other variables not used for the sampling. The use of Shannon's entropy can help to develop a sampling technique able to deal with very heterogeneous variables. A dataset of 10 000 situations is built from EUMETSAT satellite atmospheric retrievals: it includes temperature and water‐vapour profiles, four integrated ozone layers and surface temperature. The sampling increases the entropy of the original dataset from 22 to 28 (about 20% increase).

Population-based approach to study unintentional injury occurrences in Pune city, India

Most injury-related studies in developing countries are hospital based. In India, where there is a high level of poverty, limited access to the health care, many unregistered slums and pavement dwellers, this study attempted to use an innovative sampling method to identify the magnitude of injuries in a population of an urban city in India. Totally, 9014 individuals (2100 households), representative of more than 3.5 million population were selected from 14 administrative wards of the city of Pune. Semi-structured questionnaires were used to elicit information. The annual incidence rate of unintentional injuries was 174 (95% CI 164–184) per 1000 individuals. There were 26 reported cases of death in a recall period of 5 years. Maximum number of unintentional injuries were due to road traffic accidents (49.5%) followed by falls (24.9%). These results showed the magnitude of unintentional injuries among the population. The study sampling method can be employed as a reference for similar studies in other developing countries.

Using SPMDs to Assess Natural Recovery of PCB-contaminated Sediments in Lake Hartwell, SC: I. A Field Test of New In-Situ Deployment Methods

Results from the field testing of some innovative sampling methods developed to evaluate risk management strategies for polychlorinated biphenyl (PCB) contaminated sediments are presented. Semipermeable membrane devices (SPMDs) were combined with novel deployment methods to quantify the availability of PCBs at the Sangamo-Weston Lake Hartwell Superfund Site in SC. Three locations in Lake Hartwell were examined: a background site (BKG) with little detectable contamination and two contaminated sites (T-M/N and T-O). PCB availability was quantified using sediment surface samplers designed to hold SPMDs in contact with surface sediments, benthic dome samplers designed to enclose and suspend SPMDs at the sediment-water interface, and commercially obtained SPMD cages suspended in the water column. A two-way analysis of variance showed significant effects by sampler type (P < 0.0001) and site (P < 0.0001) for mean time-weighted average (TWA) total PCBs (t-PCBs). Regardless of the SPMD sampler used, mean TWA t-PCBs were directly proportional to the level of contamination present (BKG < T-M/N < T-O). Water column and surface sediment sampler t-PCB uptake patterns were described by a significant linear fit of the data (r2 = 0.9625, p < 0.0001, and r2 = 0.8188, p < 0.0001, respectively). Dome and sediment surface SPMD samples had a higher percentage of higher chlorinated PCBs compared to water column samples.

History matching of approximated lithofacies models under uncertainty

In history matching of lithofacies reservoir model, we attempt to find multiple realizations of lithofacies configuration that are conditional to dynamic data and representative of the model uncertainty space. This problem can be formalized in the Bayesian framework. Given a truncated Gaussian model as a prior and the dynamic data with its associated measurement error, we want to sample from the conditional distribution of the facies given the data. A relevant way to generate conditioned realizations is to use Markov chains Monte Carlo (MCMC). However, the dimensions of the model and the computational cost of each iteration are two important pitfalls for the use of MCMC. Furthermore, classical MCMC algorithms mix slowly, that is, they will not explore the whole support of the posterior in the time of the simulation. In this paper, we extend the methodology already described in a previous work to the problem of history matching of a Gaussian-related lithofacies reservoir model. We first show how to drastically reduce the dimension of the problem by using a truncated Karhunen-Loeve expansion of the Gaussian random field underlying the lithofacies model. Moreover, we propose an innovative criterion of the choice of the number of components based on the connexity function. Then, we show how we improve the mixing properties of classical single MCMC, without increasing the global computational cost, by the use of parallel interacting Markov chains. Applying the dimension reduction and this innovative sampling method drastically lowers the number of iterations needed to sample efficiently from the posterior. We show the encouraging results obtained when applying the methodology to a synthetic history-matching case.

Sampling strategies for contaminated brownfield sites

Abstract. Brownfield sites often require a geochemical survey to assess the extent of contamination that is present as a result of previous industrial activities. These measurements are subsequently assessed to ascertain whether the site presents the possibility of causing significant harm to those who may use the site for specified purposes. The measurement process comprises both field sampling and chemical analysis, with sampling being of crucial importance, since previous studies have repeatedly shown that it is the sampling phase that generates the highest component of uncertainty. A variety of methods are currently available for sampling brownfield sites, such as different sampling patterns and the choice of depth and mass recovered. An investigator may also choose to employ more innovative sampling methods, such as in situ measurement strategies that can significantly reduce the overall time taken to complete the survey. The general aim of a sampling strategy is to take representative samples for chemical analysis, although this is rarely achieved due to the inherent heterogeneity of contaminants within any given site. Since it is practically impossible to sample an entire site, and thus achieve a truly representative sample, it is becoming increasingly understood that the uncertainty of the measurements should be estimated, to provide a more reliable interpretation of the survey. Various methods are currently available to estimate the measurement uncertainty that arises from both sampling and analysis, which vary in terms of complexity and cost. The level of uncertainty estimated during a site investigation should also be judged on its fitness‐for‐purpose (i.e. whether subsequent decisions based upon it are acceptable). The ‘optimized contaminated land investigation’ (OCLI) method is a new approach that can be used to balance the site‐specific variables of any given investigation, such as the measurement costs against the level of uncertainty and costs that may arise from misclassification. This provides an objective and traceable judgement of whether the measurements are fit‐for‐purpose.

Bulimia: An Analysis of Moods and Behavior

An innovative sampling method was used to compare normal-weight bulimic patients to normal controls on four dimensions: (1) overall moods, (2) extent of mood fluctuating, (3) degree of social isolation, and (4) extent of food-related behavior. In addition, a sequence analysis was conducted to explore the impact of binging and purging episodes on various affective states among the bulimics. Results indicated that the bulimics experienced significantly more dysphoric and fluctuating moods than normal controls and that they spent much more time alone and in food-related behavior than the control group. The discussion presents a hypothetical integration regarding the etiology and maintenance of the bulimic behavior based on the results of the data and post-trial interviews with the bulimic patients.