Influential Predictor Variables Research Articles

Predicting geogenic Arsenic in Drinking Water Wells in Glacial Aquifers, North‐Central USA: Accounting for Depth‐Dependent Features

AbstractChronic exposure to arsenic (As) via drinking groundwater is a human health concern worldwide. Probabilities of elevated geogenic As concentrations in groundwater were predicted in complex, glacial aquifers in Minnesota, north‐central USA, a region that commonly has elevated As concentrations in well water. Maps of elevated As hazard were created for depths typical of drinking water supply and with well construction attributes common for domestic wells. Conventional variables describing aquifer properties and materials, position on the hydrologic landscape, and soil geochemistry were among the most influential for predicting the probability of elevated As. We also found that certain well construction attributes were influential in predicting As hazard. Smaller distances between the top of the well screen and overlying aquitard (proximity) and shorter well screen lengths were each associated with higher probabilities of elevated As. Influential predictor variables, which are either mapped across the region or are well construction attributes, are proxies in the model for measurable physical or geochemical causes of elevated As (e.g., redox condition, till or aquifer sediment chemistry, and water chemistry), which are not mapped across the region. Our setting shares some important characteristics with deltaic and other high‐As aquifers in Southeast Asia: late Quaternary age, complex layering of coarse‐ and fine‐grained materials, low‐As sediment concentrations, and geochemical controls on As mobilization. Translating three‐dimensional geologic and geochemical understanding of As mobility to quantifiable variables for modeling with powerful, flexible statistical tools could improve predictions and help identify safer groundwater supply options in the USA, Southeast Asia, and elsewhere.

Landscape effects on demersal fish revealed by field observations and predictive seabed modelling.

Nature conservation and fisheries management often focus on particular seabed features that are considered vulnerable or important to commercial species. As a result, individual seabed types are protected in isolation, without any understanding of what effect the mixture of seabed types within the landscape has on ecosystem functions. Here we undertook predictive seabed modelling within a coastal marine protected area using observations from underwater stereo-video camera deployments and environmental information (depth, wave fetch, maximum tidal speeds, distance from coast and underlying geology). The effect of the predicted substratum type, extent and heterogeneity or the diversity of substrata, within a radius of 1500 m around each camera deployment of juvenile gadoid relative abundance was analysed. The predicted substratum model performed well with wave fetch and depth being the most influential predictor variables. Gadus morhua (Atlantic cod) were associated with relatively more rugose substrata (Algal-gravel-pebble and seagrass) and heterogeneous landscapes, than Melanogrammus aeglefinus (haddock) or Merlangius merlangus (whiting) (sand and mud). An increase in M. merlangus relative abundance was observed with increasing substratum extent. These results reveal that landscape effects should be considered when protecting the seabed for fish and not just individual seabed types. The landscape approach used in this study therefore has important implications for marine protected area, fisheries management and monitoring advice concerning demersal fish populations.

The impact of over-regulation on small enterprises

Khale (2015), Marivate (2014) and Asah, Fatoki & Rungani (2015) have highlighted key obstacles of sustained growth and development in start-up enterprises in South Africa. All authors have shown that lack of efficient services, too much bureaucracy, over-regulation, lack of entrepreneurial skills and lack of good governance constitute key obstacles to growth and development in start-up enterprises. This paper is a result of a 3-year long survey (2012 to 2014) that was conducted in the City of Tshwane in order to identify and quantify key predictors of adequate municipal services that are routinely provided to customers who operate newly established small businesses in the Tshwane region of Gauteng Province in South Africa. Data was collected by using a structured, pre-tested and validated questionnaire of study from a stratified random sample of size 1, 058 small businesses. The aim of study was to assess the impact of over-regulation and bureaucracy on the long-term survival and viability in small enterprises. Data analyses were performed by using probit analysis and the Cox Proportional Hazards Model. Additional analyses were performed by using in-depth interviews. The study showed that there was a significant association between the perception of over-regulation and failure in small enterprises. The results showed that 74% of businesses that failed were operated by individuals who had the perception of over-regulation and too much bureaucracy. The corresponding figure for viable businesses was only 11%. The viability of businesses was significantly influenced by 3 predictor variables. These 3 influential predictor variables were: negative perception on the quality of municipal services provided to newly established businesses [Hazard Ratio = 3.58; P=0.000; 95% C. I. = (1.45, 5.46)], inappropriate policy [Hazard Ratio = 3.19; P=0.000; 95% C. I. = (1.39, 5.28)], and lack of tailor made training programmes directed at newly established small businesses [Hazard Ratio = 2.89; P=0.000; 95% C. I. = (1.24, 4.77)], in a decreasing order of strength. Similar findings were obtained from the analyses of in-depth interviews.

Supplemental oxygen users with pulmonary fibrosis perceive greater dyspnea than oxygen non-users

Background: Exertional dyspnea is a hallmark symptom of fibrosing interstitial lung disease (fILD), and oxygen (O2) desaturation is common among patients with fILD. Supplemental O2 is prescribed to maintain normoxia and alleviate dyspnea. We sought to better understand the associations between O2 and dyspnea in fILD during the 6-min walk test (6MWT).
 Methods: 1326 fILD patients compose the sample group. Borg dyspnea and other 6MWT variables were compared between subjects who performed the test without (non-users) versus with O2 (users).
 Results: There were 812 users and 514 non-users; users were older, more likely to have smoked, had greater body mass index, and had more severe fILD. Despite a similar 6-min SpO2, users perceived greater dyspnea than non-users (Borg 3.9 ± 2.0 vs 2.9 ± 1.7, p < 0.0001). Whether subjects became hypoxemic (6-min SpO2 < 89 %) or not during the walk, the results were the same: users perceived greater dyspnea than non-users (hypoxemic: users 3.5 ± 2.1 vs non-users 2.7 ± 1.8, p < 0.0001; non-hypoxemic: users 3.4 ± 1.9 vs non-users 2.4 ± 1.6, p < 0.0001). Among subjects who did not desaturate (SpO2 drop < 4 %), users walked a shorter distance (944.9 ± 367.0 vs 1385.3 ± 322.4 feet, p < 0.0001) but perceived greater dyspnea than non-users (3.3 ± 1.6 vs 2.3 ± 1.7, p = 0.005). No combination of potentially influential predictor variables entered in multivariate models explained more than 11 % of the variance in dyspnea ratings.
 Conclusion: Dyspnea is a complex perception, and in patients with fILD, O2 may lessen, but does not resolve, it. Further research is needed to clarify why fILD patients who use O2 perceive greater levels of dyspnea with activity than O2 non-users.

Supplemental oxygen users with pulmonary fibrosis perceive greater dyspnea than oxygen non-users.

BackgroundExertional dyspnea is a hallmark symptom of fibrosing interstitial lung disease (fILD), and oxygen (O2) desaturation is common among patients with fILD. Supplemental O2 is prescribed to maintain normoxia and alleviate dyspnea. We sought to better understand the associations between O2 and dyspnea in fILD during the 6-min walk test (6MWT).Methods1326 fILD patients compose the sample group. Borg dyspnea and other 6MWT variables were compared between subjects who performed the test without (non-users) versus with O2 (users).ResultsThere were 812 users and 514 non-users; users were older, more likely to have smoked, had greater body mass index, and had more severe fILD. Despite a similar 6-min SpO2, users perceived greater dyspnea than non-users (Borg 3.9 ± 2.0 vs 2.9 ± 1.7, p < 0.0001). Whether subjects became hypoxemic (6-min SpO2 < 89 %) or not during the walk, the results were the same: users perceived greater dyspnea than non-users (hypoxemic: users 3.5 ± 2.1 vs non-users 2.7 ± 1.8, p < 0.0001; non-hypoxemic: users 3.4 ± 1.9 vs non-users 2.4 ± 1.6, p < 0.0001). Among subjects who did not desaturate (SpO2 drop < 4 %), users walked a shorter distance (944.9 ± 367.0 vs 1385.3 ± 322.4 feet, p < 0.0001) but perceived greater dyspnea than non-users (3.3 ± 1.6 vs 2.3 ± 1.7, p = 0.005). No combination of potentially influential predictor variables entered in multivariate models explained more than 11 % of the variance in dyspnea ratings.ConclusionDyspnea is a complex perception, and in patients with fILD, O2 may lessen, but does not resolve, it. Further research is needed to clarify why fILD patients who use O2 perceive greater levels of dyspnea with activity than O2 non-users.

Identifying Suitable Locations for Mesophotic Hard Corals Offshore of Maui, Hawai‘i

Mesophotic hard corals (MHC) are increasingly threatened by a growing number of anthropogenic stressors, including impacts from fishing, land-based sources of pollution, and ocean acidification. However, little is known about their geographic distributions (particularly around the Pacific islands) because it is logistically challenging and expensive to gather data in the 30 to 150 meter depth range where these organisms typically live. The goal of this study was to begin to fill this knowledge gap by modelling and predicting the spatial distribution of three genera of mesophotic hard corals offshore of Maui in the Main Hawaiian Islands. Maximum Entropy modeling software was used to create separate maps of predicted probability of occurrence and uncertainty for: (1) Leptoseris, (2) Montipora, and (3) Porites. Genera prevalence was derived from the in situ presence/absence data, and used to convert relative habitat suitability to probability of occurrence values. Approximately 1,300 georeferenced records of the occurrence of MHC, and 34 environmental predictors were used to train the model ensembles. Receiver Operating Characteristic (ROC) Area Under the Curve (AUC) values were between 0.89 and 0.97, indicating excellent overall model performance. Mean uncertainty and mean absolute error for the spatial predictions ranged from 0.006% to 0.05% and 3.73% to 17.6%, respectively. Depth, distance from shore, euphotic depth (mean and standard deviation) and sea surface temperature (mean and standard deviation) were identified as the six most influential predictor variables for partitioning habitats among the three genera. MHC were concentrated between Hanaka‘ō‘ō and Papawai Points offshore of western Maui most likely because this area hosts warmer, clearer and calmer water conditions almost year round. While these predictions helped to fill some knowledge gaps offshore of Maui, many information gaps remain in the Hawaiian Archipelago and Pacific Islands. This approach may be used to identify other potentially suitable areas for MHCs, helping scientists and resource managers prioritize sites, and focus their limited resources on areas that may be of higher scientific or conservation value.

Differential Factors of Efficiency in the Management of Solid Waste in the City of Tshwane, South Africa

The objective was to investigate factors that affect the efficient management of solid waste produced by commercial businesses operating in the City of Pretoria, South Africa. Data were gathered from 1,034 businesses. Efficiency in solid waste management was assessed using a structural time-based model designed for evaluating efficiency as a function of the length of time required to manage waste. Data analysis was performed using statistical procedures such as frequency tables, Pearson's chi-squared tests of association and binary logistic regression analysis. Odds ratios estimated from logistic regression analysis were used to identify key factors that affect efficiency in the proper disposal of waste. The study showed that 857 of the 1,034 businesses selected for the study (83%) were found to be efficient enough with regards to the proper collection and disposal of solid waste. Based on odds ratios estimated from binary logistic regression analysis, efficiency in the proper management of solid waste was significantly influenced by 4 predictor variables. These 4 influential predictor variables are: lack of adherence to waste management regulations, wrong perception, failure to provide customers with enough trash cans, and operation of businesses by employed managers, in decreasing order of importance.

An Attempt at Quantifying Factors that Affect Efficiency in the Management of Solid Waste Produced by Commercial Businesses in the City of Tshwane, South Africa

Objective. The objective was to investigate factors that affect the efficient management of solid waste produced by commercial businesses operating in the city of Pretoria, South Africa. Methods. Data was gathered from 1,034 businesses. Efficiency in solid waste management was assessed by using a structural time-based model designed for evaluating efficiency as a function of the length of time required to manage waste. Data analysis was performed using statistical procedures such as frequency tables, Pearson's chi-square tests of association, and binary logistic regression analysis. Odds ratios estimated from logistic regression analysis were used for identifying key factors that affect efficiency in the proper disposal of waste. Results. The study showed that 857 of the 1,034 businesses selected for the study (83%) were found to be efficient enough with regards to the proper collection and disposal of solid waste. Based on odds ratios estimated from binary logistic regression analysis, efficiency in the proper management of solid waste was significantly influenced by 4 predictor variables. These 4 influential predictor variables are lack of adherence to waste management regulations, wrong perception, failure to provide customers with enough trash cans, and operation of businesses by employed managers, in a decreasing order of importance.

Spousal characteristics as predictors of well-being in older couples.

This study examined the relations between spousal variables and the psychological well-being of husbands and wives in older couples to determine if spousal characteristics were more important determinants of well-being for wives than for husbands. One hundred-twenty older married men and women completed standardized self-report measures and a short interview. The variables investigated included education, verbal intelligence, personality, physical health, marital adjustment, psychological well-being, as well as response bias to marital defensiveness. Spousal variables significantly predicted wives' well-being (R2 = 29%) with the three most influential predictor variables being the husbands' perception of the marriage, positive dimension of well-being and physical health. In contrast, spousal variables did not significantly predict husbands' well-being. The study supported the hypothesis of differential responsiveness of men and women to spousal variables and highlighted the importance of marital adjustment for the psychological well-being of older wives.