Nuisance Effects Research Articles

Neuroimaging of emotion: empirical effects of proportional global signal scaling in fMRI data analysis

Global variations of BOLD-fMRI signal are often considered as nuisance effects. This unwanted source of variance is commonly eliminated using proportional global signal scaling (PGSS). However, application of PGSS relies on the assumption that global variations of BOLD signal and experimental conditions are uncorrelated. It has been shown for cognitive tasks that the unjustified application of PGSS might greatly distort statistical results. The present study examined this issue in the domain of emotion research. Specifically, fMRI data were obtained in a block-design, while 21 subjects passively viewed high and low emotionally arousing pleasant, unpleasant, and neutral pictures. Violations of the orthogonality assumption were found for analyses of emotional pictures high in arousal, causing dramatically different outcomes when compared to analyses performed without PGSS. Application of PGSS was associated with attenuated emotional activation in visual cortical areas, insensitivity to emotional activations in limbic and paralimbic regions, and widely distributed artificial deactivations. In contrast, the orthogonality assumption was not violated for low arousing emotional materials. Thus, the validity of using PGSS varied as a function of the emotional arousal of the stimuli. Taken together, the unwarranted use of PGSS might contribute to conflicting results in affective neuroscience fMRI studies, in particular with respect to limbic and paralimbic structures.

A HIERARCHICAL SPATIAL MODEL OF AVIAN ABUNDANCE WITH APPLICATION TO CERULEAN WARBLERS

Surveys collecting count data are the primary means by which abundance is indexed for birds. These counts are confounded, however, by nuisance effects including observer effects and spatial correlation between counts. Current methods poorly accom- modate both observer and spatial effects because modeling these spatially autocorrelated counts within a hierarchical framework is not practical using standard statistical approaches. We propose a Bayesian approach to this problem and provide as an example of its imple- mentation a spatial model of predicted abundance for the Cerulean Warbler (Dendroica cerulea) in the Prairie-Hardwood Transition of the upper midwestern United States. We used an overdispersed Poisson regression with fixed and random effects, fitted by Markov chain Monte Carlo methods. We used 21 years of North American Breeding Bird Survey counts as the response in a loglinear function of explanatory variables describing habitat, spatial relatedness, year effects, and observer effects. The model included a conditional autoregressive term representing potential correlation between adjacent route counts. Cat- egories of explanatory habitat variables in the model included land cover composition and configuration, climate, terrain heterogeneity, and human influence. The inherent hierarchy in the model was from counts occurring, in part, as a function of observers within survey routes within years. We found that the percentage of forested wetlands, an index of wetness potential, and an interaction between mean annual precipitation and deciduous forest patch size best described Cerulean Warbler abundance. Based on a map of relative abundance derived from the posterior parameter estimates, we estimated that only 15% of the species' population occurred on federal land, necessitating active engagement of public landowners and state agencies in the conservation of the breeding habitat for this species. Models of this type can be applied to any data in which the response is counts, such as animal counts, activity (e.g., nest) counts, or species richness. The most noteworthy practical application of this spatial modeling approach is the ability to map relative species abundance. The functional relationships that we elucidated for the Cerulean Warbler provide a basis for the development of management programs and may serve to focus management and monitoring on areas and habitat variables important to Cerulean Warblers.

Median-of-Subsets Normalization of Intensities for cDNA Array Data

cDNA arrays allow quantitative measurement of expression levels for thousands of genes simultaneously. The measurements are affected by many sources of variation, and substantial improvements in the precision of estimated effects accompany adjustments for these effects. Two generic nuisance variations, one associated with the magnitude of expression and the other associated with array location, are common in data from filter arrays. Procedures, like normalization using lowess regression, are effective at reducing variation associated with magnitude, and they have been widely adopted. However, variation associated with location has received less attention. Here, a simple, but effective method based on localized median is expounded for dealing with these nuisance effects, and its properties are discussed. The proposed methodology handles location-dependent variation ("splotches") and magnitude-dependent variation (background and/or saturation) effectively. The procedure is related to lowess when implemented to adjust magnitude-dependent variation, and it performs similarly. The proposed methodology is illustrated with data from the National Center for Toxicological Research (NCTR), where treatment differences in levels of mRNA from rat hepatocytes were assessed using 33P-labeled samples hybridized to cDNA spotted arrays. Normalizing intensities by the median-of-subsets removes systematic variation associated with the location of a gene on the array and/or the level of its expression. This procedure is easy to implement using iteratively reweighted least-squares algorithms. Although less sophisticated than lowess, this procedure works nearly as well for normalizing intensities based upon their magnitude. Unlike lowess, it can adjust for location-dependent effects.

Median-of-Subsets Normalization of Intensities for cDNA Array Data

cDNA arrays allow quantitative measurement of expression levels for thousands of genes simultaneously. The measurements are affected by many sources of variation, and substantial improvements in the precision of estimated effects accompany adjustments for these effects. Two generic nuisance variations, one associated with the magnitude of expression and the other associated with array location, are common in data from filter arrays. Procedures, like normalization using lowess regression, are effective at reducing variation associated with magnitude, and they have been widely adopted. However, variation associated with location has received less attention. Here, a simple, but effective method based on localized median is expounded for dealing with these nuisance effects, and its properties are discussed. The proposed methodology handles location-dependent variation ("splotches") and magnitude-dependent variation (background and/or saturation) effectively. The procedure is related to lowess when implemented to adjust magnitude-dependent variation, and it performs similarly. The proposed methodology is illustrated with data from the National Center for Toxicological Research (NCTR), where treatment differences in levels of mRNA from rat hepatocytes were assessed using 33P-labeled samples hybridized to cDNA spotted arrays. Normalizing intensities by the median-of-subsets removes systematic variation associated with the location of a gene on the array and/or the level of its expression. This procedure is easy to implement using iteratively reweighted least-squares algorithms. Although less sophisticated than lowess, this procedure works nearly as well for normalizing intensities based upon their magnitude. Unlike lowess, it can adjust for location-dependent effects.

Effects of System and Environment Parameters on the Performance of Network-Based Mobile Station Position Estimators

This paper provides an asymptotic performance evaluation of network-based or multilateral positioning systems, where the times and/or angles of arrival of the signals traveling from a mobile station (MS) to a set of fixed stations (FSs) are used to estimate the MS's position. The effects of the various system-design parameters as well as the effects of biased bearing and time measurements are analyzed, and explicit formulas are derived. Biased measurements can result, for example, from hardware calibration errors or multipath effects, including the lack of line of sight (LoS). Among other results, it is shown that only a few system and cellular parameters can be used to minimize their nuisance effects. The mathematical analysis is based on the Cramer-Rao lower bound (CRLB) and the maximum likelihood theory. It is completed with numerical simulations and a discussion of the positioning performance for two important second-generation cellular systems, GSM and IS-95.

Automated detection of informative combined effects in genetic association studies of complex traits.

There is a growing body of evidence suggesting that the relationships between gene variability and common disease are more complex than initially thought and require the exploration of the whole polymorphism of candidate genes as well as several genes belonging to biological pathways. When the number of polymorphisms is relatively large and the structure of the relationships among them complex, the use of data mining tools to extract the relevant information is a necessity. Here, we propose an automated method for the detection of informative combined effects (DICE) among several polymorphisms (and nongenetic covariates) within the framework of association studies. The algorithm combines the advantages of the regressive approaches with those of data exploration tools. Importantly, DICE considers the problem of interaction between polymorphisms as an effect of interest and not as a nuisance effect. We illustrate the method with three applications on the relationship between (1). the P-selectin gene and myocardial infarction, (2). the cholesteryl ester transfer protein gene and plasma high-density-lipoprotein cholesterol concentration, and (3). genes of the renin-angiotensin-aldosterone system and myocardial infarction. The applications demonstrated that the method was able to recover results already found using other approaches, but in addition detected biologically sensible effects not previously described.

Is Comprehensive Education Really Free?: A Case-Study of the Effects of Secondary School Admissions Policies on House Prices in One Local Area

SummaryThe paper reports on a study that tests the anecdotal hypothesis that parents are willing to pay a premium to secure places for their children in popular and oversubscribed comprehensive schools. Since many local education authorities use admissions policies that are based on catchment areas and places in popular schools are very difficult to obtain from outside these areas—but very easy from within them—parents have an incentive to move house for the sake of their children's education. This would be expected to be reflected in house prices. The study uses a cross-sectional sample based on two popular schools in one local education authority area, Coventry. Differences in quality of housing are dealt with by using the technique of hedonic regression and differences in location by sample selection within a block sample design. The sample was chosen from a limited number of locations spanning different catchment areas to reduce both observable and unobservable variability in nuisance effects while maximizing the variation in catchment areas. The results suggest that there are strong school catchment area effects. For one of the two popular schools we find a 20% premium and for the other a 16% premium on house prices ceteris paribus.

Assessing the environmental impact of WWTP expansion: odour nuisance and its minimization

As part of the effort to provide proper wastewater disposal for the City of Milan, the expansion of the WWTP located in Peschiera Borromeo has been planned and is currently under completion. The plant, sized for a population of less than 300,000, will soon treat the wastes from the south-east areas of Milan for a total capacity of over 500,000 p.e. The paper describes the approach to find a satisfactory solution of an alleged odour problem that is slowing down the completion of the plant restructuring. This included a survey of the existing plant and analysis of its final design, identification of odour emission sources and their quantification, and the examination of different alternatives for odour abatement. These were carried out using air quality modelling techniques consisting of dynamic, continuous "puff" models capable of reproducing diffusion even at very low pollutant concentrations. Several intervention hypotheses were tested and compared with the few existing regulatory norms and guidelines for odour pollution. In all but the minimum and the no-action hypotheses, proposed actions would results in a drastic reduction of nuisance effects at the receptors. Under the strongest intervention hypothesis (the one adopted by the WWTP agency), odour impact would be virtually eliminated.

Estimation of the Head Sensitivity Function in Scanning Magnetoresistance Microscopy

We apply Bayesian image analysis techniques to a problem in a newly developed scanned probe technology that uses commercial magnetoresistive (MR) record and playback heads as probes to sense magnetic fields. This technology can be used for magnetic imaging and for evaluating playback and record processes in magnetic recording. In MR microscopy, an MR head is raster scanned while in physical contact with a magnetic sample (e.g., hard disk media, tape, or fine magnetic particles). By plotting the MR resistance as a function of position, a very high resolution (on the order of .1 × 1.0μm) magnetic image of the sample is constructed. This case study focuses on characterizing the head sensitivity function (HSF), which depends on the physical dimensions and the magnetic properties of the MR head. These sensitivity functions are of great practical interest because they ultimately relate to the head's performance in a high-density data storage environment. Estimating the HSF requires a deconvolution that has features that prevent the problem from being straightforward: both the HSF and the source being scanned are unknown, and there is a substantial amount of correlated noise in the scanned image. We take a Bayesian approach to model and estimate the HSF, while accounting for noise and other nuisance effects such as thermal drift. Besides yielding a point estimate, which is a fairly difficult task here, this approach also quantifies uncertainty so we can assess whether certain features of the estimated head sensitivity function appear to be genuine.

Assessment of uncertainty in parameter evaluation and prediction

Like in all experimental science, chemical data is affected by the limited precision of the measurement process. Quality control and traceability of experimental data require suitable approaches to express properly the degree of uncertainty. Noise and bias are nuisance effects reducing the information extractable from experimental data. However, because of the complexity of the numerical data evaluation in many chemical fields, often mean values from data analysis, e.g. multi-parametric curve fitting, are reported only. Relevant information on the interpretation limits, e.g. standard deviations or confidence limits, are either omitted or estimated. Modern techniques for handling of uncertainty in both parameter evaluation and prediction are strongly based on the calculation power of computers. Advantageously, computer-intensive methods like Monte Carlo resampling and Latin Hypercube sampling do not require sophisticated and often unavailable mathematical treatment. The statistical concepts are introduced. Applications of some computer-intensive statistical techniques to chemical problems are demonstrated.

Pyrethroid-induced paresthesia--a central or local toxic effect?

Pyrethroid-induced paresthesia is frequently seen after dermal exposure to pyrethroids. Affected individuals experience a sensation of burning, tingling, itching, or numbness, most commonly in the face. This occurs 1-2 hours after the beginning of exposure and resolves spontaneously. Paresthesia occurs as a result of a direct effect on intracutaneous nerve endings at very low pyrethroid doses. It is related to potency of the pyrethroid with pyrethroids without an alpha-cyano group generally showing the weakest effect. Doses sufficient to cause paresthesia are far lower than those causing central or systemic toxicity. Paresthesia is therefore considered to be a localized nuisance effect. The best advice to affected individuals is to prevent paresthesia from occurring through appropriate hygiene measures and personal protection.

Measuring the Impact of Light Rail Systems on Single-Family Home Values: A Hedonic Approach with Geographic Information System Application

In theory, proximity to light rail transit (LRT) may have two different effects on residential property values. On the one hand, accessibility (proximity to LRT stations) may increase property values. On the other hand, nuisance effects (proximity to the LRT line and stations) may decrease property values. Existing empirical studies are inconclusive, and failure to separate the effects of accessibility from the nuisance effects may explain some of the ambiguity. An examination is presented of the impact of the light rail system (MAX) in Portland, Oregon, on single-family home values using distance to rail stations as a proxy for accessibility and distance to the line itself as a proxy for nuisance effects. Geographic information system techniques are employed to create spatial-related variables and merge data from various sources. The study results confirm the hypothesis that the light rail has both a positive effect (accessibility effect) and a negative effect (nuisance effect) on single-family home values. The positive effect dominates the negative effect, which implies a declining price gradient as one moves away from LRT stations for several hundred meters. Without controlling for the nuisance effect of the distance to the rail line, the estimated coefficients on distance from stations appear to be biased and would underestimate the accessibility effect. The finding of an independent nuisance effect suggests that previous hedonic models may have reached contradictory results because the nuisance effect differs with different types of rail or other local characteristics.

Politics and Markets in the Articulation of Preferences for Attributes of the Rapidly Changing Food and Agricultural Sectors: Framing the Issues

AbstractIndustrialization of the food and agricultural sectors changes the pattern of external effects. Participants helped or harmed in the process attempt to influence outcomes through markets and politics. Decisions about property rights and boundaries determine benefits and burdens and the relative cost of animal agriculture in different jurisdictions. Prescriptions to redefine property rights are influenced by selective perception of rights to share in the benefits and be protected from costs. Political choices about the appropriate jurisdiction (state versus local) for addressing environmental and nuisance effects of animal agriculture affect whose preferences count and will influence the development of these sectors.

A Semiparametric Transformation Approach to Estimating Usual Daily Intake Distributions

Abstract The distribution of usual intakes of dietary components is important to individuals formulating food policy and to persons designing nutrition education programs. The usual intake of a dietary component for a person is the long-run average of daily intakes of that component for that person. Because it is impossible to directly observe usual intake for an individual, it is necessary to develop an estimator of the distribution of usual intakes based on a sample of individuals with a small number of daily observations on a subsample of the individuals. Daily intake data for individuals are nonnegative and often very skewed. Also, there is large day-to-day variation relative to the individual-to-individual variation, and the within-individual variance is correlated with the individual means. We suggest a methodology for estimating usual intake distributions that allows for varying degrees of departure from normality and recognizes the measurement error associated with one-day dietary intakes. The estimation method contains four steps. First, the original data are standardized by adjusting for nuisance effects, such as day-of-week and interview sequence. Second, the daily intake data are transformed to normality using a combination of power and grafted polynomial transformations. Third, using a normal components-of-variance model, the distribution of usual intakes is constructed for the transformed data. Finally, a transformation of the normal usual intake distribution to the original scale is defined. The approach is applied to data from the 1985 Continuing Survey of Food Intakes by Individuals and works well for a set of dietary components that are consumed nearly daily and exhibit varying distributional shapes.

Introducing insecticide impregnated bednets in an area of low bednet usage: an exploratory study in north-east Ghana.

To find out the acceptability of the use of insecticide impregnated bednets before launching a large-scale trial to evaluate their impact on child mortality, 96 permethrin impregnated bednets were distributed in 4 communities within the Kassena Nankana district of the Upper East Region of Ghana, where previously only 4% of the people had owned a mosquito net. The nets were readily accepted and used by the recipients. The major benefit perceived by the users was the reduction of the nuisance effect of mosquitoes and other insects. The people in the study area normally sleep on mats in either an open courtyard or a sleeping room depending on the weather but this did not deter them from using the nets. The white nets distributed for this study became dirty with use, and users thought they needed to be washed. In order to discourage this, it is recommended that dark coloured nets be used in the main intervention trial. After having used the nets for a year, the community members expressed willingness to buy the nets if they were made available after the harvest season when they had sold their crops and had enough money to pay for them. The results of this study have been used to plan and conduct a large intervention trial.

The assessment of individual and population bioequivalence.

We develop a statistical methodology for the assessment of individual bioequivalence when a crossover design is invoked. The location parameters for our model consist of population-averaged parameters for formulation, population-averaged parameters for nuisance effects (sequence, period, carryover, etc.), and subject-specific parameters for formulation. We do not impose any distributional assumptions other than the existence of first- and second-order moments. We derive unbiased estimators for all of the parameters in the model and construct subject-specific bioequivalence scores which exclude the effects of the nuisance parameters. We assess individual bioequivalence by constructing distribution-free tolerance intervals based on the sample of bioequivalence scores.

Road traffic nuisance in residential and commercial areas

Air pollution from traffic is one of the main factors considered in the environmental appraisal of road schemes. Currently this appraisal concentrates on the emission and roadside concentration of those regulated pollutants which are potentially harmful to the health or well-being of human, animal or plant life, or to ecological systems. However, vehicle emissions, especially those from diesel vehicles, may also cause a number of aesthetic and nuisance problems, such as visibility reduction, urban soiling and physical irritation. A methodology to investigate the subjective nuisance effects of air pollution from road traffic on the public has been developed and tested. The data indicates that vehicle-derived air pollution was an issue of high relative importance to the public when compared to other major social issues. On a local level, the physical presence of road traffic and its associated pollution appeared to be the largest contributors to outdoor public environmental nuisance. Indoors, the public appeared to experience only minor disturbances from vehicle-derived pollution, with the average respondent being not very bothered by vehicle-derived smoke, fumes and odour, dust and dirt and general air pollution. Noise appeared to cause the greatest indoor traffic-related nuisance, although many respondents complained about soiling from dust/dirt. The surveys suggest that outdoor disturbance from vehicle-derived air pollution was fairly high, with smoke, fumes and odour causing the greatest annoyance. The main reason given for disturbance from outdoor smoke, fumes and odour and dust/dirt was concern that they would harm the public's health. Other important specific reasons included soiling and the smell of the fumes. The data also suggests that there can be significant differences in disturbance between sites in the same and different cities, between males and females and between different age groups. No significant differences in annoyance were noted between smokers/non-smokers and different socio-economic groupings. In addition, the level of nuisance experienced by people in urban areas did not depend upon the proximity of their home/workplace to a road.

The occurrence of Gonyostomum semen (Ehr.) Diesing in Finnish lakes

Since the early nineteen-eighties swimmers have complained of the nuisance effect of Gonyostomum semen in Finnish lakes. This alga causes an unpleasant slimy coating on the skin after swimming. Although it was first identified in Finland in 1894, the first complaints concerning G. semen were reported to the Finnish water authorities in 1978. During the period 1978–1989 a total of 110 water samples were qualitatively microscoped for G. semen. According to the results the alga seems to have spread from the south-eastern part of Finland throughout the southern part of the country and northwards almost to the Arctic circle. 139 quantitative samples from monitored lakes were also analysed. The alga seems to prefer dystrophic and eutrophic conditions.

The effect of relocation on the externality fields of football stadia: The case of St Johnstone FC

Abstract Football grounds generate negative externalities on their surrounding areas. This is largely a function of their location on cramped inner‐city sites which are surrounded by high‐density residential areas. It has been suggested that one of the advantages of the relocation of football clubs to edge‐of‐town locations will be the elimination of such negative externalities. This hypothesis is examined by means of a case study of St Johnstone FC based in Perth, Scotland, which relocated to a new edge‐of‐town stadium in 1989. The study concludes that relocation has not eliminated football‐generated nuisance effects. However, because about three‐quarters of the new stadium's externality field comprises non‐residential areas, the number of people who experience football‐generated nuisances is less than was the case at the club's former inner‐city stadium.

Resistance of Permethrin to Weathering in Fabrics Treated for Protection Against Mosquitoes (Diptera: Culicidae)

Two different methods of treating cotton and nylon-cotton fabrics with permethrin were evaluated for protection from mosquito bites after laboratory weathering. Cotton fabric treated by the individual dynamic absorption method provided consistently better protection than cotton fabric treated by the aerosol method. The nylon-cotton fabric provided similar protection regardless of the treatment method. After weathering, the toxic effects of both types of permethrin-treated fabrics treated by both methods diminished much more rapidly than did the repellent effect. Low residual amounts of permethrin in the fabrics provided 85% protection from bites against Aedes aegypti (L.) and 93% protection against Anopheles stephensi Liston. Permethrin-treated fabrics were effective in providing protection from mosquito bites for long periods, even after exposure to weathering, and appear to be an effective means of reducing nuisance effects and disease transmission by mosquitoes.