Thomas J. Fisher

• PhD
• Professor (Associate) at Miami University

Cisco (Otoonapii in Ojibwe; Coregonus artedi Lesueur, 1818), is a widely distributed stenothermic freshwater fish whose embryos typically incubate under ice and in the dark. We used Cisco as a model organism for testing the potential of UV‐induced escape hatching behaviour. Owing to reduced ice cover and increased water transparency in north temper...

Agricultural land cover in the U.S. Midwest is a major source of nutrient pollution that has led to impairment of stream water quality. This study examines the impact of a forested state park on nutrient concentrations within an agriculturally dominated watershed. Water samples were collected over a 2‐year study period from eight stream sampling si...

Elevated nutrient and suspended sediment concentrations often result in negative environmental impacts within freshwater environments. Studies that directly compare suspended sediment and bioavailable nutrients between predominantly agricultural and predominantly urban watersheds during baseflow conditions are largely lacking. The purpose of this s...

It is the concern of policymakers every year in New York City to consider whether or not the enacted rent control policy has a positive effect on the rental market. In order to measure the efficacy of the rent control policy, we aim to study the change in housing quality of people who live in rent controlled homes compared to those in non-rent cont...

We explore the quality of life of immigrants in New York City through housing and neighborhood conditions by creating a happiness metric to measure a household’s quality of life. Utilizing data provided by the New York City Housing and Vacancy Survey, the New York City Police Department, the New York City Department of Education, the New York City...

One of the more popular usages of predictive modeling is in the forecasting of weather. We use machine learning techniques to spatially extend provided forecasts to sites across the continental United States. The forecasts and observed weather for 113 sites across the United States (2014–2017) were used, along with supplementary data on observed we...

A new portmanteau test statistic is proposed for detecting nonlinearity in time series data. The new portmanteau statistic is calculated from the log of the determinant of a matrix comprised of the autocorrelations and cross-correlations of the residuals and squared residuals of a fitted time series. The asymptotic distribution of the proposed test...

We propose a framework to detect and model shifts in a time series of continuous proportions, that is, a vector of proportions measuring the parts of a whole. By reparameterizing the shape of a Dirichlet distribution, we can model the location and scale separately through generalized linear models. A hidden Markov model allows the coefficients of t...

Each year the National Highway Traffic Safety Administration and Insurance Institute for Highway Safety release safety ratings for popular makes and models of vehicles produced. We link these safety ratings with the crash data provided in the National Automotive Sampling System General Estimates System to study the efficacy of safety ratings as a p...

The comparison of two time series often arises in climatology, environmental science, and econometrics. Through natural and physical circumstances these series are often dependent. We develop a hypothesis test for the equality of autocovariance functions for two linearly dependent multivariate time series. Previous tests for two independent series...

Despite the precipitous decline of airborne lead concentrations following the removal of lead in gasoline, lead is still detectable in ambient air in most urban areas. Few studies, however, have examined the health effects of contemporary airborne lead concentrations in children. Methods: We estimated monthly air lead exposure among 263 children...

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Mosquitoes have increased in their abundance and geographic distribution in northeastern North America, coinciding with an increase in extreme precipitation events and up to a doubling of dissolved organic matter (DOM) concentrations in some inland waters. Increases in DOM can reduce exposure of mosquito larvae to solar ultraviolet (UV) radiation....

We study the problem of determining if two time series are correlated in the mean and variance. Several test statistics, originally designed for determining the correlation between two mean processes or goodness-of-fit testing, are explored and formally introduced for determining cross-correlation in variance. Simulations demonstrate the theoretica...

Celebrity suicides that are reported heavily in the media may increase risk for others' suicidal behavior. This study examined whether Internet search volumes for suicide-related terms changed after three celebrity suicide deaths (Robin Williams, Chester Bennington, and Alexander McQueen) and three celebrities who died by means other than suicide (...

Impacts between urban and agricultural land cover on storm flow water quality are poorly understood for the Eastern Corn Belt Ecoregion in SW Ohio. Storm flow water samples were collected from May 2017 to October 2017 across seven SW Ohio watersheds which ranged in urban land cover from 6% to 92% and in agricultural land cover from 4% to 70%. Two w...

Stream water quality can be greatly influenced by changes in agricultural practices, but studies of long‐term dynamics are scarce. Here we describe trends over 21 yr (1994–2014) in nutrients and suspended sediments in three streams in a Midwestern US agricultural watershed. During this time, the watershed experienced substantial changes in agricult...

In recent decades, terrestrial dissolved organic matter (DOM) has increased in many northeastern North American and European lakes and is contributing to long-term browning. We used a long-term dataset (1988–2014) to study the consequences of browning-related decreased water transparency on dissolved oxygen dynamics in 2 small temperate lakes in Pe...

The correlation structure of time series is of fundamental importance in diagnostic procedures. The squared autocorrelation function of the residuals of a fitted model is generally used as a measure of the goodness-of-fit; multivariate analogues are available for vector time series. As an alternative, we propose a logarithmic transformation of the...

Surface water temperatures are warming in many lakes across the globe, and this is widely attributed to warming air temperatures. Yet two lakes in Pennsylvania (USA) have shown long-term increases in surface water temperatures over the past 27 summers during a period with no significant increase in regional air temperature. We examined the relation...

Critical values and p-values of statistical hypothesis tests are often derived using asymptotic approximations of sampling distributions. However, this sometimes results in tests that are conservative (i.e., understate the frequency of an incorrectly rejected null hypothesis by employing too stringent of a threshold for rejection). Although computa...

This article presents a new test for serial correlation in an observed stationary time series. Rather than using the traditional portmanteau tests based on the sample autocorrelation function, we propose a test based on the Cauchy estimator of correlation. A goodness-of-fit statistic for fitted autoregressive moving average models is also derived a...

Recent work in the literature has shown weighted variants of the classic portmanteau test for time series can be more powerful in many situations. In this article, we study the asymptotic distribution of weighted sums of the squared residual autocorrelations where both the sample size n and maximum lag of the statistic m grow large. Several weighti...

An often studied problem in time series analysis is that of testing for the independence of two (potentially multivariate) time series. Toeplitz matrices have demonstrated utility for the related setting of time series goodness-of-fit testing - ergo, herein, we extend those concepts by defining a nontrivial block Toeplitz matrix for use in the sett...

We study goodness-of-fit testing for non-causal autoregressive time series with non-Gaussian stable noise. To model time series exhibiting sharp spikes or occasional bursts of outlying observations, the exponent of the non-Gaussian stable variables is assumed to be less than two. Under such conditions, the innovation variables have no finite second...

We exploit ideas from high-dimensional data analysis to derive new portmanteau tests that are based on the trace of the square of the mth order autocorrelation matrix. The resulting statistics are weighted sums of the squares of the sample autocorrelation coefficients that, unlike many other tests appearing in the literature, are numerically stable...

This article explores the problem of testing the hypothesis that the covariance matrix is an identity matrix when the dimensionality is equal to the sample size or larger. Two new test statistics are proposed under comparable assumptions to those statistics in the literature. The asymptotic distribution of the proposed test statistics are found and...

Fragment size, distance between mutation and marker insertion site, and efficiency of mutation incorporation for gsSSG mutagenesis. This Excel file lists the efficiency of incorporating the targeted mutation among total FOAR isolates for each targeted transformation using gsSSG mutagenesis. Column A shows the strain transformed with a PCR fragment...

Fragment size, distance between near end and marker insertion site, and efficiency of marker replacement for standard SSG mutagenesis. This Excel file lists the efficiency of marker replacement (i.e. the recombinant fraction) among total FOAR isolates for each targeted transformation using standard SSG mutagenesis. Column A shows the strain transfo...

Fragment size, distance between near end and marker insertion site, and efficiency of marker replacement forgsSSG mutagenesis. This Excel file lists the efficiency of marker replacement (i.e. the recombinant fraction) among total FOAR isolates for each targeted transformation using gsSSG mutagenesis. Column A shows the strain transformed with a PCR...

Precise targeted mutations are defined as targeted mutations that do not require the retention of other genetic changes, such as marker genes, near the mutation site. In the yeast, S. cerevisiae, there are several methods for introducing precise targeted mutations, all of which depend on inserting both a counter-selectable marker and DNA bearing th...

Many applications require an estimate for the covariance matrix that is non-singular and well-conditioned. As the dimensionality increases, the sample covariance matrix becomes ill-conditioned or even singular. A common approach to estimating the covariance matrix when the dimensionality is large is that of Stein-type shrinkage estimation. A convex...

In this paper we propose a new test procedure for sphericity of the covariance matrix when the dimensionality, p, exceeds that of the sample size, N=n+1. Under the assumptions that (A) 0trΣi/p∞ as p→∞ for i=1,…,16 and (B) p/n→c∞ known as the concentration, a new statistic is developed utilizing the ratio of the fourth and second arithmetic means of...