Genetic Interactions and Gene-by-Environment Interactions in Evolution

The phenotypic effect of a mutation depends on both genetic interactions (G×G) and gene-by-environment interactions (G×E). G×G and G×E can distort the additive relationship between genotypes and phenotypes and complicate biological and biomedical studies. Understanding the patterns and mechanisms of these interactions is important for predicting evolutionary trajectories, designing plant and animal breeding strategies, detecting “missing heritability”, and guiding “personalized medicine”. In this thesis, I study how G×G and G×E affect mutational effects, including developing new methods and new models. Recent advancements in high-throughput DNA sequencing and high-throughput phenotyping provide powerful tools to study the relationships among genotypes, phenotypes, and the environment at unprecedented scales. Therefore, I take advantage of several published large datasets in my study, each containing hundreds to thousands of different genotypes of model organisms and their corresponding phenotypes in tens of environments. In Chapter 2, I report some general patterns of G×E and demonstrate the importance of considering potential environmental variations in mapping quantitative trait loci. In Chapter 3, I report how the environment affects diminishing returns epistasis and propose a modular life model to explain the patterns of diminishing returns. In Chapter 4, I propose and demonstrate that genetic dominance is a special case of diminishing returns epistasis. In Chapter 5, I report how and why the relationship between growth rate (r) and carrying capacity (K) in density-dependent population growth varies across environments. In Chapter 6, I demonstrate the existence of an intermediate optimal mating distance for hybrid performance in three model organisms. Overall, I find that large genomic and phenomic data are useful resources to address classical genetic questions, such as the origin of dominance (Chapter 4), the relationship between r and K (Chapter 5), and presence of an optimal mating distance (Chapter 6). The environment is a key player in the phenotypic effects of mutations, but it is also a high-dimension complex system that is hard to quantify. In this thesis, I define environment quality (Q) as the average fitness of many different genotypes measured in the environment. I demonstrate that Q is useful in studying how the environment affects additive (Chapter 3), interactive (Chapters 3 and 4), and pleiotropic mutational effects (Chapter 5). Many classical theories and models were developed based on observations made in a single environment, and they are often insufficient to explain across-environment observations. Studying across-environment effects provides valuable information for testing old models and for designing new models when old models fail. I conclude that studying G×G and G×E shed light on underlying biological mechanisms.PHDEcology and Evolutionary BiologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/144160/1/xinzhuw_1.pd

Universal service obligations in developing countries

This paper develops a model to analyze the impacts of asymmetric information on optimal universal, service policy in the public utilities of developing countries. Optimal universal service policy is implemented using two regulatory instruments: pricing and network investment. Under discriminatory pricing asymmetric information leads to a higher price, and smaller network in the rural area, than under full information. Under uniform pricing, the price is also lower but the network is even smaller. In addition, under both pricing regimes, not only the firm, but also taxpayers have incentives to collude with the regulator.Environmental Economics&Policies,Knowledge Economy,Insurance&Risk Mitigation,Economic Theory&Research,Insurance Law,Education for the Knowledge Economy,Knowledge Economy,Economic Theory&Research,Environmental Economics&Policies,Geographical Information Systems

Scattering of SH wave by surface depression or convex in density inhomogeneous media

L'abstract è presente nell'allegato / the abstract is in the attachmen

Mechanical photoluminescence excitation spectra of a strongly driven spin-mechanical system

We report experimental studies of a driven spin-mechanical system, in which a nitrogen vacancy (NV) center couples to out-of-plane vibrations of a diamond cantilever through the excited-state deformation potential. Photoluminescence excitation studies show that in the unresolved sideband regime and under strong resonant mechanical driving, the excitation spectra of a NV optical transition feature two spectrally sharp peaks, corresponding to the two turning points of the oscillating cantilever. In the limit that the strain-induced frequency separation between the two peaks far exceeds the NV zero-phonon linewidth, the spectral position of the individual peak becomes sensitive to minute detuning between the mechanical resonance and the external driving force. For a fixed optical excitation frequency near the NV transition, NV fluorescence as a function of mechanical detuning features resonances with a linewidth that can be orders of magnitude smaller than the intrinsic linewidth of the mechanical mode. This enhanced sensitivity to mechanical detuning can potentially provide an effective mechanism for mechanical sensing, for example, mass sensing via measurements of induced changes in the mechanical oscillator frequency

French Horn Students’ Performance Improvement and Their Perceptions of Learning through Synchronous Virtual Classroom: An Empirical Research at Hunan Normal University

Synchronous virtual classroom has been widely used by universities as an alternative teaching method under the covid-19 pandemic, however, in the world of French horn education, there is a lack of scholarly attention on discovering how synchronous virtual classroom could affect students’ performance improvement and perceptions. The purpose of this study is to use a synchronous virtual classroom course to assess the sample participants’ performance improvement and perceptions; and then to analyze and evaluate the results from the assessment. This study used a paired sample t-test analysis to investigate whether this learning approach has caused significant improvement on students’ performances; and used a questionnaire analysis and a template analysis based on data collected from interviews to investigate how the students think about the course, and to explore the potential benefits and drawbacks that this learning approach has. The main research findings of this study indicate that, in terms of performance improvements, synchronous virtual classroom significantly improved French horn students’ overall performance improvement; in terms of students’ perceptions, such a learning method is mentally acceptable by the students, in which they were generally satisfied with this learning approach