Extinction of Chromosomes due to Specialization is a Universal Occurrence

Title from PDF of title page viewed January 6, 2020Thesis advisor: Gerald J. WyckoffVitaIncludes bibliographical references (page 38-49)Thesis (M.S.)--School of Medicine. University of Missouri--Kansas City, 2019The human X and Y chromosomes evolved from a pair of autosomes approximately 180 million years ago. Despite their shared evolutionary origin, extensive genetic decay has resulted in the human Y chromosome losing 97% of its ancestral genes while gene content and order remain highly conserved on the X chromosome. Five ‘stratification' events, most likely inversions, reduced the Y chromosome's ability to recombine with the X chromosome across the majority of its length and subjected its genes to the erosive forces associated with reduced recombination. The remaining functional genes are ubiquitously expressed, functionally coherent, dosage-sensitive genes, or have evolved male-specific functionality. It is unknown, however, whether functional specialization is a degenerative phenomenon unique to sex chromosomes, or if it conveys a potential selective advantage aside from sexual antagonism. We examined the evolution of mammalian orthologs to determine if the selective forces that led to the degeneration of the Y chromosome are unique in the genome. The results of our study suggest these forces are not exclusive to the Y chromosome, and chromosomal degeneration may have occurred throughout our evolutionary history. The reduction of recombination could additionally result in rapid fixation through isolation of specialized functions resulting in a cost-benefit relationship during times of intense selective pressure.Introduction -- Methodology -- Results -- Discussion -- Appendix A. Supplementary materia

Injectors for Multipoint Injection

An injector for a multipoint combustor system includes an inner air swirler which defines an interior flow passage and a plurality of swirler inlet ports in an upstream portion thereof. The inlet ports are configured and adapted to impart swirl on flow in the interior flow passage. An outer air cap is mounted outboard of the inner swirler. A fuel passage is defined between the inner air swirler and the outer air cap, and includes a discharge outlet between downstream portions of the inner air swirler and the outer air cap for issuing fuel for combustion. The outer air cap defines an outer air circuit configured for substantially unswirled injection of compressor discharge air outboard of the interior flow passage

Multi-Point Combustion System: Final Report

A low-NOx emission combustor concept has been developed for NASA's Environmentally Responsible Aircraft (ERA) program to meet N+2 emissions goals for a 70,000 lb thrust engine application. These goals include 75 percent reduction of LTO NOx from CAEP6 standards without increasing CO, UHC, or smoke from that of current state of the art. An additional key factor in this work is to improve lean combustion stability over that of previous work performed on similar technology in the early 2000s. The purpose of this paper is to present the final report for the NASA contract. This work included the design, analysis, and test of a multi-point combustion system. All design work was based on the results of Computational Fluid Dynamics modeling with the end results tested on a medium pressure combustion rig at the UC and a medium pressure combustion rig at GRC. The theories behind the designs, results of analysis, and experimental test data will be discussed in this report. The combustion system consists of five radially staged rows of injectors, where ten small scale injectors are used in place of a single traditional nozzle. Major accomplishments of the current work include the design of a Multipoint Lean Direct Injection (MLDI) array and associated air blast and pilot fuel injectors, which is expected to meet or exceed the goal of a 75 percent reduction in LTO NOx from CAEP6 standards. This design incorporates a reduced number of injectors over previous multipoint designs, simplified and lightweight components, and a very compact combustor section. Additional outcomes of the program are validation that the design of these combustion systems can be aided by the use of Computational Fluid Dynamics to predict and reduce emissions. Furthermore, the staging of fuel through the individually controlled radially staged injector rows successfully demonstrated improved low power operability as well as improvements in emissions over previous multipoint designs. Additional comparison between Jet- A fuel and a hydrotreated biofuel is made to determine viability of the technology for use with alternative fuels. Finally, the operability of the array and associated nozzles proved to be very stable without requiring additional active or passive control systems. A number of publications have been publis

Fishery collapse, recovery, and the cryptic decline of wild salmon on a major California river

Fall-run Chinook salmon (Oncorhynchus tshawytscha) from the Sacramento–San Joaquin River system form the backbone of California’s salmon fishery and are heavily subsidized through hatchery production. Identifying temporal trends in the relative contribution of hatchery- versus wild-spawned salmon is vital for assessing the status and resiliency of wild salmon populations. Here, we reconstructed the proportion of hatchery fish on natural spawning grounds in the Feather River, a major tributary to the Sacramento River, using strontium isotope (87Sr/86Sr) ratios of otoliths collected during carcass surveys from 2002 to 2010. Our results show that prior to the 2007–2008 salmon stock collapse, 55%–67% of in-river spawners were of hatchery origin; however, hatchery contributions increased drastically (89%) in 2010 following the collapse. Data from a recent hatchery marking program corroborate our results, showing that hatchery fish continued to dominate (∼90%) in 2011–2012. Though the rebound in abundance of salmon in the Feather River suggests recovery of the stock postcollapse, our otolith chemistry data document a persistent decline of wild spawners, likely leading to the erosion of locally adapted Feather River salmon populations

Analysis and design of lean direct injection fuel nozzles by eddy resolved turbulence simulation

Combustion systems in gas turbine engines are subjected to particular scrutiny in regards to the emissions which they produce. Of special interest are the emissions of Oxides of Nitrogen (NOx), which have a direct impact on air quality as well as health aspects. There is a need in the industry for elegant designs for these combustion systems which reduce the formation of NOx. The present study includes an in depth analysis of a state-of-the art prefilming airblast injector which is designed for achieving low NOx. The design has been studied through the use of turbulence resolving simulation to differentiate what is important for the design of this system. The OpenFOAM CFD software, with a Delayed Detached Eddy Simulation (DDES) model recently developed at Iowa State University, is shown to provide a suitable design tool which has been used to accurately predict a variety of parameters important to this combustion system. Of particular interest are the mixing characteristics of the atomizer, which have been studied through a series of CFD simulations including single-phase, multi-species, and multi-phase simulations. Turbulence simulations are validated by comparison to United Technologies Aerospace Systems (UTAS) data with air only. It is shown how DDES is able to capture the downstream mixing of air streams. Finally, a novel atomizer has been designed with these methods which is intended to promote thorough mixing. The CFD mixing characteristics are described and compared to the existing injector.</p

Computational simulation of separated flow in a three-dimensional diffuser using v2-f and zeta-f models

Computational prediction of separated flows is an area of interest, specifically in applications to gas turbine engines, liquid pumps, and many other engineering applications. Although these types of flows are governed by the Navier-Stokes equations, direct numerical simulation (DNS) of practical engineering flows is currently too expensive in terms of the required computational time. It is therefore a case to attempt simulation of these flows using the Reynolds-Averaged Navier-Stokes (RANS) equations which must be closed by utilizing a turbulence closure model.;The present study used the NASA Glenn-HT code, a compressible Navier-Stokes solver, with two different turbulence models, the u2 --f model of Durbin and the zeta-- f model of Hanjalic, to observe their abilities to predict separated flows. The elliptic relaxation turbulence models and their implementation in Glenn-HT are described. Three cases are described to show the ability and limitations of these turbulence models.</p

National Oceanic and Atmospheric Administration Report 2

Report about the unusual mortality of Hawaiian Monk Seals that includes extensive background information and research along with a prospective contingency plan to respond to the issue of unusual mortality for this species

Faculty Recitals

A faculty and student recital performed at UNT College of Music Voertman Hall

Prevalence of sleep disturbances during COVID-19 outbreak in an urban Chinese population: a cross-sectional study

Objective: The COVID-19 pandemic is a large-scale public health emergency that likely precipitated sleep disturbances in the community. This study aimed to investigate the prevalence and correlates of sleep disturbances during the early phase of COVID-19 pandemic. Methods: This web-based cross-sectional study recruited 1138 Hong Kong adults using convenience sampling over a two-week period from 6th April 2020. The survey collected data on sleep disturbances, mood, stress, stock of infection control supplies, perceived risk of being infected by COVID-19, and sources for acquiring COVID-19 information. The participants were asked to compare their recent sleep and sleep before the outbreak. The Insomnia Severity Index (ISI) was used to assess their current insomnia severity. Prevalence was weighted according to 2016 population census. Results: The weighted prevalence of worsened sleep quality, difficulty in sleep initiation, and shortened sleep duration since the outbreak were 38.3%, 29.8%, and 29.1%, respectively. The prevalence of current insomnia (ISI score of ≥10) was 29.9%. Insufficient stock of masks was significantly associated with worsened sleep quality, impaired sleep initiation, shortened sleep duration, and current insomnia in multivariate logistic regression (adjusted OR = 1.57, 1.72, 1.99, and 1.96 respectively, all p &lt; 0.05). Conclusion: A high proportion of people in Hong Kong felt that their sleep had worsened since the COVID-19 outbreak. Insufficient stock of masks was one of the risk factors that were associated with sleep disturbances. Adequate and stable supply of masks may play an important role to maintain the sleep health in the Hong Kong general population during a pandemic outbreak