Geek Media and Identity

Honors (Bachelor's)AnthropologyUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/79473/1/rachelyu.pd

The Brine Shrimp \u3ci\u3eArtemia franciscana\u3c/i\u3e in Closed Microalgal-Based Microcosms (Biospheres)

The purpose of this study was to examine the effects of three experimental variables on the stability and fecundity of a brine-shrimp community in a closed, micro algal-based microcosm. Xenic microalgal cultures and brine shrimp (Artemia franciscana Kellogg) in 300-cc acrylic spheres (referred to as biospheres or microcosms) were subjected to three experimental variables: (1) the culture volume (150 ml or 250 ml), (2) presence or absence of daily culture mixing (sphere rotation), and (3) a microcosm atmosphere that was either closed or open to the surrounding atmosphere. Each sphere started with 200 brine shrimp cysts and the microalga Nannochloris at a density of 5-7 x 107 cells/ml in a culture medium of 35 ppt total salts. The biospheres were monitored twice a week with closeup color photography, noting culture color and transparency, oxygen bubble accumulation, settling of planktonic algae, and the density, size, and maturity of the brine shrimp over time. The brine shrimp copulated by 21/2 weeks; a second generation of nauplii appeared in ca 30 days, temporarily increasing the density. These observations constitute the first report of brine shrimp sexual reproduction (ovoviviparity) in closed microcosms. The density of the brine shrimp appeared to stabilize during days 50-82, at an approximated 0.08 individuals/ml. Because all biospheres were yellow in the final weeks, i.e. showed no signs of Nannochloris, the brine shrimp were likely sustained by bacteria generated from the brine-shrimp feces. Blue-green algal filaments, a culture contaminant, at the air-water interface, out of the reach of brine shrimp, appeared to have provided oxygen in the absence of Nannochloris

Are the ultra-high-redshift galaxies at z > 10 surprising in the context of standard galaxy formation models?

A substantial number of ultra-high redshift (8 < z < 17) galaxy candidates have been detected with JWST, posing the question: are these observational results surprising in the context of current galaxy formation models? We address this question using the well-established Santa Cruz semi-analytic models, implemented within merger trees from the new suite of cosmological N-body simulations GUREFT, which were carefully designed for ultra-high redshift studies. Using our fiducial models calibrated at z=0, we present predictions for stellar mass functions, rest-frame UV luminosity functions, and various scaling relations. We find that our (dust-free) models predict galaxy number densities at z~11 (z~ 13) that are an order of magnitude (a factor of ~30) lower than the observational estimates. We estimate the uncertainty in the observed number densities due to cosmic variance, and find that it leads to a fractional error of 30-70% at z=11 (25-150% at z=13) for the available observed fields. We explore which processes in our models are most likely to be rate-limiting for the formation of luminous galaxies at these early epochs, considering the halo formation rate, gas cooling, star formation, and stellar feedback, and conclude that it is mainly efficient stellar-driven winds. We find that a modest boost of a factor of ~4 to the UV luminosities, which could arise from a top-heavy stellar initial mass function characteristic of Pop III stars, would bring our current models into agreement with the observations.Comment: 20 pages, 15 figures, submitted to MNRA

Semi-analytic forecasts for Roman – the beginning of a new era of deep-wide galaxy surveys

The Nancy Grace Roman Space Telescope, NASA’s next flagship observatory, will redefine deep-field galaxy survey with a field of view two orders of magnitude larger than Hubble and an angular resolution of matching quality. These future deep-wide galaxy surveys necessitate new simulations to forecast their scientific output and to optimise survey strategies. In this work, we present five realizations of 2-deg2 lightcones, containing a total of & 25 million simulated galaxies with −16 & MUV & −25 spanning z ∼ 0 to 10. This dataset enables a new set of experiments with the impacts of survey size on the derived galaxy formation and cosmological constraints. The intrinsic and observable galaxy properties are predicted using a well-established, physics-based semi-analytic modelling approach. We provide forecasts for number density, cosmic SFR, field-to-field variance, and angular two-point correlation functions, and demonstrate how the future wide-field surveys will be able to improve these measurements relative to current generation surveys. We also present a comparison between these lightcones and others that have been constructed with empirical models

A Systematic Review of Studies Describing the Effectiveness, Acceptability, and Potential Harms of Place-Based Interventions to Address Loneliness and Mental Health Problems

Given the links between the built environment and loneliness, there is interest in using place-based approaches (addressing built environment characteristics and related socio-spatial factors) in local communities to tackle loneliness and mental health problems. However, few studies have described the effectiveness, acceptability, or potential harms of such interventions. This review aimed to synthesize the literature describing local community-based interventions that target place-based factors to address loneliness and mental health problems, informing the development of future public health approaches. We searched PsycINFO, Medline, and Embase using a structured search strategy to identify English-language studies evaluating the effectiveness, acceptability, and potential harms of place-based community interventions in addressing loneliness and mental health problems, both in general and clinical populations. Seven studies met the inclusion criteria, classified as evaluating provision of community facilities (such as clubhouses), active engagement in local green spaces, and housing regeneration. None were randomised trials. Quantitative and qualitative findings suggested promising effects and/or acceptability of six interventions, with minimal potential harms. There is a clear need for randomised trials or quasi-experimental studies of place-based interventions to describe their effectiveness in addressing loneliness and mental health problems, as well as complementary qualitative work investigating acceptability. This will inform future policy development

Virulence determinants, drug resistance and mobile genetic elements of Laribacter hongkongensis: a genome-wide analysis

<p>Abstract</p> <p>Background</p> <p><it>Laribacter hongkongensis </it>is associated with community-acquired gastroenteritis and traveler's diarrhea. In this study, we performed an in-depth annotation of the genes in its genome related to the various steps in the infective process, drug resistance and mobile genetic elements.</p> <p>Results</p> <p>For acid and bile resistance, <it>L. hongkongensis </it>possessed a urease gene cassette, two <it>arc </it>gene clusters and bile salt efflux systems. For intestinal colonization, it possessed a putative adhesin of the autotransporter family homologous to those of diffusely adherent <it>Escherichia coli </it>(<it>E. coli</it>) and enterotoxigenic <it>E. coli</it>. To evade from host defense, it possessed superoxide dismutase and catalases. For lipopolysaccharide biosynthesis, it possessed the same set of genes that encode enzymes for synthesizing lipid A, two Kdo units and heptose units as <it>E. coli</it>, but different genes for its symmetrical acylation pattern, and nine genes for polysaccharide side chains biosynthesis. It contained a number of CDSs that encode putative cell surface acting (RTX toxin and hemolysins) and intracellular cytotoxins (patatin-like proteins) and enzymes for invasion (outer membrane phospholipase A). It contained a broad variety of antibiotic resistance-related genes, including genes related to β-lactam (n = 10) and multidrug efflux (n = 54). It also contained eight prophages, 17 other phage-related CDSs and 26 CDSs for transposases.</p> <p>Conclusions</p> <p>The <it>L. hongkongensis </it>genome possessed genes for acid and bile resistance, intestinal mucosa colonization, evasion of host defense and cytotoxicity and invasion. A broad variety of antibiotic resistance or multidrug resistance genes, a high number of prophages, other phage-related CDSs and CDSs for transposases, were also identified.</p

Transport genes and chemotaxis in Laribacter hongkongensis: a genome-wide analysis

<p>Abstract</p> <p>Background</p> <p><it>Laribacter hongkongensis </it>is a Gram-negative, sea gull-shaped rod associated with community-acquired gastroenteritis. The bacterium has been found in diverse freshwater environments including fish, frogs and drinking water reservoirs. Using the complete genome sequence data of <it>L. hongkongensis</it>, we performed a comprehensive analysis of putative transport-related genes and genes related to chemotaxis, motility and quorum sensing, which may help the bacterium adapt to the changing environments and combat harmful substances.</p> <p>Results</p> <p>A genome-wide analysis using Transport Classification Database TCDB, similarity and keyword searches revealed the presence of a large diversity of transporters (n = 457) and genes related to chemotaxis (n = 52) and flagellar biosynthesis (n = 40) in the <it>L. hongkongensis </it>genome. The transporters included those from all seven major transporter categories, which may allow the uptake of essential nutrients or ions, and extrusion of metabolic end products and hazardous substances. <it>L. hongkongensis </it>is unique among closely related members of <it>Neisseriaceae </it>family in possessing higher number of proteins related to transport of ammonium, urea and dicarboxylate, which may reflect the importance of nitrogen and dicarboxylate metabolism in this assacharolytic bacterium. Structural modeling of two C^₄-dicarboxylate transporters showed that they possessed similar structures to the determined structures of other DctP-TRAP transporters, with one having an unusual disulfide bond. Diverse mechanisms for iron transport, including hemin transporters for iron acquisition from host proteins, were also identified. In addition to the chemotaxis and flagella-related genes, the <it>L. hongkongensis </it>genome also contained two copies of <it>qseB/qseC </it>homologues of the AI-3 quorum sensing system.</p> <p>Conclusions</p> <p>The large number of diverse transporters and genes involved in chemotaxis, motility and quorum sensing suggested that the bacterium may utilize a complex system to adapt to different environments. Structural modeling will provide useful insights on the transporters in <it>L. hongkongensis</it>.</p