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AJUR Volume 14 Issue 3 (November 2017)


Links to individual manuscripts, abstracts, and keywords are provided below.

 

p.5 Strategies for Making Best Offers on eBay
William J. Britt, William E. Gryc, Jamie A. Oliva, Brittney N. Tuff, & Charli E. White
ABSTRACT: We model for “Buy-It-Now or Best Offer” auctions on eBay using two different models. In the first model, risk-neutral bidders submit bids in serial and try to surpass a stochastic seller threshold while taking into account how many previous failed bids were made by other bidders. We compute optimal strategies for this model and show that bidder expected surplus decreases in the number of previous failed bids. In the second model we assume bidders do not know how many previous failed bids have been made, and instead use a first-price sealed-bid mechanism with a buy-out price where bidders serially submit bids with the knowledge that no previous bidders have used the buy-out price. We derive a unique equilibrium bidding strategy for risk-neutral bidders in this serial model, show that any equilibrium in a similar parallel bidding model is the same as the equilibrium in the serial model, and compute seller revenue. In particular, under certain circumstances, bidders will bid more in this format than they would in a standard first-price sealed-bid auction, but that a seller maximizes expected revenue by setting a buy-out price higher than any bidder is willing to pay thereby making the auction essentially a first-price auction.
KEYWORDS: Auction Theory; eBay; Buy-It-Now or Best Offer; Symmetric Bayesian Nash Equilibrium; Buy-Out Price; First-Price Sealed-Bid

p. 37 The Relationship Between Parenting Styles and Substance Use Among University Students
Zackaria I. Niazi, Danielle Dick, Amy Adkins, & Megan Cooke
ABSTRACT: Parenting styles are important in the behavioral development of adolescents. The environment created by the parent, in regards to communication with their child and level of independence given to their child, may influence the child’s susceptibility to risk behaviors. This study examines the relationship between parenting style and substance use among university students. We hypothesized that university students exposed to lower levels of autonomy granting (AG) or parental involvement (PI) parenting styles would have an increased likelihood of alcohol and nicotine use. We also hypothesized that religiosity, parental education level, ethnicity, and gender would act as moderators of parenting styles and alcohol and nicotine use. Data from a diverse university-wide sample was collected in the fall semester of the student’s freshman year from 2011-2014 (N = 9889, 61.5% female). Results demonstrated that AG had a significant, negative association with alcohol use (B = -0.033, p = 0.006) and nicotine use (B = -0.066, <0.001). All moderators were found to be significant predictors of alcohol use, however only father education level demonstrated a borderline significant moderation of the relationship between PI and alcohol use. Religiosity, Black race, Asian race, and gender were found to be significant predictors of nicotine use. Only gender moderated the association between PI and nicotine use. Even though alcohol and nicotine use and AG were associated, our results indicate that once students enter university, previous parenting style does not have a strong effect on alcohol and nicotine use behaviors in our sample.
KEYWORDS: Parenting Styles; University Students; Risky Behaviors; Autonomy Granting; Parental Involvement; Alcohol; Nicotine; Drug; Behavioral Biology; Substance Use

p.45 Matricial Representations of Certain Finitely Presented Groups Generated by Order-2 Generators and Their Applications
Ryan Golden Ilwoo Cho
ABSTRACT: In this paper, we study matricial representations of certain finitely presented groups Γ2Nwith N-generators of order-2. As an application, we consider a group algebra A2 of Γ22; under our representations. Specifically, we characterize the inverses g-1of all group elements g in Γ22; in terms of matrices in the group algebra A2. From the study of this characterization, we realize there are close relations between the trace of the radial operator of A2; and the Lucas numbers appearing in the Lucas triangle.
KEYWORDS: Matricial Representation; Group Presentation; Group Algebras; Lucas Numbers; Lucas Triangle; Finitely Presented Group;Group Relations; Free Probability

p.69 Evolution of Leucyl-tRNA Synthetase Through Eukaryotic Speciation
Katelyn E. Unvert, Frank A. Kovacs, Chi Zhang, Rachel A. Hellmann-Whitaker, & Katelin N. Arndt
ABSTRACT: Aminoacyl-tRNA synthetases (aaRSs) are part of the cellular translation machinery and as such, they are essential enzymes for every known cell. Due to their ubiquitous nature, their evolutionary history has been intensely researched to better understand the origins of life on a molecular level. Herein, we examine the evolutionary relatedness of leucyl-tRNA synthetases (LeuRS) from each major eukaryotic branch through the speciation process. This research effort was centered on amino acid sequence data as well as generating homology protein models for each LeuRS enzyme. Comparative analysis of this sequence and structural data for LeuRS amongst eukaryotes has indicated a high level of conservation within the active sites of these enzymes. Phylogenetic analysis confirmed this high degree of conservation as well as established evolutionary relatedness between these LeuRS enzymes. Based on this data, vertical gene transfer propagated LeuRS throughout the eukaryotic domain. Horizontal gene transfer and domain acquisition events were not observed within the eukaryotic organisms studied. Our data also highlighted LeuRS adaptation through the speciation process due to slight variability of scaffolding residues outside of the active site regions. We hypothesize that this variability may be due to mechanistic differences amongst LeuRS enzymes that have assumed non-translational functionality through the evolutionary process.
KEYWORDS: tRNA Synthetase; Leucyl-tRNA Synthetase; Eukaryotic Evolution; LeuRS Conservation; Vertical Gene Transfer; Horizontal Gene Transfer; Convergent Evolution; Primordial Enzymes

p.85 The Effect of CO2, Intracellular pH and Extracellular pH on Mechanosensory Proprioceptor Responses in Crayfish and Crab
Viresh Dayaram, Cole Malloy, Sarah Martha, Brenda Alvarez, Ikenna Chukwudolue, Nadera Dabbain, Dlovan Mahmood, Slavina Goleva, Tori Hickey, Angel Ho, Molly King, Paige Kington, Matthew Mattingly, Samuel Potter, Landon Simpson, Amanda Spence, Henry Uradu, Jacob Van Doorndlovan faiq, & Robin L. Cooper
ABSTRACT: Proprioceptive neurons monitor the movements of limbs and joints to transduce the movements into electrical signals. These neurons function similarly in species from arthropods to humans. These neurons can be compromised in disease states and in adverse environmental conditions such as with changes in external and internal pH. We used two model preparations (the crayfish muscle receptor organ and a chordotonal organ in the limb of a crab) to characterize the responses of these proprioceptors to external and internal pH changes as well as raised CO2. The results demonstrate the proprioceptive organs are not highly sensitive to changes in extracellular pH, when reduced to 5.0 from 7.4. However, if intracellular pH is decreased by exposure to propionic acid or saline containing CO2, there is a rapid decrease in firing rate in response to joint movements. The responses recover quickly upon reintroduction of normal pH (7.4) or saline not tainted with CO2. These basic understandings may help to address the mechanistic properties of mechanosensitive receptors in other organisms, such as muscle spindles in skeletal muscles of mammals and tactile as well as pressure (i.e., blood pressure) sensory receptors.
KEYWORDS: Proprioception; Sensory; Invertebrate; Carbon Dioxide; Protons; Mechanosensory; Intracellular pH; Extracellular pH

p.101 Derivation of Explicit Solutions Describing Early Stages of Platelet Activation
Rachel Austin, Scott Fones, Dominic Santoleri, Kaitlyn Thomesen, & Pak-Wing Fok
ABSTRACT: The formation of blood clots is vital for biological repair of injured blood vessels. When a blood vessel is injured, platelets come into contact with collagen, causing glycoprotein VI (GPVI) to undergo a conformational change and initialize the clotting process. This project aimed to simplify and solve a system of coupled ordinary differential equations (ODEs) proposed in Model A of Regulation of Early Steps of GPVI Signal Transduction by Phosphatase: A Systems Biology Approach by JL Dunster et al., modeling early platelet activation kinetics. In doing so, the ODEs were non-dimensionalized and the approximate analytical solutions were then found. The approximate solutions compare favorably to the numerical solutions and provide deeper insight into the signal regulation pathway. Most notably, the solutions expose a time at which the pathway dynamics change drastically. This illustrates the critical role of cytosolic spleen tyrosine kinase (Syk) as a molecular timer in the cascade.
KEYWORDS: Platelet Activation; Signal Cascade; Coupled Differential Equations; Asymptotic Analysis; Systems Biology; Mathematical Modeling; Model Simplification; Glycoprotein VI; Spleen Tyrosine Kinase; Syk Activation Dynamics