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Search Results: 1 - 10 of 87528 matches for " Rebecca W. Black "
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The language of Webkinz: Early childhood literacy in an online virtual world
Rebecca W. Black
Digital Culture & Education , 2010,
Abstract: In recent years there has been an explosion of virtual worlds intended for early childhood populations; however, because the majority of research on games and such worlds has focused on adults and adolescents, we know very little about these spaces. This article attempts to address this gap by providing a qualitative content analysis of the affordances that Webkinz World an online environment that as of March 2010 had over 3 million unique site visitors per month, offers for children’s literacy and language development. Analyses suggest that the site provides unique opportunities for immersion in literacy-rich contexts and academically-oriented practices that may enhance those that are readily available in many children’s daily lives. However, looking beyond the discrete linguistic and technical aspects of learning in Webkinz World reveals a designed culture with limitations on learning and a constrained set of literacies and social messages that warrant further critical exploration.
Cohomological invariants of groups of order p^3
Rebecca Black
Mathematics , 2015,
Abstract: We show that the nonabelian groups of order p^3 for odd prime p have no nontrivial cohomological invariants of degree 3.
Consumption Patterns in the Aftermath of the Financial Crisis: The Case of Baby Boomers  [PDF]
Rebecca Abraham, Charles W. Harrington
Modern Economy (ME) , 2015, DOI: 10.4236/me.2015.62022
Abstract: This study examines the consumption decisions of baby boomers (40 - 64 year-old age cohort) with $75,000 - $140,000 in household income in the immediate aftermath of the financial crisis of 2007-2008 using the Consumer Expenditure Survey data of Bureau of Labor Statistics in 2009. Increasing unemployment and foreclosures of primary homes led to variability of income, which became a major consideration in evaluating consumption choices. In addition, we draw on Weberian social class theory to identify social influence on consumption decisions. Gender differences in processing information pertaining to new product purchases provided yet another means of stratifying the sample. By juxtaposing economic variables on social identification and gender-based preferences, this study sets forth the explanatory variables underlying eight separate product purchase decisions. Principal findings included Variability of Income and Risk of Foreclosure determined the Rent or Buy a home decision. The predictor of Expenditure on New Cars included the Cost of a New Car. For Expenditure on Used Cars, Deviation from New Car Buyers and Cost of a Used Car were the relevant predictors. For Lunch Brought from Home to the workplace, Lunch Consumed at Restaurants and Conformity to Own Referent Group were the most important explanatory variables. For Lunch Consumed at Restaurants, Lunch at Home and Socialization Opportunities explained the criterion. Conformity to the Referent Group explained Expenditure on Vacations, Furniture and Appliances and Small Appliances.
Bad boys, bad men
Black Donald W
Revista Brasileira de Psiquiatria , 2001,
A Theoretical Model of Directional Volume on Acquirer Stock in Cash Mergers  [PDF]
Mark W. Zikiye, Rebecca Abraham, Charles Harrington
Theoretical Economics Letters (TEL) , 2014, DOI: 10.4236/tel.2014.43033

The acquisition of a target firm in a transaction financed by cash is a cash merger. Announcements of cash mergers release the positive signal that the acquirer possesses cash reserves. As stock prices rise, informed traders may obtain abnormal returns by purchasing call options, selling put options or purchasing stock. This paper constructs a theoretical model in which call buy volume forms the upper bound of the final stock price, put sell volume forms the lower bound of the final stock price and stock purchase volume reveals the final stock price.

Trading Responses to Negative Signals  [PDF]
Mark W. Zikiye, Rebecca Abraham, Charles Harrington
Theoretical Economics Letters (TEL) , 2014, DOI: 10.4236/tel.2014.46049

Mergers may be undertaken by giving shareholders of the target firm the right to exchange their stock for stock in the combined firm. Such stock mergers release the negative signal that the acquiring firm lacks cash. Informed traders seeking immediate gain may short sell acquirer stock or buy puts and sell calls. Liquidity traders, desiring longterm gain, may purchase stock or call options to benefit from lower stock prices, or sell stock or buy put options to maintain liquidity. This paper constructs a theoretical model in which option volume forms the bounds of the final stock price for informed traders while random stock purchase or sale volume establishes the final stock price for liquidity traders.

A Theoretical Model of Competitive Equilibria in the New Car Market  [PDF]
Rebecca Abraham, Mark W. Zikiye, Charles Harrington
Theoretical Economics Letters (TEL) , 2015, DOI: 10.4236/tel.2015.52024
Abstract: In the United States, the automobile purchase decision is consequential for both households and car producers. In households, adults typically own their own vehicles for personal use such as commuting to work or college. The need for multiple, safe cars per household represent a significant allocation of household income on an ongoing basis as old vehicles are replaced. Customer needs are represented by groups of demand utility functions which specify the demand for increasingly expensive safety features and styling changes. Auto manufacturers respond to the need for a variety of styles and safety features by producing vehicles in as many as 16 different product-market segments. They offer multiple financing options such as leases, late models, and stretching out payments to accommodate capital rationing by their customers. The quantity sold in each segment provides the profit per segment which adds across segments to provide the overall profit for the firm. This is a monopolistically competitive environment in which brand loyalty drives sales per segment, with each segment being considerably different from others in vehicle characteristics and customer income. This paper theoretically develops the demand utility functions within each segment, develops the producer’s profit function and then equates the supply and demand functions to obtain the optimal quantity per segment. Practical implications are discussed. One such implication is that the quantity of sales may not be realized in any one market, so that sales may have to be realized across markets for auto firms to achieve consistent, long-term profits. Thus, our quantity specification may provide a justification for the globalization of the auto industry.
Heterotrimeric G protein subunits are located on rat liver endosomes
Rebecca W Van Dyke
BMC Physiology , 2004, DOI: 10.1186/1472-6793-4-1
Abstract: By Western blotting Gsα, Giα1,2, Giα3 and Gβ were enriched in both canalicular (CM) and basolateral (BLM) membranes but also readily detectable on three types of purified rat liver endosomes in the order recycling receptor compartment (RRC) > compartment for uncoupling of receptor and ligand (CURL) > multivesicular bodies (MVB) >> purified secondary lysosomes. Western blotting with antibodies to Na, K-ATPase and to other proteins associated with plasma membranes and intracellular organelles indicated this was not due to contamination of endosome preparations by CM or BLM. Adenylate cyclase (AC) was also identified on purified CM, BLM, RRC, CURL and MVB. Percoll gradient fractionation of liver postnuclear supernatants demonstrated co-occurrence of endosomes and heterotrimeric G protein subunits in fractions with little plasma membrane markers. By confocal microscopy, punctate staining for Gsα, Giα3 and Gβ corresponded to punctate areas of endocytosed Texas red-dextran in hepatocytes from control and cholera toxin-treated livers.We conclude that heterotrimeric G protein subunits as well as AC likely traffic into hepatocytes on endosome membranes, possibly generating downstream signals spatially separate from signalling generated at the plasma membrane, analogous to the role(s) of internalized insulin receptors.Heterotrimeric G proteins, important for signal transduction in hepatocytes, attach through lipid modifications to the cytoplasmic face of plasma membranes, particularly lipid rafts, where they interact with G protein coupled-receptors (GPCR) to initiate signal transduction [1,2]. Gsα, Giα1,2, Giα3 and Gβ have been identified on rat liver basolateral (BLM) and canalicular (CM) membranes [3,4]. Although current concepts of signal transduction envision interaction of the cytoplasmic tails of activated receptors with intracellular signal transduction cascades at the plasma membrane, insulin and epidermal growth factor (EGF) receptors and some GPCRs are internalized
Red Giants in the Halo of the S0 Galaxy NGC 3115: A Distance and a Bimodal Metallicity Distribution
Rebecca A. W. Elson
Physics , 1996, DOI: 10.1093/mnras/286.3.771
Abstract: Using the Hubble Space Telescope, we resolve the red giant branch in the halo of the S0 galaxy NGC 3115. We measure magnitudes and $(V-I)$ colours for stars down to 1.5 magnitudes below the tip of the red giant branch. From the brightest stars we estimate a distance modulus $(m-M)_0=30.21 \pm 0.30$, corresponding to a distance of $11.0 \pm 1.5$ Mpc. This is in excellent agreement with the value $(m-M)_0=30.17 \pm 0.13$ determined from the planetary nebula luminosity function. Our results rule out the shorter distance modulus $(m-M)_0=29.65$ determined from surface brightness fluctuations. A histogram of $(V-I)$ colours shows a clear bimodality, indicating the presence of two distinct halo populations of roughly equal size. One has [Fe/H]$\sim -0.7$ and one has [Fe/H]$\sim -1.3$. This is the most distant galaxy in which a Population II halo has been resolved, and it is the first time a colour bimodality has been observed among the halo stars of any early-type galaxy.
Structure and assembly of bacteriophage T4 head
Venigalla B Rao, Lindsay W Black
Virology Journal , 2010, DOI: 10.1186/1743-422x-7-356
Abstract: The T4-type bacteriophages are ubiquitously distributed in nature and occupy environmental niches ranging from mammalian gut to soil, sewage, and oceans. More than 130 such viruses that show similar morphological features as phage T4 have been described; from the T4 superfamily ~1400 major capsid protein sequences have been correlated to its 3D structure [1-3]. The features include large elongated (prolate) head, contractile tail, and a complex baseplate with six long, kinked tail fibers radially emanating from it. Phage T4 historically has served as an excellent model to elucidate the mechanisms of head assembly of not only T-even phages but of large icosahedral viruses in general, including the widely distributed eukaryotic viruses such as the herpes viruses. This review will focus on the advances in the past twenty years on the basic understanding of phage T4 head structure and assembly and the mechanism of DNA packaging. Application of some of this knowledge to develop phage T4 as a surface display and vaccine platform will also be discussed. The reader is referred to the comprehensive review by Black et al [4], for the early work on T4 head assembly.The overall architecture of the phage T4 head determined earlier by negative stain electron microscopy of the procapsid, capsid, and polyhead, including the positions of the dispensable Hoc and Soc proteins, has basically not changed as a result of cryo-electron microscopic structure determination of isometric capsids [5]. However, the dimensions of the phage T4 capsid and its inferred protein copy numbers have been slightly altered on the basis of the higher resolution cryo-electron microscopy structure. The width and length of the elongated prolate icosahedron [5] are Tend = 13 laevo and Tmid = 20 (86 nm wide and 120 nm long), and the copy numbers of gp23, Hoc and Soc are 960, 155, and 870, respectively (Figure 1).The most significant advance was the crystal structure of the vertex protein, gp24, and by inference
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