University of Arkansas

About: University of Arkansas is a education organization based out in Fayetteville, Arkansas, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 17225 authors who have published 33329 publications receiving 941102 citations. The organization is also known as: Arkansas & UA.

Specific dynamic action: a century of investigation.

Abstract: Specific dynamic action (SDA) is the term used to refer to the increased metabolic expenditure that occurs in postprandial animals. Postprandial increases in metabolism were first documented in animals over two hundred years ago, and have since been observed in every species thus far examined. Ironically, the ubiquity of this physiological response to feeding understates its complex nature. This review is designed to summarize both classical and modern hypotheses regarding the causality of SDA as well as to review important findings from the past century of scientific research into SDA. A secondary aim of this work is to emphasize the importance of carefully designed experiments and systematic hypothesis testing to make more rapid progress in understanding the physiological processes that contribute to SDA. I also identify three areas in SDA research that deserve more detailed investigation. The first area is identification of the causality of SDA in ‘model’ organisms. The second area is characterization of SDA responses in novel species. The third area is exploration of the ecological and potential evolutionary significance of SDA in energy budgets of animals.

Strategic human resource management, human capital and competitive advantage: is the field going in circles?

Abstract: The resource-based view (RBV) of the firm has been consistently used as a backdrop in strategic human resource management (SHRM) research and has the potential to bridge the ‘micro–macro’ divide. The tension between the SHRM and the strategic human capital literature, however, signifies that RBV has not reached its potential. In this paper, we begin with a brief review of the conceptual logic linking human resource management (HRM) practices and firm outcomes that aim at highlighting the different treatment of RBV in the SHRM and strategic human capital literatures. We then propose a conceptual model that suggests that HRM practices are not simple levers that enable firms to create sustainable competitive advantage, as most of the strategic human capital research postulates. On the contrary, we argue that HRM practices can contribute to a firm's sustainable competitive advantage not only by enhancing employees' ability, and offering motivation and opportunities, but also by shaping supply-side and demand-side mobility constraints.

2D Intrinsic Ferromagnets from van der Waals Antiferromagnets.

Abstract: Intrinsically ferromagnetic 2D semiconductors are essential and highly sought for nanoscale spintronics, but they can only be obtained from ferromagnetic bulk crystals, while the possibility to create 2D intrinsic ferromagnets from bulk antiferromagnets remains unknown. Herein on the basis of ab initio calculations, we demonstrate this feasibility with the discovery of intrinsic ferromagnetism in an emerging class of single-layer 2D semiconductors CrOX (CrOCl and CrOBr monolayers), which show robust ferromagnetic ordering, large spin polarization, and high Curie temperature. These 2D crystals promise great dynamical and thermal stabilities as well as easy experimental fabrication from their bulk antiferromagnets. The Curie temperature of 2D CrOCl is 160 K, which exceeds the record (155 K) of the most-studied dilute magnetic GaMnAs materials, and could be further enhanced by appropriate strains. Our study offers an alternative promising way to create 2D intrinsic ferromagnets from their antiferromagnetic b...

Simultaneous detection of Escherichia coli O157:H7 and Salmonella Typhimurium using quantum dots as fluorescence labels.

Abstract: In this study, we explored the use of semiconductor quantum dots (QDs) as fluorescence labels in immunoassays for simultaneous detection of two species of foodborne pathogenic bacteria, Escherichia coli O157∶H7 and Salmonella Typhimurium. QDs with different sizes can be excited with a single wavelength of light, resulting in different emission peaks that can be measured simultaneously. Highly fluorescent semiconductor quantum dots with different emission wavelengths (525 nm and 705 nm) were conjugated to anti-E. coli O157 and anti-Salmonella antibodies, respectively. Target bacteria were separated from samples by using specific antibody coated magnetic beads. The bead–cell complexes reacted with QD–antibody conjugates to form bead–cell–QD complexes. Fluorescent microscopic images of QD labeled E. coli and Salmonella cells demonstrated that QD–antibody conjugates could evenly and completely attach to the surface of bacterial cells, indicating that the conjugated QD molecules still retain their effective fluorescence, while the conjugated antibody molecules remain active and are able to recognize their specific target bacteria in a complex mixture. The intensities of fluorescence emission peaks at 525 nm and 705 nm of the final complexes were measured for quantitative detection of E. coli O157∶H7 and S. Typhimurium simultaneously. The fluorescence intensity (FI) as a function of cell number (N) was found for Salmonella and E. coli, respectively. The regression models can be expressed as: FI = 60.6log N − 250.9 with R2 = 0.97 for S. Typhimurium, and FI = 77.8log N − 245.2 with R2 = 0.91 for E. coli O157∶H7 in the range of cell numbers from 104 to 107 cfu ml−1. The detection limit of this method was 104 cfu ml−1. The detection could be completed within 2 hours. The principle of this method could be extended to detect multiple species of bacteria (3–4 species) simultaneously, depending on the availability of each type of QD–antibody conjugates with a unique emission peak and the antibody coated magnetic beads specific to each species of bacteria.

Effect of free amino acids and vitamins on cleavage and developmental rate of bovine zygotes in vitro.

Abstract: Due to the complicated media used for culturing bovine embryos, most of the nutrient requirements are unknown. Recently, we developed a simple, serum-free medium (CR1) that allows bovine embryos to develop in vitro. Therefore, our objective was to determine whether development of bovine embryos would be improved by the addition of free amino acids and vitamins to CR1. Oocytes were recovered from slaughterhouse ovaries and matured 22 +/- 2 h, following which the oocytes were randomly allotted to treatment. The experiment was a randomized block design with a 2 x 5 factorial treatment structure. The oocytes were fertilized with or without cumulus cells intact. The five fertilization media were 1) Control (CR1 +/- 10 micrograms/mL of phenol red); 2) control + basal medium Eagle (BME) essential amino acids (EAA) + minimum essential medium (MEM) nonessential amino acids (NEA) + MEM vitamins (VIT); 3) control + EAA + NEA; 4) control + EAA + VIT; and 5) control + NEA + VIT. Cleavage rate was greater (P < .001) when cumulus cells remained on the oocytes during fertilization (51.7 vs 73.2% without and with cumulus cells, respectively). The frequency of blastocysts was increased (P < .001) when EAA or NEA were added to CR1; however, adding VIT had no effect or tended (P = .12) to decrease the frequency of embryos attaining the blastocyst stage. This experiment demonstrates that development of bovine embryos in vitro can be improved by the addition of free amino acids to a simple medium. Contrary to work in rodents, the mixture of vitamins in MEM was not beneficial for bovine embryos.