Alteration of aspartate 101 in the active site of Escherichia coli alkaline phosphatase enhances the catalytic activity

The function of aspartic acid residue 101 in the active siteof Escherichia coli alkaline phosphatase was investigated bysite-specific mutagenesis. A mutant version of alkaline phosphatasewas constructed with alanine in place of aspartic acid at position101. When kinetic measurements are carried out in the presenceof a phosphate acceptor, 1.0 M Tris, pH 8.0, both the k_cat andthe K_m, for the mutant enzyme increase by –2-fold, resultingin almost no change in the k_cat/K_m ratio. Under conditions ofno external phosphate acceptor and pH 8.0, both the k_cat andthe K_m for the mutant enzyme decrease by {small tilde}2-fold,again resulting in almost no change in the k_cat/K_m ratio. Thek_cat for the hydrolysis of 4-methyl-umbelliferyl phosphate andp-nitrophenyl phosphate are nearly identical for both the wild-typeand mutant enzymes, as is the K₁ for inorganic phosphate. Thereplacement of aspartic acid 101 by alanine does have a significanteffect on the activity of the enzyme as a function of pH, especiallyin the presence of a phosphate acceptor. At pH 9.4 the mutantenzyme exhibits 3-fold higher activity than the wild-type. Themutant enzyme also exhibits a substantial decrease in thermalstability: it is half inactivated by treatment at 49°C for15 min compared to 71°C for the wild-type enzyme. The datareported here suggest that this amino acid substitution altersthe rates of steps after the formation of the phospho-enzymeintermediate. Analysis of the X-ray structure of the wild-typeenzyme indicates that the increase in catalytic rate of themutant enzyme in the presence of a phosphate acceptor may bedue to an increase in accessibility of the active site nearSerl02. The increased catalytic rate of this mutant enzyme maybe utilized to improve diagnostic tests that require alkalinephosphatase, and the reduced heat stability of the mutant enzymemay make it useful in recombinant DNA techniques that requirethe ability to heat-inactivate the enzyme after use.     

Augmented reality in language learning: A state-of-the-art review of 2014–2019

This systematic review study synthesizes research findings pertaining to the use of augmented reality (AR) in language learning. Published research from 2014 to 2019 has been explored and specific inclusion and exclusion criteria have been applied resulting in 54 relevant publications. Our findings determined: (a) devices and software employed for mastering AR; languages and contexts in which AR had been applied; theoretical perspectives adopted for guiding the use of AR; the number of participants in AR activities and benefits from using AR as an educational tool in the language classroom; (b) alignment of the affordances of Augmented Reality with the KSAVE (Knowledge, Skills, Attitudes, Values, Ethics) 21st-century skills framework; (c) future directions in AR research and practice. The main findings from this review demonstrate the popularity of mobile-based AR for supporting vocabulary (23.9%), reading (12.7%), speaking (9.9%) writing (8.5%) or generic language skills (9.9%). Our findings also uncovered areas that merit future attention in the application of AR in language learning – for instance learning theories were not often considered in the implementation of AR. The study concludes with suggestions for future research especially in the areas of instructional design and user experience.     

La1−xSrxMyFe1−yO3−δ perovskites as oxygen-carrier materials for chemical-looping reforming

The use of perovskites with the general formula La_1−xSr_xM_yFe_1−yO₃ (M = Ni, Co, Cr, Cu) as oxygen carriers for syngas generation from methane by Chemical Looping Reforming is investigated in the present work. The experimental study concerns the oxidation of a fuel, using the oxygen from a solid oxygen carrier, instead of oxygen from air. Subsequent oxidation of the reduced solid is performed either with gaseous oxygen or with water. In the latter case additional hydrogen is produced, which is very pure and therefore appropriate to be used in fuel cell applications. The performance of the candidate materials is ranked by taking into account the hydrogen and carbon monoxide yields during the fuel oxidation step as well as the amount of oxygen per mole solid (δ) that can be delivered reversibly to the fuel. The effect of the materials composition and of NiO addition is examined. The best performance was obtained with the La_0.7Sr_0.3Cr_0.1Fe_0.9O₃ sample mixed with 5% NiO. The H₂ yield was up to 90%.     

Dynamically Driven Emergence in a Nanomagnetic System

Emergent behaviors occur when simple interactions between a system's constituent elements produce properties that the individual elements do not exhibit in isolation. This article reports tunable emergent behaviors observed in domain wall (DW) populations of arrays of interconnected magnetic ring-shaped nanowires under an applied rotating magnetic field. DWs interact stochastically at ring junctions to create mechanisms of DW population loss and gain. These combine to give a dynamic, field-dependent equilibrium DW population that is a robust and emergent property of the array, despite highly varied local magnetic configurations. The magnetic ring arrays’ properties (e.g., non-linear behavior, “fading memory” to changes in field, fabrication repeatability, and scalability) suggest they are an interesting candidate system for realizing reservoir computing (RC), a form of neuromorphic computing, in hardware. By way of example, simulations of ring arrays performing RC approaches 100% success in classifying spoken digits for single speakers.     

Computer-mediated communication in computer-assisted language learning: implications for culture-centered design

This study explores the research development pertaining to computer-mediated communication (CMC) in the field of computer-assisted language learning (CALL). The basic premise of this study is that language and consequently communication are essential elements of culture; thus, deep understanding of the role of technology in facilitating communication in online environments can deepen our understanding of the notion of culture and contribute to the specification of a universal design approach in culture-centered design. The authors applied a six-stage approach for conducting a systematic review of the research development in CALL between January 2009 and September 2010. This approach resulted in the development of the CALL map which consisted of 11 themes with which CALL researchers are concerned. This study focuses on CMC, a category which maintains its popularity for more than a decade, thus sustaining itself as a major area in the field. The review brings to the forefront key themes and findings of research in these areas, as well as core concepts emerging from the literature. The study discusses empirical findings and delineates how CMC can enhance language learning, concluding with possible future directions and implications for research and practice.     

An empirical comparison between stochastic and deterministic centroid initialisation for K-means variations

Machine Learning - K-Means is one of the most used algorithms for data clustering and the usual clustering method for benchmarking. Despite its wide application it is well-known that it suffers...     

Scanned images resolution improvement using neural networks

A novel method of improving the spatial resolution of scanned images, by means of neural networks, is presented in this paper. Images of different resolution, originating from scanner, successively train a neural network, which learns to improve resolution from 25 to 50 pixels-per-inch (ppi), then from 100 to 200 ppi and finally, from 50 to 100 ppi. Thus, the network is provided with consistent knowledge regarding the point spread function (PSF) of the scanner, whilst it gains the generalization ability to reconstruct finer resolution images unfamiliar to it. The novelty of the proposed image-resolution-enhancement technique lies in the successive training of the neural structure with images of increasing resolution. Comparisons with the image scanned at 400 ppi demonstrate the superiority of our method to conventional interpolation techniques.     

Interferon Lambda Regulates Cellular and Humoral Immunity in Pristane-Induced Lupus

A pivotal role of type I interferons in systemic lupus erythematosus (SLE) is widely accepted. Type III interferons (IFN-λ) however, the most recently discovered cytokines grouped within the interferon family, have not been extensively studied in lupus disease models yet. Growing evidence suggests a role for IFN-λ in regulating both innate and adaptive immune responses, and increased serum concentrations have been described in multiple autoimmune diseases including SLE. Using the pristane-induced lupus model, we found that mice with defective IFN-λ receptors (Ifnlr1^−/−) showed increased survival rates, decreased lipogranuloma formation and reduced anti-dsDNA autoantibody titers in the early phase of autoimmunity development compared to pristane-treated wild-type mice. Moreover, Ifnlr1^−/− mice treated with pristane had reduced numbers of inflammatory mononuclear phagocytes and cNK cells in their kidneys, resembling untreated control mice. Systemically, circulating B cells and monocytes (CD115⁺Ly6C⁺) were reduced in pristane-treated Ifnlr1^−/− mice. The present study supports a significant role for type III interferons in the pathogenesis of pristane-induced murine autoimmunity as well as in systemic and renal inflammation. Although the absence of type III interferon receptors does not completely prevent the development of autoantibodies, type III interferon signaling accelerates the development of autoimmunity and promotes a pro-inflammatory environment in autoimmune-prone hosts.