1,722,019 research outputs found
N-terminal extension of canine glutamine synthetase created by splicing alters its enzymatic property
No full textIt was found that an extra exon exists in the first intron of glutamine synthetase gene, generated by means of alternative splicing ( Shin, D., Park, S., and Park, C. (2003) Biochem. J. 374, 175 - 184). Inclusion of this exon decreased the translation of glutamine synthetase (GS) in human, dog, and mouse. When translated in vitro with the canine GS transcript containing the exon, we obtained two different species of GS enzymes. Besides the known 45-kDa protein, the extended form of GS was identified with additional 40 amino acids on its N-terminal end. An upstream ATG in the extra exon served as a translation initiator for the long form of GS. When the long transcript was translated in vivo in animal cells, only the long GS was expressed. On the other hand, the long GS is less predominant relative to the short one in canine tissues including brain and liver. Subcellular fractionation of canine brain revealed that the long GS is present in all cellular compartments as is the short one, which is consistent with fluorescence microscopy data obtained with green fluorescent protein fused to GS. The short (SGS) and long (LGS) forms of canine GS were purified in Escherichia coli and shown to have similar K-m values for L-glutamate and hydroxylamine. However, the K-m values for ATP were slightly altered, 1.3 and 1.9 mM for the short and long GSs, respectively. The K(i)s for L-methionine-S-sulfoximine (MSOX), a highly potent ATP-dependent inactivator of GS, were considerably different such that the values are 0.067 and 0.124 mM for the short and long forms, respectively. When the intrinsic fluorescences of tryptophans were monitored upon bindings of chloride and metal ions without any effect on the oligomeric state, the pattern of quenching in LGS was significantly different from that of SGS. Taken together, the N-terminal extension in the long isoform of GS induces a conformational change of core enzyme, leading to a change in affinity to its substrates as well as in the effector-induced conformational alterations
A simply connected surface of general type with p(g)=0 and K-2=4
No full textAs a continuation of the recent results of Y Lee and the second author [5] and the authors [6], we construct a simply connected minimal complex surface of general type with p(g) = 0 and K-2 = 4 by using a rational blow-down surgery and Q-Gorenstein smoothing theory.X1124sciescopu
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Modelling of ensemble-averaged premixed flame front under harmonic oscillation
No full textCombustion instabilities are one of the most important operability issues associated with low-NOx combustion technology. This paper develops numerical and theoretical analyses of the nonlinear dynamics of harmonically-forced turbulent premixed flames that drive thermoacoustic combustion instability. A key objective of this work is to develop a model that enables tracking of ensemble-averaged turbulent flame fronts. A previous study introduced an equation for modeling the ensemble-averaged turbulent flame dynamics, in which the turbulent flame speed model used a turbulent Markstein length to account for the effect of flame-brush curvature on the propagation speed. This study improves upon the previous modelling by introducing an additional modeling parameter – an effective convection speed – that is required in order to account for nonlinearity associated with turbulent transport. Three-dimensional simulations of the harmonically-forced flame dynamics are performed using the G-equation approach and a flow field involving stochastic velocity fluctuations. The new model equation provides an improved description of the ensemble-averaged flame dynamics that is in close agreement with the G-equation simulation results. Through asymptotic analysis, explicit expressions are derived for the un-curved turbulent flame speed, the turbulent Markstein length, and the effective convection speed. The asymptotic models that have been derived give accurate predictions of the flame dynamics in the vicinity of the flame holder. More general solutions are also derived for flame dynamics in the far field and these provide a basis for general modeling of turbulent flame speeds in harmonically-forced flow
The combustion of simulated waste particles in a fixed bed
No full textStable combustion of waste in an incinerator is necessary for optimal operation. However, complicated reactions, as well as heat and mass transfer, make understanding the process difficult. An experimental bed reactor is utilized to investigate the combustion of simulated waste particles, and a computational model is introduced to predict the phenomena. When the bed is brought into a radiating environment, an apparent flame zone is formed at the bed's top surface after a certain time delay. Subsequently, the flame front moves downwards into the bed of fuel. The flame propagation speed, i.e., the rate of progress of the apparent flame zone, is dependent on the air supply rate, the calorific value of the solid fuel, and the particle size. Based on the availability of oxygen, two distinct reaction modes are identified: the oxygen-limited mode and the reaction-limited mode. An increase in the flow rate of air eventually leads to flame extinction, as a result of excessive cooling by convection. The numerical results show good agreement with the experimental observations. The transient behavior of the local temperature and the rate of oxygen consumption are adequately reproduced. The effect of the combustion parameters on combustion in the bed is also discussed further. (C) 2000 by The Combustion Institute
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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