1,721,042 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Enhancing carbon fixation in Escherichia coli using genetic engineering and metabolic profiling
No full textCarbon reduction and carbon neutrality are common goals in combating global warming. Biological carbon fixation presents a promising future for addressing excess CO2 levels, while the low efficiency and growth rate of natural autotrophic systems is challenging their carbon fixation. To enhance carbon fixation, extensive metabolic engineering studies have focused on enhancing the Calvin-Benson-Bassham (CBB) cycle and implementing carboxysome-based CO2-concentrating mechanisms (CCMs). However, the performance of various CCM components in the engineered systems and metabolic response to such engineering remain poorly understood.
In studies reported in this thesis, we established a functional CBB cycle in E. coli for CO2 fixation by heterologous expressing phosphoribulokinase (Prk), α-carboxysomes containing Rubisco and carbonic anhydrase (CA), as well as various inorganic carbon (Ci) transporters. Successful expression of Prk and α-carboxysomes was confirmed in E. coli, with their functionality validated through growth profiles, demonstrating superior carboxylation activity of α-carboxysome compared to Rubisco alone. Ci transporters were incorporated to enhance bicarbonate accumulation. Evaluation of four Ci transporters (Dab1, Dab2, BicA, and SbtA) revealed Dab2 as the most efficient transporter, although the inclusion of different Ci transporters did not enhance carbon fixation in the engineered E. coli. Furthermore, a mutant strain (ΔAB, deleting rpiA and rpiB genes) reliant on the CO2 fixation pathway to survive on glycerol was developed to serve as a platform for CBB cycle integration. The restored growth of the ΔAB mutant on glycerol was achieved with the CBB cycle integrated after evolution. Furthermore, evolution in the presence of Dab2 enabled CO2 fixation under ambient air conditions. Genomic sequencing identified mutations in three genes (araB, rnapT7 and gnd) on the chromosome, possibly contributing to CBB cycle integration. Metabolic profiling using gas chromatography-mass spectrometry (GC-MS) revealed significant alterations in 30 metabolites out of 257 detected features in response to the expression of α-carboxysomes, Prk, and Dab2, indicating an accelerated carbon flux in the engineered E. coli via the CBB cycle. Pathways such as arginine biosynthesis and the tricarboxylic acid cycle were influenced by these heterologously expressed proteins. Notably, strains expressing different Ci transporters exhibited uniform metabolic responses, consistent with growth profile observations.
In summary, we developed an engineered E. coli harbouring a functional CBB cycle and CCM, enabling carbon fixation in ambient air conditions. The limited contribution of Ci transporters suggests the existence of alternative Ci suppliers awakened during evolution. Metabolic profiling offers insights into the metabolic response to heterologous protein expression, aiding in the refinement of the carbon fixation system utilising the CBB cycle
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Towards the Study of Bacterial Communities at Single-Cell Level Using Vibrational Spectroscopy
Get PDFBacteria can be found in virtually all environments on earth, from soil and the ocean to toxic sludge, and are find on and inside all animal and plant bodies. Within these environments, they form complex ecosystems and interact with each other to competitive and cooperative ends through biochemical means. These interactions are vital towards our understanding of the role that bacteria play within these different niches; however, their small size places stringent limitations on our ability to study them in isolation or their interactions with other bacteria or their eukaryotic hosts. Most common methods involve biological testing, either through the probing of specific metabolisms or growth rates or genomic research. These methods, while powerful, are also often laborious and only provide a part of the overall picture.
Vibrational spectroscopy is a family of physicochemical methods probing the presence of various functional groups through bond excitation. These provide a holistic image of the bacterial phenotype without necessitating external labelling, making them a relatively quick and simple option. Furthermore, recent developments in optical photothermal infrared (O-PTIR) spectroscopy and the first commercial instrument utilising this method, presents the opportunity to bypass the spatial resolution limitations of infrared spectroscopy engendered by the diffraction limit to study single bacterial cells.
In this work, the information obtainable from individual bacteria via O-PTIR was studied using the Staphylococcus genus as a case study. First, intergenetic, interspecific and intraspecific discrimination were tested using two strains of S. capitis, two strains of S. epidermidis and one strain of Micrococcus luteus and benchmarked against bulk measurements of millions of cells from the already established Fourier transform infrared (FTIR) spectroscopy. Alongside successful discrimination, small spectral differences putatively assigned to protein secondary structure were described. Then, 22 strains of S. capitis comprising both subspecies capitis and urealyticus were studied, aiming not only to find the limit of bacterial discrimination of O-PTIR, but also to compare phenotypic classification obtained from O-PTIR and FTIR with genotypic classification obtained from whole-genome sequencing. FTIR and O-PTIR classifications did not match genotypic classification or each other demonstrating that, given the experimental conditions, the portion of the phenotype probed via infrared spectroscopy is unable to fully differentiate between these two subspecies. Third, a method was developed to probe differences in the phenotypes of S. capitis ssp. capitis and ssp. urealyticus when cultured in consortia and axenic conditions using FTIR spectroscopy and the Transwell® co-culture insert system. While these cultures could be discriminated, significant differences were also noticed based on growth conditions, notably between cells cultured in the insert and the well.
Additionally, this thesis contains an aside involving a study started during the COVID pandemic that successfully quantified the propylene glycol: glycerol ratio and nicotine content of e-cigarette liquids using portable Raman spectroscopy
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
APPLICATIONS OF METABOLOMICS APPROACHES FOR THE IMPROVEMENT OF MICROBIAL BIOPROCESS
Get PDFA bioprocess encompasses any process that utilises biological organisms or systems to facilitate specific chemical or physical transformations, leading to the production of value-added materials. One of the most prominent applications of microbial bioprocessing is recombinant protein production, a critical component of the biopharmaceutical industry. Optimising the efficiency of recombinant protein production is paramount to enhancing both product quality and yield. The current research investigated the metabolic responses of bacterial cells under stress conditions, such as recombinant protein production and exposure to propranolol, using a variety of analytical techniques. FT-IR spectroscopy, GC-MS, LC-MS, and NMR spectroscopy were employed to assess metabolic changes in different organisms under varying conditions. This includes optimising culture conditions for Streptomyces lividans RedStrep strains transformed with the pIJ486-mRFP plasmid and studying the metabolic effects of cytochrome b5-producing Escherichia coli N4830-1 using FT-IR and GC-MS. Additionally, the project explored the metabolic impact of Pseudomonas putida under propranolol stress through FT-IR fingerprinting and lipid profiling using LC-MS and NMR. The study highlights the diverse applications of metabolomics in microbial bioprocesses, with each analytical platform offering unique strengths and limitations. The combination of techniques—FT-IR for rapid fingerprinting, GC-MS for metabolic profiling, LC-MS for lipid profiling, and NMR for detailed metabolite analysis—provides a comprehensive understanding of the cellular processes involved in recombinant protein production. These insights will help identify bottlenecks and inform strategies to enhance production efficiency and optimise the bioprocess
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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