118 research outputs found
The role of light in photosynthetic cyanophages : from physiology to gene expression
No full textIt is estimated that there are approximately 1030 ocean virioplankton (Suttle 2007; Parsons et al. 2012). A large component of the oceanic viriosphere are the cyanophages, viruses that specifically infect cyanobacteria. Recent advances in genomics has revealed such viruses encode a multitude of genes, often acquired horizontally, that act to redirect metabolism for their own gains (Mann et al. 2003; Lindell et al. 2004a; Millard et al. 2009; Sullivan et al. 2010; Hurwitz et al. 2013; Enav et al. 2014). These genes have been named auxiliary metabolic genes (AMGs). They include multiple subunits of complexes involved with photosynthetic electron transport (PET) and CO2 fixation (Mann et al. 2003; Lindell et al. 2004; Millard et al. 2009; Sullivan et al. 2010; Thompson et al. 2011; Puxty et al. submitted), leading to the hypothesis that cyanophages directly participate in photosynthesis to provide carbon and energy for their own replication.
Cyanophages face a dynamically changing light environment during their rather lengthy infection cycles ~12hrs. Therefore, it was hypothesised that changes in light intensity may affect the physiology of phage infection in terms of photosynthesis, CO2 fixation and infection dynamics. During infection of the marine cyanobacterium Synechococcus sp. WH7803 with the well characterised cyanophage S-PM2 I show that decoupling of the photochemical and CO2 fixation reactions of photosynthesis occurs (Chapter 3), which presumably redirects metabolism towards energy generation and away from growth. Moreover, S-PM2 acts to modify the PET which results in improved functioning of PSII at HL. The result is that the lytic cycle is significantly shortened during infection of the Synechococcus host under HL compared with low light (LL) conditions. To understand whether this early lysis is a regulated process, whole transcriptome sequencing of S-PM2 was performed in HL and LL (Chapter 5). This revealed a general increase in expression of all genes in HL but only the cyanophage psbA gene was significantly up-regulated above this background. This AMG encodes a core complex of photosystem II (PSII) of the PET and therefore plays a vital role in supplying energy through photophosphorylation. It is concluded that light poses a metabolic constraint on cyanophage development that requires large amounts of energy for synthesis and assembly of the structural components of the virion. Cyanophages have therefore acquired and evolved coordinated expression of PSII genes to maintain this supply of energy.
I further hypothesise that gene expression may pose a significant barrier in the acquisition of AMGs from their host due to incompatible gene regulation. To test this, the phage transcriptome was analysed (Chapter 4) to validate the model of temporal transcriptional regulation in cyanophage S-PM2 as previously proposed by comparison to enterobacteriophage T4. It is shown that the experimental data is largely congruent with the proposed model. This also revealed unpredicted characteristics of the transcriptome, including genome wide transcriptional read-through and antisense expression. It is suggested that this is facilitated by either inefficient transcriptional termination or pervasive transcription initiation and may be a biologically relevant process that allows for moderate expression of recently acquired genes. In addition, genome-wide antisense transcription may act to regulate the inventory or temporal expression of specific mRNAs in these regulatory limited phages. Attempts were therefore made to characterise a previously detected non-coding RNA (ncRNA) antisense to the light regulated S-PM2 psbA gene (Chapter 6). A model is proposed suggesting that the asRNA may act to tweak psbA expression under LL conditions to prevent accumulation of unnecessary PSII proteins. This mechanism has an interesting effect on the rate of splicing of a group I intron encoded by the psbA gene.
This study provides an important leap forward in our understanding of the factors that regulate the infection dynamics and therefore ecology of cyanophages. In so doing it also reveals transcriptional constraints and adaptations that go some way to explaining the evolution of cyanophage genomes
Existe-t-il une recherche comptable globale en Europe ? Une étude des communications présentées à l'EAA
No full textAu milieu des années 1990, de nombreux articles ont montré que la recherche comptable était très locale (Lukka and Kasanen, 1996; Panozzo, 1997; Carmona et al. 1999). Ce constat contraste avec l'internationalisation croissante de la profession comptable (normes IFRS, convergence US GAAP /IFRS,...). Dans cet article, nous réexaminons la nature locale de la recherche comptable à l'heure de la mise en place des normes comptables internationales (IFRS) à partir de l'analyse des communications aux congrès de l'EAA. L'étude de communications (plutôt que des articles publiés) est intéressante dans la mesure où elle permet de donner une image fidèle de l'activité des chercheurs. En effet, de nombreux auteurs ont montré que les revues académiques sont largement dominées par les auteurs nord-Américains (Lukka et Kasanen, 1996 ; Raffournier et Schatt, 2006). Par ailleurs, de nombreux chercheurs de pays européens et non européens participent aux congrès de l'EAA qui nous semble dès lors être un forum ‘global' de la recherche comptable. A partir des congrès de 2000 et de 2005, nos résultats montrent qu'une part croissante des communications peut être qualifiée de globale. Deux facteurs semblent expliquer la globalisation de la recherche comptable. Tout d'abord, elle dépend du thème de recherche : la recherche en comptabilité financière est deux fois plus globale que la recherche en contrôle de gestion. Ensuite, la stratégie de collaboration de recherche (coauteurs) compte : les papiers qualifiés de globaux ont plus de coauteurs que les papiers locaux. Cette étude enrichit la compréhension de la dynamique de la recherche comptable et illustre la relation complexe qui existe entre la globalisation de la pratique comptable et celle de la communauté de recherche comptable.Recherche comptable; Association européenne de comptabilité
Theoretical studies of the historical development of the accounting discipline: a review and evidence
No full textMany existing studies of the development of accounting thought have either been atheoretical or have adopted Kuhn's model of scientific growth. The limitations of this 35-year-old model are discussed. Four different general neo-Kuhnian models of scholarly knowledge development are reviewed and compared with reference to an analytical matrix. The models are found to be mutually consistent, with each focusing on a different aspect of development. A composite model is proposed. Based on a hand-crafted database, author co-citation analysis is used to map empirically the entire literature structure of the accounting discipline during two consecutive time periods, 1972–81 and 1982–90. The changing structure of the accounting literature is interpreted using the proposed composite model of scholarly knowledge development
Förenkling, inte alltid så enkelt - En studie om Bokföringsnämndens K-projekt
No full textSyfte: Att identifiera problematik med K-projektet i praktiken. Metod: Studien använder en induktiv ansats och en kvalitativ forskningsmetod. Arbetsprocessen baseras på grundad teori. Teoretiskt perspektiv:Enligt American Accounting Association är redovisning ett ämne som är svårt att fånga i teoretiska modeller. Denna uppsats använder istället samhällsutvecklande teorier av Sten Jönsson och Anthony Puxty et al. för att beskriva viktiga faktorer som påverkar reglering av redovisning. Empiri:Studiens empiri består av primärdata insamlad genom semistrukturerade intervjuer med revisorer och redovisningsexperter, samt av sekundärdata från litteratur och offentliga debatt. Resultat:Studien intar en ifrågasättande hållning till K-projektet och presenterar ett kritiskt perspektiv till det sätt som redovisning regleras i Sverige. Ett av de största problemen är att K-projektet är politiskt initierat och inte tar nog hänsyn till de behov som finns ute hos företagen. Samtidigt är Bokföringsnämnden tilldelade för lite resurser för att på ett tillfredsställande sätt kunna kommunicera med omvärlden. Det har heller inte kunnat påvisas att K-projektet faktiskt kommer att leda till en förenklad redovisning. Dock är det ännu för tidigt för att helt utvärdera projektet
Small-scale reactor for data oriented process development
No full textDuring the early stages of research and development chemical industry needs flexible and versatile tools to investigate chemical reaction systems. An important part of the optimisation of a process considering economic factors, risk analysis and environmental impacts is the determination of a reaction mechanism and its associated parameters (i.e. activation energies, rates and heat of reactions). We present here a new fully automated small-scale reaction calorimeter combining a power-compensation heater and a thermoelectrically regulated metal surrounding. This dual temperature control makes the reactor highly suitable for fast and exothermic reactions and eliminates the need for time-consuming calibration of heat transfer coefficients. With a working volume from 25 to 45ml the device is particularly suited for the fine and pharmaceutical chemical industries where only small amounts of test substances are available. An integrated ATR-IR probe coupled to an FT-IR spectrometer allows the investigation of complex reaction mechanisms. Moreover, the new reactor design allows the simultaneous use of various additional in-situ analytics such as UV-Vis, gas intake/uptake and particle size analysis. The performance of the new reaction calorimeter has already been successfully demonstrated based on several reactions [1, 2, 3]. Different analytical techniques may point to different optimum reaction parameters. Algorithms and mathematical tools, such as multi-objective multivariate kinetic modelling, become an important research area in data oriented process development. Only a short introduction into these methods will be given here. [1] Zogg, A., Fischer, U., & Hungerbühler, K. (2003). A new small-scale reaction calorimeter that combines the principles of power compensation and heat balance. Industrial & Engineering Chemistry Research, 42, 767-776. [2] Visentin, F., Gianoli, S. I., Zogg, A., Kut, O. M., & Hungerbühler, K. (2004). Pressure-resistant smallscale reaction calorimeter that combines the principles of power compensation and heat balance (CRC.v4). Organic Process Research & Development, 8(5), 725-737. [3] Visentin, F., Puxty, G., Kut, O. M., & Hungerbühler, K. (2006). Study of the hydrogenation of selected nitro compounds by simultaneous measurements of calorimetric, FT-IR, and gas-uptake signals. Industrial & Engineering Chemistry Research, 45(13), 4544-4553.IG
Reading accounting writing
No full textAccounting texts are generally taken as unproblematically linked to the intentions of their authors, whether they be the writers of articles and papers or the producers of financial statements themselves. This paper argues against the logocentric notion of an intentional unitary author and in doing so grants the reader the freedom to actively read a text. The post-structuralist insights of Roland Barthes are used to show the workings of logocentrism and how the text can be disrupted by the reader. The disruption is exemplified in the paper through the undertaking of a detailed deconstruction of a magazine article on an accounting subject
Real-time kinetic hard-modelling for the optimisation of reaction conditions and the detection of process upset in semi-batch reactors
No full textProcess Analytical Technology (PAT) has greatly evolved in the last decades due to the development of multivariate online sensors that are able to monitor the properties of industrial processes in real time [1, 2]. The online monitoring of product quality and the detection of process upsets are important for the pharmaceutical and fine chemical industry in order to maintain their product specifications and their commitments regarding safety, health and environment. Most frequent sources of deviations from normal operating conditions in semi-batch processes are due to slightly imprecise initial conditions or impurities in the initial reactants causing unexpected side reactions [3]. Online monitoring of industrial processes usually relies on calibration methods, such Principal Component Regression (PCR), Partial Least Squares (PLS) or Black Box models (e.g. Neural Networks) [4, 5]. A drawback of these calibration methods is their poor behaviour regarding extrapolation, requiring a constant effort for the operator to maintain the calibration conditions. Kinetic modelling techniques [6] do not suffer from this drawback as they are based on first principal models and can also be adapted for the monitoring of highly fluctuating processes, e.g. semi-batch processes. In this contribution, we propose a method for the online monitoring of semi-batch processes based on kinetic hard-modelling. The proposed method assumes that the kinetic model and the associated rate constants have already been determined at an earlier stage in R&D. In a first phase, the algorithm corrects estimates for the initial concentrations from dosing a small amount of reagent and fitting the kinetic model to the measured signals, e.g. mid-IR, UV-vis or released/consumed heat. In a second phase, if no process upset is detected, the corrected initial concentrations are fed back into the kinetic model and the algorithm optimises the dosing rate of the reagent or the operating temperature by maximising a property of the process, e.g. yield, selectivity or conversion. When optimum operating conditions are found, the algorithm forces the reactor to work under these improved conditions and the process is continuously re-optimised to detect possible process upsets. The method will be discussed based on simulated and experimental data taken from our high performance small scale reaction calorimeter coupled to in-situ mid-IR and UV-vis ATR-spectroscopy [7]. [1] P. Gemperline, G. Puxty, M. Maeder, D. Walker, F. Tarczynski, M. Bosserman, Analytical Chemistry 76 (2004) 2575-2582. [2] J. Workman, M. Koch, D. Veltkamp, Analytical Chemistry 77 (2005) 3789-3806. [3] E.N.M. van Sprang, H.J. Ramaker, H.F.M. Boelens, J.A. Westerhuis, D. Whiteman, D. Baines, I. Weaver, Analyst 128 (2003) 98-102. [4] M. Spear, Chemical Processing 70 (2007) 20-26. [5] T.J. Thurston, R.G. Brereton, D.J. Foord, R.E.A. Escott, Journal of Chemometrics 17 (2003) 313-322. [6] M. Maeder, Y.M. Neuhold, Practical Data Analysis in Chemistry, Elsevier, Amsterdam NL, 2007. [7] F. Visentin, S.I. Gianoli, A. Zogg, O.M. Kut, K. Hungerbühler, Organic Process Research & Development 8 (2004) 725-737.IGMPresented as an Oral contributio
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