We have previously shown that the widely expressed human transcription factor TCF11/LCR-F1/Nrf1 interacts with small Maf proteins and binds to a subclass of AP1-sites. Such sites are required for beta-globin 5' DNase I hypersensitive site 2 enhancer activity, erythroid porphobilinogen deaminase inducibility, hemin responsiveness by heme-oxygenase 1 and expression of the gene NAD(P)H:quinone oxidoreductase1. Here we report the optimal DNA-binding sequences for TCF11/LCR-F1/Nrf1 alone and as a heterodimer with MafG, identified by using binding-site selection. The heterodimer recognises a 5'-TGCTgaGTCAT-3' binding-site that is identical to the established NF-E2-site, the antioxidant response element and the heme-responsive element while the binding specificity of the homomer is less stringent. To investigate the activity of TCF11 through this selected site, both alone and in the presence of MafG, we have used a transient transfection assay. TCF11 alone activates transcription while MafG alone acts as a repressor. When co-expressed, MafG interferes with TCF11 transactivation in a dose dependent manner. This indicates that MafG protein, which heterodimerises efficiently with TCF11 in vitro (the heterodimer having a higher affinity for DNA than TCF11 alone), does not co-operate with TCF11 in transactivating transcription. We propose that since both these factors are widely expressed, they may act together to contribute to the negative regulation of this specific target site. Efficient positive regulation by TCF11 may require alternative partners with perhaps more restricted expression patterns.
The human TCF11 gene encodes a ubiquitously expressed bZIP transcription factor of the cap n' collar (CNC) domain family. It has a high sequence similarity to the erythroid-specific bZIP factor p45 NF-E2 in the CNC domain, which is involved in DNA binding. LCR-F1, a TCF11 isoform, is a more potent transcriptional activator than p45 NF-E2 in erythroid cells. We show here that the TCF11 protein interacts to form heterodimers with small Maf proteins, previously shown to dimerize with p45 NF-E2, ECH and Fos. Such heterodimerization significantly alters the DNA binding characteristics of TCF11. While TCF11 alone binds in vitro to the tandem NF-E2 site derived from 5' DNase hypersensitive site 2 in the beta-globin locus control region and to the single NF-E2 site in the porphobilinogen deaminase gene promoter, stronger binding is detected in the presence of small Maf proteins. Using antibodies, TCF11 isoforms bound to the single NF-E2 site were detected in K562 erythroid cell nuclear extracts. These findings place TCF11 as a good candidate for the proposed widely expressed factor(s) known to interact with small Maf proteins and bind NF-E2 sites in a sequence-specific manner resembling NF-E2.
Floating offshore wind turbines (FOWTs) are an opportunity for large energy consumers in the oil and gas industry to reduce emissions. As the oil and gas structures are often installed in deep waters, the connecting power cables conventionally laying on the seabed have very long transmission distances leading to power losses and large cable sizes. In the present study, the novel concept of a suspended power cable between a FOWT and a Floating Production Storage and Offloading Unit (FPSO) in a large water depth of 1000 m is investigated. In this study, the power cable is kept floating between the sea surface and the seabed without touching neither of them. The power cable configuration is varied. A catenary configuration is investigated, as well as two configurations with subsea buoys attached at different locations along the cable. The OC3-Hywind 5 MW reference FOWT is set up with a deepwater mooring system and a spread moored FPSO is modeled having characteristics similar to existing FPSOs. Simulations are carried out in the analysis program OrcaFlex. Environmental conditions for the Campos Basin, Brazil, are assumed. The different configurations are evaluated in a steady-state analysis. The largest tensions occur for the catenary configuration, whereas it shows the lowest cable excursions and hang-off declination. A suspended configuration with buoys attached results in lower tensions that are below common limits but has larger excursions. This setup is studied further with a dynamic analysis. The tension at floater hang-off increases compared to steady-state results. The floater motions and the current seem to be the main factors influencing the suspended cable. The design of a suspended cable configuration is a balance between cable tensions and excursions, versus the amount and distribution of buoyancy attached.
The paper gives an overview of the analysis procedures involved in analyzing the global motion performance of tension leg platforms such as the Snorre and Heidrun platforms. The Aker Engineering TLP analysis system involves a suite of specially adapted purchased computer programs as well as in house developed programs. These programs are assembled into procedures for efficient and highly accurate analysis of all motion dependent parameters important for TLP design such as:Offset, set-down, air-gap etc. due to wave, wave drift and wind gustRiser and Tether extreme loads and fatigue lifeTemporary phases such as towing, station keeping and tether installationStructural analysis The paper addresses the hybrid panel/space frame model where all radiation and diffraction effects are accounted for and superimposed on stochastically linearized viscous drag which is particularly important to achieve correct damping values for the important slowly varying effects of wave drift and wind gust. Sum-frequency excitations and its effect on tether fatigue life and extreme forces are also discussed. The implementation of coupled TLP/tether dynamic analysis is outlined. INTRODUCTION To the hydrodynamicist, the award of the Snorre TLP Main Engineering Contract represented one of the most challenging involvements that one could hope for in a life time. The compliancy of such a structure, the considerable dynamic amplification of all 6 degrees of freedom resonances as well as its critical dependency on the tethers meant that state-of-the-art analysis techniques had to be stretched to the limit. For some aspects of the global motion performance, techniques only available in research institutions had to be transformed into practical design analysis tools for the first time. Presently, the Aker Engineering hydrodynamics are engaged by Norwegian Contractors, which is another Aker Company, to assist in all major analysis wrt. the Heidrun Tension Leg Platform. Due to the deep draft of the Heidrun TLP. which will be the first concrete floating production platform ever to be constructed, the demand for even further refinements of the hydrodynamics analysis procedures has been pressing. This paper reviews some of the more important adaptations made to the procedures and it outlines how the suite of tightly connected computer programs performs all hydrodynamic and global motion performance analysis tasks required for the TLP hull, tethers and risers. TLP ANALYSIS TOOLS The following is a summary of the major components of the TLP motion performance analysis tools:(available in full paper) GEOMETRY MODELLING All radiation and diffraction data is derived from a wetted surface discretization of the TLP hull, whilst the viscous drag is represented by projected areas in combination with drag coefficients according to the well known Morison equation. This means that the TLP hull has to be modelled by both a panel and a space frame model. All global motion analysis will, however, be performed on a space frame representation of the TLP hull. To achieve a transformation of panel based radiation and diffraction pressures to a space frame Morison type coefficient representation a table of panel numbers versus space frame members must be established.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.