Bibliografie tematiche / Futile repair

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Letteratura scientifica selezionata sul tema "Futile repair"

Autore: Grafiati

Pubblicato: 25 gennaio 2025

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Articoli di riviste sul tema "Futile repair"

Gupta, Dipika, Bo Lin, Ann Cowan e Christopher D. Heinen. "ATR-Chk1 activation mitigates replication stress caused by mismatch repair-dependent processing of DNA damage". Proceedings of the National Academy of Sciences 115, n. 7 (29 gennaio 2018): 1523–28. http://dx.doi.org/10.1073/pnas.1720355115.

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The mismatch repair pathway (MMR) is essential for removing DNA polymerase errors, thereby maintaining genomic stability. Loss of MMR function increases mutation frequency and is associated with tumorigenesis. However, how MMR is executed at active DNA replication forks is unclear. This has important implications for understanding how MMR repairs O6-methylguanine/thymidine (MeG/T) mismatches created upon exposure to DNA alkylating agents. If MeG/T lesion recognition by MMR initiates mismatch excision, the reinsertion of a mismatched thymidine during resynthesis could initiate futile repair cycles. One consequence of futile repair cycles might be a disruption of overall DNA replication in the affected cell. Herein, we show that in MMR-proficient HeLa cancer cells, treatment with a DNA alkylating agent slows S phase progression, yet cells still progress into the next cell cycle. In the first S phase following treatment, they activate ataxia telangiectasia and Rad3-related (ATR)-Checkpoint Kinase 1 (Chk1) signaling, which limits DNA damage, while inhibition of ATR kinase activity accelerates DNA damage accumulation and sensitivity to the DNA alkylating agent. We also observed that exposure of human embryonic stem cells to alkylation damage severely compromised DNA replication in a MMR-dependent manner. These cells fail to activate the ATR-Chk1 signaling axis, which may limit their ability to handle replication stress. Accordingly, they accumulate double-strand breaks and undergo immediate apoptosis. Our findings implicate the MMR-directed response to alkylation damage as a replication stress inducer, suggesting that repeated MMR processing of mismatches may occur that can disrupt S phase progression.

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Mu, David, Tadayoshi Bessho, Lubomir V. Nechev, David J. Chen, Thomas M. Harris, John E. Hearst e Aziz Sancar. "DNA Interstrand Cross-Links Induce Futile Repair Synthesis in Mammalian Cell Extracts". Molecular and Cellular Biology 20, n. 7 (1 aprile 2000): 2446–54. http://dx.doi.org/10.1128/mcb.20.7.2446-2454.2000.

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ABSTRACT DNA interstrand cross-links are induced by many carcinogens and anticancer drugs. It was previously shown that mammalian DNA excision repair nuclease makes dual incisions 5′ to the cross-linked base of a psoralen cross-link, generating a gap of 22 to 28 nucleotides adjacent to the cross-link. We wished to find the fates of the gap and the cross-link in this complex structure under conditions conducive to repair synthesis, using cell extracts from wild-type and cross-linker-sensitive mutant cell lines. We found that the extracts from both types of strains filled in the gap but were severely defective in ligating the resulting nick and incapable of removing the cross-link. The net result was a futile damage-induced DNA synthesis which converted a gap into a nick without removing the damage. In addition, in this study, we showed that the structure-specific endonuclease, the XPF-ERCC1 heterodimer, acted as a 3′-to-5′ exonuclease on cross-linked DNA in the presence of RPA. Collectively, these observations shed some light on the cellular processing of DNA cross-links and reveal that cross-links induce a futile DNA synthesis cycle that may constitute a signal for specific cellular responses to cross-linked DNA.

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Ohba, Shigeo, Kei Yamashiro e Yuichi Hirose. "Inhibition of DNA Repair in Combination with Temozolomide or Dianhydrogalactiol Overcomes Temozolomide-Resistant Glioma Cells". Cancers 13, n. 11 (24 maggio 2021): 2570. http://dx.doi.org/10.3390/cancers13112570.

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Resistance to temozolomide and intratumoral heterogeneity contribute to the poor prognosis of glioma. The mechanisms of temozolomide resistance can vary within a heterogeneous tumor. Temozolomide adds a methyl group to DNA. The primary cytotoxic lesion, O6-methylguanine, mispairs with thymine, leading to a futile DNA mismatch repair cycle, formation of double-strand breaks, and eventual cell death when O6-methylguanine DNA methyltransferase (MGMT) is absent. N7-methylguanine and N3-methyladenine are repaired by base excision repair (BER). The study aim was to elucidate temozolomide resistance mechanisms and identify methods to overcome temozolomide resistance in glioma. Several temozolomide-resistant clones were analyzed. Increased homologous recombination and mismatch repair system deficiencies contributed to temozolomide resistance. Inhibition of homologous recombination resensitized resistant cells with high homologous recombination efficiency. For the mismatch repair-deficient cells, inhibition of BER by PARP inhibitor potentiated temozolomide-induced cytotoxicity. Dianhydrogalactiol is a bifunctional DNA-targeting agent that forms N7-alkylguanine and inter-strand DNA crosslinks. Dianhydrogalactiol reduced the proliferation of cells independent of MGMT and mismatch repair, inducing DNA double-strand breaks and apoptosis in temozolomide-resistant cells. Further, inhibition of chk1 or homologous recombination enhanced dianhydrogalactiol-induced cytotoxicity in the cells. Selecting treatments most appropriate to the types of resistance mechanisms can potentially improve the prognosis of glioma.

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Hashimoto, K. "Futile short-patch DNA base excision repair of adenine:8-oxoguanine mispair". Nucleic Acids Research 32, n. 19 (28 ottobre 2004): 5928–34. http://dx.doi.org/10.1093/nar/gkh909.

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Overmeer, René M., Jill Moser, Marcel Volker, Hanneke Kool, Alan E. Tomkinson, Albert A. van Zeeland, Leon H. F. Mullenders e Maria Fousteri. "Replication protein A safeguards genome integrity by controlling NER incision events". Journal of Cell Biology 192, n. 3 (31 gennaio 2011): 401–15. http://dx.doi.org/10.1083/jcb.201006011.

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Single-stranded DNA gaps that might arise by futile repair processes can lead to mutagenic events and challenge genome integrity. Nucleotide excision repair (NER) is an evolutionarily conserved repair mechanism, essential for removal of helix-distorting DNA lesions. In the currently prevailing model, NER operates through coordinated assembly of repair factors into pre- and post-incision complexes; however, its regulation in vivo is poorly understood. Notably, the transition from dual incision to repair synthesis should be rigidly synchronized as it might lead to accumulation of unprocessed repair intermediates. We monitored NER regulatory events in vivo using sequential UV irradiations. Under conditions that allow incision yet prevent completion of repair synthesis or ligation, preincision factors can reassociate with new damage sites. In contrast, replication protein A remains at the incomplete NER sites and regulates a feedback loop from completion of DNA repair synthesis to subsequent damage recognition, independently of ATR signaling. Our data reveal an important function for replication protein A in averting further generation of DNA strand breaks that could lead to mutagenic and recombinogenic events.

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Weimbs, Thomas. "Regulation of mTOR by Polycystin-1: is Polycystic Kidney Disease a Case of Futile Repair?" Cell Cycle 5, n. 21 (20 ottobre 2006): 2425–29. http://dx.doi.org/10.4161/cc.5.21.3408.

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Manapkyzy, Diana, Botagoz Joldybayeva, Alexander A. Ishchenko, Bakhyt T. Matkarimov, Dmitry O. Zharkov, Sabira Taipakova e Murat K. Saparbaev. "Enhanced thermal stability enables human mismatch-specific thymine–DNA glycosylase to catalyse futile DNA repair". PLOS ONE 19, n. 10 (18 ottobre 2024): e0304818. http://dx.doi.org/10.1371/journal.pone.0304818.

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Human thymine-DNA glycosylase (TDG) excises T mispaired with G in a CpG context to initiate the base excision repair (BER) pathway. TDG is also involved in epigenetic regulation of gene expression by participating in active DNA demethylation. Here we demonstrate that under extended incubation time the full-length TDG (TDGFL), but neither its isolated catalytic domain (TDGcat) nor methyl-CpG binding domain-containing protein 4 (MBD4) DNA glycosylase, exhibits significant excision activity towards T and C in regular non-damaged DNA duplex in TpG/CpA and CpG/CpG contexts. Time course of the cleavage product accumulation under single-turnover conditions shows that the apparent rate constant for TDGFL-catalysed excision of T from T•A base pairs (0.0014–0.0069 min−1) is 85–330-fold lower than for the excision of T from T•G mispairs (0.47–0.61 min−1). Unexpectedly, TDGFL, but not TDGcat, exhibits prolonged enzyme survival at 37°C when incubated in the presence of equimolar concentrations of a non-specific DNA duplex, suggesting that the disordered N- and C-terminal domains of TDG can interact with DNA and stabilize the overall conformation of the protein. Notably, TDGFL was able to excise 5-hydroxymethylcytosine (5hmC), but not 5-methylcytosine residues from duplex DNA with the efficiency that could be physiologically relevant in post-mitotic cells. Our findings demonstrate that, under the experimental conditions used, TDG catalyses sequence context-dependent removal of T, C and 5hmC residues from regular DNA duplexes. We propose that in vivo the TDG-initiated futile DNA BER may lead to formation of persistent single-strand breaks in non-methylated or hydroxymethylated chromatin regions.

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Weimbs, Thomas. "Polycystic kidney disease and renal injury repair: common pathways, fluid flow, and the function of polycystin-1". American Journal of Physiology-Renal Physiology 293, n. 5 (novembre 2007): F1423—F1432. http://dx.doi.org/10.1152/ajprenal.00275.2007.

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The root cause for most cases of autosomal-dominant polycystic kidney disease (ADPKD) is mutations in the polycystin-1 (PC1) gene. While PC1 has been implicated in a perplexing variety of protein interactions and signaling pathways, what its normal function is and why its disruption leads to the proliferation of renal epithelial cells are unknown. Recent results suggest that PC1 is involved in mechanotransduction by primary cilia measuring the degree of luminal fluid flow. PC1 has also recently been shown to regulate the mTOR and signal transducers and activators of transcription (STAT) 6 pathways. These two pathways are normally dormant in the healthy kidney but are activated in response to injury and appear to drive a proliferative repair response. This review develops the idea that a critical function of PC1 and primary cilia in the adult kidney may be to sense renal injury by detecting changes in luminal fluid flow and to trigger proliferation. Constitutive activation of these pathways in ADPKD would lead to the futile attempt to repair a nonexisting injury, resulting in cyst growth. The existence of many known cellular and molecular similarities between renal repair and ADPKD supports this model.

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Fujii, Shingo, e Robert P. Fuchs. "Accidental Encounter of Repair Intermediates in Alkylated DNA May Lead to Double-Strand Breaks in Resting Cells". International Journal of Molecular Sciences 25, n. 15 (26 luglio 2024): 8192. http://dx.doi.org/10.3390/ijms25158192.

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In clinics, chemotherapy is often combined with surgery and radiation to increase the chances of curing cancers. In the case of glioblastoma (GBM), patients are treated with a combination of radiotherapy and TMZ over several weeks. Despite its common use, the mechanism of action of the alkylating agent TMZ has not been well understood when it comes to its cytotoxic effects in tumor cells that are mostly non-dividing. The cellular response to alkylating DNA damage is operated by an intricate protein network involving multiple DNA repair pathways and numerous checkpoint proteins that are dependent on the type of DNA lesion, the cell type, and the cellular proliferation state. Among the various alkylating damages, researchers have placed a special on O6-methylguanine (O6-mG). Indeed, this lesion is efficiently removed via direct reversal by O6-methylguanine-DNA methyltransferase (MGMT). As the level of MGMT expression was found to be directly correlated with TMZ efficiency, O6-mG was identified as the critical lesion for TMZ mode of action. Initially, the mode of action of TMZ was proposed as follows: when left on the genome, O6-mG lesions form O6-mG: T mispairs during replication as T is preferentially mis-inserted across O6-mG. These O6-mG: T mispairs are recognized and tentatively repaired by a post-replicative mismatched DNA correction system (i.e., the MMR system). There are two models (futile cycle and direct signaling models) to account for the cytotoxic effects of the O6-mG lesions, both depending upon the functional MMR system in replicating cells. Alternatively, to explain the cytotoxic effects of alkylating agents in non-replicating cells, we have proposed a “repair accident model” whose molecular mechanism is dependent upon crosstalk between the MMR and the base excision repair (BER) systems. The accidental encounter between these two repair systems will cause the formation of cytotoxic DNA double-strand breaks (DSBs). In this review, we summarize these non-exclusive models to explain the cytotoxic effects of alkylating agents and discuss potential strategies to improve the clinical use of alkylating agents.

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Cheon, Na Young, Hyun-Suk Kim, Jung-Eun Yeo, Orlando D. Schärer e Ja Yil Lee. "Single-molecule visualization reveals the damage search mechanism for the human NER protein XPC-RAD23B". Nucleic Acids Research 47, n. 16 (2 agosto 2019): 8337–47. http://dx.doi.org/10.1093/nar/gkz629.

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Abstract DNA repair is critical for maintaining genomic integrity. Finding DNA lesions initiates the entire repair process. In human nucleotide excision repair (NER), XPC-RAD23B recognizes DNA lesions and recruits downstream factors. Although previous studies revealed the molecular features of damage identification by the yeast orthologs Rad4-Rad23, the dynamic mechanisms by which human XPC-RAD23B recognizes DNA defects have remained elusive. Here, we directly visualized the motion of XPC-RAD23B on undamaged and lesion-containing DNA using high-throughput single-molecule imaging. We observed three types of one-dimensional motion of XPC-RAD23B along DNA: diffusive, immobile and constrained. We found that consecutive AT-tracks led to increase in proteins with constrained motion. The diffusion coefficient dramatically increased according to ionic strength, suggesting that XPC-RAD23B diffuses along DNA via hopping, allowing XPC-RAD23B to bypass protein obstacles during the search for DNA damage. We also examined how XPC-RAD23B identifies cyclobutane pyrimidine dimers (CPDs) during diffusion. XPC-RAD23B makes futile attempts to bind to CPDs, consistent with low CPD recognition efficiency. Moreover, XPC-RAD23B binds CPDs in biphasic states, stable for lesion recognition and transient for lesion interrogation. Taken together, our results provide new insight into how XPC-RAD23B searches for DNA lesions in billions of base pairs in human genome.

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Più fonti

Tesi sul tema "Futile repair"

Manapkyzy, Diana. "In vitro characterization of aberrant and futile DNA repair initiated by human Thymine-DNA glycosylase". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASL131.

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La Thymine-ADN glycosylase humaine (TDG) est connue pour initier l'élimination de la T mis-appariée avec la G dans un contexte CpG dans la voie de réparation par excision de base (BER), prévenant l'effet mutagène de la désamination spontanée de la 5-méthylcytosine (5mC) dans l'ADN. Des études ont montré que TDG joue un rôle clé dans la régulation de la transcription en interagissant avec divers récepteurs nucléaires et facteurs de transcription, soulignant ainsi sa fonction dans la régulation d'expression des gènes, en particulier pendant le développement. De plus, TDG est impliquée dans la régulation épigénétique de transcription en empêchant la méthylation de novo des promoteurs riches en CpG en participant dans la déméthylation active de l'ADN avec les enzymes TETs. TDG humaine est également capable d'initier une voie de BER aberrante en excisant la thymine appariée à une adénine endommagée dans le contexte de la séquence TpG/CpX, où X est une adénine modifiée. L'acide aristolochique, un composé trouvé dans des plantes médicinales chinoises, est activé par des nitroréductases cellulaires, ce qui entraîne la formation des adduits de 7-(désoxyadénosine-N6yl) aristolactame (dA-ALI et dA-ALII) dans l'ADN cellulaire. Des études récentes sur le cancer induit par d'acides aristolochiques ont identifié des transversions de T→A multiples dans le contexte de séquence CpTpG/CpApG, qui ressemble fortement au contexte préféré pour l'excision aberrante de T par TDG dans le duplex endommagé T•X. Étant donné que les adduits dA-AL ne sont pas réparés sur le brin d'ADN non transcrit et peuvent donc persister dans les cellules, nous avons émis l'hypothèse d'une possible implication de TDG dans la mutagénèse induit par l'acide aristolochique.Pour étudier cela nous avons reconstitué la réparation in vitro en utilisant des oligonucléotides contenant dA-AL marqués de manière radioactive. De manière inattendue, après une incubation prolongée à 37 °C, l'enzyme TDG de longueur complète (TDGFL) a montré une activité glycosylase envers les bases C et T normales appariées avec G et A, respectivement, plutôt que T appariée aux adduits dA-AL. TDG cible préférentiellement les pyrimidines non endommagées dans un duplex d'ADN régulier dans les contextes TpG/CpA et CpG/CpG, ce que nous avons appelé « réparation futile ». La cinétique de réparation en conditions de turnover unique montre que le taux maximal d'excision de base (kobs) de T dans le duplex T•A (0.0014 min-1) catalysé par TDGFL est 300 fois plus lent que pour T•G (0,470 min-1). Notamment, TDGFL native, mais non le domaine catalytique tronqué TDG (TDGCAT), a montré une stabilité accrue à 37°C en présence de concentrations équimolaires de duplex d'ADN non spécifiques, suggérant que les domaines désordonnés N- et C-terminaux de la protéine TDG interagissent avec l'ADN, stabilisant ainsi la conformation de la protéine. De plus, nous avons montré que 5mC n'est pas excisée par TDGFL, tandis que 5-hydroxyméthylcytosine (5hmC), au contraire, est excisée aussi bien que la cytosine normale dans le contexte CpG. Ces résultats suggèrent un rôle possible de TDG dans la génération de cassures monocaténaires (SSB) dans les enhancers (amplificateurs) des cellules neuronales postmitotiques, un processus qui pourrait contribuer aux maladies neurodégénératives, car les cassures ont été principalement observées à proximité des sites de déméthylation de l'ADN et des îlots CpG. En conclusion, nos résultats démontrent que dans des conditions expérimentales, TDGFL catalyse la réparation futile des résidus de pyrimidine dans les duplex d'ADN réguliers dépendante du contexte de séquence, ce qui, dans des conditions in vivo, pourrait conduire à la formation persistante de SSB dans les régions non méthylées de l'ADN chromosomique. La découverte de la réparation lente des résidus 5hmC dans l'ADN par la voie TDG/BER est l'un des principaux points d'intérêt pour les études et perspectives futures
The human thymine-DNA glycosylase (TDG) is known for excising T mispaired with G in CpG context and initiating the base excision repair (BER) pathway, thus preventing the mutagenic effect of spontaneous deamination of 5-methylcytosine (5mC). Initially TDG was considered as an inefficient repair enzyme, due to the low catalytic activity on G•T mismatch, with no significant biological function. However, further studies have shown that TDG plays a key role in the regulation of transcription by interacting with various nuclear receptors and transcription factors, emphasizing its function in gene expression, particularly during development. Furthermore, TDG has been implicated in epigenetic regulation of gene expression by preventing CpG-rich promoters from de novo DNA methylation by excising 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC) residues. Human TDG protein is also able to initiate aberrant BER pathway by excising regular T opposite to damaged adenine residue in the TpG/CpX sequence context, where X is a modified adenine.Previously, it was shown that Aristolochic acid, compound found in certain plants used in traditional Chinese medicine, is activated by cellular nitroreductases, resulting in the formation of reactive intermediates that bind covalently to DNA to produce 7-(deoxyadenosin-N6yl)aristolactam (dA-ALI and dA-ALII) adducts. Recent studies on cancer induced by consumption of aristolochic acids have identified mutation hotspots corresponding to T→A transversion in CpTpG/CpApG sequence context, which in turn resembles very much to the preferred sequence context of TDG-catalysed aberrant excision of T in T•X base pair. Given that aristolactam dA-AL adducts are not repaired on the non-transcribed DNA strand and thus can persist in cells, we hypothesized a possible involvement of TDG in the aberrant excision of T opposite to dA-AL adduct, potentially leading to error-prone BER and mutation fixation. To study the involvement of TDG in the initiation of aberrant BER, we carried out reconstitution of repair in vitro using radioactively labeled oligonucleotide DNA substrates. Unexpectedly, under the experimental conditions used, prolonged incubation at 37°C, the full-length TDG (TDGFL) enzyme exhibited glycosylase activity toward normal C and T paired with G and A, respectively, rather than T paired with the dA-AL adducts. TDG targets non-damaged pyrimidines in regular DNA duplex preferentially in TpG/CpA and CpG/CpG contexts, here we referred this unusual activity as “futile repair”. Time course of the cleavage product generation under single-turnover conditions shows that the maximal rate of base excision (kobs) of T from T•A duplex catalyzed by TDGFL (0.0014) is 300-fold lower than that for T•G (0.470 min-1). Notably, native TDGFL, but not the truncated catalytic domain TDG (TDGCAT), exhibited enhanced stability at 37°C in the presence of equimolar concentrations of non-specific DNA duplexes, suggesting that the disordered N- and C-terminal domains of TDG interact with DNA, stabilizing the protein's conformation. Additionally, we showed that 5mC is not excised by TDGFL, while 5hmC, on the contrary, is excised as well as regular cytosine in CpG context. Taken together, these findings imply a possible role of TDG in the generation of single-strand breaks (SSB) in enhancer regions of postmitotic neuronal cells, a process that might contribute to neurodegenerative diseases, as breaks were predominantly observed near sites of DNA demethylation and CpG islands. In conclusion, our findings demonstrate that under experimental conditions used TDGFL catalyses sequence context-dependent futile removal of pyrimidine residues in regular DNA duplex, which under in vivo conditions could lead to persistent SSB formation in non-methylated regions of chromosomal DNA. The discovery of slow repair of 5hmC residues in DNA by TDG/BER pathway is one of the main points of interest for future studies and perspectives

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Pittas, Pantelis Aristeidis 1977. "Global ship-repair industry : evaluation of current situation and future trends". Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/8967.

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Thesis (S.M. in Ocean Systems Management)--Massachusetts Institute of Technology, Dept. of Ocean Engineering; and, (S.M. in Naval Architecture and Marine Engineering)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1999.
Includes bibliographical references (leaves 96-98).
This thesis is an analysis of the Global Ship-repair market. This subject is of great interest to all involved in the shipping industry, as it is one of the industry's major components. There are many yards that specialize in ship-repair and bear the necessary equipment and facilities to meet shipowners' needs and specifications. The service mix varies though, depending upon the strategic decisions made by the different shipyards so as to optimize their efficiencies. Different shipyards and geographical regions offer different varieties of services and specialization. Thereby, my aim is to define, analyze, and understand the mechanisms of the ship-repair market. To do so, I will first look on the market as a single unit. I will then segment the whole ship-repair industry into geographical regions, analyze them separately, and compare them. Through this process, I shall establish a way for a shipowner to more appropriately choose the shipyard that best meets his needs. So as to carry out the above analysis, I will have to compare the different yards on a common basis. For that purpose, a dry docking specification for an existing 34,000 dwt bulk-carrier vessel was sent to numerous yards around the globe on request for offers. Collecting data was not trouble-free; some shipyards did not respond to our drydocking specification at all, while others did not have free space to facilitate the vessel. After several attempts, more than thirty offers from around the world were aggregated, providing an ample set of data to carry out the necessary calculations. What follows next is a look into the future trends of the ship-repair market.
by Pantelis Aristeidis Pittas.
S.M.in Naval Architecture and Marine Engineering
S.M.in Ocean Systems Management

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Karim, Hawzheen. "Improved Road Design for Future Maintenance - Analysis of Road Barrier Repair Costs". Licentiate thesis, Stockholm : Division of Highway Engineering, Royal Institute of Technology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9260.

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Karim, Hawzheen. "Road Design for Future Maintenance : Life-cycle Cost Analyses for Road Barriers". Doctoral thesis, Högskolan Dalarna, Vägteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:du-5474.

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The cost of a road construction over its service life is a function of design, quality of construction as well as maintenance strategies and operations. An optimal life-cycle cost for a road requires evaluations of the above mentioned components. Unfortunately, road designers often neglect a very important aspect, namely, the possibility to perform future maintenance activities. Focus is mainly directed towards other aspects such as investment costs, traffic safety, aesthetic appearance, regional development and environmental effects. This doctoral thesis presents the results of a research project aimed to increase consideration of road maintenance aspects in the planning and design process. The following subgoals were established: Identify the obstacles that prevent adequate consideration of future maintenance during the road planning and design process; and Examine optimisation of life-cycle costs as an approach towards increased efficiency during the road planning and design process. The research project started with a literature review aimed at evaluating the extent to which maintenance aspects are considered during road planning and design as an improvement potential for maintenance efficiency. Efforts made by road authorities to increase efficiency, especially maintenance efficiency, were evaluated. The results indicated that all the evaluated efforts had one thing in common, namely ignorance of the interrelationship between geometrical road design and maintenance as an effective tool to increase maintenance efficiency. Focus has mainly been on improving operating practises and maintenance procedures. This fact might also explain why some efforts to increase maintenance efficiency have been less successful. An investigation was conducted to identify the problems and difficulties, which obstruct due consideration of maintainability during the road planning and design process. A method called “Change Analysis” was used to analyse data collected during interviews with experts in road design and maintenance. The study indicated a complex combination of problems which result in inadequate consideration of maintenance aspects when planning and designing roads. The identified problems were classified into six categories: insufficient consulting, insufficient knowledge, regulations and specifications without consideration of maintenance aspects, insufficient planning and design activities, inadequate organisation and demands from other authorities. Several urgent needs for changes to eliminate these problems were identified. One of the problems identified in the above mentioned study as an obstacle for due consideration of maintenance aspects during road design was the absence of a model for calculating life-cycle costs for roads. Because of this lack of knowledge, the research project focused on implementing a new approach for calculating and analysing life-cycle costs for roads with emphasis on the relationship between road design and road maintainability. Road barriers were chosen as an example. The ambition is to develop this approach to cover other road components at a later stage. A study was conducted to quantify repair rates for barriers and associated repair costs as one of the major maintenance costs for road barriers. A method called “Case Study Research Method” was used to analyse the effect of several factors on barrier repairs costs, such as barrier type, road type, posted speed and seasonal effect. The analyses were based on documented data associated with 1625 repairs conducted in four different geographical regions in Sweden during 2006. A model for calculation of average repair costs per vehicle kilometres was created. Significant differences in the barrier repair costs were found between the studied barrier types. In another study, the injuries associated with road barrier collisions and the corresponding influencing factors were analysed. The analyses in this study were based on documented data from actual barrier collisions between 2005 and 2008 in Sweden. The result was used to calculate the cost for injuries associated with barrier collisions as a part of the socio-economic cost for road barriers. The results showed significant differences in the number of injuries associated with collisions with different barrier types. To calculate and analyse life-cycle costs for road barriers a new approach was developed based on a method called “Activity-based Life-cycle Costing”. By modelling uncertainties, the presented approach gives a possibility to identify and analyse factors crucial for optimising life-cycle costs. The study showed a great potential to increase road maintenance efficiency through road design. It also showed that road components with low investment costs might not be the best choice when including maintenance and socio-economic aspects. The difficulties and problems faced during the collection of data for calculating life-cycle costs for road barriers indicated a great need for improving current data collecting and archiving procedures. The research focused on Swedish road planning and design. However, the conclusions can be applied to other Nordic countries, where weather conditions and road design practices are similar. The general methodological approaches used in this research project may be applied also to other studies.

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Morel, Daphné. "Identifying Synthetic Lethal and Selective Approaches to Target PBRM1-Deficiency in Clear Cell Renal Cell Carcinoma PBRM1 Deficiency in Cancer is Synthetic Lethal with DNA Repair Inhibitors Exploiting Epigenetic Vulnerabilities in Solid Tumors: Novel Therapeutic Opportunities in the Treatment of SWI/SNF-Defective Cancers Combining Epigenetic Drugs with other Therapies for Solid Tumours — Past Lessons and Future Promise Targeting Chromatin Defects in Selected Solid Tumors Based on Oncogene Addiction, Synthetic Lethality and Epigenetic Antagonism". Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASL017.

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L’inactivation de polybromo-1 (PBRM1) est un évènement fréquent dans de nombreux cancers. En particulier, les carcinomes rénaux à cellules claires présentent une déficience en PBRM1 dans 40 à 50% des cas. A ce jour, il n’existe pas d’approche de médecine précision connue capable de cibler spécifiquement les cellules tumorales déficientes en PBRM1.Pour identifier des cibles de létalité synthétique associées à la perte de PBRM1, nous avons (i) réalisé un criblage pharmacologique à haut débit évaluant la sensibilité à 167 molécules dans un modèle cellulaire isogénique pour PBRM1, et (ii) étudié l’impact transcriptomique et protéomique de la perte de PBRM1 dans ce même modèle.Nous avons ensuite caractérisé les mécanismes sous-jacents à la relation de létalité synthétique découverte.Nous avons identifié et validé une relation de létalité synthétique existante entre la perte tumorale de PBRM1 et l’inhibition pharmacologique de PARP, pouvant être potentialisée par l’ajout d’un inhibiteur d’ATR.Cette relation de létalité synthétique était caractérisée par un niveau basal élevé de stress cellulaire chez les cellules déficientes en PBRM1, associant anomalies mitotiques, stress transcriptionnel et stress réplicatif – tous ces phénomènes étant exacerbés à l’ajout d’inhibiteurs de PARP, jusqu’à dépasser les capacités cellulaires à maintenir un phénotype compatible avec la survie.Ces observations apportent la preuve de concept préclinique que les inhibiteurs de PARP sont de potentiels candidats thérapeutiques pour cibler spécifiquement les tumeurs déficientes en PBRM1
Polybromo-1 (PBRM1) inactivation occurs in multiple malignancies and is of particular importance in clear cell renal cell carcinomas (ccRCC), as it drives 40 to 50% of cases. Currently, no precision-medicine approach uses PBRM1 deficiency to specifically target tumour cells. To uncover novel synthetic lethal approaches to treat PBRM1-defective cancers, we performed (i) a high-throughput pharmacological screening, evaluating the sensitivity to 167 small molecules in a PBRM1-isogenic cellular model, and the (ii) systematic mapping of the whole transcriptomic and proteomic profiles associated with PBRM1 loss-of-function within this model. We further investigated the mechanism underlying this synthetic lethal relationship.We identified and validated synthetic lethal effects between PBRM1 loss and both PARP and ATR inhibition. Combinatorial use of PARP with ATR inhibitors exerted additive cytotoxic effects in PBRM1-defective tumor cells. These synthetic lethal relationships were characterized by a pre-existing replication stress in PBRM1-deficient cells associated with mitosis and DNA damage repair abnormalities, which were exacerbated upon PARP inhibition selectively in PBRM1-defective cells.These data provide the preclinical basis for evaluating PARP inhibitors as a monotherapy or in combination in patients with PBRM1-deficient ccRCC

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Nunes, Joana Rita Lopes Ribeiro. "Production of Composites for Future Application in Tendon/Ligament Repair". Master's thesis, 2020. https://hdl.handle.net/10216/128382.

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As lesões nos tendões e ligamentos estão entre os problemas de saúde mais comuns e debilitantes que afetam a população adulta em todo o mundo. Os tratamentos actuais, reparações cirúrgicas ou enxertos, têm demonstrado um sucesso limitado. Devido a esta procura do mercado, foram desenvolvidos vários scaffolds sintéticos biológicos e não degradáveis, mas falham a longo prazo devido à fraca integração dos implantes ou desempenho mecânico. As limitações descritas poderão ser ultrapassadas através da utilização de materiais biodegradáveis. Contudo, as suas fracas propriedades mecânicas restringem a sua utilização nestas aplicações que suportam elevadas tensões. O objectivo deste projecto é o desenvolvimento de fibras compósitos biodegradáveis, através da associação de um material de reforço em polímeros biocompatíveis e biodegradáveis, para serem utilizados no futuro em scaffolds com o desempenho mecânico e biológico necessário para a reparação de tendões/ligamentos.
Tendon and ligament injuries are among the most common and debilitating health problems affecting the adult population worldwide. Current treatments, surgical repair or grafts, have shown limited success. Driven by this market demand, several biological and non-degradable synthetic scaffolds have been developed but they fail in the long-term due to lack of implant integration or mechanical performance. The described shortcomings could be overcome through the use of biodegradable materials. However, their poor mechanical properties restrict their use in these load-bearing applications. The aim of this project is the development of biodegradable composite fibers, through the association of a reinforcing material into biocompatible and biodegradable polymers, to be used in the future in scaffolds with the required mechanical and biological performance for tendon/ligament repair.

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Nunes, Joana Rita Lopes Ribeiro. "Production of Composites for Future Application in Tendon/Ligament Repair". Dissertação, 2020. https://hdl.handle.net/10216/128382.

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Libri sul tema "Futile repair"

Morley, Richard E. Techshock caution: Future under repair. Triangle Park, NC: International Society of Automation, 2009.

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Morley, Richard E. Techshock caution: Future under repair. Triangle Park, NC: International Society of Automation, 2009.

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Morley, Richard E. Techshock caution: Future under repair. Triangle Park, NC: International Society of Automation, 2009.

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Davies, Andrew. Naval gazing: The future of Australia's naval shipbuilding and repair sector. [Barton, A.C.T.]: Australian Strategic Policy Institute, 2010.

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Committee for Economic Development of Australia. e Australian Housing and Urban Research Institute., a cura di. Pacific Highway: The future of the nation : a discussion paper on the current and planned improvements to the Pacific Highway. [Melbourne]: Committee for Economic Development of Australia, 1998.

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New York (State). Governor's Roadway Improvement Committee. A discussion of future state highway and bridge needs and financing. Albany, NY: New York State Dept. of Transportation, 1987.

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Stuebing, Susan. Approaches to school maintenance: Assuring the future life of school buildings in New Jersey. Trenton, N.J: The Commission, 1990.

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United States. Dept. of Housing and Urban Development. Office of Policy Development and Research. e ICF Incorporated, a cura di. Future accrual of capital repair and replacement needs of public housing: Final report. Washington, D.C: U.S. G.P.O., 1989.

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United States. Dept. of Housing and Urban Development. Office of Policy Development and Research e ICF Incorporated, a cura di. Future accrual of capital repair and replacement needs of public housing: Final report. Washington, D.C: The Office, 1989.

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1953-, Semmler Jaleh, Atomic Energy of Canada Limited. e Chalk River Laboratories. Reactor Chemistry Branch., a cura di. Chemical cleaning processes, present and future. Chalk River, Ont: Reactor Chemistry Branch, Chalk River Laboratories, 1996.

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Capitoli di libri sul tema "Futile repair"

Lambert, Bernard, Evelyne Segal-Bendirdjian, Bernard P. Roques e Jean-Bernard Le Pecq. "Induction of Futile DNA Repair Processes by Bifunctional Intercalators". In DNA Repair Mechanisms and Their Biological Implications in Mammalian Cells, 639–52. Boston, MA: Springer US, 1989. http://dx.doi.org/10.1007/978-1-4684-1327-4_51.

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Hendrich, Christian, Norbert Schütze, Thomas Barthel, Ulrich Nöth e Jochen Eulert. "Cartilage Injury and Repair". In Cartilage Surgery and Future Perspectives, 9–15. Berlin, Heidelberg: Springer Berlin Heidelberg, 2003. http://dx.doi.org/10.1007/978-3-642-19008-7_2.

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Lomanto, Davide. "Future Consideration". In Techniques of Abdominal Wall Hernia Repair, 267–68. New Delhi: Springer India, 2019. http://dx.doi.org/10.1007/978-81-322-3944-4_26.

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Peters, Brian S., Priscila R. Armijo e Dmitry Oleynikov. "Robotic Technologies (Past, Present and Future)". In Robotic Assisted Hernia Repair, 3–27. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-23025-8_1.

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Wei, Chang Jia, Ong Zhen Liang e Ehsan Nikbakht Jarghouyeh. "Experimental Investigation of Effectiveness of FRP Composite Repair System on Offshore Pipelines Subjected to Pitting Corrosion Under Axial Compressive Load". In Lecture Notes in Civil Engineering, 209–18. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-1748-8_17.

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AbstractThe application of FRP composite is quite well demonstrated in strengthening on RC structures but on strengthening of steel structures is still being investigated by many researchers. The aggressive marine environment can cause corrosion to the offshore pipelines which would affect the structural performance such as pitting corrosion which could be considered as the most destructive corrosion was simulated in this research. This study had attempted to carry out experimental investigation of effectiveness of FRP composite repair system on offshore pipelines subjected to pitting corrosion under axial compressive load. 3 groups of specimens have been categorized such as intact, corroded and repaired. Results such as compressive peak load, failure modes and load–displacement behavior were concerned in this study. The pitting corrosion has been investigated and proved that it has significant effect on the ultimate strength of pipelines. Number of CFRP layer such as 3 layers has been investigated which the results showed the FRP composite repair system capable of strengthening of corroded offshore pipelines. However, more detailed studies are required to be conducted in the future such as consideration of internal pressure in order to expand the understanding of this composite repair system.

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Gracia, C., e S. Morales-Conde. "The Future of Laparoscopic Ventral Hernia Repair". In Laparoscopic Ventral Hernia Repair, 543–53. Paris: Springer Paris, 2003. http://dx.doi.org/10.1007/978-2-8178-0752-2_49.

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Hudetz, Damir, Željko Jeleč, Eduard Rod, Igor Borić, Mihovil Plečko e Dragan Primorac. "The Future of Cartilage Repair". In Personalized Medicine in Healthcare Systems, 375–411. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-16465-2_29.

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Angel, Michael J., Jordan Kerker e Nicholas Sgaglione. "Meniscus Repair and Future Directions". In Knee Arthroscopy, 25–40. New York, NY: Springer US, 2009. http://dx.doi.org/10.1007/978-0-387-89504-8_3.

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Gobbi, Alberto, Anup Kumar, Georgios Karnatzikos e Norimasa Nakamura. "The Future of Cartilage Repair Surgery". In Techniques in Cartilage Repair Surgery, 369–76. Berlin, Heidelberg: Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-41921-8_31.

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von Freeden, Justus, Jesper de Wit, Stefan Caba, Susanne Kroll, Huan Zhao, Jinchang Ren, Yijun Yan, Farhan Arshed, Abdul Ahmad e Paul Xirouchakis. "Composite Repair and Remanufacturing". In Systemic Circular Economy Solutions for Fiber Reinforced Composites, 191–214. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-22352-5_10.

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AbstractFor the reuse of components and structures made of fiber composite materials, a complete remanufacturing process chain is necessary to prepare the parts for a further life cycle. The first step is to dismantle the parts to be reused. Fiber composite components are mostly joined using adhesive technology, so that solution techniques are required for adhesive connections. One possibility is the separation of the adhesive layer by means of thermally expanding particles. Adhesive residues are removed by laser so that the components can be glued again after reprocessing. The decisive factor for which process is used for the remanufacturing of the components is the state at the end of the life cycle. Non-destructive testing methods offer a very good option for detecting damage, planning necessary repairs and direct reuse of damage-free components. Repairs to fiber composite structures have been carried out in aviation for a long time and are accordingly established. These processes can be transferred to the repair of automotive fiber composite components. Many technical solutions were developed and tested as part of the project. Future research work is aimed at further development, particularly with regard to the automation of the technologies in order to enable an industrial application of the recycling of automobile components made of fiber composites.

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Atti di convegni sul tema "Futile repair"

Johnson, Tyler, Curtis Mokry, Chris Apps, Nima Parsibenehkohal e Matthew Henderson. "Literature Review of Repair Technologies for Wrinkled Pipelines". In 2022 14th International Pipeline Conference. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/ipc2022-86760.

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Abstract Wrinkles on a pipeline, whether produced intentionally by construction methods of vintage pipelines or unintentionally by bending loads from subsurface geotechnical movements, introduce significant stress concentration factors. However, common options for pipeline repair usually cannot be used given the protruding wrinkle geometry (e.g. steel sleeves), or are costly and can introduce additional safety concerns (e.g. pipe replacement). Numerous composite repair technologies have been developed that take the form of the underlying structure and, thus, may provide an alternative for this application. However, composite repairs have focused on restoring axial defects in pipelines (i.e. hoop reinforcement), while restoring the bending capacity of wrinkled pipe is less common. Therefore, this literature review consolidates the current state of knowledge regarding the effects of composite repairs on the bending load capacity of pipes. The reviewed literature identified 14 studies (using finite element analysis, full-scale testing, or a combination of both) that investigated composite repairs on wrinkled pipe or under bending loads. Typically, for pipe with non-sharp flaws (e.g. corrosion or wrinkles), the bending capacity of the pipe with a sufficient repair is increased near or beyond that of pristine pipe. The latter case usually results in a new wrinkle forming outside of the repaired pipe section. Most repairs have also been shown to prevent significant plastic deformation of the base pipe beneath the repair. However, knowledge gaps are also identified by this review and present opportunities for future studies to further improve the performance of composite repairs for this application.

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Tronskar, Jens P., e Chon Gee Lee. "Cofferdam and Hyperbaric “Live” Repair of Gas Pipeline Leaks". In ASME 2016 35th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/omae2016-55077.

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Offshore pipelines may face many threats. Apart from internal and external corrosion third party threats represent major hazards to submarine pipelines. Recent pipeline leaks caused by third party as well as construction and installation have been repaired online in a two-step process involving installation of a leak clamp followed by a permanent repair by installation of a welded stand-off sleeve. The welding has depending on the water depth been executed in a hyperbaric habitat or in shallow water using purpose built cofferdams. A concept proposed by DNV GL has been successfully applied to repair of leaking submarine pipelines. To ensure the safety of the repair crew the concepts involves using a gas containment barrier installed over a traditional mechanical leak clamp. The gas containment barrier is either purged with inert gas or nitrogen or it is maintained with a constant inert gas pressure that is monitored continuously during the repair. In the event of a sudden gas leak into the gas containment barrier a pre-set pressure relief valve will open and dump the gas leak outside the habitat. This paper describes the details of a few cases of leaking submarine gas pipelines and the immediate causes of the leak, the repair method selection, the repair method details, cofferdam or hyperbaric welding qualification and execution. The paper also describes the various steps in the process to ensure that the pipeline damage is stable and that the repairs can be safely undertaken to restore the pipelines to their original design condition without reduction of pressure or flow rate. The paper describes the method of global and local finite element analyses as well as fracture mechanics assessment by FEA to assess the stability of the flaws causing the gas leaks. The pipelines in question have all been gas transmission lines carrying gas to gas fired power plants for which gas pressure reduction or shutdown were completely unacceptable. Future development is expected to involve development of remotely controlled repairs using similar concepts at water depths where diver/welders cannot be employed due to the various country regulations or simply because the water depths are too deep for saturation divers. Methodology according to DNV RP-A203 [1] is described for qualification of new technology for underwater pipeline repairs. Further references are made to the recent updates to the DNV RP-F113 Pipeline Subsea Repair [2] with regards to requirements for “live” pipeline repairs. The DNV RP-F113 refers to the PRCI Weld Thermal analyses [3] and requirements to perform full scale mock-up tests of the repair as part of the repair method qualification based on DNV OS-F101 Submarine Pipelines [4].

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Møller, Peter H. "Monitoring the performance of concrete repairs". In IABSE Conference, Copenhagen 2018: Engineering the Past, to Meet the Needs of the Future. Zurich, Switzerland: International Association for Bridge and Structural Engineering (IABSE), 2018. http://dx.doi.org/10.2749/copenhagen.2018.344.

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<p>A monitoring system for measuring the durability of concrete repairs has been developed and tested for 6 years as part of a pilot project for renovation of bridge piers. Beside testing traditional repair methods, the possible service life extension from cast-in sacrificial anodes was tested.<p>The system was focused on the zone between original concrete and repair material where corrosion often starts. It was seen that this zone for most of the repairs can be expected to reduce service life to <50years. But the monitoring system cannot determine the service life precisely, but precision is highly increased compared to other methods, e.g. surface based mapping of reinforcement potentials. The results furthermore indicated that cast-in anodes can increase the service life by 10- 20 years. By the new anode model, Galva Shield XP2, service life be might increased by 15-30 years.<p>It was found that corrosion risk at repairs has high areal- and time-based variations and to obtain an overview of the durability of the repairs several repairs must be monitored for a long time.

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Haladuick, Shane, e Markus R. Dann. "Risk Based Inspection Planning for Deteriorating Pressure Vessels". In ASME 2016 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/pvp2016-63138.

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Pressure vessels are subject to deterioration processes, such as corrosion and fatigue. If left unchecked these deterioration processes can lead to failure; therefore, inspections and repairs are performed to mitigate this risk. Oil and gas facilities often have regular scheduled shutdown periods during which many components, including the pressure vessels, are disassembled, inspected, and repaired or replaced if necessary. The objective of this paper is to perform a decision analysis to determine the best course of action for an operator to follow after a pressure vessel is inspected during a shutdown period. If the pressure vessel is inspected and an unexpectedly deep corrosion defect is detected an operator has two options: schedule a repair for the next shutdown period, or perform an immediate unscheduled repair. A scheduled repair is the preferred option as it gives the decision maker lead time to accommodate the added labour and budgetary requirements. This preference is accounted for by a higher cost of immediate unscheduled repairs relative to the cost of a scheduled repair at the next shutdown. Depending on the severity of deterioration either option could present the optimal course of action. In this framework the decision that leads to the minimum expected cost is selected. A stochastic gamma process was used to model the future deterioration growth using the historical inspection data, considering the measurement error and uncertain initial wall thickness, to determine the probability of pressure vessel failure. The decision analysis framework can be used to aid decision makers in deciding when a repair or replacement action should be performed. This method can be used in real time decision making to inform the decision maker immediately post inspection. A numerical example of a corroding pressure vessel illustrates the method.

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Bamford, Warren, Bruce Newton e Don Seeger. "Recent Experience With Weld Overlay Repair of Indications in Alloy 182 Butt Welds in Two Operating PWRs". In ASME 2006 Pressure Vessels and Piping/ICPVT-11 Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/pvp2006-icpvt-11-93891.

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Recent service experience with Alloy 182/82 butt welds in PWR primary piping and its joints with major components has revealed stress corrosion cracking. This mechanism of environmental cracking is known to have long incubation times, so these incidences of cracking have not been numerous to date, but it is becoming increasingly evident that this may not be the case in the future. This paper provides a summary of two recent repairs which were performed as a result of the finding of indications during in-service inspections. The weld overlay repairs followed the guidelines of code case N504, but a number of supplementary requirements were added. In each case, the repair had to be initiated with no warning other than the knowledge that the inspection was underway. The design of the weld overlay repair was done while the repair equipment was being mobilized, and the repair went as planned, with the final inspections showing that the weld overlay was flawless. In each case excellent cooperation between the plant personnel, the engineering designers, the inspectors, and the welders made for an excellent end product. In addition to a review of the processes used for each of the key steps in the repair, a review of lessons learned will be provided, so that operating plants which may face similar issues in the future can benefit from this experience.

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van Alphen, H., A. Guyt, U. Nienhuis e J. C. van der Wagt. "Virtual Manufacturing In Shipbuilding Processes". In European Shipbuilding, Repair and Conversion – The Future. RINA, 2004. http://dx.doi.org/10.3940/rina.eu.2004.5.

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Sinha, A., e G. Bruce. "The Role of New Technologies Within The Shiprepair and Conversion Industry By Enhancing The Supply Chain Logistics". In European Shipbuilding, Repair and Conversion – The Future. RINA, 2004. http://dx.doi.org/10.3940/rina.eu.2004.1.

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Wijnolst, N., e F. A. J. Waals. "European Shortsea Shipping: Scrap-Sell-Build Programme". In European Shipbuilding, Repair and Conversion – The Future. RINA, 2004. http://dx.doi.org/10.3940/rina.eu.2004.3.

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Kelsall, S., e N. Taylor. "VT Shipbuilding – Improving Productivity". In European Shipbuilding, Repair and Conversion – The Future. RINA, 2004. http://dx.doi.org/10.3940/rina.eu.2004.10.

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Nienhuis, U., e J. F. J. Pruijn. "Shipbuilding Strategy Classes In Dutch Academic Marine Education". In European Shipbuilding, Repair and Conversion – The Future. RINA, 2004. http://dx.doi.org/10.3940/rina.eu.2004.9.

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Rapporti di organizzazioni sul tema "Futile repair"

Johnson, Derek, e Nigel Clark. PR-746-22204-R01 Review of Technologies to Enable In-situ Valve Service to Reduce Methane Emissions. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), marzo 2024. http://dx.doi.org/10.55274/r0000058.

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Leaking gas industry valve stem seals are recognized as a substantial source of atmospheric methane, which is a greenhouse gas. Newly proposed regulations include methane alongside volatile organic compound emissions, with leak detection and repair requirements. If a leak is identified a first attempt at repair must occur no later than five calendar days after identification, or else be justifiably delayed. The objective of this report is to review valve technology and methods used to address in-situ valve stem leak repair that offers an economical solution with reduced service disruption. A wide variety of valves are employed in natural gas facilities, with valve stems that rotate or translate, and with seals ranging from packings to O-rings. Low emissions valve designs are available, but turnover of legacy valves is slow. Precise causes of failures are not well documented, although stem misalignment, intrusive dirt, and corrosion may exacerbate seal damage. Injection of lubricants and sealants into the valve packing or seal area offers the simplest remedy for leakage control. However, more work is required to identify optimal sealants for each application and to predict durability of the repair using injection. Safety must be assured where seals must be replaced, but there are varying practices in addressing isolation of the seal area from high pressure gas. Where double block (or isolation) and bleed are required, knowledge of the valve main seal design is essential. Blowdown of line sections may be required, but the methane release is of concern. Methods exist to capture or else oxidize the methane. Opinions on the protection offered by backseating of gate valves varies. Improved understanding and practice will require comprehensive record keeping on the history of each valve, permitting analysis and quality improvement using the resulting operations database. This is key to recommendations in a future roadmap that includes study of failure modes and optimized use of sealants. Monitoring success of repairs would be better served by measuring leak rate than concentration. Record keeping and better understanding of failures and success of repair approaches also support decisions on immediate versus deferred repair, use of sealants, and on whether a valve should be replaced or repaired. Hardware and practice innovations are anticipated in response to leak detection and repair requirements.

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Seaman. PR-185-07701-R01 Evaluation of Magnetic Pulse Welding for Improved Casing Repair. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), gennaio 2010. http://dx.doi.org/10.55274/r0010701.

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Alternative repair methods for natural gas storage well casings are required to lower the costs of casing repairs and to reduce operational constraints that result from repair methods that reduce the cross sectional area of the casing. The objective of this project is to determine the feasibility of expansion mode magnetic pulse welding (MPW) to affect improved casing repair. Finite element modeling (FEM) was used to develop an expansion welding coil system and to simulate its performance. The critical welding velocity was determined and preliminary MPW parameters identified, thus validating the theoretical feasibility of expansion MPW of steel. One coil system was designed; two coil systems were fabricated and experimentally evaluated. Welding trials indicated that the current coil design is not able to produce sufficient kinetic energy at the interface to produce a weld. Based on the performance of this coil design, three additional coil designs have been identified for future welding trials.

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Alexander e Bedoya. L52328 Composite Repair of Mechanically-Damaged Pipes. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), aprile 2012. http://dx.doi.org/10.55274/r0010019.

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Composite materials continue to gain wider acceptance in the pipeline industry for repairing a range of pipeline anomalies. This success is due in large part to two factors. The first contributor is the execution of comprehensive research programs such as the first PRCI MATR-3-3, State of the Art Assessment of Composite Repair Systems and this second program contained herein focused on evaluating composite materials to repair damaged pipelines. The second factor associated with the widespread use of composite materials is the successful two-decade history that composite materials have had in repairing pipelines. While there have been a few unfortunate incidents in the field (primarily related to poor installation), composite materials have proven themselves to be well suited for repairing high pressure gas and liquid pipelines. The need existed for a set of integrity assessment procedures and guidelines to ensure proper use and application of composite repair materials for mechanically-damaged pipes. The results of this program indicate that when properly designed and installed, composite repair systems are able to restore integrity to mechanically-damaged pipes to a state that makes them fit for continued use at their normal design conditions. When composite materials are used for repairs, whether the repair involves corrosion, dents, or other anomalies, an integrity assessment should be completed. The integrity assessment procedures and guidelines presented in this report include an estimate of the future operating conditions to ensure that the design is adequate for the intended service.

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Hajj, Ramez, e Yujia Lu. Current and Future Best Practices for Pothole Repair in Illinois. Illinois Center for Transportation, febbraio 2021. http://dx.doi.org/10.36501/0197-9191/21-003.

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This report presents a review of flexible pavement pothole-patching materials, equipment, and techniques within Illinois Department of Transportation as well as other transportation agencies in the United States. The research team conducted a literature review to examine recent studies and available state department of transportation guidance on pothole patching. Overall, this review revealed a lack of recent studies on this topic, and a greater need for them. The review also revealed that most states do not have centralized guidance for pothole repair best practices. The researchers also met with all nine Illinois Department of Transportation districts to determine their current state of practice for pothole patching. The meetings revealed a wide range of materials and techniques in use among the nine districts as well as areas where improvements can be made. The final chapter of this report includes overall recommendations for improvement.

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Sennett, Michael S. Field Repair of Composite Materials in Army Service: Planning for the Future. Fort Belvoir, VA: Defense Technical Information Center, maggio 1989. http://dx.doi.org/10.21236/ada210732.

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Hall, Zachary G. C-17A Sustainment Performance Metrics Assessment: Repair Source Impact on Sustainment for Future Business Case Analysis Development. Fort Belvoir, VA: Defense Technical Information Center, giugno 2013. http://dx.doi.org/10.21236/ada586369.

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Kenny, J. P. PR-189-9216-R01 Subsea Repair of Gas Pipelines without Water Flooding. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), agosto 1993. http://dx.doi.org/10.55274/r0012174.

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The primary aims of the study were to: � review the existing scene describing the equipment, methods, and the vendors active at the present time. This is presented in detail in the report and is intended to provide a ready reference for PRC members; � to investigate future developments, the systems required, and the potential of the existing equipment to meet the projected demand, namely for isolation systems capable of performing in subsea, mid-line scenarios. � to outline the immediate industry requirements for development work and the concept and feasibility studies necessary to support the anticipated industry requirements.

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Krishnamurthy, Ravi. PR328-214501-R01 Methods to Reduce Pipeline Blowdowns for Repair and Inspections. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), gennaio 2022. http://dx.doi.org/10.55274/r0012199.

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New regulations and modifications to existing environmental regulations are currently underway. The natural gas industry has consistently attempted to mitigate the release of greenhouse gases into the atmosphere. Blowdown mitigation represents an opportunity to directly reduce the extent of methane emissions released to the atmosphere and can have an immediate positive impact on reducing the effects of global warming. This work presents the current techniques available to minimize blowdowns by the pipeline industry during repair and replacements based on research and interviews. Industry best practices are presented and future work is proposed to further improve the blowdown mitigation techniques presented in this work.

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Ersoy, Daniel, e Ernest Lever. DTPH56-15-T-00006 Characterization and Fitness for Service of Corroded Cast Iron Pipe. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), dicembre 2018. http://dx.doi.org/10.55274/r0012163.

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The Cast Iron Fitness-For-Service model described in the main body of this report forms an ideal basis for a simulation tool that can display aggregate system performance in a geospatial database. This simulation tool can provide the operator risk-informed geospatial input into their mitigation programs. The tool can also be extended to temporal consideration of future repair/replace programs.

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Schissler, Limo, Sanjana Ahershinge, Ahmed Ibrahim, Larry Fahnestock, James LaFave e Ahmed Elbanna. Report on Agency Survey and National Bridge Inventory Analysis for Damaged Steel Girders. Illinois Center for Transportation, novembre 2024. http://dx.doi.org/10.36501/0197-9191/24-024.

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Bridge strikes—events where over-height vehicles impact bridge superstructures—are common across the United States and pose significant challenges for bridge owners. When a bridge strike occurs, bridge owners must assess the damage and determine what, if any, action is required. A survey of state highway agencies was conducted, and 23 responses were received. States reported general metrics about low-clearance bridges and bridge strikes, and data from the National Bridge Inventory were analyzed to provide additional insight. States also reported information about inspection, analysis, and repair practices for damaged girders. Overall, reported practices vary greatly between states and rely significantly on engineering judgement; there is potential to improve efficiency and efficacy. Results can be used to inform future research directions regarding steel girders damaged in bridge strikes, such as innovative methods for damage inspection, assessment, and repair.

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