Littérature scientifique sur le sujet « Paraloid »
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Articles de revues sur le sujet "Paraloid"
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Ntelia, Eleni, et Ioannis Karapanagiotis. « Superhydrophobic Paraloid B72 ». Progress in Organic Coatings 139 (février 2020) : 105224. http://dx.doi.org/10.1016/j.porgcoat.2019.105224.
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Ibrahim, Mohamed Moustafa, Wael Sabry Mohamed et Hamdy Mohamed Mohamed. « Comparative and Experimental Studies for Evaluation of Paraloid B-72 in Traditional and Nano Forms for Joining of Pottery Samples ». Journal of Nano Research 61 (février 2020) : 61–71. http://dx.doi.org/10.4028/www.scientific.net/jnanor.61.61.
Texte intégralRésumé :
Many of the excavated pottery artifacts are suffering from different deterioration aspects. The pressure of burial environment is considered the most deteriorative agent for pottery in soil, which leads to damage of the artifact. Therefore, it is necessary to join these damaged parts to be suitable for museum display. The adhesive materials play a significant role in the joining processes of these artifacts. In this study, Paraloid B-72 in its traditional and nano form was prepared (50% in acetone) as adhesive for pottery artifacts. Twelve pottery tiles (14 ×4×1 cm) were prepared and then were adhered together with the adhesive in traditional and nano forms. The pottery samples were exposed to artificial aging as follows; accelerated heat-humid aging (temperature 100°C and 60% relative humidity) and light aging by U.V lamp for 100 hours. Visual assessment and several analytical techniques were used for the evaluation of the selected adhesive. The analytical techniques are transmission electron microscope (TEM), scanning electron microscope (SEM), color change and tensile strength. The results obtained from transmission electron microscope showed that grain size of nano paraloid was ranging from 33 to 51 nm where the particle size of the traditional paraloid was in the range between 103 to 150 nm. Visual assessment proved that nano paraloid had some simple changes in appearance. Scanning electron microscope revealed that the nano paraloid was more resistance for aging than traditional form. Color change revealed that nano paraloid gave the lowest level of total color differences (ΔE) after light, heat-humid and light-heat aging with 2.31, 3.26 and 4.60 respectively. The tensile strength revealed that nano paraloid gave highest tensile strength (81.3 N/mm2). According to these results, we recommend the use of nano paraloid in joining of archaeological pottery artifacts.
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Li, Wenjuan, Junling Lin, Yaru Zhao et Zihe Pan. « The Adverse Effects of TiO2 Photocatalycity on Paraloid B72 Hybrid Stone Relics Protective Coating Aging Behaviors under UV Irradiation ». Polymers 13, no 2 (14 janvier 2021) : 262. http://dx.doi.org/10.3390/polym13020262.
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The incorporation of photocatalytic nanomaterials into polymer coatings is used to protect stone relics from weathering. However, the photocatalytic nanomaterials might generate excess free radicals to degrade the polymer matrix. In this work, a certain amount of TiO2 nanoparticles were dispersed into Paraloid B72 and applied onto sandstone relics to explore the adverse effects of TiO2 nanoparticles on Paraloid B72 under ultraviolet (UV) irradiation. To fulfill this goal, the effects of TiO2 on pore formation and the structure of Paraloid B72 was studied by scanning electron microscopy (SEM). Moreover, the surface chemical composition, pore structure, surface roughness and surface wettability were explored via Fourier transform infrared (FTIR) spectroscopy, SEM, optical profilometer and water contact angle measurement under UV irradiation. Results showed that the incorporation of TiO2 nanoparticles prohibited the generation of pores in Paraloid B72 and there were no pores formed when the content of TiO2 exceeded 0.8 wt%. The water contact angle of origin Paraloid B72 and TiO2/Paraloid B72 decreased with the prolonging UV irradiation. Moreover, TiO2 nanoparticles were extracted from the matrix and the pores cannot be detected with the prolonging UV irradiation time under a higher content of TiO2. These research findings might promote the understanding of using photocatalytic nanomaterials in developing stone relics’ protective coating.
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Švadlena, J., et J. Stoulil. « Evaluation of protective properties of acrylate varnishes used for conservation of historical metal artefacts ». Koroze a ochrana materialu 61, no 1 (1 mars 2017) : 25–31. http://dx.doi.org/10.1515/kom-2017-0003.
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Abstract Acrylate varnishes are due to their suitable properties frequently used in restoration and preservation on variety of historical objects and materials. Common practice of their application involves using as an adhesive agents, consolidants and protective coatings. The purpose of protective coatings especially on metal artefacts is to reduce access of pollutants to the surface of the artefact. In this paper, coatings prepared from two acrylate polymers Paraloid B72 and Paraloid B48N are compared in terms of permeability for water and level of protective properties against air pollutants. For this purpose, electrochemical impedance spectroscopy and resistometric method were chosen for analysis of the coatings. Obtained results show lower permeability for water in case of Paraloid B72. However, same coating provided lower protection against air pollutants than Paraloid B48N coating.
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Haldoko, Leliek Agung. « Shellac dan Gelatin untuk Konsolidasi Artefak Kayu ». Jurnal Konservasi Cagar Budaya 15, no 2 (31 décembre 2021) : 44–58. http://dx.doi.org/10.33374/jurnalkonservasicagarbudaya.v15i2.259.
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Wood is a hygroscopic organic material, prone to damage and weathering, especially by humidity. The moisture in the wood will trigger biotic activities such as fungus, which can decompose of wood materials, that is, cellulose. Moreover, wood is susceptible to insect attacks such as termites. This condition will cause the wood to become brittle so that the strength of the wood will decrease. To strengthen brittle wood, consolidation treatments are needed. Material for wood consolidation that has been used is Paraloid B72 with acetone solvent, which is not easy to find everywhere
Materials tested for wood artifacts consolidations were shellac and gelatin with a concentration of 5%, 7,5%, and 10%. As a comparison, the material used for wood consolidation is Paraloid B72 10%. Test parameters used include SEM test, density test, compressive strength test, color change test, fungal growth observation, and FTIR test.
Test results have shown that shellac 7,5% and 10% can be an alternative to Paraloid B72 as a wood artifacts consolidation material. Shellac 7,5% is the optimum concentration for wood artifacts consolidation because materials will be more efficient. This material can fill the wood pores and increase the density by 13,89%. The resulting compressive strength value reached 248,01 kg/cm2 or increased by 43,18%, higher than Paraloid B72 10%. Shellac 7,5% does not change the color of the wood and safe from fungal growth when applied to wood. This material also does not change the chemical composition of wood.
Keywords: wood, artifact, consolidation, shellac, gelatin, Paraloid B72
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Russell, Rhian, et Brandon Strilisky. « Keep it together : An evaluation of the tensile strengths of three select adhesives used in fossil preparation ». Collection Forum 30, no 1-2 (1 janvier 2016) : 85–95. http://dx.doi.org/10.14351/0831-4985-30.1.85.
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Abstract The tensile strength of a select group of common fossil adhesives (50% w/w Paraloid B-72 in acetone, Paleobond PB100, and Devcon 2-Ton epoxy) was tested over a period of 9 months. Because the testing process is destructive, the tests needed to be standardized to draw valid conclusions, and because large sample sizes were desired for the most statistically accurate results, limestone adherends were used as a proxy for real fossil specimens. Paraloid B-72 in acetone at 50% w/w demonstrated long solvent retention and took several months to attain full strength. Although it was the statistically weakest of the three adhesives, it still required a significantly large force to be exerted (275.56 lbs/in2; 19.37 kg/cm2) in order for it to fail after only 3 days. If fossil specimens joined with Paraloid B-72 are provided with appropriate archival support, then the adhesive will slowly attain full strength. Devcon 2-Ton epoxy was stronger than the limestone adherends and created minor or major substrate failure in the majority of samples, indicating that its use be restricted only to specific situations, such as heavy specimens that cannot be supported externally. Paleobond PB100 samples failed on average between 535 and 636 lbs/in2 (37.6 and 44.7 kg/cm2) and generally demonstrated adhesive failure, with some minor substrate damage. Paraloid B-72 demonstrated substantial tensile strength in this study and has excellent long-term stability and reversibility. Therefore, Paraloid B-72 should be considered the default adhesive in the majority of fossil preparation practices.
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Siedlecka, Beata, et Monika Marchwicka. « Influence of modification of aged spruce wood by in situ polymerization with ethyl methacrylate and methyl acrylate and paraloid B72 on color and water absorption ». Annals of WULS, Forestry and Wood Technology 120 (28 décembre 2022) : 45–56. http://dx.doi.org/10.5604/01.3001.0016.2315.
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Influence of modification of aged spruce wood by in situ polymerization with ethyl methacrylate and methyl acrylate and paraloid B72 on color and water absorption. Wood is hydrophilic in nature, which creates problems such as dimensional instability and susceptibility to biological degradation. By using chemical modification, wood can be refined into new products with improved properties. Such a combination of wood and polymer is called a wood-polymer composite (WPC). The presented work compares the modification of aged wood by two methods. In situ polymerization with ethyl methacrylate and methyl acrylate with modification with Paraloid B72 solution. The determinants of the modifications carried out are percentage weight gain (WPG), color change and water absorption. Unmodified wood aged and unaged were the control samples. Also unaged and modified wood samples were prepared to compare results. The greatest change in color intensity and total color difference after the aging process was recorded for samples modified with Paraloid B72, and after UV light treatment - modified by the in situ polymerization. The in situ-modified samples had the lowest water absorption among aged samples, and Paraloid B72-modified samples had the lowest water absorption among unaged samples. The highest WPG was obtained from the aged samples modified by the in situ polymerization.
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Stagno, Valeria, Chiara Genova, Nicole Zoratto, Gabriele Favero et Silvia Capuani. « Single-Sided Portable NMR Investigation to Assess and Monitor Cleaning Action of PVA-Borax Hydrogel in Travertine and Lecce Stone ». Molecules 26, no 12 (17 juin 2021) : 3697. http://dx.doi.org/10.3390/molecules26123697.
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In this work, we investigated the potential of PVA-borax hydrogel for cleaning limestones and the dependence of the cleaning on the porosity of the rock and on the action time of the hydrogel treatment. Towards this goal, we used a nuclear magnetic resonance (NMR) spectrometer, developed for non-invasive and non-destructive applications on cultural heritage. T2-NMR parameters were quantified on different samples of Lecce stone and Travertine cut perpendicular (Pe) and parallel (Pa) to the bedding planes under different experimental conditions: untreated samples, treated with Paraloid B72 and cleaned with PVA-PEO-borax hydrogel applied for 4 min and 2 h. The T2 results suggest that the effectiveness of the cleaning strongly depended on the porosity of the stones. In Lecce stone, the hydrogel seemed to eliminate both the paramagnetic impurities (in equal measure with 4 min and 2 h treatment) and Paraloid B72. In Travertine Pe, characterized by a smaller pore size compared to Lecce stone, no significant effects were found regarding both the cleaning and the treatment with Paraloid B72. In Travertine Pa, characterized by a larger pore size than the other two samples, the hydrogel seemed to clean the paramagnetic agents (it worked better if applied for a longer time) but it did not appear to have any effect on Paraloid B72 removal.
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Abo Elgat, Wael A. A., Ayman S. Taha, Martin Böhm, Eva Vejmelková, Wael S. Mohamed, Yahia G. D. Fares et Mohamed Z. M. Salem. « Evaluation of the Mechanical, Physical, and Anti-Fungal Properties of Flax Laboratory Papersheets with the Nanoparticles Treatment ». Materials 13, no 2 (13 janvier 2020) : 363. http://dx.doi.org/10.3390/ma13020363.
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In the present study, novel mixed additives of Chitosan or Paraloid B-72 combined with nanoparticles (NPs) of Ag, ZnO, or cellulose (NCL) were examined for their effects on the mechanical, optical, and fungal inhibition properties of the papersheets produced. The highest tensile, tear, and burst indices of the papersheets were observed for flax pulp treated with additives of Paraloid B-72 + ZnO NP (1%), Chitosan + ZnO NP (3%), and Chitosan + NCL (3%) at levels of 59.93 N·m/g, 18.45 mN·m2/g, and 6.47 kPa·m2/g, respectively. Chitosan + ZnO NP (1%) added to flax pulp showed the highest fungal mycelial inhibition (FMI) (1.85%) against Aspergillus flavus. Chitosan + Ag NP (1%) exhibited the highest FMI percentage (11.48%) when added to pulp against A. terreus. Pulp treated with Paraloid B-72 + Ag NP (1%) exhibited the highest activity against Stemphylium solani with an FMI value of 3.7%. The results indicate that the technological properties of the papersheets were enhanced with the addition of novel mixtures to the pulp.
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Iancu, Lorena, Ramona Marina Grigorescu, Rodica-Mariana Ion, Madalina Elena David et Sofia Slamnoiu-Teodorescu. « The Effect of UV Irradiation on the Stability of Coated Fir Wood Samples ». Scientific Bulletin of Valahia University - Materials and Mechanics 18, no 19 (1 octobre 2022) : 8–14. http://dx.doi.org/10.2478/bsmm-2022-0012.
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Abstract The aim of the paper consists in assessing the protection of fir wood samples against UV degradation by using polyacrylates and titanium dioxide as absorber. The irradiation was achieved for 648 hours, considered as about 2 years of weathering. Colorimetric, water absorption, and mechanical investigations were performed on samples before and after irradiation. The structural changes were evidenced by FTIR spectroscopy. Small changes in color for coated wood samples are observed after maximum 648 h of UV treatment, with the best results obtained for the specimen covered with Paraloid B72-TiO2. Higher compressive strengths were observed for the polymer-TiO2 coatings, in correlation with a smaller water absorption capacity of the studied samples. FTIR revealed shifted peaks with increased intensities as proof of structural changes produced by irradiation of lignin and polyacrylates. The results highlight that Paraloid B72 and Paraloid B67 mixed with TiO2 can be used as efficient UV protective coatings for fir wood.
Thèses sur le sujet "Paraloid"
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Santos, Maria Margarida de Sousa dos. « Cerâmica Arqueológica, estudo comparativo da eficácia inicial de dois consolidantes – polímero acrílico e silicato de etilo ». Master's thesis, Faculdade de Ciências e Tecnologia, 2011. http://hdl.handle.net/10362/7524.
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Dissertação para obtenção do Grau de Mestre em
Conservação e RestauroÉ frequente, em peças de cerâmica arqueológica, o aparecimento de fenómenos de desagregação. Para a conservação deste material há a necessidade de aplicação de produtos que aumentem a sua coesão e resistência mecânica. Dado existirem poucos trabalhos científicos sobre o desempenho de consolidantes alternativos, a utilizar em cerâmica arqueológica, sentiu-se a necessidade de desenvolver um trabalho laboratorial sobre essa temática. Assim, efectuou-se o estudo comparativo de avaliação da eficácia inicial de dois produtos comerciais, o Tegovakon V® e o Paraloid B-72®, como consolidantes. Foram utilizados provetes (sãos) em cerâmica vermelha cozida a 980 °C. Os consolidantes foram aplicados por imersão total e por pincelagem. A cerâmica foi caracterizada por DRX e os consolidantes por FTIR. A micro-estrutura da cerâmica foi caracterizada, antes e após a consolidação, por MEV-EDE, PM e μ-CT. A eficácia inicial do processo de consolidação foi avaliada através de uma série de ensaios laboratoriais, nomeadamente: porosidade acessível à água, absorção de água por capilaridade, velocidade de propagação de ondas longitudinais, resistência à compressão pontual, ângulo de contacto, tempo de absorção da micro-gota e caracterização colorimétrica. A consolidação é um procedimento que interfere nas propriedades físicas e comportamentais da cerâmica intervencionada. Essas alterações nas propriedades da cerâmica são função do consolidante e do método de aplicação. Nos provetes consolidados, por imersão, com Tegovakon V® verificou-se a redução de 62% da porosidade e 98% da capilaridade, o aumento de 4,8% da resistência mecânica e a alteração de ΔΕ de aproximadamente 7,7. Nos provetes consolidados, por imersão, com Paraloid B-72® verificou-se a redução de 4,5% da porosidade e 87% da capilaridade e o aumento de 4,5% da resistência mecânica. A alteração de ΔΕ, aproximadamente 12, foi superior nos provetes consolidados por pincelagem. Com base nestes resultados podemos afirmar que o consolidante que apresenta melhor desempenho, no que diz respeito à eficácia inicial, é o Tegovakon V® aplicado por imersão.
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Watters, George Murray. « Models of parasitism and hyperparasitism on Paralomis spinosissima / ». Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1997. http://wwwlib.umi.com/cr/ucsd/fullcit?p9823698.
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Taylor, M. R. G. « Mechanism of action of Rad51 paralogs ». Thesis, University College London (University of London), 2015. http://discovery.ucl.ac.uk/1458671/.
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Homologous recombination (HR) is an essential DNA break repair mechanism that remains incompletely understood. HR is a complex multistep process initiated by the loading of RAD-51 recombinase as filaments onto single stranded DNA (ssDNA). This structure directly invades an intact homologous duplex, which serves as a template for repair DNA synthesis. Numerous positive regulators of HR have been described, including the Rad51 paralogs, but the mechanism of action of Rad51 paralogs in promoting HR is unknown. In this study, I have characterized the mechanism of action of a novel Rad51 paralog complex, RFS-1/RIP-1, from C. elegans. RFS-1 is a Rad51 paralog required for RAD-51 focus formation at stalled replication forks, indicating an early positive regulatory role in HR. I demonstrate that RFS-1 interacts with a nematode-specific orphan protein, RIP-1. I identify a cryptic Walker B ATPase-like motif within RIP-1, which is functionally important in establishing the RFS-1/RIP-1 interaction interface. rip-1 and rfs-1 mutant animals phenocopy for essentially all phenotypes analysed. Together these data suggest RFS-1/RIP-1 functions as a constitutive complex. I show recombinant RFS-1/RIP-1 can be purified and specifically binds ssDNA but lacks measurable ATPase activity. RFS-1/RIP-1 also strongly stimulates strand invasion activity by RAD-51, consistent with a pro-recombinogenic function in vivo. I define for the first time the mechanism of action underlying the intrinsic ability of Rad51 paralogs to stimulate HR. Using a combination of biochemical and biophysical approaches, notably electrophoretic mobility shift assays, stopped-flow reaction kinetics and nuclease protection assays, I show RFS-1/RIP-1 dramatically alters the properties of RAD-51-ssDNA filaments such that RAD-51 is more stably associated with ssDNA yet the ssDNA is more sensitive to nuclease degradation. RFS-1/RIP-1 exerts these effects primarily downstream of filament formation, ruling out a major role in RAD-51 loading. I propose RFS-1/RIP-1 remodels RAD-51-ssDNA filaments to a conformation poised for pairing with the template duplex and strand invasion.
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Tarabay, Yara. « Functional studies of mouse Tex19 paralogs during spermatogenesis ». Thesis, Strasbourg, 2013. http://www.theses.fr/2013STRAJ091.
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La spermatogenèse est le processus par lequel les cellules germinales se différencient pour former les spermatozoides. Elle se déroule à l’intérieur des tubes séminifères. Pendant la période embryonnaire, les précurseurs des cellules germinales adultes constituent un pool de cellules appelées cellules germinales primordiales (Primordial Germ Cells, PGCs), qui vont migrer pour aller coloniser les gonades (Durcova-Hills and Capel, 2008; Surani et al., 2008). Au cours de leur migration, les PGCs vont subir une reprogrammation épigénétique de l’ensemble de leur génome, qui leur sera nécessaire pour passer de l’état somatique à l’état de totipotence (Ohinata et al., 2005). Durant cette reprogrammation, l’ADN est massivement démethylé, entrainant l’activation de plusieurs gènes qui sont importants pour le développement des PGCs, mais également l’activation des éléments transposables (ETs) (Hajkova et al., 2008; Sasaki and Matsui, 2008; Surani and Hajkova, 2010). Ces derniers constituent environ 50% du génome des mammifères. Ils sont subdivisés en deux classes et sont connus par leur capacité à être mobilisés dans le génome (Zamudio and Bourc'his, 2010). Cette mobilisation se fait au hasard et constitue ainsi un risque considérable de mutations, qui peuvent provoquer des tumeurs, des pathologies de développement et une infertilité (Zamudio and Bourc'his, 2010). Pour cela, leur expression doit être contrôlée pour maintenir l’intégrité du génome de la lignée germinale. Pour toutes ces raisons, les PGCs ainsi que les cellules germinales en cours de méiose ont développé des stratégies de défenses pour contrôler la mobilisation et l’expression des ETs basées entre autre sur la voie des piwi-interacting RNA (piRNA) (Chuma and Pillai, 2009; Pillai and Chuma, 2012b). Dans le laboratoire du Pr. Stéphane Viville, mes travaux de thèse se sont concentrés sur l’étude d’un gène nommé Tex19 pour Testis Expressed gene chez la souris. Nous avons démontré que ce gène est spécifique des mammifères et est dupliqué chez le rat et la souris en deux paralogues nommés Tex19.1 et Tex19.2. Deux domaines hautement conservés ont été identifiés par alignement multiple des protéines TEX19 et nommés MCP et VPTEL. Ces domaines ne présentent aucune homologie avec des domaines déjà caractérisés, prévenant ainsi toute prédiction de leurs fonctions (Kuntz et al., 2008). L’étude du profil d’expression de Tex19.1 et Tex19.2 a montré que ces deux gènes sont exprimés dans l’ectoderme et les PGCs. Ils sont aussi co-exprimés dans le testicule de l’âge embryonnaire à l’âge adulte. Néanmoins, seul Tex19.1 est exprimé dans les ovaires et le précurseur du placenta appelé cône ectoplacentaire (Celebi et al., 2012). Le knockout (KO) de Tex19.1 provoque une infertilité masculine chez la souris avec un arrêt de la spermatogenèse au stade pachytène, accompagnée d’une surexpression d’un rétrotransposon, MMERVK10C (Ollinger et al., 2008). Récemment, il a été démontré que Tex19.1 joue aussi un rôle dans le développement du placenta (Reichmann et al., 2013). Au cours de mes trois années de thèse, nous avons approfondie l’étude du KO de Tex19.1dans le testicule, les cellules embryonnaires souches (Embryonic Stem Cells, ESCs) et le placenta (Tarabay et al., 2013). Nous avons également étudié le phénotype observé suite au double KO de Tex19.1 et Tex19.2. [...]We recently characterized two new mammalian specific genes, Tex19.1 and its paralog Tex19.2. Both genes are expressed in pachytene spermatocytes in adult testes. In addition, Tex19.1 is expressed in pluripotent cells (ES, EG, iPS and PGC cells), the inner cell mass of the blastocysts and the placenta. In order to decipher Tex19 functions, we generate three types of knockout (KO): i) KO of Tex19.1 ii) KO of Tex19.2 iii) double KO (DKO) of both genes. All Tex19.1-/- KO animals are growth-retarded and half of them die just after birth. This phenotype is probably linked to placenta defects. Surviving adults Tex19.1-/- KO males display a variable spermatogenesis phenotype, associated with an up-regulation of one endogenous retrovirus, MMERVK10C. Tex19.2 KO mice exhibit a subtle phenotype. Few seminiferous epitheliums are degenerated while the rest appear normal. DKO show a fully penetrant phenotype similar to the most severe Tex19.1-/- phenotype. DKO males exhibit small testes. Despite the presence of spermatogonia and spermatocytes, spermatogenesis is blocked at the pachytene stage. By RNA deep-sequencing on 10 days old DKO and WT testes, prior to histological phenotype, 114 genes are significantly up-regulated and 320 genes significantly down-regulated in the DKO compared to the WT. Gene ontology analyses show that among of these genes, two essential pathways are altered: meiosis and the piRNA pathway. Consistent with that, GST-pulldown and immunoprecipitation experiments demonstrate that MIWI, MILI, MAEL and MVH are partners of TEX19. Considering PIWI proteins function in the silencing of transposable elements through the piRNA pathway, we checked if TEX19 paralogs bind piRNA. By immunoprecipitation using WT and KO testes, we show that both TEX19.1 and TEX19.2 bind small RNA of 30 nucleotides through their VPTEL domain. This study highlights the pivot role of Tex19 paralogs in three essential functions of mammalian life cycle, i.e. pluripotency, placenta-supported in utero growth and fertility. The functional similarities of both paralogs, through the expression control of one endogenous retrovirus and the binding of piRNAs, lead us to propose that Tex19 paralogs are new members of the piRNA pathway
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Buffleben, George M. « Interactions of human and drosophila Rad 51 paralogs ». Scholarly Commons, 2010. https://scholarlycommons.pacific.edu/uop_etds/751.
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Damage to DNA from a variety of sources can lead to damaged proteins, genomic instability, aneuploidy, and cancer. It is therefore essential to repair DNA damage, and to do so a variety of DNA repair mechanisms have evolved. One of the repair mechanisms, known as homologous recombination (HR) repair, uses an undamaged sister chromatid as a template to make error free repairs to double-strand (ds) DNA breaks. While many proteins are involved in HR, this work focuses on testing the interactions of a subset of these proteins known as the Rad51 paralogs.
The goal of this study is to determine if the putative Rad51 paralogs in Drosophila melanogaster are sufficiently conserved as to function in the same manner as their human counterparts. This research is part of a larger project to determine if Drosophila melanogaster is a good model organism for studying HR in humans (Hs).
The D. melanogaster Rad51 gene, and its four paralogs Spn D, Spn B, Rad51D, XRCC2 (the last 2 identified by sequence homology), and human hsRad51D and hsXRCC2, were cloned into Invitrogen's TOPO protein expression vector. When induced with IPTG, the resulting fusion proteins contains either aN-terminal Xpress TM epitope or a C-terminal V5 epitope. The fusion proteins were used in immunoprecipitation assays with antibodies against the epitope tags to test for proteinprotein interactions.
While many of the assays were inconclusive and are still being optimized, the interaction of the C-terminally tagged dmXRCC2 with theN-terminally tagged hsRad51D gave a positive result. This single interspecies result suggests that homologous recombination is highly conserved between D. melanogaster and humans.
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Seberg, Hannah Elizabeth. « Transcription factor AP2 paralogs in melanocytes and melanoma ». Diss., University of Iowa, 2018. https://ir.uiowa.edu/etd/6278.
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During development, neural crest (NC) cells arise from the neural plate border and are further differentiated into multiple cell types, including melanocytes. Each step of this process is controlled by a gene regulatory network (GRN), and disruption of the GRN governing melanocyte differentiation contributes to the pathogenesis of pigmentation disorders and melanoma. While many of the factors within this network have been well studied, the role of Transcription Factor Activating Enhancer-Binding Protein 2 (TFAP2) paralogs has been unclear. TFAP2A and TFAP2C are required for NC induction. Later, TFAP2A is also expressed in melanocytes, and TFAP2A mutations cause pigmentation phenotypes in humans, mice, and zebrafish. Other paralogs with high homology to TFAP2A, particularly TFAP2B in mouse and Tfap2e in zebrafish, also function redundantly with TFAP2A in the melanocyte lineage.
Here, we have used ChIP-seq and expression profiling to identify direct transcriptional targets of TFAP2A in melanocytes, which include genes involved in melanin synthesis and melanosome biology. Furthermore, we show that TFAP2A directly regulates many of the same genes as Microphthalmia-associated Transcription Factor (MITF), the “master regulator” of the melanocyte lineage. MITF activity has been described as a rheostat in melanoma, with high levels promoting differentiation and lower levels promoting invasiveness. The overlap between TFAP2A and MITF transcriptional targets in melanocytes suggests that TFAP2A may influence the MITF rheostat, driving it toward the differentiated state. To study the role of other TFAP2 paralogs in NC and melanocytes, we generated zebrafish lines that are double and triple mutant for tfap2a, tfap2c, and tfap2e and confirm genetic compensation among these paralogs. We also demonstrate that melanocyte-specific inhibition of Tfap2 activity by Kctd15 affects differentiation and that Kctd15 may participate in a negative feedback loop regulating Tfap2 expression. In support of a pro-differentiation role for TFAP2A in melanocytes, we show that overexpression of tfap2a in a zebrafish melanoma model significantly delays tumor formation. Together these results indicate that, in addition to its earlier roles in the NC, TFAP2A acts within the melanocyte GRN to directly regulate differentiation genes in parallel with MITF. This, combined with the tumor-suppressor function of TFAP2A in melanoma, implicates TFAP2A and the factors that regulate it as potential targets for melanoma therapies.
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Behera, Jyoti, et Aruna Kilaru. « Comparative in Silico Analysis of WRINKLED1 Paralogs in Angiosperms ». Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/etsu-works/7723.
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Behera, Jyoti, Shina Bhatia et Aruna Kilaru. « Comparative in Silico Analysis of WRINKLED1 Paralogs in Angiosperms ». Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/etsu-works/7724.
Texte intégralRésumé :
WRINKLED 1(WRI1), a member of AP2/EREBP class of transcription factors regulates carbon allocation between glycolytic and fatty acid biosynthetic pathway. Additionally, among the four WRI1 paralogs in Arabidopsis, WRI3 and 4 but not WRI2, are also able to increase fatty acid content in different tissues. While the role of WRI1 is well established in seeds, the potential or WRI1 or its paralogs as master regulators in oilrich nonseed tissues is poorly understood. Recent transcriptome studies of avocado (Persea americana) mesocarp revealed that the ortholog of WRI2, along with WRI1 and WRI3 was highly expressed during oil accumulation.Through transient expression assays, wefurther demonstrated thatbothPaWRI1 andPaWRI2 can accumulate oil in tobacco leaves. We conducted a comprehensive and comparative in silico analysis of WRI paralogs from a dicot, monocot and a basal angiosperm to identify distinct features associated with function. These data provide insights into the possible evolutionary changes in WRI1 homologs and allow for identification of new targets to enhance oil biosynthesis in diverse tissues.
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Merhi, Rawan. « Functional Characterization of parla and parlb Paralogs in Zebrafish ». Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/42409.
Texte intégralRésumé :
Parkinson’s disease (PD) is the second most prevalent neurodegenerative disease, featuring motor signs such as tremors, bradykinesia, and impaired gait that are often preceded by nonmotor symptoms such as anxiety/depression and olfactory dysfunction. Interestingly, significant olfactory loss was found to be manifested in the majority of PD patients and may precede motor symptoms by years, and thus can be used for the risk assessment of developing PD in
asymptomatic individuals. The main pathological feature of PD is the progressive and irreversible loss of dopaminergic (DA) neurons in the substantia nigra pars compacta of the midbrain. Although the detailed etiology of PD remains unclear, most PD cases were found to be sporadic and can be associated with environmental factors. Only 5–10% of patients result from familial PD. With considerable effort in the past two decades, a number of genes associated with familial PD have been identified and interestingly, many of these genes are involved in regulating and maintaining mitochondrial function. The presenilin-associated rhomboid-like (PARL) gene was found to contribute to mitochondrial morphology and function and was linked to familial
Parkinson’s disease (PD). The PARL gene product is a mitochondrial intramembrane cleaving protease that acts on a number of mitochondrial proteins involved in mitochondrial morphology, apoptosis, and mitophagy. To date, functional and genetic studies of PARL have been mainly performed in mammals. However, little is known about PARL function and its role in dopaminergic (DA) neuron development in vertebrates. The zebrafish genome comprises two PARL paralogs: parla and parlb. Here, we show novel information concerning the role of PARL in zebrafish by establishing a loss-of-function mutation in parla and parlb via CRISPR/Cas9-
mediated mutagenesis. We examined DA neuron numbers in the adult brain and expression of genes associated with DA neuron function in larvae and adults. We show that loss of parla function, as well as loss of both parla and parlb function result in loss of DA neurons in the olfactory bulb and telencephalon of adult zebrafish brain. Changes in the levels of tyrosine hydroxylase transcripts supported this neuronal loss. Expression of fis1, a gene involved in mitochondrial fission, was increased in parla mutants and in fish with loss of parla and parlb function. Furthermore, we showed that loss of parla and/or parlb function translates into altered locomotion parameters and that loss of parla but not parlb function results in impaired olfaction. Finally, increased susceptibility to neurotoxin exposure was identified in mutants with loss of both parla and parlb function but not with loss of parla or parlb function. These results suggest an evident role for parla in the development and/or maintenance of DA neuron function in zebrafish and confirm the existence of redundant and non-redundant functions for the two paralogs, parla and parlb.
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Murphy, Lita. « Interaction between the ovine Bst-2 paralogs and sheep Betaretroviruses ». Thesis, University of Glasgow, 2012. http://theses.gla.ac.uk/3113/.
Texte intégralRésumé :
There is a delicate evolutionary balance between viruses and their hosts. The host has evolved the intrinsic, innate and adaptive immunity to fight viral infections. However, viruses have acquired several counteracting measures to evade host defences. Ovine Betaretroviruses, including the exogenous and pathogenic Jaagsiekte sheep retrovirus (JSRV) and the highly related endogenous enJSRVs are a unique model system to investigate virus-host interaction over long evolutionary periods. Sheep have co-opted some defective enJSRV loci to (i) counteract infection by exogenous viruses and likely (ii) to cope with the continuous retroviral invasion of their genome. In addition, various genes of the innate and intrinsic immunity of the host have evolved to block viral replication. The work presented in this thesis focuses on the ovine bone marrow stromal cell antigen 2 (Bst-2)/ tetherin, a recently identified cellular restriction factor with a broad antiviral activity, and its interaction with sheep Betaretroviruses. In sheep, the BST-2 gene is duplicated into two paralogs termed oBST-2A and -2B. Studies presented in this thesis show that oBST-2B possesses several biological properties distinct from the paralog oBST-2A and from all the other BST-2 orthologs. oBST-2A prevents the release of JSRV/enJSRV viral particles by ‘tethering’ them at the cell membrane similarly to what observed by human BST-2. On the other hand, oBST-2B, does not reach the cell membrane but remains within the Golgi stacks and the trans-Golgi network. Several lines of evidence obtained in this thesis suggest that oBST-2B reduces significantly Env incorporation into viral particles. Therefore, oBST-2B possesses a unique antiviral activity that complements the classical tethering restriction provided by oBST-2A.
Livres sur le sujet "Paraloid"
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Bidyābinoda, Haridāsa. Paraloka. Kalikātā : Nabapatra Prakāśana, 1997.
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Śarmā, Aruṇakumāra. Paraloka vijñāna. Vārāṇasī : Ārṇava Prakāśana, 1996.
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Pāṭhaka, Hīrā Rāmanārāyaṇa. Paraloke patra. Amadāvāda : Gūrjara Grantharatna Kāryālaya, 1989.
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Brahmacārī, Tārāpraṇaba. Eloka paraloka. Kalakātā : De'ja Pābaliśiṃ, 1993.
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Mr̥tyu o paraloka. Kalakātā : Karuṇā Prakāśanī, 1991.
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D̲oumprou, Iōanna. Vorinē paralia : Mythistorēma. Athēna : Ekdoseis Patakē, 2019.
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Nigurananda. Mrityu o paralok. Calcutta : Karuna, 1991.
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Paralo gūñja. Chandigarh : Lokgeet Parkashan, 2006.
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Candra, Śakīla. Paraloka samācāra : Nukkaṛa nāṭaka. Dillī : Sārāṃśa Prakāśana, 1998.
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Demi attici della Paralia. Lanciano : Carabba, 2015.
Trouver le texte intégralChapitres de livres sur le sujet "Paraloid"
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Mehlhorn, Heinz. « Paralogs ». Dans Encyclopedia of Parasitology, 2039. Berlin, Heidelberg : Springer Berlin Heidelberg, 2016. http://dx.doi.org/10.1007/978-3-662-43978-4_4152.
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Mehlhorn, Heinz. « Paralogs ». Dans Encyclopedia of Parasitology, 1. Berlin, Heidelberg : Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-642-27769-6_4152-1.
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Srinivasan, Ramachandran. « Paralogs ». Dans Encyclopedia of Systems Biology, 1625. New York, NY : Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4419-9863-7_957.
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Kokubo, Tetsuro. « TAF Paralogs ». Dans Encyclopedia of Systems Biology, 2120–21. New York, NY : Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4419-9863-7_1602.
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Altenhoff, Adrian M., Natasha M. Glover et Christophe Dessimoz. « Inferring Orthology and Paralogy ». Dans Methods in Molecular Biology, 149–75. New York, NY : Springer New York, 2019. http://dx.doi.org/10.1007/978-1-4939-9074-0_5.
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Altenhoff, Adrian M., et Christophe Dessimoz. « Inferring Orthology and Paralogy ». Dans Methods in Molecular Biology, 259–79. Totowa, NJ : Humana Press, 2012. http://dx.doi.org/10.1007/978-1-61779-582-4_9.
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Cebrat, Stanisław, Jan P. Radomski et Dietrich Stauffer. « Genetic Paralog Analysis and Simulations ». Dans Computational Science - ICCS 2004, 709–17. Berlin, Heidelberg : Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-540-25944-2_92.
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Prade, Henri, et Gilles Richard. « Analogy, Paralogy and Reverse Analogy : Postulates and Inferences ». Dans KI 2009 : Advances in Artificial Intelligence, 306–14. Berlin, Heidelberg : Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-04617-9_39.
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Gueudré, Thomas, Carlo Baldassi, Andrea Pagnani et Martin Weigt. « Predicting Interacting Protein Pairs by Coevolutionary Paralog Matching ». Dans Methods in Molecular Biology, 57–65. New York, NY : Springer US, 2019. http://dx.doi.org/10.1007/978-1-4939-9873-9_5.
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Debenay, Jean-Pierre, Jean-Jacques Guillou, Fabrice Redois et Emmanuelle Geslin. « Distribution Trends of Foraminiferal Assemblages in Paralic Environments ». Dans Topics in Geobiology, 39–67. Boston, MA : Springer US, 2000. http://dx.doi.org/10.1007/978-1-4615-4167-7_3.
Texte intégralActes de conférences sur le sujet "Paraloid"
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Barreda Usó, Gemma, et María Antonia Zalbidea Muñoz. « Tratamientos de consolidación de soporte rocoso con manifestaciones de arte rupestre. Abric de Pinos (Benissa-Alicante). » Dans III Congreso Internacional de Investigación en Artes Visuales : : ANIAV 2017 : : GLOCAL. Valencia : Universitat Politècnica València, 2017. http://dx.doi.org/10.4995/aniav.2017.5861.
Texte intégralRésumé :
El presente trabajo de investigación muestra el estudio comparativo entre diversos materiales consolidantes para su aplicación en soportes rocosos con manifestaciones de arte rupestre, cuya superficie muestre una determinada problemática en forma de descohesión microscópica generando pulverulencia. Este es el caso que presenta el Abric de Pinos (Benissa-Alicante), en cuyo soporte se analizan los diferentes consolidantes seleccionados en esta investigación, tanto orgánicos como: Paraloid B-72®, Acril ME®, Fluoline CP®, e inorgánicos como el Nanorestore®. Con el objetivo de obtener unos resultados que permitan establecer una comparativa entre los distintos productos y su interacción con el soporte. Para ello, fue necesario la elaboración de probetas que previamente fueron sometidas tanto a la acción de degradación medioambiental natural, depositándolas in situ, como a diversos ensayos en laboratorio. De este modo se observan y evalúan las propiedades de estos materiales, estableciendo resultados que mejoran su uso y aplicación en futuras intervenciones. Uno de los productos más utilizados en consolidación, ha sido el Paraloid B-72®, su uso viene derivado de otros campos de conocimiento afines al arte rupestre, como la pintura mural y los monumentos pétreos. Realizada una revisión bibliográfica del uso de este material, se encuentran numerosos defensores y detractores. En cuanto al arte rupestre, se ha justificado su uso por la carencia de estudios y de materiales aplicables a tales menesteres. Esta investigación supone un avance en la conservación de pintura rupestre, tan abundante en los territorios de la Comunidad Valenciana. Destacando el gran interés de las instituciones por la salvaguarda de este patrimonio, han permitido la realización de intervenciones de conservación y restauración, incrementadas desde que el Arte Rupestre fuera declarado Patrimonio de la Humanidad en 1981. A través de este estudio se establecen unas premisas para el desarrollo y aplicación de consolidantes en el tratamiento de superficies con arte rupestre. http://dx.doi.org/10.4995/ANIAV.2017.5861
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Bailão, Ana, Ana Bidarra, Bruna Silva Pereira, Ana Rita Esperança et Teresa Desterro. « CONTACT LENSES ON THE CHROMATIC REINTEGRATION PROCESS OF THE EYEBALLS OF A WOOD SCULPTURE ». Dans RECH6 - 6th International Meeting on Retouching of Cultural Heritage. València : Editorial Universitat Politècnica de València, 2021. http://dx.doi.org/10.4995/rech6.2021.13559.
Texte intégralRésumé :
Chromatic reintegration aims to decrease deterioration evidences in the artwork and retrieve the visual interpretation of its iconographic shapes and contents. This case study will focus on the chromatic reintegration process of the eyeballs of a wood sculpture representing Saint Teotónio. Instead of applying colour over the eyeballs, it was decided to make thin lenses that could be placed directly on the surface. Experiments were carried out with different resins, on one centimetre in diameter moulds. The resins tested were Paraloid B72; PVA Inpainting Medium (Gustav Berger's Berger's O.F.); Mowilith DS 5/2; Aquazol 200; Plextol B500 and the monomer 2-ethyl hexyl acrylate (2 EHA). The selected resin was the monomer 2 EHA, which was then tested in a mixture with acrylic paint to achieve an accurate colour representation of the iris and pupil of the eye.
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Marcattili, Letizia, et Maria Canavan. « Retouching a Retouched Painting : Evaluation and re-treatment of historic retouchings in the conservation of a painting by Lavinia Fontana ». Dans RECH6 - 6th International Meeting on Retouching of Cultural Heritage. València : Editorial Universitat Politècnica de València, 2021. http://dx.doi.org/10.4995/rech6.2021.13544.
Texte intégralRésumé :
A major conservation and research project on The Visit of the Queen of Sheba to King Solomon by Lavinia Fontana was completed at the National Gallery of Ireland in Dublin in 2021. The painting, a large-scale oil on canvas (256 x 325 cm), was one of a number of pictures restored in the late 1960s by a team of conservators from the Istituto Centrale del Restauro in Rome, who came to Dublin during the establishment of the first conservation studio at the Gallery. The visiting restorers brought novel ideas and materials with them from the Istituto that would shape the Irish approach to conservation for decades to come. The prevailing ethos at the time in Italy was based on a minimal intervention approach with the use of novel, synthetic materials that had not yet been introduced to the collection of the National Gallery of Ireland. The painting, after treatment by the Istituto team, recorded material evidence of a particular moment in the development of conservation in Italy and Ireland. Large areas of historic loss and damage across the surface of the painting had been reintegrated by the Italian restorers with the application of retouchings in the tratteggio style, also known as rigatino, using a Paraloid-based medium. In some cases, portraits and other significant details in the image were fully reconstructed by the retouchings. Underlying instability required the removal of some of these retouchings during the most recent treatment, but others could be retained if desired. With the help of archival images and documentation, a decision-making model was developed to evaluate the quality and historic value of these retouchings and to determine which to preserve, which to modify and which to remove. Reduction of retouchings often necessitates replacement, and the partial preservation of the historic retouchings brought further factors to bear on the decision-making model for the chromatic reintegration of the painting. A return to the tratteggio technique was chosen for the larger instances of loss compensation in the treatment, albeit with a finer hatching so that the newer reintegration remains distinguishable from the historic one. This was complemented with a pointillist technique over textured fillings for smaller and shallower losses. Furthermore, where blistering and heat damage in the paint layers resulted in uneven topography, a third auxiliary technique was used. The desired texture was found when testing Paraloid-based gels on a mock-up and applied to bring continuity the surface texture in these areas of the painting. With this approach we intend to meet the conservation needs of the object, restore the legibility of the image and retain the evidence of the historic intervention of this founding team of Italian restorers at the National Gallery of Ireland.
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Tobin, Genevieve Mary. « The silver lining : preliminary research into gold-coloured varnishes for loss compensation in two 19th C silver gilded frames ». Dans RECH6 - 6th International Meeting on Retouching of Cultural Heritage. València : Editorial Universitat Politècnica de València, 2021. http://dx.doi.org/10.4995/rech6.2021.13498.
Texte intégralRésumé :
Golden varnishes appear on frames, furniture, wall hangings, leatherwork, panel paintings, mural paintings, and polychromy, and were applied to white metal gilding to imitate gold and other semi-precious materials. Despite the number of examples in cultural heritage there are few publications that discuss the ethical considerations of treating coloured silver gilded surfaces. The chromatic reintegration of gold-coloured varnishes on white metal gilding present specific material and technical challenges. In 2021 the Art Gallery of New South Wales (AGNSW) treated two identical late 19th century silver gilded frames for portraits by Joseph Backler from the Australian collection. In addition, a third portrait required the fabrication of a reproduction frame identical to the others. Conservation of the frames presented an opportunity for carrying out experiments into coloured coatings for loss compensation on silver gilding exploring applications for select conservation paints, dyes, and synthetic resins as substitutes for shellac. The results of experiments demonstrate that with the right application Liquitex Soluvar Gloss Varnish, Laropal A81 and Paraloid B72, present gloss levels and visual film forming properties comparable to shellac coatings when applied to burnished gilding. Additional tests with various dye colours illustrate that Orasol ® dye mixtures in colours Yellow 2GLN, Yellow 2RL, and Brown 2GL are reliable colour imitations for traditional gold-coloured varnishes. Although this research is preliminary, it may inform the selection and application of appropriate retouching materials for compensating losses to burnished silver leaf and golden varnishes in gilding conservation.
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Vlachos, Evangelos, Michelle L. Goodstein, Michael A. Kozuch, Shimin Chen, Babak Falsafi, Phillip B. Gibbons et Todd C. Mowry. « ParaLog ». Dans the fifteenth edition of ASPLOS. New York, New York, USA : ACM Press, 2010. http://dx.doi.org/10.1145/1736020.1736051.
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Charles, Henri-Pierre, Jian-Jin Li et Serge Miguet. « Three-dimensional image processing on distributed memory paralled computers ». Dans IS&T/SPIE's Symposium on Electronic Imaging : Science and Technology, sous la direction de Raj S. Acharya et Dmitry B. Goldgof. SPIE, 1993. http://dx.doi.org/10.1117/12.148651.
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CAO, MENGFEI, et LENORE J. COWEN. « WHEN SHOULD WE NOT TRANSFER FUNCTIONAL ANNOTATION BETWEEN SEQUENCE PARALOGS ? » Dans Proceedings of the Pacific Symposium. WORLD SCIENTIFIC, 2016. http://dx.doi.org/10.1142/9789813207813_0003.
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Leneveu, Romain, Benoit Schiltz, Julien Manera et Stéphane Caro. « Paralled DGM scheme for LEE applied to exhaust and bypass problems ». Dans 13th AIAA/CEAS Aeroacoustics Conference (28th AIAA Aeroacoustics Conference). Reston, Virigina : American Institute of Aeronautics and Astronautics, 2007. http://dx.doi.org/10.2514/6.2007-3510.
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Zhang, XuePing, YanXia Zhu et Nan Hua. « Improved paralled algorithm for mining frequent item-set used in HRM ». Dans 2010 Seventh International Conference on Fuzzy Systems and Knowledge Discovery (FSKD). IEEE, 2010. http://dx.doi.org/10.1109/fskd.2010.5569250.
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Auyeung, V., N. R. Bhakta, B. Backes, D. Maly, P. Woodruff, D. Sheppard et F. Papa. « Roles for IRE1 Paralogs and the Unfolded Protein Response in Asthma ». Dans American Thoracic Society 2019 International Conference, May 17-22, 2019 - Dallas, TX. American Thoracic Society, 2019. http://dx.doi.org/10.1164/ajrccm-conference.2019.199.1_meetingabstracts.a2906.
Texte intégralRapports d'organisations sur le sujet "Paraloid"
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Barg, Rivka, Erich Grotewold et Yechiam Salts. Regulation of Tomato Fruit Development by Interacting MYB Proteins. United States Department of Agriculture, janvier 2012. http://dx.doi.org/10.32747/2012.7592647.bard.
Texte intégralRésumé :
Background to the topic: Early tomato fruit development is executed via extensive cell divisions followed by cell expansion concomitantly with endoreduplication. The signals involved in activating the different modes of growth during fruit development are still inadequately understood. Addressing this developmental process, we identified SlFSM1 as a gene expressed specifically during the cell-division dependent stages of fruit development. SlFSM1 is the founder of a class of small plant specific proteins containing a divergent SANT/MYB domain (Barg et al 2005). Before initiating this project, we found that low ectopic over-expression (OEX) of SlFSM1 leads to a significant decrease in the final size of the cells in mature leaves and fruits, and the outer pericarp is substantially narrower, suggesting a role in determining cell size and shape. We also found the interacting partners of the Arabidopsis homologs of FSM1 (two, belonging to the same family), and cloned their tomato single homolog, which we named SlFSB1 (Fruit SANT/MYB–Binding1). SlFSB1 is a novel plant specific single MYB-like protein, which function was unknown. The present project aimed at elucidating the function and mode of action of these two single MYB proteins in regulating tomato fruit development. The specific objectives were: 1. Functional analysis of SlFSM1 and its interacting protein SlFSB1 in relation to fruit development. 2. Identification of the SlFSM1 and/or SlFSB1 cellular targets. The plan of work included: 1) Detailed phenotypic, histological and cellular analyses of plants ectopically expressing FSM1, and plants either ectopically over-expressing or silenced for FSB1. 2) Extensive SELEX analysis, which did not reveal any specific DNA target of SlFSM1 binding, hence the originally offered ChIP analysis was omitted. 3) Genome-wide transcriptional impact of gain- and loss- of SlFSM1 and SlFSB1 function by Affymetrix microarray analyses. This part is still in progress and therefore results are not reported, 4) Search for additional candidate partners of SlFSB1 revealed SlMYBI to be an alternative partner of FSB1, and 5) Study of the physical basis of the interaction between SlFSM1 and SlFSB1 and between FSB1 and MYBI. Major conclusions, solutions, achievements: We established that FSM1 negatively affects cell expansion, particularly of those cells with the highest potential to expand, such as the ones residing inner to the vascular bundles in the fruit pericarp. On the other hand, FSB1 which is expressed throughout fruit development acts as a positive regulator of cell expansion. It was also established that besides interacting with FSM1, FSB1 interacts also with the transcription factor MYBI, and that the formation of the FSB1-MYBI complex is competed by FSM1, which recognizes in FSB1 the same region as MYBI does. Based on these findings a model was developed explaining the role of this novel network of the three different MYB containing proteins FSM1/FSB1/MYBI in the control of tomato cell expansion, particularly during fruit development. In short, during early stages of fruit development (Phase II), the formation of the FSM1-FSB1 complex serves to restrict the expansion of the cells with the greatest expansion potential, those non-dividing cells residing in the inner mesocarp layers of the pericarp. Alternatively, during growth phase III, after transcription of FSM1 sharply declines, FSB1, possibly through complexing with the transcription factor MYBI serves as a positive regulator of the differential cell expansion which drives fruit enlargement during this phase. Additionally, a novel mechanism was revealed by which competing MYB-MYB interactions could participate in the control of gene expression. Implications, both scientific and agricultural: The demonstrated role of the FSM1/FSB1/MYBI complex in controlling differential cell growth in the developing tomato fruit highlights potential exploitations of these genes for improving fruit quality characteristics. Modulation of expression of these genes or their paralogs in other organs could serve to modify leaf and canopy architecture in various crops.
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Dubcovsky, Jorge, Tzion Fahima et Ann Blechl. Molecular characterization and deployment of the high-temperature adult plant stripe rust resistance gene Yr36 from wheat. United States Department of Agriculture, novembre 2013. http://dx.doi.org/10.32747/2013.7699860.bard.
Texte intégralRésumé :
Stripe rust, caused by Puccinia striiformis f. sp. tritici is one of the most destructive fungal diseases of wheat. Virulent races that appeared within the last decade caused drastic cuts in yields. The incorporation of genetic resistance against this pathogen is the most cost-effective and environmentally friendly solution to this problem. However, race specific seedling resistance genes provide only a temporary solution because fungal populations rapidly evolve to overcome this type of resistance. In contrast, high temperature adult plant (HTAP) resistance genes provide a broad spectrum resistance that is partial and more durable. The cloning of the first wheat HTAP stripe rust resistance gene Yr36 (Science 2009, 323:1357), funded by our previous (2007-2010) BARD grant, provided us for the first time with an entry point for understanding the mechanism of broad spectrum resistance. Two paralogous copies of this gene are tightly linked at the Yr36 locus (WKS1 and WKS2). The main objectives of the current study were to characterize the Yr36 (WKS) resistance mechanism and to identify and characterize alternative WKSgenes in wheat and wild relatives. We report here that the protein coded by Yr36, designated WKS1, that has a novel architecture with a functional kinase and a lipid binding START domain, is localized to chloroplast. Our results suggest that the presence of the START domain may affect the kinase activity. We have found that the WKS1 was over-expressed on leaf necrosis in wheat transgenic plants. When the isolated WKS1.1 splice variant transcript was transformed into susceptible wheat it conferred resistance to stripe rust, but the truncated variant WKS1.2 did not confer resistance. WKS1.1 and WKS1.2 showed different lipid binding profiling. WKS1.1 enters the chloroplast membrane, while WKS1.2 is only attached outside of the chloroplast membrane. The ascorbate peroxidase (APX) activity of the recombinant protein of TmtAPXwas found to be reduced by WKS1.1 protein in vitro. The WKS1.1 mature protein in the chloroplast is able to phosphorylate TmtAPXprotein in vivo. WKS1.1 induced cell death by suppressing APX activity and reducing the ability of the cell to detoxify reactive oxygen. The decrease of APX activity reduces the ability of the plant to detoxify the reactive H2O2 and is the possible mechanism underlying the accelerated cell death observed in the transgenic plants overexpressing WKS1.1 and in the regions surrounding a stripe rust infection in the wheat plants carrying the natural WKS1.1 gene. WKS2 is a nonfunctional paralog of WKS1 in wild emmer wheat, probably due to a retrotransposon insertion close to the alternative splicing site. In some other wild relatives of wheat, such as Aegilops comosa, there is only one copy of this gene, highly similar to WKS2, which is lucking the retrotransposon insertion. WKS2 gene present in wheat and WKS2-Ae from A. showed a different pattern of alternative splice variants, regardless of the presence of the retrotransposon insertion. Susceptible Bobwhite transformed with WKS2-Ae (without retrotansposon insertion in intron10), which derived from Aegilops comosaconferred resistance to stripe rust in wheat. The expression of WKS2-Ae in transgenic plants is up-regulated by temperature and pathogen infection. Combination of WKS1 and WKS2-Ae shows improved stripe rust resistance in WKS1×WKS2-Ae F1 hybrid plants. The obtained results show that WKS1 protein is accelerating programmed cell death observed in the regions surrounding a stripe rust infection in the wheat plants carrying the natural or transgenic WKS1 gene. Furthermore, characterization of the epistatic interactions of Yr36 and Yr18 demonstrated that these two genes have additive effects and can therefore be combined to increase partial resistance to this devastating pathogen of wheat. These achievements may have a broad impact on wheat breeding efforts attempting to protect wheat yields against one of the most devastating wheat pathogen.