Academic literature on the topic 'Coude β'
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Journal articles on the topic "Coude β"
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Kolev, D., and E. Georgeva. "A Spectroscqpic Study of the Bp-Star θ Aur." International Astronomical Union Colloquium 90 (1986): 295–98. http://dx.doi.org/10.1017/s0252921100091685.
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AbstractThe atmosphere parameters, spectral variability and the magnetic field geometry of the Bp-star θ Aur are evaluated from 30 coude-spectrograms. We adopt Te = 10 800K and lgg = 3.40 (with lower reliability of lg g ) . The equivalent widths of the metalic lines show a relatively great scattering which troubles the period search. The best fit to our data gives the period P = 3.620d, but the variability is clearly seen only for Sill lines. The uncertainties in the star parameters obtained bring to a great uncertainty in the magnetic dipole geometry: i = 86° + 39° and β = 18° + 80°. We adopt the most plausible star parameters to be: R = 3.8R⊙ M = 3.5R⊙, i = 80°, β = 20°, Bp = 1 KGs.
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Marson, R. G., T. R. Bedding, and J. G. Robertson. "Multi-wavelength Optical Aperture Synthesis." Publications of the Astronomical Society of Australia 10, no. 1 (1992): 71–73. http://dx.doi.org/10.1017/s1323358000019299.
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AbstractThe technique of aperture synthesis is well developed in radio astronomy. When applied to the optical regime, aperture synthesis allows one to partially overcome the blurring effects of the atmosphere and increase the angular resolution of large telescopes to the diffraction limit. MAPPIT (Masked APerture-Plane Interference Telescope) is a multi-element interferometer which operates at the coude focus of the 3.9 m Anglo-Australian Telescope. This instrument has recently been reconfigured to operate in a dispersed mode so that simultaneous observations in a band of wavelengths are possible. We will discuss this instrument’s new mode and present observations of the double star δ Sco and an angular diameter of the previously unresolved red giant β Gru.
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Ford, Ethan, and Dimitris Thanos. "The transcriptional code of human IFN-β gene expression." Biochimica et Biophysica Acta (BBA) - Gene Regulatory Mechanisms 1799, no. 3-4 (March 2010): 328–36. http://dx.doi.org/10.1016/j.bbagrm.2010.01.010.
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Joo, Hyun, and Jerry Tsai. "An amino acid code for β-sheet packing structure." Proteins: Structure, Function, and Bioinformatics 82, no. 9 (April 16, 2014): 2128–40. http://dx.doi.org/10.1002/prot.24569.
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BASU, MANJUSRI, and BANDHU PRASAD. "AVERAGE DISTANCE AND MINIMUM AVERAGE DISTANCE OF BINARY CONSTANT WEIGHT CODE AND ITS PROPERTIES." Discrete Mathematics, Algorithms and Applications 02, no. 03 (September 2010): 379–88. http://dx.doi.org/10.1142/s1793830910000723.
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Let [Formula: see text] denote the average Hamming distance of a binary constant weight code C. Ai is the distance distribution of C and Bj is the transform quantity of Ai. Let β(n, M, w) denote the minimum average Hamming distance of a binary constant weight code with length n, size M, and weight w. In this paper, we have established the relation among Bj, [Formula: see text] and Ai. We also study the problem of determining β(n, M, w) and bounds of β(n, M, w) for different values of M.
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Banjar, Haneen R., Galila F. Zaher, Hanadi S. Almutiry, Asma S. A. Alshamarni, Ghaidaa I. Almouhana, Hatem M. Alahwal, Salem Bahashwan, Ahmed S. Barefah, Salwa A. Alnajjar, and Hajar M. Alharbi. "Web-based expert system with quick response code for beta-thalassemia management." Health Informatics Journal 27, no. 1 (January 2021): 146045822198939. http://dx.doi.org/10.1177/1460458221989397.
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β-thalassemia is an inherited blood disorder in which the body cannot produce hemoglobin normally. Since patients with this condition receive blood transfusions regularly, iron builds up primarily in organs such as the heart, liver and endocrine glands. Accumulation of iron in the organs necessitates chelation therapy. These patients must visit the hospital frequently to assess and follow up on their health condition. Physician intervention is required after each regular assessment to adjust the treatment. Lifelong healthcare support using a web-based expert system with a quick response code is designed for β-thalassemia management in order to deliver benefits to patients, physicians, and other healthcare providers. The aim of this study is to implement a web-based expert system for β-thalassemia management in order to provide treatment recommendations and support the lifelong healthcare of patients. The system provides patient-related details, such as medical history, medicines, and appointments, in real-time. It has been also tested in real-life cases and shown to enhance β-thalassemia management.
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Hannachi, Ibtissem, Spiros Alexiou, and Roland Stamm. "Line Shape Code Comparison of the Effect of Periodic Fields on Hydrogen Lines." Atoms 12, no. 4 (March 22, 2024): 19. http://dx.doi.org/10.3390/atoms12040019.
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Spectral line shapes code in plasmas (SLSPs) code comparison workshops have been organized in the last decade with the aim of comparing the spectra obtained with independently developed analytical and numerical models. Here, we consider the simultaneous effect of a plasma microfield and a periodic electric field on the hydrogen lines Lyman-α, Lyman-β, Balmer-α, and Balmer-β for plasma conditions where the Stark effect usually dominates line broadening.
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Gagnon, Laurence, Yubo Cao, Aaron Cho, Dana Sedki, Thomas Huber, Thomas P. Sakmar, and Stéphane A. Laporte. "Genetic code expansion and photocross-linking identify different β-arrestin binding modes to the angiotensin II type 1 receptor." Journal of Biological Chemistry 294, no. 46 (September 17, 2019): 17409–20. http://dx.doi.org/10.1074/jbc.ra119.010324.
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The angiotensin II (AngII) type 1 receptor (AT1R) is a member of the G protein–coupled receptor (GPCR) family and binds β-arrestins (β-arrs), which regulate AT1R signaling and trafficking. These processes can be biased by different ligands or mutations in the AGTR1 gene. As for many GPCRs, the exact details for AT1R–β-arr interactions driven by AngII or β-arr–biased ligands remain largely unknown. Here, we used the amber-suppression technology to site-specifically introduce the unnatural amino acid (UAA) p-azido-l-phenylalanine (azF) into the intracellular loops (ICLs) and the C-tail of AT1R. Our goal was to generate competent photoreactive receptors that can be cross-linked to β-arrs in cells. We performed UV-mediated photolysis of 25 different azF-labeled AT1Rs to cross-link β-arr1 to AngII-bound receptors, enabling us to map important contact sites in the C-tail and in the ICL2 and ICL3 of the receptor. The extent of AT1R–β-arr1 cross-linking among azF-labeled receptors differed, revealing variability in β-arr's contact mode with the different AT1R domains. Moreover, the signature of ligated AT1R–β-arr complexes from a subset of azF-labeled receptors also differed between AngII and β-arr–biased ligand stimulation of receptors and between azF-labeled AT1R bearing and that lacking a bias signaling mutation. These observations further implied distinct interaction modalities of the AT1R–β-arr1 complex in biased signaling conditions. Our findings demonstrate that this photocross-linking approach is useful for understanding GPCR–β-arr complexes in different activation states and could be extended to study other protein–protein interactions in cells.
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Sadoul, Karin, Clotilde Joubert, Sophie Michallet, Elsie Nolte, Lauralie Peronne, Sacnicté Ramirez-Rios, Anne-Sophie Ribba, and Laurence Lafanechère. "Déchiffrage du code tubuline." médecine/sciences 34, no. 12 (December 2018): 1047–55. http://dx.doi.org/10.1051/medsci/2018295.
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Les microtubules sont des fibres du cytosquelette formées par l’assemblage d’hétérodimères d’α- et de β-tubuline. Ils contribuent à l’établissement de la forme des cellules et de leur polarité, ainsi qu’à leur mobilité. Ils jouent aussi un rôle important dans le transport intracellulaire et dans la division cellulaire. Le réseau microtubulaire s’adapte constamment aux besoins de la cellule. Il peut être constitué de microtubules très dynamiques ou d’autres plus stables. Pour moduler dans l’espace et le temps les différentes fonctions de ces fibres, de nombreuses modifications post-traductionnelles réversibles de la tubuline sont mises en jeu, à l’origine de ce qui est maintenant appelé le « code tubuline ». Dans cette revue, nous nous intéresserons au rôle de deux modifications caractéristiques des microtubules stables : l’acétylation et la détyrosination de l’α-tubuline. Nous discuterons également de l’implication de leur dérégulation dans certaines pathologies.
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Tatsuzawa, Fumi, Kazuhisa Kato, Motoki Sato, Shun Ito, Hiroki Muraoka, Yoshihito Takahata, and Satoshi Ogawa. "Acylated Cyanidin 3-sophoroside-5-glucoside in Purple-violet Flowers of Moricandia arvensis (Brassicaceae)." Natural Product Communications 10, no. 3 (March 2015): 1934578X1501000. http://dx.doi.org/10.1177/1934578x1501000321.
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A new acylated anthocyanin was isolated as a major pigment, along with a known anthocyanin ( Moricandia arvensis anthocyanin 1: MAA-1), from a strain of Moricandia arvensis (Code No. MOR-ARV-3) with purple-violet flowers, and identified as cyanidin 3- O-[2- O-(2- O-(4- O-(6- O-(4- O-(β-glucopyranosyl)- trans-caffeoyl)-P-glucopyranosyl)- trans-caffeoyl)-β-glucopyranosyl)-6- O-( trans-sinapoyl)-β-glucopyranoside]-5- O-[6- O-(malonyl)-β-glucopyranoside].
Dissertations / Theses on the topic "Coude β"
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Jean, Fabienne. "Incorporation d'un mime de coude β dans deux protéines : études synthétiques, structurales et fonctionnelles." Lille 1, 1997. http://www.theses.fr/1997LIL10215.
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Chronologiquement, l'incorporation d'elements non naturels dans les proteines a tout d'abord consiste en l'introduction d'acides amines d, comportant une chaine laterale modifiee, ou d'une liaison chimique mimant la liaison peptidique. Nous proposons de nous placer plus loin dans le domaine de l'ingenierie des proteines en incorporant un element non naturel (mime de coude ) issu de la synthese organique, en remplacement d'un motif structural. L'incorporation de ce mime a structure dibenzofurane (mime-dbf) a ete decrite de facon tres precise dans des peptides et nous voulions etudier son comportement dans un contexte proteique. Dans un premier temps, nous avons etudie une nouvelle approche de synthese du mime-dbf afin de reduire le nombre d'etapes et de permettre sa fonctionnalisation. La nouvelle strategie repose notamment sur une reaction de metallation ou deux groupements ortho-directeurs sont en competition. L'optimisation des parametres temperature, stoechiometrie de l'agent de lithiation, nature et composition du solvant ont permis d'obtenir une bonne regioselectivite en faveur de la position voulue. Le mime-dbf a ete incorpore en utilisant la synthese peptidique en phase solide dans deux modeles proteiques : la scyllatoxine, une toxine de venin de scorpion, et le domaine b1 de la proteine g du streptocoque. Dans les deux cas, la structure tridimensionnelle des proteines modifiees, etudiee par rmn et modelisation moleculaire, est conservee. La scyllatoxine analogue conserve l'activite biologique au niveau des canaux potassium calcium-dependants mais le domaine b1 analogue, quant a lui, ne reconnait pas les immunoglobulines g dans les conditions du test utilise. D'autre part, le travail effectue lors d'un stage dans le laboratoire du professeur ramage a edimbourg est presente.
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Larregola, Maud. "Développement de mimes de coude β inhibiteurs d'interaction protéine-protéine : une étude à l'interface entre chimie organique, chimie structurale et biochimie." Paris 6, 2009. http://www.theses.fr/2009PA066475.
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Les coudes β étant des motifs de reconnaissance fréquents entre protéines, l’objectif de ce travail a été de développer des mimes potentiels de coudes β et de les évaluer sur le plan structural et comme inhibiteurs d’interactions protéine-protéine. Le complexe α amylase/tendamistat a constitué notre modèle d’étude et nous avons développé trois approches pour mimer le coude β du tendamistat. Dans une première approche, des peptides contenant des enchaînements d’acides β-aminés ont été synthétisés. L’analyse structurale par RMN a montré que ces peptides ne sont pas structurés en coude β en solution mais ils possèdent une affinité pour l’α amylase similaire à celle de l’α peptide de référence et présentent l’avantage d’être résistants à la protéolyse. L’utilisation d’un peptide biotinylé a permis de capturer spécifiquement l’α amylase dans un mélange complexe de protéines, la reproductibilité des expériences devant encore être optimisée. Dans une deuxième approche, trois α hexapeptides cycliques ont été synthétisés pour comparer les effets conformationnels des cyclisations par liaison amide, pont disulfure et chimie « click ». Alors que le dernier peptide présente un équilibre conformationnel, un repliement en coude β est observé dans le méthanol et l’eau pour le peptide cyclisé par liaison amide et dans le méthanol et lors de l’interaction avec l’α amylase pour l’analogue contenant un pont disulfure. Ces deux peptides sont deux fois plus affins pour la protéine que l’α peptide contrôle. Enfin, nous avons montré que les enchaînements Dprolinoamino acide-Nméthylamino acide et Dprolinoamino acide-cyclopropylamino acide induisent le repliement en coude β de pseudotétrapeptides.
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Marques, da Ressurreição Ana Sofia. "Synthesis, conformational analysis and biological evaluation of peptidomimetics acting as β-sheet inducers." Paris 11, 2008. http://www.theses.fr/2008PA114830.
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Nous avons conçu et synthétisé un nouveau motif dicétopipérazine utilisé pour porter des séquences peptidiques. L’analyse conformationnelle des nouveaux peptidomimétiques préparés a révélé que le motif dicétopipérazine agit comme un élément inducteur d’une structure secondaire conduisant à la formation de mimes d’épingles à cheveux. Ce motif a également été utilisé pour synthétiser un peptidomimétique cyclique contenant la séquence arginine-glycine-aspartate (RGD), qui a été testé comme ligand sélectif de l����intégrine αvβ3. La protéase du VIH-1 (PR) est un homodimère constitué de deux sous-unités identiques de 99 acides aminés. La forme dimérique de la protéase est la seule forme active et est essentiellement stabilisée par un feuillet b à 4 brins antiparallèles formé par les extrémités C- et N- terminales de chacun des monomères de la PR. Nous avons conçu et synthétisé des pinces moléculaires portant des nouveaux brins peptidomimétiques destinées à inhiber la dimérisation de la PRA new bifunctional diketopiperazine (DKP) scaffold was synthesised and used to grow peptide sequences. Conformational analysis of the new prepared peptidomimetics reveals that the DKP scaffold acts as a secondary structure inducing element leading to formation of b-hairpin mimics. The scaffold was also used to synthesise a cyclic peptidomimetic containing the arginine-glycine-aspartate (RGD) motif that was tested as a selective ligand for the integrin αvβ3. HIV-1 protease (PR) is a homodimer of two identical 99-amino acid subunits in which the active site is generated by self-assembly of these subunits. The PR is only active in its dimeric form, which is essentially stabilized by the antiparallel b-sheet formed by interdigitation of N- and C-terminal strands of each PR monomer. By targeting this highly conserved dimerization interface, we demonstrated that HIV-1 PR dimer is disrupted with loss of activity by constrained molecular tongs containing new peptidomimetic fragments
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Cristau, Pierre. "Synthèses totales des mauritines A, B, C et F ; synthèse de macrocycles orientée pour la diversité structurale : conception et synthèse d'un cyclophane support d'un coude β." Paris 11, 2003. http://www.theses.fr/2003PA112184.
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Dans la première partie de ce manuscrit, nous avons decrit la première synthèse totale des mauritines a, b, c et f, alcaloi͏̈des cyclopeptidiques à 14 chaînons biologiquement actifs. La stratégie de synthèse que nous avons développé est basée sur une cycloétherification par réaction de s(n)ar intramoléculaire et met en jeu un tripeptide linéaire intact, ce qui rend la stratégie très convergente. Le rendement global de ces synthèses totales est de 6. 7-10. 2 pour cent pour 13-14 étapes. Une étude complète par spectroscopie rmn a été réalisée sur les mauritines a, b, c et f, permettant notamment d'attribuer, pour la première fois, tous les signaux correspondant aux protons mais aussi à tous les carbones. Dans la deuxième et troisième partie de ce manuscrit, nous avons décrit une nouvelle séquence ugi-s(n)ar permettant de synthétiser efficacement des macrocycles, analogues de produits naturels biologiquement actifs, qui comportent soit un motif biaryl éther soit un motif aryl-x-alkyl endocyclique (x = nh, 0, s). Cette séquence permet d'introduire une grande diversité structurale dans les molécules cibles et des macrocycles à 14, 15, 16 et 17 chaînons ont pu être synthétisés. Enfin, la séquence ugi-s(n)ar permettant d'accéder aux macrocycles comportant un motif biaryl éther a pu être appliquée aussi efficacement sur support solide (résine de wang). Dans la dernière partie de ce manuscrit, nous avons conÇu et synthétisé un nouveau cyclophane de type cycloisodityrosine, support externe potentiel d'un coude béta. Ainsi, quatre molécules cibles ont été synthétisées puis entièrement caractérisées. Une analyse conformationnelle détaillée (rmn, dichroi͏̈sme circulaire) a montré que cette unité cycloisodityrosine constitue vraisemblablement un bon support externe d'un coude béta du type ii, qui pourrait permettre le développement d'une nouvelle classe de peptidomimetiquesIn the first part of this manuscript, we have detailled the first total syntheses of mauritines a, b, c and f, 14-membered cyclopeptide alkaloids with biological activity. Our strategy is very convergent and is based on the intramolecular s(n)ar cycloetherification which involves an intact linear tripeptide. The overall yield of these total syntheses is 6. 7-10. 2 per cent for 13-14 steps. For the first time detailled nmr studies allowed all proton and carbon signals to be attributed. In the second and third part of this manuscript, we have detailled a new ugi-s(n)ar sequence which allow the easy access to natural product-like macrocycles containing either an endocyclic biaryl ether or an aryl-x-alkyl pattern (x = nh, o, s). This sequence allow the introduction of broad structural diversity into the targetted molecules and 14 to 17-membered macrocycles have been synthesized. A solid supported version of this sequence was also developped for the synthesis of biaryl ether containing macrocycles (wang resin). In the last part of this manuscript, we have designed and synthesized a new macrocyclic beta turn scaffold. Thus four cycloisodityrosine-like macrocycles have been synthesized and fully characterized. A detailled conformational study (nmr, circular dichroi͏̈sm) showed that these targetted molecules are probably type ii beta turns. Therefore this new scaffold could be further considered for the developpment of a new class of peptidomimetics
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Durand, Ana Margarida Alves da Silva. "Alternariose em couve-brócolo no Ribatejo e Oeste." Master's thesis, ISA/UL, 2017. http://hdl.handle.net/10400.5/13962.
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Mestrado em Engenharia Agronómica - Protecção de Plantas - Instituto Superior de Agronomia - ULNeste trabalho efetuaram-se estudos em laboratório com o objectivo de esclarecer quais as espécies associadas a alternariose em couve-brócolo na região do Ribatejo e Oeste. A alternariose nas brássicas é responsável por grandes prejuízos a nível mundial em espécies para produção de óleo e em espécies hortícolas. Nas brássicas cultivadas pela inflorescência ou folha, as espécies A. brassicicola e A. brassicae são consideradas de maior importância. Devido à intensificação da produção de brássicas em Portugal tem sido detectada uma maior incidência desta doença em couve-brócolo, couve-flor e couve-repolho, o que justifica o estudo desta patologia. Assim, na sequência das prospeções de campo, constitui-se uma coleção de isolados para os quais foram estudadas caraterísticas morfoculturais e moleculares. Foram igualmente realizados testes de patogenicidade e de virulência em discos de plantas com isolados das diferentes espécies identificadas. Os resultados da caraterização morfocultural e da sequenciação revelaram que a maioria dos isolados, recolhidos no ecossistema de produção de couves, pertencem à espécie A. brassicicola, ainda que outras espécies tenham sido identificadas, nomeadamente A. brassicae, A. infectoria e A. tenuissima e Alternaria sp., Secção Alternata. Os estudos de patogenicidade e de virulência em cultivares de couve-brócolo, couve-flor e couve-repolho mostraram que isolados da espécie A. brassicicola obtidos de couve-brócolo foram mais virulentos que isolados desta espécie obtidos de couve-flor e que o isolado da espécie A. brassicae
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Klementieva, Oxana. "Influence of Cu(II) and Glycodendrimers on Amyloid-beta-Peptide Aggregation." Doctoral thesis, Universitat Internacional de Catalunya, 2012. http://hdl.handle.net/10803/78910.
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La malaltia d’Alzheimer es caracteritza per l’acumulació de plaques extracel.lulars amiloides, formades pels anomenats pèptids amiloides (Aβ40). L’homeòstasi del coure (Cu) es veu afectada en l’etiologia de la malaltia d’Alzheimer, encara que el seu rol és un fet controvertit.
Per a l’estudi de la influència del Cu(II) en l’agregació del pèptid amiloide, la morfologia i l’estructura secundària dels agregats amiloides formats en presència de Cu(II) s’han utilitzat AFM, TEM, SEM, SAXS, FTIR i espectrometria de fluorescència. A més, els efectes tòxics d’aquests agregats s’han estudiat en cèl.lules neuronals. Els resultats obtinguts mostren que aquests agregats són amorfos i presenten una toxicitat més alta que les fibres. Per a l’estudi dels dendrímers de maltosa com a possibles moduladors de l’agregació i de la toxicitat del pèptide amiloide. S’ha confirmat que aquests dendrimers no són tòxics en cèl.lules neuronals i que són capaços de modular l’agregació i toxicitat del pèptid amiloide. Aquests resultats permeten considerar als dendrimers de maltosa com a possibles eines per a reduir la toxicitat dels pèptids amilodies.Senile plaques of Alzheimer’s disease patients are composed primarily of the amyloid-β-peptide (Aβ). Recent studies implicate Cu(II) in the aetiology of AD. The role of Cu(II) in ADis currently highly disputed. Influence of Cu(II) on Aβ aggregation and amyloidogenic properties of glycodendrimers were investigated in this thesis. AFM, TEM, SEM, SAXS, FTIR and fluorescence spectroscopy were used to study a morphology and a secondary structure of Aβ-Cu(II) aggregates. The toxic effects of Aβ40-Cu(II) amorphous aggregates was confirmed for neuronal cell lines. It was shown that maltose glycodendrimers can be efficiently used to modulate Alzheimer’s amyloid peptide aggregation and inhibit cell toxicity by facilitating the clustering of amyloid fibrils. These results show that glycodendrimers are promising non-toxic agents in the search for anti-amyloidogenic compounds. It was also suggested that fibril clumping may be anti-amyloid toxicity strategy.
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Fuchs, Patrick. "Etudes bioinformatiques et biophysiques des coudes β dans les polypeptides. Applications aux protéines élastomériques élastine et abductine." Reims, 2001. http://www.theses.fr/2001REIMS010.
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Benhelli, Mokrani Houda. "Rôle du facteur YY1 et du remodelage de la chromatine dans la régulation de la transcription du gène de l'interféron β." Paris 6, 2008. http://www.theses.fr/2008PA066543.
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Constitutivement réprimé, le gène codant l’interféron est transitoirement activé après infection virale. Cette activation nécessite le recrutement coordonné de différents facteurs formant l’enhanceosome IFN . Le facteur YY1 qui se fixe au niveau des sites -90 et -122 de ce promoteur est capable de réguler de façon positive ou négative l’activité transcriptionnelle du gène ifn . Nous avons démontré que le rôle activateur de YY1 consistait au recrutement de la HAT CBP, essentiel à l’activation du promoteur IFN et qu’il nécessitait la fixation simultanée de YY1 sur les sites -90 et -122. Nous avons également mis en évidence une régulation de la fixation de YY1 sur son site -122 ainsi qu’une fixation différentielle de YY1 sur ses sites -90 et -122, qui semble réguler la capacité de YY1 d’agir en activateur ou répresseur transcriptionnel du gène ifn . La capacité du promoteur IFN à être activé par un traitement à la TSA (une drogue inhibant spécifiquement les HDACs) a permis une nouvelle approche dans l’étude des mécanismes nécessaires à la levée de la répression constitutive du promoteur IFN . D’après les résultats obtenus, nous proposons un modèle de régulation de l’expression du gène ifn , incluant un rôle de la localisation subnucléaire du locus ifn vis-à-vis de l’hétérochromatine péricentromérique et discutons l’éventuel rôle des modifications post traductionnnelles des histones dans la cinétique de l’activation du promoteur IFN par la TSA ou l’infection viraleVirus-induced activation of the constitutively repressed interferon gene necessitates the orderly recruitment of transcriptional factors allowing IFN enhanceosome formation. Transcription factor YY1 binds the IFN promoter at position -90 and -122 playing a dual activator/repressor role. We demonstrate here that simultaneous binding of YY1 to positions -90 and -122 is necessary to allow CBP recruitment and K8H4/K14H3 acetylation at the IFN- promoter region, both these events being essential for promoter transcriptional activation. Our results also show that whereas binding of YY1 to its –90 site occurs before as well as after virus infection, YY1 binding to position -122 is regulated during viral infection so that it predominantly occurs after viral infection. We suggest that the dual role of YY1 is related to the degree of occupancy of its –90 and –122 sites. IFN promoter has also been shown to be activated by TSA treatment (a drug that specifically inhibit the HDACs). We show here that TSA-induced promoter activation is mainly correlated with HP1 subnuclear redistribution and pericentromeric heterochromatin clusters rearrangements. We discuss here the role of histone methylation and constitutive heterochromatin during the establishment of the promoter silent state and the necessity to counteract the repressive effect of heterochromatin in order to allow promoter activation
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Vázquez, Bigas Guillem. "Oligopeptides as highly versatile agents against copper-mediated oxidative stress and amyloid-β aggregation." Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/666586.
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Alzheimer’s disease (AD), for which no cure is known yet, is currently the most prevalent cause of dementia for the elderly population. The aberrant aggregation of β-amyloid peptide (Aβ) is believed to trigger the events leading to the pathology, yet such processes are not fully understood. Although Aβ fibres represent the major components of the senile plaques found in AD brains, oligomeric aggregates are currently considered the most toxic species.
Aβ has been found to bind Cu(I/II) ions (which are imbalanced in AD), modulating its aggregation. Copper has been reported to stabilise toxic oligomeric species and to catalyse the generation of ROS. Hence, preventing the copper-associated toxicity of Aβ may represent a promising approach to develop anti-AD agents.
Histidinic peptides represent valuable synthons for the discovery of new, highly biocompatible drugs aimed at reducing the copper-associated toxicity of Aβ. In the present PhD thesis, short peptides containing the efficient Cu(II)-binding His-Xaa- His motif (Xaa = randomly-chosen amino acid) were rationally designed to be applied in i) the chelation and detection of copper ions, ii) their grafting onto gold nanocarriers and iii) the detection of Aβ aggregates. Chapter 1 comprises a detailed introduction on the state-of-the-art in the field and the description of the objectives of the present work.
In Chapter 2, the Fmoc solid-phase synthesis of fluorescent Cu(II)-chelating peptides is described. The chelating agents contained a tryptophan residue, or emissive probes for their application as fluorescent sensors.
In Chapter 3, the evaluation of the Cu(II)-binding properties and the Cu(II)-binding affinities of the His-Xaa-His tripeptides is reported. N-terminal free peptides presented a 4N albumin-like (ATCUN) coordination donor set, and were able to remove Cu(II) ions bound to Aβ(1-16), and to inhibit the copper-induced stabilisation of oligomeric Aβ species and the generation of ROS. N-terminal protected peptides acted as a different donor set involving the two imidazole rings, and were less effective regarding their inhibition of the Cu-induced production of ROS.
In Chapter 4, the generation of Aβ(1-40) dityrosine cross-links in the presence of copper(II) and H2O2 is described. Dityrosine-bridged Aβ dimers have been proposed as initiators of Aβ aggregation in AD brains, where they are believed to display a
prolonged Cu-induced redox activity. Dityrosine-cross-linked Aβ(1-40) did not lead to the formation of fibres; the addition of an ATCUN peptide restored the fibrillation process.
Chapter 5 explains the preparation of spherical gold nanoparticles functionalised with carboxyl-terminated PEG chains and a fluorescently-labelled Cu(II)-chelating peptide Ac-His-Xaa-His-Lys-NH2. The peptide-functionalised nanoparticles were able to (partially) extract Cu(II) ions bound to Aβ(1-16). Besides, they presented no toxicity towards neuronal embryo cells of wildtype mice.
In Chapter 6, the design and preparation of fluorescent dyes to detect aggregated Aβ are reported. An analogue of the amyloid-selective fluorescent dye thioflavin T and its lysine derivative were prepared by click chemistry. Unfortunately, spectroscopic changes did not take place upon interaction with fibrillary Aβ. The environment-sensitive properties of a naphthalimide probe were then exploited for the detection of different types of Aβ aggregates. This probe and its His-Xaa-His peptides acted as bimodal probes in the presence of different types of Aβ aggregates, also in the presence of Cu(II) and Zn(II) ions.
The promising results achieved during this doctoral research validate the proposed approach to use fluorescent His-containing Cu(II)-chelating peptides to reduce the copper-associated toxicity of Aβ and to detect Cu(II) ions and Aβ aggregates. Such peptides may hence find applications in therapy, diagnosis, and theranosis of AD.Es creu que l’agregació aberrant del pèptid β-amiloide (Aβ) origina l’aparició de l’Alzheimer, actualment la causa més freqüent de demència en la gent gran i per a la qual no es coneix cura. S’ha trobat que el coure (que es troba en nivells alterats al cervell dels malalts d’Alzheimer) estabilitza els oligòmers d’Aβ, considerats les espècies més tòxiques, i que catalitza la producció d’espècies oxidants. En aquesta tesi doctoral, pèptids curts amb la seqüència His-Xaa-His (Xaa = qualsevol aminoàcid excepte His i Pro) han sigut dissenyats racionalment per a la quelació i detecció d’ions Cu(II), la connexió a nanotransportadors d’or i la detecció d’agregats d’Aβ. El Capítol 1 conté una detallada introducció amb la informació més actualitzada sobre el camp i la descripció dels objectius d’aquest treball. Al Capítol 2 es descriu la preparació en fase sòlida de pèptids quelants que contenen diferents sondes fluorescents mitjançant química Fmoc. Al Capítol 3 es presenten les propietats quelants i l’afinitat dels tripèptids His-Xaa- His envers els ions Cu(II). Al Capítol 4 es descriu la generació de ponts de ditirosina en Aβ(1-40) en presència de coure(II) i H2O2, i la inhibició d’aquesta amb un dels pèptids quelants. Al Capítol 5 es presenta la preparació de nanopartícules esfèriques d’or funcionalitzades amb un pèptid quelant, la seva caracterització, l’estudi de l’extracció dels ions Cu(II) units a l’Aβ i l’avaluació de la seva toxicitat amb i sense el pèptid en cèl·lules neuronals de ratolins. Al Capítol 6 s’explica la utilització d’un anàleg del pigment selectiu a amiloide tioflavina T, així com d’una sonda sensible a l’entorn de tipus naftalimida, per detectar agregats d’Aβ. Els prometedors resultats obtinguts en aquesta tesi doctoral validen l’estratègia proposada d’emprar pèptids fluorescents quelants d‘ions Cu(II) per reduir la toxicitat de l’Aβ associada al coure i per a la detecció d’aquest ió i dels agregats d’Aβ.
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Migliore, Mattia. "Recherche par modélisaion moléculaire de signatures RMN et DC caractéristiques pour les coudes β et y dans les peptides bioactifs. Characterization of β-turns by electronic circular dichroism spectroscopy : a coupled molecular dynamics and time-dependent density functional theory computational study." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMR001.
Full textAbstract:
Ce travail de thèse a porté sur la recherche, par modélisation moléculaire, de signatures RMN et DC caractéristiques pour les coudes γ et β dans les peptides bioactifs. Les coudes γ et β, avec les hélices, constituent des motifs privilégiés de reconnaissance des peptides bioactifs par leurs cibles. Or, bien qu’il existe, au sein des structures de polypeptides, plusieurs catégories de coudes possédant des géométries différentes (2 types de coudes γ et 12 types de coudes β), peu d’outils expérimentaux sont disponibles pour aider à leur distinction. Ainsi, seuls 4 types de coudes β (I, I’, II et II’) ont, pour l’instant été caractérisés par RMN et il n’existe pas de spectre DC de référence fiable pour aucun motif de type coude. Dans un premier temps, afin d’élargir la base de données de RMN pour tous les types de coudes β (I, I’, II, II’, IV₁, IV₂, IV₃, IV₄, Via1, Via2, VIb et VIII) et γ (classique et inverse), nous avons analysé les paramètres structuraux caractéristiques de RMN (distances inter-hydrogènes et constantes de couplages ᶾJʜɴ-ʜꭤ) sur un ensemble de peptides modèles, extraits de la banque de protéines PDB et représentatifs de ces coudes. Les analyses des distances inter-hydrogènes ont permis d’identifier des signatures RMN caractéristiques pour différencier les deux types de coudes γ et certains types de coudes β (IV₁, IV₂,, VIb et VIII). La constante de couplage ᶾJʜɴ-ʜꭤ pourra servir à confirmer l’identification et à lever des ambiguïtés. Dans un second temps, en couplant dynamique moléculaire et TDDFT, nous avons simulé les spectres de DC de référence de peptides modèles adoptant des conformations de coudes β de type I, I’, II et II’. Les simulations ont permis de discerner deux familles de spectres DC caractéristiques : les types I/II’ d’un côté et les types I’/II de l’autre. L’ensemble de ces résultats indique que les coudes ne présentent pas nécessairement les mêmes signatures pour les deux techniques. La combinaison des signatures discriminantes de RMN et de DC pourrait donc permettre une meilleure identification des natures et des différents types de coudesThe aim of this work is to identify NMR and CD characteristic patterns for β- and γ-turns in bioactive peptides by molecular modelling. With helices, β- and γ-turns constitute favoured recognition motifs in bioactive peptides by their targets. Even though several classes of turns with different geometries exist in polypeptide structures (2 γ-turn types and 12 β-turn types), few experimental tools are available for their characterization. Thus, only 4 types of β-turns (I, I’, II et II’) have been, at present, described by NMR and there are no reliable reference CD spectra for turns. In order to extend the NMR data for all β- and γ-turn types, we analyzed NMR structural parameters (inter-hydrogen distances and ᶾJʜɴ-ʜꭤ coupling constants) in a representative peptide model dataset extracted from the PDB. The inter-hydrogen distance analysis allowed to identify specific NMR patterns for the two γ-turn types and for four β-turn types (IV₁, IV₂,, VIb and VIII). ᶾJʜɴ-ʜꭤ coupling constant may be used to confirm the identification and to remove ambiguities. Then, we simulated the reference CD spectra of model peptides adopting type I, I’, II and II’ β-turn conformations by combining molecular dynamic simulations and TDDFT computations. These computations allowed to determine two families of specific CD spectra : types I/II’, on one side and types I’/II, on the other. All these results indicate that the turns do not present the same patterns in both techniques. The combination of NMR and CD could therefore allow a better identification of the nature and the different types of turns
Book chapters on the topic "Coude β"
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Murase, Yuito, Yuichi Nishiwaki, and Atsushi Igarashi. "Contextual Modal Type Theory with Polymorphic Contexts." In Programming Languages and Systems, 281–308. Cham: Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-30044-8_11.
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AbstractModal types—types that are derived from proof systems of modal logic—have been studied as theoretical foundations of metaprogramming, where program code is manipulated as first-class values. In modal type systems, modality corresponds to a type constructor for code types and controls free variables and their types in code values. Nanevski et al. have proposed contextual modal type theory, which has modal types with fine-grained information on free variables: modal types are explicitly indexed by contexts—the types of all free variables in code values.This paper presents $$\lambda _{\forall []}$$ λ ∀ [ ] , a novel extension of contextual modal type theory with parametric polymorphism over contexts. Such an extension has been studied in the literature but, unlike earlier proposals, $$\lambda _{\forall []}$$ λ ∀ [ ] is more general in that it allows multiple occurrence of context variables in a single context. We formalize $$\lambda _{\forall []}$$ λ ∀ [ ] with its type system and operational semantics given by $$\beta $$ β -reduction and prove its basic properties including subject reduction, strong normalization, and confluence. Moreover, to demonstrate the expressive power of polymorphic contexts, we show a type-preserving embedding from a two-level fragment of Davies’ $$\lambda _{\bigcirc }$$ λ ◯ , which is based on linear-time temporal logic, to $$\lambda _{\forall []}$$ λ ∀ [ ] .
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Zhang, Chengtao, and Shuang Zhao. "Wind-Induced Vibration Coefficient of Landscape Tower with Curved and Twisted Columns and Spiral Beams Based on Wind Tunnel Test Data." In Advances in Transdisciplinary Engineering. IOS Press, 2022. http://dx.doi.org/10.3233/atde220890.
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Wind-induced vibration coefficient β is an essential parameter for the structural wind-resistant design. In order to provide accurate design wind loads, β of a landscape tower with curved and twisted columns and spiral beams (short for LT) is studied by wind tunnel test and numerical simulation. The results show that the displacement wind-induced vibration coefficient is greatly affected by wind yaw angle. Moreover, the inertial load wind-induced vibration coefficients increase along the height and increase sharply at the platform position. Due to the influence of nonuniform shape and mass distribution and wind yaw angle, β calculated by the Chinese and American load code does not apply to LT structures. In addition, this article puts forward some suggestions for the shortcoming in the use of code to calculate β of LTs and made some prospects for future research on wind-resistant design of LTs, hoping to provide theoretical guidance and thinking inspiration for future research.
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"New Concept of the Genetic Code (in the Space of Higher Dimension)." In Biochemistry in the Space of the Highest Dimension, 182–93. IGI Global, 2024. http://dx.doi.org/10.4018/979-8-3693-0588-1.ch009.
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Spatial models of the β - structures of protein molecules, forming layers of amino acids, in principle, of unlimited length for different conformations have been constructed. It is shown that the simplified flat Pauling models do not reflect the spatial structure of these layers. Using the recently developed theory of higher - dimensional polytopic prismahedrons, models of the volumetric filling of space with amino acid molecules are constructed. The constructed models for the first time mathematically describe the native structures of globular proteins. A model that simultaneously contains β - structures in parallel and anti - parallel positions and α - spirals. The turn of the polypeptide chain, which is often found in globular proteins, has been studied in higher dimensional space.
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Ilango, Sindana D., Kevin Gonzalez, Linda Gallo, Matthew A. Allison, Jianwen Cai, Carmen R. Isasi, H. Dean Hosgood, et al. "Long-Term Exposure to Ambient Air Pollution and Cognitive Function Among Hispanic/Latino Adults in San Diego, California." In Advances in Alzheimer’s Disease. IOS Press, 2021. http://dx.doi.org/10.3233/aiad210025.
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Background: Hispanics/Latinos in the United States are more likely to live in neighborhoods with greater exposure to air pollution and are projected to have the largest increase in dementia among race/ethnic minority groups. Objective: We examined the associations of air pollution with performance on cognitive function tests in Hispanic/Latino adults. Methods: We used data from the San Diego site of the Hispanic Community Health Study/Study of Latinos, an ongoing cohort of Hispanics/Latinos. This analysis focused on individuals ≥45 years of age who completed a neurocognitive battery examining overall mental status, verbal learning, memory, verbal fluency, and executive function (n = 2,089). Air pollution (PM2.5 and O3) before study baseline was assigned to participants’ zip code. Logistic and linear regression were used to estimate the associations of air pollution on overall mental status and domain-specific standardized test scores. Models accounted for complex survey design, demographic, and socioeconomic characteristics. Results: We found that for every 10 μg/m3 increase in PM2.5, verbal fluency worsened (β: −0.21 [95% CI: −0.68, 0.25]). For every 10 ppb increase in O3, verbal fluency and executive function worsened (β: −0.19 [95% CI: −0.34, −0.03]; β: −0.01 [95% CI: −0.01, 0.09], respectively). We did not identify any detrimental effect of pollutants on other domains. Conclusion: Although we found suggestions that air pollution may impact verbal fluency and executive function, we observed no consistent or precise evidence to suggest an adverse impact of air pollution on cognitive level among this cohort of Hispanic/Latino adults.
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Rachida, Barkallah, Rym Taktak, Noamen Guermazi, Fahmi Zaïri, and Jamel Bouaziz. "Combination of Numerical, Experimental and Digital Image Correlation for Mechanical Characterization of Al2O3/β-TCP Based on CDM Criterion." In Advances in Fatigue and Fracture Testing and Modelling. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.99357.
Full textAbstract:
Cracks in engineering materials and structures can undergo different modes of deformation. This chapter presents a numerical and experimental approaches aimed to assess the fracture toughness and the Fracture behavior under tensile and shear loading of bioceramics based on commercial Alumina (Al2O3), synthesized Tricalcium phosphate (β-TCP). Conditioning was conducted at different percentages of TCP. After a sintering process at 1600°C for 1 hour, The Crack Straight Through Brazilian Disc were performed by image correlation during a mechanical test and numerical tests were carried out in order to find the angle where the pure mode II. A CDM based constitutive model was selected and implemented into a finite element code to study the damage of our bioceramics. The result of this combination was compared with the direction of crack propagation obtained experimentally. The directions of crack propagation found numerically were found in good agreement with those experimentally obtained by a mechanical test. Alumina-10 wt.% Tricalcium phosphate composites displayed the highest values of the fracture toughness. This value reached 8.76 MPa m1/2 MPa. The same optimal composition for the mode I and mode II stress intensity factor with maximum values of 7.6 MPa m1/2 and 8.45 MPa m1/2 respectively.
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David, Serge. "ABH and related blood group antigens." In The Molecular and Supramolecular Chemistry of Carbohydrates: Chemical Introduction to the Glycosciences, 265–76. Oxford University PressOxford, 1997. http://dx.doi.org/10.1093/oso/9780198500476.003.0016.
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Abstract Antigenic determinants are trisaccharide A, 16.1, trisaccharide B, 16.2, and disaccharide H, 16.3. The reader will recognize that trisaccharides A and B are glycosidation products of disaccharide H at position 3 of galactose by an N-acetylgalactosamine unit and a galactose unit, respectively, and in the two cases by an a-anomeric linkage. Thus the A and B determinants differ only by their substitution at position 2 on their D-galacto non-reducing terminal end, N-acetyl in the A substance, and hydroxyl in the B substance. Note as well the participation of the deoxygenated sugar fucose and finally the α-1,2-cis bonds, not as common as the β-1,2-trans bonds in glycoconjugates. These disaccharides and trisaccharides are located at the non-reducing terminal ends of the oligosaccharide chains of glycoproteins and glycolipids and possibly their branches. Blood group A individuals have the A determinant and a certain quantity of H, but not B, whereas those of blood group B have B and H but not A, in a symmetrical fashion. Blood group O individuals only have the H determinant. This immediately implies an incomplete biosynthesis due to the absence or the non-expression of genes which code for the A or B glycosyltransferases. Carrier molecules are found in the membrane of erythrocytes and determinants are exposed towards the outside. In blood group A individuals, the B molecule is recognized as a foreign substance and gives rise to the appearance of anti-B antibodies. For the same reason, anti-A antibodies are found in people with blood group B and and anti-A and anti-B antibodies in those with blood group 0. Problems observed during blood transfusions were due to the presence of these antibodies. Thus the donor of blood group A who has anti-B antibodies causes the agglutination of erythrocytes in a receiver of blood group B. ABH antigens are also present on cell surfaces in the majority of organs and in secretions. Their presence is one of the major causes of the failure of organ transplants between a donor and receiver of different blood groups. For this reason, they should also be named histo-blood group antigens.
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"3 Power and sample size for ABE in the 2× 2 design Here we give formulae for the calculation of the power of the TOST procedure assuming that there are in total n subjects in the 2× 2 trial. Suppose that the null hypotheses given below are to be tested using a 100(1 − α)% two-sided confidence interval and a power of (1 − β) is required to reject these hypotheses when they are false. H :µ ≤− ln 1.25 H :µ ≥ ln 1.25. Let us define x to be a random variable that has a noncentral t-distribution with df degrees of freedom and noncentrality parameter nc, i.e., x ∼ t(df,nc). The cumulative distribution function of x is defined as CDF(t,df,nc) = Pr(x≤ t). Assume that the power is to be calculated using log(AUC). If σ is the common within-subject variance for T and R for log(AUC), and n/2 subjects are allocated to each of the sequences RT and TR, then 1−β = CDF(t , df,nc )−CDF(t , df,nc ) (7.1) where √ n(log(µ )− log(0.8)) nc = 2σ √ n(log(µ )− log(1.25)) nc = 2σ √ (n− 2)(nc −nc = ) df 2t and t is the 100(1 − α)% point of the central t-distribution on n− 2 degrees of freedom. Some SAS code to calculate the power for an ABE 2 × 2 trial is given below, where the required input variables are α, σ value of the ratio µ and n, the total number of subjects in the trial." In Design and Analysis of Cross-Over Trials, 361. Chapman and Hall/CRC, 2003. http://dx.doi.org/10.1201/9781420036091-16.
Full textConference papers on the topic "Coude β"
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Zheng, Lei, Kaiwen Li, and Kan Wang. "On-the-Fly Treatment of Discrete Representation Thermal Neutron Scattering Data in RMC Code." In 2020 International Conference on Nuclear Engineering collocated with the ASME 2020 Power Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/icone2020-16066.
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Abstract A proper treatment of thermal neutron scattering data is required for the high-fidelity neutronics calculation of thermal reactors. Monte Carlo codes typically use an S(α, β) treatment to describe scattering events in the thermal region if the S(α, β) data is available for the material. The S(α,β) model stores a large majority of scattering physics and can handle thermal scattering process accurately. In neutronic-thermohydraulic coupling calculations, the temperature effect on nuclear data must be treated properly. The on-the-fly sampling method or the on-the-fly interpolation method are typically used in thermal region. In this paper, the on-the-fly interpolation method for the discrete representation S(α,β) data was introduced. The two-dimensional linear-linear interpolation was used to calculate the scattering cross sections and the secondary information for inelastic scattering, coherent elastic scattering and incoherent elastic scattering. The implemented on-the-fly capability was tested by a series of benchmarks that contain various thermal materials, including light water, beryllium and beryllium oxide. The integral kinf eigenvalues, the efficiency and the fine energy spectra of the on-the-fly treatment capacity were compared with those of the references. Results show that the on-the-fly treatment capability has high accuracy, and the computational time increases up to 20%.
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Shen, Xinwei, and Shuting Lei. "Cutting Simulation of Laser Assisted Milling of Silicon Nitride Ceramics Using PFC2D." In ASME 2009 International Manufacturing Science and Engineering Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/msec2009-84041.
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Since laser assisted milling (LAMill) exhibits complicated characteristics in ceramic machining, this paper applies a distinct-element code, PFC2D (Particle Flow Code in Two-Dimensions), to conduct cutting simulation of laser assisted slab milling and explore its machining mechanism. The microstructure of a β-type silicon nitride ceramic (β-Si3N4) is modeled at grain scale. Clusters are used to simulate the rod-like grains of β-Si3N4. Parallel bonds are employed to represent the connection between intergranular glass phase and grains. A temperature-dependent PFC specimen is created for simulation of LAMill. A special milling cutter is designed for improving the computing efficiency. Simulation results show that the cutting force is strongly related to crack formation and propagation. The specific cutting energy decreases as the cutting temperature increases.
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Kwok, H. S., M. Sheik-Bahae, and T. Rossi. "Tunneling-induced two-photon absorption in InSb." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1987. http://dx.doi.org/10.1364/oam.1987.wi7.
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There has been considerable interests in InSb as a nonlinear medium for the CO2 laser due to its large nonlinearity. Optical bistability and optical switching are among some of the recent applications. The two-photon absorption of InSb has been studied extensively in the past. However, no conclusive experimental value has been established. We report here an accurate measurement of the two-photon absorption coefficient β making use of the self-defocusing effect.1 The defocusing process is the direct result of self-phase modulation and plasma-induced refractive-index change. The self-defocusing experiment was performed at two CO2 laser wavelengths of 10.6 and 9.6 μm. From the experimental data, the value of β can be calculated using a beam propagation computer code. It is in strong disagreement with a previous measurement.2 The frequency dependence of β is consistent with a tunneling process and is not consistent with a perturbation calculation either with or without the nonparabolic band approximation.
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Dier, Adrian F., Philip Smedley, Gunnar Solland, and Hege Bang. "New Data on the Capacity of X-Joints Under Tension and Implications for Codes." In ASME 2008 27th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/omae2008-57650.
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This paper reviews available static strength data and presents results of finite element analyses on first crack loads and ultimate loads of X-joints in tension. A critique of existing guidance for such joints is given. An examination of hot spot stress for such joints is presented, together with new capacity formulations based on test data. The new formulations are verified with reference to new data from a finite element analysis. The new capacity formulations will be of interest to regulatory authorities, to designers of new offshore installations and to engineers carrying out assessments of existing structures. It is also expected that the formulations will be considered by code drafting committees, e.g. for API RP2A, ISO 19902 and NORSOK, during code revisions. The paper demonstrates that present guidance is unduly conservative in two respects: (1) high γ joints (i.e. thin-walled chords) in the range 0.7 ≤ β ≤ 0.9 joints (i.e. moderately high brace/chord diameter ratios), and (2) joints with β = 1.0 having low γ. However, it is shown that present guidance may be optimistic for low γ joints with β < 0.9. The new capacity formulations proposed in this paper correct these deficiencies. As one example, the new formulations give an increase of 60% in capacity compared to existing guidance for a joint with β = 1.0 and γ = 10, not untypical of many joints in service. In the near term, the paper may be most appreciated by those involved with structural integrity assessment studies. There have been some recent examples where existing guidance has indicated that some primary structural joints are under-strength. This has prompted extensive numerical work to prove the adequacy of the joints. A worst case scenario would be the implementation of unnecessary offshore strengthening work.
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Abd Alsalam, Sana, and Bassam Jubran. "Film Cooling of Compound Angle Upstream Sister Holes." In ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-90518.
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Abstract This study introduces a novel and simple strategy; compound angle upstream sister holes (CAUSH) to increase film cooling performance of the cylindrical hole by combining two techniques: Sister holes; (two small round holes placed upstream the primary hole) and compound angle hole. Whereas the upstream sister holes were injected at several compound angles β = 0°, 45°, 75°, and 90°, while the main hole was injected to the streamwise direction at 35° on a flat plate. FLUENT-ANSYS code was used to perform the simulation by solving the 3D Reynolds Averaged Navier-Stokes Equations. The capability of three types of k-ε turbulence modeling combined with the enhanced wall treatment is investigated to predict the film cooling performance of sister holes. A detailed computational analysis of the cooling performance of the (CAUSH) and the flow field was done at a density ratio equal to two (D.R = 2) and four blowing ratios M = 0.25, 0.5, 1.0 and 1.5 to predict the centerline and laterally averaged film cooling performance. The centerline effectiveness results showed that the highest cooling performance from the examined (CAUSH) was obtained at β = 0°, 45°, and 90° for low and high blowing ratio, the highest laterally averaged film cooling performance was captured at β = 0° and 90° for all tested blowing ratios. Also, the results indicated that the upstream sister hole with 90° compound angle holes has the best overall film cooling effectiveness while the worst performance is attained at β = 75°.
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Chan, K. S., and M. P. Enright. "A Probabilistic Micromechanical Code for Predicting Fatigue Life Variability: Model Development and Application." In ASME Turbo Expo 2005: Power for Land, Sea, and Air. ASMEDC, 2005. http://dx.doi.org/10.1115/gt2005-68983.
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This paper summarizes the development of a probabilistic micromechanical code for treating fatigue life variability resulting from material variations. Dubbed MicroFaVa (Micromechanical Fatigue Variability), the code is based on a set of physics-based fatigue models that predict fatigue crack initiation life, fatigue crack growth life, fatigue limit, fatigue crack growth threshold, crack size at initiation, and fracture toughness. Using microstructure information as material input, the code is capable of predicting the average behavior and the confidence limits of the crack initiation and crack growth lives of structural alloys under LCF or HCF loading. This paper presents a summary of the development of the code and highlights applications of the model to predicting the effects of microstructure on the fatigue crack growth response and life variability of the α + β Ti-alloy Ti-6Al-4V.
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Desclaux, Cécilia, Valéry Lacroix, and Kunio Hasegawa. "Improvement and Assessment of the Plastic Collapse Bending Moment Equations in Circumferentially Cracked Pipe." In ASME 2021 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/pvp2021-61989.
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Abstract The plastic collapse bending moment in a pipe cross-section with a circumferential crack is defined in ASME B&PV Code Section XI, Appendix C using simplified equilibrium equations by approximating the pipe mean radius Rm and the neutral axis angle β. In previous papers it was demonstrated by the authors that, for externally cracked pipes, those simplified equilibrium equations are not conservative and hence improved equations were developed and proposed which account for the cracked pipe ligament mean radius Rmc. In this paper, it is demonstrated that the accuracy of the collapse bending moment equation can be refined by taking into account the neutral axis position Yna of the cracked pipe section. This leads to exact collapse bending moment equations without any approximation on the pipe mean radius Rm nor on the neutral axis angle β. In this framework, it is shown that, for externally cracked pipes, the Appendix C equations could lead to more than 20% less conservative collapse bending moment than with the exact equations. An extended finite element method analysis completes this study to assess the relevance of the model used to determine the plastic collapse bending moment.
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Timite, Brahim, Cathy Castelain, and Hassan Peerhossaini. "Pulsating Flow for Mixing Intensification in a Twisted Curved Pipe." In ASME/JSME 2007 5th Joint Fluids Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/fedsm2007-37065.
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This work concerns the manipulation of a twisted curved pipe flow for mixing enhancement. Previous work [1,2,3] has shown that geometrical perturbations to a curved pipe flow can increase mixing and heat transfer by chaotic advection. In this work the flow entering the twisted pipe undergoes a pulsatile motion. The flow was studied experimentally and numerically. The numerical study is carried out by CFD code (Fluent 6) in which a pulsated velocity field is imposed as an inlet condition. The experimental setup involves principally a “Scotch-yoke” pulsatile generator and a twisted curved pipe. Laser Doppler velocimetry (LDV) measurements have shown that the Scotch-yoke generator produces pure sinusoidal instantaneous mean velocities with a mean deviation of 3%. Visualizations by laser-induced fluorescence (LIF) and velocity measurements, coupled with the numerical results, have permitted analysis of the evolution of the swirling secondary flow structures that develop along the bends during the pulsation phase. These measurements were made for a range of steady Reynolds number (300 ≤ Rest ≤ 1200), frequency parameter (1 ≤ α = r0.(ω/υ)1/2 < 20), and two velocity components ratios (β = Umax,osc/Ust). We observe satisfactory agreement between the numerical and experimental results. For high β, the secondary flow structure is modified by a Lyne instability and a siphon effect during the deceleration phase. The intensity of the secondary flow decreases as the parameter α increases during the acceleration phase. During the deceleration phase, under the effect of reverse flow, the secondary flow intensity increases with the appearance of Lyne flow. Experimental results also show that pulsating flow through a twisted curved pipe increases mixing over the steady twisted curved pipe. This mixing enhancement increases with β.
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Kamio, Takeshi, Makoto Iida, and Chuichi Arakawa. "Numerical Simulation and Optimization of a Wave Energy Converter for the Izu Islands Sea in Japan." In ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/omae2014-23544.
Full textAbstract:
The purpose of this study is the numerical simulation and control optimization of a wave energy converter to estimate the power at a test site in the Izu Islands. In Japan, ocean energy is once again being seriously considered; however, since there are many inherent problems due to severe conditions such as the strong swells and large waves, estimations are important when designing such devices. The numerical simulation method in this study combines the wave interaction analysis software WAMIT and an in-house time-domain simulation code using the Newmark-β method, and introduces approximate complex-conjugate control into the code. The optimized parameters were assessed for a regular sine wave and an irregular wave with a typical wave spectrum. With the optimized parameters, average and maximum output power were estimated for the observed wave data at the test site. The results show a more than 100 kW average power output and a several times larger maximum power output.
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Marie, S., and M. Ne´de´lec. "A New Plastic Correction β for Underclad Defect in a Vessel Submitted to a Pressurised Thermal Shock." In ASME 2006 Pressure Vessels and Piping/ICPVT-11 Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/pvp2006-icpvt-11-93680.
Full textAbstract:
In the frame of the Reactor Pressured Vessel integrity demonstration, a defect assessment has to be performed considering a Pressurized Thermal Shock. Several approaches are proposed in different reference codes and standards. Usually, the analyses are based on analytical methods. An important effort has been made recently by CEA to improve these tools in the frame of R&D activities funded by IRSN. For the assessment of an underclad defect in a vessel submitted to a pressurized thermal shock, the plasticity induced by cladding yielding is considered through the amplification β of the elastic stress intensity factor KI in the ferritic part of the vessel. The current solution in the French RSE-M code has been developed from a fitting of F.E. calculation results. A more physical solution is proposed in this paper. It takes into account two phenomena: the amplification of the elastic KI due to the plasticity in the cladding and a plastic zone correction in the ferritic part. The first amplification is determined assuming that the plasticity in the cladding could be represented as an imposed opening displacement on the crack lips.