726 resultados para Substitutions
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No presente trabalho propõe-se estudar a tensão superficial de vários perfluorocarbonetos lineares, cíclicos, aromáticos e [alfa]-substituídos bem como líquidos iónicos com o catião imidazolium em comum. Apesar do seu interesse inerente, informação sobre esta propriedade para os compostos seleccionados é escassa e quando disponível apresenta discrepâncias consideráveis entre si. As medições foram realizadas no intervalo de temperaturas (283 to 353) K usando o método do anel de Du Noüy. Para os fluorocarbonetos, os dados experimentais demonstram que a estrutura molecular é o factor primordial no comportamento da superfície uma vez que os fluorocarbonetos aromáticos apresentam a tensão superficial mais elevada, seguida pelos fluorocarbonetos cíclicos e substituídos. Os perfluorocarbonetos lineares apresentam os menores valores de tensão superficial, aumentando ligeiramente com o aumento do número de carbonos. Os líquidos iónicos estudados foram seleccionados com o objectivo de fornecerem um estudo compreensivo sobre a influência do tamanho da cadeia alquílica do catião, o número de substituições no catião e a influência do anião. A influência do conteúdo de água na tensão superficial foi estudada em função da temperatura e da fracção molar de água para o liquido iónico mais hidrofóbico, [omim][PF6], e para o mais higroscópico, [bmim][PF6]. As funções termodinâmicas de superfície, como a entropia e entalpia de superfície, foram derivadas a partir da dependência da tensão superficial com a temperatura. Os dados obtidos para o fluorocarbonetos foram comparados com a correlação proposta por Faizullin, apresentando um desvio inferior a 4 % e demonstrando a sua aplicabilidade para com esta classe de compostos. A metodologia adoptada neste trabalho requer o conhecimento das densidades dos compostos de modo a aplicar a necessária correcção hidrostática. Contudo, para os líquidos iónicos esta informação é limitada ou mesmo inexistente. Por este motivo realizaram-se medições de densidade em função da pressão (0.10 < p/MPa < 10.0) e da temperatura (293.15 < T/K < 393.15). Desta dependência, as propriedades termodinâmicas, tais como compressibilidade isotérmica, expansividade isobárica, coeficiente térmico da pressão e dependência da capacidade calorífica com a pressão foram investigadas. A influência do teor de água na densidade foi também estudada para o líquido iónico mais hidrofóbico, [omim][PF6]. Um modelo simples de volume-ideal foi aplicado de forma preditiva para os volumes molares dos líquidos iónicos, em condições ambientais, descrevendo bem os dados experimentais. ABSTRACT: This work aims at studying the surface tension of some linear, cyclic, aromatic, [alfa]-substituted perfluorocarbons and imidazolium based ionic liquids. Despite its fundamental interest, information about this property for these compounds is scarce and the available data present strong discrepancies among each other. The measurements were carried out in the temperature range (283 to 353) K with the Du Noüy ring method. For the fluorocarbons, the analysis of the experimental data shows that the molecular structure is the main factor in the surface since the aromatic fluorocompounds present the highest surface tensions, followed by the cyclic and substituted fluorocompounds. The linear n-perfluoroalkanes exhibit the lowest surface tension values, slightly increasing with the carbon number. The set of selected ionic liquids was chosen to provide a comprehensive study of the influence of the cation alkyl chain length, the number of cation substitutions and the anion on the properties under study. The influence of water content in the surface tension was studied for several ILs as a function of the temperature as well as a function of water mole fraction, for the most hydrophobic IL investigated, [omim][PF6], and one hygroscopic IL, [bmim][PF6]. The surface thermodynamic functions such as surface entropy and enthalpy were derived from the temperature dependence of the surface tension values. The perfluorocarbons experimental data were compared against the Faizullin correlation, and it is shown that this correlation describes the measured surface tensions with deviations inferior to 4 %. The methodology adopted in this work requires the knowledge of the densities of the compounds under study in order to apply an hydrostatic correction. However, for ionic liquids these information is scarse and in some cases unavailable. Therefore, experimental measurements of the pressure (0.10 < p/MPa < 10.0) and temperature (293.15 < T/K < 393.15) dependence of the density and derived thermodynamic properties, such as the isothermal compressibility, the isobaric expansivity, the thermal pressure coefficient, and the pressure dependence of the heat capacity of several imidazolium-based ionic were determined. The influence of water content in the density was also studied for the most hydrophobic IL used, [omim][PF6]. A simple ideal-volume model was employed for the prediction of the imidazolium molar volumes at ambient conditions, which proved to agree well with the experimental results.
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The planar design of solid oxide fuel cell (SOFC) is the most promising one due to its easier fabrication, improved performance and relatively high power density. In planar SOFCs and other solid-electrolyte devices, gas-tight seals must be formed along the edges of each cell and between the stack and gas manifolds. Glass and glass-ceramic (GC), in particular alkaline-earth alumino silicate based glasses and GCs, are becoming the most promising materials for gas-tight sealing applications in SOFCs. Besides the development of new glass-based materials, new additional concepts are required to overcome the challenges being faced by the currently existing sealant technology. The present work deals with the development of glasses- and GCs-based materials to be used as a sealants for SOFCs and other electrochemical functional applications. In this pursuit, various glasses and GCs in the field of diopside crystalline materials have been synthesized and characterized by a wide array of techniques. All the glasses were prepared by melt-quenching technique while GCs were produced by sintering of glass powder compacts at the temperature ranges from 800−900 ºC for 1−1000 h. Furthermore, the influence of various ionic substitutions, especially SrO for CaO, and Ln2O3 (Ln=La, Nd, Gd, and Yb), for MgO + SiO2 in Al-containing diopside on the structure, sintering and crystallization behaviour of glasses and properties of resultant GCs has been investigated, in relevance with final application as sealants in SOFC. From the results obtained in the study of diopside-based glasses, a bilayered concept of GC sealant is proposed to overcome the challenges being faced by (SOFCs). The systems designated as Gd−0.3 (in mol%: 20.62MgO−18.05CaO−7.74SrO−46.40SiO2−1.29Al2O3 − 2.04 B2O3−3.87Gd2O3) and Sr−0.3 (in mol%: 24.54 MgO−14.73 CaO−7.36 SrO−0.55 BaO−47.73 SiO2−1.23 Al2O3−1.23 La2O3−1.79 B2O3−0.84 NiO) have been utilized to realize the bi-layer concept. Both GCs exhibit similar thermal properties, while differing in their amorphous fractions, revealed excellent thermal stability along a period of 1,000 h. They also bonded well to the metallic interconnect (Crofer22APU) and 8 mol% yttrium stabilized zirconium (8YSZ) ceramic electrolyte without forming undesirable interfacial layers at the joints of SOFC components and GC. Two separated layers composed of glasses (Gd−0.3 and Sr−0.3) were prepared and deposited onto interconnect materials using a tape casting approach. The bi-layered GC showed good wetting and bonding ability to Crofer22APU plate, suitable thermal expansion coefficient (9.7–11.1 × 10–6 K−1), mechanical reliability, high electrical resistivity, and strong adhesion to the SOFC componets. All these features confirm the good suitability of the investigated bi-layered sealant system for SOFC applications.
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Hymenochirin-1b (Hym-1B; IKLSPETKDNLKKVLKGAIKGAIAVAKMV.NH2) is a cationic, α-helical amphibian host-defense peptide with antimicrobial, anticancer, and immunomodulatory properties. This study investigates the abilities of the peptide and nine analogues containing substitutions of Pro5, Glu6, and Asp9 by either l-lysine or d-lysine to stimulate insulin release in vitro using BRIN-BD11 clonal β cells or isolated mouse islets and in vivo using mice fed a high-fat diet to produce obesity and insulin resistance. Hym-1B produced a significant and concentration-dependent increase in the rate of insulin release from BRIN-BD11 cells without cytotoxicity at concentrations up to 1 µM with a threshold concentration of 1 nM. The threshold concentrations for the analogues were: [P5K], [E6K], [D9K], [P5K, E6K] and [E6K, D9k] 0.003 nM, [E6K, D9K] and [D9k] 0.01 nM, [P5K, D9K] 0.1 nM and [E6k] 0.3 nM. All peptides displayed cytotoxicity at concentrations ≥1 µM except the [P5K] and [D9k] analogues which were non-toxic at 3 µM. The potency and maximum rate of insulin release from mouse islets produced by the [P5K] peptide were significantly greater than produced by Hym-1B. Neither Hym-1B nor the [P5K] analogue at 1 µM concentration had an effect on membrane depolarization or intracellular Ca2+. The [P5K] analogue (1 µM) produced a significant increase in cAMP concentration in BRIN-BD11 cells and stimulated GLP-1 secretion from GLUTag cells. Down-regulation of the protein kinase A pathway by overnight incubation with forskolin completely abolished the insulin-releasing effects of [P5K]hym-1B. Intraperitoneal administration of the [P5K] and [D9k] analogues (75 nmol/kg body weight) to high-fat-fed mice with insulin resistance significantly enhanced glucose tolerance with a concomitant increase in insulin secretion. We conclude that [P5K]hym-1B and [D9k]hym-1B show potential for development into anti-diabetic agents.
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Tese de doutoramento, Farmácia (Bioquímica), Universidade de Lisboa, Faculdade de Farmácia, 2014
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Thesis (Ph.D.)--University of Washington, 2014
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OBJECTIVE: To provide a detailed phenotype/genotype characterization of Bietti crystalline dystrophy (BCD). DESIGN: Observational case series. PARTICIPANTS: Twenty patients from 17 families recruited from a multiethnic British population. METHODS: Patients underwent color fundus photography, near-infrared (NIR) imaging, fundus autofluorescence (FAF) imaging, spectral domain optical coherence tomography (SD-OCT), and electroretinogram (ERG) assessment. The gene CYP4V2 was sequenced. MAIN OUTCOME MEASURES: Clinical, imaging, electrophysiologic, and molecular genetics findings. RESULTS: Patients ranged in age from 19 to 72 years (median, 40 years), with a visual acuity of 6/5 to perception of light (median, 6/12). There was wide intrafamilial and interfamilial variability in clinical severity. The FAF imaging showed well-defined areas of retinal pigment epithelium (RPE) loss that corresponded on SD-OCT to well-demarcated areas of outer retinal atrophy. Retinal crystals were not evident on FAF imaging and were best visualized with NIR imaging. Spectral domain OCT showed them to be principally located on or in the RPE/Bruch's membrane complex. Disappearance of the crystals, revealed by serial recording, was associated with severe disruption and thinning of the RPE/Bruch's membrane complex. Cases with extensive RPE degeneration (N = 5) had ERGs consistent with generalized rod and cone dysfunction, but those with more focal RPE atrophy showed amplitude reduction without delay (N = 3), consistent with restricted loss of function, or that was normal (N = 2). Likely disease-causing variants were identified in 34 chromosomes from 17 families. Seven were novel, including p.Met66Arg, found in all 11 patients from 8 families of South Asian descent. This mutation appears to be associated with earlier onset (median age, 30 years) compared with other substitutions (median age, 41 years). Deletions of exon 7 were associated with more severe disease. CONCLUSIONS: The phenotype is highly variable. Several novel variants are reported, including a highly prevalent substitution in patients of South Asian descent that is associated with earlier-onset disease. Autofluorescence showed sharply demarcated areas of RPE loss that coincided with abrupt edges of outer retinal atrophy on SD-OCT; crystals were generally situated on or in the RPE/Bruch's complex but could disappear over time with associated RPE disruption. These results support a role for the RPE in disease pathogenesis.
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Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Civil na Área de Especialização de Edificações
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This paper refers to the assessment on site by semi-destructive testing (SDT) methods of the consolidation efficiency of a conservation process developed by Henriques (2011) for structural and non-structural pine wood elements in service. This study was applied on scots pine wood (Pinus sylvestris L.) degraded by fungi after treatment with a biocidal product followed by consolidation with a polymeric product. This solution avoids substitutions of wood moderately degraded by fungi, improving its physical and mechanical characteristics. The consolidation efficiency was assessed on site by methods of drill resistance and penetration resistance. The SDT methods used showed good sensitivity to the conservation process and could evaluate their effectiveness. (C) 2015 Elsevier Ltd. All rights reserved.
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Aprender a ler é um dos maiores desafios que as crianças enfrentam quando entram para a escola. A dificuldade no domínio do código alfabético, nos níveis da consciência fonológica e a falta de fluência na leitura são fatores que interferem em larga escala na aprendizagem global dos alunos. Habilitar um aluno para a prática da leitura é um estímulo que tem vindo a dar origem a várias investigações e intervenções no campo da educação. Este projeto descreve dois programas de treino: “Programa de treino da percepção Visual” e “Programa de promoção do desenvolvimento da consciência fonológica”, num aluno do 2º ciclo do ensino básico com dificuldade de fluência na leitura, ao longo de quinze aulas de 90 minutos. No que respeita aos resultados do primeiro estudo, que teve por base o “Programa de treino da percepção visual”, não foram encontradas diferenças relevantes quanto ao seu efeito na fluência da leitura do aluno. No entanto, no segundo estudo, que se centrou na aplicação do “Programa de promoção do desenvolvimento da consciência fonológica” em complemento com o “Programa de treino da percepção visual”, mostrou que o aluno ficou mais fluente na leitura diminuindo o número de erros de precisão (substituições, omissões, inversões, adições e erros complexos). Assim, sugere-se uma monotorização sistemática das aprendizagens dos alunos para que as intervenções possam ser cada vez mais precoces e direcionadas para as suas necessidades.
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We have suggested previously that both the negatively and positively charged residues of the highly conserved Glu/Asp-Arg-Tyr (E/DRY) motif play an important role in the activation process of the alpha(1b)-adreneric receptor (AR). In this study, R143 of the E/DRY sequence in the alpha(1b)-AR was mutated into several amino acids (Lys, His, Glu, Asp, Ala, Asn, and Ile). The charge-conserving mutation of R143 into lysine not only preserved the maximal agonist-induced response of the alpha(1b)-AR, but it also conferred high degree of constitutive activity to the receptor. Both basal and agonist-induced phosphorylation levels were significantly increased for the R143K mutant compared with those of the wild-type receptor. Other substitutions of R143 resulted in receptor mutants with either a small increase in constitutive activity (R143H and R143D), impairment (R143H, R143D), or complete loss of receptor-mediated response (R143E, R143A, R143N, R143I). The R413E mutant displayed a small, but significant increase in basal phosphorylation despite being severely impaired in receptor-mediated response. Interestingly, all the arginine mutants displayed increased affinity for agonist binding compared with the wild-type alpha(1b)-AR. A correlation was found between the extent of the affinity shift and the intrinsic activity of the agonists. The analysis of the receptor mutants using the allosteric ternary complex model in conjunction with the results of molecular dynamics simulations on the receptor models support the hypothesis that mutations of R143 can drive the isomerization of the alpha(1b)-AR into different states, highlighting the crucial role of this residue in the activation process of the receptor.
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The fire ant Solenopsis invicta and its close relatives display an important social polymorphism involving differences in colony queen number. Colonies are headed by either a single reproductive queen (monogyne form) or multiple queens (polygyne form). This variation in social organization is associated with variation at the gene Gp-9, with monogyne colonies harboring only B-like allelic variants and polygyne colonies always containing b-like variants as well. We describe naturally occurring variation at Gp-9 in fire ants based on 185 full-length sequences, 136 of which were obtained from S. invicta collected over much of its native range. While there is little overall differentiation between most of the numerous alleles observed, a surprising amount is found in the coding regions of the gene, with such substitutions usually causing amino acid replacements. This elevated coding-region variation may result from a lack of negative selection acting to constrain amino acid replacements over much of the protein, different mutation rates or biases in coding and non-coding sequences, negative selection acting with greater strength on non-coding than coding regions, and/or positive selection acting on the protein. Formal selection analyses provide evidence that the latter force played an important role in the basal b-like lineages coincident with the emergence of polygyny. While our data set reveals considerable paraphyly and polyphyly of S. invicta sequences with respect to those of other fire ant species, the b-like alleles of the socially polymorphic species are monophyletic. An expanded analysis of colonies containing alleles of this clade confirmed the invariant link between their presence and expression of polygyny. Finally, our discovery of several unique alleles bearing various combinations of b-like and B-like codons allows us to conclude that no single b-like residue is completely predictive of polygyne behavior and, thus, potentially causally involved in its expression. Rather, all three typical b-like residues appear to be necessary.
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Pygmy Shrews in North America have variously been considered to be one species (Sorex hoyi) or two species (S. hoyi and S. thompsoni). Currently, only S. hoyi is recognized. In this study, we examine mitochondrial DNA sequence data for the cytochrome b gene to evaluate the level of differentiation and phylogeographic relationships among eleven samples of Pygmy Shrews from across Canada. Pygmy Shrews from eastern Canada (i.e., Ontario, Quebec, New Brunswick, Nova Scotia, and Prince Edward Island) are distinct from Pygmy Shrews from western Canada (Alberta, Yukon) and Alaska. The average level of sequence divergence between these clades (3.3%) falls within the range of values for other recognized pairs of sister species of shrews. A molecular clock based on third position transversion substitutions suggests that these two lineages diverged between 0.44 and 1.67 million years ago. These molecular phylogenetic data. combined with a reinterpretation of previously published morphological data, are suggestive of separate species status for S. hoyi and S. thompsoni as has been previously argued by others. Further analysis of specimens from geographically intermediate areas (e.g., Manitoba. northern Ontario) is required to determine if there is secondary contact and/or introgression between these two putative species.
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Vax1 and Vax2 have been implicated in eye development and the closure of the choroid fissure in mice and zebrafish. We sequenced the coding exons of VAX1 and VAX2 in 70 patients with anophthalmia/microphthalmia. In VAX1, we observed homozygosity for two successive nucleotide substitutions c.453G>A and c.454C>A, predicting p.Arg152Ser, in a proband of Egyptian origin with microphthalmia, small optic nerves, cleft lip/palate and corpus callosum agenesis. This mutation affects an invariant residue in the homeodomain of VAX1 and was absent from 96 Egyptian controls. It is likely that the mutation results in a loss of function, as the mutation results in a phenotype similar to the Vax1 homozygous null mouse. We did not identify any mutations in VAX2. This is the first description of a phenotype associated with a VAX1 mutation in humans and establishes VAX1 as a new causative gene for anophthalmia/microphthalmia. ©2011 Wiley Periodicals, Inc.
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Contient : « Recompensacion de dommaine pour domaine à Eglisez ». Pièce incomplète du commencement. Chinon. Septembre ; « Eschange fait par le roy Charles » V « avec la contesse d'Artois, de Jailly, ou bailliage de Troies, à l'encontre de Saint Florentin en icellui bailliage » ; « Eschange de certaines terres et seigneuries faittes (sic) entre le roy... CHARLES » V ? « et l'evesque de Gap » ; « Transport de Vie[r]zon à monseigneur de Reims, en deducion de grant sonme que le roy... CHARLES » VII « li doit ». Poitiers, 7 août 1425 ; « Confirmacion et approbacion du roy... CHARLES » VII « du transport et don de Vie[r]zon, fait par l'arcevesque de Reims, et à l'euvre et accroissement du mariage de sa niepce avec le sire de Vauvert » ; Privilège de JEAN LE BON en faveur de l'abbaye de St-Denis. En latin ; « Carta quod consules Lemovicenses possint tenere feoda velut nobiles ». En latin ; « Ottroy aux Jacobins de Sens d'un cymentière » ; Série de pièces relatives au collège de Navarre ; « Lectre de foy et hommage faiz à monseigneur de Guienne,... LOUIS » DE FRANCE, fils de Charles VI, « à cause de la terre et viconté de Mortaigne » ; « Baillie de homme par le roy à l'evesque d'Aucerre, pour lui faire hommage à cause de la conté d'Aucerre » ; « Sommation du roy CHARLES VI à Guillaume de Bavière, comte d'Ostrevant, de lui faire la foy et hommage du comté d'Ostrevant. 1391 » ; « Super eodem au duc Aubert de Bavière, avec l'exécutoire... au bailli de Vermandois » ; Pièces relatives à la levée de la taille ; « Aide miz suz sel pour aider à la fortifficacion de Chinon » ; « Continuacion de creue sur sel pour Celles en Berry » ; « Prorrogacion d'ung aide à Chinon » ; « Povoir à messire Philibert de Bercy, cappitaine de La Guierche en Touraine, de mectre suz l'apetissement du vin vendu en groz et à détail ès villes eux retrayans oud. chastel, pour l'emparement d'iceluy » ; Collations de bénéfices ; Prébendes ; Présentations à une cure ; Dons de chapelles ; Maladreries et léproseries ; Bourse du collège de Champagne ; Bourses du collège de Navarre ; Nominations diverses ; Surrogations ; Licenccs d'élire ; Dons de fruits de bénéfices ; Curatelles ; Emprisonnements ; Élargissements ; Louveterie ; Loutrerie ; Compulsoires, exécutoires et contraintes ; Visites de forteresses ; « Lettre de faire visiter denrées et de faire payer amende à ceulx qui vendent mauvaisez denrées » ; « Recouvrements » ; « Recouvrement et reprinse de terres données ou Daulphiné, selon la révocacion sollempnelment faitte à l'assemblée des troix estas des royaulme et Daulphiné » ; « Certification de monseigneur... LOYS », duc « DE GUIENNE », 3e fils de Charles VI, « d'avoir délivré prisonnier à son joyeux advenement » en la « ville de Vernon » ; « Rex... KAROLUS » V « omnibus certificat et asserit » Johannam, « reginam Jherusalem » et « Sicilie, esse consanguineam suam, inhibendo ne quis contra ipsam aliquod attemptare presumat » ; « Approbations : Que aucun ne soit tenu pour infame, à qui ung chien a mengié l'oreille » ; « Déclarations... sur le debat de l'office du vicomte de Conches,... sur les offices de grenetier de Bourges » ; « Vidimus » ; « Consentements : de absolucione quorumdam qui inimicis regni victualia... ministraverint... quod celestini religiosi habeant mense quolibet unam bursam » ; « Tollerances » ; « Sermens » ; « Mutacions » ; Rétablissement de l'atelier monétaire du Puy en Velay ; Restauration d'hôpital à St-Quentin ; « Limitations et divisions » ; « Substitutions » : le sire de Mouy substitué au sire de Boquereaux dans l'office de bailli de Vermandois ; « Ratifications » : pièces relatives aux rapports avecle saint siège ; « Significations ou Significamus » ; « Recommendatoires » ; « Exortoire » ; « Lettres du roy CHARLES VI aux Anglois les priant de venger la mort de leur roy Richard, qui avoit été misérablement tué, 1406 » ; « Semblables lettres en françois aux precedens, qui sont en latin » ; « Rogat rex quandam villam », Aix la Chapelle, « ut de reliquiis corporis cujusdam sancti », S. Charlemagne, « sibi mittant » ; « Rex... KAROLUS,... rogat priorem et diffinitores capituli generalis Cartusiensis, ut orent Deum pro ipso » ; « Insinuatoire et notificatoire : Lictera super appellacionibus per barones, gentes ducatus Acquitanie, a principe Gallie et Acquitanie, filio regis Anglie, interpositis et emissis, racione gravaminum eisdem collatorum, directis principi Juliacensi et pluribus aliis regibus et principibus christianis, ad ostendendum justam causam regis » KAROLI « ad regnum Anglie guerram super hoc inferendam » ; « Instrumens... Johannes Le Boursier, miles... confessus fuit se debere... domino Georgio de Suliaco, militi... summam mille regalium auri ». 20 août 1432 ; « Nomina baillivorum et senescallorum regni... » ; Sur les lettres royaux ; « De litteris missivis seu clausis » ; Lettres sur faits de chasse ; Tarif de chancellerie ; « Cy commence le Livre de l'audience, où les notaires font le serment et mettent leurs seings manuels... » ; Autre suite de formules ; « Deffiances du duc de Guerles contre le roy de France » ; « Deffiances envoiées par le roy de France au duc de Juliers » ; « Instructions abrégées pour avoir cognoissance du stile de parlement et des manières de procéder en la cour de France » ; « Quelz sont les pers de France et quelle prérogative ilz ont » ; Collations de bénéfices et de prébendes ; Nouvelle suite de formules ; « Chapitre de diverses lettres diffuses » ; « Lettres de finances » ; « Lictera per quam rex concessit et voluit quod prior et fratres ordinis Celestinorum Parisius habeant et capiant per manum audienciarii regis, sub emolumento sigilli regis cancellarie, quod habent notarii et secretarii regis seu consueverunt habere racione officii notariatus, quolibet mense unam bursam sicut unus dictorum notariorum et secretariorum... ». Acte de CHARLES V, donné à Paris en décembre 1368 ; « Rotulus notariorum regiorum », pièce relative à une « fraternitas » des clercs et notaires royaux, suivie des noms de ceux « qui ad premissa voluerunt se consentire » ; Acte de CHARLES VI, daté de Paris, 20 avril 1402. Il donne pour demeure aux prevôts de Paris présent et avenir, son « petit chastellet » ; Actes relatifs aux gardes et sauvegardes
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Although exceptions may be readily identified, two generalizations concerning genetic differences among species may be drawn from the available allozyme and chromosome data. First, structural gene differences among species vary widely. In many cases, species pairs do not differ more than intraspecific populations. This suggests that either very few or no gene substitutions are required to produce barriers to reproduction (Avise 1976). Second, chromosome form and/or number differs among even closely related species (White 1963; 1978; Fredga 1977; Wright 1970). Many of the observed chromosomal differences involve translocational rearrangements; these produce severe fitness depression in heterozygotes and were, thus, long considered unlikely candidates for the fixation required of genetic changes leading to speciation (Wright 1977). Nonetheless, the fact that species differences are frequently translocational argues convincingly for their fixation despite prejudices to the contrary. Haldane's rule states that in the F of interspecific crosses, the heterogametic sex is absent or sterile in the preponderance of cases (Haldane 1932). This rule definitely applies in the genus Dr°sophila (Ehrman 1962). Sex chromosome translocations do not impose a fitness depression as severe as that imposed by autosomal translocations, and X-Y translocations may account for Haldane's rule (Haldane 1932). Consequently a study of the fit ness parameters of an X·yL and a yS chromosome in Drosophila melanogaster populations was initiated by Tracey (1972). Preliminary results suggested that x.yL//YSmales enjoyed a mating advantage with X·yL//X·yL females, that this advantage was frequency dependent, that the translocation produced sexual isolation and that interactions between the yL, yS and a yellow marker contributed to the observed isolation (Tracey and Espinet 1976; Espinet and Tracey 1976). Encouraged by the results of these prelimimary studies, further experiments were performed to clarify the genetic nature of the observed sexual isolation, S the reality of the y frequency dependent fitness .and the behavioural changes, if any, produced by the translocation. The results of this work are reported herein. Although the marker genes used in earlier studies, sparkling poliert an d yellow have both been found to affect activity,but only yellow effects asymmetric sexual isolation. In addition yellow effects isolation through an interaction with the T(X-y) chromosomes, yS also effects isolation, and translocational strains are isolated from those of normal karyotype in the absence of marker gene differences. When yS chromosomes are in competition with y chromosomes on an X.yL background, yS males are at a distinct advantage only when their frequency is less than 97%. The sex chromosome translocation alters the normal courtship pattern by the incorporation of circling between vibration and licking in the male repertoire. Finally a model of speciation base on the fixation of this sex chromosome translocation in a geographically isolated gene pool is proposed.