Academic literature on the topic 'Repeating units'

Segments are a structured presentation style that is commonly used on late-night talk and variety television shows. Research has shown that shows that contain segments with both entertaining and informative content (e.g., The Daily Show) have increased students’ political knowledge. This study investigated how the structure of segments could be adapted to present material in classroom lectures to promote recall of both learning events and course content. For the first two units in a three-unit child development course, students experienced segments along with traditional lecture activities. Although performance varied across measures, results indicated that segments are a useful teaching tool to promote retention of material and recall of learning events. The use of segments in other types of courses is discussed.

The synthesis of a glycodendrimer by incorporating repetitive mannoside units onto a glucoside core was completed in order to prepare a multivalent probe to study fundamental carbohydrate-protein interactions.

Polysilsesquioxanes were synthesized with end functional double-decker silsesquioxanes (DDSQ) and the polymers were characterized with 1H NMR, 29Si NMR and size exclusion chromatography (SEC). Polysilsesquioxane containing iso-butyl end capped DDSQ showed better solubility compared to that of methyl end capped DDSQ. Thermal properties investigated with TGA showed that the polymers exhibited exceptionally high stabilities in the range of 470-530°C even in both nitrogen and air atmosphere. The average residual weights of the polymers at 760°C were around 80% in the nitrogen atmosphere.

1. Activity of up to 10 single units was recorded in parallel from frontal areas of behaving monkeys. 2. Spatiotemporal firing patterns were revealed by a method that detects all excessively repeating patterns regardless of their complexity or single-unit composition. 3. Excess of repeating patterns was found in 30-60% of the cases examined when timing jitter of 1-3 ms was allowed. 4. An independent test refuted the hypothesis that these patterns represented chance events. 5. In a given behavioral condition there were usually many different patterns, each repeating several times, and not one (or a few) pattern repeating many times. 6. In 13 out of 20 cases, when a single unit elevated its firing rate in association with an external event beyond 40/s, most of the spikes within that period were associated with excessively repeating spatiotemporal patterns. 7. Of 157 types of patterns whose excess was most marked, 107 were composed of spikes from one single unit, 45 of the patterns contained spikes from two single units, and only one was composed of spikes from three different single units. 8. These properties suggest that the patterns were generated by reverberations in a synfire mode within self-exciting cell assemblies.

Two glucans, one α-glucan (TM-I) and one β-glucan (TM-II) were isolated from an edible mushroom, Termitomyces microcarpus by extraction with 5% NaOH/0.05% NaBH4, followed by a precipitation with 1 M acetic acid. The repeating units of two polysaccharides have been identified by means of NMR studies (1H, 13C, DEPT-135 and HSQC) and chemical investigations. The structures of repeating units of two polymers were established as

In a previous communication (Biosci. Rep. 3, 517–525, 1993) we described quantitative X-ray diffraction studies of α-keratin which were shown to be consistent with the presence of finite arrays of repeating units, successive arrays being set down at axial intervals of 470 Å. In addition the axial interval between repeating units in an array was shown to be 197.9 Å. It was suggested that this could most readily be explained by supposing that a surfacelattice was present which contained a dislocation along a helical path with unit height h = 470 Å and unit twist |t| = 49.1°. The number of repeating units was shown to be in the range 7–9. With 7 repeats the mismatch of the lattice along the dislocation is small and this choice was used to develop a detailed model for the filament. Subsequent studies of molecular interactions have shown however that the coiled-coil rope segments in the rod domain of the molecule are most probably oriented parallel to the dislocation, and so minimization of lattice mismatch may be less important than originally supposed. In the present communication it is shown that the choice of 8, rather than 7, for the number of repeating units yields a model which is more compatible with estimates of the linear density and also provides the basis for a general model for polymorphism in intermediate filament lattices.

Abstract Bacterial cell surface polysaccharides are primarily present as lipopolysaccharides or capsular polysaccharides. They are used by cells for both structure and function and have been shown to be a virulence factor of bacterial pathogens. Cell surface polysaccharides are widely utilised as antigenic components in vaccines and play an important role in the protection against numerous diseases including meningococcal disease and shigellosis. This study is composed of two parts: a computational section, which investigates the capsular polysaccharide (CPS) repeating unit (RU) conformations of meningococcal Y and W CPS vaccines and a second experimental component that involves synthetic studies toward the O-specific polysaccharide (O-SP) RU of Shigella sonnei. The CPS RU of MenY [→6)-α-D-Glc(1→4)-α-D-NeuNAc-(2→] and MenW [→6)-α-D-Gal(1→4)-α-D-NeuNAc-(2→] differ only in the orientation of the C-4 hydroxyl: equatorial in MenY and axial in MenW. However, groups Y and W CPS vaccines have different levels of antibody cross-protection. The purpose of the computational study was to determine if these observed differences may be attributed to CPS RU conformation. Potential of mean force calculations were applied to disaccharide RUs of MenY and MenW, and larger three repeating units (3RU) were simulated with molecular dynamics (MD) in solution. The molecular modelling showed that differences in RU conformation between the meningococcal groups arise primarily due to the structural differences between glucose and galactose; affecting the behaviour and orientation of the 2→6 dihedral linkage. The 2→6 linkages in the MenY 3RU adopt a single preferred orientation and consequently it has a single dominant molecular conformation. In contrast, the 2→6 linkages in the MenW 3RU move frequently between different rotameric conformations resulting in multiple conformational families. These results indicate significant conformational differences between the MenY and MenW CPS RUs, which may account for the different levels of cross-protection observed. The synthetic component was part of a larger study to develop a novel route towards the O-SP RU of S. sonnei for use in biological testing and physicochemical characterisation for vaccine development. The O-SP RU of S. sonnei is →4-α-L-AltNAc-(1→3)-β-D-FucNAc4N(1→. The multi-step synthesis was performed using known methodology as well as methods developed by the research group. The key 2,3-oxazolidinone protected intermediate was successfully synthesised in good yields and due to time constraints the final product synthesised was two steps away from the protected FucNAc4N residue. Additional studies were performed on the 2,3-oxazolidinone intermediate as part of a divergent synthesis strategy toward the AltNAcA residue of S. sonnei. Reactions were conducted whereby β and α derivatives of the 2,3-oxazolidinone intermediate were successfully synthesised in large scale and good yields for further studies to be performed by the group. i

2008/2009
Argomento di questa tesi di dottorato sono i polisaccaridi (sia capsulari, CPSs, sia esopolisaccaridi, EPSs), prodotti da batteri e rilasciati nell’ambiente circostante, ed il loro ruolo nelle infezioni batteriche. Sono stati presi in considerazione batteri opportunisti responsabili di infezioni polmonari in pazienti affetti da fibrosi cistica (CF). I risultati riportati in questa tesi di dottorato comprendono diverse linee di ricerca e contribuiscono a chiarire le diverse caratteristiche chimiche e biologiche dei polisaccaridi batterici presi in considerazione. La prima linea di ricerca riguarda due EPSs strutturalmente simili prodotti da Inquilinus limosus, un batterio recentemente isolato dalle secrezioni polmonari di pazienti con CF. Si è voluto valutare se i due EPSs fossero in grado di assumere conformazioni differenti e quindi ipoteticamente producessero diverse attività biologiche. Le proprietà conformazionali sono state valutate mediante misure di dicroismo circolare ed immagini ottenute mediante microscopia a forza atomica. Studi di modellistica molecolare sono stati effettuati dalla Dr.ssa M. Kuttel (Dip. di Chimica, Univ. di Cape Town). I due polimeri esibiscono effettivamente differenti conformazioni elicoidali (strutture secondarie), che vengono stabilizzate da legami idrogeno e caratterizzate dalla presenza di gruppi piruvato carichi esposti sulla superficie esterna dell’elica. Questo risultato conferma l’ipotesi che la biosintesi di più specie polisaccharidiche può risultare un mezzo utile per il batterio per diversificare i propri strumenti di difesa da possibili minacce esterne. La seconda linea di ricerca ha preso in considerazione l’esopolisaccaride cepaciano, prodotto dalla maggioranza dei ceppi appartenenti al complesso della Burkholderia cepacia (Bcc). L’unità ripetitiva (RU) di questo EPS è stata isolata dalla membrana interna batterica, dove si trova legata a un trasportatore lipidico prima della polimerizzazione. Durante il lavoro di questa tesi, è stato sviluppato un protocollo per isolare l’unità ripetitiva e la sua RU biologica è stata determinata mediante analisi ESI-MS. Questo studio, che nasce dalla collaborazione con la Dr.ssa C. Lagatolla (Dip. di Scienze della Vita, Univ. di Trieste), impegnata nella ricerca dei geni coinvolti nella biosintesi del cepaciano, ha inoltre permesso di determinare lo schema di acetilazione della stessa, utile per la possibile comprensione del ruolo biologico dei gruppi acetili, e di investigare alcuni passi del processo biosintetico dell’unità ripetitiva del polisaccaride. L’utilizzo di enzimi in grado di degradare il polisaccaride cepaciano è utile per demolire la matrice esopolisaccaridica presente attorno ai batteri e consentirne l’utilizzo in sinergia con terapie antibiotiche. In precedenza era stato trovato un enzima, prodotto da un ceppo ambientale di Bacillus, con attività liasica verso il cepaciano. Il suo isolamento per un futuro sequenziamento è stato oggetto di questa tesi. Questo enzima è in grado di idrolizzare una catena laterale dello scheletro polisaccaridico del cepaciano, così lasciando intatta la natura polimerica dell’EPS. Benché l’eliminazione di questa catena laterale provochi una decisa diminuzione della viscosità, probabilmente dovuta alla perdita di aggregazione, la ricerca di altri enzimi in grado di idrolizzare lo scheletro polimerico a frammenti a basso peso molecolare sarà oggetto di ricerche future. La quarta linea di ricerca ha coinvolto lo studio dell’interazione tra diversi EPSs con tre peptidi antimicrobici del sistema dell’immunità innata, appartenenti alla famiglia delle catelicidine. Negli esperimenti sono stati utilizzati esopolisaccaridi prodotti da Pseudomonas aeruginosa, Inquilinus limosus e ceppi clinici del Bcc. L’inibizione dell’attività dei peptidi è stata valutata tramite saggi di minima concentrazione inibente su un ceppo di Escherichia coli di riferimento in presenza o meno degli EPSs. La formazione di complessi tra peptidi ed EPSs è stata studiata per mezzo di misure di dicroismo circolare, di spettroscopia di fluorescenza e di microscopia a forza atomica. E’ stato infine proposto un modello in cui peptidi strutturati ad α-elica interagiscono con gli esopolisaccaridi mediante interazioni elettrostatiche e non covalenti. Infine, la ricerca ha coinvolto il polisaccaride capsulare prodotto da Neisseria meningitidis gruppo A, usato per sviluppare un vaccino coniugato dal Prof. N. Ravenscroft (Dip. di Chimica, Univ. di Cape Town). In base alle sue osservazioni sulla scarsa reattività del polisaccaride durante il processo di derivatizzazione necessario per la coniugazione con le proteine, è stata formulata l’ipotesi di una possibile aggregazione del polisaccaride capsulare in presenza di ioni Ca2+, derivanti dal processo di purificazione dello stesso. Per capire e risolvere questo problema, le proprietà conformazionali e morfologiche del CPS in presenza di ioni NH4+, Na+ e Ca2+ sono state studiate nel laboratorio di Trieste, mediante tecniche quali dicroismo circolare, spettroscopia di fluorescenza, viscosimetria e microscopia a forza atomica. La presenza di ione ammonio porta le catene polimeriche ad una conformazione più allungata, mentre lo ione sodio favorisce il ripiegamento delle catene in una conformazione globulare. L’addizione di calcio produce aggregazione di un limitato numero di polisaccaridi globulari per formare una struttura ‘toroidal-like’. Questi risultati giustificano la bassa solubilità del polimero in forma calcio e offrono una spiegazione della sua bassa reattività nella preparazione del coniugato proteico.
This PhD thesis focuses on polysaccharides (both capsular, CPSs, and exopolysaccharides, EPSs) produced by bacteria and released in the external environment as well as on their role in bacterial infections. For this, opportunistic bacteria involved in lung infections in cystic fibrosis (CF) patients were investigated. The results reported in the PhD thesis involved several topics and contributed to clarify different biological and chemical characteristics of bacterial polysaccharides. The first topic of the research has taken in account two structurally similar EPSs produced by a bacterium recently isolated from respiratory secretions of CF patients, Inquilinus limosus. The working hypothesis was that the two EPSs assume different conformations and therefore exert different biological activity. The conformational properties of these two EPSs were investigated by circular dichroism (CD) and atomic force microscopy (AFM) techniques, whereas the molecular modelling studies were carried out by Dr. M. Kuttel (Dept. of Chemistry, Univ. of Cape Town). The two polymers were shown to exhibit different helical conformations, stabilised by hydrogen bonding and characterised by charged pyruvate groups on the external helical surface. These findings confirming that the biosynthesis of two polymeric species might offer multiple tools to protect bacteria from external threats. The second part of the research involved cepacian, the EPS produced by the majority of bacteria belonging to the Burkholderia cepacia complex (Bcc). In this case, the isolation of its repeating unit (RU) from the internal bacterial membrane where it is bound to a lipid carrier prior to the EPS polymerisation was performed. A procedure to isolate cepacian repeating units was developed and the structure of the biological RU was determined by ESI-MS analysis. At the same time, the RU was useful to determine the acetylation scheme of cepacian, which could be connected with the biological role of acetyl groups, and to obtain information on its biosynthetic sequence. All the data obtained were considered in connection with the genetic investigation on the cepacian biosynthesis, carried out by Dr. C. Lagatolla (Dept. of Life Sciences, Univ. of Trieste). The third topic involved the search and identification of enzymes that can degrade cepacian in order to find biochemical tools able to degrade the EPS matrix present around bacteria and possibly used in synergy with antibiotic therapies. One lyase was found produced by Bacillus spp. and its isolation and sequencing is in progress. This lyase cleaves one of the lateral chains of cepacian backbone, thus living intact the polymeric nature of the EPS. Although the elimination of this lateral chain produces a marked lowering of the cepacian viscosity probably due to loss in aggregation ability, the search of different enzymes able to cleave the EPS backbone into oligosaccharides is still active. The fourth topic of the research focused on the interactions between different bacterial EPSs and three antimicrobial peptides, belonging to the cathelicidin family of primate’s innate immune system, to investigate the possible EPSs protective role towards bacterial cells. The experiments involved EPSs produced by Pseudomonas aeruginosa, Inquilinus limosus and clinical isolates of the Burkholderia cepacia complex. The inhibition of the peptides activity was assessed by minimum inhibitory concentration assays on a reference Escherichia coli strain in the presence and in the absence of EPSs. The complex formation between peptides and EPSs was investigated by means of CD, fluorescence spectroscopy and AFM. As a result, a model was proposed where peptides with a α-helical conformation interact with the EPSs backbone through electrostatic and non-covalent interactions. The last issue of the research involved the capsular polysaccharide produced by Neisseria meningitidis group A; this CPS is used to develop a protein conjugate vaccine by Prof. N. Ravenscroft (Dept. of Chemistry, Univ. of Cape Town). He observed that the derivatisation process, necessary prior to protein conjugation, yielded less product, in terms of protein-conjugate, than expected, and he thought that this was due to CPS aggregation in the presence of Ca2+, used in the purification steps. In order to solve this problem, the conformational and morphological properties of the CPS, in the presence of NH4+, Na+ and Ca2+ cations, were investigated in the Trieste laboratory. The study was carried out using different techniques such as circular dichroism, fluorescence spectroscopy, viscosity measurements and atomic force microscopy. It was shown that ammonium ions were associated with the presence of single polymer chains in an elongated conformation, whereas sodium ions favoured the folding of chains into a globular conformation. The addition of calcium ions produced the aggregation of a limited number of globular polysaccharide chains to form a ‘toroidal-like’ structure. This effect justified the polymer low solubility in the presence of calcium ions and offered an explanation of the polymer low reactivity in the preparation of the protein conjugate.
XXII Ciclo
1981

This study is devoted to the development of an integrated numerical modeling enabling one to investigate the static and the dynamic behaviors and failures of 2-D textile composite as well as 3-D orthogonal woven composite structures weakened by cracks and subjected to static-, impact- and ballistic-type loads. As more complicated modeling about textile composite structures is introduced, some of homogenization schemes, geometrical modeling and crack propagations become more difficult problems to solve. To overcome these problems, this study presents effective mesh-generation schemes, homogenization modeling based on a repeating unit cell and sinusoidal functions, and also a cohesive element to study micro-crack shapes. This proposed research has two: 1) studying behavior of textile composites under static loads, 2) studying dynamic responses of these textile composite structures subjected to the transient/ballistic loading. In the first part, efficient homogenization schemes are suggested to show the influence of textile architectures on mechanical characteristics considering the micro modeling of repeating unit cell. Furthermore, the structures of multi-layered or multi-phase composites combined with different laminar such as a sub-laminate, are considered to find the mechanical characteristics. A simple progressive failure mechanism for the textile composites is also presented. In the second part, this study focuses on three main phenomena to solve the dynamic problems: micro-crack shapes, textile architectures and textile effective moduli. To obtain a good solutions of the dynamic problems, this research attempts to use four approaches: I) determination of governing equations via a three-level hierarchy: micro-mechanical unit cell analysis, layer-wise analysis accounting for transverse strains and stresses, and structural analysis based on anisotropic plate layers, II) development of an efficient computational approach enabling one to perform transient response analyses of 2-D plain woven, 2-D braided and 3-D orthogonal woven composite structures featuring matrix cracking and exposed to time-dependent ballistic loads, III) determination of the structural characteristics of the textile-layered composites and their degraded features under smeared and discrete cracks, and assessment of the implications of stiffness degradation on dynamic response to impact loads, and finally, IV) the study of the micro-crack propagation in the textile/ceramic layered plates. A number of numerical models have been carried out to investigate the mechanical behavior of 2-D plain woven, 2-D braided and 3-D orthogonal woven textile composites with several geometrical representations, and also study the dynamic responses of multi-layered or textile layered composite structures subjected to ballistic impact penetrations with a developed in-house code.
Ph. D.

Chapter 1 describes, in a schematic manner, various approaches to the synthesis of the repeating disaccharide unit of H. pleuropneumoniae serotype 4 capsular polysaccharide. Chapter 2 describes an indirect use of thioglycosides, by conversion into glycosyl halides, and their direct use with promoters such as dimethyl (methylthio) sulfonium triflate (DMTST) and N-bromosuccinimide (NBS). Chapter 3 describes the development of the concept of active and latent thioglycosyl donors which combines the features of armed and disarmed glycosyl donors is presented. Reactivation of latent donor para-nitrophenyl thioglycoside is also proposed. In Chapter 4, we describe the synthesis of a complex series of thioglycosides under PTC conditions. During this approach we discovered that the use of the lipophilic PTC catalyst tretrabutylammonium hydrogen sulfate (TBAHS) (1 eq.) and ethyl acetate as solvent greatly improve the reaction rates. Chapter 5 presents our approaches to the stereospecific syntheses of 1,2-trans-aryl-1-thio-$\beta$-D-glycobiosides, active and latent tioglycosyl donors, as well as 1,2-trans-$\beta$-D-glycosyl phosphates by PTC. Chapter 6 describes our approaches to the synthesis of the repeating disaccharide unit of H. pleuropneumoniae serotype 4 (CPS) via thioglycosyl donors using different thiophilic promoters such as NBS, DMTST and N-iodosuccinimide (NIS)/trifluoromethanesulfonic acid (TfOH). (Abstract shortened by UMI.)

This dissertation examines how Philippine (or Filipino) authors emphasise the need for articulating or “re/membering” cultural identity. The researcher mainly draws from the theory of Caribbean critic, Stuart Hall, who views cultural identity as an articulation which allows “the fragmented, decentred human agent” to be considered as one who is both “subject-ed” by power but/and one who is capable of acting against those powers (Grossberg 1996 [1986]: 157, emphasis mine). Applied to the Philippine context, this writer argues that, instead of viewing an apparent fragmented Filipino identity as a hindrance to “defining” cultural identity, she views the “damaged” (Fallows 1987) Filipino history as a the material itself which allows articulation of identity. Instead of reducing the cultural identity of a people to what-they-could-have-been-had-history-not-intervened, she puts forward a vision of identity which attempts to transfigure these “damages” through the efforts of coming-to-terms with history. While this point of view has already been shared by other critics (such as Feria 1991 or Dalisay 1998:145), the author’s contribution lies in presenting re/membering to describe a specific type of articulation which neither permits one to deny wounds of the past nor stagnate in them. Moreover, re/membering allows one to understand continuous re-articulations of “new” identities (due to current migration), while putting an “arbitrary closure” (Hall) to simplistic re-articulations which may only further the “lines of tendential forces” (such as black or brown skin bias) or hegemonic practices.

Written as such (with a slash),“re/membering” encapsulates the following three-fold meaning: (1) a “re-membering”, to indicate “a putting together of the dismembered past to make sense of the trauma of the present” (Bhabha 1994:63); as (2) a “re-membering” or a re-integration into a group and; as (3) “remembering” which implies possessing “memory or … set [ting] off in search of a memory” (Ricoeur 2004:4). As a morphological unit, “re/membering” designates, the ways in which Filipino authors try to articulate cultural identity through the routes of colonisation, migration and dictatorship.

The authors studied in this thesis include: Carlos Bulosan, Bienvenido Santos, N.V.M. Gonzalez, Nick Joaquin, Frank Sionil José, Ninotchka Rosca, Jessica Hagedorn, and Merlinda Bobis. Sixty-years separate Bulosan’s America is in the Heart (1943) from Hagedorn’s Dream Jungle (2003). Analysis of these works reveals how articulation is both difficult and hopeful. On the one hand, authors criticize the lack of efforts and seriousness towards articulation of cultural identity as re/membering (coming to terms with the past, fostering belonging and cultivating memory). Not only is re/membering challenged by double-consciousness (Du Bois 1994), dismemberment and forgetting, moreover, its necessity is likewise hard to recognize because of pain, trauma, phenomena of splitting, escapist attitudes and preferences for a “comfortable captivity”.

On the other hand, re/membering can also be described as hopeful by the way authors themselves make use of literature to articulate identity through research, dialogue, time, reconciliation and re-creation. Although painstaking and difficult, re/membering is important and necessary because what is at stake is an articulated Philippine cultural identity. However, who would be prepared to make the effort?

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Cette thèse démontre que, pour les auteurs philippins, l’articulation ou « re/membering » l'identité culturelle, est nécessaire. Le chercheur s'appuie principalement sur la théorie de Stuart Hall, qui perçoit l'identité culturelle comme une articulation qui permet de considérer l’homme assujetti capable aussi d'agir contre des pouvoirs (cf. Grossberg 1996 [1986]: 157). Appliquée au contexte philippin, cet auteur soutient que, au lieu de la visualisation d'une identité fragmentée apparente comme un obstacle à une « définition » de l'identité culturelle, elle regarde l’histoire philippine «abîmée» (Fallows 1987) comme le matériel même qui permet l'articulation d’identité. Au lieu de réduire l'identité culturelle d'un peuple à ce qu’ ils auraint pû être avant les interventions de l’histoire, elle met en avant une vision de l'identité qui cherche à transfigurer ces "dommages" par un travail d’acceptation avec l'histoire.

Bien que ce point de vue a déjà été partagé par d'autres critiques (tels que Feria 1991 ou Dalisay 1998:145), la contribution de l'auteur réside dans la présentation de « re/membering » pour décrire un type d'articulation sans refouler les plaies du passé, mais sans stagner en elles non plus. De plus, « re/membering » permet de comprendre de futures articulations de « nouvelles » identités culturelles (en raison de la migration en cours), tout en mettant une «fermeture arbitraire» (Hall) aux ré-articulations simplistes qui ne font que promouvoir des “lines of tendential forces” (Hall) (tels que des préjugés sur la couleur brune ou noire de peau) ou des pratiques hégémoniques.

Rédigé en tant que telle (avec /), « re/membering » comporte une triple signification: (1) une «re-membering », pour indiquer une mise ensemble d’un passé fragmenté pour donner un sens au traumatisme du présent (cf. Bhabha, 1994:63); (2) une «re-membering» ou une ré-intégration dans un groupe et finalement, comme (3)"remembering", qui suppose la possession de mémoire ou une recherche d'une mémoire »(Ricoeur 2004:4). Comme unité morphologique, « re/membering » désigne la manière dont les auteurs philippins tentent d'articuler l'identité culturelle à travers les routes de la colonisation, les migrations et la dictature.

Les auteurs inclus dans cette thèse sont: Carlos Bulosan, Bienvenido Santos, NVM Gonzalez, Nick Joaquin, Frank Sionil José, Ninotchka Rosca, Jessica Hagedorn, et Merlinda Bobis. Soixante ans séparent America is in the Heart (1943) du Bulosan et le Dream Jungle (2003) du Hagedorn. L'analyse de ces œuvres révèle la façon dont l'articulation est à la fois difficile et pleine d'espoir. D'une part, les auteurs critiquent le manque d'efforts envers l'articulation en tant que « re/membering » (confrontation avec le passé, reconnaissance de l'appartenance et cultivation de la mémoire). Non seulement est « re/membering » heurté par le double conscience (Du Bois 1994), le démembrement et l'oubli, en outre, sa nécessité est également difficile à reconnaître en raison de la douleur, les traumatismes, les phénomènes de scission, les attitudes et les préférences d'évasion pour une captivité "confortable" .

En même temps, « re/membering » peut également être décrit comme plein d'espoir par la façon dont les auteurs eux-mêmes utilisent la littérature pour articuler l'identité à travers la recherche, le dialogue, la durée, la réconciliation et la re-création. Bien que laborieux et difficile, « re/membering » est important et nécessaire car ce qui est en jeu, c'est une identité culturelle articulée des Philippines. Mais qui serait prêt à l'effort?

Doctorat en Langues et lettres
info:eu-repo/semantics/nonPublished

博士
國立清華大學
生物資訊與結構生物研究所
104
摘要 1,6-環化脫水醣胺是由C6位置上的羥基與變旋異構中心的羥基進行分子內合環後脫水而得，此類醣體可以有效的利用於合成不同結構的天然化合物或是作為複合醣體及生物活性化合物的前驅物。本文主要在研究關於1,6-環化脫水醣胺的合成，以及由還原醚化反應、選擇性磷酸化、甲基胺基磷酸酯化反應後立體位向選擇性及功能性的探討，並利用製備出的去羥基醣胺進行空腸彎曲桿菌NCTC 11168 的莢膜多醣體重覆單元的合成。 第一章先介紹如何有效的利用乙腈促進HMDS進行矽烷基化的反應。我們可以藉由羥基與胺基的特性，先進行首次的選擇性保護，再對醣胺上的胺基轉換成疊氮。 在第二章，為了進行1,6-環化脫水醣胺的製成，以TMSOTf或是TfOH作為催化劑並以傳統加熱或是微波的方式促使反應進行。並利用所做出的脫水醣酐簡單的合成出珍貴的半乳醣胺或是阿洛醣胺硫代糖苷。 在第三章中，我們可以藉由微波的方式有效的在單一步驟合成出1,6-anhydro--D-galactofuranosamine，並藉由二氯磷酸苯酯(methyl benzylphosphoramidochloridate)進行甲基磷胺化(methyl phosphoramidation)，此外，在此也會介紹關於以-核糖與N-乙醯基半乳醣胺組成的二醣基作為莢膜的四醣基重覆單元，進行空腸彎曲桿菌NCTC11168莢膜多醣的首次合成。

According to the traditional paradigm, carbohydrates are considered to be poorly immunogenic, T-cell independent antigens. Pure polysaccharides induce specific IgM responses, with minimal class switch to IgG. However, a series of recent investigations has found that a class of zwitterionic polysaccharides (ZPSs)induces a variety of T-cell specific responses such as cell proliferation,cytokine secretion, and regulation of antibody production. The two most studied among this family of molecules is capsular polysaccharide (PS) A1 from the Bacteroides fragilis and the type 1 Streptococcus pneumoniae polysaccharide capsule (Sp1). Active ZPSs share a common structural motif; a high density of positively charged amino and negatively charged carboxyl or phosphate groups. These features are essential for the activity of ZPSs. Since the biological repeating unit of the polysaccharides is not known and biological activity will most likely depend upon a precise sequence, synthesis of the repeating unit of these capsular polysaccharides was undertaken. The goal of this work is to synthesize the repeating unit [3)--DFucpN2AcN4-( 14)--D-GalpA-(13)--D-GalpA-(1] of the type 1 capsular polysaccharide (Sp1) found in S. pneumoniae. 2-Acetamido-4-amino-2,4,6- trideoxy-D-galactopyranose is one of the three monosaccharides of the repeating unit of the Sp1 of Streptococcus pneumoniae. This rare amino sugar is also present in a number of bacterial polysaccharides such as Bacteroids fragilis, Streptococcus mitis and Shigella sonnei. We have developed a novel method to synthesize the orthogonally protected 2-acetamido-4-amino-2,4,6-trideoxy-Dgalactopyranose on a gram scale with high yield starting from readily available Dglucal. The crucial elements of this approach are the introduction of a 4 amino function via intramolecular cyclization of a 3-O-N-benzylcarbamate. The resulting N-benzyloxazolidinone derivative after conversion to the corresponding glycosyl trichloroacetimidate was shown to be an effective glycosyl donor. The assembly of the trisaccharide was successfully carried out from the appropriate galactopyranosides selectively protected at O-6 to permit oxidation to uronic acid derivatives after successful assembly of the target trisaccharide. The trisaccharide was tested for its ability to stimulate interleukin 10 (IL-10) and Interferon-gamma (IFN-) in collaboration with Dr. Dennis L. Kasper (Channing Laboratory, Department of Medicine, Brigham and Womens Hospital, Harvard Medical School, Boston, Massachusetts, USA). Unfortunately the trisaccharide was not active.
Chemistry

碩士
國立清華大學
生醫工程與環境科學系
94
Chemical studies reveal that the structure of OPS are linear or branched among P. syringae strains. The linear backbone is composed of L-, D-, or both L-and D-rhamnose. The branch OPS is composed of linear backbone with homogenous or hetrogenous saccharide substitution. Above all, the pivot issue of this thesis is to synthesize the linear backbone motif of P. syringae, a trisaccharide structure of Rha(1→3) Rha(1→2)Rhap. Utilizing the anomeric center activation manner of imidate and manipulating all factors and condition during glycosylation, we accomplish the synthesis of rhamnose linear backbone, unique biological feature of OPS , in the P. syringae LPS. Our synthesis strategy is to prepare disaccharide which is composed of electron-donating group protected donor 14 and anomeric center thio protected acceptor 19. The reducing end of the disaccharide is follewed by deprotection and activation of anomeric center, and then perform glycosylation with acceptor 18 for further synthesis of trisaccharide structure 23. As for donor, having synthesized Ac, Bz and Bn protected donors, we choose electron-donating Bn type donor 14 as buiding block of disaccharide synthesis for the sake of reactivity and synthesis strategy consideration. As for acceptor, through a acetal protection on C-2 and C-3 follewed by selective deprotection of C-2 or C-3, we could easily create precursor of aceeptor 19 and 18. It makes the synthesis of Rha(1→3) Rha(1→2)Rhap feature trisaccharide to be more facile.

This article addresses multilevel models in which units are nested within one another. The focus is primarily two-level models. It also describes cross-unit heterogeneity. Moreover, it assesses the fixed and random effects from the multilevel model. It generally tries to convey the scope of multilevel models but in a very compact way. Multilevel models provide great promise for exploiting information in hierarchical data structures. There are a range of alternatives for such data and it bears repeating that sometimes, simpler-to-apply correctives are best.

This chapter examines the idea of classicism being connected with the counting of homogeneous time units, or mātras, and of local music being oriented to an irregular sequence of accents marked by syllables and claps. It considers the ways in which drum patterns might be linked to texts and accented syllables, as well as the importance of reciting drum syllables not only in the learning process but also in performances. Four principles for organizing drum patterns that do not depend on cycles with a fixed number of pulses are discussed: the number of stressed beats, repeating motives, tone melody, and verbal formulas. The chapter also presents four case studies: Kota and Aruntiyar (Cakkiliyar) drumming in Tamil Nadu; Dalit drumming in Hyderabad, Andhra Pradesh; Muhājir drumming in Hyderabad, Sindh, by men of Agra heritage; and Mamraj's dhol-tāshā group, associated with the Nizamuddin shrine in Delhi.

Most rock songs fall into one of three formal types: simple verse (with a short, repeating verse-refrain section), AABA (with a verse-refrain and a contrasting bridge), and verse-chorus (with an alternation between verse and chorus, usually with contrasting material after the second chorus). This chapter adopts this framework, though it also emphasizes the strong connections between AABA and verse-chorus forms. Since the 1960s, verse-chorus form has been predominant; together, a verse and chorus form a “verse-chorus unit,” or VCU. An issue of particular interest is the opposition between verses and choruses; the two section types turn out to have a number of distinctive, contrasting features. After surveying other section types, the chapter examines some songs with interesting and unusual formal structures.

AbstractPsychometric models typically represent encounters between persons and dichotomous items as a random variable with two possible outcomes, one of which can be labeled success. For a given item, the stipulation that each person has a probability of success defines a construct on persons. This model specification defines the construct, but measurement is not yet achieved. The path to measurement must involve replication; unlike coin-tossing, this cannot be attained by repeating the encounter between the same person and the same item. Such replication can only be achieved with more items whose features are included in the model specifications. That is, the model must incorporate multiple items. This chapter examines multi-item model specifications that support the goal of measurement. The objective is to select the model that best facilitates the development of reliable measuring instruments. From this perspective, the Rasch model has important features compared to other models.

Korean has highly formulaic patterns of repeating a sentence two or more times with a variation of speech level indicated by the sentence-final particles. The repetition usually involves progressive downward modulation of the speech level from more formal to less formal. The repeated sentences occur within a single intonation contour, thus forming an utterance unit, and carry diverse intersubjective and interpersonal functions that are not available in the mere repetition of an identical sentence. By virtue of having the pairing of a syntactic pattern and a non-compositional meaning, these patterns are best considered a construction, named here as Multiply Juxtaposed Sentences (MJSs). MJSs encode the speaker’s subtle negative attitude toward the addressee.

Our goal is to develop constitutive relations for the behavior of a solid polymer during high-strain-rate deformations. In contrast to the classic thermodynamic techniques for deriving stress-strain response in static (equilibrium) circumstances, we employ a statistical-mechanics approach, in which we evolve a probability distribution function (PDF) for the velocity fluctuations of the repeating units of the chain. We use a Langevin description for the dynamics of a single repeating unit and a Lioville equation to describe the variations of the PDE Moments of the PDF give the conservation equations for a single polymer chain embedded in other similar chains. To extract single-chain analytical constitutive relations these equations have been solved for representative loading paths. By this process we discover that a measure of non-uniform chain link displacement serves this purpose very well. We then derive an evolution equation for the descriptor function, with the result being a history-dependent constitutive relation.

Native tissues are composed of functional three-dimensional (3D) units on the scale of 100–1000μm. The 3D architecture of these repeating units underlies the coordination of multicellular processes such as proliferation, differentiation, migration and apoptosis[1]. The requirement for 3D biomimetic matrices to mimic in vitro the ECM microarchitecture found in vivo becomes relevant in complex and vascularized tissue engineered models[2]. Among others, photopolymerizable hydrogels offer tunable geometrical features similar to the macromolecular-based components of soft ECM [3], can be crosslinked either in vivo or in vitro in the presence of a photoinitiator agent (PI) using visible or ultraviolet (UV) light irradiation, and have shown good compatibility with several protocols for cell embedding at different size-scales. In the present study, a new protocol to obtain cell-laden hydrogel micropatterns with highly controlled geometrical features is presented, based on the combination of polydimethylsiloxane (PDMS) replica molding and UV photopolimerization of methacrylate gelatin (GelMA).

Skeletal muscle has a complex hierarchical structure which is mainly composed of myofibers and the surrounding extracellular matrix (ECM) including endomysium, perimysium, and epimysium. Myofibers are long, cylindrical, multinucleated cells composed of repeating sarcomeres, which are basic functional units for skeletal muscle contraction. In order to produce body movement, the force generated by myofiber has to be transmitted from individual fiber to the tendon. The commonly accepted site for force transmission is the myotendinous junction (MTJ) where the myofibers connect to the tendon. However, the myofibers mainly end within the muscle fascicles without reaching the MTJ in many muscles, in which case the force has to be transmitted laterally to adjacent fiber through shear and to the tendon eventually.

The early stages of fibrin polymerization were investigated by rotatory shadowing and electron microscopy. Individual molecules within initial oligomers were found to be unaligned and contacted neighbouring molecules by single E + D and D + E contacts, suggesting an intermediate phase of activation (des A-fibrin). The interacting molecular domains were separated by a distance of 2 to 3 nm, indicating that (both or at least one) binding sites are located on protruding segments of the polypeptide chains. Upon completion of fibrin activation (des AA-fibrin), molecules within the early oligomers aligned to form single-stranded polymers,o these being characterized by repeating trinodular units of 230 A in length. Based upon these findings, a new interlocking single-stranded model for fibrin polymerization was designed and tested. The model is consistent with previous experimental data on fibrin polymerization such as that obtained by X-ray diffraction and negative staining. Moreover, early branching and lateral association phenomena are easily explained.

"Flexible learning has been associated with e-learning, even before the COVID-19 pandemic. Flexible learning gives the students large degrees of freedom to learn what, when, how and where they want. The aim of this study was to evaluate students’ preferences in e-learning and traditional classroom teaching, and was conducted from October 2019 to January 2020. Students from four courses were assigned randomly to two groups, an online and a classroom group. The study included two phases: three lectures by the lecturer (podcasts vs. classroom) and seven classroom units with student presentations and discussions. Performance and different personal characteristics and attitudes of 93 students were examined. Knowledge on the course topic was measured before the first lecture took place (t1), after the three lectures (t2) and after the following seven units (t3). Statistical analyses found no performance differences between the two groups (online/classroom); this held true for all three points in time. All students appreciated the opportunity of an intermediate exam at t2 (a change in comparison to former courses on the topic). Qualitative data showed that students felt a need for interaction with their colleagues and the lecturer, which they decided could be better fulfilled in the classroom, whereas the flexible learning setting had advantages for the exam preparation (e.g. repeating listening to the podcasts, taking breaks and learning tempo). Students’ arguments fit well to previous literature. Altogether, the study gives valuable insights into the didactic design of flexible learning."

This study determines the simultaneous effects of spatial disturbance and flow pulsation on micromixing by using three different metrics: concentration distribution, Lyapunov exponent and axial vorticity. Numerical simulations are performed for both steady and pulsating flows through a microchannel made up of C-curved repeating units. Moreover, a straight microchannel is analyzed to compare the effects of chaotic advection and molecular diffusion, the main mechanisms of transverse mixing in the chaotic and straight mixer respectively. Simulations are carried out in the steady flow for the Reynolds number range 1≤Re≤50 and in the pulsating flow for velocity amplitude ratios 1≤β≤2.5, and the ratio of the peak oscillatory velocity component to the mean flow velocity, Strouhal numbers 0.1≤St≤0.5. It was found that chaotic advection improves mixing without significant increase in pressure drop. The analysis of concentration distribution implied that full mixing occurs after Reynolds number 50 in the steady flow. When the flow is pulsatile, small and moderate values of the Strouhal number (0.1≤St≤0.3) and high values of velocity amplitude ratio (β ≥ 2) are favorable conditions for mixing enhancement. Moreover, mixing has an oscillating trend along the microchannel due to the coexistence of regular and chaotic zones in the fluid. These results correlate closely with those obtained using two other metrics, analysis of the Lyapunov exponent and axial vorticity.

Self-healing macromolecular structures, submicron capsules and fibers with molecular recognition, stimuliresponsive molecules, solvent-free rheological reversibility, multivalency in rational drug design, and the emergence of new fields of adaptive and evolutive chemistry will require a predictive synergy of tailored non-covalent and covalent bonding in molecular design. Supramolecular chemistry has emerged as a stimulating focal point that will enable these scientific and technological discoveries, and biorecognition and biomolecular organization often serve as the inspiration for the future design of supramolecular assemblies. Linear and branched macromolecules are conventionally prepared using unique combinations of step-growth and chain polymerization strategies wherein the repeating units are irreversibly connected using stable covalent bonds. Moreover, optimum physical properties and commercial success of macromolecules are derived from our ability to prepare exceptionally high molecular weights in a controlled fashion. Although high molecular weight linear macromolecules are desirable for the optimization of physical performance and commercial impact, high molecular weights often compromise future solvent-free manufacturing, melt processability, thermal stability, and recyclability of the final products. Our recent efforts have demonstrated the utility of living anionic polymerization techniques to place functionality at desired positions on the polymer backbone. This control allowed investigation of the relationship between topology and tailored functionality, a fundamental investigation that may lead to interesting adaptive and smart applications. Specifically, the synthesis of polyisoprene homopolymers in a variety of topologies was performed, as well as the introduction of complementary hydrogen bonding to diverse families of hydroxyl containing polymeric and monomeric precursors.

Abstract This paper describes how business analytics novel software tools combined with advanced data management techniques can be integrated to management workflows and decision-making processes of a Coiled Tubing Service Company (CTSC). An advanced data wrangling process (transforming and mapping data) was designed and implemented to unify current and historical coiled tubing operational data into a single data set. The latter was regularly updated with the latest operational information through an automated data querying process that eliminated the need for manually repeating the data wrangling. A Business Analytics Software (BAS) was used to accelerate the engineering of a Data Analytics (DA) process, identify correlations and trends, design data models, and create relevant Key Performance Indicators (KPI). Finally, BAS visualization tools were used to prepare and publish comprehensive cloud-based Business Intelligence (BI) dashboards and reports. The BI dashboard allows the coiled tubing company to quickly perform accurate and efficient analysis of the KPI trends of its coiled tubing units and well interventions. The cloud-based Dashboard enables the CTSC to: Effectively identify Coiled Tubing Strings utilization, costs, failures, vendors, and design performance trends based on factual data, thus enabling informed pipe management decisions. Clearly Identify high performance coiled tubing units and crews and make strategic decisions for high profile jobs. Identify equipment failures, non-productive time (NPT) trends and define, implement, and monitor maintenance and asset management strategies to tackle the failures with mayor impact on operations performance. Easily incorporate fresh operational data and detect record-breaking operations. Improve Customer Relationship Management by a quickly responding to customer inquiries for tailor-made operations performance reports. Decrease workload on repetitive processes by enabling reports generation with relevant and accurate data faster that previous methods in place. Quickly customize and create accurate documentation compiling relevant performance data in a consistent and standardized fashion. Perform well interventions technical analysis. The contemporary approach to integrate BI Software to coiled tubing operations is a step change in how service companies and operators are analyzing and monitoring performance (efficiency, safety, and quality) to differentiate from each other, optimize results and minimize costs. This paper describes an example of a simple yet sophisticated and effective way of incorporating digital tools in the oilfield services processes by utilizing in house talent and resources.