High Field NMR Spectroscopy Analysis of Beta-limit Dextrins From Starch-like Polysaccharides: an Approach to the Understanding of Amylopectine Crystallinity

International audienceAmongst all branched alpha-1,4 glucans, amylopectine is outstanding. Its specific, well-ordered alpha-1,6 branching pattern, originating from a complex enzymatic control, permits a very efficient packing of short linear chains within the currently accepted cluster model and allows amylopectine to grow into exceptionally large macromolecules. These characteristics lead to unique physicochemical properties such a s gelling properties, reversible swelling, crystallinity of high water content, complexes with linear and apolar molecules as well as several others. It is essential to uncover this intimate branching organisation in order to understand the unique architecture of amylopectine and its relations to some of starch's macroscopic properties

Notes on nn-point Witten diagrams in AdS2{}_2

Witten diagrams provide a perturbative framework for calculations in Anti-de-Sitter space, and play an essential role in a variety of holographic computations. In the case of this study in AdS$_2$, the one-dimensional boundary allows for a simple setup, in which we obtain perturbative analytic results for correlators with the residue theorem. This elementary method is used to find all scalar $n$-point contact Witten diagrams for external operators of conformal dimension $\Delta=1$ and $\Delta=2$, and to determine topological correlators of Yang-Mills in AdS$_2$. Another established method is applied to explicitly compute exchange diagrams and give an example of a Polyakov block in $d=1$. We also check perturbatively a recently proposed multipoint Ward identity with the strong coupling expansion of the six-point function of operators inserted on the 1/2 BPS Wilson line in $\mathcal{N}$=4 SYM.Comment: 39 pages, 10 figure

Extrusion réactive des polymères naturels. Intensification des réactions de modification des Lignines et amidons

International audienceReactive extrusion technology is presented as an alternative to intensifying chemical modification reactions of synthetic polymers as well as polymers of natural origin. The principle of the technology as well as the materials on the laboratory scale and on the industrial scale is explained, then examples of polysaccharides and lignins chemical modifications are developed.La technologie d'extrusion réactive est présentée comme un alternative d'intensification des réactions de modification chimiques des polymères de synthèse ainsi que les polymères d'origine naturelle. Le principe de la technologie ainsi que les matériels à l'échelle laboratoire et à l'échelle industrielle est expliqué puis les exemples de réalisation sur des modifications chimiques de polysaccharides et de lignines sont développés

In the depth of oligosaccharidic structural complexity The example of multiply branched glycans

International audienceRandom clivage of branched reserve polysaccharides composed of two different (malto-, m) and (isomalto-, i) linking types lead to complex oligomeric mixtures of various polymeric degree (DP). Each DP is a mixture of molecules containing potentially all combinations of (m) and/or (i) sub-structures. Industrial hydrolysis of starches polysaccharides produce syrups with a low DP (typically from 1 to 20). The number of potential oligosaccharidic structures accessible by random hydrolysis grow exponentially with the DP. The number of isomeric structures for each given DP (n) is a Catalan number, noted C(n), calculated as (2n choose n)/(n+1) = (2n)!/(n!(n+1)!). The calculation gives 2 isomers (maltose and isomaltose) for (DP2), 16796 deca-saccharides potential isomers (DP10) and more than 6 billions eicosasaccharide isomers (DP20)

NEO-AMYLOPECTINYL MODELS SYNTHESIS OF COMPLEX BETA-BRANCHED MALTO-OLIGOSACCHARIDES IN SOLUBLE AND SOLID PHASE

International audienceStarch is the ubiquitous glucidic reserve compound in nature. Synthesized by most plants from solar energy it is easily produced in very large scale cultures (cereals, tubers, legumes…). Besides its irreplaceable position in the food chain Starch is also a widely used commodity for its non-alimentary properties (paper, textile industry, adhesive, gels…) in almost all human activities. Though the polysaccharidic nature and the basic structure : poly-alpha(1,4) glucopyrannose of its minor constituent Amylose, and alpha-1,6) branched alpha-1,4-polyglucopyrannose of the major amylopectin has long been known, to date, the fine primary structure of the former still remains to be described ! The branching pattern found in amylopectin can reach extreme complexity. The determination of amylopectins' primary structures from various botanical origins families can be a real challenge. Moreover, though the enzymes involved in starch synthesis have been well-described, no satisfactory in-vitro synthesis has been achieved to date, one of the reasons invoked being the lack of proper primer substrate. In this paper we present an investigation of such structural diversity by rebuilding well-defined branched malto-oligosaccharidic model structures through chemical hemisynthesis, in order to obtain such substrates. Several isoamylase resistant, beta-branched neo-amylopectinyl oligosaccharides having degrees of polymerisation (DP) 4 to 8, with well-defined structures, were obtained. The construction of these models was performed using chemically modified malto-oligosaccharides in solution. All structures were confirmed by long distance heteronuclear NMR spectroscopy. Using activated Wang resin, solid-phase supported oligosaccharides were synthesised and the structures analysed by HR-MAS NMR

Perturbative and non-perturbative analysis of defect correlators in AdS/CFT

In dieser Arbeit betrachten wir zwei Ansätze zur Untersuchung von Korrelationsfunktionen in eindimensionalen konformen Feldtheorien mit Defekten (dCFT1), insbesondere solche, die durch 1/2-BPS-Wilson-Linien-Defekte in den drei- und vierdimensionalen superkonformen Theorien definiert sind, die für die AdS/CFT-Korrespondenz relevant sind. Zunächst verwenden wir den analytischen konformen Bootstrap, um zwei Beispiele von Defektkorrelatoren auszuwerten. Der Vier-Punkt-Korrelator des Verschiebungs-Supermultipletts, das auf der 1/2-BPS-Wilson-Linie in der ABJM-Theorie eingefügt ist, wird bis zur dritten Ordnung in einer starken Kopplungsexpansion berechnet und reproduziert die expliziten Witten-Diagramm-Berechnungen erster Ordnung. Anschließend wird der Fünf-Punkt-Korrelator von 1/2-BPS-Operatoren, die auf der 1/2-BPS-Wilson-Linie in N=4 Super-Yang-Mills eingefügt sind, untersucht und in einer starken Kopplungsexpansion bis zur ersten Ordnung gebootstrapped. Anschließend werden die CFT1-Daten extrahiert, die bestätigen, dass das Mischen von Operatoren die anomale Dimension erster Ordnung nicht beeinflusst. Der zweite Ansatz betrachtet die allgemeine Struktur von Korrelatoren in effektiven Theorien in AdS2. Es werden alle skalaren n-Punkt-Kontakt-Witten-Diagramme für externe Operatoren mit ganzzahligem konformem Gewicht berechnet. Effektive Theorien in AdS2, die durch eine Wechselwirkungslagrange mit einer beliebigen Anzahl von Ableitungen definiert sind, werden dann betrachtet und mit Hilfe eines neuen Formalismus der Mellin-Amplituden für 1d-CFTs bis zur ersten Ordnung gelöst. Schließlich wird die diskretisierte Wirkung der Cusped-Wilson-Linie als alternative Möglichkeit zur Gewinnung nicht-perturbativer Daten vorgestellt: durch die Gitterfeldtheorie.In this thesis, we consider two approaches to the study of correlation functions in one-dimensional defect Conformal Field Theories (dCFT1), in particular those defined by 1/2-BPS Wilson line defects in the three- and four-dimensional superconformal theories relevant in the AdS/CFT correspondence. In the first approach, we use the analytic conformal bootstrap to evaluate two examples of defect correlators. The four-point correlator of the displacement supermultiplet inserted on the 1/2-BPS Wilson line in ABJM theory is computed to the third order in a strong-coupling expansion and reproduces the explicit first-order Witten diagram calculations. The CFT1 data are then extracted from this correlator, and the operator mixing is solved at first order. Consequently, all-order results are derived for the part of the correlator with the highest logarithm power, uniquely determining the double-scaling limit. Then, the five-point correlator of 1/2-BPS operators inserted on the 1/2-BPS Wilson line in =4 super Yang-Mills are studied. The superblocks are derived for all channels of the OPE, and the five-point correlator is bootstrapped to first order in a strong coupling expansion. The CFT1 data are then extracted, confirming that operator mixing does not affect the first-order anomalous dimension. The second approach considers the general structure of correlators in effective theories in AdS2. All scalar n-point contact Witten diagrams for external operators of integer conformal weight are computed. Effective theories in AdS2 defined by an interaction Lagrangian with an arbitrary number of derivatives are then considered and solved to first order using a new formalism of Mellin amplitudes for 1d CFTs. Finally, the cusped Wilson line discretised action is presented as an alternative way to obtain non-perturbative data: through Lattice Field Theory

NEO-AMYLOPECTINYL MODELS SYNTHESIS OF COMPLEX BETA-BRANCHED MALTO-OLIGOSACCHARIDES IN SOLUBLE AND SOLID PHASE

International audienceStarch is the ubiquitous glucidic reserve compound in nature. Synthesized by most plants from solar energy it is easily produced in very large scale cultures (cereals, tubers, legumes…). Besides its irreplaceable position in the food chain Starch is also a widely used commodity for its non-alimentary properties (paper, textile industry, adhesive, gels…) in almost all human activities. Though the polysaccharidic nature and the basic structure : poly-alpha(1,4) glucopyrannose of its minor constituent Amylose, and alpha-1,6) branched alpha-1,4-polyglucopyrannose of the major amylopectin has long been known, to date, the fine primary structure of the former still remains to be described ! The branching pattern found in amylopectin can reach extreme complexity. The determination of amylopectins' primary structures from various botanical origins families can be a real challenge. Moreover, though the enzymes involved in starch synthesis have been well-described, no satisfactory in-vitro synthesis has been achieved to date, one of the reasons invoked being the lack of proper primer substrate. In this paper we present an investigation of such structural diversity by rebuilding well-defined branched malto-oligosaccharidic model structures through chemical hemisynthesis, in order to obtain such substrates. Several isoamylase resistant, beta-branched neo-amylopectinyl oligosaccharides having degrees of polymerisation (DP) 4 to 8, with well-defined structures, were obtained. The construction of these models was performed using chemically modified malto-oligosaccharides in solution. All structures were confirmed by long distance heteronuclear NMR spectroscopy. Using activated Wang resin, solid-phase supported oligosaccharides were synthesised and the structures analysed by HR-MAS NMR

Context Dependent Expression of Life-History Trade-Offs

Life history trade-offs are one of the central principles of life history theory and have been widely studied by evolutionary ecologists. They can be described as negative correlations between fitness related traits in organisms. For instance, the cost-of-reproduction, one of the most studied trade-offs, is depicted as a negative correlation between one organism’s survival and its reproduction. Life history trade-offs are constraints that arise from individuals needing to allocate their limited resources between different functions, such that an increase in one function will be at the expense of the other. Despite their theoretical simplicity and ubiquitousness, and despite them being the focus of much research, these allocation trade-offs are still hard to find in observational data. One reason hindering their detection is that the expression of trade-offs is likely dependent on the environmental context, something that has seldom been accounted for in past studies. As a consequence, little is known about the demographic consequences of the context dependence of trade-offs. In this dissertation, I aim to address these shortcomings by using a multifaceted approach to study context-dependent trade-offs, proposing models that explicitly account for their dependence to the environmental context. In chapter 2, I investigate a trade-off between a behavioral trait — flight initiation distance (FID) — and survival in yellow-bellied marmots. FID is a behavioral metric measuring the boldness of individuals. I employ commonly used multivariate models to explore whether bolder marmots tend to have higher or lower summer and winter survival. I did not find any fitness consequences for this behavioral trait, which seemed unrelated to the longer term survival of marmots. This highlights that either FID truly has no long term fitness effects in marmots, or that the failure to find associations could have other causes. Among others, one main reason could be that the environmental context-dependence of trade-offs should be taken into account, hence the need for new modeling approaches. In chapter 3, I repurpose a new modeling approach to estimate the context-dependence of trade-offs. This “covariance reaction norm” model is a multivariate hierarchical model that allows for the inclusion of covariates on a covariance matrix, essentially enabling the study of context-dependent phenotypic correlations. I perform a validation of this model on simulated data, highlighting that it can be used on typical individual-based demographic data. I then apply it to long term data from yellow-bellied marmots and Soay sheep as a proof-of-concept. This model has the potential to be applied to many long term dataset, and could help solve van Noordwijk and de Jong’s conundrum of invisible trade-offs. In chapter 4, following Lack’s principle and his seminal work on the significance of birds’ clutch sizes, I focus on the environmental and ecological dependence of the among-individual correlations between three traits: brood size, offspring mass, and offspring recruitment into the population in following years. I explore under which ecological contexts these reproductive trade-offs are relaxed in a population of great tits from Wytham Woods. Overall, I find that the trade-off between brood size and offspring quality is highly constrained, displaying limited dependence to the environmental context. However, I find evidence of context dependence in the correlation between offspring quality and recruitment, such that mothers producing larger offspring experience higher offspring recruitment only when conditions are unfavorable, while recruitment is not associated with offspring quality in favorable years. This work highlights the new insights that can be gained from exploring old questions with new statistical tools. In chapter 5, I develop an individual-based simulation where covariation in demographic rates varies with the environment, to study the population dynamic consequences of context-dependent trade-offs across various life histories. I find that slow life histories tend to be more affected by among-individual covariation between traits. My findings also highlight that different types of trade-offs have different effects on population stability, but these effects are mostly driven by the average trade-off strength rather than its temporal variability. Altogether, I find that changes in the expression of trade-offs can influence generation time, which ultimately affect population dynamics. In conclusion, my thesis provides a detailed exploration of life history trade-offs and their dependence to the environmental context. While the idea that trade-offs are context dependent is already well established, I provide new modeling tools to estimate the influence of environmental or ecological variables on phenotypic correlations using long term demographic data. In addition, this work also highlights the complex effects that such temporally variable trade-offs among individuals have on population dynamics. Altogether, this thesis should contribute to our understanding of life history theory, and hopefully spur further research on the context dependence of trade-offs

Perturbative and non-perturbative analysis of defect correlators in AdS/CFT

In this thesis, we consider two approaches to the study of correlation functions in one-dimensional defect Conformal Field Theories (dCFT$_1$), in particular those defined by 1/2-BPS Wilson line defects in the three- and four-dimensional superconformal theories relevant in the AdS/CFT correspondence. In the first approach, we use the analytic conformal bootstrap to evaluate two examples of defect correlators. The four-point correlator of the displacement supermultiplet inserted on the 1/2-BPS Wilson line in ABJM theory is computed to the third order in a strong-coupling expansion and reproduces the explicit first-order Witten diagram calculations. The CFT$_1$ data are then extracted from this correlator, and the operator mixing is solved at first order. Consequently, all-order results are derived for the part of the correlator with the highest logarithm power, uniquely determining the double-scaling limit. Then, the five-point correlator of $1/2$-BPS operators inserted on the 1/2-BPS Wilson line in $\mathcal{N}=4$ super Yang-Mills are studied. The superblocks are derived for all channels of the OPE, and the five-point correlator is bootstrapped to first order in a strong coupling expansion. The CFT$_1$ data are then extracted, confirming that operator mixing does not affect the first-order anomalous dimension. The second approach considers the general structure of correlators in effective theories in AdS$_2$. All scalar $n$-point contact Witten diagrams for external operators of integer conformal weight are computed. Effective theories in AdS$_2$ defined by an interaction Lagrangian with an arbitrary number of derivatives are then considered and solved to first order using a new formalism of Mellin amplitudes for 1d CFTs. Finally, the cusped Wilson line discretised action is presented as an alternative way to obtain non-perturbative data: through Lattice Field Theory.Comment: PhD Thesis: 210 pages, 27 figure