Some comments on jet fragmentation models andα s determinations

A number of interrelated topics on jet properties ine ⁺ e ^? annihilation is discussed. The need for differentα _s values in different fragmentation models is explained, with particular emphasis on the sensitivity to the choice of momentum conservation scheme in independent fragmentation models. Also other factors leading to a broad range of experimentalα _s values are discussed. Old and new methods to distinguish different fragmentation models are presented, with particular emphasis on gluon jet fragmentation properties.     

Noncommutative classical invariant theory

In this thesis, we consider some aspects ofnoncommutative classical invariant theory, i.e., noncommutative invariants ofthe classical group SL(2, k). We develop asymbolic method for invariants and covariants, and we use the method to compute some invariant algebras. The subspace? _d ^m of the noncommutative invariant algebra? _d consisting of homogeneous elements of degreem has the structure of a module over thesymmetric group S _m . We find the explicit decomposition into irreducible modules. As a consequence, we obtain theHilbert series of the commutative classical invariant algebras. TheCayley—Sylvester theorem and theHermite reciprocity law are studied in some detail. We consider a new power series H(? _d,t) whose coefficients are the number of irreducibleS _m -modules in the decomposition of? _d ^m , and show that it is rational. Finally, we develop some analogues of all this for covariants.     

Quantitative ultramikrospektrographische Verfahren

Zusammenfassung Die mikrochemische Untersuchung einzelner Strukturen in lebenden Zellen verlangt die Entwicklung von Gruppen spezieller Methoden. Diese Forderung ist in erster Linie durch die minimale Größe dieser Strukturen und ferner durch ihre Empfindlichkeit bedingt. Es wurden verschiedene Wege gegangen, die vor allem auf qualitative Untersuchung zielten, aber infolge technischer Schwierigkeiten doch nur begrenzten Wert haben.Nunmehr wurde versucht, wirklich quantitative Methoden für das in Frage kommende Dimensionsgebiet zu entwickeln, die sich gleichzeitig speziell für das biologische Objekt eignen sollen. Innerhalb dieses Instiutes wurde ein Programm aufgestellt, das die Ausnutzung der optischen mikrospektrographischen Methoden bis an die Grenze ihrer Möglichkeiten für Zellstrukturuntersuchung zum Ziel hat. Durch die Kombination von spektrographischem Messen in verschiedenen Wellengebieten, weitgehende Automatisierung der Meßverfahren und der Werteanalyse, sowie durch Entwicklung einer Reihe von Hilfsmethoden wurde eine Gruppe von Apparaten und Arbeitsverfahren geschaffen, die es erm oglichen, in Routinearbeit eine große Anzahl im optischen Gebiet absorbierender Substanzen mit besserer Auflösung als l in situ zu messen, Trockengewichtsbestimmungen und die Analyse gewisser Elemente innerhalb der Zellstrukturen durchzuführen.

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Summary The microchemical investigation of individual structures in living cells requires the development of groups of special methods. This requirement is conditioned primarily by the minimum size of these structures and further by their sensitivity. Various paths were followed, whose objective was qualitative study above all, but they had no more than limited value because of technical difficulties.It has now been attempted to develop really quantitative methods for the region of dimensions involved, and these should also be suitable in particular for the biological objective. A program has been set up in the writer's department with the goal of employing to the greatest possible limit the optical microspectrographic methods for studying cell structures. By combining spectrographic measurements in various wave ranges with automation of the measuring process and analysis of the data, and also by developing a series of auxiliary methods, it was possible to create a group of devices and procedures which made it possible, in routine work, to measure in situ a large number of absorbing substances in the optical range with better resolution than 1. It was also possible to make dry weight determinations and analyses of certain elements within the cell structures.

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Résumé L'étude microchimique de structures particulières dans des cellules vivantes exige la mise au point d'un groupe de méthodes spéciales. Cette exigence résulte au premier chef de la petite taille de ces structures et encore plus de leur sensibilité. On étudie plusieurs méthodes qui visent avant tout à une étude qualitative, mais qui par suite de difficultés techniques n'ont encore qu'une valeur restreinte.On a donc recherché des méthodes réellement quantitatives pour le domaine de dimensions envisagé qui puissent en même temps servir en biologie. Un programme fut établi dans cet institut avec comme but l'exploitation des méthodes de microspectrographie optique jusqu'à la limite de leurs possibilités. La juxtaposition de mesures spectrographiqu.es dans différents domaines de longueurs d'onde, une large automaticité des procédés de mesure, l'étude des résultats aussi bien que la découverte de toutes une série de méthodes auxiliaires, ont permis la mise au point d'un groupe d'appareils et de méthodes de travail. Ceux-ci permettent pour du travail de routine d'étudier in situ avec une sensibilité inférieure à 1g un grand nombre de substances opaques à la lumière visible ainsi que d'effectuerdes déterminations de poids et le dosage d'éléments à l'intérieur de la structure cellulaire.

     

A multivariate characterization of crystal transformations of cellulose

A spectroscopic study of cellulose transformation processes, such as alkali treatment and annealing, showed that, in combination with multivariate data analysis techniques, a detailed understanding of the crystalline transformation processes could be reached.¹³C cross-polarization magic-angle spinning (CPMAS) NMR and near-infrared (NIR) spectroscopy of cotton linters and softwood pulps analysed during the processing revealed information, after data reduction using principal components data analysis, that could be connected to structural changes of the cellulose polymorphs. The data showed that alkali treatment of cotton linters led to a cellulose conversion from cellulose I to II, while annealing, both for linters and pulps, yielded a transformation from I to I.     

Partition Affinity Ligand Assay (PALA)

In a competitive binding assay, the ligand to be quantified competes with a fixed amount of labeled ligand for the sites on a limiting amount of binding protein. The amount of label bound is therefore dependent on the ratio between native and labeled ligand. In a binding assay, one must separate the free ligands from bound. The better the separation, the higher the sensitivity of the assay. But effective methods are often laborious and time-consuming and thus we have developed a novel approach, the Partition Affinity Ligand Assay (PALA).     

A comparison of feasible direction methods for the stochastic transportation problem

The feasible direction method of Frank and Wolfe has been claimed to be efficient for solving the stochastic transportation problem. While this is true for very moderate accuracy requirements, substantially more efficient algorithms are otherwise diagonalized Newton and conjugate Frank–Wolfe algorithms, which we describe and evaluate. Like the Frank–Wolfe algorithm, these two algorithms take advantage of the structure of the stochastic transportation problem. We also introduce a Frank–Wolfe type algorithm with multi-dimensional search; this search procedure exploits the Cartesian product structure of the problem. Numerical results for two classic test problem sets are given. The three new methods that are considered are shown to be superior to the Frank–Wolfe method, and also to an earlier suggested heuristic acceleration of the Frank–Wolfe method.     

On the complexation of proteins and polyelectrolytes

Both natural and synthetic polyelectrolytes form strong complexes with a variety of proteins. One peculiar phenomenon is that association can take place even when the protein and the polyelectrolyte carry the same charge. This has been interpreted as if the ion-dipole interaction can overcome the repulsive ion-ion interaction. On the basis of Monte Carlo simulations and perturbation theory, we propose a different explanation for the association, namely, charge regulation. We have investigated three different protein-polymer complexes and found that the induced ionization of amino acid residues due to the polyelectrolyte leads to a surprisingly strong attractive interaction between the protein and the polymer. The extra attraction from this charge-induced charge interaction can be several kT and is for the three cases studied here, lysozyme, alpha-lactalbumin, and beta-lactoglobulin, of the same magnitude or stronger than the ion-dipole interaction. The magnitude of the induced charge is governed by a response function, the protein charge capacitance Z2-Z2. This fluctuation term can easily be calculated in a simulation or measured in a titration experiment.     

Light-driven tyrosine radical formation in a ruthenium-tyrosine complex attached to nanoparticle TiO2

We demonstrate a possibility of multistep electron transfer in a supramolecular complex adsorbed on the surface of nanocrystalline TiO(2). The complex mimics the function of the tyrosine(Z)() and chlorophyll unit P(680) in natural photosystem II (PSII). A ruthenium(II) tris(bipyridyl) complex covalently linked to a L-tyrosine ethyl ester through an amide bond was attached to the surface of nanocrystalline TiO(2) via carboxylic acid groups linked to the bpy ligands. Synthesis and characterization of this complex are described. Excitation (450 nm) of the complex promotes an electron to a metal-to-ligand charge-transfer (MLCT) excited state, from which the electron is injected into TiO(2). The photogeneration of Ru(III) is followed by an intramolecular electron transfer from tyrosine to Ru(III), regenerating the photosensitizer Ru(II) and forming the tyrosyl radical. The tyrosyl radical is formed in less than 5 micros with a yield of 15%. This rather low yield is a result of a fast back electron transfer reaction from the nanocrystalline TiO(2) to the photogenerated Ru(III).