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Search Results: 1 - 10 of 5667 matches for " Markus Thiemann "
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Liquid Etherification of Alkoxybenzyl Alcohols, Cinnamyl Alcohols and Fluorinated Phenylalkenols with Platinum on Carbon (Pt/C) and Palladium on Carbon (Pd/C)  [PDF]
Thies Thiemann
International Journal of Organic Chemistry (IJOC) , 2018, DOI: 10.4236/ijoc.2018.81005
Abstract: In the presence of either Pd/C or Pt/C, 4-alkoxybenzyl alcohols, 4-alkoxy-phenylalkyl alcohols and cinnamyl alcohols undergo liquid etherification to bis(4-alkoxybenzyl) ethers, bis[(4-alkoxybenzyl)alkyl] ethers and bis(cin-namyl) ethers at temperatures of 100°C - 135°C. In a number of cases, Pt/C and Pd/C as catalysts, also when they are doped with Ru, show distinct differences when the reactions run in air, with an oxidative dehydrogenation of the alcohols as side-reaction, yielding the corresponding ketones and aldehydes as by-products. Also, the reactivity of fluorinated phenylalkenols under these conditions has been investigated. Furthermore, the immobilization of alkyl aryl ethers on silica within a column with passage of hexane as solvent was found to lead to the formation and elution of styrenes from the column in fair yield.
Niobium stripline resonators for microwave studies on superconductors
Markus Thiemann,Daniel Bothner,Dieter Koelle,Reinhold Kleiner,Martin Dressel,Marc Scheffler
Physics , 2014, DOI: 10.1088/1742-6596/568/2/022043
Abstract: Microwave spectroscopy is a powerful experimental tool to reveal information on the intrinsic properties of superconductors. Superconducting stripline resonators, where the material under study constitutes one of the ground planes, offer a high sensitivity to investigate superconducting bulk samples. In order to improve this measurement technique, we have studied stripline resonators made of niobium, and we compare the results to lead stripline resonators. With this technique we are able to determine the temperature dependence of the complex conductivity of niobium and the energy gap $\Delta(0)=2.1$ meV. Finally we show measurements at the superconducting transition of a tantalum bulk sample using niobium stripline resonators.
Analogies for Teaching Mutant Allele Dominance Concepts  [PDF]
Rebecca L. Seipelt-Thiemann
Creative Education (CE) , 2012, DOI: 10.4236/ce.2012.326133
Abstract: Analogies connect new and familiar concepts and ideas by providing a comfortable and known framework within which students can integrate new concepts. Use of analogies to aid understanding of abstract and/or complex ideas is commonly used in molecular sciences, such as genetics, molecular biology, and biochemistry. Five analogies for different mechanisms of mutant allele dominance, a seemingly counter-intuitive idea in genetics, were designed and assessed in an upper division undergraduate/masters level course. Each of the five mechanisms, haploinsufficiency, acquired function, poison product, increased activity, and inappropriate expression, was described in the context of a human disease and molecular mechanism and followed by a descriptive analogy which mirrored the molecular mechanism using real world items or a video clip. The majority of students reported increased interest, understanding, and engagement following the analogies, as well as decreased confusion.
Hydrogenation of Alkenes with NaBH4, CH3CO2H, Pd/C in the Presence of O- and N-Benzyl Functions  [PDF]
Nuha Al Soom, Thies Thiemann
International Journal of Organic Chemistry (IJOC) , 2016, DOI: 10.4236/ijoc.2016.61001
Abstract: NaBH4, CH3CO2H, Pd/C has been described as an effective reagent system to hydrogenate alkenes. Here, we show that the hydrogenation occurs chemoselectively, making it possible to hydrogenate alkenes under Pd/C catalysis with hydrogen created in situ without O- or N-debenzylation.
Das Leben als Erz hlung. Zur Problematik biographischen Schreibens am Beispiel der spanischen Humanistin Luisa Sigea (1522–1560)
Susanne Thiemann
querelles-net , 2006,
Gegen die Macht der Determination Against the Power of Determination
Susanne Thiemann
querelles-net , 2006,
Abstract: Petra Dodell leistet eine u erst anregende und innovative Re-Lektüre der Novellen von Cervantes, Céspedes, Lugo und Zayas, die als obligatorisch für alle, die sich mit der spanischen Novellistik des Siglo de Oro auseinandersetzen, einzusch tzen ist. Ihre Herangehensweise, die ausgew hlten Texte mit dem Handwerkszeug der (Raum)-Semiotik und der Narratologie strukturell und in Bezug auf das Verh ltnis von Vermittlungsebene“ und Geschichte“ hin zu analysieren und die hiermit in enger Beziehung stehenden Frauenbildern auf ihren Grad an Dialogizit t hin zu untersuchen, führt zu einer Fülle von Einzelergebnissen, die sich nicht auf eine einzelne These reduzieren lassen. Somit erfüllt die Arbeit den Anspruch, den sie an die von ihr untersuchten Texte stellt, selbst: Sie formuliert keinen absoluten Wahrheitsanspruch, sondern schl gt eine Leseweise vor, die als erg nzend zu den bisherigen verstanden werden kann. Petra Dodell accomplishes an exceedingly stimulating and innovative rereading of novellas by Cervantes, Céspedes, Lugo, and Zayas, a study that will prove to be obligatory for all who deal with Spanish novelistic of the Siglo de Oro. She compares the chosen texts with the tools of (spatial) semiotics and structural narratology in order to examine the dialogistic relationship between the “level of mediation” and “story” as well as the closely related images of women. This approach leads to ample results that cannot be reduced to one single thesis. Thus the work fulfills the claim that it alleges based on the studied texts: It formulates no absolute claim to truth but instead suggests a reading that can be understood as supplemental to those that already exist.
A completely solvable model with an infinite number of Dirac observables for a real sector of complexified Ashtekar gravity
T. Thiemann
Physics , 1993,
Abstract: We introduce a reduced model for a real sector of complexified Ashtekar gravity that does not correspond to a subset of Einstein's gravity but for which the programme of canonical quantization can be carried out completely, both, via the reduced phase space approach or along the lines of the algebraic quantization programme.\\ This model stands in a certain correspondence to the frequently treated cylindrically symmetric waves.\\ In contrast to other models that have been looked at up to now in terms of the new variables the reduced phase space is infinite dimensional while the scalar constraint is genuinely bilinear in the momenta.\\ The infinite number of Dirac observables can be expressed in compact and explicit form in terms of the original phase space variables.\\ They turn out, as expected, to be non-local and form naturally a set of countable cardinality.
Quantum Spin Dynamics (QSD) II
T. Thiemann
Physics , 1996, DOI: 10.1088/0264-9381/15/4/012
Abstract: We continue here the analysis of the previous paper of the Wheeler-DeWitt constraint operator for four-dimensional, Lorentzian, non-perturbative, canonical vacuum quantum gravity in the continuum. In this paper we derive the complete kernel, as well as a physical inner product on it, for a non-symmetric version of the Wheeler-DeWitt operator. We then define a symmetric version of the Wheeler-DeWitt operator. For the Euclidean Wheeler-DeWitt operator as well as for the generator of the Wick transform from the Euclidean to the Lorentzian regime we prove existence of self-adjoint extensions and based on these we present a method of proof of self-adjoint extensions for the Lorentzian operator. Finally we comment on the status of the Wick rotation transform in the light of the present results.
Quantum Spin Dynamics (QSD)
T. Thiemann
Physics , 1996, DOI: 10.1088/0264-9381/15/4/011
Abstract: An anomaly-free operator corresponding to the Wheeler-DeWitt constraint of Lorentzian, four-dimensional, canonical, non-perturbative vacuum gravity is constructed in the continuum. This operator is entirely free of factor ordering singularities and can be defined in symmetric and non-symmetric form. We work in the real connection representation and obtain a well-defined quantum theory. We compute the complete solution to the Quantum Einstein Equations for the non-symmetric version of the operator and a physical inner product thereon. The action of the Wheeler-DeWitt constraint on spin-network states is by annihilating, creating and rerouting the quanta of angular momentum associated with the edges of the underlying graph while the ADM-energy is essentially diagonalized by the spin-network states. We argue that the spin-network representation is the ``non-linear Fock representation" of quantum gravity, thus justifying the term ``Quantum Spin Dynamics (QSD)".
Anomaly-free formulation of non-perturbative, four-dimensional Lorentzian quantum gravity
T. Thiemann
Physics , 1996, DOI: 10.1016/0370-2693(96)00532-1
Abstract: A Wheeler-Dewitt quantum constraint operator for four-dimensional, non-perturbative Lorentzian vacuum quantum gravity is defined in the continuum. The regulated Wheeler-DeWitt constraint operator is densely defined, does not require any renormalization and the final operator is anomaly-free and at least symmmetric. The technique introduced here can also be used to produce a couple of other completely well-defined regulated operators including but not exhausting a) the Euclidean Wheeler-DeWitt operator, b)the generator of the Wick rotation transform that maps solutions to the Euclidean Hamiltonian constraint to solutions to the Lorentzian Hamiltonian constraint, c) length operators, d) Hamiltonian operators of the matter sector and e) the generators of the asymptotic Poincar\'e group including the quantum ADM energy.
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