Real-time determination of laser beam quality by modal decomposition

We present a real-time method to determine the beam propagation ratio M2 of laser beams. The all-optical measurement of modal amplitudes yields M2 parameters conform to the ISO standard method. The experimental technique is simple and fast, which allows to investigate laser beams under conditions inaccessible to other methods.Comment: 8 pages, 4 figures, published in Optics Expres

Linearization of Hyperbolic Finite-Time Processes

We adapt the notion of processes to introduce an abstract framework for dynamics in finite time, i.e.\ on compact time sets. For linear finite-time processes a notion of hyperbolicity namely exponential monotonicity dichotomy (EMD) is introduced, thereby generalizing and unifying several existing approaches. We present a spectral theory for linear processes in a coherent way, based only on a logarithmic difference quotient, prove robustness of EMD with respect to a suitable (semi-)metric and provide exact perturbation bounds. Furthermore, we give a complete description of the local geometry around hyperbolic trajectories, including a direct and intrinsic proof of finite-time analogues of the local (un)stable manifold theorem and theorem of linearized asymptotic stability. As an application, we discuss our results for ordinary differential equations on a compact time-interval.Comment: 32 page

Metal and Substituent Influence on the Cytostatic Activity of Cationic Bis‐cyclometallated Iridium and Rhodium Complexes with Substituted 1,10‐Phenanthrolines as Ancillary Ligands

Synthesis and characterization of the new cyclometalated complex salts [Rh(ptpy)2(5.6‐dimethyl‐1,10‐phenanthroline)]PF6 (1a) [Rh(ptpy)2(2.9‐dimethyl‐4.7‐diphenyl‐1,10‐ phenanthroline)]PF6 (2a), [Rh(ptpy)2(5‐amino‐1,10‐phenanthroline)] PF6 (3a), and [M(ptpy)2 (pyrazino‐[2.3‐f]‐1,10‐phenanthroline)]PF6 (M = Rh, 4a; M = Ir, 4b), (ptpy = 2‐(p‐tolyl)pyridinato) are described. The molecular structures of compounds 1b and 4a in the solid state were determined by single‐crystal X‐ray diffraction. All these compounds and their already known Iridium counterparts 1b – 3b display significant cytotoxicity against human cancer cell lines MCF‐7 (human breast adenocarcinoma) and HT‐29 (colon adenocarcinoma) with IC50 values in the low micromolar range

Ru(ii)-Peptide bioconjugates with the cppH linker (cppH = 2-(2'-pyridyl)pyrimidine-4-carboxylic acid): synthesis, structural characterization, and different stereochemical features between organic and aqueous solvents

Three new Ru(ii) bioconjugates with the C-terminal hexapeptide sequence of neurotensin, RRPYIL, namely trans,cis-RuCl2(CO)2(cppH-RRPYIL-\u3baNp) (7), [Ru([9]aneS3)(cppH-RRPYIL-\u3baNp)(PTA)](Cl)2 (8), and [Ru([9]aneS3)Cl(cppH-RRPYIL-\u3baNp)]Cl (11), where cppH is the asymmetric linker 2-(2'-pyridyl)pyrimidine-4-carboxylic acid, were prepared in pure form and structurally characterized in solution. The cppH linker is capable of forming stereoisomers (i.e. linkage isomers), depending on whether the nitrogen atom ortho (No) or para (Np) to the carboxylate on C4 in the pyrimidine ring binds the metal ion. Thus, one of the aims of this work was to obtain pairs of stereoisomeric conjugates and investigate their biological (anticancer, antibacterial) activity. A thorough NMR characterization clearly indicated that in all cases exclusively Np conjugates were obtained in pure form. In addition, the NMR studies showed that, whereas in DMSO-d6 each conjugate exists as a single species, in D2O two (7) or even three if not four (8 and 11) very similar stable species form (each one corresponding to an individual compound). Similar results were observed for the cppH-RRPYIL ligand alone. Overall, the NMR findings are consistent with the occurrence of a strong intramolecular stacking interaction between the phenol ring of tyrosine and the pyridyl ring of cppH. Such stacking interactions between aromatic rings are expected to be stronger in water. This interaction leads to two stereoisomeric species in the free cppH-RRPYIL ligand and in the bioconjugate 7, and is somehow modulated by the less symmetrical Ru coordination environments in 8 and 11, affording three to four very similar species

Modeling measurement error in tumor characterization studies

<p>Abstract</p> <p>Background</p> <p>Etiologic studies of cancer increasingly use molecular features such as gene expression, DNA methylation and sequence mutation to subclassify the cancer type. In large population-based studies, the tumor tissues available for study are archival specimens that provide variable amounts of amplifiable DNA for molecular analysis. As molecular features measured from small amounts of tumor DNA are inherently noisy, we propose a novel approach to improve statistical efficiency when comparing groups of samples. We illustrate the phenomenon using the MethyLight technology, applying our proposed analysis to compare <it>MLH1 </it>DNA methylation levels in males and females studied in the Colon Cancer Family Registry.</p> <p>Results</p> <p>We introduce two methods for computing empirical weights to model heteroscedasticity that is caused by sampling variable quantities of DNA for molecular analysis. In a simulation study, we show that using these weights in a linear regression model is more powerful for identifying differentially methylated loci than standard regression analysis. The increase in power depends on the underlying relationship between variation in outcome measure and input DNA quantity in the study samples.</p> <p>Conclusions</p> <p>Tumor characteristics measured from small amounts of tumor DNA are inherently noisy. We propose a statistical analysis that accounts for the measurement error due to sampling variation of the molecular feature and show how it can improve the power to detect differential characteristics between patient groups.</p

Information Retrieval with the Help of Geographic Information Systems

Digital geo-information is already an important resource for many jobs and every day life. Through initiatives such as INSPIRE, its presence will grow even more in the years to come. Consequently, many curricula for secondary education mandate students to learn how to use geographic information systems (GIS), the key technological basis for dealing with digital geo-information. This paper reviews current research and theoretical considerations regarding the competencies needed for retrieving information with the help of GIS, as well as some of their cognitive foundations, as a basis for building a competency model.Peer Reviewe

Regionale Klimafolgen erkennen, analysieren und beurteilen – ein Beitrag zur Klimawandelbildung von Jugendlichen

KlimafolgenIm Kontext der Folgen des globalen Klimawandels rückt die Entwicklung geeigneter Anpassungsstrategien immer mehr in den Fokus. Das gilt insbesondere für die konkreten Auswirkungen des Klimawandels auf regionaler und lokaler Ebene. Ziel des in der Abteilung Geographie der Pädagogischen Hochschule Heidelberg angesiedelten Umweltbildungsprojekts „Regionalen Klimawandel beurteilen lernen – ReKli:B“ ist es daher, Jugendliche mit den Klimafolgen „vor der eigenen Haustüre“ zu konfrontieren und diese aus verschiedenen Perspektiven zu analysieren. Neben einem fundierten Verständnis kann so eine Beurteilungskompetenz der Jugendlichen auch in Bezug auf die Vor- und Nachteile unterschiedlicher Anpassungsstrategien oder auf den Umgang mit widersprüchlichen Klimainformationen gefördert werden. Den Kern des „ReKli:B“-Projekts bildet ein methodisch-didaktischer Dreiklang aus Erhebungen im Gelände, vertiefender Analyse im Labor und vereinfachender Erarbeitung einzelner Prozesse im Experiment und Modell. Hierzu dienen drei Themenfelder – Landwirtschaft, Forstwirtschaft und naturnahe Ökosysteme – mit unmittelbarem Lebensweltbezug zu den Jugendlichen. Bisherige und zukünftige Auswirkungen des Klimawandels auf Bodeneigenschaften oder Vegetationscharakteristika lassen sich so an regionalen Beispielen problem- und handlungsorientiert erkennen, analysieren und beurteilen. Im „ReKli:B“-Lernmodul zum Baumwachstum wird beispielsweise der Einfluss der sich ändernden klimatischen Bedingungen auf die Zusammensetzung der heimischen Wälder aufgezeigt, während das Modul zur Phänologie auf Veränderungen im Jahresgang der Vegetation fokussiert. Im Modul zur Bodenfruchtbarkeit wird die Rolle von Humus als Kohlenstoffspeicher thematisiert, während die systemische Betrachtung natürlicher und anthropogener Einflussfaktoren im Mittelpunkt des Moduls zur Bodenerosion steht. Die Suche nach geeigneten Anpassungsstrategien integriert schließlich im Sinne der Nachhaltigkeit jeweils ökologische, ökonomische und soziale Aspekte des Klimawandels und seiner regionalen Folgen und bildet den Rahmen für eine umfassende Förderung von individueller Handlungsbereitschaft. Die Kooperation mit fünf Stützpunktschulen und mit dem UNESCO Geo-Naturpark Bergstraße-Odenwald ist Ausgangspunkt für eine dauerhafte Verankerung der Bildungskonzepte von „ReKli:B“, die mit Hilfe von Methodenkoffern und einem mehrstufigen Fortbildungsverfahren auch über die Projektregion hinaus nutzbar gemacht werden. Ergänzt durch eine Kooperation mit dem Potsdam-Institut für Klimafolgenforschung (PIK), der Forstlichen Versuchs- und Forschungsanstalt Baden-Württemberg (FVA) sowie Landwirten, Winzern und Förstern der Region vernetzt das von der Deutschen Bundesstiftung Umwelt (DBU) geförderte Projekt seit Projektbeginn im April 2012 Umweltforscher, Umweltbildner und Umweltakteure auf vielen Ebenen

Bis‐cyclometalated Rhodium and Iridium Chloride Complexes Yield Different Products Upon Reaction With 9,10‐Diaminophenanthrene

The reaction of 9.10‐diaminophenanthrene with [{Rh(μ‐Cl)(ptpy)2}2] yields – quite unexpected – the new cyclometalated complex salts [Rh(ptpy)2(9,10‐diiminophenanthrene)]PF6 (1), whereas with the corresponding dinuclear iridium compound the “usual” [Ir(ptpy)2(9,10‐diaminophenanthrene)]PF6 (2) is obtained. The molecular structure of compound 1 was confirmed by single‐crystal X‐ray diffraction. 1 crystallized in the monoclinic space group P21/n as a dichloromethane solvate. Both compounds display significant cytotoxicity against human cancer cell lines with the IC50 values in the low micromolar range