Femtosecond photoelectron and photoion spectrometer with vacuum ultraviolet probe pulses

We describe a setup to study ultrafast dynamics in gas-phase molecules using time-resolved photoelectron and photoion spectroscopy. The vacuum ultraviolet (VUV) probe pulses are generated via strong field high-order harmonic generation from infrared femtosecond laser pulses. The band pass characteristic in transmission of thin indium (In) metal foil is exploited to isolate the $9^{\text{th}}$ harmonic of the 800 nm fundamental (H9, 14 eV, 89 nm) from all other high harmonics. The $9^{\text{th}}$ harmonic is obtained with high conversion efficiencies and has sufficient photon energy to access the complete set of valence electron levels in most molecules. The setup also allows for direct comparison of VUV single-photon probe with 800 nm multi-photon probe without influencing the delay of excitation and probe pulse or the beam geometry. We use a magnetic bottle spectrometer with high collection efficiency for electrons, serving at the same time as a time of flight spectrometer for ions. Characterization measurements on Xe reveal the spectral width of H9 to be $190\pm60$ meV and a photon flux of $\sim1\cdot10^{7}$ photons/pulse after spectral filtering. As a first application, we investigate the S$_1$ excitation of perylene using time-resolved ion spectra obtained with multi-photon probing and time-resolved electron spectra from VUV single-photon probing. The time resolution extracted from cross-correlation measurements is $65\pm10$ fs for both probing schemes and the pulse duration of H9 is found to be $35\pm8$ fs

The Influence of Light on a Three-Arm Azobenzene Star: A Computational Study

Light is one of the most advantageous stimuli to manipulate functional materials because it can be applied contactless and with high precision. A common strategy to prepare light-responsive physical systems is the embedding of photoswitchable groups such as the dye molecule azobenzene (azo). Upon irradiation with UV light, azobenzene undergoes photoisomerization from the trans to the cis isomer, whereas blue light triggers the inverse conversion. The two isomers differ with respect to their shape, solubility, and light absorption. Up to now, comparatively little research has been focusing on compounds that unite several photoswitchable groups. Such so-called multiphotochromes are promising multi-state molecular systems that can be controlled by light. In this thesis, the object of study is a star-shaped multiphotochromic molecule denoted TrisAzo. It is composed of three azo groups, which are centrally linked by a light-inert BTA group. The molecule has four photoisomers, ranging from the all-trans to the all-cis isomer. Furthermore, TrisAzo is the elementary building block of light-responsive supramolecular aggregates in solution. Previous experimental works report severe morphological changes of the aggregates under UV–Vis light but the underlying molecular mechanisms are still debated. The objective of this thesis is to elucidate the effects of light on TrisAzo – first, concerning its molecular properties and second, regarding the structure and stability of its supramolecular aggregates. In the presented work, the photoisomers of an azobenzene star with a BTA core are studied for the first time via computational methods, particularly using density functional theory and fully atomistic molecular dynamics (MD) simulations. The solvational and optical properties of TrisAzo are quantified as a function of its isomerization state. The solubility of TrisAzo in polar solvents improves with an increasing fraction of the cis-azo arms due to a redistribution of electron density. The absorption spectra of the TrisAzo isomers are nearly linear superpositions of the individual azo arm spectra but with slight deviations. These deviations indicate weak electronic coupling effects between the connected azo groups. Supramolecular aggregates of TrisAzo molecules in water are modeled using fully atomistic MD simulations for extensive investigations on the molecular scale. In equilibrium conditions, it is verified that randomly distributed TrisAzo molecules self-assemble into column-shaped stacks. Simulations of pre-assembled TrisAzo stacks provide detailed insights into their intermolecular interactions. The binding energies are dominated by π-π interactions between conjugated parts of the stacked molecules, especially the azo groups, while hydrogen bonds between the BTA cores play a subordinate but stabilizing role. To implement the effects of light into the simulations, a stochastic model of the repeated photoisomerization of azobenzene is developed. This model reproduces the photoisomerization kinetics of TrisAzo in good agreement with theory and previous experimental results. Based on this approach, light of various intensities and wavelengths is applied on an equilibrated TrisAzo stack. In contrast to prior assumptions, the simulations indicate that a stacked TrisAzo aggregate irradiated by light does not break or disassemble into separate fragments. The stack instead develops defects in the form of molecular shifts and reorientations. As a result, the aggregate eventually loses its columnar shape. The mechanism and driving forces behind these structural changes are clarified based on the simulation results. Thus, this work provides a new interpretation of the experimentally observed morphological changes. The obtained insights on the molecular scale may facilitate the design of light-responsive gels and supramolecular polymers.:Abstract v Kurzfassung vii 1 Introduction 1 2 Properties of Azobenzene and Azobenzene-Containing Materials 5 2.1 Azobenzene 5 2.1.1 Isomers and Photoisomerization 6 2.1.2 The Photostationary State 10 2.2 Multiphotochromic Molecules Based on Azobenzene 10 2.2.1 Azobenzene Stars 11 2.2.2 The Benzene-1,3,5-Tricarboxamide Linker Unit 11 3 Computational Methods and Models 15 3.1 Density Functional Theory 15 3.1.1 Functional and Basis Set 16 3.1.2 Implicit Solvation Models 17 3.1.3 Time-Dependent Density Functional Theory 17 3.2 Molecular Dynamics Simulations 18 3.2.1 All-Atom MD Simulations 18 3.2.2 Force Fields 19 4 Simulation Techniques 23 4.1 Thermodynamic Integration 23 4.1.1 Implementation in Atomistic Simulations 24 4.2 Modeling Photoisomerization in MD Simulations 27 4.2.1 Implementation of the Rotation Pathway 28 4.3 Modeling Light-Irradiated Azo-Materials in MD Simulations 30 4.3.1 The Cyclic Photoisomerization Model 31 5 Photoisomers of an Azobenzene Star 35 5.1 Object of Study: The Molecule TrisAzo 35 5.1.1 Isomers and Conformers 35 5.2 Ground State Properties in the Gas Phase and in Solvents 36 5.2.1 Energies and Standard Enthalpies of Formation 37 5.2.2 Geometry and Shape Properties 38 5.2.3 Dipole Moments 42 5.2.4 Molecular Properties Upon Hydration in Explicit Water 44 5.3 Solubility 47 5.3.1 Influence of Solvent Polarity 48 5.3.2 Influence of Isomerization State 48 5.3.3 Hydration Free Energy 49 5.4 Absorption Spectra and Intramolecular Coupling 51 5.4.1 Influence of the Number of Azo Groups and Their Isomerization State 52 5.4.2 Effect of the Solvent Polarity 54 5.5 Summary 56 6 Equilibrium Properties of TrisAzo Clusters 59 6.1 Supramolecules of Azobenzene Stars in the Experiment 60 6.1.1 Light-Induced Morphological Transition 60 6.2 Self-Assembly Starting from a Random Distribution 62 6.2.1 Radial Distribution Function 63 6.2.2 Cluster Analysis 65 6.3 Intermolecular Energy of a TrisAzo Dimer 69 6.3.1 Total Intermolecular Energy 70 6.3.2 Energy Decomposition 71 6.4 Structural Properties of Columnar TrisAzo Clusters 75 6.4.1 Considered Cluster Arrangements (Cluster Types) 75 6.4.2 Inner Structure of the Clusters 79 6.4.3 Effect of Cluster Size 79 6.5 Intermolecular Energy of Columnar TrisAzo Clusters 82 6.5.1 Total Intermolecular Energy 82 6.5.2 Energy Decomposition 83 6.5.3 The Role of Hydrogen Bonding 88 6.5.4 Rationalizing the Structural Differences of the Considered Cluster Types 91 6.6 Summary 93 7 Columnar TrisAzo Clusters Under UV–Vis Light 97 7.1 TrisAzo Stacks in the Full Photoisomerization Model 97 7.1.1 Cluster Structure Before and After Irradiation 98 7.1.2 Intermolecular Energy 101 7.2 TrisAzo Stacks in the Cyclic Photosomerization Model 104 7.2.1 Photoisomerization Kinetics 104 7.2.2 Cluster Structure Under Irradiation 108 7.2.3 Intermolecular Energy of TrisAzo Stacks Under Irradiation 112 7.2.4 Mechanism of Defect Formation 116 7.2.5 Comparison with Simulations of Comparable Systems 118 7.3 Summary 118 8 Summary and Outlook 121 8.1 Summary 121 8.2 Outlook 123 A Functional Form of the Force Fields 125 A.1 DREIDING Force Field 125 A.2 Polymer Consistent Force Field (PCFF) 129 B Additional Details about Thermodynamic Integration 133 B.1 Derivation of the Formalism 133 B.2 Avoiding Singularities and Instabilities 134 C Details of the Computational Models 137 C.1 DFT and TD-DFT Calculations 137 C.1.1 DFT Calculations 137 C.1.2 TD-DFT Calculations 138 C.2 MD Simulations of TrisAzo Molecules in PCFF 138 C.2.1 Parametrization 139 C.2.2 Preparation of Initial Configurations 139 C.2.3 Simulation Settings 140 C.3 MD Simulations of TrisAzo Molecules in DREIDING 140 C.3.1 Parametrization 141 C.3.2 Preparation of Initial Configurations 141 C.3.3 Simulation Settings 141 C.4 Intermolecular Energy Calculations of TrisAzo Dimers in PCFF and DREIDING 142 C.5 Visualization of Molecular Structures 142 D Equilibrium Properties of TrisAzo Clusters: Additional Material 143 D.1 From Experiments to Simulations 143 D.2 Cluster Analysis for TrisAzo Self-Assembly: Additional Material 144 D.3 Intermolecular Energy of a TrisAzo Dimer: PCFF Results 145 D.3.1 Total Intermolecular Energy 145 D.3.2 Energy Decomposition 145 D.3.3 Estimated Total Intermolecular Energy of TrisAzo-H 148 D.4 Structural Properties of Columnar TrisAzo Clusters: Additional Material 149 D.5 Intermolecular Energy of Columnar TrisAzo Clusters: Additional Material 150 D.5.1 Defect Detection Algorithm 151 D.6 The Role of Hydrogen Bonds: Additional Material 152 E Columnar TrisAzo Clusters Under UV–Vis Light: Additional Material 155 E.1 TrisAzo Stacks in the Full Photoisomerization Model: Additional Material 155 E.2 TrisAzo Stacks in the Cyclic Photosomerization Model: Additional Material 156 F Code Availability 161 Bibliography 163 List of Publications 183 Copyright of Published Articles 187 Acknowledgements / Danksagung 189 List of Abbreviations 191 List of Symbols 193 List of Physical Constants and Unit Conversions 195 Eidesstattliche Erklärung 197Licht ist einer der vorteilhaftesten Stimuli für die Manipulation responsiver Funktionsmaterialien, da es berührungslos und mit hoher Präzision angewendet werden kann. Ein weit verbreiteter Ansatz zur Herstellung lichtresponsiver physikalische Systeme ist der Einbau lichtschaltbarer Gruppen wie das Farbstoffmolekül Azobenzol (Azo). Unter UV-Licht vollzieht Azobenzol eine Photoisomerisation vom trans- zum cis-Isomer, während blaues Licht die umgekehrte Umwandlung auslöst. Die beiden Isomere unterscheiden sich vor allem durch ihre räumliche Gestalt, Löslichkeit und Lichtabsorption. Noch unzureichend erforscht sind Moleküle, die mehrere lichtschaltbare Gruppen in sich vereinen. Solche sogenannten Multiphotochrome sind vielversprechende molekulare Mehrzustandssysteme, die durch Licht geschaltet werden können. Untersuchungsobjekt dieser Arbeit ist ein sternförmiges multiphotochromes Molekül namens TrisAzo. Es besteht aus drei Azogruppen, die zentral über eine gegenüber Licht inerte BTA-Gruppe verknüpft sind. Dementsprechend existieren vier Photoisomere dieses Moleküls, vom all-trans- bis zum all-cis-Isomer. Des Weiteren ist TrisAzo der elementare Baustein lichtempfindlicher supramolekularer Aggregate in Lösung. Frühere experimentelle Arbeiten berichten starke morphologische Strukturänderungen der Aggregate unter Lichteinfluss, jedoch sind die zugrundeliegenden molekularen Mechanismen bisher ungeklärt. Ziel dieser Arbeit ist es, die Auswirkungen von Licht auf TrisAzo aufzuklären, erstens in Bezug auf dessen molekulare Eigenschaften und zweitens hinsichtlich der Struktur und Stabilität der supramolekularen Aggregate. In der vorgestellten Arbeit werden erstmals die Photoisomere eines Azosterns mit BTA-Kern auf Basis computerbasierter Methoden untersucht. Eingesetzt werden dabei Dichtefunktionaltheorie und atomistische Molekulardynamiksimulationen (MD). Insbesondere wird die Löslichkeit und das Lichtabsorptionsverhalten von TrisAzo in Abhängigkeit seines Isomerisationszustands analysiert. Die Löslichkeit von TrisAzo verbessert sich mit steigendem Anteil der cis-Azogruppen aufgrund einer damit einhergehenden Umverteilung der Elektronendichte. Die Absorptionsspektren der TrisAzo-Isomere sind in erster Näherung lineare Superpositionen der Einzelspektren jedes Molekülarms, jedoch mit geringen Abweichungen. Diese Abweichungen deuten auf schwache elektronische Kopplungseffekte zwischen den Azogruppen hin. Supramolekularen Aggregate von TrisAzo-Molekülen in Wasser werden für umfangreiche Untersuchungen auf molekularer Ebene in atomistischen MD-Simulationen modelliert. Im thermodynamischen Gleichgewicht bestätigt sich, dass sich zufällig verteilte TrisAzo-Moleküle in säulenförmig gestapelten Aggregaten zusammenfinden. Weitere Simulationen vorgestapelter TrisAzo-Aggregate liefern detaillierte Rückschlüsse auf deren intermolekulare Wechselwirkungen. Die Bindungsenergien werden von π-π-Wechselwirkungen zwischen den konjugierten Bereichen der aufeinanderliegenden Moleküle dominiert. Wasserstoffbrücken zwischen den BTA-Gruppen haben eine untergeordnete, aber stabilisierende Rolle. Um den Effekt von Licht in die Simulationen einzubauen, ist ein stochastisches Modell für die wiederholte Photoisomerisation der Azogruppen entwickelt worden. Dieses Modell reproduziert die Photoisomerisationskinetik von TrisAzo in guter Übereinstimmung mit Theorie und vorigen Experimenten. Basierend auf diesem Ansatz wird Licht verschiedener Intensitäten und Wellenlängen auf die gestapelten TrisAzo-Aggregate angewandt. Entgegen früherer Annahmen zerfallen die Aggregate daraufhin nicht in Einzelfragmente. Stattdessen entwickeln sie Defekte in Form von Molekülumordnungen sowie -reorientierungen und verlieren dadurch ihre säulenartige Form. Der Mechanismus und die Ursachen dieser Strukturänderungen werden anhand der Simulationen aufgeklärt. Damit liefert diese Arbeit eine neue Interpretation der experimentell beobachteten morphologischen Veränderungen. Die gewonnenen Erkenntnisse können die Entwicklung lichtresponsiver Gele und supramolekularer Polymere unterstützen.:Abstract v Kurzfassung vii 1 Introduction 1 2 Properties of Azobenzene and Azobenzene-Containing Materials 5 2.1 Azobenzene 5 2.1.1 Isomers and Photoisomerization 6 2.1.2 The Photostationary State 10 2.2 Multiphotochromic Molecules Based on Azobenzene 10 2.2.1 Azobenzene Stars 11 2.2.2 The Benzene-1,3,5-Tricarboxamide Linker Unit 11 3 Computational Methods and Models 15 3.1 Density Functional Theory 15 3.1.1 Functional and Basis Set 16 3.1.2 Implicit Solvation Models 17 3.1.3 Time-Dependent Density Functional Theory 17 3.2 Molecular Dynamics Simulations 18 3.2.1 All-Atom MD Simulations 18 3.2.2 Force Fields 19 4 Simulation Techniques 23 4.1 Thermodynamic Integration 23 4.1.1 Implementation in Atomistic Simulations 24 4.2 Modeling Photoisomerization in MD Simulations 27 4.2.1 Implementation of the Rotation Pathway 28 4.3 Modeling Light-Irradiated Azo-Materials in MD Simulations 30 4.3.1 The Cyclic Photoisomerization Model 31 5 Photoisomers of an Azobenzene Star 35 5.1 Object of Study: The Molecule TrisAzo 35 5.1.1 Isomers and Conformers 35 5.2 Ground State Properties in the Gas Phase and in Solvents 36 5.2.1 Energies and Standard Enthalpies of Formation 37 5.2.2 Geometry and Shape Properties 38 5.2.3 Dipole Moments 42 5.2.4 Molecular Properties Upon Hydration in Explicit Water 44 5.3 Solubility 47 5.3.1 Influence of Solvent Polarity 48 5.3.2 Influence of Isomerization State 48 5.3.3 Hydration Free Energy 49 5.4 Absorption Spectra and Intramolecular Coupling 51 5.4.1 Influence of the Number of Azo Groups and Their Isomerization State 52 5.4.2 Effect of the Solvent Polarity 54 5.5 Summary 56 6 Equilibrium Properties of TrisAzo Clusters 59 6.1 Supramolecules of Azobenzene Stars in the Experiment 60 6.1.1 Light-Induced Morphological Transition 60 6.2 Self-Assembly Starting from a Random Distribution 62 6.2.1 Radial Distribution Function 63 6.2.2 Cluster Analysis 65 6.3 Intermolecular Energy of a TrisAzo Dimer 69 6.3.1 Total Intermolecular Energy 70 6.3.2 Energy Decomposition 71 6.4 Structural Properties of Columnar TrisAzo Clusters 75 6.4.1 Considered Cluster Arrangements (Cluster Types) 75 6.4.2 Inner Structure of the Clusters 79 6.4.3 Effect of Cluster Size 79 6.5 Intermolecular Energy of Columnar TrisAzo Clusters 82 6.5.1 Total Intermolecular Energy 82 6.5.2 Energy Decomposition 83 6.5.3 The Role of Hydrogen Bonding 88 6.5.4 Rationalizing the Structural Differences of the Considered Cluster Types 91 6.6 Summary 93 7 Columnar TrisAzo Clusters Under UV–Vis Light 97 7.1 TrisAzo Stacks in the Full Photoisomerization Model 97 7.1.1 Cluster Structure Before and After Irradiation 98 7.1.2 Intermolecular Energy 101 7.2 TrisAzo Stacks in the Cyclic Photosomerization Model 104 7.2.1 Photoisomerization Kinetics 104 7.2.2 Cluster Structure Under Irradiation 108 7.2.3 Intermolecular Energy of TrisAzo Stacks Under Irradiation 112 7.2.4 Mechanism of Defect Formation 116 7.2.5 Comparison with Simulations of Comparable Systems 118 7.3 Summary 118 8 Summary and Outlook 121 8.1 Summary 121 8.2 Outlook 123 A Functional Form of the Force Fields 125 A.1 DREIDING Force Field 125 A.2 Polymer Consistent Force Field (PCFF) 129 B Additional Details about Thermodynamic Integration 133 B.1 Derivation of the Formalism 133 B.2 Avoiding Singularities and Instabilities 134 C Details of the Computational Models 137 C.1 DFT and TD-DFT Calculations 137 C.1.1 DFT Calculations 137 C.1.2 TD-DFT Calculations 138 C.2 MD Simulations of TrisAzo Molecules in PCFF 138 C.2.1 Parametrization 139 C.2.2 Preparation of Initial Configurations 139 C.2.3 Simulation Settings 140 C.3 MD Simulations of TrisAzo Molecules in DREIDING 140 C.3.1 Parametrization 141 C.3.2 Preparation of Initial Configurations 141 C.3.3 Simulation Settings 141 C.4 Intermolecular Energy Calculations of TrisAzo Dimers in PCFF and DREIDING 142 C.5 Visualization of Molecular Structures 142 D Equilibrium Properties of TrisAzo Clusters: Additional Material 143 D.1 From Experiments to Simulations 143 D.2 Cluster Analysis for TrisAzo Self-Assembly: Additional Material 144 D.3 Intermolecular Energy of a TrisAzo Dimer: PCFF Results 145 D.3.1 Total Intermolecular Energy 145 D.3.2 Energy Decomposition 145 D.3.3 Estimated Total Intermolecular Energy of TrisAzo-H 148 D.4 Structural Properties of Columnar TrisAzo Clusters: Additional Material 149 D.5 Intermolecular Energy of Columnar TrisAzo Clusters: Additional Material 150 D.5.1 Defect Detection Algorithm 151 D.6 The Role of Hydrogen Bonds: Additional Material 152 E Columnar TrisAzo Clusters Under UV–Vis Light: Additional Material 155 E.1 TrisAzo Stacks in the Full Photoisomerization Model: Additional Material 155 E.2 TrisAzo Stacks in the Cyclic Photosomerization Model: Additional Material 156 F Code Availability 161 Bibliography 163 List of Publications 183 Copyright of Published Articles 187 Acknowledgements / Danksagung 189 List of Abbreviations 191 List of Symbols 193 List of Physical Constants and Unit Conversions 195 Eidesstattliche Erklärung 19

Laurentius Valla and the Donation of Constantine

Generally, historians refer to Laurentius Valla, or Lorenzo Valla, or just plain Laurentius with a line or two and then dismiss his real significance. Quite evidently there is more to the man Valla, than a mere sentence of praise or condemnation. He must have done something to earn for himself the title as the greatest critic of his age, as a forerunner of the Lutheran \u27heresy’, as the first scientific critical historian. He was not just an ordinary person, if be received the praise of a Luther and an Erasmus. This readily becomes apparent, even inspite of the limited character of this study, when we look into the writings of his contemporaries and into his own writings and there find revealed a picture of his fame. The treatise of Valla on the Donation of Constantine is perhaps his greatest single achievement and it gives one a better understanding of his great courage, of his marvelous ability and of his personality and character. The presentation of these impressions is the subject matter of this investigation

Nitrogen availability and retention in clayey steppe soils of semi-arid North Kazakhstan

Obwohl Stickstoff (N) das am häufigsten vorkommende Element auf der Erde ist, ist es für die meisten Organismen in terrestrischen Systemen das doch am wenigsten verfügbare. Steppen-Böden der nördlichen Hemisphäre spielen global eine sehr wichtige Rolle, da sie große Mengen N in Form organischer Bodensubstanz (SOM) speichern. Eben wegen ihrer hohen potentiellen Fruchtbarkeit sind diese Böden weitreichend unter intensiver landwirtschaftlicher Nutzung, welche die Verfügbarkeit von Nährelementen stark beeinflusst. Besonders die als globaler Brotkorb fungierenden semi-ariden Steppen-Böden Nord Kasachstans wurden während der „Neulandkampagne“ nicht nachhaltig bearbeitet, mit Bodendegradation und einer Verringerung der Produktivität als Folge. Jedoch fehlen bisher weiter Informationen über den N Kreislauf und die N Verfügbarkeit in diese Ton-reichen, landwirtschaftlich genutzten semi-ariden Steppe-Böden. Daher zielt diese Arbeit darauf ab, (i) die Verfügbarkeit und Retention von N unter der aktuell üblichen landwirtschaftlichen Praxis zu untersuchen, und (ii) zu testen, ob mit geringfügigen und Kosten-beschränkten Änderungen hin zu einer Klima-adaptierten und nachhaltigeren landwirtschaftlichen Praxis, die N Verfügbarkeit gesteigert werden kann. Hierzu wurden drei Experimente mit Böden von fünf Standorten in Nord Kasachstan durchgeführt. Die erste Labor-Studie untersuchte die brutto N Mineralisation und biotische sowie abiotische Retention von Dünger N im Frühjahr in Grassland- und Acker-Böden. Im zweiten in vitro Experiment wurden Grassland- und Acker-Böden verschiedenen Klima- Szenarien ausgesetzt um den Effekt des Klimawandels auf die N Verfügbarkeit zu untersuchen (netto N Mineralisation). Und schließlich wurde im dritten Experiment der Effekt von Dünger- und Bodenbearbeitungs-Form auf die Pflanze-Mikroorganismen Konkurrenz um verfügbares N im Feld getestet. Unsere Ergebnisse zeigen ähnliche Raten für die brutto N Mineralisation und Immobilisation auf, welches in einer geringen netto N Mineralisation resultiert und lassen somit eine geringe natürliche N Verfügbarkeit unter der aktuell üblichen landwirtschaftlichen Praxis schließen. Landnutzung, Düngung, oder Veränderungen in Temperatur und Bodenfeuchte hatten keinen Einfluss auf die Verfügbarkeit von N. Ein Umstieg der Düngerform erhöhte weder die Pflanzenproduktivität noch die N Aufnahme von Pflanzen. Unsere Ergebnisse lassen weiter vermuten, dass eine reduzierte keiner Bodenbearbeitung in diesen Ton-reichen semi-ariden Böden vorzuziehen sein könnte. Die Gehalte anorganischer N Formen in diesen tonreichen und semi-ariden Böden ist stark limitiert und kann der starken abiotischen Retention von N zugeordnet werden. Daher ist die Konkurrenz für das begrenzt verfügbare anorganische N in diesen Böden hoch. Stickstoff wird effektiv im System Boden-Pflanze gehalten. Dennoch ist die Verfügbarkeit an anorganischen N für Pflanzen stark durch abiotische Retentions-Prozesse limitiert welche die Bodenfruchtbarkeit gefährden. Eine an die spezifischen Charakteristika dieser Ton-reichen, semi-ariden Böden adaptierte N Düngung ist notwendig um die Produktivität und Nachhaltigkeit der Weizen Produktion in diesem globalen Brotkorb in Zukunft aufrecht zu erhalten.Though nitrogen (N) is the most abundant element on earth, it is the least available for most organisms in terrestrial systems. Northern hemisphere steppe soils are globally very important as they store huge amounts of N as soil organic matter (SOM). Because of their potential high fertility, these soils are widely under intensive agricultural use which strongly affected nutrient availability. Especially in the semi-arid steppe soils of North Kazakhstan, which serve as a global bread basket, soils were unsustainable managed during the “Virgin Land Campaign”, resulting in soil degradation, low contents of mineral N and a decreasing productivity. However, there is yet a lack of information on the N cycle and its availability in these clayey, semi-arid agricultural used steppe soils. Therefore this thesis aimed at (i) investigating the N availability and retention of N under the current common agricultural practice, and (ii) tested if with slight and cost-limited changes towards a climate adapted and more sustainable agricultural practice, N availability can be increased. Therefore, three experiments were conducted with soil samples from North Kazakhstan. The first laboratory study investigated the gross N mineralization and biotic and abiotic retention of fertilizer N in grassland and arable soil in spring time. In the second in vitro study, grassland and arable soils were subjected to different climatic scenarios to investigate the effect of climate change on the N availability (net N mineralization). And lastly, the third study aimed at testing the effect of fertilizer and tillage form on the plant-microorganism competition for available N in the field. Our results suggest similar rates of gross N mineralization and immobilization which results in low net N mineralization and hence low natural N availability under the current agricultural practice. Land use, fertilization or changes in temperature and soil moisture did not affect N availability. A transition of fertilizer form did not enhance plant productivity and plant N uptake. But our results suggest that reduced soil tillage might be favorable over no tillage in these clayey and semi-arid soils. Contents of inorganic N forms are strongly limited in these clay-rich semi-arid soils and attributed to strong abiotic N retention processes. Hence, competition for limited inorganic N in these soils is severe. Nitrogen is effectively kept in the soil-plant system; however the availability of inorganic N is strongly limited by abiotic N retention processes, which jeopardize soil fertility. Nitrogen fertilization adapted to the specific characteristics of these clay-rich semi-arid soils is necessary to ensure productive and sustainable wheat production in this global bread basked in the future.BMBF/Client II - ReKKS/FKZ 01LZ1704A/E

Tehnika i taktika odbojke na pijesku: usporedba karakteristika igre muškaraca i žena

The aim of the study was to compare the playing characteristics of male and female athletes in professional beach volleyball. Video material, including 15 matches from the women’s and 14 matches from the men’s Grand Slam in Klagenfurt 2005, was analysed with the game analysis software “Statshot”. Applied technique, position, quality, direction and movement behaviour of athletes were evaluated. By analysing every action of the six basic beach volleyball elements - serve, reception, setting, attack, block and defence - it was possible to gain complete game statistics. The comparison indicated that male and female top players apply different techniques for success. Chi-square tests were used to evaluate significant differences between genders. The differences in distributions of applied techniques were significant for all six elements: service (p<.01), reception (p<.05), setting (p<.01), attack (p<.01), block (p<.01) and defence (p<.01). Concerning quality distribution, statistical significance was found only within the elements serve and attack. Tactical considerations and gender-specific differences in anthropometry and physiology may be reasons for the different approaches.Uvod Dosadašnja istraživanja u odbojci na pijesku orijentirala su se na utvrđivanje razlika između pobjedničkih i poraženih ekipa, na učinke promjena pravila igre i opće karakteristike igre (vremensku strukturu, tehniku, taktiku i fizičke zahtjeve). Razlike u igri između muškaraca i žena mogle su se vidjeti u tim istraživanjima, ali nisu bile identificirane. Cilj je ovog istraživanja fokusirati se upravo na spolne razlike u igri profesionalnih igrača i igračica odbojke na pijesku. Pretpostavka za istraživanje bila je da će se razlike u antropometrijskim karakteristikama i fizičkim sposobnostima između dva spola, kao i visina mreže (2.24 za žene i 2.43 m za muškarce) na igralištu istih dimenzija (8 x 16 m) odraziti i na samu igru. Metode Video materijal, koji je uključivao 15 susreta sa ženskog i 14 susreta s muškog turnira Grand Slam u Klagenfurtu, održanom 2005. godine, analiziran je programom za analizu igre pod nazivom "Statshot". Kamera je bila postavljena oko 9 m iza osnovne linije i 7 m iznad terena. Vrednovale su se korištene tehnike, pozicije, kvaliteta izvedbe te smjer i način kretanja sportaša i sportašica. Analizom akcija svakog od šest osnovnih elemenata odbojke na pijesku: servisa, prijema, dizanja, napada, blokiranja i obrane bilo je moguće dobiti kompletnu statistiku igre. Ukupno su kod muškaraca analizirane 7393 akcije, dok je kod žena analizirano ukupno 7776 akcija. Kvaliteta izvedbe svakog elementa bila je procijenjena skalom od 4 ocjene. Kvalitetni igrači odbojke na pijesku, osposobljeni za rad s programom, vrednovali su kvalitetu izvedbe. Pouzdanost i objektivnost mjernog instrumenta procijenjeni su na uzorku od 100 akcija putem Scottova p-koeficijenta, a iznosili su .93, odnosno .90. Detaljan opis testova može se vidjeti u Tilp i sur., 2006. Rezultati Usporedba je pokazala kako se muški i ženski vrhunski igrači odbojke na pijesku razlikuju po primjeni tehničkih elementa u igri. Za utvrđivanje značajnosti razlika između spolova u primjeni tehničkih elemenata koristio se hi-kvadrat test. Razlike u distribucijama primijenjenih tehničkih elemenata bile su značajne za 6 elemenata: servis (p<.01), primanje (p<.05), dizanje (p<.01), napad (p<.01), blok (p<.01) i obrana (p<.01). Statistička značajnost razlika u kvaliteti izvedbe pojedinih elemenata utvrđena je samo u varijablama servis i napad. Rezultati su pokazali da muškarci i žene preferiraju različite tehničke elemente za početak poena. Približno polovina (47%) svih analiziranih servisa u muškoj konkurenciji bili su skok servisi. Naprotiv, u ženskoj konkurenciji zabilježeno je 48% ravnih servisa bez skoka, iako je skok servis zabilježen kao najuspješniji servis i u muškaraca i u žena u smislu izravnog poena (muškarci 5% i žene 9%). Rezultati ovog istraživanja pokazuju da su tehnike prijema podjednako kvantitativno raspoređene i u muškaraca i u žena. I jedni i drugi uspješno su izveli više od 50% prijema lopte (žene 55% i muškarci 60%). Velika razlika zabilježena je u tehničkim elementima koji pripadaju pripremi poena. Muškarci se koriste tehnikom dizanja čekićem i vršnom tehnikom u jednakom omjeru (46% svaki), dok je žene ipak preferiraju tehnike dizanja čekićem (84%) u odnosu na vršnu tehniku (9%). Analizom faze napada potvrđeni su očekivani rezultati da muškarci vole završavati napade smečiranjem (59%). Dok je u muškoj konkurenciji odigrano 41% plasiranih udaraca, u ženskoj je konkurenciji zabilježeno 50% plasiranih udaraca i 50% smečeva. Distribucija kvalitete za fazu napada pokazala je statistički značajnu razliku između muškaraca i žena (p<.01). Strategiju bloka u muškaraca karakterizira 88% dinamičnih akcija na mreži, dok se žene odmiču od mreže u 27% zabilježenih situacija u bloku te zauzimaju obrambenu poziciju duboko u samom terenu. Zabilježeno je i da su odbojkašice uspješno obranile više napada koji su izvedeni plasiranjem (46%) dok su se manje morale braniti od napada smečiranjem (35%). Takva razlika u uspješnosti u fazi obrane nije vidljiva i u odbojkaša koji su podjednako uspješno branili napade plasiranjem (38%) i napade smečiranjem (40%). Diskusija i zaključci Rezultati ovog istraživanja pokazuju da žene koriste drugačiju strategiju igre nego muškarci, profesionalne igračice i igrači u međunarodnoj odbojci na pijesku. Razlike su osobito naglašene u kvantitativnoj distribuciji korištenih tehničkih elemenata. Najveća razlike između spolova zabilježena je u omjeru dizanja izvedenih vršnom tehniko, koji su muškarci koristili 46%, a žene 9% u fazi postavljanja napada. Ovaj rezultat je vrlo zanimljiv i zapanjujući budući da su odbojkaški stručnjaci uvjereni da je ova tehnika odigravanja najpreciznija. Zanimljiv je i podatak da odbojkašice kad izvode početni udarac, izvode tek 20% skok-servisa iako njime postižu više izravnih bodova, u čemu su identične s odbojkašima. Razlozi različitih pristupa igri vjerojatno leže u taktičkim zamislima te spolnim razlikama koje se očituju u antropometriji i fiziologiji odbojkašica i odbojkaša. Budućim istraživanjima potrebno je utvrditi razloge i motiviranost za takav način ponašanja u igri

Customer Ranking Model for Project Businesses: A Case Study from the Automotive Industry

For technology-orientated enterprises that operate project-based businesses, the goal-oriented allocation of scarce marketing resources has great potential to help consolidate their competitive position. An important precondition for goal-oriented management is the identification of the most valuable customers. This enables technology-orientated enterprises to segment markets in order to make tactical marketing decisions. This theory-based paper aims to develop and test a holistic customer ranking model. By deploying the five steps presented in this paper, customer relationship managers are better able to identify and to rank their customers in project-based businesses. A case study provides an example of the application of the method from the automotive industry in Austria. The experiences derived from this case study show that using a customer ranking framework is a crucial factor for enterprises in narrow technology markets to be successful and to achieve their corporate goals

Temperature and food quantity effects on the harpacticoid copepod Nitocra spinipes : combining in vivo bioassays with population modeling

The harpacticoid copepod Nitocra spinipes has become a popular model species for toxicity testing over the past few decades. However, the combined influence of temperature and food shortage, two climate change-related stressors, has never been assessed in this species. Consequently, effects of three temperatures (15, 20 and 25˚C) and six food regimes (between 0 and 5 × 10^5 algal cells/mL) on the life cycle of N. spinipes were examined in this study. Similarly to other copepod species, development times and brood sizes decreased with rising temperatures. Mortality was lowest in the 20˚C temperature setup, indicating a close-by temperature optimum for this species. Decreasing food concentrations led to increased development times, higher mortality and a reduction in brood size. A sex ratio shift toward more females per male was observed for increasing temperatures, while no significant relationship with food concentration was found. Temperature and food functions for each endpoint were integrated into an existing individual-based population model for N. spinipes which in the future may serve as an extrapolation tool in environmental risk assessment. The model was able to accurately reproduce the experimental data in subsequent verification simulations. We suggest that temperature, food shortage, and potentially other climate change-related stressors should be considered in environmental risk assessment of chemicals to account for non-optimal exposure conditions that may occur in the field. Furthermore, we advocate combining in vivo bioassays with population modeling as a cost effective higher tier approach to assess such considerations

Image-based window detection: an overview

Automated segmentation of buildings’ façade and detection of its elements is of high relevance in various fields of research as it, e. g., reduces the effort of 3 D reconstructing existing buildings and even entire cities or may be used for navigation and localization tasks. In recent years, several approaches were made concerning this issue. These can be mainly classified by their input data which are either images or 3 D point clouds. This paper provides a survey of image-based approaches. Particularly, this paper focuses on window detection and therefore groups related papers into the three major detection strategies. We juxtapose grammar based methods, pattern recognition and machine learning and contrast them referring to their generality of application. As we found out machine learning approaches seem most promising for window detection on generic façades and thus we will pursue these in future work