Photosynthetic acclimation of <i>Symbiodinium</i> <i>in hospite</i> depends on vertical position in the tissue of the scleractinian coral <i>Montastrea curta</i>

Coral photophysiology has been studied intensively from the colony scale down to the scale of single fluorescent pigment granules as light is one of the key determinants for coral health. We studied the photophysiology of the oral and aboral symbiont band of scleractinian coral Montastrea curta to investigate if different acclimation to light exist in hospite on a polyp scale. By combined use of electrochemical and fiber-optic microsensors for O(2), scalar irradiance and variable chlorophyll fluorescence, we could characterize the physical and chemical microenvironment experienced by the symbionts and, for the first time, estimate effective quantum yields of PSII photochemistry and rates of electron transport at the position of the zooxanthellae corrected for the in-tissue gradient of scalar irradiance. The oral- and aboral Symbiodinium layers received ∼71% and ∼33% of surface scalar irradiance, respectively, and the two symbiont layers experience considerable differences in light exposure. Rates of gross photosynthesis did not differ markedly between the oral- and aboral layer and curves of PSII electron transport rates corrected for scalar irradiance in hospite, showed that the light use efficiency under sub-saturating light conditions were similar between the two layers. However, the aboral Symbiodinium band did not experience photosynthetic saturation, even at the highest investigated irradiance where the oral layer was clearly saturated. We thus found a different light acclimation response for the oral and aboral symbiont bands in hospite, and discuss whether such response could be shaped by spectral shifts caused by tissue gradients of scalar irradiance. Based on our experimental finding, combined with previous knowledge, we present a conceptual model on the photophysiology of Symbiodinium residing inside living coral tissue under natural gradients of light and chemical parameters

An investigation into the relevance of flexibility- and interoperability requirements for implementation processes for workflow-management-applications

Flexibility and Interoperability have become important characteristics for organisations and their business processes. The need to control flexible business processes within an organisation’s boundaries and between organisations imposes major requirements on a company’s process control capabilities. Workflow Management Systems (WFMS) try to fulfil these requirements by offering respective product features. Evidence suggests that the achievement of flexible business processes and an inter-organisational process control is also influenced by implementation processes for Workflow Management Applications (WFMA). [A WFMA comprises the WFMS and "all WFMS specific data with regard to one or more business processes" [VER01]]. The impact of a WFMA implementation methodology on the fulfilment of these requirements is the research scope of the project. The thesis provides knowledge in the following areas: 1. Review of the relationship between workflow management and the claim for process flexibility respectively -interoperability. 2. Definition of a research-/evaluation framework for workflow projects. This framework is composed of all relevant research variables that have been identified for the thesis. 3. Empirical survey of relevant workflow-project objectives and their priority in the context of process flexibility and –interoperability. 4. Empirical survey of the objectives’ achievement. 5. Empirical survey of methodologies / activities that have been applied within workflow projects. 6. Derivation of the project methodologies’ effectiveness in terms of the impact that applied activities had on project objectives. 7. Evaluation of existing workflow life-cycle models in accordance with the research framework. 8. Identification of basic improvements for workflow implementation processes with respect to the achievement of flexible and interoperable business processes. The first part of the thesis argues the relevance of the subject. Afterwards research variables that constitute the evaluation framework for WFMA implementation processes are stepwise identified and defined. An empirical study then proves the variables’ effectiveness for the achievement of process flexibility and –interoperability within the WFMA implementation process. After this the framework is applied to evaluate chosen WFMA implementation methodologies. Identified weaknesses and effective methodological aspects are utilised to develop generic methodological improvements. These improvements are later validated by means of a case study and interviews with workflow experts.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Spatial patterns and links between microbial community composition and function in cyanobacterial mats

We imaged reflectance and variable fluorescence in 25 cyanobacterial mats from four distant sites around the globe to assess, at different scales of resolution, spatial variabilities in the physiological parameters characterizing their photosynthetic capacity, including the absorptivity by chlorophyll a (Achl), maximum quantum yield of photosynthesis (Ymax), and light acclimation irradiance (Ik). Generally, these parameters significantly varied within individual mats on a sub-millimeter scale, with about 2-fold higher variability in the vertical than in the horizontal direction. The average vertical profiles of Ymax and Ik decreased with depth in the mat, while Achl exhibited a sub-surface maximum. The within-mat variability was comparable to, but often larger than, the between-sites variability, whereas the within-site variabilities (i.e., between samples from the same site) were generally lowest. When compared based on averaged values of their photosynthetic parameters, mats clustered according to their site of origin. Similar clustering was found when the community composition of the mats' cyanobacterial layers were compared by automated ribosomal intergenic spacer analysis (ARISA), indicating a significant link between the microbial community composition and function. Although this link is likely the result of community adaptation to the prevailing site-specific environmental conditions, our present data is insufficient to identify the main factors determining these patterns. Nevertheless, this study demonstrates that the spatial variability in the photosynthetic capacity and light acclimation of benthic phototrophic microbial communities is at least as large on a sub-millimeter scale as it is on a global scale, and suggests that this pattern of variability scaling is similar for the microbial community composition. © 2014 Al-Najjar, Ramette, Kühl, Hamza, Klatt and Polerecky

An investigation into the relevance of flexibility- and interoperability requirements for implementation processes for workflow-management-applications

Flexibility and Interoperability have become important characteristics for organisations and their business processes. The need to control flexible business processes within an organisation’s boundaries and between organisations imposes major requirements on a company’s process control capabilities. Workflow Management Systems (WFMS) try to fulfil these requirements by offering respective product features. Evidence suggests that the achievement of flexible business processes and an inter-organisational process control is also influenced by implementation processes for Workflow Management Applications (WFMA). [A WFMA comprises the WFMS and "all WFMS specific data with regard to one or more business processes" [VER01]]. The impact of a WFMA implementation methodology on the fulfilment of these requirements is the research scope of the project. The thesis provides knowledge in the following areas: 1. Review of the relationship between workflow management and the claim for process flexibility respectively -interoperability. 2. Definition of a research-/evaluation framework for workflow projects. This framework is composed of all relevant research variables that have been identified for the thesis. 3. Empirical survey of relevant workflow-project objectives and their priority in the context of process flexibility and –interoperability. 4. Empirical survey of the objectives’ achievement. 5. Empirical survey of methodologies / activities that have been applied within workflow projects. 6. Derivation of the project methodologies’ effectiveness in terms of the impact that applied activities had on project objectives. 7. Evaluation of existing workflow life-cycle models in accordance with the research framework. 8. Identification of basic improvements for workflow implementation processes with respect to the achievement of flexible and interoperable business processes. The first part of the thesis argues the relevance of the subject. Afterwards research variables that constitute the evaluation framework for WFMA implementation processes are stepwise identified and defined. An empirical study then proves the variables’ effectiveness for the achievement of process flexibility and –interoperability within the WFMA implementation process. After this the framework is applied to evaluate chosen WFMA implementation methodologies. Identified weaknesses and effective methodological aspects are utilised to develop generic methodological improvements. These improvements are later validated by means of a case study and interviews with workflow experts.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Tracking heterogeneous structural motifs and the redox behaviour of copper-zinc nanocatalysts for the electrocatalytic CO₂ reduction using operando time resolved spectroscopy and machine learning

Copper-based catalysts are established catalytic systems for the electrocatalytic CO2 reduction reaction (CO2RR), where wasteful CO2 is converted into valuable industrial resources, such as energy-dense C2+ products, using energy from renewable sources. However, better control over the catalyst selectivity, especially at industrially relevant high current density conditions is needed to expedite the economically viability of the CO2RR. For this purpose, bimetallic materials, where copper is combined with a secondary metal, comprise a promising and a highly tunable catalyst for CO2RR. However, the synergy between copper and the selected secondary metal species, the evolution of the bimetallic structural motifs under working conditions and the effect of the secondary metal on the kinetics of the Cu redox behavior require careful investigation. Here, we employ operando quick X-ray absorption spectroscopy (QXAFS), coupled with machine-learning based data analsysis and surface-enhanced Raman spectroscopy (SERS) to investigate the time-dependent chemical and structural changes in catalysts derived from shape-selected Zn/Cu2O nanocubes under CO2RR conditions at current densities up to -500 mA/cm2. We furthermore relate the transformation observed under working conditions to the catalytic activity and selectivity and correlate potential-dependent surface and subsurface processes. We report that the addition of Zn to a Cu-based catalyst has crucial impact on the kinetics of subsurface processes, while redox processes of the Cu surface layer remain largely unaffected. Interestingly, the presence of Zn was found to contribute to the stabilization of cationic Cu(I) species, which is of catalytic relevance since Cu(0)/Cu(I) interfaces have been reported beneficial for the efficient CO2 conversion to complex multicarbon products. At the same time, we attribute the increase of the C2+ product selectivity to the formation of Cu-rich CuZn alloys in samples with low Zn content, while Zn-rich alloy phases result in an increased formation of CO paralleled by an increase of the parasitic hydrogen evolution reaction

Test of Time Dilation Using Stored Li+ Ions as Clocks at Relativistic Speed

We present the concluding result from an Ives-Stilwell-type time dilation experiment using 7Li+ ions confined at a velocity of beta = v/c = 0.338 in the storage ring ESR at Darmstadt. A Lambda-type three-level system within the hyperfine structure of the 7Li+ triplet S1-P2 line is driven by two laser beams aligned parallel and antiparallel relative to the ion beam. The lasers' Doppler shifted frequencies required for resonance are measured with an accuracy of < 4 ppb using optical-optical double resonance spectroscopy. This allows us to verify the Special Relativity relation between the time dilation factor gamma and the velocity beta to within 2.3 ppb at this velocity. The result, which is singled out by a high boost velocity beta, is also interpreted within Lorentz Invariance violating test theories

Isotope Shift Measurements of Stable and Short-Lived Lithium Isotopes for Nuclear Charge Radii Determination

Changes in the mean-square nuclear charge radii along the lithium isotopic chain were determined using a combination of precise isotope shift measurements and theoretical atomic structure calculations. Nuclear charge radii of light elements are of high interest due to the appearance of the nuclear halo phenomenon in this region of the nuclear chart. During the past years we have developed a new laser spectroscopic approach to determine the charge radii of lithium isotopes which combines high sensitivity, speed, and accuracy to measure the extremely small field shift of an 8 ms lifetime isotope with production rates on the order of only 10,000 atoms/s. The method was applied to all bound isotopes of lithium including the two-neutron halo isotope Li-11 at the on-line isotope separators at GSI, Darmstadt, Germany and at TRIUMF, Vancouver, Canada. We describe the laser spectroscopic method in detail, present updated and improved values from theory and experiment, and discuss the results.Comment: 34 pages, 24 figures, 14 table