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This work is concerned with the numerical approximation of solutions to models that are used to describe atmospheric or oceanographic flows. In particular, this work concen- trates on the approximation of the Shallow Water equations with bottom topography and the compressible Euler equations with a gravitational potential. Numerous methods have been developed to approximate solutions of these models. Of specific interest here are the approximations of near equilibrium solutions and, in the case of the Euler equations, the low Mach number flow regime. It is inherent in most of the numerical methods that the quality of the approximation increases with the number of degrees of freedom that are used. Therefore, these schemes are often run in parallel on big computers to achieve the best pos- sible approximation. However, even on those big machines, the desired accuracy can not be achieved by the given maximal number of degrees of freedom that these machines allow. The main focus in this work therefore lies in the development of numerical schemes that give better resolution of the resulting dynamics on the same number of degrees of freedom, compared to classical schemes.
This work is the result of a cooperation of Prof. Klingenberg of the Institute of Mathe- matics in Wu¨rzburg and Prof. R¨opke of the Astrophysical Institute in Wu¨rzburg. The aim of this collaboration is the development of methods to compute stellar atmospheres. Two main challenges are tackled in this work. First, the accurate treatment of source terms in the numerical scheme. This leads to the so called well-balanced schemes. They allow for an accurate approximation of near equilibrium dynamics. The second challenge is the approx- imation of flows in the low Mach number regime. It is known that the compressible Euler equations tend towards the incompressible Euler equations when the Mach number tends to zero. Classical schemes often show excessive diffusion in that flow regime. The here devel- oped scheme falls into the category of an asymptotic preserving scheme, i.e. the numerical scheme reflects the behavior that is computed on the continuous equations. Moreover, it is shown that the diffusion of the numerical scheme is independent of the Mach number.
In chapter 3, an HLL-type approximate Riemann solver is adapted for simulations of the Shallow Water equations with bottom topography to develop a well-balanced scheme. In the literature, most schemes only tackle the equilibria when the fluid is at rest, the so called Lake at rest solutions. Here a scheme is developed to accurately capture all the equilibria of the Shallow Water equations. Moreover, in contrast to other works, a second order extension is proposed, that does not rely on an iterative scheme inside the reconstruction procedure, leading to a more efficient scheme.
In chapter 4, a Suliciu relaxation scheme is adapted for the resolution of hydrostatic equilibria of the Euler equations with a gravitational potential. The hydrostatic relations are underdetermined and therefore the solutions to that equations are not unique. However, the scheme is shown to be well-balanced for a wide class of hydrostatic equilibria. For specific classes, some quadrature rules are computed to ensure the exact well-balanced property. Moreover, the scheme is shown to be robust, i.e. it preserves the positivity of mass and energy, and stable with respect to the entropy. Numerical results are presented in order to investigate the impact of the different quadrature rules on the well-balanced property.
In chapter 5, a Suliciu relaxation scheme is adapted for the simulations of low Mach number flows. The scheme is shown to be asymptotic preserving and not suffering from excessive diffusion in the low Mach number regime. Moreover, it is shown to be robust under certain parameter combinations and to be stable from an Chapman-Enskog analysis.
Numerical results are presented in order to show the advantages of the new approach.
In chapter 6, the schemes developed in the chapters 4 and 5 are combined in order to investigate the performance of the numerical scheme in the low Mach number regime in a gravitational stratified atmosphere. The scheme is shown the be well-balanced, robust and stable with respect to a Chapman-Enskog analysis. Numerical tests are presented to show the advantage of the newly proposed method over the classical scheme.
In chapter 7, some remarks on an alternative way to tackle multidimensional simulations are presented. However no numerical simulations are performed and it is shown why further research on the suggested approach is necessary.
This dissertation focuses on the performance evaluation of all components of Software Defined Networking (SDN) networks and covers whole their architecture. First, the isolation between virtual networks sharing the same physical resources is investigated with SDN switches of several vendors. Then, influence factors on the isolation are identified and evaluated. Second, the impact of control mechanisms on the performance of the data plane is examined through the flow rule installation time of SDN switches with different controllers. It is shown that both hardware-specific and controller instance have a specific influence on the installation time. Finally, several traffic flow monitoring methods of an SDN controller are investigated and a new monitoring approach is developed and evaluated. It is confirmed that the proposed method allows monitoring of particular flows as well as consumes fewer resources than the standard approach. Based on findings in this thesis, on the one hand, controller developers can refer to the work related to the control plane, such as flow monitoring or flow rule installation, to improve the performance of their applications. On the other hand, network administrators can apply the presented methods to select a suitable combination of controller and switches in their SDN networks, based on their performance requirements
Background:
The compound eyes of insects allow them to catch photons and convert the energy into electric signals. All compound eyes consist of numerous ommatidia, each comprising a fixed number of photoreceptors. Different ommatidial types are characterized by a specific set of photoreceptors differing in spectral sensitivity. In honey bees, males and females possess different ommatidial types forming distinct retinal mosaics. However, data are lacking on retinal ontogeny and the mechanisms by which the eyes are patterned. In this study, we investigated the intrinsic temporal and circadian expression patterns of the opsins that give rise to the ultraviolet, blue and green sensitive photoreceptors, as well as the morphological maturation of the retina during pupal development of honey bees.
Results:
qPCR and histological labeling revealed that temporal opsin mRNA expression differs between sexes and correlates with rhabdom elongation during photoreceptor development. In the first half of the pupal stage, when the rhabdoms of the photoreceptors are still short, worker and (dorsal) drone retinae exhibit similar expression patterns with relatively high levels of UV (UVop) and only marginal levels of blue (BLop) and green (Lop1) opsin mRNA. In the second half of pupation, when photoreceptors and rhabdoms elongate, opsin expression in workers becomes dominated by Lop1 mRNA. In contrast, the dorsal drone eye shows high expression levels of UVop and BLop mRNA, whereas Lop1 mRNA level decreases. Interestingly, opsin expression levels increase up to 22-fold during early adult life. We also found evidence that opsin expression in adult bees is under the control of the endogenous clock.
Conclusions:
Our data indicate that the formation of the sex-specific retinal composition of photoreceptors takes place during the second half of the pupal development, and that opsin mRNA expression levels continue to increase in young bees, which stands in contrast to Drosophila, where the highest expression levels are found during the late pupal stage and remain constant in adults. From an evolutionary perspective, we hypothesize that the delayed retinal maturation during the early adult phase is linked to the delayed transition from indoor to outdoor activities in bees, when vision becomes important.
The diffraction contrast modalities accessible by X-ray grating interferometers are not imaged directly but have to be inferred from sine-like signal variations occurring in a series of images acquired at varying relative positions of the interferometer’s gratings. The absolute spatial translations involved in the acquisition of these phase stepping series usually lie in the range of only a few hundred nanometers, wherefore positioning errors as small as 10 nm will already translate into signal uncertainties of 1–10% in the final images if not accounted for. Classically, the relative grating positions in the phase stepping series are considered input parameters to the analysis and are, for the Fast Fourier Transform that is typically employed, required to be equidistantly distributed over multiples of the gratings’ period. In the following, a fast converging optimization scheme is presented simultaneously determining the phase stepping curves’ parameters as well as the actually performed motions of the stepped grating, including also erroneous rotational motions which are commonly neglected. While the correction of solely the translational errors along the stepping direction is found to be sufficient with regard to the reduction of image artifacts, the possibility to also detect minute rotations about all axes proves to be a valuable tool for system calibration and monitoring. The simplicity of the provided algorithm, in particular when only considering translational errors, makes it well suitable as a standard evaluation procedure also for large image series.
Background
The impact of risk factors on poor outcome after ischemic stroke is well known, but estimating the amount of poor outcome attributable to single factors is challenging in presence of multimorbidity. We aim to compare population attributable risk estimates obtained from different statistical approaches regarding their consistency. We use a real-life data set from the PROSCIS study to identify predictors for mortality and functional impairment one year after first-ever ischemic stroke and quantify their contribution to poor outcome using population attributable risks.
Methods
The PROSpective Cohort with Incident Stroke (PROSCIS) is a prospective observational hospital-based cohort study of patients after first-ever stroke conducted independently in Berlin (PROSCIS-B) and Munich (PROSCIS-M). The association of baseline factors with poor outcome one year after stroke in PROSCIS-B was analysed using multiple logistic regression analysis and population attributable risks were calculated, which were estimated using sequential population attributable risk based on a multiple generalized additive regression model, doubly robust estimation, as well as using average sequential population attributable risk. Findings were reproduced in an independent validation sample from PROSCIS-M.
Results
Out of 507 patients with available outcome information after 12 months in PROSCIS-B, 20.5% suffered from poor outcome. Factors associated with poor outcome were age, pre-stroke physical disability, stroke severity (NIHSS), education, and diabetes mellitus. The order of risk factors ranked by magnitudes of population attributable risk was almost similar for all methods, but population attributable risk estimates varied markedly between the methods. In PROSCIS-M, incidence of poor outcome and distribution of baseline parameters were comparable. The multiple logistic regression model could be reproduced for all predictors, except pre-stroke physical disability. Similar to PROSCIS-B, the order of risk factors ranked by magnitudes of population attributable risk was almost similar for all methods, but magnitudes of population attributable risk differed markedly between the methods.
Conclusions
Ranking of risk factors by population impact is not affected by the different statistical approaches. Thus, for a rational decision on which risk factor to target in disease interventions, population attributable risk is a supportive tool. However, population attributable risk estimates are difficult to interpret and are not comparable when they origin from studies applying different methodology. The predictors for poor outcome identified in PROSCIS-B have a relevant impact on mortality and functional impairment one year after first-ever ischemic stroke.
Overwintering temperature and body condition shift emergence dates of spring-emerging solitary bees
(2018)
Solitary bees in seasonal environments must align their life-cycles with favorable environmental conditions and resources; the timing of their emergence is highly fitness relevant. In several bee species, overwintering temperature influences both emergence date and body weight at emergence. High variability in emergence dates among specimens overwintering at the same temperatures suggests that the timing of emergence also depends on individual body conditions. However, possible causes for this variability, such as individual differences in body size or weight, have been rarely studied. In a climate chamber experiment using two spring-emerging mason bees (Osmia cornuta and O. bicornis), we investigated the relationship between temperature, emergence date, body weight, and body size, the last of which is not affected by overwintering temperature. Our study showed that body weight declined during hibernation more strongly in warm than in cold overwintering temperatures. Although bees emerged earlier in warm than in cold overwintering temperatures, at the time of emergence, bees in warm overwintering temperatures had lower body weights than bees in cold overwintering temperatures (exception of male O. cornuta). Among specimens that experienced the same overwintering temperatures, small and light bees emerged later than their larger and heavier conspecifics. Using a simple mechanistic model we demonstrated that spring-emerging solitary bees use a strategic approach and emerge at a date that is most promising for their individual fitness expectations. Our results suggest that warmer overwintering temperatures reduce bee fitness by causing a decrease in body weight at emergence. We showed furthermore that in order to adjust their emergence dates, bees use not only temperature but also their individual body condition as triggers. This may explain differing responses to climate warming within and among bee populations and may have consequences for bee-plant interactions as well as for the persistence of bee populations under climate change.
Recently, our research group identified in a study novel proalgesic targets in acute and chronic inflammatory pain: oxidized phospholipids (OxPL). OxPL, endogenous chemical irritants, are generated in inflamed tissue and mediate their pain-inducing function by activating the transient receptor potential channels TRPA1 and TRPV1. Both channels are sensors for chemical stimuli on primary afferent nociceptors and are involved in nociception. Here, with the help of calcium imaging and whole cell patch clamp recording techniques, it was found that OxPL metabolites acutely activate TRPA1 and TRPV1 ion channels to excite DRG neurons. OxPL species act predominantly via TRPA1 ion channels and mediate long- lasting non-selective inward currents. Notably, one pure OxPL compound, PGPC, activated a TRPA1 mutant lacking the binding site for electrophilic agonists, suggesting that OxPL activate TRP ion channels by an indirect mechanical mechanism. Next, it was investigated how OxPL influence the excitability of primary sensory neurons. Acute stimulation and fast calcium imaging revealed that OxPL elicit repetitive, spike-like calcium transients in small- diameter DRG neurons, which were fully blocked by antagonists against TRPA1/V1 and N- type voltage-gated calcium channels.
In search of a mechanism that drives repetitive spiking of DRG neurons, it was asked whether NaV1.9, a voltage-gated sodium channel involved in subthreshold excitability and nociception, is needed to trigger OxPL-induced calcium spikes and action potential firing. In electrophysiological recordings, both the combination of local application of OxPL and current injection were required to efficiently increase the action potential (AP) frequency of small-diameter sensory neurons. However, no difference was monitored in the resting membrane potential or OxPL-induced AP firing rate between wt and NaV1.9-deficient small diameter DRG neurons. To see whether NaV1.9 needs inflammatory conditions to be integrated in the OxPL-induced excitation cascade, sensory neurons were pretreated with a mixture of inflammatory mediators before OxPL application. Under inflammatory conditions both the AP and the calcium-spike frequency were drastically enhanced in response to an acute OxPL stimulus. Notably, this potentiation of OxPL stimuli was entirely lost in NaV1.9 deficient sensory neurons. Under inflammatory conditions, the resting membrane potential of NaV1.9-deficient neurons was more negative compared to wt neurons, suggesting that NaV1.9 shows resting activity only under inflammatory conditions.
In conclusion, OxPL are endogenous irritants that induce excitability in small-diameter DRG
neurons, a cellular model of nociceptors, via TRP activation. This effect is potentiated under inflammatory conditions. Under these conditions, NaV1.9 functions as essential mediator as it eases the initiation of excitability after OxPL stimulation.
As mutants in the human NaV1.9 mediate an enhanced or painless perception, this study provides new insight into the mechanism on how NaV1.9 amplifies stimuli of endogenous irritants under inflammatory conditions.
Purpose:
The prescribing of oral chemotherapy agents has introduced the new challenge of ensuring patients’ adherence to therapy. Aspects of a close patient–doctor relationship are reported to be correlated with adherence to oral anticancer drugs, but data on capecitabine are scarce.
Patients and methods:
Sixty-four outpatients with a diagnosis of cancer and prescribed capecitabine were recruited from a German Comprehensive Cancer Center. We used the Patient–Doctor Relationship Questionnaire (PDRQ-9), the Medical Adherence Rating Scale (MARS), the Beliefs about Medicines Questionnaire (BMQ), and the Satisfaction with Information about Medicines Scale (SIMS) to assess patients’ perceptions and behavior. Medical data were extracted from the charts.
Results:
Non-adherence was reported by 20% of the 64 participants. The perceived quality of the patient–doctor relationship was high in general, but it did not emerge as a predictor of adherence in our survey (odds ratio [OR]=0.915, P=0.162, 95% CI=0.808–1.036). However, beliefs about medicine (OR=1.268, P<0.002; 95% CI=1.090–1.475) as well as satisfaction with information about medicine (OR=1.252, P<0.040, 95% CI=1.010–1.551) were predictors of adherence and the quality of the patient–doctor relationship was correlated with both variables (r=0.373, P=0.002 for SIMS sum score; r=0.263, P=0.036 for BMQ necessity/concern difference). Overall, adherence to capecitabine was high with a conviction that the therapy is necessary. However, concerns were expressed regarding the long-term effect of capecitabine use. Patients have unmet information needs regarding interactions of capecitabine with other medicines and the impairment of their intimate life.
Conclusions:
In order to ensure adherence to capecitabine, our results seem to encourage the default use of modern and perhaps more impersonal means of information brokerage (eg, email, internet). However, the contents of some of patients’ informational needs as well as the associations of patients’ beliefs and satisfaction about the information received suggest a benefit from a trustful patient–doctor relationship.
Increasing evidence indicates that forest disturbances are changing in response to global change, yet local variability in disturbance remains high. We quantified this considerable variability and analyzed whether recent disturbance episodes around the globe were consistently driven by climate, and if human influence modulates patterns of forest disturbance. We combined remote sensing data on recent (2001–2014) disturbances with in-depth local information for 50 protected landscapes and their surroundings across the temperate biome. Disturbance patterns are highly variable, and shaped by variation in disturbance agents and traits of prevailing tree species. However, high disturbance activity is consistently linked to warmer and drier than average conditions across the globe. Disturbances in protected areas are smaller and more complex in shape compared to their surroundings affected by human land use. This signal disappears in areas with high recent natural disturbance activity, underlining the potential of climate-mediated disturbance to transform forest landscapes.
Fanconi anaemia (FA) is an inherited disease with bone marrow failure, variable congenital and developmental abnormalities, and cancer predisposition. With improved survival, non-haematological manifestations of FA become increasingly important for long-term management. While renal abnormalities are recognized, detailed data on patterns and frequency and implications for long-term management are sparse. We reviewed clinical course and imaging findings of FA patients with respect to renal complications in our centre over a 25-year period to formulate some practical suggestions for guidelines for management of renal problems associated with FA. Thirty patients including four sibling sets were reviewed. On imaging, 14 had evidence of anatomical abnormalities of the kidneys. Two cases with severe phenotype, including renal abnormalities, had chronic kidney disease (CKD) at diagnosis. Haematopoietic stem cell transplantation was complicated by significant acute kidney injury (AKI) in three cases. In three patients, there was CKD at long-term follow-up. All patients had normal blood pressure. Evaluation of renal anatomy with ultrasound imaging is important at diagnostic workup of FA. While CKD is uncommon at diagnosis, our data suggests that the incidence of CKD increases with age, in particular after haematopoietic stem cell transplantation. Monitoring of renal function is essential for management of FA. Based on these long-term clinical observations, we formulate some practical guidelines for assessment and management of renal abnormalities in FA.
Obligate intracellular pathogenic Chlamydia trachomatis express several serine proteases whose roles in chlamydial development and pathogenicity are not completely understood. The chlamydial protease CPAF is expressed during the replicative phase of the chlamydial developmental cycle and is secreted into the lumen of the Chlamydia-containing vacuole called inclusion. How the secreted protease is activated in the inclusion lumen is currently not fully understood. We have identified human serine peptidase inhibitor PI15 as a potential host factor involved in the regulation of CPAF activation. Silencing expression as well as over expression of PI15 affected normal development of Chlamydia. PI15 was transported into the chlamydial inclusion lumen where it co-localized with CPAF aggregates. We show that PI15 binds to the CPAF zymogen and potentially induces CPAF protease activity at low concentrations. However, at high concentrations PI15 inhibits CPAF activity possibly by blocking its protease domain. Our findings shed light on a new aspect of chlamydial host co-evolution which involves the recruitment of host cell proteins into the inclusion to control the activation of bacterial proteases like CPAF that are important for the normal development of Chlamydia.
Sarcoidosis is a multisystem granulomatous disorder of unknown etiology that can involve virtually all organ systems. Whereas most patients present without symptoms, progressive and disabling organ failure can occur in up to 10% of subjects. Somatostatin receptor (SSTR)-directed peptide receptor radionuclide therapy (PRRT) has recently received market authorization for treatment of SSTR-positive neuroendocrine tumors.
Methods:
We describe the first case series comprising two patients with refractory multi-organ involvement of sarcoidosis who received 4 cycles of PRRT.
Results:
PRRT was well-tolerated without any acute adverse effects. No relevant toxicities could be recorded during follow-up. Therapy resulted in partial response accompanied by a pronounced reduction in pain (patient #1) and stable disease regarding morphology as well as disease activity (patient #2), respectively.
Conclusion:
Peptide receptor radionuclide therapy in sarcoidosis is feasible and might be a new valuable tool in patients with otherwise treatment-refractory disease. Given the long experience with and good tolerability of PRRT, further evaluation of this new treatment option for otherwise treatment-refractory sarcoidosis in larger patient cohorts is warranted.
CD8 T cells protect the liver against viral infection, but can also cause severe liver damage that may even lead to organ failure. Given the lack of mechanistic insights and specific treatment options in patients with acute fulminant hepatitis, we develop a mouse model reflecting a severe acute virus-induced CD8 T cell-mediated hepatitis. Here we show that antigen-specific CD8 T cells induce liver damage in a perforin-dependent manner, yet liver failure is not caused by effector responses targeting virus-infected hepatocytes alone. Additionally, CD8 T cell mediated elimination of cross-presenting liver sinusoidal endothelial cells causes endothelial damage that leads to a dramatically impaired sinusoidal perfusion and indirectly to hepatocyte death. With the identification of perforin-mediated killing as a critical pathophysiologic mechanism of liver failure and the protective function of a new class of perforin inhibitor, our study opens new potential therapeutic angles for fulminant viral hepatitis.
Background:
We hypothesized, that periprosthetic joint infection (PJI) accounts for the major proportion of first (primary) and repeated (secondary) Total Knee Arthroplasty revisions at our university referral arthroplasty center.
Methods:
One thousand one hundred forty-three revisions, performed between 2008 and 2016 were grouped into primary (55%) and secondary (45%) revisions. The rate of revision indications was calculated and indications were categorized by time after index operation. The odds ratios of the indications for primary versus secondary revision were calculated.
Results:
In the primary revision group PJI accounted for 22.3%, instability for 20.0%, aseptic loosening for 14.9% and retropatellar arthrosis for 14.2%. PJI (25.6%) was the most common indication up to 1 year after implantation, retropatellar arthrosis (26.8%) 1–3 years and aseptic loosening (25.6%) more than 3 years after implantation. In the secondary revision group PJI accounted for 39.7%, aseptic loosening for 16.2% and instability for 13.2%. PJI was the most common indication at any time of revision with 43.8% up to one, 35.4% 1–3 years and 39.4% more the 3 years after index operation. The odds ratios in repeated revision were 2.32 times higher (p = 0.000) for PJI. For instability and retropatellar arthrosis the odds ratios were 0.60 times (p = 0.006) and 0.22 times (p = 0.000) lower.
Conclusions:
PJI is the most common indication for secondary TKA revision and within one year after primary TKA. Aseptical failures such as instability, retropatellar arthrosis and aseptical loosening are the predominant reasons for revision more than one year after primary TKA.
The regulation of immune cell migration throughout the body is essential to warrant immunosurveillance and to maintain immune homeostasis. Marking and tracking of these cells has proven important to study mechanisms of immune cell trafficking and cell interaction in vivo. Photoconversion is a well-suited technique for intravital application because it enables contactless time- and location-specific marking of cells in the tissue without surgically manipulating the microenvironment of the cells in question. However, in dividing cells the converted fluorescent protein may decline quickly. Here, we provide a detailed description of the photoconversion technique and its applicability to tracking highly proliferating T cells from the priming site of T cell activation to peripheral target organs of effector function in a preclinical model. Dendra2+ T cells were photoconverted in the Peyer’s patches during the initiation phase of acute graft-versus-host disease (GvHD) and tracked through the mesenteric lymph nodes and the peripheral blood to the small intestine with flow cytometry and intravital two-photon microscopy. Photoconverted alloreactive T cells preserved the full proliferative capacity, homing, and migration of alloreactive T cells in the intestinal lamina propria. We conclusively proved that photoconversion of highly proliferative alloreactive T cells in the Peyer’s patches is an effective tool to study trafficking of alloreactive T cells under physiologic conditions and to GvHD target tissues. This technique can also be applied to the study of immune cell tracking under inflammatory and non-inflammatory conditions.
This thesis will outline studies performed on the fluorescence dynamics of phenyl-benzo-
[c]-tetrazolo-cinnolium chloride (PTC) in alcoholic solutions with varying viscosity using
time-resolved fluoro-spectroscopic methods. Furthermore, the properties of femtosecond
Laguerre-Gaussian (LG) laser pulses will be investigated with respect to their temporal
and spatial features and an approach will be developed to measure and control the spatial
intensity distribution on the time scale of the pulse.
Tetrazolium salts are widely used in biological assays for their low oxidation and reduction
thresholds and spectroscopic properties. However, a neglected feature in these applications
is the advantage that detection of emitted light has over the determination of the
absorbance. To corroborate this, PTC as one of the few known fluorescent tetrazolium
salts was investigated with regard to its luminescent features. Steady-state spectroscopy
revealed how PTC can be formed by a photoreaction from 2,3,5-triphenyl-tetrazolium
chloride (TTC) and how the fluorescence quantum yield behaved in alcoholic solvents
with different viscosity. In the same array of solvents time correlated single photon counting
(TCSPC) measurements were performed and the fluorescence decay was investigated.
Global analysis of the results revealed different dynamics in the different solvents, but
although the main emission constant did change with the solvent, taking the fluorescence
quantum yield into consideration resulted in an independence of the radiative rate from
the solvent. The non-radiative rate, however, was highly solvent dependent and responsible
for the observed solvent-related changes in the fluorescence dynamics. Further studies
with the increased time resolution of femtosecond fluorescence upconversion revealed an
independence of the main emission constant from the excitation energy, however the dynamics
of the cooling processes prior to emission were prolonged for higher excitation
energy. This led to a conceivable photoreaction scheme with one emissive state with a
competing non-radiative relaxation channel, that may involve an intermediate state.
LG laser beams and their properties have seen a lot of scientific attention over the past two
decades. Also in the context of new techniques pushing the limit of technology further to
explore new phenomena, it is essential to understand the features of this beam class and
check the consistency of the findings with theoretical knowledge. The mode conversion
of a Hermite-Gaussian (HG) mode into a LG mode with the help of a spiral phase plate
(SPP) was investigated with respect to its space-time characteristics. It was found that
femtosecond LG and HG pulses of a given temporal duration share the same spectrum
and can be characterized using the same well-established methods. The mode conversion
proved to only produce the desired LG mode with its characteristic orbital angular momentum
(OAM), that is conserved after frequency doubling the pulse. Furthermore, it
was demonstrated that temporal shaping of the HG pulse does not alter the result of its
mode-conversion, as three completely different temporal pulse shapes produced the same
LG mode. Further attention was given to the sum frequency generation of fs LG beams
and dynamics of the interference of a HG and a LG pulse. It was found that if both are
chirped with inverse signs the spatial intensity distribution does rotate around the beam
axis on the time scale of the pulse. A strategy was found that would enable a measurement
of these dynamics by upconversion of the interference with a third gate pulse. The results
of which are discussed theoretically and an approach of an experimental realization had
been made. The simulated findings had only been reproduced to a limited extend due to
experimental limitations, especially the interferometric stability of the setup.
The noninvasive magnetic resonance imaging technique allows for the investigation of functional processes in the living plant. For this purpose during this work, different NMR imaging methods were further developed and applied.
For the localisation of the intrusion of water into the germinating rape seed with the simultaneous depiction of the lipid-rich tissue via a 3D rendering, in Chap. 5 the technique of interleaved chemical selective acquisition of water and lipid was used in the germinating seed. The utilization of high-resolution MR images of germinated seeds enabled the localization of a predetermined water gap in the lipid-rich aleurone layer, which resides directly under the seed coat. The for a long time in biology prevalent discussion, whether such a gap exists or the seed soaks up the water from all sides, rather like a sponge, could hereby, at least for the rapeseed seed, be answered clearly. Furthermore, the segmentation and 3D visualization of the vascular tissue in the rapeseed seeds was enabled by the high-resolution datasets, a multiply branched structure preconstructed in the seed could be shown. The water is directed by the vascular tissue and thus awakens the seed gradually to life. This re-awakening could as well be tracked by means of invasive imaging via an oxygen sensor. In the re-awakened seeds, the lipid degradation starts, other than expected, not in the lipid-rich cotyledons but in the residual endosperm remaining from seed development and in the aleurone layer which previously protected the embryo. Within this layer, the degradation could be verified in the high-resolution MR datasets.
The method presented in Chap. 6 provides a further characteristic trait for phenotyping of seeds and lipid containing plants in general. The visualization of the compounds of fatty acids in plant seeds and fruits could be achieved by the distinct utilization of chemical shift-selective imaging techniques. Via the application of a CSI sequence the fatty acid compounds in an olive were localized in a 2D slice. In conjunction with an individually adjusted CHESS presaturation module Haa85 the high-resolution 3D visualization of saturated and unsaturated fatty acid compounds in different seeds was achieved. The ratio maps calculated from these datasets allow to draw conclusions from the developmental stage or the type of seed. Furthermore, it could be shown that the storage condition of two soybean seeds with different storage time durations lead to no degradation of the fatty acid content.
Additional structural information from inside of dry seeds are now accessible via MRI. In this work the imaging of cereal seeds could be significantly improved by the application of the UTE sequence. The hitherto existing depictions of the lipid distribution, acquired with the spin echo sequence, were always sufficient for examinations of the lipid content, yet defects in the starchy endosperm or differences in the starch concentration within the seed remained constantly unseen with this technique. In a direct comparison of the datasets acquired with the previous imaging technique (spin echo) and with UTE imaging, the advantage of data acquisition with UTE could be shown. By investigating the potential seed compounds (starch, proteins, sugar) in pure form, the constituent parts contributing to the signal could be identified as bound water (residual moisture) and starch. The application of a bi-exponential fit on the datasets of the barley seed enabled the separate mapping of magnetization and of relaxation time of two components contributing to the NMR signal. The direct comparison with histological stainings verified the previous results, thus this technique can be used for the selective imaging of starch in dry seeds.
Conclusions on the translocation characteristics in plants can be drawn by the technique proposed in Chap. 8. The associated translocation velocities can now, even in the range of several um/h, be determined in the living plant. Based on calculated concentrations of an MR contrast agent, which was taken up by the plant, these translocation velocities were estimated both in longitudinal direction, thus along the vascular bundle, and in horizontal direction, thus out of the bundle. The latter velocity is located below the contrast agent's velocity value of free diffusion. By adjusting a dynamic contrast-enhancing imaging technique (DCE-Imaging, Tof91) the acquisition duration of a T1-map was significantly reduced. By means of these maps, local concentrations of the contrast agent in plant stems and the siliques of the rapeseed plant could be determined.
Numerous questions in plant science can only be answered by non-invasive techniques such as MRI. For this reason, besides the experimental results achieved in this work, further NMR methods were tested and provided for the investigation of plants.
As an example, the study on the imaging of magnetic exchange processes are mentioned, which provided the groundwork for a possible transfer of CEST experiments (Chemical Exchange Saturation Transfer) to the plant. The results are presented in the bachelor thesis of A. Jäger Jae17, which was performed under my supervision, they find great interest under biologists.
The development of new technologies, which extend the possibilities for the investigation of living organisms, is of great importance. For this reason, I have contributed to the development of the currently unpublished method RACETE (Refocused Acquisition of Chemical Exchange Transferred Excitations [Jak17, Reu17, Gut18a]). By rephasing the transferred magnetization the utilization of properties which have not been available in chemical "`exchange"' experiments is enabled. With this method a positive contrast is generated, thus a reference experiment is not mandatory. Furthermore, the image phase, which in classical experiments contains no information about the exchanged protons, can be used for the distinct identification of multiple substances which have been excited simultaneously.
This recently at the Department of Experimental Physics V developed method can be used in particular for the identification of lipids and for the localization of sugars and amino acids, thus it can serve the enhancement and improvement of non-invasive analytical methods.
Impervious surface areas (ISA) are heavily influenced by urban structure and related structural features. We examined the effects of object-based impervious surface spatial pattern analysis on land surface temperature and population density in Guangzhou, China, in comparison to classic per-pixel analyses. An object-based support vector machine (SVM) and a linear spectral mixture analysis (LSMA) were integrated to estimate ISA fraction using images from the Chinese HJ-1B satellite for 2009 to 2011. The results revealed that the integrated object-based SVM-LSMA algorithm outperformed the traditional pixel-wise LSMA algorithm in classifying ISA fraction. More specifically, the object-based ISA spatial patterns extracted were more suitable than pixel-wise patterns for urban heat island (UHI) studies, in which the UHI areas (landscape surface temperature >37 °C) generally feature high ISA fraction values (ISA fraction >50%). In addition, the object-based spatial patterns enable us to quantify the relationship of ISA with population density (correlation coefficient >0.2 in general), with global human settlement density (correlation coefficient >0.2), and with night-time light map (correlation coefficient >0.4), and, whereas pixel-wise ISA did not yield significant correlations. These results indicate that object-based spatial patterns have a high potential for UHI detection and urbanization monitoring. Planning measures that aim to reduce the urbanization impacts and UHI intensities can be better supported.
Glycine receptors (GlyRs) are important mediators of fast inhibitory neurotransmission in the mammalian central nervous system. Their function is controlled by multiple cellular mechanisms, including intracellular regulatory processes. Modulation of GlyR function by protein kinases has been reported for many cell types, involving different techniques, and often yielding contradictory results. Here, we studied the effects of protein kinase C (PKC) and cAMP-dependent protein kinase A (PKA) on glycine induced currents in HEK293 cells expressing human homomeric \(\alpha\)1 and heteromeric \(\alpha\)1-\(\beta\) GlyRs using whole-cell patch clamp techniques as well as internalization assays. In whole-cell patch-clamp measurements, modulators were applied in the intracellular buffer at concentrations between 0.1 \(\mu\)M and 0.5 \(\mu\)M. EC50 of glycine increased upon application of the protein kinase activators Forskolin and phorbol-12-myristate-13-acetate (PMA) but decreased in the presence of the PKC inhibitor Staurosporine aglycon and the PKA inhibitor H-89. Desensitization of recombinant \(\alpha\)1 receptors was significantly increased in the presence of Forskolin. Staurosporine aglycon, on the other hand decreased desensitization of heteromeric \(\alpha\)1-\(\beta\) GlyRs. The time course of receptor activation was determined for homomeric \(\alpha\)1 receptors and revealed two simultaneous effects: cells showed a decrease of EC50 after 3-6 min of establishing whole-cell configuration. This effect was independent of protein kinase modulators. All modulators of PKA and PKC, however, produced an additional shift of EC50, which overlay and eventually exceeded the cells intrinsic variation of EC50. The effect of kinase activators was abolished if the corresponding inhibitors were co-applied, consistent with PKA and PKC directly mediating the modulation of GlyR function. Direct effects of PKA-and PKC-modulators on receptor expression on transfected HEK cells were monitored within 15 min of drug application, showing a significant increase of receptor internalization with PKA and PKC activators, while the corresponding inhibitors had no significant effect on receptor surface expression or internalization. Our results confirm the observation that phosphorylation via PKA and PKC has a direct effect on the GlyR ion channel complex and plays an important role in the fine-tuning of glycinergic signaling.
Species' functional traits set the blueprint for pair-wise interactions in ecological networks. Yet, it is unknown to what extent the functional diversity of plant and animal communities controls network assembly along environmental gradients in real-world ecosystems. Here we address this question with a unique dataset of mutualistic bird-fruit, bird-flower and insect-flower interaction networks and associated functional traits of 200 plant and 282 animal species sampled along broad climate and land-use gradients on Mt. Kilimanjaro. We show that plant functional diversity is mainly limited by precipitation, while animal functional diversity is primarily limited by temperature. Furthermore, shifts in plant and animal functional diversity along the elevational gradient control the niche breadth and partitioning of the respective other trophic level. These findings reveal that climatic constraints on the functional diversity of either plants or animals determine the relative importance of bottom-up and top-down control in plant-animal interaction networks.