Characterization of structure and dynamics of submicrometric systems via fluorescence correlation spectroscopy

The presented thesis revolves around the study of thermally-responsive PNIPAAm-based hydrogels in water/based environments, as studied by Fluorescence Correlation Spectroscopy (FCS).rnThe goal of the project was the engineering of PNIPAAm gels into biosensors. Specifically, a gamma of such gels were both investigated concerning their dynamics and structure at the nanometer scale, and their performance in retaining bound bodies upon thermal collapse (which PNIPAAm undergoes upon heating above 32 ºC).rnFCS’s requirements, as a technique, match the limitations imposed by the system. Namely, the need to intimately probe a system in a solvent, which was also fragile and easy to alter. FCS, on the other hand, both requires a fluid environment to work, and is based on the observation of diffusion of fluorescents at nanomolar concentrations. FCS was applied to probe the hydrogels on the nanometer size with minimal invasivity.rnVariables in the gels were addressed in the project including crosslinking degree; structural changes during thermal collapse; behavior in different buffers; the possibility of decreasing the degree of inhomogeneity; behavior of differently sized probes; and the effectiveness of antibody functionalization upon thermal collapse.rnThe evidenced results included the heightening of structural inhomogeneities during thermal collapse and under different buffer conditions; the use of annealing to decrease the inhomogeneity degree; the use of differently sized probes to address different length scale of the gel; and the successful functionalization before and after collapse.rnThe thesis also addresses two side projects, also carried forward via FCS. One, diffusion in inverse opals, produced a predictive simulation model for diffusion of bodies in confined systems as dependent on the bodies’ size versus the characteristic sizes of the system. The other was the observation of interaction of bodies of opposite charge in a water solution, resulting in a phenomenological theory and an evaluation method for both the average residence time of the different bodies together, and their attachment likelihood.

Organic lasing: correlation between molecular structure, optical and optoelectronic properties

In this thesis mainly two alternating indenofluorene-phenanthrene copolymers were investigated with a variety of spectroscopic and optoelectronic experiments. The different experimental techniques allowed to retrieve deeper insights into their unique optical as well as optoelectronic properties. The motivation of the research presented in this work was to correlate their photophysical properties with respect to their application in electrically pumped lasing. This thesis begins with the description of optical properties studied by classical absorption and emission spectroscopy and successively describes an overall picture regarding their excited state dynamics occurring after photoexcitation studied by time-resolved spectroscopy. The different spectroscopic methods do not only allow to elucidate the different optical transitions occurring in this class of materials, but also contribute to a better understanding of exciton dynamics and exciton interaction with respect to the molecular structure as well as aggregation and photooxidation of the polymers. Furthermore, the stimulated emission properties were analyzed by amplified spontaneous emission (ASE) experiments. Especially one of the investigated materials, called BLUE-1, showed outstanding optical properties including a high optical gain, a low threshold for ASE and low optical losses. Apart from the optical experiments, the charge carrier mobility was measured with the time-of-flight technique and a comparably high hole mobility on the order of 1 x 10-² cm²/(Vs) was determined for BLUE-1 which makes this material promising for organic lasing. The impact of the high charge carrier mobility in this material class was further analyzed in different optoelectronic devices such as organic LEDs (OLEDs) and organic solar cells.

Predictive ability of a modified Örebro Musculoskeletal Pain Questionnaire in an acute/subacute low back pain working population

The original 'Örebro Musculoskeletal Pain Questionnaire' (original-ÖMPQ) has been shown to have limitations in practicality, factor structure, face and content validity. This study addressed these concerns by modifying its content producing the 'Örebro Musculoskeletal Screening Questionnaire' (ÖMSQ). The ÖMSQ and original-ÖMPQ were tested concurrently in acute/subacute low back pain working populations (pilot n = 44, main n = 106). The ÖMSQ showed improved face and content validity, which broadened potential application, and improved practicality with two-thirds less missing responses. High reliability (0.975, p < 0.05, ICC: 2.1), criterion validity (Spearman's r = 0.97) and internal consistency (α = 0.84) were achieved, as were predictive ability cut-off scores from ROC curves (112-120 ÖMSQ-points), statistically different ÖMSQ scores (p < 0.001) for each outcome trait, and a strong correlation with recovery time (Spearman's, r = 0.71). The six-component factor structure reflected the constructs originally proposed. The ÖMSQ can be substituted for the original-ÖMPQ in this population. Further research will assess its applicability in broader populations.

Inefficient Preparatory fMRI-BOLD Network Activations Predict Working Memory Dysfunctions in Patients with Schizophrenia

Patients with schizophrenia show abnormal dynamics and structure of temporally ­coherent networks (TCNs) assessed using fMRI, which undergo adaptive shifts in preparation for a cognitively demanding task. During working memory (WM) tasks, patients with schizophrenia show persistent deficits in TCNs as well as EEG indices of WM. Studying their temporal relationship during WM tasks might provide novel insights into WM performance deficits seen in schizophrenia. Simultaneous EEG-fMRI data were acquired during the performance of a verbal Sternberg WM task with two load levels (load 2 and load 5) in 17 patients with schizophrenia and 17 matched healthy controls. Using covariance mapping, we investigated the relationship of the activity in the TCNs before the memoranda were encoded and EEG spectral power during the retention interval. We assessed four TCNs – default mode network (DMN), dorsal attention network (dAN), left and right working memory networks (WMNs) – and three EEG bands – theta, alpha, and beta. In healthy controls, there was a load-dependent inverse relation between DMN and frontal midline theta power and an anti-correlation between DMN and dAN. Both effects were not significantly detectable in patients. In addition, healthy controls showed a left-lateralized load-dependent recruitment of the WMNs. Activation of the WMNs was bilateral in patients, suggesting more resources were recruited for successful performance on the WM task. Our findings support the notion of schizophrenia patients showing deviations in their neurophysiological responses before the retention of relevant information in a verbal WM task. Thus, treatment strategies as neurofeedback ­targeting prestates could be beneficial as task performance relies on the preparatory state of the brain.

Preference Structure and Random Paths to Stability in Matching Markets

This paper examines how preference correlation and intercorrelation combine to influence the length of a decentralized matching market's path to stability. In simulated experiments, marriage markets with various preference specifications begin at an arbitrary matching of couples and proceed toward stability via the random mechanism proposed by Roth and Vande Vate (1990). The results of these experiments reveal that fundamental preference characteristics are critical in predicting how long the market will take to reach a stable matching. In particular, intercorrelation and correlation are shown to have an exponential impact on the number of blocking pairs that must be randomly satisfied before stability is attained. The magnitude of the impact is dramatically different, however, depending on whether preferences are positively or negatively intercorrelated.

Bank Performance: Market Power or Efficient Structure?

Regulatory change not seen since the Great Depression swept the U.S. banking industry beginning in the early 1980s, culminating with the Interstate Banking and Branching Efficiency Act of 1994. Significant consolidations have occurred in the banking industry. This paper considers the market-power versus the efficient-structure theories of the positive correlation between banking concentration and performance on a state-by-state basis. Temporal causality tests imply that bank concentration leads bank profitability, supporting the market-power, rather than the efficient-structure, theory of that positive correlation. Our finding suggests that bank regulators, by focusing on local banking markets, missed the initial stages of an important structural change at the state level.

Supply and Demand Side Limitations Affecting the Structure of Agriculture and the Rural Economy. Factor Markets Working Paper No. 21, February 2012

The paper criticises the neo-classical assumptions of perfect factor markets and of complete information, which constitute central elements in labour market theory. Based on literature review and on economic reports from transition economies, as well as developing countries and more advanced economies, this deliverable focuses on the structural impediments and imperfections which often characterise rural labour markets and which may prevent an efficient allocation of labour. According to empirical studies, transactions costs and rigidities hinder the well-functioning of labour markets and constrain labour adjustments. The paper attempts to classify the various limitations of rural labour markets from both supply and demand side, although the distinction is not always clear-cut as some problems occur on both sides. The identification of these issues is extremely important as it allows us to highlight the inefficiencies and the failures in labour markets and to understand their impact on labour allocation. In this context, market intervention is desirable and the paper provides particular support for rural development policies such as investments in human capital. Lastly, labour institutions can play a key role in promoting the well functioning of labour markets, thus it is fundamental that they are well in place.

The Impact of CAP Reforms on Farm Labour Structure. Factor Markets Working Document No. 63, August 2013

The labour force engaged in the agricultural sector is declining over time, and one can observe the reallocation of labour from family members to hired workers. Using farm-level data, this paper analyses the on-farm labour structure in Greece and assesses the factors driving its evolution over the period 1990-2008. The impact of agricultural policies and farm characteristics is examined in a dynamic panel analysis. Family and hired labour are found to be substitutes rather than complements, while agricultural support measures appear to negatively affect demand for both family and hired labour. Decoupled payments and subsidies on crops are found to have a significant impact on both sources of labour, as well as subsidies for rural development that do not favour on-farm labour use. The paper also finds that structural labour adjustments are the result of farm characteristics, such as farm size and location. The results are robust to various estimation techniques and specifications.

Structure as Process: The Regularized Intergovernmentalism of Franco-German Bilateralism, CES Germany & Europe Working Papers, No.02.3, 2002

This article systematically scrutinizes the intergovernmental and administrative aspects of Franco- German relations with the 1963 Elysée Treaty at their core. This treaty, together with its various additions and extensions, has defined the basic processes of bilateral interaction between the French and German states. Recurrent tension in Franco-German relations notwithstanding, many observers and participants have viewed France and Germany to be connected particularly closely since the 1960s. This article explores key elements of what it is that links France and Germany. Thereby it clarifies the concept of regularized intergovernmentalism, suggests viewing this specific set of international practices from a social-structural perspective, and evaluates the effects and limits of such regularized procedures. Its findings suggest that bilateral structures have complemented and undergirded a broadly multilateral post-World War II world and are likely to continue to do.

Survey of antimalarial agents. Chemotherapy of plasmodium gallinaceum infections; toxicity; correlation of structure and action

Mode of access: Internet.