Altered structural and effective connectivity in anorexia and bulimia nervosa in circuits that regulate energy and reward homeostasis.

Anorexia and bulimia nervosa are severe eating disorders that share many behaviors. Structural and functional brain circuits could provide biological links that those disorders have in common. We recruited 77 young adult women, 26 healthy controls, 26 women with anorexia and 25 women with bulimia nervosa. Probabilistic tractography was used to map white matter connectivity strength across taste and food intake regulating brain circuits. An independent multisample greedy equivalence search algorithm tested effective connectivity between those regions during sucrose tasting. Anorexia and bulimia nervosa had greater structural connectivity in pathways between insula, orbitofrontal cortex and ventral striatum, but lower connectivity from orbitofrontal cortex and amygdala to the hypothalamus (P<0.05, corrected for comorbidity, medication and multiple comparisons). Functionally, in controls the hypothalamus drove ventral striatal activity, but in anorexia and bulimia nervosa effective connectivity was directed from anterior cingulate via ventral striatum to the hypothalamus. Across all groups, sweetness perception was predicted by connectivity strength in pathways connecting to the middle orbitofrontal cortex. This study provides evidence that white matter structural as well as effective connectivity within the energy-homeostasis and food reward-regulating circuitry is fundamentally different in anorexia and bulimia nervosa compared with that in controls. In eating disorders, anterior cingulate cognitive-emotional top down control could affect food reward and eating drive, override hypothalamic inputs to the ventral striatum and enable prolonged food restriction

Terahertz electromodulation spectroscopy on organic semiconductors

Die Entdeckung von halbleitenden organischen Materialien eröffnete ein faszinierendes Forschungsgebiet und ebnete den Weg für heute nicht mehr wegzudenkende Entwicklungen. Trotz der Vorteile hinsichtlich günstiger Produktion und vielfältiger Herstellungsmöglichkeiten, sind organische Halbleiter ihren kristallinen Gegenspielern in ihrer Leitfähigkeit unterlegen. Auf die Fragen warum das so ist und welche Mechanismen den Ladungsträgertransport maßgeblich hemmen, können keine eindeutigen Antworten gegeben werden. Diese Arbeit versucht den Anworten mithilfe der Terahertz (THz) Elektromodulations-Spektroskopie näher zu kommen, denn diese Methode erlaubt einen Einblick in die intrinsischen Transport-Phänomene von molekularen Halbleitern. Hierfür wird zu Beginn der Arbeit der experimentelle Aufbau des THz Spektrometers, die untersuchten Dünnfilm Strukturen, die Analyse der Elektromodulations-Daten sowie die Vorteile und Grenzen der Technik im Detail erklärt. Es stellt sich heraus, dass sich diese Technik hervorragend dafür eignet, alle heutzutage relevanten organischen Halbleiter-Materialien mit Mobilitäten bis hinab zu 1 cm²/Vs zu untersuchen. Ein besonderer Fokus dieser Arbeit liegt auf den Einflüssen der Grenzschichten innerhalb der Bauelemente. Wie die Rauigkeit der Isolator-Halbleiter Grenzfläche die Ladungsträgerverteilung im Bauelement bestimmt wird mithilfe von Berechnungen der selbstkonsistenten Poisson Gleichung ermittelt. Schon Rauigkeiten in der Größenordnung von einer molekularen Schicht resultieren in einer drastischen Verringerungen der Leitfähigkeit in dem Halbleiter. Bei der Untersuchung des Einflusses von Gold als Elektrodenmaterial wurde festgestellt, dass Gold-Ionen in Gegenwart eines elektrischen Feldes in den organischen Halbleiter migrieren. Dort agieren die Gold-Ionen als effiziente Loch-Fallen, was die Stabilität des Bauteils drastisch reduziert. Der Migrationsprozess ist thermisch aktiviert, teilweise umkehrbar und kann komplett umgangen werden, wenn man anstatt Gold Molybdänoxid verwendet. Die daraus resultierende verbesserte Stabilität der Bauelemente ist eine absolut notwendige Vorraussetzung für aussagekräftige frequenzaufgelöste THz Spektroskopie. Temperaturabhängige und frequenzaufgelöste Messungen an DBTTT Strukturen zeigen, dass weder Phonon-Streuung noch dynamische Lokalisierung die limitierenden Mechanismen der Leitfähigkeit sind. Es stellt sich heraus, dass nur ein Teil der injizierten Ladungsträger zum Bandtransport beiträgt. Der Großteil der Ladungsträger ist nicht mobil oder bewegt sich mit dem langsamen Hüpf-Transport. Insgesamt zeigt diese Arbeit, dass die THz Elektromodulations-Spektroskpie ein einzigartiges und fähiges Werkzeug ist, um organische Dünnfilme zu untersuchen. Außerdem unterstreicht sie, wie wichtig der Einfluss von Grenzflächenphänomenen innerhalb organischer Bauelemente auf den Ladungsträgertransport ist.The discovery of semiconducting organic materials opened a new fascinating field of research and paved the way for exciting developments. Besides the benefits of cheap fabrication and variable processing possibilities, organic semiconductors still exhibit worse performance in comparison to their crystalline counterparts. The corresponding questions "Why?" and "What mechanisms limit charge transport within organic electronic devices?" cannot be answered unambiguously. Within this work, the technique of terahertz (THz) electromodulation spectroscopy is used to gather unprecedented insight into the intrinsic charge transport mechanisms of molecular semiconducting thin-film devices. Therefore, the experimental THz spectroscopy setup, the investigated thin-film devices, the electromodulation data analysis methodology as well as advantages and limitations of the technique are presented in detail. It is shown, that this method is a powerful tool for most of today’s relevant organic materials as its sensitivity allows the detection of mobilities as low as 1 cm2/Vs. Furthermore, relevant interfaces within the field-effect devices are systematically investigated. The impact of the roughness of the insulator-semiconductor interface on the charge carrier distribution is inspected by combining two-dimensional atomic force microscopy scans with three-dimensional self-consistent Poisson calculations as this cannot be solely addressed by experimental means. It is found that the majority of charge carriers accumulates near the insulator interface. Thus, roughness in the order of already one molecular monolayer leads to a severe reduction in conductivity. Additionally, it is shown that charge carriers rarely undergo thermally activated hopping but travel within two-dimensional percolation pathways. Moreover, the influence of gold as top contact material is examined by THz spectroscopy. In presence of an applied bias, gold ions migrate into the devices accumulation channel and act as efficient hole traps. This phenomenon is found to be thermally-activated, partially reversible and can be circumvented by exchanging the gold with molybdenum oxide. The resulting devices exhibit long-term stability, which is crucial for frequency-resolved THz spectroscpy investigations. Field-effect devices with the small molecule semiconductor DBTTT are investigated using temperaturedependent and frequency-resolved THz electromodulation spectroscopy. Results show that neither phonon scattering nor dynamic localization are the main limiting mechanisms. It is found, that only a fraction of the injected charge carriers contribute to band transport while the vast majority is immobile or performs hopping transport. This work highlights the applicability of THz electromodulation spectroscopy as a unique and powerful tool for the investigation of organic thin-film devices and emphasizes the importance of interface phenomena on the intrinsic charge transport within molecular semiconductors

Master of Science

thesisIntrauterine growth restriction (IUGR) is associated with impaired lung development and function. Lung function is impaired in IUGR rats, in part, by altered surfactant composition. The lipid profile in lungs determines surfactant lipid composition. Our IUGR rats have decreased lung palmitoleic acid (16:1). Stearoyl CoA Desaturase (SCD), the rate-limiting enzyme in synthesis of palmitoleic acid, is a target of transcription factor peroxisome proliferator activated receptor gamma (PPARγ) and is susceptible to transcriptional regulation through epigenetic modifications. There are a number of genes in the lung that show altered mRNA levels in association with decreased PPARγ levels and epigenetic modifications in the presence of IUGR. The effect of IUGR on the epigenetic profile of SCD as well as SCD mRNA and protein levels in the newborn rat lung is unknown. We hypothesize that IUGR will be associated with reduced SCD mRNA and protein levels consistent with the previously observed decrease in PPARγ levels in the lungs of d0 rat pups. We further hypothesize that there will be gender-specific changes in the epigenetic profile along the length of the SCD gene. This hypothesis was tested using a uteroplacental insufficiency (UPI) model of IUGR in rats. Whole lung tissue was harvested at birth (d0) and used to assess SCD mRNA and protein levels by RT-PCR and western blot analysis. Epigenetic modifications (H3K14Ac and H3K36Me3) were assessed along the SCD gene using chromatin immunoprecipitation (ChIP). Results showed that, in control lungs females have 153% higher SCD mRNA than males (p=0.005). A consistent decrease in SCD mRNA levels was found in both male and female IUGR rats at birth relative to controls (p=0.009, p=0.0023). H3K14Ac was increased at SCD exon 4 in IUGR females to 210% of the level detected in gender-matched controls (p=0.037). H3K3Me3 was decreased at SCD exon 4 in IUGR males by 43% (p=0.044) and at SCD 3'UTR in IUGR females by 65% relative to gender-matched controls (p=0.036). There was no change in SCD protein levels in IUGR rats at birth. In conclusion IUGR is associated with decreased SCD mRNA levels and gender-specific changes to the epigenetic profile along the SCD gene

Terahertz Electromodulation Spectroscopy for Characterizing Electronic Transport in Organic Semiconductor Thin Films

Terahertz (THz) spectroscopy is a well-established tool for measuring the high-frequency conductance of inorganic semiconductors. Its application to organic semiconductors, however, is challenging, because of the low carrier mobilities in organic materials, which rarely exceed 10cm(2)/Vs. Furthermore, low charge carrier densities in organic field-effect devices lead to sheet conductivities that are often far-below the detection limits of conventional THz techniques. In this contribution, we present the application of THz electromodulation spectroscopy for characterizing charge transport in organic semiconductors. Pulses of THz radiation are transmitted through organic field-effect devices and are time-resolved by electro-optic sampling. A differential transmission signal is obtained by modulating the gate voltage of the devices. This controls charge injection into the semiconductors, where the charge carriers reduce the THz transmission by their Drude response. Advantageous is that a nearly noise-free differential transmission can be obtained. Furthermore, electromodulation allows to sense specifically either injected electrons or holes. Because the method exclusively probes transport of mobile carriers, it provides access to fundamental transport properties, which are difficult to access with conventional characterization methods, such as conductance measurements of organic field-effect transistors. The outstanding property that a relative differential signal is measured allows to obtain charge carrier mobilities with high reliability. Mobilities as small as 1cm(2)/Vs can be probed, which makes THz electromodulation spectroscopy an attractive tool for studying charge transport in most technologically relevant organic semiconductors

The Part-Time Revolution: Changes in the Parenthood Effect on Women’s Employment in Austria across the Birth Cohorts from 1940 to 1979

Comparing employment rates of mothers and childless women over the life course across the birth cohorts from 1940 to 1979 in Austria, we address the question of whether the parenthood effect on employment has declined. By following synthetic cohorts of mothers and childless women up to retirement age, we can study both the short-term and long-term consequences of having a child. We consider employment participation as well as working time and also perform analyses by educational level. Our study is based on the Austrian microcensus, conducted between 1986 and 2016, and uses descriptive methods, logistic regression models, and decomposition analysis. The results show that the increase in the proportion of part-time work has led to a declining work volume of mothers with young children, despite employment rates of mothers having increased across cohorts. Return to the workplace is progressively concentrated when the child is 3–5 years old, but the parenthood effect has become weaker only from the time children enter school. Part-time employment is primarily adopted (at least with younger children) by highly educated mothers and often remains a long-term arrangement

Regional context and realization of fertility intentions: the role of the urban context

Despite regional variation in fertility, rural–urban differences in the realization of fertility intentions have not been addressed in previous research. This paper analyzes the realization with data from 11 European countries, employing binomial and multinomial logistic regression models, decomposition analyses, and examining the role of contextual factors. The results demonstrate that realization is lower in urban than in rural regions. In cities, postponement of childbearing is much more common. This can be partly explained by differences in characteristics (e.g., age, partnership status) of inhabitants who intend to have a(nother) child. Furthermore, contextual factors such as educational and economic opportunities play a role