Effects of interface morphology and geometry on the thermoelectric properties of artificially structured ZnO-based thin-films

Thermoelectricity may play a major role in waste heat recovery of fossil fuel consuming devices. Unfortunately thermoelectric generators to date only have poor conversion efficiencies (5 %). One way to improve the efficiency is to improve the performance of the active thermoelectric material. For this the figure of merit Z is given by Z=(S^2 sigma)/kappa, where S denotes the Seebeck coefficient, sigma the electrical conductivity, and kappa; the thermal conductivity. Z can be improved by either increasing the numerator S^2 sigma; (the so called power factor) or decreasing the denominator. The typical and best understood thermoelectric materials so far are based on Te, such as Bi2Te3 or PbTe. Unfortunately, for a mass application of thermoelectric devices, estimations show that the tellurium resources will be consumed very quickly. Hence it is worth trying to develop novel thermoelectric materials which are more sustainable and “green”. Exemplarily the thermoelectric properties of ZnO as an ideal model system were investigated in the framework of this thesis. Main goal of the work was to get a better understanding of the influence of effects on the microscopic length scale (e.g. due to thin-films, grain boundaries, artificial structuring) on the macroscopic behavior of the sample. In this context the following results were found: Investigations of degenerately doped thin ZnO:Al films and subsequent annealing in air showed that at very high carrier concentrations, where the samples have metallic character, a sign reversal of S may occur. Although the sample is clearly n-type, small positive Seebeck coefficients can be measured, changing their sign with decreasing temperature. This is due to changes of the density of states at the Fermi-energy in a degenerately doped semiconductor. The energy filtering effect due to grain boundaries, e.g. the increase of the power factor with increasing carrier concentration only works to a certain extend: If the carrier concentration n exceeds a certain value, screening effects diminish the barrier height and width leading to a decrease of the power factor. Concerning the investigation of interfaces first measurements on a multilayer sample series of alternating ZnO/ZnS layers in in-plane geometry gave hints for the formation of interface layers of very high electrical conductivity between ZnO and ZnS, dominating the transport behaviour at large layer thicknesses (d > 100 nm). At smaller d, where d becomes comparable to the typical fluctuation length of the interface roughness, the transport path and hence the thermoelectric properties are strongly determined by the surface fluctuations. These results could be approved qualitatively by simulations within a Network Model (NeMo). Stronger impact on the thermoelectric parameters, especially on the thermal conductivity, were found in cross plane direction, i.e. perpendicular to the interfaces. Unfortunately measurements of multilayers in cross-plane direction are very difficult to perform. To overcome this problem lateral structuring of thin-films offers attractive possibilities. To realize bar structures of alternating materials the method of self-aligned pattern transfer was developed and employed. Measurements perpendicular to the interfaces show that the number of interfaces as well as their shape (i.e. length) and morphology has a strong influence on the power factor. Supported by numerous NeMo simulations the results indicated that the thermoelectric properties across the sample are dominated by the shortest path of electrical conductance. The transport path is strongly influenced by assuming space-charge regions of different width and conductivity. Best agreement between experiment and simulations has been achieved by replacing a certain fraction of the lowly conducting material with a highly conducting space-charge region. However, the origin of this highly conducting surface region requires further clarifications. The findings of this work suggest that due to its high Seebeck coefficients and the possibility to tune the electrical conductivity by doping, ZnO is a promising candidate for an environmentally friendly and sustainable n-type thermoelectric material. The fact that its thermal conductivity is quite high may be overcome by a combination with ZnS. However this back door shown by theory still needs to be approved by experiment.Thermoelektrizität kann eine wichtige Rolle bei der Nutzung der bei der Verbrennung fossiler Rohstoffe entstehenden Abwärme spielen. Leider weisen thermoelektrische Generatoren bisher nur geringe Wirkungsgrade (5%) auf. Eine Möglichkeit, die Effizienz zu verbessern, ist die Leistung des thermoelektrisch aktiven Materials zu verbessern. Kennzahl dafür ist der Gütefaktor Z Z=(S^2 sigma)/kappa, wobei S den Seebeck-Koeffizienten, sigma die elektrische Leitfähigkeit und kappa die thermische Leitfähigkeit bezeichnen. Z kann entweder durch Erhöhen des Zählers S^2 sigma (der sog. Leistungsfaktor) oder Verringern des Nenners verbessert werden. Die zurzeit typischen und am besten verstandenen thermoelektrischen Materialien basieren auf Tellur (Te), wie Bi2Te3 oder PbTe. Für eine breite Anwendung thermoelektrischer Bauteile zeigen allerdings Abschätzungen, dass die Tellurvorkommen schnell aufgebraucht sein werden. Somit macht es Sinn, neue nachhaltige und „grüne“ Materialien zu untersuchen. Beispielhaft wurden dafür innerhalb dieser Arbeit die thermoelektrischen Eigenschaften des idealen Modellsystems ZnO untersucht. Hauptziel dabei war es, die Auswirkungen der Effekte auf mikroskopischer Ebene (z. B. durch Dünnschichten, Korngrenzen, künstliche Strukturierung) auf das makroskopische Verhalten der Probe besser zu verstehen. In diesem Zusammenhang wurden folgende Ergebnisse gefunden: Untersuchungen an entartet dotierten - und anschließend an Luft getemperten ZnO:Al Schichten zeigen, dass bei sehr hohen Ladungsträgerkonzentrationen, bei denen die Proben metallischen Charakter aufweisen, ein Vorzeichenwechsel von S stattfindet. Obwohl die Proben klar n-Typ sind, konnten kleine positive Seebeck-Koeffizienten gemessen werden, die mit abnehmender Temperatur das Vorzeichen wechselten. Dies kann Änderungen in der Zustandsdichte am Ferminiveau dieses entarteten Halbleiters zugeschrieben werden. Der Energie-Filter Effekt bedingt durch Korngrenzen, d. h. das Ansteigen des Leistungsfaktors mit steigender Ladungsträgerkonzentration, konnte nur bis zu einem gewissen Grad beobachtet werden: Falls nämlich die Ladungsträgerkonzentration einen bestimmten Wert übersteigt, verringern sogenannte Abschirmungseffekte die Barrieren Höhe und - Breite, was wiederum zu einer Verkleinerung des Leistungsfaktors führt. Im Hinblick auf die Charakterisierung von Grenzflächen wurden erste Messungen an Übergittern aus alternierenden ZnO/ZnS Schichten in „in-plane“ Geometrie durchgeführt. Die Ergebnisse ließen auf die Ausbildung elektrisch hochleitender Grenzschichten zwischen ZnO und ZnS schließen, welche das Transportverhalten bei hohen Schichtdicken (d > 100 nm) dominieren. Zu geringeren Schichtdicken hin, wo d mit der typischen Oberflächenrauigkeit vergleichbar wird, sind die Transportpfade und damit auch die thermoelektrischen Eigenschaften stark durch Oberflächenfluktuationen bestimmt. Diese Ergebnisse konnten auch qualitativ durch Simulationen innerhalb eines Netzwerkmodells (NeMo) bestätigt werden. Ein stärkerer Einfluss auf die thermoelektrischen Parameter, insbesondere auf die Wärmeleitfähigkeit, wurde in der Literatur in „cross-plane“ Geometrie, d. h. senkrecht zur Grenze, gefunden. Unglücklicherweise sind Messungen an Übergittern in dieser Geometrie sehr schwer durchzuführen. Um dieses Problem zu umgehen bietet die laterale Strukturierung dünner Schichten attraktive Möglichkeiten. Zur Realisierung einer Stegstruktur aus abwechselnden Materialien wurde die Methode der selbstausrichtenden Strukturübertragung im Rahmen dieser Arbeit entwickelt und angewendet. Messungen senkrecht zu den Grenzen zeigen, dass die Anzahl der Grenzen sowie deren Gestalt (d. h. Länge) und Morphologie einen erheblichen Einfluss auf den Leistungsfaktor nehmen. Unterstützt von zahlreichen NeMo Simulationen zeigten die Ergebnisse, dass die thermoelektrischen Eigenschaften über die strukturierte Probe hinweg vom elektrisch kürzesten Transportpfad dominiert werden. Dieser wiederum hängt stark von der Annahme sogenannter Grenzflächenregionen verschiedener Breite und Leitfähigkeit ab. Beste Übereinstimmung zwischen Experiment und Simulationen wurde unter der Annahme erreicht, dass ein bestimmter Teil des schlecht leitenden Materials durch eine hochleitende Grenzflächenregion ersetzt wird. Der Ursprung dieser hochleitenden Region konnte jedoch noch nicht geklärt werden. Die Ergebnisse dieser Arbeit zeigen, dass aufgrund seiner hohen Seebeck-Koeffizienten und der Möglichkeiten durch Dotieren die elektrische Leitfähigkeit einzustellen, ZnO ein geeignetes Materialsystem für umweltfreundliche und nachhaltige thermoelektrische Anwendungen ist. Das Problem, dass es eine hohe Wärmeleitfähigkeit aufweist, könnte durch eine geeignete Kombination mit ZnS gelöst werden. Dieses von der Theorie gezeigte Hintertürchen konnte bislang jedoch noch nicht experimentell bestätigt werden

A new conceptual framework for revenge firesetting

Revenge has frequently been acknowledged to account for a relatively large proportion of motives in deliberate firesetting. However, very little is actually known about the aetiology of revenge firesetting. Theoretical approaches to revenge-seeking behaviour are discussed. A brief review of how revenge is accounted for in existing theoretical explanations of deliberate firesetting and the known characteristics of revenge firesetters are provided. On this basis, the authors suggest, as a motive, revenge firesetting has to date been misconceptualised. A new conceptual framework is thus proposed, paying particular attention to the contextual, affective, cognitive, volitional and behavioural factors which may influence and generate a single episode of revenge firesetting. Treatment implications and suggestions for future research are also provided

Caregiver education in Parkinson’s disease: formative evaluation of a standardized program in seven European countries

The formative evaluation of a standardized psychosocial education program for patients with Parkinson's disease (PD) and their caregivers. The results of the participation of the caregivers are presented next to the data of the patients. Caregivers (n = 137) and patients with PD (n = 151) participated in the 8-week program in separate groups. Measurements were performed on psychosocial problems (BELA-P/A-k), health state (EQ-5D VAS), quality of life (PDQ-39) and depression (SDS) 1 week before and 1 week after the program. Participants rated their mood on a visual analogue scale before and after each session, and they filled in an evaluation questionnaire after the last session. Scores on the BELA-P/A-k improved significantly on the 'bothered by scale' as well as the 'need for help scale'. No improvements were found on EQ-5D VAS, PDQ-39 and SDS. Mood ratings improved significantly after each session. Most participants evaluated the program as positive. Feedback led to improvements in the program, which are incorporated in a final manual. The program was feasible to run in the different countries. This exploratory study led to improvements in the program and recommendations for further research. A study on the effectiveness of the program is the next step.Pathophysiology of paroxysmal and chronic degenerative progressive disorder of the central and periferal nervous syste

Food-induced Emotional Resonance Improves Emotion Recognition

The effect of food substances on emotional states has been widely investigated, showing, for example, that eating chocolate is able to reduce negative mood. Here, for the first time, we have shown that the consumption of specific food substances is not only able to induce particular emotional states, but more importantly, to facilitate recognition of corresponding emotional facial expressions in others. Participants were asked to perform an emotion recognition task before and after eating either a piece of chocolate or a small amount of fish sauce – which we expected to induce happiness or disgust, respectively. Our results showed that being in a specific emotional state improves recognition of the corresponding emotional facial expression. Indeed, eating chocolate improved recognition of happy faces, while disgusted expressions were more readily recognized after eating fish sauce. In line with the embodied account of emotion understanding, we suggest that people are better at inferring the emotional state of others when their own emotional state resonates with the observed one

Obesity and nutrition behaviours in Western and Palestinian outpatients with severe mental illness

Extent: 7p.Background: While people with severe mental illness have been found to be more overweight and obese in Western nations, it is unknown to what extent this occurs in Middle Eastern nations and which eating behaviours contribute to obesity in Middle Eastern nations. Method: A total of 665 responses were obtained from patients with serious mental illness attending out-patient clinics in Western developed countries (Germany, UK and Australia; n = 518) and Palestine (n = 147). Patients were evaluated by ICD-10 clinical diagnosis, anthropometric measurements and completed a self-report measure of frequencies of consuming different food items and reasons for eating. Nutritional habits were compared against a Western normative group. Results: More participants from Palestine were overweight or obese (62%) compared to Western countries (47%). In the Western sample, obese patients reported consuming more low-fat products (OR 2.54, 95% CI 1.02-6.33) but also greater eating due to negative emotions (OR 1.84, 95% CI 1.31-2.60) than patients with a healthy body-mass index. In contrast, obese patients from Palestine reported increased consumption of unhealthy snacks (OR 3.73 95% CI 1.16-12.00). Conclusion: Patients with mental illness have poorer nutritional habits than the general population, particularly in Western nations. Separate interventions to improve nutritional habits and reduce obesity are warranted between Western nations and Palestine.David Jakabek, Frances Quirk, Martin Driessen, Yousef Aljeesh and Bernhard T Baun

Introduction : From Fundamentals to Advances in Crowdfunding Research and Practice

publishedVersio

Does neurocognitive training have the potential to improve dietary self-care in type 2 diabetes? Study protocol of a double blind randomised controlled trial

Dietary self-care is a key element of self-management in type 2 diabetes. It is also the most difficult aspect of diabetes self-management. Adhering to long-term dietary goals and resisting immediate food desires requires top-down inhibitory control over subcortical impulsive and emotional responses to food. Practising simple neurocognitive tasks can improve inhibitory control and health behaviours that depend on inhibitory control, such as resisting alcohol consumption. It is yet to be investigated, however, whether neurocognitive training can improve dietary self-care in people with type 2 diabetes. The aim of this randomised controlled trial is to investigate whether web-based neurocognitive training can improve the ability of people with type 2 diabetes to resist tempting foods and better adhere to a healthy dietary regime

Playing with the Rules: Influences on the Development of Regulation in Sport

Sport today is a rule-governed practice: constitutive rules, both prescriptive and proscriptive, define required equipment and facilities as well as setting the formal rules of play; auxiliary rules specify and control eligibility: and regulatory rules place restraints on behaviour independent of the sport itself. This article offers a broad sweep examination of the historical process of rule development in sport including an assessment of the influence over time of gambling, fair play ideology, economic pressures, technological developments and legal intervention. En route a seven-stage scheme of constitutive rule development is postulated which it is hoped will set a research agenda for sports historians to test with case studies of particular sports

A waitlist-controlled trial of group cognitive behavioural therapy for depression and anxiety in Parkinson’s disease

Background: The aim of this study was to evaluate the efficacy of a group Cognitive Behavioural Therapy (CBT) treatment for depression and anxiety in Parkinson’s disease (PD). Methods: A waitlist-controlled trial design was used. Eighteen adults with PD and a comorbid DSM-IV-TR diagnosis of depression and/or anxiety were randomised to either Intervention (8-week group CBT treatment) or Waitlist (8-week clinical monitoring preceding treatment). The Depression, Anxiety, Stress Scale-21 (DASS-21) was the primary outcome. Assessments were completed at Time 1 (pretreatment), Time 2 (posttreatment/post-waitlist) and 1-month and 6-month follow-ups. Results: At Time 2, participants who received CBT reported greater reductions in depression (Mchange = -2.45) than Waitlist participants (Mchange = .29) and this effect was large, d = 1.12, p = .011. Large secondary effects on anxiety were also observed for CBT participants, d = .89, p = .025. All treatment gains were maintained and continued to improve during the follow-up period. At 6-month follow-up, significant and large effects were observed for both depression (d = 2.07) and anxiety (d = 2.26). Conclusions: Group CBT appears to be an efficacious treatment approach for depression and anxiety in PD however further controlled trials with larger numbers of participants are required

Identification of Novel α-Synuclein Isoforms in Human Brain Tissue by using an Online NanoLC-ESI-FTICR-MS Method

Parkinson’s disease (PD) and Dementia with Lewy bodies (DLB) are neurodegenerative diseases that are characterized by intra-neuronal inclusions of Lewy bodies in distinct brain regions. These inclusions consist mainly of aggregated α-synuclein (α-syn) protein. The present study used immunoprecipitation combined with nanoflow liquid chromatography (LC) coupled to high resolution electrospray ionization Fourier transform ion cyclotron resonance tandem mass spectrometry (ESI-FTICR-MS/MS) to determine known and novel isoforms of α-syn in brain tissue homogenates. N-terminally acetylated full-length α-syn (Ac-α-syn1–140) and two N-terminally acetylated C-terminally truncated forms of α-syn (Ac-α-syn1–139 and Ac-α-syn1–103) were found. The different forms of α-syn were further studied by Western blotting in brain tissue homogenates from the temporal cortex Brodmann area 36 (BA36) and the dorsolateral prefrontal cortex BA9 derived from controls, patients with DLB and PD with dementia (PDD). Quantification of α-syn in each brain tissue fraction was performed using a novel enzyme-linked immunosorbent assay (ELISA)