Electrical Transport in Thin Film Systems for Energy Harvesting.

Many energy conversion technologies rely on the properties of thin films. In many cases, the fundamental physics underlying the structure-property-performance interrelationship are not completely understood. So it is impossible to fully exploit the true capabilities of these systems. Therefore, investigating and understanding such interrelationships in different systems is of both scientific and technological importance. In this dissertation, both conjugated polymer systems for photovoltaic application and strained silicon system for thermoelectric application are investigated in order to develop a clearer understanding of the effect of film thickness and microstructural features on electrical transport. Morphological features like domain size, phase purity are investigated in the polymers to understand the effects on charge mobility, recombination and further on device performance. With regard to silicon, the effects of lattice strain on electrical conductivity and thermopower are studied. The out-of-plane hole mobility was investigated in regioregular P3HT thin films. It was shown that the hole mobilities monotonically increased an order of magnitude when film thickness increased from 80 nm to 700 nm. Based on X-ray diffraction, spectroscopic ellipsometry and simulations, this thickness-dependent mobility is associated with substrate induced anisotropies of the P3HT film structure. The role of microstructural features on the performance characteristics of the archetypal P3HT:PCBM (1:1) bulk heterojunction solar cell was investigated. It is demonstrated that small domain sizes and correspondingly large interfacial areas accommodated a high initial carrier density. However in these materials, non-geminate recombination of carriers could be significant, leading to low open circuit voltages and low fill factors. The purity of the domains also influenced the charge carrier mobilities and non-germinate recombination. One important finding from this study is that high short circuit currents were readily achieved with smaller domain sizes than 10 nm, which is believed to the best domain size. With regard to the thermoelectric characterizations in the strained silicon thin film possessing nanomesh topology, the electrical conductivity was found to increase several folds and the power factor doubled. This enhancement is attributed to the splitting of silicon conduction band under the biaxial tensile strain, which affects the effective mass, inter-valley scattering and energy distribution of transporting electrons.PhDMaterials Science and EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/108740/1/bingyuan_1.pd

How employees view smart cycling to work:A regional survey in the Netherlands

The intent of our study is to provide insightful results regarding views and attitudes of employees towards cycling. We were especially interested in their views regarding the use of personalized rewarding schemes delivered via a smartphone app to stimulate cycling to work. The study involved a quantitative on-line survey of employees in Enschede, the Netherlands, and vicinity, wherein 1.800 employees participated. Our results show that most employees commute by bicycle, followed by a considerable percentage who commute (alone) by car. In addition, most employees consider cycling as pleasant, healthy, and refreshing. For employees who often cycle to work, feeling healthy is the most important reason for them to take up cycling. Equally important, the use of apps to stimulate cycling to work has potential, but employees need to be approached accordingly. For example, employees who sometimes cycle to work are more receptive to rewarding schemes delivered via smartphone apps. Conversely, non-cyclists are more reluctant to take up cycling, even if rewards would be offered

Effectiveness of incentives offered by mobile phone app to encourage cycling: A long‐term study

Reduction of car use is one of the most effective ways to tackle congestion-related problems. Using positive incentives to stimulate bicycle use is one possibility to reduce car use. Cycling is a sustainable transport mode that uses little space and is healthy. There is evidence that positive incentives may be more effective than punishing travellers for undesirable behaviour, and the emergence of mobile applications for delivering interventions has opened up new opportunities for influencing travellers. So far, few studies have focused on exploring the effectiveness of positive incentives on long-term behavioural change. We used the SMART app to deliver positive incentives to more than 6000 travellers in the Dutch region of Twente. The app automatically tracks users and provides incentives such as challenges with rewards, feedback, and messages. This study covers the period from March 2017 to June 2018, in which more than 1000 SMART users participated in monthly challenges. We evaluated the effects of the challenges and rewards and found that the challenges did encourage cycling and reduced car use in the short term. There is also some evidence for behavioural change over a longer time period

Au nanoparticles on citrate-functionalized graphene nanosheets with a high peroxidase-like performance

Japan Society for Promotion of Science (JSPS); National Natural Science Foundation of China [21305050]; Special Foundation for Young researchers of Health Department of Fujian [2013-2-106]; Scientific Research Foundation of Shangda Li, Jimei University [ZC2013005]; JSPS KAKENHI [2402335, 24550100]In this paper, Au nanoparticles (AuNPs) have been homogeneously deposited on citrate-functionalized graphene nanosheets (Cit-GNs) by a simple one-pot reducing method. The morphology and composition of the thus-prepared AuNPs/Cit-GNs were characterized by transmission electron microscopy (TEM), high resolution TEM, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The results showed that the AuNPs with a uniform size are well dispersed on the surface of the Cit-GNs. Significantly, the as-prepared AuNPs/Cit-GNs possess intrinsic peroxidase-like activity, which can catalyze the oxidation of the peroxidase substrate 3,3,5,5-tetramethylbenzidine (TMB) by hydrogen peroxide (H2O2) to develop a blue color in aqueous solution. The catalysis was in accordance with Michaelis-Menten kinetics and the AuNPs/Cit-GNs showed a strong affinity for both H2O2 and TMB. Moreover, by comparing with Cit-AuNPs, AuNPs/GNs and AuNPs/PVP-GNs, the AuNPs/Cit-GNs composite exhibits a higher catalytic ability with a lower Michaelis constant (Km) value, suggesting that the GNs with a large surface area and the citrate ions with more carboxyl groups around the AuNPs can greatly enhance the peroxidase-like activity of AuNPs/Cit-GNs. Taking the advantages of the high catalytic activity, the good stability and the low cost, the novel AuNPs/Cit-GNs represent a promising candidate as an enzyme mimic and may find a wide range of new applications in biochemistry and biotechnology

Male Patients With Dilated Cardiomyopathy Exhibiting a Higher Heart Rate Acceleration Capacity or a Lower Deceleration Capacity Are at Higher Risk of Cardiac Death

The effects of dilated cardiomyopathy (DCM) on cardiac autonomic regulation and electrophysiology, and the consequences of such changes, remain unclear. We evaluated the associations between heart rate acceleration capacity (AC) and deceleration capacity (DC), heart structural and functional changes, and cardiac death in 202 healthy controls and 100 DCM patients. The DC was lower and the AC was higher in DCM patients (both males and females). Multivariable, linear, logistic regression analyses revealed that in males, age was positively associated with AC in healthy controls (N = 85); the left atrial diameter (LAD) was positively and the left ventricular ejection fraction (LVEF) was negatively associated with AC in DCM patients (N = 65); age was negatively associated with DC in healthy controls (N = 85); and the LAD was negatively and the LVEF was positively associated with DC in DCM patients (N = 65). In females, only age was associated with either AC or DC in healthy controls (N = 117). Kaplan–Meier analysis revealed that male DCM patients with greater LADs (≥46.5 mm) (long-rank chi-squared value = 11.1, P = 0.001), an elevated AC (≥-4.75 ms) (log-rank chi-squared value = 6.8, P = 0.009), and a lower DC (≤4.72 ms) (log-rank chi-squared value = 9.1, P = 0.003) were at higher risk of cardiac death within 60 months of follow-up. In conclusion, in males, DCM significantly affected both the AC and DC; a higher AC or a lower DC increased the risk of cardiac death

Mucosal-Associated Invariant T Cells Improve Nonalcoholic Fatty Liver Disease Through Regulating Macrophage Polarization

Mucosal-associated invariant T (MAIT) cells, a novel population of innate-like lymphocytes, have been involved in various inflammatory and autoimmune diseases. However, their role in the development of nonalcoholic fatty liver disease (NAFLD) remains unclear. In this study, we investigated the alterations of phenotype and immunological function of MAIT cells in NAFLD. Analysis of PBMCs in 60 patients with NAFLD and 48 healthy controls (HC) revealed that circulating MAIT cell frequency decreased in NAFLD, especially in the patients with higher serum levels of γ-glutamyl transferase or total triglyceride. Functional alterations of circulating MAIT cells were also detected in NAFLD patients, such as the increased production of IL-4 whereas the decreased production of IFN-γ and TNF-α. Furthermore, elevated expression of CXCR6 was observed in circulating MAIT cells of patients. Meanwhile, we found an increased number of MAIT cells in the livers of NAFLD, and the number was even greater in patients with higher NAFLD activity score. Moreover, activated MAIT cells induced monocytes/macrophages differentiation into M2 phenotype in vitro. Additionally, MAIT cells were enriched and displayed Th2 type cytokines profile in livers of wild type mice fed with methionine and choline deficient diet (MCD). Notably, mice deficient of MAIT cells exhibited more severe hepatic steatosis and inflammation upon MCD, accompanied with more CD11c+ proinflammatory macrophages (M1) and less CD206+ anti-inflammatory macrophages (M2) in livers. Our results indicate that MAIT cells protect against inflammation in NAFLD through producing regulatory cytokines and inducing anti-inflammatory macrophage polarization, which may provide novel therapeutic strategies for NAFLD