Charge photogeneration in organic donor/acceptor blends

Polymer-small molecule blend films are of increasing interest in the field of organic solar cells. This thesis employs transient absorption spectroscopy as a mean to study charge photogeneration in these blend films. These studies allow identifying and addressing the charge photogeneration efficiency-limiting processes in polymer:perylene diimide organic solar cells. We approach the question by considering the influence of nanomorphology and phase segregation on charge photogeneration and recombination dynamics. We further report on yield of charge separated species in polythiophene / perylene diimide blend films as a function of electron acceptor’s energy levels. We find that, compared to polythiophene / PCBM blend films, charge photogeneration is significantly enhanced. Correlations between free energy for charge dissociation and charge photogeneration yield within different polymer:acceptor series are observed and indicate the generality of this relationship. Furthermore, the energetic model proposed to account for these results is consistent with the well-established Onsager and Marcus theories. It can therefore be concluded that the yield of photogenerated charges in polymer/acceptor systems is likely to be dependent upon the excess vibrational energy of the bound radical pair, such that the key kinetic competition in the photogeneration process is between vibrational relaxation and dissociation of this species Simultaneously, we investigate photoinduced charge separation in solid films of two perylene diimides and a donor-bridge-acceptor (D-B-A)molecule, exTTF-pcp-C60 relative to solution. First we find Intramolecular charge separation and recombination is correlated with a reduction in the yield of long-lived, intermolecular charge-separated species in the perylene diimide dyad. In the D-B-A system we observe the exTTF-pcp-C60 motif in this case leads to more charges than the reference compounds or a mixture of them but that the excited state of the electron acceptor, the fullerene, suffers from concentration self-quenching which severely affect the charge yield in solid films

On a New Class of Bivariate Survival Distributions Based on the Model of Dependent Lives and its Generalization

In this paper, a new class of survival distributions based on the model of dependent lives and proportional hazard rate family is introduced. This new family of bivariate survival models contains several bivariate lifetime models and is more flexible. The main purpose of this paper is to generalize this family of bivariate survival distributions of dependent lives so that more flexible models can be achieved. These new families of distributions are called the bivariate proportional hazard rate (BPHR) and the bivariate proportional hazard rate-geometric (BPHRG) families, respectively. It is also observed that, if θ = 1, then the BPHR family is a particular state of the BPHRG family. Several features of these new families of distributions such as the multivariate aging properties, the bivariate hazard gradient, and dependency structures are investigated. We design a flexible computational EM algorithm to calculate the maximum likelihood estimation of parameters. Also, several simulation studies are represented to evaluate the efficiency of the EM algorithm. Finally, we analyze three real datasets and compare the BPHRG models with the BPHR models

Acoustic Enhancement of Polymer/ZnO Nanorod Photovoltaic Device Performance

Leverhulme Trust and EPSRC. Grant Numbers: EP/J500021/1, EP/G037515/1

Towards the Analysis of Information Technology Governance and Productivity Based on COBIT Framework: An Empirical Study in E-Banking

The present study tends to evaluate information technology governance based on COBIT framework in the electronic banking system to increase productivity of banks in an empirical study. This study is an exploratory mixed research. In the qualitative section, the theoretical foundations and related models are reviewed in order to identify the components of IT governance based on COBIT framework and productivity in the electronic banking system. In the quantitative section, 258 people were randomly selected as sample. Cronbach\u27s alpha for IT governance and productivity was 79.7% and 82.3%, respectively, which indicates the reliability of this questionnaire. Qualitative results indicate that COBIT based IT governance includes four parameters (IT planning and organization, IT acquisition and implementation, IT delivery and support and IT monitoring and evaluation) and productivity includes four parameters (effectiveness, efficiency, improved performance and customer satisfaction). Quantitative results showed that the effect of COBIT based IT governance is positive on increased productivity (0.45). Moreover, the findings showed that the effect of COBIT based IT governance is significant on improved performance, efficiency and effectiveness (P < 0.01). According to the results, IT governance based on COBIT framework in the electronic banking system leads to increased productivity, efficiency, effectiveness and improved performance. Therefore, it can be concluded that deploying COBIT framework IT governance leads to a competitive advantage for electronic banking system

Epidemiological, Clinical and Paraclinical Study of Hydatid Cysts in Three Educational Medical Centers in 10 Years

Background: Echinococcosis or hydatidosis, caused by the larval stage of Echinococcus granulosus (E. granulosus), is an important public health problem in many areas of the world  and  Iran is a country of endemic situation for hydatidosis In the present study, we evaluated epidemiological, complications and clinical characteristics of hydatidosis at three University Medical Centers in Tehran over a 10-year period.Materials and Methods: This is a descriptive cross-sectional study performed in patients with hydatid cysts. Information about age, gender, number of cysts, organ involvement, morbidity and mortality and relapse were collected from medical records of hydatid patients. Paraclinic information such as CT Scan, MRI, ultrasound, complete blood count, pathological diagnosis and complication of disease were collected.Results: Overall, 81 patients, 35 (43.2%) male and 46 (56.8%) female, who were diagnosed as having hydatid cyst by clinical and radiological findings, with pathologic documentation were studied in three university medical center registries over a 10-year period (2003- 2012) in Tehran. Fourteen patients (17% of cases) had complications resulting from this disease. Patients' age ranged from 5 to 86 years, and the peak prevalence of the disease was between 20 and 40 (34% of cases).Conclusion: Iran  is a country of endemic situation for hydatidosis. Prevalence rate of hydatidosis in Iran was reported to be 0.61-2 in 100000 populations. The highest  rate of infection and complications were in patients of 20-40 years age. Clinical examination revealed that abdominal pain was the most common complaint and was present in 51.7% of the cases. Other most common complain were cough, abdominal mass, dyspnea, icterus, chest pain, dyspepsia, back pain and seizure; and it was result of occupying effect of cysts in organs. This is similar with previous studies in Ira