Multiphonon emission model of spin-dependent exciton formation in organic semiconductors

The maximum efficiency in organic light-emitting diodes (OLEDs) depends on the ratio, $r=k_S/k_T$, where $k_S$ ($k_T$) is the singlet (triplet) exciton formation rate. Several recent experiments found that r increases with increasing oligomer length from a value $r \approx 1$ in monomers and short oligomers. Here, we model exciton formation as a multi-phonon emission process. Our model is based on two assertions: (i) More phonons are emitted in triplet formation than in singlet formation. (ii) The Huang-Rhys parameter for this phonon emission is smaller in long oligomers than in short ones. We justify these assertions based on recent experimental and theoretical data.Comment: 8 pages, 7 figure

Hyperfine interaction and magnetoresistance in organic semiconductors

We explore the possibility that hyperfine interaction causes the recently discovered organic magnetoresistance (OMAR) effect. Our study employs both experiment and theoretical modelling. An excitonic pair mechanism model based on hyperfine interaction, previously suggested by others to explain magnetic field effects in organics, is examined. Whereas this model can explain a few key aspects of the experimental data, we, however, uncover several fundamental contradictions as well. By varying the injection efficiency for minority carriers in the devices, we show experimentally that OMAR is only weakly dependent on the ratio between excitons formed and carriers injected, likely excluding any excitonic effect as the origin of OMAR.Comment: 10 pages, 7 figures, 1 tabl

Strategy revision opportunities and collusion

This paper studies whether and how strategy revision opportunities affect levels of collusion in indefinitely repeated two-player games. Consistent with standard theory, we find that such opportunities do not affect strategy choices, or collusion levels, if the game is of strategic substitutes. In games of strategic complements, by contrast, revision opportunities lead to more collusion. We discuss alternative explanations for this result

Gas sensing properties of carbon nanotubes modified with calixarene molecules measured by QCM techniques

1st International Congress on Advances in Applied Physics and Materials Science (APMAS), Antalya, Turkey, 12-15 May, 2011This study focuses on the characterization and optimization of calixarene modified carbon nanotube thin films for gas detection. Calixarene molecules were synthesized individually by considering their functional groups to attract the gas. Calixarene modified carbon nanotube based sensors were fabricated using drop-casting method on a quartz crystal microbalance gold electrode. Carbon monoxide, carbondioxide, oxygen and dry air were used as active gases for adsorption process, while high-purity nitrogen gas was used for desorption process. The selectivity and sensitivity of calixarene modified carbon nanotube are investigated in detail. Our experimental results show that functional calixarene modified carbon nanotube coated quartz crystal microbalance sensors are very sensitive and selective to gas of CO 2 at room temperature operation.This research was supported by TÜBİTAK under project numbers TBAG 109 T240 and 110 M349 and IYTE research project number 2010IYTE2

Some harvesting system transforming energy wastes of compressed air to electricity

Energy harvesting devices are self-powered systems which are associated with input ambient energy and convert such energy to electrical one. In this study, we focus on input ambient energy deriving from compressed air. Using arbitrary pneumatic machine, the compressed air after work - with its typical parameters as overpressure 6 bar or higher and variable volume flow - is exhausted to atmosphere. This generates energy losses. We have constructed some device which transforms the loss of compressed air energy to electricity. It illustrates the principle of action very well and does not perturb operation of pneumatic machines being source of energy losses

Validity and reliability of the social support scale in chronic diseases-TR (SSCII-TR)

WOS: 000334020500006Objectives: The purpose of this study was to examine the reliability and validity of the Social Support Scale in Chronic Diseases (SSCII) Scale Turkish version that was developed by Hilbert-McAllister. Methods: This was planning a methodological study. Research group consists of 163 older persons that accepted to participate in this study and who had a chronic disease. Data were collected in 15th June-15th August 2012 period from two homes for aged in Izmir Provinence. The necessary ethical approval was obtained from the institutions and each participant for research. Results: SSCII Scale was translated to Turkish for language validity. For content validity, it was obtained of experts view and it was corrected according to expert's suggestions. For content validity, Kendall goodness-of-fit Correlation test was performed (Kendall's Wa = 0.167, chi(2) = 49.337, df = 37, p = 0.084). reliability and validity study, first of all, total item score correlation was examined. All items were upper than 0.20 correlation limit and there were a significant relationship between total item correlation score. Scale originally has 38 items in the latest version in Turkish. For reliability of the scale, it was performed the internal consistency analysis and it was find that Cronbach's alpha coefficient as 0.89. So, the scale has an acceptable level internal consistency coefficient. For the determining of scale's time stability, it was applied to initial 32 older persons after first survey. A significant relation found between test-retest scores (p = 0.000). Conclusion: SSCII Scale Turkish version is a reliable and valid scale for the Turkish community. (C) 2013 Elsevier Masson SAS and European Union Geriatric Medicine Society. All rights reserved.Ege University (EU) Research FundEge University [12/ASYO/001]This study was supported by Ege University (EU) Research Fund (12/ASYO/001)

Gas Sensing Properties of Carbon Nanotubes Modified with Calixarene Molecules Measured by QCM Techniques

1st International Congress on Advances in Applied Physics and Materials Science (APMAS) -- MAY 12-15, 2011 -- Antalya, TURKEYWOS: 000299603000075This study focuses on the characterization and optimization of calixarene modified carbon nanotube thin films for gas detection. Calixarene molecules were synthesized individually by considering their functional groups to attract the gas. Calixarene modified carbon nanotube based sensors were fabricated using drop-casting method on a quartz crystal microbalance gold electrode. Carbon monoxide, carbondioxide, oxygen and dry air were used as active gases for adsorption process, while high-purity nitrogen gas was used for desorption process. The selectivity and sensitivity of calixarene modified carbon nanotube are investigated in detail. Our experimental results show that functional calixarene modified carbon nanotube coated quartz crystal microbalance sensors are very sensitive and selective to gas of CO2 at room temperature operation.Istanbul Kultur Univ, Gebze Inst Technol, Doga Nanobiotech Inc, Terra Lab Inc, LOT Oriel Grp, PHYWE, Delta Elekt In