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

Large magnetoresistance at room-temperature in semiconducting polymer sandwich devices

We report on the discovery of a large, room temperature magnetoresistance (MR) effect in polyfluorene sandwich devices in weak magnetic fields. We characterize this effect and discuss its dependence on voltage, temperature, film thickness, electrode materials, and (unintentional) impurity concentration. We usually observed negative MR, but positive MR can also be achieved under high applied electric fields. The MR effect reaches up to 10% at fields of 10mT at room temperature. The effect shows only a weak temperature dependence and is independent of the sign and direction of the magnetic field. We find that the effect is related to the hole current in the devices.Comment: 3 pages, 4 figure

Monitoring Productivity and Quality of Grass-Legume Pastures Under Irrigated Condition

The performance of six grass-white clover mixtures were evaluated in winter cold zone of Eastern Anatolia. In combination with white clover, ryegrass (Lolium perenne L) cocksfoot, (Dactylis glomerata L) and smooth brome (Bromus inermis Leyss) were used in double and triple plant mixtures. Average DM production ranged from 7.5 to 10 t/ha , with no significant differences observed among the mixed swards. DM production of all mixed swards significantly varied between cutting periods and years. A gradual decrease in DM production was observed both from the first to forth cut and from the first to third year. Clover and consequently CP content increased from the first to second year and decreased in the third year. The increasing proportion of clover after first cut was also reflected in a higher content of CP. On the other hand, the persistence of grass species to frequent cutting varied but ryegrass became dominant to cocksfoot and smooth brome in triple mixtures

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

Large magnetoresistance at room-temperature in small molecular weight organic semiconductor sandwich devices

We present an extensive study of a large, room temperature negative magnetoresistance (MR) effect in tris-(8-hydroxyquinoline) aluminum sandwich devices in weak magnetic fields. The effect is similar to that previously discovered in polymer devices. We characterize this effect and discuss its dependence on field direction, voltage, temperature, film thickness, and electrode materials. The MR effect reaches almost 10% at fields of approximately 10 mT at room temperature. The effect shows only a weak temperature dependence and is independent of the sign and direction of the magnetic field. Measuring the devices' current-voltage characteristics, we find that the current depends on the voltage through a power-law. We find that the magnetic field changes the prefactor of the power-law, whereas the exponent remains unaffected. We also studied the effect of the magnetic field on the electroluminescence (MEL) of the devices and analyze the relationship between MR and MEL. We find that the largest part of MEL is simply a consequence of a change in device current caused by the MR effect.Comment: 8 figure

The effect of deuteration on organic magnetoresistance

NOTICE: this is the author’s version of a work that was accepted for publication in Synthetic Metals. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in SYNTHETIC METALS, 161, 7-8, (2011) DOI 10.1016/j.synthmet.2010.11.04

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

İnsanda fötal epidermis ve eklentilerinin farklı anatomik bölgelerdeki histomorfometrik analizi

Fetus epidermis ve eklerinin farklı anatomik bölgelerdeki kalınlığını, gelişimini ve dağılımını incelemek amacıyla histomorfometrik bir araştırma yapıldı. Fetus epidermis ve ekleri hakkında bilgi verildi. Selçuk Üniversitesi Kadın Hastalıkları ve Doğum Kliniği ve Sağlık Bakanlığı Doğum ve Çocuk Bakımevinden toplanan 40 adet fetus ve embriyo piyesi kullanıldı. Materyaller Hematoksilen-Eosin ve Masson Fontana boyası ile boyanarak x40 objektif büyütmede okulometre yardımıyla epidermis kalınlığı mikron cinsinden ölçüldü. Ekler x10 objektif büyütmede değerlendirildi (Kıl, ter, yağ bezi). Masson Fontana boyasında uyluk ve kafa derisinin kıl folliküllehndeki melanin granüllehnin görülme zamanı tesbit edildi. Epidermis yüksekliği, her 3 bölgede de ilk pikini 13. haftada yaptığı, 18, 19. haftalardan sonra belirgin bir yükselme gösterdiği tesbit edildi. Deri eklerinin ise yağ bezinin kafa derisinde 15. haftada, uyluk da 18. haftada, kafa derisi kıl follikülünün 10.5 haftada, uyluk da 13.6. haftada, ter bezinin ise kafa derisinde 20.4., uylukda yine 20.4, ayak tabanında ise 15.haftada rastlandı. Melanin granülleh kafa derisinde 15. haftada uyluk da 17.9. haftada görüldü. Bu bulgular değerlendirildiğinde epidermis kalınlığının en fazla olduğu bölge ayak tabanı, kıl folikülünün ilk geliştiği yer kafa derisi, ter bezinin ilk rastlandığı yer ayak tabanı, yağ bezinin ilk tesbit edildiği yer kafa derisi ve melanin granüllehnin ilk görüldüğü yer kafa derisi kıl folikülleri olarak değerlendirildi. Ayrıca bu çalışmada embriyo ve fetus epidermis ve ekleri ile ilgili elde edilen sayısal değerler adli tıpda düşük yaş tayininin tesbitinde faydalı olacağı kanaatindeyiz.A histomorfometrik analysis was prepared for searching the fetal epidermis and its appandages. The difference of thickness, development between different anatomical regions were considered. Summary about fetal epidermis and appandages was given previously. 40 fetusus and embryos were collected from Selçuk University Gynecology and Obstetrics Clinic and Goverment Health Hospital. Speciemens were stained with H.E. and Masson Fontana, observed under x40 magnification. With help of oculometer, the results were determined in micron units. Appandages were determined under x10 magnification using Masson Fontana stain. The first appearence of melanin granules in thigh and scalp hairfollicules were estimated. In the three regions the first pike of epidermis thickness was observed in the 13. week. And confining 18, 19. weeks the thickness increased by the time. When previous appearaces were considered about the skin appandages, sebase glands first appeared in the scalp at 15th week, in thigh 18. week, the hair follicule appeared in the scalp at 10.5 week, thigh 13.6 week, sweet gland at the scalp 20.4 week, thigh 20.4 week, at sole 15. week. Melanin granules first appeared at the scalp in 15 week and thigh 17.9 week. When we consider all of these results the most thickest epidermis is in the sole, the hair follicule first developed at the scalp, the sweet gland is first is seen at the sole, sebase gland is first seen at the scalp, previous melanin granules are observed in the scalp hair folliküles. It is thought that the results obtained from this study can be helpful in medicine for feotal age determination

MONTHLY WATER DEMAND FORECASTING BY ADAPTIVE NEURO-FUZZY INFERENCE

In this study, an adaptive Neuro-Fuzzy inference system (ANFIS) is used to forecast monthly water use from several socio-economic and climatic factors, which affect water use. Totally 108 data sets are collected and data sets are divided into two subsets, training and testing. The models consisting of the combination of the independent variables are constructed and the best fit input structure is investigated. The performance of ANFIS models in training and testing sets are compared with the observations and the best fit model forecasting model is identified. For this purpose, some criteria of performance evaluation such as, Root Mean Square Error (RMSE), efficiency (E) and correlation coefficient (CORR) are calculated for all models. Then, the best fit models are also trained and tested by Multiple Regression (MR). The results of models are compared to get more reliable comparison. The results indicated that ANFIS can be applied successfully for monthly water demand forecastin