Investigating Morphology and Stability of Fac‐tris (2‐phenylpyridyl)iridium(III) Films for OLEDs

Stable film morphology is critical for long‐term high performance organic light‐emitting diodes (OLEDs). Neutron reflectometry (NR) is used to study the out‐of‐plane structure of blended thin films and multilayer structures comprising evaporated small molecules. It is found that as‐prepared blended films of fac‐tris(2‐phenylpyridyl)iridium(III) [Ir(ppy)₃] in 4,4′‐bis(N‐carbazolyl)biphenyl (CBP) are uniformly mixed, but the occurrence of phase separation upon thermal annealing is dependent on the blend ratio. Films comprised of the ratio of 6 wt% of Ir(ppy)₃ in CBP typically used in OLEDs are found to phase separate with moderate heating while a higher weight percent mixture (12 wt%) is found to be stable. Furthermore, it is found that thermal annealing of a multilayer film comprised of typical layers found in efficient devices ([tris(4‐carbazoyl‐9‐ylphenyl)amine (TCTA)/Ir(ppy)₃:CBP/bathocuproine (BCP)]) causes the BCP layer to become mixed with the emissive blend layer, whereas the TCTA interface remains unchanged. This significant structural change causes no appreciable difference in the photo­luminescence of the stack although such a change would have a dramatic effect on the charge transport through the device, leading to changes in performance. These results demonstrate the effect of thermal stress on the delicate interplay between the chemical composition and morphology of OLED films.     

The choice of probing sites by Bracon hebetor Say (Hymenoptera: Braconidae) foraging for Ephestia kuehniella Zeller (Lepidoptera: Pyralidae)

A direct behavioral assay was conducted to investigate the preferred habitat for host searching by the parasitoid Bracon hebetor (Hymenoptera: Braconidae). The effects of mating, feeding and post-emergence experience on female parasitoid choices of searching sites were also examined. B. hebetor appears to be directed to the habitat of its host through chemical cues originating from the host larvae, frass and adults. These cues elicit a series of directed responses by the female. Generally, the data showed that flour containing 30-day-old larvae was preferred by B. hebetor females. This was followed by the flour containing the frass, then the adult host, and finally the flour containing 10-day-old larvae. It appears that cues produced by young larvae were the weakest whereas cues produced by older ones were the strongest. Feeding seemed to be important in the location of the proper searching site. Although the cues were normally learned by the immature stages of the parasitoid, and were subsequently manifested in their responses as adults, adult experience increased the ability of the parasitoid to locate the suitable habitat for searching.     

A new control technique for active power filters using a combinedgenetic algorithm/conventional analysis

In this paper, the computational problems associated with the optimization techniques used to evaluate the switching patterns for controlling variable-characteristics active power filters are presented and critically analyzed. Genetic algorithms (GAs) are introduced in this paper to generate a fast and accurate initial starting point in the highly nonlinear optimization space of mathematical optimization techniques. GAs tend to speed up the initialization process by a factor of 13. A combined GA/conventional technique is also proposed and implemented to reduce the associated computational burden associated with the control and, consequently, increasing the speed of response of this class of active filters. Comparisons of these techniques are discussed and presented in conjunction with simulation and practical results for the filter operation     

Transient response of optoelectronic integrated bistable device

In this paper, the transient response of an optical bistable device with optically controlled set and reset functions is analyzed. The device is made from a vertical integration of two heterojunction phototransistors (HPTs) and a laser diode (LD). One of the HPTs (HPT-A) is integrated just above the active layer of the LD and is utilized in the set operation, while the other HPT (HPT-B) is used to achieve the reset operation. The effect of the various device parameters on the set and reset operations is outlined. Finally, expressions for the rise time during the setting, and fall time during the resetting conditions are derived     

Electrochemical Studies on the passive behaviour of tin in different buffer solutions

The effect of pH on the passivity of Sn has been investigated in buffered (phthalate-borate, and citrate phosphate buffer series), and in unbuffered phosphate solutions, using the cyclic voltammetric technique. Two anodic peaks; the first being more pronounced than the second, and on cathodic peak have been observed in the two buffer series at different scan rates and pH values. The anodic and cathodic peak current densities (I_p) and potentials (E_p) are functions of the scan rate (v) and the pH value. Plots of I_p against v^1/2 yield straight lines at each pH value. The effect of pH on I_p for the first anodic peak shows a shallow minimum in the near neutral and slightly alkaline range at all scan rates. Straight lines are also observed between E_p and v^1/2, the extrapolation of which to v = 0 gives the spontaneous (no polarization) oxidation or reduction potentials (E′ and E″). The absence of polarization effects in E′ and E″ make them the most suitable values for comparison with thermodynamic data. Therefore, the two straight lines obtained between E′ and E″ on one hand and the pH on the other hand to give an estimate of (i) the slope (dE°/dpH), and (ii) the value of E° at pH - 0 (from intercept). Comparison of the two experimental values with all available thermodynamic data for Sn(II) and Sn(IV) oxides and hydroxides shows that: (i) the first anodic peak represents the formation of Sn(OH)₂ from Sn and OH^?, (ii) the second anodic peak represents the formation of Sn(OH)₄ directly from Sn and OH^?, and (iii) the cathodic reduction peak correponds to the reduction of Sn(IV) oxidized species to Sn. The results in citratephosphate buffer have been treated in the same manner. However, the result of (dE°/dpH) and E° at pH = 0 deviate from thermodynamic data, because of the possible participation of other anodic reactions such as the formation of soluble Sn compounds, Sn complexes, and incorporation of anions in the anodic film.     

Cell mediated immune response in chronic liver diseases: schistosomal, viral and neoplastic

Cell mediated immune response (CMIR) was studies in 120 patients having chronic liver diseases. Patients were divided into 6 groups, (20 each). (1) Early hepatosplenic Schistosomiasis. (EHSS), (2) Late hepatosplenic Schistosomiasis. (LHSS), (3) Hepatosplenic Schistosomiasis with hepatitis B and/or C infections, (4) Hepatitis B virus cases. (HBV), (5) Hepatitis C virus cases (HCV), (6) Hepatocellular carcinoma cases. (HCC). Twenty within normal subjects taken as controls. Laboratory investigations revealed significant esinophilia in patients of group (1), haemoglobin level was significantly reduced in patients of group (1, 2, 3, & 6), serum albumin was significantly reduced in group (2). The percentage of positivity of skin testing using purified protein derivative, ranged between 10% of patients with LHSS, HBV, HCC and HSS with HBV and/or HCV, 20% of patients with HCV and 25% of patients with EHSS. Percentage of positivity in control group was 100%. The mean diameter of delayed intradermal reaction (2.2 +/- 0.5-6.1 +/- 2.1 mms.) was significantly lower in patients than controls. The response of lymphocyte transformation test to phytohaemmagglutinin was significantly lower in patients when compared to controls. The association of HBV and/or HCV with hepatosplenomegaly was accompanied with a marked depression in cell mediated immune response. Anaemia, hypoalbuminemia and nutritional status of the patients with chronic liver diseases play a major role in the suppression of cell mediated immune response.     

ORGANIC GEOCHEMISTRY AND SOURCE ROCK CHARACTERISTICS OF THE ZAGROS PETROLEUM PROVINCE, SOUTHWEST IRAN

The Zagros of SW Iran and its continuation into N Iraq forms the tectonised NE margin of the Middle East basin. Sedimentation in the Zagros began in the late Precambrian and continued with comparatively few interruptions until the Pliocene, when strong earth movements affected the area and gave rise to the present day large. elongated NW-SE trending structures. Some of the world's largest structurally-controlled oil fields are located in the Zagros. The most productive pay zone is the Oligo-Miocene Asmari Formation, although significant oil pools are present also in the Cenomanian-Turonian Sarvak limestone and in the Neocomian-Jurassic Khami Group carbonates. Recently, large gas deposits have been discovered in the Permo-Triassic carbonates assigned to the Deh Ram Group. Geochemical studies were carried out five potential source beds of Eocene-Palaeocene (Pabdeh Formation). Coniacian-Neocomian (Garau Formation) and Silurian (Ghakum Formation) age. The results showed that the organic matter in these formations is almost exclusively of marine algal origin, and that the Kazhdumi is the major source of the hydrocarbons in the Asmari and Sarvak reservoirs. The origin of the hydrocarbons in the Khami and Deh Ram reservoirs is at present speculative.     

The complete dissolution of goethite

The dissolution of all except one sample of goethite obeyed the cube root kinetic law which implies a uniform rate of disappearance of the crystals. However, the electron microscope showed that this was only true in some cases and that there could be some compensation between size distribution in the sample and the increase in surface area through hole formation in the crystal.     

Galvanostatic formation of barrier-type Anodic oxides

Experimental Factors Affecting Oxide Growth Results of galvanostatic anodization of various metals with varying valve-metal behaviour including Nb, Ta, Zr, Ti, Al, W, Te, Sb, and Bi are compiled and compared with respect to the effect of various experimental factors such as surface pretreatment, stirring, solution composition, temperature of the bath, on the efficiency of oxide growth relative to that for other anodic processes. It is concluded that all of the above factors play an important role in the anodization of the non-typical valve metals, particularly Sb, Bi and W. Typical anodic charging curves associated with the process of oxide growth are given for several valve metals. Experimental data relevant to the phenomena of oxide breakdown are recorded and compared. The results indicate that the mechanism of breakdown varies for the same metal with variations in the experimental conditions.