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Shiv Nadar University

(SoNS) School of Natural Sciences

We describe and discuss the unique electrical characteristics of an organic field-effect transistor in which the active layer consists of a type II lateral heterojunction located approximately midway between the source and drain. The two active semiconductors on either side of the junction transport only one carrier type each, with the other becoming trapped, which leads to devices that operate in only the steady state when there is balanced electron and hole injections from the drain and source. We describe the unique transfer characteristics of such devices in two material systems. © 2009 American Institute of Physics.

Physics

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Applied Physics Letters

Electrical characteristics of lateral heterostructure organic field-effect bipolar transistors

The synthesis and characterization of solution processable donor-acceptor-donor (D-A-D) based conjugated molecules with varying ratios of thiophene as donor (D) and benzothiadiazole as acceptor (A) are reported. Optical, electrochemical, thermal, morphological and organic thin film transistor (OTFT) device properties of these materials were investigated. The thermal and polarized optical microscope analysis indicates that the materials having higher D/A ratios exhibit both liquid crystalline (LC) and OTFT behavior. AFM analysis of the materials having D/A ratios of 3 and 4 (3T1B and 4T1B) show well ordered structures, resulting from strong π-π interchain interactions compared to the other molecules in this study. A XRD patterns for 3T1B and 4T1B thin films also shows high crystalline ordering. Solution processed OTFTs of 3T1B and 4T1B have shown un-optimized charge carrier mobilities of 2 × 10-2 cm2 V-1 s -1 and 4 × 10-3 cm2 V-1 s -1, respectively on bare Si/SiO2 substrate. © The Royal Society of Chemistry 2009.

Journal of Materials Chemistry

Synthesis, characterization and comparative study of thiophene- benzothiadiazole based donor-acceptor-donor (D-A-D) materials

Two azine molecules, [3-{4-(dimethylamino)phenyl}prop-2-en-1-ylidene] hydrazone (HL) and [4-(dimethylamino)benzylidene]hydrazone (LL) synthesized via Schiff base condensation, show an absorption band due to intra-ligand charge transfer (ILCT). Both ligands show weak emission in the absence of a metal ion as input. When Ag+ ions are added to either compound in THF, the metal ion gets bonded to the azine moiety resulting in a high intensity emission (∼400 fold). While Cu+ shows a slight enhancement of emission, other first-row transition, alkali or alkaline-earth metal ions do not show any emission allowing Ag+ ions to be detected in the presence of these metal ions. Both the Ag+ complexes were characterised by X-ray crystallography and show solid-state spectra similar to their solution spectra. Time-resolved fluorescence measurements done on the complexes show two excited-state lifetimes. © The Royal Society of Chemistry 2009.

Chemistry

Dalton Transactions

Ag(i) induced emission with azines having donor-acceptor-donor chromophore

To expand the diversity of 1,3,5-triazine libraries to aryl and alkyl functionalities through the CC bond, we employed a novel orthogonal synthesis via Grignard monoalkylation or monoarylation of cyanuric chloride in solution to prepare aryl- or alkyl-substituted triazine building blocks. These aryl- or alkyl-substituted triazine building blocks were captured by a resin-bound amine, followed by amination and acidic cleavage with high purity. Herein, we demonstrate a novel orthogonal synthesis of a tagged aryl- and alkyl-triazine library on solid support, utilizing building blocks prepared via Grignard reaction in solution. Through incorporation of a triethylene glycol linker at one of the alternate sites on the triazine scaffold we explored an intrinsic tagged library approach. © CSIRO 2009.

Australian Journal of Chemistry

Novel orthogonal synthesis of a tagged combinatorial triazine library via grignard reaction

We analysed the responses of Anabaena doliolum to elevated levels of copper and zinc in batch and semi-continuous cultures. Approximately 10, 4 and 8 and 5-times greater inhibition in final yield of A. doliolum occurred at 1, 2 μM Cu and 2.5 and 5 μM of Zn, respectively, in semi-continuous culture in comparison to batch culture. Protein, chlorophyl a and carotenoid contents of A. doliolum showed significantly (P<0.05) higher inhibition by test metals in semi-continuous culture than in batch culture. The greater sensitivity of different parameters of the test organism was related to the high metal content of the cells grown in semi-continuous system. Moreover, enhancement of pH of the culture suspension in batch culture showed a negative relationship with metal accumulation, and therefore with toxicity. This was due to decrease in free ionic concentrations of test metals. Carotenoids acted as a metal detoxifying agent by minimizing metal-induced inhibition in batch culture as was evident from its negative relationship with metal toxicity. © EDP Sciences, 2009.

Life Sciences

Annales de Limnologie

Carotenoids and pH of the culture medium play an important role in displaying metal stress in batch and semi-continuous cultures of Anabaena doliolum

Information on valence orbitals and electronic interactions in single crystal systems can be obtained through orientation-dependent X-ray measurements, but this can be problematic for a cubic system. Polarisation-dependent X-ray absorption measurements are common, but are dominated by dipole transitions which, for a cubic system, are isotropic even though a cubic system is not. Many edges, particularly for transition metals, do have electric quadrupole features that could lead to dichroism but proximity to the dipole transition can make interpretation challenging. X-ray Raman Spectroscopy (XRS) can also be used to perform orientation-dependent near-edge measurements - not only dependent on the direction of the momentum transfer but also its magnitude, q. Previous XRS measurements on polycrystalline materials revealed that multipole (higher order than dipole) transitions are readily observable in the pre-threshold region of rare earth N4,5 edges, actually replacing the dipole at high-q. We have extended these studies to examine orientation-dependent XRS for CeO2 and MnO single crystals, as prototype systems for theoretical treatment. Dichroism is observed at both the Ce N4,5 and Mn M2,3 edges in these cubic materials. {\textcopyright} 2009 IOP Publishing Ltd.

Journal of Physics: Conference Series

Orientation-dependent X-ray Raman scattering from cubic crystals: Natural linear dichroism in MnO and CeO2

In this work we investigated the correlation between the EL, the electrical properties and the microstructure of Eu-implanted MOS light emitting devices. The EL spectrum shows a red EL line centered at 618 nm which is usually assigned to Eu3+ and a broad blue-green EL band attributed to Eu2+. It was found that the red EL is favored by low injection currents, low Eu concentrations, lower anneal temperatures and shorter anneal times, especially for flash lamp annealing. These properties are correlated with microstructural changes triggered by ion implantation and annealing, especially with the formation and ripening of Eu or Eu oxide clusters which strongly quench the red EL. Finally, the influence of Eu agglomerations at the injecting interface on the electrical properties of the light emitter is discussed. © 2009 Elsevier B.V. All rights reserved.

Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms

The correlation between electroluminescence properties and the microstructure of Europium-implanted MOS light emitting diodes

Background. Mosquitoes transmit serious human diseases, causing millions of deaths every year. Use of synthetic insecticides to control vector mosquitoes has caused physiological resistance and adverse environmental effects in addition to high operational cost. Insecticides of botanical origin have been reported as useful for control of mosquitoes. Azadirachta indica (Meliaceae) and its derived products have shown a variety of insecticidal properties. The present paper discusses the larvicidal activity of neem-based biopesticide for the control of mosquitoes. Methods. Larvicidal efficacy of an emulsified concentrate of neem oil formulation (neem oil with polyoxyethylene ether, sorbitan dioleate and epichlorohydrin) developed by BMR &amp; Company, Pune, India, was evaluated against late 3rdand early 4thinstar larvae of different genera of mosquitoes. The larvae were exposed to different concentrations (0.5-5.0 ppm) of the formulation along with untreated control. Larvicidal activity of the formulation was also evaluated in field against Anopheles, Culex, and Aedes mosquitoes. The formulation was diluted with equal volumes of water and applied @ 140 mg a.i./m2 to different mosquito breeding sites with the help of pre calibrated knapsack sprayer. Larval density was determined at pre and post application of the formulation using a standard dipper. Results: Median lethal concentration (LC50) of the formulation against Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti was found to be 1.6, 1.8 and 1.7 ppm respectively. LC50 values of the formulation stored at 26°C, 40°C and 45°C for 48 hours against Ae. aegypti were 1.7, 1.7, 1.8 ppm while LC90 values were 3.7, 3.7 and 3.8 ppm respectively. Further no significant difference in LC50 and LC90 values of the formulation was observed against Ae. aegypti during 18 months storage period at room temperature. An application of the formulation at the rate of 140 mg a.i./m2 in different breeding sites under natural field conditions provided 98.1% reduction of Anopheles larvae on day 1; thereafter 100% reduction was recorded up to week 1 and more than 80% reduction up to week 3, while percent reduction against Culex larvae was 95.5% on day 1, and thereafter 80% reduction was achieved up to week 3. The formulation also showed 95.1% and, 99.7% reduction of Aedes larvae on day 1 and day 2 respectively; thereafter 100% larval control was observed up to day 7. Conclusion: The neem oil formulation was found effective in controlling mosquito larvae in different breeding sites under natural field conditions. As neem trees are widely distributed in India, their formulations may prove to be an effective and eco-friendly larvicide, which could be used as an alternative for malaria control. © 2009 Dua et al; licensee BioMed Central Ltd.

Malaria Journal

Larvicidal activity of neem oil (Azadirachta indica) formulation against mosquitoes

Background & objectives: Gametocyte sex-ratio in Plasmodium falciparum malaria is an important determinant of transmission success and basis of disease epidemiology. Information on ratio of male to female gametocytes after an exposure of antimalarial regimens under field conditions is very limited. In this retrospective study we observed high densities of gametocytes along with high sex-ratio in P. falciparum cases, which may be responsible for persistent malaria transmission in this area. Methods: Laksar PHC of Hardwar district, Uttarakhand State, India was selected because it contributed 90 per cent of the total malaria cases. A total of 568 uncomplicated P. falciparum malaria patients were assessed to investigate prevalence of gametocytes while 339 P. falciparum thick smears containing 5620 gametocytes were screened for measuring the gametocyte density for microgametocyte (male) and macrogametocyte (female). Homology of variance ('F' test) was checked on days 7 and 14 including the variables and risk factors namely fever, parasitaemia, gametocyte carriage in sensitive and resistant chloroquine treated P. falciparum cases. Results: Slide positivity rate (SPR) increased drastically from 0.23 to 11.4 per cent with the predominance in P. falciparum infection after 1998. All 568 cases showed gametocytes in their peripheral blood, of which 109 (19%) were infected with rings and gametocytes and 459 (81%) had gametocytes stages in their peripheral blood while 422 (74.3%) cases were infected with ring stages only. Of the 339 P. falciparum positive blood smears, 5620 gametocytes were screened for their sex-ratio. The mean sex-ratio was 0.31 (3.22 female per male). Prevalence of gametocytaemia was significantly higher (P<0.05) in chloroquine (CQ)- resistant than in CQ-sensitive patients with days 7 and 14 follow up. The homology of variance with risk factors for gametocytes on days 7 and 14 were highly significant (P<0.001) in the study period but during the post-exposure period of days 3 and 5, these were insignificantly correlated. Interpretation & conclusion: A high density of P. falciparum gametocytes was observed at the time of preparation of blood slide on day 0. Improper chloroquine treatment along with poor patient compliance for radical treatment and the presence of chloroquine resistant P. falciparum malaria may have enhanced the prevalence and density of P. falciparum gametocytes which was instrumental in signaling the persistent malaria in this area.

Indian Journal of Medical Research

Plasmodium falciparum gametocytaemia with chloroquine chemotherapy in persistent malaria in an endemic area of India

The TIM23 (translocase of the mitochondrial inner membrane) complex mediates translocation of preproteins across and their insertion into the mitochondrial inner membrane. How the translocase mediates sorting of preproteins into the two different subcompartments is poorly understood. In particular, it is not clear whether association of two operationally defined parts of the translocase, the membrane-integrated part and the import motor, depends on the activity state of the translocase. We established conditions to in vivo trap the TIM23 complex in different translocation modes. Membrane-integrated part of the complex and import motor were always found in one complex irrespective of whether an arrested preprotein was present or not. Instead, we detected different conformations of the complex in response to the presence and, importantly, the type of preprotein being translocated. Two non-essential subunits of the complex, Tim21 and Pam17, modulate its activity in an antagonistic manner. Our data demonstrate that the TIM23 complex acts as a single structural and functional entity that is actively remodelled to sort preproteins into different mitochondrial subcompartments. © 2008 European Molecular Biology Organization | All Rights Reserved.