Prediction and characterization of novel microRNAs from brown plant hopper, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae)

R. Asokan,K. B. REBIJITH,H. H. RANJITHA,H. K. ROOPA,V.V. Ramamurthy 한국곤충학회 2013 Entomological Research Vol.43 No.4

MicroRNAs (miRNAs) are a family of small, endogenously initiated non‐coding RNAs that extensively regulate gene expression either by mRNA cleavage or by translational repression, thus playing important roles in the development and physiology of organisms. Experimental identification and characterization of spatially and temporally expressed miRNAs is a monumental task in insects such as the brown plant hopper, Nilaparvata lugens, a major pest of rice and also a vector of Tenuivirus. At this juncture bioinformatics approaches, which primarily depend on sequence homology and secondary structure verification, will be an invaluable tool. A total of nine novel miRNAs were identified in N. lugens using the computational approaches from 1 13 718 Expressed Sequence Tags. The phylogenetic analysis was carried out to compare their level of conservation with respect to other members of the animal kingdom. The functional annotation of these newly identified miRNAs revealed that the majority of them are involved in the transcription regulatory activity and signal transduction pathways. These regulatory impacts are promising towards insect pest management but need further experimental validation and functional analyses. Thus, the outcome of this study will help to carry out the gene knockdown and transgenesis studies for the functional analysis of the newly identified miRNA‐regulated phenotypes in N. lugens.

200 MeV Ag 15+ ion beam irradiation induced modifi cations in spray deposited MoO 3 thin films by fl uence variation

R. Rathika,M. Kovendhan,D. Paul Joseph,K. Vijayarangamuthu,A. Sendil Kumar,C. Venkateswaran,K. Asokan,S. Johnson Jeyakumar 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.8

Spray deposited Molybdenum trioxide (MoO3) thin film of thickness nearly 379 nm were irradiated with 200 MeV Ag15þ ion beam at different fluences (Ø) of 5 1011,1 1012,5 1012 and 1 1013 ions/cm2. The X-ray diffraction (XRD) pattern of the pristine film confirms orthorhombic structure and the crys-tallinity decreased after irradiation with the fluence of 5 1011 ions/cm2 due to irradiation induced defects and became amorphous at higher fluence. In pristine film, Raman modes at 665, 820, 996 cm1 belong to MoeO stretching, 286 cm1 belong to MoeO bending mode and those below 200 cm1 are associated with lattice modes. Raman peak intensities decreased upon irradiation and vanished completely for the ion fluence of 5 1012 ions/cm2. The percentage of optical transmittance of pristine film was nearly 40%, while for irradiated films it decreased significantly. Red shift was observed for both the direct and indirect band gaps. The pristine film surface had densely packed rod like structures with relatively less porosity. Surface roughness decreased significantly after irradiation. The electrical trans-port properties were also studied for both the pristine and irradiated films by Hall effect. The results are discussed.

Fabrication of p-n Junction Diode Using SnO/SnO2 Thin Films and Its Device Characteristics

R. Sathyamoorthy,K. M. Abhirami,B. Gokul,Sanjeev Gautam,채근화,K. Asokan 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.4

Present study demonstrates the feasibility of using oxides of Sn to fabricate the p-n junction diode and reports the device characteristics. Reactive thermal evaporation method was used to fabricate the p-type SnO and n-type SnO2 multilayer thin films. The x-ray diffraction (XRD) and Raman spectra depict the presence of both SnO and SnO2 layers. The interface of the p-n junction analyzed by cross-sectional transmission electron microscope (TEM) images and selected area electron diffraction (SAED) pattern confirmed the presence of SnO-SnO2 layers. The diode shows rectifying current-voltage characteristics with forward threshold voltage of 3.5 V.

Tailoring the properties of spray deposited V₂O₅ thin films using swift heavy ion beam irradiation

Rathika, R.,Kovendhan, M.,Joseph, D. Paul,Pachaiappan, Rekha,Kumar, A. Sendil,Vijayarangamuthu, K.,Venkateswaran, C.,Asokan, K.,Jeyakumar, S. Johnson Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.11

Swift heavy ion (SHI) beam irradiation can generate desirable defects in materials by transferring sufficient energy to the lattice that favours huge possibilities in tailoring of materials. The effect of Ag¹⁵⁺ ion irradiation with energy 200 MeV on spray deposited V₂O₅ thin films of thickness 253 nm is studied at various ion doses from 5 × 10¹¹ to 1 × 10¹³ ions/㎠. The XRD results of pristine film confirmed orthorhombic structure of V₂O₅ and its average crystallite size was found to be 20 nm. The peak at 394 cm^-1 in Raman spectra confirmed O-V-O bonding of V₂O₅, whereas 917 cm^-1 arise because of distortion in stoichiometry by a loss of oxygen atoms. Raman peaks vanished completely above the ion fluence of 5 × 10¹² ions/㎠. Optical studies by UV-Vis spectroscopy shows decrement in transmittance with an increase in ion fluence up to 5 × 10¹² ions/㎠. The red shift is observed both in the direct and indirect band gaps until 5 × 10¹² ions/㎠. The surface topography of the pristine film revealed sheath like structure with randomly distributed spherical nano-particles. The roughness of film decreased and the density of spherical nanoparticles increased upon irradiation. Irradiation improved the conductivity significantly for fluence 5 × 10¹¹ ions/㎠ due to band gap reduction and grain growth.

Schottky Nature of InSe/Cu Thin Film Diode Prepared by Sequential Thermal Evaporation

P. Matheswaran,R. Sathyamoorthy,K. Asokan 대한금속·재료학회 2012 ELECTRONIC MATERIALS LETTERS Vol.8 No.6

Highly oriented indium selenide (InSe) thin films were prepared by sequential thermal evaporation on tungsten (W) substrate and subsequently annealed at 300°C for 30 min in argon (Ar) atmosphere. The films were characterized by Glancing Incidence x-ray diffraction (GI-XRD), scanning electron microscopy (SEM), Energy dispersive x-ray analysis (EDX), Diffused reflectance spectroscopy (DRS) and current-voltage (I-V) measurements. Highly crystalline InSe thin film was obtained after annealing and confirmed by XRD analysis. Band gap energy of the InSe system is deduced from the DRS measurements and found to be 1.3 eV. SEM analysis revealed that selenium (Se) content plays an important role in determining the surface morphology of the film. InSe thin film diode structure was fabricated as W/InSe/Cu system. The estimated values of barrier height for the film of thickness 3000 Å and 7000 Å are 0.65 eV and 0.61 eV respectively. Thickness dependent schottky nature of the InSe/Cu thin film diode is discussed in detail.

Evidence for Phase Change Memory Behavior in In2(SexTe1-x)3 Thin Films

P. Matheswaran,R. Sathyamoorthy,K. Asokan 대한금속·재료학회 2012 ELECTRONIC MATERIALS LETTERS Vol.8 No.4

Crystalline In2(Se0.5Te0.5)3 thin films are prepared by thermal evaporation and subsequently annealed at 300°C in Ar atmosphere. SEM image of the crystalline sample shows spherical nature of constituents, distributed uniformly throughout the surface. Island structure of the surface is clearly visible after switching. Elemental composition of the sample remains unchanged even after switching. Temperature dependent I-V analysis shows stoichiometric phase change at 80°C [from In2(Se0.5Te0.5)3 to In2Te3 and In2Se3 phase], where current switches three orders of magnitude higher than that in lower temperature. Further rise in temperature results increase in current only after switching, where threshold voltage remains constant.

Study on the ferromagnetism in Co and N doped ZnO thin films

S. Ramasubramanian,R. Thangavel,M. Rajagopalan,A. Thamizhavel,K. Asokan,D. Kanjilal,J. Kumar 한국물리학회 2013 Current Applied Physics Vol.13 No.8

Present investigation reports the structural, optical and magnetic properties of co-doping of Co and N ions in ZnO samples, prepared by two distinct methods. In the first method, samples are synthesized by Solegel technique in which the Co and N are co-doped simultaneously during the growth process itself. In the second case, N ions are implanted in the Co doped ZnO thin films grown by Pulsed Laser Deposition (PLD). Structural studies showed that the nitrogen implantation on Co doped ZnO samples developed compressive stress in the films. X-ray photoelectron spectroscopy confirmed the doping of Co and N in ZnO matrix. In the Resonant Raman scattering multiple LO phonons up to fifth order are observed in the (Co, N) co-doped ZnO. Photoluminescence spectra showed that there is reduction in the bandgap due to the presence of Co in the lattice and also the presence of Zn vacancies in the films. All samples showed ferromagnetic behavior at room temperature. The magnetic moment observed in the implanted films is found to be varied with the different dosages of the implanted N ions. First principle calculations have been carried out to study the possible magnetic interaction in the co-doped system. Present study shows that the ferromagnetic interaction is due to the hybridization between N 2p and Co 3d states in the (Co, N) co-doped ZnO and is very sensitive to the geometrical configurations of dopants and the vacancy in the ZnO host lattice.

100 MeV ion irradiation in nanosized zinc ferrite

Jitendra Pal Singh,R. C. Srivastava,K. Asokan,Keun Hwa Chae 한국진공학회 2015 한국진공학회 학술발표회초록집 Vol.2015 No.2

Silencing of JHEH and EcR genes of Plutella xylostella (Lepidoptera: Plutellidae) through double stranded RNA oral delivery

B.N. Chaitanya,R. Asokan,T. Sita,K.B. Rebijith,P. Ram Kumar,N.K. Krishna Kumar 한국응용곤충학회 2017 Journal of Asia-Pacific Entomology Vol.20 No.2

Plutella xylostella (L.), Diamondback moth (DBM), is a notorious pest disrupting cruciferous crops across the world. Overuse of chemically synthesized insecticides as well as application of bio-pesticide like Bacillus thuringiensis has gained progressive resistance against them, resulting in DBM management failures. To overcome this, a more potential, non-chemical and safe technology like Ribonucleic acid interference (RNAi) is to be implemented. RNAi, is a reverse genetic tool with high sequence specificity, elicited by double-stranded RNA (dsRNA) for silencing the target genes. The objective of this study was to silence two candidate genes fromDBMviz., Juvenile Hormone Epoxide hydrolase (PxJHEH) and Ecdysteroid receptor (PxEcR) involved in regulating metamorphosis and molting respectively. In this regard, we have custom designed the dsRNAs (500 bp) by cloning and sequencing the candidate genes and delivered it orally (non-invasive mode). Further, we have assessed the extent of down regulation of target genes with five concentrations of dsRNA (1, 2, 5, 10 and 20 μg/μl) at four time points (24, 48, 72 and 96 h). The extent of gene silencing and mortality recorded for both genes were proportional to the dsRNA concentration. Our study projects that PxJHEH and PxEcR genes would be good target for dsRNA mediated gene silencing in management of insect pests such as DBM in near future.

Electronic Structure of Mn-Doped ZnO Studied by Using X-ray Absorption Spectroscopy

P. Thakur,K. H. Chae,M. Subramanain,R. Jayavel,K. Asokan 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5

Mn-doped ZnO thin films that showed ferromagnetism at room temperature were synthesized with nominal compositions Zn1-xMnxO (x = 0.03, 0.05, 0.07, 0.10 and 0.15) by using a spray pyrolysis technique. High-resolution X-ray diffraction studies suggested that the doped Mn ions occupied Zn sites and that all the samples exhibited a wurtzite hexagonal-like crystal structure similar to that of the parent compound, ZnO. The near-edge X-ray absorption fine structure (NEXAFS) measurements at the O K-edge clearly exhibited a pre-edge spectral feature, which evolved with Mn doping, similar to one observed in hole-doped cuprates and manganites. The Mn L3;2-edge NEXAFS spectra exhibited divalent Mn apart from mixed valent Mn3+ / Mn4+ states, which were well supported by Mn K-edge spectra.