Browsing by Author "S.P. Pandey"

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A study on swift (∼100 MeV) heavy (Si8+) ion irradiated crystalline Si-solar cell
(2006) P.C. Srivastava; S.P. Pandey; K. Asokan
A study on irradiation (of ∼100 MeV, Si-ion) induced degradation effects of crystalline silicon solar cells has been carried out. The cell characteristics show that the cell efficiency decreases to ∼30% (of its pre-irradiated value) after the irradiation (of swift heavy ions of, 10 12 or 1013 or 1014 ions cm-2 fluences). The reduced efficiency of the irradiated solar cells is recovered back (nearly half of the pre-irradiated efficiency) after annealing at 300 °C. The IR spectroscopic studies on the irradiated and annealed solar cells show the presence of di-vacancy and their complexes with impurities like hydrogen, carbon and oxygen. The swift heavy ion irradiation damage in solar cells causing a heavy loss of the cell efficiency has been attributed to these electrically active complexes which shall cause the carrier removal/compensation phenomena for the observed decrease of the cell efficiency. These complexes dissociate on annealing to change their role as donors/acceptors to cause the observed recovery of the cell efficiency on annealing. © 2005 Elsevier B.V. All rights reserved.
Dye sensitized solar cell based on poly(vinyl alcohol) doped with ammonium iodide solid polymer electrolyte
(National Institute of Optoelectronics, 2013) Vivek K. Singh; Annubhawi Annu; Upasana Singh; Prabhakar Singh; S.P. Pandey; Bhaskar Bhattacharya; Pramod K. Singh
A new polymer electrolyte Polyvinyl alcohol (PVA) doped with ammonium iodide (NH4I) have been developed, characterized and applied in Dye sensitized solar cell (DSSC). Polymer electrolyte shows enhancement in electrical conductivity by salt doping and then decrease after a certain composition. Infrared spectroscopy (IR) as well as x ray diffraction (XRD) affirmed composite nature of the polymer electrolyte. The polymer morphology has been studied using optical microscopy. Based on maximum conducting sample we have developed a DSSC which shows short circuit current density of 0.46 mA/cm2, open circuit voltage of 0.65 volt with overall conversion efficiency of 0.29 % at 1 sun condition.
EVALUATION OF THE IDEAL GLASS TRANSITION TEMPERATURE AND OTHER THERMODYNAMIC PROPERTIES OF GLASS FORMING LIQUIDS.
(1986) S.P. Pandey; K.S. Dubey; P. Ramachandrarao
An earlier hole theoretical model of the liquid state developed by the authors is modified to reduce the number of parameters required to describe the thermodynamic properties. It has been shown that good agreement can be achieved between observed and calculated Gibb's free energy change accompanying freezing at large undercooling for a variety of substances. Estimates of the Kauzmann glass transition temperatures of these substances also agree well with those extrapolated from relaxation and thermodynamic data. The present analysis simplifies the procedures for obtaining the viscous behavior and time-temperature transformation diagrams for glass forming substances.
High energy heavy ion irradiation in semiconductors
(Elsevier Science Publishers B.V., 1999) P.C. Srivastava; S.P. Pandey; O.P. Sinha; D.K. Avasthi; K. Asokan
Pd/n-Si and Pd/n-GaAs devices have been irradiated from high energy (approximately 100 MeV) heavy ions of Au7+ (gold) and Si7+ (silicon) to study the irradiation effects in these junction devices on semiconductor substrates. The devices have been characterized from I-V and C-V studies for electronic flow characterization. It has been found that the devices become high resistive on the irradiation and the substrates change the conductivity type from n- to p- on the irradiation of fluence of approximately 1012-1013 ions/cm2. The change in conductivity type has been understood as a result of creation of deep acceptors on the irradiation.
Humidity Effect on Ionic Conductivity of Composite Polymer Electrolytes
(John Wiley and Sons Inc, 2023) Ashish Raj; Kushal Mehrotra; S.P. Pandey; S. Venkatesan Jayakumar; Amit Saxena; Bhaskar Bhattacahrya
The solid polymer electrolytes (SPE) based electrochemical devices are an area of attention for more than two decades. The ability of thin-film preparation and leakage proof over the liquid counterpart are the key factors of SPE. In the present work, two different compositions, 80–20 and 85–15, of PVA:KI has been used as a host polymer complex. Where further 10 wt% of p-Si dispersed with PVA:KI complexes. Polymer films have been prepared with standard solution cast techniques, which are further characterized for their electrical conductivity by Electrical Impedance Spectroscopy (EIS). Also, the humidity effect on the ionic conductivity of these thin films is calculated. It is observed that the ionic conductivity of these polymer electrolytes films increases with 58%, 74%, and 89% humidity. To understand the change in this ionic conductivity, the concentration and mobility of ions are also calculated, and it is found that the change in conductivity are predominately influenced due to the mobility of charge carriers. © 2023 Wiley-VCH GmbH.
Identification of molecular marker and aggressiveness for different groups of Bipolaris sorokiniana isolates causing spot blotch disease in wheat (Triticum aestivum L.)
(2007) S.K. Jaiswal; Sweta; L.C. Prasad; S. Sharma; S. Kumar; R. Prasad; S.P. Pandey; R. Chand; A.K. Joshi
One hundred fifty-five isolates of Bipolaris sorokiniana of wheat were studied for their morphopathological characterization. These isolates were grouped in five categories-black, brown/dull black, gray cottony growth, dull white/greenish black, and white-on the basis of their growth pattern. The frequency of the black suppressed type was maximum (45.63%), whereas the white isolate displayed lowest frequency (6.96%) in the natural population. Twenty RAPD (random amplified polymorphic DNA) primers were used to observe the variability among the identified groups of B. sorokininana. From each group, eight random isolates were investigated. A total of 143 bands were amplified, out of which 107 (74.83%) were polymorphic and 36 (25.17%) were monomorphic. On an average, the total numbers of bands generated per primer were 7.15, of which 5.35 and 1.80 were polymorphic and monomorphic, respectively. Dendrograms based on molecular polymorphism unveiled a considerable amount of diversity among the isolates. Specific DNA bands were identified for selected isolates. The distinct markers appeared to be potential enough to be employed as genetic fingerprints for future strain identification and classification. The study indicated that the RAPD primers provide an easy, rapid, and simple technique for the preliminary assessment of genetic diversity among the fungal isolates. © 2007 Springer Science+Business Media, LLC.
Morphological, Histobiochemical and Molecular Characterisation of Low Lignin Phloem Fibre (llpf) Mutant of Dark Jute (Corchorus olitorius L.)
(Humana Press Inc., 2017) S.B. Choudhary; I. Chowdhury; R.K. Singh; S.P. Pandey; H.K. Sharma; A. Anil Kumar; P.G. Karmakar; N. Kumari; J. Souframanien; S.J. Jambhulkar
Lignin is a versatile plant metabolite challenging high-end industrial applications of several plant products including jute. Application of developmental mutant in regulation of lignification in jute may open up door for much awaited jute based diversified products. In the present study, a novel dark jute (Corchorus olitorius L.) mutant with low lignin (7.23%) in phloem fibre being compared to wild-type JRO 204 (13.7%) was identified and characterised. Unique morphological features including undulated stem, petiole and leaf vein distinguished the mutant in gamma ray irradiated mutant population. Histological and biochemical analysis revealed reduced lignification of phloem fibre cells of the plant. RT-PCR analysis demonstrated temporal transcriptional regulation of CCoAMT1 gene in the mutant. The mutant was found an extremely useful model to study phloem fibre developmental biology in the crop besides acting as a donor genetic stock for low lignin containing jute fibre in dark jute improvement programme. © 2017, Springer Science+Business Media New York.
Pd/Si device characteristics on 100 MeV gold ions irradiation
(Elsevier Ltd, 1997) P.C. Srivastava; S.P. Pandey; D.K. Avasthi; K. Asokan
Pd/p-Si and Pd/n-Si devices were irradiated from 100 MeV gold (7+) ions for varying doses (∼ 1011-1013 ions cm-2). The devices were characterized from I-V and C-V studies. It has been found that there is a change of conductivity type i.e. from n to p at a probed depth of ∼ 8 μm which is approximately the stopping range of the gold ions in silicon. A deep acceptor state (∼ 0.61 eV above V.B. edge) with a peak density of ∼ 109 cm-2 is observed for p-type irradiated devices at ∼ 3 μm which is attributed to the displacement damage caused by the high energy heavy ion irradiation. © 1998 Elsevier Science Ltd. All rights reserved.
Sources of inoculum and reappearance of spot blotch of wheat in rice-wheat cropping systems in eastern India
(2005) S.P. Pandey; S. Kumar; U. Kumar; R. Chand; A.K. Joshi
A study was undertaken to examine the main source of inoculum of Bipolaris sorokiniana responsible for its reappearance in rice-wheat cropping regions of eastern India. Soil samples were collected at monthly intervals during April-October in the years 2000 and 2001 from fields having rice-wheat cropping. Bipolaris sorokiniana conidia were isolated and their viability was found to decline sharply with the onset of flooding in the month of August. In contrast to 82% in April, viability was 4% and < 1% in August and September, respectively. Viable conidia were multiplied in the laboratory and inoculated on to susceptible cv. Sonalika under controlled conditions for test of pathogenicity. Appearance of symptoms typical to spot blotch were recorded after 7 days. Twenty-two different species (weeds and grasses) normally found to be associated with rice-wheat fields were tested for the presence of B. sorokiniana to evaluate their possible role as alternative hosts. Only three species, i.e. Setaria glauca, Echinochloa colonum and Pennisetum typhoids, were found to naturally harbour B. sorokiniana. Isolates from these hosts were tested for pathogenicity and also for their possible spread to wheat. When reisolated from these hosts, the pathogen did not infect wheat. Seeds of 25 different wheat genotypes were tested for B. sorokiniana infection. All genotypes were infected and the incidence of infection varied from 26% to 86%. Five isolates of wheat and one isolate from each of the three species (S. glauca, E. colonum and P. typhoids) were subjected to RAPD analysis. Two broad clusters were formed, suggesting that the wheat isolates were different from the isolates originating from other hosts. The results indicate that seeds are the most important source of inoculum for the reappearance of spot blotch of wheat in rice-wheat cropping systems in eastern India.
Spot blotch disease of wheat: the current status of research on genetics and breeding
(John Wiley and Sons Inc, 2018) P.K. Gupta; R. Chand; N.K. Vasistha; S.P. Pandey; U. Kumar; V.K. Mishra; A.K. Joshi
The spot blotch disease of wheat is caused by Bipolaris sorokiniana, which is an anamorph (teleomorph Cochliobolus sativus). The disease mainly occurs in warm, humid wheat-growing regions, and the Eastern Gangetic Plains (EGP) of South Asia is a hotspot. Significant progress has been made in recent years in characterizing the host–pathogen interaction. The study of the pathogen's life cycle and diversity have been an active area of research. A number of resistance sources have also been identified, characterized and used for breeding. Although immunity has not been observed in any genotype, cultivars displaying a relatively high level of resistance have been developed and made available to farmers. Further progress will require regular use of marker-assisted breeding, genomic selection, gene editing and transgenic interventions. This review summarizes the current state of knowledge about genetic and breeding efforts on the wheat–B. sorokiniana pathosystem and discusses ways in which emerging tools can be used for future research to understand the mechanism involved in infection and for developing cultivars exhibiting a high level of resistance. © 2017 British Society for Plant Pathology
Study of hydrogen in hydrogenated Pd/semiconductor device by ERDA
(1996) P.C. Srivastava; U.P. Singh; S.P. Pandey; D.K. Avasthi
The content of hydrogen in Pd/n-Si, Pd/p-Si, and Pd/p-GaAs devices have been measured, both in the semiconducting substrates and the palladium thin film deposited on p-type Si, n-type Si and p-type GaAs, by ERDA (Elastic Recoil Detection Analysis) using 55 Mev Si ions. The samples were hydrogenated by keeping them in the atmosphere of molecular hydrogen at a pressure of 1 aim at room temperature. It is found that there is a fairly large amount of hydrogen in the semiconductor substrates and the palladium overlayers. It seems that the hydrogen absorbed by the palladium overlayers diffuses to the semiconducting substrates through the Pd/Semiconductor interface. It is found that the p-type semiconducting substrates accommodate more hydrogen than n-type semiconducting substrates in such hydrogenated samples. Copyright © 1996 Elsevier Science Ltd.
Variability and its probable cause in natural populations of spot blotch pathogen Bipolaris sorokiniana of wheat (T. aestivum L.) in India
(2003) R. Chand; S.P. Pandey; H.V. Singh; Sundeep Kumar; A.K. Joshi
A study was undertaken to find out the extent of variability and the probable cause of its emergence in natural populations of the spot blotch pathogen Bipolaris sorokiniana of wheat. The pathogen was isolated from infected seeds and leaves on PDA and purified by monoconidial isolation. The frequency of nucleus in mycelial cells of isolates was recorded using fluorescent staining. Based on colony morphology, the isolates were grouped into five groups. Cluster analysis confirmed this classification. Maximum frequency (44.63%) of isolates in the natural populations was that of black suppressed type. This group was most aggressive and identified as the epidemic population. Lowest frequency (4.96%) was observed for white isolate which produced very few conidia. The mean radial growth of isolates on 8th day ranged form 4.77 to 8.27 cm. The monoconidial isolates, when inoculated on resistant and susceptible cultivars, showed mean AUDPC range of 176.67-1237.59 and 600.83-2144.21% days, respectively. In the epidemic population, cells with two nuclei displayed highest frequency, while in other groups, cells with three or four nuclei were most frequent. The present study revealed that the variability in Bipolaris sorokiniana was reflected in different combinations of the nuclei.