Browsing by Author "R.K. Mishra"

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AC transport properties of nanocrystalline SnO 2 semiconductor
(2012) P.P. Sahay; R.K. Mishra; S.N. Pandey; S. Jha; M. Shamsuddin
Nanocrystalline SnO 2 materials were prepared by the chemical co-precipitation route by adding ammonia solution to 0.1 M solution of SnCl 4·5H 2O. The resulting precipitate after thorough washing with distilled water and calcination at 600 °C for 10 h was investigated by XRD for phase identification and crystallite size determination. The materials have been found to be polycrystalline SnO 2, possessing tetragonal rutile crystal structure and nanocrystalline in grain size of approximately 30 nm. The TEM micrograph shows agglomerated particles (cluster of primary crystallites) with an average size of 37.4 nm. A corresponding selected area electron diffraction pattern reveals the different Debye rings of SnO 2, as analyzed in XRD. The complex dielectric constant ε * has been found to vary with frequency which is attributed to the multi-relaxation time constants of the energy states responsible for conduction mechanism. At any particular frequency, ε * has been found to increase with temperature. The frequency dependence of loss tangent tan δ has been explained with the help of the equivalent circuit model. The observed frequency dependence of ac conductivity has been found to obey the power law: σ ac ∝ ω S, where variation of S with temperature indicates multi-hopping conduction mechanism in nanocrystalline SnO 2 samples. The complex impedance plots of Z′ versus Z″ at different temperatures have been found to be single semicircular arcs with a non-zero intersection with the real axis in the high frequency region and have their centres lying below the real axis at a particular angle of depression, indicating multirelaxation processes in the material. © 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Biphasic effect of Syzygium aromaticum flower bud on reproductive physiology of male mice
(Blackwell Publishing Ltd, 2016) R.K. Mishra; S.K. Singh
The flower buds of Syzygium aromaticum (clove) have been used for the treatment of male sexual disorders in indigenous medicines of Indian subcontinent. Therefore to evaluate the efficacy of Syzygium aromaticum on the male reproductive health, chronic oral exposure of aqueous extract of flower buds of Syzygium in three doses (15 mg, 30 mg and 60 mg kg−1 BW) were studied for a single spermatogenic cycle (35 days) in Parkes (P) strain mice. Lower dose (15 mg) of Syzygium aromaticum flower buds increased serum testosterone level and testicular hydroxysteroid dehydrogenase (HSD) activities and improved sperm motility, sperm morphology, secretory activity of epididymis and seminal vesicle, and number of litters per female. On the other hand, higher doses (30 and 60 mg) of the treatment adversely affected above parameters. Further, higher doses of the extract also had adverse effects on daily sperm production, 1C cell population and on histology of testis. In conclusion, Syzygium aromaticum flower buds extract exhibits biphasic effect on reproductive physiology of male mice. Lower dose of Syzygium aromaticum flower bud extract is androgenic in nature and may have a viable future as an indigenous sexual rejuvenator, while higher doses adversely affected functional physiology of reproductive organs. © 2016 Blackwell Verlag GmbH
Effect of Berberine and (±)-Bicuculline Isolated from Corydalis chaerophylla on Spore Germination of Some Fungi
(Czech Academy of Sciences, 2002) S. Ameer Basha; R.K. Mishra; R.N. Jha; V.B. Pandey; U.P. Singh
Berberine and (±)-bicuculline were isolated from roots and leaves, respectively, of Corydalis chaerophylla. Both were effective in vitro against spore germination of some plant pathogenic fungi (Alternaria brassicicola, A. brassicae, A. cheiranthi, A. melongenae, A. solani, Colletotrichum musae, C. falcatum, Curvularia penniseti, C. lunata, C. maculans, C. pallescens, Curvularia sp., Erysiphe pisi, E. cichoracearum, Erysiphe sp., Fusarium udum, Helminthosporium spiciferum, H. penniseti, H. frumentacei, Heterosporium sp., Oidium erysiphoides and Ustilago cynodontis). Berberine and (±)-bicuculline significantly inhibited spore germination of all the fungi at concentrations of 100-1000 ppm. Berberine was effective against all the fungi at all concentrations; most of the fungi did not germinate at 1000 ppm. H. penniseti conidia did not germinate at any concentration of (±)-bicuculline. U. cynodontis was the least sensitive fungus at lower concentrations but 800 ppm dose was highly effective.
Elemental and phytochemicals profile in ethno medicinal plants used for treating cardiovascular diseases by mizo-tribe of North Eastern India
(Chemical Publishing Co., 2019) J.P. Rajan; R.K. Mishra; K.B. Singh
Proton induced X-ray emission (PIXE) and gas chromatography-mass spectroscopy (GC-MS) were used to detect elements as well as phytochemicals in the Centella asiatica and Elsholtzia communis having possible roles for cardio-protections. Elements namely K, Cl, Ca, Fe, Mn, Zn and Cu were present in varying concentration with notable concentration of K, Cl and Fe. Phytochemicals such as stigmasterol, β-sitosterol, phytol and N-hexadeconic acid were detected in the C. asiatica while E. communis was found to contain β-carotene, β-sitosterol, phytol and N-hexadeconic acid. The study reveals that these two ethnomedicinal herbs are found to contain elements and phytochemical known for their cardio-protective roles. © 2019 Chemical Publishing Co.. All rights reserved.
Influence of diplontic selection on micromutations in gamma-irradiated barley
(1974) R.K. Mishra; K. Das
A study was undertaken to observe the effect of diplontic selection on some quantitative characters of barley. Seeds of barley variety K12 were irradiated with 20, 30 and 40 kR of gamma rays. R3 and subsequent generations were comprised of progenies from the first five and the later formed five tillers of R1 plants. R3 and R4 progenies were grown in a randomized block design. Induced variability for six quantitative traits were characterized considering mean and coefficient of variation in the R3 and R4 generations. Results showed that the mean shifted in either direction in R3 and in the negative direction in R4. However, the selection basis of the two spike categories did not result in any significant differential mutability of polygenes between the first formed five tillers and the later formed five tillers of R3 and R4 generations. © 1974 Pergamon Press Ltd.
Modified multicomponent band pass optical reflection filters at oblique incidence
(2004) K.D. Misra; R.K. Mishra
Reflection and transmission characteristics of a modified long-wavelength cutoff filter using three component system with angular dependence is studied. In this case, second layer of high refractive index is sandwiched between edge layers of equivalent refractive index with base structure [G(0.5 AB0.5A)] N then an optimized structure of the form [(0.5AB0.5A)N-X (0.5AB0.5A)X (0.5AB0.5A)N-X] is taken and spectral properties are studied. In the case of short-wavelength three component cutoff filter the second layer of low refractive index is sandwiched between two edge layers of high equivalent refractive index with a base tructure [G(0.5BA0.5D)]N and its spectral characteristics are studied. Then structure is optimized [(0.5BA0.5B)N-X(0.5BA0.5B)N-X(0. 5BA0.5B)N-X and spectral characteristics of this structure is also studied. Spectral properties of band pass optical reflection filters of the type [G(XY)A] whose components represent proposed long-wavelength cutoff [(0.5AB0.5B)N-X(0.5AB0.5A)X (0.5BA0.5B)N-X] and short-wavelength cutoff [(0.5BA0.5B)N-X(0.5BA0.5B)X (0.5BA.5B)N-X] filter structures are studied with angular dependences. This increases the bandwidth with least oscillatory components at edges, can not be precisely formed by known classes of two component system at normal incidence. It is shown that the use of reflection and transmission filters with oblique bands yields an ideal polarizer. Angular dependences of the filter, transmission and reflection band shape on the parameters of high reflectance multi-layer coating, such as the thickness, refractive indices, the number of layers are analyzed in detail.
Multi-location evaluation of field pea in Indian climates: eco-phenological dynamics, crop-environment relationships, and identification of mega-environments
(Springer Science and Business Media Deutschland GmbH, 2024) Ashok K. Parihar; Kali Krishna Hazra; Amrit Lamichaney; Debjyoti Sen Gupta; Jitendra Kumar; R.K. Mishra; Anil K. Singh; Anuradha Bhartiya; Parvaze Ahmad Sofi; Ajaz A. Lone; Sankar P. Das; Rajesh Kumar Yadav; S.S. Punia; A.K. Singh; Geeta Rai; C.S. Mahto; Khajan Singh; Smita Tiwari; Ashok K. Saxena; Sunil Kumar Nair; Mangla Parikh; Vijay Sharma; Sudhakar P. Mishra; Deepak Singh; Sanjeev Gupta; G.P. Dixit
Characterization of crop-growing environments in relation to crop’s genotypic performance is crucial to harness positive genotype-by-environment interactions (GEI) in systematic breeding programs. Given that, the study aimed to delineate the impact of diverse environments on crop phenology and yield traits of dwarf-statured field pea, pinpointing location(s) favoring higher yield and distinctiveness within breeding lines. We tested twelve field pea breeding lines across twenty locations in India, covering Central Zone (CZ), North Western Plain Zone (NWPZ), North Eastern Plain Zone (NEPZ), and Northern Hill Zone (NHZ). Across these locations, maximum and minimum temperatures during flowering (TMAXF, TMINF) and reproductive period (TMAXRP, TMINRP) ranged 18.9–28.3, 3.3–18.0, 15.0-30.8, and 7.9-22.1oC, respectively. Meanwhile, notable variations in phenological and agronomic traits (coefficient of variation) were observed: flowering (31%), days to maturity (21%), reproductive period (18%), grain yield (48%), and 100-seed weight (18%). Combined ANOVA demonstrated an oversized impact of environment (81%) on yield, while genotype and GEI effects were 2% and 14%, respectively. The variables TMINF, TMINRP, and cumulative growing degree-day showed positive correlations with yield, while extended vegetative and maturity durations negatively influenced yield (p < 0.05). Additionally, linear mixed-models and PCA results explained that instability in crop phenology had significant influence on field pea yield. Seed weight was markedly varied within the locations (9.9–20.8 g) and both higher and lower seed weights were associated with lower yields (Optimal = 17.1 g). HA-GGE biplot-based on environment focus-scaling demonstrated three mega-environments and specific locations viz. Kota (CZ), SK Nagar (CZ), Raipur (CZ), Sehore (CZ), and Pantnagar (NWPZ) as the ideal testing-environments with high efficiency in selecting new genotypes with wider adaptability. The study findings highlight distinct impact of environments on crop phenology and agronomic traits of field pea (dwarf-type), hold substantial value in designing efficient field pea (dwarf-type) breeding program at mega-environment scale. © The Author(s) under exclusive licence to International Society of Biometeorology 2024.
On the rupture of DNA molecule
(American Institute of Physics Inc., 2015) R.K. Mishra; T. Modi; D. Giri; S. Kumar
Using Langevin dynamics simulations, we study effects of the shear force on the rupture of a double stranded DNA molecule. The model studied here contains two single diblock copolymers interacting with each other. The elastic constants of individual segments of diblock copolymer are considered to be different. We showed that the magnitude of the rupture force depends on whether the force is applied at 3′ - 3′ - ends or 5′ - 5′ - ends. Distributions of extension in hydrogen bonds and covalent bonds along the chain show the striking differences. Motivated by recent experiments, we have also calculated the variation of rupture force for different chain lengths. Results obtained from simulations have been validated with the analytical calculation based on the ladder model of DNA. © 2015 AIP Publishing LLC.
Statistical mechanics of DNA rupture: Theory and simulations
(2013) S. Nath; T. Modi; R.K. Mishra; D. Giri; B.P. Mandal; S. Kumar
We study the effects of the shear force on the rupture mechanism on a double stranded DNA. Motivated by recent experiments, we perform the atomistic simulations with explicit solvent to obtain the distributions of extension in hydrogen and covalent bonds below the rupture force. We obtain a significant difference between the atomistic simulations and the existing results in the literature based on the coarse-grained models (theory and simulations). We discuss the possible reasons and improve the coarse-grained model by incorporating the consequences of semi-microscopic details of the nucleotides in its description. The distributions obtained by the modified model (simulations and theoretical) are qualitatively similar to the one obtained using atomistic simulations. © 2013 AIP Publishing LLC.
Structural, dielectric and photoluminescence properties of co-precipitated Zn-doped SnO2 nanoparticles
(2013) P.P. Sahay; R.K. Mishra; S.N. Pandey; S. Jha; M. Shamsuddin
Zn-doped SnO2 nanoparticles were prepared by the chemical co-precipitation route. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses of these prepared nanoparticles were carried out for structural and morphological studies. All the samples have been found to have tetragonal rutile structure of the polycrystalline SnO2 having crystallite size in the range 13-25 nm. TEM micrographs show agglomeration of nanoparticles in all the samples. At a particular temperature, the dielectric constant of all the samples has been found to decrease with increasing frequencies which may be due to rapid polarization processes occurring in SnO2 nanoparticles. The ac conductivity, σ (ω), has been found to vary with frequency according to the relation σ (ω) ∝ ωS. The value of S has been found to be temperature dependent, decreasing with increasing frequency which suggests that a hopping process is the most likely conduction mechanism in these nanoparticles. The room temperature photoluminescence (PL) spectra of the undoped and Zn-doped SnO 2 nanoparticles consist of the near band-edge ultraviolet (UV) emission and the defect related visible emissions. The origin of emission peaks in the visible region is attributed to oxygen-related defects that are introduced during growth. © 2012 Elsevier B.V. All rights reserved.
Synthesis of superparamagnetic bare Fe 3O 4 nanostructures and core/shell (Fe 3O 4/alginate) nanocomposites
(2012) Manish Srivastava; Jay Singh; Madhu Yashpal; Dinesh Kumar Gupta; R.K. Mishra; Shipra Tripathi; Animesh K. Ojha
In this article we report about the synthesis of superparamagnetic bare Fe 3O 4 nanostructures and core/shell (Fe 3O 4/alginate) nanocomposites by simple low-temperature based method at pH values 5, 9, and 14. The structural morphology and magnetic behavior of Fe 3O 4 nanostructures and core/shell (Fe 3O 4/alginate) nanocomposites (Fe 3O 4/alg NCs) have been investigated by X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy (RS), ultraviolet-visible (UV-vis) spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX) and vibrating sample magnetometer (VSM). The particle size was calculated by TEM measurements and it turns out to be ∼10 nm and ∼14 nm for bare Fe 3O 4 nanoparticle and Fe 3O 4/alg NCs with core/shell structure, respectively. The magnetic properties of the synthesized products were found to be function of pH at which the synthesis has been done. The synthesized Fe 3O 4 nanoparticle and Fe 3O 4/alg NCs were found to be superparmagnetic in nature at room temperature. We observed that the value of saturation magnetization in case of Fe 3O 4/alg NCs decreases by increasing the pH value. © 2012 Elsevier Ltd. All rights reserved.