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81.
S. K. Upadhyay 《Applicable analysis》2013,92(4):415-428
Lp-norm type inequalities for pseudo-differential operators L(x,D) and H(x,D) are derived for 1 ≤ p < ∞. Product of pseudo-differential operators associated with Bessel operator Sμ are defined and its Lp-norm type inequalities are obtained. 相似文献
82.
We propose a new mathematical model for aquatic populations. This model incorporates mutual interference in all the three populations and an extra mortality term in zooplankton population and also taking into account the toxin liberation process of TPP population. The proposed model generalizes several other known models in the literature. The principal interest in this paper is in a numerical study of the model’s behaviour. It is observed that both types of food chains display same type of chaotic behaviour, short-term recurrent chaos, with different generating mechanisms. Toxin producing phytoplankton (TPP) reduces the grazing pressure of zooplankton. To observe the role of TPP, we consider Holling types I, II and III functional forms for this process. Our study suggests that toxic substances released by TPP population may act as bio-control by changing the state of chaos to order and extinction. 相似文献
83.
Kinnari Parekh László Almásy Hyo Sook Lee R. V. Upadhyay 《Applied Physics A: Materials Science & Processing》2012,106(1):223-228
Zero field cooled dc-magnetization measurements of monodispersed Mn0.5Zn0.5Fe2O4 nanoparticles dispersed in kerosene exhibit two transitions at low temperatures. These transitions correspond to (i) the
superparamagnetic to blocked superparamagnetic and (ii) the blocked superparamagnetic to surface spin-glass like/quantum superparamagnetic
state upon lowering the temperature. The existence of a disorder surface is confirmed by recording small-angle neutron scattering
data below and above the Curie temperature. Magnetic relaxation analysis shows a plateau at low temperature (below 5 K) with
a slight minimum at 3 K, which is a characteristic of the surface spin-glass-like state. This is analyzed considering the
energy distribution n(E)∼1/E. The existence of surface disorder dominates at low temperature and mimics the transition from superparamagnetic to quantum
superparamagnetic states. 相似文献
84.
An attempt has been made to identify the mechanism, which is responsible for the existence of chaos in narrow parameter range in a realistic ecological model food-chain. Analytical and numerical studies of a three species food-chain model similar to a situation likely to be seen in terrestrial ecosystems has been carried out. The study of the model food chain suggests that the existence of chaos in narrow parameter ranges is caused by the crisis-induced sudden death of chaotic attractors. Varying one of the critical parameters in its range while keeping all the others constant, one can monitor the changes in the dynamical behaviour of the system, thereby fixing the regimes in which the system exhibits chaotic dynamics. The computed bifurcation diagrams and basin boundary calculations indicate that crisis is the underlying factor which generates chaotic dynamics in this model food-chain. We investigate sudden qualitative changes in chaotic dynamical behaviour, which occur at a parameter value a1=1.7804 at which the chaotic attractor destroyed by boundary crisis with an unstable periodic orbit created by the saddle-node bifurcation. Multiple attractors with riddled basins and fractal boundaries are also observed. If ecological systems of interacting species do indeed exhibit multiple attractors etc., the long term dynamics of such systems may undergo vast qualitative changes following epidemics or environmental catastrophes due to the system being pushed into the basin of a new attractor by the perturbation. Coupled with stochasticity, such complex behaviours may render such systems practically unpredictable. 相似文献
85.
Upadhyay RV Parekh K Mehta RV 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2007,187(2):314-319
Electron spin resonance (ESR) spectra of magnetic fluids involving polydispersed Zn(0.5)Fe(0. 5)Fe(2)O(4) (FZ5) and Zn(0.7)Fe(0. 3)Fe(2)O(4) (FZ7) nanomagnetic particles are scanned from 4.2 to 300K. The FZ7 fluid exhibits certain distinct features below 40K which are different from FZ5 fluid. These include (i) an isotropic shift in resonance field in zero-field-cooled ESR study, (ii) deviation of resonance field from sin(2)theta behavior (where theta is the angle between axis of the particle and field) in field cooled (FC) sample and (iii) abrupt increase in anisotropy field for FC sample. The results are analyzed in light of the core-shell model for nanomagnetic particles. 相似文献
86.
Pundir Sachin Upadhyay Sanjay Priya Ruby Kumar Niraj Chetana S. Hossain Ismail Joshi Naveen Chandra Pandey O. P. 《Journal of Solid State Electrochemistry》2023,27(2):531-538
Journal of Solid State Electrochemistry - Electrochemical supercapacitors (ESs) still need to overcome development obstacles in order to realize their full potential while being acknowledged as a... 相似文献
87.
Abhishek Upadhyay Vinay K. Singh Rahul Dubey Narendra Kumar L.K. Sharma Rana Krishna Pal Singh 《Tetrahedron letters》2017,58(46):4323-4327
A highly efficient one pot, multicomponent synthesis of 4H-benzo[g]chromene and pyrano[2,3-g]chromene derivatives are reported by electrochemically stimulated condensation of an aromatic aldehyde, malononitrile and some enolizable acidic compounds in ethanol at room temperature under constant current density. By utilizing common electrode materials and a simple constant current protocol, this method is a new alternative to conventional methods. 相似文献
88.
Jayaraman Kannappan Aditya N. Khanvilkar Gourav M. Upadhyay Ashutosh V. Bedekar 《Tetrahedron: Asymmetry》2017,28(10):1297-1303
The design and synthesis of a few simple N-benzyl derivatives of isobornyl amine is presented. The derivatives have been assessed as chiral solvating agents for effective discrimination of the signals of some acids in NMR analysis. The single crystal X-ray analysis of the salts of (R)-mandelic acid with two of the title derivatives help to understand the supramolecular interactions and assign the induced chemical shifts in 1H NMR analysis. The title derivative is found to be suitable for quantitative determination of the enantiomeric excess of unknown enantiomeric purity as well as being efficient in resolving racemic mandelic acid. 相似文献
89.
Ram Shankar Gupta Abhitosh Upadhyay A. Sharfuddin 《Mediterranean Journal of Mathematics》2011,8(2):215-227
In this paper, we introduce the notion of a slant lightlike submanifold of an indefinite Cosymplectic manifold. We provide
a nontrivial example and obtain necessary and sufficient conditions for the existence of a slant lightlike submanifold. Also,
we give an example of a minimal slant lightlike submanifold of R92{R^{9}_{2}} and prove some characterization Theorems. 相似文献
90.
K. K. Upadhyay Shalini Upadhyay Ajit Kumar Kamlesh Thapliyal Santosh K. Srivastava 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1820-1834
Abstract 2-{[4-(Thiazol-2-ylsulfamoyl)-phenyl]-hydrazono}-malonic acid diethyl ester (R1) and 2-{[4-(5-methyl-isoxazol-3-ylsulfamoyl)-phenyl]-hydrazono}-malonic acid diethyl ester (R2) were synthesized through diazocoupling of sulfathiazole and sulfamethoxazole, respectively, with diethyl malonate. They were characterized through various spectroscopic and mass spectral studies. R2 was also characterized through a single crystal X-ray diffraction (XRD) study. Only R1 selectively recognized Hg2+ from a wide range of metal ions through naked-eye change. A color change from orange to olive green was observed upon addition of 1.0 equivalent of Hg2+ as its chloride salt to the 1 × 10?3 M DMSO solution of R1. The role of DMSO in the sensing process appears to be the crucial one, because the solvent-assisted band of R1 at 482 nm observed in its UV-Vis spectrum in DMSO did not appear in its spectra recorded in nujol or in a polar aprotic solvent. The UV-Vis and 1H NMR titrations revealed that the formation of six-membered 1:1 chelate between R1 and Hg2+ triggering the desolvation of R1 as the key step towards its sensing activity. The determination of binding stoichiometry between R1 and Hg2+ along with binding constant has also been discussed. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. GRAPHICAL ABSTRACT 相似文献