BITS Faculty Publications
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Item C60 submonolayers on the Si(1 1 1)-(7 × 7) surface: Does a mixture of physisorbed and chemisorbed states exist?(Elsevier, 200-09) Gangopadhyay, SubhashisWe have carried out a combined X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy(UPS), and scanning tunnelling microscopy (STM) study of the C60-Si(1 1 1) interaction where the XPS/UPS spectrometer and STM are integrated on a single UHV system. This enables a direct comparison of the XPS/UPS spectra with the STM data and eliminates any uncertainty in C60 coverage measurements. X-ray standing wave measurements and density functional theory calculations have been used to support and interpret the results of the XPS/UPS/STM experiments. Our data conclusively rule out models of C60 adsorption which involve a mixture of physisorbed and chemisorbed molecules [K. Sakamoto, et al., Phys. Rev. B 60 (1999) 2579]. Instead, we find that all molecules, up to 1 monolayer coverage, bond to the surface via Si–C bonds which are predominantly of covalent character.Item Performance of Farmer Producer Organisations in Rajasthan: An Empirical Assessment(Routledge, 202) Pandey, Ranjan; Sharma, Satyendra Kumar; Routroy, SrikantaIndia is predominantly an agrarian economy. According to the recent Economic Survey (2021–22), agriculture and allied sectors continue to be the mainstay of the Indian economy as it is the largest employer of the working population and contributes about 19 to the total gross value added of the country in 2021–22. Unlike the agriculture system in Western Europe, Indian agriculture is dominated mainly by small and marginal farmers, accounting for more than four-fifths of the total landholding size. More recently, due to government intervention, many strategies, including agri-business models, have been developed to tackle 384the marginalisation of farmers by bringing them under one umbrella. With the recommendation of a committee headed by YK Alagh, the formation of Farmer Producer Organisations (FPOs) has become a reality by incorporating a special provision in part IXA of the Companies Act, 1956. In this context, our attempt in this paper is to evaluate the financial performance of FPOs registered in Rajasthan.Item Performance of Hybrid THz and Multiantenna RF System With Diversity Combining(IEEE, 202-11) Zafaruddin, S.M.Recent studies investigate single-antenna radio frequency (RF) systems mixed with terahertz (THz) wireless communications. This article considers a two-tier system of THz for backhaul and multiple-antenna-assisted RF for the access network. We analyze the system performance by employing both the selection combining and maximal ratio combining receivers for the RF link integrated with the THz link using the fixed-gain amplify-and-forward protocol. We develop the probability density function and the cumulative distribution function of the end-to-end signal-to-noise ratio (SNR) of the dual-hop system over independent and nonidentically distributed α – μ fading channels with a statistical model for misalignment errors in the THz wireless link. We use the derived statistical results to develop analytical expressions of the outage probability, average bit error rate, and ergodic capacity for the performance assessment of the considered system. We develop a diversity order of the system using asymptotic analysis in the high-SNR region, demonstrating the scaling of system performance with the number of antennas. We use computer simulations to show the effect of system and channel parameters on the performance of the hybrid THz-RF link with multiantenna diversity schemes.Item Optimal use of polarimetric signature on PALSAR-2 data for land cover classification(IEEE, 217) Phartiyal, Gopal SinghSAR data is playing key role in monitoring, the current status or change in, the land cover. For unsupervised SAR image classification, polarization signatures can play a significant role. Since it is difficult to obtain specific polarization signature of real land cover, it is customary to represent them with standard canonical structures polarization signatures. A critical analysis of the complex signatures of real targets is essential thereafter it is also a challenge to decide the thresholds or class boundary value on the correlation images. Therefore, in this paper an attempt has been made to critically analyze the polarimetric signature of complex targets and based on the correlation image analysis an OTSU multi-thresholding based approach is proposed to decide the individual class boundary values which will finally help in building a decision tree (DT) based classification technique. For this purpose L band fully polarimetric SAR data (PALSAR-2) has been used. DT class thresholds are computed using OTSU multi-thresholding method, scatter plot method, and a priori information. Obtained results reveal that complementary features like polarization signatures can help in identification as well as classification of land surface objects significantly by the proposed method.Item Information arrivals, stock price variability and market efficiency in Indian stock market(ISAE, 1984) Giri, Arun KumarNB-Figures in brackets indicate percentages across the categories. cultivators owning land within the deep tubewell command area belonged only to the marginal and small size-group of farmers. The presence of the medium and large size-group of farmers was not observed. The medium and large category of farmers although existed a few years back, have now been reduced to marginal and small farmers. Out of 150 owner farmers, 77 per cent belonged to the marginal category cultivating 53.29 acres, constituting 59 per cent of the total area of 90.83 acres under the deep tubewell. The small farmers constituted only 23 per cent and cultivated 41 per cent of the land. The average size of owned land of the marginal and the small farmers within the deep tubewell command area was 046 acre and 1.10 acre respectively.Item Magnetic resonance lineshapes in powdered and amorphous systems(IAS, 1986-04) Sivasubramanian, S.C.A survey is made of the theory and applications ofEPR andNMR absorption lineshapes observed in powdered and amorphous materials. The ‘spin Hamiltonian’ and ‘resonance condition’ formalisms are reviewed, andepr andnmr lineshapes are discussed which typify the singularity characteristics in powdered materials. In the amorphous or ‘glassy’ state, the measurable spin resonance parameters often have to be viewed as being ‘randomly distributed’ according to a probability density function. Several recent probability-theory based approaches to lineshape computation for modelling the amorphous state are discussed.Item Transformation from metallic electron charge density to electron momentum(Elsevier, 1986-12) Mishra, Rashmi RanjanElectron momentum densities (EMD) in Al, V, Cr and Cu metals have been estimated from the metallic electron charge densities by applying the procedure of Burkhardt, Konya and Coulson and March. The procedure has provided spherically averaged EMD from which corresponding Compton profiles, J(q) and 〈pn〉 expectation values have been computed. These theoretical results show satisfactory agreement with the experimental data for Al, V, Cr and Cu.Item Impact of heavy metals on glutamine synthetase and nitrogenase activity in Nostoc calcicola.(J-Stage, 1987) Verma, Sanjay KumarItem Density functional calculation of Compton profiles of metals using phase-space approach(Elsevier, 1987-12) Mishra, Rashmi RanjanSpherically averaged electron momentum densities (EMD) in Al, V and Cu metals have been calculated by using density functional theory in the phase-space approach. Compton profiles, J(q) and expectation values 〈pn〉 have been computed. These theoretical results show satisfactory agreement with the experimental data for Al, V and Cu.Item Heavy metal Uptake in the Cynobacterium Nostoc calcicola.(IBS, 1988) Verma, Sanjay KumarThe literature on the inhibitory effect of copper on growth (Les &Walker, 1984), photosynthesis (Shiol et al, 1978) and nitrogen fixation (Rai & Raizada, 1985) in algae and higher plants is impressive. Heavy metals inhibit the uptake and assimilation of nutrients (Singh & Yadava, 1983, 1984). Mechanisms governing the metal uptake process in microorganisms (Bhattacharjee, 1986) and in cyanobacteria (Singh & Yadava, 1985) are investigated. The possibility of involvement of carrier (s) and energy in the metal transport across the cell membranes has been suggested (Veltrup, 1977). The toxicity of heavy metal to algae (Hargreaves & Whitton, 1976 a,b; Singh & were diluted to S hli with triple glass distilled water. A furher Pandey 1981) is influenced by environmental factors like pH, light and complexans. However, there have been only a few studies on the effect of environmental factors on copper uptake in cyanobacteria. The present investigation reports on the copper uptake kinetics and the role of various factors on Nostoc calcicola.Item Modal Characteristics of a doubly clad step- index optical fiber- general analytical approach(Canadian Science Publishing, 1988) Chaubey, V.K.Using a fairly rigorous approach, a general characteristic equation for a doubly clad step-index fibre has been derived under the assumption that the refractive-index difference between the inner and outer cladding is small. Two different profiles, i.e., the W profile and the staircase profile, have been treated together and a discussion of their common characteristics has been made. Cutoff conditions for low-order modes have been obtained. For a certain range of values of the transverse-phase parameter ratio, the singly-clad fibre has greater mode cutoff V numbers than those of a doubly clad fibre. The analysis anticipates the possibility of obtaining greater cutoff V numbers for W-profile fibres.Item Copper uptake by free and immobilized cyanobacterium(OUP, 1989) Verma, Sanjay KumarCopper uptake in free and immobilized cells of the cyanobacterium Nostoc calcicola has been examined. The immobilized cells invariably maintained a higher profile of Cu intake rate (12.7 nmol mg−1 protein min−1) over the free cells (6.0 nmol mg−1 protein min−1). The total Cu uptake in immobilized cells was almost two and a half-times more than their free cell counterpart under identical experimental conditions. Also, the immobilized cells showed a stronger positive correlation between Cu adsorption and uptake. The results have been discussed in terms of improved metabolic efficiency of immobilized cells.Item Factors regulating copper uptake in a cyanobacterium(Springer, 1990) Verma, Sanjay KumarCopper uptake in the diazotrophic cyanobacteriumNostoc calcicola was found to be typically biphasic, comprising rapid binding of the cations to the cell wall (during the first 10 min) followed by the subsequent metabolism-dependent intracellular uptake for at least 1 h, with a curvilinear kinetics saturating at 40 µM (Km 25.0 µM, Vmax 3.0 nmol Cu mg−1 protein min−1). The cellular Cu uptake was light- and ATP-dependent, and the addition of 3(3,4-dichlorophenyl)-1,1-dimethylurea or exogenous ATP proved that the energy to drive Cu transport was derived mainly through PS II reactions. The application of metabolic inhibitors and uncouplers like carbonylcyanidep-nitrofluoromethoxylphenyl hydrazone, N,N′-dicyclohexycarbodiimide, azide, and p-chloromercuribenzoate revealed that -SH group(s), proton gradient across the cell membrane, and ATP hydrolysis were involved in the transmembrane movement of Cu inN. calcicola. While monothiol (2-mercaptoethanol) caused a twofold reduction in Cu uptake rate, dithiol (dithiothreitol) contributed towards a further drop in the cation uptake rate.Item Genetic transformation of glutamine auxotrophy to prototrophy in the cyanobacterium Nostoc muscorum(Springer, 1990) Verma, Sanjay KumarItem Photophysics of doubly-charged quinine: Steady state and time-dependent fluorescence(Elsevier, 1990-04) Pant, Debi D.The quinine dication in aqueous solution (1 N H2SO4) gives two fluorescence lifetimes (τ1 = 2.80 ns and τ2 = 19.36 ns) at ambient temperature. τ2 shows a small increase with an increase in acid concentration between 0.1 N and 15 N. Quenching by Cl− shows that τ1 and τ2 are differentially quenched. The Stern—Volmer quenching constant KSV for τ1 is 10 M−1 and for τ2 is 75 M−1. In addition, KSV is dependent on emission wavelength. In acidified solution, τ2 increases with an increase in emission wavelength, whereas τ1 exhibits a behaviour which resembles a two-state mechanism with a negative amplitude in the region of longer emission wavelength. However, the two-state theory does not give an entirely satisfactory mechanism for the time-dependent emission. Time-resolved emission spectroscopy (TRES) shows a spectral relaxation which partially explains the dependence of τ2 on emission wavelength in accordance with Bakhshiev formulation. Transient and steady state fluorescence studies from 80 to 290 K show that at 160 K there is a rapid relaxation process resulting in an increase in τ2 and a sudden spectral shift. We propose that the complex behaviour of quinine decay consists of two major relaxation processes: a charge-transfer process which occurs around 160 K and a solvent reorientation process which occurs in the fluid medium.Item Photophysics of doubly-charged quinine: Steady state and time-dependent fluorescence(Elsevier, 1990-04) Pant, Debi D.The quinine dication in aqueous solution (1 N H2SO4) gives two fluorescence lifetimes (τ1 = 2.80 ns and τ2 = 19.36 ns) at ambient temperature. τ2 shows a small increase with an increase in acid concentration between 0.1 N and 15 N. Quenching by Cl− shows that τ1 and τ2 are differentially quenched. The Stern—Volmer quenching constant KSV for τ1 is 10 M−1 and for τ2 is 75 M−1. In addition, KSV is dependent on emission wavelength. In acidified solution, τ2 increases with an increase in emission wavelength, whereas τ1 exhibits a behaviour which resembles a two-state mechanism with a negative amplitude in the region of longer emission wavelength. However, the two-state theory does not give an entirely satisfactory mechanism for the time-dependent emission. Time-resolved emission spectroscopy (TRES) shows a spectral relaxation which partially explains the dependence of τ2 on emission wavelength in accordance with Bakhshiev formulation. Transient and steady state fluorescence studies from 80 to 290 K show that at 160 K there is a rapid relaxation process resulting in an increase in τ2 and a sudden spectral shift. We propose that the complex behaviour of quinine decay consists of two major relaxation processes: a charge-transfer process which occurs around 160 K and a solvent reorientation process which occurs in the fluid medium.Item Photophysics of protonated 6-methoxyquinoline: steady state and time-dependent fluorescence(Elsevier, 1990-11) Pant, Debi D.Nanosecond time-resolved emission spectroscopy was used to investigate the excited state solute—solvent interaction in 6-methoxyquinoline. A red shift in the emission maximum is observed on excitation at the red edge of the absorpton band which depends on the temperature and viscosity of the medium. The fluorescence lifetime is dependent on the emission and excitation wavelengths. A significant change in the energy of emission is observed on the nanosecond time scale. The room temperature data can be explained using the Bakhshiev formulation of solvent relaxation. However, transient and steady state fluorescence studies from 80 to 290 K reveal that, at 160 K, a rapid relaxation process occurs (not solvent relaxation). The photophysics of 6-methoxyquinoline are similar to those of the quinine dication which exhibits two relaxation processes (from 80 to 290 K) — a charge-transfer process around 160 K and a solvent relaxation process at ambient temperature.Item Evidence for energy-dependent copper efflux as a mechanism of Cu2+ resistance in the cyanobacterium Nostoc calcicola(OUP, 1991) Verma, Sanjay KumarWild-type Nostoc calcicola carried out oxygenic photosynthesis extremely sensitive to copper. A Cu(2+)-resistant mutant (Cu-R1) of the cyanobacterium grew normally at high concentrations of Cu2+. Its ability to grow under such conditions was found to be due to mutational acquisition of an energy-dependent efficient system of Cu(2+)-efflux, which rendered Cu(2+)-inhibited oxygenic photosynthesis fully reversible.Item Parallel iterative algorithms for solving fundamental mode neutron flux distribution(Elsevier, 1991) Rajagopalan, ShekharIssues relating to implementing iterative procedures, for numerical solution of neutron diffusion equations on a distributed parallel computing system, are discussed. Preliminary investigations for a reactor modelled on a 128 × 128 rectangular grid show that a speed-up of about 3.85 is achievable on a fourtransputer pipeline network.Item Excited state solvation dynamics of 6-methoxyquinoline(Elsevier, 1991-02) Pant, Debi D.Steady state and transient studies of 6-methoxyquinoline (6MQ) were undertaken. 6MQ undergoes a large change of dipole moment on excitation. The low energy absorption band Lb does not change in position with solvent polarity whereas the emission maxima shift towards lower frequencies with broadening of the spectra. The edge excitation red shift, which is associated with the time-dependent red shift of emission, is observed in all polar solvents. The fluorescence decay is monoexponential and is dependent on emission wavelength. The data are explained with the help of the Bakhshiev model of solvent relaxation. The solvent relaxation time τr and the fluorescence lifetime τf increase with the polarity of the solvent. In aqueous solution, 6MQ undergoes a protolytic reaction in the excited state. The rate constant for the proton transfer is 1.2×108 s−1.