Browsing by Author "N.P. Singh"

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A -> X BAND SYSTEM OF SrF
(Indian Academy of Sciences, 1980) N.P. Singh; J.S. Singh
[No abstract available]
A seismic study to investigate the prospect of gas hydrate in Mahanadi deep water basin, northeastern continental margin of India
(2010) Anand Prakash; B.G. Samanta; N.P. Singh
The presence of gas hydrates, one of the new alternative energy resources for the future, along the Indian continental margins has been inferred mainly from bottom simulating reflectors (BSR) and the gas stability zone thickness mapping. Gas hydrate reserves in Krishna Godawari Basin have been established with the help of gas-hydrate related proxies inferred from multidisciplinary investigations. In the present study, an analysis of 3D seismic data of nearly 3,420 km2 area of Mahanadi deep water basin was performed in search of seismic proxies related with the existence of natural gas hydrate in the region. Analysis depicts the presence of BSR-like features over a large areal extent of nearly 250 km2 in the central western part of the basin, which exhibit all characteristics of a classical BSR associated with gas hydrate accumulation in a region. The observed BSR is present in a specific area restricted to a structural low at the Neogene level. The coherency inversion of pre-stack time migration (PSTM) gathers shows definite inversion of interval velocity across the BSR interface which indicates hydrate bearing sediments overlying the free gas bearing sediments. The amplitude versus offset analysis of PSTM gathers shows increase of amplitude with offset, a common trend as observed in BSR associated with gas hydrate accumulation. Results suggest the possibility of gas hydrate accumulation in the central part of the basin specifically in the area of structural low at the Neogene level. These results would serve as preliminary information for selecting prospective gas hydrate accumulation areas for further integrated or individual study from geophysical, geological, geochemical and microbiological perspectives for confirmation of gas hydrate reserves in the area. Further, on the basis of these results it is envisaged that biogenic gas might have been generated in the region which under suitable temperature and pressure conditions might have been transformed into the gas hydrates, and therefore, an integrated study comprising geophysical, geological, geochemical and microbiological data is suggested to establish the gas hydrate reserves in Mahanadi deep water basin. © 2010 Springer Science+Business Media B.V.
Aerosol optical properties over delhi and manora peak during a rare dust event in early april 2005
(Taylor and Francis Ltd., 2011) S.K. Srivastava; M.K. Srivastava; A. Saha; S. Tiwari; S. Singh; U.C. Dumka; B.P. Singh; N.P. Singh
Dust storm events are annual phenomena observed over the Indo-Gangetic plain (IGP) during the pre-monsoon period (May-June). These dust storms affect the air quality, weather conditions and radiation budget of the region. In this paper we characterize the aerosol optical parameters associated with a rare dust storm event that hit the IGP during early April 2005. This event was considered rare as it occurred much earlier than the general occurrence of dust storms in India (May-June), and in the year 2005, the warmest year in the span of the previous hundred years. In this study we considered the optical aerosol parameters for two places in the IGP: Delhi (28.5° N, 77.2° E, 325 m asl) and the high altitude station, Manora Peak (29.4° N, 79.5° E, 1958 m asl). Of the two selected stations, Delhi represents a highly populated and polluted location whereas Manora Peak represents a cleaner location in the central Himalayan region. During this dust storm event, the aerosol optical depth (AOD) was observed to increase considerably. The increment was 2.6-4.6 times over Delhi and 1.6-3.2 times over Manora Peak at wavelengths 380 and 1020 nm, respectively, with respect to the background values, whereas the Ångström exponent (α) for both the stations remained close to zero during the event. The effect shows a considerable increase in direct dust radiative forcing in terms of a reduction in the broadband global irradiance for Delhi as well as for Manora Peak stations. The direct aerosol radiative forcing thus obtained was about 34% in the 400-1100 nm wavelength band at Manora Peak. © 2011 Taylor & Francis.
Antibiotic Susceptibility, Virulence Pattern, and Typing of Staphylococcus aureus Strains Isolated From Variety of Infections in India
(Frontiers Media S.A., 2019) Shifu Aggarwal; Smrutiti Jena; Sasmita Panda; Savitri Sharma; Benu Dhawan; Gopal Nath; N.P. Singh; Kinshuk Chandra Nayak; Durg Vijai Singh
Staphylococcus aureus is one of the major causes of nosocomial infections. This organism produces powerful toxins and cause superficial lesions, systemic infections, and several toxemic syndromes. A total of 109 S. aureus strains isolated from a variety of infections like ocular diseases, wound infection, and sputum were included in the study. Minimum inhibitory concentration (MIC) was determined against 8 antimicrobials. PCR determined the presence of 16S rRNA, nuc, mecA, czrC, qacA/B, pvl, and toxin genes in S. aureus isolates. Pulse-field gel electrophoresis (PFGE), multi-locus sequence typing (MLST), SCCmec, spa-, and agr-typing and serotyping determined the diversity among them. All isolates of S. aureus were resistant to two or more than two antibiotics and generated 32 resistance patterns. These isolates were positive for 16S rRNA and S. aureus-specific nuc gene, but showed variable results for mecA, czrC, and qacA/B and pvl genes. Of the 32 methicillin-resistant S. aureus (MRSA), 13 strains carried SCCmec type V, seven type IV, two type III, and nine carried unreported type UT6. Of the 109 strains, 98.2% were positive for hlg, 94.5% for hla, 86.2% for sei, 73.3% for efb, 70.6% for cna, 30.2% for sea, and 12.8% for sec genes. Serotypes VII and VI were prevalent among S. aureus strains. PFGE analysis grouped the 109 strains into 77 clusters. MLST classified the strains into 33 sequence types (ST) and eight clonal complexes (CCs) of which 12 were singletons, and two belong to new allelic profiles. Isolates showed 46 spa-types that included two new spa-types designated as t14911 and t14912. MRSA and methicillin-susceptible S. aureus (MSSA) isolates were diverse in terms of antibiotic resistance pattern, toxin genotypes, SCCmec types, serotypes and PFGE, MLST, and spa-types. However, few isolates from eye infection and wound infection belong to CC239, ST239, and spa-type t037/t657. The study thus suggests that S. aureus strains are multidrug resistant, virulent, and diverse irrespective of sources and place of isolation. These findings necessitate the continuous surveillance of multidrug-resistant and virulent S. aureus and monitoring of the transmission of infection. © Copyright © 2019 Aggarwal, Jena, Panda, Sharma, Dhawan, Nath, Singh, Nayak and Singh.
Application of bacterial endophytes as bioinoculant enhances germination, seedling growth and yield of maize (Zea mays L.)
(Range Management Society of India, 2013) N.P. Singh; R.K. Singh; J.P. Shahi; H.K. Jaiswal; T. Singh
Ten endophytic bacteria isolated from maize plants at farmer fields were characterized for their endophytic association and various biochemical activities such as production of phytohormones, siderophore and phosphate solubilization. All the selected isolates produced indole acetic acid. However, four isolates (BHU3, BHU8, BHU9 and BHU10) have ability for phosphate solubilization. Siderophore production was shown by six isolates (BHU1, BHU2, BHU3, BHU5, BHU8 and BHU10). Activates of endophytic bacterial isolates under field conditions indicated significant increase in seed germination, chlorophyll content, cob length, plant height, test weight, grain yield and harvest index over control. Isolates BHU3, BHU8 and BHU10 performed relatively better than the other isolates.
Application of Hankel transform in the interpretation of magnetic anomaly over semi-infinite vertical rod
(2000) N.P. Singh; T. Lal; M. Banerjee
Application of Hankel transform in the interpretation of magnetic anomaly, is illustrated for a vertically magnetized semi-infinite vertical rod. Theoretical anomaly curves, generated using linear digital filter algorithm for the three synthetic model, have been used for the estimation of depth and magnetic moment using the Hankel transform approach. The interpreted results obtained by the Hankel transform technique match significantly well with those selected for the generation of synthetic anomaly curves. Comparison of Hankel transform results with the corresponding Fourier transform results, indicates that the application of Hankel transform is more suitable for the estimation of depth and magnetic moment of a vertically magnetized semi-infinite vertical rod.
Application of LP and ML sparse spike inversion with probabilistic neural network to classify reservoir facies distribution - A case study from the Blackfoot field, Canada
(Elsevier B.V., 2018) S.P. Maurya; N.P. Singh
Sparse-Spike inversion techniques are used to estimate distribution of acoustic impedance in inter well region, the important parameters for characterizing the reservoir facies from seismic and well log data. The purpose of sparse spike impedance inversion is to obtain high-resolution impedance profile of the subsurface from the low resolution seismic data with the integration of well log data and enhance the interpretation of the prospective zone. In the present study, two types of sparse spike inversion techniques, namely, Linear Programming (LP) sparse spike inversion and Maximum Likelihood (ML) sparse spike inversion are applied to estimate acoustic impedance from seismic data of the Blackfoot region, Alberta, Canada. The principle objective of the study is assessing the relative performance of these techniques for estimation of petrophysical parameters to identification of prospective zones in the area. Initially, the inversion methods are applied to the composite trace near to well locations and inverted for acoustic impedance and compared with the actual impedance derived from the well log data. The result demonstrates that both curves are matching with each other very well. The correlation is estimated to be 0.97 and 0.93, Synthetic relative error (SRE) 0.23 and 0.34 and Root mean square (RMS) errors are 1125 m/s*g/cc and 1205 m/s*g/cc for Linear Programming sparse spike inversion (LPSSI) and Maximum Likelihood sparse spike inversion (MLSSI), respectively. The analysis for composite traces depicts the robustness and performance of the algorithm. Thereafter, the techniques are applied to seismic volume to estimate variation of acoustic impedance in inter well regions. The analysis of inverted impedance shows a low impedance anomaly in between 1060 and 1075 ms time intervals which may be due to presence of reservoir facies (sand channel). The analyses of the inverted results reiterate that both methods work satisfactory and show variation of reservoir facies in similar way. The results found by LPSSI shows slightly higher resolution compared to the MLSSI results. Thereafter, to enhance reservoir facies more clearly, porosity is predicted in inter well region by using probabilistic neural network (PNN) technique. The result shows very high porosity (> 15%) in between 1060 and 1075 ms time interval which corroborated with the low impedance zone and confirms the presence of sand channel. The qualitatively and quantitatively analysis of inversion results suggest that the LPSSI along with PNN provides better reservoir characterization than MLSSI and PNN combination for the Blackfoot field, Alberta, Canada. © 2018 Elsevier B.V.
Bacteriophages: A possible solution to combat enteropathogenic Escherichia coli infections in neonatal goats
(John Wiley and Sons Inc, 2022) K. Bhargava; K. Gururaj; G.K. Aseri; G. Nath; N.P. Singh; R.V.S. Pawaiya; A. Kumar; A.K. Mishra; V.B. Yadav; N. Jain
Due to awareness and benefits of goat rearing in developing economies, goats' significance is increasing. Unfortunately, these ruminants are threatened via multiple bacterial pathogens such as enteropathogenic Escherichia coli (EPEC). In goat kids and lambs, EPEC causes gastrointestinal disease leading to substantial economic losses for farmers and may also pose a threat to public health via the spread of zoonotic diseases. Management of infection is primarily based on antibiotics, but the need for new therapeutic measures as an alternative to antibiotics is becoming vital because of the advent of antimicrobial resistance (AMR). The prevalence of EPEC was established using bfpA gene, uspA gene and Stx1 gene, followed by phylogenetic analysis using Stx1 gene. The lytic activity of the isolated putative coliphages was tested on multi-drug resistant strains of EPEC. It was observed that a PCR based approach is more effective and rapid as compared to phenotypic tests of Escherichia coli virulence. It was also established that the isolated bacteriophages exhibited potent antibacterial efficacy in vitro, with some of the isolates (16%) detected as T4 and T4-like phages based on gp23 gene. Hence, bacteriophages as therapeutic agents may be explored as an alternative to antibiotics in managing public, livestock and environmental health in this era of AMR. © 2022 The Society for Applied Microbiology.
Biomimetic synthesis and characterization of semiconducting hybrid organic-inorganic composite materials based on polyaniline-polyethylene glycol-CdS system
(Indian Academy of Sciences, 2011) A. Singh; N.P. Singh; R.A. Singh
Triple hybrid materials based on polyaniline-polyethylene glycol and cadmium sulphide have been prepared by the duffusion-limited biomimetic route and characterized by a number of spectroscopic, XRD, SEM, thermal and electrical measurements. These hybrid materials have been prepared by controlled precipitation of cadmium sulphide by passing H2S gas and mixing the resultant colloid with the acidic solution of aniline. In situ polymerization of adsorbed anilinium ions on anionic surface of CdS resulted in hybrids. Water-soluble polyethylene glycol led to diffusion-limited growth of polyaniline and CdS resulting in a nanosized hybrid material as indicated by UV-visible spectra, X-ray diffraction (XRD) and scanning electron microscopy (SEM). AC impedance spectroscopic studies on binary and ternary nanocomposites of polyaniline with polyethylene glycol and cadmium sulphide separately and triple hybrid system have been reported. Equivalent circuits were determined and discussed in the light of contributions made from different sources such as grain, grain boundary and electrode. © Indian Academy of Sciences.
Can bacillus species enhance nutrient availability in agricultural soils?
(Springer International Publishing, 2017) Vijay Singh Meena; B.R. Maurya; Sunita Kumari Meena; Rajesh Kumar Meena; Ashok Kumar; J.P. Verma; N.P. Singh
One major challenge for the twenty-first century will be the production of sufficient food for the global human population. The negative impacts on soil-plant- microbes-environmental sustainability due to injudicious use of chemical fertilizer, pesticide, insecticide, etc. by the unaware farmers deteriorate soil and environment quality. One possible way to use efficient soil microorganisms to remediate nutrient deficiency in agricultural soils and other plant growth-promoting (PGP) activities that can be of help for plant growth and development. The Bacillus species is one the most dominant rhizospheric bacterial/rhizobacteria species like Bacillus subtilis, B. cereus, B. thuringiensis, B. pumilus, B. megaterium, etc. that can help enhance the plant growth and development by different mechanisms, which PGPR can inhibit phytopathogens is the production of hydrogen cyanide (HCN) and/or fungal cell wall degrading enzymes, e.g., chitinase and β-1,3-glucanase. Direct plant growth promotion includes symbiotic and non-symbiotic PGPR which function through production of plant hormones such as auxins, cytokinins, gibberellins, ethylene, and abscisic acid. Mitigate the challenge by adopting eco-friendly crop production practices. Some Bacillus species function as a sink for 1-aminocyclopropane- 1-carboxylate (ACC), the immediate precursor of ethylene in higher plants, by hydrolyzing it into a-ketobutyrate and ammonia and in this way promote root growth by lowering indigenous ethylene levels in the micro-rhizo environment. Bacillus species also help in solubilization of mineral phosphates, potassium, zinc, and other nutrients; rhizobacteria retain more soil organic N and other nutrients in the soil-plant system, thus reducing the need for fertilizers and enhancing release of the nutrients from indigenous or mineral sources, enhancing the economic and environmental sustainability. © Springer International Publishing AG 2016.
Can we use maize (Zea mays) Rhizobacteria as Plant Growth Promoter?
(Society for Plant Research, 2015) N.P. Singh; R.K. Singh; V.S. Meena; R.K. Meena
Plant Growth Promoting Rhizobacteria (PGPR) is a group of bacteria that has the ability to enhance plant growth and yield via various plant growth promoting substances as well as biofertilizers. Ten bacterial isolates screened from rhizosphere of maize growing at Indo- Gangetic plain of eastern Uttar Pradesh, India showed potential nutrients solubilization and plant growth promoting activities. Rhizobacterial were able to produce phytohormone auxin (IAA) in the tryptophan supplemented medium which showed maximum production by strain BHU8. Phosphate solubilization activity was highly observed in isolate BHU8 followed by BHU3, BHU9 and BHU10. Plant cell wall hydrolyzing enzymes (Cellulase and Pectinase) were expressed in BHU3, BHU8, BHU9 and BHU10 and among ten rhizobacterial strains only six strains (BHU1, BHU2, BHU3, BHU5, BHU8 and BHU10) produced siderophore. Based on 16S rDNA gene sequence strains BHU1, BHU2, BHU3, BHU8, BHU10 showed 99.6%, 99.8%, 99.8%, 99.7% and 99.9% sequence alignment respectively with Pseudomonas brassicacearum, Pseudomonas taiwanensis Pseudomonas aeruginosa, Pseudomonas saponiphila and Pseudomonas oryzihabitans, respectively whereas strains BHU4 and BHU5 showed 99.7% similarity with Rhizobium radiobacter and strains BHU6 and BHU9 showed 99.9% sequence aligned with Bacillus oceanisediminis and Bacillus flexus, respectively. Strain BHU7 exhibited 99.9% similarity with Enterobacter asburiae. © 2015 Society for Plant Research. All rights reserved.
Combining ability studies for grain yield other agronomic traits in maize (Zea mays L.)
(Indian Society of Plant Breeders, 2016) V. Kumar; S.K. Singh; N.P. Singh; V. Mahajan
The present study was aimed to investigate combining ability among twelve elite maize inbred lines in a complete diallel mating design for twelve yield and yield contributing traits. Twelve parents along with their 132 F1's including reciprocals were planted in a randomized complete block design with three replications. The analysis of variance indicated significant differences among parents for most of the traits studied except for ear diameter. Variance due to GCA and SCA were highly significant for the traits studied indicating importance of both additive and non-additive types of gene action. Preponderance of additive gene action was observed for most of the traits studied except for the grain yield plant-1, number of kernel rows ear-1, number of kernels row-1 and ear length which showed preponderance of non-additive gene action. Parent P10 was the best general combiner for grain yield followed by P9 and P1. Parent P9 was also found to be best general combiner for the all traits studied including grain yield. Parent P10 was also found to be best general combiner for early maturity, number of kernel rows ear-1 and 100 kernels weight. For the trait early maturity parent found to be best general combiners were P10, P3 and Parent P7. Total 79 cross combinations were possessing significant desirable SCA effects for grain yield. The top cross combinations possessing significant desirable SCA effects for grain yield were P2 x P6, P7 x P8, P3 x P7 and P7 x P9 which may be used for obtaining high yielding hybrids in maize.
Effect of cowpea Bradyrhizobium (RA-5) on growth parameters of pigeonpea plant under various salt concentrations at different time intervals
(Ecological Society of India, 2015) Dilruba A. Beno; R.K. Singh; N.P. Singh; Showkat A. Waza
The pot experiment was conducted to evaluate the effect of cowpea Bradyrhizobium (RA-5) on plant growth parameters in pigeonpea plant under various salt concentrations at 10,20 and 30 days after sowing (DAS). All the growth parameters studied were found to decrease progressively with the increasing salinity levels. Best growth of the plants was observed in treatment containing RA-5 with no salt. Very Poor growrth was observed in treatments applied with saline solutions containing 200 mM and 300 mM salt concentrations. The similar trend was observed at 10,20 and 30 days after sowing.
Electromagnetic response of horizontal electric dipole over horizontally stratified half-space having a layer with exponential conductivity-depth function
(1995) N.P. Singh; T. Lal
The problem of calculation of electromagnetic fields is formulated for a multi-layer earth model, with one of the layers having exponential variation of conductivity with depth. Analytical solutions are obtained for the three-layer transitional earth model with the intermediate inhomogeneous layer possessing conductivity variation as above. Computational results showing the effect of variation of transition layer thickness and conductivity contrast between the top and bottom layers are presented as a function of numerical distance. Results depict the characteristic effects of conductivity inhomogeneities.
Electromagnetic response of vertical electric dipole over vertically inhomogeneous earth models
(1995) N.P. Singh; T. Lal; A. Hakim
The problem is formulated for a general multi-layered earth model, with the assumption that the electrical conductivity of an intermediate-inhomogeneous layer varies in accordance with the linear or exponential variation with depth. Analytical expressions for the various electric and magnetic field components and the computational results are obtained for a three layer earth model with the transition layer possessing the described conductivity variation. The results for the absolute-amplitude of the Ez1 and Eφ1 components are presented as a function of the distance between the dipole and the observation point. The nature of response curves depicting characteristic variations of the models are discussed. -from Authors
EMDPLER: A F77 program for modeling the EM response of dipolar sources over the non-magnetic layer earth models
(2010) N.P. Singh; Toru Mogi
A program EMDPLER coded in FORTRAN 77 is presented for modeling the electromagnetic (EM) response of a wide class of dipolar sources (namely, vertical magnetic dipole, horizontal magnetic dipole and horizontal electric dipole) over the layered earth model in induction (f≤50 kHz) as well as higher frequency (50 kHz≤f≤1000 kHz) regions. The program is based on a semi-analytical numerical approach for evaluating infinite integrals occurring in the expressions of EM field components. It is capable of computing the EM response with or without the displacement current factor for any arbitrary position of source and/or receiver either in air or on the surface of the model due to all the conventional EM dipole sources where other available algorithms fail due to one or other reasons. The program is well documented, easy to understand and amenable to modification for the user's specification. The validity and accuracy of the program is demonstrated by computing the EM response of dipolar sources over homogeneous and multi-layer earth models, and comparing the computed results with those of published results in the literature. Response curves depict their characteristic variations. The computed results match very well with the published results for the induction region (f≤50 kHz) and are extension of their characteristic variation in the higher frequency (50 kHz≤f≤1000 kHz) region. The matching of computed results with the published results illustrates the validity of the program. © 2010 Elsevier Ltd. All rights reserved.
Enterotoxigenicity of chicken isolates of Campylobacter jejuni in ligated ileal loops of rats
(1988) S.K. Saha; N.P. Singh; S.C. Sanyal
Ligated ileal loops in rats of the Charles-Foster strain, weighing 200-250 g and aged 7-8 months, provided a sensitive and reproducible means of testing the enterotoxigenicity of Campylobacter jejuni. All of 16 chicken isolates caused fluid accumulation comparable to that produced by toxigenic Vibrio cholerae O1, strain 569B. However, 11 of the isolates required one to three consecutive passages through the rat gut before doing so. The amount of fluid produced increased after each passage. Of three culture media tested, brucella broth of pH 6.7 supported the highest degree of enterotoxigenesis. Filtrates of cultures of all 16 chicken isolates in this medium were as effective as viable C. jejuni in producing fluid in ileal loops. The enterotoxin was neutralised completely by cholera antitoxin diluted 1 in 160, indicating its close immunobiological relationship to cholera toxin.
Evidence of gas hydrate accumulation and its resource estimation in Andaman deep water basin from seismic and well log data
(Kluwer Academic Publishers, 2013) Anand Prakash; B.G. Samanta; N.P. Singh
2D and 3D seismic reflection and well log data from Andaman deep water basin are analyzed to investigate geophysical evidence related to gas hydrate accumulation and saturation. Analysis of seismic data reveals the presence of a bottom simulating reflector (BSR) in the area showing all the characteristics of a classical BSR associated with gas hydrate accumulation. Double BSRs are also observed on some seismic sections of area (Area B) that suggest substantial changes in pressure-temperature (P-T) conditions in the past. The manifestation of changes in P-T conditions can also be marked by the varying gas hydrate stability zone thickness (200-650 m) in the area. The 3D seismic data of Area B located in the ponded fill, west of Alcock Rise has been pre-stack depth migrated. A significant velocity inversion across the BSR (1,950-1,650 m/s) has been observed on the velocity model obtained from pre-stack depth migration. The areas with low velocity of the order of 1,450 m/s below the BSR and high amplitudes indicate presence of dissociated or free gas beneath the hydrate layer. The amplitude variation with offset analysis of BSR depicts increase in amplitude with offset, a similar trend as observed for the BSR associated with the gas hydrate accumulations. The presence of gas hydrate shown by logging results from a drilled well for hydrocarbon exploration in Area B, where gas hydrate deposit was predicted from seismic evidence, validate our findings. The base of the hydrate layer derived from the resistivity and acoustic transit-time logs is in agreement with the depth of hydrate layer interpreted from the pre-stack depth migrated seismic section. The resistivity and acoustic transit-time logs indicate 30-m-thick hydrate layer at the depth interval of 1,865-1,895 m with 30 % hydrate saturation. The total hydrate bound gas in Area B is estimated to be 1.8 × 1010 m3, which is comparable (by volume) to the reserves in major conventional gas fields. © 2012 Springer Science+Business Media Dordrecht.
Experimental and calculation aspects of vibrational spectra and optimized geometry of 2,3,4-tri-fluoro-benzoic acid dimer
(Elsevier B.V., 2009) V. Mukherjee; N.P. Singh; R.A. Yadav
Raman and FTIR spectra for 2,3,4-tri-fluoro-benzoic acid molecules have been recorded in the regions 50-4000cm-1 and 400-4000cm-1 respectively. The geometrical parameters have been optimized in both the monomeric and dimeric forms while vibrational frequencies have been calculated in optimum state in the dimeric form by employing DFT method. SQM force fields have also been used to calculate potential energy distributions in order to make conspicuous vibrational assignments. Raman activities calculated by DFT method have been converted to the corresponding Raman intensities using Raman scattering theory. Optimized geometries of the molecule have been interpreted and compared with the earlier reported experimental values for benzoic acid and some mono and di-fluorinated benzoic acids. Some of the vibrational frequencies of the title molecule are effected upon profusely with the fluorine substitutions in comparison to benzoic acid and these differences have been interpreted. The strong doubly hydrogen-bonded interface of the dimerized system is well demonstrated by the red shift in OH stretching frequency concomitant with the elongation of bond length. © 2009 Elsevier B.V. All rights reserved.
Experimental and theoretical studies of vibrational spectrum and molecular structure and related properties of pyridoxine (vitamin B6)
(Elsevier, 2014) Mayuri Srivastava; P. Rani; N.P. Singh; R.A. Yadav
Vibrational spectrum of pyridoxine has been investigated using experimental IR and Raman spectroscopic and density functional theory (DFT) methods. Vibrational assignments of the observed IR and Raman bands have been proposed in light of the results obtained from computations. In order to assign the observed IR and Raman frequencies the potential energy distributions (PEDs) have also been computed. Optimized geometrical parameters suggest that if the OH groups of the two methyl groups are replaced by H atoms the resulting molecule has Cs point group symmetry. To investigate molecular stability and bond strength we have used natural bond orbital analysis (NBO). Charge transfer occurs in the molecule have been shown by the calculated highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energies. The mapping of electron density iso-surface with electrostatic potential (ESP), has been carried out to get the information about the size, shape, charge density distribution and site of chemical reactivity of the molecule. © 2013 Elsevier Ltd. All rights reserved.