Browsing by Issue Date, starting with "1999"

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Synthesis, characterization and hydrogenation behaviour of composite hydrogen storage alloys, LaNi5/La2Ni7, LaNi3
(Elsevier BV, 1999) Sumita Srivastava; O.N. Srivastava
The present study deals with investigations on the composite hydrogen storage materials LaNi5/La2Ni7, LaNi3, for efficient, high energy density Ni-MH batteries. To achieve this goal extensive investigations were carried out to study the effect of presence of secondary phases on the main phase LaNi5 with reference to hydrogenation behaviour and structural-microstructural characterizations using XRD, TEM and SEM techniques. Alloys were synthesized through melt-casting with varying concentrations of secondary phases like La2Ni7, LaNi3, Ni (minor phases), i.e., 55%, 30%, 5% and 0% by a special technique of pellet encapsulation. Structural characterizations using the XRD technique confirmed the formation of secondary phases together with the major phase LaNi5. The diffraction patterns after hydrogenation did not exhibit secondary phase diffraction peaks, instead the resulting phase was found to be single phasic, exhibiting LaNi5 like diffraction patterns with an unusual intensity distribution. TEM investigations showed the presence of two types of modulated phases; one of which corresponds to a≈1.5o, c≈co and the other to a≈1.3ao, c≈co, together with the parent phase (LaNi5), in the as-synthesized and hydrogenated/dehydrogenated versions, corresponding to alloy with secondary phase concentration upto 30%, (ao and Co being lattice constants of the parent LaNi5 structure). The signature of the modulated phases were not present in XRD patterns, but could be seen in the selected area electron diffraction patterns, suggesting that modulation has taken place in local areas of the basal plane, due to ordering of hydrogen atoms. These modulated unit cells can be modeled in terms of the original lattice of LaNi5, by inserting and ordering of hydrogen atoms at viable interstitial sites. Micro structural evaluations through SEM revealed that secondary phases suppressed pulverization. Investigations of the hydrogenation behaviour of these alloys showed that hydrogen storage capacity and desorption kinetics did not decrease for minor concentrations of secondary phases, but a decrease was found for the alloys having higher concentrations of secondary phases. Similar results were obtained for alloy MmNi5, where secondary phases corresponded to Mm2Ni7 and MmNi. © 1999 Elsevier Science S.A. All rights reserved.
Study of key mortality factors in the population dynamics of chickpea pod borer, Helicoverpa armigera (Hubner) (Noctuidae: Lepidoptera) infesting chickpea, Cicer arietinum L.
(1999) Paras Nath; Rakesh Rai
The role of key mortality factors in the population dynamics of chickpea pod borer, H. armigera (Hubner) (Noctuidae: Lepidoptera) was studied during 1989-1990 and 1990-1991 by constructing the life tables of two different generations. The action of mortality factors operating in each of the two generations was different. The key mortality factors during the first and the second generations were due to the failure of newly hatched larvae to survive, parasitization of the younger larvae by Campoletis chloridae Uchida (Ichneumonidae: Hymenoptera), the older larvae by Carcelia illota Curran (Tachinidae: Diptera) and the disease caused by nuclear polyhedrosis virus. The pupal mortality was due to the unidentified disease and the unknown causes. The mortality was more in the younger larvae followed by the pupae and the older larvae in both the generations. The trend index in the first generation was found positive i.e. 1.89 and 2.24 but, the negative trend index i.e. 0.78 and 0.97 was observed in the second generation during 1989-90 and 1990-91, respectively.
Fat-soluble vitamin profile in filarial chyluria - A preliminary study
(1999) M. Sridhar; D.K. Pal; I.D. Saxena; U.S. Dwivedi; V.N.P. Tripathi; P.B. Singh
[No abstract available]
Congestive heart failure and septic abortion
(BMJ Publishing Group, 1999) S.K. Singh; Pawan Arora; Shailendra Kumar Singh; Salil Pal; K.K. Singh; J.K. Agrawal
[No abstract available]
Overtone spectroscopy of butanol
(Elsevier Science B.V., 1999) S.B. Rai; P.K. Srivastava
Overtone spectra of CH and OH stretching vibrations in normal, secondary and tertiary butanol have been studied. A large number of combination and overtone bands, along with the fundamentals have been measured and assigned in the three cases. These data have been used to obtain the vibrational frequency, anharmonicity constant and dissociation energy for the CH and OH stretch motions in the respective molecules. Effect of dilution on the OH fundamental frequency in n-butanol causes a blue shift.
Ultraviolet light-induced phase response curve for the locomotor activity rhythm of the field mouse Mus booduga
(1999) Vijay Kumar Sharma; Muniyandi Singaravel; Ramanujam Subbaraj
[No abstract available]
Synthesis and characterization of iron(II) complexes containing furoylhydrazone ligands
(Marcel Dekker Inc., 1999) B. Singh; Preeti Sahai; T.B. Singh
Complexes having the chemical compositions Fe(HL)2Cl2 [HL = 2-acetylthiophene-2-furoylhydrazone (Hatfh), 2-acetylfuran-2-furoylhydrazone (Haffh), 2-acetylpyridine-2-furoylhydrazone (Hapfh)]; Fe(Hhafh)Cl(H2O) [H2hafh = o-hydroxy-acetophenone-2-furoylhydrazone); [Fe(H2dapfh)Cl]Cl [H2dapfh = 2,6-diacetylpyridine bis(2-furoylhydrazone)]; FeL2(H2O)n [HL = Hatfh, Haffh, n = 2; L = Hapfh, n = 0]; Fe(hafh)(H2O)3 and Fe(dapfh)(H2O) have been prepared and characterized. The electrical conductivity indicates a non-ionic nature of the complexes except [Fe(H2dapfh)Cl]Cl which is a 1:1 electrolyte in solution. Magnetic susceptibility, IR and electronic spectra of the complexes were employed to establish the stereochemistry and mode of bonding of the hydrazones. Mössbauer spectra indicate that iron is in the +2 oxidation state in these complexes.
Studies on cephalosporin-C production in an air lift reactor using different growth modes of Cephalosporium acremonium
(1999) Pradeep Srivastava; Subir Kundu
This paper deals with the studies on Cephalosporin-C production in a lab-scale airlift reactor using Cephalosporium acremonium. Various growth modes, viz. pellets and Siran supported bioparticles were used to improve the process over conventional free mycelial fermentation. Cephalosporin-C production was significantly improved by using bioparticles over the free mycelial culture, probably due to the enhanced mass transfer in the fermentation broth. However, the biofilm of the bioparticles became unstable as the fermentation proceeded, and increase in the free cells in the broth occurs. The maximum specific growth rate of free cells, pellets and Siran carrier were observed to be 0.037, 0.033 and 0.045 h-1, respectively. The oxygen transfer coefficient also improved for the immobilised modes (100 h- 1, 70 h-1 for Siran carrier and pellets) and thereby enhanced specific antibiotic productivity, 18-28% were observed.
Investigation on the synthesis, characterization and hydrogenation behaviour of new Mg-based composite materials Mg-x wt.% MmNi4.6Fe0.4 prepared through mechanical alloying
(Elsevier Sequoia SA, 1999) D.J. Davidson; S.S. Sai Raman; O.N. Srivastava
Alloys with general formula Mg-x wt.% MmNi4.6Fe0.4 have been successfully synthesized through ball milling employing a high energy attritor mill. The ball milling has been done in hexane medium; various time durations and speeds (rev./min) have been employed. The hydrogenation and dehydrogenation behaviour of these new composite materials have been extensively investigated. The as-prepared (ball milled: mechanically alloyed) composite materials have been activated at 400±10 °C under a hydrogen pressure of approximately 40 kg cm-2. These composite materials have been found to possess one of the highest known storage capacities. It has been found that the highest storage capacity material (approximately 5.0 wt.% at 350 °C) corresponds to Mg-30 wt.% MmNi4.6Fe0.4. The said alloy exhibits fast absorption-desorption kinetics (about 80 cm3 min-1). It is also established that the optimum mechanically alloyed samples for hydrogen storage were obtained with milling at 400 rev./min speed and time duration of approximately 5 h. The hydriding rate and the improved hydrogen storage capacity of these composite materials have been found to be strongly correlated with the structural and microstructural characteristics as brought out through XRD and SEM techniques. For example, the ball milled samples having optimum hydrogenation characteristics exhibited highly uniform particle size distribution.
A geometry optimization and molecular electrostatic potential mapping study of structure-activity relationship for some anti-Alzheimer gents
(1999) P.S. Kushwaha; M.K. Shukla; P.C. Mishra
Molecular geometries of some substituted (pyrroloamino)pyridines which possess anti-Alzheimer activity were optimized and potential-derived CHelpG point charges were computed using ab initio SCF molecular orbital approach employing the 3-21G basis set. AM1 molecular orbital calculations were performed using these optimized geometries and thus optimized Hybridization Displacement Charges (HDC) combined with Löwdin charges continuously distributed in three dimension were obtained. Molecular electrostatic potential (MEP) maps of the molecules were obtained in two ways: (i) using the HDC-based model with the help of which MEP minima near the molecules were located, and (ii) using the CHelpG point charges, MEP values on the van der Waals surfaces of the molecules were computed. The MEP maps computed using both the methods have negative MEP regions near the pyridine nitrogen atom which appears to be the main binding site of the molecules with the appropriate receptor. Both electrostatic interaction and lipophilic association between these molecules and the receptor appear to contribute to biological activity.
Soybean (Glycine max) yield prediction from current and historical weather data using CROPGRO model
(1999) K.K. Singh; Rajesh Kumar; R.K. Mall; L.S. Rathore; Upendra Sanker; B.R.D. Gupta
A technique has been developed for obtaining reliable estimates of soybean [Glycine max (L.) Merr.] yield during the growing season by combining historical and present weather with CROPGRO Soybean model. The procedure is to place the reference year's daily weather into the model up to the time the yield prediction is to be made and sequences of historical data (one sequence per year) after that time until the end of growing season to give yield estimates. The change in predicted yield in response to current and forecast weather as the growing season progresses has been discussed for 2 contrasting years 1991 and 1995 at Jabalpur (Madhya Pradesh) with low and high yield respectively. Yield in 1991 has been determined before the end of the grain filling stage (20-25 days in advance before physiological maturity), whereas in 1995 it is at end of grain filling stage (10-12 days before physiological maturity). Weather forecast is relatively more valuable during reproductive stage in 1991 and 1995. The longer the forecast period, higher its value and earlier in the growing season its relative importance starts.
Analysis of extreme-ultraviolet off-limb spectra obtained with SUMER/SOHO: Ne VI/Mg VI emission lines
(Institute of Physics Publishing, 1999) Bhola N. Dwivedi; Werner Curdt; Klaus Wilhelm
We present results from a study of extreme-ultraviolet (EUV) off-limb spectra. These were obtained on 1996 June 20 with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) instrument on the Solar and Heliospheric Observatory (SOHO). With the capabilities of SUMER, we rastered the emitting source from 40″ off the limb outward, and secured a unique, high-quality set of high-resolution EUV spectra. The scientific objective of this observing sequence was to record Ne VI and Mg VI intercombination/forbidden lines, which provide good possibilities to study the relative element abundance of Ne (high FIP) and Mg (low FIP) in transition-region emission in the corona, and the electron density in the solar atmosphere. While this observing sequence produced excellent spectra of the Ne VI and Mg VI lines, the occurrence of a dynamic event in the corona is an added bonus of the program. We also observed several other bright, as yet unidentified lines. Among these are lines that have been observed for the first time. Using the new data, we have been able to deduce the plasma density and relative element abundance in the source. In addition, improved values of the wavelengths of the Ne VI and Mg VI intercombination/forbidden lines have been obtained. Possible identifications of the bright lines not previously observed, along with their measured intensities, are discussed.
Colour removal from dye wastewater using sugar cane dust as an adsorbent
(Multi-Science Publishing Co, Ltd, 1999) S.D. Khattri; M.K. Singh
Decolouration of dilute solutions of basic dye stuff was carried out using sugar cane dust as an adsorbent. It was found that low adsorbate concentration, small particle size of the adsorbent, a temperature of 25°C and a pH value of 7.5 for the medium all favour the removal of dye from aqueous solutions. The percentage of dye adsorbed by sugar cane dust decreased from 96.48% to 83.32% and from 90.78% to 78.02% for Malachite Green and Methylene Blue, respectively, when the concentration of the dye was increased from 6 mg/l to 12 mg/l. Similarly, the adsorption of Crystal Violet and of Rhodamine B also decreased with increasing dye concentration in the solutions. The amount of dye (Malachite Green and Rhodamine B) adsorbed decreased from 3.04 mg/g to 2.57 mg/g and from 2.53 mg/g to 2.17 mg/g when the temperature of the solution was increased from 25°C to 45°C, indicating that the process was exothermic. The values of the adsorption capacity (Q0) of Malachite Green and Rhodamine B on the adsorbent varied from 4.87 to 4.08 and from 4.26 to 3.82, respectively, as the temperature increased from 25°C to 45°C. The equilibrium data obey the requirements of the Langmuir adsorption model, demonstrating the formation of a monolayer of dye molecules on the outer surface of the adsorbent. The variation in the extent of removal with pH has been explained on the basis of surface ionisation and complexation. Various thermodynamic parameters (ΔG0, ΔH0 and ΔS0) have also been determined in order to explain the results.; Decolouration of dilute solutions of basic dye stuff was carried out using sugar cane dust as an adsorbent. It was found that low adsorbate concentration, small particle size of the adsorbent, a temperature of 25°C and a pH value of 7.5 for the medium all favour the removal of dye from aqueous solutions. The percentage of dye adsorbed by sugar cane dust decreased from 96.48% to 83.32% and from 90.78% to 78.02% for Malachite Green and Methylene Blue, respectively, when the concentration of the dye was increased from 6 mg/l to 12 mg/l. Similarly, the adsorption of Crystal Violet and of Rhodamine B also decreased with increasing dye concentration in the solutions. The amount of dye (Malachite Green and Rhodamine B) adsorbed decreased from 3.04 mg/g to 2.27 mg/g and from 2.53 mg/g to 2.17 mg/g when the temperature of the solution was increased from 25°C to 45°C, indicating that the process was exothermic. The values of the adsorption capacity (Q0) of Malachite Green and Rhodamine B on the adsorbent varied from 4.87 to 4.08 and from 4.26 to 3.82, respectively, as the temperature increased from 25°C to 45°C. The equilibrium data obey the requirements of the Langmuir adsorption model, demonstrating the formation of a monolayer of dye molecules on the outer surface of the adsorbent. The variation in the extent of removal with pH has been explained on the basis of surface ionisation and complexation. Various thermodynamic parameters (ΔG0, ΔH0 and ΔS0) have also been determined in order to explain the results.
A new phase transition in supercooled TBDA probed by low-temperature Raman study
(John Wiley and Sons Ltd, 1999) S.K. Dash; Ranjan K. Singh; B.P. Asthana; P.R. Alapati; A.L. Verma
Raman spectra of terephthalidenebis-p-n-decylaniline (TBDA) were recorded in the regions 925-1000 and 1120-1220 cm-1 from room temperature down to 20 K during both cooling and heating cycles. The subtle changes in the spectral features of the bands at ca 975 and ca 1195 cm-1 at 47 K were attributed to a hitherto unreported stable-metastable phase transition in TBDA. The dynamics of the new phase transition are explained in terms of splitting of the non-planar mode at ca 975 cm-1 due to strong steric hindrances caused by increased intermolecular interactions due to close packing in the low-temperature phase. Copyright © 1999 John Wiley & Sons, Ltd.
Elevated temperature properties of electron beam welds of an α + β titanium alloy
(Elsevier BV, 1999) T. Mohandas; D. Banerjee; V.V. Kutumbarao
The effect of base metal microstructure and post-weld heat treatment (PWHT) on the stress rupture creep and high temperature tensile properties of electron beam welds of an α+ β titanium alloy, Ti-6.8Al-3.42Mo-1.9Zr-0.21Si has been evaluated. In the as-welded condition, the stress rupture properties of the welds were poor. Stress relieving improved the properties but they were still inferior to the base metal properties. Creep strains in the as-welded condition were also large. The poor stress rupture and creep properties in the as-welded condition may be due to a metastable micro structure and possible hydrogen accumulation in the heat affected zone (HAZ), the location of failure. Welds of the base metal in the β heat treated condition (β base welds), with a coarse prior β grain size at the location of failure exhibited superior stress rupture properties and predominant intergranular fracture, while welds of the base metal in the α + β heat treated condition (α + β base welds) failed in a transgranular mode. PWHT of α + β base welds with predominant acicular/lenticular α microstructure just below the β transus temperature exhibited marginally superior stress rupture strength than the base metal with an equiaxed α + lenticular/acicular α microstructure. Supertransus PWHT led to poor stress rupture properties due to thick grain boundary α, and a thick and aligned β plate colony structure. High temperature tensile properties of welds were equivalent to that of the base metal. α + β base welds with a finer prior β grain size at the location of failure exhibited superior strength and ductility. Subtransus PWHT resulted in an acicular α micro structure and low ductility. PWHT in the supertransus region resulted in poor strength and ductility due to coarse and aligned transgranular α + grain boundary α. © 1999 Elsevier Science S.A. All rights reserved.
Response of the antioxidant systems of the nitrogen fixing cyanobacterium Anabaena doliolum to copper
(Elsevier GmbH, 1999) Nirupama Mallick; L.C. Rai
Different concentrations of copper have been found to produce significant increases in lipid peroxidation, carotenoid contents and activities of antioxidant enzymes like superoxide dismutase and catalase of Anabaena doliolum. In contrast to this, an appreciable decline in the GSH pool and activities of ascorbate peroxidase and glutathione reductase have also been observed. Cu was also found to inhibit chlorophyll a accumulation significantly, although appreciable resumption was observed in cultures supplied with antioxidants exogenously. This study, therefore, suggests that the antioxidant system of this cyanobacterium is not strong enough to withstand copper-induced stress, and this system may show species and stress specific responses.
The effects of swift heavy ion irradiation on the radiochemistry and melting characteristics of PET
(Elsevier, 1999) A. Biswas; S. Lotha; D. Fink; J.P. Singh; O.K. Avasthi; B.K. Yadav; S.K. Bose; D.T. Khating; A.M. Avasthi
High electronic excitation (∼10 keV/nm) induced effects on the radiochemistry and melting behaviour of semicrystalline polyethylene terephthalate (PET) have been studied by FTIR and differential scanning calorimetry (DSC) techniques. After irradiation with a 180 MeV Ag14+ ion beam, DSC measurements of PET films exhibited significant change in their melting behaviour. The gradual increase in the melting enthalpy of irradiated PET with the ion fluence is observed for the first time, which reaches a maximum when track overlapping sets in, and decreases exponentially thereafter. FTIR measurements of irradiated PET at different ion fluences have also shown partly different trend of amorphisation than the earlier observations. X-ray diffraction results of irradiated PET reveal both a shift and a reduction of the main peak, along with the appearance of a new small peak. Possible reasons for these findings are discussed. © 1999 Elsevier Science B.V. All rights reserved.
Sigmoid volvulus: Study from a North Indian Hospital
(1999) A.K. Khanna; Puneet Kumar; R. Khanna
PURPOSE: The aim of this study was to review our experience with sigmoid volvulus and to compare the various surgical procedures performed for treatment of sigmoid volvulus. METHODS: A retrospective study of 111 patients with sigmoid volvulus treated at University Hospital in northern India during last six years was performed. RESULTS: Mean age for sigmoid volvulus was 51.1 ± 15.3 years, with a male-to-female ratio of 2.5:1. Duration of symptoms was 4.3 ± 2.6 days. Plain radiographs of the abdomen suggested the diagnosis in 76 cases (68.47 percent). Resection of the bowel was performed in 40 cases with gangrenous sigmoid colon and 6 cases with viable colon. Nonresectional procedure in the form of colocolopexy (fixation of sigmoid to transverse colon) or extraperitonealization was performed in 13 and 44 cases, respectively. Mortality was 6.3 percent (n = 7). No recurrence was seen after resection and extraperitonealization, whereas 5 of 13 cases (38.5 percent) had recurrence after colocolopexy. CONCLUSION: Resection and extraperitonealization of the sigmoid colon are the suitable alternatives for nongangrenous sigmoid volvulus. Colocolopexy is not indicated, because of the associated high recurrence rate.
Chelation and fungitoxicity
(Indian Chemical Society, 1999) Lallan Mishra
This review emphasizes the importance of chelation of heterocycles (benzimidazoles, 1,3,4-oxadiazoles, 1,3,4-thiadiazoles, 1,2,4,-triazoles and uracils) with transition metal ions. The multifunctional heterocycles have a better chance to act as fungicides after chelation with metal ions or by pairing with nucleoside bases through weak bonding in the similar way as recently reported development of drug design using metal complexes as a ligand. The work done in author's laboratory in addition to brief support taken from the literature is discussed.
Synthesis, antibacterial, antifungal and anti-HIV activities of Schiff and Mannich bases derived from isatin derivatives and N-[4-(4'-chlorophenyl)thiazol-2-yl] thiosemicarbazide
(Elsevier, 1999) S.N. Pandeya; D. Sriram; G. Nath; E. Declercq
Isatin, its 5-chloro and 5-bromo derivatives have been reacted with N-[4-(4'-chlorophenyl)thiazol-2-yl] thiosemicarbazide to form Schiff bases and the N-Mannich bases of these compounds were synthesized by reacting them with formaldehyde and three secondary amines. Their chemical structures have been confirmed by means of IR, 1H-NMR data and by elemental analysis. Investigation of antimicrobial activity of compounds was done by agar dilution method against 28 pathogenic bacteria, 8 pathogenic fungi and anti-HIV activity against replication of HIV-1 (IIIB) in MT-4 cells. Among the compounds tested 1-[N,N-dimethylaminomethyl]-5-bromo isatin-3-{1'-[4''-(p-chlorophenyl) thiazol-2''-yl] thio semicarbazone} 10 showed the most favourable antimicrobial activity. Copyright (C) 1999 Elsevier Science B.V.