Research Publications (Applied Sciences)

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Methyl 2,6-diphenyl-1-p-tolyl-4-(p-tolyl- amino)-1,2,5,6-tetrahydropyridine-3- carboxylate
(Acta Cryst., 2012) Venugopala, Katharigatta Narayanaswamy; Nayak, Susanta K.; Odhav, Bharti
In the title compound, C33H32N2O2, the tetrahydropyridine ring adopts a boat conformation with the carbonyl group in an s-cis conformation with respect to the C=C bond of the six-membered tetrahydropyridine ring. The molecular conformation is stabilized by intramolecular N-H...O, C-H...O and C-H...[pi] interactions. Formation of centrosymmetric head-to-head dimers is observed through pairwise intermolecular N-H...O hydrogen bonds. Additional weak C-H...O and C-H...[pi] interactions stabilize the three-dimensional molecular assembly.
Safety of nanofood : a review
(Academic Journals, 2012-10-30) Ijabadeniyi, Oluwatosin Ademola
Introduction of genetically modified (GM) foods generated a lot of controversy few years back, now it is the turn of nanofoods. There has been debate on the safety of foods that have been produced directly or indirectly with nanomaterials. Nanoparticles or nanotechnology procedures may be used to make food products, food additives, seeds and food packaging materials to give rise to a new and novel nanofood. While a lot have been written about the benefits of nanotechnology and nanomaterials in the food system, there is little research into the toxicological and possible hazard of nanofood. In this paper, the concept of nanotechnology, its diverse applications in the food industry and recent safety issues are considered. The paper concluded that it is necessary to do a thorough risk assessment of nanofoods before they are released to the market.
Comment on invalid JWKB unstable solutions of combined inertial-Rossby waves
(Annales Geophysicae, 2012) McKenzie, J. F.
Ochratoxins--food contaminants : impact on human health
(MDPI, 2010-04-20) Reddy, Lalini; Bhoola, Kanti
Ochratoxins are secondary metabolites of Aspergillus and Penicillium, that are hazardous to health through contamination of dietary foods. Ochratoxin A (OTA) remains the single most potent member of this group of mycotoxins. OTA has a long half-life in humans and is thus easily detected in serum. Dietary intake studies have confirmed link between endemic nephrotoxicity in humans to their daily household intake of OTA. OTA has been reported to contribute to endemic nephrotoxicity and carcinogenicity in humans and animals. OTA produces renal tumours, DNA adducts and chromosomal aberrations in kidneys. OTA may be embryotoxic, teratogenic, and immunotoxic only at doses higher than those causing nephrotoxicity. The incidence of endemic nephrotoxicity has been mostly reported in northeast Europe since the early fifties. Recent studies however have warned that OTA and other toxins, such as aristolochic acid, show very similar renal pathology. There is thus the need for thorough co-occurrence studies on toxin incidence.
Nonlinear low-frequency structures in an electron–positron–ion plasma
(Cambridge University Press, 2012-03-20) Moola, S.; Lazarus, Ian Joseph; Bharuthram, R.
Nonlinear ion cyclotron and ion-acoustic waves have been studied in an electron–positron–ion plasma. Using Boltzmann distributions for the electrons and positrons and fluid equations for the ions, a set of nonlinear equations in the rest frame of the propagating wave is derived and numerically solved for the electric field. A scan of parameter space reveals a range of solutions for the parallel electric field, from sinusoidal to sawtooth to highly spiky waveforms. The results are compared with satellite observations.
Irrigation water and microbiological safety of fresh produce : South Africa as a case study : a review
(Academic Journals, 2012-09-11) Ijabadeniyi, Oluwatosin Ademola; Buys, E. M.
Irrigation water is perhaps the leading pre-harvest source of contamination of fresh produce in the world. In this review, the impact of contaminated surface irrigation water on bacterial contamination of fresh produce was examined. Some practical solutions to prevent or reduce this challenge were also considered. In South Africa, fruit and vegetables are produced on a large scale by commercial farmers who depend on surface water for their cultivation. However, the surface water, that is, rivers- has been reported to be heavily contaminated with Escherichia coli and feacal coliforms. There is a concern that contaminated surface water used for irrigation may contaminate fresh vegetables which may also have a negative effect on the export of vegetables to the EU and USA. Consumption of vegetables contaminated with foodborne pathogens presents a public health risk especially in countries like South Africa that has more than 5 million people with immune-system compromised diseases such as HIV and tuberculosis. Other groups of people that may be negatively affected because of the contaminated surface water are those who are directly and indirectly associated with the production of fresh vegetables such as pickers, handlers, packers and farmers that participate in the production of vegetables during pre-harvest and post-harvest. Prevention of contamination of fresh produce from both pre-harvest and post-harvest sources especially irrigation water still remains the only effective way to protect the public. However, for this to occur, every stakeholder in the production industry must have a culture of food safety.
Groundwater : characteristics, qualities, pollutions and treatments : an overview
(International Journal of Water Resources and Environmental Engineering, 2012-02-22) Otieno, Fredrick Alfred O.; Olumuyiwa, I. Ojo; Ochieng, George M.
This review considered groundwater resources, its characteristics, qualities, pollutions and available treatments. Groundwater refers to all the water occupying the voids, pores and fissures within geological formations, which originated from atmospheric precipitation either directly by rainfall infiltration or indirectly from rivers, lakes or canals. The chemical, physical and bacterial characteristics of groundwater determine its usefulness for various purposes. The ground water analysis reviewed includes pH, chlorine content, total dissolved solids (TDS), turbidity, dissolved oxygen and hardness others include alkalinity, chloride, toxic chemicals and the presence of coli form organisms. The treatments considered are; aeration, coagulation, flocculation, sedimentation and filtration. Appropriate technology methods such as container storage, pot chlorination, boiling and solar disinfection were discovered to be in use. The paper concluded by recommending research into quantifying groundwater, its quality and treatment based on the above overview.
Shearing radiative collapse with expansion and acceleration
(American Institute of Physics, 2012-03-28) Rajah, Surversperi Suryakumari; Thirukkanesh, S.; Maharaj, S. D.
We investigate the behaviour of a relativistic spherically symmetric radiative star with an accelerating, expanding and shearing interior matter distribution in the presence of anisotropic pressures. The junction condition can be written in standard form in three cases: linear, Bernoulli, and Riccati equations. We can integrate the boundary condition in each case and three classes of new solutions are generated. For particular choices of the metric we investigate the physical properties and consider the limiting behaviour for large values of time. The causal temperature can also be found explicitly.
Chemical composition of essential oil of Psidium cattleianum var. lucidum (Myrtaceae)
(Academic Journals, 2012-04-12) Chalannavar, Raju K.; Baijnath, Himansu; Odhav, Bharti; Venugopala, Katharigatta Narayanaswamy
The aim of this study was to investigate the essential oil composition of Psidium cattleianum var. lucidum from South Africa. The essential oils were extracted by hydrodistillation and the components were identified by gas chromatography coupled to mass spectrometry (GC-MS) to determine the chemical composition of the essential oil. A total of 53 chemical components were identified, accounting for 61% of the essential oil. The major component was caryophyllene oxide (12.43%), while other predominant constituents were identified as bicyclo(4.4.0)dec-l-ene (6.61%), 2,3-butanediol diacetate (4.84%) and patchoulene (4.73%). The presence of many terpenic and ester compounds is thought to contribute to the unique flavor of the P. cattleianum var. lucidum leaves.
Methyl (E)-2-[(3-chloro-4-cyanophenyl)imino]-4-(4-chlorophenyl)-6-methyl-1,2,3,4-tetrahydropyrimidine-5-carboxylate
(International Union of Crystallography, 2012-10) Venugopala, Katharigatta Narayanaswamy; Nayak, Susanta K.; Odhav, Bharti
In the title compound, C20H16Cl2N4O2, the dihedral angles between the planes of the chlorophenyl, chlorocyanophenylimine and ester groups and the plane of the six-membered tetrahydropyrimidine ring are 86.9 (2), 72.6 (2) and 7.9 (2)°, respectively. The Cl atom substituent on the cyanophenyl ring is disordered over two rotationally related sites [occupancy factors 0.887 (2):0.113 (2)], while the molecular conformation is stabilized by the presence of an intramolecular aromatic C-H...[pi] interaction. Both N-H groups participate in separate intermolecular hydrogen-bonding associations with centrosymmetric cyclic motifs [graph sets R22(8) and R22(12)], resulting in ribbons parallel to [010]. Further weak C-H...O hydrogen bonds link these ribbons into a two-dimensional molecular assembly.
Nonlinear, stationary electrostatic ion cyclotron waves : exact solutions for solitons, periodic waves, and wedge shaped waveforms
(American Institute of Physics, 2012-11-30) Rajah, Surversperi Suryakumari; Doyle, T. B.; McKenzie, J. F.
The theory of fully nonlinear stationary electrostatic ion cyclotron waves is further developed. The existence of two fundamental constants of motion; namely, momentum flux density parallel to the background magnetic field and energy density, facilitates the reduction of the wave structure equation to a first order differential equation. For subsonic waves propagating sufficiently obliquely to the magnetic field, soliton solutions can be constructed. Importantly, analytic expressions for the amplitude of the soliton show that it increases with decreasing wave Mach number and with increasing obliquity to the magnetic field. In the subsonic, quasi-parallel case, periodic waves exist whose compressive and rarefactive amplitudes are asymmetric about the “initial” point. A critical “driver” field exists that gives rise to a soliton-like structure which corresponds to infinite wavelength. If the wave speed is supersonic, periodic waves may also be constructed. The aforementioned asymmetry in the waveform arises from the flow being driven towards the local sonic point in the compressive phase and away from it in the rarefactive phase. As the initial driver field approaches the critical value, the end point of the compressive phase becomes sonic and the waveform develops a wedge shape. This feature and the amplitudes of the compressive and rarefactive portions of the periodic waves are illustrated through new analytic expressions that follow from the equilibrium points of a wave structure equation which includes a driver field. These expressions are illustrated with figures that illuminate the nature of the solitons. The presently described wedge-shaped waveforms also occur in water waves, for similar “transonic” reasons, when a Coriolis force is included.
Preparation, spectrochemical, and computational analysis of L-Carnosine (2-[(3-Aminopropanoyl)amino]-3-(1H-imidazol-5- yl)propanoic Acid) and Its Ruthenium (II) coordination complexes in aqueous solution
(MDPI, 2011-12-09) Branham, Michael Lee; Bisetty, Krishna; Sabela, Myalowenkosi Innocent; Govender, Thirumala; Singh, Parvesh
This study reports the synthesis and characterization of novel ruthenium (II) complexes with the polydentate dipeptide, L-carnosine (2-[(3-aminopropanoyl)amino]-3-(1H-imidazol-5-yl)propanoic acid). Mixed-ligand complexes with the general composition [MLp(Cl)q(H2O)r]·xH2O (M = Ru(II); L = L-carnosine; p = 3 − q; r = 0–1; and x = 1–3) were prepared by refluxing aqueous solutions of the ligand with equimolar amounts of ruthenium chloride (black-alpha form) at 60 °C for 36 h. Physical properties of the complexes were characterized by elemental analysis, DSC/TGA, and cyclic voltammetry. The molecular structures of the complexes were elucidated using UV-Vis, ATR-IR, and heteronuclear NMR spectroscopy, then confirmed by density function theory (DFT) calculations at the B3LYP/LANL2DZ level. Two-dimensional NMR experiments (1H COSY, 13C gHMBC, and 15N gHMBC) were also conducted for the assignment of chemical shifts and calculation of relative coordination-induced shifts (RCIS) by the complex formed. According to our results, the most probable coordination geometries of ruthenium in these compounds involve nitrogen (N1) from the imidazole ring and an oxygen atom from the carboxylic acid group of the ligand as donor atoms. Additional thermogravimetric and electrochemical data suggest that while the tetrahedral-monomer or octahedral-dimer are both possible structures of the formed complexes, the metal in either structure occurs in the (2+) oxidation state. Resulting RCIS values indicate that the amide-carbonyl, and the amino-terminus of the dipeptide are not involved in chelation and these observations correlate well with theoretical shift predictions by DFT.
Cycloaddition reactions of Azatrienes with Sulfene
(Scientific Research, 2012-04-23) Bisetty, Krishna; Singh, Parvesh
Unprecedented cycloaddition reactions of azatrienes (1) with sulfene leading to the synthesis of functionalized thiazine-dioxide derivatives (5) are described. The reactions were found be highly regioselective resulting in the formation of only [4 + 2] cycloadducts.
Densities, speeds of sound, and refractive indices for binary mixtures of 1-butyl-3-methylimidazolium methyl sulphate ionic liquid with alcohols at T = (298.15, 303.15, 308.15, and 313.15) K
(Elsevier, 2012-09-24) Singh, Sangeeta; Aznar, Martin; Deenadayalu, Nirmala
Experimental densities, speeds of sound, and refractive indices of the binary mixtures {1-butyl-3-methylimidazolium methylsulphate ([BMIM]+[MeSO4]−) + methanol, or 1-propanol, or 2-propanol, or 1-butanol} were measured over the whole range of composition at T = (298.15, 303.15, 308.15, and 313.15) K. From the experimental data, excess molar volumes, excess isentropic compressibilities, deviation in refractive indices and molar refractions were calculated. The excess molar volumes, change in isentropic compressibilities, and deviation in refractive indices were fitted by the Redlich–Kister smoothing polynomial. The Lorentz–Lorenz equation was applied to correlate the volumetric properties and predict the density or the refractive index of the binary mixtures. Results for these quantities have been discussed in terms of intermolecular interactions between the components of the mixtures. For all the systems studied, the excess molar volume and excess isentropic compressibility are negative, while the change in refractive index on mixing is always positive over the entire composition range and at all temperatures.
Solid–liquid equilibria measurements for binary systems comprising (butyric acid + propionic or pentanoic acid) and (heptanoic acid + propionic or butyric or pentanoic or hexanoic acid)
(Elsevier, 2013-02) Ramjugernath, Deresh; Deenadayalu, Nirmala; Naidoo, Paramespri; Ngema, Peterson Thokozani; Reddy, Prashant; Bahadur, Indra; Tadie, Margreth
Solid–liquid equilibria (SLE) measurements have been undertaken for carboxylic acid systems comprising (butyric acid + propionic or pentanoic acid) and (heptanoic acid + propionic or butyric or pentanoic or hexanoic acid) via a synthetic method using two complementary pieces of equipment. The measurements have been obtained at atmospheric pressure and over the temperature range of (225.6 to 270.7) K. All the acid mixtures exhibit a eutectic point in their respective phase diagrams, which have been determined experimentally. The estimated maximum uncertainties in the reported temperatures and compositions are ±1 K and ±0.0006 mole fraction, respectively. The experimental data have been satisfactorily correlated with the Wilson and NRTL activity coefficient models.
Genetically switched D-lactate production in Escherichia coli
(Elsevier, 2012-06-08) Singh, Suren
During a fermentation process, the formation of the desired product during the cell growth phase competes with the biomass for substrates or inhibits cell growth directly, which results in a decrease in production efficiency. A genetic switch is required to precisely separate growth from production and to simplify the fermentation process. The ldhA promoter, which encodes the fermentative d-lactate dehydrogenase (LDH) in the lactate producer Escherichia coli CICIM B0013-070 (ack-pta pps pflB dld poxB adhE frdA), was replaced with the λ pR and pL promoters (as a genetic switch) using genomic recombination and the thermo-controllable strain B0013–070B (B0013-070, ldhAp::kan-cIts857-pR–pL), which could produce two-fold higher LDH activity at 42 °C than the B0013-070 strain, was created. When the genetic switch was turned off at 33 °C, strain B0013-070B produced 10% more biomass aerobically than strain B0013-070 and produced only trace levels of lactate which could reduce the growth inhibition caused by oxygen insufficiency in large scale fermentation. However, 42 °C is the most efficient temperature for switching on lactate production. The volumetric productivity of B0013-070B improved by 9% compared to that of strain B0013-070 when it was grown aerobically at 33 °C with a short thermo-induction at 42 °C and then switched to the production phase at 42 °C. In a bioreactor experiment using scaled-up conditions that were optimized in a shake flask experiment, strain B0013-070B produced 122.8 g/l d-lactate with an increased oxygen-limited productivity of 0.89 g/g·h. The results revealed the effectiveness of using a genetic switch to regulate cell growth and the production of a metabolic compound.
Fine tuning the transcription of ldhA for D-lactate production
(Springer-Verlag, 2012-03-20) Singh, Suren
Nonlinear ion cyclotron and ion-acoustic waves have been studied in an electron–positron–ion plasma. Using Boltzmann distributions for the electrons and positrons and fluid equations for the ions, a set of nonlinear equations in the rest frame of the propagating wave is derived and numerically solved for the electric field. A scan of parameter space reveals a range of solutions for the parallel electric field, from sinusoidal to sawtooth to highly spiky waveforms. The results are compared with satellite observations.
Linear electrostatic waves in two-temperature electron–positron plasmas
(Cambridge University Press, 2012-05-04) Lazarus, Ian Joseph
Linear electrostatic waves in a magnetized four-component, two- temperature electron–positron plasma are investigated, with the hot species having the Boltzmann density distribution and the dynamics of cooler species governed by fluid equations with finite temperatures. A linear dispersion relation for electrostatic waves is derived for the model and analyzed for different wave modes. Analysis of the dispersion relation for perpendicular wave propagation yields a cyclotron mode with contributions from both cooler and hot species, which in the absence of hot species goes over to the upper hybrid mode of cooler species. For parallel propagation, both electron-acoustic and electron plasma modes are obtained, whereas for a single-temperature electron–positron plasma, only electron plasma mode can exist. Dispersion characteristics of these modes at different propagation angles are studied numerically.
Application of the extended real associated solution theory to excess molar enthalpies and excess molar volumes of binary mixtures of (benzene or 1-alkanol + quinoline)
(Elsevier, 2005-06-01) Deenadayalu, Nirmala; Letcher, Trevor M.
Excess molar enthalpies and excess molar volumes of binary mixtures of (benzene or methanol or ethanol or 1-propanol or 1- butanol+quinoline) as a function of composition at a pressure of 1 atm and a temperature of 298.15 K have been used to test the Extended Real Solution Theory, ERAS, of nonelectrolyte solutions. The ERAS theory accounts for free volume effects according to the Flory–Patterson theory and for association effects: self and crossassociation between the molecules involved. The ERAS theory results for the binary mixtures (benzene or an alkanol+quinoline) indicates strong hydrogen bonding effects between unlike molecules given by the predicted hydrogen bonding energy between two dissimilar compounds. Comparison is also made between the chemical and physical contribution to the ERAS theory. The Extended Real Associated Solution theory describes the published Vm E data better than the published Hm E data.
Ternary excess molar volumes of {methyltrioctylammonium bis(trifluoromethylsulfonyl)imide + ethanol + methyl acetate, or ethyl acetate} systems at T = (298.15, 303.15, and 313.15) K
(Elsevier, 2010-01-28) Gwala, Nobuhle V.; Deenadayalu, Nirmala; Tumba, Kaniki; Ramjugernath, Deresh
The activity coefficient at infinite dilution for 30 solutes: alkanes, alkenes, cycloalkanes, alkynes, ketones, alcohols, and aromatic compounds was determined from gas–liquid chromatography (glc) measurements at three temperatures (303.15, 313.15, and 323.15) K. The ionic liquid: trioctylmethylammonium bis(trifluoromethylsulfonyl)imide, was used as the stationary phase. For each temperature, values were determined using two columns with different mass percent packing of the ionic liquid. The selectivity value was calculated from the to determine the suitability of the solvent as a potential entrainer for extractive distillation in the separation of an hexane/benzene mixture, indicative of a typical industrial separation problem for benchmarking purposes.