Prediction of clay soil compaction

Field measurements were made of soil density and moisture patterns under different vehicle tire paths with varying external pressures and number of passes. In addition, laboratory index tests were performed to determine the compaction behaviour of the same soil. Using these results, a prediction equation of dry density in terms of applied pressure and moisture content was obtained for the clay soil. A previously developed equation for sandy soil was modified for the complete range of moisture contents encountered. Estimation of shear strength for the clay soil was made using plastic and liquid limits.     

A minimal composite theory for stability of non-parallel compressible boundary-layer flow

A new minimal composite theory that extends the approach of Govindarajan and Narasimha [1] is proposed here for 2D non-parallel compressible boundary-layer stability subject to 3D disturbances. The mean profiles are obtained from Hortons analysis, which provides a good approximation for a large range of Prandtl numbers at non-zero pressure gradients. In the lowest order, all effects of order lower than O(R^-2/3) anywhere in the boundary-layer are included, R being the local boundary-layer Reynolds number; the resulting non-parallel formulation yields a set of four ordinary differential equations, as compared to the five coupled equations of classical parallel flow theory of Mack [2]. The largest effect on stability of flow non-parallelism is found to be due to the wall-normal advection of velocity and temperature disturbance quantities by the mean flow. The present theory shows that the bulk viscosity, invariably included in compressible stability theories, is irrelevant at the lowest order. In comparison with the full [O(R^-1)] non-parallel theory, the present theory is marginally better than the parallel flow theory. PACS 03.50.De, 04.20-q, 42.65-k     

Vehicular traffic effects on development and yield of corn (maize)

A 52 plot experiment was performed during the growing season of 1977 in a Ste. Rosalie clay soil, using a randomized complete-block design with 13 treatments of machinery traffic within each of four blocks. Three vehicle contact pressures, four numbers of tractor passes, and a control of zero traffic were used to relate the growth and yield variables to wheel traffic and the resulting soil compaction. The number of days required for (a) plant emergence, (b) tasselling, and (c) silking were minimum in moderately compacted plots. The plant growth rate monitored at 41, 54, 68, and 105 days from the seeding time was different from plot to plot. Growth models at different times of the season were derived in terms of the wheel traffic variables, and plant and ear moisture content variation with traffic treatment was investigated. Yield and ear yield increased with increases in machine contact pressure and passes reaching a peak around 500 kPa and dropped off for further increases. The reduction in yield was over 35% in some cases, suggesting that careful traffic planning is essential to obtain better production in agricultural fields. Prediction models were obtained for all the plant growth characteristics in terms of traffic variables. A relation for yield in terms of soil bulk density was established for a dry season.     

Isolation,spectroscopic and thermal properties of hydrazinium tris(oxydiacetato)lanthanate(III) hemi(pentahydrate)

Oil-bath reaction of respective metal nitrate with an aqueous mixture of oxydiacetic acid (H₂oda) and hydrazine hydrate led to the formation of crystalline compounds with formula (N₂H₅)₃[Ln(oda)₃]·2.5H₂O (where Ln = La, Ce, Pr, Nd and Sm), which are stable for a week and undergo efflorescence. The resulting complexes were characterized by infrared spectral, thermal (air and nitrogen atmosphere), UV–visible and PXRD studies. From the thermal studies, both in air and nitrogen atmosphere, these compounds show endothermic dehydration below 100 °C to give anhydrous compounds. Next, the anhydrous compounds (in air) undergo endothermic decomposition between 190 and 225 °C to form Ln(Hoda)₃ intermediate, which further show exothermic decomposition to yield respective metal oxide as the end residue. But, in nitrogen atmosphere, the same anhydrous compounds exhibit endo-followed by exothermic decompositions to give respective metal as end product. This is observed as a continuous single step of decomposition in TG. The structure of (N₂H₅)₃[Nd(oda)₃]·2.5H₂O has been determined by single-crystal X-ray analysis. The neodymium atom is coordinated by nine oxygen atoms from three tridentate (O, O, O) oxydiacetate ions with tricapped trigonal prismatic geometry. In addition, both the parent acid and its compounds display strong fluorescent emission due to the ligand, which renders them as fluorescent materials at room temperature.     

Optimal process conditions for zeolite catalyzed acylation of anisole

Acylation of anisole is a commercially important reaction in the production of various fine chemicals, agrochemicals, pharmaceuticals and fragrances. Conventionally, it is carried out using the catalysts like AlCl₃, FeCl₃, ZnCl₃, HF, which suffer from major drawbacks such as larger consumption, corrosion and safety issues, waste disposal and the material handling. Hence the conventional catalysts are being replaced with solid acid catalysts like H-Beta, H-ZSM5 to overcome the above drawbacks. In this work, liquid phase acylation of anisole has been carried out employing H Beta, H ZSM-5 and HY catalysts and the process standardization at a macrolevel has been done with reference to parameters like temperature, reaction time, molar ratio of reactants, catalyst nature, Si/Al ratio of catalyst and the catalyst quantity. In addition, catalyst stability was investigated.     

Analysis of the ketosynthase-chain length factor heterodimer from the fredericamycin polyketide synthase

The pentadecaketide fredericamycin has the longest carbon chain backbone among polycyclic aromatic polyketide antibiotics whose biosynthetic genes have been sequenced. This backbone is synthesized by the bimodular fdm polyketide synthase (PKS). Here, we demonstrate that the bimodular fdm PKS as well as its elongation module alone synthesize undecaketides and dodecaketides. Thus, unlike other homologs, the fdm ketosynthase-chain length factor (KS-CLF) heterodimer does not exclusively control the backbone length of its natural product. Using sequence- and structure-based approaches, 48 CLF multiple mutants were engineered and analyzed. Unexpectedly, the I134F mutant was unable to turn over but could initiate and partially elongate the polyketide chain. This unprecedented mutant suggests that the KS-CLF heterodimer harbors an as yet uncharacterized chain termination mechanism. Together, our findings reveal fundamental mechanistic differences between the fdm PKS and its well-studied homologs.     

Total synthesis and biological evaluation of pederin, psymberin, and highly potent analogs

The potent cytotoxins pederin and psymberin have been prepared through concise synthetic routes (10 and 14 steps in the longest linear sequences, respectively) that proceed via a late-stage multicomponent approach to construct the N-acyl aminal linkages. This route allowed for the facile preparation of a number of analogs that were designed to explore the importance of the alkoxy group in the N-acyl aminal and functional groups in the two major subunits on biological activity. These analogs, including a pederin/psymberin chimera, were analyzed for their growth inhibitory effects, revealing several new potent cytotoxins and leading to postulates regarding the molecular conformational and hydrogen bonding patterns that are required for biological activity. Second generation analogs have been prepared based on the results of the initial assays and a structure-based model for the binding of these compounds to the ribosome. The growth inhibitory properties of these compounds are reported. These studies show the profound role that organic chemistry in general and specifically late-stage multicomponent reactions can play in the development of unique and potent effectors for biological responses.     

Experimental (FT-IR and FT-Raman), electronic structure and DFT studies on 1-methoxynaphthalene

In this work, FT-IR and FT-Raman spectra of 1-methoxynapthalene (C(11)H(10)O) have been reported in the regions 4000-400 cm(-1) and 3500-100 cm(-1), respectively. Density functional method (DFT) has been used to calculate the optimized geometrical parameters, atomic charges, vibrational wavenumbers and intensity of the vibrational bands. The vibrational frequencies have been calculated and scaled values are compared with experimental FT-IR and FT-Raman spectra. The structure optimizations and normal coordinate force field calculations are based on density functional theory (DFT) method with B3LYP/3-21G, B3LYP/6-31G, B3LYP/6-31G(d,p) and B3LYP/6-311++G(d,p) basis sets. The complete vibrational assignments of wavenumbers are made on the basis of potential energy distribution (PED). The optimized geometric parameters are compared with experimental values of naphthoic acid. The results of the calculation shows excellent agreement between experimental and calculated frequencies in B3LYP/6-311++G(d,p) basis set. The effects due to the substitutions of methyl group and carbon-oxygen bond are also investigated. A study on the electronic properties, such as excitation energies and wavelengths, were performed by time-dependent DFT (TD-DFT) approach. HOMO and LUMO energies are calculated that these energies show charge transfer occurs within the molecule.     

Vibrational spectroscopic analysis of 2-bromobenzoic and anthranilic acids: a combined experimental and theoretical study

In this work, the vibrational spectral analysis was carried out by using Raman and infrared spectroscopy in the range 100-4000 cm(-1) and 50-4000 cm(-1) respectively, for the title molecules. The molecular structure, fundamental vibrational frequencies and intensity of the vibrational bands are interpreted with the aid of structure optimizations and normal coordinate force field calculations based on Hartee-Fock (HF) and density functional theory (DFT) method and different basis sets combination. The complete vibrational assignments of wavenumbers were made on the basis of potential energy distribution (PED). The scaled B3LYP/6-311++G(d,p) results show the best agreement with the experimental values over the other methods. The effects due to the substitutions of amino group and halogen bond were investigated. The results of the calculations were applied to simulate spectra of the title compounds, which show excellent agreement with observed spectra.     

Supramolecular Synthons in Designing Low Molecular Mass Gelling Agents: L‐Amino Acid Methyl Ester Cinnamate Salts and their Anti‐Solvent‐Induced Instant Gelation

Easy access to a class of chiral gelators has been achieved by exploiting primary ammonium monocarboxylate ( PAM ), a supramolecular synthon. A combinatorial library comprising of 16 salts, derived from 5 l ‐amino acid methyl esters and 4 cinnamic acid derivatives, has been prepared and scanned for gelation. Remarkably, 14 out of 16 salts prepared (87.5 % of the salts) show moderate to good gelation abilities with various solvents, including commercial fuels, such as petrol. Anti‐solvent induced instant gelation at room temperature has been achieved in all the gelator salts, indicating that the gelation process is indeed an aborted crystallization phenomenon. Rheology, optical and scanning electron microscopy, small angle neutron scattering, and X‐ray powder diffraction have been used to characterize the gels. A structure‐property correlation has been attempted, based on these data, in addition to the single‐crystal structures of 5 gelator salts. Analysis of the FT‐IR and ¹H NMR spectroscopy data reveals that some of these salts can be used as supramolecular containers for the slow release of certain pest sex pheromones. The present study clearly demonstrates the merit of crystal engineering and the supramolecular synthon approach in designing new materials with multiple properties.