Quasi-Spectral Unscented MPSP Guidance for Robust Soft-Landing on Asteroid

Journal of Optimization Theory and Applications - A new quasi-spectral version of unscented model predictive static programming is proposed, which is a fusion of two philosophies, namely the...     

Synthesis,Characterization, and Structure of Quinoline‐based Benzimidazole Derivatives

Quinoline‐based benzimidazole compounds have been successfully synthesized and characterized by various spectroscopic techniques like FT‐IR, ¹H NMR, ¹³C NMR, and mass spectral analysis, and the structures have been authenticated by single crystal X‐ray diffraction method. Here, we report an economical, mild, and efficient procedure that involves condensation of 8‐hydroxyquinoline‐2‐carbaldehyde with various diamines as substrates to give bis‐imines. A systematic study towards both aliphatic and aromatic bis‐imines has been conducted to investigate the ring‐closure reaction that generates the benzimidazole moiety in the heterocyclic compounds discussed in this study. Aliphatic bis‐imines does not undergo cyclization; however, the bis‐imines derived from o‐phenylenediamine and derivatives generates heterocyclic compounds with benzimidazole moiety. In contrast to synthetic procedures reported earlier for benzimidazoles, the reaction conditions herein reported are simpler. Path for reactions holds initial condensation with one equivalent of 8‐hydroxyquinoline‐2‐carbaldehyde to form mono‐imine followed by immediate intramolecular ring closure. The subsequent nupleophilic attack to another equivalent of 8‐hydroxyquinoline‐2‐carbaldehyde and migration of hydride generates the benzimidazole moiety and the active methylene group. The ─CH₂ group was confirmed from ¹H and ¹³C NMR, wherein the two hydrogens appeared at around 6.40–6.52 ppm and the carbon center appeared at 51.54–51.77 ppm. The single crystal X‐ray diffraction also confirmed the formation of benzimidazole moiety and the active methylene group in the heterocyclic compounds discussed in this study.     

Correlation of fine structural characteristics and textile properties of silk fiber

The small-angle, x-ray scattering method was applied to evaluate macromolecular parameters of defated proteinous silk fibers like Eri, Muga, Tussah, and raw silk. For the experimental measurement of scattering intensities the small-angle Kratky camera, coupled with an automatic-step scanning device, pulse-height discriminator, and counter attachment was used. Macromolecular parameters like specific inner surface, percentage of void, length of coherence, range of inhomogeneity, and transversal length were evaluated by using the theories of Kratky, Porod and Debye, and Bueche. The physical properties of these defated fibers were also evaluated with Scott's IP₂-inclined plane tester. The correlation of the tertiary structural parameters with textile properties like average breaking strength of the proteinous fibers indicated a dependence of physical properties on certain macromolecular parameters.     

Vinyl polymerization of acrylonitrile by the Ce(IV)-glucose redox system

Aqueous polymerization of acrylonitrile (M) initiated by the Ce(IV)-glucose (R) redox system has been studied under nitrogen in the temperature range of 30–40 °C. The rate of polymerization (Rp) is proportional to [M]², [R] and inversely proportional to [Ce(IV)]. The rate of ceric ion disappearance is proportional to [R] and [Ce(IV)]. The end group in the polymer is characterised by IR spectra. A suitable kinetic scheme has been proposed and explained in the light of these experimental findings.     

Microwave extraction and rapid isolation of arjunic acid from Terminalia arjuna (Roxb. ex DC.) stem bark and quantification of arjunic acid and arjunolic acid using HPLC-PDA technique

Arjunic acid and arjunolic acid are main bioactive components of Terminalia arjuna stem bark and reported for various biological activities. In this study, microwave-assisted extraction (MAE) of arjunic and arjunolic acid from stem bark of T. arjuna was investigated with developed and validated HPLC-PDA method, which resulted in the isolation of a novel anticancer molecule i.e. arjunic acid. Effects of several experimental parameters, such as type and volume of extraction solvents, microwave power, microwave extraction time, on the extraction efficiencies of arjunic, and arjunolic acid from stem bark of T. arjuna were evaluated. The optimal extraction conditions identified were 5.0 g quantity of stem bark powder, 20 mL of ethyl acetate, preleaching time 10 min, microwave power 600 W, temperature 65°C, and microwave irradiation time 5 min. The results showed that MAE is a more rapid extraction method with higher yield and lower solvent consumptions than reported methods. The HPLC-PDA analysis method was developed and validated to have good linearity, precision, sensitivity, and accuracy. MAE-HPLC-PDA is a faster, convenient, and appropriate method for isolation and determination of arjunic acid and arjunolic acid in the stem bark of T. arjuna.     

Surface Aggregation of Candida albicans on Glass in the Absence and Presence of Adhering Streptococcus gordonii in a Parallel-Plate Flow Chamber: A Surface Thermodynamical Analysis Based on Acid-Base Interactions

Adhesive interactions between yeasts and bacteria are important in the maintenance of infectious mixed biofilms on natural and biomaterial surfaces in the human body. In this study, the extended DLVO (Derjaguin-Landau-Verwey-Overbeek) approach has been applied to explain adhesive interactions between C. albicans ATCC 10261 and S. gordonii NCTC 7869 adhering on glass. Contact angles with different liquids and the zeta potentials of both the yeasts and bacteria were determined and their adhesive interactions were measured in a parallel-plate flow chamber.Streptococci were first allowed to adhere to the bottom glass plate of the flow chamber to different seeding densities, and subsequently deposition of yeasts was monitored with an image analysis system, yielding the degree of initial surface aggregation of the adhering yeasts and their spatial arrangement in a stationary end point. Irrespective of growth temperature, the yeast cells appeared uncharged in TNMC buffer, but yeasts grown at 37 degrees C were intrinsically more hydrophilic and had an increased electron-donating character than cells grown at 30 degrees C. All yeasts showed surface aggregation due to attractive Lifshitz-van der Waals forces. In addition, acid-base interactions between yeasts, yeasts and the glass substratum, and yeasts and the streptococci were attractive for yeasts grown at 30 degrees C, but yeasts grown at 37 degrees C only had favorable acid-base interactions with the bacteria, explaining the positive relationship between the surface coverage of the glass by streptococci and the surface aggregation of the yeasts. Copyright 1999 Academic Press.     

Multiple periodic solutions for system of first-order differential equation

Sufficient conditions have been obtained for the existence of at least two non-negative periodic solutions to a system of first-order nonlinear functional differential equations. Applications to some ecological models are given.