Role of spacer lengths of gemini surfactants in the synthesis of silver nanorods in micellar media

In this work, we have prepared Ag-nanorods using biscationic gemini surfactant micelles as the media by a seed-mediated wet synthesis method. Towards this end, we first synthesized Ag-nanoseeds of diameter ~7 nm stabilized by trisodium citrate (as the capping agent). Then these Ag-nanoseeds were used to synthesize Ag-nanorods of different aspect ratios. With decreasing Ag-nanoseed concentration, the aspect ratios of the Ag-nanorods stabilized by these gemini surfactants increased gradually. Various Ag-nanoseeds and Ag-nanospecies were characterized using UV-Vis spectroscopy (to know the surface plasmon bands), transmission electron microscopy (to find out their particle sizes and distribution), energy-dispersive X-ray spectroscopy and X-ray diffraction. When we used micelles derived from gemini surfactants of shorter spacer -(CH(2))(n)- (n = 2 or 4) to stabilize the Ag-nanorods, the λ(max) of the longitudinal band shifted more towards the blue region compared to that of the gemini surfactant micelles with a longer spacer -(CH(2))(n)- (n = 5, 12) at a given amount of the Ag-nanoseed solution. So, the growth of Ag-nanorods in the gemini micellar solutions depends on the spacer-chain length of gemini surfactants employed.     

Preparation and characterization of molybdenum trioxide from spent hydrodesulfurization catalyst

An approach to produce molybdenum trioxide from spent hydrodesulfurization (HDS) catalyst, obtained from a petroleum refinery, is presented here. The spent catalyst was devolatilized at 600 °C so as to make it free from oils, organics and other volatile species. It was then roasted with sodium carbonate at a temperature of 850 °C for 30 min. The leaching efficiency for 20% soda roasted sample at 10% pulp density was 99.8%. From the solution molybdenum was precipitated out as ammonium molybdate at pH 1.0 with HCl and ammonium chloride. This ammonium molybdate was calcined at 750 °C to get MoO₃. The product was characterized by XRD. Its purity was determined titrimetrically and by ICP-AES.     

Development of a knowledge based hybrid neural network (KBHNN) for studying the effect of diafiltration during ultrafiltration of whey

The membrane surface dynamics is very difficult to predict and can be roughly estimated by the available models but a true depiction is always difficult since the magnitude and direction of driving forces change as a function of time. The present study is an effort to address the issue, so that the combinatorial approach of deterministic and stochastic modelling might present a better understanding of membrane dynamics. The effect of diafiltration has also been incorporated to investigate the effects it has on the membrane. A stochastic model developed by a knowledge based hybrid neural network (KBHNN) was trained using the Levenberg–Marqurt algorithm where the film layer model was used as the deterministic layer, called the first principle model (FPM). Present work employs two different types of KBHNN architecture with an effort to understand the suitability and applicability of the hybrid network in case of predictions for an ultrafiltration (UF) process. In one sort of architecture neural part was in series with the FPM and in the other one it was in parallel with the FPM. The high correlation coefficient (R²) value portrays the correctness and preciseness of the underlining assumptions and establishes the validity of the developed network.     

Gelatin‐carbohydrate phase‐separated hydrogels as bioactive carriers in vaginal delivery: Preparation and physical characterizations

The current study focuses on the alteration of properties of the gelatin hydrogels using polysaccharides (e.g., maltodextrin, dextran, and sodium carboxymethyl cellulose) for probable use in vaginal delivery of antimicrobials. The hydrogels were prepared by varying the proportions of gelatin and polysaccharides and were characterized by microscopy, mechanical testing, and impedance spectroscopy. Metronidazole (MZ), drug of choice for the treatment of bacterial vaginosis, was incorporated within the hydrogels. In vitro release studies of MZ from the hydrogels was studied in‐depth using modified Franz's diffusion cell. Antimicrobial efficiency of the MZ‐loaded hydrogels was tested against E. coli and B. subtilis. The results suggested that the incorporation of polysaccharides resulted in the phase‐separated hydrogels. The properties of the hydrogels was found be suitable for vaginal delivery. The drug release and antimicrobial efficiency from the hydrogels suggested that the developed hydrogels may be used for the delivery of antimicrobials in the vaginal lumen. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40445.     

Co-Extraction of U(VI) and HNO3 Using TBP and its Higher Homologues TiAP and TEHP: Comparison of Equilibria,Kinetics, and Rate of Extraction

In this work, bulk-liquid membrane (BLM) system is used to compare tri-n-butyl phosphate (TBP), tri-isoamyl phosphate (TiAP), and tris(2-ethylhexyl) phosphate (TEHP) for their relative ability to co-extract U(VI) and nitric acid from aqueous nitric acid feed-phase into water strip-phase, through hydrocarbon membrane-phase. The kinetics of extraction is modelled and the model is validated through experiments. The quantity which determines the efficiency of liquid emulsion membrane (LEM) process is the relative rate of extraction of U(VI) to nitric acid. This is in the order TiAP>TEHP>TBP, indicating that TiAP is most suitable for extraction of U(VI) from nitric acid using LEM.     

A study on the importance of dependent radiative effects in determining the spectral and total emittance of particulate ash deposits in pulverised fuel fired furnaces

This paper presents the results of an experimental and theoretical investigation on the importance of dependent effects in determining the emittance of ash deposits. A model has been developed to predict the spectral emittance (directional, normal, hemispherical) of semi-transparent and opaque particulate deposits without considering dependent effects. Predictions from this model have been presented to illustrate the effects of particle size and composition. Hemispherical transmission and reflection measurements have been performed on semi-transparent and opaque particular deposits over a wavelength range typical of pf fired furnances and spectral emittance has been deduced therefrom. Well characterised slag particles, with composition and size similar to ash deposits formed in pf fired furnances, have been used in the measurements. For the opaque deposit, difference between the model predictions and measurements, in terms of emittance, have been found to be significant at wavelengths up to 7 μm. This difference is believed to be largely due to dependent effects. Such measurements and comparisons appear to be the first of its kind and more experiments are recommended to quantify the effects.     

Extensional rheology of raw natural rubber from new clones of Hevea brasiliensis

Natural rubber (NR) is a biopolymer whose properties depend on the molecular structure of the 1,4‐cis polyisoprene chains, nonrubber constituents, environmental conditions, etc. NR has been characterized by Mooney viscosity, Wallace plasticity, nitrogen content (%N). However, these cannot effectively account for clone's differences. The aim of this work is to use extensional rheology to characterize and differentiate NR samples as for clone type and the season of the year in comparison to the traditional characterizations. Three IAC 300 series and RRIM 600 clones of Hevea brasiliensis tapped between October 2006 (Oct_06) and August 2008 (Aug_08) were investigated. IAC 329 clones showed the least susceptibility to seasonal changes, whereas RRIM 600 was the most influenced. An opposite trend between extensional viscosity (η_E) and %N was established. The former was very sensitive to changes in the molecular structure of NR, being fundamental for monitoring purposes and strategic development of new rubber tree clones. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Design and Synthesis of Xanthone Analogues Conjugated with Aza-aromatic Substituents as Promising G-Quadruplex Stabilizing Ligands and their Selective Cancer Cell Cytotoxic Action

We have examined the stabilization of higher-order noncanonical G-quadruplex (G4) DNA structures formed by the G-rich sequences in the promoter region of oncogenes such as c-MYC, c-KIT, VEGF and BCl2 by newly synthesized, novel nitrogen-containing aromatics conjugated to xanthone moiety. Compounds with N-heterocyclic substituents such as pyridine (XNiso), benzimidazole (XBIm), quinoxaline (XQX) and fluorophore dansyl (XDan) showed greater effectiveness in stabilizing the G4 DNA as well as selective cytotoxicity for cancer cells (mainly A549) over normal cells both in terms of UV-Vis spectral titrations and cytotoxicity assay. Both fluorescence spectral titrimetric measurements and circular dichroism (CD) melting experiments further substantiated the G4 stabilization phenomenon by these small-molecular ligands. In addition, these compounds could induce the formation of parallel G4 structures in the absence of any added salt condition in Tris ⋅ HCl buffer at 25 °C. In a polymerase stop assay, the formation of stable G4 structures in the promoter of oncogenes and halting of DNA synthesis in the presence of the above-mentioned compounds was demonstrated by using oncogene promoter as the DNA synthesis template. Apoptosis-mediated cell death of the cancer cells was proved by Annexin V-PI dual staining assay and cell-cycle arrest occurred in the S phase of the cell cycles. The plausible mode of binding involves the stacking of the xanthone core on the G4 DNA plane with the possibility of interaction with the 5’-overhang as indicated by molecular dynamics simulation studies.     

Affinity Studies of Hemicyanine Derived Water Soluble Colorimetric Probes with Reactive Oxygen/Nitrogen/Sulfur Species

Peroxynitrite (ONOO^-) is an essential endogenous reactive oxygen species (ROS) generated in mitochondria under various pathological and physiological conditions. An increase in its level in mitochondria is related to numerous diseases. Herein, we report a series of hemicyanine-derived water-soluble colorimetric probes ( 1 – 4 ) and the reactivity of which was studied with various reactive oxygen, nitrogen, and sulfur species. Probes 1 – 4 are formed by conjugating 1,2,3,3-tetramethyl-3H-indolium iodide and 4-hydroxybenzaldehyde or its derivatives through an alkene linkage formed by the Knoevenagel reaction. Oxidative cleavage of the electron-rich double bond of the conjugated hemicyanine dye revealed a discerning affinity of probe 3 towards peroxynitrite among all reactive oxygen species. The rapid change in color of 3 provides a sensitive and selective method for detecting peroxynitrite with a low detection limit of 180 nM. Notably, the water solubility of the probe displays excellent performance for the selective detection of peroxynitrite among ROS and reactive nitrogen (RNS)/sulfur species (RSS). UV-vis, ¹H NMR, and ¹³C NMR spectroscopic data and results from theoretical calculations provide further information on the interaction of peroxynitrite with probe 3 .