Reducing Sugars Production from Corncobs: A Comparative Study of Chemical and Biotechnological Methods

Two commonly used chemical pretreatment processes, sulphuric acid, and sodium hydroxide, were tested to provide comparative performance data. A connection between solid to liquid ratio (S/L) and sugars released was observed with an increase in S/L ratio between 0.02 and 0.2. Enzymatic digestibility of 1 M of NaOH-pretreated corncobs were released 210.7 mg ml^?1 of sugars. Further, compared with different concentrations of acid pretreatments at 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, and 0.5 M concentrations, sodium hydroxide pretreatment of corncob substantially increased accessibility and digestibility of cellulose. Another additional observation made was whole-cell and crude enzymatic hydrolysis of different concentrations of acid and NaOH (0.05, 0.1, 0.25 M)-treated materials released lower amount of sugars compared with the sugars released (310.9 mg ml^?1) with whole-cell hydrolysis of 1 M of NaOH-treated corncobs. NaOH-pretreated corncobs contained higher content of sugars and which is more suitable for production of reducing sugars.     

Electrical conduction of emulsion explosives

Results of experiments to obtain a spatial distribution of electrical conduction of emulsion explosives for different content of a sensitizer are presented.     

Feasibility study for detecting copper contaminants in transformer insulation using laser-induced breakdown spectroscopy

In recent times, copper sulphide (Cu₂S) diffusion in the transformer insulation is a major problem reducing the life of transformers. It is therefore essential to identify a simple methodology to understand the diffusion of Cu₂S into the solid insulation [oil impregnated pressboard (OIP)]. In the present work, laser-induced breakdown spectroscopy (LIBS) was adopted to study the diffusion of Cu₂S into the pressboard insulation and to determine the depth of diffusion. The diffusion of Cu₂S in pressboard was confirmed by electrical discharge studies. In general, flashover voltage and increase in ageing duration of pressboard insulation/Cu concentration had inverse relationship. The characteristic emission lines were also studied through optical emission spectroscopy. Based on LIBS studies with Cu powder dispersed pressboard samples, Cu I emission lines were found to be resolvable up to a lowest concentration of 5 μg/cm². The LIBS intensity ratio of Cu I–Ca II emission lines were found to increase with increase in the ageing duration of the OIP sample. LIBS studies with OIP samples showed an increase in the optical emission lifetime. LIBS results were in agreement with the electrical discharge studies.     

Synthesis and Characterization of α,ω‐bi[2,4‐dinitrophenyl (DNP)] poly(2‐methoxystyrene) Functional Polymers. Initial Evaluation of the Interaction of the Functional Polymers with RBL Mast Cells

Two series of functional polymers, α,ω‐bi[2,4‐dinitrophenyl][poly(ethylene oxide)‐b‐poly(2‐methoxystyrene)‐b‐poly(ethylene oxide)] (DNP‐PEO‐P2MS‐PEO‐DNP) and α,ω‐bi[2,4‐dinitrophenyl caproic][poly(ethylene oxide)‐b‐poly(2‐methoxystyrene)‐b‐poly(ethylene oxide)] (CDNP‐PEO‐P2MS‐PEO‐CDNP), were synthesized by anionic living polymerization. The polymers were characterized by FT‐IR, ¹H‐NMR and Gel Permeation Chromatography (GPC). The molecular weight distributions for the lower molecular weight functional polymers were slightly broad (1.3–1.5). However, the molecular weight distributions for higher molecular weight polymers were narrower (1.1–1.2). Differential scanning calorimetry (DSC) studies showed thermal transitions indicative of the presence of microphases in the polymer solid state. The polymers were white powders and soluble in tetrahydrofuran. The binding affinity of DNP‐PEO‐P2MS‐PEO‐DNP ligands towards anti DNP IgE was determined by titrations with fluorescently labeled FITC‐IgE. A water soluble CDNP‐PEO‐P2MS‐PEO‐CDNP/DMEG (dimethoxyethylene glycol) complex binds and achieves steady state binding with solution IgE within a few seconds. This strongly suggests that CDNP functional polymers with improved water solubility have potential in therapeutics. Higher molecular weight (water insoluble) CDNP‐PEO‐P2MS‐PEO‐CDNP polymers were electrosprayed as fibers (500 nm) on silicon surface. Fluorescence spectroscopy clearly showed that RBL mast cells were interacting with the fibers suggesting that the cell‐surface receptors were clustered along the fiber surface. These observations suggest that the functional polymers hold promise for developing an antibody detection device.     

Studies on the Complexation of Transition Metal Ions with Macrocyclic Compounds in Mixed Solvents by Competitive Potentiometry and Polarography

Complexation of Cu(II), Zn(II), Ni(II), Co(II), Pb(II), Cd(II), Cr(III) and Fe(III) ions with 15-crown-5, benzo-15-crown-5, 18-crown-6, dibenzo-18-crown-6, dicyclohexano-18-crown-6, dibenzo-24-crown-8, 5,6,14,15-dibenzo-1,4-dioxa-8,12-diazacyclopentadeca-5,14-diene, 1,4,10-trioxa-7,13-diazacyclopentadecane and cyclam has been investigated in 75% (v/v) DMF+water using the silver(I) ion as an auxiliary cation at 0.05?M ionic strength adjusted with tetrabutylammonium perchlorate (TBAP) by competitive potentiometry. Stability constant values obtained for the metal ion–aza macrocyclic complexes are higher than those for the oxa crowns. Shifts in the peak potential and reduction in the peak current in the differential pulse polarography (DPP) method were also used to determine the stability constants of some of the metal ions with aza and tosylated-aza macrocycles using TBAP as supporting electrolyte in 75% (v/v) DMF+water and 90% (v/v) DMSO+water media. Stability constant values determined both by shifts in the potential and by reduction in the peak current were found to be in good agreement with each other.     

Archetypical Conductive Polymer Structure for Specific Interaction with Proteins

A series of 2,4-dinitrophenyl (DNP) functionalized polypyrrole terpolymers, capable of specific binding to IgE antibodies (proteins), have been synthesized using oxidizing initiator, ammonium persulfate and were characterized by ¹H-NMR, IR, DSC, Light Scattering etc. The terpolymers were composed of monomers and macromonomers: monomer (pyrrole), macromonomer A (pyrrole with pendant ethylene glycol) and macromonomer B (pyrrole with pendant DNP) with specific functionality of conductance, processiblity and binding, respectively. The terpolymers are found to be semiconductive, (5 × 10^?6 S cm^?1) by itself without the addition of doping agents. Molecular dynamics simulation of terpolymer shows that the DNP-(2,4-dinitrophenyl) functional group extends out from the polymer backbone and thus, is available for binding. The DNP functional groups on the terpolymer achieve steady state binding with anti-DNP IgE proteins at nanomolar concentrations in solution. The terpolymer was blended with sulfonated polystyrene and processed in fibers which exhibited effective specific binding to fluorescently tagged IgE proteins and therefore, possessed the potential to be an active component in biosensor.     

Statistical sampling of carbon nanotube populations by thermogravimetric analysis

Carbon nanotubes are one of the most promising nanomaterials available with applications in electronics devices, sensing, batteries, composites and medicine. Strict control of the carbon nanotube chemistry and properties is necessary as the applications proceed into more specialized areas. Thermogravimetric analysis (TGA) is one analytical method currently utilized for the characterization of carbon nanotubes. Though TGA can provide quantitative measurements of the composition of a sample, many researchers do not ensure the variance of the sample is properly captured. This research demonstrates for four single-wall carbon nanotube (SWCNT) samples how to statistically evaluate the material with TGA to ensure that the variance within the material is represented. SEM results are used to help reach conclusions about purity of the material by providing a visual means for inspection. This data is used to select the SWCNT material with the lowest variability and highest quality, as evaluated by composition and reproducibility.     

Initiation and inhibition of dealloying of single crystalline Cu3Au (111) surfaces

Dealloying is widely utilized but is a dangerous corrosion process as well. Here we report an atomistic picture of the initial stages of electrochemical dealloying of the model system Cu(3)Au (111). We illuminate the structural and chemical changes during the early stages of dissolution up to the critical potential, using a unique combination of advanced surface-analytical tools. Scanning tunneling microscopy images indicate an interlayer exchange of topmost surface atoms during initial dealloying, while scanning Auger-electron microscopy data clearly reveal that the surface is fully covered by a continuous Au-rich layer at an early stage. Initiating below this first layer a transformation from stacking-reversed toward substrate-oriented Au surface structures is observed close to the critical potential. We further use the observed structural transitions as a reference process to evaluate the mechanistic changes induced by a thiol-based model-inhibition layer applied to suppress surface diffusion. The initial ultrathin Au layer is stabilized with the intermediate island morphology completely suppressed, along an anodic shift of the breakdown potential. Thiol-modification induces a peculiar surface microstructure in the form of microcracks exhibiting a nanoporous core. On the basis of the presented atomic-scale observations, an interlayer exchange mechanism next to pure surface diffusion becomes obvious which may be controlling the layer thickness and its later change in orientation.