Ni0.1Co0.9Fe2O4-based electrochemical sensor for the detection of paracetamol

A novel electrochemical sensor based on nickel-doped cobalt ferrite nanoparticles (Ni_0.1Co_0.9Fe₂O₄)-modified glassy carbon electrode (NCF/GCE) was presented for the sensitive detection of paracetamol. Experimental conditions such as pH, applied potentials and concentration were investigated using cyclic voltammetric and chronoamperometric techniques. The modified electrode exhibited excellent catalytic response towards the oxidation of paracetamol with good reproducibility. The overpotential for oxidation of paracetamol is decreased, and the current response enhanced significantly on the modified electrode in comparison with that of bare electrode. Linear calibration curve is obtained over the range 2 μM to 8,000 μM having a detection limit of 11 nM. The modified electrode facilitated the simultaneous detection of paracetamol, ascorbic acid, and dopamine with good reproducibility.     

Set intersection representations for almost all graphs

Two variations of set intersection representation are investigated and upper and lower bounds on the minimum number of labels with which a graph may be represented are found that hold for almost all graphs. Specifically, if θ_k(G) is defined to be the minimum number of labels with which G may be represented using the rule that two vertices are adjacent if and only if they share at least k labels, there exist positive constants c_k and c′_k such that almost every graph G on n vertices satisfies Changing the representation only slightly by defining θ;_odd (G) to be the minimum number of labels with which G can be represented using the rule that two vertices are adjacent if and only if they share an odd number of labels results in quite different behavior. Namely, almost every graph G satisfies Furthermore, the upper bound on θ_odd(G) holds for every graph. © 1996 John Wiley & Sons, Inc.     

Effect of the Dispersing Agent on the Electrochemical Response of Glassy Carbon Electrodes Modified with Dispersions of Carbon Nanotubes

The electrochemical response of a glassy carbon electrode modified with carbon nanotubes (CNT) dispersed in two solvents, water and DMF, and two polymers, chitosan and Nafion is reported. The films were homogeneous when the dispersing agent was water or DMF. In the case of polymers, the surfaces present areas with different density of CNTs. A more sensitive electrochemical response was obtained when CNTs are dispersed in the solvents. In the case of CNT dispersed with polymers, the nature of the polymer demonstrated to be a critical parameter not only for dispersing the nanotubes but also for the electrochemical activity of the resulting electrodes.     

Purification of neutral protease by dye affinity chromatography

Twenty triazinic dyes were assayed as ligands for the chromatographic affinity purification of a neutral protease from Flavourzyme^™, a commercial preparation. Screening at pH 4.0 allowed the selection of eight dyes on the basis of their high protease adsorption. When the pH was set to 5.0 in order to increase selectivity, only Yellow HE-4R, Red HE-3B, and Cibacron Blue F3G-A maintained protease adsorption at high values. Neither maximum capacities nor dissociation constants calculated from isotherms measured at 8 and 25°C showed great differences. By contrast, a strong temperature effect was evidenced in the elution step: elution at 8°C allowed 70, 81, and 98% recovery of adsorbed protease with Yellow HE-4R, Red HE-3B, and Cibacron Blue F3G-A, respectively, whereas only 20% recovery was attained at 25°C. Based on the results obtained, a purification process for the neutral protease contained in Flavourzyme with Cibacron Blue F3G-A as the affinity ligand was developed, yielding 96% of electrophoretically pure enzyme in a single step, the specific activity rising from 850 to 3650 U/mg.     

Applications of Vibrational Spectroscopy for Analysis of Connective Tissues

Advances in vibrational spectroscopy have propelled new insights into the molecular composition and structure of biological tissues. In this review, we discuss common modalities and techniques of vibrational spectroscopy, and present key examples to illustrate how they have been applied to enrich the assessment of connective tissues. In particular, we focus on applications of Fourier transform infrared (FTIR), near infrared (NIR) and Raman spectroscopy to assess cartilage and bone properties. We present strengths and limitations of each approach and discuss how the combination of spectrometers with microscopes (hyperspectral imaging) and fiber optic probes have greatly advanced their biomedical applications. We show how these modalities may be used to evaluate virtually any type of sample (ex vivo, in situ or in vivo) and how “spectral fingerprints” can be interpreted to quantify outcomes related to tissue composition and quality. We highlight the unparalleled advantage of vibrational spectroscopy as a label-free and often nondestructive approach to assess properties of the extracellular matrix (ECM) associated with normal, developing, aging, pathological and treated tissues. We believe this review will assist readers not only in better understanding applications of FTIR, NIR and Raman spectroscopy, but also in implementing these approaches for their own research projects.     

Thermoresponsive Ionic Liquid/Water Mixtures: From Nanostructuring to Phase Separation

The thermodynamics, structures, and applications of thermoresponsive systems, consisting primarily of water solutions of organic salts, are reviewed. The focus is on organic salts of low melting temperatures, belonging to the ionic liquid (IL) family. The thermo-responsiveness is represented by a temperature driven transition between a homogeneous liquid state and a biphasic state, comprising an IL-rich phase and a solvent-rich phase, divided by a relatively sharp interface. Demixing occurs either with decreasing temperatures, developing from an upper critical solution temperature (UCST), or, less often, with increasing temperatures, arising from a lower critical solution temperature (LCST). In the former case, the enthalpy and entropy of mixing are both positive, and enthalpy prevails at low T. In the latter case, the enthalpy and entropy of mixing are both negative, and entropy drives the demixing with increasing T. Experiments and computer simulations highlight the contiguity of these phase separations with the nanoscale inhomogeneity (nanostructuring), displayed by several ILs and IL solutions. Current applications in extraction, separation, and catalysis are briefly reviewed. Moreover, future applications in forward osmosis desalination, low-enthalpy thermal storage, and water harvesting from the atmosphere are discussed in more detail.