Garlic peroxidase immobilized into chitosan matrix suitable for biosensors applications

Peroxidase X₁ (POX₁) isoenzyme was purified from garlic bulb (Allium sativum L.). Native-PAGE profile showed two isoforms partially purified (designated POX_1A and POX_1B). A POX_1B-based electrode showed great potential for monitoring hydrogen peroxide in biological samples. Chitosan was used as a matrix for enzyme immobilization. The enzyme activities were studied by photometry. Immobilization was accomplished by either inclusion in a thin film or adsorption to cross-linked microspheres. Two linkage agents were used: glutaraldehyde and glyoxal. The best immobilization and activity yields (82%, 95%) were obtained when POX_1B was incorporated within a chitosan/glyoxal film. The effect of temperature on the immobilized enzyme was tested. Results showed that full activity was retained after 40 min incubation at 40 °C. Anchored POX_1B inside chitosan was used for biosensor design. Cyclic voltammetry and impedance spectroscopy were employed to analyze electrochemical properties of the modified gold electrode and to monitor hydrogen peroxide. The biosensor was very sensitive and attained a detection limit of 100 nM.     

Effects of Extraction Solvents and Provenances on Phenolic Contents and Antioxidant Activities of Cumin (Cuminum cyminum L.) Seeds

Polyphenol contents and 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) scavenging activity of cumin (Cuminum cyminum L.) seed extracts were compared depending on their geographical origin (Tunisia and India: TCS and ICS, respectively) and the extraction solvent polarity. The ??-carotene bleaching assay, the chelating ability and the reducing power of the most promising solvent extracts were also assessed. In addition, TCS and ICS extracts were acid-hydrolyzed and the phenolics identified by reversed-phase high-performance liquid chromatography (HPLC). Seed phenolic contents and antioxidant activity appeared to be accession and solvent dependent. Extraction with 80% acetone led to the highest polyphenol (18.60 and 16.50?mg gallic acid equivalents (GAE)/g dry weight (DW)), flavonoid (5.91 and 4.99?mg catechin equivalents (CE)/g DW) and tannin (83.23 and 80.23?mg CE/g DW) contents, respectively for TCS and ICS. DPPH scavenging activity, ??-carotene bleaching assay, chelating ability and reducing power were maximal in 80% acetone for both TCS and ICS. HPLC analysis revealed several phenolic compounds in C. cyminum seeds, with p-coumaric (4.83 and 2.33?mg/g DW), trans-2-dihydrocinnamic (1.09 and 1.20?mg/g DW) and rosmarinic (0.70 and 1.04?mg/g DW) acids as major phenolics in TCS and ICS, respectively. Thus, phenolic composition of cumin seeds is also origin dependent. Taken together, our findings indicate that cumin might constitute a rich and novel source of natural antioxidants as food additives in food industry and that acetone 80% would be the most appropriate solvent for seed extraction.     

Thermal and optical properties of tellurite glasses doped erbium

Er³⁺-doped tellurite glasses with molar compositions of 75TeO₂–20ZnO–(5 − x) Na₂O–xEr₂O₃ (x = 0, 0.5, 1, 2, 3, and 4 mol%) have been elaborated from the melt-quenching method. The effects of Er₂O₃ concentration on the thermal stability and optical properties of tellurite glasses have been discussed. From the differential scanning calorimetry (DSC) profile, the glass transition temperature T _g, and crystallization onset temperature T _x are estimated. The thermal stability factor, defined as ∆T = T _x − T _g, was higher than 100 °C. It suggests that tellurite glass exhibits a good thermal stability and consequently is suitable to be a potential candidate for fiber drawing. Furthermore, the stability factor increases with Er₂O₃ concentration up to 2 mol% then presents a continue decrease suggesting of beginning of crystallization of highly doped tellurite glasses. The refractive index and extinction coefficient data were obtained by analyzing the experimental spectra of tanΨ and cos∆ measured by spectroscopic ellipsometry (SE). The complex dielectric functions (ε = ε₁ + iε₂) of the samples were estimated from regression analysis. The fundamental absorption edge has been identified from the optical absorption spectra and was analyzed in terms of the theory proposed by Davis and Mott. The values of optical band gap for direct and indirect allowed transitions have been determined. An important decrease of the optical band gap was found after Er doping. It was assigned to structural changes induced from the formation of non-bridging oxygen. The absorption coefficient just below the absorption edge varies exponentially with photon energy indicating the presence of Urbach’s tail. The origin of the Urbach energy is associated with the phonon-assisted indirect transitions.     

An explanation for an apparent failure of the box-hill procedure for model discrimination

Froment and Mezaki made an early attempt to verify, by using real experimental results, that the Box-Hill procedure could accomplish more efficient model discrimination than less sophisticated procedures. They found rapid convergence but the conclusion varied, depending on the conditions of the initial experimental trials. In attempting to remedy this inconsistency several workers have found changes in the Box-Hill method which can eliminate it. In this investigation an explanation of the failure is sought and found in terms of the requirements of the method. It is shown that direct application of the unmodified procedure is successful if the dependent variable is chosen so as to minimize the effect of errors in the independent variables even though this means changing the form of the model from linear to nonlinear in the parameters.     

Directions of arrival estimation with planar antenna arrays in the presence of mutual coupling

Directions of arrival (DoAs) estimation of multiple sources using an antenna array is a challenging topic in wireless communication. The DoAs estimation accuracy depends not only on the selected technique and algorithm, but also on the geometrical configuration of the antenna array used during the estimation. In this article the robustness of common planar antenna arrays against unaccounted mutual coupling is examined and their DoAs estimation capabilities are compared and analysed through computer simulations using the well-known MUltiple SIgnal Classification (MUSIC) algorithm. Our analysis is based on an electromagnetic concept to calculate an approximation of the impedance matrices that define the mutual coupling matrix (MCM). Furthermore, a CRB analysis is presented and used as an asymptotic performance benchmark of the studied antenna arrays. The impact of the studied antenna arrays geometry on the MCM structure is also investigated. Simulation results show that the UCCA has more robustness against unaccounted mutual coupling and performs better results than both UCA and URA geometries. The performed simulations confirm also that, although the UCCA achieves better performance under complicated scenarios, the URA shows better asymptotic (CRB) behaviour which promises more accuracy on DoAs estimation.     

An Efficient Shortest Triangle Paths Algorithm Applied to Multi-camera Self-calibration

We propose a novel minimum uncertainty approach to relative pose selection for multi-camera self-calibration. We show how this discrete global optimization problem can be expressed as a shortest triangle paths problem. For the latter, we present an efficient algorithm and prove its correctness. It has several advantages compared to a similar approach of Vergés-Llahí, Moldovan and Wada. In quantitative experiments on publically available data, we show that our relative pose selection method provides improvements compared to naive, random and greedy selection, without and with subsequent bundle adjustment.     

Dielectric investigation of the sol‐gel transition in the acrylamide/N,N′ methylenebisacrylamide system

The acrylamide/N,N′‐methylenebisacrylamide gelation process was studied by time dependent measurement of real ϵ^I and imaginary ϵ^II parts of the complex dielectric permittivity. The measurements were carried out in the frequency interval 500 Hz to 13 MHz. Strong relaxation behavior of ϵ^I and ϵ^II was observed in all dielectric spectra during the transformation from the sol to the gel state. At all frequencies a maximum in the imaginary part of dielectric constant ϵ^II was observed. The gel point was found by extrapolating this maximum to zero frequency. The behavior of ϵ^I and ϵ^II related to the gelation mechanism is discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 463–466, 2000     

Etude du systeme KPO3-LaP3O9. Donnees cristal lographiques sur K2La(PO3)5 et (NH4)2La(PO3)5

The system KPO₃-LaP₃O₉ has been studied for the first time by differential thermal analysis and X ray diffraction. The system shows two compounds KLa(PO₃)₄ and K₂La(PO₃)₅ which melt in a peritectic decomposition at 880°C and 770°C respectively. An eutectic point appears at 705°C; The eutectic point corresponds to a concentration of 10% molar LaP₃O₉.Infra Red absorption spectra are typical of chain phosphates.The new compound K₂La(PO₃₅ is isotypic whith (NH₄)₂La(PO₃)₅ which has been synthetized for the first time. They belong to the triclinic system whith space group P1 and Z = 2. The parameters of the unit cell are: $\text{a = 7.309(4)}\text{A}\text{?}$$\text{b = 13.35(2)}\text{A}\text{?}$$\text{c = 7.155(7)}\text{A}\text{?}$α = 90°3(1) β = 109°17(7) γ = 89°90(4) for K₂La(PO₃)₅ and: $\text{a = 7.174(8)}\text{A}\text{?}$$\text{b = 13.38(2)}\text{A}\text{?}$$\text{c = 7.35(2)}\text{A}\text{?}$α = 90°6(2) β = 107°4(1) γ = 89°82(7) for (NH₄)₂La(PO₃)₅.