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New modified electrode materials, based on a combination of hybrid nanocomposites such as magnetic nanoparticles, inorganic polymer (SiO2) and different types of organic polymers, were studied. Thr...

In today’s global context, entrepreneurship is recognized as the engine of sustainable economic growth, competitiveness and employment in the economy of any nation. In order to improve the measures aimed at encouraging the creation of new businesses, an enhanced understanding of the drivers of nascent entrepreneurship seems essential. Drawing on planned behavior theory and the approach of entrepreneurial perceived behavioral control (PBC) as a motivational antecedent in starting a new business, the current study seeks to understand how the personal characteristics of the entrepreneurs influence entrepreneurial PBC. Three types of characteristics were assessed in a sample of 212 Romanian nascent entrepreneurs: personality traits (Big Five model), empathy, and assertiveness. The hierarchical multilinear regression analysis, in which entrepreneurial PBC was treated as a dependent variable, showed that the model with the highest explanatory power for the variance of results of entrepreneurial PBC included characteristics from all three levels: personality traits—Neuroticism, Extraversion, and Openness; empathy—personal distress and perspective-taking; and adaptive assertiveness. Additionally, the findings showed that adaptive assertiveness provides an effect over and above personality factors and empathy on the entrepreneurial PBC. The practical implications of these findings indicate that to enhance the effectiveness of entrepreneurship education programs, components aiming to enhance internal personal resources of entrepreneurs (such as assertive communication skills) should be added.

The development of a magnetic nanocomposites modified electrode materials, using iron oxide nanoparticles with superparamagnetic behaviour and high saturation magnetization which are embedded in silica matrix, with excellent adsorption capability is described, in order to prepare an electrochemical sensor for nitrite detection. SEM and TEM confirm the formation of magnetic nanocomposites (NP-SiO2). The structure of magnetic nanoparticles (MNPs) and magnetic nanocomposites (NP-SiO2) were confirmed by FTIR analysis. The magnetic properties were analyzed with a vibrating sample magnetometer (VSM) and the values of saturation magnetization are 81 emu/g for magnetic nanoparticles and 43 and 33 emu/g for the two different samples of magnetic nanocomposites NP-SiO2 prepared with different concentration of SiO2 precursor. The removal efficiency of magnetic nanoparticles (MNPs) and magnetic nanocomposites (NP-SiO2) for TBO was investigated in correlation with different parameters, such as pH, initial dye concentration, and absorbent material concentration and the optimum conditions of TBO adsorption on magnetic nanocomposites (NP-SiO2) were established to be: 50 mg of magnetic nanocomposites (NP-SiO2) and initial TBO solution 15 mg /ml concentration at pH = 7. The electrocatalytic effect towards nitrite oxidation was studied for two samples NP-SiO2-1 and NP-SiO2-2. A good electrocatalytic effect towards nitrite oxidation was observed for both electrodes. It can be concluded that these new modified electrodes can be used in the future as amperometric sensors for nitrite detection in environmental samples.

Carpathian Journal of Earth and Environmental Sciences, August 2018, Vol. 13, No. 2, p. 435 - 446

Novel amperometric sensors based on poly-3,4-ethylenedioxythiophene (PEDOT) were prepared and characterized for nitrite detection. An experimental matrix of two substrate materials (glassy carbon and gold) and four electrolytes used for preparation of electrodes (water, acetonitrile, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide) were investigated for the preparation of the sensors. The obtained films were characterized using scanning electron microscopy, cyclic voltammetry, amperometry, and electrochemical quartz crystal microbalance. Both glassy carbon and gold electrodes modified with PEDOT showed excellent electrocatalytic activity toward nitrite oxidation. An improved influence of the electrodes prepared in ionic liquids could be observed for the detection of nitrite, expressed by higher electrocatalytic activity and better sensitivities. The sensors showed good stability, while only weak interferences with selected cations, anions, and small biomolecules were detected.

This work demonstrates that a Fe-exchanged zeolitic volcanic tuff from Cepari (Fe/CV) (Bistrita-Nasaud County, Romania) is suitable for the amperometric detection of H 2 O 2 , using new modified carbon paste electrodes based on this material (Fe/CV-CPEs). The physical-chemical characterization of natural (CV) and modified (Fe/CV) forms was realized using chemical analysis, optical microscopy, scanning electron microscopy (SEM), X-ray diffraction spectroscopy (XRD), energy dispersive X-ray spectroscopy (EDX) and Fourier transformed infrared (FTIR) spectroscopy. The resulting electrodes (Fe/CV-CPEs) were investigated using cyclic voltammetry and chronoamperometry measurements. The new electrodes showed good electrocatalytic activity toward H 2 O 2 reduction. The calibration curve for H 2 O 2 determination was linear up to 0.1 mM, with a detection limit (signal to noise ratio of 3) of 20 μM.

In this paper, an original solution for modeling and simulation of the nonlinear electrochemical process associated to the Laviron treatment is proposed. The graphite electrodes were coated with mediator by adsorption. The Laviron treatment was firstly used to determine the efficiency of modified electrodes coatings. The experimental data were obtained using an electrochemical experiment. The mathematical model of the process is expressed using a neural network with complex structure, an aspect which represents a novel approach in this domain. The main advantages of the proposed model are: its accuracy in relation to the experimental data and the fact that its usage permits the numerical simulation of the process, with multiple future applications. Based on the proposed neural model, an original procedure to determine the parameters of the nonlinear Laviron equation is presented. Another interesting element is represented by proving the fact that the value of heterogeneous electron-transfer rate constant kS is a function depending in the potential scan rate. This aspect is possible due to the original proposed approach of the Laviron treatment as a nonlinear process, on the entire range of input signals, in contrast with the big majority of the studies from the literature which are based on the linearization of this process near particular steady state working points.

International audience; This work describes the modification of a glassy carbon electrode with poly(Toluidine Blue O) (GC/poly-TBO) and single-walled carbon nanotubes (SWCNT) for the electrocatalytic oxidation of nitrite. GC/poly-TBO was prepared by electropolymerization and used as such or after immobilizing SWCNT on the polymeric film to give a composite GC/poly-TBO-SWCNT electrode. The electrochemical and catalytic behavior of both electrodes was studied comparatively. It was observed that the presence of SWCNT contributed to enhance the electrocatalytic response for nitrite oxidation, as measured by amperometry at +0.92 V vs. Ag/AgCl/KClsat and pH 7. The response was linear with respect to the nitrite concentration in the 0.001-4 mM range, with a detection limit of 0.37 mu M (based on signal to noise ratio of 3) for GC/poly-TBO-SWCNT. The proposed method was also applied to the determination of nitrite in a wastewater sample and compared to the spectrophotometric method.

In the context of population and consumption of natural resources growth, sustainable development is a development model aimed at a balance between economic growth, quality of life and environmental preservation in the medium and long term, without increasing consumption of natural resources beyond the capacity of the Earth. A distinctive feature of the European model of development is represented by the junction between the objective of increasing competitiveness and social and environmental objectives, which leads to deeper relationships between sustainable development and competitiveness. In this paper, we address the issue of competitiveness and sustainable development from two points of view: (1) a theoretical one, researching the area of competitiveness theory considering the development of the concept and current research tendencies and (2) a practical one: identifying how firm competitiveness (measured through return on assets and return on equity) affects socio-economic sustainable development in Romania (measured through the socio-economic sustainability index), considering data over the last 10 years. Although our study underlines an increasing interest on this topic in the research area, there is no common approach with different definitions, factors, models and methodologies developed and employed. Since sustainability and competitiveness are interconnected, an extensive vision of competitiveness should be available for both the economy and the society. Our findings are the basis of developing new theoretical models, justified by the need of a sustainable economy’s development to increase the competitiveness of public and private sectors, in order to attract financial resources necessary for financing the growth of economic entities.

In the globally post – financial crisis context, a current problem is that of companies’ evaluation. When considering the diverse and rapid changes of the external environment of a company, that put pressure on the management of organizations in shaping the internal capabilities to achieve the value objectives increasing, we find both academic and professional compelling concerns towards thinking and developing methodologies and indicators that may accurately include the needs to quantify a company’s values and also to implement organizational strategies that meet the perpetual demand of value creation and enhancement. Both literature and specialty practice offer many models for determining the value of the company, however, this paper does not propose an inventory of them, but brings light for those interested in an explanation of valuation models based on financial results generated by the use of business assets and justification of the need to consider the decision mainly in those strategies that ensure growth in terms of value and in terms of cash flow. Based on the comparison of two different perspectives, generating value for the enterprise and the value based on historical cost of property, the value obtained at the expense of future results arising from the use of this property, the paper also provides strategic options with financial valence needed to be followed by the management based on the correlation between the two types of values.

Iron doped carbon aerogels have been prepared by sol-gel polymerization of potassium salt of 2,4-dihydroxybenzoic acid with formaldehyde followed by an ion-exchange process between K+ doped wet gel and Fe(II) or Fe(III) ion aqueous solutions. The resulted Fe(II) or Fe(III) doped gels have been dried in supercritical conditions with liquid CO2 and then pyrolyzed in high temperature resulting two types of iron doped carbon aerogels. These aerogels were morpho-structural investigated by using BET method, transmission electron microscopy, X-ray diffraction and elemental analysis. Also, these iron doped carbon aerogels (CAD-Fe(2+) and CAD-Fe(3+)) were tested for realization of modified carbon paste electrodes. CAD-Fe(2+) aerogel showed better electrochemical activity than CAD-Fe(3+) and also a good electrocatalytic activity towards H2O2 reduction (expressed by an electrocatalytic efficiency of 404% measured at – 500 mV vs. SCE).

This paper focuses on entrepreneurship issues, specifically entrepreneurial intention in Romania, country that according to Hofstede's 1980 model presents features that do not stimulate the propensity towards entrepreneurship. We believe that because the entrepreneur is very sensitive to its environment, he is affected by the institutional and cultural context of his countr y. The analysis was undertaken upon a specific group: 3 rd year Management students of the Faculty of Economics and Business Administration, Timisoara. The results show that this group, through its socio-demographic profile and level of education, presents a different entrepreneurship profile than the one registered at a national level.

Currently, assessing a population’s quality of life is considered one of the most important aspects in health interventions’ evaluation across most of the European countries. However, in Romania its utility is unfortunately overlooked. In this context, the paper aims at providing an accurate estimate of QALYs for healthcare investment projects, determining through a questionnaire survey the utilities associated to quality of life for five critical medical conditions and thus calculating the related QALYs. The targeted population consisted of 100 patients and 50 medical personnel from the most important hospitals in the Western Region of Romania. The study’s outcome – a list of QALYs / medical condition – represent the foundation for future national research in improving the decision process of public resources allocation in healthcare.

Natural zeolites (zeolitic volcanic tuffs) cropped out from three regions of Transilvania, Vultureni (V), Pâglisa (P) and Macicas (M), were evaluated in the process of iron (V, P, M) and copper (M) removal from wastewaters. Iron and copper removal process was studied using a fixed bed column, when equilibrium and kinetic data were acquired. Four isotherms, Langmuir, Freundlich, Langmuir–Freundlich and Redlich–Peterson, were used to fit the experimental data obtained for each natural zeolite sample. Parameters of the adsorption isotherms were estimated from the experimental equilibrium data using MATLAB. Using these data the best fit with one of the chosen isotherm can be found. Isotherm constants were determined by linear regression analysis of the experimental data. We concluded that the mathematical model based on Freundlich isotherm is the most appropriate to describe the iron and copper exchange on our natural zeolite samples.

Two new phenothiazine derivatives, 3,7-di(m-aminophenyl)-10-ethyl-phenothiazine (DAEP) and 3,7-di(m-hydroxyphenyl)-10-ethyl-phenothiazine (DHEP), were used to modify solid graphite electrodes by adsorption from DMSO solution. Cyclic voltammetry and rotating disc electrode measurements, performed under different experimental conditions (pH, potential scan rate, rotation speed and NADH concentration) showed that: (i) both compounds undergo a quasi-reversible one electron / one proton redox process (ks = 0.73 s−1 for DAEP and 0.38 s−1 for DHEP), occurring at a formal standard potential which is not affected by the nature of substituent at positions 3 and 7; (ii) the pKa values of the adsorbed mediators are slightly different (6.9 for DAEP and 7.8 for DHEP); (iii) the second order rate constant for NADH electrocatalytic oxidation is significantly larger for DAEP (kobs,[NADH]=0 = 6014 M−1 s−1) than for DHEP (kobs,[NADH]=0 = 134 M−1 s−1). Considering the mediators’ structure, we made an attempt to explain the higher electrocatalytic efficiency of DAEP mediator.

A new approach is described for the photoelectrocatalytic oxidation of Reduced s-Nicotinamide Adenine Dinucleotide (NADH). It is based on a glassy carbon electrode (GCE) modified with a film of poly-Neutral Red (poly-NR) that is obtained by electropolymerization. Electrochemical measurements revealed that the modified electrode displays electrocatalytic and photo-electrocatalytic activity towards oxidation of NADH. If irradiated with a 250-W halogen lamp, the electrode yields a strongly increased electrocatalytic current compared to the current without irradiation. Amperometric and photo-amperometric detection of NADH was performed at +150 mV vs. Ag/AgCl/KClsat and the currents obtained are linearly related to the concentration of NADH. Linear calibration plots are obtained in the concentration range from 1.0 μM to 1.0 mM for both methods. However, the slope of the current-NADH concentration curve of the photo-electrocatalytic procedure was 2-times better than that obtained without irradiation.

It was firstly described that a glassy carbon electrode electropolymerized with methylene blue shows an efficient photoelectrocatalytic activity towards NADH oxidation in a phosphate buffer solution (pH 7.0). In order to perform the photoelectrocatalytic determination of NADH in a flow injection analysis (FIA) system, a home-made flow electrochemical cell with a suitable transparent window for the irradiation of the electrode surface was constructed. The currents obtained from the photoamperometric measurements in the FIA system at optimum conditions (flow rate of carrier solution, 1.3 mL min−1; transmission tubing length, 10 cm; injection volume, 100 μL; and constant applied potential, +150 mV vs. Ag/AgCl) were linearly dependent on the NADH concentration and linear calibration curves were obtained in the range of 1.0 × 10−7–2.0 × 10−4 M. The detection limit was found to be 4.0 × 10−8 M for photoamperometric determination of NADH.

Carbon paste electrodes modified with a phenoxazine derivative, Meldola blue, and a phenothiazine derivative, methylene green, both strongly adsorbed on a synthetic zeolite were investigated using either glassy carbon powder (Sigradur K, SK) or single-walled carbon nanotubes (SWCNT) as conductive electrode material. In the case of SWCNT based electrodes, the formal potential of both mediators was pH dependent, as expected for a redox process involving proton transfer. In contrast, the formal potential of both mediators of SK based modified electrodes was practically insensitive to pH. This behavior is discussed in terms of interactions existing in the heterogeneous system mediator-zeolite-electrode material.

Electropolymerization of a new phenothiazine derivative (bis-phenothiazin-3-yl methane, BPhM) on glassy carbon electrodes leads to electroactive and conducting layers of poly-BPhM. Based on the Laviron method, the kinetic parameters (the heterogeneous electron transfer rate constants k s and transfer coefficients α) were calculated out of the experimental and theoretical data. The theoretical data have been obtained by using the analogical modelling and numerical simulating method. The modified electrodes present high values of k s(~50s−1) in phosphate buffer solutions of different pH values. A good correlation of mathematical and numerical simulated kinetic parameters has been obtained, with the experimental values and the norm of residuals being very close to zero.

Electropolymerization of a new phenothiazine derivative (bis-phenothiazin-3-yl methane; BPhM) on glassy carbon (GC) electrode generates a conducting film of poly-BPhM. in stable contact with the electrode surface. The heterogeneous electron-transfer process corresponding to the modified electrode is characterized by a high rate constant (50.4 s(-1), pH 7). The CC/poly-BPhM electrode shows excellent electrocatalytic activity toward NADH oxidation. The rate constant for catalytic NADH oxidation, estimated from rotating disk electrode (RDE) measurements and extrapolated to zero concentration of NADH, was found to be 9.4 x 10(4) M-1 s(-1) (pH 7). The amperometric detection of NADH, at +200 mV vs. SCE, is described by the following electroanalytical parameters: a sensitivity of 1.82 mA M-1, a detection limit of 2 mu M and a linear domain up to 0.1 mM NADH. (c) 2008 Elsevier Ltd. All rights reserved. (Less)

A new approach for photoelectrocatalytic oxidation of NADH is described, based on a graphite electrode (G) modified with a new phenothiazine derivative, polyphenothiazine formaldehyde (PPF). Electrochemical measurements reveal that G/PPF presents a quasireversible voltammetric response, corresponding to a 2e(-)/2H(+) transfer and that G/PPF modified electrodes show electrocatalytic activity for NADH oxidation. When the surface of the G/PPF modified electrode was irradiated with a light source (250 W Halogen lamp), a significant increase in the electrocatalytic current was observed. The second order electrocatalytic rate constant (k(obs,[NADH]=0) = 3.9 x 10(3) M-1 s(-1), pH 7.0) was calculated from rotating disk electrode experiments, performed at various NADH concentrations. From amperometric measurements, it was noticed that, in the presence of light irradiation, the sensitivity of NADH detection (calculated as I-max/K-M ratio) increased ca. 3 times. (Less)

Two new composite electrodes, based on carbon paste (CP) incorporating a synthetic zeolite (13X type; Z) or a natural mineral clay (bentonite; B), both impregnated with a new phenothiazine derivative [3,7-di(m-aminophenyl)-10-ethyl phenothiazine; EPh], were developed. The physical properties of the EPh-Z and EPh-B composite materials have been investigated using scanning electron microscopy, energy dispersive X ray spectroscopy, Fourier transform infrared spectroscopy. Cyclic voltammetry (CV) and rotating disk electrode measurements were used for electrochemical characterization of the EPh-Z-CPEs and EPh-B-CPEs electrodes. CV measurements revealed a reasonably fast electron transfer rate for both modified electrodes. No significant differences, concerning the pH effect on the formal standard potential, the magnitude of the rate constants for heterogeneous electron transfer and the electrode response stability, were observed between the investigated electrodes. Both electrodes showed a good electrocatalytic activity for β-nicotinamide adenine dinucleotide (NADH) oxidation (for example, in the case of EPh-Z-CPEs the electrocatalytic rate constant was 1.1 × 104 M−1 s−1, at pH 7).

The electrochemical behavior of a new G-2-s-triazine-based dendrimer, 2,4,6-tris-{4-{4,6-bis-{4-{4,6-bis-[(1S,2S)-1,3-dihydroxy-1-(4-nitrophenyl)-prop-2-ylamino]-s-triazin-2-yl}-piperazin-1-yl}-s-triazin-2-yl}-piperazin-1-yl}-s-triazine, (I), was studied in dimethylsulfoxide solution by cyclic voltammetry, on platinum and graphite electrodes. The electrochemical properties of I were compared with that of one of its precursor, N-{4,6-bis{4-{4,6-bis[(1S,2S)-1,3-dihydroxy-1-(4-nitrophenyl)-prop-2-ylamino]-s-triazin-2-yl}-piperazin-1-yl}-triazin-2-yl}-piperazine), (II), together with that of the starting material, (1S,2S)-2-amino-1-(4-nitrophenyl)-propane-1,3-diol (“p-nitrophenylserinol”), (III).

Foraminiferal and calcareous nannofossil assemblages from the Eastern Carpathians (northern part of the Tarcau Nappe, Romania) were documented and correlated in order to reconstruct the palaeonvironmental settings and provide a biostratigraphic framework of the Plopu Formation. The benthic foraminiferal assemblages are dominated by flysch-type agglutinated taxa, suggesting a bathyal palaeodepth with frequent oscillations of the carbon compensation depth. The agglutinated foraminifera morphogroup analyses suggest different levels of organic matter influx and oxygenation. Both the foraminifera and calcareous nannofossil assemblages suggest a shift between the warm mid Eocene to the cooler late Eocene climate. Biostratigraphic data based on calcareous nannofossils (NP15–NP19/NNTe8–NNTe12 biozones) helped to establish the age of the formation. Four assemblages of benthic agglutinated foraminifera ( Psammosiphonella cylindrica – Nothia excelsa ; Paratrochamminoides spp. – Trochamminoides spp.; Karrerulina spp.– Reticulophragmium amplectens ; Spiroplectammina spectabilis ) correlated with calcareous nannofossil bioevents supported the placement of the mid to late Eocene transition within the Plopu Formation.

Two new modified carbon paste electrodes (CPEs) based on two different X type zeolites, a natural zeolitic volcanic tuff (NZ) and a NaX type synthetic zeolite (SZ), modified with methylene green (MG) were developed. Cyclic voltammetry measurements revealed a reasonably fast electron transfer rate and a good stability for both investigated electrodes. The observed differences between the electrochemical behavior of MG-NZ-CPEs and MG-SZ-CPEs (the effect of pH on the formal standard potential, the magnitude of the rate constants for heterogeneous electron transfer and electrode response decay) were explained in terms of zeolites structure. The modified electrodes showed moderate electrocatalytic effect towards H2O2 reduction and a relatively low limit of detection (0.5 mM for MG-NZ-CPEs).

The paper presents SQL power of periodic system using for didactic aim. The article is based on a PHP application developed to present a periodic system in a form, which can be used for answer at different questions, which can be asked related at the structure of elements. There are presented all queries that are needed to be use for classification of elements after different properties, the database, and user interface design.

Natural zeolites cropped out from Pâglisa (Romania) (P), were evaluated in the process of iron removal from model solutions. Experimental data were evaluated using linear and non-linear regression analysis. A comparison analysis between the two regression methods for estimating the isotherm parameters was made. Experimental data were fitted to Langmuir, Freundlich, and Redlich-Peterson isotherm equations. All four isotherm equations showed a good fit to the experimental data. The results showed that non-linear method could be a better way to obtain the isotherm parameters. Also the Freundlich isotherm proved to describe better iron exchange on natural zeolite.

The presence of light irradiation and immobilization of carbon nanotubes on graphite electrodes modified with polyphenothiazine formaldehyde (PPF) and bis-phenothiazin-3-yl methane (BPhM) leads to an increasing of sensitivity for NADH detection (calculated as I max /K M ratio). The paper presents the analogical modelling and numerical simulation for fitting the Michaelis-Menten equation to experimental data by a regression analysis. The program determines the theoretical kinetic parameters: K M and I max and they are compared with the values of the same parameters experimentally determined.

A stable electroactive thin film of poly-hematoxylin (poly-HT) was successfully prepared on a glassy carbon electrode (GCE) surface by recording successive cyclic voltammograms of 0.3 mM HT, in a phosphate buffer solution (pH 7.0) containing 0.1 M NaNO3, in the potential range of -0.5 to +2.0 V vs. Ag/AgCl. The deposition of HT on GCE surface can be explained through the electropolymerization process. This poly-HT modified electrode exhibited a good electrocatalytic activity towards the NADH oxidation in a phosphate buffer solution (pH 7.0), and led to a significant decrease in the overpotential by more than 320 mV compared with the bare GCE. In order to perform the photoelectrocatalytic determination of NADH in a flow injection analysis (FIA) system, a home-made flow electrochemical cell with a suitable transparent window for irradiation of the electrode surface was constructed. Flow rate of carrier solution, transmission tubing length, injection volume and applied potential for the amperometric and photoamperometric FIA studies were optimized as 1.3 mL min(-1),10 cm, 100 mu L and +300 mV vs. Ag/AgCl, respectively. The currents obtained from amperometric and photoamperometric measurements in FIA system at optimum conditions were linearly dependent on the NADH concentration and linear calibration curves were obtained in the range of 1.0 X 10(-7)-1.5 X 10(-4) M and in the range of 1.0 x 10(-7)-2.5 X 10(-4) M NADH, respectively. The relative standard deviation (RH)) of six replicate injections of 6.0 x 10(-5) M NADH was calculated as 2.2% and 4.3% for the amperometric and the photoamperometric method, respectively. The limit of detection was found to be 3.0 x 10(-8) M for the photoamperometric determination of NADH. (C) 2010 Elsevier B.V. All rights reserved.

International audience; This work demonstrates that iron-enriched natural zeolitic volcanic tuff (Paglisa deposit, Cluj county, Transilvania, Romania) resulting from a previous use as adsorbent in wastewater treatment can be recycled into effective electrode modifier applied to the electrocatalytic detection of hydrogen peroxide. After physico-chemical characterization of tuff samples using various techniques such as chemical analysis, X-ray diffraction, scanning electron microscopy, infrared spectroscopy, BET analysis and X-ray photoelectron spectroscopy, the electrochemical response of the iron-enriched zeolites was studied on the basis of solid carbon paste electrodes modified with these samples. The results indicate that iron centers in the zeolite are electroactive and that they act as electrocatalysts in the voltammetric and amperometric detection of H2O2. Best performance was achieved in phosphate buffer at pH 7, showing a sensitivity of 0.57 mA M−1 cm−2, a detection limit down to 60 μM, and a linear domain up to 100 mM H2O2.

The paper presents the dispersion of the concentration y(t, s) on the length (s) with respect to time (t), corresponding to the adsorption process of a phenothiazine derivative on graphite electrodes. The numerical simulation by equations with partial derivatives of the second order with two independent variables (t and s) (PDE II.2), based on (Mpdx) which associates with Taylor series was performed. Also, the adsorption process defined by PDE II.2 was included in a regulation scheme of concentration y(t, s) with multiple freedom levels. It insures good performances and a remarkable flexibility for extending the method in similar categories of applications.

A comparative study of the modeled, simulated and experimental values of kinetic parameters corresponding to six new phenothiazine derivatives of bis-(phenothiazin-3-yl)-phenyl-methane, bis-(10H-phenothiazin-3-yl)-methane (I), a polymer of phenothiazin formaldehyde (II), bis-(10-ethyl-3-phenothiazinyl)-methane (III) and derivatives of (10H-phenothiazin-3-yl)-phenyl-methane (IV,V,VI) adsorbed on spectrographic graphite was investigated. The kinetic parameters (the heterogeneous electron transfer rate constants ks and transfer coefficients alpha) are calculated using the Laviron treatment, from cyclic voltammetric measurements realized at different potential scan rates. It was obtained a good correlation of calculated kinetic parameters with the experimental values.

Numerical modelling and simulation of Koutecky-Levich equation for NADH electrocatalytic oxidation at graphite electrodes modified with a polymer of phenothiazin formaldehyde (PPF) was performed. There were obtained the second order electrocatalytic rate constants (kobs, [NADH]=0) from rotating disk electrode experiments, at various concentrations of NADH and phosphate buffer with different pH values.

One of the central questions in entrepreneurship is why some firms succeed and others fail. Determining what factors influence performance has implications for prospective entrepreneurs, as well as advisors, investors, managers and so forth. Thus, using extensive data over a period of 14 years, this study explores and tests the sign of the relationship between microeconomic factors and financial performance. The dataset includes 55 Romanian industrial companies listed at the Bucharest Stock Exchange and covers the period of 1999-2012. Through a panel data analysis, results indicate that the sign of the relationship is positive and statistically significant; supporting the importance and independence of the sets of factors in explaining performance.