Thermal Behaviour of the N-donor Adducts of Metal Saccharinates III. Imidazole saccharinates of Co(II), Ni(II) and Cd(II)

The complexes [M(HIm)₄(H₂O)₂](sac)₂ (M=Co, Ni) and [Cd(HIm)₂(sac)₂]₂ with saccharin (sac) and imidazole (HIm) were synthesized and their thermal (TG, DTG and DTA) behaviour in the interval from room temperature up to 1000°C in a static air atmosphere was investigated. Irrespectively of whether the deprotonated saccharinato residues are present as ligands or ions or both as ligands and ions, the anhydrous complexes regularly decompose in two stages. The thermal data of 16 saccharinato complexes (including the title compounds) were correlated with the respective structural data. The general thermal stability order of the saccharinato complexes can be represented as: Pb(II)<Zn(II)<Co(II)Ni(II)<Cd(II) (the stability of the Cu saccharinates depends on the particular compound) and is dictated by several structural factors, e.g. metal ionic radii, participation of the water in the coordination sphere of the metal and other structural characteristics. This revised version was published online in August 2006 with corrections to the Cover Date.     

Vibrational Spectra of Magnesium Hydrogenphosphate Trihydrate and of its Manganese Analogue

Abstract

The infrared (IR) and Raman spectra of MgHPO₄. 3H₂O and of a series of partially deuterated analogues as well as the IR spectra of MnHPO₄. 3H₂O have been recorded and interpreted. The analysis of the IR spectra in the HOD bending region rules out the possibility of existence of H₃OC⁺ ions in the structure.     

Glassy carbon electrode modified with a film of poly(Toluidine Blue O) and carbon nanotubes for nitrite detection

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/KCl_sat 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 μM (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.     

Numerical modelling and simulation of Laviron treatment for poly-phenothiazine derivative-modified glassy carbon electrodes

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.     

Clusters in weighted macroeconomic networks: the EU case. Introducing the overlapping index of GDP/capita fluctuation correlations

GDP/capita correlations are investigated in various time windows (TW), for the time interval 1990–2005. The target group of countries is the set of 25 EU members, 15 till 2004 plus the 10 countries which joined EU later on. The TW-means of the statistical correlation coefficients are taken as the weights (links) of a fully connected network having the countries as nodes. Thereafter we define and introduce the overlapping index of weighted network nodes. A cluster structure of EU countries is derived from the statistically relevant eigenvalues and eigenvectors of the adjacency matrix. This may be considered to yield some information about the structure, stability and evolution of the EU country clusters in a macroeconomic sense.     

Adsorption process of phenothiazine solution in dimethyl sulfoxide on graphite electrodes

In this paper, an original solution for the modeling and simulation of the adsorption process of a phenothiazine derivative on graphite electrodes is presented. The adsorption process is considered a distributed parameter one, due to the fact that the adsorbed phenothiazine quantity is a function depending on two independent variables. The structure parameters of the adsorption process, which define the influence of both independent variables, are determined using an experimental identification method. The experimental data are obtained through an experiment which is based on the process step response. In order to simulate the adsorption process, the approximate analytical solution, representing the process model, is determined. The simulation results prove the model generality; it is being simulated in relation to both independent variables.     

Structural studies of some o-substituted S-phenyl thiobenzoates. I. Crystal structure of S-phenyl o-chlorothiobenzoate and S-phenyl o-bromothiobenzoate

Structural characteristics ofS-phenylo-chlorothiobenzoate (I) andS-phenylo-bromothiobenzoate (II) have been investigated by single crystal X-ray diffraction. It was shown that the crystals are isomorphous and crystallize in the monoclinic space groupP2₁ withZ=2. The unit cell parameters are:a=10.150(3),b=7.672(2),c=7.595(2) Å,=91.28(1)° for C₁₃H₉ClOS (compoundI) anda=10.141(3),b=7.764(2),c=7.653(2) Å,=90.14(3)° for C₁₃H₉BrOS (compoundII). The structures were solved by heavy-atom methods and refined by full-matrix least-squares, from room-temperature data collected with a Philips PW 1100 diifractometer, to conventionalR factors of 0.056 forI and 0.044 forII. The structures consist of independent molecules held together by intermolecular interactions. Molecular packing is influenced by the presence ofo-substituted Cl or Br atoms. The Cl atoms in structureI as well as the Br ones in structureII are directed to the centers of the pi-electronic system of theo-substituted phenyl rings belonging to the neighboring molecules. The six ClC and BrC distances range from 3.651(10) to 3.869(9) Å and from 3.644(6) to 3.890(6) Å, respectively. The C1 (or Br) atom is additionally directed towards the two carbon atoms (C3 and C4) in anothero-substituted phenyl ring, the C1lC and BrC distances being 3.786(9) and 3.849(10) Å inI and 3.727(6) and 3.881(6) Å inII. The torsion angle C6-C7-S-C8 is-170.2(7)° inI and 168.6(4)° inII. The angles between the planar O-C7-S central fragment of the molecule, on the one hand, and theo-substituted phenyl ring, on the other, are 113.9(3)° in I and 110.9(2)° inII. The corresponding values for the angles between the O-C7-S fragment and the nonsubstituted phenyl ring are 115.8(3)° and 114.3(2)° in compoundsI andII, respectively.     

Application of linear regression analysis for iron and copper removal process using natural zeolites

Natural zeolites (zeolitic volcanic tuffs) cropped out from three regions of Transilvania, Vultureni (V), Pagli?a (P) and M?cica? (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?CFreundlich and Redlich?CPeterson, 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.     

Vibrating Portable Machine-Tools Acting on Human Operator

This paper will be a short presentation of the specialized literature and international standards about the importance of vibration action of portable machine tools on human body and particularly on the hand-arm system. Exposure to harmful vibrations can lead to health problems and disorders, especially in the upper joints and dorsal region of the human body. A detailed understanding of the undesirable effects of vibration on the human body is essential to achieve administrative and technical prevention. In modern times, vibration studies become more frequent, decisive for the many machines, vehicles and construction. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)