Synthesis,crystal and molecular structure of the novel complex [dinitrato{N,N-bis(1–methylbenzimidazol-2–ylmethyl)methylamine}]cobalt(II)

Co(NO3)2·6H2O reacts with N,N-bis(1–methylbenzimidazol-2–ylmethyl)methylamine (Me2L) in MeOH/ Et2O solution at ca. 5°C, yielding a novel, penta-coordinate complex, formulated as [Co(NO3)2(Me2L)], which was characterized by means of structural, spectroscopic and magnetic measurements. The Co atom is coordinated in distorted trigonal bipyramidal geometry by three N and two O atoms. The ligand Me2L is coordinated in a facial mode and two coordinated O atoms from the nitrato ligands are in cis-positions.     

Gradual transformation of Ca(OH)<Subscript>2</Subscript> into CaCO<Subscript>3</Subscript> on cement hydration

The low temperature of decomposition of some calcium carbonates and the bending of the TG curves of hydrated cement between 500 and 800°C suggested the presence of some complex compound(s), which needed complementary investigation (XRD, TG). Stepwise transformation of portlandite (and/or lime) into calcium carbonate, with intermediate steps of calcium carbonate hydroxide hydrates (CCH-1 to CCH-5), was indicated by the previous study of two OPC. This was checked here on four cements ground for t _g=15, 20, 25 and 30 min and hydrated either in water vapour, successively at RH=1.0, 0.95 and 0.5 for 2 weeks each (WR1, WR2 and WR3, respectively) or as mortars in liquid water (1m), followed by WR as above. The d[001] spacing of portlandite was confirmed to vary: here between the lowest and the highest standard values. The diffractograms of n=32 different samples were analyzed for presence of standard CCH peaks, generally slightly displaced. These were: CCH-1 [Ca₃(CO₃)₂(OH)₂]: N=11 peaks, of three different d[hkl] spacings, CCH-2 [Ca₆(CO_2.65)₂(OH₆₅₇)₇(H₂O)₂]: N=10 for two d[hkl], CCH-3 [Ca₃(CO₃)₂(OH)₂·1.5H₂O]: N=14 for five d[hkl], CCH-4, ikaite [CaCO₃(H₂O)₆]: N=13 for six d[hkl], CCH-5[CaCO₃(H₂O)]: N=15 for five d[hkl]. Thus the most probable is the presence of the last three. The stepwise transformation of Ca(OH)₂ into CaCO₃ was confirmed:     

Separation of microorganisms using electromigration techniques

Like other colloidal particles bacteria have a surface charge that originates from the ionization of surface molecules and of the adsorption of ions from solution. Bacterial cell wall and membranes containing numerous proteins, lipid molecules, teichoic acids, lipopolisaccharides which give them characteristic charge. Therefore, bacterial cells undergo electrophoresis in a free solution with their own mobility depending on ionic strength and pH of buffer solution. Various electromigration techniques can be used to separate and determine the intact cells. Successful separation of five species of bacteria was obtained using a trimethylchlorosilane-modified capillary and a divinylbenzene-modified with suppressed EOF over a short distance (8.5 cm). The utilization of coated capillaries prevents adsorption of bacteria to the capillary wall. Another approach is utilization of a dilute dissolved polymer, polyethylene oxide (PEO) in the running buffer as a non-bonded coating for the purpose of altering the EOE These experiment have proved the possibility of diagnosing a variety of diseases and the ability to separate and identify viable cells.     

Optimizing Carbon Nanotubes Dispersing Agents from the Point of View of Ion‐selective Membrane Based Sensors Performance – Introducing Carboxymethylcellulose as Dispersing Agent for Carbon Nanotubes Based Solid Contacts

The influence of dispersing agent used to prepare carbon nanotubes solid‐contact on the performance of all‐solid state ion‐selective electrodes has been evaluated. It is shown that excess of surfactant dispersing agent is leading to deterioration of sensor performance, however, removal of dispersing agent – a typically applied approach – is resulting in substantial change of transducer layer physical properties, which can influence sensor performance. As remedy we propose application of a polymeric dispersing agent – carboxymethylcellulose. Thus obtained ion‐selective electrodes are characterized by high potential readings stability both within day and between days.     

Nanocomposites of gold nanoparticles and graphene oxide towards an stable label-free electrochemical immunosensor for detection of cardiac marker troponin-I

A stable label-free amperometric immunosensor is presented based on gold nanoparticles and graphene oxide nanocomposites for detection of cardiac troponin-I in the early diagnosis of myocardial infarction. For designing of the sensing platform, firstly the nanocomposites based on GO and AuNPs were prepared and anchored on electrode surfaces. The formed nanocomposites provided a platform with big surface area for loading anti-cTnI capture antibody, and worked as a bridge for fast electron transfer subsequently increased the sensitivity. Moreover, the linkages between AuNP, GO, and electrodes were based on covalent bonding by aryldiazonium salt coupling chemistry, which favors the stability of the sensing interface. Finally, the anti-cTnI detection antibody was immobilized on GO tailored with ferrocene molecules, functioning as the signal reporter for the detection of cTnI. The modification process was monitored using electrochemistry, SEM, XPS. The herein immunosensor demonstrates a good selectivity and high sensitivity against human-cTnI, and is capable of detecting cTnI at concentrations as low as 0.05 ng mL⁻¹, which is 100 times lower than that possible by conventional methods. It is potential to design the portable sensing platform based on AuNPs and GO nanocomposites for future point-of-care diagnostics.     

Experimental (FT‐IR) and theoretical (DFT) studies on prototropy and H‐bond formation for pyrazine‐2‐amidoxime

The results of the first structural studies (with the use of both experimental and theoretical methods) on pyrazine‐2‐amidoxime (PAOX) were shown and discussed. FT‐IR spectra were recorded in different concentrations of the PAOX in apolar solvent to check the possibility of the inter‐ or intramolecular hydrogen‐bond formation. All possible tautomers–rotamers of PAOX were then theoretically considered at the DFT(B3LYP)/6‐311+G** level in vacuo. For selected isomers, calculations were also performed at higher levels of theory {B3LYP/6‐311+G(3df,2p) and G3B3}. Based on the results of DFT calculations, the most stable isomers were found, and their total free energies and infrared spectra were calculated. The energy variation plots for the N8?C7?N9?O10 and N1?C2?C7?N9 dihedral angles were also computed to find two energy barriers, one for E/Z isomerization around the C7?N9 double bond and the other one for rotation of the pyrazinyl ring around the C2?C7 single bond. The results show that the stability of the PAOX isomers strongly depend on their configuration and orientation of the substituents. The possibilities of inter‐ and intramolecular hydrogen bonds were also experimentally and theoretically checked. Finally, a potential of mean force was determined in CHCl₃ for a dimer of PAOX with hexamethylphosphoramide. Both, experimental and theoretical results are in agreement. Copyright © 2016 John Wiley & Sons, Ltd.     

Krause's model of opinion dynamics on isolated time scales

We analyze a bounded confidence model, introduced by Krause, on isolated time scales. In this model, each agent takes into account only the assessments of the agents whose opinions are not too far away from its own opinion. We show that the behavior of the model depends strongly on the graininess function μ: If μ takes values in the interval ]0,1], then our discrete time scale model behaves similarly to the classical one, but if μ takes values in ]1,+∞[, then the model has different properties. Simulations are performed to validate the theoretical results. Copyright © 2016 John Wiley & Sons, Ltd.     

Determination of the lipophilicity of quinolinesulfonamides by reversed-phase HPLC and theoretical calculations

Reversed-phase high-performance liquid chromatography analyses were used for the determination of the retention factor (log k) of a set of quinolinesulfonamides. The analyses utilized a mixture of acetonitrile/water as the mobile phase. The log k values were linearly dependent on the concentration of acetonitrile and extrapolated to 100% water and gave the lipophilicity parameter log k_w. The parameter log P_HPLC was determined from log k_w values using the calibration curve obtained for five standards. The log P_HPLC parameters are discussed in terms of structure–lipophilicity relationships. Furthermore, the theoretical lipophilic parameters (log P_calc) for all compounds were calculated using chemical programs (e.g., Advanced Chemistry Development (ACD/ logP), miLogP, AlogP, ClogP, and Pallas). The determined log P_HPLC and calculated log P_calc values were compared by linear regression analysis.     

Total Colorings of Graphs with Minimum Sum of Colors

The total chromatic sum of a graph is the minimum sum of colors (natural numbers) taken over all proper colorings of vertices and edges of a graph. We construct infinite families of graphs for which the minimum number of colors to achieve the total chromatic sum is larger than the total chromatic number.     

Infinite sheet structure of disodium tetra-μ-acetato- dichlorodirhodate(II) tetrahydrate

The binuclear rhodium(II) complex Na2[Rh2Cl2(OAc)4]· 4H2O has an infinite sheet structure. Binuclear anionic complexes [Rh2Cl2(OAc)4]2– are bound with cationic entities. The Na+ cation has pseudooctahedral coordination and is surrounded by two chloro ligands and two oxygen atoms of bridging acetato ligands of two [Rh2Cl2(OAc)4]2– anions and two water molecules. Both Cl and H2O are bridging ligands involved in formation of the Na+ chains. The remaining water molecules are located between sheets.