Non-isothermal studies on crystallization kinetics of tellurite 20Li<Subscript>2</Subscript>O-80TeO<Subscript>2</Subscript> glass

Structural and thermal properties of the 20Li₂O-80TeO₂ glass were studied using X-ray diffraction analysis and differential scanning calorimetry techniques to understand and control the crystallization process on this glass. The γ-TeO₂, α-TeO₂ and α-Li₂Te₂O₅ phases were identified during the crystallization in this glass. Activation energies and Avrami exponent n were calculated from non-isothermal measurements for glasses with different particle size. The mean values of Avrami exponent were obtained for glasses with 63–75 and 45–63 μm particle sizes such as , but glasses with particle size 38–45 μm and smaller than 38 g,m presented .     

Calculation of the specific heat close to the multicritical and second order phase regions in ND<Subscript>4</Subscript>Cl

We calculated the specific heat C _V of ND₄Cl under the prediction of an Ising model presented here. Our calculated C _V agrees with the experimental C _P data for the multicritical (P = 0.1 MPa) and second order (P = 150 MPa) phase regions in this crystalline system. This agreement is particularly good above T _C 250 K) for the multicritical regime and below T _C 261 K) for the second order phase transition in ND₄Cl. This shows that the observed behaviour of ND₄Cl can be well described by an Ising model close to the phase transitions considered in this crystalline system.     

Binding of nontarget microorganisms from food washes to anti-<Emphasis Type="Italic">Salmonella</Emphasis> and anti-<Emphasis Type="Italic">E. coli</Emphasis> O157 immunomagnetic beads: minimizing the errors of random sampling in extreme dilute systems

For most applications, 3–5 observations, or samplings (n), are utilized to estimate total aerobic plate count in an average population (μ) that is greater than about 50 cells, or colony forming units (CFU), per sampled volume. We have chosen to utilize a 6 × 6 drop plate method for bacterial colony selection because it offers the means to rapidly perform all requisite dilutions in a 96-well format and plate these dilutions on solid media using minimal materials. Besides traditional quantitative purposes, we also need to select colonies which are well-separated from each other for the purpose of bacterial identification. To achieve this goal using the drop plate format requires the utilization of very dilute solutions (μ < 10 CFUs per sampled drop). At such low CFU densities the sampling error becomes problematic. To address this issue we produced both observed and computer-generated colony count data and divided a large sample of individual counts randomly into N subsamples each with n = 2–24 observations (N × n = 360). From these data we calculated the average total mean-normalized (, n = 360) deviation of the total standard deviation (s _tot) from each jth subsample’s estimate (s _j ), which we call Δ. When either observed or computer-generated Δ values were analyzed as a function of , a set of relationships () were generated which appeared to converge at an n of about 18 observations. This finding was verified analytically at even lower CFU concentrations (). Additional experiments using the drop plate format and n = 18 samplings were performed on food samples along with most probable number (MPN) analyses and it was found that the two enumeration methods did not differ significantly. Any reference to a particular brand or company name does not constitute an endorsement of it by the U.S. Department of Agriculture over other similar brands or companies that are not mentioned.     

Thermodynamic characteristics of the system NaNO<Subscript>2</Subscript>-NaNO<Subscript>3</Subscript>

The activities and activity coefficients of the components of the system NaNO₂-NaNO₃, obtained from experimental saturated vapor pressures measured at 798, 823, and 848 K, were used to calculate the total and excess partial molar Gibbs energies , , entropies , , and total relative and excess thermodynamic properties G, G ^ex, S, S ^ex of the system.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 10, 2004, pp. 1747–1749.Original Russian Text Copyright © 2004 by Glazov, Dukhanin, Dkhaibe, Losev.     

Kinetics of the uninhibited and ethanol-inhibited CoO,Co<Subscript>2</Subscript>O<Subscript>3</Subscript> and Ni<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyzed autoxidation of sulfur(IV) in alkaline medium

For getting an insight into the mechanism of atmospheric autoxidation of sulfur(IV), the kinetics of this autoxidation reaction catalyzed by CoO, Co₂O₃ and Ni₂O₃ in buffered alkaline medium has been studied, and found to be defined by Eqs. I and II for catalysis by cobalt oxides and Ni₂O₃, respectively.

Relative thermodynamic stabilities of the isomeric dihydrofurans and isomeric dihydropyrans. An experimental and DFT study

The relative thermodynamic stabilities of 2,5-dihydrofuran (1) and 2,3-dihydrofuran (2), and of 3,4-dihydro-6H-pyran (3) and 3,4-dihydro-2H-pyran (4), were determined at several temperatures by base-catalyzed equilibration in DMSO solution. For 1 → 2, = –15.4±0.1 kJ mol⁻¹, =–12.6±0.5 kJ mol⁻¹, and =9.5±1.3 J K⁻¹ mol⁻¹ at 298.15 K. The second-law reaction enthalpy agrees with literature data based on calorimetric enthalpies of hydrogenation of the isomeric forms in hexane. For 3 → 4, =–19.3±0.2 kJ mol⁻¹, = –18.9±1.1 kJ mol⁻¹ and =1.1±3.0 J K⁻¹ mol⁻¹ at 298.15 K: the experimental reaction enthalpy is in marked disagreement with literature data based on estimation. On the other hand, both of the experimental reaction enthalpies of the present study are in good agreement with DFT calculations using the B3LYP functional and 6-311+G(2d,p) basis set.     

On the interaction between mercury(II) salts and 3-methylpyrazoline-5-one. The first crystal structure of a cyclic organomercuric compound with a dimercurated methylenic carbon atom

Synthesis and characterization of two types of novel organomercury derivatives of 3-methylpyrazoline-5-one (MepzH₂-one), (XHg)₂(MepzH-one) (X = Cl⁻, Br⁻) and Hg(MepzH-one)₂ are described. The ¹H and ¹³C NMR data revealed existence of dimercurated compounds in the dimethylsulfoxide-d ₆ solution. NMR spectra confirmed that the mercuration took place at the C-4 atom of the pyrazole ring. X-ray crystal structure analysis of 4,4-bis(chloromercurio)-3-methylpyrazoline-5-one revealed almost linear coordination of both mercury atoms [Hg–C 2.099(6) and 2.104(5) ; Hg–Cl 2.330(2) and 2.338(2) ; C–Hg–Cl 171.1(2) and 174.4(2)°]. The slight deviation from linearity is caused by contacts with nitrogen or oxygen atoms from the neighbouring molecule [HgN 2.768(5) and HgO 2.748(5) ]. The molecules are interconnected by hydrogen bonds N–HCl of 3.286(5) .     

An exact expression for the wiener index of a TUC<Subscript>4</Subscript>C<Subscript>8</Subscript>(R) nanotorus

The Wiener index of a graph G is defined as , where V(G) is the set of all vertices of G and for denotes the length of a minimal path between x and y. A C ₄ C ₈ net is a trivalent decoration made by alternating squares C ₄ and octagons C ₈. It can cover either a cylinder or a torus. In this paper, an algorithm for computing the distance matrix of a C ₄ C ₈(R) nanotorus T = T[p,q] is given. Using this matrix, the Wiener index of T is computed.     

Binuclear cobalt(II/II) and cobalt(II/III) chelates with O<Subscript>2</Subscript>N<Subscript>2</Subscript> ligands: synthesis,structure and magnetic studies

Abstract  The title complexes and have been synthesized in excellent yields by reacting Co(OAc)₂·4H₂O with H₂L¹ and H₂L², respectively, in acetonitrile solution. Here, [L¹]²⁻ and [L²]²⁻ are the deprotonated forms of N,N-bis(2-hydroxybenzyl)-N′,N′-dimethylethylenediamine and N,N-bis(2-hydroxybenzyl)-2-picolylamine, respectively. The crystal structures of and were determined by x-ray crystallography. In , each cobalt atom has distorted trigonal bipyramid geometry, while in , each cobalt atom has distorted octahedral geometry. Variable temperature magnetic moment measurements show weak antiferromagnetic interaction in . The magnetic characterization for is in agreement with the presence of Co(II) and Co(III) centers. Graphical Abstract  The title complexes and have been synthesized in excellent yields by reacting Co(OAc)₂·4H₂O with dianionic N₂O₂ coordinating ligands. In complex 1, each cobalt atom has distorted trigonal bipyramid geometry, while in complex 2, each cobalt atom has distorted octahedral geometry. Variable temperature magnetic moment measurements show weak antiferromagnetic interaction in complex 1. The magnetic characterization for complex 2 is in agreement with the presence of Co(II) and Co(III) centers. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Dielectric and tunable properties of highly (110)-oriented (Ba<Subscript>0.65</Subscript>Sr<Subscript>0.35</Subscript>)TiO<Subscript>3</Subscript> thin films deposited on Pt/LaNiO<Subscript>3</Subscript>/SiO<Subscript>2</Subscript>/Si substrates

Highly (110)-oriented Ba_0.65Sr_0.35TiO₃ films were deposited on Pt/LaNiO₃/SiO₂/Si substrates by a sol–gel method. It was found that the (110)-preferred Pt film was very effective for growing (110)-oriented ferroelectric films with perovskite structure. The as-grown Ba_0.65Sr_0.35TiO₃ films showed good dielectric properties with dielectric constant and loss tangent tan δ = 0.026. Excellent dielectric tunability was also achieved in the (110)-oriented films. With applying an electric field of 230 kV/cm at 100 kHz, the dielectric tunability and the figure of merit can reach up to 63.4% and 16, respectively. These results indicate that the highly (110)-oriented Ba_0.65Sr_0.35TiO₃ film is a promising candidate for the applications in microwave tunable devices.     

Syntheses and Structure of Gd<Subscript>3</Subscript>Rh<Subscript>1.940(7)</Subscript>In<Subscript>4</Subscript>

Summary. The gadolinium–rhodium–indide Gd₃Rh_1.940(7)In₄ was prepared by arc-melting of the elements and subsequent annealing in a corundum crucible in a sealed silica tube. Gd₃Rh_1.940(7)In₄ adopts the hexagonal Lu₃Co_1.87In₄ type, space group , a = 781.4(5), c = 383.8(3) pm, wR2 = 0.0285, BASF = 0.375(1) (merohedric twinning via a twofold axis (xx0)), 648 F² values, 22 variables. The structure is derived from the well known ZrNiAl type through an ordering of rhodium and indium atoms on the Ni2 sites. The Rh/In ordering forces a reduction of the space group symmetry from to , leading to merohedric twinning for the investigated crystal. The Rh1 site has an occupancy of only 94.0(7)%. The investigated crystal had a composition Gd₃Rh_1.940(7)In₄. The main geometrical motif are three types of centered, tricapped trigonal prisms, i.e., [Rh1In2₆Gd₃], [Rh2Gd₆In2₃], and [In1Gd₆In2₃]. The shortest interatomic distances occur for Rh–In (276–296 pm) followed by In–In (297 pm). Together, the rhodium and indium atoms build up a three-dimensional [Rh_1.940(7)In₄] network, in which the gadolinium atoms fill slightly distorted pentagonal channels. The crystal chemistry of Gd₃Rh_1.940(7)In₄ is discussed on the basis of a group-subgroup scheme.     

Densities and Volumetric Properties of Binary Mixtures of Formamide with 1-Butanol, 2-Butanol, 1,3-Butanediol and 1,4-Butanediol at Temperatures between 293.15 and 318.15 K

The densities of binary mixtures of formamide (FA) with 1-butanol, 2-butanol, 1,3-butanediol, and 1,4-butanediol, including those of the pure liquids, over the entire composition range were measured at temperatures (293.15, 298.15, 303.15, 308.15, 313.15 and 318.15) K and atmospheric pressure. From the experimental data, the excess molar volume, V _m ^E, partial molar volumes, and , at infinite dilution, and excess partial molar volumes, and , at infinite dilution were calculated. The variation of these parameters with composition and temperature of the mixtures are discussed in terms of molecular interactions in these mixtures. The partial molar expansivities, and , at infinite dilution and excess partial molar expansivities, and , at infinite dilution were also calculated. The V _m ^E values were found to be positive for all the mixtures at each temperature studied, except for FA + 1-butanol which exhibits a sigmoid trend wherein V _m ^E values change sign from positive to negative as the concentration of FA in the mixture is increased. The V _m ^E values for these mixtures follow the order: 1-butanol < 2-butanol < 1,3-butanediol < 1,4-butanediol. It is observed that the V _m ^E values depend upon the number and position of hydroxyl groups in these alkanol molecules.     

Constant current anodic stripping chronopotentiometric determination of uranium in uranium mineral ores via accumulation of K<Subscript>2</Subscript>UO<Subscript>2</Subscript>[Fe(CN)<Subscript>6</Subscript>] on the palladium plated aluminum electrode

In the present work the uranyl hexacyanoferrate (K₂UO₂[Fe(CN)₆]) is deposited on the palladized aluminum (Pd-Al) electrode from a \textUO₂^{2 +} + \textFe( \textCN )₆ ^{- 3} {\text{UO}}_{2}^{2 + } + {\text{Fe}}\left( {\text{CN}} \right)_{6}^{ - 3} solution. Then the anodic stripping chronopotentiometry (ASCP) was used to strip the K₂UO₂[Fe(CN)₆] from the Pd-Al surface. The operational conditions including: pH, K₃Fe(CN)₆ concentration, deposition potential, deposition time and stripping current were optimized. The ASCP calibration graph was linear in concentration range 10–460 μM. of \textUO₂^{2 +} {\text{UO}}_{2}^{2 + } and the detection limit was 8.5 μM. The interference of some concomitant ions during the deposition process of K₂UO₂[Fe(CN)₆] was studied. The proposed method was successfully applied for analysis of some uranium mineral ores.     

Synthesis and Structure of the Copper(II) Complex with <Emphasis Type="Italic">ortho</Emphasis>-Phthalic Acid and 1-Methylimidazole [Cu(HPht)<Subscript>2</Subscript>(1-CH<Subscript>3</Subscript>Im)<Subscript>2</Subscript>]

A new Cu(II) complex [Cu(HPht)₂(1-CH₃Im)₂] (I), where HPht is the monoanion of o-phthalic acid and 1-CH₃Im is 1-methylimidazole, is synthesized and characterized by IR spectroscopy, thermogravimetry, and X-ray diffraction analysis. Compound I contains molecular complexes in which the o-phthalic acid residue is monodeprotonated and linked to a metal through the carboxyl group in a 1,3-chelate mode. The cis-octahedral coordination of copper is formed by two HPht residues and two 1-CH₃Im molecules. The distances are Cu-N1.945(6) Å, Cu-O2.018(5) Å and 2.374(6) Å. Polymeric chains are formed in complex I due to intermolecular hydrogen bonds. The chains are unified into layers by the interactions between the 1-CH₃Im molecules of the adjacent complexes.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 8, 2005, pp. 630–635.Original Russian Text Copyright © 2005 by Gherco.     

Theoretical study of static electric properties of benzothiazole containing push–pull systems as potential candidates for NLO materials

The dipole moments μ, static polarizabilities , and first hyperpolarizabilities β _vec of benzothiazole based push–pull chromophores have been theoretically investigated by means of SCF-HF and DFT (B3LYP, B3PW91) methods with cc-pVDZ basis sets at geometries optimized with 3-21G basis sets. The main attention has been paid to hyperpolarizability β _vec as a microscopic quantity directly linked with the nonlinear optical (NLO) response of materials with the aim to choose the most suitable candidate(s) for NLO materials from the set of 24 molecules. The 4-dimethylamino-4′-nitrostilbene (DANS) has also been included as a reference compound. The influence of various structural modifications of benzothiazole containing chromophores on μ,, and β _vec has been studied. These modifications involve the variation in unsaturated chain length connecting the aromatic units, different positions of electron withdrawing NO₂ and CN group attached to four possible positions in benzothiazole fragment, addition of the second NO₂ group, and the replacement of benzene by five-membered heteroaromatic rings (pyrrole, furan, thiophene) at N(CH₃)₂ site. The structural parameters, frontier orbitals and relative stabilities of these systems are also reported. The DFT scheme exaggerates the magnitude as well as the chain length dependence of β _vec with respect to the HF results. Both B3LYP and B3PW91 functionals give very close results. The DFT optimized structures are characterized by larger delocalization, planarity, and polarization of substituents. The best candidates for NLO materials have been identified from the studied series based on the β _vec values.     

Electrochemical dissolution of Mn<Subscript>3</Subscript>O<Subscript>4</Subscript> in acid solutions

The present study deals with the electrochemical reductive dissolution of Mn₃O₄, which was added to carbon-paste electroactive electrodes (CPEEs) in acid solutions. It was found that in the experimental conditions the thermodynamically stable form of manganese was . Kinetic features of the electrochemical reductive dissolution of Mn₃O₄, which was realized under potential cycling conditions (+1.0 V→−0.7 V→+1.0 V), were determined by the electrode polarization direction. It was shown that the cathodic reduction of Mn₃O₄ was accomplished in three stages. Manganese was dissolved in the supporting solution only at the third stage. The first two stages involved solid-phase reactions. The anodic cycling stage included an active dissolution of Mn₃O₄ and the lower manganese oxide (MnO) accumulated on the electrode surface during the cathodic reduction.     

Synthesis and magneto-structural correlation of a new maleato bridged copper(II) coordination polymer

A one-dimensional (1-D) copper(II) coordination polymer [Cu(maleate)(2,2′-bipyridyl)] _n ·2H₂O has been synthesised. Single crystal X-ray diffraction study reveals that maleate ion bridges two adjacent copper(II) centres along the chain in a syn–anti fashion. A complete cryomagnetic investigation of the title complex correlates well with the distorted square pyramidal geometry of the central copper(II) ion and bridging nature of the maleate. A τ value of 0.26 indicates the distortion towards tbp coordination allowing the magnetic orbital to acquire some character leading to a weak antiferromagnetic interaction having J = −0.26 cm⁻¹. The complex has also been firmly established from several other instrumental techniques like Fourier transform infrared (FT-IR) and EPR spectroscopies.     

An <Emphasis Type="Italic">ab initio </Emphasis> Quantum-Chemical Study of C<Subscript>6</Subscript>H<Subscript>5</Subscript>S(O)CH<Subscript>3</Subscript> and C<Subscript>6</Subscript>H<Subscript>5</Subscript>S(O)CF<Subscript>3</Subscript>

The potential functions of internal rotation around the C -S bond in the C₆H₅S(O)CH₃ and C₆H₅S(O)CF₃ molecules were obtained by ab initio MP2(full)/6-31+G* calculations. The stationary points were identified by solving the vibrational problems. The structures in which the plane of the C -S-C bonds is approximately perpendicular to the benzene ring plane correspond to the energy minimum. The barriers to rotation around the C -S bond, corrected for the zero-point vibration energy, are 21.29 [C₆H₅S(O)CH₃] and 28.98 [C₆H₅S(O)CF₃] kJ mol⁻¹. The bond angles (deg) are as follows: 95.7 (CSC), 107.1 (C SO), 106.3 (C SO) in C₆H₅S(O)CH₃; 93.5 (CSC), 108.2 (C SO), 105.2 (C SO) in C₆H₅S(O)CF₃. The bond lengths are as follows (Å): 1.520 (S=O), 1.804 (C -S), 1.810 (C -S) in C₆H₅S(O)CH₃; 1.507 (S=O), 1.799 (C -S), 1.870 (C -S) in C₆H₅S(O)CF₃. According to the results of NBO calculations, the formally double S=O bond consists of a strongly polarized covalent σ bond (S→O) and an almost ionic bond. An increase in the S=O bond multiplicity relative to a single bond is mainly due to hyperconjugation by the mechanism n(O)→σ*(C -S) and n(O)→σ*(C -S) and, to a lesser extent, by interaction of the oxygen lone electron pairs with the Rydberg orbitals of the S atoms, characterized by a large contribution of the d component.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 1, 2005, pp. 96–104.Original Russian Text Copyright © 2005 by Bzhezovskii, Il’chenko, Chura, Gorb, Yagupol’skii.     

A Strong Luminescent Quaternary Dimeric Complex [Tb(BAA)<Subscript>2</Subscript>(Phen)(NO<Subscript>3</Subscript>)]<Subscript>2</Subscript>: Hydrothermal Synthesis,Structure, and Photophysics

In terms of the molecular fragment principle, a quaternary complex is assembled under hydrothermal conditions and characterized as [Tb(BAA)₂(Phen)(NO₃)]₂ (BAA is benzoyl acetic acid, Phen is 1,10- phenanthroline) by elementary analysis and IR, UV, fluorescence excitation, and emission spectra. The X-ray single-crystal diffraction data indicate that the title complex crystallizes in triclinic system, space group , with unit cell parameters a = 8.953(6), b = 13.332(9), c = 13.431(9) Å, α = 60.669(7)°, β = 89.649(8)°, γ = 72.068(9)°, V = 1309.3(15) ų, ρ(calcd) = ∼ 1.703 g/cm³, Z = 1 (per dimeric unit), F(000) = 664, GOOF = 1.071, R ₁ = 0.0627. The terbium complex forms a dimer with a coordination number of nine in which each pair of adjacent terbium ions is bridged by four BAA groups via two types of coordination modes. The dimer exhibits strong green luminescence of Tb³⁺.__________From Koordinatsionnaya Khimiya, Vol. 31, No. 6, 2005, pp. 472–478.Original English Text Copyright © 2005 by Bai, Yan, Chen.     

Thermochemical Properties of Dissolution of Nicotinic Acid C<Subscript>6</Subscript>H<Subscript>5</Subscript>NO<Subscript>2</Subscript>(s) in Aqueous Solution

Nicotinic acid (also known as niacin) was recrystallized from anhydrous ethanol. X-ray crystallography was applied to characterize its crystal structure. The crystal belongs to the monoclinic system, space group P2₍₁₎/c. The crystal cell parameters are a = 0.71401(4) nm, b = 1.16195(7) nm, c = 0.71974(6) nm, α = 90°, β = 113.514(3)°, γ = 90° and Z = 4. Molar enthalpies of dissolution of the compound, at different molalities m/(mol·kg^?1) were measured with an isoperibol solution–reaction calorimeter at T = 298.15 K. The molar enthalpy of solution at infinite dilution was calculated, according to Pitzer’s electrolyte solution model and found to be \( \Delta_{\text{sol}} H_{m}^{\infty } = ( 2 7. 3 \pm 0. 2) \) kJ·mol^?1 and Pitzer’s parameters (\( \beta_{{\text{MX}}}^{{\text{(0)}L}} \), \( \beta_{{\text{MX}}}^{{\text{(1)}L}} \) and \( C_{{\text{MX}}}^{\phi L} \)) were obtained. The values of apparent relative molar enthalpies (\( {}^{\phi }L \)) and relative partial molar enthalpies (\( \overline{{L_{2} }} \) and \( \overline{{L_{1} }} \)) of the solute and the solvent at different molalities were derived from the experimental enthalpy of dissolution values of the compound. Also, the standard molar enthalpy of formation of the anion \( {\text{C}}_{ 6} {\text{H}}_{ 4} \text{NO}_{2}^{-} \) in aqueous solution was calculated to be \( {\Delta_{\text{f}}^{} H}_{\text{m}}^{\text{o}} ({\text{C}}_{ 6} {\text{H}}_{ 4} {\text{NO}}_{2}^{-} \text{,aq}) = - \left( {603.2 \pm 1.2} \right)\;{\text{kJ}}{\cdot}{\text{mol}}^{-1} \).