Effect of some cationic detergents on the macromolecular stabilised emulsion with special reference to pepsin as emulsifier

Summary The effect of some cationic detergents viz Phenyl Trimethyl Ammonium Chloride, Lauryl pyridinium chloride, Cetyl pyridinium Bromide and Aerosol C-61, on the nujol/water emulsion stabilised by pepsin, has been studied. The detergents were added in two ways: 1. before emulsification; 2. after emulsification. The results were compared by their flocculation concentrations obtained at zero point of charge. From these values it is observed that the flocculation concentrations before emulsification are higher than those obtained after emulsification. The stability of the present system is discussed in the light of DVO theory. The high potential energy barriers obtained obviated the possibility of flocculation in primary minima. Therefore, to explain the results, the flocculation was assumed to occur in the secondary minima. The flocculation studies were carried out haemocytometrically which enabled to calculate the degrees of aggregation (D). In order to account for the observed values of D, the effective van der Waals constant of the system should be 1.0×10⁻¹² erg. The binding parameters and free energies have also been calculated.     

Thermoanalytical behaviour of carbaryl and its copper(II) and zinc(II) complexes

Non-isothermal techniques, i.e. thermogravimetry (TG) and differential scanning calorimetry (DSC), have been applied to investigate the thermal behaviour of carbaryl (1-naphthyl-N-methylcarbamate = 1-Naph-N-Mecbm) and its complexes, M(1-Naph-N-Mecbm)₄X₂, where M = Cu, X = Cl, NO₃ and CH₃COO and M = Zn, X = Cl. Carbaryl and Zn(1-Naph-N-Mecbm)₄Cl₂ complex exhibit two-stage thermal decomposition while the copper(II) complexes exhibit three and four-stage decomposition in their TG curves. The nature of the metal ion has been found to play highly influential role on the nature of thermal decomposition products as well as energy of activation ‘E*’. The presence of different anions does not seem to alter the thermal decomposition patterns. The complexes display weak to medium intensity exothermic and endothermic DSC curves, while the free ligand exhibits two endothermic peaks. The kinetic and thermodynamic parameters namely, the energy of activation ‘E*’, the frequency factor ‘A’ and the entropy of activation ‘S*’ etc. have been rationalized in relation to the bonding aspect of the carbaryl ligand. The nature and chemical composition of the residues of the decomposition steps have been studied by elemental analysis and FTIR data.     

Photoinduced Electron Transfer Supramolecular Fluorescent Switch of Mono-6-p-nitrobenzoyl-β-cyclodextrin with Porphyrin Derivative

A novel supramolecular fluorescence switch system consisted of a perfect host/electron-acceptor mono-6-p-nitrobenzoyl-β-cyclodextrin (p-NBCD) and an ideal guest/electron-donor (adamantane-C₄-porphyrin) was reported. The ‘ON’ and ‘OFF’ states of fluorescence switch were droved by solvent polarity.     

Influence of shearing on impact polypropylene copolymer: Phase morphology,thermal and rheological behavior

The influences of shearing conducted by a Brabender rheometer on phase morphology,thermal and rheological behavior of a commercial impact polypropylene copolymer(IPC) were studied.The crystallization and melting traces show that short-time annealing at 210°C is unable to completely erase the influence of shearing on the samples.When the samples which were treated at a rotation speed of 80 r/min crystallize at a cooling rate of 10 K/min,their 7_cs and corresponding T_ms obviously rise with the increase of shearing time.Furthermore,the POM results reveal that the shearing can lead to the formation of shish-kebab and the shish-kebab amount is proportional to shearing time.The rheological measurement results show that the treated samples exhibit different G’~ωdependences.The ’second plateau’ appears when the sample is treated at a rotation speed of 60 r/min or 80 r/min for 10 min,and linear G’~ωdependence is observed at other rotation speeds.In addition,it is found that the appearance of the ’second plateau’ depends on the shearing time when the rotation speed is fixed. According to SEM observations,it is proposed that the ’second plateau’ of IPC samples should be ascribed to the aggregation of dispersion particles.     

Ternary Chlorides of the Trivalent Early Lanthanides. Phase diagrams,crystal structures and thermodynamic properties

A comprehensive review on phase diagrams, crystal structures and thermodynamics of ternary chlorides formed in systems ACl/LnCl₃ (A=Cs, Rb, K, Na; Ln=La−Gd) is presented. The review summarizes the author’s own studies, published since 1985, and original papers of other scientists. With the larger alkali metal ions compounds such as A₃LnCl₆, A₂LnCl₅ and ALn₂Cl₇were obtained. With sodium additional compounds NaLnCl₄ and Na₃Ln₅Cl₁₈ were obtained. The crystal structures are discussed with the concept of ionic radii, which determine the coordination numbers of Ln³⁺ and A⁺ cations against Cl⁻ anions. The formation enthalpies of the compounds from ACl and LnCl₃ were determined by solution calorimetry. Gibbs’ free energies and entropies for these reactions were obtained by e.m.f. measurements vs. temperature. The stability of a ternary chloride in a systemACl−LnCl₃ is given by the ‘free enthalpy of synproportionation’, that is, the formation of a compound from its neighbour compounds in the system. This ΔG ⁰ _syn must be negative. A surprising result is, that the highest-melting compounds in the systems, A₃LnCl₆, are formed from ACl+A₂LnCl₅ by a loss in lattice energy. They exist as high-temperature compounds due to sufficiently high gain in entropy at temperatures whereTΔS>ΔH. This revised version was published online in August 2006 with corrections to the Cover Date.     

Sulfonium Ion Derivatization,Isobaric Stable Isotope Labeling and Data Dependent CID- and ETD-MS/MS for Enhanced Phosphopeptide Quantitation,Identification and Phosphorylation Site Characterization

An amine specific peptide derivatization strategy involving the use of novel isobaric stable isotope encoded ‘fixed charge’ sulfonium ion reagents, coupled with an analysis strategy employing capillary HPLC, ESI-MS, and automated data dependent ion trap CID-MS/MS, -MS³, and/or ETD-MS/MS, has been developed for the improved quantitative analysis of protein phosphorylation, and for identification and characterization of their site(s) of modification. Derivatization of 50 synthetic phosphopeptides with S,S′-dimethylthiobutanoylhydroxysuccinimide ester iodide (DMBNHS), followed by analysis using capillary HPLC-ESI-MS, yielded an average 2.5-fold increase in ionization efficiencies and a significant increase in the presence and/or abundance of higher charge state precursor ions compared to the non-derivatized phosphopeptides. Notably, 44% of the phosphopeptides (22 of 50) in their underivatized states yielded precursor ions whose maximum charge states corresponded to +2, while only 8% (4 of 50) remained at this maximum charge state following DMBNHS derivatization. Quantitative analysis was achieved by measuring the abundances of the diagnostic product ions corresponding to the neutral losses of ‘light’ (S(CH₃)₂) and ‘heavy’ (S(CD₃)₂) dimethylsulfide exclusively formed upon CID-MS/MS of isobaric stable isotope labeled forms of the DMBNHS derivatized phosphopeptides. Under these conditions, the phosphate group stayed intact. Access for a greater number of peptides to provide enhanced phosphopeptide sequence identification and phosphorylation site characterization was achieved via automated data-dependent CID-MS³ or ETD-MS/MS analysis due to the formation of the higher charge state precursor ions. Importantly, improved sequence coverage was observed using ETD-MS/MS following introduction of the sulfonium ion fixed charge, but with no detrimental effects on ETD fragmentation efficiency.     

The Influence of Drawing in Hot Water on The Morphological Properties of Pet Films as Measured by DSC and Modulated DSC

PET films uniaxially drawn in hot water are studied by means of conventional DSC and modulated DSC (MDSC).Glass transition is studied by MDSC which allows to access the glass transition temperature T _g and the variations of ΔC _p=C _p1−C _pg (difference between thermal capacity in the liquid-like and glassy states at T=T _g). Variations of T _g with the water content (which act as plasticizer) and with the drawing (which rigidifies the amorphous phase) are discussed with regard to the structure engaged in these materials. The increments of ΔC _p at T _g are also interpreted using a three phases model and the 'strong-fragile’ glass former liquid concept. We show that the ‘fragility’ of the medium increases due to the conjugated effects of deformation and water sorption as soon as a strain induced crystalline phase is obtained. Then, ‘fragility’ decreases drastically with the occurring rigid amorphous phase. This revised version was published online in August 2006 with corrections to the Cover Date.     

Estimation of flocculation structure in filled polymer composites by dynamic rheological measurements

 The frequency and concentration dependences of the storage modulus (G ^′) for carbon black and short-carbon-fiber-filled polymer composites were investigated by means of dynamic rheological measurements. It was found that G ^′ at low frequencies and amplitudes could be used as a sensitive experimental parameter for detecting the flocculation structure of the ultra-fine-particle-filled polymer composites. Correlation of electrical resistivity of the composites to the relative storage modulus, G ^′ _r(=G ^′ _c/ G ^′ _p), revealed that the three-dimensional interparticle networks start to construct through the matrix when G ^′ _r increases to 7 regardless of the composite systems. Quantitative calculations in order to determine the flocculation structure were carried out by means of the modified Kerner equation. A plot of the calculated value, defined as the floc index A, dependence of electrical resistivity for various systems was found to be a universal curve. Accordingly, we suggest that A might universally correspond to the flocculation structure of the filler, which is independent of the nature of the filler, the molecular weight, the chemical composition of the polymer and the temperature at which the measurement is made. This method is particularly effective for estimating the flocculation structure of ultra-fine-particle-filled polymer composites no matter whether the filler is conductive or not. Received: 26 May 1999/Accepted in revised form: 28 September 1999     

Determination of weak (2.0–2.5) dissociation constants of non-UV absorbing solutes by capillary electrophoresis

Summary Capillary electrophoresis (CE) has proved to be a fast and convenient method for the determination of the dissociation constants of non-UV absorbing solutes in the acidic pK _A range (2.0–2.5). The electroosmotic flow was reversed by washing the capillary with 0.2% polybren aqueous solution. A series of background electrolytes was prepared with phenylphosphonic acid (pK _A=1.29) and β-alanine (pK _A=3.55) with the same ionic strength and a high buffer capacity in order to improve the repeatability (0.1–0.2 %) of the electrophoretic mobility and to determine the values of pK _A accurately. This procedure was applied to the determination of the dissociation constants of several alkyl-alkylphosphonic acids whose pK _A values have not yet been published in the literature. In this work, their dissociation constants have been found to vary between 1.91 and 2.34 for alkyl-methylphosphonic acids and between 2.10 and 2.38 for alkyl-ethylphosphonic acids.     

DFT studies and AIM analysis of AlN-polycycles

The structure and properties of AlN-polycycles were studied by DFT (density functional theory) method. The results of calculations were obtained at B3LYP/6-311G(d, p) level on model species. Topological parameters such as electron density, its Laplacian, kinetic electron energy density, potential electron energy density, and total electron energy density at the ring critical points (RCP) from Bader’s ‘Atoms in molecules’ (AIM) theory were analyzed in detail. These results indicate a good correlation between ρ(3, +1), G(r), H(r), and V(r) averaged values and hardness of AlN-polycycles. The aromaticity of all molecules has been studied by nucleus-independent chemical shift. There is a linear correlation between ΣNICS(0.0)_molecule values and polarizability.     

Evaluation of thermodynamic functions for complexation reactions involving bivalent metal ions and ethyl-2,3-dioxobutyrate-2 p -bromophenylhydrazone

Complexation reactions of bivalent metal ions and ethyl-2,3-dioxobutyrate-2p-bromophenylhydrazone (EDOB-2p-BPH) have been studied potentiometrically in 50% (v/v) ethanol/water medium at different ionic strengths with respect to NaClO₄ and at different temperatures and their stability constants determined. The method of Bjerrum and Calvin as modified by Irving and Rossotti has been used to determine then andpL values. S_min values which have the same significance as ‘T²’ have also been calculated. The thermodynamic stability constants and standard free energy change (ΔG) have also been calculated. ΔG values are negative in all cases indicating that the reactions are spontaneous. The ligand field stabilization energy (δH) has also been calculated for the 3d transition metals.     

Ion-Solvation Behavior of Pyridinium Dichromate in Water–N,N-Dimethyl Formamide Solvent Mixtures

The electrical conductances of pyridinium dichromate have been measured in N,N-dimethyl formamide–water mixtures of different compositions in the temperature range 283–313 K. The limiting molar conductance, Λ₀, association constant of the ion pair, K _A, and dissociation constant K _C have been calculated using the Shedlovsky and Kraus–Bray equations. The effective ionic radii (r _i ) of C₅H₅NH⁺ and Cr₂O₇ ^-\mathrm{Cr}_{2}\mathrm{O}_{7}^{ -} have been determined from the L_i⁰\Lambda_{i}^{0} values using Gill’s modification of Stokes’ law. The influence of the mixed solvent composition on the solvation of ions is discussed with the help of the ‘R’-factor ( R = \frachL _±⁰(solvent)hL _±⁰(water)R = \frac{\eta \Lambda_{ \pm}^{0}(\mathrm{solvent})}{\eta\Lambda_{ \pm}^{0}(\mathrm{water})}). Thermodynamic parameters are evaluated and reported. The results of this study are interpreted in terms of ion–solvent interactions and solvent properties.     

The study of alanine oscillating reaction catalyzed by tetraazamacrocyclic nickel(II) complex

A closed oscillation system comprised of alanine, KBrO₃, H₂SO₄ and acetone catalyzed by tetraazamacrocyclic nickel(II) complex is introduced, and quantitatively characterized with kinetic parameters, namely the rate constant (k _in, k _p), the apparent activation energy (E _in, E _p) and pre-exponential constant (A _in, A _p) and thermodynamic functions (ΔH _in, ΔG _in, ΔS _in and ΔH _p, ΔG _p, ΔS _p), where indexes “in” and “p” mean “induction period” and “oscillation period,” respectively. The results indicate that tetraazamacrocyclic nickel(II) complex can catalyze alanine oscillating reaction and the reaction corresponds exactly to the feature of irreversible thermodynamics as the entropy of system is negative.     

Volumetric and Viscometric Studies on Sodium Nitrate and Potassium Nitrate in Aqueous and H<Subscript>2</Subscript>O-urea Solutions

Summary.  Density and viscosity of NaNO₃ and KNO₃ in aqueous and in H₂O-urea solutions were determined as a function of electrolyte concentrations at 308, 313, 318, 323, and 328 K, respectively. The apparent molal volume (φ _v ) of the electrolytes were found to be linear functions of the square root of the solute molality (b). The φ _v and data were fitted to the Masson equation [1] by the least square method to obtain the apparent molar volume at infinite dilution (φ _v ^{^}), which is practically equal to the partial molar volume . The viscosity coefficients A and B were calculated on the basis of the viscosity of the solutions and the solvent concerned using the Jones–Dole [2] equation. The activation parameters for viscous flow (ΔG ^≠, ΔS ^≠, and ΔH ^≠) were calculated according to Eyring [3]. The values of for the two systems were also calculated from B-coefficient data. The results were found to be of opposite nature in the two electrolyte systems. Where sodium nitrate showed structure making behaviour both in aqueous and in H₂O-urea solutions, KNO₃ showed structure breaking behaviour in aqueous solutions and structure making behaviour in 5 molal H₂O-urea solutions in the studied temperature range. The behaviour of these two electrolytes in aqueous binary and in aqueous-urea ternary systems are discussed in terms of charge, size, and hydrogen bonding effects. Corresponding author. E-mail: chemistry_ru@yahoo.com Received January 24, 2002; accepted (revised) April 5, 2002     

Injection effect on the sensitivity in an isothermal titration calorimeter

By using electrical calibrations and with the injection of liquids with very different heating capacities (water and cyclohexane), it is made a thorough evaluation of the ‘injection effect’ in terms of the parameter ρc _p f (ρc _p – volumetric heat capacity, f – injection flow) in an isothermal titration calorimeter. This effect can be evaluated accurately in the case of non-volatile liquids, however, when dealing with volatile liquids, the uncertainty in their determination increases because of the vaporization heat.     

Influence of the Degree of Dehydroxylation of Kaolinite on the Properties of Aluminosilicate Glasses

The degree of dehydroxylation of kaolinite, D_TG and D_IR, respectively, is characterized by thermogravimetric analysis (TG) and Fourier transform infrared spectroscopy (FTIR). The relation between DTG and DIR based on the infrared absorptions at 3600–3700, 915, 810, and 540 cm⁻¹ is established. Three regions can clearly be distinguished: the dehydroxylation region (D_TG<0.9), the metakaolinite region (0.9<D_TG<1) and the ‘spinel’ region(D_TG=1). The effect of the degree of dehydroxylation of kaolinite on the amount of reactive material is measured by the reaction enthalpy, ΔH, of the low-temperature reaction of the dehydroxylated kaolinite with a potassium silicate solution using differential scanning calorimetry (DSC). |ΔH| increases almost linearly with DTG in the dehydroxylation region. In the metakaolinite region, ΔH and thus the amount of reactive material, becomes constant. |ΔH| is sharply decreasing when metakaolinite transforms into other phases in the ‘spinel’ region. No significant differences in the reactivity of the dehydroxylates is detected with DSC. According to FTIR, the use of partially dehydroxylated kaolinite is not influencing the molecular structure of the low-temperature synthesized aluminosilicates, but residual kaolinite is retrieved as an additive. This revised version was published online in August 2006 with corrections to the Cover Date.     

Optical Study of Radicals (OH, O, H, N) in a Needle-plate Negative Pulsed Streamer Corona Discharge

Optical emission spectroscopy has been applied to study the OH radicals and O, H, and N active atoms produced by a high-voltage negative pulsed streamer corona discharge of N₂ and H₂O mixture gas in a needle-plate reactor at one atmosphere. The relative vibrational populations and the vibrational temperature of N₂(C, v′) were determined. The effects of pulsed peak voltage, pulsed repetition rate, and the addition of O₂ on the relative populations of OH(A²Σ) radicals, O(3p⁵P), H_α (3P), and N(3p⁴P) active atoms were investigated. It was found that the relative populations of those radicals increase with increasing pulsed peak voltage and pulsed repetition rate. The relative population of OH(A²Σ) radicals decreases with increasing O₂ flow rate, while the relative populations of O (3p⁵P), H_α (3P), and N (3p⁴P) active atoms exhibit a maximum over the studied range of the O₂ flow rate. The involved physicochemical processes have also been discussed.     

Interaction between two double layers for Na3PO4 types electrolytes at y0 > yd > 0

Interaction between two double layers for the Na₃PO₄ type electrolytes at y ₀ > y _d > 0 were investigated with the aid of λ parameter methods and the accurate numeral results were given. The maximum of the interaction energies between two double layers for A_v+ B_v- A_{v_ + } B_{v_ - } type electrolytes at y ₀ > y _d > 0 is independent of y ₀, but increases with y _d . The interaction energies between two double layers for NaCl, CaCl₂, FeCl₃, Na₂SO₄ and Na₃PO₄ type electrolytes at y ₀ = 5 and y _d = 2 were compared. If the negative or positive ions for A_v+ B_v- A_{v_ + } B_{v_ - } type electrolytes have the same charge number, the maximum of their interaction energies increases with the charge number of the ions of opposite charge. If the negative or positive ions of the electrolytes have different charge numbers, the relative heights of the maxima of their interaction energies are indefinite. For the in pairs conjugate type electrolytes like CaCl₂ and Na₂SO₄ or FeCl₃ and Na₃PO₄, the larger the charge number of the negative ions of the electrolytes is, the higher the maximum of their interaction energies is. The results for Na₃PO₄ type electrolytes at y ₀ > y _d > 0 can also be applied to FeCl₃ type electrolytes at y ₀ > y _d > 0.     

Interaction between two double-layers for FeCl<Subscript>3</Subscript> and Na<Subscript>3</Subscript>PO<Subscript>4</Subscript> type electrolytes in case the signs of potentials on two plates are opposite

The interaction energies between two double layers for FeCl₃ or Na₃PO₄ type electrolytes at y ₀ > 0 >y _d>—y ₀ were calculated with the aid of 7n parameter methods and the accurate numeral results were given when the dimensionless surface potential of two double layers changes from -20 to +20. When ∣y _d∣ > 5, the absolute value of the interaction energies, ∣V’∣, for FeCl₃ type electrolytes at y ₀= 1 stops to increase. When y ₀> 8, the ∣V’∣ for FeCl₃ type electrolytes at y _d= -1 ceases to change. The influence of y _d on ∣V’∣ for FeCl₃ type electrolytes is more significant than the influence of y ₀. The variation of ∣V’∣ with y _d and y ₀ for Na₃PO₄ type electrolytes is opposite to that for FeCl₃ type electrolytes. The interaction energies between two dissimilar double layers for Na₂SO₄, CaCl₂, NaCl, Na₃PO₄ and FeCl₃ type electrolytes at y ₀= 1 and y _d = -10 are compared and the results indicate that the interaction energies close to each other for FeCl₃ and CaCl₂ type electrolytes and for Na₃PO₄ and Na₂SO₄ type electrolytes, respectively. ∣V’∣ increases with the raises of y ₀ or ∣y _d∣, but decreases with the raises of z ₊ or z _-.     

Inactivity of iridium–triphenylphosphine complexes for catalytic imine hydrogenation: formation of neutral, dihydrido-ortho-metallated species

Reactions of cis,trans,cis-[Ir(H)₂(PPh₃)₂(MeOH)₂]PF₆ in MeOH with the imines Ph(R′)C=NR under 1 atm H₂ precipitate the neutral, Ir(III)-dihydrido complexes [Ir(H)₂{RN=C(R′)(o-C ₆H₄)}(PPh₃)₂], where R = alkyl or benzyl, and R′ = Ph, H, or Me; the dihydrides are well characterized through elemental analysis, NMR and IR data and, in one case, with the imine Ph₂C=NCH₂Ph, an X-ray structure. These products are formed via intermediate ortho-metallated species, exemplified by [Ir(H){PhCH₂N=CPh(o-C ₆H₄)}(PPh₃)₂(MeOH)]PF₆ in the case of the Ph₂C=NCH₂Ph reaction; the intermediate then reacts with H₂ (via net heterolytic cleavage: H₂ → H⁻ + H⁺) to give the neutral dihydride and HPF₆ as co-product. The ‘unique’ imine PhCH=NPh, under the same conditions, does not form a dihydride and instead is readily catalytically hydrogenated to PhCH₂N(H)Ph; remarkably, we have shown previously that this imine is ‘unique’ within the corresponding Rh system in that no catalytic hydrogenation occurs because the amine product ‘poisons’ the Rh centre by coordination through the N-phenyl ring.