Values Of Λ0 Research Articles

Gamma irradiation-induced changes in structural, linear/nonlinear optical, and optoelectrical properties of PVB/BiVO4 nanocomposite for organic electronic devices

Herein, nanocomposite films based on polyvinyl butyral (PVB) and BiVO4 plates were synthesized through solution casting. The present study aims to investigate the impact of varying doses of gamma irradiation (0, 15, 30, 60, and 90 kGy) on the structural, dispersion, linear/nonlinear optical, and optoelectrical properties of PVB/BiVO4 nanocomposite films. The effects of gamma irradiation on various optical characteristics, such as refractive index (n), extinction coefficient (k), and other related parameters, have been observed. The study of dielectric behavior and the derivation of optoelectrical parameters, including high-frequency dielectric constant (ε∞), plasma frequency (ωP), relaxation time (τ), and optical mobility (µopt.), were conducted using the real and imaginary parts of the dielectric constants εr and εi. In addition, the linear optical susceptibility (χ(1)), the third-order nonlinear optical susceptibility (χ(3)), and the nonlinear refractive index (n2) were studied as a function of gamma irradiation doses. Furthermore, the results demonstrate that the average oscillator wavelength (λ0) values, oscillator strength (S0), and optical conductivity (σopt) vary significantly after gamma radiation treatment. Overall, the strong correlations between the linear/nonlinear optical and optoelectrical parameters of the irradiated PVB/BiVO4 nanocomposite films make them suitable for application in flexible organic electronic devices.

Experimental and theoretical study on ion association in [Hmim][halide] + water/isopropanol mixtures

The electrical conductivities of the dilute solutions containing ionic liquids (1-hexyl-3-methylimidazolium chloride [Hmim]Cl, 1-hexyl-3-methylimidazolium bromide [Hmim]Br, and 1-hexyl-3-methylimidazolium iodide [Hmim]I) with water and isopropanol were determined in the temperature ranging from 293.15 to 313.15 K. The liquid densities of all binary mixtures were further determined for model parameterization. In theoretical modeling, the limiting molar conductivities Λ0(T) were first obtained using the Debye-Hückel-Onsager (DHO) equation, and thereafter the ion association constants KA(T) were determined using the Shedlovsky equation. The effects of temperature, dielectric constant, and anion size on the values of Λ0(T) and KA(T) were systematically discussed. The Eyring activation enthalpy of charge transport ∆H* and the Walden values Λ0η for all studied binary mixtures were obtained from the temperature-dependent Λ0(T).

ИССЛЕДОВАНИЕ ПРОЦЕССА ВЗАИМОДЕЙСТВИЯ ЛИНТА С КОЛОСНИКАМИ В МОДУЛЕ ЛИНТООЧИСТИТЕЛЯ

The interaction of lint with grates in the cleaning module, as well as the impact interaction of the pulp with the grate, was studied with the effective extraction of impurities in time, taking into account changes in the density of the material. The dependences determining the release of weed impurities from the fiber during passage through each grate are given. The influence of the installation angle of the grates relative to the saw cylinder on the cleaning effect of the machine is determined. The influence of the number of grid-irons on the lint cleaning efficiency at various values of λ0 and λ1 has been analytically determined.

Towards Automatic Artifact Rejection in Resting-State MEG Recordings: Evaluating the Performance of the SOUND Algorithm.

In this study, a new automated noise rejection algorithm, the SOurce-estimate-Utilizing Noise-Discarding algorithm (SOUND), was evaluated on magnetoencephalographic (MEG) resting-state signals in order to select its optimal configuration parameters. Different values of the epoch length and the regularization parameter λ0 were assessed in three scenarios with ascending noise levels. Results show that it is possible to remarkably improve the Signal-to-Noise Ratio, without overly altering the signal of interest. An optimal λ0 value of 0.1 was obtained. However, the epoch length should be adapted to the specific problem. In conclusion, our results suggest that the SOUND algorithm is an appropriate and useful tool to be applied in a preprocessing pipeline for MEG restingstate signals.

Effects of cation distribution on microwave dielectric properties of Mg1−xZnxAl2O4 ceramics

The effects of duration of ball-milling on cation distribution of calcined-MgAl2O4 and -ZnAl2O4 powders were investigated by 27Al solid-state nuclear magnetic resonance (NMR) measurement; the degree of inversion (λC), which corresponds to the fraction of Al3+ in tetrahedral site, of the MgAl2O4 powder increased from 0.33 to 0.42 when the duration of ball-milling varied from 0 to 24 h, though that of the ZnAl2O4 powders ranged from 0.04 to 0.07. Thus, the preferential occupation of Al3+ cation in tetrahedral site was obtained for the calcined-MgAl2O4 powders prepared by ball-milling for 24 h. As a result, the Q·f value of the MgAl2O4 ceramics extremely increased from 85,100 to 187,200 GHz with increasing the duration of ball-milling of the calcined powders, while that of the ZnAl2O4 ceramics was almost constant with a Q·f value of approximately 100,000 GHz. Moreover, the effects of Zn substitution for Mg on the microwave dielectric properties and cation distribution of the Mg1−xZnxAl2O4 ceramics were also investigated. 27Al NMR measurement revealed that the high λ0 values, implying the degree of the redistribution of the Al3+ cation in the octahedral site during firing, were observed in the composition range of 0–0.75 and the highest Q·f value of 222,600 GHz was obtained for the Mg1−xZnxAl2O4 ceramics at x = 0.75. Thus, it is considered that the preferential occupation of Al3+ cation at tetrahedral sites of the calcined-powders caused by the ball-milling is effective to enhance the Q·f value of the Mg1−xZnxAl2O4 ceramics.

Conductivities of 1-Alkyl-3-methylimidazolium Chloride Ionic Liquids in Disaccharide + Water Solutions at 298.15 K

Conductivities for ionic liquids (ILs) 1-alkyl-3-methylimidazolium chloride ([Cnmim]Cl, n = 4, 6, 8, 10) + sucrose + water solutions and [C4mim]Cl + maltose + water solutions were measured at 298.15 K. Meanwhile, densities, viscosities, and relative permittivities for water + disaccharide mixtures were also measured. The Lee–Wheaton conductivity equation was used to acquire the limiting molar conductivities (Λ0). The Walden products (Λ0η0) were also calculated. The interaction of ILs with disaccharide was discussed in terms of the structure of disaccharides and ILs. Furthermore, values of Λ0 for inorganic salts (ordinary electrolyte, such as NaCl/KCl) and ILs (special electrolyte) were compared, indicating that they have approximate limiting molar conductivities, namely, they have not too much difference in electrical conductivity.

Conductometric analysis of 1-butyl-3-methylimidazolium ibuprofenate as an active pharmaceutical ingredient ionic liquid (API-IL) in the aqueous amino acids solutions

In this work, electrical conductivities of the active pharmaceutical ingredient in ionic liquid form (API-IL), 1-butyl-3-methylimidazolium ibuprofenate, [BMIM][Ibu] in water and in the aqueous solutions of amino acids, glycine and l-alanine have been measured at T=(288.15–318.15)K. The calculated molar conductivity data were analyzed by two famous conductivity models, low concentration Chemical Model (lcCM) and Fernandez-Prini (FP). The results show that the FP equation is more appropriate for analysis of the molar conductivity data because the calculated parameters are not highly influenced by the initial guess values of the parameters. Using these models, the limiting molar conductivities (Λ0), ion association constants (KA) and standard Gibbs energy (ΔGA0) for the ion association process of the API-IL have been calculated. The values of Λ0 and KA decrease as the concentration of amino acid increase. This trend may be attributed to low mobility of the ions with large radii produced during the solvation of the ions by zwitterions of the amino acids. The values of Λ0 and KA also increase from glycine to l-alanine solutions. The ions of [BMIM][Ibu] are more solvated by (COO−/NH3+) zwitterionic centers of glycine rather than l-alanine. The more negative values of ΔGA0 for [BMIM][Ibu] in l-alanine rather than glycine solutions indicates that more spontaneously and more feasibility of the ion association process in this amino acid.

Stiffness parameter of brush-like polymers with rod-like side chains.

The stiffness parameter λ(-1) of brush-like polymers having rod-like side chains with the hard core potential was calculated. Side chains are, first, assumed to be connected with a free joint to the main chain. The free energy per molecule F was calculated invoking the single contact approximation in which only the interaction between two side chains is considered and the higher interactions are ignored. In the calculation, the contact is assumed to occur when the two side chains are in a plain and the condition for the angles between the side chain and the main chain to make a triangle by two side chains and the main chain was exactly taken into account. The change of F after bending the main chain with a certain curvature from the straight state was calculated to obtain λ(-1). The resulting λ(-1) came close to the experimental value for brush-like polymers with a poly(methacrylate) main chain and poly(hexylisocyanate) (PHIC) side chains if we add a constant as the intrinsic stiffness of the main chain, λ0 (-1), to it. By considering the potential function having a minimum when the angle between the side and main chains equals π/2, the data for brush-like polymers with a poly(styrene) main chain and PHIC side chains were also closely fitted by the theoretical values with an appropriate value of λ0 (-1) and the force constant of the angle.

On the Theory of Tetragonality of Martensite Crystals Surrounded with Elastic Matrix

The paper is dedicated to the study of thermodynamic stability of tetragonal and cubic states of dilute Fe–C interstitial solid solutions. The combination of the thermodynamic theory and atomistic simulations results was used. This approach allowed us to analyze a widespread theory of carbon ordering in martensite crystal lattice enclosed in an elastic matrix developed by A.G. Khachaturyan. The key parameter of the theory is λ0, the strain interaction parameter. The value of λ0 calculated by A.G. Khachaturyan for a free martensite crystal (2.73 eV/atom ) yields the critical concentration of carbon ccrit=0,55 wt. % for room temperature. In fact, according to the experimental works this concentrations is close to 0.25 wt. %. A.G. Khachaturyan offered an improved theory of carbon ordering based on the assumption that decreasing the sizes of crystals along z axis will cause elastic resistance from surrounding crystals. The stresses arising when the martensite crystal is enclosed in an elastic matrix causes the appearance of a “tail” of order parameter at concentrations below the ccr for free crystal, which explained the discrepancy between Khachaturian’s theory and the experimental data. However our analysis shows the absence of this “tail” that means incorrect calculation of λ0 parameter. Over the last ten years the calculations of the strain interaction parameter λ0 have been made. The values of the parameter λ0 range from 5 to 10 eV/atom, in contrast to 2.73 eV/atom as defined by A.G. Khachaturyan. This fact has a great effect on the estimates of the critical carbon concentration at room temperature. This concentration becomes close to 0.2 wt. %, the value previously indicated by G.V. Kurdjumov. The reasons of abnormal tetragonality observed in the 0.2–0.6 wt. %C range are also considered.

Tetragonality and the distribution of carbon atoms in the Fe–C martensite: Molecular-dynamics simulation

In the statistical theory of the ordering of carbon atoms in the z sublattice of martensite, the most important role is played by the parameter of the strain interaction of carbon atoms λ0, which determines the critical temperature of the bcc–bct transition. The values of this parameter (6–11 eV/atom) obtained in recent years by the methods of computer simulation differ significantly from the value λ0 = 2.73 eV/atom obtained by A. G. Khachaturyan. In this article, we calculated the value of λ0 by two methods based on the molecular-dynamics simulation of the ordering of carbon atoms in the lattice of martensite at temperatures of 500, 750, 900, and 1000 K in a wide range of carbon concentrations, which includes ccrit. No tails of ordering below ccrit have been revealed. It has been shown analytically that there is an inaccuracy in the Khachaturyan theory of ordering for the crystal in an elastic environment. After eliminating this inaccuracy, no tails of the order parameter appear; the tetragonality changes jumpwise from η = 0 to ηcrit = 0.75 at ccrit = 2.9kT/λ0 instead of ηcrit = 0.5 and ccrit= 2.77kT/λ0 for an isolated crystal. Upon the simulation, clustering of carbon atoms was revealed in the form of platelike pileups along {102} planes separated by flat regions where no carbon atoms were present. The influence of short-range order in the arrangement of neighboring carbon atoms on the thermodynamics of ordering is discussed.

Conductometric study of ionic liquids in the presence of N,N′-bis(2-pyridylmethylidene)-1,2-diiminoethane (BPIE) Schiff base in acetonitrile solutions at 298.15 K

In recent years, Schiff bases and their metal complexes in the presence of ionic liquids (ILs) have been used in synthesis of various chemical compounds. To better understanding of ionic liquid influence on these processes, it is required to obtain information about the ion association behavior of the ionic liquids. Therefore, in this work, the molar conductivities of the ILs [RMIm]X (R= propyl, pentyl, and hexyl; X= Br− and Cl−) in different concentrations of N,N′-bis(2-pyridylmethylidene)-1,2-diiminoethane (BPIE) Schiff base+acetonitrile solutions were determined at 298.15K. The obtained conductivity data were analyzed by low concentration Chemical Model (lcCM) conductivity equation to calculate the limiting molar conductivities (Λ0) and ion association constants (KA). The results show that BPIE, alkyl chain length of cation, and anion type have effect on the ionic association process of the ILs. The Λ0 and KA values decrease as the Schiff base concentration, alkyl chain length of cation, and anion size increase in the solution. The association constants were also used to calculate the standard Gibbs energy (ΔG0A) of ion-pairing association. The resulted ΔG0A values are negative and become more negative as the alkyl chain length of the cation and the size of anion increase. The large negative values of the standard Gibbs energy obtained for [HMIm]Br indicates the more spontaneity and the more feasibility of the association process for this ionic liquid.

Thermodynamic Studies of Ion Association of s-Acetylthiocholine Halides and Perchlorate in Methanol Solutions

Thermodynamic parameters (ΔH0, ΔG0, ΔS0) and the activation energy (ΔEs) were calculated to explain the limiting equivalent conductance (Λ0) and ion association constant (KA) of s-acetylthiocholine halides and perchlorate in methanol solutions at different temperatures by using conductance measurements. It has been evaluated by using Fuoss-Onsager equation. It is evident that the values of (Λ0) increase regularly with increase in temperature. For all salts of s-acetylthiocholine, (Λ0) indicates that higher mobility of the ions in all solvent systems studied. The free energy change ΔG0 values are negative for all salts (Br-, I- and ClO4-) in solvent systems studied. Clearly strengthening the interionic association at higher temperatures is largely caused by a decrease in the permitivity of the solvent. The positive values of (ΔH0) for three salts (Br-, I- and ClO4-) show that the association processes are endothermic in nature. Entropy change (ΔS0) values were positive for all salts because of decrease in solvation of ion-pair compared to that of the free ion. This may be attributed to increase in the degree of freedom upon association, mainly due to the release of solvent molecules.

Conductance Determination of the Ion Association of Tris-(ethylenediamine)chromium(III) Chloride in Dimethyl Sulfoxide–Water Mixtures at Various Temperatures

The electrical conductances of tris-(ethylenediamine)chromium chloride, ([Cr(en)3]Cl3; en = ethylenediamine) were measured as functions of temperature and concentration in 20–80 wt% dimethyl sulfoxide (DMSO)–water mixtures. Conductance data were analyzed by the Kraus–Bray and Shedlovsky models. Also, density and viscosity values for 20–80 wt% DMSO–water mixtures have been determined experimentally at temperatures varying from (288.15 to 318.15) K. The limiting molar conductance, Λ 0, and the association constant, K A, for ([Cr(en)3]Cl3 were computed by using Shedlovsky’s equation. The Λ 0 values decrease with increase in the percentage of DMSO in the mixed solvent. The K A values increase with increasing temperature and increasing percentage of DMSO in the mixed solvent at all temperatures. This may be attributed to the increase in association constant with the decrease in the relative permittivity of the mixed solvent. Thermodynamic parameters (Gibbs energy, enthalpy and entropy changes) were determined from the temperature dependence of K A for ([Cr(en)3]Cl3. The results of the study have been interpreted in terms of ion–solvent interactions and solvent properties.

Ion association constants of ionic liquids, 1-hexyl-3-methylimidazolium halide, in aqueous d-fructose solutions

In this paper, the interactions of 1-hexyl-3-methylimidazolium halides ([HMIm]Cl and [HMIm]Br) with aqueous d-fructose solutions have been studied by using conductance properties. Limiting molar conductivity (Λ0), association constant (KA) and distance parameter (R) were calculated using low concentration Chemical Model (lcCM) at temperatures ranges of (298.15–328.15)K and concentrations (0.05, 0.10 and 0.20)molkg−1 of d-fructose solutions. The Λ0 values increase with increasing temperature and decrease during the addition of d-fructose. The greater values of association constant for [HMIm]Cl relative to [HMIm]Br is due to the high surface charge density of the Cl− anion proposing strong association tendency with [HMIm]+ cation. Moreover, an enhancement was observed in the KA values as temperature is increased suggesting that ion-pair formation is an endothermic process. The mobility of ions was found to be completely controlled by the bulk viscosity (η) and consequently the Walden products (Λ0η) were estimated and discussed. The association constants were used to study the thermodynamic of association process. Consequently, Gibbs free energy (ΔGA0), enthalpy (ΔHA0) and entropy (ΔSA0) of ion-pair formation have been obtained at different temperatures. It was observed that the ion-association process exhibits a negative value of ΔGA0 and becomes more negative with increasing temperature proposing the spontaneity and feasibility of the association at high temperatures.

OBSERVABLE QUANTITIES IN WEYL GRAVITY

In this paper, the cosmological "constant" and the Hubble parameter are considered in the Weyl theory of gravity, by taking them as functions of r and t, respectively. Based on this theory and in the linear approximation, we obtain the values of H0 and Λ0 which are in good agreement with the known values of the parameters for the current state of the universe.

ChemInform Abstract: Conductivity of N-Methylpyridinium Iodide and Its Methyl Substituted Derivatives in Water-Ethanol Mixture

The conductivity of N-methylpyridinium iodide (NMPI) and its methyl substituted derivatives at 2-, 3-, and 4-positions in water–ethanol solvent mixtures is reported at 25°C. The conductivity data are analyzed by the Shedlovsky method to get both Λ0 and KA, the association constant, simultaneously. The Λ0 values decrease or increase with increase or decrease of the viscosity of the solvent mixtures. The values of Λ0 and K are in the order of H>3->4->2-. The Walden product Λ0η for these iodide salts behaves in a manner as is expected for highly hydrogen bonded water-alcohol mixtures. A mole fraction of 0.15 to 0.2 in ethanol indicates maximum interaction between water and ethanol. The values of Λ0 and KA indicate greater solvation and hence less ion-ion interaction in case of NMPI and 3-CH3 salts than 2- and 4-CH3 salts.

Conductivity and Dissociation Constants of Quaternary Ammonium Perchlorates and Picrates in 4-Methyl-pentan-2-one

The dissociation of 14 ionophores, namely, seven symmetrical (C1 to C7) and five asymmetrical quaternary ammonium perchlorates and two tetraalkylammonium picrates (all with linear hydrocarbon chains), in 4-methyl-pentan-2-one was studied at 25 °C (er = 12.92) using the conductance method. The values of the association constants of the quaternary ammonium cation, Ct+, with ClO4− vary from (7.4 ± 0.3)·103 L·mol−1 for tetramethylammonium to (2.4 ± 0.1)·103 L·mol−1 for tetrahexyl- and tetraheptylammonium; a distinct dependence on the size of the Ct+, especially for symmetrical cations, is evident. The values of the limiting molar conductivities Λ0/S·mol−1·cm2 vary from 122.8 to 90.0 (± 0.7). The plot of Λ0 versus the reciprocal cube root of the total van der Waals volume of the cations, VCt−1/3, is close to linear up to tetrapentylammonium and hexadecyltrimethylammonium, while for larger cations (with 21 to 28 carbon atoms) the Λ0 values stay practically constant. At the same time, symmetrical and asymmetrica...

Volumetric Properties and Conductivities of 1-Butyl-3-methylimidazolium Tetrafluoroborate + Sucrose + Water Mixtures

Densities, limiting molar conductivities (Λ0), and Walden products (Λ0η) for 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4])−sucrose−water solutions were determined at 298.15 K. The measured densities were used to calculate the apparent molar volumes of sucrose (VΦ,S) and [Bmim][BF4] (VΦ,IL) in the studied solutions. Infinite dilution apparent molar volumes, VΦ,S∞ and VΦ,IL∞, have been evaluated, together with the standard transfer volumes of the sucrose (ΔtVS∞) from water to aqueous solutions of [Bmim][BF4] and those of [Bmim][BF4] (ΔtVIL∞) from water to aqueous sucrose solution. It was shown that the ΔtVS∞ and ΔtVIL∞ values are positive and increase with increasing molalities of [Bmim][BF4] and sucrose, respectively. The volumetric interaction parameters for [Bmim][BF4]−sucrose pairs in water were also obtained and interpreted by the structural interactions model. Additionally, the Λ0 values for [Bmim][BF4] decrease with the molality of sucrose (mS), as well as Walden products (Λ0η), due to ...

Studies on Hydrophobic Interaction from the Conductometric Studies of Medicinal Compounds (as Salts)

Abstract The Λ0 values and association constants of some salts of medicinal interest in aqueous solution have been determined. The division of Λ0 of salts into single ion values λ0 + and λ0 − have been made using λ0 Na+ and λ0 Cl− values from the literature. The Λ0, λ0 + and λ0 − values have been found to be fairly high in aqueous solution and comparatively lesser than those in acetonitrile. Most of the drugs have been found to be dissociated as ions though association of some of the salts has been observed. The calculations of r ± of ions in water show considerable decrease in the radii values of ions in water from which inference regarding the extent of hydrophobic interactions can be made.

Behaviour of Some Copper(I) and Cobalt(III) Complexes in Acetonitrile and n-Butyronitrile at 298.15K

Abstract Molar conductances of a large number of copper(I) and cobalt(III) complexes, behaving as strong 1:1 electrolytes, have been measured in acetonitrile (AN) and n-butyronitrile (n-BTN) at 298.15K. The conductance data have been analyzed by the Shedlovsky method to evaluate Λ0 and K A values of these electrolytes. Limiting ion conductances (λ i 0) for various ions in AN have been calculated by using transference number data. In n-BTN, where no transference number data is available, such values have been calculated by an indirect method using Bu4NBPh4 as a reference electrolyte. The actual ionic radii (ri ) for various ions in solution have been calculated using a modified form of Stokes’ law. The ionic radii (ri ) for various complex ions have been compared with the ionic radii of two reference ions, Bu4N+ and Ph4B−, which are not solvated in dipolar aprotic solvents, to throw light on the solvation behaviour of these complex ions.