Nonadditive Change Research Articles

Контракция неводных растворов спиртов и кислот

Contraction is a non-additive change in the volume of a solution with a change in the concentration of one of its components. Contraction is caused by the formation of compounds based on mole-cules / ions of the solute and molecules of the solvent due to electrostatic interaction and the occur-rence of hydrogen or other bonds. This effect, inherent in all true solutions, is still rarely taken into account in the analysis of hydrodynamic and heat/mass transfer phenomena. The reason for this situation is the lack of information on contraction for most liquidsystems. To eliminate this draw-back, the presented study determines the contraction of non-aqueous solutions of mono-and polya-tomic alcohols and carboxylic acids. The obtained data are systematized and analyzed, a number of fluidsystems are proposed for laboratory modeling of diffusion processes in microgravity.

Uncovering the Mechanism of Dystrophin through Spectroscopic Characterization

Human dystrophin is a cytoplasmic protein that consists mainly of 24 spectrin domains positioned in tandem. Mutations in these highly conserved spectrin motifs are known to cause muscle degeneration, highlighting their role in maintaining the integrity of muscle fibers during movement. Through circular dichroism (CD), fluorescence spectroscopy (FS), and differential scanning calorimetry (DSC), the spectrins in their monomeric (S17), dimeric (S17-18), and trimeric (S17-19) forms were thermally denatured. Global fitting of CD and FS data, constrained with DSC, revealed a non-additive change in ΔGunfolding consistent with a negative coupling mechanism where the spectrins undergo mutual destabilization. This mechanism was further explored by means of Electron Paramagnetic Resonance (EPR) and Nuclear Magnetic Resonance (NMR) studies with the hypothesis that the addition of spectrin repeats confers increased structural disorder. EPR scans of S17 and S17-19 show that the trimer experiences a higher degree of mobility as compared to the monomer, supporting our hypothesis. Additionally, we will continue to investigate the conformational disorder and overall stability of hydrated spectrin constructs through Overhauser Dynamic Nuclear Polarization (ODNP), which will provide a better understanding of the local water matrix and spatial heterogeneity surrounding the hydration layer of the spectrins. From the cumulative spectroscopic data obtained through these integrated approaches, we aim to derive a more comprehensive understanding of dystrophin's elusive mechanism.

Adsorption of arsenic by hybrid anion–exchanger based on titanium oxyhydrate

The article has investigated the removal of anion–exchange forms of As(V) by organic anion–exchangers Dowex Marathon 11, Dowex SBR-P and organoinorganic anion–exchangers containing titanium oxyhydrate, from 0.2–2.0 mM solutions of NaH2AsO4 in the range of equilibrium values pH 3–10. It has been found that introduction of an inorganic component in the amount of 7 fractions of total mass, % results in non-additive (up to 50 fractions of total mass, %) increase of absorption of ions of As(V) in adsorption from weakly alkaline solutions. It was assumed that nonadditive change of the value of absorption may be caused by the influence of the negative charge of the surface of oxide component of organic anion–exchangers. It is shown that in acid media and also at an increase of the amount of the introduced titanium oxyhydrate the values of adsorption and distribution coefficient of As(V) ions approaches additive ones.

Extreme behavior of Li-ion conductivity in the Li2O–Al2O3–P2O5 glass system

Aluminophosphate glasses with compositions 50Li2O–xAl2O3–(50−x)P2O5 have been synthesized and analyzed in the x=0–10 range. The influence of alumina content on the glass transition temperature (Tg), crystallization temperature, thermal stability, density and ionic conductivity has been investigated. When Al2O3 substitutes for P2O5, Tg increases in all glass compositions. Crystallization stability has been found to be a function of alumina content. Ionic conductivity has been studied by impedance spectroscopy. Ionic conductivity and density exhibit a non-linear and non-additive change with a maximum at 6.25mol% of Al2O3. IR spectroscopy study has indicated the phosphate network depolymerization. NMR technique revealed dramatic structural changes in the glass at x>6.25. These changes lead to extreme behavior of molar volume and, as a consequence, to a maximum in ionic conductivity.

Ionic Conductivity of Mixed Glass Former 0.35Na2O + 0.65[xB2O3 + (1 – x)P2O5] Glasses

The mixed glass former effect (MGFE) is defined as a nonlinear and nonadditive change in the ionic conductivity with changing glass former fraction at constant modifier composition between two binary glass forming compositions. In this study, mixed glass former (MGF) sodium borophosphate glasses, 0.35Na2O + 0.65[xB2O3 + (1 - x)P2O5], 0 ≤ x ≤ 1, have been prepared, and their sodium ionic conductivity has been studied. The ionic conductivity exhibits a strong, positive MGFE that is caused by a corresponding strongly negative nonlinear, nonadditive change in the conductivity activation energy with changing glass former content, x. We describe a successful model of the MGFE in the conductivity activation energy terms of the underlying short-range order (SRO) phosphate and borate glass former structures present in these glasses. To do this, we have developed a modified Anderson-Stuart (A-S) model to explain the decrease in the activation energy in terms of the atomic level composition dependence (x) of the borate and phosphate SRO structural groups, the Na(+) ion concentration, and the Na(+) mobility. In our revision of the A-S model, we carefully improve the treatment of the cation jump distance and incorporate an effective Madelung constant to account for many body coulomb potential effects. Using our model, we are able to accurately reproduce the composition dependence of the activation energy with a single adjustable parameter, the effective Madelung constant, that changes systematically with composition, x, and varies by no more than 10% from values typical of oxide ceramics. Our model suggests that the decreasing columbic binding energies that govern the concentration of the mobile cations are sufficiently strong in these glasses to overcome the increasing volumetric strain energies (mobility) caused by strongly increasing glass-transition temperatures combined with strongly decreasing molar volumes of these glasses. The dependence of the columbic binding energy term on the relative high-frequency dielectric permittivity suggests that the increased polarizability of the bridging oxygens connecting SRO tetrahedral boron units to phosphorus units causes further charge delocalization away from the negatively charged tetrahedral boron units, leading to a lowering of the charge density, and is the underlying cause of the MGFE.

Structural Studies of Mixed Glass Former 0.35Na2O + 0.65[xB2O3 + (1 – x)P2O5] Glasses by Raman and 11B and 31P Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopies

The mixed glass former (MGF) effect (MGFE) is defined as a nonlinear and nonadditive change in the ionic conductivity with changing glass former composition at constant modifier composition. In this study, sodium borophosphate 0.35Na(2)O + 0.65[xB(2)O(3) + (1 - x)P(2)O(5)], 0 ≤ x ≤ 1, glasses which have been shown to exhibit a positive MGFE have been prepared and examined using Raman and (11)B and (31)P magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopies. Through examination of the short-range order (SRO) structures found in the ternary glasses, it was determined that the minority glass former, B for 0.1 ≤ x ≤ 0.7 and P for 0.7 ≤ x ≤ 0.9, is "overmodified" and contains more Na(+) ions than would be expected from simple linear mixing of the binary sodium borate, x = 1, and sodium phosphate, x = 0, glasses, respectively. Changes in the intermediate range order (IRO) structures were suggested by changes in the NMR spectral chemical shifts and Raman spectra wavenumber shifts over the full composition range x in the Raman and MAS NMR spectra. The changes observed in the chemical shifts of (31)P MAS NMR spectra with x are found to be too large to be caused solely by changing sodium modification of the phosphate SRO structural groups, and this indicates that internetwork bonding between phosphorus and boron through bridging oxygens (BOs), P-O-B, must be a major contributor to the IRO structure of these glasses. While not fully developed, a first-order thermodynamic analysis based upon the Gibbs free energies of formation of the various SRO structural units in this system has been developed and can be used to account for the preferential formation of tetrahedral boron groups, B(4), by the reaction of B(3) with P(2) groups to form B(4) and P(3) groups, respectively, where the superscript denotes the number of BOs on these units, in these glasses. This preference for B(4) units appears to be a predominate cause of the changing modifier to glass former ratio with composition x in these ternary MGF glasses and appears to be associated with the large negative value of the Gibbs free energy of formation of this group.

The glass transition temperature of mixed glass former 0.35Na2O + 0.65[xB2O3 + (1 − x)P2O5] glasses

The mixed glass former effect (MGFE) is defined as the non-linear and non-additive change in the ionic conductivity with changing glass former fraction at constant modifier composition between two binary glass former compositions. In this study, sodium borophosphate glasses, 0.35Na2O+0.65[xB2O3+(1−x)P2O5] with 0≤x≤1, have been prepared and their glass transition temperatures (Tg) have been examined as an alternative indicator of the MGFE and as an indicator of changes in the short range order (SRO) structural network units that could cause or contribute to the MGFE. The changes in Tg show a positive non-additive and non-linear trend over the changing glass former fraction, x. The increase in Tg is related to the increasing number of bridging oxygens (BO) in the glass samples, which is caused by the increase in the number of tetrahedral boron, B4, units in the SRO structure.

The densities of mixed glass former 0.35 Na2O + 0.65 [xB2O3 + (1 − x)P2O5] glasses related to the atomic fractions and volumes of short range structures

The mixed glass former effect (MGFE) is defined as a non-linear and non-additive change in the ionic conductivity with changing glass former fraction at constant modifier composition between two binary glass forming compositions. In this study, mixed glass former (MGF) sodium borophosphate glasses, 0.35 Na2O+0.65 [xB2O3+(1−x)P2O5], 0≤x≤1, which have been shown to have a strong positive MGFE, have been prepared and their physical properties, density and molar volume, have been examined as predictors of structural change. The density exhibits a strong positive non-linear and non-additive change in the density with x and a corresponding negative non-linear and non-additive change in the molar volume. In order to understand the structural origins of these changes, a model of the molar volume was created and best-fit to the experimentally determined molar volumes in order to determine the volumes of the short range order (SRO) structural units in these glasses, how these volume change from the molar volumes of the binary glasses, and how these volumes change across the range of x in the ternary glasses. The best-fit model was defined as the model that required the smallest changes in the volumes of the ternary phosphate and borate SRO structural groups from their values determined by the densities of the binary sodium phosphate and sodium borate glasses. In this best-fit molar volume model, it was found that the volumes of the various phosphate and borate SRO structural groups decreased by values ranging from a minimum value of ~1% for x=0.1 and 0.9 to a maximum value of ~6% for the phosphate and ~9% for the borate SRO groups at the minimum in molar volume at x=0.4. The free volume was found to have a negative deviation from linear which is unexpected given the positive deviation in ionic conductivity.

Nonadditive changes in genome size during allopolyploidization in the wheat (aegilops-triticum) group.

Interspecific or intergeneric hybridization, followed by chromosome doubling, can lead to the formation of new allopolyploid species. Recent studies indicate that allopolyploid formation is associated with genetic and epigenetic changes. Despite these studies, it is not yet clear whether the C value of an allopolyploid is the sum of its diploid parents. To address this question, six newly synthesized wheat allopolyploids and their parental plants were investigated. It was found that allopolyploids have a genome size significantly smaller than the expected value. The reduction of the nuclear genome size in the synthetic allotetraploids and allohexaploids was 2 pg DNA at 2C. It was also found that changes in the genome size already existed in the first generation amphiploids, indicating that the change was a rapid event. There was no difference in the reduction of nuclear genome size between the allotetraploid and the allohexaploid. These data clearly show that genome differentiation in allopolyploids was not related to the ploidy level. The data obtained clearly suggested that the nonadditive change in genome size that occurred during allopolyploidization may represent a preprogrammed adaptive response to genomic stress caused by hybridization and allopolyploidy, which serves to stabilize polyploid genomes.

Effect of inclusion level of linseed on the nutrient utilisation of diets for growing broiler chickens

1. Diets containing linseed at inclusions of 0, 80, 120 and 160 g/kg were evaluated for digestibility of nutrients and AME n content with male broiler chickens. 2. Increasing the concentration of linseed decreased the retention of nitrogen and the digestibility of amino acids, crude fat and fatty acids of diets. 3. Dietary AME n (MJ/kg) was also affected by the rate of inclusion of linseed, values decreasing from 14.39 to 12.49. 4. In general, a linear regression model explained the relationship between dietary linseed content and nutritive parameters. However, the quadratic response found for the digestibility of several amino acids and fatty acids indicated a non-additive change in their digestibility. 5. Viscosity of jejunal digesta was markedly increased by each increment of linseed in the diets. This is attributable to the presence of mucilage in linseed and it might explain many of the results obtained in this study.

Predicting retention indices of methyl-substituted pyridines in gas capillary chromatography on the basis of the principle of the nonadditive change in the energy of sorption

1. Based on the experimental determination of the retention indices of the methylpyridines, the retention indices of six dimethyl and trimethyl pyridine derivatives have been determined with good accuracy by taking into account the nonadditive change of the energy of sorption of methylene groups. 2. The calculated values of the retention indices can be used for identifying methyl-substituted pyridines in complex mixtures for analyses performed on glass capillary columns with OV-101, OV-17, and PEG-40M. 3. The deviations from additivity of the energy of sorption of methyl-substituted pyridines have been thermodynamically evaluated, and data on the dispersion nature of this phenomenon have been obtained.

Synthesis and copolymerization of 4-(1′- o-carboranyl) styrene with acryloyl ferrocene and study of the properties of the copolymers obtained

A method is proposed for obtaining 4-(1′- o-carboranyl) styrene on the basis of which copolymers with acryloyl ferrocene have been synthesized. The influence of unit heterogeneity appearing on copolymerization on the glass transition point and thermal stability is analysed. It is shown that unit heterogeneity in this case leads to additive change in the glass transition point and non-additive change in thermal stability with the composition of the copolymer.

Structure peculiarities of mixed alkali silicate glasses

The thermal properties and structure of alkali and mixed alkali (Li, Na, K) silicate glasses by means of differential scanning calorimetry (DSC), the positron annihilation method, X-ray fluorescence and infrared (300-30 cm −1) spectroscopy were studied. Introduction of different alkali cations in glass results in nonadditive change in their electron structure (bond “covalence degree” growth) and the thermal behaviour. The different manifestations of mixed alkali effect can be explained by the lessening of long-distance Coulomb interactions and strengthening the short-range forces in the mixed alkali glasses.

Modification by cyanide of the aniline-binding reaction with cytochrome P-450

Hydroxylation of aniline to p-aminophenol catalyzed by the cytochrome P-450-containing monooxygenase system of liver microsomes is inhibited by cyanide, but microsomal NADPH-cytochrome c reductase is insensitive to this inhibitor. The interaction of aniline with membrane-bound cytochrome P-450, according to spectrophotometric analyses, consists of two phases with respect to aniline concentration, and cyanide interferes differently with these two reaction phases. Noncompetitive and competitive (or mixed type) inhibitions of the aniline-binding reaction by cyanide are observed in reaction systems containing low and, high concentrations of aniline, respectively, a situation similar to the inhibitory action of cyanide on aniline hydroxylase activity. Abnormal aniline-induced difference spectra appeared when cyanide was added as the spectral modifier, and the magnitude of the spectral change in the presence of both aniline and cyanide was a nonadditive change. These results suggest the dissociation of the cytochrome P-450·cyanide complex by aniline. A similar result indicating dissociation of the complex was also obtained by epr spectroscopy. We therefore suggest that addition of a high concentration of substrate causes insensitivity of the microsomal hydroxylase system to cyanide.