The resonance and pre‐resonance Raman scattering in the low energy 11B2u and 11B3u states of 1,4,5,8‐naphthalenetetracarboxy dianhydride in terms of DFT methods. The aggregation of NTCDA molecules in the ethanol and methanol solutions

The absorption, pre‐resonance, and resonance Raman spectra of 1,4,5,8‐naphthalenetetracarboxy dianhydride (NTCDA) molecule are examined in terms of time‐dependent density functional theory at TD‐B3LYP/aug‐cc‐pVDZ and TD‐SVWN/aug‐cc‐pVDZ levels. The Franck–Condon analysis performed for two 1¹A_g → 1¹B_2u and 1¹A_g → 1¹B_3u overlapping transitions leads to an excellent agreement between the theoretical predictions and experimental data providing that the calculated absorption is confronted with that measured in chloroform or acetonitrile but not in the ethanol (methanol) solution. We argue that absorption spectra measured in ethanol solution already known in literature do not characterize NTCDA molecule. On the basis of the absorption and resonance scattering spectra, we may deliberate that the dimerization of NTCDA is responsible for utterly different absorption observed in ethanol (methanol) comparing with less active solvents (chloroform and acetonitrile). That conclusion is supported by the dimer vibronic theory and by the TD‐B97d computations at the aug‐cc‐pVDZ basis set level. Copyright © 2013 John Wiley & Sons, Ltd.     

The principle of the minimum of the dissipation potential for non-isothermal processes

In this paper, we contribute to the methodology of material modeling by presenting a potential-based approach for non-isothermal inelastic processes. It is based on the principle of the minimum of the dissipation potential which was used previously only in the isothermal context. In contrast to the principle of maximum dissipation, the presented procedure results in mathematically simplified equations. Due to its variational character, the inclusion of constraints is very simple. After derivation of our method, we use the examples of non-isothermal perfect plasticity and shape memory alloys for demonstration of the validity and performance of the concept.     

Interpreting early land management through compound specific stable isotope analyses of archaeological soils

Compound specific stable isotope analyses of managed soils using isotope ratio mass spectrometry have been undertaken as a means of determining early land use practices. delta (15)N amino acid signals demonstrate differences between manured grassland, unmanured grassland and continuous cereal cultivation under long-term experimental land use control conditions, with delta (15)N in hydrophobic amino acids providing the most distinctive signals. Analysis of early modern/medieval and of Bronze age anthropogenic soils from Orkney demonstrates that such signals are retained in archaeological contexts. delta (13)C analyses of n- alkanoic acid components of the fossil, Bronze Age, anthropogenic soils suggest a major terrestrial input to these soils, with uniform composition of formation materials. Surficial soils demonstrate the assimilation of isotopically lighter carbon, providing a means of assessing the mobility of the n- alkanoic acids within soils and sediments. Copyright 1999 John Wiley & Sons, Ltd.     

Correlated electromigration of H in the switchable mirror YH(3-delta)

Electromigration of hydrogen in YH(3-delta) is studied by exploiting the H concentration dependence of the optical transmission of YH(3-delta). We find the effective valence Z* of H in YH(3-delta) to be negative. Its value is dominated by a huge wind-force-like term, i.e., Z* approximately K/rho, with K approximately -60 mOmega cm. This value is 3 orders of magnitude larger than typical for H in metals. In an Arrhenius plot, the ratio of hydrogen and electron fluxes extrapolates to unity at infinite temperature, suggesting a one-to-one correlation of hydrogen and electron hopping. We discuss our results in the light of strong electron correlation theories which predict each proton to bind two electrons in a sort of Zhang-Rice singlet.     

N‐[tert‐Butoxy­carbonyl­glycyl‐(Z)‐α,β‐dehydro­phenyl­alanylglycyl‐(E)‐α,β‐dehydro­phenyl­alanylphenyl­alanyl]‐4‐nitro­aniline ethanol solvate

The α,β‐dehydro­phenyl­alanine residues influence the conformation of the title penta­peptide Boc⁰–Gly¹–Δ^ZPhe²–Gly³–Δ^EPhe⁴–l ‐Phe⁵–p‐NA ethanol solvate, C₄₂H₄₃N₇O₉·C₂H₅OH. The first unsaturated phenyl­alanyl (Δ^ZPhe²) and the third glycyl (Gly³) residues form a type I β turn, while the second unsaturated phenyl­alanyl (Δ^EPhe⁴) and the last phenyl­alanyl (l ‐Phe⁵) residues are part of a type II β turn. All the amino acids in the peptide are linked trans to one another. The crystal structure is stabilized by intra‐ and inter­molecular hydrogen bonds.     

Configurational forces and couples in fracture mechanics accounting for microstructures and dissipation

Configurational forces and couples acting on a dynamically evolving fracture process region as well as their balance are studied with special emphasis to microstructure and dissipation. To be able to investigate fracture process regions preceding cracks of mode I, II and III we choose as underlying continuum model the polar and micropolar, respectively, continuum with dislocation motion on the microlevel. As point of departure balance of macroforces, balance of couples and balance of microforces acting on dislocations are postulated. Taking into account results of the second law of thermodynamics the stress power principle for dissipative processes is derived.Applying this principle to a fracture process region evolving dynamically in the reference configuration with variable rotational and crystallographic structure, the configurational forces and couples are derived generalizing the well-known Eshelby tensor. It is shown that the balance law of configurational forces and couples reflects the structure of the postulated balance laws on macro- and microlevel: the balance law of configurational forces and configurational couples are coupled by field variable, while the balance laws of configurational macro- and microforces are coupled only by the form of the free energy. They can be decoupled by corresponding constitutive assumption.Finally, it is shown that the second law of thermodynamics leads to the result that the generalized Eshelby tensor for micropolar continua with dislocation motion consists of a non-dissipative part, derivable from free and kinetic energy, and a dissipative part, derivable from a dissipation pseudo-potential.     

Solution behavior of ionomers. I. Metal sulfonate ionomers in mixed solvents

The solution behavior of metal sulfonate-containing ionomers has been investigated in various mixed solvent systems. Ionomers, such as lightly sulfonated polystyrene (sodium salt) and sulfonated ethylene-propylene-diene terpolymer (metal salts) are generally insoluble in typical hydrocarbon solvents, but readily dissolve when small amounts of alcohols or other polar cosolvents are present. At relatively low polymer concentration these ionomers display unusually high thickening behavior in nonpolar solvents when compared with nonionic polymers because of association of the metal sulfonate groups. The addition of modest levels of polar cosolvent markedly decreases the solution viscosity and gives rise to viscosity-temperature relationships different from those of conventional polymer solutions. For example, such solutions can display vicosities which increase, are relatively constant, or display maxima or minima over broad temperature ranges. These observations are interpreted as arising from a temperature-dependent preferential interaction of the cosolvent with the sulfonate groups. While these ionomers can be regarded as polyelectrolytes of low charge density, they do not display the typical “polyelectrolyte” behavior often observed in aqueous solutions. This anomalous behavior is attributed to the fact that the metal sulfonate groups are largely un-ionized in solvents of low dielectric constant. Therefore, the solution behavior is dominated by ion pair interactions rather than free ions.     

The role of memory effects in scholastics approach to collinear diatom—diatom collisions

The role of memory effects in the stochastic approach to vibrational—vibrational transitions in collinear diatom—diatom collisions is studied. It is shown that with the help of a new recurrence relation for Clebsch—Gordan coefficients we were able to solve exactly a non-markovian master equation for a model hamiltonian. The derived solution for probabilities of V—V transitions is compared with markovian as well as exact semiclassical results over a wide range of velocities of the colliding molecules. We have found a substantial improvement of markovian results, both qualitative and quantitative, when the non-markovian effects have been included in the stochastic theory. This is in contrast with a recent study by King and Schatz who got for a restricted V—T model more accurate probabilities from the markovian approach than from the non-markovian one. The reasons for this are also discussed.     

Testing of nickel phosphate (NiP) catalyst for ethylbenzene oxydehydrogenation by means of isopropanol dehydration

It has been shown that NiP catalyst, if fresh, contains a high concentration of the same type acid-base surface centers as those participating in i-PrOH dehydration on -Al₂O₃. The concentration of these centers diminishes rapidly after a modification of NiP surface in a stream of ethylbenzene (EtPh) oxydehydrogenation products.

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, NiP - , , i-PrOH -Al₂O₃. NiP .