Rheological properties of asphalt/SBS/clay blends

The effect of the addition of clay as a third component in polymer modified asphalts has been investigated. After a preliminary investigation on the binary asphalt/clay and polymer/clay blends, the tertiary blends were prepared by adding the clay and polymer to the asphalt, either separately or in the form of a premixed master batch. Intercalated nanocomposites with comparable interlayer distances and glass transition temperatures were obtained in both cases. However, the results show that the mixing procedure significantly affected the final rheological properties. The master curves built in the linear viscoelastic range and represented in both the frequency and the temperature domains help to visualize and evaluate such differences.     

Non-Markovian diffusion process in polymers and stretched exponential relaxation

In this contribution, we model the long-time behaviour of the desorption from an LDPE sheet, using non-Markovian random walks. It is shown that the mass of penetrant in the final stage of desorption decays as t ^–m , where m is proportional to the exponent of the probability distribution (t) t ^–(1+u), 0 < v < 1. Furthermore, it is shown that this model may lead to the so-called mechanical stretched exponential relaxation, and that Wagner's memory function can be obtained as a special case.Presented at the second conference Recent Developments in Structured Continua, May 23–25, 1990, in Sherbrooke, Québec, Canada     

A general method for enclosing solutions of interval linear equations

We describe a general method for enclosing the solution set of a system of interval linear equations. We present a general theorem and an algorithm in a MATLAB-style code.     

On Rump’s characterization of <Emphasis Type=Italic>P</Emphasis>-matrices

The necessary and sufficient P-matrix condition by Rump (Linear Algebra Appl 363:237–250, 2003) is simplified by showing that one of its assumptions can be deleted without affecting validity of the result.     

Pyrazinecarboxamides as potential elicitors of flavonolignan and flavonoid production in Silybum marianum and Ononis arvensis cultures in vitro

The effect of new synthetic pyrazinecarboxamide derivatives as potential elicitors of flavonolignan and flavonoid production in Silybum marianum and Ononis arvensis cultures in vitro was investigated. Both tested elicitors increased the production of flavonolignans in S. marianum callus and suspension cultures and flavonoids in O. arvensis callus and suspension cultures. Compound I, 5-(2-hydroxybenzoyl)-pyrazine-2-carboxamide, has shown to be an effective elicitor of flavonolignans and taxifoline production in Silybum marianum culture in vitro. The maximum content of silydianin (0.11%) in S. marianum suspension culture was induced by 24 h elicitor application in concentration of 1.159 × 10?3 mol/L. The maximum content of silymarin complex (0.08%) in callus culture of S. marianum was induced by 168 h elicitor application of a concentration 1.159 × 10?? mol/L, which represents contents of silydianin (0.03%), silychristin (0.01%) and isosilybin A (0.04%) compared with control. All three tested concentrations of compound II, N-(2-bromo-3-methylphenyl)-5-tert-butylpyrazin-2-carboxamide increased the flavonoid production in callus culture of O. arvensis in a statistically significant way. The best elicitation effect of all elicitor concentrations had the weakest c? concentration (8.36 × 10?? mol/L) after 168 h time of duration. The maximum content of flavonoids (about 5,900%) in suspension culture of O. arvensis was induced by 48 h application of c? concentration (8.36 × 10?? mol/L).     

Insights into Antimalarial Activity of N-Phenyl-Substituted Cinnamanilides

Due to the urgent need of innovation in the antimalarial therapeutic arsenal, a series of thirty-seven ring-substituted N-arylcinnamanilides prepared by microwave-assisted synthesis were subjected to primary screening against the chloroquine-sensitive strain of P. falciparum 3D7/MRA-102. The lipophilicity of all compounds was experimentally determined as the logarithm of the capacity factor k, and these data were subsequently used in the discussion of structure-activity relationships. Among the screened compounds, fourteen derivatives exhibited IC₅₀ from 0.58 to 31 µM, whereas (2E)-N-(4-bromo-2-chlorophenyl)-3-phenylprop-2-enamide (24) was the most effective agent (IC₅₀ = 0.58 µM). In addition, (2E)-N-[2,6-dibromo-4-(trifluoromethyl)- phenyl]-3-phenylprop-2-enamide (36), (2E)-N-[4-nitro-3-(trifluoromethyl)phenyl]-3-phenylprop- 2-enamide (18), (2E)-N-(2-bromo-5-fluorophenyl)-3-phenylprop-2-enamide (23), and (2E)-3-phenyl-N-(3,4,5-trichlorophenyl)prop-2-enamide (33) demonstrated efficacy in the IC₅₀ range from 2.0 to 4.3 µM, comparable to the clinically used standard chloroquine. The results of a cell viability screening performed using THP1-Blue™ NF-κB cells showed that none of these highly active compounds displayed any significant cytotoxic effect up to 20 μM, which makes them promising Plasmodium selective substances for further investigations.     

Steric Effects on Reaction Rates. Part IX. Force-Field Parameters for Bridgehead and Rigid Tertiary Carbenium Ions

Molecular-mechanics calculations for strain of carbenium ions are tested using Bentley's unified reactivity scale for bridgehead solvolysis as reference. Excellent correlations are obtained for solvolytic bridgehead reactivity with the calculated steric-energy difference (ΔE_st) between substrate (R? H or R? OH) and cation (R⁺). After adjustment of appropriate force-field parameters, the approach is successfully extended to the rigid, but planar cations derived from structures 15 – 20 ; however, the general set of parameters cannot be applied to highly strained systems such as the cation formed from 17 . With all of the 18 sets of parameters tested, the 2-endo-norbornyl derivative 16 , is adequately correlated, while the exo isomer 15 exhibits enhanced reactivity by a factor of ca. 10² to 10³.     

Configuration interaction calculations of the valence and the inner valence levels of the CS molecule

CI calculations were performed on the energies and relative intensities of the outer and inner valence levels of the CS molecule. Breakdown of the one-particle model is discussed in terms of CI, and the results are compared with the analogous investigations using the Green's function technique.     

Calculation of vibrational structure in the core and valence esca spectra of CO and N2

The vibrational excitations in the core and valence ESCA bands of CO and N₂ have been investigated by means of Franck—Condon (FC) analysis. FC factors obtained from optimized geometries and from the force constants of the neutral ground and ionized states are compared with those obtained from calculated ionized-state energy gradients. Geometries, force constants, and energy gradients are calculated both from frozen-orbital energies and from OS RHF wavefunctions. The differences between the results of the methods employed are discussed in the light of experimental data.