Stress-strain relationships with nonlinear deformation of orthotropic glass-reinforced plastics

A theory of nonlinear elasticity of anisotropic bodies of the flow theory type is used to investigate nonlinear strains in orthotropic glass-reinforced plastics. Its applicability is experimentally confirmed (for two types of GRP) and the strain-hardening function employed in the theory is plotted. Simplified relationships are derived for direct loading and the relations obtained are compared with the strain theory of nonlinearelastic anisotropic bodies.Mekhanika Polimerov, Vol. 1, No. 4, pp. 28–34, 1965     

Simulation of the deformation processes of nonlinear viscoelastic media

Questions of the similarity and the possibility of simulating the deformation processes of nonlinear viscoelastic medía are investigated. Systems of characteristic parameters are given. It is established that simulation based on the same material is possible only if the characteristic time of the process is the same and the stresses and strains at similar points of the model and the simulated object are equal. The characterstic time for a model made of different material is different from that for the simulated object.Mekhanika Polimerov, Vol. 3, No. 2, pp. 221–226, 1967     

Nonlinear interaction of vibrational mode interactions in radiationless transitions

A method is proposed for calculating the transition probability in a two-level electron-vibration system, using a generating functional. Harmonic terms are used for the zeroth approximation. In the analysis of anharmonic terms the method makes it possible to transcend the limits of conventional perturbation theory with respect to the anharmonicity parameter. In the formulated cumulant expansion the method can be used to obtain a representation for the transition probability with allowance for convergence of the vibrational energy levels toward the dissociation limit.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 68–72, June 1981.     

Lysine-specific molecular tweezers are broad-spectrum inhibitors of assembly and toxicity of amyloid proteins

Amyloidoses are diseases characterized by abnormal protein folding and self-assembly, for which no cure is available. Inhibition or modulation of abnormal protein self-assembly, therefore, is an attractive strategy for prevention and treatment of amyloidoses. We examined Lys-specific molecular tweezers and discovered a lead compound termed CLR01, which is capable of inhibiting the aggregation and toxicity of multiple amyloidogenic proteins by binding to Lys residues and disrupting hydrophobic and electrostatic interactions important for nucleation, oligomerization, and fibril elongation. Importantly, CLR01 shows no toxicity at concentrations substantially higher than those needed for inhibition. We used amyloid β-protein (Aβ) to further explore the binding site(s) of CLR01 and the impact of its binding on the assembly process. Mass spectrometry and solution-state NMR demonstrated binding of CLR01 to the Lys residues in Aβ at the earliest stages of assembly. The resulting complexes were indistinguishable in size and morphology from Aβ oligomers but were nontoxic and were not recognized by the oligomer-specific antibody A11. Thus, CLR01 binds already at the monomer stage and modulates the assembly reaction into formation of nontoxic structures. The data suggest that molecular tweezers are unique, process-specific inhibitors of aberrant protein aggregation and toxicity, which hold promise for developing disease-modifying therapy for amyloidoses.     

Preparation and characteristics of composites based on polypropylene and ultradispersed calcium carbonate

Feasibility studies directed at the parallel increase in the elastic modulus and impact toughness of polypropylene via introduction of ultradispersed CaCO₃ particles with sizes of 100 (Socal U1S2) and 60 nm (Socal 312V) have been performed. The effects of the content and sizes of CaCO₃ particles and the nature of a surfactant on the character of distribution of particles, the thermophysical characteristics of the polymer matrix, and the mechanical characteristics and heat resistance of the nanocomposites are analyzed. Microscopic studies reveal that nanoparticles show a tendency toward structuring. DSC studies have proved the nucleating action of ultrafine particles during the crystallization of PP. For the composites containing 15 vol % of Socal 312V CaCO₃ nanoparticles, the increase in the tensile elastic modulus achieves its maximum; depending on the nature of the surfactant, the reinforcing effect increases by 70-40%. As compared to the initial PP, the presence of ultrafine particles in the composites prevents a decrease in the storage modulus of PP with increasing temperature from 0 to 50°C; as a result, the reinforcing effect increases from 30-40% at temperatures below the glass transition temperature to 40–75% at 50°C. For the nanocomposites with U1S2 in the presence of Triton X-100 or fluorinated alcohol telomer, the impact toughness increases over the entire filler content interval; when the filler concentration is 15 vol %, the impact toughness of nanocomposites is higher than that of the initial PP by factors of 3 and 4.5, respectively. It has been found that nanocomposites containing 5 vol % CaCO₃ nanoparticles show the effect of thermal stabilization, which comes up to about 50°C.