A method for approximate calculation of the energy integral for notched and cracked bodies

We propose an approximate method for the calculation of the energyJ-integral for bodies with notches (cracks) subjected to elastoplastic deformations based on an analysis of stress and stress concentration at the tip of the notch (crack). The formulas for theJ-integral are obtained in terms of the theoretical stress concentration factor (stress intensity factor), nominal stresses, radius of the notch tip (crack length), and elastoplastic properties of the material. These formulas enable one to representJ-based design curves with account of the effect for material hardening.Blagonravov Institute of Mechanical Engineering, Russian Academy of Sciences, Moscow; Moscow Institute of Engineering Physics, Moscow. Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 30, No. 3, pp. 82–87, May–June, 1994.     

Preparation and characterization of multilayered ZrO<Subscript>2</Subscript> coatings on silicon carbide fibers for SiC/SiC composites

We have studied the surface morphology, phase composition, and oxidation resistance of multilayered tetragonal zirconia coatings produced on silicon carbide fibers by a sol-gel process and measured the tensile strength of individual fibers as a function of the number of layers in the coating. SiC-fiber-reinforced silicon carbide minicomposites have been prepared through pyrolysis of an organosilicon polymer, and their fracture surfaces have been examined. Using microindentation, we have determined the critical fiber-matrix debonding stress. The results demonstrate that the ZrO₂ coating on the fibers has the form of uniform, weakly bonded layers. The presence of a multilayered ZrO₂ interphase alters the fracture behavior of the SiC/SiC composites. The fiber debond stress in the composites markedly decreases with an increase in the number of layers in the interphase.     

Monitoring the stress-corrosion defects of gas mains

In contrast to direct investigations and the study of nucleation and growth of stress-corrosion flaws under different external actions, statistical analysis allows one to reveal the state of a gas main and the dependence of the stress-corrosion process on different external actions. The advantage of this approach is the ability to study the actual defects of a pipeline under operating conditions; the objectiveness of the results is determined by the representativeness of a sample of the database, which rests upon a broad spectrum of external and internal actions that are revealed by intrapipe nondestructive testing (IPNT) and the possibility of accomplishing the comparative assessment of the significance of the influence factors.     

Expanding the Repertoire of Low-Molecular-Weight Pentafluorosulfanyl-Substituted Scaffolds

The pentafluorosulfanyl (-SF₅) functional group is of increasing interest as a bioisostere in medicinal chemistry. A library of SF₅-containing compounds, including amide, isoxazole, and oxindole derivatives, was synthesised using a range of solution-based and solventless methods, including microwave and ball-mill techniques. The library was tested against targets including human dihydroorotate dehydrogenase (HDHODH). A subsequent focused approach led to synthesis of analogues of the clinically used disease modifying anti-rheumatic drugs (DMARDs), Teriflunomide and Leflunomide, considered for potential COVID-19 use, where SF₅ bioisostere deployment led to improved inhibition of HDHODH compared with the parent drugs. The results demonstrate the utility of the SF₅ group in medicinal chemistry.     

Synthesis of reactive copolymers with peroxide functionality for cross-linking water-soluble polymers

A series of reactive copolymers with peroxide functionality (RCPFs) were synthesized via radical copolymerization of monomer mixtures in an organic solvent comprised of a peroxide monomer 5-(tert-butyl peroxy)-5-methylhex-1-en-3-yne, acrylamide, maleic anhydride, and butyl methacrylate. Peroxide functionality allows the RCPFs to initiate a variety of radical processes, including cross-linking of organic polymers. Hydrophilic monomer subunits (acrylamide and maleic anhydride) within the RCPF macromolecules promote cross-linking of water-soluble polymers. We aimed to investigate RCPF comonomer ratio and its effects on copolymerization kinetics and composition, as well as physico-chemical and colloidal properties. We also evaluated and characterized the kinetic parameters of the thermal decomposition of peroxide moieties in the synthesized RCPF. Findings revealed that RCPF possessed surface-active properties and reduced surface tension at its aqueous solution–air interface. The data indicated that the decomposition process complied with the first-order kinetics, and complex thermal analysis confirmed the presence of peroxide moieties. RCPFs' ability to cross-link water-soluble polymers was demonstrated on poly(acrylamide) and poly(vinyl alcohol).     

Nano-Theranostic Modality for Visualization of the Placenta and Photo-Hyperthermia for Potential Management of Ectopic Pregnancy

Ectopic pregnancy (EP) is the leading cause of maternity-related death in the first trimester of pregnancy. Approximately 98% of ectopic implantations occur in the fallopian tube, and expedient management is crucial for preventing hemorrhage and maternal death in the event of tubal rupture. Current ultrasound strategies misdiagnose EP in up to 40% of cases, and the failure rate of methotrexate treatment for confirmed EP exceeds 10%. Here the first theranostic strategy for potential management of EP is reported using a near-infrared naphthalocyanine dye encapsulated within polymeric nanoparticles. These nanoparticles preferentially accumulate in the developing murine placenta within 24 h following systemic administration, and enable visualization of implantation sites at various gestational stages via fluorescence and photoacoustic imaging. These nanoparticles do not traverse the placental barrier to the fetus or impact fetal development. However, excitation of nanoparticles localized in specific placentas with focused NIR light generates heat (>43 °C) sufficient for disruption of placental function, resulting in the demise of targeted fetuses with no effect on adjacent fetuses. This novel approach would enable diagnostic confirmation of EP when current imaging strategies are unsuccessful, and elimination of EP could subsequently be achieved using the same nano-agent to generate localized hyperthermia resulting in targeted placental impairment.