On Question of Metals’ Plasticity

Straightforward and reverse descriptions are used to describe the metal’s plasticity zone. For the straightforward descriptions of the hardening zone, the “reference” point is the relative deformation εy corresponding to the yield strength σy. The deviation of the relative deformations in the metal hardening zone is measured relative to εy, and the deviation of the normal stresses is measured relative to σy. For the reverse descriptions of the metal hardening zone, the “reference” point is the relative deformation εu corresponding to the ultimate strength σu. The deviation of the relative deformations in the metal hardening zone is measured relative to εu, and the deviation of the normal stresses is measured relative to σu.

Calculation of Stress-Strain State and Contact Stresses in the Process of Chip Formation

The reported paper presents a field pattern of sliding lines in a plastic zone of flow chip formation in the process of cutting metals considered for front and rear angles on the cutting blade other than zero. Equations of sliding lines for these conditions are proposed. Using calculation data, plasticity zone border lines are plotted for positive and negative front angles. The paper suggests methods and calculation data on average stress and plane stress state components in nodal points of the plastic zone of chip formation. The study provides data for plotting distribution diagrams of normal and tangential stresses of contact stresses on work surfaces of a cutting blade.

Mutational Analysis of the Chlamydia muridarum Plasticity Zone

Pathogenically diverseChlamydiaspp. can have surprisingly similar genomes.Chlamydia trachomatisisolates that cause trachoma, sexually transmitted genital tract infections (chlamydia), and invasive lymphogranuloma venereum (LGV) and the murine strainChlamydia muridarumshare 99% of their gene content. A region of high genomic diversity betweenChlamydiaspp. termed the plasticity zone (PZ) may encode niche-specific virulence determinants that dictate pathogenic diversity. We hypothesized that PZ genes might mediate the greater virulence and gamma interferon (IFN-γ) resistance ofC. muridarumcompared toC. trachomatisin the murine genital tract. To test this hypothesis, we isolated and characterized a series ofC. muridarumPZ nonsense mutants. Strains with nonsense mutations in chlamydial cytotoxins,guaBA-add, and a phospholipase D homolog developed normally in cell culture. Two of the cytotoxin mutants were less cytotoxic than the wild type, suggesting that the cytotoxins may be functional. However, none of the PZ nonsense mutants exhibited increased IFN-γ sensitivity in cell culture or were profoundly attenuated in a murine genital tract infection model. Our results suggest thatC. muridarumPZ genes are transcribed—and some may produce functional proteins—but are dispensable for infection of the murine genital tract.