Pulsed magnetron oscillators sometimes show an instability known as “twinning” in which the spectrum shows two, or more, closely spaced peaks. This phenomenon is undesirable and can lead to problems when it occurs in magnetrons used in radars. An experimental investigation of twinning is described from which conclusions are drawn about the design parameters that affect it. It has been shown tha...

OBJECTIVE To characterize the incidence and risk factors for monochorionic diamniotic(MC-DA) twinning after assisted reproductive technologies (ART). DESIGN Retrospective population-based study. SETTING The study was conducted in China; Department of Reproductive Medicine Center at The First Affiliated Hospital of Anhui Medical University. POPULATION A cohort of 8860 clinical pregnancies ...

D anny de Vito would be happy to hear that for twin formation the paradigm 'smaller is stronger' still prevails. Twinning is a deformation process in crystals defined as the collective shearing of one portion of the crystal with respect to the rest. However, compared with plasticity based on dislocation glide, twinning has been scarcely studied in the deformation of metals. This is because twin...

Twinning in Holstein dairy cows has increased over time concurrent with increased milk production. More than 95% of twins in Holsteins arise due to double ovulations resulting in dizygotic twins. It is now clear that low progesterone during growth of a preovulatory follicle increases the incidence of double ovulation. Increased hepatic metabolism of progesterone as a result of the increased fee...

Cândido Godói (CG) is a small municipality in South Brazil with approximately 6,000 inhabitants. It is known as the "Twins' Town" due to its high rate of twin births. Recently it was claimed that such high frequency of twinning would be connected to experiments performed by the German Nazi doctor Joseph Mengele. It is known, however, that this town was founded by a small number of families and ...

Deformation twinning at the tip of a straight crack or notch is analyzed using a phase-field method that seeks equilibrium twin morphologies via direct minimization of a free energy functional. For isotropic solids, the tendency to twin under mode I or mode II loading is found to depend weakly on Poisson’s ratio and elastic nonlinearity and strongly on surface energy and twinning shear (i.e. ei...

Molecular dynamics simulations are performed to study the atomistic mechanisms governing the pseudoelasticity and shape memory in nickel–titanium (NiTi) nanostructures. For a h110i – oriented nanopillar subjected to compressive loading–unloading, we observe either a pseudoelastic or shape memory response, depending on the applied strain and temperature that control the reversibility of phase tr...

Twinning on the plane is a common mode of plastic deformation for hexagonal-close-packed metals. Here we report, by monitoring the deformation of submicron-sized single-crystal magnesium compressed normal to its prismatic plane with transmission electron microscopy, the reorientation of the parent lattice to a 'twin' lattice, producing an orientational relationship akin to that of the conventio...