Exciting Mutual Inclination in Planetary Systems with a Distant Stellar Companion: The Case of Kepler-108

We study the excitation of mutual inclination between planetary orbits by a novel secular-orbital resonance in multi-planet systems perturbed by binary companions, which we call “ivection.” The ivection resonance happens when the nodal precession rate of the planet matches a multiple of the orbital frequency of the binary, and its physical nature is similar to the previously studied evection resonance. Capture into an ivection resonance requires encountering the resonance with slowly increasing nodal precession rate, and it can excite the mutual inclination of the planets without affecting their eccentricities. We discuss the possible outcomes of ivection resonance capture, and we use simulations to illustrate that it is a promising mechanism for producing the mutual inclination in systems where planets have significant mutual inclination but modest eccentricity, such as Kepler-108. We also find an apparent deficit of multi-planet systems that would have a nodal precession period comparable to the binary orbital period, suggesting that ivection resonance may inhibit formation of or destablize multi-planet systems with an external binary companion.

Application of non-destructive neutron resonance capture analysis for investigation of women’s Old Believer cross dating back to the second half of the 17th century

Neutron Resonance Capture Analysis (NRCA) is presently being developed at the Frank Laboratory of Neutron Physics (FLNP) to determine the elemental composition of samples. The NRCA is a nondestructive method that allows measuring objects’ bulk composition. The procedure is based on detecting neutron resonances in radiative capture and the measurement of the yield of reaction products in these resonances. The experiments are carried out at the Intense REsonance Neutron source (IREN). In this study, we applied the NRCA to investigate an archaeological object provided by the Museum and Exhibition Complex (MVK) "Volokolamsk Kremlin". The object was a women’s Old Believer cross (second half of the 17th century) found in the Moscow region, Volokolamsk district, the village of Chubarovo.

Improvement of Conversion Ratio of Thorium Fuel in LWR by Adding Neutron Absorber

The reproduction factor of Th232 is high in the thermal energy range and there is a possibility to achieve the breeding in LWRs. However, it is necessary to improve the conversion ratio since the breeding is difficult in LWRs. The conversion ratio can be improved by suppressing capture rate of Pa233 and by promoting capture rate of Th232. In addition, these capture rates can be modified by adding neutron absorber. Therefore, the neutron absorber is focused for improving the conversion ratio in this study. The high resonance peaks of Pa233 capture cross section exist around 1∼100 eV. The resonance peaks of Th232 are higher than 10 eV. Thus, when the 1∼10 eV neutrons are suppressed in the fuel, the Pa233 resonance capture reaction is suppressed and the Th232 resonance capture reaction is promoted by neutron spectrum hardening. Therefore, six neutron absorbers that have high capture cross section peaks at 1∼10 eV were selected. The PWR pin cell calculations were carried out by Monte Carlo code MVP. The fuels are composed of a base material and an absorber. The base material is an oxidized fuel composed of U233(10 wt%), Th232(89.95 wt%), and Pa233(0.05 wt%). The amount of neutron absorber was adjusted so that the infinite multiplication factor becomes 1.33. The impact of adding neutron absorber on the reaction rate was evaluated. As the result, the hardening of the neutron spectrum leads increase of the capture rate of Pa233, and the capture rate of Th232 in the epithermal energy range is increased. The change of capture rate of Th232 is greater than that of Pa232. Therefore, the conversion ratio is found to be improved by adding neutron absorber.

Controlling the Chaotic Motions of an Airfoil with a Nonlinear Stiffness Using Closed-Loop Harmonic Parametric Excitation

The purpose of this research is to conduct a preliminary investigation into the possibility of suppressing the flutter and post-flutter (chaotic) responses of a two-dimensional self-excited airfoil with a cubic nonlinear stiffness (in torsion) and linear viscous damping via closed-loop harmonic parametric excitation. It was found that the initial configuration of the proposed control scheme caused the torsional/pitch dynamics to act as a nonlinear energy sink; as a result, it was identified that the mechanisms of vibration suppression are the resonance capture cascade and the short duration or isolated resonance capture. It is the isolated resonance capture that is responsible for the second-order-like damping and full vibration suppression of the aeroelastic system. The unforced and closed-loop system was subjected to random excitation to simulate aerodynamic turbulence. It was found that the random excitation suppresses the phase-coherent chaotic response, and the closed-loop system is susceptible to random excitation.

A hitherto unknown stability of DNA basepairs

The resonance capture of very low energy electrons (vLEEs) into the π* orbitals of nucleobases is a potential doorway to DNA damage. A rapid nonenzymatic structural response specific to the complementary basepairing is found to prevent direct damages.