The resilience of Kepler systems to stellar obliquity

The Kepler mission and its successor K2 have brought forth a cascade of transiting planets. Many of these planetary systems exhibit multiple members, but a large fraction possess only a single transiting example. This overabundance of singles has lead to the suggestion that up to half of Kepler systems might possess significant mutual inclinations between orbits, reducing the transiting number (the so-called "Kepler Dichotomy"). In a recent paper, Spalding & Batygin (2016) demonstrated that the quadrupole moment arising from a young, oblate star is capable of misaligning the constituent orbits of a close-in planetary system enough to reduce their transit number, provided that the stellar spin axis is sufficiently misaligned with respect to the planetary orbital plane. Moreover, tightly packed planetary systems were shown to be susceptible to becoming destabilized during this process. Here, we investigate the ubiquity of the stellar obliquity-driven instability within systems with a range of multiplicities. We find that most planetary systems analysed, including those possessing only 2 planets, underwent instability for stellar spin periods below ~3 days and stellar tilts of order 30 degrees. Moreover, we are able to place upper limits on the stellar obliquity in systems such as K2-38 (obliquity <20 degrees), where other methods of measuring spin-orbit misalignment are not currently available. Given the known parameters of T-Tauri stars, we predict that up to 1/2 of super-Earth mass systems may encounter the instability, in general agreement with the fraction typically proposed to explain the observed abundance of single-transiting systems.Comment: 13 pages, 8 figures, accepted to The Astronomical Journa

Environ 2.5 — A Mine Ventilation and Cooling Network Simulation Tool

As mining operations progress, ore reserves are depleted and alternative are almost invariably found at increasing depth and a host of attendant difficulties in this regard face· the mine operator. Most significant among these is the control of the increasingly hostile environment encountered at depth in terms of both ground behaviour and the increasing hot environment. To enable the practical and economical design of mine ventilation and cooling systems, ventilation practitioners need effective and efficient tools to perform their duty. One such tool is the Environ 2.5, an interactive network simulation program that allows for the simultaneous simulation of airflow and air thermodynamic behaviour in an underground mine. The program can simulate networks consisting of up to 600 components such as shafts, tunnels, regulators, coolers, stopes etc. to determine optimal designs and future requirements. This paper describes the need for such software, provides a brief overview of the program\u27s functions and operation and highlights the application and benefits of Environ 2. 5

The "Spontaneous” Formation of Rudimentary Carpels on Leaf Tissue

A number of photoperiodic pea plants (Pisum sativum L.), which remained vegetative under a short photoperiod, formed rudimentary carpels on leaf tissue. Laminar tissue became folded upward and fused to form the adaxial suture. Styles and stigmas of the rudimentary carpels closely resembled the same structures of normal carpels. The finding is believed to support the classical interpretation: that the carpel is a modified lea

Nuclear quantum effects in solids using a colored-noise thermostat

We present a method, based on a non-Markovian Langevin equation, to include quantum corrections to the classical dynamics of ions in a quasi-harmonic system. By properly fitting the correlation function of the noise, one can vary the fluctuations in positions and momenta as a function of the vibrational frequency, and fit them so as to reproduce the quantum-mechanical behavior, with minimal a priori knowledge of the details of the system. We discuss the application of the thermostat to diamond and to ice Ih. We find that results in agreement with path-integral molecular dynamics can be obtained using only a fraction of the computational effort.Comment: submitted for publicatio