Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

Boise State University

Selected Works

2008

Articles 1 - 10 of 10

Full-Text Articles in Physical Sciences and Mathematics

Tidal Heating Of Terrestrial Extrasolar Planets And Implications For Their Habitability, Brian Jackson, Rory Barnes, Richard Greenberg Nov 2008

Tidal Heating Of Terrestrial Extrasolar Planets And Implications For Their Habitability, Brian Jackson, Rory Barnes, Richard Greenberg

Brian Jackson

The tidal heating of hypothetical rocky (or terrestrial) extrasolar planets spans a wide range of values depending on stellar masses and initial orbits. Tidal heating may be sufficiently large (in many cases, in excess of radiogenic heating) and long-lived to drive plate tectonics, similar to the Earth's, which may enhance the planet's habitability. In other cases, excessive tidal heating may result in Io-like planets with violent volcanism, probably rendering them unsuitable for life. On water-rich planets, tidal heating may generate subsurface oceans analogous to Europa's with similar prospects for habitability. Tidal heating may enhance the outgassing of volatiles, contributing to …

Go to article

Clathrin Triskelia Show Evidence Of Molecular Flexibility, Matthew L. Ferguson, Kondury Prasad, Hacene Boukari, Dan L. Sackett, Susan Krueger, Eileen M. Lafer, Ralph Nossal Aug 2008

Clathrin Triskelia Show Evidence Of Molecular Flexibility, Matthew L. Ferguson, Kondury Prasad, Hacene Boukari, Dan L. Sackett, Susan Krueger, Eileen M. Lafer, Ralph Nossal

Matthew L. Ferguson

The clathrin triskelion, which is a three-legged pinwheel-shaped heteropolymer, is a major component in the protein coats of certain post-Golgi and endocytic vesicles. At low pH, or at physiological pH in the presence of assembly proteins, triskelia will self-assemble to form a closed clathrin cage, or “basket”. Recent static light scattering and dynamic light scattering studies of triskelia in solution showed that an individual triskelion has an intrinsic pucker similar to, but differing from, that inferred from a high resolution cryoEM structure of a triskelion in a clathrin basket. We extend the earlier solution studies by performing small-angle neutron scattering …

Go to article

Tidal Heating Of Extrasolar Planets, Brian Jackson, Richard Greenberg, Rory Barnes Jul 2008

Tidal Heating Of Extrasolar Planets, Brian Jackson, Richard Greenberg, Rory Barnes

Brian Jackson

Extrasolar planets close to their host stars have likely undergone significant tidal evolution since the time of their formation. Tides probably dominated their orbital evolution once the dust and gas cleared away, and as the orbits evolved there was substantial tidal heating within the planets. The tidal heating history of each planet may have contributed significantly to the thermal budget governing the planet's physical properties, including its radius, which in many cases may be measured by observing transit events. Typically, tidal heating increases as a planet moves inward toward its star and then decreases as its orbit circularizes. Here we …

Go to article

Spin-Orbit Coupling In An In0.52Ga0.48As Quantum Well With Two Populated Subbands, P. J. Simmonds, S. N. Holmes, H. E. Beere, D. A. Ritchie Jun 2008

Spin-Orbit Coupling In An In0.52Ga0.48As Quantum Well With Two Populated Subbands, P. J. Simmonds, S. N. Holmes, H. E. Beere, D. A. Ritchie

Paul J. Simmonds

Structural inversion asymmetry controls the magnitude of Rashba spin-orbit coupling in the electron energy spectrum of a narrow band gap semiconductor. We investigate this effect for a series of two-dimensional electron gases in In0.52Ga0.48As quantum wells, surrounded by In0.52Al0.48As barriers, where either one or two electric subbands are populated. Structural inversion asymmetry does not exist at low carrier density while at higher carrier densities (above (4–5) × 1011 cm−2), a finite spin splitting is observed. The spin orbit coupling coefficients (α) are determined from the power spectrum …

Go to article

Engineers, Development, And Engineering Education: From National To Sustainable Community Development, J. Lucena, J. Schneider Jun 2008

Engineers, Development, And Engineering Education: From National To Sustainable Community Development, J. Lucena, J. Schneider

Jen Schneider

In October 2007, Norman Borlaug wrote in Science magazine that ‘more than 200 science journals throughout the world will simultaneously publish papers on global poverty and human development – a collaborative effort to increase awareness, interest, and research about these important issues of our time’. Borlaug, Nobel Peace Prize laureate and father of the green revolution, was demonstrating that the scientific community is at last taking questions seriously of sustainability and development. Borlaug's own contentious role in the history of ‘development,’ however, points to the complexity of the term and the contested role scientists and engineers have played in that …

Go to article

Tides And The Evolution Of Planetary Habitability, Rory Barnes, Sean N. Raymond, Brian Jackson, Richard Greenberg Jun 2008

Tides And The Evolution Of Planetary Habitability, Rory Barnes, Sean N. Raymond, Brian Jackson, Richard Greenberg

Brian Jackson

Tides raised on a planet by the gravity of its host star can reduce the planet's orbital semi-major axis and eccentricity. This effect is only relevant for planets orbiting very close to their host stars. The habitable zones of low-mass stars are also close in, and tides can alter the orbits of planets in these locations. We calculate the tidal evolution of hypothetical terrestrial planets around low-mass stars and show that tides can evolve planets past the inner edge of the habitable zone, sometimes in less than 1 billion years. This migration requires large eccentricities (>0.5) and low-mass stars …

Go to article

Technology Development & Design For 22 Nm Ingaas/Inp-Channel Mosfets, Paul J. Simmonds May 2008

Technology Development & Design For 22 Nm Ingaas/Inp-Channel Mosfets, Paul J. Simmonds

Paul J. Simmonds

Because of the low electron effective mass and the high resulting carrier velocities, we are developing InGaAs/InP MOSFETs for potential application in VLSI circuits at scaling generations beyond 22 nm. We will report device design, review gate dielectric growth processes, and describe in detail the development of process modules for fabrication of fully self-aligned enhancement-mode devices. Key design challenges include the effect of the low density of states upon drive current and the effect of the low carrier mass on vertical confinement. Target electrical parameters include ~5 mA/μm drive current and ~7 mS/μm2 transconductance. Key fabrication challenges include formation …

Go to article

Tidal Evolution Of Close-In Extrasolar Planets, Brian Jackson, Richard Greenberg, Rory Barnes May 2008

Tidal Evolution Of Close-In Extrasolar Planets, Brian Jackson, Richard Greenberg, Rory Barnes

Brian Jackson

The distribution of eccentricities e of extrasolar planets with semimajor axes a > 0.2 AU is very uniform, and values for e are relatively large, averaging 0.3 and broadly distributed up to near 1. For a < 0.2 AU, eccentricities are much smaller (most e < 0.2), a characteristic widely attributed to damping by tides after the planets formed and the protoplanetary gas disk dissipated. Most previous estimates of the tidal damping considered the tides raised on the planets, but ignored the tides raised on the stars. Most also assumed specific values for the planets' poorly constrained tidal dissipation parameter Qp. Perhaps most important, in many studies the strongly coupled evolution between e and a was ignored. We have now integrated the coupled tidal evolution equations for e and a over the estimated age of each planet, and confirmed that the distribution of initial e values of close-in planets matches that of the general population for reasonable Q values, with the best fits for stellar and planetary Q being ~105.5 and ~106.5, respectively. The accompanying evolution of a values shows most close-in planets had significantly larger a at the start of tidal migration. The earlier gas disk migration did not bring all planets to their current orbits. The current small values of a were only reached gradually due to tides over the lifetimes of the planets. These results may have important implications for planet formation models, atmospheric models of "hot Jupiters," and the success of transit surveys.

Go to article

A Note On Mustata's Computation Of Multiplier Ideals Of Hyperplane Arrangements, Zach Teitler May 2008

A Note On Mustata's Computation Of Multiplier Ideals Of Hyperplane Arrangements, Zach Teitler

Zach Teitler

In 2006, M. Mustata used jet schemes to compute the multiplier ideals of reduced hyperplane arrangements. We give a simpler proof using a log resolution and generalize to non-reduced arrangements. By applying the idea of wonderful models introduced by De Concini–Procesi in 1995, we also simplify the result. Indeed, Mustat¸˘a’s result expresses the multiplier ideal as an intersection, and our result uses (generally) fewer terms in the intersection.

Go to article

Quantum Transport In In0.75Ga0.25As Quantum Wires, P. J. Simmonds, F. Sfigakis, H. E. Beere, D. A. Ritchie, M. Pepper, D. Anderson, G. A.C. Jones Apr 2008

Quantum Transport In In0.75Ga0.25As Quantum Wires, P. J. Simmonds, F. Sfigakis, H. E. Beere, D. A. Ritchie, M. Pepper, D. Anderson, G. A.C. Jones

Paul J. Simmonds

In addition to quantized conductance plateaus at integer multiples of 2e2/h, the differential conductance G=dI/dV shows plateaus at 0.25(2e2/h) and 0.75(2e2/h) under applied source-drain bias in In0.75Ga0.25As quantum wires defined by insulated split gates. This observation is consistent with a spin-gap model for the 0.7 structure. Using a tilted magnetic field to induce Landau level crossings, the g factor was measured to be ~9 by the coincidence method. This material, with a mobility of 1.8×105 cm …

Go to article