All-optical combiner-splitter and gating devices based on straight waveguides

A two-mode optical combiner-splitter device is designed based on all straight waveguides that maintains the integrity of the two modes during propagation and allows for an analytic analysis. The design analysis has the potential to improve the precision of the device fabrication. The design is used in an analytic optical gate based on a nonlinear Mach-Zehnder interferometer. The design reduces the size of a previously proposed device and simplifies its analysis

Projecting the Economic Impact of the Fayetteville Shale Play for 2005-2008

This study projects the general economic impact from exploration and development activities related to the Fayetteville Shale. The Fayetteville Shale is an unconventional gas reservoir located on the Arkansas side of the Arkoma Basin, ranging in thickness from 50 to 325 feet and ranging in depth from 1,500 to 6,500 feet. The Fayetteville Shale is aerially extensive and may be present across numerous counties in central and eastern Arkansas, including the counties of Cleburne, Conway, Faulkner, Independence, Johnson, St. Francis, Prairie, Van Buren, White, and Woodruff

Projecting the Economic Impact of the Fayetteville Shale Play for 2005-2008

This study projects the general economic impact from exploration and development activities related to the Fayetteville Shale. The Fayetteville Shale is an unconventional gas reservoir located on the Arkansas side of the Arkoma Basin, ranging in thickness from 50 to 325 feet and ranging in depth from 1,500 to 6,500 feet. The Fayetteville Shale is aerially extensive and may be present across numerous counties in central and eastern Arkansas, including the counties of Cleburne, Conway, Faulkner, Independence, Johnson, St. Francis, Prairie, Van Buren, White, and Woodruff

Triple-Star Candidates Among the Kepler Binaries

We present the results of a search through the photometric database of eclipsing Kepler binaries (Prsa et al. 2011; Slawson et al. 2011) looking for evidence of hierarchical triple star systems. The presence of a third star orbiting the binary can be inferred from eclipse timing variations. We apply a simple algorithm in an automated determination of the eclipse times for all 2157 binaries. The "calculated" eclipse times, based on a constant period model, are subtracted from those observed. The resulting O-C (observed minus calculated times) curves are then visually inspected for periodicities in order to find triple-star candidates. After eliminating false positives due to the beat frequency between the ~1/2-hour Kepler cadence and the binary period, 39 candidate triple systems were identified. The periodic O-C curves for these candidates were then fit for contributions from both the classical Roemer delay and so-called "physical" delay, in an attempt to extract a number of the system parameters of the triple. We discuss the limitations of the information that can be inferred from these O-C curves without further supplemental input, e.g., ground-based spectroscopy. Based on the limited range of orbital periods for the triple star systems to which this search is sensitive, we can extrapolate to estimate that at least 20% of all close binaries have tertiary companions.Comment: 19 pages, 13 figures, 3 tables; ApJ, 2013, 768, 33; corrected Fig. 7, updated references, minor fixes to tex

Survey of the Labor Market for New Ph.D. Hires in Economics 2005-2006

This year, the survey questionnaire was sent to 372 organizations. Questionnaires were returned by 150 (40.3 percent) for a response rate that was lower than the 2004-05-survey response rate of 49.1 percent. Of this year’s responses, 102 (68.0 percent) were from those who responded to last year’s survey; 48 (32.0 percent) came from new respondents. Among the academic institutions responding, the distribution of highest degrees offered was as follows: Ph.D.—32.0 percent; Master—14.7 percent; Bachelor—39.3 percent. The remaining 14.0 percent did not indicate their highest degree offered. One of the respondents was a non-academic organization. The responses are reported for all respondents (including the non-academic institution and schools that did not report “highest degree offered”), and separately for Ph.D. degree-granting institutions and for schools whose highest degree offered is the Bachelor or Master degree. Data for institutions in the National Research Council’s Research Doctorate Report, 1995, are reported as a subset of Ph.D. degree-granting schools. They are referred to as the Top 30

Survey of the Labor Market for New Ph.D. Hires in Economics 2005-2006

This year, the survey questionnaire was sent to 372 organizations. Questionnaires were returned by 150 (40.3 percent) for a response rate that was lower than the 2004-05-survey response rate of 49.1 percent. Of this year’s responses, 102 (68.0 percent) were from those who responded to last year’s survey; 48 (32.0 percent) came from new respondents. Among the academic institutions responding, the distribution of highest degrees offered was as follows: Ph.D.—32.0 percent; Master—14.7 percent; Bachelor—39.3 percent. The remaining 14.0 percent did not indicate their highest degree offered. One of the respondents was a non-academic organization. The responses are reported for all respondents (including the non-academic institution and schools that did not report “highest degree offered”), and separately for Ph.D. degree-granting institutions and for schools whose highest degree offered is the Bachelor or Master degree. Data for institutions in the National Research Council’s Research Doctorate Report, 1995, are reported as a subset of Ph.D. degree-granting schools. They are referred to as the Top 30

Survey of the Labor Market for New Ph.D. Hires in Economics 2004-2005

This year, the survey questionnaire was sent to 371 organizations. Questionnaires were returned by 182 (49.1 percent) for a response rate that was higher than the 2003-04-survey response rate of 48.4 percent. Of this year’s responses, 120 (65.9 percent) were from among those who responded to last year’s survey; 62 (34.1 percent) came from new respondents. Among the academic institutions responding, the distribution of highest degrees offered was as follows: Ph.D.—44.5 percent; Master—13.2 percent; Bachelor—33.0 percent. The remaining 9.3 percent did not indicate their highest degree offered. Two of the respondents were non-academic organizations. The responses are reported for all respondents (including the non-academic institutions and schools that did not report “highest degree offered”), and separately for Ph.D. degree-granting institutions and for schools whose highest degree offered is the Bachelor or Master degree. Data for institutions in the National Research Council’s Research Doctorate Report, 1995, are reported as a subset of Ph.D. degree-granting schools. They are referred to as the Top 30

Survey of the Labor Market for New Ph.D. Hires in Economics 2006-2007

This year, the survey questionnaire was sent to 385 organizations. Questionnaires were returned by 160 (41.6 percent) for a response rate that was higher than the 2005-06-survey response rate of 40.3 percent. Of this year’s responses, 92 (57.9 percent) were from those who responded to last year’s survey; 68 (42.1 percent) came from new respondents. Among the academic institutions responding, the distribution of highest degrees offered was as follows: Ph.D.—41.3 percent; Master—20.0 percent; Bachelor—38.8 percent. The responses are reported for all respondents, and separately for Ph.D. degree-granting institutions and for schools whose highest degree offered is the Bachelor or Master degree. Data for institutions in the National Research Council’s Research Doctorate Report, 1995, are reported as a subset of Ph.D. degree-granting schools. They are referred to as the Top 30

Holocene carbon-cycle dynamics based on CO2 trapped in ice at Taylor Dome, Antarctica

A high-resolution ice-core record of atmospheric CO2 concentration over the Holocene epoch shows that the global carbon cycle has not been in steady state during the past 11,000 years. Analysis of the CO2 concentration and carbon stable-isotope records, using a one-dimensional carbon-cycle model,uggests that changes in terrestrial biomass and sea surface temperature were largely responsible for the observed millennial-scale changes of atmospheric CO2 concentrations

An Empirically Derived Three-Dimensional Laplace Resonance in the Gliese 876 Planetary System

We report constraints on the three-dimensional orbital architecture for all four planets known to orbit the nearby M dwarf Gliese 876 based solely on Doppler measurements and demanding long-term orbital stability. Our dataset incorporates publicly available radial velocities taken with the ELODIE and CORALIE spectrographs, HARPS, and Keck HIRES as well as previously unpublished HIRES velocities. We first quantitatively assess the validity of the planets thought to orbit GJ 876 by computing the Bayes factors for a variety of different coplanar models using an importance sampling algorithm. We find that a four-planet model is preferred over a three-planet model. Next, we apply a Newtonian MCMC algorithm to perform a Bayesian analysis of the planet masses and orbits using an n-body model in three-dimensional space. Based on the radial velocities alone, we find that a 99% credible interval provides upper limits on the mutual inclinations for the three resonant planets ($\Phi_{cb}<6.20^\circ$ for the "c" and "b" pair and $\Phi_{be}<28.5^\circ$ for the "b" and "e" pair). Subsequent dynamical integrations of our posterior sample find that the GJ 876 planets must be roughly coplanar ($\Phi_{cb}<2.60^\circ$ and $\Phi_{be}<7.87^\circ$), suggesting the amount of planet-planet scattering in the system has been low. We investigate the distribution of the respective resonant arguments of each planet pair and find that at least one argument for each planet pair and the Laplace argument librate. The libration amplitudes in our three-dimensional orbital model supports the idea of the outer-three planets having undergone significant past disk migration.Comment: 19 pages, 11 figures, 8 tables. Accepted to MNRAS. Posterior samples available at https://github.com/benelson/GJ87