Long term evolution of planetary systems with a terrestrial planet and a giant planet

We study the long term orbital evolution of a terrestrial planet under the gravitational perturbations of a giant planet. In particular, we are interested in situations where the two planets are in the same plane and are relatively close. We examine both possible configurations: the giant planet orbit being either outside or inside the orbit of the smaller planet. The perturbing potential is expanded to high orders and an analytical solution of the terrestrial planetary orbit is derived. The analytical estimates are then compared against results from the numerical integration of the full equations of motion and we find that the analytical solution works reasonably well. An interesting finding is that the new analytical estimates improve greatly the predictions for the timescales of the orbital evolution of the terrestrial planet compared to an octupole order expansion. Finally, we briefly discuss possible applications of the analytical estimates in astrophysical problems.Comment: Accepted for publication in MNRA

Efficient First-Order Temporal Logic for Infinite-State Systems

In this paper we consider the specification and verification of infinite-state systems using temporal logic. In particular, we describe parameterised systems using a new variety of first-order temporal logic that is both powerful enough for this form of specification and tractable enough for practical deductive verification. Importantly, the power of the temporal language allows us to describe (and verify) asynchronous systems, communication delays and more complex properties such as liveness and fairness properties. These aspects appear difficult for many other approaches to infinite-state verification.Comment: 16 pages, 2 figure

Near Infrared Spectroscopy Describes Physiologic Payback Associated With Excess Postexercise Oxygen Consumption in Healthy Controls and Children With Complex Congenital Heart Disease

Exercise creates a physiologic burden with recovery from such effort crucial to adaptation. Excess postexercise oxygen consumption (EPOC) refers to the body’s increased metabolic need after work. This investigation was designed to determine the role of near infrared spectroscopy (NIRS) in the description of exercise recovery in healthy controls (NL) and children with congenital heart disease (CHD). Subjects were recruited with exercise testing performed to exhaustion. Exercise time (EXT), heart rate (HR), and oxygen consumption (VO2) were measured. Four-site NIRS (brain, kidney, deltoid, and vastus lateralis) were measured during exercise and into recovery to establish trends. Fifty individuals were recruited for each group (NL = 26 boys and 24 girls; CHD = 33 boys and 17 girls). Significant differences existed between EXT, VO2, and peak HR (P \u3c 0.01). NIRS values were examined at four distinct intervals: rest, peak work, and 2 and 5 min after exercise. Significant cerebral hyperemia was seen in children with CHD post exercise when compared to normal individuals in whom redistribution patterns were directed to somatic muscles. These identified trends support an immediate compensation of organ systems to re-establish homeostasis in peripheral beds through enhanced perfusion. Noninvasive NIRS monitoring helps delineate patterns of redistribution associated with EPOC in healthy adolescents and children with CHD

Archival Search for X-ray Emission From Type Ib/c Supernovae

We present results from an ongoing archival search for X-ray emission from all known Type Ib/c supernovae using data from the Chandra X-ray Observatory. For each supernova, we search all possible observations to find those with coverage in X-rays. For those observations with coverage of a supernova, we extract an X-ray spectrum at the location of the supernova and create response files. We model those spectra with an absorbed hot plasma model in order to determine luminosities or set upper limits. These results are then used to determine or set limits on the mass-loss history of the pre-supernova stars, thus giving insight into the late stages of stellar evolution

Do Time-Compressed General Education Courses Increase Course and Semester Retention Rates?

Access to higher education remains a fundamental principle of the community college mission. Community colleges provide a critical starting point for many traditional and nontraditional students who enter higher education. Yet, in recent years, community colleges have endured public criticism for low graduation rates and the extended time students take to graduate. Many community colleges adapted long-held practices by implementing student success initiatives, including offering time-compressed courses to address concerns. The purpose of this study was to examine the effects of time-compressed courses on course retention rates and fall-to-spring semester retention rates of students. Quantitative methods were used to compare retention rates of students enrolled in standard 16-week and time-compressed general education courses at a community college in the southwestern United States. Results of the study revealed significant differences in course retention rates of students enrolled in time-compressed courses compared to those enrolled in standard 16-week general education courses as well as significant differences in retention rates between academic divisions. There was also a significant difference in fall-to-spring retention rates for first-time college students who took three or more time-compressed general education courses in a 16-week semester

An evaluation of unsaturated flow models in an arid climate

The objective of this study was to evaluate the effectiveness of two unsaturated flow models in and regions. The area selected for the study was the Area 5 Radioactive Waste Management Site (RWMS) at the Nevada Test Site in Nye County, Nevada. The two models selected for this evaluation were HYDRUS-1D [Simunek et al., 1998] and the SHAW model [Flerchinger and Saxton, 1989]. Approximately 5 years of soil-water and atmospheric data collected from an instrumented weighing lysimeter site near the RWMS were used for building the models with actual initial and boundary conditions representative of the site. Physical processes affecting the site and model performance were explored. Model performance was based on a detailed sensitivity analysis and ultimately on storage comparisons. During the process of developing descriptive model input, procedures for converting hydraulic parameters for each model were explored. In addition, the compilation of atmospheric data collected at the site became a useful tool for developing predictive functions for future studies. The final model results were used to evaluate the capacities of the HYDRUS and SHAW models for predicting soil-moisture movement and variable surface phenomena for bare soil conditions in the and vadose zone. The development of calibrated models along with the atmospheric and soil data collected at the site provide useful information for predicting future site performance at the RWMS