An analysis of port-visit costs of U.S. Navy aircraft carriers

The United States Navy is seeking substantial cost savings in the operation of its aircraft carrier fleet, including the costs of port visits. This thesis analyzes data on aircraft carrier port visits from fiscal years 2002 through 2007 to develop statistical models for characterizing and predicting port-visit costs. The models account for explanatory factors that include the ship and port, whether the ship is moored pier side or at anchor, length of the port visit, and the arrival date. A total of 13 U.S. Navy Carrier Vessel (CV) and Carrier Vessel Nuclear (CVN) aircraft carriers made 118 visits to ports in 25 countries during the period under study. For each port visit, individual lineitem expenses are aggregated into four categories and by total cost. Regression modeling is then used to identify factors that explain these categorized and total costs. For total costs, the average regression prediction error is about 17 percent. Costs are found to vary across ships and, more substantially, across ports. These findings can be used in the formulation of initiatives aimed at reducing the costs of aircraft carrier port visits. An automated spreadsheet tool is developed to implement the model1ing techniques presented in the thesis.http://archive.org/details/annalysisofportv109454102US Navy (USN) author.Approved for public release; distribution is unlimited

Improved chemistry restraints for crystallographic refinement by integrating the Amber force field into Phenix.

The refinement of biomolecular crystallographic models relies on geometric restraints to help to address the paucity of experimental data typical in these experiments. Limitations in these restraints can degrade the quality of the resulting atomic models. Here, an integration of the full all-atom Amber molecular-dynamics force field into Phenix crystallographic refinement is presented, which enables more complete modeling of biomolecular chemistry. The advantages of the force field include a carefully derived set of torsion-angle potentials, an extensive and flexible set of atom types, Lennard-Jones treatment of nonbonded interactions and a full treatment of crystalline electrostatics. The new combined method was tested against conventional geometry restraints for over 22 000 protein structures. Structures refined with the new method show substantially improved model quality. On average, Ramachandran and rotamer scores are somewhat better, clashscores and MolProbity scores are significantly improved, and the modeling of electrostatics leads to structures that exhibit more, and more correct, hydrogen bonds than those refined using traditional geometry restraints. In general it is found that model improvements are greatest at lower resolutions, prompting plans to add the Amber target function to real-space refinement for use in electron cryo-microscopy. This work opens the door to the future development of more advanced applications such as Amber-based ensemble refinement, quantum-mechanical representation of active sites and improved geometric restraints for simulated annealing

Quantifying the effectiveness of shoreline armoring removal on coastal biota of Puget Sound

Shoreline armoring is prevalent around the world with unprecedented human population growth and urbanization along coastal habitats. Armoring structures, such as riprap and bulkheads, that are built to prevent beach erosion and protect coastal infrastructure from storms and flooding can cause deterioration of habitats for migratory fish species, disrupt aquatic–terrestrial connectivity, and reduce overall coastal ecosystem health. Relative to armored shorelines, natural shorelines retain valuable habitats for macroinvertebrates and other coastal biota. One question is whether the impacts of armoring are reversible, allowing restoration via armoring removal and related actions of sediment nourishment and replanting of native riparian vegetation. Armoring removal is targeted as a viable option for restoring some habitat functions, but few assessments of coastal biota response exist. Here, we use opportunistic sampling of pre- and post-restoration data for five biotic measures (wrack % cover, saltmarsh % cover, number of logs, and macroinvertebrate abundance and richness) from a set of six restored sites in Puget Sound, WA, USA. This broad suite of ecosystem metrics responded strongly and positively to armor removal, and these results were evident after less than one year. Restoration responses remained positive and statistically significant across different shoreline elevations and temporal trajectories. This analysis shows that removing shoreline armoring is effective for restoration projects aimed at improving the health and productivity of coastal ecosystems, and these results may be widely applicable

The NASA-UC Eta-Earth Program: II. A Planet Orbiting HD 156668 with a Minimum Mass of Four Earth Masses

We report the discovery of HD 156668b, an extrasolar planet with a minimum mass of M_P sin i = 4.15 M_Earth. This planet was discovered through Keplerian modeling of precise radial velocities from Keck-HIRES and is the second super-Earth to emerge from the NASA-UC Eta-Earth Survey. The best-fit orbit is consistent with circular and has a period of P = 4.6455 d. The Doppler semi-amplitude of this planet, K = 1.89 m/s, is among the lowest ever detected, on par with the detection of GJ 581e using HARPS. A longer period (P ~ 2.3 yr), low-amplitude signal of unknown origin was also detected in the radial velocities and was filtered out of the data while fitting the short-period planet. Additional data are required to determine if the long-period signal is due to a second planet, stellar activity, or another source. Photometric observations using the Automated Photometric Telescopes at Fairborn Observatory show that HD 156668 (an old, quiet K3 dwarf) is photometrically constant over the radial velocity period to 0.1 mmag, supporting the existence of the planet. No transits were detected down to a photometric limit of ~3 mmag, ruling out transiting planets dominated by extremely bloated atmospheres, but not precluding a transiting solid/liquid planet with a modest atmosphere.Comment: This planet was announced at the 2010 AAS meeting in Wash. DC; 12 pages, 8 figures, 3 tables, submitted to Ap

The Host Galaxy and Redshift of the Repeating Fast Radio Burst FRB 121102

The precise localization of the repeating fast radio burst (FRB 121102) has provided the first unambiguous association (chance coincidence probability $p\lesssim3\times10^{-4}$) of an FRB with an optical and persistent radio counterpart. We report on optical imaging and spectroscopy of the counterpart and find that it is an extended ($0.6^{\prime\prime}-0.8^{\prime\prime}$) object displaying prominent Balmer and [OIII] emission lines. Based on the spectrum and emission line ratios, we classify the counterpart as a low-metallicity, star-forming, $m_{r^\prime} = 25.1$ AB mag dwarf galaxy at a redshift of $z=0.19273(8)$, corresponding to a luminosity distance of 972 Mpc. From the angular size, the redshift, and luminosity, we estimate the host galaxy to have a diameter $\lesssim4$ kpc and a stellar mass of $M_*\sim4-7\times 10^{7}\,M_\odot$, assuming a mass-to-light ratio between 2 to 3$\,M_\odot\,L_\odot^{-1}$. Based on the H$\alpha$ flux, we estimate the star formation rate of the host to be $0.4\,M_\odot\,\mathrm{yr^{-1}}$ and a substantial host dispersion measure depth $\lesssim 324\,\mathrm{pc\,cm^{-3}}$. The net dispersion measure contribution of the host galaxy to FRB 121102 is likely to be lower than this value depending on geometrical factors. We show that the persistent radio source at FRB 121102's location reported by Marcote et al (2017) is offset from the galaxy's center of light by $\sim$200 mas and the host galaxy does not show optical signatures for AGN activity. If FRB 121102 is typical of the wider FRB population and if future interferometric localizations preferentially find them in dwarf galaxies with low metallicities and prominent emission lines, they would share such a preference with long gamma ray bursts and superluminous supernovae.Comment: 12 pages, 3 figures, Published in ApJ Letters. V2: Corrected mistake in author lis

Simulated cost-effectiveness and long-term clinical outcomes of addiction care and antibiotic therapy strategies for patients with injection drug use-associated infective endocarditis

Importance: Emerging evidence supports the use of outpatient parenteral antimicrobial therapy (OPAT) and, in many cases, partial oral antibiotic therapy for the treatment of injection drug use-associated infective endocarditis (IDU-IE); however, long-term outcomes and cost-effectiveness remain unknown. Objective: To compare the added value of inpatient addiction care services and the cost-effectiveness and clinical outcomes of alternative antibiotic treatment strategies for patients with IDU-IE. Design, Setting, and Participants: This decision analytical modeling study used a validated microsimulation model to compare antibiotic treatment strategies for patients with IDU-IE. Model inputs were derived from clinical trials and observational cohort studies. The model included all patients with injection opioid drug use (N = 5 million) in the US who were eligible to receive OPAT either in the home or at a postacute care facility. Costs were annually discounted at 3%. Cost-effectiveness was evaluated from a health care sector perspective over a lifetime starting in 2020. Probabilistic sensitivity, scenario, and threshold analyses were performed to address uncertainty. Interventions: The model simulated 4 treatment strategies: (1) 4 to 6 weeks of inpatient intravenous (IV) antibiotic therapy along with opioid detoxification (usual care strategy), (2) 4 to 6 weeks of inpatient IV antibiotic therapy along with inpatient addiction care services that offered medication for opioid use disorder (usual care/addiction care strategy), (3) 3 weeks of inpatient IV antibiotic therapy along with addiction care services followed by OPAT (OPAT strategy), and (4) 3 weeks of inpatient IV antibiotic therapy along with addiction care services followed by partial oral antibiotic therapy (partial oral antibiotic strategy). Main Outcomes and Measures: Mean percentage of patients completing treatment for IDU-IE, deaths associated with IDU-IE, life expectancy (measured in life-years [LYs]), mean cost per person, and incremental cost-effectiveness ratios (ICERs). Results: All modeled scenarios were initialized with 5 million individuals (mean age, 42 years; range, 18-64 years; 70% male) who had a history of injection opioid drug use. The usual care strategy resulted in 18.63 LYs at a cost of $416 570 per person, with 77.6$412 150 per person. Compared with the OPAT strategy, the partial oral antibiotic strategy had an ICER of $163 370 per LY. Increasing IDU-IE treatment uptake and decreasing treatment discontinuation made the partial oral antibiotic strategy more cost-effective compared with the OPAT strategy. When assuming that all patients with IDU-IE were eligible to receive partial oral antibiotic therapy, the strategy was cost-saving and resulted in 0.0247 additional discounted LYs. When treatment discontinuation was decreased from 3.30$100 000 per LY threshold. Conclusions and Relevance: In this decision analytical modeling study, incorporation of OPAT or partial oral antibiotic approaches along with addiction care services for the treatment of patients with IDU-IE was associated with increases in the number of people completing treatment, decreases in mortality, and savings in cost compared with the usual care strategy of providing inpatient IV antibiotic therapy alone

Droplet Size Impact on Efficacy of a Dicamba-plus-Glyphosate Mixture

Chemical weed control remains a widely used component of integrated weed management strategies because of its cost-effectiveness and rapid removal of crop pests. Additionally, dicamba-plus-glyphosate mixtures are a commonly recommended herbicide combination to combat herbicide resistance, specifically in recently commercially released dicamba-tolerant soybean and cotton. However, increased spray drift concerns and antagonistic interactions require that the application process be optimized to maximize biological efficacy while minimizing environmental contamination potential. Field research was conducted in 2016, 2017, and 2018 across three locations (Mississippi, Nebraska, and North Dakota) for a total of six site-years. The objectives were to characterize the efficacy of a range of droplet sizes [150 μm (Fine) to 900 μm (Ultra Coarse)] using a dicamba-plus-glyphosate mixture and to create novel weed management recommendations utilizing pulse-width modulation (PWM) sprayer technology. Results across pooled site-years indicated that a droplet size of 395 μm (Coarse) maximized weed mortality from a dicamba-plus-glyphosate mixture at 94 L ha–1. However, droplet size could be increased to 620 μm (Extremely Coarse) to maintain 90% of the maximum weed mortality while further mitigating particle drift potential. Although generalized droplet size recommendations could be created across site-years, optimum droplet sizes within each site-year varied considerably and may be dependent on weed species, geographic location, weather conditions, and herbicide resistance(s) present in the field. The precise, site-specific application of a dicamba-plus-glyphosate mixture using the results of this research will allow applicators to more effectively utilize PWM sprayers, reduce particle drift potential, maintain biological efficacy, and reduce the selection pressure for the evolution of herbicide-resistant weeds

The climate of HD 189733b from fourteen transits and eclipses measured by Spitzer

We present observations of seven transits and seven eclipses of the transiting planet system HD 189733 taken with Spitzer IRAC at 8 microns. We use a new correction for the detector ramp variation with a double-exponential function. Our main findings are: (1) an upper limit on the variability of the day-side planet flux of 2.7% (68% confidence); (2) the most precise set of transit times measured for a transiting planet, with an average accuracy of 3 seconds; (3) a lack of transit-timing variations, excluding the presence of second planets in this system above 20% of the mass of Mars in low-order mean-motion resonance at 95% confidence; (4) a confirmation of the planet's phase variation, finding the night side is 64% as bright as the day side, as well as an upper limit on the night-side variability of 17% (68% confidence); (5) a better correction for stellar variability at 8 micron causing the phase function to peak 3.5 hrs before secondary eclipse, confirming that the advection and radiation timescales are comparable at the 8 micron photosphere; (6) variation in the depth of transit, which possibly implies variations in the surface brightness of the portion of the star occulted by the planet, posing a fundamental limit on non-simultaneous multi-wavelength transit absorption measurements of planet atmospheres; (7) a measurement of the infrared limb-darkening of the star, in agreement with stellar atmosphere models; (8) an offset in the times of secondary eclipse of 69 sec, which is mostly accounted for by a 31 sec light travel time delay and 33 sec delay due to the shift of ingress and egress by the planet hot spot; this confirms that the phase variation is due to an offset hot spot on the planet; (9) a retraction of the claimed eccentricity of this system due to the offset of secondary eclipse; and (10) high precision measurements of the parameters of this system.Comment: 18 pages, 19 figures, accepted for publication in the Astrophysical Journa

Five Kepler target stars that show multiple transiting exoplanet candidates

We present and discuss five candidate exoplanetary systems identified with the Kepler spacecraft. These five systems show transits from multiple exoplanet candidates. Should these objects prove to be planetary in nature, then these five systems open new opportunities for the field of exoplanets and provide new insights into the formation and dynamical evolution of planetary systems. We discuss the methods used to identify multiple transiting objects from the Kepler photometry as well as the false-positive rejection methods that have been applied to these data. One system shows transits from three distinct objects while the remaining four systems show transits from two objects. Three systems have planet candidates that are near mean motion commensurabilities---two near 2:1 and one just outside 5:2. We discuss the implications that multitransiting systems have on the distribution of orbital inclinations in planetary systems, and hence their dynamical histories; as well as their likely masses and chemical compositions. A Monte Carlo study indicates that, with additional data, most of these systems should exhibit detectable transit timing variations (TTV) due to gravitational interactions---though none are apparent in these data. We also discuss new challenges that arise in TTV analyses due to the presence of more than two planets in a system.Comment: Accepted to Ap