Nonlinear Semi-Analytic Methods for Trajectory Estimation

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76298/1/AIAA-29106-621.pd

Precession of Mercury’s Perihelion from Ranging to the MESSENGER Spacecraft

The perihelion of Mercury's orbit precesses due to perturbations from other solar system bodies, solar quadrupole moment (J [subscript 2]), and relativistic gravitational effects that are proportional to linear combinations of the parametrized post-Newtonian parameters β and γ. The orbits and masses of the solar system bodies are quite well known, and thus the uncertainty in recovering the precession rate of Mercury's perihelion is dominated by the uncertainties in the parameters J [subscript 2], β, and γ. Separating the effects due to these parameters is challenging since the secular precession rate has a linear dependence on each parameter. Here we use an analysis of radiometric range measurements to the MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) spacecraft in orbit about Mercury to estimate the precession of Mercury's perihelion. We show that the MESSENGER ranging data allow us to measure not only the secular precession rate of Mercury's perihelion with substantially improved accuracy, but also the periodic perturbation in the argument of perihelion sensitive to β and γ. When combined with the γ estimate from a Shapiro delay experiment from the Cassini mission, we can decouple the effects due to β and J [subscript 2] and estimate both parameters, yielding (β -1)=(-2.7 ± 3.9) x 10[superscript -5] and J [subscript 2] = (2.25 ± 0.09) × 10[superscript −7]. We also estimate the total precession rate of Mercury's perihelion as 575.3100 ± 0.0015''/century and provide estimated contributions and uncertainties due to various perturbing effects

Bias Varies for Bioimpedance Analysis and Skinfold Technique when Stratifying Collegiate Male Athletes Fat-free Mass Hydration Levels

Bioelectrical impedance analysis (BIA) and skinfold (SF) techniques are commonly used to estimate body composition in athletic settings. Both methods are based upon a 2-compartment (2C) model approach, which assumes the hydration of fat-free mass (FFM) is constant (73.80%). Deviations from assumed constants such as FFM hydration have previously been observed in athletes. However, the magnitude of error associated with deviations in FFM hydration are scarce. PURPOSE: The purpose of this study was to evaluate the accuracy of BIA- and SF-based body fat percentage (BF%) estimates in collegiate athletes when stratifying FFM hydration levels. METHODS: FFM hydration levels for the entire sample ranged from 64.55–73.84%. Therefore, athletes were analyzed as a whole (FFM-HydrationALL: n=63) and at the FFM hydration levels of 64.00-68.99% (FFM-HydrationL1: n=37) and 69.00-74.00% (FFM-HydrationL2: n=26). A 3-compartment model utilizing air displacement plethysmography for body volume and bioimpedance spectroscopy for total body water was employed in order to determine the accuracy of BIA and SF for the 3 separate groups. RESULTS: The results of this study demonstrated that BIA had significant constant error (CE) when analyzed in FFM-HydrationALL, FFM-HydrationL1, and FFM-HydrationL2 (all p \u3c 0.001; CE = 5.64, 6.27, and 4.73%, respectively). However, the CE was not statistically significant for SF when evaluating FFM-HydrationALL, FFM-HydrationL1, and FFM-HydrationL2 (all p \u3e 0.05; CE = -0.04, -1.36, and 1.83%, respectively). The BIA device revealed proportional bias for FFM-HydrationALL and FFM-HyrdrationL1 (coefficients = -0.19 and -0.21; both p \u3c 0.05). However, the proportional bias was not present for BIA when analyzed in FFM-HydrationL2 (coefficient = -0.16; p = 0.06). Lastly, the SF method only had significant proportional bias when examined in FFM-HydrationALL (coefficient = 0.17; p = 0.02).CONCLUSIONS: The current study results revealed that proportional bias for BIA is removed when FFM hydration levels approach the assumed 73.80% commonly employed in 2C models. In contrast, the large variance in FFM hydration levels did not impact the SF technique. Therefore, practitioners are encouraged to utilize the SF technique over BIA when assessing BF% in collegiate male athletes

Does Io Have a Magma Ocean?

Future space missions will further our knowledge of tidal heating and orbital resonances, processes thought to create spectacular volcanism and oceans of magma or water on other worlds

The Efficient Synthesis and Biological Evaluation of Novel Bi-Functionalized Sarcophagine for 64Cu Radiopharmaceuticals

Purpose We and others have reported that Sarcophagine-based bifunctional chelators could be effectively used in the syntheses of 64Cu radiopharmaceuticals. The resulted 64Cu-Sarcophagine complexes demonstrated great in vivo stability. The goal of this study was to further derivatize Sarcophagine cage with amino and maleimide functional groups for conjugation with bioligands

The afterglow and kilonova of the short GRB 160821B

GRB 160821B is a short duration gamma-ray burst (GRB) detected and localized by the Neil Gehrels Swift Observatory in the outskirts of a spiral galaxy at z=0.1613, at a projected physical offset of 16 kpc from the galaxy's center. We present X-ray, optical/nIR and radio observations of its counterpart and model them with two distinct components of emission: a standard afterglow, arising from the interaction of the relativistic jet with the surrounding medium, and a kilonova, powered by the radioactive decay of the sub-relativistic ejecta. Broadband modeling of the afterglow data reveals a weak reverse shock propagating backward into the jet, and a likely jet-break at 3.5 d. This is consistent with a structured jet seen slightly off-axis while expanding into a low-density medium. Analysis of the kilonova properties suggests a rapid evolution toward red colors, similar to AT2017gfo, and a low nIR luminosity, possibly due to the presence of a long-lived neutron star. The global properties of the environment, the inferred low mass (M_ej < 0.006 Msun) and velocities (v > 0.05 c) of lanthanide-rich ejecta are consistent with a binary neutron star merger progenitor.Comment: 14 pages, 6 figures, MNRAS, in press. Moderate revision, added Figure 5 and X-ray data to Table

Altered skeletal muscle mitochondrial phenotype in COPD: disease vs. disuse

Patients with chronic obstructive pulmonary disease (COPD) exhibit an altered skeletal muscle mitochondrial phenotype, which often includes reduced mitochondrial density, altered respiratory function, and elevated oxidative stress. As this phenotype may be explained by the sedentary lifestyle that commonly accompanies this disease, the aim of this study was to determine whether such alterations are still evident when patients with COPD are compared to control subjects matched for objectively measured physical activity (PA; accelerometry). Indexes of mitochondrial density [citrate synthase (CS) activity], respiratory function (respirometry in permeabilized fibers), and muscle oxidative stress [4-hydroxynonenal (4-HNE) content] were assessed in muscle fibers biopsied from the vastus lateralis of nine patients with COPD and nine PA-matched control subjects (CON). Despite performing similar levels of PA (CON: 18 ± 3, COPD: 20 ± 7 daily minutes moderate-to-vigorous PA; CON: 4,596 ± 683, COPD: 4,219 ± 763 steps per day, P \u3e 0.70), patients with COPD still exhibited several alterations in their mitochondrial phenotype, including attenuated skeletal muscle mitochondrial density (CS activity; CON 70.6 ± 3.8, COPD 52.7 ± 6.5 U/mg, P \u3c 0.05), altered mitochondrial respiration [e.g., ratio of complex I-driven state 3 to complex II-driven state 3 (CI/CII); CON: 1.20 ± 0.11, COPD: 0.90 ± 0.05, P \u3c 0.05), and oxidative stress (4-HNE; CON: 1.35 ± 0.19, COPD: 2.26 ± 0.25 relative to β-actin, P \u3c 0.05). Furthermore, CS activity (r = 0.55), CI/CII (r = 0.60), and 4-HNE (r = 0.49) were all correlated with pulmonary function, assessed as forced expiratory volume in 1 s (P \u3c 0.05), but not PA (P \u3e 0.05). In conclusion, the altered mitochondrial phenotype in COPD is present even in the absence of differing levels of PA and appears to be related to the disease itself

Quadriceps exercise intolerance in patients with chronic obstructive pulmonary disease: the potential role of altered skeletal muscle mitochondrial respiration

This study sought to determine if qualitative alterations in skeletal muscle mitochondrial respiration, associated with decreased mitochondrial efficiency, contribute to exercise intolerance in patients with chronic obstructive pulmonary disease (COPD). Using permeabilized muscle fibers from the vastus lateralis of 13 patients with COPD and 12 healthy controls, complex I (CI) and complex II (CII)-driven State 3 mitochondrial respiration were measured separately (State 3:CI and State 3:CII) and in combination (State 3:CI+CII). State 2 respiration was also measured. Exercise tolerance was assessed by knee extensor exercise (KE) time to fatigue. Per milligram of muscle, State 3:CI+CII and State 3:CI were reduced in COPD (P \u3c 0.05), while State 3:CII and State 2 were not different between groups. To determine if this altered pattern of respiration represented qualitative changes in mitochondrial function, respiration states were examined as percentages of peak respiration (State 3:CI+CII), which revealed altered contributions from State 3:CI (Con 83.7 ± 3.4, COPD 72.1 ± 2.4%Peak, P \u3c 0.05) and State 3:CII (Con 64.9 ± 3.2, COPD 79.5 ± 3.0%Peak, P \u3c 0.05) respiration, but not State 2 respiration in COPD. Importantly, a diminished contribution of CI-driven respiration relative to the metabolically less-efficient CII-driven respiration (CI/CII) was also observed in COPD (Con 1.28 ± 0.09, COPD 0.81 ± 0.05, P \u3c 0.05), which was related to exercise tolerance of the patients (r = 0.64, P \u3c 0.05). Overall, this study indicates that COPD is associated with qualitative alterations in skeletal muscle mitochondria that affect the contribution of CI and CII-driven respiration, which potentially contributes to the exercise intolerance associated with this disease

Quantitative, Simultaneous PET/MRI for Intratumoral Imaging with an MRI-Compatible PET Scanner

Noninvasive methods are needed to explore the heterogeneous tumor microenvironment and its modulation by therapy. Hybrid PET/MRI systems are being developed for small-animal and clinical use. The advantage of these integrated systems depends on their ability to provide MR images that are spatially coincident with simultaneously acquired PET images, allowing combined functional MRI and PET studies of intratissue heterogeneity. Although much effort has been devoted to developing this new technology, the issue of quantitative and spatial fidelity of PET images from hybrid PET/MRI systems to the tissues imaged has received little attention. Here, we evaluated the ability of a first-generation, small-animal MRI-compatible PET scanner to accurately depict heterogeneous patterns of radiotracer uptake in tumors. Methods: Quantitative imaging characteristics of the MRI-compatible PET (PET/MRI) scanner were evaluated with phantoms using calibration coefficients derived from a mouse-sized linearity phantom. PET performance was compared with a commercial small-animal PET system and autoradiography in tumor-bearing mice. Pixel and structure-based similarity metrics were used to evaluate image concordance among modalities. Feasibility of simultaneous PET/MRI functional imaging of tumors was explored by following ^(64)Cu-labeled antibody uptake in relation to diffusion MRI using cooccurrence matrix analysis. Results: The PET/MRI scanner showed stable and linear response. Activity concentration recovery values (measured and true activity concentration) calculated for 4-mm-diameter rods within linearity and uniform activity rod phantoms were near unity (0.97 ± 0.06 and 1.03 ± 0.03, respectively). Intratumoral uptake patterns for both ^(18)F-FDG and a ^(64)Cu-antibody acquired using the PET/MRI scanner and small-animal PET were highly correlated with autoradiography (r > 0.99) and with each other (r = 0.97 ± 0.01). On the basis of these data, we performed a preliminary study comparing diffusion MRI and radiolabeled antibody uptake patterns over time and visualized movement of antibodies from the vascular space into the tumor mass. Conclusion: The MRI-compatible PET scanner provided tumor images that were quantitatively accurate and spatially concordant with autoradiography and the small-animal PET examination. Cooccurrence matrix approaches enabled effective analysis of multimodal image sets. These observations confirm the ability of the current simultaneous PET/MRI system to provide accurate observations of intratumoral function and serve as a benchmark for future evaluations of hybrid instrumentation