The Apparent Anomalous, Weak, Long-Range Acceleration of Pioneer 10 and 11

Recently we reported that radio Doppler data generated by NASA's Deep Space Network (DSN) from the Pioneer 10 and 11 spacecraft indicate an apparent anomalous, constant, spacecraft acceleration with a magnitude $\sim 8.5\times 10^{-8}$ cm s$^{-2}$, directed towards the Sun (gr-qc/9808081). Analysis of similar Doppler and ranging data from the Galileo and Ulysses spacecraft yielded ambiguous results for the anomalous acceleration, but it was useful in that it ruled out the possibility of a systematic error in the DSN Doppler system that could easily have been mistaken as a spacecraft acceleration. Here we present some new results, including a critique suggestions that the anomalous acceleration could be caused by collimated thermal emission. Based partially on a further data for the Pioneer 10 orbit determination, the data now spans January 1987 to July 1998, our best estimate of the average Pioneer 10 acceleration directed towards the Sun is $\sim 7.5 \times 10^{-8}$ cm s$^{-2}$.Comment: Latex, 7 pages and 2 figures. Invited talk at the XXXIV-th Rencontres de Moriond Meeting on Gravitational Waves and Experimental Gravity. Les Arcs, Savoi, France (January 23-30,1999). Corrected typo

Anderson et al. Reply (to the Comment by Murphy on Pioneer 10/11)

We conclude that Murphy's proposal (radiation of the power of the main-bus electrical systems from the rear of the craft) can not explain the anomalous Pioneer acceleration.Comment: LaTex, 3 pages, Phys. Rev. Lett. (to be published

Anderson et al. Reply (to the Comment by Katz on Pioneer 10/11)

We conclude that Katz's proposal (anisotropic heat reflection off of the back of the spacecraft high-gain antennae, the heat coming from the RTGs) does not provide enough power and so can not explain the Pioneer anomaly.Comment: LaTex, 3 pages, Phys. Rev. Lett. (to be published

A simple, reliable and robust reinforcement method for the fabrication of (RE)–Ba–Cu–O bulk superconductors

Abstract: Bulk high temperature superconductors (HTS) based on the rare-earth barium cuprates [(RE)BCO] have the potential to be applied in a variety of engineering and technological applications such as trapped field magnets, rotating electrical machines, magnetic bearings and flywheel energy storage systems. The key materials figure of merit for most practical applications of bulk superconductors is simply the product of the maximum current density that can be supported, which correlates directly with the maximum achievable trapped magnetic field, and the physical length scale over which the current flows. Unfortunately, however, bulk (RE)BCO superconductors exhibit relatively poor mechanical properties due to their inherent ceramic nature. Consequently, the performance of these materials as trapped field magnets is limited significantly by their tensile strength, rather than critical current and size, given that the relatively large Lorentz forces produced in the generation of large magnetic fields can lead to catastrophic mechanical failure. In the present work, we describe a simple, but effective and reliable reinforcement methodology to enhance the mechanical properties of (RE)BCO bulk superconductors by incorporating hybrid SiC fibres consisting of a tungsten core with SiC cladding within the bulk microstructure. An improvement in tensile strength by up to 40% has been achieved via this process and, significantly, without compromising the superconducting performance of the bulk material

Resolving Decades of Periodic Spirals from the Wolf-Rayet Dust Factory WR 112

WR 112 is a dust-forming carbon-rich Wolf-Rayet (WC) binary with a dusty circumstellar nebula that exhibits a complex asymmetric morphology, which traces the orbital motion and dust formation in the colliding winds of the central binary. Unraveling the complicated circumstellar dust emission around WR 112 therefore provides an opportunity to understand the dust formation process in colliding-wind WC binaries. In this work, we present a multi-epoch analysis of the circumstellar dust around WR 112 using seven high spatial resolution (FWHM $\sim0.3-0.4''$) N-band ($\lambda \sim12$ $\mu$m) imaging observations spanning almost 20 years and includes newly obtained images from Subaru/COMICS in Oct 2019. In contrast to previous interpretations of a face-on spiral morphology, we observe clear evidence of proper motion of the circumstellar dust around WR 112 consistent with a nearly edge-on spiral with a $\theta_s=55^\circ$ half-opening angle and a $\sim20$-yr period. The revised near edge-on geometry of WR 112 reconciles previous observations of highly variable non-thermal radio emission that was inconsistent with a face-on geometry. We estimate a revised distance to WR 112 of $d = 3.39^{+0.89}_{-0.84}$ kpc based on the observed dust expansion rate and a spectroscopically derived WC terminal wind velocity of $v_\infty= 1230\pm260$ km s$^{-1}$. With the newly derived WR 112 parameters we fit optically-thin dust spectral energy distribution models and determine a dust production rate of $\dot{M}_d=2.7^{+1.0}_{-1.3}\times10^{-6}$ M$_\odot$ yr$^{-1}$, which demonstrates that WR 112 is one of the most prolific dust-making WC systems known.Comment: 17 pages, 9 figures, 1 animated gif, accepted for publication in Ap

Resolving Decades of Periodic Spirals from the Wolf–Rayet Dust Factory WR 112

WR 112 is a dust-forming carbon-rich Wolf–Rayet (WC) binary with a dusty circumstellar nebula that exhibits a complex asymmetric morphology, which traces the orbital motion and dust formation in the colliding winds of the central binary. Unraveling the complicated circumstellar dust emission around WR 112 therefore provides an opportunity to understand the dust formation process in colliding-wind WC binaries. In this work, we present a multi-epoch analysis of the circumstellar dust around WR 112 using seven high spatial resolution (FWHM ~ 0farcs3–0farcs4) N-band (λ ~ 12 μm) imaging observations spanning almost 20 yr and that includes images obtained from Subaru/COMICS in 2019 October. In contrast to previous interpretations of a face-on spiral morphology, we observe clear evidence of proper motion of the circumstellar dust around WR 112 consistent with a nearly edge-on spiral with a θ_s = 55° half-opening angle and a ~20 yr period. The revised near edge-on geometry of WR 112 reconciles previous observations of highly variable nonthermal radio emission that was inconsistent with a face-on geometry. We estimate a revised distance to WR 112 of d = 3.39_(-0.84)^(+0.89) kpc based on the observed dust expansion rate and a spectroscopically derived WC terminal wind velocity of v_∞ = 1230 ± 260 km s⁻¹. With the newly derived WR 112 parameters, we fit optically thin dust spectral energy distribution models and determine a dust production rate of Ṁ_d = 2.7_(-1.3)^(+1.0) x 10⁻⁶ M_⊙ yr⁻¹, which demonstrates that WR 112 is one of the most prolific dust-making WC systems known

Indication, from Pioneer 10/11, Galileo, and Ulysses Data, of an Apparent Anomalous, Weak, Long-Range Acceleration

Radio metric data from the Pioneer 10/11, Galileo, and Ulysses spacecraft indicate an apparent anomalous, constant, acceleration acting on the spacecraft with a magnitude $\sim 8.5\times 10^{-8}$ cm/s$^2$, directed towards the Sun. Two independent codes and physical strategies have been used to analyze the data. A number of potential causes have been ruled out. We discuss future kinematic tests and possible origins of the signal.Comment: Revtex, 4 pages and 1 figure. Minor changes for publicatio

Spatiotemporal characteristics of atrial fibrillation electrograms: a novel marker for arrhythmia stability and termination

Background: Sequentially mapped complex fractionated atrial electrograms (CFAE) and dominant frequency (DF) sites have been targeted during catheter ablation for atrial fibrillation (AF). However, these strategies have yielded variable success and have not been shown to correlate consistently with AF dynamics. Here, we evaluated whether the spatiotemporal stability of CFAE and DF may be a better marker of AF sustenance and termination. Methods: Eighteen sheep with 12 weeks of "one-kidney, one-clip" hypertension underwent open-chest studies. A total of 42 self-terminating (28–100 s) and 6 sustained (>15 min) AF episodes were mapped using a custom epicardial plaque and analyzed in 4-s epochs for CFAE, using the NavX CFE-m algorithm, and DF, using a Fast Fourier Transform. The spatiotemporal stability index (STSI) was calculated using the intraclass correlation coefficient of consecutive AF epochs. Results: A total of 67,733 AF epochs were analyzed. During AF initiation, mean CFE-m and the STSI of CFE-m/DF were similar between sustained and self-terminating episodes, although median DF was higher in sustained AF (p=0.001). During sustained AF, the STSI of CFE-m increased significantly (p=0.02), whereas mean CFE-m (p=0.5), median DF (p=0.07), and the STSI of DF remained unchanged (p=0.5). Prior to AF termination, the STSI of CFE-m was significantly lower (p<0.001), with a physiologically non-significant decrease in median DF (−0.3 Hz, p=0.006) and no significant changes in mean CFE-m (p=0.14) or the STSI of DF (p=0.06). Conclusions: Spatiotemporal stabilization of CFAE favors AF sustenance and its destabilization heralds AF termination. The STSI of CFE-m is more representative of AF dynamics than are the STSI of DF, sequential mean CFE-m, or median DF