Parameter estimation on compact binary coalescences with abruptly terminating gravitational waveforms

Gravitational-wave astronomy seeks to extract information about astrophysical systems from the gravitational-wave signals they emit. For coalescing compact-binary sources this requires accurate model templates for the inspiral and, potentially, the subsequent merger and ringdown. Models with frequency-domain waveforms that terminate abruptly in the sensitive band of the detector are often used for parameter-estimation studies. We show that the abrupt waveform termination contains significant information that affects parameter-estimation accuracy. If the sharp cutoff is not physically motivated, this extra information can lead to misleadingly good accuracy claims. We also show that using waveforms with a cutoff as templates to recover complete signals can lead to biases in parameter estimates. We evaluate when the information content in the cutoff is likely to be important in both cases. We also point out that the standard Fisher matrix formalism, frequently employed for approximately predicting parameter-estimation accuracy, cannot properly incorporate an abrupt cutoff that is present in both signals and templates; this observation explains some previously unexpected results found in the literature. These effects emphasize the importance of using complete waveforms with accurate merger and ringdown phases for parameter estimation.Comment: Very minor changes to match published versio

The Road from Medical Injury to Claims Resolution: How No-Fault and Tort Differ

In the area of medical malpractice, no-fault has been offered as a response to the criticisms leveled against tort litigation for medical injuries. Five issues of no-fault are examined within the context of obstetrical malpractice

Intracellular calcium movements during relaxation and recovery of superfast muscle fibers of the toadfish swimbladder

© The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of General Physiology 143 (2014): 605-620, doi:10.1085/jgp.201411160.The mating call of the Atlantic toadfish is generated by bursts of high-frequency twitches of the superfast twitch fibers that surround the swimbladder. At 16°C, a calling period can last several hours, with individual 80–100-Hz calls lasting ∼500 ms interleaved with silent periods (intercall intervals) lasting ∼10 s. To understand the intracellular movements of Ca2+ during the intercall intervals, superfast fibers were microinjected with fluo-4, a high-affinity fluorescent Ca2+ indicator, and stimulated by trains of 40 action potentials at 83 Hz, which mimics fiber activity during calling. The fluo-4 fluorescence signal was measured during and after the stimulus trains; the signal was also simulated with a kinetic model of the underlying myoplasmic Ca2+ movements, including the binding and transport of Ca2+ by the sarcoplasmic reticulum (SR) Ca2+ pumps. The estimated total amount of Ca2+ released from the SR during a first stimulus train is ∼6.5 mM (concentration referred to the myoplasmic water volume). At 40 ms after cessation of stimulation, the myoplasmic free Ca2+ concentration ([Ca2+]) is below the threshold for force generation (∼3 µM), yet the estimated concentration of released Ca2+ remaining in the myoplasm (Δ[CaM]) is large, ∼5 mM, with ∼80% bound to parvalbumin. At 10 s after stimulation, [Ca2+] is ∼90 nM (three times the assumed resting level) and Δ[CaM] is ∼1.3 mM, with 97% bound to parvalbumin. Ca2+ movements during the intercall interval thus appear to be strongly influenced by (a) the accumulation of Ca2+ on parvalbumin and (b) the slow rate of Ca2+ pumping that ensues when parvalbumin lowers [Ca2+] near the resting level. With repetitive stimulus trains initiated at 10-s intervals, Ca2+ release and pumping come quickly into balance as a result of the stability (negative feedback) supplied by the increased rate of Ca2+ pumping at higher [Ca2+].This work was supported by a grant to S.M. Baylor from the National Institutes of Health (GM 086167) and a grant to L.C. Rome from the National Science Foundation (IOS-1145981)

Magnetic-Field Amplification in the Thin X-ray Rims of SN1006

Several young supernova remnants (SNRs), including SN1006, emit synchrotron X-rays in narrow filaments, hereafter thin rims, along their periphery. The widths of these rims imply 50 to 100 $\mu$G fields in the region immediately behind the shock, far larger than expected for the interstellar medium compressed by unmodified shocks, assuming electron radiative losses limit rim widths. However, magnetic-field damping could also produce thin rims. Here we review the literature on rim width calculations, summarizing the case for magnetic-field amplification. We extend these calculations to include an arbitrary power-law dependence of the diffusion coefficient on energy, $D \propto E^{\mu}$. Loss-limited rim widths should shrink with increasing photon energy, while magnetic-damping models predict widths almost independent of photon energy. We use these results to analyze Chandra observations of SN 1006, in particular the southwest limb. We parameterize the full widths at half maximum (FWHM) in terms of energy as FWHM $\propto E^{m_E}_{\gamma}$. Filament widths in SN1006 decrease with energy; $m_E \sim -0.3$ to $-0.8$, implying magnetic field amplification by factors of 10 to 50, above the factor of 4 expected in strong unmodified shocks. For SN 1006, the rapid shrinkage rules out magnetic damping models. It also favors short mean free paths (small diffusion coefficients) and strong dependence of $D$ on energy ($\mu \ge 1$).Comment: Accepted by ApJ, 49 pages, 10 figure

Structural basis for substrate gripping and translocation by the ClpB AAA+ disaggregase.

Bacterial ClpB and yeast Hsp104 are homologous Hsp100 protein disaggregases that serve critical functions in proteostasis by solubilizing protein aggregates. Two AAA+ nucleotide binding domains (NBDs) power polypeptide translocation through a central channel comprised of a hexameric spiral of protomers that contact substrate via conserved pore-loop interactions. Here we report cryo-EM structures of a hyperactive ClpB variant bound to the model substrate, casein in the presence of slowly hydrolysable ATPγS, which reveal the translocation mechanism. Distinct substrate-gripping interactions are identified for NBD1 and NBD2 pore loops. A trimer of N-terminal domains define a channel entrance that binds the polypeptide substrate adjacent to the topmost NBD1 contact. NBD conformations at the seam interface reveal how ATP hydrolysis-driven substrate disengagement and re-binding are precisely tuned to drive a directional, stepwise translocation cycle

Comparative Visual Function in Predatory Fishes from the Indian River Lagoon

Visual temporal resolution and spectral sensitivity of three coastal teleost species (common snook [Centropomus undecimalis], gray snapper [Lutjanus griseus], and pinfish [Lagodon rhomboides]) were investigated by electroretinogram. Temporal resolution was quantified under photopic and scotopic conditions using response waveform dynamics and maximum critical flicker fusion frequency (CFFmax). Photopic CFFmax was significantly higher than scotopic CFFmax in all species. The snapper had the shortest photoreceptor response latency time (26.7 ms) and the highest CFFmax (47 Hz), suggesting that its eyes are adapted for a brighter photic environment. In contrast, the snook had the longest response latency time (36.8 ms) and lowest CFFmax (40 Hz), indicating that its eyes are adapted for a dimmer environment or nocturnal lifestyle. Species spectral responses ranged from 360 to 620 nm and revealed the presence of rods sensitive to dim and twilight conditions, as well as multiple cone visual pigments providing the basis for color and contrast discrimination. Collectively, our results demonstrate differences in visual function among species inhabiting the Indian River Lagoon system, representative of their unique ecology and life histories