Results from regular monitoring of relativistic compact binaries like PSR 1913+16 are consistent with the dominant (quadrupole) order emission of gravitational waves (GWs). We show that observations ...associated with the binary black hole (BBH) central engine of blazar OJ 287 demand the inclusion of gravitational radiation reaction effects beyond the quadrupolar order. It turns out that even the effects of certain hereditary contributions to GW emission are required to predict impact flare timings of OJ 287. We develop an approach that incorporates this effect into the BBH model for OJ 287. This allows us to demonstrate an excellent agreement between the observed impact flare timings and those predicted from ten orbital cycles of the BBH central engine model. The deduced rate of orbital period decay is nine orders of magnitude higher than the observed rate in PSR 1913+16, demonstrating again the relativistic nature of OJ 287's central engine. Finally, we argue that precise timing of the predicted 2019 impact flare should allow a test of the celebrated black hole "no-hair theorem" at the 10% level.
We present the results of our power spectral density analysis for the BL Lac object OJ 287, utilizing the Fermi-LAT survey at high-energy γ-rays, Swift-XRT in X-rays, several ground-based telescopes ...and the Kepler satellite in the optical, and radio telescopes at GHz frequencies. The light curves are modeled in terms of continuous-time autoregressive moving average (CARMA) processes. Owing to the inclusion of the Kepler data, we were able to construct for the first time the optical variability power spectrum of a blazar without any gaps across ∼6 dex in temporal frequencies. Our analysis reveals that the radio power spectra are of a colored-noise type on timescales ranging from tens of years down to months, with no evidence for breaks or other spectral features. The overall optical power spectrum is also consistent with a colored noise on the variability timescales ranging from 117 years down to hours, with no hints of any quasi-periodic oscillations. The X-ray power spectrum resembles the radio and optical power spectra on the analogous timescales ranging from tens of years down to months. Finally, the γ-ray power spectrum is noticeably different from the radio, optical, and X-ray power spectra of the source: we have detected a characteristic relaxation timescale in the Fermi-LAT data, corresponding to ∼150 days, such that on timescales longer than this, the power spectrum is consistent with uncorrelated (white) noise, while on shorter variability timescales there is correlated (colored) noise.
A newly developed laboratory, Meteoric Ablation Simulator (MASI), is used to test model predictions of the atmospheric ablation of interplanetary dust particles (IDPs) with experimental Na, Fe, and ...Ca vaporization profiles. MASI is the first laboratory setup capable of performing time-resolved atmospheric ablation simulations, by means of precision resistive heating and atomic laser-induced fluorescence detection. Experiments using meteoritic IDP analogues show that at least three mineral phases (Na-rich plagioclase, metal sulfide, and Mg-rich silicate) are required to explain the observed appearance temperatures of the vaporized elements. Low melting temperatures of Na-rich plagioclase and metal sulfide, compared to silicate grains, preclude equilibration of all the elemental constituents in a single melt. The phase-change process of distinct mineral components determines the way in which Na and Fe evaporate. Ca evaporation is dependent on particle size and on the initial composition of the molten silicate. Measured vaporized fractions of Na, Fe, and Ca as a function of particle size and speed confirm differential ablation (i.e., the most volatile elements such as Na ablate first, followed by the main constituents Fe, Mg, and Si, and finally the most refractory elements such as Ca). The Chemical Ablation Model (CABMOD) provides a reasonable approximation to this effect based on chemical fractionation of a molten silicate in thermodynamic equilibrium, even though the compositional and geometric description of IDPs is simplistic. Improvements in the model are required in order to better reproduce the specific shape of the elemental ablation profiles.
Ablation of Mg from meteoroids entering the Earth's atmosphere was studied experimentally using a Meteoric Ablation Simulator: micron‐sized particles of representative meteoritic material were flash ...heated to simulate atmospheric entry and the ablation rate of Mg with respect to Na measured by fast time‐resolved laser‐induced fluorescence. Over the range of particle diameters and entry velocities studied, Mg ablates 4.3 ± 2.1 times less efficiently than Na and 2.4 ± 0.8 times less efficiently than Fe. The resulting evaporation profiles indicate that Mg mostly ablates around 84 km in the atmosphere, compared with Fe at 88 km and Na at 95 km. The chemical ablation model Chemical Ablation Model predicts satisfactorily the measured peak ablation altitudes and relative ablated fractions of Mg, Na, Fe, and Ca but does not capture the breadth of the ablation profiles, probably due to the inhomogeneity of the minerals present in meteoroids combined with experimental limitations.
Plain Language Summary
About 40 t of cosmic dust enters the Earth's atmosphere every day. These meteoroids, which contain minerals composed of metallic elements such as iron, sodium, calcium, and magnesium enter the Earth's atmosphere at high speeds (between 24,000 and 160,000 mph). The resulting flash heating caused by high‐energy impacts with air molecules can lead to melting and in some cases complete evaporation of the particles—a process termed ablation. In this study, ablation is simulated using particles from different types of meteorite which are rapidly heated to well over 1700°C (3100°F) during the few seconds this would occur in the atmosphere. Lasers probe the resulting evaporation of a variety of metals. Here we show that magnesium evaporates less efficiently and at lower altitudes than sodium and iron, which is consistent with the predicted thermodynamics of the molten particles.
Key Points
Differential ablation of Mg with respect to Na, Fe, and Ca observed from a range of meteoritic samples
Experimental simulations confirm predictions of a chemical ablation model based on melt thermodynamics and Langmuir evaporation
Mg should mostly ablate in the atmosphere between 80 and 90 km, with an ablation peak 4 km below that of Fe and 11 km below Na
•The efficient post-multicomponent synthesis of the chloride salt of 1-(3,6-dihydropyrimidin-2-yl)urea hydrated based on Biginelli´s products is described.•The structure of the compound was confirmed ...by single crystal X-ray analysis in conjunction with HRMS, FTIR and NMR spectroscopy techniques.•Intermolecular interactions were examined using X-ray diffraction results and compared with those obtained by Hirshfeld surface analysis.•Hirshfeld surfaces and 2D fingerprint plots were used to clarify intermolecular interactions in the crystal lattice of the title compound.
The postmulticomponent synthesis and crystal structure of 1-(3,6-dihydropyrimidin-2-yl)urea salt, 5-(ethoxycarbonyl)-4-methyl-6-phenyl-2-ureido-3,6-dihydropyrimidin-1-ium chloride monohydrate, C15H21O4N4+·ClH2O; structurally related to dihydropyrimidinon-2-ylurea-type RNA-binding ligands is reported. The structure of this new type of hydrated organic salt was investigated by FT-IR, NMR and HRMS methods, and its structure was unambiguous confirmed using X-ray single crystal diffraction techniques. X-ray diffraction analysis show that this material crystallizes in the monoclinic space group P21/c (N°14), Z = 4 with the 3,6-dihydropyrimidin-1-ium ring in a pucked-boat conformation attached to the ester group in an s−trans relationship. The molecular structure and crystal packing are stabilized by intermolecular N − H···O, O − H···O, and N − H···Cl hydrogen bonds formed an infinite three-dimensional (3D) network. Furthermore, the Hirshfeld surface analysis confirms that the most important contributions for the crystal packing are the C − H···H (52.5%), C − H···C (17.8%), C − H···O (15.4%) and N − H···Cl (5.80%) surface contacts.
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We present a path forward on a long-standing issue concerning the flux of small and slow meteoroids, which are believed to be the dominant portion of the incoming meteoric mass flux into the Earth's ...atmosphere. Such a flux, which is predicted by dynamical dust models of the Zodiacal Cloud, is not evident in ground-based radar observations. For decades this was attributed to the fact that the radars used for meteor observations lack the sensitivity to detect this population, due to the small amount of ionization produced by slow-velocity meteors. Such a hypothesis has been challenged by the introduction of meteor head echo (HE) observations with High Power and Large Aperture radars, in particular the Arecibo 430 MHz radar. Janches et al. developed a probabilistic approach to estimate the detectability of meteors by these radars and initially showed that, with the current knowledge of ablation and ionization, such particles should dominate the detected rates by one to two orders of magnitude compared to the actual observations. In this paper, we include results in our model from recently published laboratory measurements, which showed that (1) the ablation of Na is less intense covering a wider altitude range; and (2) the ionization probability, β ip , for Na atoms in the air is up to two orders of magnitude smaller for low speeds than originally believed. By applying these results and using a somewhat smaller size of the HE radar target we offer a solution that reconciles these observations with model predictions.
The molecular hallmark of the Ewing's family of tumors is the presence of balanced chromosomal translocations, leading to the formation of chimerical transcription factors (that is, EWS/FLI1) that ...play a pivotal role in the pathogenesis of Ewing's tumors by deregulating gene expression. We have recently demonstrated that DAX1 (NR0B1), an orphan nuclear receptor that was not previously implicated in cancer, is induced by the EWS/FLI1 oncoprotein and is highly expressed in Ewing's tumors, suggesting that DAX1 is a biologically relevant target of EWS/FLI1-mediated oncogenesis. In this study we demonstrate that DAX1 is a direct transcriptional target of the EWS/FLI1 oncoprotein through its binding to a GGAA-rich region in the DAX1 promoter and show that DAX1 is a key player of EWS/FLI1-mediated oncogenesis. DAX1 silencing using an inducible model of RNA interference induces growth arrest in the A673 Ewing's cell line and severely impairs its capability to grow in semisolid medium and form tumors in immunodeficient mice. Gene expression profile analysis demonstrated that about 10% of the genes regulated by EWS/FLI1 in Ewing's cells are DAX1 targets, confirming the importance of DAX1 in Ewing's oncogenesis. Functional genomic analysis, validated by quantitative RT-PCR, showed that genes implicated in cell-cycle progression, such as CDK2, CDC6, MCM10 or SKP2 were similarly regulated by EWS/FLI1 and DAX1. These findings indicate that DAX1 is important in the pathogenesis of the Ewing's family of tumors, identify new functions for DAX1 as a cell-cycle progression regulator and open the possibility to new therapeutic approaches based on DAX1 function interference.
A prospective, randomised, blinded controlled study was performed to determine the anaesthetic and cardiorespiratory effects of a constant-rate infusion (CRI) of alfaxalone in 12 sheep anaesthetised ...with desflurane, and undergoing experimental orthopaedic surgery. Sheep were sedated with dexmedetomidine (4 μg/kg, intravenously) and butorphanol (0.3 mg/kg, intravenously). Anaesthesia was induced with alfaxalone (1 mg/kg/minute to effect, intravenously) and maintained with desflurane in oxygen and alfaxalone 0.07 mg/kg/minute or saline for 150 minutes (range 150-166 minutes). The anaesthetic induction dose of alfaxalone, the desflurane expiratory fraction required for anaesthetic maintenance, cardiorespiratory measurements and blood-gases were recorded at predetermined intervals. Quality of sedation, anaesthetic induction and recovery were assessed. The alfaxalone induction dose was 1.7 mg/kg (1.2 to 2.6 mg/kg). The desflurane expiratory fraction was lower (22 per cent) in sheep receiving alfaxalone CRI (P=0). Also, heart rate (P=0), cardiac index (P=0.002), stroke index (P=0) and contractility (P=0) were higher, and systemic vascular resistance (P=0.002) was lower. Although respiratory rate tended to be higher with alfaxalone, there was no difference in PCO2 between the groups. Recovery times were significantly longer in sheep given alfaxalone (25.4 v 9.5 minutes) but recovery quality was similar. Alfaxalone reduced requirements of desflurane and maintained similar cardiorespiratory function, but recovery time was more prolonged.
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