Evapotranspiration (ET) is an important component of the global hydrological cycle. However, to what extent transpiration ratios (T/ET) are controlled by vegetation and the mechanisms of global‐scale ...T/ET variations are not clear. We synthesized all the published papers that measured at least two of the three components (E, T, and ET) and leaf area index (LAI) simultaneously. Nonlinear relationships between T/ET and LAI were identified for both the overall data set and agricultural or natural data subsets. Large variations in T/ET occurred across all LAI ranges with wider variability at lower LAI. For a given LAI, higher T/ET was observed during later vegetation growing stage within a season. We developed a function relating T/ET to the growing stage relative to the timing of peak LAI. LAI and growing stage collectively explained 43% of the variations in the global T/ET data set, providing a new way to interpret and model global T/ET variability.
Key Points
We reported the practical upper limit of vegetation control on T/ETFor a given leaf area, higher T/ET ratios occurred in the latter growing stage within a seasonGrowing stage and LAI explain 43% of the global T/ET variability
Electromagnetic ion cyclotron (EMIC) waves have been suggested to be a cause of radiation belt electron loss to the atmosphere. Here simultaneous, magnetically conjugate measurements are presented of ...EMIC wave activity, measured at geosynchronous orbit and on the ground, and energetic electron precipitation, seen by the Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) campaign, on two consecutive days in January 2013. Multiple bursts of precipitation were observed on the duskside of the magnetosphere at the end of 18 January and again late on 19 January, concurrent with particle injections, substorm activity, and enhanced magnetospheric convection. The structure, timing, and spatial extent of the waves are compared to those of the precipitation during both days to determine when and where EMIC waves cause radiation belt electron precipitation. The conjugate measurements presented here provide observational support of the theoretical picture of duskside interaction of EMIC waves and MeV electrons leading to radiation belt loss.
Key Points
EMIC waves and MeV electron precipitation are observed at the same UT and MLT
EMIC wave and precipitation timing, extent, and drivers are examined
Results provide observational confirmation of duskside EMIC‐electron interactions
ABSTRACT We present astrophysical false positive probability calculations for every Kepler Object of Interest (KOI)-the first large-scale demonstration of a fully automated transiting planet ...validation procedure. Out of 7056 KOIs, we determine that 1935 have probabilities <1% of being astrophysical false positives, and thus may be considered validated planets. Of these, 1284 have not yet been validated or confirmed by other methods. In addition, we identify 428 KOIs that are likely to be false positives, but have not yet been identified as such, though some of these may be a result of unidentified transit timing variations. A side product of these calculations is full stellar property posterior samplings for every host star, modeled as single, binary, and triple systems. These calculations use vespa, a publicly available Python package that is able to be easily applied to any transiting exoplanet candidate.
THE McGILL MAGNETAR CATALOG OLAUSEN, S A; Kaspi, V M
The Astrophysical journal. Supplement series,
05/2014, Letnik:
212, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We present a catalog of the 26 currently known magnetars and magnetar candidates. We tabulate astrometric and timing data for all catalog sources, as well as their observed radiative properties, ...particularly the spectral parameters of the quiescent X-ray emission. We show histograms of the spatial and timing properties of the magnetars, comparing them with the known pulsar population, and we investigate and plot possible correlations between their timing, X-ray, and multiwavelength properties. We find the scale height of magnetars to be in the range of 20-31 pc, assuming they are exponentially distributed. This range is smaller than that measured for OB stars, providing evidence that magnetars are born from the most massive O stars. From the same fits, we find that the Sun lies ~ 13-22 pc above the Galactic plane, consistent with previous measurements. We confirm previously identified correlations between quiescent X-ray luminosity, L sub(X), and magnetic field, B, as well as X-ray spectral power-law indexes, Gamma and B, and show evidence for an excluded region in a plot of L sub(X) versus Gamma. We also present an updated kT versus characteristic age plot, showing that magnetars and high-B radio pulsars are hotter than lower-B neutron stars of similar age. Finally, we observe a striking difference between magnetars detected in the hard X-ray and radio bands; there is a clear correlation between the hard and soft X-ray fluxes, whereas the radio-detected magnetars all have low, soft X-ray flux, suggesting, if anything, that the two bands are anticorrelated.
The highly stable spin of neutron stars can be exploited for a variety of (astro)physical investigations. In particular, arrays of pulsars with rotational periods of the order of milliseconds can be ...used to detect correlated signals such as those caused by gravitational waves. Three such ‘pulsar timing arrays’ (PTAs) have been set up around the world over the past decades and collectively form the ‘International’ PTA (IPTA). In this paper, we describe the first joint analysis of the data from the three regional PTAs, i.e. of the first IPTA data set. We describe the available PTA data, the approach presently followed for its combination and suggest improvements for future PTA research. Particular attention is paid to subtle details (such as underestimation of measurement uncertainty and long-period noise) that have often been ignored but which become important in this unprecedentedly large and inhomogeneous data set. We identify and describe in detail several factors that complicate IPTA research and provide recommendations for future pulsar timing efforts. The first IPTA data release presented here (and available online) is used to demonstrate the IPTA's potential of improving upon gravitational-wave limits placed by individual PTAs by a factor of ∼2 and provides a 2σ limit on the dimensionless amplitude of a stochastic gravitational-wave background of 1.7 × 10−15 at a frequency of 1 yr−1. This is 1.7 times less constraining than the limit placed by Shannon et al., due mostly to the more recent, high-quality data they used.
The Fine Time Measurement (FTM) protocol introduced by IEEE 802.11 includes a new ranging method, named Wi-Fi Round Trip Time (Wi-Fi RTT), which can be used for indoor localization. Pedestrian Dead ...Reckoning (PDR) can provide accurate pedestrian tracking through inertial sensors in a short time. Information fusion of PDR and existing wireless technology is widely used in indoor localization to ensure the robustness and stability. In this paper, we propose a fusion indoor localization method of Wi-Fi RTT and PDR. Firstly, an adaptive filtering system consisting of multiple Extended Kalman Filter (EKF) and a new outlier detection method is proposed to reduce the localization error of Wi-Fi RTT. Secondly, the fusion algorithm based on the Federated Filter (FF) and observability is designed to combine Wi-Fi RTT with PDR. Finally, to further improve the localization performance of the fusion algorithm, a real-time smoothing method with fixed interval is used. We evaluate the proposed method in four different scenarios. The results show that the proposed indoor localization method has better stability and robustness, and the average localization error decreased by 37.4-67.6% compared with the classic EKF-based method.
The transfer of high-quality time-frequency signals between remote locations underpins many applications, including precision navigation and timing, clock-based geodesy, long-baseline interferometry, ...coherent radar arrays, tests of general relativity and fundamental constants, and future redefinition of the second. However, present microwave-based time-frequency transfer is inadequate for state-of-the-art optical clocks and oscillators that have femtosecond-level timing jitter and accuracies below 1 × 10-17 . Commensurate optically based transfer methods are therefore needed. Here we demonstrate optical time-frequency transfer over free space via two-way exchange between coherent frequency combs, each phase-locked to the local optical oscillator. We achieve 1 fs timing deviation, residual instability below 1 × 10-18 at 1,000 s and systematic offsets below 4 × 10-19 , despite frequent signal fading due to atmospheric turbulence or obstructions across the 2 km link. This free-space transfer can enable terrestrial links to support clock-based geodesy. Combined with satellite-based optical communications, it provides a path towards global-scale geodesy, high-accuracy time-frequency distribution and satellite-based relativity experiments.
Accelerated multi‐dimensional NMR spectroscopy is a prerequisite for high‐throughput applications, studying short‐lived molecular systems and monitoring chemical reactions in real time. Non‐uniform ...sampling is a common approach to reduce the measurement time. Here, a new method for high‐quality spectra reconstruction from non‐uniformly sampled data is introduced, which is based on recent developments in the field of signal processing theory and uses the so far unexploited general property of the NMR signal, its low rank. Using experimental and simulated data, we demonstrate that the low‐rank reconstruction is a viable alternative to the current state‐of‐the‐art technique compressed sensing. In particular, the low‐rank approach is good in preserving of low‐intensity broad peaks, and thus increases the effective sensitivity in the reconstructed spectra.
A low rank is an advantage: High‐quality NMR spectra are reconstructed from a small number of non‐uniformly sampled data points. Significant reduction in measurement time is obtained using the so far unexploited general property of NMR signal—its low rank (see picture; NUS=non‐uniform sampling).
Conventional microneedles (MNs) have been extensively reported and applied toward a variety of biosensing and drug delivery applications. Hydrogel forming MNs with the added ability to electrically ...track health conditions in real‐time is an area yet to be explored. The first conductive hydrogel microneedle (HMN) electrode that is capable of on‐needle pH detection with no postprocessing required is presented here. The HMN array is fabricated using a swellable dopamine (DA) conjugated hyaluronic acid (HA) hydrogel, and is embedded with poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) to increase conductivity. The catechol‐quinone chemistry intrinsic to DA is used to measure pH in interstitial fluid (ISF). The effect of PEDOT:PSS on the characteristics of the HMN array such as swelling capability and mechanical strength is fully studied. The HMN's capability for pH measurement is first demonstrated using porcine skin equilibrated with different pH solutions ranging from 3.5 to 9. Furthermore, the HMN‐pH meter is capable of in vivo measurements with a 93% accuracy compared to a conventional pH probe meter. This HMN technology bridges the gap between traditional metallic electrochemical biosensors and the direct extraction of ISF, and introduces a platform for the development of polymeric wearable sensors capable of on‐needle detection.
A conductive hydrogel microneedle working electrode (HMN‐WE) capable of on‐needle pH detection with no postprocessing is presented here. The HMN‐WE comprises of dopamine conjugated hyaluronic‐acid embedded with poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate, and measures pH using catechol‐quinone chemistry. Characterization and rat models demonstrate its capability of real‐time pH measurements with 93% accuracy.
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