Abstract Although migrations are essential for soil microorganisms to exploit scarce and heterogeneously distributed resources, bacterial mobility in soil remains poorly studied due to experimental ...limitations. In this study, time-lapse images collected using live microscopy techniques captured collective and coordinated groups of B. subtilis cells exhibiting “crowd movement”. Groups of B. subtilis cells moved through transparent soil (nafion polymer with particle size resembling sand) toward plant roots and re-arranged dynamically around root tips in the form of elongating and retracting “flocks” resembling collective behaviour usually associated with higher organisms (e.g., bird flocks or fish schools). Genetic analysis reveals B. subtilis flocks are likely driven by the diffusion of extracellular signalling molecules (e.g., chemotaxis, quorum sensing) and may be impacted by the physical obstacles and hydrodynamics encountered in the soil like environment. Our findings advance understanding of bacterial migration through soil matrices and expand known behaviours for coordinated bacterial movement.
ABSTRACT We present new results on PHL 5038AB, a widely separated binary system composed of a white dwarf and a brown dwarf, refining the white and brown dwarf parameters and determining the binary ...separation to be $66^{+12}_{-24}$ au. New spectra of the white dwarf show calcium absorption lines suggesting that the hydrogen-rich atmosphere is weakly polluted, inferring the presence of planetesimals in the system, which we determine are in an S-type orbit around the white dwarf in orbits closer than 17–32 au. We do not detect any infrared excess that would indicate the presence of a disc, suggesting that all dust present either has been totally accreted or is optically thin. In this system, we suggest that the metal pollution in the white dwarf atmosphere can be directly attributed to the presence of the brown dwarf companion disrupting the orbits of planetesimals within the system.
ABSTRACT
The binary nature of the M8.5 dwarf DENIS J063001.4−184014AB (DE0630−18) was discovered with astrometric monitoring from the ground, which determined the unresolved photocentric orbit and ...the trigonometric parallax of the system. Here we present radial velocity monitoring and resolved observations in the near-infrared with Keck aperture masking that allows us to measure the system’s relative separation and brightness. By combining all available information, we determine the individual dynamical masses of the binary components to be $M_1 = 0.052^{+0.009}_{-0.008}$MSun and $M_2 = 0.052^{+0.005}_{-0.004}$MSun, both firmly in the substellar regime. These masses are surprising, given the object’s M8.5 optical spectral type and equivalent absolute magnitude, and the significant difference in brightness between the components (ΔK = 1.74 ± 0.06 mag). Our results suggest that DE0630−18 is a relatively young system (∼200 Myr) with a secondary component that is itself a potentially unresolved binary.
Aims. We report the discovery of CFBDS J005910.90-011401.3 (hereafter CFBDS0059), the coolest brown dwarf identified to date. Methods. We found CFBDS0059 using i' and z' images from the ...Canada-France-Hawaii Telescope (CFHT), and present optical and near-infrared photometry, Keck laser-guide-star adaptive optics imaging, and a complete near-infrared spectrum, from 1.0 to 2.2 μm. Results. A side-to-side comparison of the near-infrared spectra of CFBDS0059 and ULAS J003402.77-005206.7 (hereafter ULAS0034), previously the coolest known brown dwarf, indicates that CFBDS0059 is ~50 ± 15 K cooler. We estimate a temperature of $T_\mathrm{eff} \sim$ 620 K and gravity of log g ~ 4.75. Evolutionary models translate these parameters into an age of 1–5 Gyr and a mass of 15-30 MJup. We estimate a photometric distance of ~13 pc, which puts CFBDS0059 within easy reach of accurate parallax measurements. Its large proper motion suggests membership in the older population of the thin disk. The spectra of both CFBDS0059 and ULAS J0034 show probable absorption by a wide ammonia band on the blue side of the H-band flux peak. If, as we expect, that feature deepens further for still lower effective temperatures, its appearance will become a natural breakpoint for the transition between the T spectral class and the new Y spectral type. Together, CFBDS0059 and ULAS J0034 would then be the first Y0 dwarfs.
The discovery of an M4+T8.5 binary system Burningham, Ben; Pinfield, D. J.; Leggett, S. K. ...
Monthly Notices of the Royal Astronomical Society,
05/2009, Letnik:
395, Številka:
3
Journal Article
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We report the discovery of a T8.5 dwarf, which is a companion to the M4 dwarf Wolf 940. At a distance of 12.50+0.75−0.67 pc, the angular separation of 32 arcsec corresponds to a projected separation ...of 400 au. The M4 primary displays no Hα emission, and we apply the age–activity relations of West et al. to place a lower limit on the age of the system of 3.5 Gyr. Weak Hα absorption suggests some residual activity, and we estimate an upper age limit of 6 Gyr. We apply the relations of Bonfils et al. for V−Ks and to determine the metallicity, Fe/H=−0.06 ± 0.20 for Wolf 940A, and by extension the T8.5 secondary, Wolf 940B. We have obtained JHK NIRI spectroscopy and JHKL′ photometry of Wolf 940B, and use these data, in combination with theoretical extensions, to determine its bolometric flux, Fbol= 1.75 ± 0.18 × 10−16 W m−2, and thus its luminosity log (L*/L⊙) =−6.07 ± 0.04. Using the age constraints for the system and evolutionary structural models of Baraffe et al., we determine Teff= 570 ± 25 K and log g= 4.75 − 5.00 for Wolf 940B, based on its bolometric luminosity. This represents the first determination of these properties for a T8+ dwarf that does not rely on the fitting of T dwarf spectral models. This object represents the first system containing a T8+ dwarf for which fiducial constraints on its properties are available, and we compare its spectra with those of the latest very cool BT–Settl models. This clearly demonstrates that the use of the (WJ, K/J) spectral ratios (used previously to constrain Teff and log g) would have overestimated Teff by ∼100 K.
IntroductionChronic pain is highly prevalent and associated with a large burden of illness; there is a pressing need for safe, home-based, non-pharmacological, interventions. Virtual reality (VR) is ...a digital therapeutic known to be effective for acute pain, but its role in chronic pain is not yet fully elucidated. Here we present a protocol for the National Institute of Health (NIH) Back Pain Consortium (BACPAC) VR trial that evaluates the effectiveness of three forms of VR for patients with chronic lower back pain (cLBP), a highly prevalent form of chronic pain.Methods and analysisThe NIH BACPAC VR trial will randomise 360 patients with cLBP into one of three arms, each administered through a head-mounted display: 1) skills-based VR, a program incorporating principles of cognitive behavioural therapy, mindful meditation and physiological biofeedback therapy using embedded biometric sensors; 2) distraction-based VR, a program using 360-degree immersive videos designed to distract users from pain; and 3) sham VR, a non-immersive program using two-dimensional videos within a VR headset. Research participants will be monitored for 12 weeks using a combination of patient-reported outcomes administered via REDCap (Research Electronic Data Capture), wearable sensor data collected via Fitbit Charge 4 and electronic health record data. The primary outcome will be the NIH Patient-Reported Outcomes Measurement Information System (PROMIS) Pain Interference scale. Secondary outcomes will include PROMIS Anxiety, PROMIS Sleep Disturbance, opioid prescription data and Pain Catastrophizing Scale Short Form. A subgroup analysis will explore patient level predictors for VR efficacy.Ethics and disseminationEthics approval was obtained from the Institutional Review Board of Cedars-Sinai Health System in April 2020. The results will be disseminated in a peer-reviewed journal.Trial registration numberNCT04409353.
Techniques that monitor in situ the setting and hardening of calcium aluminate cements (CACs) are of interest to the engineering community. This paper focuses on one non-destructive technique, X-ray ...computed tomography (CT). The early hydration of the cement can be followed from a few minutes to a few hours after mixing. This technique is based on both X-ray absorption measurements and qualitative observations in chosen axial cross-sections. Results concerning an aluminous cement, Secar 71, are presented (water-to-cement weight ratio: 0.33; duration: 0–24 h). Information deduced from these measurements clearly show that a strong variation of X-ray absorption values occurs during the early age of hydration. Both quantitative and qualitative analyses of CT data allow a chronology of cement setting to be proposed.
Planet Hunters IX. KIC 8462852 – where's the flux? Boyajian, T. S; LaCourse, D. M; Rappaport, S. A ...
Monthly notices of the Royal Astronomical Society,
04/2016, Letnik:
457, Številka:
4
Journal Article
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Over the duration of the Kepler mission, KIC 8462852 was observed to undergo irregularly shaped, aperiodic dips in flux of up to ∼20 per cent. The dipping activity can last for between 5 and 80 d. We ...characterize the object with high-resolution spectroscopy, spectral energy distribution fitting, radial velocity measurements, high-resolution imaging, and Fourier analyses of the Kepler light curve. We determine that KIC 8462852 is a typical main-sequence F3 V star that exhibits no significant IR excess, and has no very close interacting companions. In this paper, we describe various scenarios to explain the dipping events observed in the Kepler light curve. We confirm that the dipping signals in the data are not caused by any instrumental or data processing artefact, and thus are astrophysical in origin. We construct scenario-independent constraints on the size and location of a body in the system that are needed to reproduce the observations. We deliberate over several assorted stellar and circumstellar astrophysical scenarios, most of which have problems explaining the data in hand. By considering the observational constraints on dust clumps in orbit around a normal main-sequence star, we conclude that the scenario most consistent with the data in hand is the passage of a family of exocomet or planetesimal fragments, all of which are associated with a single previous break-up event, possibly caused by tidal disruption or thermal processing. The minimum total mass associated with these fragments likely exceeds 10−6 M⊕, corresponding to an original rocky body of >100 km in diameter. We discuss the necessity of future observations to help interpret the system.
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