Atomic resolution imaging at 2.5 GHz using near-field microwave microscopy

Atomic resolution imaging is demonstrated using a hybrid scanning tunneling/near-field microwave microscope (microwave-STM). The microwave channels of the microscope correspond to the resonant frequency and quality factor of a coaxial microwave resonator, which is built in to the STM scan head and coupled to the probe tip. We find that when the tip-sample distance is within the tunneling regime, we obtain atomic resolution images using the microwave channels of the microwave-STM. We attribute the atomic contrast in the microwave channels to GHz frequency current through the tip-sample tunnel junction. Images of the surfaces of HOPG and Au(111) are presented.Comment: 9 pages, 5 figures, submitted to Applied Physics Letter

BlockGAN: Learning 3D Object-aware Scene Representations from Unlabelled Images

We present BlockGAN, an image generative model that learns object-aware 3D scene representations directly from unlabelled 2D images. Current work on scene representation learning either ignores scene background or treats the whole scene as one object. Meanwhile, work that considers scene compositionality treats scene objects only as image patches or 2D layers with alpha maps. Inspired by the computer graphics pipeline, we design BlockGAN to learn to first generate 3D features of background and foreground objects, then combine them into 3D features for the wholes cene, and finally render them into realistic images. This allows BlockGAN to reason over occlusion and interaction between objects' appearance, such as shadow and lighting, and provides control over each object's 3D pose and identity, while maintaining image realism. BlockGAN is trained end-to-end, using only unlabelled single images, without the need for 3D geometry, pose labels, object masks, or multiple views of the same scene. Our experiments show that using explicit 3D features to represent objects allows BlockGAN to learn disentangled representations both in terms of objects (foreground and background) and their properties (pose and identity).Comment: For project page, see https://www.monkeyoverflow.com/#/blockgan/ Accepted to Conference on Neural Information Processing Systemsm, NeurIPS 202

BlockGAN: Learning 3D Object-aware Scene Representations from Unlabelled Images

We present BlockGAN, an image generative model that learns object-aware 3D scene representations directly from unlabelled 2D images. Current work on scene representation learning either ignores scene background or treats the whole scene as one object. Meanwhile, work that considers scene compositionality treats scene objects only as image patches or 2D layers with alpha maps. Inspired by the computer graphics pipeline, we design BlockGAN to learn to first generate 3D features of background and foreground objects, then combine them into 3D features for the whole scene, and finally render them into realistic images. This allows BlockGAN to reason over occlusion and interaction between objects’ appearance, such as shadow and lighting, and provides control over each object’s 3D pose and identity, while maintaining image realism. BlockGAN is trained end-to-end, using only unlabelled single images, without the need for 3D geometry, pose labels, object masks, or multiple views of the same scene. Our experiments show that using explicit 3D features to represent objects allows BlockGAN to learn disentangled representations both in terms of objects (foreground and background) and their properties (pose and identity).This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 66599

The luminosity dependence of thermally-driven disc winds in low-mass X-ray binaries

We have carried out radiation-hydrodynamic simulations of thermally-driven accretion disc winds in low-mass X-ray binaries. Our main goal is to study the luminosity dependence of these outflows and compare with observations. The simulations span the range $\rm{0.04 \leq L_{acc}/L_{Edd} \leq 1.0}$ and therefore cover most of the parameter space in which disc winds have been observed. Using a detailed Monte Carlo treatment of ionization and radiative transfer, we confirm two key results found in earlier simulations that were carried out in the optically thin limit: (i) the wind velocity -- and hence the maximum blueshift seen in wind-formed absorption lines -- increases with luminosity; (ii) the large-scale wind geometry is quasi-spherical, but observable absorption features are preferentially produced along high-column equatorial sightlines. In addition, we find that (iii) the wind efficiency always remains approximately constant at $\rm{\dot{M}_{wind}/\dot{M}_{acc} \simeq 2}$, a behaviour that is consistent with observations. We also present synthetic Fe XXV and Fe XXVI absorption line profiles for our simulated disc winds in order to illustrate the observational implications of our results.Comment: Accepted for publication in MNRA

A Self-Occulting Accretion Disk in the SW Sex Star DW UMa

We present the ultraviolet spectrum of the SW Sex star and nova-like variable DW UMa in an optical low state, as observed with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope (HST). The data are well described by a synthetic white dwarf (WD) spectrum with T_eff = 46,000 +/- 1000 K, log g = 7.60 +/- 0.15, v*sin(i) = 370 +/- 100 km/s and Z/Z_solar = 0.47 +/- 0.15. For this combination of T_eff and log g, WD models predict M_WD = 0.48 +/- 0.06 M_solar and R_WD = (1.27 +/- 0.18) * 10^9 cm. Combining the radius estimate with the normalization of the spectral fit, we obtain a distance estimate of d = 830 +/-150 pc. During our observations, DW UMa was approximately 3 magnitudes fainter in V than in the high state. A comparison of our low-state HST spectrum to a high-state spectrum obtained with the International Ultraviolet Explorer shows that the former is much bluer and has a higher continuum level shortward of 1450 A. Since DW UMa is an eclipsing system, this suggests that an optically thick accretion disk rim blocks our view of the WD primary in the high state. If self-occulting accretion disks are common among the SW Sex stars, we can account for (i) the preference for high-inclination systems within the class and (ii) their V-shaped continuum eclipses. Moreover, even though the emission lines produced by a self-obscured disk are generally still double-peaked, they are weaker and narrower than those produced by an unobscured disk. This may allow a secondary line emission mechanism to dominate and produce the single-peaked, optical lines that are a distinguishing characteristic of the SW Sex stars.Comment: 9 pages, including 2 figures; accepted for publication in Astrophysical Journal Letters; New version matches version in press (footnote added to discussion section; figures now use color

Observations of the SW Sextantis star DW Ursae Majoris with the Far Ultraviolet Spectroscopic Explorer

We present an analysis of the first far-ultraviolet observations of the SW Sextantis-type cataclysmic variable DW Ursae Majoris, obtained in November 2001 with the Far Ultraviolet Spectroscopic Explorer. The time-averaged spectrum of DW UMa shows a rich assortment of emission lines (plus some contamination from interstellar absorption lines including molecular hydrogen). Accretion disk model spectra do not provide an adequate fit to the far-ultraviolet spectrum of DW UMa. We constructed a light curve by summing far-ultraviolet spectra extracted in 60-sec bins; this shows a modulation on the orbital period, with a maximum near photometric phase 0.93 and a minimum half an orbit later. No other periodic variability was found in the light curve data. We also extracted spectra in bins spanning 0.1 in orbital phase; these show substantial variation in the profile shapes and velocity shifts of the emission lines during an orbital cycle of DW UMa. Finally, we discuss possible physical models that can qualitatively account for the observed far-ultraviolet behavior of DW UMa, in the context of recent observational evidence for the presence of a self-occulting disk in DW UMa and the possibility that the SW Sex stars may be the intermediate polars with the highest mass transfer rates and/or weakest magnetic fields.Comment: accepted by the Astronomical Journal; 36 pages, including 12 figures and 4 table

Rotation Dependence of Electric Quadrupole Hyperfine Interaction in the Ground State of Molecular Iodine by High-Resolution Laser Spectroscopy

Doppler-free high-resolution spectroscopy is applied to molecular iodine at 532 nm by Nd:YAG lasers. The main hyperfine components as well as the crossover lines are measured for R(56)32−0 and P(54)32−0 transitions by heterodyne beating of two I2-stabilized lasers. The measured hyperfine splittings including both main and crossover lines are fitted to a four-term Hamiltonian, which includes the electric quadrupole, spin–rotation, tensor spin–spin, and scalar spin–spin interactions, with an average deviation of ∼1 kHz. Absolute values of the electric quadrupole hyperfine constants for both the upper and the lower states are obtained. The rotation dependence of the ground-state (v\u22=0) electric quadrupole constant eQq\u22 is found to be eQq\u22(J)=−2452.556(2)−0.000164(5)J(J+1)−0.000000005(2)J2(J+1)2 MHz

Can Regenerative Agriculture increase national soil carbon stocks? : Simulated country scale adoption of reduced tillage, cover cropping, and ley-arable integration using RothC

ACKNOWLEDGMENTS We would like to thank Dr Andrew C. Martin for advice on our modelling framework. The authors would like to acknowledge the use of the University of Oxford Advanced Research Computing facility in carrying out this work. This work was supported by funding from the Biotechnology and Biological Sciences Research Council (BBSRC) [grant number BB/M011224/1]. PCB would like to acknowledge funding by Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy [EXC 2075 – 390740016]. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.Peer reviewedPostprin

Time of emergence and large ensemble intercomparison for ocean biogeochemical trends

Anthropogenically forced changes in ocean biogeochemistry are underway and critical for the ocean carbon sink and marine habitat. Detecting such changes in ocean biogeochemistry will require quantification of the magnitude of the change (anthropogenic signal) and the natural variability inherent to the climate system (noise). Here we use Large Ensemble (LE) experiments from four Earth system models (ESMs) with multiple emissions scenarios to estimate Time of Emergence (ToE) and partition projection uncertainty for anthropogenic signals in five biogeochemically important upper-ocean variables. We find ToEs are robust across ESMs for sea surface temperature and the invasion of anthropogenic carbon; emergence time scales are 20-30 yr. For the biological carbon pump, and sea surface chlorophyll and salinity, emergence time scales are longer (50+ yr), less robust across the ESMs, and more sensitive to the forcing scenario considered. We find internal variability uncertainty, and model differences in the internal variability uncertainty, can be consequential sources of uncertainty for projecting regional changes in ocean biogeochemistry over the coming decades. In combining structural, scenario, and internal variability uncertainty, this study represents the most comprehensive characterization of biogeochemical emergence time scales and uncertainty to date. Our findings delineate critical spatial and duration requirements for marine observing systems to robustly detect anthropogenic change

Phase II Study of Vicriviroc versus Efavirenz (both with Zidovudine/Lamivudine) in Treatment-Naive Subjects with HIV-1 Infection

Background. Vicriviroc (VCV) is a CCR5 antagonist with nanomolar activity against human immunodeficiency virus (HIV) replication in vitro and in vivo. We report the results of a phase II dose-finding study of VCV plus dual nucleoside reverse-transcriptase inhibitors (NRTIs) in the treatment-naive HIV-1-infected subjects. Methods. This study was a randomized, double-blind, placebo-controlled trial that began with a 14-day comparison of 3 dosages of VCV with placebo in treatment-naive subjects infected with CCR5-using HIV-1. After 14 days of monotherapy, lamivudine/zidovudine was added to the VCV arms; subjects receiving placebo were treated with efavirenz and lamivudine/zidovudine; the planned treatment duration was 48 weeks. Results. Ninety-two subjects enrolled. After 14 days of once-daily monotherapy, the mean viral loads decreased from baseline values by 0.07 log10 copies/mL in the placebo arm, 0.93 log10 copies/mL in theVCV25 mg arm, 1.18 log10 copies/mL in the VCV 50 mg arm, and 1.34 log10 copies/mL in the VCV 75 mg arm (P < .001 for each VCV arm vs. the placebo arm). The combination-therapy portion of the study was stopped because of increased rates of virologic failure in the VCV 25 mg/day arm (relative hazard [RH], 21.6; 95% confidence interval [CI], 2.8-168.9) and the VCV 50 mg/day arm (RH, 11.7; 95% CI, 1.5-92.9), compared with that in the control arm. Conclusion. VCV administered with dual NRTIs in treatment-naive subjects with HIV-1 infection had increased rates of virologic failure, compared with efavirenz plus dual NRTIs. No treatment-limiting toxicity was observed. Study of higher doses of VCV as part of combination therapy is warrante