Spaceborne digital elevation models (DEMs) are a fundamental input for many geoscience studies, but they still include nonnegligible height errors. Here we introduce a high‐accuracy global DEM at 3″ ...resolution (~90 m at the equator) by eliminating major error components from existing DEMs. We separated absolute bias, stripe noise, speckle noise, and tree height bias using multiple satellite data sets and filtering techniques. After the error removal, land areas mapped with ±2 m or better vertical accuracy were increased from 39% to 58%. Significant improvements were found in flat regions where height errors larger than topography variability, and landscapes such as river networks and hill‐valley structures, became clearly represented. We found the topography slope of previous DEMs was largely distorted in most of world major floodplains (e.g., Ganges, Nile, Niger, and Mekong) and swamp forests (e.g., Amazon, Congo, and Vasyugan). The newly developed DEM will enhance many geoscience applications which are terrain dependent.
Key Points
A high‐accuracy global digital elevation model (DEM) was developed by removing multiple height error components from existing DEMs
Landscape representation was improved, especially in flat regions where height error magnitude was larger than actual topography variation
The improved‐terrain DEM is helpful for any geoscience applications which are terrain dependent, such as flood inundation modelling
Plain Language Summary
Terrain elevation maps are fundamental input data for many geoscience studies. While very precise Digital Elevation Models (DEMs) based on airborne measurements are available in developed regions of the world, most areas of the globe rely on spaceborne DEMs which still include non‐negligible height errors for geoscience applications. Here we developed a new high accuracy map of global terrain elevations at 3" resolution (~90m at the equator) by eliminating multiple error components from existing spaceborne DEMs. The height errors included in the original DEMs were separated from actual topography signals and removed using a combination of multiple satellite datasets and filtering techniques. After error removal, global land areas mapped with ±2m or better accuracy increased from 39% to 58%. Significant improvements were found, especially in flat regions such as river floodplains. Here detected height errors were larger than actual topography variability, and following error removal landscapes features such as river networks and hill‐valley structures at last became clearly represented. The developed high accuracy topography map will expand the possibility of geoscience applications that require high accuracy elevation data such as terrain landscape analysis, flood inundation modelling, soil erosion analysis, and wetland carbon cycle studies.
ABSTRACT
υ Sgr is the prototype of four known hydrogen-deficient binary (HdB) systems. These are characterized by a hydrogen-deficient A-type primary, variable hydrogen emission lines, and a ...normally unseen secondary presumed to be an upper main-sequence star. Orbital periods range from tens of days to 360 d. TESS observations of all four HdBs show a flux variation with well-defined period in the range 0.5–0.9 d, too short to be associated with the supergiant primary, and more likely to be the rotation period of the secondary and associated with a chemical surface asymmetry or a low-order non-radial oscillation. The observed rotation period supports a recent analysis of the υ Sgr secondary. The observations give a direct glimpse of the secondary in all four systems, and should help to explain how the primary has been stripped to become a low-mass hydrogen remnant.
ABSTRACT
Transiting Exoplanet Survey Satellite photometry of the extremely helium-rich hot subdwarfs BD+37°442 and BD+37°1977 demonstrates multiperiodic low-amplitude variability with principal ...periods of 0.56 and 1.14 d, respectively, and with both first and second harmonics present. The light curves are not perfectly regular, implying additional periodic and/or non-periodic content. Possible causes are examined, including the binary hypothesis originally introduced to explain X-ray observations, differentially rotating surface inhomogeneities, and pulsations. If the principal photometric periods correspond to the rotation periods, the stars are rotating at approximately 0.7 and 0.3 × break-up, respectively. Surface Rossby waves (r modes) therefore provide the most likely solution.
Innocuous touch of the skin is detected by distinct populations of neurons, the low-threshold mechanoreceptors (LTMRs), which are classified as Aβ-, Aδ-, and C-LTMRs. Here, we report genetic labeling ...of LTMR subtypes and visualization of their relative patterns of axonal endings in hairy skin and the spinal cord. We found that each of the three major hair follicle types of trunk hairy skin (guard, awl/auchene, and zigzag hairs) is innervated by a unique and invariant combination of LTMRs; thus, each hair follicle type is a functionally distinct mechanosensory end organ. Moreover, the central projections of Aβ-, Aδ-, and C-LTMRs that innervate the same or adjacent hair follicles form narrow LTMR columns in the dorsal horn. These findings support a model of mechanosensation in which the activities of Aβ-, Aδ-, and C-LTMRs are integrated within dorsal horn LTMR columns and processed into outputs that underlie the perception of myriad touch sensations.
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► Genetic labeling reveals low-threshold mechanoreceptor circuitry in the mouse ► Low-threshold mechanoreceptors innervate hair follicles and form lanceolate endings ► Each hair follicle type displays a unique combination of mechanoreceptor endings ► Central endings of mechanoreceptors form columns in the spinal cord dorsal horn
Genetic labeling of neurons in the mouse skin enables visualization of touch circuits and shows that different types of hair follicles are innervated by a unique combination of mechanosensory neurons, suggesting that each hair follicle is a functionally distinct mechanosensory organ.
Using linear non-adiabatic pulsation analysis, we explore the radial-mode (p-mode) stability of stars across a wide range of mass (
$0.2 \le M \le 50{\,\rm M_{{\odot }}}$
), composition (0 ≤ X ≤ 0.7, ...Z = 0.001, 0.02), effective temperature (3000 ≤ T
eff ≤ 40 000 K), and luminosity (0.01 ≤ L/M ≤ 100 000 solar units). We identify the instability boundaries associated with low- to high-order radial oscillations (0 ≤ n ≤ 16). The instability boundaries are a strong function of both composition and radial order (n). With decreasing hydrogen abundance we find that (i) the classical blue edge of the Cepheid instability strip shifts to higher effective temperature and luminosity, and (ii) high-order modes are more easily excited and small islands of high radial-order instability develop, some of which correspond with real stars. Driving in all cases is by the classical κ-mechanism and/or strange modes. We identify regions of parameter space where new classes of pulsating variable may, in future, be discovered. The majority of these are associated with reduced hydrogen abundance in the envelope; one has not been identified previously.
Catalytic dehydrogenation is a critical and growing technology for the production of olefins, especially for propylene production. This paper will give an overview of advances in the catalysis ...science and technology for production of olefins by catalytic dehydrogenation, including the concomitant removal of H
2
by selective oxidation. For light paraffin dehydrogenation, UOP has licensed the Oleflex™ process widely for production of polymer-grade propylene as well as isobutylene with over 12 million metric tons of capacity announced. Today there are nine UOP C
3
Oleflex™ units in operation accounting for 55 % of the installed world-wide propylene production capacity from propane dehydrogenation technology. The heart of the process is a noble metal multi-metallic catalyst and the continuous catalyst regeneration (CCR) process. The coupling of catalytic dehydrogenation with selective oxidation of hydrogen allows one to design a process, which greatly improves equilibrium conversions while maintaining very high selectivity to olefin. The Lummus/UOP SMART™ SM process (Styrene Monomer Advanced Reheat Technology) allows 30–70 % capacity expansion, achieves a higher per-pass ethylbenzene conversion, and provides the most cost-effective revamp for higher capacity. Styrene Monomer Advanced Reheat Technology (SMART™) uses an oxidation catalyst and novel reactor internals to allow oxidative reheating between dehydrogenation stages. In the case of selective oxidation catalysts containing dispersed metal active sites, the role of diffusion and pore architecture is as important as the active metal sites.
We investigate the gravitational wave (GW) signal generated by a population of double neutron-star (DNS) binaries with eccentric orbits caused by kicks during supernova collapse and binary evolution. ...The DNS population of a standard Milky Way-type galaxy has been studied as a function of star formation history, initial mass function (IMF) and metallicity and of the binary-star common-envelope ejection process. The model provides birthrates, merger rates and total number of DNS as a function of time. The GW signal produced by this population has been computed and expressed in terms of a hypothetical space GW detector (eLISA) by calculating the number of discrete GW signals at different confidence levels, where ‘signal’ refers to detectable GW strain in a given frequency-resolution element. In terms of the parameter space explored, the number of DNS-originating GW signals is greatest in regions of recent star formation, and is significantly increased if metallicity is reduced from 0.02 to 0.001, consistent with Belczynski et al. Increasing the IMF power-law index (from −2.5 to −1.5) increases the number of GW signals by a large factor. This number is also much higher for models where the common-envelope ejection is treated using the α-mechanism (energy conservation) than when using the γ-mechanism (angular-momentum conservation). We have estimated the total number of detectable DNS GW signals from the Galaxy by combining contributions from thin disc, thick disc, bulge and halo. The most probable numbers for an eLISA-type experiment are 0–1600 signals per year at S/N ≥ 1, 0–900 signals per year at S/N ≥ 3, and 0–570 at S/N ≥ 5, coming from about 0–65, 0–60 and 0–50 resolved DNS, respectively.
Venezuelan equine encephalitis virus (VEEV) poses a major public health risk due to its amenability for use as a bioterrorism agent and its severe health consequences in humans. ML336 is a recently ...developed chemical inhibitor of VEEV, shown to effectively reduce VEEV infection in vitro and in vivo. However, its limited solubility and stability could hinder its clinical translation. To overcome these limitations, lipid-coated mesoporous silica nanoparticles (LC-MSNs) were employed. The large surface area of the MSN core promotes hydrophobic drug loading while the liposome coating retains the drug and enables enhanced circulation time and biocompatibility, providing an ideal ML336 delivery platform. LC-MSNs loaded 20 ± 3.4 μg ML336/mg LC-MSN and released 6.6 ± 1.3 μg/mg ML336 over 24 hours. ML336-loaded LC-MSNs significantly inhibited VEEV in vitro in a dose-dependent manner as compared to unloaded LC-MSNs controls. Moreover, cell-based studies suggested that additional release of ML336 occurs after endocytosis. In vivo safety studies were conducted in mice, and LC-MSNs were not toxic when dosed at 0.11 g LC-MSNs/kg/day for four days. ML336-loaded LC-MSNs showed significant reduction of brain viral titer in VEEV infected mice compared to PBS controls. Overall, these results highlight the utility of LC-MSNs as drug delivery vehicles to treat VEEV.
ABSTRACT
We investigate the effects of mass transfer and gravitational wave (GW) radiation on the orbital evolution of contact neutron-star–white-dwarf (NS–WD) binaries, and the detectability of ...these binaries by space GW detectors (e.g. Laser Interferometer Space Antenna, LISA; Taiji; Tianqin). A NS–WD binary becomes contact when the WD component fills its Roche lobe, at which the GW frequency ranges from ∼0.0023 to 0.72 Hz for WD with masses ∼0.05–1.4 M⊙. We find that some high-mass NS–WD binaries may undergo direct coalescence after unstable mass transfer. However, the majority of NS–WD binaries can avoid direct coalescence because mass transfer after contact can lead to a reversal of the orbital evolution. Our model can well interpret the orbital evolution of the ultra-compact X-ray source 4U 1820–30. For a 4-yr observation of 4U 1820–30, the expected signal-to-noise-ratio (SNR) in GW characteristic strain is ∼11.0/10.4/2.2 (LISA/Taiji/Tianqin). The evolution of GW frequencies of NS–WD binaries depends on the WD masses. NS–WD binaries with masses larger than 4U 1820–30 are expected to be detected with significantly larger SNRs. For a $(1.4+0.5) \, {\rm M}_{\odot }$ NS–WD binary close to contact, the expected SNR for a one week observation is ∼27/40/28 (LISA/Taiji/Tianqin). For NS–WD binaries with masses of $(1.4+\gtrsim 1.1) \, {\rm M}_{\odot }$, the significant change of GW frequencies and amplitudes can be measured, and thus it is possible to determine the binary evolution stage. At distances up to the edge of the Galaxy (∼100 kpc), high-mass NS–WD binaries will be still detectable with SNR ≳ 1.
Abstract
SALT spectra of the helium-rich hot subdwarf EC 22536-5304 show strong absorption lines of triply-ionized lead. Analysis of the HRS spectrum and a follow-up SALT/RSS spectrum show ...EC 22536-5304 to have surface properties (temperature, gravity, helium/hydrogen ratio) similar to other heavy-metal subdwarfs. With a lead overabundance of 4.8 dex relative to solar, EC 22536-5304 is the most lead-rich intermediate helium subdwarf discovered so far.
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