Time Scale Of Several Hours Research Articles

Thermal Stability of Chalcogenide Perovskites.

Chalcogenide perovskites (CPs) have recently attracted interest as a class of materials with practical potential in optoelectronics and have been suggested as a more thermally stable alternative to intensely studied halide perovskites (HPs). Here we report a comparative study of the thermal stability of representative HPs, MAPbI3 (MA = CH3NH3+, methylammonium) and CsPbI3, and a series of CPs with compositions BaZrS3, β-SrZrS3, BaHfS3, SrHfS3. Changes in the crystal structure, chemical composition, and optical properties upon heating in air up to 800 °C were studied using thermogravimetric analysis, temperature-dependent X-ray diffraction, energy-dispersive X-ray spectroscopy, and diffuse reflectance spectroscopy. While HPs undergo phase transitions and thermally decompose at temperatures below 300 °C, the CPs show no changes in crystal phase or composition when heated up to at least 450 °C. At 500 °C CPs oxidize on time scales of several hours, forming oxides and sulfates. The structural origins of the higher thermal and phase stability of the CPs are discussed.

Examining the effects of a pre-noon annular Solar Eclipse on equatorial electrodynamics: Evidence for a subsequent post-noon enhancement in plasma density

On 26 December 2019, an annular solar eclipse occurred in the southern part of the Indian subcontinent, which falls within the Equatorial ElectroJet (EEJ) region. This presented an opportunity to study the effects of a high-obscuration annular solar eclipse (93.3%) and of the special tides that accompany an eclipse. Eclipses are known to affect the electrodynamics of the equatorial region and the distribution of plasma in the low-latitude ionosphere. On December 26, 2019, different phenomena were indeed seen over different time scales. Around the time of the eclipse, there was a depletion in the total electron content (TEC) of the ionosphere, as inferred from GNSS receiver systems placed along the eclipse path in and around the EEJ region. Magnetometer measurements indicated a weakening of the EEJ current in this area not just when the eclipse took place but for the rest of the day as well. Observations from a digital-ionosonde located in Trivandrum (8.52°N, 76.94°E; 0.33°N dip-latitude) revealed that the ionospheric F-layer moved downwards just after obscurity maximum. Shortly after the F region was observed to move back upward, a one-hour long strong blanketing sporadic E-layer was triggered even though there was only a weakening of the EEJ but no reversal in the associated magnetic perturbations. Simulations from our quasi-two dimensional model clearly show that though there was no Counter Electrojet, there was indeed a weakening of the zonal field on 26 December 2019 during the eclipse and the post-eclipse period. The overall weakening trend lasted until late afternoon. Other notable features were uncovered on a time scale of several hours after the passage of the eclipse. While the day-long weakening of the EEJ is consistent with special tides related to the lunar trajectory, we also observed unusually large amplitude undulations in both vertical-TEC and F2-region peak plasma density over a five-hour time scale, starting around 2:00 PM LT. These undulations were consistent with the zonal electric field variations reconstructed from the magnetometer data.

Staring at the Sun with the Keck Planet Finder: An Autonomous Solar Calibrator for High Signal-to-noise Sun-as-a-star Spectra

Extreme precision radial velocity (EPRV) measurements contend with internal noise (instrumental systematics) and external noise (intrinsic stellar variability) on the road to 10 cm s−1 “exo-Earth” sensitivity. Both of these noise sources are well-probed using “Sun-as-a-star” RVs and cross-instrument comparisons. We built the Solar Calibrator (SoCal), an autonomous system that feeds stable, disk-integrated sunlight to the recently commissioned Keck Planet Finder (KPF) at the W. M. Keck Observatory. With SoCal, KPF acquires signal-to-noise ratio (S/N) ∼ 1200, R = 98,000 optical (445–870 nm) spectra of the Sun in 5 s exposures at unprecedented cadence for an EPRV facility using KPF’s fast readout mode (<16 s between exposures). Daily autonomous operation is achieved by defining an operations loop using state machine logic. Data affected by clouds are automatically flagged using a reliable quality control metric derived from simultaneous irradiance measurements. Comparing solar data across the growing global network of EPRV spectrographs with solar feeds will allow EPRV teams to disentangle internal and external noise sources and benchmark spectrograph performance. To facilitate this, all SoCal data products are immediately available to the public on the Keck Observatory Archive. We compared SoCal RVs to contemporaneous RVs from NEID, the only other immediately public EPRV solar data set. We find agreement at the 30–40 cm s−1 level on timescales of several hours, which is comparable to the combined photon-limited precision. Data from SoCal were also used to assess a detector problem and wavelength calibration inaccuracies associated with KPF during early operations. Long-term SoCal operations will collect upwards of 1000 solar spectra per six-hour day using KPF’s fast readout mode, enabling stellar activity studies at high S/N on our nearest solar-type star.

3-APTES on Dendritic Fibrous Mesoporous Silica Nanoparticles for the pH-Controlled Release of Corrosion Inhibitors.

Mesoporous silica nanoparticles (MSNPs) are currently used in different fields like catalysis, nanomedicine, and conservation science, taking advantage of their high surface area. Here, we synthesized and functionalized mesoporous dendritic fibrous nanoparticles to realize a smart delivery system of protective agents for metals. Different MSNPs were obtained via the microemulsion method followed by a hydrothermal or refluxing treatment at different w/o ratios, times, and temperatures. Dendritic spherical silica nanoparticles with specific features such as an appropriate size (450 nm), a very large surface area (600 m2 g-1), and a high yield synthesis (86%) were selected for surface modification. The fiber surface of the selected MSNPs was functionalized with 3-aminopropyl triethoxysilane (3-APTES). 3-APTES works as a pH-driven "nanogate", suppressing the immediate leakage of the total guest molecule load and modulating the release as a function of pH conditions. Surface-modified MSNPs were tested as a reservoir of the most diffused corrosion inhibitors: Mercaptobenzothiazole (MBT) and 1H-Benzotriazole (BTA); their release properties were studied in solutions with pH = 4 and 7. Functionalized and non-functionalized MSNPs showed a good loading efficiency of guest molecules (34-64%) and a pH-dependent release of the corrosion inhibitors on a timescale of several hours.

Thermally-driven scintillator flow in the SNO+ neutrino detector

The SNO+ neutrino detector is an acrylic sphere (radius 6 m) with a thin vertical neck containing almost 800 tonnes of liquid scintillator. The apparatus is immersed in a water-filled underground cavern, the neck protruding upward into a manifold above water level, with scintillator filling the sphere and rising up the neck some 6 m to an interface with purified nitrogen gas. Time-dependent flow simulations have been performed to investigate convective motion of the scintillator fluid, motivated by observations of a transient radon (222Rn) contamination layer which, over a period of two weeks, sank from near the base of the neck to the detector’s equator. According to simulations, this motion may have been induced by heat transfer through the detector wall, that resulted in buoyant ascending flow within a thin wall boundary layer and compensating sink elsewhere. This mechanism can result in transport down the neck to the sphere on a time scale of several hours. If the scintillator happens to be thermally stratified, the same forcing by a weak wall heat flux produces internal gravity waves in the spherical flow domain, at the Brunt–Väisälä frequency. Nevertheless as oscillatory motion is by its nature non-diffusive, simulations confirm that imposing strong thermal stratification over the depth of the neck can mitigate mixing due to transient heat fluxes.

Daphnia magna uptake and excretion of luminescence‐labelled polystyrene nanoparticle as visualized by high sensitivity real-time optical imaging

The environmental and ecological consequences of nanoplastics (NPs) draw increasing research interests and social concerns. However, the in situ and real‐time detection of NPs from living organisms and transferring media remains as a major technical obstacle for scientific investigation. Herein we report a novel time-gated imaging (TGI) strategy capable of real-time visualizing the intake of NPs by an individual living organism, which is based on the polystyrene NPs labelled with lanthanide up‐conversion luminescence. The limit of detection (LOD) of the TGI apparatus was 600 pg (SNR = 3) in a field of view of 2.4 × 3.8 mm. Taking Daphnia magna as the aquatic model, we investigated the dynamics of uptake and accumulation of NPs (500 μg/L) for 24 h, and the subsequent excretion process (in clean medium) for 48 h, and quantitively analyzed the distribution and the overall mass of NPs deposited in D. magna. The uptake of NPs via filter‐feeding occurred in a few minutes, whereas a longer accumulation was found, in a timescale of several hours. And similar behaviors (bi-phase elimination) were also seen in the excretion, indicating the migration of NPs into the circulatory system. The average mass of NPs accumulated in an individual D. magna was ∼12 ng after 24 h exposure, indicating that D. magna as a filter feeder tends to retain NPs. The observed NPs accumulation in D. magna exemplifies the potential risk of aquatic ecosystem on exposure to NP contamination.

Galactic Cosmic Rays at Mars and Venus: Temporal Variations from Hours to Decades Measured as the Background Signal of Onboard Microchannel Plates

A microchannel plate (MCP) is a component widely used for counting particles in space. Using the background counts from MCPs on the Mars Express and Venus Express orbiters—operating over 17 yr and 8 yr, respectively—we investigated the galactic cosmic ray (GCR) characteristics of the inner solar system. The MCP background counts at Mars and Venus, on a solar cycle timescale, exhibited clear anticorrelation with the sunspot number. We concluded that the measured MCP background counts contained GCR information. The GCR characteristics measured using the MCP background counts at Mars showed features consistent with measurements on Earth in Solar Cycle 24. The time lag between the sunspot number and the MCP background counts was found to be ∼9 months at Mars. The shorter-term background data recorded along the orbits (with a timescale of several hours) also showed evident depletion of the background counts, due to absorption of the GCR particles by the planets. Thanks to the visible planetary size change along an orbit, we developed a model to separate the GCR contribution to the MCP background counts from the internal contribution caused by the β-decay of radioactive elements in the MCP glass. Our statistical analysis of the GCR absorption signatures at Mars implies that the effective absorption radius of Mars for the GCR particles is >100 km larger than the radius of the planet. However, the cause remains an open question.

Patches of Magnetic Switchbacks and Their Origins

Parker Solar Probe (PSP) has shown that the solar wind in the inner heliosphere is characterized by the quasi omnipresence of magnetic switchbacks (“switchback” hereinafter), local backward bends of magnetic field lines. Switchbacks also tend to come in patches, with a large-scale modulation that appears to have a spatial scale size comparable to supergranulation on the Sun. Here we inspect data from the first 10 encounters of PSP focusing on different time intervals when clear switchback patches were observed by PSP. We show that the switchbacks modulation, on a timescale of several hours, seems to be independent of whether PSP is near perihelion, when it rapidly traverses large swaths of longitude remaining at the same heliocentric distance, or near the radial-scan part of its orbit, when PSP hovers over the same longitude on the Sun while rapidly moving radially inwards or outwards. This implies that switchback patches must also have an intrinsically temporal modulation most probably originating at the Sun. Between two consecutive patches, the magnetic field is usually very quiescent with weak fluctuations. We compare various parameters between the quiescent intervals and the switchback intervals. The results show that the quiescent intervals are typically less Alfvénic than switchback intervals, and the magnetic power spectrum is usually shallower in quiescent intervals. We propose that the temporal modulation of switchback patches may be related to the “breathing” of emerging flux that appears in images as the formation of “bubbles” below prominences in the Hinode/SOT observations.

A Rapid Localized Deceleration of Earth's Radiation Belt Relativistic Electrons Driven by Storm Proton Injection

AbstractEarth's radiation belt relativistic electron dropouts frequently occur during the main phase of geomagnetic storms, which have been partially attributed to the ring current ion enhancements causing geomagnetic field reconfigurations. In contrast to early studies on the global radiation belt response to the ring current buildup on a timescale of several hours, we here describe a rapid, localized, significant decay of relativistic electrons driven by freshly injected energetic protons during the 27 May 2017 geomagnetic storm. Near the proton injection front, the magnetic field lines were stretched outward, with an inferred migration of their equatorial crossings by ∼0.5 RE during several minutes. Because of the betatron and Fermi decelerations, the relativistic electron fluxes decreased by 2–3 orders of magnitude with pitch‐angle distributions evolving from pancake/flat‐top type to cigar type. This rapid localized response pattern of relativistic electrons could be general over strong particle injections during both geomagnetic storms and substorms.

Triggering micronovae through magnetically confined accretion flows in accreting white dwarfs

ABSTRACT Rapid bursts at optical wavelengths have been reported for several accreting white dwarfs. In these bursts, the optical luminosity can increase by up to a factor of 30 in less than an hour, before fading on time-scales of several hours, and the energy release can reach ~1039 erg (‘micronovae’). Several systems have also shown these bursts to be semirecurrent on time-scales of days to months, and the temporal profiles of these bursts strongly resemble those observed in Type-I X-ray bursts in accreting neutron stars. It has been suggested that the observed micronovae may be the result of localized thermonuclear runaways in the surface layers of accreting white dwarfs. Here we propose a model in which the magnetic confinement of accretion streams on to the accreting magnetic white dwarf may trigger localized thermonuclear runaways. The model proposed to trigger micronovae appears to favour magnetic systems with both a high white dwarf mass and a high mass-transfer rate.

Reducing Number Fluctuations in an Ultracold Atomic Sample Using Faraday Rotation and Iterative Feedback

We demonstrate a method to reduce number fluctuations in an ultracold atomic sample using real-time feedback. By measuring the Faraday rotation of an off-resonant probe laser beam with a pair of avalanche photodetectors in a polarimetric setup, we produce a proxy for the number of atoms in the sample. We iteratively remove a fraction of the excess atoms from the sample to converge on a target proxy value in a way that is insensitive to environmental perturbations and robust to errors in light polarization. Using absorption imaging for out-of-loop verification, we demonstrate a reduction in the number fluctuations from $3\mathrm{%}$ to $0.45\mathrm{%}$ for samples at a temperature of $16.4\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{K}$ over the time scale of several hours, which is limited by temperature fluctuations, beam-pointing noise, and photon shot noise.

Biofilm viscoelasticity and nutrient source location control biofilm growth rate, migration rate, and morphology in shear flow

We present a numerical model to simulate the growth and deformation of a viscoelastic biofilm in shear flow under different nutrient conditions. The mechanical interaction between the biofilm and the fluid is computed using the Immersed Boundary Method with viscoelastic parameters determined a priori from measurements reported in the literature. Biofilm growth occurs at the biofilm-fluid interface by a stochastic rule that depends on the local nutrient concentration. We compare the growth, migration, and morphology of viscoelastic biofilms with a common relaxation time of 18 min over the range of elastic moduli 10–1000 Pa in different nearby nutrient source configurations. Simulations with shear flow and an upstream or a downstream nutrient source indicate that soft biofilms grow more if nutrients are downstream and stiff biofilms grow more if nutrients are upstream. Also, soft biofilms migrate faster than stiff biofilms toward a downstream nutrient source, and although stiff biofilms migrate toward an upstream nutrient source, soft biofilms do not. Simulations without nutrients show that on the time scale of several hours, soft biofilms develop irregular structures at the biofilm-fluid interface, but stiff biofilms deform little. Our results agree with the biophysical principle that biofilms can adapt to their mechanical and chemical environment by modulating their viscoelastic properties. We also compare the behavior of a purely elastic biofilm to a viscoelastic biofilm with the same elastic modulus of 50 Pa. We find that the elastic biofilm underestimates growth rates and downstream migration rates if the nutrient source is downstream, and it overestimates growth rates and upstream migration rates if the nutrient source is upstream. Future modeling can use our comparison to identify errors that can occur by simulating biofilms as purely elastic structures.

Membrane fusion of phospholipid bilayers under high pressure: Spherical and irreversible growth of giant vesicles

Membrane fusion of giant vesicles (GVs) for binary bilayers of unsaturated phospholipids, dioleoylphosphatidyl-ethanolamine (DOPE) having an ability to promote membrane fusion, and its homolog dioleoylphosphatidylcholine (DOPC) having an ability to form GV, was investigated under atmospheric and high pressure. While DOPC formed GVs in the presence of inorganic salts with a multivalent metal ion under atmospheric pressure, an equimolar mixture of DOPE and DOPC formed GVs both in the absence and the presence of LaCl3. We examined the change in size and shape of the GVs of this binary mixture in the absence and presence of LaCl3 as a function of time under atmospheric and high pressure. The size and shape of the GVs in the absence of LaCl3 under atmospheric and high pressure and those in the presence of LaCl3 under atmospheric pressure hardly changed with time. By contrast, the GV in the presence of LaCl3 under high pressure gradually changed in the size and shape with time on a time scale of several hours. Namely, the GV became larger than the original GV due to accelerated membrane fusion and its shape became more spherical. This pressure-induced membrane fusion was completely irreversible, and the growth rate was correlated with the applied pressure. The reason for the GV growth by applying pressure was considered on the basis of thermodynamic phase diagrams. We concluded that the growth is attributable to a closer packing of lipid molecules in the bilayer resulting from their preference of smaller volumes under high pressure. Furthermore, the molecular mechanism of the pressure-induced membrane fusion was explored by observing the fusion of two GVs with almost the same size. From their morphological changes, we revealed that the fusion is caused by the actions of Laplace and osmotic pressure.

Electrofuel Synthesis from Variable Renewable Electricity: An Optimization-Based Techno-Economic Analysis.

Sectors such as aviation may require low-carbon liquid fuels to dramatically reduce emissions. This analysis characterizes the economic viability of electrofuels, synthesized from CO2 from direct air capture (DAC) and hydrogen from electrolysis of water, powered primarily by solar or wind electricity. This optimization-based techno-economic analysis suggests that using today's technology, hydrocarbon electrofuels would cost upward of $4/liter of gasoline equivalent (lge), potentially falling to $1.7-1.8/lge in the next decade and <$1/lge by 2050. Only in the latter case are electrofuels potentially less costly than using petroleum fuels offset with DAC with sequestration. Achieving low-end electrofuel costs is contingent on substantial reductions in the capital cost of DAC, electrolyzers, and renewable electricity generation. However, the system also requires sufficient operational flexibility to efficiently power this capital-intensive equipment on variable electricity. Such forms of flexibility include various types of storage, supplementary natural gas and grid electricity interconnections (penalized with a steep carbon price), curtailment, and the ability to modestly adjust fuel synthesis and DAC operating levels over time scales of several hours to days.

A Robust Bioassay of the Human Bradykinin B2 Receptor That Extends Molecular and Cellular Studies: The Isolated Umbilical Vein

Bradykinin (BK) has various physiological and pathological roles. Medicinal chemistry efforts targeted toward the widely expressed BK B2 receptor (B2R), a G-protein-coupled receptor, were primarily aimed at developing antagonists. The only B2R antagonist in clinical use is the peptide icatibant, approved to abort attacks of hereditary angioedema. However, the anti-inflammatory applications of B2R antagonists are potentially wider. Furthermore, the B2R antagonists notoriously exhibit species-specific pharmacological profiles. Classical smooth muscle contractility assays are exploited over a time scale of several hours and support determining potency, competitiveness, residual agonist activity, specificity, and reversibility of pharmacological agents. The contractility assay based on the isolated human umbilical vein, expressing B2R at physiological density, was introduced when investigating the first non-peptide B2R antagonist (WIN 64338). Small ligand molecules characterized using the assay include the exquisitely potent competitive antagonist, Pharvaris Compound 3 or the partial agonist Fujisawa Compound 47a. The umbilical vein assay is also useful to verify pharmacologic properties of special peptide B2R ligands, such as the carboxypeptidase-activated latent agonists and fluorescent probes. Furthermore, the proposed agonist effect of tissue kallikrein on the B2R has been disproved using the vein. This assay stands in between cellular and molecular pharmacology and in vivo studies.

Effects of Extended Aqueous Processing on Structure, Chemistry, and Performance of Polycrystalline LiNixMnyCozO2 Cathode Powders.

The prospect of aqueous processing of LiNixMnyCozO2 (NMC) cathodes has significant appeal to battery manufacturers for the reduction in materials cost, toxicological risk, and environmental impact compared to conventional N-methyl-2-pyrrolidone (NMP)-based processing. However, the effects of aqueous processing of NMC powders at industrial timescales are not well studied, with prior studies mostly focusing on relatively brief water washing processes. In this work, we investigate the bulk and surface impacts of extended aqueous processing of polycrystalline NMC powders with different compositions. We demonstrate that at timescales of several hours, polycrystalline NMC is susceptible to intergranular fracture, with the severity of fracture scaling with the NMC nickel content. While bulk crystallinity and composition are unchanged, surface sensitive techniques such as X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) indicate that the exposure of water leads to a level of delithiation, nickel reduction, and reconstruction from the layered to rock-salt structure at the surface of individual grains. Dynamic single NMC microparticle compression testing suggests that the resulting mechanical stresses weaken the integrity of the polycrystalline particle and increases susceptibility of intergranular fracture. The initially degraded surfaces along with the increased surface area lead to faster capacity fade and impedance growth during electrochemical cycling. From this work, it is demonstrated that NMC powders require surface or grain boundary modifications to make industrial-scale aqueous cathode processing viable, especially for next-generation nickel-rich NMC chemistries.

Single-cell adhesion force kinetics of cell populations from combined label-free optical biosensor and robotic fluidic force microscopy

Single-cell adhesion force plays a crucial role in biological sciences, however its in-depth investigation is hindered by the extremely low throughput and the lack of temporal resolution of present techniques. While atomic force microcopy (AFM) based methods are capable of directly measuring the detachment force values between individual cells and a substrate, their throughput is limited to few cells per day, and cannot provide the kinetic evaluation of the adhesion force over the timescale of several hours. In this study a high spatial and temporal resolution resonant waveguide grating based label-free optical biosensor was combined with robotic fluidic force microscopy to monitor the adhesion of living cancer cells. In contrast to traditional fluidic force microscopy methods with a manipulation range in the order of 300–400 micrometers, the robotic device employed here can address single cells over mm-cm scale areas. This feature significantly increased measurement throughput, and opened the way to combine the technology with the employed microplate-based, large area biosensor. After calibrating the biosensor signals with the direct force measuring technology on 30 individual cells, the kinetic evaluation of the adhesion force and energy of large cell populations was performed for the first time. We concluded that the distribution of the single-cell adhesion force and energy can be fitted by log-normal functions as cells are spreading on the surface and revealed the dynamic changes in these distributions. The present methodology opens the way for the quantitative assessment of the kinetics of single-cell adhesion force and energy with an unprecedented throughput and time resolution, in a completely non-invasive manner.

Controlling the persistence of photoconductivity through additional sub-bandgap photoexcitation in individual m-axial GaN nanowires

The persistence of photoconductivity after switching off the photoexcitation is investigated in individual m-axial n-GaN nanowires as a function of temperature. At room temperature, photoconductivity is found to decay with a time scale of several hours. The capture barrier height is estimated to be ∼450 meV from the stretched exponential fitting of the decay characteristics recorded at different temperatures. This energy value is found to be much less than the surface band-bending energy of ∼770 meV, which is believed to act as the capture barrier in this system. This finding indicates the tunneling of electrons through the top part of the band-bending barrier. Interestingly, the decay rate of photoconductivity is observed to reduce significantly when the photoconductivity in these wires is quenched by an additional sub-bandgap illumination prior to the switching off the photoexcitation. A rate equation model is proposed to explain the upward band bending at the surface as well as the persistent photoconductivity effect in terms of the transfer of holes between the valence band and acceptor-type surface states of the nanowires. Photoconductivity decay profiles simulated from the model are found to match very well with the experimental data recorded at different temperatures in both quenched and unquenched cases.

Impact of photodoping on inter- and intralayer exciton emission in a MoS2/MoSe2/MoS2 heterostructure

The illumination of monolayer transition metal dichalcogenides can dynamically photoionize donor centers, increasing the concentration of free carriers. Here, we investigate the effect of such photodoping on the interlayer exciton formed across a MoS2/MoSe2/MoS2 heterostructure. We first identify the photodoping effect by monitoring the increase in the trion dissociation energy, accompanied by a characteristic tuning of the exciton/trion photoluminescence (PL) intensity ratio in MoSe2 upon exposure to laser light. At the same time, the PL intensity of the interlayer exciton significantly decreases, while the combined PL intensity of the exciton and the trion in MoSe2 is enhanced, showing that the interlayer charge transfer can be controlled by the doping level. This effect is persistent on a timescale of several hours, provided that the sample is maintained under vacuum, suggesting a mechanism involving laser induced desorption of molecules physisorbed on the surface of the heterostructure. This hypothesis is supported by the observation of a significantly faster photodoping effect when the sample is excited with a pulsed laser with the same average power.

Propagation and Damping of Two-Fluid Magnetohydrodynamic Waves in Stratified Solar Atmosphere

An extreme ultra-violet (EUV) wave is characterized as a bright pulse that has emanated from the solar eruption source and can propagate globally in the solar corona. According to one leading theory, the EUV wave is a fast magnetoacoustic wave, as the coronal counterpart of the Moreton wave in the chromosphere. However, previous observations have shown that the EUV wave differs significantly from the Moreton wave in both velocity and lifetime. To reconcile these differences, here we analyze the wave characteristics of a two-fluid MHD model in the stratified solar atmosphere with a height-dependent ionization rate. It is found that the collision between neutral and ionized fluids is able to attenuate the wave amplitude, while causing a slight change in its propagation velocity. Because the chromosphere has the lower ionization rate and the stronger magnetic fields than the corona, the velocity of the Moreton wave is much higher than that of the EUV wave. In contrast to the Moreton waves damped strongly by the collision between neutral and ionized fluids, the EUV wave in the fully ionized corona is able to propagate globally on a time scale of several hours. Our results support the previous theory that fast magnetoacoustic waves account for both EUV and Moreteon waves in the different layers of the solar atmosphere.