12 research outputs found
Bayesian Maximum Entropy Integration of Ozone Observations and Model Predictions: A National Application
To improve ozone exposure estimates
for ambient concentrations
at a national scale, we introduce our novel Regionalized Air Quality
Model Performance (RAMP) approach to integrate chemical transport
model (CTM) predictions with the available ozone observations using
the Bayesian Maximum Entropy (BME) framework. The framework models
the nonlinear and nonhomoscedastic relation between air pollution
observations and CTM predictions and for the first time accounts for
variability in CTM model performance. A validation analysis using
only noncollocated data outside of a validation radius <i>r</i><sub><i>v</i></sub> was performed and the <i>R</i><sup>2</sup> between observations and re-estimated values for two
daily metrics, the daily maximum 8-h average (DM8A) and the daily
24-h average (D24A) ozone concentrations, were obtained with the OBS
scenario using ozone observations only in contrast with the RAMP and
a Constant Air Quality Model Performance (CAMP) scenarios. We show
that, by accounting for the spatial and temporal variability in model
performance, our novel RAMP approach is able to extract more information
in terms of <i>R</i><sup>2</sup> increase percentage, with
over 12 times for the DM8A and over 3.5 times for the D24A ozone concentrations,
from CTM predictions than the CAMP approach assuming that model performance
does not change across space and time
Data_Sheet_1_Characteristics of soil microbiota and organic carbon distribution in jackfruit plantation under different fertilization regimes.docx
Manure amendment to improve soil organic carbon (SOC) content is an important strategy to sustain ecosystem health and crop production. Here, we utilize an 8-year field experiment to evaluate the impacts of organic and chemical fertilizers on SOC and its labile fractions as well as soil microbial and nematode communities in different soil depths of jackfruit (Artocarpus heterophyllus Lam.). Three treatments were designed in this study, including control with no amendment (CK), organic manure (OM), and chemical fertilizer (CF). Results showed that OM significantly increased the abundance of total nematodes, bacterivores, bacteria, and fungi as well as the value of nematode channel ratio (NCR) and maturity index (MI), but decreased plant-parasites and Shannon diversity (Hā²). Soil microbial and nematode communities in three soil depths were significantly altered by fertilizer application. Acidobacteria and Chloroflexi dominated the bacterial communities of OM soil, while Nitrospira was more prevalent in CF treatment. Organic manure application stimulated some functional groups of the bacterial community related to the C cycle and saprotroph-symbiotroph fungi, while some groups related to the nitrogen cycle, pathotroph-saprotroph-symbiotroph and pathotroph-saprotroph fungi were predominated in CF treatment. Furthermore, OM enhanced the soil pH, contents of total soil N, P, K, and SOC components, as well as jackfruit yield. Chemical fertilizers significantly affected available N, P, and K contents. The results of network analyses show that more significant co-occurrence relationships between SOC components and nematode feeding groups were found in CK and CF treatments. In contrast, SOC components were more related to microbial communities than to nematode in OM soils. Partial least-squares-path modeling (PLS-PM) revealed that fertilization had significant effects on jackfruit yield, which was composed of positive direct (73.6%) and indirect effects (fertilization ā fungal community ā yield). It was found that the long-term manure application strategy improves soil quality by increasing SOM, pH, and nutrient contents, and the increased microbivorous nematodes abundance enhanced the grazing pressure on microorganisms and concurrently promoted microbial-derived SOC turnover.</p
Charge Transport Behavior in Solution-Grown Methylammonium Lead Tribromide Perovskite Single Crystal Using Ī± Particles
Methylammonium
(MA) lead hybrid perovskite single crystal recently
received attention as a potential radiation detection material. Here,
we report the MAPbBr<sub>3</sub> bulk crystals grown by the modified
antisolvent vapor-assisted crystallization method. The growth rate
is determined by diluting the antisolvent, which results in the average
size of MAPbBr<sub>3</sub> crystals to significantly increase from
2 Ć 2 Ć 1 to 15 Ć 15 Ć 5 mm<sup>3</sup>. The morphology
evolution of MAPbBr<sub>3</sub> crystals, which is contributed by
the growth anisotropy, has been discussed according to the molar ratios
of precursors and the bond theory. The resulting centimeter-sized
MAPbBr<sub>3</sub> crystals exhibit high resistivity (5.6 Ć 10<sup>8</sup> Ī©Ā·cm) at room temperature. The mobilityālifetime
(Ī¼Ļ) products are measured under <sup>241</sup>Am (5.48
MeV) Ī± particles irradiation, with the values of 2.2 Ć
10<sup>ā4</sup> and 4.2 Ć 10<sup>ā4</sup> cm<sup>2</sup>/V for electrons and holes, respectively. Simultaneously,
the electrons and holes mobility are estimated to be 24.6 and 59.7
cm<sup>2</sup>/(VĀ·s), respectively, using the Ī±-source-induced
transient waveforms
Ligand-Free, Quantum-Confined Cs<sub>2</sub>SnI<sub>6</sub> Perovskite Nanocrystals
Tin-halide
perovskite nanocrystals are a viable precursor for lead-free,
high-efficiency active layers for photovoltaic cells. We describe
a new synthetic procedure for quantum-confined Cs<sub>2</sub>SnI<sub>6</sub> nanocrystals with size-dependent band gaps in the long-visible
to near-infrared (1.38ā1.47 eV). Hot injection synthesis produces
particles with no organic capping ligands, with average diameters
that increase from 12 Ā± 2.8 nm to 38 Ā± 4.1 nm with increasing
reaction temperature. The band gap, energies of the first excitonic
peak, ground-state bleach peak (in the transient absorption spectrum),
and photoluminescence peak depend linearly on the inverse square of
diameter, consistent with quantum-confined excitons with an effective
mass of (0.12 Ā± 0.02)<i>m</i><sub>0</sub>, where <i>m</i><sub>0</sub> is the mass of an electron, a factor of 4.6
smaller than that in the bulk material. Transient absorption measurements
show that approximately 90% of the bleach amplitude decays within
30 ps, probably because of carrier trapping on unpassivated surface
sites. The films made by simple drop-casting of Cs<sub>2</sub>SnI<sub>6</sub> nanocrystal solutions, with no postsynthetic ligand exchange
or removal, are smooth and uniform, resist delamination, and have
no visible gaps at the filmāsubstrate interface
Gradient Structure Design of Flexible Waterborne Polyurethane Conductive Films for Ultraefficient Electromagnetic Shielding with Low Reflection Characteristic
Highly efficient
electromagnetic shielding materials entailing
strong electromagnetic wave absorption and low reflection have become
an increasing requirement for next-generation communication technologies
and high-power electronic instruments. In this study, a new strategy
is employed to provide flexible waterborne polyurethane composite
films with an ultra-efficient electromagnetic shielding effectiveness
(EMI SE) and low reflection by constructing gradient shielding layers
with a magnetic ferro/ferric oxide deposited on reduced graphene oxide
(rGO@Fe<sub>3</sub>O<sub>4</sub>) and silver-coated tetraneedle-like
ZnO whisker (T-ZnO/Ag) functional nanoparticles. Because of the differences
in density between rGO@Fe<sub>3</sub>O<sub>4</sub> and T-ZnO/Ag, a
gradient structure is automatically formed during the film formation
process. The gradient distribution of rGO@Fe<sub>3</sub>O<sub>4</sub> over the whole thickness range forms an efficient electromagnetic
wave absorption network that endows the film with a strong absorption
ability on the top side, while a thin layer of high-density T-ZnO/Ag
at the bottom constructs a highly conductive network that provides
an excellent electromagnetic reflection ability for the film. This
specific structure results in an āabsorbāreflectāreabsorbā
process when electromagnetic waves penetrate into the composite film,
leading to an excellent EMI shielding performance with an extremely
low reflection characteristic at a very low nanofiller content (0.8
vol % Fe<sub>3</sub>O<sub>4</sub>@rGO and 5.7 vol % T-ZnO/Ag): the
EMI SE reaches 87.2 dB against the X band with a thickness of only
0.5 mm, while the shielding effectiveness of reflection (SE<sub>R</sub>) is only 2.4 dB and the power coefficient of reflectivity (<i>R</i>) is as low as 0.39. This result means that only 39% of
the microwaves are reflected in the propagation process when 99.9999998%
are attenuated, which is the lowest value among the reported references.
This composite film with remarkable performance is suitable for application
in portable and wearable smart electronics, and this method offers
an effective strategy for absorption-dominated EMI shielding
Self-Assembly of Nanoporous ZIF-8-Based Superstructures for Robust Chemical Sensing of Solvent Vapors
Self-assembly
of metalāorganic frameworks (MOFs) to construct
optical sensors has been proposed to detect chemicals by acclimating
colors in response to analytes that adsorbed on the surface of MOF
nanoparticles and in the interspaces between particles. However, the
instability of the weakly assembled optical structures held together
by van der Waals forces limits their active sensing application. Here,
we propose full-color tunable superstructures that are constructed
by self-assembled ZIF-8 nanoparticles and postsynthetic poly(dimethylsiloxane)
(PDMS) coating, which behave as robust optical sensors. The optical
band was tuned by controlling the size of the ZIF-8 particles and
also responded to the adsorption of chemicals with different refractive
indexes in the micropores of the ZIF-8 particles. In addition, PDMS-coated
ZIF-8 superstructures (ZIF-8@PDMS) were fabricated by thermal evaporation
to optimize the optical quality and improve the robustness and solvent
resistance during chemical sensing. Static and dynamic sensing results
showed that the hierarchical porous structures endow the ZIF-8@PDMS
superstructure with higher optical saturation and faster response
in comparison to their counterparts configured with a ZIF-8 superstructure
Geochronology and petrogenesis of the early Silurian Zeluo mafic-ultramafic intrusion, eastern Tibet: implications for the tectonic setting and evolution of the eastern Proto-Tethys Ocean
The Tibetan Plateau is a key region to understand the evolution of the Tethys Oceans. To better constrain the tectonic evolution of the Proto-Tethys Ocean on the western margin of the Yangtze plate, we present an integrated petrography, geochemistry, and zircon U-Pb-Lu-Hf isotope study on newly recognized early Silurian gabbro and serpentinite rocks from the eastern Yidun terrane of the Tibetan Plateau. Zircon U-Pb dating of the gabbro yields an Early Silurian age of 438.2Ā Ā±Ā 2.8Ā Ma. Zircon ĪµHf(t) values of 5.4 to 8.5 suggest a single-stage model age (TDM1) ranging from 729 to 858Ā Ma. The gabbros exhibit low total rare earth element abundances but are moderately enriched in the light rare earth elements and the large-ion lithophile elements (e.g. Rb, Ba, and Sr), and display representative negative high-field strength elemental anomalies for Nb, Ta, Zr, and Hf on spidergrams. The gabbro and serpentinites were derived from a depleted mantle-like source made of garnet-spinel lherzolite composition, from a sub-arc mantle wedge that was metasomatized by slab dehydration. Thus, the gabbro and serpentinites record an Early Silurian subduction event of the Proto-Tethys Ocean under the Yangtze plate. Furthermore, this study confirms that the Yidun terrane on the western margin of the Yangtze plate is underlined by a Precambrian crystalline basement.</p
Role of Stoichiometry in the Growth of Large Pb<sub>2</sub>P<sub>2</sub>Se<sub>6</sub> Crystals for Nuclear Radiation Detection
Pb<sub>2</sub>P<sub>2</sub>Se<sub>6</sub> as a heavy element, chemically
robust semiconductor, has been identified as a promising material
for cost-effective room temperature X/Ī³-ray detection. Here,
we report the properties of Pb<sub>2</sub>P<sub>2</sub>Se<sub>6</sub> crystals grown by a vertical Bridgman method under off-stoichiometric
Se-rich and Pb-rich conditions. Regardless of the conditions the resulting
single crystals exhibited high bulk resistivity on the order of 10<sup>11</sup> Ī©Ā·cm. However, the photoconductivity and charge
transport properties varied based on growth condition indicating the
different dominant defects associated with the type of stoichiometric
deviation. The formation and nature of intrinsic defects in Pb<sub>2</sub>P<sub>2</sub>Se<sub>6</sub> crystals were also studied by
first-principles density functional theory (DFT) calculations as well
as thermally stimulated current (TSC) spectroscopy. The TSC results
indicated that four traps were common to both Se-rich and Pb-rich
Pb<sub>2</sub>P<sub>2</sub>Se<sub>6</sub>, while a higher density
of shallow defects were observed in Se-rich Pb<sub>2</sub>P<sub>2</sub>Se<sub>6</sub>. DFT calculations predict that the antisite defects
P<sub>Pb</sub><sup>+</sup>, P<sub>Se</sub><sup>ā</sup> and
Pb<sub>P</sub><sup>ā</sup> are the dominant deep donors and
acceptors in Se-rich and Pb-rich Pb<sub>2</sub>P<sub>2</sub>Se<sub>6</sub>, respectively, which leads to the degradation of mobility
lifetime product (Ī¼Ļ) on the order of 10<sup>ā5</sup> cm<sup>2</sup>Ā·V<sup>ā1</sup> as measured under <sup>241</sup>Am (5.48 MeV) alpha particles irradiation. Nevertheless,
Pb<sub>2</sub>P<sub>2</sub>Se<sub>6</sub> detectors with a thickness
of 2 mm show reliable linear response under a series of radiation
sources, including <sup>241</sup>Am and <sup>57</sup>Co Ī³-ray
sources. A high X-ray sensitivity comparable to that of amorphous
Se for Pb-rich Pb<sub>2</sub>P<sub>2</sub>Se<sub>6</sub> detectors
was realized, with the value of 68.3 Ī¼CĀ·Gy<sub>air</sub><sup>ā1</sup> cm<sup>ā2</sup> under 40 kVp Ag X-rays
at an electrical field of 50 VĀ·cm<sup>ā1</sup>
Cu<sub>2</sub>I<sub>2</sub>Se<sub>6</sub>: A MetalāInorganic Framework Wide-Bandgap Semiconductor for Photon Detection at Room Temperature
Cu<sub>2</sub>I<sub>2</sub>Se<sub>6</sub> is a new wide-bandgap
semiconductor with high stability and great potential toward hard
radiation and photon detection. Cu<sub>2</sub>I<sub>2</sub>Se<sub>6</sub> crystallizes in the rhombohedral <i>R</i>3Ģ
<i>m</i> space group with a density of <i>d</i> = 5.287
gĀ·cm<sup>ā3</sup> and a wide bandgap <i>E</i><sub>g</sub> of 1.95 eV. First-principles electronic band structure
calculations at the density functional theory level indicate an indirect
bandgap and a low electron effective mass <i>m</i><sub>e</sub>* of 0.32. The congruently melting compound was grown in centimeter-size
Cu<sub>2</sub>I<sub>2</sub>Se<sub>6</sub> single crystals using a
vertical Bridgman method. A high electric resistivity of ā¼10<sup>12</sup> Ī©Ā·cm is readily achieved, and detectors made
of Cu<sub>2</sub>I<sub>2</sub>Se<sub>6</sub> single crystals demonstrate
high photosensitivity to Ag KĪ± X-rays (22.4 keV) and show spectroscopic
performance with energy resolutions under <sup>241</sup>Am Ī±-particles
(5.5 MeV) radiation. The electron mobility is measured by a time-of-flight
technique to be ā¼46 cm<sup>2</sup>Ā·V<sup>ā1</sup>Ā·s<sup>ā1</sup>. This value is comparable to that of
one of the leading Ī³-ray detector materials, TlBr, and is a
factor of 30 higher than mobility values obtained for amorphous Se
for X-ray detection
Stoichiometric Effects on the Photoelectric Properties of LiInSe<sub>2</sub> Crystals for Neutron Detection
<sup>6</sup>LiInSe<sub>2</sub> is a promising semiconductor candidate
for thermal neutron detection due to its large capture cross-section.
However, the charge collection efficiency is still insufficient for
high resolution for the grown-in defects induced by the stoichiometric
deviation. In this work, we report photoelectric properties of stoichiometric
LiInSe<sub>2</sub> crystal boules up to 70 mm in length and 20 mm
in diameter grown by the vertical Bridgman method. Inductively coupled
plasma measurements demonstrate that the ratio of Li, In, and Se of
the as-grown crystal is very close to 1:1:2, which is optimized by
low temperature synthesis processing. The obtained single crystals
display high bulk resistivity in the range of 10<sup>11</sup>ā10<sup>12</sup> Ī©Ā·cm and a direct band gap of 2.01ā2.83
eV with a changeable color from red to yellow. The electronic structure
of LiInSe<sub>2</sub> was studied using first-principles density functional
theory calculations, which predicts that the antisite defects of In<sub>Li</sub> and Li<sub>In</sub> are the dominant factor for the different
crystal colors observed. The stoichiometric LiInSe<sub>2</sub> crystal
gives an improved energy resolution, for a semiconductor detector
when illuminated with a <sup>241</sup>[email protected] MeV Ī± source,
of 23.3%. The electron mobility-lifetime product (<i>Ī¼Ļ</i>) is ā¼2.5 Ć 10<sup>ā5</sup> cm<sup>2</sup> V<sup>ā1</sup>