•Citral-SLNs were prepared via high pressure homogenization method.•Citral-SLN was successfully obtained confirmed by its microstructure and property.•Encapsulate citral in SLNs could improve its ...stability in the acid environment.
Citral-loaded solid lipid nanoparticles (citral-SLNs) were prepared via a high-pressure homogenization method, using glyceryl monostearate (GMS) as the solid lipid and a mixture of Tween 80 (T-80) and Span 80 (S-80) at a weight ratio of 1:1 as the surfactant. The microstructure and properties of the citral-SLNs were characterized by dynamic light scattering (DLS), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermal gravimetric analysis (TGA). The chemical stability of citral in the citral-SLNs was analyzed by solid-phase microextraction gas chromatography (SPME-GC). The GC results showed that 67.0% of the citral remained in the citral-SLN suspensions after 12 days, while only 8.22% remained in the control. Therefore, the encapsulation of citral in the solid lipid can enhance its stability in acidic surroundings.
The discovery of unconventional superconductivity in (La,Ba)
CuO
(ref.
) has motivated the study of compounds with similar crystal and electronic structure, with the aim of finding additional ...superconductors and understanding the origins of copper oxide superconductivity. Isostructural examples include bulk superconducting Sr
RuO
(ref.
) and surface-electron-doped Sr
IrO
, which exhibits spectroscopic signatures consistent with a superconducting gap
, although a zero-resistance state has not yet been observed. This approach has also led to the theoretical investigation of nickelates
, as well as thin-film heterostructures designed to host superconductivity. One such structure is the LaAlO
/LaNiO
superlattice
, which has been recently proposed for the creation of an artificially layered nickelate heterostructure with a singly occupied Formula: see text band. The absence of superconductivity observed in previous related experiments has been attributed, at least in part, to incomplete polarization of the e
orbitals
. Here we report the observation of superconductivity in an infinite-layer nickelate that is isostructural to infinite-layer copper oxides
. Using soft-chemistry topotactic reduction
, NdNiO
and Nd
Sr
NiO
single-crystal thin films are synthesized by reducing the perovskite precursor phase. Whereas NdNiO
exhibits a resistive upturn at low temperature, measurements of the resistivity, critical current density and magnetic-field response of Nd
Sr
NiO
indicate a superconducting transition temperature of about 9 to 15 kelvin. Because this compound is a member of a series of reduced layered nickelate crystal structures
, these results suggest the possibility of a family of nickelate superconductors analogous to copper oxides
and pnictides
.
The occurrence of unconventional superconductivity in cuprates has long motivated the search for manifestations in other layered transition metal oxides. Recently, superconductivity is found in ...infinite‐layer nickelate (Nd,Sr)NiO2 and (Pr,Sr)NiO2 thin films, formed by topotactic reduction from the perovskite precursor phase. A topic of much current interest is whether rare‐earth moments are essential for superconductivity in this system. In this study, it is found that with significant materials optimization, substantial portions of the La1−xSrxNiO2 phase diagram can enter the regime of coherent low‐temperature transport (x = 0.14 ‐ 0.20), with subsequent superconducting transitions and a maximum onset of ≈9 K at x = 0.20. Additionally, the unexpected indication of a superconducting ground state in undoped LaNiO2 is observed, which likely reflects the self‐doped nature of the electronic structure. Combining the results of (La/Pr/Nd)1−xSrxNiO2 reveals a generalized superconducting dome, characterized by systematic shifts in the unit cell volume and in the relative electron‐hole populations across the lanthanides.
By refining the synthesis of high‐quality thin films, a superconducting dome is observed in La1−xSrxNiO2. Perhaps more surprisingly, undoped LaNiO2 also shows a strong indication of superconductivity. A generalized superconducting dome can be obtained by combining the La/Pr/Nd systems, revealing systematic shifts in the unit cell volume and the relative electron–hole population across the lanthanides.
The recent observation of superconductivity in Formula: see text has raised fundamental questions about the hierarchy of the underlying electronic structure. Calculations suggest that this system ...falls in the Mott-Hubbard regime, rather than the charge-transfer configuration of other nickel oxides and the superconducting cuprates. Here, we use state-of-the-art, locally resolved electron energy-loss spectroscopy to directly probe the Mott-Hubbard character of Formula: see text Upon doping, we observe emergent hybridization reminiscent of the Zhang-Rice singlet via the oxygen-projected states, modification of the Nd 5d states, and the systematic evolution of Ni 3d hybridization and filling. These experimental data provide direct evidence for the multiband electronic structure of the superconducting infinite-layer nickelates, particularly via the effects of hole doping on not only the oxygen but also nickel and rare-earth bands.
•Approaches were evaluated for estimating entire soil water characteristic curve.•The MV-vG approach estimation was improved by incorporating structure features.•The J-FX approach outperformed the ...MV-vG approach and its modification.
Three approaches were compared for estimating continuous soil water characteristic curves (SWCCs) from easily accessible soil properties. The approaches included combining the Mohammadi and Vanclooster (2011) method (the MV method) with the van Genuchten (1980) model (MV-vG approach), the modified MV-vG approach, and combining the Jensen et al. (2015) method with the Fredlund and Xing (1994) model (the J-FX approach). A total of 195 disturbed soil samples and 195 undisturbed soil cores were collected from 1-m soil profiles in an arid region of northwestern China. Particle size distribution (PSD) and organic matter (OM) content were determined. The volumetric water content and matric potential data pairs of each sample during the drying process were measured using a high speed centrifuge. All of the measured soil properties were used to evaluate the applicability of the approaches for continuous SWCC estimation. The MV method has a robust physical basis and is independent of any experimental SWCC data pairs. Some intrinsic shortcomings affect the estimation of continuous SWCC by the MV-vG approach. The integration of a soil structure feature improved the estimation of the modified MV-vG approach. The estimation of the J-FX approach for SWCC is robust for the five textural classes, and outperformed the MV-vG approach and the modified MV-vG approach. The good performance of the J-FX approach can be attributed in part to the fact that it distinguishes the dominant forces governing water retention of dry and wet ranges, and relates the PSD, specific surface area, and OM content to the pore size distribution. All these factors are vital for soil water retention, but have been simplified or ignored by the MV method. Both the modified MV-vG approach and the J-FX approach are promising for estimating continuous SWCCs at a regional scale. The modified MV-vG approach may be suitable for rigid soils with medium textures at potentials above wilting point. The J-FX approach is applicable for the whole range of water retention from saturation to oven dryness for soils with substantially varying bulk density, soil texture and organic matter content at a regional scale. The results of this study are fundamental for use in simulating the transfer of water and solutes in layered-structured soil profiles and for estimating the vegetation carrying capacity of soil available water in arid regions.
The recent observation of superconductivity in Nd0.8Sr0.2NiO2 calls for further investigation and optimization of the synthesis of this infinite-layer nickelate structure. Here, we present our ...current understanding of important aspects of the growth of the parent perovskite compound via pulsed laser deposition on SrTiO3 (001) substrates and the subsequent topotactic reduction. We find that to achieve single-crystalline, single-phase superconducting Nd0.8Sr0.2NiO2, it is essential that the precursor perovskite Nd0.8Sr0.2NiO3 thin film is stabilized with no visible impurity phases; in particular, a Ruddlesden–Popper-type secondary phase is often observed. We have further investigated the evolution of the soft-chemistry topotactic reduction conditions to realize full transformation to the infinite-layer structure with no film decomposition or formation of other phases. We find that capping the nickelate film with a subsequent SrTiO3 layer provides an epitaxial template to the top region of the nickelate film, much like the substrate. Thus, for currently optimized growth conditions, we can stabilize superconducting single-phase Nd0.8Sr0.2NiO2 (001) epitaxial thin films up to ∼10 nm.
To address current challenges of difficult standardisation of dynamic determination of roadbed bearing capacity and excessive deviations in deflection control, this paper proposes a improved ...measurement method for roadbed load-bearing capacity based on the dynamic modulus control using a portable falling weight deflectometer (PFWD). The detection range of PFWD is determined by theoretical analysis. Based on the range, a finite element numerical model was developed, the spatial distribution and attenuation of the dynamic stress of the roadbed soil in the depth and horizontal directions are determined. The variation of the vertical dynamic stress with depth is not characterized by a gradual decrease, as is commonly believed, but rather by an increase followed by a decrease. The underlying reasons for the difference between static and dynamic indicators are explored. Using the improved method, a prediction model with dynamic bending as the detection index and static rebound modulus as the control index was developed. The proposed model can improve precision accuracy as well as detection efficiency, verify the effectiveness of the improved method, which is important for accurate dynamic measurement and evaluation of highway roadbed bearing capacity.
Knowledge of the spatial pattern of soil organic carbon (SOC) and the factors influencing it in various landscapes is essential for understanding carbon cycles. An arid region with an area of 100km2 ...in northwestern China consisted of desert, cropland and wetland was investigated. The vertical patterns of SOC density in the three different landscapes and the horizontal distribution of SOC density in the study area were evaluated. The differences in SOC density among different landscapes and soil layers were analyzed, and the primary factors influencing SOC density were determined. The density of SOC was low and remained homogeneous in the profiles of desert soil. The vertical distributions of SOC density in cropland and wetland were well described by logarithmic functions (R2=0.97 and 0.92, respectively, P<0.001). Geostatistical analysis showed that SOC density presented moderate spatial variability and strong spatial dependence across all depths. Wetland and desert were easily recognized by the highest and lowest SOC densities in the study area, respectively. The densities of SOC in the 3-m profiles were 59.35, 149.6 and 174.4Mgha−1 for desert, cropland and wetland, respectively. The SOC in the 1–3m layer represented 67.0, 52.7 and 58.0% of the total SOC stored in the 0–3m profiles of desert, cropland and wetland, respectively. Clay and silt particles were the major determinant of SOC in the study area. The variability in SOC density explained by clay+silt content increased with depth ranging from 46.0 to 82.2% in desert and from 45.3 to 76.7% in cropland. The variability in SOC density accounted for by clay+silt content decreased from 52.2% in the 0–0.3m layer to 43.3% in the 0–1m layer of wetland. The remaining SOC density variability could be attributed to factors not included in this study, such as geography, vegetation and the degree of erosion. Errors in the measurement of SOC concentration and the distribution of soil-particle size, however, may introduce uncertainty in the determination of soil bulk density and thus the estimation of SOC density. The concentration of SOC in the 0–0.3m layer increased by 196.3% after the reclamation of native desert less than 40years ago and decreased by 5.3% after the cultivation of wetland as cropland for less than 30years. Short-term cultivation is insufficient to significantly alter SOC concentration in the deeper layers of desert and wetland soils. The results of this study may be of further use in optimizing strategies for the protection of wetland, ecological restoration of desertified land and the sustainable management of cropland in arid regions of northwestern China.
•We investigated the distribution and influencing factors of soil organic carbon (SOC);•Wetland and desert had the highest and the lowest SOC, respectively;•Fine particles were the major determinant of SOC for desert and cropland;•Wetland and desert both have the potential to be C sinks.
As the largest ecosystem of China, the desert ecosystem and the desertification-prone region (DPR) occupies 44% of China's land area. The past, present, and the future of China's desert ecosystems ...were reviewed. Following desert ecosystem classifications adopted by most scholars and the criteria of DPR determinations proposed by United Nations Convention to Combat Desertification (UNCCD), the total area of desert ecosystems in China are presently 2.08 × 106 km2, and total area of DPR is 2.13 × 106 km2. The desert ecosystem developed during the Quaternary period in most regions of northeastern China, but this area is not currently classified as this ecosystem. At present, the xeric shrub, sandy, gravel, saline-alkaline, clay-based, and alpine-cold desert ecosystems are found in China, and their areas are 6.34%, 27.49%, 26.99%, 6.88%, 19.98%, and 12.31%, respectively, of the total desert ecosystem area. There were no great variations in the areas of the gravel and alpine-cold desert ecosystems in China throughout the Quaternary period to the present because of the control exerted by long-term climate change and the Qinghai-Tibet Plateau uplift. Close relationships exist between xeric shrub and clayed-based ecosystem development and drought events. The formation and development of the saline-alkaline desert ecosystem has been mainly controlled by variations in groundwater levels and human activities such as irrigation and dam building. Among all of the desert sub-ecosystems, the sandy ecosystem appears to be more sensitive to climate change, and its area in the Holocene Optimum was only 60% of that in the Last Glacial Maximum. Over the past half-century, the development of the sandy desert ecosystem has been consistent with trends of aeolian activity, achieving its maximum area in the late 1980s, and then decreasing from that time to the present. Due to the influence of both climate change and human activities in China, some desert sub-ecosystems have evolved into other types of desert ecosystems. In addition, considering the impact of human activities on soil and vegetation in desert ecosystems, at present only 0.10–0.35% of China's desert ecosystem area is associated with human activities. Data provided by World Climate Research Programme (WCRP) Coupled Model Intercomparison Project (CMIP) (Phase 6) indicates that the area of desert ecosystems may decrease by 9.30%, 13.40%, and 17.30% in 2050, 2070, and 2100, respectively.
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•The desert ecosystem and the desertification-prone region (DPR) occupies 44% of China’s land area•The total area of modern China’s desert ecosystem and DPR are 2.08 × 106 and 2.13 × 106 km2, respectively•Despite emergence of the desert ecosystem in the Quaternary period in northeast China, this region should not currently be classified as such•Only 0.10–0.35% of China’s desert ecosystem area is associated with human activities•Desert ecosystem area may decrease by 9.30%, 13.40%, and 17.30% in 2050, 2070, and 2100, respectively
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