Enhanced and reduced solute transport and flow strength in salt finger convection in porous media

We report a pore-scale numerical study of salt finger convection in porous media, with a focus on the influence of the porosity in the non-Darcy regime, which has received little attention in previous research. The numerical model is based on the lattice Boltzmann method with a multiple-relaxation-time scheme and employs an immersed boundary method to describe the fluid-solid interaction. The simulations are conducted in a two-dimensional, horizontally-periodic domain with an aspect ratio of 4, and the porosity is varied from 0.7 to 1, while the solute Rayleigh number ranges from 4*10^6 to 4*10^9. Our results show that, for all explored Rayleigh number, solute transport first enhances unexpectedly with decreasing porosity, and then decreases when porosity is smaller than a Rayleigh number-dependent value. On the other hand, while the flow strength decreases significantly as porosity decreases at low Rayleigh number, it varies weakly with decreasing porosity at high Rayleigh number and even increases counterintuitively for some porosities at moderate Rayleigh number. Detailed analysis of the salinity and velocity fields reveals that the fingered structures are blocked by the porous structure and can even be destroyed when their widths are larger than the pore scale, but become more ordered and coherent with the presence of porous media. This combination of opposing effects explains the complex porosity-dependencies of solute transport and flow strength. The influence of porous structure arrangement is also examined, with stronger effects observed for smaller porosity and higher Rayleigh number. These findings have important implications for passive control of mass/solute transport in engineering applications

Distribution of Heavy Metals in Core Sediments from Baihua Lake

AbstractIn the present research, five core sediments from Baihua Lake, a man-made reservoir located in the karst area on the Yunnan-Guizhou Plateau in China, were analyzed to study the distribution, origin and contamination of three selected heavy metals (Cu, Zn and Mn). The results showed that the concentrations of these heavy metals in sediments varied from different sampling locations and layers. The average concentrations of these heavy metals at the same sampling location followed the order of Mn>Zn>Cu. The mean concentrations of Zn and Mn in the samples at the depth of 0-5cm and the depth of 5-10cm of the core sediments were higher than those in the other layers. All of Cu, Zn and Mn presented similar distribution characteristics at sampling site CFZ, and different distribution characteristics from the other four sampling locations. A statistical analysis indicated that there were some correlations between the concentrations of these three heavy metals and other studied six elements occurring in the core sediment samples. Three components were obtained with principal component analysis (PCA) analysis of heavy metals concentrations in core sediment samples

Stellar Parameters of Main Sequence Turn-off Star Candidates Observed with the LAMOST and Kepler

Main sequence turn-off (MSTO) stars have advantages as indicators of Galactic evolution since their ages could be robustly estimated from atmospheric parameters. Hundreds of thousands of MSTO stars have been selected from the LAMOST Galactic sur- vey to study the evolution of the Galaxy, and it is vital to derive accurate stellar parameters. In this work, we select 150 MSTO star candidates from the MSTO stars sample of Xiang that have asteroseismic parameters and determine accurate stellar parameters for these stars combing the asteroseismic parameters deduced from the Kepler photometry and atmospheric parameters deduced from the LAMOST spectra.With this sample, we examine the age deter- mination as well as the contamination rate of the MSTO stars sample. A comparison of age between this work and Xiang shows a mean difference of 0.53 Gyr (7%) and a dispersion of 2.71 Gyr (28%). The results show that 79 of the candidates are MSTO stars, while the others are contaminations from either main sequence or sub-giant stars. The contamination rate for the oldest stars is much higher than that for the younger stars. The main cause for the high contamination rate is found to be the relatively large systematic bias in the LAMOST surface gravity estimates.Comment: accepted by RA

The effect of Sm 3+ co-doping on the luminescence properties of Ca 2 · 85 Li 0 · 15 (PO 4 ) 1 · 85 (SO 4 ) 0.15 : Dy 3+ white-emitting phosphors

Abstract(#br)A novel white emitting phosphate-based phosphor Ca 3- x Li x (PO 4 ) 2- x (SO 4 ) x :Dy 3+ , Sm 3+ with high emission intensity and lower correlated color temperature were successfully synthesized via the sol-gel method.(#br)The structures of these prepared phosphors matched well with standard Ca 3 (PO 4 ) 2 . The Dy 3+ -doped Ca 3- x Li x (PO 4 ) 2- x (SO 4 ) x phosphors showed white luminescence via the combination of blue (487 nm) and yellow (578 nm) emissions, which were attributed to the 4 F 9/2 → 6 H 15/2 and 4 F 9/2 → 6 H 13/2 electron transitions of Dy 3+ , respectively. The synthesized phosphor exhibited a significant enhancement in luminescence intensity at the optimum value of x = 0.15. With the incorporation of Sm 3+ , a warm white emission with lower correlated color temperature (4281 K) was achieved in Dy 3+ /Sm 3+ co-doped samples. The obtained external quantum efficiency reached 21.7% in the optimized phosphor. The improved performance was strongly associated with red emission supplemented by Sm 3+ , and it demonstrated the existence of efficient energy transfer between the Dy 3+ and Sm 3+ ions ( 4 F 9/2 → 4 G 7/2 and 4 F 9/2 → 4 G 5/2 ). Overall, the investigation carried out by us has revealed that the luminescence properties of Ca 3 (PO 4 ) 2 phosphor can be significantly improved through Li + /S 6+ partial substitution and Dy 3+ /Sm 3+ co-doping

Analysis between ABO blood group and clinical outcomes in COVID-19 patients and the potential mediating role of ACE2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become the most common coronavirus that causes large-scale infections worldwide. Currently, several studies have shown that the ABO blood group is associated with coronavirus disease 2019 (COVID-19) infection and some studies have also suggested that the infection of COVID-19 may be closely related to the interaction between angiotensin-converting enzyme 2 (ACE2) and blood group antigens. However, the relationship between blood type to clinical outcome in critically ill patients and the mechanism of action is still unclear. The current study aimed to examine the correlation between blood type distribution and SARS-CoV-2 infection, progression, and prognosis in patients with COVID-19 and the potential mediating role of ACE2. With 234 patients from 5 medical centers and two established cohorts, 137 for the mild cohort and 97 for the critically ill cohort, we found that the blood type A population was more sensitive to SARS-CoV-2, while the blood type distribution was not relevant to acute respiratory distress syndrome (ARDS), acute kidney injury (AKI), and mortality in COVID-19 patients. Further study showed that the serum ACE2 protein level of healthy people with type A was significantly higher than that of other blood groups, and type O was the lowest. The experimental results of spike protein binding to red blood cells also showed that the binding rate of people with type A was the highest, and that of people with type O was the lowest. Our finding indicated that blood type A may be the biological marker for susceptibility to SARS-CoV-2 infection and may be associated with potential mediating of ACE2, but irrelevant to the clinical outcomes including ARDS, AKI, and death. These findings can provide new ideas for clinical diagnosis, treatment, and prevention of COVID-19

Viral Etiologies of Hospitalized Acute Lower Respiratory Infection Patients in China, 2009-2013

Our findings could serve as robust evidence for public health authorities in drawing up further plans to prevent and control ALRIs associated with viral pathogens. RSV is common in young children and prevention measures could have large public health impact. Influenza was most common in adults and influenza vaccination should be implemented on a wider scale in China

Total Energy Cost Optimization for Data Collection With Boat-Assisted Drone: A Study on Large-Scale Marine Sensor

Collecting broad ocean region data to leverage large-scale sensors is a valid method to handle ocean health problems associated with human activities (wind turbine deployment, nuclear wastewater discharge, etc.). When using the novel collection scheme, reducing the total energy consumption (TEC) of boat-assisted drones to collect sensor data is challenging. The objective of this study was to minimize the TEC of boats and drones (owing to their limited battery capacity) during marine environment sensor data collection. To achieve this, new models for drone hovering in wind, data collection, and related wireless communication have been developed, and the TEC minimization problem has been formulated as a new specialized distance-constrained capacitated vehicle routing problem. The problem is divided into four subproblems to reduce complexity. Based on these four subproblems, an improved heuristic algorithm was proposed. In the algorithm, the drone hovering position and boat waypoint are determined using the K-means clustering algorithm and the smallest enclosing circle algorithm. Based on the position and waypoint, the routes of drones and boats were optimized using the Lin-Kernighan heuristic 3 algorithm, thus minimizing the TEC. The simulation results demonstrate that when the boat waypoint is 3 and the sensor number is 2000, owing to the strong local and global search ability, the TEC in the scheme is $0.03{\times }10 ^{8}\text{J}$ less than that of the graph attention neural network method (GANN), while the scheme also provides time saving, scalability, and flexibility