Warming decreased plant litter decomposition by modulating soil fauna interactions in a Tibetan alpine meadow.

Litter decomposition is a vital process for maintaining ecosystem carbon cycling. It is affected by soil fauna which are predators and decomposers of litter. However, how the interactions of soil fauna communities affect litter decomposition remains unclear under warming. Here, we conducted a five-year in-situ manipulative warming experiment by Open-Top Chamber (OTC) in an alpine meadow on the Tibetan Plateau to reveal how warming affects litter decomposition. The results demonstrated that warming decreased the litter decomposition rate by 29 %, the soil collembola abundance by 25 %, and the nematode abundance by 27 %. Nematode ecological indices remain stable but a shift in the decomposition of litter to the fungivores pathway under warming. The piecewise structural equation modelling result revealed that the combined reduction in soil collembola and nematodes synergistically leads to a massive decline in litter decomposition rate under warming. Our results highlight that the interactions of soil fauna can regulate litter decomposition under warming, and collembola abundance as the "speed-limiter" of litter decomposition. Therefore, the response of changes in soil fauna relationships to warming should be completely considered in future climate change modelling of the grassland carbon cycle.

The effect of low molecular weight heparin combined with air pressure in the prevention of lower extremity venous thrombosis after cesarean section: A single-center retrospective study.

In this study, we investigated the effect of low-molecular-weight heparin combined with pneumatic pressure in preventing lower extremity deep vein thrombosis after cesarean section, as well as on the visual analog scale (VAS) score. 120 women who underwent cesarean sections at full term in our hospital from January 2019 to January 2022 were included and divided into a control group (55 cases) and an observation group (65 cases) based on the different treatment methods: the control group was treated with low-molecular-weight heparin and the observation group was treated with pneumatic compression therapy based on the control group. The 2 groups were analyzed for thrombosis, clinical efficacy of the treatment methods, and VAS scores. The incidence of deep vein thrombosis in the observation group were significantly lower than in the control group (4.62% vs 21.82%, P < .05). There were no statistically significant differences in activated partial thromboplastin time, prothrombin time, and thrombin time between the 2 groups (P > .05) before treatment; however, after treatment, activated partial thromboplastin time, prothrombin time, and thrombin time in the observation group were significantly higher than those in the control group (P < .05). The clinical efficacy was significantly higher in the observation group compared with the control group (95.38% vs 78.18%, respectively). The VAS scores in the observation group were significantly lower than those in the control group (P < .05). Hence, low-molecular-weight heparin combined with pneumatic pressure therapy significantly reduces the incidence of lower limb deep vein thrombosis after cesarean section. It also improves the coagulation index and reduces post-operative pain. Therefore, it should be considered for use in clinical practice.

Granular cooling of ellipsoidal particles in microgravity.

A three-dimensional granular gas of ellipsoids is established by exposing the system to the microgravity environment of the International Space Station. We use two methods to measure the dynamics of the constituent particles and report the long-time development of the granular temperature until no further particle movement is detectable. The resulting cooling behavior can be well described by Haff's cooling law with time scale τ. Different analysis methods show evidence of particle clustering towards the end of the experiment. By using the kinetic theory for ellipsoids we compare the translational energy dissipation of individual collision events with the overall cooling time scale τ. The difference from this comparison indicates how energy is distributed in different degrees of freedom including both translation and rotation during the cooling.

Force chains in crystalline and frustrated packing visualized by stress-birefringent spheres.

Force networks play an important role in the stability of configurations when granular material is packed into a container. These networks can redirect part of the weight of grains inside a container to the side walls. We employ monodisperse stress-birefringent spheres to visualize the contact forces in a quasi-2D and a nearly-2D configuration of these spheres in a thin cuboid cell. The packing structures are particularly simple: a hexagonal lattice in the ground state when the cell width is equal to the sphere diameter, and a frustrated, slightly distorted lattice in thicker cells. The force redistribution is substantially changed by this geometrical modification. In both cases, we observe an 'inverse' Janssen effect with the pressure decreasing from the top to the bottom of the container when the material is loaded with a weight on top of the vessel.

Effects of cadmium addition on net nitrogen mineralization processes in the urban constructed wetland soils of a Chinese delta.

Heavy metal pollution is a serious problem in wetland ecosystems, and the toxicity of heavy metals affects microorganisms, thus influencing the biogeochemical process of nitrogen (N). To investigate the effects of heavy metal cadmium (Cd) pollution on N mineralization in urban constructed wetland soils of the Pearl River Delta, a 40-day aerobic incubation experiment was conducted under three Cd addition treatments [no Cd addition (control), low Cd addition (LCA) and high Cd addition (HCA)]. The results showed that compared with the control, the LCA treatment enhanced the soil N mineralization rate (RM), while the HCA treatment inhibited RM, with the average RM values in the control treatment of 0.40 mg kg-1 day-1, LCA treatments (0.66 mg kg-1 day-1), and HCA treatments (0.21 mg kg-1 day-1). The average ammonification rate values in the LCA treatments (- 3.15 to 2.25 mg kg-1 day-1) were higher than those in the HCA treatments (- 2.39 to 0.74 mg kg-1 day-1) and the control treatment (- 0.68 to 0.90 mg kg-1 day-1) (P < 0.05). However, the nitrification values in the HCA treatments (- 0.37 to 3.36 mg kg-1 day-1) were higher than those in the LCA treatments (0.42-1.93 mg kg-1 day-1) and the control treatment (0.20-1.45 mg kg-1 day-1) (P < 0.05). The net N mineralization accumulation generally increased over the entire incubation time in different Cd addition treatments. The percentage of NH4+-N to total inorganic N showed a decrease, while an increase was observed for NO3--N over the incubation time. The urease activities were significantly inhibited in the LCA and HCA treatments and showed a "decreasing before increasing" trend. The abundance of ammonia oxidizing archaea (AOA) was higher in the two Cd addition treatments than the control treatment, and higher in the LCA treatments than in the HCA treatment. AOA was the dominant microorganism in the ammonia oxidation process of N mineralization in constructed wetland soils. The findings of this work indicate that Cd addition has a profound effect on the balance of N mineralization and may further impact the plant productivity and water quality of constructed wetlands.

Velocity Distribution of a Homogeneously Cooling Granular Gas.

In contrast to molecular gases, granular gases are characterized by inelastic collisions and require therefore permanent driving to maintain a constant kinetic energy. The kinetic theory of granular gases describes how the average velocity of the particles decreases after the driving is shut off. Moreover, it predicts that the rescaled particle velocity distribution will approach a stationary state with overpopulated high-velocity tails as compared to the Maxwell-Boltzmann distribution. While this fundamental theoretical result was reproduced by numerical simulations, an experimental confirmation is still missing. Using a microgravity experiment that allows the spatially homogeneous excitation of spheres via magnetic fields, we confirm the theoretically predicted exponential decay of the tails of the velocity distribution.

Acoustic waves in granular packings at low confinement pressure.

Elastic properties of a granular packing show a nonlinear behavior determined by its discrete structure and nonlinear inter-grain force laws. Acoustic waves show a transition from constant, pressure-dependent sound speed to a shock-wave-like behavior with an amplitude-determined propagation speed. This becomes increasingly visible at low static confinement pressure as the transient regime shifts to lower wave amplitudes for lower static pressure. In microgravity, confinement pressure can be orders of magnitude lower than in a ground-based experiment. In addition, the absence of hydrostatic gradients allows for much more homogeneous and isotropic pressure distribution. We present a novel apparatus for acoustic wave transmission measurements at such low packing pressures. A pressure control loop is implemented by using a microcontroller that monitors static force sensor readings and adjusts the position of a movable wall with a linear-motor until the desired pressure is reached. Measurements of acoustic waves are possible using accelerometers embedded in the granular packing as well as piezos. For excitation, we use a voice-coil-driven wall, with a large variety of signal shapes, frequencies, and amplitudes. This enables experiments in both the linear and strongly nonlinear regimes.

Magnetic excitation of a granular gas as a bulk thermostat.

A thermostat utilizing a varying magnetic field has been developed to agitate soft ferromagnetic particles in microgravity platforms for an investigation of an energy-dissipative granular gas. Although the method has experimentally realized a reasonably homogeneous spatial distribution of particles, the physics behind the magnetically excited particles has not been understood. Therefore, a numerical calculation based on the discrete element method is developed in this paper to explain the realization of homogeneously distributed particles. The calculation method allows considering inelastic and magnetic interactions between particles and tracking the motions due to those interactions during the excitation of the granular gas. The calculation results, compared with the experimental result, show that magnetic interactions between particles, a time-domain variation of magnetic-excitation directions, and random collisions of particles between each magnetic excitation contribute to distribute particles homogeneously.

Magnetically excited granular matter in low gravity.

Due to the undesired impact of gravity, experimental studies of energy-dissipative gaseous systems are difficult to carry out on ground. In the past several years, we developed a series of experimental devices suitable for various kinds of microgravity platforms. The central idea adopted in our devices is to use long-range magnetic forces to excite all the particles within the system. Through the development of our devices, different component configurations, excitation protocols, and image-capturing methods have been tried and optimized to achieve best excitation and the maximum capability for data analysis.

Temporal and spatial variation of extreme temperatures in an agro-pastoral ecotone of northern China from 1960 to 2016.

The agro-pastoral ecotone of northern China is one of the areas most sensitive to global temperature change. To analyze the temporal and spatial trends of extreme temperature events in this area, we calculated the values of 16 extreme-temperature indices from 1960 to 2016 based on data from 45 national meteorological stations. We found that the coldest-temperature indices decreased significantly and the warmest-temperature indices increased significantly. The warming of night temperatures contributed more than warming of day temperatures to the overall warming trend. In addition, the warm-temperature indices appeared to be increasing since the late 1980s and early 1990s. Overall, though the four extremal indices showed an increasing trend, the rate of change in the minimum temperature was greater than that of the maximum temperature; thus, the minimum temperature contributed most strongly to the overall temperature increases. The growing season is being prolonged in higher-elevation areas, but vegetation maturation in lower-elevation areas has been accelerated by the high temperatures, potentially leading to a shorter growing season at low altitudes. However, the impacts of land-use changes caused by human activities on the temperature increases will require additional study.