Aims
Absorptive and transport roots (diameter ≤ 2 mm) are closely related to soil resource uptake for plant growth, carbon budget and nutrient cycling in forest ecosystems, but how and why the ...relative share of root biomass or root length for both root functional types changes with tree species is not well understood. Our aims were to examine the inter-specific variations of root biomass and length per unit area of absorptive and transport roots, and their relationships with stand structure and soil characteristics, root morphological and architectural traits.
Methods
We measured root biomass and length per unit area, diameter, specific root length (SRL), root tissue density (RTD), and branching ratio of the first five order roots, stand and soil characteristics in seven forests consisting of different tree species at a common site. The first order roots were classified as absorptive roots and the other orders as transport roots based on our earlier work.
Results
Biomass ratios of absorptive to transport roots varied from 1:5.56 to 1:1.12 among species, and length ratios ranged from 1:1.56 to 1:0.29. Root biomass was not influenced by root morphology or architecture, nor by stand or soil characteristics. Absorptive root length was significantly correlated with SRL, RTD, and branching ratio of the first to second order roots among species, whereas transport root length was significantly correlated with stem density.
Conclusions
The relative share of biomass and length for absorptive and transport roots differed among tree species, which may influence belowground carbon allocation and resource competition.
Lower limb injuries occur frequently in vehicle-to-pedestrian collisions and vehicle front-end shape has a significant influence on pedestrian lower limb injuries Therefore, the aim of the current ...study is to propose an effective optimization framework for vehicle front-end design and to predict safer vehicle front-end shapes for pedestrian lower limb protection using this optimization framework. To achieve this, an optimization framework combining the genetic algorithm (GA) in MATLAB and finite element (FE) simulations in LS-DYNA was proposed and applied to predict safer vehicle frontend shapes for pedestrian lower limb protection. The optimization results indicate that it is feasible and reliable to use the proposed optimization framework in vehicle front-end shape optimization for pedestrian lower limb protection. The predicted safer vehicle front-end shapes suggest that the vehicle front-end designs with a lower bumper stiffener close to the ankle, a bumper absorber higher than the knee and a bonnet leading edge above the hip joint would be beneficial for pedestrian lower limb protection. Biomechanical analysis implies that a plane-approximating support to both the upper and lower leg from the vehicle front-end structure could reduce lower limb lateral bending and hence injury risk greatly.
Key message
In the organic layer, absorptive fine roots of
Larix gmelinii
represent a significant proportion of the total fine-root biomass and can morphologically adjust during the growing season to ...optimize resource acquisition.
Larix gmelinii
is a foundational tree species in forests of northern China and Far-East Russia. A better understanding of the species’ belowground resource acquisition strategy is important for soil nutrient and carbon estimates. Here, we investigated seven traits of absorptive fine-roots at four depth levels, from the organic layer (organic, decomposed litter from dead plants) down to a soil depth of 30 cm in May, July and September of 2016. Biomass and functional traits of absorptive fine roots varied significantly, indicating the species ability to adjust its resource acquisition across the four depth layers. From the organic layer to deeper mineral soil layers, root diameter and tissue density increased, while specific root length decreased, in other words, roots become longer and thinner with increasing values of soil water and nutrient concentrations. At the same time, the average biomass and length of absorptive fine roots in the organic layer accounted for 14% and 16% of the total, respectively. With increasing soil depth, the averaged proportion of biomass and length density of absorptive fine roots to the total fine roots decreased significantly from almost 57 to 32%, and 80–62%, respectively. Finally, total soil nitrogen concentration showed the strongest link with absorptive fine-root traits, such as root diameter, specific root length, root standing biomass and length density. Our results indicate that absorptive fine roots in the organic layer play a crucial role in belowground resource acquisition and carbon cycle in a common and economical important species.
The influence of interface temperature on the damage characteristics of C–Cu contacts’ interface plays a critical role in the current-carrying friction process which occurs between the contact pairs. ...In this paper, a method is proposed to adjust the interface temperature via settling an external heat source. The damage morphology and material transfer of C–Cu contacts are focused on when the range of interface temperature varies from the room temperature (25 °C) to 300 °C. Based on the experimental results, it can be found that high interface temperature can inhibit the surficial erosion of carbon materials, which tends to be obvious, especially along with the increment of current. Moreover, both the delamination wear of carbon surface and the copper-to-carbon transfer behavior decrease with the thermal surge of interface. This beneficial effect of interface temperature results in the reduction in friction coefficient by 14.3%, whereas the negative impacts brought from the high interface temperature are the surface cracking and the rapid recovery of wear rate of carbon materials, under high-current condition.
Graphical abstract
The grounding electrode line is an important part of the Ultra high voltage direct current (UHVDC) transmission system. It acts as the channel to conduct the unbalanced current and the grounding ...current.The arcing horn consists of a pair of electrodes installed in parallel at both ends of the insulator string, which provides a discharge channel for the fault current by an air gap to protect the insulators. In this paper, the voltage and current distributions of the arcing horn were studied when the grounding electrode line was struck by lightning. It is found that the current and voltage gradually decrease along the direction from the converter station to the earth electrode. An active arc extinguishing method based on variable resistance for arcing horn was proposed. An electromagnetic transient simulation model of the grounding electrode line is established based on the electrical parameters of a ±800 kV UHVDC transmission system. It is found that the absorbed energy of the arc extinguishing unit needs to be at least 31.2 and 49.6 kJ when the lightning current is 20 and 50kA, respectively. According to the calculation results, the arcing horn with arc extinguishing unit was developed and tested. The test results verifies that the designed arcing horn can meet the requirements of engineering application.
In this work, an active arc extinguishing method based on variable resistance for arcing horn was proposed. To design the arcing horn within active arc extinguishing function, the grounding electrode line and arcing horn model were established based on a ±800kV UHVDC transmission system. The electrical characteristics of the arcing horn were calculated under different grounding currents andlightning currents.
An accurate formula for calculating the pressure loss in concrete pumping plays a significant guiding role in the design and service process of pump trucks. Based on the flow characteristics of ...concrete pumping, a straight pipe one-dimensional model for the pressure loss is developed, in which both the viscous force of the mortar in the lubrication layer and the blocking effect of coarse aggregate particles are considered. First, the complex geometrical shapes of the aggregate particles are geometrically reconstructed by using a HandySCAN noncontact scanner and the reverse modeling software Geomagic Design X (v.19.0.2). Then, the equivalent spherical size of nonspherical aggregate particles is calculated according to the equal hydraulic radius principle. The blocking effect of the aggregate particles is converted into the wall roughness. Finally, an explicit expression for the pressure loss in concrete pumping is deduced by using Modi’s equation, Bernoulli’s equation, and Darcy’s formula, and the calculated value is compared with the measured value at a corresponding experimental site. The results indicate that the pressure loss values calculated with the one-dimensional flow model are closer to the actual pumping pressure loss values. The relative error between the results and the actual pumping pressure loss value is about 20.2%.
Phenomena of the pantograph arcing have become a challenge for the further development of high-speed electrified railway system. Despite of the large attention that has been paid to the radiated ...electromagnetic interference, materials ablation as well as the power-quality decline resulted from pantograph arcing, the specific dynamics of pantograph arcing with a high time resolution are still in absence. In this paper, the pantograph arcing phenomena in a laboratory simulation system were experimentally studied by high-speed photography. Synchronized electrical voltage and current waveforms were obtained to acquire a more comprehensive understanding on the underlying physics. The overall dynamics of the pantograph arcing from ignition to extinguishment were recorded. Three stages of the electriccontact process, from approaching arc, mechanical contact to the drawn arc, were well distinguished. A much intensified drawn arc was observed than the approaching arc. Typical lasting time of the drawn arcing is found ~4 times larger than the approaching arcing for our test setup. Maximum diameter of 3.3 mm was reached at around the current-peak moment. An interesting stable arc voltage of ~23 V was found during the drawn arcing. Intense material splash above the carbon strip was observed during the arcing process. The transient resistance during a typical arcing period was also analyzed, and a minimum value of ~100 mQ was determined.
Prostate cancer (PCa) is one of the most common malignancy in men. However, the molecular mechanism of its pathogenesis has not yet been elucidated. In this study, we demonstrated that CYLD, a novel ...deubiquitinating enzyme, impeded PCa development and progression via tumor suppression. First, we found that CYLD was downregulated in PCa tissues, and its expression was inversely correlated with pathological grade and clinical stage. Moreover, we discovered that CYLD inhibited tumor cell proliferation and enhanced the sensitivity to cell ferroptosis in PCa in vitro and in vivo, respectively. Mechanistically, we demonstrated that CYLD suppressed the ubiquitination of YAP protein, then promoted ACSL4 and TFRC mRNA transcription. Then, we demonstrated that CYLD could enhance the sensitivity of PCa xenografts to ferroptosis in vivo. Furthermore, we discovered for the first time that there was a positive correlation between CYLD expression and ACSL4 or TFRC expression in human PCa specimens. The results of this study suggested that CYLD acted as a tumor suppressor gene in PCa and promoted cell ferroptosis through Hippo/YAP signaling.
