Synthesis of SiC-based composites using microwave(MW)-assisted reactive infiltration is a promising way to obtain these materials at lower costs due to a reduction in processing time and energy ...consumption. Hot spots are likely to form during this process due to the different dielectric properties of the various phases and the exothermic nature of the reaction between Si and C. To study these effects Cf/SiC composites were subjected to high-temperature treatments (1800, 2000, 2200 °C) to simulate hot spots within the material. Microstructural changes were evaluated after the thermal treatments and thermo-mechanical properties were measured and correlated to the microstructural changes. Our results indicate that evaporation of silicon is the primary damaging mechanism, causing a decrease in the bending strength of the composite due to formation of porosity and a volume increase. These effects are countered by the densification of carbon phases that improve the intrinsic thermal properties of the material.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Neutrophils are major inflammatory cells that rapidly infiltrate wounds to provide antimicrobial functions. Within the damaged tissue, neutrophil migration behavior often switches from exploratory ...patrolling to coordinated swarming, giving rise to dense clusters that further disrupt tissue architecture. This aggregation response is self-organized by neutrophil paracrine chemoattractant signaling (most notably of the inflammatory mediator leukotriene B4 LTB4). The coordination mechanism and possible evolutionary benefits of neutrophil swarms are elusive. Here, we show that neutrophil swarms require mutual reinforcement of damage signaling at the wound core. New biosensors and live imaging in zebrafish revealed that neutrophil chemoattractant synthesis is triggered by a sustained calcium flux upon contact with necrotic tissue that requires sensing of the damage signal ATP. This “calcium alarm” signal rapidly propagates in the nascent neutrophil cluster in a contact-dependent manner via connexin-43 (Cx43) hemichannels, which are mediators of active ATP release. This enhances chemoattractant biosynthesis in the growing cluster, which is instrumental for coordinated motion and swarming. Inhibition of neutrophil Cx43 compromises clearance of wound-colonizing P. aeruginosa bacteria and exacerbates infection-induced morbidity. Thus, cooperative production of alarm signals among pioneer clustering neutrophils fuels the growth of dense antimicrobial cell masses that effectively seal off breached tissue barriers from opportunistic pathogens.
Display omitted
•Calcium alarm signals in neutrophil clusters locally promote attractant synthesis•Calcium alarm signals are dependent on ATP sensing and contact with necrotic tissue•Clustering neutrophils initiate and propagate calcium alarm signals via Cx43 channels•Neutrophil swarms and Cx43 restrict wound colonization by opportunistic bacteria
Poplimont et al. show that frontline neutrophils clustering at wound sites centrally coordinate damage sensing, calcium alarm signals, and the escalation of the inflammatory response. Intracluster coordination of signaling requires connexins and leads to dense swarms, which protect the breached tissue from opportunistic pathogens.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Subsoiling is an essential practice in conservation tillage technology. The amount of disturbed soil at various depths resulting from subsoilers with different parameters has an important effect on ...soil properties (e.g., bulk density and water infiltration). The information regarding the effects of subsoiling on the characteristics of soil water infiltration is essential for the design of subsoiling tools. In this study, the effects of the wing mounting height (h) (75–155 mm) of the subsoiler on soil disturbance and soil water infiltration were modelled using HYDRUS-2D and validated using field experiments. Results showed that reducing h values resulted in larger soil disturbance area ratios, soil water infiltration rates (f(t)), distances of vertical wetting front movement (DVWs), accumulative infiltrations (AINs), and soil moisture contents at depths of 10–30 cm. The relationships among characteristics of soil water infiltration, h and time (t), were developed. The stable infiltration rates (fs) varied quadratically with h and the corresponding coefficient of determination (R2) was 0.9869. The Horton model is more suitable for describing the relationship between f(t) and t under the tested soil conditions, as compared with the Kostiakov and Philip models. According to the results of soil water content at different depths from the HYDRUS simulations and field experiments, the developed soil water infiltration model had a good accuracy, as indicated by RMSEs of <0.05, R2 values of >0.95, and mean relative errors of <12%. The Above results indicated that increasing the hardpan disturbance by optimizing wing parameters of the subsoiler could improve soil water infiltration characteristics.
Air infiltration has a significant impact on building energy performance and the indoor environment. An accurate estimate of air infiltration rate informs envelope retrofit decisions to improve ...airtightness. However, air mobility and other environmental factors, such as wind or indoor-outdoor temperature differences, often make the accurate measurement of air infiltration challenging. Further, conventional air infiltration testing approaches such as fan pressurization and tracer gas tests possess certain drawbacks limiting their applicability in commercial buildings. To address the limitations of air infiltration tests, this study proposes a low-cost inverse model-based approach for estimating air infiltration rates by extracting the naturally occurring indoor CO2 and relative humidity (RH) data from a building automation system (BAS). These data were used to develop a linear regression model, and a tracer gas experiment was also used to verify the applicability of the proposed approach. The results indicated that the proposed method could conveniently lend itself to estimate air infiltration rates at a reasonable accuracy using existing CO2 data; however, humidity ratio data (converted from RH and temperature sensor measurements) may only help to track building infiltration characteristics over time due to inaccuracies caused by adsorptive and desorptive properties of various building materials.
•Infiltration rates in a private office are analyzed.•An inverse model-based approach is developed for infiltration estimates.•CO2 and humidity ratio data extracted from a building automation system are used.•Tracer gas tests are conducted to verify the application of the inverse model-based approach.•Pre-requisites of using the proposed approach are discussed.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract
Research on soil water infiltration in equatorial climates like Indonesia is limited. Despite Papua accounting for 29% of Indonesia’s surface water, there’s a shortage of hydrological data. ...This study aimed to identify the best infiltration model tailored to the characteristics of basic infiltration rates in Papua’s small watersheds. Observations were made at 95 points across 11 small watersheds in Papua. Based on equatorial basic infiltration rate theories, analysis classified infiltration values against observation time. The performance of four infiltration models — Horton, Philip, Kostiakov, and Green Ampt — were compared. The results indicated the Philip model as superior, with average scores of 0.901 (R), 0.814 (NSE), and 0.424 (RSR), followed by the Horton and Green Ampt models. These three models showed excellent performance. However, the Kostiakov model was found lacking and needs modification. Further research on rapid and very rapid classifications is vital for enhancing infiltration rate predictions in small equatorial watersheds.
Role of slope on infiltration: A review Morbidelli, Renato; Saltalippi, Carla; Flammini, Alessia ...
Journal of hydrology (Amsterdam),
February 2018, 2018-02-00, Volume:
557
Journal Article
Peer reviewed
•Infiltration models have to be adapted to account for the effects of surface slope.•Conflicting results have been reported on the role of surface slope on infiltration.•We summarize the salient ...points from previous studies.•We offer suggestions to advance our knowledge of infiltration over sloping surfaces.
Partitioning of rainfall at the soil-atmosphere interface is important for both surface and subsurface hydrology, and influences many events of major hydrologic interest such as runoff generation, aquifer recharge, and transport of pollutants in surface waters as well as the vadose zone. This partitioning is achieved through the process of infiltration that has been widely investigated at the local scale, and more recently also at the field scale, by models that were designed for horizontal surfaces. However, infiltration, overland flows, and deep flows in most real situations are generated by rainfall over sloping surfaces that bring in additional effects. Therefore, existing models for local infiltration into homogeneous and layered soils and those as for field-scale infiltration, have to be adapted to account for the effects of surface slope. Various studies have investigated the role of surface slope on infiltration based on a theoretical formulations for the dynamics of infiltration, extensions of the Green-Ampt approach, and from laboratory and field experiments. However, conflicting results have been reported in the scientific literature on the role of surface slope on infiltration. We summarize the salient points from previous studies and provide plausible reasons for discrepancies in conclusions of previous authors, thus leading to a critical assessment of the current state of our understanding on this subject. We offer suggestions for future efforts to advance our knowledge of infiltration over sloping surfaces.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Soil infiltration is an inevitable process of the mutual transformation of surface water and groundwater in the ecological hydrologic cycle that helps to transport nutrients required by plants to the ...root system, thus promoting vegetation growth and maintaining ecological stability. It is of utmost importance to simulate the process of soil infiltration and calculate the key parameters of soil water migration accurately. Yet, a scale effect in the determination of soil infiltration can seldom be avoided. Based on the scale effect law caused by a change in the inner-ring diameter of the double-ring infiltrometer and common infiltration models, empirical models of soil infiltration scale transfer (SIST) are proposed and established to improve the simulation accuracy of the steady infiltration rate, while reducing test difficulty and consumption. The results show that the four SIST models established based on the infiltration models well simulate the infiltration process of five different sizes of double-ring infiltrometers. The simulation Adj-R2 of the three infiltration zones in the study area was between 0.66 and 0.95, and the validation Adj-R2 ranged from 0.72 to 0.94, indicating that the SIST models showed good applicability in the investigated semi-arid grassland. The results further showed that the double-ring infiltrometer with an inner-ring diameter larger than 90 cm and an outer ring buffer coefficient of 0.33 was not accompanied by the scale effect during measurement. Moreover, the SIST models were used to predict the steady infiltration rate in the study area, providing an accurate data basis for the establishment of regional eco-hydrological models.
•SIST functions for double ring infiltration with different bi and di were proposed.•Suitable inner ring diameters can ensure the accuracy and reduce consumption.•Final infiltration rate free from infiltrometer scale effect is predicted.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Catch Crops (CC) and Weeds (W) increase soil organic matter and infiltration rates.•CC and W delay runoff discharge, and reduce soil and water losses.•However, farmers’ perception about CC and W is ...negative.•Thus, farmers should be educated, and given initial subsidies for introducing CC and W practices.
It is needed to find the proper management from a biophysical point of view to promote sustainable agriculture. However, it is also necessary that farmers accept new strategies that propose cultural and technical shifts. A survey of the farmerś perception, and an assessment of the biophysical impact of catch crops (CC) and weeds (W) on soil organic matter, bulk density, infiltration capacity, runoff initiation, runoff discharge and soil detachment at the pedon scale were carried out. The field measurements in the Alcoleja experimental station demonstrated that organic matter and bulk density after 10 years of Vicia sativa L. and Avena sativa L. catch crops and weeds managed plots are similar. Both CC and W plots enhanced high infiltration rates under single ring ponding conditions, the runoff discharge was delayed and decreased; and soil erosion rates were lower in comparison to soil erosion rates measured in chemically managed farms. Soil quality was high for both management strategies and soil erosion rates much sustainable due to the live mulch that catch crops and weeds developed. However, an assessment of the farmerś perception in the Cànyoles river watershed citrus production area in Eastern Spain demonstrated that the farmer’s community did not accept the use of catch crops or weeds. The survey proved that the farmers would accept the use of CC and W if subsidies were paid. The farmers claimed for the payment of the seeds and sowing expenses plus a 57 € ha−1 for the CC and 75 € ha−1 for W on average. The farmers considered the use of CC and W as benefit for the society, but not for them.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Contribution of root decay process on soil water replenishment was assessed.•The macropore formed by decayed root increased the infiltration rate at each stage.•The decayed roots maintain rapid ...preferential infiltration by reducing root density.•Soil water replenishment significantly increased with root decay ages.
Large-scale afforestation has seriously aggravated the consumption of soil water and caused soil desiccation and even the dry soil layers, which has been restricting the survival and sustainability of vegetation in semi-arid areas. How to solve soil water deficit reasonably is an important practical problem we are facing. Here, a field experiment of the decayed roots with different times on soil water infiltration processed was conducted in planted forestland by a double-ring infiltration instrument, to determine the contribution of decayed tree roots on soil water infiltration process and replenishment. Results showed that the decayed process of tree roots in forestland could significantly reduce root density (RD) and increase the relative porosity improved by the roots (RPIR) (P < 0.05). The macropore formed by root decay could not only significantly increase the infiltration rate at each stage (P < 0.05), but also reduce the decrease rate of infiltration rate. Compared with bare land, the decayed roots of the 1–4 yr, the 5–8 yr, and the 9–12 yr increased the amount of soil water replenishment by 37.12%, 217.52%, and 259.85%, respectively. Overall, the decayed tree roots could maintain a relatively high and stable infiltration rate by reduced root density, which increased the effective replenishment of soil water of dry soil layers in forestland. These findings have potential implications for understanding the effect of decay process of tree roots on soil water replenishment, and provide a theoretical basis for the solution to dry soil layers and sustainable management of forestland in semi-arid areas.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Water-repellent (WR) soil greatly influences infiltration behavior. This research determined the impacts of WR levels of silt loam soil layer during infiltration. Three column scenarios were ...utilized, including homogeneous wettable silt loam or sand, silt loam over sand (silt loam/sand), and sand over silt loam (sand/silt loam). A 5-cm thick silt loam soil layer was placed either at the soil surface or 5 cm below the soil surface. The silt loam soil used had been treated to produce different WR levels, wettable, slightly WR, strongly WR, and severely WR. As the WR level increased from wettable to severely WR, the cumulative infiltration decreased. Traditional wetting front-related equations did not adequately describe the infiltration rate and time relationships for layered WR soils. The Kostiakov equation provided a good fit for the first infiltration stage. Average infiltration rates for wettable, slightly WR, strongly WR, and severely WR during the 2nd infiltration stage were 0.126, 0.021, 0.002, and 0.001 mm min−1 for the silt loam/sand scenario, respectively, and 0.112, 0.003, 0.002, and 0.000 5 mm min−1 for the sand/silt loam scenario, respectively. Pseudo-saturation phenomena occurred when visually examining the wetting fronts and from the apparent changes in water content (ΔθAP) at the slightly WR, strongly WR, and severely WR levels for the silt loam/sand scenario. Much larger ΔθAP values indicated the possible existence of finger flow. Delayed water penetration into the surface soil for the strongly WR level in the silt loam/sand scenario suggested negative water heads with infiltration times longer than 10 min. The silt loam/sand soil layers produced sharp transition zones of water content. The WR level of the silt loam soil layer had greater effects on infiltration than the layer position in the column.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
PDF
