This paper describes a study that used permeability measurement along with physical and hydrological characteristics of 20 pervious concrete pavements in parking lots throughout California. The ...permeability was measured at five locations: the main entrance, an area with no traffic, and three separate measurements within a parking space at each parking lot. Hydrological and physical site characteristics such as traffic flow, erosion, vegetation cover, sediments accumulation, maintenance practice, presence of cracking, rainfall, and temperature data were also collected for each parking lot. These data were used to perform detailed statistical analysis to determine factors influencing changes in permeability and hence assessing possible cause of clogging. In addition, seven representative core samples were obtained from four different parking lots with permeability ranging from very low to very high. Porosity profiles produced from CT scanning were used to assess the possible nature and extent of clogging.
Results showed that there is a large variation in permeability within each parking lot and between different parking lots. In general, the age of the parking lot is the predominant factor influencing the permeability. Statistical analysis revealed that fine sediment (particles less than 38
μm) mass is also an important influencing factor. Other influencing factors with lower significance included number of days with a temperature greater than 30
°C and the amount of vegetation next to the parking lot. The combined scanned image analysis and porosity profile of the cores showed that most clogging occurs near the surface of the pavement. While lower porosity generally appeared to be limited to the upper 25
mm, in some core samples evidence of lower porosity was found up to 100
mm below the surface.
► Twenty pervious parking lots were used to investigate possible clogging. ► Hydraulic conductivity within each parking lot was substantially different. ► Hydraulic conductivity of older parking lots was lower than newer parking lots. ► Two dominant factors influencing the hydraulic conductivity were pavement age and particles <38
μm. ► Scan image showed that the porosity of the top 25
mm was generally lower and may be the cause of clogging.
Abstract
Escalating burned area in western US forests punctuated by the 2020 fire season has heightened the need to explore near-term macroscale forest-fire area trajectories. As fires remove fuels ...for subsequent fires, feedbacks may impose constraints on the otherwise climate-driven trend of increasing forest-fire area. Here, we test how fire-fuel feedbacks moderate near-term (2021–2050) climate-driven increases in forest-fire area across the western US. Assuming constant fuels, climate–fire models project a doubling of forest-fire area compared to 1991–2020. Fire-fuel feedbacks only modestly attenuate the projected increase in forest-fire area. Even models with strong feedbacks project increasing interannual variability in forest-fire area and more than a two-fold increase in the likelihood of years exceeding the 2020 fire season. Fuel limitations from fire-fuel feedbacks are unlikely to strongly constrain the profound climate-driven broad-scale increases in forest-fire area by the mid-21st century, highlighting the need for proactive adaptation to increased western US forest-fire impacts.
•Bio-derived ashes, such as rice hull and rice straw ash, can be used in concrete.•Use of rice straw ash is not as well analyzed as rice hull ash in concrete.•Use of rice hull ash in concrete can ...improve certain mechanical properties.•Further analysis is necessary to understand the effects on concrete durability.•Additional analysis is needed to quantify environmental and economic impacts.
The demand for concrete continues to grow with increases in population and increased urbanization. This demand, in turn, increases the need to reduce the environmental impacts of concrete while continuing to provide the same or better performance. Increasing population also creates growing demand for food and energy resources. The cultivation of rice, the staple food of over half the world's inhabitants, results in the production of additional biomass. Rice biomass, such as hulls and straw, can be combusted as a renewable energy source and, under specific combustion conditions, the resulting ash can be used as a supplementary cementitious material or beneficial filler in the production of concrete, which can potentially lead to reduced environmental impacts in concrete.
This paper reviews rice-based ash and its influence on concrete properties to address current understanding of these ashes as an alternative mineral admixture. The review of the literature shows that under proper combustion conditions as well as through use of pre- and post-combustion treatments, highly pozzolanic (reactive) ash can be produced from rice hulls. These reactive ashes have the ability to improve several properties of concrete when used as a partial replacement for cement. Additionally, the production of rice-based ash can offer a lower greenhouse gas emitting pozzolan than portland cement and some conventional supplementary cementitious materials. Further research into the utilization of rice-straw ash, durability properties, and high performance concrete could lead to the production of rice ash as a cost- and environmentally-competitive alternative in the production of concrete.
With the rapid development of cities, more attention has been paid to the stormwater runoff pollution on roads. In this paper, a kind of photocatalytic water purification pavement coated with ...nano-TiO2was developed, which could improve the water purification performance of porous concrete. Through removal rate analysis of three typical pollutants, the improvement of its water purification performance was evaluated. The skid resistance of road surface and durability of purification effect were also studied by using pendulum apparatus and artificial accelerated aging method. The results showed that the removal rates of COD, TP and NH3-N could reach 50%, 60% and 40%, respectively. The application of photocatalytic coating would reduce skid resistance of pavement relatively. Besides, appropriate increase of nano-TiO2content will improve the weather resistance. This study will provide useful insights for the preparation of nano-TiO2photocatalytic coatings for porous cement concrete to improve the water purification effect of roads.
Fully permeable pavement is gradually gaining support as an alternative best management practice (BMP) for stormwater runoff management. As the use of these pavements increases, a definitive test ...method is needed to measure hydraulic performance and to evaluate clogging, both for performance studies and for assessment of permeability for construction quality assurance and maintenance needs assessment. Two of the most commonly used permeability measurement tests for porous asphalt and pervious concrete are the National Center for Asphalt Technology (NCAT) permeameter and ASTM C1701, respectively. This study was undertaken to compare measured values for both methods in the field on a variety of permeable pavements used in current practice. The field measurements were performed using six experimental section designs with different permeable pavement surface types including pervious concrete, porous asphalt and permeable interlocking concrete pavers. Multiple measurements were performed at five locations on each pavement test section. The results showed that: (i) silicone gel is a superior sealing material to prevent water leakage compared with conventional plumbing putty; (ii) both methods (NCAT and ASTM) can effectively be used to measure the permeability of all pavement types and the surface material type will not impact the measurement precision; (iii) the permeability values measured with the ASTM method were 50–90% (75% on average) lower than those measured with the NCAT method; (iv) the larger permeameter cylinder diameter used in the ASTM method improved the reliability and reduced the variability of the measured permeability.
► This study compares the permeability measured by ASTM C1701 and NCAT methods. ► Mix design and binder type did not significantly impact the measurement precision. ► Strong correlation (R2 > 0.72) was observed between the two measurement methods. ► Permeability values measured by the ASTM were generally 50–90% lower than the NCAT method. ► Larger permeameter diameter used in the ASTM reduced the measurement variability.
In Keynes' model, no variety of private sector spending plays a more critical role than investment. This is so because reaching full employment requires that it be large enough to offset the volume ...of saving that would be forthcoming at that level of economic activity, which occurs only rarely and by coincidence. Despite its key role, very few Post Keynesians have undertaken empirical studies of Keynes' approach (as opposed to one based on Keynes). While I suspect that there are a number of reasons for this, perhaps the greatest stumbling block is one related to data: how do we measure not just investors' expectations, but the difference between what was expected and what actually transpired? I believe I have developed a defensible solution to this problem, one that not only allows for a more direct test of Keynes' theory but also offers tremendous support for it.
► We determined the changes in asphalt concrete (AC) microstructure under trafficking. ► We determined the contribution of densification to total accumulated AC rutting. ► Majority of densification ...is occurring at the bottom of construction lift for the PG64-28PM mix. ► A significant shear flow pattern in the direction of traffic was observed for RHMA-G test sections. ► Earlier failure of RHMA-G is due to the gradation and aggregate size induced excessive shear flow.
In this study, a new approach was used to evaluate changes in asphalt concrete microstructure under full-scale accelerated pavement test loading with a Heavy Vehicle Simulator (HVS) of composite pavement. The approach compared X-ray computed tomography (CT) images taken before and after HVS rut testing. Results were used to identify the differences in the movement of aggregate and changes in air-void content and distribution occurring during rutting accumulation of rubberized gap graded and polymer modified dense graded mixes for two overlay thicknesses (64 and 114mm). Although high air void content for the sections constructed with rubberized gap graded mix were expected to cause more densification related rutting and earlier failure related to this densification, the actual reason behind the earlier failure was determined to be primarily greater shear flow to the sides of the wheelpath associated with the gap gradation and small aggregate size. Significant movement of aggregate was observed in the direction of travel as well as to the side under the pushed wheel. Important differences in aggregate movement and air-void changes were also observed between different overlay thicknesses indicating the depth of the rut phenomenon, important information for the design of overlays on aged asphalt concrete as well.
Treating KRAS-mutant lung adenocarcinoma (LUAD) remains a major challenge in cancer treatment given the difficulties associated with directly inhibiting the KRAS oncoprotein. One approach to ...addressing this challenge is to define mutations that frequently co-occur with those in KRAS, which themselves may lead to therapeutic vulnerabilities in tumors. Approximately 20% of KRAS-mutant LUAD tumors carry loss-of-function mutations in the KEAP1 gene encoding Kelch-like ECH-associated protein 1 (refs. 2, 3, 4), a negative regulator of nuclear factor erythroid 2-like 2 (NFE2L2; hereafter NRF2), which is the master transcriptional regulator of the endogenous antioxidant response. The high frequency of mutations in KEAP1 suggests an important role for the oxidative stress response in lung tumorigenesis. Using a CRISPR-Cas9-based approach in a mouse model of KRAS-driven LUAD, we examined the effects of Keap1 loss in lung cancer progression. We show that loss of Keap1 hyperactivates NRF2 and promotes KRAS-driven LUAD in mice. Through a combination of CRISPR-Cas9-based genetic screening and metabolomic analyses, we show that Keap1- or Nrf2-mutant cancers are dependent on increased glutaminolysis, and this property can be therapeutically exploited through the pharmacological inhibition of glutaminase. Finally, we provide a rationale for stratification of human patients with lung cancer harboring KRAS/KEAP1- or KRAS/NRF2-mutant lung tumors as likely to respond to glutaminase inhibition.
To evaluate the efficacy and safety of high-dose, hypofractionated proton beam therapy for hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (ICC).
In this single-arm, phase II, ...multi-institutional study, 92 patients with biopsy-confirmed HCC or ICC, determined to be unresectable by multidisciplinary review, with a Child-Turcotte-Pugh score (CTP) of A or B, ECOG performance status of 0 to 2, no extrahepatic disease, and no prior radiation received 15 fractions of proton therapy to a maximum total dose of 67.5 Gy equivalent. Sample size was calculated to demonstrate > 80% local control (LC) defined by Response Evaluation Criteria in Solid Tumors (RECIST) 1.0 criteria at 2 years for HCC patients, with the parallel goal of obtaining acceptable precision for estimating outcomes for ICC.
Eighty-three patients were evaluable: 44 with HCC, 37 with ICC, and two with mixed HCC/ICC. The CTP score was A for 79.5% of patients and B for 15.7%; 4.8% of patients had no cirrhosis. Prior treatment had been given to 31.8% of HCC patients and 61.5% of ICC patients. The median maximum dimension was 5.0 cm (range, 1.9 to 12.0 cm) for HCC patients and 6.0 cm (range, 2.2 to 10.9 cm) for ICC patients. Multiple tumors were present in 27.3% of HCC patients and in 12.8% of ICC patients. Tumor vascular thrombosis was present in 29.5% of HCC patients and in 28.2% of ICC patients. The median dose delivered to both HCC and ICC patients was 58.0 Gy. With a median follow-up among survivors of 19.5 months, the LC rate at 2 years was 94.8% for HCC and 94.1% for ICC. The overall survival rate at 2 years was 63.2% for HCC and 46.5% ICC.
High-dose hypofractionated proton therapy demonstrated high LC rates for HCC and ICC safely, supporting ongoing phase III trials of radiation in HCC and ICC.
► We developed micromechanical (MM) FE models to predict the shear modulus of asphalt mixes. ► Developed 3D MM FE model is predicting shear modulus at high test temperatures with high accuracy. ► 2D ...numerical models always under predicted the shear modulus for all cases. ► Large vertical displacements occur in the RHMA-G due to the small aggregate size and gradation.
The main objective of this study was to develop 2D and 3D micromechanical finite element (FE) models to predict the shear modulus of two asphalt mixture types, PG 64-28 PM (dense-graded polymer modified mixture) and RHMA-G (gap-graded rubberized mixture). The internal microstructure of the asphalt mixtures were determined by X-ray computed tomography (CT) imaging. X-ray CT images were processed to create 2D and 3D meshed asphalt mixture FE model structures. Meshed model structures were exported to the FE modeling software ABAQUS. Elastic and viscoelastic assumptions were used for modeling aggregate and mastic subdomains, respectively. Shear modulus predictions for 2D and 3D models were compared to the measured values to determine the effectiveness of each model type for the simulation of the shear frequency sweep at constant height (FSCH) test. It was concluded that the 3D micromechanical FE model is capable of predicting shear modulus at relatively high test temperatures with high accuracy across a range of loading frequencies. On the other hand, 2D numerical models always under predicted the shear modulus values at all simulation temperatures and loading frequencies because the reduced microstructure for the 2D models decreased the accuracy of numerical predictions. It is expected that developed 3D models will serve as a valuable tool to understand certain problems in the current design methods of asphalt concrete pavements.
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