In this study a new procedure is developed to obtain core samples from field sections to assess clogging mechanisms of open graded friction course (OGFC) pavements using X-ray computed tomography ...(CT) imaging. The approach compared X-ray computed tomography (CT) images taken before and after: (1) rainfall simulations without trafficking to investigate particle-related clogging and (2) full-scale accelerated pavement rutting tests (APT) to investigate deformation related clogging of OGFC layers. Rainfall simulations were performed with runoff water of known total suspended solids (TSS) and particle size distributions (PSDs). Full-scale accelerated rutting tests were performed under controlled temperature and loads. Both investigations were performed for three different OGFC pavements with different layer thicknesses and mix types. The clogging of rutting test sections were also evaluated by comparing the surface permeability measurements performed before and after APT testing.
The results of X-ray CT image processing revealed a significant reduction in air-void content of core samples after APT rutting tests. The highest air-void reduction was concentrated at the bottom of the OGFC layers. Permeability measurements also showed a 40%–90% reduction in permeability after APT trafficking. X-ray CT image processing of core samples tested under simulated rainfall showed that air void content reduction is concentrated in the lower part (2–6 mm from the bottom) of the OGFC layers as a result of particle accumulation. Small changes in air void contents were observed in the upper part of the OGFC layers (10–15 mm) while these reductions in air void contents were not significant to cause surface overflow and hence it is expected that the tested OGFC pavements will have sufficient permeability to infiltrate water during most average storm events.
•We investigated OGFC clogging under HVS and rainfall simulations.•We developed a new procedure to core pavement samples for X-ray CT image evaluation.•Air void content (AVC) of OGFCs reduced by 22–35% due to permanent deformation.•Particle related clogging did not affect the infiltration functionality.•Majority of the permeability reduction in OGFC was related to rutting.
Both Helicobacter pylori infection and a high-salt diet are risk factors for gastric cancer. We previously showed that a mutation in
(encoding the ferric uptake regulator variant Fur-R88H) was ...positively selected in H. pylori strains isolated from experimentally infected Mongolian gerbils receiving a high-salt diet. In the present study, we report that continuous H. pylori growth in high-salt conditions
also leads to positive selection of the
-R88H mutation. Competition experiments with strains containing wild-type
or
-R88H, each labeled with unique nucleotide barcodes, showed that the
-R88H mutation enhances H. pylori fitness under high-salt conditions but reduces H. pylori fitness under routine culture conditions. The fitness advantage of the
-R88H mutant under high-salt conditions was abrogated by the addition of supplemental iron. To test the hypothesis that the
-R88H mutation alters the regulatory properties of Fur, we compared the transcriptional profiles of strains containing wild-type
or
-R88H. Increased transcript levels of
, which encodes a predicted TonB-dependent outer membrane transporter, were detected in the
-R88H variant compared to those in the strain containing wild-type
under both high-salt and routine conditions. Competition experiments showed that
contributes to H. pylori fitness under both high-salt and routine conditions. These results provide new insights into mechanisms by which the
-R88H mutation confers a selective advantage to H. pylori in high-salt environments.
•Rutting mechanisms of open-graded asphalt friction courses (OGFC) under full-scale loading is investigated.•We measured the full-scale load related changes in OGFC microstructure using X-ray CT ...imaging.•Thick DGAC layers under OGFC might also induce early rutting failures.•Densification is the major factor controlling OGFC and DGAC rutting.•OGFC layer thickness is the major factor affecting the OGFC rutting mechanisms and performance.
This study aims to identify the permanent deformation accumulation mechanisms of open graded friction course (OGFC) mixes under full-scale loading. Changes in OGFC and underlying dense graded asphalt concrete (DGAC) layers’ microstructures under full scale trafficking were determined using X-ray computed tomography (CT) images taken before and after accelerated pavements tests (APT). Image processing and particle tracking methods were used to identify changes in air-void and aggregate distributions to evaluate the rutting mechanisms of multi-layered (OGFC on DGAC) asphalt concrete sections. Densification was observed to be the major factor controlling the rutting on test sections while shear related deformation was just a minor contributor. Based on APT and laboratory test results, OGFC layer thickness was determined to be the major factor affecting the OGFC rutting mechanisms and performance. Displacement vector distributions for the OGFC layers appeared to be larger than the distributions for the DGAC layers due to the high initial air void content for the OGFC layers. However, significant deformation of the DGAC layers suggested that thick underlying DGAC layers might also induce early rutting failures. Results of this study provide experimental data for continued development of multi-scale continuum mechanics and discrete element method analysis approaches for multi-layered flexible pavement structures.
IMPORTANCE: In one-third of older men with anemia, no recognized cause can be found. OBJECTIVE: To determine if testosterone treatment of men 65 years or older with unequivocally low testosterone ...levels and unexplained anemia would increase their hemoglobin concentration. DESIGN, SETTING, AND PARTICIPANTS: A double-blinded, placebo-controlled trial with treatment allocation by minimization using 788 men 65 years or older who have average testosterone levels of less than 275 ng/dL. Of 788 participants, 126 were anemic (hemoglobin ≤12.7 g/dL), 62 of whom had no known cause. The trial was conducted in 12 academic medical centers in the United States from June 2010 to June 2014. INTERVENTIONS: Testosterone gel, the dose adjusted to maintain the testosterone levels normal for young men, or placebo gel for 12 months. MAIN OUTCOMES AND MEASURES: The percent of men with unexplained anemia whose hemoglobin levels increased by 1.0 g/dL or more in response to testosterone compared with placebo. The statistical analysis was intent-to-treat by a logistic mixed effects model adjusted for balancing factors. RESULTS: The men had a mean age of 74.8 years and body mass index (BMI) (calculated as weight in kilograms divided by height in meters squared) of 30.7; 84.9% were white. Testosterone treatment resulted in a greater percentage of men with unexplained anemia whose month 12 hemoglobin levels had increased by 1.0 g/dL or more over baseline (54%) than did placebo (15%) (adjusted OR, 31.5; 95% CI, 3.7-277.8; P = .002) and a greater percentage of men who at month 12 were no longer anemic (58.3%) compared with placebo (22.2%) (adjusted OR, 17.0; 95% CI, 2.8-104.0; P = .002). Testosterone treatment also resulted in a greater percentage of men with anemia of known cause whose month 12 hemoglobin levels had increased by 1.0 g/dL or more (52%) than did placebo (19%) (adjusted OR, 8.2; 95% CI, 2.1-31.9; P = .003). Testosterone treatment resulted in a hemoglobin concentration of more than 17.5 g/dL in 6 men who had not been anemic at baseline. CONCLUSIONS AND RELEVANCE: Among older men with low testosterone levels, testosterone treatment significantly increased the hemoglobin levels of those with unexplained anemia as well as those with anemia from known causes. These increases may be of clinical value, as suggested by the magnitude of the changes and the correction of anemia in most men, but the overall health benefits remain to be established. Measurement of testosterone levels might be considered in men 65 years or older who have unexplained anemia and symptoms of low testosterone levels. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00799617
In the future, permeable pavements including the full depth permeable pavement (FDPP) will be part of an integrated sustainable transportation program. When designed properly, FDPP can be used as an ...alternative best management practice (BMP) for stormwater runoff management. From a practical point of view, FDPP must maintain specific characteristics throughout the life of the pavements: (1) have adequate subgrade reservoir capacity to capture runoff volume, (2) surface pavement remain highly permeable and unclogged, (3) allowing minimum permeability of subgrade soil to infiltrate the captured runoff, and (4) assuring no adverse impact on underground water. During the past ten years the University of California Pavement Research Center (UCPRC) conducted numerous research studies to address some of the above critical questions related to the application of permeable pavement with respect to the highway stormwater runoff management. The focus of this paper is to discuss and summarize the major findings of these collective studies related to: (1) hydraulic performance evaluation of permeable pavement, (2) permeability measurement of porous asphalt and pervious concrete paved surfaces, (3) clogging evaluation of permeable pavement surfaces, and (4) water quality and pollution control issues.
colonizes the stomach in about half of the world's population.
strains containing the
pathogenicity island (
PAI) are associated with a higher risk of gastric adenocarcinoma or peptic ulcer disease ...than
PAI-negative strains. The
PAI encodes a type IV secretion system (T4SS) that mediates delivery of the CagA effector protein as well as nonprotein bacterial constituents into gastric epithelial cells.
-induced nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation and interleukin-8 (IL-8) secretion are attributed to T4SS-dependent delivery of lipopolysaccharide metabolites and peptidoglycan into host cells, and Toll-like receptor 9 (TLR9) activation is attributed to delivery of bacterial DNA. In this study, we analyzed the bacterial energetic requirements associated with these cellular alterations. Mutant strains lacking Cagα, Cagβ, or CagE (putative ATPases corresponding to VirB11, VirD4, and VirB4 in prototypical T4SSs) were capable of T4SS core complex assembly but defective in CagA translocation into host cells. Thus, the three Cag ATPases are not functionally redundant. Cagα and CagE were required for
-induced NF-κB activation, IL-8 secretion, and TLR9 activation, but Cagβ was dispensable for these responses. We identified putative ATP-binding motifs (Walker-A and Walker-B) in each of the ATPases and generated mutant strains in which these motifs were altered. Each of the Walker box mutant strains exhibited properties identical to those of the corresponding deletion mutant strains. These data suggest that Cag T4SS-dependent delivery of nonprotein bacterial constituents into host cells occurs through mechanisms different from those used for recruitment and delivery of CagA into host cells.
•Suggestions are presented to improve Hamburg Wheel Tracking Device (HWTD) test.•2D-MMFE analysis has demonstrated significant gap/bonding and specimen shape effects on test results.•The analysis ...suggests the best method for defining the “rut depth” to ensure consistent results.•Rut depths should be collected from stations near the centers of specimens.•An agency should not allow both specimen setups to be used interchangeably.
The Hamburg Wheel-Track Device (HWTD) test has recently gained popularity among many state highway departments of transportation (DOTs) for use in hot mix asphalt (HMA) moisture sensitivity evaluation. In this paper, suggestions are presented to improve and provide more consistent and representative results for this test as described in AASHTOT324 – Hamburg Wheel-Track Testing of Compacted Hot Mix Asphalt (HMA). In the AASHTOT324 specification, either a cylindrical or a slab specimen can be tested. Use of a two-dimensional micromechanics finite element (2D-MMFE) analysis has demonstrated significant gap/bonding and specimen shape effects on HWTD test results for the cylindrical specimen setup. In addition, the analysis suggests the best method for defining the “rut depth” to ensure consistent results between two specimen setups. Results of this study have concluded that: (1) slab specimens can provide more reliable test results due to larger size and uniform geometry; (2) two cylindrical specimens (cores) should be glued together to prevent localized failure due to larger peak maximum principal strains when there is no bonding; (3) measurements of average rut depth should be collected from stations near the centers of cylindrical specimens to keep the specimen shape effects to the lowest possible level; and, (4) an agency should not allow both specimen setups to be used interchangeably in the HWTD specifications. The investigation also suggests that the average rut depth evolution curve fitted using a three-stage Weibull approach can define the number of passes to failure and define the stripping initiation point (SIP) better than the visually determined SIP.
AbstractThe California Department of Transportation has proposed to add a low amount of crumb-rubber modifier into dense-graded asphalt mixes, in addition to current policies of using gap- and ...open-graded mixes with a high content of rubber (around 20% by weight of binder) as the surface layers. The objectives are to reduce landfill disposal of scrap tires and to obtain equal or better performance compared to current dense-graded mixes containing unmodified binders. This paper investigated a new type of rubberized dense-graded mix containing 5% and 10% of the crumb-rubber modifier. The rubberized binder and the unmodified binder were compared at the same performance grade to meet the specific climate requirement. Their corresponding mixes met the Superpave volumetric design requirements. The laboratory experiment evaluated the rubberized mix and the conventional mix in terms of fatigue and fracture properties using a flexural bending fatigue test and semicircular bending test, respectively. A long-term oven-aging protocol and the uniaxial thermal stress and strain testing were used to evaluate the mix resistance to low-temperature cracking. Those laboratory test results indicated that the rubberized dense-graded mix had an extended fatigue life, higher fracture resistance, and better thermal cracking resistance than the standard dense-graded mix. Mechanistic-empirical (ME) design using the California ME design software simulated the performance of these mixes in various pavement structures and climate/traffic conditions to assess the interactions of stiffness and strain-controlled fatigue property for those mixes. The simulation results revealed that the new rubberized dense-graded mix mostly provided the same or better field performance as the conventional mix. The ME design analysis should be performed to optimize the application of those mixes in a case by case scenario.
Stay-green plants retain green leaves longer after anthesis and can have improved yield, particularly under water limitation. As senescence is a dynamic process, genotypes with different senescence ...patterns may exhibit similar final normalised difference vegetative index (NDVI). By monitoring NDVI from as early as awn emergence to maturity, we demonstrate that analysing senescence dynamics improves insight into genotypic stay-green variation. A senescence evaluation tool was developed to fit a logistic function to NDVI data and used to analyse data from three environments for a wheat (Triticum aestivum L.) population whose lines contrast for stay-green. Key stay-green traits were estimated including, maximum NDVI, senescence rate and a trait integrating NDVI variation after anthesis, as well as the timing from anthesis to onset, midpoint and conclusion of senescence. The integrative trait and the timing to onset and mid-senescence exhibited high positive correlations with yield and a high heritability in the three studied environments. Senescence rate was correlated with yield in some environments, whereas maximum NDVI was associated with yield in a drought-stressed environment. Where resources preclude frequent measurements, we found that NDVI measurements may be restricted to the period of rapid senescence, but caution is required when dealing with lines of different phenology. In contrast, regular monitoring during the whole period after flowering allows the estimation of senescence dynamics traits that may be reliably compared across genotypes and environments. We anticipate that selection for stay-green traits will enhance genetic progress towards high-yielding, stay-green germplasm.
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