Mycobacterium tuberculosis (Mtb) is an obligate aerobe that is capable of long-term persistence under conditions of low oxygen tension. Analysis of the Mtb genome predicts the existence of a branched ...aerobic respiratory chain terminating in a cytochrome bd system and a cytochrome aa3system. Both chains can be initiated with type II NADH:menaquinone oxidoreductase. We present a detailed biochemical characterization of the aerobic respiratory chains from Mtb and show that phenothiazine analogs specifically inhibit NADH:menaquinone oxidoreductase activity. The emergence of drug-resistant strains of Mtb has prompted a search for antimycobacterial agents. Several phenothiazines analogs are highly tuberculocidal in vitro, suppress Mtb growth in a mouse model of acute infection, and represent lead compounds that may give rise to a class of selective antibiotics.
This paper systematically studies the effects of asphalt foam characteristics and pulverized asphalt pavement (PAP) material attributes on foamed asphalt mix strength. A fracture face image analysis ...procedure was employed to quantify asphalt dispersion, which was key to establishing the relationships between material microstructural features and measured strengths. Foamability of asphalts was found to be one of the primary factors determining foamed asphalt mix quality. Foams with higher expansion ratios and longer half-life have better dispersion through granular materials, resulting in greater strength improvement. High fines contents in the PAP materials negatively affect mix strength by producing a continuous and weak unbonded mineral filler phase. The microstructural analysis found that typically unquantified physical, chemical and/or mineralogical characteristics of the PAP materials significantly affect asphalt dispersion quality and mastic strength. Therefore, the suitability of PAP materials and available binders for foamed asphalt stabilization should be evaluated for each individual project.
An ongoing research effort seeks to develop alternative asphalt surface mixes that will be quiet and durable without sacrificing safety. The effects of several common combinations of binder type and ...additive on noise reduction and durability of an open-graded asphalt mix with small aggregate size were investigated. Five binder types and two additives were selected for a 4.75-mm nominal maximum aggregate size gradation. A series of laboratory tests was conducted to evaluate their performance-related pavement surface properties. Results showed that the use of polymer-modified or rubberized binders instead of unmodified binder in the 4.75-mm open-graded mixture reduced permeability but increased acoustic absorption, with the mixture containing asphalt rubber binder showing the most acoustic absorption improvement. The use of asphalt rubber could also increase the mixture resistance to moisture damage, premature failure, raveling, and rutting. There were preliminary indications of friction improvement by replacement of conventional binder with asphalt rubber binder in the small-size-aggregate, open-graded asphalt mix.
Abstract
Because of abundant reserves and renewable and environmentally friendly properties, the utilization of woody biomass waste in road engineering can alleviate the shortage of fossil fuels and ...carbon emissions so as to mitigate global climate change and achieve sustainable development of road engineering. This paper synthesizes the state of the art about the strategies of applying five kinds of resources derived from waste woody biomass, including biochar, bio-oil, lignin, wood ash and nanocellulose to road construction. Based on the characteristics analysis of the five materials, it can be concluded that biochar can comprehensively improve the road performance of asphalt and its mixtures, and has the potential of runoff purification; bio-oil can soften asphalt and improve its low-temperature performance, but has negative effects on high-temperature performance; lignin increases the asphalt ageing resistance and can be used as a regenerant, and will improve the overall performance of asphalt mixtures if combined with other modifiers; wood ash can increase subgrade bearing capacity and bring significant environmental benefits; nanocellulose improves the strength of cement mortar, but there is a lack of research on its effects on performance of pavement materials and the interaction mechanism; the lifecycle environmental and economic assessment of woody biomass-modified road materials is not comprehensive. Moreover, prospects were also summarized to show the opportunities for future study, such as the establishment of a database for biomass. This review provides useful insights for the utilization of woody biomass as road materials to achieve waste management and sustainable development.
Highlights
• Reveal the characteristics of five kinds of materials derived from woody biomass wastes for use as road materials.
• The effects of biochar, bio-oil, lignin, wood ash and nanocellulose on road material performance are summarized.
• The use of woody biomass such as biochar and bio-oil in road materials contributes to reducing carbon emissions.
• Existing problems and future research prospects about the woody biomass waste used in the road structure are put forward.
► We develop a fully heterogeneous viscoelastic finite element model for full-scale accelerated pavement testing. ► We examine changes in the strain and displacement distributions for four test ...sections. ► Performance rankings from the fully heterogeneous FE models are similar to the in-situ performance rankings. ► High near-surface shear strains can be an important cause of near surface rutting failure on highways. ► Asphalt mix type is an important factor controlling critical strain locations within the depth of AC layers.
This paper presents a full-scale fully heterogeneous finite element (FE) pavement model developed from X-ray computed-tomography images of asphalt concrete (AC) samples. The model was first developed to simulate a laboratory shear test. Second, model parameters determined for the laboratory shear tests were used to develop FE models for full-scale pavement test sections. A virtual strain gauge was also included in the models for calibration. Calibrated models were used to evaluate the strain-displacement distributions for all test sections. Recommendations are also presented for future use of the model developed in this study to investigate important problems in the design of asphalt pavements.
Binder blending charts are used to determine the selection of virgin binder grade of asphalt mixes containing more than 25% reclaimed asphalt pavement (RAP) as part of the Superpave volumetric mix ...design procedures. However, the extraction and recovery of RAP binder used as part of the binder blending charts process is expensive, hazardous, and poses potential threats to human health and the environment due to the solvents used. An alternative two-phase approach was developed in this study that uses fine aggregate matrix (FAM) mix testing with the help of predictive models. The first phase is to determine the predictive model fitting parameters using the results of virgin binders and virgin FAM mixes. The second phase involves using these model-fitting parameters along with the predictive models to estimate the performance grade of the binders within the FAM mixes containing RAP. The predicted performance grades are compared with the actual performance grade of the RAP/virgin binder blend. The results indicate that the proposed approach can be used to estimate the intermediate and low PG temperatures of the blended binder within the FAM mixes containing RAP with an acceptable accuracy compared to the blending charts approach. The use of FAM mixes also allows consideration of the blending of the RAP and virgin binders, compared with solvent extraction which results in complete blending.
In this study, predictions of full-scale micromechanical (MM) finite element (FE) models, developed from X-ray computed tomography images of asphalt concrete samples that were sawn from the ...accelerated pavement test sections, were used to evaluate the accuracy of layered elastic theory (LET) models that are used in pavement design today. First, MM FE and LET models were both calibrated using the measured strain gauge responses. Predictions of calibrated models were compared to evaluate the reasonableness of LET model outputs at high temperatures. Second, asphalt concrete stiffnesses measured in the laboratory were directly used for LET model development without performing any strain gauge calibration to evaluate the actual predictive capability of LET models in pavement design by using the calibrated MM FE model outputs as the ground truth. Recommendations were also made for future use of the MM FE models to improve the predictive capability of LET models.
AbstractThis paper summarizes the results of numerous simulations to assess the hydraulic performance of fully permeable highway shoulder retrofits designed to capture all the rainfall runoff falling ...onto conventional highway surface pavements. The simulations were performed using commercially available HYDRUS software that uses unsaturated flow theory. The hydraulic properties of subgrade soil and pavement materials were measured in the laboratory and used as input for numerical simulation. The simulations were performed for three rainfall regions in California representing high, medium, and low annual rainfall events. The simulations were performed based on 24-h actual rainfall data using 2-, 50-, and 100-year storm recurrences to determine the critical thickness of aggregate needed to capture the highway runoff volume without surface ponding and/or overflow. Sensitivity analyses were performed to evaluate the influence of material, hydrologic, and geometric factors on the critical aggregate base thickness. Results indicated that an aggregate depth of about 1.5 m was adequate for most California areas with two-lane highways. Sensitivity analyses also revealed that the saturated hydraulic conductivity (Ks) of the subgrade soil is the most important parameter to be considered in the design of fully permeable pavements, with a minimum effective allowable value of approximately 10-5 cm/s.
Kawasaki disease is an acute vasculitis of infants and young children that is recognized through a constellation of clinical signs that can mimic other benign conditions of childhood. The etiology ...remains unknown and there is no specific laboratory-based test to identify patients with Kawasaki disease. Treatment to prevent the complication of coronary artery aneurysms is most effective if administered early in the course of the illness. We sought to develop a diagnostic algorithm to help clinicians distinguish Kawasaki disease patients from febrile controls to allow timely initiation of treatment.
Urine peptidome profiling and whole blood cell type-specific gene expression analyses were integrated with clinical multivariate analysis to improve differentiation of Kawasaki disease subjects from febrile controls.
Comparative analyses of multidimensional protein identification using 23 pooled Kawasaki disease and 23 pooled febrile control urine peptide samples revealed 139 candidate markers, of which 13 were confirmed (area under the receiver operating characteristic curve (ROC AUC 0.919)) in an independent cohort of 30 Kawasaki disease and 30 febrile control urine peptidomes. Cell type-specific analysis of microarrays (csSAM) on 26 Kawasaki disease and 13 febrile control whole blood samples revealed a 32-lymphocyte-specific-gene panel (ROC AUC 0.969). The integration of the urine/blood based biomarker panels and a multivariate analysis of 7 clinical parameters (ROC AUC 0.803) effectively stratified 441 Kawasaki disease and 342 febrile control subjects to diagnose Kawasaki disease.
A hybrid approach using a multi-step diagnostic algorithm integrating both clinical and molecular findings was successful in differentiating children with acute Kawasaki disease from febrile controls.
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