Search

The morphological characteristics of mineral filler particles, such as contour shape, angularity and surface texture, are closely related to their mineralogy and size and the crushing process used. In the present study, the importance and effects of particle mineralogy and size on the morphology of different mineral fillers were examined. A total of 12 mineral filler fractions were prepared using the same grinding process and sieving method, and analyzed by digital imaging. Six parameters were used to describe the 2-dimensional characteristics of mineral filler particles based on digital image processing. The sensitivity of these parameters was analyzed by correlation and analysis of variance methods. The results show that for mineral fillers of the same particle mineralogy, as the particle size decreases, the contour shape becomes more regular and the angularity and surface texture becomes less abundant. For mineral fillers of the same particle size, the granite filler particles have a more regular contour shape and richer angularity and surface texture than the limestone and basalt filler particles. The form factor, angularity parameter AI1 and fractal dimension can best reflect the sensitivity of contour shape, angularity and surface texture characteristics of mineral filler particles to particle mineralogy and size.

The objective of this present work was to evaluate the rheological and cracking behavior of mastics fabricated with different sized particles and asphalt types. Two asphalts (base and modified) and three fillers with different sized particles (C, M and F) were investigated. The rheological functions including the creep and recovery property and the fatigue property were measured by multiple stress creep-recovery (MSCR) and time sweep (TS) tests, respectively, while the cracking behavior of asphalt materials was investigated using extensile (ES) tests. Moreover, the dispersion characteristics of various sized particles inside a bituminous matrix and the associated mastic morphology were assessed by a scanning electron microscope (SEM). The results revealed that the presence of coarse-sized particles in matrix increased the non-recoverable compliance and fracture energy but decreased fatigue life of the mastics. The presence of medium-sized particles in matrix enhanced the high-temperature elasticity recovery behavior and degraded the low-temperature fracture energy and the cohesive strength of asphalt mastics, regardless of asphalt types. When filler particle size dropped down to a minimum dimension, asphalt type had negligible effects on the fatigue response and exerted a positive effect on the low-temperature cohesive strength for the related mastics. In addition, the dispersion characteristics of various sized particles inside a bituminous matrix and the associated mastic morphology can account for the rheological response and cracking behavior of the corresponding mastics.

Water damage is one of the main forms of early damage of highway asphalt pavement, which seriously affects the service performance of asphalt pavement. To address the problem of early water damage of asphalt pavement, the addition of anti-stripping agents in asphalt is an effective technical means. To further analyze the influence of anti-stripping agents on asphalt performance, Qingchuan rock asphalt, acylamine anti-stripping agent, fatty amine anti-stripping agent, rock asphalt + acylamine anti-stripping agent and rock asphalt + fatty amine anti-stripping agent were selected to modify the base asphalt. The rheological properties of modified asphalt were tested using a dynamic shear rheometer and bending beam rheometer. Combined with the mathematical-model-fitting test results of Sigmoidal, Burgers, viscoelastic continuum damage model (VECD), etc., the effects of different anti-stripping agents on the rheological properties of asphalt were evaluated through model parameters. The results showed that the Qingchuan rock asphalt could improve the high-temperature resistance to deformation of asphalt and improved the resistance to deformation of asphalt in a wide frequency domain but increased the risk of low-temperature cracking of asphalt. Acylamine anti-stripping agents and aliphatic amine anti-stripping agents reduced the elastic recovery ability and deformation resistance under a wide frequency domain of asphalt at high temperatures but enhanced the flexible deformation and ductility of asphalt at low temperatures. The compound anti-stripping agent not only improved the high-temperature deformation resistance of asphalt, but also improved the deficiency of rock asphalt’s low-temperature performance and effectively enhanced its performance.

The primary objective of this study was to investigate the feasibility of the dispersion of fillers dispersion as individual particles and evaluate the effects of the morphological characteristics of filler particles on the rheological properties of asphalt mastics at high and medium temperatures. For a given source and filler, three various filler particle sizes produced from different crushers (i.e., a jaw crusher, an impact crusher and a ball grinding mill) were obtained, namely, F1 (P200-R300: passing a 200-mesh and retained by a 300-mesh sieve), F2 (P400-R500) and F3 (P800-R1000). The binary image particle analysis system was employed to acquire the morphological characteristics of filler particles such as form factor, angularity and surface texture. By applying multiple stress creep and recovery (MSCR) tests at high temperature and time sweep (TS) tests at medium temperature, the rheological properties of asphalt mastics prepared with different filler particle sizes were also investigated. Furthermore, the correlations between the morphological characteristics of filler particles and the high/medium-temperature properties of asphalt mastics were studied by grey relational analysis (GRA) method. Results showed that the proposed new approach to sample preparation was demonstrated to be effective in achieving filler particle dispersion. The GRA demonstrated that the rheological properties of asphalt mastics at high and medium temperatures were significantly affected by the morphological characteristics of the filler particles. Percent recovery (R) and fatigue law fitting coefficients (A and B) were more sensitive to porosity, angularity index, average diameter, aspect ratio and fractal dimension but less sensitive to feature roughness, roundness, convexity ratio, density and specific surface area. In terms of non-recoverable creep compliance (Jnr), the sensibility was apparently reversed, with the reference sequence Jnr presenting less susceptibility to porosity, angularity index, average diameter, aspect ratio and fractal dimension. The GRA results can inform engineers regarding the selection of filler particles that produce asphalt mastics with desired performance characteristics, such as specific rutting resistance and fatigue failure.

7530 Background: Patients undergoing allogeneic hematopoietic cell transplant (HCT) or solid organ transplant (SOT) are at risk of developing Epstein–Barr virus driven post-transplant lymphoproliferative disorder (EBV+ PTLD), a rare hematologic malignancy, which is often aggressive and life-threatening. Patients with relapsed or refractory (r/r) EBV+ PTLD have few treatment options with poor outcomes, demonstrating a clear unmet medical need. Tabelecleucel is an investigational, off-the-shelf, allogeneic EBV-specific T-cell immunotherapy being studied in patients with serious EBV+ diseases (NCT04554914 & NCT03394365) that has demonstrated clinical benefit and favorable safety profile in the treatment of EBV+ PTLD after failure of rituximab (R) ± chemotherapy (Prockop, EBMT 2021, ATC 2021, ASH 2021). Methods: Atara Biotherapeutics supports an ongoing expanded access program (EAP) in Europe for patients with EBV+ diseases who have no other treatment options. Here we report demographics, efficacy and safety results of r/r EBV+ PTLD patients following SOT or HCT who presented between Jul 2020 and Nov 2021 and consented to research. Results: A total of 48 EAP requests from 9 countries for patients with EBV+ diseases were received. Twenty-two patients from 7 countries consented to this research: 16 EBV+ PTLD and 6 EBV+ non-PTLD. Of the 16 PTLD patients 15 received at least one dose of tabelecleucel. Overall, 9 out of 15 (60%) patients achieved a response as assessed by the treating physician, with 6 complete responses and 3 partial responses. Eight out of nine responses were seen after the first cycle. No adverse events were reported as related to tabelecleucel by the treating physician. Conclusions: The successful execution of this European EAP demonstrates the feasibility to deliver an off-the-shelf allogeneic EBV+ T-cell therapy in time-sensitive clinical situations when no other treatment options exist. These data show clinically meaningful outcomes for patients with r/r EBV+PTLD post-SOT or post-HCT treated with tabelecleucel consistent with previously reported favorable safety and efficacy profile (Prockop, ASH 2021).[Table: see text]

Asphalts often have filler particles added to improve their mechanical properties. Three distinct filler particle fractions were produced by a planetary high-energy ball mill from limestone aggregates (2.36–4.75 mm). Their particle sizes and shapes were studied by binary image processing and related to milling time and aperture size. The relaxation properties of asphalt mastics prepared with fillers of various sizes and shapes were investigated at a constant strain. Insights into the effects of particle size and shape on mastic relaxation behavior were gained by single regression analysis (SRA) in conjunction with grey relational analysis (GRA). The results show that particle size distributions had noticeable local differences in their slopes and spread, while particle shape distributions showed a narrow range of variability for the studied shape descriptors. Based on stress relaxation curves, fine particles were found to cause binders to become stressed more rapidly than coarse particles. Modified mastics showed much faster stress relaxation than corresponding base mastics at stage I, and exhibited higher stable stress levels than base mastics at stage II. A stress relaxation model was established and found to agree well with experimental data, indicating that mastic relaxation properties can be effectively modeled. Furthermore, the SRA coupled with GRA can provide a simple and effective approach to predicting the effects of particle size and shape on mastic relaxation behavior.

The performance of asphalt can be improved using various additives, such as SBS (styrene-butadienestyrene) and crumbed rubber (CR). This paper investigated the influence of CR particle size and SBS structure on the properties of CR/SBS modified binders. CR/SBS composite modified asphalts were obtained by mixing asphalt, CR of various particle sizes, and SBS copolymers with various molecular structures, and were then subjected to conventional measurements, rheological characterization, and thermal storage tests. The results demonstrated that larger CR particles enhanced rutting and fatigue resistance but reduced low-temperature cracking resistance and storage stability. Modified asphalt containing 20 wt% styrene showed the best rheological properties, followed by those with 30 wt% and 40 wt% styrene. Meanwhile, SBS copolymers with lower styrene contents showed better thermal storage stability. Addition of larger CR particles and lower-styrene SBS copolymers increased rutting and fatigue resistance, while smaller CR particles and lower-styrene SBS copolymers benefited low-temperature cracking resistance and stability. The combination of CR and SBS copolymers has a synergistic effect on asphalt’s rheological properties, thereby lowering the amounts of additives required and improving the cost-effectiveness of CR/SBS modified asphalt.

Background and Objective: The popular assumption of ignorability simplifies analyses with incomplete data, but if it is not satisfied, results may be incorrect. Therefore it is necessary to assess the sensitivity of empirical findings to this assumption. We have created a user-friendly and freely available software program to conduct such analyses. Method: One can evaluate the dependence of inferences on the assumption of ignorability by measuring their sensitivity to its violation. One tool for such an analysis is the index of local sensitivity to nonignorability (ISNI), which evaluates the rate of change of parameter estimates to the assumed degree of nonignorability in the neighborhood of an ignorable model. Computation of ISNI avoids the need to estimate a nonignorable model or to posit a specific magnitude of nonignorability. Our new R package, named isni, implements ISNI analysis for some common data structures and corresponding statistical models. Result: The isni package computes ISNI in the generalized linear model for independent data, and in the marginal multivariate Gaussian model and the linear mixed model for longitudinal/clustered data. It allows for arbitrary patterns of missingness caused by dropout and/or intermittent missingness. Examples illustrate its use and features. Conclusions: The R package isni enables a systematic and efficient sensitivity analysis that informs evaluations of reliability and validity of empirical findings from incomplete data.

The application of asphalt with low penetration in warm areas to improve rutting-resistance has attracted great interest in recent years. Deoiled asphalt (DOA) and slurry, by-products of solvent deasphalting and fluid catalytic cracking respectively, are utilized with low value-added. The objective of this work was to prepare paving grade asphalt by blending various proportion of FCC slurry with DOA. The effect of chemical composition on viscoelastic characteristics of the blend was investigated and special emphasis was placed on the linear viscoelasticity and viscous flow behavior as well as on empirical tests. The results revealed that SARA fractions of the blends are close to asphalt and are compromise between DOA in which the content of asphaltenes is high and slurry in which is rich in aromatics. Also, SARA fractions have a significant influence on the rheological properties of the blends. Asphaltenes have been proved to enhance the moduli of asphalt and low penetration blends have demonstrated high rutting and deformation resistance especially at high temperatures. Taking into account the balance between workability and in-service performance, application of the 40 wt% slurry in DOA is highly recommended. It is indicated that a more inferior aging resistance with the increase of slurry in DOA. As a result, it is a highly effective and meaningful way to utilize DOA and FCC slurry.

The rheological properties and storage stability of CR/SBS modified asphalt have been investigated in this study. Crumb rubber (CR) as well as SBS was blended with asphalt having different chemical composition to prepare CR/SBS modified asphalt by high-shear mixer. Linear viscoelastic and viscous measurements, fluorescence microscopy as well as storage stability tests were performed on unmodified and CR/SBS modified asphalt. The results revealed that the addition of CR/SBS to asphalt produces a remarkable improvement in viscoelastic characteristics and viscosity compared with neat asphalt. Consequently, an enhanced resistance to permanent deformation is expected in road. Crumb rubber replacing parts of SBS to produce CR/SBS modified asphalt is feasible because failure temperature, moduli and viscosity undergo a significantly increase when the dosage of SBS exceeds 1%. The chemical composition of base asphalt for this special modification is crucial. In other words, moderate asphaltenes and high aromatics are suggested in order to achieve desired rheological properties. CR/SBS modified asphalt appears obvious phase separation at the storing period resulting from coalescence of SBS particle at the top of sample and sedimentation of rubber particles at the bottom. Thus, CR/SBS modified asphalt must be used swiftly after which has been produced owing to its poor storage stability. Anyhow, crumb rubber could be an alternative for reducing use of virgin SBS from economic and environmental point of view.

Recycled-polymer modified asphalt has been extensively used in road construction, especially the recycled tire scrap rubber-modified asphalt (TSRMA). However, the main problem during the application of TSRMA is poor storage stability which finally affects the service performance of the pavement. The objective of this work is to evaluate viscous properties, storage stability and morphology of TSRMA and to reveal the relationship of microstructure with rheological behavior and storage stability. With this aim, two different penetration grade asphalts were modified by rubber particles with various mean diameter in a four-paddle mixer at 170 °C. Steady state flow measurements, frequency sweep tests in linear viscoelastic region, storage stability tests as well as fluorescence microscopy were carried out on mixes. Rheological evaluation reveals that the addition of tire scrap rubber to asphalt lead to a significant increase in viscosity at 60 °C, improving rutting or permanent deformation resistance. Furthermore, the increase in particle size causes an enhancement in viscosity and the steady flow behavior tend to turn into non-Newtonian fluid with increasing particle size and temperature. Storage tests presented that the viscosity of samples obtained from the bottom section of a tube are always higher and the difference also becomes significant as the increase of rubber particles size, tending to poor stability. Fluorescence microscopy shows that dispersed particles in asphalt are the elongated features or strip-type and the aspect ratio (length/diameter) increases with particle size. In addition, smaller particle tend to be unobvious in matrix under microscopy view, indicating improved compatibility between rubber and asphalt.

Fatigue cracking is caused by repeated traffic loads and environmental conditions (temperature, ageing, etc.); it predominantly initiates within the mastic phase in the form of micro-cracks. In this sense, bituminous mastics (comprised of a binder, filler and entrapped air) play a significant role in the anti-fatigue performance of asphalt mixes. In this paper, the effects of filler particle size and ageing on the fatigue behaviour of bituminous mastics were evaluated. Prior to this, the rheological properties of the studied samples were evaluated using physical tests and frequency sweep tests. Moreover, the mastic morphology and filler distribution inside a bituminous matrix were characterized by Scan Electronic Microscope (SEM). The results revealed that ageing had a greater effect than filler particle size on the rheological behaviour of SBS-modified bituminous mastics, especially for mastics containing coarse filler particles. According to the ageing responses derived from log-log fatigue law plots, aged mastics containing coarse filler particles had higher slopes (represented by coefficient B) and lower intercepts (identified by coefficient A) than un-aged mastics. However, opposite fatigue behaviour was observed with fine filler granules, where coefficient B slightly decreased while coefficient A slightly increased after ageing. In addition, mastic morphology and filler dispersion inside a bituminous matrix were characterized by SEM, providing insight to possible relationships between morphological characteristics and fatigue performance.

Crumb rubber (CR) modified asphalt always presents very poor storage stability. In addition, CR modified asphalt is often prepared with a large amount of CR powders to obtain superior performance, but this modification results in increased instability. In this context, the use of polyphosphoric acid (PPA) was proposed to alleviate these issues. The influences of PPA content and asphalt composition on the properties of CR modified asphalt and its microstructure were studied by conventional test, rheological test, thermal storage test and attenuated total reflection Fourier transform infrared spectrometer (ATR-FTIR) characterization. It was found that the rheological behaviors of CR modified asphalt were improved by adding PPA. PPA also improved the storage stability by increasing the viscosity of CR modified asphalt at the storage temperature. Moreover, asphalt composition also has an influence on the properties. High asphaltenes content increases the rutting resistance and low temperature cracking resistance but reduces the fatigue resistance, while high resins content helps increase the storage stability. ATR-FTIR characterization results demonstrated that PPA/CR modification is both a chemical and a physical process. The adsorption peak area ratio (PAR) value derived from ATR-FTIR can indicate the degree of PPA/CR modification from the microscopic perspective. The relationship between the PAR value and PPA content helps determine the acid concentration of modified asphalt. In conclusion, PPA/CR modification is very promising for its potential in improving the storage stability and the rheological behaviors of CR modified asphalt.

In this study, the conventional and rheological analysis methods are employed to evaluate the effects of filler particle size and filler/bitumen (F/B) ratio on the high and low temperature performance of asphalt mastics. It is found that the addition of mineral fillers can significantly improve the high temperature rutting resistance of asphalt mastics. Meanwhile, it is detrimental to thermal cracking behavior. As the increase of particle size, the percent recovery R, creep stiffness S and m-value increase, while non recoverable creep compliance Jnr decrease. In addition, scanning electron microscope (SEM) imaging analysis shows that the dispersion degree and the morphology of asphalt mastics with various particle sizes have the great differences.

Talin mediates integrin signaling by binding to integrin cytoplasmic tails through its FERM domain which consists of F1, F2 and F3 subdomains. TA205, an anti-talin monoclonal antibody, disrupts actin stress fibers and focal adhesion when microinjected into fibroblasts. Here, we showed that TA205 caused an allosteric inhibition of integrin alphaIIb beta3 binding to the talin FERM domain and mapped the TA205 epitope to residues 131-150 in talin F1. Furthermore, binding of a talin rod fragment to talin head was partially inhibited by TA205. These findings suggest that talin F1 may be important in regulation of integrin binding and talin head-rod interaction.

Talin, consisting of a 47-kDa N-terminal head domain (residues 1-433) and a 190-kDa C-terminal rod domain (residues 434-2541), links integrins to the actin cytoskeleton. We previously reported that the binding stoichiometry of integrin alpha(IIb)beta(3):talin is approximately 2:1. More recently, an integrin binding site has been localized to the talin head domain. In the present study, we identified another integrin binding site at the C-terminal region of the talin rod domain. In a solid phase binding assay, RGD affinity-purified alpha(IIb)beta(3) bound in a dose-dependent manner to microtiter wells coated with the isolated 190-kDa proteolytic fragment of the talin rod domain. Additionally, alpha(IIb)beta(3) also bound to the talin rod domain captured by 8d4, an anti-talin monoclonal antibody. Polyclonal antibodies raised against a recombinant protein fragment corresponding to the entire talin rod domain (anti-talin-R) inhibited alpha(IIb)beta(3) binding to intact talin by approximately 50% but completely blocked alpha(IIb)beta(3) binding to the talin rod domain. To localize the integrin binding site, we examined alpha(IIb)beta(3) binding to recombinant polypeptide fragments corresponding to partial sequences of the talin rod domain. Whereas alpha(IIb)beta(3) bound effectively to talin-(1075-2541) and talin-(1984-2541), it failed to bind to talin-(434-1076) and talin-(434-1975). Furthermore, the binding of alpha(IIb)beta(3) to talin-(1984-2541) was inhibited by anti-talin-R. These results indicate that an integrin binding site is located within residues 1984-2541 of the talin rod domain. Thus, talin contains two integrin binding sites, one in the homologous FERM (band four-point-one, ezrin, radixin, moesin) domain and another near its C terminus. Because talin exists as an anti-parallel homodimer in focal adhesions, the two integrin binding sites in the adjacent talin molecules would be in close proximity with each other.