Resting-State Quantitative Electroencephalography Reveals Increased Neurophysiologic Connectivity in Depression

Symptoms of Major Depressive Disorder (MDD) are hypothesized to arise from dysfunction in brain networks linking the limbic system and cortical regions. Alterations in brain functional cortical connectivity in resting-state networks have been detected with functional imaging techniques, but neurophysiologic connectivity measures have not been systematically examined. We used weighted network analysis to examine resting state functional connectivity as measured by quantitative electroencephalographic (qEEG) coherence in 121 unmedicated subjects with MDD and 37 healthy controls. Subjects with MDD had significantly higher overall coherence as compared to controls in the delta (0.5–4 Hz), theta (4–8 Hz), alpha (8–12 Hz), and beta (12–20 Hz) frequency bands. The frontopolar region contained the greatest number of “hub nodes” (surface recording locations) with high connectivity. MDD subjects expressed higher theta and alpha coherence primarily in longer distance connections between frontopolar and temporal or parietooccipital regions, and higher beta coherence primarily in connections within and between electrodes overlying the dorsolateral prefrontal cortical (DLPFC) or temporal regions. Nearest centroid analysis indicated that MDD subjects were best characterized by six alpha band connections primarily involving the prefrontal region. The present findings indicate a loss of selectivity in resting functional connectivity in MDD. The overall greater coherence observed in depressed subjects establishes a new context for the interpretation of previous studies showing differences in frontal alpha power and synchrony between subjects with MDD and normal controls. These results can inform the development of qEEG state and trait biomarkers for MDD

High-temperature rheological behavior and fatigue performance of lignin modified asphalt binder

The objective of this study was to introduce lignin as a bio-additive to modify the base asphalt and investigate the high-temperature rheological performances of lignin modified asphalts and virgin asphalt. In this study, asphalt PG 58-28 was selected as the virgin asphalt, and four contents, 2%, 4%, 6% and 8%, of the total binder by weight of lignin were incorporated in the base binder. Rotational viscosity (RV), dynamic shear rheometer (DSR), and multiple stress creep recovery (MSCR) tests were conducted to characterize the rheological performances of different types of asphalts. Linear amplitude sweep (LAS) test was employed to evaluate the fatigue performance. The results showed that the incorporation of lignin increased the viscosity of virgin asphalt at different rotational speeds. The activation energy showed an increasing trend as the lignin increased compared with the virgin asphalt. Meanwhile, the lignin incorporated into the asphalt binder increased the elastic components, and improved the resistance of asphalt binder to the permanent deformation regardless of the lignin contents. The addition of lignin in the asphalt binder could retard oxidation reactions that occurred in the asphalt during the rolling thin film oven aging. In addition, the incorporation of lignin may degrade the fatigue life of asphalt. However, when the content of lignin was less than 8%, the reduction was small. This study could provide a prospective foundation for the utilization of lignin extracted from waste biomass as an exceptional and renewable bio-additive in the field of asphalt pavement engineering

Laboratory investigation of fatigue parameters characteristics of aging asphalt mixtures: A dissipated energy approach

The objective of this paper is to reveal the effects of aging on the fatigue performance of asphalt mixture based on variation patterns of fatigue parameters with aging degrees. Specimens with different aging degrees were prepared by modified SHRP’s Long-Term-Oven Aging (LTOA) test method, in which five different aging durations, included 0, 1, 3, 5, 7 days, were adopted to substitute the fixed 5 days. The fatigue parameters, including stiffness modulus, fatigue life, phase angle, Plateau Value (PV), and cumulative dissipation energy of specimens with different aging degrees under different stress ratios were obtained by the tensile fatigue test. The relationship of fatigue parameters with aging degrees and stress ratios were established. It could be observed from the results that the aging degree and stress ratio had dramatic influences on the fatigue performance of asphalt mixture. Sensitivity analysis showed that aging had the most significant effect on the initial stiffness modulus of asphalt mixture, and should be used as a control index in fatigue design. Statistical models of the relation between (PV) and fatigue life (Nf) established by the Rate of Dissipated Energy Change (RDEC) approach has an effective correlation. The Plateau Value model eliminated the effects of aging degrees and reflected the uniqueness of material parameters. Also, it could provide novel ideas for effective prediction of the fatigue life of asphalt mixtures with different aging degrees based on plateau value

The performance of asphalt binder with trichloroethylene: Improving the efficiency of using reclaimed asphalt pavement

The objectives of this research are to investigate the effect of solvent in asphalt binder, and to propose a method to determine the actual performance of asphalt binder extracted from asphalt mixture thus improving the efficiency of using RAP. The Fourier-transform infrared spectroscopy (FTIR) test was used to analyze the functional groups of trichloroethylene (TCE) and asphalt binder with TCE. This test also qualitatively and quantitatively evaluated the influence of solvent in asphalt binder. Dynamic Shear Rheometer (DSR) test was employed to measure the complex shear modulus (|G∗|) of asphalt binder with different TCE contents and to establish the relationship between the TCE contents and the |G∗| of asphalt binder. Based on the testing results, functional group = C–H of TCE can be used as an indicator to verify the existence of TCE in the extracted asphalt binder. Both band areas 834-848 cm-1 and 918-938 cm-1 changed for PG 58–28 and Pressure Aging Vessel (PAV) aged PG 58-28 binder after the addition of TCE. Band area 918-938 cm-1 can better reflect the influence of TCE in asphalt binder. Band area 834-848 cm-1 did not change when TCE content was at a low level. Both the existence of TCE and the content of TCE had a significant influence on the |G*| of unaged and PAV aged PG 58–28 asphalt binder. A regression function was built to establish the relationship between the TCE content and |G*|. With the method developed in this study, the correlation between the TCE amount and the FTIR spectrum area was quantified. The actual |G∗| of asphalt binder without TCE can be back calculated. The method used in this study provided guidance for the determination of asphalt binder performance extracted from RAP, which can be beneficial to the design of asphalt mixtures with RAP

Waste cathode-ray-tube glass powder modified asphalt materials: Preparation and characterization

Cathode-ray-tube (CRT) is the ingredient of glass used in obsolescent televisions or computer monitors. CRT glass contains a considerable amount of heavy metals, and the landfilling of CRT glass is significantly harmful to the environment. In an effort to recycle waste CRT glass instead of landfilling it, recycled CRT glass powders were introduced to asphalt binders as a modifier in this preliminary investigation. The recycled CRT glass was processed to a particle size smaller than 0.075 mm and mixed with asphalt binder (PG 58–28) to produce asphalt mastics with four different concentrations (0, 5, 10, and 15 wt%). The rheological performance was characterized with the rotational viscosity (RV), dynamic shear rheometer (DSR), and multiple stress creep recovery (MSCR) tests. The fatigue performance was evaluated by linear amplitude sweep (LAS) test. Meanwhile, the low-temperature properties were measured by the asphalt binder cracking device (ABCD). The hazard materials leaching test was applied to evaluate the leaching potential of lead content into the external environment due to the high lead content in the modified asphalt. The test results revealed that the increase of CRT glass powder content improved the energy of activation compared with that of virgin binder, as well as the resistance of permanent deformation. Furthermore, the incorporation of CRT glass powder may slightly increase the fatigue life of asphalt because of the improved physicochemical interaction between glass and bitumen. The low-temperature cracking temperature first decreased with the increase of CRT glass powder content and then increased as the CRT content increased further. The leaching test demonstrated that the CRT glass powders incorporated into asphalt binders represented a lower lead leaching content than that of the original CRT glass powder, where the lead leaching amount of CRT glass modified asphalt binder is obviously lower than the specified level of 5 mg/L. Therefore, it is possibly acceptable to recycle CRT glass powders in asphalt binders as an additive as an environmental-friendly recycling method, in which the optimal addition content of CRT glass powders could be up to 10% (wt.)

Laboratory Performance and Field Case Study of Asphalt Mixture with Sasobit Treated Aramid Fiber as Modifier

The use of fiber in asphalt mixtures can improve the mixture’s tensile strength and increase its cracking resistance, but the clumping of fiber in the mixture can weaken the improvement effect. The aim of this research is to assess the properties of Sasobit treated aramid fiber modified asphalt mixture and to validate the field case study. The rutting and stripping resistance of the fiber-modified mixture was identified with the Hamburg wheel tracking device. The low-temperature cracking characteristics of the asphalt mixture were quantified with the disk-shaped compact tension test. Moreover, the dynamic modulus test was adopted to reflect the response of the mixture to different loads and frequencies. The creep slope and stripping slope decreased by 67%, and the number of passes to stripping point and fail point increased by more than 250% after fiber modification. The fracture energy, peak load, and maximum crack mouth opening displacement (CMOD) of the mixture increased more than 10% after fiber modification. The dynamic modulus, rutting parameter, and fatigue parameter of the mixture were improved after fiber modification. The fiber in the mixture improved the stiffness of the mixture at high temperatures. The tensile strength improvement at low temperatures promoted the cracking resistance of the mixture. The cracking number in the fiber modified asphalt pavement was less than that in the control asphalt pavement. Thus, fiber modification could significantly restrict the propagation of cracking in the asphalt mixture. The implementation of fiber in the project can provide experience for future fiber application in asphalt pavement

Investigation of hot mixture asphalt with high ground tire rubber content

Stockpiles of waste tires pose concerns of potential contamination of local groundwater, and fire risk from the large amounts of tires. To sustainably use the waste tires, Ground Tire Rubber (GTR) that produced from waste tires has been used in the pavement industry for decades. The typical GTR content is approximately 1–3% by weight of the asphalt mixture. To utilize more waste tires, there is an increasing demanding of using higher amount of GTR in recent years. The objective of this study was to determine the high GTR content that can be used in the asphalt pavement without sacrificing performance. In this study, gap-graded mixtures modified with differing GTR contents were designed. These GTR contents were 2.6%, 3.4%, 3.7%, 4.1% and 4.5% by weight of the mixture. Statistical analysis was conducted to determine the influence of GTR content on the mixture performance. It was found that the fracture energy of the GTR modified mixture was two to three times higher than that of the control mixture. All of the mixtures seemed to provide adequate rutting resistance for low-volume traffic, signifying that after 5000 wheel passes, the rutting depth did not exceed the 12.5-mm. The GTR modified gap-graded mixtures had high resistance to low-temperature cracking and high-temperature rutting. This can partly be attributed to the addition of GTR and the skeleton structure from gap gradation. The result of multiple comparisons suggested that even though the addition of GTR in dense-graded mixtures did not significantly improve the high-temperature performance, the addition of GTR in asphalt mixtures significantly improved the low-temperature performance