Oxidation Hardening Kinetics of the Rheological Function G′/(η′/G′) in Asphalts

Abstract

The authors used 9 asphalts oxidized at various temperatures and pressures to determine the hardening kinetics for the DSR function, an easily measured and meaningful surrogate for 15°C ductility that relates well to age-related binder deterioration. For each asphalt, there is a rapid initial period that slows to a constant rate period. This constant rate period can be represented by carbonyl formation (oxidation) rate times a hardening susceptibility (HS). For the DSR function and viscosity, the HS and initial jump were pressure- but not temperature-dependent. The DSR function initial jump was relatively higher than the viscosity initial jump.     

Oxygen Diffusivity in Asphalts and Mastics

Determination of oxygen diffusivity in binders was made by comparing the oxidation rates at the surface and at a solid–binder interface of an asphalt film of known reaction kinetics. For neat asphalts, oxygen diffusivities (D _{O 2} ) ranged from 10^?10 to 10^?11 m²/s, with log(D _{O 2} /T) varying linearly with log(η _o *) for both base asphalts and polymer-modified binders (PMBs). For asphalt mastics, oxygen diffusivity was observed to decrease as the filler volume fraction increased. Quantitatively, this effect follows a theoretical estimate of the effect of a dilute suspension of spherical inclusions on diffusivity.     

Modeling Asphalt Oxidation in Pavement With Field Validation

A model for asphalt oxidation in pavement was developed based on fundamentals of oxygen diffusion in the mastic and reaction with asphalt. Diffusion depth, a concept different from the conventional film thickness, defined the oxygen diffusion region in the mastic. A field calibration factor accounted for the factors not considered in the model such as the effect of small aggregate particles on oxygen diffusion. Carbonyl area and viscosity of binders recovered from field cores were measured and were used for model calibration and validation. Results demonstrated that the proposed model estimates carbonyl growth over time in pavement, layer by layer, quite well.     

Identification and characterization of Saccharomyces cerevisiae strains isolated from West African sorghum beer

The occurrence and characterization of yeasts isolated from sorghum beer produced in Ghana and Burkina Faso, West Africa, were investigated. The yeasts involved in the fermentations were found to consist of Saccharomyces spp. almost exclusively. Of the isolates investigated, 45% were identified as Saccharomyces cerevisiae, whereas more than half of the isolates (53%) had physiological properties atypical of S. cerevisiae or any other member of the complex sensu strictu, as they were able to assimilate only glucose, maltose and ethanol as carbon sources. Both ITS-PCR RFLP and PFGE strongly indicated that these isolates were related to S. cerevisiae, regardless of their phenotypic characteristics. Sequencing of the D1/D2 domain of the 26S rDNA confirmed the close relatedness to S. cerevisiae with 0.5% nucleotide differences. The MAL1 and MAL3 loci were found for all isolates as the only recognized MAL loci. Besides, for 40% of the isolates the MAL61 probe hybridized to a position of about 950 kbp, which has not formerly been described as a MAL locus. The results showed that the spontaneous fermentation of West African sorghum beer is dominated by a variety of strains of S.cerevisiae not previously described, among which starter cultures should be selected.     

Intelligent scheduling with tabu search: An application to jobs with linear delay penalties and sequence-dependent setup costs and times

In this article we study thetabu search (TS) method in an application for solving an important class of scheduling problems. Tabu search is characterized by integrating artificial intelligence and optimization principles, with particular emphasis on exploiting flexible memory structures, to yield a highly effective solution procedure. We first discuss the problem of minimizing the sum of the setup costs and linear delay penalties when N jobs, arriving at time zero, are to be scheduled for sequential processing on a continuously available machine. A prototype TS method is developed for this problem using the common approach of exchanging the position of two jobs to transform one schedule into another. A more powerful method is then developed that employs insert moves in combination with swap moves to search the solution space. This method and the best parameters found for it during the preliminary experimentation with the prototype procedure are used to obtain solutions to a more complex problem that considers setup times in addition to setup costs. In this case, our procedure succeeded in finding optimal solutions to all problems for which these solutions are known and a better solution to a larger problem for which optimizing procedures exceeded a specified time limit (branch and bound) or reached a memory overflow (branch and bound/dynamic programming) before normal termination. These experiments confirm not only the effectiveness but also the robustness of the TS method, in terms of the solution quality obtained with a common set of parameter choices for two related but different problems.     

ExoPranayama: a biofeedback-driven actuated environment for supporting yoga breathing practices

Both breathing and internal self-awareness are an integral part of any yoga practice. We describe and discuss the development of ExoPranayama, an actuated environment that physically manifests users’ breathing in yoga. Through a series of trials with yoga practitioners and expert teachers, we explore its role in the practice of yoga. Our interview results reveal that biofeedback through the environment supported teaching and improved self-awareness, but it impacted group cohesion. Two practical uses of the technology emerged for supporting breath control in yoga: (1) biofeedback can provide new information about users’ current internal states; (2) machine-driven feedback provides users with a future state or goal and leads to improved cohesiveness.     

THE EFFECT OF ASPHALT COMPOSITION ON THE FORMATION OF ASPHALTENES AND THEIR CONTRIBUTION TO ASPHALT VISCOSITY

Interactions among asphalt components have significant effects on the performance of asphalt binder. To understand those interactions, four asphalts, SHRP AAA-I, AAD-I, AAF-I, and AAG-I, were fractionated into three generic fractions according to Corbett's procedure and reblended into asphaltenes/aromatics/saturates ternary mixtures in various ratios. Mixtures were oxidatively aged with atmospheric air at temperatures of 87.7, 93.3, and 98.8°C for 5 to 33 days. The changes in chemical composition and physical properties were monitored using fourier transform infrared spectroscopy (FT-IR) and dynamic mechanical rheometry

The formation of asphaltenes is a major factor in the hardening of asphalt with aging. The data collected in this study indicate that the saturate content in the maltene phase has a profound impact on the contribution that asphaltenes have on the viscosity of aged asphalt. The data also suggest that the aromatics fraction is solely responsible for the formation of asphaltenes as an asphalt oxidizes.     

Major hydrocarbons of the post-pharyngeal glands of mated queens of the red imported fire antSolenopsis invicta

Thin layer and column chromatographic analyses showed that hydrocarbons were the major lipoidal components of post-pharyngeal glands of mated queens of the red imported fire ant,Solenopsis invicta. Gas liquid chromatographic analyses on an OV-17 column showed four major hydrocarbons which have been identified and confirmed by synthesis and comparative mass spectral analyses as 13-methylheptacosane, 13,15-dimethylheptacosane, 3-methylheptacosane, and 3,9-dimethylheptacosane. When microgram quantitites of the natural alkanes on filter paper were placed in colonies of ants, the ants clustered on the paper about the sample and proceeded to masticate the paper in the area containing the alkanes.     

Rational approximation of a class of infinite-dimensional systems I: Singular values of hankel operators

In order to establish the optimal rates of convergence for the infinity-norm rational approximation problem, upper and lower bounds on the singular values of a class of Hankel operators are established. These asymptotically accurate estimates are derived from results on the singular values of Hankel operators with symbol equal to the product of a rational function and an exponential function, combined with results on Hankel integral operators (in continuous time) whose kernels have certain smoothness properties.     

Filial therapy with Native Americans on the Flathead Reservation.

[Correction Notice: An erratum for this article was reported in Vol 18(1) of International Journal of Play Therapy (see record 2009-00564-006). This article was originally published with the wrong first page. Printed issues contain the first page for the preceding article, "Effectiveness of Filial Therapy for Korean Parents," by Mikyung Jang. The online version has been revised to present the correct first page. The URL for the corrected online version is provided in the erratum.] Examined the effectiveness of the 10-wk filial therapy model as an intervention for 25 Native American parents (aged 23–46 yrs) and their 21 children (aged 3–10 yrs) residing on the Flathead Reservation in Montana. Results show that Native American parents significantly increased their level of empathy in their interactions with their children. Children significantly increased their level of desirable play behaviors with their parents. (PsycINFO Database Record (c) 2010 APA, all rights reserved)