Relating Ndesign to Field Compaction: A Case Study in Minnesota

High field density helps in increasing the durability of asphalt pavements. In a current research effort, the University of Minnesota and the Minnesota Department of Transportation (MnDOT) have been working on designing asphalt mixtures with higher field densities. One critical issue is the determination of the Ndesign values for these mixtures. The physical meaning of Ndesign is discussed first. Instead of the traditional approach, in which Ndesign represents a measure of rutting resistance, Ndesign is interpreted as an indication of the compactability of mixtures. The field density data from some recent Minnesota pavement projects are analyzed. A clear negative correlation between Ndesign and field density level is identified, which confirms the significant effect of Ndesign on the compactability and consequently on the field density of mixtures. To achieve consistency between the laboratory and field compaction, it is proposed that Ndesign should be determined to reflect the real field compaction effort. A parameter called the equivalent number of gyrations to field compaction effort (Nequ) is proposed to quantify the field compaction effort, and the Nequ values for some recent Minnesota pavement projects are calculated. The results indicate that the field compaction effort for the current Minnesota projects evaluated corresponds to about 30 gyrations of gyratory compaction. The computed Nequ is then used as the Ndesign for a Superpave 5 mixture placed in a paving project, for which field density data and laboratory performance test results are obtained. The data analysis shows that both the field density and pavement performance of the Superpave 5 mixture are significantly improved compared with the traditional mixtures. The results indicate that Nequ provides a reasonable estimation of field compaction effort, and that Nequ can be used as the Ndesign for achieving higher field densities.

Entorhinal cortex directs learning-related changes in CA1 representations

Learning-related changes in brain activity are thought to underlie adaptive behaviors. For instance, the learning of a reward site by rodents requires the development of an over-representation of that location in the hippocampus. However, how this learning-related change occurs remains unknown. Here we recorded hippocampal CA1 population activity as mice learned a reward location on a linear treadmill. Physiological and pharmacological evidence suggests that the adaptive over-representation required behavioral timescale synaptic plasticity (BTSP). BTSP is known to be driven by dendritic voltage signals that we hypothesized were initiated by input from entorhinal cortex layer 3 (EC3). Accordingly, the CA1 over-representation was largely removed by optogenetic inhibition of EC3 activity. Recordings from EC3 neurons revealed an activity pattern that could provide an instructive signal directing BTSP to generate the over-representation. Consistent with this function, exposure to a second environment possessing a prominent reward-predictive cue resulted in both EC3 activity and CA1 place field density that were more elevated at the cue than the reward. These data indicate that learning-related changes in the hippocampus are produced by synaptic plasticity directed by an instructive signal from the EC3 that appears to be specifically adapted to the behaviorally relevant features of the environment.

Field Density Investigation of Asphalt Mixtures in Minnesota

In a current research effort, University of Minnesota and Minnesota Department of Transportation have been working on designing asphalt mixtures that can be constructed at 5% air voids, similar to the Superpave 5 mix design. High field density of asphalt mixtures is desired because it increases the durability and extends the service life of asphalt pavements. The paper investigates the current situation of field densities in Minnesota, to better understand how much improvement is needed from the current field density level to the desired level, and to identify possible changes to the current mix design to improve field compactability. Field densities and material properties of 15 recently constructed projects in Minnesota are investigated. First, a statistical analysis is performed to study the probability distribution of field densities. Then, a two-way analysis of variance is conducted to check if the nominal maximum aggregate size and traffic levels have any significant effect on field densities. A correlation analysis is then conducted to identify significant correlations between the compactability of mixtures and their material properties. The results show that the field density data approximately obey normal distribution, with an average field density of 93.4% of theoretical maximum specific gravity; there are significant differences in field density between mixtures with different traffic levels; compactability of mixtures is significantly correlated with fine aggregate angularity and fine aggregate gradation of the mixtures.

Korelasi Nilai CBR Dengan kepadatan Lapangan Subbase Course

The durability of the road flexural pavement structure is largelydetermined by the performance of each layer. One of these factors isthe strength and resilience of the subbase. Compaction inaccordance with applicable standards will produce roads with goodquality so that the road life is longer and there is less damage. Thepurpose of this study is to analyze the carrying capacity using CBR,the value of the field density with the sand cone test and thecorrelation of the CBR value and the Sand cone value of the B gradefoundation layer on the Tugu Munajah network. The researchmethod used is laboratory and field testing combined with adescriptive statistic approach.The results of the study indicate that the carrying capacity using theCBR amounted to 55.02% <60%, the density value field with sandcone test of 72.50% <90%. Correlation of CBR and Sand cone value atthe base layer (sub base course) is very strong at 0.998.

Characterization and Optimization of Isotachophoresis Parameters for Pacific Blue Succinimidyl Ester Dye on a PDMS Microfluidic Chip

Isotachophoresis (ITP) for Pacific Blue (PB) dye using a polydimethylsiloxane (PDMS) microfluidic chip is developed and characterized by determining the types and concentrations of electrolytes, the ITP duration, and the electric field density. Among candidate buffers for the trailing electrolyte (TE) and leading electrolyte (LE), 40 mM borate buffer (pH 9) and 200 mM trisaminomethane hydrochloride (Tris-HCl) (pH 8) were selected to obtain the maximum preconcentration and resolution of the PB bands, respectively. With the selected TE and LE buffers, further optimization was performed to determine the electric field (EF) density and the ITP duration. These ITP parameters showed a 20–170,000 preconcentration ratio from initial PB concentrations of 10 nM–100 fM. Further demonstration was implemented to preconcentrate PB-conjugated lactate dehydrogenase (LDH) using the PDMS microfluidic chip. By utilizing the quenching nature of PB-LDH conjugation, we were able to identify concentrations of LDH as low as 10 ng/mL. This simple PDMS microfluidic chip-based ITP for PB preconcentration enables highly sensitive biological and chemical analyses by coupling with various downstream detection systems.

Improving Durability of Asphalt Pavements in Louisiana through Increased In-Place Field Density

The objective of this project was to evaluate the effects of increasing the initial in-place density of asphalt pavements on expected field performance and durability. This study was completed as part of the FHWA’s demonstration project on “Enhanced Durability through Increased In-Place Pavement Density.” Two approaches for increasing in-place density were explored: (i) the addition of an Evotherm warm-mix asphalt (WMA) additive at a dosage rate of 0.6% by the weight of mix; and (ii) the addition of 0.2% asphalt binder (Plus AC) to the design optimum asphalt binder content of standard dense-graded mixtures. The field component of the research involved three 4,000-ft long test sections representing control hot-mix asphalt (HMA) mixtures, Evotherm WMA mixtures, and the Plus AC HMA mixtures. Each test section included a binder and a wearing course for a total of six mixtures. Density measurements were determined in the laboratory from field cores taken at each test section. The high- and intermediate-temperature properties of field cores were evaluated using the Loaded Wheel Tracking and Semi-Circular Bending tests, respectively. Further, the Indirect Tensile Dynamic Modulus (IDT |E*|) test was conducted for full viscoelastic characterization of the asphalt mixtures. The two approaches considered in this study were successful in increasing field density, especially for the binder course mixtures. The two strategies for increasing in-place density also resulted in better than expected resistance to cracking and rutting, as well as an increase in mixture stiffness as measured by the IDT |E*|.