Effect of warm mix additives on the interfacial bonding characteristics of asphalt binders

The quality of the interfacial bonding between asphalt binder and aggregates plays a significant role in determining the durability of asphalt mixtures. Warm mix asphalt (WMA) modifiers have been used extensively in the last decade primarily to reduce production and compaction temperatures as well as to improve workability of asphalt mixtures. This study aimed to provide better understanding of the effects of these WMA modifiers on the interfacial bonding between asphalt binders and aggregates. The evaluation focused on measuring surface energy of binders in unaged and aged states and aggregates and then calculating energy parameters that describe the potential of a given asphalt-aggregate combination to resist fatigue cracking and moisture damage. Results show that the combination of asphalt-WMA additive, as well as the content applied of WMA additive has a significant impact on the fatigue cracking and moisture damage resistance. The results suggest that it is poor practice to use a given type and percentage of WMA modifier without regard for binder type. Instead, test methods are recommended to evaluate the compatibility of asphalt binder, WMA additive type/content, and aggregates for improved performance at different conditions.     

A novel human type II cytokeratin, K6hf, specifically expressed in the companion layer of the hair follicle

In an attempt to identify new members of the human type II hair keratin family by means of 3'- and 5'-RACE methods and cDNA from anagen hair follicles, we detected a sequence that encoded a hitherto unknown type II cytokeratin. The novel cytokeratin comprises 251 amino acids and exhibits the highest sequence homology with K5. Comparative one- and two-dimensional western blots of keratins from anagen hair bulbs, containing or not containing the outer and inner root sheaths (ORS/IRS), and from footsole epidermis with an antibody against the new cytokeratin, revealed its comigration with K6 and its expression in the ORS/IRS complex. We have therefore named the new cytokeratin K6hf, to distinguish it from the various K6 isoforms and to indicate its expression in the hair follicle. Both in situ hybridization with a K6hf-specific cRNA probe and indirect immunofluorescence with the K6hf antibody showed that K6hf is exclusively expressed in the so-called "companion layer" of the hair follicle, a single layered band of flat and vertically oriented cells between the cuboidal ORS cells and the IRS that stretches from the lowermost bulb region to the isthmus of the follicle. Concomitant K17 and K16 expression studies showed that besides suprabasal ORS cells, these cytokeratins are sequentially expressed subsequent to K6hf in companion cells above the hair bulb. Our study confirms the view of a vertically oriented companion layer differentiation. The clearly delayed K17 and K16 expression relative to that of K6hf in companion cells most probably excludes these keratins as possible type I partners of K6hf and suggests the existence of a still unknown type I partner of its own. Thus, not only morphologically but also biochemically, the companion layer is different from the ORS and can therefore be regarded as an independent histologic compartment of the hair follicle.     

Cancer predisposition, radiosensitivity and the risk of radiation-induced cancers. IV. Prediction of risks in relatives of cancer-predisposed individuals

Individuals carrying cancer-predisposing germline mutations are known to be at a higher risk for cancers than those who do not carry them. This is also true of their biological relatives because they have a higher probability of being carriers of such mutant genes than unrelated individuals in the population. Further, there are now sufficient grounds for assuming that cancer-predisposed individuals may also be at a higher risk for cancers induced by ionizing radiation. In our earlier work, we examined the impact of this heterogeneity (with respect to cancer predisposition and radiosensitivity differentials) on risks of radiation-induced cancer at the population level. This paper is focused on the question of risks of radiation-induced cancer in relatives of cancer-predisposed individuals. Using an autosomal dominant model of cancer predisposition and radiosensitivity developed earlier and applying it to breast cancer risks associated with mutations in the BRCA1 gene, we show that: (1) The risk ratio (i.e. the ratio of risk of radiation-induced cancer in relatives to that in unrelated individuals) in the population increases with the degree of biological relatedness of the relative, being higher for close than for distant relatives; incomplete penetrance of the mutant gene "dilutes" this risk ratio. (2) The proportion of excess radiation-induced cancers in relatives (i.e. the attributable fraction) is higher than in unrelated individuals. (3) In relatives, the proportion of excess cancers due to radiosensitivity differentials alone depends on the strength of predisposition, the radiosensitivity differentials assumed, the radiation dose, the proportion of cancers due to predisposition, the mutant gene frequency and the penetrance of the mutant gene. This is in contrast to the situation for unrelated individuals, for whom the above-mentioned proportion is dependent on the first three but not on the last three of these factors. Further, even when the proportion of excess cancers is small, most of it is due to radiosensitivity differential alone both in unrelated individuals and in relatives. (4) For values of predisposition strength and radiosensitivity differential <10, even when the estimated frequency of a mutant BRCA1 gene is 0.0047 and the proportion of breast cancers due to these mutations is 38% (as is the case for Ashkenazi Jewish women under age 30), the increase in breast cancer risks is only marginal even for first-degree relatives. (5) These findings support the conclusion that increases in radiation risks to relatives (compared to those in unrelated individuals), to be detectable epidemiologically, will occur only when the mutant alleles are common and the strength of predisposition and radiosensitivity differentials are conjointly dramatic.     

Evaluation of terrain and canopy height products in central African tropical forests

Since the introduction of space-based altimetry data into the science community, global products associated with elevation and vegetation metrics have been heavily utilized for a variety of ecological applications. Satellite remote sensing enables the collection of global (or near-global), standardized data sets, which can be used in their original form or used as inputs along with other data sets in generating new products. Recent effort has focused on using available data to generate maps of tree heights at a global scale in the service of a better understanding of above ground biomass distribution and its effects on global carbon storage. However, global data sets, while validated at a global scale, often display local and regional variations in accuracy which must be quantified before applying those data sets to smaller scale studies. This work addresses the need for a better understanding of the quality of the Shuttle Radar Topography Mission (SRTM) 90 m digital elevation model and a global 1 km canopy height model in the dense tropical forests of Gabon by using a small-footprint airborne lidar survey and large-footprint, space-based waveform lidar data from teh National Air and Space Administration’s Ice, Cloud, and land Elevation Satellite (ICESat) for validation. As expected, the study found SRTM elevations to be heavily biased by vegetation in this biome, with elevations consistently located within the canopy volume. In addition, the global canopy height model consistently underestimates maximum canopy height at both local and regional scales.     

Pseudo-tandem stenosis of the internal carotid artery

Two cases of pseudo-tandem stenosis of the internal carotid artery are presented. Proximal stenosis was produced by a large, focal atherosclerotic plaque. The severe intracranial "stenosis" was thought to be an angiographic artifact. Repeat cerebral angiography after carotid endarterectomy revealed normal intracranial arteries. The recognition of this entity is important because a decision to operate is based largely upon angiographic findings.     

Optical sensing of biomolecules using microring resonators

A biosensor application of vertically coupled glass microring resonators with Q/spl sim/12 000 is introduced. Using balanced photodetection, very high signal to noise ratios, and thus high sensitivity to refractive index changes (limit of detection of 1.8/spl times/10/sup -5/ refractive index units), are achieved. Ellipsometry and X-ray photoelectron spectroscopy results indicate successful modification of biosensor surfaces. Experimental data obtained separately for a bulk change of refractive index of the medium and for avidin-biotin binding on the ring surface are reported. Excellent repeatability and close-to-complete surface regeneration after binding are experimentally demonstrated.     

Viscoplastic modeling of asphalt mixes with the effects of anisotropy, damage and aggregate characteristics

This paper presents an approach for constitutive modeling of the viscoplastic behavior of asphalt mixes. This approach utilizes an anisotropic non-associated flow rule based on the Drucker–Prager yield surface. The selection of this yield surface is motivated by the field stress paths and material properties associated with permanent deformation at high temperatures. The efficacy of the model is demonstrated by analyzing data from compressive triaxial tests conducted at different confining pressures and strain rates for three different mixes. The model parameters are related to the experimental measurements of aggregate shape characteristics, aggregate surface energy, inherent anisotropic distribution of aggregates, and microstructure damage measured using X-ray computed tomography and image analysis techniques. Establishing the relationship between the model parameters and material properties is important in order to optimize the mix properties, and achieve desirable mix performance.     

Radiation Heat Transfer and Vapor Shielding in a Two-Dimensional Model of an Electrothermal Plasma Source

Electrothermal (ET) plasma discharges are emerging as valuable mechanisms for pellet injection in magnetic confinement fusion reactors. They have been shown to be capable of achieving the required pellet velocities and pellet launch frequencies required for edge localized mode control. Another advantage of ET plasma discharges is their ability to simulate fusion disruption events by depositing large heat fluxes on exposed materials. A deeper understanding of the heat transfer processes occurring in ET plasma discharges will aid in this particular application. ET plasma discharges involve the passage of high currents (order of tens of kA) along the axis of a narrow, cylindrical channel. As the current passes through the channel, radiant heat is transferred from the plasma core to the capillary wall. Ablated particles eventually fill the plasma channel and the partially ionized plasma is ejected. It is well known that the ablated material separating the plasma core from the ablating surface can act as a vapor shield and limit the radiation heat flux reaching the ablating surface. In this work, the results from a two-dimensional simulation model for ET plasma discharges are presented. The simulation of the plasma in a two-dimensional domain combined with the diffusion approximation for radiation heat transfer is shown to successfully simulate the effects of the vapor shield layer that develops inside these devices.