Functional and environmental performance of plant-produced crumb rubber asphalt mixtures using the dry process

Incorporating crumb rubber (CR) using the dry process, directly in the asphalt mixture rather than into the bituminous binder requires no plant retrofitting, and therefore is the most practical industrial method for CR incorporation into asphalt mixtures. Nevertheless, very few large scale studies have been conducted. This work uses a holistic approach and reports on the functional and environmental performance of asphalt mixtures with different concentrations of CR fabricated employing the dry process in asphalt plants. Gaseous emissions were monitored during the production and laboratory leaching tests simulating the release of pollutants during rain, was conducted to evaluate the toxicology of both the CR material alone and the modified asphalt mixtures. In addition, laboratory compacted samples were tested to assess their fatigue behavior. Furthermore, noise relevant surface properties of large roller compacted slabs were evaluated before and after being subjected to a load simulator (MMLS3) to evaluate their resistance to permanent deformation. The results confirm that comparable performance can be achieved with the incorporation of CR using the dry process for high performance surfaces such as semi-dense asphalt, which usually require the use of polymer modified binders. Environmental performance improvement can be achieved by a washing step of the CR material that could remove polar CR additives which have commonly been used as vulcanization accelerator during rubber production.

Concomitant behavior of arsenic and selenium from the karst infillings materials of the fractured carbonate Dogger Aquifer (Hydrogeological Experimental Site, Poitiers, France)

Petrographic and mineralogical analyses combined with sequential extractions and leaching experiments as a function of pH were performed on black clayey sediments fulfilling karsts in the Hydrogeological Experimental Site (HES) of Poitiers (France) to investigate the behavior of arsenic and selenium in a fractured limestone aquifer. Sequential extractions showed that arsenic is mainly associated with pyrite (about 35%) and secondary iron oxyhydroxides (around 13%), along with a substantial exchangeable fraction (about 13%). The soluble fraction and the fraction associated to organic matter are ∼2% and ∼5%, respectively. The distribution of selenium is mainly pyritic (around 39%) or associated with organic matter (about 18%). Its association to secondary iron oxyhydroxides minerals is low (around 2%), whereas its soluble fraction is around 5%. SEM analyses revealed the presence of arsenic "hot spots" into euhedral pyrite crystals surrounded by a halo of iron oxyhydroxides resulting from their alteration, and both are enriched with arsenic. Selenium has a similar pyritic origin but after alteration, it is predominantly associated with organic matter. Despite different distributions, the leaching experiment as a function of pH showed that the mobilization of arsenic and selenium overlapped below pH 2 and above pH 8. The main differences were observed between pH 2 and 8 with a plateau at 5% of released selenium, whereas the amount of mobilized arsenic continuously decreased. The pH-dependence of both elements is attributed to the partial dissolution of pyrite in acidic conditions combined with desorption processes at higher pH values.

High Performance Liquid Chromatographic Determination of Carbohydrates in Chocolate: Collaborative Study

A collaborative study determining sucrose, glucose, fructose, maltose, and lactose in chocolate products was conducted using a previously published high performance liquid chromatographic (HPLC) method. Five samples (2 milk chocolates, 1 dark chocolate, 1 powdered mix, and 1 sirup) were analyzed in duplicate by 7 collaborators. The results indicate adequate method precision. In addition, the HPLC method allows for the simultaneous determination of 5 saccharides in chocolate products in 15 min. The method has been adopted as official first action.

Vitamin D in Infant Formula and Enteral Products by Liquid Chromatography: Collaborative Study

Results from a collaborative study of a new liquid chromatographic (LC) method for determination ofvitamin D in infant formulas and enteral products are presented. Each of 15 laboratories was provided with 11 blind duplicate samples covering a range ofapproximately 200-500 International Units/quart (normal dilution), a system suitability sample, and the U.S. Pharmacopeia ergo- and cholecalciferol standards. Product types included liquid and powder forms of milk (whey and casein), soy, and hydrolyzed protein-based infant formulas and enteral products. The method includes a single liquid-liquid extraction following saponification, solid-phase extraction,and then concentration by evaporation. An isocratic, nonaqueous, chromatographic system with reversed-phase, zero end- capped C18 column, and UV detector set at 265 nm are used. Statistical evaluation ofdata from participating laboratories showthe average reproducibility and repeatability of the method across all samples to be excellent, with RSDR and RSDr values of 13.48 and 9.44, respectively, after elimination of out liers. The LC method for determination of vitamin D in infant formulas and enteral products has been adopted by AOAC INTERNATIONAL.

ASSESSING THE CONTRIBUTION OF CROSS-SECTIONS TO THE UNCERTAINTY OF MONTE CARLO CALCULATIONS IN MICRO- AND NANODOSIMETRY

Within EURADOS Working Group 6 'Computational Dosimetry', the micro and nanodosimetry task group 6.2 has recently conducted a Monte Carlo (MC) exercise open to participants around the world. The aim of this exercise is to quantify the contribution to the uncertainty of micro and nanodosimetric simulation results arising from the use of different electron-impact cross-sections, and hence physical models, employed by different MC codes (GEANT4-DNA, PENELOPE, MCNP6, FLUKA, NASIC and PHITS). Comparison of the participants' simulation results for both micro and nanodosimetric quantities using different MC codes was the first step of the exercise. The deviation between results is due to different cross-sections but also different tracking methods and particle transport cut-off energies. The second step of the exercise will involve using identical cross-section datasets to account only for the other variations in the first step, thus enabling the determination of the uncertainty contribution due to different cross-sections. This paper presents a comparison of the MC simulation results obtained in the first part of the exercise. For the microdosimetric simulations, particularly in the configuration where the electron source is contained within the micrometric target, the choice of MC code has a small influence on the results. For the nanodosimetric results, on the other hand, the mean ionisation cluster size distribution (ICSD) was sensitive to the physical models used in the MC codes. The ICSD was therefore chosen to study the influence of different cross-section data on the uncertainty of simulation results.

A New Standard DNA Damage (SDD) Data Format

Our understanding of radiation-induced cellular damage has greatly improved over the past few decades. Despite this progress, there are still many obstacles to fully understand how radiation interacts with biologically relevant cellular components, such as DNA, to cause observable end points such as cell killing. Damage in DNA is identified as a major route of cell killing. One hurdle when modeling biological effects is the difficulty in directly comparing results generated by members of different research groups. Multiple Monte Carlo codes have been developed to simulate damage induction at the DNA scale, while at the same time various groups have developed models that describe DNA repair processes with varying levels of detail. These repair models are intrinsically linked to the damage model employed in their development, making it difficult to disentangle systematic effects in either part of the modeling chain. These modeling chains typically consist of track-structure Monte Carlo simulations of the physical interactions creating direct damages to DNA, followed by simulations of the production and initial reactions of chemical species causing so-called "indirect" damages. After the induction of DNA damage, DNA repair models combine the simulated damage patterns with biological models to determine the biological consequences of the damage. To date, the effect of the environment, such as molecular oxygen (normoxic vs. hypoxic), has been poorly considered. We propose a new standard DNA damage (SDD) data format to unify the interface between the simulation of damage induction in DNA and the biological modeling of DNA repair processes, and introduce the effect of the environment (molecular oxygen or other compounds) as a flexible parameter. Such a standard greatly facilitates inter-model comparisons, providing an ideal environment to tease out model assumptions and identify persistent, underlying mechanisms. Through inter-model comparisons, this unified standard has the potential to greatly advance our understanding of the underlying mechanisms of radiation-induced DNA damage and the resulting observable biological effects when radiation parameters and/or environmental conditions change.

Influence of lane departure warnings onset and reliability on car drivers' behaviors

Lane departures represent an important cause of road crashes. The objective of the present study was to assess the effects of an auditory Lane Departure Warning System (LDWS) for partial and full lane departures (onset manipulation) combined with missed warnings (reliability manipulation: 100% reliable, 83% reliable and 66% reliable) on drivers' performances and acceptance. Several studies indicate that LDWS improves drivers' performances during lane departure episodes. However, little is known about the effects of the warning onset and reliability of LDWS. Results of studies which looked at forward collision warning systems show that early warnings tend to improve drivers' performances and receive a better trust judgement from the drivers when compared to later warnings. These studies also suggest that reliable assistances are more effective and trusted than unreliable ones. In the present study, lane departures were brought about by means of a distraction task whilst drivers simulated driving in a fixed-base simulator with or without an auditory LDWS. Results revealed steering behaviors improvements with LDWS. More effective recovery maneuvers were found with partial lane departure warnings than with full lane departure warnings and assistance unreliability did not impair significantly drivers' behaviors. Regarding missed lane departure episodes, drivers were found to react later and spend more time out of the driving lane when compared to properly warned lane departures, as if driving without assistance. Subjectively, LDWS did not reduce mental workload and partial lane departure warnings were judged more trustworthy than full lane departure ones. Data suggests the use of partial lane departure warnings when designing LDWS and that even unreliable LDWS may draw benefits compared to no assistance.

Assessment of an action against environmental noise: Acoustic durability of a pavement surface with crumb rubber

Environmental noise is a worldwide problem that has an adverse effect in the quality of life of urban population. Some work has shown that there is a correlation between environmental noise and health issues as sleep disturbance or annoyance. This study presents the time evolution of a test track fabricated with an asphalt mixture with 20% of crumb rubber by weight of bitumen, added by the wet process. A complete surface characterization has been performed by determining tire/pavement sound levels, road texture profiles, in-situ dynamic stiffness and sound absorption of compacted and extracted sample cores. Two measurement campaigns were performed: just after mixture laying and after 3 years in service. This study confirms that the use of crumb rubber as a modifier of bituminous binders (CRMB) can improve the pavement characteristics: gap-graded mixtures with crumb rubber can be used in the action plans as urban rehabilitation measure to fight noise pollution. However, this noise reduction seems to decrease with age at a rate of approximately 0.15 dB(A) per year.

An algorithm to assess the need for clinical Monte Carlo dose calculation for small proton therapy fields based on quantification of tissue heterogeneity

PURPOSE

In proton therapy, complex density heterogeneities within the beam path constitute a challenge to dose calculation algorithms. This might question the reliability of dose distributions predicted by treatment planning systems based on analytical dose calculation. For cases in which substantial dose errors are expected, resorting to Monte Carlo dose calculations might be essential to ensure a successful treatment outcome and therefore the benefit is worth a presumably long computation time. The aim of this study was to define an indicator for the accuracy of dose delivery based on analytical dose calculations in treatment planning systems for small proton therapy fields to identify those patients for which Monte Carlo dose calculation is warranted.

METHODS

Fourteen patients treated at our facility with small passively scattered proton beams (apertures diameters below 7 cm) were selected. Plans were generated in the XiO treatment planning system in combination with a pencil beam algorithm developed at the Massachusetts General Hospital and compared to Monte Carlo dose calculations. Differences in the dose to the 50% of the gross tumor volume (D50, GTV) were assessed in a field-by-field basis. A simple and fast methodology was developed to quantify the inhomogeneity of the tissue traversed by a single small proton beam using a heterogeneity index (HI)-a concept presented by Plugfelder et al. [Med. Phys. 34, 1506-1513 (2007)] for scanned proton beams. Finally, the potential correlation between the error made by the pencil beam based treatment planning algorithm for each field and the level of tissue heterogeneity traversed by the proton beam given by the HI was evaluated.

RESULTS

Discrepancies up to 5.4% were found in D50 for single fields, although dose differences were within clinical tolerance levels (<3%) when combining all of the fields involved in the treatment. The discrepancies found for each field exhibited a strong correlation to their associated HI-values (Spearman's ρ=0.8, p<0.0001); the higher the level of tissue inhomogeneities for a particular field, the larger the error by the analytical algorithm. With the established correlation a threshold for HI can be set by choosing a tolerance level of 2-3%-commonly accepted in radiotherapy.

CONCLUSIONS

The HI is a good indicator for the accuracy of proton field delivery in terms of GTV prescription dose coverage when small fields are delivered. Each HI-value was obtained from the CT image in less than 3 min on a computer with 2 GHz CPU allowing implementation of this methodology in clinical routine. For HI-values exceeding the threshold, either a change in beam direction (if feasible) or a recalculation of the dose with Monte Carlo would be highly recommended.

Fasting plasma peptide YY concentrations are increased in patients with major depression who associate weight loss

BACKGROUND

Many patients with major depression refer a decreased appetite and weight loss among their symptoms. Peptide YY (PYY) and ghrelin belong to the family of peptides of the gut-brain axis implicated in the regulation of appetite and energy metabolism. PYY stimulates a powerful central satiety response and ghrelin increases food intake and weight gain. Brain-derived neurotrophic factor (BDNF) also contributes to the central control of food intake as an anorexigenic factor.

AIM

To study fasting plasma total and acylated ghrelin, plasma PYY and serum BDNF levels in patients with major depression with weight loss as one of their symptoms and compare them with matched healthy controls.

SUBJECTS AND METHODS

Fifteen adult patients, 9 male and 6 female, with recent diagnosis of major depression, and 16 healthy adult subjects, matched by age and anthropometric parameters were studied. All depressed patients referred weight loss and were not under antidepressant therapy. Fasting total PYY, total ghrelin and acylated ghrelin and BDNF were determined.

RESULTS

Fasting total PYY was higher in patients than controls (2.01±0.09 vs 1.29±0.16 pmol/l). There were no differences in fasting total ghrelin, acylated ghrelin or BDNF levels.

CONCLUSIONS

Major depressed patients, with weight loss at diagnosis, showed higher fasting plasma PYY levels that could contribute to their reduced appetite.

MO-F-BRB-03: A Method to Assess the Need for Clinical Monte Carlo Dose Calculations for Small Proton Therapy Fields

PURPOSE

Due to multiple Coulomb scattering in complex geometries, small field dosimetry in proton therapy is challenging. Our goal was to define an indicator for the accuracy of dose delivery based on analytical dose calculations in treatment planning systems for small (e.g. radiosurgery) proton therapy fields.

METHODS

Seven patients whose treatment involved one or more small fields (below ∼3.6cm in diameter) were selected. We developed a fast methodology to quantify the inhomogeneity of the tissue traversed by a single beam using a heterogeneity index (HI). The implementation was based on the dose calculation approach taken by our pencil beam algorithm. Plans created with the treatment planning system were verified against Monte Carlo dose calculations on a field- by-field basis. DVHs were analyzed and differences in the dose to the GTV were assessed. The correlation between the HI-values and the discrepancies between planning system and Monte Carlo in terms of absolute dose to the target was studied.

RESULTS

Our treatment planning system overestimates the dose within the GTV for very small fields by up to ∼8%, even if proper output factor normalization is done in water. The differences are strongly correlated to HI (Spearman's ρ=0.8, rho<0.0001). More complex heterogeneities within the beam path caused larger errors by the analytical algorithm. With the established correlation a threshold for the HI can be set by choosing a tolerance level.

CONCLUSIONS

The HI as defined in this study appears to be a good indicator of the accuracy of proton field delivery in terms of GTV prescription dose when small fields are being delivered. Each HI-value was obtained in less than 2 minutes allowing implementation of the HI algorithm in clinical routine. For HI- values exceeding a certain threshold, either a change in beam incidence or a Monte Carlo dose calculation should be considered.