Hormigón fabricado con asfalto triturado como reemplazo parcial de áridos naturales

The paper focuses on the reuse of crushed asphalt (GA) as a partial replacement (up to 20%) of natural aggregates for concrete manufacture. Addition of GA aggregates produced a positive effect on workability loss. The GA mixes, however, showed a significant tendency to bleed and segregate at the highest replacement percentage applied. GA led to a decrease of compressive strength in concrete (with respect to that of the reference concrete) up to 50% due to the weakness of the cement paste / recycled aggregate interface. To compensate for this negative effect, a reduction of w/c for the GA concretes was necessary. A decrease of w/c allowed the GA concretes to show drying shrinkage values substantially similar to those of reference concrete with the same cement factor. The experimental results confirmed the possibility of partial substitution (max. 15%) of natural aggregates with crushed asphalt for making concrete.El artículo se centra en la reutilización del asfalto triturado (AM) como reemplazo parcial (hasta 20%) de áridos naturales para la fabricación de hormigón. Los áridos de AM además produjeron un efecto positivo sobre la pérdida de la trabajabilidad. Las mezclas de AM mostraron una marcada tendencia a la exudación y segregación en el más elevado porcentaje de sustitución. El AM condujo a una disminución de la resistencia a la compresión en el hormigón (con respecto al hormigón de referencia) de hasta un 50% debido a la debilidad de la pasta de cemento. Para compensar este efecto, fue necesaria una reducción de agua-cemento (a/c) para hormigones AM. Se consiguieron valores de retracción de secado sustancialmente similares a los de hormigón de referencia con el mismo contenido de cemento. Los resultados experimentales confirmaron la posibilidad de sustitución parcial (máximo 15%) de áridos naturales por asfalto triturado para la fabricación de hormigón

Analysis of the Operational and Safety Features of the In-Core Bubbling System of the Molten Salt Fast Reactor

A foreseen feature of the Molten Salt Fast Reactor is the adoption of a bubbling system for the removal of gaseous and metallic fission products (FPs). This mechanism injects helium bubbles into the core to remove FPs from the salt through floating and mass transfer mechanisms for metallic and gaseous FPs, respectively. The present work is aimed at analyzing this helium bubbling system, focusing on gaseous FPs. We investigate both operational and safety-related features in order to get information useful for the design and to assess the convenience of its adoption. Accordingly, our investigations split into two strands: (1) analyzing the characteristics of the bubbling system itself and (2) assessing the safety features of the reactor in its presence. In order to perform the above analyses, we add the capability to simulate production, transport, and mass transfer of an arbitrary number of gaseous FPs to a preexisting multiphysics solver, built with the OpenFOAM suite. In terms of operational characterization, our analyses quantify the removal efficiency through a characteristic removal time and estimate the poisoning effect of gaseous FPs. In addition, we evaluate the activity and decay heat of the removed gas, which is an aspect crucial for the design of the off-gas unit, and the effect of the bubbling system on the power versus the fuel mass flow rate curve, which is a possible control mechanism. Among our safety-related studies, we first evaluate the void coefficient, determining upper bounds on the helium flow rate in order to avoid prompt supercriticality in case of prompt loss of helium injection. The latter accidental scenario is also analyzed considering the thermal-hydraulic dynamics of the system. We also discuss another accident: complete loss of helium removal

Made-to measure galaxy models - I Methodology

We re-derive the made-to-measure method of Syer and Tremaine 1996, for modelling stellar systems and individual galaxies, and demonstrate how extensions to the made-to-measure method may be implemented and used. We illustrate the enhanced made-to-measure method by determining the mass-to-light ratio of a galaxy modelled as a Plummer sphere. From the standard galactic observables of surface brightness and line-of-sight velocity dispersion together with the h_4 Gauss-Hermite coefficient of the line-of-sight velocity distribution, we successfully recover the true mass-to-light ratio of our toy galaxy. Using kinematic data from Kleyna et al 2002, we then estimate the mass-to-light ratio of the dwarf spheroidal galaxy Draco achieving a V-band value of 539 \pm 136 M_{\odot} / L_{\odot}. We describe the main aspects of creating a made-to-measure galaxy model and show how the key modelling parameters may be determined.Comment: 18 pages, 15 figure

Incidence of white striping under commercial conditions in medium and heavy broiler chickens in Italy

Abstract Several types of muscle abnormalities are present in the poultry industry as a result of genetic selection, leading to decreased quality of meat and consequent economic loss. The appearance of thin (moderate) to thick (severe) white striping (WS) striations parallel to muscle fibers on the surface of broiler breast fillets is one of the most troubling issues in the poultry industry. White striping also has unfavorable implications on visual acceptance, nutritional value, and processing traits of breast meat. The aim of this survey was to assess the influence of market class (medium and heavy birds) and genotype (standard- and high-breast yield hybrids) on the incidence of WS in broiler chickens raised under commercial conditions in Italy. The incidence of WS for both medium and heavy broilers was high (43.0%), with 6.2% of samples considered severe. Heavy flocks had significantly higher percentages of both moderate (46.9 vs. 25.8%;P ≤ 0.001) and severe (9.5 vs. 2.7%;P ≤ 0.001) WS than medium flocks. Considering the effect of genotype, high-breast yield hybrids exhibited a higher incidence of both moderate (40.2 vs. 33.2%;P ≤ 0.001) and severe WS (7.2 vs. 5.0%;P ≤ 0.001) compared with standard-breast yield birds. In addition, within the medium class, the occurrence of WS reached higher levels in flocks of males. The heavy class consisted of male flocks separated into 2 slaughter weight categories. Birds that reached higher slaughtering weights (3.8–4.2 kg) exhibited higher incidence of WS than flocks slaughtered at lower weights (3.0–3.8 kg) at a similar age. In conclusion, the main broiler genotypes used for commercial production were affected by a high rate of WS; hybrids selected for higher breast yields were more prone to the WS abnormality. In addition, severe cases of WS are even more prevalent at higher slaughter age and weight, although reduced growth rate is associated with a lower incidence and severity of WS

On the need for multi-dimensional models for the safety analysis of (fast-spectrum) Molten Salt Reactors

This paper aims at characterizing the impact of adopting numerical models with different dimensionalities on the predicted behavior of fast-spectrum Molten Salt Reactors (MSRs). The study encompasses 1-D, 2-D, and 3-D representations of thermal-hydraulics and precursor transport/diffusion, along with spatial and point kinetics models for neutronics. We evaluate the accuracy of each model based on steady-state results and on the reactor response to 2 different transient initiators. The findings emphasize the significance of utilizing a 3-D representation with accurate thermal-hydraulics modeling, and with either spatial kinetics or carefully calibrated point kinetics incorporating a spatial description of precursors transport. 2-D and 1-D models can reproduce main trends and remain valuable tools for e.g. reactor design, control-oriented studies or uncertainty quantification. However, proper calibration of these models is needed and the user should be aware that alterations in flow patterns could jeopardize model calibration and hide first-order local effects

Effect of cyclic loading on hydrogen diffusion in low carbon steels

Carbon steels or low-alloyed steels may be affected by damaging phenomena due to Hydrogen Embrittlement (HE), which is a particular form of Environmental Assisted Cracking (EAC). The insurgence of HE depends on the intrinsic susceptibility of the steel, the applied stress, and the concentration of hydrogen inside the metal. It occurs by a mechanism of absorption and subsequent diffusion of atomic hydrogen through the metal lattice. On steels with a yield strength lower than 700 MPa, HE occurs in the plastic deformation field, in the presence of dynamic loading at slow strain rates or cyclic fatigue loading at very low frequencies. Although several important studies were carried out on the effect of loading conditions on hydrogen diffusion into the metal and HE mechanism, HE phenomena are not fully understood. In this work, the effect of the application of cyclic loads on hydrogen diffusion parameters was studied both in the elastic and in the plastic deformation field. The influence of mean load and amplitude was analyzed. Hydrogen permeation tests were performed on API 5L X65 steel, in accordance with ISO 17081:2014. The specimen behaved as bi-electrode between the two compartments of a Devanathan-Stachurski cell. The anodic side of the specimen was polarized at +340 mV vs Ag/AgCl in a 0.1 M NaOH aerated solution, while the cathodic compartment was filled with an aerated borate solution. A controller enabled temperature adjustment at 20±0.5°C. Once the passivity current registered in the anodic side reached values of 0.05 µA/cm2, a cathodic current density of 0.50 mA/cm2 was applied to charging cathodic side. The study included tests with sine waveform cycling loading, with a maximum level equal to 110% TYS, at a frequency of 10-2 Hz. The results confirmed the values of hydrogen diffusion coefficient usually indicated for low-alloyed steels with a sorbitic microstructure. Strain hardened specimens - stretched above yield strength - showed an increase of steady state current and an extension of the time lag, denoting a slight decrease in the apparent hydrogen diffusion coefficient due to traps effect in the cold deformed steel matrix. Under cyclic loading, an instantaneous peak of current with a subsequent significant transient decrease occurred after cyclic load application, whereas no relevant variation of permeation curve compared to unloaded specimens was observed if specimens were already loaded before hydrogen charging. The instantaneous current peak reached values much higher than the steady state current. This is ascribed to the rupture of the passive film – caused by loading – and its subsequent reformation; in fact, this can also be noted during tests performed on specimens without hydrogen permeation. The following transient, in which the permeation current decreases below the steady state and then returns to it, denotes a relevant trapping effect that causes the instantaneous reduction of mobile hydrogen concentration in the lattice. This becomes more significant for loads closer and closer to the yield strength, mainly beyond this, and can only be noted at the first loading step. Subsequent unloading and loading step at the same mean value showed no transient in the permeation curren

Engineering the substrate specificity of D-amino-acid oxidase

The high resolution crystal structure of D-amino-acid oxidase (DAAO) from the yeast Rhodotorula gracilis provided us with the tool to engineer the substrate specificity of this flavo-oxidase. DAAO catalyzes the oxidative deamination of D-amino acids, with the exception of D-aspartate and D-glutamate (which are oxidized by D-aspartate oxidase, DASPO). Following sequence homology, molecular modeling, and simulated annealing docking analyses, the active site residue Met-213 was mutated to arginine. The mutant enzyme showed properties close to those of DASPO (e.g. the oxidation of D-aspartate and the binding of l-tartrate), and it was still active on D-alanine. The presence of an additional guanidinium group in the active site of the DAAO mutant allowed the binding (and thus the oxidation) of D-aspartate, but it was also responsible for a lower catalytic activity on D-alanine. Similar results were also obtained when two additional arginines were simultaneously introduced in the active site of DAAO (M213R/Y238R mutant, yielding an architecture of the active site more similar to that obtained for the DASPO model), but the double mutant showed very low stability in solution. The decrease in maximal activity observed with these DAAO mutants could be due to alterations in the precise orbital alignment required for efficient catalysis, although even the change in the redox properties (more evident in the DAAO-benzoate complex) could play a role. The rational design approach was successful in producing an enzymatic activity with a new, broader substrate specificity, and this approach could also be used to develop DAAO variants suitable for use in biotechnological applications

Improving statistical power of glaucoma clinical trials using an ensemble of cyclical generative adversarial networks

Albeit spectral-domain OCT (SDOCT) is now in clinical use for glaucoma management, published clinical trials relied on time-domain OCT (TDOCT) which is characterized by low signal-to-noise ratio, leading to low statistical power. For this reason, such trials require large numbers of patients observed over long intervals and become more costly. We propose a probabilistic ensemble model and a cycle-consistent perceptual loss for improving the statistical power of trials utilizing TDOCT. TDOCT are converted to synthesized SDOCT and segmented via Bayesian fusion of an ensemble of GANs. The final retinal nerve fibre layer segmentation is obtained automatically on an averaged synthesized image using label fusion. We benchmark different networks using i) GAN, ii) Wasserstein GAN (WGAN) (iii) GAN + perceptual loss and iv) WGAN + perceptual loss. For training and validation, an independent dataset is used, while testing is performed on the UK Glaucoma Treatment Study (UKGTS), i.e. a TDOCT-based trial. We quantify the statistical power of the measurements obtained with our method, as compared with those derived from the original TDOCT. The results provide new insights into the UKGTS, showing a significantly better separation between treatment arms, while improving the statistical power of TDOCT on par with visual field measurements

Genetic characterization and relationships of traditional grape cultivars from Serbia

Reference genetic profiles were generated for 12 traditional grapevine cultivars of Serbia through a genotyping approach that included the "core set" of 9 SSR markers for genetic identification and further 13 common microsatellites for strengthening genetic relationship analysis. Consistent matching with SSR markers of grapevines cultivated in neighbouring countries or maintained in European germplasm collections was found for most of the genotypes, suggesting possible synonyms and revealing that 'Muskat Krokan' corresponds to 'Muscat fleur d’Oranger' and two 'Tamjanika' cultivars are identical to 'Moscato Giallo' and 'Moscato Rosa'. When compared with germplasm representing the classical eco-geographic grouping of grapevine cultivars, Serbian non-Muscat genotypes clustered within the Convar pontica subconvar balcanica taxon thus supporting their indigenous origin.