Modelling of NOx emission factors from heavy and light-duty vehicles equipped with advanced aftertreatment systems

NO_x emission standards are becoming stringiest over the world especially for heavy-duty vehicles. To comply with current and future regulations some vehicle manufacturers are adopting exhaust aftertreatment systems known as Selective Catalytic Reduction (SCR). The catalysts are based on Vanadium (Va) and the reductant agent based on ammonia. However, Va is listed on the California Proposition 65 List as potentially causing cancer and alternatives are being studied. This paper presents a model based on neural networks that integrated with a road vehicle simulator allows to estimate NO_x emission factors for different powertrain configurations, along different driving conditions, and covering commercial, zeolite and mordenite alternatives as the base monolith for SCR. The research included the experimental study of copper based and iron based zeolites (ZSM5 and Cuban natural mordenite). The response of NO_x conversion efficiency was monitored in a laboratory for varying space velocity, oxygen, sulfur, water, NO_x and SO₂ emulating the conditions of a Diesel engine exhaust along a trip. The experimental data was used for training neural networks and obtaining a mathematical correlation between the outputs and inputs of the SCR system. The developed correlation was integrated with ADVISOR road vehicle simulator to obtain NO_x emission factors and to test each SCR system installed on light-duty and heavy-duty vehicles for standardized driving cycles and real measured driving cycles. Despite having lower NO_x conversion efficiencies than the CATCO in the ETC/ESC and NEDC cycles, FeZSM5 maintain the Euro regulation level. Therefore FeZSM5 can be a possible candidate as far as pollutants regulation is considered.     

Optical properties of pulse laser deposited AlN thin films on silicon

Aluminium-nitride thin films were deposited on silicon Si(111) substrate with pulsed laser deposition in a Riber LDM-32 system. The optical properties of the films were studied by means of optical spectroscopy with an incoherent light source mainly covering the visible range. It is demonstrated that, in comparison with an aluminium mirror, under certain deposition conditions, the film may behave as a metallic thin film as far as the optical reflection is concerned. In this case, there is an enhanced plasmonic reflection peak in the optical spectrum and the peak may be modified according to the degree of the phase transition. The microscopic structures as well as the surface topographies of the films were also studied with X-ray photoelectron spectroscopy and scanning electron microscopy. It turns out that the density and the size of the microscopic domains in the film determine whether the film remains dielectric or becomes metallic. The diamagnetic effect in the enhanced plasma increases in the process when the sample is smoothed out with the optimized nitrogen gas pressure. The nitrogen pressure is thus identified as the most influential deposition condition to the phase transition.     

Polaritons in hollow cylinders in the presence of a dc magnetic field

We study the effects of a dc external magnetic field on the polaritons propagating in hollow dielectric cylinders, taking into account the retardation effects. In solving Maxwell's equations we show that only the TM modes can propagate in these systems, and we obtain the dispersion relation of the confined-surface-polariton modes. The effects of geometric parameters and the external magnetic field on the propagation of surface-polariton modes are also analyzed and show significant influence on the behavior of the modes. Numerical results are presented for the dispersion relation of surface polaritons with GaAs as the optically active medium.     

Polyethylene with MoS2 nanoparticles toward antibacterial active packaging

Molybdenum disulfide (MoS₂) nanoparticles, obtained from liquid phase exfoliation in the presence of chitosan, were melt mixed with a linear low-density polyethylene (LLDPE) matrix to produce novel antimicrobial active packaging materials. The LLDPE/MoS₂ composites presented exfoliated nanoparticles forming aggregates that are well dispersed in the polymer matrix. These 2D-layered MoS₂ nanoparticles at concentrations of 0.5, 1.0, and 3.0 wt% rendered several functionalities to the LLDPE, as for example an antimicrobial behavior against Salmonella typhi and Listeria monocytogenes bacteria that can be explained not only by the photoactivity of the filler but also by changes in the composite surface. For instance, the composites presented a reduction in the water contact angle (i.e., an increased hydrophilicity) and relevant changes in the surface topography (i.e., reduced roughness) as compared with pure LLDPE. Regarding the barrier properties, while MoS₂ dramatically increased the water vapor permeation (WVP) of the polymer matrix, until 15 times for composite with 3.0 wt% of filler, the oxygen permeation decreased around 25%. All these novel functionalities in the nanocomposites were obtained without significantly affecting the tensile mechanical properties of the pure LLDPE matrix. These results show that MoS₂ is a promising filler for the development of antibacterial active packaging films with behaviors as similar as other 2D-layered fillers such as graphene derivatives.     

Multicommuted Flow Analysis Procedure for Total Polyphenols Determination in Wines Employing Chemiluminescence Detection

A flow procedure based on a multicommuted flow analysis process for the determination of polyphenolic compounds in wine employing chemiluminescence as detection technique is described. The method was based on the reaction of hypochlorite with gallic acid, the remaining hypochlorite reacted with luminol in an alkaline medium generating electromagnetic radiation with maximum emission at 425 nm. The luminescence intensity presented an inverse relationship to the concentration of polyphenol compounds, which was monitored employing a homemade luminometer. The flow system manifold was designed to use solenoid mini-pumps for propelling fluids in order to obtain a setup of downsized dimension. After setting the variables control of the flow system and the concentrations of the reagent, the following features were achieved: a linear response ranging from 10 to 100 mg L^?1 gallic acid (R ²?=?0.997), a relative standard deviation of 3.4 (n?=?11) for a 50 mg L^?1 gallic acid solution, a detection limit of 6.6 mg L^?1, a sampling throughput of 180 determination h^?1, and a waste generation of 1.1 mL per determination.     

Square-Wave Adsorptive Stripping Voltammetry for Trace Determination of Dimoxystrobin and Azoxystrobin in Potatoes and Grapes

Square-wave voltammetry was used for trace determination of azoxystrobin and dimoxystrobin in potatoes, grapes, and grape juice. Experimental conditions have been optimized to achieve simultaneous determination of these analytes using the hanging mercury drop electrode. Supporting electrolyte was HCl 0.1 mol L⁻¹, and other optimized conditions were deposition potential (−300 mV), deposition time (30 s), amplitude (150 mV), frequency (150 Hz), and step height (2 mV). Azoxystrobin and dimoxystrobin redissolution peaks presented their maxima, respectively, at −928 mV and around −650 mV. Linear and homoscedastic analytical responses (r ² > 0.99) have been observed. Limits of quantification as low as 119 μg L⁻¹ (in grape juice) and 45 μg kg⁻¹ (in potatoes and grapes) were found. A previous solid-phase extraction was necessary to eliminate interferences from potato and grape samples. For grape juice, no sample treatment was required. Satisfactory recoveries (from 72.3% to 96.7% for dimoxystrobin and from 81.7% to 102.3% for azoxystrobin) were found. Interferences from other strobilurins (piraclostrobin and picoxystrobin) were evaluated.     

Quantum Biochemistry Screening and In Vitro Evaluation of Leishmania Metalloproteinase Inhibitors

Leishmanolysin, also known as major promastigote protease (PSP) or gp63, is the most abundant surface glycoprotein of Leishmania spp., and has been extensively studied and recognized as the main parasite virulence factor. Characterized as a metalloprotease, gp63 can be powerfully inactivated in the presence of a metal chelator. In this study, we first used the structural parameters of a 7-hydroxycoumarin derivative, L1 compound, to evaluate the theoretical–computational experiments against gp63, comparing it with an available metal chelator already described. The methodology followed was (i) analysis of the three-dimensional structure of gp63 as well as its active site, and searching the literature and molecular databases for possible inhibitors; (ii) molecular docking simulations and investigation of the interactions in the generated protein–ligand complexes; and (iii) the individual energy of the gp63 amino acids that interacted most with the ligands of interest was quantified by ab initio calculations using Molecular Fraction with Conjugated Caps (MFCC). MFCC still allowed the final quantum balance calculations of the protein interaction to be obtained with each inhibitor candidate binder. L1 obtained the best energy quantum balance result with −2 eV, followed by DETC (−1.4 eV), doxycycline (−1.3 eV), and 4-terpineol (−0.6 eV), and showed evidence of covalent binding in the enzyme active site. In vitro experiments confirmed L1 as highly effective against L. amazonensis parasites. The compound also exhibited a low cytotoxicity profile against mammalian RAW and 3T3 cells lines, presenting a selective index of 149.19 and 380.64 µM, respectively. L1 induced promastigote forms’ death by necrosis and the ultrastructural analysis revealed disruption in membrane integrity. Furthermore, leakage of the contents and destruction of the parasite were confirmed by Spectroscopy Dispersion analysis. These results together suggested L1 has a potential effect against L. amazonensis, the etiologic agent of diffuse leishmaniasis, and the only one that currently does not have a satisfactory treatment.