A mechanistic study of degradation of a typical automotive clearcoat caused by bird droppings

This study aims at investigating the degradation mechanism of an automotive clearcoat caused by bird droppings. Natural bird droppings and their synthetic equivalent (pancreatin) were utilized for this purpose. The presence of highly-etched areas on the surface of coatings and structural variations of clearcoat after being attacked by these materials corresponded to a catalyzed hydrolytic degradation. This finding was obtained using different analytical techniques. Based on these studies, three possible hypotheses were presented, including acid catalysis, metal ion catalysis, and enzymatic catalysis. The conditions required for the occurrence of each hypothesis were discussed. It was found that acid and metal ions have a weak contribution to catalyze the hydrolysis reaction of clearcoat, whereas enzymes existing in bird droppings were mainly responsible for this hydrolytic degradation.     

Effect of Microwave Annealing on the Structure and Magnetic Properties of Co-based Amorphous Ribbons

We investigated the structure and magnetic properties of CoFeSiB amorphous ribbons in the presence of microwave emission. Samples have been emitted onto in the microwave cavity with working frequency of 2.45 GHz at different times of emission. Structure and surface properties of samples emitted to have been investigated by X-ray diffraction and Atomic force microscopy. Also, magnetic properties of samples were investigated by magneto-optical Kerr effect measurement. Our results show that increasing in annealing time may change the crystalline state of samples and also decrease the magnetic coercivity and surface roughness.     

Modeling and experimental evaluation of vacuum-UV photoreactors for water treatment

Vacuum-UV (VUV) radiation is a promising and effective technology for the oxidation of organic contaminants. The VUV-induced degradation of a model pollutant, Formic Acid (FA), was modeled and experimentally investigated. Experimental work involved an annular flow-through reactor operated in batch mode with complete recycle of the reactants. Ozone-producing low-pressure Hg lamps were used as the source of VUV radiation. FA concentrations of up to 0.55 mmol L⁻¹ were completely degraded after 40 min of irradiation. FA degradation was accompanied by the formation of H₂O₂ at concentrations of about 0.3 mmol L⁻¹. Kinetic and radiation models were combined with the corresponding mass balances to describe the experimental results. The kinetic model accounted for the most important reactions occurring in the system, including photolysis of water and H₂O₂, side reactions between radicals, and degradation of FA. The radiation model, which was solved using the Monte Carlo method, described the propagation of photons in the reactor volume and took into account the optical properties of the solution and the emission power of the lamps, obtained by actimometry. Modeling simulations fit experimental data of FA degradation using VUV, H₂O₂/VUV, and H₂O₂/UV with a root mean square error of 7.4%. According to modeling and experimental results, the VUV-induced degradation of FA followed an apparent zero order kinetics, a fact that may suggest the reaction was limited by the availability of hydroxyl radicals (HO).     

Utilizing Taguchi design of experiment to study the surface treatment of a nanosilica with an acrylic silane coupling agent and revealing the dispersibility of particles in a urethane acrylate resin

This work aims at investigating the dispersibility of a modified hydrophilic nanosilica using methacryloxy propyltrimethoxysilane (MPTMS) in an organic phase, which contains UV-curable urethane acrylate oligomers and monomers with different functionalities. Through a Taguchi design of experiment, the impacts of influencing parameters such as silane coupling agent to silica ratio, hydrolysis ratio as well as treating bath pH were investigated. The optimum condition in which the maximum percentage of modification occurred was observed at higher stoichiometric levels of silane:silica ratio and alkaline pH conditions. Furthermore, statistical analysis demonstrated that hydrolysis ratio was not very significant. Low amounts of turbidity of prepared hybrid coatings indicated that modified particles with higher grafting contents had better dispersion stability in the acrylate resin.     

Investigating the degradation resistance of silicone-acrylate containing automotive clearcoats exposed to bird droppings

This work reports preparation of acrylic/melamine based clearcoats containing various loads of a reactive polysiloxane additive. The additive was incorporated into the clearcoat formulations up to 8 wt% to enhance its resistance against bird droppings. Contact angle measurements, ATR spectroscopy, energy dispersive X-ray analysis, appearance measurements together with different microscopic techniques were utilized to reveal the effects of additive on the properties of the coating prior and after exposure to pancreatin, the synthetic equivalent of natural bird droppings. Appearance measurements, as well as optical microscope images obviously indicated that the additive improved the clearcoats resistance against pancreatin. Results revealed that surface free energy of the films was reduced in the presence of additive. It was also found that at high concentrations of additive, a significant part of it remained in the bulk, forming a second phase. This resulted in a lack of sufficient reactive groups and lead to an under-cure state at the clearcoat surface.     

An ultralight biotelemetry backpack for recording EMG signals in moths

A two-channel FM biopotential recording system fabricated on a foldable, lightweight, polyimide substrate is presented. Each channel consists of a biopotential amplifier followed by a Colpitts oscillator with operating frequency tunable in the 88-108 MHz commercial FM band. The overall system measures 10 mm X 10 mm X 3 mm, weighs 0.74 g, uses two 1.5-V batteries, dissipates about 2 mW, and has a transmission range of 2 m. Using this system, electromyogram signals have been recorded from the dorsal ventral muscle and the dorsal longitudinal muscle of a giant sphinx moth (manduca sexta).     

A 1.48-mW low-phase-noise analog frequency modulator for wireless biotelemetry

This paper presents a low-phase-noise, hybrid LC-tank, analog frequency modulator for wireless biotelemetry employing on-chip NMOS varactors in the inversion region as the frequency tuning element. We demonstrate that a correct estimate for the destination signal-to-noise ratio, which quantifies the quality of the wirelessly received signal in a frequency-modulated biotelemetry system, is only achieved after taking into account the large-signal oscillation effect on the tank varactor. A prototype chip is fabricated using AMI 1.5-microm double-poly double-metal n-well CMOS process, and exhibits a measured gain factor of 1.21 MHz/V in the mid-range of the tuning voltage and a phase noise of -88.6 dBc/Hz at 10-kHz offset from the 95.1-MHz carrier while dissipating 1.48 mW from a 3 V power supply leading to a figure of merit (FOM) of -166.5 dBc/Hz. The VCO is successfully interfaced with a penetrating silicon microelectrode with 700 microm2 iridium recording sites for wireless in vitro recording of a 50 Hz simulated normal sinus rhythm signal from saline over a distance of approximately 0.25 m. Given a typical gain of approximately 40 dB for fully integrated front-end bioamplifiers, a wireless recording microsystem employing this VCO would be capable of detecting input biopotentials down to the submilivolt range.     

Electrosynthesis of ferrate in a batch reactor at neutral conditions for drinking water applications

We report on the electrochemical generation of ferrate species in a batch reactor at neutral conditions (pH ～7) using boron‐doped diamond (BDD) electrodes and Fe (III) salts for applications in drinking water treatment. The impact of several relevant variables, including current density (5–55 mA cm^?2), pH (5–8), and type and concentration of the dissolved iron salts on the production of ferrates were examined. In addition, linear sweep voltammetry (LSV) studies were conducted using buffered electrolytes with and without the presence of iron (III) to decouple the parasitic oxygen evolution reaction. The LSV measurements in the presence of iron (III) and with a neutral electrolyte exhibit oxidation peaks centered ～2.0 V (versus SHE), indicating the production of ferrates at this pH. The rate of ferrate generation is not strongly affected by the pH condition (≤ 20 %); however, current density and the source of iron were found to have a higher impact on the production rate of ferrates. The efficacy of the process was higher using FeCl₃ instead of other sources of iron such as Fe₂O₃ and FeO(OH). The batch reactor results were successfully interpreted by a simple model that considered the kinetics of the ferrate generation and degradation reactions.

     

Design of metasurface polarization converter for near‐field application; stacked conical horn antenna for circular polarization

In this article, a three‐layer transmission mode linear to circular polarization converter (TMCP) is proposed with low‐level reflection coefficient and axial ratio (AR) at 9 GHz. Each layer of the proposed TMCP consists of microstrip patches and lines, providing inductive TM impedance and capacitive TE impedance on each layer to produce 90° out of phase between TE and TM electromagnetic waves. By removing the middle layer of the proposed metamaterial, a two‐layer TMCP with low‐level axial ratio at 8 GHz is obtained. However, the proposed two‐layer TMCP suffers from disagreements between the reflection coefficients of the TE and TM modes, which produce fluctuations on the AR results in the near‐field application. Low‐level reflection coefficient and AR at 9 GHz achieved from the three‐layer TMCP, indeed, make it efficient for the near‐field of a horn antenna. Unit cells of the two‐layer and three‐layer TMCPs consisting patches and lines are simulated using periodic boundary conditions. In addition, the patches and lines are printed on a FR4 substrate and cut out in circle shapes. The three substrates are arranged at the determined separations and then installed in front of a profiled conical horn antenna. The measured AR of the antenna stacked by the three‐layer TMCP is below 2 dB from 8.45 up to 9.6 GHz.     

Microfluidic Synthesis of Ultrasmall Chitosan/Graphene Quantum Dots Particles for Intranasal Delivery in Alzheimer's Disease Treatment

Nanoparticles (NPs) based therapies for Alzheimer's disease (AD) attract interest due to their ability to pass across or bypass the blood-brain barrier. Chitosan (CS) NPs or graphene quantum dots (GQDs) are promising drug carriers with excellent physicochemical and electrical properties. The current study proposes the combination of CS and GQDs in ultrasmall NP form not as drug carriers but as theranostic agents for AD. The microfluidic-based synthesis of the CS/GQD NPs with optimized characteristics makes them ideal for transcellular transfer and brain targeting after intranasal (IN) delivery. The NPs have the ability to enter the cytoplasm of C6 glioma cells in vitro and show dose and time-dependent effects on the viability of the cells. IN administration of the NPs to streptozotocin (STZ) induced AD-like models lead to a significant number of entrances of the treated rats to the target arm in the radial arm water maze (RAWM) test. It shows the positive effect of the NPs on the memory recovery of the treated rats. The NPs are detectable in the brain via in vivo bioimaging due to GQDs as diagnostic markers. The noncytotoxic NPs localize in the myelinated axons of hippocampal neurons. They do not affect the clearance of amyloid β (Aβ) plaques at intercellular space. Moreover, they showed no positive impact on the enhancement of MAP2 and NeuN expression as markers of neural regeneration. The memory improvement in treated AD rats may be due to neuroprotection via the anti-inflammation effect and regulation of the brain tissue microenvironment that needs to be studied.