Graphene and carbon black filled conductive nanocomposite films for heating element applications

Graphene has ultra-high electrical and thermal conductivity, which makes graphene as the most encouraging fillers for thermally conductive composites. Graphene and/or carbon black filled conductive polymer composite (CPC) films used as heating element are smarter than the traditional heating elements due to less environmental pollution, ease of application on many surfaces and possess the merits of lightweight. In this study, we investigated mainly the production, characterization and industrial application of graphene/carbon black reinforced styrene acrylic copolymer emulsion matrix composite films deposited on polyvinyl chloride for flexible heating element. After that, the films were dried at room temperature for 24 h in air. Structural and surface properties of the CPC films were characterized by X-ray diffraction and scanning electron microscopy. Temperature, time and voltage relation of the produced composite films were investigated. Heating and electrical properties of the CPC films were determined by using a thermal camera and 4-point probe measurement system, respectively. The electrical resistivity of the CPC films decreases from ~?10⁸ to 10¹ Ω cm with increasing the filler content or using a combination of two fillers. Graphene and carbon black filled conductive polymer composites to be considered as candidates for flexible heating element applications exhibited good electrical and heating properties thanks to synergistic effect of fillers.     

Bioinspired Composite Microfibers for Skin Adhesion and Signal Amplification of Wearable Sensors

A facile approach is proposed for superior conformation and adhesion of wearable sensors to dry and wet skin. Bioinspired skin‐adhesive films are composed of elastomeric microfibers decorated with conformal and mushroom‐shaped vinylsiloxane tips. Strong skin adhesion is achieved by crosslinking the viscous vinylsiloxane tips directly on the skin surface. Furthermore, composite microfibrillar adhesive films possess a high adhesion strength of 18 kPa due to the excellent shape adaptation of the vinylsiloxane tips to the multiscale roughness of the skin. As a utility of the skin‐adhesive films in wearable‐device applications, they are integrated with wearable strain sensors for respiratory and heart‐rate monitoring. The signal‐to‐noise ratio of the strain sensor is significantly improved to 59.7 because of the considerable signal amplification of microfibrillar skin‐adhesive films.     

A genetic approach to automate preliminary design of gear drives

Determination of volume or weight of a gearbox is an important issue in preliminary design of power transmission applications. Trial and error procedure or some gear standards information sheets are commonly used in traditional design. The purpose of this paper is to automate preliminary design of gear drives by minimizing volume of gear trains. A stochastic approach Genetic Algorithm (GA) was applied to a parallel axis two stage helical gear trains problem. Static and dynamic penalty functions were introduced to the objective function for handling the design constraints. The results were compared with a deterministic design procedure developed. GA based approach produced quite well results promptly supplying preliminary design parameters of gear drives for different gear ratios to the designer.     

CuSCN Modified Back Contacts for High Performance CZTSSe Solar Cells

Optimization of the back contact interface is crucial for improving the performance of Cu₂ZnSnS₄ (CZTS) thin film solar cells. In this paper, self-depleted CuSCN is deployed as an intermediate layer at the Mo/CZTS interface to improve the quality of the back contact. This CuSCN layer, obtained via aqueous solution processing, reduces the thickness of Mo(S,Se)₂ and eliminates multi-layer crystallization of the absorber by suppressing the undesirable reaction between Mo and Se during the selenization process. By regulating the selenium infiltration into the CZTS precursor films during the selenization process, highly crystalline, single-layer Cu₂ZnSn(S,Se)₄ (CZTSSe) absorber layers are realized. The single-layer CZTSSe absorber exhibits reduced carrier recombination, enhanced carrier density and increased work function. The improved back contact and absorber layer enables 11.1% power-conversion-efficiency to be achieved.     

Material Flow Control and Optimization in High‐Pressure Sheet Metal Forming by Active‐Elastic Tools

High‐pressure forming of metal sheets is an innovative forming technology for the production of complex components and offers high potentials to improve the properties and qualities of sheet metal parts. This report describes investigations of a newly developed active‐elastic tool system referred to as ACTEC system. Unlike the use of a comparable semi‐rigid tool system, the ACTEC system shows improvements with respect to the material flow in the flange area and reduced sheet thinning in critical corner regions of the workpiece. In addition, the clamping forces respectively sealing forces necessary to avoid leakage in the tool system during the forming process can be reduced. Moreover, the specific design of the ACTEC‐system as well as current experimental examinations are presented and discussed.     

Investigating the Influence of GABA Neurons on Dopamine Neurons in the Ventral Tegmental Area Using Optogenetic Techniques

Dopamine (DA) is the key regulator of reward behavior. The DA neurons in the ventral tegmental area (VTA) and their projection areas, which include the prefrontal cortex (PFC), nucleus accumbens (NAc), and amygdala, play a primary role in the process of reward-driven behavior induced by the drugs of addiction, including nicotine and alcohol. In our previous study, we developed a novel platform consisting of micro-LED array devices to stimulate a large area of the brain of rats and monkeys with photo-stimulation and a microdialysis probe to estimate the DA release in the PFC. Our results suggested that the platform was able to detect the increased level of dopamine in the PFC in response to the photo-stimulation of both the PFC and VTA. In this study, we used this platform to photo-stimulate the VTA neurons in both ChrimsonR-expressing (non-specific) wild and dopamine transporter (DAT)-Cre (dopamine specific) mice, and measured the dopamine release in the nucleus accumbens shell (NAcShell). We measured the DA release in the NAcShell in response to optogenetic stimulation of the VTA neurons and investigated the effect of GABAergic neurons on dopaminergic neurons by histochemical studies. Comparing the photo-stimulation frequency of 2 Hz with that of 20 Hz, the change in DA concentration at the NAcShell was greater at 20 Hz in both cases. When ChrimsonR was expressed specifically for DA, the release of DA at the NAcShell increased in response to photo-stimulation of the VTA. In contrast, when ChrimsonR was expressed non-specifically, the amount of DA released was almost unchanged upon photo-stimulation. However, for nonspecifically expressed ChrimsonR, intraperitoneal injection of bicuculline, a competitive antagonist at the GABA-binding site of the GABA_A receptor, also significantly increased the release of DA at the NAcShell in response to photo-stimulation of the VTA. The results of immunochemical staining confirm that GABAergic neurons in the VTA suppress DA activation, and also indicate that alterations in GABAergic neurons may have serious downstream effects on DA activity, NAcShell release, and neural adaptation of the VTA. This study also confirms that optogenetics technology is crucial to study the relationship between the mesolimbic dopaminergic and GABAergic neurons in a neural-specific manner.     

Polysulfone-based amphiphilic copolymers: Effect of hydrophilic content on morphology and performance of ultrafiltration membranes

A series of polysulfone (PSf)-based amphiphilic graft copolymers were synthesized to investigate the effects of copolymer composition on membrane morphology and performance. PSf-based ultrafiltration membranes were prepared by phase inversion method using the blends of PSf and PSf-g-poly(ethylene glycol) methyl ether methacrylate (PEGMA) copolymers. Membranes were evaluated in terms of pure water permeability, flux recovery ratio (FRR), protein rejection, and contact angle. The morphology of the membranes was investigated by scanning electron microscopy. Contact angle of membranes was decreased from 85.7° to 51.6°, while the FRR was greatly increased from 55 to 95% upon increasing the PEGMA content of copolymers from 20 to 70 wt %. Results indicated that the ratio of hydrophilic/hydrophobic segments in amphiphilic structures is one the key parameters that control the phase inversion process by altering miscibility, viscosity, and wettability of casting solutions. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48306.     

Rigid polyurethane foams with halogen-free flame retardants: Thermal insulation,mechanical, and flame retardant properties

Rigid polyurethane foam (RPUF) composites with triphenyl phosphate (TPhP), aluminum trihydrate (ATH), and zinc borate (ZnB) alone, as well as their binary blends, were prepared via a one-shot process. The amount of flame retardant (FR) or FR blend was varied from 10 to 50% by polyol weight percentage, and the weight fraction of the blends was also fixed at 40%. The effects of additives on thermal insulation, mechanical, and flame retardancy properties of the composites were investigated. Thermal conductivity of the neat foam (RPUF) decreased from 22.53 to 21.04–21.58 mW m⁻¹ K⁻¹. The compressive strength of foams displayed an increase with increasing the amount of TPhP, ATH, and ZnB till 40% by weight. The limited oxygen index values of all foams increased and the flame spread rates of all foams significantly decreased. It was also observed that the flame was self-extinguished in some cases. The cone calorimeter test results indicated that the FR additives improved the flame retardancy of the RPUF. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 47611.     

Whole-Cell Fatty Acid Composition of Total Coliforms to Predict Sources of Fecal Contamination

The objective of this study was to test the hypothesis that total coliforms isolated from human and nonhuman sources have distinctly different whole-cell fatty acid methyl ester (FAME) profiles. The FAME profiles studied included total coliforms isolated from sewage; feces of livestock, including bovine (dairy cattle), poultry, and swine; and feces of wildlife, including waterfowl and deer. Multiple samples within each category were collected and 303 total coliform isolates were cultured. It was found that the FAMEs 12:0 2OH and 14:0 2OH were exclusively associated with sewage samples, whereas the FAMEs 18:0 and 19:0 ISO were identified only in isolates from the livestock samples. In addition to the presence of signature FAMEs, the average relative masses of 16:1 ω7c, 18:1 ω7c, and 19:0 CYCLO ω8c were significantly different between human and nonhuman sources of total coliforms. A linear discriminant function based on these differences discriminated total coliform isolates of human origin against the other five host categories at a 77% rate of correct classification (RCC). These results strongly support the validity of our hypothesis and suggest that the FAME profiles of total coliforms have the potential to be used as a phenotypic microbial source tracking (MST) tool for predicting the sources of microbial contamination in water environments.