High-yield graphene exfoliation using sodium dodecyl sulfate accompanied by alcohols as surface-tension-reducing agents in aqueous solution

The exfoliation of graphite was investigated in aqueous solutions containing sodium dodecyl sulfate (SDS) as a surfactant. The exfoliation was greatly enhanced near the surface aggregation concentration (SAC) of SDS, 2.6 mM, and then decreased for higher SDS contents. However, the flakes exfoliated near the SAC were graphite, whereas graphene was obtained above the critical micelle concentration (CMC). The effect of the use of alcohols as surface-tension-reducing agents (STRAs) on the exfoliation was then investigated. With ethyl alcohol, a dispersion of 2.1 mg ml⁻¹ graphene was achieved from 2.6 mM SDS after only 1 h of sonication, whereas a dispersion of 0.2 mg ml⁻¹ was obtained above the CMC in the absence of STRAs. The results demonstrate that the SDS content near the SAC is highly beneficial for exfoliation as long as the surface tension is maintained near 41.0 mN ml⁻¹. This finding supports the notion that the structure of the adsorbed SDS, depending on its concentration, strongly affects the exfoliation of graphite into graphene.     

Improving the multi-objective evolutionary optimization algorithm for hydropower reservoir operations in the California Oroville–Thermalito complex

This study demonstrates the application of an improved Evolutionary optimization Algorithm (EA), titled Multi-Objective Complex Evolution Global Optimization Method with Principal Component Analysis and Crowding Distance Operator (MOSPD), for the hydropower reservoir operation of the Oroville–Thermalito Complex (OTC) – a crucial head-water resource for the California State Water Project (SWP). In the OTC's water-hydropower joint management study, the nonlinearity of hydropower generation and the reservoir's water elevation–storage relationship are explicitly formulated by polynomial function in order to closely match realistic situations and reduce linearization approximation errors. Comparison among different curve-fitting methods is conducted to understand the impact of the simplification of reservoir topography. In the optimization algorithm development, techniques of crowding distance and principal component analysis are implemented to improve the diversity and convergence of the optimal solutions towards and along the Pareto optimal set in the objective space. A comparative evaluation among the new algorithm MOSPD, the original Multi-Objective Complex Evolution Global Optimization Method (MOCOM), the Multi-Objective Differential Evolution method (MODE), the Multi-Objective Genetic Algorithm (MOGA), the Multi-Objective Simulated Annealing approach (MOSA), and the Multi-Objective Particle Swarm Optimization scheme (MOPSO) is conducted using the benchmark functions. The results show that best the MOSPD algorithm demonstrated the best and most consistent performance when compared with other algorithms on the test problems. The newly developed algorithm (MOSPD) is further applied to the OTC reservoir releasing problem during the snow melting season in 1998 (wet year), 2000 (normal year) and 2001 (dry year), in which the more spreading and converged non-dominated solutions of MOSPD provide decision makers with better operational alternatives for effectively and efficiently managing the OTC reservoirs in response to the different climates, especially drought, which has become more and more severe and frequent in California.     

Spontaneous pattern transfer and selective growth of graphene on a Cu foil

When a 25-μm-thick Cu foil placed on top of a selectively FeCl₃-coated quartz substrate was heated inside a furnace at 1000 °C in a H₂/Ar atmosphere, a FeCl₃ mask pattern on a quartz was spontaneously transferred to the front side of the Cu foil. Due to this spontaneous pattern transfer, a subsequent heating process in H₂/Ar/CH₄ atmosphere led to selective growth of graphene on the front side of the Cu foil. Surface analysis revealed that a spontaneously transferred mask on a Cu foil was made of SiO₂, and Si in SiO₂ was found to be from the quartz substrate. Computational simulation of surface diffusion of Si on a Cu foil was consistent with experimentally observed microstructures of spontaneously transferred pattern boundaries, which suggests that oxidation of diffused Si atoms, which originated from the FeCl₃-coated region of a quartz, on the Cu surface was the crucial mechanism of the spontaneous pattern transfer.     

Internet use and developmental tasks: Adolescents’ point of view

This study explored adolescents’ opinions about how Internet use supports the achievement of their developmental tasks. Qualitative data were collected in focus groups interviews with 127 Italian Internet users (11–20) attending middle and high schools. Discussions were recorded, transcribed and analyzed using content analysis. Results showed that the Internet plays important functions in identity formation, personal autonomy, and relationships outside the family. It allows teens to develop their own interests, to identify with others and, at the same time, differentiate from others. The Internet is also an arena in which adolescents develop and practice autonomy. The Internet can be a source of conflict with parents, because of parents’ concerns about Internet use. However, the Internet can also be a meeting ground with parents. Finally, participants indicated the Internet is used to form close relationships with peers. Gender and age differences are discussed. Although the study is cross-sectional and relies only on adolescent report, findings illustrate how the conceptual framework of developmental goals may be helpful for understanding how the Internet can affect adolescents’ lives.     

Performance improvement of conventional and inverted polymer solar cells with hydrophobic fluoropolymer as nonvolatile processing additive

The morphology of the photoactive layer critically affects the performance of the bulk heterojunction polymer solar cells (PSCs). To control the morphology, we introduced a hydrophobic fluoropolymer polyvinylidene fluoride (PVDF) as nonvolatile additive into the P3HT:PCBM active layer. The effect of PVDF on the surface and the bulk morphology were investigated by atomic force microscope and transmission electron microscopy, respectively. Through the repulsive interactions between the hydrophilic PCBM and the hydrophobic PVDF, much more uniform phase separation with good P3HT crystallinity is formed within the active layer, resulting enhanced light harvesting and improved photovoltaic performance in conventional devices. The PCE of the conventional device can improve from 2.40% to 3.07% with PVDF additive. The PVDF distribution within the active layer was investigated by secondary ion mass spectroscopy, confirming a bottom distribution of PVDF. Therefore, inverted device structure was designed, and the PCE can improve from 2.81% to 3.45% with PVDF additive. Our findings suggest that PVDF is a promising nonvolatile processing additive for high performance polymer solar cells.     

Matrilin-3-Primed Adipose-Derived Mesenchymal Stromal Cell Spheroids Prevent Mesenchymal Stromal-Cell-Derived Chondrocyte Hypertrophy

Adipose-derived mesenchymal stromal cells (Ad-MSCs) are a promising tool for articular cartilage repair and regeneration. However, the terminal hypertrophic differentiation of Ad-MSC-derived cartilage is a critical barrier during hyaline cartilage regeneration. In this study, we investigated the role of matrilin-3 in preventing Ad-MSC-derived chondrocyte hypertrophy in vitro and in an osteoarthritis (OA) destabilization of the medial meniscus (DMM) model. Methacrylated hyaluron (MAHA) (1%) was used to encapsulate and make scaffolds containing Ad-MSCs and matrilin-3. Subsequently, the encapsulated cells in the scaffolds were differentiated in chondrogenic medium (TGF-β, 1–14 days) and thyroid hormone hypertrophic medium (T3, 15–28 days). The presence of matrilin-3 with Ad-MSCs in the MAHA scaffold significantly increased the chondrogenic marker and decreased the hypertrophy marker mRNA and protein expression. Furthermore, matrilin-3 significantly modified the expression of TGF-β2, BMP-2, and BMP-4. Next, we prepared the OA model and transplanted Ad-MSCs primed with matrilin-3, either as a single-cell suspension or in spheroid form. Safranin-O staining and the OA score suggested that the regenerated cartilage morphology in the matrilin-3-primed Ad-MSC spheroids was similar to the positive control. Furthermore, matrilin-3-primed Ad-MSC spheroids prevented subchondral bone sclerosis in the mouse model. Here, we show that matrilin-3 plays a major role in modulating Ad-MSCs’ therapeutic effect on cartilage regeneration and hypertrophy suppression.     

Experimental study to assess the effect of carbon nanotube addition on the through-thickness electrical conductivity of CFRP laminates for aircraft applications

The present paper tests experimentally the through-thickness electrical conductivity of carbon fiber-reinforced polymer (CFRP) composites laminates for aircraft applications. Two types of samples were prepared: Type A samples with carbon nanotubes (CNTs) and Type B samples without CNTs. During the electrical experiments, electrical currents of several mA were injected through the specimens. Electrical resistance was monitored simultaneously in order to deduce the changes in the through-the-thickness electrical conductivity caused by the addition of CNTs. Improvement of electrical conduction by two orders of magnitude was achieved through the addition of 1 wt% carbon nanotubes as compared to classic CFRP without CNTs. For moisture saturated samples, the influence of moisture absorption on such measures was found to be negligible.     

The prevalence of olfactory deficits and their effects on eating behavior from childhood to old age: A large-scale study in the French population

Olfaction is crucial for many aspects of daily life and its alteration is quite common. Here, we set up a large-scale investigation of olfactory deficits in a sample of French individuals in order to examine the prevalence of smell dysfunction and its effects on eating behavior across lifespan, by combining self-reports and psychophysical testing. In a sample of 3685 male and female individuals aged 4 to 89 years old, we showed that the overall prevalence of olfactory dysfunction as measured by psychophysical testing was 17% and varied with age and gender: from 10% in 4–12 year-old children to >30% after 60 years of age; overall, women were less often affected than men. When olfactory abilities were self-evaluated, the prevalence was 6%, suggesting that a large majority of participants were unaware of their olfactory disorder. The prevalence of qualitative smell disorders (parosmia and phantosmia) was much lower (1%). In terms of eating behavior, the effects were present but small: olfactory deficits impact eating behavior of people in different age groups differently. Taken together, these findings highlight the high prevalence of olfactory dysfunctions in the general population, not only in the elderly. They also emphasize the potential consequences of smell dysfunctions on eating behavior. The present results should attract health services’ attention since smell dysfunctions may have consequences on nutrition and health especially in the elderly.