Synthesis of Janus/non-Janus hollow graphene oxide micro- and nanoparticles and the effects of their localization on the thermal conductivity of blend-based polymer composites

Journal of Materials Science - In this study, the effects of Janus, hydrophilic and hydrophobic hollow graphene oxide (HO) particles on the thermal conductivity of binary polymer blends were...     

A new localization method in internet of things by improving beetle antenna search algorithm

Wireless Networks - Localization is regarded as one of the important challenges in the internet of things and Wireless Sensor Networks. The failure to localize sensors properly causes data loss and...     

A microwave-assisted new synthesis of sulfonylidene–sulfonamide via reactions of N-sulfonylketenimine and sodium arylsulfinates

A rapid practical microwave-assisted new synthesis of sulfonylidene–sulfonamide was developed via the one-pot, three-component reaction of sulfonyl azides, terminal alkynes, and sodium arylsulfinates catalyzed by copper(I) iodide in DMF in moderate to good yields.     

The influence of depressive symptoms on experimental smoking and intention to smoke in a diverse youth sample.

Numerous studies have shown associations between smoking and depression, but the generalizability of the relationship across ethnic groups remains unknown. The present study assessed the association between depression and smoking intention and experimentation among adolescents from four ethnic groups in the Los Angeles area-Chinese/Chinese American, Latino/Hispanic, Persian/Iranian, and White. Over 800 7th graders in the Los Angeles area completed measures of depressive symptoms, experimentation with smoking, intention to smoke, and sociodemographic covariates. Chinese/Chinese American students had the lowest levels of depressive symptoms, whereas Latinos/Hispanics had the highest levels. Latinos/Hispanics also were the most likely to intend to smoke in the next year and were the most likely to have started experimenting with cigarette smoking. Depressive symptoms were significantly associated with intention to smoke even after controlling for language use acculturation, socioeconomic status, gender, and ethnicity. The association between depressive symptoms and intention to smoke did not vary significantly across ethnic groups. These results indicate that the association between depressive symptoms and adolescent smoking generalizes across diverse ethnic groups.     

Optimization of Run-of-River Hydropower Plant Design under Climate Change Conditions

The assessment of climate change and its impacts on hydropower generation is a complex issue. This paper evaluates the application of representative concentration pathways (RCPs, 2.6, 4.5, and 8.5) with the change factor (CF) method and the statistical downscaling method (SDSM) to generate six climatic scenarios of monthly temperature and rainfall over the period 2020–2049 in the Karkheh basin, Iran. The identification of unit hydrographs and component flows from rainfall, evaporation and streamflow data (IHACRES) model was employed to simulate runoff for the purpose of designing a run-of-river hydropower plant in the Karkheh basin. The non-dominated sorting genetic algorithm (NSGA)-II was employed to maximize yearly energy generation and the plant factor, simultaneously. Results indicate the runoff scenarios associated with the SDSM lead to higher run-of-river hydropower generation in 2020–2049 compared to the CF results.     

Effective gas separation through graphene oxide containing mixed matrix membranes

In the present study, graphene oxide (GO) was incorporated into poly(vinylidene fluoride) (PVDF) and chemically modified PVDF (M‐PVDF) to prepare mixed matrix membranes (MMMs) for gas separation application. Performed analyses proved appropriate dispersion of exfoliated GO sheets in polymer matrices and sufficient compatibility at the interfacial phases. M‐PVDF based MMMs were thermally and mechanically more stable relative to the PVDF‐based MMMs. The oxygen containing functional groups in M‐PVDF was probably the main reason for this more stability. PVDF/GO MMMs rendered low gas permeability and high selectivity. Both impermeable GO sheets and crystalline phases of PVDF were responsible for such behavior. On the other hand, interestingly gas permeability of M‐PVDF/GO MMMs was enhanced while no substantial decline was recorded in gas selectivity. For instance, He and CO₂ permeability was increased 12.46% and 25.89%, respectively, compared to the pure PVDF membrane. This behavior originated from functional groups of M‐PVDF and the interaction of these groups with GO sheets. Since GO often amplified gas barrier properties of polymers, such increscent would be appreciable. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46271.     

Optimal SMDP‐Based Connection Admission Control Mechanism in Cognitive Radio Sensor Networks

Traffic management is a highly beneficial mechanism for satisfying quality‐of‐service requirements and overcoming the resource scarcity problems in networks. This paper introduces an optimal connection admission control mechanism to decrease the packet loss ratio and end‐to‐end delay in cognitive radio sensor networks (CRSNs). This mechanism admits data flows based on the value of information sent by the sensor nodes, the network state, and the estimated required resources of the data flows. The number of required channels of each data flow is estimated using a proposed formula that is inspired by a graph coloring approach. The proposed admission control mechanism is formulated as a semi‐Markov decision process and a linear programming problem is derived to obtain the optimal admission control policy for obtaining the maximum reward. Simulation results demonstrate that the proposed mechanism outperforms a recently proposed admission control mechanism in CRSNs.     

Increasing Angiogenesis Factors in Hypoxic Diabetic Wound Conditions by siRNA Delivery: Additive Effect of LbL-Gold Nanocarriers and Desloratadine-Induced Lysosomal Escape

Impaired wound healing in people with diabetes has multifactorial causes, with insufficient neovascularization being one of the most important. Hypoxia-inducible factor-1 (HIF-1) plays a central role in the hypoxia-induced response by activating angiogenesis factors. As its activity is under precise regulatory control of prolyl-hydroxylase domain 2 (PHD-2), downregulation of PHD-2 by small interfering RNA (siRNA) could stabilize HIF-1α and, therefore, upregulate the expression of pro-angiogenic factors as well. Intracellular delivery of siRNA can be achieved with nanocarriers that must fulfill several requirements, including high stability, low toxicity, and high transfection efficiency. Here, we designed and compared the performance of layer-by-layer self-assembled siRNA-loaded gold nanoparticles with two different outer layers—Chitosan (AuNP@CS) and Poly L-arginine (AuNP@PLA). Although both formulations have exactly the same core, we find that a PLA outer layer improves the endosomal escape of siRNA, and therefore, transfection efficiency, after endocytic uptake in NIH-3T3 cells. Furthermore, we found that endosomal escape of AuNP@PLA could be improved further when cells were additionally treated with desloratadine, thus outperforming commercial reagents such as Lipofectamine^® and jetPRIME^®. AuNP@PLA in combination with desloratadine was proven to induce PHD-2 silencing in fibroblasts, allowing upregulation of pro-angiogenic pathways. This finding in an in vitro context constitutes a first step towards improving diabetic wound healing with siRNA therapy.     

Rapid synthesis of new block copolyurethanes derived from L‐leucine‐PEG in ionic liquids under microwave irradiation

This study concerns the synthesis of novel multi block polyurethane (PU) copolymers containing eco‐friendly segments, taking the advantage of ionic liquids (IL)s under microwave irradiation. For this, L ‐leucine anhydride cyclodipeptide (LAC) was prepared and then a new class of poly(ether‐urethane‐urea)s (PEUUs) was synthesized with two types of ILs, including room temperature imidazolium (RTIL)s and molten ammonium type ILs. ILs were used as reaction media and PUs were prepared via two‐step polymerization method. Polymerization reaction was also conducted under conventional heating method in N‐methyl pyrrolidone (NMP) as reaction solvent. In the first step, 4,4′‐methylene‐bis(4‐phenylisocyanate) (MDI) was reacted with LAC to produce isocyanate‐terminated poly(imide‐urea) oligomers as hard segment. Chain extension of the resulting prepolymer with polyethyleneglycol (PEG) of molecular weights of 400 (PEG‐400) was the second step to furnish a series of new PEUUs. These multiblock copolymers are optically active, thermally stable and soluble in amide‐type solvents. PEUUs prepared in ILs under microwave irradiation showed more phase separation and crystallinity than PEUU prepared under conventional method. Some structural characterization and physical properties of these PEUUs, prepared under different methods, are reported and compared. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011