Synthesis,thermal, dielectric,and microwave reflection loss properties of nickel oxide filler with natural fiber-reinforced polymer composite

Fabrication of hybrid composite of nickel oxide (NiO) combined with oil palm empty fruit bunch (OPEFB) reinforced with polycaprolactone (PCL) has been done by using thermal Haake blending machine, which ensured mixture homogeneity. All hybrid composites' characterizations were carried out using X-ray diffraction (XRD), Fourier transform infrared spectrometry, differential thermogravimetry, thermogravimetric analysis, and scanning electron microscopy. The results showed that the XRD profile patterns of the composites clearly changed as the filler loading amount was increased. Fourier transform infrared spectra illustrated a slight change in the frequencies and positions of the peaks after adding NiO, indicating that some interactions occurred between C=O and O–H or among the fiber, NiO, and PCL. The microwave electromagnetic properties, such as reflection loss (dB), relative complex permittivity (ε_r =–j), and permeability (−j) were calculated at various microwave frequencies in the X-band (8–12 GHz) range. It was observed that the thermal stability, magnetic, and dielectric properties of NiO:OPEFB:PCL composites were modified significantly with NiO addition. This enables the new hybrid composites to be used as engineering materials in the microwave applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46998.     

Monolithic PDMS Laminates for Dielectric Elastomer Transducers through Open-Air Plasma Treatment

This study investigates the use of an open-air plasma treatment system for the surface modification of polydimethylsiloxane, to improve layer-to-layer adhesion. The procedure presented herein is more cost-efficient compared to conventional vacuum-based plasma treatment, and it is performed at different speeds and distances away from the nozzle, to investigate how these two parameters influence the resulting interfacial layer of two fully cured polydimethylsiloxane films. The plasma treatment is determined to not alter mechanical properties as compared to the single film, while peel forces are sufficient to avoid delamination during operation.     

Comparison Study of Microstructure and Phase Evolution in Mg-Nd- and Mg-Gd-Based Alloys

Microstructure and phase evolution in Mg-Nd-, Mg-Gd-, and Mg-Gd-Nd-based alloys with additions of Zn, Zr, and Y were analyzed in the as-cast, solution-treated and aged conditions. Close similarity between the as-cast microstructures and precipitation sequence during aging was revealed. Along with this, distinct features of eutectic compounds and of crystal structure, composition, and orientation relationships of β″, β′, and β ₁ phases were established. Formation of Zn₂Zr₃ rods in Mg-Nd-based alloy and cuboid-shaped particles in Mg-Gd- and Mg-Gd-Nd-based alloys is discussed. The features of the age hardening curves were connected with differences between β″ → β′ transformation and different diffusivities of Gd and Nd in Mg-matrix.     

Field research, relief work and war: does chloroquine-resistance occur in displaced populations of southern Sudan?

The Baltimore College of Dental Surgery, Dental School, University of Maryland at Baltimore offers an extensive curriculum for the study of substance abuse, alcoholism, and other chemical dependencies. This article outlines the curriculum course hours and topics of study for both dentists and dental hygienists. The goal of the curriculum is for students to understand the disease process, intervention methods, treatment options, and other aspects of chemical dependence.     

Soft and flexible conductive PDMS/MWCNT composites

Conductive elastomers based on MWCNT in polydimethylsiloxane (PDMS) have been prepared by a range of dispersion methods such as ultrasonication, speedmixing and roll milling in combination with physical or covalent modification. The ionic liquid (IL), 1‐ethyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide, was used to pre‐disperse MWCNT in a MWCNT/IL‐gel that was used for preparation of MWCVNT/PDMS composites. The method was seen to be effective at low levels of MWCNT, but required combination with a roll mill to obtain a stable dispersion at 4 wt % MWCNT. With higher amounts of MWCNT a reduction in conductivity was observed, which was attributed to a change in morphology occurring between 4 and 5 wt % MWCNT. As an alternative to IL dispersing aids a novel functionalized MWCNT was prepared by free radical polymerization using α‐methacryloxypropyl‐polydimethylsiloxane, which could be used directly for preparation of MWCNT/PDMS composites. Composites prepared by use of the IL dispersion method, use of a roll mill or by use of the f‐MWCNT all had conductivities around 0.005–0.01 s/cm and retained conductivity upon extension. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44767.     

Design of high-toughness polyacrylamide hydrogels by hydrophobic modification

Polyacrylamide (PAAm) hydrogels possessing a very large extensibility at break have been prepared via micellar crosslinking copolymerization of acrylamide monomer and N,N′-methylenebis(acrylamide) crosslinker in the presence of hydrophobic comonomers. N-butyl-, N-hexyl-, N-octyl-, and N,N-dihexylacrylamides were used as the hydrophobes in the hydrogel preparation. Incorporation of hydrophobes with an alkyl chain length x > 4 results in an increase in the loss factor tan δ of hydrogels due to the formation of temporary junction zones inside the gel network. The number N_H of the hydrophobes per hydrophobic block together with the alkyl chain length x of the pendant hydrophobic group were used to tune the loss factor of the hydrogels over two orders of magnitude. Tensile mechanical measurements show that increasing N_H or x also increases the degree of toughness of PAAm hydrogels. Keeping constant the hydrophobe level (20 mol%) at an alkyl chain length x = 6, increasing N_H from 9 to 30 increased the elongation ratio at break from 125 to 250%. Hydrogels exhibiting a high toughness, i.e., about 300% elongation ratio at break were obtained by modification of PAAm network chains with 10 mol% N-octylacrylamide.     

The effect of mineral surface nature on the mechanical properties of mineral-filled polypropylene composites

The adhesion between the polymer matrix and the inorganic filler particles are the goal of various and tremendous studies. This issue is still occupying a big part of the researchers thinking to find a proper solution, however, its difficulty returns to different factors playing roles in it. Among these factors are the filler surface, i.e., hydrophobicity and hydrophilicity, functional groups on the surface, as well as mineral filler particle size distribution, and particle shape. Therefore, in the current study, the difference in mechanical properties for two mineral fillers; namely, silica and talc, differs in their surface and rheology properties were investigated. Results showed that the difference in the mechanical properties of the same matrix when the inorganic filler is different either in type or loading. Talc showed the better results in terms of Young’s modulus and impact strength, where silica showed higher values in terms of yield stress. Moreover, both minerals addition resulted drop in all strain measures, yet silica showed relatively higher measures than talc, but the relative difference measures between the two minerals decrease with increasing their percentage of additions. In brief, the introduction of inorganic fillers to polypropylene (PP) increases toughness, stiffness and strength of the mineral-filled PP end-products.     

Shrimp waste extract and astaxanthin: rat alveolar macrophage, oxidative stress and inflammation

Astaxanthin is a carotenoid known to have antioxidant and antiinflammatory properties. This study examined if shrimp astaxanthin modulates the production of superoxide (O(-)(2)), nitric oxide (NO), and tumor necrosis factor-α (TNF-α) in rat alveolar macrophages. The oxidative effect was induced by phorbol myristate acetate and lipopolysacharide. The treatment was compared with superoxide dismutase, butylated hydroxytoluene, commercial astaxanthin, N-nitric-L-arginine methyl ester and L- canavanine, all administered as a 43.5-μg/mL dose in the presence of 1% EtOH/0.5% DMSO. All treatments maintained cell viability, as observed in the MTT assay, and shrimp extract increased the viable alveolar macrophages to 168%. Shrimp extract and commercial astaxanthin showed a suppressive effect on the generation of both free radicals O(-)(2) and NO, while purified shrimp astaxanthin was specific to NO. TNF-α secretion was correlated with NO production. However, in this correlation, the shrimp extract completely inhibited TNF-α. In the light of these findings, the antioxidant action demonstrated in this study suggests that the shrimp extract could be considered as a promising source of bioactive substances with antioxidant and anti-inflammatory activity. PRACTICAL APPLICATION: The hydrolysis process of shrimp waste generates bioactive products that add economic value to shrimp processing, mainly because they may have applications in nutraceutical and animal feed industry.     

How much weight gain occurs following smoking cessation: A comparison of weight gain using both continuous and point prevalence abstinence.

Estimates of postcessation weight vary widely. This study determined the magnitude of weight gain in a cohort using point prevalence and continuous abstinence criteria for cessation. Participants were 196 volunteers who participated in a smoking cessation program and who either continuously smoked (n?=?118), were continuously abstinent (n?=?51), or who were point prevalence abstinent (n?=?27) (i.e., quit at the 1-year follow-up visit but not at others). Continuously abstinent participants gained over 13 lbs. (5.90 kg) at 1 year, significantly more than continuously smoking (M?=?2.4 lb.) and point prevalence abstinent participants (M?=?6.7 lbs., or 3.04 kg). Individual growth curve analysis confirmed that weight gain and the rate of weight gain (pounds per month) were greater among continuously smoking participants and that these effects were independent of gender, baseline weight, smoking and dieting history, age, and education. Results suggest that studies using point prevalence abstinence to estimate postcessation weight gain may be understanding postcessation weight gain. (PsycINFO Database Record (c) 2010 APA, all rights reserved)