Investigation of current‐voltage characteristics and current conduction mechanisms in composites of polyvinyl alcohol and bismuth oxide

Temperature dependent current‐voltage (I–V) measurements of Au/Polyvinyl Alcohol + Bi₂O₃/n‐Si structure were conducted between 100 and 350 K for investigating the temperature dependence of I–V characteristics and current conduction mechanisms in the structure. Series resistance of the structure is calculated using Ohm's law and Cheungs' method. Ideality factor (n) and zero‐bias barrier height (Φ_Bo) were obtained considering thermionic emission theory. From 100 to 350 K, n changed from 32.1 to 3.54, and Φ_Bo changed from 0.27 to 0.99 eV. Obtained temperature dependent values of n and Φ_Bo suggested that thermionic emission is not the dominant current conduction mechanism. Therefore, Ln(I)–Ln(V) curves of the studied structure were plotted for investigating current conduction mechanisms in the structure and current flow is explained considering space charge limited current. Moreover, density of interface states (D_it) in the structure were calculated and its temperature dependence was investigated such that D_it values are reduced to the order of ～10¹³ eV^?1 cm^?2 from ～10¹⁴ eV^?1 cm^?2 with increasing temperature. POLYM. ENG. SCI., 54:1811–1816, 2014. © 2013 Society of Plastics Engineers     

Micro-RNA and Proteomic Profiles of Plasma-Derived Exosomes from Irradiated Mice Reveal Molecular Changes Preventing Apoptosis in Neonatal Cerebellum

Cell communication via exosomes is capable of influencing cell fate in stress situations such as exposure to ionizing radiation. In vitro and in vivo studies have shown that exosomes might play a role in out-of-target radiation effects by carrying molecular signaling mediators of radiation damage, as well as opposite protective functions resulting in resistance to radiotherapy. However, a global understanding of exosomes and their radiation-induced regulation, especially within the context of an intact mammalian organism, has been lacking. In this in vivo study, we demonstrate that, compared to sham-irradiated (SI) mice, a distinct pattern of proteins and miRNAs is found packaged into circulating plasma exosomes after whole-body and partial-body irradiation (WBI and PBI) with 2 Gy X-rays. A high number of deregulated proteins (59% of WBI and 67% of PBI) was found in the exosomes of irradiated mice. In total, 57 and 13 miRNAs were deregulated in WBI and PBI groups, respectively, suggesting that the miRNA cargo is influenced by the tissue volume exposed to radiation. In addition, five miRNAs (miR-99b-3p, miR-200a-3p, miR-200a, miR-182-5p, miR-182) were commonly overexpressed in the exosomes from the WBI and PBI groups. In this study, particular emphasis was also given to the determination of the in vivo effect of exosome transfer by intracranial injection in the highly radiosensitive neonatal cerebellum at postnatal day 3. In accordance with a major overall anti-apoptotic function of the commonly deregulated miRNAs, here, we report that exosomes from the plasma of irradiated mice, especially in the case of WBI, prevent radiation-induced apoptosis, thus holding promise for exosome-based future therapeutic applications against radiation injury.     

Effects of annealing on the structural and magnetic properties of flame spray pyrolyzed MnFe2O4 nanoparticles

In this study, manganese ferrite (MnFe₂O₄) nanoparticles were produced through flame spray pyrolysis (FSP). To investigate the effects of heat treatment, the nanoparticles were annealed between 400 and 650°C for 4 h in air in a comparative manner. The structural, chemical, morphological, and magnetic properties of the nanoparticles were evaluated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), dynamic light scattering (DLS), and vibrating sample magnetometry (VSM), respectively. The XRD results showed that the nanoparticles synthesized by the FSP method exhibited the MnFe₂O₄ spinel ferrite structure. The annealing process led to the decomposition of MnFe₂O₄ into various phases. According to the morphological analysis, the as-synthesized particles were hemispherical–cubic in shape and had an average particle size of less than 100 nm. In addition, the chemical bond structures of the nanoparticles were confirmed in detail by XPS elemental analysis. The highest saturation magnetization was recorded as 33.50 emu/g for the as-produced nanoparticles. The saturation magnetization of the nanoparticles decreased with increasing annealing temperature, while coercivity increased.     

Preparation of Gadolina Stabilized Bismuth Oxide Doped with Boron via Electrospinning Technique

In this study, boron doped and undoped poly (vinyl) alcohol/bismuth–gadolina acetate (PVA/Bi–Gd) nanofibers were prepared using electrospinning technique then calcinated at 800 °C for 2 h. The originality of this study is the addition of boron to metal acetates. The effects of boron doping were investigated in terms of solution properties, morphological changes and thermal characteristics. The characteristics of the fibers were investigated with FT-IR, XRD, SEM and BET. The addition of boron did not only increase the thermal stability of the fibers, but also their diameters, which yielded stronger fibers. XRD analyses showed that boron doping increased the peak intensities and indicated that the boron doping enhanced the crystallite size. Moreover, no shifts were noticed in diffraction angles for boron doped and undoped samples. Therefore, boron doping did not significantly alter the lattice spacing. The SEM micrograph of the fibers showed that the addition of boron resulted in the formation of cross-linked bright-surfaced fibers. The average fiber diameter for boron doped and undoped fiber mats were 204 and 123 nm, respectively. Also, grain diameters of boron doped and undoped nanocrystalline sintered powders were measured as 140 and 118 nm, respectively. The BET results showed that boron undoped and doped Bi₂O₃–La₂O₃ nanocrystalline powder ceramic structures sintered at 800 °C have surface areas of 59.72 and 39.80 m²/g, respectively.     

A Monte-Carlo simulation of the effect of surface morphology on the fracture of nanobeams

Experiments show that the strength of nanostructures can be very high and that strength statistics are dominated by surface flaws. To understand the dependence of strength on the surface morphology, a series of fracture mechanics based Monte-Carlo simulations were performed. The surfaces of previously tested Si nanobeams were measured, statistically characterized and equivalent surfaces were generated. The surface profiles consist of bunched steps with varying heights and widths. At the root of each step, there is a stress singularity defined by a stress intensity factor. The beams were assumed to fail when the stress intensity factor anywhere on the surface exceeds the fracture toughness. In agreement with experiments, simulations show that even a small increase in the surface roughness results in a significant reduction in the strength of nanostructures. Thus, careful attention to the surfaces is essential for optimum strength and reliability at the nanoscale.     

A comparative study on structural,morphological and photocatalytic properties of anodically grown ZnO nanowires under varying parameters

Journal of Materials Science: Materials in Electronics - In this study, zinc oxide (ZnO) nanowires (NWs) were successfully produced on Zn plates through electrochemical anodization in potassium...     

The effects of Cu and Al on dry sliding wear properties of eutectic Sn-9Zn lead-free solder alloy

The present study investigates the influence of Cu and Al on microstructure and wear behavior of a eutectic Sn-9Zn solder alloy. The Sn-9Zn–X alloy was produced by adding various amounts of Cu and Al through investment casting method. The produced Sn-9Zn–X alloys were characterized by a scanning electron microscope, X-ray diffraction, and hardness measurements. In wear tests at 1 ms^?1 sliding speed, 10 N load and 5 different sliding distances (400–2000 m) were used. The results show that as the amount of Cu and Al increased within Sn-9Zn alloy, the hardness of the alloy increased as well. Depending on the increase in hardness of the alloys produced by investment casting, it was observed that weight loss decreased during wear tests. Furthermore, the same proportion of added Al alloys’ hardness and weight loss were observed to be higher than the added Cu alloys. Furthermore, the Cu-added alloy exhibited higher hardness and lower weight loss than the Al-added alloy did.     

Geo-engineering properties and settlement of peaty soils at an industrial site (Turkey)

Peats consist of the partly decomposed remains of vegetation, which have accumulated in waterlogged areas. They are often unsuitable for supporting structures of any kind due to their high water content, high compressibility, low shear strength and high degree of spatial variability. The paper reports a preliminary study on peats from industrial sites in the city of Kayseri, Turkey. The soils in the study area are classified as peat to muck. The peats are fibrous at shallow depth and become amorphous as they extend to some 8 m depth. The ranges of geo-engineering properties are generally consistent with those reported in the literature, with some variation due to their higher mineral soil contents. The behavior of the peats is essentially frictional, with high friction and relatively small cohesion. The direct shear tests yielded higher shear strengths than those from the triaxial tests, due to the fact that the peat specimens used in the direct shear tests were rich in fibers and mineral soils. Back analysis of the settlement of heavy rolls of metal wires laid on the peat generally confirmed the consolidation properties of the soil determined in laboratory.