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.     

Mechanochemical processing and microstructural characterization of pure Fe2B nanocrystals

The results of current investigation demonstrate that mechanochemical processing can be used to synthesize high purity Fe₂B nanocrystals by selecting well-optimized milling conditions, reaction paths and proper starting materials. Microstructure, phase analyses, specific surface area, and magnetic properties of the synthesized nanocrystals were examined by using X-ray diffraction/spectroscopy, electron microscopy, nitrogen adsorption–desorption methods following Brunauer-Emmett-Teller equation and vibrating sample magnetometer techniques, respectively. Removal of MgO impurity phase by leaching the resulting powder in the acetic acid solution yielded single phase Fe₂B nanocrystals with the crystallite size and specific surface area of 12.5 nm and 29 m²/g, respectively. Magnetization results clearly indicated the ferromagnetic behavior of Fe₂B nanocrystals with saturation magnetization observed around 96.26 emu·g^?1. Electron microscope images revealed coaxial/spherical powder shape and morphology of the single-phase Fe₂B nanocrystals.     

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.     

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.     

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.     

Developmental changes in the electrophysiological properties of brain stem trigeminal neurons during pattern (barrelette) formation

In the brain stem trigeminal nuclei of rodents there is a patterned representation of whiskers and sinus hairs. The subnucleus interpolaris (SPI) contains the largest and the most conspicuous whisker patterns (barrelettes). Although neural activity plays a role in pattern formation, little is known about the electrophysiological properties of developing barrelette neurons. Here we examined the functional state of early postnatal SPI neurons during and after the consolidation of patterns by using in vitro intracellular recording techniques. After the consolidation of barrelettes [>/= postnatal day (P)4], responses to intracellular current injection consistently reflected the activation of a number voltage-dependent conductances. Most notable was a mixed cation conductance (IH) that prevented strong hyperpolarization and a large low-threshold Ca2+ conductance, which led to Ca2+ spikes and burst firing. At the oldest ages tested (P11-P14) some cells also exhibited an outward K+ conductance (IA), which led to significant delays in action-potential firing. Between P0-3, a time when the formation of barrelettes in the brain stem is still susceptible to damage of the sensory periphery, cells responded linearly to intracellular current injection, indicating they either lacked such voltage-gated properties or weakly expressed them. At all ages tested (P0-14), SPI cells were capable of generating trains of action potentials in response to intracellular injection of depolarizing current pulses. However, during the first few days of postnatal life, spikes were shorter and longer. Additionally, spike trains rose more linearly with stimulus intensity and showed frequency accommodation at early ages. Taken together, these results indicate that the electrophysiological properties of SPI neurons change markedly during the period of barrelette consolidation. Moreover, the properties of developing SPI neurons may play a significant role in pattern formation by minimizing signal distortion and ensuring that excitatory responses from sensory periphery are accurately received and transmitted according to stimulus strength.