Effect of Yttrium Doping in Barium Zirconium Titanate Ceramics: A Structural, Impedance, and Modulus Spectroscopy Study

In the current article, we studied the effect of yttrium [Y³⁺] ions’ substitution on the structure and electric behavior of barium zirconate titanate (BZT) ceramics with a general formula [Ba_1?x Y_2x/3](Zr_0.25Ti_0.75)O₃ (BYZT) with [x = 0, 0.025, and 0.05] which were prepared by the solid-state reaction method. X-ray diffraction patterns indicate that these ceramics have a single phase with a perovskite-type cubic structure. Rietveld refinement data confirmed [BaO₁₂], [ZrO₆], [TiO₆], and [YO₆] clusters in the cubic lattice. The Y³⁺ ions’ effects on the electric conductivity behavior of BZT ceramics as a function of temperature and frequency are described, which are based on impedance spectroscopy analyses. The complex impedance plots display a double semicircle which highlights the influences of grain and grain boundary on the ceramics. Impedance analyses showed that the resistance decreased with the increasing temperature and resulted in a negative temperature coefficient of the resistance property in all compositions. Modulus plots represent a non-Debye-type dielectric relaxation which is related to the grain and grain boundary as well as temperature-dependent electric relaxation phenomenon and an enhancement in the mobility barrier by Y³⁺ ions. Moreover, the electric conductivity increases with the replacement of Ba²⁺ by Y³⁺ ions may be due to the rise in oxygen vacancies.     

Fatty Acid, Tocopherol and Sterol Compositions of Canadian Prairie Fruit Seed Lipids

The seeds of four prairie fruits—chokecherry (Prunus virginiana), thorny buffaloberry (Shepherdia argentea), Woods’ rose (Rosa woodsii) and hawthorn (Crataegus × mordenensis)—from Southern Alberta were investigated. The lipid contents of the seeds were found to be 10.4, 11.5, 3.7 and 3.4%, respectively. The tested seed lipids contained mainly linoleic acid in the range from 27.9 to 65.6% and oleic acid from 19.7 to 61.9%. The thorny buffaloberry and Woods’ rose seed lipids contained 29.2 and 30.8% of linolenic acid, respectively. The contents of palmitic and stearic acids ranged from 3.2 to 5.4% and 1.6 to 2.2%, respectively. The contents of total tocopherols in the chokecherry, thorny buffaloberry, Woods’ rose and hawthorn seed lipids accounted for 595, 897, 2,358 and 2,837 mg/kg, respectively. The main sterols in the lipids were β-sitosterol, Δ⁵-avenasterol, cycloartenol, campesterol, stigmasterol and gramisterol. The results of the present study show that the lipids from the seeds of the investigated prairie fruits could be a good source of valuable essential fatty acids, tocopherols and sterols, thus suggesting their application as functional foods and nutraceuticals.     

AC conduction in amorphous thin films of SnO<Subscript>2</Subscript>

Alternating current (a.c.) electrical properties of thermally evaporated amorphous thin films of SnO₂ sandwiched between aluminium electrodes have been investigated for temperature during electrical measurements, film thickness, substrate temperature and post-deposition annealing. The a.c. conductivity, σ(ω), is found to vary with frequency according to the relation σ(ω) ∝ ω^s, indicating a hopping process at low temperature. The conduction is explained by single polaron hopping process as proposed by Elliott. The increase in electrical conductivity with increase in temperature during electrical measurements is ascribed to the increase in the formation and high mobility of doubly ionized oxygen vacancies. The increase in conductivity with increase in film thickness is caused by the increase in interstitial tin, oxygen vacancies and defects produced due to deviation from stoichiometry. The increase in conductivity with increase in substrate and annealing temperature may be due to the formation of singly or doubly ionized oxygen vacancies and tin species of lower oxidation state. Measurements of capacitance C as a function of frequency and temperature show a decrease in C with increasing frequency and increase in C with increasing temperature. The increase in capacitance in the high-temperature low-frequency region is probably due to space charge polarization induced by the increasing number of free carriers as a result of increasing temperature.     

Gelam Honey Scavenges Peroxynitrite During the Immune Response

Monocytes and macrophages are part of the first-line defense against bacterial, fungal, and viral infections during host immune responses; they express high levels of proinflammatory cytokines and cytotoxic molecules, including nitric oxide, reactive oxygen species, and their reaction product peroxynitrite. Peroxynitrite is a short-lived oxidant and a potent inducer of cell death. Honey, in addition to its well-known sweetening properties, is a natural antioxidant that has been used since ancient times in traditional medicine. We examined the ability of Gelam honey, derived from the Gelam tree (Melaleuca spp.), to scavenge peroxynitrite during immune responses mounted in the murine macrophage cell line RAW 264.7 when stimulated with lipopolysaccharide/interferon-γ (LPS/IFN-γ) and in LPS-treated rats. Gelam honey significantly improved the viability of LPS/IFN-γ-treated RAW 264.7 cells and inhibited nitric oxide production—similar to the effects observed with an inhibitor of inducible nitric oxide synthase (1400W). Furthermore, honey, but not 1400W, inhibited peroxynitrite production from the synthetic substrate 3-morpholinosydnonimine (SIN-1) and prevented the peroxynitrite-mediated conversion of dihydrorhodamine 123 to its fluorescent oxidation product rhodamine 123. Honey inhibited peroxynitrite synthesis in LPS-treated rats. Thus, honey may attenuate inflammatory responses that lead to cell damage and death, suggesting its therapeutic uses for several inflammatory disorders.     

Surface immobilisation of the sandwich type Na14[Fe4(Ox)4(H2O)2(SbW9O33)2]·60H2O polyoxometalate

A functionalised Fe-substituted Keggin Na₁₄[Fe₄(C₂O₄)₄(H₂O)₂(SbW₉O₃₃)₂]·60H₂O type POM termed “Fe₄Ox₄” has been successfully immobilised onto carbon electrode surfaces through the employment of conducting polypyrrole films and the layer-by-layer (LBL) technique. For the POM doped polypyrrole films the redox systems associated with the POM's tungsten-oxo framework was not apparent upon redox cycling, however a reversible redox couple associated with the Fe^III/II redox system was clearly seen within the pH range 2–7. Organised multilayer assemblies were constructed by the employment of the layer by layer (LBL) technique through alternating anionic Fe₄Ox₄ layers and cationic Ru^II metallodendrimers with poly(diallyldimethylammonium chloride) (PDDA) employed as an initial base layer. Stable redox couples associated with both the Fe^III/II and tungsten-oxo framework, for the Fe₄Ox₄ POM, and the Ru^III/II for the metallodendrimer, were clearly observed upon layer construction and redox switching within the pH domain of 2–7. The resulting multilayer assembly showed good stability towards redox cycling. Further investigations into the multilayer assembly were undertaken by determining it is charge transfer resistance using AC-impedance voltammetry. The layer also showed catalytic ability towards the reduction of H₂O₂ at pH 6.5.     

Hydrolysis of SnCl2 on polyaniline: Formation of conducting PAni‐SnO2 composite with enhanced electrochemical properties

First time in the literature, we report that polyaniline‐EB can be doped by SnCl₂ to give conducting SnO₂ doped polyaniline novel material. The composite is characterized by Fourier transform infrared, ultraviolet‐visible, X‐ray diffraction, scanning electron micrograph, transmission electron microscopy, and electrochemical methods. The new composite exhibited improved electrochemical properties compared with the virgin polymer. The composite is also expected for its high sensitivity for recognizing volatile organic compounds. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

An Enhanced A-MSDU Frame Aggregation Scheme for 802.11n Wireless Networks

The main goal of the IEEE 802.11n standard is to achieve a minimum throughput of 100 Mbps at the MAC service access point. This high throughput has been achieved via many enhancements in both the physical and MAC layers. A key enhancement at the MAC layer is frame aggregation in which the timing and headers overheads of the legacy MAC are reduced by aggregating multiple frames into a single large frame before being transmitted. Two aggregation schemes have been defined by the 802.11n standard, aggregate MAC service data unit (A-MSDU) and aggregate MAC protocol data unit (A-MPDU). As a consequence of the aggregation, new aggregation headers are introduced and become parts of the transmitted frame. Even though these headers are small compared to the legacy headers they still have a negative impact on the network performance, especially when aggregating frames of small payload. Moreover, the A-MSDU is highly influenced by the channel condition due mainly to lack of subframes sequence control and retransmission. In this paper, we have proposed an aggregation scheme (mA-MSDU) that reduces the aggregation headers and implements a retransmission control over the individual subframes at the MSDU level. The analysis and simulations results show the significance of the proposed scheme, specifically for applications that have a small frame size such as VoIP.     

Why does the public cooperate with law enforcement? The influence of the purposes and targets of policing.

This study addresses the extension of the “procedural justice” model for understanding public cooperation with law enforcement to new policing contexts and new minority populations. The study draws on four recent surveys of public reactions to policing against crime or against terrorism across different populations to examine whether the changing purpose of policing, or changes in the communities targeted for heightened policing, have an effect on how cooperative behaviors are elicited. This paper presents evidence that procedural justice mechanisms are robust across a variety of contexts and populations in the United States. Three issues in particular are addressed. First, whether the procedural justice model applies across policing functions and policed populations. Second, whether the perception that another group is the target of disproportionate policing efforts has any effect on the cooperation behavior of a non-targeted population. And third, whether people attend to different aspects of policing behavior if their community is targeted for heightened policing attention. (PsycINFO Database Record (c) 2011 APA, all rights reserved)