MC-MAC: a multi-channel based MAC scheme for interference mitigation in WBANs

Wireless body area networks (WBANs) support the inter-operability of biomedical sensors and medical institutions with convenience and high-efficiency, which makes it an appropriate solution for the pervasive healthcare. Typically, WBANs comprise in-body or around-body sensor nodes for collecting data of physiological feature. Therefore, the efficient medium access control (MAC) protocol is a crucial paramount to coordinate these devices and forward data to the medical center in an efficient and reliable way. However, the extensive use of wireless channel and coexistence of WBANs may result in inevitable interference which will cause performance degradation. Besides, contention-based access in single channel in WBANs is less efficient for dense medical traffic on account of large packet delay, energy consumption and low priority starvation. To address these issues above, we propose a multi-channel MAC (MC-MAC) scheme to obtain better network performance. Considering the characteristic and emergency degree of medical traffic, we introduce a novel channel mapping and selection mechanism, cooperating with conflict avoidance strategy, to organize nodes to access available channels without collisions. In addition, we have evaluated the performance of MC-MAC and the standard IEEE 802.15.6 via simulation and hardware test. The test is conducted by hardware platform based on prototype system of WBANs. Both of the analysis and simulation results show that MC-MAC outperforms the IEEE 802.15.6 in terms of packet delay, throughput, packet error rate and frame error rate.     

Alkylene oxide poylmerizations: identification of side reactions and by-products

In this study microwave-assisted anionic ring opening polymerization (ROP) of alkylene oxides is reported. Low molar mass polymers of propylene oxide (PO), butylene oxide (BO) and hexylene oxide (HO) are synthesized by anionic ring opening using various monohydric alcohols as initiators. The monohydric alcohols and lower molar masses allowed for monitoring of different types of possible unwanted by-products and their sources. Liquid chromatography at critical conditions (LCCC) and liquid adsorption chromatography (LAC) are used to determine the presence of oligomers other than targeted. Finally, MALDI-TOF MS of the products have clearly shown the trends and extents of different types of side reactions that are possible in anionic ring opening of alkylene oxides. Propylene oxide is most vulnerable to chain transfer reactions compared to higher alkylene oxide.     

Direct measurement and dynamic mechanical analysis on the coexistence of positive and negative electrocaloric effects in Bi0.5Na0.5TiO3-xBaTiO3 solid solutions

Abnormal electrocaloric effect (ECE) is investigated in (1-x)Bi_0.5Na_0.5TiO₃-xBaTiO₃ solid solutions by calorimetry measurements, manifesting itself by the differences in the heats released and absorbed under the application and withdrawal of electric fields, respectively. The abnormal ECE is explained by the coexistence of positive and negative ECEs close to the ferroelectric-to-antiferroelectric transition temperature, which is demonstrated by the structural and ferroelectric properties determined from dynamic mechanical analyses and thermodynamics calculations on the solid solutions under an applied electric field, respectively. A threshold electric field below which the negative ECE occurs is obtained, in comparisons with that predicted by the thermodynamics Maxwell's relations. The abnormal ECE obtained from direct measurement is compared with that calculated by the indirect measurement, and the discrepancy is discussed.     

Dietary supplementation of flaxseed oil ameliorates the effect of cisplatin on rat kidney

Cisplatin (CP) is an effective chemotherapeutic agent widely used in the treatment of many malignant tumours. However, its therapeutic utility is limited by dose dependent nephrotoxicity. Several agents/strategies have attempted to prevent CP nephrotoxicity but were not found suitable for clinical practice. Dietary flaxseed oil (FXO), a rich source of omega-3 fatty acids has been shown to prevent/reduce the progression of certain types of cardiovascular and renal disorders. The protective effect of FXO on CP induced nephrotoxic and other deleterious effects was investigated. Rats were prefed experimental diets for 10 days and then received a single dose of CP (6 mg/kg body weight) intraperitoneally while still on diet. Serum/urine parameters, enzymes of brush border membrane (BBM), oxidative stress and carbohydrate metabolism in rat kidney were analyzed. CP nephrotoxicity was recorded by increased serum creatinine and blood urea nitrogen. CP decreased the activities of metabolic enzymes, antioxidant defense system and BBM enzymes. In contrast, FXO alone increased enzyme activities of carbohydrate metabolism and brush border membrane. FXO feeding to CP treated rats markedly enhanced resistance to CP-elicited deleterious effects. Dietary FXO supplementation ameliorated CP induced specific metabolic alterations and oxidative damage due to its intrinsic biochemical antioxidant properties.     

Methemoglobin Is an Endogenous Toll-Like Receptor 4 Ligand—Relevance to Subarachnoid Hemorrhage

Neuroinflammation is a well-recognized consequence of subarachnoid hemorrhage (SAH), and may be responsible for important complications of SAH. Signaling by Toll-like receptor 4 (TLR4)-mediated nuclear factor κB (NFκB) in microglia plays a critical role in neuronal damage after SAH. Three molecules derived from erythrocyte breakdown have been postulated to be endogenous TLR4 ligands: methemoglobin (metHgb), heme and hemin. However, poor water solubility of heme and hemin, and lipopolysaccharide (LPS) contamination have confounded our understanding of these molecules as endogenous TLR4 ligands. We used a 5-step process to obtain highly purified LPS-free metHgb, as confirmed by Fourier Transform Ion Cyclotron Resonance mass spectrometry and by the Limulus amebocyte lysate assay. Using this preparation, we show that metHgb is a TLR4 ligand at physiologically relevant concentrations. metHgb caused time- and dose-dependent secretion of the proinflammatory cytokine, tumor necrosis factor α (TNFα), from microglial and macrophage cell lines, with secretion inhibited by siRNA directed against TLR4, by the TLR4-specific inhibitors, Rs-LPS and TAK-242, and by anti-CD14 antibodies. Injection of purified LPS-free metHgb into the rat subarachnoid space induced microglial activation and TNFα upregulation. Together, our findings support the hypothesis that, following SAH, metHgb in the subarachnoid space can promote widespread TLR4-mediated neuroinflammation.