Extraction and Isolation of β‐Glucan from Grain Sources—A Review

A collective report on the extraction and isolation of β‐glucan from grain sources, namely, oat, barley, and wheat is presented. An analysis on the effect of medium, pH, and temperature on the purity and yield of the β‐glucan derived under acidic/alkaline/aqueous/enzymatic conditions is also made. Water extraction and alkali extraction processes are preferred as the yield and recovery of extracted β‐glucan were good. Cost‐effective development of the process for deriving high molecular weight β‐glucan is the current requirement for its wide applications in food and pharmaceutical industries.     

Quadrature oscillator using grounded components with current and voltage outputs

This study proposes new third-order quadrature oscillator that provides several voltage and current outputs simultaneously. The circuit uses differential voltage current conveyors and grounded components, enjoys non-interactive frequency control and can be made resistor-less by using voltage-controlled differential voltage current conveyors. Non-ideal study and parasitic effects are also considered and their effects are discussed. The proposed theory is verified through PSPICE by good results.     

Improved performance of PEM fuel cell using carbon paper electrode prepared with CNT coated carbon fibers

Porous conducting carbon paper has been identified as the most suitable material to be used as a backing material for the fuel cell electrode. The surface of carbon fiber, the major constituent of the carbon paper was modified by: (1) removing the functional groups by heat cleaning process and (2) coating the non-functionalized carbon fiber with multi-walled carbon nanotubes (MWCNTs). This has a marked influence on the fiber–matrix interactions during later stages of processing of carbon paper that helped in controlling its various characteristic properties. Using the carbon paper formed with CNT coated carbon fiber as electrode, the maximum power density achieved from a unit fuel cell was found to be 783 mW/cm² as compared to 630 mW/cm² when the paper was formed with normal fiber.     

Atmospheric concentrations and air-soil gas exchange of polycyclic aromatic hydrocarbons (PAHs) in remote, rural village and urban areas of Beijing-Tianjin region, North China

Forty passive air samplers were deployed to study the occurrence of gas and particulate phase PAHs in remote, rural village and urban areas of Beijing-Tianjin region, North China for four seasons (spring, summer, fall and winter) from 2007 to 2008. The influence of emissions on the spatial distribution pattern of air PAH concentrations was addressed. In addition, the air-soil gas exchange of PAHs was studied using fugacity calculations. The median gaseous and particulate phase PAH concentrations were 222 ng/m³ and 114 ng/m³, respectively, with a median total PAH concentration of 349 ng/m³. Higher PAH concentrations were measured in winter than in other seasons. Air PAH concentrations measured at the rural villages and urban sites in the northern mountain region were significantly lower than those measured at sites in the southern plain during all seasons. However, there was no significant difference in PAH concentrations between the rural villages and urban sites in the northern and southern areas. This urban-rural PAH distribution pattern was related to the location of PAH emission sources and the population distribution. The location of PAH emission sources explained 56%-77% of the spatial variation in ambient air PAH concentrations. The annual median air-soil gas exchange flux of PAHs was 42.2 ng/m²/day from soil to air. Among the 15 PAHs measured, acenaphthylene (ACY) and acenaphthene (ACE) contributed to more than half of the total exchange flux. Furthermore, the air-soil gas exchange fluxes of PAHs at the urban sites were higher than those at the remote and rural sites. In summer, more gaseous PAHs volatilized from soil to air because of higher temperatures and increased rainfall. However, in winter, more gaseous PAHs deposited from air to soil due to higher PAH emissions and lower temperatures. The soil TOC concentration had no significant influence on the air-soil gas exchange of PAHs.