Oxidation with air of cyclohexanone to carboxylic diacids on carbon catalysts

Carbons derived from phenolic resins were used as catalysts for the aqueous phase oxidation of cyclohexanone at 140°C under air pressure. The reaction yielded mainly adipic, glutaric and succinic acids. The samples were modified by heat treatments in CO₂, air or N₂ at different temperatures and characterized to determine their surface area and porosity and to evaluate the functional groups on the surface. Treatments under CO₂ or air increased the oxidation activity. The selectivity to adipic acid was maximum (33%) after activation in air which greatly increased the surface concentration of oxygen-containing functional groups. However, it was not possible to attribute the selectivity to specific acidic, neutral or basic groups present at the surface of carbons. This revised version was published online in June 2006 with corrections to the Cover Date.     

High‐strength biodegradable poly(vinyl alcohol)/fly ash composite films

We prepared biodegradable composite films of poly(vinyl alcohol) (PVA) and fly ash (FA) spanning 5, 10, 15, 20, and 25 wt % concentrations by casting aqueous solutions. The tensile strengths of the composite films were increased proportionally via the addition of FA. The strength of the film was enhanced by 193% with 20% FA compared to the neat PVA control. Further addition of FA deviated from the linear trend. The moduli of the composites also increased proportionally with FA addition to 212% at 20 wt % FA addition compared to the control. The percentage strain at break exponentially decreased with the addition of FA. In the dynamic mechanical behavior, the storage and loss moduli both increased with FA content. The tan δ peaks corresponding to the glass‐transition temperature shifted 5–10°C higher above the control sample (73°C). This shift was attributed to a reduction in the mobility of PVA segments because they were anchored by the FA surface. The reductions in mobility manifested in strong interfacial interactions were indicative of hydrogen bonding. Broadening and reduction in the intensities of the stretching and bending peaks of ? OH, ? CH and ? C?O of PVA in the Fourier transform infrared spectra were observed. This suggested that hydrogen bonding was active between the functional groups in the FA and PVA chains. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Modifications to methods for the enumeration and detection of injured Escherichia coli O157:H7 in foods

Reliable methods are required for the detection and enumeration of potentially injured E. coli O157 in food in the presence of outnumbering competing bacteria. Selective agents can prevent or inhibit the recovery and subsequent multiplication of injured cells and direct inoculation, either into selective enrichment broths or onto selective agar plates is still used in many methods for E. coli O157 detection and enumeration. When compared with tryptone soya agar (TSA), sorbitol MacConkey agar (SMAC) was shown to underestimate the concentration of viable E. coli O157:H7 subjected to low pH and high NaCl concentration. Using a resuscitation stage on TSA followed by membrane transfer to SMAC improved recovery to levels obtained on TSA. The membrane method was used to monitor the numbers of artificially contaminated E. coli O157:H7 during the fermentation of a meat product and demonstrated better survival when compared to counts on SMAC. Six rapid methods for the detection of E. coli O157 in food (BAX E. coli O157, Reveal 8 E. coli O157-H7 screening test, VIP EHEC, VIDAS E. coli O157 (ECO), EHEC-Tek and Tecra E. coli O157 visual immunoassay), were evaluated using beetburgers, parsley and fermented meat artificially contaminated with injured cells. Methods using direct selective enrichment, with or without an elevated incubation temperature gave false-negative results. The incorporation of a non-selective pre-enrichment medium improved the detection rates of these assays by up to ten fold.     

Effect of microstructure on the strength,toughness, and stress-corrosion cracking susceptibility of a metastable beta titanium alloy (Ti−11.5Mo−6Zr−4.5Sn)

This paper describes the influence of mictrostructure on the mechanical properties of the alloy Ti?11.5Mo?6Zr?4.5Sn. The phase transformations are similar to those that occur in binary Ti?Mo alloys containing 10 to 12 pct Mo. Thus, the β phase can be retained by quenching from above 1400°F. The β phase deforms in a complex manner, including mechanical twinning, and is characterized by low strength, high ductility, and high toughness. The ω phase, which also forms on quenching, is stable at temperatures up to 800°F. Yield strengths of up to 220 ksi have been measured in (β+ω) structures, the strength level being dependent on the size and volume fraction of the ω phase. In contrast, fracture toughness reaches a minimum value of }20 ksi \(\sqrt {in} \) when the ω particle size ≥100Å. (β+α) structures show good combinations of yield strength and fracture toughness. Unfortunately, the best combinations are susceptible to stress-corrosion cracking in aqueous solutions containing halide ions.     

Analysis and synthesis of an impedance-loaded loop antenna using the singularity expansion method

The singularity expansion method (SEM) is used to represent the current on a loaded loop antenna. The shift in the poles of the loop due to impedance loading can be analyzed using contour plots in the complex frequency plane of the Fourier modal impedance transfer functions. The same plot may also be used to determine a loading function which will yield a specified pole pattern leading to frequency or time domain synthesis. A simple example of time-domain synthesis is presented.