Tunable lumped-distributed capacitively-coupled transmission-line filter

A wide tuning range filter is proposed based on lumped-distributed capacitively-coupled transmission lines. The proposed structure maintains a constant inter-resonator coupling factor over a wide centre-frequency tuning range leading to a constant fractional bandwidth design. A bandpass filter with a two-octave tuning range has been designed, fabricated and measured.     

Prevalence and numbers of coliphages and Campylobacter jejuni bacteriophages in New Zealand foods

Vegetable samples were tested for the presence of coliphages. None of the 55 samples contained these phages at concentrations greater than 10 g(-1) (the limit of detection). Spiking and recovery experiments indicated that the method was efficient at detecting coliphage T4 added to the food, and so it was concluded that phage titres were not being falsely underestimated. In addition 51 samples of chicken skin from retail portions were tested for the presence and numbers of coliphages and for presence only of Campylobacter jejuni phages. Coliphages were isolated from 46 samples (90.2% positive), at up to 2570 PFU 10 g sample(-1) but no C. jejuni phages were isolated. Several other methods were used to isolate C. jejuni phages from retail chicken but none was successful. However, when pooled whole chicken rinses from 39 flocks were tested for the presence of C. jejuni phages, 11 (28.2%) of the flocks were positive. It is possible that phages present on birds at the start of processing were either inactivated or simply diluted out during spin chilling. These data add to the body of information indicating that phages can readily be isolated from certain foods and indicate that consumers are exposed to them on a regular basis.     

Broadband-configurable bandstop-filter design employing a composite tuning mechanism

A microwave bandstop-filter design is reported, which combines both continuous and discrete tuning using varactor and PIN diodes to achieve a two-octave tuning range. The useable passband for any given tuning point is limited, however, the composite tuning mechanism in the topology facilitates the separate tuning of the centre frequency and stopband to minimum-loss passband separation. A suitable and novel filter-synthesis procedure is developed, and the filter performance is verified through experimental results     

Broadband configurable bandstop filter with composite tuning mechanism

The design and experimental performance of a bandstop filter which combines both continuous and discrete tuning using varactor and PIN diodes to achieve a two-octave tuning range is reported. The topology allows independent control of the passband and stopband frequencies.     

Phage inactivation of foodborne pathogens on cooked and raw meat

Phages infecting Salmonella Typhimurium PT160 and Campylobacter jejuni were added at a low or high (10 or 10(4)) multiplicity of infection (MOI) to either low or high (<100 or 10(4)cm(-2)) densities of host bacteria inoculated onto raw and cooked beef, and incubated at 5 and 24 degrees C to simulate refrigerated and room temperature storage. Counts of host bacteria were made throughout the incubation period, with phages being counted at the first and last sampling times. Host inactivation was variable and depended on the incubation conditions and food type. Significant host inactivations of the order of 2-3 log(10)cm(-2) at 5 degrees C and >5.9 log(10)cm(-2) at 24 degrees C were achieved compared to phage-free controls using the Salmonella phage under optimal conditions (high host cell density and MOI). These results alongside those already published indicate that phages may be useful in the control for foodborne pathogens.