Understanding urban freight activity: key issues for freight planning

Using information gathered from some 30 UK surveys undertaken over the last 15 years, this paper provides planners with an understanding of road-based urban retail freight transport activity. The findings suggest that the average High Street business could expect up to 10 core goods and 7.6 service visits per week, in non-peak trading periods with 25% additional activity during the build up to Christmas. Vans (‘light goods vehicles’) were the dominant mode, responsible for 42% of delivery activity with a mean dwell time of 10 min. Where possible, load consolidation should be encouraged by methods such as Delivery and Servicing Plans and using out-of-town freight consolidation centres to bring in goods over the last mile in shared vehicles. Where this is not possible, loading bay monitoring and control, and preferred lorry routes can help manage the movement of vehicles in and out of dense urban areas. Service vehicle activity is a significant contributor to urban freight movements and often requires vehicles to be parked close to the premises being served. Centrally coordinating elements of service provision (e.g. for cleaning, equipment maintenance, recyclate collection), or providing improved, more flexible parking provision for service vehicles could be as or more beneficial in reducing overall freight impacts than focusing on core goods deliveries. In the case of the latter, ‘pay-as-you-leave’ car park charging systems could encourage short-stay service vehicles to park off-street.

A thin-layer chromatography-bioautographic method for detecting dipeptidyl peptidase IV inhibitors in plants

A thin-layer chromatography (TLC)-bioautographic method was developed with the aim to detect dipeptidyl peptidase IV (DPP IV) inhibitors from plant extracts. The basic principle of the method is that the enzyme (DPP IV) hydrolyzes substrate (Gly-Pro-p-nitroaniline) into p-nitroaniline (pNA), which diazotizes with sodium nitrite, and then reacts with N-(1-naphthyl) ethylenediamine dihydrochloride in turn to form a rose-red azo dye which provides a rose-red background on the TLC plates. The DPP IV inhibitors showed white spots on the background as they blocked enzymolysis of the substrate to produce pNA. The method was validated with respect to selectivity, sensitivity, linearity, precision, recovery, and stability after optimizing key parameters including plate type, time and temperature of incubation, concentration of substrate, enzyme and derivatization reagents, and absorption wavelength. The results showed good lineary within amounts over 0.01–0.1 μg range for the positive control, diprotin A, with the coefficient of determination (r2) = 0.9668. The limits of detection (LOD) and quantification (LOQ) were 5 and 10 ng, respectively. The recoveries ranged from 98.9% to 107.5%. The averages of the intra- and inter-plate reproducibility were in the range of 4.1–9.7% and 7.6–14.7%, respectively. Among the nine methanolic extracts of medicinal herbs screened for DPP IV inhibitors by the newly developed method, Peganum nigellastrum Bunge was found to have one white active spot, which was then isolated and identified as harmine. By spectrophotometric method, harmine hydrochloride was found to have DPP-IV inhibitory activity of 32.4% at 10 mM comparing to that of 54.8% at 50 μM for diprotin A.