Defensive properties of pyrrolizidine alkaloids against microorganisms

The understanding of the selection factors that drive chemical diversification of secondary metabolites of constitutive defence systems in plants, such as pyrrolizidine alkaloids (PAs), is still incomplete. Historically, plants always have been confronted with microorganisms. Long before herbivores existed on this planet, plants had to cope with microbial pathogens. Therefore, plant pathogenic microorganisms may have played an important role in the early evolution of the secondary metabolite diversity. In this review, we discuss the impact that plant-produced PAs have on plant-associated microorganisms. The objective of the review is to present the current knowledge on PAs with respect to anti-microbial activities, adaptation and detoxification by microorganisms, pathogenic fungi, root protection and PA induction. Many in vitro experiments showed effects of PAs on microorganisms. These results point to the potential of microorganisms to be important for the evolution of PAs. However, only a few in vivo studies have been published and support the results of the in vitro studies. In conclusion, the topics pointed out in this review need further exploration by carrying out ecological experiments and field studies

Modelling, imaging and measurement of distortion, drag and break-up of aircraft- icing droplets

The distortion, drag and break-up of supercooled drizzle droplets in aircraft icing was investigated in ambient conditions. An effective efficient computer procedure was developed for the distortion and drag of small droplets, < 1mm, at low Reynolds numbers, 10. High-speed videos and photographs were obtained with an improved high-intensity LED strobe. Experimental measurements validated the drag model for droplets distorted by a rapidly accelerating airflow in a convergent wind tunnel. To prevent droplet coalescence, due to wake interactions, droplets were generated with a steady jet impinging of a rotating slotted disk

Role of droplet distortion and break-up in large droplet aircraft icing

Experimental and analytical evidence is presented to illustrate droplet distortion and potential break-up in the flow conditions similar those of a drizzle droplet in the vicinity of an aerofoil. The droplet size range considered is 100u m to 500u m. The current research is at ambient temperature but with equivalent parametric conditions to SLD icing. While the results support the contention that smaller droplets, <100u m, remain essentially spherical, the larger droplets become sufficiently distorted to affect their drag characteristics and can break up due to the transient aerodynamic forces

Complete Streets: A New Capability Maturity Model

Complete Streets (CS) practice in the United States is heterogeneous. While organizations like the National Complete Streets Coalition have offered guidance on the formation of a robust Complete Streets policy, the maturity of public programs for Complete Streets practice is ill-defined. This research adapts existing transportation-focused capability maturity frameworks to propose a new capability maturity model for Complete Streets that is designed to help organizations evaluate current program maturity and identify next steps for evolving practice. The model includes a self-assessment tool and a set of qualitative descriptions of incrementally increasing maturity across seven program dimensions determined to be fundamental to the success of Complete Streets programs. The proposed model is designed to assist in strategic planning and organizational capacity building