Decreasing water pressure cues ‘bailout’ in seaweed-associated crustaceans

Small mobile crustaceans are abundant on seaweeds. Many of these crustaceans rapidly abandon their host if it is detached from the seafloor and floats towards the surface, but the trigger for this ‘bailout’ behaviour is unknown. We tested 2 potential cues, i.e. rapid change in light and rapid change in water pressure, using >1 mm epifauna on the brown seaweed Carpophyllum plumosum as a model system. Bailout occurred in response to reduced water pressure, but not to changing light, as (1) bailout occurred at similar rates in light and dark, (2) bailout occurred on the seafloor when water pressure was reduced within a transparent chamber by the equivalent of ~0.5 m depth or more, and (3) little bailout occurred when water pressure was held constant within the chamber while seaweeds were raised to the surface. Increase in pressure (simulating sinking) did not induce bailout. The rate of bailout increased with increasing magnitude of pressure reduction but was not influenced greatly by the rate of change of pressure within the range tested (up to an equivalent of 0.4 m depth s-1). The use of pressure rather than light as a cue for bailout is consistent with the need for seaweed-associated crustaceans to rapidly abandon a detached host and relocate to suitable habitat during both day and night.

Experimental Optimization of Rolls-Royce AE3007 Sump Design

The original sump design of Rolls-Royce AE3007 central sump is a tangential sump. An experimental program at Purdue University was conducted to investigate the characteristics of a tangential sump design. The research employed a bespoke experimental rig consisting of modular transparent chamber to allow unprecedented view of the two-phase flow inside the bearing chamber. It was found that a persistent liquid pooling near the drain entrance of a tangential sump obstructs the outflow to the scavenge off-take. While space requirement is minimal, the scavenge performance of a tangential sump is poor. A prototype advanced sump was proposed and built with features to address various issues found in the tangential sump. In this paper, further experimental work on the refinements of the advanced sump is presented. This includes experimental study on the effect of a fence and splitter plate, off-take hole diameter and its location, the effect of gravity by tilting, upstream wall fairing, as well as the depth of the sump itself. The experiments showed that the faired upstream wall modification can reduce residence volume significantly across different operating conditions, indicating improvement in scavenge performance. The other modifications help to reduce residence volume only in certain operating conditions. The results of this study helped towards the birth of an optimized sump design, known as Indy sump. The Indy sump has been accepted as a superior sump design and has been used as a benchmark in many sump design studies.

Greenhouse gas emissions from sludge treatment reed beds

Sludge treatment reed bed systems (STRBs) are considered as an alternative technology for surplus sludge treatment. Organic matter is decomposed by various microbial reactions, resulting in gases such as CO2 and CH4 emitting into the atmosphere. The aim of this study is to investigate gas emission from STRBs. The static transparent chamber was adopted to measure gas emission; it allows sunlight to enter and plants to photosynthesise. The comparison of total solids and volatile solids showed STRBs have a higher efficiency in dewatering and mineralization than a conventional unplanted sludge drying bed (USDB). The CO2 emission ranged from 28.68 to 100.42 g CO2 m−2 d−1 in USDB, from 16.48 to 65.18 g CO2 m−2 d−1 in STRBs; CH4 emission ranged from 0.26 to 0.99 g CH4 m−2 d−1 in USDB, from 0.43 to 1.95 g CH4 m−2 d−1 in STRBs. Both gas fluxes decreased towards the end of vegetation and reached the highest rates during the hot and dry summer. After the system was loaded by sludge, the fluxes of CO2 and CH4 significantly decreased in the USDB, whereas they increased in STRBs. In terms of CO2 equivalent, the global warming potential of CH4 was 13.13 g CO2eq m−2 d−1 and 15.02 g CO2eq m−2 d−1 in USDB and STRBs, respectively.

Scavenge Flow in a Bearing Chamber With Tangential Sump Off-Take

A tangential sump design is employed in several aero-engines mainly due to its simplicity and compactness. However various problems have prompted investigations of the sump design. An experimental program at Purdue University [1, 2] was conducted to investigate the characteristics of a tangential sump design like one used in the AE3007 aero-engine. The research employed a transparent chamber to allow unprecedented view of the flow inside the bearing chamber. It was quickly found that a persistent liquid pooling near the drain entrance of a tangential sump obstructs the outflow to the scavenge pump. The air flow near the drain entrance has been shown to have strong reverse flow, even with, or perhaps due to, substantial over-scavenging. Various modifications were tested with varying degrees of success. The work highlights limitations of a tangential sump design. Based on the lessons learned, a new sump design was proposed. Preliminary test of the new sump design has shown positive results.

Effect of transparent covers for collection chambers of urine-diverting dry toilets on dehydration of faecal waste

Urine-diverting dry toilets save water, reduce the demand for wastewater treatment and provide plant nutrients. The conditions in the collection chambers and the interlinked hygienic safety of subsequent faecal matter use in crop production are affected by the building design. Comparative experiments were carried out to evaluate the potential of transparent chamber covers in comparison with non-transparent chamber covers to increase temperature and ventilation in order to enhance faecal matter dehydration and sanitation. The air temperature in the chambers with transparent covers (TC) was 1.1–1.5 °C higher and the relative air humidity about 5–7% lower than in chambers with non-transparent covers. The advantage of TCs on temperature and humidity prevailed throughout the year, but was most pronounced in months with more sunshine hours and higher irradiation. Furthermore, the airflow out of the chambers through the ventilation pipes was increased by 60% in the TCs. During two-month collection and dehydration cycles the improved drying conditions in the TCs resulted in 7% lower faecal matter moisture. A trend towards an enhanced pathogen inactivation in the faecal material was observed. The results demonstrate that in the semi-arid tropics transparent covers for collection chamber of urine diverting dry toilets improve the dehydration of faecal matter.