The effect of mesh orientation on netting drag and its application to innovative prawn trawl design

© 2014 . Prawn fisheries around the world comprise fuel intensive enterprises currently stressed financially by rising diesel costs. An avenue for relieving the situation is to improve the energy efficiency of trawling by raising the productivity of fishing per litre of fuel consumed. This paper presents work to develop a new prawn trawl design that leads to reduced trawl system drag. The trawl has a 'double-tongue' format, which refers to extensions forward of the upper and lower panels to form two additional towing points for the trawl. For this design concept, named 'W' trawl, drag generated in the trawl is largely directed to the centreline tongues and transferred forward to the trawler through a connected sled and towing wire. The associated reduction of drag-transfer to the wings makes the trawl substantially easier to spread and results in smaller otter boards being required and subsequently reduced overall drag of the trawl system. The study determined the effect on frame-line tensions of implementing T0 (diamond) and T45 (square) mesh in the main body and side sections of trawl models of conventional and 'W' configuration, with the aim to establish an optimal combination of mesh orientation for the principle parts of the 'W' trawl. The objective was to achieve minimum netting drag and beneficial strain transfer within the trawl such that maximum trawling performance (catch per unit of fuel) might be obtained in the field. T45 mesh in the side sections of the trawl was found to exhibit a progressively lower drag compared to T0 mesh as the flow speed increased, but the extent of drag reduction was not of practical significance. The 'W' trawl showed a capacity of redirecting 59% of the total netting drag to the centre line tongues when T45 netting was implemented in the body section, and only 40% when T0 orientation was used. However, the introduction of bracing ropes (at E=. 0.71) along the upper and lower centrelines of the T0 version of the "W" trawl improved the drag transfer to the tongues from 40% to 50% of the total drag. Overall, the most practical and economic configuration of the model 'W' designs tested produced an estimated drag reduction of 8.3%. ±. 0.6%, compared to the conventional trawl. It is expected that drag saving benefits in practice will be more substantial as the tested trawl models were not completely representative of practical commercial gear in that they had minimum twine area to make the experiment most sensitive to the drag-effect of mesh orientation

The association between subjective memory complaint and objective cognitive function in older people with previous major depression

The goal of this study is to investigate associations between subjective memory complaint and objective cognitive performance in older people with previous major depression-a high-risk sample for cognitive impairment and later dementia. A cross-sectional study was carried out in people aged 60 or over with previous major depression but not fulfilling current major depression criteria according to DSM-IV-TR. People with dementia or Mini-Mental State Examination score less than 17 were excluded. Subjective memory complaint was defined on the basis of a score ≧4 on the subscale of Geriatric Mental State schedule, a maximum score of 8. Older people aged equal or over 60 without any psychiatric diagnosis were enrolled as healthy controls. Cognitive function was evaluated using a series of cognitive tests assessing verbal memory, attention/speed, visuospatial function, verbal fluency, and cognitive flexibility in all participants. One hundred and thirteen older people with previous major depression and forty-six healthy controls were enrolled. Subjective memory complaint was present in more than half of the participants with depression history (55.8%). Among those with major depression history, subjective memory complaint was associated with lower total immediate recall and delayed verbal recall scores after adjustment. The associations between subjective memory complaint and worse memory performance were stronger in participants with lower depressive symptoms (Hamilton Depression Rating Scale score<7). The results suggest subjective memory complaint may be a valid appraisal of memory performance in older people with previous major depression and consideration should be given to more proactive assessment and follow-up in these clinical samples

KickStat: A Coin-Sized Potentiostat for High-Resolution Electrochemical Analysis

The demand for wearable and point-of-care devices has led to an increase in electrochemical sensor development to measure an ever-increasing array of biological molecules. In order to move from the benchtop to truly portable devices, the development of new biosensors requires miniaturized instrumentation capable of making highly sensitive amperometric measurements. To meet this demand, we have developed KickStat, a miniaturized potentiostat that combines the small size of the integrated Texas Instruments LMP91000 potentiostat chip (Texas Instruments, Dallas, TX, USA) with the processing power of the ARM Cortex-M0+ SAMD21 microcontroller (Microchip Technology, Chandler, AZ, USA) on a custom-designed 21.6 mm by 20.3 mm circuit board. By incorporating onboard signal processing via the SAMD21, we achieve 1 mV voltage increment resolution and an instrumental limit of detection of 4.5 nA in a coin-sized form factor. This elegant engineering solution allows for high-resolution electrochemical analysis without requiring extensive circuitry. We measured the faradaic current of an anti-cocaine aptamer using cyclic voltammetry and square wave voltammetry and demonstrated that KickStat&rsquo;s response was within 0.6% of a high-end benchtop potentiostat. To further support others in electrochemical biosensors development, we have made KickStat&rsquo;s design and firmware available in an online GitHub repository