Buzz off! An evaluation of ultrasonic acoustic vibration for the disruption of marine micro-organisms on sensor-housing materials.

Biofouling is a process of ecological succession which begins with the attachment and colonization of micro-organisms to a submerged surface. For marine sensors and their housings, biofouling can be one of the principle limitations to long-term deployment and reliability. Conventional antibiofouling strategies using biocides can be hazardous to the environment, and therefore alternative chemical-free methods are preferred. In this study, custom-made testing assemblies were used to evaluate ultrasonic vibration as an antibiofouling process for marine sensor-housing materials over a 28-day time course. Microbial biofouling was measured based on (i) surface coverage, using fluorescence microscopy and (ii) bacterial 16S rDNA gene copies, using Quantitative polymerase chain reaction (PCR). Ultrasonic vibrations (20 KHz, 200 ms pulses at 2-s intervals; total power 16·08 W) significantly reduced the surface coverage on two plastics, poly(methyl methacrylate) and polyvinyl chloride (PVC) for up to 28 days. Bacterial gene copy number was similarly reduced, but the results were only statistically significant for PVC, which displayed the greatest overall resistance to biofouling, regardless of whether ultrasonic vibration was applied. Copper sheet, which has intrinsic biocidal properties was resistant to biofouling during the early stages of the experiment, but inhibited measurements made by PCR and generated inconsistent results later on. SIGNIFICANCE AND IMPACT OF THE STUDY: In this study, ultrasonic acoustic vibration is presented as a chemical-free, ecologically friendly alternative to conventional methods for the perturbation of microbial attachment to submerged surfaces. The results indicate the potential of an ultrasonic antibiofouling method for the disruption of microbial biofilms on marine sensor housings, which is typically a principle limiting factor in their long-term operation in the oceans. With increasing deployment of scientific apparatus in aquatic environments, including further offshore and for longer duration, the identification and evaluation of novel antifouling strategies that do not employ hazardous chemicals are widely sought.

Pinning and avalanches in hydrophobic microchannels.

Rare events appear in a wide variety of phenomena such as rainfall, floods, earthquakes, and risk. We demonstrate that the stochastic behavior induced by the natural roughening present in standard microchannels is so important that the dynamics for the advancement of a water front displacing air has plenty of rare events. We observe that for low pressure differences the hydrophobic interactions of the water front with the walls of the microchannel put the front close to the pinning point. This causes a burstlike dynamics, characterized by series of pinning and avalanches, that leads to an extreme-value Gumbel distribution for the velocity fluctuations and a nonclassical time exponent for the advancement of the mean front position as low as 0.38.

Interconnected reversible lab-on-a-chip technology.

Interconnected lab-on-a-chip modules with minimal dead volume have been developed resulting in the 'plug and play' concept based upon a reversible bonding process. This paper describes the detail of a chip to chip interconnection method, where devices have been aligned and bonded within 15 min and rapidly disassembled in under 5 min. The transport of fluorescein between the chip modules was used as a model microfluidic system and analysed in order to demonstrate the electrophoretic performance of the device and the interconnected junction. Using this technology, in the future different modules for various applications can be developed and interconnected, depending on the required applications. In addition, this simple but rapid method of chip to chip connection overcomes potential problems associated with integrating incompatible materials on one device.

The use of the mini C-arm in the outpatient setting: evolving practice.

The mini C-arm image intensifier (mini C-arm) has now become an established diagnostic tool in the hand surgery outpatient department. This study reviews the use of the mini C-arm and formal radiographs (X-rays) in the outpatient hand surgery setting. X-rays provide a standard image whereas the mini C-arm can obtain non-standard images to aid diagnosis and treatment. The mini C-arm enables the clinician to obtain dynamic images and perform interventions such as manipulations or injections. The mini C-arm results in a significantly lower radiation exposure for the patients than a formal X-ray. Use of the mini C-arm may be cheaper, and can lead to a shorter outpatient visit with less travel between hospital departments.

An audit of the safe use of the mini c-arm image intensifier in the out-patient setting.

Mini C-arm image intensifiers are used commonly in surgery of the upper limb. With relatively low doses of emitted ionising radiation, portability and superior quality of image, they are a useful aid to the operating surgeon. However, these benefits are not so often used outside the theatre setting. This paper examines the use of a mini C-arm image intensifier in the out-patient clinic and presents an audit of 100 consecutive out-patients. We reviewed the potential benefits and effects on their care pathway. We also look at the specific radiation protection issues of the mini C-arm image intensifier in the out-patients clinic. We believe use of the mini C-arm image intensifier in the out-patient setting may speed treatment and reduce the cost of treatment.

Changes in the properties of the modulatory cerebral giant cells contribute to aging in the feeding system of Lymnaea.

This study examined whether electrophysiological changes in the endogenous properties and connectivity of the modulatory serotonergic cerebral giant cells (CGCs) contributed to the age-related changes in feeding behavior of the pond snail, Lymnaea. With increasing age there was a decrease in spontaneous CGC firing rates and decreased excitability of the CGCs to both chemosensory stimulation (0.05M sucrose applied to the lips) and direct intracellular current injection. These changes could be accounted for by a decrease in the input resistance of the neuron and an increase in the amplitude and the duration of the after-hyperpolarization. Decreases were also seen in the % of CGC pairs that were electrically coupled causing asynchronous firing. Together these changes would tend to reduce the ability of the CGCs to gate and control the frequency of the feeding behavior. Part of the ability of the CGCs to gate and frequency control the feeding network is to provide a background level of excitation to the feeding motor neurons. Recordings from B1 and B4 motor neurons showed an age-related hyperpolarization of the resting membrane potential consistent with a deficit in CGC function. Increases were seen in the strength of the evoked CGC-->B1 connection, however, this increase failed to compensate for the deficits in CGC excitability. In summary, age-related changes in the properties of the CGCs were consistent with them contributing to the age-related changes in feeding behavior seen in Lymnaea.

Effects of age on feeding behavior and chemosensory processing in the pond snail, Lymnaea stagnalis.

This study used behavioral and electrophysiological techniques to examine age-related changes in the feeding behavior and chemosensory processing in the pond snail, Lymnaea stagnalis. Increasing age was associated with a 50% decrease in long-term food consumption. Analysis of short-term sucrose-evoked feeding bouts showed an age-related increase in the number of animals that failed to respond to the stimulus. Of the animals that did respond increasing age was associated with a decrease in the number of sucrose-evoked bites and a increase in the duration of the swallow phase. These changes were observed with both 0.01 and 0.05M sucrose stimuli but were not seen when 0.1M sucrose was used as the stimulus. Electrophysiological analysis of the chemosensory pathway in semi-intact lip-CNS preparations failed to demonstrate a significant change in the neuronal information entering the cerebral ganglia from the lips via the median lip nerve, but did demonstrate an age-related deficit in the neuronal output from the cerebral ganglia. This deficit was also dependent on the sucrose concentration and mirrored the concentration-dependent changes in feeding behavior. In summary, aging appeared to affect central but not peripheral processing of chemosensory information and suggests that this deficit contributes to the age-related changes in feeding behavior.

Indirect fluorescence detection of phenolic compounds by capillary electrophoresis on a glass device.

A micromachined capillary electrophoresis system has been fabricated on a glass device for the separation and indirect fluorescence detection of phenols. Using this device two phenols viz., 2,4-dichlorophenol and pentachlorophenol, were separated within 12 s compared to under 19 min on a conventional capillary electrophoresis system using direct ultraviolet detection. The precision of the glass device ranged from 12.7%-16.7% compared to 0.42%-4.9% for the conventional system. Both systems showed good linearity in the concentration range of 0.8-6.38 mM for the glass device and 5-130 microM for the conventional system. The relationship between temperature and high voltage with baseline drift was also investigated. These results provide a foundation for the development of a miniaturised chemical analysis system for the on-line analysis of phenols in water.