Dynamic measurements of a micropump using a fibre optic based interferometer

Spatially resolved, non-contact, displacement measurements are reported from the membrane surface of a piezoelectric-driven micropump. The measurement system uses a fibre optic interferometric technique which incorporates an air path to the pump in the signal arm, allowing measurements to be made remotely. The interferometer operates at 1523nm, has a bandwidth of 200Khz, a focussed spot size of 22(mu) m and a noise equivalent displacement of 0.36nm. Membrane displacement profiles while pumping air and water have been obtained using custom designed automated fringe counting and interpolation software to interpret the digitised fringe patterns from the interferometer. Measurements show significant differences in membrane velocity, displacement and settling time between the two different pumping media. Transient underdamped vibration of the membrane surface was also detected in the rapid excursion and recursion phases of the pump cycle while pumping air. Analysis of the vibration transients allowed the resonant frequency and damping ratio of the system to be calculated. In addition, the amplitude of the membrane displacement was demonstrated to be dependent on the pumping frequency when pumping air. Analysis of the driving voltage and displacement profiles indicated that this frequency dependent relationship was primarily due to two effects: insufficient settling time between pump cycles and capacitive loading of the driving voltage at high pumping frequencie

Evaluation of color preference in zebrafish for learning and memory

There is growing interest in using zebrafish (Danio rerio) as a model of neurodegenerative disorders such as Alzheimer’s disease. A zebrafish model of tauopathies has recently been developed and characterized in terms of presence of the pathological hallmarks (i.e., neurofibrillary tangles and cell death). However, it is also necessary to validate these models for function by assessing learning and memory. The majority of tools to assess memory and learning in animal models involve visual stimuli, including color preference. The color preference of zebrafish has received little attention. To validate zebrafish as a model for color-associated-learning and memory, it is necessary to evaluate its natural preferences or any pre-existing biases towards specific colors. In the present study, we have used four different colors (red, yellow, green, and blue) to test natural color preferences of the zebrafish using two procedures: Place preference and T-maze. Results from both experiments indicate a strong aversion toward blue color relative to all other colors (red, yellow, and green) when tested in combinations. No preferences or biases were found among reds, yellows, and greens in the place preference procedure. However, red and green were equally preferred and both were preferred over yellow by zebrafish in the T-maze procedure. The results from the present study show a strong aversion towards blue color compared to red, green, and yellow, with yellow being less preferred relative to red and green. The findings from this study may underpin any further designing of color-based learning and memory paradigms or experiments involving aversion, anxiety, or fear in the zebrafish.Avdesh Avdesh, Mathew T. Martin-Iverson, Alinda Mondal, Mengqi Chen, Sreten Askraba, Newman Morgan, Michael Lardelli and David M. Grot