190 research outputs found
Oversigt over undersøgelser og forsøg vedrørende fluebekæmpelsen 1949.
Oversigt over undersøgelser og forsøg vedrørende fluebekæmpelsen 1949
Screening for multiple tick-borne pathogens in Ixodes ricinus ticks from birds in Denmark during spring and autumn migration seasons
Retningslinier for fluebekæmpelsesarbejdet i sæsonen 1950.
Retningslinier for fluebekæmpelsesarbejdet i sæsonen 1950
ac electrokinetic micropumps: The effect of geometrical confinement, Faradaic current injection, and nonlinear surface capacitance
Strongly nonlinear dynamics of electrolytes in large ac voltages
We study the response of a model micro-electrochemical cell to a large ac
voltage of frequency comparable to the inverse cell relaxation time. To bring
out the basic physics, we consider the simplest possible model of a symmetric
binary electrolyte confined between parallel-plate blocking electrodes,
ignoring any transverse instability or fluid flow. We analyze the resulting
one-dimensional problem by matched asymptotic expansions in the limit of thin
double layers and extend previous work into the strongly nonlinear regime,
which is characterized by two novel features - significant salt depletion in
the electrolyte near the electrodes and, at very large voltage, the breakdown
of the quasi-equilibrium structure of the double layers. The former leads to
the prediction of "ac capacitive desalination", since there is a time-averaged
transfer of salt from the bulk to the double layers, via oscillating diffusion
layers. The latter is associated with transient diffusion limitation, which
drives the formation and collapse of space-charge layers, even in the absence
of any net Faradaic current through the cell. We also predict that steric
effects of finite ion sizes (going beyond dilute solution theory) act to
suppress the strongly nonlinear regime in the limit of concentrated
electrolytes, ionic liquids and molten salts. Beyond the model problem, our
reduced equations for thin double layers, based on uniformly valid matched
asymptotic expansions, provide a useful mathematical framework to describe
additional nonlinear responses to large ac voltages, such as Faradaic
reactions, electro-osmotic instabilities, and induced-charge electrokinetic
phenomena.Comment: 30 pages, 17 eps-figures, RevTe
Flow reversal at low voltage and low frequency in a microfabricated ac electrokinetic pump
Microfluidic chips have been fabricated to study electrokinetic pumping
generated by a low voltage AC signal applied to an asymmetric electrode array.
A measurement procedure has been established and followed carefully resulting
in a high degree of reproducibility of the measurements. Depending on the ionic
concentration as well as the amplitude of the applied voltage, the observed
direction of the DC flow component is either forward or reverse. The impedance
spectrum has been thoroughly measured and analyzed in terms of an equivalent
circuit diagram. Our observations agree qualitatively, but not quantitatively,
with theoretical models published in the literature.Comment: RevTex, 9 pages, 6 eps figure
Correction: Large-scale electricity storage utilizing reversible solid oxide cells combined with underground storage of CO<sub>2</sub> and CH<sub>4</sub>
Migrating birds and carnivores introduce ticks and tick borne pathogens to Denmark – but are they also a public health risk?
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