10,300 research outputs found
Study directed at development of an implantable biotelemetry ion detector
A literature search was conducted to currently update known information in the field of ion-selective electrodes. The review attempts to identify present trends in cation and anions selective electrodes pertinent to the area of bioimplantable units. An electronic circuit was designed to provide the high impedance interface between the ion-selective sensors and signal-processing equipment. The resulting design emphasized the need for low power and miniaturization. Many of the circuits were constructed and used to evaluate the ion-selective electrodes. A cuvette capable of holding the ion-selective and the reference electrodes was designed and constructed. This equipment was used to evaluate commercially available ion-selective electrodes and the electrodes designed and constructed in the study. The results of the electrode tests are included
The inverse electromagnetic scattering problem in a piecewise homogeneous medium
This paper is concerned with the problem of scattering of time-harmonic
electromagnetic waves from an impenetrable obstacle in a piecewise homogeneous
medium. The well-posedness of the direct problem is established, employing the
integral equation method. Inspired by a novel idea developed by Hahner [11], we
prove that the penetrable interface between layers can be uniquely determined
from a knowledge of the electric far field pattern for incident plane waves.
Then, using the idea developed by Liu and Zhang [21], a new mixed reciprocity
relation is obtained and used to show that the impenetrable obstacle with its
physical property can also be recovered. Note that the wave numbers in the
corresponding medium may be different and therefore this work can be considered
as a generalization of the uniqueness result of [20].Comment: 19 pages, 2 figures, submitted for publicatio
Hydration and mobility of HO-(aq)
The hydroxide anion plays an essential role in many chemical and biochemical
reactions. But a molecular-scale description of its hydration state, and hence
also its transport, in water is currently controversial. The statistical
mechanical quasi-chemical theory of solutions suggests that HO[H2O]3- is the
predominant species in the aqueous phase under standard conditions. This result
is in close agreement with recent spectroscopic studies on hydroxide water
clusters, and with the available thermodynamic hydration free energies. In
contrast, a recent ab initio molecular dynamics simulation has suggested that
HO[H_2O]4- is the only dominant aqueous solution species. We apply adiabatic ab
initio molecular dynamics simulations, and find good agreement with both the
quasi-chemical theoretical predictions and experimental results. The present
results suggest a picture that is simpler, more traditional, but with
additional subtlety. These coordination structures are labile but the
tri-coordinate species is the prominent case. This conclusion is unaltered with
changes in the electronic density functional. No evidence is found for
rate-determining activated inter-conversion of a HO[H2O]4- trap structure to
HO[H2O]3-, mediating hydroxide transport. The view of HO- diffusion as the
hopping of a proton hole has substantial validity, the rate depending largely
on the dynamic disorder of the water hydrogen-bond network.Comment: 7 pages, 5 figures, additional results include
A versatile dual spot laser scanning confocal microscopy system for advanced fluorescence correlation spectroscopy analysis in living cell
A fluorescence correlation spectroscopy (FCS) system based on two independent
measurement volumes is presented. The optical setup and data acquisition
hardware are detailed, as well as a complete protocol to control the location,
size and shape of the measurement volumes. A method that allows to monitor
independently the excitation and collection efficiency distribution is
proposed. Finally, a few examples of measurements that exploit the two spots in
static and/or scanning schemes, are reported.Comment: Accepted for publication in Review of Scientific Instrumen
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