scholarly journals Positive phase error from parallel conductance in tetrapolar bio-impedance measurements and its compensation

2019 ◽  
Vol 1 (1) ◽  
pp. 71-79 ◽  
Author(s):  
Martina F. Callaghan ◽  
Torben Lund ◽  
Ivan M. Roitt ◽  
Richard H. Bayford
Keyword(s):  
Phase Error ◽  
Accurate Determination ◽  
Equivalent Circuit Model ◽  
Electrical Circuit ◽  
Circuit Model ◽  
Positive Phase ◽  
Set Up ◽  
Equivalent Electrical Circuit Model ◽  
Parallel Conductance

Abstract Bioimpedance measurements are of great use and can provide considerable insight into biological processes. However, there are a number of possible sources of measurement error that must be considered. The most dominant source of error is found in bipolar measurements where electrode polarisation effects are superimposed on the true impedance of the sample. Even with the tetrapolar approach that is commonly used to circumvent this issue, other errors can persist. Here we characterise the positive phase and rise in impedance magnitude with frequency that can result from the presence of any parallel conductive pathways in the measurement set-up. It is shown that fitting experimental data to an equivalent electrical circuit model allows for more accurate determination of the true sample impedance as validated through finite element modelling (FEM) of the measurement chamber. Finally, the equivalent circuit model is used to extract dispersion information from cell cultures to characterise their growth.

Diode Parameters and Equivalent Electrical Circuit Model of n-Type Silicon/B-Doped p-Type Ultrananocrystalline Diamond Heterojunctions Manufactured Through Coaxial Arc Plasma Deposition

2020 ◽  
Vol 20 (8) ◽  
pp. 4884-4891
Author(s):  
Rawiwan Chaleawpong ◽  
Nathaporn Promros ◽  
Peerasil Charoenyuenyao ◽  
Phongsaphak Sittimart ◽  
Satoshi Takeichi ◽  
...  
Keyword(s):  
Plasma Deposition ◽  
Electrical Circuit ◽  
Circuit Model ◽  
Arc Plasma ◽  
Equivalent Electrical Circuit ◽  
Type Silicon ◽  
Ultrananocrystalline Diamond ◽  
Electrical Circuit Model ◽  
Equivalent Electrical Circuit Model ◽  
P Type

Coaxial arc plasma deposition (CAPD) was employed to manufacture n-type silicon/boron-doped p-type ultrananocrystalline diamond heterojunctions. Measurement and analysis of their dark current density-voltage curve were carried out at room temperature in order to calculate the requisite junction parameters using the Cheung and Norde approaches. For the calculation based on the Cheung approach, the series resistance (Rs), ideality factor (n) and barrier height (Φb) were 4.58 kΩ, 2.82 and 0.75 eV, respectively. The values of Rs and Φb were in agreement with those calculated using the Norde approach. Their characteristics for alternative current impedance at different frequency values were measured and analyzed as a function of the voltage (V) values ranging from 0 V to 0.5 V. Appearance of the real (Z′) and imaginary (Z″) characteristics for all V values presented single semicircles. The centers of the semicircular curves were below the Z′ axis and the diameter of the semicircles decreased with increments of the V value. The proper equivalent electrical circuit model for the manufactured heterojunction behavior was comprised of Rs combined with the parallel circuit of resistance and constant phase element.

scholarly journals Influence of organic compound functionality on aerosol hygroscopicity: dicarboxylic acids, alkyl-substituents, sugars and amino acids

2017 ◽  
Vol 17 (9) ◽  
pp. 5583-5599 ◽  
Author(s):  
Aleksandra Marsh ◽  
Rachael E. H. Miles ◽  
Grazia Rovelli ◽  
Alexander G. Cowling ◽  
Lucy Nandy ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Amino Acids ◽  
Organic Compounds ◽  
Accurate Determination ◽  
Dicarboxylic Acids ◽  
Original Data ◽  
Set Up ◽  
Complex Organic ◽  
Selection Of

Abstract. Hygroscopicity data for 36 organic compounds, including amino acids, organic acids, alcohols and sugars, are determined using a comparative kinetics electrodynamic balance (CK-EDB). The CK-EDB applies an electric field to trap-charged aqueous droplets in a chamber with controlled temperature and relative humidity (RH). The dual micro dispenser set-up allows for sequential trapping of probe and sample droplets for accurate determination of droplet water activities from 0.45 to > 0.99. Here, we validate and benchmark the CK-EDB for the homologous series of straight-chain dicarboxylic acids (oxalic–pimelic) with measurements in better agreement with Universal Quasichemical Functional Group Activity Coefficients (UNIFAC) predictions than the original data used to parametrise UNIFAC. Furthermore, a series of increasingly complex organic compounds, with subtle changes to molecular structure and branching, are used to rigorously assess the accuracy of predictions by UNIFAC, which does not explicitly account for molecular structure. We show that the changes in hygroscopicity that result from increased branching and chain length are poorly represented by UNIFAC, with UNIFAC under-predicting hygroscopicity. Similarly, amino acid hygroscopicity is under-predicted by UNIFAC predictions, a consequence of the original data used in the parametrisation of the molecular subgroups. New hygroscopicity data are also reported for a selection of alcohols and sugars and they show variable levels of agreement with predictions.

A setup for synchrotron-radiation-induced total reflection X-ray fluorescence and X-ray absorption near-edge structure recently commissioned at BESSY II BAMline

2016 ◽  
Vol 23 (3) ◽  
pp. 820-824 ◽  
Author(s):  
U. Fittschen ◽  
A. Guilherme ◽  
S. Böttger ◽  
D. Rosenberg ◽  
M. Menzel ◽  
...  
Keyword(s):  
Accurate Determination ◽  
Total Reflection ◽  
Edge Structure ◽  
X Ray ◽  
Unknown Species ◽  
Radiation Induced ◽  
Set Up ◽  
Reflecting Surface ◽  
X Ray Absorption

An automatic sample changer chamber for total reflection X-ray fluorescence (TXRF) and X-ray absorption near-edge structure (XANES) analysis in TXRF geometry was successfully set up at the BAMline at BESSY II. TXRF and TXRF-XANES are valuable tools for elemental determination and speciation, especially where sample amounts are limited (<1 mg) and concentrations are low (ng ml−1to µg ml−1). TXRF requires a well defined geometry regarding the reflecting surface of a sample carrier and the synchrotron beam. The newly installed chamber allows for reliable sample positioning, remote sample changing and evacuation of the fluorescence beam path. The chamber was successfully used showing accurate determination of elemental amounts in the certified reference material NIST water 1640. Low limits of detection of less than 100 fg absolute (10 pg ml−1) for Ni were found. TXRF-XANES on different Re species was applied. An unknown species of Re was found to be Re in the +7 oxidation state.

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