Authors - Z

Zhang, M.I.N.; Repo, T.; Willison, J.H.M.; Sutinen, S.
Title   Electrical impedance analysis in plant tissues: On the
        biological meaning of Cole-Cole alpha in Scots pine needles
Journal European Biophysics Journal
        24
        2
        OCT
Year    1995
Page    99-106
Address T Repo
        Univ Joensuu
        Fac Forestry
        POB 111
        SF-80101 Joensuu, Finland
Serial# 0175-7571
Keys    Pinus sylvestris L (Scots pine); electrical impedance;
        membrane capacitance; transmission line; Cole-Cole alpha; air
        space
Abs.    Electrical impedance spectra (80 Hz-1 MHz) in Scots pine
        needles were found to be characterized by spectrum skewness
        in the Cole-Cole plot. These spectra were subjected to
        analysis with two distributed models: (i) the Cole-Cole
        function and (ii) an equivalent circuit which takes account
        of the presence of air spaces within the needles (Model-A).
        In analysis with untreated needles (without artificial
        infiltration with water), Model-A fitted better than the
        Cole-Cole function to the experimental data. After
        infiltration of water into the needles, the extent of
        spectrum skewness was substantially decreased compared with
        the pre-infiltration condition and the Cole-Cole function
        fitted better than Model-A to the measured impedance data.
        The Cole-Cole alpha decreased from 0.47 in non-infiltrated
        needles to 0.42 in the infiltrated needles. The
        exceptionally large value of alpha in non-infiltrated
        needles can be explained by the presence of air spaces,
        which produce transmission line properties in the
        mesophyll. In support of the validity of Model-A, this new
        model provided specific membrane resistances of 1190+/-83
        Omega cm(2) in cold hardened and non-hardened needles
        respectively. These specific membrane resistance are
        comparable with previous reports of membrane resistances in
        other biological systems. It is concluded that in this
        exceptionally spongy tissue, Cole-Cole alpha is likely to
        be due to the effects of the transmission line properties
        of cells which are surrounded by air spaces and only thin
        cell walls outside the insulating cell membranes.
 

Zhao-T-X; Shanwell-A
Electrical impedance alterations of red blood cells during
storage.
Vox Sanguinis 66(4): 258-263
1994
English
The electrical impedance of blood is determined mainly by the
resistance of the plasma (R-p), resistance of the red cell
interior fluid (R-i), and capacitance of the cell membranes (C-m).
These parameters were measured on 10 stored blood samples
consecutively during 4 or 5 weeks of storage at 4 degree C, once
every week. Compared to the values of fresh samples, a
statistically significant decrease in R-p was found mainly during
the first week of storage, R-i did not decrease significantly
until after 3 weeks, whereas C-m decreased progressively with
time. These alterations can be explained by known red cell lesions
during storage. The results indicate that electrical impedance
measurements might be blood cells.
 

Zhao-T-X; Shanwell-A
Electrical impedance alterations of red blood cells during
storage.
Vox Sanguinis 66(4): 258-263
1994
English
The electrical impedance of blood is determined mainly by the
resistance of the plasma (R-p), resistance of the red cell
interior fluid (R-i), and capacitance of the cell membranes (C-m).
These parameters were measured on 10 stored blood samples
consecutively during 4 or 5 weeks of storage at 4 degree C, once
every week. Compared to the values of fresh samples, a
statistically significant decrease in R-p was found mainly during
the first week of storage, R-i did not decrease significantly
until after 3 weeks, whereas C-m decreased progressively with
time. These alterations can be explained by known red cell lesions
during storage. The results indicate that electrical impedance
measurements might be blood cells.
 

Zhao, T.X.; Brown, B.H.; Nopp, P.; Wang, W.; Leathard, A.D.;
        Lu, L.Q.
Title   Modelling of cardiac-related changes in lung resistivity
        measured with EITS
Journal Physiological Measurement
        17
         Suppl. 4A
        NOV
Year    1996
Page    A227-A234
Address TX Zhao
        Univ Sheffield
        Royal Hallamshire Hosp
        Dept Med Phys & Clin Engn
        Glossop Rd
        Sheffield S10 2JF
        S Yorkshire, England
Serial# 0967-3334
Keys    FREQUENCY
Abs.    Resistivity data from 9.6 kHz to 1.2 MHz were recorded from
        eight normal subjects using an electrical impedance
        tomographic spectroscopy (EITS) system and then averaged to
        a mean cardiac cycle using the ECG gating technique. The
        Cole-Cole model, that is, extracellular resistance R
        connected in parallel with intracellular resistance S and
        membrane capacitance C in series, with a distribution
        parameter a, was applied to model the frequency
        characteristics and to produce parametric images. During
        systole, SC and RC were found to decrease and FR increase.
        The changes in R/S were not consistent among the subjects.
        We estimated the peak changes in R, S and C to be -2.5%, -
        3.3% and -7.6% respectively. The results can be explained
        by considering the brood vessels as spheres of different
        sizes with blood inside them. The decrease in R during
        systole might be caused by the increased blood content in
        relatively large vessels, whereas that in S by the
        increased blood volume in relatively small vessels. The
        capacitance of blood is normally smaller than that of lung
        tissue, whereas FR of blood is higher than that of lung
        tissue. Hence, as blood content increases, C should
        decrease and FR increase.