On Sep 5, 1:27*pm, Jon Mcleod wrote:
Art Unwin wrote:
What you are refering to is the induction process as applied to
present day induction cookers
available in stors for the general consumer
Best regards

Actually, no, the induction cooker uses a much stronger field. *This is
a low voltage field (1v/cm) that doesn't cook (or heat) the steak.
Supposedly it disrupts internal structures inside bacteria when they try
to divide, at least so goes the hypothesis.

Jon, the idea of heat is confusing you!. The BBC aired a segment from
Germany
where they placed a slab of ice on top of a induction oven and then
placed a cooking utensel
on top of the ice so they could cook its contents. If the induction
oven was creating heat instead of a radiation field
one could surmise that the ice would melt . This was not the case as
radiation bypassed the ice and gyrated towards
the diagmagnetic cooking utensil. The experiment may well still be
shown on U tube!
I have just to get away and do some honey dooos !
Regards
Art KB9MZ

On Fri, 05 Sep 2008 15:11:20 -0400, Jon Mcleod
wrote:

I need to research it, but I should be able to calculate the voltage
required to generate the 1v/cm field in the steak if I know the
dielectric constant of the "meat"...

Hi Jon,

The dielectric constant of anything is a sidebar, or distraction,
simply because you don't know the dc of the original work's cells
either. In all probability they are the same, but this is unnecessary
information.

More to the matter is where you derive 1V/cm from the original work's
application of an average of 550V (nearly 3 orders greater) to 1mm gap
(exactly 1 order smaller). Your 1V is off by nearly 4 orders of
magnitude.

Again, if you were a convict and they let you set the voltage DOWN by
4 orders of magnitude, you might ask for a cool drink while the threw
the switch and waited several hours for your execution. They may have
to suspend it on account of darkness until the next dawn.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
On Fri, 05 Sep 2008 18:53:53 GMT, "Dave" wrote:

The problem is made harder because the steak is not only a
dielectric material, which changes the magnitude of the field, but is also
moderately conductive, which essentially shorts out the field.

Hi Jon, through Dave,

Let's examine what is offered above, and the fault in a large T-Bone.

The original work was performed with an average of 550V across a gap
of 1mm which contained a sample of cells. Those cells, too, shorted
out the voltage, but across a shorter distance.

Most function generators will only source several volts at best, let's
call it 5.5V to simplify comparisons. We replicate the field
arrangement with a 10cM portion of steak. When we revisit the field
strength, we will find it has plunged from the normalized 550,000V/m
of the original work to the now feeble 55V/m or 4 orders of magnitude
lower field of your suggested work.

It would follow from the original author's thesis that your efforts
will show 4 orders of magnitude less results. Call it zero. There's
no point in doing it without replicating the fields as specified in
the original.

Mr. Clark,

In the introduction, they describe, "In the present study we show for
the first time, to our knowledge, that very low-intensity (
2 V/cm),
intermediate-frequency (100–300kHz), alternating electric fields induced
by insulated electrodes have specific inhibitory effects on dividing
cells in culture."

The novocure dude is talking about 2 V/cm, and the prof here is talking
about 1V/cm. I don't need to duplicate this experiment, I need to
immerse a T-Bone into a 1V/cm, 100kHz e-field. I appreciate your help
so much, but I don't understand where 550,000V/m is coming from???

Following my post, I read your source material closer to then ammend
my statements, interleaved below:

On Fri, 05 Sep 2008 12:27:57 -0700, Richard Clark
wrote:

On Fri, 05 Sep 2008 15:11:20 -0400, Jon Mcleod
wrote:

I need to research it, but I should be able to calculate the voltage
required to generate the 1v/cm field in the steak if I know the
dielectric constant of the "meat"...

Hi Jon,

The dielectric constant of anything is a sidebar, or distraction,
simply because you don't know the dc of the original work's cells
either. In all probability they are the same, but this is unnecessary
information.

In fact, they do report the dielectric constant, and as I speculated,
nearly identical to that of steak (or seawater for that matter).

More to the matter is where you derive 1V/cm from the original work's
application of an average of 550V (nearly 3 orders greater) to 1mm gap
(exactly 1 order smaller). Your 1V is off by nearly 4 orders of
magnitude.

In fact, they do report 1V/cm.
The electric field intensity was mapped within the cell, based on
the amplitude (1 V/cm), frequency (100 kHz) and waveform (sine) of
the electric field applied to the cell culture.

Unfortunately their reference for this was
11. Volakis JL, Chatterjee A, Kempel LC. Finite element method
electromagnetics: antennas, microwave circuits, and scattering
applications.
which cannot be applied to a situation where the wavelength of
excitation is 3000 meters and the gap is one thousandth meter. The
calculation of 1V/cm based upon the application of an average of 550V
across a 1mm gap flies in the face of credulity.

However, and again confounding their use of power amplifier to deliver
1 V/cm in the near field, there is the report:
The electric field intensity in the culture medium was measured by
means of a probe, consisting of two (0.25 mm in diameter)
insulated wires with exposed tips 0.5 mm apart, that was dipped in
the culture medium. The wires were connected to a high-input
impedance differential amplifier that translated the waveform
amplitude into a calibrated steady voltage that was digitally
recorded. Field intensities throughout the manuscript are
expressed in peak voltage amplitude per centimeter (V/cm).

Care was taken to eliminate any pickup from the field outside the
culture medium. Continuous field monitoring could also be made by
measuring the potential drop across a 100 Ohm resistor placed in
series with one of the field generating wires.

This last statement lacks data about what voltage was observed and
says nothing of the contribution of field's interaction with the leads
going to it to measure the voltage across them.

I can understand your desire to simply shove your function generator's
output directly into a steak. It is a choice that is tantilizingly
teased as an option given this report of 1 V/cm. It also raises the
curious aversion of the authors from performing the same test and
removing the absurd complexity of amplifiers and remote senors.
Afterall, 1 V/cm is trivial to obtain, demands no external
amplification, and whose level can be monitored from the function
generator itself.

All of this (in concert with missing data and no computation shown)
suggests a problematic correlation of results (which are inarguable)
to field strength.

Again, science would say replicate the conditions and observe if the
results follow. You can make your own correlations. All things being
practical, the application of an average of 550V across a 1mm gap
demands a better reporting of a finding of 1 V/cm in the sample.

73's
Richard Clark, KB7QHC

"Jon Mcleod" wrote in message
...
Dave wrote:

the problem is, do you want the field 'inside' the meat, or in the air
around the meat? The problem is made harder because the steak is not
only a dielectric material, which changes the magnitude of the field, but
is also moderately conductive, which essentially shorts out the field.
also, the properties depend on the direction of the field... you might
want to see if your library has this article:
http://ieeexplore.ieee.org/xpl/freea...rnumber=300250 .
personally i would probably go the other way and suspend the meat on an
insulating net horizontally and put a plate above and below it that are
bigger than the steak. it is much easier to generate a uniform field
between large parallel conductive plates than with wires... as a first
approximation make the plates about double the largest dimension of the
steak. it may be acceptible to set the steak on one of the plates
(sterilize it first) and just suspend the other one above it.

Thank you! In hindsight, obviously applying a field top to bottom will be
easier than side-to-side!

I need to research it, but I should be able to calculate the voltage
required to generate the 1v/cm field in the steak if I know the dielectric
constant of the "meat"...

One question, what if the plates both touch the steak and I use a smaller
voltage? I guess since steak is conductive, keeping the plates at a 1V/cm
potential may actually sink a lot of current through the steak and cook it
after all.

yes, that would be much harder and may result in cooking.. better to keep an
air gap.

On Fri, 05 Sep 2008 15:41:15 -0400, Jon Mcleod
wrote:
The novocure dude is talking about 2 V/cm, and the prof here is talking
about 1V/cm. I don't need to duplicate this experiment, I need to
immerse a T-Bone into a 1V/cm, 100kHz e-field. I appreciate your help
so much, but I don't understand where 550,000V/m is coming from???

Hi Jon,

Take 550V (the average of their amplifier's 300-800V capacity) and
place it across 1mm. How many volts per meter?

Consider the claim and specification of 1V/cm. How many volts per
meter?

How many volts will you need to obtain 1V/cm across a T-Bone steak
measuring 20 centimeters?

If you can solve one, you can solve them all.

Where did the missing voltage go? This is a simple series impedance
relationship that is linear with distance. To obtain 1V/cm from the
author's source demands that there is considerable impedance isolating
the sample from the excitation probes. This could be accomplished if
there were a huge air gap between the first excitation probe and the
cells' culture, and perhaps a corresponding huge air gap on the other
side of the cell culture towards the second excitation probe. The
ratio of impedances would be 550,000/10. The sum of both air gaps'
impedance would have to exceed the cell culture's impedance by this
ratio.

This is possible, but the report is obscure to that possibility. The
introduction of field measurement probes would be exceedingly
disturbing to the balance of impedances too. The diameters of those
probes consume half the gap within which the cell culture resides, and
lay in exceedingly close proximity to the excitation probes! The
probes themselves present more mass and area than the cell culture.

The claims are specific, but all the evidence points to the authors
having convinced themselves of a very problematic measurement. They
are, afterall, no more versed in the art of antenna math and finite
element modeling than you are. They got numbers to be sure, and
performed what every student would recognize as "plug-n-chug."

However, you are more interested in the results than the claims. Your
assignment, as I understand it, is to investigate what results follow
from your own variation of their work. Unless you are trying to also
validate the correlations to fields, which I seriously doubt you could
do, and would be suspect through direct attachment (as it does not
conform to the original); then I would suggest you think smaller gap
(not a T-Bone), up the voltage (as offered), and measure bacterial
activity.

Or, in your own terms:
What I ACTUALLY NEED to do is generate a 100kHz electric field, at
1v/cm, across a T-Bone steak, to measure whether it retards or
accelerates decomposition over time. The hypothesis is that the e-field
retards growth of certain bacteria inside the meat.
Set your function generator for a 1 volt output, separate two probes
by 1 centimeter, place 0.99 centimeters of steak between. I will hope
your grade isn't scored in competition to others puting their effort
into more voltage across smaller gaps.

73's
Richard Clark, KB7QHC

One question, what if the plates both touch the steak and I use a
smaller voltage? I guess since steak is conductive, keeping the plates
at a 1V/cm potential may actually sink a lot of current through the
steak and cook it after all.

Sure, you can have the plates touch the meat. If it's 1cm thick, put a
volt across it, and you're done.

As you point out, though, if you put that field on the meat itself
(whether by direct contact, or because it's suspended between two plates
with air in the middle), current will flow, and heat will be dissipated.
Your exercise is to figure out how much, and how hot it gets.

Assume the thermal capacity is the same as water.
I'd assume the conductivity is about the same as sea water (60 mS/cm) as
a start.

Do a google search on "TEM cell". That should get you pointed in the
right direction.

Roy Lewallen, W7EL

Jon Mcleod wrote:
A few weeks ago, I asked about generating an 140kHz electric field
across a leaf, part of a bio-med lab. Thanks for the answers. But it
turns out I misread the roster and was in the wrong group.

What I ACTUALLY NEED to do is generate a 100kHz electric field, at
1v/cm, across a T-Bone steak, to measure whether it retards or
accelerates decomposition over time. The hypothesis is that the e-field
retards growth of certain bacteria inside the meat.

By design, we have not been instructed exactly how to construct the
methods and apparatus. I have at my disposal a function generator and
various amplifiers.

It is a gross oversimplification to just connect one wire to one end of
the steak, and another wire at the other end, and apply 20V RMS across a
20cm steak to generate 1V/cm?

Thanks. Sorry about the idiot questions.

Dear Student Mc Leod:

Roy Lewallen has a useful suggestion. I evaluate the performance of
inanimate objects in a TEM cell, which may be thought of as an expanded
transmission line. Zapping (an old EE term) an object with 100 v/m is not
difficult, however that is not likely to be significant in your case.

Your DUT (device under test) is a piece of meat. Room temperature meat
has a significant conductivity. Even at 100 kHz, the conductivity of the
meat results in the field amplitude decreasing rapidly below the surface of
a thick piece of meat. Thus, if you were to use a TEM cell to place the DUT
into a 100 v/m field, the DUT needs to be thin or you can not say that the
whole DUT was subjected to 100 v/m. While all of this is going on, the DUT
is exposed to air-born contaminates that may well be different than those of
the control.

If I had made this assignment, it would be because I expected the good
student to perform an analysis of the experiment and prove that it was most
unlikely to be a valid experiment. Alternatively, a student who I would
recommend for graduate school would present me with a paper that shows what
improbable measures would need to be taken (and why) to have a chance of
having a valid experiment. The poor student is one who does what he or she
is told to do without critical analysis.

I have lived long enough to have several of my past students as honored
colleagues. They all are able to think.

Make friends with people in the EE department or some practical
physicists.

Do report back on what you ended up doing.

Regards, Mac N8TT

--
J. McLaughlin; Michigan, USA
Home:
"Roy Lewallen" wrote in message
treetonline...
Do a google search on "TEM cell". That should get you pointed in the right
direction.

Roy Lewallen, W7EL

Jon Mcleod wrote:

"Jon Mcleod" wrote in message
m...
A few weeks ago, I asked about generating an 140kHz electric field across a
leaf, part of a bio-med lab. Thanks for the answers. But it turns out I
misread the roster and was in the wrong group.

What I ACTUALLY NEED to do is generate a 100kHz electric field, at 1v/cm,
across a T-Bone steak, to measure whether it retards or accelerates
decomposition over time. The hypothesis is that the e-field retards
growth of certain bacteria inside the meat.

By design, we have not been instructed exactly how to construct the
methods and apparatus. I have at my disposal a function generator and
various amplifiers.

It is a gross oversimplification to just connect one wire to one end of
the steak, and another wire at the other end, and apply 20V RMS across a
20cm steak to generate 1V/cm?

Thanks. Sorry about the idiot questions.

Hi Jon

Is it practical for you to place the T-Bone between two plates?
I would try a pair of parallel plates with the T-bone between them, fed
with a 100 KHz, generator and the voltage across the plates adjusted to
produce the field strength you want.

Jerry KD6JDJ