In article ,
Jon Mcleod wrote:

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.

Jon-

Are the bacteria you want to retard inside the meat, or are they on the
surface of the meat? You can't reach those inside due to the meat's
conductivity, except by using enough energy to cook the meat.

If on the outside surface, then the problem is much simpler. Use
parallel plates but insulate the meat. Since meat is conductive
(compared to air), do not include its thickness in your calculation of
volts per meter. In other words, subtract the meat thickness from the
spacing of the plates.

Yes, the bacteria should be conductive. Their finite resistance will
interact with the capacitive current that flows in the circuit,
retarding their growth (or not!).

I suggest you try it with a third (or fourth) steak, at different field
intensities. Perhaps 0.1 v/cm, 1 v/cm, 10 v/cm, 100 v/cm or whatever
you can manage with the available equipment.

Fred

"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.


Hi Jon

At your frequencies, a slab of meat will mostly resemble a resistor with
some capacitive reactance. The resistance will vary with the thickness
and area of the slab you're applying the signal to.

Memory fades, but I recall that you will be looking at resisitivities on
the order of a few hundred ohm-cm. (R = rho * L / A).

At a field strength of 1 V/cm, the power levels will be pretty low --
the meat won't cook noticeably. The currents should be manageable, that
is, I believe that your signal generator will be able to hold the 1V/cm
without additional amplification.

This will be true as long as the load resistance is the 50ohm output
impedance of the signal generator. There is a decent chance that your
meat slab will be less than the desired impedance. In this case you
will need to measure the voltage periodically and adjust the generator
output: As the meat degrades, its conductivity should be increased by
the spillage of conductive cell contents.

You will want to apply the field directly to conductive plates which are
in contact with the meat -- if you have any air gap between a plate and
the meat,
the voltage drop will essentially be all across the air gap, none across
the test sample.

Best regards
PN2222A

NPN (Is = 14.34f Xti = 3 Eg = 1.11 Vaf = 74.03 Bf = 255.9 Ne = 1.307 Ise
= 14.34 Ikf = .2847 Xtb = 1.5 Br = 6.092 Isc = 0

Ikr = 0 Rc = 1 Cjc = 7.306p Mjc = .3416 Vjc = .75 Fc = .5 Cje = 22.01p
Mje = .377 Vje = .75 Tr = 46.91n Tf = 411.1p Itf = .6

Vtf = 1.7 Xtf = 3 Rb = 10)

PN2222A wrote:

You will want to apply the field directly to conductive plates which are
in contact with the meat -- if you have any air gap between a plate and
the meat,
the voltage drop will essentially be all across the air gap, none across
the test sample.

I've been thinking about this. There is a question on how to get an
e-field into the meat, and there is a question about whether bacteria
exist in the meat.

I am assuming there is bacteria in the meat, but I've searched all kind
of FDA and safety sites, and I don't see anything discussed except
ground meat, so I don't know. Maybe there is not, just bacteria on the
surface.

As to whether you can get an efield into the meat, I found that the
authors of the paper actually made a "helmet" to kill brain tumors in
living patients:

http://tinyurl.com/5aatcs

They use insulated electrodes (dozens of them, apparently), but you do
have to shave your head so they are close to the scalp. Are they really
driving 1V/cm into someones brain without cooking it? Or is the actual
field required to kill bacteria (and cancer) actually much smaller than
1V/cm? If the voltage is low, why don't they just put the electrodes in
contact with the skalp?

I have not idea if the trial is working, but if the device is curing
patients, then whatever this box does would kill the bacteria in the
meat (whether its there or not) without cooking the meat. I'm assuming
they have fancy DSP to control all of the electrodes, but they still
have to obey the laws of physics.... I think the field intensity to do
this job may be WAAAAAY less than 1V/cm.

On Sat, 06 Sep 2008 15:34:31 -0400, Jon Mcleod
wrote:

I've been thinking about this. There is a question on how to get an
e-field into the meat,

Hi Jon,

I think that has been examined to death (no pun). The field does not
cease to exist, it simply has plunged from 550,000V/M to 10V/M (if the
suspect methods' data exhibit any correlation to reality).

and there is a question about whether bacteria
exist in the meat.

If it does (and there is no presumption that it "cannot"), then it
would be called an infection or necrosis.

I am assuming there is bacteria in the meat, but I've searched all kind
of FDA and safety sites, and I don't see anything discussed except
ground meat, so I don't know. Maybe there is not, just bacteria on the
surface.

Take a hint from your source that had 10 microliters of cell solution
spread out over the dish. Not much volume, not much thickness to call
"inside" either.

As to whether you can get an efield into the meat, I found that the
authors of the paper actually made a "helmet" to kill brain tumors in
living patients:

http://tinyurl.com/5aatcs

This is truly Bizarre.

They use insulated electrodes (dozens of them, apparently), but you do
have to shave your head so they are close to the scalp.

A very telling question, and one they should have asked, and answered
for themselves. This link points to some very inferior quality
experimentation.

Are they really
driving 1V/cm into someones brain without cooking it? Or is the actual
field required to kill bacteria (and cancer) actually much smaller than
1V/cm? If the voltage is low, why don't they just put the electrodes in
contact with the skalp?

Another very telling question.

I have not idea if the trial is working, but if the device is curing
patients, then whatever this box does would kill the bacteria in the
meat (whether its there or not) without cooking the meat. I'm assuming
they have fancy DSP to control all of the electrodes, but they still
have to obey the laws of physics.... I think the field intensity to do
this job may be WAAAAAY less than 1V/cm.

In the 1960s, a product for cooking hotdogs (10cm) was sold. It
consisted of exposed metal prongs that penetrated to each end of the
hot dog, and were, in turn, plugged into the wall. Net result: in 3
minutes you had a broiled hot dog from 12V/cm.

73's
Richard Clark, KB7QHC

On Sat, 06 Sep 2008 10:07:22 -0700, PN2222A wrote:

"Jon Mcleod" wrote in message

All these are nice ideas and a marvel to engineering but I must say
this....

*******
Whether it's radiated or E-fielded to kill the bacteria, there will still
be **** ON MY FOOD!
*********

Why can't they just stop the contamination as I don't want any crap on my
food! I think it's very disgusting and would avoid radiated or
electrified foods as I believe manufactures would find they could offset
their cost be being less cleanly as long as they were not killing people.

Richard Clark wrote:

In the 1960s, a product for cooking hotdogs (10cm) was sold. It
consisted of exposed metal prongs that penetrated to each end of the
hot dog, and were, in turn, plugged into the wall. Net result: in 3
minutes you had a broiled hot dog from 12V/cm.

http://www.youtube.com/watch?v=qu0fWRtA4mw

I have already drawn one preliminary conclusion from this whole
exercise: I have purchased a wired (old-school, not bluetooth) earpiece
for my cellphone.. e-field or no, it sure wont hurt anything to do it.

"Jon Mcleod" wrote in message
m...

I've been thinking about this. There is a question on how to get an
e-field into the meat, and there is a question about whether bacteria
exist in the meat.


Consider the meat as a resistive material, as I've already proposed.
If you apply a voltage across the meat, that voltage will distribute
itself
across the thickness of the slab. (but with interesting distortions
around the
marbling, which has a significantly higher resistivity).
The distributed capacitance will make some second order effects but the
basic
applied voltage across a medium / voltage field in the medium effect
will remain.

I am assuming there is bacteria in the meat, but I've searched all
kind of FDA and safety sites, and I don't see anything discussed
except ground meat, so I don't know. Maybe there is not, just
bacteria on the surface.


If there are no bacteria inside the meat, what is the purpose of aging?


Are they really driving 1V/cm into someones brain without cooking it?

What's the power density of 1V/cm into a 1cm cube of meat (or brain)with
300 ohm-cm resitivity?
How does that compare to the power density reheating a quarter pounder
in a 600W microwave oven?

Quarter Pounder, Mmmmmmm.

Regards
PN2222A

Biased? Of course I'm biased!

PN2222A wrote:
"Jon Mcleod" wrote in message
....
If there are no bacteria inside the meat, what is the purpose of aging?...


Regards
PN2222A

Biased? Of course I'm biased!



You don't suppose it might have something to do with enzymatic action do
you? You know, to make the meat more tender?
73,
Tom Donaly, KA6RUH

"Jon Mcleod" wrote in message
m...
PN2222A wrote:

You will want to apply the field directly to conductive plates which are
in contact with the meat -- if you have any air gap between a plate and
the meat,
the voltage drop will essentially be all across the air gap, none across
the test sample.

I've been thinking about this. There is a question on how to get an
e-field into the meat, and there is a question about whether bacteria
exist in the meat.

i think its normally assumed that bacteria contaminate the surface of cut
meat during handling and from exposure to the air. ground meat is more
likely to contain bacteria because it is ground... that is, the outer,
possibly contaminated, surface is cut and chopped and put in contact with
lots more meat surface, so bacteria can get spread throughout the mixture...
and of course there is always the contamination probability on the grinding
equipment which is much more complicated than a simple knife or saw used for
sliced meats.

"Dave" wrote in message
news:RjEwk.582$Dj1.535@trnddc02...

"Jon Mcleod" wrote in message
m...
PN2222A wrote:

You will want to apply the field directly to conductive plates which are
in contact with the meat -- if you have any air gap between a plate and
the meat,
the voltage drop will essentially be all across the air gap, none across
the test sample.

I've been thinking about this. There is a question on how to get an
e-field into the meat, and there is a question about whether bacteria
exist in the meat.

i think its normally assumed that bacteria contaminate the surface of cut
meat during handling and from exposure to the air. ground meat is more
likely to contain bacteria because it is ground... that is, the outer,
possibly contaminated, surface is cut and chopped and put in contact with
lots more meat surface, so bacteria can get spread throughout the
mixture... and of course there is always the contamination probability on
the grinding equipment which is much more complicated than a simple knife
or saw used for sliced meats.


along the lines of another poster i would propose an alternate experiment
that could be much more closely controlled. instead of starting with
unknown contamination in meat, which is in itself a non-homogonous
substance, it would be easier to setup and control a standard Petri dish
contaminated with known bacteria samples. Those should be easily provided
by any decent biology lab, and can be properly analyzed and scored using
standard methods for measuring bacterial growth. Those methods are well
documented, and again, any decent biology lab should be able to assist in
the analysis.