cellphone emf 'sheilds' - published tests?

[blutoski]

Hi:

This is regarding cellphone emf shield devices. The ones I've seen are a metallic sticker, smaller than a dime that can be stuck to the back of a cellphone.

The manufacturers claim that this reduces emf to the phone user. None have provided citations.

I'm thinking of performing a test on one of these products.

Before I prepare a protocol, I think I should review the body of evidence thus far.

However, I was unable to find any meaningful testing of their efficacy via google or pubmed.

Is anybody familiar with published test results for this type of product?

[shuttlt]

As far as I'm aware there is none. I think there is at least one study claiming to show a ling between brain tumors and the side of the head people hold their mobiles.

[blutoski]

Originally Posted by shuttlt

As far as I'm aware there is none. I think there is at least one study claiming to show a ling between brain tumors and the side of the head people hold their mobiles.

Yes, I'm aware that there are some good studies investigating the effects of 'unshielded' phones, in an attempt to confirm or disconfirm the hypothesis that cellphones produce carcinogenic/mutagenic emf.

Thus was born the cottage industry in these protective devices.

I seem to recall a related family of hoax viral videos trying to sell these devices - the people in the videos were popping popcorn with their phone 'radiation'.

What surprised me is that these products are sold without a shred of evidence that they work to suppress emf - this is not dependent on the emf actually being proven harmful. This sounds like very blatant commercial fraud.

[KingMerv00]

To receive a signal, microwaves must be free to hit your cell phone. To transmit, microwaves must be free to leave your cell phone.

Yes, let us block the deadly microwaves. I just hope you aren't planning on using your phone.

[shuttlt]

Originally Posted by KingMerv00

To receive a signal, microwaves must be free to hit your cell phone. To transmit, microwaves must be free to leave your cell phone.

Yes, let us block the deadly microwaves. I just hope you aren't planning on using your phone.

Taking the device seriously for a moment, surely it doesn't have to block ALL the deadly microwaves, just cut them down somewhat in a specific direction. Is it impossible that they could be cutting the power by 50% in the direction of the head?

I confess my knowledge the behaviour of EMF is limited, so I'm kind of expecting to be told I don't know what I'm talking about.

[blutoski]

Originally Posted by KingMerv00

To receive a signal, microwaves must be free to hit your cell phone. To transmit, microwaves must be free to leave your cell phone.

Yes, let us block the deadly microwaves. I just hope you aren't planning on using your phone.

Well, that's the absurd part of the claim on the packaging collateral - they literally say they block the harmful radiation, but not the emf used for signal.

Forum policy question: can I upload a scan of the packaging?

[shuttlt]

Originally Posted by blutoski

Well, that's the absurd part of the claim on the packaging collateral - they literally say they block the harmful radiation, but not the emf used for signal.

Forum policy question: can I upload a scan of the packaging?

You know the whole woo theory of this though? It's not the EMF so much as very specific 'unnatural' aspects of the EMF. Power and carrier frequency aren't the central issue for most of these people.

[sol invictus]

Originally Posted by blutoski

This is regarding cellphone emf shield devices. The ones I've seen are a metallic sticker, smaller than a dime that can be stuck to the back of a cellphone.

The manufacturers claim that this reduces emf to the phone user.

First question: is the radiation which supposedly causes tumors identical to the cell phone's data transmissions? The phone may emit a spectrum of frequencies; perhaps the ones used for communication are not the ones that are claimed to be harmful. That's the only way I can see that such a device could make sense (unless it just gives you bad reception).

Second question: what's the frequency of the harmful radiation? That's going to be important to know to study whether a dime-sized sticker could possibly have any effect.

Third question: are there any instructions on where to put the sticker, say relative to the phone's antennae?

[blutoski]

Originally Posted by shuttlt

Taking the device seriously for a moment, surely it doesn't have to block ALL the deadly microwaves, just cut them down somewhat in a specific direction. Is it impossible that they could be cutting the power by 50% in the direction of the head?

That seems to be the nature of the claim.

They claim to eliminate 99.99% of harmful radiation.

Originally Posted by shuttlt

I confess my knowledge the behaviour of EMF is limited, so I'm kind of expecting to be told I don't know what I'm talking about.

That's my situation, too. This is why I wanted to review the existing research. I didn't want to test incorrectly or test for something they're not claiming to be able to do in the first place.

[blutoski]

Originally Posted by shuttlt

You know the whole woo theory of this though? It's not the EMF so much as very specific 'unnatural' aspects of the EMF. Power and carrier frequency aren't the central issue for most of these people.

Yes, I'm convinced it's an invented claim and blatant fraud.

I'm trying to kill three birds with one stone:

• Conduct a test - this would be entertaining in its own right.
• Show that the claims cannot be based in fact - since there appears to be no research that suggests their device will work in the first place
• Verify or refute the claim so the consumer will be informed when deciding to make a purchase

[blutoski]

Originally Posted by sol invictus

First question: is the radiation which supposedly causes tumors identical to the cell phone's data transmissions? The phone may emit a spectrum of frequencies; perhaps the ones used for communication are not the ones that are claimed to be harmful. That's the only way I can see that such a device could make sense (unless it just gives you bad reception).

Second question: what's the frequency of the harmful radiation? That's going to be important to know to study whether a dime-sized sticker could possibly have any effect.

I'm not really sure about any of this, which is why I'm looking for existing research. If there is an existing body of literature that has identified harmful types, then it may be fair to assume that's what the manufacturers are using as their evidence. I would attempt to verify that this is what they're saying, and then attempt to replicate the experiments.

Originally Posted by sol invictus

Third question: are there any instructions on where to put the sticker, say relative to the phone's antennae?

I'll have to get back to you when I open the package and read what looks like an enclosure with instructions.

[Prometheus]

Originally Posted by blutoski

That seems to be the nature of the claim.

They claim to eliminate 99.99% of harmful radiation.





That's my situation, too. This is why I wanted to review the existing research. I didn't want to test incorrectly or test for something they're not claiming to be able to do in the first place.

...and 99.99% of zero is...

[blutoski]

This is the distributor's website: [Safe Cell Tab]

[blutoski]

Originally Posted by Prometheus

...and 99.99% of zero is...

The point is that if I want to test their claim, I need to understand their claim. Thus, I'm asking if there are some existing studies that indicate what they expect supports their claim.

My impression from their cited analysis is that they are defining this harmful band as somewhere in the 0.8GHz to 10.525GHz range.

Does anybody know why they might have selected this range for testing?

[sol invictus]

Originally Posted by blutoski

The point is that if I want to test their claim, I need to understand their claim. Thus, I'm asking if there are some existing studies that indicate what they expect supports their claim.

My impression from their cited analysis is that they are defining this harmful band as somewhere in the 0.8GHz to 10.525GHz range.

Does anybody know why they might have selected this range for testing?

It appears that the cell phone frequency bands in use worldwide fall within the range .8-2GHz.

http://en.wikipedia.org/wiki/Cellular_frequencies

Presumably the great majority of the radiation emitted by the phone is in that band, although there could be some power in other frequencies, or near-field effects.

From your link it appears this company had their material tested and that it is a near-perfect absorber over that range*. That means if you put your phone in a bag made out of the stuff, it wouldn't work.


*Caveat: I didn't see anything specifying how much (how thick, what shape and size, etc.) material was tested.

[shuttlt]

I believe the issue is that this is non-ionizing radiation, so it should almost by definition be safe. The claim though from the woos is that it is the information content of the message that is at fault. It's all muddled up with an energy medicine view of the world. Cancer is caused by inserting a particular 'unnatural' information stream into your bodies energy field.

[arthwollipot]

Originally Posted by shuttlt

Taking the device seriously for a moment, surely it doesn't have to block ALL the deadly microwaves, just cut them down somewhat in a specific direction. Is it impossible that they could be cutting the power by 50% in the direction of the head?

For such a small object to be blocking a portion of the radiation, the source of the radiation must be just as small or smaller, and the object would need to be very precisely positioned. What do you say, blutoski? Does the thing come with instructions on where it should be positioned on various models of phone? Or does it just say "stick it on the back"?

[Vermonter]

To actually affect cells, the radiation caused by the device has to have short waves. Microwaves operate around 2.5 Ghz, and the mesh in front of the oven has holes that are small enough to deflect the radiation generated. It'd have to be ionizing radiation as well.

UV is up to 400 nm in length for each wave, whereas microwaves are around 13 cm in length. For reference, visible light is in the 790-400 THz band, or 380-750 nm, which is still non-ionizing.

Since cellphones operate on the UHF band of 0.3-3 GHz range, the corresponding wavelengths are 10 cm - 1 m.

Plainly stated, the radiation caused by cellphones is too fat to actually affect living tissue.

[shuttlt]

Originally Posted by Vermonter

To actually affect cells, the radiation caused by the device has to have short waves. Microwaves operate around 2.5 Ghz, and the mesh in front of the oven has holes that are small enough to deflect the radiation generated. It'd have to be ionizing radiation as well.

UV is up to 400 nm in length for each wave, whereas microwaves are around 13 cm in length. For reference, visible light is in the 790-400 THz band, or 380-750 nm, which is still non-ionizing.

Since cellphones operate on the UHF band of 0.3-3 GHz range, the corresponding wavelengths are 10 cm - 1 m.

Plainly stated, the radiation caused by cellphones is too fat to actually affect living tissue.

Generally this is acknowledged by the anti-EMF crowd. It's like homeopathy in that they KNOW there is an effect and they are looking for a mechanism. The "it's the information content that does the harm" claim is a reaction to Vermonter's argument.

[Vermonter]

Originally Posted by shuttlt

Generally this is acknowledged by the anti-EMF crowd. It's like homeopathy in that they KNOW there is an effect and they are looking for a mechanism. The "it's the information content that does the harm" claim is a reaction to Vermonter's argument.

In which case I claim bullhockey. XD

[Rolfe]

Why do I get the feeling that Roger Coghill rides again...?

Rolfe.

[shuttlt]

Originally Posted by Rolfe

Why do I get the feeling that Roger Coghill rides again...?

Rolfe.

Why I'd stake my life on his competence and thorough going reliability on the issue of the health effects of EMF.

[shuttlt]

He is a scientist you know!

[TheDaver]

Originally Posted by blutoski

I seem to recall a related family of hoax viral videos trying to sell these devices - the people in the videos were popping popcorn with their phone 'radiation'.

Actually, those viral videos came from a company trying to sell Bluetooth headsets.

[sol invictus]

Originally Posted by Vermonter

Plainly stated, the radiation caused by cellphones is too fat to actually affect living tissue.

That doesn't appear to be the case, if one can trust these studies:

http://www.consumeraffairs.com/news0..._motility.html
http://www.cnn.com/2008/HEALTH/condi...llphone.sperm/
http://www3.interscience.wiley.com/j...TRY=1&SRETRY=0
http://blog.kevaind.com/emr/study-ce...e-sperm-cells/

So the case for cell phone radiation damaging sperm seems to be pretty strong. The case for it causing cancer, on the other hand, seems very weak to non-existent from what I've seen.

[MRC_Hans]

Originally Posted by Rolfe

Why do I get the feeling that Roger Coghill rides again...?

Rolfe.

Roger did market such a device, maybe still does.

OK, let me try to address some of this:

1) Anybody who makes a general claim of doing something 99.99% is a fraud, period.

2) There is no distinction between the potentially harmful EMI and the wanted signal from a cell-phone. There might be slight emissions that could be done away with, but since power is very much at a premium in these devices, the manufacturers have already removed as much as technically feasible, in the construction. There is no way you can stick something on the outside of the device and further improve on that.

3) EMI can only be blocked by something in the direct path of the radiation. Thus, you would have to place the sticker over the antenna to block some of the signal.

4) Due to the power constraints mentioned above, cellphones employ a dynamic power concept, that is, they regulate their output power according to the need of the moment (distance to the repeater station, local conditions, etc.). So if you block some of the signal, the cellphone will promptly increase its output to compensate. (This is the reason you will experience shoretened battery duration when operating a cellphone in an area with poor connection)

In other words: Unadulterated BS.

Hans

[MRC_Hans]

Originally Posted by sol invictus

That doesn't appear to be the case, if one can trust these studies:

http://www.consumeraffairs.com/news0..._motility.html
http://www.cnn.com/2008/HEALTH/condi...llphone.sperm/
http://www3.interscience.wiley.com/j...TRY=1&SRETRY=0
http://blog.kevaind.com/emr/study-ce...e-sperm-cells/

So the case for cell phone radiation damaging sperm seems to be pretty strong. The case for it causing cancer, on the other hand, seems very weak to non-existent from what I've seen.

Cell-phone EMI is a non-ionizing electromagnetic radiation. The output of a normal cellphone is up to around 1W. This energy level and wavelength does not affect matter on the atomic level, thus DNA damage is unlikely. However, it IS capable of transferring energy to living tissue, especially in the form of heat, so heat-sensitive cells (very notably sperm cells) are likely to be affected under the right (wrong?) circumstances.

It is a very old tale, from military circles, that by getting a moderate irradiation from a radar, a guy could stop worrying about untimely impregnation of his girlfriend(s). Of course, if you took too much ...

Hans

[shuttlt]

Maybe the introduction of the word 'quantum' and pointing out that science doesn't know everything would go some way to explaining how this device works?

[MRC_Hans]

Originally Posted by shuttlt

Maybe the introduction of the word 'quantum' and pointing out that science doesn't know everything would go some way to explaining how this device works?

It would be as good as any other explanation.

Hans

[shuttlt]

Originally Posted by sol invictus

http://www.consumeraffairs.com/news0..._motility.html

No causal relationship is established.

Originally Posted by sol invictus

http://www.cnn.com/2008/HEALTH/condi...llphone.sperm/

This only applies to leaving you phone next to your sperm while you talk on a hands free. The sample size was small and the effect is speculated to be thermal.

Originally Posted by sol invictus

http://www3.interscience.wiley.com/j...TRY=1&SRETRY=0

Link error

Originally Posted by sol invictus

http://blog.kevaind.com/emr/study-ce...e-sperm-cells/

Quote:

Aitken, director of the Australian Research Council’s Center of Excellence in Biotechnology and Development, says the DNA damage may not have been caused by the radiation directly. Exposure to radiation causes electrons to leak from one part of a sperm cell to other parts, leading to oxidation processes that harm the DNA. The DNA damage affects other sperm-cell functions.

I vaguely recall having seen this kind of scenario mentioned before wrt EMF causing harm. Anybody got any thoughts?

[Fishstick]

These were marketed by Omega Pharma about a year ago in Belgium - thankfully they got a shitton of backlash in the press and were quickly recalled after a journalist had tinkered one open and revealed nothing but glue and a coil of copper wire.

http://www.electricpig.co.uk/2008/12...-being-cooked/
http://www.unwiredview.com/2008/12/1...e-sales-begin/
http://www.youtube.com/watch?v=loja4BhPc7o

[sol invictus]

Originally Posted by MRC_Hans

Cell-phone EMI is a non-ionizing electromagnetic radiation. The output of a normal cellphone is up to around 1W. This energy level and wavelength does not affect matter on the atomic level, thus DNA damage is unlikely. However, it IS capable of transferring energy to living tissue, especially in the form of heat, so heat-sensitive cells (very notably sperm cells) are likely to be affected under the right (wrong?) circumstances.

That sounds unlikely to me. First of all this happens even when the phone is in standby and the energy output is very low. And it happened when the phone was 3cm or so away from a sperm sample, which was presumably inside a test tube, and the heat transfer must be very low. And I don't think sperm are that sensitive to temperature variations.

But it would be very easy to test: just use some small heating elements as a control.

[sol invictus]

Originally Posted by shuttlt

Link error

http://www3.interscience.wiley.com/j...59930/abstract

Quote:

The accumulating effects of exposure to electromagnetic radiation emitted by a conventional mobile phone (standby position) on the testicular function and structure are not yet fully investigated. To study these effects longitudinally, a total of 24 adult male rabbits were randomly and equally divided into three groups. Rabbits in the first (phone) group were exposed, in specially designed cages, to radio frequency emitted from the mobile phone (800 MHz) in a standby position opposite to that of testes for 8 h daily for 12 weeks. The second group consisted of the stress controls which were kept in the same kind of cages to appreciate any cage-induced anxiety. The third group included the ordinary controls which were kept in the conventional roomy cages. Semen analysis and sperm function tests (viability, hypo-osmotic swelling and acridine orange) were conducted weekly. Histological testicular sections and serum total testosterone were also evaluated. A drop in the sperm concentration appeared in the phone group at week 6. This became statistically significant at week 8, compared with the two control (stress and ordinary) groups (133, 339 and 356 × 106/mL, respectively) and to the initial sperm count (341 × 106/mL) of this group. Motile sperm population showed similarity amongst the three study groups until week 10 when it declined significantly, and thereafter in the phone and stress control groups, with more significant decline in the phone animals (50, 61 and 72.4%, respectively). Histological examination showed also a significant decrease in the diameter of seminiferous tubules in the phone group vs. the stress and ordinary controls (191 μm vs. 206 and 226 μm, respectively). The other study points did not show any difference. In conclusion, low intensity pulsed radio frequency emitted by a conventional mobile phone kept in the standby position could affect the testicular function and structure in the adult rabbit.

[MRC_Hans]

Originally Posted by sol invictus

That sounds unlikely to me. First of all this happens even when the phone is in standby and the energy output is very low. And it happened when the phone was 3cm or so away from a sperm sample, which was presumably inside a test tube, and the heat transfer must be very low. And I don't think sperm are that sensitive to temperature variations.

But it would be very easy to test: just use some small heating elements as a control.

The power output is the same. But, right, the energy is much lower. A cellphone has a max range of several kilometers, so 3cm is not far. A test tube is made of glass, and radio signals pass through it with virtually no loss. It is important to realize that the UHF energy is dissipated directly into the cells.

However, without rigorous monitoring of the power, such an experiment is really useless.

Hans

[MRC_Hans]

Originally Posted by sol invictus

http://www3.interscience.wiley.com/j...59930/abstract

8 weeks?

OK, there is a problem here, often encountered in these protocols: They lack a control with non-emitting phones. Cellphones contain plastics, printed wiring boards, metals, batteries. If they are not brand new (and even then), they contain bacteria.

A sound protocol has to allow for possible effects from the mere presense of the device.

Hans

[sol invictus]

Originally Posted by MRC_Hans

A cellphone has a max range of several kilometers, so 3cm is not far. A test tube is made of glass, and radio signals pass through it with virtually no loss.

3cm is relevant because the test tube only occupies a fraction of the solid angle around the phone. Which raises the question of how isotropic the radiation is, in standby mode, or otherwise...

Quote:

It is important to realize that the UHF energy is dissipated directly into the cells.

Ah, I think I misunderstood you. You're not talking about heat transferred from the body of the phone simply because it's gotten warm from use, you're talking about energy deposited directly in the cells/sperm by the GHz radiation. In that case I withdraw my statement that it's unlikely, that seems plausible

Quote:

However, without rigorous monitoring of the power, such an experiment is really useless.

It's certainly not useless, it's just not as detailed as it could be.

Originally Posted by MRC_Hans

8 weeks?

OK, there is a problem here, often encountered in these protocols: They lack a control with non-emitting phones. Cellphones contain plastics, printed wiring boards, metals, batteries. If they are not brand new (and even then), they contain bacteria.

Yes, you're right. It's possible some other aspect of the phone was what is causing harm. It's a little hard to buy, but it's not impossible. But look:

men carrying cell phones in their pockets have lower sperm count
human sperm in test tubes are negatively affected by nearby phones
rabbits with phones have lower sperm counts
plus several more similar studies I saw but didn't bother to link to.

I'd say that's a preponderance of evidence for the claim that cell phone radiation damages living tissue, specifically sperm.

[MervinFerd]

Originally Posted by MRC_Hans

8 weeks?

OK, there is a problem here, often encountered in these protocols: They lack a control with non-emitting phones. Cellphones contain plastics, printed wiring boards, metals, batteries. If they are not brand new (and even then), they contain bacteria.

A sound protocol has to allow for possible effects from the mere presense of the device.

Hans

This result doesn't pass the smell test.
Phones are on standby; total microwave radiation is going to be extremely small--short bursts every few minutes. Exposure of the 'nads will depend on orientation of the rabbit relative to the phone; the rabbit's body will shield the testicles in most orientations. I suspect a rabbit would get more radiation from random EM fields in the lab.

Use of actual cell phones is amateurish; we have no way to determine the power emitted, or how much reaches the 'nads. Ordinarily, if you are looking for an effect, you would start with a high dose and work down. And you would design some apparatus that allowed the actual dose received to be determined. I would design a cage that looked a bit like a microwave oven, but with the microwaves coming from the bottom.

Finally, there were only eight rabbits in each group. Pretty small for a biology experiment. And, a decrease that is not statistically significant is NOT a decrease. It's no change.

[MRC_Hans]

Originally Posted by sol invictus

3cm is relevant because the test tube only occupies a fraction of the solid angle around the phone. Which raises the question of how isotropic the radiation is, in standby mode, or otherwise...

Another weakness of the protocol: The radiation is far from isotropic.

Quote:

Ah, I think I misunderstood you. You're not talking about heat transferred from the body of the phone simply because it's gotten warm from use, you're talking about energy deposited directly in the cells/sperm by the GHz radiation. In that case I withdraw my statement that it's unlikely, that seems plausible

OK.

Quote:

It's certainly not useless, it's just not as detailed as it could be.

OK, not very useful. If a protocol does not allow for obvious confounders, well ....

Quote:

Yes, you're right. It's possible some other aspect of the phone was what is causing harm. It's a little hard to buy, but it's not impossible. But look:

Not impossible at all. We are talking about a rabbit sitting for 8 weeks tied down next to a device the relative size of a colour TV-

Quote:

men carrying cell phones in their pockets have lower sperm count

Source for that?

Quote:

human sperm in test tubes are negatively affected by nearby phones
rabbits with phones have lower sperm counts
plus several more similar studies I saw but didn't bother to link to.

I'd say that's a preponderance of evidence for the claim that cell phone radiation damages living tissue, specifically sperm.

Oh, but I didn't reject the claim. Since sperm is very heat sensitive, it is particularly likely to be sensitive to a phenomenon that produces .... heat.

Seat-heaters in cars also seem to reduce male fertility.

Hans

[sol invictus]

Originally Posted by MervinFerd

I suspect a rabbit would get more radiation from random EM fields in the lab.

Take a first generation iphone on standby and bring it anywhere within a meter of powered speaker (a computer speaker, a home stereo with amp on, a police car with megaphone connected), and you'll hear a characteristic sound (dit dit dah dah dit). If the speakers are turned up it can be quite loud. And the 1st gen iphone is in the middle of the pack as far as cell radiation goes.

That's much stronger than any stray RFI you'd have in a normal room, let alone a shielded lab space.

Quote:

Finally, there were only eight rabbits in each group. Pretty small for a biology experiment. And, a decrease that is not statistically significant is NOT a decrease. It's no change.

That's a naive way to look at it. If your data drops steadily over time and achieves stat. sig. at some time, it's perfectly reasonable to mention that behavior, including the part before it achieved significance. But I agree that 8 rabbits/group is a little small.

Originally Posted by MRC_Hans

Another weakness of the protocol: The radiation is far from isotropic.

Well to be fair we don't know (or at least I don't since I didn't read the paper itself) how they did it. They might have rotated the phones to take an average.

Quote:

Source for that?

First link in my post above.

Quote:

Oh, but I didn't reject the claim. Since sperm is very heat sensitive, it is particularly likely to be sensitive to a phenomenon that produces .... heat.

Sure, but you're making it sound like that's different than the claim that's at issue, or what most people may worry about. We're talking about gigaherz radiation depositing energy in cells, or in sperm. At worst that radiation could to deposit significant energy specifically in the cell's DNA and cause cancer. There doesn't seem to be happening.

But what does seem to be happening, if you're right, is that the radiation is depositing energy at some other location in the cell or throughout the cell, and causing significant damage that way. It's not being deposited by ordinary thermal conduction as from a seat heater. In fact calling it "heat" is rather misleading; this radiation is not thermal and has nothing like a thermal spectrum. The energy will later thermalize as anything will, but it's not "heat" itself.

[shuttlt]

Originally Posted by sol invictus

Sure, but you're making it sound like that's different than the claim that's at issue, or what most people may worry about. We're talking about gigaherz radiation depositing energy in cells, or in sperm. At worst that radiation could to deposit significant energy specifically in the cell's DNA and cause cancer. There doesn't seem to be happening.

But what does seem to be happening, if you're right, is that the radiation is depositing energy at some other location in the cell or throughout the cell, and causing significant damage that way. It's not being deposited by ordinary thermal conduction as from a seat heater. In fact calling it "heat" is rather misleading; this radiation is not thermal and has nothing like a thermal spectrum. The energy will later thermalize as anything will, but it's not "heat" itself.

But are we saying things are more sensitive to half a degree temperature rise through mobile phone EMF than they are to half a degree temperature rise from conduction?