bionic alpha ??????

[g-sani]

Hi G-sani.
I like most Whites detectors. But I don't have an XLT. I used my brothers XLT and did not like it. The reason is because it has many automatic menus that are hard for a beginner to understand. I was worried I was discriminating out many of the targets I was looking for. I am sure an experienced user could do much better. The detection also depends on the size of the gold things in the jar, and the ground where the gold is buried. A gold medallion of 150gr is much easier to detect than 150gr of gold dust. And mineralised soil makes it harder to detect buried metals. For gold things the size of common coins or bigger, most VLF detectors can do a good job of detecting them. But Pi detectors are considered better especially in bad mineralised ground. This is why most nugget prospectors in Australia use PI detectors in their bad red soil full of iron. Of course, whether VLF or PI, the ability to detect small gold will depend on how well designed the circuits are. The cheaper detectors usually cannot detect as deep or find items as small as the sophisticated detectors that can cost triple the price or more. Your target was found at 70cm which is near the limit for most metal detectors, depending on the size of the gold items that were found.

According to LRL aficionados, their LRLs do not care about the soil. The "Phenomenon" is stronger than mineralised soil, and can be detected even for things buried at the bottom of a lake.

Best wishes,
J_P

Hi J Player, Prospecting is a good program to use for a White whith good results for gold.The only thing I am doing is changing 2 parametres in the factory's program.First is Ac sensitivity,we put it at 3/4 of max value and second is pre-amp gain about at 3/4 of max value again.
You turn these values down slowly if you see that your detector behaves eratically.Final adjustments depend on soil conditions.Don't forget to do air to ground regulations again before starting detecting.
When it comes to many coins put together then I think that the detector sees it as a whole of a metal.I beleive it makes no difference if it is coins put together or just one object of the same size.All it has to do whith the volume of the metal.Watch out if the metal has the shape of a thin band.
A long knife for example when detected at a medium depth might give a number simillar to a coin but it is not.In such a case volume is different but the detector see it the same and this is where experience needed.
Well LRLs don't suffer of things like that at last.
Many regards
g-sani

[bulsack]

OKM

If you want to get rich quick just invest in OKM on the stock market. There's a fool born every second.....

[J_Player]

When it comes to many coins put together then I think that the detector sees it as a whole of a metal.I beleive it makes no difference if it is coins put together or just one object of the same size.All it has to do whith the volume of the metal.Watch out if the metal has the shape of a thin band.

Hi Sani,
You are wrong about this. VLF and PI detectors rely on eddy currents induced in the target metal to detect the resultant magnetic field emanating from the target. The shape of the target is important for detecting it. The volume of metal can be indirectly related, but not the determining factor.

Here is an experiment I actually performed that will prove exactly what I am saying:
Get two identical copper or brass coins (old USA pennies before the cladding years work for this). Then get a file and file one of the pennies into a pile of metal filings and set them aside. Next get a small plastic container like an old film can or other small cup-shaped plastic container. Mix up some 5-minute epoxy and pour a 1/8 inch deep puddle of epoxy into the plastic container. Then dump the copper filings into the epoxy and stir them around so the filings are evenly spread into the epoxy. When the epoxy is hard, pop it out of the cup. You now have two copper targets to test that have exactly the same volume of copper in them. One is a standard USA penny and the other is an epoxy coin with the exact same volume of copper in it, but filed into smaller pieces.

Now test them with your detector. Of course, the intact penny will give a good signal, and nearly nothing from the new copper filings coin. This is because the intact penny allows a larger circuit for eddy currents to travel than the tiny filings. And these eddy currents are what send out the magnetic fields that the detector is sensing.

To illustrate further, get some thin transformer wire and cut off a length that weighs exactly the same as your penny weighs. Then wind this wire into a 2 inch diameter coil and solder the ends together. Take a look at what kind of signal you get from this same volume of copper.

Then try drilling a hole in the center of your penny and see what happens to the signal.

I think you will find that volume is not the determining factor that allows VLF or PI metal detectors to find metal targets.

Best wishes,
J_P

[g-sani]

Hi J Player, I see what you mean my friend and I agree that volume is not the determining factor for a VLF.But is one serious parameter for sure.
But you are talking again about testing a detector using just a small ammount of metal.
In my last few posts everything I wrote is a try to explain my conclusion that gold in a large quantity is not detectable from VLFs.Silver and copper or bronze are detectable no matter the size.Gold wears very litle while all other precious metals make patina easily.Ion changes so fast when burried that dust of rust appears shortly.Thats why it repllies to most frequencies when frequency generator is used.Today is 5khz and tomorrow might be 6.4khz or whatever else.
To beleive what I am saying about gold there is no other way of seen it yourself.
Borrow as much gold as you can, burry it in the ground not very deep(few cms) and test VLFs.
But then when testing a VLF the samples must be burried for a long time if somebody wants to do it properly.Very difficult!
Most makers(White) say for VLFs that the object must be in the soil for more than 30 years.PI makers don't mension it at all.
PI tests in air and ground are very similar but this doesn't apply to VLFs.

you said above that.....To illustrate further, get some thin transformer wire and cut off a length that weighs exactly the same as your penny weighs. Then wind this wire into a 2 inch diameter coil and solder the ends together. Take a look at what kind of signal you get from this same volume of copper.

Of course it won't be the same J Player.It is like if you burry a 1meter straight wire vertically in the ground.Will you have the same results?of course not.
Tests should have some resonable standards but they have to be based in a logical manner which comes up from reallity and they way that treassures are hidden.I don't think that treassure would come up in a coil form.Hahahahaaaa.....

Regards g-sani

[J_Player]

Hi J Player, I see what you mean my friend.
But you are talking again about testing a detector using just a small ammount of metal.
In my last few posts everything I wrote is a try to explain my conclusion that gold in a large quantity is not detectable from VLFs.
To beleive there is no other way of see it yourself.

Based on your post, I thought you were making the conclusion that volume of metal is what matters, regardless of whether it is a single object or a lot of smaller objects. Here is what you posted: "When it comes to many coins put together then I think that the detector sees it as a whole of a metal.I beleive it makes no difference if it is coins put together or just one object of the same size.All it has to do whith the volume of the metal". I have never heard this theory from White's or any other major metal detector company. What I have heard is a smaller collection of metal objects usually don't give as good a signal as a single target made from the same material and the same weight. I also heard that the shape and orientation of the target matter.

Borrow as much gold as you can, burry it in the ground not very deep(few cms) and test VLFs.
Anyway when testing a VLF the samples must be burried for a long time if somebody wants to do it properly.
Most makers(White) say that the object must be in the soil for more than 30 years.PI makers don't mension it at all
PI tests in air and ground are very similar but this doesn't apply to VLFs.

The last time I tested large gold, I had a little over 40 ounces of gold coins. I had no trouble detecting them with a VLF or PI detector. But I was not able to bury these coins for 30 years, so I can't say what would change after 30 years in the ground. I remember reading where a top technical employee at White's wrote there is no difference between long time buried gold and fresh gold. Can you show me a reference where White's says "the object must be in the soil for more than 30 years"?

you said above that.....To illustrate further, get some thin transformer wire and cut off a length that weighs exactly the same as your penny weighs. Then wind this wire into a 2 inch diameter coil and solder the ends together. Take a look at what kind of signal you get from this same volume of copper.

Of course it won't be the same J Player.It is like if you burry a 1meter straight wire vertically in the ground.Will you have the same results?of course not.
Tests should have some resonable standards but they have to be based in a logical manner which comes up from reallity and they way that treassures are hidden.I don't think that treassure would come up in a coil form.

Let's suppose the test of detecting a copper coil is not valid, because somebody labelled it as "transformer wire" which relates to electronic components.
Then look at the other tests I made.
Many prospectors look for gold nuggets that can come in all sizes or shapes. Some are roughly the shape of a coin. And a lot of gold comes in the form of pockets of gold dust. Aren't these forms of treasure that are found in real life? The reason I conducted the test I described was to see if it was true what the metal detector companies said about the shape of the metal targets you are hunting. I didn't have any gold that I wanted to turn into metal filings, so I used a penny instead. Have you ever tried this? Have you ever measured what happens to your signal when you drill a hole in a coin? My guess is you have not. Otherwise you would be convinced too.

Actually some treasures do come in this shape. Gold rings for example. These constitute a coil with a single turn, and provide a signal path for the eddy currents that is much better than an equal weight of gold pellets the size of rice grains. Many of the targets I find are in the shape of a ring, and they usually give a noticeably larger signal than an un-shaped chunk of the same material. Does this work for larger collections of gold? I think so, and I find it hard to believe that the VLF detection properties will change for a jar full of gold coins after it is buried 30 years.

But I have an open mind, so I will wait to read your reference where White's says it is true.

Best wishes,
J_P

[g-sani]

Allright J_P give me some time and I will show in which of their manuals(White) say that objects should be burried for a long period of time.
I admmit that I have never drilled a hole in a coin and I have never put granules of a metal piece together but I still say that I could not detect that gold coins.
I don't know what VLF you were used when you did the test whith the 40 ounches of gold.My self using my white and then a garrett missed the pot of the gold coins.We only found it when later we passed from there using a Lorenz Deepmax X3.
Since then I always have the PI whith me .
I know you are an open minded my friend and thats why I am still writing now.
Be patient, I will be back whith the reference.
Best wishes, g-sani

[g-sani]

Hi J_P, I had a quick look at whites dfx manual and it is there as well.
It doesn't say 30 years or more but it says that to achieve results regarding depth or corect discriminstion the object has to be burried for a number of years.
This in turn means that when you test on fresh burried or when you do air tests you are far away from real conditions.Here is the advantage of PIs.
Check it yourself, it is page 3 paragraph 10 The chapter is Assembly instructions.
http://media.whiteselectronics.com/m...n%20Manual.pdf
I have read the manuals of Eagle Spectum, MXT XLT and DFX in the past and I am not in a position to remember after so many years where and in which one exactly I read it.
I have to go through them again like if I have to sit on exams.
I am sure some other user from one of the detectors mentioned above read it in one of these manuals as well and it might be able to verify it.
Apart from that experience I had I used to owe all this models and this is why I know what I am saying.
Anyway I think you do not have to be very clever to understand what is going on when you read the topic I mark you above.
So you have to reconsider my friend and to beleive that a jar full of gold coins can show up having different VLF properties after it is burried for many years.
And this is the main reason why I did not even think of doing any tests like the one you did.
Apart from that I beleive that these tests you did added knowledge to you related to VLFs no matter what Whites engineers say in their manuals.
Many regards, g-sani

[J_Player]

Hi J_P, I had a quick look at whites dfx manual and it is there as well.
It doesn't say 30 years or more but it says that to achieve results regarding depth or corect discriminstion the object has to be burried for a number of years.
This in turn means that when you test on fresh burried or when you do air tests you are far away from real conditions.Here is the advantage of PIs.
Check it yourself, it is page 3 paragraph 10 The chapter is Assembly instructions.
http://media.whiteselectronics.com/m...n%20Manual.pdf
I have read the manuals of Eagle Spectum, MXT XLT and DFX in the past and I am not in a position to remember after so many years where and in which one exactly I read it.
I have to go through them again like if I have to sit on exams.
I am sure some other user from one of the detectors mentioned above read it in one of these manuals as well and it might be able to verify it.
Apart from that experience I had I used to owe all this models and this is why I know what I am saying.
Anyway I think you do not have to be very clever to understand what is going on when you read the topic I mark you above.
So you have to reconsider my friend and to beleive that a jar full of gold coins can show up having different VLF properties after it is burried for many years.
And this is the main reason why I did not even think of doing any tests like the one you did.
Apart from that I beleive that these tests you did added knowledge to you related to VLFs no matter what Whites engineers say in their manuals.
Many regards, g-sani

Hi g-sani,
Now, that's interesting!
I never thought of it that way. What they are saying is by digging a hole, you upset the ground to make it different than the surrounding ground. This brings to mind that the replaced soil will not have the same compaction as the surrounding soil, and if it is mineralized, it will probably not be as conductive as the surrounding undisturbed soil. I think this means this particular detector will detect the change in the ground consistency, and may automatically try to discriminate it out of view along with some sensitivity to the target? The XLT and DFX are among the White's detectors that use an algorithm to automatically adjust for ground variations, while many other detectors don't use automatic algorithms, or they use a simple adjustable delay rate.

As I said, I never liked the XLT because I never had time to learn the programs and controls very well, and my experience was I had difficulty finding targets that I could easily find on my other VLF and PI detectors. For one, I don't like the idea that the detector will be guessing what is good soil and bad soil and making corrections for it in a way I don't understand. I am sure the XLT is a good detector in the hands of someone experienced with it, but I prefer detectors with analog controls that I can set and tweak on the fly without using menus. I would rather set a trim pot for the ground balance and adjust it periodically as needed. My guess is the automatic algorithms in the XLT and other similar detectors can be confused when they come to disturbed ground and automatically discriminate out targets in the disturbed area. This doesn't happen with the manual versions. You may hear the disturbed ground, but you will not lose your settings due to automatic adjusting.

The way the ground can make detecting eddy currents more difficult is by having mineralization that requires more ground balancing. By increasing the ground balance, you are also reducing your detection depth. My experience is that PI detectors have been able to detect a target deeper than VLF in highly mineralized ground. But I have not used all the most exotic detectors, so there may be VLFs that do better than the PIs that I don't know about. One exception I remember is where I found a 1 inch thick layer of dry black sand at the beach that made my White's surf PI Pro useless. But a VLF detector was able to find silver and copper coins below the black sand if I adjusted the ground balance to near maximum mineralization and also held the coil about 4 inches above the ground. In this case, the maximum coin detection depth was about 5 inches below the surface.

But regardless of the ground mineralization level, I still think the shape of the target is important for determining what signal strength you will find. The physics of eddy currents does not change for long time or freshly buried metal things. The ground may trick the detector electronics into reducing its detection ability, but the buried metal will still obey the laws that govern eddy currents generating magnetic fields. My guess is you would get a stronger signal from a 10 inch gold plate held parallel to the coil than you would get from the same gold plate cut into a 1/4 inch pieces and placed in a cup, whether buried in mineralized soil or in the air.

The tests I made were air tests. I also tested the samples in dry beach sand and found the same results. So all my tests were made in equal conditions. I also made the same tests using a 1/4 inch steel nut compared to filings from a steel nut, and several other metal objects. I can say with certainty that all these objects were easier to detect when they are in a single piece instead of a lot of little pieces.

Thank you for researching the White's statements about fresh and long time buried targets. I think it answered the question why I don't like the XLT model.

Best wishes,
J_P

[g-sani]

Hallo J_P, what I believe is that if we take a long burried metal from the ground that has already some patina on it and burry it somewhere else to do tests whith a VLF then it will be much more detectable than the same metal put in the same place and depth but free from patina.
Gold wears as well but very very slowly regarding time.Its patina(if any) is invisible to the eye and this special attribute of gold is responsible for its special behaviour when it comes to detection methods especially whith VLFs.
Whites even talk about different adjustments for gold of different carats in order to be detectable from their VLFs.
Is this because their machines are completely different than the rest?
No I don't think so.Why do they do it then?
Probably they are more honnest from the rest whith their customers and this sounds more likely.Admitting something like that the only thing that it doesn't do is advertising.
Well even companies making LRLs that use a frequency generator talk about different frequencies for different carats of gold.
Have you ever thought why they don't even mention things like that when it comes to other metals?
The answer is simple. Because they don't have any problems at all detecting them.
Treasures have been recovered around the world from people and some of them used LRLs and VLFs.But most of these treasures contained some other metal apart from gold and this alone was the reason that made them detectable.
Gold alone is very difficult to be detected from VLFs and about the same applies to most LRLs as well.
But then I think of course it should be like that,to justify gold's high value.
Αnd mind you that there is nothing in the nature that can disolve gold.That says it all!
Wish you good luck, g-sani

[WM6]

The answer is simple. Because they don't have any problems at all detecting them.

The answer is even simplest. Because they don't have detect it at all.

Treasures have been recovered around the world from people and some of them used LRLs.

Yes, according principle: the same person buried gold and the same person than discovered it. In other cases this is only sweet LRL dreams.


Reason why fresh buried gold coins can not be detected by VLFs as deep as long buried, are mainly two:

1 by freshly buried gold coin is destroyed crystal structure of the soil (whic can be established over a long period of time and may include a conductive metal ions and

2 freshly buried gold coin can not have full contact with the crystal structure of the soil even if this would not be demolished, (including the establishment of this joint takes time).

Long buried gold coin has established around own surface the crystal structure of the soil and has also established contact with this crystal structure. Eddy currents, (depending on the composition of the crystal structure of soil) beat outside the surface area of gold coins in crystal structure, and thus build a stronger response in greater depth.

[J_Player]

Hallo J_P, what I believe is that if we take a long burried metal from the ground that has already some patina on it and burry it somewhere else to do tests whith a VLF then it will be much more detectable than the same metal put in the same place and depth but free from patina.

Have you actually done this test? Can you show documentation of this test being done by anyone?

Gold wears as well but very very slowly regarding time.Its patina(if any) is invisible to the eye and this special attribute of gold is responsible for its special behaviour when it comes to detection methods especially whith VLFs.
Whites even talk about different adjustments for gold of different carats in order to be detectable from their VLFs.
Is this because their machines are completely different than the rest?
No I don't think so.Why do they do it then?

The reason why gold of different karats are detected differently is because the alloys of the different karats have different conductivity than pure gold. By adding silver or copper, the gold alloy becomes more conductive, and will be able to develop stronger eddy currents than pure gold. This means the lower karat alloy will give a stronger signal than the higher karat alloy. The idea that patina will improve the signal is false. Patina on gold consists of scratching/marring to the gold surface, and sometimes dissolution of some a small trace of the alloying elements into salts at the surface. If, for example a thin film of copper sulfate formed on the surface of a 10K gold alloy ring in the ground that appeared as a patina, the coating of copper sulfate in the "patina" would be less conductive than the copper it was dissolved from, and would work to reduce the strength of the eddy current signal by an un-recognizable amount. So you would probably not see a detectable difference on your VLF detector due to patina. Or if you saw a difference, it would be a weaker signal.

Probably they are more honnest from the rest with their customers and this sounds more likely.Admitting something like that the only thing that it doesn't do is advertising.

This is not even true. Why not send a letter to the head of White's technical department and ask if it is true, or if they are talking about the conductivity and ability of metals to generate detectable eddy currents depending on the alloy variations.

Well even companies making LRLs that use a frequency generator talk about different frequencies for different carats of gold.
Have you ever thought why they don't even mention things like that when it comes to other metals?
The answer is simple. Because they don't have any problems at all detecting them.
Treasures have been recovered around the world from people and some of them used LRLs and VLFs.But most of these treasures contained some other metal apart from gold and this alone was the reason that made them detectable.
Gold alone is very difficult to be detected from VLFs and about the same applies to most LRLs as well.

Pure gold is about as hard to detect as scrap aluminum buried in the ground for a VLF detector. It is not very difficult to detect. It is common knowledge to most detectorists that ordinary jewelry alloys of gold are detectable with similar signals as scrap aluminum alloys. This is because the conductivity is similar for gold alloy and scrap aluminum. By making the gold pure, it becomes a little less conductive than when alloyed, but not enough to make it extremely difficult to detect. See here for a list of electrical conductivity for pure elements: http://environmentalchemistry.com/yo...lectrical.html
You will see that pure gold has a similar conductivity as pure aluminum, and is still among the most conductive elements along with copper and silver, which are maybe 1/3 more conductive.

But then I think of course it should be like that,to justify gold's high value.
Αnd mind you that there is nothing in the nature that can disolve gold.That says it all!

You are absolutely wrong about this. Tons of gold are dissolved in nature. Scientist have discovered more than one chemical mechanism that dissolves gold in nature without the intervention of man-made products. I have already produced links to thousands of web pages showing how scientists documented the natural dissolution of metallic gold in the ground. In fact there is a multimillion dollar industry based on measuring the amount of gold that was naturally dissolved in the ground in order to locate where gold is.

But if you wish to ignore what VLF detector circuit designers and scientists have discovered, we have a local self-proclaimed expert who has a more agreable fact about what happens at the gold surface:
"Gold is the most powerful 'self defensive' metal when it comes to avoid any harm to its structure, such as rust, oxidation, etc. Its DNA produces a substance which coats the metal to fight against those 'threats'."
From: http://www.geotech1.com/forums/showp...8&postcount=41

Perhaps the alleged substance the "gold DNA" produces to "coat the metal" is what makes it so detectable after being buried for a number of years?

Best wishes,
J_P

[g-sani]

Hi J_P, may be the way you see things does some good to yourself but please let me beleive things the way I do when it comes to myself.
The reason?
Theory proves itself only when passes through practical aspects.
Personally I discovered Treasure quite a few times the last few years and if it is God's Will this will keep on going.
No it isn't pure luck as many beleive, it is many other things that must come into account until you hit success when Treasure Hunting.
Regards g-sani

[J_Player]

Hi J_P, may be the way you see things does some good to yourself but please let me beleive things the way I do when it comes to myself.
The reason?
Theory proves itself only when passes through practical aspects.
Personally I discovered Treasure quite a few times the last few years and if it is God's Will this will keep on going.
No it isn't pure luck as many beleive, it is many other things that must come into account until you hit success when Treasure Hunting.
Regards g-sani

Hi g-sani,
You have always been free to believe what you want like everyone else. My posts that contradict what you posted are only pointing out to other readers what the facts discovered by scientists and electronic engineers are. These are not meant to disturb your collection of beliefs.

The reason I post information stating that gold dissolves in nature is because it has been proven by practical tests in the field that this is happening for thousands of tons of buried gold all over the world. And because this is a technical forum in which the rules state that we must "be factual". If we make an extraordinary claim, be prepared to get challenged. http://www.geotech1.com/forums/showp...77&postcount=1
Sure, it seems extraordinary to hear that gold dissolves in nature. And I have been challenged by skeptics about this before. So when I make these posts, these are not simply opinions of how I see things, they are facts that have been demonstrated many times by scientists and technicians actually measuring samples of excavated natural soil to see how much gold has dissolved in it. The same goes for the properties of metal alloys that metal detector electronic engineers have measured for tuning their discrimination circuits. The eddy current properties and detector electronics I described can be verified by sending an email to any engineer who designs the circuits at the major metal detector companies.

I think the reason Carl-NC made the rule to be factual in the Remote Sensing forum is because he wanted non-registered readers to be able to see both sides of the controversial topics we so often find here. Maybe he thought it is good to see posts showing the facts that can be demonstrated with practical tests as well as posts with just opinions based on anecdotal stories. This way they the non-registered readers can choose from more than one opinion of what they want to believe, just as you and the other people making posts are free to choose what they believe.

Best wishes,
J_P

[g-sani]

Hi J_P, what I said in my post above is that there is nothing in nature that can disolve gold.
I thought it was obvious that I am talking about some other "element" that can be found in nature here and not talking about 'if gold disolves in nature or not'.
May be I did not put it down the right way and you have to forgive my English.

[J_Player]

Hi J_P, what I said in my post above is that there is nothing in nature that can disolve gold.
I thought it was obvious that I am talking about some other "element" that can be found in nature here and not talking about 'if gold disolves in nature or not'.
May be I did not put it down the right way and you have to forgive my English.

Hi g-sani,
Are you saying there is nothing in nature that can dissolve gold?

It was not obvious to me that you are talking about elements. There are some elements in nature that can dissolve gold, and there are also chemical compounds found in nature that can dissolve gold. These compounds in nature that dissolve gold are made of various elements that are also found in nature.

Here is a simple example of some other "element" that can be found in nature that can dissolve gold: Mercury metal. Pure metallic mercury occurs in mineral bodies as well as does mercury compounds that are combined with other natural elements. Get 1 cc of mercury and get a small piece of gold the size of a grain of rice. Drop the piece of gold in the 1cc of mercury and stir it around. See if the gold dissolves. Caution: Do not try this experiment on expensive jewelry. You may destroy an heirloom.

There are also other elements and compounds in nature that can dissolve gold. For other metals to dissolve gold, we need to have higher temperatures such as are found in lava flows. Much of the natural gold that has been mined was dissolved in silver and copper to make alloys. In the case of natural gold nuggts, the gold can be well over 90% pure which would suggest other elements dissolved in the gold. But there is also gold that dissolves in amounts less than 50% to form nuggets where gold is not the main element in the alloy. We find that at many copper mines, a small percentage of gold is extracted from the copper, which can be sold for enough money to pay for the entire refining operation, and allow the resulting copper to be sold with less overhead costs.

If you are also referring to other "elements" in nature that are combined as compounds, there are many non-metallic compounds found in nature that dissolve gold, such as cyanide and organic acids found in the ground. In fact these compounds are dissolving gold as we speak without any un-natural processes occurring.

I can provide a lot of data to show these elements and compounds are found in nature and they dissolve gold. Can you provide data to suggest they can't?

Best wishes,
J_P