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The geoporphyrins - see Abelsonite - have formed from chlorophyll in fossils of plants. However, the Mg ion is replaced by Ni or V ion. What is the mechanism for Mg replacement with Ni or V? Namely, did this somehow happened after fossilization (how?) or did the original plants have Ni or V ions in their photopigments? Or maybe only the few porphyrin molecules that had Ni or V ion at the center of the ring survived until present, and the ones with Mg (or Fe) ion did not? Our article Porphyrin#Organic geochemistry seems to suggest that Ni- and V- containing porphyrins in oil and oil-shale came from bacteria and not from plants. Indeed, corphin has Ni ion at the center of its porphyrin ring. On the other hand, this paper suggests that the plant chlorophyll is the origin of the porphyrin in oil, and does not explain how Mg was replaced by Ni. So what`s the answer? Thanks in advance, -- Dr Dima ( talk) 00:43, 17 January 2013 (UTC)
Why is it that the atomic radius of fluorine (64pm) is less than the ionic radius of the sodium ion (98pm on the IB Chemistry data booklet, various values around/over 100pm in wikipedia articles, but in any case, still far greater than the atmoic radius of fluorine)? Applying a Bohr-Rutherford diagram (which I understand is a simplistic/somewhat inaccurate representation), it would appear that the sodium ion has a greater nuclear charge than fluorine, and the same number of electron shells. The nuclear charge, as I've been taught, overcomes the repulsion created by increased electron-electron repulsion, which should therefore lead to a smaller radius (neon illustrates this trend, as its radius, 58pm, is smaller than that of fluorine, and it has the same differences with fluorine as the sodium ion does (although neon does have 1 fewer proton)). I've asked around, and someone suggested it may have something to do with sub-levels (which I have not learned but sort-of understand through my own reading), although I do not see how this explains it. Could someone offer an explanation? (all group 1 ions appear to be smaller than group 17 and 18 atoms). Bramble claw x 02:09, 17 January 2013 (UTC)
When you peel open the shell of a crab, you'll see some soft olive-colored matter in the shell, mostly on the sides. What is that? Is it supposed to be edible?
When you pull the head of a cooked crayfish off its tail, it'll expose some olive-colored matter, soft and perhaps runny—something that seems to be in the head before. Again, what is that? Is it supposed to be edible? — Preceding unsigned comment added by 71.185.166.208 ( talk) 04:33, 17 January 2013 (UTC)
I recall watching a tv show where Michio Kaku introduced an experiment that tested the perception of time under duress (does time really slow down during an accident, for example). But I'm wondering if there have been any experiments on the perception of time between different age groups? For example, as a child, I clearly recall getting up, going to school—which dragged on forever—but then in the afternoons, you cram in as much adventure as you can, and you were able to do so. Decades later, I notice I'm getting ready for bed every day, but it feels like I just did that, even though it was 24 hours ago. Adults are always saying how fast time flies. Is it simply due to a difference in, say, stress? I'm very curious, though, if there've been actual (and good) studies on this. – Kerαunoςcopia◁ gala xies 06:31, 17 January 2013 (UTC)
I have observed that the main reason is that any given period of time, say 24 hours, as a percentage of total life experience decreases as time passes, or I should say as the total time of your life experience increases. This has been cited many times here. Example is 24 hours to a 1 day old is double the total life experience for that baby but to a one month old is 1/30 of total life experience. 165.212.189.187 ( talk) 15:30, 17 January 2013 (UTC)
I am drinking tea in a styrofoam cup (I know, I know shame on me, but in my defense i usually have a mug) and I have a bit of a cold. So I took the peel of my tangerine and ripped it into small pieces over top of the cup of tea. I could see the oils make film on the surface of the tea and got a good amount of it in my tea. a few minutes later I noticed that the styrofoam cup above the water line has been eaten away! What happened? Is this safe to drink? I wont but just wondering. not necessarily medical advice but if the reaction has leached certain chemicals into the tea the it is just lain facts. 165.212.189.187 ( talk) 15:22, 17 January 2013 (UTC)
Didn't see those in the summary at Boeing_787_Dreamliner#Manufacturing_and_suppliers 20.137.2.50 ( talk) 16:22, 17 January 2013 (UTC)
I failed to jot it down. Thanks in advance. [2] 65.88.88.71 ( talk) 22:20, 17 January 2013 (UTC)
Science desk | ||
---|---|---|
< January 16 | << Dec | January | Feb >> | January 18 > |
Welcome to the Wikipedia Science Reference Desk Archives |
---|
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages. |
The geoporphyrins - see Abelsonite - have formed from chlorophyll in fossils of plants. However, the Mg ion is replaced by Ni or V ion. What is the mechanism for Mg replacement with Ni or V? Namely, did this somehow happened after fossilization (how?) or did the original plants have Ni or V ions in their photopigments? Or maybe only the few porphyrin molecules that had Ni or V ion at the center of the ring survived until present, and the ones with Mg (or Fe) ion did not? Our article Porphyrin#Organic geochemistry seems to suggest that Ni- and V- containing porphyrins in oil and oil-shale came from bacteria and not from plants. Indeed, corphin has Ni ion at the center of its porphyrin ring. On the other hand, this paper suggests that the plant chlorophyll is the origin of the porphyrin in oil, and does not explain how Mg was replaced by Ni. So what`s the answer? Thanks in advance, -- Dr Dima ( talk) 00:43, 17 January 2013 (UTC)
Why is it that the atomic radius of fluorine (64pm) is less than the ionic radius of the sodium ion (98pm on the IB Chemistry data booklet, various values around/over 100pm in wikipedia articles, but in any case, still far greater than the atmoic radius of fluorine)? Applying a Bohr-Rutherford diagram (which I understand is a simplistic/somewhat inaccurate representation), it would appear that the sodium ion has a greater nuclear charge than fluorine, and the same number of electron shells. The nuclear charge, as I've been taught, overcomes the repulsion created by increased electron-electron repulsion, which should therefore lead to a smaller radius (neon illustrates this trend, as its radius, 58pm, is smaller than that of fluorine, and it has the same differences with fluorine as the sodium ion does (although neon does have 1 fewer proton)). I've asked around, and someone suggested it may have something to do with sub-levels (which I have not learned but sort-of understand through my own reading), although I do not see how this explains it. Could someone offer an explanation? (all group 1 ions appear to be smaller than group 17 and 18 atoms). Bramble claw x 02:09, 17 January 2013 (UTC)
When you peel open the shell of a crab, you'll see some soft olive-colored matter in the shell, mostly on the sides. What is that? Is it supposed to be edible?
When you pull the head of a cooked crayfish off its tail, it'll expose some olive-colored matter, soft and perhaps runny—something that seems to be in the head before. Again, what is that? Is it supposed to be edible? — Preceding unsigned comment added by 71.185.166.208 ( talk) 04:33, 17 January 2013 (UTC)
I recall watching a tv show where Michio Kaku introduced an experiment that tested the perception of time under duress (does time really slow down during an accident, for example). But I'm wondering if there have been any experiments on the perception of time between different age groups? For example, as a child, I clearly recall getting up, going to school—which dragged on forever—but then in the afternoons, you cram in as much adventure as you can, and you were able to do so. Decades later, I notice I'm getting ready for bed every day, but it feels like I just did that, even though it was 24 hours ago. Adults are always saying how fast time flies. Is it simply due to a difference in, say, stress? I'm very curious, though, if there've been actual (and good) studies on this. – Kerαunoςcopia◁ gala xies 06:31, 17 January 2013 (UTC)
I have observed that the main reason is that any given period of time, say 24 hours, as a percentage of total life experience decreases as time passes, or I should say as the total time of your life experience increases. This has been cited many times here. Example is 24 hours to a 1 day old is double the total life experience for that baby but to a one month old is 1/30 of total life experience. 165.212.189.187 ( talk) 15:30, 17 January 2013 (UTC)
I am drinking tea in a styrofoam cup (I know, I know shame on me, but in my defense i usually have a mug) and I have a bit of a cold. So I took the peel of my tangerine and ripped it into small pieces over top of the cup of tea. I could see the oils make film on the surface of the tea and got a good amount of it in my tea. a few minutes later I noticed that the styrofoam cup above the water line has been eaten away! What happened? Is this safe to drink? I wont but just wondering. not necessarily medical advice but if the reaction has leached certain chemicals into the tea the it is just lain facts. 165.212.189.187 ( talk) 15:22, 17 January 2013 (UTC)
Didn't see those in the summary at Boeing_787_Dreamliner#Manufacturing_and_suppliers 20.137.2.50 ( talk) 16:22, 17 January 2013 (UTC)
I failed to jot it down. Thanks in advance. [2] 65.88.88.71 ( talk) 22:20, 17 January 2013 (UTC)