Well, a lot is known about how photosynthesis splits water (though many of the discoveries are comparitively quite recent), but "unlocking the secrets" really refers to being able to do it on our own terms, using the materials available to us. Where living things use enzymes, we are largely forced to substitute inorganic catalysts. That may change somewhat as advances in bioengineering are made, but photosynthesis in particular is a process that involves so many integrated systems and molecules that the best options are to either work top-down to genetically engineer a plant to optimize the photosynthesis it already does or to work bottom up to make an artificial system that "works like" photosynthesis.
We're not nearly at the stage where we can build something like a photosynthetic reaction center, which has complicated proteins working in concert with pigments and an electron transport chain. The good news is that while plants have to use all of this together to convert light energy into chemical energy to make sugars, we'd be happy with the "electron regeneration/oxygen evolving" reaction that forms a small part of the total process. The enzyme which accomplishes this, the creatively named "oxygen evolving complex" (OEC), is again too complicated to engineer, at least on a million pound budget. At its heart, though, is an inorganic cofactor of manganese, oxygen, and calcium atoms that looks a lot like the transition metal oxide catalysts used all over in the chemical industry. There is still disagreement about the exact structure and mechanism (making this a good target for research), but the cofactor appears to hold water molecules in a series of increasingly excited transition states until enough energy has been pumped in to break the water apart.
Finding a metal oxide catalyst that replicates this process seems potentially achievable, as it does not require sophisticated protein engineering, but rather that you make a lot of rust of varying composition, and use trial and error (informed by knowledge of how the OEC is structured) to find out what works best. And by "trial and error" I mean "grad students."
It's the composition of quite a few minerals, including asbestos, but also talc and soapstone. The issue with asbestos isn't the chemical composition per se, but rather its inclination to break into micron-sized fibers that can be deposited in the lungs. Compare fine silica, which is nearly chemically inert, but poses a serious danger if inhaled.
Actually, this is possibly an excellent example of evolution minimizing complexity through the tactic of re-purposing the same system to be used in different ways in different parts of an organism. As the article notes, the neurons that may be specific to itchiness have a cell surface protein called gastrin-releasing peptide receptor. Gastrin, as the name might suggest, also plays a role in the gastrointestinal system, where it is involved in signaling the release of hydrochloric acid. What do your digestive juices have to do with itchy skin? Notably, gastrin does not work directly to release stomach acid, but rather it binds to what are called ECL cells, which secrete histamine, which then stimulate the parietal cells of the stomach to release acid. Histamine is a versatile molecule that is particularly useful for organizing inflammatory responses, though these responses aren't always welcome. That's why you might take diphenhydramine for allergies and ranitidine for heartburn- both are antihistamines, though for different histamine receptors.
Thus, strangely enough, skin itches share many of the same signaling pathways as digestion. The cell types involved (epithelial tissue) are similar though, so during the evolutionary development of skin, cells would already have inherited a sensitive network of cell surface receptors and signal transduction pathways. Why not find a way to put them to good use?
In the abstract for the actual journal article, they report the outputs for their mutant strain as current 7.6 amps per square meter and power 3.9 watts per square meter. Which is to say about 0.76mA per square centimeter, so not a gigantic number, but more impressive than what the parent predicts. One important factor that would make power generation using these microbes more attractive is that you could put them in a fuel cell that has a tremendous surface area to volume ratio.
Geobacter is an obligate anaerobe, so it does not require- indeed, cannot tolerate- access to the atmosphere, and it is not photosynthetic. You can buy carbon black, which makes a fine electrode, with a surface area to volume ratio of greater than 50 square meters per cubic centimeter. In the described experiment, they grew the bacterium on graphite, so carbon black should not pose an obstacle. A cubic meter of carbon black would have a surface area of about 50 square kilometers, but a mass of about 2 tons. An output of 3.9W/m^2 over 50 million square meters is 195 megawatts, which isn't shabby considering your input would be wastewater. Now, of course, that number is a wildly optimistic figure- good luck covering that much surface area with a bacterial biofilm- but it does suggest that you could produce enough power to say, make a wastewater treatment facility self-sufficient.
According to the paper, "KN400 (the mutant strain) also had a greater propensity to form biofilms on glass or graphite than DL1 (the wild-type), even when growing with the soluble electron acceptor, fumarate." In a fuel-cell enviroment there would be significant survival advantages to forming a biofilm. In order to run its metabolic processes, this intriguing organism needs a terminal electron acceptor in its enviroment. Instead of bringing the acceptor inside (as we do with our terminal electron acceptor, oxygen), Geobacter uses its electrically conductive pili to send its electrons outside.
An electrode would really be the ideal living enviroment for this organism- it would act as a near-infinite sink for electrons. The mutant strain KN400 seems to be better adapted to living on an electrode, so within the constraints of a fuel-cell environment, the mutant strain should outcompete against the wild strain. In the organism's native enviroment, mud in a riverbed, I'd suspect the wild-type would be more successful, since it does not prefer to anchor itself in a biofilm. In mud, the organism would be better served on the move, making use of metal oxides as it finds them, rather than being tied to one spot and risking depletion (essentially asphyxiating).
However, in the fuel cell, selection pressure will favor organisms that stick to the electrodes, maximize electron conduction, and minimize internal resistance. Even without the "pushback" current used to drive adaptation of these characteristics, my guess is that the fitness advantages they provide will cause them to be passed on to future generations.
Here's the abstract from the paper (with some line breaks inserted for readability):
Geobacter sulfurreducens produces current densities in microbial fuel cells that are among the highest known for pure cultures. The possibility of adapting this organism to produce even higher current densities was evaluated. A system in which a graphite anode was poised at 400 mV (versus Ag/AgCl) was inoculated with the wild-type strain of G. sulfurreducens, strain DL-1. An isolate, designated strain KN400, was recovered from the biofilm after 5 months of growth on the electrode. KN400 was much more effective in current production than strain DL-1. This was apparent with anodes poised at 400 mV, as well as in systems run in true fuel cell mode. KN400 had current (7.6 A/m2) and power (3.9 W/m2) densities that respectively were substantially higher than those of DL1 (1.4 A/m2 and 0.5 W/m2).
On a per cell basis KN400 was more effective in current production than DL1, requiring thinner biofilms to make equivalent current. The enhanced capacity for current production in KN400 was associated with a greater abundance of electrically conductive microbial nanowires than DL1 and lower internal resistance (0.015 versus 0.130/m2) and mass transfer limitation in KN400 fuel cells. KN400 produced flagella, whereas DL1 does not. Surprisingly, KN400 had much less outer-surface c-type cytochromes than DL1. KN400 also had a greater propensity to form biofilms on glass or graphite than DL1, even when growing with the soluble electron acceptor, fumarate.
These results demonstrate that it is possible to enhance the ability of microorganisms to electrochemically interact with electrodes with the appropriate selective pressure and that improved current production is associated with clear differences in the properties of the outer surface of the cell that may provide insights into the mechanisms for microbe-electrode interactions.
Actually, if you look at the other picture, of the rat prior to injection, it seems "normal" for its eyes is in fact red, so there's definitely been some alteration of color.
Oops. The dose of radiation used to sterilize things is more like 12-100 kilogray. I don't know how I screwed that up- I once worked on a drug whose active ingredient was sterilized prior to formulation with a gamma dose of 17.5 kGy. Kills bugs dead.
Actually, the roughly 1000-fold disparity in the radiation dose that kills bacteria versus that which kills humans is demonstrative of the range of efficacy we'd be looking at for a radiation sickness drug like the one mentioned in the story. When bacteria are killed by radiation, it's because the radiation has done significant damage to their structures- denatured proteins and lipids, damaged DNA to the point of introducing breaks. If you were to receive that level of radiation, then you're better off destroying affected cells and hoping enough healthy cells remain.
What may make us comparatively fragile to radiation, however, is that our protective anticancer mechanisms are too hasty to destroy slightly damaged cells. Your apoptosis pathway would rather just mark a radiation-exposed bone marrow cell for death than to allow for the chance of leukemia. This is a reasonable course of action for the random isolated exposures of the natural world, but perhaps an overreaction to a acute, intense exposure, since sending blood cell counts plummeting represents an immediate danger from anemia and immunodeficiency.
Here is a Medical News Today article about the drug, CBLB502, in question. I have to say I'm impressed- they used 6.5 gray (Gy) of ionizing radiation as their test dose. The Mayo Clinic considers an absorbed dose of 5.5 to 8 Gy as causing "very severe radiation sickness." (And goes on to mention, "Doses greater than 8 Gy are generally not treated successfully and usually result in death within two days to two or three weeks depending on the duration of the exposure.")
In comparison, a full-body CT scan is about 0.01 Gy, anywhere from 12-100 Gy is typically used for antimicrobial irradiation, depending on the material and microorganisms of interest, and 5000 Gy is about the threshold where Deinococcus radiodurans starts to get bothered by ionizing radiation.
That Medical News Today article is about a different set of experimental drugs from the same company. The article is also from January. It is interesting though that Cleveland BioLabs is basically developing drugs that work on the process of apoptosis in opposite ways. The "Curaxins" described in the Medical News Today article are cancer drugs that promote apoptosis, while CBLB502, their experimental anti-radiation damge drug, seems to work to prevent it.
Quite true, and one of the things that I'm worried about with the pathway described. Cellular respiration is tied to thermoregulation, and by introducing a pathway which metabolically does nothing for your cells (like the glyoxylate shunt seems to in mammals), you introduce the risk of overheating.
"It was thanks to Ultra that we won the war."
-Winston Churchill, to King George VI
I must disagree with the notion that the work at Bletchley Park was not done at peril to those involved. No, the codebreakers didn't die in the mud taking back pieces of Europe, but what they did was so important that when they went to work, they too went to battle. Secrecy was their armor. If Nazi Germany had truly known what was going on at Bletchley Park, they would have sent every plane in the Luftwaffe to turn it into a crater. Honoring those that served there does not diminish the honors bestowed on those who died on battlefields.
Well, if I understand what's going on in this process, fat metabolism is occurring because the mammalian cells given the glyoxylate shunt genes don't know how to use them "properly." That is to say, plants, bacteria, and fungi use the shunt to turn fat stores into sugars. A major reason for doing this is because they need to build polysaccharide cell walls. We don't have these, so apparently if we have access to the glyoxylate shunt, we run through it, but get nothing out of it. Indeed, less than nothing- to make the dreaded car analogy, it's like sort of like the hit in fuel economy you take by driving with the air conditioner on- your fuel is powering a second motor, but it's one that doesn't contribute to the car's motion.
In terms of energy usage, the glyoxylate shunt is one of those shortcuts that turn out to take longer in the end- isocitrate molecules that take the detour are broken apart at a net energy cost, then the glyoxylate formed grabs an acetyl-CoA that could have gone to a more productive use, and then returns to the beginning of the Krebs cycle, having accomplished nothing. The shunt steers away from a couple of highly energetically favorable reactions of the Krebs cycle, and runs through one that costs energy.
The Krebs cycle, the metabolic engine, ultimately has to turn more times to produce the same amount of energy, causing it to demand more fuel in the form of acetyl-CoA. In order to meet this need, your body turns to a particularly rich source of acetyl-CoA: the beta-oxidation of fatty acids. To finally answer the parent's first question, this is where negative feedback that regulates the breakdown of fats is likely to take place. You have an enzyme called acetyl-CoA carboxylase whose activity promotes biosynthesis of fat. As the name suggests, the enzyme adds a carboxylate group to acetyl-CoA to make malonyl-CoA, a compound which is a building block of fatty acids, as well as an inhibitor of enzymes that break down fats. If you run low on fats, acetyl-CoA carboxylase should act to prevent further fat metabolism, and promote the production of more. This will hopefully result in an equilibrium between fat synthesis and fat breakdown. I say hopefully because these tidy feedback loops do not always work as well in practice, which is why we have metabolic disorders in the first place.
To answer the parent's second question, genetic modifications that correctly integrate into the host genome can generally be expected to be permanent, and spread through dividing cells. Of course, in the lab, you can add genes into an embryo of very few cells, and expect that as an adult, virtually every cell will have the genes, and even expect that the genes will be passed on to offspring. To add genes to a developed organism however involves infecting cells with a vector (usually a modified virus) that carries the genes. It is unlikely that all cells will be infected, and that all infected cells will properly integrate the foreign genes into the genome, and extremely unlikely that the genes would infect germ-line cells and be passed on. The most likely outcome would be a mosaic individual, of whose cells only some contain the foreign genes.
Urea could be conceivably be made using a different industrial process, one that doesn't ultimately require hydrogen gas as a starting material.
The cyanamide process, for example, makes calcium cyanamide (CaCN2), which in the presence of carbon dioxide and water makes cyanamide, H2NCN, which in the presence of acid further hydrolyzes to form urea. Calcium cyanamide is made by reacting calcium carbide with nitrogen gas; calcium carbide can be produced industrially by roasting calcium oxide (quicklime) with carbon. The production of cyanamide from calcium cyanamide produces calcium carbonate (lime) as a byproduct, which can be heated to regenerate calcium oxide.
As an overall cycle, you'd be be using energy to split water into hydrogen and oxygen, and oxidizing carbon to form carbon dioxide (though much less CO2 than would be formed by combustion of hydrocarbons, and it would be produced centrally).
The catch is, it would be a lot of energy. Virtually all of the reactions outlined above require very high heat, and most are performed in carbon arc furnaces at around 2000 degrees C. The centralized production would make this process a good candidate for being powered by renewable sources of energy, however. In fact, at the turn of the 20th century, the cyanamide process was widely used to make nitrogen-based fertilizers (this was before the advent of the Haber process to make ammonia, which the parent post describes), and cyanamide manfacturers usually got their electricity from large hydroelectric projects- the plants at Niagra Falls being a prime example.
The ScienceDaily article and the/. summary seem to be confused on the experimental setup. From the Nature article, "[e]ach qubit has a split Josephson junction...." The Josephson effect is an effect where two superconductors are separated by a very thin insulating layer. A "supercurrent" composed of paired correlated electrons (Cooper pairs) can tunnel across this barrier under certain circumstances. Cooper pairs act as bosons, just as atoms do in Bose-Einstein condensates, so they have long been a focus of research for quantum computing. In this experiment, the device was a "180nm Nb film was d.c.-magnetron sputtered on the epipolished surface of an R-plane corundum wafer," meaning that the superconductor they used was niobium, and the insulator was aluminum oxide, aka corundum. They built it out of these, in other words.
They go on to mention that the apparatus was cooled to 13 millikelvin using a helium dilution refrigerator. Now, niobium is superconductive to about 9 kelvin in the pure state (and about 23 kelvin in some alloys), so I would assume the extra effort to make it that cold has more to do with preserving the delicate electronic state of the qubits than with merely chilling the superconductors.
Well, if Jobs was experiencing liver failure, it probably was accompanied by hormone imbalances- the liver is responsible for breaking down a wide variety of hormones, most notably the steroid hormones. So the idea that he was suffering from a "hormone imbalance" is probably true, but omitting the proximate cause of that hormone imbalance, if it happened to be liver failure, is being less than completely honest to the public and to Apple's investors.
If you're wondering why it is cancer can gain the ability to turn off your T-cells, it's important to remember that overactive immunity can be just as dangerous as immune insufficiency. Mutations in the CTLA-4 gene that boost its activity are associated with autoimmune diseases like lupus (yes, sometimes it is lupus), type I diabetes, and rheumatoid arthritis. In fact, Bristol-Myers-Squibb, makers of the ipilimumab (anti-CTLA-4 antibody) investigational drug discussed here already make abatacept, which is CTLA-4 fused to antibody. Abatacept, marketed as Orencia, is FDA approved for the treatment of rheumatoid arthritis, and is under investigation for treatment of other autoimmune diseases, as well as for treatment of automimmune rejection of transplanted tissues. So on both ends of the spectrum, CTLA-4 and other T-cell regulatory genes play a big role in disease, and make for promising avenues of research.
Create some subhadronic matter and see if it causes a region of space with lower pressure than the surrounding space. As a bonus, measure the temperature of that space before and after the pressure vacuum stabilizes.
Show all work. Write legibly in #2 pencil or blue or black permanent ink. Do not write on test booklet. Do not start until signaled to do so by your proctor. Destruction of the earth will result in automatic failure. You will have three (3) hours.
But to make that distinction actually takes away from the most powerful feature of the periodic table- that you may predict chemical and physical properties of unknown elements through their relationships to known elements on the table. Even though only single, highly unstable nuclei of Element 112 have ever been synthesized, we can predict that it will behave like the other Group 12 elements (zinc, cadmium, mercury). It should be a volatile metal, possibly either liquid or gas at standard temperature and pressure, it should have a +2 oxidation state and readily form oxides and sulfides, and it probably forms amalgam-type alloys the way mercury does.
I understand the trepidation to call something an "element" if its rarity and instability means that it has never existed as part of a chemical compound, but I think there is more utility in connecting these superheavy laboratory creations to the existing table of chemical elements than there is in presenting them as something altogether different.
After all, what evidence we do have strongly suggests that short-lived as they are, the transactinides do have the chemical properties predicted by their periodic table locations. Hassium (Element 108), whose most stable isotope has a half-life of about 17 minutes, for instance, has been experimentally shown to form a tetroxide, just like osmium above it in the table. And it's important to note that most of the transactinides, unstable as they are, do tend to have at least one isotope with half-life in the seconds-to-minutes range, which can be long enough to get them to participate in chemical reactions.
What I think is interesting about the hydraulic Phillips computer though is that its workings are straightforward enough to act as an aid to common sense and basic logic. An issue with using modern digital computers in economic models is that it becomes very difficult to just follow the money around. You don't get the notion that you're looking at an unsustainable bubble, because the inputs and outputs in your model are obscured by mathematical abstraction. In particular, it becomes easy to lose sight of the interconnections among companies or economic sectors.
A hydraulic system however has the advantage that a tangible working fluid connects all the areas in your economic model. The idea of "Too Interconnected to Fail" really stands out in a physical model versus a computer program. Say you're AIG. It's one thing to create a model that calculates how much collateral you would have deposit with counterparties in credit default swaps should your credit rating fall. It's another to have the executives stand there and watch as a reservoir full of water that represents your company's cash on hand is sucked dry and the pumps continue to grind in demand for more water. However, in both cases, you still have to be able to admit the possibility that your credit rating even could fall.
"An engineer uses statistics like a drunk uses a lamppost- more for support than for illumination." I think that applies just as well to economists and financiers.
This is the reaction sequence that's being proposed here: link.
Previously, the sticking point was that there was no logical way for the sugar (ribose) to spontaneously attach to the base. Organisms use enzymes to transfer a ribose phosphate group to a base, but of course, in the time before enzymes could be coded for, that wouldn't be possible. This sequence neatly sidesteps that, and also provides a more logical reason for phosphate to be involved; it is the reagent that attacks that tricyclic pyrimidosugar, breaking the bond to form ribocytidine phosphate.
Coincidentally, UV light deaminates cytosine to form uracil, which is where that second base comes from. This is why DNA uses thymine instead of uracil, by the way- as the archival storage medium for our genetic information, it would be unwise to have one base easily interconvert into another. The shorter expected lifetime of RNA means the interconversion is not a concern, though.
I have access to the International Journal of Mass Spectrometry paper (the other journals are a bit outside of my field). The article is mostly about using mass spec to present the case that their substance really has a distance between deuterium nuclei of 2.3 picometers, but they touch briefly on production:
Close to the center of the apparatus, a K doped iron
oxide catalyst (a hydrogen atom transfer catalyst) is used to produce
H(RM) and D(RM) from normal hydrogen (1.5% deuterium) or
pure deuterium gas at a pressure up to 2x10^5 mbar (uncorrected
hot cathode gauge reading).
That (RM) there is for Rydberg matter, the exotic state of matter the hydrogen or deuterium is found in. Rydberg matter is a metastable state where atoms (or molecules) cluster together, not forming covalent or ionic bonds, but rather sharing a system of delocalized electrons, similar to pi-bonding in organic aromatic systems. It's also similar to the excited state of phosphorescent materials; as with phosphorescent materials, quantum mechanical considerations allow the material to maintain this excited state for a short interval before decaying to the ground state. The catalyst used apparently desorbs hydrogen atoms (or deuterium) in this excited Rydberg state into an ultrahigh vacuum chamber, where some will cluster together to form metastable Rydberg matter clusters. Yes, the clusters are apparently stable at room temp and without a diamond anvil; it's the relaxation of their electronic state which determines their lifetime.
In this experiment, the separation between atoms in the cluster is tested by using laser pulses to essentially blow away the electrons, leaving only a cloud of positively charged protons or deuterium nuclei. The rapid repulsion of all of these particles from each other is called a Coulomb explosion, and via Coulomb's law, the energy released by this repulsion is inversely proportional to the square of the initial separation distance of the particles, which it stands to reason is the distance they had as Rydberg matter.
For hydrogen, the results indicate that the atoms were 150pm apart, which is very impressive; it implies hydrogen atoms were together in a metallic state that was thought to require pressures like those in the interior of Jupiter. What's really wild though is the "inverted metal" state of "ultra-dense deuterium." By their calculations, the deuterium atoms were 2.3pm apart. Which is about 1/10 of the radius of a single ground state hydrogen atom. This is pretty much a dense state of matter that you'd expect inside a neutron star, and apparently you can make it with a vacuum chamber, a laser, and a hydride donor. What they're proposing:
We propose that this new material
is dense atomic hydrogen (deuterium) of the type described
by Ashcroft [14] and by Militzer and Graham [15]. In this dense
atomic hydrogen the electrons can be considered to give the constant
(negative) charged background, while the nuclei move within
this charge density. (This state is either close in energy to the normal
ground state D(1) or is in fact the ground state of condensed atomic
deuterium.) This description is the reverse of the ordinary description
of a metal, where the electrons move in the dispersed positive
potential due to the ions [16].
I think there's more information on the process in one of the citations: S. Badiei, L. Holmlid, J. Phys. B: At. Mol. Opt. Phys. 39 (2006) 4191., but someone else will need to look that that one up.
Well, hydrogen is a gas at STP, STP being about 250 Kelvin above the boiling point of hydrogen, and while the higher atomic weight of deuterium does have an effect on some of its physical and chemical properties (and in the biological effects of heavy water), it is not so significant that it wouldn't be a gas under standard conditions. The assumed violent expansion has less to do with the normal phase properties of deuterium though, and more with the notion that the unbelievable promiximity of deuterium nuclei suggested here cannot be stable without gigapascals of applied pressure.
Leif Holmid's page claims this material has a bond length of 2.3pm. Picometers. 10^-12 meter. Now, the normal bond length of dihydrogen is about 74pm, so if these claims are true, the spacing between atoms has been squashed down by about a factor of 30. This distance is still too small for the strong interaction to pull the nuclei together- the effective range of the strong force is on the order of a femtometer, or 10^-15 meters. If you do happen to get the nuclei closer (by dumping in more energy), fusion would be expected to occur. Absent that, this means the predominant force at 2.3pm is going to be electrostatic repulsion between protons, which would only presumably be countered by applied force, like pressure from a diamond anvil cell. Take the pressure off, and the deuterium atoms should energetically move to increase their distances.
Slashdot Mirror
Well, a lot is known about how photosynthesis splits water (though many of the discoveries are comparitively quite recent), but "unlocking the secrets" really refers to being able to do it on our own terms, using the materials available to us. Where living things use enzymes, we are largely forced to substitute inorganic catalysts. That may change somewhat as advances in bioengineering are made, but photosynthesis in particular is a process that involves so many integrated systems and molecules that the best options are to either work top-down to genetically engineer a plant to optimize the photosynthesis it already does or to work bottom up to make an artificial system that "works like" photosynthesis.
We're not nearly at the stage where we can build something like a photosynthetic reaction center, which has complicated proteins working in concert with pigments and an electron transport chain. The good news is that while plants have to use all of this together to convert light energy into chemical energy to make sugars, we'd be happy with the "electron regeneration/oxygen evolving" reaction that forms a small part of the total process. The enzyme which accomplishes this, the creatively named "oxygen evolving complex" (OEC), is again too complicated to engineer, at least on a million pound budget. At its heart, though, is an inorganic cofactor of manganese, oxygen, and calcium atoms that looks a lot like the transition metal oxide catalysts used all over in the chemical industry. There is still disagreement about the exact structure and mechanism (making this a good target for research), but the cofactor appears to hold water molecules in a series of increasingly excited transition states until enough energy has been pumped in to break the water apart.
Finding a metal oxide catalyst that replicates this process seems potentially achievable, as it does not require sophisticated protein engineering, but rather that you make a lot of rust of varying composition, and use trial and error (informed by knowledge of how the OEC is structured) to find out what works best. And by "trial and error" I mean "grad students."
It's the composition of quite a few minerals, including asbestos, but also talc and soapstone. The issue with asbestos isn't the chemical composition per se, but rather its inclination to break into micron-sized fibers that can be deposited in the lungs. Compare fine silica, which is nearly chemically inert, but poses a serious danger if inhaled.
Actually, this is possibly an excellent example of evolution minimizing complexity through the tactic of re-purposing the same system to be used in different ways in different parts of an organism. As the article notes, the neurons that may be specific to itchiness have a cell surface protein called gastrin-releasing peptide receptor. Gastrin, as the name might suggest, also plays a role in the gastrointestinal system, where it is involved in signaling the release of hydrochloric acid. What do your digestive juices have to do with itchy skin? Notably, gastrin does not work directly to release stomach acid, but rather it binds to what are called ECL cells, which secrete histamine, which then stimulate the parietal cells of the stomach to release acid. Histamine is a versatile molecule that is particularly useful for organizing inflammatory responses, though these responses aren't always welcome. That's why you might take diphenhydramine for allergies and ranitidine for heartburn- both are antihistamines, though for different histamine receptors.
Thus, strangely enough, skin itches share many of the same signaling pathways as digestion. The cell types involved (epithelial tissue) are similar though, so during the evolutionary development of skin, cells would already have inherited a sensitive network of cell surface receptors and signal transduction pathways. Why not find a way to put them to good use?
In the abstract for the actual journal article, they report the outputs for their mutant strain as current 7.6 amps per square meter and power 3.9 watts per square meter. Which is to say about 0.76mA per square centimeter, so not a gigantic number, but more impressive than what the parent predicts. One important factor that would make power generation using these microbes more attractive is that you could put them in a fuel cell that has a tremendous surface area to volume ratio.
Geobacter is an obligate anaerobe, so it does not require- indeed, cannot tolerate- access to the atmosphere, and it is not photosynthetic. You can buy carbon black, which makes a fine electrode, with a surface area to volume ratio of greater than 50 square meters per cubic centimeter. In the described experiment, they grew the bacterium on graphite, so carbon black should not pose an obstacle. A cubic meter of carbon black would have a surface area of about 50 square kilometers, but a mass of about 2 tons. An output of 3.9W/m^2 over 50 million square meters is 195 megawatts, which isn't shabby considering your input would be wastewater. Now, of course, that number is a wildly optimistic figure- good luck covering that much surface area with a bacterial biofilm- but it does suggest that you could produce enough power to say, make a wastewater treatment facility self-sufficient.
According to the paper, "KN400 (the mutant strain) also had a greater propensity to form biofilms on glass or graphite than DL1 (the wild-type), even when growing with the soluble electron acceptor, fumarate." In a fuel-cell enviroment there would be significant survival advantages to forming a biofilm. In order to run its metabolic processes, this intriguing organism needs a terminal electron acceptor in its enviroment. Instead of bringing the acceptor inside (as we do with our terminal electron acceptor, oxygen), Geobacter uses its electrically conductive pili to send its electrons outside.
An electrode would really be the ideal living enviroment for this organism- it would act as a near-infinite sink for electrons. The mutant strain KN400 seems to be better adapted to living on an electrode, so within the constraints of a fuel-cell environment, the mutant strain should outcompete against the wild strain. In the organism's native enviroment, mud in a riverbed, I'd suspect the wild-type would be more successful, since it does not prefer to anchor itself in a biofilm. In mud, the organism would be better served on the move, making use of metal oxides as it finds them, rather than being tied to one spot and risking depletion (essentially asphyxiating).
However, in the fuel cell, selection pressure will favor organisms that stick to the electrodes, maximize electron conduction, and minimize internal resistance. Even without the "pushback" current used to drive adaptation of these characteristics, my guess is that the fitness advantages they provide will cause them to be passed on to future generations.
Well, this bacterium was originally discovered feeding off the muck at the bottom of the Potomac River. Make of that what you will....
Actually, if you look at the other picture, of the rat prior to injection, it seems "normal" for its eyes is in fact red, so there's definitely been some alteration of color.
Oops. The dose of radiation used to sterilize things is more like 12-100 kilogray. I don't know how I screwed that up- I once worked on a drug whose active ingredient was sterilized prior to formulation with a gamma dose of 17.5 kGy. Kills bugs dead.
Actually, the roughly 1000-fold disparity in the radiation dose that kills bacteria versus that which kills humans is demonstrative of the range of efficacy we'd be looking at for a radiation sickness drug like the one mentioned in the story. When bacteria are killed by radiation, it's because the radiation has done significant damage to their structures- denatured proteins and lipids, damaged DNA to the point of introducing breaks. If you were to receive that level of radiation, then you're better off destroying affected cells and hoping enough healthy cells remain.
What may make us comparatively fragile to radiation, however, is that our protective anticancer mechanisms are too hasty to destroy slightly damaged cells. Your apoptosis pathway would rather just mark a radiation-exposed bone marrow cell for death than to allow for the chance of leukemia. This is a reasonable course of action for the random isolated exposures of the natural world, but perhaps an overreaction to a acute, intense exposure, since sending blood cell counts plummeting represents an immediate danger from anemia and immunodeficiency.
Here is a Medical News Today article about the drug, CBLB502, in question. I have to say I'm impressed- they used 6.5 gray (Gy) of ionizing radiation as their test dose. The Mayo Clinic considers an absorbed dose of 5.5 to 8 Gy as causing "very severe radiation sickness." (And goes on to mention, "Doses greater than 8 Gy are generally not treated successfully and usually result in death within two days to two or three weeks depending on the duration of the exposure.")
In comparison, a full-body CT scan is about 0.01 Gy, anywhere from 12-100 Gy is typically used for antimicrobial irradiation, depending on the material and microorganisms of interest, and 5000 Gy is about the threshold where Deinococcus radiodurans starts to get bothered by ionizing radiation.
That Medical News Today article is about a different set of experimental drugs from the same company. The article is also from January. It is interesting though that Cleveland BioLabs is basically developing drugs that work on the process of apoptosis in opposite ways. The "Curaxins" described in the Medical News Today article are cancer drugs that promote apoptosis, while CBLB502, their experimental anti-radiation damge drug, seems to work to prevent it.
Quite true, and one of the things that I'm worried about with the pathway described. Cellular respiration is tied to thermoregulation, and by introducing a pathway which metabolically does nothing for your cells (like the glyoxylate shunt seems to in mammals), you introduce the risk of overheating.
"It was thanks to Ultra that we won the war." -Winston Churchill, to King George VI
I must disagree with the notion that the work at Bletchley Park was not done at peril to those involved. No, the codebreakers didn't die in the mud taking back pieces of Europe, but what they did was so important that when they went to work, they too went to battle. Secrecy was their armor. If Nazi Germany had truly known what was going on at Bletchley Park, they would have sent every plane in the Luftwaffe to turn it into a crater. Honoring those that served there does not diminish the honors bestowed on those who died on battlefields.
Well, if I understand what's going on in this process, fat metabolism is occurring because the mammalian cells given the glyoxylate shunt genes don't know how to use them "properly." That is to say, plants, bacteria, and fungi use the shunt to turn fat stores into sugars. A major reason for doing this is because they need to build polysaccharide cell walls. We don't have these, so apparently if we have access to the glyoxylate shunt, we run through it, but get nothing out of it. Indeed, less than nothing- to make the dreaded car analogy, it's like sort of like the hit in fuel economy you take by driving with the air conditioner on- your fuel is powering a second motor, but it's one that doesn't contribute to the car's motion.
In terms of energy usage, the glyoxylate shunt is one of those shortcuts that turn out to take longer in the end- isocitrate molecules that take the detour are broken apart at a net energy cost, then the glyoxylate formed grabs an acetyl-CoA that could have gone to a more productive use, and then returns to the beginning of the Krebs cycle, having accomplished nothing. The shunt steers away from a couple of highly energetically favorable reactions of the Krebs cycle, and runs through one that costs energy.
The Krebs cycle, the metabolic engine, ultimately has to turn more times to produce the same amount of energy, causing it to demand more fuel in the form of acetyl-CoA. In order to meet this need, your body turns to a particularly rich source of acetyl-CoA: the beta-oxidation of fatty acids. To finally answer the parent's first question, this is where negative feedback that regulates the breakdown of fats is likely to take place. You have an enzyme called acetyl-CoA carboxylase whose activity promotes biosynthesis of fat. As the name suggests, the enzyme adds a carboxylate group to acetyl-CoA to make malonyl-CoA, a compound which is a building block of fatty acids, as well as an inhibitor of enzymes that break down fats. If you run low on fats, acetyl-CoA carboxylase should act to prevent further fat metabolism, and promote the production of more. This will hopefully result in an equilibrium between fat synthesis and fat breakdown. I say hopefully because these tidy feedback loops do not always work as well in practice, which is why we have metabolic disorders in the first place.
To answer the parent's second question, genetic modifications that correctly integrate into the host genome can generally be expected to be permanent, and spread through dividing cells. Of course, in the lab, you can add genes into an embryo of very few cells, and expect that as an adult, virtually every cell will have the genes, and even expect that the genes will be passed on to offspring. To add genes to a developed organism however involves infecting cells with a vector (usually a modified virus) that carries the genes. It is unlikely that all cells will be infected, and that all infected cells will properly integrate the foreign genes into the genome, and extremely unlikely that the genes would infect germ-line cells and be passed on. The most likely outcome would be a mosaic individual, of whose cells only some contain the foreign genes.
Urea could be conceivably be made using a different industrial process, one that doesn't ultimately require hydrogen gas as a starting material.
The cyanamide process, for example, makes calcium cyanamide (CaCN2), which in the presence of carbon dioxide and water makes cyanamide, H2NCN, which in the presence of acid further hydrolyzes to form urea. Calcium cyanamide is made by reacting calcium carbide with nitrogen gas; calcium carbide can be produced industrially by roasting calcium oxide (quicklime) with carbon. The production of cyanamide from calcium cyanamide produces calcium carbonate (lime) as a byproduct, which can be heated to regenerate calcium oxide.
As an overall cycle, you'd be be using energy to split water into hydrogen and oxygen, and oxidizing carbon to form carbon dioxide (though much less CO2 than would be formed by combustion of hydrocarbons, and it would be produced centrally).
The catch is, it would be a lot of energy. Virtually all of the reactions outlined above require very high heat, and most are performed in carbon arc furnaces at around 2000 degrees C. The centralized production would make this process a good candidate for being powered by renewable sources of energy, however. In fact, at the turn of the 20th century, the cyanamide process was widely used to make nitrogen-based fertilizers (this was before the advent of the Haber process to make ammonia, which the parent post describes), and cyanamide manfacturers usually got their electricity from large hydroelectric projects- the plants at Niagra Falls being a prime example.
The ScienceDaily article and the /. summary seem to be confused on the experimental setup. From the Nature article, "[e]ach qubit has a split Josephson junction...." The Josephson effect is an effect where two superconductors are separated by a very thin insulating layer. A "supercurrent" composed of paired correlated electrons (Cooper pairs) can tunnel across this barrier under certain circumstances. Cooper pairs act as bosons, just as atoms do in Bose-Einstein condensates, so they have long been a focus of research for quantum computing. In this experiment, the device was a "180nm Nb film was d.c.-magnetron sputtered on the epipolished surface of an R-plane corundum wafer," meaning that the superconductor they used was niobium, and the insulator was aluminum oxide, aka corundum. They built it out of these, in other words.
They go on to mention that the apparatus was cooled to 13 millikelvin using a helium dilution refrigerator. Now, niobium is superconductive to about 9 kelvin in the pure state (and about 23 kelvin in some alloys), so I would assume the extra effort to make it that cold has more to do with preserving the delicate electronic state of the qubits than with merely chilling the superconductors.
Well, if Jobs was experiencing liver failure, it probably was accompanied by hormone imbalances- the liver is responsible for breaking down a wide variety of hormones, most notably the steroid hormones. So the idea that he was suffering from a "hormone imbalance" is probably true, but omitting the proximate cause of that hormone imbalance, if it happened to be liver failure, is being less than completely honest to the public and to Apple's investors.
If you're wondering why it is cancer can gain the ability to turn off your T-cells, it's important to remember that overactive immunity can be just as dangerous as immune insufficiency. Mutations in the CTLA-4 gene that boost its activity are associated with autoimmune diseases like lupus (yes, sometimes it is lupus), type I diabetes, and rheumatoid arthritis. In fact, Bristol-Myers-Squibb, makers of the ipilimumab (anti-CTLA-4 antibody) investigational drug discussed here already make abatacept, which is CTLA-4 fused to antibody. Abatacept, marketed as Orencia, is FDA approved for the treatment of rheumatoid arthritis, and is under investigation for treatment of other autoimmune diseases, as well as for treatment of automimmune rejection of transplanted tissues. So on both ends of the spectrum, CTLA-4 and other T-cell regulatory genes play a big role in disease, and make for promising avenues of research.
Show all work. Write legibly in #2 pencil or blue or black permanent ink. Do not write on test booklet. Do not start until signaled to do so by your proctor. Destruction of the earth will result in automatic failure. You will have three (3) hours.
But to make that distinction actually takes away from the most powerful feature of the periodic table- that you may predict chemical and physical properties of unknown elements through their relationships to known elements on the table. Even though only single, highly unstable nuclei of Element 112 have ever been synthesized, we can predict that it will behave like the other Group 12 elements (zinc, cadmium, mercury). It should be a volatile metal, possibly either liquid or gas at standard temperature and pressure, it should have a +2 oxidation state and readily form oxides and sulfides, and it probably forms amalgam-type alloys the way mercury does.
I understand the trepidation to call something an "element" if its rarity and instability means that it has never existed as part of a chemical compound, but I think there is more utility in connecting these superheavy laboratory creations to the existing table of chemical elements than there is in presenting them as something altogether different.
After all, what evidence we do have strongly suggests that short-lived as they are, the transactinides do have the chemical properties predicted by their periodic table locations. Hassium (Element 108), whose most stable isotope has a half-life of about 17 minutes, for instance, has been experimentally shown to form a tetroxide, just like osmium above it in the table. And it's important to note that most of the transactinides, unstable as they are, do tend to have at least one isotope with half-life in the seconds-to-minutes range, which can be long enough to get them to participate in chemical reactions.
What I think is interesting about the hydraulic Phillips computer though is that its workings are straightforward enough to act as an aid to common sense and basic logic. An issue with using modern digital computers in economic models is that it becomes very difficult to just follow the money around. You don't get the notion that you're looking at an unsustainable bubble, because the inputs and outputs in your model are obscured by mathematical abstraction. In particular, it becomes easy to lose sight of the interconnections among companies or economic sectors.
A hydraulic system however has the advantage that a tangible working fluid connects all the areas in your economic model. The idea of "Too Interconnected to Fail" really stands out in a physical model versus a computer program. Say you're AIG. It's one thing to create a model that calculates how much collateral you would have deposit with counterparties in credit default swaps should your credit rating fall. It's another to have the executives stand there and watch as a reservoir full of water that represents your company's cash on hand is sucked dry and the pumps continue to grind in demand for more water. However, in both cases, you still have to be able to admit the possibility that your credit rating even could fall.
"An engineer uses statistics like a drunk uses a lamppost- more for support than for illumination." I think that applies just as well to economists and financiers.
This is the reaction sequence that's being proposed here: link.
Previously, the sticking point was that there was no logical way for the sugar (ribose) to spontaneously attach to the base. Organisms use enzymes to transfer a ribose phosphate group to a base, but of course, in the time before enzymes could be coded for, that wouldn't be possible. This sequence neatly sidesteps that, and also provides a more logical reason for phosphate to be involved; it is the reagent that attacks that tricyclic pyrimidosugar, breaking the bond to form ribocytidine phosphate.
Coincidentally, UV light deaminates cytosine to form uracil, which is where that second base comes from. This is why DNA uses thymine instead of uracil, by the way- as the archival storage medium for our genetic information, it would be unwise to have one base easily interconvert into another. The shorter expected lifetime of RNA means the interconversion is not a concern, though.
That (RM) there is for Rydberg matter, the exotic state of matter the hydrogen or deuterium is found in. Rydberg matter is a metastable state where atoms (or molecules) cluster together, not forming covalent or ionic bonds, but rather sharing a system of delocalized electrons, similar to pi-bonding in organic aromatic systems. It's also similar to the excited state of phosphorescent materials; as with phosphorescent materials, quantum mechanical considerations allow the material to maintain this excited state for a short interval before decaying to the ground state. The catalyst used apparently desorbs hydrogen atoms (or deuterium) in this excited Rydberg state into an ultrahigh vacuum chamber, where some will cluster together to form metastable Rydberg matter clusters. Yes, the clusters are apparently stable at room temp and without a diamond anvil; it's the relaxation of their electronic state which determines their lifetime.
In this experiment, the separation between atoms in the cluster is tested by using laser pulses to essentially blow away the electrons, leaving only a cloud of positively charged protons or deuterium nuclei. The rapid repulsion of all of these particles from each other is called a Coulomb explosion, and via Coulomb's law, the energy released by this repulsion is inversely proportional to the square of the initial separation distance of the particles, which it stands to reason is the distance they had as Rydberg matter.
For hydrogen, the results indicate that the atoms were 150pm apart, which is very impressive; it implies hydrogen atoms were together in a metallic state that was thought to require pressures like those in the interior of Jupiter. What's really wild though is the "inverted metal" state of "ultra-dense deuterium." By their calculations, the deuterium atoms were 2.3pm apart. Which is about 1/10 of the radius of a single ground state hydrogen atom. This is pretty much a dense state of matter that you'd expect inside a neutron star, and apparently you can make it with a vacuum chamber, a laser, and a hydride donor. What they're proposing:
I think there's more information on the process in one of the citations: S. Badiei, L. Holmlid, J. Phys. B: At. Mol. Opt. Phys. 39 (2006) 4191., but someone else will need to look that that one up.
So I used the word "promiximity" in my post. Proofreading would have been a good strategery there, I guess.
Well, hydrogen is a gas at STP, STP being about 250 Kelvin above the boiling point of hydrogen, and while the higher atomic weight of deuterium does have an effect on some of its physical and chemical properties (and in the biological effects of heavy water), it is not so significant that it wouldn't be a gas under standard conditions. The assumed violent expansion has less to do with the normal phase properties of deuterium though, and more with the notion that the unbelievable promiximity of deuterium nuclei suggested here cannot be stable without gigapascals of applied pressure.
Leif Holmid's page claims this material has a bond length of 2.3pm. Picometers. 10^-12 meter. Now, the normal bond length of dihydrogen is about 74pm, so if these claims are true, the spacing between atoms has been squashed down by about a factor of 30. This distance is still too small for the strong interaction to pull the nuclei together- the effective range of the strong force is on the order of a femtometer, or 10^-15 meters. If you do happen to get the nuclei closer (by dumping in more energy), fusion would be expected to occur. Absent that, this means the predominant force at 2.3pm is going to be electrostatic repulsion between protons, which would only presumably be countered by applied force, like pressure from a diamond anvil cell. Take the pressure off, and the deuterium atoms should energetically move to increase their distances.