How about a detachable luggage compartment (boot/trunk)? You don't own the car, but you have your own luggage compartment in which you keep your miscellaneous crud. Call a car, attach your compartment, drive to the mall, detach compartment, shop and fill compartment, call another car, go home, detach, unpack at your leisure while the car goes on its next mission.
If you drive on the same streets that I do, you trust me with your safety. As my driving skills are below median, this should be a lot more worrying to you then the prospect of being in a computer-driven car. (Fortunately for you, surveys show that below-median drivers are rare.)
You seem to be under the impression that Eratosthenes measured the size of the Earth more accurately than the 18th century scientists on whose work the metre was based. If so, you are wrong.
We don't know for sure how accurate Eratosthenes measurement was, because we don't know for sure how big the 'stadia' he measured in were, but probably he was out by 16%. His method had systematic errors in it which would prevent a highly accurate measurement.
By contrast, scientists had been able to measure the non-sphericity of the Earth prior to the definition of the metre, which is a 0.5% effect.
From Wikipedia: "The circumference of the Earth through the poles is therefore slightly more than forty million metres (40,007,863 m)" which indicates a 0.02% error in the original definition of the metre.
TFA was points to a 2012 press release, but it contains not much more information. They must need to supply energy to this reaction, but whether this energy is as heat, electricity or something else is unclear.
I see two uses from the point of view of the U.S. navy. One is to put one of these chemical plants in an aircraft carrier, power it with the carrier's reactor, and generate fuel for the aircraft on board. The other is to put the chemical plant on a nuclear powered supply ship, which will then transfer the fuel to non-nuclear surface ships.
From a world energy point of view, this is a way to turn non-fossil fuel power (nuclear, hydro, wind) into hydrocarbon fuel, with the overall process being carbon neutral. Burning fossil fuels to provide the energy for this process would certainly be counter productive in terms of CO2 emission and very likely economically counter productive as you'd be better chemically processing your fossil fuel instead.
By the time you're going to all of this trouble to turn electricity into fuel, it is unlikely that you'd want to run a car on it - you'd rather just have an electric car. For aircraft we really have no good alternative to hydrocarbon fuels, so it could be used here. However, on the road to a low-carbon future, we have decades worth of lower hanging fruit (notably coal power stations) before we really need to care about whether our aircraft fuels are carbon neutral.
Conspicuously missing from the articles is the energy efficiency of this process. Given the $3-$6 per gallon projected jet fuel cost, presumably the efficiency is not too bad. (I notice this number hasn't changed since 2012 which makes me suspicious that it is more guesswork than calculation.)
If you're interested in the German side of world war cryptanalysis, an excellent book is War Secrets in the Ether, by Wilhelm Flicke. The author was a German cryptanalyst during the two world wars, and it was written shortly after the end of the second world war. (It is out of print, so I suggest looking in libraries.)
It has been a decade or more since I read it, so I may have misremembered details, but here are a few points of note:
Pre-war, he'd been analysing Russian radio usage. They had a complicated system where the same station would use different call signs depending who they were talking to. This made their intercepts more chaotic and harder to do traffic analysis on. He and all his colleagues were shifted to the western front with the outbreak of war. When the war with Russia started, in the initial shock their complicated system failed and they fell back on a more standard system. Once they started to get over the initial attack and reorganize, they returned to the complicated system. The German cryptanalysts who were present had no experience with this (the experienced ones having been moved) so they interpreted the chaoticness of the signals as showing the Russians were in complete disarray, when the exact opposite was true.
He thought that the course of Battle of Crete indicated that the allies had broken the German codes at that time. (Which was correct, but he missed that they'd broken most of the German codes for almost the entire war.)
They knew that the allies had very good intelligence, but thought that it was supplied by spies. As a result, he spend the second half of the war on a whack-a-mole mission to shut down spy radio transmitters.
He complained about the multitude of German intelligence agencies and their lack of cooperation due to infighting.
"Eighteen months ago, after the slap-stick bumbling and embarrassing forelock pulling by New Zealand authorities to their United States counterparts was revealed, I was moved to wonder if Dotcom was in fact a computer virus, slowly infecting our senior politicians and agencies of state, and transforming them into figures of fun.
Whether he is a virus, or a puckish imp, sent by the gods to mock those who would rule over us, Dotcom continues his uncanny facility to bring out the ridiculous in them."
Wherever you stand on his legal issues, business ventures and politics, he is great entertainment.
In the above book, a Martian space elevator fails (more specifically, is induced to fail by the deliberate application of high explosives.) The result is highly destructive. The Martian equator is no longer an imaginary line, but rather a prominent physical feature.
There are plenty of scientists out there who poach free online data sets and mine them for additional findings.
And this is a good thing, despite your word "poach". Analyses which would not have occurred to the original experimenters get done, and we get more science for our money. For many big data projects (e.g. the human genome project, astronomical sky surveys), giving 'poaching' opportunities is the primary purpose of the project.
A former boss of mine once, when reviewing a paper, sent a response which was something like this:
"This paper should absolutely be published. The analysis is completely wrong, but it is a wonderful data set, and somebody will quickly publish a correct analysis once the data is available."
Now I need to stop wasting time on/. and return to my work in hand, which, as it happens, is 'poaching' data from Ingman, M., H. Kaessmann, S. Paabo, and U. Gyllenstern. 2000. Mitochondrial genome variation and the origin of modern humans. Nature 408:708--713.
I'm not comparing non-reusable rocket to reusable rocket. I'm comparing reusable rocket which returns to launch pad with reusable rocket which lands downrange of launch pad.
Fuel is cheap when it is sitting in a tank on the ground. Fuel at 100 km altitude and 5km/s speed is a very different story. Fuel which you keep in stage I for 'boost back' is fuel you aren't using to put your payload into orbit, meaning you have lower maximum payload.
A parachute doesn't solve the problem of your stage being hundreds of km downrange from the launch site. A parachute can help in any of my three proposed scenarios. (I think you'd need to jettison the parachute and drop for a bit before firing the rockets, because I don't think you want to try to land while attached to or entangled in a chute. This is what Curiosity did on Mars.)
Ha! I'm going to beat him to it. I just need to steal some super-rare crystals stored at Los Alamos first, to complete my shrink ray. And a white kitten.
How does this work? The rocket will have gone far down range before the first stage separates.
* First stage reverses direction and comes back. Very fuel expensive, I'd be amazed if they're planning this. * First stage does one 'orbit' (technically it would still be 'sub-orbital') and returns to launch site from opposite direction. Requires that the stage has sufficient energy, and requires some cross-range maneuvering unless you launch from the equator. * Summary is incorrect, and stage landing site is not the launch site.
In any case, you really want your landing site to be in the middle of nowhere because some failure modes will result in a high energy impact.
I had a house-mate once who was a (non-UK) law enforcement officer, and he talked about "moving surveillance" (i.e. trailing suspects in a car.) They'd typically have three cars in such an operation, so that they could take turns being close to the suspect without arousing suspicion.
He said that according to the law, officers fully obeyed road laws during such an operation, but unofficially, it was impossible to do so. Once he got pulled over by a traffic cop, who, seeing his radio, maps etc. and badge, profusely apologized and sent him back on his way.
I imagine that moving surveillance is what they are envisioning 'spies' using this power for, rather than using an Aston Martin to chase an assassin motorcyclist through a built-in-middle-ages town on market day.
I do think it is better to recognize the reality of the situation, then you can put regulations and guidelines around what is and is not acceptable. You can't issue guidelines on how to handle a situation you pretend doesn't exist.
Actually there is a 'cathode reactant' tank and an 'anode reactant' tank. Within each tank, charged and discharged versions of the reactant are mixed. (This is shown in figure 1a of the paper: http://www.nature.com/nature/journal/v505/n7482/full/nature12909.html but that link will be pay-walled for most people.)
In the galvanic direction, peak power densities were 0.246Wcm2 and 0.600W cm2 at these same SOCs, respectively (Fig. 1c). To avoid significant water splitting in the electrolytic direction, we used a cut-off voltage of 1.5V, at which point the current densities observed at 10% and 90% SOCs were 2.25 A cm2 and 0.95Acm2, respectively, with corresponding power densities of 3.342Wcm2 and 1.414Wcm2....
The galvanic discharge capacity retention (that is, the number of coulombs extracted in one cycle divided by the number of coulombs extracted in the previous cycle) is above 99%, indicating the battery is capable of operating with minimal capacity fade and suggesting that current efficiencies are actually closer to 99%....
AQDS has an aqueous solubility greater than 1M at pH 0, and the quinone solution can thus be stored at relatively high energy density—volumetric and gravimetric energy densities exceed 50Whl1 and 50Whkg1, respectively....
As shown in Fig. 2, current efficiency starts at about 92% and climbs to about 95% over ~15 standard cycles. Note that these measurements are done near viable operating current densities for a battery of this kind. Because of this, we believe this number places an upper bound on the irreversible losses in the cell. In any case, 95% is comparable to values seen for other battery systems.
I'm not an expert in any applicable field, but as I have institutional access to the original paper, I scanned it to find what looked to me like relevant numbers. As I interpret the above:
It generates about 0.5W cm^-2 of membrane, so you'd need 2m^2 to get 1 kW output. (But presumably this can be in some compact folded/layered configuration.) It can charge much faster than it discharges: that 2m^2 of membrane would let you charge at about 4kW. The storage capacity of the battery fades at less than 1% per charge/discharge cycle. One litre of reactants lets you store 50Wh of energy (i.e. 20kg for a kilowatt hour) I think the last paragraph is saying that, neglecting pumping costs, it returns about 95% of the energy you put into it.
Note that we can expect these numbers to improve with further research, but whether there are big improvements to come or only minor ones I couldn't say.
Also: They use a two-reactant-tank set up rather than four tanks, so each tank holds a mixture of the 'charged' and 'discharged' forms of its reactants (e.g. one tank holds a mixture of Br2 and HBr.) I'd naively expected a four tank set up.
While I've not heard of a Thorne-Zytkow object before, I can apply my general astronomical knowledge to explain a bit further.
The idea of an internally inert condensed object at the centre of a star is very standard: red giants have a white dwarf at their core, indeed this is how white dwarfs are formed. The weirdness is in having a neutron star instead of a white dwarf core.
The condensed object is supported by degeneracy pressure (electron degeneracy pressure for a white dwarf, neutron degeneracy pressure for a neutron star.) (Degeneracy pressure is a quantum mechanical effect. It is only appreciable at very high densities, and is not dependent on temperature.) The surface of the condensed object will be very hot, because nuclear burning is going on nearby and it is insulated from the coldness of space by the envelope of the star (i.e. the bits of star which are not the condensed object.) The density of gas just above the surface of the core will also be large, due to the high surface gravity plus the pressure of the weight of the envelope.
High temperature and high density leads to nuclear burning (combining light nuclei into heavier ones, releasing energy.) The nuclear reactions are generally very strongly dependent on temperature (e.g. one important reaction has a rate approximately proportional to temperature to the 17th power) so the burning happens in a thin layer. The 'burnt' material settles on the core, slowly enlarging it.
The gravitational attraction of the core pulling the envelope inward is largely balanced by gas pressure and radiation pressure. While stars like our sun are dominated by gas pressure, in this case radiation pressure will dominate. As the radiation escapes outward, mass is able to migrate inwards, to the thin burning layer. An equilibrium is reached between the burning/energy production rate and the mass inflow rate.
Because they are dominated by radiation pressure, it doesn't take much extra push for something at the surface of a red giant star to escape, so these stars have strong stellar winds and high mass loss rate to winds. So the envelope gets eaten from the bottom by burning and deposition onto the growing white dwarf, and from the top by mass loss. Eventually there is no envelope left and a bare white dwarf is exposed. (The final transition is quite spectacular and is called a planetary nebula.)
Heat transport in red giants is dominated by convection rather than radiation. (I think this is a general property of being dominated by radiation pressure, but I may be mistaken.) This allows material which has been close to the burning zone to mix through the star. Various secondary nuclear reactions occur there (e.g. s-process nucleosynthesis), so the products of this are mixed to the surface, where they can be observed in the spectrum. (I'm not sure whether partly-burnt material from the main burning shell can get mixed out or not.)
Evidently (according to the article) in Thorne-Zytkow objects these reactions are different from in a normal red giant and so mix different products to the surface. The star of the article has a spectrum rich in predicted reaction products of a Thorne-Zytkow object.
While white dwarf naturally grow inside stars, the process that generates neutron stars (supernovae) removes the stellar envelope, so finding a neutron star inside an envelope requires some rare post-supernova event to supply the neutron star with stellar-mass quantities of fresh gas.
You are so fast to assume I didn't make it up myself.
In fact, your assumption is correct. It came, via one intermediary, from famous-UK-evolutionary-scientist-whose-name-escapes-me-at-the-moment-but-I'd-recognize-it-if-I-heard-it-but-not-Richard-Dawkins. In the tale as told to me, two staff members were arguing in the tea room when Famous Scientist comes in and says "If this is an argument about the world, I'm interested. If this is an argument about a word, I'm not." The arguers retreat, deflated.
Whether it was original to Famous Scientist, I don't know. (I think the scene of this tale is Cambridge, but I'm not sure. The time could have been up to a few decades ago.)
Slashdot Mirror
How about a detachable luggage compartment (boot/trunk)? You don't own the car, but you have your own luggage compartment in which you keep your miscellaneous crud. Call a car, attach your compartment, drive to the mall, detach compartment, shop and fill compartment, call another car, go home, detach, unpack at your leisure while the car goes on its next mission.
Me too - as soon as it is affordable, convenient and drives better than I do. They've got one out of three already.
If you drive on the same streets that I do, you trust me with your safety. As my driving skills are below median, this should be a lot more worrying to you then the prospect of being in a computer-driven car. (Fortunately for you, surveys show that below-median drivers are rare.)
You seem to be under the impression that Eratosthenes measured the size of the Earth more accurately than the 18th century scientists on whose work the metre was based. If so, you are wrong.
We don't know for sure how accurate Eratosthenes measurement was, because we don't know for sure how big the 'stadia' he measured in were, but probably he was out by 16%. His method had systematic errors in it which would prevent a highly accurate measurement.
By contrast, scientists had been able to measure the non-sphericity of the Earth prior to the definition of the metre, which is a 0.5% effect.
From Wikipedia: "The circumference of the Earth through the poles is therefore slightly more than forty million metres (40,007,863 m)"
which indicates a 0.02% error in the original definition of the metre.
If you're in the right part of the world, the word also means "traffic light".
If your interface allows DMA, does that not mean that a malicious device can own your computer as soon as it gets plugged in?
Also, I thought I'd read that USB had DMA and hence this security problem.
Could someone who actually knows what they're talking about comment on this please?
Guns don't kill people. Gun-obsessed people kill people.
(I suspect the high velocity lumps of lead may play a part too.)
TFA was points to a 2012 press release, but it contains not much more information. They must need to supply energy to this reaction, but whether this energy is as heat, electricity or something else is unclear.
I see two uses from the point of view of the U.S. navy. One is to put one of these chemical plants in an aircraft carrier, power it with the carrier's reactor, and generate fuel for the aircraft on board. The other is to put the chemical plant on a nuclear powered supply ship, which will then transfer the fuel to non-nuclear surface ships.
From a world energy point of view, this is a way to turn non-fossil fuel power (nuclear, hydro, wind) into hydrocarbon fuel, with the overall process being carbon neutral. Burning fossil fuels to provide the energy for this process would certainly be counter productive in terms of CO2 emission and very likely economically counter productive as you'd be better chemically processing your fossil fuel instead.
By the time you're going to all of this trouble to turn electricity into fuel, it is unlikely that you'd want to run a car on it - you'd rather just have an electric car. For aircraft we really have no good alternative to hydrocarbon fuels, so it could be used here. However, on the road to a low-carbon future, we have decades worth of lower hanging fruit (notably coal power stations) before we really need to care about whether our aircraft fuels are carbon neutral.
Conspicuously missing from the articles is the energy efficiency of this process. Given the $3-$6 per gallon projected jet fuel cost, presumably the efficiency is not too bad. (I notice this number hasn't changed since 2012 which makes me suspicious that it is more guesswork than calculation.)
If you're interested in the German side of world war cryptanalysis, an excellent book is War Secrets in the Ether, by Wilhelm Flicke. The author was a German cryptanalyst during the two world wars, and it was written shortly after the end of the second world war. (It is out of print, so I suggest looking in libraries.)
It has been a decade or more since I read it, so I may have misremembered details, but here are a few points of note:
Pre-war, he'd been analysing Russian radio usage. They had a complicated system where the same station would use different call signs depending who they were talking to. This made their intercepts more chaotic and harder to do traffic analysis on. He and all his colleagues were shifted to the western front with the outbreak of war. When the war with Russia started, in the initial shock their complicated system failed and they fell back on a more standard system. Once they started to get over the initial attack and reorganize, they returned to the complicated system. The German cryptanalysts who were present had no experience with this (the experienced ones having been moved) so they interpreted the chaoticness of the signals as showing the Russians were in complete disarray, when the exact opposite was true.
He thought that the course of Battle of Crete indicated that the allies had broken the German codes at that time. (Which was correct, but he missed that they'd broken most of the German codes for almost the entire war.)
They knew that the allies had very good intelligence, but thought that it was supplied by spies. As a result, he spend the second half of the war on a whack-a-mole mission to shut down spy radio transmitters.
He complained about the multitude of German intelligence agencies and their lack of cooperation due to infighting.
I really enjoyed this commentary. An extract:
"Eighteen months ago, after the slap-stick bumbling and embarrassing forelock pulling by New Zealand authorities to their United States counterparts was revealed, I was moved to wonder if Dotcom was in fact a computer virus, slowly infecting our senior politicians and agencies of state, and transforming them into figures of fun.
Whether he is a virus, or a puckish imp, sent by the gods to mock those who would rule over us, Dotcom continues his uncanny facility to bring out the ridiculous in them."
Wherever you stand on his legal issues, business ventures and politics, he is great entertainment.
In the above book, a Martian space elevator fails (more specifically, is induced to fail by the deliberate application of high explosives.) The result is highly destructive. The Martian equator is no longer an imaginary line, but rather a prominent physical feature.
There are plenty of scientists out there who poach free online data sets and mine them for additional findings.
And this is a good thing, despite your word "poach". Analyses which would not have occurred to the original experimenters get done, and we get more science for our money. For many big data projects (e.g. the human genome project, astronomical sky surveys), giving 'poaching' opportunities is the primary purpose of the project.
A former boss of mine once, when reviewing a paper, sent a response which was something like this:
"This paper should absolutely be published. The analysis is completely wrong, but it is a wonderful data set, and somebody will quickly publish a correct analysis once the data is available."
Now I need to stop wasting time on /. and return to my work in hand, which, as it happens, is 'poaching' data from
Ingman, M., H. Kaessmann, S. Paabo, and U. Gyllenstern. 2000.
Mitochondrial genome variation and the origin of modern humans. Nature 408:708--713.
I'm not comparing non-reusable rocket to reusable rocket. I'm comparing reusable rocket which returns to launch pad with reusable rocket which lands downrange of launch pad.
Other replies I have (above) say they do indeed intend to land back at the actual launch site.
Maybe the 'boost back' is just while they're developing the system, and 'land at Kennedy' is the long term plan.
OK, so I'm officially amazed.
Fuel is cheap when it is sitting in a tank on the ground. Fuel at 100 km altitude and 5km/s speed is a very different story. Fuel which you keep in stage I for 'boost back' is fuel you aren't using to put your payload into orbit, meaning you have lower maximum payload.
A parachute doesn't solve the problem of your stage being hundreds of km downrange from the launch site. A parachute can help in any of my three proposed scenarios. (I think you'd need to jettison the parachute and drop for a bit before firing the rockets, because I don't think you want to try to land while attached to or entangled in a chute. This is what Curiosity did on Mars.)
Nice idea, but they are landing something that looks like a pencil on its end. They need somewhere rock solid to put it down.
Ha! I'm going to beat him to it. I just need to steal some super-rare crystals stored at Los Alamos first, to complete my shrink ray. And a white kitten.
How does this work? The rocket will have gone far down range before the first stage separates.
* First stage reverses direction and comes back. Very fuel expensive, I'd be amazed if they're planning this.
* First stage does one 'orbit' (technically it would still be 'sub-orbital') and returns to launch site from opposite direction. Requires that the stage has sufficient energy, and requires some cross-range maneuvering unless you launch from the equator.
* Summary is incorrect, and stage landing site is not the launch site.
In any case, you really want your landing site to be in the middle of nowhere because some failure modes will result in a high energy impact.
Here was I thinking they'd released a Minecraft clone.
I had a house-mate once who was a (non-UK) law enforcement officer, and he talked about "moving surveillance" (i.e. trailing suspects in a car.) They'd typically have three cars in such an operation, so that they could take turns being close to the suspect without arousing suspicion.
He said that according to the law, officers fully obeyed road laws during such an operation, but unofficially, it was impossible to do so. Once he got pulled over by a traffic cop, who, seeing his radio, maps etc. and badge, profusely apologized and sent him back on his way.
I imagine that moving surveillance is what they are envisioning 'spies' using this power for, rather than using an Aston Martin to chase an assassin motorcyclist through a built-in-middle-ages town on market day.
I do think it is better to recognize the reality of the situation, then you can put regulations and guidelines around what is and is not acceptable. You can't issue guidelines on how to handle a situation you pretend doesn't exist.
Actually there is a 'cathode reactant' tank and an 'anode reactant' tank. Within each tank, charged and discharged versions of the reactant are mixed. (This is shown in figure 1a of the paper: http://www.nature.com/nature/journal/v505/n7482/full/nature12909.html but that link will be pay-walled for most people.)
In the galvanic direction, peak power densities were 0.246Wcm2 and 0.600W cm2 at these same SOCs, respectively (Fig. 1c). To avoid significant water splitting in the electrolytic direction, we used a cut-off voltage of 1.5V, at which point the current densities observed at 10% and 90% SOCs were 2.25 A cm2 and 0.95Acm2, respectively, with corresponding power densities of 3.342Wcm2 and 1.414Wcm2. ...
The galvanic discharge capacity retention (that is, the number of coulombs extracted in one cycle divided by the number of coulombs extracted in the previous cycle) is above 99%, indicating the battery is capable of operating with minimal capacity fade and suggesting that current efficiencies are actually closer to 99%. ...
AQDS has an aqueous solubility greater than 1M at pH 0, and the quinone solution can thus be stored at relatively high energy density—volumetric and gravimetric energy densities exceed 50Whl1 and 50Whkg1, respectively. ...
As shown in Fig. 2, current efficiency starts at about 92% and climbs to about 95% over ~15 standard cycles. Note that these measurements are done near viable operating current densities for a battery of this kind. Because of this, we believe this number places an upper bound on the irreversible losses in the cell. In any case, 95% is comparable to values seen for other battery systems.
I'm not an expert in any applicable field, but as I have institutional access to the original paper, I scanned it to find what looked to me like relevant numbers. As I interpret the above:
It generates about 0.5W cm^-2 of membrane, so you'd need 2m^2 to get 1 kW output. (But presumably this can be in some compact folded/layered configuration.)
It can charge much faster than it discharges: that 2m^2 of membrane would let you charge at about 4kW.
The storage capacity of the battery fades at less than 1% per charge/discharge cycle.
One litre of reactants lets you store 50Wh of energy (i.e. 20kg for a kilowatt hour)
I think the last paragraph is saying that, neglecting pumping costs, it returns about 95% of the energy you put into it.
Note that we can expect these numbers to improve with further research, but whether there are big improvements to come or only minor ones I couldn't say.
Also: They use a two-reactant-tank set up rather than four tanks, so each tank holds a mixture of the 'charged' and 'discharged' forms of its reactants (e.g. one tank holds a mixture of Br2 and HBr.) I'd naively expected a four tank set up.
While I've not heard of a Thorne-Zytkow object before, I can apply my general astronomical knowledge to explain a bit further.
The idea of an internally inert condensed object at the centre of a star is very standard: red giants have a white dwarf at their core, indeed this is how white dwarfs are formed. The weirdness is in having a neutron star instead of a white dwarf core.
The condensed object is supported by degeneracy pressure (electron degeneracy pressure for a white dwarf, neutron degeneracy pressure for a neutron star.) (Degeneracy pressure is a quantum mechanical effect. It is only appreciable at very high densities, and is not dependent on temperature.) The surface of the condensed object will be very hot, because nuclear burning is going on nearby and it is insulated from the coldness of space by the envelope of the star (i.e. the bits of star which are not the condensed object.) The density of gas just above the surface of the core will also be large, due to the high surface gravity plus the pressure of the weight of the envelope.
High temperature and high density leads to nuclear burning (combining light nuclei into heavier ones, releasing energy.) The nuclear reactions are generally very strongly dependent on temperature (e.g. one important reaction has a rate approximately proportional to temperature to the 17th power) so the burning happens in a thin layer. The 'burnt' material settles on the core, slowly enlarging it.
The gravitational attraction of the core pulling the envelope inward is largely balanced by gas pressure and radiation pressure. While stars like our sun are dominated by gas pressure, in this case radiation pressure will dominate. As the radiation escapes outward, mass is able to migrate inwards, to the thin burning layer. An equilibrium is reached between the burning/energy production rate and the mass inflow rate.
Because they are dominated by radiation pressure, it doesn't take much extra push for something at the surface of a red giant star to escape, so these stars have strong stellar winds and high mass loss rate to winds. So the envelope gets eaten from the bottom by burning and deposition onto the growing white dwarf, and from the top by mass loss. Eventually there is no envelope left and a bare white dwarf is exposed. (The final transition is quite spectacular and is called a planetary nebula.)
Heat transport in red giants is dominated by convection rather than radiation. (I think this is a general property of being dominated by radiation pressure, but I may be mistaken.) This allows material which has been close to the burning zone to mix through the star. Various secondary nuclear reactions occur there (e.g. s-process nucleosynthesis), so the products of this are mixed to the surface, where they can be observed in the spectrum. (I'm not sure whether partly-burnt material from the main burning shell can get mixed out or not.)
Evidently (according to the article) in Thorne-Zytkow objects these reactions are different from in a normal red giant and so mix different products to the surface. The star of the article has a spectrum rich in predicted reaction products of a Thorne-Zytkow object.
While white dwarf naturally grow inside stars, the process that generates neutron stars (supernovae) removes the stellar envelope, so finding a neutron star inside an envelope requires some rare post-supernova event to supply the neutron star with stellar-mass quantities of fresh gas.
You are so fast to assume I didn't make it up myself.
In fact, your assumption is correct. It came, via one intermediary, from famous-UK-evolutionary-scientist-whose-name-escapes-me-at-the-moment-but-I'd-recognize-it-if-I-heard-it-but-not-Richard-Dawkins. In the tale as told to me, two staff members were arguing in the tea room when Famous Scientist comes in and says "If this is an argument about the world, I'm interested. If this is an argument about a word, I'm not." The arguers retreat, deflated.
Whether it was original to Famous Scientist, I don't know. (I think the scene of this tale is Cambridge, but I'm not sure. The time could have been up to a few decades ago.)