Then they're not doing science either. But do not confuse a scientific conclusion which happens to support someone's agenda with advocacy; medical scientists discover things about the biology of diseases all the time, but they are not paid shills for the opponents of Mary Baker Eddy's sect.
Remember, 25 years ago these same folks were howling about 'global cooling', that should tell you something.
Except they didn't. Scientists published data on historical temperature changes and ice ages (definitely science), and noted that the Earth was currently in a part of the orbital/axial tilt cycle which has coincided with the onset of glaciation in the past. Some scientists speculated that we might be heading into a new ice age in a geologically short time (and science is what if not speculation followed by tests?). It was the media which hyped this to sell magazines and books.
You ought to read this. Then take a look at the rest of the site, and see what real climate scientists are saying. It has not one shred of hysteria in it, but plenty of it ought to worry you.
If a scientist is making statements based on what they're paid to say rather than what is supported by the evidence, are they doing science or public relations/propaganda?
Whether or not they are corporate schills is irrelevant. If they're truly fake, it shouldn't be hard to disprove what they're saying, and you shouldn't have to resort to logical fallacies to discredit them. Ad hominem attacks have no place in science.
You seem to think that selling out for a paycheck is irrelevant to the public interest. Quite the opposite; scientists holding varied views based on the incompleteness of the available evidence is quite normal and something that the scientific method is built to resolve, but personal financial interest has no standing.
A "scientist" shilling for a corporate client without first shedding the mantle of science is not only of great public interest (so we can be certain whose claims to disregard as corrupt), but attracts the justified anger and ire of real scientists for dirtying the public view of science.
You know full well what the poster was referring to in its political context. He was talking about an abortion of an embryo. Yes, that is not "an abortion". It is an "embryo abortion."
You seem to have mistaken the propaganda for reality. I know full well what the poster meant. I called the poster on his attempt to co-opt an inapplicable word (abortion) to apply to something that happens between a petri dish and the sink.
I call you on this too. There are no embryos in fertility clinics. Blastocysts can only develop into embryos after implantation at around day 6; using the word "embryo" in this context is also political propaganda rather than medical fact. (The "embryonic stage" covers zygotes, blastocysts, gastrula and the other pre-fetus stages of development. See this? That stage comes two and a half weeks AFTER implantation.) If you said "blastocyst death" I would agree that the definition is correct.
I apologize that no one has created a specialized medical term to refer specifically to the destruction of IVF embryos.
I just called it what it is. Why weren't you honest enough to do it first? Do you place propaganda effectiveness ahead of truth? People who do, deserve no respect.
He was arguing that the destruction of these embryos constitutes a more dilemma for those who believe these embryos to constitute human life
That's nice for them. Why can't they mind their own business, like people who keep kashrut or the Jains?
Well, here's a term that is defined by biology: "life'. Living things have these properties: they have a metabolism, they are homeostatic, they respond to stimuli, they reproduce
That same definition of "life" applies equally to sperm and ova. Biologically, there is no "beginning of life" in the last few billion years; there are only stages in the lives of organisms.
It follows that embryos are living humans. And the crux of the point you chose to ignore is whether these 'living humans' who are not necessarily conscious at this point still count.
Roughly two thirds of all human zygotes ever formed fail to make it to live birth, with about half lost before becoming embryos. Nobody, not even (especially!) the pro-lifers, takes their demise as any sort of tragedy. The blastocysts used for research are in the same stages of development as those which are lost to natural causes. From both the lesson of biology and the universal practice of our society it follows that they are of little value, and perhaps the application of the term "living humans" to them is inappropriate.
Ideas have consequences. Voting based on faulty ideas (no matter how high-minded the holder) can lead to terrible outcomes; it's trivial to come up with many examples from the 20th century. Sure, you can win elections based on propaganda built on distortions. You can take power. What you can't do is escape the trap that you've laid for yourself.
"If a million people say a foolish thing, it is still a foolish thing." -- Anatole France.
"It remains foolish even if the majority votes for it." -- me
The religious right position on life is that life begins at conception (when a sperm and egg unite). Under this definition, any embryo destroyed is most certainly an abortion.
Funny, in biology abortion is defined as the termination of a pregnancy. There are spontaneous abortions (miscarriages) and induced abortions. Induced abortions may be classified as therapeutic, elective or criminal.
A zygote in a Petri dish is not part of a pregnancy. Without a pregnancy, you cannot have an abortion. It's patently obvious that the attempt to classify the discarding of unused IVF zygotes as "abortions" has nothing to do with the facts, and everything to do with political posturing to an ignorant public. This resembles Humpty Dumpty redefining "glory" to suit his whim of the moment; it debases the very purpose of language, which depends on agreed-upon meanings.
you are equally misinformed.
I could get rich mining irony ore here.
This is the crux of the entire stem cell issue (from the religious right standpoint), and I'm amazed you don't understand this concept, yet choose to talk about this issue as if you are well informed.
If you mean that it's an issue (and a problem) that a large part of the American public is taking a highly-emotional political position based on what amounts to a large number of partial truths and outright falsehoods, then you begin to understand. Your problem is that the facts are opposite the stance you appear to be backing.
You can expect people to be abrasive or dismissive when you presume to lecture them on things that they've studied in depth and you have no clue about. Example:
Steam engines probably approach 80%, but I have no data to calculate that.
And you said this shortly after I gave you proof that the typical figure is closer to 50%. The turbines can recover 80% or more of the available energy in the steam, but the availability is nowhere near 80% of the heat input.
I suspect that you have no clue about the meaning of "availability" in the context of thermodynamics.
The quintessential example of the multiple cycle is a stirling engine (or thermoelectric pile) running on the exhaust of a turbine.
Show me one example of a commercial-scale system using either a Stirling or thermoelectric bottoming cycle with a gas-turbine topping cycle. (I speculate in advance that you can't, because gas turbines are inherently multi-KW to multi-MW devices, while Stirlings are piston engines and suffer from decreasing power/displacement as size increases. Thermoelectrics are just prohibitively expensive at large scale.)
The pinnacle of modern powerplant efficiency is the gas/steam turbine combined cycle. Both sections use turbines, which produce high specific power with relatively low flow losses in sizes of 100 MW or more. In contrast, the largest piston engine currently built is a diesel producing approximately 80 MW.
Turbines are not efficient at getting the low temperature (under 200 C, say) energy out.
Now you're into territory where I have a reference (the next best thing to experience). Best of all, it's an old reference; you don't have any excuse for not knowing about it. In "Direct Use of The Sun's Energy" (Farrington Daniels, 1964) there is a cite of a paper by H. Tabor (pp. 267-268). Tabor made a 2 kW vapor turbine using monochlorobenzene as the working fluid and achieved 10-15% efficiency at a hot-side temperature of 150 C; 2 kW steam engines usually have efficiencies of 5% or less. The full cite is Tabor, H. and Bronicki, J. L., Small Turbine for Solar Energy Power Package, in U.N. Conf. on New Sources of Energy, E 35-S54, Rome, 1961.
If you are going to talk thermodynamics you ought to know something about thermodynamics. This means it's time for you to log off Slashdot and do some studying. Learn how to use steam tables and work P-v and T-s diagrams. When you can support your claims with figures that you can prove are accurate, you'll be ready to discuss these matters intelligently.
Thanks for evading the question. Is 60% good or bad for that particular high-side temperature? Is it a large (good) or small (bad) fraction of the theoretical maximum?
Cogeneration can mean that, but it normally (well, for some values of normally) means that the waste heat from one carnot based cycle is used on another one.
You've just proven that you do not understand "Carnot cycle". Go take a course in thermodynamics and clear some of those misconceptions out.
Incidentally, the efficiency number claimed by Capstone is based on the lower heating value (LHV) of the fuel, not the higher heating value (HHV) which includes the heat of vaporization of the water. Thus, the energy input is understated and the efficiency is overstated.
After sitting around for decades, radioactive material must be reprocessed (as in repurified) before it can be used in the same reactor.
That's not true, and betrays a misconception. Reprocessing is required to remove fission products, which absorb neutrons and "poison" the chain reaction. You only get fission products if you have fission on-going, and they accumulate at the rate that atoms are fissioned (duh). If you run at a very high power level this will take a fractional second (think "very tightly confined atomic bomb"); if you run at a very low power level or intermittently you could run "intermittently for a million years or more."
The material used in RTG's decays at a fixed rate. Confusing the two may account for your misconception.
Did you fail to notice the emphasis on the difference between the Carnot efficiency and the actual efficiency? Change the test case and the numbers also change. Heck, look up the combustion temperature of the UHT turbines used in combined-cycle plants and calculate the Carnot efficiency for that case yourself. Is 60% good or bad?
If you look closely at that page, you'll notice that the picture of that unit is from Capstone Turbine. The electric conversion efficiency of Capstone units is about 28% peak (see graph on page 3). They can claim 80% energy recovered, but that includes the heat captured as well as the electricity generated.
(1)
we have never made any near a century life atomic batteries, and (2) we have never tried to make a generator from this technology.
You're comparing cherries and watermelons.
We've made dozens of atomic batteries, both RTG's and reactors, and launched them into space. They work. Making one work for a century is just a matter of engineering.
Making a sonic fusor get even to technical breakeven (let alone engineering breakeven) is uncertain and may not even be possible.
Let's keep looking at the physics by all means, but it's not the time for bets. If I were in charge of NASA at the moment I'd be asking nuclear scientists for power technologies based on the micron-thick solar cells for inner-system missions and nuclear reactors for trans-Jovian missions. The only way to get a look at bodies like Pluto and beyond for more than flyby missions is with nuclear power and ion propulsion, and it's silly to think about sonic fusors until we have at least had something running in the lab for a few years. (Reactors had their engineering tests before the end of WWII - they're mature.)
top of the line steam power plants are near 70% efficient
Bull. Show me one. (Combined cycle hits about 60%, but that's not a pure steam cycle.)
nuclear fuel tends not to last too well. Typically years, not decades.
Every bit of nuclear fuel we have has been hanging around since the formation of the Earth, 4.3 billion years ago. True, Pu-238 isn't good for more than about 50 years (half-life ~90 years) but we make it and we only use it because our primary missions only run about 10 years.
If the nuclear scientists were given the task of making a reactor which would put out X amount of thermal output continuously for a century, you can bet that they could do it. Say that X is 50 kW thermal, or 0.05 megawatt. Typical fuel burnups for pressurized-water reactors are running 50,000 megawatt-days per ton of fuel, so the same applied to a 100 year mission at 50 kW (36500 days * 0.05 MW = 1825 MW-days) would require 0.0365 ton of fuel, or 73 pounds.
I can't see you making even the radiator for the sono-fusion system that light.
There are human populations living at altitudes where the partial pressure of oxygen is about half that at sea level (Peru, Tibet). Even more interesting, the two populations seem to have two different adaptations to the altitude and there may be another adaptation original to Ethiopia. I doubt that we'd have any difficulty engineering ourselves with the physiological changes required to handle such conditions even if they occurred over the next century.
The rest of the ecosystem would probably not be so flexible.
The picture is quite a bit more complicated than that: when science provides so many facts (so much "truth"), it appears that human nature's "confirmation bias" leads people to entrench their positions based on the selection of those facts which support what they want. (You might notice the absence of such entrenched interests regarding asteroid strikes.)
I suggest you read the papers here and here before continuing. Actually, I suggest that EVERYONE ON SLASHDOT read those papers; they will open your eyes.
... you could go further with this than an RTG (For the same mass, more energy available).
Really? Consider total mission mass. A reactor or RTG can run its heat source at a fairly high temperature, and the power conversion hardware and radiators are not very large. A low-temperature heat source would require a very large and heavy radiator; unless you have a very long mission, the RTG and reactor can beat it by just adding more fuel.
The radiator would be the spacecraft itself.
Now you've added a requirement for the spacecraft to have sufficient area, thermal conductivity and the proper radiation characteristics to achieve the required low heat-sink temperature. What does that do to your mission mass? What else does it complicate?
(Your example of 150 K is rather extreme - at that temperature you would get nearly 50% thermal efficiency - which means you would have to be ignoring other trade-offs)
"In theory, there is no difference between theory and practice. In practice, there is."
In theory, a 300 K heat source and a 150 K heat sink can yield 50% thermal efficiency. In reality, you're going to be lucky to get 20%. Consider the case of your typical steam-cycle electric powerplant. Its boilers run at approximately 1500 degrees R, and the condensers at around 540 R (depending on time of year). The Carnot efficiency limits you to 64%. What do you actually get? Try 33-35%, a bit more than half. In a small heat engine the consequent high conduction losses, plus the requirement to trade off efficiency for reliability, would hit you even harder.
Then you've got the issue of breakeven, which fission and radioisotope power don't have. If the conversion hardware yields 20% when new and the sonic fusor gets a 6:1 multiple of its input power, your net output is (0.200 - 0.167) = 0.033, or 3.3% of the total thermal output. If the efficiency of either the fusor or the heat engine decays a bit due to wear or malfunction, the whole thing stops working. I wouldn't want to bet my mission on that.
I could see something like a micro-proton accelerator generating high-energy neutrons (via spallation) to create fission in a chunk of depleted uranium (metal or oxide). It would be small, it would be relatively light, it would be harmless until launched, and it would be a lot easier to make into a working spacecraft than sonic fusion in acetone.
Running a heat engine with a very cold sink temperature begs the question: what do you do for a radiator? Blackbody radiation scales as the fourth power of absolute temperature; cutting your radiator temperature from 300 K to 150 K multiplies the required size of your radiator by sixteen. The size of the heat engine goes up too, but not quite so badly. Eventually your probe's power supply takes over.
There comes a time to forget the nuclear phobia and go with plutonium RTG's or even a small fission reactor. An RTG is also capable of handling small power requirements, and either will get the job done.
Adding heat to a lukewarm bath of deuterated acetone is one thing. Even making bubbles in a truly hot fluid (such as water in a high-pressure boiler) is quite another. The bubble phenomenon appears to depend on there being a large enthalpy and density difference between the liquid and vapor phases; as you get toward the critical temperature and pressure, this difference decreases until it finally disappears. Supercritical = no more bubbles.
High temperatures are important. You can't run an efficient heat engine off a small temperature difference; the lower the input temperature, the more of the total energy has to be discarded as waste heat. If you can't convert enough of your fusion energy to work, you can't power your ultrasonics and thus cannot even run your plant on its own output power.
If you could form bubbles of deuterium vapor in a bath of liquid metal it might be something else, but that's a bit beyond what they're doing here.
Consider the sophistication of molecular biology, cellular science and all the other things required to make this longevity dream come true. Now consider how (relatively) little is required to clone a mammal (we've done it already).
By the time we are able to e.g. replace defective genes to rejuvenate mitochondria, checking and error-correcting the DNA on a dish full of stem cells and reprogramming them to make new ova or spermatogonia will be old hat. We should have the difficulties of artifical gestation licked too, so women won't have to put up with the nuisances and hazards of growing babies in their bellies. Making another billion babies would mean ordering the hardware and waiting nine months.
Even if you can't make fresh ovaries full of ova, we already have tested techniques for cryo-preserving ovarian tissue. As long as it can generate healthy, fertile ova a woman could put off pregnancy for centuries and still have her own children.
Uteri seems to be less of a problem; at least some women's work fine through age 66.
The actin-myosin fibers in the muscle run on ATP, but the muscle cell generates this itself. The fuel used by the cell is carbohydrates and fats, which is turned into energy (ATP) for the fibers and other processes. The energy-generating process can be either anaerobic (fermentation) or aerobic (respiration). For more information, look here.
However, the idea of mammals as predators upon juvenile dinosaurs goes back a long way. One of the older hypotheses about the demise of the dinosaurs is that mammals developed a taste for eggs and ate them into oblivion.
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Then they're not doing science either. But do not confuse a scientific conclusion which happens to support someone's agenda with advocacy; medical scientists discover things about the biology of diseases all the time, but they are not paid shills for the opponents of Mary Baker Eddy's sect.
You ought to read this. Then take a look at the rest of the site, and see what real climate scientists are saying. It has not one shred of hysteria in it, but plenty of it ought to worry you.
A "scientist" shilling for a corporate client without first shedding the mantle of science is not only of great public interest (so we can be certain whose claims to disregard as corrupt), but attracts the justified anger and ire of real scientists for dirtying the public view of science.
I call you on this too. There are no embryos in fertility clinics. Blastocysts can only develop into embryos after implantation at around day 6; using the word "embryo" in this context is also political propaganda rather than medical fact. (The "embryonic stage" covers zygotes, blastocysts, gastrula and the other pre-fetus stages of development. See this? That stage comes two and a half weeks AFTER implantation.) If you said "blastocyst death" I would agree that the definition is correct.
I just called it what it is. Why weren't you honest enough to do it first? Do you place propaganda effectiveness ahead of truth? People who do, deserve no respect. That's nice for them. Why can't they mind their own business, like people who keep kashrut or the Jains? That same definition of "life" applies equally to sperm and ova. Biologically, there is no "beginning of life" in the last few billion years; there are only stages in the lives of organisms. Roughly two thirds of all human zygotes ever formed fail to make it to live birth, with about half lost before becoming embryos. Nobody, not even (especially!) the pro-lifers, takes their demise as any sort of tragedy. The blastocysts used for research are in the same stages of development as those which are lost to natural causes. From both the lesson of biology and the universal practice of our society it follows that they are of little value, and perhaps the application of the term "living humans" to them is inappropriate."If a million people say a foolish thing, it is still a foolish thing." -- Anatole France.
"It remains foolish even if the majority votes for it." -- me
A zygote in a Petri dish is not part of a pregnancy. Without a pregnancy, you cannot have an abortion. It's patently obvious that the attempt to classify the discarding of unused IVF zygotes as "abortions" has nothing to do with the facts, and everything to do with political posturing to an ignorant public. This resembles Humpty Dumpty redefining "glory" to suit his whim of the moment; it debases the very purpose of language, which depends on agreed-upon meanings.
I could get rich mining irony ore here. If you mean that it's an issue (and a problem) that a large part of the American public is taking a highly-emotional political position based on what amounts to a large number of partial truths and outright falsehoods, then you begin to understand. Your problem is that the facts are opposite the stance you appear to be backing.I suspect that you have no clue about the meaning of "availability" in the context of thermodynamics.
Show me one example of a commercial-scale system using either a Stirling or thermoelectric bottoming cycle with a gas-turbine topping cycle. (I speculate in advance that you can't, because gas turbines are inherently multi-KW to multi-MW devices, while Stirlings are piston engines and suffer from decreasing power/displacement as size increases. Thermoelectrics are just prohibitively expensive at large scale.)The pinnacle of modern powerplant efficiency is the gas/steam turbine combined cycle. Both sections use turbines, which produce high specific power with relatively low flow losses in sizes of 100 MW or more. In contrast, the largest piston engine currently built is a diesel producing approximately 80 MW.
Now you're into territory where I have a reference (the next best thing to experience). Best of all, it's an old reference; you don't have any excuse for not knowing about it. In "Direct Use of The Sun's Energy" (Farrington Daniels, 1964) there is a cite of a paper by H. Tabor (pp. 267-268). Tabor made a 2 kW vapor turbine using monochlorobenzene as the working fluid and achieved 10-15% efficiency at a hot-side temperature of 150 C; 2 kW steam engines usually have efficiencies of 5% or less. The full cite is Tabor, H. and Bronicki, J. L., Small Turbine for Solar Energy Power Package, in U.N. Conf. on New Sources of Energy, E 35-S54, Rome, 1961.If you are going to talk thermodynamics you ought to know something about thermodynamics. This means it's time for you to log off Slashdot and do some studying. Learn how to use steam tables and work P-v and T-s diagrams. When you can support your claims with figures that you can prove are accurate, you'll be ready to discuss these matters intelligently.
The material used in RTG's decays at a fixed rate. Confusing the two may account for your misconception.
Did you fail to notice the emphasis on the difference between the Carnot efficiency and the actual efficiency? Change the test case and the numbers also change. Heck, look up the combustion temperature of the UHT turbines used in combined-cycle plants and calculate the Carnot efficiency for that case yourself. Is 60% good or bad?
- We've made dozens of atomic batteries, both RTG's and reactors, and launched them into space. They work. Making one work for a century is just a matter of engineering.
- Making a sonic fusor get even to technical breakeven (let alone engineering breakeven) is uncertain and may not even be possible.
Let's keep looking at the physics by all means, but it's not the time for bets. If I were in charge of NASA at the moment I'd be asking nuclear scientists for power technologies based on the micron-thick solar cells for inner-system missions and nuclear reactors for trans-Jovian missions. The only way to get a look at bodies like Pluto and beyond for more than flyby missions is with nuclear power and ion propulsion, and it's silly to think about sonic fusors until we have at least had something running in the lab for a few years. (Reactors had their engineering tests before the end of WWII - they're mature.)As for the small-minded ones, the aching in their brains is payback.
If the nuclear scientists were given the task of making a reactor which would put out X amount of thermal output continuously for a century, you can bet that they could do it. Say that X is 50 kW thermal, or 0.05 megawatt. Typical fuel burnups for pressurized-water reactors are running 50,000 megawatt-days per ton of fuel, so the same applied to a 100 year mission at 50 kW (36500 days * 0.05 MW = 1825 MW-days) would require 0.0365 ton of fuel, or 73 pounds.
I can't see you making even the radiator for the sono-fusion system that light.
The rest of the ecosystem would probably not be so flexible.
I suggest you read the papers here and here before continuing. Actually, I suggest that EVERYONE ON SLASHDOT read those papers; they will open your eyes.
In theory, a 300 K heat source and a 150 K heat sink can yield 50% thermal efficiency. In reality, you're going to be lucky to get 20%. Consider the case of your typical steam-cycle electric powerplant. Its boilers run at approximately 1500 degrees R, and the condensers at around 540 R (depending on time of year). The Carnot efficiency limits you to 64%. What do you actually get? Try 33-35%, a bit more than half. In a small heat engine the consequent high conduction losses, plus the requirement to trade off efficiency for reliability, would hit you even harder.
Then you've got the issue of breakeven, which fission and radioisotope power don't have. If the conversion hardware yields 20% when new and the sonic fusor gets a 6:1 multiple of its input power, your net output is (0.200 - 0.167) = 0.033, or 3.3% of the total thermal output. If the efficiency of either the fusor or the heat engine decays a bit due to wear or malfunction, the whole thing stops working. I wouldn't want to bet my mission on that.
I could see something like a micro-proton accelerator generating high-energy neutrons (via spallation) to create fission in a chunk of depleted uranium (metal or oxide). It would be small, it would be relatively light, it would be harmless until launched, and it would be a lot easier to make into a working spacecraft than sonic fusion in acetone.
There comes a time to forget the nuclear phobia and go with plutonium RTG's or even a small fission reactor. An RTG is also capable of handling small power requirements, and either will get the job done.
High temperatures are important. You can't run an efficient heat engine off a small temperature difference; the lower the input temperature, the more of the total energy has to be discarded as waste heat. If you can't convert enough of your fusion energy to work, you can't power your ultrasonics and thus cannot even run your plant on its own output power.
If you could form bubbles of deuterium vapor in a bath of liquid metal it might be something else, but that's a bit beyond what they're doing here.
By the time we are able to e.g. replace defective genes to rejuvenate mitochondria, checking and error-correcting the DNA on a dish full of stem cells and reprogramming them to make new ova or spermatogonia will be old hat. We should have the difficulties of artifical gestation licked too, so women won't have to put up with the nuisances and hazards of growing babies in their bellies. Making another billion babies would mean ordering the hardware and waiting nine months.
Uteri seems to be less of a problem; at least some women's work fine through age 66.
... can Aubrey de Gray find us a fountain of SMART?
The actin-myosin fibers in the muscle run on ATP, but the muscle cell generates this itself. The fuel used by the cell is carbohydrates and fats, which is turned into energy (ATP) for the fibers and other processes. The energy-generating process can be either anaerobic (fermentation) or aerobic (respiration). For more information, look here.
<rimshot>
(Actually, it is the California voters who are funding this. You have to wonder what they know...)
However, the idea of mammals as predators upon juvenile dinosaurs goes back a long way. One of the older hypotheses about the demise of the dinosaurs is that mammals developed a taste for eggs and ate them into oblivion.