Lithium-Sulfur Batteries Longevity Hack February 25, 2013
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(a) TEM image of the sulfur cathode before discharge. The lithium sulfide (dark) is bonded to the inner wall of the hollow nanofiber (transparent). (b) TEM image of the sulfur cathode after full discharge. The lithium sulfide has shrunk away from the carbon wall, resulting in a loss of electrical contact and capacity decay. (c) TEM image of the polymer-modified sulfur cathode before discharge. (d) TEM image of the polymer-modified sulfur cathode after full discharge. The lithium sulfide remains attached to the carbon wall, improving capacity retention. Credit: Guangyuan Zheng, et al. ©2013 American Chemical Society (copied from Phys.org)
Lithium-ion cells are currently the most commercially successful battery type, but their low energy density makes for poor long-distance travel, and they can cost about half the price of electric cars they power. Lithium-sulfur (Li-S) batteries, on the other hand, have a very high energy density that allows them to store more energy than Li-ion batteries and therefore provide a nice long trip (and are much cheaper than Li-ion batteries). Why are we using Li-ion batteries?
Lithium-Sulfur batteries tend to lose charging capacity pretty quickly, dropping to a fraction of their original energy storage capacity in a very few charge-discharge cycles (like in the tens. Not so good). Yi Cui, a prolific (or at least his graduate students are really busy) professor of materials science and engineering at Stanford University, has developed a Li-S battery that can retain more than 80% of its 1180 mAh/g capacity over 300 cycles, with the potential for similar capacity retention over thousands of cycles. This is really a huge leap in battery lifetime, like 10X.
The Transmission Electron Microscope scans above show what they did. The leftmost shows a typical cathode (sulfur); the next shows a discharged sulfur cathode. The little hollow space there is where the sulfur has drawn away from the nanofiber wall that supports it, making contact (and recharging) difficult. Several discharges will result in more mechanical damage like this. What the researchers did was to add a polymer to bind the sulfur more completely to the the inner surface of the nanofiber which holds it, making it available for charging and preventing mechanical stress.
Sulfur cathodes containing these amphiphilic polymers had very stable performance, with less than 3% capacity decay over the first 100 cycles, and less than 20% decay for more than 300 cycles. However, Li-ion batteries may have lifespans approaching 10,000 cycles, which electric vehicles require to avoid swapping batteries in just a few years (remember, batteries are HALF the cost of an electric car). Cui thinks that Li-S batteries can close this gap in the near future. "Using the amphiphilic polymer idea here in this paper, together with nanoscale materials design and synthesis, it is possible to improve the cycle life up to 10,000 cycles," Cui says. "My group is working on this. Our recent results on nanomaterials design already improved to 1000 cycles."
Homework: Guangyuan Zheng, et al. "Amphiphilic Surface Modification of Hollow Carbon Nanofibers for Improved Cycle Life of Lithium Sulfur Batteries." Nano Letters. DOI: 10.1021/nl304795g
An Interesting Week February 18, 2013
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People think nothing of importance happens during holiday weeks, but not so this week. A fellow going by the handle Mamaich over at xda-developers.com has produced a beta version of the jailbreak for running x86 Windows applications on Windows RT (ARM) tablets. He is releasing it to the wider world for others to improve upon his list of programs that run, which is pretty short at the moment:
These programs are tested to work:
- WinRar
- 3D Pinball "Space Cadet" from Windows 95. Known problem: no sound
- Heroes of Might and Magic 3 with 32-bit patch. HD mod is compatible too, see this video: http://youtu.be/3uzjV406nVs. Known problem: no music. And I’ll recommend to turn off all sounds to increase speed. [UPDATE: that’s fixed]
- "7zG.exe b" – a 7Zip benchmark. "b" here is a command line parameter.
- Lots of tiny simple prog[ram]s.
He offers hints for debugging programs users may wish to try. Pop on over and have a look.
Me, I’m still looking for a nice, cheap 64-bit laptop suitable for Win7 or Ubuntu….very cheap. Suggestions?
Next, that triumph that is the innovator’s second-best friend (after the 3D printer), LEGO. Specifically, a LEGO implementation of the first machine to ever get programmability, the loom:
The programmability hasn’t been implemented yet; I’m sure it’s waiting for the next Agile sprint.
Finally, a little something from the future of energy storage: Ambri’s molten-metal battery has dazzling energy density at a high temperature. It’s a pair of disparate metals with a salt solution between…but not active until heated to 500C. Current models are sixteen inches across and look like this:
The plan is to make them for the military, and learn how to make’em cheap while selling to the customer who doesn’t care about cost all that much. Thing is, these molten batteries are made of relatively cheap stuff (magnesium and antimony) and could last a very long time, indeed. This technology could eventually be the battery backup for the entire power grid when wind and solar are much, much larger parts of the energy equation…which is a virtual certainty when the dead dinosaurs give out.
A Cover of Duke Nukem 3D Theme Song January 30, 2013
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Properly performed, as you can see. Although to be fair, there should be flamethrowers and explosions for the percussion section. I’m just sayin’.
Cheap And Easy Gene Therapy January 8, 2013
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A precise and elegant technique for cutting and pasting DNA to insert genes into human cells would radically transform medicine, making routine what now are expensive, complicated and rare procedures for replacing defective genes in order to fix genetic diseases was discovered last year by Jennifer Doudna and Martin Jinek of the Howard Hughes Medical Institute and University of California, Berkeley (and the LBL, too), and Emmanuelle Charpentier of the Laboratory for Molecular Infection Medicine-Sweden. In the team’s June 28, 2012, Science paper the researchers described a new method of precisely targeting and cutting DNA in bacteria.
This paper caused a little stir, and other scientists began to use the method; two new papers published last week in the journal Science Express demonstrate that the technique also works in human cells. A paper by Doudna and her team reporting similarly successful results in human cells has been accepted for publication by the new open-access journal eLife (don’t be like that. Times change, man. Journals are for getting the information out, and e-journals are faster. So there).
People are already comparing the technique to PCR, the DNA-replicating technique which scored a Nobel for Cary Mullis, in terms of impact on the genetics field.
"I think this is going to be a real hit," said George Church, Professor of Genetics at Harvard Medical School and principal author of one of the Science Express papers. "There are going to be a lot of people practicing this method because it is easier and about 100 times more compact than other techniques."
How does it work? The new technique uses a single protein that requires only a short RNA molecule to program it for site-specific DNA recognition, an enzyme called Cas9, and the replacement DNA. The nice part is that these molecules are all smaller than the kind of stuff you would have to sneak into a cell to achieve the cut-and-paste effect using the current techniques. "It (the Cas9-RNA complex) is easier to make than TALEN proteins, and it’s smaller," The complex also has lower toxicity in mammalian cells than other techniques, he added. "It’s too early to declare total victory" over TALENs and zinc-fingers (the two competing techniques—bulky and complex—don’t ask), Church said, "but it looks promising."
"The beauty of this compared to any of the other systems that have come along over the past few decades for doing genome engineering is that it uses a single enzyme," Doudna said. "The enzyme doesn’t have to change for every site that you want to target – you simply have to reprogram it with a different RNA transcript, which is easy to design and implement."
The delicious and not at all surprising part of this exciting new technique is that it’s the result of some rather more pure science; Doudna was looking at the unique immune system of a bacteria that cuts the DNA of attacking viruses, incorporates it into its own DNA and uses it to make RNA to intercept the viral DNA, rendering it useless. Nature is stranger than we imagine, and stranger than we can imagine.
Homework:
RNA-programmed genome editing in human cells (accepted for publication in eLife) RNA-Guided Human Genome Engineering via Cas9 (Church article, Jan. 3 Science Express)
Multiplex Genome Engineering Using CRISPR/Cas Systems (Wang article, Jan. 3 Science Express)
CAD-assisted Drug Design Using DNA Strands January 1, 2013
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Scientists have developed a CAD drug development system that uses synthetic DNA as a programmable molecular substrate. These strands of synthetic DNA can be constructed to have any sequence of bases. And, because complementary sequences of DNA are mutually attractive, synthetic strands can be created with sequences that cause them to align with one another and bind to form nanostructures of virtually any shape. If the DNA strands are bound to other molecular species (say, tumor-killing molecules) before self-assembly is induced, the tumor killers can be pulled into desired locations by the DNA strands during self-assembly.
In other words, LEGO for molecules.*
This is paid for partly by NSF funding, but curiously enough a private company seems to have a lock on it. Parabon Nanolabs™ has simplified this concept down to CAD-based software for the budding mad scientist. The Parabon inSēquio™ Sequence Design Studio graphically enters designs and then determines the DNA sequences that will self-assemble into that design.
The graphic editor lays out a nanostructure visually. Users can rotate and bend strands, define bindings between base pairs, and copy and paste sequences and structures between design documents. The cloud-based number-crunching uses a bunch of known wet-chemistry values for the binding energies and calculates the complex molecular interactions required to make the molecule desired.
Neat, huh? This would be entirely impossible for a human to do, ever; it’s billions of calculations that need to be made and complex rules to be followed.**
Still, how they will mock up the synthesized molecules themselves should be an interesting technical feat; I would really like to see the execution of this, rather than a neat CAD program for molecules.***
Announcement here. Parabon Nanolabs here.
* Some assembly required.
** Another reason not to be a chemist.
*** It’s not impossible; use synthesizers to make the short pieces, PCR copy them, keep them salty enough that they can’t self-assemble before all the other pieces are made, mix together and pray. The devil is in these details. Maybe we can get Rob Park to do it.
The Autodoc’s Forerunner December 21, 2012
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Human health is usually described in general terms, based on averages of humans. After a hundred years of recordkeeping we have a fair idea of what an average man or woman should have in terms of height, weight, red and white cell counts, glucose levels, cholesterols good and bad, liver enzyme levels, potassium and sodium…you probably haven’t had this blood work done lately, but I have and believe me, this information is stored somewhere, and more is being collected all the time. It won’t be long before some data-harvesting medical company gets laws written to allow them to aggregate this information to provide them with diagnostic information…and then they will want more.
You think this is some kind of weird digression, but it isn’t. The graphic above is a 50-point assay (see the little red bars?) existing today which can examine most of the diagnostic panel I mentioned above using tiny little bits of antibodies, catalase, red dye and some H2O2. A drop is introduced, the antibodies cling to matching antigens (RNA or DNA chunks, lipids, whatever) and the catalase is activated. The H2O2 reacts forming O2 which pushes the red dye up the capillaries proportionally to the antigen (or whatever). Run a few calibrations and you have a good health snapshot of a human at some point in time.
Run two a year for life on thousands of people (and lots more moieties), match it to health outcomes for each person and have neural networking algorithms find correlations and you can now diagnose years in advance of some cancers, rare conditions, psychiatric disorders—all pretty inexpensively (when the patents on these antibodies expire)
Right, that’s sorted. Now I need some funding.
Multiplexed volumetric bar-chart chip for point-of-care diagnostics, Yujun Song, Yuanqing Zhang, Paul E. Bernard, James M. Reuben, Naoto T. Ueno, Ralph B. Arlinghaus, Youli Zu& and Lidong Qin, Nature Communications 3, Article number: 1283 doi:10.1038/ncomms2292
Devil’s Postpile of Graphene and Nanotubes December 4, 2012
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That, dear reader, is a cluster of carbon nanotubes attached to a graphene sheet. A candidate for the best supercapacitor substrate ever created, it’s the product of a Rice University lab that wasn’t even trying to make supercapacitor substrates. Electrical testing showed no resistance to the flow of current at the junction, and they weren’t even trying.
"The performance we see in this study is as good as the best carbon-based supercapacitors that have ever been made," Tour said. "We’re not really a supercapacitor lab, and still we were able to match the performance because of the quality of the electrode. It’s really remarkable, and it all harkens back to that unique interface."
Nanoparticulate Treatment of Autoimmunities November 18, 2012
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Scientists at Northwestern Medical have successfully reversed a mouse model of MS using 500nm particle of “antigen-decorated” polystyrene and poly[ed; some polymer of](lactide-co-glycolide) to induce toleration of the antigen, thus modulating the T-cell response to apoptosis. Big news, and even potentially bigger, since this antigen decoration business can be modified to include antigens indicated in other conditions such as diabetes or asthma.
This treatment does not suppress the entire immune system as do current therapies for MS, making patients more susceptible to everyday infections and higher rates of cancer. Instead, when the “antigen-decorated” polystyrene particles are attached to myelin antigens and injected into the mice, the immune system is reset to normal. The immune system stops recognizing myelin as an alien invader and halts its attack on it. This happened when the particles entered the spleen, which filters the blood and helps the body dispose of aging and dying blood cells. There, the particles were engulfed by macrophages, a type of immune cell, which then displayed the antigens on their cell surface. The immune system viewed the particles as ordinary dying blood cells and nothing to be concerned about. This created immune tolerance to the antigen by directly inhibiting the activity of myelin responsive T cells and by increasing the numbers of regulatory T cells which further calmed the autoimmune response.
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Microparticles bearing encephalitogenic peptides induce T-cell tolerance and ameliorate experimental autoimmune encephalomyelitis, Nature Biotechnology (2012) doi:10.1038/nbt.2434
Indistinguishable From Magic November 18, 2012
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Really, four hundred years ago this would have had you burned at the stake.
Does This Man Look Like a Geek? November 10, 2012
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He ought to look like a geek, as he spends as much time as he can tromping around Brazilian jungles looking for, well, frogs. And he finds them. Particularly, he found the only three-fingered frog I have ever heard of (full disclosure: now an amateur scientist, I was never a biologist). Brachycephalus tridactylus is his discovery and it’s a charming representative of its genus
and arguably better looking than he is. I realize that’s an apples and oranges kind of thing, but look at the color of this frog and you see real beauty.
And three fingers.
