Highlights Of The Year

APS Physics lists the highlights of the year from papers published in the APS family of journals. I'm glad to say that I mentioned many of them on this blog when they first appeared.

Zz.

Q&A With John Pendry

This is a quick question and answer with John Pendry, the person responsible for many of the physics behind metamaterials. I can totally understand why he gets tired of having being repeatedly asked about the "invisibility cloak".

Valerie Jamieson: Invisibility cloaks can guide light around objects as if they weren't there. It is awe-inspiring physics. So why the frustration?

John Pendry: It's when I give talks, particularly popular ones. Of all the things I am interested in, I am always asked about invisibility cloaks. I think, "Oh God, not another invisibility cloak lecture." I still enjoy giving them, but there are many other things I'm working on that are more profound; they just don't have that fertile soil which J. K. Rowling prepared for us.

Zz.

More Update On Feynman Lectures Online

I've been posting updates on the availability of the infamous Feynman Lectures online. Mike Gottlieb has posted a new update on Vol. 2 at Physics Forums.

I have just posted FLP Volume II at The Feynman Lectures Website and at it's speedy Caltech mirror. This more or less completes the online edition of the book, though there are still some improvements to be made that I will be working on as time allows. For example: in Volume II you will notice under the title of many chapters (linked) recommendations for review of chapters or sections in Volumes I or II, references to other books and papers, and helpful reminders such as, "In this chapter c=1." Though this kind of supplementary information was never present in Volume I, it is present in (the printed and PDF editions of) Volume III but is currently missing from the HTML edition, and I intend to add it. I also plan to improve the tables, and the typography of the text and mathematics in Volume I, and to improve figure and table placements throughout all volumes.

In addition to posting Volume II, I have made some systemic style changes. Previously the pages had margins 70 pixels wide on each side. I have reduced that to 10 pixels (max) on the left, and 65 on the right to make room for the floating menu, which is slightly narrower and now also includes a "style changer," implemented mostly for the sake of iOS users who wrote to inform us that our text was un-readable on their devices: too small. The default font sizes are the same as before (12 pt body text), but now you have a choice: you can scale the size of all fonts up by 125% or 150%, and when you do so the left margin becomes narrower and the text is no-longer justified, which saves screen space. You're style preference is remembered between pages and between sessions, so you should only have to choose once on each device you use to read FLP. (There was another problem too on tablets: our pages were sometimes not opening zoomed to fit the device width: now they should.)

I would also like to inform you that Dr. Rudi Pfeiffer and I have (finally!) completed the manuscript for our edition of "Exercises for The Feynman Lectures on Physics," which was started in 2008. It's 306 8.5"x11" pages include approximately 1000 exercises covering the main sequence material in all three volumes of FLP, with 28 pages of answers/solutions in the back. According to our Executive Editor at Basic Books, the exercise book will be available in paperback online and in stores in the summer of 2014. We will also offer a PDF edition in our "Desktop" format (the same as the printed book, but with margins all on the right). My next project will be to produce a "Tablet" edition of the new exercise book to go with our recently released Tablet Edition of FLP.

In closing, I would like to thank all those people who have written to us. You're appreciation and interest in FLP is very rewarding and encouraging. I wish to particularly thank those who informed us of _problems_ with our web interface, or errors in the text or equations of the online edition of FLP; you're input helps make FLP more accessible, and more comprehensible. So, please keep those emails coming!

Best regards,
Mike Gottlieb
Editor, The Feynman Lectures on Physics New Millennium Edition
---
www.feynmanlectures.info
www.feynmanlectures.caltech.edu

There ya go!

Zz.

Phil Anderson 90th Birthday Symposium

A symposium in honor of Nobel Laureate Phil Anderson's 90th birthday was held at Princeton this week.

The workshop to honor Anderson, the Joseph Henry Professor of Physics, Emeritus, and a senior physicist, was held Dec. 14 and 15 at the Frick Chemistry Laboratory on campus. About 150 colleagues and former students from as far away as India and Japan attended, as well as five fellow Nobel Prize winners and one Fields Medal recipient. The gathering was organized by N. Phuan Ong, the Eugene Higgins Professor of Physics at Princeton, and Piers Coleman, professor of physics at Rutgers University.

Anyone who has followed this blog for a while would have seen me mentioned Anderson's name a few times. He, of course, had a huge role to play in the formulation of the Higgs mechanism. And the discovery that bears his name, the Anderson Localization, has been a ubiquitous presence in condensed matter physics. But of course, he also championed the notion that More Is Different, an influential essay that started other physicists to question the reductionism philosophy.

The general public may not know him, but he has inserted his influence into our modern world.

Zz.

Making Better Fog With Dry Ice

In case you are ever in a school play that requires a lot of fog.....



Zz.

The Physics, And Metaphysics, Of Santa

We get this kind of articles popping up at this time of the year. So why not another one. This one has a bit more detailed description of what Santa has to do to accomplish what is said that he does (for a living). For example:

• How long would it take Santa to deliver presents to every child in the world?

Considering the 3.5 billion children on Earth (without regard to religion) and 500 million square kilometers of the Earth’s surface, Santa would need 14 years if he traveled at the speed of our fastest jets (Mach 10). Santa could finish the job in about 80 minutes assuming he travels at light speed — a timeline that even Amazon’s Jeff Bezos with his experimental army of delivery drones would find difficult to match.

Now, the more important message in this article is not really about Santa, or his reindeer, or even the problem being tackled. Rather, it is one aspect of science that is often neglected and what many in the general public aren't able to do. It was described as the "Fermi problem".

For non-geeks: Enrico Fermi was the landmark Italian-American physicist of the 20th century who discovered nuclear fission. “Fermi problems” are (in the succinct words of Wikipedia) “justified guesses about quantities that seem impossible to compute given limited available information.”

In other words, this is the wacky trivia that physicists love to debate after a couple of glasses of spiked eggnog. Santos calls them “back-of-the-envelope questions” and scratches out a typical solution within 5 or 10 minutes. He loves “the idea of being able to come up with something using as little information as possible.”

“It doesn’t tell you what the answer is,” he clarified of this more stringent estimation game. “But it tells you what the answer can’t be.”

This is often a crucial step whenever we think of something, especially when it is new. We make gross estimate of what the result should be, so that we know that at the very least, it can't be either bigger, or smaller, than such-and-such a number. But this requires, as you can see, a QUANTITATIVE understanding of it. You make an estimate and produce a value, rather than just a qualitative idea. It tells you of the SCALE of things.

For many people, this is what they do not have a feel for.

Zz.

"I Don't Know Where/How To Start!"

I get that type of plea often on physics forums and when students used to come and see me for help with homework-type problems. Often, the person asking the question simply typed in the problem, and showed nothing else other than the claim that he/she just simply didn't know how to tackle the problem. This was despite my explicit requirement that required students to show their attempts.

Not only that, this policy of forcing the person asking the question to actually show attempts, or at least, what they know, has also been criticized. Somehow, this requirement was deemed to be unusually harsh by some people

There are three separate issues here that will require a bit of explanation on why this policy is in place. And this policy is especially applicable homework problem in physics/engineering/chemistry/biology, etc.

1. In order to assist, help, and teach you how to solve a problem, we must know (i) what you know and (ii) what you don't know. We need to know what you have already understood, and then build from that. It is useless to simply tell you something that has no connection to what you've already understood, because if we do that, you will end up MEMORIZING it without understanding it, which is a recipe for disaster and failure in physics. When we can connect it to something you already know, then you can see a connection and a logical progression of your knowledge. The information isn't just hanging there in mid air. It has some logical connection with what you've learned and already know.

This is why we always need to know what you have attempted. It is not because we want to force you to do it, but a good teacher will be able to figure out what you already know and where you got stuck! We can point it out to you where you made the wrong turn. You, in turn, should also find this highly useful, because you learn more from your errors than from what you did right. You can do your own self-diagnosis on why you did something wrong, and why such-and-such is correct. This is the essence of learning!

If you simply say "I don't know where to start!", it tells us absolutely nothing. You simply must know SOMETHING in order to be given homework problems. Did you sleep through the class? Did you not even read the chapter in the book? You must know something! Can you even make a sketch of the problem? If it is a simple kinematic problem, can't you even show us a free-body diagram? At the very least, we can tell if you know what the relevant forces are! You must know something!

2. There is a misunderstanding of what a "starting" point is. When we ask you to show what you have attempted, we don't just mean "equations" or "calculations". In fact, in my personal approach, when you tell me that you don't know where to start, I will quiz you if you even know the relevant physics concepts that are applicable in the problem. Let me give you an example.

Say that I give you this problem: After a completely inelastic collision between two objects of equal mass, each having initial speed v, the two move off together with speed v/3.  What was the angle between their initial directions?

If you come to me and tell me you don't know where or how to start, I will ask you what is the relevant concept here.

If you tell me that it is the conservation of momentum, then I will at least know that you are aware of the physics being tested here. That is a big plus! And that, by itself, IS THE STARTING POINT! If I'm grading this problem, if the student simply did nothing else but indicated that this a conservation of momentum problem, he/she would have already received partial credit from me.

So now that I've already determined that the student is aware of the relevant concept, I want to see if the student can actually APPLY the concept. I will then ask "So if this is the conservation of momentum problem, what can you tell me about the momentum before and after the collision?"

If the student says that the momentum before the collision from both objects must be the same as the momentum of the two objects sticking together after the collision, then there is another indication that the student simply just didn't memorize the concept, but has some understanding of how that concept works.

Next, I will ask the student to sketch out the problem. Often, for this question, this is where the student gets stuck. The question doesn't say how they collided. Did they hit each other head on? At an angle? Via simple physics, we can rule out the former, because head on collision of identical objects with equal and opposite velocity will not result in a net velocity of a final object AFTER the collision. Furthermore, making them collide at an angle is a more "general" problem that we can solve. So if this is where the student got stuck, then we have found the source of the problem. As an instructor, I can make a mental note to make sure I emphasize on this aspect of problem solving. As a student, you learn where you got stuck, and how to get unstuck.

Note that the ability to make this sketch is crucial! By making use of the symmetry of the problem, the student will simplify this problem because the final velocity will only occur along the x-direction. This means that the momentum before and after along the y-direction will be zero! This ability requires insight, understanding, and repeated practice.

Next, I will ask the student to proceed to actually write down the mathematical form of the conservation of momentum. This will tell me if the student has the ability to translate "word concepts" into "mathematical equation", which is necessary to solve this problem. If the student gets stuck here, then I know where the problem is. This is also another common issue with many students, trying to translate conceptual ideas into mathematics. If the student realizes that this is where he/she often gets stuck, he/she can make a conscious effort to pay closer attention to when the instructor makes such a connection. I, on the other hand, as the instructor, will try to make a clearer emphasis during lecture, or when helping a student, that this is where we formulate our understanding into mathematics.

For this problem, we can write the momentum before and the momentum after, based on the sketch that we had drawn:

p1_x + p2_x = pf_x = pf

p1_y + p2_y = 0.

Notice the simple form for the y-component of the momentum as mentioned before.

From now on, it is just a matter of solving the math by substituting what we know and given from the problem. There is no more physics involved here.

2mv*cosθ = 2mv/3

cosθ = 1/3

θ = 70.5 deg.

So the angle between their initial directions is

2θ = 141 deg.

This demonstration and example is an illustration where there is a step-by-step progression in solving the problem. Every step is distinct, and as someone who wants to help the student trying to solve this problem, it must be clear if the student either understands, or is able to make each of the step. When he/she can't, then we have diagnosed the problem, and that is extremely important. One has to figure out where the source of the problem is, where the student got stuck. This is because it is a symptom of a bigger problem where there is a lack of understanding or knowledge in that particular area. Knowing where the problem is is beneficial not just to the instructor, but also to the student! He/she at least will know where to pay closer attention to and try to overcome that hurdle.

I've lost count how many times I hear students complaining that they find physics very difficult, and they can't solve physics problems. Upon undergoing a similar diagnosis such as this, more often than not, the most common problem that the students have was their lack of mathematical skills! In other words, I could have set up the problem for them and ask them to write down the vector components of the momenta, and they can't because of their lack of ability to do algebra and trigonometry. So here, we have also diagnosed the problem, and hopefully, the students realize that they have issues, not with physics, but rather with mathematics. Again, knowing this, the student has the ability to take the necessary actions to correct this.

The important thing here is that when a student is stuck, one has to figure out WHERE the sticking point is. Simply saying that "I can't do a problem" or "I don't know how to start" provides ZERO information to diagnose this.

3. If you look at the above example that I've given, you'll notice that the physics part actually comes in at the beginning. Being aware that (i) this is a conservation of momentum issue and (ii) being able to write down the mathematical form of the conservation of momentum that is relevant to this problem ARE THE PHYSICS PART! Once those are known and written down, the rest is mathematics. To put it bluntly, any monkey that knows math can, from that point on, solve this problem without knowing any physics!

This is important to realize for those who complain that we must help the student who don't know where to start. By telling them how to start, we are doing the physics for them! This is the most important part of the problem and it is why they are in the class studying it! As an instructor, I am keenly more interested in seeing how the student start and approach the problem. I have very little interest in seeing if they can deal with grinding out the math and spitting out the final answer. The physics here occurs at the very beginning!

So giving a student the starting point is not helping. It is depriving him/her of using the physics to set up the problem. The start IS the physics. You might as well tell the readers who did it at the beginning of a mystery novel. If I tell you how to start, I've practically done the physics part of the problem for you. I then have no clue if you didn't know what physics concepts were applicable, or if you've never heard of the concept, or if you didn't understand how to use it, etc. This deprive both of us in diagnosing the source of your problems, and because of that, there's a good chance that your lack of understanding will continue to perpetuate beyond this problem.

It is why I have such a policy.

Zz.

Note: The example I took here came from a terrific set of example problems from Prof. Marianne Breinig at U. of Tennessee.

http://electron9.phys.utk.edu/phys513/Modules/module2/problems2.htm

Her examples of worked problems in that link are exactly how I would teach and approach problem solving in physics, where there is a systematic identification of each step. It clearly shows where the "starting point" or how to start tackling a problem is the identification of the relevant physics concepts involved in that problem. This is what I want to see from a student.

Stephen Hawking's Snapshots of the Universe

Just saw this app on Apple's App Store. It's produced by Random House Digital. The description is rather long. The general description is that it teaches "... both adults and students the basic theories that govern our lives on earth as well as the movement of the stars and planets"

It costs $4.99. So far the review has either been good, or it has been complaints that it crashed or can't access certain levels.

Not sure if it is also available on Android.

If anyone has this, or has intention to get this, I'd like to hear what you think.

Zz.

Would You Hire Peter Higgs Today?

This is a rather thought-provoking piece on how competitive it is now in the physics job market, especially for academic position. Peter Higgs was asked if he thinks that he could get a job in today's environment. His answer was "No".

Low productivity, Higgs believes, would sink his chances for an academic post in today's job market. In the 49 years since he wrote the papers laying out what physicists now call the Higgs model, he has "published fewer than 10 papers," The Guardian notes.

Fortunately for his career, at the time Higgs did his groundbreaking work he had a faculty post at the University of Edinburgh, where he is now a professor emeritus. His scanty publication record made him "an embarrassment to the department when they did research assessment exercises," he says, as quoted in The Guardian. Only a 1980 nomination for the Nobel Prize kept him from being let go, he told the paper.

We need to keep in mind that times have changed. Things that used to work, or things that one can get away with a couple of decades ago, may no longer work now. I cringe every time I hear advices being given to people by using the examples of Einstein and Galileo and Dyson, etc. as indicating that something can be done that way. This totally ignored the reality of today and how things no longer work the way they did back then.

Zz.

NOvA: Building a Next Generation Neutrino Experiment

A closer look at the NOvA experiment.



Zz.

Dark Matter

In case you are still clueless on what we call 'dark matter', this might help.



Zz.

Genius Materials on the ISS

Advances in material science on the International Space Station.



Pay attention, kids. These are physics applications that have direct impacts on your lives. You are using, at this very moment, things that were first studied as part of physics/material science.

Zz.

Explosive Beer Trick Explained

If you were ever half-drunk at a bar and started to wonder the physics of that explosive beer trick, now your curiosity can be set to rest.

But of course, no funding agency will pay for someone to study the neat tricks one can do with beer. So there is a more "useful" consequence to this.

Explaining this phenomenon may make you the life of your next party, but Rodriguez-Rodriguez and his colleagues studied beer in order to understand bigger-picture gaseous eruptions. One example is the Lake Nyos disaster in Cameroon. Volcanic activity under this lake dissolves carbon dioxide in the water. In 1986, the lake rapidly degassed a large amount of carbon dioxide all at once, suffocating 1,700 people and thousands more livestock. This rapid degassing event, possibly caused by a landslide, could share similar physics with an erupting beer bottle.

Like I've already said many time, a lot of things are inter-related.

Zz.

Update on Feynman Lectures On Physics

I posted earlier on the availability of Feynman Lectures on Physics on the web. Mike Gottlieb just posted an update on Vol 2 and 3 of the text on Physics Forums.

Since the release of the free online edition of FLP Vol. I in September many people have written to ask whether we will publish the other two volumes of FLP online. Many have also asked whether we intend to publish PDF editions of FLP that can be read offline. In fact we originally planned to publish all three volumes online when our PDF editions became available, so we could use the release of the online edition to promote sales of the PDFs, which help support our activities. However, that plan didn't materialize for two reasons: (1) the people hired to do the LaTeX->HTML conversion only completed Vol. I, and (2) our publisher had some technical problems that delayed the publication of our PDF editions.

Today I am writing to inform you that I have been working on the conversion of FLP Vols. II and III into HTML, and I finished Volume III yesterday, so I have just published it. Please check it out at The Feynman Lectures Website or at the Feynman Lectures Mirror at Caltech. You may notice some new behavior in the floating menu's navigational controls, which now function as follows when the floating menu appears over a Volume's Table of Contents: the next/last buttons cycle through the tables of contents of the three volumes, and the "up" button takes you to the home page of the edition. (When the floating menu appears over a chapter, the navigational controls function as before: "next/last" cycle through the chapters of the volume and "up" takes you to the table of contents.)

I also wish to inform you that our PDF editions have (finally!) appeared for sale online; you can now find them listed by our other publications, with links to retailers, on The Feynman Lectures Website Buy page. Please note that while sales of the printed books benefit Caltech and Basic Books, only sales of electronic editions benefit 'The eFLP Group' (myself and Rudolf Pfeiffer), creators of the New Millennium Edition's LaTeX manuscript, who bring you the free online edition of FLP. So, if you want to help support our efforts, please buy the PDFs!

Finally, I want to give you a "heads up" to check out the Books & Arts section in the upcoming December 5th edition of Nature (International weekly journal of science), where there will be a very nice two-page spread about The Feynman Lectures on Physics written by Rob Phillips (Fred and Nancy Morris Professor of Biophysics and Biology at Caltech).

I hope you enjoy FLP Vol. III. It is my personal favorite of the three volumes! [Regarding Volume II: 10 (out of 52) chapters remain to be converted to HTML. I'm working on it as time permits, and am not sure how long it will take to finish -- hopefully not too long.]

Best regards,
Mike Gottlieb
---
Editor, The Feynman Lectures on Physics New Millennium Edition
www.feynmanlectures.info

P.S. Caveat Reader: In converting a book as long and complex as FLP from one format to another, inadvertent errors are inevitably introduced. Moreover, you are most likely reading the online edition on a platform I don't have (since I only have three: an iPad, a PC and a Mac) so you may see things I don't. If you see anything that looks wrong in the online edition -- suspicious-looking text or equations, broken links, or other errata -- we would greatly appreciate it if you would push the "contact us" button on the floating menu, and inform us of the problem. (For this free online edition, we could not afford to hire proofreaders. So, you get to be the proofreaders ;->! Thanks.

There you go!

Zz.

IceCube Is Operational

The huge neutrino detector located at the South Pole has produced its first result of possible detection of extraterrestrial neutrinos.

The $275m US-led IceCube telescope, located at the Amundsen–Scott research centre at the South Pole, comprises 86 cables, each up to 2.5 km long, suspended inside vertical holes in the ice. Attached to each cable are dozens of photomultiplier tubes. The photomultipliers record the Cerenkov radiation given off by the secondary particles created when incoming neutrinos collide with hydrogen or oxygen nuclei inside the ice.

The result was published in this week's issue of Science (Vol. 342, p. 920(2013)).

Zz.

Fermilab Physics Slam 2013

For pure entertainment purposes, I suppose this works. But for educational purposes, I don't know how effective it is. Does one actually learn physics with something like this? What exactly did one learn? I guess if you're tired of really learning, this is a good diversion.



Zz.

More "Anti-Gravity Hill"

This is the year 2013, am I right? I'm right. Yes, of course I am. For a while there, I thought I was in 2008. I'll explain why in a few moments.

This is another example why something that has been debunked many years ago, keep coming back. It is as if these people who kept making these stupid commentaries never seem to actually learned why what they say is bogus. The reason being that there is always new, knowledgeable people who will continue to buy such garbage.

This article, out of Forbes website, highlight the incredulous claim made by TV program called "European Journal" about a spot somewhere in Poland where things seem to be rolling uphill on their own.

There are places where people have observed seemingly supernatural phenomena for centuries: wandering rocks in deserts, for example, or permanent lightning storms. Scientists are often at a loss for an explanation, and that’s also true for a place in Poland, where our reporter has also discovered a fascinating phenomenon.

That Forbes article also has a link to the video on the "European Journal" site.

Now, does this sound familiar? If you've been reading this blog since 2008 (and I sincerely thank you if you have!), then you would have remembered a similar blog entry that I made on a similar topic.

So, to what extent did the reporters from European Journal actually did an actual survey of the terrain of the place beyond just looking at it with human eyes? Are they not aware of how much our eyes can succumb to optical illusions? Is this news to them?

Zz.

Quantum Cheshire Cat

.. and you thought the quantum Schrodinger Cat was already giving you nightmares!

Yakir Aharonov and colleagues have proposed a rather provocative experiment which has been dubbed the quantum Cheshire cat. The Physics World review of this paper has a rather interesting description of this proposal.

In the latest work, Aharonov has teamed up with Sandu Popescu of the University of Bristol, Daniel Rohrlich of Ben Gurion University and Paul Skrzypczyk, then at Cambridge University. The group has devised an experiment, which it says can be implemented with current technology, in which individual horizontally polarized photons pass through a beamsplitter and then traverse a series of optical devices before being registered in one of three detectors. When leaving the beamsplitter, each photon is in some kind of superposition of two different paths that it can take to reach the other devices, the two paths representing the two arms of an interferometer.

The devices are chosen and arranged so that the first of the detectors only clicks when the photon is in a specific superposition state, and it is this state that is post-selected. The researchers then consider what happens to the photon – the Cheshire cat – and its polarization – the grin – in that post-selected state. They find that while any photon detector would reveal the photon to always travel along the left-hand arm, a polarization detector would occasionally measure angular momentum in the right-hand one. "We seem to see what Alice saw," the researchers write, "a grin without a cat!"

 The researchers point out that this analysis falls down because it relies on the two kinds of detector being used at different times, and that if they were to be used simultaneously, the detectors would always show the photon and its polarization together in the same arm. But Aharonov and colleagues argue that they can "regain the paradox" by carrying out what are known as "weak measurements", which do not provide definitive values of particle parameters but do have the virtue of not completely destroying a particle's quantum state, as usually happens during the measurement process.

You can read the entire review, or the actual paper, from the links given above. Note that there are experts who still have questions about what is being measured in this scheme.

Zz.

Physics Applications and Physicists Producing Useful Products

Physics and Physicists do not produce anything of worthwhile application, you say?

Measuring the level of liquid inside a metal vessel or pipe is a huge process challenge for the petrochemical industry. Tracerco's LevelFinderPlus uses a gamma radiation source and segmented detector to accurately determine the liquid level in a vessel and the amount of other material that may have built up within the container. Andrew Hurst explains how the company's physicists addressed the challenge.

The accurate measurement of wind speeds is critical for effective siting of wind farms. The ZephIR lidar calculates wind speed and direction by projecting a laser into the air and detecting the Doppler-shifted backscatter from tiny particles and dust in the atmosphere. The process is explained here by their team of scientists.

Zz.

5 Reasons Physics Is Still Interesting

I suppose this article was in response to the widely-published news article about Hawking's disappointment at the discovery of the Higgs. He argued that physics would have been a lot more interesting had we NOT found the Higgs.

Well laa dee daa!

This article tries to debunk that by pointing out five current interesting topic in physics. They may not be of much interest to Hawking, but they certainly are a lot of interest to a lot of people.

I don't know whether this is a backhanded compliment or not, but for someone who is a "bioinformatician", this is well-covered, especially the insight to include magnetism/superconductivity in the list, something that many people often overlook.

Zz.

Still No Electric Dipole Moment For Electron

I would prefer to comment on something like this once it has been properly published, but this has been in the news media for the past couple of days. And since I've already highlighted an earlier result on this, I might as well mention it here.

A while back, a study to find the electric dipole moment of the electron didn't find any. This result is consistent with the Standard Model picture of the electron being a symmetric, point particle with no internal structure. Now along comes a study that tries to measure this property again with even greater accuracy, and they still found nothing.

The Standard Model of particle physics, which describes all the known particles in the universe, predicts a practically zero electric dipole moment for the electron. Yet theories that include additional, yet-to-be-detected particles predict a much larger dipole moment. Physicists have been searching for this dipole moment for 50 years. Now a group called the ACME collaboration, led by David DeMille of Yale University and John Doyle and Gerald Gabrielse of Harvard University, has performed a test 10 times more sensitive than previous experiments, and still found no signs of an electric dipole moment in the electron. The electron appears to be spherical to within 0.00000000000000000000000000001 centimeter, according to ACME’s results, which were posted on the preprint site arXiv. “It’s a surprise,” says Ed Hinds, also of Imperial College London, who worked with Hudson on the previous best limit, set in 2011. “Why on Earth is it still zero?”

Of course, this new result is another blow to some classes of Supersymmetry, as if that theory isn't in trouble already from what we have (or didn't have) out of the LHC.

The new result deals a significant blow to many new physics theories, most notably supersymmetry, a favored idea that suggests each known particle in the universe has a supersymmetric twin particle that has yet to be discovered. “Supersymmetry is so elegant and somehow feels so natural that many people were starting to believe it was right,” Hinds says. But if they exist, all these twin particles should arise as virtual phantoms in the cloud around electrons, giving it a measurable electric dipole moment. The lack of one so far backs supersymmetry into a pretty tight corner. “It’s getting close to the point where it’s make or break for supersymmetry,” Hudson says. Although some basic models of the theory have been ruled out by the latest measurement, more complex models predict a small electric dipole moment that could be hiding in the range physicists have yet to search. “You can endlessly make models of supersymmetry,” says Eugene Commins, an emeritus professor of physics at the University of California, Berkeley, who led the last search for the dipole moment in atoms. “A good theorist can invent a model in half an hour, and it takes an experimentalist 20 years to kill it.”

I'll try to update this post with the proper citation when this gets published.

Zz.

Meet Tyronne, the T-Rex

Hey everyone! Meet the newest member of my family. His name is Tyronne, and he is a Tyrannosaurus Rex.

I adopted him during the recent Donors Night at the Chicago's Field Museum. I have all the adoption papers and everything. He's a lovable guy, despite his bouts of temper where he will try to eat everything in front of him. Still, unlike newborn babies, this one came with clear instruction of his care and feeding:

Diet: Plenty of meat. Please keep away from small pets.

Habitat: The bigger the better. T.rex can grow as large as 40.5 feet long and 13 feet tall.

Exercise: Twice da day. Needs room to run.

Hygiene: Please brush teeth once a week. It has 58 of them and some can be as large as 6 inches.

One of his papers recommend that I take a photo of him when I bring him to interesting places. Of course, being an accelerator physicist, I had to take him a particle accelerator. So here's Tyronne admiring shinny accelerator beamline. I had to keep him in his cage all the time, for obvious reasons.

I think he wished he could hop on one of the accelerated beams and propelled himself to faster than the speed of light to travel back in time and back to the Upper Cretaceous period. Oh well, he has yet to fully settle in with me, I suppose.

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Real World Applications of Quantum Physics Is NOT That Unusual!

This news article is publicizing an upcoming seminar by Nobel Laureate Serge Haroche. The topic will be quantum physics and its application. However, the way the news is presented, it sounds as if applications of quantum physics is few and far in between, and many are yet to come.

In a talk open to the general public, Prof Haroche will speak about how research in quantum physics will open the way to new technologies that can exploit the strange logic of the quantum world to build more powerful and faster computers, create better satellite-based navigation or more sensitive systems for predicting earthquakes.
The real-world applications of quantum physics can be seen today in lasers, energy harvesters which convert heat into electricity, ultra-precise clocks for calculating trajectories of spacecraft and unbreakable cryptography.

That list of "real-world applications" that are in used today are too exotic! It makes it sound as if QM's applications are not as prevalent, when they are! All of our modern electronics are based on QM. Your iPad, iPhone, medical devices and diagnostics, etc... anything that makes use of microelectronics are essentially applications of QM.

Quantum mechanics: We're Everywhere!

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Cloaking Makes Object MORE Visible?

Well, this doesn't have quite the intended result, does it?

A new report has suggested that the various cloaking schemes that have been published so far might actually scatter more EM radiation when integrated over the range of frequencies outside of the cloaking frequency, thus making the object more visible.

According to Andrea Alù and his colleague Francesco Monticone of the University of Texas at Austin, most cloaking techniques used today, including popular ones such as transformation cloaks and plasmonic cloaks, are fundamentally limited by causality and passivity to actually scatter more than the uncloaked object, if you integrate over the entire spectrum, instead of looking at just the wavelength being cloaked. "This means that if you excite the cloak with a pulse, you would actually see it more easily than the uncloaked object it is trying to hide," says Alù. The researchers go on to explain that, apart from the scientific significance of solving the scattering problem, it is equally important for a variety of situations – from warfare to commercial uses – where it is essential that a cloaked object at a given frequency does not become a beacon in a range of the other frequencies.

The authors presented a few suggestions on how to reduce the amount of scattered light. I'm not sure how effect, and more importantly, how realistic those suggestions are based on how these devices are intended to be used.

The paper is published in PRX, which should give you open access to the paper.

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The Discovery of Mendelevium

If nothing else, this is historically fascinating just because the video actually exists. Here is the blurb from the YouTube page:

A reel of black & white film shot nearly 60 years ago has surfaced at Berkeley Lab, depicting the discovery of Mendelevium — or Element 101 — as reenacted by some of the legendary scientists who did the actual work at that time. Since the 1940s, Berkeley Lab scientists were locked in a race to synthesize new elements, and more often than not, they came out winners. Sixteen elements, most of them in the actinide series at the bottom of the periodic table, were discovered and synthesized by its researchers.

Retired Berkeley Lab physicist Claude Lyneis found the reel in a box of dusty and deteriorating films slated for disposal. Using digital editing skills he acquired to make videos of his son's lacrosse team, Lyneis has produced and narrated an excerpt of this nearly-lost footage. It is an entertaining and informative look at the pioneering physics performed at UC Berkeley and Lawrence Berkeley National Laboratory's hillside campus. Get the full story here: http://today.lbl.gov/60-year-old-film...

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The Ultimate Building Blocks of Matter?

In case you are not familiar with the Standard Model of elementary particles, here's a brief crash course.



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The Physics Of Urine Splashback

Oh, I kid you not, dear readers!

First of all, I'm sure you can guess that this isn't just something trivial with no applications elsewhere. But still, it is rather amusing that there is an active research on the problem of urine splashback.

If you don't know what it is, or maybe this is not a problem you normally have (especially if you have a different anatomy than a man), let me explain. It is the splashing that occurs when a thin stream of water hits a water surface. OK, sounds familiar? Good!

So what's the problem, you ask?

"In response to harsh and repeated criticisms from our mothers and several failed relationships with women, we present the splash dynamics of a simulated human male urine stream," reads their conference abstract.
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One might think the physics of aiming urination had already been summarised by the formula: "get it all in the bowl". But micturation is still a messier business than it needs to be, according to the research.

Taking measurements live "in the field" did not appeal to the scientists, so the duo built a urination simulator. The "Water Angle Navigation Guide" is a five-gallon bucket with hoses connected to two types of synthetic urethra.

OK, that's just way to hysterical. And oh, there's a video in the link above to show you the dynamics.

So, is anyone here going to attend the APS meeting where this will be presented? I would appreciate someone reporting back.

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"Theoretical physics – like sex, but with no need to experiment"

I'm not a theorist, and I don't play one on the internet either. Still, I had a few chuckles reading this article. It certainly presents a case justify the pursuit of theoretical physics.

Certainly, theoretical physics is what makes the rest of our work in physics not simply "stamp collecting", to quote Rutherford. It is also interesting for me to observe that many young, new students who are interested in physics tend to gravitate towards theoretical physics AND particle physics, i.e. the 'sexy' aspect of physics that are getting a lot of media coverage. It is only later on in their pursuit to be a physics major that "reality" hits them and they discover not only the experimental aspect of physics, but also other topics and fields in physics. And we must also not forget the "employment" picture.

Of course, those are not within the scope of the article that I cited. I suppose that if you are already employed as a theoretician, then certainly the general public should be aware of what you do and why it should be supported (I support it). But if you're not, it is going to be a tough nut to crack, especially in this climate of budget cuts.

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How Particle Physics Can Save Your Life

This Symmetry article highlights all the "side effects" of particle/high energy physics, and how we are benefiting from it.

You'll notice that I've mentioned similar items listed in the article in here and here. So these should be too much of a big news if you've followed this blog for a while. I just think that, in this article, they are lumping accelerator physics and particle physics to be the same thing, which in this day and age, they aren't anymore. Accelerator physics is a separate branch of physics than particle/high energy physics, even though their lives are certainly closely intertwined in some cases. But still, let's be clear that the majority of particle accelerators in the world have nothing to do with particle physics.

The one clear area where particle physics greatly impact our lives is in the detector business, as I've mentioned in my blog entry above. This is where the need of high energy physics experiments directly results in the advancement in detector physics. This then trickle down to other sector of our economy, including medical devices.

Still, this article is a good read if you are not aware of it already.

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"The Higgs and all that. How the universe works and why we should care"

A rather elementary-level lecture that I would imagine many people can comprehend. And yes, I know that there has been a lot of videos and resources on this topic, but I keep getting the same question over and over again. So I'm going to post over and over again the same stuff that have been newly-produced on this topic.



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Yes, We Have No WIMPS, So Far

I guess the big news of the week is the result out of LUX that they found no signature of dark matter candidate called WIMPS that was reported elsewhere earlier. The news was important enough that there was even a news piece on the CNN website.

After analysing three months of data taken by LUX, physicists found no evidence for dark-matter collisions. However, because the experiment is the most sensitive yet to a range of WIMP masses, LUX has provided important new information about what dark matter is not. In particular, LUX is more than 20 times more sensitive than previous experiments when it comes to detecting low-mass WIMPs – those with masses of about 5–10 GeV/c². 

Dark matter remains elusive, at least on earth and for this type. However, up in space, the Alpha Magnetic Spectrometer has a different story, obviously. We still need a better understanding of those excess positron.

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Interview With John Pendry

You heard all about those metamaterials, recent news on cloaking, and left-handed materials? Well John Pendry has a major influence on the advancement of this area.

This video is an interview about his life and his science.



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What's In A Name?

I've dealt with many non-scientists who put too much emphasis on the names or labels given in  science, and especially physics. Because they do not understand the physics attached to these names, they put all their understanding based on what the name seems to imply. Examples are the over-emphasis on the name "theory" and "law" and "model", etc.

With the Higgs, a lot of people, especially crackpots, pseudoscientists, and downright misguided people seem to have jumped on the moniker given to the Higgs by Leon Lederman, which was the "god particle". People seem to think that this particle has a more important significance or that it carries religious meanings. All this with many of these people not even having the capability to understand the physics associated with the Higgs.

This is a rather amusing article on how some of the names given in physics have a rather mundane, and utterly boring origin, devoid of any deeper significance. For example, on how the Higgs particle got its name:

There are two-and-a-half theories to explain why Higgs' name won the title, Carroll said. One is that the works of Higgs, et al., were cited in a study by Steven Weinberg in 1967, but Higgs was listed first, unintentionally leading later researchers to cite his work ahead of the others. The second is that physicist Benjamin Lee, who wrote and spoke about the theory and is credited with popularizing it, read Higgs' paper first, and began using the shorthand "Higgs" to describe it, Carroll said. And finally, he said, "Higgs boson" just sounds better than "Brout boson."

"Once it was there, there was never a strong attempt to change it," Carroll said. "And it's just a name."

This is not unusual. Often, another researcher citing another paper would tend to either give it a name, or a short abbreviation, rather than citing the full thing over and over again. In publications such as Phys. Rev. Lett., where there is a page limit, you don't want to type down the full thing. So you either give it a short name, or abbreviation (example: BCS theory). That's how many of the names and labels orginated.

Moral of the story: stop paying too much attention to the names and labels. Understand the underlying physics. That is more important.

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Leviton Says "Hello World!"

Say hello the the leviton, everyone!

A new type of quasiparticle – dubbed the "leviton" – has been seen by physicists in France and Switzerland. First predicted in 1996 by a team led by Leonid Levitov, the phenomenon involves the excitation of as few as one electron to create a wave that propagates coherently through a metal. The ability to make levitons on demand could lead to the creation of quantum-electronics circuits that involve sending single electrons through tiny circuits. 

I tell ya, the 2D electron gas universe is just so rich, we will discover a whole lot more. We already have seen fractional quantum hall effect in such a system, and it may even exhibit signs of Luttinger liquid properties. So I will not be surprised if there are more to come.

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The Physics of Whistling Tea Kettle

I kid you not.

I would think that, considering that this is quite common already, people would have known the intricate physics of the whistling kettle. Turns out, I was wrong!

Cambridge University researchers recently published a paper in the journal The Physics of Fluids, describing what’s considered the first accurate model for kettle whistling dynamics.

Think this is trivial research? It actually has more far reaching implications. According to the press release, these dynamics could be used to stop pipes in household plumbing from squealing or car exhausts from sounding, well, exhausted.

There you have it!

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MOOC On "The Discovery Of The Higgs Boson"

The registration is now open for the massive online open course (MOOC) on "The Discovery of the Higgs Boson".

This MOOC introduces the theoretic tools needed to appreciate the discovery, and presents the elementary particles at the tiniest scales ever explored. Beginning with basic concepts in classical mechanics, the story unfolds through relativity and quantum mechanics, describing forces, matter and the unification of theories with an understanding driven by the tools of mathematics.

Narrating the journey through experimental results which led to the discovery in 2012, the course invites you to learn from a team of world-class physicists at Edinburgh University. Learners participate in discussion of the consequences of the Higgs boson, to physics and cosmology, and towards a stronger understanding and new description of the universe.

Note the knowledge requirement to enroll for this course:

The course requires a basic level of mathematical skills, at the level of a final-year school pupil. A basic knowledge of physics is helpful, but not required.

So there ya go! If you are a non-physicist, and you are serious about learning about the Higgs and also a bit about elementary particle physics and the Standard Model, this is your chance! There are people trying to make it accessible for you to understand these things.

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Magnetic Levitation

You learn about magnetic levitation, and a little bit about magnetism, in this video.



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Is There A Link Between Intelligence And Entropy?

It's an interesting question, and there are certainly models that point to such a link. The latest one is a very clear example the strong possibility that intelligence can be linked to entropy.

Entropy measures the number of internal arrangements of a system that result in the same outward appearance. Entropy rises because, for statistical reasons, a system evolves toward states that have many internal arrangements. A variety of previous research has provided “lots of hints that there’s some sort of association between intelligence and entropy maximization,” says Alex Wissner-Gross of Harvard University and the Massachusetts Institute of Technology (MIT). On the grandest scale, for example, theorists have argued that choosing possible universes that create the most entropy favors cosmological models that allow the emergence of intelligent observers.

This, I think, would give some degree of a quantitative description of intelligence, a characteristics that so far defy such a clear description. And yes, I'm discounting the silly IQ test as a measure of intelligence. Linking it to a concept in physics allows for a more definite foundation to define and measure intelligence.

Will be fascinating to see how far this will lead.

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You Can't Escape The Heisenberg Uncertainty Limit

A rather interesting treatment of redefining the Heisenberg uncertainty principle, in light of recent advancement in the so-called weak-measurement experiments.

The popular conception of the Heisenberg uncertainty principle is that measurement is unavoidably invasive. We disturb an object when we observe it, thus introducing error into subsequent measurements. However, recent experiments (see 6 September 2012 Synopsis) claim to have measurement errors below the Heisenberg limit. To address this apparent contradiction, a paper in Physical Review Letters reports a new formulation of the uncertainty principle in which measurement disturbance depends on the performance of the measuring device, which is quantified as the maximum possible change in the state of the object.
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Paul Busch of the University of York in the UK and his colleagues believe there is no contradiction here, but only a misunderstanding over how to characterize the effects of measurement. Previously, measurement-induced errors have been calculated on a state-by-state basis, by comparing the state of a system “before” and “after” a measurement. But Busch et al. show that defining measurement error in a state-independent way, through a kind of calibration process of the measuring device, leads to limits in line with the uncertainty principle.

 I expect more of something like this to occur as we probe the more minute detail of QM.

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Science In The Classroom

This is a new project by Science Magazine, with funding from the US National Science Foundation. Called Science in the Classroom (SitC), this is an educational material aimed at pre-college, university students, and the public in general to read a scientific research paper (at least one) by the time he/she completes school. Or in the case of the general public, being able to at least read one scientific paper and understand how scientists work.

The initial offering so far covers topics in Chemistry, Biology, and Physics, and it is expected the amount of papers being offered will expand.

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Light Ties The Knot

An amazing theoretical advancement on a very old and well-established set of equations.

Physicists have found a very interesting solution to the well-known Maxwell Equations, one in which can form light into interesting geometries and knots.

In the late 1980s, a researcher discovered exact solutions of Maxwell’s equations in free space (containing no electric charge) with the odd property that every field line formed a closed loop, and each loop was linked to another. This structure is called a Hopf fibration, which has been found in other places such as liquid-crystal physics (see 3 June 2013 Viewpoint). Kedia et al. now go a step further with their discovery of exact solutions that are both linked and knotted: the field lines are tied around each other inside a torus.

More coverage and explanation on Physics World.

Identified by Hridesh Kedia at the University of Chicago, along with colleagues at the Polish Academy of Sciences in Warsaw and the Spanish National Research Council in Madrid, the new family of solutions to Maxwell's equations have field lines describing all "torus knots" and "links". Torus knots are those knots that can lie on the surface of a torus, whereas a link is a collection of such knots.

One solution involves magnetic-field lines that trace out a familiar "trefoil" knot around a torus that is aligned in the plane perpendicular to the direction of propagation of the light (see figure). As the light propagates, the knot is distorted but retains the topological property of being a trefoil knot. The electric-field lines have the same structure as the magnetic-field lines but are rotated about the propagation axis by an angle that depends upon the knot. Other solutions include cinquefoil knots and linked rings. 

Still plenty of surprises and interesting solutions out of the old equations!

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Paper Isn't Dead Yet

.. and no, I'm not referring to this hilarious video either! :)

Anyone who has followed this blog would have known that I'm all for new technology if it actually has a beneficial effect on what we do. I mentioned a while back of trying to use tablets instead of papers in an undergraduate intro physics labs. I think this is possible, and certainly something we should expose the students to, considering that by the time they enter the job market, these technologies will be ubiquitous in their will place.

However, I find that, in some cases, I still prefer the old-fashion paper. This has nothing to do with being stubborn and wanting to do it in ways that I'm familiar with. Rather, it has more to do with convenience. The one area that I still prefer to have a printed copy in my hands is when I referee/review a manuscript.

What I like the most about having a paper copy is that I can more easily write comments on the paper itself. This is actually not that convenient to do on a tablet. While there are apps that allow you to write on PDF documents on a tablet, I still do not find a standard tablet large enough to accommodate a substantial amount of comments/annotations/etc. Besides, the typical stylus that one use with a tablet are not as responsive as a pen-on-paper combination.

The other aspect of paper-refereeing where paper trumps over electronic version is when I have to keep on referring to figures or tables. Let me explain. A typical manuscript that I often get to be reviewed are often typed double-spaced, and the figures, tables, and captions are grouped at the end of the manuscripts. They are not imbedded within the text. This is because the typesetting will be done by the editors after the manuscript has been accepted for publication. So what usually happens is that when I read a reference to a figure or a table in the text, I often have to go back and forth looking at the figure and reading the relevant text referring to that figure. It is tedious to do electronically. One can lessen the effort on an actual computer where one opens more than one window to display the same manuscript, so that in one window, one has the text, and the other window one can display the relevant figure. So in this case, one only need to switch between windows. But try to do this on a tablet! Oy vey!

What I often do is to print a copy of the manuscript to use to read the text, but also display the manuscript on my iPad by showing the figures. This way, I can read the text, and look at the relevant figures on the tablet. I find that to be the most convenient. Still, the hard-copy print makes it a convenience.

Do you still use paper copies? In what way?

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The First Physics MOOC From MITx

This is a rather interesting article for anyone interested in online physics courses. It is a report on MIT's first Massive Online Open Course.

Abstract: Massive Open Online Courses are an exciting new avenue for instruction and research, yet they are full of unknowns. In the Spring of 2013, MITx released its first introductory physics MOOC through the edX platform, generating a total enrollment of 43,000 students from around the world. We describe the population of participants in terms of their age, gender, level of education, and country of origin, highlighting both the diversity of 8.02x enrollees as well as gender gap and retention. Using three midterm exams and the final as waypoints, we highlight performance by different demographic subpopulations and their retention rates. Our work is generally aimed at making a bridge between available MOOC data and topics associated with the Physics Education Research community.

I am still not sure how effective such a course is when compared to the traditional method of brick-and-mortar classrooms. Certainly, modern advancement inevitably will expand the way we all attend classes beyond the common practice. Still, based on the conclusion derived from this study, such a course may still not be suitable for first-time learner.

Our analysis of retention points toward the possible outcome of 8.02x being better suited for advanced degree holders versus college undergraduates. Some MOOCs have realized the importance of designing courses for population with education beyond a bachelor degree (e.g. a MOOC targeting high school physics teachers

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The Higgs Bosuns?

One sometimes wonder if news outlets have done away completely with copy editors, who should catch obvious mistakes and typos such as this.

This morning, while browsing through the news, I stumbled upon the Economist page reporting the Nobel Prizes, and had a chuckle with the title line read "Higgs's Bosuns". Maybe this is on purpose, I don't know, because the rest of the article had the correct spelling. Still, there's nothing in the article to imply anything about Higgs's "bosuns".

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2013 Physics Nobel Prize

So it is not a surprise at all that this year's Nobel Prize in Physics goes to two theorists who were the prominent figures in the development of the Higgs mechanism.

The 2013 Physics Nobel Prize has been awarded to two physicists who were instrumental in developing the theory that helps explain the origin of mass of elementary particles and predicts the existence of the Higgs Boson discovered last year. The prize, which recognizes the contributions of François Englert (Universite Libre de Bruxelles) and Peter Higgs (University of Edinburgh) for the theory of broken symmetry in electroweak physics, echoes the announcement of the 2010 American Physical Society’s J. J. Sakurai prize, which was awarded to the two Nobel Laureates as well as four additional physicists who made comparable contributions to the symmetry breaking work.

The link above also gives you access to free copies of the two relevant papers.

I think that the Nobel committee might be reserving another round to award the Nobel Prize for the experimental discovery.

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Accelerating Charge Particles Using Visible Light

This accelerating scheme should see a large interest after this proof-of-principle demonstration. Two separate papers are showing the feasibility of accelerating electrons using the E-field from visible light, as opposed to the RF fields used in a typical accelerating structures.

Two teams now report rapid acceleration of electrons using small silica structures to shape light fields into patterns similar to those in a linear accelerator. In both of the experiments, the researchers sent electrons skating just over a silica surface that contained narrow grooves in the direction perpendicular to the electron beam. They then shined ultrashort laser pulses directly onto the surface (called a grating), which generated a pattern where the electric field was alternately enhanced and diminished in neighboring “zones” just above the surface. This pattern of fields reversed direction twice during every oscillation cycle of the laser light and could accelerate electrons (see YouTube video).

Here's the YouTube video:



Of course, with any initial advancement, there's still plenty of work to do. For many applications, getting to higher energy alone isn't the only issue. In FEL's, for example, the emittance of the beam is equally crucial. So accelerating scheme such as this must show the ability to not cause an emittance blow-up. The other issue that is often critical is the question on how much charge per bunch that can be accelerated. For many applications, the standard "high-brightness" beam requires a 1 nC per bunch charge. So the scheme must be able to handle beams of that magnitude without sacrificing the quality.

Still, this promises to be another exciting avenue for future accelerators.

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US Particle Physics Community Plans For The Future

As the US govt. starts its shutdown due to the US Congress's lack of ability to do the work they were elected to do (how come we don't dock their pay when they can't come up with a budget on time?), we have a report on the last "Snomass on the Mississippi" workshop by US Particle Physicists in prioritizing the different projects that US particle physicists should be involved in. It is a rather challenging task considering the severe budget cuts and constraints being put on science funding in the US as a whole, and on high energy physics in particular.

As stated at the end of the article, the US has lost its "leader" status in high energy physics. That's gone, and if the ILC is built in Japan, and funding continues to be dismal due to the political bickering by the dimwit politicians, then I don't see it coming back. I do not see the LBNE, even if it is built to its original specifications, getting the same global interest and status as the LHC and the ILC, certainly not in the public's eye.

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How To Destroy A Magnet

Besides learning how to destroy a magnet, you get to learn why certain things are magnetic, or can be magnetized.



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Nanoscale NMR/MRI? Why, Yes We Can!

An amazing improvement in science technology and instrumentation. A new paper reports on the recent achievement of performing NMR on nanoscale size targets. You can also read the paper for free since it is published in the new APS family journal Phys. Rev. X. The one interesting aspect of this journal is that it includes a "Popular summary" of the paper that has been published. The popular summary accompanying this paper is this:

Popular Summary: Magnetic resonance imaging (MRI) is a commonly used technique for medical imaging. MRI uses static and time-dependent magnetic fields to detect the collective response of large ensembles of nuclear spins from molecules localized within millimeter-scale volumes in the body. Increasing the detection resolution from the millimeter to nanometer range would be a technological dream come true. However, detection of nanoscale magnetic resonance signals within the realm of the conventional MRI faces two challenges: The magnetic field strength and configurations required are either unrealistic or impractical, and the naturally occurring quantum spin fluctuations can overwhelm the thermal spin polarization—a fundamental property of nanoscale collections of spins. It is not difficult to imagine, then, that radically different techniques that can achieve such resolution enhancement in magnetic resonance detection would be a new breakthrough. In this experimental paper, we demonstrate a new paradigm for nuclear magnetic resonance imaging and spectroscopy on the nanometer scale.

Our technique is based on two unique components: (i) a novel spin-manipulation protocol that encodes temporal correlations in the statistical polarization of nuclear spins in the sample by periodically applying radio-frequency magnetic field pulses and (ii) the generation of intense magnetic field pulses by focusing current through a nanoscale metal constriction. Together with an ultrasensitive magnetic resonance sensor based on a silicon-nanowire oscillator, our approach allows us to coherently manipulate and detect nanoscale ensembles of nuclear spins. In a proof-of-principle demonstration, we have successfully imaged proton spins in a polystyrene sample with a roughly 10-nm spatial resolution.

Although remarkably different from the conventional MRI techniques in the two fundamental aspects discussed above, our technique can easily incorporate all established pulsed magnetic resonance techniques. Looking forward, we foresee this technique becoming a paradigm for nanoscale magnetic resonance imaging and spectroscopy.

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