Woodrow Wilson, Princeton Class of 1879, famously delivered a speech at Princeton’s 1896 sesquicentennial titled “Princeton in the Nation’s Service,” a phrase that became the school’s unofficial motto. At the time Wilson was referring to the duty of Princeton men to help guide the growing nation.
The motto has since been modified to include “and in the service of all nations,” and while the university has turned out its fair share of politicians and policy-makers, the phrase can in today’s world just as easily apply to Princeton-based scientists’ contributions to the nation and world. What follows is an overview of just some of the groundbreaking research going on across the campus.
#b#Plasma Physics Lab#/b#
You have to be a rocket scientist — or something akin to it — to work at Princeton Plasma Physics Lab, but to get a behind-the-scenes, hands-on look at the research going on there all you need is a photo ID. On Saturday, June 1, the lab opens its doors for a free, family-friendly open house from 9 a.m. to 4 p.m.
The public has good reason to take an interest in the experiments going on at the Department of Energy-funded, Princeton University-administered facility. The focal point of PPPL’s current research is a construction project that, if successful, could literally power the world.
Not tomorrow, or even next year, mind you. But the promise of nuclear fusion as a safe, clean, and inexhaustible source of energy is there, and scientists project that a commercially viable reactor may exist by 2050. Answers for the future of nuclear fusion lie with the National Spherical Torus Experiment Upgrade (NSTX-U), which is housed at PPPL and in the midst of a $94 million upgrade scheduled for completion in 2014.
To understand what NSTX-U hopes to achieve requires some basic knowledge how of nuclear fusion works. An atom consists of a nucleus with neutral neutrons and positively charged protons, surrounded by negatively charged electrons. Here, two opposing forces come into play: the nuclear force, which holds protons and neutrons together within an atom’s nucleus; and the Coulomb force, which causes like charges to repel each other. To accomplish fusion, the nuclei of two particles must come close enough to each other that the nuclear force is stronger than the Coulomb force, allowing the two nuclei to fuse into one larger nucleus.
Scientists do this by heating the particles, which strips them of their electrons and creates a plasma. The nuclei are then collided into each other at high speeds. When their nuclei fuse, the mass of the single, larger, nucleus is slightly less than the sum of the masses of the two nuclei that were fused. The leftover mass is released as energy, in accordance with Einstein’s E=MC2 (energy equals mass times the speed of light squared) formulation. That energy can then, in theory, be harnessed for practical use.
The principles behind nuclear fusion are simple — and are what power the sun and stars — but the reaction is difficult and expensive to achieve. This is where Princeton Plasma Physics Lab comes in. The National Spherical Torus Experiment is a tokamak — a device used to contain a magnetic field. The tokamak uses deuterium, an isotope of hydrogen — the most lightweight gas, which therefore requires the least energy to heat — to create helium nuclei. NSTX is a compact reactor that creates a more cost-effective apple core-shaped plasma rather than the doughnut-shaped plasmas generated by other tokamaks.
The goals of this research are several: the plasma created needs to be contained so as to not stop the reaction; the power of the magnetic field used to contain the plasma will ideally be minimized relative to the pressure generated by the plasma; and new methods of maintaining the electrical current to the plasma must be developed to prevent damage to the coil that generates the current. The upgraded equipment at PPPL will feature a much more powerful magnetic field and the capacity to heat the plasma much hotter — up to 20 million degrees celsius, or twice the temperature of the sun.
The upgrades to NSTX set it up to be a cutting edge world leader in fusion research — nothing else like it exists — and scientists hope it paves the way to a future in which the NSTX design can be used for a fusion-fueled research facility.
But while fusion may have a useful future in energy production, fusion — and its counterpart, fission, in which splitting a nucleus releases massive amounts of energy — also have destructive histories. Fission was the basis for the bombs dropped on Hiroshima and Nagasaki during World War II, and both fission and fusion occur in the detonation of a hydrogen bomb. Both types of reactions are used today to fuel nuclear warheads.
And here, PPPL becomes part of the effort to prevent nuclear proliferation. In April the lab announced that, in collaboration with physicists from Princeton University, its researchers were developing a system for determining if decommissioned nuclear weapons contain true warheads. If successful, their system would allow the identification of warheads without gathering any classified information about the device that could be disastrous if it were leaked.
The so-called zero-knowledge system combines ideas from cryptography and physics to allow testers to positively identify real and fake warheads simply by comparing them to a known true warhead — without gleaning any knowledge about the materials or processes employed by the warhead.
The project is funded by the U.S. Department of State and Global Zero, a nonprofit that aims to rid the world of all nuclear weapons. Astrophysics professor and former PPPL director Robert Goldston is working with physics professor Alexander Glaser and PPPL engineer Charles Gentile on the project.
The test process for a suspected nuclear warhead is fairly straightforward. High-energy neutrons are beamed through the warhead. Some are absorbed or scattered by whatever materials are contained within the warhead; the rest are counted by a detector on the other side. With that data in hand, scientists compare the number detected plus the number preloaded into the detector with the numbers for the known true warhead. If they match, the test warhead is real. If not, it is a decoy being used by some country trying to circumvent the decommissioning process.
Open House, Princeton Plasma Physics Lab, 100 Stellarator Road, Plainsboro. Saturday, June 1, 9 a.m. to 4 p.m. Free. Photo ID required for ages 18 and up. Parking on site and at Novo Nordisk. Visit www.pppl.gov/openhouse.
A person visiting a bar on a weeknight may score a half-price beer or appetizer, but on a Saturday night will pay full price. Why? The bar likely has no trouble attracting customers over the weekend, whereas it may need to provide an incentive to get people out for a drink on a Tuesday night. The concept is called time-dependent pricing, and it has been applied to industries well beyond the local watering hole.
The strategy becomes more relevant when it can be used to help better distribute access to a limited resource. This is where the work of Princeton University graduate student Carlee Joe-Wong takes center stage.
As an undergraduate in the math department in 2010, Joe-Wong completed a research project in which she developed mathematical models for time-dependent broadband access. Now that everyone has one or several mobile devices that are constantly streaming video, downloading music, or running apps, bandwidth is being used faster than it can be created.
But the solution may not be as simple as offering half off for using your cellphone at 4 a.m. rather than 4 p.m. Joe-Wong and a team led by electrical engineering professor Mung Chiang devised an experiment in which they paid the internet bills for 50 volunteers from the university community, then charged the volunteers based on the pricing system they had devised.
What they found was that the perceived value of a certain discount changes over time — so their mathematical models were designed to take into account how customers’ behavior changes based on past data usage.
The team also developed a popular free mobile app, DataWiz, that allows users of mobile devices to track how much data they’re using, and when.
Joe-Wong’s project exemplifies the goal of Princeton’s EDGE Lab, led by Chiang. According to its website, scenic.princeton.edu, EDGE “bridges over the theory-practice divide in networking and builds on the combined core of rigor in the answers and relevance in the questions. Through collaboration across many disciplinary boundaries as well as the academia-industry boundary, it constantly re-examines the mathematical crystallization of engineering artifacts in networking.”
What started as student independent work now involves some major players in telecommunications, including AT&T and Comcast. Last July Chiang and Soumya Sen, a postdoctoral research associate, organized Princeton’s first Smart Data Pricing Forum, which brought together academics, carriers, vendors, and other industry leaders for two days of talks and panel discussions. The result: an international series of forums scheduled for this year, and a real-life trial of Joe-Wong’s concept this summer, in which 1,000 real AT&T customers will try the novel pricing system.
#b#You Hear Me Now?#/b#
Pop quiz: a man wants to create a small-scale replica of a famous sculpture. He must a) become an artist or b) head to his nearest Staples?
If you answered b), you were correct. For $1,300 the office supply chain will sell you a three-dimensional printer, one that will layer plastic or other materials to create objects that are up to five inches high, wide, and deep.
That same type of printer, available for purchase by anyone on the Internet, may provide the ability to replicate and improve on the function of a human organ. In the case of a group of researchers based at Princeton, that organ is the ear, and they have created the world’s first “bionic ear” using a commercial 3-D printer and cell cultures.
The team of researchers, led by mechanical and aerospace engineering professor Michael McAlpine, also included Johns Hopkins professor David Gracias, Princeton graduate students Manu Manoor and Yong Lin Kong, Princeton faculty fellow Karen Malatesta, Princeton professors Winston Soboyejo and Naveen Verma, and Johns Hopkins graduate student Teena James. The most unlikely contributor, however, is Ziwen Jiang, a student at the Peddie School in Hightstown who is part of an outreach program in McAlpine’s lab.
The researchers used a process called additive manufacturing. With computer-assisted design (CAD) they designed an ear as a group of thin slices. The 3-D printer then layers the slices, which can comprise a range of materials, to create a finished product. In this case the team combined silver nanoparticles, hydrogel, and calf cells, which later formed cartilage. The finished product has a coiled antenna surrounded by cartilage. Two wires from the ear surround a cochlea, which senses sound, and can attach to electrodes.
This technique solves the problems with modeling three-dimensional biological structures in traditional tissue engineering and helps combine two fundamentally different types of materials — biological structures and electronic devices. The ear, in particular, presents an extra challenge because of its complex structure. While extensive testing is required before the bionic ear could be used on a human, it represents a bright future for restoring and improving a person’s hearing even beyond regular human capacity.
The uses of this bionic technology are not limited to ears. The ability to integrate biological and electronic elements means that sensors can be incorporated into other types of implants. The implications for the future of medicine could be massive: without any invasive testing, the sensors could allow a doctor to monitor the wear and tear on a replaced knee or hip.
And while a bionic knee or ear may never be available at Staples, what was once the stuff of science fiction movies is gradually becoming a reality in a university lab.
#b#Research in Brief#/b#
Nitrous oxide is known to most as laughing gas, but it is also a greenhouse gas released from nitrogen-based fertilizers. Scientists and regulators are eager to monitor levels of greenhouse gases, but making measurements in the field is complicated by sensors that are refrigerator-sized and require a large amount of power. Civil and environmental engineering professor Mark Zondlo has changed that with his invention of a hand-held sensor that uses a battery-powered laser and tiny calibration chamber to make accurate measurements. With a grant from Princeton’s Intellectual Property Accelerator Fund, Zondlo and his team will make tweaks to prepare the product for sale.
Another recipient of grant money from the accelerator fund is chemistry professor Tom Muir, who has developed a method to ensure that drug molecules travel directly to their target within the body, for example a tumor.
Taking advantage of the velcro-like properties of a type of protein called split inteins, which come in pairs that bind to each other, Muir attached one half of the intein to an antibody that binds to tumor-fighting immune cells and the other half to the drug molecule. When combined, the inteins attached to the antibody will find their matching pair attached to the drug molecules.