The humble neutrino, an elusive subatomic particle that passes effortlessly through normal matter, plays an outsized role among the particles that comprise our universe. To fully explain how our universe came to be, scientists need to know its mass.

But, as it turns out, the neutrino avoids being weighed.

In a published Sept. 6 in Physical Review Letters, an international team of researchers in the United States, Germany and France reported that a distinctive strategy they have used shows real promise to be the first approach to measure the mass of the neutrino. Once fully scaled up, their collaboration — — could also reveal how neutrinos influenced the early evolution of the universe as we know it.

“Project 8 is an entirely new approach to trying to solve this outstanding, fundamental problem in physics — the mass of the neutrino — and we really think it is on course to answer this question and so much more,” said co-author and Project 8 scientist , a ����Ӱ�Ӵ�ý assistant professor of physics.

In 2022, , a separate collaboration based in Germany, set a new upper limit for the neutrino’s mass — a decades-long endeavor that UW researchers helped lead. But KATRIN is eventually expected to reach the limits of how much it can narrow the range of the neutrino’s mass, leaving scientists around the world asking, “What’s next?”

Project 8 scientists believe their approach might be the answer. Their work focuses on a well-characterized phenomenon called beta decay. Many radioactive variants of elements undergo this process. Project 8 hinges on using the beta decay of tritium — a rare, radioactive variant of hydrogen — to calculate the mass of the neutrino.

When tritium undergoes beta decay, it generates a helium ion, an electron and a neutrino. Rather than try to detect the neutrino, which passes through most detector technology, the research team has instead focused on measuring the free electron generated during beta decay. These electrons carry away most — but not all — of the energy released by beta decay. And that “missing” energy is made up of the neutrino’s mass and motion.

“The neutrino is incredibly light,” said co-author Talia Weiss, a Project 8 scientist and graduate student at Yale University. “It’s more than 500,000 times lighter than an electron. So, when neutrinos and electrons are created at the same time, the neutrino mass has only a tiny effect on the electron’s motion. We want to see that small effect. So, we need a super-precise method to measure how fast the electrons are zipping around.”

In their recent paper, Project 8 scientists showed that they can use a new technique — cyclotron radiation emission spectroscopy, or CRES — to reliably track and record beta decay. According to their results, CRES could be used to calculate neutrino properties, including its mass.

“In principle, with technology developments and scale up, we have a realistic shot at getting into the range necessary to pin down the neutrino mass,” said co-author Brent VanDevender, a Project 8 scientist at the , a U.S. Department of Energy facility.

Physicists Joe Formaggio and Ben Monreal first conceived of CRES more than a decade ago at the Massachusetts Institute of Technology. An international team rallied around the idea and formed Project 8 to convert their vision into a practical tool. CRES captures the microwave radiation emitted from newborn electrons as they spiral around in a magnetic field.

Project 8 scientists spent years figuring out how to accurately tease out the electron signals from background noise. Weiss and Christine Claessens — a UW postdoctoral researcher who worked on Project 8 as a doctoral student at the University of Mainz in Germany — performed the two final analyses that placed limits on the neutrino mass using CRES data. This is the first time that tritium beta decays have been measured, and an upper limit placed on the neutrino mass, with the CRES technique.

The CRES detector, built and housed at the UW, measures that crucial electron energy with the potential to scale up beyond any existing technology. Novitski said that scalability is what sets Project 8 apart.

“Nobody else is doing this,” Novitski said. “We’re not taking an existing technique and trying to tweak it a little bit. We’re kind of in the Wild West.”

In their most recent experiment, the team tracked 3,770 tritium beta decay events over an 82-day trial window in a sample cell the size of a pea. The sample cell is cryogenically cooled and placed in a magnetic field that traps the emerging electrons long enough for the system’s recording antennas to register a microwave signal.

A subset of Project 8 researchers have also developed a suite of specialized software — each named after insects, like Katydid and Dragonfly — to convert raw data into signals that can be analyzed. And project engineers have had to design and build the hardware and detectors that make Project 8 come together.

“We do have engineers who are crucial to the effort,” Novitski said. “It’s kind of out there from an engineer’s point of view. Experimental physics is at the boundary of physics and engineering. You have to get particularly adventurous engineers and practical-minded physicists to collaborate, to make these things come into being, because this stuff is not in the textbooks.”

Now that the team has shown their experimental system works using molecules of tritium, they’re working on designs for scaling up the experiment from the pea-size sample chamber to one a thousand times larger to capture more beta decay events. They’re also developing an experimental set-up to produce, cool and trap individual atoms of tritium — no easy feat since tritium, like its more abundant cousin hydrogen, prefers to bind to other atoms and form molecules.

Meeting these goals, and scaling up the whole apparatus, will be the critical steps to reaching and ultimately exceeding the sensitivity achieved by the KATRIN experiment.

“This will be a years-long effort. But one that we think will finally give us this small answer — the mass of this tiny neutrino — with huge implications,” said co-author and Project 8 scientist , a UW professor of physics.

Other UW co-authors include current and former graduate students Ali Ashtari Esfahani, Jeremy Hartse and Eris Machado; , emeritus research professor of physics; and , professor emeritus of physics. Project 8 is funded by the U.S. Department of Energy, the National Science Foundation, the German Research Foundation and internal investments by collaborating institutions.

For more information, contact Novitski at en37@uw.edu.

Adapted from a by the Pacific Northwest National Laboratory.

An international team of scientists has for the first time detected neutrinos created by a particle collider.

The discovery, announced March 19 by the Forward Search Experiment — or collaboration —  at the 57th Rencontres de Moriond Electroweak and Unified Theories conference in Italy, promises to deepen scientists’ understanding of the nature of neutrinos, which are the most abundant particle in the cosmos. FASER’s detector picked up neutrinos generated by the Large Hadron Collider, which is based at CERN — the European Council for Nuclear Research — in Geneva, Switzerland.

The work promises to shed light on the nature of neutrinos near and far. It could unlock insights about cosmic neutrinos that travel large distances and collide with the Earth, providing a window on distant parts of the cosmos. In addition, neutrinos were critical in developing the of particle physics — the current scientific framework for fundamental particles and forces in the universe. Studying neutrinos from different sources could help scientists understand if the model needs tweaking, or more.

“This is new territory,” said FASER scientist , a ����Ӱ�Ӵ�ý associate professor of physics. “Direct observation of neutrinos originating from the Large Hadron Collider has revealed a new pathway to study the deep mysteries of the Standard Model.”

Hsu was a founding member of the FASER collaboration, which was launched by particle physicist Jonathan Feng of the University of California, Irvine. The team now includes researchers at 24 partner institutions. FASER scientists designed, built and operate a particle detector installed at the LHC site.

“We’ve discovered neutrinos from a brand new source, from particle colliders, where you have two beams of particles smashing together at extremely high energy to make the neutrinos,” said Feng.

Since their discovery in 1956, the majority of neutrinos studied by physicists have been low-energy neutrinos. But the neutrinos detected by FASER are the highest energy ever produced in a laboratory setting, and are similar to the neutrinos found when deep-space particles trigger dramatic particle showers in our atmosphere.

“They can tell us about deep space that we can’t learn in other ways,” said FASER co-spokesperson Jamie Boyd, a particle physicist at CERN. “These very high-energy neutrinos in the LHC are important for understanding really exciting observations in particle astrophysics.”

“This is a historical milestone for neutrino experiments, and will fill the gap between studies of neutrinos from other sources, including reactors and cosmic events,” said UW research scientist Ke Li, a member of the FASER team. “In the future, FASER will have the largest dataset of tau neutrinos, which are the least-understood particles in Standard Model.”

Li led efforts to integrate the tracking software used in the FASER detector, and has helped commission the first set of data generated by the experiment. Other UW scientists involved in the FASER neutrino detection are physics doctoral student Ali Garabaglu and undergraduate student David Lai. UW involvement in the FASER collaboration is funded by the National Science Foundation, the Simons Foundation and the Heising-Simons Foundation.

FASER itself is unique among particle-detecting experiments. Compared to other detectors at CERN like ATLAS, which is several stories tall and weighs thousands of tons, FASER is only about one ton and fits neatly into a small side-tunnel at CERN. It took only a few years to design and construct, using spare parts from other experiments.

Beyond neutrinos, one of FASER’s other chief objectives is to help identify the particles that make up dark matter, which physicists think comprises most of the matter in the universe, but which they’ve never directly observed before.

FASER has yet to find signs of dark matter, but with the LHC set to begin a new round of particle collisions in a few months, the detector stands ready to record them, should they appear.

For more information, contact Hsu at schsu@uw.edu.

Adapted by a from UC Irvine.

The ����Ӱ�Ӵ�ý rose from No. 7 to No. 6 on the , released on Tuesday. The UW maintained its No. 2 ranking among U.S. public institutions.

U.S. News also ranked several subjects, and the UW placed in the top 10 in 10 subject areas, including immunology (No. 4), molecular biology and genetics (No. 5) and clinical medicine (No. 6).

In another ranking out this week, Times Higher Education World University Rankings 2023 by Subject, six subject areas at the UW placed in the top 25.

“As a global public research university, the UW’s mission is to create and accelerate change for the public good,” UW President Ana Mari Cauce said. “I’m proud that these rankings reflect the outstanding and wide-ranging work of our faculty, staff and students to expand knowledge and discovery that is changing people’s lives for the better, particularly in the health sciences.”

The U.S. News ranking —  based on Web of Science data and metrics provided by Clarivate Analytics InCites — weighs factors that measure a university’s global and regional research reputation and academic research performance. For the overall rankings, this includes bibliometric indicators such as publications, citations and international collaboration.

The overall Best Global Universities ranking, now in its ninth year, encompasses the top 2,000 institutions spread across 90 countries, according to U.S. News. American universities make up eight of the top 10 spots.

Here are all the top 10 UW rankings in U.S. News’ subject rankings:

• Immunology – No. 4
• Molecular biology and genetics – No. 5
• Clinical medicine – No. 6
• Geosciences – No. 7
• Infectious diseases – No. 7
• Public, environmental and occupational health – No. 7
• Social sciences and public health – No. 7
• Biology and biochemistry – No. 8
• Microbiology – No. 10

In the rankings, UW’s programs in these areas placed in the top 25:

• : No. 15
• (includes agriculture and forestry, biological sciences, veterinary science and sport science): No. 16
• (includes medicine, dentistry and other health subjects): No. 17
• (includes communication and media studies, politics and international studies — including development studies, sociology and geography): No. 18
• (includes mathematics and statistics, physics and astronomy, chemistry, geology, environmental sciences, and Earth and marine sciences): No. 19
• (includes education, teacher training, and academic studies in education): No. 23

The subject tables employ the same used in the overall ; however, the methodology is recalibrated for each subject, with the weightings changed to suit the individual fields.

The newest experiment at CERN, the European Organization for Nuclear Research, is now in place at the Large Hadron Collider in Geneva. , or Forward Search Experiment, was approved by CERN’s research board in March 2019. Now installed in the LHC tunnel, this experiment, which seeks to understand particles that scientists believe may interact with dark matter, is undergoing tests before data collection commences next year.

“This is a great milestone for the experiment,” said , a FASER scientist and ����Ӱ�Ӵ�ý associate professor of physics. “FASER will be ready to collect data from collisions at the Large Hadron Collider when they resume in spring 2022.”

FASER is designed to study the interactions of high-energy and to search for new, as-yet-undiscovered light and weakly interacting particles, which some scientists believe interact with . Unlike visible matter, which makes up us and our world, most matter in the universe — about 85% — consists of dark matter. Studying light and weakly interacting particles may reveal clues to the nature of dark matter and other longstanding puzzles, such as the origin of neutrino masses.

�ճ���� consists of 70 members from 19 institutions and eight countries. FASER scientists at the UW include Hsu, postdoctoral researcher Ke Li, doctoral student John Spencer and undergraduates Murtaza Jafry and Jeffrey Gao. The UW team has been involved in efforts to develop software and evaluate the performance of portions of the FASER detector, as well as scrutinize data from the detector during its commissioning period. They will also monitor the performance of instruments in the detector and analyze data when collisions at LHC resume next year.

Researchers believe that LHC’s collisions produce the light and weakly interacting particles that FASER is designed to detect. These may be long-lived particles, travelling hundreds of meters before they decay into other particles that FASER will measure.

The experiment is located in an unused service tunnel along the beam collision axis, just 480 meters — or almost 1,600 feet — from the interaction point of the LHC’s six-story . That proximity puts FASER in an optimal position for detecting the decay products of the light and weakly interacting particles.

The first civil engineering works for FASER started in May 2020. In the summer, the first services and power systems were installed, and in November, FASER’s three magnets were put in place in the trench.

“We are extremely excited to see this project come to life so quickly and smoothly,” said CERN scientist Jamie Boyd, a FASER co-spokesperson. “Of course, this would not have been possible without the expert help of the many CERN teams involved!”

The FASER detector is 5 meters long, or about 16.5 feet, and two scintillator stations sit at its entrance. The stations will remove background interference by charged particles coming through the cavern wall from the ATLAS interaction point. Next is a dipole magnet 1.5 meters, or about 5 feet, long. It is followed by a spectrometer that consists of two dipole magnets, each 1 meter or just over 3 feet long, with three tracking stations, two at either end and one between the magnets. Each tracking station consists of layers of precision silicon strip detectors. Scintillator stations for triggering and precision time measurements are located at the entrance and exit of the spectrometer.

The final component is the electromagnetic calorimeter. This will identify high-energy electrons and photons and measure the total electromagnetic energy. The whole detector is cooled down to 15 C, or 59 F, by an independent cooling station.

Some of these components were assembled from spare parts of other LHC experiments, including ATLAS and , according to Boyd.

FASER will also have a subdetector, called FASERν, which is specifically designed to detect neutrinos. No neutrino produced at a particle collider has ever been detected, despite colliders producing them in huge numbers and at high energies. FASERν is made up of emulsion films and tungsten plates to act as both the target and the detector to see the neutrino interactions. FASERν should be ready for installation by the end of the year. The whole experiment will start taking data during Run 3 of the LHC, starting in 2022.

FASER is supported by the Heising-Simons Foundation and the Simons Foundation.

For more information, contact Hsu at schsu@uw.edu.

Adapted from a by CERN.

An international team of scientists has announced a breakthrough in its quest to measure the mass of the neutrino, one of the most abundant, yet elusive, elementary particles in our universe.

At the conference in Toyama, Japan, leaders from the KATRIN experiment reported Sept. 13 that the estimated range for the rest mass of the neutrino is no larger than about 1 , or eV. These inaugural results obtained earlier this year by — or KATRIN — cut the mass range for the neutrino by more than half by lowering the upper limit of the neutrino’s mass from 2 eV to about 1 eV. The lower limit for the neutrino mass, 0.02 eV, was set by previous experiments by other groups.

“Knowing the mass of the neutrino will allow scientists to answer fundamental questions in cosmology, astrophysics and particle physics, such as how the universe evolved or what physics exists beyond the Standard Model,” said , a KATRIN scientist and professor emeritus of physics at the ����Ӱ�Ӵ�ý. “These findings by the KATRIN collaboration reduce the previous mass range for the neutrino by a factor of two, place more stringent criteria on what the neutrino’s mass actually is, and provide a path forward to measure its value definitively.”

The KATRIN experiment is based at the Karlsruhe Institute of Technology in Germany and involves researchers at 20 research institutions around the globe. In addition to the ����Ӱ�Ӵ�ý, KATRIN member institutions in the United States are:

• The University of North Carolina at Chapel Hill, led by professor of physics and astronomy , a former UW faculty member
• The Massachusetts Institute of Technology, led by professor of physics
• The Lawrence Berkeley National Laboratory, led by Nuclear Science Division deputy director
• Carnegie Mellon University, led by assistant professor of physics
• Case Western Reserve University, led by associate professor of physics

Under Robertson and Wilkerson, the ����Ӱ�Ӵ�ý became one of KATRIN’s founding member institutions in 2001. Wilkerson later moved to the University of North Carolina at Chapel Hill. Formaggio and Parno began their involvement with KATRIN as UW researchers and later moved to their current institutions. In addition to Robertson, other current UW scientists working on the KATRIN experiment are research professor of physics , research associate professor of physics and Menglei Sun, a postdoctoral researcher in the UW .

Neutrinos are abundant. They are one of the most common fundamental particles in our universe, second only to photons. Yet neutrinos are also elusive. They are neutral particles with no charge and they interact with other matter only through the aptly named “weak interaction,” which means that opportunities to detect neutrinos and measure their mass are both rare and difficult.

“If you filled the solar system with lead out to fifty times beyond the orbit of Pluto, about half of the neutrinos emitted by the sun would still leave the solar system without interacting with that lead,” said Robertson.

Neutrinos are also mysterious particles that have already shaken up physics, cosmology and astrophysics. The of particle physics had once predicted that neutrinos should have no mass. But by 2001, scientists had shown with two detectors, Super-Kamiokande and the Sudbury Neutrino Observatory, that they actually do have a nonzero mass — a breakthrough with the Nobel Prize in Physics. Neutrinos have mass, but how much?

“Solving the mass of the neutrino would lead us into a brave new world of creating a new Standard Model,” said Doe.

The KATRIN discovery stems from direct, high-precision measurements of how a rare type of electron-neutrino pair share energy. This approach is the same as neutrino mass experiments from the 1990s and early 2000s in Mainz, Germany, and Troitsk, Russia, both of which set the previous upper limit of the mass at 2 eV. The heart of the KATRIN experiment is the source that generates electron-neutrino pairs: gaseous tritium, a highly radioactive isotope of hydrogen. As the tritium nucleus undergoes radioactive decay, it emits a pair of particles: one electron and one neutrino, both sharing 18,560 eV of energy.

KATRIN scientists cannot directly measure the neutrinos, but they can measure electrons, and try to calculate neutrino properties based on electron properties.

Most of the electron-neutrino pairs emitted by the tritium share their energy load equally. But in rare cases, the electron takes nearly all the energy — leaving only a tiny amount for the neutrino. Those rare pairs are what KATRIN scientists are after because — thanks to E = mc² — scientists know that the miniscule amount of energy left for the neutrino must include its rest mass. If KATRIN can accurately measure the electron’s energy, they can calculate the neutrino’s energy and therefore its mass.

The tritium source generates about 25 billion electron-neutrino pairs each second, only a fraction of which are pairs where the electron takes nearly all the decay energy. The KATRIN facility in Karlsruhe uses a complex series of magnets to channel the electron away from the tritium source and toward an electrostatic spectrometer, which measures the energy of the electrons with high precision. An electric potential within the spectrometer creates an “energy gradient” that electrons must “climb” in order to pass through the spectrometer for detection. Adjusting the electric potential allows scientists to study the rare, high-energy electrons, which carry information concerning the neutrino mass.

U.S. institutions have made broad contributions to KATRIN, including providing the electron-detector system — the “eye” of KATRIN — which looks into the heart of the spectrometer, an instrument built at the UW. The University of North Carolina at Chapel Hill led the development of the detector’s data acquisition system, the “brains” of KATRIN. MIT’s contribution was the design and development of the simulation software used to model the response of KATRIN. The Lawrence Berkeley National Laboratory contributed to the creation of the physics analysis program and provided access to national computing facilities, and quick analysis was enabled by a suite of applications that originated at the UW. The Case Western Reserve University was responsible for the design of the electron gun, central to calibrating the KATRIN apparatus. Carnegie Mellon University contributed primarily to analysis, with special attention to background and to fitting, and assisted in analysis coordination for the experiment.

With tritium data acquisition now underway, U.S. institutions are focused on analyzing these data to further improve our understanding of neutrino mass. These efforts may also reveal the existence of sterile neutrinos, a possible candidate for the dark matter that, though accounting for 85% of the matter in the universe, remains undetected.

“KATRIN is not only a shining beacon of fundamental research and an outstandingly reliable high-tech instrument, but also a motor of international cooperation, which provides first-class training of young researchers,” said KATRIN co-spokespersons Guido Drexlin of the Karlsruhe Institute of Technology and Christian Weinheimer of the University of Münster in a statement.

Now that KATRIN scientists have set a new upper limit for the mass of the neutrino, project scientists are working to narrow the range even further.

“Neutrinos are strange little particles,” said Doe. “They’re so ubiquitous, and there’s so much we can learn once we determine this value.”

The U.S. Department of Energy’s Office of Nuclear Physics has funded the U.S. participation in the KATRIN experiment since 2007.

###

For more information, contact Robertson at 206-616-2745 or rghr@uw.edu and Doe at 206-543-8862 or pdoe@uw.edu.

The research board of CERN, the European Organization for Nuclear Research, on March 5 approved a new experiment at the Large Hadron Collider in Geneva, the world’s largest particle accelerator, to search for evidence of fundamental dark matter particles. The Forward Search Experiment — or FASER — seeks to answer one of the outstanding questions in particle physics: What is dark matter made of?

“There is strong evidence that most of the matter in the universe — about 85 percent — is dark matter, and that dark matter is made up of an unknown class of fundamental particles,” said , an associate professor of physics at the ����Ӱ�Ӵ�ý and member of the FASER team. “The identity of dark matter particles is a major mystery in particle physics, and one that we think FASER could help solve by identifying a class of particles associated with dark matter.”

FASER is a partnership of 16 institutions around the globe, including the UW, and co-led by scientists at the University of California, Irvine and CERN, which operates the Large Hadron Collider, or LHC. The five-year FASER project is funded by grants of $1 million each from the Heising-Simons Foundation in California and the Simons Foundation in New York, with additional support from CERN.

FASER is trying to find indirect evidence for the light, weakly interacting particles that may interact with dark matter. So far, these particles have eluded scientists. But the FASER team will try to detect traces of these particles as they decay from the LHC’s proton beams.

“Seven years ago, scientists discovered the Higgs boson at the Large Hadron Collider, completing one chapter in our search for the fundamental building blocks of the universe, but now we are looking for new particles,” said Jonathan Feng, FASER co-spokesperson and professor of physics and astronomy at UC Irvine. “The dark matter problem shows that we don’t know what most of the universe is made of, so we’re sure new particles are out there.”

The FASER instrument is designed to be compact, measuring about 1 meter in diameter and 5 meters long. It will be placed at a specific point along the 16-mile loop of the LHC, about 480 meters, or 1,574 feet, away from the hulking, six-story instrument used by the Collaboration to discover the .

As proton beams pass through the interaction point at the ATLAS instrument, some theories indicate that they may decay to a candidate particle that interacts with dark matter, a , which in turn could decay into a pair of particles — an electron and a — as it passes through concrete in the LHC tunnel and then into the FASER instrument. The instrument will be able to measure the progress of particle decay, and will collect data when ATLAS is operating.

“The high number of particles at the LHC gives us this irresistible chance to try to detect new lightweight particles — and even trace them as they travel hundreds of meters from their source to the detector,” said Hsu.

At the UW, Hsu’s group studies simulations of detection events by the FASER instrument, working out the instrument parameters and data-analysis tools needed to accurately trace any detected particles back to their sources. These tools will help separate real signals of dark matter-associated particles from background events.

“One of the advantages of our design is that we’ve been able to borrow many of the components of FASER — silicon detectors, calorimeters and electronics — from the ATLAS and collaborations,” said Jamie Boyd, CERN research scientist and co-spokesperson for FASER. “That’s allowing us to assemble an instrument that costs hundreds of times less than the largest experiments at the LHC.”

The detector’s support platform, which will hold intricate magnets and detectors in place, will be designed and manufactured by a UW team led by laboratory engineer Bill Kuykendall in the Department of Mechanical Engineering, with input from UW physics professor .

The FASER detector, which will be one of only eight research instruments at the LHC, is being built and installed during the collider’s current hiatus and will collect data from 2021 to 2023. The LHC will be shut down again from 2024 to 2026. During that time, the team hopes to install the larger FASER 2 detector, which will be capable of unveiling an even wider array of mysterious, hidden particles.

The FASER team will consist of 30 to 40 members, a relatively small number compared to other groups conducting research at the LHC. In addition to CERN, UC Irvine and the UW, other institutions participating in the FASER endeavor are the University of Oregon, Rutgers University, the University of Geneva in Switzerland, the University of Bern in Switzerland, Italy’s National Institute for Nuclear Physics Genoa Section, China’s Tsinghua University, Technion – Israel Institute of Technology, Israel’s Weizmann Institute of Science, the Johannes Gutenberg University of Mainz in Germany, Kyushu University in Japan, Nagoya University in Japan, the “KEK” High Energy Accelerator Research Organization in Japan and the University of Sheffield in the U.K.

###

For more information, contact Hsu at schsu@uw.edu or 206-543-2760.

Adapted from a by the University of California, Irvine.

A low-cost technology may make it possible to read long sequences of DNA far more quickly than current techniques.

The research advances a technology, called nanopore DNA sequencing. If perfected it could someday be used to create handheld devices capable of quickly identifying DNA sequences from tissue samples and the environment, the ����Ӱ�Ӵ�ý researchers who developed and tested the approach said.

“One reason why people are so excited about nanopore DNA sequencing is that the technology could possibly be used to create ‘tricorder’-like devices for detecting pathogens or diagnosing genetic disorders rapidly and on-the-spot,” said Andrew Laszlo, lead author and a graduate student in the laboratory of Jen Gundlach, a UW professor of physics who led the project.

The paper “Decoding long nanopore sequencing reads of natural DNA”  describes the new technique. It appears June 25 in the advanced online edition of the journal Nature Biotechnology.

Most of the current gene sequencing technologies require working with short snippets of DNA, typically 50 to 100 nucleotides long. These must be processed by large sequencers in a laboratory. The cumbersome process can take days to weeks to complete.

Nanopore technology takes advantage of the small, tunnel-like structures found in bacterial membranes. In nature, such pores allow bacteria to control the flow of nutrients across their membranes.

UW researcher used the nanopore  (MspA). This bacterial pore has been genetically altered so that the narrowest part of the channel has a diameter of about a nanometer, or 1 billionth of a meter. This is large enough for a single strand of DNA to pass through. The modified nanopore is then inserted into a membrane separating two salt solutions to create a channel connecting the two solutions.

To read a sequence of DNA with this system, a small voltage is applied across the membrane to make the ions of the salt solution flow through the nanopore. The ion flow creates a measurable current. If a strand of DNA is added to the solution on one side of the membrane and then enters a pore, the bulky DNA molecules will impede the flow of the much smaller ion and thereby alter the current. How much the current changes depends on which nucleotides — the individual molecules adenine, guanine, cytosine and thymine that make up the DNA chain — are inside the pore. Detecting changes in current can reveal which nucleotides are passing through the nanopore’s channel at any given instant.

Since the technique was first proposed in the 1990s, researchers hoped that nanopore DNA sequencing would offer a cheap, fast alternative to current gene sequencing. But their attempts have been frustrated by several challenges. It is difficult to identify each nucleotide one-by-one as they pass through the nanopore. Instead, researchers have to work with changes in current associated with four nucleotides at a time. In addition, some nucleotides may be missed or read more than once. Consequently, current nanopore sequencing technology yields an imprecise readout of a DNA sequence.

The UW researchers describe how they bypassed these problems. The researchers first identified the electronic signatures of all the nucleotide combinations possible with the four nucleotides that make up DNA — a total of 256 combinations in all (4 x 4 x 4 x 4).

They then created computer algorithms to match the current changes generated when a segment of DNA passes through the pore with current changes expected  from DNA sequences of known genes and genomes stored in a computer database. A match would show that the sequence of the DNA passing through the pore was identical or close to the DNA sequence stored in the database. The whole process would take minutes to a few hours, instead of weeks.

To test this approach, the researchers used their nanopore system to read the sequence of bacteriophage Phi X 174, a virus that infects bacteria and that is commonly used to evaluate new genome sequencing technologies. They found that the approach reliably read the bacteriophage’s DNA sequences and could  read sequences as long as 4,500 nucleotides.

“This is the first time anyone has shown that nanopores can be used to generate interpretable signatures corresponding to very long DNA sequences from real-world genomes,” said co-author Jay Shendure, a UW associate professor of genome sciences whose lab develops applications of genome sequencing technologies.  “It’s a major step forward.”

Because the technique relies on matching readings to databases of previously sequenced genes and genomes, it cannot yet be used to sequence a newly discovered gene or genome, the researchers said, but with some  refinements, they added, it should  be possible to improve performance in this area. To accelerate research on this new technology, the scientists are making their methods, data and computer algorithms fully available to all.

“Despite the remaining hurdles, our demonstration that a low-cost device can reliably read the sequences of naturally occurring DNA and can interpret DNA segments as long as 4,500 nucleotides in length represents a major advance in nanopore DNA sequencing,” Gundlach said.

This work was supported by the National Institutes of Health, National Human Genome Research Institutes $1,000 Genome Program Grants R01HG005115, R01HG006321 and R01HG006283  and a graduate research fellowship from the National Science Foundation DGE-0718124.

Also well known is that the solid form of many materials can have numerous phases, but it is difficult to pinpoint the temperature and pressure for the points at which three solid phases can coexist stably.

Scientists now have made the first-ever accurate determination of a solid-state triple point in a substance called vanadium dioxide, which is known for switching rapidly – in as little as one 10-trillionth of a second – from an electrical insulator to a conductor, and thus could be useful in various technologies.

“These solid-state triple points are fiendishly difficult to study, essentially because  the different shapes of the solid phases makes it hard for them to match up happily at their interfaces,” said David Cobden, a ����Ӱ�Ӵ�ý physics professor.

“There are, in theory, many triple points hidden inside a solid, but they are very rarely probed.”

Cobden is the lead author of a paper describing the work, published Aug. 22 in Nature.

In 1959, researchers at Bell Laboratories discovered vanadium dioxide’s ability to rearrange electrons and shift from an insulator to a conductor, called a metal-insulator transition. Twenty years later it was discovered that there are two slightly different insulating phases.

The new research shows that those two insulating phases and the conducting phase in solid vanadium dioxide can coexist stably at 65 degrees Celsius, give or take a tenth of a degree (65 degrees C is equal to 149 degrees Fahrenheit).

To find that triple point, Cobden’s team stretched vanadium dioxide nanowires under a microscope. The team had to build an apparatus to stretch the tiny wires without breaking them, and it was the stretching that allowed the observation of the triple point, Cobden said.

It turned out that when the material manifested its triple point, no force was being applied – the wires were not being stretched or compressed.

The researchers originally set out simply to learn more about the phase transition and only gradually realized that the triple point was key to it, Cobden said. That process took several years, and then it took a couple more to design an experiment to pin down the triple point.

“No previous experiment was able to investigate the properties around the triple point,” he said.

He regards the work as “just a step, but a significant step” in understanding the metal-insulator transition in vanadium dioxide. That could lead to development of new types of electrical and optical switches, Cobden said, and similar experiments could lead to breakthroughs with other materials.

“If you don’t know the triple point, you don’t know the basic facts about this phase transition,” he said. “You will never be able to make use of the transition unless you understand it better.”

Co-authors are UW physics graduate students Jae Hyung Park, T. Serkan Kasirga and Zaiyao Fei; undergraduates Jim Coy and Scott Hunter; and postdoctoral researcher Chunming Huang. The work was funded by the U.S. Department of Energy.

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For more information, contact Cobden at 206-543-2686 or cobden@uw.edu.

The concept that current humanity could possibly be living in a computer simulation comes from a published in Philosophical Quarterly by , a philosophy professor at the University of Oxford. In the paper, he argued that at least one of three possibilities is true:

• The human species is likely to go extinct before reaching a “posthuman” stage.
• Any posthuman civilization is very unlikely to run a significant number of simulations of its evolutionary history.
• We are almost certainly living in a computer simulation.

He also held that “the belief that there is a significant chance that we will one day become posthumans who run ancestor simulations is false, unless we are currently living in a simulation.”

With current limitations and trends in computing, it will be decades before researchers will be able to run even primitive simulations of the universe. But the UW team has suggested tests that can be performed now, or in the near future, that are sensitive to constraints imposed on future simulations by limited resources.

Currently, supercomputers using a technique called lattice quantum chromodynamics and starting from the fundamental physical laws that govern the universe can simulate only a very small portion of the universe, on the scale of one 100-trillionth of a meter, a little larger than the nucleus of an atom, said , a UW physics professor.

Eventually, more powerful simulations will be able to model on the scale of a molecule, then a cell and even a human being. But it will take many generations of growth in computing power to be able to simulate a large enough chunk of the universe to understand the constraints on physical processes that would indicate we are living in a computer model.

However, Savage said, there are signatures of resource constraints in present-day simulations that are likely to exist as well in simulations in the distant future, including the imprint of an underlying lattice if one is used to model the space-time continuum.

The supercomputers performing lattice quantum chromodynamics calculations essentially divide space-time into a four-dimensional grid. That allows researchers to examine what is called the strong force, one of the four fundamental forces of nature and the one that binds subatomic particles called quarks and gluons together into neutrons and protons at the core of atoms.

“If you make the simulations big enough, something like our universe should emerge,” Savage said. Then it would be a matter of looking for a “signature” in our universe that has an analog in the current small-scale simulations.

Savage and colleagues of the University of New Hampshire, who collaborated while at the UW’s , and Zohreh Davoudi, a UW physics graduate student, suggest that the signature could show up as a limitation in the energy of cosmic rays.

In a , an online archive for preprints of scientific papers in a number of fields, including physics, they say that the highest-energy cosmic rays would not travel along the edges of the lattice in the model but would travel diagonally, and they would not interact equally in all directions as they otherwise would be expected to do.

“This is the first testable signature of such an idea,” Savage said.

If such a concept turned out to be reality, it would raise other possibilities as well. For example, Davoudi suggests that if our universe is a simulation, then those running it could be running other simulations as well, essentially creating other universes parallel to our own.

“Then the question is, ‘Can you communicate with those other universes if they are running on the same platform?'” she said.

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For more information, contact Savage at 206-543-7481 or mjs5@uw.edu; or Davoudi at 206-543-9310 or davoudi@uw.edu.