Coral skeleton formation rate determines resilience to acidifying oceans

Posted on January 27, 2022

A new University of Wisconsin–Madison study has implications for predicting coral reef survival and developing mitigation strategies against having their bony skeletons weakened by ocean acidification.

Though coral reefs make up less than one percent of the ocean floor, these ecosystems are among the most biodiverse on the planet — with over a million species estimated to be associated with reefs.

The coral species that make up these reefs are known to be differently sensitive or resilient to ocean acidification — the result of increasing atmospheric carbon dioxide levels. But scientists are not sure why.

In the study, researchers show that the crystallization rate of coral skeletons differs across species and is correlated with their resilience to acidification.

A woman holding two coral species stands in front of a body of water — “Finding solutions that are science-based is a priority,” says physics professor Pupa Gilbert, shown here with samples of scleractinian coral along the Lake Monona shoreline in Madison. | *Photo: Jeff Miller*

“Many agencies keep putting out reports in which they say, ‘Yes, coral reefs are threatened,’ with no idea what to do,” says Pupa Gilbert, a physics professor at UW–Madison and senior author of the study that was published Jan. 17 in the Journal of the American Chemical Society. “Finding solutions that are science-based is a priority, and having a quantitative idea of exactly what’s happening with climate change to coral reefs and skeletons is really important.”

Reef-forming corals are marine animals that produce a hard skeleton made up of the mostly insoluble crystalline material aragonite. Aragonite forms when precursors made up of a more soluble form, amorphous calcium carbonate, are deposited onto the growing skeleton and then crystallize.

The team studied three genera of coral and took an in-depth look at the components of their growing skeletons. They used a technique that Gilbert pioneered called PEEM spectromicroscopy, which detects the different forms of calcium carbonate with the greatest sensitivity to date.

When they used these spectromicroscopy images to compare the thickness of amorphous precursors to the crystalline form, they found that Acropora, which is more sensitive to acidification, had a much thicker band of amorphous calcium carbonate than Stylophora, which is less sensitive.

A third genus of unknown sensitivity, Turbinaria, had an even thinner amorphous precursor layer than Stylophora, suggesting it should be the most resilient of the three to ocean acidification.

two bright colored images assign a color to the form of calcium present in coral skeletons. On the left there is a thicker band of non-blue (blue is crystalline aragonite) compared to the image on the right where there is almost all blue, indicating the skeleton on the right crystallizes to aragonite more quickly — Coral skeletons were studied with PEEM spectromicroscopy, which identifies the calcium spectrum associated with each imaging pixel, then renders it in false color depending on the form of calcium. Blue is aragonite, the insoluble, crystalline form of calcium carbonate; the other colors represent one of the two amorphous precursor forms, a mix of the two, or a mix of aragonite and precursor form. Acropora spp. (left), has more non-blue pixels compared to Turbinaria spp. (right), indicating that Acropora has more of the soluble, non-crystalline form in its growing skeleton. | *Pupa Gilbert and team in JACS*

The thicker the band of uncrystallized minerals, the slower the crystallization process.

“If the surface of the coral skeleton, where all this amorphous calcium carbonate is being deposited by the living animal, crystallizes quickly, then that particular species is resilient to ocean acidification; if it crystallizes slowly, then it’s vulnerable,” Gilbert says. “For once, it’s a really simple mechanism.”

The mechanism may have worked out to be simple, but the data analysis required to process and interpret the PEEM images is anything but. Each pixel of imaging data acquired has a calcium spectrum that needs to be analyzed, which results in millions of data points. Processing the data includes many decision-making points, plus massive computing power.

The team has tried to automate the analysis or use machine-learning techniques, but those methods have not worked out. Instead, Gilbert has found that humans making decisions are the best data processors.

Gilbert did not want to base conclusions off the decision-making of just one or two people. So she hired a group of UW–Madison undergraduates, most of whom came from the Mercile J. Lee Scholars Program, which works to attract and retain talented students from underrepresented groups. This team provided a large and diverse group of decision makers.

a zoom screen showing several of the people who conducted the study — Gilbert and her research team met several times a week via Zoom, where students were assigned the same dataset to process in parallel and discuss at their next meeting. The Cnidarians — named after the phylum to which corals belong — include current and former UW–Madison undergraduates: Celeo Matute Diaz, Jorge Rivera Colon, Asiya Ahmed, Virginia Quach, Gabi Barreiro Pujol, Isabelle LeCloux, Sydney Davison, Connor Klaus, Jaden Sengkhamee, Evan Walch and Benjamin Fordyce; and graduate students Cayla Stifler, and Connor Schmidt. Schmidt was also the lead author of the study. | *Provided by Pupa Gilbert*

Dubbed the Cnidarians — from the phylum to which corals, anemones and jellyfish belong — this group of students became integral members of the team. They met several times a week via Zoom, when Gilbert would assign multiple students the same dataset to process in parallel and discuss at their next meeting.

“If multiple people come up with precisely the same solution even though they make different decisions, that means our analysis is robust and reliable,” Gilbert says. “The Cnidarians’ contributions were so useful that 13 of them are co-authors on this study.”

THIS STUDY WAS SUPPORTED BY THE DEPARTMENT OF ENERGY (DE-FG02-07ER15899 AND DE-AC02-05CHH11231), THE NATIONAL SCIENCE FOUNDATION (DMR-1603192) AND THE EUROPEAN RESEARCH COUNCIL (755876).

Magellanic Stream arcing over Milky Way may be five times closer than previously thought

Posted on November 22, 2021

Our galaxy is not alone. Swirling around the Milky Way are several smaller, dwarf galaxies — the biggest of which are the Small and Large Magellanic Clouds, visible in the night sky of the Southern Hemisphere.

Scott Lucchini

During their dance around the Milky Way over billions of years, the Magellanic Clouds’ gravity has ripped from each of them an enormous arc of gas — the Magellanic Stream. The stream helps tell the history of how the Milky Way and its closest galaxies came to be and what their future looks like.

New astronomical models developed by scientists at the University of Wisconsin–Madison and the Space Telescope Science Institute recreate the birth of the Magellanic Stream over the last 3.5 billion years. Using the latest data on the structure of the gas, the researchers discovered that the stream may be five times closer to Earth than previously thought.

The findings suggest that the stream may collide with the Milky Way far sooner than expected, helping fuel new star formation in our galaxy.

“The Magellanic Stream origin has been a big mystery for the last 50 years. We proposed a new solution with our models,” says Scott Lucchini, a graduate student in physics in Elena D’Onghia’s group at UW–Madison and lead author of the paper. “The surprising part was that the models brought the stream much closer to the Milky Way.”

Lucchini, D’Onghia, and Space Telescope Science Institute scientist Andrew Fox published their findings in The Astrophysical Journal Letters on Nov. 8.

Read the full story

a starscape showing the milky way in the distance and a rendering of the gases surrounding the large magellenic cloud — The Large and Small Magellanic Clouds as they would appear if the gas around them was visible to the naked eye. | Credits: Scott Lucchini (simulation), Colin Legg (background)

Study of high-energy particles leads PhD student Alex Wang to Department of Energy national lab

Posted on October 25, 2021

This story, by Meghan Chua, was originally published by the Graduate School

In 2012, scientists at CERN’s Large Hadron Collider announced they had observed the Higgs boson particle, verifying many of the theories of physics that rely on its existence.

Alex Wang

Since then, scientists have continued to search for the properties of the Higgs boson and for related particles, including an extremely rare case where two Higgs boson particles appear at the same time, called di-Higgs production.

“We’ve had some searches for di-Higgs right now, but we don’t see anything significant yet,” said Alex Wang, a PhD student in experimental high energy physics at UW–Madison. “It could be because it doesn’t exist, which would be interesting. But it also could just be because, according to the Standard Model theory, it’s very rare.”

Wang will have a chance to aid in the search for di-Higgs production in more ways than one. Starting in November, he will spend a year at the SLAC National Accelerator Laboratory as an awardee in the Department of Energy Office of Science Graduate Student Research Program.

The program funds outstanding graduate students to pursue thesis research at Department of Energy (DOE) laboratories. Students work with a DOE scientist on projects addressing societal challenges at the national and international scale.

At the SLAC National Accelerator Laboratory, Wang will primarily work on hardware for a planned upgrade of the ATLAS detector, one of the many detectors that record properties of collisions produced by the Large Hadron Collider. Right now, ATLAS collects an already massive amount of data, including some events related to the Higgs boson particle. However, Higgs boson events are extremely rare.

In the future, the upgraded High-Luminosity Large Hadron Collider (HL-LHC) will enable ATLAS to collect even more data and help physicists to study particles like the Higgs boson in more detail. This will make it more feasible for researchers to look for extremely rare events such as di-Higgs production, Wang said. The ATLAS detector itself will also be upgraded to adjust for the new HL-LHC environment.

a black background with orange cones and small yellow box-like dots indicate the signal events — This image of a signal-like event in the ATLAS detector comes from one of the Higgs boson-related analyses Wang works on. The red cones and cyan towers indicate particles which may have originated from the decay of two Higgs boson particles. (Photo credit: ATLAS Experiment © 2021 CERN)

“I’m pretty excited to go there because SLAC is essentially where they’ll be assembling the innermost part of the ATLAS detector for the future upgrade,” Wang said. “So, I think it’s going to be a really central place in the future years, at least for this upgrade project.”

Increasing the amount of data a sensor collects can also cause problems, such as radiation damage to the sensors and more challenges sorting out meaningful data from background noise. Wang will help validate the performance of some of the sensors destined for the upgraded ATLAS detector.

“I’m also pretty excited because for the data analysis I’m doing right now, it’s mainly working in front of a computer, so it will be nice to have some experience working with my hands,” Wang said.

At SLAC, he will also spend time searching for evidence of di-Higgs production.

Wang’s thesis research at UW–Madison also revolves around the Higgs boson particle. He sifts through data from the Large Hadron Collider to tease out which events are “signals” related to the Higgs boson, versus events that are “backgrounds” irrelevant to his work.

One approach Wang uses is to predict how many signal events researchers expect to see, and then determine if the number of events recorded in the Large Hadron Collider is consistent with that prediction.

“If we get a number that’s consistent with our predictions, then that supports the existing model of physics that we have,” Wang said. “But for example, if you see that the theory predicts we’d have 10 events, but in reality, we see 100 events, then that could be an indication that there’s some new physics going on. So that would be a potential for discoveries.”

The Department of Energy formally approved the U.S. contribution to the High-Luminosity Large Hadron Collider accelerator upgrade project earlier this year. The HL-LHC is expected to start producing data in 2027 and continue through the 2030s. Depending on what the future holds, Wang may be able to use data from the upgraded ATLAS detector to find evidence of di-Higgs production. If that happens, he also will have helped build the machine that made it possible.

Magnetic fields implicated in the mysterious midlife crisis of stars

Posted on July 28, 2021

a brightly colored sun with a cutout showing into the core, with lines suggesting the spinning motion — Artist’s impression of the spinning interior of a star, generating the stellar magnetic field. This image combines a dynamo simulation of the Sun’s interior with observations of the Sun’s outer atmosphere, where storms and plasma winds are generated. | Credit:
CESSI / IISER Kolkata / NASA-SVS / ESA / SOHO-LASCO

This post was originally published by the Royal Astronomical Society. UW–Madison physics graduate student Bindesh Tripathi is the lead author of the scientific publication.

Middle-aged stars can experience their own kind of midlife crisis, experiencing dramatic breaks in their activity and rotation rates at about the same age as our Sun, according to new research published today in Monthly Notices of the Royal Astronomical Society: Letters. The study provides a new theoretical underpinning for the unexplained breakdown of established techniques for measuring ages of stars past their middle age, and the transition of solar-like stars to a magnetically inactive future.

Astronomers have long known that stars experience a process known as ‘magnetic braking’: a steady stream of charged particles, known as the solar wind, escapes from the star over time, carrying away small amounts of the star’s angular momentum. This slow drain causes stars like our Sun to gradually slow down their rotation over billions of years.

In turn, the slower rotation leads to altered magnetic fields and less stellar activity – the numbers of sunspots, flares, outbursts, and similar phenomena in the atmospheres of stars, which are intrinsically linked to the strengths of their magnetic fields.

Bindesh Tripathi

This decrease in activity and rotation rate over time is expected to be smooth and predictable because of the gradual loss of angular momentum. The idea gave birth to the tool known as ‘stellar gyrochronology’, which has been widely used over the past two decades to estimate the age of a star from its rotation period.

However recent observations indicate that this intimate relationship breaks down around middle age. The new work, carried out by Bindesh Tripathi at UW–Madison and the Indian Institute of Science Education and Research (IISER) Kolkata, India, provides a novel explanation for this mysterious ailment. Prof. Dibyendu Nandy, and Prof. Soumitro Banerjee of IISER are co-authors.

Using dynamo models of magnetic field generation in stars, the team show that at about the age of the Sun the magnetic field generation mechanism of stars suddenly becomes sub-critical or less efficient. This allows stars to exist in two distinct activity states – a low activity mode and an active mode. A middle aged star like the Sun can often switch to the low activity mode resulting in drastically reduced angular momentum losses by magnetized stellar winds.

Prof. Nandy comments: “This hypothesis of sub-critical magnetic dynamos of solar-like stars provides a self-consistent, unifying physical basis for a diversity of solar-stellar phenomena, such as why stars beyond their midlife do not spin down as fast as in their youth, the breakdown of stellar gyrochronology relations, and recent findings suggesting that the Sun may be transitioning to a magnetically inactive future.”

The new work provides key insights into the existence of low activity episodes in the recent history of the Sun known as grand minima – when hardly any sunspots are seen. The best known of these is perhaps the Maunder Minimum around 1645 to 1715, when very few sunspots were observed.

The team hope that it will also shed light on recent observations indicating that the Sun is comparatively inactive, with crucial implications for the potential long-term future of our own stellar neighbor.

Welcome, incoming MSPQC students!

Posted on May 14, 2021

The UW–Madison Physics Department is pleased to welcome 18 students to the M.S. in Physics – Quantum Computing program. These students make up the third cohort to begin the program and are the largest entering class to date.

“We are really pleased and proud that the MSPQC program continues to grow and prosper in its third year,” says Bob Joynt, MSPQC Program Director and professor of physics. “We look forward to providing a great experience for the class of 2021. A particular focus this year will be the formation of collaborative teams that will push forward research in quantum computing.”

Of note, three women are in the entering class, marking the first time that women have enrolled in MSPQC. Other facts and figures about this year’s cohort include:

11 students are coming directly from completing their Bachelors
Three students have Master’s degrees

Six students have at least four years of professional experience, and four of those students have over 10 years professional experience
15 are international students, and seven of those students have attended U.S. institutions for previous studies
The students’ academic backgrounds include physics, astronomy, engineering, and business administration.

The department is following University guidelines and is planning for students to join us in Madison this fall, with in-person instruction. Over the summer, students can attend optional virtual orientation sessions to prepare for the program.

“The pandemic imposed restrictions on our admissions and recruitment activities which forced us to work virtually, but I believe these barriers made our programming more accessible and led to the most diverse and determined incoming cohort of MSPQC students to date,” says Jackson Kennedy, MSPQC coordinator. “Although I have been able to meet our incredibly talented students virtually, I cannot wait to greet them in-person this Fall as we celebrate a long-awaited return to campus.”

In addition to Joynt, the department thanks the other faculty who serve on the MSPQC admissions committee — Alex Levchenko, Robert McDermott, Maxim Vavilov and Deniz Yavuz — for application review. We also thank Michelle Holland and Jackson Kennedy for organizing recruiting efforts.

The MSPQC program welcomed its first students in Fall 2019 – the first-ever class of students in the U.S. to enroll in a quantum computing M.S. degree program. The accelerated program was born out of a recognized need to rapidly train students for the quantum computing workforce and is designed to be completed in 12 months. It provides students with a thorough grounding in the new discipline of quantum information and quantum computing.

names of students, UG institute and degree: Brooke Becker UW–Madison Computer Engineering Soyeon Choi Vanderbilt University Physics, Computer Science Manish Chowdhary Indian Institute of Technology Dhanbad Computer Application Hua Feng Dalian University of Technology Atomic and Molecular Physics Jacob Frederick University of Washington Computer Engineering Amol Gupta Delhi Technological University Computer Engineering Yucheng He Zhengzhou University Automation Xunyao Luo Lafayette College Physics and Neuroscience Arjun Puppala Indian Institute of Technology Roorkee Power Systems Engineering Evan Ritchie University of St Thomas - Minnesota Physics & Math Mubinjon Satymov New York City College of Technology - CUNY Applied Computational Physics Yen-An Shih National Cheng Kung University Computer Science Qianxu Wang University of Michigan Physics Jiaxi Xu UC-Berkeley Physics Anirudh Yadav Indian Institute of Technology Dhanbad Computer Science Yukun Yang Nanjing University Astronomy Jin Zhang UW–Madison Physics & Philosophy Lin Zhao UW–Madison Computer Science and Physics — The incoming 2021 class of MSPQC students

Flexible, easy-to-scale nanoribbons move graphene toward use in tech applications

Posted on May 3, 2021

greyscale scanning electron micrograph of graphene nanoribbons that looks like an intricate fingerprint. has also been described as a "zen garden"

From radio to television to the internet, telecommunications transmissions are simply information carried on light waves and converted to electrical signals.

Silicon-based fiber optics are currently the best structures for high-speed, long distance transmissions, but graphene — an all-carbon, ultra-thin and adaptable material — could improve performance even more.

In a study published April 16 in ACS Photonics, University of Wisconsin–Madison researchers fabricated graphene into the smallest ribbon structures to date using a method that makes scaling-up simple. In tests with these tiny ribbons, the scientists discovered they were closing in on the properties they needed to move graphene toward usefulness in telecommunications equipment.

“Previous research suggested that to be viable for telecommunication technologies, graphene would need to be structured prohibitively small over large areas, (which is) a fabrication nightmare,” says Joel Siegel, a UW–Madison graduate student in physics professor Victor Brar’s group and co-lead author of the study. “In our study, we created a scalable fabrication technique to make the smallest graphene ribbon structures yet and found that with modest further reductions in ribbon width, we can start getting to telecommunications range.”

For the full story, please visit: https://news.wisc.edu/flexible-easy-to-scale-nanoribbons-move-graphene-toward-use-in-tech-applications/

Searching for Sources of Gravitational Waves

Posted on May 3, 2021

The entire astrophysical world was blown away by the first-ever binary neutron star collision seen in August 2017 (called ‘GW170817’). This event, identified as a kilonova, was the first to be seen in both gravitational waves, by the LIGO and Virgo detectors, as well as the electromagnetic spectrum, from gamma rays to radio waves (and covered previously in this Oct 2017 DArchive ). Since then, there have been dozens of new gravitational wave events.

A group of researchers in DES, the DESGW team, have focused on finding more electromagnetic counterparts to these gravitational wave events. Members of the Dark Energy Survey — including University of Wisconsin–Madison physics grad student Rob Morgan and postdoc Ross Cawthon, both in Prof. Keith Bechtol’s group — look at two of the most intriguing events we have followed up with DECam since 2017.

For the full story, please visit The Dark Energy Survey post.

Introducing the Physics Ph.D. Class of 2021

Posted on April 20, 2021

After record-breaking application numbers and the most unique recruiting season yet, the Department of Physics is pleased to introduce the 30 students of the incoming Ph.D. class of 2021!

“This year’s incoming Ph.D. class is a remarkably strong and diverse cohort who have overcome truly historic obstacles to join us,” says Ph.D. admissions committee chair, Prof. Shimon Kolkowitz. “I couldn’t be more excited to welcome them to our department and to witness the great work they will accomplish in their time here.”

602 students applied for one of 91 admissions spots, the most applications the department has received in at least the past decade (based on available graduate school data).

Some highlights of the incoming class include:

Students coming from 18 U.S. states and three other countries (China, India, and Malaysia)
22 expressing a preference for experiment, with the rest expressing a preference for theory only, or either/undecided
Eight women
Three Advanced Opportunity Fellowship (AOF) eligible students
Two students who were named 2021 NSF Graduate Research Fellows

This year’s incoming class is also the first to ever participate in “Virtual Visit Days,” thanks to the COVID-19 pandemic. Though perhaps not as exciting as visiting campus in person, admitted students could still meet with faculty to discuss research opportunities, participate in discussions and virtual games nights with current students, and watch videos — many newly-created just for these visits — about the University, the city of Madison, and research in our department.

“Thank you to all the prospective students for their engagement and enthusiasm throughout the admissions and virtual visit process,” says Michelle Holland, graduate program coordinator. “We are beyond thrilled to welcome the Class of 2021 to the Physics Ph.D. Program at UW–Madison as we find our ‘new normal’ in being together on campus this fall.”  

The department would like to send a huge round of applause to everyone who participated in recruitment this year, especially current graduate students on the recruitment committee: Trevor Oxholm, Abigail Shearrow, Kunal Sanwalka, Susmita Mondal, Winnie Wang. We also thank graduate program coordinators Michelle Holland and Jackson Kennedy for organizing and running the virtual visit days, Dan Bradley for once again providing IT solutions to help the admissions process and visit days run smoothly, and Sarah Perdue for website development and video production.

The department also thanks the Ph.D. admissions committee for their thorough evaluation of the applicants. In addition to Kolkowitz, the committee members are Profs. Keith Bechtol, Stas Boldyrev, Victor Brar, Mark Eriksson, Ke Fang, and Jeff Parker.

One student accepted our admissions offer but has deferred to 2022.

Gage Bonner earns 2020 Teaching Award

Posted on March 30, 2021

Gage Bonner

Congrats to physics grad student Gage Bonner for earning a 2020 College of Letters & Sciences Continuation of Study teaching award!

This new award category recognizes graduate students in L&S who provided exceptional continuity of instruction support to their department or delivered exceptional student experience in a remote instructional setting during the COVID-19 pandemic.

Bonner was nominated for his work as a TA in Physics 109, Physics in the Arts, by one of the course’s instructors, Prof. Pupa Gilbert. Physics 109 is a quantitative-reasoning course offered to non-science majors, typically serving more than 200 students.

“The students are terrified of physics, and are not quantitative thinkers, thus it is especially important for Physics in the Arts TAs to be kind, friendly, and not intimidating,” Gilbert says. “Gage excels at all these challenges, and teaches masterfully. He is kind, intelligent, knowledgeable, and always in a good mood, making everyone feel comfortable and not intimidated.”

Gilbert nominated Bonner for the Continuation of Study award because of how effectively he adapted to the changes forced by the COVID-19 pandemic. For example, because in-person labs were no longer an option, Gilbert selected online labs, and asked the TAs to develop a series of interactive questions associated with each online experiment to help the students learn by doing. Bonner excelled at developing these questions. She also noted how well he interacts with students through the online Zoom lectures, helping to keep conversations going and being knowledgable, kind and effective with online instruction.

Based on course and TA evaluations, the students agree with Gilbert. Said one student in an evaluation:

“Gage has been a really awesome TA. He makes labs run so smoothly, responds to questions quickly and effectively, and reminds us [of] vital information. He was also super helpful in lectures. Letting the teachers know if there was a technical issue or question. He also made a really friendly and comfortable learning environment even with the restraints of BBC collaborate ultra.”

UW–Madison employs over 2,100 teaching assistants (TAs) across a wide range of disciplines. Their contributions to the classroom, lab, and field are essential to the university’s educational mission. To recognize the excellence of TAs across campus, the Graduate School supports the College of Letters & Science (L&S) in administering these awards.

Bonner has been a graduate student and TA in the department since Fall 2016.

Jimena González named Three Minute Thesis® finalist

Posted on November 23, 2020

Congrats to Jimena González, a physics graduate student in Keith Bechtol’s group, who is one of nine finalists for UW–Madison’s Three Minute Thesis® competition! Watch Jimena’s video on YouTube, and check out all nine finalists’ videos at the UW–Madison 3MT® website. The videos are only available through November 29. The finals will be held on February 3, 2021.