Eric Sembrat's Test Bonanza

Image: 

Ford Colloquium - Nature's Optics and Our Understanding of Light

Abstract

Optical phenomena visible to everyone abundantly illustrate important ideas in science and mathematics. The phenomena considered include rainbows, sparkling reflections on water, green flashes, earthlight on the moon, glories, daylight, crystals, and the squint moon. The concepts include refraction, wave interference, numerical experiments, asymptotics, Regge poles, polarization singularities, conical intersections, and visual illusions.

Special CRASI Seminar Series

Abstract 

Amphiphilic molecules have been harnessed by biology and engineering alike for their propensity to self-assemble into complex structures. In this, steric molecular-scale interactions dominate small aggregates, whilst emergent elasticity governs as objects grow to larger length-scales. 

Maelstroms in the Heart Confirmed

Thursday, February 22, 2018

Every two minutes in the U.S., a person dies of sudden cardiac arrest or fibrillation, the most common cause of death worldwide.

Doctors still do not fully understand exactly what goes on in the heart during a cardiac attack. Until now, it was impossible to visualize and characterize the dynamic processes in the fibrillating heart muscle. This week in Nature, an international team reports an imaging technique to observe the vortex-like, rotating contractions that underlie life-threatening ventricular fibrillation. The technique may enable early identification of heart rhythm disorders, better understanding of cardiac disease, and development of better treatments.

Led by Stefan Luther and Jan Christoph of the Max Planck Institute for Dynamics and Self-Organization (MPIDS), in Germany, the research team includes Flavio Fenton and Ilija Uzelac from the School of Physics at Georgia Institute of Technology.

Diagnostic breakthrough
When the heart muscle no longer contracts in a coordinated manner, but simply flutters or twitches – the condition referred to as “fibrillation” – it is a highly life-threatening situation. Medical intervention usually involves administering a strong electrical shock within a few minutes. High-energy defibrillation is excruciating and can be damaging to heart tissues.

“The key to a better understanding of fibrillation lies in a new, high-resolution imaging technique that allows processes inside the heart muscle to be observed,” Luther says.

“Until now, only surface recordings of complex fibrillation was possible,” Fenton says.

The team’s imaging method enables the fibrillating myocardium to be visually time-resolved in three dimensions. The imaging is much more accurate than previously possible and uses clinically available high-resolution ultrasound equipment.

Improved understanding of fibrillation enabled by the procedure could lead to alternative defibrillation techniques, also an area of research of Fenton’s and Luther’s. For example, researchers could improve the use of low-energy pulses to restore normal heart rhythm.

The technique could enable cardiologists to pinpoint the pathological foci of excitation. It may help in diagnosis and treatment of heart failure caused by fibrillation. It may allow doctors to detect heart failure earlier and treat it more effectively.

Electrical waves cause mechanical contractions of the heart
Every heartbeat is triggered by electrical waves of excitation that propagate through the myocardium at high speed, causing myocardial cells to contract. If these waves become turbulent, the result is cardiac arrhythmia.

In cardiac arrhythmias, rotational electrical waves of excitation swirl through the heart muscle. Investigations of cardiac arrhythmias have focused on such electrical vortices, but researchers have not been able to obtain a full picture of the dynamics.

The international team took a different approach. Instead of concentrating on electrical stimulation, they looked at the twitching contractions of the fibrillating myocardium. “Until now, little importance was attached to the analysis of muscle contractions and deformations during fibrillation,” Christoph says. “In our measurements, however, we saw that electric vortices are always accompanied by corresponding vortex-shaped mechanical deformations.”

Ventricular fibrillation in 3D
Using high-resolution measurements carried out with clinically available ultrasound equipment, the researchers visualized the trembling movements inside the heart muscle in three dimensions and correlated them with the electrical excitation of the heart.

By analyzing the image data of the muscle contractions, the researchers were able to observe exactly how areas of contracted and relaxed muscle cells move in a vortex through the myocardium during fibrillation.

They also observed filament-like structures that were previously known to physicists only in theory and from computer simulations. Such a filament-like structure resembles a thread and marks the eye of the whirlpool-like wave or cyclone moving through the myocardium. It is now possible for the first time to pinpoint these centers of the vortices inside the myocardium.

The researchers also used high-speed cameras and fluorescent markers to reveal the electrophysiological processes in the myocardium. The images confirmed that the mechanical vortices correspond very well with the electrical vortices. “In this study the correlation between electrical and mechanical vortex dynamics is assessed for the first time using a trimodal system that measures simultaneously and correlates the voltage and calcium waves with the contraction waves” Uzelac says.

From physics to medicine
The study is an example of successful interdisciplinary collaboration between physicists and doctors. "This revolutionary development will open up new treatment options for patients with cardiac arrhythmias,” says Gerd Hasenfuss, co-author of the study and chairman of the Göttingen Heart Research Center and the Heart Center at the University Medical Center Göttingen. “As early as 2018, we will use the new technology on our patients to better diagnose and treat cardiac arrhythmias and myocardial diseases.”

Media Contact: 

A. Maureen Rouhi, Ph.D.
Director of Communications
College of Sciences

Summary: 

This week in Nature, an international team reports an imaging technique to observe the vortex-like, rotating contractions that underlie life-threatening ventricular fibrillation. The technique may enable early identification of heart rhythm disorders, better understanding of cardiac disease, and development of better treatments.

Intro: 

This week in Nature, an international team reports an imaging technique to observe the vortex-like, rotating contractions that underlie life-threatening ventricular fibrillation. The technique may enable early identification of heart rhythm disorders, better understanding of cardiac disease, and development of better treatments.

Alumni: 

CRA Seminar

Abstract:

A number of ongoing surveys, such as Pan-STARRS, the Catalina Sky Survey, OSSOS, and NEOWISE, as well as planned surveys such as ZTF, LSST, and NEOCam, are designed to pursue goals ranging from constraining models of planet formation, through finding evidence of additional planets in our solar system, to fulfilling the US Congressional mandate to discover 90% of the potential hazardous asteroids with diameters exceeding 140m.

Quantum Materials Expertise at Georgia Tech

Friday, February 16, 2018

Researchers in Germany and Japan report preparing a compound that could realize a quantum spin liquid, a rarely observed and delicate state of magnetic matter. Published in the journal Nature, the paper – “A spin-orbital-entangled quantum liquid on a honeycomb lattice” – is cause for excitement among researchers in condensed-matter physics. Among them is Martin Mourigal, who wrote an accompanying News & Views piece in Nature – “The two faces of a magnetic honeycomb” – to put the research in context and convey the excitement of the field of quantum materials.

Mourigal is an assistant professor in the School of Physics. His research group studies magnetic phenomena in quantum materials. In these materials, the impact of quantum mechanics transcends the atomic scale to produce new effects up to the human scale.

“This field of research touches on the deep and profound organizing principles of the universe,” Mourigal says. “At the same time, it is an area where we can explore and test abstract theoretical ideas from a simple piece of ceramic grown in the lab.”

In the following Q&A, Mourigal explains quantum spin liquids, why the recent findings of the research team led by Hidenori Takagi are noteworthy, and the role Georgia Tech can play in quantum materials research.

What is exciting about quantum spin liquids?
They are new forms of matter, predicted to exist in some quantum materials at temperatures close to zero degree Kelvin.

Spins are atomic-scale magnetic moments that make up any magnetic material. In ferromagnets – think refrigerator magnets – the spins are frozen in a periodic pattern.

In quantum spin liquids, spins do not freeze and keep dancing even at close to absolute zero temperature. As spins fluctuate, they share the same quantum state, and their collective behavior cannot be represented by the sum of individual behaviors. This phenomenon is called quantum entanglement.

Entanglement leads to physical properties that make quantum spin liquids appealing for both fundamental inquiries and practical purposes. Entanglement is required for quantum computers to work; it may also be used to create new electronic devices and technologies for the post-Moore’s law era.

Most importantly, quantum spin liquids quench our thirst for fundamental discoveries about matter. In particular, understanding the relationship between atomic-scale properties and macroscopic behavior is a central challenge. Quantum mechanics complicates the picture, primarily because of entanglement.

What is the breakthrough reported by the researchers in Nature?
Quantum spin liquids are notoriously difficult to realize in real materials, and their confirmation involves many steps.

The group led by Takagi started from a magnetically ordered material – a well-researched iridium oxide with a honeycomb structure – known to host an important ingredient of the quantum spin liquid recipe.

That ingredient is called Kitaev interactions. Usually, spins interact with neighbors in a simple way: they align in the same or the opposite direction. Kitaev interactions are different. Each spin is getting contradictory information from its neighbors and cannot decide what to do. Because spins cannot pick a preferred direction, they remain fluctuating all the way to absolute zero temperature.

The researchers applied a soft chemistry approach to modify the original iridium oxide, heating it to 120 degrees Celsius. In solid-state synthesis, reagents are usually heated to around 1,000 degrees Celsius to make a new compound.

Despite the mild conditions, the researchers got a dramatic change in the material’s physical properties, sufficient to produce a strong contender for a quantum spin liquid. More generally, it means it is possible to realize exotic states of matter through gentle modifications of existing materials.

How did the researchers show that the new material could be a quantum spin liquid?
It is not fully confirmed that the new material is a quantum spin liquid, but it passed a first battery of tests, which included nuclear magnetic resonance and heat capacity measurements. These tests showed that the spins remain fluctuating at 1 degree Kelvin and that no magnetic order is present at 0.05 degree Kelvin, which is very exciting.

Nevertheless, more investigations are required. The challenge for the researchers is to further characterize the spin dynamics in the new material. Progress in materials research usually comes from the confluence of different experimental techniques and expertise, and I expect this new material will generate a lot of interest in that direction.

What is Georgia Tech doing about quantum materials?
Quantum materials research is on the rise at Georgia Tech. Understanding and controlling quantum states of matter is a priority for the U.S. We have a lot of talent on campus to make an impact in that burgeoning area.

First, there is strong intellectual overlap between quantum materials research and the fields of atomic physics, quantum optics, and quantum information sciences. In all these fields, a profound understanding of quantum mechanics and entanglement is central.

Furthermore, quantum materials research cuts across all material-centric disciplines on campus: from the chemistry, synthesis, and characterization of new materials to their integration in devices for new electronics.

Finally, and close to my own research, Georgia Tech is ideally located to utilize the world-class neutron-scattering facilities at Oak Ridge National Laboratory. Because neutrons themselves carry a spin, they can scatter off the excitations of magnetic materials and are thus an ideal probe of quantum spin liquids and other magnetic quantum materials.

Media Contact: 

A. Maureen Rouhi, Ph.D.
Director of Communications
College of Sciences

Summary: 

Researchers in Germany and Japan report preparing a compound that could realize a quantum spin liquid, a rarely observed and delicate state of magnetic matter. Published in the journal Nature, the paper is cause for excitement among researchers in condensed-matter physics. Among them is Martin Mourigal, who wrote an accompanying News & Views piece in Nature to put the research in context and convey the excitement of the field of quantum materials.

Intro: 

Researchers in Germany and Japan report preparing a compound that could realize a quantum spin liquid, a rarely observed and delicate state of magnetic matter. Published in the journal Nature, the paper is cause for excitement among researchers in condensed-matter physics. Among them is Martin Mourigal, who wrote an accompanying News & Views piece in Nature to put the research in context and convey the excitement of the field of quantum materials.

Alumni: 

Non-Monochromatic Wrinkles

 Abstract

The frustration that stems from Gauss’ Theorema Egregium is familiar to anybody who attempted to wrap a ball with a paper. This fundamental theorem states that one cannot change Gaussian curvature of a surface without straining it. Thin sheets, however, are nearly inextensible and do not tolerate stress. Often, they accommodate geometrically incompatible confinement by wrinkling.

Pages

Subscribe to RSS - Eric Sembrat's Test Bonanza