Do You Know The Minimum Dark Matter Evaporation Mass For Celestial Objects? (Cosmology / Astronomy)

The possibility of capture of dark matter (DM) particles by celestial bodies has a long history dating back to the mid 1980s. Already in the late 1970s, some of the potential effects of DM annihilations and scatterings on energy transport within the Sun were realized and then further proposed to alleviate the so-called solar neutrino problem. Nevertheless, these early works did not consider the process of DM capture, but assumed the required amount of accumulated DM particles. The process of capture of galactic DM particles by the Sun and the Earth was first studied by Gould and colleagues, which set the ground of further calculations. After that, it has been studied for other celestial bodies, such as, other solar system planets and satellites, exoplanets, brown dwarfs, main-sequence and post-main sequence stars, and compact objects such as white dwarfs and neutron stars.

The scattering of DM particles in galactic halos with the nuclei (or electrons) of celestial objects could bring those particles into close orbits and finally result in their gravitational capture within the objects. Nevertheless, the finite temperature of the medium sets a minimum mass, the evaporation mass, that DM particles must have in order to remain trapped. DM particles below this mass are very likely to scatter to speeds higher than the escape velocity, so they would be kicked out of the capturing object and escape.

Now, Garani and Sergio, computed the DM evaporation mass for a wide range of celestial bodies, from the smallest objects with spherical shape that can be in hydrostatic equilibrium (small satellites), M ≃ 10¯10 M, to the most massive main-sequence stars, M ≃ 100 M. They also discussed the DM evaporation mass for post-main sequence stars, white dwarfs and neutron stars. In addition, they considered a range of DM-nucleon scattering cross sections that covers ten decades, 10¯41 cm² ≤ σp ≤ 10¯31 cm², and which runs over the thin and thick regimes. Their study recently appeared on journal Arxiv.

For planetary bodies, brown dwarfs and main-sequence stars, spanning the mass range is 10¯10 M ≤ M ≤ 10² M, they obtained that for a wide range of DM-nucleon cross sections, 10¯41 cm² ≤ σp ≤ 10¯31 cm², the absolute minimum for the DM evaporation mass is mevap ≃ 350 MeV. This minimum value is obtained for the largest cross section they considered and for super-Jupiters and low-mass brown dwarfs. For very compact objects, such as white dwarfs and neutron stars, smaller DM evaporation masses are found, with values as low as mevap ≃ 1 MeV and mevap ≃ 1 keV, respectively.

© Garani and Sergio

They have also discussed the critical importance of the exponential tail of the DM evaporation rate (Fig. 1), which had already been studied for the case of the Sun, although its importance has not always been appreciated. These early papers obtained a DM evaporation mass for the Sun which is approximately given by Ec/Tχ ≃ 30, where Ec is the escape energy at the core of captured DM particles and Tχ is their temperature. Similar values are found for the DM evaporation masses obtained for the Earth and the Moon. This estimate approximately corresponds to the geometric cross section,

Here, they generalize this result for all round celestial bodies in hydrostatic equilibrium. The virial theorem is at the core of this finding.

In addition, they have also studied the dependence with other parameters, as the position of the celestial body in the galactic halo (DM density and velocity), the DM annihilation cross section, and the type of interaction (SI and SD). The DM evaporation mass, however, depends only logarithmically on these parameters, so its value is rather stable against variations of them.

© Garani and Sergio

For the geometric value of the scattering cross section, they obtained the minimum value of the DM evaporation mass for super-Jupiters and low-mass brown dwarfs (Fig. 2), mevap ≃ 0.7 GeV. According to Garani and Sergio, the fact that, these objects are optimal sites to search for effects of capture of light DM particles has been pointed out recently in many papers. Nevertheless, those papers neglected the crucial exponential tail of the evaporation rate and estimated a DM evaporation mass as low as ∼ 4.5 MeV, which represents an underestimation of the correct result by two orders of magnitude. Similarly, a too low DM evaporation mass for planets has also been suggested using similar arguments. Therefore, they argued that the conclusions reached in those papers for masses below the correct DM evaporation mass are not valid.

Finally, they stressed again, the general and robust result they obtained: for the geometric cross section, the DM evaporation mass for all spherical celestial bodies in hydrostatic equilibrium is approximately given by the simple expression Ec/Tχ ∼ 30, which provides the correct result within ≲ 30% in the mass range 10¯10 M ≤ M ≤ 10² M and in the SI scattering cross section range 10¯41 cm² ≤ σp ≤ 10¯31 cm². The dependence on the local galactic DM density, velocity, and on the scattering and annihilation cross sections is only logarithmic.


Reference: Raghuveer Garani, Sergio Palomares-Ruiz, “Evaporation of dark matter from celestial bodies”, Arxiv, pp. 1-31, 2021. https://arxiv.org/abs/2104.12757


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‘Campfires’ Offer Clue To Solar Heating Mystery (Planetary Science)

Computer simulations show that the miniature solar flares nicknamed ‘campfires’, discovered last year by ESA’s Solar Orbiter, are likely driven by a process that may contribute significantly to the heating of the Sun’s outer atmosphere, or corona. If confirmed by further observations this adds a key piece to the puzzle of what heats the solar corona – one of the biggest mysteries in solar physics.

Campfires are one of many subjects being discussed in a dedicated Solar Orbiter first results session at the European Geosciences Union (EGU) General Assembly today.

Anatomy of the Sun
Anatomy of the Sun © ESA

Mystery heating

The Sun has a mysterious feature: somehow the tenuous outer atmosphere contains gas with a temperature of a million degrees, yet the solar surface is just 5500°C. Logic would suggest that if you have a body that is very hot at the centre and relatively cool on the surface, it should be even cooler the further you go away. But the peculiar thing about the corona of the Sun – and many other stars as well – is that it starts to heat up the further you move above the surface. Many ideas have been put forward over the last decades homing in on the Sun’s magnetic field, but how the energy is generated, transported and dissipated has been a source of much debate.

Enter Solar Orbiter, with one of its key goals to probe deeper into this mystery.  

Stunning detail already provided by Solar Orbiter’s Extreme Ultraviolet Imager (EUI) ‘first light’ images  just months after launch last year and since then has revealed more than 1500 small, flickering brightenings nicknamed campfires. These short-lived campfires last for between 10 and 200 seconds, and have a footprint covering between 400 and 4000 km. The smallest and weakest events, which had not been observed before, seem to be the most abundant, and represent a previously unseen fine structure of the region where the heating mystery is suspected to be rooted. 

Model campfires

Yajie Chen, a PhD student from Peking University in China, working with Professor Hardi Peter from the Max Planck Institute for Solar System Research in Germany and colleagues, used a computer model to dive into the physics of the campfires, with exciting first results.

Modelling campfire magnetic fields © ESA

“Our model calculates the emission, or energy, from the Sun as you would expect a real instrument to measure,” explains Hardi. “The model generated brightenings just like the campfires. Furthermore, it traces out the magnetic field lines, allowing us to see the changes of the magnetic field in and around the brightening events over time, telling us that a process called component reconnection seems to be at work.”

Reconnection is a well-known phenomenon whereby magnetic field lines of opposite direction break and then reconnect, releasing energy when they do so. Typical reconnection happens between field lines pointing in opposite directions, but with so-called component reconnection the field lines are almost parallel, pointing in a similar direction, with reconnection therefore happening at very small angles.

“Our model shows that the energy released from the brightenings through component reconnection could be enough to maintain the temperature of the solar corona predicted from observations,” says Yajie.

Video: Evolution of a solar campfire © ESA

“In one of our case studies, we find that the untwisting of a flux rope [helical magnetic field lines winding around a common axis] initiates the heating instead,” adds Hardi. “It’s exciting to find these variations, and we’re looking forward to see what further insights our models bring to help us improve our theories on the processes behind the heating.”

The team cautions that it’s very early days. They have used the model to look at seven of the brightest events generated in their simulation, which likely correspond to the largest campfires observed by EUI. Key to advancing the study will be joint observations between EUI and the spacecraft’s Polarimetric and Helioseismic Imager (PHI) and Spectral Imaging of the Coronal Environment (SPICE) spectrograph once Solar Orbiter’s full science mission gets going in November. PHI will reveal the magnetic field of the Sun and how it changes on the surface, while SPICE will measure the temperature and density of the corona.

Teamwork

Further insight into the campfires has also been enabled by pairing up with NASA’s Solar Dynamics Observatory, which is in orbit around the Earth, to triangulate the height of the campfires in the solar atmosphere.

“To our surprise, campfires are located very low in the solar atmosphere, only a few thousand kilometres above the solar surface, the photosphere,” says David Berghmans, Principal Investigator of EUI. “It is very early days, and we are still learning a lot about the campfire characteristics. For example, even though campfires look like small coronal loops, their length is on average a bit short for their height, suggesting we only see part of these little loops. But our preliminary analysis also shows that campfires do not really change their height during their lifetime, setting them aside from jet-like features.”

Understanding the characteristics of the campfires and their place amongst other known solar phenomena will enable scientists to dive deeper into the solar corona heating problem.

What do we know about solar campfires so far?
What do we know about solar campfires so far? © ESA

“How fantastic to already have such promising data that may provide insight into one of solar physics’ greatest mysteries before Solar Orbiter has even begun its nominal science phase,” says ESA’s Solar Orbiter Project Scientist Daniel Müller. “Our mission is lucky to be building on the incredible ground-work of those that have flown before, and the theories and models already put forward over the last decades. We’re looking forward to see what missing details Solar Orbiter – and the solar community working with our data – will contribute to solving open questions in this exciting field.”

Solar Orbiter is currently in ‘cruise phase’, focused primarily on instrument calibration, and will begin coordinated observations between its suite of ten remote sensing and in situ instruments from November this year.

Solar Orbiter is a space mission of international collaboration between ESA and NASA.


Notes for editors

The results were discussed at EGU today and are linked to the following publications:

(1) “Transient small-scale brightenings in the quiet solar corona: a model for campfires observed with Solar Orbiter” by Y. Chen et al, accepted for publication in Astronomy and Astrophysics. (2) “Extreme UV quiet Sun brightenings observed by Solar Orbiter/EUI” by D. Berghmans et al, accepted for publication in Astronomy and Astrophysics (3) “Stereoscopy of extreme UV quiet Sun brightenings observed by Solar Orbiter/EUI” by A. Zhukov et al, submitted to Astronomy and Astrophysics. (4) The computer simulations described in this story were conducted at the Max Planck Computing and Data Facility (MPCDF) in Garching, Germany.


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Scientists Discover the Farthest Gamma-ray Emitting Active Galaxy With Narrow Emission Lines (Astronomy)

Astronomers have discovered a new active galaxy identified as the farthest gamma-ray emitting galaxy that has so far been stumbled upon. This active galaxy called the Narrow-Line Seyfert 1 (NLS1) galaxy, which is about 31 billion light-years away, opens up avenues to explore more such gamma-ray emitting galaxies that wait to meet us.

Ever since 1929, when Edwin Hubble discovered that the Universe is expanding, it has been known that most other galaxies are moving away from us. Light from these galaxies is shifted to longer (and this means redder) wavelengths – in other words, it is red-shifted. Scientists have been trying to trace such red-shifted galaxies to understand the early Universe.

Scientists from ARIES, an autonomous institute of the Department of Science & Technology (DST), Government of India, in collaboration with researchers from other institutions, studied around 25,000 luminous Active galactic nuclei (AGN) from the Sloan Digital Sky Survey (SDSS), a major optical imaging and spectroscopic survey of astronomical objects in-operation for the last 20 years and found a unique object that emits high-energy gamma rays located at a high redshift (more than 1). They identified it as a gamma-ray emitting NLS1 galaxy, which is a rare entity in space.

Powerful relativistic jets, or sources of particles in the Universe traveling nearly at speed to light, are usually produced by AGN powered by large black holes and hosted in a giant elliptical galaxy. However, detection of gamma-ray emission from NLS1 challenges the idea of how relativistic jets are formed because NLS1s are a unique class of AGN that are powered by black hole of low mass and hosted in spiral galaxy. As of today, gamma-ray emission has been detected in about a dozen NLS1 galaxies, which are a separate class of AGN identified four decades ago. All of them are at redshifts lesser than one, and no method was present till date to find NLS1 at redshifts larger than one. This discovery opens up a new way to find gamma-ray emitting NLS1 galaxies in the early Universe.

For the research, the scientists used one of the largest ground-based telescopes in the world, the 8.2 m Subaru Telescope located at Hawaii, USA. They helped establish a new method to find high redshift NLS1 galaxies that were not known previously by comparing different emission lines in their spectra. The new gamma-ray emitting NLS1 was formed when the Universe was only about 4.7 billion years old as compared to its current age of about 13.8 billion years.

The research led by Dr. Suvendu Rakshit, Scientist, ARIES, in collaboration with various scientists Malte Schramm (Japan), C. S. Stalin (IIA, India), I. Tanaka (USA), Vaidehi S. Paliya (ARIES), Indrani Pal (IIA, India), Jari Kotilainen (Finland) and Jaejin Shin (South Korea) has recently been accepted for publication in the journal Monthly Notices of Royal Astronomical Society. Motivated by this finding, Dr. Rakshit and his collaborators are keen to exploit the capabilities offered by the TIFR-ARIES Near-Infrared Spectrometer on the recently commissioned 3.6 m Devasthal Optical Telescope (DOT) at ARIES to find more such gamma-ray emitting NLS1 galaxies at much larger redshifts.

Featured image credit: Rakshit et al.


Publication links: Suvendu Rakshit, Malte Schramm, C S Stalin, I Tanaka, Vaidehi S Paliya, Indrani Pal, Jari Kotilainen, Jaejin Shin, TXS 1206 + 549: a new γ-ray-detected narrow-line Seyfert 1 galaxy at redshift 1.34?, Monthly Notices of the Royal Astronomical Society: Letters, Volume 504, Issue 1, June 2021, Pages L22–L27, DOI: https://doi.org/10.1093/mnrasl/slab031
arXiv: https://arxiv.org/abs/2103.16521


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Astronomers Detect New Chemical Signature in an Exoplanet’s Atmosphere using Subaru Telescope (Planetary Science)

An international collaboration of astronomers led by a researcher from the Astrobiology Center and Queen’s University Belfast has detected a new chemical signature in the atmosphere of an extrasolar planet – i.e., a planet that orbits a star other than our Sun. The hydroxyl radical (OH) was found on the dayside of the exoplanet WASP-33b. This planet is a so-called ‘ultra-hot Jupiter’, a gas-giant planet orbiting its host star much closer than Mercury orbits the Sun (Figure 1) and therefore reaching atmospheric temperatures of more than 2500 degrees C (hot enough to melt most metals). The lead researcher based at the Astrobiology Center and Queen’s University Belfast, Dr. Stevanus Nugroho, says, “This is the first direct evidence of OH in the atmosphere of a planet beyond the Solar System. It shows not only that astronomers can detect this molecule in exoplanet atmospheres, but also that they can begin to understand the detailed chemistry of this planetary population.”

In the Earth’s atmosphere, OH is mainly produced by the reaction of water vapor with atomic oxygen. It is a so-called ‘atmospheric detergent’ and plays a crucial role in the Earth’s atmosphere to purge pollutant gasses that are dangerous to life (e.g. methane, carbon monoxide). In a much hotter and bigger planet like WASP-33b (Figure 2, where astronomers have previously detected signs of iron and titanium oxide gas) OH plays a key role in determining the chemistry of the atmosphere through interactions with water vapor and carbon monoxide. Most of the OH in the atmosphere of WASP-33b is thought to have been produced by the destruction of water vapor due to the extremely high temperature. “We see only a tentative and weak signal from water vapor in our data, which would support the idea that water is being destroyed to form hydroxyl in this extreme environment.” explains Dr. Ernst de Mooij from Queen’s University Belfast, a co-author on this study.zoom

Astronomers Detect New Chemical Signature in an Exoplanet's Atmosphere using Subaru Telescope Figure2
Figure 2: Artist’s impression of an ‘ultra-hot Jupiter’ exoplanet, WASP-33b. (Credit: Astrobiology Center)

To make this discovery, the team used the InfraRed Doppler (IRD) instrument at the 8.2-meter diameter Subaru Telescope located in the summit area of Maunakea in Hawai`i (about 4,200 m above sea level). This new instrument can detect atoms and molecules through their ‘spectral fingerprints,’ unique sets of dark absorption features superimposed on the rainbow of colors (or spectrum) that is emitted by stars and planets. As the planet orbits its host star, its velocity relative to the Earth changes with time. Just like the siren of an ambulance or the roar of a racing car’s engine seems to changes pitch while speeding past us, the frequencies of light (i.e. color) of these spectral fingerprints change with the velocity of the planet. This allows us to separate the planet’s signal from its bright host star, which normally overwhelms such observations, despite modern telescopes being nowhere near powerful enough to take direct images of such ‘hot Jupiter’ exoplanets.

“The science of extrasolar planets is relatively new, and a key goal of modern astronomy is to explore these planets’ atmospheres in detail and eventually to search for ‘Earth-like’ exoplanets – planets similar to our own. Every new atmospheric species discovered further improves our understanding of exoplanets and the techniques required to study their atmospheres, and takes us closer to this goal” says Dr. Neale Gibson, assistant professor at Trinity College Dublin and co-author of this work. By taking advantage of the unique capabilities of IRD, the astronomers were able to detect the tiny signal from hydroxyl in the planet’s atmosphere. “IRD is the best instrument to study the atmosphere of an exoplanet in the infrared,” adds Prof. Motohide Tamura, one of the principal investigators of IRD, Director of the Astrobiology Center, and co-author of this work.

“These techniques for atmospheric characterization of exoplanets are still only applicable to very hot planets, but we would like to further develop instruments and techniques that enable us to apply these methods to cooler planets, and ultimately, to a second Earth,” says Dr. Hajime Kawahara, assistant professor at the University of Tokyo and co-author of this work.

Prof. Chris Watson (QUB) from Queen’s University Belfast, a co-author on this study, continues, “While WASP-33b may be a giant planet, these observations are the testbed for the next-generation facilities like the Thirty Meter Telescope and the European Extremely Large Telescope in searching for biosignatures on smaller and potentially rocky worlds, which might provide hints to one of the oldest questions of humankind, ‘Are we alone?'”


These results were published in the Astrophysical Journal Letters on March 23, 2021 (Nugroho et al. 2021, “First Detection of Hydroxyl Radical Emission from an Exoplanet Atmosphere: High-dispersion Characterization of WASP-33b Using Subaru/IRD“).

Featured image: Comparison of our Solar System (top) and the WASP-33 planetary system (bottom). The distances of planets in the Solar System are not to scale. WASP-33b is much closer to its host star than Mercury is to the Sun; it has a high temperature of 2500 degrees Celsius due to extreme radiation from its host star. One side of WASP-33b is constantly facing toward its host star, similar to how the same side of the Moon always faces the Earth. (Credit: WP, CC BY-SA 3.0Wikimedia Commons (top), Astrobiology Center (bottom))


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The Science of Sound, Vibration to Better Diagnose, Treat Brain Diseases (Neuroscience)

Multidisciplinary Researchers Uncover New Ways to Use Ultrasound Energy to Image and Treat Hard-to-reach Areas of Brain

A team of engineering researchers at the Georgia Institute of Technology hopes to uncover new ways to diagnose and treat brain ailments, from tumors and stroke to Parkinson’s disease, leveraging vibrations and ultrasound waves. 

The five-year, $2 million National Science Foundation (NSF) project initiated in 2019 already has resulted in several published journal articles that offer promising new methods to focus ultrasound waves through the skull, which could lead to broader use of ultrasound imaging — considered safer and less expensive than magnetic resonance imaging (MRI) technology.  

Specifically, the team is researching a broad range of frequencies, spanning low frequency vibrations (audio frequency range) and moderate frequency guided waves (100 kHz to 1 MHz) to high frequencies employed in brain imaging and therapy (in the MHz range).

“We’re coming up with a unique framework that incorporates different research perspectives to address how you use sound and vibration to treat and diagnose brain diseases,” explained Costas Arvanitis, an assistant professor in Georgia Tech’s George W. Woodruff School of Mechanical Engineering and the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. “Each researcher is bringing their own expertise to explore how vibrations and waves across a range of frequencies could either extract information from the brain or focus energy on the brain.”

Accessing the Brain Is a Tough Challenge

While it is possible to treat some tumors and other brain diseases non-invasively if they are near the center of the brain, many other conditions are harder to access, the researchers say. 

“The center part of the brain is most accessible; however, even if you are able to target the part of the brain away from the center, you still have to go through the skull,” Arvanitis said.

He added that moving just 1 millimeter in the brain constitutes “a huge distance” from a diagnostic perspective. The science community widely acknowledges the brain’s complexity, each part associated with a different function and brain cells differing from one to the other.  

According to Brooks Lindsey, a biomedical engineering assistant professor at Georgia Tech and Emory, there is a reason why brain imaging or therapy works well in some people but not in others. 


“It depends on the individual patient’s skull characteristics,” he said, noting that some people have slightly more trabecular bone ? the spongy, porous part of the bone ? that makes it more difficult to treat. 

Using ultrasound waves, the researchers are tackling the challenge on multiple levels. Lindsey’s lab uses ultrasound imaging to assess skull properties for effective imaging and therapy. He said his team conducted the first investigation that uses ultrasound imaging to measure the effects of bone microstructure — specifically, the degree of porosity in the inner, trabecular bone layer of the skull.

“By understanding transmission of acoustic waves through microstructure in an individual’s skull, non-invasive ultrasound imaging of the brain and delivery of therapy could be possible in a greater number of people,” he said, explaining one potential application would be to image blood flow in the brain following a stroke.

Refocusing Ultrasound Beams on the Fly   

Arvanitis’ lab recently found a new way to focus ultrasound through the skull and into the brain, which is “100-fold faster than any other method,” Arvanitis said. His team’s work in adaptive focusing techniques would allow clinicians to adjust the ultrasound on the fly to focus it better.

Georgia Tech researchers align the electrodynamic exciter and Laser Doppler Vibrometer setup for vibration experiments. (Photo credit: Allison Carter, Georgia Tech)

“Current systems rely a lot on MRIs, which are big, bulky, and extremely expensive,” he said. “This method lets you adapt and refocus the beam. In the future this could allow us to design less costly, simpler systems, which would make the technology available to a wider population, as well as be able to treat different parts of the brain.”

Using ‘Guided Waves’ to Access Periphery Brain Areas

Another research cohort, led by Alper Erturk, Woodruff Professor of Mechanical Engineering at Georgia Tech, and former Georgia Tech colleague Massimo Ruzzene, Slade Professor of Mechanical Engineering at the University of Colorado Boulder, performs high-fidelity modeling of skull bone mechanics along with vibration-based elastic parameter identification. They also leverage guided ultrasonic waves in the skull to expand the treatment envelope in the brain. Erturk and Ruzzene are mechanical engineers by background, which makes their exploration of vibrations and guided waves in difficult-to-reach brain areas especially fascinating. 


Erturk noted that guided waves are used in other applications such as aerospace and civil structures for damage detection. “Accurate modeling of the complex bone geometry and microstructure, combined with rigorous experiments for parameter identification, is crucial for a fundamental understanding to expand the accessible region of the brain,” he said. 

Ruzzene compared the brain and skull to the Earth’s core and crust, with the cranial guided waves acting as an earthquake. Just as geophysicists use earthquake data on the Earth’s surface to understand the Earth’s core, so are Erturk and Ruzzene using the guided waves to generate tiny, high frequency “earthquakes” on the external surface of the skull to characterize what comprises the cranial bone.

Trying to access the brain periphery via conventional ultrasound poses added risks from the skull heating up. Fortunately, advances such as cranial leaky Lamb waves increasingly are recognized for transmitting wave energy to that region of the brain.

These cranial guided waves could complement focused ultrasound applications to monitor changes in the cranial bone marrow from health disorders, or to efficiently transmit acoustic signals through the skull barrier, which could help access metastases and treat neurological conditions in currently inaccessible regions of the brain.

(L to R)  Multidisciplinary researchers Alper Erturk, Costas Arvanitis and Brooks Lindsey hope their work will make full brain imaging feasible while stimulating new medical imaging and therapy techniques. (Photo credit: Allison Carter, Georgia Tech)

Ultimately, the four researchers hope their work will make full brain imaging feasible while stimulating new medical imaging and therapy techniques. In addition to transforming diagnosis and treatment of brain diseases, the techniques could better detect traumas and skull-related defects, map the brain function, and enable neurostimulation. Researchers also see the potential for uncovering ultrasound-based blood-brain barrier openings for drug delivery for managing and treating diseases such as Alzheimer’s.

With this comprehensive research of the skull-brain system, and by understanding the fundamentals of transcranial ultrasound, the team hopes to make it more available to even more diseases and target many parts of the brain. 

This work is funded by the National Science Foundation (CMMI Award 1933158 “Coupling Skull-Brain Vibroacoustics and Ultrasound Toward Enhanced Imaging, Diagnosis, and Therapy”). 

Featured image: Graduate research assistants Eetu Kohtanen and Pradosh Dash and postdoctoral researchers Christopher Sugino and Bowen Jing test a human skull to measure and characterize its vibration response. (Photo credit: Allison Carter, Georgia Tech)


References: (1) C. Sugino, M. Ruzzene, and A. Erturk, “Experimental and Computational Investigation of Guided Waves in a Human Skull.” (Ultrasound in Medicine and Biology, 2021) https://doi.org/10.1016/j.ultrasmedbio.2020.11.019 (2) M. Mazzotti, E. Kohtanen, A. Erturk, and M. Ruzzene, “Radiation Characteristics of Cranial Leaky Lamb Waves.” (IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 2021) https://doi.org/10.1109/TUFFC.2021.3057309 (3) S. Schoen, C. Arvanitis, “Heterogeneous Angular Spectrum Method for Trans-Skull Imaging and Focusing.” (IEEE Xplore, 2020) https://ieeexplore.ieee.org/document/8902167  (4) B. Jing, C. Arvanitis, B. Lindsey, “Effect of Incidence Angle and Wave Mode Conversion on Transcranial Ultrafast Doppler Imaging.” (IEEE Xplore, 2020)   https://ieeexplore.ieee.org/document/9251477 


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University of Chicago Scientists Design “Nanotraps” to Catch, Clear Coronavirus (Medicine)

Potential COVID-19 treatment pairs nanoparticles with human immune system to search and destroy viruses

Researchers at the Pritzker School of Molecular Engineering (PME) at the University of Chicago have designed a completely novel potential treatment for COVID-19: nanoparticles that capture SARS-CoV-2 viruses within the body and then use the body’s own immune system to destroy it.

These “Nanotraps” attract the virus by mimicking the target cells the virus infects. When the virus binds to the Nanotraps, the traps then sequester the virus from other cells and target it for destruction by the immune system.

In theory, these Nanotraps could also be used on variants of the virus, leading to a potential new way to inhibit the virus going forward. Though the therapy remains in early stages of testing, the researchers envision it could be administered via a nasal spray as a treatment for COVID-19.

The results were published April 19 in the journal Matter.

“Since the pandemic began, our research team has been developing this new way to treat COVID-19,” said Asst. Prof. Jun Huang, whose lab led the research. “We have done rigorous testing to prove that these Nanotraps work, and we are excited about their potential.”

Designing the perfect trap

To design the Nanotrap, the research team – led by postdoctoral scholar Min Chen and graduate student Jill Rosenberg – looked into the mechanism SARS-CoV-2 uses to bind to cells: a spike-like protein on its surface that binds to a human cell’s ACE2 receptor protein.

To create a trap that would bind to the virus in the same way, they designed nanoparticles with a high density of ACE2 proteins on their surface. Similarly, they designed other nanoparticles with neutralizing antibodies on their surfaces. (These antibodies are created inside the body when someone is infected and are designed to latch onto the coronavirus in various ways).

Both ACE2 proteins and neutralizing antibodies have been used in treatments for COVID-19, but by attaching them to nanoparticles, the researchers created an even more robust system for trapping and eliminating the virus.

Scanning electron microscope (SEM) image of Nanotrap (orange) binding pseudotyped SARS-CoV-2 virus (cyan). © Huang Lab

Made of FDA-approved polymers and phospholipids, the nanoparticles are about 500 nanometers in diameter – much smaller than a cell. That means the Nanotraps can reach more areas inside the body and more effectively trap the virus.

The researchers tested the safety of the system in a mouse model and found no toxicity. They then tested the Nanotraps against a pseudovirus – a less potent model of a virus that doesn’t replicate – in human lung cells in tissue culture plates and found that they completely blocked entry into the cells.

Once the pseudovirus bound itself to the nanoparticle – which in tests took about 10 minutes after injection – the nanoparticles used a molecule that calls the body’s macrophages to engulf and degrade the Nanotrap. Macrophages will generally eat nanoparticles within the body, but the Nanotrap molecule speeds up the process. The nanoparticles were cleared and degraded within 48 hours.

The researchers also tested the nanoparticles with a pseudovirus in an ex vivo lung perfusion system – a pair of donated lungs that is kept alive with a ventilator – and found that they completely blocked infection in the lungs.

They also collaborated with researchers at Argonne National Laboratory to test the Nanotraps with a live virus (rather than a pseudovirus) in an in vitro system. They found that their system inhibited the virus 10 times better than neutralizing antibodies or soluble ACE2 alone.

A potential future treatment for COVID-19 and beyond

Next the researchers hope to further test the system, including more tests with a live virus and on the many virus variants.

“That’s what is so powerful about this Nanotrap,” Rosenberg said. “It’s easily modulated. We can switch out different antibodies or proteins or target different immune cells, based on what we need with new variants.”

The Nanotraps can be stored in a standard freezer and could ultimately be given via an intranasal spray, which would place them directly in the respiratory system and make them most effective.

The researchers say it is also possible to serve as a vaccine by optimizing the Nanotrap formulation, creating an ultimate therapeutic system for the virus.

“This is the starting point,” Huang said. “We want to do something to help the world.”

The research involved collaborators across departments, including chemistry, biology, and medicine.

Other authors on the paper include Xiaolei Cai, Andy Chao Hsuan Lee, Jiuyun Shi, Mindy Nguyen, Thirushan Wignakumar, Vikranth Mirle, Arianna Joy Edobor, John Fung, Jessica Scott Donington, Kumaran Shanmugarajah, Yiliang Lin, Eugene Chang, Glenn Randall, Pablo Penaloza-MacMaster, Bozhi Tian, and Maria Lucia Madariaga.

Funding: National Institutes of Health New Innovator award 1DP2AI144245, National Science Foundation Career award 1653782, and NIDDK RC2DK122394.

Featured image: Cartoon rendering of Nanotrap binding SARS-CoV-2. Nanotrap is shown with a yellow core, green phospholipid shell, and red functionalized particles to bind the virus (either ACE2 or Neutralizing Antibody). Virus protein coats are shown in gray, and are decorated with the Spike protein (green) and glycoprotein (red). © Huang Lab


Reference: “Nanotraps for the containment and clearance of SARS-CoV-2,” Chen and Rosenberg et. al, Matter, April 19, 2021, DOI: https://doi.org/10.1016/j.matt.2021.04.005


Provided by University of Chicago

Men’s Loneliness Linked to An Increased Risk of Cancer (Psychiatry)

A recent study by the University of Eastern Finland shows that loneliness among middle-aged men is associated with an increased risk of cancer. According to the researchers, taking account of loneliness and social relationships should thus be an important part of comprehensive health care and disease prevention. The findings were published in Psychiatry Research.

“It has been estimated, on the basis of studies carried out in recent years, that loneliness could be as significant a health risk as smoking or overweight. Our findings support the idea that attention should be paid to this issue,” Project Researcher Siiri-Liisi Kraav from the University of Eastern Finland says.

The study was launched in the 1980s with 2,570 middle-aged men from eastern Finland participating. Their health and mortality have been monitored on the basis of register data up until present days. During the follow-up, 649 men, i.e. 25% of the participants, developed cancer, and 283 men (11%) died of cancer. Loneliness increased the risk of cancer by about ten per cent. This association with the risk of cancer was observed regardless of age, socio-economic status, lifestyle, sleep quality, depression symptoms, body mass index, heart disease and their risk factors. In addition, cancer mortality was higher in cancer patients who were unmarried, widowed or divorced at baseline.

“Awareness of the health effects of loneliness is constantly increasing. Therefore, it is important to examine, in more detail, the mechanisms by which loneliness causes adverse health effects. This information would enable us to better alleviate loneliness and the harm caused by it, as well as to find optimal ways to target preventive measures.”


Original article:
Kraav, S., Lehto, S.M., Kauhanen, J., Hantunen, S., Tolmunen, T., 2021. Loneliness and social isolation increase cancer incidence in a cohort of Finnish middle-aged men. A longitudinal study. Psychiatry Research: https://doi.org/10.1016/j.psychres.2021.113868


Provided by University of Easter Finland

New Technology Makes Pig Farming More Environmentally Friendly (Biology)

Highlights

  • Researchers from the Biological Systems Unit at the Okinawa Institute of Science and Technology Graduate University have created a system to treat both raw and aerated wastewater.
  • The system relies on bacterial communities to break down organic material from raw wastewater and remove nitrate together with phosphate from aerated wastewater.
  • It is easy to assemble and low maintenance.
  • A proof-of-concept have been shown to work in both the lab and on a local swine farm in Okinawa, Japan.

Main text

Anyone who lives in Okinawa, a subtropical island in Japan, has an appreciation of the intensity of its pig farming industry. The farms have a large effect on the island’s economy and culture. According to Japan’s Cabinet Office, as of 2018, there were over 225,000 pigs in Okinawa. Pork is a staple in the local diet and is found in many dishes in traditional restaurants. But the presence of the pig farms has another, less welcome, impact – the odor-y kind. Drive through some particularly farm-filled areas with the car’s windows wound down and you’re sure to be filled with regret.

Pigs at one of the local swine farms. Credit: Okinawa Prefecture Livestock and Grassland Research Center.

This smell is, at least in part, caused by a byproduct of the pig farming. Across Okinawa, large amounts of wastewater are produced by the farms. Now, researchers from the Biological Systems Unit at the Okinawa Institute of Science and Technology Graduate University (OIST) have created a new system for treating this wastewater, which they’ve successfully tested on a local swine farm in Okinawa.

“Our new system uses two different chambers,” explained Dr. Anna Prokhorova, lead author of a paper recently published in Bioresource Technology. “In the one chamber, full strength swine wastewater is treated for the removal of odor, pathogens, and organic matter, whereas in the other chamber, excess nitrate and phosphate is removed from wastewater that has already been treated through the traditional aeration system. To the best of our knowledge, this is the first system to successfully treat two different types of wastewater at the same time.”

This is a stark contrast to the traditional aeration system currently utilized by farmers which mainly treats organic matter in the wastewater and also converts the ammonium present to nitrate but does not treat the nitrate further. In Japan, the nitrate discharge limit for the livestock industry will soon be lowered to one fifth of the current level (which today sits at 500 milligrams of nitrate-nitrogen per liter) to be in line with other industries. More than 35% of farms in Okinawa are likely to exceed this impending change.

“This is of huge concern because nitrate contamination can have disastrous impacts on both human health and the environment,” said Dr Mami Kainuma, group leader in the Biological Systems Unit. “When nitrate is ingested by people, it is converted to nitrite, which impacts the bloods’ ability to carry oxygen and can lead to methemoglobinemia or blue baby syndrome.”

The traditional aerated system mainly treats organic matter and converts ammonium to nitrate. © OIST

This new system relied on the existence of a rich community of bacteria to begin the process. In the first chamber – the anode chamber – the bacteria reacted with the organic molecules present, releasing electrons in the process. These electrons were then transferred to the second chamber – the cathode chamber – via the electrodes. The cathode chamber contained wastewater that had already gone through the aeration process and thus had high levels of nitrate. Bacteria on the surface of the cathode chamber accept these electrons and used them to power the conversion of nitrate to nitrogen gas. The advantage of this system is that the nitrate removal can happen in wastewater with low organic matter content, such as the already-aerated water.

To treat both kinds of water, the researchers devised an ingenious solution; they used microbes to not only drive the treatment process, but also to recover some valuable nutrients out of the wastewater at the same time. The system was created from polyacrylic reactors containing two chambers, which were separated by an ion-exchange membrane and equipped with three electrodes.

After successfully trialing this system in the lab, the researchers set up an initial pilot experiment at one of the pig farms in Okinawa Prefecture Livestock and Grassland Research Center by working with the Okinawa Prefecture Environment Science Center and Okidoyaku. There they had access to both the aeration tank and raw wastewater. The project was funded by Okinawa Prefectural Government and monitored for over a year. Because of the integral role the bacterial communities played, the researchers also analyzed which species were present, how the composition of the community changed over time, and which species were responsible for each step.

The long-term experiment showed that the dominant nitrate-removing bacteria were those that can receive electrons to grow. During the treatment, their activity was stimulated by applied potential to the electrode in a range of -0.4V – -0.6V, which led to more efficient treatment of the wastewater. Such bacterial communities grew by over 60% in total in the cathode chamber, and continued to exhibit strong activity, leading to a high rate of nitrate reduction. Another big advantage was that, as the organic matter and, in particular, the volatile fatty acids were degraded in raw wastewater, the smell was lessened, and the number of pathogens reduced.  

“We’re very happy with the results so far. It’s much more efficient than we expected,” said Dr. Prokhorova. “This system is scalable, low cost, easy to assemble, and low maintenance. We’re hopeful that, within the next few years, it will be utilized by farmers in Okinawa and other locations with similar issues, such as rural communities in mainland Japan and Southeast Asia.”

The work will be continued as a POC program in OIST. 

Article information

  • Title: Concurrent treatment of raw and aerated swine wastewater using an electrotrophic denitrification system
  • Journal:Bioresource Technology
  • Authors: Anna Prokhorova, Mami Kainuma, Rie Hiyane, Susan Boerner, Igor Goryanin
  • DOI: https://doi.org/10.1016/j.biortech.2020.124508

Provided by OIST

Horizontal Transmission Can Cause Severe and Persistent Eye Inflammation (Medicine)

Clinicians from Tokyo Medical and Dental University (TMDU) discover a novel mode of transmission for human T-cell lymphotropic virus type-1

Tokyo, Japan – Human T-cell lymphotropic virus type-1 (HTLV-1) is a retrovirus similar to human immunodeficiency virus (HIV) and has mostly been thought to be transmitted vertically (mother-to-child), or horizontally (sexually or parenterally (e.g. via blood transfusion)). The spread of this infection in metropolitan areas such as Tokyo is presumed to be due to horizontal transmission, especially sexual transmission.HTLV-1-associated diseases are thought to be caused mainly through vertical transmission. In a new study, clinicians from Tokyo Medical and Dental University (TMDU) describe that horizontal transmission route is responsible for HTLV-1 associated disease, i.e. HTLV-1 uveitis.

The clinicians saw a 57-year-old woman who presented with sudden blurred vision. An eye examination revealed profound pathologies in different anatomical locations of her eyes. Most prominent were cellular infiltrates and opacity in the vitreous body, a large gel-like substance between the lens and the back of the eye.

Imaging of HTLV-1 uveitis. Staining and leakage along the retinal vessel were observed by fluorescein angiography © TMDU

Because the pathologies were consistent with uveitis and an inflammation of the eyes, and given the patient’s age, the clinicians tested her for the presence of several autoimmune diseases, such as rheumatoid arthritis and sarcoidosis, because uveitis can be a result of those. The tests didn’t reveal anything, so the clinicians tested the patient for a number of infectious diseases, such as HTLV-1 and HIV, that can also cause uveitis. When the HTLV-1 test came back positive, the clinicians made their diagnosis of HTLV-1 uveitis.
“HTLV-1 can cause adult T-cell lymphoma, myelopathy and uveitis, among other disorders,” says senior author of the study Kyoko Ohno-Matsui. “Although we started the patient on the proper treatment, an unanswered question was how did the patient get infected with the virus in the first place.”

Because there’s no targeted therapy for HTLV-1 infections, the clinicians had to weaken the patient’s immune system with corticosteroids, because an over-reacting immune system is thought to cause harm to the patient. The clinicians started the patient on corticosteroid therapy systemically as well as with topical eye drops over 6 weeks. Over the course of the next several months, the patient suffered from several recurrences, so the clinicians started her on a maintenance corticosteroid therapy, i.e. treatment over the course of 8 months. While no recurrences happened in this time period, 18 months after the start of the maintenance therapy, the patient presented with another recurrence, including a retinal detachment, which could lead to permanent blindness. This detachment was managed by ophthalmic surgery and the patient was again started on corticosteroids, this time for 4 years. No recurrences have happened since then and the patients has remained symptom-free.

Interestingly, during follow-up the patient’s mother underwent cataract surgery at the same clinic site. Testing for HTLV-1 revealed no infection of the mother, ruling out vertical transmission to the patient. Of note, HTLV-1 can become symptomatic even decades after initial infection.

“In the current environment of increasing HTLV-1 incidence, the existence of horizontal transmission causing HTLV-1 uveitis should be acknowledged as it can result in more severe inflammation than vertical transmission. Thus, physicians should take the route of infection into consideration when providing medical care to patients with HTLV-1-associated diseases.” says first / corresponding author of the study Koju Kamoi.

The article, “Horizontal transmission of HTLV-1 causing uveitis” was published in TheLancet Infectious Diseases at DOI:10.1016/S1473-3099(21)00063-3 

Featured image: Imaging of HTLV-1 uveitis. Vitreous opacity was observed by fundus imaging. © TMDU


Provided by Tokyo Medical and Dental University