The COVID-19 Pandemic: Even Mild Disease Impacts Mental Health (Medicine)

A significant level of symptoms of depression, anxiety and post-traumatic stress may follow COVID-19 independent of any previous psychiatric diagnoses, according to new research by Columbia University Mailman School of Public Health with colleagues at Universidade Municipal de São Caetano do Sul in Brazil. Exposure to increased symptomatic levels of COVID-19 may be associated with psychiatric symptoms after the acute phase of the disease.  This is the largest study to evaluate depressive, anxiety, and post-traumatic stress symptoms in tandem among patients who had mild COVID-19 disease. The findings published online in the journal Progress in Neuro-Psychopharmacology and Biological Psychiatry shed light on a significant subpopulation at risk for mental symptoms.
 
“These results are important because the vast majority of COVID-19 patients are classified as mild cases, facing long periods of at-home isolation,” said João Mauricio Castaldelli-Maia, MD, PhD, NIDA-INVEST Postdoctoral Fellow in the Department of Epidemiology at Columbia Mailman School. “It is probable that the increased prevalence of psychiatric symptoms post-COVID-19 is a consequence of the psychological context of the disease, and patients should be closely monitored for the development of psychiatric symptoms after COVID-19 treatment discharge.”
 
Nasal swabs were collected from residents within a section of Sao Paulo, Brazil, 18 years of age or older with suspected COVID-19 symptoms. Patients were tested at their homes under the supervision of trained healthcare personnel. Those who tested positive for COVID-19 — with at least two of the following symptoms: fever, cough, sore throat, change in/loss of smell — and were classified as mild cases — were further assessed for the presence of psychiatric symptoms approximately two months later.
 
Significant levels of depressive, anxiety and post-traumatic stress symptoms were reported by 26 percent, 22 percent, and 17 percent, respectively. For comparison purposes, previous estimates of post-traumatic stress levels within Brazil were 8.5% demonstrating that the prevalence within individuals presenting with mild COVID-19 increased versus past estimates.
 
In general, survivors of critical illnesses have a high level of mental symptoms after the condition improves. Depression, anxiety and post-traumatic stress disorder are among the most reported psychiatric events in patients with these conditions, according to the researchers.  The ongoing COVID-19 pandemic has disrupted the lives of many across the globe, resulting in an increased burden of physical and mental health consequences. Brazil, to date, is one of the most affected countries, reaching around 412,000 deaths by early May 2021.
 
“These findings echo warnings from the previous SARS outbreak, when survivors of SARS infections experienced increased psychological distress, persisting one year or more subsequent to the outbreak, and similar findings were observed following the occurrence of the Middle East Respiratory Syndrome Coronavirus (MERS-CoV) in 2015,” observed Silvia Martins, MD, PhD, associate professor of Epidemiology at Columbia Mailman School.
 
“Early mental health intervention such as psychotherapy and supportive groups could play an important role in preventing incident mental health problems for post-COVID sufferers,” said Castaldelli-Maia. “While further investigations for the possible neurobiological mechanisms linking COVID-19 and mental health conditions are warranted, healthcare systems must prepare for an influx of individuals experiencing psychological distress as a result of the COVID-19 pandemic.”
 
Co-authors are Flavia Ismael, João C.S.Bizario, Tatiane Battagin, Beatriz Zaramella, and Fabio Leal from Universidade Municipal de São Caetano do Sul; Julio Torales, National University of Asuncion; Antonio Ventriglio, University of Foggia; and Megan Marziali, Columbia Mailman School of Public Health.


Reference: Flavia Ismael, João C.S. Bizario, Tatiane Battagin, Beatriz Zaramella, Fabio E. Leal, Julio Torales, Antonio Ventriglio, Megan E. Marziali, Silvia S. Martins, João M. Castaldelli-Maia, Post-infection depressive, anxiety and post-traumatic stress symptoms: A prospective cohort study in patients with mild COVID-19, Progress in Neuro-Psychopharmacology and Biological Psychiatry, Volume 111, 2021, 110341, ISSN 0278-5846, https://doi.org/10.1016/j.pnpbp.2021.110341. (https://www.sciencedirect.com/science/article/pii/S0278584621001007)


Provided by Columbia Mailman School of Public Health

Nanoplastics And Other Harmful Pollutants Found Within Disposable Face Masks (Medicine)

Swansea University scientists have uncovered potentially dangerous chemical pollutants that are released from disposable face masks when submerged in water.

The research reveals high levels of pollutants, including lead, antimony, and copper, within the silicon-based and plastic fibres of common disposable face masks.

The work is supported by the Institute for Innovative Materials, Processing and Numerical Technologies (IMPACT) and the SPECIFIC Innovation & Knowledge Centre.

Project lead Dr Sarper Sarp of Swansea University College of Engineering said:

“All of us need to keep wearing masks as they are essential in ending the pandemic. But we also urgently need more research and regulation on mask production, so we can reduce any risks to the environment and human health”.

Outlined in a recent paper, the tests carried out by the research team used a variety of masks – from standard plain face masks to novelty and festive masks for children with many currently being sold in UK retail outlets.

The rise in single-use masks, and the associated waste, due to the COVID-19 pandemic has been documented as a new cause of pollution. The study aimed to explore this direct link – with investigations to identify the level of toxic substances present.

The findings reveal significant levels of pollutants in all the masks tested – with micro/nano particles and heavy metals released into the water during all tests. Researchers conclude this will have a substantial environmental impact and, in addition, raise the question of the potential damage to public health – warning that repeated exposure could be hazardous as the substances found have known links to cell death, genotoxicity and cancer formation.

To combat this, the team advise further research and subsequent regulations be put in place in the manufacturing and testing process.

Dr Sarper Sarp continued:

“The production of disposable plastic face masks (DPFs) in China alone has reached approximately 200 million a day, in a global effort to tackle the spread of the new SARS-CoV-2 virus. However, improper and unregulated disposal of these DPFs is a plastic pollution problem we are already facing and will only continue to intensify.

There is a concerning amount of evidence that suggests that DPFs waste can potentially have a substantial environmental impact by releasing pollutants simply by exposing them to water. Many of the toxic pollutants found in our research have bio-accumulative properties when released into the environment and our findings show that DPFs could be one of the main sources of these environmental contaminants during and after the Covid-19 pandemic.

It is, therefore, imperative that stricter regulations need to be enforced during manufacturing and disposal/recycling of DPFs to minimise the environmental impact.

There is also a need to understand the impact of such particle leaching on public health. One of the main concerns with these particles is that they were easily detached from face masks and leached into the water with no agitation, which suggests that these particles are mechanically unstable and readily available to be detached.

Therefore, a full investigation is necessary to determine the quantities and potential impacts of these particles leaching into the environment, and the levels being inhaled by users during normal breathing. This is a significant concern, especially for health care professionals, key workers, and children who are required to wear masks for large proportions of the working or school day.”

The research team includes Professor Trystan Watson, Dr Javier Delgado Gallardo and Dr Geraint Sullivan.

The IMPACT operation is part-funded by the European Regional Development Fund through the Welsh Government and Swansea University.

Featured image: Microscope images of particles found in disposable face masks:  (left) microfibres from a children’s mask; (right) plastic fragments © Swansea University


Reference: G.L. Sullivan, J. Delgado-Gallardo, T.M. Watson, S. Sarp, An investigation into the leaching of micro and nano particles and chemical pollutants from disposable face masks – linked to the COVID-19 pandemic, Water Research, Volume 196, 2021, 117033, ISSN 0043-1354, https://doi.org/10.1016/j.watres.2021.117033. (https://www.sciencedirect.com/science/article/pii/S0043135421002311)


Provided by Swansea University

Aggressive Brain Tumours Can Mimic Normal Brain Repair Processes (Neuroscience)

Scientists at the UCL have made a ‘surprising’ discovery that glioblastoma, an aggressive brain cancer, mimics normal brain repair in white matter, which leads to the tumour becoming less malignant.

In the study on mice, funded by Cancer Research UK and published in Nature Communications, researchers used these novel findings to identify drugs which could be used, or repurposed, to harness this response (feature) and treat the cancer.

Using the pre-clinical mouse models, the researchers found that Pranlukast, a drug clinically approved for treating asthma in people, suppressed glioblastoma growth.

Explaining the research, lead author, Professor Simona Parrinello (UCL Cancer Institute),said:“We know glioblastoma often develops and spreads in the brain’s white matter but it has been unclear why this happens or what molecules are involved in this process. 

“In this experimental study, we wanted to understand what impact white matter has on cancerous tumour cells.”

Glioblastomas are the most aggressive type of cancer that begins within the brain. One of the main reasons that glioblastomas are so difficult to treat is that they spread into different regions of the brain. Approximately half the brain is grey matter, made up of cell bodies including neurons, the other half, referred to as white matter is composed of neuronal projections which are insulated by fatty membranes and therefore appear white. Tumour cells use the white matter as a route to spread to other brain regions.

In this study, the research team discovered that tumour cells, mimic brain repair, in that they attempt to repair the damage that the growing tumour mass causes to the brain’s white matter.

Professor Parrinello, who is Group Leader atthe Samantha Dickson Brain Cancer Unit, part of UCL Cancer Institute, explained: “To our surprise, when the tumour cells spread into the brain’s white matter, it made the glioblastoma less aggressive.

“This response is caused by the growing tumour injuring the white matter and in turn responding to this wound-like environment by attempting to repair it.

“This causes the tumour cells to mature into cells that resemble the normal brain cells that make up the white matter.

“In this mature state, tumour cells become less able to grow and spread.”

The team found that this tumour response can be exploited for glioblastoma treatment using drugs that promote normal white matter repair, such as Pranlukast.

Professor Parrinello added: “Glioblastoma is the most common and aggressive type of primary brain tumour. There are currently no effective treatments for glioblastoma, so recurrence is inevitable. As a result, prognosis for glioblastoma patients remains extremely poor with a median survival of less than 18 months. Here we identified a potential new approach to treat glioblastoma and show that a drug currently in clinical use for asthma suppresses glioblastoma growth and spread in preclinical models.”

Around 2,200 people in the UK (mostly adults) are diagnosed with glioblastoma each year and currently prognosis is extremely poor with average survival rate of around six to 18 months.  

Michelle Mitchell, chief executive of Cancer Research UK, said: “Brain tumours are notoriously hard to treat because we still don’t know enough about the biology of the disease, and current treatments are not effective enough. This early research is fascinating as it could mean an existing asthma drug may help people with glioblastoma. Repurposing a drug that has already passed safety tests would save a lot of time compared to developing a new treatment from scratch, time which would make an incredible difference to the lives of people affected by glioblastoma.”

Featured image: Tumour cells (green) invading through white matter tracts (purple): Credit Dr Lucy Brooks (UCL Cancer Institute)


Link

Brooks, L.J., Clements, M.P., Burden, J.J. et al. The white matter is a pro-differentiative niche for glioblastoma. Nat Commun 12, 2184 (2021). https://doi.org/10.1038/s41467-021-22225-w


Provided by UCL

Opinion: Climate Change – How Bad Could the Future Be If We Do Nothing? (Ecology)

Professor Mark Maslin (UCL Geography) lays out two possible futures for the future, one in which the effects of climate change ravage the planet, and one in which we do everything possible to prevent this being the case.

The climate crisis is no longer a looming threat – people are now living with the consequences of centuries of greenhouse gas emissions. But there is still everything to fight for. How the world chooses to respond in the coming years will have massive repercussions for generations yet to be born.

In my book How to Save Our Planet, I imagine two different visions of the future. One in which we do very little to address climate change, and one in which we do everything possible.

This is what the science suggests those very different realities could look like.

Year 2100: the nightmare scenario

The 21st century draws to a close without action having been taken to prevent climate change. Global temperatures have risen by over 4°C. In many countries, summer temperatures persistently stay above 40°C. Heatwaves with temperatures as high as 50°C have become common in tropical countries.

Every summer, wildfires rage across every continent except Antarctica, creating plumes of acrid smoke that make breathing outdoors unbearable, causing an annual health crisis.

Ocean temperatures have risen dramatically. After repeated bleaching events, Australia’s Great Barrier Reef has been officially declared dead.

Frequent and prolonged droughts torment vast swathes of the Earth’s land. The deserts of the world have expanded, displacing many millions of people. Around 3.5 billion live in areas where water demand exceeds what’s available.

Air pollution has a new major cause outside the traffic-choked cities: dust whipped up from now-barren farmland.

The Arctic is free of sea ice every summer. Average temperatures in the far north have risen by over 8°C as a result. The Greenland and Western Antarctic ice sheets have started to melt, releasing a huge amount of freshwater into the oceans.

Most mountain glaciers have completely melted. Skiing is now a predominantly indoor sport which takes place on giant artificial slopes. Most of the Himalayan plateau’s ice has disappeared, reducing the flows of the Indus, Ganges, Brahmaputra and Yamuna rivers which over 600 million people rely on for plentiful water.

The extra heat in the ocean has caused it to expand. Combined with water from melting ice sheets, sea levels have risen by more than one metre. Many major cities, including Hong Kong, Rio de Janeiro and Miami, are already flooded and uninhabitable. The Maldives, the Marshall Islands, Tuvalu and many other small island nations have been abandoned.

Many coastal and river areas are regularly flooded, including the Nile Delta, the Rhine valley and Thailand. Over 20% of Bangladesh is permanently under water.

Winter storms are more energetic and unleash more water, causing widespread wind damage and flooding each year.

Tropical cyclones have become stronger and affect tens of millions of people every year. Mega-cyclones, like 2013’s Typhoon Haiyan, have become more common, with sustained wind speeds of over 200 mph.

South-east Asian monsoons have become more intense and unpredictable, bringing either too much or too little rain to each region, affecting the lives of over three billion people.

Food and water insecurity has increased around the world, threatening the health and wellbeing of billions of people. Extreme heat and humidity in the tropics and subtropics has increased the number of days that it is impossible to work outside tenfold – slashing farm productivity. Extreme weather in temperate regions like Europe has made food production highly unpredictable. Half of the land devoted to agriculture in the past is now unusable, and the capacity of the rest to grow food differs widely from season to season. Crop yields are at their lowest levels since the middle of the 20th century.

Fish stocks have collapsed. The acidity of the ocean has increased by 125%. The ocean food chain has collapsed in some regions as the small marine organisms that form its base struggle to make calcium carbonate shells and so survive in the more acidic waters.

Despite advances in medical sciences, deaths from tuberculosis, malaria, cholera, diarrhoea and respiratory illnesses are at their highest levels in human history. Extreme weather events – from heat waves and droughts to storms and floods – are causing large loss of life and leaving millions of people homeless. Disease epidemics have plagued the century, spreading among populations beleaguered by widespread poverty and vulnerability.

Year 2100: humanity rises to the challenge

This is what our planet could look like if we do everything in our power to contain climate change.

Global temperatures rose to 1.5°C by 2050 and remained there for the rest of the century. Fossil fuels have been replaced by renewable energy. Over a trillion trees have been planted, sucking carbon dioxide from the atmosphere. The air is cleaner than it has been since before the industrial revolution.

Cities have been restructured to provide all-electric public transport and vibrant green spaces. Many new buildings have a photoelectric skin which generates solar energy and green roofs which cool the cities, making them a more pleasant place to live. High-speed electric trains reaching 300 mph link many of the world’s major cities. Intercontinental flights still run, using large and efficient planes running on synthetic kerosene that’s made by combining water and carbon dioxide sucked directly from the atmosphere.

Vegetation covers the exterior of a building in a Japanese city.

Global diets have shifted away from meat. Farming efficiency has greatly improved during the transition from industrial-scale meat production to plant-based sustenance, creating more land to rewild and reforest.

Half of the Earth is dedicated to restoring the natural biosphere and its ecological services. Elsewhere, fusion energy is finally set to work at scale providing unlimited clean energy for the people of the 22nd century.

Two very different futures. The outcome your children and grandchildren will live with depends on what decisions are made today. Happily, the solutions I propose are win-win, or even win-win-win: they reduce emissions, improve the environment and make people healthier and wealthier overall.

This article was originally published in The Conversation on 06 May 2021.

Featured image: Mark Maslin © UCL


Provided by University College of London

How To Save Our Planet: The Facts (Planetary Science)

UCL Professor of Earth System Science Mark Maslin (UCL Geography) aims to arm everyone ‘from the pub to Parliament’ with facts from his new book on climate change so that we can act together to save the planet.

How to Save Our Planet: The Facts, published today (6 May 2021), is packed with easily digestible facts and figures on everything from the history of the Earth to the power of the individual and government solutions to tackle the climate crisis.

The book has already caught the attention of Virgin Radio DJ Chris Evans, who told Professor Maslin how both he and his children “love it!”

Interviewed by Chris on his breakfast radio show, Professor Maslin said: “I got really frustrated reading lots of these worthy books on climate change. The big, thick ones, the doom and gloom, and I have to confess that I’ve written a couple myself!

“I went, ‘How do I write something that my mates down the pub, or who I play football with, would want to read and actually get something out of?’ Suddenly, this book came to me, where I used single sentences, double sentences, and made it all very factual and hopefully really easy to read.

“You can dive into any chapter you want. You can read it backwards. It’s just more user-friendly than most other books.”

Professor Maslin is a global expert on climate science. He has a particular interest in understanding climate change historically as well as the major challenges it presents for humanity now and in the future.

Amongst the facts he finds most shocking in his book are:

  • There are now more Lego mini figures than people on the planet – and there are 7.8 billion of us – all made of non-recyclable plastic
  • We’ve cut down 3 trillion trees – that is half the trees on the planet 
  • We’ve made enough concrete to cover the whole world in a layer 2 mm thick
  • We make 300 million tonnes of plastic – which is found in all oceans – including 7 miles deep in the Mariana trench in the NW Pacific 
  • Greenhouse gases are now higher than they have been for the last 3 million years
  • Weight of land mammals: 30% humans, 67% livestock and pets – only 3% is wild animal

Professor Maslin explained to BBC Radio 5Live’s Rick Edwards how the punchy, accessible format for his new book was inspired by the ancient Chinese military strategist Sun Tzu’s The Art of War:

“This book, is two-and-a-half thousand years old and the US Marine Corps and the British Army still use as their go-to text for how to run a war; it is full of bullet points like, ‘have more spies than the enemy.. do not attack unless you know you can win..’ really pithy things like that, and I thought, ‘Why don’t I just write a whole book like that?’”

The result: compelling content that Mark hopes will inform high quality debates on climate change everywhere from “Parliament, to dinner parties (if we’re ever allowed to have them again), the boardroom or the pub”.

On the idea that technology rather than behaviour shifts will save the planet, Professor Maslin told Rick Edwards: “What’s true is, it’s a bit of both. Technology will not fix this completely. One of the biggest things that people don’t realise is it’s our consumption – the amount of stuff that we actually buy, use and throw away. At the moment, we could not have all 7.8 billion people consuming the same amount as the average American. We just wouldn’t have any planet left!”

Every fact in the pocket-sized paperback is referenced, offering the reader a wealth of new information to explore and continue to learn from. It also lends itself to well informed posts on social media and fans are already sharing pictures of their favourite facts.

So, what are the things we can all do now to make a difference, Chris Evans asked Professor Maslin, after the Virgin Radio production team dubbed him ‘Mother Nature’s favourite son’!

“The first thing is to talk about it. It is the greatest threat to humanity and we all have a role to playing in fixing it. The second thing is we need to move to a more vegetable based diet, because it’s basically healthier for us but also helps to save the planet. And the other thing that everybody can do straight away is switch to a renewable energy tariff, because it’s probably the same price and is not going to cost you anything but sends a really big message to the energy companies that we want them to change. There are many more suggestions in the book”.

How to Save Our Planet: The Facts is published by Penguin UK.

Links

Featured Image

How to Save Our Planet: The Facts – Penguin UK


Provided by UCL

Wood Ants Show The Way When it Comes to Getting A Good Meal (Biology)

With lockdown easing it is a dilemma many of us are facing: should we choose to go to the best place to eat out, or the nearest place that is good enough?

Well, now it seems the humble wood ant faces the same dilemma.

A University of York study has shown that wood ants also face trade-offs between visiting the nearest sources of food versus heading for high-quality food.

The study revealed that wood ant colonies use simple foraging rules, not just for collecting food, but also to make sophisticated and highly effective transport networks.

Sharing

These highly cooperative ants also share food between socially connected nests. This food sharing is efficient, low cost and robust to disturbance, the study reveals. 

The researchers say the findings could have implications for humans, as transporting people and goods effectively in a complex environment is a big challenge and the highly cooperative wood ants appear to be very successful at it.

The authors of the study, which is published in the Proceedings of the Royal Society B, wanted to find out: how do ants make these successful networks? Can we learn from what the ants have achieved? 

The study combined two modelling approaches used to understand ant foraging. One describes the behaviour of the ants making and following trails, and one describes the pattern of where a colony distributes its ants depending on positive feedback.

Food sources

“Both models show us that foraging ant colonies successfully choose nearer and better food sources,” said Dr Elva Robinson, senior lecturer in ecology at the University of York.

“But these ant colonies can use foraging rules not just to solve the quality-distance trade-off when they are collecting food but also to make complex nest networks for food sharing. 

“The network properties they demonstrate, efficiency and robustness, are important for human transport networks too. Ants make successful transport networks using simple positive feedback loops that mean they use good routes again in future. We could adopt these ideas in our own network design.”

The research was funded by the National Science Foundation, while the fieldwork was funded by NERC and the National Trust.

The study involved researchers at the University of York, Harvey-Mudd College, George Washington University and Exeter University.

Featured image: The study revealed that wood ant colonies make sophisticated and highly effective transport networks. Credit Valentin Lecheval


About this research

The paper, “From foraging trails to transport networks: how the quality-distance trade-off shapes network structure”  is published in the journal, Proceedings of the Royal Society B.


Provided by University of York

3D Bioprinting Technique Controls Cell Orientation (Biology)

3D bioprinting can create engineered scaffolds that mimic natural tissue. Controlling the cellular organization within those engineered scaffolds for regenerative applications is a complex and challenging process.

Cell tissues tend to be highly ordered in terms of spatial distribution and alignment, so bioengineered cellular scaffolds for tissue engineering applications must closely resemble this orientation to be able to perform like natural tissue.

In Applied Physics Reviews, from AIP Publishing, an international research team describes its approach for directing cell orientation within deposited hydrogel fibers via a method called multicompartmental bioprinting.

The team uses static mixing to fabricate striated hydrogel fibers formed from packed microfilaments of different hydrogels. In this structure, some compartments provide a favorable environment for cell proliferation, while others act as morphological cues directing cell alignment. The millimeter-scale printed fiber with the microscale topology can rapidly organize the cells toward faster maturation of the engineered tissue.

“This strategy works on two principles,” said Ali Tamayol, coauthor and an associate professor in biological engineering at UConn Health. “The formation of topographies is based on the design of fluid within nozzles and controlled mixing of two separate precursors. After crosslinking, the interfaces of the two materials serve as 3D surfaces to provide topographical cues to cells encapsulated within the cell permissive compartment.”

Extrusion-based bioprinting is the most widely used bioprinting method. In extrusion-based bioprinting, the printed fibers are typically several hundreds of micrometers in size with randomly oriented cells, so a technique providing topographical cues to the cells within these fibers to direct their organization is highly desirable.

Conventional extrusion bioprinting also suffers from high shear stress applied to the cells during the extrusion of fine filaments. But the fine scale features of the proposed technique are passive and do not compromise other parameters of the printing process.

To direct cellular organization, according to the team, extrusion-based 3D-bioprinted scaffolds should be made from very fine filaments.

“It makes the process challenging and limits its biocompatibility and the number of materials that can be used, but with this strategy larger filaments can still direct cellular organization,” said Tamayol.

This bioprinting technique “enables production of tissue structures’ morphological features — with a resolution up to sizes comparable to the cells’ dimension — to control cellular behavior and form biomimetic structures,” Tamayol said. “And it shows great potential for engineering fibrillar tissues such as skeletal muscles, tendons, and ligaments.”

Featured image: Biofabrication of multicompartmental hydrogel fibers for formation of multiscale biomimetic constructs. © AIP Publishing


Reference: Mohamadmahdi Samandari, Fatemeh Alipanah, Keivan Majidzadeh-A, Mario M. Alvarez, Grissel Trujillo-de Santiago, and Ali Tamayol, “Controlling cellular organization in bioprinting through designed 3D microcompartmentalization“, Applied Physics Reviews 8, 021404 (2021); https://doi.org/10.1063/5.0040732


Provided by AIP Publishing

Not Just Tidal Disruption Events (TDE’s), Micro-TDE’s Are Also Occur In Active Galactic Nuclei (Cosmology / Astronomy)

An active galactic nucleus (AGN) is a compact region at the center of a galaxy that has a much-higher-than-normal luminosity. AGNs are the result of a highly accreting supermassive black hole (SMBH), in which infalling gas forms an accretion disk around the SMBH. In addition to being the source of the high central luminosity, AGN disks can also impact the dynamics of stellar remnants in the galactic center. Of particular interest has been the interaction of AGN disks with stellar-mass black holes (BHs) that have migrated to the galactic center through mass segregation. While orbiting the central SMBH, BHs periodically cross the AGN disk that gradually aligns their orbit with the disk plane. Once in the disk, BHs migrate inwards due to viscous-tidal interactions with the disk. After these processes brought two BHs in each others’ vicinity, the dense gas of the AGN disk facilitates gravitational capture and ultimately the binary merger of the two BHs through dynamical friction.

Now, Yang and colleagues examined the orbital alignment of stars with the AGN disk, and its consequences. They proposed that, similar to black holes, stars near the galactic center are also brought into the AGN disk, where they can be tidally disrupted by the stellar-mass black holes in the disk. Although, such interactions (which they called micro tidal disruption events (micro-TDEs)) with the AGN disk may have limited effect on the overall tidal disruption rate in galaxies with AGNs, these could be useful probe of stellar interaction with the AGN disk.

They found that micro-TDEs in AGNs occur at a rate of ∼ 170 Gpc¯3yr¯1 and suggested that, such micro-TDEs may be easiest to distinguish from TDEs around SMBHs by focusing on AGN-hosting galaxies in which the central SMBH’s mass is too high (M• ≳ 108M) to tidally disrupt solar-like stars. They also discussed two such TDE candidates, which have been reported so far, ASASSN-15lh and ZTF19aailpwl, both are among the highest-luminosity TDE candidates. Lets take a look on them.

1) ASASSN-15lh was an unusually bright transient first discovered by the All-Sky Automated Survey for Supernovae (ASAS-SN) in 2015 at a redshift of z = 0.232. The spectrum of ASASSN-15lh points to a TDE and rules out superluminous supernova origin. ASASSN-15lh was found to come from a galactic nucleus with SMBH mass M• = 5 × 108M, which may be a low-luminosity AGN based on its BPT classification. This is beyond the Hills mass for solar-type stars, although a highly spinning SMBH in this mass range could produce a TDE. The latetime (≳ 100 days) light curve and spectrum of ASASSN15lh could be well explained with a close to maximally spinning SMBH with mass M• ∼ 109 M, although the early light curve and the lack of radio and dim X-ray emission are not understood. The peak luminosity of ASASSN-15lh was Lpeak ∼ 5 × 1045 erg s¯1, higher than the ∼ 1044 erg s¯1 predicted from analytical micro-TDE models, which nevertheless have large uncertainties.

2) ZTF19aailpwl was a bright (Lpeak ∼ 1045 erg s¯1) transient first observed by the Zwicky Transient Facility in 2019 at a redshift of z = 0.37362. It originated from an AGN with a reconstructed SMBH mass of M• ∼ 108.2 M (although a mass < 108 M cannot be completely ruled out). Follow-up observations found that the spectral properties of ZTF19aailpwl are consistent with a TDE, but also with an AGN flare attributed to enhanced accretion. Its light curve is similar to that of TDEs, with a somewhat longer than usual rise time. For micro-TDEs, such longer rise time may be possible due to interaction with the disk wind and the low eccentricity of the stellar orbit that makes the encounter less impulsive and the tidal effects more gradual, compared to the usual SMBH-TDE case.

For both cases discussed above, the reconstructed black hole masses beyond the Hills mass point away from TDEs but are consistent with a micro-TDE origin.

Moreover, it has been suggested that, micro-TDEs can also occur outside of AGN disks, for example in stellar triples hosting a BH, or in dense stellar clusters. The rate of micro-TDEs from these channels is uncertain but could be as high as that of TDEs. These micro-TDEs could also occur in galaxies with SMBH mass above the Hills mass. Observationally, however, these micro-TDE channels will occur far from galactic centers and will not be confined to AGNs. As both ASASSN-15lh and ZTF19aailpwl were localized to the galactic center and in an AGN means that, for both of these cases, non-AGNassisted micro-TDE channels are unlikely.

“Further theoretical and observational work is needed to better understand the spectral and temporal properties of AGN-assisted micro-TDEs, and to observe them against the background of AGN variability. In particular, we suggest an observational focus on AGNs that harbor the heaviest SMBHs and exhibit unusual flaring activity”.

— concluded authors of the study

Featured image: Smoothed-particle hydrodynamics simulation of micro-TDE of a binary system consisting of a 10M BH and a 1M main sequence star, the initially circular orbit with 5R separation. The period of the initial orbit is about 0.4 days. They showed the normalized surface density of the debris at different times and give the normalization factor in each subplot. © Yang et al.


Reference: Y. Yang, I. Bartos, G. Fragione, Z. Haiman, M. Kowalski, S. Marka, R. Perna, H. Tagawa, “Micro Tidal Disruption Events in Active Galactic Nuclei”, Arxiv, pp. 1-7, 2021. https://arxiv.org/abs/2105.02342


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New Therapy Shortens Treatment For HPV-related Cancers of the Tonsils, Tongue (Medicine)

Patients with HPV-related oropharyngeal cancer who undergo surgery and are treated with chemotherapy, may be able to forgo significant radiation therapy without increasing the risk of their cancer spreading, according to the results of a clinical trial led by researchers at Mayo Clinic.

“We found that decreasing the amount of radiation therapy after a minimally invasive robotic surgery improved the quality of life of patients with HPV-related oropharyngeal cancer while delivering excellent cure rates,” saysDr. Eric Moore, a Mayo Clinic otolaryngologist. “In essence, we found exactly the right amount of treatment to deliver without over-treating these patients.”

Watch: Dr. Eric Moore discusses de-escalation radiation therapy.

Journalists: Broadcast-quality sound bites with Dr. Moore are in the downloads at the end of the post. Please courtesy: “Eric Moore, M.D. / Otolaryngology / Mayo Clinic.”

Dr. Moore and his colleagues compared 79 patients treated at Mayo Clinic for HPV-related tonsil and tongue cancer with surgery and two weeks of radiation therapy to a group of 115 patients with the same cancer who were treated with surgery, and the standard six weeks of radiation therapy and chemotherapy.

Dr. Moore and his colleagues found no decrease in survival or cancer recurrence in the group that received two weeks of radiation therapy, compared to the group that received six weeks of radiation therapy. He says that by decreasing the amount of radiation therapy after minimally invasive robotic surgery, physicians were able to improve the quality of life of patients and achieve excellent cure rates.

“In essence, we found exactly the right amount of treatment to deliver without overtreating,” says Dr. Moore.

Dr. Moore says Mayo Clinic now offers dose de-escalation radiation therapy to appropriately selected patients with HPV-related cancers of the tonsils and tongue.

“This approach shortens the treatment time for these patients by several weeks and reduces side effects without sacrificing the effectiveness of the treatment,” Dr. Moore says.


Provided by Mayo Clinic