Culture

HOUSTON - (Sept. 2, 2020) - Microscopic crystals in tantalum disulfide have a starring role in what could become a hit for 3D displays, virtual reality and even self-driving vehicles.

A two-dimensional array of the material has unique optical characteristics that can be controlled in ambient conditions and under general illumination, according to engineer Gururaj Naik and graduate student Weijian Li of Rice's Brown School of Engineering.

When they pull a two-dimensional sliver off a bulk sample (with that tried-and-true tool, adhesive tape) and shine light on it, the layered material rearranges the charge density waves of electrons that flow through, altering its refractive index.

Light emitted along the affected axis changes its color depending on the strength of the light that goes in.

The discovery is detailed in the American Chemical Society journal Nano Letters.

"We need an optical material that can change the refractive index for applications like virtual reality, 3D displays, optical computers and lidar, which is necessary for autonomous vehicles," said Naik, an assistant professor of electrical and computer engineering. "At the same time, it has to be fast. Only then can we enable these new technologies."

Tantalum disulfide, a semiconducting, layered compound with a prismatic metal center, appears to fit the bill. The material is already known for harboring charge density waves at room temperature that allow adjustments to its electrical conductivity, but the strength of light input also changes its refractive index, which quantifies the speed at which light travels through. That makes it tunable, Naik said.

When exposed to light, the tantalum layer reorganizes into a lattice of 12-atom stars, like the Star of David or sheriff's badges, that facilitate charge density waves. How these stars are stacked determines whether the compound is insulating or metallic along its c-axis.

It turns out that also determines its refractive index. Light triggers the stars to realign, changing the charge density waves enough to affect the material's optical constants.

"This belongs to a class of what we call strongly correlated materials, which means the electrons strongly interact with each other," Li said. "In this case, we can predict the properties that show a strong response to some external stimulus."

That the stimulus is as mild as ambient white light is a plus, Naik added. "This is the first material we've seen where the interaction of light happens not just with single particles, but with a collection of particles together, at room temperature," he said. The phenomenon appears to work in tantalum disulfide as thin as 10 nanometers and as thick as a millimeter, he said.

"We think this is an important discovery for those who study strongly correlated materials for applications," Naik said. "We show light is a very powerful knob to change how correlation extends in this material."

COLUMBUS, Ohio - A bioengineering technique to boost production of specific proteins could be the basis of an effective vaccine against the novel coronavirus that causes COVID-19, new research suggests.

Scientists manipulated a natural cellular process to ramp up levels of two proteins used by the virus to infect other cells, packaged the protein-boosting instructions in nanoparticles and injected them into mice. Within a month, the mice had developed antibodies against the SARS-CoV-2 virus.

The technique involves altering specific sequences of messenger RNA, molecules that translate genetic information into functional proteins. While these sequences are not translated to proteins, the researchers changed their structures to promote higher-than-usual levels of proteins. The sequences are known as untranslated regions, or UTRs.

"We've been engineering messenger RNA for four years, and earlier this year we made some progress identifying a role for UTRs - and then COVID-19 happened," said Yizhou Dong, senior author of the study and associate professor of pharmaceutics and pharmacology at The Ohio State University.

Though Phase 3 clinical trials of fast-tracked COVID-19 vaccine candidates are in progress, Dong said his lab's platform offers a potential alternative.

"If the current vaccines work well, that's wonderful. In case the field needs this, then it's an option. It worked as a vaccine is expected to, and we can scale this up very fast," he said. "For now, it's a proof of concept - we've demonstrated we can optimize a sequence of messenger RNA to improve protein production, produce antigens and induce antibodies against those specific antigens."

The study is published today in the journal Advanced Materials.

The crux of the method is typical to vaccine development: using snippets of a pathogen's structure to produce an antigen - the foreign substance that triggers an appropriate immune response - and finding a safe way to introduce it to the body.

But the engineering technique takes antigen design to a new level by making use of messenger RNA UTRs, Dong said.

His lab worked with the two UTRs that bookend the start and finish of protein assembly, functioning as regulators of that process and influencing how the resulting protein interacts with others. UTRs themselves are strings of nucleotides, the molecules that compose RNA and DNA.

"For our application we tried to optimize the UTRs to improve the protein production process. We wanted as much protein produced as possible - so we can give a small dose of messenger RNA that produces enough antigen to induce antibodies against the virus," Dong said.

The team experimented with two potential antigens that the novel coronavirus is known to use to cause infection: a spike protein on its surface and a receptor binding domain, a component of the spike protein, that the virus uses to make its way into host cells - a necessary step to make copies of itself. Both are used in other SARS-CoV-2 vaccine candidates.

After manipulating the messenger RNA for these two proteins, the team encased them in lipid nanoparticles developed previously in Dong's lab. They injected mice with the experimental vaccine and gave them a booster two weeks later. A month after the first injection, immune cells in the mice had taken up the antigens of the two proteins and developed antibodies against them.

"It takes some time for the immune system to process the antigens and have cells produce antibodies," Dong said. "In this study, we detected antibodies after 30 days."

And even if this vaccine candidate is not needed for COVID-19, he is continuing to refine this latest method of engineering messenger RNA.

"UTR is a platform that we can apply to any type of messenger RNA. We are exploring other therapeutics," Dong said.

A new study uses magnetic resonance elastography to compare the stiffness of the hippocampus in patients who have epilepsy with healthy individuals. The technique can improve the detection and characterization of the disease.

The study "Hippocampal stiffness in mesial temporal lobe epilepsy measured with MR elastography: Preliminary comparison with healthy participants" was published in NeuroImage: Clinical. The work was done through a collaboration with the Carle Neuroscience Institute and the Beckman Institute for Advanced Science and Technology at the University of Illinois Urbana-Champaign.

Mesial temporal lobe epilepsy is the most common form of epilepsy that is resistant to medication. Unfortunately, current detection methods, which include magnetic resonance imaging, can only visualize the epilepsy-induced changes in the brain after significant damage has occurred.

"The structural changes in the brain, in response to seizures, causes the death of neurons and the formation of scar tissue," said Graham Huesmann, a neurologist at Carle and a research assistant professor of molecular and integrative physiology, who is a part-time faculty member at the Beckman Institute. "By the time we see any changes on the MRI, the disease is pretty advanced. We wanted to detect these changes earlier using MRE."

MRE uses the MRI scanner to look at the stiffness of brain tissues. "MRE is a non-invasive technique. Essentially a person lies on a little vibrating pillow, sending the vibrations into the tissues which change as the composition and the organization of the tissue changes," said Hillary Schwarb, a Beckman Institute research scientist who also is affiliated with the Interdisciplinary Health Sciences Institute. "It's like hitting the surface of a pond and watching the ripples that are formed. If there is a big rock underneath the surface, those ripples are going to move and change."

MRE is already used clinically for the staging of various liver diseases and has replaced invasive liver biopsies. "For epilepsy in the brain, MRE may prove similarly useful for staging progressive epilepsies, like mesial temporal lobe epilepsy, toward earlier detection" said Aaron Anderson, a Carle Foundation Hospital-Beckman Institute Postdoctoral Fellow.

The researchers used MRE to see if there were any changes in the hippocampus. "The hippocampus is the part of the brain that is involved in memory," said Brad Sutton, a professor of bioengineering and the technical director of Beckman's Biomedical Imaging Center. "In the early stages of epilepsy, there is a little bit of damage to the structure, which we can detect with MRE."

Early detection of these changes is critical for the disease, especially because it causes very mild symptoms in the beginning stages. "It starts with a feeling of déjà vu, which becomes more common as the disease progresses. Eventually it develops into a form that is medication resistant," Huesmann said. "MRE allows us to detect these changes earlier affording us the opportunity to change the course of treatment."

"MRE can also inform doctors about when to intervene with surgery," said Tracey Wszalek, the director of the Biomedical Imaging Center. If the surgery is done too early, it may affect a part of the brain that is still in use. However, if it is done too late, the patients lose their ability to make new memories.

The researchers are now focusing on how to optimize the technique and also look at other types of epilepsy. "All of our imaging techniques currently depend on looking at brain chemistry and the static images of the brain," Huesmann said. "Using MRE to see how the brain jiggles is an exciting way to approach this problem. It is also an inexpensive technique and can therefore be used by anyone."

Below please find a summary and link(s) of new coronavirus-related content published today in Annals of Internal Medicine. The summary below is not intended to substitute for the full article as a source of information. A collection of coronavirus-related content is free to the public at http://go.annals.org/coronavirus.

COVID-19 death risk varies significantly by age, race, ethnicity and sex

Infection fatality rate 2.5 times greater than flu for patients over 60

Regardless of age, IFR 3 times higher in non-whites

COVID-19 infection fatality ratios (IFR) vary significantly and in order of magnitude by age, race, ethnicity and sex. Risk for death is significantly higher among patients who are older or those who are non-White. A brief research report is published in Annals of Internal Medicine.

Current mortality rates for COVID-19 are calculated from confirmed cases, which overestimates IFR. To calculate the true IFR among the community-dwelling population, researchers from Indiana University Richard M Fairbanks School of Public Health and the School of Medicine combined prevalence estimates from a statewide random sample with Indiana vital statistics data of confirmed COVID-19 deaths for all state residents aged 12 and older. They excluded deceased individuals, incarcerated persons, and nursing home residents from the random sample. Participants were tested April 25 to April 29 2020 for active viral infection and SARS-CoV-2 antibodies, which would indicate prior infection, and demographic information was collected.

The researchers found that the overall noninstitutionalized IFR was 0.26 percent. Persons younger than 40 years had an IFR of 0.01 percent, and those aged 60 or older had an IFR of 1.71 percent. Indiana's IFR for noninstitutionalized persons older than 60 years was found to be just below 2 percent. In comparison, the ratio is approximately 2.5 times greater than the estimated IFR for seasonal influenza, 0.8 percent, among those aged 65 years and older. With regard to race, Whites had an IFR of 0.18 percent, and non-Whites had an IFR of 0.59 percent. The researchers note that the IFR for non-Whites is more than 3 times that for Whites, despite COVID-19 decedents in that group being 5.6 years younger on average. Read the full text: https://www.acpjournals.org/doi/10.7326/M20-5352.

Media contacts: A PDF for this article is not yet available. Please click the link to read full text. To reach the lead author, Justin Blackburn, PhD, please contact Amanda Briggs at amanbrig@iu.edu.

East Hanover, NJ. September 2, 2020. Researchers conducting a large international study of progressive multiple sclerosis (MS) examined the impact of the global outbreak of coronavirus disease 2019 (COVID-19) on their study participants. Compared with pre-COVID baseline assessments, findings from a COVID Impact Survey administered during lockdown showed minimal changes in depression, anxiety, and quality of life, and in the impact of MS symptomatology on activities of daily living.

The article, "The emotional impact of the COVID-19 pandemic on individuals with progressive multiple sclerosis" (doi: 10.1007/s00415-020-10160-7) was published online August 19, 2020 in Journal of Neurology. The article is included in SpringerLink's COVID collection: https://link.springer.com/article/10.1007/s00415-020-10160-7

The authors are members of the CogEx Research Team, comprised of site investigators from Canada, the United States, Italy, the UK, Denmark, and Belgium. The COVID Impact Survey was administered during the suspension of a randomized clinical trial (RCT) involving 131 participants at 11 sites in the above six countries. The trial's principal investigator is Anthony Feinstein, MD, PhD, of the University of Toronto.

The COVID pandemic has had substantial impact on the general population, raising concern for populations at increased risk for infection, as well as for detrimental psychological and social effects of quarantine and social distancing requirements. The pause in the RCT provided an opportunity for investigators to assess the impact of the pandemic on the population with progressive MS in real time.

Participants from all sites responded to the COVID Impact Survey while under social restrictions from May 2020 to July 2020. COVID infection was reported by 4% of participants, according to lead author Nancy Chiaravalloti, PhD, director of the Centers for Neuropsychology, Neuroscience and Traumatic Brain Injury at Kessler Foundation. Comparing baseline with COVID assessments revealed minimal changes in depression, anxiety, and quality of life. Impact of MS symptomatology on daily life functions was also minimal, except in the small subset with COVID-19 infection, where the impact was significant.

"Minimal effects were not what we expected to see," said Dr. Chiaravalloti, noting that the findings were consistent across different continents. "People with progressive MS appeared to have adapted more effectively to the lockdown conditions. Knowing their increased risk, they may have been early adopters of safety precautions, which may have provided a sense of control that countered negative emotional reactions," she speculated. "They are also accustomed to living with medical uncertainly and social isolation, two major factors that fueled high levels of psychological discomfort in the general population."

The COVID Impact Survey showed that the majority of participants actively engaged in mental and physical activities during lockdown. ""This is not surprising given that the aim of the RTC was to measure the outcomes of such activities," Dr. Chiaravalloti reported. "Focusing on elements of a healthy lifestyle may have mediated the negative effects on wellbeing in this group with progressive MS."

More than half of all African American women in the United States report having at least one family member who is incarcerated, causing higher levels of depressive symptoms and psychological distress than previously understood.

The findings come from a new paper in the Journal of Marriage and Family, whose lead author, Evelyn J. Patterson, associate professor of sociology and a Vanderbilt Chancellor's Faculty Fellow, said the study sheds new light on the challenges facing African American women.

"Most studies that look at the impact of incarceration are examining people who are parents or the children of someone who is incarcerated. That means, if you're not a parent or a child of an incarcerated person, you're excluded," she said. Given that having a sibling incarcerated is the most common form of familial incarceration, prior work misses a large piece of the familial incarceration story. Further, African American women as a whole are rarely the central focus when people examine the toll of familial incarceration, especially those without children.

The study sought to measure the mental health impact on African American women of having a family member incarcerated. Further, the research examined whether social roles such as employment, marriage or parenthood added to, or eased, the psychological burden of having an immediate family member in jail or prison.

"In all models, familial incarceration was associated with worse psychological adjustment," the authors wrote. "Our findings showed that familial incarceration was associated with elevated psychological distress and depressive symptomology, extending a long line of studies documenting the consequences of familial incarceration." Examining role combinations, women who were employed but had no other social roles showed lower levels of psychological distress and depressive symptoms than women who occupied other roles such as marriage/partnership or motherhood.

In addition to Patterson, the co-authors included Ryan D. Talbert from the University of Connecticut and Tony N. Brown from Rice University. The study drew from a nationally representative survey of 1,961 never-incarcerated African American women.

Patterson said the study fits into a broader research context examining how marginalized populations, particularly African American families, face worse outcomes on measures of health and psychological well-being because of the societal burdens they face.

"From slavery, to lynching, to incarceration, generations of African American families have endured having their family members taken away. African Americans have had to learn how to compartmentalize this trauma and have survived, in part, due to their resilience," Patterson said. "But this resilience is a double-edged sword as these experiences worsen health outcomes."

With an increase in HIV and HCV infections as a consequence of the ongoing opioid epidemic, Boston Medical Center researchers found that only a small number of those who test positive for those infections at a drug detoxification center followed up for a clinical visit after their test. The study results showed that only 6 percent of those tested for HIV and HCV followed up with testing care, despite accessing healthcare multiple times. These data demonstrate the need for more coordinated approaches to help patients access testing and treatment, especially as these rates are likely to worsen due to the COVID-19 pandemic.

Published in The Journal of Infectious Diseases, the research findings show that rapid testing for HIV and HCV at a drug detoxification center has a distinct advantage over laboratory-based testing (96 percent compared to 42 percent) in venues serving hard-to-reach populations, demonstrating the opportunities for using drug detoxification centers more frequently for these tests.

One-half of US state health departments and territories are prioritizing identification of acute HIV cases, and moving away from rapid testing in community-based settings. In locations such as drug detoxification center, laboratory-based testing may result in fewer diagnoses due to loss to follow-up before result delivery. When performed in community-based setting, laboratory-based testing results take approximately three days to be delivered. In contrast, results for point-of-care rapid testing are available within 30 minutes.

"We currently have a cure for HCV and effective treatment for HIV," says Sabrina Assoumou, MD, MPH, an infectious diseases physician at Boston Medical Center. "Successfully identifying and linking patients to care at drug detoxification centers during the opioid epidemic could help decrease transmission and improve outcomes for these two infections."

A single-site randomized trial was conducted to compare test results delivery between laboratory-based and rapid testing for HIV and HCV at a short-term inpatient drug and alcohol detoxification center located in Boston. The study included 200 participants with a history of self-reported drug use and who accessed detoxification services at the center between November 2016 and July 2017. Among participants, 48 percent tested positive for HCV and 0.5 percent newly tested positive for HIV. During follow-up, reviews showed that only 6 percent with positive tests were successfully linked to care, attending an HIV or HCV-related visit within four months of testing.

By focusing on linkage to care within four months of testing, research suggests that certain individuals with a history of substance use disorder could greatly benefit from rapid testing to improve their access and continued involvement in care for these infections. Forty-one individuals who did not have a record of HCV-related follow-up utilized other healthcare services, with an average of three visits within four months, of which 61 percent were in an emergency department. Successfully implementing HIV and HCV testing at drug detoxification centers could help identify and link to care persons at-risk during the opioid epidemic, but doing so would require that results obtained in drug detoxification centers be available to nearby healthcare facilities.

"We hope that these findings will encourage changes in local and national HIV and HCV testing practices and policy at non-hospital-based settings caring for populations at-risk during the opioid epidemic," says Assoumou, also an assistant professor of medicine at Boston University School of Medicine.

DURHAM, N.C. - In just a few months, the COVID-19 pandemic swiftly and substantially worsened mental health among U.S. hourly service workers and their children - especially those experiencing multiple hardships, according to new research from the Center for Child and Family Policy at Duke University and Barnard College.

The study leverages real-time, daily survey data collected from Feb. 20, before the pandemic hit the U.S., to April 27, when it was well underway, to examine how the crisis affected parents' and children's mental well-being. The 645 survey respondents were parents of young children working in hourly service-industry positions in retail, food service or hotel industries in a large U.S. city.

Nearly half (49.5%) of the participants were Black Americans, 23% were Hispanic Americans, and 83% were women.

The findings appear today in Pediatrics.

The surveys showed strong, immediate impacts of the pandemic on vulnerable families. Parents saw quick deterioration in their own mental well-being, reporting more frequent "negative moods" since March 14, the day after the first major restrictions in response to COVID-19 were announced. The majority of respondents experienced multiple hardships, including household job loss (60%), income decline (69%), caregiving burden (45%) and illness (12%).

"The COVID pandemic has created substantial hardship for working families," said Anna Gassman-Pines, co-author of the study and associate professor of public policy at Duke's Sanford School of Public Policy. "What's worse is that the more hardship families experienced, the worse parents' and children's mental health."

Not surprisingly, those who experienced two and three hardships reported more negative moods, worse sleep quality and more uncooperative child behavior than those who did not. For both parents and children, mental health was worst among those who suffered all four hardships.

"These results should raise concern, given the strong links between parental psychological well-being and the well-being of children," the authors write.

Gassman-Pines and co-author Elizabeth Ananat of Barnard College suggest pediatricians should screen for mental health problems among children in their practices, with particular attention to children whose families are especially vulnerable to both the economic and health aspects of the crisis.

During the stressful pandemic, pediatricians should also help parents understand and watch for potential signs of mental distress, the authors write. Those may include uncooperative behavior and acting out.

The authors also urge the government to provide more support for families, through restarting expanded unemployment insurance benefits and increasing the generosity of the Supplemental Nutrition Assistance Program.

"What we really see here is that, as hardships pile up, the combined weight causes severe distress for families. Resilience only takes you so far, and the multiple dimensions of hardship caused by this pandemic -- lost jobs, lost child care and education, sickness -- are stretching families to the breaking point," said Ananat. "Families need support, from their pediatricians and, hopefully, from the government."

Phytophthora infestans is an oomycete, or water mold, that causes the devastating potato disease known as late blight or potato blight and was responsible for the famous Irish Famine of the 1840s. In a recently published study, a group of scientists focused on the effectors of that pathogen and confirmed that plant pathogens employ an array of mechanisms to escape plant immunity response. These mechanisms explain why integrated resistance in plants cannot last long.

The scientists analyzed the genomic characters of the pathogen's AVR2 gene and the physical and biochemical properties of its effectors and found a substantial variation in the nucleotide sequences of the AVR2 genes generated from different P. infestans isolates and that these sequence variations were generated by many genetic mechanisms, including base substations, partial translation of the gene to the effectors, a small loss/gain of DNA sequence, and recombination.

"Bioinformatics analyses indicate that the virulent AVR2 effectors are proteins partially lacking three-dimension structure, known as disordered proteins, while avirulent effectors are ordered proteins with predicted crystal structures," explained Jiasui Zhan, one of the scientists involved in the study. "Each of the virulent effectors has one or two short linear interaction regions of ear-marked characters of disordered proteins. No such regions are found in the avirulent effectors. Furthermore, virulent AVR2 effectors are predicted to be less stable and have a shorter protein half-life than the avirulent effectors."

These results suggest that plant pathogens adopt a novel mechanism to escape plant recognition through reordering the physical structures of effector proteins. Through combining population genome and in vivo analyses of pathogenicity, Zhan and colleagues were able to draw the evolutionary pattern in groups rather than ad hoc phenomenon of single or a few samples in the similar studies and to verify the evolutionary inferences experimentally with statistical rigidness and robustness.

"This study highlights the fact that a subtle modification in gene sequence such as single base substitution may generate a huge corresponding change in protein properties of effectors and maybe other proteins as well," Zhan said. "The most surprising discovery is that there is clear difference in protein ordering between virulent and avirulent effectors: all 31 avirulent effectors are ordered proteins with defined structure while all 27 virulent are disordered proteins."

Multidisciplinary collaboration is essential for durable disease management and evolutionary genetics should play a central role in developing management practices that can minimize pathogen evolution's to evolve. For more information, read "The Phytophthora infestans AVR2 Effector Escapes R2 Recognition Through Effector Disordering" in the July issue of MPMI.

A new paper in The Economic Journal finds that bus drivers are more likely to let white riders ride for free and less likely to let Black riders ride without paying the fee.

Police officers must issue tickets to drivers exceeding the speed limit. A grocery store worker is not allowed to hand out goods free of charge. Similarly, bus drivers require all passengers to have valid tickets before being allowed onto the bus.

This study set out to test what happens when decisionmakers have to make unmonitored judgments. Do they voluntarily provide favours? And, if so, do they reward and accommodate some people more than others?

This study tested for discretionary favours, i.e., private accommodations, in everyday consumer transactions. In the study, the researchers hired test customers randomly assigned to board public buses where they presented a travel card with a zero monetary balance and asked the bus driver if they can have a free ride to a bus stop. While the public bus company's official rules and policies mostly discourage employees from providing a service free of monetary charge, close to two-thirds of observed bus drivers granted such favours, and predominantly to lighter-skinned people.

Based on 1,552 transactions in Queensland, Australia, the authors uncovered strong evidence of racial bias: bus drivers were twice as willing to let white testers ride free as Black testers (72% versus 36% of the time). Indian testers were accepted at 51%, while Asian testers were treated similarly to whites; being offered a free ride 73% of the time. Such racial bias against Black citizens still existed after controlling for several other variables including the bus driver's age, gender, and race. Based on the data, researchers found no evidence of own-group bias: bus drivers were just as likely to grant free rides to customers from other races as they were to customers of their own race.

The study revealed strong evidence of racial discrimination. A key feature in the field experiment is that the bus drivers had only a few seconds to decide regarding a person standing in front of them. Here the bus drivers appeared to use a customer's skin colour as a proxy for other unobservable group characteristics. The uncovered white privilege was reduced but still present when test customers wore business attire or dressed in army uniforms.

"Our findings show that white privilege extends into marketplace favours, or private accommodations, that are often hidden and unregulated," said Redzo Mujcic, one of the paper's authors. "The level of white privilege found is markedly greater than previously documented in other markets and public services, such as employment and housing, where discrimination is already illegal. As a society, we need to think about ways to eliminate such bias in daily interactions, especially given the large economic and social costs that accrue to discriminated minorities. For example, white citizens can simply refuse any such gifts in future transactions."

Enteroviruses and other pathogenic viruses that make their way into surface waters can be inactivated by heat, sunshine and other microbes, thereby reducing their ability to spread disease. But researchers report in ACS' Environmental Science & Technology that global warming could cause viruses to evolve, rendering them less susceptible to these and other disinfectants, such as chlorine.

Enteroviruses can cause infections as benign as a cold or as dangerous as polio. Found in feces, they are released into the environment from sewage and other sources. Their subsequent survival depends on their ability to withstand the environmental conditions they encounter. Because globalization and climate change are expected to alter those conditions, Anna Carratalà, Tamar Kohn and colleagues wanted to find out how viruses might adapt to such shifts and how this would affect their disinfection resistance.

The team created four different populations of a human enterovirus by incubating samples in lake water in flasks at 50 F or 86 F, with or without simulated sunlight. The researchers then exposed the viruses to heat, simulated sunlight or microbial "grazing" and found that warm-water-adapted viruses were more resistant to heat inactivation than cold-water-adapted ones. Little or no difference was observed among the four strains in terms of their inactivation when exposed to either more simulated sunlight or other microbes. When transplanted to cool water, warm-water-adapted viruses also remained active longer than the cool-water strains. In addition, they withstood chlorine exposure better. In sum, adaptation to warm conditions decreased viral susceptibility to inactivation, so viruses in the tropics or in regions affected by global warming could become tougher to eliminate by chlorination or heating, the researchers say. They also say that this greater hardiness could increase the length of time heat-adapted viruses would be infectious enough to sicken someone who comes in contact with contaminated water.

For all its vast emptiness, the universe is humming with activity in the form of gravitational waves. Produced by extreme astrophysical phenomena, these reverberations ripple forth and shake the fabric of space-time, like the clang of a cosmic bell.

Now researchers have detected a signal from what may be the most massive black hole merger yet observed in gravitational waves. The product of the merger is the first clear detection of an “intermediate-mass” black hole, with a mass between 100 and 1,000 times that of the sun.

They detected the signal, which they have labeled GW190521, on May 21, 2019, with the National Science Foundation’s Laser Interferometer Gravitational-wave Observatory (LIGO), a pair of identical, 4-kilometer-long interferometers in the United States; and Virgo, a 3-kilometer-long detector in Italy.

The signal, resembling about four short wiggles, is extremely brief in duration, lasting less than one-tenth of a second. From what the researchers can tell, GW190521 was generated by a source that is roughly 5 gigaparsecs away, when the universe was about half its age, making it one of the most distant gravitational-wave sources detected so far.

As for what produced this signal, based on a powerful suite of state-of-the-art computational and modeling tools, scientists think that GW190521 was most likely generated by a binary black hole merger with unusual properties.

Almost every confirmed gravitational-wave signal to date has been from a binary merger, either between two black holes or two neutron stars. This newest merger appears to be the most massive yet, involving two inspiraling black holes with masses about 85 and 66 times the mass of the sun.

The LIGO-Virgo team has also measured each black hole’s spin and discovered that as the black holes were circling ever closer together, they could have been spinning about their own axes, at angles that were out of alignment with the axis of their orbit. The black holes’ misaligned spins likely caused their orbits to wobble, or “precess,” as the two Goliaths spiraled toward each other.

The new signal likely represents the instant that the two black holes merged. The merger created an even more massive black hole, of about 142 solar masses, and released an enormous amount of energy, equivalent to around 8 solar masses, spread across the universe in the form of gravitational waves.

“This doesn’t look much like a chirp, which is what we typically detect,” says Virgo member Nelson Christensen, a researcher at the French National Centre for Scientific Research (CNRS), comparing the signal to LIGO’s first detection of gravitational waves in 2015. “This is more like something that goes ‘bang,’ and it’s the most massive signal LIGO and Virgo have seen.”

The international team of scientists, who make up the LIGO Scientific Collaboration (LSC) and the Virgo Collaboration, have reported their findings in two papers published today. One, appearing in Physical Review Letters, details the discovery, and the other, in The Astrophysical Journal Letters, discusses the signal’s physical properties and astrophysical implications.

“LIGO once again surprises us not just with the detection of black holes in sizes that are difficult to explain, but doing it using techniques that were not designed specifically for stellar mergers,” says Pedro Marronetti, program director for gravitational physics at the National Science Foundation. “This is of tremendous importance since it showcases the instrument’s ability to detect signals from completely unforeseen astrophysical events. LIGO shows that it can also observe the unexpected.”

In the mass gap

The uniquely large masses of the two inspiraling black holes, as well as the final black hole, raise a slew of questions regarding their formation.

All of the black holes observed to date fit within either of two categories: stellar-mass black holes, which measure from a few solar masses up to tens of solar masses and are thought to form when massive stars die; or supermassive black holes, such as the one at the center of the Milky Way galaxy, that are from hundreds of thousands, to billions of times that of our sun.

However, the final 142-solar-mass black hole produced by the GW190521 merger lies within an intermediate mass range between stellar-mass and supermassive black holes — the first of its kind ever detected.

The two progenitor black holes that produced the final black hole also seem to be unique in their size. They’re so massive that scientists suspect one or both of them may not have formed from a collapsing star, as most stellar-mass black holes do.

According to the physics of stellar evolution, outward pressure from the photons and gas in a star’s core support it against the force of gravity pushing inward, so that the star is stable, like the sun. After the core of a massive star fuses nuclei as heavy as iron, it can no longer produce enough pressure to support the outer layers. When this outward pressure is less than gravity, the star collapses under its own weight, in an explosion called a core-collapse supernova, that can leave behind a black hole.

This process can explain how stars as massive as 130 solar masses can produce black holes that are up to 65 solar masses. But for heavier stars, a phenomenon known as “pair instability” is thought to kick in. When the core’s photons become extremely energetic, they can morph into an electron and antielectron pair. These pairs generate less pressure than photons, causing the star to become unstable against gravitational collapse, and the resulting explosion is strong enough to leave nothing behind. Even more massive stars, above 200 solar masses, would eventually collapse directly into a black hole of at least 120 solar masses. A collapsing star, then, should not be able to produce a black hole between approximately 65 and 120 solar masses — a range that is known as the “pair instability mass gap.”

But now, the heavier of the two black holes that produced the GW190521 signal, at 85 solar masses, is the first so far detected within the pair instability mass gap.

“The fact that we’re seeing a black hole in this mass gap will make a lot of astrophysicists scratch their heads and try to figure out how these black holes were made,” says Christensen, who is the director of the Artemis Laboratory at the Nice Observatory in France.

One possibility, which the researchers consider in their second paper, is of a hierarchical merger, in which the two progenitor black holes themselves may have formed from the merging of two smaller black holes, before migrating together and eventually merging.

“This event opens more questions than it provides answers,” says LIGO member Alan Weinstein, professor of physics at Caltech. “From the perspective of discovery and physics, it’s a very exciting thing.”

“Something unexpected”

There are many remaining questions regarding GW190521.

As LIGO and Virgo detectors listen for gravitational waves passing through Earth, automated searches comb through the incoming data for interesting signals. These searches can use two different methods: algorithms that pick out specific wave patterns in the data that may have been produced by compact binary systems; and more general “burst” searches, which essentially look for anything out of the ordinary.

LIGO member Salvatore Vitale, assistant professor of physics at MIT, likens compact binary searches to “passing a comb through data, that will catch things in a certain spacing,” in contrast to burst searches that are more of a “catch-all” approach.

In the case of GW190521, it was a burst search that picked up the signal slightly more clearly, opening the very small chance that the gravitational waves arose from something other than a binary merger.

“The bar for asserting we’ve discovered something new is very high,” Weinstein says. “So we typically apply Occam’s razor: The simpler solution is the better one, which in this case is a binary black hole.”

But what if something entirely new produced these gravitational waves? It’s a tantalizing prospect, and in their paper the scientists briefly consider other sources in the universe that might have produced the signal they detected. For instance, perhaps the gravitational waves were emitted by a collapsing star in our galaxy. The signal could also be from a cosmic string produced just after the universe inflated in its earliest moments — although neither of these exotic possibilities matches the data as well as a binary merger.

“Since we first turned on LIGO, everything we’ve observed with confidence has been a collision of black holes or neutron stars,” Weinstein says “This is the one event where our analysis allows the possibility that this event is not such a collision. Although this event is consistent with being from an exceptionally massive binary black hole merger, and alternative explanations are disfavored, it is pushing the boundaries of our confidence. And that potentially makes it extremely exciting. Because we have all been hoping for something new, something unexpected, that could challenge what we’ve learned already. This event has the potential for doing that.”

An international research collaboration including Northwestern University astronomers has witnessed the birth of an "intermediate-mass" black hole. This is the first conclusive discovery of an intermediate-mass black hole, an object which has long eluded astronomers. The cosmic event, its energy detected on Earth in the form of gravitational waves, is the most massive black hole merger yet observed in gravitational waves.

Two black holes likely collided and merged to create a more massive black hole with a final mass 142 times that of the sun, or 142 solar masses. This final black hole is the first to be found in an intermediate-mass range that lies between stellar-mass and supermassive black holes.

Another first is that the heavier of the two merging black holes, at 85 solar masses, is the first black hole so far detected within what is known as the "pair-instability mass gap."

Researchers detected the gravitational-wave signal on May 21, 2019, with the National Science Foundation's LIGO (Laser Interferometry Gravitational-wave Observatory (LIGO), a pair of identical, 4-kilometer-long interferometers in the United States, and Virgo, a 3-kilometer-long detector in Italy. The signal was dubbed GW190521.

The team of scientists, who make up the LIGO Scientific Collaboration (LSC) and the Virgo Collaboration, has reported its findings in two papers to be published Sept. 2. One, appearing in Physical Review Letters, details the discovery of the gravitational wave signal, and the other, in the Astrophysical Journal Letters, discusses the signal's physical properties and astrophysical implications.

Christopher Berry, the CIERA Board of Visitors Research Professor in Northwestern's CIERA (Center for Interdisciplinary Exploration and Research in Astrophysics), was an LSC Editorial Board reviewer for the discovery paper. Chase Kimball, also an LSC member and a Northwestern astronomy Ph.D. student, contributed to the analysis of the astrophysical origins of GW190521 in the implications paper. Kimball is co-advised by Berry and Vicky Kalogera, the principal investigator of Northwestern's LSC group, director of CIERA and the Daniel I. Linzer Distinguished University Professor of Physics and Astronomy in the Weinberg College of Arts and Sciences.

"One of the great mysteries in astrophysics is how do supermassive black holes form?" Berry said. "They are the million solar-mass elephants in the room. Do they grow from stellar-mass black holes, which are born when a star collapses, or are they born via an undiscovered means? Long have we searched for an intermediate-mass black hole to bridge the gap between stellar-mass and supermassive black holes. Now, we have proof that intermediate-mass black holes do exist."

The signal of GW190521, resembling about four short wiggles, was extremely brief in duration, lasting less than one-tenth of a second. From what the researchers can tell, it was generated by a source that is roughly 5 gigaparsecs away, when the universe was about half its current age, meaning that the signal travelled across space for 7 billion years before reaching Earth. GW190521's source is the most distant gravitational-wave source detected so far.

"This doesn't look much like a chirp, which is what we typically detect," said Virgo member Nelson Christensen, a researcher at the French National Centre for Scientific Research, comparing the signal to LIGO's first detection of gravitational waves in 2015. "This is more like something that goes 'bang,' and it's the most massive signal LIGO and Virgo have seen."

Almost every confirmed gravitational-wave signal to date has been from a binary merger, either between two black holes or two neutron stars. This newest merger appears to be the most massive yet, involving two inspiraling black holes with masses about 85 and 66 solar masses.

"Gravitational-wave observations are revolutionary," Berry said. "Each new detection refines our understanding of how black holes form. With these gravitational-wave breakthroughs, it won't be long until we have enough data to uncover the secrets of how black holes are born and how they grow."

The LIGO-Virgo team has also measured each black hole's spin and discovered that as the black holes were circling ever closer together, they could have been spinning about their own axes, at angles that were out of alignment with the axis of their orbit. The black holes' misaligned spins likely caused their orbits to wobble, or "precess," as the two Goliaths spiraled toward each other.

The new signal likely represents the instant that the two black holes merged. The merger created an even more massive black hole, of about 142 solar masses, and released an enormous amount of energy, equivalent to around 8 solar masses, spread across the Universe in the form of gravitational waves.

"LIGO once again surprises us not just with the detection of black holes in sizes that are difficult to explain, but doing it using techniques that were not designed specifically for stellar mergers," said Pedro Marronetti, program director for gravitational physics at the National Science Foundation. "This is of tremendous importance since it showcases the instrument's ability to detect signals from completely unforeseen astrophysical events. LIGO shows that it can also observe the unexpected."

In the mass gap

The uniquely large masses of the two inspiraling black holes, as well as the final black hole, raise a slew of questions regarding their formation.

All of the black holes observed to date fit within either of two categories: stellar-mass black holes, which measure from a few solar masses up ¬to tens of solar masses and are thought to form when massive stars die; or supermassive black holes, such as the one at the center of the Milky Way galaxy, that are from hundreds of thousands to billions of times the mass of our sun.

However, the 142-solar-mass black hole produced by the GW190521 merger lies within an intermediate mass range between stellar-mass and supermassive black holes. And the two black holes that produced the final black hole also seem to be unique in their size. They're so massive that scientists suspect one or both of them may not have formed from a collapsing star, as most stellar-mass black holes do.

According to the physics of stellar evolution, outward pressure from the photons and gas in a star's core support it against the force of gravity pushing inward, so that the star is stable, like the sun. After the core of a massive star fuses nuclei as heavy as iron, it can no longer produce enough pressure to support the outer layers. When this outward pressure is less than gravity, the star collapses under its own weight, in an explosion called a core-collapse supernova, which can leave behind a black hole.

This process can explain how stars as massive as 130 solar masses can produce black holes that are up to 65 solar masses. But for heavier stars, a phenomenon known as "pair instability" is thought to kick in. When the core's photons become extremely energetic, they can morph into an electron and antielectron pair. These pairs generate less pressure than photons, causing the star to become unstable against gravitational collapse, and the resulting explosion is strong enough to leave nothing behind. Even more massive stars, above 200 solar masses, would eventually collapse directly into a black hole of at least 120 solar masses. A collapsing star, then, should not be able to produce a black hole between approximately 65 and 120 solar masses -- a range that is known as the "pair-instability mass gap."

But now, the heavier of the two black holes that produced the GW190521 signal, at 85 solar masses, is the first so far detected confidently within the pair-instability mass gap. Astrophysicists think of black holes forming from stars collapsing, but an 85-solar-mass black hole should be impossible this way, Northwestern's Berry said.

"There are many ideas about how to get around this -- merging two stars together, embedding the black hole in a thick disc of material it can swallow, or primordial black holes created in the aftermath of the Big Bang," he said. "The idea I really like is a hierarchical merger where we have a black hole formed from the previous merger of two smaller black holes."

A hierarchical merger, in which the two progenitor black holes themselves may have formed from the merging of two smaller black holes, before migrating together and eventually merging, is one possibility which the researchers consider in their second paper. Kimball, Berry and Kalogera have been studying hierarchical mergers guided by independent theoretical predictions by other researchers at Northwestern.

"After so many gravitational-wave observations since the first detection in 2015, it's exciting that the universe is still throwing new things at us, and this 85-solar-mass black hole is quite the curveball," Kimball said.

For the implications paper on GW190521, Kimball calculated the merger rates, one of the key pieces of information for the astrophysical interpretation, and led the calculation of the probability that the source is the result of a hierarchical merger. The odds for or against a hierarchical merger are roughly even when considering mergers in globular clusters, dense balls of hundreds of thousands of stars and black holes, but the odds may be better for a merger in the dense heart of a galaxy.

Discussing results, Kimball said, "While GW190521's origin is a mystery, I'm particularly excited about the prospect of it being the result of a hierarchical merger. In the future, with more binary black hole mergers and a better understanding of the pair-instability mass gap, we should be able to tell more definitively whether GW190521's big black hole was itself the product of a previous merger."

"This event opens more questions than it provides answers," said LIGO member Alan Weinstein, professor of physics at the California Institute of Technology. "From the perspective of discovery and physics, it's a very exciting thing."

'Something unexpected'

There are many remaining questions regarding GW190521.

The LIGO and Virgo detectors can detect gravitational-wave signals from many sources. In the case of GW190521, the signal is sufficiently short that it may be interpreted as something other than a binary of black holes, opening the very small chance that the gravitational waves arose from a new source other than a binary merger.

"What if something entirely new produced these gravitational waves?" Kalogera said. "It's a tantalizing prospect, and in the implications paper, the scientists briefly consider other sources in the universe that might have produced the signal they detected. For instance, perhaps the gravitational waves were emitted by a collapsing star in our galaxy. The signal also could be from a cosmic string produced just after the universe inflated in its earliest moments -- although neither of these exotic possibilities matches the data as well as a binary merger."

The LIGO and Virgo detectors finished their latest observing run this past March. Data from this period are still being analyzed and are expected to contain many more gravitational-wave signals. The detectors are planned to resume observing next year after work is done to increase their detection range; the LIGO and Virgo detectors also will be joined for the first time by the Japanese KAGRA detector. The enhanced global detector network is expected to make more gravitational-wave discoveries than ever before.

"We're really in the dawn of gravitational-wave astronomy," graduate student Kimball said. "It's hard to pick a better time to come up as an astrophysicist."

Scientists observed what appears to be a bulked-up black hole tangling with a more ordinary one. The research team, which includes physicists from the University of Maryland, detected two black holes merging, but one of the black holes was 1 1/2 times more massive than any ever observed in a black hole collision. The researchers believe the heavier black hole in the pair may be the result of a previous merger between two black holes.
This type of hierarchical combining of black holes has been hypothesized in the past but the observed event, labeled GW190521, would be the first evidence for such activity. The Laser Interferometer Gravitational-Wave Observatory (LIGO) Scientific Collaboration (LSC) and Virgo Collaboration announced the discovery in two papers published September 2, 2020, in the journals Physical Review Letters and Astrophysical Journal Letters.

The scientists identified the merging black holes by detecting the gravitational waves--ripples in the fabric of space-time--produced in the final moments of the merger. The gravitational waves from GW190521 were detected on May 21, 2019, by the twin LIGO detectors located in Livingston, Louisiana, and Hanford, Washington, and the Virgo detector located near Pisa, Italy.

"The mass of the larger black hole in the pair puts it into the range where it's unexpected from regular astrophysics processes," said Peter Shawhan, a professor of physics at UMD, an LSC principal investigator and the LSC observational science coordinator. "It seems too massive to have been formed from a collapsed star, which is where black holes generally come from."

The larger black hole in the merging pair has a mass 85 times greater than the sun. One possible scenario suggested by the new papers is that the larger object may have been the result of a previous black hole merger rather than a single collapsing star. According to current understanding, stars that could give birth to black holes with masses between 65 and 135 times greater than the sun don't collapse when they die. Therefore, we don't expect them to form black holes.

"Right from the beginning, this signal, which is only a tenth of a second long, challenged us in identifying its origin," said Alessandra Buonanno, a College Park professor at UMD and an LSC principal investigator who also has an appointment as Director at the Max Planck Institute for Gravitational Physics in Potsdam, Germany. "But, despite its short duration, we were able to match the signal to one expected of black-hole mergers, as predicted by Einstein's theory of general relativity, and we realized we had witnessed, for the first time, the birth of an intermediate-mass black hole from a black-hole parent that most probably was born from an earlier binary merger."

GW190521 is one of three recent gravitational wave discoveries that challenge current understanding of black holes and allow scientists to test Einstein's theory of general relativity in new ways. The other two events included the first observed merger of two black holes with distinctly unequal masses and a merger between a black hole and a mystery object, which may be the smallest black hole or the largest neutron star ever observed. A research paper describing the latter was published in Astrophysical Journal Letters on June 23, 2000, while a paper about the former event will be published soon in Physical Review D.

"All three events are novel with masses or mass ratios that we've never seen before," said Shawhan, who is also a fellow of the Joint Space-Science Institute, a partnership between UMD and NASA's Goddard Space Flight Center. "So not only are we learning more about black holes in general, but because of these new properties, we are able to see effects of gravity around these compact bodies that we haven't seen before. It gives us an opportunity to test the theory of general relativity in new ways."

For example, the theory of general relativity predicts that binary systems with distinctly unequal masses will produce gravitational waves with higher harmonics, and that is exactly what the scientists were able to observe for the first time.

"What we mean when we say higher harmonics is like the difference in sound between a musical duet with musicians playing the same instrument versus different instruments," said Buonanno, who developed the waveform models to observe the harmonics with her LSC group. "The more substructure and complexity the binary has -- for example the masses or spins of the black holes are different--the richer is the spectrum of the radiation emitted."

In addition to these three black hole mergers and a previously reported binary neutron star merger, the observational run from April 2019 through March 2020 identified 52 other potential gravitational wave events. The events were posted to a public alert system developed by LIGO and Virgo collaboration members in a program originally spearheaded by Shawhan so that other scientists and interested members of the public can evaluate the gravity wave signals.

"Gravitational wave events are being detected regularly," Shawhan said, "and some of them are turning out to have remarkable properties which are extending what we can learn about astrophysics."

The enigmatic variations of light in a binary system, located in Sagittarius constellation, could be explained by the presence of a variable gas disk around a hot star that revolves around a cooler star. These are the conclusions published in the journal Astronomy & Astrophysics and which brought by researchers from Chile, Serbia and Poland.

It is the binary system OGLE-BLG-ECL-157529, located at 10.567 light years from Earth, which had been reported in a catalog of binary stars in the direction of the Galactic center. The system showed a peculiar variation of its brightness, with a period close to 800 days, together with typical changes of an eclipsing binary star of 24.8 days. The data analyzed cover 18.5 years and were obtained at the Las Campanas observatory in Chile, as part of the Polish OGLE project.

The object was identified as a binary star, whose cooler and evolved star transfers mass to the hottest star, forming around it a disk of gas of about 30 solar radii of extension. The disk would have a temperature of about 3.000 Kelvin, and it would undergo changes in its size and temperature as a result of variations in the amount of material it receives from the cold star.

The team of researchers was integrated by Ronald Mennickent, Juan Garcés and Dominik Schleicher, from the Department of Astronomy of University of Concepción; Gojko Djurasevic, from the Astronomical Observatory Volgina, Patryk Iwanek, Radoslaw Poleski and Igor Soszy?ski, from the University of Warsaw. "The team of co-author have been in close collaboration since decades, and includes a PhD student of mine (Garcés) and colleagues who I have met at conferences and Dr. Schleicher who is from my institution", said Mennickent.

The article shows how changes in disc properties convincingly explain the changes in the brightness of the binary system. In particular, this system shows strange variations in the depth of its eclipses which can be explained by the evolution of this gaseous disk, according to the authors. "Many stars in the Universe are binary, and the most massive ones go through these mass transfer processes, which dramatically conditions their evolution. These objects can produce in the distant future, supernovae or even emitters of gravitational radiation", Dr. Mennickent explains.