It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Wednesday, June 16, 2021
Fuel flow, heat fluctuations drive dangerous oscillations in rocket engines
Power source clusters near rocket engine fuel injectors could create combustion oscillations
IMAGE: COMBUSTION CHAMBER DURING COMBUSTION OSCILLATIONS IN A MODEL ROCKET ENGINE. view more
CREDIT: HIROSHI GOTODA
WASHINGTON, June 8, 2021 -- Combustion engines can develop high frequency oscillations, leading to structural damage to the engines and unsafe operating conditions. A detailed understanding of the physical mechanism that causes these oscillations is required but has been lacking until now.
In Physics of Fluids, by AIP Publishing, research from the Tokyo University of Science and the Japan Aerospace Exploration Agency clarifies the feedback processes that give rise to these oscillations in rocket engines.
The investigators studied simulated combustion events in a computational model of a rocket combustor. Their analysis involved sophisticated techniques, including symbolic dynamics and the use of complex networks to understand the transition into oscillatory behavior.
The symbolic dynamics techniques allowed the scientists to determine similarities in behavior between two variables that characterize the combustion event. They found a relationship between fluctuations in the flow velocity of the fuel injector and fluctuations in the heat release rate of the combustor.
A rocket engine uses injectors to deliver a fuel, typically hydrogen gas, H2, and an oxidizer, oxygen gas, O2, to a combustion chamber where ignition and subsequent combustion of the fuel occurs.
"Periodic contact of the unburnt H2/O2 mixture with high-temperature products of the H2 [and] air flame gives rise to significant fluctuations in the ignition location," said author Hiroshi Gotoda.
Fluctuations in the ignition location produce fluctuations in the heat release rate, which affects pressure fluctuations in the combustor.
"We found that the heat release fluctuations and pressure fluctuations synchronize to each other," said Gotoda.
The product of the pressure and the heat release rate fluctuations in the combustor is an important physical quantity for understanding the origin of combustion oscillations. Regions where this product is greater than zero correspond to acoustic power sources that drive the oscillations.
The investigators discovered power sources in the shear layer near the injector rim. These power sources would suddenly collapse and reemerge upstream in a periodic fashion, leading to oscillations in combustion.
"The repetition of the formation and collapse of thermoacoustic source clusters in the hydrodynamic shear layer region between the inner oxidizer and outer fuel jets plays an important role in driving combustion oscillations," said Gotoda.
The investigators believe their analysis method will lead to a better understanding of the dangerous oscillations that sometimes arise in rocket engines and other combustors.
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The article "Formation mechanism of high-frequency combustion oscillations in a model rocket engine combustor" is authored by Satomi Shima, Kosuke Nakamura, Hiroshi Gotoda, Yuya Ohmichi, and Shingo Matsuyama. The article will appear in Physics of Fluids on June 8, 2021 (DOI: 10.1063/5.0048785). After that date, it can be accessed at https://aip.scitation.org/doi/full/10.1063/5.0048785.
ABOUT THE JOURNAL
Physics of Fluids is devoted to the publication of original theoretical, computational, and experimental contributions to the dynamics of gases, liquids, and complex fluids. See https://aip.scitation.org/journal/phf.
More than a bumpy ride: turbulence offers boost to birds
ITHACA, N.Y. - Most sensible air travelers dread turbulence. A little atmospheric hiccup can shake airplanes, rattle nerves and spill beverages. A Cornell University-led study found that birds don't mind at all.
By combining wind speed data with the measured accelerations of a golden eagle outfitted with GPS tracking instruments, the researchers suggest that, rather than hindering flight, turbulence is a source of energy that birds may use to their advantage.
This counterintuitive discovery could revise what we know about avian flight, and help the aerospace industry develop faster, more efficient ways to fly in turbulent environments.
The paper, "Turbulence Explains the Accelerations of an Eagle in Natural Flight," published in PNAS. The lead author was doctoral student Kasey Laurent.
While the flight of birds may appear easy and graceful to earthbound spectators, winged animals are actually navigating air flow that is structured, textured and constantly in flux, according to Gregory Bewley, assistant professor in the Sibley School of Mechanical and Aerospace Engineering, who led the team.
In order to take his experiments out of the lab and into the sky, Bewley's team partnered with two groups - Conservation Science Global and Cellular Tracking Technologies. Scientists from these companies captured a female golden eagle in Alabama, rigged it with a solar GPS telemetry unit with an accelerometer weighing less than 3 ounces, then released the bird.
Over the course of 17 days, as the eagle migrated north along the Appalachian Mountains toward Canada, the GPS "backpack" transmitted more than 200 hours of data - including location coordinates, altitude, ground speed and tri-axial acceleration - via cellular networks.
Bewley's lab then obtained wind speed data from the National Centers for Environmental Prediction's weather history databases and mapped it onto the eagle's flight measurements, identifying the bird's various flying and nonflying behaviors.
They found a "highly irregular, fluctuating pattern" in the eagle's accelerations, which resembles the typical trajectories of particles in turbulent airflows. At timescales ranging from 0.5 to 10 seconds - which translates to approximately 1 to 25 wingbeats - the eagle's accelerations and atmospheric turbulence were completely in synch.
And just how intense are these accelerations? As a point of comparison, people riding in a car or aboard a commercial flight experience less than 0.1 g, or one factor of earth's gravitational acceleration. Meanwhile, the accelerations of birds exceed 1 g - which would throw those human passengers out of their seats.
Of course, aeronautical engineers strive to reduce turbulence as much as possible, and no airline passenger or pilot wants a bumpy ride. But Bewley believes there are opportunities to harness the energy of turbulence, particularly for person-less transport and small reconnaissance aircraft.
"If you could find a path in which every vortex is pushing you the right way, then obviously you get there a little faster with a little less energy," Bewley said. "We're still working hard to understand turbulence by itself. I think it's fascinating that there might be some practical empirical knowledge embodied in wildlife that we don't appreciate yet."
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The research was partially funded by the Friends of Talladega National Forest.
As climates change, prepare for more mosquitoes in winter, new study shows
Mosquitoes can adjust to rapid changes in temperature, indicating that mosquitoes normally dormant during winter may become active year-round
In many parts of the world, mosquitoes are a common summertime nuisance.
But in places on the front lines of climate change, these disease-spreading insects may one day be a year-round problem, according to new research from the University of Florida.
"In tropical regions, mosquitoes are active all year, but that isn't the case for the rest of the world. Outside of the tropics, winter temperatures cause mosquitoes to go into a kind of hibernation called diapause. We call these mosquitoes 'cold bounded' because their activity is limited by these lower temperatures," said Brett Scheffers, senior author of the study and an assistant professor in the UF/IFAS wildlife ecology and conservation department.
"However, with climate change, we expect summers to get longer and winters to become shorter and warmer. What will that mean for those cold bounded mosquitoes? How will they respond?" Scheffers said.
To help answer those questions, the study's authors conducted experiments with mosquitoes collected in and around Gainesville, a North Central Florida city on the dividing line between subtropical and temperate climates. Their study is published in the journal "Ecology."
The researchers compared how mosquitoes collected during different parts of the year responded to changes in temperature.
"We found that the mosquitoes in our study are what we call 'plastic,' meaning that, like a rubber band, the range of temperatures they can tolerate stretches and contracts at different times of year," Scheffers said.
The researchers found that in the spring, when nighttime temperatures are still cold and daytime temperatures begin to warm up, mosquitoes can tolerate a larger range of temperatures. Come summer, when daily temperatures are warm, that range contracts. In autumn, when temperatures begin to cool off, the range stretches again, Scheffers explained.
"That tells us that as climate change makes our autumns and winters warmer, mosquitoes in more temperate regions are well prepared to be active during those times," Scheffers said.
"Our results suggest that to better understand how well populations and species may be able to tolerate ongoing climate change, we need to measure species thermal responses across different times of the year," said Brunno Oliveira, the study's first author, who conducted the study while a postdoctoral researcher in Scheffers's lab.
"This information would help us to deliver a more accurate representation of the temperature range a species can tolerate," said Oliveira, now a postdoctoral research at University of California Davis.
For their experiment, the researchers collected the mosquitoes at more than 70 sites around Gainesville and the nearby UF/IFAS Ordway-Swisher Biological Station, a 9,500 acre research and conservation area located about 20 miles east of the city.
The scientists lured mosquitoes with special traps that emit carbon dioxide gas, the same gas that humans and animals exhale when we breath. To a mosquito, a strong whiff of carbon dioxide means a meal is nearby.
With these traps, the researchers caught more than 28,000 mosquitoes representing 18 species. From this collection, the scientists randomly sampled about 1,000 mosquitoes to test in the lab.
Each mosquito was placed in a vial that was then put in a water bath. Over time, the researchers changed the water temperature, increasing or decreasing the temperature inside the vials. The scientists monitored each mosquito's activity, noting when mosquitoes became inactive, a signal that either the upper or lower temperature thresholds were met.
"It was surprising to see how well these little creatures could tolerate high temperatures during the experiments, often well above the mean ambient temperatures measured by the weather stations," said Gécica Yogo, one of the study's co-authors.
Yogo helped conduct the study while she was research scholar trainee at UF as part of her master's program at AgroParisTech in France. She is now a soil carbon engineer at INRAE, the French National Institute for Agriculture, Food and Environment.
The researchers say they don't yet know what allows mosquitoes to adjust to rapid changes in temperature.
"Many people do not realize how quickly natural selection can act on short-lived animals," said Daniel Hahn, professor in the UF/IFAS entomology and nematology department and a co-author of the study. "Whether the changes we are seeing in mosquito thermal properties are due to rapid natural selection across seasons, seasonal plasticity - much like a dog changing its coat -- or a combination of both, is what we are working on now."
The researchers say that insights from this study can help communities better prepare for the impacts of climate change as they relate to mosquitoes, which spread diseases that affect humans and animals.
"The more mosquito activity there is, the greater the risk of these diseases spreading. Knowledge is power, and knowing that mosquitoes will be more active for more of the year can inform how we get ready for climate change," Scheffers said.
Peter Jiang, one of the study's co-authors and an entomologist with City of Gainesville's Mosquito Control division, said that residents play an important role in controlling mosquitoes now and in the future.
Simple actions can keep mosquito populations down, Jiang said.
"Neighbors are encouraged to empty, remove or cover any receptacle that would hold water -- particularly old bottles, tin cans, junk and tires -- repairing leaky pipes, outside faucets and screens, covering or turning small boats upside down, and, twice a week, changing water in wading pools, bird baths, pet dishes and vases holding flowers or cuttings," Jiang said.
Residents looking to learn more about how to control mosquitoes can contact their local UF/IFAS Extension office or their municipal or county mosquito control program.
In addition to informing decision-making, studies like this one bring into focus an aspect of climate change now getting more attention.
"When we talk about how climate change might affect plants and animals, we are often talking about species moving to new areas because the conditions are changing -- in other words, the arrival of something new. However, climate change will also affect species we live with right now, like highly flexible mosquitoes, and that's another aspect to consider," Scheffers
URI researchers: New survey method proves Rhode Island's rarest frog may not be so rare
IMAGE: THE EASTERN SPADEFOOT TOAD, ACTUALLY A PRIMITIVE FROG, MAY NOT BE SO RARE AFTER ALL ACCORDING TO A STUDY BY UNIVERSITY OF RHODE ISLAND RESEARCHERS WHO USED A SELDOM-USED METHODOLOGY... view more
CREDIT: ANNE DEVAN-SONG
KINGSTON, R.I. - June 14, 2021 - The rarest frog in Rhode Island may not be as rare as scientists once thought after a study by University of Rhode Island researchers using a seldom-used methodology turned up many more of the endangered animals than they expected.
Eastern spadefoots - often called spadefoot toads, though they are actually frogs - have long been considered highly secretive and difficult to find outside of their one- or two-day annual breeding periods on rainy nights. In some years, they don't breed at all. But after scientists reported just 50 sightings of the frogs over the previous 70 years, the Rhode Island researchers observed 42 spadefoots in 10 nights of searching last summer using the new methodology.
"We collected all the myths and misconceptions about spadefoots that have been published or told to us by herpetologists, and we decided to conduct surveys to show that the frogs aren't secretive, that they don't only come out when weather is suitable, and they can be detected easily using a noninvasive censusing method," said Anne Devan-Song, a former URI graduate student who is now a doctoral student at Oregon State University.
While working as a URI research associate in collaboration with Associate Professor Nancy Karraker, Devan-Song led a team that conducted amphibian surveys in Colonial National Historical Park in Virginia from 2015 to 2017 by using a spotlight at night to detect the animals' eyeshine in forests. A previous researcher conducted amphibian surveys at the park 15 years ago and only detected two Eastern spadefoots, but Devan-Song and her team found up to hundreds of them, even on dry nights, and a total of more than 3,000 individuals.
"It completely contradicted everything we'd read about them in the scientific literature, with the exception of recent studies in Massachusetts and Connecticut," said Devan-Song, whose research was published this month in the Journal of Herpetology. "The perception is that they're difficult to detect in large numbers outside of rainy weather conditions, but I was stumbling all over them everywhere I went at this particular site, even in drought years when I was nowhere near a known breeding pond."
To be sure that she could distinguish between the eyeshine of spadefoots and the eyeshine of other creatures active at night - a concern expressed by previous scientists who rejected the spotlighting method - Devan-Song confirmed her ability to accurately identify spadefoot eyeshine by capturing every frog whose eyeshine she detected.
Since the Virginia site may have been home to an uncharacteristically high number of the frogs, Devan-Song collaborated with Rhode Island Department of Environmental Management herpetologist Scott Buchanan to use her spotlighting technique at scattered sites around Rhode Island, where the frogs were believed to be located at only one site and were seldom seen there.
"Spadefoots are at the northern end of their range in Rhode Island and are incredibly rare there," Devan-Song said. "You can't just drive around at night and hear them, and there's little chance of finding them by chance. And yet with just a little bit of spotlighting effort, you can find them."
For sites that were occupied, the frogs were detected on nine out of ten survey nights in Rhode Island, the same rate as they were found in Virginia, and a new breeding population was discovered at a site in Westerly. In both states, the majority of spadefoots observed were sub-adults, an age class seldom detected using traditional survey methods.
"The lack of appropriate methods has hindered the study of this species, which is considered endangered in many states, including Rhode Island," said Devan-Song. "Without appropriate field methods, you can't gather information about certain demographic classes and you can't make accurate population assessments.
"By looking for them only on rainy nights or only near ponds, it has hindered the study of this species for decades," she added. "There is a huge amount of information that can be collected, especially on these overlooked demographic categories."
The research team has at least two additional scientific papers in the works that will shed more light on the life history of Eastern spadefoots, both based on the data collected from Rhode Island and Virginia. One describes the social structure of the species, which had been unknown outside the breeding season.
"The general idea had been that these frogs are solitary and don't interact much except when they go to their ponds to breed," she said. "But the reality is that they're doing lots of interesting things in the uplands. Their social structure is much more complex than we imagined."
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Head impacts and abnormal imaging findings in youth football players over consecutive seasons
IMAGE: IMAGING DATA FROM TWO FOOTBALL ATHLETE SUBJECTS SHOWING A COMPARISON BETWEEN ABNORMAL VOXELS FROM THE SEASON WITH THE HIGHER 50TH PERCENTILE NUMBER OF IMPACTS PER PRACTICE SESSION AND ABNORMAL VOXELS FROM... view more
CREDIT: COPYRIGHT 2021 AANS.
CHARLOTTESVILLE, VA (JUNE 15, 2021). In this longitudinal study, researchers from Wake Forest School of Medicine and the University of Texas Southwestern in Dallas, Texas, examined the frequency and severity of head impacts experienced by youth football players and how exposure to head impacts changes from one year to the next in returning players. The researchers then compared the resulting data with findings on neuroimaging studies obtained over consecutive years in the same athletes. The comparison demonstrated a significant positive association between changes in head impact exposure (HIE) metrics and changes in abnormal findings on brain imaging studies. Full details of this study can be found in the article "Analysis of longitudinal head impact exposure and white matter integrity in returning youth football players" by Mireille E. Kelley, PhD, and colleagues, published today in the Journal of Neurosurgery: Pediatrics.
Illustrating the considerable variability in head impacts among football players, Kelley et al. inform us that in one football season, youth football players (10-13 years of age) can sustain between 26 and 1003 head impacts, and high school players can sustain between 129 and 1258 head impacts. Fortunately, most of these impacts do not result in concussions. In fact, most of these subconcussive impacts do not produce any acute signs or symptoms attributed to concussions.
Nevertheless, there is concern that, over time, repetitive subconcussive impacts may cause damage to contact-sport athletes' brains. This is particularly of concern when we are speaking of young athletes, who have many years ahead of them in their sport and in their lives.
To examine changes in head impact exposure (HIE) from year to year, the researchers focused on a group of 47 athletes who participated in youth football for two or more consecutive years sometime between 2012 and 2017. The athletes played on a variety of teams. All wore football helmets outfitted with the Riddell Head Impact Telemetry System™, which measures linear and rotational head accelerations that occur during a head impact. The outfitted helmets were worn during all football sessions--both practices and games. Biomechanical data on head impacts were transmitted in real time via radio waves to a sideline data collection field unit for later analysis. Altogether, the data covered 109 football athlete-seasons with 41,148 head impacts. Despite the large number of head impacts, none of the 47 youth athletes sustained a clinically diagnosed concussion during the study period.
Kelley et al. examined a variety of HIE metrics: number of head impacts, 50th percentile of impacts per football session (game, practice, and both); 95th percentile peak linear and rotational accelerations measured by the Head Impact Telemetry System System™; and risk-weighted cumulative exposure, a metric summarizing the frequency and magnitude of head impacts experienced by the athlete over a single season. The researchers found that variations in HIE metrics differed from year to year and between athletes. For example, in an examination of data from three consecutive seasons, some youths experienced more impacts in their second year of play than in their first, while other youths experienced fewer impacts in later years of play.
Although trends in increasing mean number of game impacts, mean 50th percentile of impacts per football session, and mean 50th percentile of impacts per game session were identified over three seasons, the differences between the means were not statistically significant. The researchers did note "significant variability in several HIE metrics among teams," but this was not the focus of this study.
In 19 of the 47 youth football athletes, brain images were obtained pre- and post-season for two consecutive football seasons. This was done using diffusion tensor imaging (DTI), a type of magnetic resonance imaging that can be used to assess the integrity of the brain's white matter, indicating possible sites of injury. Using this technique, the researchers evaluated changes in the following scalar metrics: fractional anisotropy; mean diffusivity; and linear, planar, and spherical anisotropy coefficients.
A group of 16 youth athletes who participated in non-contact sports (for example, swimming, tennis, track) underwent DTI two times (baseline and follow-up studies, four months apart) and served as a control group. Abnormal white matter voxels (small three-dimensional areas) on youth football players' brain images were defined as voxels in which DTI scalar values increased or decreased throughout the football season significantly (two standard deviations above or below those of mean values in the control group).
Similar to the pattern of HIE, the researchers found "both increases and decreases in the number of abnormal voxels between season 1 and season 2" in the youth football athletes.
Linear regression analyses were performed to assess relationships between changes in HIE metrics and changes in DTI scalar metrics from one year to the next. There was a significant positive correlation between changes in the number of head impacts per practice session and every DTI scalar metric. In addition, significant positive correlations were determined between changes in both the 50th percentile impacts per practice sessions and the 50th percentile impacts per football sessions (including both practice and game sessions) and the various DTI scalar metrics.
In summary, the major findings of this longitudinal study include the following:
HIE varied among individual athletes from one season to the next. Increases and decreases in HIE across three consecutive seasons in individual youth football players were observed; the changes were not significant from one season to the next.
Trends in DTI imaging changes varied among individual athletes from one season to the next. Increases and decreases in the number of abnormal voxels on DTI from the first to second season were identified in individual players.
The amount of HIE an athlete experienced in football, particularly in practice, was associated with the amount of change in neuroimaging metrics. Positive associations between changes in abnormal voxels on DTI and the number of head impacts per practice session, 50th percentile impacts per practice session, and 50th percentile impacts per session overall (including both practice and game sessions) between consecutive seasons (seasons 1 and 2) were found.
Because of the significant positive correlations between changes in HIE metrics and changes in the number of abnormal voxels on DTI between consecutive seasons, the authors support efforts to reduce the number and frequency of head impacts, particularly those occurring during practice sessions, when the majority of head impacts occur. They believe this action may reduce the number of abnormal imaging findings in youth football athletes from one football season to the next.
When asked about the findings of the study, Dr. Jillian Urban, Assistant Professor at Wake Forest School of Medicine, responded, "Our findings further support ongoing efforts to reduce the number of head impacts in football practices. In an upcoming study, we plan to engage stakeholders in the youth football community to develop and test practical solutions informed by the biomechanical data we collect on field to reduce head impacts in practice."
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Article: Kelley, ME, Urban JE, Jones DA, Davenport EM, Miller LE, Snively BM, Powers AK, Whitlow CT, Maldjian JA, Stitzel JD: Analysis of longitudinal head impact exposure and white matter integrity in returning youth football players. Journal of Neurosurgery: Pediatrics, published online, ahead of print, June 15, 2021; DOI: 10.3171/2021.1.PEDS20586.
Drs. Kelley, Urban, Jones, Miller, and Stitzel are affiliated with both Wake Forest School of Medicine and Virginia Tech-Wake Forest School of Biomedical Engineering and Sciences in Winston-Salem, North Carolina. Drs. Snively, Powers, and Whitlow are affiliated with Wake Forest School of Medicine. Drs. Davenport and Maldjian are affiliated with the University of Texas Southwestern in Dallas, Texas.
Disclosure: The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.
Grant Support: Three grants from the National Institutes of Health, namely National Institute of Neurological Disorders and Stroke grants R01NS094410 and R01NS082453, and National Center for Advancing Translational Sciences grant KL2TR001421.
For additional information, please contact: Ms. Jo Ann M. Eliason, Communications Manager, Journal of Neurosurgery Publishing Group, One Morton Drive, Suite 200, Charlottesville, VA 22903. Email: joanneliason@thejns.org Phone: 434-982-1209
The Journal of Neurosurgery: Pediatrics is a monthly peer-reviewed journal focused on diseases and disorders of the central nervous system and spine in children. This journal contains a variety of articles, including descriptions of preclinical and clinical research as well as technical notes. The Journal of Neurosurgery: Pediatrics is one of six journals published by the JNS Publishing Group, the scholarly journal division of the American Association of Neurological Surgeons. Other peer-reviewed journals published by the JNS Publishing Group include the Journal of Neurosurgery, Journal of Neurosurgery: Spine, Neurosurgical Focus, Neurosurgical Focus: Video, and Case Lessons. All six journals can be accessed at http://www.thejns.org.
Founded in 1931 as the Harvey Cushing Society, the American Association of Neurological Surgeons (AANS) is a scientific and educational association with more than 10,000 members worldwide. The AANS is dedicated to advancing the specialty of neurological surgery in order to provide the highest quality of neurosurgical care to the public. All active members of the AANS are certified by the American Board of Neurological Surgery, the Royal College of Physicians and Surgeons (Neurosurgery) of Canada, or the Mexican Council of Neurological Surgery, AC. Neurological surgery is the medical specialty concerned with the prevention, diagnosis, treatment, and rehabilitation of disorders that affect the entire nervous system including the brain, spinal column, spinal cord, and peripheral nerves. For more information, visit http://www.AANS.org.
Young adults' alcohol use increases when casually dating
When young adults are more interested in socializing and casually dating, they tend to drink more alcohol, according to a new paper led by a Washington State University professor.
On the other hand, scientists found that when young adults are in serious relationships, are not interested in dating or place less importance on friendship, their alcohol use was significantly lower.
Published June 15 in the journal Substance Use & Misuse, the study included more than 700 people in the Seattle area aged 18-25 who filled out surveys every month for two years. The study used a community sample that was not limited to college students.
"Young adults shift so much in terms of social relationships that having this monthly data really allowed us to hone in on nuances and see these changes in alcohol use depending on social situations," said Jennifer Duckworth, the lead author on the paper. "The idea is to understand whether young adults may be viewing alcohol as a way to facilitate relationships. They may think of alcohol as a way to make hanging out easier or more fun."
Being able to look at young adult behavior over a longer period allowed the research team to see how alcohol use was related to socializing and relationships.
"If a college student has mid-terms, they may have less interest in spending time with friends," said Duckworth, an assistant professor in WSU's Department of Human Development. "But if it's spring break, they may place more importance on those friendships. And when friendships become more important, we found alcohol use tends to be higher."
For relationships, Duckworth and her co-authors separated single young adults into two groups: casually dating and not interesting in dating. That distinction showed a significant difference in alcohol use. Since the survey tracked people every month, they could study changes as participants moved in and out of different relationship statuses.
"For instance, one month, someone may not be interested in dating and their alcohol use tended to be lower," Duckworth said. "Then, if they start dating, alcohol use tended to be higher."
Previous research has shown that young adults in relationships tend to drink less than single people, but those studies didn't separate the term single into two separate groups based on whether or not the young adults were interested in dating.
Young adults have more high-risk alcohol use than any other age group, she said. The overall goal of this research is to understand the context for greater alcohol use by young adults.
"Understanding what's going on in their lives across time is very useful if we want to mitigate high-risk use of alcohol," Duckworth said. "We can focus on interventions that help educate young adults on what is motivating their behaviors. We're bridging alcohol use with development research in a meaningful way that can really help people."
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The young adults in the study filled out confidential monthly online surveys and received a stipend at the end of the two-year study. That combination of confidentiality, financial incentive and ease of use led to a very high retention rate, Duckworth said.
Co-authors on the paper were principal investigator Christine M. Lee, Isaac Rhew, and Anne Fairlie at the University of Washington, Megan Patrick and John Schulenberg at the University of Michigan and Jennifer L. Maggs at Pennsylvania State University.
The National Institute on Alcohol Abuse and Alcoholism (R01AA022087) provided funding for the study.
Teenagers at greatest risk of self-harming could be identified almost a decade earlier
Researchers have identified two subgroups of adolescents who self-harm and have shown that it is possible to predict those individuals at greatest risk almost a decade before they begin self-harming.
The team, based at the MRC Cognition and Brain Sciences Unit, University of Cambridge, found that while sleep problems and low self-esteem were common risk factors, there were two distinct profiles of young people who self-harm - one with emotional and behavioural difficulties and a second group without those difficulties, but with different risk factors.
Between one in five and one in seven adolescents in England self-harms, for example by deliberately cutting themselves. While self-harm is a significant risk factor for subsequent suicide attempts, many do not intend suicide but face other harmful outcomes, including repeatedly self-harming, poor mental health, and risky behaviours like substance abuse. Despite its prevalence and lifelong consequences, there has been little progress in the accurate prediction of self-harm.
The Cambridge team identified adolescents who reported self-harm at age 14, from a nationally representative UK birth cohort of approximately 11,000 individuals. They then used a machine learning analysis to identify whether there were distinct profiles of young people who self-harm, with different emotional and behavioural characteristics. They used this information to identify risk factors from early and middle childhood. The results are published in the Journal of the American Academy of Child and Adolescent Psychiatry.
Because the data tracked the participants over time, the researchers were able to distinguish factors that appear alongside reported self-harm behaviour, such as low self-esteem, from those that precede it, such as bullying.
The team identified two distinct subgroups among young people who self-harm, with significant risk factors present as early as age five, nearly a decade before they reported self-harming. While both groups were likely to experience sleep difficulties and low self-esteem reported at age 14, other risk factors differed between the two groups.
The first group showed a long history of poor mental health, as well as bullying before they self-harmed. Their caregivers were more likely to have mental health issues of their own.
For the second group, however, their self-harming behaviour was harder to predict early in childhood. One of the key signs was a greater willingness to take part in risk-taking behaviour, which is linked to impulsivity. Other research suggests these tendencies may predispose the individual towards spending less time to consider alternate coping methods and the consequences of self-harm. Factors related to their relationships with their peers were also important for this subgroup, including feeling less secure with friends and family at age 14 and a greater concern about the feelings of others as a risk factor at age 11.
Stepheni Uh, a Gates Cambridge Scholar and first author of the study, said: "Self-harm is a significant problem among adolescents, so it's vital that we understand the nuanced nature of self-harm, especially in terms of the different profiles of young people who self-harm and their potentially different risk factors.
"We found two distinct subgroups of young people who self-harm. The first was much as expected - young people who experience symptoms of depression and low self-esteem, face problems with their families and friends, and are bullied. The second, much larger group was much more surprising as they don't show the usual traits that are associated with those who self-harm."
The researchers say that their findings suggest that it may be possible to predict which individuals are most at risk of self-harm up to a decade ahead of time, providing a window to intervene.
Dr Duncan Astle said: "The current approach to supporting mental health in young people is to wait until problems escalate. Instead, we need a much better evidence base so we can identify who is at most risk of mental health difficulties in the future, and why. This offers us the opportunity to be proactive, and minimise difficulties before they start.
"Our results suggest that boosting younger children's self-esteem, making sure that schools implement anti-bullying measures, and providing advice on sleep training, could all help
Teens experienced helplessness whenexposed to secondhand racism
Activism might help
ANN & ROBERT H. LURIE CHILDREN'S HOSPITAL OF CHICAGO
This past year has been transformational in terms of not only a global pandemic but a sustained focus on racism and systemic injustice. There has been a widespread circulation of images and videos in the news and online. Just like adults, adolescents are exposed to these images with important consequences for their emotional health and coping. However, few studies have sought to understand the influence of racism experienced online.
According to a qualitative study published in JAMA Network Open adolescents expressed feelings of helplessness when exposed to secondhand racism online. Specifically, adolescents described helplessness stemming from the pervasiveness of racism in our society. This was illustrated by quotes, such as "[racist events are] just another day in the life" referring to racism as a constant force and unmovable by saying, "there's nothing I can do." However, many adolescents emphasized activism as a way to cope with the vicarious racism they experience. One adolescent stated, "Yeah, and then sometimes my response is it's something I can do something about, like right now..." Further, participation in activism may help mitigate negative feelings.
Lead study author, Dr. Nia Heard-Garris, MD, MSc is a pediatrician and physician-investigator at the Ann & Robert H. Lurie Children's Hospital of Chicago and an Assistant Professor of Pediatrics at Northwestern University Feinberg School of Medicine. The study team conducted 4 focus groups of 18 adolescents across the Chicagoland area between November 2018-April 2019. Dr. Heard-Garris noted that teens felt that adults underestimated how much they witness discrimination around them. One adolescent said, "It's funny because a lot of people think that teenagers are not socially aware, but I think the friends I keep around me, once we start talking about something, it goes on and on and on and on..."
It is important to note that this study, that took place prior to the wave of racialized violence of Black Americans publicized in the summer of 2020, however, it emphasizes the need to study how adolescents respond to witnessing these events. Dr. Nia Heard-Garris states, "Investigating adolescents' exposure and response to racism online proves critical because of the negative changes in emotional state and potential adverse physical and mental health across the life course." The researchers of this study also highlight that "this study aligns with previous studies that demonstrate social cohesion or connectedness can buffer the negative influence racism has on health generally, and the benefits of activism may be because adolescents can connect to a larger social network to draw support and participate in collective action."
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Research at Ann & Robert H. Lurie Children's Hospital of Chicago is conducted through the Stanley Manne Children's Research Institute. The Manne Research Institute is focused on improving child health, transforming pediatric medicine and ensuring healthier futures through the relentless pursuit of knowledge. Lurie Children's is ranked as one of the nation's top children's hospitals by U.S. News & World Report. It is the pediatric training ground for Northwestern University Feinberg School of Medicine. Last year, the hospital served more than 212,000 children from 49 states and 51 countries.
Original Investigation
Public Health
June 15, 2021
Adolescents’ Experiences, Emotions, and Coping Strategies Associated With Exposure to Media-Based Vicarious Racism
QuestionHow do adolescents respond to media-based vicarious racism, and do these responses affect adolescent emotional health and well-being?
FindingsThis qualitative focus group–based study with 18 participants found that adolescents experienced helplessness after exposure to media-based vicarious racism and that activism was used as a positive coping strategy.
MeaningThe findings suggest that activism may serve as a powerful coping mechanism, potentially reducing negative emotions for adolescents exposed to media-based vicarious racism; thus, activism may have implications for improving mental health outcomes and advancing societal changes.
Abstract
ImportanceAdolescents frequently encounter racism vicariously through online news and social media and may experience negative emotional responses due to these exposures. To mitigate potential adverse health impacts, including negative emotional health, it is important to understand how adolescents cope with these exposures.
ObjectivesTo examine adolescents’ responses to online and media-based vicarious racism exposure and to explore coping strategies, particularly positive coping strategies, that may be used to combat negative emotions.
Design, Setting, and ParticipantsThis qualitative study rooted in phenomenological research methods conducted 4 semistructured focus groups, with 3 to 6 English-speaking adolescents (aged 13-19 years) in each group, between November 2018 and April 2019. Focus groups were facilitated by 2 research team members. The study was conducted at community sites and youth organizations in the greater Chicago, Illinois, area. Interview transcripts were analyzed thematically.
ExposuresLived experiences of media-based vicarious racism.
Main Outcomes and MeasuresFocus group participants shared their experiences with media-based vicarious racism online, including their responses to exposure and the coping strategies used.
ResultsFour focus group sessions were conducted with a total of 18 adolescents. Participants had a mean (SD) age of 16.4 (1.6) years. Overall, 7 participants (39%) self-identified as Black/African American, 8 (44%) as Hispanic/Latinx, and 3 (17%) as White individuals; 7 (39%) were in grades 7 to 9, 8 (44%) in grades 10 to 12 grade, and 3 (17%) at the college or university level. Central themes emerged related to adolescents’ experiences, including their emotional and coping responses to media-based vicarious racism. Many participants reported helplessness as a major negative emotion associated with these exposures. Activism was endorsed as a key positive coping strategy that participants used, including online and in-person modalities.
Conclusions and RelevanceThe findings from this qualitative study suggest adolescents may experience helplessness as a primary negative emotion after exposure to media-based vicarious racism and activism may serve as a coping mechanism. Activism may represent an important and constructive means by which adolescents cope with and combat structural racism, mitigate negative emotions, and potentially prevent adverse health effects.
Introduction
Racism is entrenched in US institutions, with well-documented impacts on physical and mental health and well-being, even if experienced secondhand.1-4 Institutions such as health care, government, carceral systems as well as news and media are inextricable from the pervasive nature of racism. News and online platforms, such as social media, can be an important conduit for vicarious racism at the population level and may also affect health. Vicarious racism is the secondhand exposure to racism directed at another individual and occurs irrespective of the race of the unintended target; however, that unintended target or bystander must identify the event as racism.4 Recently, the disproportionate murders of members of racial/ethnic minority groups by police has been a type of structural vicarious racism within the public discourse and has been associated with negative repercussions for health.5
Adolescents consume news of racialized violence and other racially charged events that are disseminated through traditional and online media as well as social media outlets.6 Scholarship on media-based vicarious racism exposures is emerging, and qualitative studies have begun to describe negative emotions after media-based vicarious racism exposure in adolescents.4,7,8 Given the ubiquity of these stories and ease of internet access, adolescents may have more exposure to structural racism experienced vicariously than previous contemporary periods. Thus, youth may have an increased need for positive coping mechanisms to mitigate adverse health outcomes from this exposure.
Although structural racism may require intervention at the societal level, adolescents may not have traditional access to positions of authority or policy making. However, in today’s technology-driven and highly interconnected world, adolescents may seek out unique strategies to prevent and cope with racism. Given the nascent literature, studies have not yet explored how adolescents navigate media-based vicarious racism or identified the coping strategies that adolescents use following vicarious racism exposure.
Using an adolescent-centered, qualitative approach, we sought to (1) examine how adolescents respond to media-based vicarious racism and (2) to explore coping strategies adolescents use to mitigate negative emotions and structural racism, vicariously experienced in the media. We hypothesized that adolescents use a variety of coping skills after exposure to media-based vicarious racism. We also anticipated that adolescents would openly discuss the impact of vicarious racism on their health. Finally, structural racism and the resultant adverse health outcomes and disparities will require societal, institutional, and individual transformation. However, by focusing on individual-level experiences and strategies, adolescents may be able to actively lessen the negative consequences of racism on their own health and well-being.
