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)
Tuesday, December 13, 2022
Rural hospital closures affect operations of surrounding hospitals
Bystander hospitals see increased emergency department visits, admissions following rural hospital closures
HERSHEY, Pa. — Since 2005, more than 180 rural hospitals in the United States have closed, with nearly 1,000 more at risk of doing so. A study by Penn State College of Medicine researchers found that nearby hospitals see increased emergency department visits and admissions as a result of these closures.
“Previous studies have shown that rural hospital closures can have negative health consequences for the communities they serve,” said Daniel George, associate professor of humanities and public health sciences. George and colleagues, including a College of Medicine medical student alumnus Shayann Ramedani, who led the study, published research on how these rural hospital closures affect “bystander hospitals,” or those within a 30-mile radius of the closed facility.
“To our knowledge, we’re the first group to explore this question,” George said. “We predicted that closures would, over time, lead to increased strain on bystander institutions.”
The team studied closure information from a University of North Carolina Sheps Center for Health Services Research database. The researchers studied rural hospitals that had a more than 25-bed capacity and which closed between 2005 and 2016. They analyzed the average rate-of-change for inpatient admissions and emergency department visits at bystander hospitals two years before and two years after each nearby closure.
Overall, they identified 53 closures and 93 bystander hospitals that met the criteria. Sixty-six percent of the closures were from the southern United States, while 21% were from the Appalachian region. Average emergency department visits increased by 3.59% two years prior to a hospital’s closure, while two years following the closure, average visits increased by 10.22%. Average admissions fell by 5.73% at bystander hospitals two years before closure but increased by 1.17% in the two years following a closure. The results were published in the Journal of Hospital Medicine.
“This research confirmed a problem for the health care field that many already suspected,” George said. “The question now becomes how researchers and policymakers can develop solutions to help bystander hospitals handle increased volume.”
“We know rural areas, especially regions like Appalachia, are at increased risk for diseases of despair including alcoholism, accidental poisonings and suicide,” Kraschnewski said. “Increased burden at bystander hospitals and health care institutions may cause these problems to proliferate if other public health interventions aren’t identified and implemented.”
Douglas Leslie, chair of the Department of Public Health Sciences at Penn State College of Medicine, also contributed to this research. The researchers declare no conflicts of interest.
The National Center for Advancing Translational Sciences of the National Institutes of Health (NIH) (grant UL1 TR002014) supported this research through Penn State Clinical and Translational Science Institute. The content is solely the views of the authors and does not necessarily represent the views of the NIH.
IMAGE: DANIELLE QUINTANA, CERTIFIED PERIOPERATIVE NURSE AND ASSISTANT CLINICAL PROFESSOR AT THE UNIVERSITY OF HOUSTON COLLEGE OF NURSING, HAS CREATED A NEW MODEL OF SURGICAL CONSCIENCE AMONG PERIOPERATIVE NURSES.view more
CREDIT: UNIVERSITY OF HOUSTON
Danielle Quintana, certified perioperative nurse and assistant clinical professor at the University of Houston College of Nursing, has conducted the first concept analysis on surgical conscience among perioperative nurses, those charged with overseeing surgical safety and sterile fields, or asepsis (the absence of bacteria, viruses and other organisms), inside hospital operating rooms.
Surgical conscience is defined as the moral obligation to perform those duties no matter the cost or consequence. It is a 360-degree awareness of all activities occurring within the perioperative environment and requires personnel to monitor their own practice as well as the practices of others to ensure patients are provided with safety and care.
“Acting upon one’s surgical conscience may not always be well-received by perioperative colleagues and may require the nurse to stand strong for what is right,” reports Quintana in the cover article of AORN Journal. “Regardless of the challenge presented, surgical conscience encompasses the belief that health care professionals have a responsibility to patients and to themselves to be consistent, accurate and safe. This duty or obligation should be performed with the highest level of commitment.”
Quintana has also created a conceptual model representing surgical conscience to illustrate the use and context of the concept.
“Quintana’s work is inspiring as it leads to better patient outcomes, better communication with surgeons and the OR staff, and education of our students,” said Kathryn Tart, founding dean of the UH College of Nursing. “The Quintana Model of Surgical Conscience encapsulates the heart of what best practices should be for our patients, how we teach our students and collaborate with our surgeons and OR team.”
The perioperative environment is dynamic and complex, often requiring nurses to make difficult decisions under pressure and acts of surgical conscience may often cause delays. Examples include recognizing that a patient’s surgical site has not been correctly marked and waiting until the surgeon has properly identified the site before transporting the patient to the operating room; or, halting a procedure if a patient has a question regarding informed consent.
Despite years of training and courage on the frontlines, perioperative nurses face several possible reasons they may not feel empowered to demonstrate their moral courage and speak up, including a perceived hierarchy in the OR, a facility’s culture, navigating challenging personalities and a fear of retribution.
“Personnel should use their knowledge of sterile technique, attentively avoid and recognize breaks in technique, and immediately begin to mitigate breaks in technique when they occur,” said Quintana. In reviewing past studies, she found that nurses were also concerned about teamwork performance and that stress may have prevented them from exercising surgical conscience and thereby negatively affected surgical outcomes.
Little research exists on how surgical conscience is introduced, learned, improved or measured. Quintana’s analysis presents the current state of the science.
“This concept analysis provides a comprehensive definition of surgical conscience to guide the future research that is needed to reinforce surgical conscience and prevent conceptual dogma—a situation in which attributes of a concept lack the support of additional investigation but are still used and reinforced over time,” said Quintana. “The surgical conscience falls into several domains, including nursing, surgery, anesthesiology, surgical technology and interventional radiology.”
In the Quintana Model of Surgical Conscience, knowledge is the foundational basis of surgical conscience and includes the knowledge of professional standards and principles of aseptic technique, sterility and infection control.
“When each team member develops and follows their own surgical conscience, patients will benefit from the collective surgical conscience of the entire team working together in a culture of safety. Surgical conscience has been confirmed to be a mature, multidimensional concept that can serve as a foundation for future research to broaden and improve its usefulness for the benefit of perioperative nursing science and surgical patients.”
JOURNAL
AORN Journal
ARTICLE TITLE
Surgical Conscience: A Concept Analysis for Perioperative Nurses
Exercise, mindfulness don’t appear to boost cognitive function in older adults
In healthy older adults, neither led to measurable improvements after 6 months, 18 months
IMAGE: OLDER ADULTS WORK WITH EXERCISE TRAINERS AS PART OF A STUDY TO SEE WHETHER EXERCISE, MINDFULNESS TRAINING, OR BOTH MIGHT IMPROVE COGNITIVE PERFORMANCE IN SENIORS. A NEW STUDY DID NOT SHOW SUCH IMPROVEMENTS, THOUGH THE RESEARCHERS ARE CONTINUING TO EXPLORE WHETHER THERE MAY BE SOME COGNITIVE EFFECTS OVER A LONGER TIME PERIOD.view more
CREDIT: WASHINGTON UNIVERSITY SCHOOL OF MEDICINE
A large study that focused on whether exercise and mindfulness training could boost cognitive function in older adults found no such improvement following either intervention. Researchers at Washington University School of Medicine in St. Louis and the University of California, San Diego, studied the cognitive effects of exercise, mindfulness training or both for up to 18 months in older adults who reported age-related changes in memory but had not been diagnosed with any form of dementia.
The findings are published Dec. 13 in JAMA.
“We know beyond any doubt that exercise is good for older adults, that it can lower risk for cardiac problems, strengthen bones, improve mood and have other beneficial effects — and there has been some thought that it also might improve cognitive function,” said the study’s first author, Eric J. Lenze, MD, the Wallace and Lucille Renard Professor and head of the Department of Psychiatry at Washington University. “Likewise, mindfulness training is beneficial because it reduces stress, and stress can be bad for your brain. Therefore, we hypothesized that if older adults exercised regularly, practiced mindfulness or did both there might be cognitive benefits — but that’s not what we found.”
Lenze and his colleagues still want to see whether there may be some cognitive effects over a longer time period, so they plan to continue studying this group of older adults to learn whether exercise and mindfulness might help prevent future cognitive declines. In this study, however, the practices did not boost cognitive function.
“So many older adults are concerned about memory,” said senior author Julie Wetherell, PhD, a professor of psychiatry at UC San Diego. “It’s important for studies like ours to develop and test behavioral interventions to try to provide them with neuroprotection and stress reduction as well as general health benefits.”
The researchers studied 585 adults ages 65 through 84. None had been diagnosed with dementia, but all had concerns about minor memory problems and other age-related cognitive declines.
“Minor memory problems often are considered a normal part of aging, but it’s also normal for people to become concerned when they notice these issues,” said Lenze, who also directs Washington University’s Healthy Mind Lab. “Our lab’s principal aim is to help older people remain healthy by focusing on maintaining their mental and cognitive health as they age, and we were eager to see whether exercise and mindfulness might offer a cognitive boost in the same way that they boost other aspects of health.”
All study participants were considered cognitively normal for their ages. The researchers tested them when they enrolled in the study, measuring memory and other aspects of thinking. They also conducted brain-imaging scans.
The participants were randomly assigned to one of four groups: a group in which subjects worked with trained exercise instructors; a group supervised by trained experts in the practice of mindfulness; a group that participated in regular exercise and mindfulness training; and a group that did neither, but met for occasional sessions focused on general health education topics. The researchers conducted memory tests and follow-up brain scans after six months and again after 18 months.
At six months and again at 18 months, all of the groups looked similar. All four groups performed slightly better in testing, but the researchers believe that was due to practice effects as study subjects retook tests similar to what they had taken previously. Likewise, the brain scans revealed no differences between the groups that would suggest a brain benefit of the training.
Lenze said the study’s findings don’t mean exercise or mindfulness training won’t help improve cognitive function in any older adults, only that those practices don’t appear to boost cognitive performance in healthy people without impairments.
“We aren’t saying, ‘Don’t exercise’ or, ‘Don’t practice mindfulness,’ ” Lenze explained. “But we had thought we might find a cognitive benefit in these older adults. We didn’t. On the other hand, we didn’t study whether exercise or mindfulness might benefit older adults who are impaired, due to dementia or to disorders such as depression. I don’t think we can extrapolate from the data that these practices don’t help improve cognitive function in anyone.”
Lenze said the researchers recently received funding from the National Institutes of Health (NIH) to continue following the group of adults who participated in this study.
“They are still engaging in exercise and mindfulness,” he said. “We didn’t see improvements, but cognitive performance didn’t decline either. In the study’s next phase, we’ll continue following the same people for five more years to learn whether exercise and mindfulness training might help slow or prevent future cognitive declines.”
Lenze EJ, et al. Effects of mindfulness training and exercise on cognitive function in older adults: a randomized clinical trial. JAMA, Dec. 13, 2022.
The study was funded with support from the National Institute on Aging, the National Center for Complementary and Integrative Health, the NIH Office of Behavioral and Social Science Research, and the McKnight Brain Research Foundation. National Institutes of Health (NIH) grant numbers: R01 AG049369, P50 MH122351, P50 HD103525, P30 DK056341 and UL1 TR000448. Additional funding provided by the Taylor Family Institute for Innovative Psychiatric Research.
About Washington University School of Medicine
WashU Medicine is a global leader in academic medicine, including biomedical research, patient care and educational programs with 2,700 faculty. Its National Institutes of Health (NIH) research funding portfolio is the fourth largest among U.S. medical schools, has grown 54% in the last five years, and, together with institutional investment, WashU Medicine commits well over $1 billion annually to basic and clinical research innovation and training. Its faculty practice is consistently within the top five in the country, with more than 1,790 faculty physicians practicing at over 60 locations and who are also the medical staffs of Barnes-Jewish and St. Louis Children’s hospitals of BJC HealthCare. WashU Medicine has a storied history in MD/PhD training, recently dedicated $100 million to scholarships and curriculum renewal for its medical students, and is home to top-notch training programs in every medical subspecialty as well as physical therapy, occupational therapy, and audiology and communications sciences.
Effects of Mindfulness Training and Exercise on Cognitive Function in Older Adults: A Randomized Clinical Trial
ARTICLE PUBLICATION DATE
13-Dec-2022
COI STATEMENT
Torie Gettinger reports serving as a consultant for Pritikin ICR. Eric Lenze reports serving as a consultant for IngenioRx, Pritikin ICR, Boehringer-Ingelheim, Merck, and Prodeo and receiving grant support from Patient-Centered Outcomes Research Institute (PCORI), Fast Grants, COVID Early Treatment Fund, and Janssen. He has a patent pending for Sigma-1 receptor agonists for Covid-19. Samuel Klein reports a sponsored research agreement with Janssen Pharmaceuticals Inc., serves on scientific advisory board for Altimmune, and is a consultant for B2M Medical. Abraham Snyder is a consultant for Soraneuroscience, LLC
Paris Agreement temperature targets may worsen climate injustice for many island states
Justice-focused policies are needed to minimize impacts of sea-level rise, which will be borne disproportionately by island nations
IMAGE: THE SPATIAL DISTRIBUTION OF THE ANTARCTIC CONTRIBUTION TO SEA LEVEL RISE AT 2100 (RELATIVE TO 2000) UNDER ONE OF THE IPCC’S INTERMEDIATE EMISSIONS SCENARIOS. AOSIS MEMBERS ARE DISPROPORTIONATELY AFFECTED BY SEA LEVEL RISE. NUMBERS SHOWN IN THE MAP LEGEND ARE FACTORS IN COMPARISON TO GLOBAL MEAN SEA LEVEL, FOR INSTANCE A FACTOR OF 1.2 INDICATES THAT LOCATION EXPERIENCES SEA LEVEL RISE 1.2 TIMES THE GLOBAL MEAN VALUE.view more
CREDIT: SADAI ET AL., 10.1029/2022EF002940
AMHERST, Mass. – While the world focuses on limiting the rise in global temperature to 1.5 or 2 degrees Celsius over the preindustrial average, increasing meltwater from ice sheets presents an existential threat to the viability of island and coastal nations throughout the world. Now, research from the University of Massachusetts Amherst, recently published in the journal Earth’s Future, shows that even the most optimistic temperature targets can lead to catastrophic sea-level rise, which has already begun and will affect low-lying nations for generations to come.
While rising temperatures are having many deleterious effects on global ecosystems, economies and human wellbeing, an interdisciplinary team of researchers at the University of Massachusetts emphasize that temperature alone is not a sufficient basis for climate policy. The team focused on the Antarctic Ice Sheet, which holds the world’s largest store of freshwater—enough to raise the oceans by 58 meters, and which is melting at an accelerating pace. But the physics of the ice sheet itself also contribute to its liquification, which will continue for millennia, even if global carbon emissions are reigned in. And because melting ice can slow rising temperatures in the atmosphere, it is conceivable that the melting ice sheet could help maintain what is commonly considered a “safe” level of warming, 1.5 degrees, say, while actually allowing for devastating sea-level rise. Furthermore, all that Antarctic meltwater won’t cause the same amount of sea-level rise everywhere in the world. Some areas in the Caribbean Sea as well as the Indian and Pacific Oceans will experience a disproportionate share of the sea-level rise from Antarctic ice—up to 33% greater than the global average.
This gap between temperature and sea level has immediate repercussions for many places throughout the world, and especially for the Alliance of Small Island States (AOSIS), an organization of 39 island and coastal nations across the globe. Indeed, the paper’s authors show that, though AOSIS countries have emitted a negligible portion of the planet’s anthropogenic greenhouse gasses, they are bearing the brunt of the world’s rising waters.
“Temperature is not the only way to track global climate change,” says Shaina Sadai, the paper’s lead author, who completed this research as part of her doctoral studies in geosciences at UMass Amherst, “but it became the iconic metric in the Paris Agreement. Knowing that Antarctic melt can delay temperature rise while increasing sea levels, I wondered what it meant for climate justice. But climate science alone can’t answer that question of justice.”
Enter Regine Spector, professor of political science at UMass Amherst and one of the paper’s senior authors. Spector brought expertise in political power dynamics and the history of global inequality to the team’s work to demonstrate how politically powerful countries influence global climate negotiations and continue historic patterns of colonial exploitation experienced by AOSIS nations. “Focusing on temperature misses other real consequences of climate change, such as sea-level rise, that are being felt all over the world today,” says Spector.
The team demonstrates that an interdisciplinary approach to research, which centers the experiences of AOSIS countries, can be used to better understand climate justice impacts of international negotiations and the relationships between science, policy and political power. “We need to listen to the voices of the people facing the vanguard of climate change,” say Sadai and Spector. They hope this research can serve as a model for future studies.
This research was funded by the National Science Foundation and NASA.
In all living cells, from bacteria and fungi to plants and animals, electrons are shuttled around as part of natural, biochemical processes. But if electrodes are present, the cells can actually generate electricity that can be used externally. Previous researchers have created fuel cells in this way with bacteria, but the microbes had to be constantly fed. Instead, scientists, including Noam Adir’s team, have turned to photosynthesis to generate current. During this process, light drives a flow of electrons from water that ultimately results in the generation of oxygen and sugar. This means that living photosynthetic cells are constantly producing a flow of electrons that can be pulled away as a “photocurrent” and used to power an external circuit, just like a solar cell.
Certain plants — like the succulents found in arid environments — have thick cuticles to keep water and nutrients within their leaves. Yaniv Shlosberg, Gadi Schuster and Adir wanted to test, for the first time, whether photosynthesis in succulents could create power for living solar cells using their internal water and nutrients as the electrolyte solution of an electrochemical cell.
The researchers created a living solar cell using the succulent Corpuscularia lehmannii, also called the “ice plant.” They inserted an iron anode and platinum cathode into one of the plant’s leaves and found that its voltage was 0.28V. When connected into a circuit, it produced up to 20 µA/cm2 of photocurrent density, when exposed to light and could continue producing current for over a day. Though these numbers are less than that of a traditional alkaline battery, they are representative of just a single leaf. Previous studies on similar organic devices suggest that connecting multiple leaves in series could increase the voltage. The team specifically designed the living solar cell so that protons within the internal leaf solution could be combined to form hydrogen gas at the cathode, and this hydrogen could be collected and used in other applications. The researchers say that their method could enable the development of future sustainable, multifunctional green energy technologies.
The authors acknowledge funding from a “Nevet” grant from the Grand Technion Energy Program (GTEP) and a Technion VPR Berman Grant for Energy Research and support from the Technion’s Hydrogen Technologies Research Laboratory (HTRL).
The American Chemical Society (ACS) is a nonprofit organization chartered by the U.S. Congress. ACS’ mission is to advance the broader chemistry enterprise and its practitioners for the benefit of Earth and all its people. The Society is a global leader in promoting excellence in science education and providing access to chemistry-related information and research through its multiple research solutions, peer-reviewed journals, scientific conferences, eBooks and weekly news periodical Chemical & Engineering News. ACS journals are among the most cited, most trusted and most read within the scientific literature; however, ACS itself does not conduct chemical research. As a leader in scientific information solutions, its CAS division partners with global innovators to accelerate breakthroughs by curating, connecting and analyzing the world’s scientific knowledge. ACS’ main offices are in Washington, D.C., and Columbus, Ohio.
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The findings of this study that included 390 participants suggest that involvement in patient-facing dental clinical activities did not pose additional risk of SARS-CoV-2 infection compared with other in-person activities in the presence of intensive control measures.
Authors: William V. Giannobile, D.D.S., D.M.Sc., of the Harvard School of Dental Medicine in Boston, is the corresponding author.
Editor’s Note: Please see the article for additional information, including other authors, author contributions and affiliations, conflict of interest and financial disclosures, and funding and support.
Onset of the COVID-19 pandemic was associated with increased hospitalizations with mental health diagnoses among adolescents, according to the results of this study that included eight children’s hospitals in the United States and France. Anxiety, depression, and suicidality or self-injury were the most prevalent conditions. The increase in hospitalizations was particularly notable for adolescent females. These findings support the need for greater resources within children’s hospitals to care for adolescents with mental health conditions during the pandemic and beyond.
Authors: Paul Avillach, M.D., Ph.D., and Florence T. Bourgeois, M.D., M.P.H., of Harvard Medical School in Boston, are the corresponding authors.
Editor’s Note: Please see the article for additional information, including other authors, author contributions and affiliations, conflict of interest and financial disclosures, and funding and support.
Low-income California immigrants who avoided public programs owing to fear of harming their immigration status were twice as likely to delay needed medical care or prescription fills.
Authors: Joelle Wolstein, Ph.D., M.P.P., of the UCLA Center for Health Policy Research in Los Angeles, is the corresponding author.
Editor’s Note: Please see the article for additional information, including other authors, author contributions and affiliations, conflict of interest and financial disclosures, and funding and support.
IMAGE: (1) A PARADISE TREE SNAKE, CHRYSOPELEA PARADISE, GLIDING IN AIR. (2) 3D SNAKE BODY MODEL WITH SKELETAL JOINTS FOR HORIZONTAL UNDULATION. (3) VORTEX STRUCTURES OF THE UNDULATING SNAKE. (4) SPANWISE VORTICITY CONTOURS AT DIFFERENT SLICE-CUTS ALONG THE BODY. (5) EFFECTS OF THE UNDULATING FREQUENCY ON THE AERODYNAMIC PERFORMANCE OF THE GLIDING SNAKE.view more
CREDIT: JACK SOCHA (1) AND YUCHEN GONG (2-5)
WASHINGTON, Dec. 13, 2022 – Robots have been designed to move in ways that mimic animal movements, such as walking and swimming. Scientists are now considering how to design robots that mimic the gliding motion exhibited by flying snakes.
In Physics of Fluids, by AIP Publishing, researchers from the University of Virginia and Virginia Tech explored the lift production mechanism of flying snakes, which undulate side-to-side as they move from the tops of trees to the ground to escape predators or to move around quickly and efficiently. The undulation allows snakes to glide for long distances, as much as 25 meters from a 15-meter tower.
To understand how the undulations provide lift, the investigators developed a computational model derived from data obtained through high-speed video of flying snakes. A key component of this model is the cross-sectional shape of the snake's body, which resembles an elongated frisbee or flying disc.
The cross-sectional shape is essential for understanding how the snake can glide so far. In a frisbee, the spinning disc creates increased air pressure below the disc and suction on its top, lifting the disc into the air. To help create the same type of pressure differential across its body, the snake undulates side to side, producing a low-pressure region above its back and a high-pressure region beneath its belly. This lifts the snake and allows it to glide through the air.
"The snake's horizontal undulation creates a series of major vortex structures, including leading edge vortices, LEV, and trailing edge vortices, TEV," said author Haibo Dong of the University of Virginia. "The formation and development of the LEV on the dorsal, or back, surface of the snake body plays an important role in producing lift."
The LEVs form near the head and move back along the body. The investigators found that the LEVs hold for longer intervals at the curves in the snake's body before being shed. These curves form during the undulation and are key to understanding the lift mechanism.
The group considered several features, such as the angle of attack that the snake forms with the oncoming airflow and the frequency of its undulations, to determine which were important in producing glide. In their natural setting, flying snakes typically undulate at a frequency between 1-2 times per second. Surprisingly, the researchers found that more rapid undulation decreases aerodynamic performance.
"The general trend we see is that a frequency increase leads to an instability in the vortex structure, causing some vortex tubes to spin. The spinning vortex tubes tend to detach from the surface, leading to a decrease in lift," said Dong.
The scientists hope their findings will lead to increased understanding of gliding motion and to a more optimal design for gliding snake robots.
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The article "Computational analysis of vortex dynamics and aerodynamic performance in flying-snake-like gliding flight with horizontal undulation" is authored by Yuchen Gong, Junshi Wang, Wei Zhang, Jake Socha, and Haibo Dong. The article will appear in Physics of Fluids on Dec. 13, 2022 (DOI: 10.1063/5.0125546). After that date, it can be accessed at https://doi.org/10.1063/5.0125546.
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.
VIDEO: DROPLETS (ON THE CENTIMETER SCALE) MERGE DURING AN EXPERIMENT ON THE INTERNATIONAL SPACE STATION.view more
CREDIT: JOSH MCCRANEY
WASHINGTON, Dec. 13, 2022 – Understanding how water droplets spread and coalesce is essential for scenarios in everyday life, such as raindrops falling off cars, planes, and roofs, and for applications in energy generation, aerospace engineering, and microscale cell adhesion. However, these phenomena are difficult to model and challenging to observe experimentally.
In Physics of Fluids, by AIP Publishing, researchers from Cornell University and Clemson University designed and analyzed droplet experiments that were done on the International Space Station.
Droplets usually appear as small spherical caps of water because their surface tension exceeds gravity.
"If the drops get much larger, they begin to lose their spherical shape, and gravity squishes them into something more like puddles," said author Josh McCraney of Cornell University. "If we want to analyze drops on Earth, we need to do it at a very small scale."
But at small scales, droplets dynamics are too fast to observe. Hence, the ISS. The lower gravity in space means the team could investigate larger droplets, moving from a couple millimeters in diameter to 10 times that length.
The researchers sent four different surfaces with various roughness properties to the ISS, where they were mounted to a lab table. Cameras recorded the droplets as they spread and merged.
"NASA astronauts Kathleen Rubins and Michael Hopkins would deposit a single drop of desired size at a central location on the surface. This drop is near, but not touching, a small porthole pre-drilled into the surface," said McCraney. "The astronaut then injected water through the porthole, which collects and essentially grows an adjacent drop. Injection continues until the two drops touch, at which point they coalesce."
The experiments aimed to test the Davis-Hocking model, a simple way to simulate droplets. If a droplet of water sits on a surface, part of it touches the air and creates an interface, while the section in contact with the surface forms an edge or contact line. The Davis-Hocking model describes the equation for the contact line. The experimental results confirmed and expanded the parameter space of the Davis-Hocking model.
As the original principal investigator of the project, the late professor Paul Steen of Cornell University had written grants, traveled to collaborators worldwide, trained doctoral students, and meticulously analyzed related terrestrial studies, all with the desire to see his work successfully conducted aboard the ISS. Tragically, Steen died only months before his experiments launched.
"While it's tragic he isn't here to see the results, we hope this work makes him and his family proud," said McCraney.
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The article "Coalescence-induced droplet spreading: Experiments aboard the International Space Station" is authored by Joshua McCraney, Jonathan Michael Ludwicki, Joshua Bostwick, Susan Daniel, and Paul Steen. The article will appear in Physics of Fluids on Dec. 13, 2022 (DOI: 10.1063/5.0125279). After that date, it can be accessed at https://doi.org/10.1063/5.0125279.
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.
