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, October 20, 2020
COVID: women are less likely to put themselves in danger
Women's attitudes and behaviors may have contributed to their reduced vulnerability and mortality. A survey in 8 countries shows they consider Coronavirus a more serious problem than men and are more likely to approve and comply with health policies
The increased adherence of women to Coronavirus policies may be one of the reasons for the lower vulnerability and mortality that they experienced, compared to men, in the early phase of the epidemic. "Policy makers who promote a new normality made of reduced mobility, face masks and other behavioral changes," says Vincenzo Galasso, one of the authors of a new study on gender differences in the reaction to COVID-19, "should, therefore, design a gender-differentiated communication if they want to increase the compliance of men."
Two of the authors of the research, which appeared on PNAS (Proceedings of the National Academy of Sciences) are scholars of Bocconi University, Vincenzo Galasso and Paola Profeta, affiliated to Bocconi's COVID Crisis Lab.
The authors observe substantial gender differences in both attitudes and behaviors through a two-wave survey (March and April 2020), with 21,649 respondents in Australia, Austria, France, Germany, Italy, New Zealand, the UK and the US, which is part of the international project REPEAT (REpresentations, PErceptions and ATtitudes on the COVID-19).
Women around the world are more inclined than men to consider COVID-19 a very serious health problem (59% against 48.7% in March and 39.6% against 33% in April), they are more inclined to agree with public policies that fight the pandemic, such as mobility restrictions and social distancing (54,1 against 47,7 in an index that goes from 1 to 100 in March and 42,6 against 37,4 in April) and are clearly more inclined to follow the rules concerning COVID-19 (88,1% against 83,2% in March and 77,6% against 71,8% in April).
The share of individuals complying with the rules drops over time, particularly in Germany, from 85.8% of women and 81.5% of men in March to 70.5% of women and 63.7% of men in April, but the large gender gap persists.
"The biggest differences between men and women relate to behaviors that serve to protect others above all, such as coughing in the elbow, unlike those that can protect both themselves and others," says Profeta. Gender differences persist even after the study controlled a large number of sociodemographic characteristics and psychological factors.
However, such differences are smaller among married couples, who live together and share their views with each other, and among individuals most directly exposed to the pandemic. They decrease over time if men and women are exposed to the same flow of information about the pandemic.
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Non-obese Vietnamese Americans are 60% more likely to have diabetes
Study compares non-obese Vietnamese Americans with non-obese, non-Hispanic White Americans
A new study has found that Vietnamese-American adults who were not obese were 60% more likely to have diabetes than non-obese, non-Hispanic, White Americans, after accounting for age, sex, sociodemographic factors, smoking history and exercise level.
Overall, only 9% of Vietnamese Americans with diabetes in the study were obese -- defined as having a body mass index (BMI) of 30 or higher. In comparison, half of all non-Hispanic White Americans with diabetes were obese.
"While obesity is commonly associated with diabetes risk, the study's findings indicate that this is not necessarily the case for Vietnamese Americans," says the study's first author Leanne R. De Souza, Assistant Professor, Human Biology and Health Studies Programs, University College, University of Toronto. "As a result, health care professionals may miss screening for preventing and treating this potentially life-threatening disease in the Vietnamese-American population. Screening of Vietnamese adults who have normal weight would be helpful."
The data set used in this study did not provide information on why non-obese Vietnamese Americans have higher odds of diabetes than White Americans, but previous research provides potential answers.
Other studies have found that accumulation of excess fat in the abdomen is higher among Asian Americans than White Americans of a similar weight.
"A growing body of literature suggests that measurement of excess weight around the liver and in the abdomen may be a better way to assess diabetes risk than merely taking into account weight and height," says co-author Keith Tsz-Kit Chan, Assistant Professor, Silberman School of Social Work at Hunter College, City University of New York.
Past research has also shown that Asian Americans are less likely to be screened and are therefore more likely to be living with undiagnosed diabetes and pre-diabetes. Untreated diabetes can result in many serious complications including nerve damage, preventable amputation, blindness, heart attacks, strokes, chronic kidney disease and kidney failure.
The authors of the present study found that among non-obese Vietnamese Americans, those aged 45 and older had at least 40-fold the odds of diabetes compared to young adults.
"These findings suggest that screening for diabetes in Vietnamese Americans starting at age 45 might be warranted," says co-author Alexis Karasiuk, a research assistant at the University of Toronto.
In the subsample of non-obese Vietnamese Americans, men and those living in poverty had a much higher prevalence of diabetes compared to women and those with higher incomes, respectively. Adults who had never smoked and those with a post-secondary degree were less likely to have diabetes.
The authors hope to examine the role of diet in future studies.
"Previous research has found that each additional portion of white rice consumed daily raises the risk of diabetes by 11%. Substituting other whole grains such as brown rice instead of white rice may be a promising strategy for decreasing this risk," noted co-author Karen Kobayashi, professor in the department of Sociology and a research fellow at the Institute on Aging & Lifelong Health at the University of Victoria.
Given that non-obese Vietnamese Americans, including those as young as 45, have a relatively high prevalence of diabetes, the authors say that routine screening of this population is needed.
"Better identification of those in the 'pre-diabetes' stage may increase awareness of personal risk and interventions to promote lifestyle changes. Such interventions may substantially decrease the risk of progression to full diabetes," says senior author, Esme Fuller-Thomson, Director of the Institute for Life Course & Aging and professor at the University of Toronto's Factor-Inwentash Faculty of Social Work and Department of Family & Community Medicine.
The author's study was based upon a representative sample of community-dwelling Californians aged 18 and older from seven combined waves of the California Health Interview Survey (CHIS) conducted between 2007 and 2016. The study sample was restricted to Vietnamese Americans (n = 3,969) and non-Hispanic whites (n = 119,651) who were non-obese, defined as having a body mass index (BMI) of less than 30.
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The study was published online ahead of press in the journal Chronic Illness.
Source Article:
De Souza LR, Chan, KT, Kobayashi, K, Karasiuk, A, Fuller-Thomson, E (2020). The prevalence and management of diabetes among Vietnamese Americans: A population-based survey of an understudied ethnic group
IMAGE: RIGGING GRAVITY CORER ON THE DECK OF ICEBREAKER ODEN ON SWERUS-C3 EXPEDITION 2014. view more
CREDIT: BJÖRN ERIKSSON
Sea floor sediments of the Arctic Ocean can help scientists understand how permafrost responds to climate warming. A multidisciplinary team from Stockholm University has found evidence of past permafrost thawing during climate warming events at the end of the last ice age. Their findings, published in Science Advances, caution about what could happen in the near future: That Arctic warming by only a few degrees Celsius may trigger massive permafrost thawing, coastal erosion, and the release of the greenhouse gases carbon dioxide (CO2) and methane (CH4) into the atmosphere.
Arctic permafrost stores more carbon than the atmosphere does. When permafrost thaws, this carbon may be converted to greenhouse gases (CO2 and CH4) that then enter the atmosphere and may affect the climate system. To improve predictions of future greenhouse gas emissions from permafrost, scientists have started to look into the past, exploring how previous climate warming, for example at the end of the last ice age, affected permafrost and its vast pool of carbon.
"Our new study shows for the first time the full history of how warming at the end of the last ice age triggered permafrost thawing in Siberia. This also suggests the release of large quantities of greenhouse gases," says Jannik Martens, PhD student at Stockholm University and lead author of the study. "It appears likely that past permafrost thawing at times of climate warming, about 14,700 and 11,700 years ago, was in part also related to the increase in CO2 concentrations that is seen in Antarctic ice cores for these times. It seems that Arctic warming by only a few degrees Celsius is sufficient to disturb large areas covered by permafrost and potentially affect the climate system."
In the current study, the scientists used an eight meters long sediment core that was recovered from the sea floor more than 1 000 meters below the surface of the Arctic Ocean during the SWERUS-C3 expedition onboard the Swedish icebreaker Oden back in 2014. To reconstruct permafrost thawing on land, the scientists applied radiocarbon (14C) dating and molecular analysis to trace organic remains that once were released by thawing permafrost and then washed into the Arctic Ocean.
"From this core we also learned that erosion of permafrost coastlines was an important driving force for permafrost destruction at the end of the last ice age. Coastal erosion continues to the present day, though ten times slower than during these earlier rapid warming period. With the recent warming trends, however, we see again an acceleration of coastal erosion in some parts of the Arctic, which is expected to release greenhouse gases by degradation of the released organic matter," says Örjan Gustafsson, Professor at Stockholm University and leader of the research program. "Any release from thawing permafrost mean that there is even less room for anthropogenic greenhouse gas release in the earth-climate system budget before dangerous thresholds are reached. The only way to limit permafrost-related greenhouse gas releases is to mitigate climate warming by lowering anthropogenic greenhouse gas emissions."
Gustafsson, Martens and their colleagues are now again in the Arctic Ocean as part of the International Siberian Shelf Study (ISSS-2020) onboard the Russian research vessel Akademik Keldysh. The expedition left the port of Arkhangelsk on September 26 and is currently in the East Siberian Sea, seeking more answers to how changing climate may trigger release of carbon, including greenhouse gases, from Arctic permafrost systems, including coastal erosion and permafrost below the sea bottom preserved from the past ice age.
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Publication:
J. Martens, B. Wild, F. Muschitiello, M. O'Regan, M. Jakobsson, I. Semiletov, O. V. Dudarev, &. Gustafsson, Remobilization of dormant carbon from Siberian-Arctic permafrost during three past warming events. Sci. Adv. 6, eabb6546 (2020).
Please note! Changes in e-mail addresses due to the ongoing ISSS-2020 expedition.
With regard to the ISSS-2020 Arctic Ocean expedition (Sep 23 - Nov 06), Jannik Martens will coordinate any inquiries regarding this publication via the temporary e-mail address jannikmartens@myiridium.net
Please direct all e-mail correspondence for the time during the expedition to this address and also keep the primary SU address jannik.martens@aces.su.se in CC.
Please know that file attachments sent to jannikmartens@myiridium.net should not be larger than 300 kb and expect that file attachments sent from this address cannot be larger than 100 kb.
Short interviews via satellite phone with either Jannik Martens or Örjan Gustafsson are possible upon request or audio commentary may be recorded and transmitted electronically via e-mail.
IMAGE: RESEARCH GROUP, FROM THE LEFT: ANDRÉ ORTLIEB GUERREIRO-CACAIS (RESEARCHER), MAJA JAGODIC (DOCENT AND GROUP LEADER FOR RESEARCH ON MS EPIGENETICS), RASMUS BERGLUND (DOCTORAL STUDENT), AND TOMAS OLSSON (PROFESSOR). view more
CREDIT: ULF SIRBORN
People with multiple sclerosis (MS) gradually develop increasing functional impairment. Researchers at Karolinska Institutet have now found a possible explanation for the progressive course of the disease in mice and how it can be reversed. The study, which is published in Science Immunology, can prove valuable to future treatments.
MS is a chronic inflammatory disease of the central nervous system (CNS) and one of the main causes of neurological functional impairment.
The disease is generally diagnosed between 20 and 30 years of age. It can cause severe neurological symptoms, such as loss of sensation and trembling, difficulties walking and maintaining balance, memory failure and visual impairment.
MS is a life-long disease with symptoms that most often gradually worsen over time.
In the majority of cases the disease comes in bouts with a certain amount of subsequent recovery. A gradual loss of function with time is, however, inevitable. Research has made great progress in treatments that reduce the frequency and damaging effects of these bouts.
"Despite these important breakthroughs, the disease generally worsens when the patient has had it for 10 to 20 years," says Maja Jagodic, docent of experimental medicine at the Department of Clinical Neuroscience and the Centre for Molecular Medicine, Karolinska Institutet. "There is currently only one, recently approved, treatment for what is called the secondary progressive phase. The mechanisms behind this progressive phase require more research."
Researchers at Karolinska Institutet have now shown that recovery from MS-like symptoms in mice depends on the ability of the CNS's own immune cells - microglia - to break down the remains of damaged cells, such as myelin.
The processes was interrupted when the researchers removed a so-called autophagy gene, Atg7. Autophagy is a process where cells normally break down and recycle their own proteins and other structural components.
Without Atg7 the ability of the microglia to clean away tissue residues created by the inflammation was reduced. These residues accumulated over time, which is a possible explanation for the progressiveness of the disease.
The study also shows how microglia from aged mice resemble the cells from young mice that lacked Atg7 in terms of deficiencies in this process, which had a negative effect on the course of the disease.
This is a significant result since increasing age is an important risk factor in the progressive phase of MS. The researchers also show how this process can be reversed.
"The plant and fungi-derived sugar Trehalose restores the functional breakdown of myelin residues, stops the progression and leads to recovery from MS-like disease." says doctoral student Rasmus Berglund. "By enhancing this process we hope one day to be able to treat and prevent age-related aspects of neuroinflammatory conditions."
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The research was carried out with grants from the Swedish Research Council, the Swedish Brain Foundation, Neuro, Region Stockholm, Astra Zeneca, Horizon 2020, the European Research Council, the Knut and Alice Wallenberg Foundation, the Margaretha af Uggla Foundation, Alltid Litt Sterkere, the Foundation of Swedish MS research, NEURO Sweden and Karolinska Institutet. There are no declared conflicts of interest.
Publication: "Microglial autophagy-associated phagocytosis is essential for recovery from neuroinflammation". Rasmus Berglund, Andre Ortlieb Guerreiro-Cacais, Milena Z. Adzemovic, Manuel Zeitelhofer, Harald Lund, Ewoud Ewing, Sabrina Ruhrmann, Erik Nutma, Roham Parsa, Melanie Thessen-Hedreul, Sandra Amor, Robert A. Harris, Tomas Olsson and Maja Jagodic. Science Immunology, 16 October 2020, doi: 10.1126/sciimmunol.abb5077.
A controllable membrane to pull carbon dioxide out of exhaust streams
Electrically switchable system could continuously separate gases without the need for moving parts or wasted space
A new system developed by chemical engineers at MIT could provide a way of continuously removing carbon dioxide from a stream of waste gases, or even from the air. The key component is an electrochemically assisted membrane whose permeability to gas can be switched on and off at will, using no moving parts and relatively little energy.
The membranes themselves, made of anodized aluminum oxide, have a honeycomb-like structure made up of hexagonal openings that allow gas molecules to flow in and out when in the open state. However, gas passage can be blocked when a thin layer of metal is electrically deposited to cover the pores of the membrane. The work is described in the journal Science Advances, in a paper by Professor T. Alan Hatton, postdoc Yayuan Liu, and four others.
This new "gas gating" mechanism could be applied to the continuous removal of carbon dioxide from a range of industrial exhaust streams and from ambient air, the team says. They have built a proof-of-concept device to show this process in action.
The device uses a redox-active carbon-absorbing material, sandwiched between two switchable gas gating membranes. The sorbent and the gating membranes are in close contact with each other and are immersed in an organic electrolyte to provide a medium for zinc ions to shuttle back and forth. These two gating membranes can be opened or closed electrically by switching the polarity of a voltage between them, causing ions of zinc to shuttle from one side to the other. The ions simultaneously block one side, by forming a metallic film over it, while opening the other, by dissolving its film away.
When the sorbent layer is open to the side where the waste gases are flowing by, the material readily soaks up carbon dioxide until it reaches its capacity. The voltage can then be switched to block off the feed side and open up the other side, where a concentrated stream of nearly pure carbon dioxide is released.
By building a system with alternating sections of membrane that operate in opposite phases, the system would allow for continuous operation in a setting such as an industrial scrubber. At any one time, half of the sections would be absorbing the gas while the other half would be releasing it.
"That means that you have a feed stream coming into the system at one end and the product stream leaving from the other in an ostensibly continuous operation," Hatton says. "This approach avoids many process issues" that would be involved in a traditional multicolumn system, in which adsorption beds alternately need to be shut down, purged, and then regenerated, before being exposed again to the feed gas to begin the next adsorption cycle. In the new system, the purging steps are not required, and the steps all occur cleanly within the unit itself.
The researchers' key innovation was using electroplating as a way to open and close the pores in a material. Along the way the team had tried a variety of other approaches to reversibly close pores in a membrane material, such as using tiny magnetic spheres that could be positioned to block funnel-shaped openings, but these other methods didn't prove to be efficient enough. Metal thin films can be particularly effective as gas barriers, and the ultrathin layer used in the new system requires a minimal amount of the zinc material, which is abundant and inexpensive.
"It makes a very uniform coating layer with a minimum amount of materials," Liu says. One significant advantage of the electroplating method is that once the condition is changed, whether in the open or closed position, it requires no energy input to maintain that state. Energy is only required to switch back again.
Potentially, such a system could make an important contribution toward limiting emissions of greenhouse gases into the atmosphere, and even direct-air capture of carbon dioxide that has already been emitted.
While the team's initial focus was on the challenge of separating carbon dioxide from a stream of gases, the system could actually be adapted to a wide variety of chemical separation and purification processes, Hatton says.
"We're pretty excited about the gating mechanism. I think we can use it in a variety of applications, in different configurations," he says. "Maybe in microfluidic devices, or maybe we could use it to control the gas composition for a chemical reaction. There are many different possibilities."
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The research team included graduate student Chun-Man Chow, postdoc Katherine Phillips, and recent graduates Miao Wang PhD '20 and Sahag Voskian PhD '19. The work was supported by ExxonMobil.
Written by David L. Chandler, MIT News Office
When good governments go bad
History shows that societies collapse when leaders undermine social contracts
IMAGE: THE RUINS OF THE ROMAN FORUM, ONCE A SITE OF A REPRESENTATIONAL GOVERNMENT. view more
CREDIT: (C) LINDA NICHOLAS, FIELD MUSEUM
All good things must come to an end. Whether societies are ruled by ruthless dictators or more well-meaning representatives, they fall apart in time, with different degrees of severity. In a new paper, anthropologists examined a broad, global sample of 30 pre-modern societies. They found that when "good" governments--ones that provided goods and services for their people and did not starkly concentrate wealth and power--fell apart, they broke down more intensely than collapsing despotic regimes. And the researchers found a common thread in the collapse of good governments: leaders who undermined and broke from upholding core societal principles, morals, and ideals.
"Pre-modern states were not that different from modern ones. Some pre-modern states had good governance and weren't that different from what we see in some democratic countries today," says Gary Feinman, the MacArthur curator of anthropology at Chicago's Field Museum and one of the authors of a new study in Frontiers in Political Science. "The states that had good governance, although they may have been able to sustain themselves slightly longer than autocratic-run ones, tended to collapse more thoroughly, more severely."
"We noted the potential for failure caused by an internal factor that might have been manageable if properly anticipated," says Richard Blanton, a professor emeritus of anthropology at Purdue University and the study's lead author. "We refer to an inexplicable failure of the principal leadership to uphold values and norms that had long guided the actions of previous leaders, followed by a subsequent loss of citizen confidence in the leadership and government and collapse."
In their study, Blanton, Feinman, and their colleagues took an in-depth look at the governments of four societies: the Roman Empire, China's Ming Dynasty, India's Mughal Empire, and the Venetian Republic. These societies flourished hundreds (or in ancient Rome's case, thousands) of years ago, and they had comparatively more equitable distributions of power and wealth than many of the other cases examined, although they looked different from what we consider "good governments" today as they did not have popular elections.
"There were basically no electoral democracies before modern times, so if you want to compare good governance in the present with good governance in the past, you can't really measure it by the role of elections, so important in contemporary democracies. You have to come up with some other yardsticks, and the core features of the good governance concept serve as a suitable measure of that," says Feinman. "They didn't have elections, but they had other checks and balances on the concentration of personal power and wealth by a few individuals. They all had means to enhance social well-being, provision goods and services beyond just a narrow few, and means for commoners to express their voices."
In societies that meet the academic definition of "good governance," the government meets the needs of the people, in large part because the government depends on those people for the taxes and resources that keep the state afloat. "These systems depended heavily on the local population for a good chunk of their resources. Even if you don't have elections, the government has to be at least somewhat responsive to the local population, because that's what funds the government," explains Feinman. "There are often checks on both the power and the economic selfishness of leaders, so they can't hoard all the wealth."
Societies with good governance tend to last a bit longer than autocratic governments that keep power concentrated to one person or small group. But the flip side of that coin is that when a "good" government collapses, things tend to be harder for the citizens, because they'd come to rely on the infrastructure of that government in their day-to-day life. "With good governance, you have infrastructures for communication and bureaucracies to collect taxes, sustain services, and distribute public goods. You have an economy that jointly sustains the people and funds the government," says Feinman. "And so social networks and institutions become highly connected, economically, socially, and politically. Whereas if an autocratic regime collapses, you might see a different leader or you might see a different capital, but it doesn't permeate all the way down into people's lives, as such rulers generally monopolize resources and fund their regimes in ways less dependent on local production or broad-based taxation."
The researchers also examined a common factor in the collapse of societies with good governance: leaders who abandoned the society's founding principles and ignored their roles as moral guides for their people. "In a good governance society, a moral leader is one who upholds the core principles and ethos and creeds and values of the overall society," says Feinman. "Most societies have some kind of social contract, whether that's written out or not, and if you have a leader who breaks those principles, then people lose trust, diminish their willingness to pay taxes, move away, or take other steps that undercut the fiscal health of the polity."
This pattern of amoral leaders destabilizing their societies goes way back--the paper uses the Roman Empire as an example. The Roman emperor Commodus inherited a state with economic and military instability, and he didn't rise to the occasion; instead, he was more interested in performing as a gladiator and identifying himself with Hercules. He was eventually assassinated, and the empire descended into a period of crisis and corruption. These patterns can be seen today, as corrupt or inept leaders threaten the core principles and, hence, the stability of the places they govern. Mounting inequality, concentration of political power, evasion of taxation, hollowing out of bureaucratic institutions, diminishment of infrastructure, and declining public services are all evidenced in democratic nations today.
"What I see around me feels like what I've observed in studying the deep histories of other world regions, and now I'm living it in my own life," says Feinman. "It's sort of like Groundhog Day for archaeologists and historians."
"Our findings provide insights that should be of value in the present, most notably that societies, even ones that are well governed, prosperous, and highly regarded by most citizens, are fragile human constructs that can fail," says Blanton. "In the cases we address, calamity could very likely have been avoided, yet, citizens and state-builders too willingly assumed that their leadership will feel an obligation to do as expected for the benefit of society. Given the failure to anticipate, the kinds of institutional guardrails required to minimize the consequences of moral failure were inadequate."
But, notes Feinman, learning about what led to societies collapsing in the past can help us make better choices now: "History has a chance to tell us something. That doesn't mean it's going to repeat exactly, but it tends to rhyme. And so that means there are lessons in these situations."
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When honey flows faster than water
Physicists surprised to find that in specially coated tubes, the more viscous a liquid is, the faster it flows
VIDEO: A QUICK EXPLAINER OF THE WORK, INCLUDING SAMPLE DATA FROM THE PAPER view more
CREDIT: AALTO UNIVERSITY
It's widely known that thick, viscous liquids - like honey - flow more slowly than low-viscosity liquids, like water. Researchers were surprised to find this behaviour flipped on its head when the liquids flow through chemically coated capillaries. In fact, through these specially coated tubes, liquids a thousand times more viscous flow ten times faster.
The speed at which different fluids flow through pipes is important for a large range of applications: from industrial processes such as oil refineries to biological systems like the human heart. Traditionally, if you need to make a fluid flow faster through a pipe, you increase the pressure on it. This technique, however, has its limits; there is only so much pressure you can put into a pipe before you run the risk of bursting it. This is especially true for thin and narrow pipes, like the ones used in microfluidics for producing medicine and other complex chemicals, so researchers are investigating if they can increase the speed at which liquids flow through narrow tubes without having to increase the pressure.
In the paper published on 16 October in the journal Science Advances, researchers found that by coating the inside of the pipes with compounds that repel liquids, they could make viscous liquids flow faster than those with low viscosity.
'A superhydrophobic surface consists of tiny bumps that traps air within the coating, so that a liquid droplet that rests on the surface sits as if on a cushion of air,' explains Professor Robin Ras, whose research team at Aalto University's Department of Applied Physics has made a range of interesting discoveries in the area of extremely water repellent coatings, including recent papers in Science and Nature.
Superhydrophobic coatings themselves don't speed up the flow of the more viscous liquids. If you place a drop of honey and a drop of water on a superhydrophobic coated surface and then tilt the surface so gravity makes the droplets move, the low-viscosity water will flow down faster.
But when a droplet is confined to one of the very narrow tubes used in microfluidics, things change drastically. In this system, the superhydrophobic coating on the walls of the tube creates a small air gap between the inside wall of the tube and the outside of the droplet. 'What we found was that when a droplet is confined to a sealed superhydrophobic capillary, the air gap around the droplet is larger for more viscous liquids. This larger air gap is what allowed for the viscous fluids to move through the tube faster than the less viscous ones when flowing due to gravity,' says Dr Maja Vuckovac, the first author of the paper.
The size of the effect is quite substantial. Droplets of glycerol a thousand times more viscous than water flow through the tube more than ten times faster than water droplets. The researchers filmed the droplets as they moved through the tube, tracking not only how fast the liquid moved through the tube, but also how the liquid flowed inside the droplet. For viscous liquids, the liquid inside the droplet hardly moved around at all, whereas a fast mixing motion was detected in the lower viscosity droplets.
'The crucial discovery is that the less-viscous liquids also managed to penetrate a bit into the air cushion surrounding the droplets, rendering a thinner air gap around these. This means that the air beneath a low-viscosity droplet in the tube couldn't move out of the way as fast as for a more viscous droplet with a thicker air gap. With less air managing to squeeze past the low-viscosity droplets, these were forced to move down the tube with a slower speed than their more viscous counterparts,' explains Dr Matilda Backholm, one of the researchers on the project.
The team developed a fluid dynamics model that can be used to predict how droplets would move in tubes coated with different superhydrophobic coatings. They hope that further work on these systems could have significant applications for microfluidics, a type of chemical engineering technique that is used to precisely control liquids in small quantities and in manufacturing complex chemicals like medicines. By being able to predict how the coatings can be used to modify fluid flow, the coatings may be helpful for engineers developing new microfluidics systems.
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Read More:
Viscosity-Enhanced Droplet Motion in Sealed Superhydrophobic Capillaries Maja Vuckovac, Matilda Backholm, Jaakko V. I. Timonen, Robin H. A. Ras, Science Advances, DOI: https://dx.doi.org/10.1126/sciadv.aba5197
IMAGE: THE FLUID INCLUSIONS INSIDE THE OLIVINE CONTAIN NANODIAMONDS, APART FROM SERPENTINE, MAGNETITE, METALLIC SILICON AND PURE METHANE. view more
CREDIT: UNIVERSITY OF BARCELONA
Natural diamonds can form through low pressure and temperature geological processes on Earth, as stated in an article published in the journal Geochemical Perspectives Letters. The now found mechanism, far from the classic regard on the formation of diamonds under ultra-high pressure, is confirmed in the study, which counts on the participation of experts from the Mineral Resources Research Group of the Faculty of Earth Sciences of the University of Barcelona (UB).
Other participants in the study are the experts from the Institute of Nanoscience and Nanotechnology of the UB (IN2UB), the University of Granada (UGR), the Andalusian Institute of Earth Sciences (IACT), the Institute of Ceramics and Glass (CSIC), and the National Autonomous University of Mexico (UNAM). The study has been carried out within the framework of the doctoral thesis carried out by researcher Núria Pujol-Solà (UB), first author of the article, under the supervision of researchers Joaquín A. Proenza (UB) and Antonio García-Casco (UGR).
Diamond: the toughest of all minerals
A symbol of luxury and richness, the diamond (from the Greek αδ?μας, "invincible") is the most valuable gem and the toughest mineral (value of 10 in Mohs scale). It formed by chemically pure carbon, and according to the traditional hypothesis, it crystalizes the cubic system under ultra-high-pressure conditions at great depths in the Earth's mantle.
The study confirms for the first time the formation of the natural diamond under low pressures in oceanic rocks in the Moa-Baracoa Ophiolitic Massif, in Cuba. This great geological structure is in the north-eastern side of the island and is formed by ophiolites, representative rocks of the Oceanic lithosphere.
These oceanic rocks were placed on the continental edge of North America during the collision of the Caribbean oceanic island arch, between 70 and 40 million years ago. "During its formation in the abysmal marine seafloors, in the cretaceous period -about 120 million years ago-, these oceanic rocks underwent mineral alterations due to marine water infiltrations, a process that led to small fluid inclusions inside the olivine, the most common mineral in this kind of rock", note Joaquín A. Proenza, member of the Department of Mineralogy, Petrology and Applied Geology at the UB and principal researcher of the project in which the article appears, and Antonio García-Casco, from the Department of Mineralogy and Petrology of the UGR.
"These fluid inclusions contain nanodiamonds -of about 200 and 300 nanometres-, apart from serpentine, magnetite, metallic silicon and pure methane. All these materials have formed under low pressure (<200 MPa) and temperature (<350 ºC), during the olivine alteration that contains fluid inclusions", add the researchers.
"Therefore, this is the first description of ophiolitic diamond formed under low pressure and temperature, whose formation under natural processes does not bear any doubts", they highlight.
Diamonds formed under low pressure and temperature
It is notable to bear in mind that the team published, in 2019, a first description of the formation of ophiolitic diamonds under low pressure conditions (Geology), a study carried out as part of the doctoral thesis by the UB researcher Júlia Farré de Pablo, supervised by Joaquín A. Proenza and the UGR professor José María González Jiménez. This study was highly debated on among the members of the international scientific community.
In the published article in Geochemical Perspectives Letters, a journal of the European Association of Geochemistry, the experts detected the nanodiamonds in small fluid inclusions under the surface of the samples. The finding was carried out by using the confocal Raman maps and using focused ion beams (FIB), combined with transmission electron microscopy (FIB-TEM). This is how they could confirm the presence of the diamond in the depth of the sample, and therefore, the formation of a natural diamond under low pressure in exhumed oceanic rocks. The Scientific and Technological Centres of the UB (CCiTUB) have taken part in this study, among other infrastructures supporting the country.
In this case, the study focuses its debate on the validity of some geodynamic models that, based on the presence of ophiolite diamonds, imply circulation in the mantle and large-scale lithosphere recycling. For instance, the ophiolitic diamond was thought to reflect the passing of ophiolitic rocks over the deep earth's mantle up to the transition area (210-660 km deep) before settling into a normal ophiolite formed under low pressure (~10 km deep).
According to the experts, the low state of oxidation in this geological system would explain the formation of nano-çdiamonds instead of graphite -which would be expected under physical and chemical formation conditions of fluid inclusions.
The study counted on the support from the former Ministry for Economy and Competitiveness (MINECO), the Ramón y Cajal Program and the EU European Regional Development Fund (ERDF).
