Finishing | Zhou Shuyi, Wangxiang
The turbulent sky in Van Gogh's Starry Night is consistent with scientific theory
The mottled starlight and swirling clouds in Starry Night are thought to reflect Vincent · van Gogh's turbulent state of mind. And a new study shows that the turbulent sky in "Starry Night" is consistent with scientific theory, and Van Gogh had a deep intuitive understanding of the mathematical structure of turbulent flow. The paper was published in Physics of Fluids on September 17.
Vincent · van Gogh's Starry Night was created in 1889 AIP Publishing
Turbulence is a natural phenomenon that is widespread in fluids, such as water currents, ocean currents, blood flows, tumbling storm clouds, and smoke columns. Turbulence is essentially a chaotic state in which larger vortices are constantly forming and disintegrating into smaller vortices. In this study, the scientists used digital images of Starry Night to analyze the scales of the 14 main rotational shapes in the painting to see if they fit the physics theory of large-scale eddy currents and small-scale eddy currents colliding and interacting with each other.
《星月夜》中的涡旋/涡流 | AIP Publishing
Since it was not possible to directly measure the movement of the air currents in the sky in the painting, the researchers precisely measured the brushstrokes and compared the size of these strokes to the mathematical scale predicted in turbulence theory. To analyze physical motion, they made use of the relative brightness or luminosity of different pigment colors. It was found that the size, relative distance, and intensity of the 14 eddies in Starry Night followed the Kolmogorov theory in fluid dynamics. This theory was proposed in the 40s of the 20th century by the Soviet mathematician Andrey ·Kolmogorov and described the mathematical relationship between flow velocity fluctuations and energy dissipation rates. The study also found that, at the smallest scale, the pigments mixed with some background eddies in the way predicted by turbulence theory, following the statistical pattern of Batchler's Law, which mathematically describes how small particles, such as algae drifting in the ocean or dust in the wind, are passively mixed by turbulent flows.
The spatial scale of some of the typical strokes of the vortex in "Starry Night". AIP Publishing
"Of course, Van Gogh may not have known these equations, but he probably spent a lot of time observing turbulence in nature," the researchers said. I believe that this physical relationship is deeply ingrained in his mind, so when creating the famous Starry Night, he naturally mimicked the flow of reality. "A deeper understanding of turbulence will help improve weather forecasts, reduce flight bumps, and many other processes. Scientists have long faced difficulties in describing turbulence in fluid dynamics, and no effective way to predict this phenomenon has yet been found, and the full explanation remains a major mystery in physics.
New research reveals a striking similarity to turbulence theory behind the mysterious and fantastical sky in Van Gogh's Starry Night, revealing a subtle connection between art and science. Van Gogh subconsciously showed a unique perception of turbulence, and on that night in 1889, he may have seen much more than the excitement and loneliness of the starry sky. （AIP Publishing）
Related papers: https://doi.org/10.1063/5.0213627
Monkey predicts the United States presidential election
The monkey stared thoughtfully at the picture of Harris and Trump. Can it predict who will win the November United States presidential election? It may sound a bit ridiculous, but don't shake your head just yet. A new study notes that monkeys' gazes stay longer on the faces of ultimately defeated candidates. The paper was published in bioRxiv as a preprint on September 19 and has not been peer-reviewed.
The team of authors has been studying monkeys' facial preferences for years. In a previous experiment, they showed macaques unfamiliar faces of their own kind. It was found that macaques would only sneak a glance at a high-status male (a long gaze was seen as aggressive), while for females or low-status males, their gaze would be unbridled and linger longer. It seems that just by looking at the photo, the macaque can "perceive" the social status of the other person.
Does this skill also apply to human faces? In the new study, the authors showed monkeys the faces of United States senators, governors and presidential candidates and tracked their gaze. It was found that among the paired candidates, the monkeys usually stared at one of them. In 273 senatorial and gubernatorial races between 1995 and 2008, the monkeys watched the losers more often, longer and above random levels 54.6 percent of the time. In the "swing states" campaign, the monkey's predictions were more accurate, with a 58.1 percent correct rate. However, for the six United States presidential races from 2000 to 2020, this method is no different from a coin toss, with an accuracy rate of only 50.4%. In the three United States presidential races in 2016, 2020 and 2024, according to the "judgment" given by the monkey, Trump has a large lead over Hillary, narrows his advantage over Biden, and has no advantage over Harris.
猴子注视哈里斯（左）、特朗普（右）照片的时间大致相同。 （彩圈大小表示持注视时间长短）| Creative Commons, adapted by Yaoguang Jian
Further research has shown that macaques tend to look away from individuals with narrower cheekbones, wider and more prominent jaws, and "lateral development" of their faces. These characteristics indicate higher testosterone levels during puberty, which correlate with physical fitness and thus social status. This phenomenon seems to have continued over to human society – studies have found that the winning candidate has an average of 2% more protruding jaws than others.
Researchers say visual cues extracted from facial features may influence voters' choices in real elections. If this result can be replicated in more monkeys, it will be a strong case that humans and monkeys share common evolutionary roots in bias against facial features. However, this does not explain all voting behavior, for example, the fact that a female candidate will undoubtedly lose simply by whether her facial features are strong or not, which is not the case. Obviously, other factors can also influence voting decisions.
Former United States President Bill Clinton once said, "Americans like to be strong and wrong rather than weak and right." "The new research may shed light on the irrational side of electoral behavior – that physical characteristics can sometimes influence voters more than policy platforms." "In every aspect of voting and daily behavior, each of us has a little monkey in our hearts," the researchers said. ”
Related papers: https://doi.org/10.1101/2024.09.17.613526
To understand human evolution, scientists have "tested the DNA" of cheese about 3,500 years ago
Who moved my cheese? In the millions of years of human evolutionary history, food fermentation itself is an ancient and intelligent "fable": different groups of people and cultures have their own preferences for food fermentation, and the transformation of livelihood mode and agricultural development are also closely related to the evolution of fermentation technology. A new study has revealed the history of human application, propagation, and domestication of kefir lactic acid bacteria by studying the archaeomicrobial genome of three groups of kefir cheese about 3,500 years ago, providing a new way to understand human evolution and its interaction with the environment. The paper was published in Cell on September 25.
Bronze Age cheese samples excavated from the Xiaohe cemetery in Xinjiang are compared with glass tube caps with an outer diameter of about 1.8 cm Yang Yimin, School of Humanities, University of Chinese Academy of Sciences
The samples for the study were the earliest cheese products ever discovered, three groups of kefir cheese excavated from the Xiaohe cemetery in the Tarim Basin, Xinjiang, which are derived from kefir yogurt and are made by fermenting kefir grains (similar to koji) in milk. The spread of dairy fermentation technology has been largely accompanied by human migration and interaction, a process that has promoted the evolution of lactic acid bacteria, which play an important role in fermentation.
The research team independently designed a genome-wide probe for lactic acid bacteria to extract the genome of high-quality ancient kefir cheese from the sample. Through phylogenetic analysis, it was found that there were two differentiated branches of Kefir lactic acid bacteria used for fermentation, one branch conformed to the mainstream route of spreading from the Caucasus to the coastal areas of Europe, Asia and Southeast Asia, while the other branch mainly included strains distributed in the inland areas of East Asia (including Tibet), and the strains used by the ancient population in the Tarim Basin of Xinjiang to ferment kefir yogurt came from this branch and were located at the base. This suggests that there was another route that spread the kefir yogurt-making process from Xinjiang to the interior of East Asia through technological and cultural exchanges.
(A) Floor plan of Xiaohe cemetery in Xinjiang; (B) Mummified samples excavated from the Xiaohe cemetery in Xinjiang (known as the "Xiaohe Princess", and the cheese samples are around her neck); (C) Three groups of Bronze Age cheese samples with microbial genomes obtained from this study; (D) Microbial DNA composition in cheese samples
The authors believe that the differentiation of the two clades of Kefir lactic acid bacteria is likely to be caused by the spread of their common ancestors among different populations due to different migration paths after their common ancestors were first domesticated. This indicates that different ancient populations migrated and communicated with different routes in the process of applying and domesticating fermented microorganisms.
In addition, the study also found that the long-term application and domestication of humans may also have influenced the evolution of Kefir lactic acid bacteria. Compared with the Bronze Age Kefir lactic acid bacteria in Xinjiang, two horizontally transferred gene clusters associated with the reduction of intestinal inflammatory responses appeared in the modern Kefir lactic acid bacteria strains in Tibet, which not only facilitated the survival of Lactobacillus in the human intestine, but also promoted intestinal function. This is most likely related to the preference of the population at that time for kefir granules that carried different clades of kefir lactic acid bacteria.
According to relevant experts, this study is a rare ancient DNA study in the field that excavates new data, and brings new understanding of the migration and exchange and microbial domestication history of people in the central Eurasian steppe.
Related papers: https://www.cell.com/cell/fulltext/S0092-86742400899-7
After a month in space, the human heart will show signs of aging
How does a low gravity environment affect your body when you stay in space for a long time? A study published in PNAS on Sept. 23 found that human heart tissue began to become weakened after staying in space for a month, its beating rhythm became irregular, and it underwent molecular genetic changes similar to aging.
The researchers cultivated human induced pluripotent stem cells (iPSCs), differentiated them into cardiomyocytes, and then installed the resulting myocardial tissue samples in a heart-on-a-chip that mimics the human heart environment. In March 2020, 48 samples traveled to the International Space Station aboard SpaceX's Dragon spacecraft, after which 10 seconds of myocardial tissue monitoring data was sent back to the ground every 30 minutes.
The analysis found that after 12 days on the ISS, the contraction strength of myocardial tissue was almost halved compared to the control group that remained on the ground, and the weakening was still evident even nine days after returning to Earth. In space, the heart rhythm becomes more irregular over time. By day 19, the interval between each beat of the tissue had increased more than 5-fold. However, this irregularity disappeared upon return to Earth.
Microscopic observation of the recovered tissue showed that the sarcomere, which is responsible for muscle contraction, became shorter and more disordered; Mitochondria also become swollen and fragmented. RNA sequencing showed that gene expression associated with inflammation and oxidative damage was upregulated in tissues; At the same time, there are signs of downregulation in gene expression that produces proteins needed for normal heart contraction and mitochondrial function. The second batch of myocardial tissue samples was sent to the International Space Station in 2023 to screen for potential drugs that would protect astronauts from the adverse effects of a low-gravity environment, the researchers said.
Related papers: https://doi.org/10.1073/pnas.2404644121
On average, 1 out of every 7 papers is fake
In the age of information explosion, the line between lies and truth is indistinguishable. How many scientific papers are fake? One meta-analysis tried to give a clear answer: on average, 1 in 7 papers was fake. The study was published on the Open Science Platform (OSF) as a preprint on Sept. 24 and was not peer-reviewed.
A 2009 study showed that about 2% of scientists admitted to academic fraud at least once in their careers. This study is widely cited. James ·Heathers, the author of the new study, said that the datasets included in the 2009 study were as of 2005, and the conclusions are outdated today, 20 years later, but they have been cited again and again, and a more timely evaluation is needed.
Heathers said that much of the past research relied on asking researchers directly if they had committed academic misconduct, which is a very poor approach. "I think it's very naïve to ask people who are cheating in their research if they are cheating before answering truthfully."
As a veteran academic anti-counterfeiter, Heathers reviews 12 previous studies in the new study, all of which used online tools to assess the proportion of research fraud, including social sciences, medicine, biology and other fields, and included a sample of about 75,000 papers. "Rough estimates suggest that 1/7 of research papers are fraudulent." Heathers acknowledges that the data sources for the new study are very broad and not systematic.
Daniele Fanelli, the author of the 2009 study and Heriot-Watt University, was not convinced by ·the new study. "The sample of these papers is varied, using a variety of different approaches in different contexts, highlighting different issues," he said. The new study's one-size-fits-all approach to estimation is "not rigorous."
Gowri Gopalakrishna, an epidemio·logist at Netherlands Maastricht University, said, "I don't think it's entirely wrong, but it can be a little misleading." She argues that academic fraud is more rampant in some areas, so it may not be helpful to generalize all papers. If you want to get attention, try to change the status quo, put it all together and say, look, how big the problem is. This might be useful, but I do think a deeper, more granular study would be more important. ”
Heathers acknowledges these limitations, but believes that the problem of counterfeiting is urgent, even if the resources available are insufficient. Heathers said he would continue to study the overall proportion of academic fraud, "even if you do a very formal systematic review, I suspect you're going to get the same results as I do." ”
Source: https://retractionwatch.com/2024/09/24/1-in-7-scientific-papers-is-fake-suggests-study-that-author-calls-wildly-nonsystematic/#more-130075
Related Papers: https://osf.io/5rf2m/
Rewriting textbooks? This carbon-carbon bond, has only one electron
Nearly a century after the "covalent bond of only one electron" was first proposed, a study published in Nature on September 25 achieved a single-electron covalent bond between two carbon atoms for the first time. This discovery is not only crucial for a deeper understanding of chemical bond theory, but also provides new insights for further understanding of chemical reactions.
In a molecule, two atoms form a covalent bond by sharing electron pairs. Most covalent bonds are single bonds made up of a pair of shared electrons, or double and triple bonds made up of two or even three pairs of electrons. In 1931, chemist Lin·us Pauling proposed that there might be single-electron covalent bonds formed by single, unpaired electrons, but they were very unstable – they break easily, and there was a strong tendency to release or trap electrons to restore paired electrons. This bonding is known as a single-electron σ bond.
To achieve this, the researchers sought to remove one electron from the existing carbon-carbon two-electron covalent bond through iodine oxidation. Based on hexephenylethane (HPE), they designed the compound HPE 1, which modifies spirodibenzocycloheptene (DBCHT). Due to the steric hindrance effect generated by the surrounding aryl groups, the central carbon-carbon single bond is greatly elongated, resulting in an increase in the HOMO energy level of the molecule, which means that it is difficult for electrons elsewhere in the molecule to replace the removed electrons.
Takuya Shimajiri, author of the paper at the University of Tokyo in Japan, said that past experiments trying to remove electrons left chemical bonds that were too weak to break too quickly for exact chemical analysis, but this time the molecule they used was still stable enough after removing the electrons. The researchers analyzed it using X-ray diffraction and Raman spectroscopy, and after density functional theory calculations, determined that it had a stable covalent bond composed of single electrons, and finally confirmed the existence of a carbon-carbon single-electron σ bond.
The results constitute the first experimental evidence of a single-electron carbon-σ bond. Some chemists say this is a significant discovery. It can be expected that the realization of single-electron σ bonds in carbon will contribute to a better understanding of the fundamental properties of chemical bonds and may prompt chemists to create entirely new families of molecules.
Related papers: https://doi.org/10.1038/s41586-024-07965-1
Acting out of place under pressure? Monkeys too
Blank brain in the exam room? I can't speak at the time of the defense? On the court, you want to press the whistle and kill, but you find that you can't lift your legs? Take it easy, everyone is the same – even the monkeys. A study published Sept. 12 in Neuron suggests that "breakdowns" under stress are associated with decreased activity of neurons in the brain preparing for exercise, and are not unique to humans.
The researchers set the task of having the rhesus monkeys move the computer cursor to the designated location as quickly and accurately as possible, and then gave a reward. Before each mission, the researchers prompted the monkeys whether the reward was small, medium, large or a "jackpot". Jackpots are rare and unusually lucrative, making them a high-risk, high-reward scenario. They also implanted electrodes in the frontal lobe region of the monkey brain that controls movement to observe changes in neuronal activity under different reward scenarios.
It was found that as the reward amount increased, the monkeys' neural activity was also active and their state was better. However, in the case of a jackpot reward, neuronal activity related to athletic preparation is weakened. "Exercise preparation" and "exercise execution" encompass the cognitive process of attention, organization, and planning before exercise—similar to aiming at a target before pulling a trigger. Weakened neuronal activity meant that the monkeys were poorly prepared and therefore underperformed. Studies suggest that as the potential reward increases, neural activity peaks, beyond which the reward becomes more abundant, and neuronal activity begins to weaken, causing the brain to deviate from its optimal state.
Related papers: https://doi.org/10.1016/j.neuron.2024.08.012
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