How did science become a trending search? Cold thinking after "room temperature superconductivity" "explosion"
Room temperature superconductivity?
A farce around superconducting materials
It's over in a month
Where do scientific myths come from?
In early August, the room-temperature superconducting "Wolf" struck again. This time it was accompanied by the uproar of the Internet.
You know, it hasn't been long since the last "Wolf" came
On March 7, the team of Ranga Dias, an assistant professor at the University of Rochester in the United States, reported at the APS March Meeting of the American Physical Society that they prepared a lutetium-hydrogen-nitrogen compound. Room temperature superconductivity was achieved under conditions close to 10,000 standard atmospheres (the air pressure at sea level at 0 ° C and 45 ° latitude is called 1 atmosphere). The Dias team's paper was published on the website of the journal Nature the next day.
However, just a week later, on March 15, Wen Haihu's team at Nanjing University announced via the paper's preprint website arXiv that their experiments basically negated the Dias results; Subsequently, the paper of Wen Haihu's team was also published on the website of Nature on May 11.
In the early years, Dias twice announced the successful preparation of room temperature superconducting materials, and both were falsified. In view of this, this matter in May this year as a small academic mistake, and did not cause special "circle" attention.
Since 2017, the Dias team has claimed to have found room temperature superconductivity three times in Nature/Science journals, but there have been peer falsification, journal retraction and other phenomena.
Followers rubbed their fists and palms
Discuss this revolutionary achievement
For the technology industry
Business pattern
The impact of international relations
-- Eager to embrace the new era of history
However, the storm related to room-temperature superconducting materials is not over.
On July 22, the Korea Quantum Energy Institute team published results on arXiv, saying that the material LK-99 discovered in the early years has amazing superior characteristics: this material shows superconducting properties at a temperature of 400K (126.85℃) and atmospheric pressure; What is even more unusual is that the preparation process is quite simple by the standards of modern chemistry.
Detailed synthesis steps of LK-99. (a) Sealed vacuum transistor layout with mixed power. (b), (c), and (d) are respectively Lanshi stone, Cu3P, Pb10−xCux(PO4)O (0.9<x<1.1) heat treatment conditions (e) before reaction, all components are pre-mixed powder, white to light gray. (f) Picture of sealed sample after reaction, (g) process of sample removal from furnace, (h) shape of sealed quartz tube sample, (i) shape of sample during each process.
Compared with the Dias incident, the LK-99 incident has a little more rugged temperament, which is easy to remind people of the Taoist priest who burned Dan and refined mercury. The Korea Quantum Energy Institute is not a prestigious institute like the University of Rochester, but a technology company with only two employees in a small four-story building in Seoul. LK-99 is named independently of its chemical composition: L and K are derived from the initials of discoverers Lee Seok-bae and Kim Ji-hoon, respectively, while 99 represents the year of discovery, 1999.
On August 4, Yonhap reported that while "the Institute of Quantum Energy cites a number of companies, institutes and universities as partners on its homepage, it was revealed that they have never worked together."
"The only institution that has worked with the company so far is the Korea Energy Engineering Research Institute, which signed a research agreement on May 24 this year."
Whatever the company's background, its experimental team is at least a lot more honest than Dias's team. Dias does not disclose the ratio of the material's components, making it unclear how to prepare and test the material. In contrast, the Quantum Energy Institute team openly demonstrated the preparation method, but also put on a confident posture waiting for the world to test. What's more, with such superior characteristics and such a simple preparation method, it is simply that everyone can try it on their own.
Within a day, the news about LK-99 caused an uproar around the world: Internet users in various countries have fought a technological battle to reproduce LK-99.
Simplified Chinese Internet appeared "live to do scientific research". On August 1, Station B Up the main @Seki Yamaguchi male technician, uploaded a video recording a small piece of the magnetic levitation of LK-99 material sample. The video notes show that Wu Hao, a postdoctoral fellow at the School of Materials, Huazhong University of Science and Technology, and Yang Li, a doctoral student, under the guidance of Professor Chang Haixin, successfully verified the synthesis of LK-99 crystals that can magnetically levitate for the first time. The suspension Angle of the crystal is larger than the magnetic levitation Angle of the sample obtained by Sukbae Lee et al., and it is expected to achieve a true sense of contact-free superconducting magnetic levitation.
As of August 14, the video had been played more than 10 million times and had accumulated more than 80,000 bullet screens. The barrage of "witness history" in the video is like a firework rainstorm. "Superconducting suspension", "energy band theory" and other originally difficult terms, overnight became a topic that everyone can talk about. In the comments section, followers are gearing up for history, eager to talk about the impact of this revolutionary achievement on the technology industry, the industrial landscape and even international relations.
Twitter Science has also emerged on the U.S. Internet. On August 1, Sinead Griffin, a researcher at Lawrence Berkeley National Laboratory (LBNL), announced on arXiv: Density functional theory calculations for LK-99 can support that it is a room temperature and atmospheric pressure superconducting material. Griffin's results went viral on Twitter within just an hour, and as they went, the tweet's emphasis quickly changed to "National Lab supports LK-99 as room temperature atmospheric pressure superconducting material."
Using the computing power of the U.S. Department of Energy, Sinead Griffin's simulations have found a theoretical basis for the superconductivity of copper-doped lead apatite: isolated flat bands of Fermi levels are the hallmark of superconducting crystals. Using computer models, the paper theoretically describes what properties materials should have if they existed in the real world at room temperature superconductivity. LK-99, which is now attracting global attention, has this special property.
The financial response was also timely. According to statistics from the Nandu Big Data Research Institute, most of the 15 concept stocks in the A-share room temperature superconductivity concept plate soared from July 25 to August 2. This situation has forced several companies to issue announcements regarding trading anomalies, clarifying that their business lines are not related to superconducting materials. In the United States, the news of "National Laboratory support for LK-99" also immediately made a company called "American Superconductor (AMSC)" share price jump on August 1, the highest intraday rise of 72%. Ironically, the main business of the United States is not superconducting materials, just the name of the side, has been pushed up the stock price roller coaster.
overnight
Condensed matter Physics
"All of us understand condensed matter physics overnight!" "Joked one physics major on social media.
However, little has been said about the reaction of the physics community. In fact, even the research team that caused the screencash itself has imploded. Two of the researchers who named the LK-99 material said in interviews that the paper was published without consent by other members of the team, and they have asked for it to be retracted. That led to a sharp fall in the underlying stocks, which had soared before August 2nd; Among them, Innocent American Superconductor's share price plunged 30% on August 2.
"Superconductivity" is a physical term that refers to the resistance of certain materials that suddenly drop to zero when the temperature is lowered below a certain critical value, known as the critical temperature.
Under normal temperature and pressure conditions, all materials known at present have resistance, but the size of the resistance is different. The property of resistance plummeting to zero at a certain temperature is difficult to explain with classical physical theory. This is a quantum phenomenon, and describing the macroscopic consequences of this quantum phenomenon is an important research content of condensed matter physics. Among the many strange properties of superconductors, one is particularly noteworthy: if a superconductor is placed in an external magnetic field, the magnetic field cannot enter the inside of the superconductor. This completely diamagnetic phenomenon is named the Meissner Effect in honor of its discoverer. As a result, a piece of superconducting material can be suspended in a magnetic field; In turn, it can levitate the magnet.
Of course, just as it is impossible for all materials not to conduct electricity at all, all materials are actually more or less diamagnetic. But any solid state physics textbook will emphasize that the complete diamagnetism of superconductors is fundamentally different from normal diamagnetism. In fact, since the discovery of the Meissner effect, physicists have used zero resistance and complete diamagnetism as criteria for determining whether a material is a superconductor.
There is no doubt that zero resistance and full diamagnetism are extremely attractive features. No need to think deeper, as long as you think that "superconducting materials can reduce the loss of power transmission to zero," then its technical prospects are already very considerable.
At present, China has made important progress in the application of superconducting technology. Source: Photon Box Institute
Unfortunately, known superconducting materials are not only complex to prepare, but also require fairly low temperatures to achieve superconductivity. For example, the first superconductivity was discovered when mercury resistance dropped to 4.15K (-269 ° C) plunged to zero. The "high temperature" of what physicists call "high temperature superconductivity" is the temperature relative to liquid nitrogen (77K, or -196.15 ° C), and they are actually very demanding on the environment, and the preparation is also very complex. If we can find superconducting materials at room temperature, it will undoubtedly point the way to the next industrial revolution.
The age and critical temperature of the discovery of various types of superconductors, illustrated as typical material structures. From: Science in China
However, can the LK-99 really handle such expectations?
First of all, the simplistic preparation of LK-99 is questionable. To make your own fruit wine, for example, you can do it without too much trouble with common kitchen utensils. But if you want to turn low-alcohol fruit wine into brandy, without special distillation equipment is impossible. Of course, the industrial material is not wine, but in today's highly refined physical and chemical development, it is difficult to imagine that the properties that needed to be obtained through complex preparation processes in the past can be obtained as easily as Taoist alchemy.
"The US National Laboratory supports LK-99 as a room-temperature superconducting material" is also an overstatement - this is just a researcher at Lawrence Berkeley National Laboratory running some simulations using known physical theories. Conducting simulation calculations and Posting the results on a preprint website are standard practice in natural science research today.
Physics professionals generally gave the simulation a poor review: it was doubtful that density functional theory could handle the situation; Although it can barely explain the phenomena claimed to have been discovered, it cannot predict any new phenomena. Some professionals even believe that this kind of "simulation computing" that is busy with post-patch hot experiments is an opportunistic operation.
A series of subsequent tests on LK-99 also failed to provide strong evidence. The highly clicked "magnetic levitation verification video" can only explain that LK-99 is a diamagnetic material. However, there is an essential difference between "diamagnetism" and "complete diamagnetism". In fact, if the applied magnetic field is strong enough, even a frog can levitate. You can't say frogs are superconductors! This "verification video" is an oversimplification of existing physics knowledge and may mislead viewers who do not know the expertise.
Subsequent experimental results also step by step falsified the KQUI team's conjecture for LK-99. Even the most central evidence for "superconductivity" - resistance plummeting near a certain temperature - was falsified. The Institute of Physics of the Chinese Academy of Sciences and the National Condensed Matter Physics Laboratory in Beijing also announced through arXiv on August 8 that the resistance plunge property of LK-99 material is actually caused by the first-order phase transition of the doped cuprous sulfide impurity.
On August 8, the Chinese Academy of Sciences team published a paper saying that no zero resistivity below the transition temperature was observed. "We suggest that the so-called superconducting behavior in LK-99 is likely due to Cu2S undergoing a first-order structural phase transition at around 385K, from the β phase at high temperatures to the γ phase at low temperatures, resulting in reduced resistivity."
On August 14, another research group at the Max Planck Institute for Solid State Research in Stuttgart, Germany, reported the synthesis of pure LK-99 single crystals. The result is a transparent purple crystal - pure LK-99, Pb8.8Cu1.2P6O25. The LK-99 separated from the impurities is not a superconductor, but an insulator with a resistance of up to millions of ohms, too high to perform standard conductivity tests. It showed slight ferromagnetism and dimagnetism, but not enough to achieve partial suspension.
South Korean scientists may not have found "gold," but a new form of pyrite. Therefore, the possibility of LK-99 superconductivity is completely ruled out.
Compared with the Dias event in March this year, although LK-99 caught fire through "live scientific research" and even caused the stock price of superconducting concept stocks to rise and fall, it was quickly tested by academic peers and got a more reasonable explanation in less than a month. Although many physicists were frustrated by the initial "everyone knows about condensed matter," this result should give them some comfort.
The LK-99 incident is not only a debate within the academic community, but also a matter of public opinion. It is perfectly normal for tech watchers and investors to get excited about LK-99. On a more macro level, people are desperate to hear a bit of good news at the moment, and LK-99 happens to debut at this time, naturally assuming high hopes, which is understandable.
All of this doesn't mean that the possibility of practical room-temperature superconductors is worthless - such a thing would be a huge boon to technological development and scientific research, perhaps in ways we can't yet fully understand. But in retrospect, the enthusiasm around LK-99 may well say more about our collective desire for easy answers and a tendency for wishful thinking than the potential of the material itself.
But there are other aspects of the event that are also worth reflecting on: why does "everyone understand condensed matter" appear? Why are there no rigorously tested conclusions that preoccupy the minds of onlookers? Is this simply a collective emotional response to turbulent times?
Andrei Bernevig, a condensed matter theorist at Princeton University in the United States, even said that the different results and the associated hype were frustrating. "A lot of things in the early days were rushed and statements from all sides were not checked; In my opinion, social media, memes, etc. are totally detrimental to progress in this area... I hope we never do science like this again."
On the other hand, new developments in research that generate much discussion and bets by political and business elites have happened before, with serious consequences. The story told in "Bad Blood: Secrets and Lies of a Silicon Valley Mogul" is one example. Elizabeth Anne Holmes, an undergrad from Stanford University, founded Theranos, a blood-testing company. She claims to have invented a device that can detect the risk of several diseases from a single drop of blood. Although the technology was never peer-proven, Hilanos grew into a biotech unicorn over the years: in 2015, it was valued at $9 billion.
Of course, Hieranos did not really develop human technology, so the final collapse of the "high-tech company" built on lies can be said to be inevitable. However, it is worth noting that at the height of Hilanos's popularity, it received the support of many American political and business celebrities: former State Henry Kissinger, former Secretary of State George Pratt Shultz, former Secretary of Defense James Mattis, and so on. The most dramatic of all is Shultz: Just two hours after meeting Holmes, Shultz joined the company's board of directors; Even as the building was about to fall, Shultz was reluctant to divulge damaging inside information to the press.
Elizabeth Anne Holmes and George Pratt Shultz
On November 18, 2022, Theranos former CEO Hilanos was sentenced to 11 years and 3 months in prison by the federal court for four counts of fraud, and paid $121 million to 10 investors.
Something similar is happening again. From the "Bad Blood" back to the LK-99 event, in China, fund managers have begun to consider layout investment because of the screen of science and technology news: on August 6, several fund managers said in an interview with the "China Fund News" : If this research system is recognized, then even if LK-99 did not survive the rigorous test, there is still a room temperature superconductivity field investment. In the U.S., investor Jason Calacanis invited startup engineer Andrew McCalip and fund partner Delian Asparouhov to talk about LK-99 on August 4. Neither of the panelists is a physicist, but they talked eloquently about the possible prospects of LK-99 and even abstracted a model of technological innovation and investment. They believe that even if LK-99 is not a superconducting material, its diamagnetism has huge application potential, from laboratory manufacturing to industrial production, every link is an attractive investment opportunity.
In 2015, cartoonist Tom Dunne drew a cartoon discussing the relationship between public perception and scientific breakthroughs.
The boom and bust cycle of LK-99 is a classic demonstration of science in action.
So, should we point the finger of blame at Korean scientists, early supporters, and the media? Michael Fuhrer, a condensed matter physicist at Monash University in Australia, believes that "science is not a court of law and it is unlikely that we will get 'proof' that the original LK-99 sample does not contain any superconductors, rather, the failed replication attempts simply show that the results are more likely to be interpreted in another way... I think this is a real example of a competent scientist who believed they were right, but was fooled in a rather subtle and surprising way."
But as the afterglow of LK-99's social media-driven ups and downs fades, it may be worth taking a hard look at what drove all this excitement in the first place. In fact, the LK-99 event gives us new hope for room-temperature superconductivity; There is also no reason to think that room temperature superconductivity is impossible. Room temperature superconductivity is important because it has the potential to revolutionize many aspects of science and technology. At present, the search for superconducting materials that are stable at room temperature and can be mass-produced is another important research direction. Current room-temperature superconductors require extremely high pressures, limiting their practical applications; How to achieve room temperature superconductivity at normal or lower pressures is also a major technical challenge.
We still don't know if the field of superconductivity research will benefit from the new avenues opened up in the past few weeks if many LABS continue to work on materials similar to LK-99. In this field, theory and experiment often challenge each other, and our expectations of what might happen are often called into question by observations. While public interest will no doubt fade for the time being, a bold promise remains: A golden age of superconductivity may be on the horizon, and the role of science is clear: find a way to get us there.
It is undeniable that the development of room temperature superconductivity is bound to be tortuous and complex, and our journey of challenging the unknown and pioneering innovation will never stop; Even if the road ahead is rough, the road is smooth.
Researchers appear to have solved the mystery of LK-99. Scientific probe work found evidence that the material was not a superconductor and clarified its actual properties.
The conclusion dashed hopes for LK-99, a compound of copper, lead, phosphorus and oxygen that marked the discovery of the first superconductor to work at room temperature and ambient pressure. Instead, studies have shown that impurities in the material: copper sulfide, in particular, are responsible for the sharp drop in resistivity and partial suspension on the magnet, which looks similar to the properties exhibited by superconductors.
"I think the jury is out at this point," said Inna Vishik, a condensed matter experimentalist at the University of California, Davis.
The LK-99 saga began in late July, when a team led by Sukbae Lee and Ji-Hoon Kim of the Quantum Energy Research Center, a start-up company in Seoul, published a preprint, It is claimed that LK-99 is a superconductor at atmospheric pressure and temperatures up to at least 127 ºC (400 Kelvin). Until now, all proven superconductors have only been able to function at extreme temperatures and pressures.
The extraordinary claim quickly attracted the attention of the public and researchers interested in science, some of whom tried to replicate LK-99. Initial attempts found no signs of room-temperature superconductivity, but neither was conclusive. Now, after dozens of replication efforts, many experts are confident that the evidence shows that LK-99 is not a room-temperature superconductor.
1) Accumulate evidence
The Korean research team proposed its own idea based on two properties of LK-99: suspension over a magnet and a sharp drop in resistivity. But the team at the Chinese Academy of Sciences has found a secular explanation for these phenomena.
On August 8, the Chinese Academy of Sciences team published a paper saying that no zero resistivity below the transition temperature was observed. "We suggest that the so-called superconducting behavior in LK-99 is likely due to Cu2S undergoing a first-order structural phase transition at around 385 K, from the β phase at high temperatures to the γ phase at low temperatures, resulting in reduced resistivity."
Links:
https://arxiv.org/abs/2308.04353
Another study, conducted by researchers in the United States and Europe, combines experimental and theoretical evidence to demonstrate how the structure of LK-99 makes superconductivity infeasible. Other researchers synthesized and studied pure samples of LK-99, removing doubts about the material's structure: it was confirmed that it was not a superconductor, but an insulator.
On August 9, researchers from the United States and Europe published a paper saying that the material is more likely to be a magnet than a superconductor at normal temperature and pressure.
On August 11, the researchers published a paper that ruled out the possibility of superconductivity in the crystals.
At the time, Michael Fuhrer, a physicist at Monash University in Melbourne, Australia, commented, "Now, perhaps only the Korean team can share their samples to further confirm this."
Perhaps the best evidence of LK-99's superconductivity is a video taken by the South Korean team that shows a coin-shaped sample of the silver material slogging around on a magnet. The South Korean team said the samples were suspended because of the Meissner effect, one of the hallmarks of superconductivity, in which the material releases a magnetic field. Multiple unconfirmed videos of LK-99 levitation subsequently circulated on social media, but none of the researchers who initially tried to replicate the findings observed any levitation.
2) Only suspended "half"?
Some of the problems were spotted by Derrick van Gennep, a former condensed matter researcher at Harvard University in Cambridge, Massachusetts, who now works in finance but is interested in LK-99. In the video, the same edge of the sample appears to be stuck to the magnet, looking delicately balanced. In contrast, a superconductor suspended on a magnet can rotate and even hold backwards.
Van Gennep thinks LK-99's properties are more likely the result of ferromagnetism. So he made a particle of compressed graphite with iron filings on it. A video made by Van Gennep shows his disc (made of a non-superconducting ferromagnetic material) mimicking the behavior of LK-99.
Video address:
https://twitter.com/VanGennepD/status/1688052003216261120
On August 7, the Peking University team reported that this "semi-suspension" of their LK-99 sample was due to ferromagnetism. Study co-author Yuan Li, a condensed matter physicist, said: "It's like the iron filing experiment. The ball gets a lift, but it's not enough to levitate, it's just enough to balance on one end."
Li and his colleagues measured the resistivity of the samples and found no superconductivity. But they were unable to explain the sharp drop in resistivity that the South Korean team saw.
3) Impure samples
The Korean authors note in their preprint that at a particular temperature, the resistivity of LK-99 drops tenfold, from about 0.02 ohm-cm to 0.002 ohm-cm; The temperature was 104.8ºC.
The reaction to synthesize LK-99 uses an unbalanced formula: for every 1 part copper-doped lead phosphate crystal (pure LK-99), 17 parts copper and 5 parts sulfur are produced. These residues produce a lot of impurities, especially copper sulfide, which the Korean team found in its samples.
Jain, the copper sulfide expert, remembers that 104ºC is the temperature at which Cu2S undergo a phase transition. Below this temperature, the resistivity of Cu2S exposed to air drops dramatically - a signal that is almost identical to the superconducting phase transition claimed by LK-99.
On August 9, Prashant K. Jain published a paper stating that "Copper sulfide (I) is known to undergo a phase transition at 104 degrees Celsius, from an ordered cryogenic phase to a high-temperature superionic phase. As a result of this phase transition, copper sulfide (I) exhibits a sharp transition in terms of resistivity and thermal capacity, which is expected to coincide with the temperature-induced transition of LK-99. This means that LK-99 must be synthesized without any Cu2S to definitively verify the superconducting properties of LK-99."
In the August 8 article, the CAS team reported the effects of Cu2S impurities in LK-99. At the time, Luo Jianlin, a physicist at the Chinese Academy of Sciences, said: "Different amounts of Cu2S can be synthesized using different processes. The researchers tested two samples: the first was heated in a vacuum and had a Cu2S content of 5%; The second sample was heated in air and had a Cu2S content of 70 percent."
The resistivity of the first sample increased relatively smoothly during cooling, similar to samples in other replication attempts. But the resistivity of the second sample dropped sharply as it approached 112 ºC (385K), closely matching the observations of the South Korean team.
Temperature dependence of the resistivity of two samples (S1 and S2).
It is difficult to make a definitive statement about the properties of LK-99 because the material is delicate and the samples contain different impurities. Therefore, a sample close enough to the original is sufficient to test whether LK-99 is a superconductor under environmental conditions.
4) "Crystal clear" LK-99
With a strong explanation for the resistivity drop and semi-warping, many are convinced that LK-99 is not a room-temperature superconductor. But the mystery remains: what are the actual properties of this material?
Initial theoretical attempts to predict the structure of LK-99 using density functional theory (DFT) suggest an interesting electronic feature known as a "flat band." In these regions, electrons move slowly and may have strong correlations. In some cases, this behavior can lead to superconductivity. But these calculations are based on untested assumptions about the LK-99 structure.
To better understand the material, the US-European team performed precise X-ray imaging of its samples to calculate the structure of LK-99. On top of that, imaging allowed them to perform rigorous calculations that clarified the case for flat bands: it's not conducive to superconductivity; In contrast, the flat bands in LK-99 result from strongly localized electrons, which are unable to "hop" in the way required for superconductors.
On August 14, another research group at the Max Planck Institute for Solid State Research in Stuttgart, Germany, reported the synthesis of pure LK-99 single crystals. Unlike previous attempts at synthesis that relied on crucible, the researchers used a technique called floating zone crystal growth, which avoided introducing sulfur into the reaction and eliminated Cu2S impurities.
The result is a transparent purple crystal - pure LK-99, Pb8.8Cu1.2P6O25. The LK-99 separated from the impurities is not a superconductor, but an insulator with a resistance of up to millions of ohms, too high to perform standard conductivity tests. It showed slight ferromagnetism and dimagnetism, but not enough to achieve partial suspension.
"Therefore, we rule out the possibility of superconductivity."
The team believes that the signs of superconductivity seen in LK-99 can be attributed to the Cu2S impurity, which is not present in their crystals.
a) The susceptibility of the second batch of crystals combined with low temperature and heater options as a function of temperature measured at 7 T in both field intensity cooling (FC) and zero field intensity cooling (ZFC) modes. b) How the magnetic susceptibility of the same crystal measured at 2, 300 and 800 K varies with the field strength.
While some critics hold up the LK-99 saga as a model of scientific repeatability, others say it involved the unusually swift solution of a compelling puzzle. "Usually these things die off very slowly, it's just a rumor, no one has been able to replicate it," said physicist Michael Fuhrer of Monash University in Melbourne, Australia.
When copper oxide superconductors were discovered in 1986, researchers immediately began exploring their properties. But nearly four decades later, the material's superconducting mechanism remains controversial; This time, the effort to explain LK-99 came quickly. "The detective work covered all the parts of the original observation - I think that's really fantastic, and it's relatively rare."
Reference link：
- 2023-08-04
- 2023-07-15
- 2023-07-12
- 2023-06-16
- 2023-06-12
- 2023-06-01
- 2023-05-31
- 2023-04-25
- 2023-04-18
- 2023-03-02
- 2023-02-17
- 2023-02-16
- 2023-02-15
- 2023-01-11
- 2022-11-16
