侦探物语

Ordinary Life Resumes in Sierra Leone After Violent Protests: What Happened and Why?_我的网站

A |     

    Schematic diagram of Milky Way Photo: Courtesy of Purple Mountain Observatory (PMO)
Chinese astronomers have discovered that the Milky Way is not a simple, smoothly warped disk, but contains widespread "wrinkle-like" structures resembling ripples on a water surface, providing new clues to understanding the galaxy's 3D structure and evolutionary history.
The discovery was made by a research team from the Purple Mountain Observatory (PMO) under the Chinese Academy of Sciences, using data from the "Milky Way Imaging Scroll Painting" (MWISP) survey. The findings were published online titled "Widespread corrugations superimposed on the Galactic warp in the outer CO disk" in the journal Nature Astronomy on August 7.
For decades, astronomers have known that the Milky Way's disk is not perfectly flat. Instead, its outer regions are slightly bent upward on one side and downward on the other - a structure known as a galactic warp.
However, the latest study shows that this large-scale bending is not the whole story. Smaller-scale vertical fluctuations are also embedded within the warped disk, creating a more complicated 3D structure.
"In many illustrations and in the public imagination, the Milky Way looks like a flat vinyl record," Sun Yan, associate researcher at PMO and the first author of the paper, told the Global Times on Tuesday. "In reality, the outer part of the Milky Way is more like a record that has been heated and deformed, with one side lifted and the other side lowered. That is the warp. On top of this large-scale deformation, there are additional smaller waves, which we call corrugations," Sun explained.
Using a more everyday analogy, Sun compared the Milky Way's structure to a sea surface. The warp is like a large swell that changes the overall height of the ocean, while corrugations are smaller waves superimposed on that swell.
"The two structures exist together. In our data analysis, we first removed the large-scale warp model, which allowed us to reveal the smaller wave-like patterns hidden underneath," Sun said.
The research focused on the Milky Way's outer gas disk rather than the more familiar stellar disk. According to Sun, cold molecular gas and stars provide two complementary ways to study the galaxy.
"Molecular gas is a sensitive probe for studying the vertical structure and dynamics of the galactic disk because it is concentrated near the disk plane and responds strongly to disturbances," she said.
Molecular gas is also the raw material for star formation, meaning its distribution is closely connected with the formation of young stars. The researchers traced this gas through carbon monoxide (CO) emission, which can penetrate regions obscured by interstellar dust and provide a different perspective from optical observations of stars.
The breakthrough was made possible by the MWISP survey, conducted using China's 13.7-meter millimeter-wave telescope. 
"MWISP can be understood as giving the Milky Way a large-scale medical examination using millimeter-wave observations," Sun said.
Previous CO surveys were limited in sensitivity and coverage, making it difficult to accurately study the distant outer regions of the galaxy. In contrast, the latest study identified more than 30,000 molecular cloud samples, covering about half of the Milky Way's outer disk and extending to a distance of about 26 kiloparsecs from the Galactic center.
With such a large dataset, researchers were able to first establish a model of the overall warp and then separate subtle structures from the background. The newly identified corrugations have radial wavelengths of about 3.9-7.9 kiloparsecs and vertical amplitudes of about 100-200 parsecs.
The study also identified a corrugation structure extending about 40 kiloparsecs in azimuth at a distance of around 12.7 kiloparsecs from the Galactic center. In some spiral arm regions, vertical displacements can reach approximately 200 parsecs.
The researchers believe these large-scale vertical fluctuations are likely related to "bending waves" triggered by external gravitational disturbances, suggesting that the Milky Way might have experienced more complex interactions during its evolutionary history.
Although the newly discovered structures sound dramatic, they do not have any direct impact on Earth or the solar system. "Humans cannot directly sense these corrugations," Sun said. "Their scales reach thousands or even tens of thousands of light-years, and even if these structures are evolving, such changes would not be directly perceptible on human timescales."
The study focuses on the outer disk of the Milky Way and does not include the region around the solar system. "There is currently no evidence that these structures have any observable influence on Earth's environment," Sun said.
Instead, their significance lies in what they reveal about the past. Like geological layers recording Earth's history, these galactic structures preserve traces of the Milky Way's evolutionary journey, the researchers explained.
Researchers said future studies combining more precise motion measurements and numerical simulations could further reveal the origins of these structures and their role in the long-term evolution of the Milky Way.
。    Dozens of businesses, government offices, vehicles, and at least three police stations went up in flames in Freetown, Makeni, Kamakwie, and other cities across Sierra Leone from August 10 through 12, with over 113 people arrested and police introducing an emergency nationwide curfew and deploying tear gas and live ammunition to disperse crowds.,The curfew was lifted on August 13, with banks, businesses, government offices, and most stores reopened and communal services beginning to clear the damage. However, ramped-up security measures, including federal troop deployments to assist police, have been left in place.,What Happened?,Sierra Leone is one of the poorest nations in the world, ranking 186 out of 198 in a recent GDP purchasing power parity ranking. An estimated 80 percent of the population lives in poverty, many of them in the country’s rural areas. Like other nations in Africa, the country has faced special difficulties amid the global economic calamity brought on by COVID, and exacerbated by Western restrictions on Russian exports of agricultural goods and fertilizers amid the security crisis in Ukraine, which has caused a major jump in food prices.,AfricaAnti-Russia Sanctions Left Africa Without Access to Grain and Fertilisers, African Union Chief Says3 June, 11:13 GMT,As a net importer of both energy and food, Sierra Leone is especially vulnerable to global economic conditions, and along with food and fertilizers, fuel and electricity costs have also soared. Food prices alone have jumped by over 40 percent over the past few months, with a bag of rice once costing 350 leones now going for over 500. The country’s Central Bank recently removed three zeros from the national currency in a bid to restore confidence. The country has also been overcome by weeks of strikes by government workers, including doctors and teachers, and by small traders protesting poor conditions.,Coup Plot?,However, President Julius Maada Bio has also accused protesters of having ulterior motives beyond the cost of living crisis.,“This was not a protest against the high cost of living occasioned by the ongoing global economic crisis. The chant of the insurrectionists was for a violent overthrow of the democratically-elected government,” Bio said in an address on August 12 after returning to the country from a holiday in London.,Local media pointed to the chants of “Bio must go” among protesters as they gathered in the capital, and the president accused some of the demonstrators of consisting of “APC Warriors,” a reference to the opposition All People’s Congress party, which governed the country from 2007 until 2018, when Bio’s Sierra Leone People’s Party won national elections.,No doubt mindful of the violent civil war which shook the country between 1991 and 2002, claiming as many as 70,000 lives and displacing over 2.5 million people, Bio vowed that “in the coming weeks and months, [the] government will undertake necessary security actions meant to guarantee the peace and security of all citizens.”,“The security forces will, and must, act with great restraint and within their professional codes of service. But be assured that my government will crack down hard on violent insurrectionists, their collaborators, their sponsors and their supporters. My government will relentlessly fight those who would rather use terror and gruesome violence to achieve political goals,” the president said.,As a government, we will continue our engagement with Civil Society as we strive to promote sustainable peace, national cohesion and socio-economic development in Sierra Leone. #newdirectionagenda— President Julius Maada Bio (@PresidentBio) August 18, 2022,Bio did not elaborate on who these “sponsors” and “supporters” were, or whether they included any foreign actors.,Geopolitical Context,Like other African nations, Sierra Leone recently rejected calls by Washington and Brussels to show solidarity with the West and Ukraine and impose sanctions on Russia. But even before the escalation of the Ukraine crisis, relations between Freetown and Washington were tense at times. Last year, US President Joe Biden snubbed Bio by refusing to invite the African leader to the US’ so-called “Democracy Summit.” No reasons were given. However, neighboring Liberia, which faced mass civil unrest of its own between 2019 and 2020, and whose officials have been sanctioned by the US over suspected corruption, did get an invite.,While Sierra Leone maintains economic and political ties with its former British colonial masters, and remains a member of the Commonwealth of Nations, Freetown has sought to expand its partnerships with other geopolitical power centers, including Russia and China. President Bio attended the Russia-Africa Summit in Sochi in 2019, where he discussed ways to strengthen economic cooperation between the distant nations. In February 2021, Freetown signed onto Moscow’s efforts to prevent the deployment of weapons in outer space. In May 2021, Bio spoke by phone to President Xi Jinping of China, where they discussed the friendly, “brotherly” relations between the two nations, as well Chinese assistance to Freetown in measures against COVID, and agricultural and economic development.,In this context, the reactions of major foreign powers to this month’s unrest have been telling. While the United States, Britain, and the European Union collectively expressed “grave concern” over the “disturbing reports of violence” and urged the parties to “stay calm, promote accountability and ensure respect for human rights,” China’s Embassy smoothed over the protests altogether, refraining from wagging its finger at Freetown and instead trumpeting the expanding cooperation between the two countries.,We are gravely concerned by reports of violence surrounding today’s demonstrations in Sierra Leone. We urge all parties to stay calm, promote accountability, and ensure respect for human rights and fundamental freedoms.— Bureau of African Affairs (@AsstSecStateAF) August 10, 2022,Similarly, while UK High Commissioner to Sierra Leone Lisa Chesney lectured President Bio about how “violence has no place in a democracy and the necessary investigation into August 10 can sit alongside de-escalation,” the Russian Embassy in the Republic of Guinea, which concurrently serves as the Embassy in Sierra Leone, only presented a bare bones report on the situation in the country, Bio’s meetings with community and tribal leaders, and indicated that an internal “debriefing” was being created “regarding the causes, course and consequences of the riots on August 10.”。

B |

Current article:http://2kz.xiadiaosengchengcun.shop/news/20260826_5568.html

Published on:18:55:45