内容：Alice Ge 编辑：Alvin Wei
Wechat ID: NativeStudy / Weibo: http://weibo.com/u/3476904471
Part I: Speaker
Snapping Shrimp Make More Noise in Warmer Oceans
Source: Scientific American
https://www.scientificamerican.com/podcast/episode/snapping-shrimp-make-more-noise-in-warmer-oceans/
[Rephrase 1, 02:23]
Part II: Speed
What WHO calling the coronavirus outbreak a pandemic means
By Jonathan Lambert | 14 HOURS AGO
[Time 2]
Given its spread and rapidly growing impact, the coronavirus outbreak is now considered a pandemic, the World Health Organization announced March 11 in a news conference. So far, the virus has reached at least 114 countries, killed over 4,000 people and infected at least 120,000.
The situation is likely to get worse before it improves. “We expect to see the number of cases, the number of deaths, and the number of affected countries climb even higher,” WHO director-general Tedros Adhanom Ghebreyesus said in the news conference.
The WHO declared the coronavirus outbreak a public health emergency in late January, but declined to describe COVID-19 as a pandemic until now. “Using the word pandemic carelessly has no tangible benefit,” Ghebreyesus said in a news conference February 26. “But it does have significant risk in terms of amplifying unnecessary and unjustified fear and stigma, and paralyzing systems.” That sentiment, as well as a desire to emphasize the possibility of containing the virus once it enters a country, kept the WHO from describing COVID-19 a pandemic until now.
A pandemic differs from an epidemic in the scope of its spread. Epidemics are large outbreaks of a new disease confined to a specific region, such as in the early days of COVID-19 when cases were largely centered in China. An epidemic becomes a pandemic when multiple outbreaks persist on multiple continents, sustained by widespread human-to-human transmission that can’t be traced back to the country where the outbreak began.
[244 words]
[Time 3]
The last time that the WHO used the word pandemic to describe a rapidly spreading virus was in 2009, for a then-novel H1N1 strain of influenza, which killed hundreds of thousands of people in its first year and is now part of the group of annually circulating influenza viruses (SN: 3/26/10). A pandemic has never been sparked by a coronavirus before.
The traditional view is that epidemics are still containable, while pandemics are not. “We have never before seen a pandemic that can be controlled,” Ghebreyesus said on March 11.
But the WHO says that this situation is different. The organization emphasized that this shift in language doesn’t reflect a change in their thinking about the threat posed by COVID-19, nor does it change their response. “We are not suggesting to shift from containment to mitigation,” Ghebreyesus said, emphasizing that countries can do both. But he says the change in language should be taken as a signal to double down on efforts to contain the virus and mitigate its spread. Such efforts, experts say, can prevent huge spikes in cases that overwhelm health systems.
“Countries must take a whole-of-government, whole-of-society approach, built around a comprehensive strategy to prevent infections, save lives and minimize impact,” Ghebreyesus said. “We’re in this together, to do the right things with calm and protect the citizens of the world. It’s doable.”
Source: Science News
https://www.sciencenews.org/article/coronavirus-outbreak-who-pandemic
This ancient dinosaur was no bigger than a hummingbird
By Carolyn Gramling | 17 HOURS AGO
[Time 4]
A tiny, toothed bird that lived 99 million years ago appears to be the smallest known Mesozoic dinosaur, an era from about 252 million to 66 million years ago. The creature’s 12-millimeter-long skull was found encased in a chunk of amber originally discovered in northern Myanmar, researchers report March 11 in Nature.
Of modern birds — the only dinosaurs still living today — the bee hummingbird is the smallest. The new species, dubbed Oculudentavis khaungraae, was similar in size. But three-dimensional images of the fossilized skull created with computed tomography, a type of X-ray imaging, revealed that the Mesozoic bird had little else in common with today’s nectar-sipping hummingbirds.
Instead, the images reveal a surprising number of teeth, suggesting the little bird was a predator, the researchers report. “It had more teeth than any other Mesozoic bird, regardless of size,” says paleontologist Jingmai O’Connor at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing. As for its prey, researchers can only guess, she adds. O. khaungraae probably dined on arthropods and invertebrates, and possibly even small fish.
The ancient bird also had deep, conical eye sockets, similar to those of modern predatory birds such as owls. Those deep sockets can increase the eye’s visual ability without increasing its diameter, and suggest the ancient birds had sharp eyesight, O’Connor says. But while owls’ eyes face forward, increasing their depth perception, the eyes of the tiny bird faced out to the side.
[Time 5]
The creature may have been the product of evolutionary miniaturization, whereby animals evolve smaller adult body sizes. There are limits to how small an animal can get. “You have all these restrictions related to trying to fit sensory organs into a small body size,” O’Connor says.
Yet when O’Connor considered the possibility that this ancient bird species had undergone miniaturization, “a lot of really weird, inexplicable things about the specimen suddenly made sense,” she says. Oddities including the bird’s strangely fused teeth and the pattern of fusion in its skull “can be explained by miniaturization.”
The miniaturization may be related to island dwarfism, in which larger animals evolve to smaller body sizes over many generations because their ranges are strictly limited, such as on an island (SN: 4/10/19). Anecdotal evidence suggests that the chunk of amber containing the bird skull may have come from a region in Myanmar that millions of years ago was part of an island chain.
Although it’s just one fossil, the find can shed light on evolutionary changes to smaller body size, says Roger Benson, a paleontologist at the University of Oxford who wrote a separate commentary about the discovery published in the same issue of Nature. The earliest birds, such as Archaeopteryx, arose around 150 million years ago (SN: 3/13/18), and this find suggests that bird body sizes were reaching their lower limit by 99 million years ago, he says.
But to truly understand the evolutionary significance of O. khaungraae, researchers will need to figure out where exactly the new species belongs on the tree of life. And that’s difficult, given the bird’s bizarre features, O’Connor says. “It’s just a skull. There’s a lot you can’t say,” she says. “Who knows what new [fossils] might tell us.”
Source: Science News
https://www.sciencenews.org/article/ancient-dinosaur-smallest-size-no-bigger-than-hummingbird
Heavy metal may rain from the skies of planet WASP 76b
By Maria Temming | 17 HOURS AGO
[Time 6]
On one distant world, “heavy metal” could be a weather forecast. Telescope observations indicate that an exoplanet nearly 400 light-years away has iron rain.
The planet, dubbed WASP 76b, is an extreme kind of exoplanet known as an ultrahot gas giant (SN: 7/30/19). These worlds “are complete oddballs,” says astronomer David Ehrenreich of the University of Geneva. They get blasted with so much radiation from their suns that their dayside temperatures rival some stars (SN: 6/5/17). Meanwhile, the nightsides of ultrahot gas giants tend to be much milder.
Until now, no one has gotten a close enough look at an ultrahot gas giant to see how such stark temperature contrasts affect atmospheric chemistry across the planet. Ehrenreich’s team used the Very Large Telescope in Chile to examine starlight filtering through WASP 76b’s atmosphere as the exoplanet passed in front of its sun during two orbits in 2018. Those observations revealed the chemical components of different regions of the atmosphere.
While the atmosphere showed traces of iron gas where the planet was transitioning toward nighttime, no iron was detected at the transition from night to day, researchers report online March 11 in Nature. This suggests that, as gaseous iron on WASP 76b’s dayside swirls toward the nightside — which is almost 1,000 degrees Celsius cooler — the iron condenses into liquid raindrops. Because those raindrops fall deep into the atmosphere overnight, astronomers don’t see iron in the atmospheric gas as it moves from night to day.
“It’s a giant gaseous planet, so there’s no ground” to get covered in iron puddles, Ehrenreich says. Instead, the researchers suspect that iron raindrops eventually reach depths so hot that they vaporize back into iron gas.
Source: Science News
https://www.sciencenews.org/article/iron-rain-exoplanet-wasp76b-atmosphere
Part III: Obstacle
Individual response to COVID-19 'as important' as government action
March 6, 2020 | University of Oxford
[Paraphrase 7]
How individuals respond to government advice on preventing the spread of COVID-19 will be at least as important, if not more important, than government action, according to a new commentary from researchers at the University of Oxford and Imperial College London in the UK, and Utrecht University and the National Institute for Public Health and the Environment in the Netherlands.
As the UK moves into the "delay" phase of dealing with a possible COVID-19 epidemic, a new commentary, published today in The Lancet, looks at what we know so far about the new virus. The researchers, led by Professor Sir Roy Anderson at Imperial College and Professor Deirdre Hollingsworth at the University of Oxford's Big Data Institute, also suggest what can be done to minimise its spread and its impact.
Professor Hollingsworth said: 'Completely preventing infection and mortality is not possible, so this is about mitigation. Our knowledge and understanding of COVID-19 will change over time, as will the response. High quality data collection and analysis will form an essential part of the control effort. Government communication strategies to keep the public informed will be absolutely vital.'
Vaccine development is already underway, but it is likely to be at least a year before a vaccine can be mass-produced, even assuming all trials are successful. Social distancing is therefore the most important measure, with an individual's behaviour key. This includes early self-isolation and quarantine, seeking remote medical advice and not attending large gatherings or going to crowded places. The virus seems to largely affect older people and those with existing medical conditions, so targeted social distancing may be most effective.
Government actions will be important, including banning large events such as football matches, closing workplaces, schools and institutions where COVID-19 has been identified, and making sure that good diagnostic facilities and remotely accessed advice, like telephone helplines, are widely available. Ensuring the provision of specialist healthcare is also vital. The researchers warn, however, that large-scale measures may only be of limited effect without individual responsibility. All measures, of course, will have an economic impact, and some stricter measures, such as shutting down entire cities, as seen in Wuhan in China, may be less effective in Western democracies.
The aim of these social distancing measures is to "flatten the curve" of the infection, slowing the spread and avoiding a huge peak in the number of new infections.
Flattening the curve can avoid overwhelming health services, keep the impact on the economy to within manageable levels and effectively buy more time to develop and manufacture effective vaccines, treatments and anti-viral drug therapies.
Sir Roy said: 'Government needs to decide on the main objectives of mitigation -- is it minimising morbidity and associated mortality, avoiding an epidemic peak that overwhelms health-care services, keeping the effects on the economy within manageable levels, and flattening the epidemic curve to wait for vaccine development and manufacture on scale and antiviral drug therapies. We point out they cannot achieve all of these -- so choices must be made.'
The researchers highlight that wider support for the health service and health care workers during an epidemic is vital in any case -- during the Ebola epidemic in 2014-15, the death rate from other causes like malaria and childbirth rose sharply due to overwhelmed health services. The number of deaths indirectly caused by Ebola was higher than the number of deaths from Ebola itself.
While much has been made in the media of a number of "superspreading" events, where one infected individual has inadvertently spread the disease to many others, the authors warn that there are superspreading events in every epidemic, and care should be taken not to make too much of these.
Containing the spread of an infectious disease relies on keeping the "reproduction number," R0, the number of people infected by each infected person, below 1, when the pathogen will eventually die out. If R0 rises above 1, i.e. each infected person infects more than one other person, the pathogen will spread. Early data from China suggests that the R0 for COVID-19 could be as high as 2.5, implying that in an uncontained outbreak, 60% of the population could be infected. There are many unknowns in any new virus, however, and with COVID-19, it is not currently clear how long it takes for an infected person to become infectious to others, the duration of infectiousness, the fatality rate, and whether and for how long people are infectious before symptoms appear. It is also not currently clear if there are cases of COVID-19 which are non-symptomatic.
In comparisons with influenza-A (usual seasonal flu) and SARS, it currently seems likely that the epidemic will spread more slowly, but last longer, which has economic implications. Seasonal flu is generally limited by warmer weather, but as it is not known if this will affect COVID-19, the researchers say it will be important to monitor its spread in the Southern Hemisphere. Researchers will continue to collect and analyse data to monitor spread, while ongoing clinical research into treating seriously ill patients is also necessary.
One of the main priorities for researchers and policymakers will be contact tracing, with models suggesting that 70% of people an individual has come into contact with will need to be traced to control the early spread of the disease. The authors say other priorities include shortening the time from symptom onset to isolation, supporting home treatment and diagnosis, and developing strategies to deal with the economic consequences of extended absence from work.
Author Professor Hans Heesterbeek from the Department of Population Health Sciences at the University of Utrecht said: 'Social distancing measures are societally and economically disruptive and a balance has to be sought in how long they can be held in place. The models show that stopping measures after a few months could lead to a new peak later in the year. It would be good to investigate this further.' https://www.sciencedaily.com/releases/2020/03/200306183353.htm |
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发表于 2020-3-19 23:53:12
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