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SNAPI_Test notes that Arthur T Knackerbracket has found the following story:
The United States, Britain and Australia have called on Facebook to give authorities the ability to circumvent encryption used in its messaging services—a measure opposed by the social media giant.
Facebook has been dogged by several privacy scandals in recent years and has pledged to boost user protections by rolling out end-to-end encryption across all of its social media platforms.
But that plan risks weakening the ability of law enforcement to detect criminal acts including terrorism and child pornography, according to a joint letter signed by US Attorney General William Barr, British Home Secretary Priti Patel and Australian Home Affairs Minister Peter Dutton.
"Facebook has not committed to address our serious concerns about the impact its proposals could have on protecting our most vulnerable citizens," said the Thursday letter, addressed to company chief Mark Zuckerberg and seen by AFP.
The company already encrypts WhatsApp messages from end-to-end—meaning only the sender and recipient can read the message—and is working to extend the technology to other apps in its family, including Messenger and Instagram.
Facebook says it is intent on introducing the service without granting oversight to law enforcement agencies.
"We strongly oppose government attempts to build backdoors because they would undermine the privacy and security of people everywhere," a Facebook spokesperson said.
[...] During a livestreamed question and answer session with employees, Zuckerberg said Facebook would continue to work with authorities to strike a balance between privacy concerns and fighting crimes such as child exploitation and terrorism.
"Having the availability to look at the content is a useful signal, and when you lose that you are fighting that battle with at least a hand tied behind your back and you hope there is a lot of good stuff you can do with your other hand," Zuckerberg said.
But he added that encryption had many positive benefits such as protection for journalists and political protesters.
Arthur T Knackerbracket has found the following story:
Andromeda, a massive spiral galaxy, has swallowed several galaxies within the last few billion years before setting its sights on the Milky Way.
"The Milky Way is on a collision course with Andromeda in about four billion years,” said Dougal Mackey, co-author of a new study published in Nature and a research fellow at the Australian National University. “So knowing what kind of a monster our galaxy is up against is useful in finding out the Milky Way's ultimate fate."
The astronomers noted that the stellar halo that surrounds Andromeda is much bigger and more complex than the Milky Way, and it contains two giant globular clusters of stars that are rotating perpendicular to each other, and this indicates that it has cannibalized other galaxies in the past. They made observations using the wide-field camera on the Canada-France-Hawaii-Telescope, and this showed that the globular clusters are on the same rotation axis as a plane of dwarf galaxies that orbit Andromeda.
Andromeda is a good specimen to study the evolution of spiral galaxies like the Milky Way, Mackey explained. "One of our main motivations in studying astronomy is to understand our place in the Universe. A way of learning about our galaxy is to study others that are similar to it, and try to understand how these systems formed and evolved.”
"Sometimes this can actually be easier than looking at the Milky Way, because we live inside it and that can make certain types of observations quite difficult."
Mackey, D., Lewis, G.F., Brewer, B.J. et al. Two major accretion epochs in M31 from two distinct populations of globular clusters. Nature 574, 69–71 (2019).
Arthur T Knackerbracket has found the following story:
Unpredictable weather in Europe has produced some of the lowest honey harvests ever, particularly in France and Italy. Only about half the normal harvest was collected in Italy and only about a quarter of the usual crop in France. Even recent high honey producing countries such as Romania and Spain are seeing decreases. The reasons for the declines are varied and include frosts, droughts, and heavy rains across the affected countries, but everyone is counting on better weather conditions in the coming year. However, even if that pans out, recovery will be challenging.
To save the colonies, "the bees have killed all the males to get rid of extra mouths to feed". The lack of males for mating may lead to a "lack of fertilized queens" next spring, meaning fewer new colonies and bees.
Bee mortality has also shot up in recent years due to an "epidemic" of the Varroa parasitic mite, the uncontrolled spread of the Asian hornet in Europe, and the "intense use of pesticides in agriculture", according to the French Cyclops report.
Beekeepers are also complaining about a massive influx of low-cost Chinese honey, which they say is "adulterated," such as being cut with sugar syrup.
There is currently no European legislation requiring producers to specify the origin of honey.
Labels can state it is a "blend of honeys originating and non-originating in the European Community", even if the product contains 99 percent Chinese honey and only 1 percent of, say French honey.
In Spain, beekeepers have held several protests against low-cost Chinese honey and authorities are planning to impose new labelling requirements which would list the percentages of honey included per country of origin.
In France, a decree is expected to come into force on January 1, 2020 which would list all countries that have supplied more than 20 percent of the honey in a jar, in order of importance.
The Hopewell civilization refers to a culture shared by native Americans tribes from about 200 BC to 400 AD that spanned a region from the eastern coast to the Rocky Mountains, and from the Great Lakes to the Gulf of Mexico. The fairly rapid decline of this culture has been a mystery for many years. A group of researchers from the University of Cincinnati found evidence of a Tunguska-like airburst that struck sometime between 252 and 383 AD and affected an area of 9200 square miles (24,000 sq km). That time range coincides with a period when 69 near-Earth comets were observed and documented by Chinese astronomers, and many Native American tribes include some sort of devastating event from the skies in their oral histories.
Their results are presented in a Scientifc Reports paper:
Near-Earth comets have been increasing through time (up to 2 per year) and those with an orbital period of ~10,000 years may remain within a planetary system between 5,000 and 15,000 years. Thus, we expect to find more examples of such events in the archaeological record.
Tankersley, K.B., Meyers, S.D., Meyers, S.A. et al. The Hopewell airburst event, 1699–1567 years ago (252–383 CE). [open] Sci Rep 12, 1706 (2022). DOI: 10.1038/s41598-022-05758-y
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FeedSource: [ArsTechnica] collected from rss-bot logs
Time: 2018-02-27 23:51:33 UTC
Original URL: https://arstechnica.com/science/2018/02/did-humans-or-climate-cause-the-great-rainforest-crisis/ using UTF-8 encoding.
Title: African Rainforests Vanished For 600 Years, Then Bounced Back—Why?
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African Rainforests Vanished For 600 Years, Then Bounced Back—Why?
Arthur T Knackerbracket has found the following story:
Three thousand years ago, dense old-growth rainforests covered most of central Africa. But around 2,600 years ago, an event that ecologists call the Late Holocene Rainforest Crisis occurred, and the forests suddenly gave way to savannas dotted with islands of trees. Six hundred years later, the forests grew back almost as swiftly as they had vanished.
But for the last 20 years, paleoecologists have debated what caused the Rainforest Crisis. Most thought that the region's climate changed, bringing either less annual rain or a longer dry season with a short but intense monsoon. That climate shift, many paleoecologists argue, devastated the rainforests of central Africa but created perfect conditions for savannas. But a new study proposes that humans may actually have been the culprits.
Around the time of the Rainforest Crisis, farmers from northern Africa started migrating southward, bringing with them an advanced culture of pearl-millet cultivation, ironworking, and palm-oil harvesting, all of which take a toll on the landscape. Those northern farmers spoke Bantu languages, which are still spoken by about 300 million people in Africa today.
The currently accepted version among paleoecologists is that warming sea-surface temperatures in the Gulf of Guinea caused a shift in the region's monsoon cycle, leading to a longer, drier dry season, so people migrated south to farm millet on the open grasslands. But University of Potsdam paleoecologist Yannick Garcin and his colleagues, who just published a new study on the Rainforest Crisis, argue that it happened the other way around: people moved south into the rainforest and cleared land to plant millet. And when their population crashed 600 years later, the rainforest rebounded.
Most of the debate hinges on whether those millet farmers moved south during the Rainforest Crisis or before and on whether there's evidence of climate shift at the same time. And among paleoecologists and archaeologists, the debate is heating up. If you're not a paleoecologist, the whole debate may seem a little esoteric, but it's a great example of the scientific process at work, with both sides presenting their own sets of evidence and debating which is most accurate and whose interpretation best fits the data.
Paleoarchaeologist Jean Maley and his colleagues published a paper in October 2017 in which they argued for the climate hypothesis, citing sediment layers found in lakes in Ghana, Gabon, and the Congo. These show evidence of increased erosion around 2,650 years ago—presumably thanks to more intense monsoon rains. That lines up well with the other evidence for the climate shift.
And an earlier study sampled pollen from the sediments at the bottom of Lake Victoria, which showed that the water level 2,200 years ago was much lower than it is today and that savanna had taken over land formerly shaded by rainforest canopies.
On the other hand, Garcin and his colleagues recently took a sediment core from Lake Barombi in Cameroon. The 12-meter-long cylinder of mud held 10,500 years' worth of accumulated sediment layers, which contained microscopic bits of material called plant waxes. Plants secrete waxy mixtures of lipids to protect their outer cells, and these waxes can last for thousands of years in soil. Conveniently for paleoecologists, they record what ratio of hydrogen isotopes the plant got from its water, as well as how the plant handled carbon.
Woody plants like trees and shrubs obtain carbon differently from grasses, so their plant waxes end up with different ratios of the stable isotope carbon-13. Prior to 2,600 years ago, the plant waxes in Lake Barombi seemed to be from mostly trees and shrubs, exactly what you'd expect in a thriving rainforest. But within a century, carbon-13 ratios in the plant waxes washing into Lake Barombi started looking much more like grassland than forest, which matched the pollen data from other studies. After about 600 years, though, the carbon-14 signature of forests replaced the grasslands.
Those findings more or less confirmed what the pollen studies had to say about the timing of the Rainforest Crisis, but it didn't say anything about what caused the event. But the ratio of hydrogen isotopes in plant waxes can reveal information about climate because, on a scale of decades, those ratios generally line up with average annual rainfall. In the Lake Barombi sediment core, that evidence pointed to a long, gradual drying tend from 7,000 to 2,000 years ago, but there didn't seem to be any sudden climate shift near the beginning of the Rainforest Crisis. In fact, according to the Lake Barombi data, the area was actually wetter during the Rainforest Crisis than it is now, and today it's still mostly covered with rainforest.
Tiny shells preserved in sediment cores from the Gulf of Guinea didn't contain any evidence of a change in sea surface temperature, according to Garcin and his colleagues.
But when they examined a database of 460 archaeological sites from around the region, they found that very few sites had been dated to earlier than 4000 years ago. Human activity seems to have started picking up in the region around then, and it really exploded around 2,600 years ago. Garcin and his colleagues say that's evidence of a major population increase right around the beginning of the Rainforest Crisis.
They claim this study is clear evidence that people, not climate, caused the Late Holocene Rainforest Crisis. But not everyone is convinced. Maley told Ars Technica that the most important argument against the blame-the-humans hypothesis and in favor of a shift in climate is the sheer geographic scale of the Rainforest Crisis—it happened at nearly the same time from the Equator to the southern Sahara. Humans, on the other hand, didn't migrate south into central Africa's rainforests with same kind of synchronization.
In other words, the debate over what happened to central Africa's Late Holocene rainforests is far from settled.
Paleoecologists, archaeologists, and even linguists are still weighing in with new lines of evidence, and it's likely to be some time before they reach a consensus. Part of the uncertainty is due to the limited resolution of dating methods, whether it's radiocarbon dating or counting layers in a sediment core.
For instance, some of the evidence for the climate hypothesis comes from pollen and diatoms from the bottom of nearby Lake Ossa. But Garcin and his colleagues claim that, due to aged carbon in the sediment itself, there's about a 400-year uncertainty in dating those layers. And in Garcin's data, the Rainforest Crisis appears to have started at Lake Barombi about 200 years before Bantu agricultural sites started turning up in the region.
"We answer that we are at the limit of the precision of the dating method used to resolve such a small lag," said Garcin, "and since the Lake Barombi is at the northern edge of Central Africa, it may have witnessed first those human impacts compared to the rest of the whole region."
One thing scientists on all sides agree on is that it's important to understand the cause of past events like this, because reconstructing past climate events can help predict how humans, climate, and vulnerable ecosystems might interact in the future. And in some ways, the Rainforest Crisis is an encouraging story, because it means the rainforest can bounce back from deforestation.
"Rainforest ecosystems are very sensitive to disturbances but also resilient," said Garcin.
Title: Parsing C++ Is Literally Undecidable (2013)
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Arthur T Knackerbracket has found the following story:
Many programmers are aware that C++ templates are Turing-complete, and this was proved in the 2003 paper C++ Templates are Turing Complete.
However, there is an even stronger result that many people are not aware of. The C++ FQA has a section showing that parsing C++ is undecidable, but many people have misinterpreted the full implications of this (understandable, since the FQA is discussing several issues over the course of its questions and does not make explicit the undecidability proof).
Some people misinterpret this statement to simply mean that fully compiling a C++ program is undecidable, or that showing the program valid is undecidable. This line of thinking presumes that constructing a parse tree is decidable, but only further stages of the compiler such as template instantiation are undecidable.
For example, see this (incorrect, but top-voted) Stack Overflow answer to the question What do people mean when they say C++ has “undecidable grammar”? This answer errs when it says: “Note this has nothing to do with the ambiguity of the C++ grammar.”
In fact, simply producing a parse tree for a C++ program is undecidable, because producing a parse tree can require arbitrary template instantiation. I will demonstrate this with a short program, which is a simplification/adaptation of what is in the FQA link above.
The parse tree for this program depends on whether TuringMachine::output is SomeType or not. If it is SomeType then ::name is an integer and the parse tree for the program is multiplying two integers and throwing away the result. If it is not SomeType, then ::name is a typedef for int and the parse tree is declaring a pointer-to-int named x. These two are completely different parse trees, and the difference between them cannot be delayed to further stages of the compiler.
The parse tree itself depends on arbitrary template instantiation, and is therefore the parsing step is undecidable.
In practice, compilers limit template instantiation depth, so this is more of a theoretical problem than a practical one. But it is still a deep and significant result if you are ever planning on writing a C++ parser.
Parsing, performance, and low-level programming.
Boston Dynamics is sending off 2020 with its most impressive robot video to date – showing off its entire range dancing to the classic song “Do You Love Me?”. The fun video offers the first glimpse at two Atlas robots working together while also highlighting just how quickly this technology is developing.
Back in 2018 Boston Dynamics released a cute video of its dog-like Spot robot dancing to “Uptown Funk”. The playful video was a fun little demonstration of Spot’s broad range of movements, exciting at the time but very simplistic looking back from the vantage of today. Now the company has stepped things up delivering a long choreographed dance video featuring not only Spot, but two Atlas robots and a special appearance from Handle, a wheeled model.
Released as a kind of New Year’s gift from the company, the video is the first look at two Atlas humanoid robots working together. Atlas, still technically a prototype robot, has demonstrated a stunningly rapid evolution over the past decade from barely being able to walk in 2013, to being allowed to roam tetherless in 2015, completing a spectacular parkour routine just three years later, and finally getting acrobatic last year.
As the number of devices connected to the internet continues to increase, so does the amount of redundant data transfer between different sensory terminals and computing units. Computing approaches that intervene in the vicinity of or inside sensory networks could help to process this growing amount of data more efficiently, decreasing power consumption and potentially reducing the transfer of redundant data between sensing and processing units.
Researchers at Hong Kong Polytechnic University have recently carried out a study outlining the concept of near-sensor and in-sensor computing. These are two computing approaches that enable the partial transfer of computation tasks to sensory terminals, which could reduce power consumption and increase the performance of algorithms.
"The number of sensory nodes on the Internet of Things continues to increase rapidly," Yang Chai, one of the researchers who carried out the study, told TechXplore. "By 2032, the number of sensors will be up to 45 trillion, and the generated information from sensory nodes is equivalent to 1020 bit/second. It is thus becoming necessary to shift part of the computation tasks from cloud computing centers to edge devices in order to reduce energy consumption and time delay, saving communication bandwidth and enhancing data security and privacy."
[...] So far, the work by Chai and his colleagues primarily focused on vision sensors. However, near-sensor and in-sensor computing approaches could also integrate other types of sensors, such as those that detect acoustic, pressure, stain, chemical or even biological signals.
1.) Feichi Zhou, Yang Chai. Near-sensor and in-sensor computing, Nature Electronics (DOI: 10.1038/s41928-020-00501-9)
2). Feichi Zhou, Zheng Zhou, Jiewei Chen, et al. Optoelectronic resistive random access memory for neuromorphic vision sensors, Nature Nanotechnology (DOI: 10.1038/s41565-019-0501-3)
3.) Yang Chai. In-sensor computing for machine vision, Nature (DOI: 10.1038/d41586-020-00592-6)