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Walmart Black Friday ad features $99 Chromebook, $89 Windows 2-in-1 laptop



Walmart 2018 Black Friday ad

Walmart may not be the first place you think of when it comes to buy a new computer, but the retailing giant always manages to have a few deals on systems when Black Friday rolls around — and this year is no exception.

The company prides itself on having the lowest prices, and when it comes to Black Friday laptop sales, it’s the early leader, with a pair of notebooks selling for under $100. One is the Samsung Chromebook 3, equipped with an Intel Celeron processor, 4 gigs of RAM, 16GB of built-in storage, and an 11.6-inch display, for $99 ($100 off the regular price); the other is an RCA Cambio 2-in-1 Windows device, including Intel Atom CPU, 2GB of memory, 32GB of storage, 10.1-inch touchscreen, and detachable keyboard, for $89. Of course, RCA isn’t exactly a top-tier PC brand, but that price is $30-$40 lower than we’ve seen so far for any laptop running Windows that we’ve previewed as a Black Friday deal.

Walmart has a quartet of additional HP laptops if you don’t want the most bare-bones of specs. The Stream 11 moves up to an Intel Celeron N4000 processor, 4GB of RAM, 32 gigs of built-in storage, and a 1,366×768 11.6-inch screen for $159. For $100 more, the HP 15-inch Touch laptop uses an Intel Pentium chip, 4GB of memory, a terabyte hard drive, and a 15.6-inch touchscreen display.

A more powerful 2-in-1 option is the Pavilion x360, which features an Intel Core i5 chip, 4GB of memory, a terabyte hard drive (with 16GB of Intel Optane memory), 15.6-inch, and a digital pen for $499 ($180 off). Finally, gamers on a budget might want to consider the Pavilion Gaming Laptop, built around a Core Core i5-8300H processor, 8GB of RAM, 1TB hard drive, Nvidia GeForce GTX 1050 Ti graphics card, and 15.6-inch full HD display for $599, or $230 off the current price.

Like a few other retailers, Walmart will be selling the latest 9.7-inch iPad for $249, but unlike Target, it isn’t advertising any discount on the iPad mini 4. Cheaper tablet options include the 9.6-inch flavor of the Samsung Galaxy Tab E, which includes a $25 Google Play credit, for $129 ($60 off), and the 7-inch RCA Voyager III Android slate for a mere $28.

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Spiral shark intestines work like Nikola Tesla’s water valve, study finds



Enlarge / A CT scan image of the spiral intestine of a Pacific spiny dogfish shark (Squalus suckleyi). The beginning of the intestine is on the left, and the end is on the right.

Samantha Leigh/California State University, Dominguez Hills

In 1920, Serbian-born inventor Nikola Tesla designed and patented what he called a “valvular conduit”: a pipe whose internal design ensures that a fluid will flow in one preferred direction, with no need for moving parts, making it ideal for microfluidics applications, among other uses. According to a recent paper published in the Proceedings of the Royal Society B, the Tesla valve also provides a useful model for how food moves through the digestive system of many species of shark. Based on new CT scans of shark intestines, scientists have concluded that the intestines are naturally occurring Tesla valves.

“It’s high time that some modern technology was used to look at these really amazing spiral intestines of sharks,” said co-author Samantha Leigh of California State University, Dominguez Hills. “We developed a new method to digitally scan these tissues and now can look at the soft tissues in such great detail without having to slice into them.”

The key to Tesla’s ingenious valve design is a set of interconnected, asymmetric, tear-shaped loops. In his patent application, Tesla described this series of 11 flow-control segments as being made of “enlargements, recessions, projections, baffles, or buckets which, while offering virtually no resistant to the passage of fluid in one direction, other than surface friction, constitute an almost impassable barrier to its flow in the opposite direction.” And because it achieves this with no moving parts, a Tesla valve is much more resistant to the wear and tear of frequent operation.

Tesla claimed that water would flow through his valve 200 times slower in one direction than another, which may have been an exaggeration. A team of scientists at New York University built a working Tesla valve in 2021, in accordance with the inventor’s design, and tested that claim by measuring the flow of water through the valve in both directions at various pressures. The scientists found the water only flowed about two times slower in the nonpreferred direction.

A 2020 study found that, as flow rates increase, the Tesla valve begins to more effectively block reverse flows.
Enlarge / A 2020 study found that, as flow rates increase, the Tesla valve begins to more effectively block reverse flows.

NYU Applied Mathematics Laboratory

However, flow rate proved to be a critical factor. The valve offered very little resistance at slow flow rates, but once that rate increased above a certain threshold, the valve’s resistance would increase as well, generating turbulent flows in the reverse direction, thereby “plugging” the pipe with vortices and disruptive currents. So it actually works more like a switch, according to co-author Leif Ristroph, and can also help smooth out pulsing flows, akin to how AC/DC converters turn alternating currents into direct currents. In fact, Ristroph suggested that this may have been Tesla’s intent in designing the valve, given that his biggest claim to fame is inventing both the AC motor and an AC/DC converter.

And now the Tesla valve is providing insight into the unusual structure of shark intestines, thanks to a team of researchers hailing from three universities: California State University, Dominguez Hills, the University of Washington, and the University of California, Irvine.

Sharks are apex predators, feeding on a wide range of species, and are thus important for controlling biodiversity in the larger ecosystem. Most sharks have spiral intestines consisting of a varying number of folds in the intestinal tissue, typically in one of four basic configurations: columnar, scroll, a funnel pointing to the posterior, or a funnel pointing to the anterior. These four types of intestines are usually depicted in 2D sketches that are splayed out in two dimensions after a dissection or imaged as two-dimensional slices through the three-dimensional structure. But that doesn’t give scientists much insight into how the structure works in situ.

Last year, Japanese researchers reconstructed micrographs of histological sections from a species of catshark into a three-dimensional model, offering “a tantalizing glimpse of the anatomy of a scroll-type spiral intestine,” per the authors of this latest paper. Co-author Adam Summers, of the University of Washington’s Friday Harbor Labs, and his colleagues decided that CT scanning might accomplish something similar, since the technique involves taking a series of X-ray images from different angles and then combining them into 3D images.

“CT scanning is one of the only ways to understand the shape of shark intestines in three dimensions,” said Summers. “Intestines are so complex, with so many overlapping layers, that dissection destroys the context and connectivity of the tissue. It would be like trying to understand what was reported in a newspaper by taking scissors to a rolled-up copy. The story just won’t hang together.”

Summers et al. acquired intestines from preserved shark specimens representing 22 species from the Los Angeles Natural History Museum and from previously frozen donated shark specimens. The intestines were removed via dissection, then flushed out with deionized water so they were free of any residual contents. Next, the team filled the specimens with fluid and freeze-dried them to retain their shapes, before scanning them to produce virtual 3D models. This gave the researchers an excellent view of how the intestines are structured.

Next, the team took unfrozen samples of each of the four types of intestines and conducted several experiments. For instance, the researchers ran liquids through the spirals and found it typically took around 35 minutes for the liquids to pass through when they followed the normal direction of flow. But the process took twice as long when the intestines were turned upside down, in the opposite direction of normal flow. This is in keeping with the findings of last year’s NYU experiments with a Tesla valve.

So many guts

The team also conducted experiments with five recently euthanized Pacific spiny dogfish. The researchers ran colored liquids of varying viscosities through the spiral intestines and observed how the spiral muscles reacted to the liquid. The intestines appeared to slow the movement of food, directing it down through the gut via gravity and contractions of the smooth muscle of the gut. However, those contractions mostly served to mix and churn whatever fluids pass through; the intestine’s unusual structure is sufficient to move everything along.

As for why this peculiarly intestinal structure may have evolved in the first place, sharks can go days or weeks between large meals. The authors hypothesize that the unusual spiral structure provides an expanded surface area and volume, thereby prolonging the time that food remains in the gut. This increases the absorption of nutrients and also reduces how much energy is needed for sharks to digest their food.

The next step is to create 3D-printed models of the different types of shark intestine and run similar experiments. “The vast majority of shark species, and the majority of their physiology, are completely unknown,” Summers said. “Every single natural history observation, internal visualization, and anatomical investigation shows us things we could not have guessed at. We need to look harder at sharks and, in particular, we need to look harder at parts other than the jaws, and the species that don’t interact with people.”

DOI: Proceedings of the Royal Society B, 2021. 10.1098/rspb.2021.1359  (About DOIs).

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Bezos says he is now willing to invest in a Moon lander—here’s why



Enlarge / Blue Origin CEO Bob Smith (black hat) walks with Jeff Bezos after his flight on Blue Origin’s New Shepard into space.

Joe Raedle/Getty Images

Jeff Bezos published an open letter to NASA Administrator Bill Nelson on Monday morning and offered to pay more than $2 billion to get the agency’s Human Landing System program “back on track.” In effect, the founder of Blue Origin and world’s richest person says he will self-invest in a lunar lander because NASA does not have the money to do so.

NASA’s Artemis program aspires to land humans on the Moon by 2024 and establish a sustainable settlement on the surface. As part of this project, the agency is seeking reusable, affordable transportation to the Moon and back. It conducted a competition for a human lander (HLS) and announced in April that it would move forward with SpaceX and its Starship proposal. NASA had wanted two providers for such a lander, but due to low appropriations from Congress, it could afford only one.

Now, three months later, Bezos is offering to make up the difference out of his pocket. “Blue Origin will bridge the HLS budgetary funding shortfall by waiving all payments in the current and next two government fiscal years up to $2B to get the program back on track right now,” Bezos wrote. “This offer is not a deferral but is an outright and permanent waiver of those payments. This offer provides time for government appropriation actions to catch up.”

So why is Bezos offering to do this now? Ars hit the phones on Monday morning to get some answers.

Why is this happening now?

The timing of Bezos’ letter does not seem coincidental. He was extraordinarily upset after losing to SpaceX and has launched a multi-pronged strategy to get back into the game.

After the HLS contract decision in April, Blue Origin filed a lengthy protest to the US Government Accountability Office. A ruling is expected within the next several weeks. Blue Origin’s second tactic was to lobby a local US senator, Maria Cantwell of Washington state, to add $10 billion to NASA’s budget to pay for Blue Origin’s lander. Although the Senate passed the addition, the House said no, and it seems to have been a dead end.

So now, Bezos is turning to his third tactic after NASA’s decision on the lander award. In this case, he seems to be saying, “OK, maybe I could just pay for this myself.”

Why didn’t Blue Origin win the HLS contract, anyway?

Blue Origin put together an all-star team for the lander competition, partnering with Lockheed Martin, Northrop Grumman, and Draper. This “National Team” then proposed a three-stage lander that met NASA’s specifications for the Artemis program. The problem is that this proposal was expensive and sought about twice as much money as the $2.9 billion award SpaceX received.

In this proposal, Bezos made a critical error. NASA wanted to see companies self-invest in their hardware. The space agency wanted to be a customer for these landers, but not the only customer. “I think they realized it’s why they lost,” one politically connected source told Ars. “Meaning they did not invest properly.” So Bezos’ letter offers a mea culpa.

Isn’t it a bit late in the game?

It sure seems so. The time to state how much skin you’re willing to put into the game is during the bidding process, not after the winners have been named.

For example, under the terms of its contract award, SpaceX will receive $2.9 billion from NASA. In return, a senior company official told Ars, SpaceX plans to invest about $6 billion to develop Starship and test the launch and landing technology. We are already seeing this with the frenetic Starship activity in South Texas. So when NASA was selecting proposals, it knew it was getting a two-for-one return on its money.

Now, Blue Origin and Jeff Bezos have said they’re willing to self-invest. In effect, they’ve asked for a do-over.

So will NASA and Congress bite?

NASA’s course on lunar lander procurement will be determined by the Government Accountability Office ruling. If the GAO dismisses Blue Origin’s protest, NASA will proceed with the award to SpaceX. With the $2.9 billion, SpaceX will develop Starship and perform a “demonstration” landing on the Moon as early as 2024. NASA has asked Congress for more money afterward to have a competition for follow-on missions. This would allow the space agency to have two lander providers, which is something pretty much everyone agrees is a good idea.

If the GAO upholds Blue Origin’s protest—which is possible but not likely—NASA would need to re-do the competition. This would put the Artemis Moon program on hold.

The real question is what Congress will do, and that seems to be the real audience for Bezos’ letter. Notably, Bezos references jobs in many Congressional districts, which is the love language of legislators. NASA’s decision to select SpaceX, Bezos wrote, “also eliminated the benefits of utilizing the broad and capable supply base of the National Team (as opposed to funding the vertically integrated SpaceX approach).”

My sense is that this offer from Bezos will spur Congress to fund NASA’s idea of a Lunar Exploration Transportation Services program as an on-ramp for lunar lander vendors. Additional funding would allow NASA to buy routine astronaut transportation services throughout the Artemis program from two providers—SpaceX and Blue Origin’s National Team. We may see this funding in the final Fiscal Year 2022 budget appropriations later this year.

What’s the good news?

It’s positive to see Jeff Bezos taking an active interest in Blue Origin and putting his immense wealth behind the company. Multiple sources told Ars that Bezos was really disconnected from Blue Origin in 2020, and that hurt the company. For one thing, the approval rating of Blue Origin Chief Executive Bob Smith is a painfully low 18 percent on Glassdoor.

With this letter, Bezos appears to be acknowledging that it was a mistake not to self-invest in the Human Landing System contract. Moreover, he is taking steps to rectify that mistake. If nothing else, that has to send a positive message to his employees.

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Red planet has a big core, complex crust



Enlarge / Some seismic waves bounce off Mars’ core before reaching the InSight lander.

We’ve learned a lot about our planet’s interior simply by tracking how the seismic energy released by earthquakes moves through or reflects off the different layers present beneath Earth’s surface. For over a Martian year, we’ve had a seismograph on Mars in the hope that it would help us to figure out the red planet’s interior.

But Mars is relatively quiet seismically, and we’ve only got a single seismograph instead of an entire network. Still, with records of a handful of significant marsquakes, we now have some sense of what Mars’ interior looks like. And a set of new studies indicates that it’s pretty weird, with a large, light core and an unexpectedly warm crust.

It’s complicated

Working out the structure of a planet involves reading seismic waves, which come in two categories: shear and compressional (S and P, in geological parlance). Depending on the location of the earthquake (or marsquake), the waves may arrive directly. But many others bounce off the surface of the planet before reaching the receiver, sometimes multiple times. So P waves will be followed by PP waves, and later by PPP waves. The US Geological Survey has a great diagram of the complexity this can produce, which we’ve included at right.

But that’s far from the end of the complications. The speed of the waves, and thus the time gaps between P and PP and PPP signals, will vary based on the material the waves are traveling through. The composition, density, and even temperature of the material can all make a difference in the speed at which seismic signals move through the planet. These properties often differ dramatically between specific layers of the planet, such as the solid crust and the semi-molten mantle. These differences will refract some of the seismic waves, bending their path through the planet’s interior. Other waves will reflect off the boundary between internal layers.

All of that makes reconstruction of the interior from seismic events complicated; there are generally more than one combination of properties like distance, materials, and temperatures that are compatible with the seismic signals produced by an event. On Earth, this isn’t a problem. We have a huge collection of seismographs that allows us to zero in on the most likely interpretation of the signals. And we have lots of individual events, which allow us to identify the typical behavior of our planet’s interior.

On Mars, none of that is true. We have a grand total of one seismograph, and so even distance estimates are iffy at best. And we have very little sense of the internal temperature of the planet. There are points in reading the studies that almost feel like they’re mourning the absence of data from the failed attempt to have InSight take Mars’ internal temperature.

Mars also turns out to be very seismically quiet. There were no marsquakes with a magnitude above 4.0, and there weren’t many of any magnitude. All told, fewer than a dozen events stood out clearly from the background noise at InSight’s landing site. So, you should view the results in these papers as an initial model of Mars’ interior: they’re likely to be refined as more data comes in and may even be revised considerably.

What’s there

We have a good sense of what the outermost Martian crust looks like, given that we’ve obtained plenty of meteorites that originated on Mars, studied it from orbit, and landed hardware on it. Based on seismic waves, however, one of those studies suggest that the outer crust only extends to about 10 km beneath the planet’s surface at the InSight landing site. But there’s a lower crust, which extends down the mantle, which this study suggests starts at about 50 km deep.

The first result is in keeping with a second study, which shows a boundary somewhere between six and 11 km down. But it shows a second boundary somewhere between 15 and 25 km, which is much higher than the first. Still, it also sees some indication of a third boundary somewhere between 27 and 47 km—a figure that’s consistent with the 50 kilometer figure in the first paper. So really, the big difference between the two is about how many layers of crust are present.

The things both these studies agree on is that the crust is warmer than expected. This implies that there are more radioactive elements present than we would have predicted based on what we know about the surface composition. Why that’s the case is unclear, and the amount of excess radioactivity also depends on the exact thickness of the crust. Again, having a measure of the heat flow through the crust, as was originally intended, could have made a big difference here.

The final paper goes deep and looks for the boundary between Mars’ mantle and its core. The result is a radius just north of 1,800 km. This is unexpectedly large: it’s over half the radius of the entire planet. One of the consequences of the large core is that, to be compatible with the planet’s overall density, the core has to be lighter than expected (it’s also liquid). That implies the presence of lighter elements. Sulfur is the most reasonable candidate, but Mars isn’t expected to have enough sulfur to account for it all. So carbon, oxygen, and nitrogen can probably be found in the core as well.

One consequence of this is that the pressures at the outer edge of the core will be lower, meaning that Mars couldn’t have formed a mineral that helps trap heat in the core like Earth. This may have caused the planet to lose the heat left over from its formation more rapidly.

What’s to come

InSight has seen its mission extended, so we’ll continue to get more data from future marsquakes. While the initial data is compatible with a variety of potential conditions—the error bars on the density, temperature, and thickness of various layers are large—further data should help narrow things down.

But the large, liquid core turns out to be rather unfortunate in terms of InSight’s landing location. The core itself casts a seismic “shadow” across Mars, blocking waves from marsquakes on the opposite side of the planet from the seismograph. The larger the core, the more of the planet that’s invisible to InSight. And, unfortunately, that shadow includes the Tharsis region, which contains Mars’ largest volcanoes and is thought to have been active relatively recently.

Not being able to “see” Tharsis means we’re likely to register fewer marsquakes in total. Still, as long as the hardware holds up, we’re likely to have a steadily growing collection of data that will gradually give us a clearer picture of the red planet’s composition and evolution—something that will help us understand planet formation both within and outside of our Solar System.

Science, 2021. Papers linked from: 10.1126/science.abj8914  (About DOIs).

Listing image by Chris Bickel/Science

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