Sea Level: How Do We Measure Global Ocean Levels And Do Rising Oceans Change That Benchmark?

March 8, 2021 by Adam Zeloof 34 Comments

Every summer you go down the shore, but lately you’ve begun to notice that the beach seems narrower each time you visit. Is that the sea level rising, or is the sand just being swept away? Speaking of sea levels, you keep hearing that they rise higher every year — but how exactly is that measured? After all, you can’t exactly use a ruler. As it turns out, there are a number of clever systems in place that can accurately measure the global sea level down to less than an inch and a half.

Not only are waves always rippling across the ocean’s surface, but tides periodically roll in and out, making any single instantaneous measurement of sea level hopelessly inaccurate. Even if you plan to take hundreds or thousands of measurements over the course of weeks or months, taking the individual measurements is still difficult. Pick a nice, stable rock in the surf, mark a line on it, and return every hour for two weeks to hold a tape measure up to it. At best you’ll get within six inches on each reading, no matter what you’ll get wet, and at worst the rock will move and you’ll get a damp notebook full of useless numbers. So let’s take a look at how the pros do it.

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X-Ray Defeats Letterlocking — Unfolds And Reads Letter Sealed Since 1697

March 6, 2021 by Jenny List 24 Comments

Over recent years we’ve been treated to a series of fascinating advances in the world of x-ray imaging, as researchers have developed their x-ray microtomography techniques and equipment to the point at which they can probe and then computationally reconstruct written material within objects such as letters or scrolls in museum collections whose value or fragility means they can’t be opened and read conventionally. There is more to this challenge than simply extracting the writing though, in addition to detecting the ink the researchers also have to unpick the structure of whatever it was written upon. A particular challenge comes from letterpackets, the art of folding a letter into its own envelope, and a newly-published Nature Communications paper details work from a team of academics in the USA, the UK, and the Netherlands in tackling it.

Letterpackets were more than a practical method of packaging a missive for the mail, they also had a security function often called Letterlocking. A packet would be folded in such a way as to ensure it was impossible to open without tearing or otherwise damaging the paper, and their structure is of especial interest to historians. The researchers had a unique resource with which to work; the Brienne collection is a trunk full of undeliverable mail amassed by a 17th century postmaster couple in Den Haag in the Netherlands, and now in the possession of the Beeld en Geluid museum in that city. In it were a cache of letters including 577 never-opened letterpackets, and the x-ray technique promised a means to analyse these without compromising them.

The researchers have developed an entirely computational technique for the virtual unfolding process. Starting with a 3D volumetric x-ray scan of the unopened packet they then identify the various layers of paper and the bright spots which denote the ink. Their algorithm has to cope with areas in which two or more layers are tightly in contact, for example when multiple levels are folded, and then unpick the resulting 3-dimensional mesh into a 2-dimensional sheet. Their process for mapping the crease pattern involves applying a colour map representing the mean curve radius at a given point. The final section of the paper looks at the multiple different methods of letterlocking, and attempts to categorise them all including a security rating for each. It’s evident that this could be a highly personalised process, indeed they give as an example a letter from Mary Queen of Scots that used an intricate spiral folding technique to identify its sender.

It’s clear that this technique will reveal many more fascinating historical documents as it is both refined and extended across the many more collections of further artefacts that have lain waiting for it. As they say, individual letters do not necessarily contain earth-shattering historical discoveries, but taken together they shed an important light on the social history of past centuries.

One of the names on the paper is [David Mills], whose work has featured here before.

Do Androids Search For Cosmic Rays?

January 22, 2021 by Al Williams 20 Comments

We always like citizen science projects, so we were very interested in DECO, the Distributed Electronic Cosmic-ray Observatory. That sounds like a physical location, but it is actually a network of cell phones that can detect cosmic rays using an ordinary Android phone’s camera sensor.

There may be some privacy concerns as the phone camera will take a picture and upload it every so often, and it probably also taxes the battery a bit. However, if you really want to do citizen science, maybe dedicate an old phone, put electrical tape over the lens and keep it plugged in. In fact, they encourage you to cover the lens to reduce background light and keep the phone plugged in.

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Multi-Channel Battery Monitor Aces First Sea Trial

January 20, 2021 by Tom Nardi 4 Comments

A little over a a year ago, we covered an impressive battery monitor that [Timo Birnschein] was designing for his boat. With dedicated batteries for starting the engines, cranking over the generator, and providing power to lights and other amenities, the device had to keep tabs on several banks of cells to make sure no onboard systems were dipping into the danger zone. While it was still a work in progress, it seemed things were progressing along quickly.

But we know how it is. Sometimes a project unexpectedly goes from having your full attention to winning an all-expense-paid trip to the back burner. In this case, [Timo] only recently put the necessary finishing touches on his monitor and got it installed on the boat. Recent log entries on the project’s Hackaday.io page detail some of the changes made since the last time we checked in, and describe the successful first test of the system on the water.

Certainly the biggest issue that was preventing [Timo] from actually using the monitor previously was the lack of an enclosure and mounting system for it. He’s now addressed those points with his 3D printer, and in the write-up provides a few tips on shipboard ergonomics when it comes to mounting a display you’ll need to see from different angles.

The printed enclosure also allowed for the addition of some niceties like an integrated 7805 voltage regulator to provide a solid 5 V to the electronics, as well as a loud piezo beeper that will alert him to problems even when he can’t see the screen.

Under the hood he’s also made some notable software improvements. With the help of a newer and faster TFT display library, he’s created a more modern user interface complete with a color coded rolling graph to show voltages changes over time. There’s still a good chunk of screen real estate available, so he’s currently brainstorming other visualizations or functions to implement. The software isn’t using the onboard NRF24 radio yet, though with code space quickly running out on the Arduino Nano, there’s some concern about getting it implemented.

As we said the first time we covered this project, you don’t need to have a boat to learn a little something from the work [Timo] has put into his monitoring system. Whether you’re tracking battery voltages or temperatures reported by your BLE thermometers, a centralized dashboard that can collect and visualize that data is a handy thing to have.

The V-Bomber Ejector Seat Controversy

January 11, 2021 by Lewin Day 58 Comments

Once upon a time, bailing out of a plane involved popping open the roof or door, and hopping out with your parachute, hoping that you’d maintained enough altitude to slow down before you hit the ground. As flying speeds increased and aircraft designs changed, such escape became largely impossible.

Ejector seats were the solution to this problem, with the first models entering service in the late 1940s. Around this time, the United Kingdom began development of a new fleet of bombers, intended to deliver its nuclear deterrent threat over the coming decades. The Vickers Valiant, the Handley Page Victor, and the Avro Vulcan were all selected to make up the force, entering service in 1955 through 1957 respectively. Each bomber featured ejector seats for the pilot and co-pilot, who sat at the front of the aircraft. The remaining three crew members who sat further back in the fuselage were provided with an escape hatch in the rear section of the aircraft with which to bail out in the event of an emergency.

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How Researchers Used Salt To Give Masks An Edge Against Pathogens

December 19, 2020 by Donald Papp 32 Comments

Masks are proven tools against airborne diseases, but pathogens — like the COVID-19 virus — can collect in a mask and survive which complicates handling and disposal. [Ilaria Rubino], a researcher at the University of Alberta, recently received an award for her work showing how treating a mask’s main filtration layer with a solution of mostly salt and water (plus a surfactant to help the wetting process) can help a mask inactivate pathogens on contact, thereby making masks potentially re-usable. Such masks are usually intended as single-use, and in clinical settings used masks are handled and disposed of as biohazard waste, because they can contain active pathogens. This salt treatment gives a mask a kind of self-cleaning ability.

Analysis showing homogenous salt coating (red and green) on the surface of fibers. NaCl is shown here, but other salts work as well.

How exactly does salt help? The very fine salt coating deposited on the fibers of a mask’s filtration layer first dissolves on contact with airborne pathogens, then undergoes evaporation-induced recrystallization. Pathogens caught in the filter are therefore exposed to an increasingly-high concentration saline solution and are then physically damaged. There is a bit of a trick to getting the salt deposited evenly on the polypropylene filter fibers, since the synthetic fibers are naturally hydrophobic, but a wetting process takes care of that.

The salt coating on the fibers is very fine, doesn’t affect breathability of the mask, and has been shown to be effective even in harsh environments. The research paper states that “salt coatings retained the pathogen inactivation capability at harsh environmental conditions (37 °C and a relative humidity of 70%, 80% and 90%).”

Again, the salt treatment doesn’t affect the mask’s ability to filter pathogens, but it does inactivate trapped pathogens, giving masks a kind of self-cleaning ability. Interested in the nuts and bolts of how researchers created the salt-treated filters? The Methods section of the paper linked at the head of this post (as well as the Methods section in this earlier paper on the same topic) has all the ingredients, part numbers, and measurements. While you’re at it, maybe brush up on commercially-available masks and what’s inside them.

A Thousand Feet Under The Sea

December 11, 2020 by Al Williams 15 Comments

If you were to plumb the depth of the oceans, you could only get so far with a snorkel or a SCUBA tank. We don’t know the price, but if you have enough money, you might consider the Triton 3300/6 — a six-person submersible that can go down to 3,300 feet (hence the name–get it–3300/6). Billed as “diving for the entire family,” we aren’t sure we can load grandma and the kids in something like this, but that doesn’t mean we wouldn’t like to try.

The machine can carry up to 1,760 pounds and can make 3 knots which isn’t going to set any speed records. At around 24,000 pounds, the two main thrusters are lucky to make that speed. The view bubble is apparently optically perfect acrylic made by a German company and the company claims the 100-inch diameter bubble is the world’s largest spherical acrylic pressure hull.

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