Data Science The Stanford Way

November 12, 2023 by Al Williams 27 Comments

Data science is a relatively new term for a relatively old discipline. Essentially, it is data analysis, particularly for large data sets. It involves techniques as wide-ranging as statistics, computer science, and information theory. What to know more? Stanford has a “Data Science Handbook” that you can read online.

Topics range from how to design a study and create an analytic plan to how to do data visualization, summarization, and analysis. The document covers quite a bit but is very concise.

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Molybdenene whiskers. (Credit: Sahu et al., 2023)

Introducing Molybdenene As Graphene’s New Dirac Matter Companion

November 12, 2023 by Maya Posch 9 Comments

Amidst all the (well-deserved) hype around graphene, it’s important to remember that its properties are not unique to carbon. More atoms can be coaxed into stable 2-dimensional configuration, with molybdenene previously theoretically possible. This is now demonstrated by Tumesh Kumar Sahu and colleagues in a recent Nature Nanotechnology article, through the manufacturing of a 2D molybdenum-based material which they showed to be indeed molybdenene. Essentially, this is a 2D lattice of molybdenum atoms, a configuration in which it qualifies as Dirac matter, just like graphene. For those of us unfamiliar with Dirac materials, this gentle introduction by Jérôme Cayssol in Comptes Rendus Physique might be of use.

Manufacturing process of molybdenene. (Credit: Sahu et al., 2023)

In order to create molybdenene, the researchers started with molybdenum disulfide (MoS₂), which using a microwave-assisted field underwent electrochemical transformation into whiskers that when examined turned out to consist out of monolayers of Mo. The sulfur atoms were separated using a graphene sheet. As is typical, molybdenene sheets were exfoliated using Scotch tape, in a process reminiscent of the early days of graphene research.

Much like graphene and other Dirac materials, molybdenene has many potential uses as a catalyst, as cantilever in scanning electron microscope (SEM) tips, and more. If the past decades of research into graphene has demonstrated anything, it is that what once seemed more of a novelty, suddenly turned out to have endless potential in fields nobody had considered previously. One of these being as coatings for hard disk platters, for example, which has become feasible due to increasingly more efficient ways to produce graphene in large quantities.

Radioactive Water Was Once A (Horrifying) Health Fad

November 10, 2023 by Donald Papp 25 Comments

Take a little time to watch the history of Radithor, a presentation by [Adam Blumenberg] into a quack medicine that was exactly what it said on the label: distilled water containing around 2 micrograms of radium in each bottle (yes, that’s a lot.) It’s fascinatingly well-researched, and goes into the technology and societal environment surrounding such a product, which helped play a starring role in the eventual Food, Drug, and Cosmetic Act of 1938. You can watch the whole presentation in the video, embedded below the break. Continue reading “Radioactive Water Was Once A (Horrifying) Health Fad” →

Wind Tunnel Uses The Last Straw

November 10, 2023 by Al Williams 14 Comments

If you watch the movies, there isn’t much to a wind tunnel. Just a fan and a tunnel, right? The truth is there’s a lot more to it than that, and [ejs13] shows you how you can make a small tunnel with some basic supplies. One of the requirements for a useful tunnel is to have laminar flow — that is, flow in uniform layers with little, if any, mixing. This tunnel achieves laminar flow using an array of soda straws to direct the flow. In fact, there are 150 straws in total. You can see a short clip of the wind tunnel in action below.

The rest of the parts are easy, too. A computer fan provides wind, and there’s a little bit of wood and acrylic. You’ll notice in the video that you can easily see the airflow. That’s thanks to a light source, some water, and a bit of dry ice.

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Fastest Semiconductor May Also Be Most Expensive

November 9, 2023 by Al Williams 26 Comments

Scientists have found what they think may be the fastest known semiconductor. Sounds great, right? But it happens to made from one of the rarest elements: rhenium. That rare element combines with selenium and chlorine to form a “superatom.” Unlike conventional semiconductor material, the superatom causes phonons to bind together and resist scattering. This should allow materials that can process signals in femtoseconds,

Rhenium was the last stable element to be found in 1925. It is primarily used in combination with nickel in parts of jet engines, although it is also known as a catalyst for certain reactions. It is very rare and has a high melting point, exceeded only by tungsten and carbon. When it was discovered, scientists extracted a single gram of the material by processing 660 kg of molybdenite. Because of its rarity, it is expensive, costing anywhere from $2,800 to $10,600 per kilogram.

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All About Cats, And What Ethernet Classifications Mean Beyond ‘Bigger Number Better’

November 7, 2023 by Maya Posch 48 Comments

Although it probably feels like forever to many of us since Category 5 Ethernet cabling became prevalent, now that 2.5 and even 5 Gbit Ethernet has trickled into the mainstream, a pertinent question that many probably end up asking, is when you should replace Cat-5e wiring with Cat-6, or even Cat-7. Since most of us are likely to use copper network wiring for the foreseeable future in our domiciles and offices, it is a good question that deserves a good answer. Although swapping a Cat-5e patch cable with a Cat-7 one between a network port and computer is easy enough, replacing all the network cable already pulled through the conduits of a ‘future-proofed’ home is not.

The good news is probably that Category 8 Class II (Cat-8.2) is all you need to run your 40 Gbit Ethernet network with standard twisted pair wiring. The bad news is that you’re limited to runs of only thirty meters before signal degradation begins to kick in. If you take things down a notch to Cat-6A or Cat-7 (ISO/IEC 11801 Class E_A and F, respectively), you can do 100 meter runs at 10 Gbit/s just like 100 meters runs at 1 Gbit/s were possible with Cat-5e before. Yet what differentiates these categories exactly?

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A schematic representation of the different ionospheric sub-layers and how they evolve daily from day to night periods. (Credit: Carlos Molina)

Ham Radio Operators’ Ionospheric Science During The Solar Eclipse

October 31, 2023 by Maya Posch 3 Comments

The Earth’s ionosphere is the ionized upper part of the atmosphere, and it’s also the most dynamic as it swells and ebbs depending on whether it’s exposed to the Sun or not. It’s the ionosphere that enables radio frequency communications to reach beyond the horizon, its thickness and composition also affects the range and quality of these transmissions. Using this knowledge, a group of ham radio operators used the October 14 solar eclipse to crowdsource an experiment, as part of the Ham Science Citizen Investigation (HamSCI) community.

A solar eclipse is an interesting consideration with ionospheric RF transmissions, as it essentially creates a temporary period of night time, which is when the ionosphere is the least dense, and thus weakening these transmissions and their total range. As with previous solar eclipses, they turned it into a kind of game, where each ham operator attempts to contact as many others as possible within the least amount of time. Using the collected data points on who was able to talk to whom on the globe, the event’s effect on RF transmissions could be plotted over time. For the August 21, 2017 solar eclipse, the results were published in a 2018 paper by N. A. Frissell et al. in Geophysical Research Letters.

One point which they wished to examine during the 2023 solar eclipse were the plasma bubbles that form near the Earth’s magnetic equator, in regions like Brazil. These plasma bubbles cause a lot of interference, which in the preliminary data can be seen as a clear Doppler shift of the signal due to the diffusion of the ionosphere as the eclipse’s effect took hold. For the next solar eclipse in April 2024 another experiment is scheduled, which will give even more ham radio operators the chance to sign up and contribute to ionospheric science.

Top image: A schematic representation of the different ionospheric sub-layers and how they evolve daily from day to night periods. (Credit: Carlos Molina)