Self-Healing Concrete: What Ancient Roman Concrete Can Teach Us

Concrete is an incredibly useful and versatile building material on which not only today’s societies, but also the ancient Roman Empire was built. To this day Roman concrete structures can be found in mundane locations such as harbors, but also the Pantheon in Rome, which to this day forms the largest unreinforced concrete dome in existence at 43.3 meters diameter, and is in excellent condition despite being being nearly 1,900 years old.

Even as the Roman Empire fell and receded into what became the Byzantine – also known as the Eastern Roman – Empire and the world around these last remnants of Roman architecture changed and changed again, all of these concrete structures remained despite knowledge of how to construct structures like them being lost to the ages. Perhaps the most astounding thing is that even today our concrete isn’t nearly as durable, despite modern inventions such as reinforcing with rebar.

Reverse-engineering ancient Roman concrete has for decades now been the source of intense study and debate, with a recent paper by Linda M. Seymour and colleagues adding an important clue to the puzzle. Could so-called ‘hot mixing’, with pockets of reactive lime clasts inside the cured concrete provide self-healing properties?

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Creating A 3D Visualization Of Freely Moving Organisms Using Camera Array And Software Algorithm

Observing a colony, swarm or similar grouping of creatures like ants or zebrafish over longer periods of time can be tricky. Simply recording their behavior with a camera misses a lot of information about the position of their body parts, while taking precise measurements using a laser-based system or LiDAR suffers from a reduction in parameters such as the resolution or the update speed. The ideal monitoring system would be able to record at high data rates and resolutions, while presenting the recorded data all three dimensions. This is where the work by Kevin C. Zhou and colleagues seeks to tick all the boxes, with a recent paper (preprint, open access) in Nature Photonics describing their 3D-RAPID system.

This system features a 9×6 camera grid, making for a total of 54 cameras which image the underlying surface. With 66% overlap between cameras across the horizontal dimension, there enough duplicate data between image stream that is subsequently used in the processing step to extract and reconstruct the 3D features, also helped by the pixel pitch of between 9.6 to 38.4 µm. The software is made available via the author’s GitHub.

Three configurations for the imaging are possible, ranging from no downsampling (1x) for 13,000×11,250 resolution at 15 FPS, to 2x downsampling (6,500×5,625@60FPS) and finally 4x (3,250×2,810@230FPS). Depending on whether the goal is to image finer features or rapid movement, this gives a range of options before the data is fed into the computational 3D reconstruction and stitching algorithm. This uses the overlap between the distinct frames to reconstruct the 3D image, which in this paper is used together with a convolutional neural network (CNN) to automatically determine for example how often the zebrafish are near the surface, as well as the behavior of fruit flies and harvester ants.

As noted in an interview with the authors, possible applications could be found in developmental biology as well as pharmaceutics.

Archiving The Entirety Of DPReview Before It’s Gone

Despite the popular adage about everything on the internet being there forever, every day pages of information and sometimes entire websites are lost to the sands of time. With the imminent shutdown of the DPReview website, nearly 25 years of reviews and specifications of cameras and related content are at risk of vanishing. Also lost will be the content of forum posts, which can still be requested from DPReview staff until April 6th. All because the owner of the site, Amazon, is looking to cut costs.

As announced on r/photography, the Archive.org team is busy trying to download as much of the site as possible, but due to bottlenecks may not finish in time. One way around these bottlenecks is what is called the Archive Team Warrior, which involves either a virtual machine or Docker image that runs on distributed systems. In early April an archiving run using these distributed systems is planned, in a last-ditch attempt to retain as much of the  decades of content.

The thus archived content will be made available in the WARC (Web ARChive) format, in order to retain as much information as possible, including meta data and different versions of content.

Debugging And Analyzing Real-Mode 16-Bit X86 Code With Fresh Bread

Running a debugger like gdb with real-mode 16-bit code on the x86 platform is not the easiest thing to do, but incredibly useful when it comes to analyzing BIOS firmware and DOS software. Although it’s possible to analyze a BIOS image after running it through a disassembler, there is a lot that can only be done when the software is running on the real hardware. This is where [Davidson Francis] decided that some BREAD would be useful, as in BIOS Reverse Engineering & Advanced Debugging.

What BREAD does is provide some injectable code that with e.g. a BIOS replaces the normal boot logo with the debugger stub. This stub communicates with a bridge via the serial port, with the gdb client connecting to this bridge. Since DOS programs are also often 16-bit real-mode, these can be similarly modified to provide light-weight in-situ debugging and analysis. We imagine that this software can be very useful both for software archaeology and embedded purposes.

Thanks to [Rodrigo Laneth] for the tip.

Europe’s Proposed Right-To-Repair Law: A Game Changer, Or Business As Usual?

Recently, the European Commission (EC) adopted a new proposal intended to enable and promote the repair of a range of consumer goods, including household devices like vacuum cleaners and washing machines, as well as electronic devices such as smartphones and televisions. Depending on how the European Parliament and Council vote in the next steps, this proposal may shape many details of how devices we regularly interact with work, and how they can be repaired when they no longer do.

As we have seen recently with the Digital Fair Repair Act in New York, which was signed into law last year, the devil is as always in the details. In the case of the New York bill, the original intent of enabling low-level repairs on defective devices got hamstrung by added exceptions and loopholes that essentially meant that entire industries and types of repairs were excluded. Another example of ‘right to repair’ being essentially gamed involves Apple’s much-maligned ‘self repair’ program, that is both limited and expensive.

So what are the chances that the EU will succeed where the US has not?

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Caterpillar-Like Soft Robot With Distributed Programmable Thermal Actuation

Researchers at North Carolina State University have created a soft robot that moves in a distinctly caterpillar-like manner. As detailed in the research paper in Science Advances by [Shuang Wu] and colleagues, the robot they developed consists of a layer of liquid crystalline elastomers (LCE) and polydimethylsiloxane (PDMS) with embedded silver nanowire that acts as a heater.

The LCE is hereby designed as a thermal bimorph actuator, using a distinct thermal expansion coefficient between the LCE and PDMS sides to create a highly controllable deformation and thus motion. Since the nanowire is divided into sections that can be individually heated, the exact deformation can be quite tightly controlled, enabling the crawling motion.

(A) Schematics of the forward locomotion of a caterpillar. (B) Schematics of the reverse locomotion of a caterpillar. (C) Snapshots of the crawling robot in one cycle of actuation for reverse locomotion. (D) Snapshots of the crawling robot in one cycle of actuation for forward locomotion. (E) infrared image of the crawling robot with 0.05-A current injected in channel 1 and the tilted view of the crawling robot. (F) Infrared image of the crawling robot with 30-mA current injected in channel 2 and the corresponding tilted view of the crawling robot. (Credit: Shuang Wu, et al. (2023))
(A) Schematics of the forward locomotion of a caterpillar. (B) Schematics of the reverse locomotion of a caterpillar. (C) Snapshots of the crawling robot in one cycle of actuation for reverse locomotion. (D) Snapshots of the crawling robot in one cycle of actuation for forward locomotion. (E) infrared image of the crawling robot with 0.05-A current injected in channel 1 and the tilted view of the crawling robot. (F) Infrared image of the crawling robot with 30-mA current injected in channel 2 and the corresponding tilted view of the crawling robot. (Credit: Shuang Wu, et al. (2023))

As can be seen in the video below, the motion is fairly rapid and quite efficient, as well as decidedly caterpillar-like. Although the current prototype uses external control wires that supply the current, it might be possible to integrate a power supply and control circuitry in a stand-alone robot. Since the heater works on low voltage (5 V) and relatively little power is required, this would seem to make stand-alone operation eminently possible.

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Recreating The ZX Spectrum Unboxing Experience By Manufacturing A New Boxed One

Why scour the internet for a rare-as-hen’s-teeth new in box ZX Spectrum computer when you can instead order up some parts, assemble a basically all new ZX Spectrum along with the box, instruction manuals and more?

That seems to have been the reasoning behind [Lost Retro Tapes] when they decided to do exactly that. Along with the announcement of the completion on Reddit, the website details the BOM and sourcing the components.

For the mainboard, an existing, redrawn ZX Spectrum 48 Issue 3B PCB was found and ordered from PCBWay. As a UK-based entity, many of the other components were sourced from retro computing shops around the UK, but with all but the LM1889N IC being available for new or with currently produced alternative, it should be viable to source them locally.

Perhaps most impressive was the creation of the box (unfortunately not detailed on the website at this point), and having the manuals (system and BASIC) professionally printed and bound. Along with a few other bits and pieces, including a tape recorder and fresh Horizons tape, the total price tag came to around £412.

Thanks to [Lee Hodgson] for the tip.