Kritik sah

One of the most fun challenges in paleontology is determining characteristics of long-dead species like their behavior and body temperature based on nothing but some fossils and traces that are usually millions of years old. Something that has long vexed the paleontological community for example has been the question whether non-avian dinosaurs like the well-known Tyrannosaurus rex was cold- or warm-blooded, and if the latter, what temperature this was. Cue a recent study by [Randon J. Flores] et al. in Science Advances in which they seek to answer this question. Although modern-day dinosaurs in the form of birds are all warm-blooded – meaning capable of regulating their body temperature – species like crocodiles, who also lived alongside non-avian dinosaurs, are cold-blooded and have to cycle between sun-basking and a cool dip in a nearby river to maintain their body temperature. By looking at the temperature-dependent formation of carbonate clumped isotopes in three ...

As cool as it would have been to wield lasers that produce a beam of neutrinos, recently two papers were published by MIT researchers that seem to dampen the likelihood of such lasers being at all possible. In a review paper by [Ana Maria Rey] et al. these two papers are investigated in more detail. Although the concept behind a neutrino laser is rather simple, using the same superradiance effect involving a Bose-Einstein condensate (BEC) that allows for stimulation by photons to result in a synchronized direction of emitted photons, the idea of using a BEC of radioisotopes that naturally emit neutrinos in this fashion has now been effectively shot down. The problem lies in taking the leap from photons with a BEC and applying this to a BEC of radioisotopes. Whereas photons are relatively slow and low-energy at a mere 1 eV, a neutrino is extremely fast and at 1+ MeV correspondingly has a much greater kinetic effect on the particle that emitted it. Unlike a photon emitted by an atom...

Once you arrive at your destination via plane, it can be a drag waiting for a rental car. Why not bring your own with a replica of the Mazda suitcase car ? The heady days of the 90s brought us many wild vehicles from Japan, and in 1991, Mazda built three prototype go carts built inside Samsonite suitcases as a potential rival to the Honda Motocompo. After some appearances on the talk show circuit, two of the prototypes were destroyed, and the world moved on. [Bucket] felt wistful about the vehicle and decided it was time to build his own since the only remaining example is in collector hands, although they were able to reach out to the owner for more information on how the original prototypes functioned. Using a very small gas motor from a pocket rocket and a welded aluminum frame inside the suitcase, the builders managed to beat the stated top speed of the original, hitting 33 kph (20 mph) before the driver decided things were getting too frightening. The final build tips the scales...

Even if the world has already settled on plain old propellers as the way to make quadcopter drones fly, this doesn’t mean that you cannot give other designs a shake to see what kind of flying performance they result in. For example impeller designs that depart radically from standard propellers – themselves a sub-category of axial impellers – and go radically radial instead as in this design by [quadmovr] with accompanying demonstration video . This is itself a remix of a design by [Baba] to make it fit the target 1750KV T-mount motor. As for whether this is a design that you want to slap on your own quadcopter, the obvious disadvantage is that it’s much heavier than regular propellers. Weighing [quadmovr]’s drone without battery pack and with these 3D-printed PETG impellers shows them to weigh 189 grams. This compares to 141 grams with the standard three-bladed propellers, or a hefty 12.8 gram weight penalty per impeller. Naturally this translates into...

In the US, among other places, housing costs are skyrocketing. It can sometimes be difficult to get a feel for the scale of the issue and how it hits neighborhoods differently. [Justin Blinder] has designed a device to help people get a more visceral understanding of the problem . In New York City, Citi Bikes are everywhere in the city’s transportation landscape. [Blinder] used a GPS module plugged into an ESP32S3 to vary the amount of resistance on one of these bikes by actuating the front brake with a servo. As a rider takes the bike through different neighborhoods, the resistance varies in proportion to the rent burden experienced there. [Blinder] explains, “One of the main technical challenges was calibrating this relationship so that the changes were physically noticeable without feeling abrupt or unsafe.” As rent burden is merely the percentage of income taken up by rent in an area (by the block in this dataset), it is only one indicator of the additional frict...

Photodetectors come in a wide variety of constructions and materials, with the Cu 2 O-based photodetector that [Mad Scientist Creations] demonstrates in a recent video being a good example of a photodetector that can be created at home using nothing but some copper and a heat source. Of the two copper elements in a salt water cell, one element is heated to the point where a copper oxide layer forms, specifically Cu 2 O, which acts as a semiconductor and provides the photosensitive layer. Even a fairly crude sensor created with a regular gas stove produces enough of a current that it can be used in a simple light detection circuit. Although copper-oxide photodetectors may seem quaint, they are getting a lot of interest as they feature a very narrow bandgap at 1.2 eV. In a 2019 study by [Hyeon-Joo Song] et al. as published in  Scientific Reports such a sensor is enhanced with an optimized grain structure that improves its performance, with much higher sensitivity and faster response...