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In particular, in systems where ligands bind uniquely to receptors, the number of types of ligands limits how many different cell types or targets can be uniquely addressed. In a combinatorial system, different pairings between a small number of ligands and receptors can specify a much larger number of targets. The differences between the pairings also permit graded effects rather than an all-or-nothing response.
By combining global temperature estimates from geological data with estimates of tropical temperatures obtained from oxygen isotope studies, it is possible to produce an estimate of the global average temperature for any time in the past. The modern global average temperature is 14.5˚C. The average global temperature for the last 540 ga is 20˚C, but the temperature has fluctuated between 25˚C (hothouse) and 10˚C (icehouse). During the Permo-Triassic Extinction, the global temperature spiked above 28˚C. Most of the time, the global temperature gently rises and falls in response to gradual changes in orbital and solar parameters, ocean currents, sea level, atmospheric chemistry (greenhouse gases), and other factors. These changes occur over millions of years. Rarely, there is a drastic change in one of these factors resulting in either rapid global warming (Kidder–Worsley events) or rapid global cooling (Stoll-Schrag events). These abrupt climate excursions take place over 1000s of years, rather than millions of years.
the world was colder than today only 2% of the time in the last 540 ga.
Turing’s paper described a theoretical mechanism based on 2 substances — an activator and an inhibitor that diffuse across an area at different rates. The interaction between these 2 “morphogens,” as Turing called them, allows one to interrupt the effect of the other — creating a pattern of colored lines on a tropical fish, for example, rather than a solid color. Turing’s mechanism was indeed responsible for the stripes in the bismuth. And it demonstrated once again how robust and powerful Turing’s original insight was. Here, the stripe-forming process is driven by the forces at play among the bismuth atoms and the metal below. Bismuth atoms want to fit into particular spots on the molecular lattice of the metal. But these spots are closer together than the bismuth atoms find comfortable. Like a photograph that gets shoved into a frame that’s too small for it, the sheet of bismuth atoms buckles. The strain creates a wavy pattern that leaves some atoms raised, forming the stripes. The vertical shift — movement away from the plane of the crystal — acts as the activator in the Turing equations, while the shift within the plane acts as the inhibitor. The morphogens here are displacements, not molecules. When part of a Turing pattern is wiped out, it grows back. You might not assume that inorganic materials like bismuth crystals would be able to heal as animals do,but indeed, his team’s simulated bismuth crystal was able to mend itself.
Today, we published “Open-Ended Learning Leads to Generally Capable Agents,” a preprint detailing our first steps to train an agent capable of playing many different games without needing human interaction data. We created a vast game environment we call XLand, which includes many multiplayer games within consistent, human-relatable 3D worlds. This environment makes it possible to formulate new learning algorithms, which dynamically control how an agent trains and the games on which it trains. The agent’s capabilities improve iteratively as a response to the challenges that arise in training, with the learning process continually refining the training tasks so the agent never stops learning. The result is an agent with the ability to succeed at a wide spectrum of tasks — from simple object-finding problems to complex games like hide and seek and capture the flag, which were not encountered during training. We find the agent exhibits general, heuristic behaviors such as experimentation, behaviors that are widely applicable to many tasks rather than specialized to an individual task. This new approach marks an important step toward creating more general agents with the flexibility to adapt rapidly within constantly changing environments.
Researchers have made a discovery that may shake up the history of mathematics, revealing evidence of applied geometry being used for the purposes of land surveying 3.7 ka BP. Found on a Babylonian clay table, the etchings are believed to represent the oldest known example of applied geometry, and feature mathematical techniques linked to the Greek philosopher Pythagoras that were well ahead of their time.
When a tuna marketing executive took a bite of the dehydrated tomato seasoned with olive oil, algae extract, spices, and soy sauce early last year, he was shook. “This is going to be a problem for us”. That’s how the CEO of Mimic Seafood recalls it, designating it the highest praise she could’ve imagined for the delicate slice of tuna that—despite what the marketing executive’s taste buds indicated—contained no tuna at all. The Madrid-based startup’s Tunato product, fabricated from a specialty tomato variety grown in southern Spain that resembles sliced sushi-grade tuna in shape and size, is part of a growing class of food innovations fighting for the last empty shelf in the booming plant-based protein market: seafood.
What has emerged from 19 months of work, backed by decades of coronavirus research, is a blow-by-blow account of how SARS-CoV-2 invades human cells. Scientists have discovered key adaptations that help the virus to grab on to human cells with surprising strength and then hide itself once inside. Later, as it leaves cells, SARS-CoV-2 executes a crucial processing step to prepare its particles for infecting even more human cells. These are some of the tools that have enabled the virus to spread so quickly and claim millions of lives.
Humans have an enzyme called FTO that demethylates N6-methyladenosine through oxidation. It’s part of a large family of enzymes that do this sort of thing using an iron atom in their active sites, along with molecular oxygen. Plants, though, don’t have an FTO homolog – they have some other enzymes that can demethylate this substrate, but not like FTO itself. So the team behind this paper wanted to see what would happen if you engineered the FTO enzyme into plants. In rice and potatoes, the crop yields went up by 50%. Grain size in the rice plants didn’t change, nor did the height of the plants – they just produced a lot more rice grains in general. How does this happen? The plants’ root systems were deeper and more extensive, and photosynthetic efficiency went up by a startling 36%. Transpiration from the leaves was up 78%, but at the same time, the plants of both species showed significantly higher drought tolerance. These are highly desirable traits, and it’s worth noting that a lot of this extra biomass is coming from increased usage of carbon dioxide from the air.
Now we just need to crush the GMO luddites to roll this out.
500m wide, the beach is made of material dredged from the sea bottom 13 kilometers offshore and dumped on the existing beach. It’s an experimental coastal protection measure, its sands designed to spread over time to shield the Dutch coast from sea-level rise. The endeavor has made 21m cubic meters of Stone Age soil accessible to archaeologists. “The surprising thing is just how much DNA is still down there.”
2022-03-06: A map of Doggerland 11 ka BP:
Doggerland was, by any estimation, the most attractive landscape in northwestern Europe for Mesolithic hunter-gatherers and perhaps the continent’s most densely populated region at the time. Because of the seemingly inexhaustible resources present there, normally mobile Mesolithic societies may have been encouraged to create permanent or semipermanent settlements. While relatively few Mesolithic sites have been located on land, if Doggerland was indeed the heartland for these early Holocene communities, it stands to reason that many archaeological sites may lie beneath the North Sea. Seismic data has now given archaeologists a much better sense of Doggerland’s topography. They know where its rivers, lakes, and coastlines were located, and where its forests were found. They can use this information to speculate about where people may have lived.
This new type of research into Doggerland has the potential to once again dramatically alter the field of European prehistory. “We have a completely intact landscape with a state of preservation that we can often only dream of on land. I think we will have a lot of exciting discoveries to come. We are barely scratching the surface.”
Gregor J. Rothfuss 