All posts tagged: University of Pennsylvania

UPenn physicists make ‘light’ work of computing

UPenn physicists make ‘light’ work of computing

Published by Jenni Sidey

Eighty years after ENIAC helped launch the electronic age at the University of Pennsylvania, a new Penn-led advance points to a very different way of computing. Instead of relying on electrons, which lose energy as heat and become harder to manage as chips grow more complex, physicists are pushing light deeper into the job. Their latest work centers on a hybrid particle. This particle lets light do something it usually struggles with in computing: interact strongly enough to switch signals on and off. That hybrid, called an exciton-polariton, blends the speed of photons with the stronger interactions of matter. In the new research, Penn physicists built a system that uses these quasiparticles to perform all-optical switching with about 4 femtojoules of energy, or roughly 4 quadrillionths of a joule. Furthermore, the team says that figure sets a new benchmark for switching energy in two-dimensional exciton-polariton systems. The work, published in Physical Review Letters, could matter most in artificial intelligence, where hardware now spends huge amounts of energy moving data, processing it, and shedding heat. 2D …

Neanderthal males preferred human females, genetic study finds

Neanderthal males preferred human females, genetic study finds

Published by Jenni Sidey

Thin stretches of the human X chromosome look oddly empty when you scan for Neanderthal DNA. Geneticists even have a name for the gaps: “Neanderthal deserts.” They sit there like blank tape in an otherwise crowded recording. For years, the standard story went like this: Neanderthal DNA landed in our ancestors’ genomes. However, some of it was harmful, especially on the X chromosome. Natural selection, the thinking said, gradually stripped those “toxic” variants away. A new analysis from Sarah Tishkoff’s lab at the University of Pennsylvania argues that the emptiness may say more about who paired with whom than which genes were dangerous. In Science, the team reports a mirror-image pattern inside Neanderthal genomes. Neanderthals carried unusually high levels of modern human DNA on their X chromosomes compared with the rest of their genome. That reversal, they say, makes simple “toxicity” a much harder explanation to defend. The deserts and the old assumption “Along our X chromosomes, we have these missing swaths of Neanderthal DNA we call ‘Neanderthal deserts,’” says Alexander Platt, a senior research …