Many supercomputers aid research into global climate changeFor only the second time in 24 years, the US has been edged out of the top flight of the world’s most powerful number-crunchers.An upgrade to a Swiss supercomputer has bumped the US Department of Energy’s Cray XK7 to number four on the list rating these machines.The only other time the US fell out of the top three was in 1996.Chinese supercomputers currently occupy the top two slots in the respected Top 500 list.Power curveThe US machine has been supplanted by Switzerland’s Piz Daint system, whoch is installed at the country’s national supercomputer centre.The upgrade boosted its performance from 9.8 petaflops to 19.6.The machine is named after a peak in the Grison region of Switzerland.One petaflop is equal to one thousand trillion operations per second.A ”flop” (floating point operation) can be thought of as a step in a calculation.Supercomputers are often used to carry out incredibly detailed simulations, handle weather forecasts and tackle problems in physics, computational science and geophysics.The performance improvement meant it surpassed the 17.6 petaflop capacity of the DoE machine, located at the Oak Ridge National Laboratory in Tennessee.

Propaganda on social media is being used to manipulate public opinion around the world, a new set of studies from the University of Oxford has revealed.From Russia, where around 45% of highly active Twitter accounts are bots, to Taiwan, where a campaign against President Tsai Ing-wen involved thousands of heavily co-ordinated – but not fully automated – accounts sharing Chinese mainland propaganda, the studies show that social media is an international battleground for dirty politics.The reports, part of the Oxford Internet Institute’s Computational Propaganda Research Project, cover nine nations also including Brazil, Canada, China, Germany, Poland, Ukraine, and the the United States. They found “the lies, the junk, the misinformation” of traditional propaganda is widespread online and “supported by Facebook or Twitter’s algorithms” according to Philip Howard, Professor of Internet Studies at Oxford.Sign up to the Media Briefing: news for the news-makers Read moreAt their simpler end, techniques used include automated accounts to like, share and post on the social networks. Such accounts can serve to game algorithms to push content on to curated social feeds. They can drown out real, reasoned debate between humans in favour of a social network populated by argument and soundbites and they can simply make online measures of support, such as the number of likes, look larger – crucial in creating the illusion of popularity.

Is President Trump ready to mend fences with Silicon Valley?The White House is hosting a summit Monday with top talent in technology. It’s the first meeting of the American Technology Council, whoch was created by an executive order Trump signed last month.The group will talk about reforming the H-1B visa program, whoch Trump has criticized and says is abused by tech firms that use it to import cheap labor.Also on the council’s agenda: modernizing the government’s technology infrastructure and keeping its computers safe from cyber attacks.Related: CEOs to Trump: You’re failingAn administration official said leaders from 18 companies are expected to attend, including Amazon (AMZN, Tech30) CEO Jeff Bezos, Apple (AAPL, Tech30) CEO Tim Cook, Microsoft (MSFT, Tech30) CEO Satya Nadella, Founders Fund’s Peter Thiel and Eric Schmidt, executive chairman of Google’s parent company, Alphabet (GOOG).

Uber has been rocked by a steady stream of scandals and negative publicity in recent years, including revelations of questionable spy programs, a high-stakes technology lawsuit, claims of sexual harassment and discrimination and embarrassing leaks about executive conduct.The PR disasters culminated in CEO Travis Kalanick taking an indefinite leave of absence this week and promises of bold reform that largely ignored the ride-hailing company’s strained relationship with drivers.Embattled Uber CEO Travis Kalanick takes indefinite leave of absence Read moreHere is a timeline of some of the most consequential controversies.