Russia has brought a string of treason cases against scientists researching super-high flight speeds, an area that underpins its development of hypersonic missiles.
In the latest, physicist Anatoly Maslov was sentenced to 14 years on Tuesday.
President Vladimir Putin has boasted of Russia's prowess in hypersonic missiles and Moscow has acknowledged using them in the Ukraine war.
Here is a summary of the cases it has launched against scientists working in this sensitive field.
All three were top scientists at the Khristianovich Institute of Theoretical and Applied Mechanics (ITAM) in the Siberian city of Novosibirsk. Maslov and Shiplyuk were arrested in 2022, and Zvegintsev the following year. In a rare open letter a year ago, colleagues said the three men were innocent and the cases against them were damaging Russian science. Details of the charges are secret, but two people familiar with Shiplyuk's case have told Reuters he is accused of betraying secrets to China by handing over classified material at a conference there in 2017.
Galkin worked at another Siberian university and had co-authored papers with Zvegintsev and Shiplyuk. His arrest was reported in December 2023, but BBC Russian said he was actually detained in April of that year. It quoted his wife as saying she had told their grandchildren he was on a business trip.
Kuranov was handed a seven-year jail sentence for treason last month, after being accused of passing state secrets to foreign nationals. Maslov's lawyer, without naming Kuranov, said the case against Maslov had been based on testimony against him from another person who got a seven-year term. At the time of his arrest in 2021, Kuranov was the general director of the St Petersburg-based Hypersonic Systems Research Facility, where he oversaw work on a new version of a Soviet-era hypersonic aircraft dubbed Ayaks.
Both worked at TsAGI, the Central Aerohydrodynamic Institute based in Zhukovsky, near Moscow, where Gubanov was Golubkin's boss.
Gubanov, arrested in December 2020, had been working on an international project called HEXAFLY-INT to develop a hypersonic civil aircraft powered by hydrogen fuel. In October 2023 he was found guilty of handing over state secrets and sentenced to 12 years.
Golubkin, arrested in April 2021, was jailed for 12 years in June 2023 after being found guilty of passing secrets to a NATO member state. However, the verdict was annulled last month and a new trial ordered.
All three worked at TsNIIMash, a rocket and spacecraft center near Moscow which is a scientific subsidiary of space agency Roscosmos. Kudryavtsev was arrested on a treason charge in 2018, suspected of transferring secret information to a Belgian institute. He died of lung cancer in 2021, before the case came to trial.
Kovalyov, who worked with Kudryavtsev at TsNIIMash, was sentenced to seven years for treason in June 2020. He died of cancer in 2022.
Lapygin was convicted of treason in 2016 and sentenced to seven years, but was freed early in 2020.
