Январь 2019 г.

Российская наука и мир (по материалам зарубежной электронной прессы)

CONTENTS / ОГЛАВЛЕНИЕ


• The periodic table is 150 - but it could have looked very different
• Russia continues work on plasma engine for superfast space travel
• Anxiety-depressive disorder changes brain gene activity
• Russian scientists have found the key factor of epileptic seizures in rats
• The chill of U.S.-Russia relations creeps into space
• China, Russia, Mongolia jointly protect Siberian crane
• Molecular machinery that makes potent antibiotic revealed after decades of research
• Russia and Serbia to cooperate in nuclear power
• Mysterious lunar dust clouds, finally explained by scientists
• EU and Russia collaborate in new project on infectious diseases
• A storied Russian lab is trying to push the periodic table past its limits - and uncover exotic new elements
• High ceilings and a lovely view: Denisova Cave was home to a lost branch of humanity

ООН провозгласила 2019 год Международным годом Периодической таблицы химических элементов, созданной Дмитрием Менделеевым 150 лет назад. Гениальность этой идеи состояла даже не в том, чтобы упорядочить известные элементы в таблицу согласно их свойствам, а в том, чтобы оставить пустые места для еще неизвестных. Более того - Менделеев точно предсказал свойства некоторых из недостающих элементов.

The periodic table stares down from the walls of just about every chemistry lab. The credit for its creation generally goes to Dimitri Mendeleev, a Russian chemist who in 1869 wrote out the known elements (of which there were 63 at the time) on cards and then arranged them in columns and rows according to their chemical and physical properties. To celebrate the 150th anniversary of this pivotal moment in science, the UN has proclaimed 2019 to be the International Year of the Periodic Table.
But the periodic table didn't actually start with Mendeleev. Many had tinkered with arranging the elements. Decades before, chemist John Dalton tried to create a table as well as some rather interesting symbols for the elements (they didn't catch on). And just a few years before Mendeleev sat down with his deck of homemade cards, John Newlands also created a table sorting the elements by their properties.
Mendeleev's genius was in what he left out of his table. He recognised that certain elements were missing, yet to be discovered. So where Dalton, Newlands and others had laid out what was known, Mendeleev left space for the unknown. Even more amazingly, he accurately predicted the properties of the missing elements.
Notice the question marks in his table? For example, next to Al (aluminium) there's space for an unknown metal. Mendeleev foretold it would have an atomic mass of 68, a density of six grams per cubic centimetre and a very low melting point. Six years later Paul Émile Lecoq de Boisbaudran, isolated gallium and sure enough it slotted right into the gap with an atomic mass of 69.7, a density of 5.9g/cm³ and a melting point so low that it becomes liquid in your hand. Mendeleev did the same for scandium, germanium and technetium (which wasn't discovered until 1937, 30 years after his death).
At first glance Mendeleev's table doesn't look much like the one we are familiar with. For one thing, the modern table has a bunch of elements that Mendeleev overlooked (and failed to leave room for,) most notably the noble gases (such as helium, neon, argon). And the table is oriented differently to our modern version, with elements we now place together in columns arranged in rows.
But once you give Mendeleev's table a 90-degree turn, the similarity to the modern version becomes apparent. For example, the halogens - fluorine (F), chlorine (Cl), bromine (Br), and Iodine (I) (the J symbol in Mendeleev's table) - all appear next to one another. Today they are arranged in the table's 17th column (or group 17 as chemists prefer to call it).
It may seem a small leap from this to the familiar diagram but, years after Mendeleev's publications, there was plenty of experimentation with alternative layouts for the elements. Even before the table got its permanent right-angle flip, folks suggested some weird and wonderful twists.
One particularly striking example is Heinrich Baumhauer's spiral, published in 1870, with hydrogen at its centre and elements with increasing atomic mass spiralling outwards. The elements that fall on each of the wheel's spokes share common properties just as those in a column (group) do so in today's table. There was also Henry Basset's rather odd "dumb-bell" formulation of 1892.
Nevertheless, by the beginning of the 20th century, the table had settled down into a familiar horizontal format with the strikingly modern looking version from Heinrich Werner in 1905. For the first time, the noble gases appeared in their now familiar position on the far right of the table. Werner also tried to take a leaf out of Mendeleev's book by leaving gaps, although he rather overdid the guess work with suggestions for elements lighter than hydrogen and another sitting between hydrogen and helium (none of which exist).
Despite this rather modern looking table, there was still a bit of rearranging to be done. Particularly influential was Charles Janet's version. He took a physicist's approach to the table and used a newly discovered quantum theory to create a layout based on electron configurations. The resulting "left step" table is still preferred by many physicists. Interestingly, Janet also provided space for elements right up to number 120 despite only 92 being known at the time (we're only at 118 now).
The modern table is actually a direct evolution of Janet's version. The alkali metals (the group topped by lithium) and the alkaline earth metals (topped by beryllium) got shifted from far right to the far left to create a very wide looking (long form) periodic table. The problem with this format is that it doesn't fit nicely on a page or poster, so largely for aesthetic reasons the f-block elements are usually cut out and deposited below the main table. That's how we arrived at the table we recognise today.
That's not to say folks haven't tinkered with layouts, often as an attempt to highlight correlations between elements that aren't readily apparent in the conventional table. There are literally hundreds of variations (check out Mark Leach's database) with spirals and 3D versions being particularly popular, not to mention more tongue-in-cheek variants.
How about my own fusion of two iconic graphics, Mendeleev's table and Henry Beck's London Underground map?
Or the dizzy array of imitations that aim to give a science feel to categorising everything from beer to Disney characters, and my particular favourite "irrational nonsense." All of which go to show how the periodic table of elements has become the iconic symbol of science.

Физики из Института ядерной физики им. Г.И.Будкера СО РАН начинают следующую серию экспериментов на установке по удержанию плазмы в параметрах, необходимых для работы ракетного двигателя. Первая часть экспериментов показала, что возможность создания плазменной реактивной тяги в принципе возможна.

Scientists from Russia and around the world see plasma rocket technology as a crucial possible ingredient for speedy missions to Mars and beyond.
Physicists from the Budker Institute of Nuclear Physics of the Siberian branch of the Russian Academy of Sciences in Novosibirsk are preparing another round of experiments aimed at successfully harnessing the power of thermonuclear plasma for use in a rocket engine, institute deputy director Alexander Ivanov has told journalists. The experiments, which will begin later this month, will follow up on earlier successful tests which confirmed the feasibility of confining plasma in an experimental setup using parameters suitable for a rocket engine, Ivanov said. In late 2018, the institute began operation of a unique installation, known as the SMOLA, the Russian acronym for "Spiral-based Magnetic Open Trap", with the setup serving as the first step forward toward the creation of a fusion reactor.
The "plasma trap" allowed scientists to work on confining plasma in a linear magnetic system, which, it is hoped, can eventually help lead to the creation of prototype plasma engine suitable for space travel. "The first experiments showed that the effect exists. The space engine works, and the means to reducing plasma losses as well. Presently, standard equipment is installed. We are preparing to start experiments on it in January 2019 which should fully demonstrate its capabilities," Ivanov said.
According to the physicist, the current setup serves as a technology demonstrator, with scientists achieving a temperature of 100,000 degrees to form the plasma, and reaching a sufficient density to provide them with data suitable for further work on the creation of a plasma-based rocket engine.
In October, Energomash, a Russian power engineering company involved in the production of rocket engines, announced plans to build a high-powered electrode-less plasma rocket engine. Russia's Kurchatov Institute and the Chemical Automatics Design Bureau first reported that they were working on a plasma-based engine for space travel in 2016.
Other countries, including the United States, are engaged in similar developments. In 2015, NASA awarded private plasma rocket technology firm Ad Astra a contract on the creation of the
"Variable Specific Impulse Magnetoplasma Rocket" (VASIMR), with the proposed engines operating by heating pressurised gas to extremely high temperatures using radio waves and keeping the resulting plasma under control using magnetic fields.
Plasma-based rocket engines are one of several proposed options for human exploration of other planets in our solar system, and beyond it.

Нейробиологи Института цитологии и генетики СО РАН провели эксперимент на мышах, чтобы выяснить, как тревожно-депрессивное расстройство влияет на работу мозга. В результате подтвердилась гипотеза о том, что психоэмоциональный стресс вызывает нарушения энергетического обмена в мозге. Последствия этих нарушений могут проявляться при многих заболеваниях, в том числе шизофрении, биполярном расстройстве, депрессии.

Russian neuroscientists discovered that anxiety-depressive disorder in mice is associated with impaired energy metabolism in the brain.
The obtained data provides a fresh look at the depression development mechanism and other psycho-emotional diseases formation. The results of the study supported by Russian Science Foundation are published in the BMC Neuroscience.
The World Health Organization claims that five out of 10 major causes of disability in most countries of the world are related to mental and behavioral disorders. Up to 95 percent of people with depression have a diagnosis of anxiety disorder.
As recent research shows. such conditions might be associated with mitochondria defects. These "energy stations" of cells are responsible for the formation of ATP molecules, which are necessary for most reactions in living organisms. Defects of mitochondria appear due to congenital mutations or adverse external conditions, violating the work of mitochondrial genes with no mutations. As a result, the amount of proteins encoded by these genes changes.
Neurobiologists from the Institute of Cytology and Genetics of the Siberian Branch of the Russian Academy of Sciences conducted an experiment on depression modeled in mice to find out whether some mitochondria defects in different brain parts accompany psycho-emotional disorders in animals.
In total, the study compared the work of 47 genes encoding numerous carrier proteins located on the inner membrane of the mitochondria.
"The results of this study confirm the findings of our previous works. It means that psycho-emotional disorders due to constant social conflicts cause severe mitochondrial dysfunction in the brain. The consequences of these disorders can be observed in many neurological and psychoemotional diseases, including depression, bipolar disorder and schizophrenia. A detailed study of the mechanisms of development of mitochondrial dysfunction may provide the key to new methods of treating these diseases," said Natalia Kudryavtseva, senior researcher at the Institute of Cytology and Genetics of the SB RAS.
Scientists conducted experiments on mice placed in terms of social conflict, triggering depression and anxiety. They compared how selected genes worked in this mice group with some control mice, who did not experience such a stress. It turned out that expression of most genes in the hypothalamus, the part of the brain that regulates stress reactions, has changed. Gene expression has also changed in the hippocampus, which plays a crucial role in memory formation, emotional reactions and new neurons formation.
These data show that in chronic social conflicts that lead to the development of anxiety-depressive disorder in animals, the work of mitochondria is disrupted in several parts of the brain.

Изучив сложное взаимодействие нервных сигналов в коре височной доли мозга крыс, российские ученые определили ключевой фактор, ведущий к эпилептическим припадкам.

The scientists studied the complex changes in the temporal lobe cortex of a rat brain during prolonged epileptic seizes to identify the key factor leading to the seizures. The work has been published in Frontiers in Cellular Neuroscience.
Epistatus is the condition where a person subject to epilepsy experiences seizures which follow each other after a short time. The condition is considered to be particularly dangerous. Although scientists know that this is caused by an excessive excitation of neurons in the brain, the reason for such neuron activity is unclear.
The difficulty of analysing individual neuron signals
Anton Chizhov is a doctor of physical and mathematical sciences, senior researcher at the Ioffe Institute of RAS, and Leading Researcher at Sechenov Institute of Evolutionary Physiology and Biochemistry. Chizhov explained: "Neurons send each other signals that can be excitatory or inhibitory, depending on the type of target receptor on the cell membrane. For example, the first are those that react to glutamate and its analogues, the second are sensitive to gamma-aminobutyric acid or GABA. Yet GABA receptors of those suffering with the epilepsy also become exciting. There lies the main research difficulty: when several signals act on the neuron at once it is very difficult to assess their individual contribution."
The key mechanism causing epileptic seizures
The researchers investigated the signalling processes in the cortex of the temporal lobe before and after the rat epileptic seizures. They examined the effect of amino acids on receptors of all major types. They found that each of the components of the signal after epileptic electrical discharges becomes stronger and longer.
In order to find out what happened as a result of affecting only one amplified signal on the remaining paths, the team created a mathematical model of interacting nerve cells system.
The results showed that only the conductivity of the AMPA receptors in the network of neurons significantly changes. This leads to stronger excitation of all neurons and stronger synaptic signals recorded on one nerve cell. Chizhov added: "Further studies showed that this is the mechanism of synaptic plasticity with the incorporation of new calcium-permeable AMPA receptors into the cell membranes. Under normal conditions, such a process in the brain is associated with memory and learning, but under pathological conditions it leads to an excitability increase up to tens of minutes. Therefore, the risk of a new convulsive discharge rises, which may lead to pathology fixation."
Chizhov concluded: "Knowing that embedding calcium-permeable AMPA receptors leads to the consolidation of seizure activity, we can develop new antiepileptic drugs."

Несмотря на расхождение политических интересов, в космосе США и Россия пока вполне ладят. Однако политика способна подпортить любые отношения. В статье кратко рассматривается история сотрудничества двух стран в области освоения космоса с 1962 года до наших дней - вплоть до октябрьского падения «Союза» и последнего инцидента со срывом визита главы «Роскосмоса» в США.

On the afternoon of the failed launch, Jim Bridenstine of NASA and Dmitry Rogozin of Roscosmos had only known each other for a few days. Less than one mile from the launchpad, the heads of the American and Russian space agencies watched as the Soyuz system lofted the crew, one man from each country, into the blue sky over Kazakhstan.
But then, inside the crew capsule, alarms blared and emergency lights flashed. Instead of climbing into space, the capsule began to plunge back to Earth. In those stressful moments - before the capsule parachuted gently to the ground, before rescue crews arrived, before the would-be space travelers reunited with their family - each official considered what he might say if the failed launch ended in tragedy.
"If we're going to strengthen the partnership with the United States and Russia on space exploration, I think this was probably one way to do it," Bridenstine told me later, after he had returned to the United States. "Everybody became a lot closer on this day."
On the ground, the United States and Russia might have conflicting interests, but in space, 250 miles above Earth, they get along nicely. On the International Space Station, American astronauts and Russian cosmonauts share meals, routines, and a stunning view of our little planet. That same spirit of cooperation characterized the handling of the failed launch in October - the quick rescue response, the careful investigation of hardware, the eventual return to spaceflight less than two months later - and after Bridenstine's visit to Russia, he sought to reciprocate the invitation. Bridenstine had addressed Rogozin's alma mater, Moscow State University, and he suggested that in early 2019 Rogozin deliver a speech at his own, Rice University in Texas.
But even in a bromance as sunny as this one, sometimes politics finds a way to creep in, and Bridenstine rescinded his invitation. And according to Russian media, Rogozin isn't happy about it. Some current members of Congress and former national-security officials, mostly Democrats, saw the proposed visit as a mistake, Politico reported, and more lawmakers soon joined the chorus of opposition. The issue: Rogozin is not a typical space-agency official. He's an outspoken nationalist and a former deputy prime minister to Vladimir Putin who was sanctioned by the United States in 2014 for his involvement in the Ukraine crisis. Those strictures bar Rogozin from entering the United States, and here was Bridenstine, inviting Rogozin to an American campus and telling Russian media that he had convinced the Treasury Department to temporarily lift the sanctions.
"Rice University is located on the same street as the Johnson Space Flight Center, so I think everything will work out," Bridenstine said while in Russia, according to TASS, the state-run Russian news agency.
Earlier in 2018, another sanctioned Russian official, Sergey Naryshkin, the head of Russia's foreign-intelligence service, had come to Washington for a secretive meeting with then-CIA Director Mike Pompeo. Democratic lawmakers protested, accusing Donald Trump's administration of undermining U.S. policy. But a meeting about space exploration must have seemed less fraught than one on counterterrorism. According to The Washington Post, Bridenstine, a former member of Congress himself, said he didn't consult with the White House about inviting - and disinviting - Rogozin. He had hoped they could have "a strong working relationship that was kept separate from geopolitics," he said.
Space exploration is indeed insulated at times from politics, but it is not immune. In the middle of the 20th century, when nations began trying to reach orbit, space policy was foreign policy, thanks to the two-faced nature of the effort; rockets could launch both science instruments and bombs. But even as the focus of space policy has shifted to scientific discovery, world events and political changes have often derailed the United States' and Russia's best intentions.
As early as 1962, at the height of the space race between the United States and the Soviet Union, President John F. Kennedy and Premier Nikita Khrushchev exchanged letters about working together on uncomplicated space matters, such as weather satellites. But earnest cooperation didn't emerge until 1970, after Americans had landed on the moon and there was little left to compete over. President Richard Nixon had a new policy of closer relations with the Soviet Union, and he thought an international space project would be a political winner. (The world may have Hollywood to thank for this, too: According to historians, the Soviets warmed up to the idea after U.S. officials invoked Marooned, the 1969 film in which Soviet cosmonauts help rescue stranded American astronauts).
Soon, talks led to a high-flying maneuver between American and Soviet spacecraft in 1975. Two capsules launched 10,000 miles apart, rendezvoused in space, and locked onto each other somewhere over the Atlantic Ocean. Astronauts and cosmonauts on either side opened the hatches and exchanged handshakes.
The mission was heralded as a historic moment of unity between spacefaring nations, and plans for collaboration picked up. Officials discussed the possibility of docking an American launch vehicle, the Space Shuttle, to the Russian space station, Salyut. But the election of Jimmy Carter slowed these plans. Unlike his predecessor, Carter disliked the idea of exchanging technical information. Then, in 1979, the Soviet Union invaded Afghanistan, and by the next summer the U.S. government was boycotting the Olympic Games in Moscow instead of brainstorming space missions.
Only after the dissolution of the Soviet Union did the most significant partnerships begin to take shape. In the early 1990s, the United States sought to build an international space station and invited Russia to join, along with Japan, Canada, and nine European nations. It was a self-serving decision; while showing support for a country in crisis, the United States would also gain access to impressive space technology, reduce costs, and employ former Soviet scientists and engineers who might otherwise work for enemy governments. That politically motivated choice, though, has led to decades of productive collaboration. Today the International Space Station has been continuously occupied, by rotating crews from both nations, for 18 years.
The American-Russian partnership was tested in the spring of 2014, though. After Russia's unlawful annexation of Crimea, the United States cut Putin out of global meetings and imposed punitive measures against his cronies. The disintegrating diplomatic relations raised concerns about the International Space Station. By then, the space shuttles that had transported Americans to space for decades were sitting in museums. The U.S. government now relied on the Russian Soyuz system, which cost American taxpayers $70 million a seat. NASA officials, flooded with questions, tried to assuage concerns, while Rogozin, in response to U.S. sanctions prohibiting work with Russian aerospace companies, wrote, "After analyzing the sanctions against our space industry, I suggest the U.S. delivers its astronauts to the ISS with a trampoline."
Before he traveled to Russia last year, Bridenstine was asked about this and other inflammatory tweets, including one in which Rogozin, annoyed that the United States had asked Romania to bar his plane from entering the country's airspace, joked that he would fly in on a bomber next time. Bridenstine downplayed Rogozin's combative remarks as the grit of any elected official, whether in the House of Representatives or the Duma. "Some of his language has historically been aggressive about the United States," he told SpaceNews. "Some of my language has been aggressive about activities of Russia."
Bridenstine's professional relationship with Rogozin began with a beguiling incident last summer. The International Space Station crew discovered a tiny hole in the Russian segment that was leaking pressurized air into space. It appeared to have been drilled. While Russian officials investigated, Rogozin speculated to the press: "What was it: a defect, or some intentional acts? Where were these acts carried out? On the Earth or already on the orbit? Yet again, I am saying: We are not dismissing anything."
The remarks quickly mutated into rumors of sabotage. Bridenstine and Rogozin scheduled a phone call, their first, and released a joint statement that promised no further speculation until an investigation was complete. Russian cosmonauts patched up the hole and even conducted a spacewalk to investigate it, but the cause remains unknown.
After Bridenstine's bungled invitation to Rogozin, though, the burgeoning relationship between the space-agency leaders may be under strain. A Roscosmos spokesperson told Russian media that Bridenstine hadn't talked to Roscosmos before the Post ran a story about Bridenstine's decision to cancel. Rogozin criticized the decision in a television interview on Thursday, according to The Moscow Times, calling it a "disgrace" and "complete international lawlessness." "We are waiting for an explanation," he said, adding that Bridenstine is welcome to return to Russia.
The nasa administrator's office did not respond to a request for comment on this claim.
This tension is particularly awkward in light of the precarious future of American spaceflight. Today Russia has leverage. The U.S. government still pays to launch nasa astronauts to the ISS, at $80 million a seat now. This arrangement has persisted far longer than American politicians would like, and in 2014, nasa awarded two American companies, Boeing and SpaceX, billions of dollars to develop transportation systems that would launch from U.S. soil. This effort, known as the Commercial Crew Program, is scheduled to finally get off the ground this year. The first SpaceX test flight, without a crew, is expected in February. If those flights go well, the United States could ditch its reliance on Russia.
Meanwhile, on the ISS, it's business as usual. The current residents include an American and a Russian, working together, sharing meals, and splitting housekeeping chores such as vacuuming while their respective governments feud over matters from trade tariffs to election interference. Someday, like previous space stations, the ISS may be abandoned and deliberately plunged into the ocean. Or if future generations come up with some way to preserve it, perhaps in an orbiting museum, the ISS may keep circling Earth for centuries. Whether the station will be considered a vestige of long-lost cooperation or a mark of continued partnership depends on what happens below.

Китай, Россия и Монголия подписали меморандум о сотрудничестве в области исследования и охраны белого журавля (стерха), внесенного в Красную книгу как находящегося под угрозой исчезновения. Согласно меморандуму, российская сторона, представленная Институтом биологических проблем криолитозоны СО РАН и Институтом водных и экологических проблем ДвО РАН, сосредоточится на исследовании гнездового ареала журавля.

Six organizations from China, Russia and Mongolia signed a Memorandum of Understanding (MOU) on the conservation of the Siberian crane Thursday in east China's Jiangxi Province. Also known as the Siberian white crane, or the snow crane, the species is rated as critically endangered on the International Union for Conservation of Nature (IUCN) Red List.
The six organizations - the School of Nature Conservation of Beijing Forestry University, a Siberian cranes protection center in the city of Nanchang, two institutes of the Russian Academy of Sciences, a Mongolian bird conservation center and a nature reserve administration in Dornod Province - signed the MOU of Siberian Crane Research and Conservation in Nanchang, capital of Jiangxi.
Guo Yumin, a professor with the Beijing Forestry University, said that all parties decided to join hands to protect the Siberian crane after multiple discussions. The participants will work together to collect and share scientific data such as breeding areas, population size and different habitats.
According to the MOU, the Russian side will focus on the investigation of the breeding areas of Siberian crane, while the Chinese side is mainly responsible for the investigation of the bird's winter area, and the Mongolian side will carry out research on Siberian cranes in the summer area.
Nikolai Ivanovich Germogenov, director of the Institute of Biology of the Problem of Cryolithozone of the Siberian Branch of the Russian Academy of Sciences, said the MOU was a sign of great progress, helping make the cooperation between the three countries more flexible.
The world population of Siberian crane is estimated at about 3,600.
There are three migration routes for Siberian crane - the eastern, western and central route. The eastern populations migrate during winter to China via Russia and Mongolia. But the western and central populations have declined drastically over the past 20 years due to hunting along their migration routes and habitat degradation.

Ученые из США, России, Польши и Великобритании выяснили, каким образом фермент McbBCD «конструирует» из молекул пептидов мощный антибиотик микроцин B17. Понимание механизма этого процесса позволит создавать новые типы пептидных соединений и новые антибиотики на их основе.

Scientists at Rutgers and universities in Russia, Poland and England have solved a nearly 30-year mystery - how the molecular machinery works in an enzyme that makes a potent antibiotic.
The findings, which appear in the journal Molecular Cell, provide the tools to design new antibiotics, anticancer drugs and other therapeutics.
The potent natural antibiotic, microcin B17, kills harmful E. coli bacteria. Microbial resistance to antibiotics- due to their overuse and misuse - is one of the biggest threats facing humanity, and there's an urgent need to find new drugs. Natural antibiotics that evolved over eons represent an attractive option to overcome resistance.
The scientists studied a molecular machine: an enzyme (protein) called McbBCD. The enzyme makes microcin B17 from a smaller protein known as a peptide. Scientists have known about microcin B17 and its unusual chemical structure for decades, but they did not understand the molecular machinery that makes it until now.
The scientists found that the enzyme triggers two chemical reactions that produce several chemical "cycles" required for antibacterial activity, according to senior author Konstantin Severinov, a principal investigator at the Waksman Institute of Microbiology and professor of molecular biology and biochemistry at Rutgers University-New Brunswick.
"Our research allows rational design of new peptide compounds that could become treatments ranging from antimicrobials to anticancer drugs," Severinov said. "There may be a trove of new antibiotics that could be made from peptides, using enzyme machines like McbBCD as a production tool."
The international team included scientists at the Skolkovo Institute of Science and Technology in Russia; Russian Academy of Sciences in Russia; Jagiellonian University in Poland; John Innes Centre in England; and Lomonosov Moscow State University in Russia.

Россия и Сербия подписали межправительственное соглашение о сотрудничестве в области ядерной энергетики и совместное заявление о стратегическом партнерстве по созданию центра ядерной науки, технологий и инноваций.

Russia and Serbia have signed an intergovernmental agreement on cooperation in nuclear energy and a joint statement on strategic partnership for the construction of a centre of nuclear science, technology and innovation.
They were signed in Belgrade by Alexey Likhachov, director general of Russian state nuclear corporation Rosatom, and Nenad Popovich, Serbian minister of innovation and technological development, during a ceremony also attended by the Russian and Serbia presidents, Vladimir Putin and Alexander Vucic.
"Today we are laying a solid foundation for the development of high technologies in Serbia for many years to come," Popovich said. "Improving economic efficiency, developing agriculture, medicine, education and quality of life are difficult to imagine without the use of the peaceful atom. Signing the intergovernmental agreement marks the beginning of close and substantive cooperation in the field of innovation, digital, scientific and technical cooperation with our historical partner - Russia," he added.
The intergovernmental agreement establishes a wide range of cooperation areas between the two countries, Rosatom said. These include, but are not limited to: assistance in the creation and improvement of nuclear energy infrastructure in Serbia; the design, construction and modernisation of nuclear research reactors; development of nuclear medicine; implementation of fundamental and applied research in the field of nuclear energy; innovations, new technologies and modern digital technologies in the field of nuclear energy; radiation technologies application in agriculture, industry; and education, training and retraining of specialists for the nuclear industry.
"Serbia has unique potential and experience in the development and use of nuclear technologies," Likhachov said. "We have identified projects that will combine the human and technical competencies of Russia and Serbia. In particular, the implementation of a project to build a centre of nuclear science, technology and innovation will not only give a powerful impetus to bilateral cooperation between Russia and Serbia in a number of innovative areas, including medicine, industry and agriculture, but will also serve as a platform for cooperation at the level of the entire Central European region. Of course, all the projects will strictly comply with the highest standards of nuclear and radiation safety, taking into account the central role of the International Atomic Energy Agency in the development of such norms and standards," he added.
The intergovernmental agreement was signed as a follow-up to the joint statement on the principles of cooperation in the field of innovation and technological development in the use of nuclear energy for peaceful purposes, which was signed in May last year during the AtomExpo conference and exhibition in Sochi, Russia.

Российские астрофизики установили происхождение плазменно-пылевых облаков на Луне. Причина их появления - падение метеоритов, в результате чего образуется ударная волна и в экзосферу Луны выбрасываются частицы сыпучего лунного грунта реголита, а также капли расплава. Благодаря солнечному ветру частицы приобретают электрический заряд и образуют облака.

According to a new study carried out by Russian researchers from the Higher School of Economics and Space Research Institute, the formation of mysterious lunar dust clouds might be due to meteoroid impacts on the surface of the Moon. The research was issued recently in JETP Letters, and an excerpt of the study went live on EurekAlert.
"The collision of a meteoroid with the surface of the Moon greatly changes the properties of the surrounding dusty plasma system by throwing a large quantity of lunar soil-regolith debris - dust particles measuring 10-100 microns - into the otherwise relatively unsullied exosphere," the researchers said on EurekAlert.
About four years ago, astronomers from the Garden Observatory in Gordola, in Switzerland, observed the phenomenon of lunar dust clouds after e meteorite collided with the Moon. Back then, an international team of scientists studied the event and noticed the occurrence of two clouds of unknown composition.
Scientists Explained The Mysterious Lunar Dust Clouds
The Russian scientists from the Higher School of Economics, Space Research Institute (IKI), Moscow Institute of Physics and Technology, Sternberg Astronomical Institute, and Far Eastern Federal University explained that a meteoroid impact with the Moon is generating a massive shockwave, throwing up the regolith (lunar dust) and molten lunar soil into free space.
The fragments electrize due to solar winds and two dusty plasma clouds form. One is made of regolith, while the other consists of hardened droplets of molten material. Accordingly, mysterious lunar dust clouds that astronomers observed several times by now form due to meteoroid impacts.
"Lunar dust is a significant risk factor for spacecraft, equipment, and the astronauts' health. Equipment covered with dust can malfunction. Astronauts carry dust on their spacesuits into the lunar module where it becomes suspended weightlessly in the air, causing them to inhale the particles during their entire return trip to Earth. Therefore, understanding the mechanism by which dusty plasma clouds are formed is important for ensuring the safety of space flights to the Moon," said Sergey Popel, the study's co-author.

Ученые Евросоюза и России в рамках совместного проекта будут проводить исследования, направленные на изучение и предотвращение распространения таких заболеваний как ВИЧ, гепатит С и туберкулез, а также разработку оптимальных методов лечения. Интервью с одним из инициаторов проекта, профессором Каролинского института (Швеция) Андерсом Сеннерборгом.

A new EU project on the theme of HIV, hepatitis C and tuberculosis is a door opener for collaboration between researchers from EU countries and Russia. One of the project's initiators is Anders Sönnerborg, Professor of Clinical Virology and Infectious Diseases at KI's Departments of Laboratory Medicine, and Medicine Huddinge. The project Common Actions Against HIV/TBC/HCV Across the Regions of Europe (CARE) will mainly focus on the spread of the infections and resistance to treatment.
Tell us more about the research you'll be doing.
"It's generally about understanding and preventing the spread of HIV, hepatitis C and tuberculosis in Europe and Russia, with emphasis on counteracting development of multi-resistance to TB and HIV. There's a high rate of treatment-resistant tuberculosis in Russia and we are afraid that a similar scenario may arise also for HIV. We'll compare data from different patient groups in EU and Russia to learn from each other as well as developing methods for the identification of mechanisms of drug resistance. The long-term goal is to describe approaches for optimal treatment in all three areas and also to establish a research infrastructure which allows a continuation of research collaboration between EU and Russia after the project end."
What are your and KI's roles in the project?
"We're in charge of the HIV part and will be studying how the virus spreads and what the different viral strains look like. There's also the issue of resistance when it comes to HIV, too. The virus is constantly mutating and we want to compare the different strains circulating in Europe and Russia. The WHO now recommends a triple therapy in which a new drug, integrase inhibitors, is added. We want to see how any resistance can emerge to this drug and the consequences thereof."
You were one of the project's initiators. What difference might this make further down the line?
"Our project scored maximum points at the reviews of both EU and the Russian Ministry of Science and Education which is promising for the long-term sustainability. The idea is to set up a common infrastructure and contacts and networks for future research. The aim is to establish a research partnership between the EU and Russia for the field that can continue after this initial project phase. The project we're now running is scheduled to last two years, forming a platform for continuing knowledge-exchange and data comparison and I am convinced that KI will play a role."
Can you say more about the background and how the new collaboration is structured?
"Presently Russia can only exceptionally be a partner in EU-sponsored projects. This new innovative call is structured along two parallel processes. The EU and the Russian ministry of science and education are in charge of and finance their respective parts. These parts are combined into one project, so we're mutually dependent on each other in our research. The project also involves researchers from Georgia, Moldavia and Ukraine, as well as from EU countries.
Why study these issues now?
"We need to know about how these three infections spread and to avoid resistance problems in the future. Not only do they spread quickly, but more people are travelling more often between countries."

Репортаж из Лаборатории ядерных реакций имени Г.Н.Флерова ОИЯИ (Дубна), где идет работа по синтезу 119-го и 120-го элементов таблицы Менделеева - первых в 8-м периоде.

From certain angles, the Flerov Laboratory of Nuclear Reactions here looks more like an auto repair shop than a legendary scientific institute. Scientists in dirty blue smocks walk around while an oil pump thumps out a techno beat. Tables are strewn with bolts and cleaning fluids, including a vodka bottle half full of ethanol. And spare parts are everywhere - bins, shelves, whole walls full of metal whatsits in all manner of disrepair.
All that stuff serves the lab's six particle accelerators, some of which resemble huge mechanical caterpillars, with dozens of tractor-green segments winding through entire rooms. Or multiple rooms: When equipment doesn't fit, researchers knock holes in walls and thread things through the concrete. Seeing the whole of an accelerator requires some serious gymnastika, scaling perilously steep stairs and dodging anacondas of hanging wires. The pipes you duck under bear warning signs to watch out - not for your head, but for the equipment. At Flerov, particles have the right of way.
Deservedly so. In various iterations, these accelerators have produced nine new elements on the periodic table over the past half-century, including the five heaviest known elements, up to number 118.
The man leading that work is physicist Yuri Oganessian, who has been at Flerov since Nikita Khrushchev signed orders in 1956 to establish a secret nuclear lab in the birch forests here, 2 hours north of Moscow. Oganessian, 85, is a short man with bushy white hair whose voice squeaks when he gets excited. He wanted to study architecture in college until a bureaucratic snafu diverted him into physics. He still misses his first love: "I really need something visual with my science. I feel this deficit."
Fittingly, no living person has shaped the architecture of the periodic table more than he has, which is why element 118 is called oganesson. And he's not done yet. To push the table further, the lab has built a new $60 million facility, dubbed the Superheavy Element Factory (SHEF), which will start to hunt for element 119, 120, or both, this spring.
Some scientists argue that finding new elements is not worth the money, especially when those atoms are inherently unstable and will disappear in a blink. "I personally don't find it exciting, as a scientist, just to produce more short-lived elements," says Witold Nazarewicz, a physicist who studies nuclear structure at Michigan State University in East Lansing.
But to element hunters, the payoff is compelling. The new elements would extend the table - now seven rows deep - to an eighth row, where some theories predict exotic traits will emerge. Elements in that row might even destroy the table's very periodicity because chemical and physical properties might not repeat at regular intervals anymore. Pushing further into the eighth row also could answer questions that scientists have wrestled with since Dmitri Mendeleev's day: How many elements exist? And how far does the table go?
The decision to build the SHEF was tough in some ways. Besides the high cost, constructing the "factory" meant abandoning the old accelerators - which produced so many new elements - to other projects. "Emotionally," Oganessian says, "it's not easy to take something [offline] that gave you a lot. But there is no other way forward."
The heaviest element found in any appreciable amount in nature is uranium, atomic number 92. (The atomic number refers to the number of protons in an atom's nucleus). Beyond that, scientists must create new elements in accelerators, usually by smashing a beam of light atoms into a target of heavy atoms. Every so often, the nuclei of the light and heavy atoms collide and fuse, and a new element is born. Slamming neon (element 10) into uranium, for example, yields nobelium (102).
But the odds of fusion (and survival) decrease markedly as atoms grow heavier because of increased repulsion between the positively charged nuclei, among other factors. Creating most elements in the superheavy realm (beyond 104) therefore requires special tricks. Oganessian developed one in the 1970s: cold fusion. Unrelated to the notorious nuclear power work of the 1980s, Oganessian's cold fusion involves uniting beam and target atoms that are more similar in size than those in traditional elementmaking. And rather than smashing them together, "We bring two nuclei together so that it is a 'soft touching,'" Oganessian says. Doing that is harder than it sounds because the beam and target nuclei are both positively charged and therefore repel each other. Incoming atoms need enough speed to overcome that repulsion, but not so much that they blow the resulting superheavy nucleus apart.
A team at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany, perfected Oganessian's technique and used it to create elements 107 through 112. But the method ran into limitations as the odds of fusion and survival dropped precipitously. Starting in 2003, a team at the RIKEN Institute in Wako, Japan, tried to use cold fusion to create element 113, firing zinc (element 30) onto bismuth (83). They got one atom the next year and another in 2005, which they celebrated in their control room with cheers, beers, and sake.
Then, the agony started. Needing one more atom to confirm the discovery, the RIKEN team reran the experiment in 2006 and 2007. None appeared. They tried again in 2008 and 2009. Nothing. Not until 2012 - 7 years later - did they detect another. "Honestly, we felt that we would be not lucky," remembers RIKEN nuclear chemist Hiromitsu Haba. "Only God knows the statistics." None of the atoms survived longer than 5 milliseconds before decaying.
Getting beyond 113 required a different approach, hot fusion, which Flerov scientists had developed in the late 1990s. Hot fusion uses higher beam energies and relies on a special isotope with a large excess of neutrons, calcium-48. (Neutrons stabilize a superheavy atom by diluting the repulsive force of protons, which would otherwise tear the nucleus apart). Calcium-48 is expensive - it must be laboriously isolated from natural calcium sources - at $250,000 per gram. But the investment paid off. RIKEN sweated for 9 years to find three atoms of 113. Dubna snagged that many atoms of 114 within 6 months, a discovery Oganessian and colleagues celebrated in their control room with cheers, beers, and shots of spirits.
At that point, producing the next few superheavies was largely arithmetic. Calcium is element 20, and calcium plus americium (element 95) yielded element 115. Calcium plus curium (96) yielded element 116, and so on. By 2010, Dubna - in collaboration with scientists at Lawrence Livermore National Laboratory in California and Oak Ridge National Laboratory in Tennessee - had filled the periodic table's seventh row.
After 118, however, things stalled again. Fusion requires several milligrams of the target element, and producing enough einsteinium (element 99) to make element 119 is impossible with today's technology. Some researchers proposed replacing calcium-48 with titanium-50, which has two more protons, and then firing it at elements 97 and 98 to produce 119 and 120, respectively. But for technical reasons, the likelihood of fusion is just one-twentieth as high with titanium as with calcium. For most accelerators, that drops the odds of success into the realm of RIKEN's experiments to create 113 - God's statistics all over again.
The SHEF was built to overcome those obstacles. In contrast to the grease monkey feel of the older Flerov accelerators, the SHEF is pristine: Bubble wrap still covers the door handles, and for now the floors are spotless.
Overall, the SHEF is a fusion of the brawny and the delicate. The beam originates in an ion source and accelerator that stands two stories high, bigger than some dachas in town. The ion source fires off 6 trillion atoms per second, 10 to 20 times as many as other elementmaking accelerators. After twisting through a few 90° turns - the most compact arrangement in a tight space - the beam plummets into a massive cyclotron, whose very presence here is remarkable. The cyclotron's 1000-ton magnet was fabricated in 2014 in Kramatorsk, Ukraine, near the front line of the recent war with Russia, says Alexander Karpov, a Flerov physicist. The city endured heavy shelling and other military action then, and Karpov says lab personnel were nervous that the magnet would be damaged or destroyed.
After accelerating the beam to roughly one-tenth the speed of light, the cyclotron directs it toward the delicate part of the operation: micrometer-thin metallic foils with target atoms plated onto them. Those foils are mounted onto a disk roughly the size of a CD, which spins to keep cool. If it didn't, the beam would fry a hole in it.
If fusion occurs, the resulting superheavy atom sails through the foil. Unfortunately, the foil is so thin that gobs of other particles slip through as well, producing a blizzard of extraneous noise. That's when the separator comes into play. It consists of five magnets painted the same bright red as a fire truck and collectively weighing twice as much as one - 64 tons. Despite the bulk, the magnets are aligned to within 0.01 millimeters, and their fields are precise enough to filter out lighter atoms, including nearly all beam atoms, swerving them into a device called the beam dump.
The separator, like the beam source, gives the SHEF an advantage. Earlier separators were tuned to superheavy atoms with a narrow range of speed, charge, and direction; those that deviated too much ended up in the beam dump. The new separator is more generous, giving a pass to two to three times as many superheavy atoms.
After slaloming through the separator, an atom arrives at a silicon-germanium detector, which records the atom's position and time of arrival and then starts to monitor it. Superheavy atoms decay by emitting a series of alpha particles - bundles of two protons and two neutrons. Releasing an alpha changes the atom's identity: element 118 becomes 116, which becomes 114, and so on.
That decay chain is what allows scientists to identify, retroactively, which element they've created. Each alpha particle in the chain flies off with a characteristic energy. So if the detector spots an alpha with the right energy - and, crucially, sees that it emerged from the same point on the detector where a superheavy atom just landed - it begins to watch closely for more alphas.
To aid that search, the detector automatically shuts off the cyclotron beam to reduce the amount of cruft flying around. The shutdown also triggers a loud beep in the SHEF's control room, where a few probably bored scientists will be sitting. (On a recent visit to another control room here, two graduate students were watching a schlocky sci-fi monster flick). The bell is a moment of excitement amid the monotony.
It's also superfluous. Inside the detector, the atom will continue to shed alphas: In fact, several events in the decay chain will already have occurred before the scientists even register the sound. With superheavies, it's hard come, easy go. Only later - when the scientists comb through the raw data and match every detected alpha particle to a specific element in the decay chain - can they reconstruct which element they initially created.
The stronger beam and more generous separator should, in theory, cancel out the lower odds of titanium-50 fusion. That gives the Dubna team hope that atoms of 119 or 120 will soon reveal themselves. A team at RIKEN is also searching for 119, albeit using a different and perhaps harder method (firing vanadium, element 23, onto curium). Between the two labs, scientists are confident that 119 and 120 will appear somewhere within about 5 years.
It's the next 5 years that worry people. Creating elements heavier than 120 might be impossible with hot fusion. Detecting them will be equally hard: If the expected lifetimes drop too low, the atoms might not survive the 1-microsecond trip through the separator. They could decay midflight instead - ghost atoms that disappear without a trace.
Moving beyond 120, then, will probably require new approaches. "Multinucleon transfer reactions" would involve firing, say, uranium onto curium at relatively low speeds - another "soft touching." Their nuclei wouldn't fuse completely, but a chunk of one might break off and glom onto the other. Depending on the size of the chunk, scientists might even leap to much higher element numbers instead of inching along one atomic number at a time.
Such methods remain unproven, however. "Heavy-element scientists like to work one piece at a time," says Jacklyn Gates, leader of the heavy-element group at Lawrence Berkeley National Laboratory in California. And much beyond 120, she says, "We don't know enough to even know what to look for - what half-life to look for, what decay properties to look for."
Given those difficulties, some scientists propose ditching accelerators. In one approach, low-power nuclear blasts would induce fusion reactions in target atoms. That isn't as crazy as it sounds: Elements 99 and 100 were first identified in the fallout of atmospheric atomic bomb tests. Still, most scientists are skeptical of that approach given the obvious radiation hazards and the short lifetimes of superheavy atoms, which might expire before they could be sifted from the nuclear debris.
Other scientists suggest finding new elements the old-fashioned way: by hunting for them in nature. That was actually a popular pastime a few decades ago, as physicists scoured cosmic rays, meteorites, moon rocks, and even ancient shark teeth for superheavies. Nothing ever came of those projects. Nowadays, focus has shifted to supernova explosions and anomalous stars such as Przybylski's star, whose spectrum shows signs of einsteinium, which is otherwise never found in nature. Perhaps the star's hot, dense interior houses even heavier elements.
Still, there's no guarantee superheavy elements exist in nature. And the long dry spell - no new elements have been created since 2010 - worries some researchers. "If you look backwards over several decades," says Pekka Pyykkö, a theoretical chemist at the University of Helsinki, "people have made roughly one new element maybe every 3 years - until now." Today's barrenness could be the new normal.
Even if scientists can overcome the technical challenge of creating new elements, other questions remain: How many elements can exist, even hypothetically? How far could the periodic table go?
One prominent theory predicts an end at element 172. No one knows what will happen above that point, but for quantum mechanical reasons, an atom's nucleus might start to gobble up electrons and fuse them with protons, producing neutrons as a by-product. That process would continue until the proton count dropped back to 172, providing a hard cap on the atomic number. (And if that sounds weird, well, that's quantum mechanics).
Other research suggests elements will run out long before 172. As nuclei get larger, the repulsive force between protons becomes overwhelming. By general consensus, a nucleus must survive for at least 10^-14 seconds to count as a new element. Given how fragile elements in the 110s already are, heavier elements might struggle to hold on even that long. Some scientists predict that nuclei can overcome that problem by twisting into exotic shapes - hollow bubbles or even latticelike buckyballs. But other scientists doubt those shapes would be stable.
Which is a shame, because exciting things could happen in the 130s or 140s. In particular, the sine qua non of the periodic table - its periodicity - could break down completely.
In general, all elements within the same column of the table have similar chemical and physical properties. But that trend might not hold true forever. Scientists across the world have managed to probe the properties of single superheavy atoms by studying how they adhere to different materials. And the association between columns and chemical behavior already seems to be breaking down in the 110s.
Element 114, for instance, acts like a gas at room temperature, even though the element above it, lead, is about the most un-gas-like substance imaginable. Similarly, although element 118 falls into the noble gas column, theory predicts that it will readily attract electrons - something no other noble gas does. Those anomalies arise because of relativistic effects: The high, concentrated charge of a superheavy nucleus distorts the orbits of surrounding electrons, which affects how they behave and form bonds.
As Haba says, "The chemical properties of superheavy elements are very unique, and we cannot simply extrapolate." And although 114 and 118 seem to depart only modestly from expectations, even heavier elements could have wildly unexpected properties because relativistic effects will only grow larger as elements gain weight. So where should anomalous elements go? In the column where their atomic numbers say they should go or in a column with elements of similar properties? The answer depends on whom you ask. For some scientists, the table is primarily about underlying atomic structure, not chemical behavior. Deviations are therefore not allowed. Other researchers are more pragmatic. "The periodic table is more useful for telling me what the chemistry of an element is, so I would argue for changing it around," Gates says.
Pyykkö has pushed the idea of anomalous elements to its extreme, calculating theoretical properties for all elements through 172 and arranging them into a futuristic table. The result is jarring: At one point, the sequence of atomic numbers jumps backward from 164 to 139 and 140 before skipping ahead to 169 (see table, left). The bizarro table now hangs on his office wall.
"When I give talks," he says, "I usually joke that this periodic table should be enough for the rest of this century."
Beyond the divisions over the structure of the table, a deeper rift exists between people who think pursuing new elements is worthwhile and those who think it's a waste of time and resources. Gates voices her skepticism: "For elements 119 or 120, with our current technology, you're looking at years of beam time potentially for one atom - and what does that tell you?"
Still, she understands why some labs pursue new elements: "A new element is what makes people interested. … And it does help you get funding. I just don't think it's science that's driving the experiments. It's politics." Indeed, RIKEN's 9-year pursuit of element 113 resulted in a nice budget boost. And because 113 was the first element created in Asia, the scientists became folk heroes in Japan. Someone even published a manga comic book about their work.
Dubna scientists argue their work is not mere trophy hunting. Karpov - who owns four sports jackets and wears a different Russian-themed element lapel pin on each (dubnium, flerovium, moscovium, and oganesson) - says making new elements can verify theoretical predictions about their half-lives and other properties.
He and his colleagues will also try, during some experimental runs, to add neutrons to existing superheavy elements and produce longer-lived versions of them. Nazarewicz, skeptical of making new elements, sees the value in that. "I would like us to get more stable," he says. Tinkering with existing elements might even allow scientists to reach the island of stability - a supposed region of longer-lived superheavy elements - and study those elements' properties. If nothing else, the technologies used to make new elements can help produce radioisotopes for medicine and test how well satellite components withstand bombardment by particles.
Ultimately, though, the search for new elements is its own reward - l'art pour l'art. "There's a majesty to increasing the number of protons," Karpov says. "It's natural to come to a limit" and try to push beyond. Plus, he says with a smile, his moscovium lapel pin gleaming, "sometimes it is good to say you did something first."

Две международные группы ученых (Великобритания, Германия, Россия, Австралия) с помощью методов оптической датировки и радиоуглеродного анализа определили хронологию жизни обитателей Денисовой пещеры. Оказалось, что денисовцы заселились в пещеру первыми - почти 300 тысяч лет назад, а 100 тысяч лет спустя там появились неандертальцы.

Over the past decade, the Denisova Cave in Siberia has yielded some of the most fascinating fossils ever found. To the naked eye, they are not much to look at - a few teeth, bits of bone. But the fossils contain DNA dating back tens of thousands of years. That genetic material shows that Denisovans were a distinct branch of human evolution, a lost lineage. At some point in the distant past, the Denisovans disappeared - but not before interbreeding with modern humans. Today, people in places like East Asia and New Guinea still carry fragments of Denisovan DNA.
One of the biggest obstacles to understanding the Denisovans is their age. Standard methods for dating these fossils have left scientists perplexed.
"Everyone said, 'These Denisovans, we have no idea how old they are,'" said Katerina Douka, an archaeologist at the Max Planck Institute for the Science of Human History in Germany.
Over the past six years, Dr. Douka and other experts have been creating a sort of history of the Denisova Cave. They have dated 103 layers of sediment on the cave floor, as well as 50 items found in them, including bones, pieces of charcoal and tools.
The scientists unveiled this chronology in a pair of papers published on Wednesday. That timeline shows that humans occupied the cave for perhaps as long as 300,000 years. And it raises some intriguing hints that Denisovans may have been capable of sophisticated thought, on par with modern humans. In an accompanying commentary, Robin Dennell of the University of Exeter in England wrote that Dr. Douka and her colleagues have created "a rigorous and compelling timeline." Denisova Cave sits about 30 yards above the Anuy River. The cave has a large main chamber with a high ceiling; from there, passageways lead to smaller chambers. Over the past few hundred thousand years, sediment has slowly built up on the cave floor.
In the 1970s, Russian scientists began digging into that sediment, finding fossils of animals like hyenas and bears, fragments of humanlike bones and thousands of stone tools, as well as bracelets, beads and other ornaments. In 2010, researchers at the Max Planck Institute of Evolutionary Anthropology announced they had found DNA in teeth and bones from the cave. In addition to Denisovan DNA, they found a few bone fragments that contained Neanderthal DNA. By comparing the mutations in this DNA, the scientists got a better sense of how Denisovans and Neanderthals fit into the human family tree.
As it turned out, modern humans share a common ancestor with Denisovans and Neanderthals that lived roughly 600,000 years ago. Later - approximately 400,000 years ago - the Neanderthal and Denisovan lineages split. Ever since the digging began, Russian researchers have carefully mapped the sedimentary layers in which they found bones and tools. They tried to estimate the ages of the layers, but "the dates were all over the place," said Dr. Douka. She and her colleagues at the University of Oxford are experts on determining the age of carbon. Researchers from the University of Wollongong in Australia tried an alternate method called optical dating. The researchers combined results from the two methods to assemble a single chronology of the cave. The findings are largely in agreement: "It's definitely a unified story," said Zenobia Jacobs, an archaeologist at the University of Wollongong.
The earliest signs of human life in the cave - simple stone tools - are more than 287,000 years old. The tools alone cannot tell us if those first people were Denisovans or Neanderthals. But they are not the style known to be made by Neanderthals, suggesting Denisovans may have been the creators. It's not until about 200,000 years ago that the oldest Denisovan DNA comes to light. The researchers estimated it to be between 217,000 and 185,000 years old. A Neanderthal DNA sample comes from a layer that formed between 205,000 and 172,000 years ago. In the millenniums that followed, both Denisovans and Neanderthals left more genetic evidence in the cave. It may have been continually occupied for thousands of years by one group, then abandoned and reoccupied by others.
But Neanderthals and Denisovans must have overlapped at least once during those tens of thousands of years.
In August, researchers reported a bone fragment from a girl whose mother was a Neanderthal and father was a Denisovan. In the new study, researchers estimate that this hybrid child lived between 79,100 and 118,100 years ago.
The researchers found no Neanderthal remains in more recent layers of the cave floor - only Denisovan. A Denisovan tooth dates back to between 55,300 and 84,100 years ago; a Denisovan chip of bone is 51,600 to 76,200 years old.
Paradoxically, the most recent parts of the cave have yielded some of its biggest mysteries.
Starting around 45,000 years ago, new kinds of artifacts begin showing up in the cave floor. They include pointed pieces of bone, as well as ornaments like stone bracelets and beads. One possibility is that these new tools were made by newly arrived modern humans. Modern humans evolved in Africa and then expanded out to other continents. They may have made it to what is now Siberia: One human fossil discovered there dates to about 45,000 years ago. But Michael Shunkov, a co-author of the new studies and the director of Institute of Archaeology and Ethnography at the Russian Academy of Sciences, disagrees with that interpretation.
The sophisticated tools in the Denisova Cave show "no clear indications for outside influences," he said in an email. Instead, Dr. Shunkov believes that the Denisovans who occupied the cave for perhaps 250,000 years developed this technology on their own. One way to resolve this question would be to find human fossils from that period.
Dr. Douka and her colleagues have discovered a bone dating back between 45,900 and 50,000 years ago that contains humanlike proteins - but no DNA. It could belong to a modern human, a Neanderthal or a Denisovan. Researchers are scouring the cave floor for still more fossils. A fossil from around 45,000 years ago could be loaded with surprises. What if the ornaments from that period were made by hybrids of modern humans and Denisovans? "This dichotomy, that it has to be one or the other, is a little bit old-fashioned," Dr. Douka said.

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