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Virus

New HIV variants with high virulence found in Europe

Human immunodeficiency virus (HIV) is one of the fastest mutating viruses known. Scientists have discovered a new strain of HIV in Europe, according to a new study in Science. This strain belongs to subtype B of HIV- 1, which is more virulent and contagious than other subtype B strains, and the disease occurs faster after infection, but the existing drugs are still effective.

The researchers analyzed 109 people infected with the strain and found that compared with those infected with other subtype B strains, the viral load in the blood of those infected with the new strain increased by 2.5 to 4.5 times, and the CD4+ T cell count decreased nearly twice as fast, indicating that HIV had damaged the immune system. Based on this, the researchers estimate that if untreated, people infected with the strain will develop within 2 to 3 years after diagnosis, while for other HIV strains, this usually takes 6 to 7 years. Genome analysis shows that the strain may have originated in the Netherlands in the 1990s and spread rapidly at the beginning of the 21st century, but its spread slowed down after 2010, which may be related to the Dutch HIV prevention and control policy. Due to the mutation of nearly 300 amino acid sites in the strain, it is difficult to determine the exact mechanism leading to the increase in virulence. However, the researchers said that the existing anti-HIV drugs are still effective for the strain, and it is very important to carry out extensive HIV detection, early diagnosis and early treatment.

Spaceflight

The International Space Station will retire in 2031 and crash into the South Pacific

NASA has announced plans to retire the International Space Station in 2031 and crash into an open ocean known as Nimo Point in the South Pacific. There is no land within 2700 kilometers of the Nimo point, and it is in the South Pacific circulation, so nutrients are difficult to reach and organisms are relatively scarce. Therefore, Nimo Point is the destination of a large number of scrapped spacecraft out of orbit, also known as the "spacecraft graveyard."

The International Space Station, a cooperative project of NASA, the European Space Agency, the Russian Federal Space Agency, the Canadian Space Agency and the Japan Aerospace Exploration Agency, began its launch in 1998, completed in 2011, and has been rotated by astronauts from 19 countries since 2000. The space station was scheduled to retire in 2024, but the White House announced at the end of last year that it planned to extend the operation of the International Space Station to 2030. NASA hopes that when the International Space Station is retired, it will be replaced by a commercial space station. (thepaper.cn)

Biology

CRISPR-Cas9 system is a powerful tool for gene editing and shows the potential to develop gene therapy, but it is necessary to ensure its safety in the treatment of diseases through gene editing. Recently, a study published in the journal Nature Communications shows that CRISPR-Cas9 gene editing may not only lead to unexpected mutations, but may also be passed on to future generations.

The researchers genetically edited the fertilized eggs of zebrafish and sequenced the genomes of more than 1100 individuals from the first and next generations of zebrafish. They found that in the first generation of zebrafish, 6% of individuals had structural mutations (that is, insertions or deletions of sequences containing at least 50 base pairs), both at the target and at the off-target site. In the next generation of zebrafish, 26% of individuals carry off-target mutations and 9% carry structural mutations. The researchers believe that before gene editing is carried out in clinical applications, adequate off-target and structural variation risk assessment should be carried out in advance to avoid unexpectedly significant consequences.

Astronomy

Man discovered a "stray" black hole for the first time

In 2011, the Hubble Space Telescope discovered a microgravitational lens event in the direction of the galactic nuclear sphere, which lasted 270 days and had a high magnification. At the same time, eight observations by the Hubble Space Telescope in six years confirmed that the observed target had a significant displacement relative to the stellar background, and the parallax caused by the earth's motion was also found in the ground observation, and the research team was able to determine that the microgravitational lens was caused by a celestial body about 5000 light-years from the earth with seven times the mass of the sun. The object that caused the gravitational lens does not glow itself, and its mass has exceeded the upper limit of the mass of white dwarfs and neutron stars, so it can only be a black hole. The team also measured the speed of the black hole relative to its interstellar space at about 45 kilometers per second, indicating that it was "kicked" by a supernova explosion during its formation.

Physics

The morphology of the melting ice depends on the temperature of the water.

Water is an unusual liquid, and its density does not reach its maximum at the freezing point, but at 4 degrees Celsius. Therefore, when the temperature is below 4 degrees Celsius, the water expands rather than shrinks, causing the ice to float on the surface. However, the effect of this property of water on the morphology of melting ice has not been studied before. recently, a study published in the physical Review KuaiBao said that the temperature of the surrounding water determines the morphology of the melting ice.

The researchers dipped icicles 15-20 centimeters long and several centimeters in diameter vertically in water with a temperature of 2 to 10 degrees Celsius, and kept the water temperature around the icicle constant. They found that when the temperature of the water is below 4 degrees Celsius, the icicles begin to melt from below, forming an inverted steeple; when the temperature is between 5 and 7 degrees Celsius, the melting ice becomes wavy; when the water temperature is higher than 7 degrees Celsius, the ice forms an upward spike. After simulation tests, they confirmed that these different shapes are caused by different buoyancy of water at different temperatures. For example, when the water temperature is about 4 degrees Celsius, the density of the colder water after melting is lower than that of the surrounding water, so it will be in the upper layer of the water, bringing the bottom of the icicle close to the hotter water, thus increasing the melting rate of the ice at the bottom. This study provides a new idea for understanding the impact of global warming on ice morphology.

Meteorology

768 kilometers! 17 seconds! Scientists measure the longest lightning in history