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Zoology

The reason why giant pandas gain weight on a vegetarian diet

Giant pandas only feed on high-fiber bamboo, but they can still maintain a round posture. A new study published in the Cell report found that giant pandas show seasonal changes in their intestinal flora, helping them gain weight and store more fat during nutrient-rich bamboo shoots to adapt to the season when they can only chew bamboo leaves.

Surroundings

Geochemical pollution has broken through the stable critical value.

At present, there are about 350000 chemical compounds on the global market, including plastics, pesticides, antibiotics and so on. A large number of such substances enter the environment every year. " "Chemical pollution" is listed as one of the nine indicators of the planetary boundary model. The other eight are climate change, nitrogen and phosphorus cycle, air pollution, land transfer, ozone depletion, fresh water intake, ocean acidification and biodiversity loss, any of which is breached, it will bring irreversible damage to the earth's ecosystem. However, the specific impact of "chemical pollution" is not clear. Recently, a study on Science and Technology evaluated it quantitatively for the first time.

The study points out that the number of artificially produced chemicals has increased 50-fold since 1950 and is expected to triple current levels by 2050. Among them, the production of plastics increased by 79% in 2000-2015, and about 80% of plastics eventually entered the environment, and more secondary compounds may be released as they degrade. The assessment shows that chemical pollution, like land transfer, nitrogen and phosphorus cycling, climate change and biodiversity loss, has far exceeded the stable threshold. Scientists call for measures to be taken to reduce chemical pollution.

Material science

The influence of quantitative Star chain satellites on Astronomical observation

SpaceX's "Star chain" Internet service requires a dense cluster of satellites in orbit to provide low-latency network connectivity. At present, there are more than 1500 satellites in orbit in the whole star chain system. Astronomers worry that these satellites may leave stripes in telescope images, hampering scientific observations. To quantify the impact of the star chain, a team of researchers studied images taken by the Zwiki transient device (Zwicky Transient Facility, ZTF) at the Palomar Observatory (Palomar Observatory). The results were recently published in the Astrophysical Journal Newsletter.

The researchers found that between November 2019 and September 2021, 5301 satellite stripes appeared in images taken by ZTF. These stripes are most pronounced in dusk observations, which take place at dawn or dusk, and near-Earth asteroids in the sky can be found close to the sun. The researchers estimate that 0.5 per cent of ZTF's dusk images were affected in 2019, compared with 20 per cent now, and that almost all ZTF dusk images will contain at least one stripe after the future chain has 10, 000 satellites. The researchers said that despite the increase in image stripes, the operation of the ZTF was not strongly affected. Astronomers can also develop software to predict the position of chain satellites to avoid arranging observations when the satellite may be in the field of view.

Planetary science

Curiosity finds new clues to organic matter on Mars

NASA's Curiosity rover landed on Mars on Aug. 6, 2012 and has been collecting samples from Gale Crater and sending the results back to Earth for researchers to interpret. After analyzing carbon isotopes in sediment samples collected from six locations, the researchers found that some of the samples were enriched with carbon 12. The researchers give three explanations for this, one of which is biological. The study was recently published in the Proceedings of the National Academy of Sciences.

Compared with previous measurements of Martian meteorites and atmosphere, nearly half of Curiosity's samples are rich in carbon 12. On Earth, organisms give priority to carbon 12 in their metabolism, so the enrichment of this isotope in ancient Martian rocks can be interpreted as the result of biological processes. But the researchers say the current understanding of the Martian carbon cycle is not enough to confirm this hypothesis. The researchers suggest that the enrichment of carbon 12 may come from cosmic dust clouds or the conversion of carbon dioxide to organic compounds such as formaldehyde under ultraviolet light. All three explanations are consistent with current data, and more evidence is needed to judge whether it is right or wrong in the future.

Geoscience

Volcanic activity is the main cause of the mass extinction at the end of the Triassic.

About 200 million years ago, a mass extinction event occurred at the end of the Triassic. It is generally believed that this is related to the large-scale volcanic eruption in the Mid-Atlantic igneous Province (CAMP). However, there is no strong evidence to support the relationship between volcanism, carbon isotope drift and continental chemical weathering.

In a meta-analysis of the randomized, placebo-controlled COVID-19 vaccine trial, the researchers analyzed data from 12 COVID-19 vaccine clinical trials, including 22,578 placebo recipients and 22,802 vaccine receivers. the probability of adverse events was compared between vaccinated and placebo-injected volunteers. After the first injection, more than 35% of placebo recipients had systemic adverse events, of which fever with headache or fatigue was the most common. After the first injection, 46% of vaccine recipients experienced at least one systemic adverse event.

Considering that many adverse events also occurred in the placebo group, the researchers believe that 76% of all adverse events in the vaccine group were caused by the anti-placebo effect (patients do not believe that the treatment is effective and may worsen the condition). After the second injection, systemic adverse events decreased to 32% in the placebo group, compared with 61% of vaccinated participants. The researchers found that 52% of the adverse events reported by the vaccine group after the second vaccination were caused by the anti-placebo effect. The findings are published in the journal JAMA Network Open.