Global science

Material science

Successful development of high strength and toughness molybdenum alloy for outer space nuclear reactor

The space nuclear reactor has a broad application prospect in high-power earth orbit satellites and deep space exploration, but the materials in the space reactor need to be resistant to high temperature, neutron irradiation and other harsh conditions. Molybdenum and its alloys are key candidates for space reactors because of their high melting point and high thermal conductivity, but pure molybdenum has some problems such as low plasticity at room temperature and insufficient strength at high temperature. Recently, a study published in Acta Materialia has developed a high strength and toughness molybdenum alloy, which has obvious advantages in mechanics and radiation resistance compared with similar materials previously reported.

The researchers inserted zirconium carbide particles between molybdenum atoms by powder metallurgy and high temperature rotary forging to form molybdenum-zirconium carbide alloys. Zirconium carbide is a kind of carbide with high melting point and high strength, which can be used to improve the interfacial strength and high temperature stability of materials. In addition, the interstitial oxygen on the interface can significantly reduce the strength and ductility of the material, while zirconium carbide particles can absorb impurity oxygen, so it is beneficial to improve the stability and toughness of grain boundaries. After testing, it is found that the tensile strength of the alloy at room temperature is 928MPa and the elongation is 34.4%, which is 26% and twice higher than that of titanium-zirconium-molybdenum alloy which is widely used in industry. In addition, the tensile strength of molybdenum-zirconium carbide alloy is more than twice as high as that of molybdenum strengthened by oxide at 1200 ℃.

Medical science

Mechanism of cervical cancer induced by HPV and Chlamydia trachomatis

Cervical cancer patients are often co-infected with human papillomavirus (HPV) and Chlamydia trachomatis. However, the canceration rate of HPV infection is low, so scientists speculate that chlamydia trachomatis and HPV co-infection is an important factor in cervical cancer. However, because chlamydia rarely leaves DNA fragments and other residues in malignant cells, the specific mechanism of carcinogenesis induced by chlamydia is difficult to be clarified. A few days ago, a study published in the journal Nature Communications offers implications.

The researchers used healthy donor cells to create a model of cervical organs. After gene sequencing analysis, the researchers found that co-infection of HPV and Chlamydia trachomatis can lead to host cell reprogramming, up-regulating or down-regulating a series of gene expression, affecting host immune response and gene damage repair, thus affecting host cell and genome stability and promoting tumor progression. The cervical organs used in this study are suitable for a variety of cervical related studies, such as physiological mechanism, drug response, prognosis of chronic infection and so on, and can provide a new platform for clinical trials.

Scientific event

Material science

Reusable plastic bottles can release hundreds of chemicals.

The researchers used a combination of liquid chromatography and mass spectrometry, which enabled them to screen out all possible substances in the sample. They found that the chemicals released from plastic bottles mainly included plastic plasticizers, antioxidants, photoinitiators and diethyl toluamide (DEET). Among them, photoinitiator may interfere with human endocrine and other functions, while DEET is often used as an active substance in mosquito repellent spray. The researchers speculate that most of the substances detected are likely to be produced during the production and subsequent use of plastic bottles. Next, they will continue to explore the toxicological properties of these chemicals.

Spaceflight

A new generation of manned carrier rocket may use a new vertical take-off and landing recovery scheme

According to reports, in the coming period of time, China will carry out the development of a new generation of manned carrier rockets. The new generation of manned carrier rocket adopts modular and universal design, and has the ability to carry people and goods at the same time. The rocket adopts a two-stage series configuration for the mission of the near-Earth space station, the first stage has the ability of reuse and the carrying capacity of low-Earth orbit is about 14 tons, and the configuration of three-stage plus booster is adopted for the exploration mission far away from the moon. the carrying capacity of the earth-moon transfer orbit is about 27 tons. (science and Technology Daily)

Health

Low-meat and meat-free diets are associated with a lower overall risk of cancer

The team at the University of Oxford studied the relationship between diet and cancer risk by analyzing data from 472377 Britons between the ages of 40 and 70 recruited by the UK Biological sample Bank (UK Biobank) between 2006 and 2010. The researchers used health records to calculate their average incidence of new cancer over 11 years, taking into account diabetes and socio-demographic, socio-economic and lifestyle factors. 247571 (52%) participants ate meat more than five times a week, 205382 (44%) participants ate meat five times or less per week, 10696 (2%) participants ate only fish but no meat, and 8685 (2%) participants were general vegetarians or strict vegetarians. 54961 (12%) of the participants developed cancer during the study.

The researchers found that compared with people who ate meat more than five times a week, the overall risk of cancer decreased by 2% among those who ate meat five times a week or less, and by 10% among those who ate fish but not meat. It decreased by 14% among ordinary vegetarians and vegans. The researchers cautioned that because of the observational nature of the study, no causal relationship could be found between diet and cancer risk. In addition, the dietary data from the UK biological sample bank are collected at a single point in time, not over a continuous period of time, so they may not represent participants' lifelong dietary patterns. The study is published in the journal BMC Medicine.