Optimal growth and development in childhood and adolescence is crucial for lifelong health and well-being1–6. Here we used data from 2,325 population-based studies, with measurements of height and weight from 71 million participants, to report the height and body-mass index (BMI) of children and adolescents aged 5–19 years on the basis of rural and urban place of residence in 200 countries and territories from 1990 to 2020. In 1990, children and adolescents residing in cities were taller than their rural counterparts in all but a few high-income countries. By 2020, the urban height advantage became smaller in most countries, and in many high-income western countries it reversed into a small urban-based disadvantage. The exception was for boys in most countries in sub-Saharan Africa and in some countries in Oceania, south Asia and the region of central Asia, Middle East and north Africa. In these countries, successive cohorts of boys from rural places either did not gain height or possibly became shorter, and hence fell further behind their urban peers. The difference between the age-standardized mean BMI of children in urban and rural areas was <1.1 kg m–2 in the vast majority of countries. Within this small range, BMI increased slightly more in cities than in rural areas, except in south Asia, sub-Saharan Africa and some countries in central and eastern Europe. Our results show that in much of the world, the growth and developmental advantages of living in cities have diminished in the twenty-first century, whereas in much of sub-Saharan Africa they have amplified.
Pathogenic bacteria that give rise to diseases every year remain a major health concern. In recent years, tellurium-based nanomaterials have been approved as new and efficient antibacterial agents. In this paper, we developed the approach to directly grow tellurium nanowires (Te NWs) onto commercial carbon fiber fabrics and demonstrated their antibacterial activity. Those Te NWs can serve as templates and reducing agents for gold nanoparticles (Au NPs) to deposit. Three different Te-Au NWs with varied concentration of Au NPs were synthesized and showed superior antibacterial activity and biocompability. These results indicate that the as-prepared carbon fiber fabrics with Te and Te-Au NWs can become antimicrobial clothing products in the near future.
Stochastic process theory has recently been extended to the nonstationary case and the concepts extended to include the time-varying parameters such as evolutionary spectra. Previous papers have reviewed and concluded that despite the time variation underlined, the evolutionary spectral density function may still be estimated or measured for numerous nonstationary processes. One of the most important aspects of the practical estimates is closely related to their accuracy which is now defined in both the frequency and time dimensions. In this paper the limit of the two resolutions for the common evolutionary spectral estimators is discussed and the obvious tradeoff relationship between the two is explained in the context of the popular filter/window techniques. It is found that if the first moment Bg of the filter/window function in time together with the 3-dB cutoff frequency are selected as the uncertainty measures then the product Bg fc 3/2 would be a dimensionless quantity which purely describes the filter/window qualities. In particular, the product varies very little among nearly all conventional window functions and the average can effectively be regarded as a constant uncertainty product which may prove useful in applied spectral analysis.
Since the first triboelectric nanogenerator (TENG) was developed in 2012, it has now become a new energy technology. TENG has been applied to efficiently convert the mechanical vibration energy into electricity. The fundamental mechanism of TENG is based on the contact electrification and electrostatic effect. Among these two effects, surface charge transfer happened during the contact electrification process is the main factor to affect the electric output of TENG. The electric output of most TENG would decrease in environment with high relative humidity, which restricts their application. By using the polypeptide as contact material to construct a biocompatible TENG, we found that the electric output of the TENG can be maintained or even enhanced at a higher relative humidity.
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