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Accelerated urbanization and frequent heatwave events pose significant threats to human health. Analyses of the differences in air and land surface temperature (LST) under extreme climates can aid in understanding human-nature ecosystem coupling and the required adaptations to climate change. In this study, we quantified differences in urban and rural temperatures in China under heatwave (CHW) and non-heatwave periods (NHW) conditions and the influence of meteorological factors on these differences. Based on impervious surface data, 2421 urban and rural stations were dynamically classified from 2008 to 2017. Heatwaves were identified using relative thresholds, and differences were explored using meteorological data and MODIS LST data. For LST, urban–rural temperature difference (U-R _Tempdiff ) was highest during the day, whereas air temperature peaks occurred at night, under both NHW and CHW conditions. During CHWs, the daytime U-R _Tempdiff was greater for LST than for air temperature, reaching 4.24 ± 3.38 °C. At night, U-R _Tempdiff was slightly lower (1.04 ± 1.41 °C). The proportion of air U-R _Tempdiff contributed by rural air temperature was significantly higher during CHW nights than during NHW nights, whereas the proportion of land surface and air U-R _Tempdiff remained relatively stable during daytime. Spatially, the daytime temperature difference in the north decreased with latitude, whereas the difference in the south was lower. Under CHWs, urbanization had a stronger effect on LST than on air temperature, with a slightly smaller difference (0.01 °C yr ^−1 ) during the day and a slightly larger difference (0.03 °C yr ^−1 ) at night. The contribution of urbanization to LST was higher than that to air temperature, particularly during the day (16.34%). The effects of wind speed and precipitation on the average air urban–rural temperature difference was greater than those of LST under CHW, accounting for 16.13%, with the effects of wind speed being more significant. These results show that a comprehensive perspective is needed to understand the risks associated with a temperature rise risk under extreme climate conditions and to formulate effective mitigation measures that will they improve human thermal comfort under climate change.

We prepared two superconducting phases of (NH _3 ) _y Li _x FeSe _0.5 Te _0.5 , which show superconducting transition temperatures ( T _c ’s) as high as 20.2 and 29.5 K at ambient pressure, here called the ‘low- T _c phase’ and ‘high- T _c phase’. The temperature dependence of electrical resistance ( R ) was measured for the low- T _c phase of (NH _3 ) _y Li _x FeSe _0.5 Te _0.5 over a pressure ( p ) range of 0–14 GPa, and for the high- T _c phase of (NH _3 ) _y Li _x FeSe _0.5 Te _0.5 over 0–19 GPa, yielding double-dome superconducting T _c – p phase diagrams, i.e. two superconducting phases (SC-I and SC-II) were found for both the low- T _c and high- T _c phases under pressure. For the low- T _c phase, the maximum T _c was 20.2 K at 0 GPa for SC-I, and 19.9 K at 8.98 GPa for SC-II. For the high- T _c phase, the maximum T _c was 33.0 K at 1.00 GPa for SC-I, and 24.0 K at 11.5–13.2 GPa for SC-II. These results imply that the maximum T _c value of the high pressure phase (SC-II) does not exceed the maximum value of the SC-I, unlike what was shown in the T _c – p phase diagrams of (NH _3 ) _y Li _x FeSe and (NH _3 ) _y Cs _x FeSe investigated previously. Nevertheless, the double-dome T _c – p phase diagram was found in metal-doped FeSe _0.5 Te _0.5 , indicating that this feature is universal in metal-doped FeSe _1− _z Te _z . Moreover, no structural phase transitions were observed for either the low- T _c or high- T _c phases of (NH _3 ) _y Li _x FeSe _0.5 Te _0.5 over the wide pressure range of 0–15.3 GPa, and the T _c -lattice constant ( c ) plots for both phases were recorded to determine the critical point separating SC-I and SC-II.

A polymer waveguide Y-branch power splitter with loss compensation is proposed based on NaYF4:Er3+, Yb3+ nanocrystals prepared by a high temperature thermal decomposition method. The Y-branch power splitter is designed as a structure of embedded waveguide, and its core material is nanocrystals-doped SU-8. The insertion loss of the device is ∼15 dB. For an input signal power of 0.05 mW and a pump power of 267.7 mW, the two branches with 5.81-dB and 5.41-dB loss compensations at 1530 nm are achieved respectively. A polymer waveguide Y-branch power splitter with loss compensation has an important research significance. [ABSTRACT FROM AUTHOR]

A new superconducting sample, Ba1−xCsxTi2Sb2O, was prepared and characterized in a wide pressure range. The maximum value of superconducting transition temperature, Tc, of Ba1−xCsxTi2Sb2O was 4.4 K for x = 0.25 at ambient pressure. The crystal structure was determined to be tetragonal [space group of P4/mmm (No. 123)]. The charge density wave/spin density wave transition was observed at 44 K for Ba1−xCsxTi2Sb2O (nominal x = 0.25) at ambient pressure, but the transition was suppressed by applying pressure. The pressure dependent X-ray diffraction showed no structural phase transition up to 23.4 GPa, but very interesting Tc–pressure (p) behavior was observed, i.e. the Tc decreases with an increase in pressure up to 4.0 GPa, but it increased above 4.0 GPa, suggestive of non-BCS type behavior. Thus, the systematic study on new pnictide superconductor, Ba1−xCsxTi2Sb2O, was achieved, and the fascinating behavior of superconductivity against pressure was discovered. [ABSTRACT FROM AUTHOR]

A polymer waveguide thermo-optical switch with loss compensation based on NaYF4: 18% Yb3+, 2% Er3+ nanocrystals, fabricated by traditional semiconductor processes, has been investigated. NaYF4: 18% Yb3+, 2% Er3+ nanocrystals were prepared by a pyrolysis method. The morphology and luminescent properties of the nanocrystals were characterized. The nanocrystals were doped into SU-8 as the core material of an optical waveguide amplifier. The size of the device was optimized for its optical and thermal fields as well as its transmission characteristics. The device was fabricated on a silica substrate by spin coating, photolithography, and wet etching. The insertion loss of the switch device is ∼ 15 dB. The rise and fall times of the device are 240 μs and 380 μs, respectively, as measured by application of a 304 Hz square wave voltage. The extinction ratio of the device is about 14 dB at an electrode-driving power of 7 mW. When the pump light power is 230 mW and the signal light power is 0.1 mW, the loss compensation of the device is 3.8 dB at a wavelength of 1530 nm. Optical devices with loss compensation have important research significance. [ABSTRACT FROM AUTHOR]

The magnetism of highly oriented pyrolytic graphite (HOPG) induced by ion implantation is investigated with electron spin resonance (ESR) spectroscopy and magnetization measurements. The results indicate that the ESR spectra of the HOPG sample correlate with ion species, incident energy and dose of implantation. The correlation of the ESR spectra and magnetism of the HOPG sample with 12C+ ion implantation and H+ ion implantation are studied in detail. The ferromagnetism of the HOPG sample is likely related to the asymmetric L1 line, which may be attributed to the interaction between localized defects and itinerant electrons occupied in the ‘impurity’ band induced by ion implantation. [ABSTRACT FROM AUTHOR]