Monitoring landslide associated with reservoir impoundment using synthetic aperture radar interferometry: A case study of the Yalong reservoir

The construction of large reservoirs can address the problem of uneven distribution of rivers in time and space,thereby meeting the needs of human production and living.However,the huge elevation of the water level in some areas may modify the distribution of the groundwater level,causing geological disasters,such as surface deformation and landslides.The Yalong reservoir supplies water to the downstream area of Shannan,Tibet;however,since the reservoir started storing water in 2017,the government has discovered two ancient landslides.In this study,to monitor the deformation of the Yalong reservoir since its construction in 2014,we first used synthetic aperture radar(SAR) data and the multidimensional small baseline subset(MSBAS) method to obtain the deformation in the east-west and vertical directions.The result indicated the presence of three large,slow-moving landslides:Landslides I and II,located on the right bank of the Yalong reservoir,which are consistent with the results obtained by the actual survey,and a new discovery,Landslide Ⅲ,located on the left side of the reservoir.Meanwhile,the experimental results indicated that the dam had undergone obvious deformation after impoundment,which should not be ignored.The global positioning system and interferometric SAR(InSAR) timeseries deformation residual data were used to verify the accuracy of the InSAR method.The results also showed that the deformation caused by the three landslides had te nded to accele rate after the rese rvoir’s impoundment,and that the failure mode was retrogressive landslide.We found that InSAR plays a vital role in landslide detection and failure mode research around reservoirs,and assists in providing early warning for subsequent landslide disasters.

Influence of ocean tidal loading on InSAR offshore areas deformation monitoring

The ocean tide can cause the redistribution of the seawater mass, resulting in earth＇s surface deforma- tion, namely ocean tidal loading （OTL）. OTL vertical displacement may reach several centimeters, especially in coastal areas, so its effect in the field of high precision geodesy must be considered. This study concentrates on the influences of OTL on InSAR deformation measurements. We improve the osu.chinasea.2010 regional model and then compare the improved regional model with other regional models. It turns out that the improved regional model can achieve higher precision. Then we use it to replace the offshore part of the global model to generate the present model. We find that the displacement observed by the present model is 2-3 mm larger than that of other models on some sites. Finally, the present model is used to correct the deformation observed by InSAR of Shanghai and Los Angeles. A comparison between the displacements of IGS station with the corrected data shows that the OTL correction can improve the accuracy of InSAR deformation results by about 20%.

Compact pulsed thulium‐doped fiber laser for topographical patterning of hydrogels

We report the generation of high energy 2μm picosecond pulses from a thulium-doped fiber master oscillator power amplifier system.The all-fiber configuration was realized by a flexible large-mode area photonic crystal fiber(LMA-PCF).The amplifier output is a linearly-polarized 1.5 ns,100 kHz pulse train with a pulse energy of up to 250μJ.Pulse compression was achieved with(2+2)-pass chirped volume Bragg grating(CVBG)to obtain a 2.8 ps pulse width with a total pulse energy of 46μJ.The overall system compactness was enabled by the all-fiber amplifier design and the multi-pass CVBG-based compressor.The laser output was then used to demonstrate high-speed direct-writing capability on a temperature-sensitive biomaterial to change its topography(i.e.fabricate microchannels,foams and pores).The topographical modifications of biomaterials are known to influence cell behavior and fate which is potentially useful in many cell and tissue engineering applications.

SARS-CoV-2 spike-specific TFH cells exhibit unique responses in infected and vaccinated individuals

Long-term humoral immunity to SARS-CoV-2 is essential for preventing reinfection. The production of neutralizing antibody (nAb)and B cell differentiation are tightly regulated by T follicular help (T_(FH)) cells. However, the longevity and functional role of T_(FH) cellsubsets in COVID-19 convalescents and vaccine recipients remain poorly defined. Here, we show that SARS-CoV-2 infection andinactivated vaccine elicited both spike-specific CXCR3^(+) T_(FH) cell and CXCR3^(-) T_(FH) cell responses, which showed distinct responsepatterns. Spike- specific CXCR3^(+) T_(FH) cells exhibit a dominant and more durable response than CXCR3^(-) T_(FH) cells that positivelycorrelated with antibody responses. A third booster dose preferentially expands the spike-specific CXCR3^(+) T_(FH) cell subset inducedby two doses of inactivated vaccine, contributing to antibody maturation and potency. Functionally, spike-specific CXCR3^(+) T_(FH) cellshave a greater ability to induce spike-specific antibody secreting cells (ASCs) differentiation compared to spike-specific CXCR3^(-) T_(FH)cells. In conclusion, the persistent and functional role of spike-specific CXCR3^(+) T_(FH) cells following SARS-CoV-2 infection andvaccination may play an important role in antibody maintenance and recall response, thereby conferring long-term protection. Thefindings from this study will inform the development of SARS-CoV-2 vaccines aiming to induce long-term protective immunememory.

Polarization-robust mid-infrared carpet cloak with minimized lateral shift

With the advent and rapid development of the transformation optics and metamaterials,invisibility cloaks have captivated much attention in recent years.While most cloaking schemes suffer from limited bandwidth,the carpet cloak,which can hide an object on a reflecting plane,can operate over a broadband frequency range.However,the carpet cloaks experimentally realized thus far still have several limitations.For example,the quasi-conformal mapping carpet cloak leads to a lateral shift of the reflected light ray,while the birefringent carpet cloak only works for a specific polarization.In this work,we propose a conformal transformation scheme to tackle these two problems simultaneously.As an example,we design a mid-infrared carpet cloak in a silicon platform and demonstrate its polarization-insensitive property as well as the minimized lateral shift over a broad frequency band from 24 to 28.3 THz.