探测激子极化激元在超薄范德华微晶中的光传播

激子极化激元是一种准粒子,过渡金属二硫族化合物材料即使在室温下也能支持传播激子极化子,是非常好的纳米光子学研究平台.已有研究表明,通过散射型扫描近场光学显微镜可以对过渡金属二硫族化合物薄片中激子极化激元进行实空间探测,但波导厚度仅限于低至30 nm.本文采用三种不同波长的入射光(1550和1064 nm的近红外以及633 nm的可见光),通过基于原子力显微镜的散射型扫描近场光学显微镜测量,探测到MoS2和WSe2薄片中激子极化子普通横电模式的纳米光学成像.在厚度分别低至~3 nm(相当于4原子层)和~8 nm(相当于12原子层)的超薄MoS2和WSe2薄片上,可以清楚地观察到干涉条纹图案,大大打破了之前的测量厚度限制.当厚度接近几个原子层时,波矢量始终保持在1.6k0~1.7k0左右,而不是理论预言的1k0.这些模式的特性表明,体系是由近乎悬浮的过渡金属二硫族化合物薄片的三层对称波导构成,其对激子极性子的传播产生限域效应.研究结果为探索基于超薄过渡金属二硫族化合物材料的近红外区极化器件提供了深入的理解和开辟了新的途径.

First light for the sodium laser guide star adaptive optics system on the Lijiang 1.8 m telescope

A first generation sodium Laser Guide Star Adaptive Optics System （LGS-AOS） was developed and integrated into the Lijiang 1.8 m telescope in 2013. The LGS-AOS has three sub-systems： （1） a 20W long pulsed sodium laser, （2） a 300-millimeter-diameter laser launch telescope, and （3） a 37-element com- pact adaptive optics system. On 2014 January 25, we obtained high resolution images of an my 8.18 star, HIP 43963, during the first light of the LGS-AOS. In this paper, the sodium laser, the laser launch telescope, the compact adaptive optics system and the first light results will be presented.

Pump pulse characteristics of quasi-continuous-wave diode-side-pumped Nd:YAG laser

The influence of pumping laser pulse on the property of quasi-continuous-wave(QCW)diode-side-pumped Nd:YAG laser is investigated theoretically and experimentally.Under remaining a fixed duty cycle,the average output power increases,and the corresponding thermal focal length shorten with the increase of the pump pulse duration,which attributes to the decrease of the ratio of pulse buildup time to the pulse duration.At a pump power of 146 W,the laser output power changes from 65.1 W to 81.2 W when the pulse duration is adjusted from 150μs to 1000μs,confirming a significant enhancement of 24.7%.A laser rate equation model incorporating the amplified spontaneous emission is also utilized and numerically solved,and the simulated results agree well with the experimental data.

A sodium laser guide star coupling efficiency measurement method

A large telescope＇s adaptive optics （AO） system requires one or more bright artificial laser guide stars to improve its sky coverage. The recent advent of a high power sodium laser is perfect for such application. However, besides the output power, other parameters of the laser also have a significant impact on the brightness of the generated sodium laser guide star, mostly in non-linear relationships. When tuning and optimizing these parameters it is necessary to tune based on a laser guide star generation performance metric. Although return photon fluxis widely used, variability of the atmosphere and sodium layer makes it difficult to compare results from different sites or even within a short time period for the same site. A new metric, coupling efficiency, is adopted in our field tests. In this paper, we will introduce our method for measuring the coupling efficiency of a 20W class pulse sodium laser for AO application during field tests that were conducted during 2013-2015.

Numerical study of a 20W class QCW pulsed sodium guide star laser's performances at five sites in China

In the past few years,Chinese astronomical community is actively testing astronomical sites for several new optical/infrared ground-based telescopes.These site testing campaigns conducted were mainly focused on fundamental performances of the sites,such as cloud coverage,seeing,temperature,etc.With increasing interests in sodium laser guide star adaptive optics for these new telescopes in the Chinese astronomical community,it is interesting to investigate the performance of the laser guide star at these sites,especially considering that the sodium laser guide star’s on-sky performance is significantly influenced by sites’local performances,such as geomagnetic field,sodium layer dynamics,density of air molecule,etc.In this paper,we studied sodium laser guide star’s performance of a 20 W class Quasi Continuous Wave(QCW)pulsed laser developed by TIPC with numerical simulation for five selected sites in China.

声学指数在城市森林鸟类多样性评估中的应用

鸣声是鸟类之间进行沟通和传递信息的重要方式,这为通过声学监测评估鸟类多样性提供了独特的机会。利用声学指数快速评估生物多样性是一种新兴的调查方法,但城市森林中的复杂声环境可能会导致声学指数的指示结果出现偏差。为了解声学指数在城市森林中应用的可行性,本研究在北京市东郊森林公园设置了50个矩阵式调查样点,于2021年4–6月每月进行1次鸟类传统观测和同步鸣声采集,通过比较两种方法的结果来探究声学监测的有效性。采用Spearman相关分析和广义线性混合模型评估6个常用声学指数与鸟类丰富度和多度的关系,并衡量了每个指数的性能。结果表明:(1)本研究共记录到鸟类10目23科35种,通过声学监听识别的总物种数与传统鸟类观测相等,但具体鸟种存在差异;(2)不同月份间声学指数与鸟类丰富度和多度的相关性有明显差别,声学复杂度指数(ACI)和标准化声景差异指数(NDSI)优于其他指数,是评估鸟类多样性的关键变量;(3)声学指数对鸟类多度的预测能力(R2m=0.32,R2c=0.80)要高于丰富度(R2m=0.12,R2c=0.18)。声学指数为快速评估生物多样性提供了有前景的分析手段,但仍需继续探讨改进。随着方法的逐步完善和处理技术的提升,声学监测在城市生物多样性保护和跟踪管理方面的潜力也越来越大。

Combinatorial metabolic engineering of Saccharomyces cerevisiae for improved production of 7-dehydrocholesterol

7-Dehydrocholesterol(7-DHC),a key pharmaceutical intermediate in the production of vitamin D3,has a wide range of applications.To explore fermentative synthesis of 7-DHC,a 7-DHC-producing Saccharomyces cerevisiae strain was constructed by blocking the competitive pathway,eliminating rate-limiting steps,altering global reg-ulation,and pathway compartmentalization.After blocking the competitive pathway by disrupting ERG5 and ERG6 and introducing DHCR24 from Gallus gallus,S.cerevisiae produced 139.72 mg/L(17.04 mg/g dry cell weight,hereafter abbreviated as DCW)7-DHC.Subsequent alteration of global regulation by deleting ROX1 and overexpressing UPC2-1 increased 7-DHC production to 217.68 mg/L(37.56 mg/g DCW).To remove the accu-mulated squalene,the post-squalene pathway was strengthened by co-overexpression of PGAL1-driven ERG11 and PGAL10-driven ERG1,which improved 7-DHC titer and yield to 281.73 mg/L and 46.78 mg/g DCW,respectively,and reduced squalene content by 90.12%.We surmised that the sterol precursors in the plasma membrane and peroxisomes may not be accessible to the pathway enzymes,thus we re-localized DHCR24p and Erg2p-GGGGS-Erg3p to the plasma membrane and peroxisomes,boosting 7-DHC production to 357.53 mg/L(63.12 mg/g DCW).Iron supplementation further increased 7-DHC production to 370.68 mg/L in shake flasks and 1.56 g/L in fed-batch fermentation.This study demonstrates the power of global regulation and subcellular relocalization of key enzymes to improve 7-DHC synthesis in yeast.

VEGF-B antibody and interleukin-22 fusion protein ameliorates diabetic nephropathy through inhibiting lipid accumulation and inflammatory responses

Diabetic nephropathy(DN)is considered the primary causes of end-stage renal disease(ESRD)and is related to abnormal glycolipid metabolism,hemodynamic abnormalities,oxidative stress and chronic inflammation.Antagonism of vascular endothelial growth factor B(VEGF-B)could effi-ciently ameliorate DN by reducing renal lipotoxicity.However,this pharmacological strategy is far from satisfactory,as it ignores numerous pathogenic factors,including anomalous reactive oxygen species(ROS)generation and inflammatory responses.We found that the upregulation of VEGF-B and downregulation of interleukin-22(IL-22)among DN patients were significantly associated with the progression of DN.Thus,we hypothesized that a combination of a VEGF-B antibody and IL-22 could protect against DN not only by regulating glycolipid metabolism but also by reducing the accumulation of inflammation and ROS.To meet these challenges,a novel anti-VEGFB/IL22 fusion protein was developed,and its therapeutic effects on DN were further studied.We found that the anti-VEGFB/IL22 fusion protein reduced renal lipid accumulation by inhibiting the expression of fatty acid transport proteins and ameliorated inflammatory responses via the inhibition of renal oxidative stress and mitochondrial dysfunction.Moreover,the fusion protein could also improve diabetic kidney disease by increasing insulin sensitivity.Collectively,our findings indicate that the bifunctional VEGF-B antibody and IL-22 fusion protein could improve the progression of DN,which highlighted a novel therapeutic approach to DN.

A quantum inspired genetic algorithm for multimodal optimization of wind disturbance alleviation flight control system

This paper develops a Quantum-inspired Genetic Algorithm(QGA) to find the sets of optimal parameters for the wind disturbance alleviation Flight Control System(FCS). To search the problem domain more evenly and uniformly, the lattice rule based stratification method is used to create new chromosomes. The chromosomes are coded and updated according to quantuminspired strategies. A niching method is used to ensure every chromosome can converge to its corresponding local minimum in the optimization process. A parallel archive system is adopted to monitor the chromosomes on-line and save all potential feasible solutions in the optimization process. An adaptive search strategy is used to gradually adjust the search domain of each niche to finally approach the local minima. The solutions found by the QGA are compared with some other Multimodal Optimization(MO) algorithms and are tested on the FCS of the Boeing 747 to demonstrate the effectiveness of the proposed algorithm.

High-power wavelength-tunable and power-ratio-controllable dual-wavelength operation at 1319 nm and 1338 nm in a Q-switched Nd:YAG laser

We report the first demonstration on three types of 1.3 μm spectral region in a Q-switched Nd:YAG laser. In order to dissipate the heat deposition effectively to obtain good beam quality, the Nd:YAG rod crystal with 1° cut-angle on end faces is side-pumped by the quasi-continuous-wave pulsed laser diode. A Suprasil etalon is well designed as the intracavity mode-selector to obtain wavelength-tunable single line or power-ratio-controllable dual line operation at1319 nm and 1338 nm. With the pump pulse width of 200 μs and pump power of 410 W, the acousto-optic Q-switched laser delivered a pulse width of 117 ns at 400 Hz repetition rate, and the M2factor was measured to be about 1.87. 1319 nm together with 1338 nm single-wavelength laser achieved an average output power of 47.6 W and 39.9 W with a linewidth of 0.48 nm and 0.32 nm, and a tunable range of 111.2 pm and108.6 pm, respectively. Among dual-wavelength oscillation, both lines can be tuned at almost equal intensity level with 45.7 W total output power, which is input into an LBO crystal to generate red light of 11.4 W for 659 nm,6.7 W for 664 nm, and 7.5 W for 669 nm. The 1.3 μm wavelength-selectable operation realized by using the same laser configuration may enhance the application in the fields of tunable lasers and THz frequency generation.