Modulation of High-Order Harmonic Generation from a Monolayer ZnO by Co-rotating Two-Color Circularly Polarized Laser Fields

By numerically solving the two-dimensional semiconductor Bloch equation,we study the high-order harmonic emission of a monolayer ZnO under the driving of co-rotating two-color circularly polarized laser pulses.By changing the relative phase between the fundamental frequency field and the second one,it is found that the harmonic intensity in the platform region can be significantly modulated.In the higher order,the harmonic intensity can be increased by about one order of magnitude.Through time-frequency analysis,it is demonstrated that the emission trajectory of monolayer ZnO can be controlled by the relative phase,and the harmonic enhancement is caused by the second quantum trajectory with the higher emission probability.In addition,near-circularly polarized harmonics can be generated in the co-rotating two-color circularly polarized fields.With the change of the relative phase,the harmonics in the platform region can be altered from left-handed near-circularly polarization to right-handed one.Our results can obtain high-intensity harmonic radiation with an adjustable ellipticity,which provides an opportunity for syntheses of circularly polarized attosecond pulses.

Potential role of hippocampal neurogenesis in spinal cord injury induced post-trauma depression

It has been reported both in clinic and rodent models that beyond spinal cord injury directly induced symptoms, such as paralysis, neuropathic pain, bladder/bowel dysfunction, and loss of sexual function, there are a variety of secondary complications, including memory loss, cognitive decline, depression, and Alzheimer's disease. The largescale longitudinal population-based studies indicate that post-trauma depression is highly prevalent in spinal cord injury patients. Yet, few basic studies have been conducted to address the potential molecular mechanisms. One of possible factors underlying the depression is the reduction of adult hippocampal neurogenesis which may come from less physical activity, social isolation, chronic pain, and elevated neuroinflammation after spinal cord injury. However, there is no clear consensus yet. In this review, we will first summarize the alteration of hippocampal neurogenesis post-spinal cord injury. Then, we will discuss possible mechanisms underlie this important spinal cord injury consequence. Finally, we will outline the potential therapeutic options aimed at enhancing hippocampal neurogenesis to ameliorate depression.

Internal collision double ionization of molecules driven by co-rotating two-color circularly polarized laser pulses

The double ionization process of molecules driven by co-rotating two-color circularly polarized fields is investigated with a three-dimensional classical ensemble model. Numerical results indicate that a considerable part of the sequential double ionization(DI) events of molecules occur through internal collision double ionization(ICD), and the ICD recollision mechanism is significantly different from that in non-sequential double ionization(NSDI). By analyzing the results of internuclear distances R = 5 a.u. and 2 a.u., these two recollision mechanisms are studied in depth. It is found that the dynamic behaviors of the recollision mechanisms of NSDI and ICD are similar. For NSDI, the motion range of electrons after the ionization is relatively large, and the electrons will return to the core after a period of time. In the ICD process,electrons will rotate around the parent ion before ionization, and the distance of the electron motion is relatively small. After a period of time, the electrons will come back to the core and collide with another electron. Furthermore, the molecular internuclear distance has a significant effect on the electron dynamic behavior of the two ionization mechanisms. This study will help to understand the multi-electron ionization process of complex systems.

Tunable spectral continuous shift of high-order harmonic generation in atoms by a plasmon-assisted shaping pulse

We delve into the phenomenon of high-order harmonic generation within a helium atom under the influence of a plasmon-assisted shaping pulse.Our findings reveal an intriguing manipulation of the frequency peak position in the harmonic emission by adjusting the absolute phase parameter within the frequency domain of the shaping pulse.This phenomenon holds potential significance for experimental setups necessitating precisely tuned single harmonics.Notably,we observe a modulated shift in the created harmonic photon energy,spanning an impressive range of 1.2 eV.This frequency peak shift is rooted in the asymmetry exhibited by the rising and falling edges of the laser pulse,directly influencing the position of the peak frequency emission.Our study quantifies the dependence of this tuning range and the asymmetry of the laser pulse,offering valuable insights into the underlying mechanisms driving this phenomenon.Furthermore,our investigation uncovers the emergence of semi-integer order harmonics as the phase parameter is altered.We attribute this discovery to the intricate interference between harmonics generated by the primary and secondary return cores.This observation introduces an innovative approach for generating semi-integer order harmonics,thus expanding our understanding of high-order harmonic generation.Ultimately,our work contributes to the broader comprehension of complex phenomena in laser-matter interactions and provides a foundation for harnessing these effects in various applications,particularly those involving precise spectral control and the generation of unique harmonic patterns.

Knockdown of HE4 suppresses tumor growth and invasiveness in lung adenocarcinoma through regulation of EGFR signaling

It has been shown that the high expression of human epididymis protein 4(HE4)in most lung cancers is related to the poor prognosis of patients,but the mechanism of pathological transformation of HE4 in lung cancer is still unclear.The current study is expected to clarify the function and mechanism of HE4 in the occurrence and metastasis of lung adenocarcinoma(LUAD).Immunoblotting evaluated HE4 expression in lung cancer cell lines and biopsies,and through analysis of The Cancer Genome Atlas(TCGA)dataset.Frequent HE4 overexpression was demonstrated in LUAD,but not in lung squamous cell carcinoma(LUSC),indicating that HE4 can serve as a biomarker to distinguish between LUAD and LUSC.HE4 knockdown significantly inhibited cell growth,colony formation,wound healing,and invasion,and blocked the G1-phase of the cell cycle in LUAD cell lines through inactivation of the EGFR signaling downstream including PI3K/AKT/mTOR and RAF/MAPK pathways.The first-line EGFR inhibitor gefitinib and HE4 shRNA had no synergistic inhibitory effect on the growth of lung adenocarcinoma cells,while the third-line EGFR inhibitor osimertinib showed additive anti-proliferative effects.Moreover,we provided evidence that HE4 regulated EGFR expression by transcription regulation and protein interaction in LUAD.Our findings suggest that HE4 positively modulates the EGFR signaling pathway to promote growth and invasiveness in LUAD and highlight that targeting HE4 could be a novel strategy for LUAD treatment.

Generation of quasi-chirp-free isolated attosecond pulses from atoms under the action of orthogonal two-color combined pulse of fundamental frequency and higher intensity second harmonic fields

The intrinsic chirp of high-order harmonic generation is an important factor limiting the production of ultrashort attosecond pulses.Based on numerically solving the time-dependent Schrodinger equation,the generation process of highorder harmonic from the He atom under the action of orthogonal two-color combined pulse of fundamental frequency and higher intensity second harmonic fields is studied.In this paper,we propose to achieve quasi-chirp-free isolated attosecond pulses by superimposing a higher second-harmonic field on the orthogonal direction of the fundamental frequency field.It is found that the high-energy part of its harmonic emission exhibits small chirp characteristics,which can be used to synthesize isolated attosecond pulses.Through the analysis of the wave packets evolution and the classical motion trajectories of the electron,it is demonstrated that the quasi-chirp-free harmonic can be attributed to the simultaneous return of electrons ionized at different times to the parent particle.The influence of the relative phase of the two pulses on the harmonics is further analyzed,and it is observed that this phenomenon is sensitive to the relative phase,but it can still generate isolated attosecond pulses within a certain phase.

High-order harmonic generation of the cyclo[18]carbon molecule irradiated by circularly polarized laser pulse

High-order harmonic generation of the cyclo[18]carbon(C_(18) ) molecule under few-cycle circularly polarized laser pulse is studied by time-dependent density functional theory. Compared with the harmonic emission of the ring molecule C_(6)H_(6) having similar ionization potential, the C_(18) molecule has higher efficiency and cutoff energy than C_(6)H_(6) with the same laser field parameters. Further researches indicate that the harmonic efficiency and cutoff energy of the C_(18) molecule increase gradually with the increase of the laser intensity of the driving laser or decrease of the wavelength, both are larger than those of the C_(6)H_(6) molecule. Through the analysis of the time-dependent evolution of the electronic wave packets, it is also found that the higher efficiency of harmonic generation can be attributed to the larger spatial scale of the C_(18) molecule,which leads to a greater chance for the ionized electrons from one atom to recombine with others of the parent molecule.Selecting the suitable driving laser pulse, it is demonstrated that high-order harmonic generation in the C_(18) molecule has a wide range of applications in producing circularly polarized isolated attosecond pulse.

杂萘联苯结构共聚芳醚砜的合成与性能

文中以4-(4-羟基苯基)-2,3-二氮杂萘-1-酮(DHPZ)、2,2-二(4-羟基苯基)丙烷(BPA)及4,4′-二氯二苯砜(DCS)为单体,环丁砜为溶剂,采用两步投料法进行高温溶液逐步聚合,通过调控单体的比例,制备了系列高分子量含杂萘联苯结构共聚芳醚砜(PPAESs)。通过红外光谱、核磁共振氢谱及广角X射线衍射分析表明所合成聚合物的结构与设计结构相一致。高温凝胶渗透色谱分析(GPC)结果表明,与一步投料法相比,PPAESs的数均分子量可达5×10^(4)以上;通过差示扫描量热分析和热重分析表明,聚合物的玻璃化转变温度在197~257℃之间,5%热失重温度为486~495℃,聚合物的耐热性及耐热稳定性提高;可溶于三氯甲烷、N,N-二甲基乙酰胺、N-甲基吡咯烷酮等极性非质子性溶剂,表现出良好的溶解性;对共聚芳醚砜薄膜进行拉伸性能实验,其拉伸强度为55~77 MPa、弹性模量为1.71~1.94 GPa、断裂伸长率为4%~7%。

粗铅精炼除铜反应的热分析动力学

加硫除铜是粗铅火法精炼除铜的主要方法,根据硫化铅和铜的反应温度和动力学条件,分别对硫化铅和铜摩尔比1∶1和1∶2的固相反应进行差热分析,利用Kissinger方程和FWO方程求得反应活化能。结果表明,反应开始温度在350℃左右,升温速率越大,峰形越宽,峰值温度越高,反应峰向高温方向移动,出现反应滞后现象。通过动力学方程计算,硫化铅和铜摩尔比为1∶1混合的反应活化能为233.32 kJ/mol,按1∶2混合的反应活化能为257.66 kJ/mol。硫化铅过量,反应活化能随反应温度降低而降低,有利于提高除铜效率。研究结果可为改进粗铅除铜工艺提供理论指导。

发动机小直径管X射线底片数字化图像增强技术

针对X射线胶片扫描后图像退化问题,提出一种基于麻雀搜索的改进多尺度Retinex(Multi-Scale Retinex,MSR)增强算法。以航空发动机小直径管数字化图像为研究对象,把图像梯度、频域特性和信息熵作为麻雀搜索算法的种群适应度函数,寻找双边滤波器中关键参数σ;最优值,实现自适应图像增强。两类典型实际图像测试结果表明,相比限制对比度直方图均衡化和传统MSR处理方法,本研究算法不仅在主观图像上能更加清楚地显示缺陷,而且在客观评价指标上至少提高10%以上,明显改善图像质量。

A Correct Smoothed Particle Method to Model Structure-Ice Interaction

This paper studies the effect of ice resistance on the icebreaking capacity and speed of an icebreaking vessel.We combine an improved Correct Smoothed Particle Method(CSPM)with a material low-speed collision fracture model to numerically simulate the continuous icebreaking and rolling process of crushed.Using this model,we investigate the icebreaking resistance and immersion resistance during the icebreaking process,taking into account the fluid(water)as the elastic boundary support and the fluid-solid coupling interaction.We compare the icebreaking resistance and broken ice fracture shapes obtained by the numerical calculation with the theoretical analytical results,and thus validate the improved CSPM method.Further,we compare the immersion resistance results from our simulation against that from Puntigliano[Puntigliano,Hamburgische Schiffbau-Versuchsanstalt GmbH(1995)],and demonstrate that the proposed method can accurately predict ice resistance.

科技项目后评估现状与对策研究

深入分析了科技项目后评估与项目验收的区别,以及目前国内科技项目后评估的现状。通过研究,提出了一套适合目前科技项目后评估的指标体系,对项目的技术创新性、综合效益和影响、立项决策的科学性、组织管理的有效性等进行分析和评价,为指导科技规划与后续项目立项起到借鉴作用。

Overview of Position Servo Control Technology and Development of Voice Coil Motor

Voice coil motor(VCM) is a special direct drive linear motor, which can convert electric energy directly into mechanical energy without the use of transmission mechanism. VCM has the advantages of simple structure, good rigidity, fast response, silence, high linearity, no cogging force, no pulsation et al. It is widely used in the field of high-precision control. This paper reviews and summarizes the results of VCM research conducted by scholars from various countries, and summarizes the general situation of VCM servo control technology. Firstly, a basic description of VCM’s mathematical model and common control mechanisms is provided. The benefits, drawbacks, and application of control techniques in the field of VCM are all explored in detail;At the same time, the methods to improve control strategy are proposed;Then, combined with the analysis and research of scholars in various countries on VCM, the problems of difficult to establish accurate model, friction disturbance and mechanical vibration of VCM and the solutions to the corresponding problems are summarized;Finally, a summary of VCM’s application fields is provided.

Effects of Exogenousα-Ketoglutaric Acid on 2-Acetyl-1-Pyrroline,Yield Formation and Grain Quality Characters of Aromatic Rice

The improvement of grain quality in aromatic rice is very important for farmer to increase their income.Present study was conducted with a two-year field experiment and three aromatic rice cultivars in order to study the effects of exogenousα-ketoglutaric acid on yield formation,grain quality characters and the biosynthesis of 2-acetyl-1-pyrroline(2-AP,key component of aromatic rice’s fragrance)in aromatic rice.At heading stage,0.50 mmol L^(-1)(T1)and 1.00 mmol L^(-1)(T2)α-ketoglutaric acid solutions were overhead sprinkle to aromatic rice plants,respectively while the treatment which was overhead sprinkled with distilled water was set as control(CK).The results showed that 17.34%-33.04%and 21.39%-34.74%higher grain 2-AP contents were recorded in T1 and T2 treatments,respectively.Compared with CK,T1 and T2 treatments significantly reduced the transcript level of gene BADH2 which is related to the 2-AP biosynthesis in aromatic rice.3.86%-7.51%higher grain protein contents and 1.15%-3.37%higher head rice rates were also recorded inα-ketoglutaric acid treatments than CK.Moreover,T1 and T2 treatments remarkably decreased the chalky rice rate,chalkiness and grain amylose content.However,there was no remarkable difference in grain yield and related trails(effective panicle number,grain number per panicle,seed-setting rate and 1000-grain weight)among CK,T1 and T2 treatments.In conclusion,application of exogenousα-ketoglutaric acid enhanced 2-AP biosynthesis and improved grain quality of aromatic rice.

Tunable spectral shift of high-order harmonic generation in atoms using a sinusoidally phase-modulated pulse

High-order harmonic generation(HHG)from an atom illuminated by a sinusoidally phase-modulated pulse is investigated by solving the time-dependent Schrödinger equation.The spectral shift that occurs in atomic HHG can be achieved easily using our laser pulse.It is shown that the photon energy of the generated harmonics is controllable within the range of 1 eV.The shift of the frequency peak position is rooted in the asymmetry of the rising and falling parts of the laser pulse.We also show that by varying the phase parameters in the frequency domain of the laser one can adjust and control the shift in atomic harmonic spectra.

Dynamic stabilization of atomic ionization in a high-frequency laser field with different initial angular momenta

We investigated the ionization of an atom with different orbital angular momenta in a high-frequency laser field by solving the time-dependent Schr¨odinger equation.The results showed that the ionization stabilization features changed with the relative direction between the angular momentum of the initial state and the vector field of the laser pulse.The ionization mechanism of the atom irradiated by a high frequency was explained by calculating the transition matrix and evolution of the time-dependent wave packet.This study can provide comprehensive understanding to improve atomic nonadiabatic ionization.

电动汽车无线充电技术研究

电动汽车的无线充电技术因其高安全性、智能操作和灵活便利而受到广泛关注。本文介绍了无线充电技术体系结构、电动汽车的种类和特点,然后建立了一个基于磁耦合谐振技术的无线充电系统。分析了PSpice中无线电力传输系统的特点,并在MATLAB/Simulink中建立了充电系统和DC/DC降压变换器电路。通过公式推导和仿真研究了补偿拓扑、谐振频率、谐振线圈降压变换器与系统传输效率和输出功率之间的关系。结果表明,改变线圈参数(如增加线圈半径和匝数),选择合适的工作频率、补偿和逆变电路,可以提高系统的输电效率和负载功率。最后,分析了无线充电技术在电动汽车中可能的发展趋势和应用趋势。

玄武岩纤维增强树脂基复合材料界面改性策略

近年来,工业界和学术界都将注意力聚焦在可持续天然纤维复合材料的开发上。玄武岩纤维具有高强度、高模量、耐高温、耐酸碱、隔热隔音、热振稳定性好、介电性能优异、绿色无污染及成本低等优点,玄武岩纤维增强树脂基复合材料凭借其优异的机械性能和可设计性被广泛地应用于飞行器、汽车、船舶、建筑、石油化工管道及风力发电机叶片等领域。然而,玄武岩纤维与聚合物基底间差的相容性导致玄武岩纤维增强树脂基复合材料存在诸多缺陷和不足。其中,界面强度不够高、界面相易被破坏的问题成为制约玄武岩纤维增强树脂基复合材料发展的瓶颈之一,因此许多玄武岩纤维增强树脂基复合材料研究工作集中在提高其界面结合能力上。本文介绍了玄武岩纤维增强树脂基复合材料的主要研究方向,以及几种常见的复合材料界面作用机理,并综述了近年来国内外关于玄武岩纤维增强树脂基复合材料界面增强改性方面的研究工作。

牛樟芝免疫调节蛋白的过量表达及活性分析

【目的】用大肠杆菌高效表达牛樟芝免疫调节蛋白(Antrodia camphorata immunomodulatory protein,ACA)。【方法】借助DNAworks3.2.4设计引物合成大肠杆菌密码子偏好性的ACA基因,构建于pET-32a和pGEX-4t-2,转化大肠杆菌,测序后分别命名为pET-32a-ACA/BL21和pGEX-4t-2-ACA/BL21;探索密码子偏好性、载体、培养基种类和诱导条件对ACA表达的影响并使用响应面法优化蛋白表达。纯化重组ACA(recombinant ACA,rACA)并干预小鼠巨噬细胞RAW264.7,通过测定rACA对巨噬细胞增殖能力、吞噬能力、细胞形态及产NO、肿瘤坏死因子α(tumor necrosis factor-α,TNFα)、白介素lβ(interleukin-1β,IL-1β)等细胞因子能力的影响来评估rACA的活性。【结果】pET-32a-ACA/BL21更适合ACA表达;在优化的SOB(酵母粉8.92 g/L)中培养pET-32a-ACA/BL21,添加0.42 mmol/L IPTG 25℃诱导7 h时rACA以可溶性表达为主,产量达187.122μg/mL,是目前大肠杆菌表达真菌免疫调节蛋白的最高报道。纯化的rACA能显著促进小鼠巨噬细胞增殖、提高细胞的吞噬活性和改变细胞形态,显著诱导巨噬细胞分泌NO、TNF-α和IL-1β。【结论】rACA的高效可溶性表达及类似天然ACA的活性使它可以替代天然ACA作为制药行业的食品添加剂或者免疫调节剂,甚至可以用于药物研究。